查看更多>>摘要：Co06/Ni60A duplex coating was fabricated on copper substrate by plasma cladding. To clarify the evolution of microstructure and wear resistance of the coating during high-temperature, the coating samples were heat treated at 500 C for up to 500 h in air. After heat treatment, the phases in the coating such as Cr7C3, Cr23C6 and the crystal grains of the gamma-Co solid solution had a tendency to grow up, and remained basically stable after 100 h. No martensite transformation (gamma-Co -> e-Co) was observed. The mass fraction of Cr23C6 reinforcement phase had an increasing trend, which was attributed to the conversion of Cr7C3 and the precipitation of gamma-Co solid solution. The diffusion degree of elements at the Co-Ni interface and Ni-Cu interface also showed a trend of stabilizing. Due to the coarsening of microstructure, the diffusion of copper and the reduction of Cr7C3, the wear resistance of the coating changed from 6.2 times to 2.9 times that of the copper substrate. The wear mechanism transformed from abrasive wear to abrasive wear + adhesive wear. Results showed that the properties of the coating have a certain decline in the initial stage, but it tended to be stable after long-time service.
查看更多>>摘要：In the present work, laser cladding of vanadium carbide (VC)-reinforced Inconel 625 (In625) metal matrix composite (MMC) coating was carried out on grade 304 stainless steel substrates. The microstructure, hardness, and abrasive wear performance were studied by changing the weight fraction of VC at 0, 5, 10, and 15 wt%, respectively. The effects of increasing the reinforcement phase on the microstructure evolution, composition, hardness, and abrasion resistance properties were evaluated on the obtained coatings. The results indicated the formation of defect-free coatings alongside the formation of secondary strengthening precipitates were observed within the primary gamma-Ni matrix in the In625 clad. Complex secondary carbides were formed on all MMC coatings near the In625-VC interface region, indicating the formation of an interphase which guaranteed the bonding between the matrix and reinforcement. The results also showed an almost linear relationship between the amount of VC into the In625 alloy clads and the clads hardness. With a VC content of 15 wt%, the clads hardness increased approximately 65% with respect to a 100% In625 coating. On the other hand, while the addition of 5 wt% of VC slightly improves the abrasion resistance of the In625, further increased of the reinforcement phase content led to a reduction of the clads behaviour.
查看更多>>摘要：This study aims to optimize the fabrication parameters of nickel-iron phosphate (NiFe-P) electrode to achieve a high areal capacity electrode for supercapattery. The fabrication of binder-free NiFe-P electrode on nickel foam (NF) employs a one-step hydrothermal synthesis method. Further, central composite design (CCD) under the response surface methodology (RSM) is used to optimize the electrode's performance. The factors evaluated are synthesis temperature (60 to 180 ?degrees C), time (6 to 24 h), and the molar ratio of precursor solution (1:3, 1:1, 3:1 of Fe: Ni), whereas the response is the areal capacity of NiFe-P electrode at the scan rate of 3 mV/s in a standard three-electrode cell system. The optimal temperature, time, and molar ratio (Fe:Ni) are determined to be 100 ?degrees C, 14 h, and 3:1, respectively. The model is confirmed within the confidence interval and prediction as well as comparable with a 10% percentage error between the experimental and predicted specific capacity. The specific capacity of the optimized electrode is 446 C/g at a scan rate of 3 mV/s using cyclic voltammetry (CV) and 413.75 ?degrees C/g at a current density of 1 A/g in 1 M KOH using a standard three-electrode cell system. Supercapattery is fabricated by combining NiFe-P and activated carbon electrodes (NiFe-P//AC) as positive and negative electrodes, respectively, to evaluate the two-electrode cell system. The results show the maximum power density of NiFe-P//AC supercapattery is 2250 W/kg at an energy density of 45.6 Wh/kg. Furthermore, the NiFe-P//AC supercapattery demonstrated excellent stability and coulombic efficiency by retaining 87.6% and 98.7% of the initial specific capacity values and coulombic efficiency, respectively.
Murugan, A.Kumar, N. SharathSankar, Mamilla RaviNagahanumaiah...
