Manitoba Materials Conference 2012
May 9, 2012 Engineering & Information Technology Complex Atrium

The Manitoba Materials Conference poster competition brings together students and postdoctoral fellows from 32 research groups from the University of Manitoba, Lakehead University and the University of North Dakota in the departments of Biosystems Engineering, Chemistry, Electrical & Computer Engineering, Geological Sciences, Mechanical & Manufacturing Engineering, Physics & Astronomy, Food Science and Textile Science.

This competition is sponsored by the Manitoba Institute for Materials and our partners NSERC Prairies Regional Office, EnviroTREC, the University Graduate Student Association and Manitoba Hydro.
 
Conference Chair: Dr. Derek Oliver, Electrical & Computer Engineering
MIM Director: Dr. Michael Freund, Chemistry


Crystalline Materials and Nanostructures

[1]    InN/GaN Heterostructure Growth by Migration Enhanced Epitaxial Afterglow (MEAglow)
Binsted, Peter, Ph.D. Candidate
Lakehead University, Electrical Engineering    
Advisor: Dr. D. Alexandrov & Dr. K. S. Butcher

The formation of device quality GaN/InN heterostructures on a 2 inch c-axis oriented sapphire substrate is discussed. Such a heterostructure is suitable for applications in light emitting diodes (LED), solar cells, and field effect transistors (FET) intended to operate in both high radio frequency range and harsh environments. Growth is accomplished using a new method coined Migration Enhanced Epitaxial Afterglow (MEAglow), an improved form of low pressure Plasma Enhanced Metal Organic Chemical Vapour Deposition (MOCVD). Basically this technique involves pulsed delivery of the metal-organic as a means of improving the crystallinity of the material. Metal rich pulses are delivered followed by a continuous plasma nitridation. A conducting layer of InN is put down on the insulating GaN layer and the GaN layer provides a template for the InN growth. Initial x-ray diffraction (XRD) analysis results show an InGaN alloy layer forming under the InN. No GaN was seen. It was postulated that Indium metal deposited prior to complete nitridation converted the GaN layer to InGaN. To verify the integrity of the insulating GaN layer, a third party GaN substrate was substituted. Results were unchanged. Parameters were then modified to reduce the amount of Indium used for the initial metal deposition. XRD results indicate a good break between the insulating GaN and conductive InN layer. Growth appears to be c-axis and epitaxial. Hall effect measurements showing carrier concentration and conductivity are included. We’ve shown that the growth of a device suitable heterostructure using III-Nitride is possible using the MEAglow technique.

[3]    ⁴³Ca MAS NMR of Natural Minerals at Moderate and Ultrahigh Fields
Wren, John, Ph.D. Candidate
University of Manitoba, Chemistry    
Advisor: Dr. S. Kroeker

Calcium is one of the most important alkaline earth metals, being the fifth most abundant element in the Earth’s crust, and yet the field of ⁴³Ca NMR is still in its infancy due to its inherently low sensitivity. Recent advances in solid-state NMR, particularly the accessibility of ultra-high magnetic fields, have resulted in many recent successes, however ⁴³Ca NMR can also be profitably done at moderate fields. We demonstrate the application of ⁴³Ca MAS NMR at both 14.1 T and 21.1 T to a variety of minerals as an investigative probe of calcium cationic environments. Utilizing experimental NMR parameters and quantum chemical calculations, quadrupolar and chemical shift interactions were correlated with local geometry. Borate minerals, featuring both single and multiple calcium sites were studied.

[5]    GISAXS study on the annealing behavior of sputtered HfO₂ thin films
Belo, Gustavo, Ph.D. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D. A. Buchanan

Grazing Incidence small-angle X-ray scattering (GISAXS) is a versatile technique in nano and micro thin films surfaces analysis. The scattering image depends on the form and distribution of the scatters objects. In this present work GISAXS is used to study the annealing behavior of sputtered hafnium dioxide (HfO₂) thin films. The data analysis were computed in the framework of the distorted-wave Born approximation (DWBA) for supported islands and it was assumed that there is no correlation between the kind of the scattering object and its position (Decoupling Approximation). The results reveal that the scattering objects are ellipsoids with diameter in the 5-6 nm range and follow a Gaussian size distribution function. The surface roughness was estimated to be ~1 nm.

[7]    Solid-State NMR of Gold Cyanide Coordination Polymers
Cavers, Heather, Undergraduate Student
University of Manitoba, Chemistry
Advisor: Dr. S. Kroeker

Coordination polymers containing gold cyanide [Au(CN)₂]^- ligands have shown promise in a variety of applications, ranging from chemical sensors to birefringent materials. Tl[Au(CN)₂] and three derivatives modified with phenanthroline-based ancillary ligands were synthesized and characterized by single-crystal x-ray diffraction and birefringence measurements. ²⁰⁵Tl solid-state nuclear magnetic resonance (NMR) spectroscopy was conducted on this series, providing unique information about the electron lone-pair activity not available from routine diffraction studies. The highly sensitive ²⁰⁵Tl chemical shift anisotropy allows diagnostic correlations with ligand basicity and the lone-pair activity of the Tl(I) ion.  Group 2 (Ba²⁺, Sr²⁺, Ca²⁺ and Mg²⁺) gold cyanide complexes, M[Au(CN)₂]₂, exhibit intense luminescence with cation-dependant wavelengths. It has been proposed that this is the result of aurophilic interactions, but complete structural characterization by diffraction-based methods is limited by structural disorder in these systems. Solid-state ¹³C and ¹⁵N MAS NMR experiments using direct- and cross-polarization were employed as structural probes of the cyanide units and their connectivity, while also giving insight into the role of water in the production of these luminescent properties.

[9]    Seebeck Rectication Enabled by Intrinsic Thermoelectrical Coupling in Magnetic Tunneling Junctions
Zhang, Zhaohui, Undergraduate Student
University of Manitoba, Physics and Astronomy    
Advisor: Dr. C.M. Hu    

An intrinsic thermoelectric coupling in the linear response regime of magnetic tunneling junctions (MTJs) is discovered. In the DC response, it leads to a nonlinear correction to Ohm's law. Dynamically, it enables a novel Seebeck rectification and second harmonic generation, which apply for a broad frequency range and can be magnetically controlled. A phenomenological model on the footing of the Onsager reciprocal relation and the principle of energy conservation explains very well the experimental results obtained from both direct current and frequency dependent transport measurements performed up to GHz frequencies. This work refines and revises previous understanding of magnetotransport and microwave rectification in MTJs. It forms a new foundation for utilizing spin caloritronics in high-frequency applications.

[11]    Impact behavior of 4340 steel at high strain rates and large strains
Boakye-Yiadom, Solomon, Ph.D. Candidate
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. N. Bassim

Adiabatic shear bands (ASBs) is a failure mechanism in materials under high strain rates (>103S^-1) and large strains of deformation. Their formation leads to crack nucleation and propagation, resulting in catastrophic failure almost instantaneously. Although there have been numerous investigations on ASBs, the mechanism of nucleation and propagation remain less understood. This is due in part to the complexity of the problem of formation of these indicators of damage and the short duration between deformation and failure. In this study, cylindrical 4340 steel specimens were heat treated at 315OC, 425OC and 620OC, for 1hr or 2hrs and studied using x-ray diffraction and electron microscopy to determine the initial structure of the steel prior to impact. This was followed by impact using the Direct Impact Hopkinson Pressure Bar (DIHPB) to create distinct shear bands. The initial structure of the steel prior to impact were characterized by martensite laths with precipitated spherical and platelet carbides. Platelet carbides were predominant on the martensite lath boundaries and on packet boundaries.  After impact, the XRD results showed that shear bands in 4340 steel do not form by phase transformation. However, dynamic recrystallization, which has been reported in most cases as being the mechanism of formation of adiabatic shear bands was observed only in regions away from the shear bands. Inside the shear bands, crushing of brittle intermetallic carbides and martensite lathes was predominant due to the very high strains in these regions and is believed to be the source of the ASBs.

[13]    Thermal history of the Kapoeta meteorite: A study of Fe-Mg ordering in orthopyroxene by single-crystal XRD and Mössbauer spectroscopy
Abdu, Yassir, Postdoctoral Fellow
University of Manitoba, Geological Sciences
Advisor: Dr. F.C. Hawthorne

Kapoeta is an achondrite meteorite that belongs to the howardite group. Howardites, eucrites, and diogenites meteorites (HED) are believed to originate from igneous processes on the asteroid 4 Vesta. Kapoeta is characterized as a polymict breccia with a light-dark structure, and the rock consists almost entirely of pyroxene. The study of intracrystalline distribution of Fe and Mg between the nonequivalent octahedral sites M1 and M2 in pyroxenes is very useful in tracing the thermal history of a rock. In unshocked and slowly cooled pyroxenes to ~ 500 °C and below, Fe orders at the M2 site whereas Mg occurs predominately at the M1 site. In crystals that have been rapidly cooled from high temperatures, a more disordered Fe-Mg distribution over the M1 and M2 sites is observed.
Single-crystal X-ray diffraction was used to determine Fe-Mg degree of ordering on orthopyroxene crystals from the Kapoeta meteorite, through the intracrystalline distribution parameter, p, defined as: p = (Fe(M1).Mg(M2))/(Fe(M2).Mg(M1)), which is then used to calculate the Fe-Mg ordering closure temperature (Tc). The distribution of Fe and Mg over the M1 and M2 sites determined by the structure refinement gives Tc values in the range 350-450 °C, in agreement with those previously obtained on some orthopyroxene crystals from Kapoeta having similar compositions to our orthopyroxenes (Mg/(Mg+Fe) range: 70-80%), all are within the Tc values reported on orthopyroxenes from diogenites. These closure temperatures indicate a slow cooling rate for these Kapoeta orthopyroxenes, and the similarities of Tc and composition to those of diogenites may suggest a diogenitic origin deep within the parent body of the HED meteorites. Mössbauer spectra collected on powdered samples from both the light and dark structures of Kapoeta are characteristic of orthopyroxene. The light and dark structures have almost identical Mössbauer spectra. The spectra are fitted with two doublets due to Fe²⁺ at the M1 and M2 sites in orthopyroxene. In contrast to the low Tc values determined by structure refinement, the distribution of Fe²⁺ between the M1 and M2 sites determined by Mössbauer spectroscopy suggests a Tc value of ~ 900 °C, indicating a fast cooling. The results are discussed in relation to the thermal and shock histories of the HED parent body.

