Chemical Modification of Niobium Layered Oxide by Tetraalkylammonium Intercalation
نویسندگان
چکیده
A modificação química do material lamelar K 4 Nb 6 O 17 foi investigada sistematicamente através da reação de sua forma protônica (H 2 K 2 Nb 6 O 17 ) em soluções alcalinas contendo os cátions tetrametilamônio (tma), tetraetilamônio (tea) ou tetrapropilamônio (tpa). A quantidade intercalada corresponde a 50% (para tma), 25% (para tea) e 15% (para tpa) da carga negativa do H 2 K 2 Nb 6 O 17 (considerando a troca iônica na região interlamelar I). As amostras de hexaniobato apresentam reflexões basais (020) de 23,0, 26,3 e 26,5 Å quando intercaladas, respectivamente, com tma, tea e tpa. Aquecendo-se as amostras acima de 200-250 C, observa-se a liberação de CO 2 ; a reação de eliminação de Hofmann também é observada para as amostras de hexaniobato-tpa. As imagens de microscopia eletrônica de varredura mostram a presença predominante de partículas em forma de placas; partículas em forma de bastões também são observadas nas amostras contendo íons volumosos. A reação de intercalação é promovida na ordem tma > tea > tpa, enquanto a formação de uma dispersão de partículas coloidais é facilitada na ordem inversa.
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