Method and device for nondestructively measuring permeation of porous graphene by using low-pressure airflow

Abstract

The invention discloses a method and a device for nondestructive measurement of porous graphene permeation by using low-pressure airflow, and belongs to the field of preparation and application of metal-based composite materials. The device comprises an air source, a pressure regulating module, a testing module and a releasing module which are sequentially connected through pipelines in the airflow direction, pressure sensors are arranged on the connecting pipelines at the two ends of the testing module, and a flow sensor is arranged on the pipeline of the releasing module; the pressure sensor and the flow sensor are used for collecting airflow pressure and flow values and sending the airflow pressure and flow values to the upper computer for control and calculation; the test module comprises a test cavity, a gas deceleration buffer structure and a porous material, the gas deceleration buffer structure and the porous material are mounted in the test cavity, and gas flow entering an inlet of the test cavity is decelerated and pressurized through the gas deceleration buffer structure so as to compensate for gas pressure loss caused by a pipeline. The flow velocity and the pressure of the air flow passing through the to-be-measured porous material can be controlled, and the measurement process of the permeability coefficient of the porous material is ensured to be nondestructive measurement.

Description

Technical Field

[0001] The invention belongs to the field of preparation and application of metal-based composite materials, and in particular relates to a method and a device for non-destructively measuring the penetration of porous graphene using low-pressure airflow. Background Art

[0002] The excellent mechanical properties of metal matrix composites make them widely used in aerospace, national defense, space exploration and other fields. With the continuous upgrading and development of technologies such as national defense industry, deep space exploration, and manned spaceflight, the demand for composite materials with integrated structure and function is increasing day by day. Nano-carbon materials represented by graphene and carbon nanotubes are important materials for preparing metal matrix composite materials with integrated structure and function.

[0003] Freeze-drying graphene to prepare a porous material with a three-dimensional continuous pore structure can achieve its uniform structural dispersion, and combined with the liquid metal infiltration process to prepare a metal-based composite material, so as to give full play to the excellent thermal and electromagnetic properties of graphene materials. In the process of preparing composite materials by infiltration, the permeability of the porous graphene preform is the key factor in the liquid alloy infiltration process, and the permeability of the porous material is characterized by the permeability coefficient. For porous materials, the size of the permeability coefficient will affect the difficulty of liquid metal to penetrate into it. When the infiltration difficulty is small (the permeability coefficient is large), the external force required for the infiltration process is small; conversely, when the infiltration difficulty is large (the permeability coefficient is small), a large external pressure is required to overcome the infiltration resistance. However, if the infiltration process uses a load size that exceeds the preform can bear, the pore structure of the preform will be completely destroyed, resulting in infiltration failure. Therefore, obtaining the permeability coefficient of the porous graphene preform is of vital importance for the infiltration preparation of graphene-enhanced metal-based composites. At present, the existing methods for measuring the permeability coefficient of porous media include using porous materials such as artificial bones and porous metals. This type of method is relatively simple, but has certain requirements for the test materials: the porous material itself needs to have a higher compressive strength, and the test process does not need to consider the impact of the fluid flow rate on the pore structure.

[0004] Graphene preforms are easily impacted by high-speed fluids, which may damage their pore structures. Therefore, the flow rate of the test fluid needs to be reduced. Currently, the pressure difference is measured by gas decompression, but this technology cannot control the flow rate of the gas and has a relatively complex structure, making it difficult to apply to permeability tests. The fluid pressure buffer device disclosed in the prior art has a cavity filled with a large amount of particulate matter. When high-pressure fluid flows into the buffer cavity, part of the kinetic energy of the fluid is consumed by viscous resistance, reducing the pressure of the fluid. However, after the fluid flows out of the cavity, the flow rate of the fluid will gradually return to the level before entering the cavity. Therefore, the device is also unable to obtain flow rate fluid.

