• 한국세라믹학회지
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• 제31권7호
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• pp.804-812
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• 1994

Stable PZT coating sol was prepared using chelating agent, ethylacetoacetate(EAcAc) by sol-gel processing under ambient atmosphere. Through FT-IR spectrum analysis on solution of each reaction step, formation of metal complex was confirmed and prepared PZT sol was stable over several months. Through TG-DTA, XRD, FT-IR spetrum analysis of PZT gel powder, it was understood that the addition of EAcAc could reduce the transition temperature to ferroelectric phase, due to the increased homogeneity by matching the hydrolysis and condensation rates by chelation. Single perovskite phase was obtained by the heat-treatment at 54$0^{\circ}C$ for 30 min. The film was coated on ITO-coated glass substrate by dip coating method. After heat-treatment, PZT thin film had thickness in the range of 20~130 nm. The maximum dielectric constant of its thin film at room temperature and 1 kHz was 128.

• 열처리공학회지
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• 제25권3호
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• pp.138-145
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• 2012

An ${\alpha}$-Ferrite (Fe) powder dispersed with 4 vol.% of $Al_2O_3$ was successfully produced by a simple miling at 210 K with a mixture of $Fe_2O_3$, Fe and Al ingredient powders, followed by 2 step high temperature consolidation: Hot Pressing (HP) at 1323 K and then Hot Isostatic Pressing at 1423 K. The microstructure of the consolidated material was characterized by standard metallographic techniques such as XRD (X-ray Diffraction), TEM and STEM-EDS. The results of STEM-EDS analysis showed that the HIPed materials comprised a mixture of pure Fe matrix with a grain size of ~20 nm and $Al_2O_3$ with a bimodal size distribution of extremely fine (~5 nm) and medium size dispersoids (~20 nm). The mechanical properties of the consolidated materials were characterized by compressive test and micro Vickers hardness test at room temperature. The results showed that the yield strength of the ODS (Oxide Dispersion Strengthened) Fe alloy are as much as $674{\pm}39$ MPa and the improvement of the yield strength is attributed to the presence of the fine $Al_2O_3$ dispersoid.

• 열처리공학회지
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• 제19권5호
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• pp.249-256
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• 2006

Structural studies have been performed on precipitation hardening found in $L1_2$ ordered ${\gamma}^{\prime}-Ni_3(Al,Ti)$ alloys using transmission electron microscopy. A uniform solid solution of ${\gamma}^{\prime}-L1_2$ ordered phase supersaturated with Ni can be obtained by solution annealing in a suitable temperature range. The ${\gamma}^{\prime}$ phase hardens appreciably by the fine precipitation of disordered ${\gamma}$. The shape of ${\gamma}$ precipitates formed during aging is initially spherical or round-cubic and grow into platelets as aging proceeds. High resolution electron microscopy revealed that the ${\gamma}$ precipitates are perfectly coherent with the matrix ${\gamma}^{\prime}$ as long as the ${\gamma}$-precipitates are plates. The loss of coherency initiates by the introduction of dislocations at the ${\gamma}/{\gamma}^{\prime}$ interface followed by the step formation at the dislocations. The ${\gamma}$ precipitates become globular after the loss of coherency. The strength of ${\gamma}^{\prime}-Ni_3(Al,Ti)$ increases over the temperature range of experiment by the precipitation of fine ${\gamma}$ particles. The peak temperature where a maximum strength was obtained shifted to higher temperature.

• 열처리공학회지
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• 제21권6호
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• pp.281-286
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• 2008

In the 1.1 Mn steel containing boron, effects of the 0.1 V addition and processing condition were studied. In the $550^{\circ}C$ interrupted cooling where the main structure is (ferrite + pearlite), the impact toughness decreased as the tensile strength increased by the 0.1 V addition. The $800^{\circ}C$ rolling including two step rolling of $800-770^{\circ}C$, exhibited better strength-toughness balance, as compared to the $770^{\circ}C$ rolling. This seems to be kind of conditioning effect at higher temperature, e.g., more uniform deformation effect. In the accelerated cooling after the $750^{\circ}C$ rolling in a dual phase range, the impact toughness was enhanced, despite a large increase in tensile strength. This is believed to be related to the change of main structure from (ferrite + pearlite) to (ferrite + bainite).

• 열처리공학회지
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• 제3권2호
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• pp.1-9
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• 1990

Since the reverse shape memory effect(RSME) was reported in a CuZnAl alloy, further study has been done on the mechanism of this phenomenon and reported that it occurs by the bainitic transformation. But the present authors revealed in the previous work that the RSME in a B2 CuZnAl alloy is not caused by the shear process involved in the bainitic transformation and also that the RSME takes place as the remaining ${\alpha}^{\prime}{_2}$ phase, which is two-step transformed strain induced martensite, is newly transformed into ${\alpha}$ phase. In order to provide further evidence in supporting the facts, thus, more detailed investigations have been carried out in a $DO_3$ CuZnAl alloy.