9页
查看更多>>摘要：Heat dissipation is one of the major factors that inhibit the miniaturisation of electronic components. Thermal interface materials (TIMs) that dissipate heat help in improving device performance. Commercially available conformal TIMs such as indium foils, thermal pads, polymer matrix with thermal conductive films are not very useful in heat transfer due to low thermal conductivity and high thermal expansion coefficient. This research focuses on developing novel thin-film nanocomposites consisting of Carbon nanotubes (CNTs) as TIMs. CNTs based nanocomposites behave as nano fins for heat dissipation. CNTs that are almost vertically aligned are deposited on silicon (Si) substrates using Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RFPECVD). Metallic thin films of Aluminium, Copper, Titanium, and Nickel are sputtered using a Direct Current Magnetron target-based Physical Vapour Deposition on the CNT films to form a nanocomposite sandwich. The nanocomposite morphology is studied using SEM, structure using TEM, polycrystalline and elemental determination using XRD. The produced nanocomposite is modelled using Solid Works software, and thermal simulation of the same is performed using ANSYS. The equivalent thermal conductivity of Ni/CNT/Si, Al/CNT/Si, Cu/CNT/Si, and Ti/CNT/Si network is 1045.6 W/mK, 1120.8 W/mK, 886.56 W/mK and 463.6 W/mK when derived using mathematical modelling. The thermal conductivity values after experimentation for CNT/Si, Al/CNT/Si, Cu/ CNT/Si, Ti/CNT/Si and Ni/CNT/Si nanocomposites were found to be 255-282 W/mK, 52-15 W/mK, 195-236 W/mK, 15-20.5 W/mK and 7.7-9.1 W/mK, respectively.
Walters, JorieMaier, BenjaminLi, XiaodongRoache, David C....
12页
查看更多>>摘要：Here, we investigate the coupled thermomechanical fracture mechanisms of coated nuclear fuel claddings at Light Water Reactor (LWR) operating temperatures. These coated claddings are a highly attractive, near-term solution, which addresses the demands for accident-tolerant fuel systems and provide greater oxidation resistance. However, the fracture mechanisms of these coatings, which may create channels for oxidation ingression, must be fully understood prior to implementation. Thus, high-temperature expanding plug experiments were conducted on coated cladding specimens at a temperature of 315 C, consistent with the operating environment of LWRs. In-situ thermomechanical deformation was measured with stereo digital image correlation during heating and mechanical testing to separately resolve contributions of thermal and mechanical strain. Digital image correlation, supported by acoustic emissions (AE) detection, was also leveraged to track cracking activity during loading. Coating fracture was found to initiate at total hoop strains of 0.34%. The thermal deformation of the coated claddings was investigated via finite element simulations, revealing a bidirectional stress-state within the coating with axial and circumferential strains of 0.026 and 0.031%. This bidirectional stress-state was attributed with the generation of off-axis fracture pattern within the coating as identified via post-experiment scanning electron microscopy. Thus, this study unveiled critical, coupled thermomechanical mechanisms governing the coating fracture of coated claddings at LWR temperatures.
查看更多>>摘要：The growth defects in the sputtered CrN coatings can worsen their tribological and corrosion properties. To improve the above deficiency, the atomic layer deposited TiN was deposited on the sputtered CrN layer, oxidized and then again coated by CrN to form the sandwich-structured CrN/TiOxNy/CrN composite coating. The insertion of the TiOxNy interlayer resulted in (111) preferred orientation and the grain refinement of CrN crystals, leading to the improvement in its mechanical performance and corrosion resistance. As the thickness of the TiOxNy layer increased, the mechanical and corrosion properties of the composite coatings were further improved. The composite coating inserted with a 30 nm-thick TiOxNy interlayer delivered the greatest corrosion resistance, the lowest friction coefficient and wear rate as well as high hardness and adhesion strength, which could be attributed to the synergistic effect of the multilayered TiOxNy interlayer.
