Electrically conductive epoxy‐based nanocomposite adhesives loaded with silver‐coated copper and silver‐coated reduced graphene oxide nanoparticles

In this research, a conductive adhesive based on epoxy resin as the polymer matrix and silver‐coated copper powder and silver‐coated reduced graphene oxide as conductive fillers was synthesized. Graphene oxide was synthesized by modified Hummer's method. It was reduced and modified by silver powder. Copper particles were coated with silver using the electroless plating method. Finally, conductive nanocomposite adhesives were prepared using conductive fillers with different weight fractions. The structural properties of fillers were identified by Fourier‐transform infrared (FTIR) and induced coupled plasma (ICP) analysis and the morphology of the samples by scanning electron microscopy (SEM). Finally, conductive properties, lap shear strength, and thermal stability of adhesive were evaluated. The conductive adhesive prepared with optimized properties have 70% weight percentage silver‐coated copper powder and 1% weight percentage silver‐coated reduced graphene oxide. The bulk resistivity of the optimum sample was 1.6 × 10^‐2 Ω.cm, and the lap shear strength was 7.10 MPa. Also, thermogravimetric analysis showed that the weight loss of adhesive decreased from 88.72% to 30.55% during heating, which showed the addition of fillers improves the thermal stability of adhesive.     

Influence of MgO/CeO2 ratio on CO2-oxidative transformation of C2H6 to C2H4 over highly active and stable Cr/MgO(x)–CeO2(100−x) nanocatalysts

Cr/MgO(x)–CeO₂(100?x) nanocatalysts were synthesized by a coprecipitation method and characterized by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM), energy-dispersive x-ray (EDX) spectroscopy, diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller (BET) analysis. The effect of ceria addition on their physicochemical characteristics was investigated, and the results were correlated with their catalytic performance in oxidative dehydrogenation of ethane. A decrease in the size of the metal particles was found when adding a suitable content of ceria to the support. Crystalline Cr₂O₃ was not found in the calcined samples, indicating good dispersion of Cr species on the support. All samples showed nanosized particles with uniform morphology, with the best surface morphology for the Cr/MgO(50)–CeO₂(50) sample, on which the particle distribution mainly lay in the range of 40–60 nm. Variation of the amount of Ce in the support led to an enhancement of the Cr⁶⁺/Cr³⁺ ratio, with the highest value for the Cr/MgO(50)–CeO₂(50) sample. This catalyst effectively dehydrogenated ethane to ethylene with CO₂ at 700 °C even after 5 h on-stream, giving 42.76 % ethylene yield.

     

Upgrading the Iranian national laboratory standard to conform to ISO 15189:2012

Accreditation and Quality Assurance - The Reference Health Laboratory (RHL) of Iran is the national authority responsible for making policies and plans for providing quality laboratory services...     

Phosphorus phenyl-group activation by reduced zirconium and niobium complexes stabilized by the [P2N2] macrocycle.

Reduction of [P2N2]ZrCl2 (where [P2N2] = PhP(CH2SiMe2NSiMe2CH2)2PPh) with KC8 under argon generates the phosphorus phenyl bridged bimetallic complex where the bridging phenyl groups are formally reduced to bis(allyl) dianions. Similar reduction of [P2N2]NbCl caused the one-electron reduction of the phosphorus phenyl group to generate a cyclohexadienyl moiety via a C-C bond formation between the ipso carbons of the two phenyl groups.     

Inherent safety evaluation in process plants— a comparison of methodologies

A global population increase and an improved standard of living are generally expected. To meet these demands, an increased production of chemicals will be necessary while protecting human health and the environment. However, most current methods of chemical production are unsustainable. New designs must result in plants that assure process and operator safety, the sustained health of workers and the community, and the protection of the environment. Traditional safety precautions and process controls minimize risk but cannot guarantee the prevention of accidents followed by serious consequences. Therefore, the general approach to environmental and safety problems must be changed from reactive to proactive. One way is to further develop the concept of inherent safety. In this paper some methods for inherent safety evaluations are reviewed. The aim of the study is to analyze the different tools available for inherent safety evaluation and identify the most important criteria in determining the inherent safety of a process plant. A model is proposed to show the interactions of different factors on the inherent safety level of a process and the model is illustrated by a case study.     

