Porous nanoceramic reinforcing agent, lightweight nanocomposite ceramic insulator and preparation process thereof

Abstract

The application discloses a porous nano ceramic reinforcing body, a light-weight nano composite ceramic insulator and a preparation method thereof. 2‑x Cu x P2O7, and a multi-stage pore-forming agent and silane coupling agent interface modification technology is used to construct a three-level pore structure with macroscopic pores, microscopic pores and nanopores. The reinforcing body is prepared through an optimized gel injection molding and gradient sintering process, high strength under high porosity is achieved, and the overall material has near-zero thermal expansion characteristics by using the negative thermal expansion effect. The size instability and internal thermal stress caused by the sharp change of temperature are solved, and the long-term reliable operation of the insulator under extreme climate is laid a foundation.

Description

Technical Field

[0001] This invention relates to the field of ceramic insulator preparation technology, specifically to a porous nano-ceramic reinforcement, a lightweight nano-composite ceramic insulator, and its preparation process. Background Technology

[0002] Insulators are key basic components in power transmission networks, playing a vital role in mechanical support, electrical insulation, and physical isolation. With the rapid development of ultra-high voltage power transmission, urban power grid expansion, and rail transit, more stringent requirements have been placed on the comprehensive performance of insulators: while ensuring high insulation reliability, they must possess characteristics such as lightweight, high strength, excellent thermal shock resistance, and long-term dimensional stability.

[0003] In existing technologies, composite insulators achieve a certain degree of weight reduction and good hydrophobicity by employing a glass fiber reinforced resin core rod and an outer silicone rubber shed structure. However, the core rod material (such as epoxy resin) is susceptible to aging under long-term ultraviolet radiation, humid and hot environments, and corona discharge. Its mechanical strength, especially its long-term creep resistance, is insufficient to meet the service requirements under extreme conditions such as ultra-high voltage and long-span transmission lines. Furthermore, stress concentration easily occurs at the connection interface between the end fittings and the core rod, posing a risk of creep fracture.

[0004] To overcome these shortcomings, the industry has attempted to develop porous ceramic materials to further reduce the weight of insulators. While adding pore-forming agents can achieve a certain degree of weight reduction, the introduction of pores often leads to a significant decrease in mechanical strength, making it difficult to simultaneously achieve the dual goals of lightweight and high strength. More importantly, porous structures exacerbate stress concentration under thermal cycling conditions, worsening thermal shock resistance. Furthermore, the mismatch in thermal expansion coefficients between porous ceramics and metal fittings or external coating materials easily generates significant thermal stress at the interface during temperature changes, leading to interface debonding, cracking, and other failure phenomena.

[0005] In view of this, the present invention proposes a lightweight nanocomposite ceramic insulator with multi-level porosity and extremely low coefficient of thermal expansion, which reduces the weight of the insulator while improving the stability of the insulator in use.

[0006] In view of this, the present invention proposes a lightweight nanocomposite ceramic insulator with a multi-level porous structure and a thermal expansion coefficient close to zero. While achieving lightweight insulator, it maintains its high strength and interfacial stability, thereby improving the long-term service reliability of the insulator under complex working conditions. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a porous nano-ceramic reinforcement, a lightweight nanocomposite ceramic insulator, and a preparation process thereof. In the technical solution of this invention, the porous nano-ceramic reinforcement comprises, by mass percentage:

[0008] Si3N4 powder 50-60 wt%;

[0009] Sintering aid 10-12 wt%;

[0010] NTE functional phase 15-25 wt%

[0011] Pore-forming agent 15-25 wt%;

[0012] Specifically, the NTE functional phase is Zn externally coated with a silane coupling agent. 2-x Cu x P2O7 powder, where x = 0.04-0.1, silane coupling agent and Zn 2-x Cu x The mass ratio of P2O7 powder is 0.5%-1.5%:1;

[0013] The porous nano-ceramic reinforcement has a three-level pore structure, wherein the primary pore size is 50-300 μm, the secondary pore size is 1-50 μm, and the tertiary pore size is 10-500 nm; the porosity of the porous nano-ceramic reinforcement is 60%-85%, and the compressive strength is not less than 50 MPa.

[0014] Furthermore, in the technical solution of the present invention, the sintering aid includes Al2O3 and Y2O3, wherein the mass ratio of Al2O3 to Y2O3 is 1-2:1-2.

[0015] Furthermore, in the technical solution of the present invention, the pore-forming agent includes a PVA pore-forming agent and a starch pore-forming agent, wherein the mass ratio of the PVA pore-forming agent to the starch pore-forming agent is 2-3:1.

