Nanocrystalline composite ceramic insulating material, preparation method and application thereof

Abstract

The invention discloses a nanocrystalline composite ceramic insulating material and a preparation method thereof, and belongs to the field of nanocrystalline ceramic material preparation. Raw materials of the catalyst comprise the following components by mole percent: 40-50% of SiO2; 30%-38% of CaCO3 (calcium carbonate); 13% to 18% of Na2CO3; 0.5 to 2.5 percent of TiO2; zrO2: 0.5% to 2.5%; 1 to 3 percent of Al2O3; and 0.5 to 4.5% of K2O. The preparation method comprises the following steps: weighing the raw materials according to the proportioning requirement, fully mixing the raw materials, and carrying out ball milling treatment; keeping the temperature of the mixture at 850-950 DEG C for more than 2 hours, then keeping the temperature at the temperature not lower than 1450 DEG C for 60-90 minutes, then pouring the mixture into a preheated brass mold, and keeping the temperature at 500-550 DEG C and annealing for more than 10 hours; heat treatment is carried out in an air atmosphere through a two-step method, heat preservation is carried out at the temperature of 600-650 DEG C for a certain time, then heat treatment is carried out at the temperature of 650-700 DEG C, and the temperature interval between the heat treatment and the heat treatment is 50-100 DEG C. The nanocrystalline composite ceramic insulating material disclosed by the invention has more excellent mechanical strength and dielectric property, and is of great significance in promoting a power transmission and transformation system to develop towards a direction of higher voltage, longer distance and more reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanocrystalline ceramic material preparation, and particularly relates to a nanocrystalline composite ceramic insulating material, a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of modern power systems in China towards extra-high voltage, super capacity and intelligentization, unprecedented high standards are put forward for the comprehensive performance of key insulating materials in power grid systems. The insulator plays the functions of electrical insulation and mechanical support in the power transmission line equipment, and its performance plays an important role in guaranteeing the safe operation of the power transmission line and improving the power quality. The traditional insulator materials are mainly ceramic insulators and tempered glass insulators. However, the ceramic insulator has the problem of "zero value" or "low value", that is, its insulating performance will slowly decrease due to internal defects or long-term aging, but this degradation cannot be directly judged from the appearance, resulting in high maintenance cost, and its high brittleness makes it difficult to withstand external impact force. The tempered glass insulator solves the problem of "zero value" detection through the "self-explosion" feature. When the manufacturing stress is uneven, the operating temperature difference changes suddenly or is slightly damaged by external force, the glass insulator may occur without warning self-explosion, resulting in an increase in line failure rate, and the hydrophilicity of the glass surface in the contaminated area easily forms a continuous water film, increasing the risk of "pollution flashover", threatening the safety of the power grid. The ideal insulator material has dual requirements for mechanical properties and dielectric properties. The development of insulator materials with excellent mechanical properties and dielectric properties is of great significance to promote the power transmission system to develop in the direction of higher voltage, longer distance and more reliability. SUMMARY

[0003] The present application aims at providing a nanocrystalline composite ceramic insulating material, a preparation method and application thereof to solve the problems in the prior art. The nanocrystalline composite ceramic insulating material has excellent mechanical properties and dielectric properties, and the preparation process is simple and low in cost.

[0004] To achieve the above object, the technical scheme adopted by the present application is as follows: A nanocrystalline composite ceramic insulating material, the raw material composition includes the following components in terms of molar percentage: SiO2: 40-50%; CaCO3: 30-38%; Na2CO3: 13-18%; TiO2: 0.5-2.5%; ZrO2: 0.5-2.5%; Al2O3: 1-3%; K2O: 0.5-4.5%.

[0005] Further, the above technical scheme, 72%≤SiO2+CaCO3≤80%, according to the molar ratio: 0.7≤Na / Ca≤1.2, 0.8≤Ti / Zr≤1.2, 0.2≤Al / K≤2.

