• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.560-563
• /
• 2004

Invar is a compound metal of Fe-Ni system and contain 36％ Ni. The most distinction characteristic of Invar is the coefficient of thermal expansion is 1.0 10$^{-6}$ /$^{\circ}C$. That is a tenth of general steel material. This low thermal expansion characteristic of Invar is applied to the missile, aircraft, monitor CRT and frontier display's shadow mask such as FED and OLED. The usage of the Invar shadow mask for display is increasing due to the requirement of larger size and flatness monitor. The Invar shadow mask is machined by two ways electro-forming and laser now. However the electro-forming takes a too long time and the laser machining is accompanied with Burr. In this study, PEMM(pulse electrochemical micro machining) is conducted to machine the micro hole to the Invar and 80${\mu}{\textrm}{m}$ hole was machined.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.5
• /
• pp.548-557
• /
• 2015

This paper is results on Chemisorption of organic compound for the sea water fire fighting line of naval vessels. The quantitative analysis of Chemisorption has been investigated in seawater after immersion in 0.1 % of NaDDTC solutions for 43 hours. The morphology and topography were investigated by FE-SEM and AFM. The chemical elements were analyzed by SEM-EDS, XPS and the depth of chemical elements was measured by depth profiles. The effect of NaDDTC comes from Chemisorption between Copper and Sulfur of NaDDTC. As a result, test results showed that sulfur is helpful to protect a corrosion of seawater line.

• Journal of Hydrogen and New Energy
• /
• v.8 no.1
• /
• pp.31-41
• /
• 1997

In order to investigate the mechanism of electrochemical hydrogenation reaction on Zr-based Laves phase hydrogen storage alloy electrodes, electrochemical charge/discharge characteristics, potentiostatic/dynamic polarizations and electrocehmical impedance spectroscopy(EIS) of Zr-Ti-Mn-Ni and Zr-Ti-Mn-Ni-M(M=Fe, Co, Al) alloys were examined. Electrochemical discharge capacities of the alloys were quite different with gas charge capacities. Therefore, it was considered that discharge capacities of the alloys depend on electrochemical kinetic factors rather then thermodynamic ones. Discharge efficiencies were increased linearly with exchange current densities. The results of potentiostatic/dynamic polarization measurements showed that electrochemical charge and discharge reaction of Zr-based Laves phase hydrogen storage alloys is controlled by charge transfer process at the electrode surface. The EIS measurements also confirmed this result.

• Journal of the Korean Society for Heat Treatment
• /
• v.15 no.4
• /
• pp.166-171
• /
• 2002

The effects of Ni and N addition to 304 stainless steel on mechanical properties and microstructure were investigated within temperature ranged from $-196^{\circ}C$ to $25^{\circ}C$. The addition of nickel and nitrogen induced the stability against the formation of provide significantly enhanced ductility at $-196^{\circ}C$ and reduce the Md temperature. Fe-18Cr-10Ni-0.2N alloy showed the ${\gamma}$ phase in deformed structure which it was beneficial to enhance the tensile strength and elongation at $25^{\circ}C$ and $-196^{\circ}C$.

• Journal of Korea Foundry Society
• /
• v.22 no.1
• /
• pp.42-48
• /
• 2002

Effects of coating treatment of metallic Cu, Ni-P film on $SiC_p$, for $SiC_p$/iron aluminide composites were studied. Porous hybrid preforms were fabricated by reactive sintering after mixing the coated $SiC_p$, Fe and Al powders. Then the final composites were manufactured by squeeze casting after pouring AC4C Al alloy melts in preforms. The change of reactive temperature, density, microstructure of the preforms and microstructure of the composites were investigated. The exprimental results were summarized as follows. The thickness of Cu and Ni-P metallic layer formed on $SiC_p$ by electroless plating method were about $0.5{\mu}m$ and coated uniformly. There was no remakable change in the ignition temperature with variation of the mixing ratio of Fe and Al powder while in the case of coated $SiC_p$ it was lower about $20^{\circ}C$ than in the non-coated $SiC_p$. The maximum reaction temperature increased with increasing Al contents, but decreased with increasing $SiC_p$ contents. Expansion ratio of preform after reactive sintering increased with amount of Cu coated $SiC_p$. In the case of Fe-70at.%Al, the expansion ratio was about 7% up to 8wt.% of $SiC_p$, addition but further addition of $SiC_p$, increased the ratio significantly. And in the case of Fe-50 and 60at.%Al, it was about 20% up to 16wt.% of $SiC_p$ addition and about 28% in 24wt.% of $SiC_p$, addition. The microstructures of compounds showed that the grains became finer as amount of $SiC_p$, and mixing ratio of iron powder increased and the shape of compounds was changed gradually from irregular to spheroidal.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.4
• /
• pp.1195-1198
• /
• 2013

