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Artykuły w czasopismach na temat "Electronic Structure - Chemical Hydrogen Storage"
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Cai, Yingxiang, Jiamin Xiong, Yabo Liu i Xuechun Xu. "Electronic structure and chemical hydrogen storage of a porous sp3 tetragonal BC2N compound". Journal of Alloys and Compounds 724 (listopad 2017): 229–33. http://dx.doi.org/10.1016/j.jallcom.2017.06.343.
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Szarek, Pawel, Kouhei Watanabe, Kazuhide Ichikawa i Akitomo Tachibana. "Electronic Stress Tensor Study of Aluminum Nanostructures for Hydrogen Storage". Materials Science Forum 638-642 (styczeń 2010): 1137–42. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1137.
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We report the new structures of aluminum hydrides derived from the Al4 tetrahedral cages. We perform ab initio quantum chemical calculation for these new aluminum hydrides. Our calculation of binding energies of the new aluminum hydrides reveal that stability of these hydrides increases as more hydrogen atoms are adsorbed, while stability of Al-H bonds decreases. We also calculate electronic stress tensor to evaluate the chemical bonds of these hydrides. As a result, we find that the bonds of the Al4 tetrahedral cage are strengthened as more hydrogen atoms are adsorbed on the aluminum hydrides. Our calculation of the potential energy surfaces and the regional chemical potential show that hydrogen atoms are likely to adsorb on bridge site at first.
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Ichikawa, Kazuhide, Yuji Ikeda, Ryo Terashima i Akitomo Tachibana. "Aluminum Hydride Clusters as Hydrogen Storage Materials and their Electronic Stress Tensor Analysis". Materials Science Forum 706-709 (styczeń 2012): 1539–44. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1539.
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We study the chemical bonds of small Al clusters (Aln, n=2-8) and hydrogenated Al clusters (AlnHm , n=1-8 and m=1,2) using electronic stress tensor. We calculate the bond order based on energy density for these clusters. We also study the electronic structure under the presence of electronic current by the electronic stress tensor for AlH3 molecule.
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Morinaga, Masahiko, i Hiroshi Yukawa. "Characteristics of Electronic Structures and Chemical Bonding in Hydrogen-Storage Compounds". Materials Science Forum 426-432 (sierpień 2003): 2237–42. http://dx.doi.org/10.4028/www.scientific.net/msf.426-432.2237.
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Seo, Okkyun, Jaemyung Kim, Akhil Tayal, Chulho Song, L. S. R. Kumara, Shun Dekura, Hirokazu Kobayashi, Hiroshi Kitagawa i Osami Sakata. "The relationship between crystalline disorder and electronic structure of Pd nanoparticles and their hydrogen storage properties". RSC Advances 9, nr 37 (2019): 21311–17. http://dx.doi.org/10.1039/c9ra02942g.
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Smaller Pd nanoparticles have a high degree of disordering and a lower coordination number on the surface part, which causes a change in electronic structure to have different hydrogen storage properties.
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Cui, Hong, Ying Zhang, Weizhi Tian, Yazhou Wang, Tong Liu, Yunjian Chen, Pengyue Shan i Hongkuan Yuan. "A study on hydrogen storage performance of Ti decorated vacancies graphene structure on the first principle". RSC Advances 11, nr 23 (2021): 13912–18. http://dx.doi.org/10.1039/d1ra00214g.
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Gao, Peng, Zonghang Liu, Jiefeng Diao, Jiaao Wang, Jiwen Li, Yuebin Tan, Guangtong Hai i Graeme Henkelman. "Calculated Outstanding Energy-Storage Media by Aluminum-Decorated Carbon Nitride (g-C3N4): Elucidating the Synergistic Effects of Electronic Structure Tuning and Localized Electron Redistribution". Crystals 13, nr 4 (11.04.2023): 655. http://dx.doi.org/10.3390/cryst13040655.
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Hydrogen, as an important clean energy source, is difficult to store and transport, which hinders its applications in real practice. Developing robust yet affordable storage media remains to be a challenge for scientists. In this study, Ab Initio Molecular Dynamics (AIMD) simulations were employed to evaluate the performance of aluminum (Al) decorated carbon nitride (g-C3N4, heptazine structure) in hydrogen storage; and a benchmarking study with Mg-doped g-C3N4 was also performed to provide theoretical insights for future study. We found that each 2 × 2 supercell can accommodate four Al atoms, and that partial charge from single Al sites can be transferred to adjacent nitrogen atoms of g-C3N4. These isolated Al sites tend to be electronically positive charged, serving as active sites for H2 adsorption, predominately by triggering enhanced electrostatic interactions. The H2 molecules are adsorbed by both Al and N atoms, and are easily polarized, giving rise to electrostatic interactions between the gas molecules and the surface. Effective adsorption sites were determined by electronic potential distribution maps of the optimized configurations. Each 2 × 2 supercell can adsorb up to 36 H2 molecules, and the corresponding adsorption energies are within the range of −0.10 to −0.26 eV. The H2 storage capacity of the Al-decorated g-C3N4 is 7.86 wt%, which surpasses the goal of 5.5 wt%, set by the US department of energy. This proposed Al-decorated g-C3N4 material is therefore predicted to be efficient for hydrogen storage. This work may offer some fundamental understandings from the aspect of electronic sharing paradigm of the origin of the excellent hydrogen storage performance by metal decorated 2D materials, acting as an demonstration for guiding single metal atom site-based materials’ designing and synthesis.
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Zhang, Jun-Jun, Meng-Yang Li, Xiang Li, Wei-Wei Bao, Chang-Qing Jin, Xiao-Hua Feng, Ge Liu, Chun-Ming Yang i Nan-Nan Zhang. "Chromium-Modified Ultrathin CoFe LDH as High-Efficiency Electrode for Hydrogen Evolution Reaction". Nanomaterials 12, nr 7 (6.04.2022): 1227. http://dx.doi.org/10.3390/nano12071227.
