• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.191-199
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• 2001

In this paper molecular dynamics simulations have been carried out to investigate energy and momentum transfer of hydrogen ions impacted on the Ni (100) surface with $45^{\circ}$ and $90^{\circ}$ incident angles. The initial kinetic energies of the hydrogen ion were ranged from 100 eV to 1,600 eV to study the layer-by-layer energy variation as a dependence of incident energies and angles. At low incident energies, the scattering energy transfer is dominated by the normal motion of surface layers due to thermal vibrations and multiple collision effects. For higher incident energies, the scattering energy transfer in a normal direction is greater than that in a parallel direction. In the case of penetration, the amount of transferred energies do not affect much on Ni layers at low incident energy. It was found channeling effects through Ni layers with increasing incident energies.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.272-277
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• 2001

NiO-doped $WO_3$ thick films were prepared by a screen printing technique. The electrical Property and microstructure of the films were investigated with the partial pressure of oxygen and the amount of NiO. The grain size of NiO-doped $WO_3$ was smaller than that of undoped $WO_3$ but the grain sixte of 0.1, 1, 10 mol% NiO-doped$ WO_3$ were nearly the same. The electrical conductance of the $WO_3$ thick films decreased with the oxygen partial pressure, and increased with the amount of NiO to the limit of solid solution. The variation of the electrical conductance with temperature is not so large in the extrinsic region, but it changed rapidly in the intrinsic region. The conductance decreased with adsorption of oxygen in the intermediate range between the extrinsic and intrinsic region.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.251-255
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• 1999

NiFe(60 $\AA$)/Co(0$\AA$$\leq$x$\AA$$\leq$15$\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valve thin films were prepared on 4$^{\circ}$ tilt-cut Si(111) substrates with a 50 $\AA$ thick Cu underlayer without applying any external magnetic field during the deposition, and the effects of inserted ultrathin Co layer on magnetic anisotropy and GMR properties of the NiFe(60 $\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valves were investigated. As the ultrathin Co layer was inserted into the NiFe/Cu interface of the spin valves, GMR ratio was increased from about 1.5% to 3.5%, and the easy axis of NiFe(60 $\AA$) layer was rotated by 90$^{\circ}$. Accordingly, it was aligned along the same direction with the easy axis of Co(30 $\AA$)layer. Therefore, squared R-H curves was obtained in the spin valves, which is favorable properties for the digital GMR devices such as MRAM. In order to investigate the change of magnetic anisotropy of NiFe layer of the spin valves in more details,XRD measurement was performed using NiFe(500 $\AA$) and NiFe(500 $\AA$)/Co(10 $\AA$) thin films on the same templates. Strong (220) NiFe peak was observed in both films regardless of the inserted Co layer, so it was thought that the variation of magnetic anisotropy of NiFe layer is from the interface effect, the change of interface from NiFe/Cu to NiFe/Co, rather than the volume effect such as the change of magnetocrystalline effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.275-282
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• 2002

Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). In this study, TiNi fiber was used to solve the tensile residual stress as the reinforced material. TiNi fiber improves the tensile strength of composite by occurring compressive residual stress in matrix using shape memory effect of it. Pre-strain was added to generate compressive residual stress inside TiNi/A16061 composite. It was also evaluated the effect of compressive residual stress corresponding to pre-strains variation. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain difference of TiNi/A16061 shape memory alloy composite.

• Journal of Magnetics
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• v.17 no.4
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• pp.245-250
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• 2012

Ferromagnetic resonance and X-ray specular reflectivity measurements were performed on $Ni_{81}Fe_{19}/Ir_{20}Mn_{80}/Co_{90}Fe_{10}$ exchange bias trilayers, which were grown using the pulsed-DC magnetron sputtering technique on Si(100)/$SiO_2$(1000 nm) substrates, to investigate the evolution of the interface roughness and exchange bias and their dependence on the NiFe layer thickness. The interface roughness values of the samples decrease with increasing NiFe thickness. The in-plane ferromagnetic resonance measurements indicate that the exchange bias field and the peak-to-peak line widths of the resonance curves are inversely proportional to the NiFe thickness. Furthermore, both the exchange bias field and the interface roughness show almost the same dependence on the NiFe layer thickness. The out-of plane angular dependent measurements indicate that the exchange bias arises predominantly from a variation of exchange anisotropy due to changes in interfacial structure. The correlation between the exchange bias and the interface roughness is discussed.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.72-77
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• 2001

Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). In this study, TiNi fiber was used to solve the tensile residual stress as the reinforced material. TiNi fiber improves the tensile strength of composite by occurring compressive residual stress in matrix using shape memory effect of it. Pre-strain was added to generate compressive residual stress inside TiNi/A16061 composite. It was also evaluated the effect of compressive residual stress corresponding to pre-strains variation. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain difference of TiNi/A16061 shape memory alloy composite.

