APPLIED PHYSICS LETTERS
VOLUME 80, NUMBER 13
1 APRIL 2002
Intense sonoimplantation of atoms from gases into metals
Yoshiaki Arata and Yue-Chang Zhang
Cooperation Research Center for Science and Technology, Osaka University, 11-1 Mihogaoka, Ibaraki,
Osaka 567-0047, Japan
共Received 6 August 2001; accepted for publication 4 February 2002兲
It was found that various gaseous atoms can be easily implanted into metal powders under ultrasonic
cavitation inside a vessel with water 共H2 O,D2 O or a mixture thereof兲. Inert gases 共3 He, 4He, Ne,
and Ar兲 and others 共N2 , air, H2 , and D2 兲 were strongly sonoimplanted into metals such as Ti, Fe,
Ni, Cu, Zr, Pd, Ag, Ta, Pt, and Au, which were originally set in the vessel as foils, and were broken
into ultrafine metal powders during intense ultrasonic processing. A large amount of implanted
atoms was verified to exist in these powders from mass spectroscopic analyses. © 2002 American
Institute of Physics. 关DOI: 10.1063/1.1465110兴
In recent years, sonoluminescence from imploding
bubbles formed by the irradiation of ultrasonic waves in liquid has been discovered and studied extensively.1– 4 This peculiar phenomenon is understood in terms of the appearance
of a localized ultrahigh energy density zone in sono-induced
bubbles within a very short period, and the sonodissociation
of gas molecules associated with it has also been studied.5–9
We have recently reported10,11 a phenomenon concerned with
the sonodissociation of H2 O or D2 O in the presence of metallic foils such as Pd, Ag, Ta, Pt, and Au. In this process,
hydrogenated/deuterated metallic fine powders 共hereafter
called ‘‘sono powders’’兲 were produced when the metals kept
in H2 O, D2 O, and a mixture thereof 共called the ‘‘working
liquid’’兲 were irradiated by ultrasonic waves. Mass analyses
of the remaining sono powders revealed substantial amounts
of sono-implanted hydrogen and deuterium, and it was also
found that the D implantation in D2 O was much stronger
than the H implantation in H2 O. This provided a method of
‘‘sonoimplantation’’ of hydrogen and deuterium into metals.
In this letter, we report an effect of sonoimplantation for
other gases, in which not only D and/or H atoms dissociated
from the D2 O and/or H2 O working liquid, but also atoms of
all gases supplied 共‘‘working gases’’兲 filled inside a sonovessel were strongly implanted into metals by ultrasonic irradiation.
Figure 1 shows a schematic diagram of experimental apparatus used.11 We applied ultrasonic waves inside an enclosed vessel 共‘‘working space’’兲 in which the working liquid
共H2 O,D2 O, or a mixture of the two兲 and metallic foils were
placed. After being evacuated the working space was filled
with working liquid and working gases of inert gases 共3 He,
4
He, Ne, and Ar兲 or molecular ones 共N2 , air, H2 , and D2 兲 up
to about 200 kPa. Various rectangular metallic foils 共Ti, Fe,
Ni, Cu, Zr, Pd, Ag, Ta, Pt, and Au兲 1 – 2 mm⫻1 – 2 mm
⫻0.1 mm in size were initially placed in the bottom of the
vessel. An ultrasonic wave of about 300 W was applied using
a sono generator of 19 kHz. The foils were gradually broken
up into small pieces and finally became fine powders 共sono
powders兲 whose minimum size was a few nanometers in diameter after 20 h irradiation. The sono powders were then
enclosed in a high-vacuum chamber for mass analyses. Hereafter we designate the combination of metal foil X in a work-
ing liquid of H2 O, D2 O, and the mixture of the two with
working gas Y as X 关 H2 O兴 (Y ), X 关 D2 O兴 (Y ), and X 关 MIX兴
⫻(Y ), respectively. When 共Y兲 is indicated as 共no gas兲, for
instance, X 关 H2 O兴 共no gas兲, it means that the sono vessel is
filled with only working liquid and no working gas. Furthermore, X 关 Virgin兴 indicates an X foil immersed 20 h in the
working liquid without ultrasonic irradiation.
The mass analyses for gases released from sono powders
were performed using a quadrupole mass spectrometer
共QMS兲 system. A sample of about 20 mg was mounted into a
small Ta crucible and the system, with a total volume about 5
L, was kept at high vacuum of 10⫺7 Pa. The main pump was
closed after evacuation for about 6 h but the getter pump
kept operating. Then the sample was heated and the gases
released were analyzed.
Figure 2 shows a typical example of the spectrum intensity of gases 共mass: M 2, M 3, M 4, M 20, M 22, M 40兲 released from the Pd sono powder samples which were heated
to about 1300 °C in the cases of Pd关 H2 O兴 (Y ), Pd关 D2 O兴
⫻(Y ), and Pd关 MIX兴 (Y ), where Y ⫽ 3 He, 4He, Ne, and Ar,
respectively. The vertical spectrum intensity of 10⫺11 A in
the 4He case corresponds roughly to 3⫻1011 atoms enclosed
in the QMS chamber. We can see in Fig. 2 that most of
the gases gradually decay as time elapses due to Ti getter
pump action, except the inert gas which was supplied as a
FIG. 1. Schematic of the ultrasonic vessel used for the experiment.
