Sol-Gel


Terms and words used frequently in the Sol-Gel area.

Their literal definitions  were taken from Academic Press Dictionary of Science and Technology  and they are published as they appear. 

(with the permission of Academic Press)


aerogel

Chemistry. The dispersion of a gas in a solid or liquid medium, such as foam; the reverse of an aerosol, where the medium is a gas and the dispersed material is particles of a solid or liquid.

alcosol

Chemistry. A solution made with a mixture of a colloid and an alcohol.

alcogel   

Chemistry. A colloidal gel made with alcosol.

antireflection coating   

Engineering. Surface treatment with dielectric material to reduce the reflection of electromagnetic radiation while increasing light transmission.

azeotropic drying   

Chemistry. A method of removing water from a liquid at temperatures lower than 100°C; a second liquid that forms an azeotropic mixture with water is added to the sample liquid.

capillarity  

Fluid Mechanics. The general behavior of fluids acting with surface tension on interfaces or boundaries.

capillary drying   

Engineering. The evaporation of moisture from the surface of a porous mass and the subsequent capillary movement of moisture from the interior of the mass to its surface; eventually the amount of moisture on the surface and interior of the mass stabilizes.

ceramic   

Materials.  1. Of or relating to products, such as pottery, porcelain, or tile, that are made from nonmetallic mineral  2. an object made of such a material. an object made of such a material.

ceramic coating   

Metallurgy.  1. The process of applying a layer of ceramic material, such as alumina, onto a metallic product in order to protect against extremely high temperatures. 2. the material thus applied.

critical point drying   

Microbiology. A procedure used in preparing a specimen for electron microscopic examination, in which damage to the specimen during its drying step is minimized by avoiding exposure to a liquid-gas boundary.

coating   

Graphic Arts.  1. any mineral substance used to cover the surface of a printing paper, such as blanc fixe or china clay. 2. the application of such a substance to a sheet of paper. 3. the application of a varnish or photosensitive solution to a printing plate.  
Materials Science
. a material that forms a continuous layer over a surface, or the film formed by such a material.

colloid  

Physical Chemistry.  1. A substance consisting of very tiny particles that are usually between 1 nanometer and 1000 nanometers in diameter and that are suspended in a continuous medium, such as a liquid, a solid, or a gaseous substance. 2. the translucent, pale yellow, gelatinous substance resulting from colloid degeneration.

colloidal particle   

Physical Chemistry. Any of the individual particles of a colloid.

colloidal silica   

Materials. A colloid of fine particles of silica that are negatively charged by a small addition of alkali, forming a high-concentration solution that is used to make molded ceramics or to treat textiles.

colloidal instability   

Meteorology. A condition of clouds in which the particles tend to aggregate into masses large enough to precipitate.

colloidal suspension   

Physical Chemistry. A mixture of two substances, one of which (the colloid) is uniformly distributed throughout the other (the dispersion medium); either substance may be gaseous, liquid, or solid. 

dispersion   

A process of scattering or separating; specific uses include:  
Physical Chemistry
. a two-phase system consisting of finely divided particles (the disperse phase) distributed throughout a bulk substance (the continuous phase); for example, fog is a dispersion of liquid particles in a gas; paint is a dispersion of solid particles in a liquid.  
Physics
. the separation of a complex wave containing several frequencies into its individual component waves by virtue of different wave speeds.  
Astrophysics
. the slowing down of a radio signal's propagation velocity as it passes through an ionized gas or plasma in the interstellar medium; short frequencies are the least affected and long ones the most affected.  
Electromagnetism
. the scattering of microwave radiation by an obstruction.  
Mineralogy
. the characteristic and specific manner in which a monopaque mineral will refract white light.  

drying   

Chemistry.  1. The removal of most of the water from a substance (usually 92-95%), often through heat exposure. 2. the removal of solvents other than water from a substance.

drying agent   

Chemistry. A substance having an affinity for water, used to dry fluid substances; a desiccant.

flash-drying   

Chemical Engineering. The quick evaporation of liquid from a granular or porous solid by a rapid reduction in pressure or an updraft of warm air. 

