Determining factor of median diameter in intermetallic compound nanoparticles prepared by pulsed wire discharge

摘要

The preparation of NiAl intermetallic compound nanoparticles was carried out by pulsed wire discharge (PWD) using twisted pure Ni and Al wires in N_2 ambient gas with varying number of turns of the wire (N_t), energy ratio (K), and ambient gas pressure (P). From the voltage and current waveforms during the wire heating, the energy deposition ratio up to the voltage peak (K_p) was calculated. It increased with an increase in N_t to 0.4 turns/mm and with increases in K and P. Under all the conditions, with an increase in K_p, the Ni composition ratio of the prepared particles (C_(Nj)) became closer to that of the wire (＝ 51.2mol%). Furthermore, the collection rate (R_c) increased and the median particle diameter (d_(50)) decreased. In particular, the change in d_(50) due to the change in N_t was not predicted by the relationship of d_(50) and Dth in our previous report. Single-phase NiAl intermetallic compound nanoparticles were successfully prepared under the condition in which N_t is 0.4 turns/mm, K is 3.4, and P is 100kPa, where relatively high value of K_p was obtained. From these results, K_p was determined to be an important factor that determines the composition, collection rate, and median diameter of intermetallic compound nanoparticles synthesized by PWD using different kinds of twisted wires under various experimental conditions. This may be because of the selective wire heating in high-resistance parts that are associated with the introduction of lattice defects and/or necks by overwinding.