Modeling of biliverdin reduction process: regio-specificity and H-bonding

Octa ethyl biliverdin (OEBV) has been employed as a model for natural biliverdin and its geometry has been optimized by using semiempirical (AM1, PM3), DFT, and hybrid ONIOM methods. Geometries and energetics of formation of octa ethyl bilirubin (OEBR) formed by reduction from OEBV via three carbon sites β, γ, and δ have been obtained. It has been shown that γ-OEBR has two configurational isomers (named γ₁ and γ₂), which can convert to each other by internal 1,5-hydrogen shift. The results show that, within the accuracy level of semiempirical methods, all three isomers namely, β, γ₁, and δ-OEBR are of similar stability whereas, at higher level of theory, γ₁-OEBR is less stable than others. Moreover, γ₂-isomer with one more of its pyrrole rings being aromatic can achieve a higher symmetry, and is the most stable among others by at least 5–6 kcal mol⁻¹ based on various methods employed. It is interesting to note that the ridge-tile conformation, which has been confirmed for natural bilirubin was not observed for calculated geometries of γ₁- and γ₂-isomers. A conformational analysis show that an energy barrier of 25 kcal mol⁻¹ must be surmounted for γ₂ to obtain the ridge-tile geometry.

OEBV was synthesized and purified from octa ethyl porphyrin iron (III) chloride, and was reduced to OEBR by sodium borohydride (NaBH₄). Chemical reduction of OEBV with NaBH₄ was followed in CDCl₃ and CD₃OD solutions and the product was characterized by ¹H NMR and UV–Vis spectroscopy. The results show that γ₂-isomer as the major product, forms along with γ₁ via an equilibrium tautomerization reaction.     

Optimal capacitor placement to minimizing cost and power loss in Tehran metro power distribution system using ETAP (A case study)

Most loads in the power distribution system of Tehran Metro (Subway) are inductive and lead to poor power factor (PF) especially in Lighting and Power Substation. One of the methods of PF correction is adding or producing the capacitive components within the circuit to eliminate the effect of inductive loads. Optimal capacitor placement (OCP), with the objects of power system voltage profile improvement, PF correction, loss reduction, and line reactive power decrease are of particular importance in power system control and planning. These objects depend on how the capacitive components are installation and to achieve them, since the capacitor placement is nonlinear problem and has some equally and inequality constraint. This article investigates OCP in the actual power distribution grid of Tehran Metro (Line 2) in the presence of nonlinear loads. The placement problem is solved using Genetic Algorithms as implemented in the Electrical Transient Analyser Program software. Results (capacity release, total generation, loading, demand, power losses and number of capacitor banks, costs and annual benefits) are obtained and analysed. This study and simulation shows that by OCP can calculate reduce annual losses and release capacity of equipment in power distribution grid of Tehran Metro such as cables and transformers from reactive power and that will maximize profits. © 2016 Wiley Periodicals, Inc. Complexity 21: 483–493, 2016     

Borepine: A Density Functional Approach toward Structural Features and Properties

The structure and properties of borepine and substituted borepines have been studied theoretically at the B3LYP/6-311++G(d,p) level. The calculations include the frontier orbitals, vibrational analysis, optical properties, electronic spectrum analysis, aromaticity and thermodynamic. The effects of the substituent groups on the structure, electronic properties, ionization potential (IP), electron affinity (EA), and reorganization energy has been studied. Aromaticity of molecules has been explored based on NICS values and delocalization index. The NICS values indicated increasing of aromaticity in electron withdrawing substituents.     

A novel efficient numerical method to simulate electrochemical process for a lithium ion battery

The simulation plays an important role in understanding of electrochemical behavior and internal process of lithium ion batteries. The existing finite difference method (FDM) to conduct the simulation of electrochemical process is time-consuming and computationally expensive. In this paper, a novel numerical method is proposed to accelerate the solution of the electrochemical model for a lithium ion battery. It is implemented in three steps. In the first step, physical analogy of electrochemical process to an electric circuit is used to solve charge conservation equations. In the second and third step, control volume method is used to solve species conservation equations. The simulation results show that the proposed method is much faster than the FDM by 2.2 times while maintain high accuracy which is verified by simulation and experimental data as well.