Device for measuring thermal conductivity of nanofiber and method thereof

Abstract

The present disclosure provides a kind of nanofiber thermal conductivity measuring device, including middle hollow base, first and second side wall are formed around the hollow place and oppositely arranged third and fourth side wall;Two conductive electrodes are formed on the first and second side wall respectively;And support layer, adhesive layer and suspension electrode are sequentially stacked from bottom to top, the suspension electrode is supported on the first and second side wall by support layer, current is applied to the suspension electrode by two conductive electrodes to make it as hot end, the thermal resistance of suspension electrode is greater than the thermal resistance of the nanofiber to be measured, the two ends of nanofiber are supported on the suspension electrode and the fourth side wall respectively, the surface of nanofiber carries uniformly distributed temperature measuring particles, the relative Raman signal of temperature measuring particle is not less than the intensity of its relative air peak and temperature measuring particle does not have fluorescence signal.The present disclosure can accurately and effectively measure the thermal conductivity of nanofiber with weak Raman signal or strong metal fluorescence signal by means of temperature measuring particle.

Description

Technical Field

[0001] This disclosure belongs to the field of nanomaterial thermal conductivity measurement technology, and specifically relates to a device and method for measuring the thermal conductivity of nanofibers. Background Technology

[0002] Measuring the thermal conductivity of nanofibers is one of the cutting-edge research topics in low-dimensional materials. Existing methods for measuring the thermal conductivity of nanofibers fall into two categories: contact measurement methods and non-contact measurement methods.

[0003] Contact methods typically involve applying an electric current to the sample or bringing the material into contact with an energized electrode, causing a temperature rise and distribution on the sample material, and then calculating the thermal conductivity of the nanofibers based on this temperature change. However, this method cannot eliminate the influence of the contact thermal resistance between the sample and the measuring electrode on the thermal conductivity measurement.

[0004] Non-contact methods can eliminate the influence of contact resistance, resulting in higher measurement accuracy. Non-contact methods include transient thermal reflectance (TDR) and Raman spectroscopy. TDR obtains the sample's temperature information by measuring changes in the reflectance of the sample surface, thereby extracting the sample's thermal properties. However, this method has stringent requirements for sample surface roughness, typically requiring additional coatings to meet these requirements, which introduces measurement errors. Raman spectroscopy determines the sample temperature by measuring the position shift of the Raman peaks, thereby measuring the sample's thermal conductivity parameters. However, this method is only suitable for samples with strong Raman signals and weak fluorescence signals. For nanofibers with weak Raman signals (e.g., polymer nanofibers) or strong fluorescence signals (e.g., metal-containing fibers), the measurement accuracy is severely affected.

[0005] Therefore, it is necessary to develop a measurement device and method for the thermal conductivity of nanofibers with weak Raman signals and strong fluorescence signals, so as to further broaden the applicability of the Raman signal method. Summary of the Invention

[0006] This disclosure aims to address at least one of the technical problems existing in the prior art.

[0007] Therefore, this disclosure provides a device and method for measuring the thermal conductivity of nanofibers, which can accurately and effectively measure the thermal conductivity of nanofibers with weak Raman signals or strong metallic fluorescence signals. Moreover, it is non-contact, which broadens the universality of Raman spectroscopy in the measurement of the thermal properties of nanomaterials.

[0008] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0009] The first aspect of this disclosure provides a device for measuring the thermal conductivity of nanofibers, comprising:

[0010] The base has a hollowed-out center, and a first sidewall and a second sidewall, as well as a third sidewall and a fourth sidewall, are formed around the hollowed-out area.

