• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.298-303
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• 2011

Mg-23.5 wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment from a Mg-23.5 wt%Ni-5 wt%Cu alloy synthesized by the gravity casting method. They were then ground under $H_2$ to obtain a fine powder. Among these samples the Mg-23.5Ni-2.5Cu sample had the highest hydriding and dehydriding rates after activation. The Mg-23.5Ni-2.5Cu sample absorbed 3.59 and 4.01 wt%H for 10 and 60 min, respectively, at 573K under 12 bar $H_{2}$. The activated 88(87.5Mg-10Ni-2.5Cu)-$5Nb_{2}O_{5}-7NbF_{5}$ sample absorbed 2.93 wt%H for 10 min, and 3.14 wt%H for 60 min at 573K under 12 bar $H_{2}$.

• The Journal of Korean Academy of Prosthodontics
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• v.18 no.1
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• pp.49-57
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• 1980

The adhesive mechanisms on the metal-ceramic restorations have been reported to be mechanical interlocking, chemical bonding, compressive force, and Van der Waal's force, etc. Of these, the mechanical interlocking and chemical bonding forces are thought to affect the adhesive force between Ni-Cr alloy and porcelain. This study investigates the adhesion of Ni-Cr alloy to porcelain according to surface treatment. For this purpose, the following experiments were made; The compositions of Ni-Cr alloy as cast by emission spectrograph, and the oxides produced on Ni-Cr alloy during degassing at $1850^{\circ}F$ for 30 minutes in air and in vacuum were analyzed by X-ray diffractograph. The metal phases of Ni-Cr alloy were observed according to porcelain-baking cyclic heat treatment by photo microscope and the distribution and the shift of elements of Ni-Cr alloy and porcelain and the failure phases between Ni-Cr alloy and porcelain by scanning electron microscope. The adhesive force between Ni-Cr alloy and porcelain was measured according to surface treatment with oxidization and roughening by Instron Universal Testing Machine. Results were as follows; 1. The metal phases of Ni-Cr alloy as cast and degassing state showed the enlarged and fused core, but when subjected to porcelain-baking cyclic heat treatment, showed a dendrite growing. 2. The kinds of metal oxides produced on Ni-Cr alloy during degassing were found to be NiO and $Cr_2O_3$. 3. The distribution of elements at the interface of Ni-Cr alloy and porcelain in degassing state showed demarcation line, but in roughening state, showed mechanical interlocking phase. 4. The shift of elements at the interface occurred in both states, but the shift amount was found to be larger in roughening than in degassing. 5. The adhesive force between Ni-Cr alloy and porcelain was found to be $3.45{\pm}0.93kg/mm^2$, in degassing and $3.82{\pm}0.99kg/mm^2$, in roughening. 6. The failure phase between Ni-Cr alloy and porcelain showed the mixed type failure.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.322-329
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• 2007

The interaction of oxygen with the ordered $Ni_3Al(111)$ alloy surface at 800 K and 1000 K has been investigated using LEED, STM, HREELS, UPS, and PAX. The clean $Ni_3Al(111)$ surface exhibits a "$2{\times}2$" LEED pattern corresponding to the ordered bulk-like terminated surface structure. For an adsorption of oxygen at 800 K, LEED shows an unrelated oxygen induced superstructure with a lattice spacing of $2.93\;{\AA}$ in addition to the ($1{\times}1$) substrate spots. The combined HREELS and the UPS data point to an oxygen chemisorption on threefold aluminum sites while PAX confirms an islands growth of the overlayer. Since such sites are not available on the $Ni_3Al(111)$ surface, we conclude the buildup of an oxygen covered aluminum overlayer. During oxygen exposure at 1000 K, however, we observe the growth of ${\gamma}'-Al_2O_3$ structure on the reordered $Ni_3Al(111)$ substrate surface. This structure has been identified by means of HREELS and STM. The HREELS data will show that at 800 K the oxidation shows a very characteristic behavior that cannot be described by the formation of an $Al_2O_3$ overlayer. Moreover, the STM image shows a "Strawberry" structure due to the oxide islands formation at 1000 K. Conclusively, from the oxygen interaction with $Ni_3Al(111)$ alloy surface at 800 K and 1000 K an islands growth of the aluminum oxide overlayer has been found.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.407-411
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• 2022

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1080-1086
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• 2003

Effects of E$_2$O$_3$. HO$_2$O$_3$ and Dy$_2$O$_3$ addition on dielectric properties of non-reducible BaTiO$_3$ based X7R dielectrics with Ni electrode have been studied in a reduced atmosphere. As the content of rare-earth with E$_2$O$_3$. HO$_2$O$_3$, Dy$_2$O$_3$ was less than 3wt%, The TCC(Temperature Capacitance Change) and insulation resistance characteristics were improved by compensate the oxygen vacancies due to occupy either the Ba or Ti site. We developed the composition of X7R (EIA standard) for higher capacitance MLCC which had high reliability electric properties by the addition of Er ion into BaTiO$_3$ + MgO + Y2O$_3$ + MnO + (Ba$\sub$0.4/Ca$\sub$0.6/)SiO$_3$ composition.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.291-296
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• 1999

