Hafnium Metallo-Organic Films and Gels Produced by Sol-Gel Processing

1989 ◽  
Vol 155 ◽  
Author(s):  
Charles D. Gagliardi ◽  
Kris A. Berglund
Keyword(s):  
Light Scattering ◽  
Sol Gel ◽  
Organic Films ◽  
Spin Casting ◽  
Synthesis Technique ◽  
Refractory Oxides ◽  
Sol Gel Process ◽  
Optically Transparent ◽  
Acid Catalyzed ◽  
Gel Processing

ABSTRACTMetallo-organic materials are often used as precursors for highly refractory oxides and hightemperature composites. The feasibility of producing hafnium metallo-organic films and gels by sol-gel techniques is demonstrated in the present study. Since hafnium alkoxides are not commercially available, their preparation is an obstacle in the development of their sol-gel processing applications. A common synthesis technique was used to produce hafnium isopropoxide, which was subsequently hydrolyzed under acid catalyzed conditions to produce films and gels. The films were prepared by spin casting and remained optically transparent. Initially, the gels were also optically transparent, but became translucent upon drying. Raman, IR, and light scattering spectroscopies were used to characterize this sol-gel process, and it is compared with the analogous processing of titanium and zirconium alkoxides.

Sol-Gel Processing Using Aminofunctional Silanes

1994 ◽  
Vol 346 ◽  
Author(s):  
Wanqing Cao ◽  
Arlon J. Hunt
Keyword(s):  
Light Scattering ◽  
Sol Gel ◽  
Gel Formation ◽  
Fluoride Ions ◽  
Homogeneous Microstructure ◽  
Acid Catalyzed ◽  
Gel Processing

ABSTRACTClear gels have been made from TEOS and the aminofunctional silane under acid-catalyzed conditions and light scattering of the gels has been related to pH and the concentration of fluoride ions in the sol as well as the amount of the aminosilane used. We have succeeded in preparing a series of gels containing Ni2+ or Cu2+ ions immobilized by chelation either before or after the gel formation. Aerogels made from these gels in particular, doped by the method of impregnation, have had a homogeneous microstructure on the scale of only a few nanometers.

Crystallization of nanosized titania particles prepared by the sol-gel process

1994 ◽  
Vol 9 (8) ◽  
pp. 2102-2108 ◽  
Author(s):  
E. Haro-Poniatowski ◽  
R. Rodríguez-Talavera ◽  
Heredia M. de la Cruz ◽  
O. Cano-Corona ◽  
R. Arroyo-Murillo
Keyword(s):  
Particle Size ◽  
Steady State ◽  
Light Scattering ◽  
Sol Gel ◽  
X Ray ◽  
Constant Size ◽  
Size Profile ◽  
Nanosized Titania ◽  
Sol Gel Process ◽  
Kinetics Of

Sols of titania were obtained by the sol-gel method and their size profile was followed by dynamical light scattering. In the early stages of the reaction an unstable behavior was detected. After this unstable regime the particle size reaches a steady state where the sols have a constant size while increasing in number. Once the sol concentration reaches its overlap value, the gelation regime takes place. For samples prepared in this way Raman spectra and x-ray diffractometry were used to characterize the kinetics of crystallization of the material.

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.

Preparation of SiO2 Antireflective Film by a Base/Acid Two-Step Catalyzed Sol-Gel Process

2013 ◽  
Vol 860-863 ◽  
pp. 845-848 ◽  
Author(s):  
De Yi Li ◽  
Kun Peng ◽  
Ling Ping Zhou ◽  
Jia Jun Zhu
Keyword(s):  
Raw Materials ◽  
Salt Spray ◽  
Sol Gel ◽  
Acid Base ◽  
Gel Method ◽  
Antireflective Film ◽  
Sol Gel Process ◽  
Acid Catalyzed ◽  
Antireflective Films ◽  
Silica Sols

SiO2 antireflective films were prepared by two-step catalyzed sol-gel method with TEOS as the raw materials, acid and ammonia as catalyst. Effects of the ratio of acid-catalyzed and base-catalyzed silica sols on the transmittance and stability of SiO2 film were investigated. The transmittance can be adjusted by change the ratio of base-catalyzed sols, and a higher transmittance can be obtained in the higher ratio of base-catalyzed coatings. A higher stability of SiO2 film in salt spray can be obtained in higher ratio of acid-catalyzed AR coatings. AR coatings with excellent transmittance and stability can be obtained by adjusting the ratio of acid/base catalyzed silica sols.

