Dispersity of materials obtained by mechanical activation and laser sintering of Al-C systems and used for production of electrochemical capacitors

Characteristics of materials designed for electrodes of electrochemical capacitors based on mechanically activated Al-C composites applied onto aluminum foil by laser sintering are considered. The methods of X-ray diffraction, X-ray photoelectron spectroscopy, and transmission and scanning electron microscopy are used to study the structure and composition of synthesized layers. It is established that mechanical activation of aluminum in the presence of graphite followed by high-speed laser sintering of the obtained material on an aluminum foil substrate noticeably increases material dispersity with a rise in its specific surface area from an initial value of 4 m²/g to a value on the order of 1000 m²/g, as estimated from the data on the capacity of the electrical double layer.     

Transmission and fractionation of micro-sized particle suspensions

In processes aimed at the fractionation of a multi-component feed stream, transmission of particles through the membrane is at least as important as retention of larger particles. In this paper, we describe the mechanisms of transmission of mono-disperse latex particles through a polymer membrane. The effects of process parameters, such as transmembrane pressure, cross flow velocity and feed concentration were investigated. In dead end filtration mode, we found that, depending on the transmembrane pressure, four particle transmission regimes could be distinguished.

Particle deposition on polymer membranes and polymer microsieves was investigated in-line with confocal scanning laser microscopy (CSLM). It was observed that with the polymer membrane random depth deposition took place, while the microsieve exhibited in-pore fouling.

In addition, bi-disperse particle suspensions were fractionated with dead end and cross flow membrane filtration, and various effects were charted. Based on the phenomena observed, it is concluded that the design of a fractionation process starts with defining a stable transmission regime for small particles, and subsequently choosing the process conditions for minimal deposition of the larger particles.     

Hysteresis loss as a measure of metal–rubber adhesion

As in the case of reinforcing filler-induced increase in hysteresis in rubbers, placement of aluminum (A1) foil to the surface of a rubber blend of epichlorohydrin rubber and carboxylated nitrile base induces increased hysteresis of the rubber due to adhesion between Al and the rubber blend. Changes in hysteresis loss due to Al foil can be correlated with the peel strength of Al-rubber-Al joints. © 1995 John Wiley & Sons, Inc.     

Ceramic microsieves: influence of perforation shape and distribution on flow resistance and membrane strength

Ceramic microsieves with slit-shaped perforations were compared to sieves with circular-shaped perforations, regarding flow resistance and membrane strength. Destructive tests show that the highest strength is obtained if the perforations are placed in a non-alternating pattern. Especially for slits, alternating patterns should be avoided as they make the structure unnecessarily flexible. The highest stress occurs at the edges of the membrane where it is attached to the support. Flexible structures bend stronger and therefore cause a higher stress at the edge, resulting in an easier rupture of the membrane. Our results show that ceramic microsieves with slits show a four to five-fold decrease in flow resistance for comparable strength related to sieves with circular pores.     

Silica-supported biomimetic membranes

The hybridization of lipid membranes with inorganic silica-based framework results in mechanically stable biomembrane mimics. This account describes three types of silica-based biomimetic membranes. As the first example, a Langmuir monolayer of dialkylalkoxysilane was polymerized and immobilized onto a porous glass plate. Permeability through the monolayer-immobilized glass was regulated by phase transition of the immobilized monolayer. In the second example, spherical vesicles covalently attached to a silica cover layer (Cerasome) were prepared. The Cerasome was stable enough to be assembled into layer-by-layer films without destruction of its vesicular structure. This material could be an example of the multicellular assembly. Mesoporous silica films densely filling peptide assemblies (Proteosilica) are introduced as the third example. The Proteosilica was synthesized as a transparent film through template sol-gel reaction using amphiphilic peptides.     

Flux stabilization of silicon nitride microsieves by backpulsing and surface modification with PEG moieties

The influence of the surface properties of chemically modified silicon nitride microsieves on the filtration of protein solutions and defatted milk is described in this research. Prior to membrane filtrations, an antifouling polymer based on poly(ethylene glycol), poly(TMSMA-r-PEGMA) was synthesized and applied on silicon-based surfaces like silicon, silicon nitride, and glass. The ability of such coating to repel proteins like bovine serum albumin (BSA) was confirmed by ellipsometry and confocal fluorescence microscopy. In BSA and skimmed milk filtrations no differences could be seen between unmodified and PEG-coated membranes (decreasing permeability in time). On the other hand, reduced fouling was observed with PEG-modified microsieves in combination with backpulsing and air sparging.     

