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5УДК 611.666.2
DEVELOPMENT OF TECHNOLOGY FOR GRAPHITATION OF AMORPHOUS CARBON MATERIALS OBTAINED BASED ON LOCAL RAW MATERIALS
Ubaydullaev Mamasidik Maxammatsolievich NICI, PhD, [email protected], tel:+99891183 2996
Parmonov Sarvar Toshpo'latovich Tashkent State Technical University Olmalik branch, Ph.D.
E-mail: [email protected], tel:+99(894) 224 0005
Abstrakt: In the article, samples of amorphous carbon material containing petroleum coke + molasses obtained on the basis of local raw materials were subjected to the graphitization process at high temperatures, in a medium vacuum environment, in a special laboratory furnace, and the degree of graphitization formed in them was studied, and the analytical results on the formation of graphite crystal quantities were presented.
Аннотация: Маколада мах,аллий хомашё асосида олинган нефт кокси + меласса таркибли аморф углеродли материал намуналарини юкори хароратларда, урта вакуум мух,итида, махсус лаборатрия печида графитлаш жараёнидан утказилиб ва уларда х,осил булган графитланиш даражаси урганилди х,амда графит кристалл микдорларини х,осил булиши буйича тах,лилий натижалар келтирилган.
Аннотация: В статье рассмотраны образцы аморфного углеродного материала, содержащего нефтяной кокс + меласса, полученные на основе местного сырья, были подвергнуты процессы графитизации при высоких температурах, в среде среднего вакуума, в специальной лабораторной печи, а степень изучена; образует в них графитизация и представлены аналитические результаты по образованию количеств кристаллов графита.
Keywords: technology, carbon graphite, graphite, coke, oil, electrical engineering, molasses, degree of graphitization, specific resistance, density, pitch, voltmeter, thermocouple, anisotropy.
Калит сузлар: технология, углеграфит, графит, кокс, нефт, электротехника, меласса, графитланиш даражаси, солиштирма каршилик, зичлик, смола, вольтметр, термопара, анизотропия.
Ключевые слова: технология, углеграфит, графит, кокс, нефть, электротехника, паток, степень графитизации, удельное сопротивление, плотность, пек, вольтметр, термопара, анизотропия.
Objective. It consists of the theoretical basis of the graphitization technology of amorphous carbon materials obtained on the basis of local raw materials and the test processes on the change of the degree of graphitization depending on time as a result of heating the material at different temperatures.
Methods. The experiment was carried out in a furnace operating in a high vacuum environment at the Tashkent State Technical University. The formation of graphite crystals was studied as a result of searching samples of amorphous carbon material containing petroleum coke and molasses at temperatures of 1600...2500 oC for 1 hour. Heating processes were carried out in a vacuum environment of 10-3. The degree of graphitization was determined by X-ray diffractometer (XRD) "MiniFlex 600".
Results. According to the obtained results, the degree of graphitization of the samples
increased as the temperature increased. The degree of graphitization of the sample at a temperature of 1600 oC for 1 hour was 17%, at a temperature of 1800 oC it was 22%, at a temperature of 2200 oC it was 45% and at a temperature of 2500 oC it was 58%.
Conclusion. Based on the analysis of the obtained experimental results, it was found that the processing of amorphous carbon materials based on local raw materials at a temperature of 2500 oC for 1 hour was not enough for complete graphitization of the samples in terms of size.
Keywords: technology, carbon graphite, graphite, coke, oil, electrical engineering, molasses, degree of graphitization, specific resistance, density, pitch, voltmeter, thermocouple, anisotropy.
Introduction.
It is known that the degree of graphitization of carbon materials is evaluated by the reduction of the interplanar distance in the X-ray image, or by the ratio of acceleration of different lines, or by the size of the material crystals [1].
According to the results of research conducted by scientists on the degree of graphitization of carbon materials, the degree of graphitization of amorphous carbon depends primarily on temperature [2, 3]. In this case, the degree of graphitization of amorphous carbon reaches a certain limit at a constant temperature [4-7]. However, according to the data presented in a number of literature, kinetic studies of the graphitization of amorphous carbon showed that the graphitization of amorphous carbon depends on the duration of the process in addition to the temperature. According to calculations made by scientists - according to books, a temperature of 2420 oC is sufficient for the graphitization process of petroleum coke. At other lower temperatures, petroleum coke takes 13 hours at 2150 oC, one month at 1900 oC, 1.5 years at 1500 oC, 3200 years at 1000 oC[8-10] to reach this result.
It is difficult to observe changes in the properties of carbon materials during processing at high temperatures. Usually, in researching the properties of carbon materials, amorphous carbon is first processed at high temperature, and then the sample is completely cooled, which can complicate the research process and cause a number of inaccuracies [11-14].
Methods.
Graphitization process of a tube-shaped sample with coke + molasses made from local raw materials, size: outer diameter 96 mm, inner diameter 76 mm, height 240 mm in the furnace at temperatures of 1600...2500 0C and 1 hour at each value of these temperatures we did.
The special laboratory furnace is designed to heat samples prepared by the powder metallurgy method in a high vacuum or protective gas environment up to a temperature of 2500 oC. The outer part of the oven is made of two-layer steel sheets, and the oven is continuously cooled by passing water between the sheets so that the oven does not overheat [Fig. 1].
The chemical compoCition of the research samples and technological indicators of the graphitization process are presented in Table 1.
