Role of Oxidation State of Vanadium in Vanadium Oxide-Hematite Nanoparticles

2013 ◽  
Vol 1494 ◽  
pp. 185-190
Author(s):  
Monica Sorescu ◽  
Tianhong Xu ◽  
Collin Wade
Keyword(s):  
Solid Solutions ◽  
Single Phase ◽  
Milling Process ◽  
X Ray ◽  
Grain Sizes ◽  
Intermediate Phases ◽  
Transformation Pathway ◽  
Important Intermediate ◽  
Mechanochemical Milling

ABSTRACTSingle phase, a FeVO4 triclinic crystalline structure was successfully synthesized by annealing the mechanochemically milled xV2O5·(1-x)α-Fe2O3 composites (x = 0.5) at 550 °C for 1 h. X-ray powder diffraction (XRD) and Mössbauer spectroscopy were combined for a detailed study of the assisting role of the mechanochemical milling process. Mechanochemical milling homogeneously mixed the starting materials of α-Fe2O3 and V2O5 and substantially decreased their average grain sizes. The partially V5+-substituted α-Fe2O3 phase and Fe3+-substituted V2O5 could be the important intermediate phases in the production of FeVO4 single phase. In addition, xV2O3·(1-x)α-Fe2O3 (x = 0.1, 0.3, 0.5, and 0.7) solid solutions were successfully synthesized by mechanochemical activation of V2O3 and α-Fe2O3 mixtures. Complete solid solutions exist after 12 h ball-milling time for all studied x values. The synthesized xV2O3·(1-x)α-Fe2O3 solid solutions with x = 0.5 and 0.7 were mainly paramagnetic at room temperature. The study demonstrates that the transformation pathway is related to the valence state of the metallic specie of the oxide used in connection with hematite.

HIGH THERMAL STABILITY OF MICROWAVE DIELECTRIC PROPERTIES OF CaTi1-x(Nb1/2Fe1/2)xO3 CERAMICS

2011 ◽  
Vol 01 (04) ◽  
pp. 417-427 ◽  
Author(s):  
A. D. S. BRUNO COSTA ◽  
M. C. ROMEU ◽  
R. C. S. COSTA ◽  
T. S. M. FERNANDES ◽  
F. W. DE O. AMARANTE ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
Solid Solutions ◽  
Microwave Dielectric Properties ◽  
Titanium Content ◽  
Milling Process ◽  
Solid State Method ◽  
Small Shift ◽  
X Ray ◽  
Microwave Dielectric

This paper presents a study of the structure and microwave properties of [Formula: see text] substituted into the Ti 4+ site of calcium titanate ceramics. The structural and dielectric properties of solid solutions in CaTi 1-x( Nb 1/2 Fe 1/2)x O 3, was done. The microwave dielectric properties of solid solutions in CaTi 1-x( Nb 1/2 Fe 1/2)x O 3, (CNFTOX with x = 0.1 to x = 1) is discussed. The modified CaTiO3 (CTO) ceramics were prepared by a new procedure in the solid-state method. A study of the variations of the ball-milling process was done. The calcinations were done at 900°C for 3 and 5 h respectively, and the sintering at 1100°C, for 3 h. The structural property studies of the ceramics were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The X-ray analysis showed that all samples have an orthorhombic structure. The refinement analysis of all samples were also duly performed and discussed. The nine scattering bands centered at 183, 227, 247, 288, 338, 470, 490 and 805 cm-1 were observed. Several peaks presented a small shift as a function of the x value. All Raman spectra in the studied samples showed a small band at 805 cm-1, which is a function of the x value. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. For both calcination treatments (900°C for 3 and 5 h), the dielectric permittivity decreased with a decrease of the titanium content. Dielectric permittivity values in the range of 20 to 80 were obtained. It was also observed that a higher number of balls in the milling process contribute to the increase of the εr values. The CNFTO has an excellent microwave property at x = 0.6, with a temperature coefficient of resonant frequency (τf) near zero (τf = 2.8 ppm/°C).

Role of boron on grain sizes and magnetic correlation lengths in recording media as determined by soft x-ray scattering

2002 ◽  
Vol 80 (7) ◽  
pp. 1234-1236 ◽  
Author(s):  
Olav Hellwig ◽  
D. T. Margulies ◽  
B. Lengsfield ◽  
Eric E. Fullerton ◽  
J. B. Kortright
Keyword(s):  
Recording Media ◽  
Correlation Lengths ◽  
X Ray ◽  
Magnetic Correlation ◽  
Grain Sizes ◽  
X Ray Scattering ◽  
Ray Scattering

Role of Heat Treatment in Magnetic Properties of Fe-Co-Ni-Al-Cu-Ti Alloy

2012 ◽  
Vol 510-511 ◽  
pp. 394-398 ◽  
Author(s):  
S. Imran ◽  
M.S. Awan ◽  
M.N. Sarwar ◽  
S. Akhtar ◽  
M. Farooque
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Single Phase ◽  
Permanent Magnets ◽  
X Ray ◽  
Casting Technique ◽  
Alloy Casting ◽  
The Matrix ◽  
Metallurgical Structure

