Boron carbide has notable properties and is extensively used. Boron carbide is second most effective to diamond and cubic boron nitride in hardness. It has many advantages, along with excessive melting factor, low density, excessive strength, broad neutron absorption go-phase, high-quality thermoelectric overall performance, and proper mechanical stability. And we will use it in aerospace, national defense, nuclear energy, and put on-resistant era.
At present, the carbothermal reduction is the number one method for the commercial manufacturing of boron carbide. besides, the practices of boron carbide manufacturing include self-propagating thermal reduction, mechanochemical approach, direct synthesis, sol-gel method, and so forth.
1. Carbothermal discount
The carbothermal reduction method generally makes use of boric acid or boric anhydride as raw material and carbon as a reducing agent to carry out high-temperature reduction reaction in an electric powered arc furnace. At gift, this technique is the primary technique of business manufacturing of boron carbide, which has the benefits of easy reaction and occasional value.
Boric acid and carbon black had been used as uncooked materials and saved at 1700-1850 ℃ for zero.5-1.zero h. The boron carbide powder with excessive purity was calcined. The carbon content material turned into 20.7%, near the theoretical cost. but, the disadvantages of this approach are: it desires to be finished at a higher temperature, which consumes a variety of power; the boron carbide production is simple to agglomerate, which desires to be overwhelmed; the product is blended with unreacted carbon, which wishes to be eliminated by means 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 raw materials, energetic metal substance (normally mg) as lowering agent or flux, and the warmth generated through self-propagating combustion reaction of metallic substance are used to synthesize boron carbide. The reaction equation is as follows: 6mg + C + 2b2o3 = 6mgo + B4C
This technique has the benefits of low initial reaction temperature (a thousand-1200 ℃), energy saving, rapid response, and easy device. The synthesized B4C powder has high purity and superb particle size (zero.1 – four.0 μ m) and commonly does not want to be beaten.
the use of Na2B4O7, Mg, and C as uncooked materials, Jiang et al. prepared B4C powder with a particle size of zero.6 μ m by means of self-propagating thermal discount. but the MgO produced through the reaction need to be removed by means of additional manner, and it’s miles tough to do away with.
The mechanochemical approach makes use of boron oxide powder, magnesium powder and graphite powder as raw substances, using the rotation or vibration of the ball mill to make the harder ball milling medium impact, grind and stir the uncooked substances vigorously, and set off the chemical response at a temperature slightly better than the room temperature to put together boron carbide powder. The education temperature of this approach is low, so it’s miles a promising guidance approach.
Deng et al. organized B4C powder with B2O3: C: Mg mass ratio of 10:1:eleven through the mechanochemical technique. The particle size of the powder become one hundred-200 nm. consistent with yogurt et al., the fine mass ratio of Mg: C is nine:2 – 10:1. but, MgO, the spinoff of this technique, is challenging to be obliterated, and it usually takes a long term for ball milling.
4. Direct synthesis
The direct boron carbide production approach is to prepare via thoroughly blending the carbon powder and boron powder and reacting in a vacuum or inert environment of 1700 – 2100 ℃. The purity of boron carbide prepared by direct synthesis is high, and the B / C ratio in the reaction is simple to manipulate. still, the practise method of boron carbide used for synthesis is fantastically complicated and high fee. therefore, this method has a few barriers.
5. Sol-gel technique
Sol-gel technique (Sol-gel) refers back to the approach of solidifying inorganic or metallic alkoxides via the answer, sol, and gel, after which warmth-treated to gain solid compounds. the prevalence of this method is that the aggregate of raw substances is more uniform, the reaction temperature is low, the product is bulky, and the particle length of B4C powder is small.
Sinha et al. mixed the boric acid and citric acid under the conditions of pH=2-three and eighty four-122. obvious and solid gold gel can be fashioned. while heated to 700 tiers in a vacuum furnace, the porous smooth borate citric acid precursor may be received. The precursor is saved below vacuum for a thousand-1450 at 2h, and the B4C powder with a particle size of approximately 2.25 M can be obtained.
Luoyang Tongrun crew studied the impact of reaction time, temperature, and extraordinary raw material ratio on the B4C within the boric acid citric acid gel response device. whilst controlling the initial mass fee of boric acid and citric acid to two.2:1, the content material of unfastened carbon within the product become 2.38% when the response temperature become 1500 three.5H. however, the manufacturing efficiency of this method is low, and it is not handy to get massive-scale applications.
With the development of latest technological know-how and technology, boron carbide performs a more and more critical position in enterprise and existence. therefore, a suitable boron carbide manufacturing can be an essential determinant of the improvement of boron carbide inside the future.