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Full-Text Articles in Engineering
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 …
Morphological And Structural Characterization Of Mgal2o4 Spinel, Nina Obradović, Suzana Filipović, William Fahrenholtz, Bojan A. Marinkovic, Jelena Rogan, Steva Lević, Antonije Đorđević, Vladimir B. Pavlović
Morphological And Structural Characterization Of Mgal2o4 Spinel, Nina Obradović, Suzana Filipović, William Fahrenholtz, Bojan A. Marinkovic, Jelena Rogan, Steva Lević, Antonije Đorđević, Vladimir B. Pavlović
Materials Science and Engineering Faculty Research & Creative Works
Magnesium aluminate has the spinel structure along with good mechanical, chemical, and thermal properties. Magnesium aluminate has a wide range of applications including refractory ceramics, optically transparent ceramic windows, and armors. Its low dielectric permeability and low loss tangent enable its applications for integrated electronic devices, as well. In this paper, MgO and Al2O3 powders were mixed in a one-to-one molar ratio and calcined at temperatures ranging from 1500 to 1800o C to produce phase pure spinel. Thereafter, pellets were crushed and treated in a planetary ball mill for 60 min to obtain a fine powder. All …
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 …
Microstructural And Optical Properties Of Mgal2o4 Spinel: Effects Of Mechanical Activation, Y2o3 And Graphene Additions, Nina Obradovic, William Fahrenholtz, Cole Corlett, Suzana Filipovic, Marko Nikolic, Bojan A. Marinkovic, Simone Failla, Diletta Sciti, Daniele Di Rosa, Elisa Sani
Microstructural And Optical Properties Of Mgal2o4 Spinel: Effects Of Mechanical Activation, Y2o3 And Graphene Additions, Nina Obradovic, William Fahrenholtz, Cole Corlett, Suzana Filipovic, Marko Nikolic, Bojan A. Marinkovic, Simone Failla, Diletta Sciti, Daniele Di Rosa, Elisa Sani
Materials Science and Engineering Faculty Research & Creative Works
Magnesium Aluminate and Other Alumina-Based Spinels Attract Attention Due to their High Hardness, High Mechanical Strength, and Low Dielectric Constant. MgAl2O4 Was Produced by a Solid-State Reaction between MgO and Α-Al2O3 Powders. Mechanical Activation for 30 Min in a Planetary Ball Mill Was Used to Increase the Reactivity of Powders. Yttrium Oxide and Graphene Were Added to Prevent Abnormal Grain Growth during Sintering. Samples Were Sintered by Hot Pressing under Vacuum at 1450◦C. Phase Composition and Microstructure of Sintered Specimens Were Characterized by X-Ray Powder Diffraction and Scanning Electron Microscopy. Rietveld Analysis Revealed 100% …
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% …
Characterization Of Mgal₂O₄ Sintered Ceramics, Nina Obradovic, William Fahrenholtz, Suzana Filipovic, Cole Corlett, Pavle Dordevic, Jelena Rogan, Predrag J. Vulic, Vladimir Buljak, Vladimir Pavlovic
Characterization Of Mgal₂O₄ Sintered Ceramics, Nina Obradovic, William Fahrenholtz, Suzana Filipovic, Cole Corlett, Pavle Dordevic, Jelena Rogan, Predrag J. Vulic, Vladimir Buljak, Vladimir Pavlovic
Materials Science and Engineering Faculty Research & Creative Works
Single phase MgAl2O4 was made from a one-to-one molar ratio of MgO and Al2O3 powders mixed using ball-milling. Mixtures of MgO and Al2O3 were subsequently treated in planetary ball mill for 30, 60, 90 and 120 minutes in air. The aim of this study was to examine phase composition, microstructure, and densification behavior of sintered specimens. After sintering in dilatometer at 1500 °C, the powder was converted to single phase MgAl2O4. The results show that mechanical activation improved the densification behavior of MgAl2O4 sintered …
Freeze-Form Extrusion Fabrication Of Functionally Graded Material Composites Using Zirconium Carbide And Tungsten, Ang Li, Aaron S. Thornton, Bradley K. Deuser, Jeremy Lee Watts, Ming-Chuan Leu, Greg Hilmas, Robert G. Landers
Freeze-Form Extrusion Fabrication Of Functionally Graded Material Composites Using Zirconium Carbide And Tungsten, Ang Li, Aaron S. Thornton, Bradley K. Deuser, Jeremy Lee Watts, Ming-Chuan Leu, Greg Hilmas, Robert G. Landers
