Structure of Ceramics and Glasses

Uhlmann, Introduction to Ceramics. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc. 

Magnesium silicate, Mg2Si04, consists of a HCP arrangement of ions with the cations occupying interstitial spaces. Use the ionic radii of the elements given in Table 1.9 to answer the following questions. 

Person 1 What is the coordination number for the Mg + ions and what type of interstitial site will they occupy  

Combine your information. According to Table 1.16, what is the fraction of the total type of interstitial site occupied by each cation, and what is the structure name of this compound  

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Catalytic A catalytic-membrane reactor is a combination heterogeneous catalyst and permselective membrane that promotes a reaction, allowing one component to permeate. Many of the reactions studied involve H2. Membranes are metal (Pd, Ag), nonporous metal oxides, and porous structures of ceramic and glass. Falconer, Noble, and Sperry [in Noble and Stern (eds.), op. cit., pp. 669-709] review status and potential developments. 

The subject of sol-gel science is cova-ed in great depth in Ref. 1. We outlined the basic steps in sol-gel processing in ChaptCT 1 when we surveyed the common methods used for the production of ca-amics. This chapter provides a more detailed examination of the science and practice of the process for the fabrication of ceramics and glasses. We shall pay particular attention to the sol-gel processing of silica glass not only because of its practical interest but also because of the heightened understanding of the process mechanisms and structural evolution developed from numerous studies. 

Incorporating organic polymers or molecules within the structure of ceramics or glasses is a unique feature of the sol-gel process. Organic-inorganic hybrids have emerged recently as a novel family of materials with new and unique properties (Coltrain, 1996 Laine, 1998 Mackenzie, 1990 1992, 1994, 1998 Bescher, 1998). 

Due to these virtues, solid state NMR is finding increasing use in the structural analysis of polymers, ceramics and glasses, composites, catalysts, and surfaces. 

Phenolic-neoprene contact cements are used for structural metal-metal bonding. especially where fatigue resistance and low temperature performance are important [209]. They are also used for bonding textiles, wood, rubbers, plastics, ceramics, and glass to metal and to one another. Solvent toxicity and flammability has greatly reduced the use of contact cements in the wood products industry. Water-based contact cements persist, but generally do not perform as well as the solvent systems, thus allowing market erosion by alternative binders. 

Fuller treatments of the phase relations and structures of polyphosphates, and their uses as glasses, ceramics, refractories, cements, plasters and abrasives, are available. 

Like the natural iron oxide pigments, the synthetics are used for colouring concrete, bitumen, asphalt, tiles, bricks, ceramics and glass. They are also used extensively in house and marine paints. Because the shapes of the particles can be accurately controlled and the particle size distribution is narrow, synthetic iron oxides have a greater tinting strength than the natural ones and so, are chosen where paint colour is important, i. e., for top coats. Red iron oxides are used in primers for automobiles and steel structures. 

Figure 1.52 Micro structure of a typical glass ceramic with a fine grain size, minimal residual glass, and little porosity (P). From W. E. Lee and W. M. Rainforth, Ceramic Microstructures. p. 59 Copyright 1994 by William E. Lee and W. Mark Rainforth, with kind permission of Kluwer Academic Publishers.

Bach. H. and D. Krause Anatssis of the Composition uinl Structure of Gloss tutd Glass Ceramics. Springer-Verlag, Inc.. New York. NY. 1999. 

The aminosilane coupling agent 3-aminopropyltriethoxysilane or y-amino-propyltriethoxy silane—also abbreviated as 3-APS, y-APS, APS or A1100 (Union Carbide)—is widely used to promote adhesion between polyimide thin films and mineral surfaces such as native-oxide silica, alumina and various glass ceramics [1, 2]. The structure of APS and the hydrolysis reaction sire shown in Fig. 1. Typically, dilute aqueous solutions of 0.1 vol% or approximately 0.080 wt % are employed to prime the mineral surface. The mechanism for the interaction of the bifunctional aminosilane with the mineral surface is the subject of much speculation, although it is conjectured by Linde and Gleason [3] that the amine end initially forms an electrostatic bond with surface hydroxyls. Subsequently, possibly as the result of elevated temperatures, the silanol end of the molecule proceeds to form a siloxane-like bond with the surface and the amine... 

Heat resistance of organic polymers is far lower than that of metals, ceramics, and glass. There have been major improvements, based on aromatic and heterocyclic resonance, ladder structures, and other mechanisms, and we may see further improvement in the future. Perhaps more serious limitations are the high cost of synthesis and the difficulty of processing these polymers into the desired final products. This is an area where the polymer chemist could use more help from the plastics engineer. 

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