• Title/Summary/Keyword: Amorphous

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Fabrication and Characteristics of Thermal Sprayed Ni-Cr-B-Si System Amorphous Coatings (Ni-Cr-B-Si계 비정질 용사피막의 제조 및 특성)

  • 정하윤;김태형;박경채
    • Journal of Welding and Joining
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    • v.17 no.4
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    • pp.53-59
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    • 1999
  • Amorphous alloys have also been called glassy alloys or non-crystalline alloys. They are made by the rapid solidification. The solidification occurs so rapid that the atoms are frozen in their liquid configuration. There are unique magnetic, mechanical, electrical and corrosive behaviors which result form their amorphous structure. In the study. amorphous coatings were manufactured with Ni-Cr-B-Si powders by flame spray. Measurement of hardness, were resistance, corrosion resistance and observation of microstructures and XRD, DSC were performed to investigate characteristics of amorphous coatings. The experimental results obtained as follow: 1) Amorphous powders could not be manufactured with the spraying in the spraying in the liquid nitrogen. But, amorphous coatings could be manufactured with the rotation cooling method by liquid nitrogen. In the fabrication of amorphous coatings, major factor was the rapid cooling by rotation of the substrate. 2) Hardness of coatings was obtained Hv 960 by formation of amorphous phase. But, wear resistance decreased. That was due to porosity in the coatings by the rapid cooling. 3) In the case of corrosion resistance, amorphous coatings were superior to air-cooled coatings. That was due to formation of amorphous phase. 4) After amorphous coatings were heat-treated at 520℃ for 1hr. hardness increased 80% and wear resistance increased 30% comparing with air cooled coatings. These were due to crystallization of amorphous phase and decrease of porosity by heat-treatment.

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Electrical Characteristics of $(Ba,Sr)TiO_3/RuO_2$ Thin films

  • Park Chi-Sun
    • Journal of the Microelectronics and Packaging Society
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    • v.11 no.3 s.32
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    • pp.63-70
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    • 2004
  • The structural, electrical properties of $(Ba, Sr)TiO_3[BSTO]/RuO_2$ thin films were examined by the addition of amorphous BSTO layer between crystlline BSTO film and $RuO_2$ substrate. We prepared BSTO films with double-layered structure, that is, amorphous layers deposited at $60^{\circ}C$ and crystalline films. Crystalline films were prepared at 550 on amorphous BSTO layer. The thickness of the amorphous layers was varied from 0 to 170 nm. During the deposition of crystalline films, the crystallization of the amorphous layers occurred and the structure was changed to circular while crystalline BSTO films showed columnar structure. Due to insufficient annealing effect, amorphous BSTO phase was observed when the thickness of the amorphous layers exceeded 30 nm. Amorphous BSTO layer could also prevent the formation of oxygen deficient region in $RuO_2$ surface. Leakage current of total BSTO films decreased with increasing amorphous layer thickness due to structural modifications. Dielectric constant showed maxi-mum value of 343 when amorphous layer thickness was 30 nm at which the improvement by grain growth and the degradation by amorphous phase were balanced.

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Fabrication and Characterization of Cu-based Amorphous Coatings by Cold Spray Process (저온 분사를 이용한 Cu계 비정질 코팅층의 제조 및 특성 연구)

  • Jung, Dong-jin;Park, Dong-Yong;Lee, Jin Kyu;Kim, Hyung Jun;Lee, Kee-Ahn
    • Korean Journal of Metals and Materials
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    • v.46 no.5
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    • pp.321-327
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    • 2008
  • Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_6$) coating was produced by cold spraying as a new fabrication process. The microstructure and macroscopic properties of amorphous coating layer was investigated and compared with those of cold sprayed pure Cu coating. Amorphous powders were prepared by gas atomization and Al 6061 was used as the substrate plate. X-ray diffraction results showed that Cu based amorphous powder could be successfully deposited by cold spraying without any crystallization. The Cu based amorphous coating layer ($300{\sim}400{\mu}m$ thickness) contained 4.87% porosity. The hardness of Cu based amorphous coating represented $412.8H_v$, which was correspond to 68% of the hardness of injection casted bulk amorphous material. The wear resistance of Cu based amorphous coating was found to be three times higher than that of pure Cu coating. The 3-point bending test results showed that the adhesion strength of Cu based amorphous coating layer was higher than that pure Cu coating. It was also observed that hard Cu base amorphous particle could easily deform soft substrate by particle collisions and thus generated strong adhesion between coating and substrate. However, the amorphous coating layer unexpectedly represented lower corrosion resistance than pure Cu coating, which might be resulted from the higher content of porosity in the cold sprayed amorphous coating.

