Articles de revues : « Absorption/desorption kinetic »

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Liu, Yongfeng, Jianjiang Hu, Zhitao Xiong, Guotao Wu et Ping Chen. « Improvement of the hydrogen-storage performances of Li–Mg–N–H system ». Journal of Materials Research 22, n^o 5 (mai 2007) : 1339–45. http://dx.doi.org/10.1557/jmr.2007.0165.

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Li2MgN2H2 can reversibly store more than 5.5 wt% hydrogen. However, the high activation energy of hydrogen desorption poses a kinetic barrier for low-temperature operation. In this work, the composition of the Li–Mg–N–H system has been modified by the partial substitution of Mg or Li by Na. The changes in structure and hydrogen absorption/desorption kinetics have been investigated. It was found that the peak temperature for hydrogen desorption was decreased by ∼10 °C, and that the hydrogen absorption/desorption isotherms were also significantly changed. Furthermore, the activation energy calculated by the Kissinger’s approach was reduced after the substitution of Mg or Li by Na. In addition, the different dehydrogenation structures were detected at different molar ratios of Mg, Li, and Na.

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Lívanský, Karel. « Kinetics of pH equilibration in solutions of hydrogen carbonate during bubbling with a gas containing carbon dioxide ». Collection of Czechoslovak Chemical Communications 50, n^o 3 (1985) : 553–58. http://dx.doi.org/10.1135/cccc19850553.

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The kinetics of the title process is approximated by differential equations based on kinetic and equilibrium data for carbon dioxide. The course of pH after a sudden change of the concentration of CO2 in the gas is calculated by numerical integration. The course of pH during absorption of CO2 is different from that during desorption. The course of pH during desorption calculated on the assumption that the rate of the noncatalysed hydration of CO2 is sufficient to ensure chemical equilibrium is in good agreement with experimental data from the literature. During absorption of CO2 in a solution of hydrogen carbonate, the chemical reaction rate is sometimes insufficient to ensure chemical equilibrium prior to pH measurement.

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Skryabina, N. E., Vladimir M. Pinyugzhanin et Daniel Fruchart. « Relationship between Micro-/Nano-Structure and Stress Development in TM-Doped Mg-Based Alloys Absorbing Hydrogen ». Solid State Phenomena 194 (novembre 2012) : 237–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.194.237.

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In the most recent years, MgH2has attracted considerable attention for reversible hydrogen storage purposes because of a large 7.6 w% H-uptake, single plateau reaction at low pressure and abundance of metal. If the Mg ↔ H reactions take place at rather high temperature (> 300°C), the kinetic remains very low. However, early transition metal based additives (Ti, V, Nb...) improve dramatically the kinetics of hydrogen absorption/desorption, while having no essential impact on the reversible sorption capacity. Systematic analysis of many experimental data led to question chemical, physical, mechanical... parameters contributing significantly to improve the kinetics of absorption/desorption. Besides, results of theoretical and numerical computation enlighten the impact of structural and mechanical parameters owing to the local bonds of Mg/MgH2with of TM elements, in terms of total energy and electronic structure. More specifically, we found highly relevant to consider 1 - the impact of the crystallite sizes of Mg and the TM-phase, 2 - the role of internal and external stresses, as well as 3 - the role of texture on the kinetics of hydrogen absorption/desorption. Apart the previous considerations, we like to underline the role of specific TM in trapping intermediately hydrogen thus forming TMHxprior initiating the Mg ↔ MgH2nucleation process.

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ITO, Koin, Kazuo AMANO et Hiroshi SAKAO. « Kinetic study on nitrogen absorption and desorption of molten iron. » Transactions of the Iron and Steel Institute of Japan 28, n^o 1 (1988) : 41–48. http://dx.doi.org/10.2355/isijinternational1966.28.41.

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Abdi, Mohammad, Ramin Ebrahimi et Ebad Bagherpour. « Improvement of Hydrogenation and Dehydrogenation Kinetics of As-Cast AZ91 Magnesium Alloy via Twin Parallel Channel Angular Extrusion Processing ». Crystals 12, n^o 10 (9 octobre 2022) : 1428. http://dx.doi.org/10.3390/cryst12101428.

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In the current study, Twin Parallel Channel Angular Extrusion (TPCAE) as a developed SPD processing technique is used to improve the hydrogen storage properties of AZ91 cast alloy. The processing is conducted at different temperatures, ranging from 340 °C down to 200 °C. The hydrogen absorption and desorption tests are conducted kinetically at three different temperatures, using a Sievert-type apparatus. Remarkable improvement in the absorption kinetic is achieved as a result of the TPCAE processing. A maximum absorption capacity of 6.1 wt.% within a time span of 2000 s is achieved for the sample with three passes of processing complemented at 250 °C. Also, the kinetic of dehydrogenation is improved significantly and complete desorption at 350 °C is achieved for all the processed samples within a time span of maximum 2500 s. By calculating the activation energy of hydrogenation and evaluating the microstructure changes, it is found that implementing sufficient thermomechanical work level along with applying the last pass of the process at lower temperature results in a reduction of the activation energy and improvement of the hydrogenation kinetic.

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Yang, Xinglin, Jiaqi Zhang, Quanhui Hou et Xintao Guo. « Regulation of Kinetic Properties of Chemical Hydrogen Absorption and Desorption by Cubic K2MoO4 on Magnesium Hydride ». Nanomaterials 12, n^o 14 (19 juillet 2022) : 2468. http://dx.doi.org/10.3390/nano12142468.

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Transition metal catalysts are particularly effective in improving the kinetics of the reversible hydrogen storage reaction for light metal hydrides. Herein, K2MoO4 microrods were prepared using a simple evaporative crystallization method, and it was confirmed that the kinetic properties of magnesium hydride could be adjusted by doping cubic K2MoO4 into MgH2. Its unique cubic structure forms new species in the process of hydrogen absorption and desorption, which shows excellent catalytic activity in the process of hydrogen storage in MgH2. The dissociation and adsorption time of hydrogen is related to the amount of K2MoO4. Generally speaking, the more K2MoO4, the faster the kinetic performance and the shorter the time used. According to the experimental results, the initial dehydrogenation temperature of MgH2 + 10 wt% K2MoO4 composite is 250 °C, which is about 110 °C lower than that of As-received MgH2. At 320 °C, almost all dehydrogenation was completed within 11 min. In the temperature rise hydrogen absorption test, the composite system can start to absorb hydrogen at about 70 °C. At 200 °C and 3 MPa hydrogen pressure, 5.5 wt% H2 can be absorbed within 20 min. In addition, the activation energy of hydrogen absorption and dehydrogenation of the composite system decreased by 14.8 kJ/mol and 26.54 kJ/mol, respectively, compared to pure MgH2. In the cycle-stability test of the composite system, the hydrogen storage capacity of MgH2 can still reach more than 92% after the end of the 10th cycle, and the hydrogen storage capacity only decreases by about 0.49 wt%. The synergistic effect among the new species MgO, MgMo2O7, and KH generated in situ during the reaction may help to enhance the absorption and dissociation of H2 on the Mg/MgH2 surface and improve the kinetics of MgH2 for absorption and dehydrogenation.

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Cova, F., F. C. Gennari et P. Arneodo Larochette. « CNT addition to the LiBH4–MgH2 composite : the effect of milling sequence on the hydrogen cycling properties ». RSC Advances 5, n^o 109 (2015) : 90014–21. http://dx.doi.org/10.1039/c5ra19504g.

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Somo, Thabang Ronny, Thabiso Carol Maponya, Moegamat Wafeeq Davids, Mpitloane Joseph Hato, Mykhaylo Volodymyrovich Lototskyy et Kwena Desmond Modibane. « A Comprehensive Review on Hydrogen Absorption Behaviour of Metal Alloys Prepared through Mechanical Alloying ». Metals 10, n^o 5 (26 avril 2020) : 562. http://dx.doi.org/10.3390/met10050562.