[0005] The pore permeability coefficient of the preform will be affected by the process and change, resulting in different permeability coefficients of different preforms in the same batch. The graphene preform has a low compressive strength, is not resistant to high-speed fluid impact, and is susceptible to sudden changes in environmental pressure, causing destruction of the pore structure. The above-mentioned test method for the test fluid of water or high-pressure gas (>0.1MPa) and the device for generating low-pressure gas are applied to the permeability coefficient measurement of low-strength graphene preforms, which will inevitably cause the destruction of the pore structure of the graphene preform. Therefore, it is necessary to design a permeability coefficient measurement method and a measuring device of low-pressure and low-speed gas for low-strength graphene preforms. Summary of the invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the prior art, the present invention provides a method and device for non-destructively measuring the permeability of porous graphene using low-pressure airflow. A special gas deceleration buffer structure is adopted to restore the pressure loss caused by the pipeline and reduce the resulting gas pressure flow rate. That is, the airflow velocity and pressure passing through the porous material to be measured can be controlled to ensure that the permeability coefficient measurement process of the porous material is a non-destructive measurement.

[0008] The technical solution of the present invention is: a method for non-destructively measuring the permeability of porous graphene using low-pressure airflow, and the specific steps are as follows:

[0009] The porous material to be tested is placed in the test chamber, and a gas deceleration buffer structure is arranged upstream of the porous material to be tested in the chamber to compensate for the gas pressure loss caused by the pipeline;

[0010] The input end of the test chamber is connected to the gas source through a pipeline, and the output end discharges the gas through the pipeline, and pressure sensors are set at the input / output ends to obtain input and output pressure values;

[0011] A pressure regulating module is arranged on the input end pipeline to obtain an airflow that meets the pressure requirements;

[0012] The pressure sensor and the pressure regulating module are connected to a host computer, and the host computer controls the pressure regulating module to output a set pressure airflow, and the two pressure sensors transmit the acquired input and output pressure values ​​to the host computer;

[0013] The collected data is calculated by a host computer to obtain the permeability coefficient of the porous graphene preform.

[0014] A further technical solution of the present invention is: the host computer is connected to the pressure regulating module through a function generator, the host computer sends a signal of linear pressure increase, which is transmitted to the function generator through a signal line, the function generator generates a voltage control signal with a specific slope, and is transmitted to the pressure regulating module through the signal line, so as to achieve a steady increase in gas pressure; at the same time, the pressure sensor performs pressure feedback, the host computer performs pressure comparison, and enters the data acquisition stage after reaching a predetermined value.

[0015] A further technical solution of the present invention is: the host computer and the function generator control the entire measurement process to ensure the smooth operation of the three processes of gas pressure linear increase stage, pressure holding stage, and pressure linear reduction stage during the entire measurement process; data measurement is performed when in the pressure holding stage.

[0016] A further technical solution of the present invention is: the permeability coefficient calculation method of the porous material is:

[0017] Calculate the pressure difference based on the measured pressure values ​​at the input end and the output end;

[0018] The pressure gradient is obtained by dividing the calculated pressure difference by the thickness of the porous material;

[0019] The air flow rate through the porous material is obtained by a flow sensor;

[0020] Based on the above results, the permeability coefficient of the porous material was calculated according to Darcy's law.

[0021] A device for non-destructively measuring the permeability of porous graphene using low-pressure airflow, comprising an air source, a pressure regulating module, a test module, and a release module connected in sequence along the airflow direction through a pipeline, wherein pressure sensors are provided on the connecting pipelines at both ends of the test module, and a flow sensor is provided on the pipeline of the release module; airflow pressure and flow values ​​are collected by the pressure sensor and the flow sensor and sent to a host computer for control and calculation;

[0022] The test module includes a test cavity and a gas deceleration buffer structure and a porous material installed therein. The gas deceleration buffer structure is used to decelerate and pressurize the airflow entering the entrance of the test cavity to compensate for the air pressure loss caused by the pipeline.

[0023] A further technical solution of the present invention is: the gas deceleration buffer structure is a flat plate structure arranged perpendicular to the airflow direction, with multiple conical holes on its end surface, the small diameter end facing the inlet end of the test cavity, and the large diameter end facing the porous material.

[0024] A further technical solution of the present invention is: the arrangement of the multiple conical holes on the gas deceleration buffer structure is: one is set at the center position, and four are evenly distributed along the circumference of the end surface; and the inlet diameter of the conical hole is 2 to 4 mm, and the outlet diameter is 1.1 to 2 times the inlet diameter.

