• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 춘계 학술발표강연 및 논문개요집
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• pp.79-79
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• 2002

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 추계학술강연 및 발표대회
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• pp.32-32
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• 2002

• Transactions on Electrical and Electronic Materials
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• 제13권1호
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• pp.19-22
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• 2012

Transformation behavior of rapidly solidified Ti-47.3Ni (at%) alloy ribbons and thermal stability of the R phase in the ribbons were investigated by means of differential scanning calorimetry (DSC), X-ray diffraction, and transmission electron microscopy. Rapidly solidified Ti-47.3Ni alloy ribbons showed the two-stage B2-R-B19' martensitic transformation behavior. The B2-R transformation in the ribbons was observed even after annealing at 1,223 K, which was attributed to the fact that a specific orientation relationship between $Ti_2Ni$ and matrix in the ribbons is maintained after annealing at 1,223 K. The DSC peak temperature of the B2-R transformation ($T_R^*$) decreased with raising annealing temperature, which was attributed to the increased volume fraction of $Ti_2Ni$, thus causing an increased Ni content in the matrix.

• 한국세라믹학회지
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• 제37권5호
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• pp.491-496
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• 2000

Single phae Pb(Mg1/3Nb2/3)O3-based solid solutions, the Mg2+ of which are replaced by 20mol% of Ni2+, Zn2+, Cd2+, and the Pb2+ of which are replaced by 0∼20 mol% of La3+, were synthesized and their ordering structures of B-site cations were investigated by XRD and TEM. The B'-site cations (Mg2+, Ni2+, Zn2+, Cd2+) are disordered while these B'-site cations and the B"-site cations (Nb5+) are nonstoichiometrically 1:1 ordered within the ordered nano-domains dispersed in the Nb5+-rich disordered matrix. The charge imbalance between the B'-rich ordered nano-domains and the B"-rich disordered matrix are compensated by the doping of electron donor such as La3+, which enhances the degree of nonstoichiometric 1:1 ordering. For a given La3+ content, the degree of nonstoichiometric 1:1 ordering increases as the average ionic size difference between the B'-and B"-site cations increases, Ni2+

• 한국주조공학회지
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• 제29권5호
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• pp.187-191
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• 2009

Microstructures and shape memory characteristics of $Ti_{50}Ni_{20}Cu_{30}$ alloy strips fabricated by arc melt overflow have been investigated by means of XRD, optical microscopy and DSC. The microstructure of as-cast strips exhibited columnar grains normal to the strip surface. X-ray diffraction analysis showed that one-step martensitic transformation of B2-B19 occurred in the alloy strips. According to the DSC analysis, it was known that the martensitic transformation temperature ($M_s$) of B2 $\rightarrow$ B19 in $Ti_{50}Ni_{20}Cu_{30}$ strip is $57^{\circ}C$. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $3.7^{\circ}C$ and 1.6%, respectively. The as-cast strip of $Ti_{50}Ni_{20}Cu_{30}$ alloy also showed a superelasticity and its stress hysteresis was as small as 14 MPa. These mechanical properties and shape memory characteristics of the alloy strips were ascribed to B2-B19 transformation and the controlled microstructures produced by rapid solidification of the arc melt overflow process.

• 한국자기학회지
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• 제17권3호
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• pp.120-123
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• 2007

이 연구에서는 Ta 45/Ru 9.5/IrMn 10/CoFe $3/AlO_x$/자유층/$AlO_x$/CoFe 7/IrMn 10/Ru 60(nm) 구조를 갖는 이중장벽 자기터널접합(double-barrier magnetic tunnel junction: DMTJ)를 다루었다. 자유층은 $Ni_{16}Fe_{62}Si_8B_{14}\;7nm$, $Co_{90}Fe_{10}(fcc)$ 7 nm 및 $CoFet_1$/NiFeSiB $t_2$/CoFe $t_1$으로 구성하였으며 두께 $t_1,\;t_2$는 변화시켰다. 즉 TMR비와 RA를 개선하기 위하여 부분적으로 CoFe층을 대체할 수 있는 비정질 NiFeSiB층이 혼합된 자유층 CoFe/NiFeSiB/CoFe을 갖는 DMTJ를 연구하였다. NiFeSiB($t_1=0,\;t_2=7$)만의 자유층을 갖는 DMTJ는 터널자기저항(TMR)비 28%, 면적-저항곱(RA) $86k{\Omega}{\mu}m^2$, 보자력($H_c$) 11 Oe 및 층간 결합장($H_i$) 20 Oe를 나타내었다. $t_1=1.5,\;t_2=4$인 경우의 하이브리드 DMTJ는 TMR비 30%, RA $68k{\Omega}{\mu}m^2$ 및 $H_c\;11\;Oe$를 가졌으나 $H_i$는 37 Oe로 증가하였다. 원자현미경(AFM)과 투과전자현미경(TEM)측정을 통하여 NiFeSiB층 두께가 감소하면 $H_i$가 증가하는 것을 확인하였다. 비정질 NiFeSiB층이 두꺼워지면 보통 계면의 기복을 유도하는 원주형성장(columnar growth)를 지연시키는데 유효하였다. 그러나 NiFeSiB층이 얇으면 표면거칠기는 증가하고 전자기적 Neel 결합 때문에 Hi는 커졌다.

