CC BY
11ÏSHS2019
Moscow, Russia
CLAD POWDERS BY COMBINED USE OF METAL REDUCTION AND HIGH-ENERGY BALL MILLING IN SALT SOLUTIONS: THEIR
PREPARATION AND IGNITION
S. G. Vadchenko
Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of
Sciences, Chernogolovka, Moscow, 142432 Russia e-mail: [email protected]
DOI: 10.24411/9999-0014A-2019-10183
The cladding (plating) of metal powders with other metals can be performed in several ways [1, 2]. The process of cladding is normally carried out in mills or vibratory machines from a mixture of basic and cladding metals. Usually the clad layers obtained via metal reduction from aqueous solution of salts exhibit weak adhesion to the surface of basic powder.
This work aimed at elaboration of a new method for fabrication of clad powders by combined use of metal reduction and high-energy ball milling (HEBM). The latter affords for formation of composite powders with a fine laminate structure of individual particulates showing elevated reactivity. If constituent metals are capable of reacting with heat release, such composite powders can be used as green mixtures for SHS production of materials or fabrication of items by sintering. In this work, Cu-Ti and Ni-Al clad particle were obtained by deposition of Ni and Cu onto Ti and Al powders from aqueous solution of their chlorides, sulfates, and nitrates. The reduction of metals takes place during HEBM and can be facilitated by reductants, such as glycine, hydrazine sulfate, and sodium hyposulfite. Thus, prepared clad powders were characterized by SEM and XRD.
Figure 1 shows the deposits of Cu (bright) on Al (a) and Ti (b) powder particles formed at the initial stages of milling the Al-CuSO4-5H2O and Ti-CuSO4-5H2O mixtures. Copper is deposited in the form of small particles with a size of below 0.2 ^m.
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(a) (b)
Fig. 1. SEM images showing the deposits of Cu (bright) on Al (a) and Ti (b) powder particles.
Figure 2 presents the temperature profiles of thermal explosion in Ti-Al pellets prepared from different mixtures. The ignition profiles for the pellets prepared from composite particles obtained in the combined process markedly differ from those prepared from unprocessed and milled Ni-Al mixtures (Fig.2). The onset of temperature rise for the mixture of Al with the Ni reduced from NiSO4-7H2O (curve 1) is by 200-300°C lower than that for unprocessed Ni-Al mixture (curve 6). The former is seen to proceed in two stages due to the melting of excessive Al.
S. G. Vadchenko 499
XV International Symposium on Self-Propagating High-Temperature Synthesis
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Fig. 2. Thermograms of thermal explosion in Ti-Al pellets prepared from: (1) mixture of Al with the Ni reduced from NiSO4-7H2O; (2) mixture of Ni and Al nanopowders; (3) fine fraction of Ni-Al mixture milled in water; (4) Ni-Al nanofoils; and (5) milled Ni-Al mixture; and (6) unprocessed Ni-Al mixture.
This research was financially supported by the Russian Foundation for Basic Research (project no. 18-03-00438).
1. A.G. Meilakh, Steel production from nickel-plated iron powder, Steel in Translation, 2014, vol. 44, no. 2, pp. 162-165.
2. Yu.V. Kontsevoi, A.V. Dolmatov, E.A. Pastukhov, T.F. Grigor'eva, Mechanical plating of Fe-Al and Fe-Cu systems under dynamic loading, Poroshk. Metall. Funkts. Pokr., 2015, no. 1, pp. 8-11.
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