[0011] A first conductive electrode and a second conductive electrode are respectively formed on the first sidewall and the second sidewall; and

[0012] The structure consists of a support layer, an adhesive layer, and a suspension electrode stacked sequentially from bottom to top. The suspension electrode is supported by the support layer on the first and second sidewalls. Both ends of the suspension electrode are connected to the first and second conductive electrodes, respectively. Current is applied to the suspension electrode through the first and second conductive electrodes, making the suspension electrode a hot end. Both ends of the nanofiber are supported on the suspension electrode and the fourth sidewall, respectively. The surface of the nanofiber is loaded with uniformly distributed temperature-sensing particles. The relative Raman signal of the temperature-sensing particles is not less than the intensity of the temperature-sensing particles relative to the air peak, and the temperature-sensing particles do not have metallic fluorescence signals.

[0013] In some embodiments, the distribution density of the temperature-sensing particles on the nanofibers ranges from 0.05 to 1 particle / μm.

[0014] In some embodiments, the temperature-sensing particles are attached to the surface of the nanofibers by electrostatic spraying, ultrasonic spraying, or probe movement.

[0015] In some embodiments, the thermal resistance of the suspension electrode should be greater than or equal to 10% of the thermal resistance of the nanofiber.

[0016] In some embodiments, the length of the suspension electrode does not exceed 250 μm and the cross-sectional area through which the current flows does not exceed 2.5 μm. 2 .

[0017] In some embodiments, the distance between the suspension electrode and the fourth sidewall is no more than 25 μm, and the distance from the bottom of the support layer to the bottom of the substrate should be greater than or equal to 200 μm.

[0018] In some embodiments, the coefficient of thermal expansion of the material used to make the suspension electrode does not exceed 1.8 × 10⁻⁶. -5 ℃ -1 The coefficient of thermal expansion of the material used to make the support layer does not exceed 1.8 × 10⁻⁶. -5 ℃ -1 .

[0019] In some embodiments, the adhesive layer is made of metal to ensure the bonding between the suspension electrode and the support layer.

[0020] In some embodiments, the substrate is made of an insulating material and the temperature of the substrate is kept consistent with the ambient temperature.

[0021] The measurement method provided in the second aspect of this disclosure according to any embodiment of the measuring apparatus of the first aspect of this disclosure includes:

[0022] The relationship between the Raman shift of the calibrated temperature measuring particles and temperature;

[0023] The temperature coefficient of resistance of the suspension electrode is calibrated to determine the relationship between the resistance of the suspension electrode and temperature.

[0024] The thermal conductivity of the suspension electrode is determined based on the relationship between its resistance and temperature, using the following formula:

[0025]

[0026] Where λ is the thermal conductivity of the suspension electrode, q v Where is the heating power of the suspension electrode, and L is the length of the suspension electrode. t0 is the average temperature of the suspension electrodes, and t0 is the ambient temperature. This is the average temperature rise of the suspension electrodes;

[0027] The two ends of the nanofiber carrying the temperature measuring particles are supported on the suspension electrode and the fourth sidewall, respectively. The above operation of calibrating the thermal conductivity of the suspension electrode is repeated to obtain the change law of the average temperature rise of the suspension electrode with the heating power before and after the nanofiber is placed. The difference between the two can be used to obtain the heat flow through the nanofiber under any average temperature rise of the suspension electrode.

[0028] The Raman shift of thermometric particles at different positions on the nanofiber is measured, and the temperature of the thermometric particles at different positions on the nanofiber is estimated based on the relationship between the Raman shift of the calibrated thermometric particles and temperature, thereby obtaining the temperature gradient of the nanofiber. Finally, the thermal conductivity of the nanofiber is calculated by using Fourier's law of thermal conductivity based on the heat flux and temperature gradient of the nanofiber.

