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Full-Text Articles in Engineering
Vacancy Ordering In Zirconium Carbide With Different Carbon Contents, Yue Zhou, Jeremy Lee Watts, Cheng Li, William Fahrenholtz, Gregory E. Hilmas
Vacancy Ordering In Zirconium Carbide With Different Carbon Contents, Yue Zhou, Jeremy Lee Watts, Cheng Li, William Fahrenholtz, Gregory E. Hilmas
Materials Science and Engineering Faculty Research & Creative Works
Zirconium carbide (ZrCx) ceramics with different carbon contents were prepared by reactive hot-pressing. The rock-salt structure of ZrCx was the only phase detected by x-ray diffraction of the hot pressed ceramics. The relative densities of ZrCx decreased as carbon content increased, in general. The actual carbon contents were measured by completely oxidizing the ZrCx ceramics to ZrO2. For most compositions, the actual carbon contents were higher than nominal batched compositions, presumably due to carbon uptake from the graphite furnace and hot press dies. Selected area electron diffraction and neutron powder diffraction revealed the presence of carbon vacancy ordering …
Conductive 3d Nano-Biohybrid Systems Based On Densified Carbon Nanotube Forests And Living Cells, Roya Bagheri, Alicia K. Ball, Masoud Kasraie, Aparna Chandra, Xinqian Chen, Ibrahim Miskioglu, Zhiying Shan, Parisa Pour Shahid Saeed Abadi
Conductive 3d Nano-Biohybrid Systems Based On Densified Carbon Nanotube Forests And Living Cells, Roya Bagheri, Alicia K. Ball, Masoud Kasraie, Aparna Chandra, Xinqian Chen, Ibrahim Miskioglu, Zhiying Shan, Parisa Pour Shahid Saeed Abadi
Michigan Tech Publications, Part 2
Conductive biohybrid cell-material systems have applications in bioelectronics and biorobotics. To date, conductive scaffolds are limited to those with low electrical conductivity or 2D sheets. Here, 3D biohybrid conductive systems are developed using fibroblasts or cardiomyocytes integrated with carbon nanotube (CNT) forests that are densified due to interactions with a gelatin coating. CNT forest scaffolds with a height range of 120–240 µm and an average electrical conductivity of 0.6 S/cm are developed and shown to be cytocompatible as evidenced from greater than 89% viability measured by live-dead assay on both cells on day 1. The cells spread on top and …
Synthesis, Densification, And Cation Inversion In High Entropy (Co,Cu,Mg,Ni,Zn)Al2o4 Spinel, Cole A. Corlett, Nina Obradovic, Jeremy Lee Watts, Eric W. Bohannan, William Fahrenholtz
Synthesis, Densification, And Cation Inversion In High Entropy (Co,Cu,Mg,Ni,Zn)Al2o4 Spinel, Cole A. Corlett, Nina Obradovic, Jeremy Lee Watts, Eric W. Bohannan, William Fahrenholtz
Materials Science and Engineering Faculty Research & Creative Works
The synthesis, densification behavior, and crystallographic site occupancy were investigated for four different spinel-based ceramics, including a high-entropy spinel (Co0.2Cu0.2Mg0.2Ni0.2 Zn0.2)Al2O4. Each composition was reacted to form a single phase, but analysis of X-ray diffraction patterns revealed differences in cation site occupancy with the high-entropy spinel being nearly fully normal. Densification behavior was investigated and showed that fully dense ceramics could be produced by hot pressing at temperatures as low as 1375°C for all compositions. Vickers' hardness values were at least 10 GPa for all compositions. The …
Final-Stage Densification Kinetics Of Direct Current–Sintered Zrb2, Austin D. Stanfield, Steven M. Smith, Suzana Filipović, Nina Obradović, Vladimir Buljak, Gregory E. Hilmas, William Fahrenholtz
Final-Stage Densification Kinetics Of Direct Current–Sintered Zrb2, Austin D. Stanfield, Steven M. Smith, Suzana Filipović, Nina Obradović, Vladimir Buljak, Gregory E. Hilmas, William Fahrenholtz
Materials Science and Engineering Faculty Research & Creative Works
Final-stage sintering was analyzed for nominally phase pure zirconium diboride synthesized by borothermal reduction of high-purity ZrO2. Analysis was conducted on ZrB2 ceramics with relative densities greater than 90% using the Nabarro–Herring stress–directed vacancy diffusion model. Temperatures of 1900°C or above and an applied uniaxial pressure of 50 MPa were required to fully densify ZrB2 ceramics by direct current sintering. Ram travel data were collected and used to determine the relative density of the specimens during sintering. Specimens sintered between 1900 and 2100°C achieved relative densities greater than 97%, whereas specimens sintered below 1900°C failed to …
Investigation Of Ceramic Firing Processes For Investment Casting Shell Molds, Leonardo Ken Hoaakua Nakamura, Rileigh Anne Cotter
Investigation Of Ceramic Firing Processes For Investment Casting Shell Molds, Leonardo Ken Hoaakua Nakamura, Rileigh Anne Cotter
