Carbon-source-doped structured SiOC ceramic as well as preparation method and application thereof
By using a carbon-doped structured SiOC ceramic preparation method, combined with 3D printing technology and negative Poisson's ratio structure, the problems of poor tolerance and insufficient mechanical strength of ceramic sensors in extreme environments were solved, achieving high-sensitivity pressure detection and stability under high-temperature conditions.
Patent Information
- Application Number
- CN202511157258.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-19
- Publication Date
- 2025-12-09
AI Technical Summary
Existing ceramic sensors have poor tolerance to extreme environments, insufficient mechanical strength, low piezoresistive sensitivity, and high brittleness during processing, making it difficult to meet the long-term stability requirements under high-temperature environments.
A structured SiOC ceramic preparation method using carbon source doping is adopted. By combining the carbon source material with the SiOC ceramic precursor solution through 3D printing technology, a negative Poisson's ratio structure is formed, a strong interfacial bond is established, and a high-density conductive phase network is formed, thereby improving the conductivity and mechanical strength of the material.
It achieves high-sensitivity pressure detection of materials under high-temperature conditions, significantly improves electrical conductivity and piezoresistive performance, avoids catastrophic structural failure under impact, and has good environmental tolerance and mechanical properties.
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Figure CN121085643A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of ceramics, in particular to a carbon source doped structured SiOC ceramic and a preparation method and application thereof. BACKGROUND
[0002] Various sensors have been applied in precision instruments in different industries to accurately monitor the operating conditions of the equipment, capture signals and warn of danger. Sensors often work in extreme environments, exploring unknown things. For example, rescue robots usually work in high temperature, high pressure or corrosive gas. Sensors are an important part of the equipment and should have high environmental tolerance. Pressure monitoring in harsh environments such as turbine engines, submersibles and nuclear reactors is of great significance. Pressure sensors with high load capacity, high sensitivity and environmental tolerance are still scarce.
[0003] Polymer-derived ceramic (PDC) materials, as a kind of functional ceramic, have high load capacity, high temperature stability, and good creep resistance and oxidation resistance, which can ensure safety in harsh environments for a long time. At the same time, due to the piezoresistive effect of PDC, i.e. the resistance changes with pressure, it is expected to be used for pressure sensing applications. In addition, the structure can be customized according to different application requirements, and their deformation-resistant structure can ensure the integrity and connectivity of the sensing layer, maintaining regular sensing ability under pressure load. However, the mechanical processing of ceramic structure is poor. Hard machining often leads to unnecessary quality degradation. Therefore, it is necessary to explore a feasible, simple and non-destructive method to prepare customized ceramics. SUMMARY
[0004] In view of the deficiencies in the above background art, the present application mainly solves the technical defects of the existing ceramic sensor, such as large brittleness, poor high temperature environment tolerance, insufficient mechanical strength and low piezoresistive sensitivity, and at the same time solves the problems of insufficient electrical conductivity and poor long-term cycle stability. The present application provides a carbon source doped structured SiOC ceramic and a preparation method and application thereof. The method realizes the semiconductorization regulation and control of the electrical conductivity of SiOC ceramic by regulating and controlling the type and doping amount of carbon source material, obtains a high value piezoresistive coefficient to accurately monitor the change of pressure while ensuring good high temperature resistance; combined with doping content optimization and sintering process parameter adjustment, the electrical conductivity is improved by orders of magnitude. The preparation method adopts 3D printing technology, which has the advantages of simple process, large structural design freedom and good repeatability.
[0005] The first object of the present application is to provide a preparation method of a carbon source doped structured SiOC ceramic, comprising the following steps: preparing a SiOC ceramic precursor solution; uniformly dispersing a carbon source material in the SiOC ceramic precursor solution to obtain a doped solution; The doped solution is used to obtain SiOC precursor polymers with negative Poisson's ratio structure by 3D printing technology; The SiOC precursor polymers are sequentially subjected to solidification, pyrolysis and heat treatment to obtain carbon source-doped structured SiOC ceramics; The SiOC ceramic precursor solution is prepared according to the following steps: An equal amount of polyhydrogenmethylsiloxane and tetramethyltetra vinyl cyclo tetra siloxane are mixed, then a Pt catalyst is added, and the mixture is stirred to form a prepolymer; Linear methyl-terminated polydimethylsiloxane is added to the prepolymer, and after uniform mixing, 3-methacryloxypropyl trimethoxy is added, and the mixture is stirred under acidic conditions, then a photoinitiator is added, and then the solution viscosity is adjusted by propoxylated neopentyl glycol diacrylate to obtain a SiOC ceramic precursor solution.
