The significance of nanoparticles on bond strength of polymer concrete to steel

Polymer concrete (PC) is a commonly used material in construction due to its improved durability and good bond strength to steel substrate. PC has been suggested as a repair and seal material to restore the bond between the cement annulus and the steel casing in wells that penetrate formations under consideration for CO₂ sequestration. Nanoparticles including Multi-Walled Carbon Nano Tubes (MWCNTs), Aluminum Nanoparticles (ANPs) and Silica Nano particles (SNPs) were added to an epoxy-based PC to examine how the nanoparticles affect the bond strength of PC to a steel substrate. Slant shear tests were used to determine the bond strength of PC incorporating nanomaterials to steel; results reveal that PC incorporating nanomaterials has an improved bond strength to steel substrate compared with neat PC. In particular, ANPs improve the bond strength by 51% over neat PC. Local shear stresses, extracted from Finite Element (FE) analysis of the slant shear test, were found to be as much as twice the apparent/average shear/bond strength. These results suggest that the impact of nanomaterials is higher than that shown by the apparent strength. Fourier Transform Infrared (FTIR) measurements of epoxy with and without nanomaterials showed ANPs to influence curing of epoxy, which might explain the improved bond strength of PC incorporating ANPs.     

New unstructured mesh water quality model for coastal discharges

A new unstructured mesh coastal water and air quality model has been developed that includes species transport, nonlinear decay, byproduct formation and mass-exchange between sea and atmosphere. The model has been programmed with a graphical interface and is applicable to coastal seawater, lakes and rivers. Focused on species conversion and interaction with the atmosphere, the water and air quality model follows a modular approach. It is a compatible module which simulates distributions based on fluid dynamic field data of underlying existing hydrodynamic and atmospheric simulations. Nonlinear and spline approximations of decay and growth kinetics, byproduct formation and joint sea–atmosphere simulation have been embedded. The Windows application software includes functions allowing error analysis concerning mesh and finite volume approximation. In this work, an anoxic submerged process-water discharge has been simulated. An error analysis has been carried out by varying vertical meshing, time-steps and comparing results based on explicit and implicit finite volume approximation.     

Investigation of voltage reduction in nanostructure-embedded organic light-emitting diodes

We investigated the reduction of the operating voltage in organic light-emitting diodes containing WO₃ nanoislands. The thickness of the organic layer and the periodicity of the nanoislands were varied in order to quantitatively analyze the electrical changes. The thickness of the N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB) layer was varied from 150 nm to 600 nm, and various periodic nanoislands of 300 nm, 330 nm, and 370 nm were fabricated. Two geometric factors, which are the effective length and effective area, influence the operating voltage. The effective length is determined by the relative thickness of the nanoislands compared with the organic thickness, and the reduction of the operating voltage is linearly proportional to the relative thickness. The effective area is a nonlinear function of periodicity, and the voltage is reduced as the periodicity decreases.     

Reliable synthesis of bismuth nanoparticles for heavy metal detection

A reliable and facile pathway is described here for preparing high-quality bismuth nanoparticles. Combined with hydrothermal method and confined growing effect of polymer, bismuth nanoparticles with uniform size and shape were obtained with remarkable productivity. The nanoparticles is proved to be pure Rhombohedral structure Bi crystals with R-3m space group and the diameter of the nanoparticles is about 80 nm with a quite narrow particle size distribution. Those bismuth nanoparticles were predicted to grow from a rolling process by sheet-like Bi nanocrystal intermediates. The obtained bismuth nanoparticles were used to prepare modified electrode for the detection of Cd²⁺ and Pb²⁺ in water solution by stripping analysis. Compared with naked glassy carbon electrodes, the modified electrode showed two obvious responses at −0.85 V and −0.62 V, corresponding to the reduction process of Pb²⁺ and Cd²⁺ and this well-resolved stripping response can be observed when the concentration is as low as 10 μg/L, indicating potential application in electroanalysis for environmental inspection.     

