The Effect of Nanosized Layered Materials on the Structure-Property Relationship of Poly(aniline)s: An FTIR Kinetic Study

Aniline (ANI) was chemically polymerized in the presence of two different nanosized layered materials, zirconylphosphate (ZP) and molyptic acid (MA) under different experimental conditions with nitrogen purging at 45°C. The effect of nanosized layered materials on the rate of polymerization (R_p) and Fourier transform infra red-relative intensities (FTIR-RI) of benzenoid and quinonoid forms of poly(aniline) (PANI) were tested. The thermal stability and electrical conductivity values were boosted with the help of nanosized materials. High resolution transmission electron microscope (HRTEM) determined the size of nano material and its uniform distribution on the PANI matrix. For the sake of comparison, o-toluidine (OT) was polymerized under the same experimental conditions and its structure-property relationship in the presence of nano materials were also tested and critically compared with PANI systems.     

Structural state of electroless nickel–boron deposits (5 wt.% B): Characterization by XRD and TEM

The structure of electroless nickel–boron with a boron content around 5 wt.% was investigated in the as deposited and heat treated states by X-ray diffraction and by transmission electron microscopy on thinned cross-sections prepared by focused ion beam technique.     

Linear and cyclic oligomers in polybutylene terephthalate for food contact materials

Polybutylene terephthalate (PBT) is a polyester (PES) gaining more importance on the food contact material (FCM) market. However, little is known about the potential migration of PBT oligomers which are formed during polymer production. In this work, PBT pellets and a slotted spoon manufactured from this material by injection moulding were analysed on extractable oligomers and their migration potential into hydrophilic foods. Overall 27 oligomers (cycles and linears) could be identified in different extracts by HPLC-DAD/ESI-MS data, but without confirmation by reference substances. The oligomers were quantified by HPLC-DAD using bis(2-hydroxyethyl) terephthalate (BHET) as external standard and the total amount of oligomers isolated by reprecipitation from the pellets and the spoon were 0.69 and 0.71%, respectively. While cyclic oligomers made up for approximately 90% of the extractable oligomers, linear oligomers proved to be more relevant for migration into aqueous foodstuffs. Furthermore, it was shown that hydrolysis of oligomers can take place in water at elevated temperatures. Consequently, the qualitative and quantitative composition of PBT oligomers in aqueous foods from FCMs does not only depend on migration but also on hydrolysis. Migration testing of the PBT spoon under repeat use conditions with water at 100°C for 2 h resulted in 0.29 mg item^?1 of linear oligomers and 0.05 mg item^?1 of the cyclic PBT dimer in the third migrate.     

Modeling of the electromechanical coupling between crack propagation and piezoelectric behavior in active layers of smart devices

In this article, a new computational approach is investigated to predict the crack propagation inside some smart structures equipped with surface-bonded piezoelectric layers; meanwhile, the electromechanical coupling is exploited. The current industrial need of analyzing rather irregular geometries motivates resorting to a numerical approach. Therefore, the finite element method (FEM) is used to predict both the fracture behavior and the coupled response of piezoelectric material through a suitable interoperation of the two computational environments, available in some commercial code like the ABAQUS^©. The two solutions are then coupled by means of a subroutine, in this case operated through the ISIGHT^© tool. After a preliminary analysis and a validation, results of some numerical simulations are shown to highlight some significant peculiarities of the coupled behavior of the piezoelectric material.     

Model for practical prediction of natural carbonation in reinforced concrete: Part 1-formulation

A model is proposed for prediction of natural carbonation in reinforced concrete (RC) structures, and is potentially applicable to existing and new RC structures. The major components of the model comprise mathematical functions applied to predict the influence of concrete composition, and environmental factors on natural carbonation.This paper introduces the model concept and explains its structure including derivation, optimization and calibration. Over 163 data sets taken from a 10-year carbonation study were used in the model development and calibration. Only the experimental data that were based on outdoor natural exposure environment were employed in this research. Also in this study, the proposed model is compared with fib-Model Code 2010 using carbonation predictions generated from 346 data sets involving real world, highway structures. It is shown that the proposed model is comparably accurate and involves mainly basic tests with no major anticipated costs.     

Structural and electrical properties of Cr-doped SrTiO3 porous materials

Series of single-phase materials with assumed formula SrTi_1?xCr_xO₃ (where x = 0, 1, 4, 6 mol.%) were obtained by sol-gel method. The structure and microstructure of materials were characterised by X-ray diffraction and scanning electron microscopy methods. Moreover, the study of electrical properties and evaluation of chemical stability in CO₂/H₂O atmosphere was performed by electrochemical impedance spectroscopy and thermogravimery methods, respectively. The possibility of participation of Cr-doped strontium titanate in oxidation–reduction processes was analysed by temperature-programed reduction (TPR) and temperature-programed oxidation (TPOx) measurements. The changes of lattice parameters together with XPS analysis, the Seebeck coefficient measurements results and TPR profiles obtained for SrTi_1?xCr_xO₃ materials prove the presence of chromium on +3 and +6 oxidation stages. Thus, chromium can be treated as both acceptor- and donor-type dopant in the SrTiO₃ structure. The Cr³⁺/Cr⁶⁺ ratio strongly affects the electrical properties, as the change of conduction mechanism was observed. The results of performed stability test clearly indicate that incorporation of chromium into SrTiO₃ structure results with decrease of chemical stability in CO₂ atmosphere.     

Room temperature response and enhanced hydrogen sensing in size selected Pd-C core-shell nanoparticles: Role of carbon shell and Pd-C interface

In the present work, the effect of carbon shell around size selected palladium (Pd) nanoparticles on hydrogen (H₂) sensing has been studied by investigating the sensing response of Pd-C core-shell nanoparticles having a fixed core size and different shell thickness. The H₂ sensing response of sensors based on Pd and Pd-C nanoparticles deposited on SiO₂ and graphene substrate has been measured over a temperature range of 25 °C–150 °C. It is observed that Pd-C nanoparticle sensor shows higher sensitivity with increase in shell thickness and faster response/recovery in comparison to that of Pd nanoparticle samples. Pd-C nanoparticles show room temperature H₂ sensitivity in contrast to Pd nanoparticles which respond only at higher temperatures. Role of carbon shell is also understood by investigating H₂ sensing properties of Pd and Pd-C nanoparticles on graphene substrates. These results show that higher catalytic activity and electronic interaction at Pd-C interface, a complete coverage and protection of Pd surface by carbon and presence of structural defects in nanoparticle core are important for room temperature and higher sensing response.     

Method for analysis of 68 organic contaminants in food contact paper using gas and liquid chromatography coupled with tandem mass spectrometry

Food contact materials (FCMs) have been reported as a source of various xenobiotics. This study investigates the possibility of simultaneous analysis of 68 potential contaminants in paper FCMs, specifically phthalates, polycyclic aromatic hydrocarbons, photoinitiators, bisphenols, and polyfluorinated compounds. Target compounds were co-isolated using a technique based on ultrasonic extraction by mixture of acetonitrile and water followed by QuEChERS-like liquid–liquid partition in the presence of inorganic salts. Resulting extracts were analyzed using gas and high performance liquid chromatography coupled with tandem mass spectrometry (GC–MS/MS, HPLC–MS/MS). Acceptable recoveries (70–120%) and RSDs (<20%) were achieved for most of the analytes at spiking levels of 0.05, 0.2 and 1 mg/kg. LOQs ranged from 0.0013 to 0.22 mg/kg. The proposed method was successfully applied to analysis of 15 real samples. Complex mixtures of contaminants reaching levels up to 48 mg/kg were identified in the samples.