• Korean Journal of Materials Research
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• v.9 no.3
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• pp.327-332
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• 1999

The recovery activation energy, the order of reaction and the recovery rate constant were detemined by isochronal and isothermal annealing treatment to investigate the recovery behaviors of neutron irradiated Mn-Mo-Ni low alloy steels$(fluence: 2.3\times10^{19}ncm^{-2}, 553K, E\geq1.0 MeV)$. Vickers microhardness tests were conducted to trace the recovery behavior after heat treatments. The results were analyzed in terms of recovery stages, behavior of responsible defects and recovery kinetics. It was shown that recovery occurred through two annealing stages(stage I : 703-753K, stage n : 813-873K) with re$\infty$very activation energies of 2.5 eV and 2.93 eV for each stage I and n, respectively. From the comparison of unirradiated and irradiated isochronal anneal curves, a radiation anneal hardening(RAH) peak was identified at around 813K. Most of recovery have occurred during about 120 min irrespective of isothermal annealing temperatures of 743K and 833K. Recovery rate constants were determined to be $3.4\times10^{-4}min^{-1} and 7.1\times10^{-4}min^{-1}$ for stage I and II, respectively. The order of reaction was about 2 for both recovery stages. Comparing the obtained data with those of previously reported results on neutron irradiated Mn- Mo- Ni steels, the thermal recovery be­havior of the present material seems to occur by the dissociation of point defect clusters formed during irradiation, and by the recombination process of self-interstitials and vacancies from dissociated vacancy clusters.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.46-55
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• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.426-438
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• 2023

Lithium-sulfur batteries, recently attracting attention as next-generation batteries, have high energy density but are limited in application due to sulfur's insulating properties, shuttle phenomenon, and volume expansion. This study used an economical and simple vacuum filtration method to prepare a freestanding electrode without a binder and collector. Carbon nanotubes (CNTs) are used to improve the electrical conductivity of sulfur, where CNT also acts as both collector and conductor. In addition, metal oxides (MO_x, M=Ni, Mg), which are easy to adsorb lithium polysulfide, are added to the CNT/S electrode to suppress the shuttle reaction in lithium-sulfur batteries, which is a result of suppressing the loss of active sulfur material due to the excellent adsorption of lithium polysulfide by metal oxides. The MO_x@CNT/S electrode exhibited higher capacity characteristics and cycle stability than the CNT/S electrode without metal oxides. Among the MO_x@CNT/S electrodes, the NiO@CNT/S electrode displayed a high discharge capacity of 780 mAh g^-1 at 1 C and an extreme capacity decrease to 134 mAh g^-1 after 200 cycles. Although the MgO@CNT/S electrode exhibited a low discharge rate of 544 mAh g^-1 in the initial cycle, it showed good cycle stability with 90% of capacity retention up to 200 cycles. Further, to achieve high capacity and cycle stability, the Ni_0.7Mg_0.3O@CNT/S electrode, mixed with Ni:Mg in the ratio of 0.7:0.3, manifested an initial discharge rate of 755 mAh g^-1 (1 C) and a capacity retention rate of more than 90% after 200 cycles. Therefore, applying binary metal oxides to CNT/S provides a freestanding electrode for developing economical and high-performance Li-S batteries, effectively improving lithium polysulfide's high capacity characteristics and dissolution.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.245-250
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• 2016

The layered $Na_{0.6}Li_{0.6}[Mn_{0.72}Ni_{0.18}Co_{0.10}]O_2$ composite with well crystalized and high specific capacity is prepared by molten-salt method and using the substitution of Na for Li-ion battery. The effects of annealing temperature, time, Na contents, and electrochemical performance are investigated. In XRD analysis, the substitution of Na-ion resulted in the P2-$Na_{2/3}MO_2$ structure ($Na_{0.70}MO_{2.05}$), which co-exists in the $Na_{0.6}Li_{0.6}[Mn_{0.72}Ni_{0.18}Co_{0.10}]O_2$ composites. The discharge capacities of cathode materials exhibited $284mAhg^{-1}$ with higher initial coulombic efficiency.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.4
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• pp.161-167
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• 2019

Impact toughness and fracture behavior were studied in five kinds of non-heat treating steels containing bainite; standard(0.25C-1.5Mn-0.5Cr-0.2Mo-0.15V), high V(0.3V), Ni(0.5Mn-2Ni), W(0.4W instead of Mo), and high C-Ni(0.35C-0.5Mn-2Ni) steels. The good hardness and impact toughness balance was exhibited in the $1100^{\circ}C$-rolled condition, while the impact toughness was deteriorated due to coarse grained microstructure in the $1200^{\circ}C$-rolled condition. The impact toughness decreased with increasing the hardness in all steels studied. The fracture behavior was also basically identical, that is, the fracture area was divided into 3 zones; shear and fibrous zone, fracture transition zone with ductile dimples and cleavage cracks, where the cracks initiate and grow to critical size, unstable cleavage fracture propagation zone. The energy absorbed for the critical crack formation through the plastic deformation inside the plastic zone in front of the notch root contributed to a mostly significant portion of the total impact energy.

