• 한국분말재료학회지
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• 제31권5호
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• pp.390-398
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• 2024

The AlSi10Mg alloy has garnered significant attention for its application in laser powder bed fusion (L-PBF), due to its lightweight properties and good printability using L-PBF. However, the low production speed of the L-PBF process is the main bottleneck in the industrial commercialization of L-PBF AlSi10Mg alloy parts. Furthermore, while L-PBF AlSi10Mg alloy exhibits excellent mechanical properties, the properties are often over-specified compared to the target properties of parts traditionally fabricated by casting. To accelerate production speed in L-PBF, this study investigated the effects of process parameters on the build rate and mechanical properties of the AlSi10Mg alloy. Guidelines are proposed for high-speed additive manufacturing of the AlSi10Mg alloy for use in automotive parts. The results show a significant increase in the build rate, exceeding the conventional build rate by a factor of 3.6 times or more, while the L-PBF AlSi10Mg alloy met the specifications for automotive prototype parts. This strategy can be expected to offer significant cost advantages while maintaining acceptable mechanical properties of topology-optimized parts used in the automobile industry.

• 한국분말재료학회지
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• 제30권2호
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• pp.116-122
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• 2023

Because magnets fabricated using Nd-Fe-B exhibit excellent magnetic properties, this novel material is used in various high-tech industries. However, because of the brittleness and low formability of Nd-Fe-B magnets, the design freedom of shapes for improving the performance is limited based on conventional tooling and postprocessing. Laser-powder bed fusion (L-PBF), the most famous additive manufacturing (AM) technique, has recently emerged as a novel process for producing geometrically complex shapes of Nd-Fe-B parts owing to its high precision and good spatial resolution. However, because of the repeated thermal shock applied to the materials during L-PBF, it is difficult to fabricate a dense Nd-Fe-B magnet. In this study, a high-density (>96%) Nd-Fe-B magnet is successfully fabricated by minimizing the thermal residual stress caused by substrate heating during L-PBF.

• 한국압력기기공학회 논문집
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• 제19권1호
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• pp.11-19
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• 2023

Additive manufacturing technology, called as 3D printing, is one of fourth industrial revolution technologies that can drive innovation in the manufacturing process, and thus should be applied to nuclear industry for various purposes according to the manufacturing trend change in the future. In this paper, we performed tensile tests of 3D printed stainless steel 316L as-built specimens manufactured by two types of technology; DED (Directed Energy Deposition) and PBF (Powder Bed Fusion). Their mechanical properties (tensile strength, yield strength, elongation and reduction of area) were compared. As a result of comparison, the mechanical properties of the PBF specimens were slightly better than those of DED specimens. In the same additive type of specimens, the tensile and yield strength of specimens in the X and Y direction were higher than those in the Z direction, but the elongation and ROA were lower.

• 한국토양비료학회지
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• 제38권1호
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• pp.15-24
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• 2005

Enterobacter intermedium은 호기조건에서 glucose를 gluconic acid로 이를 다시 2-ketogluconic acid로 산화시킨다. 리터당 22.5 g의 glucose와 8.3 g gluconic acld, 그리고 40 g 인광석을 포함한 배지에서 배양 10일 후 $1028mg\;L^{-1}$ 의 수용성 인산이 얻어졌으며, 이 배양액을 인산생물비료로 사용하였다. E. intermedium에 의해 인광석이 용해된 인산생물비료를 평가하기 위하여 다섯 가지 처리구가 사용되었다 (PBF1/3, PBF2/3, PBF3/3, BP 그리고 MF). MF와 BP처리구에서는 인산비료가 10a당 $5.9kg\;P_2O_5$ 기준으로 시용되었으나, PBF1/3, PBF2/3 그리고 PBF3/3처리구는 10a당 $5.9kg\;P_2O_5$ 에 해당하는 인산량의 1/3, 2/3, 3/3에 해당하는 인광석 용해 배양액이 각각 시용되었다. 상추 정식 후 20일, 35일 그리고 50일 후에 성장요소, biomass, 토양효소 활성 그리고 토양 화학성이 분석되었다. 근권의 dehydrogenase 활성과 유효인산농도가 인산생물비료 (PBF1/3, PBF2/3 그리고 PBF3/3)처리구에서 BP 및 MF처리구에 비해 일반적으로 높았다. 토양 미생물 blomass는 생육초기에 BP 및 MF처리구에 비해 PBF3/3처리구에서 매우 높았다. 모든 결과를 고려할 때, PBF2/3처리구에서는 MF처리구와 비교하여 생체중이 23% 증가하고 인산흡수가 50% 증가하였다. 즉, 인산생물비료는 무기인산비료의 대용으로 사용 가능성을 나타내었다.

