Performance of ferrite fillers on electrical behavior of polymer nanocomposite electrolyte

Dispersal of nanofillers in polymer electrolytes have shown to improve the ionic properties of Polyethylene oxide (PEO)-based polymer electrolytes in recent times. The effects of different nanoferrite fillers (i.e., Al–Zn ferrite, Mg–Zn ferrite, and Zn ferrite) on the electrical transport properties have been studied here on the composite polymer electrolyte system. The interaction of salt/filler with electrolyte has been investigated by XRD studies. SEM image and infrared spectral studies give an indication of nanocomposite formation. In conductivity studies, all electrolyte systems are seen to follow universal power law. Composition dependence (with ferrite filler) gives the maximum conductivity in [93PEO–7NH₄SCN]: X ferrite (where X?=?2% in Al–Zn ferrite, 1% Mg–Zn ferrite, and 1% Zn ferrite) system.     

Laser Doppler velocimeter using a single longitudinal mode solid-state laser source

An experimental demonstration of using a single longitudinal mode solid-state laser source in laser Doppler velocimeter (LDV) is presented. The technology of frequency spectrum correction is used in processing Doppler signal. The results of the experiments show that: the magnitude and signal-to-noise ratio (SNR) of Doppler signal are both enhanced by the solid-state laser; the measurement accuracy of LDV is improved by the technology of frequency spectrum correction, and the variance of the measured Doppler frequency is larger than the Cramer-Rao low bound (CRLB) of Doppler frequency about one order of magnitude.     

Li ion conduction in TiO2 filled polyvinylidenefluoride-co-hexafluoropropylene based novel nanocomposite polymer electrolyte membranes with LiDFOB

This paper describes, nanocomposite polymer electrolyte (NCPE) based on polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP), which comprises the novel lithium difluoro(oxalato)borate (LiDFOB). Ehtylene carbonate (EC) and diethyl carbonate (DEC) mixture was used as gelling agent and nanoparticulate TiO₂ used as filler. The NCPE membranes were subjected to a.c. impedance, tensile strength, Raman studies, TG/DTA and morphological studies. 5 wt% TiO₂ comprising membranes exhibited enhanced conductivity of 0.56 mS cm⁻¹and the Young’s modulus was increased from 1.32 to 2.74 MPa. The structural change of α to β phase was confirmed by Raman studies. The thermal stability of the NCPE membrane is found to be 130 °C. Calculation of activation energy and synthesis of LiDFOB has also been presented.     

3-D microbattery electrolyte by self-assembly of oligomers

This paper reports the preparation and characterization of novel thin film electrolytes by UV cross-linking of poly(propylene glycol) diacrylate in the presence of polyetheramine (glyceryl poly(oxypropylene)triamine) and LiTFSI. The oligomeric surfactant polyetheramine facilitates self-assembly of the electrolyte, enabling it to be applied conformally onto a complex substrate which is necessary for 3D-microbatteries, while the acrylate network supplies mechanical stability. Conformal coatings onto LiFePO₄ electrodes and Cu nanopillars were confirmed by SEM. Ionic conductivities of 3.5 × 10^− 6 and 5.8 × 10^− 5 S/cm were measured at room temperature and 60 °C, respectively, at Li:O = 1:20 and PEA:PPGDA = 2:1 ratios. The electrochemical stability window test showed that the electrolyte is stable above 5.0 V vs. Li/Li⁺. Thermal analyses by TGA and DSC demonstrated that the polymer electrolyte is amorphous and thermally stable up to 300 °C.     

Laser printing of enamels on tiles

A Nd:YAG laser beam is used as a tool to print patterns of coloured enamels on tile substrates. For this, the laser beam is scanned over a layer of raw enamel previously sprayed on the tile surface. The possibility to focus the laser energy to heat a small zone without affecting the rest of the piece presents some advantages in front of traditional furnace techniques in which the whole piece has to be heated; among them, energy saving and the possibility to apply enamels with higher melting temperatures than those of the substrate. In this work, we study the effects of laser irradiation of a green enamel, based in chromium oxide pigment and lead frit, deposited on a white tile substrate. Lines obtained with different combinations of laser beam power and scan speeds were investigated with the aim to optimize the process from the point of view of the quality of the patterns. For this purpose, the morphology of the lines and their cross-sections is studied. The results show that lines with good visual properties can be printed with the laser. The characteristics of the marked lines were found to be directly related with the accumulated energy density delivered. Moreover, there is a linear relationship between the accumulated energy density and the volume of melted material. A minimum accumulated energy density is required to melt a shallow zone of the glazed substrate to allow the adhesion of the enamelled lines.     