Porous latex composite membranes: fabrication and properties

A new class of microfiltration (MF) and ultrafiltration (UF) membranes has been developed. By placing latex particles onto the surface of a microporous substrate and stabilizing the porous array, voids are formed between the particles which provide narrowly distributed pores that serve as separation channels. The size of the interstitial voids in the array is governed by the diameter of the latex particle. This aqueous based technology has advantages relative to other membrane fabrication processes in terms of the high asymmetry of the membranes, the facile adjustment of pore sizes, and the ability to easily modify pore surfaces during the synthesis of particles.A number of approaches were examined for placement of particles and stabilization of latex composite membranes (LCMs). Filtration of particles with reactive surface groups that provide covalent linkages at the contact points in the particle array proved most effective in obtaining stable membranes. These membranes had narrow size distributions in both the UF and MF range and were capable of being cleaned and backflushed. The membranes were characterized in terms of gas permeabilities, pure water permeabilities and electron microscopy. The rejection properties of LCMs were also examined during filtration of monodispersed latex particles and a broadly dispersed dextran mixture.     

Initial stage of pore formation process in anodic aluminum oxide template

The initial stage of pore formation and the growth process in anodic aluminum oxide (AAO) template have been carefully investigated. Detailed features are found concerning the nanostructure configuration formed on the electropolished aluminum foil and the additional fine structures in the first and second anodization resulting from the current limitation effect during the beginning time of about 2 s. It sheds new light onto the mechanism of the pore-organizing process of AAO templates.     

Preparation of composite membranes with bicontinuous structure

Composite membranes with a hierarchical structure comprising thin regions with a bicontinuous structure and thick regions providing mechanical strength have been prepared by casting inorganic zeolite particles and mixtures that yield organic polymers onto substrates that were decorated with sessile droplets of aqueous solutions. Analysis by scanning electron microscopy (SEM) showed a membrane structure with well-ordered imprints caused by the sessile template droplets. These imprints were open at the bottom and covered on the top with a thin sheet composed of particles and polymer. The particles protruded out of the polymer sheet at the top and bottom of the membrane in the thin regions. A significant number of the particles protruded out of both interfaces at the same time. Thus, these parts of the membrane can be considered to be bicontinuous. The imprints are surrounded by thick regions. These regions act as a supporting structure. Thus, the membranes are stable enough to be handled without special precautions and might be applicable to membrane separation processes.     

Using breath figure patterns on structured substrates for the preparation of hierarchically structured microsieves

Microsieves are advanced filtration membranes characterized by a uniform pore size, a high pore density, and a thickness smaller than the pore diameter. The uniform pore size provides a high selectivity; the small thickness gives rise to a high flux and allows efficient removal of any filter cake by backflushing. However, microsieves are sensitive to mechanical stress. Thus, they need either an external macroporous support or a hierarchical structure that provides an integrated supportive structure. We prepare microsieves with a hierarchical pore structure by creating breath figure patterns within layers of solutions of polymers in a volatile solvent that are spread out on top of structured supports. For the formation of breath figure patterns, the volatile solvent is evaporated in a moist atmosphere. This cools the surface to such an extent that dew droplets form on the thin film, partially penetrate into the layer, and create a concave imprint in the final solid polymer layer. This procedure is usually done on flat surfaces; in our case the spreading of the polymer solution is done on a support decorated with protrusions. In this procedure, the dew droplets touch the protrusions of the structured support before the polymer solution vitrifies. At the same time, the trenches of the structured substrate are filled with polymer much deeper than the penetration depth of the dew droplets. After the separation of the vitrified layer from the substrate, we obtain thin polymer membranes with a hierarchical structure consisting of an ultrathin active separation layer with submicrometer pores and a supporting layer with larger pores.     

