• Korean Journal of Metals and Materials
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• v.47 no.6
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• pp.372-377
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• 2009

We report on hysteresis behavior in the electrical resistance-hydrogen concentration of Pd thin films. The variation of the electrical resistance has been investigated during the process of absorption and desorption of hydrogen gas ($H_{2}$) as a function of thickness of Pd thin films. The hysteresis behavior in the electrical resistance with $H_{2}$ concentration was found for Pd thin films and consists of $\alpha$ phase, ${\alpha}+{\beta}$ phase, and $\beta$ phase regions. The sensitivity of Pd thin films with $H_{2}$ concentration was found to follow Sieverts' law in the $\alpha$ phase region. However, the sensitivity was observed to increase abruptly with $H_{2}$ concentration in the ${\alpha}+{\beta}$ phase co-exist region. This is because Pd-H interaction is stronger in the $\beta$ phase than in the $\alpha$ phase and needs a higher concentration gradient as a driving force to desorb. The formation of the $\beta$ phase also was observed to cause the structural change because of the lattice expansion during absorption. The hysteresis height and the trace of structural change were affected by the thickness of the Pd film. As the film becomes thinner, the hysteresis height becomes lower and the amount of delamination on the surface becomes smaller. For films thinner than 20 nm in thickness, the delamination was not found but electrical resistance hysteresis was still observed.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.112-118
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• 2013

In this study, constant loading test (CLT) was performed to evaluate the hydrogen embrittlement resistance for multipass FCA weld metals of 600MPa tensile strength grade. The microstructures of weld metal-2 having the smallest carbon equivalent (Ceq=0.37) consisted of grain boundary ferrite and widmanstatten ferrite in the acicular ferrite matrix. The weld metal-1 having the largest Ceq=0.47, showed the microstructures of grain boundary ferrite, widmanstatten ferrite and the large amount of bainite (vol.%=19%) in the acicular ferrite matrix. The weld metal-3 having the Ceq=0.41, which was composed of grain boundary ferrite, widmanstatten ferrite, and the small amount of bainite (vol.%=9%) in the acicular ferrite matrix. Hydrogen desorption spectrometry (TDS) used to analyze the amount of diffusible hydrogen and trapping site for the hydrogen pre-charged specimens electrochemically for 24 hours. With increasing the current density of hydrogen pre-charging, the released amount of diffusible hydrogen was increased. Furthermore, as increasing carbon equivalent of weld metals, the released diffusible hydrogen was increased. The main trapping sites of diffusible hydrogen for the weld metal having a low carbon equivalent (Ceq=0.37) were grain boundaries and those of weld metals having a relatively high carbon equivalent (Ceq: 0.41~0.47) were grain boundaries and dislocation. The fracture time for the hydrogen pre-charged specimens in the constant loading test was decreased as the carbon equivalent increased from 0.37 to 0.47. This result is mainly due to the increment of bainite that is vulnerable to hydrogen embrittlement.

• Journal of Environmental Health Sciences
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• v.27 no.1
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• pp.83-87
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• 2001

In this study, the characteristics of lead removal by PVA and alginate bead which used widely as immobilizing agents were investigated, and the difference of removal amounts between pure PVA/alginate bead and Sargassum thunbergii immobilized bead was studied. All PVA beads, pure and S. thunbergii immobilized, reached an equilibrium state in about 1 hour, and S. thunbergii immobilized bead adsorbed more lead than pure one. But in the case of alginate beads, they needed much time, about 5 hours, to reach an equilibrium state, and adsorbed lead four times higher than PVA beads. Therefore, it was considered that alginate beads had more mass transfer resistance and function groups which adsorb lead such as hydroxyl, carboxyl and etc. than PVA bead. To examine the continuous usage of alginate beads, the process of adsorption/desorption of lead was conducted repeatedly. As the process proceeded, the amounts of lead adsorption decrease, so it was indicated that the non-desorbed lead from alginate bead at first adsorption/desorption process remained constantly.

• Journal of Hydrogen and New Energy
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• v.4 no.1
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• pp.41-50
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• 1993

The hydrogen absorption and desorption characteristics of microencapsulated (CFM)$Ni_{4.7}Al_{0.2}Fe_{0.1}$ and $MmNi_4Fe$ powder with Ni and/or Cu by means of chemical plating method have been investigated. Initial hydrogen absorption rate and activation property were increased remarkably by encapsulation and subsequent compacting. Pellets abtained by compacting of Cu-encapsulated fine powder have fairly good strength even after 30 cycles of hydriding and dehydriding. Encapsulated alloy powder and their compacts show a good resistance to degradation by $O_2$ or CO in hydrogen.

• Journal of Hydrogen and New Energy
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• v.10 no.3
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• pp.171-175
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• 1999

Pd films($180{\sim}670{\AA}$ thick) were made by thermal evaporation. Electrical resistance of the films was measured during hydrogen absorption-desorption process at room temperature. Resistance changes as a function of hydrogen pressure in thin films of the PdH system show a strong dependence on film thickness. $({\Delta}R_{\infty}/R_0)_{{\beta}min}$ for a $\670{\AA}$ film is 0.61. For a $\180{\AA}$ film, this is 0.34. Resistance change also depends on sample preparation condition.