[0006] Preferably, the nanocrystalline composite ceramic insulating material has a volume resistivity greater than 1.5*10 11 Ω m, a bending strength greater than 120 MPa, a Vickers hardness greater than 6 GPa, a relative dielectric constant between 7 and 9 at a frequency of 1 MHz, a loss factor less than 2*10 -4 -2, and an electric breakdown strength greater than 20 kV / mm.

[0007] Further, the nanocrystalline composite ceramic insulating material is prepared by a melt quenching method, and then obtained by a two-step heat treatment in an air atmosphere.

[0008] According to the above scheme, the melt quenching method is as follows: the mixture is kept at 850-950℃ for more than 2 hours, then kept at a temperature not lower than 1450℃ for 60-90 minutes, and then poured into a preheated brass mold and annealed at 500-550℃ for more than 10 hours.

[0009] According to the above scheme, the two-step heat treatment is as follows: first kept at 600-650℃ for a certain time, and then kept at 650-700℃ for heat treatment, with a temperature interval of 50-100℃ between the two steps.

[0010] According to the above scheme, the heat treatment time of the first step is in the range of 2-20 hours, and the heat treatment time of the second step is in the range of 1-2 hours.

[0011] The second aspect of the present application provides a preparation method of the nanocrystalline composite ceramic insulating material, which specifically comprises the following steps: (a) weighing the raw materials according to the required proportions, and fully mixing and ball milling the raw materials; (b) keeping the mixture obtained in step (a) at 850-950℃ for more than 2 hours, then keeping at a temperature not lower than 1450℃ for 60-90 minutes, and then pouring into a preheated brass mold and annealing at 500-550℃ for more than 10 hours; (c) using a two-step heat treatment in an air atmosphere: first keeping at 600-650℃ for a certain time, and then keeping at 650-700℃ for heat treatment, with a temperature interval of 50-100℃ between the two steps, to obtain the nanocrystalline composite ceramic material.

[0012] Further, in the above technical solution, the ball milling speed in step (a) is 600-700 revolutions per minute, the ball milling time is not less than 10 hours, and the ball milling sub is zirconia with a size distribution of 2, 3 and 5 mm, each accounting for one third.

[0013] Further, in the above technical solution, in step (c), the heating rate in the two-step heat treatment in the air atmosphere is 3-8℃ / min.

[0014] The third aspect of the present application provides the use of the nanocrystalline composite ceramic insulating material in the preparation of an insulator.

[0015] The present application uses SiO2, CaCO3 and Na2CO3 as main raw materials, adds TiO2, ZrO2, Al2O3 and K2O, and controls the preparation of the raw materials by adjusting the amount of each component. The melt is obtained by melting and quenching, poured into a mold and annealed to prepare a base glass. Then, the base glass is heat treated in air atmosphere by a two-step method, and the nucleation and crystallization processes are optimized independently to achieve high density and small spherical nanocrystals. By controlling the heating rate of the nucleation and crystallization processes, the uniformity and density of the nucleation stage are better optimized. The obtained nanocrystalline ceramic insulator material contains Na4CaSi3O9 (JCPDS-37-0282), KAlSi3O8 (JCPDS-19-0926), K2Al2O4 (JCPDS-45-0849) and glass phase.

[0016] In the present application, TiO2 and ZrO2 play the following three roles. On the one hand, a large number of uniformly distributed small particles are generated in the glass, providing heterogeneous nucleation sites and reducing the crystallization activation energy. On the other hand, the bulk material is prone to surface crystallization, and the nucleating agent helps to achieve volume crystallization, ensuring that the crystallization process occurs uniformly throughout the ceramic, resulting in a structure of uniform nanocrystalline ceramic material without bubbles. Finally, the coordinated action of TiO2 and ZrO2 better improves the comprehensive performance. In the present application, Al2O3 plays the following two roles. On the one hand, aluminum enters the network in the form of AlO4, which fixes Na + , reduces free ions, reduces non-bridging oxygen to make the network more connected, and improves the mechanical properties and thermal stability of the nanocrystalline ceramic material. On the other hand, it inhibits the phase separation of the material and improves the uniformity and long-term stability of the ceramic material. In the present application, K2O plays the following two roles. Na + , K + coexist to trigger the mixed alkali effect, and the addition of K + ions reduces the ion mobility, thereby improving the volume resistivity and improving the electrical properties of the ceramic material.

