A study of the processing characteristics and mechanical properties of multiple recycled rigid PVC

This study focuses on the ability of U‐PVC to be processed a number of times. Three different types of U‐PVC were investigated: virgin lead‐stabilized material; virgin calcium/zinc‐stabilized material; and reground, 20‐year‐old, post‐consumer windows. Each material was extruded four times, without any addition of any stabilizers. Samples were taken at each stage for rheological and mechanical analysis. J. Vinyl Addit. Technol. 10:174–178, 2004. © 2004 Society of Plastics Engineers.     

Phosphorylated cation‐exchangers from cotton stalks and their constituents

Cation‐exchangers were prepared by phosphorylation of cotton stalks and their isolated constituents (lignin, soda‐anthraquinone pulp, and bleached cellulose pulp). FTIR spectra of the phosphorylated materials showed new absorption bands at 950–1200 cm^?1 of the C? O? P bonds as a result of phosphorylation. The adsorption of different heavy metal ions (lead, copper, nickel, cobalt, chromium, and cadmium) at different metal ion concentrations (50–1500 μg) by the phosphorylated cotton stalks was studied. The adsorption of metal ions by the phosphorylated cotton stalks increased by increasing their concentration. The binding capacity of phosphorylated cellulose, lignin, and soda‐anthraquinone pulp was measured at 1000 μg metal ion concentration. The adsorption of the different heavy metal ions by phosphorylated‐lignin and ‐bleached cellulose pulp was higher than that of phosphorylated cotton stalks. Thermogravimetric analysis of the raw and phosphorylated cotton stalks showed that the resistance of the phosphorylated cotton stalks to thermal degradation was higher than that of raw cotton stalks (lower rate of weight loss), despite the lower degradation onset temperature of the phosphorylated cotton stalks. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2950–2956, 2003     

Reaction Time and Film Thickness Effects on Phase Formation and Optical Properties of Solution Processed Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> Thin Films

Copper-zinc-tin-sulfide (Cu₂ZnSnS₄ or CZTS) is a promising p-type semiconductor material as absorber layer in thin film solar cells. The sulfides of copper and tin as well as zinc and sulfur powders were dissolved in hydrazine. The effect of chemical reaction between precursor species, at room temperature, was assessed for 6 to 22 h. For 22 h reaction time, the effect of spin coated film thickness on the resulting composition, after annealing under N₂ flow at 500 °C for 1 h, was investigated. The morphology, composition, and optical properties of the annealed films were determined by means of x-ray diffraction, scanning electron microscope, and spectrophotometer studies. It was found that, for less than optimal reaction time of 22 h or film thickness below 1.2 µm, other ternary phases namely Cu₄SnS₄, Cu₅Sn₂S₇, and ZnS co-exist in different proportions besides CZTS. Formation of phase-pure CZTS films also exhibited a tendency to minimize film cracking during annealing. Depending on the processing conditions, the band gap (E _g) values were determined to be in the range of 1.55 to 1.97 eV. For phase-pure annealed CZTS film, an increase in the E _g value may be attributed to quantum confinement effect due to small crystallite size.     

Application of adaptive Lyapunov-based UPFC supplementary controller by neural network algorithm in multi-machine power system

In this paper, a new adaptive unified power flow controller (UPFC) based on the Lyapunov method and neural network structure is presented. The corresponding energy function is derived for the single machine infinitive bus system with classic generator model representation. Damping control strategy to improve transient behavior of the system is determined by considering the dynamic modeling of the UPFC. The Lyapunov-based controller is extended to interconnected power system by considering the two-machine equivalent model and the center of inertia concept. The recurrent neural network (RNN) with back propagation algorithm is also used to overcome the uncertainty issues and also to consider the more detailed power system. The designed Lyapunov-RNN-based controller is applied to the interconnected power system between the Esfahan–Yazd region transmission network in Iran power system. The performance of the proposed controller is compared with other different controllers by applying some disturbances in the system. Finally, simulation results are presented and the effectiveness of the proposed method for power system stability enhancement is discussed as well.     

Synthesis and Characterization of Anionic Polymeric Surfactants Based on Sulfonated Styrene

A novel series of three anionic polymeric surfactants was prepared by polymerization of sulfonated styrene and allyl esters of long chain fatty acid chlorides (decanoyl, lauroyl and palmitoyl chloride). The unique structural features of these surfactants were confirmed by different spectroscopic tools (IR and H-NMR). The surface properties of these compounds such as surface tension, interfacial tension, emulsion stability, wetting power, foam height, solubilization and dispersant properties in disperse dye systems were determined and evaluated. A comparative study was done between the chemical structures and surface properties of these compounds. Biodegradability and stability to hydrolysis in acidic and alkaline medium were also determined and evaluated.     

