Showing papers by "Patrick S. Nicholson published in 1991"
TL;DR: In this article, the authors electrophoretically deposited BiSr•Ca•Cu•O thick films (≊5−40 μm) on silver foil using ethyl alcohol as the suspending liquid.
Abstract: Bi‐Sr‐Ca‐Cu‐O thick films (≊5–40 μm) were electrophoretically deposited on silver foil using ethyl alcohol as the suspending liquid. The deposition voltage was ≊70 V/cm and the current ≊550 μA/cm2. X‐ray diffraction of the as‐deposited sample shows texturing. This texturing was enhanced by pressing the film uniaxially at ≊82 MPa. Samples were sintered at 810 °C in a 10% oxygen‐in‐argon atmosphere. Liquid at the sintering temperature promotes textured grain growth. The critical current density (Jc) of the film determined by magnetic measurement at 5 K in a 2 kOe field is ≊1.3×104 A/cm2.
37 citations
TL;DR: In this article, composite bioactive glass-ceramics reinforced with 30 vol% Ti particles were produced by warm-forging and in situ crystallization, and the bend strength of the composite was 87 ± 7 MPa.
Abstract: Composite bioactive glass-ceramics reinforced with 30 vol% Ti particles were produced by warm-forging and in situ crystallization. The bend strength of the composite was 87 ± 7 MPa. A fracture mechanical study in air and Ringer's bioactive solution determined crack velocity vs stress intensity factor and the effect of stressing rate on the bend strength. Time to failure of 10 years is predicted for the composite loaded at 10 MPa in Ringer's solution or 50 MPa in air. A disappointing fatigue performance of the relatively tough metal/ceramic composite illustrates that satisfactory short-time fracture resistance does not guarantee lifetime under fatigue conditions (long-term fracture resistance).
19 citations
TL;DR: In this article, the grain and grain-boundary electrical conductivities of polycrystalline β-aluminas were measured, and it was found that grainboundaries decrease the material conductivity substantially, especially when large ions are involved.
11 citations
TL;DR: In this paper, the X-ray matrix-flushing method was used to determine the phase composition of the Bi-Pb-Sr-Ca-Cu-O superconductor system.
11 citations
TL;DR: In this article, the optimum composition and preparation conditions for improved protonconductive β″/β alumina precursors were determined for extended-time sintering techniques which favor formation of β″-alumina and cleaner grain boundaries.
7 citations
TL;DR: In this article, the ion conduction behavior of microstructurally designed β″-Al 2 O 3 ceramics was studied by ac impedance spectroscopy, and the experimental results for textured alkali and ammonium β″aluminas were presented.
3 citations
TL;DR: In this article, an ultrasonic shear wave attenuation study has been carried out to investigate ionic motion in Na+- and K+-β-aluminas as a function of temperature.
3 citations
TL;DR: In this article, an equation is developed that predicts the optimum active diameter for a piezoelectric material of given working frequency and the predictions are compared with experimental data, based on which the authors develop a high frequency (>25 MHz) compressional wave transducers using lead metaniobate composite ceramics, which have a thickness coupling coefficient, k t, of >70% and relative dielectric constant, e τ, of 13.
2 citations
TL;DR: The ultrasonic longitudinal wave attenuation peak caaused by the hydronium ions in H3O+-β″ -alumina has been generated as mentioned in this paper, which gives 0.15 eV as the activation energy for H 3O+ motion and 0.8 GHz as the ion hopping rate at room temperature.
2 citations
TL;DR: In this paper, the hydronium-exchange process of bulk polycrystalline β″/β-Al2O3 has been investigated under different conditions, including field assistance and acetic acid ion exchange temperature and pressure.
1 citations
TL;DR: In this article, the attenuation of longitudinal ultrasound in NH + 4 /H 3 O + -Rb + -β″-Al 2 O 3 ceramics has been studied.
TL;DR: In this paper, the influence of the mixed alkali effect on the conductivity and activation energy for conduction was determined and found significant in both grain boundaries and grains at the low temperatures.