A waterproof protective coating for a ceramic sensor chip and a method of manufacturing the same
By preparing a multi-layer composite coating on the ceramic sensor chip, the problem of insufficient waterproof performance of ceramic sensors under high temperature, high pressure and corrosive environments is solved, achieving excellent waterproof performance and thermal shock resistance, and meeting the stringent cold start emission limits.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA FAW CO LTD
- Filing Date
- 2026-02-26
- Publication Date
- 2026-05-29
Smart Images
Figure CN122102744A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sensor element technology, and more specifically, to a waterproof protective coating for a ceramic sensor chip and its preparation method, particularly to a waterproof protective coating technology for ultra-wide-range sensors, which is especially suitable for fields such as automobiles, industrial automation, and environmental monitoring. Background Technology
[0002] As an important branch of modern sensing technology, ceramic sensors occupy a crucial position in automotive sensor systems due to their excellent mechanical strength, chemical inertness, and thermal stability. In particular, the application of advanced ceramic materials such as alumina ceramics and zirconia ceramics enables ceramic sensors to outperform traditional sensors in high-temperature, high-pressure, and corrosive environments.
[0003] In recent years, with increasingly stringent policies and regulations, future heavy-duty gasoline vehicles and commercial vehicles may face stricter cold-start emission limits, requiring shorter sensor start-up times and improved water resistance. Despite the numerous advantages of ceramic sensors, their insufficient waterproofing performance has become increasingly prominent in practical applications, primarily causing the following problems: 1. Moisture adsorbs onto the surface of the resistive element, leading to resistance characteristic drift; 2. Ionic components in the liquid accelerate the corrosion of the electrode material; 3. Temperature changes caused by moisture generate additional thermal stress, and thermal shock to the sensor element can lead to cracking.
[0004] Therefore, there is an urgent need to develop a new type of waterproof protective coating technology for ceramic sensor cores to improve the water resistance and thermal shock resistance of the sensor cores, shorten the sensor ignition time, and meet regulatory requirements to achieve the goal of high moisture resistance and fast ignition of sensors.
[0005] In view of this, the present invention is hereby proposed. Summary of the Invention
[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a waterproof protective coating for ceramic sensor chips and its preparation method. This coating possesses excellent waterproof performance, good bonding strength, and chemical stability, and can adapt to harsh environmental conditions such as high temperature and high humidity. It significantly improves the waterproof performance and thermal shock resistance of ceramic sensor chips, effectively extends the service life of ceramic sensors, and expands the application range of ceramic sensors. The preparation method of this coating should be simple and feasible, and suitable for industrial production.
[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A waterproof protective coating for a ceramic sensor chip core, wherein the waterproof protective coating 4 is a multi-layer composite coating covering the surface of the chip core substrate 1, and the waterproof protective coating 4 includes a dip coating 2 covering the surface of the chip core substrate 1 and a spray coating 3 covering the surface of the dip coating 2.
[0008] Furthermore, the core substrate 1 is made of YSZ ceramic material.
[0009] Furthermore, the coating layer 2 is an alumina ceramic material coating or a zirconia ceramic material coating.
[0010] Furthermore, the sprayed coating 3 is an alumina ceramic material coating or a zirconia ceramic material coating.
[0011] Furthermore, the porosity of the coating layer 2 is 20-50%, and the thickness is 100-500 μm.
[0012] Furthermore, the porosity of the sprayed coating 3 is 19-50%, and the thickness is 100-300 μm.
[0013] A method for preparing a waterproof protective coating for a ceramic sensor chip includes the following steps: Step S1: Roughen the core substrate 1; Step S2: Prepare ceramic material raw powder; Step S3: Mix the ceramic material powder, binder, pore-forming agent and dispersant to obtain a slurry; Step S4: The slurry obtained in step S3 is coated onto the surface of the core substrate 1, dried and sintered, and the slurry is cured into a layer to obtain the coating layer 2; Step S5: Dry the slurry obtained in step S3 to obtain modified ceramic powder, spray it onto the surface of the dip coating 2 to obtain the spray coating 3, and finally form a multi-layer composite coating on the core substrate 1 as a waterproof protective coating 4.
