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101.
《International Journal of Hydrogen Energy》2019,44(52):28123-28133
Using free and sustainable solar energy to produce hydrogen is the most promising strategy to resolve the environmental pollution and global energy crisis. The properties of sensitized matrix and co–catalyst, including the dispersibility, lattice structure and electrical performance, are usually two the decisive factors for photocatalytic hydrogen evolution. This paper reports a facile synthetic process of surface–clean monodisperse Pt(100) nanocubes supported on graphene surface using amide functional groups as induction sites. The prepared catalyst (AG/Pt(100)) not only incorporate plentiful amide functional groups that act as the dispersant and stabilizer into surface and edge of graphene, but also significantly dislodge the oxygen–containing functional groups, which hold strong promise for improving conductivity, carrier concentration and mobility of sensitized matrix. Simultaneously, the monodisperse Pt(100) nanocubes supported on graphene surface exposure more active sites. These results provide the necessary conditions for efficient catalysts. Without any pre–treatment, it exhibits high H2 generation activity (553.7 μmol for 2 h) and apparent quantum efficiency (AQE) (33.9% at 430 nm) under visible light irradiation when Eosin Y is used as photosensitizer. These superior production H2 activities can attribute to enhance the dispersion and conductivity of sensitized matrix, construct special geometry of Pt(100) nanocubes and prolong the lifetime of photogenerated electron. 相似文献
102.
The transport phenomena in Metal-Oxide-Semiconductor (MOS) structures having silicon nanocrystals (Si-NCs) inside the dielectric layer has been investigated by high frequency Capacitance-Voltage (C-V) method and the Deep-Level Transient Spectroscopy (DLTS). For the reference samples without Si-NCs, we observe a slow electron trap for a large temperature range, which is probably a response of a series electron traps having a very close energy levels. A clear series of electron traps are evidenced in DLTS spectrum for MOS samples with Si-NCs. Their activation energies are comprised between 0.28 eV and 0.45 eV. Moreover, we observe in this DLTS spectrum, a single peak that appears at low temperature which we attributed to Si-NCs response. In MOS structure without Si-NCs, the conduction mechanism is dominated by the thermionic fast emission/capture of charge carriers from the highly doped polysilicon layer to Si-substrate through interface trap-states. However, at low temperature, the tunneling of charge carriers from highly Poly-Si to Si-substrate trough the trapping/detrapping mechanism in the Si-NCs contributed to the conduction mechanism for MOS with Si-NCs. These results are helpful to understand the principle of charge transport of MOS structures having a Si-NCs in the SiOx = 1.5 oxide matrix. 相似文献
103.
Four kinds of paper-based friction materials reinforced with carbon fibers of 100, 400, 600 and 800 μm were prepared by paper-making processes. Experimental results showed that the friction materials became porous with fiber length increasing. The friction torque curves were flat except the sample with 100 μm fibers. The wear rate of the sample with 100 μm fibers was only 1.40×10−5 mm3/J. Tiny debris and fine scratches formed in the worn surface were the reason for excellent wear resistance of friction pairs with 100 μm fibers. The friction pairs with 400, 600 and 800 μm fibers showed typically abrasive wear and fatigue wear. 相似文献
104.
The compressive mechanical properties of two kinds of closed-cell aluminum foam–polymer composites (aluminum–epoxy, aluminum–polyurethane) were studied. The nonhomogeneous deformation features of the composites are presented based on the deformation distributions measured by the digital image correlation (DIC) method. The strain fluctuations rapidly grow with an increase in the compressive load. The uneven level of the deformation for the aluminum–polyurethane composite is lower than that for the aluminum–epoxy composite. The region of the preferentially fractured aluminum cell wall can be predicted by the strain distributions in two directions. The mechanical properties of the composites are investigated and compared to those of the aluminum foams. The enhancement effect of the epoxy resin on the Young’s modulus, the Poisson’s ratio and the compressive strength of the aluminum foams is greater than that of the polyurethane resin. 相似文献
105.
