Mud material for medium-high aluminum electroceramic hollow insulator and preparation process of mud material

Abstract

The invention discloses pug for a medium-high aluminum electric porcelain hollow insulator and a preparation process of the pug, and relates to the technical field of electric porcelain hollow insulators, the pug is prepared from the following raw materials in parts by weight: 25-35 parts of refined bauxite, 15-25 parts of aluminum powder, 20-30 parts of kaolin, 5-10 parts of quartz and 5-10 parts of a potassium-sodium additive; wherein the refined bauxite is prepared by the following method: crushing and ball-milling bauxite, adding the bauxite into an oxalic acid solution I with the pH value of less than 2, stirring and reacting at 25-40 DEG C for 1-3 hours, performing solid-liquid separation, washing with an oxalic acid solution II, and drying to obtain solid slag; polysilazane resin powder and hexagonal boron nitride nanosheets are uniformly mixed, then a catalyst and solid slag are added, the mixture is uniformly mixed and calcined to obtain refined bauxite, and the refined bauxite has lower iron oxide content and tantalum carbide content and smaller porosity, so that the strength of the electroceramic hollow insulator can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic materials, and in particular to a clay material for medium- and high-aluminum electric porcelain hollow insulators and a preparation process thereof. Background Art

[0002] Porcelain hollow insulators have an unshakable position in transmission lines. As the distance of transmission lines continues to increase and the voltage level continues to increase, the requirements for the mechanical properties of porcelain hollow insulators continue to increase. Medium and high aluminum porcelain insulators have attracted much attention due to their high electromechanical strength and good reliability.

[0003] In the manufacture of medium and high aluminum hollow insulators, aluminum can be obtained through bauxite or industrial alumina. Since the aluminum oxide in industrial alumina cannot be read higher, its effect as a raw material is significantly better than bauxite. However, the cost of industrial alumina is much higher than that of bauxite. Due to production cost considerations, industrial alumina is not the best choice for the preparation of medium and high aluminum hollow insulators. Generally, bauxite is still used as the key raw material.

[0004] Generally speaking, the performance of electrical porcelain is best when the high-alumina content is 25%-35%. However, in actual production, bauxite often has problems with excessive iron and titanium content. Iron elements easily form low-melting-point phases during high-temperature sintering, destroying the crystal structure and causing a decrease in material strength. Titanium elements are enriched at the grain boundaries, forming stress concentration points and reducing the toughness of the material. At the same time, there is abundant structural water in bauxite ore, which will produce a strong volume shrinkage during heating, which is not conducive to the firing of electrical porcelain. It must be pre-fired before use. However, during the pre-firing process, water molecules will be discharged and leave pores. These pores will mostly be distributed in the structural phase in the form of isolated spheres during the subsequent sintering process. Large and irregular pores will significantly reduce the mechanical strength of the product. From the perspective of crack propagation, the pore phase reduces the effective bearing area, reduces the crack propagation resistance, and makes cracks easier to propagate. In addition, the presence of pores also hinders the normal growth of crystals during the sintering process, affecting the final mechanical properties of the product. Summary of the Invention

[0005] The purpose of the present invention is to provide a clay material for medium- and high-aluminum hollow insulators and a preparation process thereof, to solve the following technical problems:

[0006] How to improve the mechanical strength performance of high-aluminum porcelain hollow insulators.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The invention discloses a clay material for medium-high aluminum electrical porcelain hollow insulators, which is composed of the following raw materials in parts by weight: 25-35 parts of refined bauxite, 15-25 parts of aluminum powder, 20-30 parts of kaolin, 5-10 parts of quartz, and 5-10 parts of potassium and sodium additives;

[0009] Preferably, it is composed of the following raw materials in parts by weight: 30 parts of refined bauxite, 20 parts of aluminum powder, 25 parts of kaolin, 8 parts of quartz, and 8 parts of potassium and sodium additives.

