• Journal of Adhesion and Interface
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• v.4 no.4
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• pp.15-21
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• 2003

Polysulfone/organophilic layered silicate nanocomposites were prepared in the range of 0.25 to 9 wt% of organophilic-layered silicate by solution blend. Nano-hybridized films were cast from the blend solution. Exfoliation and intercalation of the polysulfone/organophiliclayered silicate nanocomposite films were confirmed by an X-ray diffractometer and a transmission electron microscope. Surface morphologies of polysulfone/organophilic layered silicate nanocomposite films were determined by a scanning electronic microscope and an atomic force microscope. When the organophilic layered silicate was added more than 1.5 wt%, the surface roughness (RMS) was rapidly increased because clusters of intercalated organophilic layered silicate particles existed on the polysulfone/organophilic-layered silicate film surface. Surface tension revealed an upward tendency over the contents of 1.5 wt% organophilic layered silicate in polysulfone/organophilic layered silicate nanocomposite. The change of surface morphology in polysulfone/organophilic layered silicate nanocomposite were affected by nano scale dispersed and intercalated organophilic layered silicate particles.

• Journal of the Korean Chemical Society
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• v.61 no.4
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• pp.179-184
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• 2017

In this paper, a $ZnO/SiO_2$ nano-composite was prepared by a simple chemical method at room temperature. For the synthesis of ZnO nanoparticles (NPs), a sonochemical method was used, and $SiO_2$ NPs were prepared by precipitation method. The formation of $ZnO/SiO_2$ NCs was characterized by X-ray diffractometer (XRD) and confirmed by field-emission scanning electron microscopy (FE-SEM) and Fourier transform infra-red spectroscopy(FT-IR). The photocatalytic properties of $ZnO/SiO_2$ NCs formed at different concentrations of $SiO_2$ were evaluated by rhodamine-B dye. It was confirmed that increasing $SiO_2$ concentration resulted in an increase in the photocatalytic property. In addition, the antibacterial activity of $ZnO/SiO_2$ NCs was conducted against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). As a result, the antibacterial activities of E.coli and S. aureus were increased in the presence of thick SiO NPs layer.

• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.52-59
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• 2000

The reaction gel mixtures of molar composition (0.3${\sim}$2.1) $SiO_2:\;(0.10{\sim}0.50)\;CTABr:\;0.15{\sim}0.23)\;TMAOH:\;(20{\sim}100)\;H_2O$ we prepared and then aged at room temperature for a definite duration. The aged gel is reacted hydrothermally at $150^{\circ}C$ for 2 days. The pH of reaction gel during synthesis is strongly influenced by the concentration of TMAOH and silica source. The pH change affects the phase of product, which is monitored by X-ray diffractometer. With increasing the TMAOH ratio from 0.19 to 0.23, the gel becomes more basic, and the product involves more lamellar phase. At TMAOH ratio lower than 0.19, the hexagonal phase is lower with decrease of pH. The content of the lamellar phase increases at a lower $SiO_2$ concentration, and higher concentrations have a clear detrimental effect on the crystallinity ofMCM-41 due to an excess silica source. The best quality MCM-41 is synthesized from a reaction gel composition of $1.0\;SiO_2:\;0.27\;CTABr:\;0.19\;TMAOH:\;40\;H_2O$. The pH values of this gel, aged one for 24 hr, and reacted one at $150^{\circ}C$ for 2 days are 12.3, 11.5, and 10.5, respectively. Gel aging for 24 h is essential for preparing high quality MCM-41. Longer aging causes a decrease of hexagonal phase.

• 한국해양학회지
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• v.26 no.4
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• pp.313-323
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• 1991

Fine-grained sediments of the Han River and adjacent Kyonggi Bay have been studied using the powder x-ray diffractometer in order to study the distributional characteristics of clay minerals in the bottom and suspended sediments. The result of the XRD analyse shows that the major clay minerals in the lower Han River are composed of illite (57.1%), kaolinite (22.9%), and chlorite (19.6%) and that those of the Han River Estuary are composed of illite (67.2%), chlorite (16.5%), kaolinite 915.5%), and smectite (1.3%). The variation of mineral content shows distinct distributional characteristics depending on sedimentary environments. The illite content increases gradually approaching the Kyonggi Bay and kaolinite content decreases toward the sea within the range between 11% and 23%. The trend of chlorite is similar to that of kaolinite, the amount of which ranges between 14% and 19%. Smectite content is lower than 3%. Analysis of illite using peak-intensity ratio (001/002) indicates that two types of illites occur in the study area. Dioctahedral-type illite occurs as an indicator of the marine sediments. The illites distributed between the Kyonggi Bay and the Han River are mixtures of dioctahedral- and trioctahedral-types. This study indicates that the distribution of illite, kaolimite, and chlorite has been influenced mainly by the supply from the Han River and redistributed by estuarine circulation, such as tidal circulation and seasonal variation of river discharge. However, smectite is apparently supplied from other sources such as Yellow Sea or China. This study suggests that estuarine mixing system and seasonal variations of river discharge are the major factors controlling the distribution pattern of clay minerals in the study area.

