scholarly journals Prereduction of Nchwaning Ore in CO/CO2/H2 Gas Mixtures

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1097
Author(s):  
Trygve Schanche ◽  
Merete Tangstad
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Iron Oxides ◽  
Reduction Rate ◽  
Gas Mixtures ◽  
X Ray Diffraction ◽  
Co2 Gas ◽  
X Ray ◽  
Reduction Of Iron ◽  
Partial Pressures

Prereduction of Nchwaning manganese ore was investigated by isothermal reduction between 600 and 800 °C to optimize the conditions for industrial pretreatment of manganese ores. Experiments were conducted in CO/CO2 gas mixtures with and without hydrogen at two different oxygen partial pressures. Ore in the size fraction 9.52–15 mm was reduced in a thermogravimetric furnace, and the O/Mn ratio from the chemical analysis was used to determine the extent of prereduction. The samples were investigated by X-ray diffraction to investigate the evolution of phases under the course of reduction. The X-ray diffraction revealed that bixbyite and braunite (I and II) were reduced to manganosite with no or limited formation of hausmannite. Reduction of iron oxides subsided with wüstite, which is stabilized by manganese in the monoxide phase, and hydrogen was seen to improve the reduction of iron oxides. Modeling revealed that the reduction rate increased 2.8-fold upon increasing the CO content from 30% to 70% in a CO/CO2 gas mixture. The addition of hydrogen improved the reduction rate with factors of 1.3 and 2.6 for the low and the high oxygen partial pressures, respectively. Hence, the optimal conditions for pretreatment can be achieved by keeping the oxygen partial pressure as low as possible while adding hydrogen to the reducing gas and ensuring a high reduction temperature. Successful pretreatment limits the extent of the Boudouard reaction in the submerged arc furnace, reducing the amount of CO produced and, thus, reducing the CO available for pretreatment. Hydrogen is a useful addition to the pretreatment unit since it lowers the oxygen partial pressure and improves the kinetics of prereduction.

Structural, Electrical and Dielectric Properties of DC Reactive Magnetron Sputtered ZrO2 Films for Metal-Oxide-Semiconductor Devices

2014 ◽  
Vol 781 ◽  
pp. 155-165
Author(s):  
P. Kondaiah ◽  
S. Uthanna
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Optical Band Gap ◽  
Spectroscopic Studies ◽  
Oxide Semiconductor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partial Pressures ◽  
Electrical And Dielectric Properties ◽  
Metallic Target

Thin films of zirconium oxide (ZrO2) were deposited by DC magnetron sputtering of metallic target of zirconium on to quartz and p-Si (100) substrates at various oxygen partial pressures in the range 2x10-2 - 6x10-2 Pa. The crystallinity, surface morphology and optical absorption of the films were influenced by the oxygen partial pressure. X-ray photoelectron spectroscopic studies revealed that the films formed at oxygen partial pressure of 4x10-2 Pa were of stoichiometric ZrO2. X-ray diffraction profiles indicated that the grown films were of nanocrystalline with crystallite size increased from 5 nm to 9 nm with increase of oxygen partial pressure from 2x10-2 Pa to 6x10-2 Pa. The optical band gap of the films increased from 5.65 to 5.80 eV and the refractive index increased from 2.02 to 2.08 with the increase of oxygen partial pressure from 2x10-2 to 6x10-2 Pa respectively. The fabricated MOS structure with the configuration of Al/ZrO2/p-Si showed the dielectric constant of 22 and leakage current density of 1x10-6 A/cm2.

Tensile Properties and Creep Behavior of SiC-Based Fibers under Various Oxygen Partial Pressures

2005 ◽  
Vol 475-479 ◽  
pp. 1333-1336 ◽  
Author(s):  
Jan Ji Sha ◽  
J.S. Park ◽  
Tatsuya Hinoki ◽  
Akira Kohyama ◽  
J. Yu
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Tensile Properties ◽  
Creep Behavior ◽  
Elevated Temperatures ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Sic Fibers ◽  
Partial Pressures ◽  
Ar Gas

Three kinds of atmospheres (air, highly-pure Ar and ultra highly-pure Ar gas) with different oxygen partial pressures were applied to investigate the tensile properties and creep behavior of SiC fibers such as Hi-NicalonTM and TyrannoTM-SA. These fibers were annealed and crept at elevated temperatures ranging from1273-1773 K in such environments. After annealing at 1773 K, the room temperature tensile strengths of SiC-based fibers decreased with decreasing the oxygen partial pressure and the near stoichiometric fiber TyrannoTM-SA shows excellent strength retention. At temperatures above the 1573 K, the creep resistance of SiC fibers evaluated by bending stress relaxation (BSR) method under high oxygen partial pressure was lower than that of in low oxygen partial pressure. The microstructural features on these fibers were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Effect of Oxygen Partial Pressure on Stability of High-Tc Phase in Sintered Bi-Pb-Sr-Ca-Cu-O Superconductos

