• Title/Summary/Keyword: high temperatures

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Effects of glass powder on the characteristics of concrete subjected to high temperatures

  • Belouadah, Messaouda;Rahmouni, Zine El Abidine;Tebbal, Nadia
    • Advances in concrete construction
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    • v.6 no.3
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    • pp.311-322
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    • 2018
  • This paper presents an experimental investigation on the performance of concrete with and without glass powder (GP) subjected to elevated temperatures. Mechanical and physicochemical properties of concretes were studied at both ambient and high temperatures. One of the major environmental concerns is disposal or recycling of the waste materials. However, a high volume of the industrial production has generated a considerable amount of waste materials which have a number of adverse impacts on the environment. Further, use of glass or by-products in concrete production has advantages for improving some or all of the concrete properties. The economic incentives and environmental benefits in terms of reduced carbon footprint are also the reason for using wastes in concrete. The occurrence of spalling, compressive strength, mass loss, chemical composition, crystalline phase, and thermal analysis of CPG before and after exposure to various temperatures (20, 200, 400, and $600^{\circ}C$) were comprehensively investigated. The results indicated that, the critical temperature range of CPG was between $400^{\circ}C$ and $600^{\circ}C$.

A Prediction Model on Porosity of Hardened Cement Paste under High Temperatures (고온시의 경화된 시멘트 페이스트의 공극률 예측모델)

  • Lee, Jae-Sung;Jung, Sung-Jin;Jung, Young-Han;Kim, Heung-Youl;Kim, Hyung-Jun
    • Fire Science and Engineering
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    • v.23 no.3
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    • pp.103-109
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    • 2009
  • The thermal degradation of concrete results mainly from two mechanisms. The first one is related to phase transformations of constituents at different temperatures. The initial constituents transform to other phases due to elevated temperature. The second mechanism is related to the temperature sensitivity of the mechanical properties of the constituents in concrete. Therefore, the degradation of concrete under high temperatures must be studied from both mechanical and chemical points of view. This study was performed as a basic study to propose the material models of concrete exposed to high temperatures considering above two mechanisms. This study presents a prediction model on the porosity of hardened cement paste considering phase changes according to temperature increase.

Properties and durability of concrete with olive waste ash as a partial cement replacement

  • Tayeh, Bassam A.;Hadzima-Nyarko, Marijana;Zeyad, Abdullah M.;Al-Harazin, Samer Z.
    • Advances in concrete construction
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    • v.11 no.1
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    • pp.59-71
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    • 2021
  • This research aims to study the utilization of olive waste ash (OWA) in the production of concrete as a partial substitute for cement. Effects of using OWA on the physical and mechanical properties of concrete mixtures have been investigated. This is done by carrying out tests involving the addition of various percentages of OWA to cement (0%, 5%, 10% and 15%). For each percentage, tests were performed on both fresh and hardened concrete; these included slump test, unit weight test and compressive strength test after 7, 28 and 90 days. Durability tests were investigated in solutions containing 5% NaOH and MgSO4 by weight of water. In addition, resistance to high temperatures was tested by subjecting the cubes to high temperatures of up to 170℃. The results of this research indicate that a higher percentage of OWA gives a lower compressive strength and lower workability but higher performance in terms of durability against both different weather conditions and high temperatures.

High-temperature Deformation Behavior of 5052 Aluminum Alloy for Hot Shearing Process (고온전단가공을 위한 5052 알루미늄 합금의 고온 변형거동)

  • Song, Shin-Hyung;Choi, Woo Chun
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.25 no.3
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    • pp.177-181
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    • 2016
  • Hot shearing is a method of producing various high-quality planar machine parts by using reduced punch load. In order to predict the results of this process, the deformation behavior of work material at elevated temperatures need to be studied. In this research, a tensile test was carried out for 5052 aluminum alloy at high temperatures of $240-540^{\circ}C$ and strain rates of 0.001-0.1/s. The results of the tensile tests were studied to predict the deformation of the alloy during the hot shearing process. The results showed that hot shearing within a temperature range of $340-440^{\circ}C$ and a strain rate rage of 0.001-01/s will be the most effective in reducing punch load and increasing the sheared edge in the case of 5052 aluminum alloy.

Investigation of soldered low-resistance joints for coated conductors

  • Balashov, N.N.;Degtyarenko, P.N.;Ivanov, S.S.
    • Progress in Superconductivity and Cryogenics
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    • v.17 no.1
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    • pp.25-27
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    • 2015
  • The experimental investigation of resistance and thermal impacts stability of coated conductor joints has been carried out. We measured resistances of solder layers with the thicknesses ca. 10, 20, 30 and $40{\mu}m$ and additionally studied their stability against thermal impacts. The obtained results show a high quality of this joints and their applicability, e.g., for design of current leads in various superconductive energy applications.

