Preparation and characterization of Sr0.09Ce0.91O1.91, SrCeO3, and Sr2CeO4 by glycine–nitrate combustion: Crucial role of oxidant-to-fuel ratio

2004 ◽  
Vol 19 (11) ◽  
pp. 3181-3188 ◽  
Author(s):  
S.V. Chavan ◽  
A.K. Tyagi
Keyword(s):  
Least Squares Method ◽  
Combustion Process ◽  
Phase Identification ◽  
Stoichiometric Ratio ◽  
X Ray ◽  
Fuel Ratio ◽  
Metal Nitrates ◽  
Phase Pure ◽  
20 Nm ◽  
Glycine Nitrate Combustion

The title compositions were prepared by the gel-combustion process using glycine as the fuel and the corresponding metal nitrates as oxidants. The powders after calcination at 600 °C were characterized by x-ray diffraction for phase identification. The lattice parameters were refined by least squares method for each of the title compounds. Sr0.09Ce0.91O1.91 could be prepared in situ, that is, without any further external heating at higher temperatures, whereas phase pure SrCeO3 and Sr2CeO4 could be prepared only after calcination at 950 °C for 3 h. Sr0.09Ce0.91O1.91 was prepared using three different oxidant-to-fuel ratios: the fuel-deficient ratio, the propellant chemistry (stoichiometric) ratio, and the fuel-excess ratio. The crystallite size as calculated by x-ray line broadening was found to be 13 nm, 20 nm, and 42 nm for the products from fuel-deficient, propellant, and fuel-excess ratios, respectively. It was found that the extreme fuel-deficient ratio of 1:0.5 failed to give phase pure Sr0.09Ce0.91O1.91. The transmission electron microscopy studies showed that majority of the particles were in the range 80–100 nm and 200–250 nm for SrCeO3 and Sr2CeO4, respectively. The compositional characterization was done by energy dispersive x-ray. A careful control of the oxidant-to-fuel ratio was found to be necessary to get the desired products, due to their different thermodynamic stabilities. Thus, the versatility of combustion process in synthesizing the products with different thermodynamic stabilities has been shown, which was hitherto unexplored.

Highly sinter-active nanocrystalline RE2O3 (RE = Gd, Eu, Dy) by a combustion process, and role of oxidant-to-fuel ratio in preparing their different crystallographic modifications

2007 ◽  
Vol 22 (3) ◽  
pp. 587-594 ◽  
Author(s):  
V. Bedekar ◽  
S.V. Chavan ◽  
A.K. Tyagi
Keyword(s):  
Combustion Process ◽  
Sintering Behavior ◽  
Stoichiometric Ratio ◽  
Monoclinic Modification ◽  
Fuel Ratio ◽  
Metal Nitrates ◽  
Powder Properties ◽  
Very High ◽  
Scanning Electron

Highly sinter-active powders of RE2O3 [rare earth (RE) = Gd, Eu, Dy] have been prepared using the corresponding metal nitrates as the oxidants, and glycine and citric acid as the fuels. Two different oxidant-to-fuel ratios, namely stoichiometric ratio and fuel-deficient ratio were used to explore the possibility of preparing different crystallographic modifications. By a careful control of oxidant-to-fuel ratio, nanocrystalline Eu2O3 and Gd2O3 could be prepared in cubic (C-type) as well as monoclinic (B-type) modifications. However, the high-temperature monoclinic modification could not be obtained for Dy2O3 due to a very high C-to-B-type phase transition temperature. The crystallite size, surface area, and sintering behavior were also studied for powders prepared using different oxidant-to-fuel ratios, and the results showed a remarkable correlation between different fuel contents and powder properties. Some of these powders resulted in pellets of nearly theoretical density. The sintered microstructure was studied by scanning electron microscopy.

Synthesis, characterization, and properties of lead-based relaxor ferroelectrics

1996 ◽  
Vol 11 (5) ◽  
pp. 1210-1218 ◽  
Author(s):  
Michael M. A. Sekar ◽  
Arvind Halliyal ◽  
K. C. Patil
Keyword(s):  
Thermal Evolution ◽  
Combustion Process ◽  
Diffraction Method ◽  
Relaxor Ferroelectrics ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
X Ray ◽  
Metal Nitrates ◽  
Different Temperatures ◽  
Solution Combustion Process

Lead-based relaxor ferroelectrics such as Pb(Mg1/3Nb2/3)O3 (PMN), Pb(Zn1/3Nb2/3)O3 (PZN), and their solid solutions with BaTiO3 and PbTiO3 have been prepared by a solution combustion process which involves metal nitrates/oxalate and tetraformal trisazine (TFTA) at 350 °C. Thermal evolution of perovskite relaxors has been investigated at different temperatures of calcination using the powder x-ray diffraction method. Particles are fine and sinter-active at low temperature (1050 °C). Both particulate and dielectric properties are compared.

