Showing papers by "Kenneth J. D. MacKenzie published in 2011"
TL;DR: The most successful sol-gel synthesis of a germanate compound with the properties of an inorganic polymer was of an aluminogermanate containing Na + and K + as the exchangeable cations.
16 citations
TL;DR: A combined sol-gel and solid-state method reported for the synthesis of gallium silicate analogues of aluminosilicate inorganic polymers has also been extended to the formation of related compounds with a range of Al-for Ga substitutions.
Abstract: A combined sol–gel and solid-state method reported for the synthesis of gallium silicate analogues of aluminosilicate inorganic polymers has also been extended to the formation of related compounds with a range of Al-for Ga substitutions. Homogeneous, robust products were obtained at an optimum composition of SiO2:(Ga2O3 + Al2O3) = 7. After curing at 40 °C, all the products were typically X-ray amorphous, and the Al and Ga was shown by 27Al and 71Ga MAS NMR spectroscopy to be in solely tetrahedral coordination. The 29Si MAS NMR spectra were as expected for silicate inorganic polymers, but also indicated the presence of some unreacted silica. Electron microscopy in conjunction with EDS elemental mapping showed that the Ga, Al and Si was homogeneously distributed in the products. Thermal treatment of these compounds results in endothermic water loss at about 75–160 °C followed by an exothermic event at about 950 °C corresponding to crystallization of KGaSi2O6 in the gallium end-member. By contrast, the Al-substituted compounds never fully crystallised, but melted at 1200 °C to an X-ray amorphous product.
12 citations
TL;DR: In this article, two different mesoporous silicas (MPSs) were synthesized by hydrothermal treatment in NaOH solution of two SiO2 sources, and they were derived from selectively acid leached metakaolinite and tetraethylorthosilicate (TEOS).
Abstract: Two different mesoporous silicas (MPS) were synthesized by hydrothermal treatment in NaOH solution of two SiO2 sources. These were microporous silica (MicroPS) derived from selectively acid leached metakaolinite and tetraethylorthosilicate (TEOS). The hydrothermal syntheses of the MPSs were performed at a ratio of SiO2/cetyltrimethyl- ammonium bromide (CTABr)/NaOH/H2O = 1/0.1/0.3/150. The specific surface areas (S
BET) of the MPSs from MicroPS (MPS(M)) and TEOS (MPS(T)) were 1070 and 1020 m2/g, respectively. Composites of MPS (75 mass%) with TiO2 (25 mass%) were prepared using both SiO2 and two commercial TiO2 powders, P25 and ST-01. The adsorption–desorption behavior of methylene blue (MB) by the four resulting composites and the two MPSs alone was unique in showing partially reversible behavior. The maximum MB adsorption, observed in the composite of ST-01 with MPS(M), designated (S/M), was 0.034 mmol/g. The rates of MB adsorption in the dark and photodecomposition under UV illumination were considerably different for the four composites and two TiO2 powers, and followed the order ST-01 < S/T < P25 < P/T ≈ P/M ≪ S/M. The removal rate of MB by the composite S/M by adsorption and photodecomposition was further enhanced by heating at 700 °C. Direct photodecomposition of MB without adsorption in the dark was greatly enhanced in the composites, especially in that composed of MPS(M) and ST-01.
7 citations