Ceramic sensing elements, their fabrication methods, and sensors

Abstract

This application relates to the field of sensor technology, providing a ceramic sensing element, its fabrication method, and a sensor. The ceramic sensing element includes a first electrode plate, a second electrode plate, and multiple protrusions in an integral structure. The first and second electrode plates are disposed opposite to each other, and the multiple protrusions are spaced apart between the first and second electrode plates to connect them. The sensor of this application significantly amplifies the electrical response of the piezoresistive effect of ceramic materials, greatly improving detection sensitivity.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to ceramic sensing elements, their preparation methods, and sensors. Background Technology

[0002] Various mechanical parameters of aero-engines have a crucial impact on structural performance and safety. To avoid sensor interference with airflow and to facilitate installation and replacement in confined spaces, sensors often require miniaturized and integrated designs. However, the ambient temperature in aero-engines is extremely high, ranging from 300°C to 700°C in the compressor section, 1300°C to 1700°C in the turbine, and even exceeding 2000°C in the combustion chamber. Traditional piezoresistive sensors use bulk ceramic as the sensing element, relying primarily on the intrinsic piezoresistive coefficient of the material. Although ceramic materials possess excellent high-temperature stability, their detection sensitivity is low. Summary of the Invention

[0003] Therefore, it is necessary to provide highly sensitive ceramic sensing elements, their preparation methods, and sensors.

[0004] In a first aspect, this application provides a ceramic sensing element, including a first electrode plate, a second electrode plate, and a plurality of protrusion structures that are integrally formed. The first electrode plate and the second electrode plate are disposed opposite to each other, and the plurality of protrusion structures are spaced apart between the first electrode plate and the second electrode plate to connect the first electrode plate and the second electrode plate.

[0005] In some implementations, the ceramic sensing element satisfies at least one of the following conditions:

[0006] (1) The material of the ceramic sensing element includes at least one of silicon carbonitride, boron silicon carbonitride, and silicon carbon oxide;

[0007] (2) The thickness of the first electrode plate is 100μm~1000μm;

[0008] (3) The thickness of the second electrode plate is 100μm~1000μm;

[0009] (4) The height of the protrusion is 100μm~1000μm, and the center-to-center distance between adjacent protrusions is 300μm~1300μm;

[0010] (5) The protruding structure is in the shape of a platform, and the bottom and top surfaces of the protruding structure are respectively connected to the first electrode plate and the second electrode plate; the equivalent diameter of the bottom surface of the protruding structure is 100μm~1000μm, and the equivalent diameter of the top surface is 50μm~500μm;

[0011] (6) The protruding structure is in the shape of a quadrangular frustum. The length of each side of the bottom surface of the protruding structure is 100μm~1000μm, and the length of each side of the top surface is 50μm~500μm.

[0012] Secondly, this application provides a method for preparing a ceramic sensing element, comprising the following steps:

[0013] A mixture is obtained by mixing a ceramic organic precursor and a curing agent;

[0014] The mixture is injected into the first mold and cured to form a first electrode preform with a raised structure on the surface;

[0015] The mixture is injected into the second mold and cured to form the second electrode plate preform; the second electrode plate preform is attached to the side of the first electrode plate preform with the protruding structure, and the mixture is pre-coated at the contact surface between the second electrode plate preform and the first electrode plate preform, and cured to form the sensitive element preform.

[0016] After sintering the preform of the sensing element, a ceramic sensing element is prepared.

[0017] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0018] (1) Ceramic organic precursors include at least one of polysilazane, polysiloborazane and polysiloxane;

[0019] (2) The number-average molecular weight of the ceramic organic precursor is 900~3000, and the ceramicization yield is ≥65%;

[0020] (3) The amount of curing agent added is 3% to 8% of the mass of the ceramic organic precursor;

[0021] (4) Curing agents include light curing agents.

[0022] In some embodiments, the ceramic organic precursor includes a conductive modified ceramic organic precursor, and the modification method of the ceramic organic precursor includes: mixing the ceramic organic precursor and a conductive modifier to prepare an electrically modified ceramic organic precursor.

[0023] In some embodiments, a third mold is used to bond the first electrode preform and the second electrode preform, including the following steps:

[0024] The second electrode plate preform is placed in the receiving groove of the third mold, and the depth of the receiving groove is greater than the thickness of the second electrode plate preform.

[0025] A mixture is applied to the surface of the second electrode preform to form a liquid coating layer; then the side of the first electrode preform with the protruding structure is placed on the second electrode preform so that the protruding structure is immersed in the liquid coating layer and comes into contact with the second electrode preform.

[0026] In some embodiments, the sintering step includes sequentially performing a first sintering stage, a second sintering stage, and a third sintering stage on the sensitive element preform.

[0027] The temperature of the first sintering stage is 180℃~350℃, the time is 25min~35min, the heating rate is 1℃ / min~3℃ / min, and the atmosphere is a protective atmosphere.