[15]    X-ray Photoelectron Spectroscopy Analysis of GaN thin films grown by Migration Enhanced Afterglow Epitaxy (MEAglow)
Gergova, Rositsa, Ph.D. Candidate
Lakehead University, Chemistry
Advisor: Dr. D. Alexandrov

X-Ray Photoelectron Spectroscopy (XPS) was used for determination of the chemical composition of the surface of GaN thin films. The GaN samples were grown under different conditions on c-oriented sapphire by a new technique called Migration Enhanced Afterglow Epitaxy (MEAglow) which is a form of pulsed delivery Plasma Enhanced Chemical Vapour Deposition (PECVD). A comparison was done between the XPS data from the grown samples and the data from a commercial sample of GaN. Curve fitting was performed for deconvolution of the peaks using the CasaXPS software and a tentative assignment of the different photoelectron lines was performed. Atomic Force Microscopy (AFM) images of the samples showing very low RMS surface roughness will also be presented.

[17]    Complex magnetic behaviour in the potential multiferroic Pb₃TeCo₃V₂O₁₄
Silverstein, Harlyn, Ph.D. Candidate
University of Manitoba, Chemistry
Advisor: Dr. C. Wiebe

The langasites are a diverse group of materials that display a broad range of phenomena including applicably prized behaviours like piezoelectricity and multiferroicity. In Ba₃NbFe₃Si₂O₁₄, Fe³⁺ occupies the vertices of isolated triangles which stack between 2D kagomé layers. Geometric frustration steers this compound to order into a helix at T=26 K, where only one chiral domain is preferred. As a result of the broken symmetry, multiferroic behaviour ensues. Attempts to raise the transition temperature have failed as Fe³⁺ occupies a tetrahedral site that other magnetic ions find unfavourable. Insight from B.V. Mill (Russ. J. Inorg. Chem., 2010) led us to circumvent this problem by using Te⁶⁺; this ion only exists in octahedral coordination thus forcing other magnetic ions into the tetrahedral site. We have optimized the synthesis of Pb₃TeCo₃V₂O₁₄, a compound related to the natural mineral dugganite (Pb₃TeZn₃As₂O₁₄) and isostructural to the langasite, Ba₃NbFe₃Si₂O₁₄. Characterization of this compound shows remarkably divergent behaviour from the langasite, including most notably, two magnetic transition temperatures at T=8.6 K and T=6.0 K. Neutron scattering experiments provide evidence of coexisting static and dynamic spins in the first structure, while the second structure orders with propagation vector k = (5/6, 5/6, 1/2). Analysis of the dielectric constant indicates anomalies at both transition temperatures indicating evidence of magnetoelectric coupling. Drawing comparisons with the langasite and other Co-V systems, the potential for multiferroic behaviour in this material is promising.

[19]    Platinum Uptake in Doped Barium Cerate Perovskites
Lussier, Joey, Undergraduate Student
University of Manitoba, Chemistry
Advisor: Dr. M. Bieringer

The perovskite structure (ABO₃) provides exceptionally diverse applications for magnetic, ferroelectric, dielectric, multiferroic, thermoelectric, catalytic and ion conducting materials etc. The diversity of the perovskite system is largely due to compositional tolerance which is enabled through a variety of cooperative distortion modes and superstructure formations capable of accommodating almost any cation.
We are focusing on the A³⁺ doped BaCeO₃ system. The indium doped barium cerate has been utilized as the key-intermediate for the preparation of indium doped CeO₂ oxide ion conductors (Bhella, S.S., et al., Inorg. Chem.2010, 49, 1699-1704). Previously we reported the formation of indium doped BaCeO₃ and have reinvestigated the formation of Ba₂Ce_(2-x)Pt_xO₆ double perovskites with emphasis on the formation and decomposition of the A³⁺ doped analogues. Particularly intriguing is the irreversible platinum uptake and liberation during in-situ diffraction experiments during heating and cooling. This presentation will highlight the importance of the identity of the A³⁺ dopant for the double perovskite formation. Furthermore comments regarding reductive versus oxidative reaction conditions will be provided. The discussion will be supported by ambient temperature X-ray diffraction, TGA/DTA as well as in-situ powder X-ray and powder neutron diffraction data.

[21]    Optimization of Lead Oxide (PbO) Technology for Application in Direct Conversion Fluoroscopic Detectors
Semeniuk, Oleksii, M.Sc. Candidate
Lakehead University, Physics
Advisor: Dr. A. Reznik

Polycrystalline Lead Oxide (PbO) is the most promising X-Ray to charge transducer for direct conversion X-Ray detectors that are used in fluoroscopy and radiology. Previous usage of PbO films in Plumbicon vacuum tubes for optical imaging, ensures its appropriate photoconductive properties, which in combination with high X-Ray absorption coefficient and theoretical conversion gain indicates enormous potential for radiological medical imaging application.
However, at the current stage of PbO technology the theoretical charge yield has not yet been achieved because of the limitations in applied electric field F which is restricted to 3.5 V/m to keep dark current acceptably low. Here we present our study on optimization of PbO technology (deposition rate, temperature, pressure) to produce uniform layers capable of withstanding elevated electric fields with extremely low dark current previously achievable only in optical grade thin PbO films used in Plumbicons.
Field dependencies of charge yield, dark current kinetics are reported. An improvement in electron-hole pair creation energy is shown although the theoretical value is not achieved yet. The proposed way for the further improvement in the characteristics of Lead Oxide is development of a PbO blocking structure that will suppress injection from bias electrodes. Once developed, the new PbO photoconductor technology will achieve higher sensitivity and better spatial resolution over existing detectors.

[23]    Unprecedented nanocomposites of functionalized silica-coated gold nanoparticles with a nematic liquid crystal
Mirzaei, Javad, Ph.D. Candidate
University of Manitoba, Chemistry
Advisor: Dr. T. Hegmann

Developing liquid crystal (LC) mixtures for brighter, higher contrast liquid crystal displays (LCDs) consuming less power will be important for saving energy and critical energy resources. A promising class of materials with an enormous potential for improving LC properties are nanomaterials. It has been shown that composites of metallic nanoparticles (NPs) or semiconductor quantum dots with nematic liquid crystals (NLCs) can have unique effects on optical and electro-optical characteristics of the NLC such as molecular alignment, improved response time, lower Freedericksz transition voltage and dielectric permittivity [1]. However, instability of NPs mainly due to ligand desorption has been a major concern in NPs-doped LC mixtures. The purpose of this project is to synthesize robust silica-coated gold NPs to overcome the stability challenge. Simultaneously, following functionalization provides hydrophobic NPs and structurally more compatible with host LC molecules. Furthermore, we study unique optical as well as electro-optical effects of silica-coated gold NPs on NLCs with respect to size, surface properties and concentrations of NPs. Comparison between the new results with existing data [1,2] from other types of NPs without silica layer or different sizes will reveal further the mechanism of interaction between NPs and LC molecules.

1) U. Shivakumar, J. Mirzaei, X. Feng, A. Sharma, P. Moreira, T. Hegmann, Liq. Cryst. 2011, 38, 1495-1514. 2) J. Mirzaei, M. Urbanski, Kui Yu, H.-S. Kitzerow, T. Hegmann, J. Mater. Chem. 2011, 21, 12710-12716.

[25]    Cobalt driven enhancement of nanomagnetism in iron-oxide nanoparticles encapsulated in a synthetic ferritin shell
Skoropata, Elizabeth, M.Sc. Candidate
University of Manitoba, Physics and Astronomy
Advisor: Dr. J. van Lierop    

We have examined the effects of Co doping (0-12% relative to total metal) on the magnetic properties of iron-oxide nanoparticles incorporated in a synthetic ferritin shell. Mössbauer spectroscopy revealed that the nanoparticles consisted of a mixture of Fe₃O₄ and γ-Fe₂O₃, and that Co was integrated exclusively into the B-sites of the Fe₃O₄ phase. Cobalt doping resulted in the formation of Co_xFe_3-xO₄/γ-Fe₂O₃ nanoparticles with x = 0, 0.25, 0.51, 0.56, and 0.63. Magnetometry and susceptometry experiments showed that substantial enhancements in the coercivities, blocking temperatures and anisotropy constants of the nanoparticles occurred for all Co doping levels. Our results show that the Co altered significantly the local atomic Fe magnetism and enhanced the magnetic nanoparticle anisotropy considerably.

[27]    Self-assembly and manipulation of liquid crystal functionalized gold nanorods
Feng, Xiang, Ph.D. Candidate
University of Manitoba, Chemistry
Advisor: Dr. T. Hegmann    

The significant interest in anisometric nanomaterials arises from their unique optical and electronic properties that can easily be tuned through small changes in size, structure and shape. However, the fabrication of orientational ordered arrays of anisotropic nanoparticles from the bottom up remains a challenging quest.
To address this problem, we fabricated hydrophobic gold nanorods coated with liquid crystals organosilanes to trigger the self-assembly of these liquid crystal surface-functionalized gold nanorods (LC-GNRs). Fascinatingly, we found that these LC-GNRs can be manipulated by thermal annealing and with magnetic fields with the LC-GNR orientation following the magnetic field lines. Moreover, we dispersed nematic LC-GNRs in nematic liquid and utilized different types of surface-modified substrates to obtain planar (homogeneous) or homeotropic alignment of liquid crystals and the dispersed gold nanorods. The quality of liquid crystal and nanorod alignment were characterized by polarized optical microscopy and polarized visible spectrophotometry, respectively.

