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마이크로 분말사출성형용 마이크로/나노분말 피드스톡의 혼합 및 열분해 특성분석
최준필,하태호,정민교,송여울,이필호 한국생산제조학회 2023 한국생산제조학회지 Vol.32 No.3
This study evaluates the characterization of powder loading for 316L stainless steel (STS 316L) micro/nano powder feedstock through torque rheometry and thermal analysis. The feedstock was prepared using a bimodal powder mixture consisting of 75 vol.% micro powder (D50, 4.1 μm) and 25 vol.% nano powder (D50, 100 nm) with a wax-based binder system. The torque variation was measured to determine the critical powder loading during the feedstock mixing. Furthermore, thermogravimetric analysis (TGA) was conducted to evaluate the decomposition behavior of the feedstock at varying powder loadings. The results indicate that a powder loading of 66 vol.% exhibits an optimal microstructure and low sensitivity to the debinding temperature, considering a suitable powder loading for micro powder injection molding (μ-PIM) of STS 316L. These findings provide significant insights for optimizing the powder loading of STS 316L feedstock for μ-PIM applications.
선택적 레이저 용융공정을 이용한 316L 스테인리스강 분말 3차원 조형체의 미세조직 및 경도 연구
신기훈,최준필,김경태,김병기,유지훈,Shin, Gi Hun,Choi, Joon Phil,Kim, Kyung Tae,Kim, Byoung Kee,Yu, Ji Hun 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.3
In this study, STS316L powders prepared by gas atomization are used to manufacture bulk structures with dimensions of $10{\times}10{\times}10mm^3$ using selective laser melting (SLM). The microstructures and hardness of the fabricated 316L stainless steel has been investigated with the laser beam overlap varied from 10% to 70%. The microstructures of the fabricated STS316L samples show a decrease in the balling and satellite of powders introducing defect in the bulk samples and the porosity caused by the gap between the molten metal pools disappearing as the overlap ratio increases, whereas a low overlap ratio results in significant balling and a large amount of isolated powders due to the increased gap between the melt pools. Furthermore, the highest value in Vickers hardness is obtained for the sample fabricated by 30% overlapped laser beams. These results show that the overlap ratio of laser beams in the SLM process should be considered as an important process parameter.
과산화 티타늄 복합체를 이용한 염료감응형 태양전지용 페이스트의 제조 및 열처리 온도에 따른 특성
박현수,주소영,최준필,김우병,Park, Hyunsu,Joo, Soyeong,Choi, Joon-Phil,Kim, Woo-Byoung 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.6
The organic binder-free paste for dye-sensitized solar cell (DSSC) has been investigated using peroxo titanium complex. The crystal structure of $TiO_2$ nanoparticles, morphology of $TiO_2$ film and electrical properties are analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectra (EIS), and solar simulator. The synthesized $TiO_2$ nanopowders by the peroxo titanium complex at 150, 300, $400^{\circ}C$, and $450^{\circ}C$ have anatase phase and average crystal sizes are calculated to be 4.2, 13.7, 16.9, and 20.9 nm, respectively. The DSSC prepared by the peroxo titanium complex binder have higher $V_{oc}$ and lower $J_{sc}$ values than that of the organic binder. It can be attributed to improvement of sintering properties of $TCO/TiO_2$ and $TiO_2/TiO_2$ interface and to formation of agglomerate by the nanoparticles. As a result, we have investigated the organic binder-free paste and 3.178% conversion efficiency of the DSSC at $450^{\circ}C$.
마이크로 PIM용 Fe 마이크로-나노 혼합분말 피드스톡의 다이성형 및 소결거동
유우경 ( Woo Kyung You ),최준필 ( Joon Phil Choi ),이재성 ( Jai Sung Lee ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.1
The present investigation was performed on the die compaction and sintering behavior of Fe micronano mixed powder with a mixed binder for powder injection molding. Warm die compaction of the feedstock for simulation of the static injection molding process was conducted using a cylindrical mold of 10 mm diameter at 100℃ under 4MPa. The die compaction of the micro-nanopowder feedstock underwent a uniform molding behavior showing a homogeneous distribution of nanopowders among the micropowders without porosity and distortion. After debinding, the powder compact maintained a uniform structure without crack and distortion, leading to a high green density of 64.2% corresponding to the initial powder loading of 65%. The sintering experiment showed that the micro-nanopowder compact underwent a near full and isotropic densification process during sintering. It was observed that the nanopowders effectively suppressed the growth of micropowder grains during densification process. Conclusively, the use of nanopowder for PIM feedstock might provide a new concept for processing a full density PIM parts with fine microstructure.
대형 3D프린팅 부품 제작을 위한 이축 압출 스크류 헤드 기반 적층제조 시스템 개발
이필호,하태호,정민교,최준필,양창근 한국생산제조학회 2023 한국생산제조학회지 Vol.32 No.3
Large-scale material extrusion additive manufacturing is a promising alternative to the wooden mold industry, which faces challenges such as poor working conditions and an aging workforce. However, the current commercial single-screw extrusion heads have limitations owing to their weight and volume, requiring the use of expensive equipment. This study proposes the development of a twin-screw extrusion head that can be easily installed on an existing large-scale CNC milling machine, creating a prototype for additive manufacturing based on screw extrusion. The developed prototype is used to evaluate the extrusion additive manufacturing of ABS polymer composite material impregnated with glass fiber, the mechanical properties of printed specimens, the microstructure of the specimen fracture surface, and the performance of additive manufacturing shape implementation. The experiment confirmed that the proposed system achieved precision in the laminated shape and mechanical performance and could replace the wood pattern process in the existing wooden mold industry.