C.Q. Xu
,
Y.W. Tian
,
Y.C. Zhai
,
Z.J. Guo
,
Z.Q. Huang
金属学报(英文版)
The differential thermal analysis (DTA) curves were measured at different heating rates in flowing air for studying the synthesis of the spinel LiMn2O4 with Li2CO3 and MnO2. The reaction began at about 503K, and finished at about 873K. The apparent activation energy of Kissinger method was about 122.77kJ·mol-1, the reaction order was 1.67, the frequency factor was 7.81×10 9, and therefore the kinetic equation was ＝ Ａ·ｅｘｐ（－）·（1-δ)n = 7.81×10 9 ｅｘｐ（－）·(1-δ)1．６７. Coats-Redfern integral method was used to analyze the DTA curves of the samples at different heating rates, and the calculated apparent activation energy and frequency factor were 112.13kJ·mol-1 and 1.18×10 9, respectively, rather close to that of Kissinger method. X-ray diffraction (XRD) and scanning electron microscope (SEM) results shown that the synthesized LiMn2O4 possesses pure phase, regular shape and normal particle distribution.
关键词:
lithium manganese oxides
,
null
,
null
A.A.A. Saleh
,
X.J. Zhai
,
Y.C. Zhai
,
Y. Fu
,
M.M. Elomella
金属学报(英文版)
Photocatalytic degradations of p-nitrochlorbenzene (p-NCB) with distilled water were
investigated with ZnO crystals (catalyst) of 70nm in diameter under UV irradiation.
The suitable experimental conditions are determined as: ZnO 0.25g, pH 7, p-NCB
concentration 30mg/L. These variables in terms of the degradation rate have been
discussed, which was defined as the rate of the initial degradation to the final degradation of p-NCB. When all of the experimental degradation rate values are plotted as a
function of irradiation time, all of the points appeared on a single line for wide range of
p-NCB degradations. On the basis of these results, it has been concluded that at lower
ZnO catalyst amount, much of the light is transmitted through the slurry in the container beaker, while at higher catalyst amount, all the incident photons are observed
by the slurry. Degradation rates of p-NCB were found to decrease with increasing
solution pH. It has been concluded that the maximum degradation rate values of p-NCB under principally the same experimental conditions mentioned above are 97.4%,
98.8% and 95.5% at 100min respectively. The results suggest that the photocatalytic
degradation is initiated by an oxidation of the p-NCB through ZnO surface-adsorbed
hydroxyl radicals. Absorption spectra are recorded using spectrophotometer before and
after UV-irradiation in the wavelength range 200--400nm at room temperature. It
is found that the variation of irradiation time over the range 20--100min resulted in
change in the form of the spectrum linear absorption and a higher maximum value
will be obtained at longer irradiation time.
关键词:
reactive evaporation method
,
null
,
null
,
null
A.A.A. Saleh
,
X.J. Zhai
,
Y.C. Zhai
金属学报(英文版)
Nanometer ZnO particles were synthesized by evaporating of zinc powders of averageparticle size of 370μm studied by XRD, TEM and electron diffraction. The particleswere formed by the oxidation of evaporated zinc vapor in the air. It was found that theparticles range from 70 to 100nm in average particle size. The effect of experimentalparameters was investigated, the increase of the air flow-rates reduced the averageparticle size, while increasing the evaporation temperature and the amount of metalcharged increased the average particle size. TEM of the particles collected showedthat the crystal habits of particles have a tetrapod-like of wurtzite structure consists offour needle crystals. It was found by electron diffraction that all particles were singlecrystal.
关键词:
M.S. Zhao
,
Y.C. Zhai
,
Y.W. Tian
金属学报(英文版)
The reaction process during synthesis of LiMn2 O4 with LiOH. H2 O and MnO2 was studied by means of DTA in dynamical air atmosphere, and it could be applied as an important theoretical principle for preparing LiMn2 O4. The active energies of four reaction processes were obtained with Doyle-Ozawa method and Kissinger method as follows: 66.299, 72.640, 128.111 and 113.876 kJ. mol-1, respectively. Reaction orders,frequency factors and kinetic equations of each reaction were determined by using Kissinger method. XRD, SEM and TEM showed that the synthesized LiMn2 O4 is a pure phase, with regular appearance and higher ratio-surface.
