Synthesis and structure screening of nanostructured chromium oxide powders (original) (raw)
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Synthesis and Characterization of Chromium Oxide Nanoparticles
Chromium oxide nanoparticles (NPs) have been rapidly synthesized by precipitation method using ammomia as precipitating agent and are characterized by using X-ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA), UV-Visible absorption (UV), Infrared Spectoscopy (IR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). XRD studies show that chromium oxide NP is formed as Cr 2 O 3 and it has hexagonal structure. The shape and particle size of the synthesized Cr 2 O 3 NPs is determined by SEM and TEM. The images showed that the size of NPs of Cr 2 O 3 varied from 20 nm to 70 nm with average crystalline size 45 nm. UV-Visible absorption and IR spectoscopy confirm the formation of nanosized Cr 2 O 3 . TGA verifies that the Cr 2 O 3 NPs are thermally stable upto 1000 °C.
Microporous and Mesoporous Materials, 2008
Chromium oxide nanocrystals were synthesized by solid thermal decomposition using cetyltrimethylammonium bromide (CTAB) or a triblock copolymer (P123) as template agent at low temperature. The chromium oxide nanocrystals possess lamellar phase with disordered mesopore. The template surfactants (P123 or CTAB) and hydrated water play an important bridging role in the aggregation of inorganic chromium species in the thermal decomposition of chromium nitration. The mesopores of chromium oxide are formed by eliminating CTAB or P123 from the Cr-surfactants composites with small shrinkage.
Nanocrystalline Cr2O3 and amorphous CrO3 produced by solution combustion synthesis
Journal of the European Ceramic Society, 2006
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 2 O 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 2 O 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 .
Sol-gel combustion method; Chromium oxide; Nanostructure; PVA. KEYWORDS ABSTRACT The paper presents deals with the effect of poly vinyl alcohol (PVA) amount as gel making agent of sol-gel combustion method on the morphology and the particles sizes of chromium oxide nanostructures (CONS). Chromium nitrate is dissolved in 1:1 water ethanol mixed solvent. Some different amounts are dissolved in the chromium nitrate solution under controlled temperature to make a sol. The solvent of the sol is evaporated under controlled temperature to obtain a high viscous material which called gel. The suitable pyrrolysis temperature of the gel is found by TGA/DTA analysis. The homogenous gel is slowly pyrrolized under 500 ºC by an electrical furnace to obtain a CONS sample. Five different samples are synthesized by using different amounts of PVA. The morphology, particles sizes and the composition of the CONS is characterized by SEM, TEM, XRD and DLS.
Authors personal copy Saleh Mani et al Cr2O3 nanoparticles 2011
Monodispersed spherical particles of chromium (III) oxide, a-Cr 2 O 3 , were successfully synthesized from a diluted solution of KCr(SO 4 ) 2 Á 12H 2 O using the Aqueous Chemical Growth (ACG) technique. The spherical a-Cr 2 O 3 particles obtained were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy for structural, surface morphological, chemical, and physical properties, as a function of deposition time. The XRD and Raman spectroscopy showed that aging had no apparent effect on the structure of the obtained uniform fine (in the range of micronnano-level)-spherical particles of a-Cr 2 O 3 . The use of SEM demonstrated that aging had a clear influence on the size and the particles size distribution. Accordingly, the time dependence of the average diameter of a-Cr 2 O 3 spherical particles follows the d 3 law as required for diffusion-limited Ostwald ripening.