1 - table
Chemical compoCition of research samples and technological indicators of graphitization
Т/р Chemical compoCition, % Graphitization temperature, оС Duration of the procedure, hour
1 Coke + molasses 1600 1
2 1800
3 2200
4 2500
1 - vacuum pump; 2 - thermocouple; 3 - manometer; 4 - thermal sensor; 5 - ammeter; 6 -voltmeter; 7 - cooling system; 8 - automatic; 9 - thyristor block; 10 - test sample; 11 - bronze
contact; 12 - radiator; 13 - current conductor. Figure 1. Baking in a special laboratory oven and testing the physical and mechanical
properties of the material
5 4 J
1 - sample; 2 - thyristor; 3 - ammeter; 4 - voltmeter; 5 - thermocouple. 2 - picture. Schematic view of the graphitization process. Fig. 2.The electrical scheme of the oven developed for the graphitization of samples is
shown in
In order to determine the degree of graphitization of amorphous carbon samples, we cut fragments from the graphitized samples and analyzed their structure-phase compoCition in "MiniFlex 600" X-ray diffractometer (XRD). Fig. 3 shows the maxima of the diffraction profiles of the 002 crystallographic planes of the studied carbon samples.
24 26 и
Fig.3. 002 crystallographic planes diffraction profiles maxima of carbon samples subjected to the graphitization process at different temperatures
In this case, the P-integral width of the 002 diffraction line decreased from 1.56 to 0.2o as the processing temperature increased. The change of the integral width in this order is primarily due to the change of the average size of the coherence scattering regions of X-rays towards the direction of the Ls - crystallographic "s" axis, and with the increase of the processing temperature, Ls gradually increased by 5 nm at a temperature of 1500 oC and 45 nm at a temperature of 2500 oC. . With an increase in the processing temperature, the size of the coherence scattering regions increased, and the center of the diffraction profiles of the 002 crystallographic planes shifted to the right (larger angles) (Fig. 3). This is due to the fact that the distance between d002 crystallographic planes decreases from 0.344 nm at a temperature of 1500 oC to 0.33 nm at a temperature of 2500 oC.
Results.
Data obtained by processing the results of quantitative X-ray structural-phase analysis on the samples subjected to the graphitization process at different temperatures using relative units are presented graphically in Figure 4.
1 (101--------
0 5 10 15 20 io 40 50 6(1 Graphitization time, minutes 1 - 1600 oC; 2 - 1800 oC; 3 -2200 oC; 4 - 2500 oC. Figure 4. Effect of process temperature on the degree of graphitization of
amorphous carbon
According to the obtained experimental results, the degree of graphitization of the amorphous carbon sample increases from 0% to 58% within 1 hour with the increase of the temperature of the graphitization process and the time of holding at this temperature. For example, the degree of graphitization of the sample at a temperature of 1600 oC for 1 hour is 17%, at a temperature of 1800 oC it is 22%, at a temperature of 2200 oC it is 45% and at a temperature of 2500 oC it is 58%. It can be seen that the higher the temperature in carbon materials, the higher their degree of graphitization. In addition, it can be seen from Figure 4 that even treatment at 2500 oC for 1 hour is not enough to completely graphitize the carbon samples by volume.
Discussion.
V.I. from a number of scientists of the world in research work on identifying new types of binders rich in carbon in the production of amorphous carbon and graphitized carbon materials in world practice, studying their properties. In the works of Kostikov, V.I.Kasatochkin, A.T.Kaverov, the principles of kinetics of obtaining graphitized carbon materials, adding petroleum coke as a filler and coal tar as a binder and influencing the physico-mechanical and operational properties of the material were studied [15-18 ].
The thermal conductivity of the samples increases in direct proportion to the logarithm of the processing time at different temperatures. This is based on experimental results obtained by scientists in Figure 5.
It can be assumed that the formation of the graphite structure from amorphous carbon takes place in several stages and is complicated by the influence of various additional processes
(Fig. 6).
К
Ql
1
г
■i"
i i
10
]
J" " г ji'1
........." 3 д ■ ■■-™ 1
L-.....ТГ*-^ ......... ^^Jt J
iO too
Tims (mmute)
1 - 2500 0C; 2 - 2200 0C; 3 - 1900 0C; 4 - 1600 0C Figure 5. A graph showing the variation of the thermal conductivity of the samples as a
function of the logarithm of the isothermal holding time and the temperature
0.9
0,S
0,7 0,6 «0,5
I 0.4
0.3 0,2
0,1
i
s/N 2
*
* i
S
\ h
0 60 90
Time (minute)
150
1 - 2000 0C; 2 - 2150 0C; 3 - 2300 0C; 4 - 2420 0C Figure 6. Dependence on (1-a) processing time of petroleum coke at different temperatures (according to V.I. Kasatochkin and A.T. Kaverov).
During graphitization of amorphous carbon, the amorphous structure changes to the crystalline structure. One of the important indicators of the graphitization process is the process temperature. According to the analysis of the literature, graphitization of carbon with an amorphous structure by heating it at a temperature of 1600...2500 oC ensures the transition of the amorphous structure to a fully crystalline structure (Fig. 7) [8].
According to the graph presented in figure 3 below, the crystallization of amorphous carbon materials increased depending on the temperature of the process and the time of holding at this temperature.
Figure 7. Influence of amorphous carbon on the degree of graphitization, the temperature of the graphitization process and the time of holding at this temperature.
World scientists used petroleum coke as raw material, petroleum tar and coal tar as binding materials for coal coke in the development of graphitization technology of amorphous carbon materials[19-21].
Conclusion.
As a result of the conducted research, it can be concluded as follows: It was determined that the degree of graphitization of amorphous carbon materials containing petroleum coke and molasses depends on temperature and time. The resulting graphite material made it possible to produce products used in the fields of electrical engineering and metallurgy.
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