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Synergy Day 2015 Abstracts
WINNER – BEST RAPID FIRE RESEARCH ABSTRACT
Title: Solar Rechargeable Redox Flow Battery
Authors: Mohammad Ali Mahmoudzadeh, Ashwin R. Usagaocar and John D. Madden Abstract: Large-‐scale storage of electricity is a vital requirement for the realization of a carbon-‐neutral electricity grid. Electrochemical energy storage is the preferred method for this application due to its flexibility and scalability. However, such systems suffer from high capital cost even for the cheapest technology (lead acid battery). Integration of energy conversion and storage is one method to reduce the cost of solar energy systems. An integrated solar-‐battery structure based on two relatively well-‐established technologies of the redox flow battery and the dye-‐sensitized solar cell is designed and demonstrated. The cell consists of a sensitized electrode in a redox flow battery structure. The design enables independent scaling of power and energy rating of the system thus it is applicable for large-‐scale storage purposes. Areal energy capacity of 52 μWhcm-‐2, charge capacity of 1.2 mAh L-‐1, energy efficiency of 78% and almost perfect Coulombic efficiency are observed for the integrated cell.
WINNER – BEST POSTER ABSTRACT
Title: Electrolessly deposited Pt/Nafion composite catalysts Authors: Isaac Martens, Blaise Pinaud, Jeanette Leeuwner, Amin Nouri,
Elod Gyenge, David Wilkinson, and Dan Bizzotto
RAPID FIRE RESEARCH ABSTRACTS (Abstracts Presented as Three-Minute Talks)
Comprehensive study of exfoliated thin flake of FeSe Authors: Rui Yang and Shun Chi Abstract: As the simplest member of Ironbased superconductors, FeSe can help people understand superconductivity in Ironbased superconductors. FeSe has layered structure, making it possible for exfoliation. We successfully made superconducting FeSe thin flakes and developed technique for making microleads. We studied its properties with transport, Rama and SIMS. Our study indicates that Oxygen from air exposure probably can enter interstitial positions of FeSe thin flakes, leading to quenched superconductivity.
Effect of niobium and molybdenum alloying elements in high strength low-‐alloyed steels Authors: Jean-‐Yves Maetz, PhD and Professor Matthias Miilitzer Abstract: High strength low alloyed (HSLA) steels are continuously in development, especially for automotive applications, because vehicle weight reduction to improve fuel economy and high crash performance materials for passenger safety are central priorities. According to the fact that the mechanical properties of material are directly correlated to its microstructure, especially by varying the alloying composition and manufacturing process, a careful control of the microstructure is required to optimize material performance. Different microstructural strengthening effects are known to enhance mechanical properties, such as grain refinement, solute strengthening, precipitation hardening, etc. In this project, the strengthening effect of Nb and Mo alloying elements is investigated, especially during coiling by precipitation hardening. Industrial processing, including coiling, is simulated in laboratory, in order to quantify the strengthening contribution in steels because of Nb and Mo, based on a systematic experimental study. The final goal of the study is to develop a model for precipitation strengthening applicable as a function of composition and heat treatment conditions, in particular coil cooling. Effect of electrostatics on entrainment in gas-‐solid fluidized bed Authors: Farzam Fotovat, Xiaotao T. Bi and John R. Grace Abstract: Many chemical and physical processes such as combustion, gasification, cracking, drying, filtration, coating, separation and polymerization feature fluidization of particulate materials. In view of the widespread application of these processes, fluidized beds are of central importance in many areas, including power stations, chemical, pharmaceutical and food industries. Fluidized beds, especially those operating at high gas velocity, suffer from entrainment of fine particles leading to loss of valuable solids and to air pollution. To avoid these problems and ensure the technical and economic success of fluidized beds, proper design of solids recovery equipment such as cyclones is essential. This requires deep insight and accurate prediction on the entrainment. Numerous studies have been conducted on the entrainment, and several empirical correlations have been proposed to predict the entrained rate; however, due to the use of empirical constants and the absence of fundamental understanding of the underlying phenomena, huge discrepancies are observed between predictions and reported values. Recent work at UBC has shown that electrostatics is one of the factors influencing the entrainment of fine particles. Electrostatic charges are produced because of the continuous motion and rubbing among bed particles. No allowance has yet been considered for electrostatic charges in the correlations predicting entrainment rate in fluidized beds. Ignoring the contribution of electrostatic effects could be the dominant reason the enormous scatter seen in the literature on entrainment. To address this issue, experiments are being undertaken in a unique column capable of measuring both electrostatic charges and entrainment. The next step is seeking to make recommendations to significantly improve the predictability of entrainment on the basis of the experimental results. The preliminary observations show that under the same operating conditions, the entrainment flux of different fine materials largely depends on the amount of the electrostatic charges they carry, which in turn is a function of their electrical properties such as dielectric constant and conductivity. In this regard,
the next step is to determine and explain the parameters governing the magnitude and polarity of the charged particles by affecting the mechanisms of generation, separation and transfer of electrostatic charges. Furthermore, the impact of the electrostatic forces on entrainment of fines will be quantified by measuring the electrostatic forces and introducing them into the correlations predicting the entrainment flux. Pronounced polarization-‐induced energy level shifts at boundaries of organic semiconductor nanostructures Authors: K. A. Cochrane, A. Schiffrin, T. S. Roussy, M. Capsoni and S. A. Burke Abstract: Organic semiconductor devices rely on the movement of charge at and near interfaces, making an understanding of energy level alignment at these boundaries an essential element of optimizing materials for electronic and optoelectronic applications. Here we employ low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) to investigate a model system: two-‐dimensional nanostructures of the prototypical organic semiconductor, PTCDA (3,4,9,10-‐perylenetetracarboxylic dianhydride) adsorbed on NaCl (2ML)/Ag(111). Pixel-‐by-‐pixel STS allows mapping of occupied and unoccupied electronic states across these nano-‐islands with sub-‐molecular spatial resolution, revealing strong electronic differences between molecules at the edges and those in the “bulk”, with energy level shifts of up to 400 meV. We attribute this to the change in electrostatic environment at the boundaries of clusters, namely via polarization of neighboring molecules. The observation of these strong shifts illustrates a crucial issue: interfacial energy level alignment can differ substantially from the bulk electronic structure in organic materials.
The Laboratory for Atomic Imaging Research: An ultra-‐low vibration facility Author: Ben MacLeod Abstract: The Scanning Tunneling Microscope (STM) can probe matter topographically and spectroscopically at the atomic scale and is therefore of enormous value in fundamental materials science research. The signal from this type of instrument – a tunneling current – is extremely sensitive to minute displacements. This sensitivity underlies both the atomic imaging capabilities of these instruments and
their vulnerability to vibrational disturbances. To achieve high performance and reliable operation, extreme care must be taken to isolate STMs from environmental sources of vibration. The Laboratory for Atomic Imaging Research is an ultra-‐low vibration facility designed specifically to house high-‐performance Scanning Tunneling Microscopes. The facility consists of three pneumatically suspended massive concrete inertia blocks (20,40,80 tons), each enclosed in a heavy concrete acoustic enclosure and each supporting a different STM experiment. This facility has achieved vibration levels among the lowest in the world and is located in the basement of the AMPEL building on the Vancouver campus of the University of British Columbia. In this paper I present a review of the design, construction and performance of this facility as well as findings relevant to the design of future such facilities. Characterization of the Internal Parameters of Nanostructured Light Induced Thermionic Emission Devices for Energy Conversion Authors: Amir H. Khoshaman, Andrew T. Koch, Mike Chang, Harrison D. E. Fan, and Alireza Nojeh Abstract: We propose a method to calculate the output current-‐voltage (I-‐V) characteristics of a light induced thermionic emission (LITE) device. This approach improves on the existing methods by having both a higher precision and higher range in evaluating the associated integrals, resulting in simulated device characteristics with a wider range of parameters. This method represents a significant step towards the characterization of emergent LITE devices due to the unknowns involved in their internal parameters. More importantly, its high numerical precision and flexibility allows one to solve the reverse problem and evaluate the internal parameters of the device from experimental I-‐V curves. Based on this, the internal parameters of a carbon nanotube (CNT)-‐based LITE device are calculated, including several parameters, the estimation of which was previously not feasible with one single type of experiment. Motivation Solar thermionic convertors have salient features such as an exponential dependence of current density on temperature, which make them attractive candidates for clean energy applications. We have previously reported a localized heating effect in a multi-‐walled CNT forest using a low-‐power input light source 1,2. This device overcomes some of the main obstacles facing LITE devices, such as heat spread in the cathode. Thermionic devices fabricated using nanomaterials, though having the same working principles as traditional devices, have several distinct features. Firstly, the workfunction of nanomaterial-‐based electrodes are highly dependent on various experimental conditions3, whereas traditional refractive metals have well-‐known work functions. Secondly, the entire electrode area of a traditional electrode is heated, whereas, a small portion (about 100 μm radius) is heated in the case of nanomaterials. Hence, the temperature will be highly dependent on the local morphology of the nanomaterial, and the influence of a temperature gradient is more substantial. Consequently, it is important to improve the numerical calculation precision and to develop a reliable algorithm to extract the internal parameters of the device particular to each experiment. 1 P. Yaghoobi, M.V. Moghaddam, and A. Nojeh, Solid State Communications 151, 1105 (2011). 2 P. Yaghoobi, M. Vahdani Moghaddam, and A. Nojeh, AIP Advances 2, 042139 (2012). 3 P. Liu, Q. Sun, F. Zhu, K. Liu, K. Jiang, L. Liu, Q. Li, and S. Fan, Nano Lett. 8, 647 (2008). 4 G.N. Hatsopoulos and E.P. Gyftopoulos, Thermionic Energy Conversion -‐ Vol. 2: Theory, Technology, and Application (The MIT Press, 1979).