[29]    Magnetic Ground States of the Germanate Pyrochlores
Hallas, Alannah, M.Sc. Candidate
University of Manitoba, Chemistry
Advisor: Dr. C. Wiebe

Extreme frustration arises in the pyrochlore lattice, A₂B₂O₇, when the A-site, which is situated at the vertices of corner sharing tetrahedra, is occupied by a magnetic rare earth ion. Magnetic pyrochlores are renowned for the novel ground states they adopt due to frustration. The germanate pyrochlores, A₂Ge₂O₇ (A = Tb, Dy, Ho) were synthesized via a high temperature and high pressure technique. In comparison to other magnetic pyrochlores, the germanate pyrochlores have a significantly reduced lattice size and thus, stronger magnetic interactions. DC susceptibility, heat capacity and X-ray diffraction measurements for these compounds will be reported. Additionally, the results of a polarized neutron scattering experiment on Ho₂Ge₂O₇ will be presented. The bulk property measurements for both Dy₂Ge₂O₇ and Ho₂Ge₂O₇ demonstrate spin ice behavior, including residual entropy equal to the Pauling value for water ice. The spin ice state is a short-range ordered ground state in which two spins point inwards and two spins point outwards from the center of each tetrahedron. Spin ices are notable for being the only known hosts of magnetic monopoles, emergent quasiparticles with net magnetic charge. The reduced lattice size in the germanate pyrochlores gives rise to a higher density of magnetic monopoles, making them superior hosts for the study of monopoles. We also report that Tb₂Ge₂O₇ demonstrates spin liquid behavior, the absence of magnetic order in the limit of 0 K.

[31]    Layer by Layer Assembly of Epidermal Growth Factors on Polyurethane Films for Chronic Wound Closure
Abhilash Kulkarni, M.Sc. Candidate
University of Manitoba, Textile Science
Advisor: Dr. S. Liu

Tissue Injury happens frequently in our lives and is more prone to happen in ageing people. Proper wound dressing is required to protect the destroyed skin in chronic wounds and these dressing should also be able to achieve cell migration and proliferation for the complete closure of wound. Chronic wounds have always shown to have decreased levels of growth factors, thereby retarding the healing process. The use of recombinant growth hormones in chronic wounds offers interesting possibilities to modulate wound healing microenvironments. However, the outcome of clinical studies demonstrates that an important and often underestimated aspect of the growth factor wound healing paradigm is the effective delivery of the polypeptides to the wound site. These polypeptides suffer degradation during delivery especially in chronic wounds such as diabetic ulcers where active inflammation results in expression of large quantities of proteases. In this proposal a novel dressing is designed which can enhance the wound healing efficiency by releasing EGF (epidermal growth factors) in a benign environment to expedite the healing process. The EGF is encapsulated on a polyacrylic acid modified PU film using layer-by-layer assembly. The amount of encapsulated EGF is tunable with higher amount of encapsulation when the number of CH/EGF bilayer goes from 5 to 20 indicating successful deposition and the tunability of the system. The released EGF was bioactive i.e. 90% of the released EGF retained its biological activity.  The cell proliferation rate in a wound healing model is much faster in the case of EGF loaded PU film than control film.

[33]    Work Function Tuning of Reactively Sputtered Hf-Si-N-Metal Gate Electrodes for Advanced CMOS Technology
Rekha Chaudhari, M.Sc. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D.A. Buchanan

Due to aggressive reduction of transistor dimensions, the conventional poly-silicon gated complementary metal oxide semiconductor devices have revealed short channel effects. The conventional poly-silicon is known to suffer from short channel effects such as poly depletion, high gate resistance and dopant penetration . To replace the conventional poly-silicon gate, extensive research on work function engineering of potential metal gates is being carried out globally to keep up with the scaling requirements for future CMOS devices . The ability to tune the work function of a single metal gate technology, over desired range is highly preferable. The purpose of this research is to discover the tuning of the Hf-Si-N gate work function through the incorporation of nitrogen.
Metal oxide semiconductor (MOS) capacitors are fabricated using thermal SiO₂ as gate oxide on lightly doped p-type Si wafer. Hafnium and Silicon target are reactively co-sputtered at 12mTorr in presence of N₂ and Ar. The gas flow ratio RN=N₂/ (N₂+Ar), is adjusted to vary the nitrogen concentration in Hf-Si-N films.
Electrical characterization measurements are performed on Hf-Si-N/SiO₂/Si gate stacks to extract the Hf-Si-N work function and other MOS device parameters, including gate oxide thickness, the acceptor doping concentration and flatband voltage. Interfacial barrier heights are measured using internal photo-emission (IPE) as an independent confirmation of the Hf-Si-N gate work function.

Composite Material Systems

[2]    Dielectric permittivity mapping of heterogeneous dielectric materials by dynamic electrostatic force microscopy.
Sommayeh, Asgari, Ph.D. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D. Oliver

Dielectric spectroscopy (DS), both in time domain (TD) and frequency domain (FD) has shown to be a very useful technique for characterizing homogenous dielectric materials. However, the dielectric spectroscopy techniques have a fundamental limitation: they are both bulk measurement techniques. Lack of spatial resolution is considered as an important limitation for analyses of the local properties of heterogeneous or nano-structured materials. We describe a dynamic electrostatic force microscopy method to quantitatively map the dielectric permittivity of  heterogeneous dielectric materials. By operating this technique with an amplitude modulation of mechanical resonance frequency of cantilever with a high frequency signal of interest at the probe, we show the capability for undertaking frequency domain dielectric spectroscopy measurement with sub-micron resolution.

[4]    Optimizing Photocatalytic Properties of Cu₂O for Removal of Organic Contaminants from Potable Water
Bruce, Jared, Undergraduate Student
University of Manitoba, Chemistry
Advisor: Dr. M.S. Freund    

The inability to completely remove all organic matter from water prior to chlorination disinfection for the production of potable water is of increasing concern due to the production of carcinogenic trihalomethanes (THM’s). Current state-of-the-art water treatment plants utilize expensive micro and nanofiltration membrane systems to remove organic matter to a low enough level that the subsequent chlorination process will produce THM levels that will pass government regulations for potable water. Given the expense and frequent maintenance required for these complex systems, municipalities are looking into more cost effective and robust methods to provide safe drinking water to their communities. Cuprous oxide (Cu₂O), a p-type semiconductor has been investigated as a potential photocatalytic material for removing organic matter from water. This oxide, with a band gap of 2.18 eV, absorbs light in the visible range of the spectrum, making it highly desirable in terms of its ability to capture a significant fraction of the solar spectrum. This is in contrast to TiO₂ systems that utilize the much smaller ultra-violet fraction of the solar light spectrum. While Cu₂O has been shown to have limited success when used as a powder synthesized using solution based chemical methods, its full potential will not be realized until control over crystal growth of the oxide is achieved as well as its immobilization on a solid support. Electrochemistry would be an ideal technique for achieving the control and simplicity desired to embed Cu₂O on a porous conducting substrate. Electrochemistry allows for control of the amount of material, adequate coverage of the surface, completeness of reduction from Cu(II) to Cu(I) and the  morphology of the crystallites. Immobilization also allows for better recovery of the catalyst and ease of integration into a device or new filtration system. The catalytic work in this study was followed by monitoring the degradation of methylene blue over time under 1 sun illumination. This organic dye is a strong absorber of visible light and was monitored with UV-vis spectroscopy.  Crystal morphology was investigated using scanning electron microscopy (SEM). The investigation into completeness of reduction was followed using x-ray photoelectron spectroscopy (XPS).

[6]    Intracellular pH triggered anti-cancer drug release from poly[2-(dimethylamino)ethyl acrylate] functionalized mesoporous silica nanoparticles
Tian, Ye, Postdoctoral Fellow
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. M.M. Xing    

Cancer is a leading cause of morbidity worldwide. Mesoporous nanomaterials with stimuli sensitivity have received a burgeoning interest as efficacious anti-cancer drug carriers recently. Here, we have designed and synthesized hybrid mesoporous nanoparticles of PEG protected mesoporous silica nanoparticle-poly[2-(dimethylamino)ethyl acrylate] (PEGylated MSN-PDMAEA). The nanoparticles behave a pH-sensitive drug release mechanism with highly efficient operation in vitro at intercellular pH values of tumor. Moreover, the pH sensitive functionality is switchable, which results in a controllable release of the drug at will. Confocal laser scanning microscope (CLSM) images and three-dimensional images show that the nanoparticles can enter into the human liver hepatoecellular carcinoma cell line (HepG2) through endocytosis with high cellular uptake efficiency, and deliver doxorubicin (DOX) into cell nuclei effectively to inhibit cell growth with efficacy. By MTT assay, the DOX loaded PEGylated MSN-g-PDMAEA have similar efficacy to inhibit MCF-7 cell growth as pure DOX, and the nanoparticle itself has low cytotoxicity. This work provides a novel nano drug carrier with high drug loading efficiency and specifically drug release into tumor cells. Moreover, it also provides a simple method to prepare pH sensitive nanomedicine based on inorganic materials and tertiary amine containing polymers.

[8]    Acoustic Resonators for Far Field Control of Sound on a Subwavelength Scale
Lemoult, Fabrice, Postdoctoral Fellow
University of Manitoba, Physics and Astronomy
Advisor: Dr. J.H. Page    

On top of being soda containers, cans act as simple acoustic resonators. Anyone can verify this property blowing inside one of them and hearing a pure monochromatic tone. In a recent letter [1], we used this property but instead of using a single can, we used an array of cans which opens fascinating physical results. The first result is not surprising for anyone who has already studied resonant phenomena: the array of cans does not resonate at a pure tone but gives rise to polychromatic ones. The second interesting result concerns the spatial scale of these resonances. Anyone knows that sound in air must vary at the scale of its wavelength giving rise to the so called diffraction limit. In our case, the collective response of cans varies on a scale that can be as small as the size of a single soda can. In other words, we have built sound waves that vary deeply smaller than the wavelength. Exploiting those properties and the idea of Time Reversal we demonstrated the possibility to squeeze sound onto spots as tight as 1/25th of a wavelength, which is normally forbidden. Our approach, evidenced with soda cans for the sake of simplicity, is very general and can be realized using any resonator. We believe it opens up exciting possibilities for the control of audible sound in new ways, but also for the design of smart sensors, actuators and MEMS, and also for the physical properties of materials made of resonators such as real crystals.
[1] F. Lemoult, M. Fink, and G. Lerosey. Acoustic resonators for far-field control of sound on a subwavelength scale. Phys. Rev. Lett., 107(6):064301, Aug 2011.

