Sound matching layer suitable for ultrasonic gas meter transducer under complex gas source working condition and preparation method of sound matching layer

Abstract

The invention discloses a sound matching layer suitable for an ultrasonic gas meter transducer under a complex gas source working condition and a preparation method of the sound matching layer, and relates to the technical field of ultrasonic gas meters. The sound matching layer comprises the following components: epoxy resin, a curing agent, modified hollow glass beads, acetone, carboxyl-terminated nitrile rubber, a defoaming agent, polyoxyethylene fatty acid, graphene nanoplatelets, hydrophobic silicon dioxide and fumed silica. According to the scheme, the surface-coated modified hollow glass beads are adopted, then plasma activation and grafting modification are utilized, the interfacial compatibility of the beads and epoxy resin is improved, the agglomeration phenomenon is reduced, meanwhile, the epoxy resin and the functional additive are blended, the uniformity of the internal structure of the material is optimized, and the effect of stable matching of acoustic impedance is achieved; according to the ultrasonic transducer, the reflection loss of sound waves on a gas-solid interface is effectively reduced, the energy attenuation is reduced, the transmitting and receiving sensitivity of the ultrasonic transducer is improved, and the stability of the metering precision of the gas meter under the complex gas source working condition is ensured.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic gas meter technology, specifically to an acoustic matching layer for ultrasonic gas meter transducers under complex gas source conditions and its preparation method. Background Technology

[0002] As the core component of ultrasonic gas meters, the ultrasonic transducer functions to convert electrical energy into mechanical energy (ultrasound) through piezoelectric ceramic materials. The performance improvement of gas-medium ultrasonic transducers depends on the performance of the acoustic impedance matching layer. Existing acoustic matching layers generally adopt a composite system of low-density fillers and polymer matrices. A typical scheme is to prepare a single-layer structure using hollow glass microspheres as fillers and epoxy resin as the matrix. By adjusting the filler content, the composite acoustic impedance is reduced to approach the requirements of gas medium matching.

[0003] Currently, under complex gas source conditions, the acoustic matching layer of ultrasonic gas meter transducers is generally made by directly mixing hollow glass microspheres with epoxy resin. Due to the insufficient surface activity of hollow glass microspheres, the compatibility is poor, and there is a lack of targeted functional additives. At the same time, uneven dispersion, many residual bubbles, and high curing stress during the preparation process result in poor acoustic impedance matching of the acoustic matching layer. In gas sources containing impurities, water vapor, and corrosive gases, performance degradation and structural damage are likely to occur, resulting in low transducer sensitivity and reduced metering accuracy, which cannot meet the requirements for long-term stable operation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an acoustic matching layer for ultrasonic gas meter transducers under complex gas source conditions and its preparation method, thus solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, wherein the acoustic matching layer comprises the following components by weight: 100-300 parts epoxy resin, 15-40 parts curing agent, 40-60 parts modified hollow glass microspheres, 3-5 parts acetone, 2-6 parts carboxyl-terminated butadiene-acrylonitrile rubber, 1-2 parts defoamer, 1-3 parts fatty acid polyoxyethylene ester, 1-3 parts graphene microsheets, 2-5 parts hydrophobic silica, and 2-5 parts fumed silica.

[0006] Preferably, the preparation method of the modified hollow glass microspheres is as follows: A1. Prepare raw materials: hollow glass microspheres and silane coupling agent. Place the hollow glass microspheres in a plasma chamber, start the vacuum pump of the plasma chamber to make the vacuum degree in the plasma chamber reach the set value, and introduce oxygen to maintain the flow rate. Turn on the radio frequency power supply to activate the surface of the hollow glass microspheres to obtain pretreated hollow glass microspheres. A2. Dissolve the silane coupling agent in a mixed solution of ethanol and water, and add acetic acid to adjust the pH to 4.5 to obtain a silane solution. Then add the pretreated hollow glass microspheres to the silane solution, stir at a constant temperature, filter under reduced pressure, wash with ethanol 3 times, and vacuum dry at 80°C for 4 hours to obtain microspheres with surface grafted double bonds. A3. Add polyacrylamide and the microspheres to an N,N-dimethylformamide solution and stir at 40°C for 3 hours. The blend is washed and filtered three times with N,N-dimethylformamide to remove residual monomers and dried at 60°C for 10 hours to obtain modified hollow glass microspheres with a polyacrylamide coating.