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Hydrogen evolution reaction (HER) has a dominant function in energy conversion and storage because it supplies a most effective way for converting electricity into sustainable high-purity hydrogen. Layered double hydroxides (LDHs) have shown promising performance in the process of electrochemical water oxidation (a half-reaction for water splitting). Nevertheless, HER properties have not been well released due to the structural characteristics of related materials. Herein, a simple and scalable tactics is developed to synthesize chromium-doped CoFe LDH (CoFeCr LDH). Thanks to oxygen vacancy, optimized electronic structure and interconnected array hierarchical structure, our developed ternary CoFeCr-based layered double hydroxide catalysts can provide 10 mA cm−2 current density at −0.201 V vs. RHE with superior long-term stability in alkaline electrolyte. We anticipate that the simple but feasible polymetallic electronic modulation strategy can strengthen the electrocatalytic property of the layered double hydroxides established in the present study, based on a carbon neutral and hydrogen economy.
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Gao, Peng, Xihao Chen, Jiwen Li, Yue Wang, Ya Liao, Shichang Liao, Guangyu Zhu, Yuebin Tan i Fuqiang Zhai. "Computational Evaluation of Al-Decorated g-CN Nanostructures as High-Performance Hydrogen-Storage Media". Nanomaterials 12, nr 15 (27.07.2022): 2580. http://dx.doi.org/10.3390/nano12152580.
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Density functional theory (DFT) calculations were employed to solve the electronic structure of aluminum (Al)-doped g-CN and further to evaluate its performance in hydrogen storage. Within our configurations, each 2 × 2 supercell of this two-dimensional material can accommodate four Al atoms, and there exist chemical bonding and partial charge transfer between pyridinic nitrogen (N) and Al atoms. The doped Al atom loses electrons and tends to be electronically positive; moreover, a local electronic field can be formed around itself, inducing the adsorbed H2 molecules to be polarized. The polarized H2 molecules were found to be adsorbed by both the N and Al atoms, giving rise to the electrostatic attractions between the H2 molecules and the Al-doped g-CN surface. We found that each 2 × 2 supercell can adsorb at most, 24 H2 molecules, and the corresponding adsorption energies ranged from −0.11 to −0.31 eV. The highest hydrogen-storage capacity of the Al-doped g-CN can reach up to 6.15 wt%, surpassing the goal of 5.50 wt% proposed by the U.S. Department of Energy. Additionally, effective adsorption sites can be easily differentiated by the electronic potential distribution map of the optimized configurations. Such a composite material has been proven to possess a high potential for hydrogen storage, and we have good reasons to expect that in the future, more advanced materials can be developed based on this unit.
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Skryabina, N. E., Vladimir M. Pinyugzhanin i Daniel Fruchart. "Relationship between Micro-/Nano-Structure and Stress Development in TM-Doped Mg-Based Alloys Absorbing Hydrogen". Solid State Phenomena 194 (listopad 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.
Rozprawy doktorskie na temat "Electronic Structure - Chemical Hydrogen Storage"
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Torres, Escalona Javier. "Electronic properties study on hydrazines and nitriles complexed by Lewis acids. Towards chemical hydrogen storage". Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3051.
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Dans la problématique de l'utilisation de nouvelles énergies non polluantes, l'hydrogène est l'un des principaux carburants verts du futur. Les dérivés d'hydrazine et de borane sont potentiellement intéressants pour le stockage chimique de l'hydrogène. Les complexes entre hydrazines ou nitriles avec des boranes ou des alanes sont à la base de cette étude. Ces composés ont été synthétisés afin d'étudier leur structure électronique avant et après la création de la liaison entre les acides et les bases de Lewis. La spectroscopie photoélectronique à rayonnement UV (UV-SPE) est utilisée comme outil principal de caractérisation fournissant des énergies d'ionisation (IE). L’interprétation des résultats expérimentaux est supportée par des calculs quantiques comme ΔSCF + TD-DFT, OVGF, P3 et SAC-CI. Des simulations et des expériences par Flash Vacuum Thermolysis (FVT) ont été effectuées, portant sur l’élimination d'hydrogène à partir de dérivés d'hydrazine boraneWithin the problematic of the use of new non-polluting energies, hydrogen is one of the main green fuels of the future. Hydrazine borane derivatives are potentially interesting chemical hydrogen storage materials. Complexes between hydrazines or nitriles with boranes or alanes are the basis of this study. These compounds were synthesized in order to study their electronic structure before and after creation of the bond between the Lewis acids and bases. Ultraviolet Photoelectron Spectroscopy (UV-PES) is used as a main characterization tool, providing Ionization Energies (IE). The interpretation of the experimental results is supported by Quantum Chemical Calculations as ΔSCF+TD-DFT, OVGF, P3 and SAC-CI methods. Simulations and experiments by Flash Vacuum Thermolysis (FVT) were carried out on hydrogen release from hydrazine borane derivatives
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Rai, Chaudhuri Anjana. "Electronic structure and bond energy trends in silicon-hydrogen and germanium-hydrogen bond activation by transition metals". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184731.
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The electronic structure factors that control Si-H and Ge-H bond activation by transition metals are investigated by means of photoelectron spectroscopy. Molecular orbital calculations are also used to gain additional insight into the orbital interactions involved in bond activation. The complexes studied have the general molecular formula (η⁵-C₅R'₅)Mn(CO)(L)HER₃, where R' is H or CH₃, L is CO or PMe₃, E is Si or Ge and R is Ph or Cl. These compounds are interesting models for catalysts in industrial processes like hydrosilation. The compounds display different stages of interaction and "activation" of the E-H bonds with the metal. One purpose is to measure the degree of Mn, Si, H 3-center-2-electron bonding in these complexes. The three-center interaction can be tuned by changing the substituents on Si, methylating the cyclopentadienyl ring, changing the ligand environment around the metal and substituting Si with Ge. The degree of activation is measured by observing the shifts in the metal and ligand ionizations relative to starting materials and free ligand in the photoelectron spectrum. Changing the substituent on Si extensively changes the degree of activation. Photoelectron spectral studies on (η⁵-C₅H₅)Mn(CO)₂HSiPh₃ show this to be a Mn(I) system. Progressive methylation of the cyclopentadienyl ring increases the electron richness at the metal center with no substantial effect on the degree of activation. Substitution on the metal (PMe₃ for CO) is less able to control the electronic structure factors of activation than the substitution on the Si atom. The magnitude of Ge-H bond activation is found to be of the same order as the Si-H bond activation for analogous compounds as found by studying (η⁵-C₅H₅)Mn(CO)₂HGePh₃, (η⁵-CH₃C₅H₄)Mn(CO)₂HGePh₃ and (η⁵- C₅(CH₃)₅)Mn(CO)₂HGePh₃ complexes by photoelectron spectroscopy. The photoelectron spectra of CpFe(CO)₂SiCl₃ and CpFe(CO)₂SiMe₃ were measured to study the electron charge shift from the metal to the ligand in these complexes as compared to CpMn(CO)₂HSiR₃ complexes. The photoelectron spectroscopic studies include numerous perturbations of the ligand and metal center to observe the extent of bond interaction and remain one of the best techniques to detect activation products.