[10]    Conducting Polymer Composites For Artificial Photosynthesis Applications
McFarlane, Shaune, Postdoctoral Fellow
University of Manitoba, Chemistry
Advisor: Dr. M.S. Freund    

To address future energy needs, while simultaneously stabilizing atmospheric carbon dioxide levels, scientists and engineers need to design and develop new materials and artificial photosynthetic device constructs that can effectively scale to meet society's vast and ever growing energy demands. A functional and effective artificial photosynthetic system will require the efficient production and separation of fuels that can be used as an on-demand source of energy. In contrast to fuel cells, such a system will require a membrane that conducts both ions associated with redox processes and electrons/holes associated with the absorption of light . The poster presents an approach to preparing a composite material fashioned from conducting polymer wires and ionically conducting polymers that may meet these demands while maintaining low light absorption.

[12]    Impedance analysis of polymeric thin films
Shenouda, Mina, M.Sc. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D. Oliver

Impedance (dielectric) spectroscopy of a material sample is typically, undertaken by depositing metallic contacts onto opposing surfaces to create a parallel plate capacitor. However, such an approach is not well-suited to thin films that are not free-standing and/or cannot withstand the promising environment associated with electrode deposition. This work discusses approaches for polymeric thin-film sample preparation so that, the frequency response of thin dielectric character may be studied using a HP 4291A impedance analyzer.

[14]    Floating gate metal oxide semiconductor (FGMOS) based olfactory sensor
Tareq, Md. Obaej, Ph.D. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D.A. Buchanan    

A semiconductor based electrochemical olfactory sensor has been developed to mimic human nose action. A floating gate MOS (FGMOS) structure fabricated by standard CMOS process has been used as a basic sensing device. An extension pad using a metal (Al and Cu alloy) layer has been added with the floating gate which is acting as a sensing pad. The odor sensitive conducting polymers have been electrochemically deposited on this sensing pad. In the presence of any analytes, polymers change their electrical properties, such as charge density, conductivity, and permittivity. Any changes in the charge density on the sensing pad changes the threshold voltage of the floating gate device. The device is pre-programmed in sub-threshold region by applying a voltage on the control gate. Any small change in the threshold voltage causes a significant change in the source-drain current. An 8x8 sensor array has been designed using both n and p type devices. Required driving circuits have been fabricated on the same chip. An output amplifier circuit has been designed to convert the small output current to a corresponding voltage level.

[16]    Anisotropy and damping in CoFeAlSi via electrical detection of FMR
Bai, Lihui, Postdoctoral Fellow
University of Manitoba, Physics and Astronomy
Advisor: Dr. C.M. Hu

Heusler alloy CoFeAlSi (CFAS) is a promising candidate of ferromagnetic electrodes in spintronics devices due to its high spin polarization. The spin polarization was estimated around 70% and 81% for a B2 and L21 structures, respectively. In application as electrodes, anisotropic energy plays as a barrier to against thermal fluctuation. CFAS has a general X₂YZ composition where Co ions make a simple-cubic structure. Hence, a thin film deposited along (001) has an in-plane four fold anisotropic symmetry.
Conventionally, the anisotropic properties is studied in a static method by detecting coercive field. With the developing of high-speed devices, the magnetization in a magnetic sensor or a memory element is reversed in an ultra-high frequency, where the magnetization dynamics plays a dominated role. Therefore, we prepared a CFAS thin film and studied the ferromagnetic resonance (FMR) for investigation of spin dynamics and magnetic anisotropy. We also estimated the damping constant and we find that damping is sensitive to the anisotropies.

Microelectromechanical Systems (MEMS)

[18]    MEMS Ultrasound Transducer Imager Array
Emadi, Arezoo, Postdoctoral Fellow
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D.A. Buchanan

Capacitive micromachined ultrasonic transducers (CMUTs) are an alternative imager system to the conventional piezoelectric transducers. They benefit from microfabrication techniques that offer developing CMUTs in various shapes and dimensions, as well as 1- and 2-D arrays. In this work, a CMUT imager array is designed and structurally optimized for ‘water tree’ detection in the XLPE underground power cable insulation. COMSOL simulations are performed, indicating the ability of such an array in beam width modulation through electrically addressing of CMUT cells in different orders. It is also shown that unlike piezoelectric transducers, a MEMS transducer can also operate at a relatively wider frequency range.

[20]    Inductively coupled corrosion sensor for reinforced concrete structure health monitoring with Time Domain Gating Interrogation
Perveen, Khalada, M.Sc. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D.J. Thomson

Corrosion is a major problem for civil infrastructure and is one of the leading factors in infrastructure deterioration.  Techniques such as half-cell potential can be used to periodically monitor corrosion, but can be difficult to reliably interpret. Wired systems have large installation cost and long-term reliability issues due to wire corrosion. In this paper an embedded inductively coupled coil sensor able to monitor the corrosion potential of reinforcement steel in concrete is presented. The sensor is based on a coil resonator whose resonant frequency changes due to the corrosion potential being applied across a parallel varactor diode. The corrosion potential can be monitored externally using an inductively coupled coil. An accelerated corrosion test shows that it can measure corrosion potentials with a resolution of less than 10 mV. A PCB layout of this senor has been designed for future reinforced concrete slab test. This sensor will detect corrosion at the initiation stage before observable corrosion has taken place. The wireless sensor is passive and simple in design, making it an inexpensive, battery less option for long-term monitoring of the corrosion potential of reinforcing steel.

[22]    Frequency Dependent Analysis of Polystyrene Microspheres
Cabel, Tim, M.Sc. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. G. Bridges

Polystyrene micropheres (PSS) are a tool commonly used in the calibration and characterization of microfluidic devices. They can be manufactured on a very small scale (down to 10s of nanometers) with a very low variance in diameter and have a well known bulk dielectric constant. When a dielectric particle in fluidic suspension is subject to a non-uniform electric field a force, known as the dielectrophoretic force, is exterted on the particle. The magnitude and polarity of this force is dependent on the size of the particle, the gradient of the squared electric field magnitude, and the contrast of the complex dielectric constants of the particle and the suspension medium. Since the complex dielectric constant of both the particle and the suspension medium are typically frequency dependent, the dielectrophoretic force will change depending on the frequency of the applied electric field. In this work, PSS are suspended in deionized water and flowed through a microfluidic channel over a set of electrodes. The PSS are then subject to a non-uniform AC electric field and a corresponding dielectrophoretic force resulting in a change in elevation which can be measured using a set of sensing electrodes. This change in elevation is then converted into a force and is compared with simulation for a number of frequencies (100kHz-10MHz) and particle diameters (1μm-10μm). From these results an accurate dielectrophoretic model can be established with well characterized bulk conductivity and surface conductance for the polystyrene microspheres.

[24]    Finite Element Analysis of Capacitive Micromachined Ultrasonic Transducers
Jeba, Dilruba Zaman, Undergraduate Student
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D.A. Buchanan

Capacitive Micromachined Ultrasonic Transducers (CMUTs) have substantial advantages over piezoelectric transducers in various aspects, such as sensitivity, the ease of fabricating large arrays, transducer efficiency, bandwidth, and the potential for direct integration with microelectronic circuits. Finite element analysis of a single cell CMUT has been performed using electromechanical simulation software (COMSOL Multiphysics package) to achieve optimum design parameters. The electromechanical simulations performed include static, frequency and transient analysis of a single CMUT. The Capacitive Ultrasonic transducer operates on applying an alternating signal to an electrostatically (DC) biased membrane, which causes the membrane to vibrate and radiate pressure waves into the surrounding medium. To optimize the CMUT properties in terms of actuation voltage, frequency as well as pressure wave, different design approaches have been explored. The Actuation voltage and frequency ranges for stable membrane deflection have been investigated. The aim of doing electrostatic and time domain simulations along with finite element analysis of CMUT is to demonstrate the feasibility of CMUTs for ultrasonic imaging.

[26]    A Simple Standalone Microfluidic Device for Gradient Generation and Cell Studies
Wadhawan, Nitin, Undergraduate Student
University of Manitoba, Physics and Astronomy
Advisor: Dr. F. Lin    

Microfluidics, a rapidly developing research field, is pushing forward to incorporate into numerous biological and biomedical applications owing to its unique ability for controlling cellular microenvironments. Particularly, microfluidic devices have been increasingly used for generating highly-controlled chemical concentration gradients that is useful for a range of applications such as cell migration studies and drug screening. In addition to the widely-used flow-based microfluidic gradient devices, different designs of microfluidic devices have demonstrated gradient generation in flow-free environments. In several previous studies, gel matrixes, long and thin channels have been used as strategies for increasing fluidic resistance to limit chemical diffusion leading to controlled gradient formation. However, those methods require complicated device preparation procedures. In the present study, we developed a simple pump-free microfluidic gradient device based on the controlled fluidic resistance but without the requirement of gel or differential channel depth. We have optimized the operation protocol and showed that the developed device can quickly generate a chemical gradient in the main channel by diffusion-based mixing of 2 different chemicals from the 2 reservoirs through multiple small connecting channels and the gradient profile can be maintained for up to 45 min or longer. To validate the function of the device at the cell level, we demonstrated the differential cell labeling by a gradient of cell tracker generated by the device. Furthermore, we demonstrated T cell chemotaxis to a chemokine gradient using this device.  The developed simple and standalone device can be useful for various cell based studies that require controlled chemical gradients without complicated external control systems.

[28]    Wireless Passive pH Sensor for Real-Time In Vivo Milk Quality Monitoring
Bhadra, Sharmistha, M.Sc. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. G.E. Bridges

A wireless passive sensor for remote in vivo milk pH measurement is presented. The sensor consists of a planar spiral inductor connected in parallel to a varactor forming a LC resonant circuit. A pH combination electrode made of an iridium/iridium oxide sensing electrode and a silver/silver chloride reference electrode, is connected in parallel to the varactor. As the milk pH changes during spoilage, the voltage across the electrodes varies shifting the resonant frequency of the sensor. For in vivo monitoring the sensor is sandwiched between dielectric spacers to encapsulate, and reduce parasitic capacitive coupling and eddy current loss. The resonant frequency of the sensor is tracked remotely by an interrogator coil coupled to the sensor inductor. In vivo measurement shows that milk pH can be monitored with 100 kHz/pH sensitivity and 0.12 pH accuracy over 6.8-4.4 pH range.

