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박정빈(Jungbin Park),김재옥(Jaeok Kim),이동현(Dong Hyun Lee),강호종(Ho-Jong Kang) 한국고분자학회 2017 폴리머 Vol.41 No.1
레이저 융착에 의한 3D 프린팅 가공 시, CO₂ 레이저 융착 조건이 구조체 형성 정밀성 및 치수 안정성에 미치는 영향을 살펴보았다. SLS 3D 프린팅 가공에 의한 구조체는 가공조건에 따라 분말/분말 근접 계면 융착 및 융융에 의하여 형성됨을 알 수 있었으며 레이저 파워, 스캔속도, 스캔간격에 의한 에너지 밀도가 증가될수록 근접된 분말의 용융화가 더 잘 진행된다. 그 결과, 구조체 밀도 및 치수안정성은 향상되나 근접 분말의 용융화에 의한 구조체 형성 선폭 및 두께 증가로 인한 형성 정밀성 감소에 따라 SLS 3D 적층 공정에 문제점을 야기시킴을 알 수 있었다. The effects of polymer powder sintering by CO₂ laser printing on the shaping accuracy and dimensional stability of produced samples were investigated in selective laser sintering (SLS) 3D printing. It was found that the laser sintering resulted in both the surface fusion and melting between closely contacted powders. Increasing the energy density by laser power, scan speed, and scan spacing caused the enhancement in the density and dimensional stability of samples due to the increase of melting process of powders. However, it caused the lowering of dimensional accuracy in shaping such as the obtained width and thickness in 3D printing, and then the difficulty of powders slicing for next lay-up process was found.
방전플라즈마소결로 제조된 나노결정 FeNiCrMoMnSiC 합금의 오스테나이트 안정성과 기계적 특성
박정빈,전준협,서남혁,김광훈,손승배,이석재,Park, Jungbin,Jeon, Junhyub,Seo, Namhyuk,Kim, Gwanghun,Son, Seung Bae,Lee, Seok-Jae 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.4
In this study, a nanocrystalline FeNiCrMoMnSiC alloy was fabricated, and its austenite stability, microstructure, and mechanical properties were investigated. A sintered FeNiCrMoMnSiC alloy sample with nanosized crystal was obtained by high-energy ball milling and spark plasma sintering. The sintering behavior was investigated by measuring the displacement according to the temperature of the sintered body. Through microstructural analysis, it was confirmed that a compact sintered body with few pores was produced, and cementite was formed. The stability of the austenite phase in the sintered samples was evaluated by X-ray diffraction analysis and electron backscatter diffraction. Results revealed a measured value of 51.6% and that the alloy had seven times more austenite stability than AISI 4340 wrought steel. The hardness of the sintered alloy was 60.4 HRC, which was up to 2.4 times higher than that of wrought steel.
다른 크기의 분말 적층을 통해 얻은 Fe-6%Mn합금의 경사 미세조직과 기계적 특성
서남혁,이준호,신우철,전준협,박정빈,손승배,정재길,이석재,Seo, Namhyuk,Lee, Junho,Shin, Woocheol,Jeon, Junhyub,Park, Jungbin,Son, Seung Bae,Jung, Jae-Gil,Lee, Seok-Jae 한국분말재료학회 (*구 분말야금학회) 2022 한국분말재료학회지 (KPMI) Vol.29 No.5
A typical trade-off relationship exists between strength and elongation in face-centered cubic metals. Studies have recently been conducted to enhance strength without ductility reduction through surface-treatment-based ultrasonic nanocrystalline surface modification (UNSM), which creates a gradient microstructure in which grains become smaller from the inside to the surface. The transformation-induced plasticity effect in Fe-Mn alloys results in excellent strength and ductility due to their high work-hardening rate. This rate is achieved through strain-induced martensitic transformation when an alloy is plastically deformed. In this study, Fe-6%Mn powders with different sizes were prepared by high-energy ball milling and sintered through spark plasma sintering to produce Fe-6%Mn samples. A gradient microstructure was obtained by stacking the different-sized powders to achieve similar effects as those derived from UNSM. A compressive test was performed to investigate the mechanical properties, including the yielding behavior. The deformed microstructure was observed through electron backscatter diffraction to determine the effects of gradient plastic deformation.
