• Progress in Superconductivity
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• 제9권1호
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• pp.62-67
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• 2007

The effects of the heat-treatment temperature on the carbon (C) substitution amount, full width at half maximum (FWHM) value, critical temperature ($T_c$), critical current density ($J_c$) have been investigated for 10 wt % malic acid ($C_4H_6O_5$)-doped $MgB_2/Fe$ wires. All the samples were fabricated by the in-situ powder-in-tube (PIT) method and heat-treated within a temperature range of $650^{\circ}C$ to $1000^{\circ}C$. As the heat-treatment temperature increased, it seemed that the lattice distortion was increased by a more active C substitution into the boron sites from the malic acid addition. These increased electron scattering defects seemed to enhance the $J_c-H$ properties in spite of an improvement in the crystallinity, such as a decrease of the FWHM value and an increase of the $T_c$. Compared to the un-doped wire heat-treated at $650^{\circ}C$ for 30 min, the $J_c$ was enhanced by the C doping in a high-field regime. The wire heat-treated at $900^{\circ}C$ resulted in a higher magnetic $J_c$ of approximately $10^4\;A/cm^2$ at 5 K and 8 T.

• 한국진공학회지
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• 제7권3호
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• pp.176-186
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• 1998

Si 기판 위에 3종의 Pt-Co 합금박막 (Pt66-Co34, Pt40-Co60, Pt18-Co82)과 순수한 Pt, Co 박막 시료를 제작하여 표면 조성분석의 정량화 및 표준화를 위한 표준시료로 제안하 였다. in-istu X-ray photoelectron spectroscopy(XPS)분석에 의해 증착된 이원 합금박막의 조성이 정확히 조절되었으며, 합금박막의 실제 조성은 유도결합플라즈마-원자방출분광법 (inductively coupled plasma-atomic emission spectroscopy: ICP-AES)과 러더퍼드 후방산 란분광법(Ruthford back-scattering spectrometry: RBS)에 의해 결정되었다. in-situ XPS 결과와 ICP에 의한 조성을 비교한 결과 매질 효과를 고려하면 비교적 정확한 조성을 구할 수 있음이 확인되었다. 이 시료를 이용한 XPS와 Auger electron spectroscopy(AES)에 의한 국내 공동분석 결과는 약4%내외의 큰 편차를 보이고 있지만, 평균 조성 값은 약1%의 오차 범위 내에서 두 방법에 의한 결과가 서로 잘 일치하였다. 이온빔 스퍼터링에 의해 Pt조성이 증가된 표면층이 형성되어 정확한 조성분석을 위해서는 선택스퍼터링에 의한 표면 변형을 정량적으로 함을 알았다.

• 한국주조공학회지
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• 제32권2호
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• pp.104-108
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• 2012

The effect of heat treatment on mechanical properties of 0.4C-2.3Si(wt%) steel with bainitic ferrite matrix were investigated. This steel has been synthesized intergrating concepts from TRIP(Transformation Induced Plasticity) steel & Austempered Ductile Cast Iron(ADI) technology. The low alloy medium carbon (0.4 %C) steel with high silicon (2.3 %Si) was initially annealed for 60 min at $800^{\circ}C$, $820^{\circ}C$ and $840^{\circ}C$ respectively in the intercritical region and then subsequently austempered at various temperatures at $260^{\circ}C$, $320^{\circ}C$ and $380^{\circ}C$ for 30 min in a salt bath. The mechanical properties were measured by using a tensile test. A detailed study of the microstructure of this steel after heat treatment was carried out by means of electron back scattering diffraction (EBSD) technic. In this study, a new low alloy steel with high strength (780~1,050MPa) and exceptionally high ductility (20~40%) was obtained.