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Culligan, Scott D. "The crystal chemistry and hydrogen storage properties of light metal borohydrides". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:5a27d358-6b0d-4287-8b5d-f18304533dde.
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This work examines various light metal borohydrides, particularly those formed from group II metals, with the aim of understanding their fundamental physical properties and improving their hydrogen storage ability. The structure of a new phase (γ) of Mg(BH4)2 is reported and the decomposition is fully characterized in a combination of diffraction and thermogravimetric studies. The bulk properties of γ-Mg(BH4)2 are compared to those of an SiO2 isostructure and probed by various neutron scattering techniques. Negative thermal expansion is observed at low temperatures and the material absorbs up to 1.5 moles of hydrogen gas to form one of the most gravimetrically hydrogen-dense materials ever reported. The structural evolution of Ca(BH4)2 under different synthetic conditions and external influences (e.g. temperature) is studied up until the material decomposes. The effects of various additives on group II metal borohydrides are also examined and the influence of each is justified by observing subtle structural changes in the mixed system via in situ synchrotron X-ray powder diffraction and 11B NMR measurements.
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Nickels, Elizabeth Anne. "Structural and thermogravimetric studies of group I and II borohydrides". Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:f18f8f7c-1837-4b96-b4bb-5f964e93899c.
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This thesis investigates the structure and thermal behaviour of LiBH4, NaBH4, KBH4, LiK(BH4)2, Ca(BH4)2 and Sr(BH4)2. LiK(BH4)2 is the first mixed alkali metal borohydride and was synthesised and characterised during this work. The crystal structures of these borohydrides were studied using variable temperature neutron and synchrotron X-ray diffraction. The synthesis of isotopically enriched samples of 7Li11BD4, Li11BD4, Na11BD4 and K11BD4 allowed high quality neutron diffraction data to be collected. Particular attention was paid to the exact geometry of the borohydride ions which were generally found to be perfect tetrahedra but with orientational disorder. New structures of Ca(BH4)2 were identified and the first crystal structure of Sr(BH4)2 was determined from synchrotron X-ray diffraction data. Solid state 11B NMR and Raman spectroscopy provided further information about the structure of these borohydrides. The thermal behaviour of the borohydrides was investigated using thermogravimetric analysis with mass spectrometry of the decomposition gas products. Hydrogen is the main decomposition gas product from all of these compounds but small amounts of B2H6 and BH3 were also detected during decomposition. Thermogravimetic analyses of Na11BD4 and K11BD4 were completed whilst collecting in-situ neutron diffraction data allowing information about structural changes and mass losses to be combined in order to better understand the decomposition process.
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Richard, Laura Amanda. "A study of the crystallographic, magnetic and electronic properties of selected ZrM2-H systems". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:276c59fe-cf45-42d2-a5a0-8c534c8b46bd.
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Dissolution of hydrogen into intermetallic compounds characteristically occurs at interstitial sites, causing little alteration to the base metal substructure but often bringing about substantial electronic and magnetic changes to the material. These hydrogen-induced alterations in the intermetallic hydrides are of interest both on a fundamental research level and in terms of technological applications; however, there exists no general theory as to how and why these alterations arise. The objective of this research is to elucidate to general effect of hydrogen on intermetallic compounds through the study of crystallographic, magnetic and electronic properties. An investigation has been carried out on the properties of three intermetallic compound - hydrogen systems of general formula ZrM₂, where M = V, Cr, Mn. All three compounds reversibly absorbed hydrogen with no change in crystal symmetry: powder diffraction studies showed that hydrogen was accommodated in interstitial sites of the existing metal sublattice via lattice expansion. The measurement of the magnetic properties of these systems was combined with the determination of conductivity and dielectric properties in order to describe the electronic e¤ects of hydrogen absorption. Despite the lack of signi
cant structural alteration in these systems, electron transfer between the metal sublattice and hydrogen may occur, as manifested in the appearance/disappearance of magnetic phenomena and the increase/decrease of electrical conductivity. Whilst the hydrogen addition in ZrM₂-H occurs simply via an expansion of the crystal structure, hydrogen does not act purely as null dilutant - there exist subtle electronic changes connected with the hydriding process as well.
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Ramzan, Muhammad. "Structural, Electronic and Mechanical Properties of Advanced Functional Materials". Doctoral thesis, Uppsala universitet, Materialteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205243.
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The search for alternate and renewable energy resources as well as the efficient use of energy and development of such systems that can help to save the energy consumption is needed because of exponential growth in world population, limited conventional fossil fuel resources, and to meet the increasing demand of clean and environment friendly substitutes. Hydrogen being the simplest, most abundant and clean energy carrier has the potential to fulfill some of these requirements provided the development of efficient, safe and durable systems for its production, storage and usage. Chemical hydrides, complex hydrides and nanomaterials, where the hydrogen is either chemically bonded to the metal ions or physiosorbed, are the possible means to overcome the difficulties associated with the storage and usage of hydrogen at favorable conditions. We have studied the structural and electronic properties of some of the chemical hydrides, complex hydrides and functionalized nanostructures to understand the kinetics and thermodynamics of these materials. Another active field relating to energy storage is rechargeable batteries. We have studied the detailed crystal and electronic structures of Li and Mg based cathode materials and calculated the average intercalation voltage of the corresponding batteries. We found that transition metal doped MgH2 nanocluster is a material to use efficiently not only in batteries but also in fuel-cell technologies. MAX phases can be used to develop the systems to save the energy consumption. We have chosen one compound from each of all known types of MAX phases and analyzed the structural, electronic, and mechanical properties using the hybrid functional. We suggest that the proper treatment of correlation effects is important for the correct description of Cr2AlC and Cr2GeC by the good choice of Hubbard 'U' in DFT+U method. Hydrogen is fascinating to physicists due to predicted possibility of metallization and high temperature superconductivity. On the basis of our ab initio molecular dynamics studies, we propose that the recent claim of conductive hydrogen by experiments might be explained by the diffusion of hydrogen at relevant pressure and temperature. In this thesis we also present the studies of phase change memory materials, oxides and amorphization of oxide materials, spintronics and sulfide materials.
