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Synthesis of Nanocrystalline Carbides of Refractory Transition Metals

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Spark Erosion Synthesis of Nanocrystalline Carbides of Refractory Transitional Metals

Tech Area / Field

  • CHE-SYN/Basic and Synthetic Chemistry/Chemistry
  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
3 Approved without Funding

Registration date
23.04.2004

Leading Institute
Kyrgyz state Pedagogical University named after Arabaev, Kyrgyzstan, Bishkek

Collaborators

  • Rutgers University / Department of Ceramic and Materials Engineering, USA, NJ, Piscataway\nUniversity of Nebraska / Center for Nontraditional Manufacturing Research, USA, NE, Lincoln

Project summary

In modern technology carbides of refractory transition metals have a wide distribution due to such properties, as high hardness, high-temperature stress, refractoriness, etc.

In this regard the study of the possibility to obtain nano-scale carbide compounds of refractory transition metals is of some interest. At matter’s nanoscale state metastable structure with the high internal energy content is emerges, the interrelation between structural fragments strengthens considerably, and therefore their physical, chemical, mechanical and other properties change sharply.

The opportunity of the wide use of nano-scale materials depends on the elaboration of technology of their production.

As we know from theory, nano-scale particles can be obtained in strongly non-equilibrium systems, while supersaturating steam when condensation nuclei are being hardened; while supercooling melts when metastable structures or phases as well as supersaturated solutions are being formed, while deforming when a solid matter is being saturated with disclinations, dislocations and lattice vacancies; while irradiating a solid matter with neutrons with a formation of various defects.

In this perspective the capability of spark erosion technology to provide such conditions is interesting.

This technique utilizes two metal conducting electrodes sparked in a suitable dielectric liquid that reacts with the particles to produce nanoscale carbide ceramic powders.

Carbide formation under conditions of spark erosion is featured by the following peculiarities:

· Input energy for a single spark is localized at near-spark space with capacity 105-106 cubic centimeter, i.e. it is completely goes for dispersion of electrode material;


· Formation of nano-scale particles is virtually simultaneously destruction of electrode’s matter that makes energy losses lower;
· High temperature and pressure occurring during spark process create thermodynamic conditions for synthesis of metastable carbide phases ending in formation of nanoscale particles;
· The high cooling rate of carbide’s particles (rapid cooling strengthening) contribute to preservation of metastable structures with the high internal energy content;
· The process is accompanied by effective hardening of forming carbide particles;
· Interrelation between structural fragments of particles strengthens considerably, and therefore their physical, chemical, mechanical and other properties change sharply;
· The synthesis is carried out under a liquid dielectric’s layer, that excludes contamination of the synthesized particles by air’s oxygen and nitrogen, i.e. there is no need to create an inert atmosphere or vacuum;
· In spark erosion conditions thermal cracking of the dielectric liquid’s molecules also occurs, and products of disintegration contribute to carbides synthesis and preservation;
· Simple equipment is needed for process realization as the system operates from a regular power grid (U = 220 V).

The technique of spark erosion is also prospective to utilize hard-alloy wastes as existing processing methods are multistage. Using spark erosion enables to produce correspondent carbides of high dispersity up to nano-scale from wastes in one stage. In spark erosion conditions any current-carrying material, including hard alloys, undergoes dispersion. Using given method allows solving problems connected to processing of hardalloyed waste products and recovery of nanoscale carbide powders of tungsten and titanium. Approach to this problem is unique and provides a cost effective alternative to remelting.

The goal of the project is to determine a relationship of formation of nano-scale particles of carbides of refractory transition metals under conditions of spark erosion and development of the physical and chemical basis for utilization of industrial hard-alloy wastes.

There are some premises needed for the project purpose in AKSPU, including research laboratories, equipped with correspondent equipment.

Project will be realized by former weapons scientists with background in appropriate fields of expertise, particularly related to the physics and chemistry of materials with unique properties. AKSPU well-qualified staff with sufficient research standing will also be attracted for the project’s realization.

The project is an applied research. The results of research and development within the frame of this project will be applied to the development of technologies to producing nanoscale carbides of refractory transition metals under conditions of spark erosion that makes it possible to expand application field of carbides as a result of creating materials with unique properties on their bases.

The project will enable the following ISTC goals: To give weapons scientists and engineers, particularly those who possess knowledge and skills related to weapons of mass destruction or missile delivery systems, in Kyrgyzstan, opportunities to redirect their talents to peaceful activities; Integrate former weapons scientists from the Kyrgyzstan into the international scientific community; Foster self-sustaining civilian activities of Kyrgyzstan scientists;

In order to achieve the above goal it is necessary to solve the following tasks:

1. Study of a relationship between phase and particle size distribution composition of nanoscale carbides and chemical composition of dielectric medium.


2. Examination of the effect of spark erosion characteristics on formation of nanoscale carbides particles.
3. Elaboration of the technology to utilize hard-alloy wastes with obtaining nanoscale carbides.

To study phase composition of carbides chemical, X ray phase, and derivatographic analysis will be used. Particle-size of products will be examined using electronic microscopy and small angle X-ray scattering as well as other physical methods.


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The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.

 

ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

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