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Thermal and pH Sensitive Blends Formed by Chitosan and Poly(N-Vinylcaprolactam)

ChemistrySelect 2025年第23期10卷

作者： Djalma A. Oliveira Maria E. G. Barros Grazielle R. Cerqueira Yêda M. B. Almeida Carolina L. Morelli Materials Science Program Federal University of Pernambuco (UFPE) Recife 50740-600 Brazil Department of Mechanical Engineering Federal University of Pernambuco (UFPE) Recife 50740-600 Brazil Department of Chemical Engineering Federal University of Pernambuco (UFPE) Recife 50740-600 Brazil

The development of smart polymeric films capable of responding to external and internal stimuli is of great interest in the biomedical and industrial fields for applications that require controlled drug release through pH variation, thermal stimuli, or both. This study aimed to develop and characterize polymeric blends composed by chitosan (CS) and poly( N -vinylcaprolactam) (PNVCL) with dual thermal and pH responsiveness. The films were prepared by solution casting using different CS/PNVCL ratios (90/10, 70/30, and 50/50) and characterized by ATR-FTIR, TGA, DSC, SEM, s-SNOM, contact angle, opacification, and swelling tests. FTIR and s-SNOM confirmed interaction and partial miscibility between the polymers. The films exhibited thermoresponsiveness, changing from transparent to opaque in temperatures from 25 °C to 32 °C, depending on composition. The pH responsiveness analysis indicated that the films demonstrated a greater increase in diameter (more than 80%), when subjected to acidic solution. The blend films presented Tg values of 72.38 °C, 140.41 °C, and 142.22 °C for the CS/PNVCL compositions 90/10, 30/70, and 50/50, respectively, intermediate to those observed for the pure precursor polymers (68.74 °C for CS and 182.39 °C for PNVCL). To the best of our knowledge, studies on solid polymeric systems responsive to pH and temperature, like those developed in this work, have not been performed.

关键词： Chitosan CS/PNVCL blends Nano-FTIR Poly(N-vinylcaprolactam) s-SNOM Thermo-pH responsive blends Thermoresponsive blends

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Electric Field Emission in GdNiO3 Microflower

SSRN

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SSRN 2024年

作者： Karmakar, Subrata Parey, Vanshree Mistari, Chetan D. Hamid, Md Abdul Emu, Injamamul Hoque Halim, Md Abdul Sanyal, Gopal Chakraborty, Brahmananda More, M.A. Droopad, Ravi Haque, Ariful Electrical Engineering Ingram School of Engineering Texas State University San MarcosTX78666 United States Institute of Chemical Research of Catalonia The Barcelona Institute of Science and Technology Av. Països Catalans 16 Tarragona43007 Spain Department of Physics Savitribai Phule Pune University Maharashtra Pune411007 India Mechanical Metallurgy Division Bhabha Atomic Research Centre Trombay Mumbai400085 India High Pressure and Synchrotron Radiation Physics Division Bhabha Atomic Research Centre Trombay Mumbai400085 India Homi Bhabha National Institute Anushaktinagar Mumbai400094 India Materials Science Engineering & Commercialization Program Texas State University San MarcosTX78666 United States

GdNiO3 microflowers were synthesized by hydrothermal method with unit sizes of about 2.2-3.5 μm and petal sizes of ~75-100 nm. The X-ray diffraction pattern (XRD) and Raman spectra reveal an orthorhombic crystal structure with the space group Pbnm and various Raman active vibrational modes i.e., Ag, B1g, B2g associated with rare earth nickelates. The total density of states (TDOS) was calculated by density functional theory (DFT) study using a hybrid functional (HSE06) and the volume of TDOS near the Fermi level confirms the semiconducting nature of GdNiO3 with band gap ~0.688 eV. The local bulk work function (φ) was estimated theoretically at ~5.35 eV from DFT calculations which is one of the essential parameters for the field enhancement factor (β). Field emission current density (J) vs. applied electric field (E) divulges a low turn-on field (Eto)~4.6 V/μm@1 μA/cm2 and a threshold field (Eth)~5.2 V/μm@10 μA/cm2 respectively. The Fowler-Nordheim (F-N) model was introduced to calculate β ~1637 and long-term field emission current stability was observed experimentally > 4 h at the preset values of current 2 μA and 10 μA, respectively. The easy preparedness, low turn-on field, and long-term current stability without significant decay suggest this material to be an efficient electron field emitting material in the rare-earth nickelates series. © 2024, The Authors. All rights reserved.

