查看更多>>摘要：The crystallographic microstructure between the electroplated Cu fillings and the substrate in a stacked-via structure and its electrical/mechanical characteristics were systematically investigated using a focused ion beam (FIB), electron backscatter diffraction (EBSD), a probe station with an ohmmeter, a quick via pull (QVP) test, and a 3D-optical microscope. A two-stage Cu electrodeposition process with various plating current densities at the early stage (j(1) = 0.3, 0.5, 1.0, or 2.0 A/dm(2)) and a fixed plating current density at the subsequent stage (j(2) = 2.0 A/dm(2)) was utilized to fill a daisy-chain blind-hole (BH) structure. The Cu crystal coherency between electroplated Cu fillings and substrate can be significantly improved with the j(1) minimization, which efficiently enhances the electrical/mechanical characteristics of the stacked-via structure. The strong dependence of the Cu crystal coherency on j(1) can be ascribed to a slow discharge rate of Cu ions at a low plating current density, allowing the Cu nuclei to laterally extend and epitaxially grow with a crystalline substrate. Therefore, the Cu crystal modification via j(1) adjustment can greatly promote the packaging reliabilities of a stacked-via structure.
查看更多>>摘要：To improve the high-temperature oxidation resistance, Al2O3-Nb2O5/NbAl3 composite coating with or without TiO2 particles was prepared on Nb-based alloy through a two-step method of halide activated pack cementation (HAPC) and micro arc oxidation (MAO). NbAl3 layer was firstly formed on the substrate by HAPC treatment. Then, TiO2 was introduced into the Al2O3-Nb2O5 coating on NbAl3 by hydrolysis reaction of K2TiF6 during MAO process. In this paper, the effect of TiO2 on the morphology and formation of the MAO coating was studied. Furthermore, the oxidation resistances of the TiO2-Al2O3-Nb2O5/NbAl3 and Al2O3-Nb2O5/NbAl3 composite coated Nb alloy were investigated. The results showed that the addition of K2TiF6 could promote the growth of MAO coating and increase the density. After oxidation at 1200 degrees C for 100 h, a dense protective oxides scale was found on the TiO2-Al2O3-Nb2O5/NbAl3 coating sample, and the weight gain was only 4.75 mg/cm(2), which was significantly lower than the coated sample without TiO2. The mechanism of oxidation resistance enhancement of coating with TiO2 should be ascribed to the formation of a dense TiO2 + Al2O3 scale, which could effectually prevent the diffusion of O and suppress the formation of Nb2O5.
查看更多>>摘要：The effect and mechanism of ultrasonic vibration on the microstructure and performance of laser cladding 316L coating has been studied, providing a theoretical basis and technical support for the application of the ultrasonic assisted laser cladding process. The results show that ultrasonic vibrations with different amplitudes can effectively improve the macroscopic forming quality of the cladding layer, among which the ultrasonic vibration with 17.5 mu m amplitude is the best. Ultrasonic vibration can also significantly improve the micro-forming quality of the cladding layer, such as homogenizing the structure, refining grains and reducing porosity. The wear mechanism of the cladding layer with an ultrasonic assistance of 17.5 mu m is mainly abrasive wear, so the wear resistance has been significantly improved. The ultrasonic-assisted cladding layer exhibits significant passivation behavior in 3.5 wt% NaCl solution. It may be that the surface roughness reduction and grain refinement caused by ultrasonic assistance can improve the integrity and compactness of the cladding layer, so the dynamic equilibrium process of the dissolution and reformation of the passive film is changed, which can improve the corrosion resistance of the surface. There are some equiaxed grains in the columnar-grains area of the ultrasonic assisted cladding layer, mainly because the inside of some primary columnar grains has gone through a process of lattice distortion -> dislocation multiplication -> substructure rotation -> formation of small-angle grain boundary -> misorientation accumulation -> formation of new grains in the process of ultrasonic-assisted laser cladding of 316L stainless steel.
