posed. And these diamonds generation requires high pressure condition. The nanodiamond can be synthe- sized with the detonation of the carbon-containing.
www.u-sonic.com - Acoustic Processes & Devices lab
Method of Obtaining the Carbonic Phase Ultradispersed Particles in the Ultrasonic Cavitation Process Olga V. Stebleva, Gennadiy V. Leonov, Alexander L. Vereshchagin Biysk Technological Institute of Altai Polsunov State Technological University Abstract - The article is dedicated to the research of the the possibility of obtaining the nanodiamonds in the acoustic cavitation fields. The microscopic and thermal analyses are examined in the article. Index Terms – Nanodiamonds, ultrasound, cavitation.
I. INTRODUCTION
A
T PRESENT throughout the world a considerable attention of researchers is paid to the methods of obtaining and analysis of the different structure ultradispersed materials properties. Ultradispersed diamond is one of the promising nanomaterials. It is connected with the possibility of obtaining the new materials, which have the unique physical, mechanical and chemical properties. A sufficiently large spectrum of technological methods to produce nanodiamonds (ND) is proposed. And these diamonds generation requires high pressure condition. The nanodiamond can be synthesized with the detonation of the carbon-containing explosives [1] and the process of hydrodynamic cavitation [2]. However, a drawback of the this technology is a need for manufacturing special detonation cameras to explode a considerable quantity of the explosives, the availability of the finished product extraction stage where the product above is being extracted from the postdetonation mass formed and where the aggressive technological media are employed. In the work is examined the possibility of obtaining the nano-dispersed carbonic phase, including ND, in the acoustic cavitation process. In the liquid medium appears the phenomenon of cavitation with the emission into the liquid of intensive ultrasonic wave. The cavitation is formation in the liquid of the cavities, filled with gas, by vapor or by their mixture. During the cavitation the relatively low average energy density of acoustic field is transformed into the high energy density inside and near the being begun to flap bubble. The acoustic cavitation is the effective mechanism of the concentration of energy. During the collapse of cavitation bubbles
in the liquid medium the pressures of order several MPa and temperature 104 K are developed [3]. The acoustic cavitation is expended on the emission of shock waves, on the local electrization of bubbles, on the excitation of sonoluminescence, formation of free radicals. It is the basic initiator of the physical and chemical processes, which appear in the liquid under the action of ultrasound. II. THE EXPERIMENTAL PART The subject of studies were hexane С6Н14 (model 1) and ethanol С2Н5ОН (model 2). The selection of this carbon-containing liquids is caused by the fact that acoustic cavitation energy is compared with tensile energy of the connection between the atoms C and H, and hydrogen possesses a sufficient diffusion rate from the collapse medium of cavitation bubble for obtaining the nanodiamond [2]. The detonation ND, obtained in FR&PC “Altay” (Biysk) from the alloy TG 60/40, was selected as the standart model Acoustic cavitation was achieved in the open stainless steel Х1810Т reservoir with a volume of 50 ml. By the source of ultrasonic emission were ultrasonic technological device "Hope 2" with the power of 200W, designed at the Biysk technological institute. The ultrasonic radiator and the generator of the ultrasonic frequency electrical fluctuations are basic elements in this device.
Fig. 1. The type of the experimental installation
The duration of ultrasonic action was 60 minutes with the power of ultrasonic apparatus 68 W and vibrations frequency of 22 kHz and wave intensity 2 W/cm2. The reservoir constantly was cooled for averting of effervescence and evaporation of liquids. The volume of the irradiated model was 25 ml. The multiplicity of experiences - 50. After working the models of liquid were dried to constant mass with 105°С, and the obtained dry residue of dark color was analyzed by the methods of electron microscopy (fig. 2) and thermal analysis (fig. 3). 1.
The electron microscopy
The morphology of the models, obtained after the ultrasonic working of hexane and ethanol was studied by the method of the scanning electron microscopy on microscope JSM-840. The pictures of detonation ND and carbonic particles generated from hexane and ethanol are shown in figures 2.
(а)
2.