Materials Engineering
PCC Structurals aims to improve the quality and consistency of their ceramic mold production for their investment casting processes to decrease product loss figures. Although their current production processes result in acceptable quantities of high-quality molds, a significant percentage of defective molds are produced. These defective molds cause appreciable product loss due to casting defects and mold failure. Available literature dictates that high-quality investment casting molds must exhibit fracture strengths within a desired range in order to perform adequately. However, information regarding specific firing procedures which consistently result in ceramic mold strengths within this range is not readily available. To …
Characterizing Non-Linear Structural, Mechanical, And Volumetric Properties Of Aliphatic And Aromatic Thermosets, Brendan Robert Ondra
Characterizing Non-Linear Structural, Mechanical, And Volumetric Properties Of Aliphatic And Aromatic Thermosets, Brendan Robert Ondra
Doctoral Dissertations
A unifying theme throughout this dissertation employs advanced experimental mechanics, including the design and development of new instruments, testing techniques, and analysis strategies. Chapter 1 covers the design and development of a new instrument for polymer and composite characterization. More specifically, a bi-fluidic, confining-fluid, pressurizable dilatometer (referred to herein as the BFCF-PVT). Whereas both classical and contemporary confining-fluid type pressurizable dilatometers utilize a bellows and / or piston system along with a Linear Variable Displacement Transducer to apply pressure and track volume changes, the BFCF-PVT that was designed and built utilizes a fluid-fluid interface (composed of two immiscible fluids that …
Densification Of Ultra-Refractory Transition Metal Diboride Ceramics, William Fahrenholtz, Greg Hilmas, Ruixing Li
Densification Of Ultra-Refractory Transition Metal Diboride Ceramics, William Fahrenholtz, Greg Hilmas, Ruixing Li
Materials Science and Engineering Faculty Research & Creative Works
The densification behavior of transition metal diboride compounds was reviewed with emphasis on ZrB2 and HfB2. These compounds are considered ultra-high temperature ceramics because they have melting temperatures above 3000°C. Densification of transition metal diborides is difficult due to their strong covalent bonding, which results in extremely high melting temperatures and low self-diffusion coefficients. In addition, oxide impurities present on the surface of powder particles promotes coarsening, which further inhibits densification. Studies prior to the 1990s predominantly used hot pressing for densification. Those reports revealed densification mechanisms and identified that oxygen impurity contents below about 0.5 wt% …
A Study Of The Sintering Mechanism Of Pzt-Based Piezoceramics, Wayne Huebner, Pei Wen Lu, Wanrong Xue
A Study Of The Sintering Mechanism Of Pzt-Based Piezoceramics, Wayne Huebner, Pei Wen Lu, Wanrong Xue
Materials Science and Engineering Faculty Research & Creative Works
The densification behavior a PZT-based composition with additions of BiFeO3 as a flux was studied. Two different PZT powders were studied with varying initial particle sizes. Results clearly showed that BiFeO3 forms a low temperature liquid that aids in the densification behavior, with 3 mole% being optimum. Fine particle sizes substantially improved the density at low temperatures, with the net result that ceramics could be densified in air without the aid of a lead source. The corresponding electromechanical properties were typical of a hard PZT formulation.
Correlation Of Wettability And Interfacial Reaction To The Densification And Dielectric Properties Of Fluxed-Batio₃, Sea-Fue Wang, Wayne Huebner, Joseph P. Dougherty
Correlation Of Wettability And Interfacial Reaction To The Densification And Dielectric Properties Of Fluxed-Batio₃, Sea-Fue Wang, Wayne Huebner, Joseph P. Dougherty
Materials Science and Engineering Faculty Research & Creative Works
Reducing the sintering temperature of BaTiO3 has typically been achieved through the use of a fluxing agent to promote densification by liquid phase sintering. Liquid phase formation in these systems is due either to the melting of the flux or to the formation of a eutectic liquid between the flux and BaTiO3. In this paper, the correlation between the wettability and interfacial reactions between fluxes and BaTiO3 with respect to the densification behavior associated with liquid phase sintering, and the resulting dielectric properties is presented. Fluxes used in this study include 5ZnO*2B2O3, 5CdO*2SiO2, Pb5Ge3O11, CuO*TiO2, 3Bi2O3*B2O3, and LiF.