Vazirgiantzikis, IosifGeorge, Sarah LouisePichon, Luc
10页
查看更多>>摘要：Surface modification of the implant surface via silver ion (Ag+) implantation shows promise in reducing the post surgery infection rates. Silver was ion implanted into polished Ti-6Al-4V and the anodically oxidised Ti-6Al-4V surfaces at two implantation fluences, namely, 0.4 and 1.2 x 10(17) ions/cm(2). Anodic oxidation was carried out using the 0.5 M H2SO4 and 2.1 M H3PO4 electrolytes. This study aims to characterise the surfaces and to determine whether surface modification of Ti-6Al-4V via anodic oxidation improves the Ag+ release from the surfaces in vivo. The tested dosages had no appreciable effect on the final amount of stored silver for both studied TiO2 layers as supersaturation of the surface with silver occurs at low dosage. Ag+ release from the anodic TiO2 layers was independent of the electrolyte used to create the anodic layer. Polished Ti-6Al-4V surfaces showed a greater potential silver storage capacity relative to the anodic TiO2 samples since the concentration of silver stored at the surface was roughly proportional to the Ag+ dosage. Comparison of Ag+ release rates of all studied samples with literature to determine the potential antimicrobial effects showed that all studied conditions had the potential to be 100% antimicrobial.
查看更多>>摘要：To analyze the formation mechanism of a dark streaky edge defect on a hot-dip galvannealed (GA) ultra-high strength steel (UHSS) sheet, multiple metallographic characterizations were performed on samples collected from different processes. It was found that this streaky defect was directly caused by differences in the coating morphology. The coating in the edge zone showed a crater morphology, while the coating in the center zone showed a flatter morphology and uniform coating thickness. Corresponding streaky edge defects were found on the annealed steel prior to hot-dipping and on the pickled steel prior to cold rolling. The root cause was finally traced back to the hot-rolled steel after coiling. A formation mechanism of this defect was proposed based on the evolution of surface microstructures in multiple processes. The difference in the amounts of internal oxides formed in the subsurface of different zones of the hot-rolled strip influenced the pickled steel surface, cold-rolled steel surface, annealed steel surface and the galvannealed coating surface.
查看更多>>摘要：The main purpose of this article is to study the effect of ultrasonic surface rolling process (USRP) on the surface properties of QAl10-3-1.5 aluminum bronze alloy under different rolling reduction and rolling times, providing ideas for improving the poor wear resistance of valve stem nuts and sealing rings. SEM, EDS and optical threedimensional profiler were used to characterize the microstructure characteristics of the surface modified layer and the surface morphology of the wear traces. The results show that the surface layer of the USRPed sample has undergone severe plastic deformation. The alpha phase is elongated, and the microstructure structure shows a fine and uniform distribution state. And the grain size of alpha phases decreased, and the number density of beta phases increased. Compared with the untreated sample (only cutting and polishing), the surface roughness of the USRPed sample reaches nearly Ra 0.04 mu m; the maximum surface micro-hardness is 323.04 HV, increasing by 75%; the maximum depth of surface hardening layer is about 570 mu m. The friction coefficient, wear mass loss and the width and depth of the wear traces of the USRPed samples are significantly reduced, while the wear resistance is significantly enhanced. By comparing the surface wear morphology of the samples under different process parameters, it is found that the main wear mechanism of the untreated samples is adhesive wear, while the main wear mechanism of the USRPed samples is abrasive wear. The improvement in wear resistance is attributed to the refined and homogenized surface microstructure, the smaller surface roughness, the larger surface micro-hardness and surface hardness layer depth after USRP.
查看更多>>摘要：With the aim of improving the corrosion and wear resistance of pure magnesium, La2O3 nano-particles are added into the PEO electrolyte. The influence of the particles on coating formation, morphology and performance is investigated. Results indicate that the porosity and thickness decrease remarkably after the particle incorporation which influences the corrosion and wear resistance in return. The coating with 1 g particle addition shows lowest porosity and highest hardness value, resulting in superior corrosion and wear performance, which implies the feasibility of the proposed strategy in fabricating functionalized PEO coatings on Mg-based materials.
Rosa Katunar, MariaIgnacio Pastore, JuanCisilino, AdrianMerlo, Julieta...
