共查询到20条相似文献,搜索用时 31 毫秒
1.
A detailed study of the system PbO-Fe2 O3 , largely by X-ray diffraction analysis, has been made. The results indicate the existence of three intermediate phases: (1) a phase (beta) extending from PbO·5Fe2 O3 to PbO·6Fe2 O3 , (2) a phase (gamma) extending from PbO - 2Fe2 O3 to PbO -21/2 Fe2 O3 , and (3) a phase (delta) 2PbO·– Fe2 O3 . Structures are proposed for the beta and gamma phases that explain their solubility limits, magnetic properties, and very great similarity in structure and in lattice dimensions. 相似文献
2.
Solid-state reactions of equimolar mixtures of Bi2 O3 and Fe2 O3 from 625° to 830°C and their kinetics were investigated. The reaction rates were determined from the integrated X-ray diffraction intensities of the strongest peaks of the reactants and products. The activation energy for the formation of BiFeO3 was 96.6±9.0 kcal/mol; that for a second-phase compound, Bi2 Fe4 O9 , which formed above 675°C, was 99.4±9.0 kcal/mol. Specific rate constants for these simultaneous reactions were obtained. The preparation of single-phase BiFeO3 from the stoichiometric mixture of Bi2 O3 and Fe2 O3 is discussed. 相似文献
3.
Silvia Schicker Daniel E. García Igor Gorlov Rolf Janssen Nils Claussen 《Journal of the American Ceramic Society》1999,82(10):2607-2612
Wet milling of Al2 O3 -aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al2 O3 and Fe2 O3 /Al/Al2 O3 powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe2 O3 /Al/Al2 O3 powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al2 O3 powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8. 相似文献
4.
M. F. YAN 《Journal of the American Ceramic Society》1980,63(7-8):443-447
Sintering and microstructural evolution were studied in Fe3 O4 as a model system for spinel ferrites. Fe3 O4 powder, purified by the salt-crystallization method, was sintered to ∼99.5% density in a CO-CO2 atmosphere. The p O2 Of the sintering atmosphere drastically affects the microstructure (grain size) of sintered Fe3 O4 without significantly affecting density. The measured grain-boundary mobilities, M , of Fe3 O4 fit the equation M=M 0 ( T ) p O2 −1/2 with M 0 ( T ) = 2.5×105 exp[-(609kJ·mol-1 / RT ](m/s)(N/m2 )−l . The grain-boundary migration process appeared to be pore-drag controlled, with lattice diffusion of oxygen as the most likely rate-limiting step. 相似文献
5.
Mark I. Pownceby Keri K. Constanti-Carey Michael J. Fisher-White 《Journal of the American Ceramic Society》2003,86(6):975-980
Subsolidus phase equilibria in the system Fe2 O3 –Al2 O3 –TiO2 were investigated between 1000° and 1300°C. Quenched samples were examined using powder X-ray diffraction and electron probe microanalytical methods. The main features of the phase relations were: (a) the presence of an M3 O5 solid solution series between end members Fe2 TiO5 and Al2 TiO5 , (b) a miscibility gap along the Fe2 O3 –Al2 O3 binary, (c) an α-M2 O3 ( ss ) ternary solid-solution region based on mutual solubility between Fe2 O3 , Al2 O3 , and TiO2 , and (d) an extensive three-phase region characterized by the assemblage M3 O5 +α-M2 O3 ( ss ) + Cor( ss ). A comparison of results with previously established phase relations for the Fe2 O3 –Al2 O3 –TiO2 system shows considerable discrepancy. 相似文献
6.
Tomoyuki Adachi Naoki Wakiya Naonori Sakamoto Osamu Sakurai Kazuo Shinozaki Hisao Suzuki 《Journal of the American Ceramic Society》2009,92(S1):S177-S180
Fe3 O4 –BaTiO3 composite particles were successfully prepared by ultrasonic spray pyrolysis. A mixture of iron(III) nitrate, barium acetate and titanium tetrachloride aqueous solution were atomized into the mist, and the mist was dried and pyrolyzed in N2 (90%) and H2 (10%) atmosphere. Fe3 O4 –BaTiO3 composite particle was obtained between 900° and 950°C while the coexistence of FeO was detected at 1000°C. Transmission electron microscope observation revealed that the composite particle is consisted of nanocrystalline having primary particle size of 35 nm. Lattice parameter of the Fe3 O4 –BaTiO3 nanocomposite particle was 0.8404 nm that is larger than that of pure Fe3 O4 . Coercivity of the nanocomposite particle (390 Oe) was much larger than that of pure Fe3 O4 (140 Oe). These results suggest that slight diffusion of Ba into Fe3 O4 occurred. 相似文献
7.
