Polycrystalline sample of Ba4Gd2Fe2Nb8O30 ceramics were prepared by a high temperature solid-state reaction technique. The structure and dielectric properties as well as the behavior of ferroelectric phase transition ...
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Polycrystalline sample of Ba4Gd2Fe2Nb8O30 ceramics were prepared by a high temperature solid-state reaction technique. The structure and dielectric properties as well as the behavior of ferroelectric phase transition have been investigated. The dielectric spectra are characterized in wide frequency (40Hz-1MHz) and temperature (25℃-600℃). At 1MHz, the room temperature dielectric constant of Ba4Gd2Fe2Nb8O30 ceramic is 160 together with dielectric loss of 0.054. Two dielectric abnormalities were detected at the temperature dependence of dielectric spectra in low and high temperature ranges, respectively. The low temperature peak (145℃) is frequency independence, while the higher temperature (300℃-600℃) one is extremely high relaxorlike, with very strong frequency dispersion. The high temperature peak was not relaxor ferroelectric but an oxygen defect induced dielectric abnormity, while the low temperature one was proposed to the ferroelectricparaelectric phase transition. The ferroelectric nature of the present materials is confirmed by the P-E hysteresis loop, with 2 Prof 1.5μC/cm2.
Bi25FeO40 powders have successfully been synthesized by simple hydrothermal method. The effect of the concentration of mineralizer and stoichiometry on the prepared samples was investigated. With the UV-Vis spectra, B...
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Bi25FeO40 powders have successfully been synthesized by simple hydrothermal method. The effect of the concentration of mineralizer and stoichiometry on the prepared samples was investigated. With the UV-Vis spectra, Bi25FeO40 powders have a broad absorption band in the range of 400-600 nm and a good visible-light-response ability. Photo-catalytic activity of Bi25FeO40 powders was evaluated by the degradation of methyl violet solution under UV-Vis light irradiation, which is found that Bi25FeO40 is efficient for photo-degradation of the methyl violet due to its own crystal structure.
CCa(Mg1/3Nb2/3)O3/CaTiO3 (CMN/CT)heterostructure dielectric thin films, with the same thickness but different arrangement patterns, were prepared by Pechini method. The effects of the heterogeneous interface on the st...
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CCa(Mg1/3Nb2/3)O3/CaTiO3 (CMN/CT)heterostructure dielectric thin films, with the same thickness but different arrangement patterns, were prepared by Pechini method. The effects of the heterogeneous interface on the structure and properties have been studied. The results showed that, in nonalternating arrangement films, single perovskite phase can only be obtained in TM heterostructure film, in which CaTiO3 layer has grown on the substrate firstly, and the dielectric properties of this film is εr=47.5, tanδ=0.020 at 1MHz. Comparing with non-alternating arrangement film, all alternating arrangement films have single perovskite phase, and the existing of heterogeneous interface enhanced the dielectric properties of TMM and MMT alternating arrangement films by introducing space charges. And the dismatch between CMN and CT layers can avoid the harmful particle forming, improve crystallization and surface morphology, and keep the dielectric loss at a low level. At 1MHz, the dielectric constant (εr) of TMM and MMT films are 66.3 and 63.6, while both dielectric loss (tanδ) are 0.021.
In present work, undoped and Co 2 O 3 -doped Ba 4 Eu 2 Fe 2 Nb 8 O 30 ceramics were fabricated by routine solid state method. Wide temperature range measurement shows two kinds of dielectric peaks. The low-temperatur...
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In present work, undoped and Co 2 O 3 -doped Ba 4 Eu 2 Fe 2 Nb 8 O 30 ceramics were fabricated by routine solid state method. Wide temperature range measurement shows two kinds of dielectric peaks. The low-temperature peak attributes to ferroelectric-paraelectric phase transition. The high-temperature peak is affected greatly by Co 2 O 3 additives. With increasing the content of Co 2 O 3 dopant the second peak vanished, indicating that it is related to space charge.
To obtain homogenous layered oxide Li（Co1/3Ni1/3Mn1/3）O2 as a lithium insertion positive electrode material, the sol-gel process using citric acid as a chelating agent was applied. The material Li（Co1/3Ni1/3Mn1/3）...
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To obtain homogenous layered oxide Li（Co1/3Ni1/3Mn1/3）O2 as a lithium insertion positive electrode material, the sol-gel process using citric acid as a chelating agent was applied. The material Li（Co1/3Ni1/3Mn1/3）O2 was synthesized at different calcination temperatures. XRD experiment indicated that the layered Li（Co1/3Ni1/3Mn1/3）O2 material could be synthesized at a lower temperature of 800℃, and the oxidation state of Co, Ni, and Mn in the cathode confirmed by XPS were ＋3, ＋2, and ＋4, respectively. SEM observations showed that the synthesized material could form homogenous particle morphology with the particle size of about 200 nm. In spite of different calcination temperatures, the charge-discharge curves of all the samples for the initial cycle were similar, and the cathode synthesized at 900℃ showed a small irreversible capacity loss of 11.24% and a high discharge capacity of 212.2 mAh·g^-1 in the voltage range of 2.9-4.6 V.
