• 한국표면공학회지
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• 제42권5호
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• pp.232-239
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• 2009

This study presented the effect of membrane thickness on hydrogen permeability. Microvoids on the surface of the membrane should not exist for the exact values of hydrogen permeability. Pd-Cu-Ni hydrogen alloy membranes were fabricated by Ni powder sintering, substrate plasma pretreatment, sputtering and Cu reflow process. And this leaded to void-free surface and dense film of Pd-Cu-Ni hydrogen alloy membrane. Hydrogen permeation test showed that hydrogen permeability increased from 2.7 to $15.2ml/cm^2{\cdot}min{\cdot}atm^{0.5}$ as membrane thickness decreased from 12 to $4{\mu}m$. This represented the similar trend as a hydrogen permeability of pure palladium membrane based on solution-diffusion mechanism.

• 한국수소및신에너지학회논문집
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• 제31권2호
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• pp.177-183
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• 2020

To utilize hydrogen energy, high-yield, high-purity hydrogen needs to be produced; therefore, hydrogen separation membrane studies are being conducted. The membrane reactor that fabricates hydrogen needs to have high hydrogen permeability, selective permeability, heatresistant and a stable mechanical membrane. Dense membranes of Pd and Pd alloys are usually used, but these have drawbacks associated with high cost and durability. Therefore, many researchers have studied replacing Pd and Pd alloys. Dense TiN membrane is highly selective and can separate high-purity hydrogen. The porous alumina has a high permeation rate but low selectivity; therefore, separating high-purity hydrogen is difficult. To overcome this drawback, the two materials are combined as composite reclamations to produce a separation membrane with a high penetration rate and high selectivity. Accordingly, TiN-alumina was manufactured using a high-energy ball mill. The TiN-alumina membrane was characterized by X-ray diffraction analysis, scanning electron microscopy, and energy dispersive spectroscopy. The hydrogen permeability of the TiN-alumina membrane was estimated by a Sievert-type hydrogen permeation membrane apparatus. Due to the change in the diffusion mechanism, the transmittance value was lower than that of the general TiN ceramic separator.

• Korean Chemical Engineering Research
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• 제57권4호
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• pp.507-511
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• 2019

고분자전해질 연료전지(PEMFC)의 고분자막 내구성을 평가하는데 수소투과도가 많이 사용되고 있다. 수소투과도를 쉽게 측정하는 방법으로 선형 주사 전압 측정법(Linear Sweep Voltammetry, LSV)이 주로 사용된다. 연구자마다 LSV 측정 방법에 차이가 있어 연구 결과를 비교하기가 어려울 때가 많다. 그래서 본 연구에서는 측정하기 어렵지만 정확한 값이라고 할 수 있는 기체 크로마토그래프에 의한 수소투과도와 DOE와 NEDO의 LSV 방법을 비교하여 정확성을 확인하고자 하였다. 온도와 상대습도를 변화시키며 수소투과도를 측정해 비교했을 때, DOE LSV 방법이 GC 방법과 비교해 오차 범위 5%이하의 정확성을 보였다. NEDO LSV 방법은 DOE방법과 같이 0.3V의 전류 값으로 수소투과전류밀도를 결정했을 때 오차는 감소하였다.

• 한국세라믹학회지
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• 제50권6호
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• pp.451-453
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• 2013

Porous ceramic membranes consisting of $Ce_{1-x}Y_xO_{2-{\delta}}$ were developed for hydrogen permeation tests. Various amounts (x = 0, 0.05, 0.1, 0.2) of yttrium were doped to ceria to study the effect of yttrium doping on ceria membranes on various properties, including hydrogen permeability. $Ce_{1-x}Y_xO_{2-{\delta}}$ powder was synthesized by the sol-gel method. These membranes were fabricated by pressing and sintering at $1300^{\circ}C$ for 6 h. As the amount of yttrium increased, the grain size of the membrane decreased. Hydrogen permeability was improved as the yttrium content increased. Selective permeability of hydrogen compared to CO is explained by electric conductivity. As the temperature rose, both the hydrogen perm-selectivity and electric conductivity on $Ce_{0.8}Y_{0.2}O_{1.9}$ improved.