查看更多>>摘要：The work presents the surface integrity of TiN/TiAlN coated surfaces produced using hexagonal boron nitride suspension in the dielectric fluid through the micro-electrical discharge coating (mu-EDC) process. The performance of the coated surfaces is evaluated on the grounds of surface topography, wettability, indentation depth, layer height, crack density, roughness profiles, residual stress, and composition analysis. The recast layer height varies between 1.53 mu m and 13.38 mu m, while the water contact angle lies in the range of 91.28 degrees to 118.23 degrees (hydrophobicity is induced). The residual stress generated due to the presence of micro-cracks on the coated surfaces prepared at a maximum voltage (60 V) and powder concentration (12 g/L) varies between 225.87 MPa and 300.93 MPa. The occurrence of Ti, Al, Cu, Zn, V, B, N, and O in EDX plots affirmed the transfer of tool and dielectric material to the work surface. The indentation depths obtained in the study lies within the range of coating thickness. The surface roughness parameters, i.e., R-a, R-q,R- R-z,R- R-sk, and R-ku are also evaluated in this work. Such micro-deposited surfaces find application in lab-on-chip devices where selective surface modification is needed.
查看更多>>摘要：To prolong the service life of heavy-duty vehicle engine parts subject to wind and sand exposure, a FeCrMoWBRe amorphous-nanocrystalline composite coating was prepared via high-velocity arc spraying for its higher wear resistance than the traditional one. The adhesive strength of the coating is approximately 60.5 MPa, the hardness is approximately 13.3 GPa, and H-3/E-r(2) is 0.07 GPa, indicating that the coating has excellent wear resistance. Under the condition of oil lubrication, the wear rates of the coating under different loads (50-150 N) are in a range of (0.993-250) x 10(-7) mm(3).N-1.m(-1); the coating performance is most stable under low and medium loads (50-100 N). It is proved that, abrasive and fatigue wear are the predominant wear mechanisms under low and medium loads (50-100 N), while abrasive, fatigue, and delamination friction as well as wear mechanisms are the dominant under higher loads (e.g., 125 and 150 N) for the coating. After adding abrasive particles, the wear rates of the coating under different loads are in the range of (3.6-259) x 10(-7) mm(3).N-1.m(-1); the wear amount is not significantly increased under higher loads (125 and 150 N). The wear mechanism is almost the same under this condition. These results indicate that the coating performs stably under low and medium loads and shows resistance to abrasive particles, especially under higher loads.
查看更多>>摘要：Ti-6Al-4V (grade 5 titanium alloy) is a widely used material for biomedical implant and prostheses. The objective of this study is to investigate the effect of surface and sub-surface characteristics (i.e., surface roughness, microstructure, phase transformation, and recast layer) of Ti-6Al-4V alloy on the cell attachment and corrosion performance after machined by Wire Electric Discharge Machining (WEDM) process. The biocompatibility of titanium alloy has been studied based on the cell adhesion and cell proliferation response of mouse osteoblastic cell MC3T3-E1 to the machined surface of different levels of surface roughness and sub-surface microstructural and phase composition. One conventionally machined surface and one tissue culture treated plastic surface were used for comparison with those four WEDM machined surfaces. It was found that cell attachment increased with increasing surface smoothness, and WEDMed Ti-6Al-4V alloy sample exhibited higher cell attachment compared to even smoother conventionally machined samples. It was found that beta phase at the sub-surface favored the cell adhesion on the machined surfaces for EDMed samples. The corrosion rate of machined Ti-6Al-4V alloy samples under simulated body fluid decreases with decreasing surface roughness. The findings suggest that WEDM has the capability of producing implant surface that can promote cell adhesion with improved corrosion performance under body fluid, thus, has the capability to manufacture implants with improved biocompatibility.
查看更多>>摘要：(CrNbTiAlV)N-x high-entropy nitride films were prepared using magnetron sputtering method. The effect of substrate bias on the microstructure, mechanical, electrochemical, and tribo-corrosion properties of the films was systematically studied. The results show that the microstructure of the film changes from a loose columnar structure to a compact nanocrystal structure with the increase of substrate bias, accompanied by the preferred orientation from (200) to (111). The hardness, modulus and residual stress are positively correlated with increased substrate bias, reaching the maximum values of 35.3 GPa, 353.7 GPa and-6.41 GPa at-156 V, respectively. Under static corrosion, the film deposited under-126 V has the most positive E(corr )of-0.05 V and the lowest i(corr) of 0.013 mu A/cm(2). Under tribo-corrosion, the films deposited at-96 V and-126 V show the lowest coefficient of friction (-0.2) and wear rate (-4.4 x 10(-7 )mm(3).N-1.m(-1)), respectively. The evolution of microstructure and mechanical property are the main factors affecting the tribo-corrosion behavior of (CrNbTiAlV)N-x films.
NSTL
Elsevier