阅读说明：本技术 一种测量固体热扩散率和比热并验证结果的方法 (Method for measuring thermal diffusivity and specific heat of solid and verifying result ) 是由 许缉熙 陈伟 陈树彬 胡丽丽 于 2021-07-21 设计创作，主要内容包括：本发明提供一种测量固体热扩散率和比热并验证结果的方法。首先为满足两种测量方法联用且互不影响的目的,对试样和标样上下表面中心特定区域镀膜,然后在侧面加工特定深度的小孔。通过分光光路对试样和标样的镀膜区域注入相同的热量,样品和标样小孔内的热电偶记录对应位置温度变化；试样和标样背面热辐射分别经全反射镜-光开关-半透半反镜和半透半反镜进入光电转换器中,通过对光开关的时序控制,得出试样和标样背面热辐射变化数据。热电偶和热辐射数据分别得出一组热扩散率和比热结果,将两种方法得出的同一参数相互比对验证得出准确的热扩散率和比热数据。(The invention provides a method for measuring thermal diffusivity and specific heat of a solid and verifying a result. Firstly, in order to meet the purpose that two measurement methods are combined and do not influence each other, the center specific areas of the upper surface and the lower surface of a sample and a standard sample are coated with films, and then small holes with specific depths are processed on the side surfaces. Injecting the same heat into the film coating areas of the sample and the standard sample through the light splitting optical path, and recording the temperature change of the corresponding positions by thermocouples in the sample and the standard sample small holes; and the back thermal radiation of the sample and the standard sample respectively enters the photoelectric converter through the holophote-optical switch-semi-transparent semi-reflective mirror and the semi-transparent semi-reflective mirror, and the back thermal radiation change data of the sample and the standard sample are obtained through the time sequence control of the optical switch. And respectively obtaining a group of thermal diffusivity and specific heat results from the thermocouple and the thermal radiation data, and mutually comparing the same parameters obtained by the two methods to verify to obtain accurate thermal diffusivity and specific heat data.)

1. A method of measuring the thermal diffusivity and specific heat of a solid and verifying the results comprising the steps of:

a preparation stage:

s1, taking the round sample (5) to be tested and the standard sample (12) with the same shape and size, and carrying out film coating and processing treatment;

the coating method comprises the following steps: setting the radius of the sample (5) to be measured and the standard sample (12) as R and the thickness as d, plating gold in the central circular areas of the upper and lower surfaces of the wafer, and then plating carbon on the surface of the gold film, wherein the diameter R of the film plating area is less than or equal to R-d.

The processing method comprises the following steps: processing small holes on the side surfaces of a sample (5) to be detected and a standard sample (12), wherein the depth m of the small holes is not more than R-R, the number of the small holes processed on the sample is 2, the distance between 2 small holes and the bottom surface of the sample is h1 and h2, h1 is less than h2, the extension lines of the 2 small holes are parallel to the upper surface and the lower surface of the sample and intersect with the central axis of the sample, and the projection included angle of the two extension lines on the surface of the sample to be detected is within the range of 0-180 degrees.

Respectively placing and fixing four thermocouple probes in two small holes of a processed sample (5) to be detected and a standard sample (12);

s2, constructing a measurement system: the measurement system includes: the device comprises a photoelectric converter (1), a controller (2), a heat source laser (3), a first half mirror (4), a first total reflector (10), an optical switch (7), a second half mirror (8) and a second total reflector (6); the photoelectric converter (1), the heat source laser (3), the optical switch (7) and the four thermocouple probes are all connected with the controller (2);

the heat source laser (3) emits a light beam with pulse width delta, the light beam is divided into two transmission light beams and two reflection light beams with the same energy through the first half-transmitting and half-reflecting mirror (4), the transmission light beams irradiate on a film coating area of a sample (5) to be detected, the reflection light beams irradiate on a film coating area of a standard sample (12) after being reflected by the first full-reflecting mirror (10), and therefore the film coating areas of the sample (5) to be detected and the standard sample (12) are subjected to the same heat input; the heat radiation signals transmitted by the sample to be detected (5) sequentially pass through the total reflector (6), the optical switch (7) and the second semi-transparent semi-reflective mirror (8) to enter the photoelectric converter (1), and the heat radiation signals transmitted by the standard sample (12) enter the photoelectric converter (1) through the second semi-transparent semi-reflective mirror (8); the photoelectric converter (1) and the optical switch (7) are connected and controlled by the controller (2).

