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신원상,김종규 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.7
We describe herein a three-dimensionally diverse micropatterning of poly(lactic acid), as a biopolymer, using 1-butyl-3-methylimidazolium-based room-temperature ionic liquids (bmim-based RTILs), [bmim]X (X = SbF6, PF6, NTf2, Cl). Utilizing the hydrophobic bmim-based RTILs, [bmim]X (X = SbF6, PF6, NTf2) and a phase separation technique, we were able to produce white and opaque membranes with a three-dimensional structure closely packed with particles (10-50 μm in diameter). The particlulate structure, made by the assistance of [bmim]NTf2 and DCM, interestingly transformed to a fibrous structure by using a cosolvent, e.g., DCM/CF3CH2OH. When we used an increased amount of [bmim]NTf2, the particles were effectively detached and macrosized (100-500 μm in diameter) and the oval-shaped beads were obtained in a powder form. By varying the counter-anion type of the imidazolium-based RTIL, for example from NTf2 − to Cl−, the particulate 3D-morphology was once more transformed to a porous structure. These reserch results could be potentially useful, as a method to fabricate particulate scaffolds, fibrous or porous scaffolds, and beads as a biopolymer device in diverse fields including drug delivery, tissue regeneration, and biomedical engineering.
Graphene-Incorporated Nanofibrous Hybrid Membrane with Enhanced Properties
신원상,박정순,오준성,이은정 한국고분자학회 2017 Macromolecular Research Vol.25 No.11
Graphene has been highlighted as an additive material to ameliorate functions of biomaterials due to its unique structure and superelasticity. In this study, graphene at different concentration (up to 10%) was incorporated into a hybrid membrane composed of chitosan and silica xerogel to enhance the functionality of the hybrid membrane for guided bone regeneration (GBR) through in situ sol-gel technique. The effect of graphene incorporation was evaluated in terms of morphology, mechanical property, and biological property. In SEM observation, graphene (G)-incorporated membranes showed macroporous structure and nanofibrous microstructure which could allow protein to attach onto membrane more efficiently. The hybrid membrane containing 10% graphene was found to have highly porous and nanofibrous structure with the highest level of protein adsorption. These G-incorporated membranes also showed improved mechanical properties compared to hybrid membrane only (control) in wet state. However, the tensile strength and elongation were decreased when 10% graphene was incorporated into the hybrid membrane. Both in vitro and in vivo tests confirmed that G-incorporated membranes had similar biological properties to those of osteogenic hybrid membrane with excellent GBR ability. These findings demonstrate that prop
신원상,백승우,김윤준 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.6
Nodular graphite cast iron is used in the railway and automobile industries because of its excellent workability, abrasion resistance, mechanical strength, and hardenability. To use nodular graphite cast iron in harsh environments, it is essential to examine their friction–wear properties in conjunction with the surface hardness of the materials. Therefore, in this study, a pin–on–disk type method was used to investigate specimens whose surface hardness was improved by the addition of Sn alloying element, followed by high-frequency heat treatment. The results revealed that Sn inhibited the growth of nodular graphite by acting as a barrier to the movement of carbon and promoted the transformation of some matrix from ferrite to pearlite. In contrast, most of the matrix of the high-frequency heat treated specimen was transformed into pearlite. Consequently, the specimens prepared using both methods achieved higher surface hardness than the as-cast state. With regards to the friction–wear properties, the Sn added alloy exhibited a relatively weak matrix, and therefore, delamination of the surface and spalling on the nodular graphite occurred, with significant wear width and depth. In contrast, surface delamination was not observed in the specimen after high-frequency heat treatment.
건설산업의 이미지 수준 비교분석 및 개선활동 효율화 방안
신원상,손창백 대한건축학회 2017 대한건축학회논문집 Vol.33 No.7
This study was conducted to analyze the level of images of the construction industry perceived by general people and construction industry workers and to suggest an improvement activity efficiency plan for getting rid of negative images perceived by general people and construction industry workers and problems of domestic construction industry image improvement activities. The results of this study are as follows. First, when images of the construction industry perceived by general people and construction industry workers were assessed, negative images were found in 'Sincerity Construction', 'Business Ethics', and 'Working Environment'. Second, it was analyzed that each organization carries out overlapped domestic construction industry image improvement activities, the activities have small improvement effect and they are less recognized. Third, for improvement in domestic construction industry images, this study presented subjects of improvement activities and management processes, contents of activities, which should be performed by each organization, and effective promotion systems suitable for characteristics of individual organizations.
신원상,조나단놀리스,김해원 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.5
An efficient and novel positive charge-doping on the sidewalls of multi-walled carbon nanotubes has been achieved in the presence of tetrahydrofuran as a dopant and Lewis acidic ionic liquids, [bmim]Sb_nF_(5n+1) (n ≥ 2;bmim = 1-butyl-3-methylimidazolium), as an activator, leaving air-stable derivatives having positively charged sidewalls and the counter anions, [MWCNT^(y+)][SbF6_^−]y (MWCNT = multi-walled carbon nanotube). The derivatization took place very fast in one-pot and under mild reaction conditions. The ionic structure enabled a tunable dissolution of the derivatives in various solvents through anion exchange.
신원상,Hyun-Ki Hong,김해원,공명선 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.5
Silver nanoparticles (<10 nm) were prepared in ultrasonic vibration-induced nanodroplets of isopropyl alcohol (IPA) in combination with hydrophobic room temperature ionic liquids (RTILs). The Ag-precursor used were silver (I) complex, Ag_2(ehac)_2(eha)_2 (ehac = 2-ethylhexylammonium carbamate; eha = 2-ethylhexylamine), in IPA, while 1-butyl-3-methylimidazolium-based ionic liquids bearing SbF_6^−, PF_6^− and NTf_2^− as counter anions were used as RTILs. During sonication for 10-90 min at room temperature, uniform silver nanoparticles with mean sizes of 2 to 8 nm were rapidly synthesized. Transmission electron micrographs also confirmed that silver nanoparticles have a spherical shape and diverse sizes depending on the reaction time (10-90 min).