Materials Science and Engineering Faculty Research & Creative Works
Ultra-high-temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as their oxidation resistance, at temperatures above 2000⁰C. However, their brittleness makes them susceptible to thermal shock failure. As graded composites, components fabricated as functionally-graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGM parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and W were developed …
Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day
Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day
Materials Science and Engineering Faculty Research & Creative Works
There is an increasing demand for synthetic scaffolds with the requisite biocompatibility, internal architecture, and mechanical properties for the bone repair and regeneration. In this work, scaffolds of a silicate bioactive glass (13-93) were prepared by a freeze extrusion fabrication (FEF) method and evaluated in vitro for potential applications in bone repair and regeneration. The process parameters for FEF production of scaffolds with the requisite microstructural characteristics, as well as the mechanical and cell culture response of the scaffolds were evaluated. After binder burnout and sintering (60 min at 700°C), the scaffolds consisted of a dense glass network with interpenetrating …
Pm Manufacturing Research Boosted By Continuous Sintering Furnace, Joseph William Newkirk
Pm Manufacturing Research Boosted By Continuous Sintering Furnace, Joseph William Newkirk
Materials Science and Engineering Faculty Research & Creative Works
University of Missouri-Rolla has recently acquired a Fluidtherm laboratory continuous sintering furnace. Custom designed and built for PM research, the furnace will allow current efforts in sintering development, pressure gas quenching of PM steels, optimisation of toughness and fatigue properties of PM parts, and production of metal matrix composites to be enhanced and extended.
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.
Fabrication Of 2-2 Connectivity Pzt/Thermoplastic Composites For High Frequency Linear Arrays, Wayne Huebner, Mary R. Reidmeyer, L. Busse, Jeffry W. Stevenson
Fabrication Of 2-2 Connectivity Pzt/Thermoplastic Composites For High Frequency Linear Arrays, Wayne Huebner, Mary R. Reidmeyer, L. Busse, Jeffry W. Stevenson
Materials Science and Engineering Faculty Research & Creative Works
An alternate approach for fabricating PZT/polymer composites with 2-2 connectivity with fine scales is described. Thin (less than or equal to 20 micrometers) sintered PZT plates and sheets of a thermoplastic polymer film (less than or equal to 10 micrometers) were bonded together via thermal processing. Stack sintering of tape cast PZT generated the necessary PZT plates, while tape cast polymers were used to control the thermoplastic thickness. Composite blocks were cut to required dimensions for linear arrays, electroded, and poled. Electromechanical properties were measured to evaluate the composites. The significance of this fabrication technique is that it is able …
Grain Size Effect On The Induced Piezoelectric Properties Of 0.9pmn-0.1pt Ceramic, U. Kumar, Wayne Huebner, P. Marsh, H. Kankul, S. F. Wang, Clyde G. Oakley
Grain Size Effect On The Induced Piezoelectric Properties Of 0.9pmn-0.1pt Ceramic, U. Kumar, Wayne Huebner, P. Marsh, H. Kankul, S. F. Wang, Clyde G. Oakley
Materials Science and Engineering Faculty Research & Creative Works
Lead magnesium niobate-lead titanate (Pb(Mg1/3Nb2/3)O3 - PbTiO3 (PT) solid solutions have been widely researched to produce devices that can be used in low- and high-electric-field applications. For some applications, such as medical ultrasonic transducers, it is necessary to prepare the ceramic with high density and small average grain size. The effect of grain size on the low- and high-field properties of 0.9-PMN-0.10-PT ceramics is described in the present work. To prepare highly dense ceramic, vibratory and attrition milled powders were sintered between 1000 and 1250 ⁰C. The average grain sizes of the sintered ceramics …