Narrow electrodes on YZ-LiNbOO3 as an alternative to etched grooves for dispersive delay lines

Narrow, open-circuited aluminum electrodes can provide controllable, weak reflectivity necessary for many applications such as surface acoustic wave (SAW) tags and dispersive delay lines (DDLs). We show, using finiteand boundary element method (FEM-BEM) based simulations and experiments, that a reflectivity of 0.3% per wavelength can be achieved easily and controlled by varying the electrode width.     

Iron-based composite oxides as alternative negative electrodes for lithium-ion batteries

Nanosized lithiated iron oxides with 10 and 50 wt.% SiO₂ were prepared by a sol–gel method using 1 M Fe(NO₃)₃ · 9H₂O and 1 M LiNO₃ aqueous solutions in a stoichiometric ratio of 1:1 and colloidal silica. Dried xerogel was calcinated at 700 °C for 4 h in air. The X-ray data of samples synthesized using 10% and 50% SiO₂ showed the presence of a mixture of two phases: α-LiFeO₂ and Li_1−x Fe₅O₈ (0 < x ≤ 0.1) for a sample containing 10% SiO₂ and LiFe(SiO₃)₂ and Fe₂O₃ (h) for a sample with 50% SiO₂. The electrochemical behaviour of the compounds was investigated galvanostatically within the 0.01–3.0 V range at a current density of 0.80 mA cm⁻². The Li/Li _x Fe _y O _z (10%) · SiO₂ cell showed a high initial reversible capacity of 1,080 mA h g⁻¹ and a capacity of 600 mA h g⁻¹ at the 30th cycle. Accounting these results is the presence of a SiO₂ phase which stabilizes the structure of the active mass on cycling. The mean charge voltage (1.8 V) and the discharge voltage of 1.0 V versus Li⁺ reference electrode as well as the high reversible capacity indicate that this material is suitable for use as anode in lithium-ion batteries.     

Pt nanowire electrodes electrodeposited in PVP for methanol electrooxidation

We report Pt nanowire electrodes fabricated by means of electrodeposition method as a function of molecular weight of polyvinylpyrrolidone (PVP-L and PVP-H). The higher molecular weight of PVP results in a smaller grain size of Pt nanophases in the electrode. The Pt nanowire array electrode electrodeposited with PVP-H shows the smallest gain size of Pt and an excellent catalytic activity for methanol electrooxidation in comparison with pure Pt nanowire array electrodes electrodeposited without PVP and with PVP-L.     

Pt nanostructure electrodes pulse electrodeposited in PVP for electrochemical power sources

In this work, we demonstrated that Pt nanostructure electrodes could be obtained by the pulse electrodeposition method in polyvinylpyrrolidone (PVP). The nanocrystal particles were confirmed by scanning electron microscopy, transmission electron microscopy and x-ray diffraction methods. The average size of Pt nanoparticles deposited in additive PVP with low and high molecular weight is 3.4 and 2.9?nm, respectively, whereas that of Pt electrodeposited without PVP is 360?nm. This means that the size of Pt nanoparticles can be controlled by PVP, resulting in an increased electrochemical surface area. The resulting Pt nanostructure electrodes showed such an improved performance for both direct methanol fuel cells and dye-sensitized solar cells.     

多壁碳纳米管改性铂型IPMC的试验研究

将一种全氟磺酸树脂(Nafion)与多壁碳纳米管(MWCNTs)分别按质量比100:1、 100:3、 100:5进行配比, 采用溶剂浇铸法配合超声波分散法制备MWCNTs/Nafion型离子交换膜(IEM), 在此基础上利用化学沉积法制备铂型离子聚合物金属复合材料(Pt-IPMC), 考察三种MWCNTs负载量对IEM及Pt-IPMC性能的影响。采用SEM配合EDAX研究Pt的沉积效果, 对IEM及Pt-IPMC试样进行拉伸测试, 采用数字信号发生器为激励源测试Pt-IPMC的动态位移。结果表明: 添加MWCNTs使Pt-IPMC的内、 外电极厚度分别增加200%~250%和180%~200%, 使IEM及Pt-IPMC的弹性模量分别提高57.92%~140.85%和9.06%~52.85%; MWCNTs有效修饰了Pt-IPMC的内电极, 并明显提升其动态位移量、 动态响应及变形速度。     

Purification of catalytically produced carbon nanotubes for use as support for fuel cell cathode Pt catalyst

