•Ce0.9Gd0.1O2-δ was employed to modify Ba-based dual-phase membrane.•The CGO-modified membrane exhibited an enhanced H2 separation flux of 0.96 mL min−1 cm−2 at 860 °C.•A high and stable H2 ...separation flux was achieved under CO2-containinig atmospheres.
Interest in mixed conducting ceramic membrane for efficient hydrogen separation is growing. However, the membranes with alkaline earth metal are susceptible to CO2 due to the drastic carbonation and irreversible deterioration of membrane, which significantly impedes their applications. Herein, gadolinium-doped ceria (Ce0.9Gd0.1O2-δ, CGO) with robust chemical stability was employed to modify Ba-based dual-phase membrane BaCe0.85Fe0.15O3-δ-BaFe0.85Ce0.15O3-δ (BCF-BFC) by a simple drop coating method. Due to the improved surface activity on the membrane, the CGO-modified BCF-BFC membrane (CGO/BCF-BFC) exhibited an enhanced H2 separation flux of 0.96 mL min−1 cm−2 at 860 °C, which is nearly 1.3-time improvement than the unmodified BCF-BFC membrane. Furthermore, benefitting from the reduction of CO2 adsorption and suppression of carbonate formation on the surface of membrane, an improved CO2-tolerance was observed over the CGO/BCF-BFC, and a high and stable H2 separation flux of 0.60 mL min−1 cm−2 was retained under CO2-containing atmosphere, while BCF-BFC membrane showcased continually deteriorating H2 separation performance at 900 °C. The achieved H2 separation flux along with the improved CO2-tolerance paves a new way towards the future application of alkaline-earth-metal-containing ceramic membrane for H2 purification.
Niobium (Nb)-doped, Li3NbO4 surface-modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes were prepared using solid-phase reactions. These modifications helped in improving the thermal stability and cycling ...performance of the cathodes. XRD and EDX measurements of the prepared samples confirmed the uniform distribution of Nb, whereas Li3NbO4 was found to occur at the grain boundaries and on the surface of primary NCM622 particles. The thermal stability of the prepared samples was evaluated by measuring the amount of O2 released from the cathode material during overcharging. This quantification was conducted using a gas chromatography–mass spectroscopy analysis. Decomposition of the NCM622 cathode material was suppressed by Nb-doping. Furthermore, electrochemical tests showed that the Nb-doped, Li3NbO4 surface-modified NCM622 exhibited an excellent cycling performance over 500 cycles in the 3.0–4.1 V voltage range at a current rate of 2 C at 60 °C, during which the sample retained 91.4% of its initial capacity. This capacity retention was much higher than that for both the samples prepared using only Nb doping without Li3NbO4 surface modification (36.8%) and that of undoped NCM622 (70.7%). Our results indicate that Nb doping and Li3NbO4 surface modification are effective for improving the cathode’s thermal stability and cycling performance, respectively.
Superhydrophilic zwitterions have been extensively exploited for surface modification to improve antifouling properties. However, it remains challenging to form layers of <20 nm with high zwitterion ...content on the surfaces with different degrees of hydrophilicity. We demonstrate that amine-functionalized sulfobetaine (SBAm) can be co-deposited with dopamine on ultrafiltration (UF) membranes, leading to a thickness of 10 nm to 50 nm and an SBAm content of up to 31 mass% in the coating layers. The covalently grafted SBAm is stable underwater and improves the antifouling properties, as evidenced by the lower trans-membrane pressure required to retain targeted water fluxes than that required for the pristine membranes. The SBAm is also more effective than conventionally used sulfobetaine methacrylate (SBMA) for the zwitterion grafting on the surface to improve antifouling properties.
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•Sulfobetaine amine (SBAm) is co-deposited with dopamine on membrane surfaces.•The coating layer can be < 20 nm and contains 31 mass% SBAm.•Surface grafting with SBAm improves antifouling properties of UF membranes.•SBAm is more effective than sulfobetaine methacrylate (SBMA) for grafting.