scholarly journals STRUCTURAL PROPERTIES AND MICROSTRUCTURE OF COBALT FERRITE PARTICLES SYNTHESIZED BY A SOL-GEL AUTO COMBUSTION METHOD

2013 ◽  
Vol 22 ◽  
pp. 558-563 ◽  
Author(s):  
ANAND RAVAL ◽  
NITAL PANCHAL ◽  
RAJSHREE JOTANIA
Keyword(s):  
Structural Properties ◽  
Cobalt Ferrite ◽  
Sol Gel ◽  
Combustion Process ◽  
Combustion Method ◽  
Xrd Analysis ◽  
Phase Identification ◽  
Ferrite Powder ◽  
Metal Nitrates ◽  
Auto Combustion

Synthesis and characterization of Cobalt ferrite powders by a sol gel combustion process is focused in the present work. The prepared precursors was calcined at 950° C for 4 hours in order to get cobalt ferrite powder. The effect of metal nitrates/citric acid ratio (referred as x) of CoFe2O4 on structural and micro-structural properties was investigated. The structural characterization on CoFe2O4 ferrite samples were carried out using the X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. Phase identification and crystallite size of calcined powder were determined using XRD analysis. The formation of the ferrite is confirmed by FTIR results. The morphology of prepared CoFe2O4 ferrite samples (with x = 0.5, 1.0, 1.5 and 2.0, where x is metal to citrate ratio) was studied using a scanning electron microscopy.

Nanocrystalline GdFeO3 via the gel-combustion process

2005 ◽  
Vol 20 (10) ◽  
pp. 2654-2659 ◽  
Author(s):  
S.V. Chavan ◽  
A.K. Tyagi
Keyword(s):  
Combustion Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Metal Nitrates ◽  
Transmission Electron ◽  
Expansion Behavior ◽  
High Temperature Xrd ◽  
Gel Combustion ◽  
Crystallite Sizes

Nanocrystalline GdFeO3 powder was synthesized by a combustion technique, using glycine as the fuel and the corresponding metal nitrates as oxidants. Five different molar ratios of fuel-to-oxidant were chosen to study the effect of fuel content on the phase formation and the powder properties. The powders after calcination were characterized by x-ray diffraction (XRD) and crystallite sizes calculated by x-ray line broadening. The crystallite sizes for the phase pure products after calcination at 600 °C were in the range 40–65 nm. The transmission electron microscopy observations clearly highlight the pronounced crystallinity for the propellant chemistry samples. The nature of the agglomerates was investigated by light scattering studies. The lattice thermal expansion behavior was also studied by high-temperature XRD.

Phase identification in SiC whisker reinforced Al2O3-R2O3-based composites

1992 ◽  
Vol 50 (1) ◽  
pp. 152-153
Author(s):  
C.M. Sung ◽  
K.J. Ostreicher ◽  
M.L. Huckabee ◽  
S.T. Buljan
Keyword(s):  
Analytical Electron Microscopy ◽  
Phase Identification ◽  
Reinforced Composites ◽  
Ion Milling ◽  
X Ray ◽  
Binary Oxides ◽  
Analytical Electron ◽  
The Matrix ◽  
Second Phases ◽  
Convergent Beam

A series of binary oxides and SiC whisker reinforced composites both having a matrix composed of an α-(Al, R)2O3 solid solution (R: rare earth) have been studied by analytical electron microscopy (AEM). The mechanical properties of the composites as well as crystal structure, composition, and defects of both second phases and the matrix were investigated. The formation of various second phases, e.g. garnet, β-Alumina, or perovskite structures in the binary Al2O3-R2O3 and the ternary Al2O3-R2O3-SiC(w) systems are discussed.Sections of the materials having thicknesses of 100 μm - 300 μm were first diamond core drilled. The discs were then polished and dimpled. The final step was ion milling with Ar+ until breakthrough occurred. Samples prepared in this manner were then analyzed using the Philips EM400T AEM. The low-Z energy dispersive X-ray spectroscopy (EDXS) data were obtained and correlated with convergent beam electron diffraction (CBED) patterns to identify phase compositions and structures. The following EDXS parameters were maintained in the analyzed areas: accelerating voltage of 120 keV, sample tilt of 12° and 20% dead time.

