六硼化钙纳米粉末的吸收光谱研究（英文）

摘要：采用CaCl2 and NaBH4为原料低温合成CaB6纳米粉末.X射线衍射结果表明生成了CaB6晶体.场发射扫描电镜（FESEM）观测到粉末由接近立方体的平均粒径为80nm的小晶粒组成，有轻微团聚现象.高分辨透射电镜（HRTEM）表明纳米颗粒为单晶，这一发现与XRD和FESEM的结果相对应，且观察到晶体是以结晶良好的CaB6为芯，外面包覆着厚约4～5nm的非晶层.CaB6纳米粉末的光学性能是通过傅立叶红外光谱和紫外-可见-近红外光谱来表征的，同时做CaB6微米粉末的光谱用以比较.与微米粉末仅有微弱的吸收带相比，纳米粉末的光谱出现明显的宽化和红移现象，这与晶格膨胀和纳米效应有关.紫外-可见-近红外光谱中，微米粉末几乎没有吸收，纳米粉末可吸收紫外线，并出现蓝移现象.总之，CaB6纳米粉末在紫外-中红外波段总有吸收，特别是在中红外区，吸收强度远大于微米粉末.

Absorption spectra of calcium hexaboride nanopowders

Abstract: Calcium hexaboride (CaB6) nanopowder was prepared by low temperature chemical reaction of CaCl2 and NaBH4. X ray powder diffraction pattern indicated the formation of CaB6 crystal, the field emission scanning electron microscope (FESEM) image showed that CaB6 nanopowder was agglomerated with cubic crystals with grain size of ～80?nm. HRTEM photographs indicated that the nanoparticles were single crystal corresponding to the FESEM and XRD results, and the CaB6 crystal consisted well crystallized CaB6 core and thin amorphous shell (4～5?nm). Fourier transform Infrared (FTIR) and Ultraviolet Visible Near Infrared (UV VIS NIS) spectra were investigated to characterize optical properties of CaB6 nanopowder, compared with micrometer CaB6 powders. Compared with the weak absorption bands of micron powder, obvious Einstein shift and band broadening occurred in nanopowder spectrum, which was thought to be related to lattice expansion and nanometer effect. UV VIS NIS spectrum showed that CaB6 nanopowder could absorb ultraviolet rays and the absorption peaks exist blue shift of spectrum, compared with micron powder. In conclusion, CaB6 nanopowder showed absorbency within all the detected regions in FTIR and UV VIS NIS spectra, especially to the infrared.