Non-contact transient high-temperature measurement system based on LIBS (laser-induced breakdown spectroscopy)

Abstract

The invention belongs to the technical field of laser high-temperature measurement, and discloses a non-contact transient high-temperature measurement system based on LIBS (laser-induced breakdown spectroscopy), which comprises an LIBS heating device; a temperature control device; a base material posture adjusting device; provided is a spectrum modulation detection device. According to the non-contact transient high-temperature measurement system based on LIBS, through accurate control of laser, a tiny breakdown area is generated on the surface of a base material, instant temperature rise is achieved, atoms or molecules in the base material are promoted to be excited, spectral signals are generated, local instant analysis of the base material and rapid capture of the sample state are achieved, and the measurement accuracy is improved. The whole base material is prevented from being analyzed, so that time and cost are saved; meanwhile, the laser beams directly irradiate the surface of the base material for analysis, direct contact with the base material is not needed, damage and pollution to the base material are avoided, and spectral pollution of water vapor and carbon dioxide is also eliminated.

Description

Technical Field

[0001] The present invention relates to the field of laser high temperature measurement technology, and in particular to a non-contact transient high temperature measurement system based on LIBS. The transmission spectrum of a sample is measured and acquired by FTIR. Through in-depth analysis of the transmission spectrum, basic parameters of the radiation characteristics of a material can be effectively identified. Background Art

[0002] In the analysis of structural heat transfer characteristics and thermal protection design, contact thermal resistance is one of the important parameters, and the accuracy of its value is directly related to the quality of thermal control design. Contact thermal resistance is a nonlinear problem that is affected by many factors such as temperature, load, medium, material thermal properties, surface roughness, material mechanical characteristics, material surface properties, and environment. Existing theoretical models are difficult to use in practice. Overestimation or underestimation of the thermal resistance between contact interfaces will affect the heat transfer of the structure, which may lead to low efficiency of the structure or cause safety hazards in severe cases.

[0003] There are two methods for measuring contact thermal resistance: steady-state measurement method and transient measurement method. The steady-state method has a simple device and a mature method, but the measurement time is long. The transient method includes laser photothermal measurement method, thermal imaging method, flash method, etc. Its advantages are fast response, non-contact, and the size of the measured sample can be as small as the nanometer level, but its measurement process is easily affected by various factors, and the formula derivation is relatively complex, and the measurement accuracy is difficult to guarantee.

[0004] Therefore, there is an urgent need for a high-temperature measurement system that avoids contact with the measurement substrate and quickly realizes the basic parameters of the radiation characteristics of the substrate to make up for the technical defects of the traditional contact thermal resistance measurement method. Summary of the invention

[0005] The purpose of the present invention is to provide a non-contact transient high temperature measurement system based on LIBS, which can realize rapid capture and analysis of sample status through precise control of laser. The high temperature generated by laser pulse is a transient process. This rapid response capability makes LIBS technology very suitable for occasions requiring real-time monitoring and rapid decision-making, such as quality control and fault analysis in industrial production, to realize instant analysis of local substrates, to quickly obtain element information, to avoid analyzing the entire substrate, and to save time and cost; at the same time, the laser beam is directly irradiated to the surface of the substrate for analysis, without direct contact with the substrate, to avoid damage and contamination to the substrate, and to eliminate spectral contamination of water vapor and carbon dioxide; the advantage of high temperature measurement in the present invention is that LIBS technology can excite extremely high temperature environments, and LIBS technology excites the original through focused pulsed laser ablation to generate transient high temperature plasma, which enables it to play an important role in high temperature environments that some traditional temperature measurement technologies are not competent for.

[0006] To achieve the above object, the present invention provides a non-contact transient high temperature measurement system based on LIBS, comprising:

[0007] (1) The LIBS heating device includes: laser, laser reflector, light receiving lens, optical fiber, and spectrometer;

[0008] LIBS uses focused pulsed laser to directly act on the surface of the substrate, causing the temperature to rise rapidly. The locally high-temperature substrate melts and evaporates instantly, generating plasma.

