Porous nano-ceramic reinforcement, lightweight nano-composite ceramic insulator and preparation process of porous nano-ceramic reinforcement and lightweight nano-composite ceramic insulator

Abstract

The invention discloses a porous nano ceramic reinforcement, a lightweight nano composite ceramic insulator and preparation thereof, silicon nitride is used as a matrix, a negative thermal expansion functional phase Zn (2-x) CuxP2O7 is compounded, and a three-level pore structure with macroscopic pores, microcosmic pores and nano pores is constructed through a multi-level pore forming agent and silane coupling agent interface modification technology. The reinforcement is prepared through an optimized gel casting and gradient sintering process, high strength under high porosity is achieved, and the overall material has the near-zero thermal expansion characteristic through the negative thermal expansion effect. The problems of size instability and internal thermal stress caused by dramatic temperature change are solved, and a foundation is laid for long-term reliable operation of the insulator in extreme climate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic insulator preparation, in particular to a porous nanoceramic reinforcing body, a lightweight nanocomposite ceramic insulator and a preparation process thereof. BACKGROUND

[0002] Insulators are key basic elements in power transmission networks, and bear the important roles of mechanical support, electrical insulation and physical isolation. With the rapid development of ultra-high voltage transmission, urban power grid expansion and rail transit, more stringent requirements are put forward for the comprehensive performance of insulators: under the premise of ensuring high insulation reliability, lightweight, high strength, excellent thermal shock resistance and long-term dimensional stability must be possessed.

[0003] In the prior art, composite insulators realize lightweight to some extent by adopting a structure of a glass fiber reinforced resin core rod and an outer silicone rubber umbrella skirt, and have good hydrophobicity. However, the core rod material (such as epoxy resin) has the risk of aging under the action of long-term ultraviolet radiation, humid heat environment and corona discharge, and the mechanical strength, especially the long-term creep resistance, is difficult to meet the service requirements under extreme working conditions such as ultra-high voltage and large span. In addition, the connection interface between the end fitting and the core rod is prone to stress concentration, and there is a risk of creep fracture.

[0004] In order to overcome the above-mentioned defects, the industry attempts to develop porous ceramic materials to further reduce the weight of the insulator. By adding pore-forming agents and other means, a certain degree of lightweight can be achieved, but the introduction of pores often leads to a significant decrease in mechanical strength, making it difficult to achieve both lightweight and high strength. More importantly, the porous structure will exacerbate stress concentration under thermal cycling conditions, deteriorating the thermal shock resistance. At the same time, the mismatch of the thermal expansion coefficients between the porous ceramic and the metal accessories and the external coating material will generate large thermal stress at the interface when the temperature changes, leading to interface debonding, cracking and other failure phenomena.

[0005] In view of this, the present application provides a lightweight nanocomposite ceramic insulator with a multi-level pore structure and a thermal expansion coefficient close to zero, which realizes the lightweight of the insulator while maintaining its high strength and interface stability, and improves the long-term service reliability of the insulator under complex working conditions.

[0006] In view of this, the present application provides a lightweight nanocomposite ceramic insulator with a multi-level pore structure and a thermal expansion coefficient close to zero, which realizes the lightweight of the insulator while maintaining its high strength and interface stability, and improves the long-term service reliability of the insulator under complex working conditions. SUMMARY

[0007] To solve the above technical problems, the present application provides a porous nanoceramic reinforcing body, a lightweight nanocomposite ceramic insulator and a preparation process thereof. In the technical solution of the present application, the porous nanoceramic reinforcing body comprises, by mass percentage:

[0008] Si3N4 powder 60-70 wt%;

[0009] sintering aid 10%-12%;

[0010] NTE functional phase 15-25 wt%;

[0011] porogen 15-25 wt%;

[0012] The NTE functional phase is specifically Zn 2-x Cu x P2O7 powder, wherein x=0.04-0.1, the mass ratio of the silane coupling agent to Zn 2-x Cu x P2O7 powder is 0.5%-1.5%:1.