[0014] Further, in step S1, the roughening pretreatment involves sandblasting the surface of the core substrate 1. The sandblasting method is as follows: using 80~150 mesh white corundum sand, setting the sandblasting pressure to 0.08~0.12MPa, the sandblasting distance to 6~18cm, and sandblasting the end of the core substrate 1. The end of the core substrate 1 is swept and sprayed 2~6 times, and finally, compressed air is turned on to blow away the sandblasted surface.
[0015] Further, in step S2, the ceramic material raw powder is obtained by sintering crushing or spray granulation, and the average particle size of the ceramic material raw powder is 10~100μm; the ceramic material raw powder is at least one of Al2O3 ceramic material raw powder and ZrO2 ceramic material raw powder, and the purity is >99.5%.
[0016] Further, the mixing process in step S3 is as follows: first, the ceramic material powder is premixed with the dispersant, using a solvent as the dispersant, then the binder is added and stirred and ground, and finally the pore-forming agent is added and mixed and ground.
[0017] Further, in step S3, the weight ratio of the ceramic material powder to the pore-forming agent is 4~6:1, and the weight ratio of the sum of the ceramic material powder and the pore-forming agent to the solvent is 1:0.5~10.
[0018] Furthermore, the solvent mentioned in step S3 is at least one of deionized water, ethanol, and glycerol.
[0019] Further, the adhesive mentioned in step S3 is at least one of polyvinyl alcohol, carboxymethyl cellulose, and polyacrylic acid.
[0020] Further, the pore-forming agent in step S3 is at least one of polystyrene, polymethyl methacrylate, ammonium bicarbonate, citric acid, sucrose, and polyethylene glycol.
[0021] Furthermore, step S4 involves preparing the dip coating 2 using either an immersion-lift-curing method or a brush-coating-curing method.
[0022] Further, step S4 involves preparing the dip coating 2 using an immersion-lift-curing process as follows: 100-200mm of the end portion of the core substrate 1 is immersed in the slurry at an immersion speed of 0.1-10mm / s; the core substrate 1 remains in the slurry for 10-60 seconds before being lifted; the core substrate 1 is lifted at a lifting speed of 0.1-50mm / s, and the slurry is deposited on the surface of the core substrate 1; the core substrate 1 immersed in the slurry is dried to remove excess solvent, and sintered at a high temperature of 1000-1500℃ to remove the pore-forming agent; the slurry is cured into a layer, resulting in a dip coating 2 with a thickness of 100-500μm and a porosity of 20-50%.
[0023] Further, step S4 involves preparing the dip coating 2 by brushing and curing as follows: immerse a brush in the slurry for 40-60 seconds, then use the brush after slurry immersion to brush the end portion (100-200mm) of the core substrate 1 along the same direction at a brushing speed of 0.1-10mm / s, brushing the five surfaces of the core substrate 1 3-5 times; dry the core substrate 1 coated with the slurry to remove excess solvent, sinter at 1000-1500℃ to remove the pore-forming agent, and cure the slurry into a layer, obtaining a dip coating 2 with a thickness of 100-500μm and a porosity of 20-50%.
[0024] Further, step S5 uses plasma spraying to prepare the coating layer 3; the process of preparing the coating layer 3 using plasma spraying is as follows: the slurry is dried to obtain modified ceramic powder, and then the modified ceramic powder is heated and melted in a plasma spraying flame to form a molten particle stream, and the molten particle stream is sprayed onto the surface of the coating layer 2.
[0025] Further, in step S5, the plasma spraying power is 28~40kW, the powder feed rate is 20~35g / min, the spraying distance is 110~180mm, and the air pressure is 0.08~0.12MPa, resulting in a sprayed layer 3 with a thickness of 100~300μm and a porosity of 19~50%.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The waterproof protective coating of the ceramic sensor chip of the present invention has excellent waterproof performance, good bonding strength and chemical stability.
[0027] 2. The waterproof protective coating of the ceramic sensor chip core of the present invention can adapt to harsh environmental conditions such as high temperature and high humidity, improve the water resistance and thermal shock resistance of the sensor chip core, shorten the sensor ignition time (≤60S), and extend the service life of the sensor (≥20000h).
[0028] 3. The method for preparing the waterproof protective coating of the ceramic sensor chip of the present invention should be simple, feasible, and suitable for industrial production.
[0029] 4. The waterproof protective coating of the ceramic sensor chip core of the present invention and its preparation method can significantly improve the waterproof performance of the ceramic sensor, expand its application range, and have important economic value and social significance. Attached Figure Description
[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0031] Figure 1 This is a schematic diagram of the ceramic sensor chip structure with a waterproof protective coating according to the present invention.
