A team of early-career scientists from the School of Computer Science & Robotics of Tomsk Polytechnic University has developed a setup for obtaining superhard materials based on titanium carbides. It is the vacuum-free method that makes it advantageous in comparison with existing counterparts. Since in this case, the production of carbides does not require gas or liquid protective media and therefore expensive equipment: it runs in the open air. In this way, in addition to titanium carbide, TPU scientists have already obtained the samples of silicon carbide and boron carbide. The refractory and superhard materials are used in the manufacturing of power electronics elements, nuclear industrial products, ceramic armor plates, and other products. An article published in Technical Physics Letters presents a method for producing titanium carbide.
The project leader, As.Prof. Alexander Pak from the TPU Division of Automation and Robotics says:
‘Such materials are produced in different ways, one of them is an electric arc method. It is based on electric arc discharge that creates the required conditions for material synthesis. The method has not been introduced in the industry yet as it is considered relatively expensive. However, in the future, our solutions might bring its introduction closer.’
According to him, many research teams, which prepare carbides by direct-current arc discharge, organize the process in a vacuum, in protective inert conditions, e.g. of argon, hydrogen or helium.
‘This causes a number of necessary technical means and, accordingly, costs. The analysis of publications throughout the world shows that only 6 % of articles describe the successful synthesis of non-oxide materials in the open air, proposing their own approaches. Our team is part of this small percent, additionally, in literature, we have found no description of synthesis of silicon, boron, and titanium carbides in the plasma of a direct-current arc discharge in the open air,’ notes the researcher.
The setup developed at TPU can be placed on a regular desk, it occupies less than one square meter. It consists of simple elements: a power source, a direct current source, electrodes, and a control system. The process of carbide synthesis lasts literally a few seconds.
‘The problem of the protective atmosphere arises because if a discharge is applied to a material in the open air it will burn, i.e. oxidize, and we will obtain an oxide. A few years ago scientists revealed that at certain conditions a current arc discharge itself can generate a protective gas-plasma region which screens the products of synthesis from air oxygen. We used just the method, developing a group of current-arc methods,’
says the scientist.
A discharge gap is formed between the electrodes to which voltage is applied, an arc discharge is initiated and, accordingly, plasma. The process is accompanied by the release of energy of the arc discharge and an increase of temperature. The initial mixture – the powders of carbon and, for example, titanium – is heated up to several thousands of degrees, substance structure is changed, carbide is synthesized.
Alexander Pak explains: ‘Our innovation which allowed significantly simplifying the setup is a special geometry of the electrode system and operation modes of discharge circuit. One electrode is made out of graphite, shaped as glass and another one is installed in the glass. The process runs inside the glass, being protected from the external environment by the discharge from air oxygen itself.’
Another important innovation is a control system of the setup. It allows operation in the automated mode.
‘Experimental research devoted to the synthesis of any material requires ensuring the repeatability of experiments, otherwise, it is impossible to achieve the stability of discharge parameters and output product parameters. The control system is responsible for this. We have already received two copyright certificates for the software of the control system of the current-arc reactor and continue to improve the software. The setup and the method for producing titanium carbide are patent pending,’ says the project leader.
According to him, the team is planning to improve the technology in order to reduce impurities in the output product and increase its amount.
The resource base of the laboratory was equipped under the grant support of the British Petroleum.