There are three basic modes of heat transfer: conduction, convection and radiation. For thermal insulation materials, thermal conduction is mainly done by the solid part of the insulation materials. The convection is mainly completed by the gas in the insulation material. No medium is required for the transmission of thermal radiation.

In 1992, the international conference of materials engineering held in the United States proposed the concept of super thermal insulation, which means that its thermal conductivity is lower than that of "non-convective air" under predetermined use conditions. The aerogel with nano pore structure is a typical super insulating material.

The super adiabatic properties of aerogel are based on the following principles:

"Infinite path" effect: due to the presence of nearly infinite nanometer holes, heat flow can only be transferred along the stomatal wall when passing through solid, and nearly infinite stomatal walls constitute a nearly "infinite path" effect, which reduces the ability of solid heat conduction to nearly the minimum limit.

"Zero convection" effect: when the pore diameter of the aerogel material is less than 70nm, the air molecules in the pore lose the ability of free flow, and attach relatively to the pore wall. At this time, the material is in a nearly vacuum state, that is, "zero convection" effect is generated.

"Infinite covering hot plate" effect: the materials within the pores are based on nanoscale pores plus material itself very low volume density, internal hole wall materials for days tend to be "an infinity", for each hole wall has covered the role of hot plate, and therefore produce almost an infinite number of covering hot plate "" effect, so that the radiation heat transfer fell to near the lowest limit. When used under the high temperature above 400 ℃, however, still need to join the sunscreen to enhance aerogel resistance to high temperature infrared radiation. Articles come from the Internet

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