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Articoli di riviste sul tema "Nanostructures et nanocomposites":
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Doan, Mai Quan, Nguyen Ha Anh, Hoang Van Tuan, Nguyen Cong Tu, Nguyen Huu Lam, Nguyen Tien Khi, Vu Ngoc Phan, Pham Duc Thang e Anh-Tuan Le. "Improving SERS Sensing Efficiency and Catalytic Reduction Activity in Multifunctional Ternary Ag-TiO2-GO Nanostructures: Roles of Electron Transfer Process on Performance Enhancement". Adsorption Science & Technology 2021 (1 ottobre 2021): 1–13. http://dx.doi.org/10.1155/2021/1169599.
Abstract (sommario):
Multifunctional nanocomposites have received great attention for years; electron transfer (ET) is considered as an explanatory mechanism for enhancement of performance of these nanostructures. The existence of this ET process has been proved in many studies using either experimental or computational approaches. In this study, a ternary nanocomposite system of Ag/TiO2/GO was prepared to evaluate the performance enhancement in two experimental models: a physical model (i.e., surface-enhanced Raman scattering (SERS) sensor) and a chemical one (i.e., catalytic reduction reaction). The metal/semiconductor heterojunction between Ag and TiO2, as well as Ti-O-C bonds, has allowed plasmonic hot electrons to be transferred in the internal structure of the material. An investigation on the role of Ag content on the SERS sensing and catalytic reduction efficiency of Ag/TiO2/GO was performed in both models. Interestingly, they all resulted in the same optimal Ag content of 50 wt%. It was then further discussed to provide a convincing evidence for the plasmon-induced electron transfer phenomena in the Ag/TiO2/GO nanostructure. These findings also suggest a pathway to design and develop high-performance, cost-effective, facile-preparation, and eco-friendly multifunctional nanostructures for detecting and removing contaminants in environment.
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Hammud, Hassan H., Ranjith Kumar Karnati, Nusaybah Alotaibi, Syed Ghazanfar Hussain e Thirumurugan Prakasam. "Cobalt–Carbon Nanoparticles with Silica Support for Uptake of Cationic and Anionic Dyes from Polluted Water". Molecules 26, n. 24 (10 dicembre 2021): 7489. http://dx.doi.org/10.3390/molecules26247489.
Abstract (sommario):
Silica-supported hierarchical graphitic carbon sheltering cobalt nanoparticles Co-HGC@SiO2 (1) were prepared by pyrolysis at 850 °C of [Co(phen)(H2O)4]SO4·2H2O complex with silica in the presence of pyrene as a carbon source under nitrogen atmosphere. Nanocomposites (2) and (3) were obtained by acid treatment of (1) with HCl and HF acid, respectively. The nanocomposites showed rough hierarchical carbon microstructures over silica support decorated with irregular cobalt nanospheres and nanorods 50 to 200 nm in diameter. The nanoparticles consist of graphitic shells and cobalt cores. SEM, EDAX and TEM elemental mapping indicate a noticeable loss of cobalt in the case of (2) and loss of cobalt and silica in the case of (3) with an increase in porosity. Nanocomposite (3) showed the highest BET surface area 217.5 m2g−1. Raman spectrum shows defect D-band and graphitic G-band as expected in carbon nanostructures. PXRD reveals the presence of cobalt(0) nanoparticles. XPS indicates the presence of Co(II) oxides and the successful doping of nitrogen in the nanocomposites. Moreover, TEM elemental mapping provides information about the abundance of Si, Co, C, N and S elements in zones. Nanocomposite (1) showed maximum uptake capacity of 192.3 and 224.5 mg/g for crystal violet CV and methyl orange MO dyes, respectively. Nanocomposite (2) showed a capacity of 94.1 and 225.5 mg/g for CV and MO dyes, respectively. Nanocomposite (4) obtained after treatment of (1) with crystal violet proved successful adsorption of CV. Co-HGC (5) prepared without addition of silica has a capacity for CV equal to 192 mg/g, while it is 769.2 mg/g with MO. Electrostatics and π–π interactions of graphite and cobalt species in the nanocomposites with aromatic rings of cationic and anionic dyes are responsible for the adsorption. Yan et al. was the best model to describe column kinetics. The thomas column adsorption model showed that the maximum uptake capacity of (1) was 44.42 mg/g for CV and 32.62 mg/g for MO. for a column packed with 0.5 gm of (1) and dye concentration of 100 mg/L at a flow rate of 1 mL/min. The column was recycled three times with no noticeable clogging or degradation of nanocomposites. Thus, Co-HGC@SiO2 adsorbents can be used efficiently to treat water contaminated with cationic and anionic dyes.
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Granitzer, Petra, Klemens Rumpf, Roberto Gonzalez-Rodriguez e Jeffery Coffer. "Metal Filled Nanostructured Silicon a Platform to Interlink Magnetism and Optics". ECS Meeting Abstracts MA2023-02, n. 21 (22 dicembre 2023): 1285. http://dx.doi.org/10.1149/ma2023-02211285mtgabs.
Abstract (sommario):
This presentation deals with the utilization of nanostructured silicon (porous silicon and silicon nanotubes) for deposition of various metals, especially magnetic ones, within the pores/tubes. The novel magnetic properties of the semiconducting/magnetic composites which arise due to the nanoscopic size of the used materials are investigated with respect to optical and magnetic on-chip applications. Porous silicon is fabricated by anodization of a silicon wafer in an aqueous hydrofluoric solution. The morphology of the porous structures depends on the doping density of the used wafer and on the applied current density as well as the electrolyte concentration. The ferromagnetic metals are deposited within the porous structures electrochemically in using the corresponding metal salt solution as electrolyte. A modification of the electrochemical parameters results in adjustable size and shape of the deposits. Ni and Co, both metals are electrodeposited within the nanostructured silicon in using aqueous NiSO4 and CoSO4 solutions by applying a current density between 10 and 20 mA/cm2 and a frequency between 0.05 and 0.2 Hz. One of our key topics is luminescent porous silicon loaded with magnetic metals to enhance the photoluminescence, with the final aim to influence/control the optical properties by a magnetic field. The metal deposits affect the optical properties but also give rise to specific magnetic behavior (1). Due to the metal filling of the porous silicon the photoluminescence is blue-shifted and furthermore an increase of the intensity is observed. The influence of the magnetic metal filling on the optical properties (photoluminescence, decay time) is discussed, and the magnetic characterization of the nanocomposites is presented. A further issue, the deposition of hard and soft magnetic materials within the nanostructures, aiming in the fabrication of arrays of permanent nanomagnets is presented (2). Here the investigation of the magnetic behavior of bi-metal nanostructures within nanostructured silicon with the aim to exploit the magnetic properties of both metals and gain control of the exchange coupling between the two metals especially with respect to their volume ratio is discussed. Furthermore, a variation of the structure size and the proximity of the metal deposits modify the exchange coupling and thus the energy product. Nanocomposite systems with an energy product as high as possible should be achieved to give rise to on-chip applications using permanent nanomagnets, especially arranged in arrays. (1) P. Granitzer, et al, Frontiers in Physics, 8 (2020) 121 (2) K. Rumpf, et.al, Phys. Stat. Sol. A, 217 (2020) 1901040
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El-Zoka, Ayman A. "(Invited) Making Nanostructured Composites Via Inner-Pore Electrodeposition into Nanoporous Metals". ECS Meeting Abstracts MA2023-02, n. 21 (22 dicembre 2023): 1281. http://dx.doi.org/10.1149/ma2023-02211281mtgabs.
