Wear of graphite anodes during electrolysis of add sulphate solutions

Graphite electrodes were prepared by mixing calcined coke and coal tar pitch. They were pressed under 250 kg cm^–2 and heat treated up to 2800° C. Rectangles measuring 70 mm x 40 mm x 8 mm were anodically polarized under galvanostatic and potentiostatic conditions. Electrolyses were conducted at 10–50 mA cm^–2 for periods ranging from 10–120 hours in Na₂SO₄ solutions acidified with sulphuric acid to various pH values. The wear of graphite anodes increased with decreasing bath temperature, increasing acid concentration, decreasing pH of the electrolyte and increasing current density. A model is suggested which assumes that corrosion takes place via the formation of a lamellar crystal compound with the formula (C ₈ ⁰ O)(OH)₃HSO ₄ ^– ·2H₂SO₄.The compound is unstable at higher temperatures when corrosion is effected by oxidation of graphite by atomic oxygen. The formation of the carbon ions was found to be a necessary precondition for the formation of the complex.     

Crashworthiness design optimization using successive response surface approximations

 Finite Element (FE) method is among the most powerful tools for crash analysis and simulation. Crashworthiness design of structural members requires repetitive and iterative application of FE simulation. This paper presents a crashworthiness design optimization methodology based on efficient and effective integration of optimization methods, FE simulations, and approximation methods. Optimization methods, although effective in general in solving structural design problems, loose their power in crashworthiness design. Objective and constraint functions in crashworthiness optimization problems are often non-smooth and highly non-linear in terms of design variables and follow from a computationally costly (FE) simulation. In this paper, a sequential approximate optimization method is utilized to deal with both the high computational cost and the non-smooth character. Crashworthiness optimization problem is divided into a series of simpler sub-problems, which are generated using approximations of objective and constraint functions. Approximations are constructed by using statistical model building technique, Response Surface Methodology (RSM) and a Genetic algorithm. The approximate optimization method is applied to solve crashworthiness design problems. These include a cylinder, a simplified vehicle and New Jersey concrete barrier optimization. The results demonstrate that the method is efficient and effective in solving crashworthiness design optimization problems. Received: 30 January 2002 / Accepted: 12 July 2002 Sponsorship for this research by the Federal Highway Administration of US Department of Transportation is gratefully acknowledged. Dr. Nielen Stander at Livermore Software Technology Corporation is also gratefully acknowledged for providing subroutines to create D-optimal experimental designs and the simplified vehicle model.     

Review on zirconate-cerate-based electrolytes for proton-conducting solid oxide fuel cell

The performance of low-to-intermediate temperature (400–800?°C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O^2-) conductors with proton (H⁺) conductors because H⁺ conductors have higher ionic conductivity and theoretical electrical efficiency than O^2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H⁺ conductors. Cerate-based electrolytes have the highest H⁺ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped cerate–zirconate and hybrid-doped cerate–zirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application.     

High-Temperature Oxidation Behavior of Refractory High-Entropy Alloys: Effect of Alloy Composition

The high-temperature oxidation behavior of a new family of refractory high-entropy alloys (HEAs) with compositions of W–Mo–Cr–Ti–Al, Nb–Mo–Cr–Ti–Al and Ta–Mo–Cr–Ti–Al was studied at 1000 and 1100 °C. Based on these equimolar starting compositions, the main incentive of this study was to select the most promising alloy system whose properties may then be successively improved. Despite the high amount of refractory elements, Ta–Mo–Cr–Ti–Al showed good oxidation resistance at 1000 and 1100 °C. Moderate values of mass gain and complex oxidation kinetics were observed for the W- and Nb-containing HEAs. These alloys formed inhomogeneous oxide scales possessing regions with thick and porous layers as well as areas revealing quite thin oxide scales due to the formation of discontinuous Cr- and Al-rich scales. The most promising behavior was shown by the alloy Ta–Mo–Cr–Ti–Al which followed the parabolic rate law for oxide growth due to the formation of a thin and compact Al-rich layer.     

Zinc oxide nanoparticles augment CD4, CD8, and GLUT‐4 expression and restrict inflammation response in streptozotocin‐induced diabetic rats

