Ti (C, N) whisker and preparation method thereof

Abstract

The invention provides a Ti (C, N) whisker and a preparation method thereof. The preparation method comprises the following steps: preparing nano TiO2 powder by adopting a sol-gel method; the preparation method comprises the following steps: carrying out ball milling on nano TiO2 powder, food cellulose, a chlorine source and catalyst powder to obtain precursor powder; preparing carbon source powder, wherein the carbon source powder comprises food cellulose; sieving the precursor powder and the carbon source powder; placing the precursor powder and the carbon source powder in a heat treatment device for high-temperature carbon thermal reduction to obtain mixed powder of Ti (C, N) whiskers and free carbon; and the mixed powder is subjected to carbon removal treatment. The Ti (C, N) whisker is prepared by adopting the preparation method. According to the preparation method of the Ti (C, N) crystal whisker provided by the invention, the food cellulose is used for reducing TiO2. The food cellulose not only is low in cost, but also can release high-concentration gaseous carbon in a whisker synthesis stage, so that the growth of the whisker is facilitated, and the yield of the whisker is remarkably improved. The Ti (C, N) whisker provided by the invention has the advantages of low cost, high yield and large-scale production.

Description

Technical Field

[0001] The present application relates to the technical field of whisker preparation, and in particular to a Ti(C,N) whisker and a preparation method thereof. Background Art

[0002] Ti(C,N)-based cermets are widely used in the fields of high-speed cutting tools and wear-resistant parts. As a typical transition metal carbonitride, Ti(C,N) whiskers have the advantages of ultra-high strength, high hardness, and low thermal expansion coefficient. What is particularly critical is that as a hard homologous carbonitride of Ti(C,N)-based cermet materials, Ti(C,N) whiskers also have the ability to form a typical "core-ring" structure. This structure can effectively avoid the disappearance of whisker characteristics due to high-temperature metallurgical reactions, making Ti(C,N) whiskers a key element that can synergistically improve the strength and toughness of Ti(C,N)-based cermet materials.

[0003] At present, the preparation process of carbide whiskers mainly adopts high-temperature carbon thermal reduction method. The existing technology mainly uses volatile carbon black as a reducing agent, however, volatile carbon black is not only expensive, but also has a low concentration of carbon atmosphere released during the whisker synthesis stage.

[0004] Therefore, providing a method for preparing Ti(C,N) whiskers with low cost and high yield is an urgent problem to be solved in the art. Summary of the invention

[0005] The purpose of the present application is to provide a Ti(C,N) whisker and a preparation method thereof, so as to solve the technical problem in the prior art that volatile carbon black is used as a carbon source, which is not only expensive but also has a low concentration of carbon atmosphere released during the whisker synthesis stage.

[0006] To achieve the above object, the technical solution adopted in the present application is: to provide a method for preparing Ti(C,N) whiskers, comprising the following steps: Nano-TiO2 powder was prepared by sol-gel method; Ball milling the nano-TiO2 powder, food cellulose, a chlorine source, and a catalyst powder to obtain a precursor powder; preparing a carbon source powder, wherein the carbon source powder comprises food cellulose; Screening the precursor powder and the carbon source powder; Placing the precursor powder and the carbon source powder in a heat treatment device for high-temperature carbothermal reduction to obtain a mixed powder of Ti(C,N) whiskers and free carbon; The mixed powder is subjected to a carbon removal treatment to obtain pure Ti(C,N) whiskers.

[0007] Furthermore, the carbon source powder also includes activated carbon, and the mass ratio of food cellulose to activated carbon in the carbon source powder is 1-3:4-12.

[0008] Furthermore, before the precursor powder and the carbon source powder are fed into the heat treatment device for reduction, the precursor powder and the carbon source powder are placed in a graphite tank, and the carbon source powder is placed at the bottom of the graphite tank and the precursor powder is placed on the top of the carbon source powder.

[0009] Furthermore, the heat treatment device is a high-temperature vacuum carbonization furnace.

[0010] Furthermore, the mixed powder is calcined in a muffle furnace for decarbonization, the calcination temperature is 500-600° C., and the holding time is 80-150 min to obtain pure Ti(C,N) whiskers.

