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Kuan Hoon Ngoi,Jia Chyi Wong,Wee Siong Chiu,Chin Hua Chia,진경식,Hyun-Joong Kim,김홍철,이문호 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.95 No.-
This study reports thefirst morphology and crystalline structure details of iron oxidenanoparticles in a comprehensive manner. A series of iron oxide nanoparticles were synthesizedin 1-octadecene from iron(III) acetylacetonate with the aid of oleic acid surfactant and thenfollowed by post thermal processes. Quantitative small and wide angle X-ray scattering analysesusing synchrotron radiation sources were performed together with electron microscopy, infraredspectroscopy and thermogravimery, providing morphology and crystalline structure details. Larger size of nanoparticles are synthesized by higher loading of the surfactant. Prolate ellipsoidalnanoparticles, rather than spherical particles, are always synthesized in single unimodal andnarrow size distribution. The individual particles are composed of core, core-shell interface, shell,and shell-surfactant interface, regardless of the sizes. Magnetite-like crystalline phases arepredominant. In addition, wüestite-like crystalline phases are discernible as minor components. For a given particle, the size and distribution are varied very little by the post thermal proccesses. Nevertheless, the other morphology characteristics, as well as the crystalline phases aresignificantly influenced through the post thermal process with a mixture of nitrogen and oxygen. In particular, the core part is thickened, the density gap between the core and the shell is reduced,and ferrimagnetic magnetite-like crystallites are enlarged and more populated. Paramagneticwüestite-like crystalline phases are decreased substantially or disappeared completely. Theseenhanced morphology and crystalline characteristics make great contributions to improvemagnetization performances significantly. Overall, this study provides the well-controlledsynthetic schemes and morphology/crystalline structure details that are essential for betterapplications of iron oxide nanoparticles in various advancedfields including biomedicine andnanotechnology.
Kuan Hoon Ngoi,Li Xiang,Jia Chyi Wong,Chin Hua Chia,Kyeong Sik Jin,Moonhor Ree 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.89 No.-
A series of silica nanoparticles (SNP-1, SNP-2, SNP-3, SNP-4, SNP-5 and SNP-6) were synthesized inethanol by the hydrolysis and polycondensation reaction of tetraethoxysilane with the aids of waterinitiator and ammonia catalyst and then investigated in a comprehensive manner in terms ofmorphological structure by using synchrotron transmission small-angle X-ray scattering and grazingincidence wide-angle X-ray scattering and combined together with dynamic light scattering, scanningelectron microscopy, infrared spectroscopy and thermogravimetry. They were confirmed to besuccessfully synthesized as oblate amorphous ellipsoids (Re = 9.70 56.30 nm, equatorial radius;e = 0.78 0.80, ellipsoidicity) with sharp surfaces in single unimodal and narrow size distributions. Theradial density profile details, including two-phases (i.e., less dense core and denser shell), weredetermined for thefirst time, in addition to a set of structural parameter details (radius of gyration,radius, core radius, shell thickness, and radius distribution). Larger particle was synthesized convenientlyby higher loading of ammonia solution with respect to the silane monomer. The as-synthesized silicaparticles were found to undergo two-step mass loss behaviors in heat treatment up to 500 C; thefirststeploss took place below 120 C due to removals of physically absorbed water molecules and possiblesolvent residues and the second-step loss above 180 C occurred by removals of water and ethanolbyproducts due to the post condensation reactions of hydroxy and ethoxy residues.
Zi Jia Low,Jia Chyi Wong,Kuan Hoon Ngoi,Chin Hua Chia,김현중,김홍철,이문호 한국고분자학회 2021 Macromolecular Research Vol.29 No.3
In this study, we reports the first quantification details of the pencil hardness, eraser abrasion resistance and steel wool abrasion resistance of optically-transparent and biaxially-oriented poly(ethylene terephthalate) (PET) films in various thicknesses before and after hard coating (HC) and/or optically clear adhesive (OCA) coating. Surprisingly, the PET base films were determined to exhibit unrealistically very low hardness and abrasion resistances although their stress-strain behavior followed a ductile and tough plastic nature as a high performance engineering plastic: the pencil hardness was only ≤9B even at a low loading force, 0.100 kgf, and the onset loading force to cause scratches was far below 0.013 kgf in both eraser and steel wool abrasions. These collectively confirmed that, without surface protections, PET base films are not suitable for any advanced applications. Such the low hardness and poor abrasion resistances could be improved substantially by only thin HC coating of di(trimethylolpropane) tetraacrylate (HC-a, an ultraviolet curable acrylic resin). In addition, the OCA coating based on an acrylic copolymer adhesive provided adhesion function to the PET films, showing excellent adhesion strength onto chemically-toughened glass. However, the OCA layer causes cushioning effect because of its easy plastic deformation nature, making negative impact on the hardness and abrasion resistance performances of the PET film. Thus, the OCA coating should be thinned until retaining good adhesion to adherends. Overall, PET films coated with HC and/or OCA are suitable for advanced applications in various fields including smart phones, foldable phones, and flexible display devices.