尺寸和微结构效应对软锰矿红外光谱的影响

合成了纳米纤维状的软锰矿β-MnO₂,其研磨后粒子形貌由纳米纤维转变为纳米粒子,相结构并没有转变．纳米纤维状粒子中心锰离子局域环境有轻微改变．当粒子形貌从长纳米纤维变到短纳米纤维再到纳米粒子时,傅里叶转换红外光谱A_2u频率逐渐从514 cm^-1到574 cm^-1再到617 cm^-1．研究发现依据功能团分析无法确定额外的振动波段来源于不同尺寸和形状粒子的A_2u．通过X射线衍射的Rietveld精修和红外光谱,认为两种MnO₆的八面体构型,如4长+2短,4短+2长,在由不同路线合成的软锰矿中都会存在．微结构对软锰矿傅里叶转换红外光谱最大振动频率的影响是显著的．在红外和远红外区域的四个振动波段都做了分类.     

尺寸和微结构效应对软锰矿红外光谱的影响

Nanofibrous pyrolusite (β-MnO₂) was synthesized. The particle shape changes from nanofibers to nanoparticles after grinding, and the phase structure does not change. The local environment around the central manganese ion has a slight change in nanoparticles related to nanofibers. Fourier transform infrared (FTIR) spectra showed that A_2u mode frequency shifts from 514 cm^-1 to 574 cm^-1 to 617 cm^-1 gradually while the particle shape and size change from long nanofibers to short fibers and to nanoparticles. The extra vibra-tional band that is unpredicted by factor group analysis originates from the contribution of A_2u mode of the particles with different sizes and shapes in the studied sample. On the basis of Rietveld refinement analysis of XRD profiles and the FTIR spectra, we think that two kinds of MnO₆ octahedral geometries, i.e., 4 long+2 short and 4 short+2 long, could exist in pyrolusites synthesized by different route. The maximum vibrational frequency in the FTIR spectra of pyrolusites is sensitive to these micro-structures. Assignment of four vibrational bands in the middle and far infrared region has been made.