[0010] Furthermore, the refined bauxite is prepared by the following method:

[0011] Step 1: crush the bauxite and add it to the oxalic acid solution with pH < 2, stir and react at 25-40℃ for 1-3h. Under the acidic condition of pH < 2, the aluminum oxide (Al 2 O 3 ) surface is passivated by hydroxyl groups and cannot be hydrolyzed, so that oxalic acid preferentially complexes Fe in bauxite 3+ and Ti 4+ , forming a soluble complex, so that the reaction system presents a solid-liquid stratification state, and after solid-liquid separation, the solid separation is washed with oxalic acid solution to further remove the residual Fe 3+ and Ti 4+ , and finally obtain solid slag after drying;

[0012] Step 2: The polysilazane resin powder and the hexagonal boron nitride nanosheets are evenly mixed, and then the catalyst and the solid slag are added and mixed evenly. The polysilazane resin powder and the hexagonal boron nitride nanosheets are evenly coated on the solid slag, that is, the outside of the bauxite particles, and calcined at 500-550 ° C for 1.5 hours. The bauxite is dehydrated and the pores shrink during this process. The released water molecules are discharged to the polysilazane resin powder and the hexagonal boron nitride nanosheets on the surface of the bauxite, so that the polysilazane resin powder absorbs water and undergoes hydrolysis and cross-linking. At the same time, the hexagonal boron nitride nanosheets are arranged in a π-π stacking direction to form a layered film, which is coated on the outer surface of the bauxite. At the high calcination temperature, the thermal expansion coefficient of the layered film is higher than that of alumina. Therefore, during the cooling process, the shrinkage stress of the outer film can promote the shrinkage of the internal bauxite, so that the pores produced after dehydration are smaller and the density is enhanced to obtain refined bauxite.

[0013] Furthermore, in step 1, the bauxite is crushed to a particle size of less than 50 μm and then ball milled. The ball milling step comprises placing the crushed bauxite in a ball mill, using zirconium oxide as grinding balls, at a ball-to-material ratio of 10:1, and a rotation speed of 500-800 rpm under an inert atmosphere for 2-4 hours;

[0014] Preferably, the bauxite is crushed to a particle size of less than 50 μm by a vertical ultrafine grinding device or a roller crusher and then ball milled. The ball milling step is as follows: the crushed bauxite is placed in a ball mill, zirconium oxide is used as the grinding ball, and the ball-to-material ratio is 10:1, the rotation speed is 650 rpm, and the ball milling is carried out for 3 hours in an inert atmosphere.

[0015] Furthermore, in step 1, the concentration of the oxalic acid solution 1 is 1-2 mol / L, and the ratio of the bauxite to the oxalic acid solution is 1 g: (5-10) mL;

[0016] Preferably, the concentration of the oxalic acid solution 1 is 1.5 mol / L, and the usage ratio of the bauxite to the oxalic acid solution is 1 g:8 mL.

[0017] Furthermore, in step 1, the solid-liquid separation method is vacuum filtration separation;

[0018] Preferably, vacuum filtration separation is performed using a vacuum filter.

[0019] Furthermore, in step 1, the concentration of the oxalic acid solution 2 is 0.1 mol / L.

[0020] Furthermore, in step 1, the drying method is: drying the washed bauxite at 80-100° C. for 2 hours; preferably drying at 90° C. for 2 hours.

[0021] Furthermore, in step 2, the weight ratio of the polysilazane resin powder, hexagonal boron nitride nanosheets, catalyst and solid slag is 10:1:0.01:(80-100);

[0022] Preferably, the weight ratio of the polysilazane resin powder, hexagonal boron nitride nanosheets, catalyst and solid slag is 10:1:0.01:90.

[0023] Furthermore, in step 2, the catalyst is metal platinum.

[0024] Based on this, a preferred method for preparing refined bauxite is obtained, comprising the following steps:

[0025] Step 1: crush the bauxite to a particle size of <50 μm using a vertical ultrafine grinding device, then add it to a ball mill, use zirconium oxide as the grinding ball, and ball mill for 3 hours under an inert atmosphere at a ball-to-material ratio of 10:1 and a speed of 650 rpm. After ball milling, add an oxalic acid solution with a pH of <2 and a concentration of 1.5 mol / L at a material-liquid ratio of 1 g:8 mL, stir and react at 35°C for 2 hours, and then transfer it to a vacuum filter for vacuum filtration separation. The obtained solid separator is then washed three times with a 0.1 mol / L oxalic acid solution. The washed solid separator is transferred to a drying oven and dried at 90°C for 2 hours to obtain a solid residue;

[0026] Step 2: Mix 10 parts of polysilazane resin powder and 1 part of hexagonal boron nitride nanosheets by weight, then put them into a stirring tank together with 0.01 parts of metal platinum and 90 parts of solid slag, mix them evenly, and calcine them at 520°C for 1.5 hours to obtain refined bauxite.