Abstract (sommario):
The selective removal of Ag from a solid solution of Ag-Au or Ag-Au-Pt yields a 3D bicontinuous, open-pore, nanoporous gold substrate (NPG), that is rich in the more noble metal(s)1 (Au and/or Pt). NPG has been successfully developed by the intelligent use of the conventionally-undesired dealloying corrosion. The excellent properties of NPG are attributed to the surface area-to-volume ratio, and high curvature of nanoligament surfaces2,3 . While a lot of recent research has been focusing on the structure/property relationships of NPG as a functional material in its own right4,5, the further use of NPG as a sophisticated template for fabricating complex nanostructured materials is worthy of attention. Previous work on atom probe tomography characterization of NPG6,7 showed the successful inner-pore electrodeposition of a fully compact Cu support, thus, opening the door to implementing that newly developed method to the creation of finely tuned nanostructures, using NPG as a template. Fabrication of functional nanostructures pertaining to the interests of the catalysis and mechanics communities will be demonstrated through the electrodeposition of Cu and Co on NPG. Key aspects that enable this unexpected complete infiltration of NPG layer will be highlighted including, a characteristic "subpotential" curvature-driven electrodeposition regime8. Insights on the associated electrodeposition mechanisms are gained through the pairing of electrochemical methods and high-resolution characterization techniques. Furthermore, recent advances in structural and chemical modifications that increase the complexity and tunability of NPG-based nanocomposites will be discussed for the first time. References Newman, R. C. 2.05 - Dealloying. in Shreir’s Corrosion (eds. Cottis, B. et al.) 801–809 (Elsevier, 2010). Zielasek, V. et al. Gold Catalysts: Nanoporous Gold Foams. Angewandte Chemie International Edition 45, 8241–8244 (2006). Xue, Y., Markmann, J., Duan, H., Weissmüller, J. & Huber, P. Switchable imbibition in nanoporous gold. Nature Communications 5, (2014). Wittstock, A., Wichmann, A., Biener, J. & Bäumer, M. Nanoporous gold: A new gold catalyst with tunable properties. Faraday Discuss (2011) doi:10.1039/c1fd00022e. Li, X. et al. Nanoporous-Gold-Based Hybrid Cantilevered Actuator Dealloyed and Driven by A Modified Rotary Triboelectric Nanogenerator. Sci Rep (2016) doi:10.1038/srep24092. El-Zoka, A. A., Langelier, B., Botton, G. A. & Newman, R. C. Enhanced analysis of nanoporous gold by atom probe tomography. Mater Charact 128, (2017). El-Zoka, A. A., Langelier, B., Korinek, A., Botton, G. A. & Newman, R. C. Nanoscale mechanism of the stabilization of nanoporous gold by alloyed platinum. Nanoscale 10, (2018). Lee, L., He, D., Carcea, A. G. & Newman, R. C. Exploring the reactivity and nanoscale morphology of de-alloyed layers. Corros Sci 49, 72–80 (2007).
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Rusu, Mihai M., Adriana Vulpoi, Isabelle Maurin, Liviu C. Cotet, Lucian C. Pop, Carmen I. Fort, Monica Baia, Lucian Baia e Ileana Florea. "Thermal Evolution of C–Fe–Bi Nanocomposite System: From Nanoparticle Formation to Heterogeneous Graphitization Stage". Microscopy and Microanalysis 28, n. 2 (1 marzo 2022): 317–29. http://dx.doi.org/10.1017/s1431927622000241.
Abstract (sommario):
Carbon xerogel nanocomposites with integrated Bi and Fe particles (C–Bi–Fe) represent an interesting model of carbon nanostructures decorated with multifunctional nanoparticles (NPs) with applicability for electrochemical sensors and catalysts. The present study addresses the fundamental aspects of the catalyzed growth of nano-graphites in C–Bi–Fe systems, relevant in charge transport and thermo-chemical processes. The thermal evolution of a C–Bi–Fe xerogel is investigated using different pyrolysis treatments. At lower temperatures (~750°C), hybrid bismuth iron oxide (BFO) NPs are frequently observed, while graphitization manifests under more specific conditions such as higher temperatures (~1,050°C) and reduction yields. An in situ heating TEM experiment reveals graphitization activity between 800 and 900°C. NP motion is directly correlated with textural changes of the carbon support due to the catalyzed growth of graphitic nanoshells and nanofibers as confirmed by HR-TEM and electron tomography (ET) for the graphitized sample. An exponential growth model for the catalyst dynamics enables the approximation of activation energies as 0.68 and 0.29–0.34 eV during reduction and graphitization stages. The results suggest some similarities with the tip growth mechanism, while oxygen interference and the limited catalyst–feed gas interactions are considered as the main constraints to enhanced growth.
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Gan’shina, Elena A., Vladimir V. Garshin, Nikita S. Builov, Nikolay N. Zubar, Alexandr V. Sitnikov e Evelina P. Domashevskaya. "Investigation of the Magnetic Properties of Amorphous Multilayer Nanostructures [(CoFeB)60C40/SiO2]200 and [(CoFeB)34(SiO2)66/C]46 by the Transversal Kerr Effect". Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 22, n. 4 (15 dicembre 2020): 438–45. http://dx.doi.org/10.17308/kcmf.2020.22/3114.
Abstract (sommario):
Magnetic properties in amorphous multilayer nanostructures [(CoFeB)60C40/SiO2]200 and [(CoFeB)34(SiO2)66/C]46 with different content of the CoFeB magnetic alloy in metal-composite layers and inverse location of non-metallic phases C and SiO2 in composite layers or in interlayers, were investigated by magneto-optical methods in the transversal Kerr effect (TKE) geometry.Using the spectral and field dependences of the transversal Kerr effect TKE, it has been established that in the samples of both magnetic multilayer nanostructures (MLNS) the magneto-optical response and magnetic order are determined by the phase composition of the composite layers.In samples of MLNS [(CoFeB)60C40/SiO2]200 with a post-percolation content of metal clusters in metal-composite layers, the maximum of absolute TKE values decrease by about 2.5 times compared with the initial amorphous Co40Fe40B20 alloy, while the field dependences of TKE in samples of this MLNS has features that are characteristic of soft ferromagnets.In samples of MLNS [(CoFeB)34(SiO2)66/C]46 with a pre-percolation content of metal clusters in the oxide SiO2–x matrix of metal-composite layers, the TKE spectral dependences fundamentally differed from the TKE of the initial amorphous Co40Fe40B20 alloy both in shape and sign. The field dependences of the TKE in the samples of this MLN were linear, characteristic of superparamagnets.
References1. Neugebauer C. A. Resistivity of cermet filmscontaining oxides of silicon. Thin Solid Films. 1970;6(6):443–447. DOI: https://doi.org/10.1016/0040-6090(70)90005-22. Gittleman J. L., Goldstain Y., Bozowski S.Magnetic roperties of granular nikel films. PhysicalReview B. 1972;5(9): 3609–3621. DOI: https://doi.org/10.1103/physrevb.5.36093. Abeles B., Sheng P., Coutts M. D., Arie Y.Structural and electrical properties of granular metalfilms. Advances in Physics. 1975;24(3): 407–461. DOI:https://doi.org/10.1080/000187375001014314. Helman J. S., Abeles B. Tunneling of spinpolarizedelectrons and magnetoresistance in granularNi films. Physical Review Letters. 1976;37(21): 1429–1433. DOI: https://doi.org/10.1103/physrevlett.37.14295. Sheng P., Abeles B., Arie Y. Hopping conductivityin granular Metals. Physical Review Letters,1973;31(1):44–47. DOI: https://doi.org/10.1103/physrevlett.31.446. Domashevskaya E. P., Builov N. S., Terekhov V. A.,Barkov K. A., Sitnikov V. G. Electronic structure andphase composition of dielectric interlayers inmultilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200. Physics of the Solid State. 2017;59(1): 168–173.DOI: https://doi.org/10.1134/S10637834170100617. Domashevskaya E. P., Builov N. S., Terekhov V. A.,Barkov K. I., Sitnikov V. G., Kalinin Y. E. Electronicstructure and phase composition of silicon oxide inthe metal-containing composite layers of a[(Co40Fe40B20)34(SiO2)66/C]46 multilayer amorphousnanostructure with carbon interlayers. InorganicMaterials. 2017;53(9): 930–936. DOI: https://doi.org/10.1134/S00201685170900608. Domashevskaya E. P., Builov N. S., Lukin A. N.,Sitnikov V. G. Investigation of interatomic interactionin multilayer nanostructures [(CoFeB)60C40/SiO2]200 and[(Co40Fe40B20)34(SiO2)66/C]46 with composite metalcontaininglayers by IR spectroscopy. InorganicMaterials. 2018;54(2): 153–159. DOI: https://doi.org/10.7868/s0002337x180200699. Domashevskaya E. P., Builov N. S., Ivkov S. A.,Guda A. A., Trigub A. L., Chukavin A. I. XPS and XASinvestigations of multilayer nanostructures based onthe amorphous CoFeB alloy. Journal of ElectronSpectroscopy and Related Phenomena. 2020;243:146979–146989. DOI: https://doi.org/10.1016/j.elspec.2020.14697910. Vonsovskii S. V. Magnetizm [Magnetism].Moscow: Nauka Publ.; 1971. 1032 p.11. Gan’shina E., Granovsky A., Gushin V.,Kuzmichev M., Podrugin P., Kravetz A., Shipil E. Opticaland magneto-optical spectra of magnetic granularalloys. Physica A: Statistical Mechanics and itsApplications. 1997;241(1-2): 45–51. DOI: https://doi.org/10.1016/s0378-4371(97)00057-512. Gan’shina E. A., Kim C. G., Kim C. O.,Kochneva M. Yu., Perov N. S., Sheverdyaeva P. M.Magnetostatic and magneto-optical properties of Cobasedamorphous ribbons. Journal of Magnetism andMagnetic Materials. 2002;239(1-3): 484–486. DOI:https://doi.org/10.1016/s0304-8853(01)00665-513. Gan’shina E. A., Vashuk M. V. 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E., Zolotukhin I. V.,Sitnikov A. V., Wagner V., Ahlers F. J. Low temperaturebehaviour of the giant magnetoresistivity in CoFeB– SiOn granular composites. Journal of Physics:Condensed Matter. 2003;15(24): 4267–4772. DOI:https://doi.org/10.1088/0953-8984/15/24/32018. Stognei O. V., Sitnikov A. V. Anisotropy ofamorphous nanogranular composites CoNbTa-SiO nand CoFeB-SiOn. Physics Solid State. 2010;52: 2518–2526. DOI: https://doi.org/10.1134/S106378341012012719. Dunets O. V., Kalinin Y. E., Kashirin M. A. et al.Electrical and magnetic performance of multilayerstructures based on (Co40Fe40B20)33.9(SiO2)66.1 composite.Technical Physics. 2013;58: 1352–1357. DOI: https://doi.org/10.1134/S106378421309013220. Gridnev S. A., Kalinin Yu. E., Sitnikov A. V.,Stognei O. V. Nelineinye yavleniya v nano imikrogeterogennykh sistemakh [Nonlinear phenomenain nano and microheterogeneous systems]. Moscow:BINOM, Laboratoriya znanii Publ.; 2012. 352 p.21. Mørup S., Tronc E. 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Ngene, Peter. "Interface Induced Fast Ion Conduction in Complex Hydride/Oxide Nanocomposites: Interplay between Hydride and Oxide Properties". ECS Meeting Abstracts MA2023-02, n. 5 (22 dicembre 2023): 886. http://dx.doi.org/10.1149/ma2023-025886mtgabs.
