• development and research of DC plasma sources and arc plasma reactors;

• research of processes and phenomena taking place in reaction arc zone and low-temperature plasma;

• research of dynamics and heat-mass transfer processes in atmospheric and reduced pressure plasma environments;

• plasma and high-temperature gas flows diagnostics and development of diagnostics measures;

• interaction of plasma jets and substances in various plasma-technological processes;

• research and implementation of plasma neutralization process of extra hazardous materials;

• synthesis and characterization of catalytic and tribological coatings in plasma environment;

• research of thermal and heterogenic processes when reacting combustion products outflow the catalytic surface;

• formation and modification of constructional material surfaces in plasma;

• synthesis of micro and nano dispersed granules and mineral fiber from hardly alloyed materials and investigation of properties.

 

Researchers of the Laboratory of Plasma Processing have over 40 years experience working in different fields of development, scientific research and application of low-temperature plasma technologies and are able to successfully simulate new plasma technologies, using plasma equipment, produced in the Laboratory.

 

 

 Plasma jet created by atmospheric pressure DC linear plasma generator

 

Different composition gas and its mixtures are used as plasma forming gas. Laboratory contains pilot production technological equipment, which is used to change and modify mechanical, tribological, chemical and optical properties of layers of different material surfaces. Constant updating of technical base, development and disposal of available analytic equipment enables to perform research of plasma sources, diagnostics of plasma flows and jets, analysis of gas dynamic characteristics and heat-mass transfer.

 

 

Laboratory of Plasma Processing have been developing novel plasma generators with no less capacity than 100 kW. Aiming at developing different construction and capacity linear plasma torches, processes occurring in reactive discharge chambers are considered. This information is obtained using similarity theory, generalizing voltamperic and thermal characteristics of plasma torches, which are determined when electric arc heats various gases under different pressures. The obtained results are compared with other conventional available data and with results of other authors’ works.

 

The following processes occurring in the reaction arc zone are investigated in the Laboratory: heat exchange, electric current strength variation at laminar and turbulent gas flow, its impact on characteristics of plasma flows and jets, impact of radiation at different gases.

 

Formation of high temperature gas flow, dynamics, heat exchange in different shape of channels and heat exchanger cells are analysed at the Laboratory of Plasma Processing. Operation regime of linear electric arc gas heaters and reactors, their operational characteristics were investigated, conditions of operation duration enhancement were determined, methods of arc turbulence and energy application in plasma devices were investigated. Thermal equilibrium conditions of atmosphere pressure plasma jet were analyzed after applying contact and contactless methods. Plasma velocity and temperature profiles were measured by cooling colorimetric probes, their local values were determined and afterwards compared to average values obtained from heat balance equations, patterns of velocity and temperature distribution were determined. Distributions of electron temperature and density were measured employing Langmuir probe with cooling sensor. It was determined that in most cases electron temperature in atmospheric pressure plasma may significantly exceed temperature of heavy particles.

 

 

Aiming at obtaining high-temperature ultra thin fibre, destroying hazardous substances, forming various coatings, synthesizing new materials, the interaction of electric arc and plasma jet with amorphous and dispersed materials is analyzed. Physical, chemical and mechanical properties of obtained materials are determined.

 

Coatings formed employing plasma method are obtained by laminating many dispersed particles, which before confronting the solid surface must be alloyed and plastic. Thus their shape and structure in the coating is very different. The interaction of particles and substrate during contact is defined by flow, deformation, and cooling processes. It has been determined that parameters of similar dispersity of the same kind of material particles are very different.

 

 

 

 

Plasma method of extra hazardous materials neutralization is applied to neutralize liquid and gaseous waste, when there is no possibility to neutralize by other thermal method. If temperature is lower than 1300 oC while firing waste in the combustion chamber, new toxic materials may be derived from organic chlorine waste – dioxines, furanes, etc. much more toxic than the initial product. Dioxines is a general name of organochlorine compounds and includes a large number of isomers, called aromatic ethers. The maximal concentration of dioxines is found in exhaust gas of domestic waste and turf firing plants. 

From 135 dioxines and 75 furanes 17 are extremely toxic. Their total limiting value is only 0.1 ng/m³. Plasma technology of toxic materials neutralization enables to completely neutralize almost all type hazardous substances, an opportunity arises to develop a mobile device. Properties of plasma device, such as very high temperature, short reaction time, opportunity to heat various gases, complete neutralization of hazardous materials, independence from fuel sources (using autonomic electricity generator), enables to use it directly in toxic materials storage sites. After performing research of hazardous waste neutralization in plasma environment it was determined that:

 

• novel, technologically innovative plasma equipment may neutralize waste and hazardous materials without polluting the environment, whereas combustion process in them may be used to produce energy;

• in plasma environment, at 5000–7000 K temperature, all organic and inorganic materials decompose into atoms, molecules and radicals;

• in all types of waste, remade by plasma technologies, none toxic materials nor secondary hazardous products remain. Final remake products is dark glass or slag, metal and hydrogen induces gas;

• destruction degree of hazardous materials in plasma devices comprises 99.99%.

