The effect of metal codoping on hydrogen storage has been meticulously studied in small cubic C8 nanocluster within the framework of density functional theory (DFT). Initially, a C8 nanocluster was doped with two Li atoms [ C8(Li)2], achieving a hydrogen uptake of 15.5 wt% with an adsorption energy of 0.16 eV. Although this configuration demonstrates a high hydrogen storage capacity, its thermodynamic stability under ambient conditions is limited due to weak binding interactions between Li and H2 molecules. By introducing metal atoms that have stronger binding with the C8 framework, it is expected to enhance the overall structural stability. For that, we have chosen Na, K, Be, Mg, Ca, Sc, Ti, V, and Cr metal atoms along with Li to investigate the influence of codoping on hydrogen storage characteristics. The Ti- and V-codoped structures exhibited significant distortion of the C8 nanocluster during optimization primarily due to strong charge transfer, steric repulsion arising from the larger atomic radii of Ti and V, and partial bond breaking within the nanocluster framework and were, therefore, excluded from further calculations. The resulting codoped structures—C8LiNa, C8LiK, C8LiBe, C8LiMg, C8LiCa, C8LiSc, and C8LiCr— yielded hydrogen uptake of 16.1 wt%, 14.6 wt%, 11.2 wt%, 13.7 wt%, 12.4 wt%, 9.8 wt%, and 11.5 wt%, respectively, all surpassing the U.S. Department of Energy 2025 target of 5.5 wt%. Among these, the LiCr codoped C8 nanocluster exhibited significantly improved adsorption energies of 0.31 eV, which is within the ideal range of 0.2–0.6 eV for faster adsorption–desorption kinetics. Furthermore, Gibbs free energy corrections to H2 adsorption energy at various temperatures and pressures revealed superior thermodynamic stability of the C8LiCr structure, suggesting its promising potential for practical hydrogen storage applications. These results highlight the significant impact of metal codoping as a powerful strategy for enhancing hydrogen uptake, stability, and overall H2 storage performance in nanostructured materials.

본 연구는 액체수소 저장 환경에서 사용되는 온도 센서 및 트랜스미터를 대상으로 신뢰성 평가를 수행하고자 FMEA(Failure Modes and Effects Analysis)와 QFD(Quality Function Deployment)를 적용하였다. 고장 심각도, 발생 가능도를 기준으로 주요 고장모드를 도출 하였으며, 사용자 요구사항과 인증기관 기준을 바탕으로 도출된 기술 요구 항목에 따라 QFD 분석을 수행하였다. FMEA 결과, Thermowell 의 풀림이 위험도 7점으로 주요 고장으로 식별되었다. QFD 분석 결과로는 내환경시험 항목으로 습도시험이 중요도 점수 5000점으로 가장 높은 중요도를 나타냈다. 이어서 수명 및 극저온 항목의 중요도도 높게 평가되어, 극저온 수소 환경에서의 센서 구성품 및 보호 구조체의 견고성과 환경 내구성 시험 전략의 중요성이 강조되었다.

본 연구는 수소 저장 용기의 지진 취약도 분석 시 요구되는 막대한 계산 자원 문제를 해결하고자, 기하학적 대칭성을 활용한 1/4 대칭 유한요소 모델(Quarter Model)을 개발하고 그 타당성을 검증하였다. 표준화된 AC 156 인공지진을 이용한 비선형 시간 이력 해석을 통해 Full Model과 응답을 비교한 결과, Quarter Model의 해석 시간을 Full Model의 20%를 가지고 해석을 완료하였으 며, 이에 따른 신뢰성 확보를 위해 최상단 변위를 통해 이를 검증하였을 때 0.13%의 미미한 오차를 보이며 변위 시간 이력 양상 역시 동일한 거동을 보이며 효율성 확보라는 연구 목표를 달성했다. 또한, 고유진동수, 강재와 콘크리트 주요부의 최대 응력에서 모두 높은 수준의 일치도를 보여 정량적 신뢰도를 입증하였다. 이를 통해 제안된 모델은 해석 정확도를 유지하면서 계산 비용을 획기적으로 절감 하는 효율적인 방법론임을 확인하였다. 다만 이는 균질 등방성 재료인 강재에 한정된 대칭 모델이며, 그 외의 재료 사용 시 추가적인 연구를 통한 모델 구축이 필요할 것으로 판단된다.