[0009] (2) Temperature control device: The temperature rise range is 300-3400K. During the heating process, the difference between the set temperature and the temperature control temperature is ensured to be less than 3%, so that the heating power remains stable;

[0010] (3) Substrate posture adjustment device: Based on the molybdenum specimen holder, the substrate posture is adjusted;

[0011] (4) Spectral modulation detection device: Use FTIR to identify the basic parameters of the substrate radiation characteristics.

[0012] Preferably, in the LIBS heating device, the laser generates laser pulses with high energy and power density required for the experiment;

[0013] The laser reflector changes the optical path of the laser pulse, focuses the laser pulse to a point along a direction perpendicular to the substrate, and then acts on the substrate;

[0014] The light collecting lens collects light generated by plasma excitation;

[0015] The optical fiber transmits the light collected by the light-collecting lens to the spectrometer.

[0016] Preferably, the LIBS heating device is equipped with pre-vacuum equipment, argon backfilling equipment, water cooling equipment, and temperature measuring equipment.

[0017] Preferably, the molybdenum specimen holder is composed of a loading platform, a load-bearing balance plate and an elastic sealing ring; in a hot state, the molybdenum specimen holder can rotate ±180° with an accuracy of 0.01°, and the rotation operation of the molybdenum specimen holder is completely achieved by a computer controlling a stepping motor through instructions.

[0018] Preferably, the stage comprises a slot and a support structure so that the substrate does not slip when rotating with the molybdenum specimen holder;

[0019] The load-bearing balance plate uses a lever principle to adjust the horizontal posture of the molybdenum specimen support using a multi-layer load-bearing balance plate to ensure that the stage carries the substrate horizontally;

[0020] During the rotation of the molybdenum specimen holder, the elastic sealing ring always isolates the heating chamber from the outside world, ensuring the high-pressure argon atmosphere in the heating chamber.

[0021] Preferably, the identification of the basic parameters of the radiation characteristics of the substrate by FTIR is carried out in the following specific steps:

[0022] S1. After the light emitted by the light source enters the interferometer, half of the energy is irradiated onto the moving mirror through the beam splitter, and then reflected back to the beam splitter by the moving mirror; the other half of the energy is reflected multiple times by the static mirror and then returns to the beam splitter;

[0023] S2, after modulation by the beam splitter, interference occurs between the two split beams, and the interference pattern is obtained by Fourier transform, and then the spectrum distribution diagram is obtained by inverse Fourier transform;

[0024] S3. The detected radiation energy is converted into a response voltage signal through a photodetector and output.

[0025] Preferably, the photodetector comprises: an InGaAs diode photodetector with a detection range of 0.85-2.5 μm and a noise equivalent power NEP < 2×10 -14 W·Hz -1 / 2 ;

[0026] DLATGS pyroelectric detector, detection range 0.8-28.6μm, specific detection rate D * >4×10 8 cm·Hz -1 / 2 ·W -1 .

[0027] Preferably, by detecting the light source signal voltage response U 0,λ and the transmission signal voltage response U t,λ , and obtain the normal-normal transmittance of the sample, as shown below:

[0028]

[0029] Among them, U 0,λ is the light source signal voltage response, U t,λ is the voltage response of the transmission signal.

[0030] Preferably, the relationship between the offset distance δ and the incident light beam convergence angle is as follows:

[0031]

[0032] Preferably, the transmittance of a single-layer medium is as follows:

[0033]

[0034] The transmittance is shown below:

[0035]

[0036] The interface reflectivity is shown below:

[0037]

[0038] Among them, τ t represents the transmittance of a single-layer medium, κ represents the absorption index of the material, and λ represents the wavelength.

[0039] Therefore, the present invention adopts the above-mentioned LIBS-based non-contact transient high temperature measurement system, and the beneficial effects are as follows:

[0040] (1) The present invention generates a very small breakdown area on the surface of the substrate through precise control of the laser, and excites the original element through focused pulse laser ablation, which instantly heats up the temperature, causing the atoms or molecules in the substrate to be excited, generating transient high-temperature plasma, and generating spectral signals, thereby achieving instant heating of the substrate locally, quickly obtaining element information, avoiding analysis of the entire substrate, and saving time and cost.

