CN112745125B

CN112745125B - Preparation method of silicon carbide material, silicon carbide and application thereof

Info

Publication number: CN112745125B
Application number: CN202110046184.5A
Authority: CN
Inventors: 王龙山; 刘洋洋; 李云钊; 鲍恩成; 李文廷; 张宏科
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2021-01-14
Filing date: 2021-01-14
Publication date: 2022-07-12
Anticipated expiration: 2041-01-14
Also published as: CN112745125A

Abstract

The invention discloses a preparation method of a silicon carbide material, silicon carbide and application thereof. Adopting pre-nucleation process, pre-sintering CoO and Ni₂O partially converts it to NiCo₂O₄Nucleating agent and adding NiCo₂O₄The nucleating agent is uniformly dispersed in the unsintered silicon carbide matrix through the steps of stirring, mixing and the like, and the silicon carbide material is prepared through hot-pressing sintering and molding. The silicon carbide material prepared by the method has the advantages of low cracking tendency, high density, high strength, high toughness and the like, the high-temperature operation time during sintering is relatively short, the safe production coefficient is improved, and the energy consumption is reduced. The silicon carbide material prepared by the method can be used for temperature measuring structures of pipelines, equipment and the like.

Description

Preparation method of silicon carbide material, silicon carbide and application thereof

Technical Field

The invention relates to the technical field of ceramic processing, in particular to a preparation method of a silicon carbide material, silicon carbide and application thereof, which can meet the temperature measurement requirements of pipelines and equipment with strong corrosion, particularly dew point corrosion.

Background

In order to effectively monitor the temperature of the medium in the normal running process of equipment and pipelines, a thermometer is required to measure the temperature of the medium. However, the materials of the conventional thermometers are mainly metal materials, and cannot bear strong corrosive environments such as strong acid and the like. The silicon carbide ceramic serving as a high-temperature structural ceramic has excellent wear resistance, high thermal conductivity and heat resistance, and good corrosion resistance and high-temperature stability, and is widely applied to the industrial fields of machinery, electronics, petrochemical industry, metallurgy and the like. The current forming method of the silicon carbide ceramic mainly comprises hot-pressing sintering, ultrahigh-pressure sintering, high-vacuum sintering, microwave sintering and the like. The above method still has certain problems. For example, the hot-pressing sintering process has high sintering temperature, long heat preservation time, large grain size of the prepared sample and low mechanical property; although the silicon carbide material prepared by adopting the ultrahigh pressure sintering and high vacuum sintering processes has higher density, the equipment cost is expensive and the material cost is higher due to high pressure or vacuum degree; the microwave sintering process has the advantages of fast heating and short heat preservation time, but because the heating and heat preservation time is short, the material has higher internal residual stress value after undergoing the circulation of room temperature, high temperature and low temperature in a short time, and the cracking risk is high.

Therefore, it is necessary to develop a method for preparing silicon carbide material, simplify the preparation process, improve the mechanical properties of silicon carbide material, and widen the application range of silicon carbide material in the petrochemical field, especially in the environments with strong corrosivity such as dew point corrosion, acid corrosion, and the like.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a preparation method of a silicon carbide material, the method can shorten the heat preservation time of a hot-pressing sintering process, and the prepared silicon carbide material has higher strength and good toughness.

Another object of the present invention is to provide a silicon carbide material product obtained by the preparation method.

The invention also aims to provide the application of the silicon carbide material in temperature measuring structures of pipelines and equipment, and the silicon carbide material has better applicability in strong acid corrosion environments and scouring environments.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a silicon carbide material comprises the following steps:

1) binding agents CoO and Co₂O₃And Ni₂O is presintered to partially convert it to NiCo₂O₄A nucleating agent is sintered and then cooled to room temperature to obtain a pre-formed core material;

2) and uniformly mixing the pre-formed core material and a matrix material containing silicon carbide, and preparing the silicon carbide material by adopting a hot-pressing sintering forming process.