• Polymer(Korea)
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• v.37 no.4
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• pp.494-499
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• 2013

Modified polypropylene (m-PP) was fabricated by furfuryl sulphide (FS) as branching agent and m-PP/nano-filler composites were prepared with silicate and multi-walled carbon nanotube (MWCNT), using a twin screw extruder. The chemical structures and thermal properties of the m-PP were investigated by FTIR and DSC. The chemical structure of the m-PP was confirmed by the existence of =C-H stretching peak of the branching agent at 3100 $cm^{-1}$. There was no district change in melting temperature in case of m-PP, but a certain increase in crystallization temperature was notified and the increase was in the range of $10-20^{\circ}C$. The rheological properties, filler dispersion and foaming behaviors of the m-PP/nano-filler composites were investigated by dynamic rheometer, X-ray diffractometer (XRD) and scanning/transmission electron microscope (SEM/TEM). m-PP/nano-filler composites showed a high complex viscosity at a low frequency, an increase in melt elasticity, and a high shear thinning effect. Compared to pure PP, m-PP and m-PP/nano-filler composites were sufficient to enhance the foaming behavior.

• Journal of the Mineralogical Society of Korea
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• v.16 no.4
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• pp.321-331
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• 2003

We researched the variation of mineral composition with depth and the Cu adsorption behavior of Hwangto in the Okjong area, Hadong. The 4 Hwangto samples were collected from depth 10 cm, 25 cm, 2∼3 m and under 3 m from surface, and analyzed using the X­ray Diffractometer. The Hwangto samples were mostly composed of clay minerals such as kaolinite and halloysite. Two samples from 10 cm and 25 cm contained Fe or Al hydroxide minerals, for example goethite or gibbsite. As depth increases, the content of quartz decreases but that of kaolinite increases. The amount of Cu removal was rapidly rised from pH 4, and reached about 90％ at pH 6 and above 90％ at pH 7. It is regarded that the trend of Cu removal was affected by the difference in mineral composition. It was relatively well matched between experimental value and calculated value by MINTEQA2 program in the case of high Cu concentration. From this study the precipitation has important role for the removal of Cu ions, particularly in the case of high Cu concentration. However, it was discord between experimental value and calculated one in the dilute concentration circumstances. The reason may be the mistake in parameters, insufficient reaction time, and inadequate consideration of reaction site in mineral surface.

• Journal of the Korean institute of surface engineering
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• v.41 no.5
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• pp.181-188
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• 2008

A.C. impedance properties of HA/Ti compound layer coated Ti-30Ta-($3{\sim}15$)Nb alloys have been studied by electrochemical method. Ti-30Ta binary alloys contained 3, 7, 10 and 15 wt% Nb were manufactured by the vacuum furnace system. And then specimen was homogenized at $1000^{\circ}C$ for 24 hrs. The sample was cut and polished for corrosion test and coating. It was coated with HA/Ti compound layer by magnetron sputter. The non-coated and coated morphology of Ti alloy were analyzed by X-ray diffractometer (XRD), energy X-ray dispersive spectroscopy (EDX) and filed emission scanning electron microscope (FE-SEM). The corrosion behaviors were investigated using A.C. impedance test (PARSTAT 2273, USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Ti-30Ta-($3{\sim}15\;wt%$)Nb alloys showed the ${\alpha}+{\beta}$ phase, and $\beta$ phase peak was predominantly appeared in the case of increasingly Nb contents. The microstructures of Ti alloy were transformed from needle-like structure to equiaxed structure as Nb content increased. From the analysis of coating surface, HA/Ti composite surface uniformed coating layer with 750 nm thickness. The growth directions of film were (211), (112), (300) and (202) for HA/Ti composite coating on the surface after heat treatment at $550^{\circ}C$, whereas, the growth direction of film was (110) for Ti coating. The polarization resistance ($R_p$) of HA/Ti composite coated Ti-alloys were higher than those of the Ti and HA coated samples in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Especially, corrosion resistance of Ti-Ta-Nb system increased as Nb content increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.2
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• pp.69-73
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• 2010

