• Title/Summary/Keyword: heat evolution amount

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Effect of VC Addition on the Microstructural Evolution of Fe-TiC Cermet (VC의 첨가에 따른 Fe-TiC계의 미세조직변화)

  • 채기웅
    • Journal of the Korean Ceramic Society
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    • v.36 no.4
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    • pp.366-371
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    • 1999
  • The effect of VC addition on the microstructural evolution of Fe-TiC cermet has been investigated. The microstructures of the Fe-TiC varied with the amount of VC addition. The addition of 1wt% VC enhanced the instability of liquid-solid interface ; the dissolving interface showed round shape instead of facetted one which was ascribed to the increase of lattice mismatch between TiC and solid-solution carbide. in the speci-men with 10wt% VC the new set of solid-solution carbide grains of uniform and small size was formed in-side coarse TiC particles by diffusion induced recrystallizatin (DIR). With increasing the heat-treatment time fine recrystallized grains were dispersed homogeneously in the matrix and resulted in the increase in fracture strength.

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The Effect of Ground Granulated Blast-Furnace Slag on the Control of Temperature Rising in High Strength Concrete (고강도용 콘크리트의 온도상승 억제를 위한 고로슬래그 미분말의 효과)

  • 문한영;최연왕
    • Magazine of the Korea Concrete Institute
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    • v.10 no.4
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    • pp.195-204
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    • 1998
  • Generally, in order to maintain high strength in concrete, it needs high cement content and low water-cement ratio.makes internal temperature rising after concrete placing inevitably, and happens temperature stress that makes initial cracks of concrete structure. Therefore, to control the thermal stress of high-strength concrete, we made 3 types of the fineness of ground granulated blast-furnace slag and 4 steps replacement. and then measured an amount of temperature rising and elapsed time of maximum temperature and strength of concrete. Also we considered the test results of heat evolution amount and heat evolution of cement paste made with 5 steps replacement by GGBF slag.As result of this study, in case of the 50% of replacement and the 6,000$\textrm{cm}^2$/g of fineness, we obtained satisfactory results that not only the controlled effect of temperature rising but strength at early ages.

Heat Liberation in the Reaction of $YBa_2Cu_3O_{7-}\delta$, $Y_2BaCuO_5$, and Binary Compounds in the Ba-Cu-O System with Water ($YBa_2Cu_3O_{7-}\delta$, $Y_2BaCuO_5$ 및 Ba-Cu-O계 화합물의 수분과의 반응에 의한 열방출에 관한 연구)

  • 김배연
    • Journal of the Korean Ceramic Society
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    • v.32 no.1
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    • pp.83-89
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    • 1995
  • YBa2Cu3O7-$\delta$, Y2BaCuO5, and binary compounds in the Ba-Cu-O system with the nominal composition of Ba2CuO3, BaCuO2, Ba3Cu4O7, Ba3Cu5O8 were synthesized to investigate the heat evolutions and crystalline phases in the hydration reaction of orthorhombic YBa2Cu3O7-$\delta$ phase. The observed crystalline phases were YBa2Cu3O7-$\delta$, Y2BaCuO5, and BaCuO2, or Ba2Cu3O5+x, and some amount of noncrystalline phase in the Ba-Cu system comounds. In contact with distilled water, YBa2Cu3O7-$\delta$ and Y2BaCuO5 did not have considerable heat liberation, but in the binary compounds of the Ba-Cu-O system, the amount of total heat liberation was increased with respect to the Cu content. It might be that the reaction of high temperature superconductor YBa2Cu3O7-$\delta$ with water and/or moisture originated from the unusual oxidation state of Cu ion and the presence of amorphous Ba-Cu oxide compound. The degradation of high Tc superconductor by moisture and water could be controlled by restricting the heterogeneous distribution of Tc comlposition and the formation of second phase, such as stable Y2BaCuO5, and the resulting unstable Ba-Cu oxide compound.

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Energy and Mass Balance of Snowpack - Rapid snowmelt during Fohn events in the Takada plain -

  • ;Shinichi Takami
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.32 no.E
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    • pp.88-94
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    • 1990
  • Several models physically based to predict the evolution of the snowpack have been proposed. Validity of these models for hourly estimation is, however, questionable, since they have been tested only on a daily basis. A computational model to predict the amount of snowpack on an hourly basis in terms of snowload from a set of meterological measurements was developed and investigated the rapid snowmelt conditions during Fohn events in the Takada plain.

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Behavior of Eutectic Si and Mechanical Properties of Sr Modified Al-7Si-0.35Mg alloy with Solid Solution Treatment for Sand Casting (Sr 개량처리된 사형주조 Al-7Si-0.35Mg 합금의 열처리에 따른 공정 Si상 변화거동 및 특성평가)

  • Kim, Myoung-Gyun;Hwang, Seok-Min
    • Journal of Korea Foundry Society
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    • v.38 no.1
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    • pp.1-8
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    • 2018
  • In this study, we focused on the correlation between the solidification structure, heat treatment and mechanical properties of the A356 alloy according to the conditions of Sr modification. The microstructural evolution of the eutectic Si and ${\alpha}-Al$ phase in the A356 alloy castings depending on the amount of Sr were investigated during solid solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the elongation. This is supported by the fracture surface in the tensile test.

