共查询到20条相似文献,搜索用时 0 毫秒
1.
A. P. Kazin M. N. Rumyantseva V. E. Prusakov I. P. Suzdalev Yu. V. Maksimov V. K. Imshennik S. V. Novochikhin A. M. Gaskov 《Inorganic Materials》2010,46(11):1254-1259
Nanocrystalline nickel ferrite with a crystallite size from 3 to 40 nm has been prepared by spray pyrolysis. The 57Fe Mössbauer spectrum of NiFe2O4 samples has been found to vary systematically with crystallite size. The sensing response of the nanocrystalline nickel ferrite to 50 ppm NH3 has been studied using in situ conductance measurements. NiFe2O4 offers a strong sensing response to ammonia at the level of its maximum concentration limit. The optimum nickel ferrite crystallite size and temperature for ammonia detection are determined. 相似文献
2.
Seo Hee Ju Do Youp Kim Eun Byul Jo Yun Chan Kang 《Journal of Materials Science》2007,42(14):5369-5374
Spinel LiMn2O4 particles with fine sizes and regular morphologies were successfully synthesized by ultrasonic spray pyrolysis at the severe
preparation conditions from a spray solution with citric acid and ethylene glycol. The as-prepared particles with spherical
shapes, porous structures and micron sizes turned into LiMn2O4 particles with submicron size and narrow size distribution at the post-treatment temperature of 800 °C. The discharge capacities
of the particles prepared from the spray solution with citric acid and ethylene glycol changed from 90 to 127 mAh/g when the
post-treatment temperature was changed from 700 to 1,000 °C. The LiMn2O4 particles had maximum discharge capacities at the post-treatment temperature of 800 °C. The discharge capacity of the LiMn2O4 particles dropped from 127 to 108 mAh/g by the 30th cycle. 相似文献
3.
R. S. Ingole S. B. Kondawar B. J. Lokhande 《Journal of Materials Science: Materials in Electronics》2017,28(3):2385-2391
A scheme of substrate dependent self-organization of vanadium oxide has been used to create unique supercapacitor electrodes. In present work, thin films of V2O5 were prepared on different substrates by using well known spray pyrolysis technique.The sample depositions were carried out at 673 K, by spraying 0.05 M, 40 ml solution of ammonium metavanadate at the spray rate 10 ml/min. V2O5 thin films grown on aluminum (Al), copper (Cu) and stainless steel (SS) substrates shows porous valley and mountains, rough and dense morphology with overgrown agglomeration of nano grains. In electrochemical characterizations, by using standard electrode configurations, specific capacitance values were evaluated from cyclic voltammetry in 1 M KCl, these are 18.43, 1500.0, 439.60 and 250.58 F/g at 5 mV/s for the electrodes deposited on Al, Cu, SS substrates and two electrode cell respectively. Charge discharge behavior of the SS electrode and two electrode cell was observed using chronopotentiometry. This exhibits specific energy, specific power, and coulombic efficiency (η) 84.91 Wh/kg, 120.00 kW/kg and 89.51 % for SS electrode and 19.92 Wh/kg, 65.00 kW/kg and 99.90 % for two electrode cell respectively. Impedance study was carried out in the frequency range 1 mHz–1 MHz depicts less internal resistance of SS electrode ~2.69 Ω and two electrode cell ~3.04 Ω. 相似文献
4.
Spray pyrolysis has been used to produce X-ray amorphous precursors with the nominal composition SrFe12O19 · 6SrB2O4 in the form of spherical particles 0.3 to 2 μm in diameter. Heat treatment of the precursors at temperatures from 650 to
900°C has produced platelike strontium hexaferrite particles embedded in a SrB2O4 matrix. With increasing annealing temperature, the average dimensions of the hexaferrite particles increase from 80 × 20
to 450 × 100 nm and the coercivity of the material rises from 240 to 440 kA/m. 相似文献
5.
