Device and method for measuring melting point of ultrahigh-temperature material

Abstract

The invention discloses an ultrahigh-temperature material melting point measuring device and method. The ultrahigh-temperature material melting point measuring device comprises a closed measuring chamber (10), a sample table (20) arranged in the measuring chamber (10) and used for placing a to-be-measured sample (100), a plasma system connected to at least one side of the measuring chamber (10) and used for generating plasma jet as a heat source to heat the to-be-measured sample (100), and a non-contact temperature measuring unit used for measuring the temperature of the to-be-measured sample (100), the measuring chamber (10) is provided with at least one temperature measuring window (11) corresponding to the non-contact temperature measuring unit and at least one observation window (12) used for shooting and recording. The device adopts a plasma heating mode to heat the sample (100) with the melting point to be measured, the sample (100) to be measured can be melted in a surface heating mode, the melting point of the sample (100) to be measured can be obtained by combining temperature measurement, and the problems of small light spots and difficulty in temperature information extraction of laser measurement of the melting point are solved; by synchronously measuring the deformation process of the to-be-measured sample (100) when the to-be-measured sample (100) is heated by the plasma and the temperature, the measurement accuracy is improved.

Description

Ultra-high temperature material melting point measuring device and method Technical Field

[0001] The present invention relates to the technical field of material melting point measurement, and in particular to a device and method for measuring the melting point of an ultra-high temperature material. Background Art

[0002] Melting point is a key physical property of a substance, the temperature at which it transitions from solid to liquid. The melting point of nuclear materials is a fundamental parameter in nuclear device design and is crucial to device safety.

[0003] On March 23, 2022, the National Nuclear Safety Administration (NNSA) released the "Guidelines for the Review of Nuclear Fuel Assemblies for Pressurized Water Reactor Nuclear Power Plants." Appendix 1 of the guidelines outlines the design basis for nuclear fuel assemblies. The explanation for the design basis "pellet-cladding interaction" states that two criteria are adopted. The second criterion is that "pellet volume changes caused by fuel melting should be avoided." This is because the increase in pellet volume associated with melting can cause stress on the cladding caused by the centrally melted pellet. Preventing fuel melting can avoid this pellet-cladding interaction. Therefore, the melting point of nuclear fuel pellets becomes one of the design criteria for fuel assembly review.

[0004] In the field of ATF research and development, SiC cladding is an important direction, and the melting point of the SiC material used to prepare the cladding is also one of the important parameters in nuclear design.

[0005] Regarding the melting point of substances, the measurement method recommended by the ICTA Standardization Committee is differential thermal analysis. Using standard substances as a reference, equal amounts of the substance to be tested and the standard substance are subjected to the same heating and cooling rates at a certain experimental temperature. A thermocouple is used to compare the temperatures of the two. The temperature value when a temporary temperature difference increases or decreases is used as the basis for judging whether the material has undergone a phase change.

[0006] However, when measuring high-phase transition point materials in the temperature range of 1000°C to 2500°C, the phase transition point test is affected by the physical properties of the reference material at high temperatures. Furthermore, when using thermocouples such as tungsten-rhenium thermocouples at temperatures above 2500°C, measurement accuracy is poor, resulting in low confidence in the results. Furthermore, when using ultra-high-temperature ceramic materials in some industries, understanding their melting points is crucial. Examples include UO2, UN nuclear fuel pellets, and SiC cladding materials in the nuclear industry, as well as HfC and TaC materials used in the aerospace industry. These materials have melting points reaching 3000°C, and some even higher, making their measurement a significant challenge.

