Showing papers by "Patrick S. Nicholson published in 1972"
TL;DR: In this article, the content of free ZrO2 in partially stabilized zirconia ceramics by X-ray diffraction techniques was determined by linear calibration curves.
Abstract: Linear calibration curves were developed for determining the content of free ZrO2 in partially stabilized zirconia ceramics by X-ray diffraction techniques. Two methods were studied. The matrix method, in which free ZrO2 was considered to be distributed in a matrix (the cubic phase), gave approximately equal mass absorption coefficients for the monoclinic and cubic phases. The polymorph technique, in which the cubic phase was considered to be a polymorph of ZrO2 and in which integrated intensities were used, gave the better results.
1,302 citations
TL;DR: Partially stabilized zirconia (PSZ) ceramics in the system CaO-ZrO2 were characterized by optical microscopy as mentioned in this paper, which revealed that the microstructure provided an effective stress-relieving mechanism during thermal shock.
Abstract: Partially stabilized zirconia (PSZ) ceramics in the system CaO-ZrO2 were characterized. The microstructure, as revealed by optical microscopy, consisted of grains of pure ZrO2 distributed in a matrix of fully stabilized material. Electron microscopy showed that the matrix grains have a complex substructure of 1000-A domains of cubic and monoclinic ZrO2. The grains appeared to fit Ubbelohde’s concept of a hybrid single crystal. Evidence obtained indicated that the substructure provides an effective stress-relieving mechanism during thermal shock. It is proposed that initiation of phase inversion in pure ZrO2 domains, even at subtransition temperatures (by thermal stresses), creates an extremely large microcrack density. On the basis of Hasselman’s thermal-shock criterion, only quasi-static crack propagation occurs during thermal shock of PSZ; evidence is presented to support this concept.
204 citations
TL;DR: In this paper, transmission electron microscopy using in situ heating was used to investigate the dehydroxylation and enstatite development during the decomposition of talc, and evidence of preferential bubble nucleation at dislocations was obtained.
Abstract: Dehydroxylation and enstatite development during the decomposition of talc were investigated by transmission electron microscopy using in situ heating. Bubbles and voids are produced during dehydroxylation, and enstatite then precipitates near the voids. Evidence of preferential bubble nucleation at dislocations was obtained. Enstatite crystallites of random orientation were observed initially but on further heating the product phase was formed topotactically.
13 citations
TL;DR: In this article, the kinetics of the solid-state reaction of CaO and β-quartz were studied between 1000° and 1200°C in wet and dry N2.
Abstract: The kinetics of the solid-state reaction of CaO and β-quartz were studied between 1000° and 1200°C in wet and dry N2. Parabolic kinetics were observed in all cases; Ca2SiO4 was the only reaction product. The reaction was faster on the basal plane of the β-quartz than on the prism plane, and although moisture enhanced the reaction rates on both planes, the enhancement of the basal-plane reaction was significantly higher. Activation energies and results of marker experiments indicated that Ca2+ diffusion in the product was rate-controlling and that α-Ca2SiO4 possibly formed on the basal plane of the β-quartz and α'-Ca2SiO4 on the prism plane. A model for the observed kinetic enhancement in the presence of moisture is proposed on the basis of creation of interstitial Ca2+ sites in the products.
11 citations