PROCEEDING OF THE 1ST INTERNATIONAL CONFERENCE ON ADVANCED RESEARCH IN PURE AND APPLIED SCIENCE (ICARPAS2021): Third Annual Conference of Al-Muthanna University/College of Science
The nanoparticles were synthesized from chromium oxide using Roselle extract in two methods, the first by (simple chemical method) and the second by (sol-gel method). These technologies are a new, environmentally friendly and cheap. Roselle contains plant materials and biomolecules (phenols, alkalis, vitamins, amino acids, quinones, etc.) that convert chromium chloride hexahydrate (CrCl3.6H2O) into chromium nanoparticles. The plant extracts also act as diluents, stabilizers and anti-caking agents Chromium oxide (Cr2O3) nanoparticles were prepared by sol-gel method. Nano powders are annealing at different. X-ray diffraction (XRD) analysis showed that the size of the crystals decreased from (16.12) nm by the simple chemical method to (13.8) nm of Cr2O3 using sol-gel (200),(13.5)nm using solgel(400),(13.3)nm of Cr2O3 using sol0gel(600). The (Scanning electron microscopy (SEM) showed that the nanoparticles of Cr2O3 NPs with (36.38) nm in a simple chemical method while the (SEM) in sol-gel method (200) showed that the nanoparticles of Cr2O3 NPs using Roselle extract are spherical or semispherical in shape) with a particle size of (89.83) nm in scale 200nm, the results no similar any source. Ultraviolet-visible (UV-Vis) showed value the band gap from of 2.9 eV of Cr2O3 NPs in a simple chemical method, while in a sol-gel method of Cr2O3 NPs was (3, 3.2, 3.35, 3.5) ev at different temperatures, In this research were obtain on high pure, small particle size, and large energy gap of chromium oxide NPs in a sol-gel method better than of chromium oxide NPs in a simple chemical method. The study revealed that the Chromium oxide nanoparticles synthesized using Roselle extracts could be used as antibacterial agent for human pathogenic bacteria. The aim of this research is to obtain chromium oxide (Cr2O3) nanoparticles using inexpensive and available materials, in Simple method.
Effect of temperature on synthesis of chromium oxide
Acta Crystallographica Section A Foundations and Advances, 2017
Our synthesis of Chromium oxide nanoparticle involves hydrothermal method using Chromium anhydride and anhydrous alcohol as the raw materials.Variation of temperature in particle size of nanoparticle is observed by increasing and decreasing the temperature.Various characterization method including XRD,TEM and SEM were used for characterizing the synthesised product.It was found that with increase in temperature good particle size of Chromium oxide is formed.As the process is simple and easy it can be used in various applications such as catalysis,colorants any many more.
Synthesis of Cr 2O 3 nanoparticles by mechanochemical processing
Acta Materialia, 2000
AbstractÐThe synthesis of chromium oxide (Cr 2 O 3 ) nanoparticles by mechanochemical reaction and subsequent heat treatment was investigated. A solid-state displacement reaction Na 2 Cr 2 O 7 S 4 Cr 2 O 3 Na 2 SO 4 was induced during mechanical milling of Na 2 Cr 2 O 7 S powder mixture, forming amorphous Cr 2 O 3 nanoparticles. Annealing the as-milled powder under vacuum above 5208C resulted in the formation of crystalline Cr 2 O 3 nanoparticles separated from each other in a salt matrix. A simple washing process to remove the matrix yielded Cr 2 O 3 particles of 10±80 nm in size, having a plate-like morphology. 7
Synthesis, characterization, and growth mechanism of α-Cr< sub> 2 O< sub> 3 monodispersed particles
Journal of Physics and …, 2011
Monodispersed spherical particles of chromium (III) oxide, a-Cr 2 O 3 , were successfully synthesized from a diluted solution of KCr(SO 4 ) 2 Á 12H 2 O using the Aqueous Chemical Growth (ACG) technique. The spherical a-Cr 2 O 3 particles obtained were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy for structural, surface morphological, chemical, and physical properties, as a function of deposition time. The XRD and Raman spectroscopy showed that aging had no apparent effect on the structure of the obtained uniform fine (in the range of micronnano-level)-spherical particles of a-Cr 2 O 3 . The use of SEM demonstrated that aging had a clear influence on the size and the particles size distribution. Accordingly, the time dependence of the average diameter of a-Cr 2 O 3 spherical particles follows the d 3 law as required for diffusion-limited Ostwald ripening.
Iraqi Journal of Physics (IJP), 2021
Nanostructure of chromium oxide (Cr2O3-NPs) with rhombohedral structure were successfully prepared by spray pyrolysis technique using Aqueous solution of Chromium (III) chloride CrCl3 as solution. The films were deposited on glass substrates heated to 450°C using X-ray diffraction (XRD) shows the nature of polycrystalline samples. The calculated lattice constant value for the grown Cr2O3 nanostructures is a = b = 4.959 Å & c = 13.594 Å and the average crystallize size (46.3-55.6) nm calculated from diffraction peaks, Spectral analysis revealed FTIR peak characteristic vibrations of Cr-O Extended and Two sharp peaks present at 630 and 578 cm-1 attributed to Cr-O “stretching modes”, are clear evidence of the presence of crystalline Cr2O3. The energy band gap (3.4 eV) for the chromium oxide nanostructures was measured using the UV-VIS-NIR Optical Spectrophotometer. It was found that by scanning electron microscopy (SEM) and image results, there is a large amount of nanostructure with an...