• Journal of Ocean Engineering and Technology
• /
• v.18 no.6 s.61
• /
• pp.96-100
• /
• 2004

Inconel 625 is useful in a variety of industrial applications because of the resistance to attack in various corrosive media at temperatures from $200^{\circ}C$ to over $1090^{\circ}C$, in combination with good low and high temperature mechanical strength. Rencently this material has also been widely used in offshore processing piping in order to extend the maintenance term and improve the quality of anti-corrosion. In general, high quality weldings for this material are readily produced by commonly used processes. How, not all processes are applicable to this material group of Ni-alloys. Metallurgical or the unavailability of matching, position or suitable welding processes produce a lower quality. Nowadays, the flux cored wire is developed and applied for increased productivity in several welding positions, including the vertical position. In this study, the weldability and weldment characteristics(mechanical properties) of inconel 625 are considered in FCAW(Flux Core Arc Welding) associated with the several shielding gases$(80\%Ar+20\%CO2,\;50\%Ar+50CO2,\;100CO2)$ in view of welding productivity.

• Journal of the Korean Society of Safety
• /
• v.20 no.3 s.71
• /
• pp.9-13
• /
• 2005

Inconel 625 is useful in variety of industrial applications because of the resistance to attack on various corrosive media at temperature from $200^{\circ}C$ to over $1090^{\circ}C$, in combination with good low and high temperature mechanical strength. Recently, this material is also used widely in offshore processing piping in order to extend the maintenance term and improvement the quality of anti-corrosion. In general, high quality weldments for this material are readily produced by commonly used processes. Not all processes are applicable to this material group, Ni-alloys. Metallurgical characteristics or the unavailability of matching, position or suitable welding process. Nowadays, the flux cored wire is developed and applied for the better productivity in several welding position including the vertical position. In this study, the weldability and weldment characteristics(mechanical properties) of inconel 625 are considered in FCAW(Flux Cored Arc Welding) associated with the severial shielding gases($80%Ar+20%CO_2,\;50%Ar+50%CO_2,\;100%CO_2$) in viewpoint of welding productivity.

• 한국연소학회:학술대회논문집
• /
• 2001.11a
• /
• pp.90-96
• /
• 2001

Catalytic ignition of $H_2/O_2/CO_2$ mixtures over platinum catalyst is experimentally investigated by using microcalorimetry. For comparison, $N_2$ and Ar is also used as diluent gas. The gas mixture flows toward platinum foil heated by electric current at atmosphere pressure and ambient temperature. The ignition temperature range 350-445K according to the fuel ratio, dilution ratio and diluent gas. It increases as the fuel ratio and dilution ratio increase. $H_2/O_2$ mixture with $CO_2$ ignites at higher temperature than with other diluents by 30-50K. Several experimental evidences show the inhibition effects of $CO_2$ in $H_2-O_2$ heterogeneous reaction is considerable

• Journal of the Korean Magnetics Society
• /
• v.10 no.5
• /
• pp.232-236
• /
• 2000

CoSm thin films with a Cr underlayer have received continuous attention as a potential material for a high density longitudinal magnetic recording media. In this study the Ax gas sputtering pressure effects on the magnetic properties of CoSm thin films, which were fabricated by using a dc magnetron sputtering machine, were investigated. The magnetic switching volume is especially important parameter to understand the thermal stability of the written information, magnetization reversal process and media noise. Therefore, in this paper the effects of sputtering pressure on the magnetic switching volume of CoSm thin films grown on Cr underlayer with the same sputtering conditions was studied. As the Ar sputtering pressure during sputtering of the CoSm magnetic layer increases from 5 to 30 mTorr, the measured switching volumes decreased from 9.0 to 5.2$\times$10$^{-18}$ cm$^3$. The calculated diameter of switching unit from V＊ was less than 22 nm, which satisfies the Sharrock's requirement on the thermal stability of the high density longitudinal magnetic recording media.