Abstract (sommario):
Solid-state electrolytes are crucial for next generation batteries with high energy density, long lasting and improved safety. The compatibility of most solid electrolytes with metallic anodes such as Li and Na metals, and cathodes such as sulfur, makes them suitable for high-capacity batteries (e.g., Li-S). They also address the safety concerns of current batteries by eliminating the flammable organic solvents in liquid electrolytes and by preventing/limiting dendrite formation. The lithium and sodium containing complex metal hydrides (e.g., LiBH4, NaBH4, LiCB11H12) have recently gained attention as solid-state electrolyte. They show high ionic conductivities but only at elevated temperatures (typically above 110 °C). Extending the high ionic conductivities to ambient temperatures is pivotal to the application of this fascinating class of solid electrolytes [1]. In this contribution, we will use LiBH4 and NaBH4 as examples to show that the ionic conductivities of complex hydrides can be greatly enhanced through interface effects resulting from the formation of nanocomposites with metal oxides. This strategy can lead to several orders of magnitude increase in the room temperature ionic conductivity [2]. Using DSC, DRIFT, solid-state NMR, and XRS (Xray Raman scattering), I will discuss how nanocomposite formation and presence of interfaces modifies either the phase stability, the defect concentration and/or leads to the formation of tertiary phase, and thereby increase profoundly the ion mobility of the complex hydrides. Systematic studies with different oxide nanoscaffolds and surface modified metal oxides, reveal that these effects can be optimized by tuning/engineering the nanostructure and interfaces in the nanocomposites. [3-4]. We will show that the effects also depend on a complex interplay between the stability of the metal hydride and surface properties of the metal oxide. Finally, the performance of some of the nanocomposite electrolytes in all-solid-state batteries, will be highlighted [5] References [1] L.M de Kort, P. Ngene et al. J. Journal of Alloys and Compounds 901 (2022) 163474 [2] D. Blanchard et al., Advanced Functional Material. 25 (2015), 182. [3] P. Ngene et al. Physical Chemistry Chemical Physics 21 (40), 22456-22466 [4] L.M de Kort, P. Ngene et al. Journal of Materials Chemistry A 8.39 (2020): 20687-20697 [5] D. Blanchard et al, J. Electrochem. Soc. (2016).
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Yang, Bao Juan, Rui Xia, Su Bin Jiang e Mei Zhen Gao. "SnSe/Cu<sub>2</sub>SnSe<sub>3</sub> Heterojunction Structure with High Initial Coulombic Efficiency for Lithium-Ion Battery Anodes". Key Engineering Materials 905 (4 gennaio 2022): 135–41. http://dx.doi.org/10.4028/www.scientific.net/kem.905.135.
Abstract (sommario):
Due to high theoretical specific capacity and abundant reserves, tin selenide-based materials have received tremendous attentions in the fields of lithium-ion batteries. Nevertheless, the huge volume changes during insertion/de-intercalation processes deteriorate the Coulombic Efficiency greatly. In order to solve it, the researchers have made great efforts by means of controlling nanoparticles granularity, carbon coating, ion doping et al. In this study, SnSe/Cu2SnSe3 heterojunction nanocomposites were synthesized by solvo-thermal method. The resulting SnSe/Cu2SnSe3 is a three-dimensional flower-like hierarchical nanostructure composed of nanoscale thin lamellae of a thickness of 8-12 nm. The unique nanostructure could shorten the diffusion path of lithium ions and expedite charge transfer, and therefore enhance the reaction kinetics. Compared with SnSe, the initial Coulombic efficiency of SnSe/Cu2SnSe3 is raised from 59% to 90% as the anode material of lithium-ion batteries.
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Urper, Osman, Prabin Kharel, Nivedhitha Jothinarayanan, Karoline Krogstad, Lars Eric-Roseng, Miina Saebo, Walter Aker e Kaiying Wang. "Eco-Friendly TiO2 and ZnO Biocar Nanocomposites: Transforming Water Decontamination and Bacteria Inactivation". ECS Meeting Abstracts MA2023-02, n. 47 (22 dicembre 2023): 2292. http://dx.doi.org/10.1149/ma2023-02472292mtgabs.
Abstract (sommario):
Water pollution ranging from harmful chemical substances to pathogenic bacteria is a growing problem from industry to society as a whole[1-2].There is a need to find new, cost-effective sustainable materials with high efficacy to clean up water and to protect the environment. Biocarbon (BC), a material with high specific surface area and large porosity, has some potential for removing water pollutants, but it also has many limitations. However, biocarbon-based composites can be tailored and may have a greater potential for removing contaminants in water. ZnO biochar and TiO2 biochar nanocomposites have been shown to effectively remove harmful chemical substances, such as industrial dyes, and additionally kill potential pathogenic bacteria[2–8]. In this project, we combined TiO2 and ZnO with biochar to create an active nanocomposite surface to see if this could be a cost-effective method to deactivate bacteria and degrade specific dyes. We present the fabrication and examination of TiO2/biochar (BC) and ZnO/BC composite photocatalysts, synthesized via hydrolysis technique. These catalysts were designed for the purpose of methyl orange (MO) degradation and bacterial strain inactivation. A comprehensive assessment of these catalysts was carried out using a number of sophisticated methods, including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectrophotometry for evaluation of degradation. Moreover, the direct contact method was used for antibacterial analysis. Our findings underline the exceptional properties of these composites for water decontamination and antibacterial efficacy. The nanocomposites showed remarkable photocatalytic performance in MO removal from wastewater, achieving a superior removal efficiency of 92%, as shown in Figure 1. This can be attributed to their outstanding electron transfer efficacy. In addition, the TiO2/BC and ZnO/BC nanocomposites manifested robust antibacterial properties, and they showed an antibacterial effectiveness of 85% against Escherichia coli (E. coli) (Table 1). This research highlights the promising potential of TiO2/BC and ZnO/BC nanocomposites as eco-friendly and multifaceted materials, suggesting a wide range of potential applications in water purification and antibacterial activity. Acknowledgments: The authors acknowledge the research grants from project # 6000237-13 Figure: Figure 1. Photocatalytic degradation of MO (initial concentration; 20 mg/L) under solar light irradiation, a) Pure BC and TiO2, and composite TiO2/BC catalysts, b) Pure BC and ZnO, and ZnO/BC catalysts. Table: Table 1. Antimicrobial efficiency of 5 different catalysts against E. coli. References [1] A. S. Eltaweil, I. M. Mamdouh, E. M. Abd El-Monaem, and G. M. El-Subruiti, “Highly Efficient Removal for Methylene Blue and Cu2+onto UiO-66 Metal-Organic Framework/Carboxylated Graphene Oxide-Incorporated Sodium Alginate Beads,” ACS Omega, 2021, doi: 10.1021/acsomega.1c03479. [2] J. Hidalgo-Jimenez et al., “Phase transformations, vacancy formation and variations of optical and photocatalytic properties in TiO2-ZnO composites by high-pressure torsion,” Int J Plast, vol. 124, pp. 170–185, Jan. 2020, doi: 10.1016/j.ijplas.2019.08.010. [3] A. S. Eltaweil, A. M. Abdelfatah, M. Hosny, and M. Fawzy, “Novel Biogenic Synthesis of a Ag@Biochar Nanocomposite as an Antimicrobial Agent and Photocatalyst for Methylene Blue Degradation,” ACS Omega, vol. 7, no. 9, pp. 8046–8059, Mar. 2022, doi: 10.1021/acsomega.1c07209. [4] S. Riaz and S. J. Park, “An overview of TiO2-based photocatalytic membrane reactors for water and wastewater treatments,” Journal of Industrial and Engineering Chemistry, vol. 84. Korean Society of Industrial Engineering Chemistry, pp. 23–41, Apr. 25, 2020. doi: 10.1016/j.jiec.2019.12.021. [5] L. Lu, R. Shan, Y. Shi, S. Wang, and H. Yuan, “A novel TiO2/biochar composite catalysts for photocatalytic degradation of methyl orange,” Chemosphere, vol. 222, pp. 391–398, May 2019, doi: 10.1016/j.chemosphere.2019.01.132. [6] R. Zha, R. Nadimicherla, and X. Guo, “Ultraviolet photocatalytic degradation of methyl orange by nanostructured TiO2/ZnO heterojunctions,” J Mater Chem A Mater, vol. 3, no. 12, pp. 6565–6574, Mar. 2015, doi: 10.1039/c5ta00764j. [7] J. Liu et al., “Preparation, environmental application and prospect of biochar-supported metal nanoparticles: A review,” Journal of Hazardous Materials, vol. 388. Elsevier B.V., Apr. 15, 2020. doi: 10.1016/j.jhazmat.2020.122026. [8] J. Liu et al., “Preparation, environmental application and prospect of biochar-supported metal nanoparticles: A review,” Journal of Hazardous Materials, vol. 388. Elsevier B.V., Apr. 15, 2020. doi: 10.1016/j.jhazmat.2020.122026. Figure 1
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Steier, Katharina, Peter James Kelly e Justyna Kulczyk-Malecka. "Vanadium-Doped Ni/YSZ Anode Functional Layers for Solid Oxide Fuel Cells Produced via Magnetron Sputtering". ECS Meeting Abstracts MA2023-01, n. 54 (28 agosto 2023): 76. http://dx.doi.org/10.1149/ma2023-015476mtgabs.
