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Research Articles and Materials (Chemical and Materials Engineering)

This collection houses journal articles and other research material produced by the Department of Chemical and Materials Engineering.
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  1. Quantification of Dendritic and Eutectic Nucleation Undercooling in Rapidly Solidified Hypo-Eutectic Al-Cu Droplets [Download]

    Title: Quantification of Dendritic and Eutectic Nucleation Undercooling in Rapidly Solidified Hypo-Eutectic Al-Cu Droplets
    Creator: A-A. Bogno
    Description: This paper reports on the quantification of primary dendritic and eutectic nucleation undercoolings during rapid solidification of impulse atomized hypo-eutectic Al-Cu droplets. The procedure consists in determining the eutectic fraction of each investigated droplet from the fraction of intermetallic Al2Cu obtained by Rietveld refinement analysis of neutrons scattering data. The corresponding eutectic nucleation undercooling is then deduced from the metastable phase diagram of the alloy. The dendritic nucleation undercooling is subsequently determined using semi-empirical coarsening models of secondary dendrite arms. The two nucleation undercoolings are finally used as input variables to run a microsegregation model for binary alloys. The fractions of eutectic computed by the microsegregation model compare very favourably with the experimental results.
    Subjects: Impulse Atomization, Rapid Solidification, Aluminum-Copper, Undercooling, Microsegregation, Neutron Diffraction, Thermodynamic Equilibrium Calculations, Coarsening
    Date Created: 2016
  2. Characterization of Dendrite Morphologies in Rapidly Solidified Al-4.5wt.%Cu Droplets [Download]

    Title: Characterization of Dendrite Morphologies in Rapidly Solidified Al-4.5wt.%Cu Droplets
    Creator: M. Bedel
    Description: The Impulse Atomization process developed at the University of Alberta (Canada) enables metallic powders to be solidified with well controlled process parameters. The inner microstructure of several droplets of Al-4.5wt.%Cu alloy produced by this technique has been investigated by using both synchrotron X-ray micro-tomography and electron backscattered diffraction (EBSD). The 3D reconstructions obtained by micro-tomography are used to visualize cross sections of the droplets in any spacial directions. A wide range of dendrite morphologies are observed for different droplets of similar diameter and produced in the same batch. Microstructural features indicate that the development of the dendrite arms (primary and of higher orders) occurs in most droplets along <111> crystallographic axes. This was unexpected as <100> directions are observed in conventional casting technologies. EBSD measurements were carried out on a selection of representative droplets after their characterization by synchrotron X-ray micro-tomography. Results confirm that most of the droplets are single grains and the relationship between the dendrite growth directions and the crystal orientation is determined unambiguously. Moreover, the large number of droplets analyzed by micro-tomography enabled a statistical analysis of the dendrite morphology as a function of droplet size and cooling atmosphere. The impact of different processing parameters on the final distribution of dendrite morphologies is also discussed.
    Subjects: Rapid Solidification, Impulse Atomization, Synchrotron X-ray Micro-Tomography, Electron Backscattered Diffraction, Dendrite Morphology
    Date Created: 2016
  3. Microstructure and Mechanical Characterization of Rapidly Solidified Cr-C Tool Steel - Annealing Effects [Download]

    Title: Microstructure and Mechanical Characterization of Rapidly Solidified Cr-C Tool Steel - Annealing Effects
    Creator: P. Delshad Khatibi
    Description: The effect of isochronal annealing on D2 tool steel powder, rapidly solidified via both Impulse Atomization and Water Atomization, has been evaluated using high-resolution scanning electron microscopy and Vickers microhardness. The amount of supersaturation of the alloying elements inside the retained austenite phase as a function of eutectic undercooling was calculated. The fraction of austenite transformed to ferrite at different annealing temperatures (from 350°C to 810°C) was also determined, using Rietveld analysis. The results show that although the particles with larger eutectic undercooling have larger supersaturation of alloying elements within the retained austenite phase, they have a smaller fraction of austenite to ferrite transformation at the temperature in which transformation starts. The maximum hardness was achieved at an annealing temperature of 550°C, due to the formation of fine and well-distributed carbides.
    Subjects: Tool Steel, Powder Processing, Retained Austenite, Microstructure, Rapid Solidification
    Date Created: 2016
  4. Amorphous Phase Formation Analysis of Rapidly Solidified CoCr Droplets [Download]

