• 한국자기학회지
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• 제5권5호
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• pp.880-894
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• 1995

B의 함유량을 6 at% 고정하고 Nd함유량을 3~5 at%로 변화시킨 $\alpha$-Fe기 Nd-Fe-B 합금의 자기특성이 조사 되었다. 급속응고법으로 제조된 $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}(x=\;3,\;4,\;5)$ 비정질합금은 열처리에 의하여 초미세결정립으로 결정화하며, Nd의 함유량에 따라 잔류자화 및 보자력이 변한다. x=3의 경우 최적열처리조건에서 $\alpha$-Fe(Co) 부피분율의 증가로 잔류자 화는 증가하나, 보자력은 감소한다. 그러나 Nd 함유량의 증가는 $Nd_{2}{(Fe,\;Co)}_{14}B$ 부피분율의 증가로 인하여 잔류자화는 감소하나 보자력은 향상된다. $640^{\circ}C$, 10 min 열처리조건에서 $Nd_{5}{(Fe_{0.9}Co_{0.1})}_{85}B_{6}Nb_{3}Cu_{1}$의 결정립크기는 약 20 nm이며, 잔류자화, 보자력 및 최대에너지적 은 각각 1.35 T, 219 kA/m (2.75 kOe) 및 $129\;kJ/m^{3}$ (16.2 MGOe)으로 가장 우수하다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.196-197
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• 2005

The $ZnNb_2O_6$ ceramics with 3wt% CuO and $B_2O_2$(1,3,5wt%) were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $1000^{\circ}C\sim1050^{\circ}C$ for 3hr. in air. The structural properties were investigated with sintering temperature by XRD and SEM. Also, the microwave dielectric properties were investigated with sintering temperature. Increasing the sintering temperature, the peak of second phase ($Cu_3Nb_2O_8$) was increased. But no significant difference was observed as sintering temperature. In the $ZnNb_2O_6$ ceramics with 3wt% CuO and 5wt% $B_2O_3$ sintered at $1025^{\circ}C$ for 3hr, the dielectric constant, quality factor, temperature coefficient of the resonant frequency were 22.92, 20,271GHz, -14.27ppm/$^{\circ}C$, respectively.

• Progress in Superconductivity
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• 제4권1호
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• pp.80-85
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• 2002

In order to disseminate the IEC international standard of RRR measurement of Cu／Nb／-Ti composite superconductors, a measuring system was developed at KRISS. The system consisted of helium reservoir, base plate, thermometer, voltmeter and current source. The helium reservoir and base plate provided a stable temperature of a range from 4.2 K to 300 K and the voltmeter measured several order of $mutextrm{V}$ on specimen for obtaining RRR of the Cu／Nb-Ti composite superconductor. Three specimens of the Cu／Nb-Ti composite superconductors were measured using this system for characterizing their RRR. The resistance-temperature curves ortho specimens showed 10／sup -6／ to 10／sup -5／ Ohms near transition temperature and 10／sup -4／ to 10／sup -3／ Ohms at 293 K. The RRR values of the specimens were 145, 71 and 140, respectively.

• 한국재료학회지
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• 제17권12호
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• pp.634-636
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• 2007

The texture and microstructure in Cu/Nb added ultra low carbon steels through the different thickness layer were studied after hot rolling. It was found that the two ultra low carbon steels all show the inhomogeneity of hot rolling texture and the Cu-added ultra low carbon steel was far more inhomogeneous than Nb-added one. In the center layer, the strong ${\alpha}\;fibre,\;{\gamma}\;fibre$ textures and the shear textures including 001<110>, 111<112> were founded. Near the surface, the ${\alpha}\;fibre$ texture and the orientation texture caused by a typical plane-strain deformation condition of bcc metals were observed.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.57-64
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• 2020

The water-gas shift reaction for the compact reformer was carried out at a gas hourly space velocity of 72,152 h^-1 over the Cu-Nb-CeO₂ catalysts prepared by co-precipitation method. In order to investigate the effect of Nb₂O₅ promotion over a Cu-CeO₂ catalyst, the Nb₂O₅ loading amount was systematically changed from 0 to 5 wt.%. Among the prepared catalysts, the Cu-Nb-CeO₂ (1%) catalyst showed the highest catalytic activity (CO conversion=61% at 400℃) as well as 100% CO₂ selectivity. The high activity and stability of Cu-Nb-CeO₂ (1%) catalyst are correlated to high Brunauer-Emmett-Teller surface area, small metallic Cu crystallite size, and enhanced redox property.