• 한국주조공학회지
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• 제32권3호
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• pp.138-143
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• 2012

This steel has been synthesized integrating concepts from Austempering Ductile Cast Iron (ADI) technology. While ADI has excellent mechanical and physical properties, the Young's modules of ADI is approximately 20% lower than steel. In addition, the presence of graphite nodules in ADI can be sites of crack initiation, where fracture takes place at graphite matrix interface. Because of this limitations of ADI, there has been a growing interest in austempered steels as structural materials in resent years. In this investigation, a new steel with microstructure composed of ferrite and austenite and with simultaneous high tensile strength (1,150 MPa) and high ductility (33%) was developed. The goal of this investigation is to obtain a better understanding of deformation and transformation behaviour in high carbon retained austenite(${\gamma}_{HC}$) and over-saturated ferrite(${\alpha}$) during the plastic deformation. A detailed study of the microstructure of this steel was carried out by means of X-ray diffraction (XRD) and electron back scattering diffraction (EBSD) technic. In this way it was shown that BCC phase (BCC) took up the larger part of the nominal strain whereas the a part of retained austenite responded to the mechanincal load by partial martensite transformation, and misorientation change in the retained austenite after plastic strain could be attributed to the large elongation.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.333-333
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• 2006

We synthesized two novel polynorbornene derivatives, chiral poly(norbornene acid methyl ester) (C-PNME) and racemic poly(norbornene acid n-butyl ester) (R-PNME), which are potential low dielectric constant materials for applications in advanced microelectronic and display devices. Thin films of these polymers deposited on substrates were investigated by structural analyses using synchrotron grazing incidence X-ray scattering, specular reflectivity and ellipsometry. These analyses provided important information on the structure, electron density gradient across film thickness, chain orientation, refractive index and thermal expansion of the polymers in substrate-supported thin films. The structural characteristics and properties of the thin films were first dependent on the polymer chain' tacticity and further influenced by film thickness and thermal annealing.

• 폴리머
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• 제37권3호
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• pp.332-341
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• 2013

H-shaped amphiphilic pentablock copolymers $(PSt)_2-b-PCL-b-PEO-b-PCL-b-(PSt)_2$ was synthesized via chemoenzymatic method by combining enzyme-catalyzed ring-opening polymerization (eROP) of ${\varepsilon}$-caprolactone (${\varepsilon}$-CL) and atom transfer radical polymerization (ATRP) of styrene. By this process, we obtained copolymers with controlled molecular weight and low polydispersity. The structure and composition of the obtained copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and infrared spectroscopy analysis (IR). The crystallization behavior of the copolymers was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The crystallization behavior of the H-shaped block copolymers demonstrated a PCL dominate crystallization. The self-assembly behavior of the copolymers was investigated in aqueous media. The hydrodynamic diameters of the copolymer micelles in aqueous solution were measured by dynamic light scattering (DLS). The morphology of the copolymer micelles was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The hydrodynamic diameters of spherical micelles declined gradually with the increase of the hydrophobic chain lengths of the copolymers. The critical micelle concentration (CMC) values were determined from fluorescence emission, and it was found that the CMCs decreased with an increase of PSt hydrophobic block lengths.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1994년도 제6회 학술발표회 논문개요집
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• pp.50-50
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• 1994

Half-metallic Heusler alloys (NiMnSb, ppdMnSb, pptMnSb) have attracted much attention due to their unique electronic and magnetic structures. Sppin-ppolarized band structure calculation ppredicts metallic behavior for the majority sppin states and semiconductor behavior for the minority sppin states. We have studied the electronic structures of these half-metallic Heusler alloys by core-level pphotoemission sppectroscoppy of Mn 2pp and 3s XppS sppectra. We found large intensities of Mn 2pp satellites and 3s exchange spplitting comppared with other metal Mn-alloys. These satellite structure can be understood by applying Anderson imppurity model. This fact supports the calculated sppin pprojected ppartial density of states which suggests that the valence electrons be highly sppin ppolarized near Fermi level and that the electrons involved with charge-transfer be mainly minority sppin ones which have semiconducting band structure. The trend of charge transfer energies Δ from ligands (Sb 5pp) to Mn 3d, obtained from our model fitting, is consistent with that calculated from sppin pprojected ppartial density of state. Also the trend of d-d electron correlation energies U calculated from Mn Auger line L3 VV by Mg $K\alpha$ source is comppatible with that resulted from our model fitting. We fitted the Mn 3s curve in the same way as for insulating Mn comppounds by using the same pparameters calculated from Mn 2pp curve fitting exceppt for the Coulomb interaction energy Q between core hole and d-electrons. The 3s sppectra were analyzed by combing the charge transfer model and a simpple model taking into account the configuration mixing effect due to the intra-shell correlation. We found that the exchange interaction between 3s hole and 3d electrons is mainly respponsible for the satellite of Mn 3s sppectra. This is consistent with the neutron scattering data, which suggests local 3d magnetic moment. We find that the XppS analysis results of Mn 2pp and 3s satellite structures of half-metallic Heusler alloys are very similar to those of insulating transition metal comppounds.

