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In the present work the effect of milling time (2-16h), milling speed (320 and 420rpm), as-received aluminum particle size (21 and 71 μm), B₄C size (90, 700 and 1200nm) and its content (5% and 10%) on the characteristics of Al-B₄C powder particles during milling was investigated by scanning electron microscopy (SEM) and laser particle size (LPS) analyzer. X-ray diffraction was used to investigate the crystal size and internal strains within the processed aluminum particles at different conditions. It was concluded that powder particles size increased after 4h milling but further milling (up to 16h) resulted in decreased powder particles size. By increasing milling speed from 320rpm to 420rpm, finer aluminum powder particle sizes were obtained in any specific milling time. XRD results confirmed that nanocrystalline structures with the size of 80nm for aluminum powder particles can be achieved in different milling conditions. SEM micrographs and EDX maps of Al-B₄C mixtures confirmed that milling at optimum conditions breaks the reinforcement particle clusters and a homogenous distribution of B₄C nanoparticles in Al-B₄C powder mixture can be achieved after milling.

In this research, the effect of milling time and annealing temperature on a heat activated synthesis of barium hexaferrite from mechanically activated mixture of hematite and barium acetate was investigated. The properties of samples were examined by XRD, DTA/TGA, SEM and VSM methods. The initial mixture with Fe/Ba molar ratio of 11 was milled for 24–48 h and then annealed at 800–1100°C. The XRD results showed the reflections of hematite as a major phase and barium hydroxide as a minor phase during mechanical milling in all three samples. It was observed that the specimen milled for 48 h exhibits the smallest mean crystallite size of 25 nm for hematite, as major phase. XRD results showed that annealing at 1100°C produces more pure barium hexaferrite phase comparing to lower temperatures. So, it was concluded that single phase BaFe₁₂O₁₉ can be achieved by milling for 48 h and then annealing at 1100°C. The sample processed at these conditions exhibited nano-crystalline barium hexaferrite powders with a mean crystallite size of 46 nm, mean particle size of about 200 nm and high coercivity of 334.2 kA/m.