[0013] The porous nanoceramic reinforcing body has a three-level pore structure, wherein the first-level pore has a pore size of 50-300 μm, the second-level pore has a pore size of 1-50 μm, and the third-level pore has a pore size of 10-500 nm; the porosity of the porous nanoceramic reinforcing body is 60%-85%, and the compressive strength is not less than 50 MPa.

[0014] Further, in the technical solution of the present application, the sintering aid comprises Al2O3 and Y2O3, and the mass ratio of the Al2O3 to Y2O3 is 1-2:1-2.

[0015] Further, in the technical solution of the present application, the porogen comprises a PVA porogen and a starch porogen, and the mass ratio of the PVA porogen to the starch porogen is 2-3:1.

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

[0017] Further, in the technical solution of the present application, the silane coupling agent is selected from one or more of aminopropyl triethoxysilane, γ-glycidoxypropyl trimethoxysilane, γ-methacryloyloxypropyl trimethoxysilane and vinyl trimethoxysilane.

[0018] Further, in the technical solution of the present application, the three-level pore structure is formed by the joint action of the PVA porogen, the starch porogen and the partial pyrolysis of the silane coupling agent.

[0019] Further, in the technical scheme of the present application, the porous nanoceramic reinforcement preparation step comprises:

[0020] ①Preparation of silane coupling agent alcohol aqueous hydrolysate, Zn 2-x Cu x P2O7 powder is immersed in the hydrolysate, reacted at 70°C for 3.5 hours, and then solidified at 110°C for 20 minutes to obtain the NTE functional phase;

[0021] The mass ratio of the silane coupling agent, ethanol and deionized water in the silane coupling agent alcohol hydrolysate is 20:72:8, acetic acid is added to adjust the pH to 4.5, and stirring is carried out at room temperature for 30-40 min to obtain the hydrolysate;

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

[0023] ②Mixing the NTE functional phase with Si3N4 powder, pore-forming agent and sintering aid in proportion, and obtaining uniform slurry after ball milling;

[0024] The dispersion medium is water, the solid content of the mixed solution is 50%-60%, and 0.5wt% of polyethyleneimine is added during ball milling;

[0025] ③Adding 2wt% of acrylamide monomer and crosslinking agent to the slurry, and initiating polymerization and solidification by heating at 60°C after injection into the mold to obtain the green body;

[0026] ④Sintering the green body at under a protective atmosphere to obtain the porous nanoceramic reinforcement, and the specific sintering process is as follows:

[0027] First stage: heating rate 1-3°C / min, heating to 120-150°C, constant temperature 0.5-1.5 hours; continue heating to 500°C, constant temperature 1-2 hours;

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

[0029] Third stage: cooling rate 10°C / min, cooling to 1150°C, constant temperature 3 hours, and cooling to room temperature with the furnace.

[0030] Further, in the technical scheme of the present application, in the constant temperature stage at 120-150°C, the silane coupling agent and the surface hydroxyl group of the powder undergo dehydration condensation reaction to form Si-O-M covalent bond and establish initial interfacial bonding;

[0031] At the constant temperature stage of 500℃, PVA and pore-forming agent decompose and volatilize to form primary and secondary pores, and the organic part of silane coupling agent pyrolyzes to generate nano-scale tertiary pores at the interface;

[0032] At the holding stage of 1150℃, the interface atomic interdiffusion and bonding between NTE functional phase and ceramic matrix are promoted, and the excessive grain growth is inhibited.

[0033] A light-weighted nanocomposite ceramic insulator, comprising the above porous nanoceramic reinforcement;

[0034] Steel end fittings fixed at both ends of the porous nanoceramic reinforcement;

[0035] And a silicone rubber umbrella skirt formed by mold pressing and coated on the outside of the reinforcement.

