• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.11a
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• pp.10-10
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• 2000

Mechanical alloying (MA) is a powder metallurgy processing technique involving cold welding, fracturing, and rewelding of powder particles in a high-energy ball mill. This has now become an established commercial technique in producing oxide dispersion strengthened (ODS) nickel- and iron-based materials. The technique of MA is also capable of synthesizing non-equilibrium phases such as supersaturated solid solutions, metastable crystalline and quasicrystalline intermetallic phases, nanostructures, and amorphous alloys. In this respect, the capabilities of MA are similar to those of another important non-equilibrium processing technique, viz, rapid quenching of metallic melts. however, the science of MA is being investigated only during the past ten years or so. The technique of mechanochemistry, on the other hand, has had a long history and the materials produced this way have found a number of technological applications, e.g., in areas such as hydrogen storage materials, heaters, gas absorber, fertilizers. catalysts, cosmetics, and waste management. The present talk will concentrate on the basic mechanisms of formation of non-equilibrium phases by the technique of MA and these aspects will be compared with those of rapid quenching of metallic melts. Additionally, the variety of technological applications of mechanically alloyed products will be highlighted.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.89-93
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• 1991

A new kind of a non-contact torque sensor which uses the difference of the maximum magnetic inductions as measurand was constructed. The torque sensor utilizes the tensile and compressive stress of two cores which are attached on the rotating shaft. This sensor shows that the linearity was better than 1 %, and the transient torque can be measured at the sampling rate of 10 kHz which is the same as magnetizing frequency of the core.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.387-395
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• 2006

본고에서는 고유한 원자구조에 기인한 우수한 특성으로 인해 구조재료 및 기능재료로서 그 활용이 기대되고 있는 벌크 아몰퍼스 소재에 있어 온간압출, 온간압연, 방전 플라즈마 소결(Spark Plasma Sintering)등 과냉각액체온도구간에서의 점성유동을 이용한 고화성형 공정의 최근 기술동향에 대해 간략히 소개했다.

• Journal of Korea Foundry Society
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• v.23 no.5
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• pp.286-290
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• 2003

본 연구에서는 Ni-Zr-Ti의 3원계 합금을 기본으로 하여, Si 및 Sn 등의 원소를 첨가하여 Ni-rich 영역에서 벌크 비정질 합금을 제조하였다. $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ 조성의 합금에서 injection casting에 의하여 약 58 K의 과냉각액상영역을 가지고 있는 직경 3 mm의 벌크 비정질 시편을 제조하였다. 이러한 우수한 비정질 형성능은 액상온도의 저하로 인해 낮은 온도까지 액상이 쉽게 과냉되기 때문인 것으로 사료된다. $Ni_{59}Zr_{20}Ti_{16}Si_5$ 합금은 두 단계에 걸쳐 결정화가 일어나는 반면, $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ 합금은 단일 단계에 의해 orthorhombic $Ni_{10}{(Zr,Ti)}_7$ 결정상과 cubic NiTi 결정상으로 결정화가 일어난다. 벌크 비정질 $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ 합금의 경우 압충강도는 2.7 GPa, 연신율은 약 2% 정도의 값을 가진다.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.90-97
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• 2000

Effect of alloy elements on joinability of insert metal for liquid phase diffusion bonding of heat resistant alloys was investigated in this study. Also, optimum chemical composition of insert metal was explained using interpolation method. The insert metals utilized was commercial Ni-base amorphous foils and newly developed Ni-base filler metals with B, Si and Cr in this study. Melting point and critical interlayer width(CIW) decreased with increasing additional amount of B, Si and Cr, melting point lowering element of the insert metal. Optimized chemical composition of insert metals could be estimated by interpolation method. The optimum amount of B, Si, Cr addition into the insert metal were found to be about 3%, 4% and 3%, respectively. The measured characteristic values, melting point, microhardness in the bonded interlayer and CIW of the insert metals were the almost identical to ones of the calculated results by interpolation method.

