Wetting of YSZ by molten Sn–8Zr,Sn–4Zr–4Ti,and Sn–8Ti alloys at 800–900 °C

The wetting of 3% yttria-stabilized zirconia (YSZ) by Sn–8Zr, Sn–4Zr–4Ti, and Sn–8Ti alloys was studied at 800–900 °C. Both Zr and Ti improve the wettability via the formation of reaction products and adsorption. In the systems containing Zr additives in the alloys, ZrO_2-x precipitates preferentially, and the wettability is dominated by interface adsorption. An anomalous temperature dependence was found in the final wettability of these systems owing to the decrease in adsorption with an increase in the temperature. The spreading dynamics are controlled by the dissolution of Zr, followed by the formation of a wetting ridge. The wettability of the Sn–8Ti/YSZ system is dominated by the precipitation of reaction products (Ti₂O₃ and Ti_11.31Sn₃O₁₀). The reaction kinetics is the limiting factor for spreading in Sn–8Ti/YSZ, and the adsorption at the interface significantly decreased the energy barrier for wetting.     

Synthesis and plasma treatment of nitrogen-doped graphene fibers for high-performance supercapacitors

Graphene fiber-based supercapacitor has aroused great interest as a flexible power source in future wearable electronics. However, the low electrochemical performance of graphene fibers (GFs) usually causes the serious limitation of use in practical applications due to the material stacking, hydrophobicity and fabrication process complexity. In this work, a facile and effective plasma-assisted strategy is put forward to increase specific surface area, tune hierarchically porous structure and promote wettability of nitrogen-doped graphene fibers (NGFs), resulting in the improvement of electrochemical performance. The supercapacitor assembled from plasma-treated NGFs shows superior capacitance (878 mF/cm² at 0.1 mA/cm² current density) and high energy density (19.5 μW h/cm² at 40 mW/cm² power density), which is 23.7% and 131.4% higher than that of NGFs and GFs, respectively. Additionally, the fiber-based supercapacitor based on plasma-treated NGFs exhibits high rate capability of 59.8% and excellent cyclic performance (95.8% retention over 10,000 cycles). These plasma-treated NGFs can be promising candidates for high-performance and flexible power sources in future wearable electronics.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.     

析晶污垢生长影响因素概述

结垢问题存在于各个行业,尤其在油田表现更甚。但材料表面特性对油田采出水中析晶污垢的影响并没有得到太多关注。主要对影响析晶污垢生长的三种主要表面特性因素进行简要综述。     

The mechanical and thermal properties,CMAS corrosion resistance,and the wettability of novel thermal barrier material GdTaO4

Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ, the design of novel thermal barrier materials is a hotspot. GdTaO₄ is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity. In this study, the mechanical and thermal properties, CMAS corrosion resistance, and the wettability of the GdTaO₄ were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO₄ are 14.1 × 10⁻⁶ K⁻¹ (1350 °C) and 534.2 Hv_0.3 respectively. The thickness of CMAS reaction layer of GdTaO₄ is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO₄. The main reaction product is Ca₂Ta₂O₇, and the anorthite phase may not be detected, which is similar to YTaO₄. By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO₄ is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO₄ can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO₄ are smaller than those of YSZ in the same situation. These findings suggest that GdTaO₄ possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material.     

Recent progress of the gas diffusion layer in proton exchange membrane fuel cells: Material and structure designs of microporous layer

Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities.     

Experimental investigation on high temperature wettability and structural behaviour of SAW fluxes using MgO–TiO2–SiO2 and Al2O3–MgO–SiO2 flux system

To establish the relationship between wettability and structure with the change in SAW flux composition, the contact angle measurement study was performed at 1700 K. For MgO–TiO₂–SiO₂ and Al₂O₃–MgO–SiO₂ flux system the wetting behaviour was studied by evaluating the contact angle as well as surface tension properties. Sessile drop method was used to determine the wetting properties of SAW fluxes. Twenty-one SAW fluxes were designed & developed by applying mixture design approach of design of experiments. Chemical, phase and structural properties of SAW fluxes were measured using modern techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD) & Fourier Transform Infra-red spectroscopy (FTIR). As per the calculated contact angle value, different surface tension values for MgO–TiO₂–SiO₂ and Al₂O₃–MgO–SiO₂ flux system was calculated using Young's & Boni's equations. Using Dupre's equation the adhesion energy for twenty-one basic fluxes was also calculated. Measured contact angle value increased with increase in the TiO₂/MgO & TiO₂/Al₂O₃ flux ratio. Lower contact angle gives higher wettability between the flux and the heating substrate. With increase of TiO₂/SiO₂ ratio up to 1.5 to 2.0 the calculated surface tension value is decreasing while after that it is increased with increase in TiO₂/SiO₂ ratio.     