[0025] A further technical solution of the present invention is: the pressure regulating module includes a main gas circuit valve, a pressure reducing valve, and an electrical proportional valve which are sequentially connected to the pipeline, and the on-off of the gas source is controlled by the main gas circuit valve; the gas flowing out of the gas source is depressurized by the pressure reducing valve to ensure that the gas pressure flowing into the electrical proportional valve is not greater than 50kPa; the gas pressure is secondary depressurized by the electrical proportional valve to ensure that the air flow pressure in the pipeline is the set pressure flowing through the porous material.

[0026] A further technical solution of the present invention is: the release module includes a buffer gas bottle and an exhaust switch which are sequentially connected to the pipeline, and the exhaust flow rate is measured by a flow sensor installed on the pipeline at the gas outlet end.

[0027] A further technical solution of the present invention is: the gas source is a gas cylinder, and the output gas pressure of the gas cylinder is greater than 0.1 MPa.

[0028] Beneficial Effects

[0029] The beneficial effects of the present invention are as follows: the present invention provides a device for obtaining low-pressure and low-speed gas and a method for measuring the permeability coefficient of a porous graphene preform. The device can be used to measure the permeability coefficient of a porous graphene preform non-destructively. The porous material after the test can be used for permeability experiments and composite material preparation. The specific advantages are as follows:

[0030] (1) The present invention designs a gas deceleration buffer structure with a tapered hole structure based on the continuity equation of fluid flow. The flow rate of the fluid is reduced by increasing the channel area through which the fluid flows, thereby reducing the risk of high flow rate impact damage to the pores. At the same time, according to the Bernoulli equation, a reduction in fluid flow rate will lead to the recovery of static pressure. Therefore, the pipeline connected to the output end before the test will cause the gas pressure to be lost in the pipeline. By providing a gas deceleration buffer structure, the gas pressure can be partially restored at the outlet end of the gas deceleration buffer structure, reducing the pressure loss, that is, accurate pressure control can be obtained. The buffer structure can be used to obtain a low-pressure and low-speed fluid.

[0031] (2) The linear pressure control technology of the present invention is combined with the gas flow rate buffer structure to effectively reduce the risk of damage to the prefabricated structure caused by the "water hammer effect" caused by the sudden pressure change in the pipeline caused by the opening and closing of the valve body.

[0032] (3) The method for calculating the permeability coefficient of porous media of the present invention requires relatively few parameters, including the thickness and diameter of the porous media, the viscosity of the test gas, the gas flow rate and pressure. The measuring device can directly measure the gas flow rate and pressure. The thickness and diameter are measured with a caliper before the test, and the viscosity of the test gas is obtained by referring to the manual. The permeability, the core parameter of the porous preform to be measured, is calculated based on the existing parameters and Darcy's law.

[0033] (4) The method of the present invention can measure the permeability coefficient of porous media of different sizes (diameter, thickness), ensure the structural integrity of the porous structure, and can be applied to actual production without any treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A device for measuring the permeability coefficient of a porous graphene preform in an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of a gas deceleration buffer structure with a tapered hole structure in an embodiment of the present invention;

[0036] Figure 3 Schematic diagram of the effect of the change in the cone hole outlet radius on the flow velocity of the cone hole in an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of the effect of the change in the cone hole height on the fluid flow rate in an embodiment of the present invention;

[0038] Figure 5 This is a simulation diagram of the fluid flow rate of the buffer structure with a tapered hole in an embodiment of the present invention;

[0039] Figure 6 The first waveform of the air pressure control gradient change in the embodiment of the present invention;

[0040] Figure 7 The second waveform of the air pressure control gradient change in the embodiment of the present invention;

[0041] Explanation of the reference numerals: 1-gas circuit main valve; 2-pressure reducing valve; 3-electric proportional valve; 4-inlet pipeline; 5-inlet pressure sensor; 6-test chamber; 7-gas deceleration buffer structure; 8-porous material; 9-outlet pipeline; 10-outlet pressure sensor; 11-signal line; 12-gas flow sensor; 13-signal line; 14-buffer gas cylinder; 15-exhaust switch; 16-signal line; 17-function generator; 18-signal line; 19-gas cylinder; 20-signal line; 21-control computer. DETAILED DESCRIPTION