The thermal analysis
By the methods of differential thermal analysis and thermogravimetry was determined models reactivity by the beginning of their oxidation in air and the indices spread of the oxidation effect parameters of the detonation ND. Conditions for conducting the experiments: - the atmosphere - air; - the temperature interval of heating - from 50 to 1000°C; - the temperature interval of the kinetic parameters calculation from 450 to 700°C. The results of a thermal analysis of the ND are represented in table 1,2 and in figure 3
Fig. 3. The thermal analysis
As can be seen from obtained data, oxidation temperatures of the hexane models and detonation ND are located in one range, and the ethanol model oxidation begins to 50 °C earlier. TABLE 1 (b)
(c) Fig. 2. a) DND; b) cavitation nanoparticles from ethanol c) cavitation nanoparticles from hexane (the electron microscopy 2000and 8000 fold resolution).
In the central section of the particles, shown on the photographs, the brown inclusions to be considered as the amorphous carbonic mass are visible, whose output comprises less than 1% of the mass of initial organic liquid.
Model
THE OXIDATION OBTAINED MODELS Tempera- Temperature Thermal ture of the of the oxioxidation oxidation dation end, effect, kJ/g beginning, °C °C
Model 1 hexane
533,0,
557,89
3,64
Model 2 ethanol
483,54
549,83
5,94
DND
535,20
585,53
28,38
The thermal effect of the detonation ND oxidation almost is 5 times more than obtained models, since the nanocarbon models contain carbon with the higher oxidation degree (larger quantity of connections C=O). Since oxide atoms do not enter into the composition of hexane, it is possible to assume their formation as a result of the oxidation reaction with the participation of atmospheric oxygen.
ТABLE 2 THE MODELS MASS LOST Model
Mass, mg
Loss of mass in the section 50-1000 °С
Loss of mass at the oxidation stage, %
Model 1 hexan
9,653
91,4
44
Model 2 ethanol
7,016
90,3
32,1
DND
6,635
95,7
89,8
The loss of the mass of the nanocarbon models (Tab. 2) at the oxidation stage is close to detonation ND, whiches indicate the identical content of inorganic admixtures in all models. In the process of collapsing the cavitation bubbles is separated the quantity of energy, sufficient for the break of the chemical bonds between C and H in the liquid, which leads to the formation of the carbonic phase of substance. Pressure developed in this case is sufficient for the transformation of nondiamond carbon into denser modification carbon. III. CONCLUSION The obtained particles are the aggregates of nanocrystalline structures. In the part of similar aggregates is identified carbon of denser modification with the great probability. The possibility of the synthesis of ultradispersed carbon phase in the acoustic cavitation process in the carbon-containing liquids is experimentally proven. REFERENCE [1]
[2]
[3]
Staver A.M., Gubarev N.V., Lyamkin A.I., Petrov E.A. et.al. The ultra-dispersed diamond powders, obtained with the use of explosive energy // FGV, 1984. V.20. № 5. pp. 100-104. (in Rissian) Galimov E.M. et al. The experimental confirmation of the diamond synthesis in the process of cavitation / Reports of the sciences academy, 2004. V. 395. № 2. pp. 187-191. (in Rissian) Margulis M.A. Sonicchemical reactions and sonoluminescence / М.: Chemistry, 1986. - 288 p. (in Rissian) Olga V. Stebleva (post graduate student) was born in Biysk, Russia in 1982. She received degree on information systems and technologies from Altay State Technical University. Her main research interests are nanodiamonds and ultrasonic devices.
Alexander L. Vereshchagin (Doctor of Chemical Science, Professor) was born in Osipovichi Byelorussia in 1949. Graduated in 1972 from Byelorussian State University. He has defended a thesis of PhD degree in 1978 and thesis of Doctor’s degree in 2005. Now he is head of chair “General chemistry and expertise of consumer goods”. His research and scientific interests are detonation nanodiamonds. Gennadiy V. Leonov (Doctor of Technical Science, Professor). He was born on Jan. 29 of 1948. Graduated in 1973 from Leningrad Technological Institute. He has defended a thesis of PhD degree in 1976 and thesis of Doctor’s degree in 1998. Now he is rector of Biysk Technological Institute, head of Methods and Means of Measuring and Automation, head the “Laboratory of modeling”. Scientific spheres: Mathematic modeling, Control systems, Information measuring thecnique and technologies.