Mechanical Behavior and Physical Properties of Zr-Ti-Cu-Ni-Be Amorphous and Partially Crystallized Alloy Extracted from a Commercial Golf Club Head (Zr-Ti-Cu-Ni-Be 합금으로 제조된 상용 골프클럽헤드의 부위별 물리적 특성 및 기계적 거동)

  • Choi, Young-Chul;Hong, Sun-Ig
    • Korean Journal of Materials Research
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    • v.15 no.11
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    • pp.697-704
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    • 2005
  • The deformation behavior of a bulk amorphous and crystallized amorphous $Zr_{22.5}Ti_{14}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy extracted from a commercial golf club head was characterized at room temperature ana $300^{\circ}C$. At room temperature, amorphous specimens revealed higher yield stress and ductility than partially crystallized alloy specimens. Amorphous alloy displayed some plasticity before fracture, which resulted from strain hardening and repeated crack initiation and propagation. The fracture is mainly localized on one major shear band, and the compressive fracture angle of the amorphous specimen between the stress axis and the fracture plane was about $40^{\circ}$ Scanning electron microscope observations revealed mainly a vein-like structure in the amorphous alloy But the fracture surface of partially crystallized amorphous alloy consisted of vein-like and featureless fracture structure. The partially crystallized alloy extracted from the thick part of the club fractured in the elastic region, at a much lower stress level than the amorphous, suggesting that relatively coarse crystal particles formed during cooling cause the brittle fracture.

Dynamic Deformation Behavior of Zr-Based Bulk Amorphous Alloy after Annealing Treatments (벌크형 비정질 Zr계 합금의 결정화 열처리에 따른 동적변형 거동)

  • Chang J. J;Lee B. J;Hwang J. I;Park I. M;Cho K. M;Cho Y. R
    • Korean Journal of Materials Research
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    • v.14 no.3
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    • pp.181-185
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    • 2004
  • The mechanical properties of a bulk amorphous alloy ($Zr_{41.2}$ $Ti_{13.8}$ /$Cu_{10}$ $Ni_{10}$ $Be_{22.5}$ /at.%) before and after an annealing treatment were investigated. For the bulk amorphous alloy, the compressive strength was about 2.0 GPa, irrespective of the strain rates in the range of $10^{-4}$ to $10^3$$ sec^{-1}$ . Fine-sized nanocrystalline particles (10~100 nm) were precipitated homogeneously in the bulk amorphous matrix after the annealing treatments. Compared to the bulk amorphous materials, these composite materials, composed of the nanocrystalline phases and a bulk amorphous matrix had much different mechanical properties. The strength and strain of coposite materials measured by a compressive test showed a peak-maximum values at 7 vol.% of the nanocrystalline phases. The values in higher volume fraction of the crystalline phases in the amorphous matrix were decreased, as measured by both quasi-static and high strain rate. The decrease in fracture strength is due to presence of the dispersed large-crystalline phases in the amorphous matrix.

A Feasibility Study on the Brazing of Zircaloy-4 with Zr-Be Binary Amorphous Filler Metals (비정질 이원계 합금 Zr-Be 용가재를 이용한 지르칼로이-4의 브레이징 타당성 검토)

