• Journal of Sensor Science and Technology
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• v.16 no.2
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• pp.85-90
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• 2007

This paper presents the growth conditions and characteristics of polycrystalline 3C-SiC (silicon carbide) thin films for M/NEMS applications related to harsh environments. The growth of the 3C-SiC thin film on the oxided Si wafers was carried out by APCVD using HMDS (hexamethyildisilane: $Si_{2}(CH_{3})_{6})$ precursor. Each samples were analyzed by XRD (X-ray diffraction), FT-IR (fourier transformation infrared spectroscopy), RHEED (reflection high energy electron diffraction), GDS (glow discharge spectrometer), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope) and TEM (tunneling electro microscope). Moreover, the electrical properties of the grown 3C-SiC thin film were evaluated by Hall effect. From these results, the grown 3C-SiC thin film is very good crystalline quality, surface like mirror and low defect. Therefore, the 3C-SiC thin film is suitable for extreme environment, Bio and RF M/NEMS applications in conjunction with Si fabrication technology.

• Macromolecular Research
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• v.15 no.4
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• pp.330-336
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• 2007

Luminescent CdSe/ZnS QDs, with emission in the red region of the spectrum, were synthesized and encapsulated in poly(ethylene glycol)-poly(D,L-lactide) diblock copolymer micelles, to prepare water-soluble, bio-compatible QD micelles. PEG-PLA diblock copolymers were synthesized by ring opening polymerization of D,L-lactide, in the presence of methoxy PEG as a macro initiator. QDs were encapsulated with PEG-PLA polymers using a solid dispersion method in chloroform. The resultant polymer micelles, with encapsulated QDs, were characterized using various analytical techniques, such as UV- Vis measurement, light scattering, fluorescence spectroscopy, transmission electron microscopy (TEM) and atomic forced microscopy (AFM). The polymer micelles, with encapsulated QDs, were spherical and showed diameters in the range of 20-150 nm. The encapsulated QDs were highly luminescent, and have high potential for applications in biomedical imaging and detection.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.1
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• pp.27-30
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• 2013

Catalyst-free graphene nano-sheets without substrates have been synthesized using fullerene and a high direct current (dc) pulse in the spark plasma sintering (SPS) process. Graphene nano-sheets were synthesized directly in the gas phase of carbon atoms which are generated from fullerene at a temperature of $600^{\circ}C$. Characterization has been carried out by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.293-293
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• 2010

Carbon nanotubes (CNTs) have attracted considerable attention as possible routes to device miniaturization due to their excellent mechanical, thermal, and electronic properties. These properties show great potential for devices such as field emission displays, CNT based transistors, and bio-sensors. The metals such as nickel, cobalt, gold, iron, platinum, and palladium are used as the catalysts for the CNT growth. In this study, diamond-like carbon (DLC) was used for CNT growth as a nonmetallic catalyst layer. DLC films were deposited by a radio frequency (RF) plasma-enhanced chemical vapor deposition (RF-PECVD) method with a mixture of methane and hydrogen gases. CNTs were synthesized by a hot filament plasma-enhanced chemical vapor deposition (HF-PECVD) method with ammonia (NH3) as a pretreatment gas and acetylene (C2H2) as a carbon source gas. The grown CNTs and the pretreated DLC filmswere observed using field emission scanning electron microscopy (FE-SEM) measurement, and the structure of the grown CNTs was analyzed by high resolution transmission scanning electron microscopy (HR-TEM). Also, using energy dispersive spectroscopy (EDS) measurement, we confirmed that only the carbon component remained on the substrate.

• Journal of the Korean Wood Science and Technology
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• v.42 no.2
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• pp.119-129
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• 2014

This work undertook to prepare nanofibers of cellulose nanofibrils (CNF)/polyvinyl alcohol (PVA) composite by electrospinning, and characterize the electrospun composite nanofibers. Different contents of CNFs isolated from hardwood bleached kraft pulp (HW-BKP) by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation were suspended in aqueous polyvinyl alcohol (PVA) solution, and then electrospun into CNF/PVA composite nanofibers. The morphology and dimension of CNFs were characterized by transmission electron microscopy (TEM), which revealed that CNFs were fibrillated form with the diameter of about $7.07{\pm}0.99$ nm. Morphology of the electrospun nanofiber observed by field-emission scanning electron microscopy (FE-SEM) showed that uniform CNF/PVA composite nanofibers were manufactured at 1~3% CNF contents while many beads were observed at 5% CNF level. Both the viscosity of CNF/PVA solution and diameter of the electrospun nanofiber decreased with an increase in CNF content. The diameter and its distribution of the electrospun nanofibers helped explain the differences observed in their morphology. These results show that the electrospinning method was successful in preparing uniform CNF/PVA nanofibers, indicating a great potential for manufacturing consistent and reliable cellulose-based nanofibrils for scaffolds in future applications.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.56.2-56.2
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• 2012