결정화 거동이 SLS 3-D 프린팅 가공 특성에 미치는 영향
김재옥(Jaeok Kim),박정빈(Jungbin Park),이동현(Dong Hyun Lee),강호종(Ho-Jong Kang) 한국고분자학회 2017 폴리머 Vol.41 No.5
나일론과 폴리케톤의 결정화 거동에 따른 열적 특성과 치수안정성 변화가 SLS(selective laser sintering) 3-D 프린팅 가공 특성에 미치는 영향을 살펴보았다. 기핵제 첨가에 의하여 냉 결정화 온도 증가, 결정화도 및 결정 크기감소와 같은 결정화 거동의 변화를 확인하였다. 냉 결정화 온도 증가는 융융 온도와 냉 결정화 온도의 차이로 나타내는 SLS 3-D 프린팅의 가공 윈도우 감소를 초래하나 결정화도 및 결정 크기 감소에 따른 치수안정성을 증가시킨다. 그 결과 SLS 3-D 프린팅 융착 공정에 의하여 만들어지는 성형 층의 균일성을 향상시켜 반복적인 적층을 위한 분말 슬라이싱 공정에 있어서 치수 변형에 따른 문제점을 최소화할 수 있음을 확인하였다. The effect of crystallization behavior, which caused the change of thermal properties and dimensional stability in nylon and polyketone, on the characteristics of SLS (selective laser sintering) 3-D printing process was studied. The increase of cold crystallization temperature and lowering of crystallinity and crystallite size were found by addition of nucleation agent. As a result, the processing window for SLS 3- D printing which was defined by the difference between melting temperature and cold crystallization temperature was narrowed. However, this caused the enhancement of dimensional stability in the layer made by laser sintering process and it was expected that the powder stacking difficulty due to the distortion of layer may be minimized in the repeated slicing process in SLS 3-D printing.
밀링 조건이 고엔트로피 합금의 미세조직 및 기계적 특성에 미치는 영향
서남혁,전준협,김광훈,박정빈,손승배,이석재,Seo, Namhyuk,Jeon, Junhyub,Kim, Gwanghoon,Park, Jungbin,Son, Seung Bae,Lee, Seok-Jae 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.2
High-entropy alloys have excellent mechanical properties under extreme environments, rendering them promising candidates for next-generation structural materials. It is desirable to develop non-equiatomic high-entropy alloys that do not require many expensive or heavy elements, contrary to the requirements of typical high-entropy alloys. In this study, a non-equiatomic high-entropy alloy powder Fe<sub>49.5</sub>Mn<sub>30</sub>Co<sub>10</sub>Cr<sub>10</sub>C<sub>0.5</sub> (at.%) is prepared by high energy ball milling and fabricated by spark plasma sintering. By combining different ball milling times and ball-to-powder ratios, we attempt to find a proper mechanical alloying condition to achieve improved mechanical properties. The milled powder and sintered specimens are examined using X-ray diffraction to investigate the progress of mechanical alloying and microstructural changes. A miniature tensile specimen after sintering is used to investigate the mechanical properties. Furthermore, quantitative analysis of the microstructure is performed using electron backscatter diffraction.
염산/에탄올로 유도된 위손상 동물모델에서 HT074의 항궤양 효과
김영식 ( Young-sik Kim ),박효진 ( Hyojin Park ),송정빈 ( Jungbin Song ),이동헌 ( Donghun Lee ),김호철 ( Hocheol Kim ) 대한본초학회 2018 大韓本草學會誌 Vol.33 No.4
Objectives : This study aimed to investigate the anti-ulcer effect of an standardized herbal extracts mixture of Inulae Flos and Paeoniae Radix (HT074) on acidified ethanol induced gastric injury and its potential mechanisms. Methods : Antioxidant activities of HT074 and its constituents were measured by DPPH (2,2-Diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging capacity. After the oral administration of HT074 at doses of 100, 300 ㎎/㎏ twice per day for 14 days, Gastric lesions were induced by oral administration of acidified ethanol in Sprague Dawley rats. Oxidative stress markers, such as super oxide dismutase (SOD) activity, concentrations of catalase (CAT) and glutathione (GSH) were measured in gastric mucosal tissues. Additionally, the expression of human mucin gene, Mucin 5AC (MUC5AC) mRNA in gastric mucosal tissues was measured. Results : HT074 showed dose dependent radical scavenging activities against DPPH and ABTS radicals. Oral administration of HT074 300 ㎎/㎏for 14 consecutive days significantly decreased gastric lesions and histological damages induced by HCl/EtOH in rats. HT074 treatment significantly increased the activity of SOD (300 ㎎/㎏) and concentration of GSH (100 and 300 ㎎/㎏), however catalase concentration was not significantly increased. MUC5AC mRNA expression was significantly increased by HT074 100, 300 ㎎/㎏ treatment. Conclusions : HT074 protects the gastric mucosa from oxidative stress caused by acidified ethanol by increasing the activity of SOD, concentration of GSH and mucin biosynthesis. These findings suggest that HT074 could be an effective candidate for prevention and treatment of gastritis and gastric ulcer.