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Missouri University of Science and Technology
Materials Science and Engineering
Materials Science and Engineering Faculty Research & Creative Works
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Articles 1 - 7 of 7
Full-Text Articles in Engineering
Oxygen And Phosphorus Coordination Around Iron In Crystalline Ferric Ferrous Pyrophosphate And Iron-Phosphate Glasses With Uo₂ Or Na₂O, C. H. Booth, P. G. Allen, J. J. Bucher, N. M. Edelstein, D. K. Shuh, G. K. Marasinghe, Mevlüt Karabulut, C. S. Ray, D. E. Day
Oxygen And Phosphorus Coordination Around Iron In Crystalline Ferric Ferrous Pyrophosphate And Iron-Phosphate Glasses With Uo₂ Or Na₂O, C. H. Booth, P. G. Allen, J. J. Bucher, N. M. Edelstein, D. K. Shuh, G. K. Marasinghe, Mevlüt Karabulut, C. S. Ray, D. E. Day
Materials Science and Engineering Faculty Research & Creative Works
Fe K-edge x-ray absorption fine-structure (XAFS) measurements were performed on glass samples of (Fe3O4)0.3(P2O5)0.7 with various amounts of Na2O or UO2. Near-edge and extended-XAFS regions are studied and comparisons are made to several reference compounds. We find that iron in the base glass is ~25% divalent and that the Fe2+ coordination is predominantly octahedral, while Fe3+ sites are roughly split between tetrahedral and octahedral coordinations. Also, we measure roughly one FeñOñP link per iron. Substitution of Na2O or UO2 up to 15 mo1% primarily affects the first FeñO shell. The results are compared to data from the related material Fe3(P2O7)2.
Why Does Ni Suppress Superconductivity In La₁.₈₅Sr₀.₁₅Cu1-YNiYO₄?, Daniel Haskel, Edward A. Stern, Victor Z. Polinger, Fatih Dogan
Why Does Ni Suppress Superconductivity In La₁.₈₅Sr₀.₁₅Cu1-YNiYO₄?, Daniel Haskel, Edward A. Stern, Victor Z. Polinger, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
The role played by Ni impurities in destroying the superconducting state of La2-xSrxCuO4 is still unclear. This is partly due to the lack of clear experimental evidence on the effect of Ni substitution upon the atomic and electronic structure of this cuprate. To provide this information, we performed Ni K-edge polarized XAFS measurements on oriented powder. A special magnetic alignment geometry allowed us to measure pure ĉ and âb-polarized XAFS in identical experimental conditions. We found that the NiO6 octahedra are contracted along the ĉ-axis by 0.16(Å) relative to the CuO6 octahedra in …
Structural Disorder And The Origin Of High-Tc Suppression In La₁.₈₇₅Ba₀.₁₂₅ Cuo4−Δ, Daniel Haskel, Edward A. Stern, Fatih Dogan, Arnie R. Moodenbaugh
Structural Disorder And The Origin Of High-Tc Suppression In La₁.₈₇₅Ba₀.₁₂₅ Cuo4−Δ, Daniel Haskel, Edward A. Stern, Fatih Dogan, Arnie R. Moodenbaugh
Materials Science and Engineering Faculty Research & Creative Works
No abstract provided.