  • 고진현;박춘호;김수성
    • Journal of Welding and Joining
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    • v.17 no.4
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    • pp.26-31
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    • 1999
  • An attempt was made in this study to investigate the brazing characteristics of Zr-Be binary amorphous alloys for the development of a new brazing filler metal for joining Zircaloy-4 nuclear fuel cladding tubes. This study was also aimed at the feasibility study of rapidly solidified amorphous alloys to substitute the conventional physical vapor-deposited(PVD) metallic beryllium. The $Zr_{1-x}Be_{x}$($0.3\leq$x$\leq0.5$) binary amorphous alloys were produced in the ribbon form by the melt-spinning method. It was confirmed by x-ray diffraction that the ribbons were amorphous. The amorphous. the amorphous alloys were used to join bearing pads on Zircaloy-4 nuclear fuel cladding tubes. Using Zr-Be amorphous alloys as filler metals, it was found that the reduction in the tube wall thickness caused by erosion was prevented. Especially, in the case of using $Zr_{0.65}Be_{0.35}$ and $Zr_{0.7}Be_{0.3}$ amorphousalloys, the smooth and spherical primary $\alpha$-Zr particles appeared in the brazed layer, which was the most desirable microstructure from the corrosion-resistance standpoint.

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Microstructural Evolution and Dielectric Response Characteristics During Crystallization of Amorphous Pb(Fe2/3W1/3)O3

  • Kim, Nam-Kyung;David A. Payne
    • The Korean Journal of Ceramics
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    • v.1 no.2
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    • pp.75-80
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    • 1995
  • Development of phases, evolution of microstructures, and dielectric response characteristics of amorphous lead iron tungstates during crystabllization were investiageted. A series of mircographs showing the evolution sequence of microstructures is presented. Crystallization was observed to initiate from inside of the amorphous material. A cubic perovskite phase developed fully at $760^{\circ}C$ from amorphous state via intermediate metastable crystalline structures. Dielectric constant of amorphous PFM was totally insensitive to the temperature change around the Curie temperature of crystalline material. Sintered pellet, with relative density of 96% and an almost pore-free dense internal microstructure, could be prepared from amorphous powder.

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Deformation Behavior of $CU_{54}Ni_6Zr_{22}Ti_{18}$ Bulk Amorphous Alloy during Multi-Pass Warm Rolling (동계 벌크 아몰퍼스의 다단 온간 압연시 변형 거동)

  • Park E. S.;Kim H. J.;Bae J. C.;Huh M. Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.10a
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    • pp.139-142
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    • 2005
  • Cu-Ni-Zr-Ti bulk amorphous thin strips were produced by multi-pass warm rolling of the amorphous powder at temperatures in the supercooled liquid region. Process variables for rolling of the bulk amorphous strips were properly controlled to prevent onset of crystallization and failure during rolling up to three passes. During rolling of the amorphous powder, both the deformation and densification took place and the newly developed surface on the deformed amorphous particles enhances the consolidation leading to an increase in the strength. The strain state during rolling was analyzed by FEM.

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Amorphous Metal and Amorphous Transformer (아몰퍼스 메탈과 이를 이용한 아몰퍼스 변압기)

  • Son, Hak-Sik;Kim, Jea-Cheol;Kim, In-Soo;Park, Seung-Yoon
    • Proceedings of the KIEE Conference
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    • 2001.11b
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    • pp.9-14
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    • 2001
  • On the side of that necessity, it is known that the development of Amorphous metal take effects on lowering eddy current loss in a core system. If a amorphous transformer and a motor to which "Amorphous Metal" is applied be widespread, electricity saving should be enormous with the several hundreds billion won of economic effects like cutting the cost of power plants and the unhealthy gases. This paper carried out general evaluation about the characters of Amorphous metal, the expected energy saving effects of a amorphous transformer, the environmental contribution, the increasement of electricity quality, and the features of harmonic.

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Electrical Properties of Organic Materials as Low Dielectric Constant Materials

  • Oh Teresa;Kim Hong Bae;Kwon Hak Yong;Son Jae Gu
    • Journal of the Semiconductor & Display Technology
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    • v.4 no.3 s.12
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    • pp.5-9
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    • 2005
  • The bonding structure of organic materials such as fluorinated amorphous carbon films was classified into two types due to the chemical shifts. The electrical properties of fluorinated amorphous carbon films also showed very different effect of two types notwithstanding a very little difference. Fluorinated amorphous carbon films with the cross-link break-age structure existed large leakage current resulting from effect of the electron tunneling. Increasing the cation due to the electron-deficient group increased the barrier height of the films with the cross-link amorphous structure, therefore the electric characteristic of the final materials with low dielectric constant was also improved. The lowest dielectric constant is 2.3 at the sample with the cross-link amorphous structure.

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