In a specific embodiment, the pre-nucleation material prepared in step 1) further comprises the step of fully grinding by using a ball mill to obtain pre-nucleation powder; preferably, the particle size of the ground pre-nucleation powder is 50-100nm, and the mixing and stirring time of the pre-nucleation powder and the matrix material containing silicon carbide is 2-6 h.

In a specific embodiment, the pre-sintering temperature in the step 1) is 260-460 ℃, and the sintering time is 1-1.5 h.

In a particular embodiment, the binders CoO, Co₂O₃And Ni₂The atomic molar ratio of Co to Ni in O is 1: 1.

In a specific embodiment, the sintering temperature of the hot-pressing sintering molding process is 1800-1900 ℃, and the sintering time is 0.5-2 h.

In a specific embodiment, the matrix material containing silicon carbide comprises a matrix agent submicron silicon carbide fine powder, a sintering aid, a plasticizer, a blending agent; preferably, the sintering aid is selected from BC, Na₂O、TiO₂、SiO₂The plasticizer is methyl cellulose, and the mixture comprises water, a lubricant, a dispersant, a defoaming agent and an auxiliary agent.

In a specific embodiment, the mass parts of the components in the binder and the matrix material containing silicon carbide are as follows: 94-97 parts of matrix agent submicron silicon carbide fine powder, 0.5-1 part of sintering aid, 0.2-0.5 part of binder, 0.5-1 part of plasticizer and 1.5-4.5 parts of mixing agent; preferably, the lubricant in the mixture is selected from glycerol or oleic acid, the dispersant is selected from tetramethylammonium hydroxide or sodium polymethacrylate, the defoaming agent is selected from polyether or polyether polyol, and the auxiliary agent is phosphorus pentoxide.

In a specific embodiment, the mixture comprises the following components in percentage by mass: 25-55% of water, 25-35% of a lubricant, 5-25% of a dispersant, 6-21% of a defoaming agent and 0-0.6% of an auxiliary agent.

In another aspect of the present invention, the silicon carbide material is prepared by the above-mentioned method.

In another aspect of the invention, the silicon carbide prepared by the preparation method of the silicon carbide material has better applicability in temperature measurement structures of pipelines or equipment, especially in strong acid corrosion environments and scouring environments.

Compared with the prior art, the invention has the following beneficial effects:

(1) the preparation method adopts a pre-nucleation process and pre-sinters CoO and Ni₂O, making CoO, Ni₂Partial transformation of O to NiCo₂O₄A nucleating agent, wherein the pre-nucleating material is uniformly dispersed in the unsintered silicon carbide matrix through the steps of stirring, mixing and the like. This portion transforms into NiCo formed during the hot press sintering process₂O₄The nucleating agent can be used as CoO and Ni₂The solid phase matrix of O non-spontaneous nucleation transformation greatly improves the nucleation rate and transformation rate, namely NiO and CoO are transformed into NiCo₂O₄The proportion of (2) is increased, the heat preservation time is shortened during hot-pressing sintering, and the temperature is reduced to 1h from more than 2h of high-temperature sintering in the prior art. And pre-nucleated NiCo₂O₄The crystal can be adsorbed on NiCo which is transformed and finished by hot-pressing sintering₂O₄And the crystal is prevented from further growing, so that the mechanical property of the silicon carbide material is improved.

(2) The silicon carbide tube prepared by the method has the advantages of low cracking tendency, high density, high strength, high toughness and the like, relatively short high-temperature operation time during sintering, improved safety production coefficient and reduced energy consumption.

Detailed Description

The following examples further illustrate the method of the present invention in order to better understand the technical solution of the present invention, but the present invention is not limited to the listed examples, and also includes any other known modifications within the scope of the claims of the present invention.

