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.
查看更多>>摘要：In this work, optical emission spectroscopy and electrical measurements are implemented to investigate a reactive HiPIMS TiO2 deposition process running at duty cycles lower than 16% and at a repetition rate of 1 kHz. Investigations focus on both the effect of the discharge pulse duration and the reactive gas (O-2) content in an Ar/O-2 gas mixture at fixed working pressures. It is shown that a competition occurs between the pulse duration and the target poisoning, the latter being favored with short pulse duration although the mean power is kept constant. An unusual hysteresis shape observed between the two sputtering modes is also discussed. From combined analyses of Ti emission line intensity, discharge current and deposited TiO2 coating thickness, it is established that plasma diagnostics can be used effectively to control the deposition rate and to precisely manage the transition between metal and composite sputtering modes. Using these to calibrate a power feedback control loop could provide a better response compared to gas feedback control loop.
查看更多>>摘要：The boronizing treatment has been an effective way to strengthen and enhance the lubrication performance of alloys. However, the traditional power-pack boronizing method has been limited due to its time-consuming. Improving the boronizing efficiency is highly demanded for the strengthening and industry application of the high-entropy alloys (HEAs). In this study, the electrochemical boronizing strategy was applied to improve the surface hardness and self-lubrication performance of AlCoCrFeNi2.1 eutectic HEA (EHEA). The microstructure, phase formation and hardness of boronized alloys were studied. Results confirm the high efficiency of electro-chemical boronizing to form a boronized layer with a thickness of about 35 mu m in 30 min. The surface hardness of the boronized AlCoCrFeNi2.1 HEA reached to about 18 GPa due to the presence of NiB, FeB and Cr3B4 in the boronized layer. Tribological tests reveal that the self-lubrication property of AlCoCrFeNi2.1 HEA in water condition was significantly enhanced by the electrochemical boronizing treatment, e.g., the friction and wear reductions reach to about 25% and 80%, respectively. Lubrication mechanism investigation by X-ray photo-electron spectroscopy (XPS) analysis showed the formation of a H3BO3 tribofilm on the sliding surface during the friction process, which effectively reduce friction and wear. This study provided a novel and fast approach for surface hardening and self-lubrication enhancement of HEA systems using the electrochemical boronizing strategy.
查看更多>>摘要：The incorporation of a fourth element in Ti1-xAlxN, like Ta, and a multilayer architecture are possible concepts to further enhance the coating performance in cutting applications. In the present study, both concepts are combined, focusing on the investigation of the microstructure and the fracture properties of two Ti1-x-yAlxTayN single layer coatings (Ti0.55Al0.44Ta0.01N and Ti0.33Al0.54Ta0.13N) and two corresponding multilayer coatings with the same bilayer thickness but an inverse layer sequence with different layer thicknesses. Energy dispersive X-Ray spectroscopy was utilized to determine the average composition of the coatings, confirming that the Al and Ta contents increase from single layer Ti0.55Al0.44Ta0.01N via the two multilayers to single layer Ti0.33Al0.54Ta0.13N. The residual stress and microstructure were studied using X-ray diffraction and scanning electron microscopy revealing higher compressive stress and grain refinement with higher Al and Ta content, which provoked an increasing hardness as evidenced by nanoindentation experiments. In contrast, the contribution of the multilayer architecture to the hardness increase is only minor. Additionally, micromechanical bending tests revealed a trend of higher fracture stress with increasing Al and Ta content. The fracture toughness was constant for all coatings as different toughening mechanisms occur.
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：The microstructure of the phosphate coating on implant surface is critical for successful osseointegration. Based on the morphological variability of phosphate crystals, the microstructure of the coating can be regulated by designing the composition of the phosphate solution. In this study, a strontium-zinc-phosphate (SrZn2(PO4)(2), SZP) coating was prepared on titanium (Ti) surface by phosphate chemical conversion (PCC) method. The effect of Zn2+ concentration in phosphate solution, which was regulated by increasing the addition amount of Zn (H2PO4)(2).2H(2)O, on the microstructure and properties of the SZP coating was investigated. The characterization of the coating was carried out by scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), laser scanning confocal mi-croscope (LSCM), contact angle goniometer, and electrochemical workstation system. The results revealed that the increase of Zn2+ concentration in phosphate solution could induce the crystal morphology of the SZP coating to evolve from irregular granules (Zn(H2PO4)(2).2H(2)O: 1 g/L) to regular cubic blocks (Zn(H2PO4)(2).2H(2)O: 8 g/L). This morphological evolution process was accompanied by an increase in thickness (from 4.8 +/- 1.2 to 20.6 +/- 1.9 mu m), an improvement in wettability and corrosion resistance, as well as a decrease in the release amount of Sr2+ (from 3.97 +/- 0.26 to 0.86 +/- 0.12 ppm) and Zn2+ (from 0.31 +/- 0.01 to 0.18 +/- 0.01 ppm) after 21 days of im-mersion. In vitro evaluations proved that the adhesion, proliferation, and differentiation of MC3T3-E1 pre-os-teoblasts on SZP coatings, especially for the coating with tiny cubic-block crystals, were significantly enhanced compared with pure Ti. This study clarified the rule of morphological evolution of the SZP crystal that is caused by changing the Zn2+ concentration in the phosphate solution, which contributes to the structural optimization of the SZP coating to obtain high osteogenic activity.
