Synthesis of Irregular Tantalum Pentoxide (Ta₂O₅) Microparticles by Direct Thermal Oxidation of Ta Foils in Atmospheric Oxygen

Abstract

In this work, Tantalum pentoxide (Ta2O5) microparticles were achieved by one-step thermal oxidation of Tantalum (Ta) foils under 600 °C for 6 h. The effect of time and temperature was explored in the process (50 to 600 °C, 1 to 6 h). Thus, Ta foil was chemically cleaned with nitric and hydrochloric acid and then was immersed in water; finally it was dried with Nitrogen flux. The foils were isothermally oxidized in a horizontal furnace with 21 wt. % Oxygen atmosphere in a constant flux of 20 L/min. The x-ray diffraction, scanning electron microscopy, Raman and energy dispersive x-ray spectroscopy led to the conclusion that formation mechanism of microparticles is mainly constituted by lattice parameters mismatching between Ta and Ta2O5 and crystallite size difference. Along the oxidation process at 600 °C, the phase transformation across time carries defect concentrations on entire material experimentally demonstrated by Ta2O5 Raman shift and then the sample is broken in irregular shape. As oxidation time reaches 6 h value, phase transformation in Ta foil causes mismatching that firstly diminishes crystallite size, then evolves to cracks and finish by the formation of the particles in the micrometer order size.

Comparison of laser cladding properties of tantalum and tantalum pentoxide powders on titanium substrates

“…Ta 2 O 5 powder (see Fig. 1(b)) was obtained from the Ta powder via a one-step thermal oxidation process in which the Ta powder was heated to 900°C at a heating rate of 5°C/min and held for 30 min [34]. The Ta 2 O 5 particles were noticeably smaller than the Ta particles, with sizes ranging from 2 to 20 µm.…”

“…The Ta 2 O 5 particles were produced by the thermal oxidation of the Ta powder and have a small size since the density of Ta (16.6 g/cm 3 ) is approximately twice that of Ta 2 O 5 (8.8 g/cm 3 ). In particular, as Ta completes its phase transformation to polycrystalline Ta 2 O 5 , its volume expands signi cantly, causing the material to break owing to internal stress and form smaller particles [34].…”