The Role of Chemical Additives in Sol-Gel Processing

1986 ◽  
Vol 73 ◽  
Author(s):  
L. L. Hench ◽  
G. Orcel ◽  
J. L. Nogues
Keyword(s):  
Chemical Reactions ◽  
Acid Catalysis ◽  
Structural Model ◽  
Sol Gel ◽  
Silica Sol ◽  
Chemical Additives ◽  
Solubility Test ◽  
Acid Solubility ◽  
Gel Processing

ABSTRACTThe effect of various concentrations of formamide with and without acid catalysis on TMOS derived silica sol and gel structures and physical properties is described using a quantitative structural model. The model is based upon 29Si NMR, SAXS, Raman and FTIR spectroscopy, and an acid solubility test. Changes in chemical reactions during drying due to formamide are presented using FTIR, DSC and TGA data.

Sol-Gel Process form Heterometallic Alkoxides to Incorporate Alkaline- and Rare Earths in Alumina for automotive Applications

1996 ◽  
Vol 431 ◽  
Author(s):  
C. K. Narula
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Automotive Applications ◽  
Automotive Catalysts ◽  
Heterometallic Alkoxides ◽  
Sol Gel Process ◽  
Alkaline Earths ◽  
Cost Of Materials ◽  
Gel Processing

AbstractThe high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, we briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. We will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.

Sol-Gel Processing of Lithium Niobate Thin-Layers on Silicon

1988 ◽  
Vol 121 ◽  
Author(s):  
Dennis J. Eichorst ◽  
D. A. Payne
Keyword(s):  
Sol Gel ◽  
Solution Chemistry ◽  
Thin Layers ◽  
Processing Route ◽  
High Quality ◽  
Spin Casting ◽  
Evolution Of Structure ◽  
Stable Solutions ◽  
Gel Processing

ABSTRACTSol-gel processing was used for the fabrication of LiNbO3 thin-layers on semiconductors. Two different alkoxide systems were investigated (i.e., ethoxide vs. methoxyethoxide) to determine the role of solution chemistry on the evolution of structure in LiNbO3 layers. An alcohol exchange reaction, which produced lithium niobium methoxyethoxide, proved advantageous with respect to the amount of hydrolysis water content which could be added to give stable solutions. Spin-casting was used for the deposition of thin-layers which crystallized at 500 C on Si. The refractive index of sol-gel derived LiNbO3 was determined to be similar to sputtered or epitaxially grown films. Data are reported for the processing route and the material characteristics. Methoxyethanol based systems appeared to be more forgiving than ethanol based solutions for the fabrication of high-quality thin-layer devices.

The role of drying-control chemical additives on the preparation of sol-gel derived PLZT thin films

1993 ◽  
Vol 28 (24) ◽  
pp. 6691-6698 ◽  
Author(s):  
De -An Chang ◽  
Yi -Hung Choh ◽  
Wen -Feng Hsieh ◽  
Pang Lin ◽  
Tseung -Yuen Tseng
Keyword(s):  
Thin Films ◽  
Sol Gel ◽  
Chemical Additives ◽  
Control Chemical ◽  
Plzt Thin Films

Sol-Gel Processing of Transparent MgAl2O4

1988 ◽  
Vol 121 ◽  
Author(s):  
Yuan-Fu Yu ◽  
Sangvavann Heng ◽  
Tai-Il Mah ◽  
Edward E. Hermes
Keyword(s):  
Sol Gel ◽  
Ceramic Materials ◽  
Metal Alkoxide ◽  
Solvent Ratio ◽  
Processing Conditions ◽  
Chemical Additives ◽  
Control Chemical ◽  
High Degree ◽  
Gel Processing ◽  
Hydrolysis Of

ABSTRACTHigh-purity, transparent monolithic spinel (MgAl2O4) was synthesized via the hydrolytic thermal decomposition of mixed alkoxide organo-metallic precursors. Several factors, such as the metal alkoxide concentration in various solvents, the water to solvent ratio, and the reaction temperatures affect the hydrolysis of the mixed alkoxides. These factors also influence the transparency of the resulting sols and gels. The degree of transparency of the sols and gels is also influenced by such factors as pH and drying control chemical additives. Variations in the processing conditions during drying, aging, and sintering of the gels produced ceramic materials with high degree of transparency.

New insight in the role of modifying ligands in the sol-gel processing of metal alkoxide precursors: A possibility to approach new classes of materials

2006 ◽  
Vol 40 (2-3) ◽  
pp. 163-179 ◽  
Author(s):  
Vadim G. Kessler ◽  
Gerald I. Spijksma ◽  
Gulaim A. Seisenbaeva ◽  
Sebastian Håkansson ◽  
Dave H. A. Blank ◽  
...  
Keyword(s):  
Sol Gel ◽  
Metal Alkoxide ◽  
Gel Processing ◽  
Alkoxide Precursors

Studies of the Initial Steps in Sol-Gel Processing of Si(OR)4:29Si NMR of Alkoxysilane and Alkoxysiloxane Solutions

1986 ◽  
Vol 73 ◽  
Author(s):  
Carol A. Balfe ◽  
Sheryl L. Martinez
Keyword(s):  
Aqueous Solution ◽  
Acid Catalysis ◽  
Chemical Shifts ◽  
Sol Gel ◽  
29Si Nmr ◽  
Methanol Solutions ◽  
Hydrolysis And Condensation ◽  
Silicic Acids ◽  
Starting Solutions ◽  
Gel Processing

ABSTRACTSilicon-29 NMR has been used to investigate the initial steps of hydrolysis and condensation of tetramethoxysilane (TMOS), hexamethoxydisiloxane, and octamethoxytrisiloxane in both basic and acidic methanol solutions. Comparisons of the spectra obtained from the various starting solutions and literature reports of mono-, di-, and tri-silicic acids in aqueous solution were used to identify and assign chemical shifts to condensation intermediates in the TMOS system. The observation of cyclic intermediates in the acid catalysis of TMOS in methanol and the chemical shifts of several products of its hydrolysis and condensation are reported.

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