4. Material Science and Radiation Effects

概要

TITLE:

4. Material Science and Radiation
Effects

AUTHOR(S):

CITATION:

4. Material Science and Radiation Effects. KURNS Progress Report 2022,
2021: 110-136

ISSUE DATE:
2022-07

URL:
http://hdl.handle.net/2433/275847
RIGHT:

CO4-1

Characterization of Additive Aggregation in Lubricant using Small-Angle X-ray Scattering

Y. Oba, M. Hino1, R. Motokawa, N. Adachi2, Y. Todaka2,
R. Inoue1, and M. Sugiyama1
Materials Sciences Research Center, Japan Atomic Energy Agency
1
Institute for Integrated Radiation and Nuclear Science,
Kyoto University
2
Department of Mechanical Engineering, Graduate
School of Engineering, Toyohashi University of Technology
INTRODUCTION: In lubricants, nanostructures of
additives are closely related to their lubrication properties.
Although small-angle scattering is a promising means to
characterize such nanostructures [1,2], it is not commonly
used in the field of tribology. While small-angle neutron
scattering (SANS) has been conducted in those previous
studies, we have recently examined the application of
small-angle X-ray scattering (SAXS) to the characterization of the additives in the lubricants [3]. The results
show that SAXS is useful for the observation of the additives. While SANS can precisely analyze the nanostructures using contrast matching and variation techniques
with deuterated samples, SAXS can provide easy access
to experiments. However, a part of samples shows very
weak scattering. Therefore, in this study, denser samples
are measured to discuss the detail of the nanostructures of
the additives.
EXPERIMENTS: SAXS measurements were performed using the in-house SAXS instrument with Mo K
radiation. Scattering patterns were obtained using a
two-dimensional detector (PILATUS 100k) equipped
with a 1000 µm-thick silicon sensor. The path of X-ray
between the entrance slit and up to the detector including
the sample area was in vacuum to eliminate background
scattering from air and vacuum windows. Oleic acid
(OA) and oleyl acid phosphate (OLAP) were chosen as
the additive and poly--olefin (PAO) as base oil. In our
previous study, we measured 5 mass% OA and 1 mass%
OLAP dispersed in PAO [3]. In the current study, 20
mass% OA and 10 mass% OLAP in PAO were measured.
The samples were sealed in sample cells with the optical
path length of 10 mm. Two samples-to-detector distances
(SDD), 0.4 and 1.8 m, were used to cover wide q range,
where q is the magnitude of the scattering vector. The
measurement times are 1 hour and 5 hours for 0.4 m and
1.8 m conditions, respectively.
RESULTS: Fig. 1 shows the SAXS profiles of 20
mass% OA in PAO, 10 mass% OLAP in PAO, and pure
PAO. Based on our previous report [3], a peak at around
q = 4.5 nm-1 reflects the nanostructures in PAO. Both OA
and OLAP show additional scattering compared to PAO.
Therefore, we successfully observe the nanostructures of
these additives using SAXS. Compared to our previous

Intensity (arb. unit)

2

10

-1
8
7
6
5
4
3
2

10

10% oleyl acid phosphate
20% oleic acid
PAO

-2

10

-1

0

10

1

-1

10

q (nm )

Fig. 1. SAXS profiles of 20 mass% OA in PAO, 10
mass% OLAP in PAO, and pure PAO. Open and
filled symbols indicate the profiles obtained using
SDD = 1.8 and 0.4 m, respectively.
study, OA indicates significant scattering. This is attributed to the denser concentration of 20 mass%. In the q
range higher than 3.4 nm-1, the scattering intensity of
PAO exceeds that of 20 mass OA in PAO. This is probably due to the partial specific volume of OA.
Fig. 1 also shows that the SAXS profile of 10 mass%
OLAP has a significant shoulder in the q range lower
than about 2.5 nm-1. This feature corresponds to the gyration radius of about 0.7–0.8 nm and larger than the size of
a single OLAP molecule [4]. Hence, OLAP probably
forms aggregate in PAO.
These result will promote further development of advanced lubricants in conjunction with the nanostructural
characterization by SAXS.
ACKNOWLEDGMENTS: A part of this work was
supported by JST "Collaborative Research Based on Industrial Demand" Grand Number JPMJSK1511, Japan.
REFERENCES:
[1] M. J. Covitch et al., Adv. Chem. Eng. Sci., 5 (2015)
134-151.
[2] M. T. Savoji et al., Ind. Eng. Chem. Res., 57 (2018)
1840-1850.
[3] Y. Oba et al., KURNS Progress report 2019, (2020)
148.
[4] Y. Oba et al., Chem. Lett. 49, (2020) 823.

