Bicrystal high-temperature ultrasonic probe and preparation method thereof

Abstract

The invention relates to the field of nondestructive testing, in particular to a bicrystal high-temperature ultrasonic probe and a preparation method thereof. The probe comprises a transmitting end and a receiving end, the transmitting end and the receiving end are the same in structure, and a sound insulation plate is arranged between the transmitting end and the receiving end. The transmitting end comprises a piezoelectric wafer and a wedge block; cables are led out of the upper electrode layer and the lower electrode layer of the piezoelectric wafer; the lower part of the piezoelectric wafer is bonded with the wedge block; the piezoelectric crystal plate, the wedge block and the sound insulation plate are connected through an inorganic-organic hybrid adhesive which is solidified in a gradient manner; the inorganic-organic hybrid adhesive keeps stable bonding strength and acoustic impedance matching at the temperature of more than or equal to 300 DEG C; the piezoelectric wafer is made of piezoelectric ceramics sintered at a high temperature of not lower than 1200 DEG C; the outer parts of the transmitting end and the receiving end are sleeved with neck bushes; the tops of the neck bushes and the backing are combined together through staged curing and vacuum hot pressing; dense air holes are formed in the sound insulation board and are non-through holes. The method is suitable for nondestructive testing of the high-temperature pipeline.

Description

Technical Field

[0001] The present invention relates to the field of nondestructive testing, and in particular to a double-crystal high-temperature ultrasonic probe and a preparation method thereof. Background Art

[0002] Leaks in high-temperature piping in the conventional island of operating nuclear power units are a common problem. For nuclear power plants, this directly impacts the safe and stable operation of the units. If leaks trigger a shutdown or reactor outage, they can result in significant economic losses. Inspections of high-temperature piping in the conventional island of nuclear power plants are typically performed after the units have been shut down, their insulation removed, and have cooled.

[0003] Currently, domestic power plants typically employ two approaches when encountering pipeline media (steam or water) leaks in operating units. The first approach involves performing pressurized plugging operations, typically while avoiding downtime or reducing operating pressure and temperature. The primary measures employed are seam removal and fixture installation. However, if the presence of thinning or weld defects in the breached area is unknown before performing these operations, direct intervention can lead to further expansion of the defects, resulting in burns and, in severe cases, even pipe bursts, posing a direct threat to the lives of on-site workers. The second approach involves reducing the power output of the nuclear power plant units until the fluid temperature in the pipeline has cooled to a lower level before performing testing with conventional thickness gauges. However, this approach wastes considerable time and places significant strain on plant operations, potentially leading to financial losses. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dual-crystal high-temperature ultrasonic probe and a preparation method thereof, which are suitable for non-destructive testing of high-temperature pipelines.

[0005] The present invention provides a dual-crystal high-temperature ultrasonic probe, comprising: a transmitting end and a receiving end, the transmitting end and the receiving end having the same structure, and a sound insulation board arranged between the two; The transmitting end includes a piezoelectric wafer and a wedge; Cables are led out from the upper electrode layer and the lower electrode layer of the piezoelectric chip; The lower part of the piezoelectric chip is bonded to the wedge; The piezoelectric chip, wedge and sound insulation board are connected by a gradient-cured inorganic-organic hybrid adhesive; the inorganic-organic hybrid adhesive maintains stable bonding strength and acoustic impedance matching at a temperature of ≥300°C; the piezoelectric chip is made of piezoelectric ceramics sintered at a temperature of not less than 1200°C; The outer portion of the transmitting end and the receiving end is covered with an inner sleeve, and the top of the inner sleeve is combined with the backing by staged curing and vacuum hot pressing; The interior of the sound insulation board has dense pores which are non-through holes.

[0006] In a specific embodiment of the present invention, the wedge is made of an aramid fiber reinforced polyimide resin-based composite material, and the preparation method of the aramid fiber reinforced polyimide resin-based composite material is as follows: Step S1: grafting and modifying aramid fiber using toluene diisocyanate to obtain modified aramid fiber; Step S2: placing the modified aramid fiber in a polyamic acid solution for grafting modification to obtain a precursor solution; Step S3: performing gradient curing on the precursor solution to obtain an aramid fiber reinforced polyimide resin composite material; The gradient curing method is specifically as follows: first, the temperature is raised to 330-340°C and allowed to stand for N1 hour; then, the temperature is raised to 350-360°C and allowed to stand for N2 hours; finally, the temperature is raised to 370-380°C and allowed to stand for N3 hours, and the sum of N1, N2 and N3 is 1-1.5 hours.