Abstract (sommario):
The electrode performance of solid oxide fuel cells (SOFC) strongly depends on its microstructural characteristics, such as the porosity, percolated paths of ionically and electronically conductive phases and in particular, the grain size1. Deploying alternative manufacturing techniques that deposit nanostructured materials results in finer particle sizes and thus, increases the quantity of triple-phase boundaries. For that reason, the magnetron sputtering technique, which offers elemental distribution at the nanoscale, high deposition rates, reproducibility, scalability and excellent uniformity over large-area substrates has been chosen as the deposition method to fabricate anode functional layers (AFLs) for SOFCs. Nanostructured NiO-YSZ thin films have been previously produced by reactive pulsed DC magnetron co-sputtering of metallic targets of zirconium-yttrium and nickel, defining the optimal deposition parameters to create state-of the-art AFLs. Former studies reported limitations of the process control during reactive magnetron sputtering, regarding the film’s composition 1,2. Since the composition strongly relies on the amount of reactive gas, i.e., oxygen, present during deposition, a feedback control system is required to prevent oxygen built-up leading to target poisoning and lower deposition rates. Herein, we present a reactive feedback control system, that manages quantities of oxygen introduced to the sputtering chamber during deposition based on the oxygen partial pressure. This facilitates stable operation conditions, prevents target poisoning, and maintains the coating characteristics, i.e., its microstructure and desired composition when varying process parameters, such as the deposition pressure, target-substrate distance, or the deposition angle. Based on recent studies 3–5, the future of oxide-based anode materials for SOFCs will greatly focus on reducing the Ni catalyst content through alternative non-precious metal doping and increasing the cell performance by tailoring the microstructure of the AFL. This would allow Ni coarsening to be mitigated and maintain the nanostructure over the lifetime of the cell. Therefore, in this study complex transition metal oxides, such as vanadium, tantalum or manganese oxides, were doped into SOFC anodes to study their influence on the structural and morphological properties of magnetron sputtered AFL. The effect of dopant concentration on the properties of Ni-YSZ films in as-deposited, pre-annealed and reduced state was analysed using SEM, EDS, XRD and XPS. To characterise the electrochemical performance of the deposited films, polarisation curves were obtained from SOFC single stack assemblies under hydrogen and air flows for anode and cathode, respectively, at operating temperatures of 750, 800 and 850 ℃. References Lim, Y., Lee, H., Hong, S. & Kim, Y. B. Co-sputtered nanocomposite nickel cermet anode for high-performance low-temperature solid oxide fuel cells. J. Power Sources 412, 160–169 (2019). Ionov, I. V. et al. Reactive co-sputter deposition of nanostructured cermet anodes for solid oxide fuel cells. Jpn. J. Appl. Phys. 57, 30–34 (2018). Atkinson, A. et al. Advanced anodes for high-temperature fuel cells. Nat. Mater. 3, 17–27 (2004). Van Overmeere, Q. & Ramanathan, S. Thin film fuel cells with vanadium oxide anodes: Strain and stoichiometry effects. Electrochim. Acta 150, 83–88 (2014). Garcia-Garcia, F. J., Beltran, A. M., Yubero, F., Gonzalez-Elipe, A. R. & Lambert, R. M. High performance novel gadolinium doped ceria / yttria stabilized zirconia / nickel layered and hybrid thin film anodes for application in solid oxide fuel cells. J. Power Sources 363, 251–259 (2017). Figure 1
Tesi sul tema "Nanostructures et nanocomposites":
1
Belchi, Raphaëlle. "Architectures à base de nanostructures de carbone et TiO₂pour le photovoltaïque". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS329/document.
Abstract (sommario):
Le photovoltaïque est une énergie renouvelable pouvant aider à lutter contre le réchauffement climatique et l’épuisement des ressources fossiles utilisées pour la production d’énergie. La filière émergente à base de matériaux pérovskites (photovoltaïque de 3ème génération) est très prometteuse car elle utilise des matériaux abondants et faciles à mettre en œuvre (technologie bas-coût) et a montré de plus des rendements record compétitifs en peu de temps. Il reste cependant des verrous technologiques à lever afin de pouvoir développer cette technologie à grande échelle. L’un deux consiste à améliorer la couche de TiO₂ qui transporte les électrons et dont les défauts limitent les performances et la durée de vie des cellules photovoltaïques pérovskites. Ce travail propose l’utilisation de matériaux à base de nanostructures de carbone et de TiO₂ pour améliorer le transport et la collecte des électrons au sein de ces cellules photovoltaïques et ainsi améliorer leur rendement. Pour cela, la pyrolyse laser, technique singulière de production continue de nanoparticules, a été adaptée pour l’élaboration de nanocomposites TiO₂/graphène aux propriétés contrôlées. Ces matériaux ont été caractérisés puis intégrés aux cellules photovoltaïques pérovskites qui ont démontré une meilleure efficacité en présence de graphène. Par ailleurs, ce travail présente une architecture innovante à base de nanotubes de carbone alignés verticalement, en vue d’une application pour la collecte des électrons photo-générés des cellules photovoltaïques pérovskites. Les matériaux carbonés présentent donc de fortes potentialités pour l’optoélectronique, et plus particulièrement pour le photovoltaïque de 3ème générationPhotovoltaic is a promising renewable energy to tackle global warming and the depletion of fossil resources. The emerging field of perovskite solar cells (3rd generation photovoltaic) is very attractive because it uses abundant and easy-processing materials (low-cost technology) and provides competitive efficiencies.Still, efforts remain to be performed to develop this technology, especially concerning the improvement of efficient and reliable charge transporting electrodes. Titanium dioxide layer, commonly used for electron extraction, presents defects that limit the performance and lifetime of the perovskite solar cells.This work proposes the use of materials based on TiO₂ and carbon nanostructures to improve the electron transport and collection within the solar cells, in order to enhance the power conversion efficiency. The singular technique of laser pyrolysis, which is a continuous process of nanoparticles synthesis, was adapted to produce TiO₂/graphene nanocomposites with well-controlled properties. These materials have been characterized and integrated into perovskite solar cells that demonstrate an improved efficiency in presence of graphene.Besides, this work presents an innovating architecture based on vertically aligned carbon nanotubes for the electron collection of a perovskite solar cell. We show then the strong potential of carbon materials for optoelectronic, especially 3rd generation photovoltaic
2
Do, Isabelle. "Nanocomposites nanotubes de carbone/élastomère : Propriétés rhéologiques et électriques". Pau, 2007. http://www.theses.fr/2007PAUU3005.
