Kinetic spray deposition provides a new means for producing composite materials with tailored physical properties. We report on measurements of the thermal conductivity and thermal-expansion coefficient for several compositional variations of kinetically sprayed Al–SiC metal-matrix composites. As a result of the deposition process, inclusion of SiC particles saturates in the 30–40% volume fraction range.

Indian clays are known for their smecticity. One such clay sample collected from Bhuj (Gujarat) was characterised and modified by successive sedimentation processes for different time intervals. The non-plastic components of clay, viz., quartz, illite, iron oxide, CaO, MgO, and organic matter were removed in different steps, as the heavy impurities in the clay-water suspensions, settle down during sedimentation. The free iron oxide present in clay suspension was reduced by giving sodium citrate-bicarbonate-dithionite treatment and iron content was further reduced from 1215 per cent to 57 per cent respectively. The organic matter was removed by sodium acetate-H 2 O 2 treatment. The modified clay so obtained was characterised by thermal analysis, FTIR, and XRD, SEM and TEM. The cation exchange capacities of original and modified clays were determined both by methylene blue method and ammonium acetate method. The cation exchange capacity is found to enhance from 120130 meq/100 g to 135145 meq/100 g. Using the above procedure, 92 per cent smecticity was obtained. Organophilisation of purified clay (smectite) was carried out by intercalation with alkyl ammonium salt. The XRD analysis showed enhancement of interlamellar spacing from 1.294 nm to 2.855 nm.

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