• 대한전자공학회논문지SD
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• 제41권11호
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• pp.7-13
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• 2004

두께가 약 3 nm 인 게이트 산화막을 갖는 P 및 NMOSFET를 제조하여 높은 압력 (5 atm.)의 중수소 및 수소 분위기에서 후속 열처리를 각각 행하여 중수소 효과(동위원소 효과)를 관찰하였다. 소자에 대한 스트레스는 -2.5V ≤ V/sub g/ ≤-4.0V 범위에서 100℃의 온도를 유지하며 진행되었다. 낮은 스트레스 전압에서는 실리콘 계면에 존재하는 정공에 의하여 게이트 산화막의 열화가 진행되었다. 그러나 스트레스 전압을 증가시킴으로써 높은 에너지를 갖는 전자에 의한 계면 결함 생성이 열화의 직접적인 원인이 됨을 알 수 있었다. 본 실험조건에서는 실리콘 계면에서 phonon 산란이 많이 발생하여 impact ionization에 의한 "hot" 정공의 생성은 무시할 수 있었다. 중수소 열처리를 행함으로써 수소 열처리에 비해 소자의 파라미터 변화가 적었으며, 게이트 산화막의 누설전류도 억제됨이 확인되었다. 이러한 결과로부터 impact ionization이 발생되지 않을 정도의 낮은 스트레스 전압동안 발생하는 게이트 산화막내 결함 생성은 수소 결합과 직접적인 관계가 있음을 확인하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 춘계종합학술대회
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• pp.451-454
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• 2000

임팩트이온화는 고전계하에서 고에너지를 지닌 캐리어간 산란으로써 전자전송해석에 필수적인 요소이다. 임팩트이온화율 계산은 풀밴드 E-k관계와 페르미의 황금법칙을 이용하였다. 본 연구에서는 풀밴드 Monte Carlo 시뮬레이션을 이용하여 온도 및 전계에 대한 Si 임팩트이온화계수를 조사하였다. 임팩트이온화 모델에 의해서 계산된 look의 임팩트이온화계수는 실험값과 잘 맞았다. 온도상승에 따른 임팩트이온화계수와 전자의 에너지는 포논산란의 emission 모드의 증가 때문에 감소함을 알 수 있었다. 임팩트이온화계수의 대수는 온도와 전계에 대한 선형함수로 fitting 되었다. 이 선형함수의 오차는 5%이내이다. 결과적으로 임팩트이온화계수의 대수는 선형적으로 온도와 전계에 의존함을 알 수 있었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권3호
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• pp.262-267
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• 2006

The objective of this study was to develop new self-organized nanogels as a means of drug delivery in patients with cancer. Pullulan (PUL) and deoxycholic acid (DOCA) were conjugated through an ester linkage between the hydroxyl group in PUL and the carboxyl group in DOCA. Three types of PUL/DOCA conjugates were obtained, differing in the number of DOCA substitutions (DS; 5, 8, or 11) per 100 PUL anhydroglucose units. The physicochemical properties of the resulting nanogels were characterized by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The mean diameter of DS 11 was the smallest (approx. 100 nm), and the size distribution was unimodal. To determine the organizing behavior of these conjugates, we calculated their critical aggregation concentrations (CACs) in a 0.01-M phosphate buffered saline solution. They were $10.5{\times}10^{-4}mg/mL,\;7.2{\times}10^{-4} mg/mL,\;and\;5.6{\times}10^{-4} mg/mL$ for DS 5, 8, and 11, respectively. This indicates that DOCA can serve as a hydrophobic moiety to create self-organized nanogels. To monitor the drug-releasing behavior of these nanogels, we loaded doxorubicin (DOX) onto the conjugates. The DOX-loading efficiency increased with the degree of DOCA substitution. The release rates of DOX from PUL/DOCA nanogels varied inversely with the DS. We concluded that the PUL/DOCA nanogel has some potential for use as an anticancer drug carrier because of its low CAC and satisfactory drug-loading capacity.