[0028] The second sintering stage is conducted at a temperature of 400℃~600℃ for 25min~35min, with a heating rate of 1℃ / min~3℃ / min, and in a protective atmosphere.

[0029] The temperature of the third sintering stage is 1000℃~1300℃, the time is 230min~250min, the heating rate is 1℃ / min~3℃ / min, and the atmosphere is a protective atmosphere.

[0030] Thirdly, this application provides a sensor including a pressure-sensitive element and a temperature-sensitive element, wherein the pressure-sensitive element and the temperature-sensitive element are respectively independently prepared using the ceramic sensing element preparation methods of the first aspect and / or the ceramic sensing element preparation methods of the second aspect.

[0031] In some implementations, the sensor further includes:

[0032] The cover has a through hole.

[0033] The base is fastened to the cover to form a receiving cavity between the cover and the base, and both the pressure-sensitive element and the temperature-sensitive element are disposed in the receiving cavity;

[0034] The pressure block assembly includes a pressure block and an elastic element disposed in a receiving cavity. The pressure block includes a pressure head and a connecting part. The pressure head is disposed in the receiving cavity to press the pressure-sensitive element, and the connecting part is connected to the pressure head and extends out of the receiving cavity through a through hole. The elastic element is disposed between the pressure head and the cover body to provide a clamping force for the pressure head to press the pressure-sensitive element.

[0035] In some embodiments, the sensor further includes a first insulating layer disposed on a base and a limiting plate disposed on the first insulating layer. The limiting plate has a first limiting groove and a second limiting groove, and the pressure-sensitive element and the temperature-sensitive element are respectively disposed in the first limiting groove and the second limiting groove. The first insulating layer is also provided with electrodes at positions corresponding to the pressure-sensitive element and the temperature-sensitive element, and the electrodes are respectively connected to the pressure-sensitive element and the temperature-sensitive element.

[0036] The sensor also includes a second insulating layer, which is disposed between the pressure-sensitive element and the pressure head. The second insulating layer has a groove at the position corresponding to the temperature-sensitive element, and the groove is used to prevent the pressure head from pressing on the temperature-sensitive element.

[0037] Compared with traditional technologies, this application has at least the following beneficial effects:

[0038] This application employs an integrated ceramic sensing element. By utilizing the protrusion structure between the first and second electrodes, and through the controllable stress concentration effect, the electrical response of the piezoresistive effect of the ceramic material is significantly amplified, thereby greatly improving the detection sensitivity. Attached Figure Description

[0039] Figure 1 This is a cross-sectional schematic diagram of a ceramic sensing element in one embodiment of this application;

[0040] Figure 2 This is a schematic diagram of the internal structure of a ceramic sensing element in one embodiment of this application;

[0041] Figure 3 This is a schematic diagram of the process of bonding and curing the first electrode preform and the second electrode preform provided in one embodiment of this application;

[0042] Figure 4 This is a schematic diagram of the sensor's appearance in one embodiment of this application;

[0043] Figure 5 This is a disassembly diagram of a sensor in one embodiment of this application;

[0044] Figure 6 This is another disassembly diagram of the sensor in one embodiment of this application;

[0045] Figure 7 This is a schematic diagram showing another disassembly of the sensor in one embodiment of this application;

[0046] Figure 8 This is a schematic diagram of the structure of the groove inside the sensor cover and the second insulating layer in one embodiment of this application;

[0047] Figure 9 This is a structural diagram of a Wheatstone bridge provided in one embodiment of this application.

[0048] Wherein, 100-Ceramic sensitive element; 110-First electrode plate; 120-Second electrode plate; 130-Protruding structure; 100a-Pressure-sensitive element; 100b-Temperature-sensitive element; 200-Cover body; 210-Through hole; 220-Lead hole; 300-Base; 400-Pressure block assembly; 410-Pressure block; 411-Pressure head; 412-Connecting part; 420-Elastic element; 500-First insulating layer; 600-Limiting plate; 610-First limiting groove; 620-Second limiting groove; 700-Second insulating layer; 710-Groove.

[0049] 10 - First electrode plate preform; 20 - Second electrode plate preform; 30 - Liquid coating layer. Detailed Implementation

[0050] The present application will be further described in detail below with reference to the embodiments and examples. These embodiments and examples are only for illustrating the present application and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. In addition, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0051] In this application, the terms "first aspect," "second aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first aspect," "second aspect," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0052] In traditional piezoresistive sensors, bulk ceramics are used as sensing elements, relying primarily on the intrinsic piezoresistive coefficient of the material. Although ceramic materials possess excellent high-temperature stability, their detection sensitivity is low, making it difficult to meet the comprehensive requirements of aerospace and other fields for high sensitivity, high stability, and wide-temperature-range reliability. Furthermore, while flexible sensors can improve sensitivity by constructing microarrays on the electrode surface to introduce stress concentration, the high hardness, high chemical inertness, and excellent thermal stability of ceramic materials make it difficult to achieve high-precision and highly consistent structural fabrication using traditional processing techniques, further limiting the realization of high-performance ceramic sensing elements.