[30]    Microfluidic Device for Studying Cell Migration in Single or Co-Existing Chemical Gradients and Electric Fields
Li, Jing, M.Sc. Candidate
University of Manitoba, Physics and Astronomy
Advisor: Dr. F. Lin    

Cell migration is involved in physiological processes such as wound healing, host defense, and cancer metastasis. The movement of various cell types can be directed by chemical gradients (i.e. chemotaxis). In addition to chemotaxis, many cell types can respond to direct current electric fields (dcEF) by migrating to either the cathode or the anode of the field (i.e. electrotaxis). In tissues, physiological chemical gradients and dcEF can potentially co-exist and the two guiding mechanisms may direct cell migration in a coordinated manner. Recently, microfluidic devices that can precisely configure chemical gradients or dcEF have been increasingly developed and used for chemotaxis and electrotaxis studies. However, a microfluidic device that can configure controlled co-existing chemical gradients and dcEF that would allow quantitative cell migration analysis in complex electrochemical guiding environments is not available. In this study, we developed a PDMS-based microfluidic device that can generate better controlled single or co-existing chemical gradients and dcEF. Using this device, we showed chemotactic migration of T cells toward a chemokine CCL19 gradient or electrotactic migration toward the cathode of an applied dcEF. Furthermore, T cells migrated more strongly toward the cathode of a dcEF in the presence of a competing CCL19 gradient, suggesting the higher electrotactic attraction. Taken together, the developed microfluidic device offers a new experimental tool for studying chemical and electrical guidance for cell migration, and our current results with T cells provide interesting new insights of immune cell migration in complex guiding environments.

[32]    A simple craft cutting based microfluidic device for chemical gradient generation and cell migration studies
Wu, Jiandong, M.Sc. Candidate
University of Manitoba, Biosystems Engineering
Advisor: Dr. F. Lin and Dr. D. Levin    

Microfluidic devices provide a powerful quantitative test bed for biological and biomedical research owing to its unique ability for controlling cellular microenvironments, reduced reagent consumption and high experimental throughput. Particularly, various microfluidics-based strategies have been developed to configure defined chemical concentration gradients for cell migration studies. On the other hand, the device fabrication methods for existing devices are time consuming and thus limit their ability for fast prototyping of different device designs. Recently, a study demonstrated a simple method for making microfluidic devices using a craft cutter that can cut the channel in adhesive tapes and assemble the device within short period of time. To further explore the use of this new method, we in the present study applied this method to fabricate microfluidic gradient devices and validated its use for cell migration studies. Specifically, we fabricated and assembled the device based on the craft cutting method and developed a simple PDMS interface for chemical infusion. Using this device, we verified chemical gradient formation and furthermore we demonstrated neutrophil chemotaxis in the device. The developed device can be useful for cell migration and other relevant studies in a rapid and inexpensive manner without the requirement of specialized fabrication facilities and hours or longer of device preparation procedures.

Surfaces and Interfaces

[34]    Characterization of Junctions between Tungsten Oxide (WO₃) and PEDOT
Tan, Damaris, M.Sc. Candidate
University of Manitoba, Chemistry
Advisor: Dr. M.S. Freund

Tungsten oxide (WO₃) is an indirect band gap semiconductor that is low cost and had been widely studied for solar cell applications. PEDOT-PSS is a p-type semiconductor that is commercially available, stable, high conductivity and transparency suited for membranes in solar water splitting. The junction between two materials is important since it determines the performance of the system. In this work, the nature of the junction of tungsten oxide (WO₃), a potential n-type semiconductor photoanode and PEDOT-PSS membrane is investigated for an artificial photosynthetic system. Tungsten oxide is electrodeposited while PEDOT-PSS is spin-coated on a conducting substrate. I/V measurements demonstrate hysteresis behavior on the forward bias. The hysteresis behavior is believed to be a function of the mobile cations in the WO₃ creating a region of variable doping.

[36]    An STM study on self-assembled Fe(III) meso-Tetra(4-carboxyphenyl) Porphyrin chloride chains
Nicholls, Dylan, Ph.D. Candidate
University of North Dakota, Physics and Astrophysics
Advisor: Dr. N. Oncel    

Fe(III) meso-Tetra(4-carboxyphenyl) porphyrin chloride (Fe-TCPP) molecules co-deposited together with 5-(octadecyloxy) isophthalic acid (5-OIA) molecules on a highly-ordered pyrolytic graphite (HOPG) are studied with the help of a scanning tunneling microscope under ambient conditions. The measurements were carried out at solid-liquid interface. STM images show the formation of one-dimensional Fe-TCPP chains stretching tens of nanometers across the surface. The driving mechanism behind the formation of these chains is the physical interaction between the molecules.

[38]    Response of polypyrrole based gas sensors to organic vapors: Effect of dopant anions and oxidation states
Mani, Ramesh Kumar, Postdoctoral Fellow
University of Manitoba, Chemistry    
Advisor: Dr. M.S. Freund    

For the past two-decades, intrinsically conducting polymers are getting much attention in the field of gas sensors, compared to metal-oxide based semiconductors because these polymers can be synthesized and doped easily by chemical or electro-chemical methods. In our work, a conducting polymer, polypyrrole was electrochemically deposited on gold coated sensors of an electronic chip, using either aqueous or non-aqueous solutions of pyrrole monomer with various dopants on it. Then, the polymer films on separate sensors were oxidized/reduced at different potentials using LiClO₄/acetonitrile solution, so that the polymer films that are at different oxidation states would behave differently for their exposure to a variety of vapors. A multi-functional meter was used to record the changes in resistance of the polymer films when they are exposed to the vapors. The resistance-ratio and the principal component analysis plots indicate that using different dopants, or changing the oxidation state of the polymer has huge effect on its resistance during its interaction with any vapor analyte. Depending on their dopant and oxidation state, the polymer films show specificity differently to a variety of vapors. Thus by having an array of numerous sensors (each sensor with a particular dopant and at a certain oxidation state), and fingerprint of all sensor's responses to a wide range of vapors, we can easily detect any unknown vapor or vapor mixture qualitatively, and sometimes even quantitatively.

[40]    An STM study on self-assembled Ir-silicide nanowires on Si(001)
Oncel, Nuri, Assistant Professor
University of North Dakota, Physics and Astrophysics

Iridium (Ir) modified Silicon (Si) (001) surface is studied with low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The surface exhibits 2.2 domains on LEED intensity images. The STM images confirm the existence of these 2.2 structures and points out that the basis of the crystal lattice is not a single atom but dimers. The alignment of dimers parallel to one of the lattice vectors of 2.2 domains leads the formation of quasi one-dimensional Ir-silicide nanowires.

[42]    Managing Junction Potentials in Ion Exchange Membranes with Permanent pH Gradients for Artificial Photosynthesis
McDonald, Michael, Ph.D. Candidate
University of Manitoba, Chemistry
Advisor: Dr. M.S. Freund

Sophisticated membranes will be required for solar fuel production to separate the reaction products and connect the preferred electrode architecture. Due to the limited photovoltages available from photoexcitation in current electrocatalyst materials, feasible systems must be void of energetically detrimental components and maximize the potential available to the electrochemical cell. Additionally, elementally abundant catalysts and semiconductors are generally unstable in aqueous conditions and are pH-dependent. It is possible to improve the operating stability as well as adjust the reaction potentials by using different pH conditions at each electrode, separated by a membrane selective to the sign of the charge and size of ions in the solutions. The introduction of a gradient and new interfaces creates junction potentials which have not yet been investigated. This presentation will propose a variety of ion exchange membrane and solution configurations and demonstrate their impact on the potentials needed to run a cell under conditions pertinent to solar water splitting. Explanations for the contribution of each phase of the cell will be proposed based on theory spanning semiconductors, electrodialysis and general kinetics.

[44]    Surface spin stability in copper coated maghemite nanoparticles
Desautels, Ryan, Ph.D. Candidate
University of Manitoba, Physics and Astronomy
Advisor: Dr. J. van Lierop

Magnetic ordering from exchange interactions between atoms in a "bulk" crystal is a well understood phenomenon. However, a fundamental understanding of the physics of the magnetism of nanomagnetic materials remains elusive since surface and finite-size effects typically frustrate the magnetic ordering process. One common result is that single-phase nanomagnetic materials with sizes well below the single-domain limit often exhibit multiple magnetic populations with different magnetic properties, including bulk-like behaviour, an ordered magnetic core and a spin-glass-like surface. These surface effects can be problematic for applications as they can significantly reduce the total magnetization of a nanoparticle.  We have demonstrated an innovative way to alter the surface nanomagnetism by coating gamma-Fe₂O₃ nanoparticles with a Cu shell.  We have shown that a change in the nanoparticle's surface environment can result in an improvement of the overall magnetic properties of the system.  Element specific x-ray absorption spectroscopy and magnetic circular dichroism identified Cu magnetism in the shell that was superexchange coupled to the iron oxide core. This enhanced the intrinsic iron magnetism of the nanoparticles.  This novel copper-based nanomagnetism modified the intrinsic magnetism of the maghemite nanoparticle. The copper appeared to "pin" the iron surface moments so as to recapture the lost maghemite surface magnetism.

[46]    Finite element analysis of a test sample design for taper corrision testing of artifical hip joints
Hildebrand, Stacey, Undergraduate Student
University of Manitoba, Biosystems Engeering
Advisor: Dr. U. Wyss and Dr. J. Morrison    

Modular femoral hip prostheses and the Morse taper locking mechanism are commonly used in total hip replacement surgeries.  It is well known that corrosion can occur at the interface between the head and neck of such prostheses.  Fatigue corrosion testing is a method used to understand the factors leading to corrosion.  This testing requires the use of custom test samples with tapers akin to the studied prosthesis.  Two key concerns arise with custom samples: is the test sample representative of the hip prosthesis; and is the test sample strong enough to withstand testing.  This study designed and analyzed a custom test sample to facilitate future fatigue corrosion testing of prosthesis Morse tapers.  The design consists of the head and neck portion of a femoral prosthesis with a shoulder for mounting during assembly and testing.  A finite element stress analysis was performed to determine the strength of the design for CoCr-alloy and Ti-alloy neck materials.  An additional finite element model of a minimally modified femoral prosthesis provided a control to compare the design with.  The analysis results under axial loading conditions show the design has a factor of safety of greater than 7.25 for the CoCr-alloy and 9.98 for the Ti-alloy.  Both materials have comparable stress patterns and magnitudes (within 4%).  Under compressive axial loading the stress magnitudes for the test sample design model are also within 4% of the control model and the stress patterns are comparable near the taper interface.  Under tensile axial loading the peak stress in the control model is nearly 10 times larger than in the design model.  Thus the design is: strong enough to withstand the axial loading aspect of fatigue corrosion testing; representative of a femoral prosthesis under axial compressive loading; but not representative under axial tension.