The effect of Tin additionon on Structural and magnetic properties of the stannoferrite Li0.5+0.5XFe2.5-1.5XSnXO4

2016 ◽  
Vol 12 (3) ◽  
pp. 4307-4321 ◽  
Author(s):  
Ahmed Hassan Ibrahim ◽  
Yehia Abbas
Keyword(s):  
Particle Size ◽  
Fine Particles ◽  
Magnetic Moments ◽  
Lithium Ferrite ◽  
Tem Analysis ◽  
Weiss Temperature ◽  
X Ray ◽  
Two Phases ◽  
Nanocrystalline Ferrite ◽  
20 Nm

The physical properties of ferrites are verysensitive to microstructure, which in turn critically dependson the manufacturing process.Nanocrystalline Lithium Stannoferrite system Li0.5+0.5XFe2.5-1.5XSnXO4,X= (0, 0.2, 0.4, 0.6, 0.8 and 1.0) fine particles were successfully prepared by double sintering ceramic technique at pre-sintering temperature of 500oC for 3 h andthepre-sintered material was crushed and sintered finally in air at 1000oC.The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction (XRD) and the Rietveld method.The refinement results showed that the nanocrystalline ferrite has a two phases of ordered and disordered phases for polymorphous lithium Stannoferrite.The particle size of as obtained samples were found to be ~20 nm through TEM that increases up to ~ 85 nmand isdependent on the annealing temperature. TEM micrograph reveals that the grains of sample are spherical in shape. (TEM) analysis confirmed the X-ray results.The particle size of stannic substituted lithium ferrite fine particle obtained from the XRD using Scherrer equation.Magneticmeasurements obtained from lake shore’s vibrating sample magnetometer (VSM), saturation magnetization ofordered LiFe5O8 was found to be (57.829 emu/g) which was lower than disordered LiFe5O8(62.848 emu/g).Theinterplay between superexchange interactions of Fe3+ ions at A and B sublattices gives rise to ferrimagnetic ordering of magnetic moments,with a high Curie-Weiss temperature (TCW ~ 900 K).

Investigation of the products of carbothermal reduction of yttrium oxide by the hydrolysis method

1984 ◽  
Vol 49 (4) ◽  
pp. 936-943 ◽  
Author(s):  
Bohumil Hájek ◽  
Pavel Karen ◽  
Vlastimil Brožek
Keyword(s):  
Yttrium Oxide ◽  
Carbothermal Reduction ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrolysis Method ◽  
Sample Decomposition ◽  
Products Of Reaction ◽  
Hydrolysis Of ◽  
Lower Carbon

For the investigation of the products of reaction of yttrium oxide with carbon mixed in various proportions, the chemical and X-ray diffraction methods of analysis were combined with the gas chromatographic analysis of the mixture of hydrocarbons and hydrogen formed on the sample decomposition with water. The carboreduction of Y2O3 was examined at relatively low temperatures, convenient for obtaining the reaction intermediates in higher yields. At 1 600 °C and pressures of 10-3 Pa the reduction of a mixture of Y2O3 with carbon in a stoichiometric ratio of 1 : 7 yields YC2 in equilibrium with 20% of Y2OC phase. At lower carbon contents (down to the Y2O3 : C ratio of 1 : 2) tha fraction of the Y2OC phase increases up to approximately 30%. In addition to Y2O3, the reaction mixture contains also Y2C, Y2OC and a phase giving propyne on hydrolysis. The presence of traces of C3 hydrocarbons and small amounts of methane in the product of hydrolysis of the carbide sample prepared by the carbothermal reduction of the oxide can be explained in terms of the occurrence of the Y15C19 phase, probably substituted in part by oxygen, and of the Y2OC phase. The results are compared with those obtained previously for the Sc2O3 + C system.

scholarly journals An Insight into Chemistry and Structure of Colloidal 2D-WS2 Nanoflakes: Combined XPS and XRD Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1969
Author(s):  
Riccardo Scarfiello ◽  
Elisabetta Mazzotta ◽  
Davide Altamura ◽  
Concetta Nobile ◽  
Rosanna Mastria ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Xrd Analysis ◽  
Crystal Habit ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Morphological Evaluation ◽  
Rational Understanding ◽  
Structural Inspection