9页
查看更多>>摘要：Osteoporosis is a skeletal disorder characterized by a decrease in bone strength leading to a higher risk of fracture. In this scenario, many osteoporotic patients require permanent prosthesis. Surface modification is a strategy to improve the osseointegration for cementless implants. This work assesses the in vivo performance of a surface modification consisting in a bioactive silica-based layer with strontium-doped bioactive glass particles. The layer was made by sol-gel and applied onto titanium nail-shaped implants. Osseointegration tests were performed on an osteoporotic rat model generated by ovariectomization. The effectiveness of the osteoporotic rat model was systematically analyzed for structure and bone quality using classic and novel techniques: nano indentation, micro-Raman spectroscopy and digital image processing. It was found that Sr-glass coatings applied on nail-shaped implants result with lower numbers of particles than for plane samples. The positive effect of bioactive Sr-glass coatings on the new bone tissue formation was evident from the results of the Raman tests. Besides, histomorphometric results showed that the newly formed bone thicknesses around coated Sr-bioactive implants are 15% larger than those formed around titanium materials 15 and 30 days after implantation. These results indicated that even when the nail-shaped implants have a relative low number of bioactive Sr-glass particles, they have a positive effect to induce the formation of new bone. Further research is needed to find the means to increase the number of particles in the coating, while tests at longer times are necessary to investigate the period of effectiveness.
查看更多>>摘要：Based on the excellent thermodynamic and service performances of nano-structured coatings, 8YSZ nano agglomerated spraying powder and its nano-structured thermal barrier coating (TBC) were successfully prepared by the integrated application of nanotechnology and atmospheric plasma spraying. The influences of spraying granulation process (solid content of slurry and inlet air temperature) on the spraying powder characteristics and the water quenching-thermal shock cycling behavior at 1050 ?degrees C of 8YSZ nano-structured TBC were investigated, respectively. The results showed that the nano-agglomerated powders exhibit apple-like, hollow spheroids with relatively uniform particle size when the spraying granulation process involved a 40% solid content of slurry, a 240 ?degrees C inlet air temperature, and a 35 Hz atomizer rotation frequency. The fluidity and apparent density were 57.53 s/50 g and 1.39 g/cm(3), respectively. The nano-agglomerated 8YSZ spraying powders met the requirements of plasma-spraying technology. The plasma-sprayed 8YSZ nano-structured coating was composed of a single t-ZrO2 phase, had a layered structure and a certain amount of nanostructures, and presented a special "bimodal microstructure ". The average porosity of the coating was 7.49%. 8YSZ nano structured TBC failed layer-by-layer after water quenching-thermal shock 264 cycles at 1050 ?degrees C. The main reasons for the failure of 8YSZ nano-structured TBC were the large thermal stress and cracks in the substrate caused by the water quench-thermal shock cycle, and the mismatch of thermal expansion between the metal bond coat and the ceramic coat.
查看更多>>摘要：The unique self-repair function of slippery liquid-infused porous surfaces (SLIPS) exerts an important effect on maintaining the continuity and stability of lubricating film. In the self-repair process of SLIPS, the exudation of lubricant in the porous matrix is a common phenomenon. Meanwhile, the exudation behavior of lubricant in the pores is still unclear. This study established a numerical model for describing the exudation of oil droplet in micropore. The morphological evolution and flow characteristics were explored to reveal the flow mechanism of oil droplet spreading to oil film. Results show that the exudation process of lubricant on porous surface involves the rise of lubricant inside the pore, the generation, breaking and spreading of droplet on porous surface. During the rise of lubricant inside the pore, the internal pressure of the lubricant was negative. When the lubricant rose to the top edge of the pore, the contact line was pinned for the first time. And the Laplace pressure of the lubricant changed from negative to positive. Then the droplet generated and grew continuously on the porous surface. The contact line was pinned again until the droplet spread to the adjacent pore. As the apparent contact angle reached the maximum advancing angle, the droplet was depinning. Therefore, both pinning of the contact line occurred at the edge of the pore in the exudation process. Under the constant competition between the volume of droplet and the surface tension, the contact line was depinning, thus promoting the spread of the droplet into a film.
NSTL
Elsevier