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Andrieux, Jérome. "Stockage de l'hydrogène dans les borohydrures alcalins : hydrolyse du borohydrure de sodium". Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00654299.
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Le contexte environnemental (réchauffement climatique) et économique (épuisement des ressources en énergies fossiles) entraîne une nécessaire mutation du paysage énergétique mondial. L'hydrogène est présenté comme un vecteur d'énergie propre pouvant, par l'intermédiaire d'une pile à combustible, fournir de l'électricité pour diverses applications (nomade, portable, automobile et stationnaire). Cependant, son développement reste tributaire de son mode de stockage. Parmi les composés présentant de bonnes capacités de stockage, le borohydrure de sodium NaBH4 se distingue puisqu'il permet aussi un dégagement contrôlé de l'hydrogène d'après la réaction d'hydrolyse suivante : ( ) (2 ) ( ) ( ) 4 ( ) 4 2 2 2 2 NaBH ++ x H O l→NaBO . xH O + H g Il constitue ainsi une solution sûre et facile d'utilisation, et est donc envisageable pour des applications grand public. La thèse avait pour objectif l'approfondissement des connaissances relatives à la réaction catalysée d'hydrolyse du borohydrure de sodium selon deux axes principaux: la catalyse de la réaction et l'étude des produits d'hydrolyse. Concernant le premier axe, notre objectif était de mieux comprendre et d'améliorer la cinétique de la réaction d'hydrolyse, les catalyseurs étudiés étant à base de cobalt. Un catalyseur " modèle " a été utilisé et comparé à des nanoparticules métalliques synthétisées et d'autres espèces chimiques à base de cobalt (oxyde, hydroxyle et carbonate). Le modèle cinétique de Langmuir-Hinshelwood a permis de décrire la cinétique de l'hydrolyse. Un mécanisme réactionnel basé sur les adsorptions en surface du catalyseur de BH4 - et de H2O a été proposé. Enfin, la nature des sites actifs en surface a été discutée. En ce qui concerne le second axe de la thèse, nous avions deux objectifs : identifier les phases formées en fonction des conditions expérimentales et approfondir les connaissances thermodynamiques du système binaire NaBO2-H2O pour définir les différents équilibres se formant à l'issu de la réaction d'hydrolyse. Pour ce faire, les borates ont d'abord été synthétisés, puis caractérisés en termes de structure cristallographique et de stabilité en température. C'est ainsi qu'un nouveau borate de sodium, Na3[B3O4(OH)4] ou NaBO2*2/3H2O, a été obtenu. D'autre part, l'étude des équilibres liquide+solide, solide+solide et liquide+vapeur nous a permis d'établir le diagramme binaire NaBO2-H2O à pression atmosphérique.
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Shen-DunLiang i 梁信惇. "The electrochemical properties of Mg2Ni hydrogen storage alloy with core-shell structure fabricated by mechanical alloying and chemical plating Ni". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30005489409901059086.
Pełny tekst źródłaKsiążki na temat "Electronic Structure - Chemical Hydrogen Storage"
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Rai, Dibya Prakash, red. Advanced Materials and Nano Systems: Theory and Experiment - Part 2. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/97898150499611220201.
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The discovery of new materials and the manipulation of their exotic properties for device fabrication is crucial for advancing technology. Nanoscience, and the creation of nanomaterials have taken materials science and electronics to new heights for the benefit of mankind. Advanced Materials and Nanosystems: Theory and Experiment covers several topics of nanoscience research. The compiled chapters aim to update students, teachers, and scientists by highlighting modern developments in materials science theory and experiments. The significant role of new materials in future technology is also demonstrated. The book serves as a reference for curriculum development in technical institutions and research programs in the field of physics, chemistry and applied areas of science like materials science, chemical engineering and electronics. This part covers 12 topics in these areas: 1. Recent advancements in nanotechnology: a human health Perspective 2. An exploratory study on characteristics of SWIRL of AlGaAs/GaAs in advanced bio based nanotechnological systems 3. Electronic structure of the half-Heusler ScAuSn, LuAuSn and their superlattice 4. Recent trends in nanosystems 5. Improvement of performance of single and multicrystalline silicon solar cell using low-temperature surface passivation layer and antireflection coating 6. Advanced materials and nanosystems 7. Effect of nanostructure-materials on optical properties of some rare earth ions doped in silica matrix 8. Nd2Fe14B and SmCO5: a permanent magnet for magnetic data storage and data transfer technology 9. Visible light induced photocatalytic activity of MWCNTS decorated sulfide based nano photocatalysts 10. Organic solar cells 11. Neodymium doped lithium borosilicate glasses 12. Comprehensive quantum mechanical study of structural features, reactivity, molecular properties and wave function-based characteristics of capmatinib
Części książek na temat "Electronic Structure - Chemical Hydrogen Storage"
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Lin, Yu Fang, Dongliang Zhao i Xin Lin Wang. "Alloying Effect on the Electronic Structure of LaNi5-Based Hydrogen Storage Alloys". W Materials Science Forum, 3123–26. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-960-1.3123.
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Scerri, Eric R. "7. Electronic structure". W The Periodic Table: A Very Short Introduction, 85–98. Oxford University Press, 2019. http://dx.doi.org/10.1093/actrade/9780198842323.003.0007.
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‘Electronic structure’ examines the work that went into determining the properties of electrons in atoms. Quantum theory was devised by Max Planck in 1900, and was applied to hydrogen atoms by Niels Bohr in 1913. Bohr hypothesized that electrons existed in set shells around a nucleus and then extrapolated this theory, using chemical rather than physical observations, to other elements. G. N. Lewis hypothesized a cube model of electron arrangement around the nucleus. Despite this not being correct, Lewis concluded that chemical bonding was due to the pairing of electrons, an idea still central to modern chemistry. Finally, Charles Bury determined that electron shells around a nucleus did not need to be filled in a particular order.
