Microphase separation and hard domain assembly in thermoplastic polyurethane/multiwalled carbon nanotube nanocomposites

We studied the role of multiwalled carbon nanotubes (MWCNTs) on microphase separation and hard domain assembly in the thermoplastic polyurethane/multiwalled carbon nanotube nanocomposites via combination of rheology and thermal analysis (DSC and DMA). The strong solid‐like response observed at low frequency together with very low rheological percolation threshold (0.15 wt%) shown by the samples at their disordered state temperature revealed great capability of TPU in dispersing MWCNTs. The results of microphase separation kinetics measured for the fast‐cooled samples using the time sweep experiments under isothermal condition together with thermal analysis showed a significant enhancing effect of MWCNTs on accelerating kinetics as well as promoting the extent of hard domain formation. These results could be attributed to increased thermodynamic incompatibility between hard and soft domain of TPU matrix as a result of greater affinity of MWCNTs with hard segments. This allowed the MWCNTs to act as attractive platforms for formation and assembly of hard domains. POLYM. ENG. SCI., 55:2163–2173, 2015. © 2015 Society of Plastics Engineers     

A Mathematical Model for Prediction of Pore Size Distribution Development during Activated Carbon Preparation

A new modeling approach was introduced for the prediction of pore size distribution development during activated carbon preparation. The mathematical model is based on the modification of a single-pore model for pore growth rate estimation using a population balance and applying a variable structural parameter random-pore model. The model predictions were compared with experimental pore size distributions and conversions at various times for pistachio shell char activation by steam between 800° and 950°C, and the kinetic parameters were estimated.     

Spectrofluorometric Method for Determination of Al3+ with 3-Hydroxy-2-Naphthalenecarboxylic Acid and its Application to Milk Samples

On the basis of affinity of Al³⁺ ions toward functional groups of 3-hydroxy-2-naphthalenecarboxylic acid (3H2NA), a high stable complex between Al³⁺ and 3H2NA in 5 % methanol/water solution was established. The mole ratio method showed that a stable complex by taking part of acetate and 3H2NA with the stoichiometric ratio of 1:1:1 and stability constant of 8.6?×?10⁶ is formed. Under the optimum conditions for the complex formation, a rapid spectrofluorometric determination of trace amounts of Al³⁺ (λ _ex?=?366 nm, λ _em?=?460 nm) was proposed. The optimum conditions involve 3H2NA concentration of 1.0?×?10^?5 M, buffering pH of 4.5 (acetic/acetate system), and ionic strength of 0.01 M. The fluorescence intensity exhibited a good linearity against the Al³⁺ concentration in the range 5.0?×?10^?8–5.0?×?10^?6 M with the detection limit of 1.3?×?10^?8 M. No considerable interference was observed due to the presence of coexisting anions and cations. The method was applied successfully to the determination of trace amounts of Al³⁺ in milk. Validation of the measurements was confirmed using graphite furnace atomic absorption spectrophotometry.     

Review on effective parameters in electrochemical hydrogen storage

Today, energy has become one of the most important concerns of developing countries. The use of non-renewable energy sources, as well as the production of pollution, has led to growing efforts to replace fossil fuels, which are the most important energy sources in the modern world. Hydrogen as a clean fuel has attracted a lot of attention in recent years. Various methods have been reported for the production and storage of hydrogen. According to their advantages and disadvantages, it can be said that electrochemical hydrogen storage method is superior to other methods in terms of cost, safety, and optimum condition. The electrochemical hydrogen storage is done in a variety of techniques, and in recent years, the chronopotentiometry method has become one of the most popular methods for scientists. In chronopotentiometry technique, several parameters such as the reference electrode, the counter electrode, the working electrode, electrolyte, and current density are important. In this review, we investigated the articles that have been done in this regard from 2000 to 2020. This review can help scientists to better understand the electrochemical hydrogen storage system.     