Results The I-‐V characteristics were calculated in the three modes of operation, i.e., retarding, space-‐charge and saturation mode (Fig. 1). In the space charge mode, Poisson’s and Vlaslov’s equations were solved self-‐consistently in the inter-‐electrode region based on the method proposed by Hatsopoulus4. This was further improved by employing multiple iterations at each step, leading to higher precision calculations in the transition from the retarding to the space charge mode (critical point, Vc and Ic in Fig. 2). The errors caused by following the assumptions made in ref. [4] compared to the rigorous calculations proposed in this work are depicted in Fig. 2. The influence of a linear temperature gradient on the overall I-‐V characteristics is illustrated in Fig. 3. Experimentally, a CNT forest used as the emitter was illuminated with varying powers of a 532-‐nm laser beam (Fig. 4). I-‐V characteristics were obtained by sweeping the voltage from negative (retarding) to positive (collection) values and fitted to the simulation results (Fig. 5). The area of the heat spot from simulation matched closely to that obtained experimentally by a CCD camera. The estimated temperature and workfunction are also well in agreement with the values reported previously.
Fig. 1: A typical simulated I-‐V curve illustrating the different modes of operation of a thermionic device. Φ, μ, and V represent the workfunction, Fermi level and applied bias. Subscripts E and C indicate emitter and collector.
Fig. 2: The errors caused when the critical voltage is calculated following the assumptions made in ref. [4]. (left) TE and (right) d represent the interelectrode resistance and emitter’s temperature, respectively. Vc,Hat represents the critical voltage calculated based on ref. [4].
Fig. 3: (left) Contributions of rings with different temperatures to current along a hot spot size of radius 200 μm. (right) Temperature map along a quadrant of the hot spot with radius r.
Fig. 4: Schematic diagram and photograph of the experimental set-‐up. (left) A secondary electron micrograph and (right) a CCD image of the locally heated area.
Fig. 5: Experimental I-‐V characteristics fitted to simulation curves and the calculated internal parameters of the system. High Performance Electrodes for Novel Li-‐S Batteries Authors: Timothy Watson, Saeid Soltanian, Frank Ko and Peyman Servati
Abstract: The rapid progression of portable and wearable electronics and the advancement of next generation energy solutions necessitate the development of high performance energy storage devices. One potential candidate for future widespread energy storage is the lithium sulphur (Li-‐S) battery, which has many advantages compared to other energy storage devices, such as a high theoretical energy capacity that is about five times greater than that for current lithium-‐ion batteries as well as utilizing more green and readily available materials compared to Li-‐Ion batteries. Although extensive attempts have been made during the last few years to develop Li-‐S based energy storage devices, they suffer from several drawbacks such as poor cycling stability and poor active material utilization. This work presents our research on the development of novel materials and components for application in high performance and flexible Li-‐S batteries. Highly conductive and porous carbon (C) based nanostructure materials such as nanofiber mesh as well as C-‐composites that possess high flexibility, mechanical stability and capacity to adsorb the necessary sulphur molecules are being developed and utilized as cathodes. We will also present potential challenges in this research that include optimization of the electrical properties of the cathode, mitigation of shuttling effect as well as maintaining stability, flexibility and mechanical strength. In collaboration with another research groups, the developed novel materials will be utilized for fabrication of a new generation of Li-‐S battery.
This research is supported by an NSERC Strategic Research Grant Low-‐roughness, Charge-‐selective Nanofibrous Transparent Conductors for Organic Solar Cells Authors: R. Rahmanian, S. Soltanian, P. Servati Abstract: Transparent conductors (TCs) used for solar cells and optoelectronic devices are still dominated by brittle indium-‐tin oxide (ITO). Mechanical flexibility needed in emerging flexible electronics, along with increasing price of indium, calls for alternative TCs. In attempt to find a substitute for ITO which can meet the combined expectations of low sheet resistance, high optical transmittance, and mechanical flexibility, various nanostructures have been suggested, e.g., carbon nanotubes, graphene, metallic nanowires, and conductive polymers. Matching high mechanical flexibility with outstanding optoelectronic performance is a major challenge in flexible TCs. Conductive polymer TCs, showing the highest stretchability, generally have high sheet resistances. Metallic nanowires, while attaining optoelectronic performances comparable to ITO, show far less flexibility. To address the requirements of superior flexibility as well as optoelectronic performance, we have developed a compliant core-‐shell nanofibrous mesh consisting of high-‐aspect-‐ratio electrospun PAN nanofibers (NFs), metallized by a conformal coating of gold, to function as a stretchable TC. Transferred onto a PDMS substrate, the nanofibrous TCs exhibit more than 100% stretchability while maintaining a performance comparable to ITO. A drawback of as-‐transferred nanofibrous TCs is their high surface roughness that limits their application as bottom electrodes for organic solar cells. To address this issue, we have covered the nanofibers with a layer of transparent electron-‐selective ZnO nanoparticles, which also serves the double purpose of further decreasing the sheet resistance and providing a charge-‐selective coating on the electrodes. The proposed structure can be rendered flexible by partially embedding the ZnO-‐coated NFs near the surface of a PDMS layer. The resulting TC can undergo up to 10% tensile strain, showing reversible recovery of sheet resistance over repeated stretching cycles. Deformability-‐based Sorting of Red Blood Cells to Enrich for Parasitized Cells in Falciparum Malaria
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Authors: Quan Guo, Kerryn Matthews, Xiaoyan Deng, Simon Duffy, and Hongshen Ma Abstract: As one of the oldest scourges, malaria has caused significant morbidity and mortality for ages, particularly in the developing countries. As the most virulent species of malaria, Plasmodium falciparum is responsible for approximately 90% of the infected population. The gold standard in clinical malaria diagnosis is microscopic observation of Giemsa stained blood smears despite the availability of low-‐cost rapid diagnostic tests (RDTs) and highly sensitive PCR-‐based tests. Microscopy has an estimated detection threshold of 50-‐100 parasites per µl of blood in field conditions, which is often insufficient for asymptomatic patients with low parasitemia. A central aspect of malaria parasitism is the loss of deformability of Plasmodium falciparum infected red blood cells (Pf-‐iRBCs), which occurs even at the early stages of infection and allows these cells to be discriminated from uninfected RBCs (uiRBCs). Using this principle, we develop a microfluidic device for deformability-‐based sorting of RBCs to enrich for early stage Plasmodium falciparum infected RBCs (Pf-‐iRBCs). Our method is able to enrich the parasitemia of an infected blood sample up to 2000X (from 0.0004% to ~1%), enabling samples that are currently undetectable using microscopy and RDTs, to be readily detectable using both methods. Figure below illustrates the design principle and operation of the device. Here, we sort RBCs using a matrix of funnels where the pore sizes gradually decrease from the bottom to the top row (Figure 1C). RBCs infused into the bottom-‐left corner (Figure 1B) are propelled by a vertical oscillatory flow and a constant horizontal flow, which causes them to follow a zig-‐zag diagonal path (Figure 1A) until reaching a limiting funnel size, where they proceed horizontally between the funnel rows. The limiting funnel size depends on RBC deformability thereby enabling deformability based sorting. Specifically, we sorted Pf-‐iRBC samples using a matrix of funnels with pore sizes ranging from 1.5 to 7.5 µm (Figure 1D) leading to nine outlets. To demonstrate the ability to enrich the parasitemia of clinically relevant blood samples, we prepared samples containing 0.0004-‐0.03% early stage Pf-‐iRBC and showed that our process can increase the parasitemia of these samples to 1-‐5%, equivalent of 100~2000X enrichment. This capability enables detection of samples with parasitemia currently below the sensitivity limit of microscopy and RDTs. In summary, we developed a method to sort RBCs based on deformability and then used this process to enrich for early stage Pf-‐iRBCs to significantly increase the sensitivity of malaria diagnosis on clinically relevant samples.
