Freeze-gelation, is a form of sol-gel processing of ceramics that enables a ceramic object to be fabricated in complex shapes, without the need for high-temperature sintering. The process is similar to freeze-casting.
The process is simple, but the science is, as of 2005, not well understood. The most common process involves the mixing of a silica solution with a filler powder. For example, if we were making a component out of alumina, aluminium oxide, then we would still use a silica sol, but alumina filler powder. The relative amounts used differ, normally between 3 and 4 times more filler than sol is added by weight.
A wetting agent is added, such that the filler powder disperses properly in the sol, which is mostly water. This makes the mixture doughy and stiff. The mixture is, however, highly thixotropic, so that when vibrated it turns liquid. The stiff dough is placed in a mold and the mold vibrated to liquefy the mixture, filling the mold and releasing any trapped air.
The filled mold is then frozen. On freezing, silica precipitates from the sol, forming a gel. This gel holds the filler powder together in something approximating a sintering greenform. The component is then dried in a furnace, leaving the component.
The advantages of freeze-geleation over sintering are essentially cost-based. It doesn't require high pressure equipment or powerful furnaces (drying temperatures are only just above water's boiling point), yet it creates a useful product which takes the shape of the mold very accurately.
Freeze-gelation, is a form of sol-gel processing of ceramics that enables a ceramic object to be fabricated in complex shapes, without the need for high-temperature...
require additional curing after gelation (i.e., network perfection) in order to strengthen the aerogel network. Once the gelation is completed, the liquid surrounding...
binder is burnt out and the final scaffold sintering will take place. Freezegelation Colloidal crystal Somiya, Shigeyuki (May 2013). Handbook of Advanced...
of silicon or metals, or by partial crystallization of a liquid, as in freeze distillation, also called normal freezing or progressive freezing. The initial...
water inside the fuel tank has started to freeze, gelling is more likely to occur. When the fuel is gelled it is not effective until the temperature is...
Mechanics of gelation describes processes relevant to sol-gel process. In a static sense, the fundamental difference between a liquid and a solid is that...
alternative techniques. Other forms of livestock identification include freeze branding, inner lip or ear tattoos, earmarking, ear tagging, and radio-frequency...
not until the late 80's the freeze-drying industry discovered the allurement and longevity of freeze-dried flowers. Freeze dried flowers are fresh flowers...
mechanism of gelation involves the oligopeptide precursors self-assemble into fibers that become elongated, and entangle to form cross-linked gels. One notable...
are resistant to industrial stresses such as acidic pH, sterilisation, freeze conditions, and can help food industries to formulate with natural ingredients...
(1978). "Transmission-electron microscopic observations of freeze-etched polyacrylamide gels". J. Chromatogr. A. 166 (2): 563–575. doi:10.1016/S0021-9673(00)95641-3...
gel network and lead to an increase in textural properties such as hardness, springiness, cohesiveness, and gumminess. In Japan, two kinds of freeze-dried...
pp. 209–235. ISBN 9781420052534. Fellows, P. (Peter) (2017). "Freeze drying and freeze concentration". Food processing technology : principles and practice...
he was President of Columbia University; three Continental Can Company freeze-dried food bags made for the Apollo 11 flight; an 1864 Remington New Model...
aestivum), used as a food, drink, or dietary supplement. Wheatgrass is served freeze dried or fresh, and so it differs from wheat malt, which is convectively...
Shampoo only. This Limited Edition Shampoo + Conditioner came out with Freeze anti-itch shampoo. The scent seems to rival the Fever body wash and body...
such as the surface of red blood cells. Techniques include using heat, a freeze-thaw cycle, ultrasound, acids or organic solvents. No single method is best...
higher density than liquid hydrogen. It is commonly formed by repeating a freeze-thaw process. This is most easily done by bringing liquid hydrogen near...
created a three-dimensional structure. The synthesis was accomplished by the freeze-drying of carbon nanotube solutions and large amounts of graphene oxide...
2018). "Trans dermal estrogen (oestrogel) for endometrial preparation in freeze embryo transfer cycle: An RCT". Int J Reprod Biomed (Yazd). 16 (1): 51–56...
available technology for desalination which has been developed is freeze-thaw desalination Freeze-thaw desalination, also known as cryo-desalination or simply...
may be beneficial as a defense strategy. A solid glass cytoplasm would freeze subcellular structures in place, preventing damage, while allowing the transmission...
of the deep ocean drops gradually with depth. As saline water does not freeze until it reaches −2.3 °C (27.9 °F) (colder as depth and pressure increase)...
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