Thermo-chemical technique was used to synthesize Cu-Al2O3, nanocomposite powders. The process was carried out by addition of Cu powder to aqueous solution of aluminum nitrate. Afterwards, a thermal treatment at 850℃ ...Thermo-chemical technique was used to synthesize Cu-Al2O3, nanocomposite powders. The process was carried out by addition of Cu powder to aqueous solution of aluminum nitrate. Afterwards, a thermal treatment at 850℃ for 1 hr was conducted to get insitu powders of CuO and stable alumina (Al2O3, ). The CuO was reduced in hydrogen atmosphere into copper powder. The nanocomposite powders of both copper and alumina were thoroughly mixed, cold pressed into briquettes and sintered at 850℃ in hydrogen atmosphere. The x-ray diffraction and scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) were used to characterize the structure of the obtained powders. The results showed that alumina nanoparticles (20 nm) and ultra fine copper crystallite (200 nm) were obtained. SEM and EDS showed that the alumina particles were uniformly dispersed within the copper crystallite matrix. The structure also revealed formation of a third phase (CuAlO2) at copper-alumina interface. The hardness and density results showed that the gain in hardness was found to be dependent on the alumina contents rather than on the relative densities. The alumina content up to 12.5% resulted in an increase of 47.9% in hardness and slight decrease (7.6%) in relative densities. The results of compression tests showed considerable increase in compression strength (67%) as alumina content increased up to 12.5%. The compression strength showed further increase in compression strength (24%) as strain rates were increased from 10-4 s to 10s. Strain hardening and strain rate parameters “n” and “m” have shown positive values that improved the total strain and they can be used to predict formability of the nanocomposite.展开更多
文摘Thermo-chemical technique was used to synthesize Cu-Al2O3, nanocomposite powders. The process was carried out by addition of Cu powder to aqueous solution of aluminum nitrate. Afterwards, a thermal treatment at 850℃ for 1 hr was conducted to get insitu powders of CuO and stable alumina (Al2O3, ). The CuO was reduced in hydrogen atmosphere into copper powder. The nanocomposite powders of both copper and alumina were thoroughly mixed, cold pressed into briquettes and sintered at 850℃ in hydrogen atmosphere. The x-ray diffraction and scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) were used to characterize the structure of the obtained powders. The results showed that alumina nanoparticles (20 nm) and ultra fine copper crystallite (200 nm) were obtained. SEM and EDS showed that the alumina particles were uniformly dispersed within the copper crystallite matrix. The structure also revealed formation of a third phase (CuAlO2) at copper-alumina interface. The hardness and density results showed that the gain in hardness was found to be dependent on the alumina contents rather than on the relative densities. The alumina content up to 12.5% resulted in an increase of 47.9% in hardness and slight decrease (7.6%) in relative densities. The results of compression tests showed considerable increase in compression strength (67%) as alumina content increased up to 12.5%. The compression strength showed further increase in compression strength (24%) as strain rates were increased from 10-4 s to 10s. Strain hardening and strain rate parameters “n” and “m” have shown positive values that improved the total strain and they can be used to predict formability of the nanocomposite.