And (3) a measuring stage:

at the time of S3 and t0, the heat source laser (3) is turned on, so that the sample (5) to be tested and the standard sample (12) are subjected to the same heat input, the optical switch (7) is turned on at a certain time interval through time sequence control, and the photoelectric converter (1) records the sum of heat radiation signals of the back surfaces of the sample (5) to be tested and the standard sample (12); closing the optical-optical switch (7) at a specific time interval, wherein the photoelectric converter (1) only records a back heat radiation signal of the standard sample (12); recording thermal radiation data at the moment of t0, and then performing interpolation fitting and subtraction on the two groups of data to obtain the change data of thermal radiation on the back surfaces of the sample and the standard sample along with time;

s4, the four thermocouple probes respectively measure the change data of the temperature of the corresponding position along with the time, and the thermal diffusivity alpha of the sample (5) to be measured is calculated according to the heat transfer model_s1And specific heat Cp_s1(ii) a Thermal diffusivity alpha of standard sample (12)_r1And specific heat Cp_r1；

The photoelectric converter (1) records thermal radiation data, and calculates the thermal diffusivity alpha of the sample (5) to be measured according to a heat transfer model_s2And specific heat Cp_s2(ii) a Thermal diffusivity alpha of standard sample (12)_r2And specific heat Cp_r2；

And (3) comparison stage:

s5, obtaining thermal diffusivity and specific heat alpha when the thermocouple probe of the sample to be measured (5) measures_s1，Cp_s1Thermal diffusivity and specific heat alpha obtained from measurement of thermal radiation_s2，Cp_s2Satisfies alpha_s1＝α_s2And Cp_s1＝Cp_s2If so, the test result is proved to be accurate, otherwise, the step S3 is returned;

s6, the reference value of the standard sample thermal diffusivity is known as alpha_r0Reference value of specific heat of standard sample is Cp_r0And calculating the measurement error of the thermocouple probe standard sample, wherein the formula is as follows:

Δα₁＝|α_r1-α_r0|/α_r0；ΔCp1＝|Cp_r1-Cp_r0|/Cp_r0；

calculating the measurement error of the thermal standard sample of the photoelectric converter, wherein the formula is as follows:

Δα₂＝|α_r2-α_r0|/α_r0；ΔCp2＝|Cp_r2-Cp_r0|/Cp_r0。

2. the method of claim 1 wherein the optical switch control frequency is 1/2 times the sampling frequency of the optical-to-electrical converter.

The technical field is as follows:

the invention relates to the technical field of testing of thermal properties of solid materials, in particular to a method for measuring thermal diffusivity and specific heat of a solid and verifying a result.

Background art:

the thermal diffusivity, specific heat and other thermal property parameters of the solid material are very important for the application of the material in the scientific research field and the engineering technology, so that the accurate measurement of the numerical values of the thermal diffusivity, specific heat and other thermal property parameters of the solid material plays an important role. Current measurement techniques can be divided from the model heat transfer states into: the method comprises the steps of steady-state measurement and transient measurement, wherein the time required by steady-state heat transfer is longer, and the transient measurement has the characteristics of short time and high efficiency; the data acquisition mode can be divided into contact measurement and non-contact measurement, wherein the contact measurement can directly measure the temperature or other property changes caused by the temperature, related thermal parameters are deduced through a heat transfer model, the calculation is convenient and fast, but the arrangement of the experimental probe can influence the heat transfer of a sample and deviate from an ideal heat transfer model, so that errors are caused. While non-contact measurement typically uses light as a medium or signal source to detect changes in temperature or other related parameters of a solid material during heat transfer, non-contact measurement methods sometimes fail to measure specific values of temperature or deviate from a model due to limitations of the material itself, resulting in gross errors in measuring certain thermal parameters. Furthermore, different measurement methods have their applicable test conditions and corresponding material properties. When a certain method is actually applied, errors are generated on the measurement results from two aspects of method model and technology implementation, and the size of the measurement errors is very important for some application occasions, but the current common measurement method for thermal diffusivity and specific heat can only obtain a thermal parameter to obtain a measurement value after the measurement is finished, the accuracy judgment and error analysis on the result cannot be carried out after one-time measurement is finished, an error range is often required to be given by means of other measurement methods or multiple measurements, and the accuracy of the result is difficult to directly judge according to experimental measurement data.

