scholarly journals Phase Stability of The Mixed-Conducting Sr-Fe-Co-O System

1997 ◽  
Vol 496 ◽  
Author(s):  
B. Ma ◽  
U. Balachandran ◽  
J. P. Hodges ◽  
J. D. Jorgensen ◽  
D. J. Miller ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Elevated Temperatures ◽  
Cobalt Content ◽  
Ceramic Membranes ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Ceramic Oxides ◽  
Partial Pressures ◽  
Dense Ceramic ◽  
Increasing Temperature

ABSTRACTMixed-conducting ceramic oxides have potential uses in high-temperature electrochemical applications such as solid oxide fuel cells, batteries, sensors, and oxygen-permeable membranes. The Sr-Fe-Co-O system combines high electronic/ionic conductivity with appreciable oxygen permeability at elevated temperatures. Dense ceramic membranes made of this material can be used to separate high-purity oxygen from air without the need for external electrical circuitry, or to partially oxidize methane to produce syngas. Samples of Sr2Fe3-xCoxOy (with x = 0,0.6,1.0, and 1.4) were prepared by solid-state reaction method in atmospheres with various oxygen partial pressures (pO2) and were characterized by X-ray diffraction, scanning electron microscopy, and electrical conductivity testing. Phase components of the sample are dependent on cobalt concentration and pO2. Electrical conductivity increases with increasing temperature and cobalt content in the material.

scholarly journals Crystal Structures of Mixed-Conducting Oxides Present in The Sr-Fe-Co-O System

1997 ◽  
Vol 496 ◽  
Author(s):  
J. P. Hodges ◽  
J. D. Jorgensen ◽  
D. J. Miller ◽  
B. Ma ◽  
U. Balachandran ◽  
...  
Keyword(s):  
Solid Oxide Fuel Cells ◽  
Elevated Temperatures ◽  
Ceramic Membranes ◽  
Rechargeable Batteries ◽  
Quantitative Phase Analysis ◽  
Ceramic Oxides ◽  
Conducting Oxides ◽  
Oxidation Of Methane ◽  
Dense Ceramic ◽  
Potential Applications

ABSTRACTThe potential applications of mixed-conducting ceramic oxides include solid-oxide fuel cells, rechargeable batteries, gas sensors and oxygen-permeable membranes. Several perovskite-derived mixed Sr-Fe-Co oxides show not only high electrical-conductivity but also appreciable oxygen-permeability at elevated temperatures. For example, dense ceramic membranes of SrFeCo0.5O3-δ can be used to separate oxygen from air without the need for external electrical circuitry. The separated oxygen can be directly used for the partial oxidation of methane to produce syngas. Quantitative phase analysis of the SrFeCo0.5O3-δ material has revealed that it is predominantly composed of two Sr-Fe-Co-O systems, Sr4Fe6-xCoxO13 and SrFe1−xCoxO3-δ. Here we report preliminary structural findings on the SrFe1−xCoxO3-δ (0 ≤ x ≥ 0.3) system.

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).

Electrical Conductivity Prediction in Langasite for Optimized Microbalance Performance at Elevated Temperatures

2002 ◽  
Vol 756 ◽  
Author(s):  
Huankiat Seh ◽  
Harry Tuller ◽  
Holger Fritze
Keyword(s):  
Electrical Conductivity ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
High Temperatures ◽  
Gas Sensors ◽  
Elevated Temperatures ◽  
Operating Conditions ◽  
Total Conductivity ◽  
Defect Model ◽  
Partial Pressures

ABSTRACTThe performance of the langasite-based crystal microbalance is limited due to reductions in its resistivity at high temperatures and reduced oxygen partial pressures. In this work, we utilize a recently developed defect model to predict the dependence of the ionic and electronic contributions to the total conductivity of langasite on temperature, oxygen partial pressure and acceptor and donor dopants. These results are used to select the type and concentrations of dopants expected to provide extended operating conditions for langasite-based gas sensors and crystal microbalances.

scholarly journals An Experimental Study of the Formation of Talc through CaMg(CO3)2–SiO2–H2O Interaction at 100–200°C and Vapor-Saturation Pressures

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Ye Wan ◽  
Xiaolin Wang ◽  
I-Ming Chou ◽  
Wenxuan Hu ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Fused Silica ◽  
X Ray Diffraction ◽  
In Situ Raman Spectroscopy ◽  
X Ray ◽  
In Situ Raman ◽  
Geological Processes ◽  
Partial Pressures ◽  
Increasing Temperature

