TY - JOUR
T1 - Structure of hybrid (organic/inorganic) TiO2-SiO2 xerogels II
T2 - Thermal behavior as monitored by temperature-programmed techniques and spectroscopy
AU - Larsen, Gustavo
AU - Buechler-Skoda, Melissa
AU - Nguyen, Chao
AU - Vu, David
AU - Lotero, Edgar
N1 - Funding Information:
A grant from the National Science Foundation (CTS-9733756) is gratefully acknowledged. We thank also the partial support from the state of Nebraska, through a Nebraska Research Initiative grant.
PY - 2001/2
Y1 - 2001/2
N2 - Titanium-containing xerogels made by acid pre-hydrolysis of tetraethylorthosilicate (TEOS) and dimethyl-dimethoxysilane (SiMe2(OMe)2), followed by reaction with dichloro-diisopropyl titanium (TiCl2(i-OPr)2) were characterized by means of several techniques. The decomposition patterns of these xerogels, both in the presence and in the absence of oxygen are discussed in terms of the gaseous products' evolution under temperature-programmed (TP) reaction conditions, and diffuse reflectance infrared spectroscopy (DRIFTS). The primary decomposition routes of residual alkoxide groups are: (i) auto-redox (CO, CO2) and dehydration (to olefins) under pyrolysis conditions; (ii) oxidative (CO, CO2) under flowing air. The decomposition of the Si-C bond upon heating, as monitored by all three techniques, follows a pattern independent of that of (CH) species from -OR groups. The 29Si MAS/NMR of these materials is dominated by the so-called D2 (Me2Si(OX)2), Q3 ((OR)Si(OX)3) and Q4 (Si(OX)4) resonances. Fairly homogeneous proton envelopes around Si centers are evident from the NMR spectra of these materials in the proton cross-polarization mode.
AB - Titanium-containing xerogels made by acid pre-hydrolysis of tetraethylorthosilicate (TEOS) and dimethyl-dimethoxysilane (SiMe2(OMe)2), followed by reaction with dichloro-diisopropyl titanium (TiCl2(i-OPr)2) were characterized by means of several techniques. The decomposition patterns of these xerogels, both in the presence and in the absence of oxygen are discussed in terms of the gaseous products' evolution under temperature-programmed (TP) reaction conditions, and diffuse reflectance infrared spectroscopy (DRIFTS). The primary decomposition routes of residual alkoxide groups are: (i) auto-redox (CO, CO2) and dehydration (to olefins) under pyrolysis conditions; (ii) oxidative (CO, CO2) under flowing air. The decomposition of the Si-C bond upon heating, as monitored by all three techniques, follows a pattern independent of that of (CH) species from -OR groups. The 29Si MAS/NMR of these materials is dominated by the so-called D2 (Me2Si(OX)2), Q3 ((OR)Si(OX)3) and Q4 (Si(OX)4) resonances. Fairly homogeneous proton envelopes around Si centers are evident from the NMR spectra of these materials in the proton cross-polarization mode.
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U2 - 10.1016/S0022-3093(00)00414-2
DO - 10.1016/S0022-3093(00)00414-2
M3 - Article
AN - SCOPUS:0035251274
SN - 0022-3093
VL - 279
SP - 161
EP - 168
JO - Journal of Non-Crystalline Solids
JF - Journal of Non-Crystalline Solids
IS - 2-3
ER -