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991.
Paule Njiwa Aurélie Hadj-Aïssa Pavel Afanasiev Christophe Geantet Françoise Bosselet Béatrice Vacher Michel Belin Thierry Le Mogne Fabrice Dassenoy 《Tribology Letters》2014,55(3):473-481
Seed-assisted solution synthesis of hollow IF-MoS2 nanoparticles allows independent control of particles size and MoS2 slabs crystallinity. Variations of the reaction mixture composition influence the particle size in the range 50–150 nm. As demonstrated by Rietvelt refinement of the X-ray diffraction patterns, the sulfide crystallinity depends only on the post-treatment temperature (350–750 °C) and not on the particle size. The tribological properties of new MoS2 nanoparticles prepared by seed-assisted solution technique were investigated and showed a strong decrease in the friction coefficient and wear compared with base oil. Small particles of 50–60-nm size showed the best results. The particle size above 100 nm is deleterious for the lubrication properties since it hinders particles penetration into the contact zone. MoS2 slabs crystallinity had lesser influence on the lubrication efficiency. However, less-crystallized samples treated at 350 °C showed better lubrication, apparently because of easier exfoliation of the individual MoS2 slabs, leading to more efficient formation of tribofilm. 相似文献
992.
Christophe Vega 《纺织导报》2006,(9):33-34
事实上.除了地毯丝以外,对于超过500D的加捻丝.都可以归为“工业丝”范畴。这些纱线包括:塑料制品增强材料.用于帆布和防水布;橡胶制品增强材料.如车用风扇带、轮胎和胶管:登山绳、吊装带和农用绳;人工草坪和体育用品面料等。 相似文献
993.
Claude Lamy Deborah J. Jones Christophe Coutanceau Pascal Brault Sergueï Martemianov Yann Bultel 《Electrochimica acta》2011,56(28):10406
The membrane electrode assembly (MEA) is the key component of a PEMFC stack. Conventional MEAs are composed of catalyzed electrodes loaded with 0.1–0.4 mgPt cm−2 pressed against a Nafion® membrane, leading to cell performance close to 0.8 W cm−2 at 0.6 V. Due to their limited stability at high temperatures, the cost of platinum catalysts and that of proton exchange membranes, the recycling problems and material availability, the MEA components do not match the requirements for large scale development of PEMCFs at a low cost, particularly for automotive applications.Novel approaches to medium and high temperature membranes are described in this work, and a composite polybenzimidazole–poly(vinylphosphonic) acid membrane, stable up to 190 °C, led to a power density of 0.5 W cm−2 at 160 °C under 3 bar abs with hydrogen and air. Concerning the preparation of efficient electrocatalysts supported on a Vulcan XC72 carbon powder, the Bönnemann colloidal method and above all plasma sputtering allowed preparing bimetallic platinum-based electrocatalysts with a low Pt loading. In the case of plasma deposition of Pt nanoclusters, Pt loadings as low as 10 μg cm−2 were achieved, leading to a very high mass power density of ca. . Finally characterization of the MEA electrical properties by Electrochemical Impedance Spectroscopy (EIS) based on a theoretical model of mass and charge transport inside the active and gas diffusion layers, together with the optimization of the operating parameters (cell temperature, humidity, flow rate and pressure) allowed obtaining electrical performance greater than 1.2 W cm−2 using an homemade MEA with a rather low Pt loading. 相似文献
994.
Abdellah Saboni Silvia Alexandrova Maria Karsheva Christophe Gourdon 《American Institute of Chemical Engineers》2011,57(7):1684-1692
The unsteady mass transfer from a contaminated fluid sphere moving in an unbounded fluid is examined numerically for unsteady‐state transfer. The effect of the interface contamination and the flow regime on the concentration profiles, inside and outside a fluid sphere, is investigated for different ranges of Reynolds number (0 < Re < 200) and Peclet number (0 < Pe < 105), viscosity ratio between the dispersed phase and the continuous phase (0 < κ < 10), and the stagnant‐cap angle (0° < θcap < 180°). It was found that the stagnant‐cap angle significantly influences the mass transfer from the sphere to a surrounding medium. For all Peclet and Reynolds numbers and κ, the contamination reduces the mass transfer flux. The average Sherwood number increases with an increase of stagnant‐cap angle and reaches a maximum equal to the average one for a clean fluid sphere at low viscosity ratio and large Peclet numbers. A predictive equation for the Sherwood number is derived from these numerical results. © 2010 American Institute of Chemical Engineers AIChE J, 2011 相似文献
995.