[0027] Furthermore, the kaolin is a mixture of Guangdong washed mud, Zuoyun mud-black, Zuoyun mud-white, Zhangcun mud, and ash mud in a ratio of 25:5:5:15:3.

[0028] Furthermore, the potassium and sodium additives are potassium sodium tartrate or a mixture of potassium nitrite and sodium nitrite in a weight ratio of 1:1.

[0029] In a second aspect, the present invention further discloses a process for preparing a clay material for medium- and high-aluminum hollow insulators of insulators, comprising the following steps: mixing refined bauxite, aluminum powder, kaolin, quartz, and potassium and sodium additives in proportion, ball milling, sieving, iron removal, clay squeezing, aging, vacuum clay kneading, sample preparation, and sintering to obtain medium- and high-aluminum hollow insulators of ...

[0030] (1) Ball milling: The raw materials were put into a ball mill according to the proportion, with chlorine oxide as the grinding ball. The grinding balls and water were added in a ratio of material: ball: water = 1:2:1.5, and the ball milling time was set to 15 h.

[0031] (2) Screening: The ball milled slurry is screened with a 250-mesh sieve, and the slurry that does not pass through the sieve is returned to the grinding mill until all of it is screened;

[0032] (3) Iron removal: Use an iron magnet to repeatedly remove iron from the sieved slurry;

[0033] (4) Mud pressing: Use a filter press to dehydrate the mud and press it into a mud cake;

[0034] (5) Aging: Remove the middle part of the squeezed mud cake with more water and age it for 24 hours;

[0035] (6) Vacuum mud refining: Place the aged mud cake in a vacuum mud refining machine and repeatedly refine the mud to remove excess air;

[0036] (7) Sample preparation: The mud cake after kneading is made into a hollow insulator mold base;

[0037] (8) Firing: The mold is heated to 650-800°C at a heating rate of 5°C / min in a reducing atmosphere, kept at this temperature for 3.5 hours, and then continued to be heated to 1280°C at a heating rate of 5°C / min, kept at this temperature for 0.6 hours, and then allowed to cool naturally to obtain a medium-high aluminum electric porcelain hollow insulator.

[0038] Beneficial effects of the present invention:

[0039] 1. The bauxite in the clay material for the medium and high aluminum electric porcelain hollow insulator of the present invention is a specially treated refined bauxite. The bauxite is placed in an acidic oxalic acid solution with a pH value less than 2. 2 O 3 The surface is passivated by hydroxyl groups and cannot be hydrolyzed, so oxalic acid preferentially complexes Fe in bauxite. 3+ and Ti 4+ , forming a soluble complex, making the reaction system present a solid-liquid stratification state, and after solid-liquid separation, washing the solid separation with oxalic acid solution to further remove the residual Fe 3+ and Ti 4+ , thereby reducing the content of iron oxide and titanium oxide in bauxite, increasing the concentration of alumina, and thus improving the quality of bauxite, so that it can achieve the same effect as industrial alumina at a cost much lower than industrial alumina.

[0040] 2. The bauxite in the slurry for the medium- and high-aluminum hollow insulators of the present invention is specially treated refined bauxite. The bauxite particles are coated with polysilazane resin powder and hexagonal boron nitride nanosheets and then calcined. During this process, the bauxite is dehydrated and its pores shrink. The released water molecules are discharged onto the polysilazane resin powder and hexagonal boron nitride nanosheets on the surface of the bauxite, causing the polysilazane resin powder to absorb water and undergo hydrolysis and cross-linking. Simultaneously, the hexagonal boron nitride nanosheets are arranged in a π-π stacking pattern to form a layered film that coats the outer surface of the bauxite. At high calcination temperatures, the layered film has a higher thermal expansion coefficient than alumina. Therefore, during cooling, the shrinkage stress of the outer film promotes the contraction of the bauxite inside, resulting in smaller pores and increased density. The resulting refined bauxite is used as the main raw material to make hollow insulators of insulators, which significantly improves their mechanical strength. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in literature in the field or in accordance with product specifications. The materials and reagents used in the following examples, unless otherwise specified, were commercially available. For example, the bauxite, polysilazane, hexagonal boron nitride nanosheets, platinum metal, aluminum powder, kaolin, quartz, and potassium sodium tartrate used in the following preparations, examples, and comparative examples were obtained as follows.