[0011] Furthermore, the chlorine source is KCl.

[0012] Furthermore, the molar ratio of TiO2, food cellulose, chlorine source and catalyst powder in the precursor powder is 0.5~1:3~6:0.5~1.5:0.02~0.1.

[0013] Furthermore, when the precursor powder and the carbon source powder are fed into the heat treatment device for high-temperature carbon thermal reduction, the heat treatment device is heated from room temperature to 800°C at a heating rate of 15~20°C / min, and from 800°C to 1000~1450°C at a heating rate of 5~10°C / min, and the insulation time is 60~300min.

[0014] The beneficial effects of the preparation method of Ti(C,N) whiskers provided in the present application are: The preparation method of Ti(C,N) whiskers provided in the present application uses food cellulose to reduce TiO2. Food cellulose is not only low in cost, but also releases a high concentration of carbon atmosphere during the whisker synthesis stage, which can promote whisker growth and significantly increase whisker yield. Therefore, large-scale production of Ti(C,N) whiskers can be achieved.

[0015] The present application also provides a Ti(C, N) whisker, which is prepared using the above-mentioned Ti(C, N) whisker preparation method.

[0016] The Ti(C,N) whiskers provided in this application have the following beneficial effects: The Ti(C,N) whiskers provided in the present application have the advantages of low cost, high yield and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A flow chart of a method for preparing Ti(C,N) whiskers provided in this application; Figure 2 A schematic diagram of a process for preparing a Ti(C,N) whisker provided in the present application; Figure 3 SEM images of different growth morphologies of Ti(C,N) whiskers provided in this application; Figure 4 A schematic diagram of the internal furnace structure of a high-temperature vacuum carbonization furnace for a method for preparing Ti(C,N) whiskers provided in the present application; Figure 5 A schematic diagram of a chloride-assisted carbothermal reduction reaction of a method for preparing Ti(C,N) whiskers provided in the present application; Figure 6 A line graph of the decomposition of KCl and NaCl at different temperatures provided in this application; Figure 7 The SEM image of Ti(C,N) whiskers prepared by using KCl and NaCl provided in this application; Figure 8 A schematic diagram showing the effect of carbon thermal reduction reaction kinetics on CO partial pressure in a method for preparing Ti(C,N) whiskers provided in the present application; Fig. 9 This is a SEM image of the product effect of Example 1 of the present application; Fig.10 This is a SEM image of the product effect of Example 2 of the present application. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0021] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] See also Figures 1 to 10 The present invention provides a method for preparing Ti(C,N) whiskers, comprising the following steps: S1: Nano-TiO2 powder is prepared by sol-gel method. Nano-TiO2 has a high specific surface area, which helps to combine with Cl atom gas to generate TiClx during the sintering process. Among them, the specific steps of preparing nano-TiO2 powder by sol-gel method are as follows: tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, hydrochloric acid, and distilled water are mixed and stirred according to a mass ratio of 10:3.5:1:2:2, and water and nitric acid are dripped into the stirring process to generate TiO2 particles, and then the obtained TiO2 particles are allowed to stand and age to convert into gel, and then dried and calcined to form nano-TiO2 powder. The hydrolysis reaction 1 and polycondensation reaction 2 of butyl titanate and the overall reaction 3 in its preparation process are as follows: Reaction 1: Ti(OR)4 +4H2O→Ti(OH)4+4ROH; Reaction 2: Ti(OH)4+Ti(OR)4→2TiO2+4ROH; Reaction three: 2Ti(OH)4→2TiO2+4H2O.

[0024] S2: ball-mill the nano-TiO2 powder, food cellulose, chlorine source, and catalyst powder to obtain a precursor powder. The ball milling method used in the ball milling step of the nano-TiO2 powder, food cellulose, chlorine source, and catalyst powder is drum ball milling, the ball milling medium is anhydrous ethanol, the grinding balls are alumina balls, the ball-to-material ratio is 2:1, the ball milling speed is 30r / min, the ball milling time is 6h, and the sieve mesh is 60 mesh. It should be noted that the catalyst powder includes iron powder, nickel powder and / or cobalt powder, which is not limited here. S3: preparing carbon source powder, wherein the carbon source powder includes food cellulose.