[0007] A method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, the method specifically includes the following steps: S1. Prepare a high-speed shearing machine, mix hydrophobic silica and graphene micro-sheets with epoxy resin and put them into the high-speed shearing machine and start it. After shearing and dispersing, a pre-dispersed slurry is formed. Add the pre-dispersed slurry, epoxy resin, curing agent, carboxyl-terminated nitrile rubber, defoamer and fatty acid polyoxyethylene ester into the mixer in sequence and start it. S2. The mixer is continuously stirred, and the modified hollow glass microspheres are added to the mixer in two batches. When the modified hollow glass microspheres are added for the first time, the mixer is stirred at a speed of 800-1000 r / min at room temperature for 5 minutes. When the modified hollow glass microspheres are added again, the stirring speed of the mixer is adjusted to 1500-2000 r / min, and the mixer is stirred at room temperature for 15-25 minutes. Then the fumed silica is added to the stirred mixture to obtain a premix. S3. Prepare a vacuum chamber, place the premix in the vacuum chamber and start it. The premix is ​​degassed in the vacuum chamber at a vacuum degree of 0.05-0.07MPa for 5-8 minutes. After the degassed treatment is completed, the vacuum degree of the vacuum chamber is increased to 0.08-0.1MPa and degassed for 10-15 minutes to obtain the degassed material. S4. Pour the deaerated material into the sound matching layer mold, let it stand at room temperature for 1-2 hours to initially level it, then put the sound matching layer mold into a drying oven, start the drying oven and set the initial drying temperature from room temperature to 60℃ at a rate of 20℃ / h and dry for 30 minutes, then raise it to 80-100℃ at a rate of 20℃ / h and keep it at that temperature for 1-2 hours, and finally raise the temperature to 120-150℃ at a rate of 20℃ / h. Then transfer the sound matching layer mold to a water bath device for curing. During the curing process, the water bath device uses constant temperature hot water circulation heating. S5. After curing, the material in the acoustic matching layer mold is cooled and annealed. The acoustic matching layer mold is first cooled to 100°C at a rate of 5-10°C / h and held for 1.5h, then cooled to 80°C at a rate of 5-10°C / h and held for 1h, and finally cooled to room temperature at a rate of 5-10°C / h. The cured acoustic matching layer is then removed from the mold to obtain the cured acoustic matching layer.

[0008] Preferably, the constant temperature of the hot water in the water bath device is 120-150℃, the hot water circulation flow rate of the water bath device is 2-5L / min, and the curing time of the acoustic matching layer mold in the water bath device is 2-3h.

[0009] Preferably, after the acoustic matching layer is demolded in step S6, its edges and surface are ground with a diamond grinding wheel with a particle size of 800-1200. After grinding, the acoustic matching layer is placed in an ultrasonic cleaner and cleaned with anhydrous ethanol.

[0010] Preferably, the ultrasonic cleaner has a cleaning power of 150-200W, uses an ultrasonic frequency of 30-40kHz during the cleaning process, and has a cleaning time of 10-15 minutes.

[0011] Preferably, in step S1, the high-speed shearing machine has a dispersion speed of 3000-4000 r / min and a shearing dispersion time of 15-20 min, the mixer is stirred at room temperature for 10-15 min, and the stirring speed of the mixer is 800-1200 r / min.

[0012] Preferably, in step S3, the vacuum chamber is evacuated from atmospheric pressure to 0.05-0.07 MPa in the first stage, and the evacuation rate is 0.01-0.015 MPa / min. In the second stage, the vacuum chamber is evacuated from 0.05-0.07 MPa to 0.08-0.1 MPa, and the evacuation rate is 0.008-0.012 MPa / min.

[0013] Preferably, the epoxy resin in step S1 is pretreated before mixing. The epoxy resin pretreatment is to preheat at a temperature of 40-50°C for 30-40 minutes, and the epoxy resin is stirred and degassed at 200-300 r / min during the preheating process.

[0014] Preferably, in step S5, the material in the acoustic matching layer mold is cooled and annealed by an inert gas for protection. The inert gas is nitrogen, and the flow rate of the inert gas is 0.5 to 1 L / min.

[0015] This invention provides an acoustic matching layer for ultrasonic gas meter transducers under complex gas source conditions and its preparation method. It has the following beneficial effects: (1) By using surface-coated modified hollow glass microspheres, plasma activation and grafting modification are used to improve the interfacial compatibility between microspheres and epoxy resin, reducing agglomeration. At the same time, epoxy resin and functional additives are blended to optimize the uniformity of the internal structure of the material, achieving a stable matching effect of acoustic impedance, effectively reducing the reflection loss of sound waves at the gas-solid interface, reducing energy attenuation, improving the transceiver sensitivity of the ultrasonic transducer, and ensuring the stability of the metering accuracy of the gas meter under complex gas source conditions.

[0016] (2) The hydrophobic silica added to the formula can form a continuous hydrophobic barrier inside the material, preventing water vapor from penetrating into the acoustic matching layer. The graphene microplates, with their excellent barrier properties, construct an anti-corrosion network, delaying the erosion of the material by corrosive gases. At the same time, the tight bonding between the modified hollow glass microspheres and the resin matrix reduces structural defects and enhances the material's weather resistance and corrosion resistance. Therefore, when the acoustic matching layer is used for a long time in a gas source environment containing impurities, high humidity and corrosiveness, it is not easy for the performance of the acoustic matching layer to degrade or the structure to break down, which greatly improves the service life and operational reliability of the ultrasonic gas meter transducer.

