Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (11): 1979-1986.doi: 10.3866/PKU.WHXB201409251

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

EXAFS Study of the Structure of Amorphous Nickel Borate

LIU Hong-Yan1,2, FANG Chun-Hui1, FANG Yan1, ZHOU Yong-Quan1, ZHU Fa-Yan1, GE Hai-Wen1, YANG Zi-Xiang1,2, TANG Yu-Ling1,2   

  1. 1. CAS Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, P. R. China;
    2. University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2014-08-06 Revised:2014-09-25 Published:2014-10-30
  • Contact: FANG Chun-Hui, FANG Yan E-mail:fangch@isl.ac.cn;fangy8@isl.ac.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21373251) and Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences, China (KZCX2-EW-307).

Abstract:

In this work, two amorphous hydrated nickel borates were synthesized with nickel chloride hexahydrate and borax as reactants at mole ratios of 1:2 and 1:8, respectively. The chemical compositions of these nickel borates were determined to be NiO·0.8B2O3·4.5H2O and NiO·B2O3·3H2O through thermogravimetryderivative thermogravimetry (TG-DTG) and chemical analysis, in which the main anions were determined to be B3O3(OH)52- and B2O(OH)62-, respectively, by Raman spectroscopy. The local structure of these samples was studied by synchrotron radiation extended X-ray absorption fine structure (EXAFS). Based on the processing and fitting of the EXAFS experimental data, the neighboring coordination atoms type, the interatomic distances, and the atom-pair numbers of Ni were determined. The fitting results of the amorphous nickel borate show that the local structure around the Ni atom has a similar structure to that of the Ni3B2O6 crystal. The neighboring coordination atoms of Ni in these amorphous nickel borates are O, B, and Ni. For NiO·0.8B2O3·4.5H2O, the interatomic distances for Ni―O, Ni―B, and Ni―Ni are 0.208, 0.263, and 0.311 nm, and the atom-pair numbers are 5.7, 3.8, and 3.8, respectively. The interatomic distances of NiO·B2O3·3H2O are 0.207, 0.262, and 0.310 nm, and the atom-pair numbers are 6.0, 4.0, and 4.0, respectively. The first shells of Ni2+ in NiO·0.8B2O3·4.5H2O and NiO·B2O3·3H2O are octahedral with six oxygen atoms.

Key words: Nickel borate, Nickel hydroxide, Extended X-ray absorption fine structure, Local structure, Coordination atom

MSC2000: 

  • O641