• 생명과학회지
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• 제9권6호
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• pp.692-697
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• 1999

주정폐액과 같은 고 농도의 유기성 폐액의 효율적 처리에는 혐기적, 호기적인 생물학적인 처리와, 생물학적으로 난분해성 물질의 화학적 처리가 요구되었다. 난분해성 COD성분을 제거하기 위하여 Fenton처리 전에 가능한 많은 유기물의 제거가 요구되며, 이때 $FeCl_3$,alum,cationic polymer의 처리가 효과적이었다. 이 처리과정 중은 몰론 Fenton 처리과정 중에 생성되는 슬러지의 제거 효율에 따라 전체 폐수처리효율리 크게 영향을 받게되 슬러지의 효과적인 제거과정이 필요하였다, 이를 위해 기포의 직경이 80-120 um 정도되는 기존의 DAF방식에 비해 새로 도입한 PBF법에 의해 생성되는 직경 20-50um 의 미세포기는 슬러지의 부상을 촉진시켜 화학적 슬러지의 제거 효율이 훨씬 뛰어남을 알 수 있었다. 이에 따라 PBF법에 의한 슬러지의 제거는 기존의 DAF법에 비해 약품 사용량, 용수의 절감, 방류량의 감소 등으로 전체 운전비용을 약 30%정도 줄일 수 있었다.

• 한국기계가공학회지
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• 제19권8호
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• pp.94-103
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• 2020

This study investigated the effects of ultrasonic nanocrystal surface modification (UNSM) on the deteriorated surface of AISI SUS316L additively manufactured (AM) using the powder bed fusion (PBF) technique. Specifically, the effects of UNSM conditions on surface topology, hardness, and anti-corrosion were examined. Before UNSM treatment, the stainless steel 316L powder was processed via the PBF machine to prepare a substrate. We observed surface changes due to UNSM treatments in PBF SUS316L substrates and examined the correlation between topology changes, roughness, hardness, and anti-corrosion. After UNSM treatment, the coarse as-built surface was refined, and a regular micro-profile was implemented. Compared to the non-treated PBF sample, the waviness and roughness of the surfaces after UNSM treatment decreased by up to 56.0% and 94.5%, respectively, and decreased further as the interval decreased. The hardness improved by up to 63.0% at a maximum depth of 500 ㎛ from top surface by the UNSM treatment. The results of the corrosion test showed that the corrosion resistance of the UNSM specimens was moderately improved compared to that of the untreated surface. This study confirmed that UNSM is an effective post-processing technique for additively manufactured parts.

• 대한의생명과학회지
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• 제11권3호
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• pp.365-373
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• 2005