• Resources Recycling
• /
• v.30 no.5
• /
• pp.49-56
• /
• 2021

In this study, using strontium sulfate (SrSO₄) recovered from magnetite ore in Hongcheon, the Black Ash process was used to produce strontium carbonate (SrCO₃). In the carbothermic reaction step, SrSO₄ was reacted with carbon (C) at 1273 K under Ar gas atmosphere using a gas-tight quartz reactor to produce strontium sulfide (SrS). Afterward, water leaching of the residues produced from the carbothermic reaction at 353 K and carbonation of the leaching solution using sodium carbonate (Na₂CO₃) at 298 K were conducted to produce SrCO₃. The results of this study demonstrate the feasibility of the production of SrCO₃ via the Black Ash process using domestic magnetite ore containing strontium (Sr).

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.39-39
• /
• 2009

고강도강의 용접성은 저온균열 저항성으로 대변되는데, TMCP강과 HSLA강 등이 개발되면서 고강도강의 저온균열저항성이 크게 향상되어 무예열 용접성이 확보되었다. 그러나 용접재료 측면에서는 그에 상응하는 재료의 개발이 지연되어 용착금속부에서의 저온균열이 심각한 문제로 대두되고 있는 실정이다. 이러한 문제는 800 MPa급인 HY-100강재를 HSLA-100강으로 대체하는 과정에서 현실적인 문제로 제기 되었다. 즉 HSLA강은 용접 예열이 필요치 않았으나 기존의 용접재료, 즉 HY-100 강재에 사용하던 용접재료를 사용하게 되면 용착금속부에서 저온균열이 발생하여 용접예열을 생략할 수 없다는 판단에 이르게 되었던 것이다. 이에 본 연구의 목적은 HSLA-100강을 무예열 용접할 수 있는 GMA 용접와이어 개발하는 것이며, 구체적인 개발 목표는 무예열 용접조건에서 800 MPa 이상의 인장강도를 가지며 $-50^{\circ}C$에서의 충격인성이 50 J 이상인 GMA 용접와이어 개발하는 것이다. 이러한 용접재료를 합금설계함에 있어 무예열 용접성을 확보하기 위하여 용접재료의 탄소함량을 0.01% 수준으로 하고, 용착금속의 인장강도와 저온 충격치에 미치는 Mn과 Mo 함량의 영향을 검토하고 각각의 조성을 실험계획법으로 확정하였다. 그리고 확산성수소량에 따른 저온균열 발생 여부를 확인하여 무예열용접성을 확보하기 위해서는 확산성수소량이 3ml/100g 이하가 되어야 한다는 사실을 실험적으로 확인하였다. 그리고 이를 달성하기 위해서는 원자재인 와이어로드의 표면 품질이 중요하다는 사실도 확인할 수 있었다. 다음으로는 실험계획법에 의거하여 선정된 합금조성의 신뢰성을 검증하기 위하여 800kg 중량의 시제품을 생산하였으며, 생산된 시제품에 대해서는 실험계획법에서 사용한 Ar+5%CO2외에도 Ar+20%CO2를 적용하여 보호가스의 영향을 검토하였다. 검토 과정에서 Ar+20%CO2용으로 사용하기 위해서는 용접재료의 Si 및 Mn 함량이 상향조정되어야 함을 확인할 수 있었다. 그리고 탄소함량을 0.05% 수준으로 증가시키면 Mo 함량을 크게 저하시킬 수 있음도 확인할 수 있었다. 이러한 과정을 거쳐 개발된 GMA 용접재료는 무예열 용접조건에서 저온균열이 발생하지 않았으며, 인장강도는 830 MPa이었으며 $-50^{\circ}C$에서의 충격치는 90 J 이상이었다.