The process of use catalyst or functional material that contains iron ion to weaken -O-H-O- hydrogen bond of the thick oil to reduce viscidity or crack, in aspects of the ion charge. covalent bond order, total energy ...
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The process of use catalyst or functional material that contains iron ion to weaken -O-H-O- hydrogen bond of the thick oil to reduce viscidity or crack, in aspects of the ion charge. covalent bond order, total energy and the average distance of Fe-O. is studied with density function theory and discrete variational method （DFT-DVM）, one of the first principle methods. With the decrease of the distance of Fe-O. the charge of Fe ion increases, the charge of hydrogen ion decreases, and hydrogen bond is weakened. There are obvious and more stable effects to use the catalyst that contains multiple metal ions or increase the catalyst amount in weakening hydrogen bond of the thick oil. This theoretic work is helpful to exploit and process the thick oil of petroleum and maybe overcome the crisis of petroleum energy is approaching to us.
The coprecipitation precursors with nominal composition of xFe+BaFe12O19(0≤x≤1, Δx=0.2) were prepared by chemical coprecipitation process. The crystallization behavior of the precursor under the spark plasma sinter...
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The coprecipitation precursors with nominal composition of xFe+BaFe12O19(0≤x≤1, Δx=0.2) were prepared by chemical coprecipitation process. The crystallization behavior of the precursor under the spark plasma sintering (SPS) conditions and the magnetic properties of the SPS samples were investigated. The results show that the crystallization of intermediate such as Fe2O3did not occur in all the SPS samples. The SPS samples for 03O4and Ba2Fe14O22(Fe2Y) and for 0.8≤x≤1.0 were composed of Fe3O4and Fe2Y, though the SPS sample for x=0 was composed of single-phase BaM. BaM gradually reduced and Fe3O4and Fe2Y gradually increased as the x increased. Needle Fe2Y mainly occurred in the interface area between Fe3O4and BaM. However, Fe2Y and Fe3O4are randomly distributed in these samples without BaM. The saturation magnetization first reduced significantly and remained almost constant, finally remarkably decreased again and then slightly increased. This accorded with the evolution characteristics of the phase composition of the SPS samples with the increase of x. The coercivity first increased significantly and then decreased slightly with the increase of x, which was attributed to the corresponding increases in the content of Fe3O4and Fe2Y, the reduction in the content of BaM, and the growth of Fe3O4and Fe2Y.
Mg2Si1-xSnx (0&lex&le1) Solid Solutions have been fabricated by the low-temperature solid state reaction and spark plasma sintering, and the influence of tin concentration on thermoelectric properties was inve...
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Mg2Si1-xSnx (0&lex&le1) Solid Solutions have been fabricated by the low-temperature solid state reaction and spark plasma sintering, and the influence of tin concentration on thermoelectric properties was investigated. Results indicated that the thermoelectric properties of Mg2Si1-xSnx are sensitive to tin concentration. With the increases of tin content, the electrical conductivity increases while the absolute value of Seebeck coefficient decreases, and the lattice thermal conductivity first decreases, reaching a minimum value when x=0.4, then increases with tin content further increases. The lattice thermal conductivity of Mg2Si1-xSnx solid solution is considerably lower than the binary Mg2Si and Mg2Sn alloy, which is about one third and one half the value at room temperature for Mg2Si and Mg2Sn alloy, respectively. The highest dimensionless figure of merit reaches 0.16 at 640 K for sample x=0.2.
5083 aluminum Alloy was prepared by cryomilling method. The microstructure, microstructural evolution and thermal stability and of sample powder were investigated by XRD, SEM and DSC. The results showed that the parti...
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5083 aluminum Alloy was prepared by cryomilling method. The microstructure, microstructural evolution and thermal stability and of sample powder were investigated by XRD, SEM and DSC. The results showed that the particles size of 5083 alloy powder during cryomilling was gradually reduced, Mg phase was gradually disappeared and super-saturated to Al;Milling time and milling speed were the main factors of affected alloy structure and performance, and high speed cryomilling could result in more uniform nanometer grains. Energy spectrum analysis and DSC suggest that the thermal stability of the cryomilling 5083 alloy powder was improved at certain extent, it may be attributed to the presence of nano-scale Al2O3 particles.
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