[0016] Furthermore, in the technical solution of this invention, Zn 2-x Cu x The x-value of P2O7 powder is preferably 0.04-0.05, and the particle size is 200-500 nm.

[0017] Furthermore, in the technical solution of the present invention, the silane coupling agent is selected from one or more of aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

[0018] Furthermore, in the technical solution of the present invention, the tertiary pore structure is formed by the combined action of partial pyrolysis of PVA pore-forming agent, starch pore-forming agent and silane coupling agent.

[0019] Furthermore, in the technical solution of this invention, the preparation steps of the porous nano-ceramic reinforcement include:

[0020] ①Preparing the silane coupling agent alcohol-water hydrolysate, Zn 2-x Cu x P2O7 powder was immersed in hydrolysate and reacted at 70°C for 3.5 hours, and then cured at 110°C for 20 minutes to obtain the NTE functional phase.

[0021] In the silane coupling agent alcohol hydrolysate, the mass ratio of silane coupling agent, ethanol and deionized water is 20:72:8. Acetic acid is added to adjust the pH to 4.5, and the mixture is stirred at room temperature for 30-40 minutes to obtain the hydrolysate.

[0022] The Zn 2-x Cu x The mass ratio of P2O7 powder to silane coupling agent in the hydrolysate is 1:0.9%-1.2%;

[0023] ② The NTE functional phase is mixed with Si3N4 powder, pore-forming agent and sintering aid in a certain proportion, and then ball-milled to obtain a uniform slurry;

[0024] The dispersion medium is water, the solid content of the mixture is 50% to 60%, and 0.5 wt% polyethyleneimine is added during ball milling.

[0025] ③ Add 2 wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, and heat it at 60°C to initiate polymerization and curing to obtain a green body;

[0026] ④ Place the raw material in A porous nano-ceramic reinforcement was obtained by multi-stage gradient sintering under a protective atmosphere. The specific sintering process is as follows:

[0027] First stage: Heating rate 1-3℃ / min, heat to 120-150℃, hold for 0.5-1.5 hours; continue heating to 500℃, hold for 1-2 hours;

[0028] Second stage: heating rate 10℃ / min, continue heating to 1400-1450℃, hold for 20-30 minutes;

[0029] Third stage: Cooling rate 10℃ / min, cooling to 1150℃, holding at a constant temperature for 3 hours, and then cooling to room temperature with the furnace.

[0030] Furthermore, in the technical solution of the present invention, during the isothermal stage of 120-150°C, the silane coupling agent undergoes a dehydration condensation reaction with the hydroxyl groups on the powder surface to form Si-OM covalent bonds and establish initial interfacial bonding.

[0031] During the isothermal stage at 500℃, PVA and starch pore-forming agent decompose and volatilize to form primary and secondary pores, while the organic part of the silane coupling agent pyrolyzes, generating nanoscale tertiary pores at the interface.

[0032] During the heat treatment stage at 1150℃, inter-diffusion and bonding of NTE functional phase and ceramic matrix at the interface are promoted, and excessive grain growth is inhibited.

[0033] A lightweight nanocomposite ceramic insulator includes the aforementioned porous nanoceramic reinforcement.

[0034] Steel end fittings fixed to both ends of the porous nano-ceramic reinforcement;

[0035] And a silicone rubber umbrella skirt formed by compression molding and covering the outside of the reinforcement.

[0036] A process for manufacturing ceramic insulators includes the following steps:

[0037] ① The porous nano-ceramic reinforcement is bonded to the steel end fitting using a press-fit technique under a pressure of 5 MPa;

[0038] ② The porous nano-ceramic reinforcement surface after bonding hardware is sprayed with a 2wt% silane coupling agent alcohol solution;

[0039] ③ The treated reinforcement is placed in a mold, silicone rubber is injected, and it is molded and cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight nanocomposite ceramic insulator;

[0040] During and after the silicone rubber injection process, a vacuum is maintained at a pressure of -0.095 MPa to -0.1 MPa for 5-15 minutes. The vacuum is then slowly released, followed by heating and molding for curing.

[0041] Effective gain:

[0042] In the technical solution of this invention, Zn is used... 2-x Cu xDuring the heating process, the unique bridging oxygen bonds within the P2O7 functional phase undergo lateral thermal vibration, causing the entire lattice network to contract inward. This manifests as a reduction in volume, actively compensating for the thermal expansion of the matrix material. Ultimately, this results in the entire composite reinforcement exhibiting near-zero thermal expansion within the operating temperature range of -50℃ to 150℃. This fundamentally eliminates dimensional instability and internal thermal stress caused by drastic temperature changes, laying the foundation for the long-term reliable operation of insulators under extreme climate conditions.

