14^^pecialists^n^heFieldoimÊamÊpmÊm
SOME ASPECTS OF THE USING OF GRAPHITE AND GRAPHITE-BASED
MATERIALS IN MACHINERY
Ziyodilla Mirtolipov
Bachelor student
Nodirjon Qayumjonovich Tursunov
PhD, Dr., Scientific advisor Tashkent State Transport University mirtolipov98 @mail .ru
G r a p h i t e that was mentioned in consideration of iron alloys with carbon is also of interest as an independent material applied in engineering.
Being a polymorphic modification of carbon with a hexagonal crystalline lattice (Fig.1), graphite has an unconventional combination of physical and mechanical properties stipulating is application as constructional and antifriction materials.
Fig.1. Scheme of graphite crystalline lattice: a,c, lattice parameters
Technical graphite materials unified with the term graphite consist of pure carbon and are distinguished from each other in structure and properties depending on the properties of the initial raw materials and the technology of their processing. The main advantages of materials in this group are low density, high-temperature strength, and increased strength on heating, antifrictionality and easiness of mechanical treatment.
Natural graphite does not have wide application as constructional material due to high anisotropy and low strength. It is used as a component for production of consistent lubricants, electroconductive rubber, lubricant solid films, dyes, pastes and chemical sources of current.
April 21-22
450
^^pecialists^n^heFieldoimÊamÊpmÊm
Artificial graphitized carbon materials are subdivided into three classes: technical graphite, pyrolytic graphite and glass carbon.
Technical graphite is obtained by heating of a mixture of petroleum coke, pitch and other hard carbon-containing materials.
Pyrolytic graphite (pyrographite) is obtained by sedimentation of products of thermal degradation (pyrolysis ) on a carrier with a subsequent heating of the formed sediment to temperature of 2500-3000°C at pressure of about 50 MPa.
Carbon fibre (glass carbon) is a product of thermal treatment of cellulose or synthetic fibres. Carbon fibres and tissues have wide application as strengthening components of composite materials.
Various types and brands of graphitized carbon materials are considerably
"5
distinguished in density (from 200 to 2230 kg/m ). Graphites with the density of 200-
"5
1200 kg/m3 fall in the category of porous materials (porosity is up to 85%) which are used for production of porous electrodes and high-temperature heat insilation.
"5
Pyrographites have density of 1800-1900 kg/m and porosity of 15-30%. The density
"5
of glass carbon is 1400-1500 kg/m . The porosity is 0.2-1.0%. To decrease porosity as well as gas- and water permeability technical graphite is subjected to thermochemical and thermomechanical treatments. Such treatments result in recrystallized graphite distinguished from the initial one by low defect ordered polycrystalline structure.
Graphite combines high heat stability, electrical conductance and heat conductance. The heat conductance of technical graphite approaches to the heat conductance of aluminium (230 Wt/ (mK)), whereas pyrographite has heat conductance of 320 Wt/(mK) and carbon fibres - up to 13 Wt/(mK). Graphite does not melt but is sublimated at the temperature of 3800°C. The maximum working temperature of graphite of different trade marks is from 1000 to 2500°C in inert atmosphere and vacuum.
The amazing property of graphite distinguishing it from other constructional materials is that its strength increases as the temperature rises. On heating pyrographite to 2000°C the strength increases linearly (but insignificantly) and over the temperature range of 2400-2600°C the values for graphite strength double compared to those measured at room temperature.
Density and gas impermeability of graphite increase simultaneously. The hardness on the Mohs scale varies from 1 to 5 units depending on the direction of measurement. Glass carbon having low gas
April 21-22
451
^^pecialists^n^heFieidofmÊamÊpaam
permeability and high stability to corrosive media at high temperatures is a promising constructional material.
Graphitized carbon materials are widely used in products exposed to the action of high temperatures, such as systems of heat insulation of aircrafts, elements of jet nozzles and coatings of combustion chambers. Chemically pure technical graphite is used as neutron moderator in nuclear reactors, which is related to its high capability for capturing neutrons and slow down their rate.
It was believed for a long time that carbon on a monoatomic base can form only two polymer crystalline phases, graphite and diamond.
One of the prominent events in the chemistry of the late 20th century was discovery of new molecular carbon forms, f u l l e r e n e s.
The term fullerenes is used to name closed molecules, such as C28 , C 32 ,C50, C60, C70 ,C76, C84, etc. in which all carbon atoms are located at the tops of regular pentagons and hexagons covering the surface of either a sphere or a spheroid.
The central place among fullerenes is occupied by a molecule with the "magic" number of atoms C60 which is characterized by the highest symmetry and, as a consequence, by the greatest stability. In this molecule (Fig.2), resembling an outer cover of a football ball and having the structure of a regular truncated icosahedron, carbon atoms are located on the spherical surface at the tops of 20 regular hexagons and 12 regular pentagons (icosahedron is one of five types of regular polyhedrons. It has 20 facets, 30 edges, 12 tops; five edges come together at each top).
Fig.2. Schematic representation of fullerene C6o molecule
Fullerenes in condensed state are named fullerites and those alloyed by metals are termed fullerides.
Fullerite is a crystal with a densely packed hexagonal structure or a face-centered cubic structure (depending on the
April 21-22
452
Tashkent State Transport University Volume 3 | TSTU Conference 1 | 2022
Google Scholar indexed Prospects for Training International
DOI: 10.24412/2181-1385-2022-1-89-94 Specialists in the Field of Transport
conditions of crystal production) in which each molecule has 12 closest neighbors (Fig3).
Fullerite is a typical molecular crystal in which the interaction between carbon atoms inside a molecule is much stronger than that between the atoms of the neighboring molecules which are retained in the crystalline lattice due to the Van der Waals forces.
