查看更多>>摘要：Recently, flexible and wearable sensors are extensively developed in advanced coating materials, especially in label-free and culture-free rapid detection. Surface-enhanced Raman scattering (SERS) detection is the one of the "fingerprinting" and rapid sensing technology, which combined with noble metal nanoparticle arrays and Raman spectroscopy. The bionic 3D regular structures can induce the multiple reflection of the laser in 3D structures to increase SERS intensity. In this study, we used the natural organism wings (cicada wings, CW) as the substrate. Homogenous nano-columnar structures with the size of 69-72 nm were observed on the CW by scanning electron microscope. Ag nano-island arrays were further deposited on the CW by thermal evaporation. The interparticle spacing of the Ag nano-columnar would decrease with increasing the deposited thickness, which could produce a very strong 3D hot-spots effect for enhancing Raman signals. The results show that the optimal SERS signals were found at 100 nm deposited thickness of Ag nano-islands on the CW nanostructure. The limit of detection (LOD) is lower than 10-9 M and the related standard deviation (RSD%) is about 13.7%, showing the high sensitivity and reproducibility of SERS signal for small molecules detection. Particularly, SERS intensity of CW-Ag-100 nm would increase ~1.7 times while bending inner angle achieves 15o, displaying its flexible characterization.
查看更多>>摘要：A composite coating consisting of the plasma electrolytic oxidation (PEO) and aluminum phosphate layer was fabricated to improve the ignition resistance of ZM5 alloy. The influences of PEO coating and PEO/aluminum phosphate composite coating on the ignition resistance of ZM5 alloy were investigated by torch ignition and non isothermal oxidation test. The ZM5 alloy with PEO/aluminum phosphate composite coating possesses the best ignition resistance and does not ignite when exposes to flame for 20 min, about 16 min longer than that of ZM5 alloy with PEO coating, and about 18 min longer than that of bare ZM5 alloy. The ignition protection was achieved through synergetic combination increased oxidation resistance, high strengthening and thermal expansion coefficient match of the composite coating. The incombustible ceramic component and metallurgical bond to the substrate endow the PEO coating with a self-extinguishing property. In addition, three characteristic stages (protective oxidation, non-protective oxidation and burning) of ZM5 alloy and its coating were identified based on the non-linear mass gain behaviors at different temperatures. The ZM5 alloy with PEO/aluminum phosphate composite coating had higher non-protective oxidation initial temperature (605 ?degrees C) than 437 ?degrees C of the bare ZM5 alloy. Meanwhile, the non-protective oxidation energy of the ZM5 alloy coated with PEO/aluminum phosphate composite coating was remarkably improved from 61 kJ/mol to 136 kJ/mol.
Kucuk, YilmazDoleker, K. MertGok, M. SabriDal, Serkan...
12页
查看更多>>摘要：Boronizing processes were carried out at 900 degrees C, 950 degrees C and 1000 degrees C for 2, 4 and 6 h to improve the wear performance of Monel 400 alloy. According to microstructure analyses and nanoindentation tests, Ni2B, FeNiB and FeB phases were detected as dominant phases in the boronized layer. Apart from this, it was observed that the amount of Cu deposits in the boronized layers increased depending on the increasing boronizing temperature. After the boronizing process, the boride layer thickness and hardness values were found to be in the range of 32-272 mu m and 12.76-17.83 GPa, respectively. From the results of dry sliding wear test, the wear volume loss values of the boronized Monel 400 alloy decreased by approximately 25 times compared to the untreated samples. The lowest volume loss value among all test samples was observed in the boronized sample at 950 degrees C for 4 h. In addition to the hardness value, it was determined that the morphology and mechanical properties of the boronized layer were also effective on the wear results. Plastic deformation, delamination and oxidation type wear mechanisms were observed as the dominant wear mechanisms in the room and high temperature tests of boronized samples.
查看更多>>摘要：In this study, an aluminide coating was applied to the surface of the Inconel 600 (IN600) superalloy to improve the high-temperature oxidation and wear resistance. The low-temperature aluminizing process was carried out for 3 and 5 h at 650 and 700 C temperatures without using a protective atmosphere. A continuous and homogeneous coating has been created by providing aluminium diffusion inward in the cross-section of the alloy processed under low temperature and high activity conditions with the pack cementation method. It was observed that there was a super bonding between matrix and coating layers which are smooth, dense and porosity free. Dominant phases of Ni2Al3 and NiAl3 were detected by XRD analysis. The layer thickness was measured from the surface to the matrix and changed from 25 to 75 mu m which was increased with increasing process duration and temperature. The aluminizing process positively affected the wear resistance with the durable layers formed on the surfaces. After the isothermal oxidation tests, IN600 and aluminized IN600 show a break-away oxidation trend. The formation of the alumina layer provided better protection for aluminized samples but the formation of pits led to spallation of oxide scale in the oxidation stages.