[0043] Simultaneously, the partial pyrolysis of PVA pore-forming agent, starch pore-forming agent, and alkane coupling agent constructs a macroscopic-microscopic-nanoscopic three-level pore structure. The coordination of the three-level pore structure enables the material to maintain extremely low density while possessing higher mechanical strength and thermal shock resistance.

[0044] Furthermore, during sintering, the silane coupling agent, through low-temperature condensation and medium-temperature decomposition, provides strong interfacial bonding, ensuring the effective transfer of the zero expansion effect; it also creates nanoscale stress buffer pores, improving the damage tolerance of the interface. This enables the NTE-reinforced phase to function stably and persistently.

[0045] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0046] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating the preparation process of the lightweight nanocomposite ceramic insulator of the present invention.

[0048] Figure 2 This is a cross-sectional view of the lightweight nanocomposite ceramic insulator of the present invention.

[0049] Among them, 1 is a porous nano-ceramic reinforcement and 2 is a silicone rubber umbrella skirt. Detailed Implementation

[0050] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0051] This invention proposes a porous nano-ceramic reinforcement, wherein the raw materials comprise, by mass percentage;

[0052] Si3N4 powder 50-60wt%;

[0053] Sintering aid 10-12 wt%;

[0054] NTE functional phase 15-25 wt%

[0055] Pore-forming agent 15-25 wt%;

[0056] Specifically, the NTE functional phase is Zn externally coated with a silane coupling agent. 2-x Cu x P2O7, where x = 0.04-0.1, silane coupling agent and Zn 2-x Cu x The mass ratio of P2O7 is 0.5%-1.5%:1, the sintering aids include Al2O3 and Y2O3, the mass ratio of Al2O3 to Y2O3 is 1-2:1-2; the pore-forming agents include PVA pore-forming agent and starch pore-forming agent, the mass ratio is 2-3:1.

[0057] Specifically, in this embodiment, the Si3N4 powder is selected from Shanghai Jinpan Biotechnology Co., Ltd., and the model number is Si3N4-002.

[0058] Specifically, in this embodiment, Zn 2-x Cu x The preferred X value for P2O7 is 0.04-0.05, and the particle size is 200-500 nm.

[0059] Specifically, in this embodiment, the silane coupling agent is one or more of aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

[0060] Specifically, in this embodiment, Al2O3 is selected from Wuhu Xinda New Material Technology Co., Ltd., with model number XD-LA35B or XD-LA99Z, purity ≥99.5%, and primary crystal particle size of 3-5 micrometers; Y2O3 is selected from Hangzhou Jikang New Material Co., Ltd., with model number SS-Y430, purity ≥99.995%, and primary particle size of 30-70 nanometers.

[0061] Specifically, in this embodiment, the PVA pore-forming agent has a diameter of 50-250μm and is selected from Polymer, with models PL-50, PL-80, PL-120, PL-150 and PL-250; the starch pore-forming agent is selected from Zhucheng Xingmao, with a D50 of 5-25μm and a D90 < 50μm.

[0062] Furthermore, the preparation of the above-mentioned porous nanoceramic reinforcement includes the following steps:

[0063] ① Preparation of silane hydrolysate:

[0064] Prepare a solution by mixing silane coupling agent, ethanol, and deionized water in a mass ratio of 20:72:8, and add acetic acid to adjust the pH to 4.5. Stir at room temperature for 30-40 minutes to obtain the hydrolysate.

[0065] ②NTE powder treatment:

[0066] Zn 2-x Cu x P2O7 powder with a particle size of 200-500 nm was immersed in a hydrolysate, reacted at 70°C for 3.5 hours, and then cured at 110°C for 20 minutes to obtain the NTE functional phase.

[0067] It should be noted that Zn 2-x Cu x The mass ratio of P2O7 powder to silane coupling agent in the hydrolysate is 1:0.5% to 1.5%; in this embodiment, Zn is preferred. 2-x Cu x The mass ratio of P2O7 powder to silane coupling agent is 1:0.9% to 1.2%.

[0068] ③ Mix NTE functional phase, Si3N4 powder, pore-forming agent and sintering aid in proportion, use water as dispersion system, the solid content in the mixture is 50% to 60%, and add 0.5 wt% polyethyleneimine as dispersant to ensure uniformity. Use a ball mill at 300 rpm for 4 hours to obtain a mixed slurry.

