High-precision low-temperature thermal conductivity measuring device and method

Abstract

The invention provides a high-precision low-temperature thermal conductivity measuring device and method. The high-precision low-temperature thermal conductivity measuring device comprises a refrigerating machine, a radiation screen, a sample carrying table and a temperature control module. The refrigerating machine comprises a secondary cold head and a cold head flange, and the radiation screen is connected with the cold head flange to form a sealing cavity surrounding the sample carrying table. The temperature control module comprises a sample temperature control unit and a radiation screen temperature control unit, the sample temperature control unit is used for controlling and monitoring the temperature of the sample to be detected, and the radiation screen temperature control unit is used for controlling and monitoring the temperature of the radiation screen. The refrigerator is used for providing stable low-temperature cooling capacity, the sample temperature control unit and the radiation screen temperature control unit are matched with each other to reduce interference on temperature detection of a to-be-detected sample from heat radiation outside the radiation screen and heat radiation of the radiation screen body, and a guarantee is provided for constructing a stable low-temperature environment. The thermal conductivity of the to-be-measured sample is accurately measured, the purpose of high-precision measurement of the thermal conductivity of the material in a low-temperature region is achieved, and the device has the effects of high measurement precision, wide temperature region coverage and high stability.

Description

Technical Field

[0001] This application relates to the field of cryogenic measurement technology, and in particular to a high-precision cryogenic thermal conductivity measuring device. Background Technology

[0002] Thermal conductivity is a core physical property parameter characterizing a material's thermal conductivity. Its measurement accuracy directly impacts the reliability and safety of spacecraft thermal control systems, the cryogenic stability of superconducting magnets, the thermal management of quantum devices, and cryogenic engineering designs. Currently, in the 4.2K–50K temperature range, the mainstream method for thermal conductivity testing remains the steady-state axial heat flow method. This method, based on Fourier's law of heat conduction, calculates thermal conductivity by establishing a steady-state temperature gradient across the sample and accurately measuring the heat flow and temperature difference. Therefore, the accuracy of temperature measurement directly determines the accuracy of the thermal conductivity result.

[0003] In related technologies, copper-encapsulated thermometers (CU) are commonly used to acquire temperature signals. These thermometers are widely adopted in engineering practice due to their high encapsulation strength, convenient installation, and reliable lead soldering. However, their structural characteristics also bring insurmountable drawbacks. For example, in low-temperature environments of 4.2K–50K, radiative heat transfer has a particularly significant impact on temperature measurement. CU-encapsulated thermometers typically have a large surface area and need to be fixed to the sample surface using screws or clamps, inevitably resulting in contact between the thermometer and the sample. Furthermore, most of the thermometer is exposed outside the sample holder, making it highly susceptible to thermal radiation interference from the secondary radiation shield. This causes the measured temperature value to deviate from the true sample temperature, leading to a systematic deviation in the calculated thermal conductivity.

[0004] Therefore, how to provide a high-precision low-temperature thermal conductivity measurement device and method that can improve the accuracy of copper-encapsulated thermometers in measuring the true temperature of samples and reduce the deviation of thermal conductivity calculation results has become a technical problem that urgently needs to be solved by those in the field. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art.

[0006] Therefore, the first objective of this application is to propose a high-precision low-temperature thermal conductivity measurement device and method, which can improve the accuracy of copper-encapsulated thermometers in measuring the true temperature of samples and reduce the deviation of thermal conductivity calculation results.

[0007] To achieve the above objectives, a first aspect of this application provides a high-precision low-temperature thermal conductivity measuring device, comprising:

[0008] A refrigeration unit, including a two-stage cold head and a cold head flange connected to the two-stage cold head;

[0009] The radiant screen is sealed to the cold head flange and together with the cold head flange forms a sealed cavity;

[0010] A sample stage is used to support the sample to be tested. The sample stage is located inside the sealed cavity, and one end of the sample stage is connected to the cold head flange so that the sample to be tested is located inside the sealed cavity and does not contact the cavity wall of the sealed cavity.

