Synthesis Of Chromium Oxide Research Articles

Effect of temperature on synthesis of chromium oxide

Effect of temperature on synthesis of chromium oxide

Preparation, material analysis, and morphology of Cr2 − xTixO3 + z for gas sensors

AbstractTitanium substituted chromium oxide (Cr2 − xTixO3 + z, CTO) has gained increasing interest concerning gas sensing applications. CTO is prepared by synthesis of chromium oxide and titanium oxide. Different techniques for verification of successful synthesis of CTO have been investigated. Solid state Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were performed in addition to the common analysis via X‐ray diffraction (XRD). The spectroscopic methods offer a fast, qualitative verification of a complete synthesis. CTO was synthesized in a high temperature sintering step, and powders and dispersions of CTO were prepared. A high energy grinding process leads to the required particle size reduction. The size distribution and crystallite size of the CTO particles were measured. Furthermore morphology and surface coverage analysis on novel type gas‐sensing CTO layers, deposited via inkjet technology, were performed and specific adsorption energies of nitrogen dioxide on printed CTO layers were derived. High porosity with sub‐micron particles was shown to be characteristic for the layers, resulting in a highly sensitive gas‐sensing behavior, with 500 ppb of nitrogen dioxide being clearly detectable.

Nanocrystalline Cr 2O 3 and amorphous CrO 3 produced by solution combustion synthesis

The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio. Amorphous CrO 3 and crystalline Cr 2O 3 were synthesized. The results suggest that glycine is a better complexing/combustible agent for ammonium dichromate than urea. Addition of extra ammonium nitrate to stoichiometric compositions improved the specific surface area and reduced the crystallite size. The smallest crystallite size (≈20 nm) of Cr 2O 3 was obtained with glycine as fuel/complexant agent in fuel-lean mixtures. The highest specific surface area (63 m 2/g) was observed with urea in fuel-rich mixtures, forming amorphous CrO 3.

Synthesis of Cr 2O 3 nanoparticles by mechanochemical processing

The synthesis of chromium oxide (Cr 2O 3) nanoparticles by mechanochemical reaction and subsequent heat treatment was investigated. A solid-state displacement reaction Na 2Cr 2O 7+S→Cr 2O 3+Na 2SO 4 was induced during mechanical milling of Na 2Cr 2O 7+S powder mixture, forming amorphous Cr 2O 3 nanoparticles. Annealing the as-milled powder under vacuum above 520°C resulted in the formation of crystalline Cr 2O 3 nanoparticles separated from each other in a salt matrix. A simple washing process to remove the matrix yielded Cr 2O 3 particles of 10–80 nm in size, having a plate-like morphology.