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
,
Y. Fu
,
X.J. Zhai
金属学报(英文版)
Nano-ZnO particle was produced by evaporating zinc powders in air at air °ow-rate
from 0.2 to 0.6m3/h. Nano-ZnO particles was formed by the oxidation of the evapo-
rated zinc vapor. X-ray di®raction shows the powders to be ZnO with lattice parame-
ters of a=0.3249nm and c=0.5205nm. The particle size is dependent upon the transit
time from the source to the collection area. The size of particles was ranged between
81 to 103nm. The average density resulted was 4.865g/cm3.
Normal ZnO and nano-ZnO were investigated to use them in aluminum metallurgy as
an inert anode material. A certain amount of both oxides were molded subsequently
inserted to the molten cryolite-aluminum oxide to investigate the corrosive behavior
of both oxides. When the sintering temperature increased up to 1300±C, the weight
loss ratio rose to 5.01%{7.33% and up to 7.67%{10.18% for nano-ZnO and normal
ZnO, respectively. However, when the samples in the molten cryolite aluminum oxide
were put for long time, the corrosive rate was found to be higher. It was found that
the corrosive loss weight ratio of nano-ZnO anode was much lower than the normal
one made from ordinary-ZnO providing that the nano-ZnO is more possible to be use
inert anode material.
关键词:
reactive evaporation method
,
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:
