Sol-gel processing effect

Miyata, N., Fuke, K., Chen, Q., Kawashita, M., Kokubo, T. and Nakamura, T. (2002) Apatite-forming ability and mechanical properties of PTMO-modified CaO-Si02 hybrids prepared by sol-gel processing Effect of CaO and PTMO contents. Biomaterials, 23, 3033—3040. 

Akkari R, Ghorbel A, Essayem N, Figueras F, (2007) Synthesis and characterization of mesoporous silica-supported nano-crystalline sulfated zirconia catalysts prepared by a sol-gel process Effect of the S/Zr molar ratio. Appl Catal A 328 43-51... 

The major design concept of polymer monoliths for separation media is the realization of the hierarchical porous structure of mesopores (2-50 nm in diameter) and macropores (larger than 50 nm in diameter). The mesopores provide retentive sites and macropores flow-through channels for effective mobile-phase transport and solute transfer between the mobile phase and the stationary phase. Preparation methods of such monolithic polymers with bimodal pore sizes were disclosed in a US patent (Frechet and Svec, 1994). The two modes of pore-size distribution were characterized with the smaller sized pores ranging less than 200 nm and the larger sized pores greater than 600 nm. In the case of silica monoliths, the concept of hierarchy of pore structures is more clearly realized in the preparation by sol-gel processes followed by mesopore formation (Minakuchi et al., 1996). 

Similarly to the above-mentioned entrapment of proteins by biomimetic routes, the sol-gel procedure is a useful method for the encapsulation of enzymes and other biological material due to the mild conditions required for the preparation of the silica networks [54,55]. The confinement of the enzyme in the pores of the silica matrix preserves its catalytic activity, since it prevents irreversible structural deformations in the biomolecule. The silica matrix may exert a protective effect against enzyme denaturation even under harsh conditions, as recently reported by Frenkel-Mullerad and Avnir [56] for physically trapped phosphatase enzymes within silica matrices (Figure 1.3). A wide number of organoalkoxy- and alkoxy-silanes have been employed for this purpose, as extensively reviewed by Gill and Ballesteros [57], and the resulting materials have been applied in the construction of optical and electrochemical biosensor devices. Optimization of the sol-gel process is required to prevent denaturation of encapsulated enzymes. Alcohol released during the... 

The realization of the reasons for poor biocompatibility of general alkoxides with biopolymers led to the development of approaches to minimize or eliminate the problem of the detrimental effect of alcohols. This can be done in two ways modification of the sol-gel processing or the silica precursor. This is considered in some detail below. 

Poly(oxyethylene)-Si02 ormosils have been prepared as an approach to the preparation of biologically active polymer-apatite composites. For this purpose, Yamamoto et al. [72] obtained these Class II hybrids from triethoxysilyl-terminated poly(oxyethylene) (PEG) and TEOS by using the in situ sol-gel process. After being subjected to the biomimetic process to form the bone-like apatite layer, it was found that a dense apatite layer could be prepared on the hybrid materials, indicating that the silanol groups provide effective sites for CHA nucleation and growth. 

Huang, H.H., Orler, B. and Wilkes, G. L. (1985) Ceramers — hybrid materials incorporating polymeric oligomeric species with inorganic glasses by a sol-gel process. 2. Effect of acid content on the final properties. Polymer Bulletin, 14, 557-564. 

Bailey, J. K. 1992. Solvent quality effects in sol-gel processing. In Better Ceramics Through Chemistry V, edited by Hampden-Smith, M. J. Klemperer, W. G. Brinker, C. J. Mat. Res. Soc. Symp. Proc. 271 219-224. 

Ogawa, T. and Ohkoshi, M. (1997). Properties of medium density fibreboards produced from thermoplasticized wood fibers by aUylation without adhesives. Mokuzai Gakkaishi, 43(1), 61-67. Ogiso, K. and Saka, S. (1993). Wood-inorganic composites prepared by sol-gel process II. Effects of ultrasonic treatments on preparation of wood-inorganic composites. Mokuzai Gakkasihi, 39(3), 301-307. 

Saka, S. and Tanno, F. (1996). Wood-inorganic composites prepared by the sol-gel process VI. Effects of a property-enhancer on fire-resistance in Si02-P205 and Si02-B203 wood-inorganic composites. Mokuzai Gakkaishi, 42(1), 81-86. 

The key effect of oxide supports on the catalytic activities of metal particles is exerted through the interface between oxides and metal particles. The key objective of this study is to develop synthesis methodologies for tailoring this interface. Here, an SSG approach was introduced to modify the surface of mesoporous silica materials with ultrathin films of titanium oxide so that the uniform deposition of gold precursors on ordered mesoporous silica materials by DP could be achieved without the constraint of the low lEP of silica. The surface sol-gel process was originally developed by Kunitake and coworkers.This novel technology enables molecular-scale control of film thickness over a large 2-D substrate area and can be viewed as a solution-based... 

Figure 5.5 shows the variation of the pore size distribution as a function of cycles of surface-modification-based N2 adsorption isotherms. The pore size decreases with the modification cycle number. The reduction of the mesopore size for each cycle should be about twice the single-layer thickness. Accordingly, the effective singlelayer thickness is about 6 to 7 A based on the above BET measurements. This value is close to those estimated from the frequency changes of a quartz crystal balance for ultrathin fihns prepared by the surface sol-gel process on 2-D substrates." " ... 

Recently we published a short review of the single source precursor concept in chemical vapor deposition (CVD) and in the sol/gel process [1]. hi this article we described in which way several constituent elements of a targeted material can be assembled in a precursor molecule and how this assembly has an effect on the properties of the hnal material. Three types of precursors have been distinguished (1) Precursors which contain the correct ratio of metallic elements (SSP-I), (2) precursors which besides the correct ratio of metallic elements also have ligands which interact with one another to form only few side-products (SSP-II), and (3) precursors with a surplus of one metallic element compared to a thermodynamically stable phase and which form biphasic mixed-materials on a nanometer scale (SSP-III) [1],... 

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