[0011] The temperature control module includes a sample temperature control unit and a radiation screen temperature control unit. The sample temperature control unit includes a first temperature sensor and a second temperature sensor disposed at both ends of the sample to be tested, and a first heat source disposed at the end of the sample to be tested near the first temperature sensor. The radiation screen temperature control unit includes a second heat source, a third temperature sensor, and a fourth temperature sensor connected to the radiation screen. The third temperature sensor is disposed on the side near the second heat source, and the fourth temperature sensor is disposed on the side away from the second heat source.

[0012] Optionally, a connecting ring is further included between the cold head flange and the radiation screen. The connecting ring is an I-shaped connecting ring, and the cold head flange and the radiation screen are sealed together through the connecting ring.

[0013] Optionally, the connecting ring is composed of an insulating material with low thermal conductivity, including glass fiber epoxy resin or polytetrafluoroethylene.

[0014] Optionally, the sample stage includes a vertical connecting plate and a horizontal carrier plate, one end of the vertical connecting plate is connected to the cold head flange, and the other end is connected to the horizontal carrier plate; the horizontal carrier plate is used to support the sample to be tested.

[0015] Optionally, the sample to be tested is located at the cold end near the horizontal carrier plate and at the hot end extending vertically away from the horizontal carrier plate, with the first temperature sensor and the first heat source disposed at the hot end and the second temperature sensor disposed at the cold end.

[0016] Optionally, the radiation screen includes a bottom wall and a side wall, the second heat source and the third temperature sensor are disposed on the bottom wall, and the fourth temperature sensor is disposed on the side of the side wall away from the second heat source.

[0017] A high-precision low-temperature thermal conductivity measurement method includes using the high-precision low-temperature thermal conductivity measurement device described in any one of 1 to 6 above, and further includes:

[0018] S1, the sample to be tested is placed on the sample stage, and the first heat source and the first temperature sensor are installed at the end of the sample to be tested away from the sample stage, and the second temperature sensor is installed at the end of the sample to be tested close to the sample stage;

[0019] S2, the initial temperature of the sample stage is controlled by the refrigerator to bring the sample to a first stable state, and the temperature values ​​of the first temperature sensor and the second temperature sensor are recorded simultaneously in the first stable state.

[0020] S3, use the first heat source to heat the end of the sample to be tested away from the sample stage, and simultaneously use the second heat source to heat the radiation screen, so that the sample to be tested reaches the second stable state, and simultaneously record the temperature values ​​of the first temperature sensor and the second temperature sensor in the second stable state.

[0021] S4, the initial temperature of the sample stage is adjusted using a refrigerator, and the temperature of the radiation screen is adjusted simultaneously using the second heat source, so that the sample to be tested reaches the third stable state, and the temperature values ​​of the first temperature sensor and the second temperature sensor are recorded simultaneously in the third stable state.

[0022] S5. Based on the thermal conductivity calculation formula, and the temperature values ​​of the first temperature sensor and the second temperature sensor in the second and third stable states, the size parameters of the sample to be tested, and the heat parameters of the first heat source, calculate the thermal conductivity of the sample to be tested at different temperatures.

[0023] Optionally, when the sample to be tested reaches the first stable state, the temperature fluctuation of both the first temperature sensor and the second temperature sensor is less than 1 mK.

[0024] Optionally, when the sample to be tested reaches the second stable state and / or the third stable state, the temperature difference between the third temperature sensor and the fourth temperature sensor is less than a preset temperature threshold, and the temperature difference between the third temperature sensor and the second temperature sensor is less than 0.1K.

[0025] Optionally, the formula for calculating thermal conductivity satisfies:

[0026]

[0027] Wherein, λ is the thermal conductivity of the sample to be tested; Q is the total power of the first heat source; q is the heat leakage of the first heat source; L is the center-to-center distance between the first temperature sensor and the second temperature sensor; S is the cross-sectional area of ​​the sample to be tested; t1' is the temperature value of the first temperature sensor in the second or third stable state; t2' is the temperature value of the second temperature sensor in the second or third stable state.

