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ZnO fine crystals with various growth forms were developed by condensation of the high-temperature ultrasupersaturated gas generated from ZnO powder by means of the conically converging shock-wave technique utilizing detonation of explosive charge. The morphology and structure of ZnO fine crystals were investigated by electron microscopy. They were conveniently classified into plates, columns, pyramids, hollow crystals, stellar-shaped crystals, spheres, whiskers, and dendrites. Most of them have the hexagonal structure, while small number of crystals which apparently have the cubic structure also were obtained.

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(1) It was found, by means of the thermal and magnetic balance, that the decomposition temperatures of silver oxide and of silver oxide containing silver carbonate are 354 and 372°C, respectively. (2) The magnetic susceptibilities of metallic silver obtained by the decomposition and of silver oxide are −0.21×10−6and −0.48×10−6 units per gram at room temperature, respectively. Metallic silver is normally diamagnetic from room temperature to 1100°C. (3) Under the present experimental conditions, the rate of decomposition is represented by the equation dx⁄dt=aitbi for the whole course of the decomposition, where i is the subscript for each stage, and generally both ai and bi depend on the temperature. It is considered that nuclei are created at intervals as the reaction proceeds.

α‐SiC and β‐SiC crystals are prepared from vapor by sublimation of β‐SiC powder subjected to a conically converging shock‐wave generated by detonating an explosive charge. α‐SiC crystals are mainly 6H modifications and their features are plates, pyramids, needles, and filaments grown in the [0001] direction; 4H‐SiC filaments are also obtained. α‐SiC rods having a triangular cross section develop parallel to the [111] direction.