[0029] The present disclosure provides a device and method for measuring the thermal conductivity of nanofibers, which have the following characteristics and beneficial effects:

[0030] This disclosure provides a device and method for measuring the thermal conductivity of nanofibers. The device and method enable non-contact measurement of the thermal conductivity of nanofibers with weak Raman signals or strong metallic fluorescence signals, broadening the applicability of Raman spectroscopy in measuring the thermal properties of nanomaterials. Furthermore, the suspension electrode, serving as the hot end, features a long electrode length and a small current flow area, resulting in a thermal resistance far greater than that of conventional single-fiber measurement devices. This solves the problem of low signal-to-noise ratio in measuring the thermal conductivity of low-thermal-conductivity nanofibers. Simultaneously, the support layer under the suspension electrode effectively increases its mechanical strength, ensuring test repeatability and device durability. Therefore, this disclosure can also accurately and effectively measure the thermal conductivity of low-thermal-conductivity nanofibers. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the nanofiber thermal conductivity measuring device provided in the embodiments of this disclosure;

[0032] Figure 2 This is a graph showing the relationship between the Raman displacement of the temperature-measuring particles carried on the surface of the nanofiber and their temperature during the measurement of thermal conductivity using the above-described measuring device, as provided in this embodiment of the present disclosure.

[0033] Figure 3 In the embodiments of this disclosure, (a) and (b) are respectively a temperature control history diagram for calibrating the temperature coefficient of suspension electrode resistance and a diagram showing the relationship between suspension electrode resistance and temperature during the measurement of thermal conductivity using the above-described measuring device.

[0034] Figure 4 In the figure, (a), (b), (c), and (d) are respectively the voltage control process at both ends of the suspension electrode, the relationship between the resistance of the suspension electrode and the heating power of the suspension electrode, the relationship between the average temperature rise of the suspension electrode and the heating power of the suspension electrode, and the value of the thermal conductivity of the suspension electrode during the calibration process.

[0035] Figure 5 This is a graph showing the relationship between the average temperature rise of the suspension before and after the nanofibers are placed and the heating power of the suspension electrodes.

[0036] Figure 6 This is a graph showing the temperature distribution of the nanofiber at different distances from the cold end.

[0037] In the picture:

[0038] 1. Base; 11. First sidewall; 12. Second sidewall; 13. Third sidewall; 14. Fourth sidewall;

[0039] 21. First conductive electrode; 22. Second conductive electrode;

[0040] 3. Support layer;

[0041] 4. Adhesive layer;

[0042] 5. Suspension electrodes;

[0043] 6. Temperature-measuring particles;

[0044] 7. Nanofibers. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0046] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0047] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the foundation or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. 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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0048] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0049] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] See Figure 1 This disclosure provides a device for measuring the thermal conductivity of nanofibers. The nanofibers to be measured have the characteristics of weak Raman signals or strong metallic fluorescence signals. The measuring device includes:

[0051] The base 1 has a hollowed-out center, and a first sidewall 11 and a second sidewall 12, as well as a third sidewall 13 and a fourth sidewall 14, are formed around the hollowed-out area.

[0052] The first conductive electrode 21 and the second conductive electrode 22 are respectively formed on the first sidewall 11 and the second sidewall 12 of the substrate;

[0053] The support layer 3, adhesive layer 4, and suspension electrode 5 are stacked sequentially from bottom to top. The suspension electrode 5 is supported by the support layer 3 on the first sidewall 11 and the second sidewall 12 of the substrate 1. An adhesive layer 4 is processed between the suspension electrode 5 and the support layer 3 to ensure good bonding between the two. The two ends of the suspension electrode 5 are connected to the first conductive electrode 21 and the second conductive electrode 22, respectively. Current is applied to the suspension electrode 5 through the first conductive electrode 21 and the second conductive electrode 22 to make the suspension electrode 5 a hot end. The two ends of the nanofiber 7 are supported on the suspension electrode 1 and the fourth sidewall 14 of the substrate 1, respectively. The surface of the nanofiber 7 is loaded with uniformly distributed temperature-sensing particles 6. The relative Raman signal of the temperature-sensing particles 6 is not less than the intensity of the temperature-sensing particles 6 relative to the air peak (0.2 in this embodiment) and the temperature-sensing particles 6 do not have a metallic fluorescence signal.