The immobilization of APTMS(3-(2-aminoethylamino)propyltrimethoxysilane) and AAPTMS(3-(2-(2-aminoethyl)aminoethylanino)propyltrimethoxysilane) on the surface of high quality mesoporous molecular sieves MCM-41 and MCM-48 have been confirmed by F.T.-IR spectroscopy, Raman spectroscopy, 29Si solid state NMR, and a surface polarity measurement using Reichardt's dye. The formation of metal (Co(Ⅱ), Ni(Ⅱ), and Cu(Ⅱ)) complexes by immobilized aminosilanes have been investigated by photoacoustic spectroscopy(PAS). The assignment of UV-Vis. PAS bands makes it possible to identify the structure of metal complexes within mesoporous molecular sieves. Co(Ⅱ) ion may be coordinated mainly in a tetrahedral symmetry by two APTMS onto MCM-41, and in an octahedral one by two AAPTMS. Both Ni(Ⅱ) and Cu(Ⅱ) coordinated by aminosilanes within MCM-41 form possibly the octahedral complexes such as [Ni(APTMS)2(H20)2]2+, [Ni(AAPTMS)2]2+, [Cu(APTMS)2(H2O)2]2+, and [Cu(AAPTMS)(H2O)3]2+, respectively. The PAS band shapes of complexes onto MCM-48 are similar to those of corresponding MCM-41 with the variation of PAS intensity. Most of metal ion(Ⅱ) within MCM-41 and MCM-48 are coordinated by aminosilanes without the impregnation on the surface.

• Journal of Surface Science and Engineering
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• v.51 no.2
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• pp.104-109
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• 2018

Fe-2 wt.%Ni alloys were fabricated by metal powder injection molding, and their oxidation behavior at $600-700^{\circ}C$ for 30 h in air was studied in order to find the effect of the small addition of Ni in the iron matrix on the high-temperature oxidation. Oxide scales that formed after oxidation consisted primarily of $Fe_2O_3$, where microscopic voids were scattered. Nickel was segregated initially at the scale/matrix interface, and later at the lower part of the $Fe_2O_3$ scale. At $600^{\circ}C$, Fe-2wt.%Ni alloys oxidized parabolically initially, and linearly after 15 h. At $650-700^{\circ}C$, they oxidized linearly from the initial period. Although Fe-2wt.%Ni alloys oxidized slower than pure iron, their oxidation rates were relatively fast.

• Korean Journal of Materials Research
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• v.7 no.11
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• pp.934-941
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• 1997

C $r_{3}$ $C_{2}$-20wt% NiCr 이 크래드된 분말을 이용하여 HVOF 용사층의 특성(미세조직, 결정상, 경도 그리고 erosion rate)에 미치는 연료/산소 비(=3.2,3.0,2.8,2.6)의 영향을 조사했다. 실험범위 내에서 F/O=3.0의 경우가 C $r_{3}$ $C_{2}$-20wt%(NiCr)크래드 분말의 최적용사조건 이었다. XRD분석결과 F/O비에 관계없이 카바이드분해는 일어 났다. C $r_{3}$ $C_{2}$에서C $r_{7}$ $C_{3}$로의 상변화는 F/O비가 감소함에 따라 증가했다. 열처리 온도가 높아짐에 따라 C $r_{7}$ $C_{3}$분율은 증가 하였으며, 100$0^{\circ}C$에서 50시간 열처리후 용사층의 주된상은 C $r_{7}$ $C_{3}$이였다. 용사상태에서 경도값은 F/O=3.0조건으로 용사된 코팅층이 $H_{v300}$-1040으로 가장 높았으며, 공기중에서 $600^{\circ}C$, 50시간 열처리한 후, 경도값은 1340으로 증가하였다. 그리고 80$0^{\circ}C$열처리 후 경도값은 약간 감소하였다. 그러나 100$0^{\circ}C$ 열처리 후에도 1060정도로 용사상태의 경우 보다는 높은 경도값을 유지하였다. 이와같이 경도값이 증가하는 이유는 열처리에 따라 용사층이 치밀하게 되고 또한 C $r_{2}$ $O_{3}$의 산화물이 C $r_{3}$ $C_{2}$/C $r_{7}$ $C_{3}$ 내에 생성되어 탄화물/산화물 복합체를 이루기 때문으로 생각된다. 용사상태에서 drosion rate는 F/O비에 따라 2.6-3.05x$10^{-4}$mg/g까지 변화하였다. 또한 $600^{\circ}C$열처리 후에는 2.15-2.3 x $10^{-4}$mg/g이였으며, 80$0^{\circ}C$에서 열처리한 후에는 2.3-2.4x$10^{-4}$mg/g으로 $600^{\circ}C$열처리후 보다 약간 높은 결과를 보였다.결과를 보였다.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.603-608
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• 2001

$MO-SiO_2$ (M = Zn, Sn, In, Ag, Ni) binary silica gels were synthesized by sol-gel method and their structural change with the kind of metal ions was characterized by XRD, FT- IR and $^{29}$Si-NMR. Although X-ray analysis showed partial recrystallization of $AgNO_3$ in $Ag-SiO_2$gel, crystalline phase formed by the bonding between metal ion and the silica matrix didn't appear in all $MO-SiO_2$ gels. The FT-IR analysis showed that Zn, Sn and in partially formed Si-O-M bonding in silica matrix and made an shift of absorption peak to by Si-O-Si symmetrical vibration. In addition, $^{29}Si-NMR$ studies showed that Zn, Sn and In didn't affect sol-gel process of silica and were linked with non-bridging oxygen of the linear silica structure, which formed imperfect network because of low temperature sol-gel process. Ag and Ni make a role of catalysis on sol-gel process, resulting in densifying the silica network structure.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.10a
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• pp.65-66
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• 2003

1. The oxidation resistance of $Y_{2}O_{3}$ containing Ni-base alloy is superior to that of the alloy without $Y_{2}O_{3}$. 2. The appearance of oxides of Ni-20Cr-20Fe-5Nb-$1Y_{2}O_{3}$ alloy is similar to that of oxides in commercial PM1000 and MA754 alloy. 3. The oxides in ODS alloy are grown mainly at particle boundaries.