Effect of curing temperature on the development of hard structure of metakaolin-based geopolymer

Adsorption of organic molecules on silica surface.

Infrared spectra-structure correlations for organosilicon compounds

The synthesis and characterization of Ta-TMS1, a new member of a growing family of hexagonally packed transition-metal oxide mesoporous molecular sieves (termed TMS1) is described. Ta-TMS1 exhibits a hexagonal array of pores which can be varied in size from 20 to 40 A and surface areas of over 500 m2/g. The thermal and hydrothermal stabilities of Ta-TMS1 are 500 and 450 °C, respectively, making this system the most stable transition-metal oxide molecular sieve yet isolated. The high hydrocarbon adsorption capacities of this material make it a promising candidate as a catalyst support for hydrocarbon re-forming processes. The synthesis of this material was achieved by a novel approach involving the careful hydrolysis of long-chain primary amine complexes of Ta(OEt)5. This ligand-assisted templating mechanism represents a new approach to the synthesis of porous materials in that the inorganic precursor is covalently bonded to the template throughout synthesis. The high thermal stability, ease of synthesis a...

Synthesis and Characterization of Hexagonally Packed Mesoporous Tantalum Oxide Molecular Sieves

The structure of alkoxysilane-derived SiO 2 gels which were prepared under the partial hydrolysis condition and contained a considerable amount of unhydrolyzed alkoxy groups, and the structure change of the gels in the early stage of gel to glass conversion were investigated as a function of the behavior of a small IR band peaking at 550–600 cm −1 . The 550–600 cm −1 peak was assigned to the skeletal vibration of the 4-fold siloxane rings by reference to various cyclic siloxanes and silicate minerals. The presence of unhydrolyzed alkoxy groups was important for the formation or retention of 4-fold rings in the gels. On heating the gels in air, it was found that the 4-fold siloxane rings were broken to form SiOH bonds with release of alkoxy groups around 200°C, at which temperature the siloxane network was degraded, followed by healing through the condensation of SiOH at a higher temperature.

A. C. Jones

Papers

An Infrared Study of the Water-Silica Gel System