Laser welding of thin polymer films to container substrates for aseptic packaging

Keyhole laser welding of polymers is a subject well covered and researched, but relatively little information exists regarding the welding of thin polymer films, particularly to a heavier substrate. This paper presents the design of a suitable test apparatus for laser welding thin film to a heavier substrate, and shows the results of an investigation into the feasibility of laser welding multi-layer polymer film lids to tubs for the manufacture of aseptic food containers. A consistent weld, free from defects, is the key to process success. Typical welding defects have been synthesised in order to investigate, and consequently remove, their cause. The result is a reliable welding method based on even film clamping. With careful attention to machine design, a seal of high mechanical strength and chemical integrity is possible.     

Noise characteristic of sum-frequency mixing orange solid-state laser

A laser-diode-pumped Nd:YVO₄ orange solid-state laser is described in this paper. The fundamental wavelengths at 1064 and 1342 nm oscillate simultaneously and generate the 593.5 nm wavelength by intracavity sum-frequency mixing in a KTP crystal using type II phase matching. The noise characteristic of laser output has been measured and analyzed at different pumping powers. The relationship between the amplitude noise of sum-frequency mixing output and the longitudinal modes of fundamental frequency has been investigated. The results show that the sum-frequency mixing output has low noise if one of the fundamental wavelengths is single longitudinal mode. The experiment shows that amplitude noise of the intracavity sum-frequency mixing laser is lower than that of intracavity frequency doubled laser with the same structure.     

Preparation and characterization of the polymer electrolyte system ENR50/PVC/EC/PC/LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript> for electrochemical device applications

Polymer electrolytes containing epoxidised natural rubber (ENR50)/poly(vinyl chloride) (PVC) blend as a polymer host, a solvent mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and lithium imide, LiN (CF₃SO₂)₂, as a salt were studied. Polymer electrolytes that were obtained by solvent cast yielded solid dry rubbery films with a thickness range of 110–125 μm. Impedance spectroscopy, Fourier transform infra red (FTIR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were performed on these samples. The prepared solid polymer electrolytes exhibit ionic conductivities in the order 10⁻⁴ S cm⁻¹ at room temperature as expected. However, the physical properties of the electrolytes have improved significantly when optimal composition has been selected. Paper presented at the International Conference on Solid State Science and Technology 2006, Kuala Terengganu, Malaysia, Sept. 4–6, 2006.     

Biodegradable nanocomposite magnetite stent for implant-assisted magnetic drug targeting

This study shows, for the first time, the fabrication of a biodegradable polymer nanocomposite magnetic stent and the feasibility of its use in implant-assisted-magnetic drug targeting (IA-MDT). The nanocomposite magnetic stent was made from PLGA, a biodegradable copolymer, and iron oxide nanopowder via melt mixing and extrusion into fibers. Degradation and dynamic mechanical thermal analyses showed that the addition of the iron oxide nanopowder increased the polymer’s glass transition temperature (T_g) and its modulus but had no notable effect on its degradation rate in PBS buffer solution. IA-MDT in vitro experiments were carried out with the nanocomposite magnetic fiber molded into a stent coil. These stent prototypes were used in the presence of a homogeneous magnetic field of 0.3 T to capture 100 nm magnetic drug carrier particles (MDCPs) from an aqueous solution. Increasing the amount of magnetite in the stent nanocomposite (0, 10 and 40 w/w%) resulted in an increase in the MDCP capture efficiency (CE). Reducing the MDCP concentrations (0.75 and 1.5 mg/mL) in the flowing fluid and increasing the fluid velocities (20 and 40 mL/min) both resulted in decrease in the MDCP CE. These results show that the particle capture performance of PLGA-based, magnetic nanocomposite stents are similar to those exhibited by a variety of different non-polymeric magnetic stent materials studied previously.     

Laser polymerization-based novel lift-off technique

The fabrication of microstructures by two-photon polymerization has been widely reported as a means of directly writing three-dimensional nanoscale structures. In the majority of cases a single point serial writing technique is used to form a polymer model. Single layer writing can also be used to fabricate two-dimensional patterns and we report an extension of this capability by using two-photon polymerization to form a template that can be used as a sacrificial layer for a novel lift-off process.A Ti:sapphire laser, with wavelength 795 nm, 80 MHz repetition rate, 100 fs pulse duration and an average power of 700 mW, was used to write 2D grid patterns with pitches of 0.8 and 1.0 μm in a urethane acrylate resin that was spun on to a lift-off base layer. This was overcoated with gold and the grid lifted away to leave an array of gold islands.The optical transmission properties of the gold arrays were measured and found to be in agreement with a rigorous coupled-wave analysis simulation.     

