Search

The wetting behavior of glass coatings on samarium-cobalt alloys with different roughness at elevated temperatures in air was investigated by a sessile drop method. The wetting properties were analyzed through several parameters, including apparent contact angle, height and diameter of a glass cylinder on the samarium-cobalt alloy, determined by using a high temperature microscope. The morphology evolution of the glass coating was observed by using a scanning electron microscope. The results show that the glass cylinder contracts initially, and then swells followed by wetting and spreading on the samarium-cobalt alloy substrate. This process is explained by the role of air and the increase of capillary number. The dependence of apparent contact angle on surface roughness is related to interface reaction. It is concluded that the surface roughness firstly increases the contact angle, but then promotes wetting due to the wetting transition changing from the Cassie−Baxter state to the Wenzel state in the non-reactive wetting range. The surface roughness hinders the spreading of the glass melt due to the interface reaction between glass and samarium-cobalt alloys in the reactive wetting range.

Porous SiC ceramic membrane supports are widely employed in a wide variety of high-temperature applications, such as hot flue gas filtration, porous burners and molten metal filters. Herein, SiC supports, with a porosity of ~37%, were prepared by using low-temperature bonding techniques and the influence of different bonding phases, such as mullite, cordierite and glass, on ambient-temperature flexural strength, hot modulus of rupture (HMOR), thermal shock resistance and oxidation resistance were systematically investigated. The results reveal that the glass-bonded SiC (GBSC) support exhibited the highest ambient-temperature flexural strength of 33.6 MPa, whereas the flexural strength of mullite-bonded SiC (MBSC) and cordierite-bonded SiC (CBSC) supports ranged from 22 to 25 MPa. However, the presence of glass phase deteriorated the high-temperature properties of the support. MBSC support rendered superior mechanical strength at high temperature and self-strengthening in a certain temperature range, such as HMOR improved 47.5% at 900 °C, but HMOR of glass-bonded support was only 57.4% of the ambient-temperature strength. Moreover, MBSC and CBSC supports exhibited better thermal shock resistance than GBSC supports and the critical temperature difference of water quenching for MBSC supports was ~200 °C higher than GBSC supports. In addition, MBSC support rendered superior oxidation resistance and exhibited a weight gain rate of ~0.1% at 1150 °C for 24 h, which is 54.4% and 42.2% lower than CBSC and GBSC supports, respectively.

In order to develop filter material that can be used for high-temperature gas cleaning, porous SiC ceramic membrane support was fabricated by in situ reaction bonding. Pressureless sintering was carried out in the temperature range of 1280–1480 °C in air. Green bodies were formed by uniaxially pressing coarse SiC particles (150–180 μm) as a skeleton, fine SiC particles and ρ-Al2O3 powder as bonding additives, basic magnesium carbonate as sintering aid and polyvinyl alcohol (PVA) as binder. Effects of sintering temperature and ρ-Al2O3 content on mechanical performance and physical properties of porous SiC ceramics were systematically investigated. Results revealed that interconnected pores of support were mainly formed due to the packing of SiC coarse particles. Mullite (3Al2O3·2SiO2) was formed due to in-situ reaction between cristobalite obtained by SiC surface oxidation and α-Al2O3 converted from ρ-Al2O3 at higher temperatures. SiC particles were strongly bonded by mullite and oxidation-derived SiO2, which resulted in highly porous SiC membrane support with excellent mechanical properties. Open porosity of samples decreased with an increase in sintering temperature and ρ-Al2O3 content. In addition, flexural strength initially increased up to threshold limit, followed by gradual decrease. The sample with 9 wt. % ρ-Al2O3 exhibited the highest flexural strength after sintering at 1430 °C for 3 h. As-prepared SiC support with 9 wt. % ρ-Al2O3 demonstrated flexural strength of 25.1 MPa and air permeability of 4.8 × 10−12 m2. Moreover, as-prepared support exhibited excellent resistance to cyclic thermal shock, which indicates that these supports can be used for high-temperature flue gas cleaning under normal pressure.

Micro pin fin arrays have been widely used in electronic cooling, micro reactors, catalyst support, and wettability modification and so on, and a facile way to produce better micro pin fin arrays is demanded. Herein, a simple electrochemical method has been developed to fabricate copper vertical micro dendrite fin arrays (Cu-VMDFA) with controllable shapes, number density and height. High copper sulphate concentration is one key point to make the dendrite stand vertically. Besides, the applied current should rise at an appropriate rate to ensure the copper dendrite can grow vertically on its own. The Cu-VMDFA can significantly enhance the heat transfer coefficient by approximately twice compared to the plain copper surface. The Cu-VMDFA may be widely used in boiling heat transfer areas such as nuclear power plants, electronic cooling, heat exchangers, and so on.

Janus effect has been studied for emerging materials like Janus membranes, Janus nanoparticles, etc., and the applications including fog collection, oil/water separation, CO 2 removal and stabilization of multiphasic mixtures. However, the Janus effect on oil/water separation is still unclear. Herein, Janus Cu mesh decorated with Ni-NiO/Ni(OH) 2 core-shell nanoparticles is synthesized via selective electrodeposition, in which we keep one side of Cu mesh (Janus A) to be superhydrophilic, while manipulate the wettability of another side (Janus B) from hydrophobic to superhydrophilic. Experimental results indicate that Cu mesh with both-side superhydrophilic shows the superior oil/water separation performance (separation efficiency >99.5%), which is mainly due to its higher water capture percentage as well as larger oil intrusion pressure. Further, we demonstrate the orientation of Janus membranes for oil/water separation, and summarize that the wettability of the upper surface plays a more important role than the lower surface to achieve remarkable performance. Our work provides a clear insight of Janus effect on oil/water separation, it is significative to design high-performance membranes for oil/water separation and many other applications.