[0025] S4: Screening the precursor powder and the carbon source powder. It should be noted that if wet grinding is used in S2, the precursor powder and the carbon source powder need to be dried before screening.

[0026] S5: Place the precursor powder and the carbon source powder in a heat treatment device for high-temperature carbon thermal reduction to obtain a mixed powder of Ti(C,N) whiskers and free carbon. Taking the catalyst powder as nickel powder as an example, the high-temperature carbon thermal reduction reaction process is as follows: Reaction 4: 4TiO2(s)+C(s)→Ti4O7(s)+CO(g); Reaction 5: 3Ti4O7(s)+C(s)→4Ti3O5(s)+CO(g); Reaction 6: Ti3O5(s)+9Cl(g)+5C(s)→3TiCl3(g)+5CO(g); Reaction 7: TiCl3(g)+2CO(g)+1 / 2N2→Ti(C,N)w(s)+3Cl(g)+CO2(g) TiCl3(g)+Ni–C–N(l)→Ni–C–N–Ti(l)+3Cl(g); Reaction 8: Ti3O5(s)+8C(s)+3 / 2N2(g)→3Ti(C,N)(s)+5CO(g) Ni–C–N–Ti(l)→TiNxC1−x(s).

[0027] S6: Decarbonizing the mixed powder to obtain pure Ti(C,N) whiskers.

[0028] The growth mechanism of whiskers will change due to the high or low carbon concentration. When there is a lack of carbon source, the whiskers grow by catalysis of a small amount of catalyst powder, and the number of whiskers is small. When there is enough carbon source, the main growth mechanisms include gas-liquid-solid and gas-solid. The growth morphology of the two is different. Please refer to the attached Figure 3 Under low saturation conditions, the gas-solid reaction mainly uses the low energy surface (111) rich in kinks and flanges as nucleation sites, adsorbing gaseous substances during condensation. <100> The direction of preferential growth, at this time the high energy surface growth is limited by saturation, the crystal aspect ratio increases. Therefore, in this embodiment, food cellulose is used to reduce TiO2, and the concentration of carbon atmosphere released during the whisker synthesis stage is high, which can promote whisker growth and improve whisker yield. In addition, food cellulose has low cost and can achieve large-scale production of Ti(C,N) whiskers.

[0029] In some embodiments of this application, please refer to Figures 1 to 10The carbon source powder also includes activated carbon, and the mass ratio of food cellulose to activated carbon in the carbon source powder is 1~3:4~12.

[0030] Furthermore, before the precursor powder and the carbon source powder are sent to the heat treatment device for reduction, the precursor powder and the carbon source powder are placed in a graphite tank, and the carbon source powder is placed at the bottom of the graphite tank and the precursor powder is placed on the top of the carbon source powder.

[0031] In this embodiment, the solid phase reaction between excessive solid carbon and TiO2 powder can be avoided, and the mixing of activated carbon and food cellulose helps to slow down the release of gaseous carbon, resulting in sufficient carbon atmosphere in the synthesis stage to promote whisker growth.

[0032] In some embodiments of this application, please refer to Figures 1 to 10 , the heat treatment device is set as a high temperature vacuum carbonization furnace.

[0033] In this embodiment, a high-temperature vacuum carbonization furnace is used, which can sinter and prepare Ti(C,N) whiskers with high strength and stable chemical properties. Compared with the solution using a tubular furnace in the prior art, the high-temperature vacuum carbonization furnace has the advantage of high production efficiency and can realize large-scale production.

[0034] In some embodiments of this application, please refer to Figures 1 to 10 The mixed powder is calcined in a muffle furnace for decarbonization, the calcination temperature is 500-600°C, and the holding time is 80-150 minutes to obtain pure Ti(C,N) whiskers.

[0035] In this embodiment, the mixed powder is calcined in a muffle furnace for carbon removal. Compared with the traditional liquid-liquid separation method, it can more effectively remove free carbon in the product, reduce the harmful elements remaining in the sample, and is more efficient and economical.