[0006] Preferably, the carbon source material includes one or more of carbon nanotubes, graphene, and graphyne.
[0007] Preferably, the doping amount of the carbon source material is 1-4% of the mass of the polyhydrogenmethylsiloxane.
[0008] Preferably, the amount of linear methyl-terminated polydimethylsiloxane used is 8-12 wt.%. The mass ratio of the polyhydrogenmethylsiloxane to the Pt catalyst is 1:0.01-0.5.
[0009] Preferably, the solidification is irradiation of the SiOC precursor polymer under a UV lamp for 1-2 h.
[0010] Preferably, the pyrolysis is performed under the protection of an inert gas, with a temperature increase rate of 1-2 ℃ / min, and the temperature is sequentially maintained at 50-100 ℃, 300-400 ℃, 420-480 ℃, 650-700 ℃, and 720-780 ℃ for 1-2 h, then the temperature is increased to 800-1000 ℃, maintained for 2-4 h, then decreased to 500-600 ℃ at a rate of 1-2 ℃ / min, and then cooled to room temperature in the furnace.
[0011] Preferably, the heat treatment is performed on the pyrolyzed product, with a temperature increase rate of 2-3 ℃ / min, and the temperature is increased to 500-600 ℃, then increased to 1200-1400 ℃ at a rate of 5 ℃ / min, maintained for 1-3 h, then decreased to 500-600 ℃ at a rate of 2-3 ℃ / min, and then cooled to room temperature in the furnace.
[0012] Preferably, the Poisson's ratio structure includes a re-entrant honeycomb structure, a four-helix honeycomb structure, or a chiral twist enhancement structure.
[0013] The second objective of this invention is to provide a carbon-doped structured SiOC ceramic.
[0014] The third objective of this invention is to provide an application of carbon-doped structured SiOC ceramics in pressure sensors.
[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a carbon-doped structured SiOC ceramic, its preparation method, and its applications. The invention utilizes miscible PDMS, PHMS, and D4Vi to form a uniform, transparent solution. Under heating, a low-viscosity prepolymer is formed through a Pt-catalyzed hydrosilylation reaction of Si-H and CH-CH2 groups. The PSO / PDMS system provides porous spaces during the curing stage, facilitating carbon source material doping and promoting uniform dispersion. Through precursor mixing and uniform dispersion, covalent bonds are established between the carbon source material surface and the SiOC precursor during subsequent high-temperature pyrolysis, forming a strong interfacial bond and a high-density conductive phase network within the ceramic matrix. This significantly improves the material's conductivity to the semiconductor range. The carbon source material doping enhances the material's conductivity, increasing its sensitivity as a piezoresistive sensor. The negative Poisson's ratio structured ceramic of this invention exhibits lateral contraction rather than expansion deformation behavior under compressive loads and lateral expansion rather than contraction deformation behavior under tensile loads. This property is the opposite of the lateral deformation behavior of conventional non-negative Poisson's ratio materials under pressure / tension, thus effectively preventing catastrophic failure of structural components under impact conditions. Simultaneously, this property allows for further material contact within the material under pressure; when the conductive phase concentration reaches a certain threshold, a tunneling effect occurs, causing a change in its resistance. Therefore, this combination of semiconductor materials and negative Poisson's ratio structures can be used for pressure detection.
[0016] The preparation method provided by this invention offers good flexibility in designing and printing negative Poisson's ratio structures, is simple in process, has good repeatability, and is low in cost.
[0017] The carbon-doped structured SiOC ceramics in this invention are suitable for large-area fabrication and are not limited to the dimensions specified in the specification. They mainly depend on the maximum size range that the printer can fabricate.