Bauer C Teuscher J Brauer JC Punzi A Marchioro A Ghadiri E De Jonghe J Wielopolski M Banerji N Moser JE 《Chimia》2011,65(9):704-709
Photoinduced electron transfer (PET) across molecular/bulk interfaces has gained attention only recently and is still poorly understood. These interfaces offer an excellent case study, pertinent to a variety of photovoltaic systems, photo- and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. They play in particular a key role in the emerging fields of third-generation photovoltaic energy converters and artificial photosynthetic systems aimed at the production of solar fuels, creating a need for a better understanding and theoretical treatment of the dynamics and mechanisms of interfacial PET processes. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test and alter modern theory and computational modeling. One example illustrating recent investigations into the details of the ultrafast processes that form the basis for photoinduced charge separation at a molecular/bulk interface relevant to dye-sensitized solar cells is briefly presented here: Kinetics of interfacial PET and charge recombination processes were measured by fs and ns transient spectroscopy in a heterogeneous donor-bridge-acceptor (D-B-A) system, where D is a Ru(II)(terpyridyl-PO3)(NCS)3 complex, B an oligo-p-phenylene bridge, and A nanocrystalline TiO2. The forward ET reaction was found to be faster than vibrational relaxation of the vibronic excited state of the donor. Instead, the back ET occurred on the micros time scale and involved fully thermalized species. The D-A distance dependence of the electron transfer rate was studied by varying the number of p-phenylene units contained in the bridge moiety. The remarkably low damping factor beta = 0.16 angstroms(-1) observed for the ultrafast charge injection from the dye excited state into the conduction band of TiO2 is attributed to the coupling of electron tunneling with nonequilibrium vibrations redistributed on the bridge, giving rise to polaronic transport of charges from the donor ligand to the acceptor solid oxide surface. 相似文献
996.
Hans Danneels Valentijn De Smedt Christophe De Roover Cedric Walravens Soheil Radiom Marian Verhelst Michiel Steyaert Wim Dehaene Georges Gielen 《Analog Integrated Circuits and Signal Processing》2014,80(3):531-540
This paper presents an ultra-low-power, low-voltage sensor node for wireless sensor networks. The node scavenges RF energy out of the environment, resulting in a limited available power budget and causing an unstable supply voltage. Hence, accurate and extensive power management is needed to achieve proper functionality. The fully integrated, autonomous system is described, including the scavenging circuitry with integrated antenna, the power detection and power control circuits, the on-chip clock reference, the UWB transmitter and the digital control circuitry. The wireless sensor node is implemented in \(0.13 \,\upmu \hbox {m}\) CMOS technology. The only external components are a storage capacitor and a UWB transmit antenna. The system consumes only \(113\, \upmu \hbox {W}\) during burst mode, while only 8 nW is consumed during the scavenging operation, enabling an efficiency of 5.35 pJ/bit which is significantly better than current state-of-the-art UWB tags. Due to the use of impulse-radio UWB, also cm-accurate localization of the tag can be achieved. 相似文献
997.