[0042] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0043] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0044] Based on the problems that existing methods for measuring permeability coefficients of materials may damage the materials themselves, or cause inaccurate measurement data due to the inability to restore air pressure loss, the present invention provides a device for non-destructively measuring the permeability of porous graphene using low-pressure airflow, comprising an air source, a pressure regulating module, a test module, and a release module connected in sequence along the airflow direction through pipelines, pressure sensors are provided on the connecting pipelines at both ends of the test module, and a flow sensor is provided on the pipeline of the release module; airflow pressure and flow values ​​are collected by the pressure sensor and the flow sensor and sent to a host computer for control and calculation; the test module comprises a test cavity and a gas deceleration buffer structure and a porous material installed therein, and the gas deceleration buffer structure is used to decelerate and pressurize the airflow entering the inlet of the test cavity to compensate for the air pressure loss caused by the pipeline.

[0045] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0046] In one embodiment, referring to Figure 1 As shown, a process device for non-destructively measuring the permeability coefficient of a porous graphene preform using a low-pressure gas flow (<0.05MPa) includes a gas path system and a control system:

[0047] Specifically, the gas circuit system includes: a gas circuit main switch 1, a pressure reducing valve 2 (first-stage pressure reducing), an electric proportional valve 3 (second-stage pressure reducing), an air inlet pipeline 4, an air inlet pressure sensor 5, a cavity 6, a gas deceleration buffer structure 7, an air outlet pipeline 9, an air outlet pressure sensor 10, a gas flow sensor 12, a buffer gas cylinder 14, a buffer gas cylinder exhaust switch 15, and a gas cylinder 19. Among them, the gas cylinder switch 1 is used to control the on-off of the gas cylinder 19; the pressure reducing valve 2 reduces the pressure of the gas (>0.1MPa) flowing out of the gas cylinder 19 to ensure that the gas pressure flowing into the electric proportional valve 3 is not greater than 50kPa; the gas pressure flowing into the test cavity is secondary reduced by the electric proportional valve 3; the gas flowing out of the electric proportional valve 3 is called "low-pressure gas", which is used to test the permeability of porous media. The value of "low-pressure gas" is specifically set according to the experimental measurement needs. After the "low-pressure gas" flows out of the proportional regulating valve 3, it enters the cavity 6; the pressure sensor 5 and the pressure sensor 10 are used to detect the pressure changes at both ends of the cavity 6; the gas deceleration buffer structure 7 and the porous material 8 to be measured are installed inside the cavity 6; the "low-pressure gas" flows in from the air inlet of the cavity 6, and after passing through the gas deceleration buffer structure 7, the flow rate of the "low-pressure gas" is reduced, reducing the impact on the pore structure of the porous material 8. The gas outlet pipe 9, the gas flow sensor 12, the buffer gas bottle 14, and the buffer gas bottle switch 15 form an exhaust pipeline for measuring the exhaust flow.

[0048] Specifically, the control system is composed of an electric proportional valve 3, an air inlet pressure sensor 5, an air outlet pressure sensor 10, a flow sensor 12, a function generator 17, a control computer 21, a signal line 11, a signal line 13, a signal line 16, a signal line 18, and a signal line 20. The control system needs to ensure the smooth operation of the three processes of the gas pressure linear increase (before data acquisition) stage, the pressure maintenance (measurement stage) stage, and the pressure linear reduction (after data acquisition) stage during the entire measurement process to avoid the occurrence of a large pressure (or flow rate) step process. Before data acquisition, the control loop composed of the electric proportional valve 3, the signal line 18, the function generator 17, the signal line 20, and the control computer 21 is responsible for measuring the linear increase of the pressure. The control computer 21 sends a signal of linear pressure increase, which is transmitted to the function generator 17 through the signal line 20. The function generator 17 generates a voltage control signal with a specific slope and transmits it to the electric proportional valve 3 through the signal line 18 to achieve a stable increase in gas pressure. The pressure sensor 5 performs pressure feedback, and the control computer 21 performs pressure comparison. After reaching a predetermined value, the data acquisition stage is entered. In the pressure acquisition stage, the signal lines 16, 11, and 13 transmit the data of the pressure sensor 5, the pressure sensor 10, and the flow sensor 12 to the control computer 21, respectively, and the control computer 21 stores the data; after the data acquisition, the control computer 21 sends a pressure gradient reduction signal, and the function generator 17 and the electrical proportional valve 3 execute the gas pressure gradient reduction process until the pressure is steadily reduced to 0 Pa. Finally, the control computer 21 calculates the collected data to obtain the permeability coefficient of the porous graphene preform.

