Single crystal particles of mesoporous (Nb, Ta)_2O_5

摘要

Mesoporous Nb-Ta mixed oxide, (Nb, Ta)_2O_5, with whormhole mesopore structure was prepared by using a block co-polymer template and metal chlorides in ethanol. The mesoporous (Nb, Ta)_2O_5 calcined at 673 K for 20 h showed 140 m~2·g~(-1) of BET surface area and 3.0 nm of pore size. The amorphous wall of the mesoporous (Nb, Ta)_2O_5 was crystallized by further calcination at 923 K for 1 h. The BET surface area and pore size estimated by N_2 adsorption isotherm of the crystallized (Nb, Ta)_2O_5 were 48 m~2·g~(-1) and 10.0 nm, respectively. Detailed analysis of transmission electron microscope (TEM) and electron diffraction (ED) revealed that each particle of sub-micron size was a mesoporous single crystal. The pore size and crystallinity observed by TEM were in good agreement with N_2 adsorption-desorption isotherms and powder X-ray diffraction patterns. Similar mesoporous (Nb, Ta)_2O_5 single crystal particles were also obtained by using amorphous precursor prepared by ligand-assisted templating method. Therefore, mixing two similar elements, Nb and Ta, is suspected to be beneficial for crystallization with sustaining the mesoporores.