[0053] The first aspect of this application provides a ceramic sensing element, such as... Figure 1 and Figure 2As shown, the ceramic sensing element 100 includes a first electrode plate 110, a second electrode plate 120, and a plurality of protrusions 130 that are integrally formed. The first electrode plate 110 and the second electrode plate 120 are disposed opposite to each other, and the plurality of protrusions 130 are spaced apart between the first electrode plate 110 and the second electrode plate 120 to connect the first electrode plate 110 and the second electrode plate 120.

[0054] It is understood that in this application, the first electrode plate 110, the second electrode plate 120, and the protrusion structure 130 are integrally connected, meaning that the first electrode plate 110, the second electrode plate 120, and the protrusion structure 130 are integrally connected without obvious connection interfaces, which has good structural stability. Compared with the traditional technology where the two electrode plates are bonded with other materials, it can effectively avoid the relative displacement of the contact interface of the electrode plates due to expansion at high temperatures, thereby effectively ensuring the stability and reliability of the detection results.

[0055] In some embodiments, the material of the ceramic sensing element 100 includes at least one of silicon carbonitride, boron silicon carbonitride, and silicon carbide.

[0056] In some embodiments, the thickness of the first electrode 110 is 100 μm to 1000 μm, for example, it can be 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1000 μm. The thickness of the second electrode 120 is 100 μm to 1000 μm, for example, it can be 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1000 μm.

[0057] In some embodiments, such as Figure 1 As shown, the height h of the protrusion structure 130 is 100μm to 1000μm, for example, it can be 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm or 1000μm; the center-to-center distance between adjacent protrusion structures 130 is 300μm to 1300μm, for example, it can be 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm, 1100μm, 1200μm or 1300μm.

[0058] Optionally, the protruding structure 130 is in the shape of a platform, and its bottom and top surfaces are respectively connected to the first electrode plate 110 and the second electrode plate 120. The equivalent diameter a2 of the bottom surface of the protruding structure 130 is 100μm to 1000μm, for example, it can be 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, or 1000μm; the equivalent diameter a1 of the top surface is 50μm to 500μm, for example, it can be 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, or 500μm. Optionally, the protrusion 130 is shaped like a frustum, with each side of the base having an independent length of 100μm to 1000μm, and each side of the top having an independent length of 50μm to 500μm. Optionally, the ratio of the base side length to the top side length is 4:1 to 1.5:1. It should be noted that the equivalent diameter refers to the diameter corresponding to the shape and area of ​​the top or bottom surface being equivalent to a circle.

[0059] In some embodiments, the number of protrusions is 6×6 to 15×15.

[0060] As mentioned above, this application selects the size of the protrusion structure 130. By utilizing the negative correlation between parameters such as the bottom side length, the ratio of the bottom side length to the top side length, and the number of protrusion structures and the device sensitivity, it ensures that the device has high sensitivity and low nonlinearity. In addition, it also has high fabrication precision and the overall structural strength meets the requirements of pressure sensors.

[0061] A second aspect of this application provides a method for preparing a ceramic sensing element, comprising the following steps:

[0062] A mixture is obtained by mixing a ceramic organic precursor and a curing agent;

[0063] The mixture is injected into the first mold and cured to form a first electrode preform with a raised structure on the surface;

[0064] The mixture is injected into the second mold and cured to form the second electrode plate preform; the second electrode plate preform is attached to the side of the first electrode plate preform with the protruding structure, and the mixture is pre-coated at the contact surface between the second electrode plate preform and the first electrode plate preform, and cured to form the sensitive element preform.

[0065] After sintering the preform of the sensing element, a ceramic sensing element is prepared.

[0066] This application employs a casting process to separately form a first electrode preform and a second electrode preform with protruding structures. A mixture containing a ceramic organic precursor is then used as an adhesive to solidify the first and second electrode preforms, followed by sintering to obtain a monolithic ceramic sensing element. The casting method using a first mold ensures the processing accuracy and consistency of the protruding structure array arrangement, effectively improving detection sensitivity.

[0067] It is understandable that the first mold and the second mold only need to have groove structures corresponding to the first electrode plate preform and the second electrode plate preform, so as to ensure the formation of a first electrode plate preform with multiple protruding structures and a second electrode plate preform with a flat plate structure.

[0068] It is understood that the appropriate ceramic organic precursor can be selected based on the ceramic material. In some embodiments, the ceramic organic precursor includes at least one of polysilazane, polysiloborazane, and polysiloxane. For example, vinyl liquid polysilazane can be used.

[0069] In some embodiments, the number-average molecular weight of the ceramic organic precursor is 900-3000, for example, 900, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, or 3000; the ceramicization yield is ≥65%. The molecular weight of the ceramic organic precursor selected in this application is moderate in the amount of gas generated during pyrolysis, with uniform volume shrinkage and a high ceramic yield, resulting in a dense structure and fewer defects in the formed ceramic product, exhibiting good mechanical properties and thermal stability. If the molecular weight is relatively low, a large amount of small molecule gas may escape rapidly during pyrolysis. Due to significant and uneven volume shrinkage, the ceramic product has high porosity, insufficient density, and an increased tendency to crack, leading to a decline in the overall mechanical properties of the ceramic.

