• 유기물자원화
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• 제21권3호
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• pp.43-52
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• 2013

본 연구에서는 유입 슬러지에 다양한 전처리 방법을 적용하여 전처리 방법이 중온혐기-고온호기 복합 슬러지 처리 공정의 슬러지 소화효율과 메탄가스 생성량에 미치는 영향을 비교 검증하였다. 실험실 규모의 슬러지 소화장치를 제작하여 서로 다른 유입 슬러지 전처리방법을 적용하여 4단계로 실험을 진행하였다. 1단계에서는 전처리를 하지 않은 슬러지를 공급하였고, 2, 3, 4단계에서는 각각 열처리, 열-알칼리처리, 장기 알칼리 처리(7일)를 거친 유입 슬러지를 공급하였다. 실험 결과, 1단계에서 4단계까지 진행되는 동안 총COD 제거율은 44%에서 76%까지 증가하였으며, 메탄 생성량 또한 101mL/L/day에서 165, 256mL/L/day까지 크게 증가하였다. 한편, 4단계에서는 7일간의 장기 알칼리 처리를 하였음에도 불구하고 3단계에 비해 총COD 제거율과 메탄 생성량이 증가하지 않았다. 결론적으로, 유입 슬러지의 전처리를 통해 복합 슬러지 처리 공정의 슬러지 제거 효율과 메탄생성량을 크게 증가시킬 수 있었으며, 여러 가지 전처리 방법 중 열-알칼리 처리법이 가장 효율적임을 실험결과를 통해 알 수 있었다.

• Corrosion Science and Technology
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• 제13권1호
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• pp.28-35
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• 2014

Recently, the fuel oil of diesel engines of marine ships has been increasingly changed to heavy oil of low quality as the oil price is getting higher and higher. Therefore, the spiral gear attached at the motor of the oil purifier which plays an important role to purify the heavy oil is also easy to expose at severe environmental condition due to the purification of the heavy oil in higher temperature. Thus, the material of the spiral gear requires a better mechanical strength, wear and corrosion resistance. In this study, the heat treatment(tempering) with various holding time at temperature of $500^{\circ}C$ was carried out to the alloy of Cu-7Al-2.5Si as centrifugal casting, and the properties of both hardness and corrosion resistance with and without heat treatment were investigated with observation of the microstructure and with electrochemical methods, such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and a.c. impedance. in natural seawater solution. The ${\alpha}$, ${\beta}^{\prime}$ and ${\gamma}_2$ phases were observed in the material in spite of no heat treatment due to quenching effect of a spin mold. However, their phases, that is, ${\beta}^{\prime}$ and ${\gamma}_2$ phases decreased gradually with increasing the holding time at a constant temperature of $500^{\circ}C$. The hardness more or less decreased with heat treatment, however its corrosion resistance was improved with the heat treatment. Furthermore, the longer holding time, the better corrosion resistance. In addition, when the holding time was 48hrs, its corrosion current density showed the lowest value. The pattern of corroded surface was nearly similar to that of the pitting corrosion, and this morphology was greatly observed in the case of no heat treatment. It is considered that ${\gamma}_2$ phase at the grain boundary was corroded preferentially as an anode. However, the pattern of general corrosion exhibited increasingly due to decreasing the ${\gamma}_2$ phase with heat treatment. Consequently, it is suggested that the corrosion resistance of Cu-7Al-2.5Si alloy can be improved with the heat treatment as a holding time for 48 hrs at $500^{\circ}C$.

• 열처리공학회지
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• 제31권3호
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• pp.91-96
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• 2018

Microstructural development of ferritic 11Cr-3.45W heat-resistance steel for ultra-supercritical power plant during creep and thermal aging was investigated using electron microscopy. The test samples were isothermally aged at $700^{\circ}C$ for up to 4000 hours and subjected to creep loading at $700^{\circ}C$ for predetermined periods of lifetime to prepare the damaged materials. In this structural material, a various secondary phases are the primary influence on mechanical properties of ferritic heat-resistance steel. The typical precipitates of $M_{23}C_6$, MX and $M_2X$ secondary phases had been analyzed through qualitative and quantitative manner. Coarsening of precipitates and increase of lath width were observed during creep and thermal aging. This phenomenon was remarkable for creep process compared with isothermal aging process.

