Preparation of Hierarchically Porous Niobium(V) Oxide and Alkaline Niobate Monoliths via Sol-Gel Accompanied by Phase Separation

被引:3
作者
Sato, Yuji [1 ]
Kanamori, Kazuyoshi [1 ]
Nakanishi, Kazuki [2 ,3 ]
机构
[1] Kyoto Univ, Grad Sch Sci, Dept Chem, Kyoto, Kyoto 6068502, Japan
[2] Nagoya Univ, Inst Mat & Syst Sustainabil, Div Mat Res, Nagoya, Aichi 4648601, Japan
[3] Kyoto Univ, Kyoto Univ Inst Adv Study, Inst Integrated Cell Mat Sci, Kyoto, Kyoto 6068501, Japan
基金
日本科学技术振兴机构;
关键词
HYDROTHERMAL SYNTHESIS; PROPYLENE-OXIDE; PORE STRUCTURE; AEROGELS; ROUTE; TEMPERATURE; TRANSITION;
D O I
10.1021/acs.chemmater.3c00916
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Hierarchically porous niobium(V)oxide monoliths were preparedthrough the sol-gel process accompanied by phase separationand subsequent heat treatment. Macroporous and mesoporous characteristicsas well as crystal structures were investigated in detail. Macroporousstructures were controlled by the starting composition to manipulatephase separation, whereas mesoporous structures were modified by heattreatment in air to crystallize niobium(V) oxide. The results showedthat by heat treating the as-dried gel at 550 & DEG;C in air, a hierarchicallyordered macro/mesoporous material with BET surface area of 54 m(2) g(-1) was obtained. With an increase of theheat treatment temperature, an increase in the mesopore size accompaniedby a decrease in the specific surface area was observed as a resultof crystallite growth. Heat treatment under a N-2 atmosphereresulted in the formation of phases with lower-valence niobium suchas NbO2 and Nb12O29, which were derivedfrom the reduction by the carbothermal reaction due to the presenceof carbonized organic compounds. The conversion of niobium(V) oxideinto niobium-containing complex oxides was also examined. Alkalinemetals, namely, Li, Na, and K, were incorporated by postgelation treatments.Niobium-rich alkaline niobate phases were obtained when alkaline chloridewas incorporated, whereas the majority of lithium niobate (LiNbO3) phases were obtained when samples were treated with lithiumhydroxide.
引用
收藏
页码:5177 / 5184
页数:8
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