The invention provides a preparation method of a silicon carbide temperature measurement structure material for pipelines and equipment. The main body of the material is silicon carbide ceramic, a pre-formed core hot-pressing sintering forming process is adopted, wherein the matrix agent is submicron silicon carbide fine powder, for example, the granularity of the fine powder is 0.7 mu m, the granularity of the fine powder is low, and good forming can be ensured during subsequent sinteringAnd bonding strength. The sintering aid is BC and Na₂O、TiO₂、SiO₂The part can effectively lower the sintering temperature of the silicon carbide and accelerate the inter-ion transfer. The binder is CoO or Co₂O₃And Ni₂O, prepared by adopting a pre-nucleation process, wherein the atomic molar ratio of Co to Ni is controlled to be 1: about 1, NiCo prepared by partial pre-nucleation in the hot-pressing sintering process₂O₄Can be used as CoO and Ni₂The solid phase matrix of O non-spontaneous nucleation transformation greatly improves the nucleation rate and the transformation rate and can be adsorbed on NiCo which is transformed₂O₄And the crystal is prevented from further growing, so that the mechanical property of the silicon carbide material is improved.

The innovation of the invention lies in improvement on the basis of a hot-pressing sintering process, and the improvement of the sintering efficiency is promoted by adding a pre-sintered binder into a base material, wherein the hot-pressing sintering forming process can refer to the prior art.

Specifically, the preparation method of the silicon carbide temperature measurement structure material for pipelines and equipment comprises the following steps:

1) binding agents CoO and Co₂O₃And Ni₂Mixing O according to the proportion of 1:1, and presintering NiCo at 260-460 ℃ after mixing₂O₄Pre-nucleating, wherein the sintering time is 1-1.5 h, and fully grinding the pre-sintered sample by adopting a dry ball mill to prepare pre-nucleating powder; the pre-nucleation powder after grinding typically has a particle size of 50-100nm, preferably 80 nm;

2) mixing the matrix agent silicon carbide powder, the sintering aid and the plasticizer according to a ratio, and uniformly stirring by using a stirrer for 4-8 hours, preferably 6 hours to prepare a mixture A;

3) adding the ground binder into the mixture A, and continuously mixing and stirring for 2-6 h, preferably 4h after the addition is finished to prepare a finished mixture B;

4) independently adding the defoaming agent into the mixture B, and stirring for 2-4 h, preferably 3h to obtain a mixture C;

5) uniformly stirring water, a lubricant, a dispersant and an auxiliary agent to obtain a mixed solution D for later use;

6) uniformly stirring the mixture C and the mixed solution D by using a stirrer, pugging the uniformly stirred raw materials on a vacuum pug mill, and repeating for 5-9 times, preferably for 6-8 times;

7) placing the pug in a micro-negative pressure environment for 6-36 h, preferably 8-16 h;

8) injecting the pug into a specific mold in an injection molding mode, and placing the mold for 2-8 days, preferably 4 days after molding;

9) placing the die in a specific sintering furnace for presintering, wherein the sintering temperature is 400-800 ℃, the heat preservation time is 4-8 h, preferably 6h, and the temperature rise rate during sintering is about 1-5 ℃/min

10) After pre-sintering, cooling the die along with the furnace, taking out the die after completely cooling to room temperature, opening the die, and taking out the preformed sleeve;

11) placing the formed sleeve in a sintering furnace for secondary pre-sintering, wherein the sintering temperature is 600-1000 ℃, the sintering heat preservation time is 4-8 hours, preferably 6 hours, and the heating rate is 1-6 ℃;

12) after the secondary pre-sintering is finished, keeping the heating power of the sintering furnace unchanged, raising the temperature to 1800-1900 ℃, and keeping the temperature for 0.5-2 h. Cooling to room temperature when the temperature is lower than 400 ℃, and sintering to obtain the required silicon carbide sample.

The invention is further illustrated, but not limited, by the following more specific examples.

