土壤学报2013，Vol.50Issue(1)：96-105,10.
不同氧化度六方水钠锰矿的结构研究
STRUCTURE OF HEXAGONAL BIRNESSITES AS AFFECTED BY OXIDATION STATE
摘要
Abstract
Powder X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques were used to investigate variations of the structures of hexagonal birnessites as related to average oxidation states of manganese therein (Mn AOS).As the synthesized series of hexagonal birnessites from HB1 to HB6 decrease from 3.92 to 3.67 in Mn AOS,but increase from 2.838 (A) to 2.848 (A) in unit cell parameter b.The series also decrease from 12.0 nm to 7.0 nm in the coherent scattering domains (CSD) in the a-b layer plane,forming a stack of ～ 10.6-13.4 layers of manganese oxide octahedron along axis c.With the decrease in Mn AOS,the content of octahedral voids declines from 18％ to 8％.Mn AOS and vacancy content have a very significant positive linear relationship,and they both show negatively linear relationships with unit cell parameter b.Linear fitting of X-ray absorption near edge structure spectroscopy (XANES) shows that Mn in these samples is dominated by Mn4+ and the proportion of Mn2+/3+ increases with the decreasing content of octahedral voids.Fitting analysis of Mn K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) with a full multiple scattering model demonstrates that the samples,though different in Mn AOS,are similar in crystal structure and Mn local coordination environment.With the decrease in content of octahedral voids and particle size,apparent Mn site occupancy (focc) decrease from 0.74 for HB1 to O.66 for HB6,and with the decrease in Mn AOS,the average bond-length of MnMn(O) shells increase.关键词
水钠锰矿/八面体空位/锰平均氧化度/粉末X射线衍射/X射线吸收光谱Key words
Birnessite/ Octahedral voids/ Mn average oxidation state/ Powder X-ray diffraction/ X-ray absorption spectroscopy分类
资源环境引用本文复制引用
殷辉,冯雄汉,赵巍,胡天斗,谭文峰,刘凡..不同氧化度六方水钠锰矿的结构研究[J].土壤学报,2013,50(1):96-105,10.基金项目
国家自然科学基金项目(40830527,41271253)、全国优秀博士论文专项基金(200767)、教育部新世纪优秀人才支持计划项目(NCET-09-0399)资助 （40830527,41271253）
