• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.191-196
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• 2012

In this study, tin phosphate glass system($SnO_2-(1-x)P_2O_5-xB_2O_3$) that occur during the melting of the metal oxide inhibition of the oxidation reaction, and to reduce oxides of high melting temperature in the following three methods were melting. The first is the general way in the atmosphere, and the second by injecting $N_2$ gas under a neutral atmosphere, and finally in the air were melted by the addition of a reducing agent Melt in the atmosphere when the oxidation of the metal oxide is inhibited by low temperatures were melting. In addition, the deposition of crystals within glassy or inhibit devitrification phenomenon is also improved over 80% transmittance. This phenomenon, when the melting of glass, many of $Sn^{4+}$ ions are reduced to the $Sn^{2+}$ was forming oxides SnO, because it acts as a modifier oxide.

• Transactions of Materials Processing
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• v.22 no.6
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• pp.334-339
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• 2013

Direct Laser Melting is a prototyping process whereby a 3-D part is built layer wise by melting the metal powder with laser scanning. This process is strongly influenced by the shielding gas and the laser operating parameters such as laser power, scan rate, layering thickness, and rescanning. The shielding gas is especially important in affecting the microstructure and mechanical properties. In the current study, fabrication experiments were conducted in order to analyze the effect of shielding gas on the forming characteristics of direct laser melting. Cylindrical parts were produced from a Fe-Ni-Cr powder with a 200W fiber laser. Surface quality, porosity and hardness as a function of the layering thickness and shield gas were evaluated. By decreasing the layering thickness, the surface quality improved and porosity decreased. The selection of which shield gas, Ar or $N_2$, to obtain better surface quality, lower porosity, and higher hardness was examined. The formability and mechanical properties with a $N_2$ atmosphere are better than those parts formed under an Ar atmosphere.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.528-535
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• 1997

$LiTaO_3$ single crystals of congruently melting composition were grown by the halogen lamp type floating zone system. Calcination and sintering parameters for the growth were established. Optimum crystal growth conditions were investigated by a controlling of growth rates, rotation speeds and atmospheres. Based on the melting aspect and the shape of molten zone, stable conditions could not be found in air or Na atmosphere. However the growth stability in Ar atmosphere was more regular than that in air or $N_2$. The grown crystals were characterized using Laue back reflection, Curie temperature, refractive index and transmittance. Curie temperature fluctuation in the section of the grown crystal part of top, body and tail was $1^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.108-110
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• 2000

The aim of this paper is to investigate the effect of Al and Ti on microstructure of Fe-Cr-Al alloy systems for applying electrical resistance wires of electrical furnace. From the preliminary study, the amount of recovered addition elements increased in the case of both vacuum and Ar-atmosphere melting than that in the case of air-atmosphere melting. Also, optimum Cr content for good performance at high temperature was approximately 24wt% from the observation of microstucture. The precipitates of Fe-Cr, Al-Cr and Al phases were observed, adding Al and Ti. Especially, Sharp rectangular shapes of precipitates were observed with increasing amount of Ti.

• Journal of Powder Materials
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• v.18 no.2
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• pp.141-148
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• 2011

Carbon material shows relatively high strength at high temperature in vacuum atmosphere and can be easily removed as CO or $CO_2$ gas in oxidation atmosphere. Using these characteristics, we have investigated the applicability of carbon mold for precision casting of high melting point metal such as nickel. Disc shape carbon mold with cylindrical pores was prepared and Ni-base super alloy (CM247LC) was used as casting material. The effects of electroless Nickel plating on wettability and cast parameters such as temperature and pressure on castability were investigated. Furthermore, the proper condition for removal of carbon mold by evaporation in oxidation atmosphere was also examined. The SEM observation of the interface between carbon mold and casting materials (CM247LC), which was infiltrated at temperature up to $1600^{\circ}C$, revealed that there was no particular product at the interface. Carbon mold was effectively eliminated by exposure in oxygen rich atmosphere at $705^{\circ}C$ for 3 hours and oxidation of casting materials was restrained during raising and lowering the temperature by using inert gas. It means that the carbon can be applicable to precision casting as mold material.