Figure 1: Micrograhs of the microfluidic
sorting mechanism. (A) Overview of the design; (B) RBCs infused into the funnel matrix;
(C) funnel matrix showing the RBCs blocked at certain pore sizes; (D) 9 different outlets forming the deformability gradient with the most deformable RBCs collected at outlet 1 and most rigid RBCs at outlet 9. Red Blood Cell Trans-‐dispersion Enabling High-‐Throughput Deformability Analysis of Malaria Parasitism Authors: Aline T. Santoso, Xiaoyan Deng, Jeong Hyun Lee, Kerryn Matthews, Emel Islamzada, Sarah McFaul, Marie-‐Eve Myrand-‐ Lapierre, Mark D. Scott and Hongshen Ma Abstract: Gel electrophoresis is a fundamental technology enabling modern molecular biology and genetics. This process involves migrating DNA or protein molecules in agarose gel using an electric field, where the final positions of the molecules in the gel indicate their size relative to known controls. We present an analogous process for red blood cells (RBCs), here termed trans-‐dispersion, where individual cells are transported through aseries of micro-‐scale constrictions in a microchannel using pressure-‐driven flow (Figure 1). The final positions of RBCs indicate their deformability, similar to intensity bands in a DNA gel, thereby enabling repeatable, high throughput, and parallelized measurements of RBC deformability. We show the throughput and sensitivity of the trans-‐dispersion mechanism is sufficient to 1) detect rare subpopulations of ring-‐stage Plasmodium falciparum infected RBCs (iRBCs) at clinically relevant parasitemia (<1%), and 2) enable in vitro assays for antimalarial drug-‐efficacy that could be used for drug screening. Background RBC deformability plays a central role in the pathogenesis of P. falciparum malaria, and therefore could potentially enable simple, rapid, and reagent-‐free biophysical assays [1]. A key challenge, however, is that pathological cells often comprise only a small fraction of the sample, which requires testing of a large number of individual cells in order to detect these key subpopulations. Additionally, it is often desirable to perform multiple assays simultaneously, which require technologies capable of parallelized analysis. Recent microfluidic methods, based on the measurement of transit time [2,3] or transit pressure [4,5] through a micro-‐scale constriction, are difficult to parallelize because of the need to monitor the deformation process using a video recording or to integrate electrical sensors on a disposable microfluidic chip. Mechanism and Results The cellular trans-‐dispersion mechanism provides a sensitive and consistent method for measuring single RBC deformability by designing the geometry of each constriction to form a temporary seal with the cell during the transiting process. Supporting microchannels form a self-‐compensating network to generate a consistent pressure drop in each microchannel (Figure 1). After undergoing repeated deformations, the final position of each RBC, indicating its deformability, is determined using simple bright-‐field microscopy and automated image processing, and thereby enables high-‐throughput and massively parallel analysis of RBC deformability. We evaluated the performance of trans-‐dispersion mechanism by detecting changes in RBC deformability resulting from chemical degradation, malaria parasitism and exposure to anti-‐malarial drugs. Figure 2 shows the distribution of tested RBCs following chemical degradation using glutaraldehyde. Figure 3 shows the deformability profiles of iRBCs, shown as cumulative distribution, and synchronized at the ring-‐stage of infection. From this data, the linear correlation between the parasitemia and the percentage of non-‐transiting cells could potentially be used to infer the parasitemia of clinical
specimens (Figure 4). Finally, we used this approach to measure the deformability of iRBCs following exposure to all known clinical antimalarials relative to their unexposed controls (Figure 5). Our results show that rigidification of iRBCs may be a universal biomarker for antimalarial drug efficacy and cellular trans-‐dispersion may be an appropriate method for alternative screens for new antimalarials. References: [1] Nash GB, O’Brien E, Gordon-‐Smith EC, Dormandy J a. Abnormalities in the mechanical properties of red blood cells caused by Plasmodium falciparum. Blood 1989;74:855–61. [2] Adamo A, Sharei A, Adamo L, Lee B, Mao S, Jensen KF. Microfluidics-‐based assessment of cell deformability. Anal Chem 2012;84:6438–43. doi:10.1021/ac300264v. [3] Zheng Y, Sun Y. Microfluidic devices for mechanical characterisation of single cells in suspension. Micro Nano Lett 2011; 6:327. doi: 10.1049/mnl.2011.0010. [4] Guo Q, Reiling SJ, Rohrbach P, Ma H. Microfluidic biomechanical assay for red blood cells parasitized by Plasmodium falciparum. Lab Chip 2012;12:1143–50. doi: 10.1039/c2lc20857a. [5] Myrand-‐Lapierre M-‐E, Deng X, Ang RR, Matthews K, Santoso AT, Ma H. Multiplexed fluidic plunger mechanism for the measurement of red blood cell deformability. Lab Chip 2015; 15:159–67. Doi: 10.1039/C4LC01100G.
Figure 1: Trans-‐dispersion mechanism. (A) Trans-‐dispersion chip with 8 parallel trans-‐dispersion arrays. (B) Structure and components of a single trans-‐dispersion array. (C) Position of the cells along the device indicates their transit speed and hence, their deformability. More deformable cells will travel further along the device than less deformable cells. (D) Micrograph of a zoomed-‐in section of deformation microchannels (scale bar = 75 μm).
Figure 2: Sensitivity of the trans-‐dispersion mechanism was established using RBCs treated with mild glutaraldehyde (GTA) fixation (p < 0.0001).
Figure 3: Deformability profiles of RBCs parasitized with ringstage synchronized P. falciparum at increasing population fraction, from least to most deformable and (insert) scatter plotat 2% least deformable fraction shows significant difference between 0% and 1% parasitemia samples (p < 0.0001 with n = 9074 for control and a minimum n = 978 for 2%).
Figure 5: Evaluating antimalarial drug efficacy. Antimalarial drug response (> 4 x EC50) in late-‐stage iRBCs shows a decreased deformability for all antimalarial drugs (p < 0.0001) except for tetracycline (p = 0.54).
