Sol-gel particles

Antireflective (AR) coatings are required on optics to reduce the reflective surface losses. Vitreous siHca coatings in the form of porous or multilayer films are used extensively in this appHcation. Antireflective coatings have been developed which employ coUoidal fused siHca sol—gel particles made from organometaUic materials (253). 

J.H. Shin, S.M. Marxer, and M.H. Schoenfisch, Nitric oxide-releasing sol-gel particle/polyurethane glucose biosensors. Anal. Chem. 76, 4543 1549 (2004). 

Diffusion-limited aggregation of particles results in a fractal object. Growth processes that are apparendy disordered also form fractal objects (30). Sol—gel particle growth has also been modeled using fractal concepts (3,20). The nature of fractals requires that they be invariant with scale, ie, the fractal must look similar regardless of the level of detail chosen. The second requirement for mass fractals is that their density decreases with size. Thus, the fractal model overcomes the problem of increasing density of the classical models of gelation, yet retains many of its desirable features. The mass of a fractal, Af, is related to the fractal dimension and its size or radius, R, by equationS ... 

Bulk oxide fuels are fabricated by cold compaction followed by sintering at an elevated temperature. Loose particles or optimum mixtures of several sizes of spherical (sol-gel) particles are packed directly into the cladding, and such particulate fuel is subjected to vibratory compaction. 

Shin, J.H., Marxer, S.M., Schoenfisch, M.H., 2004. Nitric oxide-releasing sol-gel particle/ polyurethane glucose biosensors. Analytical Chemistry 76, 4543-4549. 

The first route is based on generating sol—gel particles in an hydrophobic medium. Since the Stober process is based oti water or alcohol solvents and uses agents (ammonium hydroxide) that are not miscible with the polymerization medium of toluene, adaption was necessary. Higher alcohol (butanol, pentanol, octanol), toluene and toluene-ethanol mixtures were screened and, in addition to TEOS, TBOS (tetrabutoxy silane) was used as precursor [85]. It was found that the formation of defined and spherical particles is not easily achieved. For example, in a... 

The major challenge in the production of nanoparticle-polymer nanocomposite is the ability to achieve a homogeneous filler dispersion, which determines the overall performance of the nanocomposites. Chemical surface functionaliTa-tion and effective mixing methods are the two main routes that can lead to a homogeneous filler distribution. Three main methods can be identified for the production of sol-gel particle-polymer nanocomposite (i) solution mbdng,... 

In situ production of particles can follow two major routes either the inorganic and the organic polymerization occur at the same time or the sol-gel particles are produced in the presence of a preformed polymer. The production of both species at the same time resulting in a homogeneous material is usually carried out under acidic conditions. However, the formation of distinct particles has to be carried out under basic conditions, which leads more often to phase separation by an in situ production of both species. Therefore, the route of using a... 

Porous sol-gel foams have also been produced using the more traditional polymer foam reticulation [75], but the process offers little benefit over the sol-gel foaming method unless ordered mesoporosity is required [76]. Polymer foam reticulation involves using a polymer (usually polyurethane) foam as a negative template. The sol (or sol-gel particles) can be coated on the polymer foam, which is then burned out in the furnace. Reticulated foams often have hollow struts, which reduces their mechanical properties. 

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