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Freeze-cast alumina that has been partially sintered. The freezing direction in the image is up. Freeze-casting, also frequently referred to as ice-templating, freeze casting, or freeze alignment, is a technique that exploits the highly anisotropic solidification behavior of a solvent (generally water) in a well-dispersed solution or slurry to controllably template directionally porous ...
Fractional freezing is a process used in process engineering and chemistry to separate substances with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, as in freeze distillation, also called normal freezing or progressive freezing.
In solvent casting and particulate leaching (SCPL), a polymer is dissolved in an organic solvent. Particles, mainly salts, with specific dimensions are then added to the solution. The mixture is shaped into its final geometry. For example, it can be cast onto a glass plate to produce a membrane or in a three-dimensional mold to produce a scaffold.
Although the exact temperature can be hard to control, the weight ratio of salt to ice influences the temperature: −10 °C can be achieved with a 1:2.5 mass ratio of calcium chloride hemihydrate to ice. −20 °C can be achieved with a 1:3 mass ratio of sodium chloride to ice. [citation needed]
Directional freezing can freeze water, from only one direction or side of a container, into clear ice. [1] [2] [3] Directional freezing in a domestic freezer can be done by putting water in a insulated container so that the water freezes from the top down, and removing before fully frozen, so that the minerals in the water are not frozen. [4]
It is unlikely then that freeze-cast components could be used structurally (without further processing – more later), but they have other properties that make them useful. They are rather light, with freeze-cast alumina components having a density somewhere in the region of 2.5 g/cm 3, similar to aluminium. They are easy and cheap to make ...
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The Stefan condition: () = ((),) where is the Stefan number, the ratio of latent to specific sensible heat (where specific indicates it is divided by the mass). Note this definition follows naturally from the nondimensionalisation and is used in many texts [ 8 ] [ 9 ] however it may also be defined as the inverse of this .