• 한국초전도ㆍ저온공학회논문지
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• 제15권3호
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• pp.1-4
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• 2013

We investigated the effect of Nb substitution for Ru on the structural and magnetic properties of $(Ru_{1-x}Nb_x)\;Sr_2(Sm_{1.4}Ce_{0.6})Cu_2O_z$ Samples. X-ray diffraction measurements indicated that nearly single-phase samples are formed in the range from x = 0 to 1.0. The superconducting transition temperature determined from the inflection in the field-cooled magnetic susceptibility decreased only slightly from $T_c$ = 25 K for x = 0 to $T_c$ = 22 K for x = 1.0, in consistent with the change in room temperature thermopower of the samples. However, the Nb substitution for Ru above x = 0.25 significantly suppressed the weak ferromagnetic component of the field-cooled magnetic susceptibility. It was also found that the Nb substitution for Ru results in an enhanced diamagnetic susceptibility with Nb content above x = 0.5 in both zero field-cooled and field-cooled magnetization measurements, in contrast to the behavior of the samples with $x{\leq}0.5$ in which the diamagnetic susceptibility decreases as the Nb content increases.

• Journal of Magnetics
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• 제16권4호
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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.

• Progress in Superconductivity
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• 제10권2호
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• pp.128-132
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• 2009

Polycrystalline samples of $(Ru_{0.8}Nb_{0.2})Sr_2(Gd_{1.5-x}Nd_xCe_{0.5})Cu_2O_z$($ 0{\leq}x{\leq}1.25$) have been synthesized by a solid-state reaction route. The X-ray diffraction data revealed that the Nd solubility limit can be placed between x=0.5 and x=0.75. The superconducting transition temperature decreased with increasing Nd content, confirming that Nd entered the lattice. Room-temperature thermoelectric power measurements showed that all the samples are in the underdoped state and the partial substitution of Nd for Gd resulted in a decrease in the carrier density on the superconducting layers.

• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.873-877
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• 2007

In order to apply a complex multilayer chip LC filter, this study has estimated the interfacial reaction and coupling properties of dielectric materials $Pb(Fe_{1/2}Nb_{1/2})O_3$ and Ni-Zn-Cu ferrite materials through low-temperature co-sintering (LTCS). PFN powders were fabricated using double calcinated at $700^{\circ}C$ and then $850^{\circ}C$. While the perovskite phase rate was found to be 91 %, after heat treatment at $900^{\circ}C$ for 6h, the perovskite phase rate and density exhibited a value of 100 % and 7.46$g/cm^3$, respectively. The PFN/Ni-Zn-Cu ferrite, PFN/CUO (or $Pb_2Fe_2O_5$) and ferrite/CuO (or $Pb_2Fe_2O_5$) were mechanically coupled through interfacial reactions after the specimen was co-sintered at $900^{\circ}C$ for 6 h. No intermediate layer exists for the mutual coupling reaction. This result indicates the possibility of low-temperature co-sintering without any interfacial reaction layer for a multilayer chip LC filter.

• 한국자기학회지
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• 제4권1호
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• pp.12-19
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• 1994

비정질 $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ 합금의 $552^{\circ}C$에서 등온열처리시간에 따른 결정화 거동을 $M\"{o}ssbauer$ 분광법으로 연구하였다. 열처리된 시료는 $Do_{3}-FeSi$ 초미세결정립, Cu-cluster 및 비정질이 공존함이 $M\"{o}ssbauer$ spectrum 분석에 의해 확인되었다. 결정화 초기단계에 Cu-cluster가 형성되기 때문에 FeSi 초미세결정립의 Si함량은 높아지며, 열처리시간이 60분이 될 때까지 Si함량은 감소하는데 이는 FeSi 초미세결정립의 평균초미세자기장의 증가를 일으키며, 이후 Si함량은 거의 일정하다. 60분 이후의 열처리에서 FeSi 초미세결정립과 잔류비정질의 체적분율이 미소하게 변화함에도 잔류비정질의 평균초미세자기장이 감소하는 것은 잔류비정질에서의 Nb, B원자의 존재비의 증가에 기인된다. $552^{\circ}C$에서 60분 열처리 할 경우 FeSi 초미세결정립과 잔류비정질의 초미세자기장의 방향이 모두 무질서하게 분포된다. FeSi 초미세결정립과 Cu-cluster의 Avrami지수는 각각 0.51, 0.65, 잠복기는 각각 2.4분, 0.8분, 활성화에너지는 각각 2.35 eV, 2.44 eV이며, Cu-cluster가 FeSi 초미세결정립보다 먼저 생성된다는 것은 Cu 원자가 FeSi 초미세결정립의 생성을 촉진시킨다는 해석과 부합한다.