High-precision material in-plane thermal conductivity measuring device and method

Abstract

The invention relates to the technical field of thermophysical property measurement, in particular to a high-precision material in-plane thermal conductivity measuring device and method.A low-temperature refrigeration module generates a working medium with a set temperature in a vacuum heat insulation module, and the working medium is transferred to a space where a sample is located and the cold end of a heat flow meter in a heat conduction mode; the vacuum heat insulation module comprises at least one stage of anti-radiation screen and a vacuum cavity which are arranged in the outer side space of the sample and the heat flow meter; the heat-flow meter comprises a hot-end heat-flow meter and a cold-end heat-flow meter which are arranged in parallel; the cold-end heat-flow meter and the hot-end heat-flow meter are respectively clamped at two ends of the sample; the pressure-bearing sample table module bears and fixes a heat flow meter and a sample, and the sample is a film material; the distance measurement and control module controls and measures the distance between the cold end heat flow meter and the hot end heat flow meter; the temperature measurement and control module obtains the temperature of the heat flow meter and comprises a temperature measurement probe inserted into the heat flow meter, and the temperature measurement probe is connected with a temperature sensor. Through a specific heat flow meter structure, measurement of in-plane heat conductivity is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal property measurement, and in particular to a high-precision device and method for measuring the in-plane thermal conductivity of a material. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Thermal conductivity is the core parameter of the heat transfer performance of materials, which is divided into out-of-plane thermal conductivity (λ cross-plane ) and in-plane thermal conductivity (λ in-plane Out-of-plane thermal conductivity refers to the ability to conduct heat in a direction perpendicular to the plane of the material, usually measured along the thickness of the material; in-plane thermal conductivity refers to the ability to conduct heat within the plane of the material, usually measured along the two-dimensional plane of the material.

[0004] For isotropic materials (such as metallic glass), the two values are similar; while for anisotropic materials (such as single crystal graphite), their in-plane thermal conductivity (up to 1000 W·m -1 ·K -1 ) and out-of-plane thermal conductivity (as low as 8W·m -1 ·K -1 ) are significantly different, and their mechanisms of action are vastly different.

[0005] For example, for graphite materials, their in-plane thermal conductivity is mainly determined by the in-plane heat carrier conduction characteristics, while the out-of-plane thermal conductivity is not only affected by the characteristics of the heat carriers themselves, but also significantly affected by interlayer interactions.

[0006] There are significant differences between the concepts, measurement methods, and subsequent applications of out-of-plane and in-plane thermal conductivity. Especially in the case of localized high power densities found in high-power electronic devices, flexible electronics, and new energy systems, heat must diffuse in the in-plane direction. Therefore, in-plane thermal conductivity and its accurate measurement directly determine device heat dissipation efficiency and system reliability.

[0007] Existing measurement methods still have the following technical bottlenecks:

[0008] Existing high-precision measurement methods have high requirements for the sample surface: Although the time-domain thermal reflectance method can achieve high-precision measurement of in-plane thermal conductivity, this method requires the sample surface to have extremely high flatness and smoothness (usually reaching the nanometer level), which cannot adapt to most rough and non-ideal surface materials, restricting the engineering measurement of in-plane thermal conductivity.

[0009] Universal measurement methods face the difficulties of controlling the direction of heat flow and accurately measuring it: although the laser flash method and the steady-state method are suitable for most rough and non-ideal surface materials, their heat flow is usually transmitted along the sample thickness direction (i.e., the out-of-plane direction) and is used for out-of-plane thermal conductivity measurement; when measuring in-plane, the laser flash method using a point light source as the excitation heat source is easily disturbed by the lateral heat diffusion of the sample. Although the steady-state method can make the heat flow mainly transmitted along the sample surface direction through reasonable design, the natural convection and radiation heat loss caused by the high specific surface area of the thin film material sample are significant, causing the heat flow to decay nonlinearly. Its attenuation law is difficult to measure accurately, resulting in deviations in the thermal conductivity of the sample cross section, making it difficult to achieve accurate measurement of the in-plane thermal conductivity.

[0010] The contact thermal resistance has a great influence: When measuring thin film materials using the traditional steady-state method, a clamping structure is required to contact and squeeze the sample to fix it. The contact thermal resistance introduced by this is close to or even exceeds the intrinsic thermal resistance of the low thermal conductivity sample in magnitude, resulting in large errors in the thermal conductivity measurement of the sample. Summary of the Invention

[0011] In order to solve the technical problems existing in the above background technology, the present invention provides a high-precision material in-plane thermal conductivity measurement device and method, which is suitable for the in-plane thermal conductivity performance test of thin film materials.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A first aspect of the present invention provides a high-precision material in-plane thermal conductivity measurement device, comprising:

[0014] The heat flux generation and control module includes heating and cooling units with independently controllable temperatures at both ends of the sample, as well as hot-end and cold-end heat flux meters arranged in parallel. This module establishes a stable temperature gradient field along the sample axis to calculate the heat flux through the sample cross section.

[0015] The vacuum insulation module includes at least one level of radiation shield and vacuum chamber arranged outside the sample and heat flux meter. The radiation shield adopts a high-reflectivity metal foil stacking design and is thermally linked to the cold end. The thermal radiation energy is gradually attenuated through the reflection-absorption-reradiation mechanism. The vacuum chamber isolates the natural convection disturbance and conducts heat in a direction along the sample plane, ensuring that the axial heat flux distribution approaches the ideal one-dimensional model.

[0016] The pressure sample stage module is used to carry and fix the heat flow meter and the sample, which is a thin film material;

[0017] The spacing measurement and control module uses a servo linear motor, a displacement transmission screw and a displacement sensor to control and measure the spacing between the cold and hot end heat flow meters, so as to facilitate the replacement of heat flow meters of different lengths and the clamping of samples of different lengths;

[0018] The temperature measurement module is used to obtain the temperature gradient of the heat flow meter, including a thermocouple inserted into the heat flow meter and an external temperature display and acquisition instrument.

[0019] Furthermore, the hot-end heat flux meter and the cold-end heat flux meter both include a heat flux meter body, a chuck is provided at one end of the heat flux meter body for clamping the sample, and the heat flux meter body is a rectangular parallelepiped or a cylinder.

[0020] Furthermore, the vacuum cavity is a metal cavity of a set thickness, and is provided with at least one level of radiation protection screen inside.

[0021] Furthermore, the servo linear motor drives the displacement transmission screw to move in the vertical direction, the displacement transmission screw is connected to the bellows to transmit the displacement into the vacuum chamber, and the displacement is transmitted to the end of the heat flow meter clamping the sample through the displacement transmission screw.

[0022] Furthermore, the heat flux generation and control module also has a hot end heater and a cold end temperature regulator, the hot end heater is connected to the top end of the hot end heat flux meter, and the cold end temperature regulator is connected to the bottom end of the cold end heat flux meter.