[0018] The carbon-doped structured SiOC ceramic prepared by this invention can withstand high temperatures exceeding 1300℃, and the highest piezoresistive rate of SiOC with 2% carbon nanotube doping is 51.2%. The polymer precursor ceramic manufactured exhibits stable performance in piezoresistive cycling tests, and the piezoresistive rate of SiOC ceramic containing carbon-doped materials is 4 times that of SiOC ceramic containing non-carbon-doped materials.
[0019] This invention allows for the control of the electrical conductivity of SiOC ceramics by altering the content of the doped carbon source material, achieving semiconductor-level conductivity and a high piezoresistive coefficient, thus enabling effective monitoring of pressure changes. By controlling the doping content and sintering process, the conductivity can be increased by hundreds or even thousands of times. Attached Figure Description
[0020] Figure 1 The present invention describes negative Poisson's ratio structures designed using SolidWorks software and fabricated using a digital light processing printer, including re-entrant honeycomb structures, quadruple helical honeycomb structures, and chiral torsion-enhanced three-dimensional structures. Figure 2 The resistivity change of carbon nanotubes doped with SiOC in Example 1 under pressure; Figure 3 The resistivity change under pressure of graphene, the carbon source material in Example 2, after being doped with SiOC; Figure 4 The resistivity change of the carbon source material graphyne doped with SiOC under pressure in Example 3; Figure 5 To compare the resistivity change of SiOC without carbon source material doping under pressure in Example 1; Figure 6 The resistance change of the carbon nanotubes in Example 1 after being doped with SiOC and subjected to 400N pressure for 100 cycles is shown. Detailed Implementation
[0021] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.
[0022] The present invention aims to provide a carbon-doped structured SiOC ceramic, its preparation method, and its applications. It primarily focuses on an optimization method for SiOC pressure sensors based on polymer-derived ceramics, synergistically improving device performance through structural design and precursor molecular editing. This technical solution employs 3D printing moldless molding technology combined with a customizable rapid prototyping process. Molecular editing is used to chemically modify the silicon-containing polymer precursor, adapting it to various additive manufacturing technology requirements. Therefore, functional PDCs can be designed and fabricated into various structures. PDCs exhibit high stability, good environmental tolerance, and mechanical properties, maintaining their function in harsh environments, avoiding catastrophic breakage, and ensuring long-term operational safety. This invention further improves the mechanical and piezoresistive properties of SiOC pressure sensors by addressing both the structural design of SiOC polymer-derived ceramics and the molecular editing of polymer precursors.
[0023] To achieve the above objectives, a first aspect provides a method for preparing carbon-doped structured SiOC ceramics, characterized by comprising the following steps: Preparation of SiOC ceramic precursor solution; A carbon source material is uniformly dispersed in a SiOC ceramic precursor solution to obtain a doped solution; The doped solution was used to obtain a SiOC precursor polymer with a negative Poisson's ratio structure using 3D printing technology; The SiOC precursor polymer was sequentially cured, pyrolyzed, and heat-treated to obtain carbon-doped structured SiOC ceramics. The carbon source material includes one or more of carbon nanotubes, graphene, and graphyne.
[0024] The doping amount of the carbon source material is 1 to 4% of the mass of the polyhydromethylsiloxane.
[0025] In this invention, the carbon source material is doped at a content of 1% to 4% relative to the mass of polyhydromethylsiloxane. When the doping content is too low, an effective conductive phase network cannot be formed. When the doping content is too high, phase separation is likely to occur after sintering, resulting in the sample being misshapen or having extremely low strength. Therefore, the optimal doping range of the carbon source material is 1% to 4% of the mass of polyhydromethylsiloxane resin.
[0026] The Poisson's ratio structure includes a re-entrant honeycomb structure, a quadruple helical honeycomb structure, or a chiral torsion-reinforced structure.