[0054] In some embodiments, the substrate 1 serves as the main support component and cold end of the measuring device, maintaining a consistent ambient temperature. The central hollow design ensures that the suspension electrode 5 only contacts the first conductive electrode 21 and the second conductive electrode 22 at its two ends, respectively. Other locations can be considered as adiabatic boundary conditions under vacuum, thus ensuring that the measurement results do not change due to the substrate being placed on different media, increasing the robustness of the measuring device. The substrate 1 is made of an insulating material; preferably, it can be formed by photolithography of silicon, silicon nitride, silicon oxide, gallium arsenide, germanium, or silicon carbide. In this embodiment, a silicon substrate with a central hollow design is used.

[0055] In some embodiments, the first conductive electrode 21 and the second conductive electrode 22 are made of conductive materials, and their thermal resistance should be much smaller than that of the nanofiber 6 to be measured. Therefore, the two conductive electrodes also serve as cold ends during the measurement process, consistent with the boundary conditions of the subsequent calculation model. In this embodiment, the two conductive electrodes are fabricated by magnetron sputtering and symmetrically disposed on the first sidewall 11 and the second sidewall 12 of the substrate 1 by ion beam etching.

[0056] In some embodiments, the suspension electrode 5 serves as a hot end during measurement and is made of a conductive material.

[0057] In some embodiments, temperature-sensing particles 6 can be uniformly loaded onto the surface of nanofibers 7 using electrostatic spraying, ultrasonic spraying, probe-moving methods, or other methods capable of uniformly attaching particles to the fiber surface. The temperature-sensing particles 6 possess strong Raman signals but lack metallic fluorescence properties. Temperature signals at different locations on the nanofibers 7 can be obtained through the temperature-sensing particles 6 without generating fluorescence signals during the measurement process. Therefore, combined with Raman spectroscopy, the thermal conductivity of nanofibers with weak Raman signals or strong metallic fluorescence signals can be accurately measured. Furthermore, the distribution density of temperature-sensing particles 6 on the nanofibers 7 should not be too high, otherwise the influence of heat transfer within the temperature-sensing particles 6 on the thermal measurement will be non-negligible; conversely, the distribution density of temperature-sensing particles 6 on the nanofibers 7 should not be too low, otherwise there will be too few temperature measurement points and a poor signal-to-noise ratio. Preferably, the distribution density of temperature-sensing particles 6 on the nanofibers 7 ranges from 0.05 to 1 particle / μm. Furthermore, in order to achieve stable adhesion of the temperature-sensing particles 6 to the nanofibers 7, and to minimize the influence of the temperature-sensing particles 6 on the measurement results of the thermal conductivity of the nanofibers, the diameter of the temperature-sensing particles 6 should not exceed 150% of the diameter of the nanofibers 7. Regarding the measurement device provided in this embodiment, the nanofibers 7 to be measured can be placed on the fourth sidewall 14 of the substrate and the suspension electrode 5 of the measurement device using a micro-manipulation probe, and then the temperature-sensing particles 6 can be loaded onto the surface of the nanofibers 7, i.e., the temperature-sensing particles can be loaded onto the surface of the nanofibers 7 in situ; alternatively, the temperature-sensing particles 6 can be loaded onto the surface of the nanofibers 7 on another platform, and then the nanofibers 7 with the temperature-sensing particles 6 loaded can be placed on the fourth sidewall 14 of the substrate and the suspension electrode 5 of the measurement device.