[0017] (3) During the preparation process, the acoustic matching layer ensures the uniform distribution of each functional additive through staged shearing and dispersion. The vacuum high-temperature degassing process reduces the residual bubbles inside the material. The curing and annealing treatment effectively releases the curing stress, avoids the generation of microcracks, and improves the material density and structural stability. This makes the mechanical properties of the acoustic matching layer more uniform, the sound wave propagation path smooth, and the signal distortion will not be caused by local structural defects. This achieves the long-term stable electroacoustic conversion performance of the transducer and meets the long-term use requirements of high-precision metering under complex gas source conditions. Attached Figure Description

[0018] Figure 1 This is a flowchart of the acoustic matching layer preparation steps for an ultrasonic gas meter transducer suitable for complex gas source conditions and its preparation method, according to the present invention. Figure 2 This is a flowchart illustrating the steps involved in preparing modified hollow glass microspheres for an acoustic matching layer suitable for ultrasonic gas meter transducers under complex gas source conditions, as described in this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example Reference Figure 1-2 This invention provides an acoustic matching layer for ultrasonic gas meter transducers under complex gas source conditions and its preparation method. To achieve the above objectives, this invention is implemented through the following technical solution: The acoustic matching layer comprises the following components by weight: 100 parts epoxy resin, 15 parts curing agent (phenolic curing agent), 40 parts modified hollow glass microspheres, 3 parts acetone, 2 parts carboxyl-terminated butadiene-acrylonitrile rubber, 1 part defoamer (selected as polyether-modified polysiloxane defoamer), 1 part fatty acid polyoxyethylene ester, 1 part graphene microsheets, 2 parts hydrophobic silica, and 2 parts fumed silica.

[0021] The specific preparation method of modified hollow glass microspheres is as follows: A1. Prepare the raw materials hollow glass microspheres and silane coupling agent. Place the hollow glass microspheres in the plasma chamber, start the vacuum pump of the plasma chamber to make the vacuum degree in the plasma chamber reach the set value, and introduce oxygen to maintain the flow rate. Turn on the radio frequency power supply to activate the surface of the hollow glass microspheres to obtain pretreated hollow glass microspheres. A2. Dissolve the silane coupling agent in a mixed solution of ethanol and water, and add acetic acid to adjust the pH to 4.5 to obtain a silane solution. Then add the pretreated hollow glass microspheres to the silane solution, stir at a constant temperature, filter under reduced pressure, wash with ethanol 3 times, and vacuum dry at 80℃ for 4 hours to obtain microspheres with surface grafted double bonds. A3. Polyacrylamide and microspheres were added to an N,N-dimethylformamide solution and stirred at 40°C for 3 hours. The blend was washed and filtered three times with N,N-dimethylformamide to remove residual monomers and dried at 60°C for 10 hours to obtain modified hollow glass microspheres with a polyacrylamide coating.

[0022] The specific steps in preparing the acoustic matching layer include: S1. Prepare a high-speed shearing machine. Mix hydrophobic silica and graphene micro-sheets with epoxy resin and put them into the high-speed shearing machine and start it. The dispersion speed of the high-speed shearing machine is 3000 r / min and the shearing and dispersion time is 15 min. After shearing and dispersion, a pre-dispersed slurry is formed. Add the pre-dispersed slurry, epoxy resin, curing agent, carboxyl-terminated nitrile rubber, defoamer and fatty acid polyoxyethylene ester into the mixer in sequence and start it. Mix the mixer at room temperature for 10 min and the mixing speed of the mixer is 800 r / min. S2. The modified hollow glass microspheres are added to the mixer in two batches. When the modified hollow glass microspheres are added for the first time, the mixer is stirred at 800 r / min at room temperature for 5 minutes. When the modified hollow glass microspheres are added again, the stirring speed of the mixer is adjusted to 1500 r / min and stirred at room temperature for 15 minutes. Then, fumed silica is added to the mixture to obtain a premix. S3. Prepare a vacuum chamber, place the premix in the vacuum chamber and start it. The premix is ​​degassed in the vacuum chamber at a vacuum degree of 0.05MPa for 5 minutes. After the degassed treatment is completed, the vacuum degree of the vacuum chamber is increased to 0.08MPa and degassed for 10 minutes to obtain the degassed material. S4. Pour the deaerated material into the sound matching layer mold and let it stand at room temperature for 1 hour to initially level it. Then, put the sound matching layer mold into a drying oven, start the drying oven, and set the initial drying temperature to rise from room temperature to 60°C at a rate of 20°C / h and keep it at that temperature for 30 minutes. Then, rise the temperature to 100°C at a rate of 20°C / h and keep it at that temperature for 1 hour. Finally, rise the temperature to 150°C at a rate of 20°C / h. Then, transfer the sound matching layer mold to a water bath device for curing. During the curing process, the water bath device uses constant temperature hot water circulation heating. The constant temperature hot water temperature of the water bath device is 120°C, the hot water circulation flow rate of the water bath device is 2L / min, and the curing time of the sound matching layer mold in the water bath device is 2 hours. S5. After curing, the material in the acoustic matching layer mold is cooled and annealed. During the cooling and annealing process, inert gas (nitrogen) is introduced for protection. The inert gas flow rate is 0.5 L / min. The acoustic matching layer mold is first cooled to 100°C at a rate of 5°C / h and held for 1.5 h, then cooled to 80°C at a rate of 5°C / h and held for 1 h, and finally cooled to room temperature at a rate of 5°C / h. The cured acoustic matching layer is then removed from the mold. After demolding, the edges and surface of the acoustic matching layer are ground with a 1000-mesh diamond grinding wheel. After grinding, the acoustic matching layer is placed in an ultrasonic cleaner and cleaned with anhydrous ethanol. The ultrasonic cleaner has a cleaning power of 150W and uses an ultrasonic frequency of 30kHz for 10 minutes to obtain the cured acoustic matching layer.

