Modified Sol-Gel Processing

S.3.2 Sol-Gel Encapsulation of Reactive Species Another new and attractive route for tailoring electrode surfaces involves the low-temperature encapsulation of recognition species within sol-gel films (41,42). Such ceramic films are prepared by the hydrolysis of an alkoxide precursor such as, Si(OCH3)4 under acidic or basic condensation, followed by polycondensation of the hydroxylated monomer to form a three-dimensional interconnected porous network. The resulting porous glass-like material can physically retain the desired modifier but permits its interaction with the analyte that diffuses into the matrix. Besides their ability to entrap the modifier, sol-gel processes offer tunability of the physical characteristics... 

Guney, V., Jones, F.R., James, PR, and Bailey, J.E., Alumina ceramic matrices for fibre composites prepared by modified sol-gel processing. Institute of Physics Publishing, London, 1990. 

The second example is the synthesis of -y-alumina nanorods from boehmite nanofibers using a modified sol-gel process (42). First, a solution of aluminum iso-propoxide in anhydrous ethanol is prepared. To this, ethanol with 4% water is added leading to a viscous liquid after 15 h. The viscous hquid heated at 600°C leads to y-alumina nanorods (diameter < 10 nm length 50 to 200 nm). Since in the synthesis, less water is taken, only partial hydrolysis takes place. The removal of one water molecule from two A10(0H) octahedra leads to the formation of AI2O3 nanorods, (CH3CH2CH20)3A1 + 2H2O A10(0H) + 3CH3CH2CH2OH. 

Jorand et al. (1995) developed a modified sol-gel process for synthesis ofzirconia in which the precursor was a mixed monomeric solution in association with organic polymers. This precursor was sprayed in an ammonium hydroxide solution to obtain gel particles. These particles, heat-treated at 700°C for 4 h, yielded doped zirconia particles of composition Zr02-3.6 mol% Y2O3. X-ray diffraction showed them to be 100% tetragonal zirconia. The particle size dso—average particle size at 50% cumulative mass) was 34 /rm, mean crystallite size 9 nm, and the specific surface area had a relatively high value of 100 m /g. 

Liu D., Zhang H., Cai W., Wu X., Zhao L. Synthesis of PZT nanocrystalline powder by a modified sol-gel process using zirconium oxynitrate as zirconium source. Mater. Chem. Phys. 1997 51 186-189... 

S. Rengakuji have reported a modified sol-gel process, and insisted that sol-gel reaction in a mixture of alcohol and hydrophilic solvent like benzene affords stable solvated titanate oligomer and the resulting coating film shows higher crystallinity and excellent photocatalytic activities (Rengakuji, 2002). 

Jaferzadeh, M., Rahman, lA., and Sipaut, C.S. (2009) Synthesis of silica nanoparticles by modified sol-gel process the effect of mixing modes of the reactants and drying techniques. /, Sol-Gel Set Technol, 50 (3), 328-336. 

Sol—Gel Sintered Aluminum Oxide. A new and much more versatile sintered alumina abrasive is now produced from aluminum monohydrate, with or without small additions of modifiers such as magnesia, by the sol—gel process (see Sol-gel technology). The first modified sol—gel abrasive on the market, Cubitron, was patented (27) and produced by the 3M Corporation for products such as coated belts and disks. The success of this material promoted intensive research into sol—gel abrasives. 

Solar energy, 6, 488 surface modified electrodes, 6, 30 Sol-Gel process fast reactor fuel, 6, 924 Solid state reactions, 1, 463-471 fraction of reaction, 1, 464 geometric, 1, 464 growth, 1, 464 nucleation, 1, 464 rate laws, 1,464 Solochrome black T metallochromic indicators, 1,555 Solubility... 

Fig. 2.12 Electrode modified with vitamin B12 by the sol-gel process and electrolysis of benzyl bromide at the electrode surface. Adapted from [61], H. Shimakoshi et al., Dalton Trans,...

Chen, Q., Miyata, N., Kokubo, T. and Nakamura, T. (2000) Bioactivity and mechanical properties of PDMS-modified Ca0-Si02-Ti02 hybrids prepared by sol-gel process. Journal of Biomedical Materials Research, 51, 605-611. 

On the basis of the sol-gel process, much more attention has been paid to silicate-containing Class II hybrids, also referred to as organically modified silicas, ormosils. In this section, the synthesis of some of the most characteristic ormosils for bone and dental applications are described. 

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