[0023] Furthermore, the cold-end temperature regulator is compatible with wet cooling media (such as water, liquid nitrogen, liquid hydrogen, and liquid helium) and dry cooling devices (such as GM refrigerators and pulse tube refrigerators), and can be applied to testing requirements in different temperature zones.

[0024] A second aspect of the present invention provides a high-precision method for measuring in-plane thermal conductivity of a material, comprising the following steps:

[0025] Initialize the distance between the cold and hot end heat flow meters;

[0026] The hot-end heat flux meter rises a set distance, and the sample to be tested with an effective length of L1 is clamped between the hot and cold-end heat flux meters (the effective length is defined as the length between the end faces of the hot and cold-end heat flux meters). The height of the hot-end heat flux meter and its relative position to the cold-end heat flux meter are adjusted until the sample plane is parallel to the axis direction of the hot and cold-end heat flux meters; the vacuum insulation module is reinstalled;

[0027] Adjust the cold and hot end temperature regulators to the set temperature. Under the action of the axial high and low temperature difference, heat is conducted axially in the sample, forming a stable temperature field and axial heat flow. Obtain the temperature of the set measuring points in the cold and hot end heat flow meters.

[0028] Under the current ambient temperature and the cold and hot end temperatures, and the same clamping area length, clamp the same sample with a length of L2 between the cold and hot end heat flow meters, and measure the temperature of each measuring point when the sample length is L2;

[0029] According to Fourier's law of heat conduction, the thermal resistance difference of samples with different lengths is calculated.

[0030] Furthermore, according to Fourier's law of heat conduction, the in-plane thermal conductivity of the sample is calculated, including the following steps:

[0031] According to the cross-sectional area and thermal conductivity of the heat flow meter at the cold and hot ends, as well as the temperature data of each measuring point, the heat flow at the cross section of the sample with a length of L1 is obtained;

[0032] According to the temperature difference between the two temperature measurement points adjacent to the sample L1 and the heat flow at the cross section of the sample L1, the thermal resistance ∑R between the end faces of the cold and hot end heat flow meters when the sample length is L1 is obtained;

[0033] When the sample length is L2, the heat flux at the cross section of the sample with a length of L2 is obtained based on the cross-sectional area and thermal conductivity of the heat flow meters at the cold and hot ends, as well as the temperature data at each temperature measurement point. The thermal resistance ∑R' between the end faces of the heat flow meters at the cold and hot ends when the sample length changes to L2 is obtained based on the temperature difference at two temperature measurement points adjacent to the sample L2, and the thermal resistance difference of samples of different lengths is further obtained.

[0034] The in-plane thermal conductivity of the sample is obtained based on the cross-sectional area of the sample, the length change value, and the thermal resistance change value caused by the change in sample length.

[0035] Furthermore, based on the cross-sectional area and thermal conductivity of the heat flow meters at the cold and hot ends, as well as the temperature data at each measuring point, the heat flow at the cross section of the sample with a length of L1 is obtained; as shown in the following formula:

[0036]

[0037] Among them, Q 13 and Q 46 are the average heat flux of the hot end heat flux meter and the cold end heat flux meter, λ2 and λ5 are the thermal conductivities of the hot end heat flux meter and the cold end heat flux meter at temperatures T2 and T5, respectively. 13 and A 46 are the cross-sectional areas of the hot-end heat flux meter and the cold-end heat flux meter, respectively, and d is the spacing between the temperature measuring points.

[0038] Furthermore, based on the temperature data at the two temperature measurement points adjacent to sample L1 and the heat flow at the cross section of sample L1, the thermal resistance ∑R between the end faces of the cold and hot end heat flow meters when the sample length is L1 is obtained; as shown in the following formula:

[0039]

[0040] Among them, Q L1 is the heat flux at the cross section of the sample with a length of L1, T3 and T4 are the temperature data of the heat flux meter end faces near the cold and hot ends when measuring sample L1, respectively.

[0041] Furthermore, when the sample length is L2, based on the temperature data at the two temperature measurement points adjacent to the sample L2, the thermal resistance ∑R' between the end faces of the cold and hot end heat flow meters when the sample length changes to L2 is obtained; as shown in the following formula:

[0042]

[0043] Among them, Q L2 is the heat flux at the cross section of the sample with a length of L2, T3' and T4' are the temperature data of the heat flux meter end faces near the cold and hot ends when measuring sample L2, respectively.

[0044] Furthermore, the difference between ∑R and ∑R' is the thermal resistance change value caused by the change in sample length ΔL = L1-L2, which can eliminate the influence of the contact thermal resistance at the contact surface between the heat flow meter and the sample on the sample thermal resistance measurement, thereby obtaining the thermal resistance ΔR of the sample with a length of ΔL sample , as shown below:

[0045] ΔR sample =∑R-∑R'.

[0046] Furthermore, the in-plane thermal conductivity of the sample is obtained according to the change in sample length, the thermal resistance of the sample, and the cross-sectional area of the sample, as shown in the following formula:

[0047]

[0048] ΔL=L1-L2;

[0049] Where, ΔR sample is the thermal resistance of the sample, A sample is the cross-sectional area of the sample.

[0050] Compared with the existing technology, one or more of the above technical solutions have the following beneficial effects:

[0051] 1. Compatible with rough surfaces, achieving accurate in-plane thermal conductivity measurement of non-ideal surface materials. Compared with the problem that optical measurement methods such as non-contact time-domain thermal reflection are difficult to adapt to rough surfaces, this invention uses a rigid contact heat flux meter to clamp the sample, directly establish a steady-state heat conduction path with the sample end face, and perform contact temperature measurement without relying on optical reflection signals. This significantly improves the adaptability to rough and non-ideal surface materials and meets the needs of engineering measurement.

[0052] 2. Construct a stable one-dimensional axial heat flow field to improve measurement accuracy. To address the issue of heat flow being susceptible to lateral diffusion and heat loss in traditional laser flash and steady-state methods, this invention introduces a vacuum chamber and multi-stage radiation shielding to significantly reduce natural convection and radiation heat loss. Combining a coaxially symmetrical heat flux meter and a temperature control module creates a stable temperature difference across the sample, ensuring strict one-dimensional heat flow conduction in the in-plane direction. This improves the directional control capability of heat flow and measurement accuracy.

[0053] 3. Use the dual-length differential method to effectively eliminate contact thermal resistance interference. To address the shortcomings of the laser flash method or steady-state method in dealing with contact thermal resistance interference, this paper proposes a "dual-length differential measurement method." By using the thermal resistance difference of samples of different lengths under the same clamping method, the interference of the contact thermal resistance between the fixture and the sample is eliminated, making the measured thermal conductivity closer to the material's intrinsic value and improving the reliability of the results.