[0036] A ceramic insulator preparation process, comprising the following steps:

[0037] ① Using a pressure bonding technique, the porous nanoceramic reinforcement is combined with the steel end fittings under a pressure of 5 MPa;

[0038] ② The surface of the porous nanoceramic reinforcement after the combination of the fittings is sprayed with a silane coupling agent alcohol solution with a concentration of 2wt%;

[0039] ③ The treated reinforcement is placed in a mold, and silicone rubber is injected, and mold pressing solidification is carried out at 150℃ and 1 MPa for 4 hours to obtain a light-weighted nanocomposite ceramic insulator;

[0040] Wherein, the vacuum is maintained during and after the silicone rubber injection process, the vacuum pressure is-0.095 MPa to-0.1 MPa, the pressure is maintained for 5-15 min, and the vacuum is slowly released and subjected to temperature mold pressing solidification.

[0041] Effective gain:

[0042] In the technical scheme of the present application, Zn 2-x Cu x During the temperature rising process, the special bridge oxygen bond in the lattice of the P2O7 functional phase will undergo transverse thermal vibration, causing the entire lattice network to shrink inward, which macroscopically manifests as a decrease in volume, actively compensating for the thermal expansion of the matrix material, and ultimately making the entire composite reinforcement exhibit near-zero thermal expansion in the working temperature range of-50℃ to 150℃. This fundamentally eliminates the size instability and internal thermal stress caused by drastic temperature changes, laying a foundation for the long-term reliable operation of the insulator under extreme weather conditions.

[0043] At the same time, the PVA pore-forming agent, starch pore-forming agent and alkyl coupling agent are partially pyrolyzed, macro-micro-nano three-level pores are constructed, the three-level pores are coordinated with each other, so that the material has higher mechanical strength and thermal shock resistance while maintaining extremely low density.

[0044] In addition, the silane coupling agent provides strong interfacial bonding force through low-temperature condensation and medium-temperature decomposition during the sintering process, ensures the effective transmission of zero expansion effect, and creates nanoscale stress buffer holes to improve the damage tolerance of the interface. This enables the NTE reinforcing phase to stably and durably exert its function.

[0045] Other features and advantages of the present application will be set forth in the following description. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0047] Figure 1 A flow chart for preparing the lightweight nanocomposite ceramic insulator of the present application.

[0048] Figure 2 A sectional view of the lightweight nanocomposite ceramic insulator of the present application.

[0049] 1 porous nanoceramic reinforcing body, 2 silicone rubber umbrella skirt. DETAILED DESCRIPTION

[0050] In order to make the purpose, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0051] The present application proposes a porous nanoceramic reinforcing body, the raw materials include, by mass percentage:

[0052] Si3N4 powder 50-60wt%;

[0053] Sintering aid 10-12wt%;

[0054] NTE functional phase 15-25wt%;

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

[0056] NTE functional phase is Zn 2-x Cu x P2O7, wherein x = 0.04-0.1, the mass ratio of silane coupling agent to Zn 2-x Cu x P2O7 is 0.5%-1.5%:1, the sintering aid includes Al2O3 and Y2O3, the mass ratio of Al2O3 to Y2O3 is 1-2:1-2; the pore forming agent includes PVA pore forming agent and starch pore forming agent, the mass ratio is 2-3:1.

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

[0058] Specifically, in the embodiment, the Zn 2-x Cu x The preferred X value of Zn

[0059] Specifically, in the embodiment, the silane coupling agent is one or more of aminopropyl triethoxysilane, γ-glycidoxypropyl trimethoxysilane, γ-methacryloyloxypropyl trimethoxysilane and vinyl trimethoxysilane.

[0060] Specifically, in the embodiment, the Al2O3 is selected from Wuhu Xinda New Material Technology Co., Ltd., and the model is XD-LA35B or XD-LA99Z, the purity is ≥99.5%, and the original grain size is 3-5 microns; the Y2O3 is selected from Hangzhou Ji New Material Co., Ltd., and the model is SS-Y430, the purity is ≥99.995%, and the primary particle size is 30-70 nanometers.

[0061] Specifically, in the embodiment, the PVA pore forming agent has a diameter of 50-250 μm, is selected from Baoli Mei, and the model is PL-50, PL-80, PL-120, PL-150 and PL-250; the starch pore forming agent is selected from Zhucheng Xing Trade, and D50 is 5-25 μm while D90<50 μm.