[0007] Currently, there are mainly two methods for measuring the melting point of materials:

[0008] Laser heating is used to melt the material and then measure the melting point using the cooling process. However, these methods have the following drawbacks: Optical path design (reflection and refraction) and modulation are complex and require a high level of experimental skill. Different pulse powers and exposure times must be tried to induce melting, or the laser power must be increased to achieve melting and the melting point determined using the cooling temperature plateau. Because the required temperature is above the material's melting point, physical processes such as sublimation and evaporation occur during the melting process, reducing the sample volume and affecting the measurement. Furthermore, ablation above the melting point may cause changes in the material's composition. Therefore, laser heating methods often require a high-pressure sample chamber, increasing the technical difficulty. During measurement, the pyrometer must be focused on the melting zone. The laser heating spot and the pyrometer temperature measurement spot are of the same order of magnitude. However, the radial temperature gradient in the melting zone is significant. A slight deviation of the temperature measurement spot from the center can result in unclear changes in the resulting curve or even an invisible solidification temperature plateau, making it impossible to determine the melting point (see Melting Transition Measurements in Uranium Dioxide, Fig. 8.15a).

[0009] Chinese patent CN107966468A provides a device and method for measuring the melting point of fuel pellets. This method uses an induction-heated crucible to heat a sample containing a black hole and a pyrometer to measure the temperature. However, during the induction heating process, the sides of the sample melt first, and the pyrometer measures the temperature of the upper end. Furthermore, vacuum conditions favor the decomposition of nuclear fuel materials, adversely affecting temperature measurement. Technical issues

[0010] The technical problem to be solved by the present invention is to provide a device and a method for measuring the melting point of an ultrahigh temperature material. Technical Solutions

[0011] The present invention solves the technical problem by adopting the following technical solution: providing an ultra-high temperature material melting point measuring device, comprising a sealed measuring chamber, a sample stage disposed in the measuring chamber and used to place a sample to be measured, a plasma system connected to at least one side of the measuring chamber and used to generate a plasma jet as a heat source to heat the sample to be measured, and a non-contact temperature measurement unit for measuring the temperature of the sample to be measured;

[0012] The measuring chamber is provided with at least one temperature measuring window corresponding to the non-contact temperature measuring unit and at least one observation window for photographing and recording.

[0013] Preferably, the sample stage is made of a material having a melting point higher than that of the sample to be tested.

[0014] Preferably, the sample stage is installed in the measurement chamber in a position-adjustable or angle-adjustable manner.

[0015] Preferably, the measuring chamber is provided with a sample delivery port for delivering the sample to be measured into the measuring chamber and taking it out from the measuring chamber; the sample delivery port is located above the sample stage in height.

[0016] Preferably, the measuring chamber is provided with an auxiliary sampling port; the auxiliary sampling port is located below the sample stage or at least on one side of the sample stage in terms of height.

[0017] Preferably, the plasma system comprises a plasma torch for generating a plasma jet, and a gas supply unit connected to and providing a working gas to the plasma torch;

[0018] The working gas is an inert gas.

[0019] Preferably, the plasma torch is arranged on the measurement chamber above the sample stage, so that the generated plasma jet directly heats the sample to be measured.

[0020] Preferably, the plasma torch is disposed on the measurement chamber corresponding to below or on the side of the sample stage, so that the generated plasma jet heats the sample stage.

[0021] Preferably, the non-contact temperature measurement unit includes a two-color pyrometer or an infrared thermal imager.

[0022] Preferably, the ultrahigh temperature material melting point measuring device further comprises a pressure maintaining system connected to the measuring chamber and used to control the pressure in the measuring chamber at a predetermined pressure.

[0023] Preferably, the pressure maintaining system comprises a gas container filled with inert gas; the gas container is connected to the measuring chamber via a ventilation pipe, and the pressure in the measuring chamber is controlled by delivering inert gas into the measuring chamber.

[0024] Preferably, the ultrahigh temperature material melting point measuring device further comprises a cooling unit for cooling the side wall of the measuring chamber;

[0025] The cooling unit includes a cooling pipe attached to the wall surface of the measuring chamber; or, the cooling unit includes a cooling interlayer arranged in the side wall of the measuring chamber.

[0026] Preferably, the ultra-high temperature material melting point measuring device further comprises a process gas source system; the process gas source system is connected to the measuring chamber and is used to provide gas to the measuring chamber so as to form a predetermined atmosphere in the measuring chamber.

