Twinning aluminate

Photograph 7-27 Ragged belite crystals and belite coating on alite, one of which is twinned. Note abundant dotlike impurities in alite. Coarsely crystalline matrix with gray aluminate and relatively bright ferrite. Slowly cooled clinker. (S A6647)... 

Photograph 7-41 Slowly cooled kiln buildup from the transition zone containing, for the most part, polysynthetically twinned belite (Type II, Insley) in lower left and slightly splintery gamma belite (upper right) in matrix of coarsely microcrystalline ferrite and aluminate. (S A6661)... 

Photograph 7-75 Brown prismatic (alkali-rich) aluminate crystals, some entrapping alite and appearing zoned or twinned along a prism face. Dry-process kiln. (S A6693)... 

Hasegawa et al (1995) developed a new cementitious material by combining calcium aluminate cement with a methanolic solution of a phenol resin precursor. The water-free mix must be processed by high-shear mixing in a twin-roller mill in a way similar to that used in the production of MDF materials. The rheology of the resin-cement paste may be improved by adding to the system small amounts of a modifier such as alcohol-soluble polyamide and a plasticizer. A typical mix proportion is as follows ... 

The fact that dielectric and structural properties of rare earth aluminates fulfil the demands of microwave engineering, even though some other properties (primarily the formation of twins and chemical purity of precursors) are unfavourable, should continue to support a considerable interest in the attempts to tailor new varieties of aluminate crystals. 

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