| The infrared detector is the core component of the earth observation system with high-resolution, which largely determines the development of infrared imaging technology. And a revolution of the infrared imaging systems must result from the emerging of a new type of detector. Currently, the characteristics of the4th generation infrared detector are large array, high-resolution and multi-bands. Comparing with the non-cooling imaging devices, high-performance cooling infrared detector devices have the advantages of excellent image quality and high detection sensitivity, meanwhile, they were required to work at low temperatures.As a most significant part of the high-performance cooling infrared detectors, the integrated long line array infrared detector commonly used Mo-Cu alloy at the interface of cooling ends. However, the thermal conductivity of Mo-Cu alloy,180W/m-K and200W/m-K at room temperature and100K respectively, can not meet the requirements for high resolution imaging. It is therefore necessary to search a new type of material for cold-end interface with high thermal conductivity at low temperature, as well as matching the linear expansion coefficient of the base material. This study focused on the diamond/Cu composites materials, including the following aspects.1. Optimized preparation of high thermal conductivity and low expansion diamond/Cu composite (hereinafter referred to as Diamond/Cu) at low temperature as follows:First, adopted the pressure infiltration method to prepare four groups of the composite, Diamond/CuCr, Diamond/CuB, HT-Diamond/CuCr, LT-Diamond/CuCr (in which, A:high-temperature binder; C:low-temperature binder). Then, the high-pressure infiltration method was adopted to prepare the Diamond/CuCr composite of Diamond/CuCr, Diamond/CuB, and Diamond/CuNi. This was followed by adopting the differential scanning calorimetry (PPMS) in order to analyze the variety of thermal conductivities as the temperature changes, and to build a relationship between them. Finally, Matlab was used to establish a formula for the relationship between temperature and thermal conductivity. The results show that the LT-Diamond/CuCr composite has good comprehensive performance. The thermal conductivity was650W/m-K and600W/m-K at room temperature and100K, respectively; and the coefficient of thermal expansion was5.0×10-6/K. 2. Study on the evolution of microstructure and property and thermal fatigue behavior of Diamond/Cu composite undergoing high and low temperature cyclic loads and impact loads. This study explored the changes of microstructure and property of LT-Diamond/CuCr composite after100,300and500cycles, and undergoing-65to-175℃thermal cyclic loads. The thermal conductivity of the composite decrease with the increase of cycles, for example, decreasing3.8%after100cycles, and decreasing5%after500cycles. However, it remained above570W/m-K, which met the demands for actual application.This study also explored the changes of microstructure and property of LT-Diamond/CuCr composite after100,200, and300cycles while undergoing-196to-85℃thermal impact loads. The thermal conductivity is500W/m-K after300cycles of thermal impact, and the material showes good thermal impact stability.This study investigated into the relationship between the microstructure and property of the diamond/Cu composite after the thermal cyclic and thermal impacts, and focused on the stress status at the near-interface area, and through which, the thermal fatigue behavior of the diamond/Cu composite was revealed. The microstructure shows the interfacial de-bonding and diamond fracture. The thermal conductivity and the bending strength are slightly decreased, and the thermal expansion coefficient is slightly increased after thermal cycles and impacts. However, they are still at a relatively high level and meet the requirements for the cold-end interface material of components.3. This study illustrated the microstructure of the interface of the LT-Diamond/CuCr composite which display a good comprehensive performance. According to Hasselman-Johnson thermal-conductivity model, the relationship between the thermal resistance and temperature at interface was studied for the LT-Diamond/CuCr composite. The thermal resistance of interface increases with the decrease of the temperature and increase of the cycles under thermal cycles and impact. |
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