[0032] Explanation of reference numerals in the attached diagram: 1-Core substrate; 2-Dip coating; 3-Spray coating; 4-Waterproof protective coating. Detailed Implementation
[0033] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.
[0034] A waterproof protective coating for a ceramic sensor chip core, wherein the waterproof protective coating 4 is a multi-layer composite coating covering the surface of the chip core substrate 1, and the waterproof protective coating 4 includes a dip coating 2 covering the surface of the chip core substrate 1 and a spray coating 3 covering the surface of the dip coating 2.
[0035] The waterproof protective coating of the ceramic sensor chip of this invention adopts a multi-layer composite coating structure. It is prepared by inner layer dipping and outer layer spraying to achieve excellent waterproof performance, porosity and adhesion.
[0036] Preferably, the substrate 1 of the chip core is made of YSZ ceramic material (yttrium oxide stabilized zirconia ceramic material). YSZ ceramic material is a stabilized zirconia ceramic material formed by doping yttrium oxide (Y2O3) into zirconia (ZrO2), and it is a core substrate material in modern sensor technology (especially oxygen sensors and nitrogen-oxygen sensors).
[0037] Preferably, the coating layer 2 is an alumina (Al2O3) ceramic material coating or a zirconium oxide (ZrO2) ceramic material coating.
[0038] Preferably, the porosity of the coating layer 2 is 20-50% (including but not limited to 20%, 25%, 30%, 35%, 40%, 45%, 50%), and the thickness is 100-500μm (including but not limited to 100μm, 200μm, 300μm, 400μm, 500μm).
[0039] Preferably, the sprayed coating 3 is an alumina (Al2O3) ceramic material coating or a zirconium oxide (ZrO2) ceramic material coating.
[0040] Preferably, the porosity of the sprayed coating 3 is 19-50% (including but not limited to 19%, 20%, 25%, 30%, 35%, 40%, 45%, 50%), and the thickness is 100-300μm (including but not limited to 100μm, 200μm, 300μm).
[0041] In this invention, the waterproof protective coating 4 has a high porosity, which can increase the air intake, improve sensor accuracy, and also provide better heat insulation. However, excessive porosity may reduce the bonding strength and result in poor waterproof performance.
[0042] A method for preparing a waterproof protective coating for a ceramic sensor chip includes the following steps: Step S1: Roughen the core substrate 1 to improve its roughness; Step S2: Prepare ceramic material raw powder; Step S3: Mix the ceramic material powder, binder, pore-forming agent and dispersant to obtain a slurry; Step S4: Coat the slurry obtained in step S3 onto the surface of the core substrate 1, dry to remove excess solvent, sinter to remove pore-forming agent, and cure the slurry into a layer to obtain coating layer 2. Step S5: Dry the slurry obtained in step S3 to obtain modified ceramic powder, spray it onto the surface of the dip coating 2 to obtain the spray coating 3, and finally form a multi-layer composite coating on the core substrate 1 as a waterproof protective coating 4.
[0043] Preferably, the roughening pretreatment in step S1 involves sandblasting the surface of the core substrate 1 to increase its roughness, and the core substrate 1 after roughening pretreatment is free of cracks.
[0044] Preferably, the sandblasting method in step S1 is as follows: using 80~150 mesh (including but not limited to 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh) white corundum sand, setting the sandblasting pressure to 0.08~0.12MPa (including but not limited to 0.08MPa, 0.09MPa, 0.10MPa, 0.11MPa, 0.12MPa), the sandblasting distance to 6~18cm (including but not limited to 6cm, 8cm, 10cm, 12cm, 14cm, 16cm, 18cm), the sandblasting part to be the end of the core substrate 1, the end of the core substrate 1 to be swept and sprayed 2~6 times (including but not limited to 2 times, 3 times, 4 times, 5 times, 6 times), and finally turning on compressed air to blow away the sandblasted surface.
[0045] Preferably, in step S2, the ceramic material raw powder is obtained by sintering crushing or spray granulation, and the average particle size of the ceramic material raw powder is 10~100μm (including but not limited to 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm).
[0046] Preferably, the ceramic material powder mentioned in step S2 is at least one of Al2O3 ceramic material powder and ZrO2 ceramic material powder, with a purity > 99.5%.
