• 공업화학
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• 제32권6호
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• pp.690-694
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• 2021

본 연구에서는 글루코스를 전구체로 사용하여 수열합성방법을 통해 구형탄소입자(carbon sphere, CS)를 제조하였다. 200 nm, 500 nm, 1,200 nm 크기의 중공형 TiO₂ (H-TiO₂)는 CS/TiO₂ core-shell 구조를 졸-겔 법과 열처리 방법으로 합성하였다. FE-SEM, HR-TEM, XRD 분석을 통하여 H-TiO₂의 물리적 특성을 측정하였다. H-TiO₂/polyacrylate (PA) 복합체의 UV-Vis-NIR 분석을 통해 색상변화와 일사반사율을 얻었으며, 실험실에서 제작한 차열온도 측정기를 통해 차열온도를 측정하였다. H-TiO₂/PA 복합체는 열전도도가 낮은 건조공기로 채워진 중공구조에 의한 우수한 차열 특성과 근적외선 반사율을 보였다. H-TiO₂/PA 복합체에서 중공구의 크기가 증가함에 따라 열차단 특성이 증가하였다. 1,200 nm 중공 크기의 H-TiO₂를 혼합한 PA 필름에서 측정된 차열온도가 투명 유리판의 차열온도보다 26 ℃ 감소하였다.

• 한국전기전자재료학회논문지
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• 제17권12호
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• pp.1326-1331
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• 2004

In this paper, we have investigated thermal properties and Impurities content of specimens showing by changing the content of carbon black that is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICPAES(Inductively Coupled Plasma Atomic Emission Spectrometer). Heat capacity(ΔH) and melting temperature(Tm) were measured by DSC(Differential Scanning Calorimetry). The ranges of measurement temperature were from $0^{\circ}C$ to 20$0^{\circ}C$, and heating temperature was 4$^{\circ}C$/min. And then thermal diffusivity was measured by LFA 447. The measurement temperature was $25^{\circ}C$. Impurities content was highly measured according to increasing the content of carbon black from ICPAES results. And heat capacity and melting temperature from the DSC results were simultaneously decreased according to increasing the content of carbon black, while thermal diffusivity was increased according to increasing the content of carbon black. Because ionic impurities of carbon black containg Fe, Co, Mn, Al, and Zn were rapidly increasing kinetic energy by vibration of ionic impurities through the applied heat energy.

• Composites Research
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• 제31권3호
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• pp.83-87
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• 2018

An object in the Low Earth Orbit (LEO) is affected by many environmental conditions unlike earth's surface such as, Atomic oxygen (AO), Ultraviolet Radiation (UV), thermal cycling, High Vacuum and Micrometeoroids and Orbital Debris (MMOD) impacts. The effect of all these parameters have to be carefully considered when designing a space structure, as it could be very critical for a space mission. Polybenzimidazole (PBI) is a high performance thermoplastic polymer that could be a suitable material for space missions because of its excellent resistance to these environmental factors. A thin coating of PBI polymer on the carbon epoxy composite laminate (referred as CFRP) was found to improve the energy absorption capability of the laminate in event of a hypervelocity impact. However, the overall efficiency of the shield also depends on other factors like placement and orientation of the laminates, standoff distances and the number of shielding layers. This paper studies the effectiveness of using a PBI coating on the front bumper in a multi-shock shield design for enhanced hypervelocity impact resistance. A thin PBI coating of 43 micron was observed to improve the shielding efficiency of the CFRP laminate by 22.06% when exposed to LEO environment conditions in a simulation chamber. To study the effectiveness of PBI coating in a hypervelocity impact situation, experiments were conducted on the CFRP and the PBI coated CFRP laminates with projectile velocities between 2.2 to 3.2 km/s. It was observed that the mass loss of the CFRP laminates decreased 7% when coated by a thin layer of PBI. However, the study of mass loss and damage area on a witness plate showed CFRP case to have better shielding efficiency than PBI coated CFRP laminate case. Therefore, it is recommended that PBI coating on the front bumper is not so effective in improving the overall hypervelocity impact resistance of the space structure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.489-494
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• 2004

In this paper, we investigated impurities content and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrometer), and density of specimens were measured by density meter. And then heat capacity(${\Delta}H$) and melting temperature(Tm), specific heat(Cp) were measured by DSC(Differential Scanning Calorimetry). The dimension of measurement temperature was $0[^{\circ}C]\;to\;200[^{\circ}C]$, and rising temperature was $4[^{\circ}C/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also density was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat capacity, melting temperature, and specific heat from the DSC results were simultaneously decreased according to increasing the content of carbon black. Because metallic impurities of carbon black having Fe, Co, Mn, A1 and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• 대한기계학회논문집B
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• 제22권7호
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• pp.905-914
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• 1998

