• Applied Microscopy
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• v.52
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• pp.4.1-4.11
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• 2022

Field emission scanning electron microscopy (FESEM) is an essential tool for observing surface details of specimens in a high vacuum. A series of specimen procedures precludes the observations of living organisms, resulting in artifacts. To overcome these problems, Takahiko Hariyama and his colleagues proposed the concept of the "nanosuit" later referred to as "NanoSuit", describing a thin polymer layer placed on organisms to protect them in a high vacuum in 2013. The NanoSuit is formed rapidly by (i) electron beam irradiation, (ii) plasma irradiation, (iii) Tween 20 solution immersion, and (iv) surface shield enhancer (SSE) solution immersion. Without chemical fixation and metal coating, the NanoSuit-formed specimens allowed structural preservation and accurate element detection of insulating, wet specimens at high spatial resolution. NanoSuit-formed larvae were able to resume normal growth following FESEM observation. The method has been employed to observe unfixed and uncoated bacteria, multicellular organisms, and paraffin sections. These results suggest that the NanoSuit can be applied to prolong life in vacuo and overcome the limit of dead imaging of electron microscopy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.974-978
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• 2012

The effect of Cu coating on the sensing properties of nano $SnO_2:Cu$ based sensors for the $CH_4$, $CH_3CH_2CH_3$ gas was studied. This work was focussed on investigating the change of sensitivity of nano $SnO_2:Cu$ based sensors for $CH_4$, $CH_3CH_2CH_3$ gas by Cu coating. Nano sized $SnO_2$ powders were prepared by solution reduction method using stannous chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_2$) and NaOH and subsequent heat treatment. XRD patterns showed that nano $SnO_2$ powders with rutile structure were grown with (110), (101), (211) dominant peak. The particle size of nano $SnO_2:Cu$ powders at 8 wt% Cu was about 50 nm. $SnO_2$ particles were found to contain many pores, according to SEM analysis. The sensitivity of nano $SnO_2:Cu$ based sensors was measured for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The sensitivity for both $CH_4$ and $CH_3CH_2CH_3$ gases was improved by Cu coating on the nano $SnO_2$ surface. The response time and recovery time of the $SnO_2:Cu$ gas sensors for the $CH_4$ and $CH_3CH_2CH_3$ gases were 18~20 seconds, and 13~15 seconds, respectively.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.281-286
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• 2010

Thickness effects on the structural and optical properties of ZnO thin films fabricated by spin coating method have been carried out. With increase in the thickness of the ZnO thin films, the width and density of striation shape are increased. The ZnO thin film with thickness of 450 nm has a smooth surface morphology. For the ZnO thin film with a smooth surface, orientation factor ${\alpha}_{(002)}$ is sharply increased and FWHM of (002) diffraction peak is decreased compared to the ZnO thin films with a striation shape surface. Thickness and surface morphology of the ZnO thin films hardly affect the NBE peak position. However, the DLE peak position is blue-shifted as the surface morphology is changed from striation to smooth surface. The PL intensity ratio of the NBE to DLE is increased and the FWHM of NBE peak is decreased as the thickness of the ZnO thin films is increased.

• Journal of Surface Science and Engineering
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• v.47 no.1
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• pp.13-19
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• 2014

The various surface treated conditions of Fe-3.0%Ni-0.7%Cr-1.4%Mn-X steel such as as-received, ion nitriding, DLC coated, DLC coated after nitriding for 3 hrs and 6 hrs were investigated to evaluate the beneficial effect for plastic mold steel. Micro Vickers hardness tester was used to estimate nitriding depth from the hardness profile and to measure hardness on the surface. Elastic modulus and residual stress were measured by a nanoindentator. Scratch test and SP (small ball punch test) were utilized to assess the adhesive strength of DLC coating. The depth of nitriding layer was measured as $50{\mu}m$ for the condition of 3 hrs nitriding and $90{\mu}m$ for that of 6 hrs nitriding. Hardness, elastic modulus, residual stress of DLC coating were 20.37 GPa, 162.78 GPa and -1456 MPa respectively. Residual stress on the surface of DLC coating after nitriding could increase to -3914 MPa by introducing nitriding before DLC coating. During the 'Ball-On-Disc' test ${\gamma}^{\prime}$ particles pulled out from the surface of nitrized layer tend to enhance abrasive wear mode since the fraction of ${\gamma}^{\prime}$ (Fe4N) in ion-nitrized layer is known to increases with nitriding time. Thus the specific wear rate of the nitriding layer increased. Comparing with nitriding the specific wear rate in work piece disc as well as ball decreased prominently in DLC coating due to the remarkable reduction in friction coefficient.