• Corrosion Science and Technology
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• v.20 no.4
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• pp.196-203
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• 2021

To improve corrosion resistance and reduce the hydrogen uptake of 22MnB5, up to 5% Mg was added to the AlSi coating of 22MnB5. After hot-stamping and electrocoating were done on the metallic-coated specimen, the surface characteristics of the steel, hydrogen uptake content, and corrosion resistance were examined by transmittance electron microscopy, thermal desorption spectrometry, cyclic corrosion testing, and electrochemical impedance spectroscopy. Mg was investigated as MgO on the surface layer after hot-stamping while it existed as Mg₂Si before hot-stamping. The total hydrogen content of 22MnB5 was decreased along with the Mg content. However, there was no difference at 0.2 wt% or more. When a small amount of Mg was added, the coating corrosion resistance was decreased, but when it was added at around 1.0 wt%, the greatest corrosion resistance increase was seen. However, when 3 wt% or more was added excessively, the corrosion resistance was decreased. MgO on the surface was considered to suppress H uptake by the AlSi melting solution and increase the barrier effect of the coating.

• Annals of Laboratory Medicine
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• v.38 no.6
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• pp.545-554
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• 2018

Background: The increasing morbidity and mortality rates associated with Acinetobacter baumannii are due to the emergence of drug resistance and the limited treatment options. We compared characteristics of colistin-resistant Acinetobacter baumannii (CR-AB) clinical isolates recovered from patients with and without prior colistin treatment. We assessed whether prior colistin treatment affects the resistance mechanism of CR-AB isolates, mortality rates, and clinical characteristics. Additionally, a proper method for identifying CR-AB was determined. Methods: We collected 36 non-duplicate CR-AB clinical isolates resistant to colistin. Antimicrobial susceptibility testing, Sanger sequencing analysis, molecular typing, lipid A structure analysis, and in vitro synergy testing were performed. Eleven colistin-susceptible AB isolates were used as controls. Results: Despite no differences in clinical characteristics between patients with and without prior colistin treatment, resistance-causing genetic mutations were more frequent in isolates from colistin-treated patients. Distinct mutations were overlooked via the Sanger sequencing method, perhaps because of a masking effect by the colistin-susceptible AB subpopulation of CR-AB isolates lacking genetic mutations. However, modified lipid A analysis revealed colistin resistance peaks, despite the population heterogeneity, and peak levels were significantly different between the groups. Conclusions: Although prior colistin use did not induce clinical or susceptibility differences, we demonstrated that identification of CR-AB by sequencing is insufficient. We propose that population heterogeneity has a masking effect, especially in colistin non-treated patients; therefore, accurate testing methods reflecting physiological alterations of the bacteria, such as phosphoethanolamine-modified lipid A identification by matrix-assisted laser desorption ionization-time of flight, should be employed.

• Korean Journal of Clinical Laboratory Science
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• v.55 no.4
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• pp.244-252
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• 2023

The timeliness and accuracy of test results are crucial factors for clinicians to decide and promptly administer effective and targeted antimicrobial therapy, especially in life-threatening infections or when vital organs and functions, such as sight, are at risk. Further research is needed to refine and optimize matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based assays to obtain accurate and reliable results in the shortest time possible. MALDI-TOF MS-based bacterial identification focuses primarily on techniques for isolating and purifying pathogens from clinical samples, the expansion of spectral libraries, and the upgrading of software. As technology advances, many MALDI-based microbial identification databases and systems have been licensed and put into clinical use. Nevertheless, it is still necessary to develop MALDI-TOF MS-based antimicrobial-resistance analysis for comprehensive clinical microbiology characterization. The important applications of MALDI-TOF MS in clinical research include specific application categories, common analytes, main methods, limitations, and solutions. In order to utilize clinical microbiology laboratories, it is essential to secure expertise through education and training of clinical laboratory scientists, and database construction and experience must be maximized. In the future, MALDI-TOF mass spectrometry is expected to be applied in various fields through the use of more powerful databases.

• Journal of Soil and Groundwater Environment
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• v.10 no.5
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• pp.45-51
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• 2005

The sorption/desorption characteristics of phenanthrene on the natural manganese oxide (NMD) were investigated in the presence of phenolic compounds. 4-chlorophenol (4-CP) was effectively oxidized by NMD catalyzed reaction and transformed into humic-like macromolecular compound through inter-or cross-coupling reaction between byproducts. As 4-CP was degraded with time, sorbed amount of phenanthrene on NMD was significantly increased, resulting from the formation of oxidative coupling products. These results imply that NMD can be used for simultaneous treatment of phenolic contaminants and polycyclic aromatic hydrocarbons (PAHs) in soils, sediments, or water. Also, sorbed phenanthrene on NMD in the presence of 4-CP showed high degree of desorption resistance, indicating that sequestration process of phenanthrene was ongoing with time.

• Journal of Hydrogen and New Energy
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• v.9 no.3
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• pp.127-133
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• 1998

This study was conducted to know to the effect of Pd film($180{\AA}$ thick) evaporation condition on the kinetics of hydrogen absorption-desorption. The activation energy of the forward reaction, the activation energy of the backward reaction, and the enthalpy were calculated by hydrogen absorption-desorption in ${\alpha}$-phase.($25{\sim}50^{\circ}C$ temperature) The activation energy of the forward reaction of Pd film, which is made at room temperature, is $6.4{\pm}0.4$ kcal/mol H and of the backward reaction $8.4{\pm}1.5$ kcal/mol H, which yields the reaction enthalpy -2kcal/mol H. The activation energy of forward reaction of Pd film, which is made at $300^{\circ}C$, is $-0.18{\pm}0.61$ kcal/mol H and of the backward reaction $-0.17{\pm}2.3$ kcal/mol H. The sample of $300^{\circ}C$ is more stable than the sample of room temperature in its struciural compactness and resistance value but standard error of result of $300^{\circ}C$ sample is higher than sample of room temperature do.