    Title: Amorphous Phase Formation Analysis of Rapidly Solidified CoCr Droplets
    Creator: A.-A. Bogno
    Description: This paper investigates amorphous phase formation and rapid solidification characteristics of a CoCr alloy. High cooling rate and high undercooling-induced rapid solidification of the alloy was achieved by impulse atomization in helium atmosphere. Two atomization experiments were carried out to generate powders of a wide size range from liquid CoCr at two different temperatures. Amorphous fraction and kinetic crystallization properties of impulse atomized powders were systematically quantified by means of differential scanning calorimetry. In addition, different but complementary characterization tools were used to analyze the powders microstructures. The fraction of amorphous phase within the investigated powders is found to be promoted by high cooling rate or smaller powder size. The critical cooling rate for amorphous phase formation, which is influenced by the oxygen content in the melt, is found to be ~3×104 Ks-1 and corresponds to a 160-µm-diameter powder atomized in helium. Hardness of the powders is found to follow a trend that is described by the Hall–Petch relation when a relatively high fraction of crystalline structures is present and decreases with the fraction of amorphous phase.
    Subjects: Atomization, Rapid Solidification, Co-based Alloys, Bulk Metallic Glasses, Crystallinity, High Entropy Alloys
    Date Created: 2016
  5. Characterization of a {(Fe60Co40)75B20Si5}96Nb4 Impulse Atomized Glassy Powder by Neutron Diffraction and Differential Scanning Calorimetry [Download]

    Title: Characterization of a {(Fe60Co40)75B20Si5}96Nb4 Impulse Atomized Glassy Powder by Neutron Diffraction and Differential Scanning Calorimetry
    Creator: A.-A. Bogno
    Description: This paper investigates FeCo-based alloy glass formability by high undercooling and high cooling rate solidification technique and the hardness evaluation of the generated samples. For this investigation, Impulse Atomization was used to generate {(Fe60Co40)75B20Si5}96Nb4 powders of different sizes that correspond to different cooling rates and undercoolings. The amorphous fraction and kinetic crystallization properties of the investigated powders were determined by means of Differential Scanning Calorimetry and Neutron Diffraction. The enthalpy of crystallization of a close to amorphous powder produced by gas atomization was used as a reference for the calculation of amorphous fraction by calorimetry in atomized powders. Thus, a quantitative estimation of cooling rate corresponding to each powder size and the variation of amorphous fraction with cooling rate are presented. Higher cooling rate promoted by smaller powder size and helium atomization atmosphere is found to yield higher amorphous fraction. At relatively high cooling rates Neutron Diffraction technique yields higher amorphous fractions than the Differential Scanning Calorimetry technique. The critical cooling rate for amorphous phase formation under unconstrained solidification conditions using Impulse Atomization is found to be ~15,000Ks-1 which corresponds to a powder size of about 100 μm atomized in nitrogen or about 200 μm atomized in helium.
    Subjects: Impulse Atomization, Rapid Solidification, Iron Cobalt, Bulk Metallic Glasses, Calorimetry, Calorimetry, Neutron Diffraction
    Date Created: 2015
  6. Estimation of Droplet Size and Temperature at which Solidification starts in a Drop Tube-Impulse System. [Download]

    Title: Estimation of Droplet Size and Temperature at which Solidification starts in a Drop Tube-Impulse System.
    Creator: P. Delshad Khatibi
    Description: D2 tool steel powders were produced using a drop tube-impulse atomization technique. In order to measure the radiant energy and droplet size of atomized D2 steel droplets, DPV-2000 (Tecnar Automation Ltée, St. Hubert Quebec, Canada) was utilized. In-situ velocity and droplet size of the atomized droplets were also measured using shadowgraphy technique (Sizing Master Shadow from LaVision GmbH in Gottingen, Germany). A 3D translation stage was designed, constructed and installed inside the drop tube system. DPV-2000 and shadowgraph were then mounted on the translation stage. Using this stage, online measurements were conducted at 4 cm, 18 cm and 28 cm distances below the crucible. Using liquid (fully undercooled) and semi-solid behavior of droplets, it was possible to estimate the droplet size and temperature at which solidification starts. These values were then confirmed by the thermal model using experimentally estimated primary phase undercooling values. It was concluded that DPV-2000 is not accurate enough to detect the amount of recalescence during solidification of the droplets as they fall. But, comparing to the results from the heat loss model, reasonable estimates were obtained for different particle sizes solidifying at different distances using online measurement tools.
    Subjects: Atomization, Rapid Solidification, Undercooling, In-situ Measurements, Heat Transfer
    Date Created: 2016
  7. Demulsifier Performance in Diluted Bitumen De-watering: Effects of Mixing and Demulsifier Dosage [Download]