The Quantum Materials Spectroscopy Centre at the Canadian Light Source Authors: S. Zhdanovich, M. Schneider, D. Wong, P. Dosanjh, G. Levy, S. Gorovikov, B. Yates, and A. Damascelli Abstract: The Quantum Materials Spectroscopy Center (QMSC) currently under construction at the Canadian Light Source (CLS) is a state-‐of-‐art beamline facility equipped with endstations for angle-‐resolved photoemission spectroscopy (ARPES) and spin-‐resolved ARPES. QMSC will operate in the photon
energy range from 10 to 1200 eV, with full polarization control. The main components of the beamline are the low-‐ and high-‐energy 4 m long APPLE type undulators, installed side-‐by-‐side in a switch-‐yard arrangement, and a variable line-‐spacing plane-‐grating monochromator (VLS PGM). The photon flux will be in the range of 1012 – 1013 photons/second at the endstations, with a resolving power higher than 104 over the full pho-‐ton energy range. Complete polarization control, in both linear and circular modes, will be available. In addition, the quasiperiodic magnetic structure of the low-‐energy undulator will guarantee the optimized suppression of higher-‐order harmonics. The ARPES endstation is based on a VG Scienta R-‐4000 hemispherical analyzer with 1 meV energy resolution and a 0.1° angular resolution. The spin-‐ARPES endstation employs the same analyzer paired with a VG Scienta VLEED single-‐hole transfer system and spin detector capable of resolving out-‐of-‐plane as well as in-‐plane spin components. The integrated MCP/CCD detector will enable sample alignment and characterization in ARPES mode, prior to spin measurements. A 6-‐axis cryogenic manipulator installed on both endstations will al-‐low a sample rotation of ±65° and +30° to -‐70°, respectively, with respect to horizontal and vertical planes. In addition, a closed-‐cycle cryostat will enable the sample temperature to be quickly varied between 4 and 300K. Both endstations will allow for in-‐situ sample preparation and manipulation with sputtering, annealing, and adatom evaporation capabilities, as well as the ability to grow oxide materials via integrated molecular beam epitaxy (MBE) systems. In situ ultrasound treatment of collagen type I assembly for microfabricated 3D tumor cell encapsulation Author: Solmaz Karamikamkar Abstract: 3D tumor spheroids (TSs) have gained increasing recognition as an effective tool for cancer research. The TSs are composed of tumor cells growing in a 3D extracellular matrix (ECM) polymers. The ECM polymers are formed as hydrogel beads to simulate the micro-‐environmental conditions of tumor tissue1. Zhang et al.2 showed that the hydrogel beads mimic 3D structure of tumors in vivo more faithfully compared to 2D in vitro and monolayer cultures. One of the commonly used techniques in forming hydrogel beads is the use of microfluidic systems, which can produce beads with high uniformity. Generally, the gelation of natural polymers is reported to be less controllable, though they are more compatible for cell-‐encapsulation3. Collagen type I solutions undergo self-‐assembly into beta-‐sheet structures induced by pH or temperature and form hydrogels. For TS production process, collagen gelation can be prohibited by using a cooling system during bead production to prevent chip clogging. However, this technique reduces the cells efficiency to proliferate for desired time length. In this study, a new ultrasound-‐based treatment (UST) is developed to induce in situ structural transition of collagen in a controllable manner to enhance the proliferation of human source Michigan Cancer Foundation-‐7 breast tumor cells (MCF-‐7). Materials & methods
MCF-‐7 cells were cultured in RPMI media supplemented with 10% Fetal Bovine Serum and 1% antibiotics for 24h under 5% CO2 at 37°C. MCF-‐7 cells were detached with 0.025 mM trypsin, centrifuged, and washed in media. Briefly, a mixture containing sodium alginate (2% w/v, medium viscosity), collagen solution (1.5 mg/ml), calcium carbonate suspension (80 mM, anhydrous), and MCF-‐7 cells (5×106 cells/ml) was prepared. The pH was set to 7.4 by the drop-‐wise addition of calcium bicarbonate (S1: no sonication). Additional mixtures were likewise prepared and ultrasound energy at power of 2000 J/ml in a continuous wave fashion was applied on mixtures for 30 min in a water bath at temperatures of 32°C, 37°C, and 42°C (S2, S3, and S4). The temperature was increased from 32°C up to 42°C to see the temperature effect on the possible structural changes and distribution of collagen fibers. The viability of MCF-‐7 cells is first monitored by counting viable cells, applying Trypan blue exclusion immediately after bead production. MCF-‐7 cell proliferation was measured by the standard MTS assay in which the cell-‐laden beads and MTS solution were mixed 5:1 in a 96-‐well plates and cultured in an incubator at 37°C and 5% CO2 for 4h 4. Second harmonic generation backward propagation (SHG) was employed to monitor the distribution of the collagen fibers within the mixtures. Generally, the focusing objective of a 2p 25X water dipping with 1.05 numerical aperture (NA) (Olympus objectives), the illumination wavelength was centered at 810 nm, and blocking of the fundamental was carried out with channel one HQ 405/30M-‐2P filter and channel two HQ 495/25M-‐2P filter. Results Table 1 shows the size distribution of the beads (number of beads=80) that are represented by their coefficient of variation. Beads from S4 had the highest uniformity compared to S1, and S2. S1 showed the least bead uniformity compared to the sonicated samples. The resultant spheroids (7 days after bead generation) from sonicated sample showed much better uniformity than non-‐sonicated sample. Fig. 1 presents the SHG images of collagen fibers in the empty (no cells) sonicated and non-‐sonicated hydrogels, both before and after bead generation. Collagen fibers exhibit a strong photo-‐stable SHG signal produced from their shell while treated collagen do not produce significantly detectable backward-‐propagating SHG signal5. There are more noticeable fiber structures in S1 compared to S2, S3, and S4. This might be due to the deformation of collagen fibers structure into non-‐shelled structure through the breakage of hydrogen bonding after UST. Fig. 2 illustrates the proliferation rate for samples S1, S2, S3, and S4. Proliferation rate for S1 was dramatically higher than S3 (Fig. 2). UST at 37°C improved MCF-‐7 proliferation comparing S1 and S2. This observation is in agreement with the results presented by Choi et al. 6. Discussion and conclusion The data indicate that MCF-‐7 cells survive and proliferate longer within the sonicated collagen/alginate bead culture than the non-‐sonicated sample. Beads made of the sonicated mixture retained their structure for 16 days whereas beads made of the non-‐sonicated mixture started to degrade after only 5 days. As SHG observation indicates (Fig. 2), the higher the temperature of UST, the better the collagen distribution among the mixture. Uniformly positioned deformed collagen fibers induced by UST allows having uniform spheroids than those made from the non-‐sonicated mixture. Since sonication treatment breaks the lateral hydrogen bonds in collagen fibers, it generates more nano-‐sized collagen in the system that pack cells inside the beads. The size distribution and MTS assay demonstrate that the most uniform
spheroid is obtained from UST at 37°C. In conclusion, it is shown and confirmed that UST is an useful technique in producing the most uniform spheroids with long proliferation. References 1. Sutherland, R., et al., Cancer Res. 41, 2980–2984 (1981). 2. Zhang, X. et al., Biotechnol. Prog. 21, 1289–1296 (2005). 3. Lee, C. H., et al., Int. J. Pharm. 221, 1–22 (2001). 4. Huyck, L., et al., Assay Drug Dev. Technol. 10, 382–392 (2012). 5. Williams, R. M., et al., Biophys. J. 88, 1377–1386 (2005). 6. Choi, B. H., et al., J. Biomed. Mater. Res. A 79, 858–864 (2006). Optical Trapping and Diagnostic Analysis of sub-‐60nm Gold Nanoparticles Using Photonic Crystal Slot Microcavity Authors: S. Hamed Mirsadeghi, Jonathan Massey-‐Allard and Jeff young Abstract: Here, we report our recent advances in using silicon-‐on-‐insulator (SOI) photonic integrated circuits for trapping gold nanoparticles of sizes as small as 20 nm, with sub-‐mW laser powers. Using a novel analysis of our device transmission time-‐series data, when nanoparticle trapping occurs, we contrast the dynamics of trapped Au spheres and nanorods." In-‐situ grain size measurement in a cobalt super alloy using laser-‐ultrasonics Authors: Mahsa Keyvani, Thomas Garcin, D. Fabrègue, Matthias Militzer, K. Yamanaka, A. Chiba Abstract: Laser ultrasonic for metallurgy (Lumet) is dedicated to in-‐situ monitoring of microstructure evolution during thermo-‐mechanical treatments. In this technique, broadband ultrasound pulses are generated and detected with lasers. For anisotropic materials, ultrasonic attenuation is caused by scattering at grain boundaries and can be related to grain size. The objective of the present work is to further explore the LUMet potential for in-‐situ grain size measurements. The response of ultrasonic attenuation to grain growth is evaluated during isothermal annealing at various temperatures in cobalt super alloy. Correlations have been found between the average grain size and the frequency dependence of attenuation. The applicability of these relationships to quantify the changes in grain size distribution during abnormal grain growth is examined. The results of this investigation establish LUMet as a powerful tool to study evolution of microstructure in cobalt super alloys during their processing at high temperatures to get the best mechanical strength. Setpoint effects in Fourier transform scanning tunneling spectroscopy Authors: A.J. Macdonald, YS. Tremblay-‐Johnston, S. Grothe, S. Chi, and S. Burke
Abstract: The basement of AMPEL houses vibrationally isolated pods, which allow for the measurements on the atomic scale of condensed matter materials. The Laboratory for Atomic Imaging Research (LAIR) group uses scanning tunneling microscope (STM) to probe novel properties of materials such as single molecule solar cells and high temperature superconductors.