[0058] In some embodiments, the nanofibers to be tested may also have low thermal conductivity (generally not exceeding 10 W·(m·K)). -1When considering the characteristics of the current flow, the suspension electrode 5 should be made of a conductive material with a thermal resistance higher than that of the nanofiber being measured. Furthermore, to obtain a good measurement signal-to-noise ratio, the thermal resistance of the suspension electrode 5 should be greater than or equal to 10% of the thermal resistance of the nanofiber 6. Even further, to balance good manufacturability with high thermal resistance requirements, the length of the suspension electrode 5 should not exceed 250 μm, and the cross-sectional area through which the current flows should not exceed 2.5 μm. 2 The lower limits of the length of the suspension electrode 5 and the cross-sectional area through which the current flows are determined by the manufacturing process. The distance between the suspension electrode 5 and the fourth sidewall 14 of the substrate 1 does not exceed 25 μm to ensure that the fiber thermal resistance does not exceed the accurate measurement range of the device. Furthermore, the material used to manufacture the suspension electrode 5 should also meet the requirement that the suspension electrode will not crack due to thermal expansion during heating; furthermore, the coefficient of thermal expansion of the material used to manufacture the suspension electrode 5 does not exceed 1.8 × 10⁻⁶. -5 ℃ -1 In this embodiment, the suspension electrode 5 is made of gold, with a coefficient of thermal expansion of 1.42 × 10⁻⁶. -5 ℃ -1 The suspension electrode 5 has a length of 200 μm (i.e., the dimension along the distance from the first sidewall to the second sidewall), a width of 4 μm (i.e., the dimension along the distance from the third sidewall to the fourth sidewall), and a thickness of 250 nm (i.e., the dimension along the stacking direction from the suspension electrode 5 to the support layer 3). The gold electrode is fabricated by magnetron sputtering, with a power control of 500 W and a sputtering rate control of 0.25 nm / min. The distance between the suspension electrode 5 and the fourth sidewall 14 is 20 μm.

[0059] In some embodiments, due to the relatively weak mechanical strength of the suspension electrode 5, a support layer 3 is provided below the suspension electrode 5 to ensure its mechanical strength and prevent it from breaking or detaching from the conductive electrode due to device vibration, temperature changes, or thermal stress during measurement. To balance good machinability with support layer strength, the thickness of the support layer 3 is not less than 150 μm, and the distance between the bottom of the support layer 3 and the bottom of the device (i.e., the bottom of the substrate) should be greater than or equal to 200 μm. Furthermore, the coefficient of thermal expansion of the material used to make the support layer 3 does not exceed 1.8 × 10⁻⁶. -5 ℃ -1 To prevent the support layer from cracking due to thermal expansion during heating, in this embodiment, the support layer 3 is made of silicon nitride, which has a coefficient of thermal expansion of 3.2 × 10⁻⁶. -6 ℃ -1 The support layer 3 has a length of 200 μm, a width of 4 μm, and a thickness of 200 nm. The support layer 3 is prepared by low-pressure chemical vapor deposition, with specific parameters including: the gases used are NH3 (flow rate of 280 mL / min) and SiH2Cl2 (flow rate of 70 mL / min), the temperature is 800 °C, and the growth rate is 4 nm / min.

[0060] In some embodiments, the adhesive layer 4 is used to enhance the interaction between the support layer 3 and the suspension electrode 5, further improving the mechanical strength and durability of the suspension electrode 5, and is generally made of a metallic material. In this embodiment, the adhesive layer 4 is made of chromium, with a coefficient of thermal expansion of 4.9 × 10⁻⁶. -6 ℃ -1 The adhesion layer 4 has a length of 200 μm, a width of 4 μm, and a thickness of 50 nm. The adhesion layer 4 was prepared by magnetron sputtering at a power of 200 W and a sputtering rate of 0.12 nm / min.