A purification method based on HCl treatment under reflux was employed for purification of carbon nanotube (CNT) samples, obtained by the electric discharge method utilizing Zr(Co_0.5Ni_0.5)₂, Ce₃(Co_0.5Ni_0.5)₂ and Ce(Co_0.5Ni_0.5)₅ as catalysts. Raman Spectroscopy provided information on the SWCNT presence in the untreated samples. Scanning Electron Microscopy (SEM) showed CNT with different diameters and lengths. Different acid treatment conditions were employed and the best results were achieved for HCl 3 mol/L aqueous solution during 24 h reflux. Transmission Electron Microscopy (TEM) images, associated with EDS, revealed the catalyst removal from the original sample and the presence of other carbon structures near the CNT formation. CNT acid functionalization for Pt nanoparticles dispersion was successful, resulting in a homogeneously dispersed system, as seen in TEM images. Temperature Programmed Oxidation (TPO) analysis of the raw and purified samples indicated that after purification there are three different carbon species present on the purified material, each one showing a different behavior towards O₂ oxidation.     

Pervaporation as an alternative to headspace

The use of pervaporation as an alternative to headspace is proposed. The analytical system involves the speciation of organomercury compounds in solid samples using pervaporation, which has been coupled for the first time to gas chromatography. The speciation of mercury as Me(2)Hg, Et(2)Hg, and MeHgCl has been carried out without any derivatization of the analytes, which, after separation from the solid matrix, are preconcentrated on a Tenax minicolumn prior to desorption and chromatographic separation on a semicapillary column (HP-1) prior to atomic fluorescence detection. No column degradation was observed. Linear ranges and detection limits slightly better than those obtained by headspace GC were observed for mercury species in solid samples. Excellent recoveries (between 95 and 107%) for mercury species added to complex solid samples were obtained by this extremely simple and easily automated setup.     

Graphene as an anti-permeation and protective layer for indium-free transparent electrodes

We show that graphene can be used as a protective layer for transparent electrodes made of materials which would otherwise deteriorate when exposed to the environment. In particular, we investigate aluminum-doped zinc oxides and ultrathin copper films capped with a one-atom graphene layer in damp heat (95% relative humidity and 95?°C) and high temperature (up to 180?°C) conditions. The results clearly indicate that a graphene layer can strongly reduce degradation of the electrodes' electrical, optical properties and surface morphology, thus preserving the functionality of the transparent electrodes. The proposed technique is particularly suitable for flexible optoelectronic devices thanks to the mechanical strength of graphene when subjected to bending.     

UF as an alternative pretreatment step for producing drinking water

This article describes membrane research which focuses on exploring the use of open ultrafiltration as an alternative to conventional separation technologies used for producing drinking water. Four different water types, originating from three water sources, are investigated. Four open ultrafiltration membranes are used, of which three are of a hollow-fibre configuration while one is tubular. On the one hand it was found that permeate quality was always very good, compared with conventional techniques — no bacteria, suspended solids or turbidity were present. Moreover, the quality was independent of operational conditions or the membrane type. On the other hand, it was found that operational conditions strongly differ in terms of ‘raw’ water quality, or the membrane type used.     

Ionic liquids as an attractive alternative solvent for thermal lens measurements

The use of ionic liquids (ILs) as a solvent for thermal lens measurements has been investigated. It was found that ILs provide a better medium for thermal lens measurements than water. Specifically, not only the ILs offer at least 20 times higher sensitivity than water but that the enhancement can be appropriately adjusted by changing either the cation or the anion of the ILs. For example, the sensitivity in [BMIm]+[Tf2N]- is approximately 26 times higher than in water. It can be increased up to 31 times by changing the anion to [PF6]- (i.e., [BMIm]+[PF6]-) or to 35 times by changing the cation to [OMIm]+ (i.e., [OMIm]+[Tf2N]-). In fact, the sensitivity of thermal lens measurements in ILs is comparable to those in volatile organic solvents such as benzene, carbon tetrachloride, and hexane. However, the ILs are more desirable as they have virtually no vapor pressure. Furthermore, additional sensitivity enhancement (up to 42 times higher than that in water) can be achieved by simply adding surfactants into the ILs. Based on the thermal conductivity (k) and dn/dT values, calculated from the measured thermal time constant tc and thermal lens strength theta, it is evident that the observed sensitivity enhancement by the ILs is due to their relatively better thermooptical properties. More specifically, the enhancement is due not to the relatively modest lowering of the thermal conductivity but rather to the substantial increase in their dn/dT values. Because of the relationship between dn/dT and drho/dT, it is expected that ILs can serve as an attractive and superior solvent not only for thermal lens measurements but also for other photothermal and photoacoustic techniques as well. Also equally important is the fact that the thermal lens technique in particular and photothermal techniques, in general, can offer a unique means to determine themooptical and thermal physical properties of the ILs (e.g., thermal conductivity, thermal diffusivity, and phase transition temperatures). This type of data is currently lacking but is of extreme importance for implementing ILs as a solvent in various industrial applications.     