[0069] ④ Add 2wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, heat it at 60℃ to initiate polymerization and curing, and obtain the green body;

[0070] ⑤ Place the green blanks in a high-temperature atmosphere sintering furnace. Under protection, sintering is performed, and the specific sintering curve is as follows:

[0071] First stage: Increase the temperature to 120-150℃ at a rate of 1-3℃ / min, hold the temperature for 0.5-1.5 hours, then continue to increase the temperature to 500℃ and hold for 1-2 hours.

[0072] Specifically, within the temperature range of 120-150℃, the silane coupling agent undergoes a dehydration condensation reaction with the surface of the inorganic powder. The resulting silanol groups (-SiOH) generated through hydrolysis react with Zn... 2-x Cu xThe hydroxyl groups (-OH) on the surface of P2O7 powder and the Si3N4 matrix react to form strong Si-O-Si or Si-OM covalent bridges, where M is a metal or inorganic element. This chemically bonded layer acts as a "molecular anchor," tightly connecting the NTE functional phase to the ceramic matrix, thereby significantly improving the interfacial bonding strength. During the 500℃ holding stage, the pore-forming agent PVA and starch decompose and volatilize, forming primary and secondary pores. Simultaneously, the organic parts of the silane coupling agent molecules, such as the aminopropyl chain, undergo thermal decomposition and volatilize to generate gas. This gas leaves nanoscale voids within the already formed strong bonded network and at the interface, forming tertiary pores.

[0073] Furthermore, the primary pores have a diameter of 50-300 μm, achieving lightweighting and providing stress buffer space; the secondary pores have a diameter of 1-50 μm, increasing the specific surface area and assisting stress transfer; and the tertiary pores have a diameter of 10-500 nm, buffering interfacial stress, inhibiting crack propagation, and enhancing toughness.

[0074] Second stage: Increase the temperature to 1400-1450℃ at 10℃ / min and hold for 20-30 minutes to initially densify the matrix.

[0075] Specifically, at high temperatures of 1400-1450℃, the atomic activity on the surface of Si3N4 ceramic particles increases, and atoms migrate towards the particle contact points through surface diffusion, forming a strong neck connection between particles and establishing initial strength. Grain boundaries between adjacent particles begin to migrate, the interparticle porosity is initially compressed, and the material density increases, achieving initial densification of the matrix. Simultaneously, sintering aids Al2O3 and Y2O3 form a liquid phase, greatly accelerating mass transport through a dissolution-precipitation mechanism and promoting densification.

[0076] The third stage: the temperature is lowered to 1150℃ and held for 3 hours to promote interfacial bonding and inhibit excessive grain growth. The furnace is then cooled to room temperature to obtain a porous nano-ceramic reinforcement.

[0077] Specifically, prolonged holding at 1150℃ drives atomic interdiffusion and solid-state reaction at the interface between the NTE functional phase and the ceramic matrix, forming strong chemical bonds and further improving interfacial bonding strength. Simultaneously, the rapidly formed non-equilibrium grain boundaries at high temperatures relax during this stage, and the internal pore shape tends towards more stable spheroidization, reducing stress concentration. Furthermore, this temperature is below the critical temperature for rapid grain growth, effectively suppressing abnormal grain growth and obtaining a uniform and fine microstructure, avoiding damage to mechanical properties caused by coarse grains.

[0078] Another aspect of this invention proposes a lightweight nanocomposite ceramic insulator:

[0079] Please see Figure 2The structure includes the aforementioned porous nano-ceramic reinforcement, 1, steel end fittings fixed to the upper and lower ends of the porous nano-ceramic reinforcement, and a silicone rubber umbrella skirt 2 covering the periphery of the porous nano-ceramic reinforcement.

[0080] Specifically, the silicone rubber umbrella skirt 2 material is a composite insulator-specific silicone rubber produced by Guangdong Polymer Technology.

[0081] Specifically, in this embodiment, the steel end fittings are selected from Dalian Sanjian Electric Porcelain Fittings Co., Ltd., and are a series of steel feet, flanges, and connecting fittings for line porcelain insulators, composite insulators, and post insulators.

[0082] Understandably, the NTE functional phase shrinks upon heating, offsetting the positive expansion of the matrix through strong interfaces. This significantly reduces the overall CTE of the composite material, bringing it close to zero. Simultaneously, the presence of nanopores increases the thermal boundary resistance, delaying heat transfer and allowing the thermal contraction of the NTE functional phase to couple more synchronously with the thermal expansion of the matrix. This reduces instantaneous thermal stress, and the enhanced interfacial bonding reduces the delamination or phase transformation of the NTE functional phase during thermal cycling, extending component life. When applied to insulators, this can prevent ceramic core cracking or silicone rubber delamination caused by thermal stress.

