The noble effect of aging on the thermal conductivity of modified CNTs-ethylene glycol nanofluids

In order to improve the heat transfer process by using nanofluids, different nanoparticles and base fluids have been studied. In this work, stability and effect of aging and temperature on the thermal conductivity of CNTs-ethylene glycol (EG) nanofluids were investigated. Chemical functionalisation was used to oxidise the surface of CNTs. The functionalised CNTs were used to prepare the nanofluids by a two-step method. The stability of nanofluids was measured by UV-vis spectroscopy and the results showed that the nanofluids had a good stability over several days. Immediately after nanofluid preparation not too much increase was observed for thermal conductivity but the nanofluid aging had a great influence on the improvement of the thermal conductivity, as after 65 days, about 50% increase was observed. The increase has been attributed to forming an ordered nanolayer of EG molecules around the CNTs. Also no significant temperature dependence of thermal conductivity was observed up to 50°C possibly due to the lack of temperature dependence of CNTs Brownian motions.     

Optical and hydrophilic properties of Cr doped TiO2-SiO2 nanostructure thin film

Cr doped TiO₂-SiO₂ nanostructure thin film on glass substrates was prepared by a sol-gel dip coating process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structural and chemical properties of the films. A UV-vis spectrophotometer was used to measure the transmittance spectra of the thin film. The hydrophilicity of the thin film during irradiation and storage in a dark place was measured by a contact angle analyzer. The results indicated that Cr doping has a significant effect on the transmittance and super-hydrophilicity of TiO₂-SiO₂ thin film.     

A Promising Material for Selective Sensing Biomarker Gas Molecules

Russian Journal of Physical Chemistry A - The interaction of many biomarker gas molecules on pure, AlB-doped and GaB-doped boron nitride nanotube was studied by the density functional theory method...     

Locating and capacity planning for retailers of a new supply chain to compete on the plane

This paper investigates the network design problem of a two-level supply chain (SC), which is applicable for industries such as automotive, fuel and tyre manufacturing. Models presented in this paper aim at locating retail facilities of an SC and identifying their required capacities in the presence of existing competing retailers of a rival SC. We consider feasible locating space of the retail facilities on the continuous plane with bounded constraints and static competition among the rivals of the markets with deterministic demands. The problem is used for both essential and luxury product cases; hence, we consider elastic and inelastic demands, both. The models discussed in this paper are non-linear and non-convex which are difficult to solve. We use interval branch-and-bound as optimization algorithm for small size single-retailer problems, but for large-scale, multi-retailer problems we need to have more efficient methods. Therefore, we apply a heuristic algorithm (H1), a simulated annealing (SA) algorithm, an interior point (IP) algorithm, a genetic algorithm (GA) and a pattern search algorithm for solving multi-retailer problem with elastic and inelastic demands. Computational results obtained from performing different solution approaches for both elastic and inelastic show that mostly IP, PS, and H1 methods outperform the other approaches. The computational results on a real-life case are also promising. Several extended mathematical models and an example of a typical case with details are presented in the appendices of the paper.     

A Theoretical Study on Chapman Rearrangement

Some Chapman rearrangements are investigated using HF and B3LYP methods combined with two different basis sets (6‐31G** and 6‐31++G**) and both finite difference model and Janak's approximation. It is shown that although minimum polarizability (MPP) and maximum hardness (MHP) principles are always valid in these reactions, minimum electrophilicity principle (MEP) is followed just when DFT method (B3LYP) is used. The Morrel's rules are also successfully applied in predicting the validity of MEP in these rearrangements. Therefore, it seems that in the study of this kind of reaction, the results of DFT are more reliable than those of HF.     

Synthesis and morphology control of surface functionalized nanoscale yttrium aluminum garnet particles via supercritical hydrothermal method

Organic-functionalized nanoscale yttrium aluminum garnet (YAG) particles were synthesized via a simple rapid supercritical hydrothermal method in the presence of oleylamine and oleic acid as organic surface modifiers. The presence of the organic molecules resulted in the various morphologies of the produced YAG particles, including cubic, spherical and chainlike structures. Because of their hydrophobic surface character, as-synthesized particles were dispersible in organic solvents.     

Chlorodiphenylphosphine as Highly Selective and Efficient Reagent for the Conversion of Alcohols,Tetrahydropyranyl and Silyl Ethers to Thiocyanates and Isothiocyanates

Abstract

A simple, highly selective and efficient method is described for the conversion of primary alcohols, tetrahydropyranyl and silyl ethers to thiocyanates by use of chlorodiphenylphosphine and ammonium thiocyanate. Secondary substrates produce both the two isomeric products, thiocyanate and isothiocyanate, while tertiary ones give isothiocyanates as the only products by this new method. In contrast to previously reported methods based on trivalent phosphorus for this transformation, the present method does not require an electrophile in the presence of trivalent phosphorus (ClPPh₂). The order of activity of these substrates is silyl ether> alcohol > tetrahydropyranyl ether. The present method not only interestingly distinguishes between primary, secondary and tertiary substrates but also converts them to the corresponding thiocyanates with excellent chemoselectivity in the presence of several other functional groups.     

One-pot reaction as an efficient method for rigid molecular tweezers

Rigid molecular tweezers are compounds of increasing scientific interest. As the structural requirements for such compounds are highly specific, few types of these tweezers are thus far known. The preparation of examples of rigid large-pincered molecular tweezers based on bis Troger's bases derived from 1,4-benzenediamine is described. In addition, evidence is presented of the different binding abilities of the diastereoisomers of such compounds.