《International Journal of Hydrogen Energy》2019,44(5):2960-2975
The hydrogen adsorption capacity of dual-Ti-doped (7, 7) single-walled carbon nanotube (Ti-SWCNTs) has been studied by the first principles calculations. Ti atoms show different characters at different locations due to local doping environment and patterns. The dual-Ti-doped SWCNTs can stably adsorb up to six H2 molecules through Kubas interaction at the Ti2 active center. The intrinsic curvature and the different doping pattern of Ti-SWCNTs induce charge discrepancy between these two Ti atoms, and result in different hydrogen adsorption capacity. Particularly, eight H2 molecules can be adsorbed on both sides of the dual-Ti decorated SWCNT with ideal adsorption energy of 0.198 eV/H2, and the physisorption H2 on the inside Ti atom has desirable adsorption energy of 0.107 eV/H2, ideal for efficient reversible storage of hydrogen. The synergistic effect of Ti atoms with different doping patterns enhances the hydrogen adsorption capacity 4.5H2s/Ti of the Ti-doped SWCNT (VIII), and this awaits experimental trial. 相似文献
106.
《International Journal of Hydrogen Energy》2019,44(33):18415-18424
To improve oxidation resistance, prevent Cr evaporation and maintain appropriate electrical conductivity of AISI 430 stainless steel (430 SS) as the solid oxide fuel cells' (SOFCs) interconnect, a double-layered Co-Mn-O spinel coating is fabricated successfully on 430 SS via a simple double glow plasma alloying process (DGPA) followed by heating in the air (preoxidation treatment). The double-layered Co-Mn-O spinel coating is composed of a thick MnCo2O4 spinel outlayer and a thin mutual-diffused (MnCoFe)3O4 oxide innerlayer. The isothermal and cyclic oxidation measurements are used to investigate the oxidation resistance, and the ASR test is performed to evaluate the conductivity for the coated and uncoated specimens. The coated specimen has a lower oxidation kinetics rate constant (9.0929 × 10−4 mg2 cm−4 h−1) than the uncoated one (1.900 × 10−3 mg2 cm−4 h−1) and the weight gain of the coated specimen (0.84 mg cm−2) is less than that of bare steel (1.29 mg cm−2) after 750 h oxidation. Meanwhile, the coated specimen holds a lower area specific resistance (0.029 Ω cm2) compared to the uncoated one (2.28 Ω cm2) after 408 h oxidation. Furthermore, the compact Co-Mn-O spinel coating can effectively impede Cr-volatilization. Additionally, the probable mechanism of the Co-Mn alloy conversion into spinel and the electronic conduction behavior in the spinel are discussed. The effects of mutual-diffused oxide innerlayer on oxidation behavior and conductivity are investigated. 相似文献
107.
《International Journal of Hydrogen Energy》2019,44(36):20529-20544
The effect of age-hardening regime on peculiarities of hydrogen-assisted fracture and tensile properties in two high-nitrogen Fe-23Cr-17Mn-0.1C-0.6N and Fe-19Cr-22Mn-1.5V-0.3C-0.9N steels was studied. A large number of intergranular (austenite/austenite) and interphase boundaries (austenite/coarse particle) provides high fraction of trapping sites for hydrogen atoms in V-alloyed steel. This leads to a change in fracture regime from transgranular brittle mode in coarse-grained V-free steel to intergranular brittle fracture of hydrogen-assisted surface layers in fine-grained V-alloyed steel with coarse (V,Cr)(N,C) particles. The formation of cells (Cr2(N,C) particles and austenite) along the grain boundaries due to discontinuous precipitate-hardening reaction facilitates predominantly interphase hydrogen-assisted fracture for both steels. The complex reaction of the particle-strengthening mechanisms including discontinuous precipitation with formation of austenite/Cr2(N,C)-plates interfaces or homogeneous nucleation of coherent (V,Cr)(N,C) particles in austenite (age-hardening regime 700 °C, 10 h) promotes mainly transgranular cleavage-like fracture mode under hydrogen-charging. The structural scheme is proposed to describe a change in hydrogen-assisted fracture micromechanisms and tensile properties of the steels with different density and distribution of interphase and intergranular boundaries. 相似文献
108.
