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What are the factors that affect the thermal conductivity of alumina ceramics?
Time: 2019-01-19   Writer: mingrui

What are the factors that affect the thermal conductivity of alumina ceramics?

What are the factors that affect the thermal conductivity of alumina ceramics?Abstract: alumina ceramics is a kind of thermal material, its thermal conductivity and what factors?

Alumina ceramics is a kind of thermal material, and its thermal conductivity is related to what factors?

All the factors that affect the phonon mean free path will affect the thermal conductivity of zirconia ceramics.The more complex the chemical composition and the more impurities, the more obvious the reduction of the thermal conductivity.This is because the addition of the second component and impurities destroys the integrity of the crystal and easily causes or produces lattice distortion, distortion and dislocation, making the crystal structure complex.The original lattice produced a kind of additional "disturbance" similar to thermal motion, which caused the increase of phonon scattering.With the increase of non-simple harmonic vibration, the phonon mean free path decreases and the thermal conductivity decreases.
995 alumina ceramic ring
Similarly, the phonon scattering and thermal conductivity of materials with complex crystal structure increase.Stomata can cause phonon scattering, and the thermal conductivity of gas in stomata is very small.All kinds of defects, such as point defects, line defects and surface defects, are the center of phonon scattering, so they all reduce the average free path of phonons, thus decreasing the thermal conductivity.Among all the factors affecting thermal conductivity, porosity and temperature have a particularly obvious influence on thermal conductivity under a given mineral composition. The following discussion mainly discusses the influence of temperature on thermal conductivity:

Temperature is the most basic and important factor that affects the thermal conductivity.For pure crystal materials, the thermal conductivity is inversely proportional to the absolute temperature can be obtained from the above six theoretical equations.This is because the higher the temperature is, the more non-simple harmonic vibration will be produced, which reduces the average free path of phonons, and thus the thermal conductivity decreases.
Since the average free path of the vitreous body is small, the thermal conductivity depends on temperature differently.Above room temperature, the phonon mean free path of vitreous body can be considered as a constant basically, so its thermal conductivity increases proportionally with the increase of heat capacity.
Relationship between thermal conductivity and temperature of ceramic materials
Ceramics are the combination of crystals and vitreous bodies, so the relationship between their thermal conductivity and temperature depends on the relative proportion of the crystalline minerals they contain to the glass.In this section, the thermal conductivity of several representative ceramic blanks at different temperatures was measured, and the crystal phase and vitreous composition of each ceramic blank were calculated, and different k-t curves were obtained.For high quartz porcelain with high crystal phase content, its thermal conductivity value is larger and decreases linearly with the increase of temperature.However, the thermal conductivity of other ceramic blanks with little difference between crystal phase and glass phase increases linearly with the increase of temperature.

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