This study numerically investigated thermal-structural characteristics of a liquefied hydrogen (LH) storage cylinder with varying inner pressures and surrounding temperatures. A thermal-structure coupled analysis approach was used to predict the thermal-structural characteristics of the LH storage cylinder. For the simulation, the shape of the LH storage cylinder was simplified using SUS 316L and Carbon Fiber Reinforced Plastic (CFRP) materials. As a result, the inner pressure was a crucial factor determining the structural property (i.e., stress and deformation) of the LH storage cylinder. The high pressure led to increased stress and deformation. Additionally, the surrounding temperature affected the stress and deformation of the LH storage cylinder. For example, at a high surrounding temperature, the temperature gradient along the cylinder increased, thereby causing the occurrence of thermal stress. However, this temperature effect on the stress was negligible compared to the effect of inner pressure. The findings of this study will provide meaningful data for improving the structural safety of LH storage systems.

This study analyzed the methods and characteristics of hydrogen production, storage, transportation, charging, and use of hydrogen presented as an energy supply and demand system for hydrogen. Hydrogen produced by reforming hydrogen, which exists in the form of compounds, is essential to use metal materials exposed to the hydrogen atmosphere in storage and transportation. The mechanism of hydrogen embrittlement and damage cases, which are phenomena in which hydrogen atoms penetrate into the crystal lattice of metal and cause crack failure, were investigated. In addition, it is intended to present a research direction related to the evaluation of physical properties such as thermal conductivity, thermal expansion coefficient, and heat capacity, which are the criteria for selecting materials for hydrogen in a cryogenic environment.

The recent surge in energy consumption has sharply increased the use of fossil fuels, leading to a steep rise in the concentration of greenhouse gases in the atmosphere. Interest in hydrogen is growing to mitigate the issue of global warming. Currently, hydrogen energy is transported in the form of high-pressure gaseous hydrogen, which has the disadvantages of low safety and energy efficiency. To develop commercial hydrogen vehicles, liquid hydrogen should be utilized. Liquid hydrogen storage tanks have supports between the inner and outer cylinders to bear the weight of the cylinders and the liquid hydrogen. However, research on the design to improve the structural safety of these supports is still insufficient. In this study, through a thermal-structural coupled analysis of liquid hydrogen storage tanks, the model with three supports, which had the lowest maximum effective stress in the outer tank, inner tank, and supports as proposed in the author's previous research, was used to create analysis models based on the diameter of the supports. A structurally safe design for the supports was proposed.

In this study, numerical analysis was performed on a type IV hydrogen storage tank to analyze the temperature change of hydrogen inside the tank and the filling performance by changing the inlet nozzle outlet angle and the number of outlets. Considering the residual state of charge (SOC) inside the initial tank, the initial pressure was 10 MPa, and the temperature of hydrogen inside the tank and the SOC results were analyzed when hydrogen with a temperature of 233 K was introduced under the conditions of liner, wrap, and outside temperature of 298 K. The results of the analysis showed that the charging completion rate reached the charging limit pressure. The analysis showed that time of filling completion, when the filling limit pressure is reached, the SOC result is about 94% for all geometry change conditions, and the filling completion time increases by 5s as the number of outlets decreases. The temperature change of the wrap area at the end of filling is up to 3.6K, which shows that the outside air temperature has a negligible effect on the hydrogen temperature change inside the tank.

The government declared ‘2050 carbon neutrality’ as a national vision in October 2020 and subsequently pursued the establishment of a ‘2050 carbon neutrality scenario’ as a follow-up response. Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support structures for liquid hydrogen storage tanks, a thermal-structural coupled analysis technique was developed using Ansys Workbench. Analytical models were created based on the number and arrangement of supports to propose structurally safe support designs.

Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. However, the low density of hydrogen makes its storage an urgent technical problem for hydrogen energy development. Compared with the density of gas hydrogen, the density of liquid hydrogen is more than 1.5 times higher. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support for liquid hydrogen storage tank, technique of thermal-structural coupled analysis including geometry, mesh, and boundary condition were developed using Ansys workbench, and equivalent stress and deformation distributions were analyzed.

본 연구에서는 수소 자원의 활용도가 높아짐에 따라 수소 저장 용기의 내진 성능을 평가하기 위해 수소 저장 시설을 방문하여 현장 조사를 수행하였다. 외관 조사 중, 수조 저장 용기의 지지부에서 부식이 진행됨을 확인하였고, 이에 대한 대책안 으로 내부식성 재료인 CFRP로 대체하여 성능을 평가, 검증하였다. 이를 위해 현장 조사 결과를 바탕으로 상용 유한요소해석 프 로그램인 ABAQUS를 사용하였으며, 해석 결과 CFRP로 제작된 수소 저장 용기의 지지부는 강재 대비 약 12배 이상 뛰어난 성 능을 보였다. Hashin Damage Criteria를 기반으로 CFRP 지지부의 안전성 검토를 수행한 결과 최대 손상 지수가 0.065로 확인되 었다. 기초부 콘크리트의 경우, 쪼갬 및 휨 인장 응력에 대한 안전성을 검토하였으며, 허용 강도 대비 7~36%의 안전도를 보였 다. 이를 근거로 CFRP를 수소 저장 용기의 지지부에 적용하는 것은 합리적이며, 뛰어난 경제성을 보인다. 다만, 이러한 결과는 수치 해석에 의하므로 실규모 지진동 모사 시험을 통해 해석 모델의 신뢰성을 보충할 필요가 있다.

Mg81Ni19-8wt.% REO (oxides of Lanthanum and Cerium) alloys were successfully prepared using mechanical alloying method with Mg-Ni alloy and REO powder. Phase analysis, structural characterization, and microstructure imagine of the alloys were conducted using X-ray diffraction (XRD), metallurgical microscope, and transmission electron microscopy (TEM) methods. Multi-phase structures, including the primary phase of Mg2Ni and several secondary phases of Mg + Mg2Ni, MgNi-LaO, and MgNi-CeO, were found in in the as-cast Mg81Ni19- 8wt.% REO alloys. XRD and TEM results showed that Ce exhibits variable valence behavior at various stages, and the addition of REO promotes the nanocrystalline of the alloy. The hydrogen absorption capacity of ball-milled Mg81Ni19 and Mg81Ni19- 8wt.%REO alloy for 2 h at 343 K is 1.34 wt.% and 1.83 wt.%, which are much larger than 0.94 wt.% of as-cast Mg81Ni19 alloy. The addition of REO led to a decrease of the thermal decomposition temperature of the alloy hydride by approximately 20 K and a reduction of the activation energy of the hydrogen desorption reaction by 10% and 13%, respectively.

For the commercialization of hydrogen energy, a technology enabling safe storage and the transport of large amounts of hydrogen is needed. Porous materials are attracting attention as hydrogen storage material; however, their gravimetric hydrogen storage capacity (GHSC) at room temperature (RT) is insufficient for actual use. In an effort to overcome this limitation, we present a N-doped microporous carbon that contains large proportion of micropores with diameters below 1 nm and small amounts of N elements imparted by the nitrogen plasma treatment. The N-doped microporous carbon exhibits the highest total GHSC (1.59 wt%) at RT, and we compare the hydrogen storage capacities of our sample with those of metal alloys, showing their advantages and disadvantages as hydrogen storage materials.