[0047] Preferably, the mixing process in step S3 is as follows: first, the ceramic material powder is premixed with a dispersant, a solvent is used as a dispersant, then a binder is added and stirred and ground, and finally a pore-forming agent is added and mixed and ground.
[0048] Preferably, in step S3, the weight ratio of the ceramic material powder to the pore-forming agent is 4 to 6:1 (including but not limited to 4:1, 5:1, 6:1), and the weight ratio of the sum of the weights of the ceramic material powder and the pore-forming agent to the weight of the solvent is 1:0.5 to 10 (including but not limited to 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10).
[0049] Preferably, the solvent in step S3 is at least one of deionized water, ethanol, and glycerol; the binder is at least one of polyvinyl alcohol, carboxymethyl cellulose, and polyacrylic acid; and the pore-forming agent is at least one of polystyrene, polymethyl methacrylate, ammonium bicarbonate, citric acid, sucrose, and polyethylene glycol.
[0050] Preferably, step S4 uses an immersion-lift-curing or brush-coating-curing method to prepare the dip coating 2.
[0051] Preferably, the process of preparing the dip coating 2 using the dip-lift-curing method is as follows: The end portion of the core substrate 1, 100-200mm (including but not limited to 100mm, 120mm, 150mm, 180mm, 200mm), is immersed in the slurry at a constant speed (without shaking). The immersion speed is controlled at 0.1-10mm / s (including but not limited to 0.1mm / s, 0.5mm / s, 1mm / s, 2mm / s, 5mm / s, 8mm / s, 10mm / s) to ensure complete wetting of the surface of the core substrate 1. After the core substrate 1 remains in the slurry for a certain period of time, it is lifted out, with a dwell time of 10-60 seconds (including but not limited to 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds) to ensure that the slurry is fully adsorbed onto the substrate surface. The core substrate 1 is then lifted out at a constant speed, and the slurry is deposited on the surface of the core substrate 1. The speed is 0.1~50mm / s (including but not limited to 0.1mm / s, 0.5mm / s, 1mm / s, 2mm / s, 5mm / s, 8mm / s, 10mm / s, 20mm / s, 30mm / s, 50mm / s); the core substrate 1 impregnated with slurry is dried in an oven to remove excess solvent, and finally sintered at 1000~1500℃ (including but not limited to 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃) to remove the pore-forming agent, and the slurry is cured into a layer to obtain a coating layer 2 with a thickness of 100~500μm (including but not limited to 100μm, 200μm, 300μm, 400μm, 500μm) and a porosity of 20~50% (including but not limited to 20%, 25%, 30%, 35%, 40%, 45%, 50%).
[0052] Preferably, the process of preparing the dip coating 2 by brushing and curing is as follows: immerse a brush in the slurry for 40-60 seconds (including but not limited to 40, 45, 50, 55, and 60 seconds), then use the brush after slurry immersion to brush the end portion of the core substrate 1 (100-200 mm) in the same direction at a constant speed (without shaking). The brushing speed is controlled at 0.1-10 mm / s (including but not limited to 0.1 mm / s, 0.5 mm / s, 1 mm / s, 2 mm / s, 5 mm / s, 8 mm / s, and 10 mm / s). Brush the five sides of the core substrate 1 3-5 times (including but not limited to 3, 4, and 5 times). The five surfaces of the core substrate 1 (front, back, left, right, and top) are coated with a brush, while the bottom surface of the core substrate 1 is left uncoated. The core substrate 1 coated with the slurry is dried in an oven to remove excess solvent. Finally, it is sintered at a high temperature of 1000~1500℃ (including but not limited to 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, and 1500℃) to remove the pore-forming agent. The slurry is then cured into a layer, resulting in a coating layer 2 with a thickness of 100~500μm (including but not limited to 100μm, 200μm, 300μm, 400μm, and 500μm) and a porosity of 20~50% (including but not limited to 20%, 25%, 30%, 35%, 40%, 45%, and 50%).
[0053] Preferably, step S5 uses plasma spraying to prepare the coating layer 3.