[0070] In some embodiments, the preparation method further includes: degassing the mixture to avoid the presence of air bubbles in the mixture, which would affect the density of the cured material.

[0071] In some embodiments, the amount of curing agent added is 3% to 8% of the mass of the ceramic organic precursor, for example, it can be 3%, 4%, 5%, 6%, 7% or 8%.

[0072] In some embodiments, the curing agent includes a photocuring agent. Optionally, the photocuring agent includes phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0073] It is understandable that the mixture contains a curing agent, and premature curing should be avoided. Taking UV curing agents as an example, exposure to UV light should be avoided during mixing; mixing under warm light is preferable to prevent UV irradiation from causing the material to harden or become sticky. Furthermore, the curing method for the mixture can be selected based on the type of curing agent used. Using UV curing agents as an example, a UV curing instrument is used to fix the mixture, with a wavelength of 365nm and a power of 300W~350W.

[0074] In some embodiments, the ceramic organic precursor includes a conductive-modified ceramic organic precursor. The modification method of the ceramic organic precursor includes mixing the ceramic organic precursor and a conductive modifier to prepare an electrically modified ceramic organic precursor. This application improves the conductivity of ceramics by conductively modifying the ceramic organic precursor.

[0075] Optionally, the amount of conductive modifier added is 10% to 30% of the mass of the ceramic organic precursor, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%.

[0076] Optionally, the conductive modifier includes at least one of divinylbenzene, ferrocene, and TiB2. The carbon content and electrical conductivity of the ceramic pyrolysis products can be adjusted by controlling the amount of divinylbenzene added. When the conductive modifier is an organic conductive modifier such as divinylbenzene, heating can be performed during mixing to allow the divinylbenzene or similar material to react with and graft onto the ceramic organic precursor, thereby improving the dispersion uniformity of the divinylbenzene or similar material in the mixture. For example, after mixing the ceramic organic precursor and divinylbenzene, the mixture can be heated in a water bath at 60°C to 80°C to obtain a conductive modified ceramic organic precursor.

[0077] In some embodiments, the materials of the first mold and the second mold can be polydimethylsiloxane (PDMS) independently. PDMS is a material with high elasticity, low surface energy, and good mold release properties.

[0078] Optionally, a release agent can be applied to the first and second molds before injecting the mixture to ensure easy demolding of the first and second electrode preforms. For example, the release agent may be at least one of tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane, liquid silicone oil, and polydimethylsiloxane spray.

[0079] It is understood that, in the process of assembling the first electrode preform and the second electrode preform, the mixture is sufficient to stabilize the bonding between the two. For example, the mixture can be coated on the first electrode preform, or on the second electrode preform, or on both the first and second electrode preforms. In some embodiments, such as Figure 3 As shown, the first electrode plate preform 10 and the second electrode plate preform 20 are bonded together using a third mold, including the following steps:

[0080] The second electrode preform 20 is placed in the receiving groove of the third mold, and the depth of the receiving groove is greater than the thickness of the second electrode preform 20.

[0081] A mixture is applied to the surface of the second electrode preform 20 to form a liquid coating layer 30; then the side of the first electrode preform 10 with the protruding structure is placed on the second electrode preform 20 so that the protruding structure is immersed in the liquid coating layer 30 and in contact with the second electrode preform 20.

[0082] Optionally, the thickness of the liquid coating layer 30 can be 10μm to 100μm, for example, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm.

[0083] This application employs a third mold to form a liquid coating layer 30 of a certain thickness on the second electrode preform, ensuring a stable bond between the first and second electrode preforms. Specifically, during the curing process after bonding the first and second electrode preforms, pre-curing can be performed in the third mold to reduce the fluidity of the liquid coating layer 30 and prevent the mixture from failing to maintain its liquid coating layer state. Then, the bonded first and second electrode preforms are removed and cured again to ensure complete curing and formation of the sensitive element preform.

[0084] Optionally, the difference between the depth of the receiving groove in the third mold and the thickness of the second electrode preform is greater than or equal to the thickness of the liquid coating layer 30.

[0085] In some embodiments, the sintering method can be embedded sintering, specifically including: embedding the sensing element preform in inert powder and performing heat treatment in a high-temperature furnace. This application utilizes embedded sintering to suppress green body deformation, cracking, and foreign matter contamination, thereby improving ceramicization quality and yield. The inert powder refers to a powder that does not react with the ceramic material in the ceramic sensing element. Preferably, the inert powder has a coefficient of thermal expansion similar to that of the ceramic material and possesses high-temperature resistance and good thermal conductivity. For example, boron nitride powder can be used as the inert powder.