Abstract (sommario):
L'incorporation de nanotubes de carbone (NTC) dans une matrice polymère est difficile du fait de leur forte tendance à s'agglomérer, ce qui réduit leur intérêt en tant que renforts. Afin de pallier ce problème, beaucoup de solutions reposent sur la modification de l'interface NTC/polymère. Le but de notre étude est d'établir la relation existant entre la nature de l'interface NTC/polymère et l'organisation spatiale des NTC d'une part, les propriétés rhéologiques et électriques du nanocomposite NTC/polyacrylate de méthyle (PMA) obtenu, d'autre part. L'interface NTC/matrice est contrôlée via l'utilisation de polyacide acrylique (PAA), soit en le greffant à la surface des nanotubes, soit en l'utilisant comme agent de surface. L'étude de la morphologie des composites par microscopie électronique a montré la nécessité de distinguer la distribution des NTC au sein de la matrice (c'est-à-dire la répartition des amas de nanotubes dans tout l'échantillon), de leur dispersion (c'est-à-dire leur individualisation au sein de ces amas). Cette distinction est centrale, car elle permet d'expliquer les propriétés physiques des nanocomposites. L'étude des propriétés viscoélastiques linéaires et électriques des composites obtenus a permis de mettre en évidence un phénomène de percolation. Nous avons également montré que les propriétés électriques des composites sont sensibles à la dispersion des NTC, alors que les propriétés rhéologiques le sont à la qualité de distribution. L'utilisation de PAA, greffé ou adsorbé sur les nanotubes, permet d'augmenter la conductivité électrique et de mieux disperser les NTC, abaissant ainsi les seuils de percolation électriqueSince carbon nanotubes (CNT) tend to remain as entangled agglomerates, homogeneous dispersed states within a polymer is not easily obtained, which reduces the interest of nanotubes as reinforcements. Many of the solutions proposed to address this issue rely on the modification of the interface between carbon nanotubes and the polymer matrix. The aim of the study is to establish the relationship between the nature of the CNT/polymethylacrylate (PMA) interface and the spatial organization of the CNTs in the matrix, on the one hand, and rheological and electrical properties of the nanocomposites, on the other hand. The interface is controlled by using polyacrylic acid (PAA), either by grafting it on the nanotubes surface, or by using it as a surfactant. The study of the morphology of the composites by electronic microscopy showed the importance of distinguishing the distribution of CNTs in the matrix (i. E. The repartition of the nanotubes clusters in the whole sample), from their dispersion (i. E. Their individualization within the clusters). This distinction is central as it allows explaining the physical properties of the nanocomposites. The studies of the linear viscoelastic and electrical properties of the composites highlighted the existence of percolation phenomena. We also showed that the electrical properties of the composites are sensitive to the CNTs dispersion, whereas the rheological ones are sensitive to the quality of distribution. The use of PAA, either grafted or adsorbed on nanotubes, allows an increase in electrical conductivity as well as a better dispersion of the nanotubes, thus lowering the electrical percolation thresholds
3
Mayne-L'Hermite, Martine. "Elaboration, microstructure et comportement au fluage de nanocomposites Si3N4/SiC". Limoges, 1997. http://www.theses.fr/1997LIMO0021.
Abstract (sommario):
L'objectif de ce travail a ete d'elaborer des nanocomposites si#3n#4/sic presentant une aptitude au formage a chaud. Pour cela, une seconde phase nanometrique sicn(o) ou sic(o) a ete introduite au sein de la matrice si#3n#4 de maniere a developper des microstructures a grains fins et equiaxes favorables a la deformation plastique a haute temperature. Les poudres nanometriques sicn(o) synthetisees par pyrolyse laser possedent des caracteristiques communes, a savoir la presence d'agregats durs au sein desquels les particules sont liees par des liaisons fortes. Ces poudres se decomposent sous atmosphere d'helium ou se niturent sous atmosphere d'azote. Un protocole de melange des poudres dans un liquide organique (acetophenone) et de mise en forme de precompacts a ete adapte a la realisation des nanocomposites. La densite elevee des precompacts obtenus par coulage (57%) temoigne de la bonne desagglomeration et de l'homogeneite des barbotines. L'etude cinetique de la densification des nanocomposites par frittage sous charge en presence d'ajouts (y#2o#3, al#2o#3) montre que la vitesse de densification depend de la nature et de la composition de la seconde phase nanometrique. Les nanocomposites sont constitues de plusieurs phases a savoir si#3n#4 , si#3n#4 , sic et une phase intergranulaire vitreuse (ysialonc). On a pu montrer que le carbure de silicium entraine une augmentation du taux de transformation si#3n#4 (equiaxe) (aciculaire), d'autant plus importante que la teneur en sic est elevee. De plus, la presence de nanoparticules de carbure de silicium aux joints de grains limite la croissance aciculaire des grains si#3n#4. La resistance au fluage en compression des nanocomposites est accrue lorsque la teneur en nanoparticules sic augmente. A partir d'une certaine duree, la deformation est regie par un mecanisme de diffusion aux joints de grains, contrairement au monolithe pour lequel il existe un long stade pseudo-stationnaire. Ce phenomene suggere une stabilite microstructurale induite par les nanoparticules de carbure de silicium. Les nanocomposites contenant 10% de carbure de silicium presentent une aptitude a la deformation en traction a haute temperature (1600 c - 1650c). Des allongements de l'ordre de 40%, obtenus en traction, devraient permettre la fabrication de pieces par formage a chaud.
4
Hoang, Minh Tuan. "Modélisation et simulation multi échelle des effets de taille et des couplages électromécaniques dans les nanostructures". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1074/document.
Abstract (sommario):
Les nanostructures, et en particulier les nanofils semi-conducteurs, ont suscité ces dernières années un très grand intérêt pour de nombreuses applications comme les systèmes de récupération d'énergie ou les capteurs de très haute précision. Dans de telles structures des expérimentations et des calculs théoriques ab-initio ont mis en évidence des effets de taille, pouvant modifier significativement les propriétés électromécaniques pour des diamètres de fils en dessous de 10 nm. L'objectif de ce travail de thèse est de proposer des modélisations multi échelle des nanostructures électromécaniques, telles que les nanofils ioniques et des nanocomposites stratifiés, permettant de reproduire les effets de taille associés à l'échelle nanométrique dans un cadre continu, en se basant sur des calculs ab-initio pour identifier et valider les modèles. Dans une première partie, les effets de surface dans des nanofils piézoélectriques isolés homogènes sont modélisés. Une approche multi échelle est développée, incluant une modélisation continue des nanofils en prenant en compte une énergie de surface supplémentaire dans un cadre piézoélectrique, dont les paramètres associés sont identifiés par calculs ab-initio. Pour cela, une procédure basée sur un modèle de films minces est développée, permettant au travers de calculs ab-initio sur des films d'épaisseurs successives d'isoler l'énergie volumique et de surface, et d'en déduire les coefficients élastiques et piézoélectriques de surface. Les équations du modèle continu sont ensuite résolues par une méthode d'éléments finis incluant des éléments de surface adaptés. Le modèle multi échelle continu est comparé à des calculs ab-initio impliquant des modèles atomistiques complets de nanofils de différents diamètres (de 0,6 à 3,9 nm) pour valider les effets de taille des propriétés électromécaniques. Dans une deuxième partie, des modèles multi échelles sont construits en vue de modéliser les effets de taille pour des nanostructures hétérogènes. Ces structures incluent des nanofils revêtus, ou des nanocomposites stratifiés. Pour les nanofils avec hétérogénéités radiales, l'approche précédemment développée est étendue au cas des surfaces revêtues, et le modèle continu fait intervenir une énergie de surface incluant les effets du revêtement. Pour les nanocomposites stratifiés AlN/GaN, les effets de taille observés par calculs ab-initio sont dus à des effets d'interface et induisent des propriétés élastiques dépendantes des épaisseurs des couches. Un modèle de matériau homogénéisé continu est proposé, incluant un modèle d'interface imparfaite, permettant d'inclure les effets de taille, identifié par calculs ab-initio. Dans une dernière partie, des applications à des systèmes de nanogénérateurs à base de nanofils sont proposées, faisant intervenir des ensembles de nanofils alignés dans une matrice polymère et surmontés par une feuille de graphène. Les approches précédemment développées sont utilisées pour modéliser ces structures par éléments finisNanostructures, and more specifically semiconductor nanowires, have drawn special attention in recent years for many applications such as energy harvesting systems or sensors of very high precision. Many recent experiments and theoretical ab-initio calculations have evidenced size effects, which can significantly modify the electromechanical properties of nanowires for diameters below 10 nm. The objective of this thesis is to provide multi-scale modeling of electromechanical properties of nanostructures, such as ionic nanowires and laminated nanocomposites, to reproduce the size effects associated with nanoscale in a continuum model, based on ab-initio calculations to identify and validate the models. In a first part, the surface effects in isolated homogeneous piezoelectric nanowires are modeled. A multi-scale approach is developed, including continuous nanowires modeling taking into account an additional surface energy in the piezoelectric laminates where the associated parameters are identified by ab-initio calculations. For this, a procedure based on slabs is developed, allowing through first-principles calculations on successive slabs thicknesses to isolate the surface energy and to deduce the surface elastic and piezoelectric coefficients. The equations of the continuous model are then solved by a finite element method including appropriate surface elements. The continuous multi-scale model is compared with ab-initio calculations involving full atomistic models of nanowires with different diameters (from 0.6 to 3.9 nm) to validate model regarding size effects of electromechanical properties. In the second part, multi-scale models are constructed to describe the size effects for heterogeneous nanostructures. These structures include coated nanowires or laminated nanocomposites. For nanowires with radial heterogeneity, the previously developed approach is extended to the case of coated surfaces, and involves a continuous surface energy incorporating the effects of the coating. For laminated AlN/GaN nanocomposites, size effects observed by ab-initio calculations are caused by the presence of the interfaces and induce size-dependent elastic properties with respect to the layer thickness. A continuum model based on an imperfect interface is proposed to describe the size dependent effective elastic properties of the overall composite, which are identified by ab-initio calculations. In the last part, nanogenerators system based on nanowires are modeled, involving nanowires arrays aligned in polymer substrates with graphene electrode. The previously developed finite element models are used to simulate the electromechanical properties of such systems
5
Habis, Christelle. "Development of ZnO-FTO nanocomposites for the use in transparent conductive thin films". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0192.