The microstructural change of the $Sm_{0.5}Sr_{0.5}CoO_3$ (SSC) electrode for a cathode material of solid oxdie fuel cells (SOFCs) deposited by the electrostatic spray deposition (ESD) technique was characterized. Samarium chloride hexahydrate $(SmCl_3{\cdot}6H_2O)$, strontium chloride hexahydrate $(SrCl_2{\cdot}gH_2O)$, cobalt nitrate hexahydrate $(Co(No_3)_2{\cdot}6H_2O)$ as starting materials and methyl alcohol as solvent were used to make precursor solution. The suitable porous SSC films for a cathode of SOFCs were deposited on Si substrate and it is observed that the microstructure was strongly dependent on processing parameters such as deposition time, substrate temperature, and applied voltage. Scanning Electron Microscope (SEM) and X-ray Diffractometer (XRD) measurement were used to investigate the microstructure and crystallinity of the SSC films. The ESD technique is shown to be an efficient method in which the SOFCs' cathode film can be fabricated with the desired phases and microstructure.

• Korean Chemical Engineering Research
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• v.43 no.4
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• pp.495-502
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• 2005

Copper was plated on the tungsten substrate by use of a direct copper electroless plating. The optimum deposition conditions were found to be with a concentration of $CuSO_4$ 7.615 g/L, EDTA of 10.258 g/L, and glyoxylic acid of 7 g/L, respectively. The solution temperature was maintained at $60^{\circ}C$. The pH was varied from 11.0 to 12.8. After the deposition, the properties of the copper film were investigated with X-ray diffractometer (XRD), Field emission secondary electron microscope (FESEM), Atomic force microscope (AFM), X-ray photoelectron spectroscope (XPS), and Rutherford backscattering spectroscope (RBS). The best deposition condition was founded to be the solution pH of 11.8. In the case of 10 min deposition at the pH of 11.8, the grain shape was spherical, Cu phase was pure without impurity peak ($Cu_2O$ peak), and the surface root mean square roughness was about 11 nm. The thickness of the film turned out to be 140 nm after deposition for 12 min and the deposition rate was found to be about 12 nm/min. Increase in pH induced a formation of $Cu_2O$ phase with a long rectangular grain shape. The pH control seems to play an important role for the orientation of Cu in electroless deposition. The deposited copper concentration was 99 atomic percent according to RBS. The resulting Cu/W film yielded a good adhesive strength, because Cu/W alloy forms during electroless deposition.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.3
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• pp.213-232
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• 2009

This document was prepared to review and summarize the analytical methods for airborne and bulk asbestos. Basic principles, shortcomings and advantages for asbestos analytical instruments using phase contrast microscopy(PCM), polarized light microscopy(PLM), X-ray diffractometer (XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM) were reviewed. Both PCM and PLM are principal instrument for airborne and bulk asbestos analysis, respectively. If needed, analytical electron microscopy is employed to confirm asbestos identification. PCM is used originally for workplace airborne asbestos fiber and its application has been expanded to measure airborne fiber. Shortcoming of PCM is that it cannot differentiate true asbestos from non asbestos fiber form and its low resolution limit ($0.2{\sim}0.25{\mu}m$). The measurement of airborne asbestos fiber can be performed by EPA's Asbestos Hazard Emergency Response Act (AHERA) method, World Health Organization (WHO) method, International Standard Organization (ISO) 10312 method, Japan's Environmental Asbestos Monitoring method, and Standard method of Indoor Air Quality of Korea. The measurement of airborne asbestos fiber in workplace can be performed by National Institute for Occupational Safety and Health (NIOSH) 7400 method, NIOSH 7402 method, Occupational Safety and Health Administration (OSHA) ID-160 method, UK's Health and Safety Executive(HSE) Methods for the determination of hazardous substances (MDHS) 39/4 method and Korea Occupational Safety and Health Agency (KOSHA) CODE-A-1-2004 method of Korea. To analyze the bulk asbestos, stereo microscope (SM) and PLM is required by EPA -600/R-93/116 method. Most bulk asbestos can be identified by SM and PLM but one limitation of PLM is that it can not see very thin fiber (i.e., < $0.25{\mu}m$). Bulk asbestos analytical methods, including EPA-600/M4-82-020, EPA-600/R-93/116, OSHA ID-191, Laboratory approval program of New York were reviewed. Also, analytical methods for asbestos in soil, dust, water were briefly discussed. Analytical electron microscope, a transmission electron microscope equipped with selected area electron diffraction (SAED) and energy dispersive X-ray analyser(EDXA), has been known to be better to identify asbestiform than scanning electron microscope(SEM). Though there is no standard SEM procedures, SEM is known to be more suitable to analyze long, thin fiber and more cost-effective. Field emission scanning electron microscope (FE-SEM) imaging protocol was developed to identify asbestos fiber. Although many asbestos analytical methods are available, there is no method that can be applied to all type of samples. In order to detect asbestos with confidence, all advantages and disadvantages of each instrument and method for given sample should be considered.