0003-6951/2002/80(13)/2416/3/$19.00
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© 2002 American Institute of Physics
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Appl. Phys. Lett., Vol. 80, No. 13, 1 April 2002
Y. Arata and Y.-C. Zhang
2417
FIG. 2. 共Color兲 Effect of sonoimplantation of inert working gases demonstrated by the QMS spectrum intensity.
working gas. Among various mass species M 2 (⫽H2 ,D),
M 3 (⫽HD, H3 , 3He), M 4 (⫽D2 , H2 D, 4He), M 20
(⫽D2 O, 20Ne), M 22 (⫽D2 18O, 22Ne), and M 40 (⫽ 40Ar,
C3 H2 D, C3 D2 , C3 H4 ), only those of inert gases keep a constant intensity as is seen at M 3⫽ 3 He in Fig. 3共a兲, M 4
⫽4He 关Fig. 3共b兲兴, M 20⫽ 20Ne and M 22⫽ 22Ne 关Fig. 3共c兲兴,
and M 40⫽ 40Ar 关Fig. 3共d兲兴, respectively. All other molecular
species decay over a short time span by the Ti gettering
action described already.
Figure 3 shows bar graphs of the spectrum intensities of
M 3, M 4, M 20, M 22, and M 40 at the end of heating of the
sono powders in Figs. 2共a兲–2共d兲, respectively. In this diagram, the white bars indicate the intensity of 3He, 4He, 20Ne,
22
Ne, and 40Ar which were used as working inert gases. It is
remarkable that Ne atoms were implanted from natural Ne
working gas into metals with a ratio of 20Ne: 22Ne⯝10:1
which is the natural abundance ratio in the atmospheric pressure environment. For Ar gas the ratio also indicates a similar tendency of 40Ar: 36Ar⯝250:1. The blue bars in Fig. 3
indicate the implanted intensities without working gases, i.e.,
the working space inside the sono vessel was filled with the
working liquid only. For instance, when only a
D2 O–working liquid was used without working gas, i.e., at
the Pd关 D2 O兴 共no gas兲 condition, the sono powders were implanted mostly by D atoms dissociated from the working
liquid 共D implantation兲. H implantation can also occur by
using only H2 O–liquid, i.e., at Pd关 H2 O兴 共no gas兲. As a result, when inert gases were used as working gases, these
gases were strongly implanted into sono powders independent of the applied working liquid species.
We furthermore found that similar sonoimplantation occurred even in various molecular gases. Figure 4 is a typical
example that shows the sonoimplantation effect in the case
of N2 working gas, in which the intensities of both the white
bars, Pd关 H2 O兴 (N2 ), and blue bars, Pd关 H2 O兴 共no gas兲, are
compared. In this case most of the sono-implanted nitrogen
atoms released by heating the sono powders of Pd关 H2 O兴
⫻(N2 ) changed to various nitrides inside the QMS chamber,
and they were distributed in many mass species 共, . . . , M 18,
M 19, M20, . . . , M 30, . . . ,兲 as indicated by the white bars
data. On the contrary, the blue bars indicate that various hy-
FIG. 3. 共Color兲 Comparison of the effect of sonoimplantation between inert
working gases 共white bars兲 and no working gases 共blue bars, using only the
FIG. 4. 共Color兲 Comparison of the effect of sonoimplantation between N2
working liquid兲.
working gas 共white bars兲 and no working gas 共blue bars兲.
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Appl. Phys. Lett., Vol. 80, No. 13, 1 April 2002
drides are distributed in the same masses in hydrogenated
sono powders produced in Pd关 H2 O兴 共no gas兲 without nitrogen. Apparently, more nitrogen atoms were implanted into
powders when N2 working gas was used. Similar events
were confirmed in other sono powders of Ti, Fe, Ni, Cu, Zr,
Ag, Ta, Pt, and Au using various working gases of N2 , air,
D2 , H2 and working liquids of D2 O, H2 O, and a mixture of
the two.
In conclusion, we have demonstrated that a large amount
of various atoms can be sono implanted from working gasses
into metallic powders under ultrasonic irradiation of metal
foils together with water as the working liquid. Whereas it
has so far been believed that atoms cannot easily penetrate
into metals unless they are accelerated, the present method,
‘‘sonoimplantation of atoms into metal powders,’’ was used
to provide a powerful way in which to achieve abundant
implantation of atoms into metals.
Part of this work was supported by a research grant from
the Japan Society for the Promotion of Science 共JSPS兲. The
authors would like to thank Dr. K. Sugimoto and Dr. T.
Y. Arata and Y.-C. Zhang
Yamazaki, Professors Emeritus at the University of Tokyo,
Dr. H. Fujita, Professor Emeritus at Osaka University, and
Professor T. Yokobori, M.J.A. for their strong interest and
kind discussions on this research. They also thank Dr. S.
Miyake, Professor, Osaka University, and Dr. M. Futamata,
Professor, Kitami Institute of Technology, for their interest in
this research.
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