[0027] Preferably, the ultrahigh temperature material melting point measuring device further comprises a gas purification system connected to the measuring chamber;

[0028] The gas purification system includes a cooler, a filter and an exhaust fan connected in sequence; the cooler receives the gas discharged from the measuring chamber and cools the gas; the filter filters the cooled gas; the exhaust fan is used to provide power to extract the gas in the measuring chamber to drive the gas to pass through the cooler and the filter in sequence.

[0029] Preferably, the ultra-high temperature material melting point measuring device further comprises a control and acquisition system; the control and acquisition system is respectively connected to the plasma system and the non-contact temperature measurement unit for controlling their opening and closing and collecting measurement data.

[0030] Preferably, the sample to be tested is a fuel pellet, a cladding tube or a ceramic component.

[0031] The present invention further provides a method for measuring the melting point of an ultrahigh temperature material, using any of the ultrahigh temperature material melting point measuring devices described above, the method comprising the following steps:

[0032] S1. Send the sample to be tested into the measuring chamber and place it on the sample table;

[0033] S2. Start the plasma system, which generates a plasma jet and fully contacts the sample to be tested, heating the sample to be tested to cause a phase change; at the same time, the phase change process of the sample to be tested is recorded through the observation window on the measurement chamber;

[0034] S3, measuring the temperature of the sample to be tested by a non-contact temperature measurement unit to obtain the temperature change of the sample to be tested during the phase change process;

[0035] S4. Determine the melting point or phase transition point of the sample to be tested based on the recorded phase transition region and the corresponding temperature of the sample to be tested.

[0036] Preferably, step S2 further includes: delivering inert gas into the measuring chamber through a pressure maintaining system to maintain the pressure in the measuring chamber at a predetermined pressure; and / or, providing gas to the measuring chamber through a process gas source system to form a predetermined atmosphere in the measuring chamber.

[0037] Preferably, step S2 further comprises: cooling the side walls of the measuring chamber by flowing cooling water, so that the outer wall temperature of the measuring chamber is not higher than 50°C and the inner wall temperature is not higher than 800°C.

[0038] Preferably, the sample to be tested is a fuel pellet, a cladding tube or a ceramic component. Beneficial effects

[0039] The beneficial effects of the present invention include: using plasma heating to heat the sample to be tested for melting point, being able to melt the sample to be tested by surface heating, and obtaining the melting point of the sample to be tested in combination with temperature measurement, thereby solving the problem of excessive material ablation and temperature measurement difficulties caused by too small a melting area in the laser method, and reducing the problem of small light spot and difficulty in extracting temperature information in laser melting point measurement; and improving the measurement accuracy by synchronously measuring the deformation process of the sample to be tested when heated by plasma with the temperature.

[0040] The present invention is applicable to the measurement of melting points and phase transition points of high-melting-point materials of nuclear fuel assemblies (including the temperature during the phase transition process, such as decomposition and sublimation temperatures), and is also applicable to the measurement of melting points and phase transition points of other high-melting-point materials, such as ultra-high-temperature ceramics and refractory metal materials in the aerospace field, thermal protection materials, metallurgical refractory materials and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0042] FIG1 is a block diagram of a device for measuring the melting point of ultrahigh temperature materials according to an embodiment of the present invention;

[0043] FIG2 is a structural block diagram of an apparatus for measuring the melting point of ultrahigh temperature materials according to another embodiment of the present invention. Modes for Carrying Out the Invention

[0044] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0045] As shown in FIG1 and FIG2 , the ultrahigh temperature material melting point measuring device of the present invention may include a sealed measuring chamber 10 , a sample stage 20 , a plasma system, and a non-contact temperature measurement unit (not shown).

[0046] A sample stage 20 is disposed within the measurement chamber 10 and serves as a support for the sample 100 to be tested. A plasma system is connected to at least one side of the measurement chamber 10 to generate a plasma jet as a heat source to heat the sample 100. A non-contact temperature measurement unit is used to measure the temperature of the sample 100 before, after, and during heating.