[0086] In some embodiments, the sintering step includes sequentially performing a first sintering stage, a second sintering stage, and a third sintering stage on the sensitive element preform.

[0087] Optionally, the temperature of the first sintering stage is 180℃~350℃, for example, 180℃, 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, or 350℃; the time is 25min~35min, for example, 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min, or 35min; the heating rate is 1℃ / min~3℃ / min, for example, 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, or 3.0℃ / min; and the atmosphere is a protective atmosphere. The protective atmosphere refers to a gas that does not react with the raw materials during the sintering process, such as an inert gas like argon. This application performs the first sintering stage as described above, further solidifying the sensitive element preform through heating, improving structural stability, and preventing structural damage during the sintering process.

[0088] Optionally, the temperature of the second sintering stage is 400℃~600℃, for example, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, or 600℃; the time is 25min~35min, for example, 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min, or 35min; the heating rate is 1℃ / min~3℃ / min, for example, 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, or 3.0℃ / min; and the atmosphere is a protective atmosphere. The second sintering stage described above promotes gas release from the sensitive element preform, further ensuring the structural stability of the sensitive element preform.

[0089] Optionally, the temperature of the third sintering stage is 1000℃~1300℃, for example, 1000℃, 1030℃, 1060℃, 1090℃, 1120℃, 1150℃, 1180℃, 1210℃, 1240℃, 1270℃, or 1300℃; the time is 230min~250min, for example, 230min, 232min, 234min, 236min, 238min, 240min, 242min, 244min, 246min, 248min, or 250min; the heating rate is 1℃ / min~3℃ / min, for example, 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, or 3.0℃ / min; and the atmosphere is a protective atmosphere. This application performs the third sintering stage as described above to ensure the amorphous formation of the sensitive element. If the sensitive element preform is sintered directly at the temperature of pyrolysis amorphization, small molecule gases may be released rapidly and local overheating may occur under high temperature conditions, resulting in increased porosity and uneven volume shrinkage, or even cracking of the element.

[0090] In some embodiments, the ceramic sensing element is cooled after sintering at a rate of 2°C / min to 4°C / min. Further, the ceramic sensing element can be cooled to 200°C to 400°C at a rate of 2°C / min to 4°C / min, and then allowed to cool naturally to room temperature.

[0091] Exemplarily, a method for preparing the above-mentioned ceramic sensing element is provided, comprising the following steps:

[0092] First, the ceramic organic precursor and the conductive modifier are mixed evenly, and then a curing agent is added for degassing treatment to obtain a mixture.

[0093] After spraying a release agent onto the first mold, the mixture is injected into the first mold and cured to form a first electrode preform with a raised structure on the surface.

[0094] After spraying a release agent onto the second mold, the mixture is injected into the second mold and cured to form the second electrode plate preform.

[0095] The second electrode preform is attached to the side of the first electrode preform with the protruding structure, and a mixture is pre-coated at the contact surface between the second electrode preform and the first electrode preform, and then cured to form a sensitive element preform.

[0096] After sequentially performing first-stage sintering, second-stage sintering, and third-stage sintering on the preform of the sensing element, the ceramic sensing element is prepared by cooling.

[0097] A third aspect of this application provides a sensor, such as... Figure 4 , Figure 5and Figure 6 As shown, it includes a pressure-sensitive element 100a and a temperature-sensitive element 100b, which are ceramic sensing elements prepared independently using the preparation methods of the ceramic sensing elements of the first aspect and / or the ceramic sensing elements of the second aspect.

[0098] This application introduces a pressure-sensitive element 100a and a temperature-sensitive element 100b with identical structures into the sensor. The temperature-sensitive element 100b is used for temperature detection, and hardware-based temperature self-compensation is provided for the pressure-sensitive element 100a, which effectively improves the measurement stability and anti-interference ability in a wide temperature range environment.

[0099] In some embodiments, such as Figure 4 and Figure 5 As shown, the sensor also includes a cover 200, a base 300, and a pressure block assembly 400. The cover 200 has a through hole 210. The base 300 is fastened to the cover 200 to form a receiving cavity between the cover 200 and the base 300, in which the pressure-sensitive element 100a and the temperature-sensitive element 100b are both disposed. It is understood that the cover 200 and the base 300 can be connected by filling with sealant.

[0100] like Figure 5 As shown, the pressure block assembly 400 includes a pressure block 410 disposed in a receiving cavity and an elastic member 420. The pressure block 410 includes a pressure head 411 and a connecting portion 412. The pressure head 411 is disposed in the receiving cavity to press the pressure-sensitive element 100a; the connecting portion 412 is connected to the pressure head 411 and extends out of the receiving cavity through the through hole 210. The elastic member 420 is disposed between the pressure head 411 and the cover 200 to provide a clamping force for the pressure head 411 to press the pressure-sensitive element 100a. It can be understood that the connecting portion 412 can transmit the force applied externally to the sensor to the pressure head 411, thereby applying pressure to the pressure-sensitive element 100a. The elastic member 420 is mainly used to press and fix the pressure-sensitive element 100a onto the base 300 to maintain the continuity and stability of the force transmission path and effectively avoid poor contact of the pressure-sensitive element 100a caused by vibration or thermal expansion. For example, the elastic element 420 can be a spring sleeved on the connecting part 412, and a suitable spring can be selected according to the requirements of different pressure-sensitive elements 100a. Furthermore, in order to ensure the positioning of the elastic element 420, a connecting groove can be opened in the inner wall of the pressure head 411 and the cover 200 to ensure the accuracy of the spring's position.