Membrane distillation (MD) is one of the potential technologies that may meet the freshwater demands by using solar energy. In this study, based on the commercial flat sheet PVDF membrane, a kind of ...superhydrophobic photothermal MD membrane was prepared by surface spraying with the TiC and TiO2 nanoparticle mixed solution. The surface characteristics and the desalination performances in vacuum membrane distillation (VMD) were carried out, and the influences of the photothermal layers on the heat and mass transfer process were investigated through the numeric simulation models. The results showed that the modified membrane possessed a superhydrophobic surface, with a water contact angle of 162.5° ± 2.1° and a sliding angle of 5.7° ± 1.2°. Compared to the solar-free process, a flux increment of 0.64 kg m−2 h−1 was obtained in VMD applications when the solar intensity was 1000 W m−2 at room temperature. While improving the feed temperature to 80 °C and solar irradiation to 1500 W m−2, the permeate flux reached 31.41 kg m−2 h−1, which was 5.66 kg m−2 h−1 higher than the solar-free process. The simulation results indicated that the surface temperature of the solar-aid MD process was much higher than the solar-free process, which provided the additional energy for water evaporation. Further, the anti-fouling tests showed that the modified membrane nearly had no flux decline and kept high salt rejection (above 99.95%) in a 156 h operation with 70 g L−1 (NaCl + CaCl2) feed solution, which showed the potential in both MD process and the solar-driven desalination process.
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•Superhydrophobic photothermal membrane was prepared by surface spraying method.•High feed temperature significantly improves the solar driven permeate flux.•The surface temperature of solar-aid membrane is higher than the solar-free process.•The solar irradiation provides additional energy for water evaporation.
Carbon nanotubes (CNTs) as functional materials have aroused great interest among researchers due to their remarkable mechanical, electrical, thermal, and other photoelectric properties. However, ...CNTs tend to agglomerate into crystalline bundles because of the strong Van der Waals attraction force, adversely affecting their properties. This tendency to self-aggregate has been an important barrier to their chemical and physical manipulation and thus to their practical applications. To overcome this barrier, advances in the maximum-effective dispersion (denoted as mono-dispersion) of CNTs in the liquid phase (water and organic solvent) or solid remain critical to realizing many important commercial applications. Herein we summarize recent breakthroughs in the strategies of CNTs dispersion and highlight the key ongoing research challenges. Studies for currently understanding the aggregation and dispersion kinetics of CNTs are mainly consisting of two aspects, covalent or non-covalent bonding functionalization, which are usually introduced to nullify or reduce their Van der Waals force, thus improving their self-assembling characteristics. In particular, the roles of non-covalent bonding modifications, including electrostatic interaction, π-π stacking interaction, dipole interactions, Van der Waals interactions, hydrogen bond, and coordination, are more attractive in CNTs dispersion without disturbing their internal electronic structure. The surface modification techniques and potential applications are also highlighted.
Graphical representations of CNT dispersion mechanism and applications. Display omitted
The aim of this study was to evaluate the effects of air abrasion and plasma treatment on the bond strength between resin and ceriastabilized tetragonal zirconia polycrystals/alumina (Ce-TZP/Al2O3). ...Ce-TZP/Al2O3 specimens were ground with #1000 silicon-carbide paper, air abraded with alumina, and then exposed to glow-discharge plasma (Abrasion/Plasma). Specimens without air abrasion and/or plasma exposure were also prepared as controls (Abrasion/No plasma, No abrasion/Plasma, and No abrasion/No plasma). The specimens were bonded to resin composite disks with a self-adhesive resin cement (SA) or a luting composite containing no functional monomer (LC). Shear bond strengths were determined after 10,000 thermocycles at 4 and 60°C, and the data were analyzed by nonparametric tests (α=0.05, n=8/group). When using SA, the Abrasion/Plasma specimens exhibited the highest bond strength, followed by the Abrasion/No plasma, No abrasion/Plasma, and No abrasion/No plasma specimens. For LC, neither air abrasion nor plasma treatment exhibited any significant effect on bond strength.