• Journal of Magnetics
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• v.20 no.2
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• pp.138-147
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• 2015

The unique nano-scale inter-lamellar microstructure and unparalleled heat treatment process give our developed metal powder composite its outstanding magnetic property for power inductor & motor applications. Compared to the conventional polycrystalline Fe or amorphous Fe-Cr-Si-B alloys, our unique designed inter-lamellar microstructure strongly decreases the intra-particle eddy current loss at high frequencies by blocking the mutual eddy currents. The combination of optimum permeability, magnetic flux and extremely low core loss makes this powder composite suitable for high frequency applications well above 10 MHz. Moreover, it can be also possible to SMC core for high speed motor applications in order to increase the motor efficiency by decreasing the core loss.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.4
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• pp.171-177
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• 2000

Metal hydride used as hydrogen storage material usually needs the activating process to store the hydrogen at high temperature or high pressure. In general as the particle size of metal hydride becomes smaller, approached to the micro, furthermore, nano scale, storage ability and reaction kinetics are reported to be increased, because the specific surface is extremely increased. But the experimental results demonstrated that the optimum particle size is existed for the best absorbing performance, opposite to the usual expectation. This results from the particles to be come amorphous with their approaching to micro and nano scale, in the storage site within the metal hydride lattice is decreased, which is proved by XRD and SEM.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.487-493
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• 1996

Diamond films were grown at lower temperatures (630-813K) on Si, Al (1100P), and Al-Si(8A, 8B, BC) alloy substrates using improved microwave plasma CVD apparatus in a mixed methane and hydrogen plasma. Improved microwave plasma CVD apparatus equipped water cooled substrate holder and the substrates were set up lower position than bottom line of the applicator waveguide. When the methane concentration was high and growth was conducted at lower pressures the diamond films were synthesized. Moreover the deposits on the scratched substrates formed flat surfaces consisting of fine grains. XRD results, the deposits were identified to cubic diamond. An analysis using Raman spectroscopy, further confirmed that diamond films deposited on the Si substrates were high quality. The deposits on the Al substrates, in contrast, contained amorphous carbon. While the quality of the deposits on the Al-Si substrates were differed with the substrate alloys.

• Journal of Powder Materials
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• v.11 no.3
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• pp.193-201
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• 2004

1960년 Au-Si계 합금에서 처음으로 비정질상이 급속 응고법에 의해 보고된 이래/sup 1)/ 지난 40년 간 많은 합금계에서 비정질상이 보고되어졌다. 대표적으로 Fe-, Ni-, Co기 합금 등 많은 합금계에서 비정질상이 보고되었으나, 비정질상의 형성을 위해서는 약 105 K/s이상의 높은 냉각속도를 필요로 하였다. 1980년대 수백 K/s의 낮은 냉각속도 하에서도 비정질상이 형성될 수 있는 다원계 합금(multi-component alloy)이 Mg-Ln-(Ni, Cu, Zn), Ln-Al-TM 합금에서 보고되어 졌으나 많은 관심을 받지 못하다가 1993년 Zr-Ti-Ni-Cu-Be 합금에서 수 ㎝ 크기의 비정질합금 제조가 보고되면서 전 세계적으로 많은 관심을 받게 되었다. Zr-Ti-Ni-Cu-Be계 벌크 비정질 합금이 보고된 후 Zr-(Nb,Pd)-Al-TM, Pd-Cu-Ni-P, Fe-Co-Zr-Mo-W-B, Ti-Zr-Ni-Cu-Sn등 여러 합금계에서 벌크 비정질 합금이 보고되었다. (중략)

• Journal of the Korean institute of surface engineering
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• v.31 no.5
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• pp.245-250
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• 1998

There is clear pressing need to reduce bias field(Ha,) used on linear magenetomechanical resonator tag by at least a factor of two to allow low-bias operation near the frequency minimum since reducing Ha causes a dramatic increase in well depth, which implies increased stability. However, this makes it more difficult to maintain tight frequncy specs. It can be solved by a reduction of magnetomechanical coupling(k). We determined from an equivalent circuit model that optimal reduced, k, is near 0.3 Also, We determiend the material properties($lambda_s$, :saturated magenetostriction, $M_s$, and,$H_a$) that give k=0.3. From these evaluations, we suggested that on optimal comosition with adequate mathrial properties is $Fe_{55}Co_{15}Cr_6Nb_2B_{18}Si_4$.