Synthesis and characterization of Nb2O5@C core-shell nanorods and Nb2O5nanorods by reacting Nb(OEt)5via RAPET (reaction under autogenic pressure at elevated temperatures) technique

The reaction of pentaethoxy niobate, Nb(OEt)5, at elevated temperature (800 °C) under autogenic pressure provides a chemical route to niobium oxide nanorods coated with amorphous carbon. This synthetic approach yielded nanocrystalline particles of Nb2O5@C. As prepared Nb2O5@C core-shell nanorods is annealed under air at 500 °C for 3 h (removing the carbon coating) results in neat Nb2O5nanorods. According to the TEM measurements, the Nb2O5crystals exhibit particle sizes between 25 nm and 100 nm, and the Nb2O5crystals display rod-like shapes without any indication of an amorphous character. The optical band gap of the Nb2O5nanorods was determined by diffuse reflectance spectroscopy (DRS) and was found to be 3.8 eV

Eutectic Al2O3-GdAlO3 composite consolidated by combined rapid quenching and spark plasma sintering technique

A mixture of Al2O3 and GdAlO3 was melted and rapid quenched to produce an amorphous film. Dense eutectic composites were consolidated from ground amorphous powder using both conventional and spark plasma sintering (SPS). Conventional sintering at temperatures above 1600degreesC for 24 h was required for complete sintering. However, using SPS complete sintering could be obtained at temperatures between 1300 and 1500degreesC with no soaking. The SPS technique could consolidate ultrafine eutectic structure from rapid quenched amorphous material, whilst conventional sintering was not successful owing to grain growth. A combination of rapid quenching and SPS resulted in an ultrafine eutectic Al2O3-GdAlO3 structure

Symmetry-Driven Spontaneous Self-Assembly of Nanoscale Ceria Building Blocks to Fractal Superoctahedra

A combination of long-term aging studies and molecular dynamics (MD) simulations has been successfully used to explain the time-dependent hierarchical assembly of ceria nanoparticles (CNPs). When the CNPs were aged in as-synthesized condition at room temperature in water, it was observed that the individual 3−5 nm CNPs result in octahedral superstructures through a fractal assembly. This hierarchical fractal self-assembly was observed despite the absence of any surfactant, at room temperature, and under atmospheric pressure. High resolution transmission electron microscopy (HRTEM) and fast Fourier transform (FFT) analysis have been used to explore the assembly of the individual nanoparticles into fractal superoctahedra. Both experimental work and theoretical analysis showed that the initial octahedral and truncated octahedral seeds symmetrically assemble and result in the superoctahedra with intermediate transformation ste

Iron-57 Mossbauer spectroscopic studies of the high temperature properties of metal-doped iron oxides

Fe-57 Mossbauer spectra recorded in situ in vacuo from chromium- and gallium-doped Fe3O4 at elevated temperatures show the dopant ions to depress the Curie temperature of Fe3O4 by ca. 70 K. Spectra recorded from aluminium-doped. gamma-Fe2O3 show the onset of conversion to aluminium-doped alpha-Fe2O3 to begin at ca. 750 K, which is ca. 100 K above the conversion temperature for undoped. gamma-Fe2O3. The variation in magnetic hyperfine fields at temperatures exceeding ca. 750 K is similar to that recorded from alpha-Fe2O3 when doped with zinc or magnesium. At temperatures exceeding 900 K the zinc doped alpha-Fe2O3 partially converts to spinel-related ZnFe2O4