[0028] The low-temperature thermal conductivity measuring device and method provided in this application have at least the following beneficial effects:

[0029] This application provides a high-precision low-temperature thermal conductivity measurement device and method, including a refrigerator, a radiation screen, a sample stage, and a temperature control module. The refrigerator includes a two-stage cold head and a cold head flange. The radiation screen, connected to the cold head flange, forms a sealed cavity surrounding the sample stage, and the sample to be tested is suspended within the sealed cavity. The temperature control module includes a sample temperature control unit and a radiation screen temperature control unit. The sample temperature control unit is used to control and monitor the temperature of the sample to be tested, and the radiation screen temperature control unit is used to control and monitor the temperature of the radiation screen. This application utilizes the refrigerator to provide stable low-temperature cooling, while the cooperation between the sample temperature control unit and the radiation screen temperature control unit reduces the interference of external and internal thermal radiation from the radiation screen body on the temperature detection of the sample to be tested, thereby ensuring a stable low-temperature environment for the sample to be tested. The temperature control module achieves precise measurement of the thermal conductivity of the sample by separately adjusting the temperature gradient of the sample and the temperature of the radiation screen. It achieves the goal of high-precision measurement of material thermal conductivity in the low temperature range, and has the effects of high measurement accuracy, wide temperature coverage, and strong stability. It can provide reliable material thermophysical property data for scientific research and engineering design in aerospace, low temperature superconductivity and other fields.

[0030] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0031] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 This is a schematic cross-sectional view of a high-precision low-temperature thermal conductivity measuring device according to an embodiment of this application.

[0033] Figure 2 This is a flowchart illustrating a high-precision low-temperature thermal conductivity measurement method according to an embodiment of this application.

[0034] 1. Secondary cold head; 2. Cold head flange; 3. Connecting ring; 4. Fourth temperature sensor; 5. Radiation screen; 6. Second heat source; 7. Sample stage; 8. First heat source; 9. Sample to be tested; 10. First temperature sensor; 11. Second temperature sensor; 12. Third temperature sensor. Detailed Implementation

[0035] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0036] According to the first aspect of this application, a high-precision low-temperature thermal conductivity measuring device is provided, such as... Figure 1 As shown, the device includes a refrigerator, a radiation screen 5, a sample stage 7, and a temperature control module.

[0037] In some embodiments, the refrigerator acts as a cold source, its core function being to provide a stable low-temperature cooling capacity for the entire thermal conductivity measurement device. The refrigerator includes a two-stage cold head and a cold head flange 2 connected to the two-stage cold head. The two-stage cold head 1, as a key component for cooling capacity output, transfers the cooling capacity generated by the refrigerator to the cold head flange 2 through its connection with the flange. The cold head flange 2 then transfers the cooling capacity to the sample 9 connected to it, thereby providing a stable low-temperature measurement environment for the sample 9.

[0038] As an example, the low-temperature range provided by the refrigeration unit for thermal conductivity measurement is 4.2K to 50K.

[0039] As an example, the temperature of the refrigeration unit can be precisely controlled by a Lakeshore temperature controller to ensure that the secondary cold head 1 can be kept stable within the target temperature range, including gradually increasing the temperature from 4.2K to each measurement temperature point, thus providing a basis for forming a stable temperature gradient for the nine test samples.

[0040] In some embodiments, the radiation shield 5, as a key radiation isolation and temperature control component, is arranged around the periphery of the sample 9 to be tested and forms a sealed cavity through connection with the flange of the secondary cold head 1. This allows the sample to be located within the sealed cavity, thereby reducing or avoiding the influence of stray heat radiation from the external environment (such as other components of the refrigeration unit or the external space of the device) on the temperature of the sample 9. In other words, the core function of the radiation shield 5 is to solve the problem of thermal radiation interference in low-temperature thermal conductivity measurements due to the large exposed area of ​​CU-packaged or large-size thermometers through the dual effects of physical isolation and precise temperature control.