[0101] In some embodiments, such as Figure 6 and Figure 7As shown, the sensor also includes a first insulating layer 500 disposed on the base 300 and a limiting plate 600 disposed on the first insulating layer 500. The limiting plate 600 has a first limiting groove 610 and a second limiting groove 620, and the pressure-sensitive element 100a and the temperature-sensitive element 100b are respectively disposed in the first limiting groove 610 and the second limiting groove 620.

[0102] Optionally, such as Figure 7 As shown, the limiting plate 600 also has lead wire grooves to facilitate the connection of electrode leads to the pressure-sensitive element 100a and the temperature-sensitive element 100b. It is understood that, as Figure 5 As shown, a lead wire hole 220 can also be made on the cover 200 at the position where the lead wire is led out, so as to facilitate the lead wire being led out from the receiving cavity.

[0103] In some embodiments, such as Figure 6 As shown, the sensor also includes a second insulating layer 700, which is disposed between the pressure-sensitive element 100a and the pressure head 411, as... Figure 8 As shown, a groove 710 is provided in the second insulating layer 700 corresponding to the position of the temperature-sensitive element 100b. The groove 710 is used to prevent the pressure head 411 from pressing on the temperature-sensitive element 100b. In this application, the pressure head 411 transmits force evenly to the pressure-sensitive element 100a through the second insulating layer 700. At the same time, by providing the groove 710 in the second insulating layer 700, the second insulating layer 700 is prevented from directly applying pressure to the temperature-sensitive element 100b, so that the temperature-sensitive element 100b only senses temperature changes and is not affected by pressure changes, thereby achieving self-compensation of the pressure-sensitive element 100a in terms of temperature.

[0104] It is understood that first electrodes are respectively disposed on the first insulating layer 500 at positions corresponding to the pressure-sensitive element 100a and the temperature-sensitive element 100b, with the pressure-sensitive element 100a and the temperature-sensitive element 100b respectively contacting the first electrodes; second electrodes are disposed on the second insulating layer 700 at positions corresponding to the pressure-sensitive element 100a and on the surface of the temperature-sensitive element 100b facing away from the first insulating layer 500. The first and second electrodes on both sides of the pressure-sensitive element 100a are used to detect the resistance of the pressure-sensitive element 100a, and the first and second electrodes on both sides of the temperature-sensitive element 100b are used to detect the resistance of the temperature-sensitive element 100b. Furthermore, the sensor can connect the pressure-sensitive element 100a and the temperature-sensitive element 100b to a Wheatstone bridge to convert resistance changes into voltage signals. For example, Figure 9 As shown, a Wheatstone bridge is a bridge circuit composed of four known resistors. In this application, the varistor 100a and the temperature-sensitive element 100b are respectively placed in adjacent arms of the Wheatstone bridge (e.g., the varistor 100a is connected to R1, and the first electrode of the varistor 100a is connected to -V). out The second electrode is connected to +V inThe temperature-sensitive element 100b is connected to R4, and the first electrode of the temperature-sensitive element 100b is connected to -V. out The second electrode is connected to -V in ), in V in An excitation voltage is applied to the terminal, V out The output voltage signal is a single value related to the pressure. This voltage signal has a one-to-one correspondence with the parameters detected by the pressure-sensitive element 100a and the temperature-sensitive element 100b. Therefore, by measuring the voltage signal respectively, the pressure parameter detected by the pressure-sensitive element 100a and the temperature parameter detected by the temperature-sensitive element 100b can be output.

[0105] In some embodiments, the cover 200 and the base 300 are independently made of high-temperature resistant and corrosion-resistant materials. For example, the cover 200 and the base 300 can be made of stainless steel (such as 504 stainless steel). The first insulating layer 500, the second insulating layer 700, and the limiting plate 600 can be made of materials that are high-temperature resistant, have high hardness, are non-catalytically active, and have good insulation properties. For example, the first insulating layer 500, the second insulating layer 700, and the limiting plate 600 can be made of corundum-type α-Al2O3. The electrodes and leads can be made of high-temperature resistant materials, such as platinum electrodes. For example, the electrodes can be platinum electrodes, and the leads can be made of Ti / Ni / Au alloy materials.

[0106] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0107] In the following examples, vinyl polysilazane was purchased from Shenzhen Langbowan Advanced Materials Co., Ltd. Its number-average molecular weight is approximately 1500, and its ceramic yield is approximately 75%. The first mold, second mold, and third mold are all made of PDMS material.

