An extruded magnesium oxide tube and its processing technology

Abstract

This invention discloses an extruded magnesium oxide tube and its processing technology, relating to the field of functional ceramics. The process comprises the following steps: ball-milling magnesium oxide and inorganic auxiliary materials; adding a binder, extruding, and sintering to produce the magnesium oxide tube. The inorganic auxiliary materials are a mixture of aluminum oxide and titanium boride in a mass ratio of (0.5-3.0):1. By adding the inorganic auxiliary materials, the aluminum oxide and magnesium oxide undergo a solid-phase reaction to form a magnesium-aluminum spinel phase, improving the thermal shock stability, high-temperature resistance, and thermal conductivity of the sintered product. The introduced titanium boride reacts with volatile gases generated during the sintering of the binder, synergizing with the sintered products of the binder to form a three-dimensional ceramic between the magnesium oxide particles, improving the hardness, high-temperature resistance, and stability of the sintered product and enhancing its heat transfer efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of functional ceramics, in particular to an extruded magnesium oxide tube and a processing technology thereof. Background Art

[0002] Due to their excellent high-temperature insulation and thermal conductivity, magnesium oxide products are widely used in high-temperature insulation applications such as electric heating pipes, armored heating cables, and temperature measuring wires. As a functional ceramic, magnesium oxide products are often manufactured in the form of magnesium oxide tubes, which are formed by mixing magnesium oxide with a binder, extruding it, and then sintering it. Using an aqueous binder can cause the magnesium oxide to hydrate, forming magnesium hydroxide. This can severely affect the extrusion performance of the magnesium oxide, resulting in poor quality of the sintered magnesium oxide tubes. Therefore, we propose an extruded magnesium oxide tube and its processing technology. Summary of the Invention

[0003] The object of the present invention is to provide an extruded magnesium oxide tube and a processing technology thereof to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solution: an extruded magnesium oxide tube, comprising the following components by mass: 92 to 96 parts of magnesium oxide, 4 to 8 parts of inorganic auxiliary materials, and 1 to 16 parts of a binder.

[0005] Furthermore, the inorganic auxiliary material is a mixture of one or more of silicon dioxide, aluminum oxide, titanium dioxide, magnesium fluoride, and titanium boride.

[0006] Furthermore, the binder is one of a cellulose binder and an organosilicon binder, or a mixture of the two.

[0007] A processing technology for extruded magnesium oxide tubes, comprising the following processes:

[0008] The magnesium oxide and inorganic auxiliary materials are mixed and ball-milled; a binder is added, extruded and sintered to obtain a magnesium oxide tube.

[0009] Furthermore, the ball milling process conditions are: a rotation speed of 300-500 r / min for 3-6 hours; then, the powder is sieved through a 300-600 mesh screen. 2-4 wt% oleic acid is added during the ball milling process to assist in the milling process. After the ball mill is sieved, the powder is magnetically conveyed to remove iron.

[0010] After extrusion molding, the products are dried, cut and laid flat, air-dried, bundled, cut, blown into powder, and packed in saggers. They are then sintered at high temperature (the above sintering). After sintering, they are inspected and packaged.

[0011] Furthermore, the sintering process conditions are as follows: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1520-1600°C at a rate of 5°C / min, keeping warm for 2-3 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0012] Furthermore, after ball milling, a boric acid compound is added to the magnesium oxide and the inorganic auxiliary material, and the mixture is stirred at a rotation speed of 300 to 500 rpm for 10 to 30 minutes.

[0013] Furthermore, the inorganic auxiliary material is a mixture of aluminum oxide and titanium boride, with a mass ratio of (0.5-3.0):1.

[0014] In the above technical scheme, nano-aluminum oxide is selected as an inorganic auxiliary material to participate in the solid phase sintering of magnesium oxide. The tiny particles of nano-aluminum oxide are diffusely distributed around the magnesium oxide grains by diffusion, and as the sintering reaction proceeds, they gradually diffuse to the magnesium oxide grain boundaries and grain boundary pores, and react with magnesium oxide in a solid phase to generate magnesium aluminum spinel phase. As the amount of alumina increases, the magnesium aluminum spinel phase grains gradually grow up, pinned at the grain boundaries, filling the pore positions, inhibiting the grain boundary movement of the magnesium oxide grains, hindering their growth, thereby promoting the densification of the sintered product system structure, and its densification degree deepens with the increase of sintering temperature. The doping of the magnesium aluminum spinel phase formed in the sintered product in the magnesium oxide sintered product can effectively improve the thermal shock resistance and corrosion resistance of the sintered product. At the same time, its thermal conductivity is high, which can assist in improving the high temperature resistance and thermal conductivity of the sintered product, and is more suitable for the use environment of the magnesium oxide tube.