[0062] Further, the preparation of the above porous nanoceramic reinforcing body includes the following steps:

[0063] ① Preparation of silane hydrolysis solution:

[0064] The silane coupling agent, ethanol and deionized water are mixed in a mass ratio of 20:72:8 to form a solution, and acetic acid is added to adjust the pH to 4.5, and then stirred at room temperature for 30-40 min to obtain the hydrolysis solution;

[0065] NTE powder treatment:

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

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

[0068] III. The NTE functional phase, Si3N4 powder, pore-forming agent, and sintering aid are mixed in proportion, water is used as the dispersion system, the solid content in the mixed solution is 50%-60%, and 0.5 wt% polyethyleneimine is added as a dispersant to ensure uniformity, and then the mixture is ball milled in a ball mill at a speed of 300 rpm for 4 hours to obtain a mixed slurry;

[0069] IV. 2 wt% acrylamide monomer and a crosslinking agent are added to the slurry, and the slurry is injected into a mold, heated at 60°C to initiate polymerization and solidification, and a green body is obtained;

[0070] V. The green body is placed in a high-temperature atmosphere sintering furnace, sintered under protection, and the specific sintering curve is as follows:

[0071] First stage: 1-3°C / min to 120-150°C, constant temperature for 0.5-1.5 hours, then continue to heat to 500°C, and keep for 1-2 hours.

[0072] Specifically, in the temperature range of 120-150°C, the silane coupling agent undergoes a dehydration condensation reaction with the surface of the inorganic powder, and the silanol groups (-SiOH) generated by hydrolysis react with the hydroxyl groups (-OH) on the surface of the Zn 2-x Cu x P2O7 powder and the Si3N4 matrix to form a strong Si-O-Si or Si-O-M covalent bond bridge, where M is a metal or an inorganic element. This layer of chemical bonding serves as a "molecular anchor" to tightly connect the NTE functional phase with the ceramic matrix, thereby greatly improving the interfacial bonding strength. During the 500°C holding stage, the pore-forming agents PVA and starch decompose and volatilize to form primary and secondary pores, and the organic part of the silane coupling agent molecule, such as the aminopropyl chain, will undergo thermal decomposition and volatilize to produce gas. This gas leaves nanoscale voids inside the already formed strong bonding network and at the interface, forming tertiary pores.

[0073] Further, the first-stage pore has a diameter of 50-300 mu m, realizes lightweight, and provides stress buffering space; the second-stage pore has a diameter of 1-50 mu m, increases the specific surface area, and assists stress transmission; and the third-stage pore has a diameter of 10-500 nm, buffers interface stress, inhibits crack propagation, and enhances toughness.

[0074] The second stage: temperature is increased to 1400-1450 DEG C at a rate of 10 DEG C / min, and the matrix is preliminarily densified by keeping the temperature for 20-30 minutes.

[0075] Specifically, under the high temperature of 1400-1450 DEG C, the atomic activity on the surface of Si3N4 ceramic particles is enhanced, the particles are migrated to the contact points of the particles through surface diffusion, a firm neck connection is formed between the particles, preliminary strength is established, the grain boundaries of adjacent particles start to migrate, the pores between the particles are preliminarily compressed, the density of the material is increased, and the preliminary densification of the matrix is realized. At the same time, the sintering aids Al2O3 and Y2O3 form a liquid phase, greatly accelerate the material transmission through the dissolution-precipitation mechanism, and promote the densification.

[0076] The third stage: the temperature is decreased to 1150 DEG C, and the interface bonding is promoted by keeping the temperature for 3 hours, the abnormal grain growth is inhibited, the temperature is decreased to room temperature in the furnace, and the porous nanoceramic reinforcing body is obtained.