[0054] 4. Modular design adapts to various sample sizes, and the system is flexible and adjustable. Compared to conventional steady-state measurement devices with fixed structures and poor adjustability, the present invention adopts a high-precision spacing control system driven by a servo motor and a modular design. This allows for flexible replacement of heat flow meters of different lengths. While ensuring measurement accuracy, it can adapt to thin film material samples with different thermal conductivity characteristics, improving the versatility and scalability of the device.

[0055] 5. It has a wide applicable temperature range and can be used for thermal property testing under extremely low temperature conditions. In view of the problem that conventional thermal conductivity measuring devices are usually limited to room temperature or medium and low temperature ranges, the present invention integrates a vacuum insulation system, a low heat leakage transmission structure and a design that can be used in conjunction with a liquid helium refrigerator refrigeration module to achieve a wide temperature range from room temperature to liquid helium temperature zone (4.2K) Stable operation capability. The system can still establish a clear in-plane temperature gradient in an extremely low temperature environment, and obtain heat flow information in combination with a high-precision temperature measuring probe. It is suitable for high-precision thermal property parameter measurements in a variety of temperature zones, and is particularly suitable for application requirements in scenarios such as low-temperature electronic devices and superconducting materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0057] Figure 1 is the in-plane thermal conductivity (λ) of the material provided by one or more embodiments of the present invention. in-plane ) and out-of-plane thermal conductivity (λ cross-plane ) Schematic diagram;

[0058] Figure 2 is a schematic diagram of the principle of measuring out-of-plane thermal conductivity provided by one or more embodiments of the present invention;

[0059] Figure 3 is a schematic structural diagram of a measuring device provided in Example 1 of the present invention;

[0060] Figure 4 is a schematic structural diagram of the hot and cold end heat flow meters in the measuring device provided by one or more embodiments of the present invention;

[0061] Figure 5Schematic diagram of the principle of measuring in-plane thermal conductivity using hot and cold end heat flow meters provided by one or more embodiments of the present invention;

[0062] Figure 6 Schematic diagram of the measurement principle of in-plane thermal conductivity provided by one or more embodiments of the present invention;

[0063] Figure 7 It is a structural diagram of the measuring device provided in the second embodiment of the present invention.

[0064] Figure 3 In: 1.1 Chiller, 1.2 Compressor, 1.3 Refrigerator, 1.4 Refrigerator bracket, 2.1 Vacuum chamber bracket, 2.2 Bellows, 2.3 Vacuum chamber, 2.4 Multi-layer insulation first-level radiation shield, 2.5 Radiation shield second-level radiation shield, 2.6 Copper braided thermal bridge, 3.1 Oxygen-free copper fixture, 3.2 Thermal damping sheet, 3.3 Cold end temperature regulator, 3.4 Pressure-bearing cold plate, 3.5 Solid epoxy resin support rod, 3.6 Solid polytetrafluoroethylene Support rod, 3.7 stainless steel support rod, 4.1 linear servo press, 4.2 displacement transmission screw, 4.3 pressure sensor, 4.4 contact displacement sensor, 4.5 hollow stainless steel tube tie rod, 4.6 solid polytetrafluoroethylene tie rod, 4.7 solid epoxy resin tie rod, 4.8 limit plate, 4.9 limit screw, 5.1 hot end heater, 5.2 temperature probe, 5.3 temperature sensor, 5.4 hot end heat flux meter, 5.5 cold end heat flux meter;

[0065] Figure 4 Middle: 3.10 sample, 5.61 fixing hole, 5.62 fixture;

[0066] Figure 7 Middle: 1.5 water cooling tube, 1.6 water cooling plate, 1.7 cold end temperature regulator, 2.7 radiation shield, 3.8 heat flux meter fixture, 3.9 pressure sample table, 5.6 heat flux meter, 5.7 temperature controller, 5.8 controller. DETAILED DESCRIPTION

[0067] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0068] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0069] It should be noted that the terms herein are intended only to describe specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0070] Explanation of terms:

[0071] In-plane thermal conductivity and out-of-plane thermal conductivity are two different concepts. For isotropic materials (such as metallic glass), the two values are similar; while for anisotropic materials (such as graphene), the in-plane thermal conductivity (up to 1000 W·m -1 ·K -1 ) and out-of-plane thermal conductivity (as low as 8W·m -1 ·K -1 ) are significantly different, and their mechanisms of action are vastly different.

[0072] Out-of-plane thermal conductivity (λ cross-plane ), refers to the ability to conduct heat perpendicular to the plane of the material, usually measured along the thickness of the material.

[0073] In-plane thermal conductivity (λ in-plane ), refers to the ability of heat to be conducted within the plane of a material, usually measured along the two-dimensional plane of the material (such as the basal plane of graphene).

[0074] For materials with anisotropic thermal conductivity, the thermal conductivity is divided into out-of-plane thermal conductivity (λ cross-plane ) and in-plane thermal conductivity (λ in-plane ),like Figure 1 shown.

[0075] The out-of-plane thermal conductivity is measured along the thickness direction of the material and is affected by interlayer interactions. For example, the out-of-plane thermal conductivity of two-dimensional materials is usually low and is generally used in thermal barrier coatings, thermal insulation materials and other fields.

[0076] In-plane thermal conductivity is measured along the plane of the material. It is affected by the material's crystal structure, chemical bonds, defects, and impurities. The in-plane thermal conductivity of two-dimensional materials is usually high and is generally used in fields such as heat dissipation of electronic devices.

[0077] like Figure 2 As shown, in the traditional steady-state thermal conductivity measurement method, the heat flow meter can only fix non-standard thermal interface materials (such as silicone grease, etc.) by horizontal extrusion, so that the heat flow can only be transmitted from the upper and lower surfaces of the sample. Only out-of-plane thermal conductivity can be measured, and it cannot be applied to the measurement device of in-plane thermal conductivity.

[0078] Therefore, the following embodiments provide a high-precision device and method for measuring the in-plane thermal conductivity of materials. Through a specific heat flow meter structure, heat flow is directed from one end to the other along the in-plane direction of a thin film material sample, achieving in-plane thermal conductivity measurement and resolving the problems of the prior art. This technological breakthrough is achieved through the following methods:

[0079] The contact heat flow meter structure is compatible with samples with rough surfaces. A direct heat conduction path is established through mechanical contact between the rigid heat flow meter and the sample end face, allowing for non-optical contact measurement. This avoids the reliance of optical measurements on nanoscale surface roughness, eliminates the need for complex sample surface processing, and significantly improves compatibility with actual sample surface roughness.