Gel permeation chromatography followed by pyrolysis-gas chromatography-mass spectrometry via a solvent-evaporative interface

The measurement of chemical composition as a function of molecular weight has always been a challenge for analytical chemists. In this paper, we present a unique way to combine gel permeation chromatography (GPC) with pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) for this purpose. A commercially available solvent-evaporative interface, originally designed for GPC-IR measurements, was used to deposit the eluent of GPC onto aluminum foil. Small strips of aluminum foil were cut and subjected to Py-GC-MS analysis. Compared with the GPC-IR measurements, the proposed technique offers the advantage of being able to distinguish between structurally similar monomers in a complex copolymer. As an example, a copolymer composed of four monomers was analyzed. The results clearly demonstrate that this technique can be applied to complex polymeric systems to yield information regarding chemical heterogeneity versus molecular weight.     

纳米ZnO薄膜的制备及其可见光催化降解甲基橙

采用溶胶-凝胶方法制备ZnO透明溶胶, 在铝箔上涂膜后经500 ℃处理制得具有可见光响应的纳米ZnO薄膜光催化剂. 以甲基橙模拟有机污染物, 在可见光下研究了薄膜的降解性能, 结果表明, 用一片有效面积为200 cm2的ZnO/Al薄膜作为催化剂, 甲基橙的降解率达到96.3％, 比ZnO负载在玻璃上制得的ZnO/glass薄膜催化剂活性高得多. 采用扫描电镜与原子力显微镜对ZnO/Al薄膜制备条件进行了表征, 结果发现多孔ZnO/Al薄膜比致密ZnO/Al薄膜具有更高的活性, 实验制备的具有高活性的ZnO/Al薄膜颗粒平均直径为52.2 nm. 采用本方法制备的ZnO/Al薄膜是一种具有应用前景的, 能在可见光下降解有机物的有效光催化剂.     

Simple and economical CALB/polyethylene/aluminum biocatalyst for fatty acid esterification

Candida antarctica lipase B was immobilized for the first time (at the author's knowledge) onto linear low density polyethylene (LLDPE) films. Polymer films were previously bonded to a commercial aluminum sheet using a simple support preparation method. Biocatalyst performance was evaluated in penthyl oleate synthesis at room temperature. Two different catalyst geometries were tested and compared: one aluminum‐polyethylene 50 mm × 50 mm foil (50CAT) or near 5 mm × 5 mm aluminum‐polyethylene foils (5CAT). The obtained results demonstrate that the biocatalyst obtained with 50 mm × 50 mm aluminum‐polyethylene foil or 50CAT is reusable in up to 7 cycles, easy to separate from reaction products, and economical in comparison with commercial Novozym 435. Novel and economical CALB/LLDPE/Al biocatalyst is an attractive alternative for possible applications in a continuous monolithic reactor and future industrial scaling up.     

Fe2+ Catalyzed Synthesis of Radiation Grafted Functional Membranes and Application in Fuel Cells and Ion Recovery

Summary: 1-Vinylimidazole is grafted onto Poly(ethylene-alt-tetrafluoroethylen (ETFE) by means of pre-irradiation technique with electron beam doses between 50 and 150 kGy. The degree of grafting is significantly increased to values of up to 115% by addition of 20-50 mmol/L of an Fe²⁺ salt that facilitates the decomposition of the peroxide structures within the irradiated films. The obtained mechanically stable and flexible ETFE-graft-poly(1-vinylimidazole) membranes exhibit a homogenous distribution of the graft polymer for degrees of grafting greater than 50 wt.-% and show thermal stability up to 250 °C. The applicability of these membranes as anhydrous proton conducting material when doped with phosphoric acid and the complexation capability for Cu²⁺ ions is demonstrated.     

