• Journal of Radiation Protection and Research
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• v.39 no.4
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• pp.199-205
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• 2014

In the field of neutron detections, $^3He$ gas, the so-called "the gold standard," is the most widely used material for neutron detections because of its high efficiency in neutron capturing. However, from variable causes since early 2009, $^3He$ is being depleted, which has maintained an upward pressure on its cost. For this reason, the demands for $^3He$ replacements are rising sharply. Research into neutron converting materials, which has not been used well due to a neutron detection efficiency lower than the efficiency of $^3He$, although it can be chosen for use in a neutron detector, has been highlighted again. $^{10}B$, which is one of the $^3He$ replacements, such as $BF_3$, $^6Li$, $^{10}B$, $Gd_2O_2S$, is being researched by various detector development groups owing to a number of advantages such as easy gamma-ray discrimination, non-toxicity, low cost, etc. One of the possible techniques for the detection is an indirect neutron detection method measuring secondary radiation generated by interactions between neutrons and $^{10}B$. Because of the mean free path of alpha particle from interactions that are very short in a solid material, the thickness of $^{10}B$ should be thin. Therefore, to increase the neutron detection efficiency, it is important to make a $^{10}B$ thin film. In this study, we fabricated a $^{10}B$ thin film that is about 60 um in thickness for neutron detection using well-known technology for the manufacturing of a thin electrode for use in lithium ion batteries. In addition, by performing simple physical tests on the conductivity, dispersion, adhesion, and flexibility, we confirmed that the physical characteristics of the fabricated $^{10}B$ thin film are good. Using the fabricated $^{10}B$ thin film, we made a proportional counter for neutron monitoring and measured the neutron pulse height spectrum at a neutron facility at KAERI. Furthermore, we calculated using the Monte Carlo simulation the change of neutron detection efficiency according to the number of thin film layers. In conclusion, we suggest a fabrication method of a $^{10}B$ thin film using the technology used in making a thin electrode of lithium ion batteries and made the $^{10}B$ thin film for neutron detection using suggested method.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.1-7
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• 1998

For the purpose of finding new cathode materials for medium-temperature $(700\~800^{\circ}C)$ solid oxide fuel cells, $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$ are prepared, and their thermal stability and conductivity characteristics are investigated. Also, the cathodic activities are measured after the cathode layer being attached on CGO (cerium-gadolinium oxide) electrolyte disk. The X-ray analyses indicate that the materials prepared by calcining the citrate-gels at $800^{\circ}C$ have the orthorhombic perovskite structure without discernible impurities. The thermal stability of the undoped Co perovskite is so poor that it is decomposed to the individual binary oxide even at $1300^{\circ}C$. But the partially Fe-doped cobaltates exhibit a better thermal stability to retain their structural integrity up to $1400^{\circ}C$. The observation whereby both the undoped and Fe-doped cobaltates melt at ca. $1300^{\circ}C$ leads us to perform the electrode adhesion at <$1300^{\circ}C$. The cathodic activity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$, electrodes is superior to $La_{0.9}Sr_{0.1}MnO_3$, among the samples of $x=0.0\~0.5$, the x=0.2 cathode shows the best activity for the oxygen reduction reaction. It is likely that the Fe-doping provides a better thermal stability to the materials but in turn imparts an inferior cathodic activity, such that the optimum trade-off is made at x=0.2 between the two factors. The total electrical conductivity and ion conductivity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3$, are measured to be 51 S/cm and $6.0\times10^{-4}S/cm\;at\;800^{\circ}C$, respectively. The conductivity values illustrate that the materials are a mixed conductor and the reaction sites can be expanded to the overall electrode surface, thereby providing a better cathodic activity than $La_{0.9}Sr_{0.1}MnO_3$.

• Korean Journal of Heritage: History & Science
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• v.53 no.2
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• pp.242-253
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• 2020

Six ornamental metal quiver fittings were excavated from stone chamber No.1 of the ancient tombs of Jeongchon, Bokam-ri, Naju. The ornamental quiver fittings are metal, but the body of the quiver was made of organic material, so that it corroded and disappeared in the burial environment. The ornamental metal quiver fittings were made in pairs, and decorated one quiver according to the location they were found in and their forms. The ornamental metal quiver fitting can be divided into two types: A band style ornament (帶輪狀金具) which decorates the arrow pouch, and a board style ornament (板狀金具) which decorates the board connecting the waist belt. Two ornamental metal quiver fittings excavated from wooden coffin 2 of stone chamber No.1, were made in the band style, while the ornamental metal quiver fittings from southeast of stone chamber No.1 were identified as two boardstyle ornaments and two band-style ornaments for what was presumed to be belt loops. Material analysis of the ornamental metal quiver fittings shows that they are made of a gilt bronze plate attached to an iron plate, and the surface is marked with a speck of chisel to make lines and patterns. Chemical composition analysis (XRF) established that 24~40wt% Au and 50~93wt% Cu were detected on the gold surface, and it was confirmed that bronze corrosion had taken place on the gilt surface. SEM-EDS analysis of the gold plating layer identified a working line for glossing, and 7~9wt% Hg and an amalgam of gilt layers was detected, confirming the amalgam gilding. CT and FT-IR analysis established that the band style was double-layered with silk fabric under the iron plate, and there was also a lacquer piece underneath. The band-style ornaments have two layers of silk under the iron plate, along with lacquer pieces. Adding the fabric to the arrow pouch increases adhesion and decorative value. It is assumed that the lacquer pieces indicate that the surface of the lacquered arrow pouch had fallen together with the ornaments. On the other hand, the board-style ornaments have a thick layer of organic matter under the iron plate, but this is difficult to identify and appears to be a remnant of the quiver board. The characteristics of these ornamental metal quiver fittings were similar in Baekje, Silla, and Gaya cultures from the late 4th to the late 5th centuries, and enable us to identify the art of ancient gold craftwork at that time.