[0041] (2) At the same time, the laser beam is directly irradiated onto the surface of the substrate for analysis without direct contact with the substrate, thus avoiding damage and contamination to the substrate and eliminating spectral contamination from water vapor and carbon dioxide. LIBS technology plays an important role in high-temperature environments where traditional temperature measurement technologies are unable to cope.

[0042] (3) For materials with strong transmission signals, the present invention utilizes the internal precision optical path design of FTIR to measure and obtain the transmission spectrum of the sample. Through in-depth analysis of the transmission spectrum, the basic parameters of the material's radiation characteristics can be effectively identified, providing important experimental basis and theoretical support for material performance research, quality control and the development of new materials.

[0043] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0045] Figure 2 This is a LIBS heating structure diagram of the LIBS-based non-contact transient high temperature measurement system of the present invention;

[0046] Figure 3 1 is a LIBS device diagram of the LIBS-based non-contact transient high temperature measurement system of the present invention;

[0047] Figure 4 This is a LIBS high temperature detection flow chart of the LIBS-based non-contact transient high temperature measurement system of the present invention;

[0048] Figure 5 It is a relationship diagram between heating power and set temperature of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0049] Figure 6 It is a temperature difference diagram between the set temperature and the controlled temperature of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0050] Figure 7 It is a rotating molybdenum specimen holder of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0051] Figure 8 It is a control interface of a rotating molybdenum specimen support of a non-contact transient high temperature measurement system based on LIBS of the present invention;

[0052] Fig. 9 This is a measurement principle diagram of the FTIR spectrometer of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0053] Fig.10 This is a schematic diagram of the internal optical path of the FTIR spectrometer of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0054] Fig.11 The light focusing point of the non-contact transient high temperature measurement system based on LIBS of the present invention after being refracted by the substrate is located inside the substrate;

[0055] Fig.12 The light focusing point of the non-contact transient high temperature measurement system based on LIBS of the present invention after being refracted by the substrate is located outside the substrate;

[0056] Fig.13 It is the refractive index curve of a typical optical window material of the non-contact transient high temperature measurement system based on LIBS of the present invention;

[0057] Fig.14 The non-contact transient high temperature measurement system based on LIBS of the present invention can measure the maximum thickness of typical optical window materials using an FTIR spectrometer. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0059] like Figure 1As shown, for the measurement of radiation characteristics of substrates under high temperature conditions, the present invention designs a non-contact transient high temperature measurement system based on Laser-Induced Breakdown Spectroscopy (LIBS), including:

[0060] (1) The LIBS heating device includes: laser, laser reflector, light receiving lens, optical fiber, and spectrometer;

[0061] LIBS uses focused pulsed laser to directly act on the surface of the substrate, causing the temperature to rise rapidly. The locally high-temperature substrate melts and evaporates instantly, generating plasma.

[0062] (2) Temperature control device: The temperature rise range is 300-3400K. During the heating process, the difference between the set temperature and the temperature control temperature is ensured to be less than 3%, so that the heating power remains stable;

[0063] (3) Substrate posture adjustment device: Based on the molybdenum specimen holder, the substrate posture is adjusted;

[0064] (4) Spectral modulation detection device: Fourier Transform infrared spectroscopy (FTIR) is used to identify the basic parameters of the radiation characteristics of the substrate. Among them, the FTIR spectrometer has the following advantages:

[0065] 1) Multi-channel: several times that of traditional slit spectrometers;

[0066] 2) High resolution: resolution up to 0.1-0.0035cm -1 ;

[0067] 3) High throughput: signal-to-noise ratio up to 55,000:1;

[0068] 4) Fast scanning speed: the continuous scanning sampling rate can reach 105 images / second, and the step scanning time resolution can reach 5ns;

[0069] 5) High sensitivity: 100-1000 times the sensitivity of dispersive instruments.

[0070] The measurement system can measure the transmittance and reflectance of typical translucent materials in multiple directions, with a high signal-to-noise ratio. The main technical indicators are: temperature range: 210-3000K; the measurement accuracy of transmittance and reflectance is better than 0.1%, that is, the maximum allowable error is 0.1%; working wavelength range: 0.4-15μm.