[0083] Furthermore, the porous nanoceramic reinforcement achieves lightweight, high strength, and low thermal expansion in the prepared composite ceramic insulator through the coordination between the three levels of pores, the reduction of weight through macroscopic pores, the increase of specific surface area through microscopic pores, and the buffering of thermal stress by nanopores.

[0084] This invention also proposes a process for manufacturing ceramic insulators, comprising the following steps:

[0085] The porous nano-ceramic reinforcement was bonded to a steel end fitting using a press-fit technique under a pressure of 5 MPa.

[0086] The surface of the porous nano-ceramic reinforcement is pre-coated with a 2wt% silane coupling agent alcohol solution, and then placed in a mold of a compression molding machine. Silicone rubber is injected into the mold, and a vacuum is maintained during and after the silicone rubber injection process. The vacuum pressure is -0.095 MPa to -0.1 MPa, and the pressure is maintained for 5-15 minutes. The vacuum is then slowly released, and the material is cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight nano-composite ceramic insulator.

[0087] To further understand the present invention, the lightweight nanocomposite ceramic insulator provided by the present invention will be described below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0088] Example 1

[0089] ① Prepare a solution by mixing 1.2g of aminopropyltriethoxysilane with ethanol and deionized water in a mass ratio of 20:72:8, and add acetic acid to adjust the pH to 4.5. Stir at room temperature for 30 minutes to obtain the hydrolysate.

[0090] ②Put 100g Zn 2-x Cu x P2O7 powder was immersed in hydrolysate, reacted at 70°C for 3.5 hours, and then cured at 110°C for 20 minutes to obtain the NTE functional phase.

[0091] ③ Mix 15g NTE functional phase, 60g Si3N4 powder, 16g PVA pore-forming agent, 8g starch pore-forming agent, 6g Al2O3 and 5g Y2O3, add 200ml deionized water and mix evenly, then add 0.5 wt% polyethyleneimine as a dispersant, and ball mill at 300 rpm for 4 hours to obtain a mixed slurry;

[0092] ④ Add 2 wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, heat it at 60℃ to initiate polymerization and curing, and obtain the green body;

[0093] ⑤ Place the green blanks in a high-temperature atmosphere sintering furnace. Under protection, sintering is performed, and the specific sintering curve is as follows:

[0094] First stage: Increase the temperature to 120℃ at a rate of 1℃ / min, hold the temperature for 1.5 hours, then continue to increase the temperature to 500℃ and hold for 2 hours.

[0095] Second stage: Heat to 1400℃ at 10℃ / min and hold for 20 minutes to initially densify the matrix.

[0096] The third stage: the temperature is lowered to 1150℃, held for 3 hours, and then cooled to room temperature in the furnace to obtain a porous nano-ceramic reinforcement.

[0097] ⑥ The porous nano-ceramic reinforcement is bonded to the steel end fittings using a press-fit technique under a pressure of 5 MPa.

[0098] ⑦ The surface of the porous nano-ceramic reinforcement is pre-coated with a 2wt% silane coupling agent alcohol solution, and then placed in the mold of a molding machine. Silicone rubber is injected into the mold, and a vacuum is maintained during and after the silicone rubber injection process. The vacuum pressure is -0.095 MPa, and the pressure is maintained for 10 minutes. The vacuum is then slowly released, and the material is cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight nano-composite ceramic insulator.

[0099] Example 2

[0100] ① Prepare a solution by mixing 0.9g of aminopropyltriethoxysilane with ethanol and deionized water in a mass ratio of 20:72:8, and add acetic acid to adjust the pH to 4.5. Stir at room temperature for 30 minutes to obtain the hydrolysate.

[0101] ②Put 100g Zn 2-x Cu x P2O7 powder was immersed in hydrolysate, reacted at 70°C for 3.5 hours, and then cured at 110°C for 20 minutes to obtain the NTE functional phase.

[0102] ③ Mix 25g NTE functional phase, 50g Si3N4 powder, 10g PVA pore-forming agent, 5g starch pore-forming agent, 5g Al2O3 and 5g Y2O3, add 200ml deionized water and mix evenly, then add 0.5 wt% polyethyleneimine as a dispersant, and ball mill at 300 rpm for 4 hours to obtain a mixed slurry;

[0103] ④ Add 2 wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, heat it at 60℃ to initiate polymerization and curing, and obtain the green body;

[0104] ⑤ Place the green blanks in a high-temperature atmosphere sintering furnace. Under protection, sintering is performed, and the specific sintering curve is as follows:

[0105] First stage: Increase the temperature to 120℃ at 3℃ / min, hold the temperature for 1 hour, then continue to increase the temperature to 500℃ and hold for 1 hour.

