• Korean Journal of Materials Research
• /
• v.12 no.3
• /
• pp.182-189
• /
• 2002

The Zr-0.2Sn-0.8Nb-X(X = 0~200ppm Si, 0~0.4wt.% Mo and Mn respectively) ingots for test specimens were manufactured by a vacuum arc re-melting method to find out the effect of Si, Mo, and Mn on the corrosion characteristics of the Zr-0.2Sn-0.8Nb alloy. After being heat-treated and rolled repeatedly out to be flat materials, they were finally heat-treated at 51$0^{\circ}C$ for three hours and used as the specimens for corrosion tests. The corrosion behavior of the specimens was studied in both 40$0^{\circ}C$ steam for 200 days and in aqueous 70 ppm LiOH solution at 36$0^{\circ}C$ for 90 days. From the study it was found that Si from 80 to 200 ppm contributed to increasing the corrosion resistance of Zr-0.2Sn-0.8Nb alloy in both steam and LiOH solution. This study also showed that Mn from 0.1 to 0.4% caused to go up the corrosion resistance, whereas Mo played a apart in improving the corrosion resistance only between 0.05 and 0.2 wt.%.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.571-576
• /
• 1998

This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.16 no.6
• /
• pp.273-277
• /
• 2006

High velocity of oxy-fuel (HVOF) thermal spray coating is progressively replacing the other classical hard coatings such as chrome plating and ceramic coating by the classical methods, since the very toxic $Cr^{6+}$ ion is well known as carcinogen causing lung cancer, and the ceramic coatings are brittle. Co-alloy T800 powder is coated on the Inconel 718 substrates by the HVOF coating procesess developed by this laboratory. For the study of the possibility of replacing of chrome plating, the wear properties of HVOF Co-alloy T800 coatings are investigated using the reciprocating sliding tester with a counter sliding SUS 304 ball both at room and at an elevated temperature of $1000^{\circ}F\;(538^{\circ}C)$. The possibility as durability improvement coating is studied for the application to the high speed spindles vulnerable to frictional heat and wear. Wear mechanisms at the reciprocating sliding wear test are studied far the application to the systems similar to the sliding test such as high speed spindles. Wear debris and frictional coefficients of T800 coatings both at room and at an elevated temperature of $538^{\circ}C$ are drastically reduced compared to those of non-coated surface of Inconel 718 substrates. Wear traces and friction coefficients of both coated and non-coated surfaces are drastically reduced at a high temperature of $538^{\circ}C$ compared with those at room temperature. These show that the coating is highly recommendable far the durability Improvement coating on the surfaces vulnerable to frictional heat and wear.

• Journal of the Korean Society of Safety
• /
• v.25 no.6
• /
• pp.92-97
• /
• 2010

A study is conducted on thermal characteristics of biodiesel which is already being produced in many countries because of its stable supply of energy in non oil-producing countries and economical benefits against increasing oil price, and environment conservation. So biodiesel has been used as important energy source in the fuel fields and a mount of production has increased year by year. Therefore, it is very important to find out the thermal characteristics of biodiesel for ignition temperature, maximum pressure and thermal behavior. The purpose of this study is to compare on thermal characteristics of biodiesel, petroleum diesel and those mixtures. Also, the main study was performed by flash point testers and modified closed type of pressure vessel test (MCPVT). Based on the data of flash point and MCPVT, the ignition temperature and the maximum pressure of biodiesel was $182^{\circ}C$ and 40.1bar, and petroleum diesel was $54^{\circ}C$ and 29.8bar.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.475-481
• /
• 2017

In this paper, high speed camera images were used to analyze the supercritical injection behavior of liquid hydrocarbon compounds used as main components of propellant fuel. Decane and Methylcyclohexane (MCH), which have different critical points among kerosene constituents, were selected as experimental fluid and Shadowgraphy technique was used for the analysis. The difference in the temperature variation from the initial injector state of the subcritical condition until the vaporization occurs was represented by the different behaviors of Decane and MCH. However, under the Supercritical conditions, the enthalpy of vaporization near the critical point approaches zero and the phase change to the Supercritical phase occurs instead of vaporization process. In the phase change of the Supercritical system, there was no rapid density change, so the liquid state image was observed in both the Decane and MCH.

