Wide temperature range ultrasonic gas meter matching layer material and application thereof

Abstract

The application discloses a wide-temperature-range ultrasonic gas meter matching layer material and application thereof, and belongs to the technical field of ultrasonic sensing. The technical scheme is as follows: the matching layer material comprises the following raw materials: an epoxy resin matrix, a curing agent, hollow glass microbeads, a coupling agent, a toughening agent, a thixotropic agent and a defoaming agent. The application of the wide-temperature-range ultrasonic gas meter matching layer material is characterized in that the material is integrally formed with piezoelectric ceramics and comprises the following steps: 1) ceramic pretreatment; 2) base material mixing; 3) additive adding; 4) filler mixing; 5) overall mixing; 6) vacuum dispersion; 7) preforming; 8) mold pressing; 9) gradient curing; and 10) cooling and demolding. The application enables the matching layer material to maintain high sensitivity in a wide temperature range of-40 DEG C to 70 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic sensing technology, specifically relating to a wide-temperature-range ultrasonic gas meter matching layer material and its application. Background Technology

[0002] Ultrasonic gas meters, with their advantages of high precision, wide measurement range, and no mechanical wear, are gradually replacing traditional diaphragm gas meters. The ultrasonic transducer is the core component of the gas meter, and its performance directly affects the measurement accuracy. The acoustic impedance of the piezoelectric ceramic in the transducer (approximately 30-35 MRayl) differs from the acoustic impedance of the gas being measured (approximately 400 Rayl) by 4-5 orders of magnitude. Therefore, a matching layer must be placed on the piezoelectric ceramic emitting surface to achieve a gradient transition of acoustic impedance and improve sound wave transmittance.

[0003] In the prior art, the preparation and assembly of the matching layer usually adopts a separate process, that is, firstly, an independent matching layer sheet is prepared by molding or casting, and then adhesives such as epoxy glue and acrylic glue are used to bond the matching layer to the piezoelectric ceramic sheet. This split-type bonding process has the following prominent problems: the adhesive layer introduces additional acoustic losses. The adhesive layer itself has a certain thickness and acoustic impedance, and it is difficult to ensure complete uniformity. Sound waves will be reflected and scattered when passing through the interfaces of piezoelectric ceramic / adhesive layer and adhesive layer / matching layer, resulting in a decrease in transducer sensitivity; the bonding reliability is poor, and it is prone to debonding after long-term use. In actual use, gas meters face complex conditions such as high and low temperature cycles (-40℃~70℃), high humidity environments (up to 95%RH), and mechanical vibration. The thermal expansion coefficients of the adhesive, ceramic, and matching layer materials are different. Repeated temperature changes will generate alternating stress at the bonding interface, leading to adhesive layer fatigue, microcrack propagation, and eventually local debonding or even matching layer detachment; in addition, the split-type process requires first forming the matching layer (controlling thickness and density), then applying adhesive, aligning, pressing, and curing, involving multiple positioning and multiple process parameters; existing matching layer materials are difficult to meet the long-term stable operation requirements of gas meters under all climate conditions.

[0004] Therefore, developing a matching layer material and preparation method that can eliminate the adhesive layer, achieve integrated molding of the matching layer and piezoelectric ceramic, and maintain stable performance over a wide temperature range has significant technological value and market prospects. Summary of the Invention

[0005] This invention provides a wide-temperature-range ultrasonic gas meter matching layer material and its application. By directly embedding piezoelectric ceramics into the matching layer material during the matching layer molding process, the matching layer forms a tight bond with the ceramic surface without adhesive after curing. At the same time, by optimizing the formula system, the matching layer material maintains high sensitivity in a wide temperature range of -40℃ to 70℃.

[0006] The technical solution of this invention is as follows: The first aspect discloses a matching layer material for a wide-temperature-range ultrasonic gas meter, comprising the following raw materials in parts by weight: Epoxy resin matrix: 40-60 parts; Hardener: 10-30 parts; Hollow glass microspheres: 20-45 parts; Coupling agent: 0.2-1.5 parts; Toughening agent: 0.5-2 parts; Thixotropic agent: 0.5-2 parts; Defoamer: 0.1-0.5 parts.

[0007] Preferably, the epoxy resin matrix is ​​one of bisphenol A type epoxy resins E-51, E-44, and CYD-128; the curing agent is a modified amine curing agent, which is prepared by an addition reaction of alicyclic amines and polyether amines with a monofunctional epoxy diluent and cashew phenol; the defoamer is a modified polysiloxane, which is prepared by a hydrosilylation reaction of hydrogen-containing polydimethylsiloxane with allyl polyether.

