A method for producing carbide whiskers

Abstract

The present invention discloses a method for producing carbide whiskers, comprising the following steps: adding an appropriate amount of an organic mixture of an organic acid and / or a sugar to a raw material for the carbide whiskers to form a precursor powder, wherein the organic mixture constitutes 1 to 10% of the total mass of the raw material; and calcining the precursor powder in a protective atmosphere to obtain the carbide whiskers. The carbide whisker production method of the present invention features a simple process, convenient operation, a short production cycle, a low sintering temperature, low energy consumption, low production cost, and minimal pollution, making it suitable for large-scale industrial production and possessing broad application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of whisker preparation, in particular to a production process of carbide whiskers. Background Art

[0002] The higher the level of structural ceramic material, the higher the requirements for mechanical properties. To date, ceramic whiskers with a high elastic modulus remain the best additive phase to overcome the inherent brittleness of structural ceramics and significantly improve their various mechanical properties.

[0003] Whiskers are highly oriented, fibrous single crystals with an aspect ratio typically greater than 10. Because they are single crystals with few defects, their strength approaches the theoretical value of a complete crystal. Ceramic whiskers, with their high elastic modulus, are highly effective additives for ceramics, metals, and polymers due to their high strength, high melting point, and corrosion resistance. They can significantly improve the flexural strength and fracture toughness of composite materials, as well as their resistance to high temperatures, corrosion, and thermal shock.

[0004] SiC whiskers are currently the only high-elastic modulus ceramic whiskers with good marketability and wide application. However, SiC whiskers have the disadvantages of a low thermal expansion coefficient and poor wettability with most metals, which hinders the whiskers from fully realizing their toughening and reinforcing effects. TiC whiskers also have the advantages of high strength, high melting point, and corrosion resistance. At the same time, they have a high thermal expansion coefficient and good wettability with most metals. Therefore, for many ceramic and metal materials, TiC whiskers are a more ideal toughening and reinforcing phase. In addition, TiC also has good electrical conductivity. Adding an appropriate amount of TiC whiskers to non-conductive ceramic materials can make them into materials with good electrical conductivity that can be processed by electrical discharge machining, thereby greatly improving the machinability of the ceramic materials.

[0005] Currently, the main processes used to produce TiC whiskers are chemical vapor deposition (CVD) and carbothermal reduction (CTR). The CVD method is costly and difficult to mass-produce. The powder produced by the CTR method suffers from disadvantages such as a low whisker content, poor quality, and high levels of impurities, and similarly poses difficulties in mass production. Consequently, this significantly limits the application and widespread adoption of TiC whiskers.

[0006] Therefore, TiC whisker synthesis technology, how to prepare high-quality TiC whiskers on the basis of reducing costs, has become a bottleneck for its application in composite materials. Summary of the Invention

[0007] The first technical problem to be solved by the present invention is: in view of the shortcomings of the existing technology, a method for producing carbide whiskers with simple process, low energy consumption, low cost, less pollution and mass production is provided, and the carbide whiskers produced by this method have a high proportion, large aspect ratio, high straight crystal rate and smooth surface.

[0008] The second technical problem to be solved by the present invention is to provide a method for producing carbide whiskers and obtain carbide whiskers.

[0009] In order to solve the above-mentioned first technical problem, the technical solution of the present invention is:

[0010] A method for producing carbide whiskers comprises adding an appropriate amount of an organic mixture of organic acids and / or sugars to reaction raw materials of the carbide whiskers to prepare a precursor powder, wherein the organic mixture accounts for 1 to 10% of the total mass of the reaction raw materials; and calcining the precursor powder in a protective atmosphere to obtain the carbide whiskers.

[0011] As an improved technical solution, the organic acid in the organic mixture includes at least one of oxalic acid, tartaric acid, and benzoic acid; the sugar in the organic mixture includes at least one of glucose or cellulose.

[0012] As a further improved technical solution, the mass ratio of organic acid in the organic mixture is 10-90%, and the remainder is sugars.

[0013] As a preferred technical solution, the mass percentages of the components in the organic acid are: oxalic acid 0-50%, tartaric acid 0-100%, benzoic acid 0-50%; the mass percentages of the components in the sugar are: glucose 0-100%, and the remainder is cellulose.