Anisotropic (Fe-24Co-15Ni-7.5Al-3Cu-0.3Ti) permanent magnets were prepared by alloy casting technique. Samples were characterized for structural, microstructural and magnetic properties using x-ray diffractrometer (XRD), Scanning electron microscope (SEM) equiped with energy dispersive x-ray spectrometer and DC magnetometer. There is a relation between metallurgical structure and magnetic properties. The magnetic properties of this type of alloy depend on heat-treatment that is controlling the cooling rate in the presence of magnetic field and double aging. How magnetic properties vary with heat treatment is discussed in this work. XRD studied revealed that the alloy was single phase (bcc) with (110) as the major crystallographic plane. Optical and SEM micrographs showed the presence of (Ti,S)-rich precipitates which are randomly distributed in the matrix. Their composition was analyzed by EDX analysis.

Effects of V2O5 on the synthesis of Ba2Ti9O20 powders

2005 ◽  
Vol 20 (10) ◽  
pp. 2741-2744 ◽  
Author(s):  
Huixing Lin ◽  
Wei Chen ◽  
Lan Luo
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Scanning Electron Microscopy ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Eutectic Liquid ◽  
X Ray ◽  
Intermediate Phases ◽  
Phase Pure ◽  
Scanning Electron

Phase-pure Ba2Ti9O20 powders were made by doping 3 wt% of V2O5 to a Ba:Ti = 2:9 molar composition, and the effects of the dopant on the phase formation were investigated. The study shows that BaTiO3, BaTi2O5, and BaTi4O9 were the intermediate phases before the formation of Ba2Ti9O20 for samples with or without V2O5. However, with V2O5 doping, the temperature at which Ba2Ti9O20 occurred were lowered from 1150 to 1050 °C and single phase Ba2Ti9O20 powders was easily obtained at 1150 °C for 2 h. Microstructure of the powders was examined by field emission scanning electron microscopy. No evidence of V2O5–Ba2Ti9O20 solid-solution was found by x-ray diffraction and energy-dispersive spectroscopy. The benefit of V2O5 to facilitate the Ba2Ti9O20 synthesis is most probably due to a vanadium-containing eutectic liquid phase which accelerates the migration of reactant species.

Phase Assembly of Ti2SnC Powders

2011 ◽  
Vol 412 ◽  
pp. 187-190 ◽  
Author(s):  
Chun Long Guan ◽  
Guo Qin Liu ◽  
Ying Chun Shan
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Intermetallic Compounds ◽  
Single Phase ◽  
Reaction Path ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermediate Phases ◽  
Reaction Equations ◽  
Phase Relationships

Ti2SnC powders (Ti: Sn: C =2: 1.2: 1, mol.%) were synthesized by pressureless sintering in argon in the temperature range of 600 to 1050°C using Ti, Sn and graphite powders as the initial materials. The phase relationships during reaction in the ternary system Ti-Sn-C have been investigated. The products for identification and analysis were characterized by X-ray diffraction (XRD) and differential thermal analysis (DTA). The reaction path for the formation of Ti2SnC can be described in the following steps. Sn melted at 230°C, which provided a favorable liquid circumstance for the reactions between Ti and Sn to form Ti-Sn intermetallic compounds. Results showed that Ti6Sn5 and Ti5Sn3 intermediate phases were formed in turn with increase of temperature. Up to 1050°C, with consumption of Ti5Sn3 phases completely, the amount of Ti2SnC increased significantly. Single phase Ti2SnC with small amount of TiC was produced. Combined with the results of differential thermal analysis (DTA) and X-ray diffraction (XRD), it is revealed that Ti2SnC phase is formed by the reaction of Ti–Sn intermetallic compounds, Ti and graphite. In addition, the reaction equations of the process from 230 to 1050°C were given.

Effect of Isovalent Substitution on the Formation and Luminescence Properties of Solid Solutions BiPXV1-XO4 Doped with Europium (III)

2015 ◽  
Vol 230 ◽  
pp. 62-66 ◽  
Author(s):  
Konstantin L. Bychkov ◽  
Katerina V. Terebilenko ◽  
Rostyslav P. Linnik ◽  
Nikolay S. Slobodyanik
Keyword(s):  
Solid Solution ◽  
Solid State ◽  
Luminescence Spectrum ◽  
Powder Diffraction ◽  
Solid Solutions ◽  
Single Phase ◽  
Photoluminescence Spectroscopy ◽  
Electronic Transitions ◽  
X Ray ◽  
Isovalent Substitution

Solid solution BiP0.9V0.1O4 from BiPXV1-XO4 system has been synthesized by solid state synthesis at 973 K. It has been shown that the phosphate-vanadate can be prepared as a single phase for x =0.9, while higher degree of (P/V)O4 substitution in BiVO4 has not been detected for the range studied. The substitution peculiarities have been investigated by X-Ray powder diffraction, infrared and photoluminescence spectroscopy. The luminescence spectrum of BiPXV1-XO4:Eu3+ solid solution reveal intensive photoluminescence lines related to f-f electronic transitions in Eu3+ ions.

