• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.129-135
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• 2006

In this study, a two-axis ultra-precision stage driven by piezoelectric elements is presented. The stage has a flexure-type parallel linear guide mechanism consisting of quad-symmetric simple parallel linear springs and quad-symmetric double compound linear springs. While the simple parallel linear springs guide the linear motion of a moving plate in the stage, the double compound linear springs follow the motion of the simple parallel linear spring as well as compensate the parasitic motions caused by the simple parallel linear springs. The linear springs are designed by rectangular beam type flexures that are deformed by bending deflection rather than axial extension, because the axial extension is smaller than the bending deflection at the same force. The designed guide mechanism is analyzed by finite element method(FEM). Then two-axis parallel linear stage is implemented by the linear guide mechanism combined with piezoelectric elements and capacitance type displacement sensors. It is shown that the manufactured ultra-precision stage achieves 3 nm of resolution in x- and y-axis within 30 ${\mu}m$ of operating range.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.271-280
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• 2016

When a single inorganic precursor is used for the synthesis of a sol-gel coating, there is a problem of cracking on the surface of coating layer. In order to solve this problem of surface cracking, we synthesized inorganic-organic coatings that have hybrid properties of inorganic and organic materials. Sols of various ratios (1:0.07, 0.2, 0.41, 0.82, 1.64, 3.26, 6.54, 13.2) of an inorganic precursor of Tetrabutylorthotitanate ($Ti(OBu)_4$, TBOT) and an organic precursor of ${\gamma}$-Methacryloxy propyltrimethoxysilane (MAPTS) were prepared and coated on stainless steels (SUS316L) by dip coating method. The binding structure and the physical properties of the synthesized coatings were analyzed by FT-IR, FE-SEM, FIB (Focused Ion Beam), and a nano-indenter. Dynamic polarization testing and EIS (electrical impedance spectroscopy) were carried out to evaluate the micro-defects and the corrosion properties of the coatings. The prepared coatings show hybrid properties of inorganic oxides and organic materials. Crack free coatings were prepared when the MAPTS ratio was above a critical value. As the MAPTS ratio increased, the thickness and the corrosion resistance increased, and the hardness decreased.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.367-367
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• 2013

Commercial applications of indium tin oxide (ITO) can be separated into two useful areas. As it is perceived to bear electrical properties and optical transparency at once, its chance to apply to promising fields, usually for an optical device, gets greater in the passing time. ITO is one of the transparent conducting oxides (TCO), and required to carry the relative resistance less than $10^{-3}{\Omega}$/cm and transmittances over 80 % in the visible wavelength of light. Because ITO has considerable refractive index, there exist applications for anti-reflection coatings. Anti-reflection properties require gradual change in refractive index from films to air. Such changes are obtained from film density or nano-clustered fractional void. Glancing angle deposition (GLAD) method is a well known process for adjusting nanostructure of the films. From its shadowing effects, GLAD helps to deposit well-controlled porous films effectively. In this study, we are comparing the reference sample to samples coated with controlled ITO multilayer accumulated by an e-beam evaporation system. At first, the single ITO layer samples are prepared to decide refractive index with ellipsometry. Afterwards, ITO multilayer samples are fabricated and fitted by multilayer ellipsometric model based on single layer data. The structural properties were measured by using atomic force microscopy (AFM), and by scanning X-ray diffraction (XRD) measurements. The ellipsometry was used to determine refractive indices and extinction coefficient. The optical transmittance of the film was investigated by using an ultraviolet-visible (UV-Vis) spectrophotometer.

• Advances in nano research
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• v.6 no.3
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• pp.279-298
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• 2018

Present investigation deals with the free vibration characteristics of nanoscale-beams resting on elastic Pasternak's foundation based on nonlocal strain-gradient theory and a higher order hyperbolic beam model which captures shear deformation effect without using any shear correction factor. The nanobeam is lying on two-parameters elastic foundation consist of lower spring layers as well as a shear layer. Nonlocal strain gradient theory takes into account two scale parameters for modeling the small size effects of nanostructures more accurately. Hamilton's principal is utilized to derive the governing equations of embedded strain gradient nanobeam and, after that, analytical solutions are provided for simply supported conditions to solve the governing equations. The obtained results are compared with those predicted by the previous articles available in literature. Finally, the impacts of nonlocal parameter, length scale parameter, slenderness ratio, elastic medium, on vibration frequencies of nanosize beams are all evaluated.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.54-61
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• 2015