Fundamental Properties High-Strength Antiwashout Underwater Concrete (고강도 수중불분리성콘크리트의 기초물성에 대한 연구)

  • Moon, Han-Young;Kim, Seong-Soo;Song, Yong-Kyu;Jeon, Joong-Kyu
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.195-198
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    • 2000
  • Recently, the anriwashout underwater concrete has been increasingly used for underwater structures such as vary high diaphrame walls of high strength massive concrete structures. In this study, experiments were made on the fundamental properties of antiwashout underwater concrete replaced with Fly Ash from 10% to 30% to improve its properties. Resultant to the test, we got the results as follows; the value of slump flow wasi ncreased, the setting, time was very delayed, and the heat evolution amount decreased, whereas the amount of suspended solids became high, and pH value became low as to increasing the replacement ratio of Fly Ash. Also the ratios of compressive strength (in water compared to in air) at 28day were obtained over 90%, and these values were satisfied with 70% of a criterion.

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Synthesis and Their Properties of (0.8PPV+0.2DMPPV)/Silica Glass, Borosilicate Glass Composites by Sol-Gel Process (Sol-Gel법을 이용한 (0.8PPV+0.2DMPPV)/Silica Glass, Borosilicate Glass 복합체의 합성과 그 특성)

  • 이병우;김병호;윤영권;한원택
    • Journal of the Korean Ceramic Society
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    • v.34 no.9
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    • pp.993-1001
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    • 1997
  • The (0.8PPV+0.2DMPPV) copolymer and silica/borosilicate composites were synthesized by sol-gel process. The organic-inorganic hybrid solution was prepared by using of (0.8PPV+0.2DMPPV) copolymer precursor solution as a raw material for organic components and TEOS and TMB for glass components. Then by drying the solution in vacuum at 5$0^{\circ}C$ for 7days and subsequent heat treatment in vacuum at 15$0^{\circ}C$~30$0^{\circ}C$ for 2h~72h with heating rate of 0.2$^{\circ}C$/min and 1.8$^{\circ}C$/min, the organic-inorganic composites were synthesized. Microstructural evolution of the composites was characterized by DSC, IR spectrocopy, UV/VIS spectroscopy, and TEM. Elimination of the polymer precursor and degradation of the polymer were observed by DSC and Si-O and trans C=C absorption peaks were identified by IR spectra. The polymer was found to be successfully incorporated into the glass matrix and it was confirmed by the absorption peaks from the polymer in the UV/VIS spectra and the TEM results. The absorption peak of the composites was found to shift toward short wavelength side compared to that of the pure polymer and the amount of the blue shift increased with increasing the heat treatment temperature and heat treatment time and with decreasing the heating rate.

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Properties of Hydration Heat with Compressive Strength Level of High Flowing Self-Compacting Concrete (고유동 자기충전 콘크리트의 압축강도 수준에 따른 수화발열 특성)

  • Choi, Yun Wang;Jung, Jea Gwone;Lee, Jae Nam;Kim, Byoung Kwon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.5A
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    • pp.531-541
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    • 2009
  • The research analyzes and investigates conventional concrete, hydration heat, set, and mechanical properties by making high flowing self-compacting concretes of binary blend and ternary blend as one of evaluations about the properties of the hydration heat of high flowing self-compacting concrete with a strength of 30, 50, and 70 MPa. In addition, it estimates concrete adiabatic temperatures by calculating a thermal property value of powder obtained by measuring a heat evolution amount for powder used in concrete, a thermal property value of concrete obtained by conducting a simple adiabatic temperature test, and a normal thermal property value of material used in concrete, using a simple equation. Moreover, it analyzes and investigates the hydration heat property of high flowing self-compacting concrete and the thermal stress caused by hydration heat by conducting a 3D temperature stress analysis for the hydration heat and the adiabatic temperature obtained by temperature analysis, using MIDAS CIVIL 06 program.

Numerical Analysis of Laboratory Heating Experiment on Granite Specimen (화강암의 실내 가열실험에 대한 수치해석적 검토)

  • Dong-Joon, Youn;Changlun, Sun;Li, Zhuang
    • Tunnel and Underground Space
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    • v.32 no.6
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    • pp.558-567
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    • 2022
  • The evolution of temperature and thermal stress in a granite specimen is studied via heating experiment in the context of a high-level radioactive waste repository. A heating condition based on the decay-induced heat is applied to a cubic granite specimen to measure the temperature and stress distributions and their evolution over time. The temperature increases quickly due to heat conduction along the heated surfaces, but a significant amount of thermal energy is also lost through other surfaces due to air convection and conduction into the loading machine. A three-dimensional finite element-based model is used to numerically reproduce the experiment, and the thermo-mechanical coupling behavior and modeling conditions are validated with the comparison to the experimental results. The most crucial factors influencing the heating experiment are analyzed and summarized in this paper for future works.

Effects of Portland Cement Characters and Working Temperature on the Physical Properties of Cement Mortars (시멘트의 특성과 사용 온도가 모르터의 물성에 미치는 영향)

  • 김원기;김창은
    • Journal of the Korean Ceramic Society
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    • v.37 no.5
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    • pp.410-417
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    • 2000
  • In this study the effects of specifics surface area of cement, addition amount of gypsum and substitution ratio of gypsum anhydrite ont he physical properties of cement mortars were investigated by measruements of setting time, flow, compressive strength and hydration heat evolution rate. The results showed that fluidity of mortars was increased by 40 wt.% of maximum flow change with the decreasing specific surface area of cement from 3,500$\textrm{cm}^2$/g to 3,300${\pm}$50$\textrm{cm}^2$/g and affected by the relationship between the cement and balancing between the chemical activityof cement and solubility of calcium sulfate are desirable to prevent the fluidity of concrete from decreasing by high temperature in summer season.

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