[0054] Preferably, the process of preparing the coating layer 3 by plasma spraying is as follows: the slurry is dried to obtain modified ceramic powder, and then the modified ceramic powder is heated and melted in a plasma spraying flame to form a molten particle stream. The molten particle stream is sprayed onto the surface of the coating layer 2. The spraying power is 28~40kW (including but not limited to 28kW, 30kW, 32kW, 34kW, 36kW, 38kW, 40kW), the powder feed rate is 20~35g / min (including but not limited to 20g / min, 25g / min, 30g / min, 35g / min), and the spraying distance is 110~180mm (including but not limited to 110mm). The coating material 3 has a thickness of 100-300μm (including but not limited to 100μm, 200μm, and 300μm) and a porosity of 19-50% (including but not limited to 19%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%), and is subjected to an air pressure of 0.08-0.12MPa (including but not limited to 0.08MPa, 0.09MPa, 0.10MPa, 0.11MPa, and 0.12MPa).
[0055] The present invention prepares a dip coating layer 2 on the core substrate 1 by dip-coating or brushing, and then sprays a spray coating layer 3 on the dip coating layer by plasma spraying technology. Finally, a waterproof protective coating layer 4 is obtained on the core substrate 1. It has the advantages of low energy consumption of dip coating and high bonding strength and uniform thickness of plasma spraying. The prepared waterproof protective coating layer 4 has a porosity of 20~50%, a bonding strength of up to 35N, and greatly improved moisture resistance, with a water spray resistance of ≥380μL.
[0056] Example 1 A method for preparing a waterproof protective coating for a ceramic sensor chip includes the following steps: 1. Use 100-mesh white corundum sand, set the sandblasting pressure to 0.1MPa, and the sandblasting distance to 12~14cm. Sweep and spray the end of the core substrate 1 3 times, and finally turn on the compressed air to blow away the sandblasted surface. 2. Using Al2O3 powder obtained by sintering and crushing as the raw powder of ceramic material, deionized water as the dispersant, polyvinyl alcohol as the binder, polystyrene as the pore-forming agent, the weight ratio of alumina powder to pore-forming agent is 4:1, and the weight ratio of the sum of the weight of ceramic material raw powder and pore-forming agent to the weight of deionized water is 1:5, a slurry is prepared. 3. Immerse the end 150mm of the sensor core substrate 1 into the slurry prepared in step 2 at a constant speed (without shaking), with the immersion speed controlled at 5mm / s and the dwell time at 45 seconds; pull the core substrate 1 up at a constant speed of 20mm / s; dry the core substrate 1 impregnated with the slurry in an oven to remove excess solvent; sinter at 1100℃ to remove the pore-forming agent, and the slurry solidifies into a layer to obtain a coating layer 2 with a thickness of 295μm and a porosity of 28.3%; 4. The slurry prepared in step 2 is dried to obtain modified ceramic powder. The modified ceramic powder is then sprayed onto the surface of the coating layer 2 using plasma spraying technology. The spraying power is set to 36W, the powder feed rate is 25g / min, the spraying distance is 150mm, and the air pressure is 0.1MPa to obtain a coating layer 3 with a thickness of 150μm and a porosity of 22.7%.
[0057] Example 2 A method for preparing a waterproof protective coating for a ceramic sensor chip includes the following steps: 1. Use 100-mesh white corundum sand, set the sandblasting pressure to 0.1MPa, and the sandblasting distance to 12~14cm. Sweep and spray the end of the core substrate 1 3 times, and finally turn on the compressed air to blow away the sandblasted surface. 2. ZrO2 powder obtained by sintering and crushing is used as the raw powder of ceramic material, deionized water is used as the dispersant, polyvinyl alcohol is used as the binder, and polystyrene is used as the pore-forming agent. The weight ratio of ZrO2 powder to pore-forming agent is 4:1, and the weight ratio of the sum of the weight of ceramic material raw powder and pore-forming agent to the weight of deionized water is 1:8. The slurry is prepared accordingly. 3. Immerse the end 150mm of the sensor core substrate 1 into the slurry prepared in step 2 at a constant speed (without shaking), with the immersion speed controlled at 5mm / s and the dwell time at 30 seconds; pull the core substrate 1 out at a constant speed of 30mm / s; dry the core substrate 1 impregnated with the slurry in an oven to remove excess solvent; sinter at 1100℃ to remove the pore-forming agent, and the slurry solidifies into a layer to obtain a coating layer 2 with a thickness of 350μm and a porosity of 29.2%; 4. The slurry prepared in step 2 is dried to obtain modified ceramic powder. The modified ceramic powder is then sprayed onto the surface of the coating layer 2 using plasma spraying technology. The spraying power is set to 38.5W, the powder feed rate is 25g / min, the spraying distance is 150mm, and the air pressure is 0.1MPa to obtain a coating layer 3 with a thickness of 165μm and a porosity of 19.2%.
