Synthesis, Structure and Properties of Material Based on V 2 AlC MAX Phase
- PDF / 1,168,899 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 203 Views
CTURE, PHASE TRANSFORMATIONS, AND DIFFUSION
Synthesis, Structure and Properties of Material Based on V2AlC MAX Phase V. A. Gorshkova, *, A. V. Karpova, D. Yu. Kovaleva, and A. E. Sycheva aMerzhanov
Institute of Structural Macrokinetics and Problems of Materials Science, Russian Academy of Sciences (ISMAN), Chernogolovka, 142432 Russia *e-mail: [email protected] Received February 20, 2020; revised April 28, 2020; accepted April 30, 2020
Abstract–A material based on the V2AlC MAX phase has been obtained for the first time by the method of self-propagating high-temperature synthesis (SHS) using a reaction mixture of vanadium oxide(V) and (IV) powders with aluminum and carbon (graphite). The obtained material was characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy. The Rietveld method was used to perform quantitative analysis. The synthesized material based on the V2AlC MAX phase is an electrical conductor that demonstrates the metallic behavior of conductivity in the entire measured temperature range of 300–1300 K in the vacuum of 2 × 10–3 Pa. It has been suggested that the V2AlC phase makes a decisive contribution to the electrical resistance of the synthesized material that may be caused by the formation of V2AlC nanolaminate grains contacting with each other in the bulk of the material. Keywords: SHS, combustion, pressure of gas, synthesis, MAX phase, V2AlC, nanolaminate structure, electrical resistance DOI: 10.1134/S0031918X20080037
These compounds have high melting points above 1973 K, but low oxidation resistance due to the forma-
765
C 1.0
Graphite
0.9 0.7 0.6
0.5 VC
0.4
0.3 0.2
1774 K
0.8
C cti on fra
The V–Al–C phase diagram was first studied in [1], where the existence of the V2AlC triple phase was shown. The high-temperature V4AlC3 phase was later synthesized [2, 3]. Both compounds V2AlC and V4AlC3 belong to the group of phases Mn + 1AXn (or MAX phases), where M is a transition metal, A is an element of group A (mainly group IIIA and IVA), X is either C or N. The V4AlC3 phase is stable at temperatures above 1392 K and in the isothermal section at 1773 K [4]. Figure 1 shows the regions of existence of the two phases V2AlC and V4AlC3 and a small range of solid solutions at 1773 K. Some solubility of C in bcc is seen at this temperature. The solubility of carbon gradually decreases when increasing Al content. These compounds exhibit interesting properties as a result of the formation of layered structure. They are elastically rigid, easy to process, and heat-resistant. These materials are also electrically conductive. A compacted material based on V2AlC was synthesized by the hot isostatic pressing (HIP) [5], magnetron sputtering [6], and hot pressing [7]. V2AlC-based material was obtained in [8] using the SHS method from a mixture of powders of V, Al, and C elements. The adiabatic temperature of the 2V–Al–C system is 2767 K. The product synthesized using thermal explosion mode consists of V2AlC and small amounts of VCx and AlV3,
while V2AlC grains are in the form of lamella
Data Loading...