[0080] A steady-state, axial heat flux excitation structure is constructed to ensure heat flow is conducted in the in-plane direction. Coaxial, symmetrical hot-end and cold-end heat flux meters are designed, and the sample is clamped between the two heat flux meters. A controllable temperature differential of 5–200K is created across the sample using a hot-end heater and a cold-end refrigeration unit. This forces heat transfer parallel to the sample plane, forming a stable in-plane heat flow path. The coaxiality of the heat flux meter and the parallelism of the heat flux meter axis with the sample plane are calibrated in real time using a precision displacement adjustment mechanism to ensure the accuracy of the heat flow conduction direction.

[0081] Introducing vacuum insulation module to suppress heat loss outside the heat flow surface. By building vacuum insulation module with vacuum cavity and radiation shield, the heat loss is as low as <10 3 Pa's vacuum environment can greatly reduce natural convection heat loss, and the high-reflectivity aluminum / copper foil screen can greatly suppress radiation heat loss, ensuring that the heat flow is strictly and stably conducted along the in-plane direction of the material.

[0082] A dual-length differential method is introduced to eliminate contact thermal resistance interference. To address the systematic errors caused by contact thermal resistance introduced during sample clamping, a dual-length differential measurement method is proposed. This method uses the difference in thermal resistance of two identical samples of different lengths (L1, L2) with the same clamping distance to eliminate the influence of contact thermal resistance uncertainty on the measurement, ensuring that the thermal conductivity results reflect only the intrinsic properties of the material.

[0083] A vacuum-adaptable drive mechanism is designed to enhance the compatibility of the heat flow meter's length. Using a servo press or stepper motor as the drive, combined with a screw-bellows composite drive structure, the heat flow meter's position can be precisely adjusted within a vacuum-sealed environment. This structure allows for interchangeable heat flow meters of varying lengths based on sample size and heat transfer characteristics, flexibly adjusting the heat flow meter's temperature distribution and ensuring a sufficiently discernible temperature gradient even when testing low-thermal conductivity samples. This effectively improves the controllability of heat flux density and gradients in traditional devices.

[0084] A wide-temperature controllable system is constructed, suitable for thermophysical property testing from ambient to cryogenic temperatures. The device's cold-end temperature control system can be connected to wet cooling media such as water, liquid nitrogen, liquid hydrogen, and liquid helium, as well as dry cryogenic equipment such as GM refrigerators and pulse tube refrigerators. Due to the presence of a vacuum chamber and radiation shield, the measurement system can operate stably from ambient temperature to liquid helium (~4K), making it suitable for precise measurement of in-plane thermal conductivity across this temperature range.

[0085] With the synergistic effect of the above technologies, an in-plane thermal conductivity measurement accuracy of ±10% can be achieved, providing a highly reliable tool for measuring the in-plane thermal conductivity of thin film materials with non-ideal surfaces.

[0086] Example 1:

[0087] A high-precision material in-plane thermal conductivity measurement device, comprising:

[0088] The low-temperature refrigeration module is used to generate a working medium of a set temperature in the vacuum insulation module and transfer it to the sample space and the cold end of the heat flow meter by heat conduction;

[0089] The heat flux generation and control module includes a hot end heater, a cold end heater, and a hot end heat flux meter and a cold end heat flux meter arranged in parallel. The hot and cold end heaters are used to control the hot and cold end temperatures respectively. The cold and hot end heat flux meters are used to clamp the two ends of the sample respectively and conduct heat in the sample plane direction;

[0090] A vacuum insulation module, comprising at least one level of radiation shielding and a vacuum cavity arranged in the space outside the sample and the heat flow meter;

[0091] The pressure sample stage module is used to carry and fix the heat flow meter and the sample, which is a thin film material or a two-dimensional material;

[0092] The spacing measurement and control module uses a servo linear motor, a displacement transmission screw and a displacement sensor to control and measure the spacing between the cold and hot end heat flow meters to clamp samples of different sizes;

[0093] The temperature measurement module is used to obtain the temperature gradient of the heat flow meter, including inserting a thermocouple inside the heat flow meter.

[0094] This embodiment takes the device for measuring the in-plane thermal conductivity of a thin film material sample in the liquid helium temperature range (4.2K) as an example. The structure of the formed measuring device is as follows: Figure 3 shown.

[0095] Low-temperature refrigeration module: This module uses a refrigerator to provide an ultra-low-temperature experimental environment within a certain temperature range (e.g., 4.2-20K). It mainly includes a chiller 1.1, a compressor 1.2, a refrigerator 1.3, and a refrigerator support 1.4.

[0096] Vacuum insulation module: This module reduces heat leakage from the device to the environment by evacuating the device and installing multi-layer radiation shields. It primarily includes a vacuum chamber support 2.1, bellows 2.2, vacuum chamber 2.3, multi-layer insulation first-level radiation shield 2.4, radiation second-level radiation shield 2.5, and a copper braided thermal bridge 2.6.

[0097] Pressure sample stage module: used to carry and secure the sample and heat flow meter. It mainly includes an oxygen-free copper fixture 3.1, a thermal damping plate 3.2, a cold-end temperature regulator 3.3, a pressure cold plate 3.4, solid epoxy resin support rods 3.5, solid polytetrafluoroethylene support rods 3.6, and stainless steel support rods 3.7.

[0098] Gap measurement and control module: Equipped with a contact displacement sensor, this module uses a servo linear motor and drive rod combination to control and measure the gap between the hot and cold end heat flux meters. This module primarily includes a linear servo press 4.1, a drive rod 4.2, a pressure sensor 4.3, a contact displacement sensor 4.4, a hollow stainless steel tube drive rod 4.5, a solid polytetrafluoroethylene drive rod 4.6, a solid epoxy resin drive rod 4.7, a limit plate 4.8, and a limit screw 4.9.

[0099] Temperature measurement and control module: By inserting a high-precision temperature probe into the heat flow meter, this module eliminates errors caused by replacing heat flow with heater power. It also reduces temperature differences caused by deviations in the temperature measurement position, ensuring measurement accuracy. This module primarily includes the hot-end heater 5.1, temperature probe 5.2, temperature sensor 5.3, hot-end heat flow meter 5.4, and cold-end heat flow meter 5.5.

[0100] In this embodiment, the sample is a thin film material, and its two ends are fixed by a hot end heat flux meter 5.4 and a cold end heat flux meter 5.5 respectively.

[0101] like Figure 3 As shown, in this measuring device, the refrigerator 1.3 provides the low temperature of the liquid helium temperature range for the measuring device, the chiller 1.1 is connected to the compressor 1.2 through a cooling water circuit, the compressor 1.2 is connected to the refrigerator 1.3 through a high-pressure helium circuit, and the refrigerator 1.3 is fastened to the refrigerator bracket 1.4 by threads.

[0102] The entire device is placed in a vacuum chamber 2.3 supported by a vacuum chamber bracket 2.1. The vacuum chamber 2.3 is made of stainless steel with a thickness of 20 mm. In order to reduce radiation heat leakage, a multi-layer insulating first-level radiation shield 2.4 made of multiple layers of aluminum foil with a total thickness of approximately 20 mm and a second-level radiation shield 2.5 made of oxygen-free copper sheet with a thickness of approximately 2 mm are provided in the vacuum chamber 2.3.

