What is the best High Temperature Thermal Insulation Material?

There are several options: Mica, Exfoliated vermiculite, Calcium silicate board, and Vermiculite. Depending on the temperature of the environment, these options may be more or less appropriate. Nevertheless, there are some things that you should keep in mind. These materials should be lightweight, flexible, or semi-rigid to achieve the desired results.

Vermiculite
When heated, vermiculite expands up to 30 times its original length. The term vermiculite comes from the Latin verb "vermiculor," meaning to breed worms. Mining and using vermiculite became a profitable commercial venture in the 1920s. Now, the material is used in many applications, including high-temperature thermal insulation. Here are some applications:
Mica
Mica is used in the electrical and electronic industry for a number of reasons. Its unique thermal, electrical and mechanical properties make it a good choice for wire and cable insulation. Furthermore, mica is light in weight and can be easily molded and cut to precise tolerances. Thus, mica is a good choice for high temperature thermal insulation. Here are some of its advantages. Let's take a closer look.
Exfoliated vermiculite
Shear-mixing and ultrasounds were used to exfoliate the vermiculite. This process yielded material with an equivalent number of mono-layer flakes and a similar thickness distribution to ultrasound-assisted exfoliation. Shear-mixing also induced the formation of multilayered flakes, increasing the total number of flakes from 16 to 20 percent. AFM images of raw and exfoliated vermiculite revealed a narrow distribution of lateral sizes with a peak of 300 nm.
Calcium silicate board
The determination of reliable thermal conductivity values for high-temperature thermal insulation materials is an important task for target-oriented material research, product development and quality management. To this end, reference materials should be used for such measurements. The use of porous calcium silicate board as a reference material for high-temperature thermal insulation measurements was investigated in this study. The material was tested at temperatures ranging from 300 K to 1100 K, and the results were compared with those obtained for seven participating laboratories.