A SiC composite refractory material co-reinforced with Si2N2O and TiN and its preparation method

Abstract

The present invention relates to a SiC composite refractory material co-reinforced with Si2N2O and TiN and a preparation method thereof. The method comprises weighing silicon carbide, silicon powder, and titanium oxide powder as raw materials and a binder according to a proportion, stirring them evenly, and making a slurry; pressing the slurry into a green body, and subjecting the green body to drying, nitriding, and sintering to obtain the SiC composite refractory material co-reinforced with Si2N2O and TiN. The method of the present invention solves the shortcomings and defects of existing Si3N4-SiC composite materials, such as the easy generation of free Si and the poor chemical stability of the Si3N4 binding phase, which leads to poor performance of the material. Compared with Si3N4, both Si2N2O and TiN have better chemical stability. TiN also has excellent corrosion resistance and thermal shock resistance, and Si2N2O has excellent oxidation resistance.

Description

Technical Field

[0001] The present invention belongs to the field of refractory materials, and in particular relates to a SiC composite refractory material co-reinforced by Si2N2O and TiN and a preparation method thereof. Background Art

[0002] Si3N4-SiC composite materials have good alkali corrosion resistance, resistance to molten cryolite wettability, oxidation resistance, wear resistance, high thermal conductivity, thermal shock resistance and extremely low electrical conductivity. They are widely used in the middle and lower parts, waist and belly of large blast furnaces, side walls of aluminum electrolytic cells, waste incinerators, etc.

[0003] The main preparation method of Si3N4-SiC refractory materials is to uniformly mix SiC particles of a certain particle size distribution with silicon powder and a binder, and then form bricks by pressing or vibration. After the bricks are dried, they are sintered in a flowing nitrogen atmosphere. During the nitriding sintering process, Si reacts with N2 to form a Si3N4 binding phase between the SiC particles, giving it a certain strength. The nitriding reaction of Si is exothermic. If the reaction is too intense, the heat will not have enough time to diffuse outward, causing the local temperature to rise sharply. If the local temperature is higher than the melting point of Si (1412°C), the silicon in the raw material will melt into a liquid phase, and the nitrogen will not be able to better contact the unreacted Si, resulting in incomplete Si nitriding and a certain amount of free silicon in the product. Under repeated heating and cooling conditions, free silicon will cause cracks in Si3N4-SiC products, affecting their service life.

[0004] Furthermore, recent studies have shown that elemental Fe promotes the decomposition of Si3N4 at temperatures above 1000°C, producing elemental Si and nitrogen. Furthermore, when a carbon source (solid C and CO) is present in the environment, Si3N4 readily converts to SiC at temperatures above 1500°C, accompanied by volume shrinkage. Therefore, during blast furnace service, the combined effects of the presence of Fe and CO in the environment can easily decompose the Si3N4 binding phase and convert it to SiC, leading to product damage and a reduced service life. When used in aluminum electrolytic cells, the Si3N4 binding phase is also a weak point of the Si3N4-SiC composite material: 1) Si3N4 easily reacts with HF gas to generate SiF4 and corrode; 2) At the electrolysis temperature, Si3N4 will also react with the aluminum liquid to generate AlN and Si, and AlN is very easy to hydrate, which will accelerate the corrosion and damage of the material; 3) Because there is usually a certain amount of sodium in the aluminum liquid, the material is prone to sodium vapor permeation and the permeation of air and anode gas, which leads to a chemical reaction between Na(g) and Si3N4 to generate Na2SiO3, causing corrosion of the material. In summary, during the aluminum electrolysis process, the gas, electrolyte and aluminum liquid will cause the Si3N4 to undergo unstable transformation, resulting in the failure of the Si3N4-SiC composite material.

[0005] The problem of free silicon easily generated during the preparation process of Si3N4-SiC composite refractory materials and the poor stability of the Si3N4 binding phase under service environment have greatly restricted their development and application, making it difficult to meet the increasingly stringent high-temperature service requirements.