[0106] Second stage: Heat to 1400℃ at 10℃ / min and hold for 30 minutes to initially densify the matrix.

[0107] The third stage: the temperature is lowered to 1150℃, held for 3 hours, and then cooled to room temperature in the furnace to obtain a porous nano-ceramic reinforcement.

[0108] ⑥ The porous nano-ceramic reinforcement is bonded to the steel end fittings using a press-fit technique under a pressure of 5 MPa.

[0109] ⑦ The surface of the porous nano-ceramic reinforcement is pre-coated with a 2wt% silane coupling agent alcohol solution, and then placed in the mold of a molding machine. Silicone rubber is injected into the mold, and a vacuum is maintained during and after the silicone rubber injection process. The vacuum pressure is -0.095 MPa, and the pressure is maintained for 10 minutes. The vacuum is then slowly released, and the material is cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight nano-composite ceramic insulator.

[0110] Example 3

[0111] ① Prepare a solution by mixing 0.9g of aminopropyltriethoxysilane with ethanol and deionized water in a mass ratio of 20:72:8, and add acetic acid to adjust the pH to 4.5. Stir at room temperature for 30 minutes to obtain the hydrolysate.

[0112] ②Put 100g Zn 2-x Cu x P2O7 powder was immersed in hydrolysate, reacted at 70°C for 3.5 hours, and then cured at 110°C for 20 minutes to obtain the NTE functional phase.

[0113] ③ Mix 20g NTE functional phase, 50g Si3N4 powder, 15g PVA pore-forming agent, 5g starch pore-forming agent, 5g Al2O3 and 5g Y2O3, add 200ml deionized water and mix evenly, then add 0.5 wt% polyethyleneimine as a dispersant, and ball mill at 300 rpm for 4 hours to obtain a mixed slurry;

[0114] ④ Add 2 wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, heat it at 60℃ to initiate polymerization and curing, and obtain the green body;

[0115] ⑤ Place the green blanks in a high-temperature atmosphere sintering furnace. Under protection, sintering is performed, and the specific sintering curve is as follows:

[0116] First stage: Increase the temperature to 120℃ at 3℃ / min, hold the temperature for 1 hour, then continue to increase the temperature to 500℃ and hold for 1 hour.

[0117] Second stage: Heat to 1400℃ at 10℃ / min and hold for 30 minutes to initially densify the matrix.

[0118] The third stage: the temperature is lowered to 1150℃, held for 3 hours, and then cooled to room temperature in the furnace to obtain a porous nano-ceramic reinforcement.

[0119] ⑥ The porous nano-ceramic reinforcement is bonded to the steel end fittings using a press-fit technique under a pressure of 5 MPa.

[0120] ⑦ The surface of the porous nano-ceramic reinforcement is pre-coated with a 2wt% silane coupling agent alcohol solution, and then placed in the mold of a molding machine. Silicone rubber is injected into the mold, and a vacuum is maintained during and after the silicone rubber injection process. The vacuum pressure is -0.095 MPa, and the pressure is maintained for 10 minutes. The vacuum is then slowly released, and the material is cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight nano-composite ceramic insulator.

[0121] Comparative Example 1

[0122] Commercially available high-voltage composite insulators are selected from China XD Electric Co., Ltd., model number FXBW4-110 / 100.

[0123] Comparative Example 2

[0124] ① Add 10g of Zn 2-x Cu x P2O7 powder, 60g Si3N4 powder, 10g PVA pore-forming agent, 5g starch pore-forming agent, 5g Al2O3 and 5g Y2O3 are mixed, 200ml of deionized water is added and mixed evenly, and then 0.5 wt% polyethyleneimine is added as a dispersant. The mixture is then ball-milled at 300 rpm for 4 hours to obtain a mixed slurry.

[0125] ② Add 2 wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, and heat it at 60℃ to initiate polymerization and curing to obtain the green body;

[0126] ③ Place the green blanks in a high-temperature atmosphere sintering furnace. Under protection, sintering is performed, and the specific sintering curve is as follows:

[0127] First stage: Increase the temperature to 120℃ at 3℃ / min, hold the temperature for 1 hour, then continue to increase the temperature to 500℃ and hold for 1 hour.

[0128] Second stage: Heat to 1400℃ at 10℃ / min and hold for 30 minutes to initially densify the matrix.

[0129] Third stage: Cool down to 1150℃, hold for 3 hours, and then cool to room temperature with the furnace to obtain ceramic reinforcement.

[0130] ④ The ceramic reinforcement is bonded to the steel end fitting using a press-fit technique under a pressure of 5 MPa.