[0017] The beneficial effects of the present application are: The nanocrystalline composite ceramic material of the present application combines the advantages of traditional glass and ceramic insulating materials, has more excellent mechanical strength and dielectric properties, and the uniform nanocrystalline structure inside makes it more climate-resistant and stable than traditional glass insulating materials, which is of great significance for the development of the power transmission system to higher voltage, longer distance and more reliable direction. The volume resistivity of the nanocrystalline composite ceramic sample obtained by the present application is greater than 1.5 x 10 11Ω m, the relative dielectric constant is 7-9 at 1 MHz frequency, the loss factor is less than 2x10 -4 , the electric breakdown strength is greater than 20 kV / mm, the bending strength is greater than 120 MPa, and the Vickers hardness is greater than 6 GPa.

[0018] The application uses SiO2, CaCO3 and Na2CO3 as main raw materials, adds TiO2, ZrO2, Al2O3 and K2O, and adjusts the amount of each component to prepare the raw materials, melts and quenches to prepare the base glass, and then uses a two-step heat treatment in an air atmosphere to prepare the nano-crystal composite ceramic insulator with simple preparation process, low cost, easy pouring into a specific insulator shape, and good forming ability. After the ceramic material is prepared, there are no bubbles, stripes and other defects in the interior and surface, and it is easy to prepare a large-size nano-crystal composite ceramic insulator at low cost. BRIEF DESCRIPTION OF DRAWINGS

[0019] To make the technical solutions of the present application clearer, the drawings of the specification will be briefly described below. It should be understood that the drawings shown here are only part of the embodiments of the present application, not all. Those skilled in the art can obtain other related drawings without creative labor on the basis of these drawings.

[0020] Figure 1 : a physical map of the nano-crystal ceramic prepared in Example 2; Figure 2 : XRD diagram of the nano-crystal ceramic prepared in Examples 1-4, which can obviously see that the nano-crystal ceramic insulator material contains Na4CaSi3O9, KAlSi3O8, K2Al2O4 and glass phase; Figure 3 : SEM diagram of the nano-crystal composite ceramic in Example 2 after etching for 3 seconds by 2 mol% HF, and the precipitation of nano-crystals is observed, and the surface grain size is not uniform; Figure 4 : TEM diagram of the nano-crystal composite ceramic in Example 2, and the spacing of 0.19, 0.27 and 0.23 nm is observed, which respectively corresponds to the (800), (521) and (541) crystal faces of K2Al2O4, Na4CaSi3O9; Figure 5 : bending strength of the glass sample (PG) and the nano-crystal ceramic after nucleation at 600℃ for 20 hours and heat treatment at 680℃ / 2 hours in Examples 1-4; Figure 6 : relative dielectric constant diagram of the nano-crystal composite ceramic in Examples 1-4; Figure 7 : XRD diagram of the sample prepared in Comparative Example 11. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0022] The equipment and raw materials used in the present application can be purchased from the market or are commonly used in the art. The methods in the following examples are conventional methods in the art unless otherwise specified.

[0023] The present application provides a nanocrystalline composite ceramic insulating material, the raw material formula of which comprises the following components in terms of mole percentage: SiO2: 40-50%; CaCO3: 30-38%; Na2CO3: 13-18%; TiO2: 0.5-2.5%; ZrO2: 0.5-2.5%; Al2O3: 1-3%; K2O: 0.5-4.5%.

[0024] Further, in the above technical solution, 72%≤SiO2+CaCO3≤80%, in terms of mole ratio: 0.7≤Na / Ca≤1.2, 0.8≤Ti / Zr≤1.2, 0.2≤Al / K≤2.

[0025] Na2O and CaO are both network modifiers, and the excess of Na2O increases the tendency of surface crystallization, which directly leads to excessive crystallization. The content changes of SiO2 and CaO will directly affect the network connectivity and crystallization kinetics of the glass, and controlling the content changes of the two is conducive to the precipitation of target crystal phase. Further, TiO2 and ZrO2 act as crystal nucleus agents, which improve the mechanical strength of the material through fine-grain strengthening mechanism and nucleation coordination. Appropriate addition and control of the content ratio of the two are conducive to obtaining finer and more uniform grains, and excessive addition may lead to material embrittlement and nucleation of the nucleating agent itself.

