Classification of refractories

The classification of refractories can be approached in a number of different ways chemical composition, type of applications, or operating temperature range. 

TaUe 10.14. Classification of primary refractories by chemistry Category (definition) Description 

Dead burned magnesia with chromite Fused magnesia Magnesia-carbon bricks 

Chemically bonded bricks (75-85 wt.% AljO,) Alumina-chrome bricks Alumina-carbon bricks 

Zircon (ZrSiO,) and fused zirconia (ZrO,) Fused silica 

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Table 16.1 Application Classification of Refractory Carbides and Nitrides...

There are small differences in different classifications of refractory materials among ISO, DIN, and ASTM standards [1 ]. The most common definition is that refractories are shaped and unshaped materials that are durable at high temperature (>1,500 °C). Usually, heat refractory insulation materials have a service temperature of 800-1,100 °C. 

The classification of refractory heat-insulating materials is based on the density and temperature interval within which the maximum shrinkage does not exceed 2 % [5,6]. It is necessary to keep in mind that the classification temperature according to ASTM 155 [5] and ISO-2245 [6] does not correspond to the safe temperature of refractory application, which we will discuss later. 

The classification of refractory compounds in the above-mentioned three classes, as proposed by the author, is based on concepts of the periodic regularity of the change in character of the chemical bond with variation in the acceptor capacity of the atoms of the transition metals and the ionization potentials of the atoms of nonmetals. 

It is fortunate that Professor G. V. Samsonov, the leading expert on refractory compounds in the Soviet Union, undertook the compilation of these data in tabular form by properties. His immense knowledge is based on his own outstanding research work and his great familiarity with the international literature. He is one of the very few experts in the world who are qualified to survey the wide, complex, and complicated field of refractory compounds. Professor Samsonov s attempts at proposing principles in the classification of refractory compounds have been appreciated by everyone working with such materials. 

G. V. Samsonov, "Principles in the Classification of Refractory Compounds, in "Soviet Powder Metallurgy" (a translation of "Poroshkovaya Metallurgiya") No. 2, pp, 73-76, 1962, Consultants Bureau, New York. 

Provisional supplementary classification of refractory ramming materials and mouldables 1973 1978... 

Fig. 2. Thermal conductivity of refractories where ASF = aluminosiUcate fiber and ZF = 2ii conia fiber. See Table 13 for group classifications (5,25).

Describe the modified Vaughan-Williams classification of antiarrhythmic drugs, and compare and contrast the effects of available antiarrhythmic drugs on ventricular conduction velocity, refractory period, automaticity, and inhibition of specific myocardial ion channels. 

The Vaughan-Williams classification of antiarrhythmic drugs has been criticized for a number of reasons. The classification is based on the effects of drugs on normal, rather than diseased, myocardium. In addition, many of the drugs may be placed into more than one class. For example, the class IA drugs prolong repolarization/refractoriness, either via the parent drug8,9 or an active metabolite,10 and therefore also maybe placed in class III. Sotalol is also a 3-blocker, and therefore fits into class II. Amiodarone inhibits sodium and potassium channels, is a non-competitive inhibitor of 3-receptors, and inhibits calcium... 

This model assumes a more simplified classification of the DOM pool than the one described in Section HI. The labile and semilabile DOM fractions shown in Fig. 6 have been combined to form the labile DOC pool the recalcitrant DOC (RDOC) pool remains the same as that defined in Fig. 6 and the refractory DOC pool is not part of the model. 

Biochemical classification may also be applied and indeed would be most appropriate. However, the three main biochemical classes (polysaccharides, proteins, lipids) represent only approximately 20-30% of the NOM in freshwater bodies, the remainder being an ill-characterised mixture of varying proportions of refractory pedogenic and aquagenic organic matter (PROM and AROM, respectively). The major differences between PROM and AROM are (Buffle, 1988, Chapter 4), for the former ... 

Selection of a refractory in practice is usually based on the requirement that the two substances in contact should be related chemically so that mutual chemical reactions arc precluded. This is why the medium to be in contact with the refractory is specified either as acidic or basic, using the classification similar to that of refractory materials (cf. p. 354). 

This schematic representation is of course simplified, rather like the suggested classification of magnesite and other basic refractories published by Biggar and Weymouth (1976) on the basis of phase composition in the system MgO — CaO —.4I2O3—Si02- The latter authors distinguish the following materials ... 

However, Goldschmidt s scheme only relates to the condensation of major elements into mineral phases. As the solar nebula hypothesis gained credence, it became clear that there are other element groupings which relate to the condensation of a high-temperature solar gas. These are the refractory elements - those which formed above the condensation temperature of the Mg silicates and Fe-Ni metal, at 1,300-1,400 K, the moderately volatile elements - those formed in the range 1,300-670 K, and the volatile elements - those that formed below the condensation temperature of FeS, at 670 K (Larimer, 1988). Palme and O Neill (2003) have proposed a cosmochemical/geo-chemical classification of the elements based on these two elemental groupings (Table 2.1). 

TABLE 2.1 A cosmochemical and geochemical classification of the elements based upon their Lithophile/siderophile/chalcophile affinities and their refractory or volatile character (after Palme and O Neill, 2003). ... 

Table 9-7.4. Characteristics of High-tbmpebaturb Insulation. Classification and Use Properties of Refractory Brick...

Tabi 9-7C. Characteristics of Hiqh-temperature Insulation. Classification op Refractory Castables (Refractory aggregates plus hydraulic cement)... 

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