High-power nanosecond electromagnetic pulses and dielectric barrier discharge in air consequences on structural and structure sensitive properties of ilmenite surface

The paper presents the results of experimental studies on the influence of two types of nonequilibrium electrical discharges (high-power nanosecond electromagnetic pulse (HPEMP) and dielectric barrier discharges (DBD) in air at atmospheric pressure) have on the surface morphology, microhardness, and physicochemical properties of natural ilmenite (Juina deposit of Brazil). Scanning electron microscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), microhardness testing, contact angles of surface wetting, and streaming potentials are used to examine the morphology, defects, chemical composition of ilmenite surfaces, and its structure sensitive properties. Using FTIR, we established, the following possible mechanisms of the nonthermal effect of HPEMP and DBD low temperature plasma irradiation, which modify the structural state of ilmenite surfaces: (i) the transformation (destruction) of the mineral’s crystalline structure; (ii) the electrical disintegration and removal of fine films of iron oxides (hydroxides) from the ilmenite surfaces, and (iii) the subsequent hydroxylation and/or oxidation of Fe2+ to Fe3+ iron ions on the surfaces, due to the effect of the products of microdischarge plasmas. Advantages of using brief energy treatments (ttreat = 10–30 s) to modify the structural-chemical state of ilmenite surfaces and the physicochemical properties of mineral in order to improve the efficiency of processing complex titanium ores are shown. Keywords: ilmenite, high-power nanosecond electromagnetic pulses, dielectric barrier discharge, surface, microscopy, spectroscopy, microhardness, electrokinetic potential, contact angle.