Iranian Journal of Materials Science and Engineering

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Abstract: The direct reduction of copper sulfide concentrate from Iranian Sarcheshme deposits with carbon in the presence of lime was investigated in the temperature range of 800-1000 ºC. The reduction kinetics was determined by means of weight loss measurements. It was found that the rate of reaction increased considerably with increasing the temperature. The kinetics was also improved when large excesses of lime and carbon were present in the mixture. The effects of catalytic additives of Na2CO3 and K2CO3 were also investigated. It was realized that the rate of reaction increased by higher concentrations of additives. X-ray diffraction analysis of reduced samples revealed that sulfur was fixed as solid CaS, and metallic copper was formed.

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Metakaolinite-based geopolymer has been synthesized at about 25 °C from metakaolin which has been calcined in different temperatures (600-900 °C) and different Na2O/SiO2 ratio activator (0.3-1.1). Compressive strength and microstructure of cement pastes after 7-28 days curing at ambient temperature were measured. Compressive strength tests on the samples showed that the sample made with calcined kaolin at 700 °C and molar ratio of 0.6 has highest average compressive strength of 32 MPa after 28 days of curing. Evaluation of infrared spectroscopy (FTIR) and microstructure showed that geopolymer cement developed and new molecular structure established

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In this work, we report the synthesis of silver decamolybdate, Ag₆Mo₁₀O₃₃, nanostructure by a simple mechanohemical process followed by calcination treatment using acetamide as driving agent. Morphological study by scanning electron microscopy (SEM) images revealed bundles of rods grown closely together with an average diameter of 92 nm for Ag₆Mo₁₀O₃₃ sample. Ni-substituted Ag₆Mo₁₀O₃₃ compound was prepared via introducing nickel cation to precursor system in mechanical milling step. The particle size decreased to 87 nm by incorporating nickel units in substituted polymolybdate. It was concluded that the suitable selection of reagents can direct solid phase reaction towards producing nanostructured products. This technique is easy and simple for preparation of various mixed metal oxides without using any solvents and or complex procedures. In addition, the photocatalytic activity of the prepared products was studied on the removal of 4-nitro phenol (4-NP) as organic pollutant from water. The obtained results were also discussed in detail.

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Niobium addition is an appropriate approach for improvement of superalloy’s operation. The purpose of this study is twofold: (1) to investigate on the η and γ^/ phase precipitations along with (2) to identify the high-temperature tensile properties in A286 and Nb-A286, as a modified type. The heat treatment of both alloys was carried out in a two-stage aging procedure at 760°C for 16 h and 820°C for 2 to 30 hours, following characterized by optical and Scanning electron (SEM-EDS) microscopies, differential thermal analysis (DTA) and high temperature tensile tests. The results showed that niobium addition was increased the volume fraction of γ^/ phase, from 10.7% to 12%, decreased its size, from 94 to 71 nm, and rising the γ^/-dissolution temperature from 987°C to 1007°C. Moreover, the γ^/ to η phase transformation was sluggishly occurred in Nb-A286 due to more stable of γ^/ precipitations. Furthermore, the Nb-A286 alloy demonstrates higher mechanical properties than A286 one, approximately 100MPa improvement, which it was contributed to the much large volume fraction and finer size of more stabilized γ^/ phase.