[0131] ⑤ The surface of the ceramic reinforcement is pre-coated with a 2wt% silane coupling agent alcohol solution, and then placed in the mold of the molding machine. Silicone rubber is injected into the mold, and a vacuum is maintained during and after the silicone rubber injection process. The vacuum pressure is -0.095 MPa, and the pressure is maintained for 10 minutes. The vacuum is then slowly released, and the material is cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight composite insulator.

[0132] Test example:

[0133] The contact mechanical properties of the insulators in Examples 1 and 2 and Comparative Examples 1 and 2 were tested according to IEC 61109 / GB / T 19519 and IEC 61109 / GB / T 19519 standards. The specific results are shown in Table 1.

[0134] The coefficient of thermal expansion (CTE) of the insulators in Examples 1 and 2 and Comparative Examples 1 and 2 was determined according to ASTM E228 / GB / T 4339 standard. The specific results are shown in Table 1.

[0135] According to IEC 62217 standard, the interface bonding strength test was carried out on the insulators in Examples 1 and 2 and Comparative Examples 1 and 2. The specific results are shown in Table 1.

[0136] Long-term mechanical load (creep) tests were conducted on the insulators in Examples 1 and 2 and Comparative Examples 1 and 2 according to IEC 61952 standard. The specific results are shown in Table 1.

[0137] Temperature cycling tests were conducted on the insulators in Examples 1 and 2 and Comparative Examples 1 and 2 according to the IEC 62217 standard. The specific results are shown in Table 1.

[0138]

[0139] In summary, this invention provides a porous nano-ceramic reinforcement, a lightweight nanocomposite ceramic insulator, and its preparation process, using Zn... 2-x Cu x During the heating process, the unique bridging oxygen bonds within the P2O7 functional phase undergo lateral thermal vibration, causing the entire lattice network to contract inward. This manifests as a reduction in volume, actively compensating for the thermal expansion of the matrix material. Ultimately, this results in the entire composite reinforcement exhibiting near-zero thermal expansion within the operating temperature range of -50℃ to 150℃. This fundamentally eliminates dimensional instability and internal thermal stress caused by drastic temperature changes, laying the foundation for the long-term reliable operation of insulators under extreme climate conditions.

[0140] Simultaneously, a three-tiered pore system—macro-micro-nano—is constructed. Primary pores, formed by the decomposition of PVA pore-forming agents, significantly reduce the material's density. These macro-pores achieve maximum lightweighting while maintaining the structural framework. They also provide a buffer space for stress, preventing rapid crack propagation. Secondary pores, formed by starch pore-forming agents, are distributed on the macro-pore walls, significantly increasing the material's specific surface area, effectively deflecting and terminating microcracks, consuming energy for crack propagation, and improving the material's fracture toughness. Tertiary pores, generated by the partial pyrolysis of silane coupling agents, are located at the interface between the NTE reinforcing phase and the matrix. They effectively absorb and disperse localized stress caused by thermal mismatch, preventing stress concentration that could lead to interface debonding or cracking, thus ensuring structural integrity at the molecular scale. The coordinated interaction of these three pore systems enables the material to maintain extremely low density while possessing higher mechanical strength and thermal shock resistance.

[0141] Furthermore, during the low-temperature sintering stage (120-150℃), the hydrolyzed silane coupling agent undergoes a dehydration condensation reaction between its silanol groups and the hydroxyl groups on the surface of the NTE powder and ceramic matrix, forming a strong Si-OM covalent bond. This chemically bonded layer acts as a "molecular anchor," tightly welding the NTE phase to the matrix, greatly improving the interfacial bonding strength. When the temperature rises to 500℃, the organic segments in the silane molecules undergo controlled thermal decomposition and volatilization. Within the previously formed robust Si-O-Si inorganic framework network, nanoscale tertiary pores are left in situ and uniformly. These nanopores act as micro-stress buffers, preventing brittle interfacial fracture, thereby further enhancing the toughness and reliability of the interface.

[0142] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A porous nanoceramic reinforcement, characterized in that, Raw materials, by weight percentage, include: Si3N4 powder 50-60 wt%; Sintering aid 10-12 wt%; NTE functional phase 15-25 wt% Pore-forming agent 15-25 wt%; Specifically, the NTE functional phase is Zn externally coated with a silane coupling agent. 2-x Cu x P2O7 powder, where x = 0.04-0.1, silane coupling agent and Zn 2-x Cu x The mass ratio of P2O7 powder is 0.5%–1.5%:1; The pore-forming agent includes a PVA pore-forming agent and a starch pore-forming agent, wherein the mass ratio of the PVA pore-forming agent to the starch pore-forming agent is 2-3:

1. The porous nanoceramic reinforcement has a three-level pore structure, which is formed by the combined action of PVA pore-forming agent, starch pore-forming agent and silane coupling agent through partial pyrolysis. The primary pore size is 50-300 μm, the secondary pore size is 1-50 μm, and the tertiary pore size is 10-500 nm. The porosity of the porous nanoceramic reinforcement is 60% to 85%, and the compressive strength is not less than 50 MPa.