[0007] In a specific embodiment of the present invention, a cutting groove is provided on the bonding surface between the piezoelectric wafer and the wedge.

[0008] In a specific embodiment of the present invention, the backing material is a three-phase composite system of tungsten powder, epoxy resin and ceramic microspheres, and the components are mixed in the following mass percentages: Tungsten powder: 60wt%~70wt%; Epoxy resin: 25wt%~35wt%; Ceramic microspheres: 5wt%~10wt%; Nano-alumina-modified methyltetrahydrophthalic anhydride, the addition amount is 30%~40% of the epoxy resin mass; 2-ethyl-4-methylimidazole, the addition amount is 1%~2% of the mass of nano-alumina modified methyltetrahydrophthalic anhydride; The top of the inner sleeve is connected to the backing in the following ways: The backing material is poured on top of the inner liner and cured in stages at 180-200°C; Vacuum heat pressing bonds the backing to the top of the inner sleeve.

[0009] In a specific embodiment of the present invention, the piezoelectric wafer includes an upper electrode layer, a lower electrode layer and a piezoelectric ceramic, and the piezoelectric ceramic is a lead zirconate titanate material; The preparation method of the piezoelectric chip is as follows: the lead zirconate titanate material is sintered and then cut into thin slices, which are then ground to a frequency thickness; gold electrodes are plated on the surface of the slices by a magnetron sputtering process with a thickness greater than 0.5 microns to form an upper electrode layer and a lower electrode layer.

[0010] In a specific embodiment of the present invention, the material of the sound insulation board is polyetheretherketone.

[0011] The present invention provides a method for preparing a dual-crystal high-temperature ultrasonic probe, comprising the following steps: Step 1: The piezoelectric wafer with the cable welded thereto is bonded to a wedge using an inorganic-organic hybrid adhesive to prepare a transmitter and a receiver; the wedge is bonded to the sound insulation board using an inorganic-organic hybrid adhesive to obtain a first-level semi-finished product; The inorganic-organic hybrid adhesive maintains stable bonding strength and acoustic impedance matching at ≥300°C; the bonding adopts a gradient curing process, including: pre-curing at 70-90°C, cross-linking at 140-160°C, and final curing at 240-260°C; Step 2: The first-level semi-finished product is installed as a whole into the inner sleeve, and high-temperature resistant glue is poured into the gap of the inner sleeve to bond the two products together to obtain the second-level semi-finished product; Step 3: Use a tungsten powder-epoxy resin-ceramic microsphere three-phase composite system of backing material to cast on the top of the inner sleeve, and cure it in stages at 180~200℃; vacuum hot pressing is used to combine the backing and the top of the inner sleeve.

[0012] In a specific embodiment of the present invention, the tungsten powder-epoxy resin-ceramic microsphere three-phase composite system is mixed with the following components in the following mass percentages: Tungsten powder: 60wt%~70wt%; Epoxy resin: 25wt%~35wt%; Ceramic microspheres: 5wt%~10wt%; Nano-alumina-modified methyltetrahydrophthalic anhydride, the addition amount is 30%~40% of the epoxy resin mass; 2-ethyl-4-methylimidazole, the addition amount is 1%~2% of the mass of nano-alumina modified methyltetrahydrophthalic anhydride.

[0013] In a specific embodiment of the present invention, the piezoelectric wafer includes an upper electrode layer, a lower electrode layer and a piezoelectric ceramic, and the piezoelectric ceramic is a lead zirconate titanate material; The preparation method of the piezoelectric chip is as follows: the lead zirconate titanate material is sintered at a high temperature of more than 1200°C, then cut into thin slices, and ground to the frequency thickness; gold electrodes are plated on the surface of the slices by a magnetron sputtering process with a thickness greater than 0.5 microns to form upper and lower electrode layers.