[0071] Example 1

[0072] The present invention discloses a non-contact transient high temperature measurement system based on LIBS, comprising: a LIBS heating device; a temperature control device; a substrate posture adjustment device; and a spectrum modulation detection device.

[0073] (1) LIBS heating device;

[0074] The function of LIBS is to melt and evaporate the substrate in the action area instantly through the focused pulsed laser, and ionize it to form a high-temperature plasma. Compared with the traditional atomic emission spectroscopy technology, the LIBS heating device has the advantages of no need for substrate pretreatment, multi-element synchronous detection, applicability to substrates in any state, and ability to achieve in-situ or online measurement.

[0075] like Figure 2 As shown in Figure 1, the LIBS heating device mainly includes a laser, a laser reflector, a light-collecting lens, an optical fiber, a spectrometer, etc.; the heating body is equipped with a pre-vacuum device, an argon backfilling device, a water cooling device, a temperature measuring device, etc., and has a lifting function; the technical parameters of the LIBS heating device are shown in Table 1.

[0076] Table 1 Technical parameters of the heating device

[0077] name Technical Parameters name Technical Parameters Working Mode: Argon atmosphere, 100-110 kPa Uniform temperature zone design: Φ65×90mm Allowable load: 1Kg@1800℃ Temperature uniformity performance: ±5℃@3000℃ Stage: Rotation ±180°, accuracy 0.01° Maximum temperature: 3400℃ Argon source pressure: 0.2MPa Operating Temperature: 2000℃ Installed capacity: 6KVA (kilovolt-ampere) Heating rate: 5-10℃ / min Cooling water: <25℃,0.2-0.4MPa

[0078] The function of the laser is to generate laser pulses with high energy and power density required for the experiment; the function of the laser reflector is to change the optical path of the laser pulse, focus it to a point along the direction perpendicular to the sample substrate through the focusing lens and then act on the substrate; the main function of the collecting lens is to collect the light generated by plasma excitation; the function of the optical fiber is to transmit the light collected by the collecting lens to the spectrometer; the stage and the rotating system are fixed to the base of the equipment using elastic heat sealing technology.

[0079] like Figure 3 As shown in the figure, the substrate is placed on the electric translation stage in the LIBS measurement system, and the focused pulsed laser excites the plasma, and the optical fiber spectrometer of the detector detects the plasma spectrum. The spectrometer collects these spectra and performs spectroscopic processing on these lights, and emits different spectral signals; the interaction process between the material and the laser is very complicated, because the laser pulse applied to the substrate through the focusing lens will cause the surface temperature of the material to rise rapidly, and cause the locally high-temperature substrate to ablate, thereby generating plasma, such as Figure 4 shown.

[0080] LIBS technology is a non-contact analysis method. The laser beam can be directly irradiated onto the surface of the substrate for analysis without direct contact with the substrate, thus avoiding damage and contamination to the substrate. At the same time, it can eliminate spectral contamination from water vapor and carbon dioxide.

[0081] LIBS technology uses precise control of the laser to produce a very small breakdown area on the surface of the substrate, thereby achieving local analysis of the substrate. This precise control ensures that only the targeted area is analyzed, avoiding analysis of the entire substrate, saving time and cost. When the laser breaks through the substrate, it will generate high-temperature plasma, causing the substrate to heat up instantly. This instantaneous heating is very fast, and the substrate reaches a high temperature almost immediately after laser irradiation, so a transient high-temperature environment can be achieved.

[0082] (2) Temperature control device;

[0083] The relationship between heating power and setting and control temperature in a typical heating process with a heating range of 300-3400K, such as Figure 5 As shown in the figure. The set temperature is the preset temperature at each moment of the heating process, and the temperature control temperature is the real-time measured reference temperature in the heating furnace. The heating time is designed to be 250 minutes. During the heating process, the maximum difference between the set temperature and the temperature control temperature is in the heating start section. This is because the set start temperature is 0K, while the start temperature in the heating furnace is room temperature (~300K). Figure 6 shown.

