A temperature measurement method and temperature measurement device based on diamond first-order Raman spectroscopy

Abstract

The present invention discloses a temperature measurement method based on the first-order Raman spectrum of diamond, comprising: step 1 collecting the first-order Raman spectrum data of diamond at different temperatures, and recording the corresponding temperature values ​​as a data set; step 2 fitting the data set obtained in step 1 through the Voigt fitting function to obtain the half-height width, center position and peak intensity of the corresponding Raman peak; step 3 constructing a monotonic function curve group about temperature change through nonlinear fitting; step 4 placing the diamond in the temperature field to be measured, and obtaining the half-height width, center position and peak intensity of the corresponding Raman peak based on the fitting function of step 2; step 5 inputting the data measured in step 4 into the monotonic function curve group, and outputting the final temperature value through analysis and judgment. The present invention also provides a temperature measurement device based on the above method. The method provided by the present invention ensures the accuracy of the final temperature measurement result while completing the temperature detection.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature detection, and in particular to a temperature measurement method and a temperature measurement device based on diamond first-order Raman spectroscopy. Background Art

[0002] Non-contact temperature measurement technology has the characteristics of high temperature measurement limit and non-destructive scene, and is widely used in production and life, scientific research, modern national defense and other fields. Infrared temperature measurement is a common non-contact temperature measurement method. However, this method is greatly affected by the emissivity, reflectivity and environmental atmosphere of the measured surface, which greatly reduces the measurement accuracy. For temperature measurement in harsh environments such as radiation, corrosion, high frequency and high voltage, conventional measurement methods cannot meet the requirements, so there is an urgent need to develop effective temperature measurement methods.

[0003] Diamond has excellent physical and chemical properties, such as high hardness, corrosion resistance, high thermal conductivity, etc., which give it an absolute advantage in withstanding extreme conditions. Raman spectroscopy is a scattering spectrum that is fast, efficient and non-destructive, and is not affected by the surface emissivity, reflectivity and ambient atmosphere of the sample being measured. From the perspective of scattered signal energy, Raman spectra are divided into Stokes peaks and anti-Stokes peaks. The Stokes signal is when the scattered photon energy is smaller than the incident photon energy, and the anti-Stokes signal is when the scattered photon energy is larger than the incident photon energy.

[0004] Patent document CN112683419B discloses a method for accurately detecting temperature based on the surface enhanced Raman scattering effect, comprising the following steps: (1) loading a monolayer film of plasmon nanoparticles onto a supporting substrate; (2) immersing the monolayer film substrate in a probe molecule solution, and preparing a hard substrate temperature sensor or a flexible substrate temperature sensor after drying; (3) placing the hard substrate temperature sensor or the flexible substrate temperature sensor at a gradient working temperature to collect the Raman spectrum of its surface, and establishing a standard curve between the characteristic temperature and the corresponding characteristic peak intensity; (4) placing the hard substrate temperature sensor or the flexible substrate temperature sensor within a detection range, collecting the Raman spectrum of its surface, reading the characteristic peak intensity and comparing it with the standard curve of the temperature range, thereby realizing the detection of unknown ambient temperature.

[0005] This method uses the characteristic Raman peak intensity to fit the temperature value to obtain the characteristic Raman peak intensity-temperature value curve, but the characteristic Raman peak intensity has very high requirements on the purity of the probe material, that is, the replacement of the probe will affect its recognition accuracy.

[0006] Patent document CN111896140A discloses an optical fiber temperature sensor and system, including: an optical fiber, a pulsed laser, a temperature sensing part, a diamond part and a detection part, wherein the diamond part has a plurality of nitrogen vacancy centers, and the density of the metal nanoparticles changes, thereby causing the magnetic field intensity generated by the metal nanoparticles to change. Since the diamond part contains a plurality of nitrogen vacancy centers, the diamond part can generate fluorescence under the action of the magnetic field. When the magnetic field intensity generated by the metal nanoparticles changes, the fluorescence intensity generated by the diamond part under the action of the magnetic field also changes. The temperature to be measured is obtained by detecting the change in the fluorescence intensity of the diamond part and the corresponding relationship between the fluorescence intensity and the temperature to be measured.

[0007] In this method, diamond is only used as a temperature carrier and has nothing to do with the final temperature detection, and the change of magnetic field intensity is easily affected by the external environment. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a temperature measurement method based on diamond first-order Raman spectroscopy. The method constructs a group of monotonic function curves for mutual verification based on three key parameters of the first-order Raman spectrum. On the basis of completing the temperature measurement, the accuracy of the final temperature measurement result is guaranteed at the same time.