View factor determination is very important in thermal analysis problems with surface radiation but it is very difficult to determine view factors for complex geometries. Exact calculation of view factors for crystal growth furnace is essential due to not only its high surface temperature but the radiation shield, complicated heating system. In this study, view factor calculation algorithm is introduced and applied to cylindrical crystal growth furnace. This algorithm is based on the Hemi-Cube Algorithm and the results obtained with this algorithm show good agreements with those of analytical solution. As an application of this algorithm, temperature profiles and heating value distributions for various furnaces are calculated and the shape criteria for better furnace are suggested.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1343-1344
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• 2007

In this paper, we investigated mechanical characteristics about thermal properties in semiconductor layer of power cables. Method of specimen making used solution mixing and Tensometer 2000 of Alpha used for measurement of stress and strain. Semiconductor layer made an experiment on separately environmental temperature$[25^{\circ}C]$ and high temperature$[90^{\circ}C]$ which running temperature$[90^{\circ}C]$ of cables exposed. As a result, specimen of applicable DFS(Dual Filler System) could know mechanical superiority that its structural characteristics reinforcement considered thermal characteristics.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.154-160
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• 2005

We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Density of specimens was measured by density meter, and then stress-strain of specimens was measured by TENSOMETER 2000. A speed of measurement was 200[mm/min], ranges of stress and strain were 400(Kgf/$cm^2$) and 600[$\%$]. In addition, tests of stress-strain were progressed by aging specimens at air oven. Finally surface profile was shown in order to looking for protrusion of specimens by using smoothness tester. Density was highly measured according to increasing the content of carbon black from this experimental result, and stress was decreased, while strain was increased according to increasing the content of carbon black. And stress-strain were decreased some after aging because of oxidation reaction of chemical defect. Lastly surface of specimens smoothed generally.

• 한국전기전자재료학회논문지
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• 제26권1호
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• pp.49-55
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• 2013

In this paper, semiconducting shield specimens for a DC cable os fabricated and characterized by measurement of volume resistance, tensile strength, and the coefficient of expansion to show the electrical and mechanical characteristics of the semiconducting shield. Due to the PTC phenomenon, the volume resistance at $25^{\circ}C$ increases rapidly in comparison to the volume resistance at $90^{\circ}C$. Since the compounding ration of carbon black is low, the tensile strength and density become lower and the coefficient of expansion is increased. As the general specification of the tensile strength and density is $0.8kgf/mm^2$ and 150%, respectively, the fabricated specimen in this paper has excellent mechanical characteristic.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.144-146
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• 1995

A superconducting 2 tesla MRI magnet for the animal magnetic resonance imaging has been developed as a basic model for the application of the precise supercoducting magnet technology. MRI cryostat with 210mm room temperature bore was designed and manufactured for this magnet. The cryostat was designed basically not only to extract the principal design parameters at the performance test but also for the convenience of the manufacturing. The most extinct feacture of the cryostat is that it does not have $LN_{2}$ tank and the 77K thermal shield is cooled by circuling $LN_{2}$ through copper pipe which is welded around the shield plate. It results in reduction of the total cryostat size(about 30%).

• 대한조선학회논문집
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• 제39권1호
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• pp.61-72
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• 2002

본 연구는 부유식 해양구조물(FPSO) 소각탑 구조물에 발생하는 온도 분포 및 열응력 해석 기법을 개발하는 것을 목표로 한다. 이를 위하여 소각열에 의하여 소각탑에 발생하는 온도분포를 구하는 과정을 이론화하고 온도분포 해석을 위한 과정을 제시하였다. 그리고 온도 분포가 발생시키는 열응력 해석을 위한 기본 과정을 제시하고 예를 보였다. 온도 분포 해석을 위하여 소각열에 의한 복사열전달 현상에 의한 열전달량, 설계 환경에 의한 대류 열전달량 해석 과정을 정립하였다. 정립된 과정을 근거로 온도 해석을 위한 해석 기법을 개발하였다. 또한 열응력 해석을 위한 해석 과정을 정립하고 그 과정을 근거로 열응력 해석 기법을 개발하였다. 본 연구의 결과는 부유식 해양구조물의 소각탑 열응력 해석 및 설계 과정에 활용될 수 있을 것이다.