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Surface analysis of different wood polymer composites exposed to artificial weathering

Journal of Wood Chemistry and Technology 2024年第2期44卷 88-101页

作者： Andrey Pereira Acosta Sandro Campos Amico Rafael de Avila Delucis André Luiz Missio Marlon Bender Bueno Rodrigues Ana Carolina Rodrigues Ribeiro Matheus de Paula Goularte Darci Alberto Gatto a PostGraduate Program in Mining Metallurgical and Materials Engineering Federal University of Rio Grande do Sul Porto Alegre Brazil b PostGraduate Program in Materials Science and Engineering Federal University of Pelotas Pelotas Brazil c Materials Engineering Undergraduate Course Federal University of Pelotas Pelotas Brazil

This study presents a superficial analysis of different wood polymer composites (WPC) comprising polystyrene (WPSC), poly(furfuryl alcohol) (WPFAC), and pine resin (WPRC) when exposed to artificial weathering. The study investigates the influence of resin type on the composites, focusing on their chemical, colorimetric, morphological, and thermal properties. The main findings indicate WPSC exhibits poor resistance to weathering, allowing ultraviolet radiation damage on the lignocellulosic component of the composite, leading to oxidized groups formation. Conversely, WPFAC and WPRC demonstrate good wood protection capabilities by preventing significant deterioration of holocellulose and acting as filters for radiation and moisture. Moreover, WPFAC exhibits the lowest decrease in carbonyl index and O/C ratio, with reductions of 2.6 and 11.6%, respectively. These findings are significant as they demonstrate that poly(furfuryl alcohol) and pine resin can be used to produce WPCs that delay and mitigate wood degradation by weathering, contributing to the increased potential utilization of *** AbstractDisplay full size

关键词： Chemical changes discoloration surface color UV degradation

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Synthesis of green-emitting carbon quantum dots with excitation wavelength dependent photoluminescence obtained from aqueous beetroot extract

Synthesis of green-emitting carbon quantum dots with excitat...

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作者： Andrade, George R. S. Costa, Silvânio S. L. Nascimento, Cristiane C. Gimenez, Iara F. Postgraduate Program in Materials Science and Engineering Federal University of Sergipe Saõ Cristóvaõ Brazil Postgraduate Program in Chemistry Federal University of Bahia Salvador Brazil NUPEG Federal University of Sergipe Saõ Cristóvaõ Brazil Federal Institute of Education Science and Technology of Sergipe Aracaju Brazil Department of Chemistry Federal University of Sergipe Saõ Cristóvaõ Brazil

In this work, 3 simple, fast, labour and energy efficient methodologies were used to prepare carbon quantum dots (C-dots) using a red beetroot (Beta vulgaris subsp. vulgaris var. vulgaris) aqueous extract as the carbon source: Alkali-assisted (AA), microwave-assisted (MA) and alkali-microwave-assisted (AMA) synthesis. TEM images shows nanoparticles with a nearly spherical morphology and diameters around 7.0 nm. FTIR spectra show characteristic peaks of C-H, C-O, O-H and C=C bonds for all the samples. The emission spectra show an interesting feature of the as-prepared samples: The emission band position can be tunable by changing the excitation wavelength. Comparing the 3 different methodologies in terms of photoluminescence properties, the one based only on the microwave-assisted heating has showed the most improved emission. © 2016 materials Research Society.

关键词： Semiconductor quantum dots

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Study Of The Influence Of Milling Time On The Synthesis Temperature Of Monoclinic And Orthorhombic Nanostructured Cunb2o6 Via High-Energy Milling

Study Of The Influence Of Milling Time On The Synthesis Temp...