[0009] A temperature measurement method based on diamond first-order Raman spectroscopy, comprising:

[0010] Step 1: collecting first-order Raman spectrum data of diamond at different temperatures by using a Raman spectrometer, and recording corresponding temperature values ​​as a data set;

[0011] Step 2: Based on the data set obtained in step 1, a Voigt fitting function is used to fit the data, wherein the Gauss width is consistent with the resolution of the Raman spectrometer in step 1, and the half-width value, center position and peak intensity of the Raman peak corresponding to each temperature value are obtained;

[0012] Step 3: Based on the data obtained by fitting in step 2 and the corresponding temperature values, a monotonic function curve group about temperature change is constructed through nonlinear fitting:

[0013] Based on the half-width value of the Raman peak and the corresponding temperature value, a half-width-temperature standard curve is constructed;

[0014] Based on the center position of the Raman peak and the corresponding temperature value, a Raman shift-temperature standard curve is constructed;

[0015] Based on the peak intensity of the Raman peak and the corresponding temperature value, an intensity ratio-temperature standard curve is constructed;

[0016] Step 4: placing the diamond in the temperature field to be measured, collecting the first-order Raman spectrum data at the temperature value by using a Raman spectrometer, and obtaining the half-width value, center position and peak intensity of the corresponding Raman peak by the Voigt fitting function analysis of step 2;

[0017] Step 5: Input the data measured in step 4 into the monotonic function curve group, and output the final temperature value through analysis and judgment.

[0018] The temperature values ​​and temperatures are all absolute temperatures, with the unit being Kelvin (K).

[0019] The method collects diamonds in a temperature field to be measured by using a Raman spectrometer, and obtains the actual temperature in the temperature field to be measured by back-calculating with a fitted temperature monotonic function curve group.

[0020] Preferably, the diamond in step 1 is single crystal diamond to avoid the influence of impurities on the first-order Raman spectrum data, thus ensuring the accuracy of the data.

[0021] Preferably, in step 1, data is collected at different temperatures, specifically within a certain temperature range, every 50K, and the diamond is heated for no less than 1 minute, to ensure that the first-order Raman spectrum data obtained is the final stable parameter and facilitate the subsequent fitting of the monotonic function curve.

[0022] Specifically, the emitting laser of the Raman spectrometer in step 1 is 532nm green light, and the range of collecting scattered signals is 1280cm -1 -1350cm -1 , the acquisition time is 10s.

[0023] Specifically, the middle peak intensity in step 2 includes anti-Stokes peak intensity and Stokes peak intensity.

[0024] Preferably, the analysis and judgment in step 5 is based on the difference between the maximum and minimum values ​​in the output results of the three temperature standard curves: when the difference is greater than a threshold, the temperature needs to be remeasured; when the difference is less than the threshold, the average value of the three output results is calculated as the final temperature value output.

[0025] The present invention also provides a temperature measuring device based on the temperature measuring method, which can quickly measure the actual temperature of a material or a temperature field within 300K-1200K by direct contact.

[0026] A temperature measuring device based on a temperature measuring method of diamond first-order Raman spectroscopy, comprising:

[0027] A detection module is used to contact the object to be tested or extend into the space to be tested to obtain first-order Raman spectrum data;

[0028] A spectrum analysis module, used for analyzing the first-order Raman spectrum data acquired by the detection module;

[0029] The temperature analysis module judges the analysis results of the spectrum analysis module and outputs the final temperature value.

[0030] Specifically, the detection module includes a diamond probe, a high temperature resistant and oxidation resistant material coated on the diamond, and a matching Raman spectrometer. The high temperature resistant and oxidation resistant material coated on the diamond avoids the problem of easy oxidation of the diamond at high temperature.

[0031] Preferably, the high temperature resistant and oxidation resistant material is aluminum nitride. Compared with other coating materials with the same performance, the thermal conductivity of this material is high and it is more firmly bonded with diamond, thus avoiding the coating from affecting the measurement of the actual temperature.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) Different from the traditional infrared temperature measurement method, the present invention adopts the principle that the first-order Raman spectrum data of diamond at different temperatures has a certain change law to fit a monotonic function curve related to temperature change.