[0027] This invention employs a multi-level porosity control structure with negative Poisson's ratio properties. Under compressive loads, it exhibits a lateral contraction response, while under tensile loads, it displays lateral expansion behavior, exhibiting mechanical response characteristics opposite to conventional structures. This effectively suppresses stress concentration under impact loads, which helps prevent catastrophic collisions. Furthermore, this property allows for increased internal material contact under pressure, potentially inducing carrier migration and tunneling, leading to changes in resistance. Therefore, this combination of semiconductor materials and negative Poisson's ratio structures can be used for pressure detection.
[0028] In one embodiment, carbon-doped SiOC ceramics are 3D printed with a designed negative Poisson's ratio structure, including a series of negative Poisson's ratio structures such as re-entrant honeycomb structures, quadruplex honeycomb structures, and chiral torsion-reinforced structures. The doped carbon source materials include carbon nanotubes, graphene, and graphyne mixed in a SiOC precursor solution. Simultaneously, the SiOC polymer-derived ceramic precursor solution needs to be prepared through chemical synthesis, and the 3D-printed sample needs to be pyrolyzed and heat-treated. This results in a highly sensitive modified SiOC ceramic with extreme environmental tolerance.
[0029] The carbon source-doped SiOC ceramic polymer precursor for the negative Poisson's ratio structure was designed using SolidWorks software with the following dimensions: 15mm ≤ length ≤ 100mm, 15mm ≤ width ≤ 100mm, and 15mm ≤ height ≤ 100mm.
[0030] According to the present invention, the SiOC ceramic precursor solution is prepared according to the following steps: Equal amounts of polyhydromethylsiloxane and tetramethyltetravinylcyclotetrasiloxane were mixed, followed by the addition of a Pt catalyst and stirring to form a prepolymer. Linear methyl-terminated polydimethylsiloxane was added to the prepolymer and mixed thoroughly. Then, 3-methacryloyloxypropyltrimethoxy was added, and acetic acid was added to adjust the pH value to 4.5 under acidic conditions. The mixture was stirred, and then a photoinitiator was added. Finally, the viscosity of the solution was adjusted by propoxylated neopentyl glycol diacrylate to obtain the SiOC ceramic precursor solution.
[0031] The amount of the linear methyl-terminated polydimethylsiloxane used is 8~12 wt.%; The mass ratio of the polyhydromethylsiloxane to the Pt catalyst is 1:0.01~0.5.
[0032] The curing process involves irradiating the SiOC precursor polymer under a UV lamp for 1-2 hours.
[0033] The pyrolysis is carried out under the protection of an inert gas, with the temperature increased at a rate of 1~2℃ / min, and then held at 50~100℃, 300~400℃, 420~480℃, 650~700℃, and 720~780℃ for 1~2 hours respectively, before being increased to 800~1000℃ and held for 2~4 hours. Then, the temperature is reduced to 500~600℃ at a rate of 1~2℃ / min, and then cooled to room temperature in the furnace.
[0034] The heat treatment involves heating the pyrolysis product to 500-600°C at a rate of 2-3°C / min, then heating it to 1200-1400°C at a rate of 5°C / min, holding it at that temperature for 1-3 hours, and then cooling it to 500-600°C at a rate of 2-3°C / min, followed by furnace cooling to room temperature.
[0035] In this invention, after doping SiOC ceramics with carbon source material, covalent chemical bonds are established between the surface of the carbon source material and the SiOC precursor during high-temperature pyrolysis, forming a strong interfacial bond and creating a high-density conductive phase network within the ceramic matrix. This significantly improves the material's conductivity to the semiconductor range. Under compressive loading, the reduced interphase spacing induces quantum tunneling, enabling charge carriers to cross the potential barrier and achieve conduction, resulting in a non-linear decrease in resistance with pressure. When the interphase spacing reaches a critical threshold, the resistance tends to stabilize. Simultaneously, the pinning strengthening effect induced by carbon source doping significantly improves the compressive strength and Young's modulus of SiOC ceramics.
