• 한국결정성장학회지
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• 제3권2호
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• pp.99-106
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• 1993

열분석(DTA : Differential Thermal Analysis) 방법에 의한 퀴리온도$(T_c)$ 측정방법으로부터 48.50에서 49 $Li_2O$ mole %까지의 퀴리온도$(T_c)$와 $Li_2O$ mole %(C)의 관계식 $(T_c = -17.869C^2+1840.2C-46623)$을 구하였다.$LiTaO_3$ 단결정의 congruent 조성을 결정하기 위하여 48.60 부터 48.70 mole %까지의 영역에서 쵸크랄스키법으로 $LiTaO_3$ 단결정을 육성하고 Top과 Tail 결정에서의 퀴리온도 차이,${\Delta}{T_c} (T_{c(Top)}-T{_c(Tail)})$ 그리고 결정성장 초기와 말기의 융액과 결정의 조성비로부터 분배계수(k)를 구하였다. 이 결과로부터 결정된 congruent 조성은 48.65 mole %였으며 그때의 $(T_c)$ 값은 $610{\pm}1^{\circ}C$였다.

• 폴리머
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• 제33권1호
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• pp.13-18
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• 2009

인공뼈의 잠재적인 재료로서 주목을 받는 hydroxyapatite(HA)와 Poly(L-lactide)(PLLA) 복합체의 물성을 개선하기 위하여 HA에 D-lactide(DLA)를 표면 그래프트(g-HA)하여 PLLA 사이의 스테레오 콤프렉스 형성을 도입하였다. 복합체 필름은 건조단계에서 HA의 침전을 최소화하기 위하여 용매-비용매법으로 제조하였다. 복합체의 구조와 물성은 thermal gravimetric analysis(TGA), differential scanning calorimeter, scanning electron microscopy 및 mechanical property 측정으로 확인하였다. TGA분석으로부터 HA에 대한 DLA의 표면 그래프트율은 6 wt%였고 HA에 비하여 유기용매에 대한 분산성이 증가하였다. 복합체의 스테레오 콤프렉스 형성은 용융온도의 변화로써 확인하고 HA/PLLA 복합체에 비하여 우수한 기계적 물성을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제30권4호
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• pp.783-786
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• 2009

Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and ion chromatography(IC) were employed to analyze the thermal behavior of $Li_xCoO_2$ cathode material of lithium ion battery. The mass loss peaks appearing between 60 and 125 ${^{\circ}C}$ in TGA and the exothermic peaks with 4.9 and 7.0 J/g in DSC around 75 and 85 ${^{\circ}C}$ for the $Li_xCoO_2$ cathodes of 4.20 and 4.35 V cells are explained based on disruption of solid electrolyte interphase (SEI) film. Low temperature induced HF formation through weak interaction between organic electrolyte and LiF is supposed to cause carbonate film disruption reaction, $Li_2CO_3\;+\;2HF{\rightarrow}\;2LiF\;+\;CO_2\;+\;H_2O$. The different spectral DSC/TGA pattern for the cathode of 4.5 V cell has also been explained. Presence of ionic carbonate in the cathode has been identified by ion chromatography and LiF reported by early researchers has been used for explaining the film SEI disruption process. The absence of mass loss peak for the cathode washed with dimethyl carbonate (DMC) implies ionic nature of the film. The thermal behavior above 150 ${^{\circ}C}$ has also been analyzed and presented.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.242-242
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• 2006

Increasingly complex tasks are performed by computers or cellular phone, requiring more and more memory capacity as well as faster and faster processing speeds. This leads to a constant need to develop more highly integrated circuit systems. Therefore, there have been numerous studies by many engineers investigating circuit patterning. In particular, PCB including module/package substrates such as FCB (Flip Chip Board) has been developed toward being low profile, low power and multi-functionalized due to the demands on miniaturization, increasing functional density of the boards and higher performances of the electric devices. Imprint lithography have received significant attention due to an alternative technology for photolithography on such devices. The imprint technique. is one of promising candidates, especially due to the fact that the expected resolution limits are far beyond the requirements of the PCB industry in the near future. For applying imprint lithography to FCB, it is very important to control thermal properties and mechanical properties of dielectric materials. These properties are very dependent on epoxy resin, curing agent, accelerator, filler and curing degree(%) of dielectric materials. In this work, the epoxy composites filled with silica fillers and cured with various accelerators having various curing degree(%) were prepared. The characterization of the thermal and mechanical properties wasperformed by thermal mechanical analysis (TMA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), rheometer, an universal test machine (UTM).

• 폴리머
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• 제34권4호
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• pp.369-375
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• 2010

용융 중합법을 이용하여 말단에 메틸 말레이미드(methyl maleimide) 반응성기를 가지며 방향족 에스터와 아 미드 결합을 포함하는 액정(liquid crystal, LC)을 합성하였다. 합성된 액정은 용액 캐스팅과 열처리를 거쳐 열경화 성 액정(liquid crystalline thermoset, LCT) 필름으로 제조되었다. 합성된 LC 및 LCT는 적외선 분광기(FTIR), 시차주사 열량계(DSC), 열중량 분석기(TGA), 열-기계 분석기(TMA), X-선 회절기(XRD) 및 가열판이 부착된 편광 현미경(POM) 등을 이용해서 각각 특성 분석을 하였다. 합성된 모든 액정은 스멕틱(smectic) 상을 보였으며 LC와 LCT들의 열적 성질은 주로 주사슬에 포함된 메소젠 구조에 영향을 받았다. 열팽창 계수(coefficients of thermal expansion, CTE)는 27.72~50.95 ppm/$^{\circ}C$ 사이의 값을 보였다.