The surface and structural characterization techniques of three atom-thick bi-dimensional 2D-WS2 colloidal nanocrystals cross the limit of bulk investigation, offering the possibility of simultaneous phase identification, structural-to-morphological evaluation, and surface chemical description. In the present study, we report a rational understanding based on X-ray photoelectron spectroscopy (XPS) and structural inspection of two kinds of dimensionally controllable 2D-WS2 colloidal nanoflakes (NFLs) generated with a surfactant assisted non-hydrolytic route. The qualitative and quantitative determination of 1T’ and 2H phases based on W 4f XPS signal components, together with the presence of two kinds of sulfur ions, S22− and S2−, based on S 2p signal and related to the formation of WS2 and WOxSy in a mixed oxygen-sulfur environment, are carefully reported and discussed for both nanocrystals breeds. The XPS results are used as an input for detailed X-ray Diffraction (XRD) analysis allowing for a clear discrimination of NFLs crystal habit, and an estimation of the exact number of atomic monolayers composing the 2D-WS2 nanocrystalline samples.

scholarly journals A Highly Selective Turn-On Fluorescent Probe for the Detection of Zinc

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3825
Author(s):  
Ling-Yi Shen ◽  
Xiao-Li Chen ◽  
Xian-Jiong Yang ◽  
Hong Xu ◽  
Ya-Li Huang ◽  
...  
Keyword(s):  
High Selectivity ◽  
Fluorescence Probe ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Turn On ◽  
Imine Nitrogen ◽  
System A ◽  
Plot Analysis ◽  
L System

A novel turn-on fluorescence probe L has been designed that exhibits high selectivity and sensitivity with a detection limit of 9.53 × 10−8 mol/L for the quantification of Zn2+. 1H-NMR spectroscopy and single crystal X-ray diffraction analysis revealed the unsymmetrical nature of the structure of the Schiff base probe L. An emission titration experiment in the presence of different molar fractions of Zn2+ was used to perform a Job’s plot analysis. The results showed that the stoichiometric ratio of the complex formed by L and Zn2+ was 1:1. Moreover, the molecular structure of the mononuclear Cu complex reveals one ligand L coordinates with one Cu atom in the asymmetric unit. On adding CuCl2 to the ZnCl2/L system, a Cu-Zn complex was formed and a strong quenching behavior was observed, which inferred that the Cu2+ displaced Zn2+ to coordinate with the imine nitrogen atoms and hydroxyl oxygen atoms of probe L.

scholarly journals Silver Nanoparticles from Oregano Leaves’ Extracts as Antimicrobial Components for Non-Infected Hydrogel Contact Lenses

2021 ◽  
Vol 22 (7) ◽  
pp. 3539
Author(s):  
Anastasia Meretoudi ◽  
Christina N. Banti ◽  
Panagiotis K. Raptis ◽  
Christina Papachristodoulou ◽  
Nikolaos Kourkoumelis ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Contact Lenses ◽  
Attenuated Total Reflection ◽  
Bacterial Strains ◽  
Scanning Calorimetry ◽  
X Ray ◽  
E Coli ◽  
Polymer Hydrogels ◽  
20 Nm ◽  
And Staphylococcus Aureus

The oregano leaves’ extract (ORLE) was used for the formation of silver nanoparticles (AgNPs(ORLE)). ORLE and AgNPs(ORLE) (2 mg/mL) were dispersed in polymer hydrogels to give the pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2 using hydroxyethyl–methacrylate (HEMA). The materials were characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), thermogravimetric differential thermal analysis (TG-DTA), derivative thermogravimetry/differential scanning calorimetry (DTG/DSC), ultraviolet (UV-Vis), and attenuated total reflection mode (ATR-FTIR) spectroscopies in solid state and UV–Vis in solution. The crystallite size value, analyzed with XRPD, was determined at 20 nm. The antimicrobial activity of the materials was investigated against Gram-negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). The Gram-positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus) are known to be involved in microbial keratitis by the means of inhibitory zone (IZ), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The IZs, which developed upon incubation of P. aeruginosa, E. coli, S. epidermidis, and S. aureus with paper discs soaked in 2 mg/mL of AgNPs(ORLE), were 11.7 ± 0.7, 13.5 ± 1.9, 12.7 ± 1.7, and 14.3 ± 1.7 mm. When the same dose of ORLE was administrated, the IZs were 10.2 ± 0.7, 9.2 ± 0.5, 9.0 ± 0.0, and 9.0 ± 0.0 mm. The percent of bacterial viability when they were incubated over the polymeric hydrogel discs of pHEMA@AgNPs(ORLE)_2 was interestingly low (66.5, 88.3, 77.7, and 59.6%, respectively, against of P. aeruginosa, E. coli, S. epidermidis, and S. aureus) and those of pHEMA@ORLE_2 were 89.3, 88.1, 92.8, and 84.6%, respectively. Consequently, pHEMA@AgNPs(ORLE)_2 could be an efficient candidate toward the development of non-infectious contact lenses.

Sign in / Sign up

Export Citation Format

Share Document