[0014] As a preferred technical solution, the carbide whiskers are TiC whiskers, and the preparation method of the TiC whiskers comprises the following steps:

[0015] (1) preparing a precursor powder by taking raw materials of titanium dioxide, carbon black, nickel powder, sodium chloride and an appropriate amount of organic mixture;

[0016] (2) placing the precursor powder into a graphite crucible, then placing the graphite crucible into a sintering furnace, using argon, hydrogen or argon-hydrogen mixed gas as a protective atmosphere, heating to 1300-1700° C. at a heating rate of 10-100° C. / min, and keeping the temperature for 60-300 min to obtain the TiC whisker product.

[0017] As a preferred technical solution, the molar ratio of the raw materials titanium dioxide, carbon black, nickel powder and sodium chloride is 0.8-1.2:2.5-4.0:0.02-0.1:0.1-1.

[0018] As a preferred technical solution, the method for preparing the precursor powder is to prepare a uniformly mixed precursor powder by stirring or ball milling the raw materials of titanium dioxide, carbon black, nickel powder, sodium chloride and an organic mixture of an appropriate amount of organic acid and sugar.

[0019] As an improved technical solution, in step (2), an argon-hydrogen mixture is used as the protective atmosphere, and argon is passed throughout the sintering process. The argon flow rate is 1 L / min before 1000°C, and the argon flow rate is 3-10 L / min from 1000°C to the end of the insulation reaction. After the insulation is completed, the argon flow rate is adjusted to 0.5 L / min, and the argon is turned off when the temperature drops to below 400°C; when the temperature rises to 1000°C, while maintaining the argon flow rate at 3-10 L / min, hydrogen is started to be passed, and the hydrogen flow rate is 1-6 L / min. After the hydrogen insulation reaction is carried out for 60-300 minutes, the hydrogen is turned off.

[0020] As another improved technical solution, in step (2), hydrogen is used as the protective atmosphere, and hydrogen is passed throughout the sintering process. The hydrogen flow rate is 1 L / min before 1000°C; from 1000°C to the end of the insulation reaction, the hydrogen flow rate is 3 to 10 L / min; after the insulation is completed, the hydrogen flow rate is adjusted to 0.5 L / min, and the hydrogen is turned off when the temperature drops below 400°C.

[0021] As another improved technical solution, in step (2), argon is used as the protective atmosphere, and argon is passed throughout the sintering process. The argon flow rate is 1 L / min before 1000°C; the argon flow rate is 3 to 10 L / min from 1000°C to the end of the insulation reaction; after the insulation is completed, the argon flow rate is adjusted to 0.5 L / min, and the argon is turned off when the temperature drops below 400°C.

[0022] In order to solve the above second technical problem, the technical solution of the present invention is:

[0023] The carbide whiskers prepared by the carbide whisker production method have a whisker ratio of ≥80%, a whisker diameter of 0.5-5 μm, and an aspect ratio of 20-40.

[0024] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] When preparing carbide whiskers, the present invention adds a mixture of organic acids and sugars at a mass ratio of 1 to 10% to the raw material precursor mixture. Depending on the type of carbon black used, the amount of the organic mixture added and the ratio of the organic acids and sugars in the organic mixture are adjusted to achieve the purpose of adjusting the pH value and heating loss of the carbon black. Adjusting the pH value and heating loss can promote the decomposition of NaCl, promote the migration of the catalyst Ni, improve the mass transfer process, increase the mass transfer efficiency, and optimize the whisker growth environment. As a result, the powder produced has a high whisker ratio, a large aspect ratio, a high straight crystal ratio, and a smooth surface. The whisker ratio can reach over 80%, with a whisker diameter of 0.5-5μm and an aspect ratio of 10-40.

[0026] The TiC whisker production method of the invention has simple process, convenient operation, short production cycle, low sintering temperature, low energy consumption, little pollution, is suitable for large-scale industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and examples.