[0043] Bauxite: purchased from Lingshou County Wanzhu Mineral Products Co., Ltd.

[0044] Polysilazane: purchased from Guangzhou Honghai Chemical Technology Co., Ltd.

[0045] Hexagonal boron nitride nanosheets: purchased from Zhejiang Yamei Nanotechnology Co., Ltd. (hBN-500nm);

[0046] Platinum metal: purchased from Beijing Global Jinxin International Technology Co., Ltd.; purity ≥99.95;

[0047] Aluminum powder: purchased from Yuanyang Technology; purity greater than or equal to 99.95%;

[0048] Kaolin: A mixture of Guangdong washed clay, Zuoyun clay-black, Zuoyun clay-white, Zhangcun clay, and ash clay in the ratio of 25:5:5:15:3, wherein Guangdong washed clay was purchased from Guangzhou Jialang Trading Co., Ltd., Zuoyun clay-black and Zuoyun clay-white were purchased from Datong Zuoyun Clay Factory, Zhangcun clay was purchased from Shahe Shunda Papermaking Clay Factory, and ash clay was purchased from Jilin Province Ash Ball Clay Company;

[0049] Quartz: purchased from Zhongxun Holding Group;

[0050] Potassium sodium tartrate: purchased from Tianjin Dingshengxin Chemical Co., Ltd.; CAS No. 304-59-6.

[0051] Preparation Example 1

[0052] Preparation of refined bauxite:

[0053] Step 1: crush the bauxite to a particle size of <50 μm using a vertical ultrafine grinding device, then add it to a ball mill, use zirconium oxide as the grinding ball, and ball mill for 3 hours under an inert atmosphere at a ball-to-material ratio of 10:1 and a speed of 650 rpm. After ball milling, add an oxalic acid solution with a pH of <2 and a concentration of 1.5 mol / L at a material-liquid ratio of 1 g:8 mL, stir and react at 35°C for 2 hours, and then transfer it to a vacuum filter for vacuum filtration separation. The obtained solid separator is then washed three times with a 0.1 mol / L oxalic acid solution. The washed solid separator is transferred to a drying oven and dried at 90°C for 2 hours to obtain a solid residue;

[0054] Step 2: Mix 10 parts of polysilazane resin powder and 1 part of hexagonal boron nitride nanosheets by weight, then put them into a stirring tank together with 0.01 parts of metal platinum and 90 parts of solid slag and mix them evenly. Then transfer them to a heating furnace and calcine them at 520°C for 1.5 hours to obtain refined bauxite.

[0055] Comparative Preparation Example 1

[0056] Preparation of refined bauxite:

[0057] Step 1: crush the bauxite to a particle size of less than 50 μm using a vertical ultrafine grinding device, then add the bauxite to a ball mill, use zirconium oxide as grinding balls, and ball mill for 3 hours under an inert atmosphere at a ball-to-material ratio of 10:1 and a rotation speed of 650 rpm to obtain a solid slag;

[0058] Step 2: Mix 10 parts of polysilazane resin powder and 1 part of hexagonal boron nitride nanosheets by weight, then put them into a stirring tank together with 0.01 parts of metal platinum and 90 parts of solid slag, mix them evenly, and calcine them at 520°C for 1.5 hours to obtain refined bauxite.

[0059] Comparative Preparation Example 2

[0060] Preparation of refined bauxite:

[0061] Step 1: crush the bauxite to a particle size of <50 μm using a vertical ultrafine grinding device, then add it to a ball mill, use zirconium oxide as the grinding ball, and ball mill for 3 hours under an inert atmosphere at a ball-to-material ratio of 10:1 and a speed of 650 rpm. After ball milling, add an oxalic acid solution with a pH of <2 and a concentration of 1.5 mol / L at a material-liquid ratio of 1 g:8 mL, stir and react at 35°C for 2 hours, and then transfer it to a vacuum filter for vacuum filtration separation. The obtained solid separator is then washed three times with a 0.1 mol / L oxalic acid solution. The washed solid separator is transferred to a drying oven and dried at 90°C for 2 hours to obtain a solid residue;

[0062] Step 2: The solid slag is then transferred into a heating furnace and calcined at 520° C. for 1.5 hours to obtain refined bauxite.

