• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.246-250
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• 2009

The Ni formation behavior from the reduction of NiO nano crystals in the $H_2/N_2$ gas mixtures. The NiO nano crystals were synthesized by heat-treating nickel nitrate$(Ni(NO_3)_2\cdot6H_O)$ in the air at $500^{\circ}C$, and had an octahedral shape and the particle size of 200~500 nm. The NiO nano-crystals had well-developed (111) planes which is hardly formed in normal synthetic conditions. The reduction process was carried out at 300 and $600^{\circ}C$ for 15 and 60 minutes, respectively. When the NiO nano-crystals were reduced at $300^{\circ}C$, the Ni particles sustained the same octahedral shape as NiO, while Ni particles were to agglomerate at $600^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.382-388
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• 1987

Kinetics studies on the reaction system of $[Ni(H_2O)_6]^{2+}+4CN^-{\rightleftharpoons}[Ni(CN)_4]^{2-}$ have been carried out in 0.005% gelatin solution at $25^{\circ}C$ by means of conductometry. The fifth-order kinetics were observed in the formation rate of $[Ni(CN)_4]^{2-}$ from the reaction of [Ni(H$_2O)_6]^{2+}$ and [CN]$^-$. The reaction was found first order in $[Ni(H_2O)_6]^{2+}$ and fourth order in [CN]$^-$. ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ were obtained the values of 5.15kcal/mole and -35.07 e.u., respectively. We have proposed the possible mechanism from the data obtained.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.294-299
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• 2001

Effects of the surface fluorination on the electrochemical charge-discharge properties of $Mg_2$Ni electrode in Ni-MH batteries fabricated by mechanical alloying were investigated. After 20h ball milling, Mg and Ni powder formed nanocrystalline $Mg_2$Ni. Discharge capacity of this alloy increased greatly at first one cycle, but due to the formation of Mg(OH)$_2$ passive layer, it showed a rapid degradation in alkaline solution within 10cyc1es. In case of 6N KOH +xN KF electrolyte (x = 0.5, 1, 2), a continuous and stable fluorinated layer formed by adding excess F$^{[-10]}$ ion, increased durability of $Mg_2$Ni electrode greatly and high rate discharge capability(90-100mAh/g). 2N KF addition led to the highest durability of all tested here. The reason of the improvement is due to thin MgF$_2$, which can prevent the $Mg_2$Ni electrode from forming Mg(OH)$_2$layer that is the main cause of degradation.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.145-149
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• 2015

The electrochemical behavior of $Nd_2O_3-La_2O_3-NiO$ mixed oxide including rare earth resources has been studied to synthesize $La_{0.5}Nd_{0.5}Ni_5$ alloy in a LiCl molten salt. The $Nd_2O_3-La_2O_3-NiO$ mixed oxide was converted to $NiNd_2O_4$ (spinel) and $LaNiO_3$ (perovskite) structures at a sintering temperature of $1100^{\circ}C$. The spinel and perovskite structures led a speed-up in the electrolytic reduction of the mixed oxide. Various reaction intermediates such as Ni, $NiLa_2O_4$ were observed during the electrochemical reduction by XRD analysis. A possible reaction route to $La_{0.5}Nd_{0.5}Ni_5$ in the LiCl molten salt was proposed based on the analysis result.

• Journal of the Korean Ceramic Society
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• v.13 no.3
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• pp.55-62
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• 1976

순수한 닉켈과 금 박막을 (III)규소 단 결정위에 진공 증착시켰다. Ni/Au/Si나 Au/Ni/Si시료를 진공중에서 약 55$0^{\circ}C$로 가열하였을 때 육방정 혹은 변형된 육방정의 미소 결정들이 규소 기질위에 형성되었다. 이들 미소 결정들의 형성과정 및 조성은 X-선 회절법, scanning electron microscopy 및 scanning Auger microprobe 법을 사용하여 결정하였다. 이들 미소 결정은 NiSi2임이 확인되었다. Ni/Au/Si 시료에서는 Au-Si 공융점(37$0^{\circ}C$) 이상으로 온도가 증가됨에 따라 닉켈과 규소가 Au-Si 공융체 속으로 이동한 후 반응하여 NiSi2를 형성하였다. Au/Ni/Si 시료에 있어서의 Au-Si 공융체 형성은 닉켈 박막에 있는 바늘구멍형의 표면 결함과 관련 지을 수 있겠다. 금이 닉켈 박막의 grain boundary를 통하여 Ni/Si 계면으로 확산되어 그 계면을 습윤시킨 다음 Au-Si 공융체를 형성하였다. 이런 Au-Si 공용체는 닉켈과 규소 원자에 대한 높은 확산 매질로서 작용하여 NiSi2 형성을 촉진시켰다. 표면에 평행한 (III)규소면 위의 NiSi2 미소 결정은 유사한 육방정으로 나타났으며, 경사진 미소결정은 부등변 사변형과 유사하였다. Auger 스펙트럼 및 Ni, Au 및 Si에 대한 내층조성(indepth Composition Profiles)은 NiSi2 미소 결정이 Au-Si 공융체의 matrix에 미소 부분으로 나타났음을 보여주었다.