[0077] Specifically, under the long-time keeping at 1150 DEG C, the atomic mutual diffusion and solid-phase reaction of the NTE functional phase and the ceramic matrix interface are driven, firm chemical bonding is formed, the interface bonding strength is further improved. At the same time, the non-equilibrium grain boundaries formed rapidly at high temperature are relaxed at this stage, the internal pore shape tends to be more stable and spherical, the stress concentration is reduced, and the temperature is lower than the critical temperature of rapid grain growth, so that the abnormal grain growth can be effectively inhibited, a uniform and fine microstructure is obtained, and the damage of the coarse grains to the mechanical properties is avoided.

[0078] Another aspect of the present application provides a lightweight nanocomposite ceramic insulator:

[0079] Please refer to Figure 2 , which comprises the above porous nanoceramic reinforcement, a steel end fitting fixed on the upper and lower ends of the porous nanoceramic reinforcement, and a silicone rubber umbrella skirt 2 wrapped around the porous nanoceramic reinforcement.

[0080] Specifically, the material of the silicone rubber umbrella skirt 2 is specifically a special silicone rubber for composite insulators produced by Guangdong Polymer Technology.

[0081] Specifically, in the embodiment, the steel end fitting is selected from the steel feet, flanges and connecting fittings series products for line porcelain insulators, composite insulators and supporting insulators, which are provided by Dalian Sanjian Porcelain Fitting Co., Ltd.

[0082] It can be understood that the NTE functional phase shrinks when heated, offsets the positive expansion of the matrix itself through a strong interface, greatly reduces the overall CTE of the composite material, and tends to be close to zero, while the presence of nanopores increases the thermal boundary resistance, delays heat transfer, and makes the thermal shrinkage of the NTE functional phase more synchronous coupling with the thermal expansion of the matrix, reduces the instantaneous thermal stress, and the increase of the interface bonding force reduces the peeling or phase change of the NTE functional phase in the thermal cycle, prolongs the service life of the component. When applied to an insulator, porcelain core burst or silicon rubber delamination caused by thermal stress can be avoided.

[0083] Further, the porous nanoceramic reinforcing body is coordinated through three levels of pores, the macro-pores reduce the weight, the micro-pores increase the specific surface area, and the nanopores buffer thermal stress, so that the prepared composite ceramic insulator is lightweight, high-strength and low thermal expansion.

[0084] The application also provides a ceramic insulator preparation process, which comprises the following steps:

[0085] The porous nanoceramic reinforcing body and the steel end fitting are combined at a pressure of 5 MPa by using a press connection technology.

[0086] The surface of the porous nanoceramic reinforcing body is pre-sprayed with a 2wt% silane coupling agent alcohol solution, and then placed in a mold of a mold forming machine; the silicone rubber is injected into the mold, and vacuum is maintained during and after the silicone rubber injection process, the vacuum pressure is-0.095 MPa to-0.1 MPa, the pressure is maintained for 5-15 minutes, the vacuum is slowly released, and the lightweight nanocomposite ceramic insulator is obtained by curing at 150 DEG C and 1 MPa for 4 hours.

[0087] In order to further understand the application, the lightweight nanocomposite ceramic insulator provided by the application is described below in combination with examples, and the protection scope of the application is not limited by the following examples.

[0088] Example 1

[0089] ① 1.2g of aminopropyltriethoxysilane is mixed with ethanol and deionized water in a mass ratio of 20:72:8 to form a solution, and acetic acid is added to adjust the pH to 4.5, and stirred at room temperature for 30min to obtain a hydrolysis solution;

[0090] ② 100g of Zn 2-x Cu x P2O7 powder is immersed in the hydrolysis solution, reacted at 70 DEG C for 3.5 hours, and then cured at 110 DEG C for 20 minutes to obtain the NTE functional phase.

