Investigation of the Effect of Dimethylformamide Addition on Alumina Sol-Gel Formation by 27Al NMR and Rheology Measurements

1988 ◽  
Vol 121 ◽  
Author(s):  
L. F. Nazar ◽  
L. C. Klein ◽  
D. Napier
Keyword(s):  
Room Temperature ◽  
Sol Gel ◽  
Gel Formation ◽  
27Al Nmr ◽  
Rapid Decay ◽  
Similar Treatment ◽  
High Acid ◽  
Alumina Sol ◽  
Gel Processing

ABSTRACTThe role of dimethylformamide (DMF) in the sol-gel processing of alumina at high acid/Al ratios was studied at different hydrolysis and aging temperatures by 27A1 NMR and rheology measurements. The composition of sols in which aluminum sec-butoxide was hydrolyzed in 50/50 mixtures of DMF and H2O was similar to those hydrolyzed without DMF, although the DMF sols contained a slightly lower concentration of mobile alumina species. The Al13O4 (OH)24(H2O)127+ cation predominated in both DMF and aqueous sols hydrolyzed at room temperatures at acid/Al ratios between 0.4 and 0.6. However, aging the room temperature DMF sols at 90°C for 24 hrs was found to cause rapid gelation whereas a similar treatment of the aqueous sols resulted in a decrease in viscosity. This gelation process was correlated with a more rapid decay of the Al13 and A1(H2O)63+ cations in the DMF sols. In contrast, DMF sols hydrolyzed at 90°C were found to be less viscous than their aqueous counterparts at high acid ratios.

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.

Chemical Processing and Properties of Nanocrystalline BaTiO3

1992 ◽  
Vol 271 ◽  
Author(s):  
Z. Xu ◽  
H. K. Chae ◽  
M. H. Frey ◽  
D. A. Payne
Keyword(s):  
Grain Size ◽  
Thermal Processing ◽  
Room Temperature ◽  
Sol Gel ◽  
Thin Layers ◽  
Silicon Substrates ◽  
Chemical Processing ◽  
Temperature Structure ◽  
Processing Conditions ◽  
Gel Processing

ABSTRACTBarium titanate (BaTiO3) thin layers were prepared by sol-gel processing. Details are reported for the synthesis route from methoxyethoxide precursors. Partially hydrolyzed solutions were spin-cast onto metallized silicon substrates, and a multilayering technique was used to develop sub-micron structures. Information is reported on the thermal processing conditions used and the development of structure. Crystallization started at 600°C and was fully developed by 700°C. The room temperature structure was cubic, and the grain size was 25–50 nm. Details are reported for the dielectric properties. Ferroelectricity was not observed. Dielectric constant (200–300) increased with increasing grain size, and was stable with respect to temperature, field and frequency. The properties are attractive for potential integrated capacitor applications.

Scintillators for Alpha and Neutron Radiations Synthesized by Room Temperature Sol?Gel Processing

2004 ◽  
Vol 32 (1-3) ◽  
pp. 117-123 ◽  
Author(s):  
Hee-Jung Im ◽  
Carl Willis ◽  
Suree Saengkerdsub ◽  
Rajev Makote ◽  
Michelle D. Pawel ◽  
...  
Keyword(s):  
Room Temperature ◽  
Sol Gel ◽  
Gel Processing

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.

scholarly journals Large-Pore Mesoporous Ho3Fe5O12 Thin Films with a Strong Room-Temperature Perpendicular Magnetic Anisotropy by Sol–Gel Processing

2014 ◽  
Vol 26 (7) ◽  
pp. 2337-2343 ◽  
Author(s):  
Christian Suchomski ◽  
Christian Reitz ◽  
Damir Pajic ◽  
Zvonko Jaglicic ◽  
Igor Djerdj ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetic Anisotropy ◽  
Room Temperature ◽  
Sol Gel ◽  
Perpendicular Magnetic Anisotropy ◽  
Large Pore ◽  
Gel Processing

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
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