[0047] The non-contact temperature measurement unit does not need to be located within the measurement chamber 10. To accommodate this unit, the measurement chamber 10 is equipped with at least one temperature measurement window 11, through which the non-contact temperature measurement unit measures the temperature of the sample 100 within the measurement chamber 10. Furthermore, the measurement chamber 10 also includes at least one observation window 12, which is used to record the heating process of the sample 100 and facilitates manual observation of the conditions within the measurement chamber 10.

[0048] The test sample 100 applicable to the present invention includes but is not limited to a fuel pellet, a cladding tube or a ceramic part.

[0049] Specifically, the measurement chamber 10 is provided with an openable and closable sample delivery port 13, which is used to deliver the sample 100 to be tested into the measurement chamber 10 and to remove the sample from the measurement chamber 10. The sample delivery port 13 is opened when the sample 100 to be tested is taken in and out, and is closed during the measurement process to keep the measurement chamber 10 sealed.

[0050] To facilitate the placement and placement of the sample 100 on the sample stage 20, the sample delivery and sampling port 13 is located above the sample stage 20, making it convenient to place the sample 100 on the sample stage 20 and to remove the sample from the sample stage 20. The sample delivery and sampling port 13 is preferably provided on the side wall of the measurement chamber 10.

[0051] In addition, the measurement chamber 10 may be provided with an auxiliary sampling port 14, which is located below or on at least one side of the sample stage 20. During the measurement process, if a sample falls from the sample stage 20 or when the interior of the measurement chamber 10 is purged and cleaned, the sample can be collected through the auxiliary sampling port 14.

[0052] Since the sample stage 20 serves as a carrier for the sample 100 to be tested, it is made of a material having a melting point higher than that of the sample 100 to be tested, so that the sample stage 20 will not melt when the sample 100 to be tested is heated. The sample stage 20 can be fixedly set in the measuring chamber 10, or it can be set to move with multiple degrees of freedom, that is, it can be installed in the measuring chamber 10 with adjustable position or angle, so as to facilitate temperature measurement and video observation. The movable setting of the sample stage 20 can be achieved by supporting it with a movable component, which can drive the sample stage 20 to rotate in multiple directions, such as a rotation angle of 0-150° and a pitch angle of 0-45°; the sample stage 20 can also be driven to rise and fall, thereby adjusting the distance between the sample stage 20 and the heat source. The lifting range of the sample stage 20 is H / 3, where H is the height of the measuring chamber 10.

[0053] The sample stage 20 can take any form, as long as it maintains a stable position of the sample relative to the plasma, such as a fixture, a platform, or a crucible. The sample stage 20 can also, as needed, provide cooling to prevent melting and assist in heating to maintain the structural stability of the sample 100.

[0054] In the present invention, the plasma jet generated by the plasma system is used as a heat source to heat the sample 100 to be tested, which can not only realize the surface heating method, but also the heating temperature can reach 5×10 4 K, theoretically can melt all high melting point materials, and has a wide range of applications.

[0055] The plasma system may further include a plasma torch 30 for generating a plasma jet, and a gas supply unit connected to and supplying a working gas (plasma working gas) to the plasma torch 30 .

[0056] The plasma torch 30 can utilize a variety of excitation methods, including arc, high-frequency, and microwave. The power source can be a DC power supply, a high-frequency power supply, or a microwave source. The power of the plasma torch 30 should not be too high, but should be adjustable over a wide range, preferably between 1 and 30 kW. The working gas of the plasma torch 30 is an inert gas that only heats the sample 100 without chemically reacting with it. For example, high-purity Ar or He with a purity greater than 99.999%, or a mixture thereof, is used to supply the inert gas to the plasma torch 30. A gas supply unit is used to supply the inert gas to the plasma torch 30.

[0057] The plasma system also includes cooling water to cool the plasma torch 30. The cooling water can be softened water or deionized water.

