Negative thermal expansion (NTE) oxides are interesting materials for use in controlled thermal expansion composites. Cubic ZrW 2 O 8 is one of the most promising candidates due to its strong, isotropic NTE behaviour over a large temperature range. It is easily accessible from a hydrated precursor, ZrW 2 O 7 (OH) 2 Á 2H 2 O, which enables control of particle size and morphology during the topotactic conversion to the NTE phase. The preparation of high quality composites poses a number of challenges like compatibility of NTE material and composite matrix, stability of the NTE phase and particle morphology and size, which affect mixing and homogeneity. For ZrW 2 O 8 /polymer composites, surface modification is necessary to enhance interactions between the polymer matrix and the filler particles. In addition, small particle sizes are crucial to avoid settling of filler particles during polymer processing. This review presents results on the optimization of routes to nano-ZrW 2 O 8 , particle modification to achieve compatibility with polymers, preparation of NTE/polyimide composites and potential problems that can interfere with composite formation.

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