04aE22P
マイクロ波を利用したプラズマ合成シリカ微粒子の生成制御
Production and control of silica nano-powder by microwave inductive coupledplasma (MW-ICP)
八島一哉1, 唐 観揚1, 高橋和貴1, 安藤 晃1, 小駒益弘2, 竹田 篤3
YASHIMA Kazuya1, TANG Guanyang1, TAKAHASHI Kazunori1, ANDO Akira1,
KOGOMA Masuhiro2, TAKEDA Atsushi31

東北大院工、2上智大理工、3有限会社ＩＳＩ
1
Department of Electrical Engineering, Tohoku University,
2
Sophia University, Faculty of Science and Technology, 3ISI Ltd.
Silica nano-powder have attracted bothacademic and industrial interests for years becauseof their advantages of availability in variousapplication fields, such as cosmetics, catalyst
supports, biomaterials, and medicinal additives. The
characteristics of the nano-power depends on their
particle size and shape, which have to be controlled
for future various applications. Kogoma et al. hasproposed and developed a new silica nano-powder
production method using a microwave inductive
coupled plasma (MW-ICP) in an atmosphericpressure Ar-O2 mixture gas [1]. They produced
powder particles with the size of 50- 200nm by using
chlorotrimethylsilane(CTMS) vapor. We havechanged it to less harmful material and synthesis rateof the silica nano-powder is investigated withchanging the operation conditions.
Figure 1 shows the schematic of the MW-ICP
plasma reactor. A quartz tube (inner diameter :18mm) is inserted in the microwave cylindrical
TE011 cavity and cooled by fluorinert oil. Argon(Ar) gas is injected as whirl flow to stabilize theplasma and to cool the tube. Ar-O2 mixture carrier
gas is introduced into the tube via a 9-mm-diamquartz tube, where the argon flow rate is maintained
at 1.7 L/min and the oxygen flow rate is controlled
in the range of 0.1-0.3 L/min. 2.45 GHz microwave
is injected with the power up to 1.0 kW from thewaveguide connected to a microwave cavity. It is
designed so that the wave field has a maximum atthe discharge tube center. Then the plasma is
produced only inside the discharge tube due to thepresence of the strong wave field there.
Tetramethylorthosilicate (TMOS) is vaporized byusing a bubbling system and mixed with the Ar-O2
mixture carrier gas. TMOS is dissociated andoxidized immediately by the high temperatureplasma region according to the following reaction,Si(OCH 3 ) 4  6O2  SiO2  4CO2  6H 2O . (1)The silica nano-powder is synthesized downstream

TMOS+O2+Ar
Whirl flow gas(Ar)Coolant outquartz tube (9mmdiam)
Plasma is producednear the center of thecavity.

Wave guidedischarge tube(18mm diam)

Coolant inpowder

Fig. 1. Schematic diagram of the microwave cavity
plasma reactor.
of the plasma production region.
Synthesis rate is measured as a function of theoxygen flow rate, where the rate is defined as themass of the nano-powder normalized by the TMOSmass used for the synthesis. The maximum
synthesis rate of ~50 percent is obtained at the flowrate of ~0.25 L/min. The particle diameter andstructure are also investigated by using both ascanning electron microscope and a tunneling
electron microscope. These images suggest that thediameter distribution of the nano particles arepresently in the range of 20-50 nm. The detailed
results will be presented.
Reference[1] M. Kogoma, et al. :” Silica nano-powder
production by MW plasma using TE011 modecavity” proceedings of ISPC 20 (2012).