• Journal of the Korean Magnetics Society
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• v.5 no.1
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• pp.27-33
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• 1995

The microwave absorbing characteristics and complex permeability of $Ni_{2-x}Zn_{x}Y$ - rubber composites with variation of composition and particle size were investigated. With a ferrite particle with a diameter of about $1\mu\textrm{m}$, only spin rotational resonance was observed. This behavior probably due to the particle being sufficiently small to approach single domain characteristics so that only spin rotations can occur. The first matching frequency, found in $Ni_{2-x}Zn_{x}Y$ - rubber composites, which was higher than that of spin rotational resonance, increased with spin rotational resonance frequency. It is also found that the second matching frequency is independent of spin rotational resonance frequency. Based on these findings, it could be concluded that the microwave absorbing characteristics were caused by only one type of resonance, the spin rotational resonance.

• Journal of Magnetics
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• v.16 no.4
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• pp.398-402
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• 2011

A novel laminate composite of FeCuNbSiB/FeNi /PZT is proposed, where FeCuNbSiB has a permeability of around 100000, which is much larger than that of FeNi. The high-permeability FeCuNbSiB was laminated with piezomagnetic FeNi rather than attached to its ends. It is expected that the effect produced by the high permeability will act on the whole of the piezomagnetic layer. While a FeNi layer was laminated with a FeCuNbSiB layer, the strong demagnetization produced by the latter was expected to be imposed on the FeNi layer as well as the applied fields. The distribution of applied fields was altered by the high-permeability material (both bias and ac field) and the field variation positively contributed to the ME effect in piezomagnetic/piezoelectric composites. Thus the ME voltage coefficient along with the field sensitivity were improved.

• Transactions on Electrical and Electronic Materials
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• v.8 no.4
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• pp.161-165
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• 2007

In this work, Ni thin films with different thickness from $1,523{\AA}\;to\;9,827{\AA}$ were deposited for the application of micro thermal flow sensors by a magnetron sputtering and oxidized through annealing at $450^{\circ}C$ with increasing annealing time. The initial variation of resistivity decreased radically with increasing films thickness, then gradually stabilizes as the thickness increases. The resistivity of Ni thin films with $3,075{\AA}$ increased suddenly with increasing annealing time at $450{\circ}C$, then gradually stabilizes as the thickness increases after the annealing time 9 h. In case of $3,075{\AA}\;and\;9,827{\AA}$ films, the average of TCR values, measured for the operating temperature range of $0^{\circ}C\;to\;180^{\circ}C$, were $2,413.1ppm/^{\circ}C\;and\;4,438.5ppm/^{\circ}C$, respectively. Because of their high resistivity and very linear TCR, Ni oxide thin films are superior to pure Ni and Pt thin films for flow and temperature sensor applications.

• Korean Journal of Materials Research
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• v.21 no.7
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• pp.377-383
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• 2011

Thermoelectric power, dc conductivity, and the dielectric relaxation properties of $La_2NiO_{4.03}$ are reported in the temperature range of 77 K - 300 K and in a frequency range of 20 Hz - 1 MHz. Thermoelectric power was positive below 300K. The measured thermoelectric power of $La_2NiO_{4.03}$ decreased linearly with temperature. The dc conductivity showed a temperature variation consistent with the variable range hopping mechanism at low temperatures and the adiabatic polaron hopping mechanism at high temperatures. The low temperature dc conductivity mechanism in $La_2NiO_{4.03}$ was analyzed using Mott's approach. The temperature dependence of thermoelectric power and dc conductivity suggests that the charge carriers responsible for conduction are strongly localized. The relaxation mechanism has been discussed in the frame of the electric modulus and loss spectra. The scaling behavior of the modulus and loss tangent suggests that the relaxation describes the same mechanism at various temperatures. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy of ~ 0.106eV. At low temperature, variable range hopping and large dielectric relaxation behavior for $La_2NiO_{4.03}$ are consistent with the polaronic nature of the charge carriers.