[0049] Calculation method: After the porous material 8 to be tested is loaded into the test cavity, the test process begins. The average pressure data collected by the pressure sensor within the measurement phase is recorded as p1, and the uniform pressure collected by the pressure sensor 10 is recorded as p2. The pressure difference Δp = 1.15754*p1-1.14454*p2-1053.30629. Combined with the thickness L of the porous preform 8, the pressure gradient can be obtained. The flow rate of the gas discharged measured by the flow sensor 12 is Q. From the continuity equation, it can be known that the flow rate through the porous graphene is also Q. The flow rate flowing through the porous graphene preform can be obtained as By Darcy's law It can be inferred that By substituting the gas viscosity, flow rate, preform thickness, preform diameter, and pressure difference, the permeability coefficient of the porous medium can be obtained.

[0050] In one embodiment, referring to Figure 2As shown, a buffer structure that can decelerate the fluid and reduce the gas pressure loss in a process device for non-destructively measuring the permeability coefficient of a porous graphene preform using a low-pressure gas flow (<0.05MPa) has a typical structure with 5 conical holes, 1 in the center and 4 distributed around the circumference. Taking a single conical hole as an example, the NS equation is used to simulate the effect of the size change of the conical hole on the fluid flow rate. The following gas pressure conditions are used during the simulation: inlet pressure 10kPa, outlet pressure 0kPa. Reference Figure 3 In the simulation shown, the inlet radius of the cone hole is 1 mm, the height is 5 mm, and the outlet radius of the cone hole increases within the range of 1.1-2 times the inlet radius. The simulation results are shown in Table 1.

[0051] Table 1 The effect of the change of cone hole outlet radius on the flow velocity of the cone hole

[0052] Outlet radius (mm) Cone hole inlet flow rate (m / s) Cone hole outlet flow rate (m / s) Deceleration rate (%) 1.1 16867 14437 14.41 1.2 19871 14322 27.92 1.3 22977 14142 38.45 1.4 26156 13908 46.83 1.5 29379 13641 53.57 1.6 32623 13345 59.09 1.7 35854 13025 63.67 1.8 39068 12691 67.52 1.9 42214 12339 70.77 2 45292 11981 73.55

[0053] It can be seen from the results in Table 1 that when the outlet radius of the tapered hole changes from 1 mm to 2 mm, the deceleration rate of the fluid velocity through the tapered hole increases from 14% to 73%; that is, the larger the outlet radius, the more significant the fluid deceleration effect.

[0054] Reference Figure 4 As shown in Figure 2, the influence of the height change of the cone hole on the fluid flow rate is small. The simulation conditions are that the inlet radius of the cone hole is 1mm, the outlet radius is 2mm, and the height of the cone hole increases from 6mm to 10mm. The simulation results are shown in Table 2.

[0055] Table 2 Effect of cone hole height change on fluid flow rate

[0056] Cone hole height (mm) Cone hole inlet flow rate (m / s) Cone hole outlet flow rate (m / s) Deceleration rate (%) 6 136410 36774 73.04 7 121980 32660 73.22 8 109610 29188 73.37 9 99125 26296 73.47 10 90327 23882 73.56

[0057] Reference Figure 5 As shown, the gas deceleration buffer structure is loaded into the test cavity to simulate the change of gas pressure and flow rate. The simulation results when the conical hole is designed to have an inlet radius of 1 mm and a height of 5 mm are shown in Table 3, and the simulation results when the inlet radius is 2 mm and the height is 5 mm are shown in Table 4. It can be seen from the simulation results that when the inlet diameter of the conical hole is in the range of 2 to 4 mm and the outlet diameter is in the range of 1.1 to 2 times the inlet diameter, the fluid flow rate entering the test cavity can be significantly reduced, and the impact on the graphene preform can be reduced; at the same time, the structure can significantly avoid the large pressure loss caused by fluid deceleration.