[0026] Further, when there is sufficient Na + , Al 3+ prefers to form AlO4 tetrahedron, which together with SiO4 tetrahedron forms a more solid and higher connectivity mixed network structure, reducing the tendency of surface crystallization. When Na2O and K2O coexist, a unique mixed alkali effect is produced, and the addition of K + ions reduces the ion mobility, thereby improving the volume resistivity. Controlling the introduction ratio of aluminum and potassium can better regulate the crystallization behavior and related properties of nanocrystalline ceramics.

[0027] Further, the nanocrystalline composite ceramic insulating material is prepared into a base glass by a melt quenching method, and is obtained after two-step heat treatment in an air atmosphere.

[0028] According to the above scheme, the melt quenching method is as follows: the mixed material is kept at 850-950 DEG C for more than 2 hours, then kept at a temperature not lower than 1450 DEG C for 60-90 minutes, then poured into a preheated brass mold, and kept at 500-550 DEG C for annealing for more than 10 hours.

[0029] According to the above scheme, the two-step heat treatment is as follows: kept at 600-650 DEG C for a certain time, then kept at 650-700 DEG C for heat treatment, and the temperature interval between the two is 50-100 DEG C.

[0030] Further, the heat treatment time of the first step is 2-20 hours, and the heat treatment time of the second step is 1-2 hours.

[0031] The volume resistivity of the nanocrystalline composite ceramic insulating material is greater than 1.5*10 11 Ω m, the bending strength is greater than 120 MPa, the Vickers hardness is greater than 6 GPa, the relative dielectric constant is between 7-9 at a frequency of 1 MHz, the loss factor is less than 2*10 -4 -10-6, and the electric breakdown strength is greater than 20 kV / mm.

[0032] The second aspect of the present application provides a preparation method of the nanocrystalline composite ceramic insulating material, which specifically comprises the following steps: (a) according to the ratio, the raw materials are weighed and mixed, and ball milling treatment is performed; (b) the mixed material obtained in step (a) is kept at 850-950 DEG C for more than 2 hours, then kept at a temperature not lower than 1450 DEG C for 60-90 minutes, then poured into a preheated brass mold, and kept at 500-550 DEG C for annealing for more than 10 hours; (c) two-step heat treatment is performed in an air atmosphere: first kept at 600-650 DEG C for a certain time, then kept at 650-700 DEG C for heat treatment, and the temperature interval between the two is 50-100 DEG C, so that the nanocrystalline composite ceramic material is obtained.

[0033] In some embodiments, the ball milling speed in step (a) is 600-700 revolutions per minute, the ball milling time is not less than 10 hours, the ball milling sub is zirconia, and the grading is 2, 3, and 5 mm, each accounting for one third.

[0034] In some embodiments, preferably, the raw materials in step (b) are first kept at 850-950 DEG C for more than 2 hours, which is beneficial to remove CO2 in the raw materials, and the subsequent obtained raw materials are more clear and free of defects such as air bubble stripes.

[0035] Further, in step (c), the heating speed in the two-step heat treatment is 3-8 DEG C / min.

[0036] In some embodiments, the sample size is 25x25x1mm.

[0037] The following is illustrated by specific examples. As shown in Table 1-2, which is the composition of Examples 1-8, the preparation method and the sample Vickers hardness, bending strength and relative dielectric constant, volume resistivity and other dielectric performance parameters after heat treatment.

[0038] Example 1 (1) Take 45.17mol%SiO2, 32.90mol%CaCO3, 16.20mol%Na2CO3, 1.96mol% of TiO2 and ZrO2 respectively, and 1.17mol%Al2O3, 0.63mol%K2O, mix uniformly, then pour into a ball mill pot for ball milling treatment, get the mixture. Among them, the rotation speed of ball milling is 600 revolutions per minute, the time is 24 hours, and when ball milling, zirconia is used as the ball mill, and the gradation follows: 2mm, 3mm, 5mm, each 1 / 3.

