Showing papers by "Patrick S. Nicholson published in 1992"
TL;DR: In this paper, Yttria-stabilized zirconia (YSZ)/Al2O3 laminar microcomposites with a total of 80 layers, each as thin as ∼2 μm, were fabricated by electrophoretic deposition.
Abstract: Yttria-stabilized zirconia (YSZ)/Al2O3 laminar microcomposites with a total of 80 layers, each as thin as ∼2 μm, were fabricated by electrophoretic deposition. Positively charged YSZ or Al2O3 powders were deposited on a cathode, layer by layer from 10 wt% solids/ethanol suspensions. The suspensions were characterized by their rate of deposition as a function of voltage. The deposited samples had a green density of ∼60% of theoretical. The microstructure of the sintered, theoretically dense samples was characterized by optical and electron microscopy, and microindentation was used to explore the mechanical properties.
133 citations
TL;DR: In this paper, the effect of atmosphere on the formation of the 110 K superconductor phase at different oxygen partial pressures and temperatures was studied at different levels of oxygen partial pressure and temperature, and the shortest time for single-phase 110 K phase formation was found to be 12 h between 845 and 865°C at Po 2 = 0.078 atmosphere.
Abstract: The effect of atmosphere on the formation of the 110 K (Bi2Sr2Ca2Cu3O10, 2223) superconductor phase was studied at different oxygen partial pressures and temperatures. Step heating at low oxygen partial pressures with intermediate grinding promoted 110 K phase formation. With this synergy the shortest time for single-phase 110 K superconductor formation was found to be 12 h between 845 and 865°C at Po
2 = 0.078 atmosphere. The activation energy of 110 K phase formation is 1513 KJ/mole in air.
49 citations
TL;DR: In this paper, the influence of atmosphere, temperature, and time on the formation of the Bi(Pb)2SrCa2Cu3O10 (110 K) phase in the high TC superconductor system of composition Bi:Pb:Sr::Ca:Cu=1.84:0.34:1.06
Abstract: The influence of atmosphere (PO2=10−5–1 atm), temperature (T=810–890 °C) and time (6–60 h) on the formation of the Bi(Pb)2SrCa2Cu3O10 (110 K) phase in the Bi‐Pb‐Sr‐Ca‐Cu‐O high TC superconductor system of composition Bi:Pb:Sr::Ca:Cu=1.84:0.34:1.91:2.03:3.06 has been studied. The relationships between the fraction 110 K phase, heating atmosphere, temperature, and time have been mapped via experimental data.
33 citations
TL;DR: In this article, it was suggested that the magnetic field does not influence the orientation of nuclei during the nucleation process but induces physical rotation of the monograins in the sintering liquid and influences their grain growth.
Abstract: Liquid phase reaction sintering of YBa2Cu3Ox electrophoretically deposited thick films has been conducted in a magnetic field (∼1 T). The magnetic field influences the crystallographic orientation of the final microstructural grains (texturing). It is suggested that the magnetic field does not influence the orientation of nuclei during the nucleation process but induces physical rotation of the monograins in the sintering liquid and influences their grain growth.
20 citations
TL;DR: In this paper, the Lorentz-Lorenz molar refractivity and mean refractive index of β-and β-aluminas were estimated using Refractive index and density data of oxide components and Na-β-Al 2 O 3.
6 citations
TL;DR: In this article, the rate of electrical field assisted, hydronium-ion-exchange of K + -β-β-Al 2 O 3 ceramics was investigated and a model based on ion migration from a decreasing source was proposed to interpret the kinetics of the exchange process.
4 citations
TL;DR: In this paper, the conductivity of hydronium-β, β, β-Al 2 O 3 ceramics was determined between room temperature and 300 °C in humid atmospheres with P H2O between 0.03 and 0.93 atm.
3 citations
TL;DR: In this paper, the thermodynamic stability of H 3 Oβ β ǫ n −O 2 and −H 2 O systems was investigated via phase equilibria calculations.
2 citations
Book•
01 Jan 1992
1 citations
TL;DR: In this article, the diffusion coefficients for NH 4 + and H + were estimated from the ion-exchange time and the conductivity of the NH 4+ -exchanged samples respectively.
TL;DR: In this article, the authors discuss the practical issues raised by the necessity to NDE advanced-ceramic components and discuss the implications of NDE inspection by transducers on the properties of the latter.
Abstract: Practical issues raised by the necessity to NDE advanced-ceramic components are reviewed. Ultrasonic inspection is identified as the economically viable method and implications of ceramic inspection by transducers on the properties of the latter, are discussed. The high-frequency/high-power requirements have led to the synthesis of AIN piezoelectrics and these are discussed. Economics require array transducers and their development is outlined. The establishment of a database for the ultrasonic NDE of advanced-ceramic components is described. The probes developed were used to examine model spherical inclusions (voids (≥20μm), Zr02, MgO, and Pt inclusions (≥30μm)) in model matrices (glass, crystallized glass and partially stabilized zirconia). Surface breaking cracks were also analysed. Actual frequency spectra obtained from these defects as a function of defect size are compared with their calculated spectra and good agreement obtained.