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Silicon carbide was employed as a source of silicon and carbon to produce sintered silicon steels, offering the advantages of silicon addition. This work explored the effects of low SiC contents of 1.0 and 2.0 wt.% on as-sintered and as-tempered microstructures and mechanical properties of sintered silicon steels. The experimental sintered steels were produced from mixtures of pre-alloyed Fe-1.50Mo and SiC powder. The mixtures were compacted to tensile bars, sintered at 1553 K for 2.7 ks, and cooled at 9.0 K/s with N2. Sintered specimens were tempered at 873 K and held for different times. The microstructures and mechanical properties of the sintered and tempered specimens were characterized. It was revealed that the sintered silicon-bearing steels showed low temperature phase transformations under cooling at 9.0 K/s. The sintered steel produced by 1.0 wt.% SiC addition had degenerate upper bainite microstructure and its tempered microstructure was upper bainite. The sintered steel produced by 2.0 wt.% SiC addition had a microstructure consisting of bainitic-ferrite plates, martensite plates, and austenite blocks. Its tempered microstructure was upper bainite. The tempered microstructures resembled those of sintered Si-free Fe-Mo-C steels. Tempered specimens exhibited tensile strength higher but elongation lower than sintered ones attributed to carbide precipitation strengthening. [ABSTRACT FROM AUTHOR]

Solid state transformation of supersaturated solid solution to anomalous Ni-Sn eutectic has been studied. The metastable Ni-Sn solid solution was prepared via mechanical alloying of a mixed Ni+Sn powder containing 32.5 wt-% Sn powder. The milling conditions included ball to powder ratio (BPR) of 5:1 and milling speed of 300 rpm. Milling times were varied as 5, 15, and 25 hours. Milling the mixed powder for longer than 15 hours resulted in formation of supersaturated Ni-Sn solid solution. Differential thermal analysis of the supersaturated Ni-Sn solid solution revealed two reactions, namely peritectoid and peritectic reactions, occurring at 945 and 1,141°C, respectively. Heating of the supersaturated Ni-Sn solid solution to different temperatures such as 800, 850, 900, 950, 1,100, and 1,140°C with holding time of 10 minutes resulted in development of anomalous eutectic with Ni3 Sn phase matrix embedded with Ni solution particles. Sintering and coarsening of the eutectic was depending on heating temperatures. [ABSTRACT FROM AUTHOR]

It was found that the addition of a liquid forming powder (up to 6 wt.% of a gas-atomized tin powder) to 316L powder could activate the sintering process. Sintering activation could be observed by an increase of the sintered density and selected mechanical properties. When optimized tin powder content was used, shorter sintering time and lower sintering temperature could produce sintered 316L+tin materials with excellent mechanical properties. Electron dispersive spectroscopy analyses across 316L-tin-316L grains indicated that Ni transportation during the sintering process was enhanced by the presence of liquid tin. [ABSTRACT FROM AUTHOR]

The presence of non-reactive hard particles (Al2O3) causes some effects on P/M processing of sintered Fe materials. With constant compacting pressure and sintering conditions, particle size and quantity of Al2O3 particles caused reduction of green and sintered densities. Tensile strengths, elongation and hardness of the sintered material were maximum when 2 wt.% of Al2O3 particles with particle size between 20-32 um was added. The presence of Al2O3 particles may reduce sinterability of the Fe powder. [ABSTRACT FROM AUTHOR]

CuO powder is widely used because of its high activity and selectivity in oxidation/reduction reactions. CuO nanoparticles are interesting because of their high ratio of surface area to mass, which is expected to enhance the catalytic performance of a material. Because of such importance, CuO nanoparticles were prepared by two different facile routes. The first involved the reaction of pure Cu powder with nitric acid to form Cu(NO 3 ) 2 intermediate. In the second route, glacial acetic acid was employed to react with pure Cu powder to form Cu(CH 3 COO) 2 intermediate. After purification, both intermediates were reacted with NaOH via a solid-state route to form CuO powders. The intermediates and end products were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction technique. Experimental results indicated that synthesis of the CuO nanoparticles via the Cu(NO 3 ) 2 intermediate yielded slightly higher product and fine particle sizes with a larger aspect ratio. In contrast, the Cu(CH 3 COO) 2 intermediate route yielded lower product yield and fine particle sizes with a smaller aspect ratio. However, due to the extremely fine particle size it was observed that nanoparticle agglomeration could not be avoided particularly in the CuO nanopowders produced via the Cu(CH 3 COO) 2 intermediate route. [ABSTRACT FROM AUTHOR]

Abstract: Since the Cu6Sn5 intermetallic shows its importance in industrial applications, the Cu6Sn5 intermetallic-containing powders, produced by a powder processing route with a high production rate, were characterized. The route consisted of water atomization of an alloy melt (Cu–61wt.% Sn) and subsequent heat treatment of the water-atomized powders. Characterization of the water-atomized powders and their heated forms was conducted by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Fine water-atomized powder microstructures consisted of primary hexagonal η-Cu6.25Sn5 dendrites coexisting with interdendritic η-Cu6.25Sn5 +β-Sn eutectic. Solidification of fine melt droplets was governed by surface nucleation and growth of the primary hexagonal η-Cu6.25Sn5 dendrites followed by η-Cu6.25Sn5 +β-Sn eutectic solidification of the remnant liquid. In coarse melt droplets, nucleation and growth of primary ε-Cu3Sn dendrites were followed by peritectic reaction (ε-Cu3Sn+liquid→η-Cu6.25Sn5) or direct crystallization of η-Cu6.25Sn5 phase from the undercooled melt. Finally, the η-Cu6.25Sn5 +β-Sn eutectic solidification of the remnant liquid occurred. Heating of the water-atomized powders at different temperatures resulted in microstructural homogenization. The water-atomized powders with mixed phases were transformed to powders with single monoclinic ή-Cu6Sn5 phase. [Copyright &y& Elsevier]