A method for producing TiN whiskers

Abstract

The application discloses a production method of TiN whisker, which comprises the following steps: (1) taking raw materials titanium dioxide, carbon black, nickel powder, sodium chloride and an appropriate amount of organic mixture of organic acid and saccharide to prepare precursor powder; the organic mixture is 1-10% of the total mass of the reaction raw materials; (2) putting the precursor powder into a graphite crucible, then putting the graphite crucible into a sintering furnace, using ammonia gas and nitrogen gas or nitrogen-hydrogen mixed gas as a protective atmosphere, heating to 1100-1500 DEG C at a heating speed of 10-100 DEG C / min, and keeping warm for 60-300 min to obtain the TiN whisker product. The TiN whisker production method has the advantages of simple process, convenient operation, short production period, low sintering temperature, low energy consumption, less pollution, suitability for large-scale industrial production and wide application prospect.

Description

Technical Field

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

[0002] 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 a high elastic modulus, due to their high strength, high melting point, and corrosion resistance, are highly effective additives for ceramics, metals, and polymers. They can significantly improve the flexural strength and fracture toughness of composites, as well as their resistance to high temperatures, corrosion, and thermal shock. SiC whiskers are currently the only high-elastic modulus ceramic whiskers with a good market presence and widespread application. However, SiC whiskers suffer from a low coefficient of thermal expansion and poor wettability with most metals, hindering their full toughening and reinforcing properties. TiN whiskers also offer advantages such as high strength, high melting point, and corrosion resistance. Furthermore, they have a high coefficient of thermal expansion and good wettability with most metals, making them a more ideal toughening and reinforcing phase for many ceramic and metal materials. In addition, TiN also has good electrical conductivity. Adding an appropriate amount of TiN whiskers to non-conductive ceramic materials can make them into materials with good electrical conductivity that can be processed by electrospark machining, thereby greatly improving the machinability of ceramic materials.

[0003] Currently, the main processes used to produce TiN 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 TiN whiskers.

[0004] Therefore, TiN whisker synthesis technology, how to prepare high-quality TiN whiskers on the basis of reducing costs, has become a bottleneck for its application in composite materials. Summary of the Invention

[0005] 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 TiN whiskers with simple process, low energy consumption and less pollution is provided, and the TiN whiskers produced by this method have a high proportion, large aspect ratio, high straight crystal rate and smooth surface.

[0006] The second technical problem to be solved by the present invention is to provide a method for producing TiN whiskers to obtain TiN whiskers.

[0007] In order to solve the above-mentioned first technical problem, the technical solution of the present invention is:

[0008] A method for producing TiN whiskers comprises the following steps:

[0009] (1) preparing a precursor powder from an organic mixture of raw materials including titanium dioxide, carbon black, nickel powder, sodium chloride, and an appropriate amount of organic acid and sugar; the organic mixture accounts for 1 to 10% of the total mass of the reaction raw materials;

[0010] (2) placing the precursor powder into a graphite crucible, then placing the graphite crucible into a sintering furnace, using ammonia and nitrogen, or hydrogen and nitrogen as a protective atmosphere, heating to 1100-1500° C. at a heating rate of 10-100° C. / min, and keeping the temperature for 60-300 min to obtain the TiN whisker product.

[0011] As an improved technical solution, the molar ratio of the raw materials titanium dioxide, carbon black, nickel powder and sodium chloride is 0.8-1.2:1.5-3.0:0.02-0.1:0.1-1.

[0012] 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.

[0013] As an improved technical solution, the mass ratio of organic acid in the organic mixture is 10-90%, and the remainder is sugars.

[0014] As a further improved 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 sugars are: glucose 0-100%, and the remainder is cellulose.

[0015] As an improved 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.

[0016] As an improved technical solution, in step (2), hydrogen and nitrogen are used as protective atmospheres, and nitrogen is passed throughout the sintering process. The nitrogen flow rate is 1 L / min before 1000°C. At 1000°C, the nitrogen flow rate is adjusted to 3-10 L / min, and hydrogen is started to be passed, with a hydrogen flow rate of 1-6 L / min. After keeping warm for 60-300 minutes, the hydrogen is turned off. After the insulation is completed, the nitrogen flow rate is adjusted to 0.5 L / min, and the nitrogen is turned off when the temperature drops below 400°C.