[0036] In some embodiments of this application, please refer to Figures 1 to 10 , chlorine sources include KCl.

[0037] Furthermore, the molar ratio of TiO2, food cellulose, chlorine source and catalyst powder in the precursor powder is 0.5~1:3~6:0.5~1.5:0.02~0.1.

[0038] See also Figure 5~Figure 7 The present invention prepares Ti(C,N) whiskers by KCl, from Figure 5 It can be seen that the Ti atoms required for whisker growth are mainly transported through the gas phase TiClx, and the gas concentration of TiClx depends on the decomposition amount of chloride. In practical applications, different chlorides, specifically KCl and NaCl, have different decomposition amounts at the same temperature. Please refer to Figure 6, that is, under the same temperature conditions, the decomposition amount of KCl is higher than that of NaCl. Therefore, a comparative experiment was conducted on the preparation of Ti(C,N) whiskers using different chlorides. For a comparison of the product effects, please refer to Figure 7 The yield of Ti(C,N) whiskers prepared by KCl is higher than that prepared by NaCl.

[0039] In some embodiments of this application, please refer to Figures 1 to 10 When the precursor powder and the carbon source powder are fed into the heat treatment device for reduction, the heating rate of the heat treatment device is 15-20°C / min when the temperature rises from room temperature to 800°C, and the heating rate is 5-10°C / min when the temperature rises from 800°C to 1000-1450°C, and the insulation time is 60-300min.

[0040] The kinetics of the carbothermal reduction reaction due to different heating rates affects the CO partial pressure. Figure 8 , the temperature rises too quickly, resulting in sufficient TiO2 reduction reaction in the synthesis stage. During this stage, a large amount of CO gas is released, which inhibits the occurrence of the TiCl3 reaction and thus inhibits the whisker growth reaction.

[0041] In order to enable the above implementation details and operations of the present application to be clearly understood by those skilled in the art, as well as to demonstrate the significant technological progress of the Ti(C,N) whiskers and the preparation method thereof in the embodiment of the present application, the above technical scheme is illustrated by way of examples below. Example

[0042] A Ti(C,N) whisker and a preparation method thereof, wherein the preparation method comprises the following steps: ① The sol-gel method is used to prepare nano-TiO2 powder. Nano-TiO2 has a high specific surface area, which helps to combine with Cl gas to form TiClx during the sintering process. The specific steps of preparing nano-TiO2 powder by the sol-gel method are as follows: tetrabutyl titanate, anhydrous ethanol, glacial acetic acid, hydrochloric acid, and distilled water are mixed and stirred in a mass ratio of 10:3.5:1:2:2, and water and nitric acid are dripped into the stirring process to generate TiO2 particles, and then the obtained TiO2 particles are placed and aged to be converted into gel, and then dried and calcined to form nano-TiO2 powder.

[0043] ② Ball milling the nano-TiO2 powder with food cellulose, chlorine source and catalyst powder in a molar ratio of 1:4:1:0.05 to obtain a precursor powder. The ball milling method used in the ball milling step of the nano-TiO2 powder with food cellulose, chlorine source and catalyst powder is roller ball milling, the ball milling medium is anhydrous ethanol, the grinding ball is an alumina ball, the ball-to-material ratio is 2:1, the ball milling speed is 30r / min, the ball milling time is 6h, and the sieve mesh is 60 mesh.

[0044] ③Prepare carbon source powder, the carbon source powder includes food cellulose and activated carbon. The carbon source powder including food cellulose and activated carbon is ball-milled in a mass ratio of 1:4 to obtain the carbon source powder.

[0045] ④ Screening the precursor powder and the carbon source powder. It should be noted that if wet grinding is used in ② and ③, the precursor powder and the carbon source powder need to be dried before screening.

[0046] ⑤ Place the precursor powder and the carbon source powder in a graphite tank, with the carbon source powder at the bottom of the graphite tank and the precursor powder on the top of the carbon source powder.