[0015] Titanium boride has high hardness, thermal conductivity, and high-temperature resistance, effectively improving the strength, hardness, high-temperature resistance, and thermal conductivity of magnesium oxide sintered products. When used as an inorganic auxiliary material and mixed with magnesium oxide and aluminum oxide for sintering, it undergoes partial oxidation to form titanium dioxide, an oxidation product that can replace aluminum oxide and synthesize magnesium titanate with magnesium oxide, further improving the thermal stability, high-temperature resistance, and insulation properties of the sintered product.

[0016] Furthermore, the amount of the boric acid compound is 3.9 to 10% of the mass of the binder;

[0017] The boronic acid compound is one of aminophenylboronic acid, pyridine-4-boronic acid, 4-pyrazoleboronic acid, 5-pyrimidineboronic acid, (2-methylpyrimidin-5-yl)boric acid, 2-aminopyrimidine-5-boric acid, and 6-aminopyridineboronic acid.

[0018] Furthermore, the binder is one of hydroxy silicone resin and polycarbosilane or a mixture of the two. Polycarbosilane is prepared by the following process:

[0019] Under nitrogen atmosphere, chloromethyltrichlorosilane and magnesium are mixed in tetrahydrofuran, polychlorosilane is slowly added, and the mixture is reacted at 55-65°C for 15-20 hours; the mixture is cooled to 45-52°C, an alcohol compound is added, and the mixture is refluxed for 3-5 hours; the pH value of the system is adjusted to neutral by rotary evaporation, the mixture is filtered, the precipitate is washed, and dried to obtain polycarbosilane.

[0020] Furthermore, the polychlorosilane is a mixture of one or more of 1,1,3,3-tetrachloro-1,3-disiloxane, bis(trichlorosilyl)methane, and 1,2-dimethyl-1,1,2,2-tetrachlorodisilane.

[0021] Furthermore, the molar ratio of chloromethyltrichlorosilane to polychlorosilane is 10:(0.5-2.0);

[0022] The ratio of chloromethyltrichlorosilane, magnesium (chips), and tetrahydrofuran is 10g: (1.5-2.7)g: (50-200)mL.

[0023] Furthermore, the alcohol compound is ethanol or methanol;

[0024] The molar ratio of polychlorosilane to alcohol compound is 1:(1.5-2.2).

[0025] Furthermore, when the above-mentioned adhesive is used, it is hot-pressed and cured after extrusion molding, and the process is as follows: heat to 100°C, and increase the temperature to 120-150°C at a rate of 5°C / min under a pressure of 6-12 MPa, and keep the temperature and pressure for 30-60 minutes; then cool to room temperature.

[0026] In the above technical scheme, powder is mixed with boric acid compound, boric acid compound is loaded on powder surface, forms organic coating layer, can effectively suppress the agglomeration and sedimentation of powder, improve the compatibility and dispersibility between powder and binder, obtain better processing fluidity, improve the extrusion processing ability of mixing. Under hot pressing curing conditions, boric acid compound and binder cross-linking curing reaction occurs, forms a network structure coated on the surface of powder, forms organic coating layer, builds the interface structure of powder and binder, improves mixture extrusion ability, and product to be sintered is tentatively fixed, can effectively resist shrinkage, deformation during sintering, prevent the deformation caused by thermal stress deformation caused by temperature gradient, the residual stress produced by suppressing at high temperature release caused pores, crack propagation etc. in product to be sintered, prevent sintering collapse, particle shedding to a certain extent, improve sintering quality. Boric acid compound selects nitrogen-containing boric acid compound, is stronger than the adsorbability of powder, and has better compatibility with binder, participates in condensation reaction, promotes system solidification.

