• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1321-1325
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• 2003

Nickel thin film is one of the most important materials used in micromachined structure. To measure the mechanical properties of electroplated nickel thin film, two techniques are adopted and compared quantitatively with. One is nano-indentation test to measure the elastic modulus. The other is tensile test to measure not only elastic modulus but also yield strength and plastic deformation, ultimate strength. To perform the tensile test, the test apparatus was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.47-54
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• 2003

In this study, to achieve the optimal conditions for mechanical hyper-fine pattern fabrication process, deformation behavior of the materials during indentation was studied with numerical method by ABAQUS S/W. Polymer (PMMA) and brittle materials (Si, Pyrex glass) were used as specimens, and forming conditions to reduce the elastic re cover and pile-up were proposed. The indenter was modeled a rigid surface. Minimum mesh sizes of specimens are 1 -l0nm. Comparison between the experimental data and numerical result demonstrated that the finite element approach is capable of reproducing the loading-unloading behavior of a nanoindentation test. The result of the investigation will be applied to the fabrication of the hyper-fine pattern.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.2
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• pp.75-82
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• 2010

A new advanced combined PVD/CVD technique of DLC film deposition has been developed. Deposition of a DLC film was carried out using a pulsed carbon arc discharge in vapor hydrocarbon atmosphere. The arc plasma enhancing CVD process promotes dramatic increase in the deposition rate and decrease of compressive stress as well as improvement of film thickness uniformity compared to that obtained with a single PVD pulsed arc process. The optical spectroscopy investigation reveals great increase in radiating components of $C_2$ Swan system molecular bands due to acetylene molecules decomposition. AFM, Raman spectroscopy, XPS and nano-indentation were used to characterize DLC films. The method ensures obtaining a new superhard DLC nano-material for deposition of protective coatings onto various industrial products including those used in medicine.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.169-175
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• 2020

Silicon nitride thin films are deposited by RF (13.57 MHz) magnetron sputtering process using a Si (99.999 %) target and with different ratios of Ar/N₂ sputtering gas mixture. Corning G type glass is used as substrate. The vacuum atmosphere, RF source power, deposit time and temperature of substrate of the sputtering process are maintained consistently at 2 ~ 3 × 10^-3 torr, 30 sccm, 100 watt, 20 min. and room temperature, respectively. Cross sectional views and surface morphology of the deposited thin films are observed by field emission scanning electron microscope, atomic force microscope and X-ray photoelectron spectroscopy. The hardness values are determined by nano-indentation measurement. The thickness of the deposited films is approximately within the range of 88 nm ~ 200 nm. As the amount of N₂ gas in the Ar:N₂ gas mixture increases, the thickness of the films decreases. AFM observation reveals that film deposited at high Ar:N₂ gas ratio and large amount of N₂ gas has a very irregular surface morphology, even though it has a low RMS value. The hardness value of the deposited films made with ratio of Ar:N₂=9:1 display the highest value. The XPS spectrum indicates that the deposited film is assigned to non-stoichiometric silicon nitride and the transmittance of the glass with deposited SiO₂-Si_xN_y thin film is satisfactory at 97 %.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.41-46
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• 2012

As the development of MEMS/NEMS structure and application technology the demand for an assessment of the mechanical properties have increased. The mechanical properties are mainly evaluated by using tensile test or ultrasonic wave measurement. However, the new technology have been developed such as nano-indentation, guided wave method because they have a limitation in case of a thin plate and thin film. In the study, the guided wave velocities are measured by electromagnetic-acoustic transducer(EMAT), the material properties of thin metallic foils are obtained using optimization process of the theoretical and experimental group velocity of guided wave. The Young's modulus obtained by the optimization process(201.6 GPa), nano-indentation(207.0 GPa) and literature value(203.7 GPa) of a $50{\mu}m$ thick nickel thin plate shows good agreement within 3%.

• Journal of the Korean institute of surface 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.

• Journal of Powder Materials
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• v.30 no.5
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• pp.431-435
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• 2023

An irradiation hardening of Inconel 718 produced by selective laser melting (SLM) was studied based on the microstructural observation and mechanical behavior. Ion irradiation for emulating neutron irradiation has been proposed owing to advantages such as low radiation emission and short experimental periods. To prevent softening caused by the dissolution of γ' and γ" precipitates due to irradiation, only solution annealing (SA) was performed. SLM SA Inconel 718 specimen was ion irradiated to demonstrate the difference in microstructure and mechanical properties between the irradiated and non-irradiated specimens. After exposing specimens to Fe³⁺ ions irradiation up to 100 dpa (displacement per atom) at an ambient temperature, the hardness of irradiated specimens was measured by nano-indentation as a function of depth. The depth distribution profile of Fe³⁺ and dpa were calculated by the Monte Carlo SRIM (Stopping and Range of Ions in Matter)-2013 code under the assumption of the displacement threshold energy of 40 eV. A transmission electron microscope was utilized to observe the formation of irradiation defects such as dislocation loops. This study reveals that the Frank partial dislocation loops induce irradiation hardening of SLM SA Inconel 718 specimens.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.157-158
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• 2002

A surface hardenable low alloy carbon steel was implanted with medium energy (20 - 50KeV) $N_2^+$ ions to produced a modified hardened surface. The implantation conditions were varied and are given in several doses. The surface hardness of treated and untreated steels were measured using depth sensing ultra micro indentation system (UMIS). It is shown that the hardness of nitrogen ion implanted steels varied from 20 to 50GPa depending on the implantation conditions and the doses of implantation. The structure of the modified surfaces was examined by X-ray photoelectron spectroscopy (XPS). It was found that the high hardness on the implanted surfaces was as a result of formation of non-equilibrium nitrides. High-resolution XPS studies indicated that the nitride formers were essentially C and Si from the alloy steel. The result suggests that the ion implantation provided the conditions for a preferential formation of C and Si nitrides. The combination of evidences from nano-indentation and XPS, provided a strong evidence for the existence of $sp^3$ type of bonding in a suspected $(C,Si)_xN_y$ stoichiometry. The formation of ultra hard surface from relatively cheap low alloy steel has significant implication for wear resistance implanted low alloy steels.

• Journal of Powder Materials
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• v.21 no.1
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• pp.39-43
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• 2014

Bulk nanostructured copper was fabricated by a shock compaction method using the planar shock wave generated by a single gas gun system. Nano sized powders, average diameter of 100 nm, were compacted into the capsule and target die, which were designed to eliminate the effect of undesired shock wave, and then impacted with an aluminum alloy target at 400 m/s. Microstructure and mechanical properties of the shock compact specimen were analyzed using an optical microscope (OM), scanning electron microscope (SEM), and micro indentation. Hardness results showed low values (approximately 45~80 Hv) similar or slightly higher than those of conventional coarse grained commercial purity copper. This result indicates the poor quality of bonding between particles. Images from OM and SEM also confirmed that no strong bonding was achieved between them due to the insufficient energy and surface oxygen layer of the powders.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.354-354
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• 2007

Titanium nitride (TiN) thin films are widely used for hard coatings due to their superior hardness. In this paper, we wanted see how the films properties are changed according to DC power. TiN thin films were deposited by direct current (DC) magnetron sputtering method using TiN compound target on silicon substrates. The films structural properties are examined by X-ray Diffractions (XRD) and tribological properties are measured by nano-indentation, nano-scratch tester, nano-stress tester. Especially in DC power of 150 W, the maximum hardness and the minimum residual stress of TiN film exhibited about 25 GPa and 1 GPa, respectively. And also, the critical load of TiN film prepared by magnetron sputtering method were measured over 30 N.