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Hydride-forming alloys are currently considered reliable and suitable hydrogen storage materials because of their relatively high volumetric densities, and reversible H2 absorption/desorption kinetics, with high storage capacity. Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Lately, common strategies, such as spark plasma sintering, mechanical alloying, melt spinning, surface modification and alloying with other elements have been exploited, in order to overcome kinetic barriers. Through these techniques, improvements in hydriding kinetics has been achieved, however, it is still far from that required in practical application. In this review, we provide a critical overview on the effect of mechanical alloying of various metal hydrides (MHs), ranging from binary hydrides (CaH2, MgH2, etc) to ternary hydrides (examples being Ti-Mn-N and Ca-La-Mg-based systems), that are used in solid-state hydrogen storage, while we also deliver comparative study on how the aforementioned alloy preparation techniques affect H2 absorption/desorption kinetics of different MHs. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques. The reaction mechanism, surface modification techniques and hydrogen storage properties of these various MHs were discussed in detail. We also discussed the remaining challenges and proposed some suggestions to the emerging research of MHs. Based on the findings obtained in this review, the combination of two or more compatible techniques, e.g., synthesis of metal alloy materials through mechanical alloying followed by surface modification (metal deposition, metal-metal co-deposition or fluorination), may provide better hydriding kinetics.

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Kim, Kyeong Il, et Tae Whan Hong. « Evaluations of Hydrogen Properties on MgH_x-Nb₂O₅ Composite by Mechanical Alloying ». Materials Science Forum 620-622 (avril 2009) : 9–12. http://dx.doi.org/10.4028/www.scientific.net/msf.620-622.9.

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The most attractive way to storage hydrogen safely and economically is in metal hydrides. In particular, magnesium has attracted much interest since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve the kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogen absorption properties of Mg. The effect of transition oxides, such as Nb2O5 on the kinetics of the Mg hydrogen absorption reaction was investigated. MgHx-Nb2O5 composites have been synthesized by hydrogen induced mechanical alloying. The powder synthesized was characterized by XRD, SEM, EDX, BET and simultaneous TG/DSC analysis. The hydrogenation behaviors were evaluated by using an automatic Sievert’s type PCT apparatus. Absorption/desorption kinetics and PCI of MgHx catalyzed with 5wt.%Nb2O5(as-received), 5wt.%Nb2O5(30min. milled) are determined at 423, 473, 523, 573, 623K.

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HUTCHINGS, K., M. WILSON, P. LARSEN et R. CUTLER. « Kinetic and thermodynamic considerations for oxygen absorption/desorption using cobalt oxide ». Solid State Ionics 177, n^o 1-2 (16 janvier 2006) : 45–51. http://dx.doi.org/10.1016/j.ssi.2005.10.005.

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Giraldo, Carolina, Franklin Ferraro, C. Z. Hadad, Olimpo García-Beltrán et Edison Osorio. « Structural, thermodynamic and kinetic factors in the desorption/absorption of a hydrogen molecule in the M3AlH10−xNa (M = Be or Mg ; x = 0 or 2) hydrides ». New Journal of Chemistry 43, n^o 46 (2019) : 18041–48. http://dx.doi.org/10.1039/c9nj02326g.

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In the context of the design and study of new materials for hydrogen storage, the thermodynamic and kinetic-mechanistic factors for the desorption/absorption of a hydrogen molecule in the M₃AlH_10−xNa (M = Be or Mg; x = 0 or 2) hydrides are evaluated.

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Shao, Huai Yu, et Xing Guo Li. « Kinetics and Thermodynamics of Nanostructured Mg-Based Hydrogen Storage Materials Synthesized from Metal Nanoparticles ». Advanced Materials Research 924 (avril 2014) : 189–92. http://dx.doi.org/10.4028/www.scientific.net/amr.924.189.

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Mg, Ni, Co, Cu and Fe nanoparticles with a particle size of 30-300 nm were synthesized by hydrogen plasma metal reaction method. Nanostructured Mg-based hydrogen storage materials (Mg-H, Mg-Ni-H, Mg-Co-H, Mg-Cu-H and Mg-Fe-H systems) were synthesized from these metal nanoparticles. In this work, the kinetic and thermodynamic properties of these nanostructured hydrogen storage materials were studied. It was found that nanostructure could significantly enhance the hydrogen absorption kinetics but the thermodynamics (desorption enthalpy and entropy) does not change with downsizing in the size range of 50 to 300 nm.

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Huang, Shuiming, Huihui Song, Yuhu Hu, Kai Xu, Chao Zhou et Xueling Hou. « Double-Win Properties Response of Mechanical and Hydrogen Absorption in Melt-Spun Ti-Zr-Ni-Cr Amorphous Metals ». Journal of Electronic Materials 51, n^o 4 (20 janvier 2022) : 1608–14. http://dx.doi.org/10.1007/s11664-021-09386-6.

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AbstractThe effect of spinning rates on mechanical properties and hydrogen absorption/desorption properties of Ti47Zr31Ni14Cr8 amorphous ribbons have been investigated in the present work. A fully amorphous structure was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis of the ribbons obtained from spinning rates of 30 m s−1 to 45 m s−1. The uniformity of amorphous ribbons and their mechanical properties were improved with the increase in the spinning rate. Scanning electron microscopy (SEM) revealed that the fracture surface of amorphous ribbons had a cleavage feature and vein-like pattern when the spinning rates were 30 m s−1 and 45 m s−1, respectively. Because of the influence of flow units on the kinetic process of hydrogen absorption, the hydrogenation kinetics and hydrogen desorption capacity of amorphous ribbons were enhanced with the increased spinning rates. After the amorphous ribbons absorbed a large amount of hydrogen, ZrH2, TiH2, and (ZrTi)2Ni7 crystalline phases were formed from the amorphous matrix. Hydrogen promotes amorphous phase decomposition and the crystallinity of the new phases led to deterioration of the mechanical properties.

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Zhang, Jianwei, Pengcheng Li, Gang Huang, Weiguang Zhang, Jutao Hu, Haiyan Xiao, Jian Zheng et al. « Superior Hydrogen Sorption Kinetics of Ti0.20Zr0.20Hf0.20Nb0.40 High-Entropy Alloy ». Metals 11, n^o 3 (12 mars 2021) : 470. http://dx.doi.org/10.3390/met11030470.

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High entropy alloys (HEAs) are composed of multiple main metal elements and have attracted wide attention in various fields. In this study, a novel Ti0.20Zr0.20Hf0.20Nb0.40 HEA was synthesized and its hydrogenation properties were studied, including sorption thermodynamics and hydrogen absorption/desorption kinetics. The maximum hydrogen absorption capacity was 1.5 H/atom at 573 K. X-ray diffraction (XRD) analysis indicated that the crystal structure of Ti0.20Zr0.20Hf0.20Nb0.40 HEA transformed from body-centered cubic (BCC) to body-centered tetragonal (BCT) with increasing hydrogen content, and to face-centered cubic (FCC) after hydrogen absorption to saturation. As a multi-principal element alloy, the Ti0.20Zr0.20Hf0.20Nb0.40 HEA possesses unique hydrogen absorption characteristics. The hydrogen absorption platform pressure rises gradually with the increase of the hydrogen absorption amount, which is caused by multiple kinds of BCT intermediate hydrides with consecutively increasing c/a. The full hydrogen absorption of the Ti0.20Zr0.20Hf0.20Nb0.40 HEA was completed in almost 50 s, which is faster than that of the reported hydrogen storage alloys in the literature. The experimental results demonstrate that the Ti0.20Zr0.20Hf0.20Nb0.40 HEA has excellent kinetic properties, unique thermodynamic hydrogen absorption performance, as well as a low plateau pressure at room temperature.