Effect of hot pressing on the ionic conductivity of the PEO/LiCF3SO3 based electrolyte membranes

PEO/LiCF₃SO₃ (LiTFS) /Ethylene carbonate (EC) polymer electrolyte membranes were prepared with a solution casting method followed by a hot pressing process. The effect of the hot pressing process on the in-plane conductivity of the PEO electrolyte membranes was evaluated using a four-electrode AC impedance method. The composition, morphology, and microstructure of the composite polymer electrolyte were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The AC impedance measurement results indicate that the hot pressing process can increase the room temperature conductivity of the membranes 14 times to 1.7 × 10^− 3 S cm^− 1 depending upon the duration of the hot pressing process. The SEM, FTIR, XRD, and DSC results indicate that the hot pressing process could increase the amorphous part of the polymer electrolyte membrane or convert large spherulite crystals into nano-sized crystals.     

Laser ablation of multilayers of ink from a paper substrate for tactile printing

This paper reports the effects of laser ablation upon multiple-layered coloured inks which have been printed on an ordinary white paper. The aim of this work is to examine the feasibility of generating a fully tactile three-coloured image by selectively removing ink layers to reveal underlying layers of a different colour. In this paper laser ablation has been carried out upon four layered ink samples consisting of white/cyan/white/black layers. Ablation was carried out using a Q-switched Nd : YAG laser. The results show that it is possible to selectively remove the inks to expose both the top white and the cyan layers, although charring occurs with deeper ablation. An evaporation/decomposition mechanism is proposed to describe process of ink ablation.     

Effect of gamma irradiation on the polymer electrolyte PEO-NH4ClO4

Irradiation affects the structures of materials at different scales, thus changing physical and chemical properties. We study here the effect of gamma irradiation at different doses on the polymer electrolyte PEO-NH₄ClO₄. Optical micrographs show cracks in the irradiated samples and impedance spectroscopy measurements indicate reduced ion-conductivity at room temperature but slight enhancement at higher temperature. At high frequencies, the real part of the admittance shows a power-law variation; the exponent, which is a measure of self-similarity of the structure, is reduced on irradiation. The overall results point to a more disordered structure at higher radiation doses.     

Studies on poly(vinylidene fluoride-co-hexafluoropropylene) based gel electrolyte nanocomposite for sodium-sulfur batteries

Experimental investigations on a sodium ion conducting gel polymer electrolyte nanocomposite based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with silica nanoparticles are reported. The gel nanocomposites have been obtained in the form of dimensionally stable, transparent and free-standing thick films. Physical characterization by X-ray diffraction (XRD), Fourier transform Infra-red (FTIR) spectroscopy and Scanning electron microscopy (SEM) have been performed to study the structural changes and the ion-filler-polymer interactions due to the dispersion of SiO₂ nanoparticles in gel electrolytes. The highest ionic conductivity of the electrolyte has been observed to be 4.1 × 10⁻³ S cm^− 1 at room temperature with ~ 3 wt.% of SiO₂ particles. The temperature dependence of the ionic conductivity has been found to be consistent with Vogel-Tammen-Fulcher (VTF) relationship in the temperature range from 40 to 70 °C. The sodium ion conduction in the gel electrolyte film is confirmed from the cyclic voltammetry, impedance analysis and transport number measurements. The value of sodium ion transport number (t_Na+) of the gel electrolyte is significantly enhanced to a maximum value of 0.52 on the 15 wt.% SiO₂ dispersion. The physical and electrochemical analyses indicate the suitability of the gel electrolyte films in the sodium batteries. A prototype sodium-sulfur battery, fabricated using optimized gel electrolyte, offers the first discharge capacity of ~165 mAh g^− 1 of sulfur.     

Laser Raman Spectrum of Triglycine Sulfate

Abstract

The laser Raman spectrum of ferroelectric triglycine sulfate has been determined by the use of an argon ion gas laser. The observed Raman lines are compared with reported assignments in the literature by Taurel¹ and Krishnan², Determination of depolarization ratio of the sulfate line at 980 cm^?1 shows that the Raman band is highly polarizable and the molecular vibration is totally symmetrical v₁.

The role played by the glycine groups in the spontaneous polarization and its reversal can be indirectly confirmed by Raman spectrum of TGS. Interpretation of the Raman spectrum indicates that the SO₄ groups do not have tetrahedral symmetry at roan temperature. Ferroelectric behavior of TGS is attributed to the glycine groups.     