[0061] The preparation process of the measuring device in this embodiment is as follows:

[0062] 1) Cleaning silicon substrates by plasma: the gas atmosphere is oxygen, the plasma source power is 400W, and the pressure is 80mTorr;

[0063] 2) Design and fabricate electrode photolithography masks;

[0064] 3) Fabrication of silicon nitride support layer by magnetron sputtering: The gases used were NH3 (flow rate of 280 mL / min) and SiH2Cl2 (flow rate of 70 mL / min), the temperature was 800℃, and the growth rate was 4 nm / min;

[0065] 4) A chromium adhesion layer was fabricated by magnetron sputtering: power 200W, speed 0.12nm / min, thickness 50nm;

[0066] 5) Fabrication of gold suspension electrodes by magnetron sputtering: power 500W, speed 0.25nm / min, thickness 250nm;

[0067] 6) Remove some unwanted silicon substrate by photolithography: Expose with MA6 broadband light source for 7s, develop with 2.38% TMAH developer for 45s;

[0068] 7) Obtain the desired suspension electrode, adhesion layer, support layer and conductive electrode structure by ion beam etching: ion energy: 300eV, beam current: 802mA, neutralization current: 100mA;

[0069] 8) Remove the adhesive backing by ultrasonic cleaning, using acetone and isopropanol as solvents;

[0070] 9) Design and fabricate a back-side overprinting mask;

[0071] 10) Back cover photolithography.

[0072] In this embodiment, the preparation process of loading thermometric particles 6 onto the surface of nanofiber 7 is as follows:

[0073] The platinum-carbon-ionomer composite nanofibers to be tested were placed on substrate 1. Multiple silicon nanoparticles (6) were then electrostatically sprayed onto the surface of the nanofibers 7 as temperature-sensing particles. In the electrostatically sprayed slurry, the silicon particles (average diameter 30 nm) accounted for 5% of the mass, and the solvent (isopropanol) accounted for 95% of the mass. The slurry was dispersed using an angle stirrer at a speed of 2000 r / min for 50 minutes. During electrostatic spraying, the positive voltage at the needle was 9 kV, the negative voltage at the rotary receiver was 5 kV, the rotary receiver speed was 100 r / min, the distance between the needle and the rotary receiver was 8 cm, the ambient temperature was 25°C, and the relative humidity was 30%. The distribution density of silicon particles on the nanofibers could be controlled by adjusting the electrostatic spraying time. In this embodiment, the spraying time was 40 s, and the silicon particle distribution density was 0.25 particles / μm.

[0074] This disclosure also proposes a method for measuring the thermal conductivity of nanofibers using the above-described device. During measurement, the device needs to be placed in a vacuum environment, and the ambient temperature, typically 20°C to 30°C, must be recorded. The measurement method specifically includes the following steps:

[0075] 1) Calibrate the Raman shift of the temperature-measuring particle 6 as a function of temperature. Specifically, the surface of the temperature-measuring particle 6 is irradiated with a continuous-wave laser with a wavelength of 633 nm. The Raman signal of the temperature-measuring particle 6 is obtained by measuring the frequency difference between the incident light and the scattered light from the surface of the temperature-measuring particle 6. By changing the temperature of the device, the relationship between the Raman shift of the temperature-measuring particle 6 and temperature is obtained, such as... Figure 2 As shown, as the temperature x of the thermometric particle 6 increases, its Raman shift linearity y decreases, specifically satisfying: y = -0.02436x + 527.3, with a linearity R. 2 =0.9972.

[0076] 2) The temperature coefficient of resistance of the suspension electrode 5 is calibrated to determine the relationship between the resistance of the suspension electrode and temperature. Specifically, the temperature is controlled by a sample stage with a vacuum chamber, and the resistance of the suspension electrode 5 at different temperatures is measured. The measurement results in this embodiment are as follows: Figure 3 As shown, Figure 3 Figures (a) and (b) show the temperature control history diagram and the relationship between the suspension electrode resistance and temperature, respectively, of the measurement device provided in this embodiment for calibrating the temperature coefficient of the suspension electrode resistance. The results show that the resistance of the gold suspension electrode has a linear relationship with temperature, y = 1.0506x + 862.07, and its linearity R... 2 =1.0000, where y represents resistance and x represents temperature. The resistance measurement has a small error bar, and the metal suspension electrode has good electrical characteristics.