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He, Hui, Huaqin Kou, Wenhua Luo, Tao Tang, Zhiyong Huang, Ge Sang, Guanghui Zhang, Jingwen Ba et Meng Liu. « Structural and Kinetic Hydrogen Sorption Properties of Zr0.8Ti0.2Co Alloy Prepared by Ball Milling ». Scanning 2018 (2018) : 1–13. http://dx.doi.org/10.1155/2018/5736742.

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The effects of ball milling on the hydrogen sorption kinetics and microstructure of Zr0.8Ti0.2Co have been systematically studied. Kinetic measurements show that the hydrogenation rate and amount of Zr0.8Ti0.2Co decrease with increasing the ball milling time. However, the dehydrogenation rate accelerates as the ball milling time increases. Meanwhile, the disproportionation of Zr0.8Ti0.2Co speeds up after ball milling and the disproportionation kinetics is clearly inclined to be linear with time at 500°C. It is found from X-ray powder diffraction (XRD) results that the lattice parameter of Zr0.8Ti0.2Co gradually decreases from 3.164 Å to 3.153 Å when the ball milling time extends from 0 h to 8 h, which is mainly responsible for the hydrogen absorption/desorption behaviors. In addition, scanning electron microscope (SEM) images demonstrate that the morphology of Zr0.8Ti0.2Co has obviously changed after ball milling, which is closely related to the hydrogen absorption kinetics. Besides, high-resolution transmission electron microscopy (HRTEM) images show that a large number of disordered microstructures including amorphous regions and defects exist after ball milling, which also play an important role in hydrogen sorption performances. This work will provide some insights into the principles of how to further improve the hydrogen sorption kinetics and disproportionation property of Zr0.8Ti0.2Co.

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BURKHOLDER, L., D. STACCHIOLA et W. T. TYSOE. « KINETIC AND REACTIVE PROPERTIES OF ETHYLENE ON CLEAN AND HYDROGEN-COVERED Pd(111) ». Surface Review and Letters 10, n^o 06 (décembre 2003) : 909–16. http://dx.doi.org/10.1142/s0218625x03005712.

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Several molecular adsorption states are identified following ethylene adsorption on clean and hydrogen-covered Pd(111) using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). Di-σ-bonded ethylene forms on clean Pd(111) desorbing with an activation energy of 80 kJ/mol at low coverages. The strong intermolecular lateral interactions considerably reduce the desorption temperature at higher coverages. Π-bonded ethylene is formed on hydrogen-covered Pd(111), where the proportion of π-bonded species increases with hydrogen coverage. This species converts to the more stable di-σ-bonded species on heating. Ethane formation is detected in TPD from hydrogen-precovered Pd(111), which is predominantly formed by reaction with π-bonded ethylene.

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Bouzidi, Anis, Laetitia Laversenne, Guilherme Zepon, Gavin Vaughan, Vivian Nassif et Claudia Zlotea. « Hydrogen Sorption Properties of a Novel Refractory Ti-V-Zr-Nb-Mo High Entropy Alloy ». Hydrogen 2, n^o 4 (27 octobre 2021) : 399–413. http://dx.doi.org/10.3390/hydrogen2040022.

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High entropy alloys belong to a new and promising class of functional materials for solid-state hydrogen storage. In this context, a novel single-phase body centered cubic (bcc) high entropy alloy Ti0.30V0.25Zr0.10Nb0.25Mo0.10 was prepared. The physicochemical and hydrogen sorption properties have been determined by both laboratory and large-scale facilities. This alloy can quickly absorb hydrogen up to 2.0 H/M (2.8 wt.%) at room temperature and forms a face centered cubic (fcc) hydride, as proven by synchrotron X-ray diffraction. The Pressure–Composition Isotherm and in situ neutron diffraction during hydrogen/deuterium desorption reaction suggest that the alloy experiences a reversible single step phase transition (bcc↔fcc). PDF analysis from X-ray total scattering data points out that the hydride phase possesses an average fcc structure with random atoms distribution and small lattice distortion. Despite an initial small fading of the capacity, the alloy withstands 20 absorption/desorption cycling without phase decomposition, as demonstrated by kinetic measurements coupled with X-ray diffraction and microstructural study by SEM-EDS. Moreover, the complete hydrogen absorption occurs in less than 30 s at room temperature and the kinetic improves during cycling.

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Shimohata, Yuta, Yoshiki Hamamoto, Kengo Nishi et Katsuaki Tanabe. « Improved kinetic model of hydrogen absorption and desorption in titanium with subsurface transport ». Fusion Engineering and Design 173 (décembre 2021) : 112833. http://dx.doi.org/10.1016/j.fusengdes.2021.112833.

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Garcı́a-Gómez, C., G. Carbonell et J. V. Tarazona. « Modelling the absorption and desorption of cadmium on paper pulp using kinetic approaches ». Chemosphere 55, n^o 6 (mai 2004) : 869–78. http://dx.doi.org/10.1016/j.chemosphere.2003.11.039.

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Martinez, Alejandro, Darío Peña et Daniela Bellon. « Study of the Influence of the V in the Zr₂Fe Alloy from Hydrogen Storage on Thermodynamic Properties ». Journal of Metastable and Nanocrystalline Materials 31 (janvier 2019) : 22–29. http://dx.doi.org/10.4028/www.scientific.net/jmnm.31.22.

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Hydrogen storage in its solid state is one of the main challenges for mobile and stationary applications. Some metal hydrides are potential candidates for energy storage. This is an experimental research, which represents a contribution to the study of Hydrogen storage in its solid state, by studying the influence of the proportional substitution of V for Zr in the stoichiometric ratio Zr2-XVXFe (X=0.0, 0.1 y 0.2). Results indicate that the synthesis process generates a multi-phase type microstructure, and the absorption and desorption kinetic is less than 5 minutes at room temperature, in line with the parameters established by the United States Department of Energy; however, it is clear that the desorption capacity decreases.

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Lyu, Jinzhe, Andrey Lider et Viktor Kudiiarov. « Using Ball Milling for Modification of the Hydrogenation/Dehydrogenation Process in Magnesium-Based Hydrogen Storage Materials : An Overview ». Metals 9, n^o 7 (9 juillet 2019) : 768. http://dx.doi.org/10.3390/met9070768.

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Magnesium-based hydrogen storage materials are considered to be one of the most promising solid-state hydrogen storage materials due to their large hydrogen storage capacity and low cost. However, slow hydrogen absorption/desorption rate and excessive hydrogen absorption/desorption temperature limit the application of magnesium-based hydrogen storage materials. The present paper reviews recent progress in improving the hydrogen storage properties by element substitution and additives. Ball milling is the promising technology for preparing magnesium-based hydrogen storage materials. The research and development of approaches for modifying magnesium-based hydrogen storage materials prepared by ball milling is systematically expounded. It is concluded that ball milling can significantly improve the kinetic and electrochemical properties of magnesium-based hydrogen storage materials and increase the hydrogen storage capacity. In the future, the research of magnesium-based hydrogen storage materials should be developed in terms of hydrogen storage mechanism, computer design of materials and development of a more optimized catalytic system.

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Namba, Kazuhiro, Shohei Ogura, Satoshi Ohno, Wen Di, Koichi Kato, Markus Wilde, Ivo Pletikosić, Petar Pervan, Milorad Milun et Katsuyuki Fukutani. « Acceleration of hydrogen absorption by palladium through surface alloying with gold ». Proceedings of the National Academy of Sciences 115, n^o 31 (13 juillet 2018) : 7896–900. http://dx.doi.org/10.1073/pnas.1800412115.

