Study of various aliphatic alcohols as sacrificial agents on photoelectrochemical behavior of nickel-platinum-modified Cr-TiO<Subscript>2</Subscript> nanotubes

Cr-TiO₂ nanotubes (Cr-TNTs) have been synthesized via facile one step anodization, followed by co-deposition by nickel-platinum via electroless deposition method. Field-emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD), and Raman spectroscopy have then been used to characterize the surface morphology and structure of the synthetic samples. The optical properties of the compounds have been investigated by ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy. Linear sweep voltammetry (LSV) and chronoamperometry were used to study the photoelectrochemical behavior of the obtained samples. The best electrochemical performer sample (t₂₀) was recognized and evaluated in the presence of various aliphatic alcohols, as sacrificial agents, in photoelectrochemical cells (PEC) water splitting. In terms of sacrificial agent used, photocurrent density production was as follows: methanol > ethanol > glycerol > n-propanol > isopropanol > ethylene glycol. Also methanol concentration was optimized. Thus, both co-deposition of Cr-TNTs and addition of scavengers are promising methods to enhance the performance of catalysts for PEC.     

On the stability of multiple parameter time-varying dynamic systems

A technique is presented for determaining the stability of lumped-pararaeter, time-varying, dynamic systems with aperiodic coefficients. An “energy like” function is used to develop stability conditions which are direct in terms of the coefficient matrices. The significance of what is presented here is twofold. First, it gives stability conditions applicable to systems which are not necessarily periodic. Second, is allows for a systematic categorization of the effects of the parameter changes on system response and stability, in order to provide a better understanding of the behavior of this class of dynamic systems as they arise in various areas of engineering.     

Analytical modeling of static behavior of electrostatically actuated nano/micromirrors considering van der Waals forces

In this paper,the effect of van der Waals(vdW)force on the pull-in behavior of electrostatically actuatednano/micromirrors is investigated.First,the minimum potential energy principle is utilized to find the equation governing the static behavior of nano/micromirror under electrostatic and vdW forces.Then,the stability of static equilibrium points is analyzed using the energy method.It is foundthat when there exist two equilibrium points,the smaller oneis stable and the larger one is unstable.The effects of different design parameters on the mirror’s pull-in angle andpull-in voltage are studied and it is found that vdW forcecan considerably reduce the stability limit of the mirror.Atthe end,the nonlinear equilibrium equation is solved numerically and analytically using homotopy perturbation method(HPM).It is observed that a sixth order perturbation approximation can precisely model the mirror’s behavior.The results of this paper can be used for stable operation design andsafe fabrication of torsional nano/micro actuators.     

Variation of constant formula for the solution of interval differential equations of non-integer order

In the recent years some efforts were made to propose simple and well-behaved fractional derivatives that inherits the classical properties from the first order derivative. Therefore, we propose in this research a new strategy to acquire interval solution of fractional interval differential equations (FIDEs) under interval fractional conformable derivative. This scheme is developed based on a variation of the constant formula to achieve the solution explicitly. The important characteristic of this technique is that it helps us to find a solution with decreasing length of its support which is critical for the solutions based on the interval or fuzzy notions. Two examples are experienced to illustrate our approach and validate it.     

Fischer–Tropsch synthesis using zeolitic imidazolate framework (ZIF-7 and ZIF-8)-supported cobalt catalysts

The Fischer–Tropsch synthesis using cobalt catalysts supported on zeolitic imidazolate frameworks (ZIFs), ZIF-7 and ZIF-8, has been investigated. ZIF-7, ZIF-8 and corresponding cobalt-containing catalysts, after preparation, were characterized using various techniques. Thermogravimetric analysis results show that ZIF-7 and ZIF-8 supports have good thermal stability for the Fischer–Tropsch synthesis reaction, and weaker interaction between cobalt and zinc in the ZIF-7 and ZIF-8 supports results in more cobalt reduction. The catalytic performance was evaluated in Fischer–Tropsch synthesis and compared with that of a cobalt catalyst supported on SBA-15 promoted with zinc. The pore structure of the ZIF supports plays an essential role in product selectivity for the prepared catalysts. The carbon number in hydrocarbon products and olefin selectivity depend on cobalt dispersion and support structure owing to the impacts of site density and carrier skeleton on the speed of diffusion-enhanced olefin re-adsorption reactions.     

Heat transfer analysis of micropolar hybrid nanofluid over an oscillating vertical plate and Newtonian heating

Journal of Thermal Analysis and Calorimetry - The unsteady flow of micropolar hybrid nanofluids through an oscillating vertical plate having infinite length has been analyzed in this study. This...     

Erratum to: 2D Hexagonal SnTe monolayer: a quasi direct band gap semiconductor with strain sensitive electronic and optical properties

The European Physical Journal B - The present study investigates amplitude death in an oscillator network with asymmetric connection delays and a tree graph topology. A frequency domain analysis...     

Waste to wealth: conversion of nano‐magnetic eggshell (Fe3O4@Eggshell) to Fe3O4@Ca(HSO4)2: cheap,green and environment‐friendly solid acid catalyst

Eggshell is a hazardous waste by European Union regulations, so that discarded thousands of tons per year. To convert waste (eggshell) to wealth (catalyst), nano‐magnetic eggshell was prepared based on the nano‐Fe₃O₄, and then the eggshell was converted to Ca(HSO₄)₂ with organic acid, namely, chlorosulfonic acid. Based on the back titration, 5.18 mmol SO₄H group was loaded per gram of the nano‐structure. Using this method eggshell was converted to cheap, green and environment‐friendly solid acid catalyst. The prepared catalyst (nano‐ Fe₃O₄@Ca(HSO₄)₂) was characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermal gravimetric analysis (TGA). The activity of eggshell waste‐derived catalysts was successfully evaluated in the synthesis of value‐added products, namely indazolo[1,2‐b]‐phthalazinetrione derivatives as a benchmark multicomponent reaction. In addition, design of experiments shows that increase in amount of catalyst (and temperature), boost the reaction yield, especially with steeper slope at higher temperature.     

The effects of using corrugated booster reflectors to improve the performance of a novel solar collector to apply in cooling PV cells-Navigating performance using ANN

Journal of Thermal Analysis and Calorimetry - In this study, turbulent flow and heat transfer of water in a solar collector equipped with corrugated booster reflectors to apply in cooling...     

CuCl2 heterogenized on metformine‐modified polystyrene resin as an antibacterial agent and recyclable nanocatalyst for Ullmann‐type C‐N coupling reactions

Merrifield Resin was functionalized with metformine and applied as a solid support to immobilize the CuCl₂. The Ps‐Met/CuCl₂ was characterized by several techniques including Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDX), wavelength‐dispersive X‐ray spectroscopy (WDX) and inductively coupled plasma (ICP). The Ps‐Met/CuCl₂ was used as an efficient recyclable solid nanocatalyst for N‐arylation of indole and aniline through coupling reactions of Ullmann‐type C‐N. The advantages of this method are easy workup, improved yields, and simple recovery via filtration. Ultimately, the Ps‐Met/CuCl₂ antibacterial property was examined against two bacteria (Staphylococcus aureus (Staph. aureus) and Escherichia coli (E. coli)) and indicated its antibacterial performance against gram negative (E. coli) bacteria and gram positive (Staph. aureus).