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Euro Powder Metallurgy 2023 Congress and Exhibition, PM 2023

作者： Gomes, Uilame Umbelino de Araújo, Kívia Fabiana Galvão José, Maria Lima, Santos De Souza, Vitor Manoel Silva Fernandes da Silva Lourenço, Cléber Raimundo, Rafael Alexandre Materials Science and Engineering Postgraduate Program Federal University of Rio Grande do Norte Natal59078-970 Brazil Department of Physics Federal University of Paraíba João Pessoa58051-900 Brazil

Copper niobate (CuNb2O6) has been studied for technological and environmental applications, such as in solar cells and photocatalysts, for example. And to make the application of CuNb2O6 even more feasible, in this study, therefore, high-energy milling was applied in its synthesis process with variation in the milling time, from the precursor powders Nb2O5 and CuO. The calcination occurred in a muffle with temperatures in the range of 500 °C to 1000 °C, for 3 h and heating rate of 5 °/min. Then, the powders were characterized by XRD, SEM, EDS and Raman. The powders showed crystallite sizes smaller than 80 nm, good homogeneity and high purity. The particle morphologies and the Raman spectrum are coherent with the literature. It was also verified that the increase in milling time reduced the initial formation temperature of the monoclinic phase and the calcination time for the complete formation of the orthorhombic phase. © European Powder Metallurgy Association (EPMA)

关键词： Mechanical alloying

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Devulcanization of natural rubber in composites with distinct crosslink densities by twin-screw extruder

Devulcanization of natural rubber in composites with distinc...

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作者： Barbosa, Rafael Nunes, Anderson Thadeu Ambrósio, José Donato Materials Science and Engineering Postgraduate Program - PPGCEM Federal University of São Carlos - UFSCar São Carlos SP Brazil Center of Characterization and Materials Development - CCDM Federal University of São Carlos - UFSCar São Carlos SP Brazil

In this study, the effects of the devulcanization process realized by an intermeshing co-rotating twin-screw extruder (ICTSE) on three vulcanized Natural Rubber (NR) composites with different crosslink densities (CD) have been investigated. The extrusion parameters were fixed, as well as the initial material granulometry and auxiliary thermoplastic added to the process. After composites vulcanization, they were characterized accordingly their soluble fraction (SF), crosslink density (CD), mechanical properties and thermogravimetry (TGA). The extrusion was performed on the vulcanized elastomers pursuing selectively crosslink rupture and the same characterization previously cited was conducted on the devulcanized material, except the mechanical properties analysis. The extrusion demonstrate effective devulcanization, evidenced in the increasing of soluble fractions, reduction in crosslink density and thermal stability gain. These results are directly affected by preliminary differences on materials structure and presence of ethylene vinyl-acetate (EVA) on extrusion. © 2017 Universidade Federal de Sao Carlos. All rights reserved.

关键词： Rubber

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Comparison of Cu−Al−Ni−Mn−Zr shape memory alloy prepared by selective laser melting and conventional powder metallurgy

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Transactions of Nonferrous Metals Society of China 2020年第12期30卷 3322-3332页

作者： Dennis GERA Jonadabe SANTOS Cláudio SKIMINAMI Piter GARGARELLA Postgraduate Program in Materials Science and Engineering Federal University of São CarlosSão CarlosBrazil Materials Engineering Department Federal University of São CarlosR.Washington Luískm 235-SP 310São CarlosBrazil

This work aimed to investigate and critically analyze the differences in microstructural features and thermal stability of Cu−11.3Al−3.2Ni−3.0Mn−0.5Zr shape memory alloy processed by selective laser melting(SLM)and conventional powder *** specimens were produced by sintering 106−180μm pre-alloyed powders under an argon atmosphere at 1060°C without secondary *** specimens were consolidated through melting 32−106μm pre-alloyed powders on a Cu−10Sn *** properties were measured through Vickers hardness *** scanning calorimetry was conducted to assess the martensitic transformation temperatures.X-ray diffraction patterns were collected to identify the metallurgical *** and scanning electron microscopy was used to analyze the microstructural features.b′1 martensite was found,irrespective of the processing route,although coarser martensitic variants were present in *** conventional powder metallurgy samples,intergranular eutectoid constituents and stabilized austenite also formed at room ***-specimens showed similar average hardness values to the SLM-specimens,albeit with high standard deviation linked to the *** specimens processed by SLM showed reversible martensitic transformation(T0=171°C).PM-processed specimens did not show shape memory effects.

关键词： shape memory alloys powder metallurgy additive manufacturing selective laser melting Cu-based alloys

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A Review of Carbon dots (CDs) Application in Sensing and Removing Medical Waste 5

A Review of Carbon dots (CDs) Application in Sensing and Rem...