[0058] In one embodiment, the permeability coefficient of the porous material prepared by freeze drying a low concentration graphene oxide dispersion is measured. In this example, a porous material 8 composed of graphene is prepared by freeze drying; the porous material 8 is screwed into the cavity 6 so that the side of the porous material 8 and the inner wall of the cavity 6 are tightly connected; the gas deceleration buffer structure 7 is installed at a specified position; the gas source 19 and the main gas circuit valve 1 are opened; and the control calculation 21 is used to generate the following Figure 6 The function waveform instruction shown is sent to the function generator 17; after receiving the instruction, the function generator generates a corresponding function voltage waveform, and sends the voltage signal to the electrical proportional control valve 3 through the signal line 18; the threshold of the electrical proportional valve 3 is not higher than 30kPa; the pressure data collected by the inlet pressure sensor 5 and the outlet pressure sensor 10 are transmitted to the control computer 21 in the form of electrical signals through the signal line 16 and the signal line 11 respectively; the flow sensor 12 measures the outflowing gas flow in real time, and transmits the measurement result to the control computer 21 through the signal line 13; the program in the control computer 21 performs secondary processing on the collected data, selects the stable period data collected by the inlet pressure sensor 5 and the outlet pressure sensor 10 and the flow data within the period, calculates according to Darcy's law, and gives the permeability coefficient of the corresponding porous material. Adopt Figure 2 The air pressure change generated by the waveform shown is continuous, which can avoid the impact of the step change of the measured air pressure on the structure of the porous material, causing pore damage and causing measurement errors.

[0059] In one embodiment, the permeability coefficient of a graphene preform (porous structure) prepared from a high concentration of graphene oxide dispersion is measured. In this example, a porous material 8 made of unidirectional carbon fiber stitching is used; the porous material 8 is screwed into the cavity 6 so that the side of the porous material 8 and the inner wall of the cavity 6 are tightly connected; the gas deceleration buffer structure 7 is installed at a specified position; the gas source 19 and the gas circuit main valve 1 are opened; and the control calculation 21 is used to generate the following Figure 7 The function waveform instruction shown is sent to the function generator 17; after receiving the instruction, the function generator generates a corresponding function voltage waveform, and sends the voltage signal to the electric proportional control valve 3 through the signal line 18; the threshold of the electric proportional valve 3 is not higher than 50kPa; the pressure data collected by the inlet pressure sensor 5 and the outlet pressure sensor 10 are transmitted to the control computer 21 in the form of electrical signals through the signal line 16 and the signal line 11 respectively; the flow sensor 12 measures the outflowing gas flow in real time, and transmits the measurement result to the control computer 21 through the signal line 13; the program in the control computer 21 performs secondary processing on the collected data, selects the stable period data collected by the inlet pressure sensor 5 and the outlet pressure sensor 10 and the flow data within the period, calculates according to Darcy's law, and gives the permeability coefficient of the corresponding porous material.

[0060] In one embodiment, argon gas is used as the test fluid, and the viscosity is 2.05x10 -5 Pa·s, pipe outlet diameter 4mm; the diameter of the porous material to be tested is 30mm, and the height is 7mm. A batch of samples were tested, and each sample was measured repeatedly. The results are as follows:

[0061]

[0062] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for non-destructively measuring the permeability of porous graphene using low-pressure airflow, characterized in that The specific steps are as follows: The porous material to be tested is placed in the test chamber, and a gas deceleration buffer structure is arranged upstream of the porous material to be tested in the chamber to compensate for the gas pressure loss caused by the pipeline; The input end of the test chamber is connected to the gas source through a pipeline, and the output end discharges the gas through the pipeline, and pressure sensors are set at both the input and output ends to obtain input and output pressure values; A pressure regulating module is arranged on the input end pipeline to obtain an airflow that meets the pressure requirements; The pressure sensor and the pressure regulating module are connected to a host computer, and the host computer controls the pressure regulating module to output a set pressure airflow, and the two pressure sensors transmit the acquired input and output pressure values ​​to the host computer; The collected data is calculated by a host computer to obtain the permeability coefficient of the porous graphene preform.