The invention content is as follows:

according to the problems, the invention provides a method for measuring the thermal diffusivity and the specific heat of the solid and verifying the result, and solves the problem that the result cannot be accurately judged and subjected to error analysis after one-time measurement is finished.

In order to achieve the above purpose, the present invention achieves the object by the following technical means:

a method of measuring thermal diffusivity and specific heat of a solid and verifying results, the measurement system comprising: the device comprises a photoelectric converter (1), a controller (2), a heat source laser (3), a first half mirror (4), a first total reflector (10), an optical switch (7), a second half mirror (8) and a second total reflector (6); the photoelectric converter (1), the heat source laser (3), the optical switch (7), the thermocouple probes (9), (14), (11) and (13) are all connected with the controller (2), and the controller (2) respectively controls the operation, collects and records data; the first total reflector (10) is arranged at the right side of the first half mirror (4), and the optical switch (7) is arranged between the second total reflector (6) and the second half mirror (8).

A method of measuring the thermal diffusivity and specific heat of a solid and verifying the results comprising the steps of:

a preparation stage:

s1: preparing a sample, selecting a standard sample material with similar properties according to the estimated thermal properties of the material to be detected, and processing the material to be detected and the standard sample material into round pieces with the same shape and size, wherein the radius is R and the thickness is d. Then gold is plated on the central circular areas of the upper and lower surfaces of the wafer, and then carbon is plated on the surface of the gold film, wherein the purpose of the gold film is to prevent experimental errors caused by the fact that a heating light source penetrates through the transparent sample, and the purpose of the carbon film is to enhance the absorption and emission of radiation on the surface of the sample. The diameter R of the coating area is required to be less than or equal to R-d, an enough area is provided for placing a thermocouple on the outer ring, and the influence of a small hole for placing a thermocouple probe on a heat transfer model in the central area is avoided to the maximum extent, so that the aims of combining two measurement methods and not influencing each other are fulfilled.

Processing small holes for placing thermocouple probes on the side surfaces of the two wafer samples coated with the films, wherein the depth m of each small hole is less than or equal to R-R, and the purpose is that the small holes cannot exceed the range of the non-coated area of the samples, so that the influence of the boundary caused by processing on the central heat transfer is avoided. The number of the small holes processed on the sample is 2, the distance between 2 small holes and the bottom surface of the sample is h1 and h2 (wherein h1 is less than h2), the extension lines of 2 small holes are parallel to the upper surface and the lower surface of the sample and intersect with the axis of the sample, and the included angle of the extension lines is within the range of 0-180 degrees; or 2 the extension lines of the small holes are parallel to the upper surface and the lower surface of the sample and are not intersected with the axis of the sample, and the included angle of the extension lines is within the range of 0-180 degrees, so that the purposes that the two measurement methods are combined and do not influence each other are met.

And (3) a measuring stage:

s2: during measurement, at the time of t0, the controller (2) controls the heat source laser (3) to emit a beam with pulse width delta, the heating beam is divided into two beams with the same energy through the first half-mirror (4), and the two beams irradiate on the bottom surface coating areas of the sample to be measured (5) and the standard sample (12) respectively, so that the sample to be measured (5) and the standard sample (12) are subjected to the same heat input; meanwhile, the controller (2) controls thermocouple probes (11) (13) (9) (14) installed in the sample (5) to be measured and the standard sample (12) to collect and record the change data of the temperature of the corresponding position along with the time.

