查看更多>>摘要：Laser cladding (LC) has been applied to enhance the wear resistance of 316L coatings by depositing in-situ VCCr7C3 metal matrix composites (MMCs) coating on structural steel substrate using pre-mixed powder consisting of vanadium, carbon, and 316L stainless steel. The effects of different process parameters, varied V and C contents on the phase constituents, microstructure, and the mechanical properties of 316L LC coatings were investigated systematically. The related microstructure evolution and the mechanical properties were comprehensively studied. The results indicated that under the selected laser irradiance of 80 W/mm2, scanning rate of 4 mm/s, and powder feeding rate of 10 g/min, by increasing V and C content from 0 wt % to 14 wt %, VC, Cr7C3, and Cr23C6 would be progressively precipitated at grain boundaries, and the austenite grains tended to be refined. Consequently, the microhardness of reinforced 316L coatings significantly increased from 207 HV1 to 467.8 HV1. Wear tests showed that the wear resistance improved some 8 times compared to the pure 316L layer under the dry sliding condition, and the dominating wear mechanism for the cladding transferred from adhesive wear to abrasive wear. Further microstructure characterization revealed that besides precipitation strengthening and fine-grain strengthening, the strengthening effect was also originated from the interfacial structure between the precipitated carbides, including a coherent interface for gamma/Cr7C3, semi-coherent interfaces for gamma/VC, and VC/ Cr7C3. Based on the results of thermodynamic calculation and Fe-Cr-C ternary phase diagram, the spherical VC acted as the nucleation sites for the dispersed carbide reinforcement and the austenite grains, and the inhibition against austenite matrix growth by ceramic precipitations dispersedly distributed along the grain boundaries.
查看更多>>摘要：In this study, graphene oxide (GO) and a carbon 2D materials (g-C3N4 nanosheets) were combined to construct gC3N4/GO nanosheets through 7C-7C stacking interaction. Moreover, Ag+ ions were reduced to Ag nanoparticles and further grafted onto the g-C3N4/GO nanosheets (Ag@g-C3N4/GO) to impart the dual functionality of photocatalytic degradation and surface enhanced Raman scattering (SERS) detection. The Ag@g-C3N4/GO SERS substrate can be used to detect biomolecules (adenine) and organic pollutants (methylene blue). The X-ray diffraction, scanning electron microscopy, and Raman spectroscopy observations confirmed that g-C3N4 was successfully stacked onto the GO nanosheets. In addition, the Ag@g-C3N4/GO SERS substrate displayed photocatalytic ability. Pollutants in water were photodegraded by irradiation with visible light (405 nm), making the substrate self-cleaning and reusable. Thus, the Ag@g-C3N4/GO SERS nanosheets has potential for application in the photocatalytic degradation of water pollutants and detection of biomolecules.
查看更多>>摘要：A new flexible, super-hydrophobic, and highly sensitive polydimethylsiloxane (PDMS) based-substrate would be developed for surface-enhanced Raman spectroscopy (SERS) detection. PDMS substrate is modified by nitrogen plasma and then deposited the organic conjugated molecules (alpha, omega-diperfluorohexylquaterthiophene, DFH-4T) films various thickness of Au nanoislands. The perfluorohexyl (-n-C6F13) chain of DFH-4T displays the advantages of high volatility and low vapor deposition temperature and can form a super-hydrophobic ivy-like nanostructure. After depositing the Au nanoislands on DFH-4T, the vertically arranged Au-DFH-4T nanostructure combined provides a tip-focusing effect and generates a very high electromagnetic field to enhance the Raman signal. Benefiting from the hydrophobic ivy-like nanostructure (maximum contact angle: similar to 146(o)) of Au@DFH-4T nanostructure, the hydrophobic molecule (vitamin D3, cholecalciferol) can be measured at ultralow concentration (10(-10) M). Moreover, the flexible SERS sensor exhibited acceptable efficiency and durability after 100 cycles bending tests. SERS intensity would increase similar to 1.6 time at 0.35 cm bending radius. This facile and efficient detection technique for meeting the increased demands for bio-detection, especially for hydrophobic biomolecules.
查看更多>>摘要：A metal nanomesh structure with regularly arranged nanosized holes has a light transmission property at a certain wavelength region and good conductivity; therefore, it can be applied to the wavelength-selective electrode of optical devices such as organic light-emitting diodes (OLEDs) and solar cells. In this study, Ag nanomesh structures with hole arrays of different sizes and periods were fabricated, and their electrical and optical properties were evaluated. Alq(3), a green light-emitting material for OLEDs, was deposited on the fabricated Ag nanomesh, and its transmission, scattering, and photoluminescence (PL) spectra were investigated. The PL intensity of Alq(3) was approximately four times higher than that without the Ag nanomesh. Time-resolved PL measurements showed the presence of a short-lived component in all samples with Ag nanomesh, indicating plasmonic emission enhancement. These results indicate that Ag nanomeshes can be applied as plasmonic electrodes in optical devices.& nbsp;
查看更多>>摘要：Si-doped Ga2O3 films were prepared on quartz and silicon substrates using remote plasma atomic layer depo-sition with trimethylgallium, Bis(diethylamino)silane and O-2 plasma as the precursors. Different Si-doped concentration in films were obtained by adjusting the numbers of SiO2 circulation ratio. The effect of Si-doped concentration from 0 to 20% on the qualities of the Ga2O3 thin films were studied. The experimental results showed that Ga2O3 thin film growth per cycle increases slightly with the various cycle ratio at the same total cycles of about 600. Field emission scanning electron microscopy shows that the Ga2O3 films have very smooth surface. The spectroscopic ellipsometry tests showed that the refractive index of the Si-doped Ga2O3 thin films decreases monotonically with the doping level increases. The transmittances of all the doped Ga2O3 films are exceed 90% in the visible region. The (400) preferred orientation Ga2O3 thin films were obtained after annealing at 900 degrees C in N-2 atmosphere. Moreover, the x-ray photoelectron spectroscopy investigation indicates that the doped Ga2O3 thin films is Ga-rich with the states of Ga3+ and Ga1+. High resolution transmission electron microscopy mapping measurement shows that the Si composition in the Ga2O3 thin films is uniform. Hall effect measurements demonstrated that the carrier concentration and mobility of the doped Ga2O3 films increase while the resistivity of the films decreases as the Si-doped concentration increases. The results of Si-doped Ga2O3 thin film with 20% cycle ratio shows high transmittance of 93% at 280 nm wavelength and low resistivity of 3.41 Omega.cm. Optical simulations show the potential for development of the Si-doped Ga2O3 films as the back electrode in the application of the ultraviolet C light-emitting diode.
查看更多>>摘要：Sintering is one of the critical factors leading to thermal and mechanical degradation of plasma-sprayed thermal barrier coatings (TBCs) in service under high temperature. The sintering resistance of the coating is expected to be improved through pore structure design. In this study, through a strategically improved powder feeding process, 8YSZ powders with fine-sized and coarse-sized pores were injected from the tail of plasma flame during plasma spraying to design porous coatings containing two differently flattened particles with different pore structures. The microstructural and property evolutions during sintering of the coatings were systematically studied compared with traditionally structured coatings. The effect of pore morphology on its sintering behavior was analyzed by quasi-in-situ observation of microstructure evolution. Results show that the anti-sintering performance of plasma-sprayed coating can be improved by adjusting the pore structure of coating with porous unmelted particles. In particular, the introduction of unmelted particles with coarse-sized pores can ensure that the coating has excellent thermal and mechanical properties for a long time. The results of this study provide guidance for structural design of anti-sintering plasma-sprayed coatings.
NSTL
Elsevier