Thermal technical glasses

Vitreous sihca has many exceptional properties. Most are the expected result of vitreous sihca being an extremely pure and strongly bonded glass. Inert to most common chemical agents, it has a high softening point, low thermal expansion, exceUent thermal shock resistance, and an exceUent optical transmission over a wide spectmm. Compared to other technical glasses, vitreous sihca is one of the best thermal and electrical insulators and has one of the lowest indexes of refraction. 

Gutmann, R. 1996. Thermal technologies to convert solid waste residuals into technical glass products. Glastechnische Berichte, 69, 285-299. 

Fig. 3.4-18 Linear thermal expansion coefficients of various technical glasses and of fused silica...

While sounding overly technical, we have in fact employed the zeroth law with the example of a thermometer. Let us rephrase the definition of the zeroth law and say, If mercury is in thermal equilibrium with the glass of a thermometer, and the glass of a thermometer is in thermal equilibrium with a patient, then the mercury and the patient are also in thermal equilibrium . A medic could not easily determine the temperature of a patient without this, the zeroth law. 

Considerable progress has been made during the last two decades in the discovery and investigation of halide glasses. The main justification of this research effort is the unusual and critical optical properties of these glasses. Unfortunately, the technical applications for most of them have been severely curtailed by their hygroscopicity and low thermal properties. 

Into an evacuated 150-mL Hoke stainless steel vessel equipped with a Whitey stainless steel value, SFjBr (5.69 g, 27.5 mmol) and CH CH (1.00 g, 38.5 mmol Airco, technical grade, used as received) are condensed at — 196 °C. The mixture is heated at 55 2 °C for 3.8 days. The pure, hydrolytically and thermally stable product, SF5CH=CHBr (5.13 g, 22.0mmol) is obtained by distillation in a Kontes (14/20), all glass apparatus, at atmospheric pressure (bp 86 + 2°C). Yield 80%. - ... 

The discovery of glass-ceramics as a new type of solid with unusual parameters and their rapid laboratory development have outrun the possible applications. At present, glass-ceramics have found chief application in technical fields where their specific mechanical, thermal, electrical and other properties are exploited, and in the building industry which has been focusing its attention at elements made from cheap natural or waste materials. 

The thermal decomposition of limestone - which was reported by Cato in 184 bc -at about 900 °C produces calcium oxide (lime, technically called quicklime ) (CaCOj CO2 + CaO). This is an important basic step in glass and ceramics production, and quicklime in combination with clay is also a cheap essential raw material for the cement industry. For the estimated worldwide production of cement in 1994, the consumption of limestone was about 1420x10 (metric) tons. Quicklime reacts with water to calcium hydroxide Ca(OH)2. Hydrated lime is a dry calcium hydroxide powder, while slaked lime is an aqueous suspension of calcium hydroxide particles in water. Both forms are the cheapest industrial alkaline chemical and are frequently used together with limestone as a neutralizer for acids, for example in flue gas desulfurization (see below) (Oates 1998). The annual global production of lime and lime compounds is estimated to exceed 300x10 tons, with highest amounts in China, followed by the USA, the former Soviet Union, Germany, Japan, Mexico and Brazil (Oates 2002). 

The ability to withstand thermal shock resulting from sudden changes in temperature is important for technical applications of glass. The thermal endurance of inorganic glass, studied mainly by Schott and Winkelmann [24] (see also refs. [1] and [25]), is a very complex property. The investigations have led to the definition of a coefficient of thermal endurance F ... 

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