S3: the bottom of a sample to be measured (5) is heated by a heat source, heat flow is transmitted to the back surface to cause the temperature of the back surface to rise, a heat radiation signal on the back surface of the sample to be measured (5) enters a photoelectric converter (1) through a total reflection mirror (6), an optical switch (7) and a semi-transparent semi-reflective mirror (8), and an optical signal reflecting the temperature is converted into an electric signal; the heat radiation signal on the back of the standard sample (12) enters the photoelectric converter (1) through the semi-transparent semi-reflecting mirror (8) and is also converted into an electric signal; the optical switch (7) is controlled by the controller (2) to be continuously switched on and off in a measuring time sequence, and when the optical switch (7) is switched on, the photoelectric converter (1) records the sum of heat radiation signals of the back surfaces of the sample (5) to be measured and the standard sample (12); when the photoelectric converter (1) is closed at a specific moment, the photoelectric converter (7) only records the back heat radiation signal of the standard sample (12) when the optical switch (7) is closed, and the control frequency of the optical switch (7) is 1/2 of the sampling frequency of the photoelectric converter. And recording thermal radiation data by the photoelectric converter (1) at the moment t0, and then performing interpolation fitting and subtraction on the total radiation signal and the standard sample radiation signal to obtain the change data of the thermal radiation on the back surfaces of the sample and the standard sample along with time.

S4: and after the sample is stabilized, finishing data acquisition, and then calculating the thermal diffusivity and specific heat parameters of the sample according to the data recorded by the thermocouple probe by a heat transfer model, wherein the thermal diffusivity and specific heat parameters are respectively as follows: alpha is alpha_s1，Cp_s1(ii) a The thermal diffusivity and specific heat parameters of the standard sample are respectively as follows: alpha is alpha_r1，Cp_r1. The thermal diffusivity and specific heat parameters of the sample calculated by the thermal radiation data recorded by the photoelectric converter according to the heat transfer model are respectively as follows: alpha is alpha_s2，Cp_s2(ii) a The thermal diffusivity and specific heat parameters of the standard sample are respectively as follows: alpha is alpha_r2，Cp_r2。

And (3) comparison stage:

s5, when the model is correct and the measurement is not interfered, the thermal diffusivity and the specific heat alpha obtained by the measurement result of the thermocouple probe of the sample to be measured_s1，Cp_s1Thermal diffusivity and specific heat alpha obtained from measurement of thermal radiation_s2，Cp_s2Satisfies the following conditions: alpha is alpha_s1＝α_s2；Cp_s1＝Cp_s2And if not, the result is not proved to be accurate, and the measurement step is returned to for re-measurement.

S6: calculating measurement error according to the measurement result of the standard sample and the reference data of the standard sample, wherein the reference values of the thermal diffusivity and the specific heat of the known standard sample are respectively alpha_r0，Cp_r0Therefore, the error of the thermal diffusivity and the specific heat obtained by the thermocouple probe temperature measurement method in the current measurement can be written as follows:

Δα₁＝|α_r1-α_r0|/α_r0；ΔCp1＝|Cp_r1-Cp_r0|/Cp_r0

the error of the thermal diffusivity and the specific heat obtained in the measurement by the thermal radiation method can be written as follows:

Δα₂＝|α_r2-α_r0|/α_r0；ΔCp2＝|Cp_r2-Cp_r0|/Cp_r0

the invention has the beneficial effects that:

the method comprises the steps of limiting the size of a coating film and the depth of a drilled hole according to the diameter and the thickness of a sample, simultaneously realizing the implementation of two contact-type experimental methods and non-contact-type experimental methods which are not interfered with each other, obtaining thermal diffusivity and specific heat numerical values measured by two groups of experiments, and finally obtaining the accurate thermal diffusivity and specific heat parameters of the sample to be tested by comparing and verifying the accuracy of experimental results.

Drawings

FIG. 1 is a schematic diagram of a test system for the thermal diffusivity and specific heat measurement method of the present invention;

FIG. 2 is a schematic view of a film coating area of a sample to be measured and a standard sample;

fig. 3 is a schematic diagram illustrating three possible drilling positions and thermocouple probe installation for a sample to be measured and a standard sample, wherein a is that two thermocouple probes are distributed on the same side, and the projections of the two thermocouple probes are overlapped; b, two thermocouple probes are not in the same plane, and the projection included angle is 0-180 degrees; and c, distributing two thermocouple probes on two sides, and enabling projections to coincide with each other.