[0058] In one embodiment, as shown in FIG1 , the plasma torch 30 is disposed on the measuring chamber 10 (e.g., at the top of the measuring chamber 10) corresponding to the sample stage 20, so that the generated plasma jet directly heats the sample 100 to be measured. This direct heating method is suitable for samples with relatively large volumes, such as entire fuel pellets, cladding tubes of a certain length, or ceramic sheets. Specifically, as shown in FIG1 , the plasma jet generated by the plasma torch 30 is directly output from top to bottom and directly contacts the sample 100 to be measured, heating the sample 100 to be measured using a surface heating method. In this embodiment, two temperature measurement windows 11 are provided, one located at the top of the measuring chamber 10 and one located on the side wall of the measuring chamber 10; two observation windows 12 are also provided, one located at the top of the measuring chamber 10 and one located on the side wall of the measuring chamber 10.

[0059] In another embodiment, as shown in FIG2 , the plasma torch 30 is disposed on the measuring chamber 10 (such as at the bottom or lower end of the measuring chamber 10 ) corresponding to the lower side or side of the sample stage 20 so that the generated plasma jet heats the sample stage 20, and the sample to be measured 100 is heated by heat transfer from the sample stage 20. This indirect heating method is suitable for samples with a relatively small volume or quantity, such as a small part of the structure of a fuel pellet, a small section of a cladding tube, or a ceramic sheet. Specifically, as shown in FIG2 , the plasma jet generated by the plasma torch 30 is directly output from bottom to top and directly contacts the sample stage 20, heating the sample stage 20 in a surface heating manner, thereby heating the sample to be measured 100 on the sample stage 20. In this embodiment, one temperature measuring window 11 and one observation window 12 are respectively provided, and both are located at the top of the measuring chamber 10.

[0060] The non-contact temperature measurement unit measures temperature without contact, meeting both surface and high-temperature measurement requirements. Options include a wide-range, high-precision dual-color pyrometer or infrared thermal imager, with a measurement range of 700°C to 3500°C.

[0061] To meet the need for recording through observation window 12, the ultra-high temperature material melting point measurement device of the present invention can also include an optical component for clearly recording the changes in the sample 100 during heating. The optical component can be a combination of a filter and a digital camera, with a resolution of 0.1mm. The melting process of the sample 100 observed through filming is combined with the measured temperature value, and the melting point or phase transition point of the sample 100 is determined by the synchronous deformation and temperature measurement results.

[0062] Furthermore, the ultra-high temperature material melting point measuring device of the present invention may also include at least one of the following: a pressure maintaining system 40 for controlling the pressure in the measuring chamber 10 at a predetermined pressure, a cooling unit for cooling the side wall of the measuring chamber 10, a process gas source system 50 for providing gas to the measuring chamber 10 to form a predetermined atmosphere in the measuring chamber 10, and a gas purification system.

[0063] The pressure maintenance system 40 is connected to the measurement chamber 10 and may further include a gas container containing an inert gas. The gas container is connected to the measurement chamber 10 via a ventilation pipe, and the pressure within the measurement chamber 10 is controlled by supplying inert gas into the measurement chamber 10. It is understood that the ventilation pipe is equipped with control valves and pressure gauges, which are used to control the passage of the ventilation pipe and measure the pressure of the ventilation pipe, respectively. The pressure within the measurement chamber 10 can be obtained by measuring the ventilation pipe pressure. The predetermined pressure range within the measurement chamber 10 can range from negative pressure to normal pressure and positive pressure, from -2kPa to +3MPa, to promote or inhibit the decomposition of the sample 100 to meet measurement requirements.

[0064] To cool the sidewalls of measurement chamber 10, a cooling unit may include cooling pipes attached to the walls of measurement chamber 10, or a cooling layer disposed within the sidewalls of measurement chamber 10. Cooling water, used as the cooling medium, circulates within the cooling pipes or cooling layer, removing heat from the sidewalls of measurement chamber 10. During measurement, the outer wall temperature of measurement chamber 10 is controlled to be no higher than 50°C, and the inner wall temperature is controlled to be no higher than 800°C.

[0065] The process gas supply system 50 is connected to the measurement chamber 10 and provides the required atmosphere (a non-inert gas or a mixture of inert and non-inert gases). This creates a predetermined atmosphere within the measurement chamber 10, suppressing product decomposition and facilitating measurement. For some test samples 100 that decompose and sublimate at high temperatures, positive pressure can suppress decomposition, allowing for measurement. The adjustable pressure allows for better analysis of the melting point of the test sample 100 under certain operating conditions.

