• Transactions of the Korean hydrogen and new energy society
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• v.34 no.3
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• pp.307-315
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• 2023

The physical and chemical changes exhibited by high density polyethylene (HDPE) after treatment with hydrogen at a pressure of 90 MPa followed by rapid release of the hydrogen were studied. X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, and attenuated total reflectance (ATR)-fourier transform infrared (FTIR) were used for this purpose. As a result, it was found that the degree of crystallinity of HDPE decreased after hydrogen pressure treatment, while the average thickness of lamellae that constitute the crystals and the melting temperature of the crystalline region actually increased. The decomposition temperature also increased by about 3℃. In addition, it was found that the hydrogen bonding network between -OH groups in the HDPE sample was strengthened and partial chain scission occurred. These cut chains were found to be terminated by oxidative degradation such as cross-linking between chains, -C=O, -C-O, and -CHO, or by the formation of -CH₃ at the chain ends, as confirmed by ATR-FTIR.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.117-124
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• 2012

Alkaline electrolysis needs the electrode having a low overvoltage and good corrosion resistance in alkaline solution such as KOH and NaOH, for the oxygen and hydrogen production. The commercial materials such as SUS(stainless steel)-316, Ni and NiFe were evaluated for the electrode in alkaline electrolysis. The test solution for the alkaline electrolysis used 1~9M NaOH and 1~9M KOH. The voltage increased with an increase of current density in each solution. As for the 15wt.% (about 5M) NaOH, the voltage of the tested electrode under the current density of 1.8A/$cm^2$ showed the almost same value. The voltage over the current density of 1.8A/$cm^2$ deceased in the order: Ni${\fallingdotseq}$NiFe$cm^2$ showed the almost same value. The voltage over the current density of 1.8A/$cm^2$ deceased in the order: NiFe${\fallingdotseq}$SUS-316. From the results, it was estimated that NiFe and Ni was suitable as the electrode for the alkaline water electrolysis using NaOH and KOH electrolyte.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.151-155
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• 2018

Degree of membrane degradation in Proton Exchange Membrane Fuel Cells (PEMFC) is mainly evaluated by the hydrogen crossover current density. The hydrogen crossover current density is measured by linear sweep voltammetry (LSV), which differs from the DOE protocol and the NEDO protocol. In this study, two protocols were compared during PEMFC operation and accelerated stress test. In the LSV method by the DOE method, the scan rate change affects the hydrogen crossover current density, but the NEDO method does not affect the hydrogen crossover current density. In the course of 15,000 cycles of polymer membrane wet/dry cycle, the DOE method was sensitive to membrane degradation, but the NEDO method was less sensitive to membrane degradation than the DOE method.

• Bulletin of the Korean Chemical Society
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• v.13 no.4
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• pp.367-375
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• 1992

The electronic structure change caused by insertion of hydrogen into the interstices of Pd cluster is studied. Several properties such as energy, reduced overlap population (ROP), electon density (ED) and density of states (DOS) are calculated by Extended Huckel Method. Various types of clusters are considered. The same is performed on Ni and Pt and all the results are compared. The results show that the hydrogen atom in Pd is stabilized remarkably but its wave function is almost unperturbed. The fact is compatible with noticeable solubility of hydrogen in Pd but may not be a positive enough evidence to rationalize the claimed cold fusion phenomenon. It is also found that a remarkable charge transfer from Pd atom to hydrogen atom occurs.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.1
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• pp.65-73
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• 2002

Because of low flame ion density in hydrogen-air mixture, many residual electric energy could be existed in the ignition system of hydrogen engine, If these residual energy discharged abnormally during intake stroke, it may be the cause of backfire occurrence which is serious problem in development of hydrogen fueled engine but unsolved in spite of many concerned research on it. In this study, the possibility of backfire occurrence by abnormal electric discharge and countermeasure of that were investigated by using the experimental single cylinder hydrogen fueled engine with two types of ignition system. The results show that abnormal electric discharge appeared in low load with low ion density and then results in back fire occurrence, It is also seen that countermeasure method installing larger earth resistance in high tension code is effective to control abnormal electric discharge.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.257-262
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• 2014