[0014] In a specific embodiment of the present invention, it also includes: Step 4: Assemble the secondary semi-finished product with the cured backing into the housing and secure it with the limit screws; Step 5: Solder the cables to the terminals to achieve continuity. Step 6: Fasten the connector to the housing and assemble the grommet to the connector; Step 7: Install the assembled whole into the base of the protective case, and tighten the upper shell of the protective case and the base of the protective seat.

[0015] Compared with the prior art, the dual-crystal high-temperature ultrasonic probe and its preparation method of the present invention have the following beneficial effects: (1) Through high-temperature resistant material design and precision manufacturing technology, the reliability, stability and efficiency of online pipeline detection in the nuclear power industry have been significantly improved; (2) Stable detection in high temperature environments uses piezoelectric ceramics sintered at 1200°C to ensure that the probe maintains excellent piezoelectric performance under working conditions of ≤400°C, avoiding the signal attenuation problem caused by high temperature depolarization of traditional probes; (3) The high-temperature bonding process innovation of the chip, wedge, and sound insulation layer ensures the long-term stability of the transducer's acoustic performance and meets the testing requirements; The high-temperature probe manufactured by this invention can operate continuously in the high-temperature (200-400°C), high-pressure, and strong-radiation environments of nuclear power pipelines. This enables real-time monitoring without downtime, avoiding the economic losses associated with traditional testing, which requires downtime and cooling. This probe has been successfully used to inspect the main steam pipeline of a nuclear power plant, operating continuously for 18 months at 200°C with no performance degradation and a false alarm rate of less than 0.1%, providing a key technical guarantee for the safe operation of nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram showing the structure of a dual-crystal high-temperature ultrasonic probe used for online pipe inspection in the nuclear power industry; In the figure: 1-protective shell base, 2-protective shell upper shell, 3-outer shell, 4-connector, 5-wire sleeve, 6-binding post, 7-cable, 8-backing, 9-inner sleeve, 10-upper electrode layer, 11-piezoelectric ceramic, 12-lower electrode layer, 13-wedge, 14-sound insulation board, 15-limit screw. DETAILED DESCRIPTION

[0017] In order to further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than for limiting the present invention.

[0018] The embodiment of the present invention discloses a dual crystal high temperature ultrasonic probe for online detection of pipes in the nuclear power industry, such as Figure 1 Shown, including: The transmitting end and the receiving end have the same structure, and a sound insulation board 14 is set between the two; The transmitting end includes a piezoelectric wafer and a wedge 13; The upper electrode layer 10 and the lower electrode layer 12 of the piezoelectric wafer lead out cables 7; The lower part of the piezoelectric wafer is bonded to the wedge 13; The piezoelectric chip, the wedge 13 and the sound insulation board 14 are connected by a gradient-cured inorganic-organic hybrid adhesive; the inorganic-organic hybrid adhesive maintains stable bonding strength and acoustic impedance matching at a temperature of ≥300°C; the piezoelectric chip is made of piezoelectric ceramics sintered at a temperature of not less than 1200°C; The outer portion of the transmitting end and the receiving end is covered with an inner liner 9 , and the top of the inner liner 9 is combined with the backing 8 by staged curing and vacuum hot pressing.

[0019] An inner sleeve 9 is provided in the housing 3 and is fixed to the inside of the housing 3 by means of a limit screw 15; The connector 4 is connected to the top of the housing 3. The bottom of the connector 4 is a terminal 6, which is connected to the cable 7. The top of the connector 4 is connected to the cable sheath 5. The exterior of the housing 3 is fixed by a protective shell, which includes a protective shell base 1 and a protective shell upper shell 2 ; the protective shell base 1 and the protective shell upper shell 2 are fastened by threads.

[0020] The lower edge of the wedge 13 protrudes from the lower end of the protective shell.

[0021] The material of the protective shell is polytetrafluoroethylene. The protective shell made of polytetrafluoroethylene can effectively isolate the high temperature transmitted from the pipeline through the probe, thereby protecting the probe and on-site workers.