Qingsong Lian Yan Li Tao Yang Kai Li Yifen Xu Liang Liu Jingbo Zhao Junying Zhang Jue Cheng 《Journal of Materials Science》2016,51(17):7887-7898
Allyl-based epoxy resin/Sulfur (S) system is a facile and novel dual-curing system which conducts a unique curing mechanism. In this paper, Bisphenol-A diglycidyl ether (BADGE) and 2-Allylphenol (OAP) cured by S were comparatively investigated to clarify the dual-curing mechanism of Epoxy (EP)/Allyl Compound (AC)/S system. When the temperature was above 170 °C, DSC and FTIR data showed that S could cleave to form thiyl radicals, and FTIR, NIR, and 1H NMR measurements proved the disappearance of allyl groups and the generation of thiol groups by the thiyl radicals abstracting α-H atoms of allyl groups in the OAP/S reaction system. Real-time infrared spectroscopy (RT-FTIR) results showed that the reaction of the generation of thiol groups is the dominant reaction in the two possible pathways of the OAP/S system; allyl groups and epoxy groups disappeared sequentially in the OAP/S/BADGE system. DSC curve also revealed the one-stage reaction for OAP/S system and two-stage reaction for OAP/S/BADGE system. These data were used to develop a detailed, experimentally validated pathway for the dual-curing of EP/AC/S system, in which thiol groups are important intermediate, and the dual-curing process included the crosslinking of double bonds that initiated by thiyl radicals and the ring-opening reaction of epoxy groups with thiol groups. Besides, the dual-curing mechanism of EP/AC/S system shares a close resemblance to the classical rubber vulcanization mechanism and the recent thiol-ene radical addition mechanism. 相似文献
109.
Filtration of nanofillers into porous fabric media is still an issue during the preparation of advanced fiber-reinforced composites. The assessment of resin/multiwall carbon nanotube (MWCNT) flow, MWCNT filtration, and the cure monitoring of glass fiber/carbon nanotube-polyester composites by means of the measurement of the electrical resistance was introduced. The vacuum-assisted resin transfer molding technique was used. The electrical resistances measured over the span of a composite were qualitatively correlated with MWCNT flow and the degree of MWCNT filtration. It was found that while the complexity of the fabrics could likely introduce preferential deposition of MWCNTs, their filtration is mainly affected by their dispersion state in the resin suspension. Relationships among critical parameters such as the lengths and diameters of MWCNTs, the inter- and intra-tow dimensions of glass fabrics, the dispersion level of MWCNTs, and the viscosity of nanocomposite samples are discussed and correlated to the filtration, cure, and flow phenomena. We showed that our method can also serve as an early warning to obviate defects in the resulting composite. 相似文献
110.
This paper investigates the manufacturing distortion of curved composite parts manufactured by a new Liquid Composite Molding (LCM) process called Flexible Injection (FI). This technique uses a deformable tool to speed up the fabrication but may generate manufacturing defects when strongly curved shapes are processed. The goal of the study is to evaluate the impact of such heterogeneities on the dimensional stability of the product. Curved components were first manufactured with varying processing conditions to achieve a wide range of layup quality. The shape stability of the samples was then recorded as a function of temperature to measure the thermoelastic component of distortion and experimental results were compared with predictions made by two modeling techniques. Under certain conditions, manufacturing defects can significantly affect the distortion behavior. This suggests that a robust preforming procedure is of primary importance to produce curved parts by Flexible Injection with a high level of repeatability. 相似文献