[0063] Comparative Preparation Example 3

[0064] Step 1: crush the bauxite to a particle size of less than 50 μm using a vertical ultrafine grinding device, then add the bauxite to a ball mill, use zirconium oxide as grinding balls, and ball mill for 3 hours under an inert atmosphere at a ball-to-material ratio of 10:1 and a rotation speed of 650 rpm to obtain a solid slag;

[0065] Step 2: The solid slag is then transferred into a heating furnace and calcined at 520° C. for 1.5 hours to obtain refined bauxite.

[0066] The particle size of the refined bauxite of Preparation Example 1 and Comparative Preparation Examples 1-3 was measured by using a laser particle size analyzer S3500 to detect the particle size distribution of the refined bauxite.

[0067] The test results are listed in Table 1, which is as follows:

[0068] Table 1

[0069] Preparation Example 1 Comparative Preparation Example 1 Comparative Preparation Example 2 Comparative Preparation Example 3 D10 0.25 0.62 0.75 0.91 D50 1.51 2.96 5.21 7.15 D90 5.25 13.26 20.12 25.21

[0070] By analyzing the data in Table 1, it can be seen that compared with Comparative Preparation Examples 1-3, the refined bauxite prepared in Preparation Example 1 has a significantly finer particle size.

[0071] Example 1

[0072] This embodiment discloses a clay material for medium- and high-aluminum electrical porcelain hollow insulators, which is composed of the following raw materials in parts by weight: 30 parts of refined bauxite of Preparation Example 1, 20 parts of aluminum powder, 25 parts of kaolin, 8 parts of quartz, and 8 parts of potassium sodium tartrate.

[0073] Example 2

[0074] This embodiment discloses a clay material for medium- and high-aluminum electrical porcelain hollow insulators, which is composed of the following raw materials in parts by weight: 28 parts of refined bauxite of Preparation Example 1, 18 parts of aluminum powder, 22 parts of kaolin, 6 parts of quartz, and 6 parts of potassium sodium tartrate.

[0075] Example 3

[0076] This embodiment discloses a clay material for medium- and high-aluminum electrical porcelain hollow insulators, which is composed of the following raw materials in parts by weight: 32 parts of refined bauxite of Preparation Example 1, 22 parts of aluminum powder, 28 parts of kaolin, 9 parts of quartz, and 9 parts of potassium sodium tartrate.

[0077] Example 4

[0078] This embodiment discloses a clay material for medium- and high-aluminum electrical porcelain hollow insulators, which is composed of the following raw materials in parts by weight: 25 parts of refined bauxite of Preparation Example 1, 15 parts of aluminum powder, 20 parts of kaolin, 5 parts of quartz, and 5 parts of potassium sodium tartrate.

[0079] Example 5

[0080] This embodiment discloses a clay material for medium- and high-aluminum electrical porcelain hollow insulators, which is composed of the following raw materials in parts by weight: 35 parts of refined bauxite of Preparation Example 1, 25 parts of aluminum powder, 30 parts of kaolin, 10 parts of quartz, and 10 parts of potassium sodium tartrate.

[0081] Example 6

[0082] This embodiment discloses a method for preparing clay for medium- and high-aluminum hollow insulators, which is carried out in the following steps:

[0083] Step 1, ball milling; the raw material components of the high aluminum hollow insulator clay of Example 1 were put into a ball mill in parts by weight, with Hao oxide as the grinding ball, according to the material: ball: water = 1:2:1.5 ratio, adding grinding balls and water, and then setting the ball milling time to 15h;

[0084] Step 2: Sieve the ball-milled slurry through a 250-mesh sieve, and return the slurry that does not pass through the sieve to the mill until it is completely sieved.

[0085] Step 3: Remove iron: Use a magnet to repeatedly remove iron from the sieved slurry until there is no obvious increase in iron filings on the magnet;

[0086] Step 4: Squeeze the mud; dehydrate the mud by filtering it with a filter press and press it into a mud cake;

[0087] Step 5: Aging: Remove the middle part of the squeezed mud cake with more water and age it for 24 hours;

[0088] Step 6: Vacuum mud refining: Place the aged mud cake in a vacuum mud refining machine and repeatedly refine the mud to remove excess air;

[0089] Step seven, sample preparation; the mud cake after kneading is made into a cylindrical hollow insulator mold blank with a length of 10 cm, an outer diameter of 5 cm, and an inner diameter of 2 cm;

[0090] Firing: Heat the mold to 650-800℃ at a heating rate of 5℃ / min in a reducing atmosphere, keep it warm for 3.5h, then continue to heat it to 1280℃ at a heating rate of 5℃ / min, keep it warm for 0.6h, and wait for natural cooling to obtain medium-high aluminum electrical porcelain hollow insulators.