freeze-drying   

Engineering. A process in which food or tissue is preserved, by drying it in a frozen state under high vacuum conditions; used in preparing medicines and laboratory specimens and in some forms of food preservation. 

gel   

Chemistry.  1. A colloidal suspension of a liquid in a solid, forming a jellylike material in a more solid form than a sol.  2. to form a gel.

gel point   

Physical Chemistry. The stage at which a liquid begins to take on the semisolid characteristics of a gel.

glass-ceramic   

Materials. A predominantly crystalline product created by the controlled crystallization of glass; characterized by high thermal shock resistance and low thermal expansion.

hybrid   
Science. Something that is heterogeneous; a composite.  
Genetics
.  1. an offspring of two genetically different parents, or even different species. 2. see HETEROZYGOTE.
Petrology
.  1. an igneous rock formed by the assimilation of wall rock into a magma or by the mixing of two magmas. 2. of or relating to a rock so formed. Thus, hybrid rock. of or relating to a rock so formed. 

hydrophilic   

Chemistry. Having an affinity for water; attracting, dissolving in, or absorbing water.

hydrophobic   

Chemistry. Relating to or being a hydrophobe; repelling water.  
Biology
. not tolerant of water or a wet environment.  
Medicine
. of or relating to rabies.  
Psychology
. of or relating to hydrophobia.

hydrosol   

Chemistry. A colloidal dispersion in water; a sol whose dispersion medium is water.

hydrogel   

Materials Science. A water-based gel; a gel whose liquid constituent is water.

ionic gel   

Chemistry. A gel that contains ionic groups attached to the colloid structure, preventing the groups from diffusing out into a surrounding medium.

liquid-phase sintering   

Materials Science. The progressive fusion of a ceramic material during the firing process; as it proceeds the proportion of glassy bond increases and the porosity of the fired product decreases.

monodisperse colloidal system   

Chemistry. A colloidal system having particles of the same size, interaction, and shape.

presintering   

Metallurgy. In powder metallurgy, a preliminary sintering operation performed at a temperature lower than the final sintering temperature.

reaction sintering   

Materials Science. A process in which a compacted powder is heated to a temperature where sintering takes place simultaneously with a chemical reaction; for example silicon powder heated in the presence of nitrogen to produce silicon nitride. 

silica gel   

Inorganic Chemistry. A colloidal, highly absorbent form of silicon dioxide; widely used as a dehumidifying and dehydrating agent and in many chemical processes.

sintering   

Materials Science. The process in which fine particles of a material become chemically bonded at a temperature that is sufficient for atomic diffusion.

sol-gel coating   

Materials Science. A coating produced by the sol-gel process of glassmaking, in which glass is formed at low temperatures from suitable compounds by chemical polymerization in a liquid phase; a gel is formed from which glass may be derived by the successive elimination of interstitial liquid and the collapse of the resulting solid residue by sintering.

spray-drying   

Materials Science. A ceramic processing used to create a uniform die fill for automated pressing; the slurry is fed into the spray drier, where circulating hot air evaporates the water; the resulting powder is collected for further processing.

supercritical   

Thermodynamics. A condition in which a substance experiences a change in its pressure, temperature, or volume that would normally carry the system through its critical point although no phase change is observed.  
Nucleonics. of, relating to, having, or operating with a multiplication factor greater than one.

surface tension   

Fluid Mechanics. The stretching force required to form a liquid film; equal to the surface energy of the liquid per unit length of the film at equilibrium; the force tends to minimize the area of a surface. 

thin film   

Electronics. Any of several thin layers (generally less than 1mum each) of insulating, conducting, or semiconductor material that are deposited successively on a supporting substrate in precise patterns to collectively form all or part of an integrated circuit; the deposition can be performed by mechanical, chemical, or high-vacuum evaporation methods. 

vacuum drying   

Engineering. The removal of liquid from a solid material while in a vacuum system, to lower the temperature at which evaporation takes place and thus prevent heat damage to the material.

xerogel   

Chemistry. A gel from which all volatile liquid has been removed.

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