What Are the Methods of Producing Tungsten Carbide Powder?
1. Preparation method of tungsten carbide powder - temperature programmed gas-solid reaction method
Ultrafine tungsten carbide powder was prepared by using tungstic acid as tungsten precursor, methane as carbon source and reducing gas. Among them, in the programmed temperature carbonization method, the temperature rise procedure is to rise to 500 ℃ within 30 minutes, the temperature rise rate is 18 ℃ • min-1, and then rise from 500 ℃ to 800 ℃ within 20 minutes, the temperature rise rate is 10 ℃ • min-1, react at the set temperature for 12 hours, and naturally fall to room temperature under the protection of methane.
2. Production and preparation of tungsten carbide powder - reduction and carbonization two-step method
That is, W powder is prepared from tungsten precursor, and then carbonized with carbonaceous material to form WC powder.
3. Preparation method of tungsten carbide powder - one-step reduction carbonization method
That is, tungsten precursor (such as WO3) is directly reduced and carbonized to produce WC powder. This method generally requires the preparation of tungsten precursor with high activity. The continuous process of direct reduction and carbonization can shorten the process flow, improve the efficiency of ultrafine tungsten carbide powder generation, and obtain ultrafine tungsten carbide and its alloy powder with better uniformity and smaller particle size.
4. Production and preparation of tungsten carbide powder - intermittent microwave heating method
Add 0.3g of tungsten powder into the mixture of 30% H2O2, isopropanol and water, stay overnight, add 0.7g of XC-72 carbon powder, ultrasonic treatment can obtain uniform mixture liquid, dry, and use intermittent method to heat in the microwave oven for several minutes to obtain tungsten carbide nanocrystals.
5. Preparation method of tungsten carbide powder - gas phase method
(1) Chemical vapor deposition method: plasma enhanced chemical vapor deposition device is used. Tungsten fluoride (WF6), methane (CH4) and hydrogen (H2) are used as raw gas, and argon (Ar) is used as carrier gas. The flow of each gas is controlled by a separate flowmeter. The substrate is made of metal nickel, and the substrate is cleaned with acetone, deionized water, ethanol and deionized water, respectively, and then dried and put into the reaction chamber. Before chemical vapor deposition, 100mL of hydrogen gas is injected into the hot atmosphere for 30min to remove oxides on the substrate surface. The samples after chemical vapor deposition are annealed in nitrogen. Spherical nano-tungsten carbide thin films with a diameter of 20~35 nm were prepared by plasma-enhanced chemical vapor deposition using tungsten fluoride and methane as precursors.
(2) Fixed bed chemical vapor method: weigh appropriate amount of nano WO3 powder, put it evenly in the quartz reaction boat, and place the quartz reaction boat in the high-temperature stainless steel tubular reactor（ ψ 90cm), and then place the stainless steel reactor in the tubular resistance furnace. The temperature rises from 540 ℃ to 660 ℃, which is the stage of H2 reducing nanoWO3. When the temperature gradually rises to 660 ℃, the H2 flow should be adjusted to increase. Increasing the H2 flow is beneficial to take away the water vapor and make the reaction process go smoothly. After the reaction is held at 660 ℃ for 1.5h, the nano WO3 powder in the quartz reaction boat is completely reduced to nano α- W powder. At this time, reduce the H2 flow, open the acetylene gas valve, control the acetylene flow, and the reaction enters the carbonization stage. Raise the temperature to 800 ℃ and keep it at 800 ℃ for 4h. After the carbonization process, the quartz reacts with the nano particles in the boat α- W powder is basically transformed into nano-WC powder. At this time, close the acetylene valve and reduce the H2 flow. Continue to add a small amount of high-purity H2 to the stainless steel reactor to cool to room temperature.
(3) Chemical vapor condensation method: use high-purity CO carrier gas to pass through the evaporator containing W (CO) 6 precursor. The carrier gas flow rate is 1200 mL/min, and the temperature of the evaporator is controlled at 120 ℃. Then the carrier gas carries the precursor steam in the temperature range of 600~800 ℃ in the tubular reactor, and the CO gas is decomposed into CO2 and C, and W and C are combined at about 1000 ℃ to produce nano tungsten carbide, and WC can be obtained in the collection chamber.
(4) Gas phase carbonization method: WO3 is used as raw material and methanol is used as carbon source. Under the action of Co/Fe catalyst, nanometer WC can be obtained by reaction at 450~950 ℃ for 1.5~4h. The low-temperature catalytic cracking of methanol is adopted. The methanol enters the preheating pipe through the liquid pump flowmeter, and the temperature of the preheating pipe is controlled at 300~420 ℃. After the methanol is preheated and vaporized, it is sent to the catalytic cracker. The methanol gas can be cracked at 420~550 ℃ to obtain the required reaction atmosphere CO and H2; CO and H2 react with nanometer WO3 powder for 1.5~4h to remove oxygen atoms and generate nanometer WC.