Yuanyuan Zhang Yue Chen Qiangwei Kou Zhe Wang Donglai Han Yantao Sun Jinghai Yang Yang Liu Lili Yang 《Journal of Materials Science: Materials in Electronics》2018,29(5):3665-3671
Zinc ferrite nanomaterials have been received significant attention in recent years on account of their potential applications in the fields of electronics, optoelectronics and magnetics. To enhance the magnetic properties of zinc ferrites, Nd-doped zinc ferrites (ZnFe2?xNdxO4, x?=?0, 0.01, 0.02, 0.03) nanoparticles (NPs) have been prepared by the sol–gel method. The effects of Nd doping concentration on the structural and magnetic properties of zinc ferrites were studied. The results of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy indicated that the Nd ions were incorporated into the crystal lattice of ZnFe2O4 and substituted for the Fe3+ sites. Unlike pure zinc ferrites with paramagnetism, Nd doped ZnFe2O4 NPs were superparamagnetic at room temperature. Vibrating sample magnetometry results showed, with the increase of Nd content, the saturation magnetization of Nd doped ZnFe2O4 NPs increased. 相似文献
6.
Xibao Li Gangqin Shao Xiaohua Yu Jian Wang Hongxing Gu 《Journal of Materials Science: Materials in Electronics》2011,22(2):189-192
Ce0.8Sm0.2O1.9 (SDC) powder was synthesized by spray pyrolysis at 650 °C. XRD results showed that phase-pure SDC powder with an average
crystallite size of 11 nm was synthesized. SDC electrolyte film was prepared by tape casting and sintered at different temperatures
of 1,300, 1,400 and 1,500 °C for 2 h, respectively. The SDC electrolyte film was relatively denser and showed finer microstructure
at relatively lower temperature of 1,400 °C, which might be due to the high sintering activity of the spray pyrolysis SDC
powder. The ionic conductivity of the SDC electrolyte film sintered at 1,400 °C reached a maximum value of 9.5 × 10−3 S cm−1 (tested at 600 °C) with an activation energy for conduction of 0.90 eV. 相似文献
7.
Yao Ying Lichao Wang Wangchang Li Liang Qiao Jingwu Zheng Jing Yu Wei Cai Liqiang Jiang Shenglei Che Lei Zhang Langsheng Ling 《Journal of Superconductivity and Novel Magnetism》2018,31(11):3553-3558
We investigated the magnetic properties of a geometrically frustrated magnet of ZnFe2O4 nanoparticles by carrying out the comprehensive measurements of dc magnetization and ac susceptibility. Spin glass is confirmed to occur in this weakly Fe(Zn)-ionic-inversed sample. The common characteristics of spin glass including the aging, the memory, and the rejuvenation effects were observed. By using the critical-power law to study the spin dynamics, the spin-glass transition temperature Tg is obtained to be 18 K and the dynamic exponent zν is 8.0. The weak exchange interaction disorder introduced by the ferrimagnetic JAB interaction, together with the weak nonmagnetic dilute disorder induced by the ionic inversion, is responsible for the formation of spin glass in the ZnFe2O4 nanoparticles. 相似文献
8.
We have studied the stability of the Cr6+ ion in fine-particle TiO2-Cr2O3 oxides during storage after calcination in air. The results indicate that, during storage under normal conditions for 720 days, Cr6+ is reduced to Cr3+. The redox process is due to partial surface hydration of the Cr2O3 and TiO2 crystallites. 相似文献
9.
