• Journal of Magnetics
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• 제9권2호
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• pp.27-33
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• 2004

Magnetic properties of $Nd_4Fe_{77.5}B_{18.5}$ compound in term of exchange coupling between $Nd_2Fe_{14}B$ and $Fe_3B$ magnetic nano crystals in melt spun powders were characterized by varying the quenching speed in mass production line. The exchange coupled phenomenon was characterized as functions of nano crystal size and volume fraction of each magnetic phase which was possible by employing Henkel plot (${\delta}M$) and refined Mossbauer spectroscopy. The optimized magnetic properties obtained from the present volume production line were: $B_r= 11.73 kG,{_i}H_c/ = 3.082 kOe$, and $(BH)_{max} = 12.28 MGOe.$ The volume fraction of each magnetic phase for those conditions giving the grain size of 10 nm were ${\alpha}-Fe; 4.2%, Fe_3B; 60.1 %$, and $Nd_2Fe_{14}B; 35.7%$. The superior magnetic properties in the $Nd_2Fe_{14}Fe_3B$ based nanocomposites were confirmed to be dependant on the volume fraction of $Fe_3B$.

• Journal of Magnetics
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• 제15권1호
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• pp.32-35
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• 2010

The effects of Cu-addition and die-upset temperature on the texture in the die-upset Nd-lean $Nd_xFe_{93.5-(x+y)}-Cu_yGa_{0.5}B_6$ (x = 9-12, y = 0-2) alloys were investigated. The die-upset Cu-containing Nd-lean $Nd_{12}Fe_{81.5-y}-Cu_yGa_{0.5}B_6$ (y = 1, 2) alloys showed a considerable texture. Texture in the Nd-lean alloys developed through basal plane slip deformation. The Cu-addition reduced the melting point of grain boundary phase facilitating grain gliding during the die-upsetting, and providing a greater chance for the $Nd_2Fe_{14}B$ grains to meet the deformation conditions. Die-upsetting at higher temperature facilitated grain gliding and plastic deformation, thus enhancing texture.

• 한국자기학회지
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• 제5권5호
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• pp.408-411
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• 1995

Microstructure and magnetic properties of $Fe-Nd_{13.5}-Co_{15}-B_{6-8}Ga_{0-1}-Zr_{0.2-1}$ alloys during HDDR process were studied. $ZrB_{2}$ phase was detected and identified by X-Ray diffraction. Influence of Ga, Zr and Ga+Zr additions on phase relations at different stages of HDDR process was studied by X-ray diffraction and magnetic measurements.

• 한국세라믹학회지
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• 제32권7호
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• pp.839-845
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• 1995

The structural and dielectric properties of Pb(Mg1/3Nb2/3)O3 ceramics substituted by Nd3+, La3+, K+ and Na+ were studied over 0~50 at.% substituent content. The 1 : 1 ordering behavior of Mg2+ and Nb5+ ions in the B site sublattice was observed in Nd3+-and La3+-modified compounds. The degree of ordering was increased with Nd3+, La3+ content in the compounds. But K+-or Na+-modified compounds did not exhibit the ordering behavior. This was explained by charge and size effect of A and B site cations and oxygen vacancies. As the mole fractions of substituent increased, the maximum values of dielectric constants were rapidly decreased and the phase transitions were broadened. Phase transition temperature was correlated with the covalency of A-O and B-O bonding.

• Journal of Magnetics
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• 제13권3호
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• pp.102-105
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• 2008

This study examined the feasibility of the combining HDDR-process (hydrogenation, disproportionation, desorption and recombination) with mechanical milling to prepare single domain $Nd_2Fe_{14}B$ particles from a Nd-Fe-B alloy ingot. The $Nd_{15}Fe_{77}B_8$ alloy was HDDR-treated and then subjected to a roller-milling. In the HDDR-treated $Nd_{15}Fe_{77}B_8$ alloy, very small $Nd_2Fe_{14}B$ grains comparable to their critical single domain size(0.3 ${\mu}m$) were observed. These fine individual grains were separated successfully along the grain boundaries by a roller-milling. The separated $Nd_2Fe_{14}B$ grains were found to be single domain particles. These results suggest that single domain particles of the $Nd_2Fe_{14}B$ phase can be prepared from a Nd-Fe-B ingot alloy by combining a HDDR-process with mechanical milling.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.726-729
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• 2000

Though L $a_{1+x}$S $r_{2-x}$M $n_2$ $O_{7}$ n=2 R-P phases have been well known to have CMR effect, it was generally believed that n=1 phase was insulating. But recently monolayered perovskite $Ca_{2-x}$L $n_{x}$Mn $O_4$phase has been reported to show magnetoresistance. In this study, layered perovskite $Ca_{2-x}$L $n_{x}$Mn $O_4$ (x=0, 0.5, Ln=Pr, Nd, Sm, Gd) phases were synthesized by solid state reaction and their structures were refined by Rietveld method. The space groups of $Ca_2$Mn $O_4$, N $d_{0.5}$C $a_{1.5}$Mn $O_4$phases were refined as C2cb and Fmmm, respectively.y.ely.y.y.y.y.y.y.

• E2M - 전기 전자와 첨단 소재
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• 제10권8호
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• pp.819-829
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• 1997

The microwave dielectric materials of the BaO-Nd$_2$O$_3$-TiO$_2$and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system were synthesized by conventional ceramic processing and sintered 1220 to 140$0^{\circ}C$ for 2 hours respectively. Their crystallization and dielectric properties were examined. In the BaO-Nd$_2$O$_3$-TiO$_2$ and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system. Nd$_2$Ti$_2$O$_{7}$ and (Sm, Nd)$_2$Ti$_2$O$_{7}$ were observed as a second phase respectively. The maximum relative dielectric constant were 79,99 for the BaO-Nd$_2$O$_3$-TiO$_2$system and 105.07 for the BaO-(Sm,Nd)$_2$O$_3$-TiO$_2$system and their Q-value were over 2000 at 3GHz.GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.196-199
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• 2000

Since the reports of CMR(colossal magnetoresistance) effects in some single crystal R-P phase $La_{1+x}Sr_{2-x}Mn_2O_7$, considerable researches have been carried out to find optimum composition and to understand the role of dimensionality in the CMR mechanism of this system. In this study, layered perovskite $Ln_xCa_{1-x}MnO_{4}$ (x=0.5, Ln=Pr, Nd, Sm, Gd) phases were synthesized by solid state reaction and their structures were refined by Rietveld method. Electrical and magnetic properties were measured between room temperature and liquid helium temperature and compared with those of two dimensional $La_{1.4}Sr_{1.6}Mn_2O_7$ phase.

• 한국군사과학기술학회지
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• 제23권1호
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• pp.52-58
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• 2020

In this paper, a 2-dimensional phase comparison direction finding receiver was designed and fabricated. For 2-D comparison direction finding, direction finding formulas were derived from a uniformly arranged of four antennas. Based on this, a direction finding receiver was designed using Matlab simulink, and the direction finding receiver was fabricated. To analyze the performance of the designed direction finding receiver, the injection direction finding accuracy and simulation results were compared. As a result of the test, the fabricated direction finding receiver showed a maximum of 3° RMS precision, and the result of both tests showed similar trends. Also, it was confirmed that the direction finding accuracy of elevation angle is about 2.7 times better than azimuth angle, and both models performed well within 0.7° RMS at the boresight.

• 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.