• Journal of Surface Science and Engineering
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• v.51 no.3
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• pp.164-171
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• 2018

In this study, we have fabricated pure titanium (Ti)/hydroxyapatite (HA) double layer coating on medical grade PEEK from magnetron sputtering system, an investigation was performed whether the surface can be had more improve bio-active for orthopedi/dental applications than that of non-coated one. Pure Ti and HA coating layer were obtained by a radio-frequency and direct current power magnetron sputtering system. The microstructures surface, mechanical properties and wettability of the pure Ti/HA double layer deposited on the PEEK were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), nano-indentation, and contact angle test. According to the EDS and XRD results, the composition and crystal structure of pure Ti and HA coated surface were verified. The elastic modulus and hardness value were increased by pure Ti and HA coating, and the pure Ti/HA double layer coating surface has the highest value. The contact angle showed higher value for pure Ti/HA double layered coating specimens than that of non-coated (PEEK) surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.463-463
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• 2013

This paper reports the synthesis and characterization of ZnO:Ga nano-structures deposited on Au/SiNx/Si(001) by radio-frequency sputtering. The effect of the temperature on the microstructure of the as-grown ZnO:Ga thin films was examined. The growth mode of ZnO:Ga nano-structures can be explained by the profile coating, i.e. the ZnO nano-structures were formed with a morphological replica of Au seeds. Initially, the ZnO:Ga nano-structures were overgrown on top of Au nano-crystals. Small ZnO:Ga nano-dots were then nucleated on hexagonal ZnO:Ga discs.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1235-1241
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• 2012

Aluminium (Al)-doped zinc oxide (AZO) thin films with different Al concentrations were prepared by the solgel spin-coating method. Optical parameters such as the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity were studied in order to investigate the effects of the Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at infinite wavelength of the AZO thin films were found to be affected by Al incorporation. The optical conductivity of the AZO thin films also increases with increasing photon energy.

• Advances in nano research
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• v.13 no.3
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• pp.247-257
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• 2022

Extraordinary properties of nanocomposites make them a primary replacement for many conventional materials. Anterior cruciate ligament (ACL) reconstruction, which is a frequent surgery in sport activities, is one of the fields in which nanocomposites could be utilized. In the present study, the mechanical properties of different porous scaffolds made from graphene nano-composites are presented ad load bearing capacity of these materials is calculated using finite element method. The numerical results are further compared with experimental published data. In addition, several geometrical and material parameters are analyzed to find the best configuration of nanocomposite scaffolds in reconstruction of ACL. Moreover, coating of detoxification chemicals are extremely easier on the nano-structured materials than conventional one. Detoxification potential of nano-composites in the injured body are also discussed in detail. The results indicated that nano-composite could be successfully used in place of auto- and allografts and also instead of conventional metallic screws in reconstruction of ACL.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.13-18
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• 2012

During warm forging, materials are formed in the temperature range of $300^{\circ}C\sim900^{\circ}C$. In this temperature range, the friction between the forging die and the material is very high and has a negative effect on the forming process causing severe die wear and possible defects in the component because of stick-slip. Thus, lubrication characteristics are a very important factor for productivity during warm forging. In this paper, ring compression experiments were conducted to estimate the friction factor between the die and the materials as the main factor in characterizing the lubricant. Also, ring tests using normal graphite power as a lubricant coating system were compared with tests using nano graphite powder. The results confirm that the nano graphite is superior to the normal graphite in view of its lubricating effect. In addition, the friction factor (m) was estimated with respect to the amount of the nano graphite content in the lubricant. With 10 % nano graphite the friction factor had the lowest value as compared to other amounts. It can be concluded that the amount of the nano graphite in the coating system can be optimized to obtain the best lubrication condition between the die and the material using ring test experiments.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.98-103
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• 2019

Optical filters to control light wavelength of displays or cameras are fabricated by multi-layer stacking process of low and high index thin films. The process of multi-layer stacking of thin films has received much attention as an optimal process for effective manufacturing in the optical filter industry. However, multi-layer processing has disadvantages of complicated thin film process, and difficulty of precise control of film morphology and material selection, all of which are critical for transmittance and coloring effect on filters. In this study, the composite $TiO_2$, which can be used to control of UV absorption, coated on nano hollow silica sol, was synthesized as a coating material for optical filters. Furthermore, systematic analysis of the process parameters during the chemical reaction, and of the structural properties of the coating solutions was performed using SEM, TEM, XRD and photo spectrometry. From the structural analysis, we found that the 85 nm nano hollow silica with 2.5 nm $TiO_2$ shell formation was successfully synthesized at proper pH control and titanium butoxide content. Photo luminescence characteristics, excited by UV irradiation, show that stable absorption of 350 nm-light, correlated with a 3.54 eV band gap, existed for the $TiO_2$ shell-nano hollow silica reacted with 8.8 mole titanium butoxide solution. Transmittance observed on substrate of the $TiO_2$ shell-nano hollow silica showed effective absorption of 200-300 nm UV light without deterioration of visible light transparency.