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Enhancement of hydrogen (H) absorption kinetics improves the performance of hydrogen-purifying membranes and hydrogen-storage materials, which is necessary for utilizing hydrogen as a carbon-free energy carrier. Pd–Au alloys are known to show higher hydrogen solubility than pure Pd. However, the effect of Au on the hydrogen penetration from the surface into the subsurface region has not been clarified so far. Here, we investigate the hydrogen absorption at Pd–Au surface alloys on Pd(110) by means of thermal desorption spectroscopy (TDS) and hydrogen depth profiling with nuclear reaction analysis (NRA). We demonstrate that alloying the Pd(110) surface with submonolayer amounts of Au dramatically accelerates the hydrogen absorption. The degree of acceleration shows a volcano-shaped form against Au coverage. This kinetic enhancement is explained by a reduced penetration barrier mainly caused by a destabilization of chemisorbed surface hydrogen, which is supported by density-functional-theory (DFT) calculations. The destabilization of chemisorbed surface hydrogen is attributed to the change of the surface electronic states as observed by angle-resolved photoemission spectroscopy (ARPES). If generalized, these discoveries may lead to improving and controlling the hydrogen transport across the surfaces of hydrogen-absorbing materials.

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SUN, HONG-FEI, SHU-JIN LIANG, ZHENG-XING YU et WEN-BIN FANG. « FABRICATION AND HYDROGEN STORAGE PROPERTY OF Mg-3Ni-2MnO2-nCNTS NANOCOMPOSITES ». International Journal of Modern Physics B 23, n^o 06n07 (20 mars 2009) : 1467–72. http://dx.doi.org/10.1142/s0217979209061111.

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Mg -3 Ni -2 MnO 2 hydrogen storage nanocomposites added with different composition (1%~4%) carbon nanotubes (CNTs) were prepared by mechanical milling under the atmosphere of hydrogen. Different mechanical milling process parameter has been discussed in this paper. Study on hydrogen storage ability of Mg -3 Ni -2 MnO 2- nCNTs with different composition carbon nanotubes has been carried out. The result show that Mg -3 Ni -2 MnO 2- nCNTs excellent heat conductivity and good hydrogen storage (more than 6%vol) ability, the CNTs improve the mass transfer and heat transfer properties of the Mg -3 Ni -2 MnO 2, thus enhancing the kinetic property of hydrogen absorption and desorption of the hydrogen storage nanocomposites, and raising the hydrogen storage capacity. Due to the addition of the carbon nanotubes, the milling stress in the process of preparing the Mg -based namocomposites is reduced, the components can be closely bonded easily, and the additives can play better catalytic roles enhancing the kinetic property of hydrogen absorption and desorption of the hydrogen storage nanocomposites, and raising the hydrogen storage capacity. Due to the addition of the carbon nanotubes, the milling stress in the process of preparing the Mg -based namocomposites is reduced, the components can be closely bonded easily, and the additives can play better catalytic roles.

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Jain, Ankur, Shivani Agarwal et Takayuki Ichikawa. « Catalytic Tuning of Sorption Kinetics of Lightweight Hydrides : A Review of the Materials and Mechanism ». Catalysts 8, n^o 12 (11 décembre 2018) : 651. http://dx.doi.org/10.3390/catal8120651.

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Hydrogen storage materials have been a subject of intensive research during the last 4 decades. Several developments have been achieved in regard of finding suitable materials as per the US-DOE targets. While the lightweight metal hydrides and complex hydrides meet the targeted hydrogen capacity, these possess difficulties of hard thermodynamics and sluggish kinetics of hydrogen sorption. A number of methods have been explored to tune the thermodynamic and kinetic properties of these materials. The thermodynamic constraints could be resolved using an intermediate step of alloying or by making reactive composites with other hydrogen storage materials, whereas the sluggish kinetics could be improved using several approaches such as downsizing and the use of catalysts. The catalyst addition reduces the activation barrier and enhances the sorption rate of hydrogen absorption/desorption. In this review, the catalytic modifications of lightweight hydrogen storage materials are reported and the mechanism towards the improvement is discussed.

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Edridge, John L., Kati Freimann, Daren J. Burke et Wendy A. Brown. « Surface science investigations of the role of CO 2 in astrophysical ices ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 371, n^o 1994 (13 juillet 2013) : 20110578. http://dx.doi.org/10.1098/rsta.2011.0578.

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We have recorded reflection–absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) data for a range of CO 2 -bearing model astrophysical ices adsorbed on a graphitic dust grain analogue surface. Data have been recorded for pure CO 2 , for CO 2 adsorbed on top of amorphous solid water, for mixed CO 2 :H 2 O ices and for CO 2 adsorbed on top of a mixed CH 3 OH:H 2 O ice. For the TPD data, kinetic parameters for desorption have been determined, and the trapping behaviour of the CO 2 in the H 2 O (CH 3 OH) ice has been determined. Data of these types are important as they can be used to model desorption in a range of astrophysical environments. RAIR spectra have also shown the interaction of the CO 2 with H 2 O and CH 3 OH and can be used to compare with astronomical observations, allowing the accurate assignment of spectra.

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Babkin, A. V., E. A. Neskoromnaya, I. V. Burakova, A. E. Burakov, E. S. Mkrtchyan et A. G. Tkachev. « Sorption-desorption properties of graphene oxide/polyhydroquinone nanocomposite in the extraction of rare earth elements Sm (III) ions from acetic-acetate buffer systems ». Perspektivnye Materialy 1 (2022) : 34–48. http://dx.doi.org/10.30791/1028-978x-2022-1-34-48.

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The paper describes the extraction of the rare earth element Sm3+ from aqueous buffer systems by a graphene-based nanostructured composite, modified using an organic polymer – polyhydroquinone. The authors determined the important parameters of the sorption-desorption of Sm3+ ions on a new nanocomposite “graphene oxide/polyhydroquinone” during a batch test, such as: initial concentration, the sorbent weight, pH of the solution, sorption rate constants, maximum sorption capacity of the nanocomposite, percentage sorption and desorption, entropy and enthalpy of the Sm3+ extraction process. The kinetic, isothermal and thermodynamic dependences allowed to propose of the Sm3+ ions adsorption mechanisms. The kinetic data were processed by pseudo-first- and second-order, Elovich and intraparticle diffusion models, and adsorption isotherms — using the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich equations. As a result of kinetic studies, the contact time of the samarium adsorption was determined — 15 min, while the sorption capacity was 100 mg·g–1. It was found that the absorption of Sm3+ ions proceeds by a mixed diffusion mechanism and limited by the interaction “samarium ions : sorbent functional groups”. According to the Langmuir model, the maximum sorbent sorption capacity was 333.3 mg·g–1. Thus, the high efficiency of the developed graphene oxide/polyhydroquinone nanocomposite for purification of aqueous media from rare earth elements was confirmed.

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Li, Xian Fa, et Xue Gang Luo. « Adsorption of Cd(II) and Pb(II) from Wastewater onto Porous Lignin Beads ». Advanced Materials Research 549 (juillet 2012) : 423–27. http://dx.doi.org/10.4028/www.scientific.net/amr.549.423.