[0084] During the entire heating process, the difference between the set temperature and the control temperature is less than 10 K. In the heating time range of 25-50 minutes, when the difference between the set temperature and the control temperature jumps by 10 K, the heating power also jumps unstably.

[0085] Therefore, during the heating process, especially the heat preservation process, that is, the time period of measurement, the jump of heating power should be avoided as much as possible, otherwise it will inevitably cause a jump in temperature. Figure 5 and Figure 6 As shown in the figure, when the difference between the set temperature and the control temperature is less than 5K, the heating power will be relatively stable. Therefore, in any heating process, the reasonable heating time should be ensured that the set temperature and the control temperature are less than 5K.

[0086] (3) a substrate posture adjustment device;

[0087] The measurement of the directional transmittance and reflectance designed in the present invention depends to some extent on the adjustment of the substrate posture. The substrate posture directly determines the relative relationship between the incident light, the outgoing light and the substrate, which will affect the final measurement result.

[0088] The present invention designs a molybdenum specimen holder that can rotate ±180° in a hot state with an accuracy of 0.01°. Molybdenum is selected as the specimen holder material because metal molybdenum has the characteristics of being hard and tough and not easy to deform; it is resistant to high temperatures and can still maintain good mechanical properties at high temperatures; it has a high density and can use a multi-layer load-bearing balance plate to adjust the horizontal posture of the molybdenum specimen holder.

[0089] like Figure 7 As shown in the figure, the rotating molybdenum specimen holder is mainly composed of a stage, a load-bearing balance plate and an elastic sealing ring, and can bear a substrate of 1 kg at 1800°C. The slot and support structure of the stage can prevent the substrate from slipping when the molybdenum specimen holder rotates; the load-bearing balance plate can adjust the horizontal posture of the molybdenum specimen holder through the principle of levers and use multiple layers of load-bearing balance plates to ensure that the stage carries the substrate horizontally; during the rotation of the molybdenum specimen holder, the elastic sealing ring can isolate the heating chamber from the outside world at all times, ensuring the high-pressure argon atmosphere in the heating chamber.

[0090] The rotation operation of the substrate is completely realized by the computer through the command control stepper motor, the control interface of the rotation operation, such as Figure 8 When operating the substrate rotation, first click the "Workpiece Rotation Start" button, and the button will turn green; when the "Workpiece Allowed to Rotate" button turns green, it means that the stepper motor has started and is ready to perform the substrate rotation operation; enter the angle to be rotated in the setting angle window, click the "Confirm" button, and the substrate will stop after rotating at the set angle.

[0091] The positive and negative signs when inputting the angle indicate the direction of the angle rotation (clockwise and counterclockwise). Due to the existence of gear backlash in the rotation system reducer, when the substrate is switched between forward and reverse rotation, there will be a deviation between the actual substrate rotation angle and the displayed rotation angle.

[0092] In order to eliminate this deviation, when adjusting the initial angle of the substrate, you should first adjust it and then reset it to zero, that is, return the angle to zero. Specifically, when adjusting the angle of the substrate, first rotate it in a certain direction (clockwise or counterclockwise) and exceed the set initial angle, then rotate it in the opposite direction to the angle to be set, and press the "Reset" button to return to zero. After the angle is reset to zero, during the operation of the device, it only rotates in the last rotation direction to ensure that the displayed substrate rotation angle is consistent with the actual substrate rotation angle.

[0093] (4) Spectral modulation detection device;

[0094] For materials with strong transmission signals, the transmission spectrum can be measured by using the internal optical path of the FTIR spectrometer, which can be used to identify the basic parameters of the material's radiation characteristics. The FTIR spectrometer used in the present invention is BrukerVertex 70. The measurement principle diagram of the FTIR spectrometer is as follows: Fig. 9 shown.

[0095] The FTIR spectrometer is equipped with two light sources:

[0096] The NIR light source is a halogen tungsten light source (0.66-5.0μm);

[0097] The MIR light source is a high-energy Globar ceramic light source (1-500μm) with air as the cooling medium.

[0098] The FTIR spectrometer is equipped with two types of photodetectors:

[0099] InGaAs diode photodetector, detection range 0.85-2.5μm, noise equivalent power NEP <2×10 -14 W·Hz -1 / 2 ;

[0100] DLATGS pyroelectric detector, detection range 0.8-28.6μm, specific detection rate D * >4×10 8 cm·Hz -1 / 2 ·W -1 .

