• Journal of Korea Foundry Society
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• v.14 no.1
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• pp.52-61
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• 1994

The effect of Ni addition, on the mechanical properties and fracture characteristics of Mo-Cu and Mo-Ni-Cu alloyed ductile iron austenitized at $900^{\circ}C$ and austempering temperatures of $250^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$. The tensile strength, yield strength and hardness are decreased and elongation and impact value are increased in both Mo-Cu and Mo-Ni-Cu alloyed austempered ductile iron, with increased austempering temperature. According to the austempering temperature are increased, the amount of retained austenite are increased. Maximum value of fracture toughness is obtained at $350^{\circ}C$ austempering temperature at this condition, the amount of retained austenite came to 40% in Mo-Ni-Cu alloyed ADI and 34% in Mo-Cu alloyed ADI. The fracture surface of ADI which had represented high toughness are showed a quasi-cleavage pattern and a dimple pattern with micro void. Comparing the fracture characteristics of Mo-Cu alloyed ADI with that of Mo-Ni-Cu alloyed ADI, the latter was superior to the former.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.295-298
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• 1999

High quality of $Er_{2}O_{3}$ doped $LiNbO_{3}$ single crystal thin films were grown by the liquid phase epitaxial (LPE) method using $Er_{2}O_{3}$ doped at concentrations of 1,3, and 5 mol% respectively. After the growth of single crystal thin film, the crystallinity and the lattice mismatch along the c-axis between the film and the substrate was examined as a function of the variations of{{{{{Er}_{2}{O}_{3}}}}} dopant concentration using a X-ray double crystal technique. There was no lattice mismatch along the c-axis for the undoped film and those doped with 1 and 3 mol% of $Er_{2}O_{3}$. For 5 mol% of $Er_{2}O_{3}$ doped film, the lattice mismatch was $7.86{\times}10^{-4}$nm along the c-axis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.1-4
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• 2000

Thin films of hydrogenated amorphous silicon carbide compounds ($a-Si_{x}C_{1-x}:H$) of different compositions were deposited on Si substrate by RF plasma-enhanced chemical vapor deposition (PECVD). Experiments were carried out using silane (SiH$_4$) and methane ($CH_4$) as the gas precursors at 1 Torr and at a low substrate temperature ($250^{\circ}C$). The gas flow rate was changed with the other parameters (pressure, temperature, RF power) fixed. The substrate was Si(100) wafer and all of the films obtained were amorphous. The bonding structure of $a-Si_{x}C_{1-x}:H$films deposited was investigated by X-ray photoelectron spectroscopy (XPS) for the film compositions. In addition, the surface morphology of films was investigated by atomic force microscopy (AFM).

• Journal of Korea Foundry Society
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• v.13 no.2
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• pp.175-186
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• 1993

In this study, the effect of Mo addition on the microstructure and mechanical properties of ductile cast iron have been investigated. The amounts of Mo and the thickness of specimen have been varied from 0 to 4.79wt% and 13mm, 10mm and 6mm, respectively. As the casting thickness decreases, the average size of spheroidal graphite is decreased and the hardness increases. By increasing the Mo content, the tensile strength of ferrite and pearlite matrix increases and shows maximum which is about $30{\sim}40%$ higher than ordinary ductile cast iron. After the maximum, adding more Mo results in gradual transformation of ferrite and pearlite to bainite and thus tensile strength decreases again. The elongation decreases continueously with Mo content. The addition of Mo about $0.5{\sim}1.0wt%$ improves the wear resistance and tensile strength of thin ductile cast iron.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.52-57
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• 2011

Nickel ferrite ($NiFe_2O_4$) powder was prepared through the ceramic route by calcination of a stoichiometric mixture of nickel oxide (NiO) and iron oxide ($Fe_2O_3$). The pressed pellets of $NiFe_2O_4$ were isothermally reduced in pure hydrogen at 800, 900, 1000 and $1100^{\circ}C$. Based on thermogravimetric analysis, the reduction behavior and the kinetic reaction mechanisms of the synthesized ferrite were studied. The initial ferrite powder and various reduction products were characterized by XRD, SEM, reflected light microscope and VSM to reveal the effect of hydrogen reduction on the composition, microstructure, magnetic properties and reaction kinetics of the produced Fe-Ni alloy. Complete reduction of the $NiFe_2O_4$ was achieved with synthesis of homogeneous nanocrystalline Fe-Ni alloys. Arrhenius equation with the approved mathematical formulations for a gas-solid reaction was applied for calculating the activation energy ($E_a$) values and detecting the controlling reaction mechanism.

• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.300-305
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• 2020

Corrosion of reinforcement steel rebar is a serious problem in a wide range of concrete application for buildings and infrastructures. Hydrophobizing surface treatments, such as self-assembled monolayer coating, edible oil-impregnation and silicone oil-impregnation were applied to solidified concrete. The hydrophobizing of concrete significantly reduces an absorption and transportation of water toward a steel rebar in concrete, so that the corrosion resistance of the steel rebar. In particular, the silicone oil-impregnation not only forms the hydrophobic monolayer on the concrete but also fills the inter-connected pores of concrete, thus the corrosion of steel rebar is significantly inhibited compared to the self-assembled monolayer coating and edible oil-impregnation. Therefore, the silicone oil-impregnation can be a promising candidate for preventing corrosion of steel rebar in concrete for durable performance and safety.

• Proceedings of the Korean Vacuum Society Conference
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• 1996.06a
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• pp.42-43
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• 1996

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.94-94
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• 2004

• Corrosion Science and Technology
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• v.6 no.3
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• pp.96-102
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• 2007

The resistance of the linepipe steel to hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) is very important for steel to be used in sour oil/gas environments. Welding of steels is necessary to the construction of pipe-line transporting oil/gas. In this study, HIC and SSC resistance of an electric resistance welded (ERW) steel plate which belongs to API X70 grade was evaluated by using NACE TM0284-96A and NACE TM0177-96A methods. HIC and SSC fracturing behavior was investigated by observing fractured surfaces using optical microscopy (OM) and scanning electron microscopy (SEM). It was discussed in terms of metallurgical parameters such as the distribution of primary microstructure, second phases and inclusions. Results showed that the weld joint of ERW steel is more sensitive than base metal to HIC and SSC. This is due to difference in the contribution of metallurgical parameters to HIC and SSC nucleation and propagation.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.3
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• pp.157-164
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• 1992

Barkhausen noise (BN) is created by the abrupt changes in the magnetization of materials under applied AC magnetizing field. These changes are known to be sensitive to residual and applied stresses. In this study, BN theory was reviewed and it was examined how BN intensity was affected by simultaneous stress, hardness and microstructural changes. Also, magnetoelastic effect was used to evaluate residual stresses through carrying out the cantilever beam test. An increase in BN intensity was observed when applied and residual stress changes from compression into tension. Microstructural softening by tempering also increased the amount of BN. Therefore, the quantitative evaluation of residual stress and microstructural changes will be possible, provided BN method is more studied about various materials through comparing with different stress measuring techniques.