In the figure:

1 a photoelectric converter; 2, a controller; 3, a heat source laser; 4 a first half mirror;

5, testing the sample to be tested; 6 a second total reflection mirror; 7, an optical switch; 8 a second half mirror;

9 thermocouple probes; 10 a first holophote 11 thermocouple probe; 12, standard sample;

13 thermocouple probes; 14 thermocouple probes.

Detailed Description

The following detailed description of the specific working principles of the present invention is made with reference to the accompanying drawings and examples.

The theoretical basis of the thermal conductivity measurement method is a cylinder axial transient heat transfer model considering boundary conditions, according to the description of the model, when the lower part of a cylinder is heated by heat flux and the surrounding boundary conditions are known, the change of the temperature at any position in the cylinder along with time can be obtained according to a Fourier heat transfer equation, and therefore two methods of contact measurement and non-contact measurement are arranged according to the model solution form to measure the thermal diffusivity and the specific heat of a substance. And introducing a standard sample, so that the sample and the standard sample are measured under the same condition, and calculating the experimental error according to the measurement data and the reference data of the standard sample.

The measuring system of the present invention is constructed as shown in fig. 1, including: the photoelectric converter comprises a photoelectric converter 1, a controller 2, a heat source laser 3, a first half mirror 4, a first total reflector 10, an optical switch 7, a second half mirror 8 and a second total reflector 6; the photoelectric converter 1, the heat source laser 3, the optical switch 7 and the four thermocouple probes are all connected with the controller 2, and the controller 2 respectively controls the operation, collects and records data; the first total reflector 10 is arranged at the right side of the first half mirror 4, and the optical switch 7 is arranged between the second total reflector 6 and the second half mirror 8.

In this example, a phosphate glass was selected as a sample to be measured, and a commercial type of phosphate optical glass was selected as a standard sample according to the properties of the sample to be measured, and thermal diffusivity and specific heat at room temperature of 20 ℃ were measured.

Processing a sample to be detected and a standard sample into a wafer with the diameter of 20mm and the thickness of 4 mm; first, a plating treatment was performed to form a circular plating region having a diameter of 15mm on the upper and lower surfaces, the first layer was a gold film having an appropriate thickness, and then a carbon film was further plated on the gold film. And in the second step, drilling the sample subjected to the film coating step, wherein one of three arrangement modes can be selected: the first two small holes are distributed on the same side of the circular sample, the side surfaces of the sample to be detected and the standard sample are processed into small holes with the depth of 2mm by using a superfine hard alloy drill bit with the diameter of 0.25mm, the small holes are respectively 1mm and 3mm away from the lower surface, the extension lines of the two small holes are parallel to the upper surface and the lower surface and are intersected with the central axis of the wafer, and the projections of the two extension lines on the bottom surface are superposed, as shown in a graph of fig. 3 (a); secondly, machining small holes with the depth of 2mm on the side surfaces of the sample to be detected and the standard sample by using a superfine hard alloy drill bit with the diameter of 0.25mm, wherein the small holes are respectively 1mm and 3mm away from the lower surface, the extension lines of the two small holes are parallel to the upper surface and the lower surface and are intersected with the central axis of the wafer, and the projection included angle of the two extension lines on the bottom surface is 90 degrees, as shown in fig. 3 (b); and the third two small holes are distributed on two sides of the circular sample, the side surfaces of the sample to be detected and the standard sample are processed into small holes with the depth of 2mm by using a superfine hard alloy drill bit with the diameter of 0.25mm, the small holes are respectively 1mm and 3mm away from the lower surface, the extension lines of the two small holes are parallel to the upper surface and the lower surface and are intersected with the central axis of the wafer, and the projections of the two extension lines on the bottom surface are superposed, as shown in figure 3 (c).