[0058] Example 3 A method for preparing a waterproof protective coating for a ceramic sensor chip includes the following steps: 1. Use 120-mesh white corundum sand, set the sandblasting pressure to 0.1MPa, and the sandblasting distance to 12~14cm. Sweep and spray the end of the core substrate 1 3 times, and finally turn on the compressed air to blow away the sandblasted surface. 2. Using Al2O3 powder obtained by sintering and crushing as the raw powder of ceramic material, deionized water as the dispersant, polyvinyl alcohol as the binder, polystyrene as the pore-forming agent, the weight ratio of alumina powder to pore-forming agent is 5:1, and the weight ratio of the sum of the weight of ceramic material raw powder and pore-forming agent to the weight of deionized water is 1:2, a slurry is prepared. 3. After impregnating the slurry prepared in step 2, use a brush to apply the slurry to the end 150mm of the core material at a constant speed (without shaking) in the same direction. The brushing speed is controlled at 5mm / s. Apply the slurry to the five sides of the core material 1 (front, back, left, right, and top sides; leave the bottom side uncoated) three times. Dry the core material 1 with the slurry in an oven to remove excess solvent. Sinter at 1100℃ to remove the pore-forming agent. The slurry is then cured into a layer, resulting in a coating layer 2 with a thickness of 335μm and a porosity of 25.7%. 4. The slurry prepared in step 2 is dried to obtain modified ceramic powder. The modified ceramic powder is then sprayed onto the surface of the coating layer 2 using plasma spraying technology. The spraying power is set to 36.8W, the powder feed rate is 24.5g / min, the spraying distance is 150mm, and the air pressure is 0.1MPa to obtain a coating layer 3 with a thickness of 140μm and a porosity of 19.1%.
[0059] Example 4 A method for preparing a waterproof protective coating for a ceramic sensor chip includes the following steps: 1. Use 120-mesh white corundum sand, set the sandblasting pressure to 0.1MPa, and the sandblasting distance to 12~14cm. Sweep and spray the end of the core substrate 1 3 times, and finally turn on the compressed air to blow away the sandblasted surface. 2. ZrO2 powder obtained by sintering and crushing is used as the raw powder of ceramic material, deionized water is used as the dispersant, polyvinyl alcohol is used as the binder, and polystyrene is used as the pore-forming agent. The weight ratio of ZrO2 powder to pore-forming agent is 5:1, and the weight ratio of the sum of the weight of ceramic material raw powder and pore-forming agent to deionized water is 1:1.8. The mixture is then prepared into a slurry. 3. Using a brush, apply the slurry prepared in step 2 to the end 150mm of the core material at a constant speed (without shaking) in the same direction. The brushing speed is controlled at 5mm / s. Apply the slurry to all five surfaces of the core material 1 (front, back, left, right, and top surfaces; leave the bottom surface uncoated) three times. Dry the core material 1 in an oven to remove excess solvent. Sinter at 1100℃ to remove the pore-forming agent. The slurry is then cured into a layer, resulting in a coating layer 2 with a thickness of 365μm and a porosity of 26.5%. 4. The slurry prepared in step 2 is dried to obtain modified ceramic powder. The modified ceramic powder is then sprayed onto the surface of the coating layer 2 using plasma spraying technology. The spraying power is set to 38W, the powder feed rate is 25g / min, the spraying distance is 150mm, and the air pressure is 0.1MPa to obtain a coating layer 3 with a thickness of 160μm and a porosity of 19.8%.
