Tridymite

About: Tridymite is a research topic. Over the lifetime, 840 publications have been published within this topic receiving 14831 citations.

Dense Mulliteceramic Sintered by SPS and Its Behavior Under Thermal Shock

Abstract: This article studies the influence of raw material, sintering temperature, particle size, and Al2O3 content on densification of mullite ceramics. Thermal cycle treatments were conducted to evaluate thermal shock resistance of samples. Microstructures of samples were also investigated to reveal effects of various parameters and thermal test. Flexural strength retention rises while density decreases, resulting from increasing extra space for stress release. Tridymite precipitation is found to be harmful in improving thermal shock resistance.

Molding sand for jewelry casting

Abstract: investment casting of jewelry from alloys of precious and nonferrous metals. SUBSTANCE: powder mixture from preparation of mold mixed with water in molding contains, wt.%: cristobalite, 48-78; high-strength gypsum (alpha+beta), 20-50; potassium nitrate, 0.5-2.0; potassium dihydrophosphate, the balance. Cristobalite is used with admixture of tridymite and amorphous quartz in amount of not more 20 or 40%, and alkali metal oxides, not more 2.0%. EFFECT: higher strength characteristics of molding sand ensuring high quality of castings. 3 cl, 6 tbl

Formation of multilayer interconnection

Abstract: PURPOSE:To lessen a leakage current between wirings and to prevent the generation of crack in a vitreous film by a method wherein a crystallite-containing vitreous SiO2 thin film is used as an insulating film. CONSTITUTION:A crystallite-containing SiO2 thin film or a crystal transition is promoted more than that in the case of the formation of the above thin film and a vitreous SiO2 thin film having insulation properties higher than those of the above thin film is formed. Moreover, alkali, which is used as an impurity, and other metal ions are inhibited to 10ppm or less and an annealing is performed to contrive further the stabilization of the crystallitic vitreous SiO2 thin film. As an SiO2 material, in particular a quartz glass material is amorphous and has a multitude of unstable structures of a point detect and so on, a conversion from an amorphous material to a crystallitic material is contrived for an insulating film or the crystal transition, a crystal growth and so on are promoted to contrive the removal of such the point defect. The crystal transition performs a transition of quartz tridymite, tridymite crystobalite and so on to stabilize further the crystallitic vitreous SiO2 thin film. Thereby, the effect of using the thin film as an insulating layer is further increased.

Silicifications, Flint and Growth of Crystals

Abstract: It may seem surprising to study siliceous rocks and silicifications in a treatise on clays. In fact, I hope that the reading of this chapter will show how necessary it is. Here are the principal reasons. Since clay minerals are silicates, the architecture and development of their lattice are chiefly controlled by the assemblage of oxygen tetrahedra with a central silicon ion. Now this fundamental elemental structure is that of crystallized silica in its three forms: quartz, cristobalite and tridymite. Many rocks of pedogenetic or sedimentary origin are siliceous, that is, formed chiefly of silica tetrahedra. It is obvious that these siliceous formations formed at low temperature, under conditions of the hydrosphere which are the conditions of the formation of clays; moreover, they are frequently closely associated with the latter. Thus, looking at clays and siliceous formations on a structural scale, one sees the similarity in their natures. In clays, the tetrahedra are arranged in a two-dimensional planar layer; in siliceous formations, they are arranged spatially in a three-dimensional lattice. This is the fundamental difference for the specialist in crystalline structures, but for the common people, is it not only a difference between two types of occurrence of silica? This chapter is designed to show what this difference represents for the geologist.