The Path Tracking Method as an alternative for tortuosity determination in granular beds

Tortuosity is one of the most elusive parameters of porous media. The fundamental question is whether it may be computed from the geometry only or the transport equations must be solved first. Elimination of the transport equations would significantly decrease the computation time and memory consumption and thus allow investigating larger samples. We compare the geometric to hydraulic tortuosity of a sphere-packed porous media. We applied the Discrete Element Method to generate a set of virtual beds based on experimental data taking into account the real porosity and particle distribution, the Lattice Boltzmann Method to compute the hydraulic tortuosity and geometrical approach, i.e. so-called Path Tracking Method, to calculate the geometrical tortuosity. Our study shows that the calculation time can be reduced from hours (if the LBM is used) to seconds (if the PTM is applied) without losing the accuracy of the final results. The relative error between average values of the tortuosity obtained for both used methods is less than 3%. We show that the applied geometrical method may serve as an attractive alternative to hydraulic tortuosity, particularly in large granular systems.     

Pt/AlPO4 nanocomposite thin-film electrodes for ethanol electrooxidation

The enhanced catalytic properties toward ethanol electrooxidation on Pt/AlPO₄ nanocomposite thin-film electrodes were investigated. The Pt/AlPO₄ nanocomposites with various Al/Pt ratios (0.27, 0.57, and 0.96) were fabricated by a co-sputtering method. All of the Pt/AlPO₄ nanocomposites showed a negative shift in the onset potential and a higher current density than those of pure Pt electrode for the electrooxidation of ethanol. Among the various Pt/AlPO₄ nanocomposite thin-film electrodes, the electrode with an atomic ratio of Al to Pt of 0.57 showed the highest electrocatalytic activity for ethanol electrooxidation. The activation enthalpy for the optimum Pt/AlPO₄ nanocomposite was approximately 0.05 eV lower than that of pure Pt. It is believed that the enhancement in catalytic activity is due to the electron-rich Pt resulting from the Fermi-energy difference between Pt and AlPO₄.     

A response-modeling alternative to surrogate models for support in computational analyses

Often, the objectives in a computational analysis involve characterization of system performance based on some function of the computed response. In general, this characterization includes (at least) an estimate or prediction for some performance measure and an estimate of the associated uncertainty. Surrogate models can be used to approximate the response in regions where simulations were not performed. For most surrogate modeling approaches, however, (1) estimates are based on smoothing of available data and (2) uncertainty in the response is specified in a point-wise (in the input space) fashion. These aspects of the surrogate model construction might limit their capabilities.One alternative is to construct a probability measure, G(r), for the computer response, r, based on available data. This “response-modeling” approach will permit probability estimation for an arbitrary event, E(r), based on the computer response. In this general setting, event probabilities can be computed: prob(E)=∫_rI(E(r))dG(r) where I is the indicator function. Furthermore, one can use G(r) to calculate an induced distribution on a performance measure, pm. For prediction problems where the performance measure is a scalar, its distribution F_pm is determined by: F_pm(z)=∫_rI(pm(r)z)dG(r). We introduce response models for scalar computer output and then generalize the approach to more complicated responses that utilize multiple response models.     

Method for preparing highly dispersed Pt catalysts on mesoporous carbon support

Two Pt catalysts supported on template-synthesized mesoporous carbons (MC) were prepared by the conventional wet-impregnation method (Pt-impreg/MC) and by the less commonly used colloidal deposition method (Pt-coll/MC) to examine the effect of preparation method on catalyst performance. The catalysts were characterized by transmission electron microscopy, field-emission electron microscopy, thermogravimetric analysis and X-ray diffraction. The electro-oxidation of methanol in acidic solutions for direct methanol fuel cells at room temperature was used as the test reaction. CO anodic stripping voltammetry and cyclic voltammetry both recorded enhanced performance for Pt-coll/MC relative to Pt-impreg/MC. The poorer application performance of Pt-impreg/MC can be attributed to the transport resistance in the mesopores, and to the entrapment of a sizable fraction (40%) of Pt nanoparticles in the mesopores which are not readily accessible to the reactants under the reaction conditions.     