Modified activated carbons with amino groups and their copper adsorption properties in aqueous solution

Activated carbons were prepared by two chemical methods and the adsorption of Cu (II) on activated carbons from aqueous solution containing amino groups was studied. The first method involved the chlorination of activated carbon following by substitution of chloride groups with amino groups, and the second involved the nitrilation of activated carbon with reduction of nitro groups to amino groups. Resultant activated carbons were characterized in terms of porous structure, elemental analysis, FTIR spectroscopy, XPS, Boehm titration, and pHzpc. Kinetic and equilibrium tests were performed for copper adsorption in the batch mode. Also, adsorption mechanism and effect of pH on the adsorption of Cu (II) ions were discussed. Adsorption study shows enhanced adsorption for copper on the modified activated carbons, mainly by the presence of amino groups, and the Freundlich model is applicable for the activated carbons. It is suggested that binding of nitrogen atoms with Cu (II) ions is stronger than that with H+ions due to relatively higher divalent charge or stronger electrostatic force.     

Spectrophotometric determination of mercury in water samples after cloud point extraction using nonionic surfactant Triton X-114

A cloud point extraction process using the nonionic surfactant Triton X-114 for extracting mercury from aqueous solutions was investigated. The method is based on the complexation reaction of Hg(II) with Thio-Michler's Ketone (TMK) and micelle-mediated extraction of the complex. The optimal extraction and reaction conditions (e.g., pH, reagent concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range) were obtained. Linearity was obeyed in the range of 5.0-80.0 ng mL(-1) of Hg(II) ion. The detection limit of the method was 0.83 ng mL(-1) of Hg(II) ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of mercury in water samples.     

Effect of Ni addition on electrocatalytic activity of PdCu catalysts for ethanol electrooxidation: An experimental and theoretical study

A facile and clean electrochemical method has been developed for the synthesis of ternary PdCuNi catalysts on the surface of carbon Vulcan. The composition and morphology of the PdCuNi/C were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), X?ray diffraction (XRD), EDX element mapping and transmission electron microscopy (TEM). The effect of Cu and Ni on the electrochemical activity of ternary PdCuNi alloy electrocatalysts was investigated for ethanol oxidation reaction (EOR). Between the different compositions, Pd_35%Cu_14%Ni_2%/C catalyst exhibits superior mass activity which is about 10 times higher than that of commercial Pd/C catalyst. The onset peak potential for ethanol oxidation on Pd_35%Cu_14%Ni_2%/C catalyst shifts to lower potential than that of PdCu/C and Pd/C catalysts. The stability tests revealed that the existing of Cu combined with Ni can improve the poison tolerance of Pd/C catalyst by removal of adsorbed CO-like intermediate species during ethanol oxidation. The experimental work is further investigated by theoretical study based on DFT-D calculations. The experimental and theoretical results exhibited similar trends in electrocatalytic activity of catalyst composition; indicating ternary PdCuNi alloys could be a promising anode catalyst for direct ethanol fuel cells.     

Incorporation of Iron Nanoparticles into Silicon Carbide Nanoparticles as Novel Antimicrobial Bimetallic Nanoparticles

Silicon - Zero valent iron nanoparticles have an attracting and ever growing interest in various research fields due to the fascinating potential. In the present work, antimicrobial activity of...     

Polymer–montmorillonite nanocomposites: Chemical grafting of polyvinyl acetate onto Cloisite 20A

This paper is an account of the experiments on grafting polyvinyl acetate onto organophilic montmorillonite. Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction liberates HCl, it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H⁺ ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. After the reaction, the product maintained the same basal spacing as the precursor. The radical polymerization of the product with vinyl acetate as a vinyl monomer leads to chemical grafting of polyvinyl acetate onto montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhelt extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nanocomposite materials and the grafted nano‐particles were studied by XRD, SEM, and TEM. Exfoliated nanocomposite was obtained for 0.5% clay content. Nanocomposites with 1% and 3% clay contents showed significant intercalation and agglomeration occurred at higher clay loadings. The nanocomposites were studied by thermogravimertic analysis (TGA) and dynamic mechanical analysis (DMTA). Improved thermo‐mechanical properties were observed for nanocomposite with 0.5% clay content. POLYM. COMPOS., © 2011 Society of Plastics Engineers.