[0066] When the required atmosphere in the measurement chamber 10 is an inert gas atmosphere, and the same gas is used by the pressure maintenance system 40, the process gas source system 50 can be replaced by the pressure maintenance system 40, or the two can be integrated into one system. When the required atmosphere in the measurement chamber 10 is a non-inert gas atmosphere (such as N2), the pressure maintenance system 40 can supply the inert gas, while the process gas source system 50 can also supply the non-inert gas (such as N2). Alternatively, the process gas source system 50 can directly supply a mixture of inert and non-inert gases to maintain the required pressure and atmosphere in the measurement chamber 10, eliminating the need for gas supply from the pressure maintenance system 40.

[0067] The gas purification system is used to purify the gas exhausted from the measurement chamber 10 to meet the exhaust requirements of the connected factory building. Specifically, the gas purification system may include a cooler 51, a filter 52, and an exhaust fan 53, which are connected in sequence. The cooler 51 receives and cools the gas exhausted from the measurement chamber 10; the filter 52 filters the cooled gas; and the exhaust fan 53 provides power to extract the gas from the measurement chamber 10, driving the gas through the cooler 51 and filter 52 in sequence.

[0068] Cooler 51, located upstream of filter 52, cools the high-temperature airflow generated during prolonged measurement to 250°C or below, ensuring safe operation of filter 52. Filter 52 may further include a pre-filter and a high-efficiency particulate air filter (HEPA). The pre-filter can be a ceramic filter or a bag filter. Exhaust fan 53 can be a variable-frequency fan.

[0069] Furthermore, the ultrahigh temperature material melting point measuring device of the present invention may also include a control and acquisition system (not shown). The control and acquisition system is connected to the plasma system and the non-contact temperature measurement unit respectively to control their opening and closing and collect measurement data.

[0070] The control and acquisition system can also be connected to the pressure maintaining system 40, the cooling unit, the process gas source system 50, and the gas purification system to control the opening and closing of each of them, and at the same time collect relevant data (such as pressure, temperature, etc.) during the operation of each of them.

[0071] Through the setting of the control and acquisition system, it is possible to collect and adjust the gas pressure of the measurement chamber 10, operate the plasma torch (start, adjust the power and shut down), adjust the position of the sample stage 20, etc., as well as collect all parameters such as the gas pressure of the measurement chamber 10, the temperature of the sample 100 to be tested, the heating video of the sample 100 to be tested, the plasma power, etc. for measurement completion processing.

[0072] The ultrahigh temperature material melting point measuring device of the present invention is used to measure the melting point of an ultrahigh temperature material. Referring to FIG1 and FIG2 , the ultrahigh temperature material melting point measuring method implemented by the ultrahigh temperature material melting point measuring device may include the following steps:

[0073] S0. Use high melting point materials with known melting points to calibrate the ultra-high temperature material melting point measuring device.

[0074] After the calibration is completed, the melting point measurement operation is performed using the sample 100 to be tested.

[0075] S1 . Send the sample 100 to be tested into the measuring chamber 10 and place it on the sample stage 20 .

[0076] S2. Start the plasma system, which generates a plasma jet and fully contacts the sample 100 to heat the sample 100 to cause a phase change. At the same time, the phase change process of the sample 100 is recorded through the observation window on the measuring chamber 10.

[0077] Before starting the plasma system, the cooling unit is started to cool the measuring chamber 10 by cooling water. The non-contact temperature measuring unit and the optical components for photographing and recording are turned on.

[0078] The specific operations of step S2 may be as follows:

[0079] First, the position or angle of the sample stage 20 is roughly adjusted so that it can be heated by the plasma without melting.

[0080] The plasma torch 30 of the plasma system is started, and the gas flow rate and electrical parameters are adjusted to generate a stable plasma jet to heat an area on the sample to be tested 100, thereby generating a surface heating effect.