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5th International Conference on Energy, Environmental and Information System, ICENIS 2020

作者： Alkian, Ilham Sutanto, Heri Aprimanti Utami, Bella Rafika Duri, Inten A'Yuni, Dewi Qurrota Hadiyanto, H Master Program of Environmental Science School of Postgraduate Studies Diponegoro University Semarang Indonesia Department of Physics Faculty of Science and Mathematics Diponegoro University Semarang Indonesia Department of Chemical Engineering Faculty of Engineering Diponegoro University Semarang Indonesia Smart Materials Research Center Diponegoro University Semarang Indonesia

Carbon dots materials (CDs) have the capability in the management of medical waste problem because of its advantage in the detection and degradation of pollutants. The synthesized CDs through various processes and raw materials have been applied to medical wastes, especially antibiotics such as tetracycline (TC), amoxicillin (AMX), para-Nitrophenol (p-NP), doxycycline (DC), ciprofloxacin (CIP), and oxytetracycline (OTC). These antibiotics are detected by utilizing changes in the luminescence property of CDs from the turn-off and turn-on mechanisms. Afterward, the degradation process is conducted using CDs as support materials agent semiconductors in the photosynthesis scheme. In general, CDs can be referred to as multifunction smart materials with the ability to detecting the presence of the antibiotics in simple, sensitive, and selective ways, and potency of medical pollutant removal clearly and effectively. © The Authors, published by EDP sciences, 2020.

关键词： Antibiotics

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Low temperature solvolthermally synthesized nitrogen-fluorine doped TiO2 for methyl orange photodegradation

Low temperature solvolthermally synthesized nitrogen-fluorin...

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2012 2nd International Conference on Key engineering materials, ICKEM 2012

作者： Kwamman, Tanagorn Smith, Siwaporn Meejoo Materials Science and Engineering Postgraduate Program Faculty of Science Mahidol University 272 Rama VI Road Ratchathevi Bangkok 10400 Thailand Department of Chemistry Center of Excellence for Innovation in Chemistry Mahidol University 272 Rama VI Road Ratchathevi Bangkok 10400 Thailand

ISBN: (纸本)9783037853825

A low temperature solvothermal method was employed to synthesize nitrogen-fluorine doped TiO2 materials (N/F -TiO2) at various mole ratio of Ti:F;10:1, 10:0.3 and 10:0.1, for photocatalytic applications. Doping fluorine and nitrogen in the TiO2 structure extend the spectra response of the materials toward a visible region resulting in the high efficiency to oxidize methyl orange (MO) under UV-Vis irradiation. The microstructure and photocatalytic activity of the materials appeared to depend on titanium precursors, titanium isopropoxide (TTIP) or tetrabutyl orthotitanate (TBOT), and the concentration of dopant (NH4F). The highest MO decolorization efficiency under UV-Vis irradiation for 30 minutes is about 86 % by using N-F-TiO2 (TTIP precursor) with Ti: F of 10: 3 as catalyst. The decolorization efficiencies of MO over N-F-TiO2 materials (TTIP precursor) are twice higher than that of the undoped catalyst. © (2012) Trans Tech Publications.

关键词： Titanium dioxide

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High fluorescent carbon dots/Ag as a sensitive sensor for tetracycline waste in aqueous solution 10

High fluorescent carbon dots/Ag as a sensitive sensor for te...

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10th International Seminar on New Paradigm and Innovation of Natural sciences and itsApplication, ISNPINSA 2020

作者： Alkian, I. Sutanto, H. Hadiyanto, H. Hidayanto, E. Hapsari, H.P. Wibowo, A.A. Syahida, A.N. Irianti, F.D.D. Master Program of Environmental Science School of Postgraduate Studies Diponegoro University Semarang Indonesia Departemen of Physics Faculty of Science and Mathematics Diponegoro University Semarang Indonesia Departemen of Chemical Engineering Faculty of Engineering Diponegoro University Semarang Indonesia Smart Materials Research Center Laboratory Diponegoro University Semarang Indonesia