Clinically-favored materials for bone regeneration are mainly based on bioceramics due to their chemical similarity to the mineral phase of bone. A successful scaffold in bone regeneration should have a 3D interconnected pore structure with the proper biodegradability, biocompatibility, bioactivity, and mechanical property. The pore architecture and mechanical properties mainly dependent on the fabrication process. Bioceramics scaffolds are fabricated by polymer sponge method, freeze drying, and melt molding process in general. However, these typical processes have some shortcomings in both the structure and interconnectivity of pores and in controlling the mechanical stability. To overcome this limitation, the rapid prototyping (RP) technique have newly proposed. Researchers have suggested RP system in fabricating bioceramics scaffolds for bone tissue regeneration using selective laser sintering, powder printing with an organic binder to form green bodies prior to sintering. Meanwhile, sintering process in high temperature leads to bad cost performance, unexpected crystallization, unstable mechanical property, and low bio-functional performance. The development of RP process without high thermal treatment is especially important to enhance biofunctional performance of scaffold. The purpose of this study is development of new process to fabricate ceramic scaffold at room temperature. The structural properties of the scaffolds were analyzed by XRD, FE-SEM and TEM studies. The biological performance of the scaffolds was also evaluated by monitoring the cellular activity.

• Journal of Powder Materials
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• v.19 no.3
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• pp.177-181
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• 2012

Copper composite materials have attracted wide attention for energy applications. Especially $CuInS_2$ has a desirable direct band gap of 1.5 eV, which is well matched with the solar spectrum. $CuInS_2$ nanoparticles could make it possible to develop color-tunable $CuInS_2$ nanoparticle emitter in the near-infrared region (NIR) for energy application and bio imaging sensors. In this paper, $CuInS_2$ nanoparticles were successfully synthesized by thermo-decomposition methods. Surface modification of $CuInS_2$ nanoparticles were carried out with various semiconductor materials (CdS, ZnS) for enhanced optical properties. Surface modification and silica coating of hydrophobic nanoparticles could be dispersed in polar solvent for potential applications. Their optical properties were characterized by UV-vis spectroscopy and photoluminescence spectroscopy (PL). The structures of silica coated $CuInS_2$ were observed by transmission electron microscopy (TEM).

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.927-933
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• 2011

Conducting polyaniline-poly($\varepsilon$-caprolactone) polymer composites were synthesized via in situ deposition techniques. By dissolving different weight percentages of poly($\varepsilon$-caprolactone) (PCL) (10%, 20%, 30%, 40%, and 50%), the oxidative polymerization of aniline was achieved using ammonium persulfate as an oxidant. FTIR, UV-vis spectra, and X-ray diffraction studies support a strong interaction between polyaniline (PANI) and PCL. Structural morphology of the PANI-PCL polymer composites was studied using scanned electron microscopy (SEM) and transmittance electron microscopy (TEM), and thermal stability was analyzed by thermogravimetric analysis (TGA) technique. The temperature-dependent DC conductivity of PANI-PCL polymer composite films was studied in the range of 305-475 K, which revealed a semiconducting behavior in the transport properties of the polymer films. Conductivity increased with the increase of PCL in below critical level, however conductivity of the polymer film was decreased with increase of PCL concentration higher than the critical value.

• Animal cells and systems
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• v.15 no.1
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• pp.53-61
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• 2011

The fine structural characteristics of the antennal sensory organs of a female millipede Oxidus gracilis (Polydesmida: Paradoxomatidae) were observed with both field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). We could identify four apical cones and three basic types of antennal sensillae in a. gracilis as follows: chaetiform sensilla (CS), trichoid sensilla (TS) and basiconic sensilla (BS). Of these, both types of CS and TS can be observed throughout all antennal segments except the terminal 8th article, whereas the BS are observed within the cuticular depressed regions of the articles from the 5th to the 7th segment. According to their relative microstructure and location, the BS arc divided further into three subtypes: large ($BS_1$) small ($BS_2$) and spiniform ($BS_3$). The $BS_1$ can be seen on the 5th article only, while $BS_2$ can be seen on the 5th and 6th articles. The $BS_3$ is characteristically seen within the depressive region of the 7th article. Both the CS and TS of O. gracilis are similar in structure, and they are related to the function of mechanical reception; however, four large apical cones (AP) and three subtypes of BS are likely to function in gustatory and olfactory reception.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.69-78
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• 2018

A study has been carried out of the regenerability of a commercial Ni catalyst used in the steam reforming of the volatiles from biomass pyrolysis (gases and bio-oil), determining the evolution of the reaction indices (conversion, product yields and $H_2$ production) in successive reaction-regeneration cycles. The causes of catalyst deactivation (coke deposition and Ni sintering) have been ascertained characterizing the deactivated and regenerated catalysts by TPO, TEM, TPR and XRD. Catalyst activity is not fully recovered by coke combustion in the first cycles due to the irreversible deactivation by Ni sintering, but the catalyst reaches a pseudo-stable state beyond the fourth cycle, reproducing its behaviour in subsequent cycles.