Novel Sol-Gel Synthesis of LiMn₂O₄ and LiNi_xCo_1-xO₂ Powders

Abstract

A modified complex sol-gel process was developed to synthesize LiMn2O4 and LiNixCo1-xO2 powders. Sols were prepared from 1.5 M of Mn2+ or 1 M of xNi2+ and (1-x)Co2+ acetates plus ascorbic acid aqueous solutions by alkalizing them with LiOH and NH4OH. Ascorbic acid was added to prevent precipitation in the precursor solutions. When the sols were concentrated to one-third of their initial volume under reduced pressure and then gelled by drying for 10 days, heat treatment to ≥700 °C was accompanied by foaming, violent self-ignition, and formation of carbonates in the Ni-containing species. Significant improvements to the process and resulting powders were gained by modifying the gelation step. When gelation and drying were carried out under reduced total pressure, subsequent heating produced self-ignition, but no foaming, for all heating rates. The resulting products were determined to be nearly phase pure and carbonate free by thermogravimetric, differential thermal, X-ray, and infrared spectroscopy methods.

Vitrification of Nuclear Wastes by Complex Sol-Gel Process

“…ASC has not, to the best of our knowledge, been used by others in this type of processing of a nuclear waste glass. Its use has been shown to decrease remarkably the time needed to synthesize gels [7,9]. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) were conducted in air with a Hungarian MOM (Budapest, Hungary) [8,9].…”

“…In this work, our patented complex sol-gel process (CSGP) [7][8][9] has been used to synthesize silica glasses capable of incorporating into their structures significant concentrations of high-level nuclear wastes. The surrogates of nuclear elements (denoted Me) Cs, Sr, Co, and Nd (as a surrogate for actinides) were incorporated into silica glasses, and the resulting waste forms were characterized and tested for resistance to leaching.…”

Sol-Gel Processing of Silica Nuclear Waste Glasses

“…ASC has not, to the best of our knowledge, been used previously in this type of processing of a nuclear waste glass. Its use has been shown to decrease remarkably the time needed to synthesize gels [7,9].…”

“…Thermogravimetric analysis (TG) and differential thermal analysis (DTA) were conducted in air with a Hungarian MOM (Budapest, Hungary) [8,9]. The heating rate was 10˚C /h.…”

“…In the present work, our proprietary complex sol-gel process (CSGP) [7][8][9] has been adapted to synthesize silica glasses capable of incorporating significant concentrations of high-level nuclear wastes. The heavy metals (denoted Me) Cs, Sr, Co, and, as a surrogate for actinides, Nd, were incorporated into silica glasses and the resulting waste forms were characterized and tested for leaching response.…”