• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.221-223
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• 1999

In this work, samples were manufactured variously by changing conventional calcining and sintering conditions and we tried the utilization by making the heat treatment time, which is demanded to high-Tc phase formation, much shorter. We found out optimal heat treatment conditions with the analysis on formation process at superconducting phase in term of the change of calcining and sintering time and then, examined X-ray diffraction(XRD) patterns, scanning electron microscope(SEM) measurement and energy dispersive X-ray spectrometer(EDX) of the samples manufactured under heat treatment conditions which we suggest here. As a result, 2223 high-$T_c$, phase of (Bi,Pb)SrCaCuO superconductor starting with ($Bi_l$ xPbx,)$_2$$Sr_2$$Ca_2$$Cu_3$$O_y$, composition was formed from 1 hr sintering sample at temperature nearby melting point and also the completed sample with calcining and sintering time of 9 hr was formed high-$T_c$.low-$T_c$ phase appearing in sight above the critical temperature of liquid $N_2$.

• 한국기계가공학회지
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• 제17권3호
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• pp.16-21
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• 2018

The effect of heat treatment on the fatigue crack growth behavior in welded joints between the heat-affected zone (HAZ) of SA 508 Cl.3 low-alloy steel and HAZ of AISI 316L stainless steel is investigated. When the crack propagates across SA 508 Cl.3 or AISI 316L SS and HAZ into the weldment, the fatigue crack growth rate (FCGR) in the HAZ region does not change or decrease despite the increase in stress intensity factor ${\Delta}K$. The residual stress at the HAZ region is more compressive than that at the base Δ materials and weldment. The effect of the welding residual stress on the crack growth behavior is determined by performing a residual stress relief heat treatment at $650^{\circ}C$ for 1h and subsequent furnace cooling. The FCG behavior in the HAZ region in the as-welded specimen and the residual stress relief heat-treated specimen is discussed in terms of the welding residual stress.

• 한국결정성장학회지
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• 제28권6호
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• pp.250-255
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• 2018

본 연구에서는 3D-프린팅 적층 공정으로 제조한 인공관절용 CoCrMo 합금 소재의 HIP 처리를 포함한 복합열처리 후 소재의 인장특성, 내마모 특성 등의 기계적 특성과 결정구조 및 미세조직 등의 재료특성 변화를 고찰하였다. 내부마이크로 기공을 제거하기 위한 HIP 열처리와 금속탄화물 생성을 위한 상압열처리 및 금속탄화물의 균질화를 위한 용체화 열처리를 거치는 복합열처리 공정을 실시하여 인공관절 소재로서의 특성을 부여하고자 하였다. 3D-프린팅 적층 공정으로 제조한 인공관절용 CoCrMo 합금 소재의 복합열처리 효과는 HIP 공정중의 치밀화 과정, 상압열처리 중의 금속탄화물 생성 및 용체화 열처리 과정중의 금속탄화물의 균질화 효과임을 XRD, FE-SEM, EDS 분석으로 확인하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.298-303
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• 2000

The 3 mol% yttria stabilized zirconia (3-Y PSZ) powder was heat treated at 50 0$^{\circ}C$ to evaporate the polymer binder and stabilize the tetragonal phase. The wear experiments were carried out on a ring-on-plate type reciprocating wear tester at selected temperatures with in the range room temperature to 600$^{\circ}C$ The results show that the heat treatment of powder decreases the wear rate due to the reduction of microcracks and pores in coatings and the stabilization of the tetragonal phase. Powder heat treatment enhanced the quality of the coating layer by removing remnant gases during coating process and the powder heat treatment at which tetragonal phase is stable diminished phase ratio of monoclinic. These two effects improved wear resistance characters.

• 한국표면공학회지
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• 제52권5호
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• pp.275-281
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• 2019

Anodization is widely used to enhance the properties of aluminum, such as hardness, electric resistance, abrasion resistance, corrosion resistance etc. But these properties can be enhanced with additional process. According to the partial crystallization of oxide layer with post heat treatment, enhanced hardness can be expected with partial crystallization. In this study, post heat treatments were applied to the anodized aluminum alloys of Al6061 to achieve the partial crystallization, and crystallizations were evaluated with the reduced breakdown voltages. Interestingly, remarkable enhanced hardness (21~29%), abrasion resistance (26~62%), and reduced breakdown voltage (24~44%) were observed for the sulfuric acid anodized samples when we annealed the anodized samples with 1hour post heat treatment at $360^{\circ}C$. For the Al5052 alloys, a lot of cracks were observed when we applied the post heat treatment.