[0022] The wedge block 13 is made of aramid fiber reinforced polyimide resin-based composite material, and the preparation method of the aramid fiber reinforced polyimide resin-based composite material is as follows: Step S1: grafting and modifying aramid fiber using toluene diisocyanate to obtain modified aramid fiber; Specifically include: The aramid fiber is subjected to ultrasonic treatment in a highly polar aprotic solution; the ultrasonic treatment time is 5 to 10 minutes; Toluene diisocyanate is added to a strongly polar aprotic solution and treated at 60-70°C for 0.5-1 hour, preferably at 61-65°C for 0.51-0.8 hour; the ratio of the added amount of toluene diisocyanate to aramid fiber is (0.05-0.1) mol:1g.

[0023] After the treatment, the modified aramid fiber is washed and dried to obtain the modified aramid fiber.

[0024] The longer the aramid fiber, the greater its stiffness and the greater its reinforcing effect. However, if the aramid fiber is too long, it tends to clump and tangle, making it difficult to disperse evenly, resulting in a weakened interfacial bonding with the subsequent polyimide, causing the mechanical properties of the composite material to deteriorate. Furthermore, the amount of aramid fiber added must be controlled: too little will result in limited reinforcing effect, while too much will lead to uneven dispersion, causing the mechanical properties of the composite material to deteriorate. The length of the aramid fiber is preferably 8-12 mm.

[0025] The highly polar aprotic solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone and N-methylpyrrolidone.

[0026] Step S2: placing the modified aramid fiber in a polyamic acid solution for grafting modification to obtain a precursor solution; The polyamic acid solution is prepared by: using a diamine monomer, a dianhydride monomer and benzoic acid to undergo a condensation reaction to obtain a polyamic acid solution; the molar ratio of the diamine monomer, the dianhydride monomer and the benzoic acid is 1: (0.1-1): (0.1-0.5); The polycondensation reaction time is 2 to 72 hours, preferably 20 to 50 hours; the reaction temperature is 0 to 40°C, preferably 20 to 30°C.

[0027] The mass of the aramid fiber is a, the sum of the masses of the diamine monomer and the dianhydride monomer is b, and a:b=5-10:100.

[0028] The diamine monomer is an aromatic diamine, and the aromatic diamine is m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, o-phenylenediamine sulfonate, 、 、 、 、 and At least one of; The dianhydride monomer is an aromatic dianhydride, and the aromatic dianhydride is pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 、 、 、 、 and At least one of .

[0029] Step S3: performing gradient curing on the precursor solution to obtain an aramid fiber reinforced polyimide resin composite material; The gradient curing method is specifically as follows: first, the temperature is raised to 330-340°C and allowed to stand for N1 hour; then, the temperature is raised to 350-360°C and allowed to stand for N2 hours; finally, the temperature is raised to 370-380°C and allowed to stand for N3 hours, and the sum of N1, N2 and N3 is 1-1.5 hours.

[0030] The gradient solidification is carried out under a vacuum pressure environment of 0.1-0.3 MPa.

[0031] The wedge 13 material used in the present invention has a sound velocity that changes slowly with temperature.

[0032] Specifically, the piezoelectric wafer includes an upper electrode layer 10, a lower electrode layer 12 and a piezoelectric ceramic 11, and the piezoelectric ceramic 11 is made of lead zirconate titanate material; The preparation method of the piezoelectric chip is as follows: the lead zirconate titanate material is sintered at a high temperature of more than 1200°C, cut into thin slices, and ground to the frequency thickness; gold electrodes are plated on the surface of the slices by magnetron sputtering process, with a thickness greater than 0.5 microns, to form an upper electrode layer 10 and a lower electrode layer 12.

[0033] The bonding surface between the piezoelectric wafer and the wedge 13 is provided with cutting grooves to increase the contact area and form a mechanical interlock. Combined with plasma activation, the wettability is improved, and the shear strength is increased by more than 40%.

[0034] The backing material is a three-phase composite system of tungsten powder, epoxy resin and ceramic microspheres, and the components are mixed in the following mass percentages: Tungsten powder: 60wt%~70wt%, preferably 65wt%; Epoxy resin: 25wt%~35wt%, preferably 30wt%; Ceramic microspheres: 5wt%~10wt%, preferably 5wt%; Nano-alumina-modified methyltetrahydrophthalic anhydride, the addition amount is 30%~40% of the epoxy resin mass; 2-ethyl-4-methylimidazole, the addition amount is 1%~2% of the mass of nano-alumina modified methyltetrahydrophthalic anhydride; 2-ethyl-4-methylimidazole is a accelerator to accelerate the curing reaction.