[0081] The pressure maintenance system 40 is activated to supply inert gas into the measurement chamber 10, maintaining the desired pressure and atmosphere within the measurement chamber 10, typically at 1 atm. As needed, the process gas supply system 50 is activated to supply gas to the measurement chamber 10, creating the desired atmosphere within the measurement chamber 10. If the sample 100 to be measured is a nitride, while maintaining the desired pressure with the inert gas, a predetermined partial pressure of N2 is also supplied through the process gas supply system 50.

[0082] Finely adjust the position or angle of the sample stage 20 so that the sample 100 to be tested is in full contact with the plasma jet, causing phase change processes such as melting, decomposition, and sublimation; at the same time, adjust the optical components and the non-contact temperature measurement unit to align them with the sample 100 to be tested.

[0083] During the above heating process, the side walls of the measuring chamber 10 are cooled by the flow of cooling water, so that the outer wall temperature of the measuring chamber 10 is not higher than 50°C and the inner wall temperature is not higher than 800°C.

[0084] S3. The temperature of the sample 100 to be tested is measured by a non-contact temperature measurement unit to obtain the temperature change of the sample 100 during the phase change process; at the same time, the optical component photographs and records the phase change process of the sample 100 to be tested.

[0085] S4. Combine the recorded phase change area of ​​the sample 100 to be tested and the corresponding temperature (the area where the sample 100 to be tested is deformed and the current temperature of the area) to determine the melting point of the sample 100 to be tested, that is, determine the melting point or phase change point of the sample 100 to be tested through "deformation + temperature" synchronous measurement.

[0086] In order to improve the accuracy of the measurement structure, the melting point measurement of the sample 100 to be measured is performed at least three times, that is, the above steps S1 to S4 are performed at least three times.

[0087] The present invention is suitable for measuring the melting point or phase transition point of materials with a melting point higher than 2300°C.

[0088] When the sample 100 to be measured is made of SiC material, the melting point of SiC is obtained to be 2490° C. based on the temperature distribution measured by the above measuring device and method and the deformation process observed by video.

[0089] The present invention can be used to measure the melting points of new nuclear fuel pellet materials and cladding materials in the nuclear industry, providing technical support for the research and development of new fuels; it can be used to measure the melting points of irradiated materials and to study the mechanism of the influence of irradiation effects on the changes in the melting points of materials; it can also be used in aerospace, thermal protection materials, metallurgical refractory materials and other fields.

[0090] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A device for measuring the melting point of ultra-high temperature materials, characterized in that: The device comprises a sealed measuring chamber, a sample stage arranged in the measuring chamber and used to place a sample to be measured, a plasma system connected to at least one side of the measuring chamber and used to generate a plasma jet as a heat source to heat the sample to be measured, and a non-contact temperature measuring unit for measuring the temperature of the sample to be measured; The measuring chamber is provided with at least one temperature measuring window corresponding to the non-contact temperature measuring unit and at least one observation window for photographing and recording.

2. The ultrahigh temperature material melting point measuring device according to claim 1, characterized in that: The sample stage is made of a material having a melting point higher than that of the sample to be tested.

3. The ultrahigh temperature material melting point measuring device according to claim 1, characterized in that: The sample stage is installed in the measurement chamber in a position-adjustable or angle-adjustable manner.

4. The ultrahigh temperature material melting point measuring device according to claim 1, characterized in that: The measuring chamber is provided with a sample delivery port for delivering the sample to be measured into the measuring chamber and taking it out from the measuring chamber; the sample delivery port is located above the sample stage in terms of height.

5. The ultrahigh temperature material melting point measuring device according to claim 4, characterized in that: The measuring chamber is provided with an auxiliary sampling port; the auxiliary sampling port is located below the sample stage or at least on one side of the sample stage in terms of height.

6. The ultrahigh temperature material melting point measuring device according to claim 1, characterized in that: The plasma system includes a plasma torch for generating a plasma jet, and a gas supply unit connected to and providing a working gas to the plasma torch; The working gas is an inert gas.