关键词： Rare earths

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Two Coupled Unit Problems in Shear-Lag Analysis of Fracture in Ceramic Matrix Composites

SSRN

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SSRN 2020年

作者： Raj, Rishi Materials Science and Engineering Program Department of Mechanical Engineering University of Colorado Boulder BoulderCO80309 United States

The progression of damage in ceramic matrix composites encompasses both the matrix and the fibers. The development of cracks in the matrix, and in the fibers, pose different unit problems for the shear lag analysis, even though they share the same interface. If the fracture strength of the matrix-component, normalized with its volume fraction, is weaker than the fiber-component, then it is predicted that the fiber fragments will bridge several matrix cracks. The ratio of the spacing between the breaks in the fibers, and in the matrix, is predicted to be equal to the ratio of their respective fracture loads. © 2020, The Authors. All rights reserved.

关键词： Cracks

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Interface Rotation in Cu/Nb Accumulative Roll Bonded (ARB) Nanolaminates

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SSRN 2022年

作者： Radchenko, Ihor Zhu, Wenxin Qing, Liu Navarro, Etienne Sahay, Rahul Lee, Pooi See Raghavan, Nagarajan Thomas, Olivier Budiman, Arief Suriadi Chen, Kai State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University Xi’an China School of Materials Science and Engineering Nanyang Technological University Singapore639798 Singapore Nanyang Technological University Temasek Laboratories@NTU 637553 Singapore Aix Marseille Université Université de Toulon CNRS IM2NP Marseille France Xtreme Mechanics Lab 8 Somapah Road Singapore487372 Singapore Singapore487372 Singapore Department of Manufacturing and Mechanical Engineering and Technology Oregon Institute of Technology Klamath FallsOR97601 United States Industrial Engineering Department BINUS Graduate Program—Master of Industrial Engineering Bina Nusantara University Jakarta11480 Indonesia

Metal-metal nanolaminates made by accumulative roll bonding (ARB) is a developing new class of structural nanocomposites that possesses high strength, good ductility, and can also be produced in bulk. These nanolaminates exhibit strong crystallographic textures and mechanical anisotropy. Yet, their mechanical properties are often measured only along rolling direction (RD). Using in situ pillar compression, we show that in-plane shear deformation mechanism in Cu(63 nm)/Nb(63 nm) ARB nanolaminate strongly depends on the shear direction. Plastic shear along the RD abruptly changes into crystallographic rotation and later into interface shear as the shear direction deviates away from the RD. The observed shear mechanisms are driven by competition between different slip systems in Cu layers and at the interface. We expect similar deformation anisotropy to happen in other ARB nanolaminates with sharp texture and interface orientation. Comprehensive characterization of such nanolaminates may require considering more than just the usual rolling/transverse/normal direction anisotropy. © 2022, The Authors. All rights reserved.

关键词： Anisotropy

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Cu@Nc as High-Performance and Durable Electrocatalyst for Oxygen Reduction Reaction in Alkaline Membrane Fuel Cells

SSRN

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SSRN 2022年

作者： Peera, Shaik Gouse Liu, Chao Asokan, Arunchander Suss, Matthew E. Department of Environmental Science Keimyung University 1095 Dalseo-gu Daegu42601 Korea Republic of Faculty of Materials Metallurgy and Chemistry Jiangxi University of Science and Technology Ganzhou341000 China Faculty of Mechanical Engineering Technion – Israel Institute of Technology Haifa320003 Israel Grand Technion Energy Program Technion – Israel Institute of Technology Haifa3200003 Israel Wolfson Department of Chemical Engineering Technion – Israel Institute of Technology Haifa3200003 Israel

Discovery of electrocatalysts composed of cheap transition metals are in urgent to replace the traditional Pt/C catalyst used for oxygen reduction reaction (ORR). Herein, we synthesized Cu nanoparticles encapsulated with nitrogen-doped carbon (Cu@NC) as an excellent and durable catalyst for ORR. A systematic evaluation of effect of Cu content, acid leaching and secondary heat treatment have been established with the help of half-cell studies. The morphological analysis revealed that Cu nanoparticles surrounded by a thick nitrogen doped carbon layers and further, the acid leaching and subsequent pyrolysis, boosted the electrocatalytic performance. The optimized Cu@NC catalyst showed onset potential and half-wave potential of 0.975 V vs. RHE (potential corresponding to a current density of 0.1 mA cm-2) and 0.85 V vs. RHE, surpassing Pt/C catalyst. In addition, the Cu@NC catalyst exhibited outstanding durability, tolerance to carbon monoxide and methanol molecules. In the alkaline fuel cell, Cu@NC catalyst delivered 118 mW cm-2 peak power density in alkaline fuel cell operated with H2-O2, whereas Pt/C only delivered a peak power density of 97 mW cm-2 under ambient operating conditions. High ORR activity and better stability of Cu@NC catalyst could be a potential alternative to Pt/C catalyst in alkaline fuel cells and metal-air cell cathodes. © 2022, The Authors. All rights reserved.