[0060] Comparative Example 1 A method for preparing a coating on a ceramic sensor chip includes the following steps: 1. Using Al2O3 powder obtained by sintering and crushing as the raw powder of ceramic material, deionized water as the dispersant, polyvinyl alcohol as the binder, polystyrene as the pore-forming agent, the weight ratio of alumina powder to pore-forming agent is 5:1, and the weight ratio of the sum of the weight of ceramic material raw powder and pore-forming agent to deionized water is 1:3, a slurry is prepared. 2. Immerse the end 150mm of the sensor core substrate 1 into the slurry prepared in step 1 at a constant speed (without shaking), with the immersion speed controlled at 5mm / s and the dwell time at 60 seconds; pull the core substrate 1 up at a constant speed of 10mm / s; dry the core substrate 1 impregnated with the slurry in an oven to remove excess solvent; sinter at 1100℃ to remove the pore-forming agent, and the slurry solidifies into a layer to obtain a coating with a thickness of 425μm and a porosity of 28.8%.
[0061] Comparative Example 2 A method for preparing a coating on a ceramic sensor chip includes the following steps: 1. Use 100-mesh white corundum sand, set the sandblasting pressure to 0.1MPa, and the sandblasting distance to 12~14cm. Sweep and spray the end of the core substrate 1 3 times, and finally turn on the compressed air to blow away the sandblasted surface. 2. Using Al2O3 powder obtained by sintering and crushing as the raw powder of ceramic material, polystyrene as the pore-forming agent, and alumina powder to pore-forming agent in a weight ratio of 4:1, a composite powder is mixed. The composite powder is sprayed onto the surface of the core substrate 1 by plasma spraying technology. The spraying power is set to 36W, the powder feed rate is 25g / min, the spraying distance is 170mm, and the air pressure is 0.1MPa, resulting in a coating with a thickness of 125μm and a porosity of 18.4%.
[0062] Experimental example: The coating performance test results of the ceramic sensor cores prepared in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1. The coating adhesion test method refers to ISO 27307:2015; the porosity test method refers to BS DD ENV 1071-5-1995.
[0063] Table 1. Coating performance test data of ceramic sensor chips prepared in Examples 1-4 and Comparative Examples 1-2
[0064] As shown in Table 1, the inner layer of the waterproof protective coating of this invention is a dip-coating layer, and the outer layer is a plasma-sprayed coating layer. Compared with Comparative Example 1, which only has a dip-coating layer, the waterproof protective coating of this invention has better adhesion and water resistance than Comparative Example 1. Compared with Comparative Example 2, which only has a plasma-sprayed coating layer, the waterproof protective coating of this invention has higher porosity, lower energy consumption (to achieve the same thickness as a double-layer composite coating, a single plasma spraying device would consume more electricity and water), and better thermal shock resistance. Comparative Example 2 has low porosity in its single-spray coating layer but excellent adhesion. Comparative Example 1 has high porosity in its single-dip coating layer but poor adhesion. The waterproof protective coating of this invention combines both, resulting in better performance and economy. The inner dip-coating layer has high porosity and good thermal insulation performance, while the outer spray coating layer has low porosity and good water resistance. The inner and outer layers cannot be reversed.
Claims
1. A waterproof protective coating for a ceramic sensor chip, characterized in that, The waterproof protective coating (4) is a multi-layer composite coating covering the surface of the core substrate (1). The waterproof protective coating (4) includes a dip coating (2) covering the surface of the core substrate (1) and a spray coating (3) covering the surface of the dip coating (2).
2. The waterproof protective coating of the ceramic sensor chip according to claim 1, characterized in that, It should include at least one of the following technical features: A. The core substrate (1) is made of YSZ ceramic material; B. The coating layer (2) is an alumina ceramic material coating or a zirconia ceramic material coating; C. The sprayed coating (3) is an alumina ceramic material coating or a zirconia ceramic material coating.
3. The waterproof protective coating of the ceramic sensor chip according to claim 2, characterized in that, It should include at least one of the following technical features: A. The porosity of the coating layer (2) is 20~50%, and the thickness is 100~500μm; B. The porosity of the sprayed coating (3) is 19~50% and the thickness is 100~300μm.
4. A method for preparing a waterproof protective coating for a ceramic sensor chip, characterized in that, Includes the following steps: Step S1: Roughen the core substrate (1) before processing; Step S2: Prepare ceramic material raw powder; Step S3: Mix the ceramic material powder, binder, pore-forming agent and dispersant to obtain a slurry; Step S4: The slurry obtained in step S3 is coated onto the surface of the core substrate (1), dried and sintered, and the slurry is cured into a layer to obtain the coating layer (2). Step S5: Dry the slurry obtained in step S3 to obtain modified ceramic powder, spray it onto the surface of the dip coating (2) to obtain the spray coating (3), and finally form a multi-layer composite coating on the core substrate (1) as a waterproof protective coating (4).