In this work we introduce a sustainable membrane-based synthesis–separation platform for enantioselective organocatalysis. An azido derivatized cinchona-squaramide bifunctional catalyst was ...synthesized and subsequently grafted to the surface of a polybenzimidazole-based nanofiltration membrane. The favorable effect of the covalent graftingdue to the change in geometry and increased secondary interactionson the catalytic activity due to conformational changes was confirmed by quantum chemical calculations. Asymmetric Michael and aza-Michael reactions of 1,3-dicarbonyl and indole, pyrazole, and triazole derivatives to β-nitrostyrene were performed with as high as 99% enantiomeric excess. This report on the enantioselective aza-Michael reaction of pyrazoles and triazoles opens new frontiers in the application of squaramide-based cinchona catalysts. A catalytic membrane cascade reactor was developed for an integrated synthesis–purification process allowing at least 98% product and substrate recovery, and quantitative in situ solvent recycling. The sustainability of the synthetic methodology was assessed through E-factor and carbon footprint.
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•Atmospheric-prresure plasma was applied to the surface of organosilica membranes.•The pore size decreased and affinity increased with increasing plasma exposure time.•The ...permselectivity increased with increasing plasma exposure time.•The balance between the diffusion barrier and adsorption determined PV performance.
The effects of the plasma treatment time on the gas permeation and pervaporation dehydration properties of organosilica membranes modified by atmospheric-pressure plasma were investigated. The He/N2 permeance ratio increased from 10 to over 100 as the plasma modification time increased, indicating that the pore size decreased by plasma modification. As measures of the pervaporation properties, the H2O permeance gradually increased, and the EtOH permeance gradually decreased with increasing plasma modification time, resulting in a higher H2O/EtOH permeance ratio from about 20 to over 1000. The enhanced separation performance is attributed to the densification of the pore structure with increasing plasma modification time. A comparison of the temperature dependence of the permeance for gas permeation and pervaporation dehydration indicated that plasma modification increased the affinity of the membrane matrix for water molecules. This enhanced permeation property can be attributed to the increased adsorption of water on the membrane surface with increasing plasma modification time. It was clarified that the permeation properties could be controlled through the tuning of the pore structure and water adsorption properties of the membranes by varying the plasma treatment time.
The improved resistive switching (RS) characteristics of Pt/HfO2/Ti structured RRAM are demonstrated by engineering interface with argon (Ar) plasma irradiation. The Ar plasma treatment was ...intentionally carried out on the surface of atomic layer deposited (ALD) HfO2 thin films to modulate the conducting filament size affecting RS behaviors. Compared to ALD HfO2 RRAM without Ar plasma treatment, the Ar plasma treatment on the surface of ALD HfO2 thin film leads to forming-free process, faster switching speed, tighter low resistance state (LRS) and high resistance state (HRS) current distribution, smaller variations of SET voltage and RESET voltage, and enhanced retention/endurance characteristics under HRS. These improvements are believed to be the generation of favorably modulated interface oxide layer between HfO2 and Ti. In addition, current conduction mechanism is dominated by ohmic behavior in LRS while ohmic, space charge limited conduction (SCLC), and trap filled SCLC are observed at HRS with different field regions. The Ar plasma irradiation can be an easy and facile way to achieve the reliable and uniform RRAM characteristics.
•Argon plasma irradiation was conducted on the ALD HfO2.•Ar plasma treatment produces faster switching, uniform and reliable resistive switching behaviors.•Improved reliability depends on interface reaction at Ti/HfO2.
Bulk metallic glasses (BMGs) are amorphous metallic alloys with high strength and hardness. This paper discusses the machining process of Zr-BMG using a transparent sapphire tool with direct laser ...assistance. The laser beam passes through the tool and directly heats the workpiece material to improve its machinability. Micro textures were generated on the tool rake face to facilitate chip formation. Reduced cutting forces and improved surface finish were observed with direct laser assistance. The effects of machining speed and laser power on the material deformation mechanism were investigated. A finite element model was developed to investigate the cutting forces.
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