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arXiv 2021年

作者： Toher, Cormac Oses, Corey Esters, Marco Hicks, David Kotsonis, George N. Rost, Christina M. Brenner, Donald W. Maria, Jon-Paul Curtarolo, Stefano Dept. Mechanical Engineering and Materials Science Center forAutonomous Materials Design Duke University DurhamNC27708 United States Dept. Materials Science and Engineering Pennsylvania State University University ParkPA16802 United States Dept. Physics and Astronomy James Madison University HarrisonburgVA22807 United States Dept. Materials Science and Engineering North Carolina State University RaleighNC27695 United States

Disorder enhances desired properties, as well as creating new avenues for synthesizing materials. For instance, hardness and yield stress are improved by solid-solution strengthening, a result of distortions and atomic size mismatches. Thermo-chemical stability is increased by the preference of chemically disordered mixtures for high-symmetry super-lattices. Vibrational thermal conductivity is decreased by force-constant disorder without sacrificing mechanical strength and stiffness. Thus, high-entropy ceramics propel a wide range of applications: from wear resistant coatings and thermal and environmental barriers to catalysts, batteries, thermoelectrics and nuclear energy management. Here, we discuss recent progress of the field, with a particular emphasis on disorder-enhanced properties and applications. © 2021, CC BY.

关键词： Entropy

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Fabrication of in-situ formed al3zr reinforced al sintered composites and their tribological behavior

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Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 2020年第10期67卷 536-542页

作者： NISHIMURA, Nodoka UMEDA, Junko FUJII, Hiroko JIA, Lei KONDOH, Katsuyoshi Dept. Mechanical Engineering Graduate School of Osaka University 2-1 Yamadaoka Suita565-0871 Japan Joining and Welding Research Institute Osaka University 11-1 Mihogaoka Ibaraki567-0047 Japan School of Materials Science and Engineering Xi'an University of Technology Xi'an710048 China

Powder metallurgy (PM) Al3Zr reinforced aluminum (Al) composites were fabricated by in-situ reaction during spark plasma sintering (SPS) using the pre-mixed Al and zirconium hydride (ZrH2) powders. The diffusion behavior of Al and zirconium (Zr) elements in Al matrix were studied. It was clarified that ZrH2 decomposed at around 773 K and dissolved Zr elements reacted with Al matrix to form Al3Zr layers around ZrH2 particle. Al3Zr compounds grew toward the center of ZrH2 particle due to a faster diffusion rate of Al compared to Zr element. The tribological behavior of the composite material was investigated by using pin-on-disk wear test under lubricated condition. Friction coefficient and wear volume of Al-Al3Zr composite were much lower than those of pure Al. SEM observation and SEM-EDS analysis on wear track of pin and disk specimens were investigated. The sliding surface of SUS304 stainless steel counterpart after wear test showed very slight damages and no seizure phenomenon with the pin specimen. It is concluded that PM Al-Al3Zr composite had a good tribological property and wear resistance due to hard Al3Zr particles dispersed in Al matrix preferentially contacting the counterpart material to prevent the soft Al matrix in direct contact with SUS steel surface. © 2020 Japan Society of Powder and Powder Metallurgy.

关键词： Wear of materials

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Time-space bi-fractional drift-diffusion equation for anomalous electrochemical transport

arXiv

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arXiv 2023年

作者： Allagui, Anis Paradezhenko, Georgii Pervishko, Anastasiia Yudin, Dmitry Benaoum, Hachemi Department of Sustainable and Renewable Energy Engineering University of Sharjah P.O. Box Sharjah27272 United Arab Emirates Department of Mechanical and Materials Engineering Florida International University MiamiFL33174 United States Skolkovo Institute of Science and Technology Moscow121205 Russia Dept. of Applied Physics and Astronomy University of Sharjah PO Box 27272 Sharjah United Arab Emirates

The Debye-Falkenhagen differential equation is commonly used as a mean-field macroscopic model for describing electrochemical ionic drift and diffusion in dilute binary electrolytes when subjected to a suddenly applied potential smaller than the thermal voltage. However, the ionic transport in most electrochemical systems, such as electrochemical capacitors, permeation through membranes, biosensors and capacitive desalination, the electrolytic medium is interfaced with porous, disordered, and fractal materials which makes the modeling of electrodiffusive transport with the simple planar electrode theory limited. Here we study a possible generalization of the traditional drift-diffusion equation of Debye and Falkenhagen by incorporating both fractional time and space derivatives for the charge density. The nonlocal (global) fractional time derivative takes into account the past dynamics of the variable such as charge trapping effects and thus subdiffusive transport, while the fractional space derivative allows to simulate superdiffusive transport. © 2023, CC BY.