During measurement, a thermocouple probe is fixed in a small hole machined in the last step, a sample is placed at the correct position of a measurement system, and after the temperature is stable, a heat source laser emits a laser beam with the pulse width of 1ms under the control of a controller. Laser pulse is divided into two beams with the same energy through a semi-transparent semi-reflecting mirror 4, and the two beams respectively irradiate on the bottom surface coating areas of the sample and the standard sample, so that the sample and the standard sample are subjected to the same heat input; meanwhile, the controller 2 controls the thermocouple probes arranged in the sample and the standard sample to collect and record the change data of the temperature of the corresponding position along with the time.

The bottom of the sample is heated by a heat source, heat flow is transmitted to the back surface to cause the temperature of the back surface to rise, a heat radiation signal on the back surface of the sample to be detected enters the photoelectric converter through the total reflection mirror 7, the optical switch 8 and the semi-transparent semi-reflective mirror 4, and an optical signal reflecting the temperature is converted into an electric signal; the thermal radiation signal on the back of the standard sample enters the photoelectric converter through the semi-transparent semi-reflective mirror 4 and is also converted into an electric signal; the optical switch 8 is controlled by the controller 2 to be continuously turned on and off at 2 μ s intervals in the measurement timing, and the photoelectric converter records thermal radiation data at a sampling frequency of 2 Mhz. When the optical switch 8 is opened, the photoelectric converter records the sum of the back heat radiation signals of the sample and the standard sample; when the optical switch 8 is turned off at a specific time, the photoelectric converter only records the thermal radiation signal of the back surface of the standard sample when the optical switch is turned off. the photoelectric converter 1 records the thermal radiation data at the beginning of the time t0, and then the total radiation signal and the standard sample radiation signal are subjected to interpolation fitting and subtraction to obtain the time-varying data of the thermal radiation on the back surfaces of the sample and the standard sample.

And finishing data acquisition after the sample is stabilized, and calculating the thermal diffusivity and specific heat parameters of the sample according to the data recorded by the contact measurement-thermocouple probe and the heat transfer model, wherein the thermal diffusivity and specific heat parameters are respectively as follows: alpha is alpha_s1，Cp_s1(ii) a The thermal diffusivity and specific heat parameters of the standard sample are respectively as follows: alpha is alpha_r1，Cp_r1. The thermal diffusivity and specific heat parameters of the sample calculated by the thermal radiation data recorded by the non-contact measurement-photoelectric converter according to the heat transfer model are respectively as follows: alpha is alpha_s2，Cp_s2(ii) a The thermal diffusivity and specific heat parameters of the standard sample are respectively as follows: alpha is alpha_r2，Cp_r2。

Comparing the results with each other to verify that the thermal diffusivity and the specific heat alpha are obtained from the measurement result of the thermocouple probe of the sample to be measured when the model is correct and the measurement is not interfered_s1，Cp_s1Thermal diffusivity and specific heat alpha obtained from measurement of thermal radiation_s2，Cp_s2Satisfies the following conditions:

α_s1＝α_s2；Cp_s1＝Cp_s2time, prove and measureThe test result is accurate.

The reference values of thermal diffusivity and specific heat of the phosphate optical glass in the measuring temperature range according to the commercial trade mark of the standard sample are respectively alpha_r0，Cp_r0Therefore, the error of the thermal diffusivity and the specific heat obtained in the measurement by the contact measurement-thermocouple probe temperature measurement method can be written as follows:

Δα₁＝|α_r1-α_r0|/α_r0；ΔCp1＝|Cp_r1-Cp_r0|/Cp_r0

the error of thermal diffusivity and specific heat obtained in the measurement by the non-contact measurement-thermal radiation method can be written as follows:

Δα₂＝|α_r2-α_r0|/α_r0；ΔCp2＝|Cp_r2-Cp_r0|/Cp_r0

and outputting accurate measurement results of the thermal diffusivity and the specific heat of the sample and corresponding measurement errors.

In the embodiment 1, the measured thermal diffusivity and specific heat data of the sample to be measured are returned by the measurement method of comparison verification, the accuracy of the result is verified by comparing the two methods, and the error is calculated according to the reference data of the standard sample. The result shows that the invention can verify the accuracy of each measurement result, provide the error of each measurement result data and return the accurate result.