[0039] (2) Put the mixture into a platinum crucible, then put it into a muffle furnace, heat at 900℃ for 3 hours, then transfer to a high temperature resistance furnace, heat at 1500℃ for 120 minutes, get the melt.

[0040] (3) Pour the melt into a preheated brass mold, and anneal at 550℃ for 12 hours, get the glass piece (PG).

[0041] (4) Cut the glass piece into a thin piece block sample, then sequentially perform two-step heat treatment, get the nanocrystalline ceramic material. The first heat treatment process is: from room temperature to 600℃ at a heating rate of 5℃ / min, then heat at this temperature for 20 hours. The second heat treatment process is: from 600℃ to 680℃ at a heating rate of 5℃ / min, then heat at this temperature for 2 hours.

[0042] Examples 2-4 The scheme of Examples 2-4 is basically the same as that of Example 1, the difference is the change of the formula part, the raw material formula is shown in Table 1. In addition, other parameters and conditions are unchanged. The actual picture of the nanocrystalline ceramic material (thickness of 1mm) prepared in this embodiment 2 is shown in Figure 1 It can be seen that: under the condition of not polishing, it still has good transmittance. Figure 1

[0043] Further, the nanocrystalline ceramic is analyzed by XRD, and the XRD characterization of the nanocrystalline ceramic of Examples 1-4 is shown in Figure 2 It can be seen that: under the condition of not polishing, it still has good transmittance. Figure 2 ​It can be obviously seen that the nanocrystalline ceramic insulator material contains Na4CaSi3O9, KAlSi3O8, K2Al2O4 and glass phase; Further, the nanocrystalline ceramic of Example 2 is microscopically observed by using a scanning electron microscope (SEM) and a transmission electron microscope (TEM), and it can be obviously seen that the grains of uniform size and density are precipitated, as shown in FIG. 2. Figure 4 As shown in FIG. 3, the lattice fringes of 0.23, 0.27 and 0.19 nm can be seen, which correspond to (541), (521) and (800) crystal planes of Na4CaSi3O9 and K2Al2O4 crystals, respectively.

[0044] Table 1 (%: molar percentage)

[0045] Example 5 (1) 40 mol% SiO2, 38 mol% CaCO3, 15 mol% Na2CO3, 1.96 mol% TiO2 and ZrO2, 1.87 mol% Al2O3 and 1.21 mol% K2O are taken and uniformly mixed, and then poured into a ball mill jar for ball milling treatment to obtain a mixture. During the ball milling, the rotation speed is 700 revolutions per minute, the time is 10 hours, and zirconia is used as the ball mill medium, and the grading follows: 2 mm, 3 mm and 5 mm, each accounting for 1 / 3.

[0046] (2) The mixture is loaded into a platinum crucible and then placed in a muffle furnace, and kept at 850°C for 2 hours, and then transferred to a high-temperature resistance furnace, and kept at 1450°C for 90 minutes to obtain a melt.

[0047] (3) The melt is poured into a preheated brass mold, and annealed at 500°C for 10 hours to obtain a glass piece.

[0048] (4) The glass piece is cut into a thin piece block sample, and then subjected to two-step heat treatment in sequence to obtain a nanocrystalline ceramic material. The first heat treatment process is: heated from room temperature to 600°C at a heating rate of 3°C / min, and then kept at the temperature for 20 hours. The second heat treatment process is: heated from 600°C to 650°C at a heating rate of 5°C / min, and then kept at the temperature for 2 hours.

[0049] Example 6 The scheme of Example 6 is basically the same as that of Example 2, and the difference is that the formula part is changed to 44.84 mol% SiO2, 32.66 mol% CaCO3, 18 mol% Na2CO3, 1.5 mol% TiO2, 1.5 mol% ZrO2 and 1 mol% Al2O3 and 0.5 mol% K2O, wherein Al / K = 2.