Fuel quality and operational issues for polymer electrolyte membrane (PEM) fuel cells

Polymer electrolyte membrane (PEM) fuel cells are susceptible to degradation due to the catalyst poisoning caused by CO present in the fuel above certain limits. Although the amount of CO in the fuel may be within the permissible limit, the fuel composition (% CO₂, CH₄, CO and H₂O) and the operating conditions of the cell (level of gas humidification, cell temperature and pressure) can be such that the equilibrium CO content inside the cell may exceed the permissible limit leading to a degradation of the fuel cell performance. In this study, 50 cm² active area PEM fuel cells were operated at 55–60 °C for periods up to 250 hours to study the effect of methane, carbon dioxide and water in the hydrogen fuel mix on the cell performance (stability of voltage and power output). Furthermore, the stability of fuel cells was also studied during operation of cells in a cyclic dead end / flow through configuration, both with and without the presence of carbon dioxide in the hydrogen stream. The presence of methane up to 10% in the hydrogen stream showed a negligible degradation in the cell performance. The presence of carbon dioxide in the hydrogen stream even at 1–2% level was found to degrade the cell performance. However, this degradation was found to disappear by bleeding only about 0.2% oxygen into the fuel stream.     

Laser microstructuring and annealing processes for lithium manganese oxide cathodes

It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (Li-Mn-O) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the Li-Mn-O system were synthesized by non-reactive radiofrequency magnetron sputtering of a spinel lithium manganese oxide target. For the enhancement of the power density and cycle stability, large area direct laser patterning using UV-laser radiation with a wavelength of 248 nm was performed. Subsequent laser annealing processes were investigated in a second step in order to set up a spinel-like phase using 940 nm laser radiation at a temperature of 680 °C. The interaction processes between UV-laser radiation and the material was investigated using laser ablation inductively coupled plasma mass spectroscopy. The changes in phase, structure and grain shape of the thin films due to the annealing process were recorded using Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The structured cathodes were cycled using standard electrolyte and a metallic lithium anode. Different surface structures were investigated and a significant increase in cycling stability was found. Surface chemistry of an as-deposited as well as an electrochemically cycled thin film was investigated via X-ray photoelectron spectroscopy.     

Effect of storage time on the properties of PVA–KOH alkaline solid polymer electrolyte system

Polyvinyl alcohol (PVA) and potassium hydroxide (KOH) have been used to prepare alkaline solid polymer electrolytes (ASPE) films. The films were stored in a dry environment for 30 and 100 days. The highest room temperature conductivity for the PVA:KOH film with weight percentage ratio of 1:0.67 during storage for 30 and 100 days were (8.5±0.2)×10⁻⁴ and (1.3±0.1)×10⁻⁷ S cm⁻¹, respectively. The conductivity–temperature behaviour after 30 and 100 days of storage of the alkaline polymer electrolytes is Arrhenian and liquid-like. The structural, morphological and thermal studies of the ASPE films are also presented in this paper.     

Micro-patterning for polymer electrolyte fuel cells: Single pulse laser ablation of aluminum films from glassy carbon

Microfuel cells are a possible replacement for batteries as energy sources in portable devices. At PSI a micropolymer electrolyte fuel cell was developed, whose flow fields consist of micro-structured glassy carbon plates. Micro-structuring of glassy carbon is carried out in a multi-step process. A sputtered aluminum mask is selectively removed by single pulse laser ablation from glassy carbon thereby defining micro-channels subsequently etched by reactive ion etching.A pulsed XeCl excimer laser (308 nm) is used for the single pulse patterning of a metal mask on the glassy carbon. The influence of the excimer laser typical pulse to pulse energy fluctuations on the micro-structuring process must be known to minimize defects during RIE etching of the micro-channels. To obtain a better understanding of the processes occurring during ablation, ns-shadowgraphy was performed. The formation of a shockwave was observed, followed by a similar but much slower perturbation, and the subsequent release of fragments. The calculated velocities can be correlated with the energy release during ablation. The post-ablation examination of the samples by profilometry, optical microscopy, SEM and EDX is used to measure the amount of removed material, the quality of the aluminum mask edges and aluminum residues on the glassy carbon surface. Such criteria allow us to classify the laser irradiation as a function of laser fluence: no ablation, partial ablation, complete ablation, and over-ablation.     

Depolarization loss compensated resonator for electro-optic Q-switched solid-state laser

A novel laser resonator for compensating depolarization loss that is due to thermally induced birefringence in active rod is reported. As this new structure being applied to an electro-optic Q-switched LDA side-pumped Nd:YAG laser operating at a repetition rate of 1000 Hz, substantial reduction in depolarization loss has been observed, the output pulse energy is improved about 56% from that of a traditional resonator without compensation structure. With incident pump energy of 450 mJ per pulse, linearly polarized output energy of 30 mJ per pulse is achieved, the pulse duration is less than 15 ns, and the peak power of pulse is about 2 MW. The extinction ratio of laser beam is better than 10:1, and the beam divergence is 1.3 mrad with beam diameter of around 2.5 mm.