• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.205-210
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• 2015

NbN coatings were prepared by ICP (inductively coupled plasma) assisted magnetron sputtering from a Nb metal target in $Ar+N_2$ atmosphere at various ICP powers. Effect of ICP on the microstructure, crystalline structure and mechanical properties of NbN coatings was investigated by field emission electron microscopy, X-ray diffraction, atomic force microscopy and nanoindentation measurements. The results show that ICP power has a significant influence on coating microstructure, structure and mechanical properties of NbN coatings. With the increasing of ICP power, coating microstructure evolves from the columnar structure of DC process to a highly dense one. Crystalline structure of NbN coatings were changed from cubic ${\delta}$-NbN to hexagonal ${\beta}-Nb_2N$ with increase of ICP power. The maximum nano hardness of 25.4 GPa with Ra roughness of 0.5 nm was obtained from the NbN coating sputtered at ICP power of 200 W.

• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.199-204
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• 2015

Recently, fuel cell is a good alternative for energy source. Separator is a important component for fuel cell. In this study, The surface of separator was modified for corrosion resistance and electric conductivity. Reduced graphene oxide (rGO) was made by Staudenmaier's method. Nickel, phosphorus and rGO were coated on 6061 aluminum alloy as a separator of proton exchange membrane fuel cell by composite electroless plating. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to examine the morphology of Ni-P-rGO. Surface images were shown that the rGO was dispersed on the surface of Ni-P electroless plating, and nickel was combined with the un-reduced oxygen functional group of rGO.

• Advances in nano research
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• v.5 no.2
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• pp.171-178
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• 2017

Superparamagnetic Zinc ferrite submicropheres are firstly synthesized via a one-pot solvothermal approach at $200-215^{\circ}C$ for 4-8 hours. $ZnCl_2$, $FeCl_3$ and NaAc are used as precursors with ethylene glycol solvent. The X-ray diffraction (XRD) data indicate that $ZnFe_2O_4$ nanoparticles with the grain size around $15{\pm}3nm$ can be successfully synthesized via the one-pot method. The scanning/transmission electronic microscope (SEM/TEM) images further show the samples are submicrospheres self-assembled by nanoparticles with size about 375-500 nm changed with reaction conditions. Room-temperature vibration magnetic strength measurements (VMS) demonstrates the as-obtained $ZnFe_2O_4$ submicrospheres show prefect superparamagnetism, whose coercivity force and remanence are practically nil. The reaction temperature and time influence on the crystallinity, diameter, saturated magnetic intensity and morphology of the particles.

• Journal of Radiation Industry
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• v.4 no.4
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• pp.347-352
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• 2010

In this study, we addressed a novel nanosized curdlan-silica complex, which is curdlan bound to silica, for the development of a sustain-releasing micro element fertilizer formulation. The complex was obtained as follow steps; First, Curdlan polymer, sodium silicate ($Na_2SiO_3$) and isopropyl alcohol were dissolved in DDW. Next the resultant solution was irradiated by $^{60}Co$ gamma-irradiator (150 TBq of capacity; ACEL, Canada). Then $MgSO_4$ was treated with the resultant solution. The obtained colloidal solution was dried by freeze dryer. Finally, we obtained a novel nanosized curdlan-silica formulation containing $MgSO_4$ from the colloidal solution. The morphology of the complex was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanosized curdlan-silica complex has a particle size ranging from 20 to 80 nm and high stability. Our results suggested that the nano-complex can be applicable to use in various sustain-releasing formulation for pesticide delivery system (PDS).

• Journal of Radiation Industry
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• v.5 no.1
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• pp.69-73
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• 2011

Polyamide 66 (PA66) nanofibers with Triallyl cyanurate (TAC) were obtained by electrospinning of formic acid and chloroform solution. Electron beam irradiation of PA66 nanofiber with and without TAC was carried out over a range of absorbed doses (20~100 kGy) in nitrogen. The characterization of the irradiated PA66 nanofibers and PA66 nanofibers with TAC was done by scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and universal testing machine (UTM). The results of the SEM image analysis confirmed that the morphology of PA66 nanofibers was not altered by electron beam. The amount of TAC in PA66 nanofiber with TAC was identified by $^1H-NMR$ analysis. The degradation temperature of PA66 nanofibers with TAC at an absorbed dose of 20~100 kGy was higher than the irradiated PA66 nanofiber without TAC. On the other hand, the decreasing rate of modulus of irradiated PA66 nanofibers with TAC was less than PA66 nanofibers.

• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.164-171
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• 2019

Nano-sized $SnO_2$ powders were synthesized via a solvent thermal reaction using $SnClO_4$, NaOH, and ethylene glycol at $150^{\circ}C$. TGA, SEM, FT-IR, XRD, and Potentiostat/Galvanostat were employed to investigate the chemical and electrochemical characteristics of the synthesized $SnO_2$. The structure of $SnO_2$ was amorphous, and when heat treated at $500^{\circ}C$, it was transformed into a crystalline structure. The morphology obtained by SEM micrographs of the as-synthesized $SnO_2$ showed powder features that had diameters ranging 100 to 200 nm. The electrochemical performance of the crystalline $SnO_2$ as a Li-air battery cathode was better than that of the amorphous $SnO_2$. The specific capacity of the crystalline $SnO_2$ was at least 350 mAh/g at 10 mA/g discharge rate. However, there was some capacity loss of all the cells during the consecutive cycles. Keywords : Lithium-Air Battery.

• Advances in nano research
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• v.4 no.2
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• pp.129-143
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• 2016

The present work reports a facile, rapid and an eco-friendly method for the synthesis of silver nanoparticles using Luffa acutangula (L. acutangula) leaves extract and their antibacterial and cytotoxic effects. The synthesized silver nanoparticles (AgNPs) were characterized by UV-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction analysis (XRD). Additionally the topography, morphology and the elemental composition of the particles were determined by Scanning Electron Microscopy (SEM) and Energy dispersive spectrophotometric (EDS) technique and the measured particle sizes from SEM micrographs are in the range of 12.5 to 24.5nm. The in-vitro antimicrobial activity of the synthesized nanoparticles was high against gram positive Staphylococcus aureus and moderate against gram negative Escherichia coli and Pseudomonas aeruginosa strains. Further, the cytotoxic effects of synthesized AgNPs were evaluated against Human Breast Cancer (MCF 7) cell line.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.401-406
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• 2018

We investigated the effect of ZnO seed layer thickness on the density of ZnO nanorod arrays. ZnO has been deposited using two distinct processes consisting of the seed layer deposition using ALD and subsequent hydrothermal ZnO growth. Due to the coexistence of the growth and dissociation during ZnO hydrothermal growth process on the seed layer, the thickness of seed layer plays a critical role in determining the nanorod growth and morphology. The optimized thickness resulted in the regular ZnO nanorod growth. Moreover, the introduction of ALD to form the seed layer facilitates the growth of the nanorods on ultrathin seed layer and enables the densification of nanorods with a narrow change in the seed layer thickness. This study demonstrates that ALD technique can produce densely packed, virtually defect-free, and highly uniform seed layers and two distinctive processes may form ZnO as the final product via the initial nucleation step consisting of the reaction between $Zn^{2+}$ ions from respective zinc precursors and $OH^-$ ions from $H_2O$.

• Journal of Sensor Science and Technology
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• v.31 no.4
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• pp.218-227
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• 2022

Triboelectric nanogenerators (TENGs), a new green energy, that have various potential applications, such as energy harvesters and self-powered sensors. The output performance of TENGs has been improving rapidly, and their output power significantly increased since they were first reported owing to improved triboelectrification materials and interfacial material engineering. Because the operation of a TENG is based on contact electrification in which electric charges are exchanged at the interface between two materials, its output can be increased by increasing the contact area and charge density. Material surface modification with microstructures or nanostructures has increased the output performance of TENGs significantly because not only does the sharp micro/nano morphology increases the contact area during friction, but it also increases the charge density. Chemical treatment in which ions or functional groups are added has also been used to improve the performance of TENGS by modifying the work functions, charge densities, and dielectric constants of the triboelectric materials. In addition, ultrahigh output power from TENGs without using new materials or treatments has been obtained in many studies in which special structures were designed to control the current release or to collect the charge current directly. In this review, we discuss physical and chemical treatments, bulk modifications, and interfacial engineering for enhancing TENG performance by improving contact electrification and electrostatic induction.

• Advances in nano research
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• v.12 no.4
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• pp.387-403
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• 2022

Silica nanoparticles, which have a broad range of sizes and specific surface features, have been used in many industrial applications. This study was conducted to synthesize monodispersed silica nanoparticles directly from tetraethyl orthosilicate (TEOS) with an alkaline catalyst (NH₃) based on the sol-gel process and the Stöber method. A central composite design (CCD) is used to build a second-order (quadratic) model for the response variables without requiring a complete three-level factorial experiment. The process was then optimized to achieve the minimum particle size with the lowest concentration of TEOS. Dynamic light scattering and scanning electron microscopy were used to analyze the size, dispersity, and morphology of the synthesized nanoparticles. After optimization, a confirmation test was carried out to evaluate the confidence level of the software prediction. The results revealed that the predicted optimization is consistent with experimental procedures, and the model is significant at the 95% confidence level.