[0028] Figure 1 This is an SEM image of the TiC whisker prepared in Example 1 of the present invention;

[0029] Figure 2 XRD pattern of TiC whiskers prepared in Example 1 of the present invention;

[0030] Figure 3 This is the SEM image of the TiC whisker prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0031] Below in conjunction with accompanying drawing and embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0032] like Figure 1 and Figure 2 As shown, from Figure 1 It can be seen from the SEM image that the whiskers in the obtained TiC whiskers account for 80-90%, the whiskers with an aspect ratio of 20-40 account for 50-60%, and the straight crystal rate is 85-95%.

[0033] from Figure 2 It can be seen from the XRD pattern that the product obtained in this embodiment is TiC.

[0034] Example 1

[0035] The raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to a molar ratio of 1:2.71:0.05:0.5, and an organic mixture of organic acid and sugar was weighed at 4% of the total mass of the above powders.

[0036] Commercially available C311 carbon black was used;

[0037] The organic mixture contains 90% organic acid and the remainder is sugar;

[0038] The mass percentages of the components in the organic acid are: oxalic acid (H2C2O4) 5%, tartaric acid (C4H6O6) 90%, benzoic acid (C7H6O2) 5%; the mass percentages of the components in the sugar are: glucose (C6H 12 O6) 90%, the remainder is cellulose ((C6H 10 O5)n).

[0039] Put all the above powders and organic mixture into a polyester barrel; add appropriate amount of anhydrous ethanol and alumina balls, and ball mill for 10 hours to obtain a uniformly mixed slurry. After ball milling, vacuum dry it and pass it through a 100-mesh sieve to obtain a uniformly mixed precursor powder.

[0040] Place the precursor powder into a graphite crucible, then place the graphite crucible into a box-type atmosphere sintering furnace, tighten the valve, turn on the vacuum pump to evacuate, and evacuate to a vacuum state (vacuum indication number -0.1) to ensure that the oxygen in the furnace is completely evacuated and confirm that the box-type furnace has good sealing. Then start to pass argon gas. After the vacuum gauge returns to zero, that is, after the furnace returns to one atmospheric pressure, open the exhaust valve and check whether there is gas discharged to confirm whether the exhaust is unobstructed.

[0041] The argon flow rate was adjusted to 1 L / min, and the mixture was heated to 1400°C at a heating rate of 20°C / min, and kept at this temperature for 180 minutes.

[0042] Argon was passed throughout the sintering process. The argon flow rate was 1 L / min before 1000°C and 3 L / min from 1000°C to the end of the insulation reaction.

[0043] When the temperature reaches 1000°C, hydrogen is introduced at a rate of 1 L / min while maintaining an argon flow rate of 3 L / min. After 90 minutes of heat preservation, the hydrogen is turned off. After the heat preservation is completed, the argon flow rate is adjusted to 0.5 L / min, and the argon is turned off when the temperature drops below 400°C.

[0044] When the temperature in the furnace drops below 60° C., the crucible can be taken out, and the powder in the crucible can be ground in a mortar to obtain the TiC whisker powder.

[0045] The unpurified TiC whiskers obtained in this embodiment were subjected to SEM and XRD detection, and the results were as follows: Figure 1 、 2 shown.

[0046] Example 2

[0047] Raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to a molar ratio of 1.1:3:0.08:0.8, and an organic mixture of organic acid and sugar was weighed according to 7% of the total mass of the above powders.

[0048] Commercially available C666 carbon black was used;

[0049] The organic mixture contains 88% organic acid and the remainder is sugar;

[0050] The mass percentages of the components in the organic acid are: oxalic acid (H2C2O4) 7%, tartaric acid (C4H6O6) 86%, benzoic acid (C7H6O2) 7%; the mass percentages of the components in the sugar are: glucose (C6H 12 O6) 6%, the balance is cellulose ((C6H 10 O5)n).

[0051] Put all the above powders and organic mixture into a polyester barrel; add appropriate amount of anhydrous ethanol and alumina balls, and ball mill for 8 hours to obtain a uniformly mixed slurry. After ball milling, vacuum dry it and pass it through a 100-mesh sieve to obtain a uniformly mixed precursor powder.