An STM is capable of measuring sample topography as well as spatially and energy resolved spectroscopy, provides information about the local electronic density of states, through the derivative of the tunneling current (dI/dV). Fourier analysis yields momentum resolution of the density of states, which can be used to determine the band structure and energy dispersion of electrons in a sample. These measurements are made with simplifying assumptions about the nature of the dI/dV, such as zero temperature, flat tip density of states, and energy independent matrix elements. In real experiment conditions, these assumptions do not always hold. We illustrate the different artifacts that can appear in FT-‐STS using data taken from the well-‐understood surface state of an Ag(111) single crystal at 4.2 K and under ultra-‐high vacuum conditions. We find that constant current dI/dV maps taken with a lock-‐in amplifier lead to a feature in the FT-‐STS dispersion that disperses as a function of energy below the Fermi level (EF) and becomes constant above EF. This result shows the importance of distinguishing dispersing features caused by quasiparticles in the sample from those caused by the measurement. Transparent, flexible and stretchable 'Piezoionic' tactile sensor Authors: Mirza Saquib us Sarwar, Yuta Dobashi, Ettore F. Scabeni Glitz, Meisam Farajollahi, Shahriar Mirabbasi and John D. W. Madden Solute-‐defect interactions in Al-‐Mg alloys from diffusive molecular dynamics calculations Authors: Evgeniya Dontsova, Joerg Rottler and Chad Sinclair Abstract: Segregation and precipitation of solute atoms at defects and interfaces are common phenomena in alloys, but are difficult to model atomistically as they occur on timescales that far exceed those accessible with standard molecular dynamics. I will present an adaptation of the recently developed “diffusive molecular dynamics” method, which is capable to describe the energetics and kinetics of binary alloys on diffusive timescales and at the atomic level. The potential of the technique will be illustrated by applying it to the classic problems of solute segregation to an edge dislocation in the Al-‐Mg system. Process-‐Induced Shape Distortions in Aerospace Thermoplastic Composites Authors: Gabriel Fortin and Goran Fernlund Abstract: Thermoplastic composite materials are of great interest in primary and secondary aerospace structures due to their potential for shorter manufacturing cycle times, high production rates, and their ability to be re-‐heated and shaped multiple times. Thermoplastic resins offer many new possibilities in their ease of repair, recycling, and welding capabilities [1,2]. Aerospace-‐grade thermoplastic composites such as carbon fibre reinforced pleather-‐ether-‐ketone consolidation of the material can take place. As the material is subsequently cooled down from the process temperature, residual stresses develop due to effects of material anisotropy, part geometry, and tool-‐part interactions that eventually lead to undesired shape distortions in the final party geometry. As observed with thermoset composites, common distortions include spring-‐in of corner angles and warpage of flat sections. The tight dimensional tolerances require for aerospace parts demands that process-‐induced shape distortions be well understood in order to reduce the number of scrap parts and to eliminate fitting problems during the assembly stage of the components.
In this project, L-‐shape flanges with a 90° corner are manufactured form aerospace-‐grade AS4/PEEK thermoplastic composites in a hot press using a matched-‐die tooling configuration. A thermoforming technique is employed that involves heating previously-‐manufactured flat panels of the material to the processing temperature prior to transferring and forming within a relatively cold tool held at constant load and temperature. L-‐shape flanges consisting of a quasi-‐isotropic layup of unidirectional plies as well as short randomly-‐oriented strands of AS4/PEEK are thermoformed at 105°, 215 °C, and 290 ° in the hot press. Spring-‐in angles of the manufactured parts are quantified using a coordinate measuring machine and the results from the experiments are compared with predictions form the Nelson-‐Cairns expression based on material thermal expansion anisotropy. SURFACE AND BULK POROSITY IN OUT-‐OF-‐AUTOCLAVE PREPREGS Authors: Jeremy Wells, James Kay, Anoush Poursartip, Malcolm Lane and Göran Fernlund ABSTRACT: In composites manufacturing both bulk and surface porosity are undesirable outcomes that should be minimized or eliminated. Bulk porosity negatively impacts mechanical properties whereas surface porosity produces an uneven and aesthetically unpleasing exterior. In prepreg processing, out-‐of-‐autoclave processes have a greater tendency to exhibit problems with porosity relative to autoclave processes due to the lower compaction pressures. This has led to a greater emphasis on gas removal prior to cure and more stringent requirements on high vacuum levels during processing. The formation, evolution, and removal of voids in OOA prepregs currently lack a robust scientific understanding. The present study aims to investigate the evolution of bulk and surface porosity due to dissolved volatiles, as well as the relationship between them and drivers behind them. Flat, fully evacuated laminates were cured under various processing conditions and their bulk porosity after cure was quantified by density and thickness measurements. Using a transparent glass tool and a video camera connected to a digital microscope, the tool-‐laminate interface was optically recorded in-‐situ during cure. Based on observations of resin flow and wetting, bubble movement, and bubble growth at the tool-‐laminate interface from the recorded video, an understanding of porosity drivers and mechanisms is developed. Process parameters considered in the study include resin pressure, resin moisture content and prepreg fiber architecture. Gallium Zinc Oxynitride Photocatalyst and the Corresponding Reduced Graphene Oxide Composite for Visible Light Hydrogen Generation Authors: B. Adeli and F. Taghipour Abstract: Among the various clean and renewable energy sources, sunlight by far is the largest. Solar hydrogen makes solar energy as storable and transportable as fossil fuels without their negative environmental impacts. Gallium-‐zinc oxynitride solid solution (GaN:ZnO) is one of the few photocatalysts which is capable of splitting water to hydrogen and oxygen under visible light with high and stable photocatalytic activity. The GaN:ZnO solid solution photocatalyst is typically synthesized by nitridation of a mixture of Ga2O3 and ZnO at high temperatures for 5–15 h [1] via the solid-‐state reaction. Although the photocatalyst prepared through the traditional method demonstrates high activity for overall water splitting, the long synthesis time at high temperature is considered a drawback of this synthesis technique [2].
We have synthesised nanoporous gallium-‐zinc oxynitride solid solution through a fast and cost effective synthesis technique. Pre-‐treatment of the synthesis precursor improved the homogeneity of the photocatalyst. The composition and surface structure of the solid solution were controlled by adjusting the ratio of starting materials in the precursor and the synthesis conditions. The crystalline structure of the photocatalyst was improved through post-‐heat treatment. Various characterization techniques confirmed the formation of visible-‐light activated nano-‐porous solid solution with higher surface area, comparing to the one prepared via traditional technique. The photocatalyst incorporated to graphene oxide (GO) nanosheets through facile ultra-‐sonication. The reduced graphene oxide (RGO) composite was obtained via in-‐situ photo-‐reduction reaction as a result of electron transfer from bulk of photocatalyst to the nanosheets. Structural, optical, and electrochemical characterizations confirmed the effective interaction between composites component and its superior optical properties. The overall water splitting efficiency of the composite indicated that the performance of the samples improved significantly because of efficient charge separation in the composites structure. References:
1. K. Maeda, T. Takata, M. Hara, N. Saito, Y. Inoue, H. Kobayashi, and K. Domen, J. Am. Chem. Soc., 127, 8286 (2005). 2. B. Adeli and F. Taghipour, ECS Journal of Solid State Science and Technology, 2 (7) Q118-‐Q126 (2013).