• Korean Chemical Engineering Research
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• 제55권4호
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• pp.473-477
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• 2017

고분자 전해질 연료전지(PEMFC)의 고분자 막은 PEMFC 성능과 내구성에 많은 영향을 준다. 본 연구에서는 고분자막의 두께가 성능과 내구성에 미치는 영향을 파악하기 위해 두께가 다른 Nafion 막의 수소투과도, 불소 유출 속도(FER), 수명, 성능을 측정했다. 막 두께에 따른 수소투과도, 수소투과도와 FER과의 관계, FER과 수명과의 관계로부터 막 두께와 수명의 관계를 얻었다. 막이 두꺼워지면 수소투과도와 FER이 작아지면서 수명이 증가하였다. 반면에 막이 두꺼워지면 막 저항이 증가하면서 성능은 감소하였다. 성능과 내구성을 동시에 만족시키는 막 두께 범위는 $25{\sim}28{\mu}m$였다.

• Korean Chemical Engineering Research
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• 제52권4호
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• pp.425-429
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• 2014

최근까지 대부분의 PEMFC MEA(Membrnae and Electrode Assembly) 열화 연구는 전극과 전해질 막 각각 분리되어 연구되었다. 그런데 실제 PEMFC 운전조건에서는 전극과 전해질 막은 동시에 열화된다. 동시열화과정에서 전극열화와 전해질 막 열화는 상호 작용한다. 전해질 막의 열화정도를 측정하는데 수소투과도가 많이 사용되고 있다. 그런데 동시 열화가 발생했을 때 선형 쓸음 전기량 측정법(Linear Sweep Voltammetry, LSV)에 의해 수소투과도를 측정하면 전극열화가 수소투과전류를 감소시키는데, LSV 방법이 전극 촉매의 활성 면적에 의존하기 때문이다. 본 연구에서는 전극과 막 동시 열화과정에서 기체 크로마토그래프에 의한 PEMFC 전해질막의 수소투과도를 측정하였다. 기체 크로마토그래프 측정 방법은 전극 상태와 무관하기 때문에 전극과 막 동시 열화 과정에서 수소투과도가 전극 열화 영향을 받지 않음을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제48권4호
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• pp.33.1-33.12
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• 2023

Objectives: This study aimed to evaluate the bleaching efficacy and hydrogen peroxide permeability in the pulp chamber by the at-home bleaching gel in protocols applied on different dental surfaces. Materials and Methods: Forty premolars were randomly into 4 groups: control group no bleaching, only application on the buccal surface (OB), only application on the lingual surface (OL) and application in buccal and lingual surfaces, simultaneously (BL). At-home bleaching gel (White Class 7.5%) was used for the procedure. The bleaching efficacy was evaluated with a digital spectrophotometer (color change in CIELAB [ΔE_ab] and CIEDE 2000 [ΔE₀₀] systems and Whitening Index for Dentistry [ΔWI_D]). The hydrogen peroxide permeability in the pulp chamber (㎍/mL) was assessed using UV-Vis spectrophotometry and data were analyzed for a 1-way analysis of variance and Tukey's test (α = 0.05). Results: All groups submitted to bleaching procedure showed bleaching efficacy when measured with ΔE_ab and ΔE₀₀ (p > 0.05). Therefore, when analyzed by ΔWI_D, a higher bleaching efficacy were observed for the application on the groups OB and BL (p = 0.00003). Similar hydrogen peroxide permeability was found in the pulp chambers of the teeth undergoing different protocols (p > 0.05). Conclusions: The application of bleaching gel exclusively on the OB is sufficient to achieve bleaching efficacy, when compared to BL. Although the OL protocol demonstrated lower bleaching efficacy based on the ΔWI_D values, it may still be of interest and relevant in certain clinical scenarios based on individual needs, requiring clinical trials to better understand its specificities.