1989 ◽  
Vol 169 ◽  
Author(s):  
H.K. Lee ◽  
K.W. Lee ◽  
D.H. Ha ◽  
J.C. Park
Keyword(s):  
Phase Transformation ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Superconducting Phase ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
High Tc Phase ◽  
Effect Of Oxygen

AbstractThe effect of oxygen partial pressure on stability of high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system has been investigated using x-ray diffraction, resistivity and a.c. susceptibility measurements. It was found that part of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system was transformed into the low-Tc phase (80 K) and insulating phases by heating in the temperature range 600 C to 880°C in O2 of one atmosphere. The original high-Tc phase was restored upon retreatment in a low oxygen partial pressure of 0.1 atmosphere. The reversible superconducting phase transformation is discussed in conjunction with the formation mechanism of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system.

High temperature X-ray diffraction studies of the decomposition mechanism of YBa2Cu3O7−δ at an oxygen partial pressure less than 10 Pa

1995 ◽  
Vol 10 (3) ◽  
pp. 165-169 ◽  
Author(s):  
W. Pitschke ◽  
W. Bieger ◽  
G. Krabbes ◽  
U. Wiesner
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Solid State Reaction ◽  
Peritectic Reaction ◽  
Decomposition Reaction ◽  
Primary Decomposition ◽  
X Ray Diffraction ◽  
X Ray

The crystallographic data of YBa2Cu3O7−δ, Y2BaCuO5, BaCu2O2, and YBa4Cu3O9 at high temperatures and p(O2)<10 Pa have been derived on the basis of HT-XRD measurements. Whereas Y2BaCuO5 expands nearly isotropically, YBa2Cu3O7−δ and BaCu2O2 show anisotropic expansions. Furthermore, the first decomposition step of the considered compounds at p(O2)<10 Pa was observed. BaCu2O2 melts congruently at T ≍ 1273 K and Y2BaCuO5 decomposes via a peritectic reaction into Y2O3, Y2BaO4 and melts at T ≍ 1323 K. A solid-state reaction into Y2BaCuO5 and BaCu2O2 was indicated for YBa2Cu3O7−δ at T ≍ 1123 K. Because YBa4Cu3O9 becomes unstable at T ≍ 1123 K, this compound cannot be formed by the primary decomposition reaction of YBa2Cu3O7−δ

Growth and Characterization of ZnO Thin Films Grown by Pulsed Laser Deposition

2011 ◽  
Vol 383-390 ◽  
pp. 6289-6292
Author(s):  
Jian Ting He ◽  
Bo Xue Tan ◽  
Qin Qin Wei ◽  
Yuan Bin Su ◽  
Shu Lian Yang
Keyword(s):  
Thin Films ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Pulsed Laser Deposition ◽  
Photoelectron Spectroscopy ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Zno Thin Films ◽  
X Ray ◽  
Partial Pressures

ZnO thin films were deposited on n-Si (111) substrates at various oxygen partial pressures by pulsed laser deposition (PLD). X-ray diffraction (XRD), scanning electron microscopy (SEM) were used to analyze the influence of the oxygen partial pressure on the crystallization and morphology of the ZnO thin films. An optimal crystallized ZnO thin film was observed at the oxygen partial pressure of 6.5Pa. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface components and distribution status of various elments in ZnO thin films. It was found that ZnO thin films were grown in Zn-rich state.

Inhomogeneity and Microstructure in e-Beam Evaporated ZrO2 Films

1990 ◽  
Vol 208 ◽  
Author(s):  
M. Bellotto ◽  
C. Cremnonesi ◽  
F. Parmigiani ◽  
M. Scagliotti ◽  
S. Beretta
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Oxygen Partial Pressure ◽  
Zirconium Dioxide ◽  
Oxygen Stoichiometry ◽  
Composition Gradient ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partial Pressures ◽  
Microstructure Of The Material

ABSTRACTThin films of zirconium dioxide are deposited by e-beam evaporation on optically polished borosilicate crown glass. Two different oxygen partial pressures in the chamber are used. The optical properties of the films are characterized by ellipsometry. The influence of oxygen stoichiometry on the composition and microstructure of the material is investigated by polycrystalline X-ray diffraction for different film thicknesses. The films are found to be inhomogeneous, and a composition gradient (i.e. amorphous ⇔ tetragonal ⇔ monoclinic) is observed from the substrate to the surface. The oxygen partial pressure influences the growth of the films.

In-situ analysis of chemical expansion and stability of SOFC cathodes

2014 ◽  
Vol 1655 ◽  
Author(s):  
Mirela Dragan ◽  
Scott Misture
Keyword(s):  
High Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Lattice Parameter ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Chemical Expansion ◽  
X Ray ◽  
Reducing Conditions ◽  
The Stability

ABSTRACTIn this work high-temperature X-ray diffraction has been used to investigate thermal and chemical expansion as well as overall phase stability for various cathode materials: Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF), La0.3Sr0.7CoO3 (LSC37), La0.6Sr0.4CoO3 (LSC64) and La0.6Sr0.4Fe0.8Co0.2O3 (LSCF), as a function of temperature in reducing conditions. When perovskites materials are under a low oxygen partial-pressure condition, the lattice parameter and overall dimension increase. Their chemical expansion has comparable values. From the viewpoint of the stability of these phases, the high-temperature X-ray diffraction results indicate no phase decomposition can be one of the reasons for material failure at the current experimental oxygen partial pressure. LSF is most stable, while LSC and LSCF form oxygen vacancy-ordered phases and then decompose when heated to 1000°C under atmospheres with pO2 as low as 10-5 atm.

scholarly journals Self-Organized V - Mo Oxide Fibers by the Micro-Pulling Down Method

2009 ◽  
Vol 1223 ◽  
Author(s):  
Detlef Klimm ◽  
Krzysztof Orlinski ◽  
Dorota A. Pawlak
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Eutectic Composition ◽  
Intermediate Phase ◽  
X Ray Diffraction ◽  
Simple Modification ◽  
X Ray ◽  
On Demand ◽  
Self Organized ◽  
Experimental Parameters

ABSTRACTThe V2O5-MoO3 mixtures offer a whole range of materials where properties can be adjusted by simple modification of experimental parameters, which may be utilized for manufacturing metamaterials with on-demand properties. The V2O5-MoO3 system contains an intermediate phase V9Mo6O40, with a small fraction of V4+ instead of V5+. Consequently, this system should rather be considered as pseudobinary. The V4+ content depends on the oxygen partial pressure in the atmosphere. Thus, by changing the oxygen partial pressure one can tailor the electric properties of the system, and by changing the supercooling, the morphologic structure of crystallized bodies as well. For better understanding of this system differential thermal analysis and thermodynamic modeling was performed. Fibers of eutectic composition between V9Mo6O40 and MoO3 were grown by the micro-pulling-down technique. X-ray diffraction confirmed the existence of the V9Mo6O40 intermediate phase.

Structure refinements of seven natural olivine crystals and the influence of the oxygen partial pressure on the cation distribution

1981 ◽  
Vol 155 (1-2) ◽  
Author(s):  
G. Nover ◽  
G. Will
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Extinction Coefficient ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Volcanic Origin ◽  
X Ray ◽  
Anisotropic Temperature ◽  
Natural Olivine ◽  
Temperature Factors

AbstractMg/Fe order in olivine has been determined by X-ray diffraction data, for example by Wenk and Raymond (1973). We have now studied the dependence of the Mg/Fe order vs. oxygen partial pressure. Two natural olivine samples of volcanic origin containing respectively 10 and 12 % fayalite were selected. The atomic positions, anisotropic temperature factors, extinction coefficient and site occupancies have been refined toThese experiments seem to indicate that the prevailing oxygen partial pressure determines the different Mg/Fe order found in natural olivine crystals.

scholarly journals Effect of Oxygen Partial Pressure on the Phase Stability of Copper–Iron Delafossites at Elevated Temperatures

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1888 ◽  
Author(s):  
Thomas Stöcker ◽  
Ralf Moos
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
High Temperatures ◽  
Phase Stability ◽  
Elevated Temperatures ◽  
Process Window ◽  
Thermoelectric Generators ◽  
X Ray Diffraction ◽  
Characterization Methods ◽  
X Ray

Oxide-based materials are promising candidates for use in high temperature thermoelectric generators. While their thermoelectric performance is inferior to commonly used thermoelectrics, oxides are environmentally friendly and cost-effective. In this study, Cu-based delafossites (CuFeO2), a material class with promising thermoelectric properties at high temperatures, were investigated. This work focuses on the phase stability of CuFeO2 with respect to the temperature and the oxygen partial pressure. For this reason, classical material characterization methods, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, were combined in order to elucidate the phase composition of delafossites at 900 °C at various oxygen partial pressures. The experimentally obtained results are supported by the theoretical calculation of the Ellingham diagram of the copper–oxygen system. In addition, hot-stage X-ray diffraction and long-term annealing tests of CuFeO2 were performed in order to obtain a holistic review of the phase stability of delafossites at high temperatures and varying oxygen partial pressure. The results support the thermoelectric measurements in previous publications and provide a process window for the use of CuFeO2 in thermoelectric generators.

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