[0008] Preferably, the true density of the hollow glass microspheres is 0.2-0.6 g / cm³. 3 The particle size is 30-90μm.

[0009] Preferably, the coupling agent is a silane coupling agent KH-550 or KH-560; the toughening agent is polyethylene glycol; and the thixotropic agent is a hydrophobically modified thixotropic agent, wherein the hydrophobically modified thixotropic agent is a hydrophobic fumed silica surface treated with hexamethyldisilazane.

[0010] Secondly, the application of the wide-temperature-range ultrasonic gas meter matching layer material is disclosed, which integrates the material with piezoelectric ceramics, specifically including the following steps: 1) Ceramic pretreatment: Clean the piezoelectric ceramic sheet; 2) Base material mixing: Mix the epoxy resin matrix with the curing agent and stir evenly to obtain a mixed resin base material; 3) Additives: Add coupling agent, defoamer and toughening agent to the mixed resin base, and continue to stir until uniform; 4) Filler mixing: Hollow glass microspheres and thixotropic agent are premixed evenly to obtain filler premix; 5) Overall mixing: Add the filler premix obtained in step 4) to the mixture in step 3) and stir to form a uniform solid paste; 6) Vacuum dispersion: Place the solid paste from step 5) in a vacuum chamber and vacuum stir and degas for 15-25 minutes under a vacuum degree ≤ -0.095MPa to obtain a bubble-free and uniform paste; 7) Preforming: The solid paste is cut into pieces according to the weight or volume required for a single matching layer material to obtain a preform blank; 8) Compression molding: The preformed blank is placed in the matching layer material molding fixture, and then the piezoelectric ceramic sheet is placed in. Pressure is applied to compress and mold it in one go, so that the blank tightly wraps the ceramic and fills the molding cavity; 9) Gradient curing: The molded workpiece is subjected to gradient curing, which includes: first holding at 75-95℃ for 1-2 hours, and then holding at 100-120℃ for 0.5-1 hours. 10) Cooling and demolding: After curing, cool to room temperature and demold to obtain the matching layer-ceramic composite.

[0011] Preferably, the stirring speed in step 5) is 400-800 r / min.

[0012] Preferably, the compaction pressure in step 8) is 2-3 MPa.

[0013] Thirdly, the application of the wide-temperature-range ultrasonic gas meter matching layer material in ultrasonic gas meters is disclosed.

[0014] In this invention, polyethylene glycol (PEG) not only acts as a toughening agent but also forms a hydrogen bond network with modified amine curing agents to construct a flexible-rigid double crosslinked structure. This structure can inhibit the brittle fracture of epoxy resin at low temperatures (-40°C) and prevent the material from softening and deforming at high temperatures (70°C), thereby achieving stable mechanical properties over a wide temperature range. Simultaneously, the hydrophilicity of PEG and the hydrophobic thixotropic agent form a "microphase separation," further hindering water molecule penetration and improving moisture resistance.

[0015] In addition to enhancing interfacial bonding, silane coupling agents can also undergo secondary reactions with dimethyldichlorosilane residues on the surface of hydrophobic fumed silica to form a hydrophobic network bridging structure, which "anchors" hollow glass microspheres in a hydrophobic environment and significantly reduces the path of water vapor penetration along the microsphere interface.

[0016] Hydrophobic fumed silica is not only a thixotropic agent, but also acts as a "hydrophobic barrier reinforcing agent". Its hydrophobic segments, together with the coupling agent and the hydrophobic part of the epoxy resin, form a three-dimensional hydrophobic skeleton, which reduces the overall water absorption rate of the matching layer.

[0017] Modified polysiloxane defoamers not only eliminate macroscopic bubbles in a vacuum environment but also migrate to the surface of hollow glass microspheres, reducing the interfacial tension between the microspheres and the resin, promoting uniform distribution of the microspheres, and preventing agglomeration. In synergy with gradient curing processes, the low surface tension of the defoamer can suppress microcracks caused by differences in thermal expansion coefficients during curing, forming continuous, low-defect acoustic transmission channels and improving sound wave transmittance.