[0023] Comparative Example 1 The sound matching layer comprises the following components by weight: 100 parts epoxy resin, 15 parts curing agent, 40 parts hollow glass microspheres, 3 parts acetone, 2 parts carboxyl-terminated butadiene-acrylonitrile rubber, 1 part defoamer, 1 part fatty acid polyoxyethylene ester, 1 part graphene microplates, 2 parts hydrophobic silica, and 2 parts fumed silica.

[0024] The specific steps in preparing the acoustic matching layer include: S1. Prepare a high-speed shearing machine. Mix hydrophobic silica and graphene micro-sheets with epoxy resin and put them into the high-speed shearing machine and start it. The dispersion speed of the high-speed shearing machine is 3000 r / min and the shearing and dispersion time is 15 min. After shearing and dispersion, a pre-dispersed slurry is formed. Add the pre-dispersed slurry, epoxy resin, curing agent, carboxyl-terminated nitrile rubber, defoamer and fatty acid polyoxyethylene ester into the mixer in sequence and start it. Mix the mixer at room temperature for 10 min and the mixing speed of the mixer is 800 r / min. S2. The mixer is continuously stirred, and hollow glass microspheres are added to the mixer in two batches. When the hollow glass microspheres are added for the first time, the mixer is stirred at 800 r / min at room temperature for 5 minutes. When the hollow glass microspheres are added again, the stirring speed of the mixer is adjusted to 1500 r / min, and the mixture is stirred at room temperature for 15 minutes. Then, fumed silica is added to the mixture to obtain a premix. S3. Prepare a vacuum chamber, place the premix in the vacuum chamber and start it. The premix is ​​degassed in the vacuum chamber at a vacuum degree of 0.05MPa for 5 minutes. After the degassed treatment is completed, the vacuum degree of the vacuum chamber is increased to 0.08MPa and degassed for 10 minutes to obtain the degassed material. S4. Pour the deaerated material into the sound matching layer mold and let it stand at room temperature for 1 hour to initially level it. Then, put the sound matching layer mold into a drying oven, start the drying oven, and set the initial drying temperature to rise from room temperature to 60°C at a rate of 20°C / h and keep it at that temperature for 30 minutes. Then, rise the temperature to 100°C at a rate of 20°C / h and keep it at that temperature for 1 hour. Finally, rise the temperature to 150°C at a rate of 20°C / h. Then, transfer the sound matching layer mold to a water bath device for curing. During the curing process, the water bath device uses constant temperature hot water circulation heating. The constant temperature hot water temperature of the water bath device is 120°C, the hot water circulation flow rate of the water bath device is 2L / min, and the curing time of the sound matching layer mold in the water bath device is 2 hours. S5. After curing, the material in the acoustic matching layer mold is cooled and annealed. During the cooling and annealing process, inert gas (nitrogen) is introduced for protection. The inert gas flow rate is 0.5 L / min. The acoustic matching layer mold is first cooled to 100°C at a rate of 5°C / h and held for 1.5 h, then cooled to 80°C at a rate of 5°C / h and held for 1 h, and finally cooled to room temperature at a rate of 5°C / h. The cured acoustic matching layer is then removed from the mold. After demolding, the edges and surface of the acoustic matching layer are ground with a 1000-mesh diamond grinding wheel. After grinding, the acoustic matching layer is placed in an ultrasonic cleaner and cleaned with anhydrous ethanol. The ultrasonic cleaner has a cleaning power of 150W and uses an ultrasonic frequency of 30kHz for 10 minutes to obtain the cured acoustic matching layer.

[0025] The difference between Comparative Example 1 and the Example is that the raw material used in Comparative Example 1 is unmodified hollow glass microspheres, while the other raw materials and preparation process are the same as those in the Example.

[0026] Comparative Example 2 The acoustic matching layer comprises the following components by weight: 100 parts epoxy resin, 15 parts curing agent, 40 parts modified hollow glass microspheres, 3 parts acetone, 2 parts carboxyl-terminated butadiene-acrylonitrile rubber, 1 part defoamer, 1 part fatty acid polyoxyethylene ester, and 2 parts fumed silica.

[0027] The specific preparation method of modified hollow glass microspheres is as follows: A1. Prepare the raw materials hollow glass microspheres and silane coupling agent. Place the hollow glass microspheres in the plasma chamber, start the vacuum pump of the plasma chamber to make the vacuum degree in the plasma chamber reach the set value, and introduce oxygen to maintain the flow rate. Turn on the radio frequency power supply to activate the surface of the hollow glass microspheres to obtain pretreated hollow glass microspheres. A2. Dissolve the silane coupling agent in a mixed solution of ethanol and water, and add acetic acid to adjust the pH to 4.5 to obtain a silane solution. Then add the pretreated hollow glass microspheres to the silane solution, stir at a constant temperature, filter under reduced pressure, wash with ethanol 3 times, and vacuum dry at 80℃ for 4 hours to obtain microspheres with surface grafted double bonds. A3. Polyacrylamide and microspheres were added to an N,N-dimethylformamide solution and stirred at 40°C for 3 hours. The blend was washed and filtered three times with N,N-dimethylformamide to remove residual monomers and dried at 60°C for 10 hours to obtain modified hollow glass microspheres with a polyacrylamide coating.