[0036] This invention utilizes digital light processing 3D printing technology to prepare SiOC ceramics with a negative Poisson's ratio structure. Simultaneously, it functionalizes SiOC polymer precursors through molecular editing and combines different sintering processes to prepare carbon-doped structured SiOC ceramics with a negative Poisson's ratio structure. The superior mechanical strength and piezoresistive properties overcome the shortcomings of pure SiOC, such as low mechanical strength and poor piezoresistive performance. Furthermore, the carbon-doped structured SiOC ceramics, integrally formed through digital light processing, overcome the drawbacks of traditional ceramic preparation methods, making them simple to fabricate and highly reproducible. The negative Poisson's ratio structured SiOC ceramics containing carbon source materials prepared through digital light processing overcome the high-temperature intolerance of traditional sensors and allow for easy adjustment of the SiOC ceramic's conductivity.
[0037] An exemplary method for preparing carbon-doped SiOC ceramics includes the following steps: See Figure 1 As shown, the designed ceramics with negative Poisson's ratio structures include a series of negative Poisson's ratio structures such as re-entrant honeycomb structure, four-helix honeycomb structure, and chiral torsion reinforcement structure; The doped carbon source materials include carbon nanotubes, graphene, graphyne, etc., mixed in the SiOC precursor solution; The preparation of SiOC polymer-derived ceramic precursor solutions and the curing, pyrolysis, and heat treatment of 3D printed samples are required through chemical synthesis methods; in order to obtain a highly sensitive modified SiOC ceramic pressure sensor with extreme environmental tolerance.
[0038] The preparation of the SiOC ceramic precursor solution specifically includes: S1. In a flask, 30 g of polyhydromethylsiloxane (PHMS) and 30 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) are mixed to form PSO, and then magnetically stirred with Pt catalyst (0.3 g) for 30 minutes to form a prepolymer with low viscosity.
[0039] S2. Add 10 wt.% of linear methyl-terminated polydimethylsiloxane (PDMS) to the mixture and keep stirring for 60 minutes. Add 50 ml of 3-methacryloyloxypropyltrimethoxy (KH-570) to the mixture as a coupling agent. Add acetic acid to adjust the pH value to 4.5 and stir for 6 hours.
[0040] S3. Add a certain amount of phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) to obtain photocurability, and add 20g of propoxylated neopentyl glycol diacrylate to adjust the solution viscosity.
[0041] It should be noted that the carbon source doping materials added to the SiOC-derived ceramic polymer precursor solution include carbon nanotubes, graphene, graphyne, etc., mixed in the SiOC precursor solution.
[0042] The polymer-derived ceramic precursor solution can be a SiOC-derived ceramic polymer precursor solution doped with carbon nanotubes, graphene, and graphyne. The mass of the carbon nanotubes, graphene, and graphyne incorporated is 1% to 4% of the polyhydromethylsiloxane resin content.
[0043] To ensure uniform mixing of the added carbon source doping material, the polymer-derived ceramic precursor solution was stirred for 8-12 hours after doping.
[0044] The carbon-doped SiOC precursor polymer with a negative Poisson's ratio structure printed by photocuring was cured by irradiation under a UV lamp for 1-2 hours. The solidified product was subjected to pyrolysis under Ar gas conditions at a heating rate of 1~2℃ / min. After holding at 50℃, 400℃, 700℃ and 750℃ for 1h, the temperature was raised to 900℃ and held for 2h. Then, the temperature was lowered to 600℃ at a rate of 1~2℃ / min and then cooled to room temperature in the furnace to obtain carbon-doped SiOC ceramics with a negative Poisson's ratio structure after pyrolysis.
[0045] Next, the obtained pyrolysis SiOC ceramic was heat-treated at a heating rate of 2~3℃ / min to 600℃, then heated at a rate of 5℃ / min to the required heat treatment temperature (1200~1400℃) and held for 1~3h, then cooled at a rate of 2~3℃ / min to 600℃ and cooled to room temperature in the furnace to obtain the heat-treated carbon source doped SiOC ceramic.
[0046] A second aspect of the present invention provides a carbon-doped structured SiOC ceramic.
[0047] A third aspect of the present invention provides the application of carbon-doped structured SiOC ceramics in pressure sensors.
[0048] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.