[0091] ③ 15 g NTE functional phase, 60 g Si3N4 powder, 16 g PVA pore-forming agent and 8 g starch pore-forming agent, 6 g Al2O3 and 5 g Y2O3 are mixed, 200 ml of deionized water is added and mixed uniformly, then 0.5 wt% polyethyleneimine is added as a dispersant, and the mixture is ball milled at a speed of 300 rpm for 4 hours to obtain a mixed slurry;

[0092] ④ 2 wt% of acrylamide monomer and crosslinking agent are added to the slurry, injected into a mold, and heated at 60°C to initiate polymerization and curing to obtain a green body;

[0093] ⑤ The green body is placed in a high-temperature atmosphere sintering furnace, sintered under protection, and the specific sintering curve is as follows:

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

[0095] Second stage: increase the temperature to 1400°C at a rate of 10°C / min, keep the temperature constant for 20 minutes, and make the matrix preliminary densification.

[0096] Third stage: decrease the temperature to 1150°C, keep the temperature constant for 3 hours, and cool to room temperature in the furnace, to obtain a porous nanoceramic reinforcing body.

[0097] ⑥ The porous nanoceramic reinforcing body is combined with the steel end fitting at a pressure of 5 MPa using a pressure bonding technique;

[0098] ⑦ The surface of the porous nanoceramic reinforcing body is pre-sprayed with a 2 wt% silane coupling agent alcohol solution, and then placed in the mold of a mold forming machine. Silicon rubber is injected into the mold, and vacuum is maintained during and after the injection of the silicon rubber. The vacuum pressure is -0.095 MPa, the pressure is maintained for 10 minutes, the vacuum is slowly released, and the lightweight nanocomposite ceramic insulator is obtained by curing at 150°C and 1 MPa for 4 hours.

[0099] Example 2

[0100] ① 0.9 g of aminopropyltriethoxysilane is mixed with ethanol and deionized water in a mass ratio of 20:72:8 to form a solution, and acetic acid is added to adjust the pH to 4.5. Stir at room temperature for 30 min to obtain a hydrolysis solution;

[0101] ② 100 g of Zn 2-x Cu x P2O7 powder is immersed in the hydrolysis solution, reacted at 70°C for 3.5 hours, and then solidified at 110°C for 20 minutes to obtain the NTE functional phase.

[0102] ③ 25 g NTE functional phase, 50 g Si3N4 powder, 10 g PVA pore-forming agent, and 5 g starch pore-forming agent, 5 g Al2O3 and 5 g Y2O3 are mixed, 200 ml of deionized water is added and mixed uniformly, then 0.5 wt% polyethyleneimine is added as a dispersant, and the mixture is ball milled at a speed of 300 rpm for 4 hours to obtain a mixed slurry;

[0103] ④ 2 wt% of acrylamide monomer and crosslinking agent are added to the slurry, injected into a mold, and heated at 60°C to initiate polymerization and curing to obtain a green body;

[0104] ⑤ The green body is placed in a high-temperature atmosphere sintering furnace, sintered under protection, and the specific sintering curve is as follows:

[0105] First stage: increase the temperature to 120°C at a rate of 3°C / min, keep the temperature constant for 1 hour, then continue to increase the temperature to 500°C, and keep the temperature constant for 1 hour.

[0106] Second stage: increase the temperature to 1400°C at a rate of 10°C / min, keep the temperature constant for 30 minutes, and make the matrix preliminary densification.

[0107] Third stage: decrease the temperature to 1150°C, keep the temperature constant for 3 hours, and cool to room temperature in the furnace, to obtain a porous nanoceramic reinforcing body.

[0108] ⑥ The porous nanoceramic reinforcing body is combined with the steel end fitting at a pressure of 5 MPa using a pressure bonding technique;

[0109] ⑦ The surface of the porous nanoceramic reinforcing body is pre-sprayed with a 2 wt% silane coupling agent alcohol solution, and then placed in the mold of a mold forming machine. Silicon rubber is injected into the mold, and vacuum is maintained during and after the injection of the silicon rubber. The vacuum pressure is -0.095 MPa, the pressure is maintained for 10 minutes, the vacuum is slowly released, and the lightweight nanocomposite ceramic insulator is obtained by curing at 150°C and 1 MPa for 4 hours.