The standard near-silicon liquid (2329kg/m3) is a mixture liquid of tribromopropane and dibromoethane in a certain proportion. This liquid is used to measure the density of single crystal silicon spheres by a static suspension method and the analysis of the difference in the micro density between two silicon spheres. Measuring the difference in the micro-density of the silicon spheres is of great significance for the new definition of the new mass of kilograms. In order to obtain the micro-density difference of the silicon spheres, it is necessary to calculate the static pressure value and the temperature by separately adjusting the singlecrystal silicon spheres to the same suspension state and the compression coefficient of the near-monocrystalline silicon density liquid. Through the adjustment of the same hydrostatic suspension state of a single silica ball in different suspension states, the linear constants measured by the linear model are analyzed to calculate the liquid compression coefficient. For this purpose, a static suspension measuring device for a single crystal silicon ball was designed to maintain the water bath within a range of ±0.1mk within 3 hours, and the position control of the silicon ball was determined by controlling the pressure of the upper computer.

In this work, we investigate the droplet bouncing on the hierarchical branched nanotube (BNT) arrays surface above and below 0 °C. By anodization, we fabricate large-area arrays of BNT with the BNT spacing controlled from adjacent to sparse. We evaluate the influence of the BNT spacing on the droplet bouncing. The adjacently distributed BNT (A-BNT) outperforms the sparsely distributed BNT (S-BNT). We find that the A-BNT can repel up to 3.1 m/s droplet at 20 °C and 2.3 m/s droplet at −18 °C, while the maximum bouncing velocity on the S-BNT is below 2.3 m/s at 20 °C and below 0.9 m/s at −10 °C. For the bouncing on the supercooled A-BNT surface, the droplet bouncing contact time increases as the substrate temperature decreases for the same droplet velocity, while the bouncing contact time decreases as the droplet velocity increases for the same substrate temperature. We discuss the influence of the nanosized air cushion entrapped amid the branched-arms of the BNT on the three-phase contact line on the BNT walls and bouncing performance under supercooled conditions.

The SiC ceramic membrane supports by using four different processes were prepared by extrusion molding process. Shape and distribution of pores in SiC ceramic membrane supports were observed by SEM, Meanwhile the O-ring strength was measured. By analyzing the relationship between pores’ shape, distribution and O-rings strength, the optimal data of apparent porosity and the optimal pores’ shape and distribution was obtained. By means ofusing similar particle sizes, particles modification, controlling drying rate of the green body and controlling the contents of glass phase in neck part between SiC particles formed at the high temperature, the SiC ceramic membrane supports with the O-ring strength greater than 20 MPa were prepared.

In recent years, Cu foam has attracted intensive attention owing to its remarkable performance for oil/water separation. Most research has mainly focused on Cu foam with surfactant decoration, which results in superhydrophobic or even stimuli-responsive membranes. Fabricating Cu foam with intrinsic superhydrophilicity via simple operations still remains a challenge. Herein, we synthesized superhydrophilic and under-water superoleophobic Cu foam that consists of oxy-chloridized hierarchical nanoparticles with metal Cu cores and polar Cu2O/CuO1−x/2Clx shells via the combination of anodization, HCl etching and calcination. This material shows ultrahigh water permeability (5 μl water-droplet permeating within 9 ms). The oil/water separation efficiency of superhydrophilic Cu foam (SCuF) is above 99% with the oil content in separated water lower than 3 ppm. Moreover, the oil/water separation performance of SCuF for repeated use and anti-corrosion is also excellent. To the best of our knowledge, it is the first attempt to synthesize intrinsic superhydrophilic Cu foam for effective oil/water separation. Due to the greatly enhanced specific surface area and active sites, it has potential applications in catalysis, hydrogen evolution processes, electrode materials and many other environmental protection and energy fields.

Through-hole TiO2 nanotube arrays (THTNA) are fabricated successfully by applying a large-voltage pulse (ΔV ≥ 40 V) at the end of anodization, and a mechanism is proposed that the fluoride-rich layer (FRL) between Ti substrate and nanotubes is the key factor for fabricating THTNA. In order to confirm the mechanism, the effects of temperature of voltage pulse on the morphology of the bottom of TiO2 nanotubes are explored. The results show the inner diameter of the bottom became larger with the temperature increasing due to the wall thickness of bottom of TiO2 nanotubes decreased and assisted by the increased fluorine content of the bottom, which is strong evidence for the mechanism proposed. What is more, the inner diameter of the bottom of THTNA can be manipulated via this novel mechanism.

A kind of compact bending dielectric elastomer actuator is designed and manufactured using VHB4910 as the actuating material. In the contrastive experiments, the maximum displacement of 6.1mm can be achieved, and on the voltage differences of 0.9kv, the active bending of actuator is 8.1°. The research of dielectric elastomer actuator can provide an instruction for the design, analysis and implementation of this kind of actuator.