[0103] In order to reduce the adverse effects of mechanical vibration, the vibrating refrigerator 1.3 is connected to the vacuum chamber 2.3, the multi-layer insulation first-level radiation shield 2.4, and the radiation second-level radiation shield 2.5 through a bellows 2.2 and a copper braided thermal bridge 2.6 made of high-purity oxygen-free copper.

[0104] The sample and the heat flux meter are fixed in the groove of the oxygen-free copper fixture 3.1 using the fine-tuning bolts. A thermal damping plate 3.2, made of 10 stacked stainless steel sheets approximately 1 mm thick, is placed underneath and bolted to a pressure-bearing cold plate 3.4 made of oxygen-free copper. The cold-end temperature regulator 3.3 is threaded onto the pressure-bearing cold plate 3.4.

[0105] A solid epoxy resin support rod 3.5, a solid polytetrafluoroethylene support rod 3.6, and a stainless steel support rod 3.7 are connected to the bottom of the pressure cold plate 3.4 in sequence through threads. The upper end of the solid polytetrafluoroethylene support rod 3.6 is in direct contact with the multi-layer insulation first-level radiation shield 2.4, and the stainless steel support rod 3.7 is directly fixed to the bottom surface of the inner wall of the vacuum chamber 2.3 through threads.

[0106] The linear servo press 4.1 drives the displacement transmission screw 4.2 to move vertically back and forth to achieve displacement control, and the pressure and displacement are accurately measured using the pressure sensor 4.3 fixed at the lower end of the displacement transmission screw 4.2 and the contact displacement sensor 4.4 fixed at the upper end of the displacement transmission screw 4.2.

[0107] The displacement transmission screw 4.2 is threadedly connected to the sealed end of the bellows on the outside of the vacuum chamber 2.3. The hollow stainless steel tube pull rod 4.5 is fixed on the inside of the sealed end of the bellows 2.2. The linear servo press 4.1 drives the displacement transmission screw 4.2 to move vertically up and down. The displacement transmission screw 4.2 is connected to the bellows 2.2 to transmit displacement into the vacuum chamber 2.3.

[0108] A hollow stainless steel rod 4.5 with an outer diameter of 30 mm and a wall thickness of 5 mm is used to ensure mechanical strength while reducing heat conduction leakage. Displacement is applied to the contact interface of the cylindrical sample via a solid polytetrafluoroethylene rod 4.6, a solid epoxy resin rod 4.7, and a hot-end heater 5.1.

[0109] At the same time, a limit plate 4.8 with a through hole of the same diameter as the solid polytetrafluoroethylene pull rod 4.6 is arranged around the solid polytetrafluoroethylene pull rod 4.6, and six stainless steel limit screws 4.9 with a diameter of 4 mm fix the limit plate 4.8.

[0110] The hot end heat flux meter 5.4 is fastened to the hot end heater 5.1 by screw threads, the cold end heat flux meter 5.5 is in contact with and fixed to the oxygen-free copper fixture 3.1, and the sample to be measured is clamped in the area between the hot end heat flux meter 5.4 and the cold end heat flux meter 5.5.

[0111] The high-temperature hot end heater 5.1 and the low-temperature oxygen-free copper fixture 3.1 generate axial heat flow and temperature gradient on the sample.

[0112] The two sets of heat flow meters are provided with temperature measuring holes with a diameter of 2 mm and a hole depth equal to the radius of the bottom surface of the heat flow meter. The temperature measuring probe 5.2 made of high-purity oxygen-free copper is inserted into the temperature measuring hole and fixed with varnish or the like. The temperature sensor 5.3 is screwed to the end of the temperature measuring probe 5.2 to complete the temperature measurement.

[0113] like Figure 4 As shown, the heat flux meter includes a hot-end heat flux meter 5.4 and a cold-end heat flux meter 5.5 arranged in parallel. The hot-end heat flux meter 5.4 and the cold-end heat flux meter 5.5 have the same structure. The cold-end and hot-end heat flux meters respectively clamp the two ends of the sample 3.10 through their respective clamps 5.62, and use fasteners to penetrate the fixing holes 5.61 of the clamps 5.62 to achieve clamping of the two ends of the sample 3.10.

[0114] In this embodiment, the hot-end heat flux meter 5.4 and the cold-end heat flux meter 5.5 comprise a heat flux meter body, one end of which is provided with a clamp for clamping the sample, and the other end is provided with a connector for docking with a corresponding heat flux meter fixture or hot-end heater. The heat flux meter body can be a rectangular parallelepiped or cylindrical copper material. When calculating the in-plane thermal conductivity, the cross-section of the heat flux meter body is used as the calculation parameter. To facilitate installation and removal and to facilitate the acquisition of calculation parameters, this embodiment preferably uses a rectangular parallelepiped heat flux meter body. A pair of clamps 5.62 are machined at one end of the body, with fixing holes 5.61 on either side for clamping.

[0115] Since the cross-sectional size of the thin film sample is small and the cross-sectional area is much smaller than the cross-sectional area of the heat flow meter (>2 orders of magnitude), the thermal resistance at the sample is large and heat transfer is difficult. As a result, most of the energy flow at the hot-end heat flow meter is dissipated into the environment in the form of natural convection and radiation. The heat flow at different cross-sections is not linearly correlated, and the axial energy flow at the sample is not the average of the axial energy flows of the cold and hot-end heat flow meters. Therefore, the traditional measurement method is not applicable.

[0116] This embodiment utilizes the vacuum cavity and radiation shield in the vacuum insulation module to cut off the natural convection and radiation heat dissipation paths, control the energy flow to be transmitted axially, and make the heat flow at different cross sections equal everywhere (ideal state). The energy flow at the sample cross section is the average of the cross-sectional energy of the cold and hot end heat flow meters.

[0117] In other words, by taking measures such as vacuuming and setting up a radiation shield, the heat loss channels such as natural convection and thermal radiation on the surface of the heat flow meter and the sample can be minimized, and the adverse effect of uneven axial heat flux distribution of the heat flow meter on the measurement results can be reduced.

[0118] Since the measuring device in this embodiment measures the in-plane thermal conductivity in the liquid helium temperature range, it also has the following advantages:

[0119] 1. Temperature stability design: To reduce the impact of temperature fluctuations on temperature measurement accuracy, a thermal damping sheet 3.2 is added between the pressure-bearing cold plate 3.4 and the cold-end heat flux meter 5.5. Thermal damping sheet 3.2 is composed of multiple stacked stainless steel / PTFE sheets. Low-temperature thermal interface material (indium sheet, Apiezon N grease) is added between the sheets to reduce contact thermal resistance, thereby reducing the temperature fluctuation amplitude from >100mK (the temperature amplitude of the refrigerator cold head) to <10mK.