[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention employs adhesive-free, integrated in-situ curing, eliminating adhesive layer loss and significantly improving acoustic transmission efficiency; it also uses a matching layer material to directly encapsulate the ceramic, resulting in zero interface gaps and greatly enhancing sensitivity and stability. 2. The matching layer material prepared by this invention has wide temperature range adaptability and can remain stable without degradation for a long time under complex working conditions such as extreme cold and high temperature; 3. This invention uses low-stress gradient curing, resulting in no deformation, no cracks, no bubbles, and a significantly improved lifespan; 4. The integrated molding method of this invention eliminates the processes of dispensing, drying, and assembly, thereby improving production efficiency and consistency; the ceramic is protected by the material, making it waterproof, cavitation-proof, and anti-aging, thus extending the overall lifespan of the machine. Attached Figure Description

[0019] Figure 1 This is the heating curve of step 9) in Embodiment 1 of the present invention.

[0020] Figure 2 This is an impedance performance test diagram of an ultrasonic gas sensor assembled using the matching layer prepared in Example 1 of the present invention, where a is the admittance circle diagram and b is the impedance / phase-frequency characteristic curve. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention.

[0022] The epoxy resin matrix is ​​one of the following: bisphenol A type epoxy resins: E-51, E-44, and CYD-128; Polyethylene glycol has a molecular weight of 400-1000; The modified amine curing agent is prepared by the addition reaction of alicyclic amines and polyether amines with monofunctional epoxy diluents and cashew phenol. Specifically, 350g of alicyclic amine TAC-900 and 200g of polyether amine D230 are added to a four-necked flask. Stirring is started and nitrogen is introduced for protection. After heating to 50°C, 150g of monofunctional epoxy diluent allyl glycidyl ether AGE is slowly added dropwise, controlling the addition to be completed within 1 hour and ensuring that the temperature does not exceed 70°C during the addition process. After the addition is completed, the temperature is maintained at 70°C for 1 hour. Then, 300g of cashew phenol is added, and the temperature is raised to 90°C and maintained for 3 hours until the viscosity of the system is stable and the amine value no longer decreases significantly. The temperature is then lowered to below 40°C and the product is discharged to obtain the modified amine curing agent. The specific preparation method of the hydrophobic modified thixotropic agent is as follows: the raw material composition of the hydrophobic modified thixotropic agent is 200m² specific surface area. 2The preparation of fumed silica (fumed silica), hexamethyldisilazane (HMDS) and deionized water involves adding 475g of fumed silica into a high-speed mixer, turning on the mixer and adjusting the speed to 1000rpm, spraying in 5g of deionized water to disperse and activate for 10min, then slowly adding 25g of hexamethyldisilazane and continuing high-speed stirring for 20min. The mixture is then transferred to an oven and heat-treated at 120℃ for 2h. After cooling, it is pulverized and sieved to obtain the hydrophobic modified thixotropic agent. The defoamer is a polyether-modified polysiloxane, prepared by hydrosilylation reaction of hydrogen-containing polydimethylsiloxane and allyl polyether. Specifically, the raw material composition of the polyether-modified polysiloxane defoamer is 0.18% hydrogen content and 100 mPa viscosity. The preparation process involves the following steps: 1. Hydrogen-containing polydimethylsiloxane, EO / PO random copolymer with hydroxyl value blocking, 1000 molecular weight allyl polyether allyl methyl-terminated polyether APEG-1000, 2000 ppm isopropanol solution, chloroplatinic acid catalyst, and alkynyl alcohol polymerization inhibitor 1-ethynylcyclohexanol. The process begins by adding 400 g of hydrogen-containing polydimethylsiloxane and 0.3 g of polymerization inhibitor to a four-necked flask, purging with nitrogen, stirring, and heating to 80°C. Then, 0.5 g of chloroplatinic acid catalyst is added and stirred until homogeneous. Next, 600 g of allyl polyether is slowly added dropwise over 1.5 hours while maintaining the reaction temperature at 90°C. After the addition is complete, the reaction is maintained at 90°C for 4 hours. The reaction is considered complete when the Si-H peaks are almost completely eliminated by infrared detection. Finally, the low-boiling point is removed by vacuum treatment at 80°C and -0.09 MPa for 30 minutes. The mixture is then cooled to below 40°C and filtered to obtain the polyether-modified polysiloxane defoamer.

