Refractory materials, properties

A considerable number of silica brick-only, mortar-only, and brick/mortar samples were tested. As a result of page limitations in this chapter, representative typical sample data are provided. Average data from a large number of samples are presented in some instances. Due to the nature of silica refractory brick manufacturing, it is expected that there wiU be some variation from brick to brick in material property values. However, the data presented here can be used to provide insight into the trends of mechanical material properties of silica brick. The unique brick sample data, mortar-only sample, and brick/mortar composite data on refractory material properties in this chapter are typically not found in the literature. 

Typical carbon refractory material properties are shown in Table 2. 

Table 3 Typical Semigraphite and Semigraphitized Carbon Refractory Material Properties... 

The first three chapters provide the fundamentals of refractories. Refractories deteriorate from either or both chemical and mechanical effects. The fundamentals of refractory material properties are addressed in Chapter 1. Fracture mechanics or those aspects of the mechanical deterioration of refractories are provided in Chapter 2. Chapter 3, on the corrosion of refractory brick, looks at the chemical deterioration of refractories. 

This wear is caused primarily from high thermal and mechanical stress, chemical attack, attack by iron and slag, oxidation, and severe thermal shock. Thus the design of the hearth wall and the concepts employed ate just as important as the carbon or graphite materials chosen for the refractory material. Despite their benefits and properties, no carbon or graphite material can overcome the problems of an improper hearth wall design concept. 

Today, the term solid electrolyte or fast ionic conductor or, sometimes, superionic conductor is used to describe solid materials whose conductivity is wholly due to ionic displacement. Mixed conductors exhibit both ionic and electronic conductivity. Solid electrolytes range from hard, refractory materials, such as 8 mol% Y2C>3-stabilized Zr02(YSZ) or sodium fT-AbCb (NaAluOn), to soft proton-exchange polymeric membranes such as Du Pont s Nafion and include compounds that are stoichiometric (Agl), non-stoichiometric (sodium J3"-A12C>3) or doped (YSZ). The preparation, properties, and some applications of solid electrolytes have been discussed in a number of books2 5 and reviews.6,7 The main commercial application of solid electrolytes is in gas sensors.8,9 Another emerging application is in solid oxide fuel cells.4,5,1, n... 

Niobium carbide, also known as columbium carbide, is a important refractory material with a high melting point. It is used as a CVD coating mostly on an experimental basis. Niobium carbide has two phases Nb2C and the monocarbide NbC. The latter is the only phase of industrial importance and the only one reviewed here. Its characteristics and properties are summarized in Table 9.5. 

Titanium (TiC) is an important industrial material produced extensively by CVD. It is an excellent refractory material which is unusually hard with high strength and rigidity and outstanding wear resistance. Its properties are summarized in Table 9.8. 

Like graphite, h-BN is soft and lubricious and it has a low density. It is a refractory material which sublimes at 3000°C and has exceptional chemical resistance. The characteristics and properties of CVD h-BN are shown in Table 10.2. 

For many years, research efforts in materials chemistry have focused on the development of new methods for materials synthesis. Traditional areas of interest have included the synthesis of catalytic, electronic, and refractory materials via aqueous methods (sol-gel and impregnation) and high-temperature reactions [1-3]. More recent strategies have focused on the synthesis of materials with tailored properties and structures, including well-defined pores, homogeneously distributed elements, isolated catalytic sites, comphcated stoichiometries, inorganic/organic hybrids, and nanoparticles [4-13]. A feature... 

The successful application of the sol-gel route has been realized in the International technological practice of many branches of the industries—electronics, optics, construction of engines, nuclear energetics, chemical, and food industry equipment. Among these materials are ferro-, piezo-, and dielectrics, solid electrolytes, refractory materials, membranes, protective and decorative coatings, and also films with special optical and electrophysical properties, like hightemperature superconductors. 

Commercial sintered magnesia-spinel refractory materials are divided into three categories magnesia rich, stoichiometric, and alumina rich.1 Typical properties of magnesia rich spinel bricks are given in Table 14.1.2... 

Mechanical properties and thermal shock behaviour of magnesia-spinel composite refractory materials... 

Schacht, C.A., Influence of lining restraint and non-linear material properties in predicting thermal shock fracture of refractory linings , UNITECR 89, 1989. 

W. R. Davis, Hot-Wire Method for the Measurement of the Thermal Conductivity of Refractory Materials , in Compendium of Thermophysical Property Measurement Methods, (K. D Maglic, A. Cezairliyan, and V. E. Pelet-sky, eds.), Vol. 1, Plenum Press, NY (1984). 

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