Currently, antibiotics waste produced by hospitals and pharmacies is increasing, increasing demand and public consumption. Tetracyclines are a popular type of antibiotic that can pollute the environment even in low concentrations. This study aimed to detect tetracyclines in an aqueous environment using C-dots/Ag. C-dots material was synthesized by microwave radiation method with the addition of Ag 0-4 %. C-dots/Ag is produced in the form of a brown-black powder that glows green. FTIR testing shows that C-dots/Ag contains various functional groups O-H, N-H, C-H, C=O, and C=C. The surface morphology of the C-dots based on SEM testing is round and rough. Ag's addition causes C-dots' surface morphology to agglomerate, shifting the C-dots' absorbance peaks towards a larger wavelength and decreasing the energy bandgap. C-dots/Ag 2% has the best optical properties based on the intensity of the resulting fluency. In general, C-dots/Ag has excellent potential to be a susceptible, selective, and effective tetracycline detection agent. © Published under licence by IOP Publishing Ltd.

关键词： Surface morphology

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Characterization of ZnAl2O4 spinel obtained by hydrothermal and microwave assisted combustion method: A comparative study

Characterization of ZnAl2O4 spinel obtained by hydrothermal ...

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作者： De Macedo, Heloísa Pimenta De Araújo Medeiros, Rodolfo Luíz Bezerra De Medeiros, Amanda Lucena De Oliveira, Ângelo Anderson Silva De Figueredo, Gilvan Pereira De Freitas Melo, Marcus Antônio De Araújo Melo, Dulce Maria Postgraduate Program in Science and Engineering of Materials Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil Postgraduate Program in Science and Engineering of Petroleum Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil Postgraduate Program in Chemistry Chemistry Institute Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil Chemistry Department Federal Institute of Education Science and Technology of Maranhão - IFMA São LuísMACEP 65076-091 Brazil Department of Chemical Engineering Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil

In this work, zinc aluminate spinel was prepared by two methods of directly synthesis (without calcination): microwave assisted combustion and hydrothermal method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2-adsorption/ desorption isotherms. The XRD patterns confirmed the formation of cubic ZnAl2O4 spinel structure with no secondary phases for both synthesis routes, whereas the hydrothermal method yielded powders with crystallite size 3 times smaller (6.9 nm), as compared to the powders produced by microwave assisted combustion method (25.6 nm). The micrographs revealed agglomerated powders with plate-like morphologies for both routes. Nitrogen adsorption/desorption isotherms (BET) revealed higher surface area (183 m2.g-1) and greater pore volume (0.173 cm3.g-1) for ZnAl2O4 powders prepared by the hydrothermal method. © 2017 Universidade Federal de Sao Carlos. All rights reserved.

关键词： Zinc compounds

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Deformation mechanisms in superplastic AA5083 materials

Deformation mechanisms in superplastic AA5083 materials

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作者： Kulas, Mary-Anne Green, W. Paul Taleff, Eric M. Krajewski, Paul E. McNelley, Terry R. Materials Science and Engineering Program University of Texas at Austin Austin TX 78712-0292 Department of Mechanical Engineering University of Texas at Austin Austin TX 78712-0292 Research and Development Center General Motors Corp. Warren MI 48090-9056 Department of Mechanical Engineering Naval Postgraduate School Monterey CA 93943-5146

The plastic deformation of seven 5083 commercial aluminum materials, produced from five different alloy heats, are evaluated under conditions of interest for superplastic and quick-plastic forming. Two mechanisms are shown to govern plastic deformation in AA5083 over the strain rates, strains, and temperatures of interest for these forming technologies: grain-boundary-sliding (GBS) creep and solute-drag (SD) creep. Quantitative analysis of stress transients following rate changes clearly differentiates between GBS and SD creep and offers conclusive proof that SD creep dominates deformation at fast strain rates and low temperature. Furthermore, stress transients following strain-rate changes under SD creep are observed to decay exponentially with strain. A new graphical construction is proposed for the analysis and prediction of creep transients. This construction predicts the relative size of creep transients under SD creep from the relative size of changes in an applied strain rate or stress. This construction reveals the relative size of creep transients under SD creep to be independent of temperature;temperature dependence resides in the "steady-state" creep behavior to which transients are related.

关键词： Aluminum alloys

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