[0050] Example 7 (1) Take 42.91 mol% SiO2, 35.67 mol% CaCO3, 14 mol% Na2CO3, 2.5 mol% TiO2, 2.5 mol% ZrO2, and 1 mol% Al2O3, 1.42 mol% K2O, mix uniformly, then pour into a ball mill pot for ball milling treatment, to get the mixture. The rotation speed of ball milling is 600 rpm, the time is 24 hours, and during ball milling, zirconia is used as the ball mill, and the gradation follows: 2mm, 3mm, 5mm, each 1 / 3.

[0051] (2) Put the mixture into a platinum crucible, then put it into a muffle furnace, keep it at 900°C for 2 hours, then transfer it to a high-temperature resistance furnace, keep it at 1450°C for 90 minutes, to get the melt.

[0052] (3) Pour the melt into a preheated brass mold, and keep it at 550°C for 10 hours for annealing, to get the glass piece.

[0053] (4) Cut the glass piece into a thin piece block sample, then sequentially perform two-step heat treatment, to get the nanocrystalline ceramic material. The first heat treatment process is: from room temperature, increase the temperature to 600°C at a rate of 5°C / min, then keep it at this temperature for 20 hours. The second heat treatment process is: from 600°C, increase the temperature to 680°C at a rate of 5°C / min, then keep it at this temperature for 1 hour.

[0054] Example 8 (1) Take 43.61 mol% SiO2, 32.34 mol% CaCO3, 15.35 mol% Na2CO3, 1.2 mol% TiO2, 1 mol% ZrO2, and 3 mol% Al2O3, 3.5 mol% K2O, mix uniformly, then pour into a ball mill pot for ball milling treatment, to get the mixture. The rotation speed of ball milling is 700 rpm, the time is 10 hours, and during ball milling, zirconia is used as the ball mill, and the gradation follows: 2mm, 3mm, 5mm, each 1 / 3.

[0055] (2) Put the mixture into a platinum crucible, then put it into a muffle furnace, keep it at 900°C for 2 hours, then transfer it to a high-temperature resistance furnace, keep it at 1500°C for 120 minutes, to get the melt.

[0056] (3) Pour the melt into a preheated brass mold, and keep it at 550°C for 10 hours for annealing, to get the glass piece.

[0057] (4) The glass piece is cut into a thin flake bulk sample, and then two-step heat treatment is sequentially performed to obtain a nanocrystalline ceramic material. The first heat treatment process is: heating from room temperature to 650°C at a heating rate of 5°C / min, and then keeping the temperature for 2 hours. The second heat treatment process is: heating from 600°C to 700°C at a heating rate of 5°C / min, and then keeping the temperature for 2 hours.

[0058] Comparative Example 1 The scheme of the present comparative example is basically the same as that of Example 1, except that the raw material formula of the present comparative example is: SiO2: 42.17%; CaCO3: 38.90%; Na2CO3: 13.20%; TiO2: 1.96%; ZrO2: 1.96%; Al2O3: 1.17%; K2O: 0.63%, wherein the molar content of CaCO3 is greater than 38%, and the sample does not crystallize after heat treatment at 600°C / 20 hours and 680°C / 2 hours.

[0059] Comparative Example 2 The scheme of the present comparative example is basically the same as that of Example 2, except that the raw material formula of the present comparative example is: SiO2: 40.5%; CaCO3: 30.57%; Na2CO3: 24.92%; TiO2: 0.65%; ZrO2: 0.65%; Al2O3: 1.35%; K2O: 1.36%, wherein the molar content of Na2CO3 is greater than 18%, and the sample surface crystallizes and the surface appears porcelainization and shell formation after heat treatment at 600°C / 20 hours and 680°C / 3 hours, and the sample presents a milky white ceramic shape.

[0060] Comparative Example 3 The scheme of the present comparative example is basically the same as that of Example 2, except that the heating rate of the two-step heat treatment sample in the present comparative example is 10°C / min. Due to the too fast heating rate, the crystallization process is relatively intense, which leads to too fast grain growth and obvious coarsening, and the ceramic sample forms visible particles. Except for this, other parameters and conditions remain unchanged.