[0006] Si2N2O has excellent chemical stability and better resistance to oxidation than Si3N4, but its resistance to slag erosion is slightly inferior to that of Si3N4. TiN has a high melting point, high hardness, good thermal conductivity, is not easily wetted by molten metal and slag, and exhibits excellent chemical stability, making it a non-oxide refractory material with high corrosion and thermal shock resistance. Practical research has shown that TiN deposited on the hearth and bottom of a blast furnace can effectively prevent erosion of the hearth lining by molten iron and slag, thereby extending the service life of the blast furnace. SiC composite refractory materials co-reinforced with Si2N2O and TiN are expected to replace traditional Si3N4-SiC composites and are widely used in high-temperature industries, particularly blast furnace linings, aluminum electrolytic cells, and waste incinerators. Summary of the Invention

[0007] In order to overcome the above problems existing in the prior art, the present invention provides a SiC composite refractory material co-reinforced with Si2N2O and TiN and a preparation method thereof, which are used to solve the above problems existing in the prior art.

[0008] A method for preparing a SiC composite refractory material co-reinforced with Si2N2O and TiN comprises the following steps:

[0009] S1. Silicon carbide, silicon powder, titanium oxide powder as raw materials and binder are weighed according to the ratio, stirred evenly, and made into a clay;

[0010] S2. The clay material in step S1 is pressed into a Si-Ti2O3-SiC composite body, and a SiC composite refractory material reinforced with Si2N2O and TiN is obtained through drying, nitriding and sintering steps.

[0011] According to the above aspects and any possible implementation, an implementation is further provided, wherein the mass fractions of the silicon carbide, silicon powder, and titanium oxide powder as raw materials are: silicon carbide is 65-90wt%, silicon powder is 5-20wt%, and titanium oxide is 5-15wt%, respectively, and the mass percentage of the binder is 2-5wt% of the total amount of the raw materials.

[0012] According to the above aspects and any possible implementation manner, there is further provided an implementation manner, wherein the silicon carbide includes silicon carbide aggregate and silicon carbide fine powder.

[0013] According to the above aspects and any possible implementation, an implementation is further provided, wherein the particle size of the silicon carbide aggregate is 3-1 mm and <1 mm, and the particle size of the silicon carbide fine powder is <88 μm.

[0014] According to the above aspects and any possible implementation, an implementation is further provided, wherein the particle size of the silicon powder is less than 88 μm; and the particle size of the titanium oxide powder is less than 88 μm.

[0015] According to the above aspects and any possible implementation, a further implementation is provided, wherein the Si-Ti2O3-SiC composite body is dried at a temperature range of 120 to 300°C for 12 to 60 hours.

[0016] According to the aspects and any possible implementation methods described above, an implementation method is further provided, wherein the dried Si-Ti2O3-SiC composite body is placed in a sagger, heated to 1300°C to 1600°C at a rate of 2 to 10°C / min in a nitrogen atmosphere, and kept warm for 3 to 24 hours before sintering.

[0017] According to the aspects and any possible implementation described above, an implementation is further provided, wherein the mass fraction of the silicon carbide aggregate is 60wt.%, the mass fraction of the silicon carbide fine powder is 15wt.%, the mass fraction of the silicon powder is 15wt.%, the mass fraction of the titanium oxide powder is 10wt.%, and the mass fraction of the binder is 5wt.%.

[0018] According to the aspects and any possible implementation described above, an implementation is further provided, wherein the mass fraction of the silicon carbide aggregate is 70wt.%, the mass fraction of the silicon carbide fine powder is 5wt.%, the mass fraction of the silicon powder is 18wt.%, the mass fraction of the titanium oxide powder is 7wt.%, and the mass fraction of the binder is 3.5wt.%.

[0019] The present invention also provides a SiC composite refractory material co-reinforced with Si2N2O and TiN, which is obtained by adopting the preparation method of the present invention.

[0020] Beneficial effects of the present invention

[0021] The preparation method of the SiC composite refractory material co-reinforced by Si2N2O and TiN of the present invention comprises the following steps: S1. silicon carbide, silicon powder, and titanium oxide powder as raw materials and a binder are weighed according to a proportion, stirred evenly, and made into a slurry; S2. the slurry in step S1 is pressed into a green body, and the SiC composite refractory material co-reinforced by Si2N2O and TiN is obtained through drying, nitriding and sintering processes. The method of the present invention solves the shortcomings and defects of existing Si3N4-SiC composite materials, such as the easy generation of free Si and the poor chemical stability of the Si3N4 binding phase, which leads to poor performance of the material. Specifically, in order to address the problems of the existing Si3N4-SiC composite material preparation process easily generating free silicon, the poor chemical stability of Si3N4, and the unsatisfactory performance, the present invention uses silicon carbide, silicon powder, and titanium oxide powder as raw materials to prepare a Si-Ti2O3-SiC composite body, and the dried body is fired in a nitrogen atmosphere. Through the gas-liquid-solid reaction at high temperature: 6Si+Ti2O3+N2=3Si2N2O+2TiN, a SiC composite refractory material co-reinforced by Si2N2O and TiN is prepared. Compared with Si3N4, Si2N2O and TiN both have better chemical stability, among which TiN also has excellent corrosion resistance and thermal shock resistance, and Si2N2O has excellent oxidation resistance. The specific performance is as follows:

[0022] (1) In the prior art, during the production and preparation of Si3N4-SiC composite materials, Si is easily melted at relatively high temperatures, and liquid Si is difficult to react with nitrogen to form Si3N4, and ultimately free Si remains in the material. In the present invention, Ti2O3 powder is further introduced into the Si-SiC blank. Ti2O3 easily reacts with liquid Si and is converted into more stable Si2N2O and TiN in a nitrogen atmosphere. On the one hand, this avoids the residual free Si, and on the other hand, it introduces a high-performance TiN reinforcement phase, which can greatly improve the performance of the material;

[0023] (2) A TiN reinforcement phase with better corrosion resistance and thermal shock resistance and a Si2N2O reinforcement phase with better oxidation resistance can be obtained. The two work together to greatly improve the high-temperature performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0025] To better understand the technical solutions of the present invention, the present invention includes but is not limited to the specific embodiments described below. Similar technologies and methods should be considered within the scope of protection of the present invention. To further clarify the technical problems, technical solutions, and advantages to be solved by the present invention, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments.

[0026] It should be understood that the embodiments described herein are only a portion 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 persons of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0028] like Figure 1 As shown, the preparation method of a SiC composite refractory material co-reinforced by Si2N2O and TiN of the present invention comprises the following steps:

[0029] S1. The silicon carbide, silicon powder, titanium oxide powder and binder were weighed according to the ratio to obtain a composite material, stirred evenly, and made into a clay;

[0030] S2. Use a press to press the clay material in step S1 into a Si-Ti2O3-SiC composite body, and obtain a SiC composite refractory material co-reinforced by Si2N2O and TiN through drying, nitriding and sintering steps.

[0031] The mass fractions of silicon carbide, silicon powder and titanium oxide powder as raw materials are: silicon carbide is 65-90wt%, silicon powder is 5-20wt% and titanium oxide is 5-15wt%. The mass percentage of the binder is 2-5wt% of the total amount of all the above raw materials.

[0032] Furthermore, the silicon carbide comprises silicon carbide aggregate with a particle size of 3-1 mm (or 1-3) and less than 1 mm, and silicon carbide fine powder with a particle size of less than 88 μm. The mass percentage of the silicon carbide aggregate with a particle size of 3-1 mm and less than 1 mm is 60%-85%, and the mass percentage of the silicon carbide fine powder is 5-30%. The particle size of the silicon powder is less than 88 μm, and the particle size of the titanium oxide powder is less than 88 μm. This particle size composition enables the green body to obtain the necessary porosity (5%-25%). A certain amount of porosity is beneficial for improving its thermal shock resistance, but excessive porosity will reduce the material's strength and erosion resistance. Therefore, the present invention can achieve a balanced thermal shock resistance and erosion resistance of the product through reasonable particle grading.

[0033] Preferably, the binder is a thermosetting phenolic resin binder. Thermosetting phenolic resin has a high viscosity (0.02-100 Pa·s) at room temperature (25°C), has good wettability with SiC, Ti2O3, and Si particles, can be evenly coated on the particle surface at room temperature, and is used as a binder to impart higher strength to the Si-Ti2O3-SiC composite blank. When the blank is further dried and fired at high temperature, the phenolic resin binder is heated and decomposes at 200-800°C, leaving a small amount of residual carbon, i.e., resin carbon residue. The resin carbon residue has the characteristics of high dispersibility, high activity, and ultrafineness, which can greatly improve the wettability of liquid Si to Ti2O3, thereby promoting the chemical reaction between Si and Ti2O3.

[0034] Preferably, the Si-Ti2O3-SiC composite body is dried at a temperature range of 120-300°C for 12-60 hours, until the residual water in the body is slowly evaporated to below 1%.

