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Aerosols
Published in Sue Reed, Dino Pisaniello, Geza Benke, Principles of Occupational Health & Hygiene, 2020
Linda Apthorpe, Jennifer Hines
Infrared or x-ray analysis can therefore be conducted on the sample filters; however, for infrared spectrometry, if interfering minerals are present—for example, kaolinite, amorphous silica or cristobalite—x-ray analysis will be necessary. Cristobalite can be present naturally or can exist where quartz has undergone heat treatment above 450°C.
Atomic Bonding and Crystal Structure
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
Glasses are the most widely used noncrystalline ceramic. A glass is formed when a molten ceramic composition is cooled so rapidly that the atoms do not have time to arrange themselves in a periodic structure. At temperatures below the solidification temperature, glasses are not thermodynamically stable, and the atoms would rearrange into a crystalline structure if they had the mobility. Over long periods, glass can crystallize, as evidenced by the presence of cristobalite in some volcanic glass (obsidian). The crystallization can be speeded up by increasing the temperature to a level at which atomic mobility is increased. Most engineers who have used fused silica in high-temperature applications have encountered this. At use-temperatures well below the melting temperature of 1713°C, cristobalite crystals form in the fused silica (slowly at 1200°C and relatively rapidly at 1400°C). Fused silica has a very low, nearly linear thermal expansion curve and is one of the best thermal shock-resistant ceramic materials for applications where rapid thermal cycling occurs. Crystallization to cristobalite is undesirable because the large volume change of the polymorphic transformation from high cristobalite to low cristobalite in the range 200–270°C results in cracking of the fused silica component.
Natural aggregate sources and production
Published in Mark Alexander, Sidney Mindess, Aggregates in Concrete, 2005
Mark Alexander, Sidney Mindess
Chalcedony: A fibrous form of quartz with submicroscopic porosity. Frequently occurs with chert and is usually alkali-reactive. Tridymite and Cristobalite: High temperature crystalline forms of silica associated with volcanic rocks, and alkali-reactive.
Role of addition of kaolin on the firing of white clay for Korean porcelain
Published in Journal of Asian Ceramic Societies, 2020
Hiroaki Katsuki, Shingo Hirata, Miki Inada, Cheong-Soo Choi, Jae-Hyeon Park, Ji-Hyeon Lee, Ung-Soo Kim, Kyu-Sung Han, Jin-Ho Kim, Woo-Seok Cho, Kwang-Taek Hwang
In general, significant amounts of cristobalite are formed at temperatures over 1100°C by the expulsion of excess SiO2 from the Al – Si spinel (Si3Al4O12) formed from the thermal transformation sequence of kaolin [24]. From the results in Figures 8 and 9, the formation of cristobalite was completely suppressed at 1300°C in the mixtures of Korean kaolin and Yanggu white clay. It is estimated that the fluxing action of potassium ions of muscovite in Yanggu white clay inhibited the formation of cristobalite from Korean kaolin in this study.