SOL

For other uses, see Sol.

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Goddard Institute for Space Studies. National Aeronautics and Space Administration. Retrieved June 13, Retrieved 13 July Planetary and Space Science. The Mighty Mars Rovers: The Incredible Adventures of Spirit and Opportunity. El Mundo in Spanish. Retrieved 23 April Retrieved 19 December Retrieved from " https: John the Baptist all note names were take from. From Latin solidus , a Roman coin. Cognates with Kabuverdianu sol. Shortened form of Latin solutio. From Latin solus, sola. From Latin solve in the hymn for St. Definition from Wiktionary, the free dictionary.

Danish Wikipedia has an article on: Italian Wikipedia has an article on: Singular Dual Plural Nominative sol soli soli Genitive soli solowu solow Dative soli soloma solam Accusative sol soli soli Instrumental solu soloma solami Locative soli soloma solach. The sun is shining. Formation of a metal oxide involves connecting the metal centers with oxo M-O-M or hydroxo M-OH-M bridges, therefore generating metal-oxo or metal-hydroxo polymers in solution. In both cases discrete particles or continuous polymer network , the drying process serves to remove the liquid phase from the gel, yielding a micro-porous amorphous glass or micro-crystalline ceramic.

Subsequent thermal treatment firing may be performed in order to favor further polycondensation and enhance mechanical properties. With the viscosity of a sol adjusted into a proper range, both optical quality glass fiber and refractory ceramic fiber can be drawn which are used for fiber optic sensors and thermal insulation , respectively.

In addition, uniform ceramic powders of a wide range of chemical composition can be formed by precipitation. Alkoxides are ideal chemical precursors for sol—gel synthesis because they react readily with water. The reaction is called hydrolysis, because a hydroxyl ion becomes attached to the silicon atom as follows:.

Sol (day on Mars)

Depending on the amount of water and catalyst present, hydrolysis may proceed to completion to silica:. By definition, condensation liberates a small molecule, such as water or alcohol. This type of reaction can continue to build larger and larger silicon-containing molecules by the process of polymerization. Thus, a polymer is a huge molecule or macromolecule formed from hundreds or thousands of units called monomers.

The number of bonds that a monomer can form is called its functionality. Polymerization of silicon alkoxide , for instance, can lead to complex branching of the polymer, because a fully hydrolyzed monomer Si OH 4 is tetrafunctional can branch or bond in 4 different directions. Alternatively, under certain conditions e. The mechanisms of hydrolysis and condensation, and the factors that bias the structure toward linear or branched structures are the most critical issues of sol—gel science and technology. This reaction is favored in both basic and acidic conditions. Sonication is an efficient tool for the synthesis of polymers.

Sol–gel process

Furthermore, multi-phase systems are very efficient dispersed and emulsified , so that very fine mixtures are provided. This means that ultrasound increases the rate of polymerisation over conventional stirring and results in higher molecular weights with lower polydispersities.

Ormosils organically modified silicate are obtained when silane is added to gel-derived silica during sol—gel process. The product is a molecular-scale composite with improved mechanical properties. Sono-Ormosils are characterized by a higher density than classic gels as well as an improved thermal stability. An explanation therefore might be the increased degree of polymerization.

For single cation systems like SiO 2 and TiO 2 , hydrolylsis and condensation processes naturally give rise to homogenous compositions. For systems involving multiple cations, such as strontium titante , SrTiO 3 and other perovskite systems, the concept of steric immobilisation becomes relevant. To avoid the formation of multiple phases of binary oxides as the result of differing hydrolysis and condensation rates, the entrapment of cations in a polymer network is an effective approach, generally termed the Pechini Process [13].

In this process, a chelating agent is used, most often citric acid, to surround aqueous cations and sterically entrap them. Subsequently a polymer network is formed to immobilize the chelated cations in a gel or resin. This is most often achieved by poly-esterification using ethylene glycol.

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The resulting polymer is then combusted under oxidising conditions to remove organic content and yield a product oxide with homogeneously dispersed cations. In the processing of fine ceramics , the irregular particle sizes and shapes in a typical powder often lead to non-uniform packing morphologies that result in packing density variations in the powder compact.

Sol (day on Mars) - Wikipedia

Uncontrolled flocculation of powders due to attractive van der Waals forces can also give rise to microstructural heterogeneities. Differential stresses that develop as a result of non-uniform drying shrinkage are directly related to the rate at which the solvent can be removed, and thus highly dependent upon the distribution of porosity. Such stresses have been associated with a plastic-to-brittle transition in consolidated bodies, [18] and can yield to crack propagation in the unfired body if not relieved. In addition, any fluctuations in packing density in the compact as it is prepared for the kiln are often amplified during the sintering process, yielding heterogeneous densification.

Some pores and other structural defects associated with density variations have been shown to play a detrimental role in the sintering process by growing and thus limiting end-point densities.

Differential stresses arising from heterogeneous densification have also been shown to result in the propagation of internal cracks, thus becoming the strength-controlling flaws. It would therefore appear desirable to process a material in such a way that it is physically uniform with regard to the distribution of components and porosity, rather than using particle size distributions which will maximize the green density. The containment of a uniformly dispersed assembly of strongly interacting particles in suspension requires total control over particle-particle interactions.