The main test equipment:

device name	Model number	Manufacturer of the product
			High temperature furnace	CR-MJ8	Henan Chang Rui furnace Co Ltd
Ball mill	AYM ball mill	Tin-free sea wave drying mechanical equipment
			Mixer	JZM	Zhengzhou Ruding machinery equipment Co Ltd
Laser granularity tester	LS-ROP	Oumeik science and technology Co., Ltd
			Pugging machine	PN-A	Henan Chen Fa machinery Equipment Co Ltd
Sintering furnace	ZT-40-20	Vacuum electric furnace Co Ltd in Jinzhou

The main test raw materials are as follows:

the analysis and test method comprises the following steps:

and (3) testing the density: the ceramic material volume density test method GB/T2413-1980;

bending strength: the ceramic material bending strength test method GB/T4714-1999;

static pressure strength: ceramic material compressive strength test GB/T4744-1999;

fracture toughness: the engineering ceramic impact toughness test method GB/T-199;

coefficient of heat transfer: the thermal conductivity of the non-metallic solid material is tested by GB/T10297-2015.

Example 1 Using a Pre-nucleation Process

1) Binding agents CoO and Co₂O₃And Ni₂O according to Co: mixing Ni in a molar ratio of 1:1, pre-reacting and sintering in a high-temperature furnace at the sintering temperature of 300 ℃ for 1h, and cooling to room temperature after sintering; and (3) grinding the sintered reactor by adopting a dry ball mill to prepare the pre-nucleation powder with the particle size of 70 nm.

2) Mixing matrix agent silicon carbide (SiC) powder and sintering aids (BC, Na)₂50 parts of each O) and plasticizer methylcellulose are mixed according to the mixing ratio in the table 1, and are uniformly stirred at the speed of 40r/min by a stirrer for 4 hours to prepare a finished mixture A.

3) And adding the ground binder into the mixture A according to the proportion, and continuously mixing and stirring for 2 hours after the addition is finished to prepare a finished mixture B.

4) And (3) independently adding the defoaming agent polyethylene glycol into the mixture B according to the proportion of the defoaming agent polyethylene glycol in the mixture, and stirring for 2 hours to obtain a mixture C.

5) Uniformly stirring water, a lubricant oleic acid, a dispersant sodium polymethacrylate and an auxiliary agent phosphorus pentoxide into a mixed solution D for later use.

6) And uniformly stirring the mixture C and the mixed solution D for 2 hours by using a stirrer, pugging the uniformly stirred raw materials on a vacuum pug mill, and repeating for 6 times.

7) And (5) placing the pug in a micro-negative pressure environment for 16 h.

8) And injecting the pug into a specific mould in an injection molding mode, and standing the mould for 4 days after molding.

9) And placing the die in a specific sintering furnace for presintering, wherein the sintering temperature is 600 ℃, the heat preservation time is 6 hours, and the heating rate during sintering is about 1 ℃/min.

10) And after pre-sintering, cooling the die along with the furnace, taking out the die after completely cooling to room temperature, opening the die, and taking out the preformed sleeve.

11) And placing the formed sleeve in a sintering furnace for secondary pre-sintering, wherein the sintering temperature is 1000 ℃, the sintering heat preservation time is 6 hours, and the heating rate is 6 ℃.

12) After the secondary pre-sintering is finished, keeping the heating power of the sintering furnace unchanged, raising the temperature to 1900 ℃, and keeping the temperature for 1 h. And cooling to room temperature when the temperature is lower than 400 ℃, and completing sintering to obtain the required silicon carbide sample A.

Example 2 Using a Pre-nucleation Process

Compared with the embodiment 1, the difference is the pre-forming sintering temperature in the step 1) and the sintering temperature and the heat preservation time in the step 12); the other steps and processes are exactly the same.

1) Binding agents CoO and Co₂O₃And Ni₂O according to Co: mixing Ni in a molar ratio of 1:1, pre-reacting and sintering in a high-temperature furnace at the sintering temperature of 260 ℃ for 1h, and cooling in air to room temperature after sintering; and (3) grinding the sintered reactor by adopting a dry ball mill to prepare the pre-nucleation powder with the particle size of 70 nm.

12) After the secondary pre-sintering is finished, keeping the heating power of the sintering furnace unchanged, raising the temperature to 1800 ℃, and keeping the temperature for 0.5 h. And cooling to room temperature when the temperature is lower than 400 ℃, and sintering to obtain the required silicon carbide sample C.