 

 

Plasma spray deposition technology developed at the Laboratory allowes the formation of catalytic, tribological, protective and hard ceramic coatings used to improve operational properties of surface layers of constructional materials in mechanics, chemistry, energy and medicine. They accelerate resistance to corrosion for 10²–10³ times, significantly reduce friction and enhance resistance to mechanical wear. Using plasma technology, demand for expensive constructional materials diminishes since cheap constructional materials coated with different thickness coatings replace expensive materials consumed in large amounts.

 

In the plasma device, which supplies nonequilibrium atmospheric pressure plasma jet with unbalanced separate component temperatures, various materials are activated, synthesized and reach the processed surface having different energy. This provides necessary conditions for certain chemical reactions to be blocked in plasma jet and substratum surface. γ-phase Al₂O₃ coatings with extremely developed and active surface were synthesized, and this relevant while developing catalytic coatings. After heating at certain temperature, the coating specific surface was enhanced even more.

 

At present time coatings of solid carbon derivatives are synthesized in plasma devices. They are called plasma polymers. Plasma polymers – deposited thin films in plasma applied in many fields: microelectronics, biotechnology, semiconductors manufacturing, etc. their low price and good mechanical properties – resistance to corrosion, strength, insignificant specific mass, low wetting angle enable to compete with best up-to-date materials and alloys.

 

Performing research two plasma systems for the synthesis of hard ceramic and diamond type coating were developed together with new generation modified plasma generators, providing non-equilibrium plasma jet.

 

Equipment operate in the atmospheric and rarefied gas ambient – nitrogen, argon, hydrogen, acetylene, propane-butane and their mixtures.

 

 

Traditional technology and equipment presently used to produce mineral fibre need continuous operation process, complex and expensive alloying furnaces and insulation materials. Melting raw material in furnaces, afterwards converting the alloy into fibre by mechanical methods, a fibre is derived, filament diameter of which is bigger than 10 µm. This is not enough in new contemporary heat equipment and technologies. The quality and composition of manufactured fibre is limited by melting-point of raw material: high-temperature thermoisolation fibre cannot be manufactured by this method.

 

 

  

Plasma technology is the only alternative to obtain a high quality high-temperature fibre. Melting ceramic materials and forming a mineral fibre, an experimental plasma device with high capacity plasma generator has been developed at the Laboratory of Plasma Processing. It enables to form a fibre from SiO₂, Al₂O₃, dolomite, zeolites, etc. dispersed particles, using air as plasma forming gas and auxiliary (Ar, N2, propane-butane) gas mixtures.

 

 

The impact of chemical composition, structure, boundary thickness, grain orientation, number of defects, additives of ceramics on its electric conductivity was investigated together with researchers of European countries. Yttrium stabilized zirconium oxide coatings were deposited, their structure and properties were analysed. The dependence of structure, phase composition of obtained coatings and size of crystallites on the parameters of plasma process and conditions of thermal processing was determined.

 

 

 

Plasma nitriding process, which significantly increases the solidity of the surface and substantially reduces the frictional coefficient of the surface, was realized to change the properties of surface layers of stainless steel constructional materials. It was suggested the nitriding process to realize in atmospheric pressure plasma jet, in which the concentration of nitrogen 3-4 orders exceeds the concentration of nitrogen ions in rarefied gas plasma. In such case, the nitriding process would be economical, whereas expensive vacuum technology would not be needed.

 

Patterns of heat and mass exchange processes in oxide catalytic reactor channels at flow of different composition reacting gas mixtures were analysed aiming at improving catalytic properties of coatings. Information gathered according obtained research results may be used in developing, designing and analytically calculating CO oxidizing catalytic reactors, it may also expand data base of modelling programmes since data is lacking on processes occurring in catalytic reactor. Facility which provides constant characteristics flow of combustion products was developed, novel methodology was developed to investigate catalytic properties and thermal processes of coatings, occurring at the catalytic wall.