[48]    Ferromagnetic Resonance Studies on Exchange Coupled Bilayers
Hyde, Paul, Undergraduate Student    
University of Manitoba, Physics and Astronomy
Advisor: Dr. C.M. Hu    

The behavior of molecular magnetic moments at interfaces between ferromagnetic (FM) and antiferromagnetic (AFM) materials has been studied for well over a half century, and yet remains one of the most interesting puzzles in materials science. An observed effect of the interaction of these moments, known as exchange bias, has found extensive usage in technological applications such as data storage devices.
We conducted ferromagnetic resonance (FMR) measurements on a Permalloy (Ni₈₀Fe₂₀) layer coupled to an antiferromagnetic NiO layer. These measurements, performed at medium to weak external field strengths, allow us to map the FMR frequency as a function of the applied field. The relation of these parameters has never before been measured for low external field strengths, and the obtained dispersion curves show features significantly deviating from the predictions of current FM/AFM interface models. A new model taking into account rotational anisotropy in the AFM has been developed which explains the observed characteristics, yielding new insights into the governing interactions at the FM/AFM interface.

[50]    Impact of Si Surface Functionalization on the Photo-Electrical Properties of an Individual Solar Water-Splitting Cell
Yahyaie, Iman, Ph.D. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D. Oliver and Dr. D. Thomson

The photoelectrical properties of individual p-Si microwire/PEDOT:PSS:Nafion/n-Si microwire structures, designed for use in array structures for solar water splitting, have been investigated. Temporal change in microwire/polymer junction resistance was used as a measure of the stability of the junctions. This work compared the relative stability of junctions with H-terminated Si microwires relative to methyl-terminated Si microwires prepared using a two-step radical chlorination-Grignard alkylation method. For the H-terminated samples, the observed increase in the junction resistance over time is attributed to native oxide formation at the microwire/polymer interface. To address this issue, methyl-terminated microwires were used, and more stable ohmic behavior was observed at the junctions between methyl-terminated p-Si microwires and conducting polymers. Methyl-terminated n-Si microwire/polymer junctions demonstrate strongly rectifying behavior that increases the effective resistance of the junction. This behavior is attributable to the Fermi level mismatch at the junction as well as the presence of the methyl passivation layer which adds a shift to the band edges at the interface. As a consequence, a balance must be found between the improved stability of the junction electrical properties achieved by passivation, and the detrimental impact on the effective resistance associated with the additional rectification at methyl-terminated n-Si microwire/polymer junctions.

[52]    Corrosion in Artificial Hip Joints - A Link to Pseudotumors?
Dyrkacz, Richard, Ph.D. Candidate    
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. U. Wyss    

The purpose of this investigation was to determine if there was a significant difference in the corrosion behaviour at the head-neck taper interface of artificial hip joints by performing a retrieval study. This was achieved by comparing the corrosion damage for three different head sizes (28 mm, 36 mm, and 50 mm+) that were previously implanted using a novel scoring technique as well as conducting scanning electron microscopy and energy dispersive spectroscopy. When comparing the corrosion damage scores between the three head sizes, there was a strong relationship between increasing head size and increased corrosion damage at the head-neck taper interface. After conducting the Kruskal-Wallis test, there was a statistical significant difference in the corrosion damage scores as well as the rate of corrosion damage along the heads. Additionally, 87.5% of the implants that had a head size of 50 mm or greater displayed a pseudotumor proximal to the hip prosthesis, which was not discovered in a single case for either the 28 mm or the 36 mm head size groups. This study suggests that there could be a possible link between corrosion damage at the head-neck interface of artificial hip joints and the formation of pseudotumors nearby.

Soft and Disordered Materials

[35]    pH Sensitive Functional Single-wall Carbon Nanotube for Doxorubicin Intracellular Delivery
Liu, Shuhan, M.Sc. Candidate
University of Manitoba, Textile Sciences, Mechanical and Manufacturing Engineering
Advisor: Dr. M. Xing, Dr. W. Zhong

Nowadays, stimuli-responsive drug delivery systems are built up in order to reduce the side-effect caused by administration of free drugs, so that drugs are able to target cancerous cells directly causing minimal damage to the normal cells. Carbon nanotubes (CNTs) possess large surface area and outstanding optical and electrical performance which makes it a promising carrier in drug delivery system and diagnose procedure. In this work, a pH sensitive PEG-DOX prodrug was synthesized and was used to attach onto the single wall carbon nanotubes to form the pH sensitive drug release system. The in vitro release of DOX from the DOX-loaded carbon nanotubes was evaluated upon changes of pH values and the DOX fluorescence distribution of PEG-DOX coated SWNTs was analyzed to verify the improvement of this novel anticancer drug delivery system. The cytotoxicity and cell distribution of the DOX-loaded micelles will also be studied in this paper. Although there have been many pH responsive drug delivery, to the best of our knowledge, there has been no study regarding such pH sensitive nanoparticles conjugated with carbon nanotubes applied to the rapid intracellular delivery of DOX.

[37]    Observation of infinite-range intensity correlations near the 3-D Anderson localization transition
Hildebrand, William, Ph.D. Candidate
University of Manitoba, Physics and Astronomy
Advisor: Dr. J.H. Page

Anderson localization is a phenomenon by which classical or quantum waves (photons, phonons or electrons) can be scattered so strongly by a random potential that transport ceases.  While this effect is thought to contribute to many physical systems and phenomena, such as random lasers, the thermal conductivity of glasses, and the quantum Hall effect, Anderson localization has rarely been observed directly.  Because the scattering in these disordered systems is so strong, transport is often characterized via the statistics and correlations of the randomly fluctuating transmitted intensity, or speckle pattern.  The existence of infinite range correlations in the speckle pattern, denoted ‘C₀’, due to fluctuations in the local density of states (LDOS) has been predicted for strongly scattering disordered systems. These correlations may even diverge near the Anderson transition from extended to localized modes.  In our experiments, spatial and frequency correlations of the transmitted speckle pattern are measured for samples that are known to exhibit Anderson localization.  C₀ correlations are observed, and found to grow dramatically near the expected transitions in our samples.  Analysis of the multifractal characteristics of the transmitted wave functions yields complementary results through independent experiments, providing confirmation of our experimental results, as well as verifying the link between multifractality, C₀, and the LDOS.

[39]    Coherent Backscattering Investigation of Anderson Localization of Ultrasonic Waves
Cobus, Laura, Ph.D. Candidate
University of Manitoba, Physics and Astronomy
Advisor: Dr. J.H. Page    

Wave localization is characterized by the absence of diffusion; waves (electromagnetic, acoustic, matter, etc.) in a disordered, strongly scattering material can be ‘trapped’ in space by interference effects.  While localization occurs for any amount of disorder in one and two dimensions, a material with a very large amount of disorder is required to observe the phenomenon in three dimensions.  Thus, localization of classical waves has proven very difficult to observe due to the challenge of creating materials with enough disorder.  We present an experimental study of the localization of ultrasonic waves in a sample of disordered sintered aluminum beads - a mesoscale analogue of an atomic glass.  The response of the material to an input wave pulse was probed with both transmission and reflection measurements, giving complementary results.  In transmission, we measure how localization cuts off the transport of energy from the source position via a technique called transverse confinement.  In reflection, we measure the dynamic coherent backscattering of waves from the material, an effect that is also sensitive to the spatio-temporal evolution of the intensity.  In the reflection geometry, the related wave phenomenon of ‘recurrent scattering’ was also observed, another consequence of the high degree of disorder of the sample.

[41]    pH and Reduction Dual-Sensitive Copolymeric Micelles for Intracellular Doxorubicin Delivery
Chen, Jun, Postdoctoral Fellow
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. M.M. Xing

Stimuli-responsive nanocarriers can be developed to release incorporated contents into tumor tissues upon changes in environmental conditions, such as redox potential, pH, temperature and ultrasound. In this study, a series of novel pH and reduction dual-responsive micelles were prepared and the intracellular release of DOX from these micelles was studied. To this end, we designed and synthesized a novel copolymer based on poly(ethylene glycol) (PEG) and reducible poly(β-amino ester)s (RPAE), containing disulfide bonds in the backbone of poly (β-amino ester)s. This copolymer can self-assemble into stable micelles in a physiological environment, with the RPAE constituting the core and PEG as the shell. These nanoparticles will be demicellized rapidly at high levels of reducing reagents and/or in an acidic environment. The release of DOX from the DOX-loaded micelles was evaluated upon changes of pH values and/or concentrations of a reducing agent. The cytotoxicity and cell distribution of the DOX-loaded micelles were also studied in this paper. Although there have been many pH responsive or reductive degradable copolymers synthesized for stimuli-responsive drug delivery, to the best of our knowledge, there has been no study regarding such pH and reduction dual sensitive nanoparticles applied to the rapid intracellular release of DOX.

[43]    A Novel Injectable Chitosan Hydrogel Self-crosslinked with Integral NaAlg for Tissue Engineering Applications
Gao, Haiyun, M.Sc. Candidate
University of Manitoba, Textile Sciences, Mechanical and Manufacturing Engineering
Advisor: Dr. M. Xing and Dr. W. Zhong

Hydrogel has been widely studied and applied on the tissue engineering and drug delivery system due to its excellent three dimensional and mesoporous structure that perfectly mimics inner extracellular matrix in native tissue. Alginate is a naturally derived polysaccharide biopolymer possessing good biocompatibility and cell adhesive properties. It can form a hydrogel with other polysaccharide polymers such as chitosan after oxidization. However, this traditional method can lead to devastative structure of the alginate which may cause decrease of its natural polysaccharide properties. Herein a novel method is studied to fabricate a hydrogel consisting of chitosan and modified alginate which retains the integral polysaccharide structure. Besides, this hydrogel is injectable since the gelation process can happen rapidly in situ within a few minutes at mild environment. Chemical structure and morphology of the novel hydrogel are demonstrated using FTIR, NMR and SEM. The hydrogel shows excellent cytocompatibility when cultured with human bone marrow-derived mesenchymal stem cells (hMSCs). The cell activity is characterized by various of assays such as Live/Dead and MTT assay. This novel hydrogel is quite promising in soft tissue engineering such as cartilage or brain tissue repair and drug encapsulation and delivery.

