Porous monoliths of MoO3 nanoplates were synthesized from ammonium molybdate (AHM) by freeze-casting and subsequent thermal treatment from 300 to 600 °C. Pure orthorhombic MoO3 phase was obtained at thermal treatment temperature of 400 °C and above. MoO3 monoliths thermally treated at 400 °C displayed bimodal pore structure, including large pore channels replicating the ice crystals and small pores from MoO3 sheets stacking. Transmission electron microscopy (TEM) images revealed that the average thicknesses of MoO3 sheet were 50 and 300 nm in porous monoliths thermally treated at 400 °C. The photocatalytic performance of MoO3 was evaluated through degradation of methylene blue (MB) under visible light radiation and MoO3 synthesized at 400 °C exhibited strong adsorption performance and best photocatalytic activity for photodegradation of MB of 99.7% under visible illumination for 60 min. MoO3 photocatalyst displayed promising cyclic performance, and the decolorization efficiency of MB solution was 98.1% after four cycles.

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Porous TiAl 3 intermetallics were fabricated through vacuum reactive sintering from Ti-75Al at.% elemental powder mixture. The phase compositions, expansion behaviors, pore characteristics and microstructure evolution of TiAl 3 intermetallics were investigated, and the pore formation mechanism was also proposed. It was found that the actual temperature of compacts showed an acute climb from 668 to 1244°C in 166s, while the furnace temperature maintained the linear growth of 5°C/min, which indicated that an obvious thermal explosion (TE) reaction occurred during sintering, and only single-phase TiAl 3 intermetallic was synthesized in TE products. The open porosity increased from 22.2 (green compact) to 32.8% after reactive diffusion sintering at 600°C and rised to 58.7% after TE, then decreased to 51.2% after high-temperature homogenization at 1100°C. Therefore, TE reaction is the dominated pore formation mechanism of porous TiAl 3 intermetallics. The pore evolution in porous TiAl 3 intermetallics occurred by the following mechanisms: certain intergranular pores remained among powder particles of green compact, then low-temperature sintering resulted in a further increase in porosity due to the Kirkendall effect. Moreover, TE reaction gave rise to a dramatic volume expansion because of the rapid increase in temperature, and high-temperature sintering caused densification and a slight shrinkage.