 

State funded work Research on Regularities of High-temperature Spray Pyrolysis Process, Designed for Plasma Synthesis of Coatings was completed by the Laboratory in 2008. The problem of plasma spray pyrolysis in the world-wide scientific literature was investigated, experimental gas dynamic device with specific purpose plasma generator was designed and manufactured. In accordance with similarity theory operational characteristics of plasma generators were investigated and generalized, dynamic and thermal characteristics of outflowing gas jet were investigated as well, plasma state was estimated and it was determined that electron temperature of non-equilibrium plasma jet 4–5 times exceed the temperature of heavy particles. Patterns of single phase and two phase plasma jet flow were investigated by numerical and experimental methods. After performing numerical simulation of two phase jet it was determined that under optimal flow parameters dispersed particles reach the maximum temperature at x/d = 20, whereas velocity at x/d = (7–8) distance from the plasmatron exhaust nozzle.

 

Plasma spray pyrolysis process was realized in the experimental device and its basic patterns were investigated. It was determined that the interaction of plasma jet and dispersed particles lasts for 1 ms, the most rapid phase variation of the particle begins at x/d = (3–8) from the exhaust nozzle of plasma source.

• COST 533 action Materials for Improved Wear Resistance of Total Artificial Joints (till 2009). Formation of specific coatings, designed for biomedical purposes, is carried out by plasma technologies (in cooperation with scientists of the Laboratory of Material Research and Testing and organizations from 16 European countries). YSZ coatings, designed to produce artificial joints, are developed, in atmospheric pressure low temperature plasma jet applying plasma spray deposition method;

 

 

Examples of Laboratory production at exhibition Balttechnika-2008

• COST D41 action Inorganic Oxides: Surfaces and Interfaces, till 2010. This action is related with metal oxides coatings synthesis processes and research of their surfaces and internal structure. Its main objective is to improve scientific knowledge on the properties of oxide coating surfaces and structure at microscopic level, applying theoretical knowledge and practical experience to investigate measures and methods, which enable to create the coatings of desirable properties, to control the deposition process. 16 European countries participate in the activity;

• EUREKA project E!3539 Novel Methods to Produce Mineral Fibre from Local Raw Materials and Waste, (initiated and coordinate by Laboratory researchers), till 2009. The main goal of the project is to create scientific basis for production of mineral fibre from ceramic materials, to develop experimental equipment, obtain high quality mineral wool, provide research on its properties and application. It is suggested to realise the development of mineral fibre and granules in atmoshperic pressure air plasma jet reactor, in which high temperature and high concentration of active ions are achieved. Performed research reveals that the main factor, which conditions the process efficiency is the flow of atoms and molecules activated in plasma. Developed experimental plasmachemical facility, designed for the research of Si, Mg, Ca and Al oxides and their compounds processes. The fibre, diameter of which is 0.5–2 µm, is obtained in plasma reactor, connected to constant current plasma generator. The cooperation proceeds with researchers from University of Catania (Italy) and JSC Termotechnika (Lithuania);

• Bilateral cooperation programme between Lithuania and Ukraine 2007–2008 Study of Nonequilibrium Properties in Atmospheric and Reduced Pressure methods of plasma jet parameters are developed, dynamics and heat transfer of plasma jets are investigated, properties of plasma generators and plasma are identified, possibilities are analysed to cerate specific plasma generators to realize processes of coating composition. Common projects are carried out together with Plasma Employed for Surface Modification and Fuel Conversion. The work is designed for the research of dynamic and thermal characteristics of atmospheric and reduced pressure plasma, used for the synthesis of catalytic and tribologic coatings and solid fuel conversion into gaseous. Plasma state is characterized, measuring Ukraine Gas Institute (Ukraine, Kiev);

• Bilateral cooperation in the field of scientific research between Lithuania and Ukraine 2007– 2008. Project The Creation of Plasma Technology for the Synthesis of Ultradispersed Particles and Deposition of Coatings with Specific Properties. While performing this project and cooperating with researchers from Odesa National University, technology of dispersed particles synthesis in electric arc and plasma flow is developed, the problem of symmetric ultradispersed particles mixture with plasma forming gas and introduction to plasma flow is solved, porous coatings of high specific surface for micro and nanostructural catalysts, are developed.

 

 

 

In 2008 scientific and technological production of the Laboratory was presented in 8 international and 4 national conferences. The production was demonstrated at exhibition Balttechnika-2008, during which the examples of catalytic and tribologic coatings and modified surfaces were presented, new catalytic reactors, filters, and hydrophobic coatings were demonstrated. New plasma technologies of ceramic material melting and fibre production were also presented at the exhibition.

 

 

 Since 2007 the Laboratory of Plasma Processing has been actively participating in the activity of Plasma Technologies Network of the Baltic countries

 

6 science doctors, 2 junior research associates – PhD Candidates, 1 Master student, 1 junior research associate, as well ancillary personnel: 2 engineers and high quality foreman work at the Laboratory. In 2008 the Laboratory researchers published 27 articles and participated in 22 Lithuanian and international conferences.