关键词： Electrolytic reduction

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Moisture effects on selective laser flash sintering of yttria-stabilized zirconia 30

Moisture effects on selective laser flash sintering of yttri...

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30th Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, SFF 2019

作者： Hagen, Deborah Chen, Alex Beaman, Joseph J. Kovar, Desiderio Department of Mechanical Engineering Materials Science and Engineering Program University of Texas at Austin AustinTX78712 United States

Selective laser flash sintering (SLFS) combines a uniform electric field with a localized, scanning laser as the only external heating source. The presence of a large uniform electric field can greatly increase the sintering rate and lower the sintering temperature for ceramics. The combination of lower sintering temperature and faster sintering rates may allow SLFS to be used for ceramic additive manufacturing. In this work, we study the effects of moisture on SLFS of yttria-stabilized zirconia ceramic. We compare the effects of processing parameters on the initiation of SLFS for samples exposed to a range of moisture levels. © Solid Freeform Fabrication 2019: Proceedings of the 30th Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, SFF 2019. All rights reserved.

关键词： Moisture

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Spatially regulated water-heat transport by fluidic diode membrane for efficient solar-powered desalination and electricity generation

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Nature communications 2025年第1期16卷 5050页

作者： Yuanhang Cao Jiemin Wang Weixin Guan Meng An Peng Yan Zhengtong Li Changsheng Zhao Guihua Yu College of Biomedical Engineering Sichuan University Chengdu China. College of Biomedical Engineering Sichuan University Chengdu China. jiemin@***. Materials Science and Engineering Program and Walker Department of Mechanical Engineering The University of Texas at Austin Austin TX USA. Yangtze Delta Region Academy in Jiaxing Beijing Institute of Technology JiaXing China. anmeng@photon.t.u-tokyo.ac.jp. College of Mechanical and Electrical Engineering Shaanxi University of Science and Technology Xi'an China. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing China. College of Polymer Science and Engineering State Key Laboratory of Polymer Materials Engineering Sichuan University Chengdu China. zhaochsh70@***. Materials Science and Engineering Program and Walker Department of Mechanical Engineering The University of Texas at Austin Austin TX USA. ghyu@austin.utexas.edu.

Interfacial solar-driven evaporation has attracted great research interests, given its high conversion efficiency of solar energy and transformative industrial potential for desalination. However, current evaporators with porous volume remain critical challenges by inherently balancing efficient fluid transport and effective heat localization. Herein, we propose the strategy and design of lightweight, flexible and monolayered fluidic diode membrane-based evaporators, featuring regularly arrayed macropores and dense nanopores on each side. Such a delicate microstructure offers universality in establishing asymmetric channels along macroporous-to-nanoporous to enable the diode-like directional water transport as well as facilitate the heat localization on the nanopores side. Consequently, a high evaporation rate of a maximum 3.82 kg m h can be achieved under 1 sun illumination, exceeding most 2D and 3D evaporators. Besides, the durability and practicability of our evaporators are validated through salt resistance tests, purification experiments among various contaminants, and outdoor evaluations. Moreover, the structure engineering and water-transport optimization of fluidic diode membranes also offer potentials for hydrovoltaic applications, with over 1.6 V generated by tandem devices at the ambient environment. This work provides a concept for designing high-performance monolayered membranes applicable in environmental and energy-related realms.

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Thermo-economic and environmental evaluation of thin film evaporation using novel metal-organic frameworks to enhance solar desalination performance

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Process Safety and Environmental Protection 2025年 199卷

作者： Sharshir, Swellam W. Abdo, Mohamed R. Yusuf, Kareem El-Naggar, Ahmed A. Joseph, Abanob Ismail, M. Elsaid, Ashraf Mimi El-Samadony, M.O.A. Abdelfatah, Mahmoud El-Shaer, Abdelhamid Yuan, Zhanhui College of Materials Engineering Fujian Agriculture and Forestry University Fuzhou350002 China Mechanical Engineering Department Faculty of Engineering Kafrelsheikh University Kafrelsheikh33516 Egypt Department of Physics and Engineering Mathematics Faculty of Engineering University of Kafrelsheikh Kafrelsheikh Egypt Department of Chemistry College of Science King Saud University Riyadh11451 Saudi Arabia Physics Department Faculty of Science Kafrelsheikh University Kafrelsheikh33516 Egypt Nano Science and Technology Program Faculty of Science Kafrelsheikh University Kafrelsheikh33516 Egypt Department of Mechanical Engineering Faculty of Engineering Suez University SuezP.O. Box 43221 Egypt Refrigeration and Air Conditioning Technology Department Faculty of Technology and Education Helwan University CairoP.O. Box 11282 Egypt Mechanical Power Engineering Department Faculty of Engineering Tanta University Tanta City Egypt