[0052] The precursor powder is placed in a graphite crucible with an inner diameter of 110 mm, with 50 g of precursor powder in each crucible. The graphite crucible is then placed in a box-type atmosphere sintering furnace, the valve is tightened, the vacuum pump is turned on to evacuate the furnace, and the furnace is evacuated to a vacuum state (vacuum indication number -0.1) to ensure that the oxygen in the furnace is completely evacuated and to confirm that the box-type furnace has good sealing. Then, hydrogen is started to pass through. After the vacuum gauge returns to zero, that is, after the furnace has restored to one atmospheric pressure, the exhaust valve is opened to check whether gas is discharged to confirm whether the exhaust is unobstructed.

[0053] Adjust the hydrogen flow rate to 1 L / min, heat to 1500°C at a heating rate of 40°C / min, and hold at this temperature for 150 minutes. Hydrogen is introduced throughout the sintering process, with a hydrogen flow rate of 1 L / min before 1000°C and 3 L / min from 1000°C until the end of the hold.

[0054] After the insulation is completed, the hydrogen flow rate is adjusted to 0.5L / min, and the hydrogen is turned off when the temperature drops below 400℃.

[0055] When the temperature in the furnace drops below 60° C., the crucible can be taken out and the powder in the crucible can be ground with a mortar to obtain a powder containing more than 80% TiC whiskers.

[0056] Example 3

[0057] The raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to a molar ratio of 1.0:2.8:0.04:0.6, and an organic mixture of organic acid and sugar was weighed according to 10% of the total mass of the above powders.

[0058] Commercially available n660 carbon black was used;

[0059] The organic mixture contains 60% organic acid and the remainder is sugar;

[0060] The mass percentages of the components in the organic acid are: oxalic acid (H2C2O4) 8%, tartaric acid (C4H6O6) 92%; the sugar is glucose (C6H 12 O6)100%.

[0061] Put all the above powders and organic mixture into a polyester barrel; add appropriate amount of anhydrous ethanol and alumina balls, and ball mill for 12 hours to obtain a uniformly mixed slurry. After ball milling, vacuum dry and pass through a 100-mesh sieve to obtain a uniformly mixed precursor powder.

[0062] The precursor powder is placed in a graphite crucible with an inner diameter of 110 mm, with 50 g of precursor powder in each crucible. The graphite crucible is then placed in a box-type atmosphere sintering furnace, the valve is tightened, the vacuum pump is turned on to evacuate the furnace, and the furnace is evacuated to a vacuum state (vacuum indication number -0.1) to ensure that the oxygen in the furnace is completely evacuated and to confirm that the box-type furnace has good sealing. Then, argon is started to pass through. After the vacuum gauge returns to zero, that is, after the furnace has restored to one atmospheric pressure, the exhaust valve is opened to check whether there is gas discharged to confirm whether the exhaust is unobstructed.

[0063] Adjust the argon flow rate to 1 L / min, heat to 1450°C at a heating rate of 60°C / min, and hold for 180 minutes. Maintain argon throughout the sintering process, with an argon flow rate of 1 L / min before 1000°C and 4.0 L / min from 1000°C to the end of the hold.

[0064] After the insulation is completed, the argon flow rate is adjusted to 0.5L / min, and the argon is turned off when the temperature drops below 400℃.

[0065] When the temperature in the furnace drops below 60° C., the crucible can be taken out and the powder in the crucible can be ground with a mortar to obtain a powder containing more than 80% TiC whiskers.

[0066] Comparative Example 1

[0067] The difference between Comparative Example 1 and Example 1 is that no organic mixture is added when preparing the precursor powder:

[0068] The raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to the molar ratio of 1:2.71:0.05:0.5.

[0069] Commercially available C311 carbon black was used;

[0070] Put all the above powders into a polyester barrel; add appropriate amount of anhydrous ethanol and alumina balls, and ball mill for 10 hours to obtain a uniformly mixed slurry. After ball milling, vacuum dry it and pass it through a 100-mesh sieve to obtain a uniformly mixed precursor powder.

[0071] The sintering process is the same as that in Example 1.