[0041] As an example, the radiation screen 5 may be composed of a metallic material with high thermal conductivity, including but not limited to copper.

[0042] As an example, the radiation screen 5 includes a bottom wall at the bottom and a side wall at the sides, which form a sealed cavity at both ends in the vertical direction by connecting the cold head flange 2 to the bottom wall.

[0043] As an example, both the inner and outer surfaces of the radiation screen 5 are polished, and its outer surface is wrapped with vacuum insulation paper.

[0044] Furthermore, a connecting ring 3 is provided between the radiant screen 5 and the cold head flange 2. The cold head flange 2 and the radiant screen 5 are sealed together by the connecting ring 3 to reduce the direct transfer of cold energy between the cold head flange 2 and the radiant screen 5, which can create conditions for individual temperature control of the sealed cavity.

[0045] As an example, the connecting ring 3 is an I-shaped connecting ring, which may be composed of insulating materials with low thermal conductivity, including but not limited to glass fiber epoxy resin or polytetrafluoroethylene.

[0046] In some embodiments, the sample stage 7 is located inside the sealed cavity, with one end connected to the cold head flange 2 and the other end connected to and supporting the sample 9 to be tested, so that the sample 9 to be tested can be suspended inside the sealed cavity without contacting the internal cavity wall. At the same time, the sample stage 7 can also be connected to the cold head flange 2 to transfer low-temperature cooling energy to the sample to be tested, thereby providing a stable low-temperature environment for the sample 9 to be tested.

[0047] As an example, the sample stage 7 includes a vertical connecting plate and a horizontal carrier. The vertical connecting plate is arranged in the vertical direction, with one end connected to the cold head flange 2 and the other end connected to the horizontal carrier plate arranged in the horizontal direction, so that the sample 9 to be tested can be suspended in the sealed cavity through the horizontal carrier plate.

[0048] As an example, the sample stage 7 may be composed of a metallic material with high thermal conductivity, including but not limited to copper.

[0049] In some embodiments, the temperature control module includes a sample temperature control unit and a radiation screen temperature control unit. The sample temperature control unit includes a first temperature sensor 10 and a second temperature sensor 11 disposed at both ends of the sample 9 to be tested, and a first heat source 8 disposed at the end of the sample 9 closer to the first temperature sensor 10. The radiation screen temperature control unit includes a second heat source 6, a third temperature sensor 12, and a fourth temperature sensor 4 connected to the radiation screen 5. The third temperature sensor 12 is disposed on the side closer to the second heat source 6, and the fourth temperature sensor 4 is disposed on the side farther from the second heat source 6.

[0050] As an example, by placing the first heat source 8 and the first temperature sensor 10 on the side of the sample 9 to be tested away from the horizontal carrier plate (or on the side closer to the cold head flange 2), i.e., the hot end of the sample 9 to be tested, the hot end of the sample 9 to be tested can be heated to a preset temperature by the first heat source 8, and the temperature of the hot end can be detected in real time by the first temperature sensor 10. In other words, the first heat source 8 and the first temperature sensor 10 work together to control and monitor the temperature of the hot end of the sample 9 to be tested, thereby providing a stable high-temperature environment for the hot end of the sample 9 to be tested.

[0051] Meanwhile, by placing the second temperature sensor 11 near the horizontal carrier plate, specifically at the cold end of the sample 9, the cold end of the sample 9 can be temperature-detected by the second temperature sensor 11. In other words, the sample temperature control unit provides a stable temperature gradient environment for the sample 9.

[0052] Since the first heat source 8 and the first temperature sensor 10 can provide a stable high-temperature environment for the hot end of the sample 9 to be tested, and the sample stage 7, by connecting with the cold end of the sample 9 to be tested, can provide a stable low-temperature environment for the cold end of the sample 9 to be tested. Thus, the sample 9 to be tested between the first temperature sensor 10 and the second temperature sensor 11 will generate a stable temperature gradient under the joint drive of the first heat source 8 and the refrigerator. Based on the temperature parameters and distance parameters between the first temperature sensor 10 and the second temperature sensor 11, the thermal power parameters of the first heat source 8, and the cross-sectional size parameters of the sample 9 to be tested, and combined with the thermal conductivity calculation formula, the thermal conductivity of the sample 9 to be tested at the preset temperature can be calculated and obtained.