[45]    Velocity and attenuation analysis methods for noodle dough characterization
Strybulevych, Anatoliy, Postdoctoral Fellow
University of Manitoba, Physics and Astronomy
Advisor: Dr. J.H. Page    

We have shown that ultrasonic velocity and attenuation measurements at low frequencies (approx 40 kHz) have the potential for discriminating technologically relevant properties of wheat flour dough products, including breadmaking doughs and Asian noodles made from flours milled from different wheat classes. A conventional method for analysing pulse transmission measurements is to measure the travel time and amplitude of the first minimum and maximum of the transmitted wave pulses as a function of sample thickness. In experiments conducted on noodle doughs (34 and 37 % absorption basis), small differences in velocity and attenuation values were found in the same samples from the measurements at these two different observation points in the acoustic pulse. To investigate the underlying mechanism for these differences, we propose another method in which the entire transmitted pulse is analysed using Fourier transform techniques, enabling the transmitted phase and amplitude to be compared for samples of different thickness. This new method reveals a weak frequency dependence of both velocity and attenuation over the bandwidth of the input pulse (35-45 kHz). As a result, the pulse shape changes slightly as the different frequency components of the pulse travel at different speeds through the sample, explaining the slightly different results observed for the first minimum and maximum methods. The full frequency analysis technique gives more complete information on the velocity and attenuation in this interesting dispersive soft material, pointing to additional parameters for discriminating wheat classes of different quality.

[47]    Asian Noodle Texture: Influence of Gluten Strength as Determined by Ultrasonic Measurements
Diep, Sally, M.Sc. Candidate
University of Manitoba, Food Science
Advisor: Dr. M. Scanlon and Dr. D. Hatcher

The aim of this study was to determine if differences in the biomechanical properties of Asian noodles made from two distinctly different wheat classes/varieties are distinguishable using ultrasound technology.  Yellow alkaline noodles, 34% water, 1% w/w kansui reagent and 1% w/w NaCl, were prepared from Canada Western Red Spring (CWRS - Harvest) and Canadian Prairie Spring Red (CPSR - 5701PR) wheat flours of significantly different protein content (14.4 vs 12.3%) and gluten strength.  The biomechanical properties were first characterized using standard tests, including the empirical maximum cutting stress (MCS), stress relaxation, Peleg’s k1 and k2 parameters and Farinograph dough parameters.  These measurements indicate that the viscoelastic behavior of the two noodle varieties is quite similar but is statistically different.  Longitudinal ultrasonic experiments (40 kHz) were also performed on noodle samples of varying thicknesses (2-7 layers) to determine the phase velocity and attenuation coefficient and hence the longitudinal elastic moduli.  Significant differences in ultrasonic velocity and attenuation were found between these two classes/varieties, reflecting the differences in their noodle matrix properties.  The 5701PR variety has lower ultrasonic attenuation, suggesting a more developed gluten dough.  This difference in dough development may be attributed to differences in the protein sub-units as shown in chromatograms of the flour protein extracts using reversed-phase ultra-performance liquid chromatography (RP-UPLC).  Thus, ultrasound can be used as a new analytical tool for characterizing the biomechanical properties of Asian noodles, giving additional insights into the underlying biomechanical factors responsible for texture (an important consumer quality criterion).

[49]    The Density of States of Brazed Aluminum Beads
Lee, Eric Jin Ser, M.Sc. Candidate
University of Manitoba, Physics and Astronomy
Advisor: Dr. J.H. Page    

For many years, there has been growing interest in wave transport in strongly scattering disordered materials.  Classical waves have been shown to be very suitable for studying fundamental wave physics in this mesoscopic regime, allowing the construction of novel materials with special functionalities for waves.  One example is the existence of band gaps, which prohibit wave propagation for ranges of frequencies that can be tuned via the mesoscopic structure of the material.  While band gaps are usually associated with crystals they can also exist in certain disordered materials.  In disordered materials made from brazed aluminum beads, band gaps are formed at frequencies between pass bands that are created by weak elastic coupling effects between the resonant modes of each sphere.  Such behaviour is analogous to the formation of band gaps in the tight binding model for electronic systems.  In this work, we measure the density of vibrational states (DOS) experimentally from 30 kHz to 1.5 MHz, a fundamental material’s property that is particularly sensitive to the existence of band gaps since there are no modes in a gap.  We also show that the width of the lowest frequency gap can be tuned by varying the amount of sintering between the beads.  Furthermore, below this first band gap, we find unusual behavior for the frequency dependence of the density of states, which is approximately constant over almost a decade in frequency.  Above 600 kHz, the DOS increases with frequency, exhibiting behavior that can be described on average by traditional models such as those of Debye and/or Weyl.

[51]    The effect of bubble evolution in wheat flour doughs on the ultrasonic parameters during prolonged aging times
Koksel, Havva, Ph.D. Candidate
University of Manitoba, Food Science
Advisor: Dr. M.G. Scanlon

It has been shown that the aerated structure of bread depends on the bubble size distribution within the dough (a viscoelastic matrix) at the end of the mixing stage (Campbell et al., 1991. Transactions of the IChemE, 69: 67-76). A change in the bubble size distribution of the dough will in turn affect the bubble size distribution in the final loaf of bread. This makes determination of bubble changes in dough very important to cereal and food scientists since it forms the basis for predicting the final product quality before bread is manufactured. However, predicting these changes is extremely challenging since dough is optically opaque.
Low-intensity ultrasound is very sensitive to the large density and compressibility difference between the dough matrix and the air. Furthermore air bubbles in the dough hugely attenuate sound around the resonance frequency of bubbles, so the presence of bubbles can be readily detected by propagating ultrasound through the dough (Povey, 1997. Ultrasonic Techniques for Fluid Characterization. Academic Press, USA, p. 141-163).
The objectives of this project were to produce wheat flour doughs with a range of volume fraction of air bubbles and to measure the frequency dependent ultrasonic phase velocity and attenuation coefficient of these doughs during prolonged aging times in order to determine the effects of bubble evolution on the ultrasonic parameters. It was found that the attenuation and velocity of the ultrasonic waves showed peaks as a function of frequency of ultrasonic waves. The shape and the position of these peaks were found to be related to the aging time. As the aging time increased, the shape of the peaks became narrower and the position of the peaks moved to the lower frequencies when compared to shape and position of the peaks obtained shortly after mixing.

[53]    Doxorubicin Conjugated Injectable Hydrogel for pH-Triggered Anti-Cancer Drug Delivery
Shi, Junbin, M.Sc. Candidate
University of Manitoba, Textile Science, Mechanical and Manufacturing Engineering
Advisor: Dr. M. Xing and Dr. W. Zhong    

Release drug on targeted cancer cells or tumor tissues while having low effects on health cells is a critical requirement for smart drug carriers. A novel pH sensitive drug release system is developed by using injectable in-situ formed hydrogel. This hydrogel is made of two nature polymer derivatives with drug covalently loaded. The injectable hydrogel will be partially degraded in an cancer tissue mimicking acidic environment while drugs will be released from the system. As a result, this system offers a high sensitive drug release profile under different pH value. At the same time, under normal tissue mimicking environment, the hydrogel show low cytotoxicity and good biocompatibility.

High Temperature Aerospace Materials

[54]    Influence of Laser Welding Heat Input on HAZ Cracking in Newly Developed Aerospace Superalloy Haynes 282
Osoba, Lawrence, Ph.D. Candidate
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr O.A. Ojo

Microstructural and numerical investigation into the cause of weld heat affected zone (HAZ) cracking and its dependence on weld heat input during laser beam welding of a newly developed γ’ precipitation strengthened nickel-base Haynes alloy 282 was  performed. Careful and detailed microstructural study of the nature of HAZ cracking in the alloy showed that the cracking is attributable to the formation of liquid film on HAZ grain boundaries and the inability of this liquid film to accommodate thermally and/or mechanically induced stresses generated during weld cooling. An increase in the magnitude of laser weld heat input resulted in a considerable reduction in the HAZ cracking. This cracking behavior is related to reduced time that the subsolidus HAZ region spent at peak temperatures coupled with increased thermally induced strain rate gradient in the low heat input weld. The results of the study will be presented.

[56]    Fatigue Behavior of a Newly Developed Aerospace Superalloy Haynes 282
Buckson, Richard, Ph.D. Candidate
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. O.A Ojo    

Strain-controlled Low Cycle Fatigue (LCF) and Fatigue Crack Propagation (FCP) tests were carried out on a newly developed Aerospace superalloy, Haynes 282, in its standard  heat treatment condition. LCF test results demonstrated that Haynes 282 exhibited a relatively short period of initial cyclic hardening followed by a regime of cyclic softening to specimen failure at all the strain amplitudes employed in the work. An increase in the stress ratio lead to an increased crack propagation rate. However, in contrast to common assumptions, the loading frequency was observed to have an influence on the crack growth behavior. The cyclic deformation parameters determined in the work indicate strong fatigue deformation resistance of the newly developed superalloy.

[58]    Oxidation of a P/M Nickel Based Superalloy
Murray, Clark, M.Sc. Candidate
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. N.L. Richards and Dr. W.F. Caley

Nickel-based Superalloys posses a variety of properties that make them ideally suited for high temperature aerospace applications. These include excellent fatigue, corrosion, creep and oxidation resistance at high temperatures. The oxidation resistance of a Superalloy is achieved primarily through the formation of a dense alumina and/or chromia oxide layer(s) including spinels. This resistance has been further improved in wrought and cast alloys through the addition of reactive elements such as silicon, yttrium and lanthanum, although the exact effects of these elements have not been well defined. Through previous research, a powder metallurgy processing route to fabricate coupons of a Ni-Cr-Fe-Al alloy of a composition similar to IN600 (i.e. compaction pressure and sintering profile) was optimized. In this work, several such P/M nickel-based Superalloys, containing Si and/or Y as reactive element additions, were produced and a process to reduce porosity through Gleeble thermo-mechanical deformation was developed. Subsequently, the coupons were subjected to a heat treatment procedure to ensure that the microstructures of the compacts were consistent regarding volume fraction of the intermetallic Ni₃Al. Finally, the influence of the Si/Y additions on oxidation resistance was determined via microstructural examination following static oxidation tests at 900°C in air for times up to 1000h.  