The metamorphic interaction between carbonate and silica-rich fluid is common in geological environments. The formation of talc from dolomite and silica-rich fluid occurs at low temperatures in the metamorphism of the CaO–MgO–SiO2–CO2–H2O system and plays important roles in the formation of economically viable talc deposits, the modification of dolomite reservoirs, and other geological processes. However, disagreement remains over the conditions of talc formation at low temperatures. In this study, in situ Raman spectroscopy, quenched scanning electron microscopy, micro-X-ray diffraction, and thermodynamic calculations were used to explore the interplay between dolomite and silica-rich fluids at relatively low temperatures in fused silica tubes. Results showed that talc formed at ≤200°C and low CO2partial pressures (PCO2). The reaction rate increased with increasing temperature and decreased with increasingPCO2. The major contributions of this study are as follows:(1)we confirmed the formation mechanism of Mg-carbonate-hosted talc deposits and proved that talc can form at ≤200°C;(2)the presence of talc in carbonate reservoirs can indicate the activity of silica-rich hydrothermal fluids; and (3) the reactivity and solubility of silica require further consideration, when a fused silica tube is used as the reactor in highP–Texperiments.

scholarly journals Preparation, structure, surface and impedance analysis of Na2Zn0.5Mn0.5P2O7 ceramics

2017 ◽  
Vol 57 (3) ◽  
Author(s):  
Vilma Venckutė ◽  
Antonija Dindune ◽  
Dagnija Valdniece ◽  
Aija Krumina ◽  
Martynas Lelis ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Photoelectron Spectroscopy ◽  
Impedance Analysis ◽  
Solid State Reaction Method ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Temperature Range ◽  
Two Phases

The Na2Zn0.5Mn0.5P2O7 powder was prepared by the solid state reaction method. The powder structure was studied by X-ray diffraction (XRD) in the temperature range from room temperature (RT) to 520 K. The results of XRD measurements show that the obtained Na2Zn0.5Mn0.5P2O7 is a mixture of two phases: Na2MnP2O7, which crystallizes in the triclinic space group P1, and Na2ZnP2O7, which crystallizes in the tetragonal space group P42/mmm. The chemical compositions of the powder and ceramic samples were investigated by an energy dispersive X-ray spectrometer (EDX) and X-ray fluorescence spectroscopy (XFS). The surface of ceramics was examined by X-ray photoelectron spectroscopy (XPS). The electrical conductivity and dielectric permittivity of the ceramics were investigated from RT to 700 K in the frequency range 10–109 Hz. The relaxational dispersion of electrical conductivity in the investigated frequency and temperature range was found.

Ash Fusion During Combustion of Single Corn Straw Pellets

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Ming Zhai ◽  
Xinyu Wang ◽  
Yichi Zhang ◽  
Aidin Panahi ◽  
Peng Dong ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Air Flow ◽  
X Ray Diffraction ◽  
Corn Straw ◽  
Heating Rates ◽  
X Ray ◽  
Carbon Burnout ◽  
Ash Melting ◽  
Increasing Temperature ◽  
Straw Ash

Abstract This investigation identified conditions at which corn straw ash melts and examined how this phenomenon affects the combustion of char residues. Corn straw was pelletized in cylinders and was burned at elevated temperatures in the range of 1200–1400 °C, and at different air flow velocities. The pellets were inserted in a preheated furnace, where they were subjected to moderately high heating rates. Their combustion behavior was observed with cinematography, thermometry, and thermogravimetry. Upon insertion in the furnace, the pellets devolatilized and formed volatile envelope flames, upon extinction of which, the chars experienced concurrent heterogeneous combustion and ash fusion. Residues were assessed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), coupled to energy dispersive spectroscopy (EDS). The burnout times of the volatiles and the chars decreased drastically with increasing temperature. At 1300 °C and 1400 °C, the remaining ash underwent complete melting and the final structures of the pellets collapsed to molten pools. At 1400 °C, all of the chlorine and most of the potassium were released into the gas phase. The straw ash was identified as a high-density silicate melt. Although surface ash melted completely, it flowed to the base of the pellet. Therefore, it did not significantly hinder the oxidation of the carbonaceous char. Hence, to increase the likelihood of complete corn straw carbon burnout and of ash melting and flowing to the bottom of the furnace, operating temperatures higher than 1300 °C, in conjunction with mild air flow rates, are recommended.