[0091] Example 7

[0092] This embodiment discloses a method for preparing a clay material for medium-high aluminum insulators. Compared with Example 4, the only difference is that in step 1, the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 1 are replaced by the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 2, and the other steps and conditions remain the same, and finally a medium-high aluminum insulator is prepared.

[0093] Example 8

[0094] This embodiment discloses a method for preparing a clay material for medium-high aluminum insulators. Compared with Example 4, the only difference is that the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 1 are replaced by the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 3, and the other steps and conditions remain the same, and finally a medium-high aluminum insulator is prepared.

[0095] Example 9

[0096] This embodiment discloses a method for preparing a clay material for medium-high aluminum insulators. Compared with Example 4, the only difference is that the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 1 are replaced by the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 4, and the other steps and conditions remain the same, and finally a medium-high aluminum insulator is prepared.

[0097] Example 10

[0098] This embodiment discloses a method for preparing a clay material for medium-high aluminum insulators. Compared with Example 4, the only difference is that the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 1 are replaced by the raw material components and weight ratios of the clay material for medium-high aluminum insulators in Example 5, and the other steps and conditions remain the same, and finally a medium-high aluminum insulator is prepared.

[0099] Comparative Example 1

[0100] Compared with Example 1, the only difference is that the refined bauxite of Preparation Example 1 is replaced by the refined bauxite of Comparative Preparation Example 1.

[0101] Comparative Example 2

[0102] Compared with Example 1, the only difference is that the refined bauxite of Preparation Example 1 is replaced by the refined bauxite of Comparative Preparation Example 2.

[0103] Comparative Example 3

[0104] Compared with Example 3, the only difference is that the refined bauxite of Preparation Example 1 is replaced by the refined bauxite of Comparative Preparation Example 3.

[0105] Comparative Example 4

[0106] Compared with Example 4, the only difference is that, in step 1, the raw material components and weight proportions of the mud material for medium-high aluminum electrical porcelain hollow insulators in Example 1 are replaced by the raw material components and weight proportions of the mud material for medium-high aluminum electrical porcelain hollow insulators in Comparative Example 1, and the other steps and conditions remain the same, and finally a medium-high aluminum electrical porcelain hollow insulator is obtained.

[0107] Comparative Example 5

[0108] Compared with Example 4, the only difference is that, in step 1, the raw material components and weight proportions of the mud material for medium-high aluminum electrical porcelain hollow insulators in Example 1 are replaced by the raw material components and weight proportions of the mud material for medium-high aluminum electrical porcelain hollow insulators in Comparative Example 2, and the other steps and conditions remain the same, and finally a medium-high aluminum electrical porcelain hollow insulator is obtained.

[0109] Comparative Example 6

[0110] Compared with Example 4, the only difference is that in step 1, the raw material components and weight proportions of the mud material for medium and high aluminum hollow insulators in Example 1 are replaced by the raw material components and weight proportions of the mud material for medium and high aluminum hollow insulators in Comparative Example 3, and the other steps and conditions remain the same, and finally a medium and high aluminum hollow insulator is obtained.

[0111] The performance tests of the medium- and high-aluminum hollow insulators prepared in Examples 6-10 and Comparative Examples 4-6 were conducted, including volume density, open porosity, water absorption, and bending strength. The test methods are as follows:

[0112] Bulk density: Bulk density refers to the ratio of the mass of a material containing pores to its total volume when dry, and is expressed in g / cm 3 , measured with reference to the Archime-des drainage method of GB / T2997-2000;

[0113] Open porosity: Open porosity is the ratio of the volume of all open pores in a material to the total volume of the material, expressed in %, and is measured using the Archimedes drainage method as specified in GB / T 2997-2000.

[0114] Water absorption rate: Water absorption rate is the ratio of the amount of water absorbed by the porcelain sample to the mass of the sample after the porcelain sample is saturated with water. The unit is %, and it is measured by referring to the Archime-des drainage method of GB / T2997-2000.

