Single-crystal trigonal tellurium nanowires and nanotubes were synthesized using a facile, efficient, and relatively green solution phase method with ethylene glycol as solvent and an alternative reducing agent in the presence of NaOH. Large-scale production of slender nanowires and hollow nanotubes with average diameters of 72 and 240 nm, respectively, was achieved by increasing the temperature from 170 C to 200 C. Tellurium morphology from nanowires to nanotubes was also controlled by adjusting the NaOH dosage. Scanning electron micrographs show that low temperature or NaOH insufficiency promotes the formation of slender nanowires but counteracts the synthesis of tellurium nanotubes. Detailed reaction equations based on the NaOH dosage were obtained. Preferential growth orientation of [001] was observed in the nanowire and nanotube through high-resolution transmission electron microscopy. Further formation mechanisms dependent on time were systematically studied.

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The synthesis of calcium hexaboride (CaB 6 ) powder via the reaction of calcium carbonate (CaCO 3 ) with boron carbide (B 4 C) and carbon has been investigated systematically in the present study. The influences of heating temperature and holding time on the reaction products have been studied using X-ray diffractometry, and the morphologies of CaB 6 obtained at various temperatures and holding times have been investigated via scanning electron microscopy. The interaction in the CaCO 3 -B 4 C-carbon system by which CaB 6 is formed is a solid-phase process that passes through the transition phases Ca 3 B 2 O 6 and CaB 2 C 2 . The optimal conditions for CaB 6 synthesis are a holding time of 2.5 h at a temperature of 1673 K, under vacuum (a pressure of 10 ؊2 Pa). CaB 6 powder has the same morphology as B 4 C, and the properties and the shape of CaB 6 powders can be improved by choosing good-quality raw materials.

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