Strontium PVC-membrane sensor based on 2-[(2-mercaptophenylimino)methyl]phenol

The 2-[(2-mercaptophenylimino)methyl]phenol (MPMP) was used as an excellent ionophore in the construction of a Sr²⁺ PVC-based membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 62% nitrobenzen (NB), 5.5% MPMP and 2.5% sodium tetraphenyl borate (NaTBP). This sensor demonstrates a good selectivity and sensitivity towards the strontium ion for many cations, including alkali, alkaline earth, transition and heavy metal ions. The sensor revealed a great enhancement in selectivity coefficients for strontium ions in comparison with the previously reported strontium sensors. The proposed sensor exhibits a Nernstian behavior (with a slope of 29.6 ± 0.3 mV per decade) for the concentration range of (1.0 × 10^− 6–1.0 × 10^− 1 M) with a detection limit of 5.5 × 10^− 7 M (48.2 ng/mL). It illustrates a relatively fast response time in the whole concentration range (< 10 s) and it can be used for at least 10 weeks in a pH range of 2.8–9.6. The developed sensor was successfully used as an indicator electrode in the Sr(II) titration with EDTA and the Sr²⁺ ion recovery from binary mixtures.     

Determination of Cr ions in biological and environmental samples by a chromium(III) membrane sensor based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide

A highly Cr³⁺-selective ionophore, based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide (APC) as a carrier, was synthesized in order to obtain a Cr³⁺ ion-selective electrode. The demonstrated characteristics of the sensor included a linear dynamic range between 1.0 × 10^− 6 and 1.0 × 10^− 1 M with a near Nernstian slope of 19.6 ± 0.4 mV per decade, a detection limit of 5.3 × 10^− 7 M, a very good selectivity for Cr³⁺ over other cations in a wide pH range (3.2-6.3). Furthermore, the newly-designed electrode presented a fast response time of 10 s with a lifetime of at least 2 months indicating no considerable potential divergence. The sensor accuracy was investigated by the potentiometric titration of a Cr(III) solution with EDTA as well as the monitoring of Cr(III) in mixtures of three and five different ions. As a result, the developed sensor provided satisfactory results after its application in the Cr³⁺ determination in biological samples (urine and synthetic plasma) and also in wastewater of chromium electroplating industries.     

Residual Stress Relaxation Induced by Mass Transport Through Interface of the Pd/SrTiO3

Metal interconnections having a small cross-section and short length can be subjected to very large mass transport due to the passing of high current densities. As a result, nonlinear diffusion and electromigration effects which may result in device failure and electrical instabilities may be manifested. Various thicknesses of Pd were deposited over SrTiO₃ substrate. Residual stress of the deposited film was evaluated by measuring the variation of d-spacing versus sin²ψ through conventional X-ray diffraction method. It has been found that the lattice misfit within film and substrate might be relaxed because of mass transport. Besides, the relation between residual intrinsic stress and oxygen diffusion through deposited film has been expressed. Consequently, appearance of oxide intermediate layer may adjust interfacial characteristics and suppress electrical conductivity by increasing electron scattering through metallic films.     

Metal (Co,Mn)-amine-functionalized mesoporous silica SBA-15: synthesis,characterization and catalytic properties in hydroxylation of benzene

Mesoporous silica SBA-15 was synthesized using H₃PO₄ and functionalized with ethylendiaminopropyltrimethoxysilane (H₂N–(CH₂)₂–NH–(CH₂)₃–) by grafting method. A variety of transition metals such as Co and Mn have been coordinated with amine-functionalized silica SBA-15. The materials have been characterized by XRD, FT-IR, BET, TGA, ¹³C-NMR, DR UV–Vis, atomic absorption spectroscopy (AAS) and back titration using NaOH (0.1 N). The catalytic performance of obtained catalyst was determined for hydroxylation of benzene using H₂O₂ as oxidant in the presence of O₂ atmosphere. At optimized conditions, the Mn-amine-functionlized mesoporous silica SBA-15 exhibited high catalytic activity at room temperature in the absence of solvent.     

An adaptive h-r boundary element algorithm for the laplace equation

In this paper, the combination of the h-method (mesh refinement) and the r-method (mesh redistribution) is employed to solve the Laplace equation using the boundary element procedure. The key in this approach is to derive on upper bound for the residual associated with the boundary element solution and minimize this bound with respect to an unknown grading function. The latter part is achieved by employing techniques of the calculus of variations.     

The role of implicitness in a finite element calculation of viscous flow

The turbulent boundary layer equations are discretized using a finite element technique. In the process, an implicitness parameter is introduced which governs the stability of the scheme. A computer study reveals certain points concerning the selection of the parameter and its effect on calculations as a whole.     

Utilizing Taguchi design of experiment to study the surface treatment of a nanosilica with an acrylic silane coupling agent and revealing the dispersibility of particles in a urethane acrylate resin

This work aims at investigating the dispersibility of a modified hydrophilic nanosilica using methacryloxy propyltrimethoxysilane (MPTMS) in an organic phase, which contains UV-curable urethane acrylate oligomers and monomers with different functionalities. Through a Taguchi design of experiment, the impacts of influencing parameters such as silane coupling agent to silica ratio, hydrolysis ratio as well as treating bath pH were investigated. The optimum condition in which the maximum percentage of modification occurred was observed at higher stoichiometric levels of silane:silica ratio and alkaline pH conditions. Furthermore, statistical analysis demonstrated that hydrolysis ratio was not very significant. Low amounts of turbidity of prepared hybrid coatings indicated that modified particles with higher grafting contents had better dispersion stability in the acrylate resin.     

Ferrite recrystallisation and intercritical annealing of cold-rolled low alloy medium carbon steel

Static recrystallisation of cold-rolled AISI 4130 medium carbon steel in the ferritic regime and its response to intercritical annealing treatment are studied. A fine and recrystallised microstructure with improved mechanical properties is obtained via subcritical annealing of cold-rolled sheet, where the subsequent intercritical annealing results in the enhancement of tensile strength via the formation of dual-phase microstructure. Intercritical annealing of the cold-rolled sheet is characterised by an initial drop in hardness due to recrystallisation and subsequent rise in hardness as a result of austenitisation. It is revealed that continuous martensite phase can result in a higher deformation resistance. Finally, the effects of intercritical annealing at temperatures below pearlite dissolution finish temperature (Ac_1f) are discussed.     

A note on the quadratic element in one dimension

This short technical note discusses the one-dimensional quadratic three noded element and the limitations on the positioning of the interior node within the element. The simple derivation is the basis of quarter node isoparametric elements used in fracture mechanics.