[0108] Example 1

[0109] 5.00 g of vinyl polysilazane and 1.32 g of divinylbenzene were mixed and reacted in a water bath at 70 °C with stirring at 400 rpm for 2 h to obtain conductive modified vinyl polysilazane. Then, 0.26 g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide was added, and the mixture was stirred in the yellow light region for another 4 h to ensure complete dissolution and homogeneous mixing. The mixture was then placed in a vacuum chamber and pressurized at 5 Pa for 20 min, and this process was repeated 2-3 times to degas the mixture and thoroughly remove air bubbles.

[0110] A first mold is provided, comprising a groove in the shape of the main body of the first electrode plate 110 and an array of grooves. The main body of the first electrode plate 110 is square with each side length of 6.2 mm and a depth of 250 μm. Each groove in the array is frustum-shaped with a depth of 350 μm, a square base with each side length of 100 μm, a square opening with each side length of 300 μm, and a center-to-center distance of 400 μm between adjacent grooves. First, a PDMS release agent is uniformly sprayed onto the first mold. Then, the degassed mixture is injected into the first mold. After injection, the mold is cured by irradiation using a UV curing instrument with a wavelength of 365 nm, a power of 320 W, and a curing time of 25 min. After curing, the first electrode plate preform is demolded from the first mold. One side surface of the first electrode plate preform has an array of frustum-shaped protrusions 130.

[0111] A second mold is provided, having a main body portion of the second electrode plate 120. The side length of the main body portion of the second electrode plate 120 is 6.2 mm, and the depth is 300 μm. First, a PDMS release agent is uniformly sprayed onto the first mold. Then, the degassed mixture is injected into the second mold. The mold is then cured and demolded using the same method as the preparation of the first electrode plate preform to obtain the second electrode plate preform.

[0112] The second electrode preform is placed in the groove of the third mold, and the degassed mixture is coated onto the second electrode preform to form a liquid coating layer 30 with a thickness of approximately 50 μm. Then, the side of the first electrode preform with the protruding structure 130 is attached to the side of the second electrode preform with the liquid coating layer 30 and the edges are aligned. It is first cured with ultraviolet light for 20 seconds to reduce the fluidity of the liquid coating layer 30. After removing the third mold, it is cured again using the curing parameters of the first electrode preform to obtain the sensitive element preform. The height of the protruding structure in the sensitive element preform is 300 μm, and the side length of the side in contact with the first electrode preform is 300 μm. Since the protruding structure part of the first electrode preform is immersed in the liquid coating layer 30, after curing, the side length of the side of the protruding structure in contact with the second electrode preform becomes 150 μm.

[0113] The aforementioned sensing element preform was embedded in an alumina crucible containing boron nitride powder with a particle size of approximately 50 μm. The alumina crucible was then placed in a high-temperature furnace, evacuated, and purged with nitrogen. The furnace temperature was controlled by first raising it to 300°C at a rate of 1°C / min and holding for 2 hours to further solidify the sensing element preform; then raising it to 500°C at a rate of 1°C / min and holding for 2 hours to release the gas inside the preform; finally, raising it to 1200°C at a rate of 1°C / min and holding for 4 hours to achieve amorphous forming of the ceramic sensing element 100. Finally, the furnace temperature was lowered to 300°C at a rate of 3°C / min, and the ceramic sensing element 100 was removed and allowed to cool naturally to room temperature.

[0114] Comparative Example 1

[0115] The ceramic sensing element was prepared using a method similar to that in Example 1, except that a ceramic plate sintered from an electrode preform without protrusions was used as the ceramic sensing element. The thickness of the ceramic plate was the sum of the thicknesses of the first electrode and the second electrode in Example 1.

[0116] The ceramic sensing elements prepared in the above embodiments and comparative examples were subjected to performance tests, and the test methods included:

[0117] At 25°C, pressure was gradually applied to the above-mentioned ceramic sensing element at a rate of 0.1 MPa / s up to 10 MPa, thereby measuring the relative resistance change rate and obtaining the relative resistance change rate of the ceramic sensing element.

[0118] Table 1

[0119]

[0120] Compared with Comparative Example 1, Example 1 of this application has a larger relative resistance change rate, thus exhibiting higher sensitivity.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A ceramic sensing element, characterized in that, It includes a first electrode plate, a second electrode plate, and a plurality of protrusions that are integrally formed. The first electrode plate and the second electrode plate are disposed opposite to each other, and the plurality of protrusions are spaced apart between the first electrode plate and the second electrode plate to connect the first electrode plate and the second electrode plate.