[0101] The specific steps for identifying the basic parameters of the radiation characteristics of the substrate using FTIR are as follows:

[0102] S1. After the light emitted by the light source enters the Michelson interferometer, half of the energy is irradiated onto the moving mirror through the beam splitter, and then reflected back to the beam splitter by the moving mirror; the other half of the energy is reflected multiple times by the static mirror and then returns to the beam splitter;

[0103] S2, after modulation by the beam splitter, interference occurs between the two split beams, and the interference pattern is obtained by Fourier transform, and then the spectrum distribution diagram is obtained by inverse Fourier transform;

[0104] S3. The detected radiation energy is converted into a response voltage signal through a photodetector and output.

[0105] During measurement, the voltage response U of the light source signal is detected. 0,λ and the transmission signal voltage response U t,λ , and obtain the normal-normal transmittance of the sample, as shown below:

[0106]

[0107] Considering that the incident light source in the internal optical path of the FTIR spectrometer is a converging beam, there is a certain deviation from the commonly used normal incidence assumption, so it is necessary to analyze the impact of the optical path configuration on the material transmittance measurement results. Theoretically, due to the converging characteristics of the incident light beam, the transmission path of the light in the substrate will increase. Considering the attenuation characteristics of the material, the final detected transmission signal should be smaller than the theoretical normal transmission signal.

[0108] Will be like Fig. 9 The measurement schematic shown is simplified to Fig.10The optical path shown is used as the analysis object to derive the relationship between the incident light beam convergence angle and the final detected transmission signal. The attenuation effect of the substrate is not considered in this analysis, and only the directional transmission process of the light is analyzed.

[0109] Taking the BrukerVertex70 FTIR spectrometer as the analysis prototype, we first analyze the effect of the offset distance δ between the light emission point of the ellipsoid reflector in front of the detector and the focal position of the ellipsoid reflector on whether the final light can reach the detector. The analysis found that for the detector diameter of 1mm in this study, as long as the offset distance is less than 13mm, it can ensure that all light passing through the substrate can be reflected by the ellipsoid reflector and received by the detector.

[0110] According to Snell's law, the offset distance δ (i.e. |OO 2 |) and the incident beam convergence angle, as shown below:

[0111]

[0112] like Fig.11 and Fig.12 The light transmission principle shown in FIG. 1 shows that the offset distance δ is related to three factors: the thickness of the sample, the refractive index and the incident angle of the light.

[0113] According to the above derivation results, the incident beam convergence angle of the spectrometer is about 6°, and the measurable substrate thickness of the optical window material corresponding to different refractive index curves in the internal optical path of the FTIR spectrometer is calculated respectively. The dispersion curve of a typical optical window material, such as Fig.13 As shown, the maximum thickness of the substrate that can be measured is calculated as follows: Fig.14 shown.

[0114] Analysis shows that within the near-infrared band, for common optical window materials, as long as their thickness is less than 20mm, they are suitable for this type of measurement; among them, for quartz glass with a lower refractive index, as long as the thickness to be measured is less than 40mm, it will be fine.

[0115] Through the above analysis, as long as the thickness of the substrate to be measured meets the conditions, it can be guaranteed that the FTIR spectrometer can collect all the transmitted light. The transmittance of the single-layer medium is as follows:

[0116]

[0117] Considering the convergence characteristics of the incident light beam, the expressions of transmittance and interface reflectivity need to take into account the influence of the incident angle.

[0118] Where the transmittance is given by:

[0119]

[0120] The interface reflectivity is shown below:

[0121]

[0122] If the incident light beam is parallel, the transmittance can be simplified to:

[0123]

[0124] The interface reflectivity can be simplified as:

[0125]

[0126] Among them, τ t represents the transmittance of a single-layer medium, κ represents the absorption index of the material, and λ represents the wavelength.

