Effect of hydrothermal treatment conditions on formation of nickel hydrogermanate with platy morphology

Study of the phase composition and morphology of products formed in a hydrothermal treatment of the Ni(OH)₂–GeO₂–H₂O system with Ni/Ge cation molar ratios of 1, 1.5, and 2 in water and in aqueous solutions of HCl and NaOH demonstrated that the hydrothermal treatment products are composed of particles with plate-like morphology and average plate thickness of 40 nm and width of 500 nm. In this case, the phase composition of the products depends both on the molar ratio between the Ni and Ge cations and on the composition of the hydrothermal medium. Single-phase samples with structure similar to that of lizardite were obtained by treatment of a mixture with Ni/Ge = 1 in an alkaline medium or in a mixture with Ni/Ge = 1.5, irrespective of the composition of the medium. With the excess of GeO₂, a talc-like phase is formed, whereas with the excess of Ni(OH)₂, the samples contain crystalline nickel hydroxide in addition to the lizardite-like phase. Possessing magnetic and semiconductor properties, the single-phase nanopowders obtained in the study are promising as functional nanodispersed fillers of composite materials.