Boron carbide has brilliant houses and is broadly used. Boron carbide is 2nd handiest to diamond and cubic boron nitride in hardness. It has many blessings, along with excessive melting point, low density, excessive power, extensive neutron absorption pass-phrase, tremendous thermoelectric overall performance, and correct mechanical balance. And we are able to use it in aerospace, countrywide defense, nuclear power, and wear-resistant generation.
At present, the carbothermal discount is the number one method for the industrial manufacturing of boron carbide. Besides, the practices of boron carbide production consist of self-propagating thermal discount, mechanochemical method, direct synthesis, sol-gel approach, and so on.
1. Carbothermal reduction
The carbothermal reduction technique normally makes use of boric acid or boric anhydride as raw fabric and carbon as a reducing agent to carry out excessive-temperature reduction response in an electric arc furnace. A gift, this technique is the number one method of commercial production of boron carbide, which has the advantages of simple response and occasional price.
Boric acid and carbon black have been used as raw materials and kept at 1700-1850 ℃ for 0.5-1.zero h. The boron carbide powder with excessive purity was calcined. The carbon content material became 20.7%, near the theoretical value. But, the dangers of this technique are: it needs to be finished at a higher temperature, which consumes a variety of electricity; the boron carbide manufacturing is straightforward to agglomerate, which wishes to be overwhelmed; the product is mixed with unreacted carbon, which desires to be removed by way of subsequent remedy.
2. Self-propagating thermal reduction
The self-propagating thermal discount method uses carbon black (or coke) and boric acid (or boric anhydride) as uncooked materials, energetic metallic substance (normally mg) as lowering agent or flux, and the heat generated with the aid of self-propagating combustion reaction of metal substance are used to synthesize boron carbide. The reaction equation is as follows: 6mg + C + 2b2o3 = 6mgo + B4C
This method has the benefits of low preliminary reaction temperature (a thousand-1200 ℃), energy saving, rapid reaction, and easy device. The synthesized B4C powder has excessive purity and super particle length (0.1 – four.0 μ m) and usually does not want to be overwhelmed.
Using Na2B4O7, Mg, and C as uncooked substances, Jiang et al. organized B4C powder with a particle size of 0.6 μ m by using a self-propagating thermal discount. However, the MgO produced through the response should be eliminated via an additional system, and it’s miles difficult to dispose of.
The mechanochemical technique makes use of boron oxide powder, magnesium powder and graphite powder as uncooked materials, the use of the rotation or vibration of the ball mill to make the more difficult ball milling medium impact, grind and stir the uncooked materials vigorously, and induce the chemical reaction at a temperature barely higher than the room temperature to put together boron carbide powder. The guidance temperature of this method is low, so it’s miles a promising preparation approach.
Deng et al. organized B4C powder with B2O3: C: Mg mass ratio of 10:1:eleven by way of the mechanochemical method. The particle size of the powder becomes a hundred-two hundred nm. According to yogurt et al., the satisfactory mass ratio of Mg: C is nine:2 – 10:1. However, MgO, the derivative of this approach, is challenging to be obliterated, and it commonly takes a long term for ball milling.
Four. Direct synthesis
The direct boron carbide manufacturing technique is to prepare via very well blending the carbon powder and boron powder and reacting in a vacuum or inert surroundings of 1700 – 2100 ℃. The purity of boron carbide organized by using direct synthesis is high, and the B / C ratio inside the response is simple to control. Nevertheless, the coaching manner of boron carbide used for synthesis is the fantastically complex and excessive price. Therefore, this method has a few boundaries.
5. Sol-gel technique
Sol-gel approach (Sol-gel) refers back to the technique of solidifying inorganic or steel alkoxides through the solution, sol, and gel, and then heat-handled to gain solid compounds. The superiority of this technique is that the aggregate of uncooked substances is more uniform, the response temperature is low, the product is bulky, and the particle size of B4C powder is small.
Sinha et al. combined the boric acid and citric acid below the conditions of pH=2-3 and 84-122. Transparent and strong gold gel can be formed. Whilst heated to seven-hundred tiers in a vacuum furnace, the porous soft borate citric acid precursor can be acquired. The precursor is stored under vacuum for one thousand-1450 at 2h, and the B4C powder with a particle size of about 2.25 M can be received.
Luoyang Tongrun group studied the impact of reaction time, temperature, and the specific uncooked material ratio at the B4C within the boric acid citric acid gel reaction machine. Whilst controlling the preliminary mass charge of boric acid and citric acid to 2.2:1, the content material of unfastened carbon in the product turned into 2.38% when the reaction temperature changed into 1500 3.5H. However, the production performance of this technique is low, and it isn’t always handy to get big-scale applications.
With the development of present-day science and era, boron carbide plays a more and more critical role in enterprise and life. Therefore, a suitable boron carbide production will be an essential determinant of the development of boron carbide within the future.