涂碳铝箔对磷酸铁锂电池性能影响研究

本文研究了使用涂碳铝箔作为正极集流体磷酸铁锂电池的性能。研究对比了使用普通铝箔和涂层铝箔的10 Ah软包磷酸铁锂电池的主要性能。研究表明:使用涂层铝箔不但可以提高磷酸铁锂材料的粘结性,而且使用导电涂层可以有效降低正极材料和集流体的接触内阻,从而减小电池内阻,提高电池倍率性能。与使用普通铝箔作为集流体相比,通过使用涂碳铝箔可以使得电池的内阻降低65%左右,但是,磷酸铁锂正极材料的克容量却偏低约5~10 mAh·g-1,首次效率也偏低4%左右;在快速放电15C倍率下,使用涂碳铝箔的电芯比使用普通铝箔容量提高约15%左右,10C放电倍率下,平台增加0.3~0.4 V;使用涂碳铝箔电芯的常温自放电率较高,但容量恢复率也较高;550周循环下,使用涂碳铝箔可以使得电池的循环性能提高约1%。而在电池低温性能方面,使用涂碳铝箔对低温性能并无改善。     

Film formation with latex particles

The coalescence of latex particles is investigated through small-angle neutron scattering and electron microscopy. The particles are made of a soft polymeric core protected by a hydrophilic membrane, and they are dispersed in water. This dispersion is spread on a substrate, and water is removed to form a dry film. As the membranes of neighboring particles come into contact, they may break up to allow fusion of the particle cores. This is found to occur when the membranes are made of short-chain surfactant molecules; then all hydrophilic material is expelled to the film surface or to large isolated lumps. Alternatively, the membranes may remain until the film is completely dry; this is found to occur when they are made of hydrophilic polymers which are grafted onto the core. Hence, the fusion of particles is controlled by the connectivity of membranes.This work used the neutron beams of ILL in Grenoble and LLB in Saclay     

涂碳铝箔对磷酸铁锂电池性能影响研究

本文研究了使用涂碳铝箔作为正极集流体磷酸铁锂电池的性能。研究对比了使用普通铝箔和涂层铝箔的10 Ah软包磷酸铁锂电池的主要性能。研究表明：使用涂层铝箔不但可以提高磷酸铁锂材料的粘结性,而且使用导电涂层可以有效降低正极材料和集流体的接触内阻,从而减小电池内阻,提高电池倍率性能。与使用普通铝箔作为集流体相比,通过使用涂碳铝箔可以使得电池的内阻降低65%左右,但是,磷酸铁锂正极材料的克容量却偏低约5~10 mAh·g^-1,首次效率也偏低4%左右;在快速放电15C倍率下,使用涂碳铝箔的电芯比使用普通铝箔容量提高约15%左右,10C放电倍率下,平台增加0.3~0.4 V;使用涂碳铝箔电芯的常温自放电率较高,但容量恢复率也较高;550周循环下,使用涂碳铝箔可以使得电池的循环性能提高约1%。而在电池低温性能方面,使用涂碳铝箔对低温性能并无改善。     

Influence of cotton waste and flame-retardant additives on the mechanical,thermal, and flammability properties of phenolic novolac epoxy composites

Cellulose - Phenolic novolac-type epoxy (EPN) resin composites were fabricated by reinforcing with cotton waste (CtW), along with aluminum hydroxide (AH), and boric acid (BA) particles under...     

Dye-sensitized solar cells based on nanocrystalline TiO2 films surface treated with Al3+ ions: photovoltage and electron transport studies

Nanocrystalline TiO2 films, surface modified with Al3+, were manufactured by depositing a TiO2 suspension containing small amounts of aluminum nitrate or aluminum chloride onto conducting glass substrates, followed by drying, compression, and finally heating to 530 degrees C. Electrodes prepared with TiO2 nanoparticles coated with less than 0.3 wt % aluminum oxide with respect to TiO2 improved the efficiency of the dye sensitized solar cell. This amount corresponds to less than a monolayer of aluminum oxide. Thus, the Al ions terminate the TiO2 surface rather than form a distinct aluminum oxide layer. The aluminum ion surface treatment affects the solar cell in different ways: the potential of the conduction band is shifted, the electron lifetime is increased, and the electron transport is slower when aluminum ions are present between interconnected TiO2 particles.     

Nanostructured Ion-Selective MCM-48 Membranes

Templated MCM-48 silica was prepared using CTAB as surfactant. The MCM-48 powders and thin films were characterized by different techniques. MCM-48 layers were deposited on macroporous α-alumina supports and silicon nitride microsieves. The water permeability of MCM-48 was compared with the permeability of conventional mesoporous γ-alumina membranes. The applicability of MCM-48 as ion-selective electric field-driven switchable interconnect for microfluidic devices was demonstrated.