• Progress in Superconductivity
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• v.10 no.2
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• pp.103-107
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• 2009

$Bi_2Sr_2Ca_1Cu_2O_x$(BSCCO 2212) superconductors for current lead were fabricated by centrifugal melting process(CMP). BSCCO 2212 powder was melted at $1200^{\circ}\C$ in a resistance furnace using a Pt crucible and poured in a rotating cylindrical mold preheated at $550^{\circ}\C$ for 2 hour. The solidified BSCCO-2212 samples were heat-treated by partial melting process in oxygen atmosphere. The current-voltage curves at 77 K of the samples were obtained by transport measurement, and the microstructure was investigated by scanning electron microscope. The $J_c$ values at 77 K of the tubes partially melted at $840^{\circ}C,\;860^{\circ}C\;and\;880^{\circ}C$ were 492, 430 and 398 $A/cm^2$, respectively. It was observed that the plate-like grains in BSCCO 2212 tube was more developed in the sample heat-treated at $840^{\circ}C$. It was found that the critical current of the BSCCO 2212 samples was dependent on the partial melting schedule regarding the grain shape and size of the BSCCO 2212.

• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.305-311
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• 2016

The spatial size and variation of Arctic sea ice play an important role in Earth's climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP) F13 Special Sensor Microwave/Imagers (SSMI) and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS) sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA).

• Journal of Welding and Joining
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• v.34 no.1
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• pp.75-81
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• 2016

This study applied laser surface melting process using CW(Continuous wave) Yb:YAG laser and cold-work die steel SM45C and investigated microstructure and hardness. Laser beam speed, power and beam interval are fixed at 70 mm/sec, 2.8 kW and $800{\mu}m$ respectively. Depth of Hardening layer(Melting zone) was a minimum of 0.8 mm and a maximum of 1.0 mm that exceeds the limit of minimum depth 0.5 mm applying trimming die. In all weld zone, macrostructure was dendrite structure. At the dendrite boundary, Mn, Al, S and O was segregated and MnS and Al oxide existed. However, this inclusion didn't observe in the heat-affected zone (HAZ). As a result of interpreting phase transformation of binary diagram, MnS crystallizes from liquid. Also, it estimated that Al oxide forms by reacting with oxygen in the atmosphere. The hardness of the melting zone was from 650 Hv to 660 Hv regardless of the location that higher 60 Hv than the hardness of the HAZ that had maximum 600 Hv. In comparison with the size of microstructure using electron backscatter diffraction(EBSD), the size of microstructure in the melting zone was smaller than HAZ. Because it estimated that cooling rate of laser surface melting process is faster than water quenching.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.482-489
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• 2008

Ti-Cr alloys consist of BCC solid solution, C36, C14 and C15 Laves phase at high temperature. Among others, the BCC solid solution phase was reported to have a high hydrogen storage capacity. However, activation, wide range of hysteresis at hydrogenation/dehydrogenation, and degradation of hydrogen capacity due to hydriding/dehydriding cycles must be improved for its application. In this study, to improve such problems, we added a Nb. For attaining target materials, Ti-10Cr-xNb(x=1, 3, 5wt.%) specimens were prepared by arc melting. The arc melting process was carried out under argon atmosphere. As-received specimens were characterized using XRD(X-ray diffraction), SEM(Scanning Electron Microscopy) with EDX(Energy Dispersive X-ray) and TG/DSC(Thermo Gravimetric Analysis/Differential Scanning Calorimetry). In order to examine hydrogenation behavior, the PCI(pressure-Composition-Isotherm) was performed at 293, 323, 373 and 423K.

• Resources Recycling
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• v.4 no.1
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• pp.25-30
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• 1995

In the preparatIon of reclaimed aluminium lllgot from alumimum scrap, the aluminium recovery was studied a as a function of the preliminary treatment of samples, addition of flux and melting atmosphere. AI dross is produced by an oxidation reaction at the surface of liquid metal. The recovery of AI metal increases u up to maximum 95% by adding salt up to 7%, The recovery of AI metal in the compacted chip bale without oil removal mcrease about 14% compared io non-compacted chip. In the case of the AI seed melting process, the recovery of Al metal of the crushed and compacted chip hale is 97%, In meltmg of alumimum scrap under the atmosphere of carbon and nitrogen gas, the recovery of AI metal increase, but it is decreased when the mixture of salt and carbon powder is added excessively.