Shaping nanofiltration channels in a carbonaceous membrane via controlling the pyrolysis atmosphere.

This work investigates the effect of atmosphere on pyrolysis of a polymer matrix (precursor) for directing its transformation towards more disordered graphene species and smaller graphitic nanograins. These two structural characteristics are crucial to the generation of nano-channels (NCs) pertinent to nanofiltration (NF). Two measures are explored hereby to conduct the study: varying the pyrolysis atmosphere and implementing highly dispersed nickel atomic clusters (Ni-clusters) in the coating matrix undergoing pyrolysis. A thermally reactive polymer precursor is developed to allow the above two measures to act more effectively. The various pyrolysis atmospheres employed include inert Ar, a reducing H2/N2 gas mixture, and weak oxidizing CO2. In the absence of the Ni-clusters, the H2/N2 atmosphere restrains the extent of graphitization through a chain transfer effect of H2 that ceases the free radical chain propagation, whereas CO2, owing to its high critical temperature (Tc) nature, shows the capability to reduce nanograin sizes. As for the catalytic roles of the embedded Ni-clusters, they vary with the pyrolysis atmosphere applied: offering coke nuclei for the growth of carbonaceous grains in Ar, enhancing gasification of carbon in CO2, and repressing the extent of aromatization via hydrogenation in H2/N2. The carbonaceous membranes (CnMs) obtained under the above pyrolysis conditions are distinguished by the distribution density and structure of NCs evolved, which locate primarily in the boundaries of nanograins. The NF of an aqueous solution of methylene blue (MB, 10 ppmw) is utilized to assess these CnMs to show impacts of the NCs on the separation performance.

Photoresponsive liquid marbles and dry water.

Stimuli-responsive liquid marbles for controlled release typically rely on organic moieties that require lengthy syntheses. We report herein a facile, one-step synthesis of hydrophobic and oleophobic TiO2 nanoparticles that display photoresponsive wettability. Water liquid marbles stabilized by these photoresponsive TiO2 particles were found to be stable when shielded from ultraviolet (UV) radiation; however, they quickly collapsed after being irradiated with 302 nm UV light. Oil- and organic-solvent-based liquid marbles could also be fabricated using oleophobic TiO2 nanoparticles and show similar UV-induced collapse. Finally, we demonstrated the formation of the micronized form of water liquid marbles, also known as dry water, by homogenization of the TiO2 nanoparticles with water. The TiO2 dry water displayed a similar photoresponse, whereby the micronized liquid marbles collapsed after irradiation and the dry water turned from a free-flowing powder to a paste. Hence, by exploiting the photoresponsive wettability of TiO2, we fabricated liquid marbles and dry water that display photoresponse and studied the conditions required for their collapse.

Formation of Icephobic Surface with Micron-Scaled Hydrophobic Heterogeneity on Polyurethane Aerospace Coating.

Development of an anti-icing surface on a desired industrial coating patch/object has been the persistent challenge to several industries, such as aviation and wind power. For this aim, performing surface modification to implement the icephobic property on existing commercial coatings is important for practical applications. This work accomplishes an icephobic coating overlying a PPG aerospace polyurethane coating. It manifests a clear capability to delay the formation of frost as well as to reduce the adhesion strength of ice. This icephobic coating is sustained by a unique hydrophobic heterogeneity in the micron-scale of segregation, which is realized through solution casting of a specific copolymer consisting of random rigid and soft segments, namely poly(methyl methacrylate) and poly(lauryl methacrylate-2-hydroxy-3-(1-amino dodecyl)propyl methacrylate), respectively. A wrinkled pattern developed over the coating is observed because of the diverse traits between these two segments. Besides, the OH/NH groups of the soft segment are crosslinked by a diisocyanate monomer upon drying and curing to strengthen the coating. More importantly, integration of a small dose of paraffin wax into the copolymer induces a spread of soft microdomains on the winkled pattern surface. It is hypothesized that these dual heterogeneous assemblies are responsible for the icephobicity since they instigate distinct interactions with condensed water droplets. Lastly, the thermoelectric cooling (Peltier effect) and the adhesion strength of ice on the typical coatings were assessed. This investigation also includes examination on the icephobic durability of coating, which is enhanced when a small amount of polyethylene oligomer is incorporated into the coating.

A study of interface-sustained ferromagnetism in 1/2(1-x)Ln2O3-xSrO/1/3Co3O4 nano-composite.

The binary oxide composite, consisting of rock salt-type SrO and spinel Co3O4 nano-domains, exhibits soft ferromagnetic properties at ambient temperature. This ferromagnetism is originated from interface-induction, and the magnitude of the magnetic properties can be enhanced when the spinel phase of the composite is doped by a small amount of Ln2O3 (Ln = La, Nd, for instance). In this work, we study the composites of tri-oxide, 1/2(1-x)Ln2O3-xSrO/1/3Co3O4, where 0.01 < or =1-x < or = 0.6, by focusing on three areas: (i) generation of nano-composite dominant by interfacial phase via the pyrolysis of preceramic metallo-organic gel; (ii) influence of post-pyrolysis calcination and Ln2O3 content on the phase composition of the composite; and (iii) elucidation of different magnetic responses caused by the nature of Ln2O3 dissolved in the Co3O4 phase. The Ln(3+)-doped Co3O4 oxide displays only paramagnetic behavior at room temperature, but the ferromagnetic response is attained upon its mixing with SrO in nano-scale. The SrO phase plays the role in assisting Co3O4 phase with aligning unpaired electrons through interfacial induction.