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Huang, Yingchong, Shuxuan Liu, Tuyuan Zhu, Chunyan Zhou, Zhanguo Jiang i Xuehui Gao. "Electrocatalytic Meralorganic Frameworks and OER Based on Metal-organic Frameworks and their Structure". W Advanced Catalysts Based on Metal-organic Frameworks (Part 2), 86–128. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815136029123010005.
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Electrochemical water splitting has received extensive attention and research due to its ability to effectively produce and store clean energy. Water splitting includes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The complex reaction mechanism of the two half-reactions leads to slow kinetics and high overpotentials, which need to be mitigated and reduced by increasing effective active sites and accelerating electron transfer. Hence, the development of favorable prices and robust electrocatalysts has become a research hotspot. Owing to a large specific surface area, regulatable chemical composition, pore structure, controllable topological structure, and clear surface function, metal-organic framework-based materials (MOFs) have been widely studied. Herein, we summarize relevant references in MOF-based materials with outstanding performance in water splitting and report the design, structure, and activity of a large number of MOF-based materials. In addition, great expectations are placed on the future development and application prospects of MOFbased electrocatalytic materials.
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Thakur, Vaishali, i Ekta Sharma. "Application of Carbonaceous Quantum dots in Energy Storage". W Carbonaceous Quantum Dots: Synthesis And Applications, 178–91. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815136265123010012.
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Carbon quantum dots (CQDs) are a type of carbon nanomaterial that has lately received attention as a potential replacement for standard semiconductor quantum dots (QDs). CQDs feature a quasi-spherical structure and amorphous to nanocrystalline carbon cores with diameters of 10-20 nm. Based on the carbon core, CQDs are further classified as graphene quantum dots (GQDs), carbon nanodots (CNDs), and polymer dots (PDs). CQDs exhibit unique electrical and optical properties due to their bigger edge effects and quantum confinement; better than graphene oxide nanosheets, they can also be easily split into electrons and holes due to their high dielectric constant and extinction coefficient. CQDs are crucial in the sector of energy storage and transformation because CQDs offer the advantageous properties of low toxicity, environmental friendliness, low cost, photostability, favourable charge transfer with increased electronic conductivity, and comparably simple synthesis processes. Due to their superior crystal structure and surface properties, CQD nanocomposites often helped to shorten charge transfer paths and maintain electrode material cycle stability. CQDs provide cost-effective and environmentally friendly nanocomposites used for supplying high energy density and stable electrodes for energy storage applications. This chapter provides a summary of the role that CQDs play in energy transmit technologies, including solar cells, supercapacitors, lithium-ion batteries, and hydrogen and oxygen evolution reactions.
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Wysocka-Żołopa, Monika, Emilia Grądzka i Krzysztof Winkler. "Conducting Polymer 1-D Composites: Formation, Structure and Application". W Nanocomposite Materials [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102484.
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Recent advances in the study of the synthesis, structure and applications of 1-D composites containing conducting polymers are discussed in this review. Conducting composites can form 1-D structures with metal and metal oxides, 1-D carbon nanomaterials, semiconducting materials, crystals of metalloorganic complexes. Advanced synthetic approaches allow for the formation of well-organized structures with polymeric phase deposited both on the surface of 1-D material and inside of the 1-D tubes. 1-D polymeric wires can also serve as a matrix for the formation 1-D composites with other materials. 1-D nanocomposites containing conducting polymers exhibit many exceptional properties which allow for various practical applications including energy converting and energy storage devices, electronic nanodevices, chemical, electrochemical and biochemical sensors, catalysis and electrocatalysis.
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Chemek, Mourad, Ali Mabrouk, Mourad Ben Braieck, Jany Wérry Ventirini i Alimi Kamel. "Synthesis, Experimental and Theoretical Investigations on the Optical and Electronic Properties of New Organic Active Layer for a New Generation of Organic Light-Emitting Diode". W Nanocomposite Materials for Biomedical and Energy Storage Applications. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103807.
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In this chapter, we present new attempts for the development of a new generation of high-performance organic light-emitting diodes (OLEDs). First of all, we present two strategies for obtaining a luminescent active layer. The first one is the chemical synthesis of a block copolymer based on the cross-linked Poly (N-vinyl carbazole) (PVK) and the conjugated poly(3-methylthiophene) (PMeT) system. Secondly, newly small luminescent organic molecules are chemically synthesized and studied. Photo-physical and electronic properties of the synthesized organic materials are fully investigated through experimental analysis and theoretical computations using essentially DFT and TDDFT methodologies. Optical measurements revealed the formation of a new highly luminescent organic material. Furthermore, the newly synthesized small molecules showed a high emission in the blue part. Based on the synthesized active layers, newly multi-structure OLED architectures are theoretically designed by the insertion of a single-walled carbon nanotube (SWCNTs) as a single layer. The theoretical computations show that the insertion of single-walled carbon nanotubes (SWCNTs) single layer improves the injection of electron charge carriers from the chosen cathode (Ca, Mg) to the synthesized active layers, which enhances the performance of the electronic focused devices based on the organic synthesized active layer.
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Srivastava, Manish, Anjali Banger, Anamika Srivastava, Nirmala Kumari Jangid i Priy Brat Dwivedi. "Structure and Properties of Graphene and Chemically Modified Graphene Materials". W Graphene-based Carbocatalysts: Synthesis, Properties and Applications, 43–75. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815050899123010006.
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Graphene is an allotrope of carbon that is made up of very strongly bonded carbon atoms. The structure of graphene is a hexagonal lattice. Graphene shows sp2 hybridization and an extremely thin atomic thickness of approximately 0.345Nm. This chapter deals with graphene structure, including hybridization, critical parameters of the unit cell, the formation of σ and π bonds, electronic band structure, edge orientations, and the number and stacking order of graphene layers. The remarkable characteristics of graphene occur because of the extended chain of π conjugation that results in high charge mobility, high conductivity &high Young's modulus value. Due to these attractive properties, graphene has gained much attention. Graphene, with the unique combination of bonded carbon atom structures with its myriad and complex physical properties is balanced to have a big impact on the future of material sciences, electronics, and nanotechnology. Graphene is converted to Graphene nanoparticles, Graphene oxide nanoparticles; Polymer-based graphene composite materials and Graphene nanoribbons, etc by chemical methods. Some of the application areas are batteries and ultracapacitors for energy storage and fuel cell and solar cell for energy generation and some of the possible future directions of research have been discussed.