Preparation Of A Zro₂-Al₂O₃ Nanocomposite By High-Pressure Sintering Of Spray-Pyrolyzed Powders, Rajiv S. Mishra, V. Jayaram, B. Majumdar, C. E. Lesher, A. K. Mukherjee
Preparation Of A Zro₂-Al₂O₃ Nanocomposite By High-Pressure Sintering Of Spray-Pyrolyzed Powders, Rajiv S. Mishra, V. Jayaram, B. Majumdar, C. E. Lesher, A. K. Mukherjee
Materials Science and Engineering Faculty Research & Creative Works
ZrO2-Al2O3 powders were synthesized by spray pyrolysis. These powders were sintered at 1 GPa in the temperature range of 700Ç1100 ÉC. The microstructural evolution and densification are reported in this paper. The application of 1 GPa pressure lowers the crystallization temperature from ~850 to 700 ÉC. Similarly, the transformation temperature under 1 GPa pressure for <>g ê a Al2O3 reduces from ~1100 to 700Ç800 ÉC range, and that for t <>ê m ZrO2 reduces from ~1050 to 700Ç800 ÉC range. It was possible to ob-tain highly-dense nanocrystalline ZrO2-Al2O3 composite at temperatures as low as 700 ÉC. The effect of high …
High Breakdown Strength, Multilayer Ceramics For Compact Pulsed Power Applications, Wayne Huebner, Brian L. Gilmore, Shi C. Zhang, Mike L. Krogh, B. C. Schultz, R. C. Pate, L. F. Rinehart, J. M. Lundstrom
High Breakdown Strength, Multilayer Ceramics For Compact Pulsed Power Applications, Wayne Huebner, Brian L. Gilmore, Shi C. Zhang, Mike L. Krogh, B. C. Schultz, R. C. Pate, L. F. Rinehart, J. M. Lundstrom
Materials Science and Engineering Faculty Research & Creative Works
Advanced ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (greater than 10^6/ J/m^3/) and physical size reduction. Initial materials based on slip cast TiO2 exhibited a high bulk breakdown strength (BDS greater than 300 kV/cm) and high permittivity with low dispersion (epsilon approximately equal to 100). However, strong area and thickness dependencies were noted. To increase the BDS, multilayer dielectric compositions are being developed based on glass/TiO2 composites. The addition of glass increases the density (approximately equal to 99.8% theoretical), forms a continuous grain boundary phase, and also …
Measurement Of The Dielectric Strength Of Titanium Dioxide Ceramics, Wayne Huebner, J. M. Lundstrom, L. F. Rinehart, R. C. Pate, T. L. Smith, Mike L. Krogh
Measurement Of The Dielectric Strength Of Titanium Dioxide Ceramics, Wayne Huebner, J. M. Lundstrom, L. F. Rinehart, R. C. Pate, T. L. Smith, Mike L. Krogh
Materials Science and Engineering Faculty Research & Creative Works
Titanium dioxide ceramics (TiO2) are candidate materials for high energy density pulsed power devices. Experiments to quantify the dielectric strength of TiO2 have been performed on a limited number of unoptimized samples. A high voltage test set was constructed to test the titanium dioxide. All samples had a relative dielectric constant of 100, all samples were of 3 mm nominal thickness, and all tests were performed in water dielectric to reduce the effect of the triple point field enhancement at the electrode edge. Both single layer and laminated samples were tested and the breakdown field strengths were recorded. Voltage risetimes …
Preparation Of Phase Homogeneous Mn-Zn Ferrite Powder By Spray Pyrolysis, Xinyu Zhao, Baicun Zheng, Hongchen Gu, Chunzhong Li, Shi C. Zhang, P. D. Ownby
Preparation Of Phase Homogeneous Mn-Zn Ferrite Powder By Spray Pyrolysis, Xinyu Zhao, Baicun Zheng, Hongchen Gu, Chunzhong Li, Shi C. Zhang, P. D. Ownby
Materials Science and Engineering Faculty Research & Creative Works
Two kinds of aqueous precursor solutions are used to synthesize Mn-Zn ferrite powders: (i) nitrate (NO) precursor-derived from solutions of Mn(NO3)2, Zn(NO3)2, and Fe(NO3)3; and (ii) acetate (AC) precursor-derived from solutions of Mn(CH3COOO)2, Zn(CHCH3COOO)2, and Fe(NO3)3. The composition of the powders synthesized from the precursor AC is very uniform, whereas powders derived from the precursor NO have Mn and Zn segregated on the particle surfaces. In addition, the powders synthesized from precursor AC are solid spherical …