[0110] Example 3

[0111] ① 0.9 g of aminopropyltriethoxysilane is mixed with ethanol and deionized water in a mass ratio of 20:72:8 to form a solution, and acetic acid is added to adjust the pH to 4.5. Stir at room temperature for 30 min to obtain a hydrolysis solution;

[0112] ② 100 g of Zn 2-x Cu x P2O7 powder is immersed in the hydrolysis solution, reacted at 70°C for 3.5 hours, and then solidified at 110°C for 20 minutes to obtain the NTE functional phase.

[0113] ③ 20 g NTE functional phase, 50 g Si3N4 powder, 15 g PVA pore former and 5 g starch pore former, 5 g Al2O3 and 5 g Y2O3 were mixed, 200 ml deionized water was added and mixed uniformly, then 0.5 wt% polyethyleneimine was added as a dispersant, and the mixture was ball milled at a speed of 300 rpm for 4 hours to obtain a mixed slurry;

[0114] ④ 2 wt% acrylamide monomer and crosslinking agent were added to the slurry, injected into a mold, and heated at 60°C to initiate polymerization and curing to obtain a green body;

[0115] ⑤ The green body was placed in a high-temperature atmosphere sintering furnace, and sintered under protection, with the specific sintering curve as follows:

[0116] First stage: increase the temperature to 120°C at a rate of 3°C / min, keep the temperature constant for 1 hour, then continue to increase the temperature to 500°C, and keep the temperature constant for 1 hour.

[0117] Second stage: increase the temperature to 1400°C at a rate of 10°C / min, keep the temperature constant for 30 minutes to make the matrix preliminary densification.

[0118] Third stage: decrease the temperature to 1150°C, keep the temperature constant for 3 hours, and cool down to room temperature in the furnace, to obtain a porous nanoceramic reinforcement.

[0119] ⑥ The porous nanoceramic reinforcement and steel end fittings were combined under a pressure of 5 MPa using a pressure bonding technique;

[0120] ⑦ The surface of the porous nanoceramic reinforcement was pre-sprayed with a 2 wt% silane coupling agent alcohol solution, and then placed in the mold of a mold forming machine. Silicone rubber was injected into the mold, and vacuum was maintained during and after the injection process, with a vacuum pressure of -0.095 MPa, pressure holding for 10 minutes, slow release of vacuum, and curing at 150°C and 1 MPa for 4 hours to obtain a lightweight nanocomposite ceramic insulator.

[0121] Comparative Example 1

[0122] A commercially available high-voltage composite insulator was selected from China Xidian Electrical Co., Ltd., with a model number of FXBW4-110 / 100.

[0123] Comparative Example 2

[0124] ① 10 g Zn 2-x Cu xP2O7 powder, 60 g of Si3N4 powder, 10 g of PVA pore former and 5 g of starch pore former, 5 g of Al2O3 and 5 g of Y2O3 were mixed, 200 ml of deionized water was added and mixed uniformly, then 0.5 wt% of polyethyleneimine was added as a dispersant, and the mixture was ball milled at a speed of 300 rpm for 4 hours to obtain a mixed slurry;

[0125] ② 2 wt% of acrylamide monomer and crosslinking agent were added to the slurry, injected into a mold, and heated at 60°C to initiate polymerization and curing to obtain a green body;

[0126] ③ The green body was placed in a high-temperature atmosphere sintering furnace, sintered under protection, and the specific sintering curve was as follows:

[0127] First stage: increase the temperature to 120°C at a rate of 3°C / min, keep the temperature constant for 1 hour, then continue to increase the temperature to 500°C, and keep the temperature constant for 1 hour.

[0128] Second stage: increase the temperature to 1400°C at a rate of 10°C / min, keep the temperature constant for 30 minutes, and make the matrix preliminary densification.

[0129] Third stage: decrease the temperature to 1150°C, keep the temperature constant for 3 hours, and cool to room temperature in the furnace, to obtain a ceramic reinforcement.

