Thermal conductivity and properties of cyanate Ester/nanodiamond composites

The aim of this study was to improve thermal conductivity, thermal stability, and mechanical properties of bisphenol A dicyanate ester with the addition of nanodiamond. Cyanate ester/nanodiamond composites containing various ratios of nanodiamond were prepared. Thermal stability and thermal conductivity of the samples were evaluated by thermogravimetric analysis, differential scanning calorimetry, and laser flash method, respectively. The samples were characterized with the analysis such as gel content, water absorption capacity, and stress–strain test. Hydrophobicity of the samples was determined by contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy. The obtained results prove that the cyanate ester/nanodiamond composites have good thermal and mechanical properties and can be used in many applications such as the electronic devices, materials engineering, and other emergent. Copyright © 2014 John Wiley & Sons, Ltd.     

Temperature and concentration influence on drag reduction of very low concentrated CTAC/NaSal aqueous solution in turbulent pipe flow

Some additives, like surfactants or polymers, in aqueous solutions lead to dramatic drag reducing effects. Classically the range of concentration of surfactant additive is greater than 500 ppm. It was recently demonstrated that an aqueous solution of CTAC/NaSal (cetyltrimethyl ammonium chloride and sodium salicylate) with a concentration lower than 100 ppm has been found to reduce drag. In this work, the influence of temperature (10–50 °C) and concentration (25–150 ppm) on the drag reduction is studied with an experimental set-up. A cross analysis is made from those results. It reinforces the link between the structure of the micelles (rod-like shape) and the drag reduction rate.     

Synthesis and characterization of an acrylate polymer containing chlorine-1,3-dioxalane groups in side chains

Poly[2-（4-chlorophenyl）-1,3-dioxolan-4-yl]methyl acrylate,poly（CPhDMA）,was synthesized with radical polymerization process using 2,2′-azobisisobutyronitrile as radical initiator in 1,4-dioxane at 60℃.The structure of poly（CPhDMA） was confirmed by means of UV-Vis,FT-IR,¹H-NMR,and ¹³C-NMR spectral techniques.The molecular weight distribution values of the polymer were determined with gel permeation chromatography（GPC）.The number-average molecular weight（M_n）,weight-average molecular weight（M_W） and polydispersity index（PDI） values of poly（CPhDMA） were determined to be 10300,21600 and 2.097,respectively.The thermal degradation kinetics of the polymer was investigated by using TG/DTG-DTA and DSC analyses at different heating rates in dynamic nitrogen atmosphere.The apparent activation energy values obtained by Flynn-Wall-Ozawa and Friedman methods were found to be 91.68 and 85.23 kJ mol^-1,respectively,for thermal decomposition of poly（CPhDMA）.Also,the thermal degradation activation energy value of poly（CPhDMA） was calculated by using the Kissinger method based on the DTG,DTA and DSC data.Then the mechanism function of it was determined by master plots method.Finally,electrical and optical properties of poly（CPhDMA） were determined by four-point probe and UV-Vis techniques,respectively.     

Facilitated Transfer of Alkali and Alkaline‐Earth Metal Ions by a Calix[4]arene Derivative Across Water/1,2‐Dichloroethane Microinterface: Amperometric Detection of Ca2+

The host–guest complexation reactions between 5,11,17,23‐tetra‐tert‐butyl‐25,27‐diethoxycarbonylmethoxy‐26,28‐dimethoxy calix[4]arene (BDDC4) and alkali and alkaline‐earth metal ions were investigated by facilitated ion transfer processes across water/1,2‐dichloroethane microinterface by using steady‐state cyclic voltammetry and differential pulse voltammetry. The obtained facilitated transfers for Li⁺, Na⁺, K⁺, Rb⁺ and Ca²⁺ were evaluated under the different experimental conditions, at the excess concentrations of metal ions with respect to BDDC4 and vice versa. The association constants having 1 : 1 stoichiometry for Li⁺, Na⁺, K⁺ and Rb⁺ in 1,2‐DCE were determined. Also, we demonstrated that BDDC4 can play an important role for the development of highly selective chemical sensor for Ca²⁺ among alkaline‐metal ions in the concentration range of 0.1–1.0 mM in aqueous solution.     

MoS<Subscript>2</Subscript>-Ti composite films having (002) orientation and low Ti content

MoS₂ is a solid lubricant exhibiting the properties like graphite as structure. The selection and control of deposition parameters should be attached importance very much since it exposes the properties desired from tribological and mechanical directions. Its usage is limited at atmospheric conditions because it is very sensitive to humidity. Therefore, both mechanical strength and resistant to oxidation can be provided by adding a suitable selected interleaving metal into MoS₂ matrix and by using suitable deposition parameters. In this work, MoS₂-Ti, composite films were grown on AISI 52100 steel by PMS (pulsed magnetron sputtering), and evaluated mechanically, structurally and tribologically. The produced film exhibited a low friction coefficient, low wear rate and significantly high wear life. This development was attributed to (002) basal plane orientation which is chemically inert, and low %Ti content and the use of pulsed-dc which is offers a stable deposition process, and also the accordance between the hardness values of substrate and film.     

Spectrofluorimetric Determination of Aliskiren in Tablets and Spiked Human Plasma through Derivatization with Dansyl Chloride

A simple and sensitive method has been developed and validated for the determination of aliskiren (ALS) in its dosage forms and spiked plasma. The method was based on the reaction of the drug with dansyl chloride in the presence of bicarbonate solution of pH 10.5 to give a highly fluorescent derivative which was measured at 501 nm with excitition at 378 nm in dichloromethane. Different experimental parameters affecting the development of the method and stability were carefully studied and optimized. The calibration curves were linear over the concentration ranges of 100–700 and 50–150 ng/mL for standard solution and plasma, respectively. The limits of detection were 27.52 ng/mL in standard solution, 4.91 ng/mL in plasma. The developed method was successfully applied to the analysis the drug in the commercial tablets and spiked plasma samples. The mean recovery of ALS from tablets and plasma was 100.10 and 97.81%, respectively. A proposal of the reaction pathway was presented.     

New traceability chains in the photometric and radiometric measurements at the National Metrology Institute of Turkey

Optical Standards Laboratory of the National Metrology Institute of Turkey (UME) performs photometric, radiometric and fiber optics measurements related to SI-based units. The new traceability chains in the photometric and radiometric measurements are established in 2004, where top of the chains is based on primary-level optical power measurements with a cryogenic radiometer facility.