[0028] The specific steps in preparing the acoustic matching layer include: S1. Prepare a high-speed shearing machine, put epoxy resin into the high-speed shearing machine and start it. The dispersion speed of the high-speed shearing machine is 3000 r / min and the shearing and dispersion time is 15 min. After shearing and dispersion, a pre-dispersed slurry is formed. Add the pre-dispersed slurry, epoxy resin, curing agent, carboxyl-terminated nitrile rubber, defoamer and fatty acid polyoxyethylene ester into the mixer in sequence and start it. Mix the mixer at room temperature for 10 min and the mixing speed of the mixer is 800 r / min. S2. The modified hollow glass microspheres are added to the mixer in two batches. When the modified hollow glass microspheres are added for the first time, the mixer is stirred at 800 r / min at room temperature for 5 minutes. When the modified hollow glass microspheres are added again, the stirring speed of the mixer is adjusted to 1500 r / min and stirred at room temperature for 15 minutes. Then, fumed silica is added to the mixture to obtain a premix. S3. Prepare a vacuum chamber, place the premix in the vacuum chamber and start it. The premix is ​​degassed in the vacuum chamber at a vacuum degree of 0.05MPa for 5 minutes. After the degassed treatment is completed, the vacuum degree of the vacuum chamber is increased to 0.08MPa and degassed for 10 minutes to obtain the degassed material. S4. Pour the deaerated material into the sound matching layer mold and let it stand at room temperature for 1 hour to initially level it. Then, put the sound matching layer mold into a drying oven, start the drying oven, and set the initial drying temperature to rise from room temperature to 60°C at a rate of 20°C / h and keep it at that temperature for 30 minutes. Then, rise the temperature to 100°C at a rate of 20°C / h and keep it at that temperature for 1 hour. Finally, rise the temperature to 150°C at a rate of 20°C / h. Then, transfer the sound matching layer mold to a water bath device for curing. During the curing process, the water bath device uses constant temperature hot water circulation heating. The constant temperature hot water temperature of the water bath device is 120°C, the hot water circulation flow rate of the water bath device is 2L / min, and the curing time of the sound matching layer mold in the water bath device is 2 hours. S5. After curing, the material in the acoustic matching layer mold is cooled and annealed. During the cooling and annealing process, inert gas (nitrogen) is introduced for protection. The inert gas flow rate is 0.5 L / min. The acoustic matching layer mold is first cooled to 100°C at a rate of 5°C / h and held for 1.5 h, then cooled to 80°C at a rate of 5°C / h and held for 1 h, and finally cooled to room temperature at a rate of 5°C / h. The cured acoustic matching layer is then removed from the mold. After demolding, the edges and surface of the acoustic matching layer are ground with a 1000-mesh diamond grinding wheel. After grinding, the acoustic matching layer is placed in an ultrasonic cleaner and cleaned with anhydrous ethanol. The ultrasonic cleaner has a cleaning power of 150W and uses an ultrasonic frequency of 30kHz for 10 minutes to obtain the cured acoustic matching layer.

[0029] The difference between Comparative Example 2 and the Example is that, unlike the Example, no graphene microsheets and hydrophobic silica were added to the raw materials, while the other raw materials and preparation process are the same as those in the Example.

[0030] Comparative Example 3 The acoustic matching layer comprises the following components by weight: 100 parts epoxy resin, 15 parts curing agent, 40 parts modified hollow glass microspheres, 3 parts acetone, 2 parts carboxyl-terminated butadiene-acrylonitrile rubber, 1 part defoamer, 1 part fatty acid polyoxyethylene ester, 1 part graphene microplates, 2 parts hydrophobic silica, and 2 parts fumed silica.

[0031] The specific preparation method of modified hollow glass microspheres is as follows: A1. Prepare the raw materials hollow glass microspheres and silane coupling agent. Place the hollow glass microspheres in the plasma chamber, start the vacuum pump of the plasma chamber to make the vacuum degree in the plasma chamber reach the set value, and introduce oxygen to maintain the flow rate. Turn on the radio frequency power supply to activate the surface of the hollow glass microspheres to obtain pretreated hollow glass microspheres. A2. Dissolve the silane coupling agent in a mixed solution of ethanol and water, and add acetic acid to adjust the pH to 4.5 to obtain a silane solution. Then add the pretreated hollow glass microspheres to the silane solution, stir at a constant temperature, filter under reduced pressure, wash with ethanol 3 times, and vacuum dry at 80℃ for 4 hours to obtain microspheres with surface grafted double bonds. A3. Polyacrylamide and microspheres were added to an N,N-dimethylformamide solution and stirred at 40°C for 3 hours. The blend was washed and filtered three times with N,N-dimethylformamide to remove residual monomers and dried at 60°C for 10 hours to obtain modified hollow glass microspheres with a polyacrylamide coating.