[0034] (2) The present invention selects three key parameters in the first-order Raman spectrum data and fits three monotonic function curve groups related to temperature change. Through mutual verification, the accuracy of the final measured temperature value is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic flow chart of the temperature measurement method provided by the present invention;

[0036] Figure 2 The first-order Raman spectra of diamond at different temperatures;

[0037] Figure 3 The half-width-temperature standard curve obtained by calculation in step 3 of the temperature measurement method of the present invention;

[0038] Figure 4 A Raman shift-temperature standard curve obtained by calculation in step 3 of the temperature measurement method of the present invention;

[0039] Figure 5 The intensity ratio-temperature standard curve obtained by calculation in step 3 of the temperature measurement method of the present invention;

[0040] Figure 6 This is a comparison chart of the temperature value measured by the temperature measuring device provided by the present invention and the temperature change curve of the hot stage. DETAILED DESCRIPTION

[0041] This example realizes temperature measurement based on the temperature response characteristics of the first-order Raman spectrum of single crystal diamond.

[0042] First, use a temperature-variable device to heat or cool the diamond, record the temperature value displayed by the device, and then collect its Raman spectrum at the current temperature; change the temperature and measure the Raman spectra at multiple temperatures; then, perform fitting analysis on the collected Raman spectrum, extract the center position, half-width and intensity data of the Raman peak, and establish a functional relationship between the extracted data and the temperature; then, place the diamond in the temperature field to be measured and collect the Raman spectrum; finally, substitute the extracted data into the functional relationship and reversely calculate to obtain the temperature value.

[0043] Specific steps are as follows Figure 1 As shown:

[0044] Step 1: Collect the first-order Raman spectrum data of diamond at different temperatures through a Raman spectrometer, and record the corresponding temperature values ​​as a data set:

[0045] The single crystal diamond is placed in the sample chamber of the high temperature hot stage, and the hot stage is controlled by a temperature control device connected to the hot stage to heat or cool the diamond. The temperature is kept at each temperature point of 50K for 1 minute in the temperature range of 300K-1200K, and the temperature value of the temperature point is recorded during the holding period;

[0046] When the temperature value is stable, the excitation laser (532nm green light) of the Raman spectrometer is focused on the diamond surface, and the Raman spectrometer is used to collect 1280cm -1 -1350cm -1 The scattering signal between is a single peak and the acquisition time is 10s.

[0047] like Figure 2 As shown in the figure, it is the collected first-order Raman spectrum. As the temperature increases, the Stokes peak moves toward the low-frequency direction, and is accompanied by a broadening of the peak shape and a weakening of the intensity. The position and shape of the anti-Stokes peak change symmetrically relative to the Stokes peak, and the intensity gradually increases. Moreover, the background signal is easy to deduct, and the obtained physical signal is clean with a high signal-to-noise ratio, which improves the measurement accuracy.

[0048] Step 2 is based on the data set obtained in step 1, and is fitted by the Voigt fitting function, where the Gauss width is consistent with the resolution of the Raman spectrometer in step 1, and the half-width value, center position and peak intensity of the Raman peak corresponding to each temperature value are obtained, where the peak intensity includes the anti-Stokes peak intensity and the Stokes peak intensity:

[0049] The scattered signal was fitted and analyzed by a control computer connected to the Raman spectrometer. The fitting function was the Voigt function, 0.55 cm -1The resolution of the Raman spectrometer is fixed as the Gauss width in the Voigt function, where the basic formula for fitting the Voigt function is:

[0050] y=y0+(f1(x)*f2(x))

[0051]

[0052]

[0053] Where y0 is the vertical coordinate offset between the fitting curve and the actual spectrum, x is the horizontal coordinate value of the first-order Raman spectrum, and x c is the Raman shift (peak center frequency), A is the peak area, w L is the Lorentz width, w G is the Gaussian width.

[0054] When the fit R 2 When the maximum value is reached, the half-width value, the center position of the Raman peak and the peak intensity corresponding to each temperature point are obtained, wherein the peak intensity includes the anti-Stokes peak intensity and the Stokes peak intensity.