[0053] It should be noted that before heating the hot end of the sample 9 to be tested using the first heat source 8, the initial temperatures of the hot and cold ends of the sample 9 to be tested, detected by the first temperature sensor 10 and the second temperature sensor 11 respectively, should be recorded simultaneously. When the temperatures of the hot and cold ends of the sample 9 to be tested reach their respective temperature zones and the temperature fluctuations are all less than 1 mK, the first heat source 8 is used to heat the hot end of the sample 9 to be tested using the Lakeshore temperature controller.

[0054] As an example, by placing the second heat source 6 and the third temperature sensor 12 on the bottom wall of the radiation screen 5, the radiation screen 5 can be heated to a preset temperature similar to that of the second temperature sensor 11 by the second heat source 6. Furthermore, by placing the third temperature sensor 12 on the bottom wall near the second heat source 6, the third temperature sensor 12 can monitor the heating temperature of the second heat source 6. In other words, the second heat source 6 and the third temperature sensor 12 jointly play a role in temperature control and monitoring of the radiation screen 5, ensuring the accuracy of temperature control and maintaining synchronization between the temperature of the radiation screen 5 and the cold end temperature of the sample 9. This further reduces or avoids the impact of the thermal radiation from the radiation screen 5 on the temperature detection of the first temperature sensor 10 and the second temperature sensor 11, thus improving the accuracy of thermal conductivity detection and calculation.

[0055] As an example, by placing the fourth temperature sensor 4 on the side wall of the radiation screen 5 away from the second heat source 6, the fourth temperature sensor 4 can monitor the temperature of the radiation screen 5 in real time. When the temperature of the radiation screen 5 is significantly lower than the cold end temperature of the sample 9 to be tested detected by the second temperature sensor 11, the Lakeshore temperature controller is used again to control the second heat source 6 to start heating the radiation screen 5, thereby ensuring that the temperature of the radiation screen 5 is consistent with the temperature of the cold end of the sample 9 to be tested.

[0056] It should be noted that when the temperature difference between the radiation screen 5 (the temperature detected by the fourth temperature sensor 4) and the cold end temperature of the sample 9 (the temperature detected by the second temperature sensor 11) is less than 0.1K, the second heat source 6 does not need to heat the radiation screen 5. In other words, the second heat source 6 operates when the temperature difference between the radiation screen 5 and the cold end temperature of the sample 9 is greater than 0.1K.

[0057] In one specific embodiment, the initial temperatures of the first temperature sensor 10 and the second temperature sensor 11 in a stable state can be denoted as T1 and T2, respectively. Once T1 and T2 reach their respective temperature zones and the temperature fluctuations are both less than 1 mK, the first heat source 8 is used to heat the hot end of the sample 9 under test using a Lakeshore temperature controller until the hot end temperature of the sample 9 reaches a preset temperature value. After maintaining temperature stability, a stable temperature gradient is formed on the sample 9. At this point, the temperature value of the first temperature sensor 10 in a stable state can be denoted as t1', and the temperature value of the second temperature sensor 11 can be denoted as t2'.

[0058] Simultaneously, the temperature value T4 of the fourth temperature sensor 4 is recorded. Therefore, when the temperature difference between T4 and t2' is greater than 0.1K, the Lakeshore temperature controller can be used to control the second heat source 6 to heat the radiation screen 5, while the third temperature sensor 12 monitors the heating temperature of the second heat source 6 in real time until the temperature difference between T4 and t2' is less than 0.1K. Alternatively, when the temperature difference between T4 and t2' is less than 0.1K, heating the radiation screen 5 with the second heat source 6 is not required. In other words, when the temperature difference between T4 and t2' is less than 0.1K, the thermal radiation from the radiation screen 5 can be considered to have almost no impact on the temperature detection of the first temperature sensor 10 and the second temperature sensor 11, thus ensuring the accuracy of thermal conductivity detection and calculation.