R2017
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CO4-2

Radiation Tolerance of SiC p+n Junction-Diodes for Beam Monitor Applications

T. Kishishita, M. Hagiwara1, M. M. Tanaka, H. Yashima2,
R. Kosugi3
High Energy Accelerator Research Organization, KEK
1
National Institutes for Quantum Science and Technology
2
Institute for Integrated Radiation and Nuclear Science,
Kyoto University
3
National Institute of Advanced Industrial Science and
Technology
INTRODUCTION: Silicon carbide (SiC) has been
considered as a potential alternative to Si for the manufacture of dosimeters, spectrometers, and charge particle
detectors in high energy physics experiments, by virtue of
its operation capability in strong radiation and/or
high-temperature environments. To take advantage of
such properties for future radiation detectors with a comparable size of silicon, we firstly investigated the influence of the bulk defects on the radiation sensor characteristics, by irradiating neutrons at Institute for Integrated
Radiation and Nuclear Science, Kyoto University.
EXPERIMENTS: The reverse blocking characteristics
is a primary concern of the radiation effects. The radiation-induced effects are generally divided into bulk and
surface defects. The formers are caused by the displacement of crystal atoms, introducing to the increase of the
leakage current and degraded reverse blocking characteristics. The latter include all effects in the covering dielectrics and the interface region. Since the bulk damage
caused by the elastic nuclear scattering of the lattice nuclei has a profound effect in our device, we irradiated
neutrons to pixelized diodes under unbiased conditions.
The irradiation test was conducted by putting the samples
at the Kyoto University nuclear reactor core. After disassembling of the samples, we carried out measurements of
the leakage current and compared with those of the
pre-irradiation samples.
RESULTS: The typical I-V characteristics before irradiation are shown in Figure 1. The leakage current shows
a device-to-device dependence and are distributed between 1~8 nA at a reverse bias of 1 kV (corresponding to
leakage current density of 10~83 nA/cm2). The fundamental reason of the distribution is beyond comprehension, however, the bulk defects in the crystal are the natural interpretation. Figure 2 shows the typical leakage
currents after irradiation. Compared with Fig. 1, the bulk
leakage current in reverse bias is not increased after neutron irradiation of 1.63 x 1013 neq/cm2 fluence, except the
pixel-to-pixel dependence and data fluctuation due to the
different sampling time settings. The reverse blocking
property was also retained up to 3 kV. Irradiation tests at
higher fluences are severe with the current device struc-

ture due to the radioactivation of the metals. We note that
the 1 MeV neutrons have the same efficiency in the detector degradation as 24 GeV protons at a comparable
neutron equivalent fluence. The theoretical nonionizing
energy loss (NIEL) calculation performed on SiC can be
found in Lee et al. [1]. The primary radiation defects
produced by single particles (protons and pions) or gamma-rays were not evaluated in this measurement, however, the number of primary defects is reported as low as
that of diamond. Thus, we conclude that the bulk defects
introduced by irradiation at the 1013 neutron equivalent
fluence is ignorable, in agreement with the previous
studies on neutron-irradiated pn devices [2, 3].

Fig. 1. Typical reverse blocking characteristics of
the fabricated pixel diodes.

Fig. 2. Typical reverse blocking characteristics after
1 MeV neutron irradiation of 1.63 x 1013 neq/cm2.
REFERENCES:
[1] K. K. Lee et al., Nucl. Instrum. Methods Phys. Res. B,
vol.210, pp.489-494, 2003.
[2] F. Moscatelli et al., IEEE Trans. Nucl. Sci., vol.53,
pp.1557--1563, 2006.
[3] J. M. Rafi et al, IEEE Trans. Nucl. Sci., vol.67,
pp.2481--2489, 2020.

R2102
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TDPAC Spectra of the 111Cd(←111mCd) and 117In(←117Cd) Probes in CdIn2O4

W. Sato, S. Komatsuda1, A. Taniguchi2, M. Tanigaki2, and
Y. Ohkubo2
Institute of Science and Engineering, Kanazawa
University
1
Institute of Human and Social Sciences, Kanazawa
University
2
Institute for Integrated Radiation and Nuclear Science,
Kyoto University
INTRODUCTION: Ternary spinel oxides exhibit
various physical properties depending on the constituent
metal elements and on their distribution between the
tetrahedral A site and octahedral B site. Among various
metal elements, it is known that Cd2+ is likely to occupy
the A site forming normal spinel with divalent ions and
trivalent ions on the A and B sites, respectively. In our
recent time-differential perturbed angular correlation
(TDPAC) experiments on Cd spinel compounds such as
CdFe2O4 and CdIn2O4, we noticed unexpected
phenomenon that the directional anisotropy of the
cascade γ rays emitted from the 111Cd(←111mCd) probe
shows exponential-like relaxation as if the nuclear spin
would experience dynamic perturbation from the
extranuclear field [1,2]. If the attenuation of the
anisotropy arises from dynamic perturbation, we can
expect temperature dependence of the relaxation constant
λ as in the following expression of the time-differential
perturbation factor G22(t) as a function of the time
interval t between the cascade γ-ray emission:

RESULTS: The TDPAC spectra of 111Cd(←111mCd) and
117
In(←117Cd) in CdIn2O4 are shown in Fig. 1. The
spectrum of 111Cd(←111mCd) (Fig. 1(a)) exhibits a
relaxing trend in the directional anisotropy, which is
similar to the spectra observed at room temperature and
77 K [1]. However, the relaxation time seems a little
longer for the present spectrum. ...

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