Porous SiO2 Hollow Spheres as a Solar Reflective Pigment for Coatings.

This study starts with the synthesis of silica hollow spheres (HSs) by utilizing in situ synthesized polystyrene (PS) microspheres as the template for the deposition of a silica (SiO2) shell, followed by a slow gasification step in air to remove the PS core. The size of HS and the thickness of the porous SiO2 shell are tuned by varying the synthesis conditions of the PS latex and those of the sol-gel deposition, respectively. Various HS powder samples are characterized by ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy to determine their diffuse reflectance. Furthermore, they are used as the filler in an acrylic polymer matrix for the measurement of solar reflectivity on a solar spectrum reflectometer. It turns out that both cavity size and the structure of the SiO2 shell are influential in the reflection of NIR and UV-vis light, respectively. In addition, this study examines the effect on solar reflectivity of a selected metal oxide with a SiO2 HS. In conclusion, the cavity size of the HS has a strong impact on the reflectivity to NIR light whereas the shell itself affects the reflection of UV-blue light.

Mesoporous spherical Li4Ti5O12 as high-performance anodes for lithium-ion batteries.

Porous microspherical Li4Ti5O12 aggregates (LTO-PSA) can be successfully prepared by using porous spherical TiO2 as a titanium source and lithium acetate as a lithium source followed by calcinations. The synthesized LTO-PSA possess outstanding morphology, with nanosized, porous, and spherical distributions, that allow good electrochemical performances, including high reversible capacity, good cycling stability, and impressive rate capacity, to be achieved. The specific capacity of the LTO-PSA at 30 C is as high as 141 mA h g(-1), whereas that of normal Li4Ti5O12 powders prepared by a sol-gel method can only achieve 100 mA h g(-1). This improved rate performance can be ascribed to small Li4Ti5O12 nanocrystallites, a three-dimensional mesoporous structure, and enhanced ionic conductivity.

An amphiphilic-like fluoroalkyl modified SiO2 nanoparticle@Nafion proton exchange membrane with excellent fuel cell performance.

A new route to enhance the cell performance of a Nafion proton exchange membrane is provided by incorporating fluoroalkyl modified SiO2 nanoparticles. In favor of the achieved amphiphilic-like surface characteristics of SiO2 nanoparticles, the so-formed nanocomposite membrane exhibited great enhancement of single cell performance at 80 °C: ~34% increase in output power relative to the Nafion reference and a superior maximum output power as high as 579.6 mW cm(-2).

Ion pair reinforced semi-interpenetrating polymer network for direct methanol fuel cell applications.

This paper describes the synthesis of ion-pair-reinforced semi-interpenetrating polymer networks (SIPNs) as proton exchange membranes (PEMs) for the direct methanol fuel cells (DMFCs). Specifically, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), a linear polymer proton source, was immobilized in a brominated PPO (BPPO) network covalently cross-linked by ethylenediamine (EDA). The immobilization of SPPO in the SIPN network was accomplished not only by the usual means of mechanical interlocking but also by ion pair formation between the sulfonic acid groups of SPPO and the amine moieties formed during the cross-linking reaction of BPPO with EDA. Through the ion pair interactions, the immobilization of SPPO polymer in the BPPO network was made more effective, resulting in a greater uniformity of sulfonic acid cluster distribution in the membrane. The hydrophilic amine-containing cross-links also compensated for some of the decrease in proton conductivity caused by ion pair formation. The SIPN membranes prepared as such showed good proton conductivity, low methanol permeability, good mechanical properties, and dimensional stability. Consequently, the PPO based SIPN membranes were able to deliver a higher maximum power density than Nafion, demonstrating the potential of the SIPN structure for PEM designs.

Preparation and characterization of PtRu nanoparticles supported on nitrogen-doped porous carbon for electrooxidation of methanol.

N-doped porous carbon nanospheres (PCNs) were prepared by chemical activation of nonporous carbon nanospheres (CNs), which were obtained via carbonization of polypyrrole nanospheres (PNs). The catalysts, PtRu and Pt nanoparticles supported on PCNs and Vulcan XC-72 carbon black, were prepared by ethylene glycol chemical reduction. Transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy were employed to characterize samples. It was found that PCNs containing N function groups possess a large number of micropores. Uniform and well-dispersed Pt and PtRu particles with narrow particle size distribution were observed. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that alloy catalyst (Pt(1)Ru(1)/PCN) possessed the highest catalytic activity and better CO tolerance than the other PtRu and Pt-only catalysts; PtRu nanoparticles supported on PCN showed a higher catalytic activity and more stable sustained current than on carbon black XC-72. Compared to commercial Alfa Aesar PtRu catalyst, Pt(1)Ru(1)/PCN reveals an enhanced and durable catalytic activity in methanol oxidation because of the high dispersion of small PtRu nanoparticles and the presence of N species of support PCNs.

Rechargeable battery using a novel iron oxide nanorods anode and a nickel hydroxide cathode in an aqueous electrolyte.

A rechargeable battery using novel α-Fe(2)O(3)/CNFs composite as the anode, ß-Ni(OH)(2) as the cathode and LiOH/KOH solution as the electrolyte in an aqueous rechargeable battery has been proposed. The Fe(2)O(3)/Ni(OH)(2) prototype cell exhibits a high average operational voltage of 1.5 V, high rate capability and good cycling performance.