[0027] In the above technical solution, during the sintering process, the organic groups such as methyl, hydroxyl, and phenyl on the side chains of the binder components undergo chemical reactions such as oxidation, dehydrogenation, and decomposition, resulting in thermal cracking behavior and overflow of gaseous volatiles. Its components, carbon monoxide, water, and oxygen in the sintering atmosphere can react with boron carbide to produce a ceramic reaction, which reduces the influence of gas on the quality of the sintered product to a certain extent, forms a refractory ceramic phase (boron oxide, titanium oxide), and improves the strength of the sintered product; the degree of doping with aluminum oxide, magnesium oxide, etc. increases, thereby improving the thermal stability, high temperature resistance, and electrical insulation properties of the sintered product; as the temperature rises, the silicon-oxygen bonds in the main chain of the binder break and rearrange, and the silicon methyl is thermally oxidized. The rigid groups and high bond energy BO bonds in the boric acid compound can delay the degradation of the binder at high temperature, thereby promoting the ceramic reaction and realizing the organic-inorganic ceramic transformation; the hydroxy silicone resin contained in the binder forms silicon dioxide after sintering, diffuses and reacts with MgO The solid-phase reaction can cooperate with the above-mentioned ceramic phase as a reinforcing phase to fill the pores between the magnesium oxide particles, making the magnesium oxide particles more densely bonded, promoting the formation of sintering necks between the particles, alleviating the thermal resistance caused by the pores, and improving the heat transfer efficiency between the magnesium oxide particles, thereby improving the strength and comprehensive thermal properties of the sintered products such as thermal conductivity and thermal shock resistance.

[0028] The binder also contains polycarbosilane, which is specifically a Grignard reagent prepared from chloromethyltrichlorosilane and magnesium, and is obtained by hydrolysis after coupling reaction with polychlorosilane. The product has a branched structure and multiple hydroxyl groups, which can effectively reduce the viscosity of the binder, reduce the use of water in the binder, and prevent the hydration of magnesium oxide; the cross-linking of polycarbosilane and boric acid compounds enables the product formed after hot pressing and curing to resist thermal stress deformation during the sintering process, alleviate the negative impact of residual stress, vibration, and impact on the sintered product, improve the degree of cross-linking between the binder and the boric acid compound, and effectively promote the close bonding between the powders.

[0029] After sintering, polycarbosilane produces amorphous silicon carbide, silicon dioxide, and carbon. The mixing and cross-linking of polycarbosilane with hydroxy silicone resin helps reduce the free carbon after sintering, alleviates its negative impact on the strength and insulation properties of the sintered product, and forms three-dimensional silicon carbide ceramics between the magnesium oxide particles, which can further improve the hardness, high temperature resistance, and stability of the sintered product and enhance its heat transfer efficiency. In addition, carbon can improve the thermal shock resistance of the sintered product, reduce the thermal expansion mismatch between magnesium oxide particles, enhance the material's ability to withstand rapid temperature changes, strengthen the bonding between magnesium oxide particles, improve the material's mechanical strength and toughness, and prevent particles from falling off and material collapse during sintering. It can also act as a shield, preventing or reducing the reaction of oxygen in the sintered product at high temperatures, improving the material's antioxidant capacity, and thus enabling the material to obtain good overall performance. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] In the following specific embodiments,

[0032] Magnesium oxide (MgO): AR, average particle size 3.31 μm, from Sinopharm Chemical Reagent Co., Ltd.

[0033] Alumina (Al2O3): D50 = 1-1.8 μm, sourced from Zhengzhou Xinli Wear-Resistant Materials Co., Ltd.

[0034] Titanium boride (TiB2): RDB-NM-049, average particle size 1-3 μm, from Shanghai Yanbei New Materials Technology Co., Ltd.

[0035] Silicon dioxide (SiO2): AR, average particle size 50 nm, from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0036] Magnesium chips: purity> 99%, sourced from Tianjin Hainachuan Technology Co., Ltd.

[0037] Hydroxy silicone resin: IOTA-8865H, from Anhui Aiyota Silicone Oil Co., Ltd.