• 한국표면공학회지
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• 제29권4호
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• pp.278-285
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• 1996

The structure of coating layer formed by hot dip Al-Cu alloy coating on Monel 1400 metal was studied. The coating layer consists of alloyed layer adjacent to the Monel 400 substrate and Al-Cu alloy. It was found that the hardness of coating increased with dipping time and heat treatment associated with the diffusion and the formation of intermetallic compound at the interface. However the thickness of coating layer was decreased at high dipping temperature due to tile higher viscosity of liquid coating alloy. Diffusion heat treatment at $600^{\circ}C$ after coating resulted in the disappearence of adhered Al(Cu) and $CuAl_2$ phases, and then they transformed into the new phases of CuAl and Al7Cu4Ni at coating layer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.527-530
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• 2002

A lot of efforts have been focused on the optimization of PIT parameters for Bi-2223/Ag wire. In this paper, initial annealing of Bi-2223/Ag wire to transform Bi-2212 orthorhombic from Bi-2212 tetragonal Precursor was investigated. This initial annealing step at low oxygen partial pressure were to transform Bi-2212 orthorhombic structure and to reduce the formation of second phases at superconducting wire. However Bi-2223 Phases were appeared at higher annealing temperature. Critical currents(Je) of Bi-2223/Ag tapes were sintered at low oxygen Partial pressure were higher than that of the wires sintered at atmosphere condition. In order to investigate the effect of rolling reduction ratio, Bi-2223/Ag HTS tapes were rolled with different reduction ratio. There were no clear difference of Je and filaments shape with various rolling reduction ratio.

• 열처리공학회지
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• 제3권1호
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• pp.8-16
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• 1990

Effects of thermomechanical treatments(TMT) on the microstructures and mechanical properties in Al-2.27%, Li-1.28%, Cu-0.63%, Mg-0.12%, Zr alloy were investigated. The TMT process improved the tensile strength. Growth of ${\delta}^{\prime}$, S' and $T_1$ phases was restrained by TMT processes while the density of ${\delta}^{\prime}$, S' and $T_1$ phases was increased by TMT processes. The TMT treated specimens tend to fail in inter-subboundary mode. The increases of strength by the T-HA processes were compared to those of the T-AHA processes.

• 열처리공학회지
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• 제36권5호
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• pp.261-269
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• 2023

This study aims to investigate the effects of tungsten additions on the microstructure, corrosion characteristics, and hardness of super duplex stainless steel heat-treated at two different annealing temperatures. Under the annealing temperature of 1100℃, the microstructure of the stainless steels consisted mainly of ferrite, while under the annealing temperature of 1000℃, significant amounts of austenite and secondary phases were also observed. In terms of corrosion characteristics in 3.5 wt%NaCl solution, there was not a significant difference due to W addition at the 1100℃ conditions. However, at the 1000℃, a tendency of decreased corrosion resistance was observed with increasing the tungsten content. On the other hand, the micro-hardness of the stainless steel heat-treated 1000℃ showed an increasing trend with tungsten addition. This increase can be mainly attributed to the higher fraction of secondary phases, primarily sigma, known for their high hardness.

• 열처리공학회지
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• 제37권4호
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• pp.172-181
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• 2024

In this study, the effect of addition of Ti and Co elements on microstructural evolution and characteristics of vacuum-casted Cu-25%Cr electrical contact material was investigated. The coarse and insoluble Cr phases with an average size of 300 ㎛ in commercial Cu-25%Cr alloy were reduced to tens of micrometers in vacuum casted Cu-25%Cr-X(X=Ti, Co) alloy, which can be interpreted as result controlling coarsening and the work-frame structure of the insoluble Cr phase by the formation of intermetallic compounds such as Cr₂Ti or Cr_0.5Co_1.5Ti around the Cr phase As a result, the electrical properties such as weight loss and fusion resistance against the repeated arc generation of the electrical contact material as well as the mechanical properties were greatly improved.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.155-158
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• 2002

Fabrication process of metal/intermetallic laminated composites by using self-propagating high temperature synthesis(SHS) reactions between Ni and Al elemental metal foils have been investigated. Al foils were sandwiched between Ni foils and heated in a vacuum hot press to the melting point of aluminium. SHS reaction kinetics was thermodynamically analyzed through the final volume fraction of the unreacted Al related with the initial thickness ratio of Ni:Al and diffusion bonding stage before SHS reaction. Thermal aging of laminated composites resulted in the formation of functionally gradient series of intermetallic phases. Microstructure showed that the main phases of intermetallics were NiAl and $Ni_3Al$ having higher strength at room and high temperatures. The volume fractions of intermetallic phases were measured as 82.4, 58.6, 38.4% in 1:1, 2:1, 4:1 initial thickness ratio of Ni:Al.

• 셀메드
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• 제7권2호
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• pp.6.1-6.2
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• 2017

Music therapy is a treatment for a range of disorders (physical, emotional, mental, and social) by using music. This article introduces traditional medical books, which mentioned relation between sounds and emotions or internal organs based on the five phases (五行) theory. And, authors provide the Korean traditional musical instruments related with five phases and Six Healing Sounds (六字訣).