[0120] 2. Low mechanical vibration design: To prevent the refrigerator's own mechanical vibration from being transmitted to the measurement area, the refrigerator 1.3 in the low-temperature refrigeration module 1 is placed horizontally and supported by an independent bracket. A bellows 2.2 is used to connect the refrigerator 1.3 in the low-temperature refrigeration module 1 to the vacuum chamber 2.2. A copper braided thermal bridge 2.6 is used to connect the refrigerator 1.3 to the multi-layer insulation first-level radiation shield 2.4 and the pressure cold plate 3.4. This prevents the mechanical vibration generated by the refrigerator from being transmitted to the sample. The displacement control module 2 is placed vertically and supported by the same independent bracket as the vacuum chamber.

[0121] In this embodiment, the refrigerator 1.3 in the low-temperature refrigeration module 1 is horizontally placed and supported by an independent bracket. In addition, the cold head of the refrigerator can also be placed vertically upward or downward, and the specific structural type is not limited.

[0122] 3. Low heat leakage design of transmission and support structure: Since the transmission and support rods connect the 4K sample stage and the 300K vacuum chamber, although conventional 304 stainless steel parts can provide sufficient mechanical strength, their thermal conductivity is relatively high (14-15.4W m - 1 K -1 ) Using conventional stainless steel components directly would result in significant heat leakage, directly affecting the lower temperature limit of the device. Therefore, to minimize heat leakage from the 300K vacuum chamber to the 4K sample stage while ensuring the stability of the transmission and support structures, this embodiment utilizes a stepped transmission, pull rods, and support rods that carry the sample and the heat flux meter, based on the operating temperature ranges and temperature gradients of the transmission and support rods.

[0123] The first displacement transmission component, from top to bottom, is the 4.5 hollow tie rod. This component operates in a temperature range of 50-300K. Made of mechanically strong 304 stainless steel, it has an outer diameter of 30mm and an inner diameter of 20mm. The hollow design of the tie rod ensures uniform transmission while also reducing its cross-sectional area, thereby increasing thermal resistance and minimizing heat leakage. Transmission rod 4.6 operates in a temperature range of approximately 4-50K. Made of polytetrafluoroethylene (PTFE), which has low thermal conductivity, its diameter is 50mm. Transmission rod 4.7 operates in a temperature range of approximately 4-20K. Made of epoxy resin, which has low thermal conductivity and is more resistant to low temperatures, its diameter is 30mm. The transmission rods are connected by threads. The displacement provided by the servo press is transmitted step by step to the sample interface via the step-by-step transmission tie rods to adjust the thickness outside the interface.

[0124] There is a support rod under the sample stage. The working temperature range of the support rod 3.5 is 4-50K, and its material has a thermal conductivity of 0.07-0.25W m -1 K -1 The low temperature resistant epoxy resin has a diameter of 30mm; the working temperature range of the support rod 3.6 is 50-300K, and its material is low thermal conductivity (0.25W m -1 K -1 ) of polytetrafluoroethylene, with a diameter of 50 mm; the operating temperature range of the support rod 3.7 is 250-300 K, and its material has a thermal conductivity of 14-15.4 W m -1 K -1 The above method can effectively reduce the heat leakage through the support rod and avoid deformation caused by ultra-low temperature and excessive temperature gradient.

[0125] 4. Heat flux meter installation and temperature measurement design: The pressure-bearing cold plate 3.4, thermal damping plate 3.2, and fixture 3.1 are all bolted together to transfer cooling energy. Fixture 3.1 contacts the bottom of the cold-end heat flux meter 5.5, serving as the cold end. The hot-end heater 5.1 is a solid oxygen-free copper cylinder wrapped with a heating wire, threadedly connected to the top of the hot-end heat flux meter 5.4. A temperature controller, connected to a temperature sensor fixed to the heating wire, controls the temperature of the sample's hot end, creating an axial heat flux and temperature gradient within the sample.

[0126] The oxygen-free copper fixture 3.1 is provided with a groove in the center portion, the diameter of the groove is larger than the diameter of the cold end heat flux meter 5.5, and four mutually perpendicular fine-tuning bolts are provided around the groove to adjust the coaxiality of the hot end heat flux meter 5.4 and the cold end heat flux meter 5.5.

[0127] To improve low-temperature refrigeration and increase the accuracy of temperature measurement, a plurality of integral rod-shaped, flat-ended temperature measuring probes 5.2 are made of oxygen-free copper with high thermal conductivity and are inserted equidistantly into the sample axis. A temperature sensor 5.3 crimped to the end of the temperature measuring probe 5.2 is used to measure the axial temperature gradient of a sample of known thermal conductivity. The axial heat flux of the sample is calculated based on this temperature gradient.

[0128] Example 2:

[0129] This embodiment takes the device for measuring the in-plane thermal conductivity of a sample of a thin film material at room temperature as an example to explain this solution. The structure of the formed measuring device is as follows: Figure 7 As shown, compared with Example 1, this embodiment no longer uses a liquid helium temperature zone refrigerator as a cold source, and water cooling is used instead. Since the temperature difference with the ambient temperature is not large, the corresponding insulation measures can use a vacuum cavity and a first-level radiation shield 2.7. In addition, the copper braided thermal bridge and various support rods used for insulation and reducing temperature fluctuations and mechanical vibrations in the device can be simplified.

[0130] like Figure 7 As shown, the chiller 1.1 is connected to the pressure sample platform 3.9 through the water cooling pipe 1.5 to form a cooling water circuit. The upper surface of the pressure sample platform 3.9 is connected to the heat flow meter fixture 3.8 through the water cooling plate 1.6. The heat flow meter fixture 3.8 fixes the cold end heat flow meter, and the cold end heat flow meter is provided with a cold end temperature regulator 1.7.

[0131] Since it is a normal temperature zone, the solid epoxy resin support rod 3.5, the solid polytetrafluoroethylene support rod 3.6 and the stainless steel support rod 3.7 are cancelled in the pressure sample stage module, and the water cooling plate 1.6 is directly connected to the pressure sample stage 3.9. The water cooling plate 1.6 in this embodiment has the same function as the pressure cooling plate 3.4 in Example 1. Since it is a different temperature zone, there are differences in specific specifications and models. In actual application, you can select according to the difference in temperature zones.

[0132] In this embodiment, the heat flux meter fixture 3.8 has the same function as the oxygen-free copper fixture 3.1 in the first embodiment, and both are used to fix the cold-end heat flux meter.

[0133] In this embodiment, the cold end temperature regulator 1.7 and the cold end temperature regulator 3.3 in the first embodiment are components with the same function but different specifications and models.

