As potential wave-transparent materials applied at high temperatures, 3D BNf/Si3N4 ceramic matrix composites were prepared by low pressure chemical vapor infiltration or deposition（LPCVI/CVD） process from SiCl4-NH3-H2-Ar gas precursor at 800 oC. The densification process, microstructure and dielectric properties of 3D BNf/Si3N4 composites were investigated. The results indicated that 3D BNf/Si3N4 was successfully fabricated by LPCVI/CVD, with final open porosity of 2.37% and density of 1.89 g/cm3. Densification kinetics of 3D BNf/Si3N4 is a typical exponential pattern. The Si3N4 matrix was uniformly infiltrated into porous BNf preform. The deposited Si3N4 matrix was amorphous by XRD analysis. Introduction of BN fiber into Si3N4 ceramic lowered the permittivity of Si3N4. The fabricated BNf/Si3N4 composites possess low permittivity of 3.68 and low dielectric loss of lower than 0.01, which are independent of temperature below400 oC. Transmission coefficient of BNf/Si3N4 composite is 0.57 and keeps stable below 400 oC. BNf/Si3N4 can be fabricated at low temperature and may be candidates for the microwave transparent materials.
法国国家图书馆藏Chinois 4430-4431赵宧光《说文长笺》一百卷,书中有明末清初学者刘凝的大量批注。这些批注的内容大致包括总体评价、六书研究、体例说明、补充材料、补充释义、注释、订正等七个方面,不仅体现了刘凝文字学尤其是六书研究的成就,而且有助于认识《说文长笺》的得失。该批注本经由马若瑟(Joseph de Prémare,1666—1736)流传到法国。