Geometrically Controlled Carbon Nanofibre Membrane for Fuel Cell Catalyst Support layer Sophia Chan and Dr. Frank Ko Abstract: Responding to the urgent need for clean, efficient, affordable and sustainable energy this study examines the role of carbon nanofibres in the performance of polymer electrolyte membrane fuel cell (PEMFC). Although widely used in conventional PEMFCs, the agglomerate-‐based catalyst layers have a number of disadvantages. Their microstructure is irregular, often non-‐homogeneous, with highly tortuous transport paths for electrons, protons, and gas. As a result the overall conductivity and gas diffusivity decrease, while keeping a portion of the Pt catalyst buried within the agglomerate making it inaccessible for the reaction. Specifically this study focuses on the use of carbon nanofibre as a substrate for cathode catalyst layer in a PEMFC with the aim to develop catalyst layers with more controllable design parameters. A systematic study is carried out to optimize the processing parameters, structural geometry and performance of the carbon nanofibre catalyst layer. The processing parameters studied include precursor preparation, electrospinning conditions, heat treatment, and catalyst deposition. The structural parameters studied include fibre diameter, fibre web thickness, fibre orientation, and pore geometry. The performance of the FC will be characterized based on electrical conductivity, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements. Preliminary results showed the concept of the catalyst carbon nanofibre layer is encouraging. The random nanofibre layers demonstrate high porosity, conductivity, and low fibre diameter, all of which are essential requirements for an efficient fuel cell. It was shown that the electrospinning parameters could be accurately and precisely controlled yielding fibres with the desired diameter, thickness, and porosity. The results also demonstrated that orthogonally aligned nanofibre layers could be fabricated using the electrospinning technique.
Progressive Damage Modeling of Notched Composite Materials Authors: Mina Shahbazi, and Reza Vaziri Abstract: Damage tolerance analysis of composite structures requires availability of robust and fully validated numerical tools that can capture the onset and extent of damage development in the material and the resulting degradation of the structural stiffness. A reliable prediction of the inelastic behavior of composite materials due to damage requires the simulation of several interactive failure mechanisms e.g. matrix cracking, fibre breakage, splitting and delamination that emanate and grow from pre-‐existing discontinuities such as notches in the material. An enhanced form of a Composite Damage Model (CODAM2) developed at UBC and implemented in the commercial explicit finite element software, LS-‐DYNA, is used here as a tool for modeling progressive damage in composite materials. As a macro-‐mechanical continuum damage model, the constitutive stress-‐strain response of the material is smeared over a finite representative volume element of the laminate made up of repeating sub-‐laminate blocks. The model is capable of accounting for the effects of intra-‐laminar damage mechanisms in individual plies on the stiffness degradation of the laminate. In its local form and through appropriately determined scaling laws the model addresses the issue of strain localization and mesh size dependency observed in modeling strain-‐softening materials. In its non-‐local form, the model is capable of capturing the correct path for damage growth in orthotropic media and is insensitive to the orientation of the finite element mesh.
In this study, double-‐edge-‐notched specimen configuration under tension for a highly orthotropic material layup of [90/0]s will be used. The purpose is to investigate the capability and efficiency of CODAM2 material model as a continuum damage model in capturing the smeared effect of intralaminar damage modes including splitting, matrix cracking and fibre breakage along with the interlaminar damage that occurs in the form of delamination between the layers. Fibre-‐path reconstruction in composites Author: Kyle Farnand Abstract: Fibre misalignments are considered to be some of the most mechanically detrimental defects that arise in modern composites manufacturing. While wrinkling receives most of the research attention due to its detectability, internal waviness often goes unnoticed during quality assessment. Building on the Yurgartis method of quantifying fibre misalignments from ellipse aspect ratios, in-‐plane fibre path reconstruction has been attempted from a single cross sectional micrograph. The results show promising agreement with highly destructive in-‐plane micrographs where improvements to the method are within the realm of possibility. Although microscopy is an expensive process, an automated form of this waviness quantification method could easily be implemented in manufacturing facilities where microscopy is routinely performed.
Poster Abstracts (Abstracts Presented exclusively as posters)
Effects of carbon on phosphorus diffusion in SiGe:C and the implications on phosphorus diffusion mechanisms Author: Yiheng Lin Abtract: The use of carbon (C) in SiGe base layers is an important approach to control the base layer dopant phosphorus (P) diffusion, and thus enhance PNP heterojunction bipolar transistor (HBT) performance. We performed experiments to quantitatively investigate the carbon impacts on P diffusion in Si0.82Ge0.18:C and Si:C under rapid thermal anneal conditions. The carbon molar fraction is up to 0.32%. The results showed that the carbon retardation effect on P diffusion is less effective for Si0.82Ge0.18:C than for Si:C. In Si0.82Ge0.18:C, there is an optimum carbon content at around 0.05% to 0.1%, beyond which more carbon incorporation does not retard P diffusion any more. This behaviour is different from the P diffusion behavior in Si:C and the B in Si:C and low Ge SiGe:C, which can be explained by the decreased interstitial-‐mediated diffusion from 1to 0.95 as Ge content increases from 0 to 18%. Empirical models were established to calculate the time-‐averaged point defect concentrations and effective diffusivities as a function of carbon, and was shown to agree with previous studies on boron, phosphorus, arsenic and antimony diffusion with carbon. Bandedge optical properties of MBE grown GaAsBi films measured by photoluminescence and photothermal deflection spectroscopy Authors: J.J. Andrews, M. Beaudoin, V. Bahrami-‐Yekta, R.B. Lewis, M. Masnadi-‐Shirazi, S.K. O’Leary, T. Tiedje
Abstract: The semiconductor alloy, GaAsBi, has become a focus of attention due to its interesting material properties and its potential for electronic and optoelectronic devices. With the addition of small amounts of bismuth, the energy gap of the material decreases significantly. This dramatic reduction in the energy gap points to the potential use of this material for long-‐wavelength optoelectronic device applications. This low energy gap also suggests use for solar cell applications. Adding an extra junction with a band gap of around 1eV could increase efficiency, absorbing otherwise unabsorbed regions of the solar spectrum. The band edge optical properties of GaAsBi films, as thick as 470 nm, with Bi content varying from 0.7% Bi to 2.8% Bi grown by molecular beam epitaxy on GaAs substrates are measured by mirage effect photothermal deflection spectroscopy (PDS), and compared to the photoluminescence (PL) spectra. PDS is a very powerful technique to measure low absorptions in thin films and holds advantages over the more common transmission spectroscopy. Transmission is unable to distinguish between light that is absorbed or scattered, while PDS only measures the light that is absorbed because this is what causes the thermal effects.
