A mixture of elemental Co50Si50 powders was subjected to mechanical alloying (MA) at room temperature to prepare a CoSi thermoelectric compound. Consolidation of the Co50Si50 mechanically alloyed powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 800 °C and 1,000 °C under 50 MPa. We have revealed that a nanocrystalline CoSi thermoelectric compound can be produced from a mixture of elemental Co50Si50 powders by mechanical alloying after 20 hours. The average grain size estimated from a Hall plot of the CoSi intermetallic compound prepared after 40 hours of MA was 65 nm. The degree of shrinkage of the consolidated samples during SPS became significant at about 450 °C. All of the compact bodies had a high relative density of more than 94 % with a metallic glare on the surface. X-ray diffraction data showed that the SPS compact produced by sintering mechanically alloyed powders for 40-hours up to 800 °C consisted of only nanocrystalline CoSi with a grain size of 110 nm.

Fabrication of a ferromagnetic composite powder for the magnesium and BaFe12O19 system by mechanical alloying (MA) is investigated at room temperature. Mixtures of Mg and BaFe12O19 powders with a weight ratio of Mg:BaFe12O19 = 4:1, 3:2, 2:3 and 1:4 are used. Optimal MA conditions to obtain a ferromagnetic composite with fine microstructure are investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that Mg-BaFe12O19 composite powders in which BaFe12O19 is dispersed in Mg matrix are successfully produced by MA of BaFe12O19 with Mg for 80 min. for all compositions. Magnetization of Mg- BaFe12O19 composite powders gradually increases with increasing the amounts of BaFe12O19, whereas coercive force of MA powders gradually decreases due to the refinement of BaFe12O19 powders with MA time for all compositions. However, it can be seen that the coercivity of Mg-BaFe12O19 MA composite powders with a weight ratio of Mg:BaFe12O19=4:1 and 3:2 for MA 80 min. are still high, with values of 1260 Oe and 1320 Oe compared to that of Mg:BaFe12O19=1:4. This clearly suggests that the refinement of BaFe12O19 powders during MA process for Mg:BaFe12O19=4:1 and 3:2 tends to be suppressed due to ductile Mg powders.

Synthesis of composite powders for the Fe2O3-Zn system by mechanical alloying (MA) has been investigated at room temperature. Optimal milling and heat treatment conditions to obtain soft magnetic composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that α-Fe/ZnO composite powders in which ZnO is dispersed in α-Fe matrix can be obtained by MA of Fe2O3 with Zn for 4 hours. The change in magnetization and coercivity also reflects the details of the solid-state reduction process of hematite by pure metal of Zn during MA. Densification of the MA powders was performed in a spark plasma sintering (SPS) machine at 900 ~ 1,000 ℃ under 60 MPa. Shrinkage change after SPS of sample MA'ed for 5 hrs was significant above 300 ℃ and gradually increased with increasing temperature up to 800 ℃. X-ray diffraction results show that the average grain size of α-Fe in the α-Fe/ZnO composite sintered at 900 ℃ is in the range of 110 nm.

Fabrication of soft magnetic composite powders for the Fe2O3-Ca system by mechanical alloying(MA) has been investigated at room temperature. It is found that soft magnetic composite powders in which CaO is dispersed in α-Fe matrix are obtained by MA of Fe2O3 with Ca for 5 hours. Changes in magnetization and coercivity also reflect the details of the solidstate reduction process of hematite by pure metal of Ca during MA. The saturation magnetization of MA powders increases with increasing MA time and reaches a maximum value of 65 emu/g after 7 hours of MA. The average grain size of α-Fe in MA powders, estimated by diffraction line-width, gradually decreases with increasing MA time and reaches 52 nm after 5 hours of MA. It can also be seen that the coercivity of the 5-hour MA sample is fairly high at 190 Oe, suggesting that the grain refinement of already-produced α-Fe tends to clearly occur during MA.