[0047] ⑥ The graphite tank containing the precursor powder and the carbon source powder is sent to a high-temperature vacuum carbonization furnace for carbon thermal reduction. When the room temperature rises to 800°C, the heating rate is 15°C / min. When the temperature rises from 800°C to 1100°C, the heating rate is 6°C / min, and the insulation time is 180 minutes. A mixed powder of Ti(C,N) whiskers and free carbon is obtained.

[0048] ⑦ Use muffle furnace to calcine the mixed powder for carbon removal, the calcination temperature is 550℃, and the holding time is 120min. Pure Ti(C,N) whiskers are obtained. Please refer to the product effect Fig. 9 . Example

[0049] A Ti(C,N) whisker, the preparation method of which is different from that of Example 1 in that: in step ⑥, a high-temperature vacuum carbonization furnace is used for carbothermal reduction, the carbothermal reduction temperature is increased to 1350°C, and when the temperature is increased from 800°C to 1350°C, the heating rate is 10°C / min. Please refer to the product effect Fig.10 .

[0050] The embodiment of the present application also provides a Ti(C, N) whisker, which is prepared using the above-mentioned Ti(C, N) whisker preparation method.

[0051] The Ti(C,N) whiskers provided in this embodiment have the advantages of low cost, high yield and large-scale production. In addition, compared with equiaxed Ti(C,N), the whiskers with large aspect ratio in this embodiment can increase the crack deflection path, crack bridging, and fracture work, and have a strong inhibitory effect on crack propagation, which can greatly improve the strength and toughness of metal-ceramic composite materials.

[0052] One or more embodiments in this application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments in this application should be included in the protection of this application.

Claims

1. A method for preparing Ti(C,N) whiskers, characterized in that: The following steps are involved: S1, preparing nano-TiO2 powder by sol-gel method; S2, ball-milling the nano-TiO2 powder, food cellulose, a chlorine source, and a catalyst powder to obtain a precursor powder; S3, preparing a carbon source powder, wherein the carbon source powder comprises food cellulose; S4, sieving the precursor powder and the carbon source powder; S5, placing the precursor powder and the carbon source powder in a heat treatment device for high-temperature carbothermal reduction to obtain a mixed powder of Ti(C,N) whiskers and free carbon; S6. Decarbonize the mixed powder to obtain pure Ti(C,N) whiskers.

2. The method for preparing Ti(C,N) whiskers according to claim 1, characterized in that: The carbon source powder also includes activated carbon, and the mass ratio of food cellulose to activated carbon in the carbon source powder is 1-3:4-12.

3. The method for preparing Ti(C,N) whiskers according to claim 2, characterized in that: Before the precursor powder and the carbon source powder are fed into the heat treatment device for high-temperature carbon thermal reduction, the precursor powder and the carbon source powder are placed in a graphite tank, with the carbon source powder placed at the bottom of the graphite tank and the precursor powder placed on the top of the carbon source powder.

4. The method for preparing Ti(C,N) whiskers as claimed in claim 3, characterized in that: The heat treatment device is a high-temperature vacuum carbonization furnace.

5. The method for preparing Ti(C,N) whiskers as claimed in claim 1, characterized in that: The mixed powder is calcined in a muffle furnace for decarbonization, the calcination temperature is 500-600° C., and the holding time is 80-150 min to obtain pure Ti(C,N) whiskers.

6. The method for preparing Ti(C,N) whiskers according to any one of claims 3, characterized in that: The chlorine source is KCl, and the molar ratio of TiO2, food cellulose, chlorine source and catalyst powder in the precursor powder is 0.5~1:3~6:0.5~1.5:0.02~0.

1.

7. The method for preparing Ti(C,N) whiskers according to any one of claims 6, characterized in that: When the precursor powder and the carbon source powder are fed into the heat treatment device for high-temperature carbon thermal reduction, the heat treatment device is heated from room temperature to 800°C at a heating rate of 15~20°C / min, and from 800°C to 1000~1450°C at a heating rate of 5~10°C / min, and the insulation time is 60~300min.

8. A Ti(C,N) whisker, characterized in that: The Ti(C,N) whisker is prepared by the preparation method of any one of claims 1 to 7.

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