• The Journal of the Acoustical Society of Korea
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• v.30 no.3
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• pp.158-166
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• 2011

In the present study, copper and nickel foams with an open-celled structure as trabecular-bone-mimicking phantoms were used to investigate the dependencies of group velocity and attenuation coefficient on structural properties such as trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp) in trabecular bone. The group velocity and attenuation coefficient of the copper and nickel foams were measured by a through-transmission method in water, using a pair of broadband, unfocused transducers with a diameter of 12.7 mm and a center frequency of 1.0 MHz. The separation of the Biot's fast and slow waves was consistently observed in the ultrasonic signals transmitted through the copper and nickel foams. The group velocities of the copper and nickel foams showed highly positive correlations with Tb.Th and Tb.Sp. The attenuation coefficient of the copper foam showed a highly negative correlation with Tb.Th and Tb.Sp, whereas that of the nickle foam showed a highly positive correlation with Tb.Th and Tb.Sp. These results advance our understanding of those previously reported by other researchers using trabecular bone samples or phantoms.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.446-447
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• 2010

최근 개발된 니켈 초합금 금속폼은 기존의 매연저감장치 신소재로 여겨지고 있다. 금속폼은 세가지 두드러진 특징을 갖고 있다. 첫째, 금속폼은 큰 기공의 다공성 매질로써 매연을 포집하여 축적할 수 있는 용량이 기존 필터에 비해 상대적으로 크며 그로인하여 재생 시 연소 안전성이 두드러진다. 둘째, 복잡하고 굴곡있는 기공 구조와 큰 비표면적은 물질전달 특성을 향상시켜 촉매 적용 시 촉매의 전환성능을 향상시키고 그로 인하여 귀금속 촉매량을 줄일 수 있는 장점이 있다. 셋째, 금속폼은 다양한 기공크기를 가지며, 다양한 조합의 금속폼을 개발할 수 있어 요구 성능에 따른 최적의 필터 설계를 가능케 한다. 이번연구에서는, 금속폼의 필터 성능을 다양한 실험을 통하여 측정 평가하며, 이런 이해를 기반으로 필터로 제작하여 엔진실험벤치에서 그 성능을 검증하였다. 필터의 성능은 수트 포집효율과 그에 따른 필터의 압력강하와 촉매 활성 능력으로 평가되었다. 이러한 실험과 병행하여 금속폼에서의 수트 포집과정을 모델링하고 이를 상용 프로그램인 CFD-ACE+에 추가하여 설계전용 프로그램을 개발하였으며, 엔진실험결과와 비교 검증하였다. 본 논문에서는 금속폼의 높은 매연축적용량과 향상된 물질전달 특성이 어떻게 필터의 귀금속 촉매와 체적을 줄일 수 있는지 제시하고 있다.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.37-44
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• 2007

A nickel foam, one of metal foams was seleced as a catalyst support instead of conventional ceramic materials. $Al_2O_3$ was coated on the surface of nickel foam to increase the surface area. $Al_2O_3$ coating process was based on sol-gel process. SEM image was obtained and $Al_2O_3$ coverage was confirmed. Combustion experiments were carried out using SUS combustor and $H_2$/air mixture. Temperatures were measured with different equivalence ratios and $H_2$ flow rates. $H_2$ conversion rates were calculated by the analysis of product gas using gas chromatography. Catalytic combustion of $H_2$ was complete and stable with Pt/$Al_2O_3$ coated nickel foam and influences of water vapor were confirmed during the beginning of combustion.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.383-389
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• 2010

Co-B, Co-P-B, Co-Ni-B and Co-Ni-P-B catalysts supported on Ni foam were prepared using electroless plating in the present study. The surface morphology of the catalysts/Ni foam was observed using SEM and EDS analysis. The Co-Ni-P-B/Ni foam catalyst showed the superior performance on hydrogen generation due to the uniform formation of catalyst particles on the Ni foam surface. The characteristics of hydrogen generation with Co-Ni-P-B/Ni foam catalyst was investigated at the variety of $NaBH_4$ and NaOH concentrations. Durability test was performed, resulting in the stable hydrogen generation for 6 hours.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.224.1-224.1
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• 2010