[0055] Step 3: Based on the data obtained by fitting in step 2 and the corresponding temperature values, a monotonic function curve group about temperature change is constructed through nonlinear fitting:

[0056] like Figure 3 As shown, based on the half-width value of the Raman peak and the corresponding temperature value, a half-width-temperature standard curve is constructed:

[0057] The temperature value (X) at each temperature point and the half-width (Y) of the corresponding Raman peak at each temperature point are plotted as a scatter plot, and the phonon decay model is used for nonlinear fitting to establish a half-width-temperature standard curve:

[0058]

[0059] Where Γ is the half-width; T is the absolute temperature; ω is the phonon frequency of the triple degenerate LTO phonon at the center of the diamond Brillouin zone (in cm-1), and ω is reflected in the Raman spectrum as the Raman shift;

[0060] n(ω,T)=1 / [exp(hcω / kT)-1] is the temperature-dependent Bose-Einstein phonon distribution function;

[0061] A and B are adjustable parameters, corresponding to the relative contributions of three-phonon process and four-phonon process to the half-width during phonon decay; h, c, and k are Planck constant, speed of light, and Boltzmann constant, respectively.

[0062] like Figure 4As shown, based on the center position of the Raman peak and the corresponding temperature value, a Raman shift-temperature standard curve is constructed:

[0063] The temperature value (X) of each temperature point and the center position (Y) of the corresponding Raman peak of each temperature point are plotted, and nonlinear fitting is performed to establish the Raman shift-temperature standard curve:

[0064]

[0065] Where, Ω is the Raman shift; ω0 is the Raman shift at 0K; T is the absolute temperature; ω is the phonon frequency of the triple degenerate LTO phonon at the center of the diamond Brillouin zone (in cm-1), and ω is reflected in the Raman spectrum as the Raman shift;

[0066] n(ω,T)=1 / [exp(hcω / kT)-1] is the temperature-dependent Bose-Einstein phonon distribution function;

[0067] C and D are adjustable parameters, corresponding to the relative contributions of three-phonon process and four-phonon process to the half-width during phonon decay; h, c, and k are Planck constant, speed of light, and Boltzmann constant, respectively.

[0068] like Figure 5 As shown, based on the peak intensity of the Raman peak and the corresponding temperature value, an intensity ratio-temperature standard curve is constructed:

[0069] The ratio of the anti-Stokes peak intensity to the Stokes peak intensity is calculated, and then a scatter plot is made of the temperature value (X) of each temperature point and the calculated intensity ratio (Y) of each temperature point, and a nonlinear fitting is performed to establish an intensity ratio-temperature standard curve;

[0070]

[0071] where ω l is the incident laser frequency, γ is the correction factor;

[0072] Step 4: placing the diamond in the temperature field to be measured, collecting the first-order Raman spectrum data at the temperature value by using a Raman spectrometer, and obtaining the half-width value, center position and peak intensity of the corresponding Raman peak by the Voigt fitting function analysis of step 2;

[0073] Step 5: Input the data measured in step 4 into the monotonic function curve group, and output the final temperature value through analysis and judgment.

[0074] A temperature measuring device based on a temperature measuring method of diamond first-order Raman spectroscopy, comprising:

[0075] A detection module is used to contact the object to be tested or extend into the space to be tested to obtain first-order Raman spectrum data;

[0076] A spectrum analysis module, used for analyzing the first-order Raman spectrum data acquired by the detection module;

[0077] The temperature analysis module judges the analysis results of the spectrum analysis module and outputs the final temperature value.

[0078] The detection module includes a diamond probe, aluminum nitride coated on the diamond, and a matching Raman spectrometer.

[0079] The judgment method of the device is: the spectrum analysis module outputs three temperature monotonic function curve values ​​t1, t2 and t3, which are analyzed by the temperature analysis module:

[0080] When |t1-t2|≤t0, |t1-t3|≤t0 and |t3-t2|≤t0 are true at the same time, the final output is

[0081] On the contrary, when one of the inequalities does not hold, the operator is informed to retest.

[0082] Where t0 is the preset threshold, usually 5k.

[0083] like Figure 6 As shown, in the temperature range of 300K-1200K, the output results of the three monotonic functions overlap, and the final fitted temperature change curve basically coincides with the temperature change curve of the hot stage, indicating that the temperature detection accuracy of the device is relatively high.