[0059] Therefore, based on the temperature difference (t1'-t2') and distance parameter L between the first temperature sensor 10 and the second temperature sensor 11, the thermal power parameter of the first heat source 8, and the cross-sectional size parameter of the sample 9 to be tested, and combined with the thermal conductivity calculation formula, the thermal conductivity of the sample 9 to be tested at the initial temperature can be calculated, which satisfies:

[0060]

[0061] Where Q is the total power of the first heat source 8, q is the heat leakage of the first heat source 8, and S is the cross-sectional area of ​​the sample 9 to be tested.

[0062] The total power Q and heat loss q of the first heat source 8 satisfy the following:

[0063] Q = I 2 R,

[0064] q=λ′AΔt / δ,

[0065] Where I is the current flowing through the first heat source 8, R is the on-resistance of the first heat source 8, λ′ is the thermal conductivity of the lead wire of the first heat source 8, which can be simplified to the average thermal conductivity at both ends of the lead wire during calculation, A is the cross-sectional area of ​​the lead wire of the first heat source 8, Δt is the temperature difference between the two ends of the lead wire of the first heat source 8, and δ is the length of the lead wire of the first heat source 8.

[0066] Since the thermal conductivity of the sample 9 to be tested changes with temperature in different low-temperature zones, the output cooling capacity of the refrigerator can be adjusted adaptively. This can be achieved by using a Lakeshore temperature controller to ensure that the secondary cold head 1 can be stably controlled in different target temperature zones, including gradually increasing the temperature from 4.2K to each measurement temperature point, thereby accurately obtaining the low-temperature thermal conductivity change curve of the sample 9 to be tested.

[0067] According to a second aspect of this application, a high-precision method for measuring low-temperature thermal conductivity is provided, such as... Figure 1 and 2 As shown, the apparatus, including any of the above embodiments, further includes the following steps:

[0068] S1, the sample to be tested 9 is placed on the sample stage 7, and the first heat source 8 and the first temperature sensor 10 are installed at the end of the sample to be tested 9 away from the sample stage 7, and the second temperature sensor 11 is installed at the end of the sample to be tested 9 close to the sample stage 7.

[0069] S2, the initial temperature of the sample stage 7 is controlled by the refrigerator so that the sample 9 to be tested reaches the first stable state, and the temperature values ​​of the first temperature sensor 10 and the second temperature sensor 11 are recorded simultaneously in the first stable state.

[0070] S3, the first heat source 8 is used to heat the end of the sample 9 away from the sample stage 7, and the second heat source 6 is used to heat the radiation screen 5 simultaneously, so that the sample 9 reaches the second stable state, and the temperature values ​​of the first temperature sensor 10 and the second temperature sensor 11 in the second stable state are recorded simultaneously.

[0071] S4, the initial temperature of the sample stage 7 is adjusted by the refrigerator, and the temperature of the radiation screen 5 is adjusted by the second heat source 6 at the same time, so that the sample 9 to be tested reaches the third stable state, and the temperature values ​​of the first temperature sensor 10 and the second temperature sensor 11 are recorded at the same time in the third stable state.

[0072] S5. Based on the thermal conductivity calculation formula, and the temperature values ​​of the first temperature sensor 10 and the second temperature sensor 11 in the second and third stable states, the size parameters of the sample 9 to be tested, and the heat parameters of the first heat source 8, the thermal conductivity of the sample 9 to be tested at different temperatures is calculated.

[0073] The first stable state refers to the state of the sample 9 under test when the first temperature sensor 10 and the second temperature sensor 11 reach their respective temperature zones and the temperature fluctuation is less than 1 mK.