• Korean Journal of Materials Research
• /
• v.16 no.1
• /
• pp.30-36
• /
• 2006

A novel method was proposed to grow an epitaxial $CoSi_2$ on (100)Si substrate. A $CoN_x$ interlayer was deposited by reactive sputtering of Co in an Ar+$N_2$ flow. From the Ti/Co/$CoN_x$/Si structure, a uniform and thin $CoSi_2$ layer was epitaxially grown on (100)Si by annealing above $700^{\circ}C$. Two amorphous layers were found at the $CoN_x$/Si interface, where the top layer has a silicon nitride (Si-N) bonding state with some Co content and the bottom layer has a Co-Si intermixing state. The SiNx amorphous layer seems to play a critical role of suppressing the diffusion of Co into Si substrate for the direct formation of epitaxial $CoSi_2$.

• Korean Journal of Materials Research
• /
• v.28 no.3
• /
• pp.159-165
• /
• 2018

In order to increase the efficiency of the sputtering method widely used in thin film fabrication, a dc sputtering apparatus which supplies both high frequency and magnetic field from the outside was fabricated, and cobalt thin film was fabricated using this apparatus. The apparatus can independently control the applied voltage, the target-substrate distance, and the target current, which are important parameters in the sputtering method, so that a stable glow discharge is obtained even at a low gas pressure of $10^{-3}$ Torr. The fabrication conditions using the sputtering method were mainly performed in $Ar+O_2$ mixed gas containing about 0.6 % oxygen gas under various Ar gas pressures of 1 to 30 mTorr. The microstructure of Co thin films deposited using this apparatus was examined by electron diffraction pattern and X-ray techniques. The magnetic properties were investigated by measuring the magnetization curves. The microstructure and magnetic properties of Co thin films depend on the discharge gas pressure. The thin film fabricated at high gas pressure showed a columnar structure containing a large amount of the third phase in the boundary region and the thin film formed at low gas pressure showed little or no columnar structure. The coercivity in the plane was slightly larger than that in the latter case.

• Polymer(Korea)
• /
• v.36 no.2
• /
• pp.137-144
• /
• 2012

The surface of polyethylene (PE) was modified through Ar atmospheric pressure plasma treatment and subsequent grafting of glycidyl methacrylate (GMA). Optimum plasma treatment conditions were determined through analyzing the surface free energies calculated from the contact angles between PE samples and three probe liquids, which were RF-power of 200 W, plasma treatment time of 600 sec, Ar flow rate of 5 LPM, and sample-holder moving speed of 20 mm/sec. To introduce the maximum amount of GMA on PE surface treated under the conditions, graft copolymerization conditions such as GMA concentration, temperature, and time were carefully controlled. Grafting degree (GD) was obtained through weight difference analysis of PE film before and after graft copolymerization. A maximum GD was achieved at the GMA concentration of 20 vol%, the temperature of $80^{\circ}C$, and the treatment time of 4 hr.

• Resources Recycling
• /
• v.31 no.4
• /
• pp.26-33
• /
• 2022

Owing to the demand for lithium-ion batteries, the recovery of valuable metals from waste lithium-ion batteries is required in future. A pyrometallurgical treatment is appropriate for recycling a large number of waste lithium-ion batteries, but Li loss to slag and dust present a significant challenge. This research investigated carbonation roasting and water leaching behaviors in Li-ion batteries by graphite addition to recover Li from the NCM-based cathode materials of waste Li-ion batteries. When 10 wt% of graphite was added, CO and CO₂ gases were emitted with a rapid weight reduction at apporoximately 850 K, when heated in Ar and CO₂ atmosphere. After the rapid weight reduction, NCM was decomposed and reduced to metal oxides and pure metals. In the carbonation roasting of black powder (NCM+graphite), O₂ is generated via the decomposition of NCM, and an oxides, such as Li₂O and NiO were were also generated. Subsequently, Li₂O reacts with CO₂ to generate Li₂CO₃, and a part of NiO was reduced by graphite to produce metal Ni. In addition, up to 94.5 % Li₂CO₃ with ~99.95 % purity was recovered via water leaching after carbonation roasting.