Physicochemical Properties of Soybeans as Influenced by Storage Temperatures (저장온도가 콩의 이화학적 특성에 미치는 영향)

  • 육홍선;설민숙;이현자
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.27 no.5
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    • pp.827-832
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    • 1998
  • Soybeans(Hwangkeum Kong) were stored at 5$^{\circ}C$, $25^{\circ}C$ and 35$^{\circ}C$ for 8 months to investigate the changes of the physicochemical properties. Less physicochemical changes were detected in the soybeans stored at 5$^{\circ}C$ than those stored at $25^{\circ}C$ and 35$^{\circ}C$. High temperature and long term storage caused a decrease in the nitrogen solubility index, whereas increases in acid value and organic acid content were detected. As the storage period was extended at high temperatues, the content of unsaturated fatty acids decreased, but the content of saturated fatty acids increased. Decoloration of soybeans was clearly recognized under high temperatures. The water soluble compoents such as total solids, nitrogen and reducing sugar during water-soaking at 2$0^{\circ}C$ for 16hrs were appreciably eluted from the soybeans stored for 8 months at high temperatures. The pH of the water extract slightly shifted to the acidic range.

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Filling the Submicron Contact Holes with Al Alloys (AI 합금의 Contact Hole Filling 에 관한 연구)

  • 김용길
    • Journal of the Korean Vacuum Society
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    • v.2 no.4
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    • pp.474-479
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    • 1993
  • Submicron contact hole filling with aluminum alloys has been achieved with a multistep metallization method, which utilizes a metal " flow" or self-diffusion process at elevated temperatures after the metal was sputter-deposited. A multi-chamber, modular sputtering system was employed to deposit aluminum alloys and subsequently to anneal the deposited metal films under vacuum at high temperatures. The film were deposited on 200 mm wafers with planar, dc magnetron sputtering sources without anysubstrate bias. The basic process steps studied for the multistep metallization include an initial layer deposition at low temperatures less than $100^{\circ}C$, and an annealin gstep at elevated temperatures, between 450 and $550^{\circ}C$. The degree of planarization or step coverage was dependent strongly upon the temperature and time of the flow step and complete filling of the submicron contacts with aluminum alloys was achieved. Responsible mechanisms for the enhancement in step coverge and factros determining uniform and reproducible flow of aluminum alloys during the high temperauture step are discussed.discussed.

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Reverse-bias Leakage Current Mechanisms in Cu/n-type Schottky Junction Using Oxygen Plasma Treatment

  • Kim, Hogyoung
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.2
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    • pp.113-117
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    • 2016
  • Temperature dependent reverse-bias current-voltage (I-V) characteristics in Cu Schottky contacts to oxygen plasma treated n-InP were investigated. For untreated sample, current transport mechanisms at low and high temperatures were explained by thermionic emission (TE) and TE combined with barrier lowering, respectively. For plasma treated sample, experimental I-V data were explained by TE or TE combined with barrier lowering models at low and high temperatures. However, the current transport was explained by a thermionic field emission (TFE) model at intermediate temperatures. From X-ray photoemission spectroscopy (XPS) measurements, phosphorus vacancies (VP) were suggested to be generated after oxygen plasma treatment. VP possibly involves defects contributing to the current transport at intermediate temperatures. Therefore, minimizing the generation of these defects after oxygen plasma treatment is required to reduce the reverse-bias leakage current.

The effect of annealing condition on texture and microstructure development of Ni tapes prepared by powder metallurgy (분말야금법으로 제조한 니켈 선재에서 집합조직과 미세조직 발달에 미치는 재결정 열처리의 영향)

  • 이동욱;지봉기;임준형;주진호;정태원;박해웅;정충환;전병혁;김찬중
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.02a
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    • pp.81-84
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    • 2003
  • The effect of annealing condition on the texture and microstructure development in Ni tapes fabricated by cold-rolling including powder metallurgy was investigated. The Pole-figure results showed that the Ni tapes annealed at lower temperature than 50$0^{\circ}C$ were the mixture of brass deformation texture and cube texture. The specimens annealed at high temperatures had only well-developed cube texture and the FWHMs of in-plane and out-of-plane were in the range of 8-10$^{\circ}$. The degree of texture was not significantly depended on annealing temperatures. The grain morphologies of Ni tapes prepared at low temperatures showed serrated grain boundaries due to incomplete recrystallization, but the specimens prepared at high temperatures showed stabilized grain shape without serrated grain boundaries.

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Evolution of Microstructure and Mechanical Properties of a Ni Base Superalloy during Thermal Exposure (니켈기 초내열합금의 열간노출에 따른 미세조직 및 기계적 특성 변화)

  • Kim, In-Soo;Choi, Baig-Gyu;Jung, Joong-Eun;Do, Jeong-Hyeon;Jung, In-Yong;Jo, Chang-Yong
    • Journal of Korea Foundry Society
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    • v.36 no.5
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    • pp.159-166
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    • 2016
  • The microstructural evolution of a cast Ni base superalloy, IN738LC, has been investigated after long term exposure at several temperatures. Most of the fine secondary ${\gamma}^{\prime}$ particles resolved after 2000 hour exposure at $816^{\circ}C$. At higher temperatures of $871^{\circ}C$ and $927^{\circ}C$, secondary ${\gamma}^{\prime}$ resolved after 1000 hours of exposure, and cuboidal primary ${\gamma}^{\prime}$ grew with exposure time. During the thermal exposure, ${\sigma}$ phase formed at all tested temperatures, and ${\eta}$ phase was observed around interdendritic regions due to carbide degeneration. The influence of microstructural evolution during thermal exposure on the mechanical properties has been analyzed. The effects of ${\gamma}^{\prime}$ particle growth are more pronounced on the high temperature creep properties than on the room temperature tensile properties.