[0035] Preferably, the dried green body is placed in a sagger and heated to 1300°C to 1600°C in a nitrogen atmosphere at a rate of 2-10°C / min. The heated body is then held for 3-24 hours and sintered to allow the nitridation reaction between Si and Ti2O3 to proceed fully, converting them into Si2N2O and TiN. During the high-temperature sintering process, the Si and Ti2O3 in the green body react with the nitrogen in the atmosphere through a gas-liquid-solid reaction: 6Si + Ti2O3 + N2 = 3Si2N2O + 2TiN. The high diffusion rate between solid Ti2O3 and liquid Si significantly increases the rate at which Si participates in the reaction, thereby reducing the presence of free Si. Furthermore, Si, acting as a reducing agent, promotes the reductive nitridation of Ti2O3, converting it into a stable TiN non-oxide. As the reaction proceeds, Si absorbs oxygen from Ti2O3 and nitrogen in the atmosphere, ultimately producing a SiC composite refractory reinforced with Si2N2O and TiN. Compared to Si₃N₄, both Si₂N₂O and TiN possess superior chemical stability. TiN also offers excellent corrosion and thermal shock resistance, while Si₂N₂O exhibits excellent oxidation resistance. Therefore, the method of the present invention produces molten silicon during the preparation process, which can further undergo a liquid-solid reaction with Ti₂O₃ to convert into Si₂N₂O, thereby avoiding the presence of residual free silicon.

[0036] Furthermore, the mass fraction of the silicon carbide aggregate is 60wt.%, the mass fraction of the silicon carbide fine powder is 15wt.%, the mass fraction of the silicon powder is 15wt.%, the mass fraction of the titanium oxide powder is 10wt.%, and the mass fraction of the binder is 5wt.%.

[0037] Furthermore, the mass fraction of the silicon carbide aggregate is 70wt.%, the mass fraction of the silicon carbide fine powder is 5wt.%, the mass fraction of the silicon powder is 18wt.%, the mass fraction of the titanium oxide powder is 7wt.%, and the mass fraction of the binder is 3.5wt.%.

[0038] The present invention also provides a SiC composite refractory material co-reinforced with Si2N2O and TiN, which is obtained by the preparation method of the present invention and has excellent high-temperature oxidation resistance, thermal shock resistance and erosion resistance.

[0039] The following are several specific embodiments.

[0040] Example 1

[0041] 60 wt.% silicon carbide aggregate, 15 wt.% silicon carbide fine powder, 15 wt.% silicon powder, and 10 wt.% titanium oxide powder were mixed, and 5 wt.% of a phenolic resin binder was added to the mixture. The mixture was uniformly mixed and pressed into a Si-Ti2O3-SiC composite body. The body was then dried at 200°C for 12 hours. The dried Si-Ti2O3-SiC composite body was then sintered at 1300°C for 4 hours to produce a SiC composite refractory material reinforced with Si2N2O and TiN.

[0042] The obtained Si2N2O and TiN co-reinforced SiC composite refractory material was tested and found to have an apparent porosity of 12.3% and a bulk density of 2.80 g / cm 3 The room temperature compressive strength is 171MPa, which meets the use requirements of the middle and lower parts, waist and belly of large blast furnaces, side walls of aluminum electrolytic cells, and waste incinerators.

[0043] Example 2

[0044] 70 wt.% of silicon carbide aggregate, 5 wt.% of silicon carbide fine powder, 18 wt.% of silicon powder, and 7 wt.% of titanium oxide powder were mixed, and 3.5 wt.% of a phenolic resin binder was added to the mixture. The mixture was uniformly kneaded and pressed into a Si-Ti2O3-SiC composite body. The body was then dried at 150°C for 24 hours. The dried Si-Ti2O3-SiC composite body was then sintered at 1450°C for 8 hours in a nitrogen atmosphere to produce a SiC composite refractory material reinforced with Si2N2O and TiN.

[0045] The obtained Si2N2O and TiN co-reinforced SiC composite refractory material was tested and found to have an apparent porosity of 10.9% and a bulk density of 2.76 g / cm 3The room temperature compressive strength is 124MPa, which meets the use requirements of the middle and lower parts, waist and belly of large blast furnaces, side walls of aluminum electrolytic cells, and waste incinerators.