[0061] Comparative Example 4 The scheme of the present comparative example is basically the same as that of Example 2, except that the raw material formula of the present comparative example is: SiO2: 52.5%; CaCO3: 30.5%; Na2CO3: 10.36%; TiO2: 1.45%; ZrO2: 1.65%; Al2O3: 1.75%; K2O: 1.79%, wherein SiO2 and Na2CO3 are not in the content range, and phase separation occurs after heat treatment, and there is still a large amount of glass phase, and the crystallization degree is low.

[0062] Comparative Example 5 The comparative example scheme is basically the same as example 2, except that the comparative example raw material formula is: SiO2: 51.5%; CaCO3: 30.5%; Na2CO3: 10.36%; TiO2: 2.45%; ZrO2: 1.65%; Al2O3: 1.75%; K2O: 1.79%; in the components of the comparative example, 1.2≤Ti / Zr, after heat treatment at 600°C / 20 hours, 680°C / 2 hours, the sample is turbid opaque ceramic.

[0063] Comparative example 6: The comparative example scheme is basically the same as example 8, except that the comparative example raw material does not go through the step of 900°C for 2 hours, and when the sample is cast, there are some bubbles, stripes and other defects.

[0064] Comparative example 7: The comparative example scheme is basically the same as example 2, except that after the glass sample is cast and annealed at 400°C for 10 hours, the sample cracks severely due to excessive internal stress.

[0065] Comparative example 8: The comparative example scheme is basically the same as example 2, except that the comparative example raw material formula is: SiO2: 42.84%; CaCO3: 31.66%; Na2CO3: 15.08%; TiO2: 1.95%; ZrO2: 1.95%; Al2O3: 1.21%; K2O: 5.31%; in the components of the comparative example, the content of K2O is greatly increased, and the sample is severely devitrified after heat treatment, and the Vickers hardness and bending strength are greatly reduced compared to example 2.

[0066] Comparative example 9: The comparative example scheme is basically the same as comparative example 5, except that the comparative example raw material formula is: SiO2: 50.5%; CaCO3: 30.5%; Na2CO3: 10.36%; TiO2: 2.45%; ZrO2: 2.65%; Al2O3: 1.75%; K2O: 1.79%; in the components of the comparative example, the molar content of the components is increased compared to example 2, and the content of the overall nucleating agent is increased, wherein ZrO2>2.5%, and the sample exists after heat treatment. Local crystallization and atomization.

[0067] Comparative example 10: The preparation scheme of the present comparative example is basically the same as that of Example 8, except that the raw material formula of the present comparative example is as follows: SiO2: 40.84%; CaCO3: 24.23%; Na2CO3: 24.31%; TiO2: 2.45%; ZrO2: 2.35%; Al2O3: 2.51%; K2O: 3.31%. After high-temperature melting, the sample was poured into an annealed brass mold and crystallized, and no glass sample was formed.

[0068] Comparative Example 11 The preparation scheme of the present comparative example is basically the same as that of Example 2, except that the raw material formula of the present comparative example is as follows: SiO2: 43.91%; CaCO3: 32.57%; Na2CO3: 16.51%; TiO2: 1.65%; ZrO2: 1.65%; Al2O3: 2.5%; K2O: 1.22%. Among them, Al / K>2, and other parameters and conditions are unchanged. After heat treatment at 600°C for 20 hours and at 680°C for 2 hours, the sample did not crystallize significantly. Figure 7 The XRD pattern of the sample prepared in Comparative Example 11 was prepared. The ceramic sample still has a large amount of glass phase after heat treatment, and the degree of crystallization is low.

[0069] Comparative Example 12 In this component, the molar content of the component is close to that of Example 2, but Al2O3 and K2O are not added. The raw material formula of the present comparative example is as follows: SiO2: 46.84%; CaCO3: 33.66%; Na2CO3: 16.70%; TiO2: 1.45%; ZrO2: 1.35%; Al2O3: 0%; K2O: 0%. The sample is well formed, but local surface crystallization occurs after two-step heat treatment.