The PDS spectra were fit with a modified Fernelius model, which takes into account multiple reflections within the GaAsBi layer and GaAs substrate. Three undoped samples and two samples that are degenerately doped with silicon are studied. The undoped samples show a clear Urbach absorption edge with a composition dependent bandgap that decreases by 56 meV/% Bi and a composition independent Urbach slope parameter of 25 meV due to absorption by Bi cluster states near the valence band. IN-‐SITU EVALUATION OF THE HCP TO BCC TRANSFORMATION IN COMMERCIALLY PURE TITANIUM USING LASER ULTRASONICS Authors: Alyssa Shinbine, Thomas Garcin and Chad. Sinclair Abstract: Titanium and titanium alloys are critical materials for structural applications in aerospace, biomedical, energy and marine industries. Given the complex phase transformations that can occur in titanium alloys, and the importance of processing on the microstructure and final properties of parts, techniques that allow for in-‐situ monitoring of microstructure and its evolution with processing are valuable. Laser Ultrasonics for Metallurgy (LUMet) is a technology specifically dedicated to the real time sensing of metallurgical phenomena. While this technology has been shown to be reliable for monitoring the fcc to bcc transformation in steels [1], it has rarely been used to study phase transformations in non-‐ferrous alloys. In this work, LUMet is used to examine the hcp (α) to bcc (β) phase transformation in commercially pure titanium. In particular, the evolution of the longitudinal wave velocity is studied in a polycrystalline sample. As the bulk elastic properties of the material evolve during the phase transformation, the variation of ultrasound velocity can potentially be used to extract quantitative information on the transformation kinetics. In this study, a pre-‐annealed sheet of commercially pure titanium is sectioned to produce specimens 60 x 10 x 3 mm in size. The material is graded at 99.95 wt %, with the remaining impurities consisting of Fe, O, H and N. The longitudinal velocity is measured during continuous heating and cooling at a rate of 3°C/s with a peak temperature of 1000 °C. Treatments are conducted in a Gleeble 3500 thermomechanical simulator equipped with the LUMet system. The samples are further analyzed with ex-‐situ backscatter electron imaging (BEI) and electron backscatter diffraction (EBSD) observations in order to evaluate microstructure and crystallographic texture before and after a transformation cycle. Figure 1 (a) shows the inverse pole figure map of the as received sample measured with EBSD. The microstructure is composed of polygonal grains with an equivalent area diameter of 57 μm. This material exhibits a strong basal texture, split around the rolling direction. Figure 1 (b) shows the microstructure of the sample after completion of the first treatment at 1000°C. The first cycling around the transformation lead to the formation of plate like and serrated α grains. Figure 1 (c) shows the microstructure of the sample after five temperature cycles between 700°C and 950°C at a rate of 3°C/s. A similar but larger grained microstructure to Figure 1 (b) is observed after five cycles. Quantitative analysis of the specimen texture for sample shown in Figure 1 (b) and 1 (c) is challenging due to the presence of large grains inhibiting appropriate statistics. Figure 2 (a), (b), (c) shows the variation of ultrasonic velocity measured upon heating for the first, second and fifth cycle, respectively. The velocity measured for the α phase decreases linearly with temperature up to approximately 870°C. The velocity for the β phase shows no measurable temperature dependence up to 1000°C. During the transformation, the changes in velocity vary from non-‐monotonic to monotonic behavior depending on the number of heating cycles. Specifically, the
velocity measured during the first cycle shows a clear two-‐step transition in the transformation temperature range; conversely, the velocity measured during the fifth cycle shows a continuous and monotonic decrease within the transformation domain. It is argued that the observed non-‐monotonic evolution of the velocity may be attributable to crystallographic texture and the anisotropy of elastic properties in the α phase. This idea can be shown qualitatively by calculating the ultrasound velocity in the rolling direction based on the average texture of the α and β phases measured experimentally from Figure 1: i) When all the crystallographic variants of alpha are present in the parent structure transform simultaneously, then a linear dependence of velocity and fraction transformed is predicted; ii) when however, the selection of which variants of the α and β phases form depends on the fraction transformed, then a non-‐linear behavior can be observed. As an illustration, Figure 2 (d) shows the predicted velocity change during the transformation when the α phase is transformed starting first with high velocity orientations. From the texture measured before the first cycle (Figure 1 (a)), a non-‐monotonic velocity variation is predicted by the model; however, when the texture of the material after 5 cycles is used, no such effect is observed. This observation will be discussed with reference to existing ideas of variant selection in titanium alloys.
(a) (b) (c)
(d)
Figure 1. Inverse pole figure maps of the α (hcp) phase with legend (d), for the (a) as received condition, (b) after the first cycle of treatment, and (c) after the fifth cycle of treatment
Figure 2. heating velocity profiles of commercially pure titanium treated to 950°C during the first (a), second (b), and fifth (c) treatment cycles, (d) average velocity profile calculated independent of temperature dependence (model) for the first (1x) and fifth cycle (5x) [1]. Militzer, Matthias, Thomas Garcin, and Warren J. Poole. “In-‐situ Measurements of Grain Growth and Recrystallization by Laser Ultrasonics.” Materials Science Forum 753 (March 2013): 25–30. doi: 10.4028/www.scientific.net/MSF.753.25. FABRICATION AND TESTING OF PIEZOELECTRIC HYBRID PAPER FOR SENSING APPLICATIONS Authors: Suresha K. Mahadeva, Konrad Walus and Boris Stoeber Wood cellulose is the most encountered and an abundant natural organic material; Canada in particular is the home of a strong pulp and paper industry, and is also the largest producer of wood cellulose fibre. Imparting special functionality into wood cellulose would be interesting and hence could be used as a low-‐cost functional material to develop sensing devices. In recent years, many researchers have developed piezoelectric paper through (i) a hydrothermal synthesis route, and (ii) wood fiber functionalization, and demonstrated applications of piezoelectric paper to strain sensing, electronic devices, energy harvesting, and a touch pad. Hydrothermal synthesis involves immersion of a paper substrate in a reaction bath for a specific duration, leading to the growth of zinc oxide nanostructures, while wood fiber functionalization involves embedding nanostructured barium titanate (BaTiO3) into a stable matrix of wood fibers during the paper making process. Former technique present challenges to the scalable mass production of such paper, while latter suffer from poor mechanical and piezoelectric properties; paper with significant piezoelectric properties and high mechanical strength has never been realized to best of our knowledge. Herein we describe fabrication process for hybrid paper that has a large piezoelectric coefficient (d33= 45.7±4.2 pC/N) and tensile properties (breaking strength =1.55N/mm2), similar to commercial printing paper. We employed a layer-‐by-‐layer approach to functionalize the wood fibers, which involve immersion of wood fibers in aqueous solution of poly (diallyldimethylammonium chloride); PDDA(+) and poly (sodium 4-‐styrenesulfonate); PSS (-‐) and once again in PDDA (+), and results in the creation of a positively
charged surface on wood fiber. The treated wood fibers are then immersed in a BaTiO3 (barium titanate) suspension, leading to the electrostatic binding of BaTiO3. The next step involves the activation of BaTiO3 functionalized wood fibers in a suspension of commercially available paper-‐strength-‐enhancing additive (sodium carboxymethylcellulose: CMC) with a range of concentrations (0, 2, 3, 4, 5, and 6 wt%) over 10 hours. This step ensures a uniform coating of CMC over the BaTiO3 functionalized wood fibers and results in improved fiber-‐fiber bonding. Paper hand sheets (f=16 cm) are made according to the TAPPI method T-‐205. Finally hybrid paper is subjected to corona poling to render it piezoelectric. The piezoelectric paper was subjected to electrochemical tests to evaluate its piezoelectric behavior, for that, a compressive load (from 0.5 N to 3 N to 0.5 N in steps of 0.5 N) was applied to a sample and the corresponding charge induced by the paper was measured using a charge meter. The piezoelectric coefficient d33 of the hybrid paper is found to be 45.7±4.2 pC/N. To demonstrate the physical sensing capability of our piezoelectric paper, silver electrodes were deposited on both sides of the paper and the response of the paper to pressure from a finger was measured. The magnitude of the charge induced by the paper is highly dependent on the dynamics of the force exerted in each touch event. The correlation between the induced piezoelectric charge and the magnitude of the tactile force on the sensors is high with R2 = 0.893. The rapid decay of the charge signal is indicative of charge leakage to force application at different speeds. Our study suggests that the piezoelectric paper may be a promising low cost and environment-‐friendly substrate for building various physical sensors, and just as for other piezoelectric materials, its strength might be in capturing highly dynamic events. Melting of Solids in Liquid Titanium during Electron Beam Melting Authors: Jun Ou, Steve L. Cockcroft, Daan M. Maijer, Ainul Akhtar, Lu Yao, Carl Reilly Abstract: One of the defects associated with Electron Beam Cold Hearth Melting (EBCHM) of Al-‐bearing titanium alloys is the Al-‐rich regions, which are harmful to the material’s fatigue performance and deformability. One of the main causes of these defects is condensate falling into the melt – referred to as a “drop-‐in” event industrially. The condensate consists of Al and Ti, evaporated from the melt, which has condensed on the furnace/mould walls. This work is focused on understanding the melting kinetics of condensate in liquid titanium. The work supports the melt processing of Ti407 alloy, recently patented alloy developed by Titanium Metals Corporation (TIMET). This alloy has been designed specifically to produce the fan blade casing for the Rolls-‐Royce Trent XWB engine. The fan casings purpose is to contain the debris that can be generated when a fan blade fails, and therefore, it is a critical part of airplane engine for protecting passengers. In this work the melting of commercial pure titanium (CP-‐Ti) and synthetic condensate (Ti-‐Al) in liquid titanium has been investigated with the aid of the Electron Beam Button Furnace located in AMPLE. The results show that the liquid titanium initially freezes onto the cold solid to form a shell when it was immersed into the liquid in both cases (CP-‐Ti and Ti-‐Al). This resulted in the formation of a solid/solid interface, which results in a significant resistance for heat transfer. Afterwards, in the CP-‐Ti case, the frozen titanium melted followed by melting of the rod. However, in the Ti-‐Al case, melting of the Ti-‐Al solid occurred prior to the melting of the shell since the Ti-‐Al has a lower melting temperature than the shell. After the melting, sub-‐shell boiling of the liquid Ti-‐Al occurred which significantly affected the heat transfer and melting behavior – the Ti-‐Al solid was heated up in a much slower rate comparing to the CP-‐Ti; and additionally, the shell formed in the Ti-‐Al case was much more persistent than that formed in the CP-‐Ti case.
