Third Day Poster Session, 17 June 2010 - NanoTR-VI

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Poster Session, Thursday, June 17
Theme F686 - N1123
Alternative Method to Production of Nano-Sized -SiAlON Powders
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Onur EserP P, USemra KuramaUP P* and Göktug GünkayaP
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PDepartment of Materials Science and Engineering, Anadolu University, Eskisehir, Turkey
Abstract-In this study, the optimum milling system was investigated by using sedimentation method. The effect of type of mediums and
dispersants were researched by using sedimentation tests. After the optimization of milling medium wet milling system was used to decreasing
particle size of starting powders. All the milling time results were discussed related with the particle size of milled powder.
There are some routes to prepare nano-sized SiAlON
powders such as plasma-chemical and laser synthesis [1], solgel
and as a top-to-bottom process high-energy mechanical
milling [2]. Although, this method promises very low particle
sizes (~40 nm), would increase the cost of the initial powder
[3]. In this study -SiAlON described as SiR4RAlR2ROR2RNR6R, and
doped with 5 wt.% YR2ROR3R. The weighed powders were
planetary ball milled (Pulverisette 6 Fritsch, Germany) with
SiR3RNR4R balls for 2 h in different solvent compositions (toluene,
methyl ethyl keton, ethanol) and in different ratios. The
solvent ratios were determined as given in the literature [4].
The level of agglomeration, a critical parameter for the
efficiency of the milling process, was determined using the
sedimentation method. As explained in our previous study [5],
the most dispersed solvent composition was determined for
-SiAlON system in three kinds of dispersant (oleic acid,
polyethyleneglicol, sodium tripolyphosphate). In the present
study polyvinylpyrrolidon was also investigated as an
alternative to the other three in the -SiAlON system. The
optimum solvent ratio was investigated in an ethanol:toluene
system of 70:30 vol. ratio with the highest sedimentation
height. The effect of the dispersant in the selected solvent
composition was investigated by addition of oleicacid, STPP
(sodium tripolyphosphate), PEG (polyethyleneglicol) and PVP
(polyvinylpyrrolidon) as dispersants (Figure 1).
Sediment height (mm)
130
125
120
115
110
105
100
95
0 0.5 1 1.5 2 2.5 3
PVP
(wt. %)
Time (h)
Figure 1. Effect of amount of (a) PVP on sedimentation height
According to the result, the binary solvent system of ethanol
and toluene (at a volume ratio 70:30) with 3 wt.% addition of
PVP shows the most dispersed behavior and is used as a
milling medium for milling studies. The first powder produced
by conventional method which has a powder:ball:alcohol ratio
of 1:1.5:2 and the other powder produced by high-energy
mechanical milling in wet medium at 450 rpm for different
times up to 40 hours. For the characterization of the particle
size of the milled powders, two different types of method were
used in this study. One of these is the dynamic light scattering
method, and the average particle size of the milled powders is
given in Fig. 2-3.The second method, BET, was used to
measure the surface area of the powders an the mean particle
size of (DRBETR). Comparison of the results of both methods
shows that even though the particle size of powders decrease
0.5
1.0
2.5
2.0
1.5
3.0
by increasing milling time, from sample C to N50. There was
observed differences in results. These differences can be
explained by the formation of agglomerates which are difficult
to deform, even using ultrasonic treatment in the dynamic light
scattering method. However, in the BET method the diffusion
of NR2R gas into agglomerates is possible, giving more realistic
results than the dynamic light scattering method.
Particle Size (nm)
700
600
500
400
300
200
100
0
Conventional
5
10
20
Time (h)
Figure 2. Particle size analyse of powder by dynamic light scattering
method
Particle Size (nm)
250
200
150
100
50
0
Conventional
5
10
20
Time (h)
Figure 3. Particle size analyse of powder by BET
As a consequence, the high energy milling in a wet medium
system is an effective way to produce nano- -SiAlON
starting powders. The most efficient milling medium for the
-SiAlON suspensions is investigated as 70 vol. % Ethanol-30
vol. % Toluen with the addition of 3 wt% PVP. The minimum
-SiAlON powder size was obtained as 92 nm after 50 h
milling in this medium.
This work was supported by TUBITAK under Grant No.
108T661.
*Corresponding author: skurama@anadolu.edu.tr
[1]. Bulic, F., Zalite, I., Zhilinska, N., 2004. Comparison of plasma-chemical
synthesised SiAlON nano-powder and conventional prepared SiAlON
powder, Journal of the European Ceramic Society, 24: 3303-3306.
[2]. Li, Q., Zhang, C., Komeya, K., Tatami, J., Meguro, T., Gao, L., 2003.
Nano powders of -SiAlON carbothermally produced via a sol-gel process,
Journal of Materials Science Letters, 22: 885-887.
[3]. Xu, X., Nishimura, T., Hirosaki, N., Xie, R., Yamamoto, Y., Tanaka, H.,
2005. Fabrication of -SiAlON nanoceramics by high-energy mechanical
milling and spark plasma sintering, Nanotechnology, 16 : 1569-1573.
[4] Eser, O. and Kurama, S., (2010). The effect of the wet-milling process on
sintering temperature and the amount of additive of SiAlON ceramics,
Ceramics International, doi:10.1016/j.ceramint.2009.12.025.
[5] Eser, O., Kurama, S. and Gunkaya, G., 2010. The production of -
SiAlON ceramics with low amount of additive, at low sintering temperature,
J. The European ceram. Soc,. doi: 10.1016/j.jeurceramsoc.2010.01.024.
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6th Nanoscience and Nanotechnology Conference, zmir, 2010 655