• Journal of Hydrogen and New Energy
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• v.21 no.1
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• pp.26-34
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• 2010

The electrocatalystic prperties of Pt-Co and Pt-Ni with heteropolyacids (HPAs) entrapped in covalently cross-linked sulfonated poly(ether ether ketone) (CL-SPEEK)/HPA membranes were investigated for water electrolysis. The HP As, including molybdophosphoric acid (MoPA), and tungstophosphoric acid (TPA) were both used as membrane additives and electrocatalysts. The membrane electrode assembly (MEA) was prepared by a nonequilibrium impregnation-reduction (I-R) method. $Pt(NH_3)_4Cl_2$, $NiCl_2$ and $CoCl_2$ as electrocatalytic materials and $NaBH_4$ as reducing agent were used. I order to enhance electrocatalytic activity, the catalyst layer prepared above was electrodeposited (Dep) with HP A. Surface morphologies and physico-chemical properties of MEA were investigated by means of SEM, EDX and XRD. The electrocatalytic properties of composite membranes such as the cell voltage and coulombic charge in CV were in the order of magnitude: CL-SPEEK/MoPA40 (wt%) > CL-SPEEK/TPA30 > Nafion117. In the optimum cell applications for water electrolysis, the cell voltage of Pt/CL-SPEEK-MoPA40/Pt-Co (Dep-MoPA) and Pt/CL-SPEEK-TPA30/Pt-Co (Dep-TPA) was 1.75 Vat $80^{\circ}C$ and $1\;A/cm^2$ and voltage efficiency was 87.1%. Also, the observed activity of Pt-Co (84:16 atomic ratio by EDX) is a little higher than that of Pt-Ni (86: 14). The current density peak of electrodeposited electrodes were better a little than those of unactivated electrodes based on the same membranes.

• Korean Journal of Environment and Ecology
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• v.12 no.1
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• pp.22-29
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• 1998

This study is investigated for the trace element concentration in the soils derived from different parent rocks, which are serpentinites, metamorphic rocks and black shales, and the absorption of the trace element by Pinus rigida in Hongseong and Keumsan, Chungnam, respectively. The concentrations of nickel, chrominium and cobalt are high in the serpentinites, whereas the concentrations of zinc, molybdenium and iron are high in the metamorphic rocks. These elements in black shale are lower than those in serpentinites and metamorphic rocks. The serpentine soils show high nickel, chrominium and cobalt content, while zinc and iron content are high in the mixed soils(serpentinites + metamorphic rocks) and black shales. Comparing with parent rocks, all of trace elements in their weathered soils are low. The pH of serpentine soil is high, 7.73~9.55 and that of black shale soil in 5.61. In serpentine area, the absorptions of chrominium by P. rigida is lower than its in the soils. The absorption of zinc by P. rigida is high relative to zinc concentration in soils. The Co/Ni and Fe/Ni quotient in P. rigida over serpentine soils are considerably lower than those growing over other soils tpes.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.25-30
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• 2007

The catalysts for decomposition reaction of acetaldehyde were investigated. The catalysts were prepared with transition metal Ni, Mo, Al on ${\gamma}-Al_2O_3$ support by impregnation method. Physio-chemical properties of catalysts were characterized by SEM-EDS, XRD, XPS, BET and TPR techniques. The conversion efficiency of catalysts for acetaldehyde was measured in the temperature range of $150{\sim}500^{\circ}C$ by GC through the micro reactor system. The 8 wt% $Ni/{\gamma}-Al_2O_3$ was found to be the most active catalyst of mono-metal catalysts tested, and the 1-3 wt% $Ni-Al/{\gamma}-Al_2O_3$ showed higher conversion efficiency than other bimetallic catalysts.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.240-244
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• 2006

In this paper, magnetic properties and annealing behavior of spin valve structures using Mo(MoN) layers as underlayers were studied varying the thickness of the underlayers. The spin valve structure was consisted of Si substrate/$SiO_2(2,000{\AA})/Mo(MoN)(t{\AA})/NiFe(21\;{\AA})/CoFe(28\;{\AA})/Cu(22\;{\AA})/CoFe(18\;{\AA})/IrMn(65\;{\AA})/Ta(25\;{\AA})$. Also, MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The resistivity of the MoN film increased as the $N_2$ gas flow rate was increased. After annealing at $600^{\circ}C$, XRD results did not show peaks of silicides. XPS results indicated MoN film deposited with 5 sccm of $N_2$ gas flow rate was more stable than the film deposited with 1 sccm of $N_2$ gas flow rate. The variations of MR ratio and magnetic exchange coupling fold were small for the spin valve structures using Mo(MoN) underlayers up to thickness of45 ${\AA}$. MR ratio of spin valves using MoN underlayers deposited with various $N_2$ gas flow rate was about 7.0% at RT and increased to about 7.5% after annealing at $220^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased to about 3.5%. Variation of $N_2$ gas flow rate up to 5 sccm did not change the MR ratio and $H_{ex}$ appreciably.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.275-276
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• 2015

기존의 상용화된 Ni-Cr tie-coating 물질은 내열성 시험 후 강도가 저하되고, Cr 성분이 patterning후에 완벽하게 제거 되지 않아서 누설 전류를 만드는 단점을 갖고 있다. 따라서 이 연구에서는 기존의 Ni-Cr 과 삼원계 Ni-Cr-X(X는 Nb, V, Mo, Ti) 물질의 패터닝성과 내열성을 비교하였다.