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In this paper, a crosslinked porous lignin beads (PLB) as adsorbent was adopted to adsorb toxic Pb2+ and Cd2+ ions from aqueous solutions. The pore structure and surface morphology of PLB were characterized by by a variety of techniques. The influences of pH, contact time, initial metal ions concentration, temperatures were investigated. The results showed that the adsorption of both heavy metal ions increases with pH. The adsorption equilibrium data under different temperature can be successfully described by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The Langmuir adsorption model showed the best fit to the adsorption data of Cd2+ and D-R model fits best to the adsorption data of Pb2+. The results obtained also indicated that the adsorption of Cd2+ and Pb2+ increased with increasing temperature indicating endothermic nature of the adsorption process. The kinetic study showed that Cd2+ adsorption followed pseudo-second order rate kinetics and Pb2+ adsorption followed pseudo-first order rate kinetics. Cd2+ adsorption on PLB was mainly through the chemisorption mechanism (ED-R between 12.62 kJ•mol-1 and 16.20 kJ•mol-1) while physical and chemical absorption coexistence was observed to Pb2+ adsorption. Desorption studies revealed that the desorption rate increased with increasing hydrochloric acid concentration and could finally reach 94 % and 85.1 % for Cd2+ and Pb2+, respectively, by adding 3 mol/L of HCl.

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Tal-Gutelmacher, E., Dan Eliezer et Thomas Boellinghaus. « Hydrogen's Absorption/Desorption Behavior in Gaseous-Phase Charged Duplex-Annealed Ti-6Al-4V Alloy ». Materials Science Forum 546-549 (mai 2007) : 1367–72. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1367.

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Ti-6Al-4V alloy has proven to be technically superior and cost-effective materials for a wide variety of aerospace, industrial, marine and commercial applications. The mechanical properties of Ti-6Al-4V are very sensitive to the microstructure obtained after the thermo-mechanical treatment. The duplex structures provide good tensile ductility, fatigue strength, resistance to microcrack growth and crack initiation, and are often used in demanding fatigue critical tasks. However, although Ti-6A-4V is considered to be reasonably resistance to chemical attack, severe problems can arise when it comes in contact with hydrogen-containing environments due to its susceptibility to hydrogen embrittlement. The objective of this paper is to investigate the absorption and desorption behavior of external hydrogen on a duplex-annealed Ti-6Al-4V alloy. While investigating the desorption profile, we seek to better understand the thermodynamics and the kinetic nature of the interaction between traps and hydrogen atoms, with specific emphasis on the investigation of the impact of these interactions on the microstructure of the studied aerospace applicative titanium alloy. In order to achieve these goals, thermal desorption spectroscopy (TDS) was applied and the data obtained from this analysis was supported by a variety of other experimental techniques, such as LECO hydrogen determinator, XRD and microstructure investigations by means of optic and electronic microscopy. Hydrogen was found to influence significantly the microstructure of the alloy. The process of hydrogen evolution was found to be a very complex process, being affected mainly by the phase transformations that may occur during the thermal analysis.

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Wai, Saw Khun, Chikezie Nwaoha, Chintana Saiwan, Raphael Idem et Teeradet Supap. « Absorption heat, solubility, absorption and desorption rates, cyclic capacity, heat duty, and absorption kinetic modeling of AMP–DETA blend for post–combustion CO2 capture ». Separation and Purification Technology 194 (avril 2018) : 89–95. http://dx.doi.org/10.1016/j.seppur.2017.11.024.

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Liu, Yongfeng, Kai Zhong, Kun Luo, Mingxia Gao, Hongge Pan et Qidong Wang. « Size-Dependent Kinetic Enhancement in Hydrogen Absorption and Desorption of the Li−Mg−N−H System ». Journal of the American Chemical Society 131, n^o 5 (11 février 2009) : 1862–70. http://dx.doi.org/10.1021/ja806565t.

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Varakin, V. N., et A. P. Simonov. « UV Laser Induced Chemistry of Adsorbed Dimethylcadmium ». Laser Chemistry 12, n^o 3-4 (1 janvier 1992) : 181–97. http://dx.doi.org/10.1155/lc.12.181.

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The UV laser chemistry of dimethylcadmium (DMCd) either chemisorbed at 297 K on n-type Si(100) with native oxide or physisorbed at 150 K on a photodeposited cadmium film has been studied by using mass spectrometry of desorbed species. A XeCl laser induced the heterogeneous fragmentation of these chemisorbed molecules as well as the desorption of DMCd, Cd, and CH3. The resonant absorption of a KrCl laser radiation by adsorbed DMCd led to their photolysis and the ejection of DMCd and its fragments in both neutral and ionic forms. The kinetic, laser fluence, and time-of-flight dependences of desorbed species have been measured to elucidate the mechanisms of the dissociative and desorption processes either induced by lasers or occurring spontaneously. The effects of these lasers on chemisorbed DMCd as well as KrCl laser assisted processes in chemisorbed and physisorbed molecules have been compared.

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Hang, Zhouming, Zhencan Hu, Xuezhang Xiao, Ruicheng Jiang et Meng Zhang. « Enhancing Hydrogen Storage Kinetics and Cycling Properties of NaMgH3 by 2D Transition Metal Carbide MXene Ti3C2 ». Processes 9, n^o 10 (22 septembre 2021) : 1690. http://dx.doi.org/10.3390/pr9101690.

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Metal hydrides have recently been proposed for not only hydrogen storage materials but also high-efficiency thermal storage materials. NaMgH3 contains a considerable theoretical thermal storage density of 2881 kJ/kg. However, its sluggish de/re-hydrogenation reaction kinetics and poor cycling stability exhibit unavailable energy efficiency. Doping with active catalyst into NaMgH3 is deemed to be a potential strategy to mitigate these disadvantages. In this work, the enhancement of de/re-hydrogenation kinetics and cycling properties of NaMgH3 is investigated by doping with lamellar-structure 2D carbon-based MXene, Ti3C2. Results shows that introducing 7 wt.% Ti3C2 is proved to perform excellent catalytic efficiency for NaMgH3, dramatically reducing the two-step hydrogen desorption peak temperatures (324.8 and 345.3 °C) and enhancing the de/re-hydrogenation kinetic properties with the hydrogen desorption capacity of 4.8 wt.% H2 within 15 min at 365 °C and absorption capacity of 3.5 wt.% H2 within 6 s. Further microstructure analyses reveal that the unique lamellar-structure of Ti3C2 can separate the agglomerated NaMgH3 particles homogeneously and decrease the energy barriers of two-step reaction of NaMgH3 (114.08 and 139.40 kJ/mol). Especially, lamellar-structure Ti3C2 can improve the reversibility of hydrogen storage of NaMgH3, rendering 4.6 wt.% H2 capacity remained after five cycles. The thermal storage density of the composite is determined to be 2562 kJ/kg through DSC profiles, which is suitable for thermal energy storage application.

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Révész, Ádám, Dániel G. Fodor, György Krállics, Tony Spassov et Marcell Gajdics. « Structural and hydrogen storage characterization of nanocrystalline magnesium synthesized by ECAP and catalyzed by different nanotube additives ». REVIEWS ON ADVANCED MATERIALS SCIENCE 60, n^o 1 (1 janvier 2021) : 884–93. http://dx.doi.org/10.1515/rams-2021-0056.

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Abstract Ball-milled nanocrystalline Mg powders catalyzed by TiO2 powder, titanate nanotubes and carbon nanotubes were subjected to intense plastic deformation by equal-channel angular pressing. Microstructural characteristics of these nanocomposites have been investigated by X-ray diffraction. Microstructural parameters, such as the average crystallite size, the average dislocation density and the average dislocation distance have been determined by the modified Williamson–Hall analysis. Complementary hydrogen desorption and absorption experiments were carried out in a Sieverts’ type apparatus. It was found that the Mg-based composite catalyzed by titanate nanotubes exhibits the best overall H-storage performance, reaching 7.1 wt% capacity. The hydrogenation kinetic curves can be fitted by the contracting volume function for all the investigated materials. From the fitted parameters, it is confirmed that the titanate nanotube additive results in far the best kinetic behavior, including the highest hydride front velocity.

