|
Zinc Oxide(ZnO) powders were prepared by using ammonia and triethanolamineas t
he base sources in the hydrothermal method. The differences ofcharacteristics
of ZnO powders prepared from these two methods were studied.In the system of a
mmonia, we aimed at studying the effect of several processvariables such as ag
ing temperature, aging time, pH value on the morphology,particle size and dist
ribution of ZnO powders. ZnO powders might redissolve athigh temperature (200o
C), and this caused the decrease of yield and particlesize. Because the reacti
ons of ZnO were very fast, there were no obviouschanges on particle size and m
orphology of ZnO powders with aging time. Thusthe characteristics of ZnO powde
rs mainly depended on pH value.The crystallinity, crystallite size and particl
e size increased with pH value.The morphology changed from ellipsoidal to rod
-like with increasing pH value.In the system of triethanolamine, the effect of
processing variables such asreactant concentration, aging temperature, aging
time, mixing rate and heatingrate were reserched systematically. Zinc Oxide po
wders with particle ofsubmicrometer, spherical, narrow size distribution were
prepared in the system.The morphology mainly depened on reactant concentration
and temperature.The surface of particles was smoother at high triethanolamine
concentration,however the particles broke at high aging temperature.The parti
cle size and distribution depened strongly on triethanolamineconcentration, mi
xing rate and heating rate. The high triethanolamineconcentration resulted in
large particles with broad size distribution.In addition, the particle size de
creased with increasing mixing rate andheating rate. The yield and crystallite
size decreased only with increasingtriethanolamine concentration. Under the b
est hydrothermal condition, sphericalparticles in the size of submicrometer (0
.5mm) have been obtained.
|