[0077] 3) Based on the relationship between the resistance and temperature of the suspension electrodes, the thermal conductivity of the suspension electrodes is calibrated according to the following formula:

[0078]

[0079] Where λ is the thermal conductivity of the suspension electrode, q v Where is the heating power of the suspension electrode, and L is the length of the suspension electrode. t0 is the average temperature of the suspension electrodes, and t0 is the ambient temperature. This is the average temperature rise of the suspension electrode.

[0080] The specific operating procedure is as follows: First, different voltages are applied to both ends of the suspension electrode 5 through conductive electrodes 21 and 22, and the current through the suspension electrode 5 is measured. Each voltage is stabilized for 5 minutes. Figure 4 As shown in (a); the resistance of suspension electrode 5 over time was calculated according to Ohm's law, and the resistance measurements over the last 2 minutes were averaged to obtain the relationship between the resistance of suspension electrode 5 and heating power, as shown in Figure (a). Figure 4 As shown in (b), the suspension electrode heating power x and suspension electrode heating power y satisfy the relationship: y = 3.1613x + 886.93, and its linearity R 2 =0.9999; Based on the relationship between suspension electrode resistance and temperature obtained in step 2), calculate the relationship between the average temperature rise y of the suspension electrode and the heating power x, as shown in the figure. Figure 4 As shown in (c), the suspension electrode heating power x and the average temperature rise y of the suspension electrode satisfy the relationship: y = 3.0100x, and its linearity R 2 =0.9999; Finally, the thermal conductivity of the suspension electrode is calculated according to formula (1), such as Figure 4 As shown in (d).

[0081] 4) Using a micro-manipulation probe, cut the nanofiber 7 carrying the temperature-sensing particles 6, and move and place it onto the nanofiber thermal conductivity measuring device. One end of the nanofiber 7 is placed at the center of the suspension electrode 5, and the other end is placed at the middle of the fourth sidewall 14 of the substrate 1. Repeat step 3) to obtain the variation of the average temperature rise of the suspension electrode with the heating power before and after placing the nanofiber 7, as shown in the figure. Figure 5 As shown, subtracting the two yields the heat flow through the nanofibers under any average temperature rise of the suspension electrode. In one embodiment of this application, according to the measurement results, when the average temperature rise of the suspension electrode is 12K, the heat flow through the nanofibers is 0.82μW.

[0082] 5) Measure the Raman shift of the thermometric particles 6 at different positions on the nanofiber 7, and calculate the change in the Raman shift of the silicon nanoparticles with temperature as determined in step 1) (i.e., Figure 2The temperature of the thermometric particles at different locations on the nanofiber was calculated, and the results are as follows: Figure 6 As shown, the temperature gradient of the nanofiber is 0.7349 K / μm. Finally, the thermal conductivity of the composite porous fiber is calculated to be 6.70 W·(m·K) using Fourier's law of thermal conductivity, based on the heat flux and temperature gradient of the nanofiber. -1 .

[0083] It is understood that the nanofiber thermal conductivity measurement device and method provided in this embodiment can realize non-contact measurement of the thermal conductivity of nanofibers with weak Raman signals or strong metallic fluorescence signals, thus broadening the universality of Raman spectroscopy in the measurement of the thermal properties of nanomaterials. Furthermore, the suspension electrode, as the hot end, has the characteristics of long electrode length and small current flow area, and therefore has a much greater thermal resistance than conventional single-fiber measurement devices, which can solve the problem of low signal-to-noise ratio in the measurement of low thermal conductivity nanofibers. At the same time, the support layer under the suspension electrode can effectively increase the mechanical strength of the suspension electrode, ensuring the repeatability of the test and the durability of the device. Therefore, this disclosure can also accurately and effectively measure the thermal conductivity of low thermal conductivity nanofibers.

[0084] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. 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.