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Lyu, Jinzhe, Viktor Kudiiarov et Andrey Lider. « Experimentally Observed Nucleation and Growth Behavior of Mg/MgH2 during De/Hydrogenation of MgH2/Mg : A Review ». Materials 15, n^o 22 (12 novembre 2022) : 8004. http://dx.doi.org/10.3390/ma15228004.

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With the increasing energy crisis and environmental problems, there is an urgent need to seek an efficient renewable energy source, and hydrogen energy is considered one of the most promising energy carriers. Magnesium is considered a promising hydrogen storage material due to its high hydrogen storage density, abundant resources, and low cost. However, sluggish kinetic performance is one of the bottlenecks hindering its practical application. The kinetic process of hydrogenation/dehydrogenation can be influenced by both external and internal factors, including temperature, pressure, elementary composition, particle size, particle surface states, irregularities in particle structure, and hydrogen diffusion coefficient. The kinetic performance of the MgH2/Mg system can be effectively improved by more active sites and nucleation centers for hydrogen absorption and desorption. Herein, we briefly review and discuss the experimentally observed nucleation and growth behavior of Mg/MgH2 during de/hydrogenation of MgH2/Mg. In particular, the nucleation and growth behavior of MgH2 during the hydrogenation of Mg is discussed from the aspect of temperature and hydrogen pressure.

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Lobo, Ntumba, Alicja Klimkowicz et Akito Takasaki. « EFFECT OF TiO2 + Nb2O5 + TiH2 CATALYSTS ON HYDROGEN STORAGE PROPERTIES OF MAGNESIUM HYDRIDE ». MRS Advances 5, n^o 20 (2020) : 1059–69. http://dx.doi.org/10.1557/adv.2020.29.

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AbstractMagnesium hydride (MgH2) is a prospective material for the storage of hydrogen in solid materials. It can also be envisaged for thermal energy storage applications since it has the potential to reversibly absorb hydrogen in large quantities, theoretically up to 7.6% by weight. Also, MgH2 is inexpensive, abundant, and environmentally friendly, but it operates at relatively high temperatures, and the kinetics of the hydrogenation process is slow. Mechanical milling and the addition of catalyst can alter the activation energy and the kinetic properties of the MgH2 phase. It is known that the addition of titanium hydride (TiH2) lowers the enthalpy and enhances the absorption of hydrogen from MgH2, titanium oxide (TiO2) enhances the desorption of hydrogen and niobium oxide (Nb2O5) enhances the absorption of hydrogen. In this work, the influences of the catalysts, as mentioned above on the properties of MgH2, were studied. The samples were analyzed in terms of crystal and microstructure as well as hydrogen storage properties using a pressure-composition isotherm (PCT)measurement. It has been found that the simultaneous addition of the three catalysts enhances the properties of MgH2, lowers the activation energy and operating temperature, increases the rate of intake and release of hydrogen, and provides the largest gravimetric hydrogen storage capacity.

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Hamborg, Espen S., et Geert F. Versteeg. « Absorption and desorption mass transfer rates in chemically enhanced reactive systems. Part II : Reverse kinetic rate parameters ». Chemical Engineering Journal 198-199 (août 2012) : 561–70. http://dx.doi.org/10.1016/j.cej.2012.03.051.

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Cortez, Juan J., Facundo J. Castro, Horacio E. Troiani, Santiago A. Pighin et Guillermina Urretavizcaya. « Kinetic improvement of H2 absorption and desorption properties in Mg/MgH2 by using niobium ethoxide as additive ». International Journal of Hydrogen Energy 44, n^o 23 (mai 2019) : 11961–69. http://dx.doi.org/10.1016/j.ijhydene.2019.03.096.

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Li, Ding Long, Jing Si Tian, Hou Hu Zhang, Yi Min Zhang et Yue Xiang Gao. « Kinetic Study on Phosphorus Adsorption, Phosphorus Desorption, Nitrification, and Denitrification by Using Mineralized Refuse ». Advanced Materials Research 340 (septembre 2011) : 461–66. http://dx.doi.org/10.4028/www.scientific.net/amr.340.461.

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The mineralized refuse has a well particle size distribution and is similar asirregularly polyhedron with the high contents of Fe, Al, and Ca, which might be thephosphorus pool. The absorption and desorption of phosphorus, nitrification, and denitrification in the mineralized refuse and clay has been investigated by using batch incubation, respectively. The variation of phosphorous adsorption in the mineralized refuse and clay is fitted the Langmuir isotherm equation. The maximum phosphorus adsorption capacity in the mineralized refuse calculated based on the Langmuir isotherm equation is 2914 mg kg-1. Both the maximum adsorption capacity and adsorption rate of phosphorus in the mineralized refuse are over 2.0-fold more than that of the clay. The desorption rate of phosphorus in the mineralized refuse is only about 30%. NH4+-N contents in the mineralized refuse samples fell from 129 mg N kg-1 to 83.0 mg N kg-1 within the first 24 h during the nitrification process. Accordingly, the NO3--N content in the mineralized increased from 137 mg N kg-1 to 170 mg N kg-1. While the decrease of NH4+-N contents and the increase of NO3--N contents in the clay was only 1/2 and 1/6 as large as in the mineralized refuse, respectively. During the denitrification process, the K-value of the fitted zero-order kinetics for NO3--N denitrification in the mineralized refuse was 6.5-fold higher than in the clay.

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Jiang, Hongliu, Yao Cao, Fengtao Zeng, Zewu Xie et Fuan He. « A Novel Fe3O4/Graphene Oxide Composite Prepared by Click Chemistry for High-Efficiency Removal of Congo Red from Water ». Journal of Nanomaterials 2021 (24 février 2021) : 1–11. http://dx.doi.org/10.1155/2021/9716897.

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In this paper, a magnetic graphene oxide (MGO) composite was prepared by the click reaction between the alkyne-modified Fe3O4 nanoparticles and the azide-modified graphene oxide for the purpose of removing the Congo red (CR) dye from water. The deposition of the Fe3O4 nanoparticles on the graphene oxide to successfully prepare the MGO composite was evidenced by the Fourier-transform infrared spectrometer, wide-angle X-ray diffraction equipment, scanning electron microscope, thermal gravimetric analyzer, and Raman spectrometer. The value of saturation magnetization for the MGO composite was 34.9 emu/g. The CR absorption capacities of the MGO composite increased first and then decreased as the pH value increased. It was found that the maximum adsorption capacity of the MGO composite for the CR was as high as 769.2 mg/g. In the absorption-desorption experiment, the CR absorption capacities of the MGO composite from the second cycle to the fifth cycle remained stable to be about 130 mg/g. Moreover, both the Langmuir model for the adsorption isotherm and the pseudo-second-order kinetic model could be used to describe the CR absorption behaviors of the MGO composite.

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Sun, Yulong, Haoxin Zheng, Yanfeng Pu, Hao Yang, Jianhong Wang, Shuaishuai Zhou, Qian Li et Congzhen Qiao. « Ultrahigh Adsorption Capacity Zirconium-Magnesium Composite Oxide Nanoclusters Remove Malachite Green from Aqueous Media ». Adsorption Science & ; Technology 2022 (26 novembre 2022) : 1–12. http://dx.doi.org/10.1155/2022/1946955.