[0049] The accompanying drawings in the specification only show the resistance changes under pressure of some negative Poisson's ratio three-dimensional structures, SiOC doped with non-carbon source materials and SiOC doped with carbon source materials, the compressive strength and conductivity changes of SiOC after doping with different proportions of carbon nanotubes, and the resistance changes with temperature and fitting results of SiOC doped with some carbon source materials, in order to illustrate the actual effect of the present invention.
[0050] Example 1 A method for preparing carbon-doped structured SiOC ceramics includes the following steps: 1. Design using SolidWorks software Figure 1 The re-entrant honeycomb negative Poisson's ratio structure has a length, width, and height of 15mm, 15mm, and 15mm, respectively.
[0051] 2. In a 250 mL flask, 30 g of polyhydromethylsiloxane (PHMS) and 30 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) were mixed to form PSO. The mixture was then magnetically stirred with Pt catalyst (0.3 g) for 30 minutes to form a prepolymer with low viscosity.
[0052] 3. Add 10 wt.% of linear methyl-terminated polydimethylsiloxane (PDMS) to the prepolymer and keep stirring for 60 minutes. Add 50 ml of 3-methacryloyloxypropyltrimethoxy (KH-570) as a coupling agent to the mixture and add acetic acid to adjust the pH value to 4.5 and stir for 6 hours.
[0053] 4. Add a certain amount of phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) to obtain photocurability, and add 20g of propoxylated neopentyl glycol diacrylate to adjust the solution viscosity.
[0054] 5. Add 2% (by mass) of carbon nanotube carbon source doping material relative to the mass of polyhydromethylsiloxane resin to the SiOC-derived ceramic polymer precursor solution and stir for 12 h.
[0055] 6. The above-mentioned doped solution was printed using a 405nm ultraviolet wavelength 3D digital light processing printer. It was then subjected to pyrolysis treatment under Ar gas conditions at a heating rate of 1℃ / min. After holding at 50℃, 400℃, 700℃, and 750℃ for 1 hour each, the temperature was increased to 900℃ and held at 900℃ for 2 hours. Subsequently, the temperature was reduced to 600℃ at a rate of 2℃ / min, and then cooled to room temperature in the furnace to obtain the pyrolyzed carbon-doped SiOC ceramic with a negative Poisson's ratio structure. It should be noted that a photopolymerization process was performed simultaneously during 3D printing.
[0056] 7. The pyrolyzed SiOC ceramic was heat-treated at a heating rate of 2℃ / min to 600℃, then heated at a rate of 5℃ / min to the required heat treatment temperature of 1350℃ and held for 2 hours, and then cooled to 600℃ at a rate of 2℃ / min and cooled to room temperature in the furnace to obtain carbon source doped structured SiOC ceramic.
[0057] Example 2 A method for preparing carbon-doped structured SiOC ceramics includes the following steps: 1. Design using SolidWorks software Figure 1 The chiral torsional negative Poisson's ratio structure in the figure has a length, width, and height of 20 mm, 20 mm, and 15 mm, respectively.
[0058] 2. In a 250 mL flask, 30 g of polyhydromethylsiloxane (PHMS) and 30 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) were mixed to form PSO. The mixture was then magnetically stirred with Pt catalyst (0.3 g) for 30 minutes to form a prepolymer with low viscosity.
[0059] 3. Add 10 wt.% of linear methyl-terminated polydimethylsiloxane (PDMS) to the mixture and keep stirring for 60 minutes. Add 50 ml of 3-methacryloyloxypropyltrimethoxy (KH-570) to the mixture as a coupling agent and stir for 6 hours under acidic conditions.
[0060] 4. Add a certain amount of phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) to obtain photocurability, and add 20g of propoxylated neopentyl glycol diacrylate to adjust the solution viscosity.
[0061] 5. Add 3% (by mass) of graphene carbon source dopant relative to the mass of polyhydromethylsiloxane resin to the SiOC-derived ceramic polymer precursor solution and stir for 8 hours.