• Bulletin of the Korean Chemical Society
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• 제9권5호
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• pp.283-288
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• 1988

The titled properties on reduction of the perovskite $LaBO_3$ (B = Fe, Co, Ni) have been investigated by means of temperature-programmed reduction, isothermal reduction and X-ray diffraction methods. Nominal composition of $LaFeO_{3.18},\;LaCoO_{3.00}\;and\;LaNiO_{2.92}$ are determined. Reduction reaction of these mixed oxides differed according to B-site transition metal and thermal stability on reduction decreased as following order: $LaFeO_{3.18}$ > $LaCoO_{3.00}$ > $LaNiO_{2.92}$. From the results of isothermal reaction, kinetics on reduction of the perovskite has been discussed in detail.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.803-808
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• 2002

A computer-aided alloy-designing technique to develop the insert metal for transient liquid phase (TLP) bonding was applied to high aluminum Ni-base superalloys. The main procedure of a mathematical programming method was to obtain the optimal chemical composition through rationally compromising the plural objective performances of insert metal by a grid-search which involved data estimation from the limited experimental data using interpolation method. The objective function Z which was introduced as an index of bonding performance of insert metal involved the melting point, hardness (strength), formability of brittle phases and void ratio (bonding defects) in bond layer as the evaluating factors. The contour maps of objective function Z were also obtained applying the interpolation method. The compositions of Ni-3.0%Cr-4.0%B-0.5%Ce (for ${\gamma}$/${\gamma}$/${\beta}$ type alloy) and Ni3.5%Cr-3.5%B-3%Ti (for ${\gamma}$/${\gamma}$ type alloy) which optimized the objective function were determined as insert metal. SEM observations revealed that the microstructure in bond layers using the newly developed insert metals indicated quite sound morphologies without forming microconstituents and voids. The creep rupture properties of both joints were much improved compared to a commercial insert metal of MBF-80 (Ni-15.5%Cr-3.7%B), and were fairly comparable to those of base metals.

• Journal of Magnetics
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• 제10권3호
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• pp.84-88
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• 2005

Nanoparticles $Ni_{0.7}Zn_{0.3}Fe_2O_4$ is fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with XRD, SEM, $M\ddot{o}ssbauer$ spectroscopy, and VSM. $Ni_{0.7}Zn_{0.3}Fe_2O_4$ powders annealed at $300^{\circ}C$ have a spinel structure and behaved superparamagnetically. The estimated size of $Ni_{0.7}Zn_{0.3}Fe_2O_4$ nanoparticle is about 11 nm. $Ni_{0.7}Zn_{0.3}Fe_2O_4$ annealed at 400 and $500^{\circ}C$ has a typical spinel structure and is ferrimagnetic in nature. The isomer shifts indicate that the iron ions were ferric at the tetrahedral (A) and the octahedral (B). Blocking temperature $(T_B)\;of\;Ni_{0.7}Zn_{0.3}Fe_2O_4$ nanoparticle is about 260 K. The magnetic anisotropy constant of $Ni_{0.7}Zn_{0.3}Fe_2O_4$ annealed $300^{\circ}C$ were calculated to be $1.7X10^6\;ergs/cm^3$. Also, temperature of the sample increased up to $43^{\circ}C$ within 7 minutes under AC magnetic field of 7 MHz.

• 한국재료학회지
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• 제11권11호
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• pp.947-952
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• 2001

The meso-scale microstructure of the $Ni-Ni_3Al- Ni_3V$ system is crucial to obtain both high strength and high toughness. Its evolution may be predicted with the aid of computer simulation of the compositional separation for heat-treated alloys. In this study, computer simulations of the hypothetical A-B-C ternary system, which is similar to the $Ni-Ni_3Al- Ni_3V$ system in terms of phase equilibria, have been performed using the kinetic modeling. Simulated morphologies were changed with nominal compositions and model parameters. It was showed the current model was useful and the more realistic model was proposed.