[0038] Extrusion molding was carried out in a vacuum extruder with the following process: vacuum degree -0.090MPa, extrusion pressure 10MPa;

[0039] When using the binder in Examples 1-3 and Comparative Examples 1-3, it was added in the form of an emulsion, where the "parts" are the mass of the binder. The emulsion was formed by mixing the binder and water and stirring at a speed of 3000 rpm for 30 minutes. The solid content of the emulsion was 54%.

[0040] Example 1: A process for producing an extruded magnesium oxide tube, comprising the following steps:

[0041] Step 1: Under nitrogen atmosphere, chloromethyltrichlorosilane and magnesium chips are mixed in tetrahydrofuran, polychlorosilane is slowly added, and the mixture is reacted at 55°C for 20 hours; cooled to 45°C, ethanol is added, and the mixture is refluxed for 5 hours; rotary evaporation is performed to adjust the pH of the system to neutral, the mixture is filtered, the precipitate is washed, and dried to obtain polycarbosilane; the polychlorosilane is 1,1,3,3-tetrachloro-1,3-disiloxane; the molar ratio of chloromethyltrichlorosilane to polychlorosilane is 10:0.5; the ratio of chloromethyltrichlorosilane, magnesium chips, and tetrahydrofuran is 10 g:1.5 g:50 mL; and the molar ratio of polychlorosilane to ethanol or methanol is 1:1.5;

[0042] Step 2: Mix magnesium oxide and inorganic auxiliary materials and ball mill them. The ball milling process conditions are: speed 300 r / min, time length 6 hours; then pass through a 600 mesh sieve, and add 2wt% oleic acid to assist the ball milling. The inorganic auxiliary materials are a mixture of aluminum oxide and titanium boride, with a mass ratio of 3.0:1;

[0043] Then, a boric acid compound was added and mixed, and stirred at a speed of 300 rpm for 10 minutes; the amount of the boric acid compound was 3.9% of the mass of the binder; the boric acid compound was aminophenylboric acid;

[0044] Add a binder, extrude, hot-press and cure, and sinter to obtain a magnesium oxide tube. The magnesium oxide tube includes the following mass components: 96 parts of magnesium oxide, 4 parts of inorganic auxiliary materials, and 3 parts of a binder; the binder is a mixture of hydroxy silicone resin and polycarbosilane with a mass ratio of 4:1; the hot-press curing process is: heating to 100°C, and under a pressure of 10 MPa, heating to 120°C at a rate of 5°C / min, keeping warm and pressurizing for 30 minutes, and cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1520°C at a rate of 5°C / min, keeping warm for 3 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0045] Example 2: A process for producing an extruded magnesium oxide tube, comprising the following steps:

[0046] Step 1: Under nitrogen atmosphere, chloromethyltrichlorosilane and magnesium chips are mixed in tetrahydrofuran, polychlorosilane is slowly added, and the mixture is reacted at 60°C for 18 hours; cooled to 48°C, ethanol is added, and the mixture is refluxed for 4 hours; rotary evaporation is performed to adjust the pH of the system to neutral, the mixture is filtered, the precipitate is washed, and dried to obtain polycarbosilane; the polychlorosilane is di(trichlorosilyl)methane; the molar ratio of chloromethyltrichlorosilane to polychlorosilane is 10:1.2; the ratio of chloromethyltrichlorosilane, magnesium chips, and tetrahydrofuran is 10 g:2.1 g:100 mL; and the molar ratio of polychlorosilane to ethanol or methanol is 1:1.8;

[0047] Step 2: Mix magnesium oxide and inorganic auxiliary materials and ball mill them. The ball milling process conditions are: speed 400 r / min, time length 4.5 hours; then pass through a 600 mesh sieve, and add 3wt% oleic acid to assist the ball milling. The inorganic auxiliary materials are a mixture of aluminum oxide and titanium boride, with a mass ratio of 1.8:1.

