Synthesis, Structure, and Properties of Titanium Diboride Nanoparticles
- PDF / 976,428 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 62 Downloads / 221 Views
hesis, Structure, and Properties of Titanium Diboride Nanoparticles A. A. Vinokurova, D. Yu. Kovalevb, I. I. Korobova, O. V. Kravchenkoa, S. V. Konovalikhinb, N. Yu. Khomenkob, G. V. Kalinnikova, S. E. Nadkhinaa, and S. P. Shilkina, * aInstitute
of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia b Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected] Received March 3, 2020; revised June 19, 2020; accepted June 30, 2020
Abstract—The products of reaction between TiCl4 and NaBH4 in NaCl/KCl or KBr ionic melts at 973 and 1023 K under an argon pressure of 5 MPa have been characterized by various physicochemical analysis techniques. The results demonstrate that these conditions lead to the formation of TiB2 nanoparticles with hexagonal symmetry (sp. gr. P6/mmm, AlB2 structure) and lattice parameters a = 0.3022–0.3025 nm and с = 0.3214–0.3221 nm. The average diameters of the TiB2 nanoparticles evaluated from electron microscopy, specific surface area, and X-ray diffraction (crystallite size) data for the two synthesis temperatures are ~10 and ~15, ~12 and ~17, and ~5 and ~10 nm, respectively. Keywords: nanoparticle, titanium diboride, titanium tetrachloride, sodium borohydride, NaCl/KCl ionic melt, KBr, autoclave reactor DOI: 10.1134/S0020168520110163
INTRODUCTION Titanium diboride (TiB2) combines a high melting point (3498 K), high hardness (≥25 GPa), high modulus of elasticity (≥450 GPa), low resistivity (10–30 Ω cm), high thermal conductivity (60–120 W/(m K)), good chemical stability and corrosion resistance in aggressive gaseous and liquid media, and low density (4.5 g/cm3), which allows it to find effective applications in various areas of modern engineering and industry [1–5]. Recent years have seen a considerable increase of interest in titanium diboride and related compounds because they have been used as basic components for producing nanomaterials with various and excellent physicochemical, mechanical, and other properties, differing significantly from the properties of their microcrystalline analogs (see, for example, Refs. [6, 7]). Titanium diboride nanoparticles can be prepared via the thermolysis of titanium borohydride derivatives at a temperature of ~488 K [8, 9], for example, according to the scheme
Ti (BH4 )3 ⋅ nSol v
(1) ⎯⎯→ TiB2 + 0.5B2H6 + 4.5H2 + nSol v where Solv stands for dimethoxyethane, tetrahydrofuran, diglyme, triglyme, etc. The TiB2 prepared accordt
ing to this scheme in the form of powder or film is X-ray amorphous and crystallizes in vacuum after annealing between 1173 and 1273 K. However, the described process takes a considerable time and is multistep, so the resultant TiB2 is contaminated with appreciable amounts of carbon and oxygen. TiB2 nanoparticles can also be prepared through mechanochemical interaction of titanium(III) chloride with lithium hydride and lithium borohydride in a highenergy mill according to the re
Data Loading...
