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Diamond Synthesis

#G-1112


Elaboration of New Industrial Technology for the Manufacturing of Synthetic Single Crystals of Diamond Using Small Caliber Cannons

Tech Area / Field

  • MAT-EXP/Explosives/Materials
  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
3 Approved without Funding

Registration date
22.12.2003

Leading Institute
Institute of Metallurgy, Georgia, Tbilisi

Collaborators

  • Georgia Institute of Technology / School of Materials Science and Engineering, USA, GA, Atlanta\nSouth Dakota School of Mines and Technology / College of Material Science and Engineering, USA, SD, Rapid City\nLos Alamos National Laboratory, USA, NM, Los-Alamos

Project summary

Objective of the project is elaboration of the technology for industrial manufacturing of synthesized diamonds of 1 mm in size with elevated mechanical properties using the effect of shock waves on thermally activated compacted metal-carbon-containing mixture.

State of arts in the field: investigations on synthesizing the diamond crystals based on the graphite-metal system were held simultaneously in two directions – static and dynamic modes. To this problem were dedicated investigations of the scientists such as: Wentorf R.H., Strong H.M., Vereschagin L. F., Bridgman, P.W., De Carli P.S., Jemisson J. C, Leipunski O.H., Lonsdail K., Adams A.C., Bundy F.P. and others.

Fabrication of synthetic diamonds in a static mode requires using of an expensive high pressure camera mounted in a high-powered (pressing force not less than 55 kg-bar) press equipped with heating mechanism.

Synthesizing of diamonds in dynamic conditions with the help of explosive materials induces creation of shock waves of an order of hundreds of kg-bars within the reaction mixtures, their intensity being defined by content and quantity of the explosives.

Disadvantage of the first method besides high prices of the applied equipment and of the materials used for high-pressure cameras is a limited volume of the camera itself, that as a total leading to increase of the production price.

Dynamic method favorably differs from the static one by simplicity of the equipment and of the technological mode. However the product fabricated by using this technology is relatively finely dispersed (fraction size is not more than 100 mm).

In the 80th of the last century by the scientists of the Institute of Rock Mechanics, Georgian Academy of Sciences a principally new method of fabrication synthetic diamonds was elaborated under the leadership of Dr. E. Chagelishvili. Essence of the development was fabrication of diamonds from carbon-containing materials using dynamic loadings at pressures of some ten kg-bars. The reaction mixture was compacted and preliminarily heated up to 700-900 °C. According to the offered technology dynamic loadings were created due to explosions of the explosive materials. The shock wave, going through the preliminarily heated reaction mixture, promotes phase transformation of thermally activated graphite into diamond. By this technology were obtained crystals of synthetic diamonds of the sizes of up to 500 mm. Strength tests of the obtained specimens were provided in the VNIIALMAZ by the SU standard 920670. The results showed that the diamonds with dispersion of 315/250 had strength of 2.6 kg (f) i.e. twice as much as strength of the diamonds fabricated by traditional methods for the exception of the ones marked ACC.

Disadvantage of the offered technology is a limitation of weight of the reaction mixture and as a result a restricted (from the commercial point of view) one-time volume of the obtained product. With this, the process of explosion is accompanied rather by a high sound effect which is also considered as a disadvantage for the industrial application of the method.

Novelty and Essence of the Elaboration:

A new technology offered in the project provides elimination of the disadvantages described above. The technology will be elaborated basing on the results of the investigations and inventions carried out in this direction for more than 20 years at the Institute of Rock Mechanics, Georgian Academy of Science and at the Institute of Metallurgy, Georgian Academy of Sciences.

Novelty of the project is the following: a preliminarily heated reaction mixture undergoes to double loading of shock waves and high shear stresses created by a shock worker with rotating moment, accelerated by gun-powder charge in the gunpoint while the container with the reaction mixture is thrown on the hard barrier.

This technology does not provide using of any expensive installations or materials.

The installation consisting of the gun, original sound-suppressing camera and heating device constructed at the Institute of Metallurgy allows to successfully realize the above mentioned technology.

Essence of the new technology is the following: a mixture made by compaction of copper and graphite powders is heated up to predetermined temperature and then the container is put in the sound-suppressing camera located at the end of the gunpoint. Shot of the gun bumps the plunger upon the container resulting in creation of a plane shock wave in the reaction mass while container with shock worker rushes about the hard wall. Upon bumping over the hard wall a shock wave springs up in the specimen for the second time. High shear stresses and a double spring up of the shock wave promote to phase transformation of graphite into diamond and growth of the crystals. The shock wave operation time and stress quantity are defined by the shock worker mass and its velocity. The process is safe and the accompanied sound effect is of about 100 decibel.