In order to respond to environmental pollution, developed countries, including Korea, have begun to conduct research to utilize hydrogen energy. For mass transfer of hydrogen energy, storage as liquid hydrogen is advantageous, and in this case, the volume can be reduced to 1/800. As such, the transportation technology of liquefied hydrogen for ships is expected to be needed in the near future, but there is no commercialized method yet. This study is a study on the technology to test the performance of the components constituting the membrane type storage container in a cryogenic environment as a preparation for the above. It is a study to find a way to respond by analyzing in advance the problems that may occur during the shear test of adhesives. Through this study, the limitations of ISO4587 were analyzed, and in order to cope with this, the specimen was supplemented so that fracture occurred in the adhesive, not the adhesive gripper, by using stainless steel, a low-temperature steel, to reinforce the thickness. Based on this, shear evaluation was performed under conditions lowered to minus 243℃, and it was confirmed that the breaking strength was higher at cryogenic temperatures.

In this work, highly porous carbons were prepared by chemical activation of carbonized biomass-derived aerogels. These aerogels were synthesized from watermelon flesh using a hydrothermal reaction. After carbonization, chemical activation was conducted using potassium hydroxide to enhance the specific surface area and microporosity. The micro-structural properties and morphologies were measured by X-ray diffraction and scanning electron microscopy, respectively. The specific surface area and microporosity were investigated by N2/77 K adsorption-desorption isotherms using the Brunauer-Emmett-Teller method and Barrett-Joyner-Halenda equation, respectively. Hydrogen storage capacity was dependent on the activation temperature. The highest capacity of 2.7 wt% at 77 K and 1 bar was obtained with an activation temperature of 900°C.

A 90 wt% Mg-10 wt% NbF5 sample was prepared by mechanical milling under H2 (reactive mechanical grinding). Its hydriding and dehydriding properties were then examined. Activation of the 90 wt% Mg-10 wt% NbF5 sample was not required. At n=1, the sample absorbed 3.11 wt% H for 2.5 min, 3.55 wt% H for 5 min, 3.86 wt% H for 10 min, and 4.23 wt% H for 30 min at 593K under 12 bar H2. At n=1, the sample desorbed 0.17 wt% H for 5 min, 0.74 wt% H for 10 min, 2.03 wt% H for 30 min, and 2.81 wt% H for 60 min at 593K under 1.0 bar H2. The XRD pattern of the 90 wt% Mg-10 wt% NbF5 after reactive mechanical grinding showed Mg, β-MgH2 and small amounts of γ-MgH2, NbH2, MgF2 and NbF3. The XRD pattern of the 90 wt% Mg-10 wt% NbF5 dehydrided at n=3 revealed Mg, β-MgH2, a small amount of MgO and very small amounts of MgH2 and NbH2. The 90 wt% Mg-10 wt% NbF5 had a higher initial hydriding rate and a larger quantity of hydrogen absorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% Fe2O3, which were reported to have quite high hydriding rates and/or dehydriding rates. The 90 wt% Mg-10 wt% NbF5 had a higher initial dehydriding rate (after an incubation period) and a larger quantity of hydrogen desorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% Fe2O3.

The hydrogen storage properties of pure MgH2 were studied and compared with those of pure Mg. At the first cycle,pure MgH2 absorbed hydrogen very slowly at 573 K under 12 bar H2. The activation of pure MgH2 was completed after threehydriding-dehydriding cycles. At the 4th cycle, the pure MgH2 absorbed 1.55wt% H for 5 min, 2.04wt% H for 10 min, and3.59wt% H for 60 min, showing that the activated MgH2 had a much higher initial hydriding rate and much larger Ha (60min), quantity of hydrogen absorbed for 60 min, than did activated pure Mg. The activated pure Mg, whose activation wascompleted after four hydriding-dehydriding cycles, absorbed 0.80wt% H for 5 min, 1.25wt% H for 10 min, and 2.34wt%H for 60 min. The particle sizes of the MgH2 were much smaller than those of the pure Mg before and after hydriding-dehydriding cycling. The pure Mg had larger hydrogen quantities absorbed at 573K under 12 bar H2 for 60 min, Ha (60 min),than did the pure MgH2 from the number of cycles n=1 to n=3; however, the pure MgH2 had larger Ha (60 min) than didthe pure Mg from n=4 to n=6.