Influences of Temperature on the Conversion of Ammonium Tungstate Pentahydrate to Tungsten Oxide Particles with Controllable Sizes, Crystallinities, and Physical Properties
ABSTRACT: The purpose of this
study was to investigate influences of temperature on the conversion of
ammonium tungstate pentahydrate (ATP) powder to tungsten trioxide (WO3)
particles with controllable sizes, crystallinities, and physicochemical
properties. In this study, we used a simple thermal decomposition method. In
the experimental procedure, we explored the effect of temperature on the
physicochemical properties of ATP by testing various heating temperatures (from
100 to 900 °C). The heated ATP samples were then characterized by a physical observation
(i.e. color) and various analysis methods (i.e. a thermal gravimetric and
differential thermal analysis,infrared spectroscopy, an X-ray diffraction, and
a scanning electron microscope). Experimental results showed that increases in
temperature had an impact to the decreases in particle size, the change in
material crystallinity, and the change in physical properties (e.g. change of
color from white, orange, to yellowish green). The relationships between the
reaction temperatures and the physicochemical properties of the ATP were also
investigated in detail along with the theoretical consideration and the
proposal of the WO3 particle formation mechanism. In simplification, the
phenomena can be described into three zones of temperatures: (1) Below 250 °C
(release of water molecules and some ammonium ions); (2) At 250-400 °C (release
of water molecules and ammonium ions, restructurization of tungsten and oxygen
elements, and formation of amorphous tungsten trioxide); and (3) At higher than
400 °C (crystallization of tungsten trioxide). Since ATP possessed reactivity
on temperature, its physicochemical properties changing could be observed
easily, and the experimental procedure could be done easily. The present study
will benefit not only for “chemistry and material science” but also potentially
to be used as a model material for explaining the thermal behavior of material
to undergraduate students (suitable used for a class and laboratory experiment
and demonstration).
Keywords: tungsten oxide;
ammonium tungsten pentahydrate; thermal decomposition; material science; powder
processing
Author: Asep Bayu Dani
Nandiyanto, Heli Siti Halimatul Munawaroh, Tedi Kurniawan and Ahmad Mudzakir
Journal Code: jpkimiagg160085
