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.     

Optimal network configuration and capacity expansion of railroads

Railroads ship individual cars according to blocking plans that route the cars in groups (blocks) that share common intermediate stops. An individual shipment is regrouped (reclassified) two to three times along the way from its origin to destination. Yards are crucial facilities of the rail network where cars are reclassified according to such blocking plans. Therefore, yard locations and the blocking plan impose the detour and classification of cars over the physical network. Yards are capacitated with respect to number of blocks made and number of cars classified; rail lines between major stations are capacitated with respect to number of cars that pass through. These restrictions are accounted for in designing the blocking plans. Changing the yard locations and expanding associated capacities may result in dramatic changes in blocking plans saving tens of millions of dollars in railroad transportation costs. We develop a mathematical programming formulation and propose solution methods for the yard location problem and the capacity expansion problems. We demonstrate that the railroads can save significantly by reconfiguring their networks.     

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 <Emphasis Type="Italic">Cis</Emphasis>-[V<Superscript>IV</Superscript>O(pzc)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]·2H<Subscript>2</Subscript>O (pzc: 2-pyrazinecarboxylate)

Abstract  

Hydrothermal synthesis and the structural characterization of V(IV) complex of 2-pyrazinecarboxylate (pzc), is reported. The vanadium is in a distorted octahedral environment. Pairs of pyrazine-2-carboxylate ligands are always cis to each other. The pzc ligands do not link adjacent vanadium atom directly. The remainder of the three-dimensional network is completed by intense hydrogen bonding of uncoordinated water molecules to aqua and pzc ligands. Cis-[V^IVO(pzc)₂(H₂O)]·2H₂O, 1, was characterized by means of elemental analysis (CHNS), TGA, FT-IR, manganometric titration, bond valance sum calculations and single crystal X-ray diffraction methods. Crystal data for 1: monoclinic space group P2 ₁ /c and unit-cell parameters are a = 9.1142(5), b = 16.5822(10), c = 12.8936(7) ?, β = 131.625(3)° and Z = 4. To the best of our knowledge, cis-[V^IVO(pzc)₂(H₂O)] is reported without single crystal structure by Eugenio Garribba and his colleagues in year 2006. Herein we complete full characterization of the title complex with single crystal structure and also 1 will be the first reported example of solid vanadium complex of 2-pyrazinecarboxylates involving intense hydrogen bonding.     

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.     

Synthesis,Crystal Structure Properties of {μ-Nitrato-[<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-ethylene-bis(3-methoxysalicylideneimin) diaqua nitrato Cu(II)La(III)]nitrat}

Abstract  

The [μ-NO₃-LCuLa(NO₃)·(H₂O)₂]NO₃ (I) complex has been prepared and characterized by single crystal X-ray diffraction properties. The title compound crystallizes in the monoclinic system, space group P 2₁/c, with a = 9.1699(4), b = 21.6796(8), c = 13.7068(6) ?, α = γ = 90o, β = 111.308(3)°, V = 2538.63 (18) ?³ and Z = 4. The unit cell contains four discrete the title compounds. The central region is occupied by Cu^II and La^III ions which are brigged by two phenolato oxygen atoms of ligand. The intramolecular La–Cu distance is 3.5016 (3) Ǻ. The copper (II) ion is in a distorted square pyramidal geometry with the imino nitrogen atoms N1 and N2, and the phenolic oxygen atoms O2 and O3 forming the square base. The La^III ion is deca coordinated.     

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.