[0127] If the incident light beam is parallel, the radiation characteristics of the material can be calculated by measuring the transmittance of the same material at different thicknesses, that is, the double thickness method. The initial value of the absorption index is as follows:

[0128]

[0129] The objective function is iterated using a genetic algorithm (GA) as follows:

[0130]

[0131] Among them, τ t1 and τ t2 Represent different thicknesses L 1 and L 2 The transmittance of a single layer of material under the microscope is shown in Figure 2, while the subscript e represents the experimental transmittance and the subscript c represents the calculated transmittance.

[0132] Example 2

[0133] The application of the non-contact transient high temperature measurement system based on LIBS in the present invention in different fields is as follows:

[0134] The non-contact transient high temperature measurement system based on LIBS can be used in materials science research and industrial applications, especially in measuring high temperature failure of materials. In high temperature environments, materials may fail due to thermal stress, phase change, oxidation or melting, and these failure mechanisms have a direct impact on the performance, reliability and service life of the materials. The system uses the change in the radiation energy of the object to measure the temperature without direct contact with the measured material, thus avoiding thermal interference and errors caused by contact.

[0135] This non-contact measurement method enables the system to accurately capture the transient temperature changes of materials in high-temperature environments and provide researchers with experimental data. In the measurement of high-temperature failure of materials, the non-contact transient high-temperature measurement system can monitor the temperature changes of materials during heating in real time, as well as the response of materials when the critical temperature is reached. Through these data, researchers can analyze key parameters such as thermal stability, thermal expansion coefficient, melting point, etc. of the material, and then evaluate the reliability and durability of the material in high-temperature environments.

[0136] In the transmitting unit of communication equipment and the antenna array of radar system, the transmission and processing of high-power microwave signals are often accompanied by significant heat generation. If these high-temperature areas cannot be effectively monitored, it may lead to material performance degradation, thermal failure and even system failure. By using LIBS's non-contact transient high-temperature measurement system to measure the temperature changes of materials such as transmitting units and antenna arrays during transient heating, as well as the response of materials when the critical temperature is reached, and continuously recording and analyzing these high-temperature data, engineers can evaluate the thermal tolerance limit of materials, optimize heat dissipation design, and ensure the stable operation of communication and radar systems under extreme conditions. In addition, the system can also provide valuable test data in the material research and development stage, helping researchers to screen out materials that are more suitable for high-temperature working environments, thereby improving the reliability and durability of the entire system.

[0137] LIBS's non-contact transient high temperature measurement system can also measure the thermal conductivity of materials used in spacecraft and space stations. Under extreme temperature conditions, such as the thermal protection system of high-speed spacecraft or the interface between space stations exposed to direct sunlight and the vacuum of the universe, the thermal conductivity of materials is directly related to the thermal management efficiency of the system and the safety of long-term operation. These parameters are crucial for the design and optimization of thermal protection layers of spacecraft, thermal insulation materials and heat dissipation systems of space stations. For example, when a spacecraft re-enters the atmosphere, its surface temperature rises sharply, and effective thermal protection materials need to be able to dissipate heat quickly to avoid structural overheating and potential thermal failure.

[0138] In summary, the non-contact transient high temperature measurement system has unique advantages in measuring high-temperature failure of materials, evaluating the thermal tolerance limit of materials, and screening materials with excellent thermal conductivity and high temperature resistance. It is an indispensable tool for materials science research and industrial applications.

[0139] Therefore, the present invention adopts the above-mentioned LIBS-based non-contact transient high-temperature measurement system, and through the precise control of the laser, a very small breakdown area is generated on the surface of the substrate, which is instantly heated up, so that the atoms or molecules in the substrate are excited and a spectral signal is generated, thereby realizing instant analysis of the local part of the substrate, quickly obtaining element information, avoiding analysis of the entire substrate, and saving time and cost; at the same time, the laser beam is directly irradiated onto the surface of the substrate for analysis without direct contact with the substrate, thus avoiding damage and contamination to the substrate and eliminating spectral contamination by water vapor and carbon dioxide.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. LIBS-based non-contact transient high temperature measurement system, characterized by: include: (1) The LIBS heating device includes: laser, laser reflector, light receiving lens, optical fiber, and spectrometer; LIBS uses focused pulsed laser to directly act on the surface of the substrate, causing the temperature to rise rapidly. The locally high-temperature substrate melts and evaporates instantly, generating plasma. (2) Temperature control device: The temperature rise range is 300-3400K. During the heating process, the difference between the set temperature and the temperature control temperature is ensured to be less than 3%, so that the heating power remains stable; (3) Substrate posture adjustment device: Based on the molybdenum specimen holder, the substrate posture is adjusted; (4) Spectral modulation detection device: Use FTIR to identify the basic parameters of the substrate radiation characteristics.