Cracks,microcracks and fracture in polymer structures: Formation,detection, autonomic repair

Polymers and polymer composites are susceptible to premature failure due to the formation of cracks and microcracks during their service time. Evolution of cracks and microcracks could induce catastrophic material failure. Therefore, the detection/diagnostics and effective repair of cracks and microcracks are vital for ensuring the performance reliability, cost effectiveness and safety for polymer structures. Cracks and microcracks, however, are difficult to detect and often repair processes are complex. Biologically inspired self-healing polymer systems with inherent ability to repair damage have the potential to autonomically repair cracks and microcracks. This article is a review on the latest developments on the topics of cracks and microcracks initiation and propagation in polymer structures and it discusses the current techniques for detection and observation. Furthermore, cracks and microcrack repair through bio-mimetic self-healing techniques is discussed along with surface active protection. A separate section is dedicated to fracture analysis and discusses in details fracture mechanics and formation.     

Solvent-induced 1- and 2-D Cd(II) coordination polymers based on a bent polypyridyl ligand

Two Cd(II)-tppda (tppda = N,N,N′,N′-tetrakis(2-pyridyl)-2,6-pyridinediamine) coordination polymers have been prepared via variations of the templating solvent. The solvated complex [Cd₂(tppda)(DMF)₂(μ-SCN)₂(SCN)₂]_n (1) exhibits a 1-D pseudo-helical structure, whereas the unsolvated complex [Cd₂(tppda)(μ-SCN)₄]_n (2) features a 2-D metal-organic framework (MOF). Both are luminescent in the solid state, with emission maxima 444 and 435 nm for 1 and 2, respectively.     

Fluorene derivatives for highly efficient non-doped single-layer blue organic light-emitting diodes

Diphenylamino- and triazole-endcapped fluorene derivatives which show a wide energy band gap, a high fluorescence quantum yield and high stability have been synthesized and characterized. Single-layer electroluminescent devices of these fluorene derivatives exhibited efficient deep blue to greenish blue emission at low driving voltage. The single-layer OLED of PhN-OF(1)-TAZ shows a maximum current efficiency of 1.54 cd/A at 20 mA cm⁻² with external quantum efficiency (EQE) of 2.0% and CIE coordinates of (0.153, 0.088) in deep blue region, while the single-layer device of oligothienylfluorene PhN-OFOT-TAZ shows a maximum brightness of 7524 cd/m² and a maximum current efficiency of 2.9 cd/A with CIE coordinates of (0.20, 0.40) in greenish blue.     

Control of growth and charge transport properties of quaterthiophene thin films via hexyl chain substitutions

Growth mechanism of quaterthiophene based organic thin films deposited by high vacuum deposition on Si:H(1 0 0) and SiO₂ substrates have been investigated. Especially the influence of hexyl chain end-substitutions on the growth process and the electronic transport properties of organic thin films were studied in details. Highly crystalline films were obtained for both quaterthiophene (4T) and α,ω-hexyl-quaterthiophene (DH4T) based thin films. While unsubstituted 4T shows a typical island growth, an almost perfect layer-to-layer growth was found in the case of DH4T based films. It could be demonstrated that the change in the growth mode is directly related to the molecule structure, i.e. to the presence of hexyl chain substitutions on the 4T core, and leads to an increase of the grain size of one order of magnitude under the same evaporation conditions in the case of DH4T films. The characterization of the charge transport properties of thin films based on both molecules reveals one order of magnitude higher mobilities for the DH4T molecules. By using a simple model for charge transport in polycrystalline materials a linear dependence of the mobility on the grain size, independently from the molecule substitution, could be demonstrated. The results underline the importance of the control of the film morphology and give an impressive example of such a control in the case of hexyl end-substitutions of quaterthiophene.     

Hydriding enthalpy and heat capacity of the alloyDB5800

Materials properties like hydriding enthalpy, heat capacity and volumedilation are essential for modelling and designing of metal hydride processes. The hydridingenthalpy and the heat capacity are calculated from an overall energy balance. A reactioncalorimeter has been built up, and the overall energy balance has been derived. All energy termsare calculated and compared with the energy production caused by the hydrogen storing in thealloy. It will be shown that it is justified to neglect a couple of terms to simplify the energybalance.