[0035] The tungsten powder is a high-density phase with a particle size of 1-10 μm and a purity of ≥99.5%; The epoxy resin is a matrix phase, preferably a bisphenol A epoxy resin with an epoxy value of 0.51 to 0.54; The ceramic microspheres are low-density phases, specifically hollow alumina microspheres with a particle size of 20-50 μm, a wall thickness of 1-2 μm, and a density of 0.6-0.8 g / cm³; The curing agent adopts methyltetrahydrophthalic anhydride modified by nano-alumina. The preparation method of the methyltetrahydrophthalic anhydride modified by nano-alumina is as follows: nano-alumina with a particle size of 30-50nm is added to methyltetrahydrophthalic anhydride, dispersed by ultrasound, and mixed evenly to obtain the methyltetrahydrophthalic anhydride modified by nano-alumina.

[0036] The power of the ultrasonic dispersion is 290-350 W, and the time is 20-40 minutes.

[0037] The nano-alumina accounts for 5% to 8% of the total mass of the curing agent.

[0038] The inner sleeve material used in the present invention achieves a balance between high damping and low thermal expansion. According to test data, its sound attenuation coefficient is ≥20dB / cm and CTE is ≤15×10⁻ 6 / ℃.

[0039] The method of connecting the top of the inner sleeve 9 to the backing 8 is: The backing material is poured on top of the inner liner 9 and cured in stages at 180-200°C; Vacuum hot pressing is used to combine the backing 8 and the top of the inner liner 9 together.

[0040] The interior of the sound insulation board 14 has dense pores and is non-through, which blocks sound wave crosstalk. The material of the sound insulation board 14 is preferably polyetheretherketone (PEEK). The upper end of the sound insulation board 14 is tightly attached to the backing 8, forming a high sound attenuation barrier.

[0041] An embodiment of the present invention further discloses a method for preparing a dual-crystal high-temperature ultrasonic probe, comprising the following steps: Step 1: The piezoelectric wafer with the cable welded thereto is bonded to a wedge using an inorganic-organic hybrid adhesive to prepare a transmitter and a receiver; the wedge is bonded to the sound insulation board using an inorganic-organic hybrid adhesive to obtain a first-level semi-finished product; The piezoelectric wafer includes an upper electrode layer 10, a lower electrode layer 12 and a piezoelectric ceramic 11, wherein the piezoelectric ceramic 11 is made of lead zirconate titanate material; The preparation method of the piezoelectric chip is as follows: the lead zirconate titanate material is sintered at a high temperature of more than 1200°C, cut into thin slices, and ground to the frequency thickness; gold electrodes are plated on the surface of the slices by magnetron sputtering process, with a thickness greater than 0.5 microns, to form an upper electrode layer 10 and a lower electrode layer 12.

[0042] Welding cables 7 to the upper electrode layer 10 and the lower electrode layer 12 respectively; The inorganic-organic hybrid adhesive maintains stable bonding strength and acoustic impedance matching at ≥300°C; the inorganic-organic hybrid adhesive is preferably a silicate-polyimide composite material; The bonding process uses a gradient curing process, including: pre-curing at 70-90°C, cross-linking at 140-160°C, and final curing at 240-260°C; More preferably, the pre-curing treatment is carried out at 80°C, cross-linking is carried out at 150°C, and final curing is carried out at 250°C; Step 2: The first-level semi-finished product is installed as a whole into the inner sleeve, and high-temperature resistant glue is poured into the gap of the inner sleeve to bond the two products together to obtain the second-level semi-finished product; Step 3: A tungsten powder-epoxy resin-ceramic microsphere three-phase composite backing material is poured on the top of the inner sleeve and cured in stages at 180-200°C. Vacuum hot pressing is then performed to bond the backing to the top of the inner sleeve. The tungsten powder-epoxy resin-ceramic microsphere three-phase composite system is mixed with the following components in the following mass percentages: Tungsten powder: 60wt%~70wt%; Epoxy resin: 25wt%~35wt%; Ceramic microspheres: 5wt%~10wt%; Nano-alumina-modified methyltetrahydrophthalic anhydride, the addition amount is 30%~40% of the epoxy resin mass; 2-ethyl-4-methylimidazole, the addition amount is 1%~2% of the mass of nano-alumina modified methyltetrahydrophthalic anhydride.