[0023] Example 1 The matching layer material for a wide-temperature-range ultrasonic gas meter comprises the following raw materials in parts by weight: Epoxy resin matrix E-51: 50 parts; Modified amine curing agent: 30 parts; Hollow glass microspheres (true density 0.2 g / cm³) 3 (average particle size 60 μm): 35 parts; Coupling agent KH-560: 0.5 parts; Toughening agent PEG (molecular weight 400): 1 part; Thixotropic agent: 1 part; Defoamer: 0.3 parts.

[0024] The above-mentioned wide-temperature-range ultrasonic gas meter matching layer material is integrally formed with piezoelectric ceramic, specifically including the following steps: 1) Ceramic pretreatment: Clean the piezoelectric ceramic sheet by ultrasonic cleaning with acetone, ethanol and deionized water in sequence for 8 minutes each. 2) Base material mixing: Mix the epoxy resin matrix with the modified amine curing agent and stir evenly to obtain a mixed resin base material; 3) Additives: Add coupling agent, defoamer and toughening agent to the mixed resin base, and continue to stir until uniform; 4) Filler mixing: Hollow glass microspheres and thixotropic agent are premixed evenly to obtain filler premix; 5) Overall mixing: Add the filler premix obtained in step 4) to the mixture in step 3), and stir at 600 r / min to form a uniform solid paste; 6) Vacuum dispersion: Place the solid paste from step 5) in a vacuum chamber and vacuum stir and degas for 20 minutes under a vacuum degree ≤ -0.095MPa to obtain a bubble-free and uniform paste; 7) Preforming: The solid paste is cut into pieces according to the weight or volume required for a single matching layer material to obtain a preform blank; 8) Compression molding: The preformed blank is placed in the matching layer material molding fixture, and then the piezoelectric ceramic sheet is placed in. A pressure of 2.5MPa is applied for one-time compression molding, so that the blank tightly wraps the ceramic and fills the molding cavity. One-time compression molding saves one process step compared to molding first and then bonding, saving an average of 5 minutes per piece, which is very effective for mass production. At the same time, it solves the problem that the ceramic is easily crushed due to the protruding negative electrode solder point when bonding ceramics. 9) Gradient curing: The molded workpiece undergoes gradient curing, which includes: first holding at 80℃ for 2 hours, then holding at 110℃ for 1 hour; the temperature rise curve is as follows. Figure 1 As shown.

[0025] 10) Cooling and demolding: After curing, cool to room temperature and demold to obtain the matching layer-ceramic composite.

[0026] Example 2 The matching layer material for a wide-temperature-range ultrasonic gas meter comprises the following raw materials in parts by weight: Epoxy resin matrix E-44: 40 parts; Modified amine curing agent: 15 parts; Hollow glass microspheres (true density 0.5 g / cm³) 3 (average particle size 60 μm): 20 parts; Coupling agent KH-560: 0.2 parts; Toughening agent PEG (molecular weight 600): 0.5 parts; Thixotropic agent: 0.5 parts; Defoamer: 0.1 parts.

[0027] The above-mentioned wide-temperature-range ultrasonic gas meter matching layer material is integrally formed with piezoelectric ceramic, specifically including the following steps: 1) Ceramic pretreatment: Clean the piezoelectric ceramic sheet by ultrasonic cleaning with acetone, ethanol and deionized water in sequence for 5 minutes each. 2) Base material mixing: Mix the epoxy resin matrix with the modified amine curing agent and stir evenly to obtain a mixed resin base material; 3) Additives: Add coupling agent, defoamer and toughening agent to the mixed resin base, and continue to stir until uniform; 4) Filler mixing: Hollow glass microspheres and thixotropic agent are premixed evenly to obtain filler premix; 5) Overall mixing: Add the filler premix obtained in step 4) to the mixture in step 3), and stir at 400 r / min to form a uniform solid paste; 6) Vacuum dispersion: Place the solid paste from step 5) in a vacuum chamber and vacuum stir and degas for 15 minutes under a vacuum degree ≤ -0.095MPa to obtain a bubble-free and uniform paste; 7) Preforming: The solid paste is cut into pieces according to the weight or volume required for a single matching layer material to obtain a preform blank; 8) Compression molding: The preformed blank is placed in the matching layer material molding fixture, and then the piezoelectric ceramic sheet is placed in. A pressure of 2MPa is applied to compress and mold it in one go, so that the blank tightly wraps the ceramic and fills the molding cavity; 9) Gradient curing: The molded workpiece is subjected to gradient curing, which includes: first holding at 75℃ for 2 hours, and then holding at 100℃ for 0.5 hours; 10) Cooling and demolding: After curing, cool to room temperature and demold to obtain the matching layer-ceramic composite.