    Title: Demulsifier Performance in Diluted Bitumen De-watering: Effects of Mixing and Demulsifier Dosage
    Creator: Chong, Jeng Y.
    Description: Mixing conditions were explored as a possible avenue for improvement of demulsifier performance in solvent diluted bitumen de-watering process. The effects of demulsifier bulk concentration, demulsifier injection concentration and mixing energy on water and solids removal from the oil phase were tested. All of the experiments were carried out in a confined impeller stirred tank (CIST), which provides well characterized mixing conditions and relatively uniform flow and turbulence. Results showed that lowering the injection concentration and increasing the mixing energy both improve demulsifier performance, allowing a 50% drop in the bulk concentration of demulsifier. This result agrees well with an earlier study by Laplante, et al. where a different demulsifier was investigated. In that study, it was shown that the product of mixing time and energy dissipation rate at the feed point (the mixing energy = J) provides an alternate mixing variable.
    Subjects: Diluted Bitumen, Demulsifier, Mixing Energy, Meso-mixing, De-watering, CIST
    Date Created: 2016/10/02
  8. Errata to Organ Preservation Alliance’s Organ Banking Summit abstracts as published in Cryobiology Volume 71 (1) 2015 [Download]

    Title: Errata to Organ Preservation Alliance’s Organ Banking Summit abstracts as published in Cryobiology Volume 71 (1) 2015
    Creator: Elliott, J.A.W.
    Subjects: Erratum, Error, Priority Journal, Cryopreservation, Organ Preservation
    Date Created: 2015/08/28
  9. Cryopreserved amniotic membrane as transplant allograft: viability and post-transplant outcome [Download]

    Title: Cryopreserved amniotic membrane as transplant allograft: viability and post-transplant outcome
    Creator: Perepelkin, N.M.J.
    Description: Amniotic membrane (AM) transplantation is increasingly used in ophthalmological and dermatological surgeries to promote re-epithelialization and wound healing. Biologically active cells in the epithelial and stromal layers deliver growth factors and cytokines with anti-inflammatory, anti-bacterial, anti-immunogenic and anti-fibrotic properties. In this work, confocal microscopy was used to show that our cryopreservation protocol for AM yielded viable cells in both the stromal and epithelial layers with favorable post-transplant outcome. AM was obtained from Caesarean-section placenta, processed into allograft pieces of different sizes (3 cm × 3 cm, 5 cm × 5 cm, and 10 cm × 10 cm) and cryopreserved in 10 % dimethyl sulfoxide using non-linear controlled rate freezing. Post-thaw cell viability in the entire piece of AM and in the stromal and epithelial cell layers was assessed using a dual fluorescent nuclear dye and compared to hypothermically stored AM, while surveys from surgical end-users provided information on post-transplant patient outcomes. There was no significant statistical difference in the cell viability in the entire piece, epithelial and stromal layers regardless of the size of allograft piece (p = 0.092, 0.188 and 0.581, respectively), and in the entire piece and stromal layer of hypothermically stored versus cryopreserved AM (p = 0.054 and 0.646, respectively). Surgical end-user feedback (n = 49) indicated that 16.3 % of AM allografts were excellent and 61.2 % were satisfactory. These results support the expanded clinical use of different sizes of cryopreserved AM allografts and address the issue of orientation of the AM during transplant for the treatment of dermatological defects and ocular surface disorders.
    Subjects: Amniotic membrane, Cryobiology, Cryopreservation, Dermal surgery, Epithelium, Ocular surgery, Stroma, Tissue transplantation
    Date Created: 2015/9/11
  10. Cryoprotectant agent toxicity in porcine articular chondrocytes. [Download]

    Title: Cryoprotectant agent toxicity in porcine articular chondrocytes.
    Creator: Jomha, N. M.
    Description: Large articular cartilage defects have proven difficult to treat and often result in osteoarthritis of the affected joint. Cryopreservation of articular cartilage can provide an increased supply of tissues for osteochondral allograft but cryoprotective agents are required; however, few studies have been performed on the toxicity of these agents. This study was designed to determine the order of toxicity of five commonly used cryoprotectant agents as well as interactions that occur between them. Isolated porcine articular chondrocytes were exposed to individual cryoprotectant agents and combinations of these agents at 1 M and 3 M concentrations for 5 min and 120 min. Cell viability was determined using membrane integrity dyes and a metabolic activity assay. Subsequently, a regression analysis based study was undertaken to extract the maximum amount of information from this data. Results of this study demonstrated that all 1 M solutions were minimally toxic. The 3 M solutions demonstrated varying toxicity after 120 min. Ethylene glycol and glycerol were less toxic than propylene glycol, dimethyl sulfoxide, and formamide. Combinations of cryoprotectant agents were less toxic than single cryoprotectant agents at the same concentration. This is the most comprehensive study investigating cryoprotectant agent toxicity in articular chondrocytes and has resulted in important information regarding the order of toxicity and interactions that occur between these agents.
    Subjects: statistical analysis, viability, chondrocytes, articular cartilage, cryoprotectant agents, porcine, cryopreservation
    Date Created: 2010