Proceedings of the IConSSE FSM SWCU 2015, pp. BC.110–117 ISBN: 978-602-1047-21-7
SWUP
BC.110
Synthesis and characterization of refractory cordierite precursors from rice husk silica
Simon Sembiring
a
, Wasinton Simanjuntak
b
, Rudi Situmeang
b
, Buhani
b
, Shella
c
a
Department of Physics,
b
Department of Chemistry,
c
Under Graduate Student of Physics Department, Lampung University, Jl. Prof. Soemantri Brojonegoro No.1 Bandar Lampung 35145, Indonesia
Email: simonsembiring2gmail.com
Abstract
This study describes the production of refractory cordierite ceramics by mixing silica extracted from rice husk, Al
2
O
3
and MgO powder. The mixture was sintered at different temperatures of 1050, 1110, 1170
C for 4 h. The phases formed and structure change as a result of sintering were investigated using different characterisation technique of
Fourier transform infrared FTIR, X-ray diffraction XRD and scanning electron microscopy SEM. Density, porosity, hardness and electrical resistivity were also
measured. Cordierite, spinel and cristobalite were the major phases in the samples sintered at temperature range of 1050-1170
C. µ-cordierite was formed through the intermediate phases of spinel and cristobalite at 1050
C. The final phase -cordierite
indialite was produced through µ-cordierite and cristobalite from 1110 to 1170
C. The density, hardness and electrical resistivity were found to increase with increasing of
sintering temperature, as they are strongly influenced by microstructure of the material.
Keywords cordierite, rice husk, sintering, structure, refractory
1. Introduction
It is well known that cordierite Mg
2
Al
4
Si
5
O
18
ceramics is excellent insulator and high- thermal resistant material, possessing low dielectric constant and thermal expansion
coefficient. The cordierite ceramics is a promising material as refractory material with the highest melting temperature 1460
C among silicate glass-ceramics Hamzawy Ali, 2006. Due to its low thermal expansion coefficient Kai et al., 2010, excellent thermal shock
resistance Oliveira Fernandez 2002, high refractoriness Zhu et al., 2007, therefore, cordierite ceramic is considered as a very promises for structural materials and finds
applications as heat exchangers for gas turbine engines Laokula Maensirib, 2006, electrical and thermal insulation Gonzalez-Velasco, 1999; Evans et al., 1980. In previous
studies Oliveira Fernandez, 2002; Lim Jang, 1993, have established that the excellent thermal shock resistant material when it is subjected to rapid changes in temperature. They
found that fracture toughness increases with increasing sintering temperature from 1250 to 1300
C. Several methods were developed and applied to synthesis cordierite ceramics. Among
other, solid state reaction Ghitulica et al., 2007, sol gel Simanjuntak Sembiring, 2011, spraying Rohana et al., 2004, or crystallization from glasses Rudolph et al., 1993. For
example, the studies of cordierite by solid reaction Petrovic et al., 2001 have shown that cordierite exist in three polymorphs,
-cordierite, -cordierite and µ-cordierite. Below 1450
S. Sembiring, W. Simanjuntak, R. Situmeang, Buhani, Shella
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BC.111
C, cordierite is metastable and it is slowly transforms to -cordierite. It has also been
reported that -cordierite, MgAl
2
O
4
spinel and cristobalite present at 1300 °C, while the only -cordierite phase was observed at 1350
C and 1375
C Salje, 1987. By sol gel method, the initiation of the
cordierite transformation was achieved in the temperature range 1000- 1100 °C and high stability -cordierite only at 1200 °C Kumta, 1994.
Related to natural resources as raw materials for preparation of ceramics, rice husk is a waste material derived from agriculture residu, which makes its an alternative as silica
source. In our previous research, active silica from rice husk was obtained by simple acid leaching, and has been used to produce borosilicate Sembiring, 2011, cordierite
Simanjuntak Sembiring, 2011, carboxyl Simanjuntak et al., 2012, aluminosilicate Simanjuntak et al., 2013, mullite Sembiring Simanjuntak, 2012; Sembiring et al., 2014.
The present study was carried out with the aim of exploring the feasibility of rice husk silica to produce refractory cordierite precursor as an alternative to commonly used silica
synthetics. The precursor produced was then subjected to thermal treatment to investigate the phase development, physical and thermal properties as refractory cordierite. The
functionality change of as a function of heat treatments was investigated by FTIR spectroscopy, the structure was characterized by XRD and the microstructure was studied
using SEM.
2. Materials and methods 2.1 Materials