[0028] Example 3 The matching layer material for a wide-temperature-range ultrasonic gas meter comprises the following raw materials in parts by weight: Epoxy resin matrix CYD-128: 60 parts; Modified amine curing agent: 20 parts; Hollow glass microspheres (true density 0.6 g / cm³) 3 (average particle size 60 μm): 40 parts; Coupling agent KH-550: 1.5 parts; Toughening agent PEG (molecular weight 1000): 2 parts; Thixotropic agent: 2 parts; Defoamer: 0.5 parts.

[0029] The above-mentioned wide-temperature-range ultrasonic gas meter matching layer material is integrally formed with piezoelectric ceramic, specifically including the following steps: 1) Ceramic pretreatment: Clean the piezoelectric ceramic sheet by ultrasonic cleaning with acetone, ethanol and deionized water in sequence for 10 minutes each. 2) Base material mixing: Mix the epoxy resin matrix with the modified amine curing agent and stir evenly to obtain a mixed resin base material; 3) Additives: Add coupling agent, defoamer and toughening agent to the mixed resin base, and continue to stir until uniform; 4) Filler mixing: Hollow glass microspheres and thixotropic agent are premixed evenly to obtain filler premix; 5) Overall mixing: Add the filler premix obtained in step 4) to the mixture in step 3), and stir at 800 r / min to form a uniform solid paste; 6) Vacuum dispersion: Place the solid paste from step 5) in a vacuum chamber and vacuum stir and degas for 25 minutes under a vacuum degree ≤ -0.095MPa to obtain a bubble-free and uniform paste; 7) Preforming: The solid paste is cut into pieces according to the weight or volume required for a single matching layer material to obtain a preform blank; 8) Compression molding: The preformed blank is placed in the matching layer material molding fixture, and then the piezoelectric ceramic sheet is placed in. A pressure of 3MPa is applied to compress and mold it in one go, so that the blank tightly wraps the ceramic and fills the molding cavity. 9) Gradient curing: The molded workpiece is subjected to gradient curing, which includes: first holding at 95℃ for 1 hour, and then holding at 120℃ for 0.5 hours; 10) Cooling and demolding: After curing, cool to room temperature and demold to obtain the matching layer-ceramic composite.

[0030] Comparative Example 1 Unlike Example 1, the curing agent in this comparative example is ethylenediamine (EDA), a common amine catalyst, while the rest of the preparation methods and steps are the same as in Example 1.

[0031] Comparative Example 2 Unlike Example 1, the thixotropic agent used in this comparative example is ordinary fumed silica, while the rest of the preparation methods and steps are the same as in Example 1.

[0032] Comparative Example 3 Unlike Example 1, the defoamer used in this comparative example is polydimethylsiloxane, while the rest of the preparation methods and steps are the same as in Example 1.

[0033] Comparative Example 4 Unlike Example 1, no coupling agent or toughening agent was added in this comparative example. Epoxy resin and hollow glass microspheres were mixed at a ratio of 2:1. Fumed silica was not used, and the mixture was cured at room temperature to obtain a matching layer-ceramic composite.

[0034] The matching layer-piezoelectric ceramic composite was fixed inside the molding matching layer fixture and filled with soft silicone for cushioning. Ceramic electrode leads were led out through a printed circuit board, fitted with rubber sleeves, and then encapsulated with epoxy resin to seal the lead outlets and ensure reliable device sealing. Tests were conducted under a driving voltage of 20Vpp and a propagation spacing of 60mm. The test results are shown in Table 1.

[0035] Table 1. Test results for examples and comparative examples.

[0036] An ultrasonic gas sensor was assembled using the matching layer prepared in Example 1. Impedance performance was tested using an impedance analyzer in the frequency range of 180kHz to 270kHz, with a test signal level of 1Vrms. After open-circuit / short-circuit compensation to eliminate the influence of parasitic parameters, the impedance performance test graph of the sensor was obtained as shown below. Figure 2 As shown. The impedance curve analysis is as follows: the phase curve achieves a 0° crossing at 224060.0Hz (dynamic resonant frequency Fs), corresponding to the impedance minimum point (Z) of the impedance curve. min =2.875kΩ), indicating that the sensor achieves optimal electromechanical energy conversion at this frequency, which is highly matched with the operating frequency of the ultrasonic gas meter (approximately 225kHz); the quality factor Q is calculated from the curve. m =41.87, electromechanical coupling coefficient Keff=0.435, static capacitance C0=2.299nF. All parameters meet the design requirements of piezoelectric transducers, proving that the matching layer and piezoelectric ceramic acoustic impedance are well matched and the interface loss is low. The impedance curve has a sharp peak shape and no spurious peak interference. The phase curve changes steeply, indicating that the sensor has excellent electromechanical coupling performance and parasitic vibration is effectively suppressed. The curve is smooth and has no abnormal fluctuations in the whole frequency band, proving that there are no defects such as bubbles, delamination, or debonding inside the sensor. The material has excellent uniformity and consistency, which can ensure the long-term stability of gas meter measurement.

[0037] The matching layer prepared in Example 1 was assembled into an ultrasonic gas sensor: piezoelectric ceramic was fixed inside the matching layer and filled with soft silicone for buffering; ceramic electrode leads were led out through a printed circuit board, fitted with a rubber sheath, and then encapsulated with epoxy resin to seal the lead outlets, ensuring reliable sealing of the device. The assembled sensor was subjected to wide temperature range cycling (-40℃ to +70℃), extreme high and low temperature environment tests, and mechanical performance tests. The results showed that after -40℃ / 2h... After 100 cycles at +70℃ for 2 hours, the sensor sensitivity showed no significant attenuation, signal fluctuation was ≤3%, the matching layer showed no cracking, delamination, or delamination, and the interface remained intact. After 24 hours of static treatment at -40℃, there was no brittleness or shrinkage deformation; after 24 hours of static treatment at +70℃, there was no softening or creep, and the dimensional change rate was ≤0.2%. The material's tensile strength, flexural strength, and impact toughness remained stable. It exhibited outstanding resistance to damp heat, aging, and cavitation. After high and low temperature cycling, there was no air leakage or water seepage, meeting the requirements for long-term stable use in complex environments over a wide temperature range. The test results for mechanical properties, resistance to damp heat aging, resistance to heat aging, and resistance to cavitation are shown in Table 2. Sensitivity was tested in parallel with 5 groups, and the results are shown in Table 3.

[0038] Table 2. Test results of mechanical properties, resistance to damp heat aging, resistance to heat aging, and resistance to cavitation.

[0039] Table 3 Sensitivity Test Results

Claims

1. A matching layer material for a wide-temperature-range ultrasonic gas meter, characterized in that, Including the following parts by weight of raw materials: Epoxy resin matrix: 40-60 parts; Hardener: 10-30 parts; Hollow glass microspheres: 20-45 parts; Coupling agent: 0.2-1.5 parts; Toughening agent: 0.5-2 parts; Thixotropic agent: 0.5-2 parts; Defoamer: 0.1-0.5 parts; The curing agent is a modified amine curing agent, which is prepared by the addition reaction of alicyclic amines and polyether amines with monofunctional epoxy diluents and cashew phenol. Specifically, 350g of alicyclic amine TAC-900 and 200g of polyether amine D230 are added to a four-necked flask. Stirring is started and nitrogen is introduced for protection. After heating to 50°C, 150g of monofunctional epoxy diluent allyl glycidyl ether AGE is slowly added dropwise, controlling the addition to be completed within 1 hour and ensuring that the temperature does not exceed 70°C during the addition process. After the addition is completed, the temperature is maintained at 70°C for 1 hour. Then, 300g of cashew phenol is added, and the temperature is raised to 90°C and maintained for 3 hours until the viscosity of the system is stable and the amine value no longer decreases significantly. The temperature is then lowered to below 40°C and the product is discharged to obtain the modified amine curing agent. The thixotropic agent is a hydrophobically modified thixotropic agent, which is a hydrophobic fumed silica surface treated with hexamethyldisilazane; the specific preparation method of the hydrophobically modified thixotropic agent is as follows: the raw material composition of the hydrophobically modified thixotropic agent has a specific surface area of ​​200 m². 2 To prepare a hydrophobic modified thixotropic agent, 475g of fumed silica, hexamethyldisilazane, and deionized water were added to a high-speed mixer. The mixer was started and the speed was adjusted to 1000 rpm. 5g of deionized water was sprayed in and dispersed for 10 min. Then, 25g of hexamethyldisilazane was slowly added and the mixture was stirred at high speed for 20 min. The mixture was then transferred to an oven and heat-treated at 120℃ for 2 h. After cooling, the mixture was pulverized and sieved to obtain the hydrophobic modified thixotropic agent. The defoamer is a polyether-modified polysiloxane, prepared by hydrosilylation reaction of hydrogen-containing polydimethylsiloxane and allyl polyether. Specifically, the raw material composition of the polyether-modified polysiloxane defoamer is 0.18% hydrogen content and 100 mPa viscosity. The preparation process involves the following steps:

1. Hydrogen-containing polydimethylsiloxane, EO / PO random copolymer with hydroxyl value blocking, 1000 molecular weight allyl polyether allyl methyl-terminated polyether APEG-1000, 2000 ppm isopropanol solution, chloroplatinic acid catalyst, and alkynyl alcohol polymerization inhibitor 1-ethynylcyclohexanol. The process begins by adding 400 g of hydrogen-containing polydimethylsiloxane and 0.3 g of polymerization inhibitor to a four-necked flask, purging with nitrogen, stirring, and heating to 80°C. Then, 0.5 g of chloroplatinic acid catalyst is added and stirred until homogeneous. Next, 600 g of allyl polyether is slowly added dropwise over 1.5 hours while maintaining the reaction temperature at 90°C. After the addition is complete, the reaction is maintained at 90°C for 4 hours. The reaction is considered complete when the Si-H peaks are almost completely eliminated by infrared detection. Finally, the low-boiling point is removed by vacuum treatment at 80°C and -0.09 MPa for 30 minutes. The mixture is then cooled to below 40°C and filtered to obtain the polyether-modified polysiloxane defoamer.

2. The wide-temperature-range ultrasonic gas meter matching layer material as described in claim 1, characterized in that, The epoxy resin matrix is ​​one of bisphenol A type epoxy resins E-51, E-44, and CYD-128.

3. The wide-temperature-range ultrasonic gas meter matching layer material as described in claim 1, characterized in that, The true density of the hollow glass microspheres is 0.2-0.6 g / cm³. 3 The particle size is 30-90μm.

4. The wide-temperature-range ultrasonic gas meter matching layer material as described in claim 1, characterized in that, The coupling agent is a silane coupling agent KH-550 or KH-560; the toughening agent is polyethylene glycol.

5. The application of the wide-temperature-range ultrasonic gas meter matching layer material as described in any one of claims 1-4, characterized in that, The process of integrally molding the aforementioned material with piezoelectric ceramics includes the following steps: 1) Ceramic pretreatment: Clean the piezoelectric ceramic sheet; 2) Base material mixing: Mix the epoxy resin matrix with the curing agent and stir evenly to obtain a mixed resin base material; 3) Additives: Add coupling agent, defoamer and toughening agent to the mixed resin base, and continue to stir until uniform; 4) Filler mixing: Hollow glass microspheres and thixotropic agent are premixed evenly to obtain filler premix; 5) Overall mixing: Add the filler premix obtained in step 4) to the mixture in step 3) and stir to form a uniform solid paste; 6) Vacuum dispersion: Place the solid paste from step 5) in a vacuum chamber and vacuum stir and degas for 15-25 minutes under a vacuum degree ≤ -0.095MPa to obtain a bubble-free and uniform paste; 7) Preforming: The solid paste is cut into pieces according to the weight or volume required for a single matching layer material to obtain a preform blank; 8) Compression molding: The preformed blank is placed in the matching layer material molding fixture, and then the piezoelectric ceramic sheet is placed in. Pressure is applied to compress and mold it in one go, so that the blank tightly wraps the ceramic and fills the molding cavity; 9) Gradient curing: The molded workpiece is subjected to gradient curing, which includes: first holding at 75-95℃ for 1-2 hours, and then holding at 100-120℃ for 0.5-1 hours. 10) Cooling and demolding: After curing, cool to room temperature and demold to obtain the matching layer-ceramic composite.

6. The application of the wide-temperature-range ultrasonic gas meter matching layer material as described in claim 5, characterized in that, In step 5), the stirring speed is 400-800 r / min.

7. The application of the wide-temperature-range ultrasonic gas meter matching layer material as described in claim 5, characterized in that, In step 8), the compaction pressure is 2-3 MPa.

8. The application of the wide-temperature-range ultrasonic gas meter matching layer material as described in any one of claims 1-3 in ultrasonic gas meters.

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