Suspension HVOF Spraying of Reduced Temperature Solid Oxide Fuel Cell Electrolytes

Peer reviewed: YesNRC publication: Ye

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Modeling renography data and formulating indices for quantitative means in differentiating kidney obstruction

The kidney is an organ essential to the urinary system of a body. It is responsible for blood filtration in getting rid of soluble waste material, while maintaining homeostatic functions in a body. Therefore, knowing the health status of the kidney is very much important in the medical field. A form of imaging technique, known as renography is used to diagnose renal obstruction. Due to the absence of standard procedures being applied in clinical setting for such evaluation, this project aims to look at other non-invasive method that diagnoses renal obstruction. From the quantification of renogram, a standard benchmark evaluation for each severity condition can be provided. Hence, the behavior of tracer flow starting from injection to filtration process and later out from the renal pelvis was modeled through compartmental analysis. With the model, mathematical expressions were developed to form critical index, which was compared with doctor’s clinical evaluations. A numerical benchmark for each severity case could then be determined through the comparisons. The index determined was trained on support vector machine (SVM), random forest and adaboost classifier so as to predict the obstruction level of other kidney samples. The predicted results were compared with actual clinical interpretations to identify the predicting accuracy of the classifiers. The performance of the classifiers was further evaluated by Receiver Operating Characteristic (ROC) to obtain a final preferable decision.Bachelor of Engineering (Mechanical Engineering

Performance characteristics of multi-pocket hydrostatic journal bearing

published_or_final_versionIndustrial EngineeringMasterMaster of Philosoph

Wear resistance of materials used for slurry transport

More and more slurry transport systems are used in mining operations to efficiently and cost-effectively transport ores and tailings. The materials used for slurry transport are often subjected to severe wear attack. In this study, the wear modes and wear resistance of materials commonly used for slurry transport are discussed. Slurry jet erosion, Coriolis slurry scouring erosion and slurry sliding abrasion tests are used to simulate these wear modes and to characterize the wear resistance of the materials. The wear resistance of selected materials from each material category commonly used for slurry transport, including steels, high chromium white cast irons, chrome carbide-based and tungsten carbide-based overlays, elastomers, plastics, ceramics and cermets, are reported. The relationships of the wear resistance of these materials with their mechanical properties are also briefly discussed.Peer reviewed: YesNRC publication: Ye

Effects of processing parameters on microstructures of TiO2 coatings formed on titanium by plasma electrolytic oxidation

Titanium oxide (TiO2) coatings were formed on titanium substrates in a sodium silicate (Na2SiO3) aqueous solution, using plasma electrolytic oxidation method. The effects of duty ratio, frequency, and positive/negative pulse proportion on the microstructure and phase compositions of the coatings were investigated. The coatings were mainly composed of anatase TiO2 plus a little amount of rutile TiO2. The coatings obtained at the frequency range 900\u20132700 Hz, under a duty ratio of 20%, and a positive/negative pulse proportion of 3, showed the best quality in terms of density and adhesion. The effect of positive/negative pulse proportion was relatively small. However, continuous coating could not be obtained using the positive/negative pulse proportion of 1. Compared with that of bare titanium, the property of resistance to corrosion was obviously improved for the titanium with TiO2 coating. The corrosion potential rose about 0.13 V and the corrosion current density decreased about one order of magnitude.Des rev\ueatements d\u2019oxyde de titane (TiO2) ont \ue9t\ue9 form\ue9s sur des substrats de titane dans une solution aqueuse de silicate de sodium (Na2SiO3) en faisant appel \ue0 la m\ue9thode d\u2019oxydation par plasma \ue9lectrolytique. Les effets du facteur de forme, de la fr\ue9quence et de la proportion des impulsions positives/n\ue9gatives appliqu\ue9es \ue0 la microstructure et aux compositions en phase des rev\ueatements ont \ue9t\ue9 \ue9tudi\ue9s. Les rev\ueatements \ue9taient principalement compos\ue9s de TiO2 anatase plus une petite quantit\ue9 de TiO2 rutile. Les rev\ueatements obtenus dans la plage de fr\ue9quences de 900 \ue0 2700 Hz, avec un facteur de forme de 20 % et une proportion d\u2019impulsions positives/n\ue9gatives de 3, ont permis d\u2019obtenir la meilleure qualit\ue9 sur les plans de la densit\ue9 et de l\u2019adh\ue9sion. L\u2019effet de la proportion des impulsions positives/n\ue9gatives \ue9tait relativement faible. Toutefois, il \ue9tait impossible d\u2019obtenir un rev\ueatement continu au moyen de la proportion positives/n\ue9gatives unitaire. Si on la compare avec la r\ue9sistance \ue0 la corrosion du titane nu, on constate qu\u2019elle \ue9tait nettement am\ue9lior\ue9e dans le cas du titane rev\ueatu de TiO2. Le potentiel corrosif s\u2019\ue9levait \ue0 0,13 V et la densit\ue9 du courant corrosif diminuait de pr\ue8s d\u2019un ordre de grandeur.Peer reviewed: YesNRC publication: Ye

Thermal plasma spraying for SOFCs: applications, potential advantages and challenges