[0085] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A device for measuring the thermal conductivity of nanofibers, characterized in that, include: The base has a hollowed-out center, and a first sidewall and a second sidewall, as well as a third sidewall and a fourth sidewall, are formed around the hollowed-out area. The first conductive electrode and the second conductive electrode are respectively formed on the first sidewall and the second sidewall; as well as The structure consists of a support layer, an adhesive layer, and a suspension electrode stacked sequentially from bottom to top. The suspension electrode is supported by the support layer on the first and second sidewalls. Both ends of the suspension electrode are connected to the first and second conductive electrodes, respectively. Current is applied to the suspension electrode through the first and second conductive electrodes, making the suspension electrode a hot end. Both ends of the nanofiber are supported on the suspension electrode and the fourth sidewall, respectively. The surface of the nanofiber is loaded with uniformly distributed temperature-sensing particles. The relative Raman signal of the temperature-sensing particles is not less than the intensity of the temperature-sensing particles relative to the air peak, and the temperature-sensing particles do not have metallic fluorescence signals. The distribution density of the temperature-measuring particles on the nanofibers ranges from 0.05 to 1 particle / μm.

2. The measuring device according to claim 1, characterized in that, The temperature-sensing particles are attached to the surface of the nanofibers by electrostatic spraying, ultrasonic spraying, or probe movement.

3. The measuring device according to claim 1, characterized in that, The thermal resistance of the suspension electrode should be greater than or equal to 10% of the thermal resistance of the nanofiber.

4. The measuring device according to claim 1, characterized in that, The length of the suspension electrode does not exceed 250 μm and the cross-sectional area through which the current flows does not exceed 2.5 μm. 2 .

5. The measuring device according to claim 1, characterized in that, The distance between the suspension electrode and the fourth sidewall shall not exceed 25 μm, and the distance from the bottom of the support layer to the bottom of the substrate shall be greater than or equal to 200 μm.

6. The measuring device according to claim 1, characterized in that, The coefficient of thermal expansion of the material used to manufacture the suspension electrode does not exceed 1.8 × 10⁻⁶. -5 ℃ -1 The coefficient of thermal expansion of the material used to make the support layer does not exceed 1.8 × 10⁻⁶. -5 ℃ -1 .

7. The measuring device according to claim 1, characterized in that, The adhesive layer is made of metal and is used to ensure the bonding between the suspension electrode and the support layer.

8. The measuring device according to claim 1, characterized in that, The substrate is made of insulating material, and the temperature of the substrate is kept consistent with the ambient temperature.

9. A measurement method using the measuring device according to any one of claims 1 to 8, characterized in that, include: The relationship between the Raman shift of the calibrated temperature measuring particles and temperature; The temperature coefficient of resistance of the suspension electrode is calibrated to determine the relationship between the resistance of the suspension electrode and temperature. The thermal conductivity of the suspension electrode is determined based on the relationship between its resistance and temperature, using the following formula: in, The thermal conductivity of the suspension electrode. This refers to the heating power of the suspension electrodes. The length of the suspension electrode. The average temperature of the suspension electrodes. For ambient temperature, This is the average temperature rise of the suspension electrodes; The two ends of the nanofiber carrying the temperature measuring particles are supported on the suspension electrode and the fourth sidewall, respectively. The above operation of calibrating the thermal conductivity of the suspension electrode is repeated to obtain the change law of the average temperature rise of the suspension electrode with the heating power before and after the nanofiber is placed. The difference between the two can be used to obtain the heat flow through the nanofiber under any average temperature rise of the suspension electrode. The Raman shift of thermometric particles at different positions on the nanofiber is measured, and the temperature of the thermometric particles at different positions on the nanofiber is estimated based on the relationship between the Raman shift of the calibrated thermometric particles and temperature, thereby obtaining the temperature gradient of the nanofiber. Finally, the thermal conductivity of the nanofiber is calculated by using Fourier's law of thermal conductivity based on the heat flux and temperature gradient of the nanofiber.

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