6. Preparation method of tungsten carbide powder - liquid phase method
Take open pure multi-walled carbon nanotubes (average inner diameter 50nm, outer diameter 100nm, length about 200 μ m) Immerse in 20mL ammonium paratungstate pentahydrate solution [(NH4) 10W12O41 • 5H2O] (pH ≈ 5), stir vigorously at 80 ℃ for 20min, and the resulting solution will naturally evaporate at room temperature. Then it was placed overnight, and the temperature was controlled at 120 ℃ for further drying. Finally, it was calcined at 350 ℃ for 2 hours to form tungsten carbide precursor. Chemicalbook can obtain one-dimensional tungsten carbide nanostructured materials by treating precursor at 1000~1300 ℃ under vacuum.
7. Production and preparation of tungsten carbide powder - solid phase method
(1) Supercritical CO2 heat treatment method: 1.0g tungsten powder (purity 99%, average diameter 2 μ m) 2.3 g sodium metal (purity 98%) and 10.0 g dry ice (purity>99%) were put into the autoclave respectively. Then put the sealed autoclave into the heating furnace, raise it to 600 ℃ at a heating rate of 10 ℃/min, and keep it at constant temperature for 20h. Then cool the autoclave to room temperature to obtain black solid products. Treat the sodium carbonate in the black solid products with dilute hydrochloric acid, and then heat treatment to obtain NaOH solution. Finally, wash the sample with distilled water, and dry it at 80 ℃ for 2h to obtain 0.2g product.
(2) Combustion method: the raw material blue tungsten, sodium azide and carbon black are mixed. Grind the reactant evenly in a ceramic mortar, and then press it into a stainless steel cylinder. The diameter of steel plate cylinder is 50mm, the wall thickness is 1mm, and the height is 60mm. The reaction ball weighs about 150~170g. The combustion reaction laboratory is usually conducted under the pressure of 2.5MPa argon. Put the reaction ball in the reactant, and then ignite the Ni-Cr metal wire on the top of the ball for combustion reaction.
(3) Spray heat conversion method: the ultra fast air spray heat conversion method with a temperature of 250~350 ℃ and a high pressure of 2.5~3.5MPa is used to first produce nanometer WO3 oxide powder, which is reduced to WO2.9 blue tungsten powder with hydrogen at 420~500 ℃, and then the ultra-high speed interlaminar shear crusher is used to further break the blue tungsten particles, and the particle size is graded by a high-speed rotating liquid classifier. The nano blue tungsten particle slurry is settled and separated by a continuous centrifuge, The large blue tungsten powder returns to the ultra-high speed interlaminar shear to continue shearing and crushing; In the process of blue tungsten shearing and crushing, phenolic resin isolating agent is added to coat the nano blue tungsten particles, and the tungsten powder with average particle size ≤ 80 nm is reduced at 700~740 ℃ in a reduction furnace with H2 at both ends and air extraction and drainage at the middle section. Then, the nano tungsten powder and nano carbon black powder are mixed, and phenolic resin isolating agent is added at the same time, and mixed in the ultra-high speed interlaminar shear to form a carbonization slurry, which is then centrifugally dried and carbonized at 980~1000 ℃, After being discharged from the furnace, the bridged pellets are broken by a high-speed interlaminar shear, and then separated by liquid spinning, continuous centrifugal sedimentation, centrifugal separation of alcohol, drying, and power-frequency air flow vibrating screen, passing 15 μ M sieve, WC powder with average particle size ≤ 90 nm can be made, and the particle shape is nearly spherical.
(4) Catalytic method: heat zeolite-HX, - NaX, sample KX and WO3 samples at 200 ℃ in He (99.99%) atmosphere for 2h, and then use CO (99.99%) at 100 mL/min and He (99.99%) at 20 mL/min to conduct reduction carbonization reaction with the samples at 300~750 ℃. In this way, CO and WO3 can generate WC at a lower temperature.
(5) Direct reduction carbonization method: WO3 powder and carbon powder are directly reduced and carbonized in a reducing atmosphere. The reaction is carried out in the alumina embedding device.
8. Preparation method of tungsten carbide powder - thermal decomposition method
It is a relatively simple method without template to prepare the precursor in a certain amount of surfactant, and then calcine the precursor at an appropriate temperature to decompose it to obtain one-dimensional nanomaterials. For example, PW (H3PW12O40) aqueous solution and CTAB (C13H33N (CH3) 3Br) aqueous solution are mixed to obtain white precipitate [C21.95H41.19N1.33] 3PW12O40. The precipitate was directly decomposed at 1000 ℃ for 10 h to obtain WC nanorods and WC nanoflakes.
9. Preparation method of tungsten carbide powder - magnetron sputtering method
It is a method to excite the carrier gas as a plasma to bombard the target and grow specific nanostructures on the substrate. For example, the WCX film deposited by magnetron sputtering on Si (110) substrate was heat treated to obtain W2C nanowires.
10. Production and preparation of tungsten carbide powder - explosive heating method
A special method for obtaining nanostructures by controlling the heating rate to raise the reactants from low temperature to high temperature in a very short time. For example, control the mixing powder of graphite and tungsten powder to heat and hold for 30min at a very fast heating rate (from room temperature to 1900 ℃ in one second) in the radiation furnace, and finally cool to room temperature.
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