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Variation in the Oxidation Behavior of a Polished Ferritic Stainless Steel with Thermal Cycling
( Hye Ryoung Park ),( Myoung Youp Song ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.6
One of the candidates for metallic interconnects of solid oxide fuel cells is a ferritic stainless steel, Crofer22 APU. Crofer22 APU specimens are polished and thermally cycled at 800 ℃ 4, 8, 20, 30, and 40 times, with the periods of maintaining the temperature at 800 ℃ (corresponding to the oxidation times) of 100, 200, 500, 750, and 1,000 h, respectively. The variation in their oxidation behavior with cycling is then investigated. The EDX spectra of the polished Crofer22 APU show that the atomic percentages of the elements Cr, Mn, and Fe decrease, while the atomic percentage of oxygen increases, as the number of thermal cycles, n, increases. XRD patterns of the surfaces for the polished Crofer22 APU samples after thermal cycling show that as the number of thermal cycles increases, the content of the alloy substrate phase decreases and the content of the Cr2O3 phase remains almost constant. The content of (Cr, Mn 3O4 spinel phase increases from n=4 to n=20 and remains almost constant from n=20 to n=40. The slow increase in ASR from n=4 to n=20 is considered to correspond to the formation of the (Cr, Mn)3O4, Cr2O3, and SiO2 phases. The rapid increase in ASR from n=20 to n=40 is considered to occur because the connections between particles become weak due to the expansion and contraction of particles with thermal cycling. (Received July 18, 2013)
( Hye Ryoung Park ),( Young Jun Kwak ),( Seong Ho Lee ),( Myoung Youp Song ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.12
In this work, niobium (V) fluoride was selected as an additive to heighten the hydrogen sorption rates of Mg. Specimens of pure Mg, 5 wt% niobium fluoride-added Mg, and 10 wt% niobium fluorideadded Mg were prepared by planetary ball milling in hydrogen. The hydrogen sorption properties of the specimens were then examined. An Mg-based hydrogen-storage alloy with an effective hydrogenstorage capacity of about 5.5 wt% was developed. At 593 K in 12 bar hydrogen at the first cycle (Cn = 1), the 5 wt% niobium fluoride-added Mg stored 4.37 wt% hydrogen in 5 min and 5.50 wt% hydrogen in 30 min. At 593 K in 1.0 bar hydrogen at Cn = 1, the 5 wt% niobium fluoride-added Mg released 2.11 wt% hydrogen in 10 min, 4.66 wt% hydrogen in 30 min, and 5.43 wt% hydrogen in 60 min. The planetary ball milling of Mg with NbF5 in hydrogen, which generated MgF2, NbH2, and NbF3, is believed to have produced imperfections both on the surface and in the interior of the Mg particles, created clean surfaces, and diminished the particle size of the Mg. The 5 wt% niobium fluoride-added Mg specimen stored a larger quantity of hydrogen in 30 min and a larger quantity of hydrogen was released in 60 min compared with the 10 wt% niobium fluoride-added Mg, or the pure Mg. †(Received April 5, 2016; Accepted June 27, 2016)
Hydrogen Desorption and Absorption Properties of MgH2, LiBH4, and MgH2 + LiBH4 Composite
Hye Ryoung Park,Myoung Youp Song 대한금속·재료학회 2012 대한금속·재료학회지 Vol.50 No.12
To increase the hydrogen storage capacity of Mg-based materials, a sample with a composition of 69.7 wt% MgH2 + 30.3 wt% LiBH4 was prepared by planetary ball milling under hydrogen. The absorption and desorption properties of unmilled MgH2, unmilled LiBH4, and 69.7 wt% MgH2 + 30.3 wt% LiBH4 were examined. At 648 K the unmilled MgH2 desorbed 5.70 wt% for 60 min. The unmilled LiBH4 desorbed 6.40 wt% H for 780 min at 673 K. The 69.7 wt% MgH2 + 30.3 wt% LiBH4 sample desorbed 3.10 wt% H for 50 min, and 3.32 wt% H for 300 min at 623 K at the second cycle.
