Tridymite

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

Phase Transformation and Melting Behavior of Silica Fumes

Abstract: The morphology,particle size distribution,phase transformation,and melting behaviors of three kinds of silica fumes at room temperature and heated at 800-1 200 ℃ for 3 h were investigated by X-ray fluorescence spectrometry,field emission scanning electron microscope,energy dispersive spectrometry,X-ray diffractometer(XRD) and laser particle size analysis,respectively.At room temperature,they are spherical particles with the size of 1 μm,which contain some smaller distinguished spheres in the range of 30-50 nm.The smaller spheres are adhered onto the surface of larger particles.The particles with the size of 1 μm are mostly the agglomerates.The analysis by XRD revealed that silica in all the samples appeared amorphous when heated at 800 ℃,and then be-came cristobalite and tridymite after heated at 900 ℃ and 1 200 ℃,respectively.The cohering phenomenon occurred when heated at 800 ℃,and then the deformation and softening phenomena took place with the further increase of temperature.All the samples melted after heated at 1 200 ℃ for 3 h.The phase transformation and melting behaviors of the different silica fumes were related to the parti-cle size distribution and the Na2O and K2O content.Tetragonal zirconia appeared in the ZrO2 containing silica fume after heated at 900 ℃ for 3 h,and thereafter there existed no further phase transformation when heated at a higher temperature.

Computer Simulations of Liquid Silica: Water‐Like Thermodynamic and Dynamic Anomalies, and the Evidence for Polyamorphism

Abstract: The qualitative similarities between water and silica have long been appreciated [1,2] The molecular structure of both substances is dominated by tetrahedral bonding arrangements under ambient pressure, in both the liquid and the solid states As a consequence, several of the low-pressure ice phases have isomorphic analogs among the crystalline phases of silica (eg, ice Ih and tridymite) The similarities between water and silica also extend to the properties of the liquid and amorphous solid forms Water and silica are both members of a small set of substances that exhibit a density maximum in the liquid phase [1,2]