Fig.3. Fullerite structure (C60 molecules are represented by solid spheres): a is lattice
parameter
In 1990, a relatively simple and effective technology of fullerene production in macroscopic amounts was developed. The technology is based on thermal decomposition of graphite and provides for productivity of the order of several grams per hour for C60, which is sufficient for extended studies. The electrical, optical and mechanical properties of fullerenes indicate prospects of application of these materials in electrical engineering (for production of accumulator batteries, supercoductors, etc.), optoelectronics (photoconductive materials, optical transformer, nonlinear optical elements) and in other fields of engineering. Information is available about fullerene application as a solid lubricating coating as well as additives to liquid lubricating materials.
Fullerenes are a man-made material, a fruit of highly developed science and technology. Therefore the value of this object is not only in development of new material, technologies of their production and extending the spheres of technical application, but in creating of concepts of materials science which change our views of the known and understandable phenomena of the material world.
REFERENCES
1. Нурметов, Х. И., Турсунов, Н. К., Кенжаев, С. Н., & Рахимов, У. Т. (2021). Перспективные материалы для
April 21-22
453
^^pecialists^n^heFieldoimeSmePmem
механизмов автомобильных агрегатов. Scientific progress, 2(2), 1473-1479.
2. Nurmetov, K., Riskulov, A., & Avliyokulov, J. (2021). Composite Tribotechnical Materials for Autotractor Units (No. 5039). EasyChair.
3. Nurmetov, K. I., Avliyokulov, J. S., & Alimov, M. R. (2021). Features of the structure, composition and technology of composite materials based on polytetrafluoroethylene. Frontline Social Sciences and History Journal, 1(06), 15-18.
4. Nurmetov, K. I., & Riskulov, A. A. (2021). Some aspects of industrial polymer waste recycling system.
5. Ryskulov, A. A., Liopo, V. A., Avdeichik, S. V., & Mikhailova, L. V. (2014). Features of the Physicochemical processes in a Metal-Polymer System. International Polymer science and technology, 41(8), 33-40.
6. Nurmetov, K., Riskulov, A., & Avliyokulov, J. (2021). Composite tribotechnical materials for autotractors assemblies. In E3S Web of Conferences (Vol. 264). EDP Sciences.
7. Ryskulov, A. A., Liopo, V. A., Ovchinnikov, E. V., & Eisymont, E. I. (2011). Phase transformations in tribosystems with metal-polymer components. Journal of Friction and Wear, 32(1), 30-36.
8. Nurmetov, K., & Riskulov, А. А. (2020). Perspectives on the Use of Composites.
9. Abdurazakov, A. A., Riskulov, A. A., Yuldasheva, G. B., & Avliyokulov, J. S. (2015). Technology of high-strength wear resistant fluorcomposites for mechanical engineering. Europaische Fachhochschule, (10), 43-47.
10. Антонов, А. С., Абдуразаков, А. А., Рыскулов, А. А., Струк, В. А., & Юлдашева, Г. Б. (2017). Машиностроительные композиционные материалы на основе смесей термопластов. Прогрессивные технологии и системы машиностроения, (1), 3-19.
11. Texnologiya mashinostroitel'ny'x, V. V. (2012). ftorkompozitov s ponizhenoj defektnost'yu/VV Voropaev, VA Struk, GN Gorbacevich, IL Lavry'nyuk, GB Yuldasheva. Sb. Trydov XXI veka.-Doneck, 155-164.
12. Воропаев, В. В., Струк, В. А., Горбацевич, Г. Н., Лавринюк, И. Л., & Юлдашева, Г. Б. (2012). Технология машиностроительных фторкомпозитов с пониженной дефектностью. In Сб. трудов XIX международной научнотехнической конференции. Машиностроение и техносфера XXI века (Vol. 1, pp. 155-164).
13. Yuldasheva, G. B., Huzhahmedova, H. S., & Yuldasheva, N. P. (2020). Use of nanomaterials for restoration of rubbing parts of engine. Academy, (4), 25-26.
April 21-22
454
Tashkent State Transport University Volume 3 | TSTU Conference 1 | 2022
Google Scholar indexed Prospects for Training International
DOI: 10.24412/2181-1385-2022-1-89-94 Specialists in the Field of Transport
14. Toirov, O. T., Tursunov, N. Q., Nigmatova, D. I., & Qo'chqorov, L. A. (2022). Using of exothermic inserts in the large steel castings production of a particularly. Web of Scientist: International Scientific Research Journal, 3(1), 250-256.
15. Toirov, O. T., Tursunov, N. Q., & Nigmatova, D. I. (2022, January). Reduction of defects in large steel castings on the example of" Side frame". In International Conference on Multidimensional Research and Innovative Technological Analyses (pp. 19-23).
16. Алимухамедов, Ш.П., & Гапиров, А. Д. (2018). Напряженно-деформированное состояние устройства для гашения динамических нагрузок в трансмиссии транспортных машин. Universum: технические науки, (12 (57)), 2328.
17. Алимухамедов, Ш. П., Рахимов, Р. В., Инагамов, С. Г., Мамаев, Ш. И., & Кодиров, Н. С. (2022). М . Universum: технические науки, (2-3 (95)), 8-14.
18. Авдеева, А. Н. (2020). Некоторые аспекты метода постановки вопросов и ответов при проведении аудиторных занятий. Вестник науки и образования, (20-2 (98)), 76-79.
19. Семин, А. Е., Турсунов, Н. К., & Косырев, К. Л. (2017). Инновационное производство высоколегированной стали и сплавов. Теория и технология выплавки стали в индукционных печах.
20. Турсунов, Н. К., & Тоиров, О. Т. (2021). Снижение дефектности рам по трещинам за счёт применения конструкции литниковой системы.
April 21-22
455