Hye Ryoung Park,Young Jun Kwak,Myoung Youp Song 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.9
Abstract: In this work, Zn(BH<sub>4</sub>)<sub>2</sub> was added to improve the hydrogen-storage properties of MgH<sub>2</sub>. A 99 wt% MgH<sub>2</sub>+1 wt% Zn(BH<sub>4</sub>)<sub>2</sub> sample was prepared by milling in a planetary ball mill in a hydrogen atmosphere. The proportion of the added Zn(BH<sub>4</sub>)<sub>2</sub> was small (1 wt%) in order to increase hydriding and dehydriding rates without reducing the hydrogen-storage capacity too much. Changes in the released hydrogen quantity, Hd, with temperature, T, for as-milled 99MgH<sub>2</sub>+1Zn(BH<sub>4</sub>)<sub>2</sub> was obtained by heating the sample from room temperature to 683 K with a heating rate of 5 K/min under 1.0 bar of gas. Activation of the sample was not required. 99MgH<sub>2</sub>+1Zn(BH<sub>4</sub>)<sub>2</sub> had an effective hydrogen-storage capacity (the quantity of hydrogen absorbed in 60 min) of 4.83 wt% in the first cycle. The as-purchased MgH<sub>2</sub> absorbed hydrogen slowly, absorbing 0.04 wt% H in 60 min. On the other hand, in the first cycle, 99MgH<sub>2</sub>+ 1Zn(BH<sub>4</sub>)<sub>2</sub> absorbed 3.97 wt% H in 5 min, 4.49 wt% H in10 min, and 4.83 wt% H in 60 min at 593 K under 12 bar H<sub>2</sub>. (Received February 20, 2017; Accepted May 29, 2017)
Hye Ryoung Park,Seong Ho Lee,Young Jun Kwak,Myoung Youp Song 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.11
Fe2O3, Ti, Fe, and TiCl3 were chosen as additives to increase the hydrogen absorption and release rates of Mg. Samples with compositions of 80 wt% Mg + 14 wt% Ni + 6 wt% Fe2O3 (named Mg-14Ni-6Fe2O3), 80 wt% Mg + 14 wt% Ni + 3 wt% Fe2O3 + 3 wt% Ti (named Mg-14Ni-3Fe2O3-3Ti), 80 wt% Mg + 14 wt% Ni + 2 wt% Fe2O3 + 2 wt% Ti + 2 wt% Fe (named Mg-14Ni-2Fe2O3-2Ti-2Fe), and 80 wt% Mg + 14 wt% Ni + 6 wt% TiCl3 (named Mg-14Ni-6TiCl3) were prepared by high-energy ball milling in hydrogen. The hydrogen absorption and release properties of the prepared samples were investigated and compared. The halide and nickel-added Mg, Mg-14Ni-6TiCl3, had larger quantities of hydrogen absorbed and released for 60 min and a larger initial dehydriding rate than the oxide and nickel-added Mg samples. In particular, the hydrogen absorption and release properties of Mg-14Ni-6TiCl3 were examined in more detail. The activation of Mg-14Ni-6TiCl3 was completed after two hydriding-dehydriding cycles (cycling between hydriding under 12 bar H2 at 593 K and dehydriding in vacuum at 623 K). Mg-14Ni-6TiCl3 had an effective hydrogen-storage capacity of about 5.2 wt%. At the third cycle, the sample released 1.05 wt% H for 2.5 min, 2.82 wt% H for 10 min, and 4.88 wt% H for 60 min.
박혜령(Hye-Ryoung PARK),김성곤(Seong-Gon KIM) 동아시아경상학회 2022 The East Asian Journal of Business Economics Vol.10 No.1
Purpose - Burnouts cause the workers to quit their jobs because with the heavy workloads that the employees get subjected to, they feel that they have little control over what they have to accomplish in the workplace. The purpose of this research is to provide adequate solutions using brief consultation process, reducing negative psychological factors. Research design, Data, and methodology - The current research conducted the ‘Qualitative Content Analysis’ (QCA), which is one of the most employed analytical tools; it has been used widely all over the globe in various research applications in library science and information. Primarily, this analysis is often used as a method in the quantitative tool until the recent decade. Result - Based on ultimate systematic literature analysis, excessive workloads can get addressed by finding proper solutions to the issues of depression, anxiety, irritability, and discouragement. The solutions are (1) Combating Excessive Workloads using Effective Employee Selection, (2) Employee Effective training, and (3) Job redesigning. Conclusion - Selecting or recruiting employees that have skills for the given job also makes it possible for the organization to run its employees effectively and with minimal cases of workload as an organization understands the capabilities and capacities of workload an employee can complete.