In the application of thermal conductivity analyzers in the field of ultra-high temperature insulation ceramics and composite materials, there are three challenges: technical adaptability, material properties, and measurement environment. It is necessary to achieve precise detection through interdisciplinary collaboration breakthroughs.

Technological adaptability challenges

The thermal conductivity range of ultra-high temperature materials (such as ZrC and HfC based composite materials) is wide (0.1-20W/m · K), and traditional single technology is difficult to cover the entire range. Although laser flash method (LFA) is suitable for medium to high thermal conductivity materials, it is susceptible to thermal radiation interference when measuring low thermal conductivity ceramics (such as alumina fiber reinforcement); The hot wire method requires high contact stability for powdered or non-uniform materials (such as 3D printed porous ceramics), resulting in data fluctuations exceeding 15%. In addition, the upper temperature limit of existing equipment is generally below 1800 ℃, and when ultra-high temperature ceramics are in service above 2000 ℃, it is necessary to develop high-temperature resistant sensors and vacuum/inert gas composite test chambers to avoid interference from material oxidation on measurement results.

Material Characteristics Challenge

The anisotropic thermal conductivity of ultra-high temperature ceramics is significant. For example, the thermal conductivity of carbon fiber reinforced SiC composite materials along the fiber direction can reach 80W/m · K, while in the vertical direction it is only 15W/m · K. Traditional one-dimensional measurement methods cannot capture three-dimensional heat flux distribution. Meanwhile, defects such as microcracks and pores in the material can cause local thermal resistance mutations, resulting in measurement errors of over 20% using steady-state methods. For gradient functional materials (such as metal ceramic layered composite structures), it is necessary to combine infrared thermal imaging and finite element simulation to construct a dynamic thermal conduction model to correct boundary effects.

Measuring environmental challenges

In ultra-high temperature testing, the high-temperature interaction between materials and sensors may alter the contact thermal resistance. For example, platinum rhodium thermocouples will experience creep above 1600 ℃, leading to a decrease in contact pressure and resulting in lower values measured by the heat flow method. In addition, the oxidizing environment (such as air furnace testing) can cause a glassy oxide layer to form on the surface of the material, with a thermal conductivity that differs from the substrate by more than three times. In situ X-ray diffraction analysis of the oxide layer thickness is required, and a dynamic correlation model of "composition structure thermal conductivity" should be established. At present, only arc heating plasmonic testing can partially simulate thermal shock in hypersonic airflow, but the equipment cost exceeds tens of millions of yuan, which limits its engineering application.