7. The ultrahigh temperature material melting point measuring device according to claim 6, characterized in that: The plasma torch is arranged on the measuring chamber corresponding to the top of the sample stage, so that the generated plasma jet directly heats the sample to be measured.

8. The ultrahigh temperature material melting point measuring device according to claim 6, characterized in that: The plasma torch is disposed on the measurement chamber correspondingly below or at the side of the sample stage, so that the generated plasma jet heats the sample stage.

9. The ultrahigh temperature material melting point measuring device according to claim 1, characterized in that: The non-contact temperature measurement unit includes a two-color pyrometer or an infrared thermal imager.

10. The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 9, characterized in that: The ultrahigh temperature material melting point measuring device further includes a pressure maintaining system that is in communication with the measuring chamber and is used to control the pressure in the measuring chamber at a predetermined pressure.

11. The ultrahigh temperature material melting point measuring device according to claim 10, characterized in that: The pressure maintaining system includes a gas container filled with inert gas; the gas container is connected to the measuring chamber through a ventilation pipe, and the pressure in the measuring chamber is controlled by supplying inert gas into the measuring chamber.

12. The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 9, characterized in that: The ultra-high temperature material melting point measuring device further comprises a cooling unit for cooling the side wall of the measuring chamber; The cooling unit includes a cooling pipe attached to the wall surface of the measuring chamber; or, the cooling unit includes a cooling interlayer arranged in the side wall of the measuring chamber.

13. The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 9, characterized in that: The ultra-high temperature material melting point measuring device further comprises a process gas source system; the process gas source system is connected to the measuring chamber and is used to provide gas to the measuring chamber so as to form a predetermined atmosphere in the measuring chamber.

14. The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 9, characterized in that: The ultra-high temperature material melting point measuring device further comprises a gas purification system connected to the measuring chamber; The gas purification system includes a cooler, a filter and an exhaust fan connected in sequence; the cooler receives the gas discharged from the measuring chamber and cools the gas; the filter filters the cooled gas; the exhaust fan is used to provide power to extract the gas in the measuring chamber to drive the gas to pass through the cooler and the filter in sequence.

15. The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 9, characterized in that: The ultra-high temperature material melting point measuring device also includes a control and acquisition system; the control and acquisition system is connected to the plasma system and the non-contact temperature measurement unit respectively, and is used to control their opening and closing and collect measurement data.

16. The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 9, characterized in that: The sample to be tested is a fuel pellet, a cladding tube or a ceramic part.

17. A method for measuring the melting point of ultra-high temperature materials, characterized in that: The ultrahigh temperature material melting point measuring device according to any one of claims 1 to 16 is used, and the ultrahigh temperature material melting point measuring method comprises the following steps: S1. Send the sample to be tested into the measuring chamber and place it on the sample table; S2. Start the plasma system, which generates a plasma jet and fully contacts the sample to be tested, heating the sample to be tested to cause a phase change; at the same time, the phase change process of the sample to be tested is recorded through the observation window on the measurement chamber; S3, measuring the temperature of the sample to be tested by a non-contact temperature measurement unit to obtain the temperature change of the sample to be tested during the phase change process; S4. Determine the melting point or phase transition point of the sample to be tested based on the recorded phase transition region and the corresponding temperature of the sample to be tested.

18. The method for measuring the melting point of ultrahigh temperature materials according to claim 17, characterized in that: Step S2 also includes: delivering inert gas into the measuring chamber through a pressure maintaining system to maintain the pressure in the measuring chamber at a predetermined pressure; and / or, providing gas to the measuring chamber through a process gas source system to form a predetermined atmosphere in the measuring chamber.

19. The method for measuring the melting point of ultrahigh temperature materials according to claim 17, wherein: Step S2 further includes: cooling the side walls of the measuring chamber by flowing cooling water so that the outer wall temperature of the measuring chamber is not higher than 50° C. and the inner wall temperature is not higher than 800° C.

20. The method for measuring the melting point of ultrahigh temperature materials according to any one of claims 17 to 19, characterized in that: The sample to be tested is a fuel pellet, a cladding tube or a ceramic part.

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