Surface Modification of Li3VO4 with PEDOT:PSS Conductive Polymer as an Anode Material for Li-Ion Capacitors.

Li3VO4 (LVO) is a highly promising anode material for lithium-ion batteries, owing to its high capacity and stable discharge plateau. However, LVO faces a significant challenge due to its poor rate capability, which is mainly attributed to its low electronic conductivity. To enhance the kinetics of lithium ion insertion and extraction in LVO anode materials, a conductive polymer called poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is applied to coat the surface of LVO. This uniform coating of PEDOT:PSS improves the electronic conductivity of LVO, thereby enhancing the corresponding electrochemical properties of the resulting PEDOT:PSS-decorated LVO (P-LVO) half-cell. The charge/discharge curves between 0.2 and 3.0 V (vs. Li+/Li) indicate that the P-LVO electrode displays a capacity of 191.9 mAh/g at 8 C, while the LVO only delivers a capacity of 111.3 mAh/g at the same current density. To evaluate the practical application of P-LVO, lithium-ion capacitors (LICs) are constructed with P-LVO composite as the negative electrode and active carbon (AC) as the positive electrode. The P-LVO//AC LIC demonstrates an energy density of 107.0 Wh/kg at a power density of 125 W/kg, along with superior cycling stability and 97.4% retention after 2000 cycles. These results highlight the great potential of P-LVO for energy storage applications.

Preparation of Ni(OH)2/CuO heterostructures for improved photocatalytic degradation of organic pollutants and microorganism.

In this study, the Ni(OH)2/CuO heterostructured photocatalysts have been prepared via microwave (MW) hydrothermal method. The results indicate that the Ni(OH)2/CuO heterostructured composite exhibits a strong absorption in the UV and Vis regions. The construction of the heterojunction also improves the photogenerated carrier transport and inhibits the electron-hole separation due to the enhanced absorbance and the well alignment of the energy band at the Ni(OH)2/CuO interface. The photocatalytic capability of the heterostructured composites with different Ni(OH)2/CuO molar ratios is evaluated by the photodegradation of methylene blue under visible light illumination. The results reveal that the Ni(OH)2/CuO (1:1) heterostructures show the best photocatalytic efficiency, which is 2.18 and 6.13 times higher than that of pure Ni(OH)2 and CuO, respectively. Besides, the Ni(OH)2/CuO composites also reveal remarkable biocompatibility and strong photocatalytic activity in the degradation of antibiotics such as ciprofloxacin (CIP) and tetracycline (TC) and inactivation of Escherichia coli (E. coli).

Bio-Phenolic Resin Derived Porous Carbon Materials for High-Performance Lithium-Ion Capacitor.

In this article, hierarchical porous carbon (HPC) with high surface area of 1604.9 m2/g is prepared by the pyrolysis of rubberwood sawdust using CaCO3 as a hard template. The bio-oil pyrolyzed from the rubber sawdust, followed by the polymerization reaction to form resole phenolic resin, can be used as a carbon source to prepare HPC. The biomass-derived HPC shows a three-dimensionally interconnected morphology which can offer a continuous pathway for ionic transport. The symmetrical supercapacitors based on the as-prepared HPC were tested in 1.0 M tetraethylammonium tetrafluoroborate/propylene carbonate electrolyte. The results of electrochemical analysis show that the HPC-based supercapacitor exhibits a high specific capacitance of 113.3 F/g at 0.5 A/g with superior rate capability and cycling stability up to 5000 cycles. Hybrid lithium-ion capacitors (LICs) based on the HPC and Li4Ti5O12 (LTO) were also fabricated. The LICs have a maximum energy density of 113.3 Wh/kg at a power density of 281 W/kg. Moreover, the LIC also displays a remarkable cycling performance with a retention of 92.8% after 3000 cycles at a large current density of 0.75 A/g, suggesting great potential application in the energy storage of the LIC.

Polyimide-Derived Carbon-Coated Li4Ti5O12 as High-Rate Anode Materials for Lithium Ion Batteries.

Carbon-coated Li4Ti5O12 (LTO) has been prepared using polyimide (PI) as a carbon source via the thermal imidization of polyamic acid (PAA) followed by a carbonization process. In this study, the PI with different structures based on pyromellitic dianhydride (PMDA), 4,4'-oxydianiline (ODA), and p-phenylenediamine (p-PDA) moieties have been synthesized. The effect of the PI structure on the electrochemical performance of the carbon-coated LTO has been investigated. The results indicate that the molecular arrangement of PI can be improved when the rigid p-PDA units are introduced into the PI backbone. The carbons derived from the p-PDA-based PI show a more regular graphite structure with fewer defects and higher conductivity. As a result, the carbon-coated LTO exhibits a better rate performance with a discharge capacity of 137.5 mAh/g at 20 C, which is almost 1.5 times larger than that of bare LTO (94.4 mAh/g).

Co2+-Doped BiOBrxCl1-x hierarchical microspheres display enhanced visible-light photocatalytic performance in the degradation of rhodamine B and antibiotics and the inactivation of E. coli.