关键词： Desalination

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Interfacial Structure of Metastable 4H-BaRuO3 Thin Film on (111) SrTiO3 Substrate

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Microscopy and Microanalysis 2020年第S2期6卷 1066-1067页

作者： Q. Ding W. Tian M. K. Lee E. B. Eom X. Q. Pan Dept. of Materials Science and Engineering The University of Michigan Ann Arbor MI- 48109 Dept. of Mechanical Engineering and Materials Science Duke University Duham NC- 27708

BaRuO3 chemically belongs to ARuO3 family. It has unique hexagonal structure rather than an orthorhombic GdFeO3-type structure of other members, such as SrRuO3 and CaRuO3. The structure of ARuO3 compounds can be described on the basis of the close-packed stacking of AO3 layers in which the center of oxygen octahedra is occupied by ruthenium. A number of polymorph structures exist by mixing the cubic and hexagonal close-packed stacking of AO3 *** to date, only three polymorph structures have been observed in BaRuO3 bulk materials, which are denoted by 4H, 6H and 9R structure. The 9R structure (Fig. 1 (a)) is most stable at 1100 °C at atmosphere pressure. As pressure is increased, the 9R structure will transform through metastable 4H structure (Fig. 1(b)) to metastable 6H structure. The physical properties of BaRu03 polymorphs differ significantly with the variation of the structure. Hence, it is desirable to form phase pure polymorphs of BaRuO3 to examine the structure-property relationship.

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Transition Behavior of Cellulose Nanocrystal Networks Induced by Nanoconfined Water

SSRN

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SSRN 2024年

作者： Liu, Siyuan Xu, Dan Cai, Chenyang Zhang, Xizhou Cecily Andreas, Loren B. Wang, Zengbin Song, Qun Wang, Jiaxiu Picu, Catalin R. Zhang, Kai Sustainable Materials and Chemistry Dept. Wood Technology and Wood-based Composites University of Göttingen Göttingen37077 Germany Co-Innovation Center of Efficient Processing Utilization of Forest Resource School of Materials Science and Engineering Nanjing Forestry University Nanjing210037 China NMR-based Structural Biology Max-Planck-Institute for Biophysical Chemistry Göttingen37077 Germany School of Life Sciences Anhui University Hefei230601 China Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute TroyNY12180 United States

Hydrogen bonding (HB) is essential for the mechanical properties of cellulose-based materials. However, the plastification of cellulose nanocrystals (CNC) caused by the transition of HB in the presence of water is still insufficiently understood. In this work, we quantitively describe the rigid-soft transition of nanoconfined chains in non-ordered regions of CNC surfaces by comparing their strain behaviors with amorphous cellulose. Moreover, we explore this softening (referred to as the ‘hydro-glass transition’) with increasing relative humidity (RH) and identify a threshold RH value, RHt, which characterizes the transition. The phenomenon is attributed to the monolayer to multilayer adsorption and eventually capillary condensation of water molecules in wedged mesopores of the CNC films. This triggers a rapid transition of HB from cellulose-cellulose to cellulose-water type in the vicinity of RHt. The hydro-glass transition is promoted by higher temperatures such that, for example, RHt at 65 °C is 50% of RHt measured at room temperature. Besides, the presence of surface groups with lower acid dissociation constant (comparing -SO3- and -OH/COO- moieties) also accelerates this hydro-glass transition process. This work provides a detailed understanding of the thermodynamic changes in hydrogen bonded nanoconfined polymer chains in the presence of humidity, with implications for developing nanomaterials with RH-controlled properties. © 2024, The Authors. All rights reserved.

关键词： Hydrogen bonds

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Photopolymer fiber composite structures in microgravity 18

Photopolymer fiber composite structures in microgravity

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18th European Conference on Composite materials, ECCM 2018

作者： Sarantinos, Nikolaos Loginos, Panagiotis Charlaftis, Panagiotis Argyropoulos, Alexios Filinis, Adrianos Vrettos, Katerina Adamos, Loukas Kostopoulos, Vassilis University of Patras Mechanical Engineering and Aeronautics Dept. Applied Mechanics Laboratory Panepistimioupoli Patron Rio26500 Greece University of Patras Materials Science Dept. Nanochemistry Laboratory Panepistimioupoli Patron Rio26500 Greece