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The environmental pollution caused by organic dyes has damaged serious harm to human life. Hence, a series of Zr-Mg composite oxide nanoclusters with different metal ratios were synthesized by solvothermal method for adsorption of malachite green in aqueous solution. The optimal adsorbent with Zr/Mg metal molar ratio of 1 : 2 presented good adsorption performance, which adsorption capacity reached 12647.60 mg/g, and removal rate of malachite green reached more than 99%. These adsorbents were characterized by X-ray diffraction, Fourier-transform infrared spectra, nitrogen adsorption-desorption, scanning electron microscope, transmission electron microscope, and other methods. Influence of initial concentration of malachite green solution, pH, adsorption temperature, and contact time on absorption efficiency was investigated through batch experiments. Pseudo-second-order kinetic model can well describe the adsorption kinetic data. The three-parameter Sips isotherm model was more suitable for predicting the experimental results than Langmuir and Freundlich, and the adsorption process was endothermic.

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Comanescu, Cezar. « Complex Metal Borohydrides : From Laboratory Oddities to Prime Candidates in Energy Storage Applications ». Materials 15, n^o 6 (19 mars 2022) : 2286. http://dx.doi.org/10.3390/ma15062286.

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Despite being the lightest element in the periodic table, hydrogen poses many risks regarding its production, storage, and transport, but it is also the one element promising pollution-free energy for the planet, energy reliability, and sustainability. Development of such novel materials conveying a hydrogen source face stringent scrutiny from both a scientific and a safety point of view: they are required to have a high hydrogen wt.% storage capacity, must store hydrogen in a safe manner (i.e., by chemically binding it), and should exhibit controlled, and preferably rapid, absorption–desorption kinetics. Even the most advanced composites today face the difficult task of overcoming the harsh re-hydrogenation conditions (elevated temperature, high hydrogen pressure). Traditionally, the most utilized materials have been RMH (reactive metal hydrides) and complex metal borohydrides M(BH4)x (M: main group or transition metal; x: valence of M), often along with metal amides or various additives serving as catalysts (Pd2+, Ti4+ etc.). Through destabilization (kinetic or thermodynamic), M(BH4)x can effectively lower their dehydrogenation enthalpy, providing for a faster reaction occurring at a lower temperature onset. The present review summarizes the recent scientific results on various metal borohydrides, aiming to present the current state-of-the-art on such hydrogen storage materials, while trying to analyze the pros and cons of each material regarding its thermodynamic and kinetic behavior in hydrogenation studies.

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Wu, Yongjun, Nina Xie et Lu Yu. « Preparation of Novel Ag–Si–TiO2 Composite and Research on Its Photocatalytic Degradation of Formaldehyde ». Science of Advanced Materials 13, n^o 3 (1 mars 2021) : 371–80. http://dx.doi.org/10.1166/sam.2021.3864.

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A novel Ag–Si–TiO2 composite was prepared via sol–gel method for removing residual formaldehyde in shiitake mushroom. The structure of Ag–Si–TiO2 composite was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. Ultraviolet-visible absorption spectroscopy (UV-Vis) and N2 adsorption-desorption tests showed that Ag and Si co-doped decreased the band gap, the Brunauer-Emmett-Teller (BET) specific surface area of the samples increased and the recombination probability of electron-hole pairs (e--h+) reduced. Effect on removal rate of formaldehyde with different Ag-Si co-doped content, formaldehyde concentration and solution pH were investigated, and the results showed that 6.0 wt%Ag-3.0 wt%Si-TiO2 samples had an optimum catalytic performance, and the degradation efficiency reached 96.6% after 40 W 365 nm UV lamp irradiation for 360 min. The kinetics of formaldehyde degradation by Ag–Si–TiO2 composite photocatalyst could be described by Langmuir-Hinshelwood first-order kinetic model.

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Peru, Filippo, SeyedHosein Payandeh, Georgia Charalambopoulou, Torben R. Jensen et Theodore Steriotis. « Hydrogen Sorption and Reversibility of the LiBH4-KBH4 Eutectic System Confined in a CMK-3 Type Carbon via Melt Infiltration ». C — Journal of Carbon Research 6, n^o 2 (31 mars 2020) : 19. http://dx.doi.org/10.3390/c6020019.

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Metal borohydrides have very high hydrogen densities but their poor thermodynamic and kinetic properties hinder their use as solid hydrogen stores. An interesting approach to improve their functionality is nano-sizing by confinement in mesoporous materials. In this respect, we used the 0.725 LiBH4–0.275 KBH4 eutectic mixture, and by exploiting its very low melting temperature (378 K) it was possible to successfully melt infiltrate the borohydrides in a mesoporous CMK-3 type carbon (pore diameter ~5 nm). The obtained carbon–borohydride composite appears to partially alleviate the irreversibility of the dehydrogenation reaction when compared with the bulk LiBH4-KBH4, and shows a constant hydrogen uptake of 2.5 wt%–3 wt% for at least five absorption–desorption cycles. Moreover, pore infiltration resulted in a drastic decrease of the decomposition temperature (more than 100 K) compared to the bulk eutectic mixture. The increased reversibility and the improved kinetics may be a combined result of several phenomena such as the catalytic action of the carbon surface, the nano-sizing of the borohydride particles or the reduction of irreversible side-reactions.

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Badaruddin, Muhammad, Nur Ahmad, Erni Salasia Fitri, Aldes Lesbani et Risfidian Mohadi. « Hydrochar and Humic Acid as Template of ZnAl Layered Double Hydroxide for Adsorption of Phenol ». Science and Technology Indonesia 7, n^o 4 (31 octobre 2022) : 492–99. http://dx.doi.org/10.26554/sti.2022.7.4.492-499.

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The adsorbents potential ZnAl-LDH, ZnAl-Hydrochar, and ZnAl-Humic acid were prepared using the coprecipitation method. The adsorbents were characterization by XRD, FTIR, and BET analysis. XRD peaks of ZnAl-LDH at 10.29°, 20.07°, 29.59°, 32.12°, 34.02°, 48.06°, and 60.16°. The FTIR absorption peak was observed at 3400-3500 cm−1, 1600-1700 cm−1, 1381 cm−1, 1000 cm−1, 500-700 cm−1. All adsorbents exhibited N2 adsorption-desorption isotherms type IV classified as a mesoporous structure (pore size= 2-50 nm). The surface areas of composites were higher than LDH and following order: ZnAl-Hydrochar > ZnAl-Humic acid > ZnAl-LDH. The kinetic parameter showed the pseudo-second-order kinetics model. The maximum adsorption capacity of ZnAl-LDH, ZnAl-Hydrochar, and ZnAl-Humic acid were 48.077 mg/g, 90.090 mg/g, 94.340 mg/g, respectively; with Freundlich isotherm model. Reusability after 5 times of ZnAl-LDH, ZnAl-Hydrochar, and ZnAl-Humic acid in the range 49.81-0.890%, 95.92-9.84%, and 70.02-5.72%, respectively. The adsorbent can be used up to 3 times.

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Ma, Lai-Peng, Ping Wang, Xiang-Dong Kang et Hui-Ming Cheng. « Preliminary investigation on the catalytic mechanism of TiF3 additive in MgH2–TiF3 H-storage system ». Journal of Materials Research 22, n^o 7 (juillet 2007) : 1779–86. http://dx.doi.org/10.1557/jmr.2007.0239.

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A combined structure/property investigation is performed to understand the catalytic effect of TiF3 additive on the absorption/desorption reactions of MgH2. It was found that both TiH2 and MgF2 phases identified by x-ray diffraction cannot explain the observed kinetic enhancement in the MgH2–TiF3 system, whether they are incorporated in a direct or an in situ manner. In combination with the comparative investigation on the catalytic activity of TiF3 and its analog TiCl3, as well as the samples milled under inert and reactive atmospheres, we propose that the catalytically active species is a multicomponent metastable phase composed of host Mg, transition metal Ti, and F anion, the catalytic activity of which is dependent on its interaction with the surrounding chemical environment.