• Journal of Welding and Joining
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• 제31권5호
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• pp.47-53
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• 2013

We have investigated the traits of clad metals in hot-rolled clad steel plates, including the sensitization and mechanical properties of STS 316 steel plate and carbon steel (A516), under various specific circumstances regarding post heat treatment, multilayered welds, and thick or repeated welds for repair. For evaluations, sectioned weldments and external surfaces were investigated to reveal the degree of sensitization by micro vickers hardness, tensile, and etching tests the results were compared with those of EPR tests. The clad steel plates were butt-welded using FCAW and SAW with the time of heat treatment as the variable, a that was conducted at $625^{\circ}C$, for 80, 160, 320, 640, and 1280 min. Then, the change in corrosion resistance was evaluated in these specimens. With carbon steel (A516), as the heat treatment time increased, the annealing effect caused the tensile strength to decrease. The micro-hardness gradually increased and decreased after 640 min. The elongation and contraction of the area also increased gradually. The oxalic acid etch test and EPR test on STS316 and the clad metal showed STEP structure and no sensitization. From the test results on multi-layered and repair welds, it could be concluded that there is no effect on the corrosion resistance of clad metals. The purpose of this study was to suggest some considerations for developing on-site techniques to evaluate the sensitization of stainless steels.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.71-75
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• 2003

The conduit fer superconducting cable is welded and plastically deformed during the jacketing process to make the CICC (Cable-in-Conduit-Conductors) fer a fusion magnet. The jacketing process of KSTAR (Korea Superconducting Tokamak Advanced Research) conductors is composed of several sequential steps such as rounding, welding, sizing, and square-rolling. Since the welded zone in Incoloy 908 conduit is brittle and easy to have flaws, there may be a possibility of stress corrosion cracking during the heat treatment of coil when both the induced tensile residual stress and the concentration of oxygen in the furnace are sufficiently high. The steps of the jacketing process were simulated using the finite element method of the commercial ABAQUS code, and the stress distribution in the conduit in each step was calculated, respectively. Furthermore, the variations of residual welding stresses through the steps of the jacketing process were calculated and analyzed to anticipate the possibility of the stress corrosion cracking in the conduit. The concentrated high tensile residual welding stresses along the welding bead decrease by the plastic deformation of the following sizing step. The distribution in residual stresses in the conductor for magnet coil is mainly governed by the last step of square-rolling.

• 한국식품영양과학회지
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• 제38권5호
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• pp.612-617
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• 2009

녹즙 제조 시 미생물 생육 억제를 위한 유일한 공정은 세척처리 공정이므로 비가열 살균기술인 오존 처리기술을 이용하여 녹즙 원료들의 세척공정(정선 원료, 1차 세척, 오존처리 및 2차 세척) 중 미생물 및 주요 화학성분의 변화를 측정하였다. 정선 원료의 일반세균수는 $8.2{\times}10^5{\sim}5.0{\times}10^6\;CFU/g$으로 식품공전에서 제시한 105 CFU/g보다 높은 균수를 보여 위생화가 반드시 필요하였다. 그러나 1차 세척 후 오존처리 시 $4.7{\times}10^4{\sim}6.7{\times}10^4\;CFU/g$으로 약 2 log cycle의 감균 효과를 볼 수 있었으며 2차 세척에서는 큰 차이가 없었다. 녹즙 원료의 대장균군수는 $8.0{\times}10^3{\sim}3.5{\times}10^3\;CFU/g$이었으나 오존처리 시 $1.5{\times}10^2{\times}3.0{\times}10^2\;CFU/g$로 초기에 비하여 약 1 log cycle 정도의 감균 효과를 보였다. 한편 세척공정 중 ascorbic acid, flavonoid 및 polyphenol 화합물, 무기물(카드뮴 및 납)의 함량 변화는 유의적인 함량 변화를 볼 수 없었으며 색상차이도 없는 것으로 나타났다. 따라서 녹즙 원료의 위생화를 위한 오존처리 시 미생물 수를 감소시킬 수 있었으며 화학적인 변화는 없는 것으로 나타났다.

• 공업화학
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• 제32권5호
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• pp.569-573
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• 2021

본 연구에서는 코크스, 바인더 피치 및 함침 피치를 사용하여 고밀도 탄소 블록을 제조하고, 함침 공정 시 피치의 유동성이 탄소 블록의 고밀도화에 미치는 영향을 고찰하였다. 코크스와 바인더 피치의 고압 성형을 통해 그린블록을 제조하고 열처리 공정을 통하여 탄소 블록을 얻었다. 열처리 공정 시 바인더 피치의 휘발에 의해 생성된 기공을 제거하고자 함침 공정을 진행하였다. 함침 공정은 함침 피치를 용융하는 전처리 단계와 피치를 탄소 블록에 함침하는 고압 반응 단계로 나누어 진행하였다. 함침 피치의 용융은 140~200 ℃에서 진행하였으며, 열처리 온도가 증가할수록 함침 피치의 점도가 감소하였다. 함침 피치의 점도 감소는 유동성을 향상시켜 탄소 블록 내부 기공을 효율적으로 함침하여 탄소 블록의 기공률을 83% 감소시켰고 겉보기 밀도를 5% 상승시켰다.

• 한국세라믹학회지
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• 제26권3호
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• pp.381-389
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• 1989

Effects of annealing temperature, time, and atmospehre on the flow characteristics of Atmospheric Pressure Chemical Vapor Deposition-borophosphosilicate glass were investigated. Stable step coverage can be obtained by annealing the BPSG film at 90$0^{\circ}C$ for 30 minutes in N2 atmosphere, but further heat treatment isnot effective. Flow characteristics of the BPSG film was better in steam atmosphere than in N2 atmosphere, and the factors which cause it were analyzed. The concentration of boron in the BPSG film was measured pretty accurately by FTIR spectrum. Boron content in the BPSG film was reduced by annealing treatment. The decrement of boron was greater in steam atmosphere than in the N2 atmosphere. Also it was found from the FTIR spectroscopic analysis that PH3 inhibited the oxidation of B2H6.