Abstract (sommario):
Cette thèse s'inscrit dans le cadre de développement de couches d'oxyde transparentes avec des techniques à faible cout, basées sur des matériaux non polluants permettant de fonctionnaliser des dispositifs opérationnels efficace, donc à haut rendement pour la production d'énergies renouvelables. Notre choix s'est porté plus particulièrement sur l'étude des couches TCO à base d'étain et dopés au fluor, F :SnO2, dénommées FTO pour « Fluor Tin Oxydes ». Les FTO sont des oxydes à large bande interdite, à l'instar du ZnO, TiO2, Al2O3, purs ou dopés. Ces couches possèdent en principe un facteur de diffusion, défini précédemment, élevé afin d'améliorer le chemin optique et l'absorption. De plus, la texture optique des TCO peut être facilement contrôlée par dépôt de suspensions de nanostructures avant le dépôt de la couche. Généralement, ces nanostructures sont des nanoparticules voire nano-fils de carbone ou nano-fils métalliques (argent, cuivre, …) et plus récemment des nano-fils de TiO2 (présentant l'inconvénient de l'élément titane) ou de ZnO non-dopés qui diminuent, malheureusement la conductivité du fait de l'augmentation de la résistance d'interface avec la concentration des nanoparticules. C'est pourquoi, nous proposons l'étude de couches de FTO, pures et également en présence de nanofibres de ZnO et ZnO:Al par électrofilage à partir d'une solution à base de PVA afin d'avoir une couche nanostructuré ayant des propriétés de transparence et de conductivité électrique améliorées pour être intégrer comme électrodes transparentes dans les cellules photovoltaïques, répondant aux critères performatifs définis ci-dessus. Les croissances des couches seront suivies par des études morphologiques et structurales, en utilisant des techniques de caractérisations disponibles au sein du laboratoire LMOPS et de l'Université de Lorraine ( tel que: MEB, Raman, EDX, DRX, spectroscopie UV-vis, ATG, AFM, profilomètre). Enfin, les propriétés électriques et optiques, en particulier l'absorption et le facteur de Haze, seront aussi largement investies sur les couches sélectionnées présentant les meilleures propriétés structurales et morphologiqueMy thesis work entitled “Development of ZnO-FTO nanocomposites for the use in transparent conductive thin films” is supervised by Professor Michel Aillerie at University of Lorraine. This work was mainly made at the “Laboratoire des Matériaux Optiques, Photoniques et Systèmes” LMOPS in Centrale Supélec, Metz. Although this work forms a whole in the elaboration of transparent conductive oxides, it is divided into two parts. The first part consists on identifying the properties of bulk materials (ZnO and FTO) deposited in the form of thin film. Whereas, the second part is about the elaboration and characterization of Zinc Oxide (ZnO) and Aluminum doped Zinc Oxide (AZO) nanofibers, then associated to FTO thin films to form nanocomposite. The main objective of this work is to make flexible electrodes using low cost and abundant material, but also improving the optical properties and more specifically the haze factor of the nanocomposite layers.Transparent conductive oxides (TCOs) are technologically significant class of materials extensively used in thin film solar cells due to their ability to transmit light and collect charge carriers. In addition to the fundamental qualities of transparency and conductivity, the TCOs are frequently desired to have a certain degree of surface roughness (i.e., texture) in order to effectively scatter transmitted light into the active materials, therefore lengthen the optical path and, as a result, enhance the performance of the cell and light absorption. This thesis focuses on the development of low-cost fabrication techniques for transparent oxide layers using non-polluting materials to enable the functionalization of operational devices with high efficiency for renewable energy production. The choice was made to study tin-based TCO layers doped with fluorine, F:SnO2, known as FTOs for "Fluor Tin Oxides". FTOs are wide band gap oxides, like ZnO, TiO2, Al2O3, pure or doped. In principle, these layers have a high scattering factor, as defined above, in order to improve the optical path and absorption. In addition, the optical texture of TCOs can be easily controlled by depositing suspensions of nanostructures before the film deposition. Generally, these nanostructures are nanoparticles or even carbon nanowires or metallic nanowires (silver, copper, ...) and more recently nanowires of TiO2 (presenting the disadvantage of the titanium element) or of undoped ZnO which unfortunately decrease the conductivity due to the increase of the interface resistance with the concentration of the nanoparticles.Therefore, we propose the study of FTO thin films, pure and also in the presence of ZnO and AZO nanofibers by electrospinning from a PVA-based solution in order to have a nanostructured layer with improved transparency and electrical conductivity properties to be integrated as transparent electrodes in photovoltaic cells, meeting the performance criteria defined above. With the characterization techniques available in the LMOPS laboratory and the University of Lorraine (SEM, Raman, EDX, DRX, UV-vis Spectro, ATG, AFM, profilometer) the growth will be followed by morphological and structural studies of the layers. Finally, electrical and optical properties, in particular absorption and scattering factor, will also be extensively investigated on selected layers with the best structural and morphological properties and the minimum of interface defects when deposited on a PV structure
6
Zaitsev, Andrii. "Exploration de la voie plasma pour la synthèse de nanostructures et de nanocomposites à base de polyaniline". Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1014/document.
Abstract (sommario):
Les nanostructures de polymères suscitent un grand intérêt grâce à leurs propriétés uniques comme le facteur de forme important. Cette propriété est essentielle pour l’utilisation dans des domaines où les interactions de surface sont mises en jeu. Un exemple d’une telle application est la détection de gaz. La polyaniline (PANi) s’est montrée prometteuse pour l’utilisation dans les capteurs d’ammoniac. La synthèse conventionnelle (chimique ou électrochimique) de nanofibres de PANi a été largement décrite dans la littérature mais cette voie possède de nombreux inconvénients. Parmi eux, figurent plusieurs étapes de synthèse (la synthèse, la purification, le dépôt sur le substrat) et l’utilisation de produits chimiques (oxydants, acides) peu respectueux de l’environnement. La polymérisation assistée par plasma froid (PECVD) permet de s’en affranchir car seul le monomère est utilisé qui se polymérise directement sur le substrat. Ainsi, ce travail de thèse a pour objectif d’élaborer des nanostructures de polyaniline plasma tout en conservant au mieux l’unité monomère dans le polymère. Le paramètre essentiel qui détermine le processus de nanostructuration est la puissance de décharge. A forte puissance, des films fortement structurés sont obtenus mais les molécules de monomère sont totalement fragmentées. En revanche, une faible puissance conduit à des films avec conservation de l’entité monomère mais sans structure morphologique particulière. Nous avons développé une méthode permettant de combiner les avantages de chaque régime : ce procédé dit « bottom-up » est réalisé en variant la puissance au cours du dépôt selon deux ou trois étapes. Les paramètres qui influencent les structures chimique et morphologique sont déterminés et les procédés à deux et trois étapes sont comparés. Par ailleurs, la synthèse « top-down » de nanostructures par gravure de la couche mince de PANi est également étudiée en fonction des paramètres du plasma (puissance et temps de décharge, débit du gaz de gravure et polarisation du substrat). Finalement, nous avons synthétisé, en phase plasma, des nanocomposites associant les nanostructures de PANi et des particules métalliques de Pd déposées par pulvérisation. La structure chimique des films de PANi est caractérisée par les spectroscopies UV-Vis, IR-TF et XPS. Pour mettre en évidence la nanostructuration des couches minces, les microscopies MEB et AFM sont utilisées. Cette dernière permet également de calculer la valeur de rugosité ainsi que la surface spécifique de la PANi. La spectroscopie EDX est utilisée pour mettre en évidence et pour quantifier le palladium dans les films synthétisés. Les couches obtenues sont finalement caractérisées sous gaz par mesures de variation d’absorbance afin de déterminer leur sensibilité et leur temps de réponse à l’ammoniacPolymer nanostructures are of great interest due to their unique properties such as high shape factor. This property is essential for applications where surface interactions are involved. One example of such an application is the gas detection. Polyaniline (PANi) has been shown as a promising material for ammonia detection. Conventional synthesis (chemical orelectrochemical) of PANi nanofibers has been widely described in the literature but this way has many drawbacks. They include several steps (synthesis, purification, deposition on the substrate) and the use of chemicals (oxidants, acids) which are not environmentally friendly. The polymerization assisted by cold plasma (PECVD) allows overcoming it, as only themonomer is used and is directly polymerized on the substrate. This thesis work aims to develop plasma polyanilinenanostructures while retaining the monomer unit in the polymer. The key parameter that determines thenanostructuring process is the discharge power. At high power, highly structured films are obtained but the monomer molecules are totally fragmented. On the contrary, low power allows conservation of the monomer unit but no surface structuring is observed. We developed a method which combines the advantages of each regime. This "bottom-up" process consists to vary the input power during deposition in two or three stages. Parameters influencing the chemical and morphological structures are determined and the two and three steps methods are compared. Furthermore, the "top-down" synthesis of nanostructures by etching the PANi layer is also studied according to the plasma parameters (power and discharge time, etching gas flow rate and substrate bias). Finally, in plasma phase, we synthesized nanocomposite by combining PANi nanostructures and sputtered Pd particles. The chemical structure of the PANi films is characterized by UV-Vis spectroscopy, FT-IR and XPS. In order to highlight the nanostructuring of thin films, SEM and AFM microscopy areused. The latter one allows also the calculation of the roughness and specific surface of the PANi. EDX spectroscopyis used to bring out the presence of palladium and to quantify it. Finally, the obtained layers are characterized under gas byabsorbance variation measurements in order to determine their sensitivity and response time to ammonia
7
Dubois, Jean-Baptiste. "Conducteurs nanocomposites métalliques élaborés par déformation plastique sévère : formation et stabilité thermo-mécanique des nanostructures, propriétés induites". Poitiers, 2010. http://theses.univ-poitiers.fr/26782/2010-Dubois-Jean-Baptiste-These.pdf.