[0032] The specific steps in preparing the acoustic matching layer include: S1. Prepare a high-speed shearing machine. Mix hydrophobic silica and graphene micro-sheets with epoxy resin and put them into the high-speed shearing machine and start it. The dispersion speed of the high-speed shearing machine is 3000 r / min and the shearing and dispersion time is 15 min. After shearing and dispersion, a pre-dispersed slurry is formed. Add the pre-dispersed slurry, epoxy resin, curing agent, carboxyl-terminated nitrile rubber, defoamer and fatty acid polyoxyethylene ester into the mixer in sequence and start it. Mix the mixer at room temperature for 10 min and the mixing speed of the mixer is 800 r / min. S2. The modified hollow glass microspheres are added to the mixer in two batches while the mixer is continuously stirring at 1500 r / min at room temperature for 18 min. Then, fumed silica is added to the mixture to obtain a premix. S3. Prepare a vacuum chamber, place the premix in the vacuum chamber and start it. The premix is ​​degassed in the vacuum chamber at a vacuum degree of 0.05MPa for 5 minutes. After the degassed treatment is completed, the vacuum degree of the vacuum chamber is increased to 0.08MPa and degassed for 10 minutes to obtain the degassed material. S4. Pour the deaerated material into the sound matching layer mold, let it stand at room temperature for 1 hour to initially level it, then put the sound matching layer mold into the drying oven, start the drying oven and set the drying temperature to rise from room temperature to 150℃ at a rate of 20℃ / h, dry and keep it at that temperature for 2 hours, then transfer the sound matching layer mold to a water bath device for curing. During the curing process, the water bath device is heated with constant temperature hot water circulation. The constant temperature hot water temperature of the water bath device is 120℃, the hot water circulation flow rate of the water bath device is 2L / min, and the curing time of the sound matching layer mold in the water bath device is 2 hours. S5. After curing, remove the acoustic matching layer from the mold. After demolding, grind the edges and surface of the acoustic matching layer with a diamond grinding wheel with a grit size of 1000 mesh. After grinding, put the acoustic matching layer into an ultrasonic cleaner and clean it with anhydrous ethanol. The cleaning power of the ultrasonic cleaner is 150W. The ultrasonic cleaning frequency is 30kHz and the cleaning time is 10min to obtain the cured acoustic matching layer.

[0033] The difference between Comparative Example 3 and the Example is that the modified hollow glass microspheres in Example 3 were not added and stirred at once, the mold drying was a one-time drying and curing process, the cooling annealing step was not used, and the raw materials and other steps were the same as in Example 3.

[0034] Comparative Example 4 The sound matching layer comprises the following components by weight: 100 parts epoxy resin, 15 parts curing agent, 40 parts hollow glass microspheres, 3 parts acetone, and 1 part defoamer. Pour the epoxy resin into a mixer, add acetone and stir to dilute it. The stirring speed of the mixer is 500 r / min and the stirring time is 5 min. Then add the curing agent and defoamer in sequence, and continue to stir at 500 r / min for 10 min to obtain the base resin liquid. Hollow glass microspheres were added to the base resin solution, the stirring speed was adjusted to 800 r / min, and the mixture was stirred continuously for 20 min at room temperature to obtain a mixture. The mixture was transferred to a vacuum chamber and degassed for 15 minutes under a vacuum of 0.08 MPa. After degassed, the molded material was obtained. Pour the molding material into the sound matching layer mold and let it stand at room temperature for 30 minutes to initially level it. Then, put the sound matching layer mold into an oven, set the temperature to 120℃, and cure it at a constant temperature for 3 hours. After curing, let the sound matching layer mold cool naturally to room temperature. After the sound matching layer has cooled and cured, remove it from the sound matching layer mold and use sandpaper to polish the edges and surface to obtain the finished sound matching layer.

[0035] The difference between Comparative Example 4 and the embodiment is that Comparative Example 4 uses existing technology for the preparation of the acoustic matching layer.

[0036] Product testing of sound matching layer Core acoustic performance testing Acoustic impedance test Test equipment: Acoustic impedance meter; Test method: Cut the acoustic matching layer sample into a standard sample of Φ10mm×2mm, place it in the test cavity, measure the sound pressure reflection coefficient, calculate the acoustic impedance and take the average value of 3 measurements.

[0037] Longitudinal wave speed test Test equipment: Pulse echo analyzer; Test method: The thickness of the acoustic matching layer sample was measured with a laser thickness gauge (average of 5 points). An ultrasonic pulse was emitted through the probe of a pulse echo tester, the round-trip propagation time of the sound wave was recorded, the longitudinal wave velocity was calculated, and the test was repeated 3 times and the average value was taken.

[0038] Sound attenuation coefficient test Test equipment: Ultrasonic attenuator; Test method: Measure the sound pressure amplitude of the acoustic matching layer sample at propagation distances of 0mm, 5mm, and 10mm, calculate the attenuation coefficient, and take the average value of 3 measurements.