Example 3 Using the Pre-nucleation Process

1) Binding agents CoO and Co₂O₃And Ni₂O according to the ratio of Co: mixing Ni in a molar ratio of 1:1, mixing, and addingCarrying out pre-reaction sintering in a high-temperature furnace, wherein the sintering temperature is 460 ℃, the time is 1h, and air cooling to room temperature after sintering is finished; and (3) grinding the sintered reactor by adopting a dry ball mill to prepare the pre-nucleation powder with the particle size of 70 nm.

12) After the secondary pre-sintering is finished, keeping the heating power of the sintering furnace unchanged, raising the temperature to 1900 ℃, and keeping the temperature for 2 hours. And cooling to room temperature when the temperature is lower than 400 ℃, and completing sintering to obtain the required silicon carbide sample E.

TABLE 1 compositions of ingredients under different examples

Comparative example 1-No Pre-nucleation Process

1) Binding agents CoO and Co₂O₃And Ni₂Mixing O at a ratio of 1:1, directly mixing binder, matrix agent silicon carbide powder, and sintering aid (BC, Na)₂50 parts of each O) and plasticizer methylcellulose are mixed according to the proportion, and are uniformly stirred by a stirrer at the speed of 40r/min for 4 hours to prepare a mixture A; the desired silicon carbide sample B was then prepared according to the steps 4) to 12) of example 1.

Comparative example 2-No Pre-nucleation Process

Essentially the same as example 2 (and the same batch ratios), except that steps 1) -3) were performed using the non-pre-nucleation process of step 1) of comparative example 1, to produce the desired silicon carbide sample D.

Comparative example 3-No Pre-nucleation Process

Essentially the same as example 3 (and the same batch ratios), except that steps 1) -3) were performed using the non-pre-nucleation process of step 1) of comparative example 1, to produce the desired silicon carbide sample F.

Comparative example 4-use of Pre-nucleation Process

Compared with example 1, the difference is the ratio of Co to Ni in step 1); the other steps and processes are exactly the same.

1) Binding agents CoO and Co₂O₃And Ni₂O according to the ratio of Co:mixing Ni in a molar ratio of 8:2, pre-reacting and sintering in a high-temperature furnace at 300 ℃ for 1h, and air-cooling to room temperature after sintering; grinding the sintered reactor by adopting a dry ball mill to prepare pre-nucleation powder with the particle size of 70 nm; finally, a silicon carbide sample G is prepared

Comparative example 5-use of Pre-nucleation Process

1) Binding agents CoO and Co₂O₃And Ni₂O according to Co: mixing Ni in a molar ratio of 2:8, pre-reacting and sintering in a high-temperature furnace at the sintering temperature of 300 ℃ for 1h, and cooling in air to room temperature after sintering; grinding the sintered reactor by adopting a dry ball mill to prepare pre-formed core powder with the particle size of 70 nm; finally, a silicon carbide sample H is prepared.

Comparative example 6-use of Pre-nucleation Process

Compared with the example 1, the difference is that CoO and Co in the step 1)₂O₃And Ni₂The pre-nucleation sintering temperature and time of O; the other steps and processes are exactly the same.

1) Binding agents CoO and Co₂O₃And Ni₂O according to the ratio of Co: mixing Ni in a molar ratio of 1:1, pre-reacting and sintering in a high-temperature furnace at 660 ℃ for 4 hours, and air-cooling to room temperature after sintering; grinding the sintered reactor by adopting a dry ball mill to prepare pre-formed core powder with the particle size of 70 nm; finally, a silicon carbide sample I is prepared.

