Aerogel powder exhibits great potential in the field of efficient insulation materials due to its extremely low thermal conductivity. However, its thermal conductivity is highly dependent on the environmental vacuum degree. This paper delves into the insulation mechanism of aerogel powder, analyzes the necessity and technical challenges of testing its thermal conductivity under different vacuum degrees, aiming to provide reliable data support for material research and development, performance evaluation, and application selection. 
I. Introduction: Why is it important to study the relationship between the vacuum degree and thermal conductivity of aerogel powder? 
Aerogel powder, as a "solid smoke", its nano-porous structure (with a porosity of over 90%) endows it with excellent heat insulation properties. The heat insulation mechanism mainly consists of three aspects: 
1) Gas-phase heat conduction: Convective heat transfer and heat conduction of air molecules within the pores. 
2)  Solid-state heat conduction: The heat conduction of the nano framework itself. 
3)  Radiation heat conduction: The transmission of infrared thermal radiation. 
At normal pressure, convective heat transfer in the gas phase is the dominant factor. As the environmental vacuum level increases, the air molecules within the pores are successively removed, and the average free path of gas molecules increases, effectively suppressing convective heat transfer, thereby causing the overall thermal conductivity of the material to drop sharply. 
Therefore, testing the thermal conductivity of aerogel powder under different vacuum conditions is of great significance for the following aspects: 
1) Material development and optimization: Evaluate the ultimate performance of the powder under various application scenarios (such as cryogenic insulation). 
2) Product quality control: Establish performance benchmarks to ensure consistency across batches. 
3) Application simulation and selection: Provide accurate input parameters for thermal simulation design, and guide the design of end products. 
II. Test Challenges and Core Requirements 
Conducting thermal conductivity tests on aerogel powder under varying vacuum conditions presents several unique challenges: 
1) Powder fluidity: prone to leakage, difficult to fill and stabilize, and requires consideration of cavity sealing performance. 
2) Contact thermal resistance: There is a significant contact thermal resistance between the powder and the test probe or the heating plate, which will seriously affect the test accuracy. 
3)  Vacuum control and maintenance: It is necessary to achieve stable and precise control within a wide range of vacuum levels, and ensure that there is no leakage in the system. 
Based on the above challenges, an ideal testing plan must meet the following core requirements: 
1) Sealing performance: The special powder testing chamber design prevents powder leakage and vacuum leakage. 
2)  Reliable testing method: Capable of effectively reducing or quantifying the influence of contact thermal resistance. 
3) Sample compatibility: Capable of handling powder samples of various particle sizes, densities and morphologies. 
III. Application Cases and Data Presentation

As shown in the figure, the thermal conductivity of this aerogel powder significantly decreases as the environmental vacuum level increases. At normal pressure, the thermal conductivity is approximately 0.024 W/m·K. When the vacuum level reaches 50 Pa, the thermal conductivity drops to approximately 0.012 W/m·K. 

V. Conclusion 
Understanding the thermal conductivity evolution law of aerogel powder under different vacuum conditions is the key step in promoting its application.