5. The method for preparing the waterproof protective coating of the ceramic sensor chip according to claim 4, characterized in that, In step S1, the roughening pretreatment is to perform sandblasting on the surface of the core substrate (1). The sandblasting method is as follows: use 80~150 mesh white corundum sand, set the sandblasting pressure to 0.08~0.12MPa, the sandblasting distance to 6~18cm, the sandblasting part is the end of the core substrate (1), the end of the core substrate (1) is swept and sprayed 2~6 times, and finally the compressed air is turned on to blow the sandblasted surface.
6. The method for preparing the waterproof protective coating of the ceramic sensor chip according to claim 4, characterized in that, In step S2, the ceramic material raw powder is obtained by sintering crushing or spray granulation. The average particle size of the ceramic material raw powder is 10~100μm. The ceramic material raw powder is at least one of Al2O3 ceramic material raw powder and ZrO2 ceramic material raw powder, with a purity >99.5%.
7. The method for preparing the waterproof protective coating of the ceramic sensor chip according to claim 4, characterized in that, Includes at least one of the following technical features: A. The mixing process in step S3 is as follows: First, the ceramic material powder is premixed with the dispersant, using a solvent as the dispersant, then the binder is added and stirred and ground, and finally the pore-forming agent is added and mixed and ground. B. In step S3, the weight ratio of the ceramic material powder to the pore-forming agent is 4~6:1, and the weight ratio of the sum of the ceramic material powder and the pore-forming agent to the solvent is 1:0.5~10. C. The solvent mentioned in step S3 is at least one of deionized water, ethanol, and glycerol; D. The adhesive mentioned in step S3 is at least one of polyvinyl alcohol, carboxymethyl cellulose, and polyacrylic acid; E. The pore-forming agent mentioned in step S3 is at least one of polystyrene, polymethyl methacrylate, ammonium bicarbonate, citric acid, sucrose, and polyethylene glycol.
8. The method for preparing the waterproof protective coating of the ceramic sensor chip according to claim 4, characterized in that, Includes at least one of the following technical features: A Step S4 involves preparing the dip coating (2) by dip-coating-curing or brush-coating-curing. B. Step S4 involves preparing the dip coating (2) by dip-pull-curing as follows: The end portion of the core substrate (1) of 100-200 mm is immersed in the slurry at an immersion speed of 0.1-10 mm / s; the core substrate (1) is held in the slurry for 10-60 seconds and then pulled up; the core substrate (1) is pulled up at a pulling speed of 0.1-50 mm / s, and the slurry is deposited on the surface of the core substrate (1); the core substrate (1) immersed in the slurry is dried to remove excess solvent, and sintered at a high temperature of 1000-1500℃ to remove the pore-forming agent. The slurry is cured into a layer to obtain a dip coating (2) with a thickness of 100-500 μm and a porosity of 20-50%. C. Step S4 involves preparing the dip coating (2) by brushing and curing: Immerse the brush in the slurry for 40-60 seconds, then use the brush after immersion in the slurry to brush the 100-200mm portion of the core substrate (1) along the same direction at a brushing speed of 0.1-10mm / s, brushing the five sides of the core substrate (1) 3-5 times; dry the core substrate (1) coated with the slurry to remove excess solvent, sinter at 1000-1500℃ to remove the pore-forming agent, and cure the slurry into a layer to obtain a dip coating (2) with a thickness of 100-500μm and a porosity of 20-50%.
9. The method for preparing the waterproof protective coating of the ceramic sensor chip according to claim 4, characterized in that, Step S5 uses plasma spraying to prepare the coating layer (3); the process of preparing the coating layer (3) using plasma spraying is as follows: the slurry is dried to obtain modified ceramic powder, and then the modified ceramic powder is heated and melted in the plasma spraying flame to form a molten particle stream, and the molten particle stream is sprayed onto the surface of the coating layer (2).
10. The method for preparing the waterproof protective coating of the ceramic sensor chip according to claim 9, characterized in that, In step S5, the plasma spraying power is 28~40kW, the powder feed rate is 20~35g / min, the spraying distance is 110~180mm, and the air pressure is 0.08~0.12MPa, resulting in a sprayed coating layer with a thickness of 100~300μm and a porosity of 19~50% (3).