Effect of ZrO2 nanoparticles addition to PEO coatings on Ti–6Al–4V substrate: Microstructural analysis,corrosion behavior and antibacterial effect of coatings in Hank's physiological solution

In this study, plasma electrolyte oxidation (PEO) method was employed to modify the surface of Ti–6Al–4V. Effects of different concentrations of ZrO₂ nanoparticles (0, 1, 3 and 5 g/l) into a phosphate-based electrolyte on the morphology, wettability, antibacterial and corrosion behaviors of coatings were investigated. Microstructural analyses of coatings were evaluated using scanning electron microscopy with an energy dispersive spectrometer. Also, X-ray diffraction, contact angle instrument and profilometry were respectively used to perform phase analysis, wettability, and surface roughness of the coatings. The antibacterial test was conducted with spot inoculation method on four pathogenic bacteria. Polarization and impedance spectroscopy measurements were performed in Hank's solution to investigate the corrosion behavior of coatings. The results revealed that PEO coatings without nanoparticles and by increasing the concentration of the ZrO₂ nanoparticles up to 3 g/l in the electrolyte led to a significant improvement in the antibacterial activities of gram-negative bacteria (P. aeruginosa and E. Coli). In the case of gram-positive bacteria, the PEO coated samples demonstrated improved antibacterial effects but addition of ZrO₂ nanoparticles in the PEO coatings resulted in deterioration of antibacterial effect. The sample coated with 3 g/l ZrO₂ nanoparticles showed the peak corrosion resistance compared to its counterparts.     

石墨烯增强铜基复合材料的制备技术及发展

石墨烯由于其独特的二维结构和优异的物化性能,在改善复合材料的力学性能、电学性能和热学性能等方面具有很大的潜力,已成为金属基复合材料较理想的增强体。铜合金具有优异的导电导热性能和良好的延展性,但是其强度较低、不耐磨及高温下易变形的特点阻碍了其应用和发展。因此,结合石墨烯和铜的性能特点,将石墨烯作为增强体添加到铜中,制备性能优异的石墨烯增强铜基复合材料成为目前研究的热点之一。综述了目前石墨烯增强铜基复合材料的制备方法,并对各方法的特点进行了分析比较,提出未来可采用的制备工艺的方向以及在制备过程中面临的问题和挑战,并对其未来的研究方向进行了展望。     

Surface wettability and flow properties of non-metallic pipes in laminar flow

In this paper, three liquids flowing in five pipes with the same inner diameter of 14 mm were studied to determine the relationship between the surface wettability and flow properties in laminar flow(Re b 2000). This was motivated by oilfield observations of increased pressure drops in non-metallic pipes compared to those in metal pipes,which was contrary to expectations. A new expression for the frictional coefficient that considers the Reynolds number and contact angle θ in laminar flow for non-metallic pipes was proposed based on the experimental results of single-phase flow using dimension and regression analyses. The solutions of the anomalous phenomenon were proposed from the perspectives of the pipe diameter, contact-angle difference, and the compatibility between flexible composite pipe and JLHW105 oil according to the new formula. The surprising finding was that the surface wettability could control the frictional resistance by the critical contact angle(39.9°) obtained at the same Reynolds number. If 0° b θ≤ 39.9°, the frictional coefficient increased as the contact angle increased. In contrast, if 39.9° b θ b 180°,the frictional coefficient decreased with increasing contact angle. The influences of the pipe diameter and contactangle difference on the pressure drop difference of JLHW105 oil showed an inversely proportional relation. A series of materials and liquids were tested. The selection of pipe material for transporting a given fluid can be based on the contact angle, surface tension, and critical limit of the contact angle obtained. The research results are expected to provide some guidelines for the selection of the appropriate pipe material for a given set of fluids.