[0048] Then, a boric acid compound was added and mixed, and stirred at a speed of 400 rpm for 20 minutes; the amount of the boric acid compound was 7.0% of the mass of the binder; the boric acid compound was 4-pyrazoleboric acid;

[0049] Add a binder, extrude, hot-press and cure, and sinter to obtain a magnesium oxide tube. The magnesium oxide tube includes the following mass components: 94 parts of magnesium oxide, 6 parts of inorganic auxiliary materials, and 6 parts of a binder; the binder is a mixture of hydroxy silicone resin and polycarbosilane with a mass ratio of 2.5:1; the hot-press curing process is: heating to 100°C, and under a pressure of 12 MPa, heating to 135°C at a rate of 5°C / min, keeping warm and pressurizing for 45 minutes, and cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1560°C at a rate of 5°C / min, keeping warm for 2.5 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0050] Example 3: A process for producing an extruded magnesium oxide tube, comprising the following steps:

[0051] Step 1: Under nitrogen atmosphere, chloromethyltrichlorosilane and magnesium chips are mixed in tetrahydrofuran, polychlorosilane is slowly added, and the mixture is reacted at 65°C for 15 hours; cooled to 52°C, ethanol is added, and the mixture is refluxed for 4 hours; rotary evaporation is performed to adjust the pH of the system to neutral, the mixture is filtered, the precipitate is washed, and dried to obtain polycarbosilane; the polychlorosilane is 1,2-dimethyl-1,1,2,2-tetrachlorodisilane; the molar ratio of chloromethyltrichlorosilane to polychlorosilane is 10:2; the ratio of chloromethyltrichlorosilane, magnesium chips, and tetrahydrofuran is 10 g:2.7 g:200 mL; and the molar ratio of polychlorosilane to ethanol or methanol is 1:2.2;

[0052] Step 2: Mix magnesium oxide and inorganic auxiliary materials and ball mill them. The ball milling process conditions are: speed 500r / min, time length 3h; then pass through a 600-mesh sieve, and add 4wt% oleic acid to assist the ball milling. The inorganic auxiliary materials are a mixture of aluminum oxide and titanium boride, with a mass ratio of 3:1.

[0053] Then, a boric acid compound was added and mixed, and stirred at a speed of 500 rpm for 30 minutes; the amount of the boric acid compound was 10% of the mass of the binder; the boric acid compound was 2-aminopyrimidine-5-boric acid;

[0054] Add a binder, extrude, hot-press and cure, and sinter to obtain a magnesium oxide tube. The magnesium oxide tube includes the following mass components: 92 parts of magnesium oxide, 8 parts of inorganic auxiliary materials, and 9 parts of a binder; the binder is a mixture of hydroxy silicone resin and polycarbosilane with a mass ratio of 1:1; the hot-press curing process is: heating to 100°C, and under a pressure of 15 MPa, heating to 150°C at a rate of 5°C / min, keeping warm and pressurizing for 60 minutes, and cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1600°C at a rate of 5°C / min, keeping warm for 2 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0055] Comparative Example 1: A processing technology for an extruded magnesium oxide tube, comprising the following processes:

[0056] Step 1: Under nitrogen atmosphere, chloromethyltrichlorosilane and magnesium chips are mixed in tetrahydrofuran, polychlorosilane is slowly added, and the mixture is reacted at 55°C for 20 hours; cooled to 45°C, ethanol is added, and the mixture is refluxed for 5 hours; rotary evaporation is performed to adjust the pH of the system to neutral, the mixture is filtered, the precipitate is washed, and dried to obtain polycarbosilane; the polychlorosilane is 1,1,3,3-tetrachloro-1,3-disiloxane; the molar ratio of chloromethyltrichlorosilane to polychlorosilane is 10:0.5; the ratio of chloromethyltrichlorosilane, magnesium chips, and tetrahydrofuran is 10 g:1.5 g:50 mL; and the molar ratio of polychlorosilane to ethanol or methanol is 1:1.5;

[0057] Step 2: Mix magnesium oxide and inorganic auxiliary materials and ball mill them. The ball milling process conditions are: speed 300 r / min, time length 6 hours; then pass through a 600 mesh sieve, and add 2wt% oleic acid to assist the ball milling. The inorganic auxiliary materials are a mixture of aluminum oxide and titanium boride, with a mass ratio of 3.0:1;

[0058] Add a binder, extrude, hot-press and cure, and sinter to obtain a magnesium oxide tube. The magnesium oxide tube includes the following mass components: 96 parts of magnesium oxide, 4 parts of inorganic auxiliary materials, and 3 parts of a binder; the binder is a mixture of hydroxy silicone resin and polycarbosilane with a mass ratio of 4:1; the hot-press curing process is: heating to 100°C, and under a pressure of 10 MPa, heating to 120°C at a rate of 5°C / min, keeping warm and pressurizing for 30 minutes, and cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1520°C at a rate of 5°C / min, keeping warm for 3 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0059] Comparative Example 2: A processing technology for an extruded magnesium oxide tube, comprising the following processes:

[0060] The magnesium oxide and inorganic auxiliary materials were mixed and ball-milled at a speed of 300 r / min for 6 hours. The mixture was then passed through a 600-mesh sieve and 2 wt% oleic acid was added to assist the milling. The inorganic auxiliary materials were a mixture of aluminum oxide and titanium boride at a mass ratio of 3.0:1.

[0061] Add a binder, extrude, hot-press cure, and sinter to obtain a magnesium oxide tube, which includes the following mass components: 96 parts of magnesium oxide, 4 parts of inorganic auxiliary materials, and 3 parts of a binder; the binder is a hydroxy silicone resin; the hot-press curing process is: heating to 100°C, and under a pressure of 10 MPa, heating to 120°C at a rate of 5°C / min, keeping warm and pressurizing for 30 minutes, and cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1520°C at a rate of 5°C / min, keeping warm for 3 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0062] Comparative Example 3: A processing technology for an extruded magnesium oxide tube, comprising the following processes:

[0063] Mix magnesium oxide and inorganic auxiliary materials, and ball mill them. The ball milling process conditions are: speed 300r / min, time length 6h; then pass through a 600 mesh sieve, and add 2wt% oleic acid to assist the ball milling. The inorganic auxiliary material is aluminum oxide.

[0064] Add a binder, extrude, hot-press cure, and sinter to obtain a magnesium oxide tube, which includes the following mass components: 96 parts of magnesium oxide, 4 parts of inorganic auxiliary materials, and 3 parts of a binder; the binder is a hydroxy silicone resin; the hot-press curing process is: heating to 100°C, and under a pressure of 10 MPa, heating to 120°C at a rate of 5°C / min, keeping warm and pressurizing for 30 minutes, and cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1520°C at a rate of 5°C / min, keeping warm for 3 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0065] Comparative Example 4: A processing technology for an extruded magnesium oxide tube, comprising the following processes:

[0066] Mix magnesium oxide and inorganic auxiliary materials, and ball mill them. The ball milling process conditions are: speed 300r / min, time length 6h; then pass through a 600 mesh sieve, and add 2wt% oleic acid to assist the ball milling. The inorganic auxiliary material is silicon dioxide.

[0067] Add a binder, extrude, dry, and sinter to obtain a magnesium oxide tube, which includes the following mass components: 96 parts of magnesium oxide, 4 parts of inorganic auxiliary materials, and 4 parts of a binder; the binder is a cellulose binder, specifically a 25wt% hydroxypropyl methylcellulose aqueous solution; the drying process conditions are: temperature 100°C, time 10 hours, and then cooling to room temperature; the sintering process conditions are: heating from room temperature to 1000°C at a rate of 10°C / min; heating to 1520°C at a rate of 5°C / min, keeping warm for 3 hours; then cooling to 500°C at a rate of 5°C / min, and cooling to room temperature with the furnace.

[0068] Experiment: Take the magnesium oxide tubes obtained in Examples 1-3 and Comparative Examples 1-4 to prepare samples, test their properties and record the test results:

[0069] Mechanical properties test: A universal testing machine was used to conduct a three-point bending strength test on the specimens at 25°C, with a span of 30 mm and a loading speed of 0.5 mm / min.

[0070] Thermal performance test: Use an electrochemical workstation to test the resistivity of the sample at 600°C;

[0071] Use a thermal conductivity tester to test the thermal conductivity of the sample and take the average value of the 250-950℃ pieces;

[0072] Thermal shock resistance test: Place the sample at 110℃ for 30 minutes, take it out and place it at 960℃ for 30 minutes; take it out and place it in 14℃ running water for rapid cooling for 3 minutes, take it out and dry it at 110℃ for 30 minutes. This is recorded as one thermal shock. Calculate the strength loss rate of the sample after 5 thermal shocks.