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Adarakatti, Prashanth S., i Sumedha H. N. "MXenes based 2D nanostructures for supercapacitors". W Electrochemistry, 261–303. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/bk9781839169366-00261.
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A supercapacitor is made up of three parts: separator, electrolyte, and electrodes. A supercapacitor's performance depends on electrodes with high porosity, chemical stability, and low electrical resistivity. MXenes are getting a lot of attention because of their high electrical conductivity, good mechanical properties, and Faraday pseudocapacitive charge storage mechanism. They are being used in supercapacitor applications. MXenes electrochemical characteristics are very advantageous for energy storage applications. There are three different mechanisms for supercapacitors, which will be discussed completely in this chapter. Furthermore, MXene performance can be increased by modifying the surface groups, interlayer structures, electrode morphology, or by manufacturing a composite with an additional functional material. Manufacture of the MXene electrode for testing and analysis is a vital step in getting a supercapacitor with good performance. Choosing a good blend of materials to accompany MXene is also a vital step. It's hard to find anything else like MXenes when it comes to appealing and unique properties like high electronic conductivity, tunable layer structure, and chemistry.
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Kide Mengistu, Habtamu. "Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics". W Legumes Research - Volume 1. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.99413.
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Tropical regions such as South Asia (SA) and Sub-Saharan (SSA) do have storage environment that may impose abiotic and/or biotic stress or. This book chapter aims to broaden current knowledge on the ‘Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics’. This book chapter is prepared by including all relevant studies and detailed literatures using various scholastic search approaches. Typically, published papers and abstracts are identified by a computerized search of electronic data bases that include PubMed, Science Direct, Scirus, ISI Web of Knowledge, Google Scholar and CENTRAL (Cochrane Central Register of Controlled Trials). Thus, diseases, insects, etc…, are biological factors that cause biotic stress in plants while abiotic stress is caused by either physical or chemical factors. Biotic and abiotic stresses create adverse effects on multiple procedures of morphology, biochemistry and physiology that are directly connected with growth and yield of legume grains. It is, therefore, clear that the most important factors of food grains loss are moisture, temperature, metabolic activity and respiration, insects, mites, micro-organisms, rodents, birds and storage structures. Initial grain condition or quality of the seed for storage can indirectly be affected by abiotic stresses like water scarcity, high salinity, extreme temperatures, and mineral deficiencies or metal toxicities which reduce the crop’s productivity. For maintenance of storage of initial grain’s quality, grain must be dried and cooled prior to storage, the store must be constructed for blocking rodents and birds, enabling protection from sun and light entrance, allowing aeration to keep the temperature uniform in the store. Also, bringing the temperature of the grain down to below 12°C is necessary, since this temperature is a threshold at which microorganisms’ reproductive activity is inhibited. Storage spaces with higher relative humidity (95%) and a temperature of 35°C, are detrimental for storage of legume grains. In general, legume grains should be attaining a temperature of about ≤ 10 °C before placing them in store. For storage safety, it is preferable to place the grain in the storage at moisture content of 13%, or less than 14% on wet basis. Also, combining drying and storage facilities in one and the same structure is economical, and allows further conditioning at later stages if required. In order to reduce postharvest loss from customs of traditional storage by farmers in tropics, governments should mobilize and integrate multidisciplinary management system of storage loss, and monitor precautionary measures of the stored grain throughout the storage period. They should be facilitating the selection and promotion of alternative, cost-effective and appropriate storage structures considering suitability to local conditions and sustainability.
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Shao, G. N. "Lanthanide-based Superconductor and its Applications". W Superconductors, 97–107. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644902110-5.
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Superconductors are materials that conduct electricity with no resistance below its critical temperature (Tc). To date, pure metals, metal alloys, oxides, hydrides and super hydrides are among structures that have been reported to exhibit excellent superconducting properties due to their unique electronic properties and lattice structure. Most researchers have widely reported on the fabrication, structure, properties and applications of cuprate and iron-based superconducting materials. The modification of cuprate-based and iron-based superconducting materials using lanthanides have shown to massively improve their physico-chemical properties and applications. Investigations on lanthanide superhydride superconductors which contain hydrogen framework structures such as LaH10 and YbH10 are a recent adventure in the field of superconductors. Lanthanide-based structures are considered as potential high temperature superconductors (HTSC) and can be used in high performance applications. The current chapter outlines the advances and prospects observed in lanthanide-based superconductors (LBSC) as modern and fascinating functional materials. There is some literature that has been dedicated to providing a review on superconductors but very few have reported on LBSC. This review chapter provides a general insight of the development of LBSC and their potential technological applications.
Streszczenia konferencji na temat "Electronic Structure - Chemical Hydrogen Storage"
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Pathak, Mansi, Abhijeet Gangan i Brahmananda Chakraborty. "Electronic structure and hydrogen storage capability of zirconium decorated graphyne". W DAE SOLID STATE PHYSICS SYMPOSIUM 2017. Author(s), 2018. http://dx.doi.org/10.1063/1.5028963.
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Desnavi, Sameerah, Brahmananda Chakraborty i Lavanya M. Ramaniah. "First principles DFT investigation of yttrium-doped graphene: Electronic structure and hydrogen storage". W SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4873109.
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Jain, Richa Naja, Brahmananda Chakraborty i Lavanya M. Ramaniah. "First principles DFT investigation of yttrium-decorated boron-nitride nanotube: Electronic structure and hydrogen storage". W NANOFORUM 2014. AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4917756.
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Davis, Benjamin, Nitin Muralidharan, Cary Pint i Matthew R. Maschmann. "Electrically Addressable Hierarchical Carbon Nanotube Forests". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67226.