• 소성∙가공
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• 제7권6호
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• pp.530-538
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• 1998

Elimination of the heat treatment process is very important in automation of metal forming since controlling heat treatment by computer has many difficulties and it has bottle neck problem. non-heat-treated steels materials which are not in need of heat treatment have been developed for cold forging. However to apply non-heat-treated steel to structural parts. it is necessary to prove reliability of mechanical properties. In order to define the reliability of mechanical properties we have investigated microstructure, hardness, the tensile strength compressive strength and tensile fatigue strength for both steels. Considering the results of high cycle fatigue test for both specimen the characteristics of non-heat-treated steel are decided on the yield strength, It has same tendency for heat-treated steel. Therefore non-heat-treated steel which has the appropriate yield strength may be applied in cold forging.

• 한국재료학회지
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• 제34권4호
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• pp.208-214
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• 2024

To fabricate intermetallic nanoparticles with high oxygen reduction reaction activity, a high-temperature heat treatment of 700 to 1,000 ℃ is required. This heat treatment provides energy sufficient to induce an atomic rearrangement inside the alloy nanoparticles, increasing the mobility of particles, making them structurally unstable and causing a sintering phenomenon where they agglomerate together naturally. These problems cannot be avoided using a typical heat treatment process that only controls the gas atmosphere and temperature. In this study, as a strategy to overcome the limitations of the existing heat treatment process for the fabrication of intermetallic nanoparticles, we propose an interesting approach, to design a catalyst material structure for heat treatment rather than the process itself. In particular, we introduce a technology that first creates an intermetallic compound structure through a primary high-temperature heat treatment using random alloy particles coated with a carbon shell, and then establishes catalytic active sites by etching the carbon shell using a secondary heat treatment process. By using a carbon shell as a template, nanoparticles with an intermetallic structure can be kept very small while effectively controlling the catalytically active area, thereby creating an optimal alloy catalyst structure for fuel cells.

• 한국주조공학회지
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• 제36권3호
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• pp.88-94
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• 2016

We investigated the effect of heat treatment on an ADC12 alloy produced using diecasting. The heat treatment used in this study was a typical T6 process: a solid solution treatment followed by an artificial aging treatment. As-cast specimens were solid-solution-treated at $500^{\circ}C$ and $530^{\circ}C$ for 1-16 hr, and aged at $160^{\circ}C$ and $180^{\circ}C$ for 1-8 hr. Microstructural changes in the alloy during the heat treatment were observed. Changes in mechanical properties of the alloy were measured using a micro-Vickers hardness tester. Finally, we determined the optimal heat treatment conditions for the diecast ADC12 alloy.

• Journal of Dairy Science and Biotechnology
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• 제35권4호
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• pp.270-285
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• 2017

Among milk proteins, caseins are not subjected to chemical changes during heat treatment of milk; however, whey proteins are partially denatured following heat treatment. The degree of whey protein denaturation by heat treatment is decreased in the order of high temperature short time (HTST) > low temperature long time (LTLT) > direct-ultra-high temperature (UHT) > indirect-UHT. As a result of heat treatment, several changes, including variations in milk nitrogen, interactions between beta-lactoglobulin and k-casein, variations in calcium sulfate and casein micelle size, and delay of milk coagulation by chymosin action, were observed. Lysine, an important essential amino acid found in milk, was partially inactivated during heat treatment. Therefore, the available amount of lysine decreased slightly (1~4% decrease) after heat treatment, However, the influence of heat treatment on the nutritional value of milk was negligible. Nutritional value and nitrogen balance did not differ significantly between UHT and LTLT in milk. In conclusion, our results showed that heat treatment of milk did not alter protein quality. Whey proteins denatured to a limited extent during the heat treatment process, and the nutritional value and protein quality were unaffected by heat treatment.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.33-36
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• 2010

$MgF_2$ is a current material used for optical applications in the ultraviolet and deep ultraviolet range. Process variables for manufacturing $MgF_2$ thin film were established in order to clarify the optimum conditions for the growth of the thin film, dependant upon the process conditions, and then by changing a number of the vapor deposition conditions, substrate temperatures, and heat treatment conditions, the structural and optical characteristics were measured. Then, optimum process variables were thus derived. Nevertheless, modern applications still require improvement in the optical and structural quality of the deposited layers. In the present work, in order to understand the composition and microstructure of $MgF_2$, single layers grown on a slide glass substrate using an Electron beam Evaporator (KV-660), were analyzed and compared. The surface substrate temperature, having an effect on the quality of the thin film, was changed from $200^{\circ}C$ to $350^{\circ}C$ at intervals of $50^{\circ}C$. The heat treatment temperature, which also has an effect on the thin film, was changed from $200^{\circ}C$ to $400^{\circ}C$ at intervals of $50^{\circ}C$. The physical properties of the thin film were investigated at various fabrication conditions, such as the substrate temperature, the heat treatment temperature, and the heat treatment time, by X-ray diffraction, and field emission-scanning electron microscopy.