[0062] 6. The above doped solution was printed using a 405nm ultraviolet wavelength 3D digital light processing printer. Then, it was subjected to pyrolysis treatment under Ar gas conditions with a heating rate of 2℃ / min. After holding at 50℃, 400℃, 700℃ and 750℃ for 1h respectively, the temperature was raised to 900℃ and held at 900℃ for 1h. Then, the temperature was lowered to 600℃ at a rate of 1℃ / min and then cooled to room temperature in the furnace to obtain carbon source doped SiOC ceramic with a negative Poisson's ratio structure after pyrolysis.
[0063] 7. The pyrolyzed SiOC ceramic was heat-treated at a heating rate of 2℃ / min to 600℃, then heated at a rate of 5℃ / min to the required heat treatment temperature of 1300℃ and held for 1.5h, and then cooled to 600℃ at a rate of 3℃ / min and cooled to room temperature in the furnace to obtain carbon source doped structured SiOC ceramic.
[0064] Example 3 A method for preparing carbon-doped structured SiOC ceramics includes the following steps: 1. Design using SolidWorks software Figure 1 The four-helix honeycomb structure with negative Poisson's ratio has a length, width, and height of 18mm, 18mm, and 20mm, respectively.
[0065] 2. In a 250 mL flask, 30 g of polyhydromethylsiloxane (PHMS) and 30 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) were mixed to form PSO. The mixture was then magnetically stirred with Pt catalyst (0.3 g) for 30 minutes to form a prepolymer with low viscosity.
[0066] 3. Add 10 wt.% of linear methyl-terminated polydimethylsiloxane (PDMS) to the mixture and keep stirring for 60 minutes. Add 50 ml of 3-methacryloyloxypropyltrimethoxy (KH-570) to the mixture as a coupling agent and stir for 6 hours under acidic conditions.
[0067] 4. Add a certain amount of phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) to obtain photocurability, and add 20g of propoxylated neopentyl glycol diacrylate to adjust the solution viscosity.
[0068] 5. Add 2.5% (by mass) of graphdiyne carbon source dopant relative to polyhydromethylsiloxane ester to the SiOC-derived ceramic polymer precursor solution and stir for 10 h.
[0069] 6. The above doped solution was printed using a 405nm ultraviolet wavelength 3D digital light processing printer. Then, it was subjected to pyrolysis treatment under Ar gas conditions with a heating rate of 1℃ / min. After holding at 50℃, 400℃, 700℃ and 750℃ for 1h respectively, the temperature was raised to 900℃ and held at 900℃ for 2h. Then, the temperature was lowered to 600℃ at a rate of 1.5℃ / min and then cooled to room temperature in the furnace to obtain carbon source doped SiOC ceramic with a negative Poisson's ratio structure after pyrolysis.
[0070] 7. The pyrolyzed SiOC ceramic was heat-treated at a heating rate of 3℃ / min to 600℃, then heated at a rate of 5℃ / min to the required heat treatment temperature of 1200℃ and held for 2.5h, and then cooled to 600℃ at a rate of 2℃ / min and cooled to room temperature in the furnace to obtain carbon source doped structured SiOC ceramic.
[0071] Comparative Example 1 Similar to Example 1, except that carbon nanotubes, the carbon source material, were not doped.
[0072] To illustrate the relevant properties of the carbon-doped structured SiOC ceramics provided by this invention, the accompanying drawings are provided.
[0073] Figure 2 The resistivity change of carbon nanotubes doped with SiOC in Example 1 under pressure; Figure 3 The resistivity change under pressure of graphene, the carbon source material in Example 2, after being doped with SiOC; Figure 4 The resistivity change of the carbon source material graphyne doped with SiOC under pressure in Example 3; Figure 5 To compare the resistivity change of SiOC without carbon source material doping under pressure in Example 1 from Figures 2 to 5 As can be seen, the piezoresistive properties of SiOC doped with carbon nanotubes and SiOC doped with graphene reached 51.2% and 41.6%, respectively, while the piezoresistive property of SiOC doped with graphyne reached 39.5%. In contrast, the piezoresistive property of SiOC without carbon source material doping was 12.9%. The piezoresistive property of SiOC doped with carbon source material was four times that of SiOC without carbon source material doping, which fully demonstrates the beneficial effect of SiOC doping with carbon source material on improving piezoresistive property.