[0130] ④ The ceramic reinforcement and the steel end fitting were combined under a pressure of 5 MPa using a press bonding technique;

[0131] ⑤ The surface of the ceramic reinforcement was pre-sprayed with a 2 wt% silane coupling agent alcohol solution, then placed in the mold of a mold forming machine, and the silicone rubber was injected into the mold. A vacuum was maintained during and after the injection of the silicone rubber, with a vacuum pressure of -0.095 MPa, a pressure holding time of 10 minutes, and a slow release of the vacuum. The silicone rubber was cured at 150°C and 1 MPa for 4 hours to obtain a lightweight composite insulator.

[0132] Test Example:

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

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

[0135] The insulators in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to interface bonding strength tests according to IEC 62217 standards, and the specific results are shown in Table 1.

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

[0137] The insulators in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to temperature cycle tests according to the IEC 62217 standard, and the specific results are shown in Table 1.

[0138]

[0139] In summary: the present application provides a porous nanoceramic reinforcing body, a lightweight nanocomposite ceramic insulator and a preparation process thereof, by Zn 2-x Cu x During the heating process, the special bridge oxygen bond in the lattice of the P2O7 functional phase will undergo transverse thermal vibration, causing the entire lattice network to shrink inward, which macroscopically manifests as a decrease in volume, actively compensating for the thermal expansion of the matrix material, and ultimately making the entire composite reinforcing body exhibit near-zero thermal expansion in the working temperature range of -50℃ to 150℃. This fundamentally eliminates the size instability and internal thermal stress caused by drastic temperature changes, laying the foundation for the long-term reliable operation of the insulator under extreme weather conditions.

[0140] At the same time, a macro-micro-nano three-level pore structure is constructed, with the first-level pores formed by the decomposition of the PVA pore-forming agent, greatly reducing the density of the material. These macroscopic pores ensure the structural framework while achieving maximum lightweight. At the same time, they provide a buffer space for stress, preventing rapid crack propagation; the second-level pores formed by the starch pore-forming agent are distributed in the macro-pore walls, significantly increasing the specific surface area of the material, effectively deflecting and terminating microcracks, consuming the energy of crack propagation, and improving the fracture toughness of the material; the third-level pores produced by the partial pyrolysis of the silane coupling agent are located at the interface between the NTE reinforcing phase and the matrix, and can effectively absorb and disperse local stress caused by thermal mismatch, avoiding stress concentration leading to interface debonding or cracking, thereby ensuring the integrity of the structure at the molecular scale. The three-level pores coordinate with each other to enable the material to maintain extremely low density while having higher mechanical strength and thermal shock resistance.

[0141] Moreover, the silane coupling agent is hydrolyzed at the low temperature stage of sintering 120-150℃, and the silanol group of the hydrolyzed silane coupling agent reacts with the hydroxyl group on the surface of the NTE powder and the ceramic matrix to form a strong Si-O-M covalent bond. This layer of chemical bonding serves as a "molecular anchor" to tightly weld the NTE phase and the matrix together, greatly improving the interfacial bonding strength; when the temperature rises to 500℃, the organic chain segment in the silane molecule undergoes controllable thermal decomposition and volatilization. In the previously formed strong Si-O-Si inorganic skeleton network, nanoscale tertiary pores are left in situ and uniformly. These nano-pores serve as a micro-stress buffer zone to avoid interfacial brittle fracture, thereby further enhancing the toughness and reliability of the interface.

[0142] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application 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 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.

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 pore-forming agent includes a PVA pore-forming agent and a starch pore-forming agent, and the mass ratio of the PVA pore-forming agent to the starch pore-forming agent is 2-3:

1.

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

05.

5. The porous nanoceramic reinforcement according to claim 3, characterized in that, The silane coupling agent is selected from one or more of aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

6. The porous nanoceramic reinforcement according to claim 5, characterized in that, 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.

7. The porous nanoceramic reinforcement according to claim 6, 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 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 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: 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.

8. The porous nanoceramic reinforcement according to claim 7, 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.

9. A lightweight nanocomposite ceramic insulator, characterized in that, include: The porous nanoceramic reinforcement as described in any one of claims 1 to 8; 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.

10. 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 1-8 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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