查看更多>>摘要：M50 secondary hardening steel is widely used as high-end bearing steel for engine shafts in the aerospace industry. In this study, plasma nitriding at different temperatures varying from 410 to 570 degrees C was performed on quenched M50 steel to investigate the response of the microstructure and mechanical properties to nitriding temperature and advance the scientific understanding of the mechanism involved. The nitrided samples were fully characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electron microprobe analysis, Vickers hardness tester, and Pin-on-disc tribometer. The results revealed that the nitrided layer's thickness, microstructure, hardness, and wear resistance depended on the treatment temperature. When the nitriding treatment performs at secondary-hardening temperature, the samples were endowed with excellent wear resistance and gentle hardness profile, i.e., hardness profile with a gradually reducing hardness profile towards the core, attributed to the synergistic strengthening. Moreover, the thermodynamic calculation was involved to clarify the formation mechanism of coarse intergranular precipitation, which can be connected to form a wave shape line at higher temperatures.
查看更多>>摘要：Surface-passivation is an effective way to allow the anode materials can deliver long-term superior electrochemical performance for lithium-ion batteries (LIBs). Herein, we develop a simple solution suspension-coating method to prepare thickness-controllable nano-carbon layer (NCL) on a synthesis graphite-mesocarbon microbeads (MCMB) using aqueous glucose solutions with a surfactant-triton X-100 at 25 ?degrees C. This simple process can control the thickness of the NCL on MCMB with a range of 1.5-20 nm with various glucose concentrations. The as-formed NCL can reduce the defect sites on MCMB surface and create slightly porous structures within NCL. For electrochemical performance in LIB, we observed that the carbon-coating thickness at around 4 nm shows better reversible capacity (from 295 to 347 mAh g(-1)), lower Li+ diffusion resistance, stable cycle-life, and superior C-rate performance. As our results, we provide a simple method to stabilize surface properties of MCMB and show better electrochemical performance in LIB. Moreover, this method can be easily exploited in the industrial with a massive production.
Kahl, B. A.Yang, Y. S.Berndt, C. C.Ang, A. S. M....
12页
查看更多>>摘要：Atmospheric plasma spray (APS) deposited ceramic coatings of zirconium boride (ZrB2) and hydroxyapatite (HAp) were inspected using Data-Constrained Modelling (DCM) of X-ray Micro-Computed Tomography (X-ray mu-CT) datasets to evaluate coating porosity. The DCM approach was used to quantify the porosity and void distributions in the coatings. The results from the 3D analysis were compared to 2D porosity and void distributions determined from the image analysis method. The 3D porosity determined from the ZrB2-1 model, 24.7%, agreed well with the 2D porosity estimation of 22.1 +/- 2.6%. Additionally, the 3D porosity determined from the HAp-1 model, 22.8%, was marginally greater than the estimated 2D porosity, 19.8 +/- 2.1%. However, a comparison of the 2D and 3D void distributions revealed that a 2D assessment poorly predicted the 3D microstructure of coatings and cannot be used to infer properties that depend strongly on the 3D void network. The DCM method has the ability to include the effect of fine-structure details over the 3D scan volume and hence incorporated micropores and cracks that are typically overlooked during traditional porosity inspections. Furthermore, the 3D analysis demonstrated the deficiencies in typical CT segmentation methods applied to data with a moderate CT resolution size, which was 5.4 mu m. The superior DCM approach enabled the quantification of pores below the CT resolution limit that would not have been accurately modelled using typical CT segmentation methods.
查看更多>>摘要：VO2 films were prepared on glass substrates by a two-step method, i.e., magnetron sputtering of vanadium in an atmosphere of Ar + O-2 gas mixture and followed by in-situ annealing. CoPt films were then sputter-deposited on the VO2 films to obtain the CoPt/VO2 bilayer films. The VO2 films change from monoclinic phase to rutile phase with increasing temperature from room temperature to 90 ?degrees C, accompanied by an abrupt change in resistivity. The CoPt/VO2 bilayer film with 3 nm thick CoPt layer shows strong perpendicular magnetic anisotropy and anomalous Hall effect is observed when the magnetic field is applied in the out-of-plane direction. The magneto transport properties are studied in relation to the phase transition of the VO2 layer.
查看更多>>摘要：This study focuses on the functionalized modification of Ti-6Al-4V and CoCrMo alloys substrates widely used by the biomedical domain as total joint replacements (TJRs) of the hip and knee. To improve the corrosion resis-tance of these devices, nanostructured columnar zirconium (Zr) thin films were produced by oblique angle deposition (OAD) using DC magnetron sputtering to model the particular design of the joint. The influence of the angular distribution of the incoming particle flux on the resulting film morphology (column tilt angle, porosity) and electrochemical behavior was studied by varying the substrates inclination angle theta from 15 to 90. The experimental deposition process was reproduced by kinetic Monte Carlo (kMC) models. With the increase of the flux incidence angle alpha from 0 to 70, the film thickness and the column tilt angle beta vary in agreement with the theoretical models. Additionally, the corrosion behavior of uncoated and Zr-coated alloys (CoCrMo and Ti-6Al-4V) was compared through open circuit potential chronopotentiometry and electrochemical polarization test in NaCl 0.9% solution at 37 C. It was found that the corrosion protection was successfully improved by the presence of the films. The variation of the corrosion behavior with the flux incidence angle is explained by the changes in the film density.
NSTL
Elsevier