[0072] Will Figure 1 and Figure 3 A comparison shows that, when the same C211 carbon black is used but no organic admixture is added, the powder produced has a low TiC whisker content of only 30-40%. Secondly, the whisker quality is poor, with a low straightness rate and an uneven surface. Third, the powder contains a high level of impurities. Clearly, without the addition of an organic admixture, not only does the whisker growth environment suffer, resulting in a low whisker content and poor quality, but also, due to poor mass transfer and inadequate decomposition of NaCl, the carbothermal reduction reaction is severely impacted, resulting in an incomplete reaction and excessive amounts of impurities such as residual carbon, residual NaCl, and unreacted TiO2 in the powder produced.

Claims

1. A method for producing carbide whiskers, characterized in that: Adding an appropriate amount of an organic mixture of an organic acid and a sugar to the reaction raw materials of the carbide whiskers to prepare a precursor powder, wherein the organic mixture accounts for 1 to 10% of the total mass of the reaction raw materials; calcining the precursor powder in a protective atmosphere to obtain the carbide whiskers; The carbide whiskers are TiC whiskers; The mass ratio of organic acid in the organic mixture is 10-90%, and the balance is sugars; the mass percentages of the components in the organic acid are: oxalic acid 5-50%, tartaric acid 86-100%, and benzoic acid 0-50%; the mass percentages of the components in the sugars are: glucose 6-100%, and the balance is cellulose.

2. The method for producing carbide whiskers as claimed in claim 1, wherein The following steps are involved: (1) Prepare precursor powder from raw materials of titanium dioxide, carbon black, nickel powder, sodium chloride and an appropriate amount of organic mixture; (2) The precursor powder is placed in a graphite crucible, and then the graphite crucible is placed in a sintering furnace. Argon, hydrogen or argon-hydrogen mixed gas is used as a protective atmosphere, and the temperature is heated to 1300-1700°C at a heating rate of 10-100°C / min. The reaction is kept at this temperature for 60-300 minutes to obtain the TiC whisker product.

3. The method for producing carbide whiskers according to claim 2, wherein: The molar ratio of the raw materials titanium dioxide, carbon black, nickel powder and sodium chloride is 0.8-1.2:2.5-4.0:0.02-0.1:0.1-1.

4. The method for producing carbide whiskers according to claim 2, wherein: The method for preparing the precursor powder is to prepare a uniformly mixed precursor powder by stirring or ball milling raw materials of titanium dioxide, carbon black, nickel powder, sodium chloride and an organic mixture of appropriate organic acids and sugars.

5. The method for producing carbide whiskers according to claim 2, wherein: In step (2), an argon-hydrogen mixture is used as the protective atmosphere, and argon is passed throughout the sintering process. The argon flow rate is 1 L / min before 1000°C, and the argon flow rate is 3-10 L / min from 1000°C to the end of the insulation reaction. After the insulation is completed, the argon flow rate is adjusted to 0.5 L / min, and the argon is turned off when the temperature drops below 400°C. When the temperature rises to 1000°C, while maintaining the argon flow rate at 3-10 L / min, hydrogen is started to be passed, and the hydrogen flow rate is 1-6 L / min. After the hydrogen insulation reaction is carried out for 60-300 minutes, the hydrogen is turned off.

6. The method for producing carbide whiskers according to claim 2, wherein: In step (2), hydrogen is used as the protective atmosphere. Hydrogen is passed throughout the sintering process. The hydrogen flow rate is 1 L / min before 1000°C; the hydrogen flow rate is 3 to 10 L / min from 1000°C to the end of the insulation reaction; after the insulation is completed, the hydrogen flow rate is adjusted to 0.5 L / min, and the hydrogen is turned off when the temperature drops below 400°C.

7. The method for producing carbide whiskers according to claim 2, wherein: In step (2), argon is used as the protective atmosphere and argon is passed throughout the sintering process. The argon flow rate is 1 L / min before 1000°C; the argon flow rate is 3 to 10 L / min from 1000°C to the end of the insulation reaction; after the insulation is completed, the argon flow rate is adjusted to 0.5 L / min, and the argon is turned off when the temperature drops below 400°C.

8. The carbide whiskers prepared by the method for producing carbide whiskers according to claim 1, wherein: The carbide whiskers have a whisker ratio of ≥80%, a whisker diameter of 0.5-5 μm, and an aspect ratio of 20-40.

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