[0017] As another improved technical solution, in step (2), ammonia and nitrogen are used as protective atmospheres. During the sintering process, nitrogen is first introduced at a nitrogen flow rate of 1 L / min. When the temperature rises to 1100°C, ammonia is started to be introduced, and the ammonia flow rate is adjusted to 3-10 L / min, and then the nitrogen is turned off. After the insulation reaction is completed, nitrogen is switched back and the nitrogen flow rate is adjusted to 0.5 L / min. When the temperature drops below 400°C, the nitrogen is turned off and the exhaust valve is closed.

[0018] In order to solve the above second technical problem, the technical solution of the present invention is:

[0019] The TiN whiskers prepared by the TiN whisker production method have a whisker ratio of ≥60%, a whisker diameter of 0.5-5 μm, and an aspect ratio of 20-40.

[0020] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0021] When preparing TiN 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 mass transfer efficiency, and optimize the whisker growth environment. As a result, the produced powder has a high whisker ratio, a large aspect ratio, a high straight crystal ratio, and a smooth surface. The whisker ratio can reach over 60%, with a whisker diameter of 0.5-5 μm and an aspect ratio of 10-40.

[0022] The TiN 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

[0023] The present invention will be further described below with reference to the accompanying drawings and examples.

[0024] Figure 1 This is a SEM image of the TiN whiskers prepared in Example 1 of the present invention;

[0025] Figure 2 XRD pattern of the TiN whiskers prepared in Example 1 of the present invention;

[0026] Figure 3 This is an SEM image of the TiN whisker prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0027] 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.

[0028] like Figure 1 and Figure 2 As shown, from Figure 1 It can be seen from the SEM image that the whiskers of the obtained TiN whiskers account for 60-70%, the whiskers with an aspect ratio of 20-40 account for 70-80%, and the straight crystal rate is 85-95%.

[0029] from Figure 2 It can be seen from the XRD pattern that the product obtained in this embodiment is TiN.

[0030] Example 1

[0031] The raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to a molar ratio of 1:2.0:0.05:0.5, and an organic mixture of organic acid and sugar was weighed according to 5% of the total mass of the above powders.

[0032] Commercially available C311 carbon black was used;

[0033] The mass ratio of organic acid in the organic mixture is 88%, and the remainder is sugar.

[0034] The mass percentages of the components in the organic acid are: oxalic acid (H2C2O4) 2%, tartaric acid (C4H6O6) 94%, benzoic acid (C7H6O2) 4%; the mass percentages of the components in the sugar are: glucose (C6H 12 O6) 92%, the remainder is cellulose ((C6H 10 O5)n).

[0035] 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.

[0036] 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 the furnace 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 nitrogen. 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.

[0037] The nitrogen flow rate was adjusted to 1 L / min, and the mixture was heated to 1000°C at a heating rate of 25°C / min, and the reaction was kept at this temperature for 180 minutes.

[0038] Nitrogen was introduced throughout the sintering process. The nitrogen flow rate was 1 L / min before 1000°C, and then adjusted to 3 L / min at 1000°C. Hydrogen was then introduced at a rate of 1 L / min. After 90 minutes of hydrogen-infused reaction, the hydrogen was turned off. The nitrogen flow rate was then adjusted to 0.5 L / min, and the nitrogen was turned off once the temperature dropped below 400°C.

[0039] 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 the powder with a TiN whisker content of more than 60%.

[0040] The unpurified TiN whiskers obtained in this embodiment were subjected to SEM and XRD tests, and the results were as follows: Figure 1 、 2 shown.

[0041] Example 2

[0042] The raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to a molar ratio of 0.9:2.6:0.06:0.6, and an organic mixture of organic acid and sugar was weighed according to 7% of the total mass of the above powders.

[0043] Commercially available C666 carbon black was used;

[0044] The mass ratio of organic acid in the organic mixture is 80%, and the remainder is sugar.

[0045] The mass percentages of the components in the organic acid are: oxalic acid (H2C2O4) 5%, tartaric acid (C4H6O6) 92%, benzoic acid (C7H6O2) 3%; the mass percentages of the components in the sugar are: glucose (C6H 12 O6) 65%, the balance is cellulose ((C6H 10 O5)n).

