Ben Peng

Synthesis and characterization of glass-ceramics prepared from high-carbon ferrochromium slag

Glass-ceramics have been successfully prepared from high-carbon ferrochromium slag (HCFS) and waste glass (WG), and the microstructural characterization and mechanical properties of the glass-ceramics were subsequently investigated. The development of HCFS-based glass-ceramics involves the nucleation and crystallization stages from the parent glass. With the increase in mass ratio of HCFS and WG (R(H/W)) from 0.60 to 1.67, the number of bridging oxygens of Si in the parent glass is reduced, as shown via Raman spectroscopy. Thus, their degree of polymerization decreases with it, and the temperature of nucleation and crystallization increase, which is consistent with the DSC results. The SEM images and EDS results indicate that the increasing value of R(H/W) decreases the crystal grain size and consequently increases the microhardness of the glass-ceramics. But the porosity simultaneously increases, which makes the bending strength increase at first and subsequently decrease. And the optimum properties of HCFS-based glass-ceramic samples in the present work are obtained when R(H/W) reaches 1.29, that is, a bending strength of 104 MPa and a microhardness of 9860 MPa.

Properties of regenerated MgO–CaO refractory bricks: Impurity of silicon dioxide

Abstract Regenerated MgO–CaO refractory brick samples with 0, 1·5, 3·0 wt-% SiO2 addition were prepared by using spent MgO–CaO bricks and fused magnesia as raw materials. Their phases, microstructures and flexural strength at room and 1573 K were investigated, respectively, and the maximum content of SiO2 impurity in regenerated samples had been subsequently achieved. The results showed that main phases of regenerated samples were all MgO, free CaO (f-CaO), Ca3SiO5 (C3S) and Ca2FeAlO5. Because some Al3+, Fe3+ had dissolved in the crystal lattice of C3S, it resulted in the decreasing of content of f-CaO and low melting point phase of C4AF along with the increasing of SiO2 addition, moreover, the flexural strength of regenerated samples at room temperature reduced while flexural strength at 1573 K enhanced. The maximum content of SiO2 impurity was about 4·11 wt-% in regenerated samples considering their properties for cement kiln.

Low-temperature-controlled synthesis and growth mechanism of AlN whiskers

Abstract Aluminium nitride whiskers were successfully synthesised by direct nitridation of Al and Al2O3 in graphite crucible under nitrogen atmospheres. The influence of reaction conditions such as molar ratio of Al:Al2O3 and reaction temperature on the formation of the AlN whiskers have been investigated in detail by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction and energy-dispersive X-ray spectroscopy. Through characterising the microstructure and phase constitution of the as-prepared samples, the optimum synthesis conditions of the AlN whiskers were obtained. Moreover, the growth mechanism of AlN whiskers was discussed combining thermodynamic analysis indicating that the AlN whiskers could be grown via vapour–liquid–solid mechanism.