Dense and optical transparent CdWO4 films by sol-gel processing for scintillation applications

2007 ◽  
Vol 22 (6) ◽  
pp. 1527-1536 ◽  
Author(s):  
H.M. Shang ◽  
M. Bliss ◽  
S. Heald ◽  
T.K. Sham ◽  
F. Heigl ◽  
...  
Keyword(s):  
Sol Gel ◽  
Tungstic Acid ◽  
Cadmium Nitrate ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optical Luminescence ◽  
Optically Transparent ◽  
Rapid Sintering ◽  
Gel Processing

In this paper, we report the first successful fabrication of dense and optically transparent cadmium tungstate (CWO) films by sol-gel processing and the study of their optical and x-ray scintillation properties. A new sol-gel processing method was developed using tungstic acid and cadmium nitrate as precursors and hydrogen peroxide as solvent; homogeneous and stable CWO sols were aged at room temperature and used for the preparation of CWO films. A rapid sintering process was investigated and found to be necessary to make dense and optically transparent nanocrystalline CWO films. CWO films were uniform, fully dense, and crack-free, with CWO as the only detectable crystalline phase, as determined by x-ray diffraction. The thickness, density, grain size, and crystallinity of CWO films are all found to be strongly dependent on the sintering conditions and in turn impact the optical and x-ray scintillation properties. Sol-gel-derived dense CWO films demonstrated intense photoluminescence and x-ray excited optical luminescence intensity. The relationships between sol-gel processing, nanostructures, and optical and x-ray scintillation properties are discussed in detail.

A novel bulk sol-gel process to prepare monolithic silica materials

1999 ◽  
Vol 14 (10) ◽  
pp. 4098-4102 ◽  
Author(s):  
Ce Wang ◽  
Yahong Zhang ◽  
Yunfeng Lu ◽  
Yen Wei
Keyword(s):  
Sol Gel ◽  
Silica Content ◽  
Monolithic Silica ◽  
Nonpolar Solvents ◽  
Sol Gel Process ◽  
Silica Materials ◽  
High Silica ◽  
Acid Catalyzed ◽  
Carbonate Salts ◽  
Hydrolysis Of

A bulk sol-gel process has been developed to prepare monolithic silica materials at room temperature. The process involves an acid-catalyzed hydrolysis of tetraethyl orthosilicate in tetrahydrofuran containing aqueous HC1 catalyst, followed by neutralization with carbonate salts, extraction with aliphatic nonpolar solvents, molding, gelation, and drying. This method shortens the processing time from weeks for the conventional sol-gel process to several days. The silica objects prepared from the process are transparent, crack-free, and of relatively low volume shrinkage (e.g., 52%) and high silica content (e.g., 82%).

Undoped and Doped Perovskite Films: Sol-Gel Processing and Characterization

1991 ◽  
Vol 243 ◽  
Author(s):  
Mareike Klee ◽  
Rainer Waser
Keyword(s):  
Crystal Structure ◽  
Field Strength ◽  
Remanent Polarization ◽  
Sol Gel ◽  
Insulation Resistance ◽  
Sol Gel Process ◽  
Gel Processing

AbstractThin undoped Pb(ZrxTi1−x)O3 (x=0.2-0.75), BaTiO3, SrTiO3 as well as acceptor (Mn, Ni) and donor (La, Ce) doped films with thicknesses of 0.2-1 μm have been deposited by a modified sol-gel process. The crystal structure and the morphology of the films as a function of the processing and composition were analyzed. The films were characterized with respect to their ferroelectric and dielectric properities e.g. permittivity, remanent polarization, coervice field strength, insulation resistance.

Ultrasmooth metal halide perovskite thin films via sol–gel processing

2016 ◽  
Vol 4 (21) ◽  
pp. 8308-8315 ◽  
Author(s):  
Ross A. Kerner ◽  
Lianfeng Zhao ◽  
Zhengguo Xiao ◽  
Barry P. Rand
Keyword(s):  
Thin Film ◽  
Film Formation ◽  
Sol Gel ◽  
Metal Halide ◽  
Film Morphology ◽  
Metal Halide Perovskite ◽  
Sol Gel Process ◽  
Thin Film Formation ◽  
Halide Perovskite ◽  
Gel Processing

We show that metal halide perovskite thin film formation is a sol–gel process which allows us to improve film morphology, achieving roughness ∼1 nm via process and additive engineering.

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.

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