[0046] 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.

[0047] 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, nitrogen is started to flow in. 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.

[0048] During the sintering process, nitrogen was first introduced with a nitrogen flow rate of 1 L / min, and the sample was heated to 1400°C at a heating rate of 30°C / min, and kept warm for 160 minutes.

[0049] Before 1100℃, the nitrogen flow rate is 1L / min; but when the temperature rises to 1100℃, the nitrogen is turned off and replaced with ammonia, and the ammonia flow rate is 3L / min; after the insulation is completed, the ammonia is switched to nitrogen, and the nitrogen flow rate is adjusted to 0.5L / min, and the hydrogen is turned off when the temperature drops below 400℃.

[0050] 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 the powder with a TiN whisker content of more than 60%.

[0051] Comparative Example 1

[0052] The difference between Comparative Example 1 and Example 1 is that no organic mixture is added when preparing the precursor powder:

[0053] The raw materials titanium dioxide, carbon black, nickel powder and sodium chloride were weighed respectively according to the molar ratio of 1:2.0:0.05:0.5.

[0054] Commercially available C311 carbon black was used;

[0055] Put all the above powders 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.

[0056] The sintering process is the same as that in Example 1.

[0057] Will Figure 1 and Figure 3 By comparison, it can be seen that the powder prepared without adding the organic mixture has a TiN whisker content of less than 30%, a low straight crystal rate, and a rough surface. Moreover, the powder contains a lot of impurities and is difficult to purify.

Claims

1. A method for producing TiN whiskers, characterized in that The following steps are involved: (1) A precursor powder is prepared by taking an organic mixture of raw materials including titanium dioxide, carbon black, nickel powder, sodium chloride and an appropriate amount of organic acid and sugar; the organic mixture accounts for 1 to 10% of the total mass of the raw materials; 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; the mass ratio of the organic acid in the organic mixture is 10 to 90%, and the balance is sugar; the mass percentage of each component in the organic acid is: oxalic acid 0 to 50%, tartaric acid 0 to 100%, benzoic acid 0 to 50%; the mass percentage of each component in the sugar is: glucose 0 to 100%, and the balance is cellulose; (2) The precursor powder is placed in a graphite crucible, and then the graphite crucible is placed in a sintering furnace. Ammonia and nitrogen, or hydrogen and nitrogen, are used as a protective atmosphere. The crucible is heated to 1100-1500°C at a heating rate of 10-100°C / min, and the reaction is carried out at this temperature for 60-300 minutes to obtain the TiN whisker product.

2. The method for producing TiN whiskers according to claim 1, wherein: The molar ratio of the raw materials titanium dioxide, carbon black, nickel powder and sodium chloride is 0.8-1.2:1.5-3.0:0.02-0.1:0.1-1.

3. The method for producing TiN whiskers according to claim 1, 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.

4. The method for producing TiN whiskers according to claim 1, wherein: In step (2), hydrogen and nitrogen are used as protective atmospheres. Nitrogen is passed throughout the sintering process. The nitrogen flow rate is 1 L / min before 1000°C. At 1000°C, the nitrogen flow rate is adjusted to 3-10 L / min, and hydrogen is started to flow at a hydrogen flow rate of 1-6 L / min. After keeping warm for 60-300 minutes, the hydrogen is turned off. After the end of the insulation, the nitrogen flow rate is adjusted to 0.5 L / min, and the nitrogen is turned off when the temperature drops below 400°C.

5. The method for producing TiN whiskers according to claim 1, wherein: In step (2), ammonia and nitrogen are used as protective atmospheres. During the sintering process, nitrogen is first introduced at a nitrogen flow rate of 1 L / min. When the temperature rises to 1100°C, ammonia is introduced and the ammonia flow rate is adjusted to 3-10 L / min, and then the nitrogen is turned off. After the insulation reaction is completed, nitrogen is switched back and the nitrogen flow rate is adjusted to 0.5 L / min. When the temperature drops below 400°C, the nitrogen is turned off and the exhaust valve is closed.

6. The TiN whiskers prepared by the method for producing TiN whiskers according to claim 1, wherein: The TiN whiskers have a whisker ratio of ≥60%, a whisker diameter of 0.5-5 μm, and an aspect ratio of 20-40.

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