The goal of this paper is to simplify and reduce the cost of manufacturing tungsten carbide. The work presents the results of experimental studies that prove the possibility of synthesizing fine and ultrafine crystalline phases of tungsten carbide in the DC arc discharge plasma ignited in open air by a developed vacuumless technique. The synthesis is implemented in the process of arc discharge burning between the graphite rod (anode) placed inside the cavity of the graphite cathode in the presence of graphite and tungsten powders used as initial precursors. The cathode cavity (reaction zone) is shielded from oxygen by a stream of carbon monoxide and carbon dioxide gases, which are generated during the arc discharge burning in an open air. After studying the influence of main process parameters (parameters of the discharge circuit and graphite electrode's dimensions) and optimizing the system, the authors obtained tungsten carbide phases without impurities of oxide phases. This allows simplifying significantly the technology of tungsten carbides synthesis by excluding the stage of vacuum creation.

Vacuumless synthesis of tungsten carbide in a self-shielding atmospheric plasma of DC arc discharge

A novel approach of waste tires rubber utilization via ambient air direct current arc discharge plasma

Synthesis of molybdenum carbide catalyst by DC arc plasma in ambient air for hydrogen evolution

Polymers and plastics are crucial materials in many sectors of our economy, due to their numerous advantages. They also have some disadvantages, among the most important are problems with the recycling and disposal of used plastics. The recovery of waste plastics is increasing every year, but over 27% of plastics are landfilled. The rest is recycled, where, unfortunately, incineration is still the most common management method. From an economic perspective, waste management methods that lead to added-value products are most preferred—as in the case of material and chemical recycling. Since chemical recycling can be used for difficult wastes (poorly selected, contaminated), it seems to be the most effective way of managing these materials. Moreover, as a result this of kind of recycling, it is possible to obtain commercially valuable products, such as fractions for fuel composition and monomers for the reproduction of polymers. This review focuses on various liquefaction technologies as a prospective recycling method for three types of plastic waste: PE, PP and PS.

https://www.mdpi.com/1996-1073/15/8/2719/pdf?version=1649744000

Current Trends in Waste Plastics’ Liquefaction into Fuel Fraction: A Review

Glass waste derived silicon carbide synthesis via direct current atmospheric arc plasma.

Silicon carbide (SiC) is a widely used material characterized by unique physical and chemical properties. In the paper, cubic silicon carbide nanowires are synthesized via the non-vacuum DC (direct current) arc discharge method. DC arc is generated between the graphite rod and the graphite crucible under ambient air conditions without any vacuum or applying special defenses to the used atmosphere equipment. According to experimental data, the percentage of silicon carbide of the total product in interval from 70 A to 100 A increases from 3.9% up to 26.7% (mass), and in interval from 130 A to 200 A of arc discharge current decreases from 26.1% down to 19.9% (mass). The silicon carbide wires are characterized by the typical core-shell SiC–SiOx structure. It is possible to control the phase composition and increase the yield of SiC by changing the arc discharge current amplitude. The optimal synthesis parameters using the DC source with the maximum current of 200 A are a current of 200 A, synthesis time of 12 s and a silicon fraction in the initial mixture not more than 25% (mass) to completely process the initial silicon into its carbide.

Cubic SiC nanowire synthesis by DC arc discharge under ambient air conditions

We proposed an efficient method toward the synthesis of higher tungsten boride WB5-x in the vacuumless direct current atmospheric arc discharge plasma. The crystal structure of the synthesized samples of boron-rich tungsten boride was determined using computational techniques, showing a two-phase system. The ab initio calculations of the energies of various structures with similar X-ray diffraction (XRD) patterns allowed us to determine the composition of the formed higher tungsten boride. We determined the optimal parameters of synthesis to obtain samples with 61.5% WB5-x by volume. The transmission electron microscopy measurements showed that 90% of the particles have sizes of up to 100 nm, whereas the rest of them may have sizes from 125 to 225 nm. Our study shows the possibility of using the proposed vacuumless method as an efficient and inexpensive way to synthesize superhard WB5-x without employing resource-consuming vacuum techniques.

Efficient Synthesis of WB5-x-WB2 Powders with Selectivity for WB5-x Content.

Synthesis and oxidation behavior of the materials based on carbon fibers and ultra-high temperature binary and high-entropy carbides

Ultra-refractory micropowder of the Hf-Ta-C system was synthesized using a DC atmospheric plasma electric arc discharge. The synthesis was carried out under the conditions of burning a DC arc discharge in an air environment due to the formation of a protective autonomous atmosphere from carbon dioxide and carbon monoxide gases. Hafnium and tantalum oxides and X-ray amorphous carbon were used as precursors. The main advantages of this method are simplicity of implementation, short time of the synthesis process, relatively low specific energy costs (less than 300 kJ / g), as well as the availability of equipment used for experiments. The results of studies have shown the possibility of synthesizing tantalum and hafnium carbides by the developed method. However, the product also contains phases of graphite and metal oxides, which is a disadvantage at this stage and a subject for further research. 

Yuliya Vassilyeva

Papers

Cubic SiC nanowire synthesis by DC arc discharge under ambient air conditions

A novel approach of waste tires rubber utilization via ambient air direct current arc discharge plasma

Efficient Synthesis of WB5-x-WB2 Powders with Selectivity for WB5-x Content.

Synthesis and oxidation behavior of the materials based on carbon fibers and ultra-high temperature binary and high-entropy carbides

Synthesis of ultra-high temperature metal carbides by atmospheric DC arc plasma processing