High-throughput continuous hydrothermal flow synthesis of Zn–Ce oxides: unprecedented solubility of Zn in the nanoparticle fluorite lattice

Abstract

High-throughput continuous hydrothermal flow synthesis has been used as a rapid and efficient synthetic route to produce a range of crystalline nanopowders in the CeZn oxide binary system. High-resolution powder X-ray diffraction data were obtained for both as-prepared and heat-treated (850• C for 10 h in air) samples using the new robotic beamline I11, located at Diamond Light Source. The influence of the sample composition on the crystal structure and on the optical and physical properties was studied. All the nanomaterials were characterized using Raman spectroscopy, UV-visible spectrophotometry, Brunauer-Emmett-Teller surface area and elemental analysis (via energy-dispersive X-ray spectroscopy). Initially, for 'as-prepared' Ce 1−x Zn x O y , a phasepure cerium oxide (fluorite) structure was obtained for nominal values of x = 0.1 and 0.2. Biphasic mixtures were obtained for nominal values of x in the range of 0.3-0.9 (inclusive). High-resolution transmission electron microscopy images revealed that the phase-pure nano-CeO 2 (x = 0) consisted of ca 3.7 nm well-defined nanoparticles. The nanomaterials produced herein generally had high surface areas (greater than 150 m 2 g −1 ) and possessed combinations of particle properties (e.g. bandgap, crystallinity, size, etc.) that were unobtainable or difficult to achieve by other more conventional synthetic methods.

In situ variable temperature X-ray diffraction studies on the transformations of nano-precursors to La–Ni–O phases

“…The powders were prepared using a continuous hydrothermal flow synthesis (CHFS) system as described elsewhere [26][27][28][29][30][31][32][33][34][35][36]. The as-prepared powders were mixtures of La(OH) 3 and Ni(OH) 2 nanoparticles with La/Ni metal ion ratios of 1:1, 2:1, 3:2 and 4:3.…”

“…CHFS or similar reactors have been used to rapidly and efficiently produce numerous inorganic metal oxide nanoparticles from premixed metal salt solutions, which can rapidly be co-precipitated as homogeneously mixed oxides or solid solutions when mixed with a flow of supercritical water (which is typically at 4 400 1C and 422 MPa). Further details of this process are given elsewhere [26][27][28][29][30][31][32][33][34][35][36].…”

Towards High Capacity Li-ion Batteries Based on Silicon-Graphene Composite Anodes and Sub-micron V-doped LiFePO4 Cathodes

“…The process involves the reaction of a feed of supercritical water with a reagent stream in an engineered mixer, over a period of a few seconds or minutes. This results in the formation of a metal oxide or phosphate material, usually of small particle size due to the supersaturated mixing conditions of the synthesis19. The CHFS process is scalable as reported by some authors2021, where production of ZnO has been successfully scaled up by a factor of 40 with little change observed in the crystallite size21.…”

Greener synthesis of dimethyl carbonate using a novel ceria–zirconia oxide/graphene nanocomposite catalyst

“…pressure and temperature) and hence particle properties [56][57]. Generally, the CHFS process involves mixing a flow of supercritical water with a flow of aqueous metal salt(s) to give rapid precipitation and controlled growth of nanoparticles in a continuous manner.…”