The CaO-TiO2-ZrO2 System at 1200 °C and the Solubilities of Hf and Gd in Zirconolite

1995 ◽  
Vol 412 ◽  
Author(s):  
D. Swenson ◽  
T. G. Nieh ◽  
J. H. Fournelle
Keyword(s):  
Solid Solutions ◽  
Electron Probe ◽  
Single Phase ◽  
Stoichiometric Composition ◽  
Mutual Solubility ◽  
X Ray Diffraction ◽  
Constant Concentration ◽  
Experimental Conditions ◽  
X Ray ◽  
Zro2 System

AbstractPhase equilibria are established in the CaO-TiO2-ZrO2 system at 1200 °C, using X-ray diffraction and electron probe microanalysis. The existence of two previously reported ternary phases, zirconolite (CaZrTi2O7) and calzirtite (Ca2Zr5Ti2O16), is confirmed. Each of these phases exhibits a significant range of homogeneity between TiO2 and ZrO2 while maintaining a nearly constant concentration of CaO. The ternary solubilities of the constituent binary phases are found to be negligible, with the exceptions of the perovskites, which display mutual solubility of at least 22 mol.% and may in fact form a series of continuous solid solutions. The solubilities of Hf and Gd in zirconolite are also investigated. While Hf-bearing samples did not reach thermodynamic equilibrium under the experimental conditions employed, the existence of a Hf analog to zirconolite, CaHfTi2O7, is conclusively demonstrated. The phase is stable at the stoichiometric composition, and its lattice parameters are very close to those reported in the literature for stoichiometric zirconolite. A Gd-bearing sample of the composition Ca0.88Zr0.88Gd0.24Ti2O7 is found to be essentially single phase zirconolite, in agreement with previous investigations at higher temperatures.

Effects of Cu Doping on the Microstructure and Electrical Properties of Sr3YCo4O10.5+δ Polycrystalline

2014 ◽  
Vol 934 ◽  
pp. 80-85
Author(s):  
Xiao Li Du ◽  
Lan Yu ◽  
Bin Zhang ◽  
Shi Jin Song ◽  
Guo Fang Li
Keyword(s):  
Porous Structure ◽  
Single Phase ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Cu Doping ◽  
Reaction Method ◽  
X Ray ◽  
Cu Content ◽  
Grain Sizes ◽  
Liquid Sintering

Polycrystalline samples of Sr3YCo4-xCuxO10.5+δ (x=0, 0.2, 0.4, 0.6) have been prepared by solid state reaction method. Crystal structure has been checked by X-ray diffraction (XRD) and the results indicate that Sr3YCo4-xCuxO10.5+δ (x=0, 0.2, 0.4) with single phase have been synthesized in air, and the lattice parameters of Sr3YCo4-xCuxO10.5+δ (x=0, 0.2, 0.4) increase with increasing Cu content. Microstructure analysis demonstrates that the grain sizes enlarge and the number of pores decreases with increasing Cu content. The change of porous structure with different Cu contents is discussed by the liquid sintering theory. The temperature dependence of resistivity (ρ-T) curves of Sr3YCo4-xCuxO10.5+δ show nonmetallic behavior. And the electrical resistivity decreases successively with increasing Cu content, which is caused by the porous structure scattering the carriers as well as the increase of hole carriers.

scholarly journals Investigation of the Reaction between Fe2O3 and Si Activated by Ball Milling

1996 ◽  
Vol 51 (8) ◽  
pp. 915-922 ◽  
Author(s):  
Giorgio Concas ◽  
Francesco Congiu ◽  
Anna Corrias ◽  
Carlo Muntoni ◽  
Giorgio Paschina ◽  
...  
Keyword(s):  
Ball Milling ◽  
Oxygen Transfer ◽  
Amorphous Matrix ◽  
High Energy ◽  
Milling Process ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermediate Phases ◽  
Energy Ball

Abstract The path of the reaction between Fe2O3 and Si, activated by high energy ball milling, has been investigated by X-ray diffraction and Mössbauer spectroscopy. Hematite reduction involves oxygen transfer from Fe to Si with the formation of intermediate phases containing Fe(II), which are then reduced to Fe(0). A steady state is reached in the milling process where the reduction of stoichiometric amounts of Fe2O3 and Si is not complete and an amount of Fe(II) in an amorphous matrix still remains. The same intermediate compounds are also observed in the milling process of mixtures with higher Fe2O3 /Si molar ratio.

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