This study evaluated the biochemical, molecular, and histopathological mechanisms involved in the hypoglycaemic effect of zinc oxide nanoparticles (ZnONPs) in experimental diabetic rats. ZnONPs were prepared by the sol–gel method and characterised by scanning and transmission electron microscopy (SEM and TEM). To explore the possible hypoglycaemic and antioxidant effect of ZnONPs, rats were grouped as follows: control group, ZnONPs treated group, diabetic group, and diabetic + ZnONPs group. Upon treatment with ZnONPs, a significant alteration in the activities of superoxide dismutase, glutathione peroxidase, and the levels of insulin, haemoglobin A1c, and the expression of cluster of differentiation 4+ (CD4+), CD8+ T cells, glucose transporter type‐4 (GLUT‐4), tumour necrosis factor, and interleukin‐6 when compared to diabetic and their control rats. ZnONPs administration to the diabetic group showed eminent blood glucose control and restoration of the biochemical profile. This raises their active role in controlling pancreas functions to improve glycaemic status as well as the inflammatory responses. Histopathological investigations showed the non‐toxic and therapeutic effect of ZnONPs on the pancreas. TEM of pancreatic tissues displayed restoration of islets of Langerhans and increased insulin‐secreting granules. This shows the therapeutic application of ZnONPs as a safe anti‐diabetic agent and to have a potential for the control of diabetes.Inspec keywords: nanoparticles, transmission electron microscopy, cellular biophysics, sugar, nanomedicine, nanofabrication, zinc compounds, molecular biophysics, biochemistry, tumours, enzymes, biomedical materials, biological organs, blood, diseases, patient treatment, II‐VI semiconductors, wide band gap semiconductors, scanning electron microscopy, sol‐gel processing, semiconductor growthOther keywords: molecular mechanisms, histopathological mechanisms, zinc oxide nanoparticles, experimental diabetic rats, hypoglycaemic effect, antioxidant effect, control group, diabetic group, CD4+, CD8+ T cells, glucose transporter type‐4, control rats, GLUT‐4 expression, streptozotocin‐induced diabetic rats, biochemical mechanisms, safe antidiabetic agent, inflammation response, sol‐gel method, transmission electron microscopy, scanning electron microscopy, SEM, TEM, superoxide dismutase, glutathione peroxidase, insulin levels, haemoglobin A1c, differentiation 4+ T cells, tumour necrosis factor, interleukin‐6, blood glucose control, pancreas functions, glycaemic status, therapeutic effect, pancreatic tissues, Langerhans islets, insulin‐secreting granules, ZnO     

Interfacial activity and micellar morphology of an imidazolium ring containing zwitterionic surfactants

Zwitterionic surfactants based on 3-(1-alkyl-3-imidazolio) propane-sulfonate ([ImS3-R] where R is octyl or dodecyl) is an emerging and important class of amphiphile due to their relevance as nano reactors for the synthesis of metallic nanoparticles and accelerated acid hydrolysis. The physicochemical properties of such synthesized imidazolium ring-containing zwitterionic surfactants have been characterized by surface tension and small-angle neutron scattering (SANS) techniques. Surface tension measurements were used to calculate several thermodynamic parameters over a range of concentrations and temperatures (298–313 K). The results obtained showed a weak signature representing the critical micelle concentration (CMC) for ImS3-8, however, by increasing the alkyl length of the hydrophobic group to dodecyl, that is, ImS3-8 to ImS3-12, the signature of the CMC was much more evident. As expected, the CMC for ImS3-12 shifted to a lower concentration. An increase in temperature increased the surface activity and decreased the CMC of both zwitterionic surfactants, although the changes were small. Compared to classical surfactants, that is, sodium dodecyl sulfate and dodecyl trimethylammonium bromide, the CMC of ImS3-12 is much lower. Modeling of SANS data demonstrated that the morphology of the micelles formed by these amphiphiles may be described by the “classical” model, a central hydrophobic core, with a shell of hydrated headgroups. Due to their widespread applications in colloidal and interfacial science, the present study adds new insight to the fundamental understanding of these interesting imidazolium-based surface-active ionic liquids (ImS3-R).     

A DPSK demodulator for biomedical application

In this study, a differential phase-shift-keying (DPSK) demodulator, which is implemented by digital circuit, is proposed. A differential voltage clipper is used to generate narrow pulses at the extremum of the received modulated signal. Regarding the DPSK signal, the outputs of the clipper have double frequency. In order to halve the frequency, a frequency divider is applied to get synchronous clock. Two binary counters are used to detect phase variation; the data are recovered after two times sampling. This technique removes the need for voltage controlled oscillator (VCO). The proposed demodulator is postlayout simulated in a 0.18-μm CMOS process, with a power of 64 μW and active area of 68 × 70 μm². The demodulator recovers 10 Mb/s data rate at 10-MHz carrier frequency using a 1.8-V power supply.     

Dithiocarbamate as an efficient intermediate for the synthesis of 2-(alkylthio)thiazol-4(5H)-ones

An effective approach for the synthesis of 2-(alkylthio)thiazol-4(5H)-ones from alkyl dithiocarbamates and chloroacetyl chloride in the presence of NaHCO₃ has been developed. Good to excellent yields of products, simple reaction conditions and general applicability are the most important advantages of this protocol.     

Dielectric and mechanical optimization properties of porous poly(ethylene‐co‐vinyl acetate) copolymer films for pseudo‐piezoelectric effect

In this article, the authors present a porous copolymer film with pseudo‐piezoelectric effects as a new candidate material for sensing applications. Porous films of poly(ethylene‐co‐vinyl acetate) (EVA) with a thicknesses ranging from 160 to 310 μm are fabricated by a coextrusion chemical foaming process and charged using a high‐voltage contact charging process. Output performances (piezoelectric constant and relative permittivity) with related thermal/mechanical stability are specifically studied as a function of the film porosity and of the electrical charging process. The piezoelectric constant d₃₃ increases with the cell porosity and an interesting piezoelectric constant close to 5.1 pC/N is achieved with a porous EVA film containing 65% of porosity. Actual results are then discussed using a theoretical solid–gas multilayer model to describe and predict the pseudo‐piezoelectric effect of porous polymer materials. The originality of this work lies in the fact that all the steps leading to optimize pseudo piezoelectric films are included, and also in the use of EVA which is not a standard piezoelectric material. Therefore, this work is a contribution in the development of low‐cost piezoelectric materials with potential applications as sensor in different fields such as medical, security, environment, sport, and transport. POLYM. ENG. SCI., 59:1455–1461 2019. © 2019 Society of Plastics Engineers