R. E. CARTER 《Journal of the American Ceramic Society》1960,43(9):448-451
The dissociation pressures of solid solutions from Fe3 O4 to 0.4Fe3 O4 ·0.6CoFe2 O4 have been determined as a function of temperature. Within experimental error, solid solutions within this range are thermodynamically ideal. 相似文献
8.
Phase relations in air at 1300°C were determined for the system MgO-Cr2 O3 −Fe2 O3 by conventional quenching techniques. Details of the phase equilibria were established for: (1) the sesquioxide solid solution between Cr2 O3 and Fe2 O3 , (2) the spinel solid solution field between MgCr2 O4 and MgFe2 O4 , and (3) the periclase solid solution field for MgO. Selected tie lines connecting coexisting compositions were established with X-ray diffractometer data. Diffuse reflectance spectra, diffractometer intensity ratios, and lattice parameter measurements were obtained for quenched samples to study the structural inversion in the spinel series MgCr2 O4-MgFe2 O4 . 相似文献
9.
A study of the solid solution of TiO2 , Fe2 O3 , and Cr2 03 in mullite was made by measuring the changes in lattice parameters and unit-cell volume. Synthetic mullite (3O3 -2SiO2 ) was reacted with up to 12 weight % of the oxides at temperatures ranging from 1000° to 17000C. The approximate minimum temperature required for the formation of solid solution was 12000C. for Fe2 03 and 1400°C. for Cr2 O3 and TiO3 . The maximum amount of solid solution found was 2 to 4% TiO2 at 1600°C., 10 to 12% Fe2 Os at 1300°C., and 8 to 10% CrZ O3 at 1600OC. Lattice parameters and unit-cell volumes for each solid solution series increased with increasing amounts of foreign oxide. There was good agreement between the calculated and observed increase in cell dimensions for the iron oxide series. Except in the case of titania, there was good agreement between X-ray data and petrographic observations. 相似文献
10.
Anita Fossdal Mari-Ann Einarsrud Tor Grande 《Journal of the American Ceramic Society》2005,88(7):1988-1991
The phase relations in the pseudo-ternary system La2 O3 –SrO–Fe2 O3 have been investigated in air. Isothermal sections at 1100° and 1300°C are presented based on X-ray diffraction and thermal analysis of annealed samples. Extended solid solubility was observed for the compounds Sr n +1− v La v Fe n O3 n +1−δ ( n =1, 2, 3, and ∞) and Sr1− x La x Fe12 O19 , while only limited solubility of La in Sr4− z La z Fe6 O13±δ was observed. At high Fe2 O3 content, a liquid with low La2 O3 content was stable at 1300°C. 相似文献
11.
Several experiments were conducted to investigate the formation mechanisms of the magnetoplumbite phase in La3+ -doped CaO 6Fe2 O3 . It is shown that the CaO·2Fe2 O3 phase plays a crucial role in forming the magnetoplumbite phase. The formation mechanisms are proposed and verified. 相似文献
12.
Xue-Ning Huang Chu Kun Kuo Patrick S. Nicholson 《Journal of the American Ceramic Society》1995,78(4):892-896
An epitaxial β-alumina crystal growth method was used to modify α-AI2 O3 platelet surfaces before inclusion as a reinforcing phase in partially stabilized zirconia (3Y-TZP). The as-grown surface phase was Na-β"-AI2 O3 . This was converted to Ca-β"-AI2 O3 by ion exchange, as the latter is more temperature-stable at composite sintering temperatures. The conditions of formation, thermal stability, and chemical compatibility of these interfacial phases were examined. α-AI2 O3 platelets with Ca-β"-AI2 O3 film were incorporated into 3Y-TZP. The β"-AI2 O3 /ZrO2 interface was found to promote platelet debonding and pullout, thus enhancing the α-AI2 O3 platelet/crack interactions during the fracture process. 相似文献
13.
Yoshikazu Suzuki Masanobu Awano Naoki Kondo Tatsuki Ohji 《Journal of the American Ceramic Society》1999,82(9):2557-2559
Composites of BaFe12 O19 particles dispersed throughout a 3-mol%-yttria-doped zirconia (3Y-TZP) matrix have been prepared using the pressureless reactive sintering of 3Y-TZP, BaCO3 , and γ-Fe2 O3 powders. The reaction behavior of the mixed powder was studied with an in situ , high-temperature powder X-ray diffraction technique. The composite that was sintered at 1300°C consisted of submicrometer-sized 3Y-TZP grains and BaFe12 O19 particles; the size of the 3Y-TZP grains was ∼100-300 nm, and the size of the BaFe12 O19 particles was ∼200-500 nm. Based on the grain size, most of the BaFe12 O19 grains presumably had a single-magnetic-domain structure. The 3Y-TZP/20-wt%-BaFe12 O19 composite showed high magnetization and coercivity values, despite the low concentration of ferromagnetic phase. Preliminary mechanical tests revealed that the composite possessed moderately good mechanical properties. 相似文献
14.