• Journal of Powder Materials
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• v.6 no.2
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• pp.145-151
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• 1999

Nickel silicides ($Ni_5$Si$_2$, Ni$_2$Si and NiSi) have been synthesized by mechanical alloying (MA) of Ni-27.9at.9at%Si, Ni-33.3at% and Ni-50.0at% powder mixtures, respectively. From in situ thermal analysis, eash citical milling period for the formation of the three phases was observed to be 40.2, 34.9 and 57.5 min, at which there was a rapid increase in temperature. This indicates that rapid, self-propagating high-temperature synthesis (SHS) reactions were observed to produce the three phases during room-temperature high-energy ball milling of elemental powders. Each Ni silicide, Ni and Si, however, coexisted for an extended milling time even after the critical milling period. The powders mechanically alloyed after the critical period showed the rapid increase in microhardness. The Hv values were found to be higher than 1000kgf/mm$^2$. The formation of nickel silicides by mechanical alloying and the relevant reaction rates appeared to be influenced by the critical milling period and the heat of formation of the products involved ($Ni_5$Si$_2$$\rightarrow$-43.1kJ/mol.at., Ni$_2$Si$\rightarrow$-47.6kJ/mol.at., NiSi$\rightarrow$-42.4kJ/mol.at).

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.11a
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• pp.98-99
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• 2004

(1) Using high-frequency induction heating sintering and spark plasma sintering method, the densification of WC-Ni hard materials was accomplished using ultra fine power of Ni and WC. (2) Nearly fully dense WC-Ni could be obtained within 1 min. (3) Relative density and mechanical properties of WC-Ni obtained by HFIHS were high than those obtained by SPS. And WC grain size made by HFIHS was smaller than that made by SPS. (4) The fracture toughness and hardness values of WC-8Ni, WC-10Ni, and WC-12Ni made by HFIHS were $13MPa{\cdot}m^{1/2}\;and\;1950kg/mm^2,\;13.5Mpa{\cdot}m^{1/2}\;and\;1810kg/mm^2,\;14.4MPa{\cdot}m^{1/2}\;and\;1690kg/mm^2$, respectively for 60MPa and an induced current for 90% output of total capacity, 15KW. (5) The fracture toughness and hardness values of WC-8Ni, WC-10Ni, and WC-12Ni made by SPS were $12.2MPa{\cdot}m^{1/2}\;and\;1796kg/mm^2,\;12.9MPa{\cdot}m^{1/2}\;and\;1725kg/mm^2,\;13.6MPa{\cdot}m^{1/2}\;and\;1597kg/mm^2$, respectively for 60MPa and the electric current of 2500 A

• Applied Microscopy
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• v.24 no.4
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• pp.123-131
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• 1994

In this study the initial stage nucleation and growth of Ni silicide on (001) Si by evaporation and furnace annealing have been investigated by transmission electron microscopy. The pressure was $10^{-6}$ Torr during evaporation and annealing. And the annealing temperature to produce $NiSi_2\;was\;800^{\circ}C$. From the evaporated film, $NiSi_2$ nucleus has grown into Si substrate with an epitaxial orientation relationship. Interfaces between $NiSi_2$ and Si were A-type {111} interfaces and {100} $NiSi_2$ interfaces were also observed at the initial stage of nucleation. Ni silicide grew into Si substrate, but the nucleus partly grew into the evaporated film, with no facets, from the nuclei in the Si substrate. $NiSi_2$ nucleus with (111) habit planes was also observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.72-72
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• 2007

Ni 단일박막과 Ni-Zr 합금박막을 단결정 Si 기판위에 증착한 후 RTP를 이용하여 Ni 실리사이드 형성반응을 관찰하였고, $500^{\circ}C$에서 형성된 Ni 실리사이드 박막에 $600^{\circ}C,\;650^{\circ}C$에서 후속 열처리 공정을 수행하여 열 안정성을 평가하였다. RTP를 이용하여 실리사이드를 형성할 경우, Ni/Si 계의 경우, 고온 열처리에서 $NiSi_2$ 결정립의 과대 성장 및 단락이 발생하였지만, Ni-Zr/Si 계의 경우 첨가된 내열금속 원소가 NiSi에서 $NiSi_2$ 로의 상전이와 핵생성을 지연시켜 Ni 실리사이드 박막의 열 안정성 개선 효과를 확인하였다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.70-77
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• 1998

Ni/SiC Schottky diodes have been fabricated using epitaxial 4H-SiC and 6H-SiC wafers. The epitaxial n-type layers were grown on $n^{+}$ substrates, with a doping density of 4.0$\times$10$^{16}$ c $m^{-3}$ and a thickness of 10${\mu}{\textrm}{m}$. Oxide-termination has been adopted in order to obtain high breakdown voltage and low leakage current. The fabricated Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes show excellent rectifying characteristics up to the measured temperature range of 55$0^{\circ}C$. In case of oxide-terminated Schottky barrier diodes, breakdown voltage of 973V(Ni/4H-SiC) and 920V(Ni/6H-SiC), and a very low leakage current of less than 1nA at -800V has been observed at room temperature. On non-terminated Schottky barrier diodes, breakdown voltages were 430V(Ni/4H-SiC) and 160v(Ni/6H-SiC). At room temperature, SBH(Schottky Barrier Height), ideality factor and specific on-resistance were 1.55eV, 1.3, 3.6$\times$10$^{-2}$ $\Omega$.$\textrm{cm}^2$ for Ni/4H-SiC Schottky barrier diodes, and 1.24eV, 1.2, 2.6$\times$10$^{-2}$$\Omega$.$\textrm{cm}^2$/ for Ni/SH-SiC Schottky barrier diodes, respectively. These results show that both Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes are very promising for high-temperature and high power applications.s..