Nonionic surfactant-templated mesoporous carbon as an electrocatalyst support for methanol oxidation

Two carbons were synthesized for use as platinum electrocatalyst supports for methanol oxidation. For both materials, furfuryl alcohol was used as the carbon precursor; however, one (CPEG) was made using poly ethylene glycol as the pore former, while the other (CSRF) was produced using Pluronic^® F127 as the soft template by organic–organic self-assembly. The CPEG and CSRF carbons were estimated from nitrogen physisorption experiments to be micro- and mesoporous, respectively. Platinum nanoparticles were deposited on each carbon as well as on Vulcan XC-72 carbon by the formic acid reduction method. The physicochemical properties of electrocatalysts were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX), and their electrochemical features were examined using cyclic voltammetry, chronoamperometry, and impedance spectroscopy. It was found that higher methanol oxidation peak current densities as well as lesser charge transfer resistance at electrode/electrolyte interface were obtained for Pt supported on CSRF as compared to those on Vulcan XC-72 carbon, owing to the higher specific surface area and larger total pore volume (696 m² g⁻¹ and 0.60 cm³ g⁻¹, respectively) together with superior electrical conductivity of mesoporous CSRF. On the other hand, the lower surface area and pore volume of microporous CPEG substrate confined Pt nanoparticles deposition and thus made CPEG-supported Pt an inefficient methanol oxidation electrocatalyst.     

Fog water as an alternative and sustainable water resource

As the world’s population and demand for fresh water increases, new water resources are needed. One commonly overlooked aspect of the water cycle is fog, which is an important part of the hydrology of coastal, high-altitude, and forested regions. Fog water harvesting is being investigated as a sustainable alternative water resource for drinking water and reforestation. Fog water harvesting involves using mesh nets to collect water as fog passes through them. The materials of these nets, along with environmental factors such as wind speed, influence the volume of water collected. In this article, a review of current models for fog collection, designs, and applications of fog water harvesting is provided. Aspects of fog water harvesting requiring further research and development are identified. In regions with frequent fog events, fog water harvesting is a sustainable drinking water resource for rural communities with low per capita water usage. However, an analysis of fog water harvesting potential for the coastal areas of northern California (USA) showed that fog yields are too small for use as domestic water in areas with higher household water demands. Fog water shows particular promise for application in reforestation. Fog water irrigation can increase growth rates and survivability of saplings in reforestation efforts in regions with frequent fog events. Using fog collectors, denuded areas once dependent on natural fog drip can be restored, benefiting local hydrology and ecosystem recovery. Improvement in fog collector designs, materials, and models to increase collection efficiency, perhaps by inclusion of ideas from natural systems, will expand the regions where fog harvesting can be applied.     

Lipophilic lanthanide tris(beta-diketonate) complexes as an ionophore for Cl- anion-selective electrodes

A series of novel anion-selective electrodes were developed by incorporating lipophilic lanthanide tris(beta-diketonates) into plasticized poly(vinyl chloride) membranes. The new electrodes exhibited high selectivity toward Cl(-) anion in the concentration range of Cl(-) anion between 1.0 x 10(-5) and 1.0 x 10(-1) mol/L with near-Nernstian slopes and practically low detection limits. They offered non-Hofmeister anion selectivity, and interestingly discriminated Cl(-) anion from NO(3)(-), ClO(4)(-), and other anions. Since the employed lanthanide tris(beta-diketonates) were confirmed to form 1:1 highly coordinated complexes with Cl(-) anion, the observed high selectivity for Cl(-) anion was attributed to the characteristics of lanthanide coordination chemistry. All the prepared sensors worked well at neutral pH with quite short response time, <30 s, and could be used for longer than four months without any significant divergence in performance.     

Emulsion/solvent evaporation as an alternative technique in pellet preparation

Paracetamol/Eudragit RS, paracetamol/ethylcellulose, and paracetamol/cellulose acetate pellets of different drug/polymer ratios (w/w) were prepared by the dissolution/solvent evaporation technique. These pellets were then characterized by particle size distribution analysis, ultraviolet (UV) spectroscopy, differential thermal analysis, and scanning electron microscopy (SEM). Hard gelatin capsules were filled with each particle size fraction of these pellets, and in vitro dissolution studies were performed to verify the capability of each series of pellets to control drug release. Pellets were spherical, presented a polynucleated microcapsule structure, and under certain experimental conditions, the yield of the preparation process reached very high values. The dissolution studies pointed out the slow paracetamol release from these pellets.     

Hollow spherical nanocapsules of poly(pyrrole) as a promising support for Pt/Ru nanoparticles based catalyst

Poly(pyrrole) hollow spherical nanocapsules (HSNCs-PPy) were prepared and used as an efficient support matrix to PtRu nanoparticles. γ-Radiation was utilized to load PtRu nanoparticles into Ppy-HSNC matrix. The advantageous characteristics of HSNCs-Ppy/PtRu catalyst as a support matrix for loading PtRu catalysts are presented.