2. The ceramic sensing element as described in claim 1, characterized in that, The ceramic sensing element satisfies at least one of the following conditions: (1) The material of the ceramic sensing element includes at least one of silicon carbonitride, boron silicon carbonitride, and silicon carbon oxide; (2) The thickness of the first electrode plate is 100μm~1000μm; (3) The thickness of the second electrode plate is 100μm~1000μm; (4) The height of the protrusion is 100μm~1000μm, and the center-to-center distance between adjacent protrusions is 300μm~1300μm; (5) The protruding structure is in the shape of a platform, and the bottom surface and the top surface of the protruding structure are respectively connected to the first electrode plate and the second electrode plate; the equivalent diameter of the bottom surface of the protruding structure is 100μm~1000μm, and the equivalent diameter of the top surface is 50μm~500μm; (6) The protrusion structure is in the shape of a quadrangular frustum. The length of each side of the bottom surface of the protrusion structure is 100μm~1000μm and the length of each side of the top surface is 50μm~500μm.

3. A method for preparing a ceramic sensing element, characterized in that, Includes the following steps: A mixture is obtained by mixing a ceramic organic precursor and a curing agent; The mixture is injected into a first mold and cured to form a first electrode preform with a raised structure on its surface; The mixture is injected into a second mold and cured to form a second electrode plate preform; The second electrode preform is attached to the side of the first electrode preform with the protruding structure, and the mixture is pre-coated at the contact surface between the second electrode preform and the first electrode preform, and then cured to form a sensitive element preform. The ceramic sensing element is prepared by sintering the sensing element preform.

4. The method for preparing the ceramic sensing element as described in claim 3, characterized in that, The preparation method satisfies at least one of the following conditions: (1) The ceramic organic precursor includes at least one of polysilazane, polysiloborazane and polysiloxane; (2) The number-average molecular weight of the ceramic organic precursor is 900~3000, and the ceramicization yield is ≥65%; (3) The amount of curing agent added is 3% to 8% of the mass of the ceramic organic precursor; (4) The curing agent includes a light curing agent.

5. The method for preparing the ceramic sensing element as described in claim 3, characterized in that, The ceramic organic precursor includes a conductive modified ceramic organic precursor, and the modification method of the ceramic organic precursor includes: mixing the ceramic organic precursor and a conductive modifier to prepare the conductive modified ceramic organic precursor.

6. The method for preparing the ceramic sensing element as described in claim 3, characterized in that, The first electrode plate preform and the second electrode plate preform are bonded together using a third mold, including the following steps: The second electrode preform is placed in the receiving groove of the third mold, the depth of the receiving groove being greater than the thickness of the second electrode preform; The mixture is coated onto the surface of the second electrode preform to form a liquid coating layer; then the side of the first electrode preform having the protruding structure is placed on the second electrode preform so that the protruding structure is immersed in the liquid coating layer and contacts the second electrode preform.

7. The method for preparing the ceramic sensing element according to any one of claims 3-6, characterized in that, The sintering steps include: sequentially performing a first sintering stage, a second sintering stage, and a third sintering stage on the sensitive element preform; The temperature of the first sintering stage is 180℃~350℃, the time is 25min~35min, the heating rate is 1℃ / min~3℃ / min, and the atmosphere is a protective atmosphere. The temperature of the second sintering stage is 400℃~600℃, the time is 25min~35min, the heating rate is 1℃ / min~3℃ / min, and the atmosphere is a protective atmosphere; The temperature of the third sintering stage is 1000℃~1300℃, the time is 230min~250min, the heating rate is 1℃ / min~3℃ / min, and the atmosphere is a protective atmosphere.

8. A sensor, characterized in that, It includes a pressure-sensitive element and a temperature-sensitive element, wherein the pressure-sensitive element and the temperature-sensitive element are respectively prepared independently using the ceramic sensing element preparation method described in claim 1 or 2 and / or any one of claims 3 to 7.

9. The sensor as described in claim 8, characterized in that, The sensor also includes: The cover body has a through hole; A base is fastened to the cover to form a receiving cavity between the cover and the base, and both the pressure-sensitive element and the temperature-sensitive element are disposed in the receiving cavity; The pressure block assembly includes a pressure block and an elastic element disposed in the receiving cavity. The pressure block includes a pressure head and a connecting part. The pressure head is disposed in the receiving cavity to press the pressure-sensitive element. The connecting part is connected to the pressure head and extends out of the receiving cavity through the through hole. The elastic element is disposed between the pressure head and the cover body to provide a clamping force for the pressure head to press the pressure-sensitive element.

10. The sensor as described in claim 9, characterized in that, The sensor further includes a first insulating layer disposed on the base and a limiting plate disposed on the first insulating layer. The limiting plate has a first limiting groove and a second limiting groove. The pressure-sensitive element and the temperature-sensitive element are respectively disposed in the first limiting groove and the second limiting groove. The first insulating layer is also provided with electrodes at positions corresponding to the pressure-sensitive element and the temperature-sensitive element, and the electrodes are respectively connected to the pressure-sensitive element and the temperature-sensitive element. The sensor further includes a second insulating layer, which is disposed between the pressure-sensitive element and the pressure head. The second insulating layer has a groove corresponding to the position of the temperature-sensitive element, and the groove is used to prevent the pressure head from pressing on the temperature-sensitive element.

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