Characterization of tin selenides synthesized by high-energy milling
Tin selenides SnSeX (x=1,2) were synthesized from tin and selenium powder precursors by high-energy milling in the planetary ball mill Pulverisette 6 (Fritsch, Germany). The orthorhombic tin selenide SnSe and the hexagonal tin diselenide SnSe2 phases were formed after 4 min and 5 min of milling, respectively. Specific surface area of both selenides increased with increasing time of mechanochemical synthesis. The particle size distribution analysis demonstrated that the synthesized products contain agglomerated selenide particles consisting of numerous idiomorphic tin selenide crystals, measuring from 2 to more than 100 nm in diameter, which were also documented by TEM. UV-Vis spectrophotometry confirmed that tin selenide particles do not behave as quantum dots.
Synthesis of binary copper chalcogenides by mechanical alloying
Copper sulfides (tetragonal Cu{sub 1.92}S-Cu{sub 1.99}S, rhombohedral Cu{sub 1.71}S-Cu{sub 1.89}S, CuS) selenides ({beta} Cu{sub 2{minus}x}Se, Cu{sub 3}Se{sub 2}, {gamma} CuSe, CuSe{sub 2}), and tellurides (Cu{sub 2{minus}x}Te, Cu{sub 3}Te{sub 2}) were prepared from mixtures of the elements by mechanical alloying (MA), using a high-energy ball mill. The compounds were obtained by 60--120 min of MA. It is notable that two metastable high-pressure phases were obtained by MA: tetragonal Cu{sub 2{minus}x}S and pyrite-type CuSe{sub 2}. The tetragonal phase gradually transformed to the stable phase of djurleite when kept at room temperature. Cu{sub 1.71}S-Cu{sub 1.89}S also formed a metastable rhombohedral phase.
Formation of amorphous alloys by solid state reactions
Abstract Amorphous metallic alloys have traditionally been prepared by the rapid solidification of molten alloys. Recently, new synthesis methods have been developed which are based on isothermal solid state reactions between pure metals. These reactions are carried out at temperatures that kinetically favor the interdiffusion of the species but preclude the nucleation of intermetallics. Other novel synthesis methods rely on the mechanical attrition of crystalline alloy powders. This paper reviews the basic concepts behind these novel synthesis methods and compares the amorphous alloys prepared by these techniques with those obtained by the rapid solidification of melts.