A Molecular Building-Block Approach to the Synthesis of Ceramic Materials

Abstract

Ceramic materials are generally prepared from structurally simple starting materials, with the consequence that structural properties are difficult to control on a molecular level. This difficulty might be addressed by following the approach taken in polymer chemistry in which molecular building blocks are first prepared and then polymerized in a subsequent step. In the present case, the polysilicic acid esters [Si2O](OCH3)6, [Si3O2](OCH3)8, and [Si8O12](OCH3)8 are prepared and then polymerized by hydrolysis/condensation. Silicon-29 solution nuclear magnetic resonance (NMR) spectroscopy is used to estimate the extent to which the molecular frameworks of these monomers are retained during the course of hydrolysis and condensation.

Pyrolytic conversion of an AlSiNC precursor prepared via hydrosilylation between [Me(H)SiNH]4 and [HAlN(allyl)]m[HAlN(ethyl)]n

“…29,30 This approach has been applied to chemical processing of ceramic-based composites to achieve better control of the conversion processes of precursors. 31 Since particle sizes in ceramic-based composites (1-20 nm 1 ) are similar to or larger than those of molecular building blocks, this approach is an extremely attractive route to designing precursors for ceramic-based composites.…”

Controlled partial hydrolysis of spherosilicate frameworks: syntheses of endo-[(Me3SiO)6Si6O7(OH)4] and endo-[(Me3SiO)6Si6O7{OSiMe2(CHCH2)}4] from [(Me3SiO)6Si6O9]

“…Although this resonance is in the range expected for fully condensed spherosilicates with Si 3 O 3 rings, it is also consistent with (SiO) 3 Si(OH) groups in relatively unstrained Si n O n rings. [25][26][27] On the basis of these data-as well as 1 H and 13 C NMR data, electrospray mass spectrometry data † and structure/ 29 Si chemical shift correlations observed for structurally similar cyclohexyl-substituted silsesquioxanes (i.e. 1, 2 and 6) 20 -the product obtained from the reaction of 3 with NEt 4 OH must be a C 2h -symmetric tetrasilanol derived from cleavage of both Si 3 O 3 rings.…”

On the textural and morphological properties of crystalline and amorphous α-tin phosphate

“…A sharp main peak appears at À12.1 ppm, a signal that is characteristic of crystalline a-Sn(HPO 4 ) 2 Á H 2 O, a species for which the connectivity of the phosphate tetrahedra is Q 1 0 , because no bridging oxygen atoms (-OP) surrounding the central phosphorus in a tetrahedron are present. 29,30 This peak can be clearly assigned to a HPO 4 2À group bound to three different tin atoms. Three additional smaller peaks can be seen protruding from the main peak at þ0.18, À6.2 and À19.5 ppm, corresponding to HPO 4…”