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Nuryono, Nuryono, V. V. H. Susanti et Narsito Narsito. « KINETIC STUDY ON ADSORPTION OF CHROMIUM(lIl) TO DIATOMACEOUS EARTH PRE-TREATED WITH SULFURIC AND HYDROCHLORIC ACIDS ». Indonesian Journal of Chemistry 3, n^o 1 (7 juin 2010) : 32–38. http://dx.doi.org/10.22146/ijc.21903.

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In this research, the effect of Sangiran diatomaceous earth pre-treatment with sulfuric acid (H2SO4) and hydrochloric acid (HCl) on the kinetics of adsorption for Cr(III) in aqueous solution has been studied. The research has been carried out by mixing an amount of diatomeaeous earth with HCl or H2SO4 in various concentrations for two hours at temperature of 150 - 200°C. The mixture was washed with water until neutral, and the residue was dried at 70°C for four hours. The result then was used as adsorbent. Adsorption was carried out by mixing an amount of adsorbent with Cr(III) solution in various contact times. Ion adsorbed was determined by analyzing filtrate using atomic absorption spectrophotometry. The effect of pre-treatment on adsorption kinetics was evaluated based on kinetic parameters, i.e. constant of adsorption rate by using Langmuir-Hinshelwood kinetics and using two-process kinetics (fast and slow processes). Adsorption kinetics calculated using LH equation gave negative value for adsorption rate constant of zero order (k0). On the other words, the LH kinetics might not be applied for adsorption of Cr(III) to diatomaceous earth adsorbent. Results of kinetics study approached using two processes (fast and slow) showed that adsorption of Cr(III) occurred in two processes with rate constant of fast adsorption, kc, 0.041/min, rate constant of slow adsorption, kl, 0.0089/min, and of slow desorption, k'l, 0.089/menit. Pre-treatment with HCl up to 10 M decreased either kc, kl or k'l, while pre-treatment with H2SO4 1M increased kc to 0.061/min, decreased kl to 0.00424 and k'l to 0.0139/min. On pre-treatment with H2SO4 higher than 6 M significantly decreased three constants above. Based on the Gibbs energy change (4.31 - 6.79 kJ/mole) showed that adsorption involved physical interaction. Keywords: adsorption, chromium, diatomaceous earth, kinetics, Langmuir-Hinshelwood

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Verón, M. G., L. A. Soria et M. O. Prado. « Porous Sulfonated PVA Microspheres for Controlled Molecules Delivery : A Methylene Blue Study ». Journal of Materials and Applications 10, n^o 1 (15 mai 2021) : 27–42. http://dx.doi.org/10.32732/jma.2021.10.1.27.

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Functionalized PVA microspheres are commonly used as drug carriers in the fields of pharmacy and medicine. With this aim, we obtained and test novel PVA-PVAc-AMPS sulfonated microspheres by free radical suspension polymerization of vinyl acetate (VAc) and 2-acrylamido-2-methyl-1-propanesulfonic sodium salt acid (AMPS), followed by saponification. The microspheres exhibited a porous core-shell structure with excellent sphericity, a mean size of 171 µm, and elasticity modulus comparable with commercial particles currently used in medical applications. Methylene blue (MB) which has shown similar adherence properties as the cytostatic drug doxorubicin was used as a model drug to study the drug loading/release characteristics of the sulfonated microspheres prepared in this work. 20.7 mg g-1 MB per gram of microspheres was the maximum adsorption capacity in two hours using UV-Vis absorption spectroscopy. The experimental data on adsorption were well described by the pseudo-second order kinetic model. The in vitro release profile of loaded MB microspheres showed rapid desorption in the first hour followed by slower MB release, reaching 8.6% elution at four hours. The diffusion process was found to be dominant in the MB desorption from the PVA-PVAc-AMPS microspheres.

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Kitagawa, Yuta, et Katsuaki Tanabe. « Development of a kinetic model of hydrogen absorption and desorption in magnesium and analysis of the rate-determining step ». Chemical Physics Letters 699 (mai 2018) : 132–38. http://dx.doi.org/10.1016/j.cplett.2018.03.036.

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Kuzminykh, Maria М., Viktoria V. Panteleeva et Anatoliy B. Shein. « CATHODIC HYDROGEN EVOLUTION ON IRON DISILICIDE. II. ACIDIC SOLUTION ». IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, n^o 2 (7 février 2019) : 59–64. http://dx.doi.org/10.6060/ivkkt.20196202.5750.

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The kinetics of hydrogen evolution reaction on FeSi2-electrode in 0.5 M H2SO4 solution has been studied using methods of polarization and impedance measurements. With the help of diagnostic criteria for the hydrogen evolution reaction mechanisms based on the analysis of the dependence of the parameters of the equivalent electric circuit on overvoltage, it was established that the reaction of hydrogen evolution on iron disilicide in the sulfuric acid solution proceeds along the discharge - electrochemical desorption route, where desorption is the rate-determining stage. Both stages are irreversible, the transfer coefficients α of the stages are equal, simultaneously the hydrogen absorption reaction by the electrode material proceeds in the kinetic mode (in the whole investigated range of potentials). It was found that the adsorption of atomic hydrogen is described by the equation of the Langmuir isotherm. The influence of thin oxide film on the hydrogen evolution kinetics is noted. The influence of various methods of modifying of the surface of FeSi2-electrode on the kinetics and mechanism of the cathodic process has been studied. It was found that the modification of the disilicide surface by hydrogenation at a current density of i = 30 mA/cm2, an anodic etching in 0.5 M H2SO4 at the potential E = 0.4 V relative to the standard hydrogen electrode, an anodic etching in 1.0 M NaOH at the potential E = 0.1 V, chemical etching in 5.0 M NaOH at 70 °C reduce the overvoltage of hydrogen evolution, but the mechanism of the cathodic process does not change as a result of the electrode modification. Reduction of the overvoltage of hydrogen evolution on iron disilicide is due to the action of two factors: the development of the surface and the change in the composition of the surface layer of the electrode. It has been concluded that FeSi2 in the sulfuric acid solution is a promising electrode material that exhibits activity in the electrolytic hydrogen evolution reaction.

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Jahani, Davoud, Amin Nazari, Jaber Ghourbanpour et Amir Ameli. « Polyvinyl Alcohol/Calcium Carbonate Nanocomposites as Efficient and Cost-Effective Cationic Dye Adsorbents ». Polymers 12, n^o 10 (24 septembre 2020) : 2179. http://dx.doi.org/10.3390/polym12102179.

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A novel polyvinyl alcohol (PVA)/calcium carbonate-based double-layer cationic dye adsorbent was developed. Polyvinyl alcohol (50 wt %) and calcium carbonate (50 wt %) were used together with borax as a cross-linking agent. The nanocomposite was prepared using only water, without the need for any toxic solvent or hazardous chemical. The final samples were obtained by the solvent casting method. The nanocomposite adsorbent was characterized using a Fourier transform infrared (FTIR) spectroscope and a scanning electron microscope (SEM). The adsorption performance on two cationic dyes, i.e., methylene blue and safranin was studied. Dye adsorption was quantified by measuring the nanocomposite swelling, contact time, and dye concentration. Pseudo first-order and pseudo second-order kinetic models as well as intraparticle diffusion model were used to model the adsorption kinetics. Moreover, the isotherm dye adsorption was investigated by Langmuir and Freundlich models. The results revealed that the developed nanocomposite has relatively high adsorption efficiency and short adsorption time and retains its performance after several successive absorption–desorption processes. The results also showed that the pseudo-second-order model best describes the adsorption kinetics, and the Freundlich isotherm model has a better compatibility with the experimental data. Finally, an adsorption mechanism was proposed for the dye removal process. The developed PVA/CaCO3 nanocomposite can be potentially used for efficient dye removal in wastewater treatments.

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