The growing shortage of freshwater resources has spurred the development of innovative and sustainable desalination technologies. This study presents a thermo-economic analysis of an innovative hemispherical solar still (HSS) enhanced with a novel Metal-Organic Framework (MOF), specifically Iron-Aluminum Benzene Tricarboxylate. The MOF was characterized through structural, morphological, and optical investigations and integrated into the HSS using two enhancement methods: (I) as a nanofluid (MOF-NF) at a 1 wt% concentration in the feedwater, and (II) as a heat localization material (MOF-HL) by dispersing it on a black cotton wick that spans the basin surface. An external condenser (EC) was added to further enhance condensation in a subsequent configuration. Three identical HSS systems were used for comparative performance evaluation: a baseline unit (CHSS) and two modified systems, one with a condenser and one without. The results indicated that both MOF-based approaches significantly improved the thermal performance and freshwater yield of the HSS. Notably, the MOF-HL configuration outperformed the MOF-NF configuration across all performance metrics. The configuration designated as MOF-HL-EC achieved the highest rate of freshwater production, with a 96.16 % increase in distillate productivity compared to the CHSS. Additionally, this configuration exhibited exergy and energy efficiencies of 3.18 % and 61.1 %, respectively—improvements of 80.85 % and 95.72 % over the traditional system. Economically, the MOF-HL-EC configuration reduced the production cost of distilled water to 0.0115$ per liter, marking a reduction of 25.29 %. © 2025 The Institution of Chemical Engineers

关键词： Iron analysis

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Passive sub-ambient cooling: radiative cooling versus evaporative cooling

arXiv

引用

arXiv 2021年

作者： Aili, Ablimit Yin, Xiaobo Yang, Ronggui Department of Mechanical Engineering University of Colorado BoulderCO80309 United States Materials Science and Engineering Program University of Colorado BoulderCO80309 United States State Key Laboratory of Coal Combustion School of Energy and Power Engineering Huazhong University of Science and Technology Hubei Wuhan430074 China

Day-and-night radiative sky cooling has emerged as a potential alternative to conventional cooling technologies such as refrigeration-based air conditioning and evaporative wet cooling. Both radiative cooling and evaporative cooling can passively achieve sub-ambient cooling without consuming electricity. Although both cooling techniques are subject to impacts from various weather conditions, the extents of the impacts under the same conditions are not well understood. In this work, we experimentally and theoretically study the thermal performances of a passive radiative cooler and a passive evaporative cooler when exposed to a clear night sky. We show that evaporative cooling is better suited for high-temperature and low-humidity weather conditions, with the measured sub-ambient temperatures of the radiative and evaporative coolers being −13.5℃ and −15.0℃, respectively, at a low relative humidity of 13% and a high ambient temperature of 26.0℃. On the other hand, radiative cooling is relatively more resilient than evaporative cooling under high-humidity and/or low-temperature weather conditions, with the measured subambient temperatures of the coolers being −11.5℃ and −10.5℃, respectively, at a slightly higher relative humidity of 32.0% and a slightly lower ambient temperature of 17.0℃. Depending on water availability and weather conditions, both evaporative cooling and radiative cooling can be adopted as mutually supplemental cooling technologies. © 2021, CC BY-SA.

关键词： Evaporation

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Single atom catalyst towards ammonia synthesis at mild conditions

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science China Chemistry 2018年第9期61卷 1045-1046页

作者： Zhiwei Fang Guihua Yu Materials Science and Engineering Program and Department of Mechanical Engineering The University of Texas at Austin

Nitrogen is an essential nutrient element for all living organisms,however in its sufficient molecular form,nitrogen could not be utilized to meet the crucial need for global food requirements or industrial production due to its strong nonpolar N≡N triple ***,nitrogen fixation is an essential transformation but this only occurs in the nature with the help of nitrogenases[1].Although nitrogen can be artificially transformed into ammonia through the wellestablished Haber-Bosch process,the reaction is accomplished under drastic conditions,

关键词：氨合成温和条件催化剂原子氮固定工业生产有机体三元组

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