A study has been made of the binary system Fe2 O2 -TiO2 by solid-state reactions under dry and hydrothermal conditions. Under dry conditions only one binary compound, pseudobrookite (Fe2 O3 -TiO2 ), was formed and no evidence of solid solution on either side of this compound at temperatures up to 1200°C. was obtained. The system under these conditions is a simple binary with a single binary compound. Under hydrothermal conditions of 300° C. and 1200 Ib. per sq. in. the system is apparently also binary, with a single unstable compound closely resembling, if not identical with, the naturally occurring mineral arizonite (ferric metatitanate, Fe2 (TiO3 )3 ). 相似文献
15.
ARNULF MUAN 《Journal of the American Ceramic Society》1957,40(12):420-431
Phase equilibrium data at liquidus temperatures are presented for mixtures in the system FeO–Fe2 O3 –Al2 O3 –SiO2 . The volume located between the 1 and 0.2 atm. O2 isobaric surfaces of the tetrahedron representing this system was studied in detail. Scattered data were obtained at lower O2 pressures. Results obtained in the present investigation were combined with data in the literature to construct a phase equilibrium diagram, at liquidus temperatures, for the entire system FeO–Fe2 O3 –Al 2 O3 –SiO2 . Methods for interpretation of the diagram are explained. 相似文献
16.
BILL BERGMAN 《Journal of the American Ceramic Society》1986,69(8):608-611
Diffusion couples are used to study the reaction between CaO powder and Fe2 O3 All heat treatments were performed in air. The growth and morphology of calcium ferrites is studied at different temperatures. It is shown that CaO·2Fe2 O3 , starts to form at about 1125°C, while the accepted phase diagram for equilibrium with air predicts a temperature of 1155°C. 相似文献
17.
Yang Gong-An Pu Yong-Ping Wang Jin-Fei Chen Xiao-Long Zhuang Yong-Yong 《Journal of the American Ceramic Society》2009,92(8):1891-1894
The influence of La2 O3 doped on the microstructure and dielectric properties, including the phase structure, temperature dependence of permittivity, and the hysteresis loop of BaTiO3 –Nb2 O5 –Fe2 O3 (BTNF) materials has been investigated in X-ray diffraction, SEM, and LCR analyzer, respectively. Experiments revealed that incorporation of proper content of La2 O3 basically soluted in the lattice of BaTiO3 and can control the grain-growth, reduce the dielectric loss of the BTNF materials. The development of microstructure promoted by the additives can result in the improvement of the dielectric constant. When the doping concentration of La2 O3 was 3.846 wt%, the relative dielectric constant of the sample sintered at 1280°C only for 2 h could reach 4308, and improve the dielectric-temperature characteristics markedly. As a result, a novel Y5P can be achieved in the BTNF ceramics, which is very promising for practical use in Y5P multilayer ceramic capacitors. 相似文献
18.
The broadening of selected X-ray diffraction peaks in goethite-derived Fe2 O3 was studied in terms of the structure factors of the oxygen and iron atoms. Calculation of the structure factors in the ideal corundum and Fe2 O3 lattices showed that the intensities of the broad peaks result primarily from the iron atoms. Thus, preferential line broadening in goethite-derived Fe2 O3 is interpreted in terms of incomplete displacement of iron atoms during decomposition. 相似文献
19.
Oxide crystallite formation and growth from freeze-dried sulfates were studied for the representative materials Al2 O3 and Fe2 O3 . Transmission and scanning electron micrographs showed the formation and growth of chainlike aggregates of crystallites. Aggregation occurred as part of the nucleation and growth of the oxide, and discrete oxide particles were never present. Orientation of the chain aggregates was related to the ice structure formed during freezing. X-ray line broadening data showed that crystallite size is a function of the 1/5 to 1/7 power of time for isothermal treatments. A qualitative analysis of material transport favored the surface diffusion mechanism. 相似文献
20.
Haijuan Fan Qun Xu Jinge Li Yanxia Cao 《Journal of the American Ceramic Society》2006,89(10):3065-3069
SiO2 /Fe2 O3 mesoporous composites have been prepared with a nanoscale casting process using an activated carbon (AC) template in supercritical carbon dioxide (SC CO2 ). The composite precursor and acetone solvent (for Fe2 O3 precursor) were dissolved in SC CO2 , and then coated on the AC in the desired supercritical condition. After removal of the AC template by calcinations in air at 600°C, SiO2 /Fe2 O3 mesoporous composite were obtained. Temperature, pressure, and composite precursor ratio effects were studied. Scanning electron microscopy result shows that the porous structure of AC template had been well replicated by the composite product. Transmission electron micrograph indicates that nano iron oxides were well dispersed in the composite product. 相似文献