Abstract (sommario):
Ces travaux de thèse concernent l'étude de matériaux nanocomposites métalliques à base de cuivre/niobium (Cu/Nb), combinant conductivité électrique et limite d'élasticité élevées et développés pour la fabrication de bobines résistives de champs magnétiques pulsés intenses. Les conducteurs nanocomposites Cu/Nb continus sont élaborés par une méthode de déformation plastique sévère (DPS), basée sur des cycles d'extrusions, d'étirages et d'empilements successifs, conduisant à la formation d'un matériau nanostructuré multi-échelle. Afin d'optimiser le procédé de fabrication, l'effet des traitements thermiques sur les textures ainsi que leur formation au cours de l'élaboration ont été étudiés par diffraction des rayons X en laboratoire. Des expériences complémentaires de traitements thermiques in-situ sous rayonnement synchrotron ont permis une meilleure compréhension des mécanismes élémentaires de restauration de la microstructure et la définition d'un traitement thermique optimisé. La stabilité thermique des conducteurs apparaît aussi fortement dépendante des dimensions microstructurales : une frustration des phénomènes de restauration, de recristallisation et de croissance des grains est observée pour les conducteurs nanostructurés. Ces résultats ont permis de fabriquer des conducteurs « co-axiaux » optimisés, renforcés par des nanofilaments et des nanotubes de niobium. Leurs propriétés microstructurales et physiques ont été caractérisées et comparées aux anciennes générations de conducteurs nanocomposites Cu/Nb. Les propriétés obtenues et la possibilité d'élaborer de grandes longueurs de fils rendent ces matériaux compétitifs pour les futures applications en champs pulsésThis thesis concerns the study of metallic nanocomposite copper/niobium (Cu/Nb) wires, combining high electrical conductivity and high strength, as required for the design of high magnetic field resistive coils. The reinforced continuous nanocomposite Cu/Nb conductors are fabricated via a severe plastic deformation process (SPD), which consists in repeated extrusion, drawing and bundling cycles (Accumulative Drawing and Bundling : ADB) and leads to the nanostructuration of the Nb reinforcements and a multi-scale Cu matrix. In order to optimize the process, the effect of heat treatments on texture and its development during the process were analysed by means of laboratory X-ray diffraction. Complementary in-situ heat treatments under synchrotron radiation gave a better insight into the elementary annealing mechanisms and enabled defining optimized heat treatments. These experiments also revealed that the thermal stability of Cu/Nb conductors is extremely dependent of the microstructure size: recovery, recrystallization, grain growth and all relaxation processes are frustrated in the case of nanocomposites. From these results, optimized “co-axial” conductors reinforced by Nb nanofilaments and nanotubes were processed. Their microstructure and physical properties have been characterized and compared to those of previous Cu/Nb nanocomposite conductors. With the possibility to produce long wires with improved properties, these new Cu/Nb nanocomposites offer a great alternative to existing conductors for future high magnetic field applications
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Aldroe, Hanaya. "Analyse des propriétés physiques et mécaniques des nanocomposites polyamide 12 / cloisite® 30B en lien avec leurs nanostructures". Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4034/document.
Abstract (sommario):
Les nanocomposites suscitent un intérêt croissant depuis leur développement dans les années 90 par Toyota. Par conséquent, l'amélioration des propriétés de ce type de matériaux est un enjeu fort tant d'un point de vue fondamental qu'industriel. Cette amélioration peut passer par un choix pertinent des charges renforçantes ajoutées à la matrice notamment en ce qui concerne le type, la géométrie, la proportion et le traitement de ces charges. L’optimisation des paramètres d’élaboration du mélange y joue aussi un rôle important. L’objectif de ce travail est de contribuer à l’identification et à la compréhension des mécanismes à l'origine du renforcement des matrices thermoplastiques par des nanocharges. Cet aspect est abordé à travers l’étude des propriétés thermiques et mécaniques des nanocomposites formés d’une matrice Polyamide 12 (PA12) chargées par des nanoparticules d’argile organiquement modifiée. Plus précisément, nous avons analysé les effets de la fraction massique des charges et du vieillissement naturel sur les propriétés structurales, thermiques et mécaniques de ces nanocomposites. L’influence des conditions de mélangeage sur ces propriétés ont aussi été examinées. Nous avons particulièrement mis l’accent sur l’identification des liens qui existent entre les propriétés macroscopiques et la structure des nanocomposites. Nous avons aussi fait une étude comparative des propriétés viscoélastiques de ces matériaux à l'état fondu et à l'état solide, ce qui représente une des originalités forte de ce travailNanocomposites are interestingly growing since their development in the 1990s by Toyota Company. Therefore, improving the properties of such materials is a major issue from fundamental and industrial point of view. This improvement can pass through a relevant choice of reinforcing loads added to the matrix particularly regarding the type, geometry, the proportion, and the treatment of these fillers. The processing parameters of the mixture play also a key role. The objective of this work is to contribute to the identification and understanding of the mechanisms at the origin of the reinforcing thermoplastic matrices by nanofillers. This aspect presented through the study of the thermal and mechanical properties of nanocomposites formed by a polyamide 12 matrix (PA12) filled with organically modified clay nanoparticles. More specifically, we analysed the effects of the filler mass fraction and environmental aging on structural, thermal and mechanical properties of these nanocomposites. The mixing conditions on these properties were also examined. A particular attention has been paid to the study of relationships between the macroscopic properties and the structure of nanocomposites. Viscoelastic properties of these materials in both melt and solid states were compared, which represents one of the originalities of this work
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Laurent, Christophe. "Contribution à l'étude de nanocomposites à matrice céramique. Alumine-alliages fer-chrome et alumine-zircone-fer et alliages fer-chrome". Toulouse 3, 1994. http://www.theses.fr/1994TOU30017.
Abstract (sommario):
Les nanocomposites alumine-metal, dans lesquels les particules metalliques nanometriques sont dispersees dans la matrice ceramique possedent des proprietes mecaniques superieures a celles de l'alumine pure ou renforcee par des particules metalliques micrometriques. L'elaboration de poudres nanocomposites alumine-fer, alumine-chrome et alumine-alliages fer-chrome a ete realisee par calcination puis reduction selective sous hydrogene de solutions solides d'oxydes obtenues par decomposition de precurseurs oxaliques mixtes. Une etude de l'influence des temperatures de calcination et de reduction sur la formation des nanocomposites alumine-fer a ete menee, notamment par spectroscopie mossbauer, mettant en evidence plusieurs modes de formation du fer metallique. Cette etude a ete etendue aux alliages fer-chrome, et il est montre que les particules metalliques les plus petites sont les plus riches en chrome. La localisation des nanoparticules metalliques, intragranulaire ou en surface des grains d'alumine, a ete mise en evidence par thermogravimetrie et correlee a la teneur en metal. Des composites massifs ont ete prepares par frittage sous charge des poudres nanocomposites. Les meilleures proprietes mecaniques (charge a rupture et tenacite) sont obtenues pour des composites hybrides ou la phase metallique est dispersee a la fois sous forme de particules nanometriques a l'interieur des grains d'alumine et sous forme de particules micrometriques situees aux joints de grains de la matrice. Le choix approprie des temperatures de calcination et de reduction des poudres permet d'optimiser les caracteristiques mecaniques. L'oxydation sous air de ces materiaux est negligeable jusqu'a 1000c; au-dela, les nanocomposites contenant du chrome sont plus stables que les nanocomposites alumine-fer. Des composites hybrides alumine-zircone-fer et alumine-zircone-alliages fer-chrome ont ete elabores par quatre methodes. Suivant la microstructure obtenue, il y a amelioration des proprietes mecaniques par rapport a celles des nanocomposites alumine-metal, ou bien annihilation partielle des differents mecanismes de renforcement
10
Sauvage, Xavier. "Transformations de phases induites par déformation plastique intense. Cas des aciers perlitiques tréfilés et des nanocomposites filamentaires Cu/Nb". Rouen, 2001. http://www.theses.fr/2001ROUES032.
