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