Temperature dependence of electrical resistivity and dielectric characteristics of poled and BaZrO3 modified BaTiO3 ceramics

Samples of pure BaTiO₃, pure BaZrO₃ and intermediates containing from 5 up to 30% BaZrO₃ were carefully prepared by the usual ceramic procedure followed by X-ray diffraction analysis to ensure the complete reaction. Well sintered and translucent ceramic bodies were obtained. Measurements of dielectric constant (?), dielectric loss (tan δ) and a.c. resistivity (?) were undertaken as a function of temperature up to 250°C and at various frequencies of 10–50 Kc/s before and after polarization (800 V). The effect of poling field is discussed on the basis of the presence of spontaneous polarization in BaTiO₃ lattice. Finally, it was established that the introduction of Zr⁴⁺ ions in BaTiO₃ lattice occurs in three steps: firstly, filling of Ba²⁺ vacancies, secondly solid solution formation from BaZrO₃ in BaTiO₃ lattice and thirdly, occupying interstitial sites in BaTiO₃ lattice.     

The impact of renewable energy intermittency on the operational characteristics of a stand-alone hydrogen generation system with on-site water production

In renewably powered remote hydrogen generation systems, on-site water production is essential so as to service electrolysis in hydrogen systems which may not have recourse to shipments of de-ionised water. Whilst the inclusion of small Reverse Osmosis (RO) units may function as a (useful) dump load, it also directly impacts the power management of remote hydrogen generation systems affecting operational characteristics.     

A mechanism for the corrodability of hafnium and the anodic oxide film thereon in HCl solutions

A study is made to account for the corrodability of each of the naturally developed and anodically formed oxide films on hafnium in HCl solutions. The behaviour of these oxide films was investigated by capacitance and potential measurements. The naturally developed oxide film grows spontaneously according to a direct logarithmic law. In diluted HCl (< 1 N), the rate of growth is small but the resultant film has better electrochemical insulating properties than that rapidly grown in the more concentrated solutions. On the other hand, the anodic oxide film is more liable to chemical (currentless) dissolution in HCl as the initial thickness increases. The rate determining step in the dissolution process is determined mainly by the oxide and is almost independent of the acid concentration. The behaviour of each of the two films has been correlated to changes in the fine structure of the parent oxide during its growth.     

Stability of anodic tantalum oxide films in NaOH solutions

The dissolution behaviour of the anodic oxide films formed on tantalum was investigated in NaOH solutions of different concentrations. In solutions of [OH^–]<3.0 M, no pronounced dissolution could be detected. However, in concentrated alkali solutions, [OH]>3 M, the dissolution occurred to different extents depending on the alkali concentration. As observed from capacitance and potential measurements, the barrier film on Ta was found to be defective owing to the incorporation of OH^– ions in the film. The nature of the barrier film and its dependence on formation rate, alkali concentration and solution temperature were investigated. Complex plane analysis illustrates the behaviour of the barrier film of different thickness, i.e. formation voltages, in NaOH solutions. The barrier film cannot be considered accurately as a perfect dielectric.     

Influence of powder loading on densification and microstructure of injection molded Fe‐50Ni soft magnetic alloys

Metal injection molding (MIM) is a well‐known technique capable to produce micro size electromagnetic components with intricate shape features. Powder loading is a crucial parameter in the metal injection molding process which controls the densification and microstructure of the sintered parts. The lower powder loading leads to various defects and lower densification whereas higher loading results in failure of parts during injection molding. Therefore, it is important to engineer an appropriate powder loading to achieve defect‐free parts along with higher densification and improved microstructure. In this contest, three feedstocks of Fe‐50Ni alloys are prepared with powder loadings of 52 vol.%, 54 vol.% and 57 vol.% and injection molded. After debinding, the parts are sintered at 1325 °C for 2 h. The main objective of this study is to investigate the effect of powder loading on injection molding, densification, and microstructure. In addition, scanning electron microscopy and x‐ray diffraction analysis are performed during the study. The defect‐free green parts are produced successfully from the 52 % and 54 % loading. It has been found that the optimal powder loading of 54 % is the best from the perspective of enhanced densification and improved microstructure to assure the quality parts of Fe‐50Ni alloys via metal injection molding.