Nickel hexacyanoferrate supported palladium nanoparticles (Pd-NiHCF NPs) were synthesized and studied for oxygen reduction reactions in direct methanol fuel cell. The NiHCF support was readily synthesized by a comixing of $Ni(OCOCH_3)_2$ and equimolar $K_3[Fe(CN)_6]$ solution into DI water under rigorous stirring. After the preparation of NiHCF support, Pd NPs were loaded on NiHCF via L-ascorbic acid reduction method at $80^{\circ}C$. Pd-NiHCF NPs were electrochemically active for oxygen reduction reaction in 0.1 M $HClO_4$ solution. X-ray absorption near edge structure analysis was conducted to measure the white line intensity of Pd-NiHCF to verify the OH adsorption. As a comparison, carbon supported Pd NPs exhibited same white line intensity. This study provides a general synthetic approach to easily load Pd NPs on porous coordination polymers such as NiHCF and can provide further light to load Pd based alloy NPs on NiHCF framework.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2010.06a
• /
• pp.148-150
• /
• 2010

Two-layered ferromagnetic alloy films ($Ni_{80}Fe_{20}$, $Co_{90}Fe_{10}$) with a Conetic intermediate soft magnetic layer of different thickness were investigated to correlate the coercivity values and magnetization process with the strength of the hard saturation field. The interpretation of strong, medium and weak coupling is proposed.

• Journal of Korea Foundry Society
• /
• v.41 no.6
• /
• pp.543-549
• /
• 2021

Aluminum cast iron has excellent oxidation resistance and good resistance to sulfide and corrosion. Compared to Ti and Ni alloys, it is expected to be a substitute material for structural materials and stainless steels because it is relatively inexpensive to use Fe, which is a non-strategic element. This results in a weight reduction effect of about 30% as compared to the use of stainless steel. With regard to aluminum as an alloying material, it is an element that has been widely used for the alloying of cast iron in recent years. Practical use has been delayed owing to the resulting lack of ductility at room temperature and the sharp decrease in the strength above 600℃ of this alloy, however. The cause of the weak room temperature ductility is known to be environmental embrittlement by hydrogen, and the addition of various alloying elements has been attempted in order to mitigate these shortcomings. Although alloying elements such as vanadium, chromium, and manganese are mainly used to increase the hardness and wear resistance of gray cast iron, the price of finished products containing these elements and the problems associated with alloys with this material impose many limitations.

• Plant Journal
• /
• v.4 no.2
• /
• pp.60-65
• /
• 2008

As the operating conditions in a supercritical oxidation reactor are set in high temperature with high pressure causing a reactor suffering from the harsh circumstances. It means the reactor adopts itself with Fe-Cr alloy in acidic atmosphere with low pH value and Ni alloy in basic atmosphere with high pH value due to its superior corrosion resistance. The study, whose target waster water is pertinent to the latter part, has selected Ni alloy such as ostenite type stainless steel 304 and 316, superstainless steel AL6XN, Inconel 625, MAT 21, and titanium Gr. 5 in order to measure corrosion resistance against those samples under the same conditions of temperature and pressure applied for a supercritical oxidation reactor. The result shows the identifiable difference in corrosion resistance by observing the surface states through a scanning probe microscope as well as measuring the weight loss through making the samples above deposited in wastewater for two-week and four-week stay. The purpose of this corrosion experiment is to identify the most corrosion-resistant material among sample species pre-selected according to pH concentration of wastewater in pursue of applying for a reactor exposed to the extreme corrosion environment. It is because such a reactor made of a verified material enables to safeguard a stable operation under the supercritical wastewater processing facility.

• Journal of the Microelectronics and Packaging Society
• /
• v.20 no.1
• /
• pp.39-43
• /
• 2013

The experiments were carried out in the variation of current density, pH, temperature, and duty cycle to investigate the influence of electroplating parameters on the properties of Ni-Fe invar alloys. When the current density and temperature were changed, the composition of invar alloy was varied, however, duty cycle and pH hardly affected on the composition of electrodeposited alloys. However, as the duty cycle was increased, microstructure was changed and the decrease of hardness was also observed.