The most common inorganic non-metallic insulating powder fillers include aluminum nitride, alumina flakes, zinc oxide, antimony oxide, silicon dioxide, silicon carbide, boron nitride, and the like.
aluminum oxide grinding wheel not only have good insulation properties, but also have low thermal conductivity (30w / m·K at room temperature), and have been widely used in high-voltage, high-voltage switchgear field insulation products.
Thermal Conductivity Mechanism of Alumina Beating Plate in Thermal Silicone
The thermal energy in a substance is usually transmitted in the form of vibrational energy, that is, the tiny particles in the substance collide with each other to achieve heat transfer.
For metallic materials, thermal conduction is conducted by the movement of free electrons. Since the free electrons are light in weight and unconstrained, the metal material is simultaneously electrically conductive.
The thermal conductivity of the aluminum oxide grinding wheel packing is mainly determined by the vibration of the phonons, and the heat conduction is achieved by the nonlinear thermal vibration of the crystal.
As a polymer material, silica gel is composed of asymmetric polar chains. The entire molecular chain cannot move completely freely. Only atoms, groups or chains can vibrate. Therefore, the thermal conductivity is low and it is a poor conductor heat.
Aluminum oxide grinding wheel have a wide range of sources, relatively low prices, large fillers in silica gel, and high cost performance, so they are the main insulation fillers for high-insulation silicon materials.
When the amount of aluminum oxide grinding wheel sheets added is small, the distribution of the alumina valves in the silica matrix is similar to that of the isolated islands, and the thermal conductivity is not improved.
As the amount of aluminum oxide grinding wheel added increases, the distribution of silica gel becomes denser and denser, and the particles will contact each other to form a local heat conduction chain or a heat conduction network in the composite material;
If the number of alumina beats is increased, the heat conduction chain or heat transfer network will be connected and infiltrated, thereby forming a heat conduction network through the material in the polymer matrix, thereby improving the thermal conductivity of the filler material significantly.
However, due to the increase in the amount of filler, the amount of filler is inferior to its performance, such as its fluidity and flexibility.
According to different sintering control, the crystal morphology of the aluminum oxide grinding wheel can exhibit worm-like, flaky, spherical (spherical) shape, etc., because the spherical particles of the aluminum oxide grinding wheel are small and can be filled into the matrix. The viscosity is small, it is easier to uniformly disperse in the matrix, and the filler is larger than other shapes, which is more favorable for improving the thermal conductivity of the silica gel. Therefore, at present, the morphology of the alumina flake is filled with a high heat insulating material which is spherical.