In this study, effect of laser power on hardness and microstructure of SKD61 Hot Die steel of which surface was melted and hardened with Yb:YAG disk laser was investigated. Beam speed was fixed at 70 mm/sec and distance between them was 0.8 mm about Laser surface melting. The only thing that was changed laser power. Laser powers were 2.0, 2.4 and 2.8 kW. No defect was found under all conditions. As the laser power increased, the penetration depth were deepened and the bead width was also widened. There was no hardness deviation of fusion zone at same laser power and it was higher than that of heat affected zone. In addition, the more laser power increased, the more hardness in fusion zone decreased. Fusion zone was macroscopically dendrite structure. However, core matric in dendrite was lath martensite of 100 nm size. There were $M_{23}C_6$ of 500 nm and the VC and $Mo_2C$ of a nano meters on boundary of dendrite.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.571-577
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• 2006

We fabricated thermal evaporated 10 nm-Ni/(poly)Si and 10 nm-Ni/1 nm-Ir/(poly)Si films to investigate the thermal stability of nickel monosilicide at the elevated temperatures by rapid annealing them at the temperatures of $300{\sim}1200^{\circ}C$ for 40 seconds. Silicides for salicide process was formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester is used for sheet resistance. Scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An x-ray diffractometer and an auger depth profile scope were used for phase and composition analysis, respectively. Nickel silicides with iridium on single crystal silicon actives and polycrystalline silicon gates showed low resistance up to $1200^{\circ}C$ and $800^{\circ}C$, respectively, while the conventional nickel monosilicide showed low resistance below $700^{\circ}C$. The grain boundary diffusion and agglomeration of silicides led to lower the NiSi stable temperature with polycrystalline silicon substrates. Our result implies that our newly proposed Ir added NiSi process may widen the thermal process window for nano CMOS process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.131-136
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• 2011

Many researchers are recently studying about Electroactive polymer(EAP). But it has a physical limitation, because of property of material. Carbon nanotube(CNT) is known as the promising material which has excellent electro-mechanical characteristics and is mostly defect-free. It is expected that a successful synthesis of CNT and Nafion known as a primary material for IPMC would make a great improvement on its electro-mechanic feature. This study focuses on the method of synthesis of CNT with Nafion which improves electro-mechanical characteristic. To come up with mechanical dispersion with Nafion and Isopropyl Alcohol(IPA), we dispersed Single-walled carbon nanotubes(SWCNTs). For a uniformly layer of CNT, we used a spray gun on a hot plate by a simplified method. We fabricated a disperse SWCNT/Nafion composite uniformly. Through the use of the E-beam evaporator to form an uniform electrode layer, we consummated the IPMC actuator. This result shows improving 1.5 times mechanical properties about driving force in IPMC.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.421-427
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• 2015

In this paper, a description is given of finite element method (FEM) simulations of the elastic bending modulus of multi-layered graphene sheets that were carried out to investigate the mechanical behavior of graphene sheets with different gap thicknesses through molecular mechanics theory. The interaction forces between layers with various gap thicknesses were considered based on the van der Waals interaction. A finite element (FE) model of a multi-layered rectangular graphene sheet was proposed with beam elements representing bonded interactions and spring elements representing non-bonded interactions between layers and between diagonally adjacent atoms. As a result, the average elastic bending modulus was predicted to be 1.13 TPa in the armchair direction and 1.18 TPa in the zigzag direction. The simulation results from this work are comparable to both experimental tests and numerical studies from the literature.

• Advances in nano research
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• v.3 no.1
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• pp.1-11
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• 2015

Thin film ethanol sensors made from ${\alpha}-Fe_2O_3$ decorated with multiwall carbon nanotubes(MWCNTs) were manufactured by the electron beam deposition method. The morphology of the decorated ${\alpha}-Fe_2O_3$/MWCNTs (25:1 weight ratios) nanocomposite powder was investigated using the scanning electron microscopy and X-ray diffraction techniques. The thickness of thin films has been determined from ellipsometric measurements. The response of manufactured sensors was investigated at different temperatures of the sensor work body and concentration of gas vapors. Good response of prepared sensors to ethanol vapors already at work body temperature of $150^{\circ}C$ was shown.

• Structural Engineering and Mechanics
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• v.63 no.2
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• pp.171-180
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• 2017

Static and dynamic instability of a viscoelastic carbon nanotube (CNT) embedded on a thermo-elastic foundation are investigated, in this research. The CNT is modeled based on Euler-Bernoulli beam (EBB) and nonlocal small scale elasticity theory is utilized to analyze the structure. Governing equations of the system are derived using Hamilton's principle and differential quadrature (DQ) method is applied to solve the partial differential equations. The effects of variable axial load and diverse boundary conditions on static/vibration instability are studied. To verify the result of the DQ method, the Galerkin weighted residual approach is used for the instability analysis. It is observed appropriate agreement for results of two different solution methods and satisfactory accuracy with those obtained in prior studies. The results of this work could be useful for engineers and designers in order to produce and design nano/micro structures in thermo-elastic medium.