E. Mehran Saber Farjami Shayesteh F. Nasehnia 《Journal of Superconductivity and Novel Magnetism》2016,29(5):1241-1247
We study structural and magnetic properties of magnetic ceramic Co x Zn1?x Fe2O4 nanoparticles synthesized by the co-precipitation method and optimize its size and magnetic property for possible application in wastewater treatment. The effects of long stirring time under boiling condition and the introduction of the third metal ion to the structure are investigated. To study the microstructural and magnetic characteristic of the samples, X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) analyses are carried out. The diffracted peaks of XRD pattern confirm the formation of spinel phase. In addition, we study the effect of Co doping on the peak positions in the spinel structures. To evaluate crystallite size and other lattice parameters of the samples, we use the Rietveld method as a nearly exact approximation instead of Scherrer formula. Thus, the Rietveld refinement method has been utilized and structural and lattice parameters of the samples are extracted using Reflex program. In contrast with other works, our nanoparticles show superparamagnetic behavior, larger surface area, and better crystallinity with no calcination which originates from the condition of the synthesis method. 相似文献
10.
The combustion synthesis, microstructure, chemical composition, and phase composition of cast Al2O3-Cr2O3 materials are described. The synthesized solid solutions are based on corundum or chromia, depending on the Al2O3 and Cr2O3 contents. Using self-propagating high-temperature synthesis, a cast aluminum oxynitride is obtained for the first time. 相似文献
11.
The mass transport during the oxidation of Cr2O3 in mixtures of fine-particle TiO2 and Cr2O3 in air has been studied at temperatures from 800 to 1000°C by magnetochemical analysis. The results indicate that the process leads to the oxidation of up to ten surface atomic layers. The mass transport is shown to be a stochastic, steplike process. 相似文献
12.
New solid solutions, Bi2?x?y Tm x Nb y O3+δ, with tetragonal and cubic structures have been synthesized in the Bi2O3-Tm2O3-Nb2O5 system, and their electrical conductivity has been measured at temperatures from 670 to 1020 K. The 1020-K conductivity of the tetragonal solid solution Bi1.8Tm0.15Nb0.05O3+δ is comparable to that of Bi1.75Tm0.25O3, the best conductor in the Bi2O3-Tm2O3 system. 相似文献
13.
Platelike Li1 ? x Na x Cu2O2 single crystals up to 2 × 10 × 10 mm in dimensions have been grown by slowly cooling (1 ? x)Li2CO3·xNa2O2·4CuO melts in alundum crucibles in air. Li1 ? x Na x Cu2O2 solid solutions in the LiCu2O2-NaCu2O2 system have been shown to exist in the composition range 0.78 < x < 1. The temperature stability ranges of NaCu2O2 and LiCu2O2 are 780–930 and 890–1050°C, respectively. The Mössbauer spectra and electrical conductivity of the crystals have been measured. 相似文献
14.
Semiconducting glasses of the Fe2O3-Bi2O3-K2B4O7 system were prepared by the press-quenching method and their dc conductivity in the temperature range 223–393 K was measured. The glass transition temperature values (Tg) of the present glasses were larger than those of tellurite glasses. This indicates a higher thermal stability of the glass in the present system. The density for these glasses was consistent with the ionic size, atomic weight and amount of different elements in the glasses. Mössbauer results revealed that the relative fraction of Fe increases with increasing Fe2O3 content. Electrical conductivity showed a similar composition dependency as the fraction of Fe. The glasses had conductivities ranging from 10 to 10 Scm at temperatures from 223 to 393 K. Electrical conduction of the glasses was confirmed to be due to non-adiabatic small polaron hopping and the conduction was primarily determined by hopping carrier mobility. 相似文献
15.
R. Sani A. Beitollahi Yu. V. Maksimov I. P. Suzdalev 《Journal of Materials Science》2007,42(6):2126-2131
In this work we report the phase formation and magnetic properties of CoFe2O4 nanopowder prepared by mechanical alloying technique using metallic cobalt and hematite powder (1:1 molar ratio) as the initial raw material in ambient air atmosphere. The formation of single phase cobalt ferrite of (Co 0.18 2+ Fe 0.82 3+ )[Co 0.82 2+ Fe 1.18 3+ ]O4 stoichiometry was confirmed for the samples milled above 15 h without any heat-treatment by XRD and Mössbauer techniques. The average crystallite size of the sample milled for 30 h was ~13 nm. The highest room temperature value of the magnetization measured at 1.5 T was 51 e.m.u/g for the sample milled for 25 h which was much lower than the corresponding value of the bulk cobalt ferrite (80.8 e.m.u/g at 300 K) due to the size effect. 相似文献
16.
