Multiferroic BiMnO 3 with a highly distorted perovskite structure induced by the stereochemically active 6s 2 electron lone pairs of Bi 3+ was synthesized at a high pressure of 6 GPa. Magnetization, differential scanning calorimetry, dielectric permittivity, and in situ powder x-ray diffraction as a function of temperature were carried out, respectively. In light of comprehensive evaluation, we can conclude that the synthetic BiMnO 3 ceramic displays ferromagnetic and ferroelectric orderings simultaneously, i.e., ferroelectromagnetism below its ferromagnetic Curie temperature T M ϳ 100 K.

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A Ni coating and nano-SiC/Ni composite coating were prepared on diamond surfaces by an electro-co-deposition method. The surface morphology of plated diamond grit and the bonding state between diamond and Fe-matrix bond were characterised by the scanning electron microscopy and energy-dispersive spectroscopy (EDS). The flexural strength and wear resistance performance of the Fe-matrix bonded diamond tool bits were tested. The results showed that the nano-SiC/Ni composite coating possesses a smoother, finer, and denser microstructure when compared with a pure Ni coating. Furthermore, the nano-SiC/Ni composite coating on diamond surfaces improved the flexural strength and wear resistance of Fe-matrix bonded diamond tool bits. The EDS analysis indicated that the chemical combination between diamond grits and Fe-matrix bonding was formed, thereby the mechanical properties of Fe-matrix bonded diamond tool bits were enhanced.

A series of samples of Ba 9 Co 3 (Se 1−x S x ) 15 (x = 0, 0.05, 0.1, 0.15, 0.2) with quasi-one-dimensional (1D) structure were successfully synthesized under high-temperature and high-pressure conditions. The influence of partial substitution of S for Se on the structure, electronic transport, and magnetic properties of Ba 9 Co 3 (Se 1−x S x ) 15 has been investigated in detail. The x-ray diffraction data shows that the lattice constant decreases linearly with increasing S-doping level, which follows the Vegrad's law. The doped S atoms preferentially occupy the site of Se atoms in CoSe 6 octahedron. Physical properties measurements indicate that all the samples of Ba 9 Co 3 (Se 1−x S x ) 15 are semiconducting and display spin glass behavior. As the replacement of Se by smaller size S, although the inter-chain distance decreases, the electronic hopping between CoSe/S 6 chains is weakened and leads to an increase of band gap from 0.75 eV to 0.86 eV, since the S-3p electrons are more localized than Se-4p ones. Ba 9 Co 3 (Se 1−x S x ) 15 exhibits 1D conducting chain characteristic.

Dense nanocrystalline BaTiO 3 ceramics are successfully prepared by the high pressure assisted sintering. Microstructures are observed by scanning electronic microscopes. The grain sizes are estimated to be about 30 and 150 nm. In comparison, BaTiO 3 ceramics with the grain size of 600 nm and 1.5 µm are fabricated by conventional pressure-less sintering. The thermal properties of BaTiO 3 ceramics with different grain sizes are investigated by differential scanning calorimetry and thermal expansion. The results suggest that the enthalpy values for the tetragonal-cubic transition decreased and the thermal expansion values increased with decreasing grain size. Furthermore, the Curie temperature shifts to lower temperature with decreasing grain size.

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