[0046] Example 3

[0047] 85 wt.% silicon carbide aggregate, 5 wt.% silicon carbide fine powder, 7 wt.% silicon powder, and 3 wt.% titanium oxide powder were mixed, and 4 wt.% of the above mixture as a phenolic resin binder was added. The mixture was uniformly kneaded and pressed into a Si-Ti2O3-SiC composite body. The body was then dried at 200°C for 12 hours. The dried Si-Ti2O3-SiC composite body was then sintered at 1600°C in a nitrogen atmosphere for 3 hours to produce a SiC composite refractory material reinforced with Si2N2O and TiN.

[0048] The obtained Si2N2O and TiN co-reinforced SiC composite refractory material was tested and found to have an apparent porosity of 11.3% and a bulk density of 2.73 g / cm 3 The room temperature compressive strength is 178MPa, which meets the use requirements of the middle and lower parts, waist and belly of large blast furnaces, side walls of aluminum electrolytic cells, and waste incinerators.

[0049] The foregoing description shows and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the application concept described herein by the teachings above or by techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A method for preparing a SiC composite refractory material co-reinforced with Si2N2O and TiN, characterized in that: The steps include: S1. Silicon carbide, silicon powder, titanium oxide powder as raw materials and binder are weighed according to the ratio, stirred evenly, and made into a slurry. The mass fractions of the silicon carbide, silicon powder, and titanium oxide powder as raw materials are: silicon carbide is 65-90wt%, silicon powder is 5-20wt%, titanium oxide is 5-15wt%, and the mass percentage of the binder is 2-5wt% of the total amount of the raw materials; S2. The clay material in step S1 is pressed into a Si-Ti2O3-SiC composite body, and a SiC composite refractory material co-reinforced with Si2N2O and TiN is obtained through drying, nitriding and sintering processes. Specifically, the dried Si-Ti2O3-SiC composite body is placed in a sagger, and the temperature is raised to 1300°C to 1600°C at a rate of 2 to 10°C / min in a nitrogen atmosphere, and the body is kept warm for 3 to 24 hours and fired to allow the nitriding reaction of Si and Ti2O3 to proceed fully and be converted into Si2N2O and TiN. During the high-temperature firing process, Si and Ti2O3 in the body undergo a gas-liquid-solid reaction with N2 in the atmosphere: 6Si+Ti2O3+N2=3Si2N2O+2TiN.

2. The method for preparing the SiC composite refractory material co-reinforced by Si2N2O and TiN according to claim 1, characterized in that: The silicon carbide includes silicon carbide aggregate and silicon carbide fine powder.

3. The method for preparing the SiC composite refractory material co-reinforced by Si2N2O and TiN according to claim 2, characterized in that: The particle size of the silicon carbide aggregate is 3-1 mm and less than 1 mm, and the particle size of the silicon carbide fine powder is less than 88 μm.

4. The method for preparing the SiC composite refractory material co-reinforced by Si2N2O and TiN according to claim 3, characterized in that: The particle size of the silicon powder is less than 88 μm; the particle size of the titanium oxide powder is less than 88 μm.

5. The method for preparing SiC composite refractory material co-reinforced by Si2N2O and TiN according to claim 1, characterized in that: The Si-Ti2O3-SiC composite body is dried at a temperature range of 120 to 300°C for 12 to 60 hours.

6. The method for preparing SiC composite refractory material co-reinforced by Si2N2O and TiN according to claim 2, characterized in that: The mass fraction of the silicon carbide aggregate is 60 wt.%, the mass fraction of the silicon carbide fine powder is 15 wt.%, the mass fraction of the silicon powder is 15 wt.%, the mass fraction of the titanium oxide powder is 10 wt.%, and the mass fraction of the binder is 5 wt.%.

7. The method for preparing SiC composite refractory material co-reinforced by Si2N2O and TiN according to claim 3, characterized in that: The mass fraction of the silicon carbide aggregate is 70 wt.%, the mass fraction of the silicon carbide fine powder is 5 wt.%, the mass fraction of the silicon powder is 18 wt.%, the mass fraction of the titanium oxide powder is 7 wt.%, and the mass fraction of the binder is 3.5 wt.%.

8. A SiC composite refractory material co-reinforced with Si2N2O and TiN, characterized in that: The preparation method according to any one of claims 1 to 7 is used to obtain the compound.

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