Investigations performed on the installation described above allow to establish preliminary (in the view of fabrication synthetic tetrahedral transparent single crystals of diamond of different color of about 600 mm in size) parameters of technological mode.

Basic investigations necessary for the elaboration of the new technology ensuring increase of the volume of qualitative production and intensification of the process are the following:


1. Determination of geometric parameters of the container with reaction mixture for preventing the effect of reducing waves;
2. Establishment of optimal (in the view of achieving maximum product output) reaction mass;
3. Study of the influence of temperature mode of the reaction mixture on single crystal dimensions;
4. Establishment of dependence of single crystal dimensions and of the quantity of product output on the pressure of shock wave front;
5. Determination of the influence of gaseous phase on the single crystal size and its mechanical properties;
6. Investigation of the morphology and structure of the obtained diamond crystals;
7. Summarization of the obtained results and elaboration of industrial technology.

As a result of the project implementation there will be elaborated a new technology for synthesizing high quality diamond powder in dynamic conditions. Properties of diamonds and their fitness for various goals are defined by numerous characteristics of different type. It is expected to:

1. Fabricate single crystals of diamond powder with the sizes from 0.25 to 1 mm.

2. Clarity rate – to fabricate diamond crystals without black spots so that the obtained diamond powder could be applied for work in hard conditions.

3. Sharp angles – a shape of the diamond must be compatible to the type of the work mission e.g. sawing, sharpening, grinding, polishing, etc.; the diamonds for sawing and sharpening require the crystals with sharp angles of tetrahedral form.

4. Adhesion and temperature stability – in the process of producing cutting blades the diamond grains are to be mixed with the powders of various metals, then pressed, put into the furnace and sintered at temperatures from 800 to 900 °C. With this, characteristics of the diamonds are to be kept unchanged. The new technology of fabrication of the synthesized diamonds will provide their high temperature resistance.

5. Increase strength of the diamonds by 15-20% using gaseous phase on synthesizing.

Using of the results of a new technology solves a conversion task. For the first time the cannons will be used for peaceful goals. The fabricated diamonds will be used for cutting of granite, marble, concrete, etc. in mining industry, civil engineering and other areas of the industry.

Implementation of the project provides realization of new technical solutions and using of modern standard and original methods for the research.

Original and new technical solutions are connected with using of the installation and the method allowing processing of the heated materials by blast waves where intensity of blast waves and a temperature of preliminary heating are not restricted. Quite original is also a sound-suppressing camera which localizes a blow and noise within the area of closed volume.

The diamond crystals will be studied by X-ray analysis method on ultra-modern X-ray device XIth of the “Scinted” company (USA). As a result, the reasons for the crystallization of diamond single crystals in extreme conditions will be established. According to our data these conditions are commensurable with the velocity of the blast wave formed in the compacted reaction mixture.

Competence of the project team. The project participants are high-skilled specialists in the area of metal working under pressure. In the former Soviet Union they worked mainly on defense programs of the institutions such as “Yujcosmos”, “Sredmash”, etc. More than 65 papers have been published, among them 21 - in the area of the technology relevant to the submitted project, e.g. 1. E.O. Mindeli, E.Sh. Chagelishvili, H.S. Turmanidze. A.S. # 726803. Methods of Synthetic Diamonds Production. 1980. 2. A. Nozadze, E. Chagelishvili, et all. Georgian Patent #369. Methods of Synthetic Diamonds Production. 1993. 3. A. Peikrishvili, E. Chagelishvili, et all. Possibilities of obtaining Combined Samples from Tungsten-Based Alloys by High-Temperature Shock-Wave Treatment. El-Paso, Texas, USA. August, 6-10. 1995. 4. E. Chagelishvili, T. Meshurlishvili. Georgian Patent #1956. Method for Production and Treatment of Superhard Materials and Device for its Realization. Georgia, 1999. 5. S. Zelepugin, E. Chagelishvili, A. Dorfman. Experimental Investigations and Numerical Simulation of Phase Transitions in Carbon at Moderate Shock Wave – Saint Petersburg. October, 2002.

Scientific and practical value of the project:


1. Scientific value of the project-study of the mechanism of formation and growth of high quality diamond single crystals synthesized in dynamic modes.
2. Practical value-simplification of the process of synthesis and reduction in basic cost for the product.

Role of foreign collaborators consists in mutual review of the reports, making comments on the investigation methods, joint publications, consultations on the possibilities of application of the project results, identification of the companies interested in commercialization of the project and making of business plan, joint holding of workshops.


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