ISBN: (纸本)9781510896932

Deployable structures are the future in space manufacturing. A common approach, are the pneumatically actuated deployables, which deploy using the pressure of a fluid and generally impose a low risk during deployment. However, their greater disadvantage is the low stiffness and damage tolerance. In order to solve this problem, AML-Applied Mechanics Laboratory and the AML Space Group researching the idea of deploying pre-impregnated polymer fibers fabrics into space and curing them, thus creating lightweight, high-stiffness, thin-shelled structures in space. This research was focused around the behavior of photopolymer resins in a micro-gravity environment, by participating in the ESA Fly Your Thesis 2017 campaign. In this experiment, uncured glass fiber reinforced polymer tubes stowed before flight, deployed by compressed air and cured during the micro-gravity intervals of the parabolic flights, using a UV light-source. Identical reference specimens were produced on Earth with the same equipment at 1-g gravity acceleration. The goal was to test and compare the mechanical properties and microstructure between these two batches of specimens produced in the two different gravity acceleration levels. Identifying the effect of different gravity levels on the mechanical properties and microstructure of polymeric materials, shall enable better understanding on how such polymers could be used in space manufacturing. © CCM 2020 - 18th European Conference on Composite materials. All rights reserved.

关键词： Light sources

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Regression Model for Optimum Solar Collectors’ Tilt Angles in Libya

Regression Model for Optimum Solar Collectors’ Tilt Angles ...

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Renewable Energy & Sustainability (ieCRES), International engineering Conference on

作者： Yasser F. Nassar Hala J. El- Khozondar Nasser M. Abouhmod Ahmed A. Abubaker Abdussalam A. Ahmed Abdulgader Alsharif Mohamed M. Khaleel Mohamed Elnaggar Rifa J. El-Khozondar Mechancal & Renewable energy. Eng. Dept. Wadi Alshatti University Brack-Libya Electrical Eng. and Smart Systems Dept. The Islamic University of Gaza Gaza Palestine Electrical and Electronic Eng. Dept. Eng. Faculty Wadi Alshatti University Brack-Libya Mechanical Eng. Dept. Bani Waleed University Bani Waleed Libya Faculty of Engineering Universiti Teknologi Malaysia (UTM) Johor Malaysia Dept. of Electrical and Electronic Eng. Karabu University Karabuk Turkey Engineering Program Department Palestine Technical College – Deir ElBalah Deir El-Balah Palestine Physics Departments Faculty of Science Gaza Al-Aqsa University Gaza Palestine

The present study presents a regression function for optimum tilt angle for fixed mode flat-plate solar harvesters suitable for different locations in Libya, sky conditions and albedo values. The research based on 14 years -15 minutes time series solar irradiation components which provided by Solargis database platform for 24 different locations in Libya, based on the contract signed between the Solargis Company and Wadi AlShatti University. Several transposition models are applied - corresponding to each location - for estimating the tilted global solar irradiance components according to recommendation of a local recent study. The proposed model corrects the optimum tilt angle by involving the three components of the solar irradiation: direct beam, sky-diffused and ground reflected solar irradiances. The results proved the applicability and reliability of the obtained regression model. In addition, results showed the high potential of the proposed model for use in engineering design, eco-energetic analysis and optimum design processes.

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Distortion mitigation in additive manufacturing of AlSi10Mg by multilayer laser peening

Distortion mitigation in additive manufacturing of AlSi10Mg ...

引用

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020

作者： Madireddy, G. Liu, J.F. Sealy, M.P. Dept. of Mechanical and Materials Engineering University of Nebraska LincolnNE68588 United States Sentient Science Corporation 672 Delaware Avenue BuffaloNY14209 United States

Distortion in metal additive manufacturing remains an industry barrier due to the inadequate thermal management that gives rise to residual stresses. Mitigation strategies primarily involve developing a print recipe based on the build material;however, variability among machine platforms, build strategies, and raw material stock inhibit development of universal print recipes that eliminate distortion. There is a need for a universal manufacturing technology that enables distortion free additive manufacturing. A solution to provide distortion free parts that are machine platform and build strategy independent is coupling additive manufacturing with multilayer peening. Peening enables favorable redistribution of residual stresses that drive distortion using mechanical means rather than thermal management. The cumulative nature of residual stress during layer-by-layer peening and the compounding effect on distortion is poorly understood. Thus, the research objective of this work was to measure residual stress and distortion after multilayer laser peening on AlSi10Mg printed by laser powder bed fusion on the Matsuura Lumex Avance-25. Residual stress was measured for several interlayer peening frequencies. An optimum condition was identified and evaluated for distortion mitigation. To measure deflection, bridge samples based on NIST AMB2018-01 were printed and interlayer peened. Results indicated that laser peening reduced distortion 45% over an as-printed sample. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ISEM 2020

