Journal Article•
The role of temperature in mineralogy
About: This article is published in American Mineralogist.The article was published on 1948-04-01 and is currently open access. It has received 38 citations till now.
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TL;DR: It is as biocompatible as β-TCP, but more soluble, and hydrolyses rapidly to calcium-deficient hydroxyapatite, which makes α- TCP a useful component for preparing self-setting osteotransductive bone cements and biodegradable bioceramics and composites for bone repairing.
479 citations
TL;DR: In this article, the general principles of equilibrium thermodynamics are briefly stated in a form conveniently applicable to nonhydrostatic problems, with emphasis on the aspects, absent from hydrostatic applications, that have sometimes caused confusion.
Abstract: The general principles of equilibrium thermodynamics are briefly stated in a form conveniently applicable to nonhydrostatic problems, i.e., with emphasis on the aspects, absent from hydrostatic applications, that have sometimes caused confusion. The importance of taking into account fully and clearly the constraints involved in a particular problem and of treating the work term very carefully in considering an energy variation are particularly emphasized. For illustration the following problems of geologic interest are treated: (1) equilibrium between a stressed solid and its solution, including the ‘pressure solution’ problem; (2) recrystallization under stress and the resulting crystallographic preferred orientation in aggregates; (3) coherent phase transitions under stress; and (4) diffusion in a stressed solid.
322 citations
TL;DR: The high-temperature transition monoclinic tetragonal in the rare-earth tantalates and niobates with the formula AB04 was investigated using a hightemperature X-ray diffractometer as mentioned in this paper.
Abstract: The high-temperature transition monoclinic tetragonal in the rare-earth tantalates and niobates with the formula AB04 was investigated using a high-temperature X-ray diffractometer. The transition was reversible and proceeded by a gradual change in symmetry. The temperature of the first appearance of the tetragonal phase increased as the ionic size of the rare-earth ions decreased and was considerably higher for the rare-earth tantalates than for the rare-earth niobates. The mechanism of the change is discussed.
126 citations
TL;DR: In this article, the transformation β→α in Mg-substituted Ca3(PO4)2 was studied and the results showed that, contrary to common belief, there is a binary phase field where β+α-Ca3-PO42 solid solutions coexist.
Abstract: The transformation β→α in Mg-substituted Ca3(PO4)2 was studied. The results obtained showed that, contrary to common belief, there is, in the system Mg3(PO4)2–Ca3(PO4)2, a binary phase field where β+α-Ca3(PO4)2 solid solutions coexist. This binary field lies between the single-phase fields of β- and α-Ca3(PO4)2 solid solution in the Ca3(PO4)2-rich zone of the mentioned system. In the light of the results and the Palatnik–Landau's Contact Rule of Phase Regions, a corrected phase equilibrium diagram has been proposed. The practical implications of these findings with regard to the synthesis of pure α- and β- Mg-substituted Ca3(PO4)2 powders and to the sintering of related bioceramics with improved mechanical properties are pointed out.
97 citations
TL;DR: In this paper, a transition from monoclinic to triclinic symmetry was found to exist and is described and the composition at which the transition occurs is found to be a function of temperature: Or4oAbo at ~Oo C; OrsAb9 at ~1,000 C.
Abstract: Monoclinic K-feldspars and triclinic Na-feldspars at high temperatures form a "continuous" series of mix crystals. The apparent lack of a discontinuity in the monoclinic-triclinic solid-solution series has been puzzling. A transition from monoclinic to triclinic symmetry was found to exist and is here described. The composition at which the transition occurs was found to be a function of temperature: Or4oAbo at ~Oo C.; OrsAb9 at ~1,000 C. (extrapolated). The transition considered at a fixed composition as a function of temperature has the characteristics of a displacive transformation. The investigation was carried out with natural crystals homogenized at high temperature and quenched. Winchell's term "analbite" is redefined and used for the high-temperature modification of NaA1Si30s. Besides the displacive transformation, another type, or diffusive transformation, is considered. A detailed discussion of available data led to the conclusion that the series KA1Si3Os-NaAlSi30s, stable at high temperature (as a sanidine-barbierite, analbite series), differs from those members stable at low temperature (microcline-albite) by a different distribution of the Al and Si ions-disordered at high and ordered at low temperature. A slow and (at least on the potash side) continuous process of ordering in crystals originally disordered is considered to be responsible for the variable appearance of intermediate states (orthoclase, adularia). The process of K/Na exchange is also discussed in connection with an investigation of different types of perthites, such as those with exsolved albite and those with exsolved analbite. The meaning of the mineral name "anorthoclase" is considered in connection with some remarks on nomenclature of the alkali feldspars. The extension of this nomenclature to ternary feldspars is illustrated, with some results of an investigation of feldspars from rhombporphyries.
77 citations