Selective attachment of fluorescent dye molecules to Au nanorods using DNA linkers Authors: Jonathan Massey-‐Allard, Elizabeth Fisher, Kaylyn Leung, Dan Bizzotto and Jeff F. Young Abstract: Surface plasmon resonances supported by noble metal nanoparticles can drastically enhance both the excitation and emission of nearby quantum emitters. The effect is extremely sensitive to the emitter's location relative to the nanoparticle's surface. This motivates the development of a reliable technique for the co-‐localization of quantum emitters and noble metal nanoparticles with nanometer precision. Here we report on our progress using an electroless process to selectively attach a fluorescent dye molecule to the (111) surface on the ends of Au nanorods using functionalized DNA linkers. Theoretical predictions of the excitation and emission enhancements for various coupling lengths between the dye molecule and the nanorods are also discussed. Developing a knowledge framework to sustainably transform composites manufacturing design practice Author: Janna Fabris Abstract: The insertion of advanced composites is an excellent example of a promising technology threatened by manufacturing risk. This risk is represented by design uncertainty: inherent variability in materials and process (aleatoric); and a lack of understanding root causes of this variability (epistemic). Consequently, composite manufacturers cope inadequately with unanticipated manufacturing challenges and late engineering design changes. Whilst most research effort is spent understanding the processing physics (science / knowledge) and developing predictive simulation tools (technology); the use of knowledge to prompt intelligent decision making (workflow / practice) is often overlooked. To explicitly manage this gap, my work aims to establish a knowledge framework called Knowledge in Practice. The goal is to systematically integrate the creation and application of composites manufacturing knowledge to prompt composites manufacturing experts; train new and future engineers; and educate supply chains. We believe that protecting, advancing and disrupting composites manufacturing knowledge is the necessary next step to sustainably transform composites manufacturing design practice and thus address composites manufacturing risk. In this rapid-‐fire presentation I will demonstrate the Knowledge in Practice approach with Thermal Management examples of protecting, advancing and disrupting composites manufacturing design practice. A RATE-‐TYPE CRYSTALLIZATION KINETICS MODEL FOR PROCESS MODELLING OF CARBON FIBRE PEEK MATRIX COMPOSITES Authors: Kamyar Gordnian and Anoush Poursartip ABSTRACT: Process models of composite materials are highly useful tools for understanding the effects of process variables and parameters on the dimensional changes and residual stresses in the final product. By using process models, optimal process conditions are ensured and production risks and costs are minimized. Process modeling platforms, using sub-‐model or modular approach are well established and
are widely being used for thermoset composites. These sub-‐models include thermochemical, flow, void and stress. In recent years, there have been attempts at manufacturing primary aircraft structures such as fuselage panels from thermoplastic composites. Processing of thermoplastic composites involves heating up of the material beyond melting temperature, forming and then cooling down using different temperature profiles. Whilst cooling down, the material crystallizes and modulus builds up. The same sub-‐model approach can be followed for process modeling of thermoplastic composites. The main component of thermochemical sub-‐model for thermoplastics is the crystallization kinetics model. Different isothermal and constant cooling rate non-‐isothermal crystallization models are available in the literature. In this study, we investigate the crystallization behavior of AS4/PEEK which is an aerospace class thermoplastic composite. Both isothermal DSC tests at different target temperatures and non-‐isothermal DSC tests at different cooling rates are conducted on melted AS4/PEEK tape. Experimental results from different tests indicate that the rate of crystallization is only a function of state of transformation, i.e., the temperature and degree of crystallinity, and not the thermal history. Also the results show the existence of an incubation period or induction time. For induction time in isothermal crystallization, a simple empirical model is adopted from the literature and calibrated with the experimental results. This model together with the additivity rule is used for prediction of induction time for an arbitrary temperature profile. The rate of crystallization equation and the induction time model are used for prediction of degree of crystallinity at each time instant during processing of AS4/PEEK composites. The experimental results are in good agreement with the model’s predictions. Experimental determination of band structure, superconducting gap, and electronic correlations on LiFeAs. Authors: G. Levy, R. Szedlak, S. Chi, G. Hodgson, B. Ludbrook, C. Veenstra, R. Comin, Z.-‐H. Zhu, J.A. Rosen, R. Sutarto, A. Radi, R. Liang, W.N. Hardy, D.A. Bonn, I.S. Elfimov, G.A. Sawatzky, A. Damascelli Abstract: We performed angle-‐resolved photoemission spectroscopy experiments (ARPES) on LiFeAs single crystals. The absence of a polar surface or surface reconstruction, as evidenced experimentally by low energy electron diffraction (LEED) technique, makes LiFeAs an ideal system to compare the experimentally determined band structure with ab-‐initio density functional calculations. We will discuss the pitfalls encountered on such a comparison and the different approaches to address it. From this comparison, we determine a band renormalization, which we relate to the strength of the electronic correlations obtained from Auger electron spectroscopy using Cini-‐Sawatzky theory. Once the electronic correlations are determined, we focus on their coupling with bosonic excitations as evidence by kinks on the band dispersion. Lastly, we discuss our observation of the superconducting gap and its evolution along the Fermi surface.
Nanostructure Solid Solution Photocatalyst Synthesis and the Effect of Substrate Material on Photo-‐Induced Charge Separation Authors: Babak Adeli Koudehi and Fariborz Taghipour Abstract: The development of photocatalyst system for solar to chemical energy conversion is a topic of great interest for fundamental and practical importance. Large-‐scale hydrogen production from water can potentially produce clean fuel from renewable resources. The splitting of water into hydrogen and oxygen has been studied extensively over the past decades. However, in the visible light (λ > 400 nm) region, quantum efficiency remains only a few percent or much lower. Among a few visible-‐light activated photocatalysts, GaN:ZnO solid solution demonstrated high activity for overall water splitting, controllable band gap energy, and stability in water splitting reaction condition. However, low surface area and high rate of charge recombination limited the performance of GaN:ZnO. Nanostructure photocatalysts, due to their larger interfacial surface areas than their bulk counterparts, show more efficient electron-‐hole pair separation, and allow tailoring of optical and electrical properties for optimal light absorption and energy transfer. In this work, we developed a cost effective synthesis technique for nanoporous GaN:ZnO, with higher active surface area, comparing to the one synthesized via traditional techniques. Nano-‐porosity on the surface of the sample confirmed through SEM analysis. The prepared photocatalyst incorporated into zeolite as substrate in order to enhance the charge separation. The rate of charge recombination of samples were estimated through photoluminescence spectroscopy (PL) analysis, which indicated the improvement in charge separation via composite preparation