[60]    Theoretical Modeling of Heat Affected Zone Cracking Tendency during Laser and Hybrid Laser-Arc Welding Processes
Gao, Zhiguo, Postdoctoral Fellow
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. O.A.Ojo

A two-dimensional thermal elasto-plastic numerical model is developed by finite element method to analyze and compare the mechanical factor for heat affected zone (HAZ) liquation cracking during laser welding and hybrid laser-arc welding techniques. Calculations of transient temperatures and cooling rates are used with solidification theory to analyze weld pool characteristics during weld solidification. The model is verified successfully by comparing calculated and experimental weld bead geometry and secondary dendrite arm spacing within the weld microstructure. Numerical analyses by the model provide valuable insights into why HAZ cracking can be reduced with the application of hybrid laser-arc welding compared to ordinary laser beam welding.

[62]    Effect of Pressure on the Microstructure of Linear Friction Welded Inconel 738LC Superalloy
Amegadzie, Mark, M.Sc. Candidate
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. O.A. Ojo and Dr. M.C. Chaturvedi

Inconel (IN) 738 is one of the most widely used heat resistant alloys for the hot section components of aircraft and industrial gas turbines. The alloy, however, is extremely difficult to fabricate and repair by fusion welding due to its susceptibility to heat affected zone (HAZ) grain boundary cracking. A state of the art technology that is being currently explored to produce crack-free joints in the difficult-to-weld alloy is linear friction joining. Despite that the problem of HAZ intergranular cracking is avoided during linear friction joining, oxidation along the joint during the process is a major problem. Information about the effect of process parameters on the microstructural evolution of linear friction welded nickel base alloys is very limited. In the present work, the effect of forging pressure, a very important process parameter on the microstructure of linear friction welded IN 738 was studied. The results of this study showed that increased forging pressure caused strain-induced rapid solidification of metastable liquid which resulted in complete elimination of deleterious oxides in bonded material.

[64]    Design of heat treatment procedures for a nickel-based powder metallurgy superalloy
Tellier, Gabriel R., Undergraduate Student
University of Manitoba, Mechanical and Manufacturing Engineering
Advisor: Dr. N.L. Richards and Dr. W.F. Caley    

Nickel-based superalloys show promise for high-temperature, high-load applications where resistance to both oxidation and creep are important. However, these superalloys' resistance to deformation also impede many standard operations and thus the manufacturing process. By holding the alloy at elevated temperatures below the melting point, the Gamma Prime precipitates were solutionized, softening the alloy to enable the use of standard processing techniques. The alloy was also subjected to an ageing treatment, where it is held at elevated temperatures below the solutionizing temperature of Gamma Prime to increase the size of these precipitates. A heat treatment regime was designed to achieve minimum hardness through solutionizing, and another to achieve maximum hardness through ageing. This enables the use of processes such as porosity reduction by roll, as well as restoring the alloy's superior hardness and strength afterwards.

Photonic and Phononic Interactions

[55]    Continuous wave Yb:KGW laser with polarization-independent pump absorption
Zhao, Haitao, Ph.D. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. A. Major    

The crystals of Yb:KGW are known to be an attractive gain medium for diode-pumped continuous wave and ultrafast solid-state lasers producing radiation with wavelength around 1 μm. Since pump absorption spectra of Yb:KGW are highly anisotropic, its efficient operation especially at high output power levels requires careful consideration of pumping configuration. Usually, an Nm axis is used for excitation because it has several times higher absorption coefficient than the other two principal optical axes Np and Ng. Unfortunately, the pump beam from the commonly used fiber-coupled laser diode modules is unpolarized. This causes inhomogeneous pump absorption along the length of the crystal, considerable thermal lensing, and dependence of pump absorption on its current state of polarization all of which are detrimental to the efficiency, beam quality and stability of a laser.
In this work a new method for significant reduction of these effects in Yb:KGW crystals is proposed and successfully tested. In our case the Np and Ng axes are selected for excitation at 980 nm, since they have very similar absorption coefficients. Therefore the pump absorption becomes polarization-independent. This pumping method results in several advantages: 1) the pump is absorbed more uniformly along the crystal length, reducing the focal length of the induced thermal lens by a factor of two; 2) lower pump absorption on the Np and Ng axes reduces the thermal load on the crystal’s entrance face by 60%, leading to a lower risk of damage; 3) the pump absorption, and hence output power, is insensitive to the coiling, stress and orientation of the diode module’s fiber, making performance of the laser less sensitive to mechanical disturbances. The proposed pumping technique was experimentally tested by building a 1W level continuous wave Yb:KGW laser. The obtained successful results provide a route for development of multi-Watt Yb:KGW lasers with improved performance. Such power-scaling efforts are currently underway.

[57]    Phase-matching properties of PPKTP, MgO:PPSLT and MgO:PPcLN for ultrafast optical parametric oscillation in the visible and near-infrared ranges with green pump
Manjooran, Sujith, Ph.D. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. A. Major

Ultrashort pulses with wavelength tuning in the visible and near-infrared (VNIR) ranges (here approximately 680 nm to 2000 nm) have wide application in many biomedical devices especially in imaging and spectroscopy. The theoretical studies here consider the phase-matching conditions of three periodically poled crystals (PPKTP, MgO:PPcLN and MgO:PPSLT) to use for femtosecond optical parametric oscillators (OPO) to generate wavelength tunability in this range. The basic optical properties and the wavelength tuning ranges are calculated with respect to different grating periods and temperature variation. Dispersive properties of crystals relevant to the ultrafast operation regime are also discussed. The excitation wavelength used here for the analysis is 520 nm which is the second harmonic wavelength of Yb-doped ultrashort pulse solid state lasers. The concept of the tunable femtosecond OPOs with green excitation presented here can be a better alternative to the widely used expensive Ti:Sapphire lasers.

Complex Natural Systems

[59]    Determination of the volumetric and compressibility properties of 3 dairy bioactive peptides
Maya Desdier, Luis, M.Sc. Candidate
University of Manitoba, Food Science
Advisor: Dr. M.G. Scanlon

The material properties of biological molecules can strongly influence behaviour, either during processing or in aptness for end-use purposes, e.g., nutritionally or medically.  Food industry interest in bioactive peptides has been rising lately due to their demonstrated health benefits.   Dairy proteins can be processed so that they become one important source of bioactive peptides.  High-precision ultrasonic velocity and density measurements of bioactive peptides in solution can be a valuable tool for characterizing protein/peptide structures and how they interact with water allowing us to gain insights into how molecular structure affects nutritional efficacy.  In this study, 3 different whey bioactive peptides (A, C & D) provided by Glanbia Nutritionals, were used to prepare serial dilutions with ultrapure water gravimetrically.  Density and ultrasonic measurements were performed at 25°C and were used to calculate the partial specific volume and partial specific adiabatic compressibility of the dairy bioactive peptides.  All 3 dairy peptides showed linear relationships between density and concentration and ultrasonic velocity and concentration. All 3 dairy peptides had partial specific volumes in the range from 0.69 cm³/g for dairy peptide C to 0.73 cm³/g for dairy peptide D at reasonably dilute concentrations (15-20mg/mL). Partial specific adiabatic compressibility was in the range from -0.43 mL/g in dairy peptide C to 0.61 mL/g in peptide D at the same concentrations (15-20 mg/mL).  However all 3 dairy peptides showed continuous decrease in partial specific volume and partial specific adiabatic compressibility at very low concentrations (0.465 to 2.5 mg/mL), which is consistent with increases in density and decreases in compressibility arising from rearrangement of the structure of water as ions dissociate from the peptide.  

[61]    The Incorporation of Gold Nanoparticles into a Right Handed Coiled-Coil Tetramer
McDougall, Matt, Undergraduate Student
University of Manitoba, Chemistry
Advisor: Dr. J. Stetefeld    

Organic molecule-gold nanoparticle hybrids such as DNA-Au hold great promise in the field of semiconductor development for logical operations and computing, because they induce a spin polarized current which exhibits a spin selectivity for electrons higher than any other currently known system at room temperature. This is due to the due to the chiral nature of DNA. A Right Handed Coiled-Coil (RHCC) protein derived from Staphylothermus marinus, an archaea whose optimal growth temperature is 90°C found living near black smokers under the ocean, has many advantages over DNA in semiconductor development. RHCC is chiral and contains four large cavities and the largest one is capable of holding up to 9 gold atoms. It is extremely rigid, pH- and thermo- stable, and its dipole would allow regular deposition on a surface. We have optimized expression of RHCC in E. coli in order to produce large quantities of protein, and have explored the reductive properties of amino acids that may allow gold nanoparticle assembly within the cavity from gold ions in solution. Our research has focused on the development and characterization of RHCC-Au complexes in solution for possible application in spin selective semiconductor development.

[63]    Differentiation of Biological Cells Based on Their Dielectric Properties
Bhide, Ashlesha, M.Sc. Candidate
University of Manitoba, Electrical and Computer Engineering
Advisor: Dr. D.J. Thomson

The aim of the experiment is to detect and actuate single biological cells electrically based on impedance measurements. Cells can be modeled as dielectrics. When a cell is suspended in a medium of different dielectric permittivity and is subjected to non-uniform electrical fields, the particle polarizes and experiences a force called the dielectrophoretic (DEP) force. Cells with different dielectric properties experience different DEP forces based on which they can be separated. Dielectric properties of the cells are described by the Claussius Mossotti factor (CMF) which also determines the polarity of the DEP force.
The cells are flown through a microfluidic channel with electrodes fabricated at the bottom of the channel. This electrode design allows the independent detection (at GHz frequencies) and actuation (at MHz frequencies) of cells. The cells are detected before and after actuation. The amplitude of the detected signal depends on the change in elevation before and after actuation. The change in elevation is obtained by plotting particle trajectories for different step changes in CMF within the range -0.5 to 0.5.The Force index values are predicted for different CMF’s for a given elevation. Force Index (FI) is defined as the ratio of the difference between the amplitude of signals before and after actuation over the average of the signal amplitudes before and after actuation. The simulated values and the experimental values are compared to determine the CMF for a single cell. At a given frequency, viable cells will be attracted to the electrodes (FI > 0) while the non-viable cells are repelled by the electrodes (FI <0).