본 연구에서는 천연가스 수증기 개질반응에 니켈 촉매가 코팅된 금속 구조체 촉매를 적용하여 수소를 생산하였다. 금속구조체 촉매는 기존 펠릿 촉매가 충진 된 촉매반응기에 비해 열 및 물질 전달 특성이 우수하여 이를 여러 개질반응에 적용하고자하는 연구가 수행되어 왔다. 하지만, 기존 금속구조체 촉매의 개발에 있어 촉매와 금속 지지체간의 안정한 결합을 통한 열안정성 확보에 대한 문제는 여전히 해결과제로 남아 있다. 따라서, 본 연구에서는 니켈 촉매를 금속 지지체에 안정하게 부착하기 위한 금속 지지체 표면 처리 방법을 개발하였으며 금속 구조체의 형상에 상관없이 균일한 표면처리가 가능하였다. 개발된 표면 처리방법을 적용한 금속 구조체 촉매는 촉매와 금속지지체간의 결합력 향상으로 인해 120시간 이상 안정한 반응활성을 보였다. 또한, 빠른 공간속도에서도 펠릿촉매와 표면처리를 적용하지 않은 금속 구조체 촉매에 비해 높은 촉매 활성을 보였다. 뿐만 아니라, 본 연구에서 개발된 표면처리를 모노리스와 폼을 비롯한 다양한 형상의 금속구조체 촉매에 적용하여 기하학적 표면 특성에 따른 촉매의 활성 차이를 살펴보았다. 겉보기 표면적이 넓은 금속구조체일 수록 촉매의 고분산 코팅에 유리하여 높은 활성을 보였다.

• Journal of the Korean institute of surface engineering
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• v.56 no.5
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• pp.320-327
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• 2023

In this study, the nickel hydroxide (Ni(OH)₂) electrode for supercapacitor was prepared via hydrothermal method. Based on the nickel (Ni) foam, the electrode does not require any additional binder material or post-processing. Nickel nitrate (Ni(NO₃)₂) and hexamethylenetetramine (C₆H₁₂N₄) were used for synthesis, and the synthesis condition was 12 hours at 80 ℃. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to analyze the structural characteristics of the electrode, and it shown that the nickel hydroxide was successfully prepared after only the one-step hydrothermal synthesis. The electrochemical properties were analyzed through the half-cell test. The prepared electrode shown a pair of oxidation/reduction peaks, indicating that the driving method included the redox reaction on the electrode surface. After the charge/discharge test, the specific capacitance was calculated as the value of 438 F/g at 3 A/g.

• Journal of the Korean Ceramic Society
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• v.45 no.6
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• pp.368-373
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• 2008

An electrode for supercapacitor using 3-dimensional porous nickel foam as a current collector and cobalt oxide as an active material was prepared and characterized in terms of morphology observation, crystalline property analysis, and the investigation of electrochemical property. The electrode surface showed that the cobalt oxide was homogeneously coated as the crystalline phase of $Co_3O_4$. Cyclic voltammetry for the $Co_3O_4$/nickel foam electrode exhibited higher specific capacitance values (445 F/g at 10 mV/s and 350 F/g at 200 mV/s) and excellent capacitance retention ratio (99% after $10^4$ cycles). It was proved that the nickel foam substrate played the roles in reducing the interfacial resistance with cobalt oxide and in improving the electrode density by embedding greater amount of cobalt oxide within it.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.30-35
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• 2024

In order to improve the efficiency of the water splitting system for hydrogen production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metal porous material, was used as a support, and Fe-doped β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, in order to improve OER properties, changes in the shape, crystal structure, and water splitting characteristics of Fe-Mo co-doped β-Ni(OH)₂ microcrystals synthesized by co-doping with Mo were observed. The changes in the shape, crystal structure, and applicability as a catalyst for water splitting were examined.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.3
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• pp.92-97
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• 2024

To improve the efficiency of water splitting systems for hydrogen production, the high overvoltages of electrochemical reactions caused by catalysts in the oxygen evolution reaction (OER, Oxygen Evolution Reaction) must be reduced. Among them, LDH (Layered Double Hydroxide) compounds containing transition metal such as Ni, are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metallic porous material, was used as a support, and NiCo LDH (Layered Double Hydroxide) nanocrystals were synthesized through a hydrothermal synthesis process. In addition, changes in the shape, crystal structure, and water decomposition characteristics of the Mo-doped NiCo LDH nanocrystal samples synthesized by doping Mo to improve OER properties were observed.