• Journal of the Korean Magnetics Society
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• v.5 no.1
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• pp.64-70
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• 1995

The authors have studied crystallographic and magrletic properties of $NdFe_{10.7}TiM_{0.3}(M=B,\;Ti)$ by X-ray diffraction, VSM magnetometer, and Mossbauer spectrometer. The Alloys were prepared by arc-melting under argon atmosphere. The $NdFe_{10.7}TiM_{0.3}$ has pure single phase, whereas the $NdFe_{10.7}Ti_{1.3}$ contains some $\alpha-Fe$, from powder X-ray diffractometry. The $NdFe_{10.7}TiM_{0.3}$ has the $ThMn_{12}$-type tetragonal structure with $a_{0}=8.587\;{\AA}\;and\;c_{0}=4.788\;{\AA}$. The Curie temperature ($T_c$) is $570{\pm}3\;K$ from $M\"{o}ssbauer$ spectroscopy performed at various temperatures ranging from 13 to 770 K. Each spectrum of below $T_c$ was fitted with five subspectra of Fe sites in the structure ($8i_{1},\;8i_{2},\;8j_{1},\;8j_{2}\;and\;8f$). The area fraction of the subspectra at room temperature are 16.4, 8.2, 14.8, 21.3 and 39.3 %, respectively. Magenetic hyperfine fields for the Fe sites decrease in the order, $H_{hf}(8i)>H_{hf}(8j)>H_{hf}(8f)$.

• Journal of the Korean Magnetics Society
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• v.6 no.6
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• pp.361-366
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• 1996

$NdFe_{10.7}Ti_{1.3}$ has been studied with X-ray diffraction, Mossbauer spectroscopy and vibrating sample magnet-ometer(VSM). The alloys were prepared by arc-melting under an argon atmosphere. The $NdFe_{10.7}Ti_{1.3}$ contains some $\alpha-Fe$, from X-ray and Mossbauer measurements. The $NdFe_{10.7}Ti_{1.3}$ has the $ThMn_{12}$-type tetragonal struc-ture with $a_{0}=8.607{\AA}\;and\;c_{0}=4.790{\AA}$. The Curie temperature ($T_c$) of the $NdFe_{10.7}Ti_{1.3}$ is 590 K from $M\"{o}ssbauer$ spectroscopy performed at various temperatures ranging from 13 to 800 K. Each spectrum below $T_c$ was fitted with six subspectra of Fe sites in the structure$(8i_{1},\;8i_{2},\;8j_{2},\;8j_{1},\;8f\;and\;{\alpha}-Fe)$. The area fractions of the subspectra at room temperature are 13.8%, 15.4%, 17%, 16.4%, 34.1% and 3.3%, respectively. Magenetic hyperfine fields for the Fe sites decrease in the order, $H_{hf}(8i)>H_{hf}(8j)>H_{hf}(8f)$. The abrupt changes in the magnetic hyperfine field, isomer shift and magnetic moment observed at about 180 K in $NdFe_{10.7}Ti_{1.3}$ are attributed to spin reorientation.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.108-116
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• 1991

In the non-linear behavior of many materials, there is difference between the monotonic behavior by static load and the cyclic behavior by cyclic load. In particular, the short fatigue cracks to propagate in elasto-plastic stress concentrations(notches), are governed significantly by the cyclic behavior of materials. Accordingly, it is needed to investigate and compare the monotonic and cyclic behavior of materials. In the pressent study, the stress-strain relations of materials by monotonic and cyclic load tests were examined for 2 kinds of steels(SS41, HT80) and 5 kinds of Al-alloys(A5083-O, A6N01-T5, A7N01-T4, A7016-T6, A7178-T6). And the constants for mechanical properties of the materials were determined by experimental results, Moreover, when a notch was subjected to cyclic load, the effect of cyclic hardening property of materials on the variation of stress-strain amplitude in the notch tip was discussed by the application of Neuber's rule and experiments for a center notched plate.