[0134] In this embodiment, the structure of the heat flux meter 5.6 is the same as that of the first embodiment, including a hot-end heat flux meter 5.4 and a cold-end heat flux meter 5.5 arranged in parallel. The hot-end heat flux meter 5.4 and the cold-end heat flux meter 5.5 have the same structure. The cold-end and hot-end heat flux meters respectively clamp the two ends of the sample 3.10 through their respective clamps 5.62, and use fasteners to penetrate the fixing holes 5.61 of the clamps 5.62 to achieve clamping of the two ends of the sample 3.10.

[0135] In this embodiment, the temperature sensor on the heat flow meter 5.6 is in communication connection with the temperature controller 5.7 and the controller 5.8 in sequence.

[0136] The measuring device in this embodiment takes the normal temperature zone as an example, and the specific structure and operation method of the heat flow meter therein are the same as those in Example 1. Since it is a normal temperature zone, the temperature is not much different from the ambient temperature. Therefore, the relevant structure of the insulation measures is simplified on the basis of Example 1.

[0137] Example 3:

[0138] A high-precision method for measuring the in-plane thermal conductivity of a material comprises the following steps:

[0139] Initialize the distance between the cold and hot end heat flow meters;

[0140] The hot-end heat flux meter rises to a set distance, and the sample to be measured with a length of L1 is clamped between the cold and hot-end heat flux meters. The height of the hot-end heat flux meter is adjusted until the sample is fully extended. The vacuum insulation module is reinstalled, and the low-temperature refrigeration module is started to obtain the temperature environment required for measurement.

[0141] Adjust the cold and hot end temperature regulators to the set temperature. Under the action of the axial high and low temperature difference, heat is conducted axially in the sample, forming a stable temperature field and axial heat flow. Obtain the temperature of the set measuring points in the cold and hot end heat flow meters.

[0142] At the current ambient temperature and the cold and hot end temperatures, clamp the same sample with a length of L2 between the cold and hot end heat flow meters, and measure the temperature of each measuring point when the sample length is L2;

[0143] According to Fourier's law of heat conduction, the in-plane thermal conductivity of the sample was calculated.

[0144] like Figure 5-Figure 6 As shown, the measuring principle of the measuring device is as follows:

[0145] 1. Zero adjustment: Use the servo press to adjust the position of the hot end heat flow meter so that the known thermal conductivity is λ 13 and λ 46 The surfaces of the cold and hot end heat flux meters are in contact with each other and the pressure is zero. At this time, the distance outside the surfaces of the cold and hot end heat flux meters is considered to be zero, that is, the zero point of the distance between the cold and hot end heat flux meters.

[0146] 2. Clamp the sample L1: Use the servo press to raise the hot end heat flow meter, clamp the sample to be tested with a length of L1 between the cold and hot end heat flow meters, and then adjust the height of the hot end heat flow meter until the sample is fully expanded.

[0147] 3. Adjust the temperature of the measurement area: Install the vacuum insulation module and operate the low-temperature refrigeration module to obtain the set low-temperature environment. In this embodiment, the temperature of the liquid helium temperature zone is obtained.

[0148] 4. Heat flow generation: Adjust the cold and hot end temperature regulators to the specified temperature and wait for the temperature sensor to show stable readings. Under the action of axial high and low temperature difference, heat is conducted along the axial direction in the sample, forming a stable temperature field and axial heat flow q L1 .

[0149] 5. Temperature measurement: The cold and hot end heat flux meters are made of oxygen-free copper with known thermal conductivity. Since high-precision temperature measuring probes are pre-inserted into the temperature measuring holes in the cold and hot end heat flux meters, three temperature measuring points are arranged at an equal distance d on the cold and hot end heat flux meters. The temperature readings are read and recorded as T1 to T6 from top to bottom.

[0150] 6. Measure the temperature distribution when clamping samples of different lengths: Clamp a sample of length L2 between the upper and lower heat flux meters using a clamp. The temperatures of the cold and hot ends are consistent with those when measuring sample L1. Repeat step 5. The temperatures of each measuring point when the sample length is L2 are measured as T1' to T6'.

[0151] 7. Sample thermal conductivity calculation: Calculate the sample's in-plane thermal conductivity based on the obtained temperature, sample length and other data. Specifically:

[0152] According to Fourier's law of heat conduction, the heat flow Q at the cross section of the sample is L1 Calculate according to the following formula:

[0153]

[0154]

[0155] Among them, Q 13 and Q 46 are the average heat flux of the hot end heat flux meter and the cold end heat flux meter, λ 13 and λ 46 are the thermal conductivities of the hot-end heat flux meter and the cold-end heat flux meter (oxygen-free copper material, obtained by looking up the table), A 13 and A 46 are the cross-sectional areas of the hot-end heat flux meter and the cold-end heat flux meter, respectively, and d is the spacing between the temperature measuring points.

[0156] like Figure 6 As shown, in this embodiment, the thermal resistance of the portion between the horizontal plane where the heat flux meter measuring point T3 is located and the plane where the end of the hot end heat flux meter is located is defined as R up The thermal resistance of the portion between the planes where the cold and hot end heat flux meters are located is R mid The thermal resistance between the plane where the cold end heat flux meter is located and the horizontal plane where the heat flux meter measuring point T4 is located is R down, the three thermal resistances are connected in series to form the thermal resistance ∑R, as shown in formula (4).

[0157] R up +R mid +R down =∑R (4)

[0158] Thermal resistance ∑R can be calculated according to formula (5):

[0159]

[0160] Correspondingly, when the sample length is L2, the material, cross-sectional area, and length of the clamping area of the sample and the heat flux meter remain unchanged. The thermal resistance of the portion between the horizontal plane where the heat flux meter measuring point T3 is located and the plane where the hot-end heat flux meter end is located, and the thermal resistance of the portion between the plane where the cold-end heat flux meter end is located and the horizontal plane where the heat flux meter measuring point T4 is located, are both the same as when the sample length is L1. The change in thermal resistance ∑R' At this time, the thermal resistance ∑R' satisfies the following relationship:

[0161] R up +R' mid +R down =∑R' (6)

[0162]

[0163] Subtracting equation (5) from equation (6) yields the thermal resistance ΔR of the sample with a length of ΔL = L1-L2. sample :

[0164] ΔR sample R mid -R' mid ∑R ∑R' (8)

[0165] Furthermore, the in-plane thermal conductivity of the film sample was calculated by the following formula, where A sample is the cross-sectional area of the sample:

[0166]

[0167] The in-plane thermal conductivity of a commercial copper sheet was tested at room temperature (approximately 25°C). The sample was 15mm wide and 0.5mm thick, with clamping lengths set to 28mm and 36mm, respectively. The temperature difference measurement showed that an 8mm change in length corresponds to a change in thermal resistance of 3.47kW. -1 , the thermal conductivity of the sample is calculated according to formula (9):

[0168]

[0169] This value is consistent with the measurement results of high-precision femtosecond laser time-domain thermoreflectance (TDTR) method (335W m-1 K -1 ) error is -8.18%, which verifies the feasibility of the device and method of the present invention.