[0039] Table 1 shows the test results of the core acoustic performance of the acoustic matching layer:

[0040] Appearance and mechanical performance testing Mechanical property testing Hardness: Shore D hardness tester, 5 points were evenly selected on the surface of the acoustic matching layer sample for measurement, and the average value was taken; Compressive strength: Using a material mechanics testing machine, the acoustic matching layer sample size is Φ5mm×10mm, the loading rate is 1mm / min, the maximum pressure at fracture is recorded, and the compressive strength is calculated. Appearance quality inspection Surface defects: Scratches, bubbles and cracks on the surface of the acoustic matching layer sample were observed using an optical microscope, and the number of defects was counted. Internal defects: The ultrasonic C-scan system scans the interior of the acoustic matching layer sample and records the area ratio of defects such as pores and delamination.

[0041] Table 2 shows the test results of the appearance and mechanical properties of the acoustic matching layer:

[0042] Environmental stability test High and low temperature cycling test Test equipment: High and low temperature cycling chamber; Test method: The acoustic matching layer sample was cycled 10 times from -40℃ (1h) to 85℃ (1h), and the acoustic impedance before and after the cycle was measured and the rate of change was calculated.

[0043] Damp heat aging test Testing equipment: Damp heat aging chamber; Test method: The acoustic matching layer sample was placed in an environment of 40℃ and 95%RH for 1000h, and the attenuation coefficient before and after aging was tested.

[0044] Table 3 shows the environmental stability test results of the acoustic matching layer:

[0045] Corrosion resistance, moisture resistance and bubble residue test Moisture resistance test Test procedure: Dry the acoustic matching layer sample in an oven at 105℃ for 2 hours until constant weight, and record the weight as m1. Then place it in a constant temperature and humidity chamber at 40℃ and 90% relative humidity for 1000 hours. After taking it out, use filter paper to absorb the surface moisture, record the weight as m2, and calculate the water absorption rate. Corrosion resistance test Test procedure: Place the transducer with the acoustic matching layer in a simulated gas source device, introduce dry air containing 50ppm hydrogen sulfide, run continuously for 3000h, and test the transducer sensitivity before and after the operation. Bubble Residue Rate Test Test procedure: Cut the acoustic matching layer sample along the cross-section, observe the cross-section with a microscope, randomly select 5 fields of view, calculate the bubble area ratio using image analysis software, and take the average value.

[0046] Table 4 shows the test results of the sound matching layer's corrosion resistance, moisture resistance, and bubble residue rate:

[0047] As can be seen from the above test results, the modified hollow glass microspheres with plasma activation and polyacrylamide coating used in the embodiment significantly improved the compatibility between the modified hollow glass microspheres and epoxy resin. Compared with Comparative Example 1, the acoustic impedance deviation was reduced, the attenuation coefficient was reduced, and the compressive strength was increased, proving that the modified hollow glass microspheres effectively optimized the interface bonding and reduced acoustic loss and structural defects. The addition of graphene microsheets and hydrophobic silica reduced the moisture absorption rate, the sensitivity decay rate after corrosion, and the damp heat aging decay of the example compared with Comparative Example 2, verifying that hydrophobic silica and graphene microsheets improved the corrosion resistance and moisture resistance of the acoustic matching layer under complex gas source conditions. The synergistic application of staged stirring and dispersion, vacuum degassing, multi-stage curing and annealing processes resulted in a lower bubble residue rate, improved compressive strength and improved high and low temperature cycling stability in the example compared to Comparative Example 3. This indicates that the staged stirring and dispersion, vacuum degassing, multi-stage curing and annealing processes can reduce internal defects in the acoustic matching layer, release internal stress and improve the product quality of the acoustic matching layer. Compared with Comparative Example 4, the parameters and performance of the embodiment are significantly improved, which significantly enhances the acoustic performance, mechanical strength, environmental stability and adaptability to complex gas sources of the acoustic matching layer, enabling the acoustic matching layer to meet the long-term stable operation requirements of the ultrasonic gas meter transducer under complex working conditions.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. An acoustic matching layer for ultrasonic gas meter transducers suitable for complex gas source conditions, characterized in that: The acoustic matching layer comprises the following components by weight: 100-300 parts epoxy resin, 15-40 parts curing agent, 40-60 parts modified hollow glass microspheres, 3-5 parts acetone, 2-6 parts carboxyl-terminated butadiene-acrylonitrile rubber, 1-2 parts defoamer, 1-3 parts fatty acid polyoxyethylene ester, 1-3 parts graphene microsheets, 2-5 parts hydrophobic silica, and 2-5 parts fumed silica.

2. The acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions as described in claim 1, characterized in that: The specific method for preparing the modified hollow glass microspheres is as follows: A1. Prepare raw materials: hollow glass microspheres and silane coupling agent. Place the hollow glass microspheres in a plasma chamber, start the vacuum pump of the plasma chamber to make the vacuum degree in the plasma chamber reach the set value, and introduce oxygen to maintain the flow rate. Turn on the radio frequency power supply to activate the surface of the hollow glass microspheres to obtain pretreated hollow glass microspheres. A2. Dissolve the silane coupling agent in a mixed solution of ethanol and water, and add acetic acid to adjust the pH to 4.5 to obtain a silane solution. Then add the pretreated hollow glass microspheres to the silane solution, stir at a constant temperature, filter under reduced pressure, wash with ethanol 3 times, and vacuum dry at 80°C for 4 hours to obtain microspheres with surface grafted double bonds. A3. Add polyacrylamide and the microspheres to an N,N-dimethylformamide solution and stir at 40°C for 3 hours. The blend is washed and filtered three times with N,N-dimethylformamide to remove residual monomers and dried at 60°C for 10 hours to obtain modified hollow glass microspheres with a polyacrylamide coating.