17.
Binary transition metal oxides are considered as promising anode materials for lithium-ion batteries (LIB), because they can effectively overcome the drawbacks of simple oxides. Here, a one-step hydrothermal method is described for the synthesis of regular ZnFe2O4 octahedrons about 200 nm in size at a low temperature without further annealing being required. The ZnFe2O4 octahedrons were characterized by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical performance of the ZnFe2O4 octahedrons was examined in terms of cyclic voltammetry and discharge/charge profiles. The ZnFe2O4 octahedrons exhibit a high capacity of 910 mA·h/g at 60 mA/g between 0.01 and 3.0 V after 80 cycles. They also deliver a reversible specific capacity of 730 mA·h/g even after 300 cycles at 1000 mA/g, a much better performance than those in previous reports. A set of reactions involved in the discharge/charge processes are proposed on the basis of ex situ high-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of the electrode materials. The insights obtained will be of benefit in the design of future anode materials for lithium ion batteries. 相似文献
18.
N. A. Gorodylova V. N. Baumer I. V. Zatovsky A. A. Babarik N. S. Slobodyanik O. V. Shishkin 《Inorganic Materials》2011,47(2):156-162
We have studied general trends of crystallization from high-temperature solutions in the K2O-P2O5-V2O5-Bi2O3 system at P/V = 0.5?2.0, K/(P + V) = 0.7?1.4, and Bi2O3 contents from 25 to 50 wt % and identified the stability regions of BiPO4, K3Bi5(PO4)6, K2Bi3O(PO4)3, and K3Bi2(PO4)3 ? x (VO4) x (x = 0?3) solid solutions. The synthesized compounds have been characterized by X-ray powder diffraction and IR spectroscopy, and the structure of two solid solutions has been determined by single-crystal X-ray diffraction (sp. gr. C 2/c): K3Bi2(PO4)2(VO4), a = 13.8857(8), b = 13.5432(5), c = 6.8679(4) Å, β = 114.031(7)°; K3Bi2(PO4)1.25(VO4)1.75, a = 13.907(4), b = 13.615(2), c = 6.956(2) Å, β = 113.52(4)°. 相似文献
19.
LiMn2-x
ErxO4 (x ≤ 0.02) materials were synthesized by a rheological phase reaction method. The thermal behavior of the materials was examined by thermogravimetric and differential scanning calorimetry. X-ray diffraction showed that the samples (x ≤ 0.02 ) exhibited the same phase as the pure spinel. The lattice parameter of the Er-doped spinel was smaller than that of the undoped one and decreased with increasing doping level. Cyclic voltammograms showed two reversible processes corresponding to the typical response of spinel LiMn2O4 and revealed an insertion-extraction reaction occurring at two stages in the 4-V region. The electrochemical performances of the samples were studied and displayed a better reversibility and cyclability.__________From Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 740–743.Original English Text Copyright © 2005 by Haowen Liu, Li Song, Kelli Zhang.This article was submitted by the authors in English. 相似文献
20.
Rucha Desai R. V. Mehta R. V. Upadhyay Amita Gupta A. Praneet K. V. Rao 《Bulletin of Materials Science》2007,30(3):197-203
Cadmium ferrite particles have been synthesized using co-precipitation technique followed by a low temperature (600°C) annealing
in a time scale much shorter than reported in literature. Incorporation of sodium chloride during annealing helps to form
a single phase spinel structure with a final particle size of around 50 nm. Even at such a short length scale we observe the
overall magnetic properties to be similar to those of the bulk. The observed magnetic properties can be explained on the basis
of an anti-ferromagnetic core with a shell containing ‘ferromagnetic-like’, but canted spin structure. 相似文献