Nanowires and nanostructures of lithium titanate synthesized in a continuous thermal plasma reactor

Abstract Lithium titanates were synthesized from solid reagents injected into a radiofrequency inductive thermal plasma in a continuous tubular reactor. Various types of nanomorphologies were synthetized, including nanoparticles, nanowires and nanoplatelets. Their formation mechanism was investigated by varying the reagents chemical ratio, the nature of the plasma gases and the inclusion of an autocatalytic effect induced by solid seed materials. Scanning Electron Microscopy (SEM), electrical conductivity measurements, nitrogen surface absorption (BET) and X-ray diffraction (XRD) combined with a Rietveld refinement were used to quantify the phase composition and to characterize the materials. The yield in nanowires and nanoplatelets was observed to be qualitatively increased by a reducing plasma sheath gas composition containing hydrogen. Moreover, reducing plasma conditions correlated with drastically faster treatment to achieve improved electrical conductivity. It was also shown that the addition of solid nanosized seed material in the reagents significantly improved the yield of the desired phase following what is expected to be an incomplete atomization of its molecular bonds. Thermodynamic calculations are presented to support the reaction conditions and mechanisms observed.