[0074] The second stable state refers to the state of the sample 9 under test when, based on the first stable state, the temperature of the first temperature sensor 10 and the second temperature sensor 11 stabilizes again after the first heat source 8 heats the end of the sample 9 away from the sample stage 7 (i.e., the hot end), and the temperature difference between the third temperature sensor 12 or the fourth temperature sensor 4 and the second temperature sensor 11 is less than 0.1K.

[0075] The third stable state refers to the state of the sample 9 under test, based on the second stable state, after the temperature of the end of the sample 9 near the sample stage 7 (i.e., the cold end) is adjusted using a refrigerator, and the temperatures of the first temperature sensor 10 and the second temperature sensor 11 stabilize again, and the temperature difference between the third temperature sensor 12 or the fourth temperature sensor 4 and the second temperature sensor 11 is less than 0.1K. The temperature adjustment of the cold end of the sample 9 under test using a refrigerator can be achieved by increasing the temperature of multiple measurement points starting from 4.2K.

[0076] It should be noted that when the sample 9 reaches the second and / or third stable states, and the temperature difference between the third temperature sensor 12 and the fourth temperature sensor 4 is less than the preset temperature threshold, and the temperature difference with the second temperature sensor 11 is less than 0.1K, the temperature of the radiation screen 5 does not need to be adjusted using the second heat source 6. Conversely, when the temperature difference between the third temperature sensor 12 and the fourth temperature sensor 4 is less than the preset temperature threshold, but the temperature difference with the second temperature sensor 11 is greater than 0.1K, the temperature of the radiation screen 5 needs to be adjusted using the second heat source 6 until the temperature difference between the third temperature sensor 12 or the fourth temperature sensor 4 and the second temperature sensor 11 is less than 0.1K.

[0077] In summary, this application provides a high-precision low-temperature thermal conductivity measurement device and method, including a refrigerator, a radiation screen 5, a sample stage 7, and a temperature control module. The refrigerator includes a two-stage cold head 1 and a cold head flange 2. The radiation screen 5, connected to the cold head flange 2, forms a sealed cavity surrounding the sample stage 7, and the sample 9 to be tested is suspended within the sealed cavity. The temperature control module includes a sample temperature control unit and a radiation screen temperature control unit. The sample temperature control unit is used to control and monitor the temperature of the sample 9 to be tested, and the radiation screen temperature control unit is used to control and monitor the temperature of the radiation screen 5. This application utilizes the refrigerator to provide stable low-temperature cooling, and the cooperation between the sample temperature control unit and the radiation screen temperature control unit reduces the interference of external and internal thermal radiation from the radiation screen 5 on the temperature detection of the sample 9 to be tested, thereby ensuring a stable low-temperature environment for the sample 9 to be tested. The temperature control module achieves precise measurement of the thermal conductivity of the sample 9 by separately adjusting the temperature gradient of the sample 9 and the temperature of the radiation screen 5. It achieves the goal of high-precision measurement of material thermal conductivity in the low temperature range, and has the effects of high measurement accuracy, wide temperature coverage, and strong stability. It can provide reliable material thermophysical property data for scientific research and engineering design in aerospace, low temperature superconductivity and other fields.

[0078] In the foregoing descriptions of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A high-precision low-temperature thermal conductivity measuring device, characterized in that, include: A refrigeration unit, including a two-stage cold head and a cold head flange connected to the two-stage cold head; The radiant screen is sealed to the cold head flange and together with the cold head flange forms a sealed cavity; A sample stage is used to support the sample to be tested. The sample stage is located inside the sealed cavity, and one end of it is connected to the cold head flange so that the sample to be tested is located inside the sealed cavity and does not contact the cavity wall of the sealed cavity. The temperature control module includes a sample temperature control unit and a radiation screen temperature control unit. The sample temperature control unit includes a first temperature sensor and a second temperature sensor disposed at both ends of the sample to be tested, and a first heat source disposed at the end of the sample to be tested near the first temperature sensor. The radiation screen temperature control unit includes a second heat source, a third temperature sensor, and a fourth temperature sensor connected to the radiation screen. The third temperature sensor is located on the side closer to the second heat source, and the fourth temperature sensor is located on the side farther away from the second heat source.