In this article, we have synthesized Co2+-doped BiOBrxCl1-x hierarchical nanostructured microspheres, featuring different degrees of Co2+ doping, displaying excellent photocatalytic performance. X-ray diffraction and Raman spectroscopy indicated that the Co2+ ions were successfully doped into the BiOBrxCl1-x nanocrystals. The photodegradation rate of rhodamine B mediated by a doped BiOBrxCl1-x was 150 % greater than that of the non-doped BiOBr. We ascribe the improved photocatalytic capability of the Co2+-doped BiOBrxCl1-x to a combination of its superior degree of light absorption, more efficient carrier separation, and faster interfacial charge migration. The major active species involved in the photodegradation of RhB also has been investigated. Moreover, the doped BiOBrxCl1-x possessed excellent cellular biocompatibility and displayed remarkable performance in the photocatalytic bacterial inactivation.

A Brief Note on the Magnetowetting of Magnetic Nanofluids on AAO Surfaces.

In magnetowetting, the material properties of liquid, surface morphology of solid, and applied external field are three major factors used to determine the wettability of a liquid droplet on a surface. For wetting measurements, an irregular or uneven surface could result in a significant experimental uncertainty. The periodic array with a hexagonal symmetry structure is an advantage of the anodic aluminum oxide (AAO) structure. This study presents the results of the wetting properties of magnetic nanofluid sessile droplets on surfaces of various AAO pore sizes under an applied external magnetic field. Stable, water-based magnetite nanofluids are prepared by combining the chemical co-precipitation with the sol-gel technique, and AAO surfaces are then generated by anodizing the aluminum sheet in the beginning. The influence of pore size and magnetic field gradient on the magnetowetting of magnetic nanofluids on AAO surfaces is then investigated by an optical test system. Experimental results show that increasing the processing voltage of AAO templates could result in enhanced non-wettability behavior; that is, the increase in AAO pore size could lead to the increase in contact angle. The contact angle could be reduced by the applied magnetic field gradient. In general, the magnetic field has a more significant effect at smaller AAO pore sizes.

A Hydrostatic Bearing Test System for Measuring Bearing Load Using Magnetic-Fluid Lubricants.

This paper conducts a study on the design of a hydrostatic bearing test system. It involves the determination of viscous properties of magnetic-fluid lubricants. The load of a hydrostatic thrust bearing using a water-based magnetite nanofluid of varying volume flow rate is measured under an applied external induction field via the test system. Results reveal that the presence of nanoparticles in a carrier liquid would cause an enhanced bearing load. Such an effect could be further magnified by increasing the lubricant volume flow rate or the external induction field strength.

Combined Forced and Thermocreep Convection through a Long Horizontal Microchannel.

This study examines how thermal creep affects the mixed convection in a long horizontal parallel-plate microchannel under a pressure drop and a temperature rise. The analytical solutions of the fully developed thermal-flow fields and the corresponding characteristics are derived based on the Maxwell boundary conditions with thermal creep and presented for the physical properties of air at the standard reference state. The calculated thermal-flow characteristics reveal that thermal creep has an appreciable effect on the velocity slip, flow rate, and heat transfer rate but a negligible effect on the flow drag. Such a creep effect could be further magnified by decreasing the pressure drop or increasing the Knudsen number.

Hydrodynamic modeling of targeted magnetic-particle delivery in a blood vessel.

Since the flow of a magnetic fluid could easily be influenced by an external magnetic field, its hydrodynamic modeling promises to be useful for magnetically controllable delivery systems. It is desirable to understand the flow fields and characteristics before targeted magnetic particles arrive at their destination. In this study, we perform an analysis for the effects of particles and a magnetic field on biomedical magnetic fluid flow to study the targeted magnetic-particle delivery in a blood vessel. The fully developed solutions of velocity, flow rate, and flow drag are derived analytically and presented for blood with magnetite nanoparticles at body temperature. Results reveal that in the presence of magnetic nanoparticles, a minimum magnetic field gradient (yield gradient) is required to initiate the delivery. A magnetic driving force leads to the increase in velocity and has enhancing effects on flow rate and flow drag. Such a magnetic driving effect can be magnified by increasing the particle volume fraction.

Non-Newtonian flow of dilute ferrofluids in a uniform magnetic field.

Nonequilibrium magnetization states predict non-Newtonian ferrofluid properties. It is desirable to understand the corresponding flow fields and characteristics. In this study, we derive a magnetoviscosity expression coming from the effective-field method and describing the shear-thinning non-Newtonian behavior of dilute ferrofluids with finite magnetic anisotropy. A mathematical model is developed of non-Newtonian plane flow with respect to shear and pressure driving mechanisms in the presence of an applied stationary uniform magnetic field oriented in the direction perpendicular to vorticity. The results reveal that the non-Newtonian effect tends to increase the velocity and angular velocity but to reduce the magnetization strength. Moreover, an enhanced flow rate and reduced flow drag may be obtained. The maximum non-Newtonian effect is found at a ratio of the Néel relaxation time to the Brownian relaxation time of the order of 0.1.

Comment on "Measuring the transverse magnetization of rotating ferrofluids".

Contrary to the main conclusion of Embs [Phys. Rev. E 73, 036302 (2006)], we demonstrate with amplitude correction factors that the predictions of the magnetization model proposed by Shliomis [Sov. Phys. JETP 34, 1291 (1972)] are well consistent with the experimental data for weakly nonequilibrium states and that the model proposed by Shliomis [Phys. Rev. E 64, 063501 (2001)] is valid even far from equilibrium. A model on the basis of the weak-field magnetization equation of Müller and Liu [Phys. Res. E 64, 061405 (2001)] with a "structure" modification is also shown to reproduce a wide range of experimental data. Our statement is confirmed by a more exact insight into the hydrodynamic problem of rotating ferrofluids.