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Synthesis, microstructure and mechanical properties of bronze–molybdenum composites processed via LPS and SPS methods

Memari S., Ardestani M., Abbasi A.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 4

1013--1023

EN

In this work, synthesis, densification and properties of bronze–70 wt% Mo and bronze–30 wt% Mo composite powders were investigated. The composite powders were prepared by mechanical milling of bronze–Mo powder mixtures for 16 h. The results of cold compressibility investigations showed that Heckel and Ge equations provided the best fit scenario for bronze–70 wt% Mo and bronze–30 wt% Mo, respectively. The composite powders were consolidated via pressureless and spark plasma sintering processes. The relative densities of spark plasma sintered samples with 30 and 70 wt% molybdenum were about 98%. However, the relative density of bronze–70 wt% Mo and bronze–30 wt% Mo pressureless sintered samples were 97.1 and 94.3%, respectively. The scanning electron microscopy observations revealed that the size and dispersion of Mo particles within the bronze matrix in the pressureless sintered samples was completely different from that of the spark plasma sintered ones. Furthermore, it was found that in spite of nearly close relative densities, the hardness and flexural strength of the spark plasma sintered samples were higher than that of the pressureless sintered ones which was due to different shape, size and dispersion of the Mo particles within the matrix phase in the different samples. According to the results, the preferred densification process was SPS method.

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Synthesis of Ag-ZnO composites via ball milling and hot pressing processes

Ardestani M., Zakeri M, Nayyeri M J, Babollhavaejie M R

Materials Science Poland

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2014

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Vol. 32, No. 1

121--125

EN

Ag – 8 wt. % ZnO composites were synthesized by ball milling, heat treating and hot pressing of silver and zinc oxide powder mixtures. The crystalline size and microstrain of the milled powders before and after heat treatment were determined by Debye-Scherrer andWilliamson-Hall methods. It was shown that heat treatment resulted in decrease of microstrain and increase in the crystallite size of the milled powders. The effect of uniaxial pressure magnitude and duration of hot pressing at 550 °C on the final density of the powder compacts were investigated. The results showed that both plastic flow and atomic diffusion mechanisms affected densification of the composite powders during the hot pressing process. However, the latter one had more effective role on the density of the hot-pressed samples. The synthesized composites showed homogenous microstructure with relatively high density and hardness.

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Synthesis of WC-20 wt. % Cu composite powders by co-precipitation and carburization processes

Ardestani M., Arabi H., Razavizadeh H., Rezaie H. R., Mehrjoo H.

Materials Science Poland

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2010

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Vol. 28, No. 2

413--420

EN

WC/Cu composite powders were synthesized by co-precipitation and subsequent reduction-carburization process. The precipitates contained W-Cu compounds fabricated using a chemical procedure from a mixture of copper nitrate and ammonium paratungstate in distilled water. In order to synthesize the WCCu composite powders, dried precipitates were calcined at 823 K in air and then reduced and carburized by carbon monooxide (CO). The non-isothermal mechanism of reduction-carburization of the calcined powders in carbon monoxide was investigated by thermogravimetry, differential thermogravimetry and X-ray diffraction analyses. The optimum reduction-carburization temperature was determined as 1065 K. The microstructures of the powders were characterized by the scanning electron microscopy.