Comparison of Performance

The main differences between A, C, E prepared by the pre-nucleation process and B, D, F prepared without the pre-nucleation process and the performance of G, H and different pre-sintering temperatures I at different Co and Ni ratios are as follows:

TABLE 3 comparison of properties of silicon carbide in different processes

As can be seen from the data table, no matter the sintering heat preservation time is 0.5h, 1h or 2h, the integral performance of the silicon carbide material prepared by adopting the pre-nucleation process has outstanding advantages compared with the silicon carbide material prepared without adopting the pre-nucleation process, and especially when the sintering heat preservation time is 1h, NiO and CoO in the pre-nucleation process generate NiCo₂O₄The reaction of (a) proceeds well, NiCo₂O₄The beneficial effect on the material is fully exerted, so that the fracture toughness of the material reaches 5.0 MPa.m^1/2The improvement is 42.8% compared with the sample without adopting the pre-nucleation process. In addition, the above table shows that the performance of the silicon carbide material prepared by the pre-nucleation process is not improved but is reduced to different degrees after the sintering heat preservation time is prolonged to 2 hours, which shows that the process of the invention can achieve the same or better performance as the conventional sintering process in shorter sintering time, not only can reduce the energy consumption, but also reduces the risk of production operation because the high-temperature sintering time is shortened.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. It will be appreciated by those skilled in the art that modifications and adaptations to the invention may be made in light of the teachings of the present disclosure. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

Claims

1. A preparation method of a silicon carbide material is characterized by comprising the following steps:

1) binding agents CoO and Co₂O₃And Ni₂O is presintered to partially convert it to NiCo₂O₄Sintering the nucleating agent, and cooling to room temperature to obtain a pre-formed core material;

2) uniformly mixing the pre-formed core material and a matrix material containing silicon carbide, and preparing the silicon carbide material by adopting a hot-pressing sintering molding process;

the pre-sintering temperature in the step 1) is 260-460 ℃, and the sintering time is 1-1.5 h;

the sintering temperature of the hot-pressing sintering molding process is 1800-1900 ℃, and the sintering time is 0.5-2 h;

the binder CoO, Co₂O₃And Ni₂The atomic molar ratio of Co to Ni in O is 1: 1;

the matrix material containing silicon carbide comprises submicron silicon carbide fine powder serving as a matrix agent, a sintering aid, a plasticizer and a mixture; the plasticizer is methyl cellulose, and the mixture comprises water, a lubricant, a dispersing agent, a defoaming agent and an auxiliary agent; the auxiliary agent is phosphorus pentoxide;

the adhesive and the matrix material containing silicon carbide comprise the following components in parts by mass: 94-97 parts of matrix agent submicron silicon carbide fine powder, 0.5-1 part of sintering aid, 0.2-0.5 part of binder, 0.5-1 part of plasticizer and 1.5-4.5 parts of mixing agent.

2. The method of claim 1, wherein the pre-nucleation material prepared in step 1) further comprises a step of fully grinding the pre-nucleation material with a ball mill to obtain pre-nucleation powder.

3. The method for preparing a silicon carbide material according to claim 2, wherein the particle size of the ground pre-nucleation powder is 50-100nm, and the mixing and stirring time of the pre-nucleation powder and the matrix material containing silicon carbide is 2-6 h.

4. A method of producing a silicon carbide material according to any one of claims 1 to 3, wherein the sintering aid is selected from BC, Na₂O、TiO₂、SiO₂At least any one of the above.

5. The method for preparing silicon carbide material according to claim 1, wherein the lubricant in the mixture is selected from glycerol or oleic acid, the dispersant is selected from tetramethylammonium hydroxide or sodium polymethacrylate, and the defoaming agent is selected from polyethers.

6. The method for preparing silicon carbide material according to claim 5, wherein the defoaming agent is selected from polyether polyols.

7. The preparation method of the silicon carbide material according to claim 1, wherein the mixture comprises the following components in percentage by mass: 25-55% of water, 25-35% of a lubricant, 5-25% of a dispersant, 6-21% of a defoaming agent and 0-0.6% of an auxiliary agent.

8. A silicon carbide material obtained by the method of producing a silicon carbide material according to any one of claims 1 to 7.

9. The silicon carbide material prepared by the method for preparing the silicon carbide material according to claim 8 is applied to a temperature measuring structure of a pipeline or equipment.