[0074] Figure 6 The resistance change of the SiOC ceramic doped with 2% carbon nanotubes provided in Example 1 after 100 cycles of stable operation at 800N fully demonstrates the beneficial effect of carbon source material doping on improving the piezoresistive performance of SiOC pressure sensor and maintaining long-term stable operation.
[0075] In summary, the undoped SiOC precursor polymer prepared by photopolymerization printing was cured under ultraviolet light, and then the undoped SiOC sample was obtained through pyrolysis and heat treatment. However, it has poor conductivity and a low concentration of conductive phases such as free carbon, resulting in a small change in resistance and a small piezoresistive coefficient under pressure.
[0076] This invention improves the conductivity of SiOC (SiO2) pressure sensors by doping it with 1% to 4% carbon source material, thereby achieving semiconductor-level conductivity and resulting in a significant change in resistance and a high piezoresistive coefficient under pressure. However, excessive carbon source material doping leads to high conductivity, approaching conductor levels, and no change in resistance under pressure. Therefore, achieving semiconductor-level conductivity in SiOC through doping with a certain amount of carbon source material is crucial for fabricating SiOC pressure sensors.
[0077] This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.
[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing carbon-doped structured SiOC ceramics, characterized in that, Includes the following steps: Preparation of SiOC ceramic precursor solution; A carbon source material is uniformly dispersed in a SiOC ceramic precursor solution to obtain a doped solution; The doped solution was used to obtain a SiOC precursor polymer with a negative Poisson's ratio structure using 3D printing technology; The SiOC precursor polymer was sequentially cured, pyrolyzed, and heat-treated to obtain carbon-doped structured SiOC ceramics. The SiOC ceramic precursor solution is prepared according to the following steps: Equal amounts of polyhydromethylsiloxane and tetramethyltetravinylcyclotetrasiloxane were mixed, followed by the addition of a Pt catalyst and stirring to form a prepolymer with low viscosity. Linear methyl-terminated polydimethylsiloxane was added to the prepolymer and mixed thoroughly. Then, 3-methacryloyloxypropyltrimethoxy was added and stirred under acidic conditions. A photoinitiator was then added, and the solution viscosity was adjusted by propoxylation of neopentyl glycol diacrylate to obtain the SiOC ceramic precursor solution.
2. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The carbon source material includes one or more of carbon nanotubes, graphene, and graphyne.
3. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The doping amount of the carbon source material is 1 to 4% of the mass of the polyhydromethylsiloxane.
4. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The amount of the linear methyl-terminated polydimethylsiloxane used is 8~12 wt.%; The mass ratio of the polyhydromethylsiloxane to the Pt catalyst is 1:0.01~0.
5.
5. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The curing process involves irradiating the SiOC precursor polymer under a UV lamp for 1-2 hours.
6. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The pyrolysis is carried out under the protection of an inert gas, with the temperature increased at a rate of 1~2℃ / min, and then held at 50~100℃, 300~400℃, 420~480℃, 650~700℃, and 720~780℃ for 1~2 hours respectively, before being increased to 800~1000℃ and held for 2~4 hours. Then, the temperature is reduced to 500~600℃ at a rate of 1~2℃ / min, and then cooled to room temperature in the furnace.
7. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The heat treatment involves heating the pyrolysis product to 500-600°C at a rate of 2-3°C / min, then heating it to 1200-1400°C at a rate of 5°C / min, holding it at that temperature for 1-3 hours, and then cooling it to 500-600°C at a rate of 2-3°C / min, followed by furnace cooling to room temperature.
8. The method for preparing carbon-doped structured SiOC ceramics according to claim 1, characterized in that, The Poisson's ratio structure includes a re-entrant honeycomb structure, a quadruple helical honeycomb structure, or a chiral torsion-reinforced structure.
9. A carbon-doped structured SiOC ceramic prepared by the method according to any one of claims 1 to 8.
10. The application of a carbon-doped structured SiOC ceramic as described in claim 9 in a pressure sensor.