In this article, the applications, potential advantages, and challenges of thermal plasma spray (PS) processing for nanopowder production and cell fabrication of solid oxide fuel cells (SOFCs) are reviewed. PS processing creates sufficiently high temperatures to melt all materials fed into the plasma. The heated material can either be quenched into oxide powders or deposited as coatings. This technique has been applied to directly deposit functional layers as well as nanopowder for SOFCs application. In particularly, low melting point and highly active electrodes can be directly fabricated on zirconia-based electrolytes. This is a simple processing technique that does not require the use of organic solvents, offering the opportunity for flexible adjustment of process parameters, and significant time saving in production of the cell and cost reduction compared with tape casting, screen printing and sintering processing steps. Most importantly, PS processing shows strong potential to enable the deposition of metal-supported SOFCs through the integrated fabrication of membrane-electrode assemblies (MEA) on porous metallic substrates with consecutive deposition steps. On the other hand, the application of PS processing to produce SOFCs faces some challenges, such as insufficient porosity of the electrodes, the difficulty of obtaining a thin (<10 \u3bcm) and dense electrolyte layer. Fed with H2 as the fuel gas and oxygen as the oxidant gas, the plasma sprayed cell reached high power densities of 770 mW cm 122 at 900 \ub0C and 430 mW cm 122 at 800 \ub0C at a cell voltage of 0.7 V.NRC publication: Ye

A study on sintering aids for Sm0.2Ce0.8O1.9 electrolyte

In this study, an addition of Co oxide or Cu oxide to Sm0.2Ce0.8O1.9 (SDC) was studied to improve the sinterability of SDC. It has been found that both Co and Cu oxide are very effective as sintering aids, and the SDC sintering temperature can be reduced from 1400 \ub0C without aids to below 1000 \ub0C with only 1 at.% of either Cu oxide or Co oxide. As compared to the pure SDC, a slight decrease of ionic conductivity was observed in SDC with Cu sintering aid. There is no obvious effect on electrochemical property of SDC with Co sintering aid under 2.5 at.%.NRC publication: Ye

Polarization analysis for metal-supported SOFCs from different fabrication processes

Polarization characteristics of metal-supported solid oxide fuel cells, fabricated by pulsed laser deposition and suspension plasma spray, were investigated. With the electrochemical impedance spectroscopy and current\u2013voltage polarization curves, the metal-supported SOFCs were compared and analyzed in terms of their cathode exchange current density, polarization loss and maximum power density over the temperature range of 400\u2013600 \ub0C. The electrochemical mechanism for the linear polarization characteristics observed from the experimental data was addressed. Results from experiments and simulation indicate that fabrication processes and operation temperatures play an important role in the electrochemical mechanism for linear polarization characteristics of metal-supported SOFCs.Peer reviewed: YesNRC publication: Ye

Ba1 12xPrxCo1 12yFeyO3 12delta as cathode materials for low temperature solid oxide fuel cells

Ba1 12xPrxCo1 12yFeyO3 12delta (BPCF) perovskite oxides have been synthesized and investigated as cathode materials for low temperature solid oxide fuel cells (LT-SOFCs). Compared with those of Ba0.5Sr0.5Co0.8Fe0.2O3 12delta (BSCF) and Sm0.5Sr0.5CoO3 (SSCo) cathode materials, BPCF has a lower polarization resistance at decreased temperatures. In particular, Ba0.5Pr0.5Co0.8Fe0.2O3 12delta showed the lowest polarization loss among the different compositions as a cathode material for LT-SOFCs. The area specific resistance (ASR) of Ba0.5Pr0.5Co0.8Fe0.2O3 12delta as a cathode material is 0.70 and 0.18 Omega cm2 at 500 \u25e6C and 550 \u25e6C, respectively. The maximum power density of the cell BPCF/SDC/Ni\u2013SDC with humidified hydrogen as fuel and air as oxidant reaches 860mWcm 122 at 650 \u25e6C.Des oxydes p\ue9rovskites Ba1 12xPrxCo1 12yFeyO3 12delta (BPCF) ont \ue9t\ue9 synth\ue9tis\ue9s et \ue9tudi\ue9s comme mat\ue9riaux de cathode pour des piles \ue0 combustible \ue0 oxyde solide \ue0 basse temp\ue9rature (LT SOFC) [low temperature solid oxide fuel cell]. Comparativement aux mat\ue9riaux de cathode Ba0,5Sr0,5Co0,8Fe0,2O3 12delta (BSCF) et Sm0,5Sr0,5CoO3 (SSCo), l\u2019oxyde BPCF poss\ue8de une r\ue9sistance de polarisation plus faible dans des conditions de basse temp\ue9rature. En particulier, le Ba0,5Pr0,5Co0,8Fe0,2O3 12delta a montr\ue9 la perte de polarisation la plus faible parmi les diff\ue9rentes compositions utilis\ue9es comme mat\ue9riau de cathode pour les LT SOFC. La r\ue9sistance sp\ue9cifique de surface du Ba0,5Pr0,5Co0,8Fe0,2O3 12delta comme mat\ue9riau de cathode est de 0,70 Omega cm2 \ue0 500 \u25e6C et de 0,18 Omega cm2 \ue0 550 \u25e6C. La densit\ue9 de puissance maximale de la pile BPCF/SDC/Ni SDC qui utilise l\u2019hydrog\ue8ne humidifi\ue9 comme combustible et l\u2019air comme oxydant atteint 860 mW/cm2 \ue0 650 \u25e6C.Peer reviewed: YesNRC publication: Ye