[0070] Performance Test (1) The nanocrystalline composite ceramic materials prepared in Examples 1 to 8 were subjected to mechanical and electrical performance tests, and the results are shown in Tables 2 and 3.

[0071] (2) The nanocrystalline composite ceramic materials prepared in Comparative Examples 1-4 and 8-11 were subjected to mechanical and electrical performance tests, and the results are shown in Tables 4 and 5.

[0072] Table 2

[0073] Table 3

[0074] Table 4

[0075] Table 5

[0076] The results of the comparison of the bending strength of the glass samples (PG) of examples 1-4 and the nanocrystalline ceramics after two-step heat treatment are shown in Table 1. Figure 5 In which: the bending strength of the PG samples is between 91-99 MPa, and the bending strength of the nanocrystalline ceramics prepared after two-step heat treatment is significantly improved, such as the bending strength of the sample of example 2 is 131.08 MPa.

[0077] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art can make various adjustments to the process and parameters within the essential scope of the present application, and all the modifications and changes that do not deviate from the essence of the present application fall within the protection scope defined by the claims.

Claims

1. A nanocrystalline composite ceramic insulating material, characterized in that: The raw material composition, measured by molar percentage, includes the following components: SiO2: 40-50%; CaCO3: 30-38%; Na2CO3: 13-18%; TiO2: 0.5-2.5%; ZrO2: 0.5-2.5%; Al2O3: 1-3%; K2O: 0.5-4.5%.

2. The nanocrystalline composite ceramic insulating material according to claim 1, characterized in that: 72%≤SiO2+CaCO3≤80%, based on molar ratio: 0.7≤Na / Ca≤1.2, 0.8≤Ti / Zr≤1.2, 0.2≤Al / K≤2.

3. The nanocrystalline composite ceramic insulating material according to claim 1, characterized in that: The nanocrystalline composite ceramic insulating material is prepared by melting and quenching to form a base glass, followed by a two-step heat treatment in air atmosphere.

4. The nanocrystalline composite ceramic insulating material according to claim 1, characterized in that: The method of preparing base glass by melt quenching is as follows: the mixture is kept at 850-950℃ for more than 2 hours, then kept at a temperature of not less than 1450℃ for 60-90 minutes, then poured into a preheated brass mold, and annealed at 500-550℃ for more than 10 hours.

5. The nanocrystalline composite ceramic insulating material according to claim 1, characterized in that: The two-step heat treatment method is as follows: holding at 600-650℃ for a certain time, and then performing heat treatment at 650-700℃, with a temperature interval of 50-100℃ between the two.

6. The nanocrystalline composite ceramic insulating material according to claim 5, characterized in that: The holding time for the first heat treatment is 2-20 hours, and the holding time for the second heat treatment is 1-2 hours.

7. The nanocrystalline composite ceramic insulating material according to claim 1, characterized in that: The volume resistivity of the nanocrystalline composite ceramic insulating material is greater than 1.5 × 10⁻⁶. 11 Ω m, flexural strength greater than 120 MPa, Vickers hardness greater than 6 GPa, relative permittivity between 7 and 9 at 1 MHz, and loss factor less than 2 × 10⁻⁶. -4 The electrical breakdown strength is greater than 20kV / mm.

8. The preparation method of the nanocrystalline composite ceramic insulating material according to claim 1, wherein the preparation method specifically includes the following steps: (a) Weigh the raw materials according to the required proportions, mix them thoroughly, and then ball mill them; (b) The mixture obtained in step (a) is kept at 850-950℃ for more than 2 hours, then kept at a temperature of not less than 1450℃ for 60-90 minutes, and then poured into a preheated brass mold and annealed at 500-550℃ for more than 10 hours. (c) The nanocrystalline composite ceramic material is obtained by a two-step heat treatment in air atmosphere: first, it is held at 600-650℃ for a certain time, and then heat treatment is carried out at 650-700℃, with a temperature interval of 50-100℃ between the two.

9. The preparation method according to claim 8, characterized in that: In step (c), the heating rate in the two-step heat treatment is 3-8°C / minute.

10. The application of the nanocrystalline composite ceramic insulating material according to claim 1 in the preparation of insulators.

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