• Elastomers and Composites
• /
• v.45 no.1
• /
• pp.40-43
• /
• 2010

In this study, polyimide(PI) nanofibers mats were prepared by electrospinning and three different fiber morphologies of random, uniaxial, and biaxial orientation were prepared by controlling the speed of drum-shaped collector and other parameters. The SEM studies reveal that the aforesaid morphologies were obtained on the nano-fibrous mats prepared. The ionic conductivity was measured using an in-plane type conductivity tester for the PI mats soaked in the mixture of 1M lithium trifluoro-methane-sulfonate and tetra-ethylene glycol dimethyl ether. The ionic conductivity was surprisingly higher for the biaxial PI mats. For the uniaxially-oriented mats, the ionic conductivity was found to be higher in the parallel direction compared to the perpendicular direction of the fiber orientation. A curious cyclic fluctuation was found in the ionic conductivity with time. The observed behavior was explained by considering the distance between fibers and transport speed of ions used in this study.

• Korean Journal of Materials Research
• /
• v.8 no.8
• /
• pp.685-692
• /
• 1998

Since a wet-seal area of Molten Carbonate Fuel Cell (MCFC) operated at $650^{\circ}C$ is exposed to severe environment, a life-time of MCFC is influenced by the corrosion resistance of separator. In order to improve corrosion resistance of 316L stainless steel used as separator material, AI- base alloy such as NiAI has been widely used as coat¬ing material on the wet-seal area. The purpose of this work is to develope a more protective coating material by adding yttrium on NiAI alloy. An immersion test and a polarization test were performed in molten carbonate salt at $650^{\circ}C$ to estimate corrosion resistance of the NiAI alloy and the NiAl/Y alloys with up to L5at% yttrium. NiAl/Y alloys showed better corrosion resistance than NiAI alloy. We found that more than 0.7 at% yttrium was required to improve the corrosion resistance of NiAI alloy in molten carbonate salt at $650^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.2
• /
• pp.81-88
• /
• 2010

Hydrogen energy applications have recognized clean materials and high energy carrier. Accordingly, Hydrogen energy applies for fuel cell by Mg and Mg-based materials. Mg and Mg-based materials are lightweight and low cost materials with high hydrogen storage capacity. However, commercial applications of the Mg hydride are currently hinder by its high absorption/desorption temperature, and very slow reaction kinetics. Therefore one of the most methods to improve kinetics focused on addition transition metal oxide. Addition to transition metal oxide in $MgH_x$ powder produce $MgH_x$-metal oxide composition by mechanical alloy and it analyze XRD, EDS, TG/DSC, SEM, and PCT. This report considers kinetics by transition metal oxide rate and Hydrogen pressure. In this research, we can see behavior of hydriding/dehydriding profiles by addition catalyst (transition metal oxide). Results of PCI make a excellent showing $MgH_x$-5wt.% Sc2O3 at 623K, $MgH_x$-10wt.% $Sc_2O_3$ at 573K.

• Carbon letters
• /
• v.18
• /
• pp.49-55
• /
• 2016

Refuse-derived fuel (RDF) produced using municipal solid waste was pyrolyzed to produce RDF char. For the first time, the RDF char was used to remove aqueous copper, a representative heavy metal water pollutant. Activation of the RDF char using steam and KOH treatments was performed to change the specific surface area, pore volume, and the metal cation quantity of the char. N₂ sorption, Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), and Fourier transform infrared spectroscopy were used to characterize the char. The optimum pH for copper removal was shown to be 5.5, and the steam-treated char displayed the best copper removal capability. Ion exchange between copper ions and alkali/alkaline metal cations was the most important mechanism of copper removal by RDF char, followed by adsorption on functional groups existing on the char surface. The copper adsorption behavior was represented well by a pseudo-second-order kinetics model and the Langmuir isotherm. The maximum copper removal capacity was determined to be 38.17 mg/g, which is larger than those of other low-cost char adsorbents reported previously.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.9
• /
• pp.2189-2196
• /
• 2015

According to increase environmental pollutions and fuel costs, The study of energy saving in the ship is proceeding actively. PCS is pump control system for cooling system in the ship to improve the energy efficiency by controling rotation speed of sea water pump, fresh water pump and position of 3way valve. In this paper, we develop the PCS simulator that has an environment similar to the cooling system of the actual vessel to ensure reliability of the PCS. Also, PC-based control and data storage system for PCS simulator is developed. To develop this system, National Instrument's cDAQ and LabVIEW are used. Finally, confirm the behavior of the simulator by analyzing the saving data.