• 한국추진공학회지
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• 제19권1호
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• pp.33-41
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• 2015

DSC 실험 데이터를 이용하여 고에너지 물질의 반응속도식을 추출해내는 이론적 방법을 제안하고 알루미늄 고함유 화약(RDX/HTPB/Al)에 대한 반응속도식 추출을 수행하였다. DSC 실험 결과는 Friedman 등전환법으로 분석되며 AKTS software를 사용하였다. 질량분율에 따른 활성화에너지와 빈도인자를 추출해 내어 반응속도식을 완성하였다. 추출된 반응속도식은 기존의 ODTX 실험을 통해 추출되는 화학반응속도식 형태에 비해 이론적 측면과 정확성 측면에서 상당한 장점을 갖는다. 추출된 반응속도식의 검증을 위해 화학반응률 그리고 생성물 질량분율에 대해 DSC 실험과 동일한 조건하에서 전산모사를 수행하였으며 실험값과 잘 일치함을 확인하였다. 또한 붕소 질산칼륨($B/KNO_3$)에 대한 완속가열 전산모사를 수행하였으며 실험결과와 비교하여 DSC 반응속도식의 전산모사에의 적용가능성을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.341-344
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• 2002

A matched asymptotic analysis is conducted for a compressible rotating flow in a cylindrical container when a mechanical and/or a thermal disturbance is imposed on the wall. The system Ekman number is assumed to be very small. The conditions for the Taylor-Proudman column in the interior, which were also given in the companion paper Park & Hyun, 2002) by means of the energy balancing analysis, have been re-derived. The concept of the variable, the energy content $e[{\equiv}T+2 {\alpha}^2 {\gamma}{\nu}]$, is reformulated, and its effectiveness in characterizing the energy transport mechanism is delineated. It is seen that, under the condition of the Taylor-Proudman column, numerous admissible theoretical solutions for interior flow exist with an associated wail boundary condition. Some canonical examples are illustrated with comprehensive physical descriptions. The differential heating problem on the top and bottom endwall disks is revisited by using the concept of the energy content. The results are shown to be in line with the previous findings.

• 한국표면공학회지
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• 제32권6호
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• pp.709-716
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• 1999

Ceramic is select for an alternative substrate material for high-speed circuits due to its low-thermal expansion. As, in this study, ceramic was prepared by ISG (interlayer sol-gel) process using metal salts and a metal alkoxide as the starting materials. Generally ceramic substrate is used electroless copper plating for the metallization. But it has been indicate weakely the adhesion strength between the substrate and copper layer. Therefore, this research, using the ISG process on the preparation of homogeneous and possible preparation at law temperature fabricated sol solution. Using of the dip coating method was coated for the purpose of giving the anchoring effect on the coating layer and enhancing the adhesion strength between the $Al_2$O$_3$ substrate and copper layer. This study examined primary the characteristic of the sol making condition and differential thermal analysis (DTA) X-ray diffraction (XRD) were mearsured to identify the crystal phase of heat treatment specimens. The morphology of the coated films were studied by scanning electron microscopy(SEM). As a resurt, XRD analysis was obtained patterns of $\alpha$-cordierite after heat-treatment about 2 hours at $1000^{\circ}C$. SEM analysis could have seen a large number of voids on coated film. The more contants of$ Al_2$$O_3$ Wt% was increased the more voids was advanced. Peel adhesion strength has a maximum in the contants of the TEOS:ANE of 1:0.7 mole%. In this case, adhesion strength has been measured 1150gf, peel adhesion strength were about 10 times more than uncoated of the ceramics film.

• 한국화재소방학회논문지
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• 제18권2호
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• pp.73-78
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• 2004

본 연구는 화재가 발생할 때 방화문과 바닥 면의 하부 틈새를 박아 연기와 열의 누설 또는 확산을 막을 수 있는 연기/열 차단막에 대하여 연구하였다. 본 연구에서는 제연구역의 차압과 화재발생 시 발생하는 연기의 유체부력에 의한 역학적인 힘과 열기류를 고려하여 유한요소 해석코드인 $ANSYS^{\circledR}$ 을 이용하여 해석하였다. 연구결과로부터 하중조건을 최소화할 수 있는 연기/열 차단막의 최적설계의 방향을 제시하였고, 연기/열 차단막의 형상설계에 활용함으로서 연기/열 차단 시스템의 엔지니어링 데이터를 구축하는데 도움이 되었다.

• Advances in nano research
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• 제6권4호
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• pp.399-422
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• 2018

Unwanted vibration is an issue in many industrial systems, especially in nano-devices. There are many ways to compensate these unwanted vibrations based on the results of the past researches. Elastic medium and smart material etc. are effective methods to restrain unnecessary vibration. In this manuscript, dynamic analysis of viscoelastic nanosensor which is made of functionally graded (FGM) nanobeams is investigated. It is assumed that, the shaft is flexible. The system is modeled based on Timoshenko beam theory and also environmental condition, external linear varying loads and thermal loading effect are considered. The equations of motion are extracted by using energy method and Hamilton principle to describe the translational and shear deformation's behavior of the system. Governing equations of motion are extracted by supplementing Eringen's nonlocal theory. Finally vibration behavior of system especially the frequency of system is developed by implementation Semi-analytical differential transformed method (DTM). The results are validated in the researches that have been done in the past and shows good agreement with them.