Photothermal Killing of Cancer Cells by the Controlled Plasmonic Coupling of Silica‐Coated Au/Fe2O3 Nanoaggregates 下载免费PDF全文
Georgios A. Sotiriou Fabian Starsich Athanasia Dasargyri Moritz C. Wurnig Frank Krumeich Andreas Boss Jean‐Christophe Leroux Sotiris E. Pratsinis 《Advanced functional materials》2014,24(19):2818-2827
Tumor ablation by thermal energy via the irradiation of plasmonic nanoparticles is a relatively new oncology treatment. Hybrid plasmonic‐superparamagnetic nanoaggregates (50–100 nm in diameter) consisting of SiO2‐coated Fe2O3 and Au (≈30 nm) nanoparticles were fabricated using scalable flame aerosol technology. By finely tuning the Au interparticle distance using the SiO2 film thickness (or content), the plasmonic coupling of Au nanoparticles can be finely controlled bringing their optical absorption to the near‐IR that is most important for human tissue transmittance. The SiO2 shell facilitates also dispersion and prevents the reshaping or coalescence of Au particles during laser irradiation, thereby allowing their use in multiple treatments. These nanoaggregates have magnetic resonance imaging (MRI) capability as shown by measuring their r2 relaxivity while their effectiveness as photothermal agents is demonstrated by killing human breast cancer cells with a short, four minute near‐IR laser irradiation (785 nm) at low flux (4.9 W cm‐2). 相似文献
998.
Christophe Téqui Paul Grinspan Pascal Richet 《Journal of the American Ceramic Society》1992,75(9):2601-2604
The heat capacities of liquid Li2 SiO3 and Li2 Si3 O7 have been determined through drop calorimetry measurements to complement available data on lithium, sodium, and potassium silicate melts. The composition and temperature dependences of the heat capacity depends specifically on the nature of the alkali element, indicating that the temperature-induced structural changes that take place in the melts are specific. The properties of crystalline Li2 SiO3 have also been determined above 298 K. The enthalpy of fusion at 1474 K is 71.3 ± 0.6 kJ/mol, in agreement with previous measurements. In contrast to other silicate compounds, and especially the isostructural crystal Na2 SiO3 , Li2 SiO3 shows almost no premelting effects. 相似文献
999.
Danile Roudil Jessica Bonhoure Raphaël Pik Michel Cuney Christophe Jgou F. Gauthier-Lafaye 《Journal of Nuclear Materials》2008,378(1):70-78
The issue of nuclear waste management – and especially spent fuel disposal – demands further research on the long-term behavior of helium and its impact on physical changes in UO2 and (U,Pu)O2 matrices subjected to self-irradiation. Helium produced by radioactive decay of the actinides concentrates in the grains or is trapped at the grain boundaries. Various scenarios can be considered, and can have a significant effect on the radionuclide source terms that will be accessible to water after the canisters have been breached. Helium production and matrix damage is generally simulated by external irradiation or with actinide-doped materials. A natural uranium oxide sample was studied to acquire data on the behavior of radiogenic helium and its diffusion under self-irradiation in spent fuel. The sample from the Pen Ar Ran deposit in the Vendée region of France dated at 320 ± 9 million of years was selected for its simple geological history, making it a suitable natural analog of spent fuel under repository conditions during the initial period in a closed system not subject to mass transfer with the surrounding environment. Helium outgassing measured by mass spectrometry to determine the He diffusion coefficients through the ore shows that: (i) a maximum of 5% (2.1% on average) of the helium produced during the last 320 Ma in this natural analog was conserved, (ii) about 33% of the residual helium is occluded in the matrix and vacancy defects (about 10−5 mol g−1) and 67% in bubbles that were analyzed by HRTEM. A similar distribution has been observed in spent fuel and in (U0.9,Pu0.1)O2. The results obtained for the natural Pen Ar Ran sample can be applied by analogy to spent fuel, especially in terms of the apparent solubility limit and the formation, characteristics and behavior of the helium bubbles. 相似文献
1000.
Elias Abi Abdallah Christophe Bouvet Samuel Rivallant Bernhard Broll Jean-Jacques Barrau 《Composites Science and Technology》2009,69(7-8):1238-1245
This paper presents an experimental investigation concerning low-velocity impact and quasi-static indentation tests on highly oriented laminates used in aeronautical and aerospace applications. The damage observed in such laminates is very particular. Post mortem analysis were carried out which helped to define an impact damage scenario. Microscopic observations led to explain the mechanism of permanent indentation formation which is a fundamental point of damage tolerance justification. Equivalence between static and dynamic is also discussed. 相似文献