关键词： Residual stresses

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Toward Mass-Production of Transition Metal Dichalcogenide Solar Cells: Scalable Growth of Photovoltaic-Grade Multilayer WSe2 by Tungsten Selenization

arXiv

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arXiv 2024年

作者： Neilson, Kathryn M. Hamtaei, Sarallah Nazif, Koosha Nassiri Carr, Joshua M. Rahimisheikh, Sepideh Nitta, Frederick U. Brammertz, Guy Blackburn, Jeffrey L. Hadermann, Joke Saraswat, Krishna C. Reid, Obadiah G. Vermang, Bart Daus, Alwin Pop, Eric Dept. of Electrical Engineering Stanford Univ. StanfordCA94305 United States Hasselt Univ. imo-imomec Martelarenlaan 42 Hasselt3500 Belgium Imec imo-imomec Thor Park 8320 Genk3600 Belgium EnergyVille imo-imomec Thor Park 8320 Genk3600 Belgium Univ. Colorado Boulder Materials Science & Engineering Program BoulderCO80303 United States Groenenborgerlaan 171 Antwerpen2020 Belgium Dept. of Materials Science & Engineering Stanford Univ. StanfordCA94305 United States National Renewable Energy Laboratory Chemistry and Nanoscience Center GoldenCO80401 United States University of Colorado Boulder Renewable and Sustainable Energy Institute BoulderCO80303 United States Univ. Freiburg Freiburg Germany Precourt Institute for Energy Stanford Univ. StanfordCA94305 United States

Semiconducting transition metal dichalcogenides (TMDs) are promising for high-specific-power photovoltaics due to desirable band gaps, high absorption coefficients, and ideally dangling-bond-free surfaces. Despite their potential, the majority of TMD solar cells are fabricated in a non-scalable fashion using exfoliated materials due to the absence of high-quality, large-area, multilayer TMDs. Here, we present the scalable, thickness-tunable synthesis of multilayer tungsten diselenide (WSe2) films by selenizing pre-patterned tungsten with either solid source selenium or H2Se precursors, which leads to smooth, wafer-scale WSe2 films with a layered van der Waals structure. The films have charge carrier lifetimes up to 144 ns, over 14× higher than large-area TMD films previously demonstrated. Such high carrier lifetimes correspond to power conversion efficiency of ~22% and specific power of ~64 W g-1 in a packaged solar cell, or ~3 W g-1 in a fully-packaged solar module. This paves the way for the mass-production of high-efficiency multilayer WSe2 solar cells at low cost. © 2024, CC BY.

关键词： Selenium compounds

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A review of solar chimney for natural ventilation of residential and non-residential buildings

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SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS 2022年第PartB期52卷

作者： Maghrabie, Hussein M. Abdelkareem, Mohammad Ali Elsaid, Khaled Sayed, Enas Taha Radwan, Ali Rezk, Hegazy Wilberforce, Tabbi Abo-Khalil, Ahmed G. Olab, A. G. [a]Department of Mechanical Engineering Faculty of Engineering South Valley University Qena 83521 Egypt [b]Dept. of Sustainable and Renewable Energy Engineering University of Sharjah P.O. Box 27272 Sharjah United Arab Emirates [c]Center for Advanced Materials Research University of Sharjah PO Box 27272 Sharjah United Arab Emirates [d]Faculty of Engineering Minia University Elminia Egypt [e]Chemical Engineering Department Texas A&M University College Station TX 77843-3122 USA [f]Mechanical Power Engineering Department Mansoura University El-Mansoura 35516 Egypt [g]College of Engineering at Wadi Addawaser Prince Sattam Bin Abdulaziz University Saudi Arabia [h]Mechanical Engineering and Design Aston University School of Engineering and Applied Science Aston Triangle Birmingham B4 7ET United Kingdom [i]Sustainable Energy & Power Systems Research Centre RISE University of Sharjah P.O. Box 27272 Sharjah United Arab Emirates

The requirement for passive cooling strategies in buildings has great attention in almost all countries, where hot temperatures are predominant throughout the year. The ventilation process is a crucial necessity for a healthy lifestyle and its significance is additionally highlighted through the contemporary universal outbreak of Covid19. One of the promising applications for cooling residential buildings is the solar chimney (SC) that is particularly convenient for hot and humid climates. The solar chimney is a natural draught passive method that utilizes available solar energy to build up the stack pressure. The solar chimney participates in elevating the cooling and heating efficiency of residential/non-residential spaces. The present article introduces an overview of the operation and performance of the SC. Studying the potential design and operating parameters influencing the SC performance for natural ventilation (NV) compared to the electrical high-energy technologies to sustain the acceptable indoor climatic conditions is important. As well, the natural ventilation for harsh climate conditions using SC only is not applicable so the enhanced solar ventilation systems are studied. Combined enhanced cooling/heating energy systems based on the solar chimney are considered as an effective strategy towards low energy consuming buildings.

关键词： Solar chimney Natural ventilation Thermal comfort Residential non-residential buildings ACH

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