The aim of this study was to investigate the alterations in meningeal blood flow by stimulation of trigeminovascular system. An open cranial window was prepared on the right parietal bone of male Sprague-Dawley rats. Trigeminovascular system was stimulated by electrical stimulation of trigeminal ganglion (ETS), somatosensory (whisker) stimulation, or topical applications of capsaicin and neuropeptides including substance P and calcitonin gene-related peptide (CGRP). Neonatal capsaicin pretreatment was performed with subcutaneous administration of capsaicin (50 mg/kg) within the first 24 hours after birth. Changes in regional blood flow of dural artery (rDBF) and pial artery (rPBF) were continuously measured through the cranial window by laser-Doppler flowmetry. Both ETS and capsaicin caused a chain of alterations in rPBF and rDBF responses, i.e., an immediate transient decrease followed by rapid and marked increase in rPBF, which were significantly attenuated not only by pretreatments with L-733,060, a $NK_1$ receptor blocker, $CGRP_{8-37}$, a $CGRP_1$ receptor blocker, and 7-nitroindazole monosodium salt (7-NINA), a neuronal nitric oxide synthase inhibitor but also by neonatal capsaicin treatment. Exogenous neuropeptides including substance P and CGRP increased the meningeal blood flow, which was significantly attenuated not only by pretreatment with L-733,060 and $CGRP_{8-37}$, respectively, but also by pretreatment with 7-NINA. The rPBF response to whisker stimulation was significantly attenuated not only by trigeminovascular system injuries including nasociliary nerve denervation and neonatal capsaicin treatment but also by pretreatments with L-733,060, $CGRP_{8-37}$ and 7-NINA. These results suggest that the stimulation of trigeminovascular system causes prominent alterations in meningeal blood flow, and that neuropeptides as well as nitric oxide in the trigeminovascular system are importantly implicated in the regulation of meningeal blood flow.

• KEPCO Journal on Electric Power and Energy
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• 제7권1호
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• pp.129-135
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• 2021

Recently, additive manufacturing (AM) technology such as powder bed fusion (PBF) and directed energy deposition (DED) are actively attempted as consumers' needs for parts with complex shapes and expensive materials. In the present work, the effect of processing parameters on the mechanical properties of 316L stainless steel coupons fabricated by PBF and DED AM technology was investigated. Three major mechanical tests, including tension, impact, and fatigue, were performed on coupons extracted from the standard components at angles of 0, 45, 90 degrees for the build layers, and compared with those of investment casting and commercial wrought products. Austenitic 316L stainless steel additively manufactured have been well known to be generally stronger but highly vulnerable to impact and lack in elongation compared to casting and wrought materials. The process-induced pore density has been proved the most critical factor in determining the mechanical properties of AM-built metal parts. Therefore, it was strongly recommended to reduce those lack of fusion defects as much as possible by carefully control the energy density of the laser. For example, under the high energy density conditions, PBF-built parts showed 46% higher tensile strength but more than 75% lower impact strength than the wrought products. However, by optimizing the energy density of the laser of the metal AM system, it has been confirmed that it is possible to manufacture metal parts that can satisfy both strength and ductility, and thus it is expected to be actively applied in the field of electric power section soon.

• 한국분말재료학회지
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• 제30권2호
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• pp.140-145
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• 2023

Although the Ti-6Al-4V alloy has been used in the aircraft industry owing to its excellent mechanical properties and low density, the low formability of the alloy hinders broadening its applications. Recently, laser-powder bed fusion (L-PBF) has become a novel process for overcoming the limitations of the alloy (i.e., low formability), owing to the high degree of design freedom for the geometry of products having outstanding performance used in high-tech applications. In this study, to investigate the effect of bulk shape on the microstructure and mechanical properties of L-PBFed Ti-6Al-4V alloys, two types of samples are fabricated using L-PBF: thick and thin samples. The thick sample exhibits lower strength and higher ductility than the thin sample owing to the larger grain size and lower residual dislocation density of the thick sample because of the heat input during the L-PBF process.

• 한국분말재료학회지
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• 제29권1호
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• pp.14-21
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• 2022

In the powder bed fusion (PBF) process, a 3D shape is formed by the continuous stacking of very fine powder layers using computer-aided design (CAD) modeling data, following which laser irradiation can be used to fuse the layers forming the desired product. In this method, the main process parameters for manufacturing the desired 3D products are laser power, laser speed, powder form, powder size, laminated thickness, and laser diameter. Stainless steel (STS) 316L exhibits excellent strength at high temperatures, and is also corrosion resistant. Due to this, it is widely used in various additive manufacturing processes, and in the production of corrosion-resistant components with complicated shapes. In this study, rectangular specimens have been manufactured using STS 316L powder via the PBF process. Further, the effect of heat treatment at 800 ℃ on the microstructure and hardness has been investigated.