[0043] Step 4: Assemble the secondary semi-finished product with the cured backing 8 into the housing and fix it with the limit screws 15; Step 5: Solder the cable 7 to the terminal 6 to achieve continuity; Step 6: Fasten the connector 4 to the housing, and assemble the grommet 5 to the connector 4; Step 7: Install the assembled whole into the protective shell base 1, and fasten the protective shell upper shell 2 and the protective base bottom 2.

[0044] The protective shell base 1 and the protective shell upper shell 2 are both made of polytetrafluoroethylene, which can effectively isolate the high temperature transmitted from the pipeline through the probe, and play a protective role for the probe and on-site workers.

[0045] The performance test of the dual-crystal high-temperature ultrasonic probe prepared by the present invention was carried out, and the test results are shown below: 1. Improved adaptability to high temperature environments; Temperature resistance: The probe can work stably for more than 200 hours at 250°C and can withstand temperatures up to 400°C in the short term. Thermal stability: After 100 times of -20℃~250℃ thermal cycle test, the signal attenuation is less than 10%, which is much better than traditional probes; 2. Optimize acoustic performance; Crosstalk suppression: Transmitter / receiver crosstalk is reduced to below -40dB; Frequency stability: 2MHz center frequency drift is less than 2% at 250℃, which is much better than traditional probes; 3. Improved detection efficiency; 4. Nuclear power pipeline online detection case; Testing environment: main steam pipeline of a nuclear power plant, temperature 230℃; Test results: defect detection rate 97%; false alarm rate <1%; no performance degradation after 18 months of continuous operation.

[0046] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0047] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual-crystal high-temperature ultrasonic probe, characterized in that: include: The transmitting end and the receiving end have the same structure, and a sound insulation board is set between the two; The transmitting end includes a piezoelectric wafer and a wedge; Cables are led out from the upper electrode layer and the lower electrode layer of the piezoelectric chip; The lower part of the piezoelectric chip is bonded to the wedge; The piezoelectric chip, wedge and sound insulation board are connected by a gradient-cured inorganic-organic hybrid adhesive; the inorganic-organic hybrid adhesive maintains stable bonding strength and acoustic impedance matching at a temperature of ≥300°C; the piezoelectric chip is made of piezoelectric ceramics sintered at a temperature of not less than 1200°C; The outer portion of the transmitting end and the receiving end is covered with an inner sleeve, and the top of the inner sleeve is combined with the backing by staged curing and vacuum hot pressing; The interior of the sound insulation board has dense pores which are non-through holes.

2. The dual-crystal high-temperature ultrasonic probe according to claim 1, characterized in that: The wedge is made of an aramid fiber reinforced polyimide resin-based composite material, and the preparation method of the aramid fiber reinforced polyimide resin-based composite material is as follows: Step S1: grafting and modifying aramid fiber using toluene diisocyanate to obtain modified aramid fiber; Step S2: placing the modified aramid fiber in a polyamic acid solution for grafting modification to obtain a precursor solution; Step S3: performing gradient curing on the precursor solution to obtain an aramid fiber reinforced polyimide resin composite material; The gradient curing method is specifically as follows: first, the temperature is raised to 330-340°C and allowed to stand for N1 hour; then, the temperature is raised to 350-360°C and allowed to stand for N2 hours; finally, the temperature is raised to 370-380°C and allowed to stand for N3 hours, and the sum of N1, N2 and N3 is 1-1.5 hours.

3. The dual-crystal high-temperature ultrasonic probe according to claim 1, characterized in that: The bonding surfaces of the piezoelectric wafer and the wedge are provided with cutting grooves.