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Hierarchical, branched carbon nanotube (CNT) forest assemblies were created by synthesizing a second generation of CNTs directly from the alumina-coated surface of a parent CNT forest. First, a parent CNT forest generation was synthesized using floating catalyst chemical vapor deposition (CVD) in which gaseous argon and hydrogen are flowed into a tube furnace, along with a controlled flow rate of ferrocene nanoparticles suspended in xylene solvent. Next, a thin alumina coating was applied to the parent CNT forest using atomic layer deposition (ALD). The ALD process pulses alternating gases of water vapor and trimethylaluminum (TMA) and is repeated for 100 cycles, yielding a 10nm coating. This coating adheres to the outer walls of the larger CNTs and serves as a supportive surface to enable the growth of a second CNT generation. Finally, a second CNT generation was synthesized from the parent CNT forest using a floating-catalyst CVD method similar to that used for the parent generation. The relatively low areal density of the parent CNT generation allows for gas-phase additive processing (i.e. ALD and floating catalyst CVD) to occur deep within the volume of the original parent CNT forest. Transmission electron microscopy analysis of the hierarchical CNT forests shows that second-generation CNTs nucleate and grow from the alumina-coated walls of the parent generation rather than nucleating from the original growth substrate, as has been previously reported. Further, physical confinement of the second-generation catalyst particle on the external surface of the parent generation CNTs (28 nm average diameter) leads to small-diameter CNTs (8 nm average) for the second generation. Further, radial breathing modes are detected by Raman spectroscopy, indicating single-walled or few-walled CNTs are synthesized in the second generation. The hierarchical forests exhibit many desirable properties compared to single generation forests. Because the second generation CNTs within the interstitial regions of the parent CNT forest, they increase the structural rigidity of the cellular CNT forest morphology, increasing in mechanical stiffness by ten-fold, relative to the parent CNT forest. Further, we demonstrate that electrical continuity between the CNT generations is retained. Because a thin alumina buffer layer exists between CNT generations, electrical continuity is not guaranteed. Cyclic voltammetry and electrochemical impedance spectroscopy are used to characterize the electrical resistance elements within the hierarchical forest. This hierarchical structure offers a new avenue to tailor the performance of CNT forests and offers performance enhancements for applications in thermal interfaces, electrical interconnects, dry adhesives and energy generation and storage.
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Flak, Dorota, Mieczyslaw Rekas, Artur Braun i Antje Vollmer. "P2.4.8 Effect of the Titania Substitution on the Electronic Structure and Transport Properties of FSS-made Fe2O3 Nanoparticles for Hydrogen Sensing". W 14th International Meeting on Chemical Sensors - IMCS 2012. AMA Service GmbH, Von-Münchhausen-Str. 49, 31515 Wunstorf, Germany, 2012. http://dx.doi.org/10.5162/imcs2012/p2.4.8.
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Fukuyama, Seiji, Masaaki Imade i Kiyoshi Yokogawa. "Development of New Material Testing Apparatus in High-Pressure Hydrogen and Evaluation of Hydrogen Gas Embrittlement of Metals". W ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26820.
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A new type of apparatus for material testing in high-pressure gas of up to 100 MPa was developed. The apparatus consists of a pressure vessel and a high-pressure control system that applies the controlled pressure to the pressure vessel. A piston is installed inside a cylinder in the pressure vessel, and a specimen is connected to the lower part of the piston. The load is caused by the pressure difference between the upper room and the lower room separated by the piston, which can be controlled to a loading mode by the pressure valves of the high-pressure system supplying gas to the vessel. Hydrogen gas embrittlement (HGE) and internal reversible hydrogen embrittlement (IRHE) of austenitic stainless steels and iron- and nickel-based superalloys used for high-pressure hydrogen storage of fuel cell vehicle were evaluated by conducting tensile tests in 70 MPa hydrogen. Although the HGE of these metals depended on modified Ni equivalent, the IRHE did not. The HGE of austenitic stainless steels was larger than their IRHE; however, the HGE of superalloys was not always larger than their IRHE. The effects of the chemical composition and metallic structure of these materials on the HGE and IRHE were discussed. The HGE of austenitic stainless steels was examined in 105 MPa hydrogen. The following were identified; SUS304: HGE in stage II, solution-annealed SUS316: HGE in stage III, sensitized SUS316: HGE in stage II, SUS316L: HGE in FS, SUS316LN: HGE in stage III and SUS310S: no HGE.
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Smith, Kyle C., Peter D. Gilbert, Christopher S. Polster i Timothy Fisher. "Heat Conduction in Metal Hydride Nano-Particles". W ASME 2007 2nd Energy Nanotechnology International Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/enic2007-45037.
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Metal hydrides hold significant potential for use in solid-state hydrogen storage through reversible chemical reactions of metal constituents and hydrogen. Managing heat loads in the system is critical to controlling system performance because a substantial amount of the energy content in hydrogen gas is released during the exothermic hydrogen uptake process, and this process must occur in only a few minutes for vehicle applications. These materials often are used in a powder form in which the initial particle size is 50–100 micrometers. However, as the material is cycled by hydriding (M+H2→MH) and dehydriding (M+H2←MH), particle size can decrease by several orders of magnitude. For the solid metal hydride phase, relative contributions of the electronic and phononic thermal conductivities are quantified with varying composition and particle size. Particle size effects are approximated by a boundary scattering term in the phononic thermal conductivity formulation. Also, the electronic contribution to thermal conductivity is estimated as a function of hydrogen content. The results reveal that overall thermal conductivity is highly material-specific. Materials with large electronic contributions in the pure metal state are relatively unaffected by particle size, while those with lower electronic contributions exhibit a substantial decrease in thermal conductivity with particle size.
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Yang, Jingbin, Yingrui Bai, Jinsheng Sun, Kaihe Lv, Jintang Wang, Liyao Dai, Qitao Zhang i Yuecheng Zhu. "Preparation of High Temperature Resistant High Strength Supramolecular Gels Based on Hydrophobic Association and Hydrogen Bonding and its Application in Formation Pluggingg". W SPE Western Regional Meeting. SPE, 2023. http://dx.doi.org/10.2118/213047-ms.