• Journal of the Korean Magnetics Society
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• v.10 no.6
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• pp.269-273
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• 2000

Fe-l7Cr-2M(M=Si, Nb, Mo) alloy powder was prepared by plasma electrode rotating atomizer and than the alloy powder was formed and sintered. The particle shape of the Fe-l7Cr-2M(M=Si, Nb, Mo) alloy power is spherical. The saturation magnetization of the sintered Fe-17Cr-2Mo and Fe-l7Cr-2Nb alloy are 155 emu/g. The saturation magnetization of the sintered Fe-l7Cr-2Si alloy is less than that of the sintered Fe-l7Cr-2Mo and Fe-l7Cr-2Nb alloy. The amplitude relative permeability of the sintered Fe-l7Cr-2M(M=Si, Nb, Mo) alloy has the maximum value in the range of 3∼5 Oe applied field at forming pressure 12 ton/cm$^2$, sintering temperature 1200$^{\circ}C$, and frequency 1 kHz. Power loss of the sintered Fe-l7Cr-2Nb alloy is 40 mW/cc at applied field, H$\sub$a/=5 Oe, and frequency, f=1 kHz. The power loss of the sintered Fe-l7Cr-2Nb alloy is a half of that of the sintered Fe-l7Cr-2Si and Fe-l7Cr-2Mo alloy.

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.408-412
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• 1998

Thermoelectric properties of Bi$_{2}$(Te$_{1-x}$Se$_{ x}$)$_{3}$(0.05$\leq$x$\leq$0.25) prepared by mechanical alloying and hot pressing, were investigated. Contrary to the p-type behavior of single crystals, the hot-pressed Bi$_{2}$(Te$_{1-x}$Se$_{ x}$)$_{3}$ exhibited ntype conduction without addition of donor dopant. When $Bi_2(Te_{0.85}Se_{0.15})_3$powders were annealed in (50% $H_2$ + 50% Ar) atmosphere, the hot-pressed specimen exhibited a positive Seebeck coefficient due to the reduction of the electron concentration by removal of the oxide layer on the powder surface and annealing-out of the excess Te vacancies. Among the Bi$_{2}$(Te$_{1-x}$Se$_{ x}$)$_{3}$fabricated by mechanical alloying and hot pressing, $Bi_2(Te_{0.85}Se_{0.15})_3$ exhibited a maximum figure-of-merit of 1.92 $\times$ $lO^{-3}$/K.

• Journal of Conservation Science
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• v.27 no.1
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• pp.1-11
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• 2011

For the silver artifacts in the Koryo Dynasty excavated from Neungnae-ri Ganghwa island, the metallographic section analysis and hardness and chemical analysis were conducted. After making samples in the similar ratio of the composition concentration, the changes of the microstructure were checked according to the working method and temperature. The results show that those silver artifacts are Au-Cu alloys with 2 to 6 % of Cu. From the results it is judged that Cu was artificially alloyed with them to keep the proper hardness and identified that they were gilded by the amalgamation process seeing that mercury was included at the guilt layer. Also the porous texture on the surface of them could be formed at over $400^{\circ}C$, therefore, it is assumed the hot working or heat treatment at over $400^{\circ}C$ were performed. In silver artifacts made by the relief and repousse, they have the similar composition analysis to other 7 artifacts but the hardness is lower than pure silver. Consequently from differences in the hardness, it can be inferred that the low hardness of silver artifacts is concerned with manufacturing techniques.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.4
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• pp.239-244
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• 2004

In order to enhance an oxidation resistance of the pure uranium metal under air condition, a small quantity of niobium(Nb) which is known to mitigate metal oxidation is added into uranium metal as an alloying element. A simulated metallic uranium alloy, U-Nb has been fabricated and then oxidized in the range of 200 to $300^{\circ}C$ under the environment of the pure oxygen gas. The oxidized quantity in terms of the weight gain(wt%) has been measured with the help of a thermogravimetric analyzer. The results show that the oxidation resistance of the U-Nb alloy is considerably enhanced in comparison with that of the pure uranium metal. It is revealed that the oxidation resistance of the former with the niobium content of 1, 2, 3, and 4 wt% is : 1) 1.61, 7.78, 11.76 and 20.14 times at the temperature of $200^{\circ}C$ ; 2) 1.45, 5.98, 10.08 and 11.15 times at $250^{\circ}C$ ; and 3) 1.33, 4.82, 8.87 and 6.84 times at $300^{\circ}C$ higher than that of the latter, respectively. Besides, it is shown that the activation energy attributable to the oxidation is 17.13~21.92 kcal/mol.

• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.153-160
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• 1984

The purpose of this study was to observe the tensile and bonding strength of the joined amalgam restoration. Amalgam alloys of fine-cut (F-type), spherical (S-type), and dispersed type (D-type) were selected in this study, and all specimens were divided into three groups according to the condensation methods as follows. Group I : the control group which condense the same kinds of mixed amalgam into the whole part of the mold respectively. Group II : the group which condense a mix of amalgam into one half of the mold, and then condense a new mix of amalgam into the rest half of the mold 15 minutes later. Group III : the group which condense a mixed amalgam into one half of the mold, and then condense a new mix of amalgam into the rest half of the mold 7 days later. All specimens were stored in incubator at $37{\pm}1^{\circ}C$ for seven days with immersing in saline solution before testing. The tensile and bonding strength of them were measured with Instron Universal Testing machine. The results were as follows: 1. In Group I, the order of tensile strength was F-type, S-type, and D-type. 2. In case of bonding of S-type + S-type, the difference of the bonding strength between Group II and III was not significant. (P> 0.05) 3. The bonding strength of F-type + S-type of Group II was marked the highest in value, and the lowest bonding strength was showed in bonded D-type + D-type of Group III. 4. In case of bonding with the different kinds of amalgam alloy in Group II, the specimen bonded to F-type was marked the highest bonding strength, and the specimen bonded with F-type was marked the lowest one. In Group II, the bonding strength of the specimens bonded with the same kinds of amalgam alloy was presented as the same order as that of Group I. 5. In Group III, the specimen connected with D-type marked the lowest bonding strength of all specimens. In Group III, the bonding strength of the specimens connected with the same kinds of amalgam alloy was the order of S-type + S-type, F-type + F-type, and D-type + D-type.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.43-47
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• 2001

Sn-3Ag-8Bi-5In was developed for the intermediate melting point solder. Although In-contained solder is expensive, its melting point is lower than these of Sn-Ag-Cu alloys. Sn-3Ag-8Bi-5In solder used for this research has a melting range of 188~$204^{\circ}C$. On this study wetting characteristics of Sn-3Ag-8Bi-5In were evaluated in order to investigate its availability as a Pb-free solder. Wettabilities of Sn-37Pb and Sn-3.5Ag solders were also studied to compare these of the Sn-3Ag-8Bi-5In. Experimental results showed that the zero-cross-time and wetting time at $240^{\circ}C$ for the Sn-3Ag-8Bi-5In were 1.1 and 2.2 second respectively. These values are a little better than these of Sn-37Pb and Sn-3.5Ag solders. The equilibrium wetting farce of the Sn-3Ag-8Bi-5In was 5.8 mN at $240^{\circ}C$, and it was tuned out to be a little higher than that of Sn-3.5Ag and lower than that of Sn-37Pb.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.4
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• pp.135-139
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• 2015

$Bi_2Te_3-Bi_2Se_3$ alloy which is typical n-type thermoelectric material were grown by traveling heater method (THM) technique. We investigate the effect of the composition of $100-x(Bi_2Te_3)-x(Bi_2Se_3)$ and doping of n-type dopants such as $SbI_3$ and $CdCl_2$. Maximum figure of merit of $Bi_2Te_3-Bi_2Se_3$ alloy was observed with $CdCl_2$ 0.1 wt% (Z: $2.73{\times}10^{-3}/K$) and $SbI_3$ 0.05 wt% (Z: $2.29{\times}10^{-3}/K$). Deviation along the length of $Bi_2Te_3-Bi_2Se_3$ ingot grown by THM method is low, which indicates that the ingot is very homogenized. Also we observed the close relationship of between anisotropy ratio and dopant in the $90(Bi_2Te_3)-10(Bi_2Se_3)$ alloys. And we confirmed the fact that anisotropy ratio exerts thermoelectric performance in $Bi_2Te_3$ based n-type thermoelectric material.