[0170] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A high-precision material in-plane thermal conductivity measurement device, characterized in that: include: The low-temperature refrigeration module is used to generate a working medium of a set temperature in the vacuum insulation module and transfer it to the sample space and the cold end of the heat flow meter by heat conduction; The heat flux generation and control module includes a hot end heater, a cold end heater, and a hot end heat flux meter and a cold end heat flux meter arranged in parallel. The hot and cold end heaters are used to control the hot and cold end temperatures respectively. The cold and hot end heat flux meters are used to clamp the two ends of the sample respectively and conduct heat in the sample plane direction; A vacuum insulation module, comprising at least one level of radiation shielding and a vacuum cavity arranged in the space outside the sample and the heat flow meter; The pressure sample stage module is used to carry and fix the heat flow meter and the sample, which is a thin film material; The spacing measurement and control module uses a servo linear motor, a displacement transmission screw and a displacement sensor to control and measure the spacing between the cold and hot end heat flow meters to clamp samples of different sizes; The temperature measurement module is used to obtain the temperature gradient of the heat flow meter, including a thermocouple inserted into the heat flow meter.

2. A high-precision material in-plane thermal conductivity measuring device according to claim 1, characterized in that: The hot-end heat flux meter and the cold-end heat flux meter both include a heat flux meter body. A chuck is provided at one end of the heat flux meter body for clamping a sample. The heat flux meter body is a rectangular parallelepiped or a cylinder.

3. A high-precision material in-plane thermal conductivity measuring device according to claim 1, characterized in that: The servo linear motor drives the displacement transmission screw to move in the vertical direction. The displacement transmission screw is connected to the bellows to transmit the displacement into the vacuum chamber. The displacement is transmitted to the end of the heat flow meter holding the sample through the displacement transmission screw.

4. A method for measuring in-plane thermal conductivity based on the high-precision material in-plane thermal conductivity measuring device according to any one of claims 1 to 3, characterized in that: The following steps are involved: Initialize the distance between the cold and hot end heat flow meters; The hot-end heat flux meter rises to a set distance, and the sample to be tested with an effective length of L1 is clamped between the cold and hot-end heat flux meters. The height of the hot-end heat flux meter is adjusted until the sample is fully extended; the vacuum insulation module is reinstalled; Adjust the cold and hot end temperature regulators to the set temperature. Under the action of the axial high and low temperature difference, heat is conducted axially in the sample, forming a stable temperature field and axial heat flow. Obtain the temperature of the set measuring points in the cold and hot end heat flow meters. Under the current ambient temperature and the cold and hot end temperatures, and the same clamping area length, clamp the same sample with a length of L2 between the cold and hot end heat flow meters, and measure the temperature of each measuring point when the sample length is L2; According to Fourier's law of heat conduction, the in-plane thermal conductivity of the sample was calculated.

5. A high-precision material in-plane thermal conductivity measurement method according to claim 4, characterized in that: According to Fourier's law of heat conduction, the in-plane thermal conductivity of the sample is calculated, including the following steps: According to the cross-sectional area and thermal conductivity of the heat flow meter at the cold and hot ends, as well as the temperature data of each measuring point, the heat flow at the cross section of the sample with a length of L1 is obtained; According to the temperature difference between the two temperature measurement points adjacent to the sample L1 and the heat flow at the cross section of the sample L1, the thermal resistance ∑R between the end faces of the cold and hot end heat flow meters when the sample length is L1 is obtained; When the sample length is L2, the heat flux at the cross section of the sample with a length of L2 is obtained based on the cross-sectional area and thermal conductivity of the heat flow meters at the cold and hot ends, as well as the temperature data at each temperature measurement point. The thermal resistance ∑R' between the end faces of the heat flow meters at the cold and hot ends when the sample length changes to L2 is obtained based on the temperature difference at two temperature measurement points adjacent to the sample L2, and the thermal resistance difference of samples of different lengths is further obtained. The in-plane thermal conductivity of the sample is obtained based on the cross-sectional area and length change of the sample and the change in thermal resistance caused by the change in sample length.

6. A high-precision material in-plane thermal conductivity measurement method according to claim 4, characterized in that: Based on the cross-sectional area and thermal conductivity of the cold and hot end heat flow meters, as well as the temperature data of each measuring point, the heat flow at the cross section of the sample with a length of L1 is obtained; as shown in the following formula: Among them, Q 13 and Q 46 are the average heat flux of the hot end heat flux meter and the cold end heat flux meter, λ2 and λ5 are the thermal conductivities of the hot end heat flux meter and the cold end heat flux meter at temperatures T2 and T5, respectively. 13 and A 46 are the cross-sectional areas of the hot-end heat flux meter and the cold-end heat flux meter, respectively, and d is the spacing between the temperature measuring points.

7. A high-precision material in-plane thermal conductivity measurement method according to claim 4, characterized in that: Based on the temperature difference between the two temperature measurement points adjacent to sample L1 and the heat flow at the cross section of sample L1, the thermal resistance ∑R between the end faces of the cold and hot end heat flow meters when the sample length is L1 is obtained; as shown in the following formula: Among them, Q L1 is the heat flux at the cross section of the sample with a length of L1, T3 and T4 are the temperature data of the heat flux meter end faces near the cold and hot ends when measuring sample L1, respectively.

8. A high-precision material in-plane thermal conductivity measurement method according to claim 4, characterized in that: When the sample length is L2, based on the temperature data at the two temperature measurement points adjacent to the sample L2, the thermal resistance ∑R' between the end faces of the cold and hot end heat flow meters when the sample length changes to L2 is obtained; as shown in the following formula: Among them, Q L2 is the heat flux at the cross section of the sample with a length of L2, T3' and T4' are the temperature data of the end faces of the heat flux meter close to the cold and hot ends when measuring sample L2, respectively.

9. A high-precision material in-plane thermal conductivity measurement method according to claim 4, characterized in that: The difference between ∑R and ∑R' is the thermal resistance change due to the change in sample length ΔL = L1-L2, which can eliminate the influence of the contact thermal resistance at the contact surface between the heat flow meter and the sample on the sample thermal resistance measurement, thereby obtaining the thermal resistance ΔR of the sample with a length of ΔL. sample , as shown below: ΔR sample =∑R-∑R'。 10. A high-precision material in-plane thermal conductivity measurement method according to claim 4, characterized in that: According to the change in sample length, the thermal resistance of the sample and the cross-sectional area of the sample, the in-plane thermal conductivity of the sample is obtained as shown in the following formula: ΔL=L1-L2; Where, ΔR sample is the thermal resistance of the sample, A sample is the cross-sectional area of the sample.

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