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Abstract The traditional chemical cross-linking method is based on the formation of covalent bonds between molecules to connect three-dimensional networks to enhance the strength of hydrogels. Although this method can significantly improve the mechanical properties, it also has many problems, such as irreversibility and fatigue. Therefore, the design and preparation of supramolecular hydrogels with high mechanical properties and good temperature resistance have very important research significance and practical value. This paper prepared a supramolecular gel with both temperature resistance and mechanical properties through hydrophobic association and hydrogen bonding, and evaluated its thermal stability, rheology, temperature resistance and pressure plugging ability. The results showed that the supramolecular gel had excellent thermal stability, and there was strong physical entanglement between its three-dimensional network structures, which made it difficult to be destroyed by increasing temperature. The excellent rheological properties of supramolecular gels enable them to maintain good viscoelastic changes in the linear viscoelastic region within the strain range of 0.1-30%. When the strain was greater than 30%, the supramolecular gel began to undergo different degrees of sol-gel phase transition, which showed that the energy storage modulus of supramolecular gel decreased. In addition, the energy storage modulus of supramolecular gel was always greater than the loss modulus in the whole frequency scanning range, and there was no intersection between the two gel and the gel always showed high elasticity. Meanwhile, the supramolecular gel still had good structure and strength after high temperature aging. Its tensile and compressive properties did not change significantly, but the color of the gel surface changed slightly, which could maintain good structural stability under high temperature environment. Supramolecular gel particles could be used as plugging materials for drilling fluid, and had excellent plugging ability of formation fractures and pores. The plugging ability of 1mm aperture plate model was up to 6.3MPa, and the plugging ability of 1mm seam width was up to 4.9MPa. Therefore, the development and application of supramolecular gel plays an important supporting role in drilling fluid plugging.
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Yates, Luke, Ramez Cheaito, Aditya Sood, Zhe Cheng, Thomas Bougher, Mehdi Asheghi, Kenneth Goodson i in. "Investigation of the Heterogeneous Thermal Conductivity in Bulk CVD Diamond for Use in Electronics Thermal Management". W ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2017 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ipack2017-74163.
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From a materials perspective, diamond exhibits properties that are extremely well suited for use in the thermal management of high power and high heat flux electronic devices. While bulk diamond grown via chemical vapor deposition (CVD) has been demonstrated since the 1980s, and people have measured thermal conductivities ranging from 500–2000 W/m-K, these measurements have typically taken place over a large domain that encompasses numerous diamond grains. However, many of these techniques do not reveal the heterogenous nature of the diamond thermal conductivity which arises due to the local grain structure and orientation. The diamond sample investigated in this study contained a high level of boron doping on the order of 1021cm−3, giving rise to a reduced thermal conductivity measured as 714 W/m-K with a laser flash method. Similar bulk CVD diamond samples that are undoped show thermal conductivity values of greater than 1500 W/m-K with the same measurement technique. Through the use of time-domain thermoreflectance (TDTR) we are able to measure the thermal conductivity of bulk CVD diamond at a spatial resolution smaller than the size of the columnar grains. This allows us to examine significant changes in thermal conductivity as a function of spatial location, which is of great significance when the thermal source from electronics is on the size scale of this variation. Using TDTR, we present an approach involving a variation in the laser spot size using multiple focusing objectives to yield the heterogeneous thermal conductivity in bulk CVD diamond. The data show variations in thermal conductivity near 40% over a diameter of 40 μm. Scanning Electron Microscopy (SEM) and electron backscatter diffraction (EBSD) data are presented which also show variation in microstructure over this length scale giving rise to the heterogeneity.
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Hossain, Mohammad K., Md Mahmudur R. Chowdhury, Mahesh Hosur, Shaik Jeelani i Nydeia W. Bolden. "Enhanced Properties of Epoxy Composite Reinforced With Amino-Functionalized Graphene Nanoplatelets". W ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51483.
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A systematic study has been conducted on processing and characterization of epoxy polymer composite to enhance its mechanical, viscoelastic, and thermal properties through optimization of graphene nanoplatelets (GNP). GNP having a two dimensional structure is composed of several layers of graphite nanocrystals stacked together. GNP is expected to provide better reinforcing effect in polymer matrix composites as a nanofiller along with greatly improved mechanical and thermal properties due to its planar structure and ultrahigh aspect ratio. GNP is also considered to be the novel nanofiller due to its exceptional functionalities, high mechanical strength, chemical stability, abundance in nature, and cost effectiveness. Moreover, it possesses an extremely high-specific surface area which carries a high level of transferring stress across the interface and provides higher reinforcement than carbon nanotubes (CNT) in polymer composites. Hence, this research has been focused on the reinforcing effect of the amine-functionalized GNP on mechanical, viscoelastic, and thermal properties of the epoxy resin-EPON 828 composite. Amine functionalized GNP was infused in EPON 828 at different loadings including 0, 0.1, 0.2, 0.3, 0.4, and 0.5 wt% as a reinforcing agent. GNP was infused into epoxy resin Epon 828 Part-A using a high intensity ultrasonic liquid processor followed by a three roll milling processor for better dispersion. The GNP/epoxy mixture was then mixed with the curing agent Epikure 3223 according to the stoichiometric ratio (Part A: Part B = 12:1). The mixture was then placed in a vacuum oven at 40 °C for 10 m to ensure the complete removal of entrapped bubbles and thus reduce the chance of void formation. The as-prepared resin mixture was then poured in rubber molds to prepare samples for mechanical, viscoelastic, and thermal characterization according to ASTM standards. Molds containing liquid epoxy nanocomposites were then kept in the vacuum oven at room temperature for seven days to confirm full curing of the samples according to the manufacturer’s suggestion. Similarly, neat epoxy samples were fabricated to obtain its baseline properties through mechanical, viscoelastic, and thermal characterization and compare these properties with those of nanophased ones. The reinforcing effect of the amine-functionalized GNP on the epoxy was characterized through mechanical, viscoelastic, and thermal analyses. Fracture morphology of mechanically tested samples was evaluated through scanning electronic microscopy (SEM) study. The mechanical properties were determined through flexure test according to the ASTM standard. Dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA) were performed to analyze viscoelastic and thermal performances of the composite. In all cases, the 0.4 wt% GNP infused epoxy nanocomposite exhibited the best properties. The 0.4 wt% GNP-loaded epoxy sample showed 20% and 40% improvement in flexure strength and modulus, respectively. Moreover, 16% improvement in the storage modulus and 37% decrease in the coefficient of thermal expansion were observed due to the integration of GNP reinforcement into the epoxy system. Scanning electronic micrographs exhibited smooth fracture surface for the neat sample, whereas the roughness of surface increased due to the GNP incorporation. This is an indication of change in the crack propagation during loading and a higher energy requirement to fracture the GNP-loaded sample.
Raporty organizacyjne na temat "Electronic Structure - Chemical Hydrogen Storage"
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Robertson, Ian M., i Duane D. Johnson. Reversible Hydrogen Storage Materials – Structure, Chemistry, and Electronic Structure. Office of Scientific and Technical Information (OSTI), czerwiec 2014. http://dx.doi.org/10.2172/1134549.
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