We report optical reflectivity study on pure and boron-doped diamond films grown by a hotfilament chemical vapor deposition method. The study reveals the formation of an impurity band close to the top of the valence band upon boron-doping. A schematic picture for the evolution of the electronic structure with boron doping was drawn based on the experimental observation. The study also reveals that the boron doping induces local lattice distortion, which brings an infraredforbidden phonon mode at 1330 cm −1 activated in doped sample. The antiresonance characteristic of the mode in conductivity spectrum evidences the very strong coupling between electrons and this phonon mode.

The total output of unshaped refractories has been increasing in recent years due to its short production cycle, safety and energy saving, good integrity and so on. Among them, aluminosilicate castables have been widely used. In order to improve the high temperature properties of castable, Al2O3 micro powder and SiO2 micro powder are usually used. However, few researchers have reported the effect of particle size in matrix on in-situ formation of mullite. In this paper, a mass dissolution rate model and a solution nucleation shrinkage model are established based on the control of the rate of in-situ mullite formation, which takes place by the dissolution of Al2O3 to the liquid phase formed by melting of SiO2 powder containing impurities at high temperature.The results show that with the increase of Al2O3 particle size, the mass dissolution rate of independent particles was accelerated, and the nuclear shrinkage rate of Al2O3 particles decreased fastest when the particle size is 1-10μm. The dissolution rate increases with the increase of service temperature. Moreover, the complete dissolution time is shortened with the decrease of particle size of Al2O3. When the particle size is 80μm, it takes 100.31 seconds for a single particle to dissolve completely, but only 1.00 second when the particle size of Al2O3 decreases to 8μm.