3. A method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, comprising the acoustic matching layer for an ultrasonic gas meter transducer as described in any one of claims 1-2, characterized in that: The method for preparing the acoustic matching layer specifically includes the following steps: S1. Prepare a high-speed shearing machine, mix hydrophobic silica and graphene micro-sheets with epoxy resin and put them into the high-speed shearing machine and start it. After shearing and dispersing, a pre-dispersed slurry is formed. Add the pre-dispersed slurry, epoxy resin, curing agent, carboxyl-terminated nitrile rubber, defoamer and fatty acid polyoxyethylene ester into the mixer in sequence and start it. S2. The mixer is continuously stirred, and the modified hollow glass microspheres are added to the mixer in two batches. When the modified hollow glass microspheres are added for the first time, the mixer is stirred at a speed of 800-1000 r / min at room temperature for 5 minutes. When the modified hollow glass microspheres are added again, the stirring speed of the mixer is adjusted to 1500-2000 r / min, and the mixer is stirred at room temperature for 15-25 minutes. Then the fumed silica is added to the stirred mixture to obtain a premix. S3. Prepare a vacuum chamber, place the premix in the vacuum chamber and start it. The premix is ​​degassed in the vacuum chamber at a vacuum degree of 0.05-0.07MPa for 5-8 minutes. After the degassed treatment is completed, the vacuum degree of the vacuum chamber is increased to 0.08-0.1MPa and degassed for 10-15 minutes to obtain the degassed material. S4. Pour the deaerated material into the sound matching layer mold, let it stand at room temperature for 1-2 hours to initially level it, then put the sound matching layer mold into a drying oven, start the drying oven and set the initial drying temperature from room temperature to 60℃ at a rate of 20℃ / h and dry for 30 minutes, then raise it to 80-100℃ at a rate of 20℃ / h and keep it at that temperature for 1-2 hours, and finally raise the temperature to 120-150℃ at a rate of 20℃ / h. Then transfer the sound matching layer mold to a water bath device for curing. During the curing process, the water bath device uses constant temperature hot water circulation heating. S5. After curing, the material in the acoustic matching layer mold is cooled and annealed. The acoustic matching layer mold is first cooled to 100°C at a rate of 5-10°C / h and held for 1.5h, then cooled to 80°C at a rate of 5-10°C / h and held for 1h, and finally cooled to room temperature at a rate of 5-10°C / h. The cured acoustic matching layer is then removed from the mold to obtain the cured acoustic matching layer.

4. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, as described in claim 1, is characterized in that: The constant temperature of the hot water in the water bath device is 120-150℃, the hot water circulation flow rate of the water bath device is 2-5L / min, and the curing time of the acoustic matching layer mold in the water bath device is 2-3h.

5. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, as described in claim 1, is characterized in that: After the acoustic matching layer in step S6 is demolded, its edges and surface are ground with a diamond grinding wheel with a grit size of 800-1200 mesh. After grinding, the acoustic matching layer is placed in an ultrasonic cleaner and cleaned with anhydrous ethanol.

6. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, as described in claim 5, is characterized in that: The ultrasonic cleaner has a cleaning power of 150-200W, and uses an ultrasonic frequency of 30-40kHz during the cleaning process, with a cleaning time of 10-15 minutes.

7. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, as described in claim 1, is characterized in that: In step S1, the high-speed shearing machine has a dispersion speed of 3000-4000 r / min and a shearing dispersion time of 15-20 min. The mixer is stirred at room temperature for 10-15 min, and the stirring speed of the mixer is 800-1200 r / min.

8. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, as described in claim 1, is characterized in that: In step S3, the vacuum chamber is first evacuated from atmospheric pressure to 0.05-0.07 MPa at a evacuation rate of 0.01-0.015 MPa / min in the first stage, and then evacuated from 0.05-0.07 MPa to 0.08-0.1 MPa at a evacuation rate of 0.008-0.012 MPa / min in the second stage.

9. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer under complex gas source conditions according to claim 1, characterized in that: Before mixing the epoxy resin in step S1, the epoxy resin is pretreated. The epoxy resin pretreatment is to preheat at a temperature of 40-50℃ for 30-40 minutes. During the epoxy resin preheating process, it is stirred and degassed at 200-300 r / min.

10. The method for preparing an acoustic matching layer for an ultrasonic gas meter transducer suitable for complex gas source conditions, as described in claim 1, is characterized in that: In step S5, the material in the acoustic matching layer mold is cooled and annealed by an inert gas for protection. The inert gas is nitrogen, and the flow rate of the inert gas is 0.5 to 1 L / min.

Images