In this paper, the behavior of hydrogen embrittlement of 680MPa DP sheet steel according to hydrogen charging conditions in acid and alkali electrolytes atmosphere was investigated. At this time, 0.5 M $H_2SO_4$ and 0.5M NaOH was used for electrolytes atmosphere and the effect on embrittlemnet of 680MPa DP sheet steel according to current density and charging time was evaluated by the change of subsurface microhardness in DP specimens chared hydrogen. As a result of this experiment, the microhardness of the layer directly below the surface was increased more than the microhardness of the subsurface zone in both electrolytes cases, but the change of the subsurface microhardness in both electrolytes was more affected by the increase of charging time than the increase of current density. The microhardness of subsurface zone in 0.5 M $H_2SO_4$ acid electrolyte was increased more than the microhardness in 0.5M NaOH alkali electrolyte. It was supposed that acid atmosphere was more sensitive to hydrogen embrittlement than alkali atmosphere on electrolyte atmosphere of hydrogen charge.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.4
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• pp.448-453
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• 2006

Porous Co-P catalysts electroplated on Cu in chloride based solution with an addition of $NaH_2PO_2$ and glycine were developed for hydrogen generation from alkaline $NaBH_4$ solution. The microstructures of the Co-P catalysts and their hydrogen generation properties were analyzed as a function of cathodic current density and plating time during the electrodeposition. Amorphous Co-P electrodeposits with porous structure was formed on Cu at cathodic current density of $0.05\;A/cm^2$, and showed very high hydrogen generation rate in alkaline $NaBH_4$ solution due to an increase in the surface area of the catalyst as well as the catalytic activity. The Co-P catalyst, which was obtained at cathodic current density of $0.05\;A/cm^2$ for 5 min, exhibited the best hydrogen generation rate of 2290 ml/min.g-catalyst in 1 wt. % NaOH+10 wt. % $NaBH_4$ solution at $30^{\circ}C$.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.267-276
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• 2019

The purpose of this study was to examine the influence of conditions for quenching and/or tempering on the corrosion and hydrogen diffusion behavior of ultra-strong automotive steel in terms of the localized plastic strain related to the dislocation density, and the precipitation of iron carbide. In this study, a range of analytical and experimental methods were deployed, such as field emission-scanning electron microscopy, electron back scatter diffraction, electrochemical permeation technique, slow-strain rate test (SSRT), and electrochemical polarization test. The results showed that the hydrogen diffusion parameters involving the diffusion kinetics and hydrogen solubility, obtained from the permeation experiment, could not be directly indicative of the resistance to hydrogen embrittlement (HE) occurring under the condition with low hydrogen concentration. The SSRT results showed that the partitioning process, leading to decrease in localized plastic strain and dislocation density in the sample, results in a high resistance to HE-induced by aqueous corrosion. Conversely, coarse iron carbide, precipitated during heat treatment, weakened the long-term corrosion resistance. This can also be a controlling factor for the development of ultra-strong steel with superior corrosion and HE resistance.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.379-385
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• 2005

Effects of Co and Co-P catalysts on the hydrolysis of alkaline $NaBH_4$ solution were investigated. Co and Co-P catalysts were prepared on Cu substrate by electroplating. Hydrogen generation rate of Co-P catalyst was much faster than that of Co catalyst, demonstrating that Co-P had higher intrinsic catalytic activity for the hydrolysis of $NaBH_4$ than Co. Hydrogen generation properties of Co-P catalysts largely depended on cathodic current density and electroplating time because they influenced on the P concentration of the Co-P catalysts. Maximum hydrogen generation rate of Co-P catalyst was 1066 ml/min.g-catalyst in 1 wt.% NaOH + 10 wt.% $NaBH_4$ solution at $20^{\circ}C$, which was obtained at cathodic current density of $0.01\;A/cm^2$ for 130 s.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.478-481
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• 2006

Energy is vital to global prosperity, yet dependence on fossil fuels as our primary energy source contributes to global climate change environmental degradation, and health problems. Hydrogen $(H_2)$ offers tremendous potential as a clean renewable energy currency. Hydrogen has the highest gravimetric energy density of any known fuel and is compatible with electrochemical and combustion processes for energy conversion without producing carbon-based emission that contribute to environmental pollution and climate change. Numerous methodologies have been developed for effective hydrogen production. Among them, the biological hydrogen production has gained attention, because hydrogen can be produced by cellular metabolismunder the presence of water and sunlight. The green alga Chlamydomonas reinhardtii is capable of sustained $H_2$ photoproduction when grown under sulfur deprived condition. Under sulfur deprived conditions, PSII and photosynthetic $O_2$ evolution are inactivated, resulting in shift from aerobic to anaerobic condition in the culture. After anaerobiosis, sulfur deprived algal cells induce a reversible hydrogenase and start to evolve $H_2$ gas in the light. According to above principle, we investigated the effect of induction parameters such as cell age, cell density. light intensity, and sulfate concentration under sulfur deprived condition We also developed continuous hydrogen production system by sulfate re-addition under sulfur deprived condition.