Abstract (sommario):
Les aciers perlitiques tréfilés et les nanocomposites filamentaires Cu/Nb sont élaborés par tréfilage à froid. La déformation plastique conduit à un allongement des grains le long de l'axe du fil et à une réduction importante de leurs dimensions dans la section transverse. Ainsi, les lamelles de cémentite des aciers perlitiques ne font plus que quelques nanomètres d'épaisseur et les fibres de niobium des composites Cu/Nb ont un diamètre moyen compris entre 10 et 60 nm. Ces nanostructures ont été caractérisées en microscopie ionique, sonde atomique, MET et METHR. Dans les aciers perlitiques, la dissolution partielle de la cémentite a pu être clairement mise à jour. Plus les lamelles sont fines, plus elles sont dissoutes. La dissolution est parfois totale et les zones transformées semblent alors évoluer vers une structure de type martensitique. La dissolution de la cémentite résulterait de l'accroissement considérable de la proportion d'interfaces. En considérant un effet de type Gibbs-Thomson, cette dissolution a pu être simulée. Toutefois, le taux de cémentite dissoute est sous-estimé car la modélisation de la cinétique ne prend pas en compte un terme de transport lié au champ de contraintes internes. Dans les nanocomposites filamentaires Cu/Nb, la déformation plastique n'affecte généralement pas la nature des différentes phases : le niobium et le cuivre restent purs. Toutefois, dans les zones où la taille de grains est inférieure à 15 nm, les analyses en sonde atomique révèlent une interdiffusion du cuivre et du niobium. Ces zones de mélange pourraient être amorphes comme le suggèrent nos observations en METHR. Cette amorphisation résulterait de l'accroissement considérable de l'énergie d'interface et de l'énergie élastique résultant des contraintes internes. La cinétique serait, quant à elle, favorisée par l'accroissement de la densité de lacunes au cours du tréfilage et par le champ de contraintes internes.
Libri sul tema "Nanostructures et nanocomposites":
1
Haghi, A. K. Foundations of nanotechnology. Oakville, ON, Canada: Apple Academic Press Inc., 2014.
2
Joshi, Mangala. Nanotechnology in Textiles: Advances and Developments in Polymer Nanocomposites. Jenny Stanford Publishing, 2020.
3
Joshi, Mangala. Nanotechnology in Textiles: Advances and Developments in Polymer Nanocomposites. Jenny Stanford Publishing, 2020.
4
Joshi, Mangala. Nanotechnology in Textiles: Advances and Developments in Polymer Nanocomposites. Jenny Stanford Publishing, 2020.
5
Joshi, Mangala. Nanotechnology in Textiles: Advances and Developments in Polymer Nanocomposites. Jenny Stanford Publishing, 2020.
6
Joshi, Mangala. Nanotechnology in Textiles: Advances and Developments in Polymer Nanocomposites. Jenny Stanford Publishing, 2020.
Capitoli di libri sul tema "Nanostructures et nanocomposites":
1
Hashem Abdelmohsen, Ahmed, Sherif A. El-Khodary e Nahla Ismail. "Theories, Hypothesis and Rules for Morphology Transition Engineering of 1D, 2D and 3D Nanomaterials". In Nanotechnology and Nanomaterials. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.112135.
Abstract (sommario):
Most of the chemical and physical properties of nanomaterials vary remarkably according to their size, shape, and structure. Thus morphology is a crucial parameter that controls the properties and functionality of materials. On the basis of Abdelmohsen et al.’s theories and hypothesis, which are theory for morphology transition engineering (ATMTE), theory for morphology engineering of solid compounds (ATMESC), and hypothesis for engineering of micro- and nanostructures (AHEMNS), novel approach was modified for fabricating one-, two-, and three-dimensional hybrid nanomaterials, such as hybrid ZnO nanosheets (38–150 nm), hybrid ZnO nanorods, hybrid nanocomposites, and hierarchical hybrid Cu2O nanostructures. In addition, by the help of this novel method, the fabrication of metal-oxidene (one/few atoms thick layer of metal oxides) is assumed and hybrid ZnO thin film that is expected to have extraordinary physicochemical properties. A series of selection rules and morphology engineering rules are discussed. Throughout this chapter, we will come across this novel approach as a promising technique for nanofabrication and discuss the suggested mechanisms for the evolution process during fabrication of nanomaterials. By the help of this method, we have fabricated 1D, 2D and 3D nanomaterials that are expected to have potential use for energy, catalysis, biomedical, and other applications.
Atti di convegni sul tema "Nanostructures et nanocomposites":
1
Aboul-Gheit, Ahmed K., Sawsan A. Mahmoud e Yasser M. Moustafa. "Nanostructured Ti-Fe Thin Layered Photocatalyst via Sol-Gel Technique". In ASME 2008 2nd Multifunctional Nanocomposites and Nanomaterials International Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/mn2008-47033.
Abstract (sommario):
The finding of of Zhu et al. [1] that iron-ion-doped TiO2 powders by hydrothermal hydrolysis and crystallization exhibited that the amount of doped iron ion significantly affected the phoyocatalytic degradation activity of XRG yellow dye and Fe optimum content could enhance photocatalytic activity under UV and visible light irradiation has encourage us to carry out this work. Hence, we prepared and examined the photocatalytic activities of a series of TiO2/Fe2O3 mixtures of thin layers of TiO2 and Fe2O3 using the sol-gel method and found that the TiO2(5)/Fe2O3(1) catalyst the most active for anthracene photodegradation. This catalyst acquired the highest surface area, proper pore size distribution and the smaller nano-particle size.
2
Vodopyanov, Alexander, Andrey Samokhin, Nikolay Aleksev, Mikhail Sinayskiy, Andrey Sorokin e Sergey Sintsov. "TUNGSTEN CARBIDE NANOPOWDER SYNTHESIS UNDER THE EXPOSURE OF 24 GHZ GYROTRON RADIATION ON THE NANOCOMPOSITE OF THE W-C SYSTEM OBTAINED IN A THERMAL PLASMA". In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9836.
Abstract (sommario):
Nanoscale tungsten carbide WC powders are of practical interest for the creation of nanostructured hard alloys with enhanced physical and mechanical characteristics, wear-resistant nanostructured coatings, electrocatalysts in fuel cells, metal melt modifiers [1]. An efficient method for producing tungsten carbide nanopowder is a plasma-chemical synthesis of a multi-component powder nanocomposite system W-C in combination with its subsequent heat treatment [2]. Experimental studies have shown the possibility of producing tungsten carbide WC nanopowder by this method. But the transformation of the nanocomposite in the target product is accompanied by an increase in the size of nanoparticles. We assume that this growth is associated with prolonged heating (several hours) in an electric furnace at a temperature of about 1000 ° C. This time is necessary for the complete transformation of the nanocomposite into the target product. The aim of the work was an experimental study of the formation of tungsten carbide nanopowder WC when processing a multi-component powder nanocomposite system W-C in an electromagnetic field with a frequency of 24 GHz. A multipurpose gyrotron system with a nominal power of 7 kW with at a frequency of 24 GHz was used for the experiments. The microwave application system described in [3]. The powders were treated in an argon flow. The experiments were carried varying exposure time and microwave power. The samples of nanopowders obtained in the experiments were analyzed using the following methods: XRD, TEM, SEM, BET, LDA, CEA. It was established that microwave radiation with a frequency of 24 GHz allows heating samples of powders to a temperature of 1100-1200 C almost immediately (after 1-2 s) after switching on. The tungsten carbide WC is formed in a few minutes under the exposure to microwave radiation of the original W-C nanocomposite system. There is only a slight increase in the average particle size from 20 to 30 nm. The investigations showed that the synthesis of tungsten carbide WC under the microwave heating as compared to conventional heating in an electric furnace may be carried out for significantly less time while maintaining the particles in the nanometer range.The work was carried out within the framework of the Program #14 "Physical chemistry of adsorption phenomena and actinide nanoparticles" of the Presidium of the Russian Academy of Sciences.References Z. Zak Fang, Xu Wang, et al. Int. Journal of Refractory Metals & Hard Materials, 2009, 27, 288–299.Samokhin A., Alekseev N., et al. Plasma Chem. Plasma Proc., 2013, 33, 605–616.Samokhin A., Alekseev N., et al. J. Nanotechnol. Eng. Med., 2015, 6, 011008.