[0073]

[0074] According to the data in the above table, we can clearly draw the following conclusions:

[0075] The magnesium oxide tubes obtained in Examples 1-3 were compared with the magnesium oxide tubes obtained in Comparative Examples 1-4. The test results show that:

[0076] Compared with the comparative example, the magnesium oxide tubes obtained in Examples 1-3 have higher resistivity, thermal conductivity, flexural strength data, and lower thermal shock strength loss, which fully demonstrates that the present invention achieves improvements in the mechanical and thermal properties of the magnesium oxide tubes.

[0077] Compared to Example 1, Comparative Example 1 omitted the boric acid compound; Comparative Example 2 omitted the boric acid compound and polycarbosilane, and instead produced a magnesium oxide tube made from magnesium oxide, aluminum oxide, titanium boride, and hydroxy silicone resin; Comparative Example 3 omitted the boric acid compound, polycarbosilane, and titanium boride, and instead produced a magnesium oxide tube made from magnesium oxide, aluminum oxide, and hydroxy silicone resin; and Comparative Example 4 produced a magnesium oxide tube made from magnesium oxide, silicon dioxide, and hydroxypropyl methylcellulose. The magnesium oxide tubes obtained in Comparative Examples 1-4 exhibited decreased resistivity, thermal conductivity, and flexural strength, while increased thermal shock resistance loss. This demonstrates that the present invention's configuration of magnesium oxide tube components and process improves both their mechanical and thermal properties.

[0078] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A process for processing an extruded magnesium oxide tube, characterized in that: Including the following processes: The magnesium oxide and inorganic auxiliary materials are mixed and ball-milled; a binder is added, extruded and sintered to obtain a magnesium oxide tube; The inorganic auxiliary material is a mixture of aluminum oxide and titanium boride; The binder is a mixture of hydroxy silicone resin and polycarbosilane; the polycarbosilane is prepared by the following process: Under nitrogen atmosphere, mix chloromethyltrichlorosilane and magnesium in tetrahydrofuran, slowly add polychlorosilane, and react at 55-65°C for 15-20h; Cool to 45-52°C, add an alcohol compound, and reflux for 3-5 hours; rotary evaporate, adjust the pH of the system to neutral, filter, wash, and dry the precipitate to obtain polycarbosilane; After ball milling, the boric acid compound is added to the magnesium oxide and the inorganic auxiliary material, and the mixture is stirred at a speed of 300 to 500 rpm for 10 to 30 minutes; The boric acid compound is one of aminophenylboronic acid, pyridine-4-boric acid, 4-pyrazoleboric acid, 5-pyrimidineboric acid, (2-methylpyrimidin-5-yl)boric acid, 2-aminopyrimidine-5-boric acid, and 6-aminopyridineboric acid; the amount of the boric acid compound used is 3.9-10% of the mass of the binder.

2. The process for processing an extruded magnesium oxide tube according to claim 1, characterized in that: The magnesium oxide tube comprises the following components by weight: 92 to 96 parts of magnesium oxide, 4 to 8 parts of inorganic auxiliary materials, and 1 to 16 parts of a binder.

3. The process for processing an extruded magnesium oxide tube according to claim 1, characterized in that: The polychlorosilane is a mixture of one or more of 1,1,3,3-tetrachloro-1,3-disiloxane, bis(trichlorosilyl)methane, and 1,2-dimethyl-1,1,2,2-tetrachlorodisilane.

4. The process for processing an extruded magnesium oxide tube according to claim 1, characterized in that: The molar ratio of chloromethyltrichlorosilane to polychlorosilane is 10:(0.5-2.0).

5. The process for processing an extruded magnesium oxide tube according to claim 1, characterized in that: The alcohol compound is ethanol or methanol; the molar ratio of polychlorosilane to the alcohol compound is 1:(1.5-2.2).

6. The process for processing an extruded magnesium oxide tube according to claim 1, characterized in that: When the above-mentioned adhesive is used, it is hot-pressed and cured after extrusion molding. The process is as follows: heat to 100°C, increase the temperature to 120-150°C at a rate of 5°C / min under a pressure of 10-15 MPa, keep warm and pressurized for 30-60 minutes; and then cool to room temperature.

7. An extruded magnesium oxide tube obtained according to the processing technology according to any one of claims 1 to 6.

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