4. The dual-crystal high-temperature ultrasonic probe according to claim 1, characterized in that: The backing material is a three-phase composite system of tungsten powder, epoxy resin and ceramic microspheres, and the components are mixed in the following mass percentages: Tungsten powder: 60wt%~70wt%; Epoxy resin: 25wt%~35wt%; Ceramic microspheres: 5wt%~10wt%; Nano-alumina-modified methyltetrahydrophthalic anhydride, the addition amount is 30%~40% of the epoxy resin mass; 2-ethyl-4-methylimidazole, the addition amount is 1%~2% of the mass of nano-alumina modified methyltetrahydrophthalic anhydride; The top of the inner sleeve is connected to the backing in the following ways: The backing material is poured on top of the inner liner and cured in stages at 180-200°C; Vacuum heat pressing bonds the backing to the top of the inner sleeve.

5. The dual-crystal high-temperature ultrasonic probe according to claim 1, characterized in that: The piezoelectric wafer includes an upper electrode layer, a lower electrode layer and a piezoelectric ceramic, and the piezoelectric ceramic is made of lead zirconate titanate material; The preparation method of the piezoelectric chip is as follows: the lead zirconate titanate material is sintered and then cut into thin slices, which are then ground to a frequency thickness; gold electrodes are plated on the surface of the slices by a magnetron sputtering process with a thickness greater than 0.5 microns to form an upper electrode layer and a lower electrode layer.

6. The dual-crystal high-temperature ultrasonic probe according to claim 1, characterized in that: The material of the sound insulation board is polyetheretherketone.

7. A method for preparing a dual-crystal high-temperature ultrasonic probe, characterized in that: The following steps are involved: Step 1: The piezoelectric wafer with the cable welded thereto is bonded to a wedge using an inorganic-organic hybrid adhesive to prepare a transmitter and a receiver; the wedge is bonded to the sound insulation board using an inorganic-organic hybrid adhesive to obtain a first-level semi-finished product; The inorganic-organic hybrid adhesive maintains stable bonding strength and acoustic impedance matching at ≥300°C; The bonding process uses a gradient curing process, including: pre-curing at 70-90°C, cross-linking at 140-160°C, and final curing at 240-260°C; Step 2: The first-level semi-finished product is installed as a whole into the inner sleeve, and high-temperature resistant glue is poured into the gap of the inner sleeve to bond the two products together to obtain the second-level semi-finished product; Step 3: Use a tungsten powder-epoxy resin-ceramic microsphere three-phase composite system of backing material to cast on the top of the inner sleeve, and cure it in stages at 180~200℃; vacuum hot pressing is used to combine the backing and the top of the inner sleeve.

8. The method for preparing a dual-crystal high-temperature ultrasonic probe according to claim 7, characterized in that: The tungsten powder-epoxy resin-ceramic microsphere three-phase composite system is mixed with the following components in the following mass percentages: Tungsten powder: 60wt%~70wt%; Epoxy resin: 25wt%~35wt%; Ceramic microspheres: 5wt%~10wt%; Nano-alumina-modified methyltetrahydrophthalic anhydride, the addition amount is 30%~40% of the epoxy resin mass; 2-ethyl-4-methylimidazole, the addition amount is 1%~2% of the mass of nano-alumina modified methyltetrahydrophthalic anhydride.

9. The method for preparing a dual-crystal high-temperature ultrasonic probe according to claim 7, characterized in that: The piezoelectric wafer includes an upper electrode layer, a lower electrode layer and a piezoelectric ceramic, and the piezoelectric ceramic is made of lead zirconate titanate material; The preparation method of the piezoelectric chip is as follows: the lead zirconate titanate material is sintered at a high temperature of more than 1200°C, then cut into thin slices, and ground to the frequency thickness; gold electrodes are plated on the surface of the slices by a magnetron sputtering process with a thickness greater than 0.5 microns to form upper and lower electrode layers.

10. The method for preparing a dual-crystal high-temperature ultrasonic probe according to claim 7, characterized in that: Also includes: Step 4: Assemble the secondary semi-finished product with the cured backing into the housing and secure it with the limit screws; Step 5: Solder the cables to the terminals to achieve continuity. Step 6: Fasten the connector to the housing and assemble the grommet to the connector; Step 7: Install the assembled whole into the base of the protective case, and tighten the upper shell of the protective case and the base of the protective seat.

Images