Synthesis of a Series of PEG-Based ABA Triblock Copolymers and Their Influence on Rheology of Cement Slurries

A series of water-soluble ABA triblock copolymers consisting of a polyethylene glycol central block joined to two blocks of six different homopolymers have been synthesized via simple solvent-free and ecofriendly routes and characterized by FTIR and ¹HNMR spectroscopy. Dispersing and slump-retaining abilities of the copolymers in cement slurries were evaluated by mini-slump spread method. Rheological measurements of samples with the best performance were carried out using a rate-controlled coaxial cylinder viscometer. The test results indicate that the dispersing power of the copolymers in cement pastes is strongly affected by the structure and degree of polymerization of the monomers.     

Investigation of Magnesium Incorporation within Gelatin/Calcium Phosphate Nanocomposite Scaffold for Bone Tissue Engineering

In this study, diffusional method was used to prepare a calcium phosphate/gelatin nanocomposite as a scaffold for bone tissue repair. Incorporation of magnesium (Mg) into mineral phase of the scaffold was also investigated. Addition of Mg ions to the synthesis process caused formation of magnesium phosphate (MgP) and hydroxyapatite (HAp). However, analyses data for the sample lacking Mg showed that the mineral formed within GEL had a low crystalline nature, consisting of HAp and octacalcium phosphate (OCP). With addition of Mg within the structure of precipitated minerals, morphology of minerals was dramatically changed toward being irregular and less ordered.     

Copper Ion Cementation in Presence of a Magnetic Field

The effect of an electromagnetic field (EMF) on the rate of copper(II) cementation from copper sulfate solutions on a rotating iron cylinder was investigated. The studied variables were cylinder rotation speed, magnetic field strength, and magnetic field direction. The application of EMF increased the rate of cementation in both parallel and perpendicular direction of the magnetic field where the latter proved to be more effective. The rate of mass transfer under an EMF was found to be more than doubled. The enhancement of copper recovery in presence of the EMF is due to the induced motion of Fe⁺ⁿ in the solution which is limited to a certain range of cylinder rotation speed. The power consumption for cementation of copper could be significantly reduced by utilizing EMF.     

Dielectric Properties of Basaltic Glass and Glass-Ceramics: Modeling and Applications as Insulators and Semiconductors

Silicon - Sinai basaltic rocks were melted as glass and casted into disc- and rode-shapes and subjected to thermal treatment to induce crystallization as a glass-ceramic. The dominant crystalline...     

Charge transport mechanism of graphite‐nanosheet‐loaded rubber nanocomposites

Nitrile butadiene rubber loaded with different concentrations of thin graphite nanosheets have been successfully prepared by using a two‐roll mill. The percolation concentration of the nanocomposites was 0.5 phr. The I–V characteristic curves showed that the nanocomposites exhibited ohmic behaviour at a certain voltage and then non‐linear behaviour. The Richardson–Schottky and Poole–Frenkel models were used to investigate the reason for the space charge. The experimental data fit the Schottky model well. The conductivity as a function of temperature was also studied and the data were fitted by using the Mott relation. The Mott relation showed that as the concentration of graphite nanosheets in the rubber composite increases, the hopping distance between the graphite nanosheet layers decreases, which enhances the conductivity of the nanocomposite at low concentrations. Copyright © 2011 Society of Chemical Industry     

Process synthesis and optimization of biorefinery configurations

Recently, there has been a growing interest in the development of cost‐effective technologies for the production of biofuels. A common approach to biofuel research is to invent or improve a biochemical or thermochemical conversion step. Subsequently, other conversion and separation steps are added to form a complete biorefinery flowsheet. Because this approach is structured around a specific conversion step, it may limit the possibilities of configuring optimal and innovative biorefineries. This article proposes a novel and systematic two‐stage approach to the synthesis and optimization of biorefinery configurations, given available feedstocks and desired products. In the synthesis stage, a systems‐based approach is developed to create a methodical way for synthesizing integrated biorefineries. This method is referred to as “forward‐backward” approach. It involves forward synthesis of biomass to possible intermediates and reverse synthesis starting with the desired products and identifying necessary species and pathways leading to them. In the optimization stage, Bellman's principle of optimality is applied to decompose the optimization problem into subproblems in which an optimal policy of available technologies is determined for every conversion step. An optimization formulation is utilized to determine the optimal configuration based on screening and connecting the optimal policies and generating the biorefinery flowsheet. A case study of alcohol‐producing pathways from lignocellulosic biomass is solved to demonstrate the merits of the proposed approach. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Fatty Acids in Heterocyclic Synthesis Part XII: Synthesis of Surfactants from Pyrazole, Isoxazole, Pyrimidine and Triazine, Incorporating the 1,3,4-Thiadiazole Moiety Having Dyeing and Antimicrobial Activities

The titled compounds were prepared from 2-amino-5-heptadecyl[1,3,4]thiadiazole (1). Diazotization of (1) produced (2) which was coupled with active methylene compounds and gave azo ⇌ hydrazono derivatives (3A, 3B) _a–d . It was found that there is regio-specificity for addition of different nucleophiles to these tautomers; thus, nitrogen nucleophiles such as hydrazine hydrate, hydroxylamine hydrochloride and thiourea were reacted via Azo tautomer (3A) to yield pyrazole, isoxazole and pyrimidine respectively (5-7), while carbon nucleophiles as phenylisocyanate was reacted via the hydrazono tautomer (3B) and produced triazine derivatives (4). Additionally, the diazonium chloride (2) was coupled with alkaline 2-naphthol and produced 2-(5-heptadecyl-[1,3,4]thiadiazol-2-yl)-1,2-dihydro-3-oxa-1,2-diaza-cyclopenta[a]naphthalene (8). UV–visible spectra of the synthesized colored compounds (2-8) showed λ _max at 374–398 nm, while screening these compounds in vitro against micro-organisms (including structure-activity relationship SAR study) revealed high antibacterial and moderate antifungal activities. Propoxylation of compounds 1, 3, 5, 6, 7 and 8 with 3, 5, 7 mol of propylene oxide produced nonionic surfactants I(a–c)–IX(a–c) having surface active properties so, it is clear that the tested surfactants can be used in the manufacture of dyes, drugs, cosmetics, emulsifiers, pesticides, luminphores for optical applications and many other industries with low toxicity to human beings and the environment owing to their high solubility and good biodegradability.     

Microwave assisted hydrothermal synthesis of engineered cerium oxide nanopowders

Cerium oxide nanopowders have been prepared via microwave assisted hydrothermal technique in the presence of different amounts of poly vinyl pyrrolidone (PVP). The prepared nanopowders were characterized using XRD, TEM and SAED. The results showed that the particle size of the ceria nanopowders was decreased with the increase of PVP amount. The prepared ceria has nanocrystalline cubic fluorite structure with high purity. The influence of PVP content on the densification behavior of CeO₂ was investigated by means of dilatometer and scanning electron microscopy (SEM). It was found that the increase of PVP amount reduced sintering temperature. The cold-pressed powders can be sintered to full density at temperatures starting from 1070 °C in just 10 min.     

Magnetic and Electrical Properties of Glass and Glass-Ceramics Based on Weathered Basalt

Silicon - A total of six glass batches (WB100-WB50) based primarily on weathered basalt with successive addition of bypass cement dust (with the weight content 0–50%) were melted at...