Post by Deleted on Aug 17, 2016 5:51:04 GMT -8
Crystallite:
Polycrystalline or multicrystalline materials, or polycrystals are solids that are composed of many crystallites of varying size and orientation.
Crystallites are also referred to as grains.
Most inorganic solids are polycrystalline, including all common metals, many ceramics, rocks and ice.
en.wikipedia.org/wiki/Crystallite
Grain boundary:
A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material.
Grain boundaries are defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material.
Grain boundaries disrupt the motion of dislocations through a material, so reducing crystallite size is a common way
to improve mechanical strength, as described by the Hall–Petch relationship.
en.wikipedia.org/wiki/Grain_boundary#Boundary_energy
In metal alloys the (electrical) thermal conductivity is inversely proportional to the number of grain boundaries,
as crossing a boundary requires an additional small amount of energy.
In analog form, this applies to other materials too, as well for particles in granular materials.
Amorphous and glassy materials, on the other hand, have no definite structure,
but bear similarities with very finely grained polycrystalline or multicrystalline materials.
With respect to strength and thermal conductivity fine polycrystalline or amorphous sand eg. slag
not larger than 0.2-0.3 mm is quite obviously the best choice.
Small amounts of clay can be used to increase porosity by increasing the water demand.
A geopolymer binder can easily fulfill the requirement for an aerogel.
Polycrystalline or multicrystalline materials, or polycrystals are solids that are composed of many crystallites of varying size and orientation.
Crystallites are also referred to as grains.
Most inorganic solids are polycrystalline, including all common metals, many ceramics, rocks and ice.
en.wikipedia.org/wiki/Crystallite
Grain boundary:
A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material.
Grain boundaries are defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material.
Grain boundaries disrupt the motion of dislocations through a material, so reducing crystallite size is a common way
to improve mechanical strength, as described by the Hall–Petch relationship.
en.wikipedia.org/wiki/Grain_boundary#Boundary_energy
In metal alloys the (electrical) thermal conductivity is inversely proportional to the number of grain boundaries,
as crossing a boundary requires an additional small amount of energy.
In analog form, this applies to other materials too, as well for particles in granular materials.
Amorphous and glassy materials, on the other hand, have no definite structure,
but bear similarities with very finely grained polycrystalline or multicrystalline materials.
With respect to strength and thermal conductivity fine polycrystalline or amorphous sand eg. slag
not larger than 0.2-0.3 mm is quite obviously the best choice.
Small amounts of clay can be used to increase porosity by increasing the water demand.
A geopolymer binder can easily fulfill the requirement for an aerogel.