2. The method for non-destructively measuring the permeability of porous graphene using low-pressure airflow according to claim 1, characterized in that: The host computer is connected to the pressure regulating module through a function generator. The host computer sends a signal of linear pressure increase, which is transmitted to the function generator through a signal line. The function generator generates a voltage control signal with a specific slope, which is transmitted to the pressure regulating module through a signal line to achieve a steady increase in gas pressure. At the same time, the pressure sensor performs pressure feedback, and the host computer performs pressure comparison. After reaching a predetermined value, it enters the data acquisition stage.

3. The method for non-destructively measuring the permeability of porous graphene using low-pressure airflow according to claim 2, characterized in that: The host computer and the function generator control the entire measurement process to ensure the smooth operation of the three processes of gas pressure linear increase stage, pressure holding stage and pressure linear reduction stage during the entire measurement process; data measurement is performed when in the pressure holding stage.

4. The method for non-destructively measuring the permeability of porous graphene using low-pressure airflow according to claim 1, characterized in that: The permeability coefficient calculation method of the porous material is: Calculate the pressure difference based on the measured pressure values ​​at the input end and the output end; The pressure gradient is obtained by dividing the calculated pressure difference by the thickness of the porous material; The air flow rate through the porous material is obtained by a flow sensor; Based on the above results, the permeability coefficient of the porous material was calculated according to Darcy's law.

5. A device for non-destructively measuring the permeability of porous graphene using low-pressure airflow, used for implementing the method for non-destructively measuring the permeability of porous graphene using low-pressure airflow according to any one of claims 1 to 4, characterized in that: It includes an air source, a pressure regulating module, a test module, and a release module which are sequentially connected through pipelines along the airflow direction. Pressure sensors are provided on the connecting pipelines at both ends of the test module, and a flow sensor is provided on the pipeline of the release module. The airflow pressure and flow values ​​are collected by the pressure sensor and the flow sensor and sent to the host computer for control and calculation; The test module includes a test cavity and a gas deceleration buffer structure and a porous material installed therein. The gas deceleration buffer structure is used to decelerate and pressurize the airflow entering the entrance of the test cavity to compensate for the air pressure loss caused by the pipeline.

6. The device for non-destructively measuring porous graphene permeability using low-pressure airflow according to claim 5, characterized in that: The gas deceleration buffer structure is a flat plate structure arranged perpendicular to the airflow direction, with a plurality of conical holes on its end surface, the small diameter end facing the inlet end of the test cavity and the large diameter end facing the porous material.

7. The device for non-destructively measuring porous graphene permeability using low-pressure airflow according to claim 6, characterized in that: The arrangement of the multiple tapered holes on the gas deceleration buffer structure is that one is set at the center position and four are evenly distributed along the circumference of the end surface; and the inlet diameter of the tapered hole is 2-4 mm, and the outlet diameter is 1.1-2 times the inlet diameter.

8. The device for non-destructively measuring porous graphene permeability using low-pressure airflow according to claim 5, characterized in that: The pressure regulating module includes a main gas circuit valve, a pressure reducing valve, and an electric proportional valve which are sequentially connected to the pipeline. The main gas circuit valve is used to control the on / off of the gas source. The pressure reducing valve is used to reduce the pressure of the gas flowing out of the gas source to ensure that the pressure of the gas flowing into the electric proportional valve is no more than 50 kPa. The electric proportional valve is used to reduce the pressure of the gas for a second time to ensure that the air flow pressure in the pipeline is the pressure set to flow through the porous material.

9. The device for non-destructively measuring porous graphene permeability using low-pressure airflow according to claim 5, characterized in that: The release module comprises a buffer gas cylinder and an exhaust switch which are sequentially connected to the pipeline, and measures the exhaust flow rate through a flow sensor installed on the pipeline at the gas outlet end.

10. The device for non-destructively measuring porous graphene permeability using low-pressure airflow according to claim 5, characterized in that: The gas source is a gas cylinder, and the output gas pressure of the gas cylinder is greater than 0.1 MPa.

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