Refractory properties

High refractory properties, extremely strong sensitivity to moisture and exceptionally high chemical activity of fluoride melts, especially of those containing ions of polyvalent metals, make spectral measurements of such melts extremely complicated. In order to obtain reliable results, the measurement cell must comply with three main requirements ... 

Barium nitrate is superior to either sodium or potassium nitrate with regard to physical stability, while the heat concentration is also higher because barium oxide has better refractory properties than does either potassium or sodium oxide. 

Adani, F., Spagnol, M., and Nierop, K. G. J. (2007). Biochemical origin and refractory properties of humic acid extracted from maize plants the contribution of lignin. Biogeochem. 82, 55-65. 

Carbone, T.J., Characterization and refractory properties of magnesium aluminate spinel raw materials , Interceram. Spec. Issue, 1985 91-4. 

One very important niche application for calcium aluminate (cements) is as refractory castables. Key to the success of calcium aluminates in this application are their refractory properties that contrast with those of Portland cements. Although Portland cement maintains good strength when heated, reactive components (CaO) are liberated and can absorb moisture from the atmosphere when cooled, causing expansion and deterioration of, for example, kiln linings. CACs are not much susceptible and can be used to form monolithic castables and refractory cements [28, 29],... 

New binders for castables without affecting refractory properties new dispersants and rheology studies... 

This paper describes the chemistry, reaction mechanism, and method of preparation of these high temperature materials. Their possible structures and refractory properties are also discussed. 

Calcium oxide has excellent refractory properties and many efforts have been made to commercialise its use (e.g., [32.48]). However, hydration by atmospheric water vapour has proved to be a major problem. Despite this, the nuclear industry is reported to use dead-burned calcium oxide crucibles, with an apparent density of 3.15 g/cm [32.4, 32.49]. 

Refractory describes the ability to withstand high temperatures without damage. It is also used to describe bricks with refractory properties. 

D.I. Mendeleyev was among the first to suggest polymer structure of silica. Exactly that, in his view, was the reason for non-volatility and and refractory properties of the substances with composition (SiO ). X-ray diffraction studies showed that crystalline silica is a 3D interlaced polymer of [SiOj tetrahedrons (Figure 2.43). 

Barium nitrate would be the best of the three from the standpoint of physical stability and also of heat concentration because barium oxide has considerably better refractory properties than either potassium or sodium oxide. However, the high equivalent weight of barium limits its usefulness. Barium and strontium nitrates are indispensable for green and red effects and can also be used combined for white light. In combination with potassium perchlorate and aluminum, barium nitrate is part of standard photoflash powder. Ammonium and guanidine nitrate are sometimes used because of their gas-forming properties, and lead and silver nitrate can be found in special applications. 

Barium aluminate cement exhibits significantly improved refractory properties compared with calcium aluminate cement, and may be considered for applications at temperatures of up to about 2000 °C. It has also the capacity to absorb radioactive and X-ray radiation very effectively. 

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