2. The LIBS-based non-contact transient high temperature measurement system according to claim 1, characterized in that: In the LIBS heating device, the laser generates laser pulses with high energy and power density required for the experiment; The laser reflector changes the optical path of the laser pulse, focuses the laser pulse to a point along a direction perpendicular to the substrate, and then acts on the substrate; The light collecting lens collects light generated by plasma excitation; The optical fiber transmits the light collected by the light-collecting lens to the spectrometer.

3. The LIBS-based non-contact transient high temperature measurement system according to claim 1, characterized in that: The LIBS heating device is equipped with pre-vacuum equipment, argon backfilling equipment, water cooling equipment, and temperature measuring equipment.

4. The LIBS-based non-contact transient high temperature measurement system according to claim 1, characterized in that: The molybdenum specimen holder is composed of a loading platform, a load-bearing balance plate and an elastic sealing ring; in a hot state, the molybdenum specimen holder can rotate ±180° with an accuracy of 0.01°, and the rotation operation of the molybdenum specimen holder is completely achieved by a computer controlling a stepping motor through instructions.

5. The LIBS-based non-contact transient high temperature measurement system according to claim 4, characterized in that: The stage comprises a slot and a support structure, so that the substrate does not slip when rotating with the molybdenum specimen support; The load-bearing balance plate uses a lever principle to adjust the horizontal posture of the molybdenum specimen support using a multi-layer load-bearing balance plate to ensure that the stage carries the substrate horizontally; During the rotation of the molybdenum specimen holder, the elastic sealing ring always isolates the heating chamber from the outside world, ensuring the high-pressure argon atmosphere in the heating chamber.

6. The LIBS-based non-contact transient high temperature measurement system according to claim 1, characterized in that: The specific steps for identifying the basic parameters of the radiation characteristics of the substrate using FTIR are as follows: S1. After the light emitted by the light source enters the interferometer, half of the energy is irradiated onto the moving mirror through the beam splitter, and then reflected back to the beam splitter by the moving mirror; the other half of the energy is reflected multiple times by the static mirror and then returns to the beam splitter; S2, after modulation by the beam splitter, interference occurs between the two split beams, and the interference pattern is obtained by Fourier transform, and then the spectrum distribution diagram is obtained by inverse Fourier transform; S3. The detected radiation energy is converted into a response voltage signal through a photodetector and output.

7. The LIBS-based non-contact transient high temperature measurement system according to claim 6, characterized in that: The photodetector comprises: an InGaAs diode photodetector with a detection range of 0.85-2.5 μm and a noise equivalent power NEP < 2×10 -14 W·Hz -1 / 2 ; DLATGS pyroelectric detector, detection range 0.8-28.6μm, specific detection rate D * >4×10 8 cm·Hz -1 / 2 ·W -1 .

8. The LIBS-based non-contact transient high temperature measurement system according to claim 6, characterized in that: By detecting the light source signal voltage response U 0,λ and the transmission signal voltage response U t,λ , and obtain the normal-normal transmittance of the sample, as shown below: Among them, U 0,λ is the light source signal voltage response, U t,λ is the voltage response of the transmission signal.

9. The LIBS-based non-contact transient high temperature measurement system according to claim 8, characterized in that: The relationship between the offset distance δ and the incident light beam convergence angle is as follows:

10. The LIBS-based non-contact transient high temperature measurement system according to claim 9, characterized in that: The transmittance of a single-layer medium is as follows: The transmittance is shown below: The interface reflectivity is shown below: Among them, τ t represents the transmittance of a single-layer medium, κ represents the absorption index of the material, and λ represents the wavelength.

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