• 대한한의학회지
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• 제21권4호
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• pp.193-203
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• 2000

Objectives : Hindered barrier function of vascular endothelium has been implicated in the initiation and progression of degenerative vascular diseases such as atherosclerosis. In this study, the effect of Sunghyangchungisan(SHCS) as a protectant against oxidant-induced destruction of endothelial barrier function was assessed. Methods : Toward this end, endothelial cells derived from the human umbilical vein were cultured as monolayers on permeable membrane filters. Endothelial permeability was monitored by measuring transendothelial electrical resistance and movement of low density lipoprotein (LDL) across the endothelial monolayer. Results : Along with increased movement of LDL, $H_2O_2$-induced increase in endothelial permeability was paralleled by a decrease in transendotheliaI electrical resistance. The effect of $H_2O_2$ was mimicked by phorbol 12-myristate 13-acetate (PMA), a potent activator of proteinkinase C. Calphostin-C, a protein kinase C inhibitor, effectively blocked the increase in endothelial permeability induced by $H_2O_2$ or PMA, indicating that activation of protein kinase C is associated with the $H_2O_2-induced$ permeability change. SHCS effectively protected the endothelial monolayer against $H_2O_2-induced$ increase in permeability, whereas, it did not affect PMA-induced change. Forskolin, a potent activator of adenylyl cyclase, antagonized $H_2O_2$ to increase endothelial permeability. In addition, in ${H_2O_2}-treated$ cens, intracenular cAMP concentration was significantly decreased, indicating that impaired cAMP production as well as activation of proteinkinase C is a mechanism underlying ${H_2O_2}>-induced$$H_2O_2$ with regard to its effect on intracellular cAMP content. However, SHCS itself did not affect resting cAMP concentration in endothelial cells. Conclusions : These results suggest that SHCS might operate as an effective protectant against oxidant-induced destruction of endothelial barrier function. The mechanism does not appear to involve direct interaction with protein kinase C- or cAMP-associated signaling mechanism.

• 한국수소및신에너지학회논문집
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• 제24권3호
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• pp.200-205
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• 2013

The separation of hydrogen depends on porosity, diffusivity and solubility in permeation membrane. Dense membrane is always showing a solution diffusion mechanism but porous membrane is not showing. Therefore, porous membrane has a good hydrogen flux due to pore is carried out transferred media. This mechanism is named as the Knudsen diffusion. Hydrogen molecules or hydrogen atoms are diffused along pore that is a mean free path. In this study, complex layer hydrogen permeation membrane was fabricated by hot press process. And then, it was evaluated and calculated to relationship between hydrogen permeability and membrane porosity.

• 한국세라믹학회지
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• 제51권5호
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• pp.477-480
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• 2014

An $Al_2O_3$-CuO-ZnO (ACZ) precursor powder was synthesized by a facial sol-gel process using a nonionic surfactant span 80 as the chelating agent to improve the surface area and morphology. When creating a hydrogen membrane, several kinds of properties are required, such as easy dissociation of hydrogen molecules, fast hydrogen diffusion, high hydrogen solubility, and resistance to hydrogen embrittlement. ACZ-Ni composite membranes (cermet) were prepared with this precursor and pure Ni powder via the hot press sintering (HPS) method. The ACZ powder was characterized by XRD, BET, and FE-SEM. Hydrogen permeation experiments were performed by Sievert's type of hydrogen permeation membrane equipment. The hydrogen permeability of ACZ/Ni 10 wt% and ACZ/Ni 20 wt% was obtained as 7.2 and $10molm^{-2}s^{-1}$ at RT, respectively. These values of the corresponding membranes were slightly increased with increasing pressures.