关键词:
lithium-ion battery
,
null
,
null
Physics Letters A
The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(a)B(b)C(c))(y)D, in which A, B, C and D are four different magnetic ions and form four different sublattices, are studied by using the Ising model. And the Ising model was dealt with standard mean-field approximation. The regions of concentration in which two compensation points or one compensation point exit are given in c-a, b-c and a-b planes. The phase diagrams of the transition temperature T-c and compensation temperature T-comp are obtained. The temperature dependences of the magnetization are also investigated. Some of the result can be used to explain the experimental work of the molecule-based ferro-ferrimagnet ((NiaMnbFecII)-Mn-II-Fe-II)(1.5) [Cr-III (CN)6] - zH(2)O. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
mixed ferro-ferrimagnet;Ising model;four sublattices;phase diagram;transition temperature;compensation temperature;magnetic-properties;prussian blue;alloy
Corrosion Science
The oxidation of pure Co and two Co-Y alloys containing 2 at.% and 5 at.% Y has been studied at 600-800 degrees C in air. The oxidation of pure cobalt at all temperatures followed the parabolic rate law. The oxidation of the two alloys approximately followed the parabolic rate law at 800 degrees C, but was closer to cubic behavior at 600 and 700 degrees C except Co-5Y at 600 degrees C, which deviated from the cubic and parabolic rate law. The corrosion of both alloys at the three temperatures produced an external scale containing Co oxides (Co3O4, CoO) and Y2O3 and an internal oxidation region where Co17Y2 was converted into Co and Y2O3. The distribution of Y2O3 closely followed that of the intermetallic compound (Co17Y2) in the original alloy. The corrosion mechanism of the alloys is examined. (C) 1999 Elsevier Science Ltd. All rights reserved.
关键词:
Co;Y;oxidation;high-temperature oxidation;possible scaling modes;internal oxidation;oxidant pressures;h-2-h2s mixtures;sulfidation;oxygen
Oxidation of Metals
The oxidation of Fe- Y alloys containing 2 and 5 at.% Y and pure iron has been studied at 600-800 degrees C in air. The oxidation of pure iron follows the parabolic rate law at all temperatures. The oxidation of Fe-Y alloys at 600 degrees C approximately follows the parabolic rate law, but not at 700 and 800 degrees C, where the oxidation goes through several stages with quite different rates. The oxide scales on Fe-2Y and Fe-5 Y at 700 and 800 degrees C are composed of external pure Fe oxides containing Fe2O3, Fe3O4, and FeO, with FeO being the main oxide and an inner mixture of FeO and YFeO3. The scales on Fe-2Y and Fe-5Y at 600 degrees C consist of Fe2O3, Fe3O4, and Y2O3, with a minor amount of FeO. Significant internal oxidation in both Fe-Y alloys occurred at all temperatures. The Y-containing oxides follow the distribution of the original intermetallic compound phase in the alloys. The effects of Y on the oxidation of pure Fe are discussed.
关键词:
pure Fe;Fe-Y alloys;oxidation;high-temperature oxidation;possible scaling modes;2-phase;binary-alloys;low-oxygen pressures;oxidant pressures
李鹏
,
胡耀波
,
熊惟皓
,
林真
硬质合金
doi:10.3969/j.issn.1003-7292.2000.02.001
研究了稀土元素Y对Ti(C,N)基金属陶瓷微观组织和性能的影响.Y在Ti(C,N)基金属陶瓷中可以起到净化粘结相/硬质相界面的作用,并使其包覆层的厚度略有增加,从而使硬质相颗粒得到细化.当Y含量为0.8wt%时细化效果最明显,此时Ti(C,N)基金属陶瓷的抗弯强度和硬度值最大.
关键词:
稀土元素
,
Y
,
金属陶瓷
,
组织与性能
Journal of Applied Physics
The magnetic properties of R2Co14B1-xCx (x=0, 0.5 and R=Y, Sm) compounds have been studied by measuring the temperature dependence of the easy- and hard-magnetization curves on magnetically aligned samples between 1.5 and 300 K for Y2Co14(B,C) and at 4.2 K for Sm2Co14(B,C). The magnetic anisotropy of Y2Co14B increases due to the substitution of C for B, whereas the saturation magnetization decreases. Between 1.5 and 300 K, the anisotropy field of Y2Co14B0.5C0.5 increases about 2 T and the Co moment decreases about 0.05mu(B). The anisotropy field Of Sm2Co14B also increases upon C substitution and the saturation magnetization decreases slightly. The ac susceptibilities of both SM2Co14B and Sm2Co14B0.5C0.5 exhibit anomalies that may arise from a spin reorientation within the basal plane.
关键词:
nd2fe14b;exchange;nd2co14b;r2fe14b;field