2. The high-precision low-temperature thermal conductivity measuring device according to claim 1, characterized in that, The cold head flange and the radiation screen also include a connecting ring, which is an I-shaped connecting ring, and the cold head flange and the radiation screen are sealed together through the connecting ring.

3. The high-precision low-temperature thermal conductivity measuring device according to claim 1, characterized in that, The connecting ring is made of an insulating material with low thermal conductivity, including glass fiber epoxy resin or polytetrafluoroethylene.

4. The high-precision low-temperature thermal conductivity measuring device according to claim 1, characterized in that, The sample stage includes a vertical connecting plate and a horizontal carrying plate. One end of the vertical connecting plate is connected to the cold head flange, and the other end is connected to the horizontal carrying plate. The horizontal carrying plate is used to support the sample to be tested.

5. The high-precision low-temperature thermal conductivity measuring device according to claim 4, characterized in that, The sample to be tested has a cold end near the horizontal carrier plate and a hot end extending vertically away from the horizontal carrier plate. The first temperature sensor and the first heat source are disposed at the hot end, and the second temperature sensor is disposed at the cold end.

6. The high-precision low-temperature thermal conductivity measuring device according to claim 1, characterized in that, The radiation screen includes a bottom wall and a side wall. The second heat source and the third temperature sensor are disposed on the bottom wall, and the fourth temperature sensor is disposed on the side of the side wall away from the second heat source.

7. A high-precision low-temperature thermal conductivity measurement method, comprising using the high-precision low-temperature thermal conductivity measurement device according to any one of claims 1 to 6, characterized in that, Also includes: S1, the sample to be tested is placed on the sample stage, and the first heat source and the first temperature sensor are installed at the end of the sample to be tested away from the sample stage, and the second temperature sensor is installed at the end of the sample to be tested close to the sample stage; S2, the initial temperature of the sample stage is controlled by the refrigerator to bring the sample to a first stable state, and the temperature values ​​of the first temperature sensor and the second temperature sensor are recorded simultaneously in the first stable state. S3, use the first heat source to heat the end of the sample to be tested away from the sample stage, and simultaneously use the second heat source to heat the radiation screen, so that the sample to be tested reaches the second stable state, and simultaneously record the temperature values ​​of the first temperature sensor and the second temperature sensor in the second stable state. S4, the initial temperature of the sample stage is adjusted using a refrigerator, and the temperature of the radiation screen is adjusted simultaneously using the second heat source, so that the sample to be tested reaches the third stable state, and the temperature values ​​of the first temperature sensor and the second temperature sensor are recorded simultaneously in the third stable state. S5. Based on the thermal conductivity calculation formula, and the temperature values ​​of the first temperature sensor and the second temperature sensor in the second and third stable states, the size parameters of the sample to be tested, and the heat parameters of the first heat source, calculate the thermal conductivity of the sample to be tested at different temperatures.

8. The high-precision low-temperature thermal conductivity measurement method according to claim 7, characterized in that, When the sample to be tested reaches the first stable state, the temperature fluctuation of both the first temperature sensor and the second temperature sensor is less than 1 mK.

9. The high-precision low-temperature thermal conductivity measurement method according to claim 7, characterized in that, When the sample to be tested reaches the second stable state and / or the third stable state, the temperature difference between the third temperature sensor and the fourth temperature sensor is less than a preset temperature threshold, and the temperature difference between the third temperature sensor and the second temperature sensor is less than 0.1K.

10. The high-precision low-temperature thermal conductivity measurement method according to claim 7, characterized in that, The formula for calculating thermal conductivity satisfies: Wherein, λ is the thermal conductivity of the sample to be tested; Q is the total power of the first heat source; q is the heat leakage of the first heat source; L is the center-to-center distance between the first temperature sensor and the second temperature sensor; S is the cross-sectional area of ​​the sample to be tested; t1' is the temperature value of the first temperature sensor in the second or third stable state; t2' is the temperature value of the second temperature sensor in the second or third stable state.

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