99
Effect of Soluble Salt Matrix on

99


Effect of Soluble Salt Matrix on Mechanochemical Synthesis of Zirconia
Nanoparticles
Kanatip Kumproa
1
, Apinon Nuntiya
1*
, Qiwu Zhang
2
, Fumio Saito
2
1
Department of Industrial Chemistry, Faculty of Science, Chiang Mai University,
Chiang Mai 50200, Thailand
2
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University,
2-1-1, Katahira, Aoba-Ku, Sendai 980-8577, Japan
E-mail: anuntiya@chiangmai.ac.th (A. Nuntiya)
ABSTRACT
Mechanochemical synthesis of zirconia nanocrystalline powder was performed from
zirconium oxychloride and
lithium carbonate
without and with an addition of a soluble salt
(lithium chloride). The purposes of this work are to synthesize zirconia powder via a
mechanochemical process and to study the effect of soluble salt on agglomerate size and
crystallinity of nanocrystalline powder. Zirconia powder was prepared by zirconium
oxychloride and
lithium carbonate
without and with an addition of a soluble salt
by using
planetary ball mill and heat treatment. Chemical reaction between reactant mixtures
occurs during post-milling heat treatment at 400
o
C to form composite powder. The
products of this reaction consist of nanocrystalline powder embedded within lithium
chloride as soluble salt. The nanocrystalline powder is then recovered by removing
the salt through a washing procedure. The powders were characterized using X-ray
diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis.
The results indicated that
the structure of zirconia with addition of the lithium chloride is
transformed from monoclinic form to tetragonal form and its crystallinity depends on the
concentration of lithium chloride. Furthermore
, agglomerate size of nanocrystalline
powder also depends on the concentration of lithium chloride and washing procedure.
Primary particle size of powder is approximately 30 nm.
Keywords:
Zirconia, Soluble salt, Mechanochemical synthesis,
X-ray diffraction
1. INTRODUCTION
Zirconia (ZrO
2
) has attracted the ongoing interest of researchers because the
combination of electrical, mechanical and thermal properties of this material has led
to its use in a wide range of applications, such as electronic materials, oxygen sensors,
humidity sensors, solid oxide fuel cells, catalyst support, thermal barrier coating,
tooth crowns and refractory [1]. Pure ZrO
2
exhibits four primary polymorphs that are
stabilized at different temperature ranges and different pressures: A


monoclinic
structure is stable from room temperature to 1175
o
C, as baddeleyite, a tetragonal
structure is stable at the temperature range from 1175 to 2370
o
C, a cubic structure is
stable above 2370
o
C [2] and a rhombic structure is stable at a high pressure [3].
The
monoclinic form has remarkable properties that are excellent mechanical properties