Electrical Conductivity of NiO-Gadolinia Doped Ceria Anode Material for Intermediate Temperature Solid Oxide Fuel Cells

2017 ◽  
Vol 17 ◽  
pp. 224-236 ◽  
Author(s):  
Ajith Kumar Soman ◽  
P. Kuppusami ◽  
Arul Maximus Rabel
Keyword(s):  
Electrical Conductivity ◽  
Solid Oxide Fuel Cells ◽  
Anode Material ◽  
Solid State Reaction Method ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
Ac Impedance Spectroscopy ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Total Electrical Conductivity

In this paper, NiO-Gadolinia Doped Ceria (10 mole % Gadolinia) NiO-GDC10 composite with Nickel varying from 50 to 65 wt.% has been prepared by conventional solid state reaction method. The structural and microstructural properties have been evaluated by X-ray diffraction and scanning electron microscopy, respectively. The electrochemical behavior of the composites with varying concentration of Ni has been investigated by AC impedance spectroscopy. Both the grain and grain boundary conductivities have been determined as a function of temperature in the range of 773-973 K. The highest total electrical conductivity (σGi+σGb) have been achieved as 0.28 x10-3 Scm-1 at 973 K with activation energy of 0.40 eV for composition of GDC10 with 65 wt % of NiO (NiO-GDC-65:35 wt.%). The influence of microstructure on electrical properties of the composites has been analyzed and the conductivities have been compared with the conventional NiO-YSZ (50:50) composite in order to fabricate Ni-GDC based anode material of better performance.

scholarly journals The low infrared emissivity of Ce1-xYxO2-x/2 samples at high-temperature contributed by enhanced conductivity

2018 ◽  
Vol 238 ◽  
pp. 03002
Author(s):  
Honghan Bu ◽  
Chuyang Liu ◽  
Guoyue Xu ◽  
Yong Jiang ◽  
Tengchao Guo ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Solid State Reaction Method ◽  
Potential Candidate ◽  
Aircraft Engines ◽  
Infrared Emissivity ◽  
Doping Amount ◽  
Reaction Method ◽  
Phase Structures ◽  
Increasing Temperature ◽  
Enhanced Conductivity

The Ce1-xYxO2-x/2 samples were synthesized with different doping amount by solid state reaction method. Phase structures of the samples were analyzed and characterized by XRD. The effects of different doping amount on infrared emissivity properties at 3-5µm wavebands were investigated systematically. It is found that the powder with doping molality of x=0.2 exhibits the lowest infrared emissivity value ca. 0.21 when the test temperature is 600 °C. The mechanism for the low infrared emissivity is explored thoroughly. The reduction of infrared emissivity with increasing temperature is ascribed to the enhancement of electrical conductivity. Our results suggest that Ce1-xYxO2-x/2 powder with x=0.2 is a potential candidate for stealth material of aircraft engines.

Effect of La Doped on the Conductivity of the Perovskite Type PbZrO3

2012 ◽  
Vol 59 (2) ◽  
Author(s):  
Salmie Suhana Che Abdullah ◽  
Imaduddin Helmi Wan Nordin ◽  
Siti Hawa Mohamed Salleh ◽  
Takao Esaka
Keyword(s):  
Electrical Conductivity ◽  
Single Phase ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Emf Measurements ◽  
X Ray ◽  
Perovskite Type ◽  
La Doped ◽  
Oxide Ion ◽  
Lead Site

Electrochemical properties of Pb1-xLaxZrO3+x/2 with perovskite structure have been studied. The powdery Pb1-xLaxZrO3+x/2 has been prepared by solid-state reaction method. The X-ray diffraction analysis reveals that Pb1-xLaxZrO3+x/2 (x = 0.0-0.05) sintered at 900 ˚C was single phase structure. The electrical conductivity of the material has been investigated. By doping La at the lead site, the electrical conductivity of the Pb1-xLaxZrO3+x/2 system decreased. The undoped compound showed the highest electrical conductivity of ca. 10-3 S/cm. Electromotive Force (EMF) measurements of oxygen concentration cell confirm that the charge carrier of La doped PbZrO3 was the oxide ion.

In-Situ Neutron Diffraction Studies of Mixed Conducting Sr-Fe-Co-O Materials

1998 ◽  
Vol 547 ◽  
Author(s):  
B.J. Mitchell ◽  
J.W. Richardson ◽  
B. Ma ◽  
J.P. Hodges
Keyword(s):  
Neutron Diffraction ◽  
Elevated Temperatures ◽  
Ceramic Membrane ◽  
Membrane Material ◽  
Partial Pressures ◽  
Wide Range ◽  
Dense Ceramic ◽  
Scattering Lengths ◽  
In Situ Neutron Diffraction

AbstractSrFeCo0.5Oy has been identified as a potential dense ceramic membrane material used for gas separation at elevated temperatures. Neutrons play an important role in the study of such materials, particularly due to the favorable scattering lengths of Fe, Co and O. In-situ neutron diffraction experiments allow these materials to be studied under a wide range of temperatures and oxygen partial pressures. Results indicate very complex behavior of individual phases during synthesis and under operational membrane conditions.

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