Effect of High-Energy Ball Milling on the Structural Phase State and Magnetic Properties of Boron Nitride and Iron Powde
- PDF / 1,121,668 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 105 Downloads / 188 Views
ct of High-Energy Ball Milling on the Structural Phase State and Magnetic Properties of Boron Nitride and Iron Powder Mixtures V. P. Menushenkova, *, I. O. Minkovaa, I. V. Dorofievicha, I. V. Shchetinina, D. G. Zhukova, Yu. N. Parhomenkoa, E. A. Skrylevaa, and A. G. Savchenkoa a
National University of Science and Technology (MISiS), Moscow, 119049 Russia *e-mail: [email protected] Received February 18, 2020; revised March 16, 2020; accepted March 27, 2020
Abstract—An investigation is performed of the effect the high-energy ball milling (mechanical alloying, MA) of a mixture of iron and hexagonal boron nitride (h-BN) powders at a component weight ratio of Fe : BN = 1 has on the phase composition and magnetic properties of the synthesized material. High-energy ball milling with subsequent annealing of the MA powder at 600°C is shown to alter its phase composition, structure, and magnetic characteristics substantially. DOI: 10.3103/S1062873820070199
INTRODUCTION Among the known iron–nitrogen compounds (Fe8N, Fe4N, Fe3N, Fe2N, and FeN) the first three are ferromagnetic and have high values of magnetization. Moreover, the magnetic moments of iron in ordered phase α''-Fe16N2 and in hypothetical compound Fe3N4 (3.2μB [1] and 3.26μB [2], respectively; μB in the Bohr magneton) are much greater than that of pure iron (2.22μB), making these nitrides promising materials for making permanent magnets. The widely used technique of nitriding based on interaction between a thin film of dispersed iron particles and the gas phase of NH3 or H2/NH3 has a serious flaw, due to the surface localization of the nitrogenenriched zone. An alternative way of obtaining bulk materials based on iron–nitrogen compounds could be the sintering of cakes made from mixtures of Fe and nitride (BN, AlN, or Si3N4) powders at temperatures as high as 1550°C. It has been shown that the combined effect nitrogen and boron have on the formation of iron nitrides and borides during sintering allows us to obtain materials with enhanced magnetic characteristics, including high coercive force [3–5]. Another way of introducing nitrogen into iron alloys is the high-energy milling (mechanical alloying, MA) of mixtures of powdered iron (or an initial alloy) and boron nitride [6–8]. Not only does the highenergy milling of these mixtures reduce the size of particles, it also initiates mechanochemical processes that produce iron nitrides and borides. For example, nano-
composite ε-FexN/BN consisting of iron nitride immersed in a nonmagnetic amorphous matrix of boron nitride was prepared in [6]. The authors believed the critical size of the particles of α-Fe reacting with nitrogen was around 8 nm. A similar nitriding procedure was used in [7, 8], the difference being that iron boride was obtained in [7] while nitride was synthesized in [8]. Note that the results described in [6‒8] were obtained at different combinations of mixture compositions, MA duration, and subsequent annealing. Powder weight fraction Fe : BN in particular was varied from 1 : 1 [7] to 1 : 12.5 [8]
Data Loading...