Claims

1. A temperature measurement method based on diamond first-order Raman spectroscopy, characterized in that: include: Step 1: collecting first-order Raman spectrum data of diamond at different temperatures by using a Raman spectrometer, and recording corresponding temperature values ​​as a data set; Step 2 is based on the data set obtained in step 1, and is fitted by a Voigt fitting function, wherein the Gauss width is consistent with the resolution of the Raman spectrometer in step 1, and the half-width value, center position and peak intensity of the Raman peak corresponding to each temperature value are obtained. The expression of the Voigt fitting function is as follows: y=y0+(f1(x)*f2(x)) Among them, y0 is the vertical coordinate offset between the fitting curve and the actual spectrum, x is the horizontal coordinate value of the first-order Raman spectrum, and x c is the Raman shift, A is the peak area, w L is the Lorentz width, w G is the Gaussian width; Step 3: Based on the data obtained by fitting in step 2 and the corresponding temperature values, a monotonic function curve group about temperature change is constructed through nonlinear fitting: Based on the half-width value of the Raman peak and the corresponding temperature value, a half-width-temperature standard curve is constructed; Based on the center position of the Raman peak and the corresponding temperature value, a Raman shift-temperature standard curve is constructed; Based on the peak intensity of the Raman peak and the corresponding temperature value, an intensity ratio-temperature standard curve is constructed; Step 4: placing the diamond in the temperature field to be measured, collecting the first-order Raman spectrum data at the temperature value by using a Raman spectrometer, and obtaining the half-width value, center position and peak intensity of the corresponding Raman peak by the Voigt fitting function analysis of step 2; Step 5: Input the data measured in step 4 into the monotonic function curve group, and output the final temperature value through analysis and judgment.

2. The temperature measurement method according to claim 1, characterized in that: The diamond in step 1 is single crystal diamond.

3. The temperature measurement method according to claim 1, characterized in that: The different temperatures in step 1 refer to collecting data every 50K in the temperature range of 300K-1200K, and the heating time of the diamond is not less than 1 minute.

4. The temperature measurement method according to claim 1, characterized in that: The Raman spectrometer in step 1 emits 532nm green light and collects scattered signals in the range of 1280cm -1 -1350cm -1 , the acquisition time is 10s.

5. The temperature measurement method according to claim 1, characterized in that: The peak intensity in step 2 includes anti-Stokes peak intensity and Stokes peak intensity.

6. The temperature measurement method according to claim 1, characterized in that: The analysis and judgment in step 5 is based on the difference between the maximum and minimum values ​​of the output results of the three temperature standard curves: when the difference is greater than the threshold, the temperature needs to be re-measured; When the difference is less than the threshold, the average of the three output results is calculated and output as the final temperature value.

7. A temperature measuring device for implementing the temperature measuring method based on diamond first-order Raman spectroscopy according to any one of claims 1 to 6, characterized in that: include: A detection module is used to contact the object to be tested or extend into the space to be tested to obtain first-order Raman spectrum data; A spectrum analysis module, used for analyzing the first-order Raman spectrum data acquired by the detection module; The temperature analysis module judges the analysis results of the spectrum analysis module and outputs the final temperature value; The judgment process of the temperature analysis module is as follows: Step 1: collecting first-order Raman spectrum data of diamond at different temperatures by using a Raman spectrometer, and recording corresponding temperature values ​​as a data set; Step 2 is based on the data set obtained in step 1, and is fitted by a Voigt fitting function, wherein the Gauss width is consistent with the resolution of the Raman spectrometer in step 1, and the half-width value, center position and peak intensity of the Raman peak corresponding to each temperature value are obtained. The expression of the Voigt fitting function is as follows: y=y0+(f1(x)*f2(x)) Among them, y0 is the vertical coordinate offset between the fitting curve and the actual spectrum, x is the horizontal coordinate value of the first-order Raman spectrum, and x c is the Raman shift, A is the peak area, w L is the Lorentz width, w G is the Gaussian width; Step 3: Based on the data obtained by fitting in step 2 and the corresponding temperature values, a monotonic function curve group about temperature change is constructed through nonlinear fitting: Based on the half-width value of the Raman peak and the corresponding temperature value, a half-width-temperature standard curve is constructed; Based on the center position of the Raman peak and the corresponding temperature value, a Raman shift-temperature standard curve is constructed; Based on the peak intensity of the Raman peak and the corresponding temperature value, an intensity ratio-temperature standard curve is constructed; Step 4: placing the diamond in the temperature field to be measured, collecting the first-order Raman spectrum data at the temperature value by using a Raman spectrometer, and obtaining the half-width value, center position and peak intensity of the corresponding Raman peak by the Voigt fitting function analysis of step 2; Step 5: Input the data measured in step 4 into the monotonic function curve group, and output the final temperature value through analysis and judgment.

8. The temperature measuring device according to claim 7, characterized in that: The detection module comprises a diamond probe, a high temperature resistant and oxidation resistant material coated on the diamond and a matching Raman spectrometer.

9. The temperature measuring device according to claim 8, characterized in that: The high temperature resistant and anti-oxidation material is aluminum nitride.

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