[0115] Bending strength: Refer to the national standard GB / T 6569-2006 and use a hydraulic universal testing machine for testing.

[0116] Three samples were selected from each group for testing, and the average value of the three tests was taken as the final test result.

[0117] The test results are listed in Table 2, which is as follows:

[0118] Table 2

[0119] <![CDATA[Apparent density (g / cm 3 )]]> Porosity (%) Water absorption (%) Flexural strength (MPa) Example 6 2.95 0.45 0.02 210.10 Example 7 2.89 0.49 0.02 205.25 Example 8 2.91 0.49 0.03 206.14 Example 9 2.91 0.48 0.03 207.52 Example 10 2.90 0.48 0.03 208.10 Comparative Example 4 2.56 0.98 0.24 187.58 Comparative Example 5 2.33 1.21 0.39 165.91 Comparative Example 6 2.01 1.92 0.75 110.32

[0120] By analyzing the data in Table 2, it can be seen that compared with Comparative Examples 4-6, the medium- and high-aluminum hollow insulators prepared in Examples 4-6 have a denser structure and significantly higher bending strength.

[0121] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A clay material for medium and high aluminum hollow insulators, characterized in that: The invention is composed of the following raw materials in parts by weight: 25-35 parts of refined bauxite, 15-25 parts of aluminum powder, 20-30 parts of kaolin, 5-10 parts of quartz, and 5-10 parts of potassium and sodium additives; Wherein, the refined bauxite is prepared by the following method: Step 1: crush and ball-mill the bauxite, add it to an oxalic acid solution 1 with a pH value less than 2, stir and react at 25-40° C. for 1-3 hours, separate the solid and liquid, wash with an oxalic acid solution 2, and dry to obtain a solid residue; Step 2: Mix the polysilazane resin powder and hexagonal boron nitride nanosheets evenly, then add the catalyst and solid slag and mix evenly, and calcine at 500-550° C. for 1.5 hours to obtain refined bauxite.

2. The clay material for medium and high aluminum hollow insulators according to claim 1 is characterized in that: In step 1, the bauxite is crushed to a particle size of less than 50 μm and then ball milled. The ball milling step is as follows: the crushed bauxite is placed in a ball mill, zirconium oxide is used as grinding balls, and the ball-to-material ratio is 10:1, the rotation speed is 500-800 rpm, and the ball milling is carried out for 2-4 hours under an inert atmosphere.

3. The clay material for medium and high aluminum hollow insulators according to claim 1, characterized in that: In step 1, the concentration of the oxalic acid solution 1 is 1-2 mol / L, and the usage ratio of the bauxite to the oxalic acid solution is 1 g:(5-10) mL.

4. The clay material for medium and high aluminum hollow insulators according to claim 1, characterized in that: In step 1, the solid-liquid separation method is vacuum filtration separation.

5. The clay material for medium and high aluminum hollow insulators according to claim 1, characterized in that: In step 1, the concentration of the oxalic acid solution 2 is 0.1 mol / L.

6. The clay material for medium and high aluminum hollow insulators according to claim 1, characterized in that: In step 1, the drying method is: drying the washed bauxite at 80-100° C. for 2 hours.

7. The clay material for medium and high aluminum hollow insulators according to claim 1, characterized in that: In step 2, the weight ratio of the polysiloxane resin powder, hexagonal boron nitride nanosheets, catalyst and solid slag is 10:1:0.01:(80-100).

8. The clay material for medium and high aluminum hollow insulators according to claim 1 is characterized in that: The kaolin is a mixture of Guangdong washed mud, Zuoyun mud-black, Zuoyun mud-white, Zhangcun mud and ash mud in the ratio of 25:5:5:15:

3.

9. The clay material for medium and high aluminum hollow insulators according to claim 1, characterized in that: The potassium and sodium additives are potassium sodium tartrate or a mixture of potassium nitrite and sodium nitrite in a weight ratio of 1:

1.

10. A process for preparing clay for medium- and high-aluminum hollow porcelain insulators according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: mixing refined bauxite, aluminum powder, kaolin, quartz and potassium and sodium additives in proportion, then ball milling, sieving, iron removal, mud squeezing, aging, vacuum mud kneading, sample preparation and firing to obtain medium-high aluminum electrical porcelain hollow insulators.