2. The porous nanoceramic reinforcement according to claim 1, characterized in that, The sintering aids include Al2O3 and Y2O3, and the mass ratio of Al2O3 to Y2O3 is 1-2:1-2.

3. The porous nanoceramic reinforcement according to claim 1, characterized in that, The Zn 2-x Cu x The particle size of P2O7 powder is 200-500 nm, where the x value is 0.04-0.

05.

4. The porous nanoceramic reinforcement according to claim 1, characterized in that, The silane coupling agent is selected from one or more of aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

5. The porous nanoceramic reinforcement according to claim 4, characterized in that, Its preparation steps include: ①Preparing the silane coupling agent alcohol-water hydrolysate, Zn 2-x Cu x P2O7 powder was immersed in hydrolysate and reacted at 70°C for 3.5 hours, and then cured at 110°C for 20 minutes to obtain the NTE functional phase. In the silane coupling agent alcohol-water hydrolysate, the mass ratio of silane coupling agent, ethanol and deionized water is 20:72:

8. Acetic acid is added to adjust the pH to 4.5, and the mixture is stirred at room temperature for 30-40 minutes to obtain the hydrolysate. The Zn 2-x Cu x The mass ratio of P2O7 powder to silane coupling agent in the hydrolysate is 1:0.9%-1.2%; ② The NTE functional phase is mixed with Si3N4 powder, pore-forming agent and sintering aid in a certain proportion, and then ball-milled to obtain a uniform slurry; The dispersion medium is water, the solid content of the mixture is 50% to 60%, and 0.5 wt% polyethyleneimine is added during ball milling. ③ Add 2 wt% acrylamide monomer and crosslinking agent to the slurry, inject it into the mold, and heat it at 60°C to initiate polymerization and curing to obtain a green body; ④ The green body is subjected to multi-stage gradient sintering under a N2 protective atmosphere to obtain a porous nano-ceramic reinforcement. The specific sintering process is as follows: First stage: Heating rate 1-3℃ / min, heat to 120-150℃, hold for 0.5-1.5 hours; continue heating to 500℃, hold for 1-2 hours; Second stage: heating rate 10℃ / min, continue heating to 1400-1450℃, hold for 20-30 minutes; Third stage: Cooling rate 10℃ / min, cooling to 1150℃, holding at a constant temperature for 3 hours, and then cooling to room temperature with the furnace.

6. The porous nanoceramic reinforcement according to claim 5, characterized in that, During the isothermal stage of 120-150℃, the silane coupling agent undergoes a dehydration condensation reaction with the hydroxyl groups on the powder surface to form Si-OM covalent bonds and establish initial interfacial bonding. During the isothermal stage at 500℃, PVA and starch pore-forming agent decompose and volatilize to form primary and secondary pores, while the organic part of the silane coupling agent pyrolyzes, generating nanoscale tertiary pores at the interface. During the heat treatment stage at 1150℃, inter-diffusion and bonding of NTE functional phase and ceramic matrix at the interface are promoted, and excessive grain growth is inhibited.

7. A lightweight nanocomposite ceramic insulator, characterized in that, include: The porous nanoceramic reinforcement as described in any one of claims 1 to 6; Steel end fittings fixed to both ends of the porous nano-ceramic reinforcement; And a silicone rubber umbrella skirt formed by compression molding and covering the outside of the reinforcement.

8. A process for manufacturing ceramic insulators, characterized in that, Includes the following steps: ① Using a press-fit technique, the porous nano-ceramic reinforcement as described in any one of claims 1 to 6 is bonded to a steel end fitting under a pressure of 5 MPa; ② The porous nano-ceramic reinforcement surface after bonding hardware is sprayed with a 2wt% silane coupling agent alcohol solution; ③ The treated reinforcement is placed in a mold, silicone rubber is injected, and it is molded and cured at 150℃ and 1 MPa for 4 hours to obtain a lightweight nanocomposite ceramic insulator; During and after the silicone rubber injection process, a vacuum is maintained at a pressure of -0.095 MPa to -0.1 MPa for 5-15 minutes. The vacuum is then slowly released, followed by heating and molding for curing.

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