Sidelev, D. V.Ruchkin, S. E.Syrtanov, M. S.Kashkarov, E. B....
11页
查看更多>>摘要：Cr coatings with CrN/Cr multilayers with a layer thickness of 100, 250 and 750 nm were deposited by a multi cathode magnetron sputtering on E110 zirconium alloy in Ar and Ar + N-2 atmosphere. The mechanical properties of the as-deposited coatings were measured by scratch testing and tribometry. A comparative study of crack and oxidation resistance of the Cr-coated E110 alloy was performed under thermal cycling (1000 degrees C) and high-temperature (1200-1400 degrees C) steam oxidation conditions. The influence of the CrN/Cr multilayers and their thickness on the mechanical properties and oxidation resistance of the coated E110 alloy is discussed. It is found that the CrN/Cr multilayers can limit interdiffusion between the coating and E110 alloy at high temperatures only for a short period.
查看更多>>摘要：Plasma spray coating properties frequently depend-to a great extent-on the spray parameters. However, it is difficult to analyze and obtain a comprehensive model of the entire plasma spray process due to the complex chemical and thermodynamic reactions that take place during the process. In this study, Ni60CuMo coatings were prepared on ZL109 substrates. A Back Propagation (BP) Neural Network model in the artificial neural network was used to predict the change in bonding strength, microhardness, and porosity of the coatings under different spraying distances, spraying powers, and powder feeding rates. The results show that the R-value of the trained network training is 0.8828. Comparison of experimental and predicted results reveals that both show similar trends, which verifies that the BP model can effectively predict the properties of Ni-based coatings.
查看更多>>摘要：Multi-principal-element nitride (MPEN) has great potential in the application of cutting tool protective coatings. However, the investigation of the nanostructured MPEN coatings is still insufficient. In this paper, we study (AlCrNbSiTi)N MPEN coatings deposited at various bias voltages ranging from-50 to-200 V, using RF magnetron sputtering technique. The microstructure and mechanical performance e of the coatings are systematically investigated. The results show that the (AlCrNbSiTi)N coating forms an FCC crystal structure and exhibits columnar grains. In the elongated grain, there exists a nanocomposite structure with (AlCrNbTi)N nanograins surrounded with crystallized Si3N4 interfaces. The mechanical performance and wear resistance of the coating is enhanced first and then degraded with the increasing bias voltage. The coating deposited at-150 V exhibits the highest hardness and elastic modulus of 39.8 and 436.7 GPa, respectively, and has the lowest wear rate of 6.7 x 10(-6 )mm(3).N-1.m. These results show that the (AlCrNbSiTi)N coating is a competitive candidate for protective coating applications.
查看更多>>摘要：Peri-implant angiogenesis plays important roles in osseointegration of implants. Unfulfilling neovascularization will lead to delayed union or non-union after prosthetic implanted. In this paper, a nanostructured surface composed of TiO2, CuO and Cu2O was fabricated on Ti-Cu alloy using an alkali-heat treatment. The nano structure strengthened anticorrosion but accelerated Cu ions release. Meanwhile, in vitro cells experiments proved both Cu ions release and nanostructure on the surface of Ti-Cu alloy improved the functionality of human umbilical vein endothelial cells (HUVECs) resulting in excellent pro-angiogenesis potential indicated by promoted initial adhesion and spreading, satisfied cytocompatibility, enhanced migration, improved tube formation, upregulated angiogenesis-related genes and increased VEGF protein secretion. It was suggested that the modified Ti-Cu alloy with desired angiogenesis might be a promising strategy to improve osseointegration.
NSTL
Elsevier