CC BY
29ÏSHS2019
Moscow, Russia
PRODUCTION OF ULTRAFINE-GRAINED POWDER COMPOSITES IN
BN, B4C, AND BxCyNz SYSTEMS BY SHS METHOD
Z. Aslamazashvili"*, G. Zakharov", G. Mikaberidze", M. Chikhradze", G. Tavadze",
and G. Oniashvili"
aTavadze Metallurgy and Materials Science Institute, Tbilisi, 0186 Georgia
*e-mail: zuraaslamazashvili@yahoo.com
DOI: 10.24411/9999-0014A-2019-10013
One of the main aims of modern scientific researches is to focus the production of energy and resource-saving ecologically safe technologies and their realization. In this point one of the prospective directions is self-propagating high-temperature synthesis (SHS). The main idea of the work is to study the possibility to fabricate radiation resistant and radiation protective ceramic materials from 10B and 11B containing row material (B2O3). At the first stage, this leads to elaboration of technology for production fine-grained powder composites BN, B4C, and BxCyNz in B-C-N system by using effective SHS technologies. At the second stage, Ti-B-C-N ceramic materials will be elaborated using fine-grained BN, B4C, and BxCyNz composites [1-4]. Experiments were carried out in high pressure reactors in order to obtain powder composite from the cheap raw material B2O3 produced in Turkey. The boron carbide was obtained in SHS reactor in argon atmosphere, the carbon was added in form of synthetic graphite (model: KS15) and in form of soot (Model: n803). For production of BN nitrogen was used under a pressure of 5-10 MPa; synthetic graphite KS15, soot, and nitrogen were used for production of BxCyNz. In all cases Mg was used as reductant metal. For the production of ultrafine powders, 10 wt % final product and 20 wt % NaCl were added in initial chasm. The experiment includes drying of initial components, dosing, mixing, and synthesis under 2-10 MPa. The standard chemical treatment was also applied for materials obtained in SHS reactor.
Table 1.
Content of initial chasm and possible reactions of SHS processes
Process implementation conditions
Result of experiment
Grain size of product, nm
B2O3 (98%) and synthetic graphite KS15: 2B2O3 + 6Mg + C = B4C + 6MgO B2O3 = 47.3; Mg = 48.65; C = 4.05 P0 = 0.5 MPa, Pf = 2.0 MPa, Argon Wash by HCl, efficiency: Ht = 18.92%; -qexp = 18.5% 78- -360
B2O3 (98%) and soot n803: 2B2O3 + 6Mg + C = B4C + 6MgO B2O3 = 47.3; Mg = 48.65; C = 4.05 P0 = 0.5 MPa, Pf = 1.5 MPa, Argon Wash by HCl, efficiency: Ht = 18.92%; Hexp = 18.2% 78- -350
B2O3 (98%): B2O3 + 3Mg +N2 = 2BN+ 3MgO B2O3 = 41.18; Mg= 42.35; N2 = 16.47 P0 = 5-10 MPa, Pf = 10-15 MPa, Nitrogen Wash by HCl, efficiency: Ht = 29,41%; Hexp = 29% 50 -60
B2O3 (98%) and synthetic graphite KS15: B2O3 + Mg + C + N = BxCyNz + MgO P0 = 5-10 MPa, Pf = 10-15 MPa, Nitrogen Wash by HCl, efficiency: Ht = 25.64%; Hexp = 25,3% 95- 350
B2O3 (98%) and soot n803: B2O3 + Mg + C + N = BxCyNz + MgO P0 = 5-10 MPa, Pf = 10-15 MPa, Nitrogen Wash by HCl, efficiency: Ht = 25.64%; Hexp = 25.2% 95- 350
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XV International Symposium on Self-Propagating High-Temperature Synthesis
Table1 shows the content of initial chasm and possible reactions of SHS processes and experimental results for obtaining boron carbide, boron nitride, boron carbo-nitride from cheap row materials produces in Turkey. The investigations of elemental content of BxCyNz using analyzer "EXSPERT" showed that when the initial pressure in SHS reactor is 5 MPa, the final product of boron carbo-nitride contains 8.5 wt % nitrogen, while an increase in the pressure up to 9-10 MPa gives 18-18.5 wt % content of nitrogen in final product. By changing the pressure, it is easy to change the chemical composition of final product. The final products BN, B4C, and BxCyNz were studied using micro analyzer to define granulometry and chemical content. Figure 1 shows the microstructure of boron carbide, which gives possibility to define grain sizes. Figures 2-4 presents the microstructure and chemical contents of boron carbide, boron nitride, and boron carbo-nitride in relevant points.
Fig.1. Microstructure of B4C.
Spectrum 6 Spectrum 1 Spectrum 2 Spectrum 3 Spectrum 4 Spectrum 5
B 55.68 56.18 62.36 51.89 53.67 58.01
C_39.00_35.65_31.97_43.22_37.45_33.59
Fig. 2. Microstructure of B4C and chemical compositions in marked points (wt %).
Spwtnim 7 Spectrum 12 ,.- j +
..^pectmm *....../
4t +Sp«trUm£
Spectrum 11
r +
Spectrum 7 Spectrum 8 Spectrum 9 Spectrum 10 Spectrum 11 Spectrum 12 B 32.51 56.77 33.35 39.63 56.24 64.19
C 0.80
N 50.53_33.93_46.84_40.67_36.44_29.37
Fig. 3. Microstructure of BN and chemical compositions in marked points (wt %).
Spectrum 9
Spectrum 10
Spectrum 11
Spectrum 12
B 60.46
C 9.82
N 27.33
61.61 8.27 29.74
58.06 9.97 28.70
60.00 9.15 28.18
Fig. 4. Microstructure of BxCyNz and chemical compositions in marked points (wt %).
Using the installation ELTRA-CS-800 the general content of carbon in B4C and BxCyNz was deifined (Table 2).
Table 2.
Material
Sample
Carbon content, wt %
B4C 1 24.36 24.45
B4C 2 24.05 24.02
BxCyNz 3 13.06 13.28
B4C 59 24.8 24.65
B4C 64 26.87 26.93
Conclusions
(1) Experiments showed that it is possible to obtain fine-grained B4C, BN, BxCyNz from boron oxide B2O3 produced in Turkey.
(2) By changing the pressure of nitrogen in SHS reactor it is possible to change the content of BN and BxCyNz.
(3) Structural and spectral analysis showed that it is possible to obtain fine-grained B4C and BxCyNz in the range of 500-200 nm and BN with size less than 100 nm.
(4) In B4C and BxCyNz, the total content of carbon is 24 and 13 wt %, respectively.
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3. J.C. Marra, Materials and mechanical design analysis of boron carbide reactor safety rods, Task technical and QA Plan, Task Number 91-047-1, 1991.
4. Concept of development of SHS: publishing house "Teoria", 2003.
