Effects of high temperature drying in nitrogen atmosphere on mechanical and colour properties of Norway spruce

Heat treatment and drying processes of wood are always accompanied by material changes. These changes are partly caused by oxidative reactions. This study aims to compare high temperature drying in inert gas atmosphere with conventional kiln drying of spruce wood. The mechanical properties as well as colour changes were measured after drying. In general, higher compression strength was observed for samples dried at high temperatures in nitrogen atmosphere. However, tensile and bending strength proved no significant difference. Corresponding to the strength values increased stiffness values were also observed for the compression samples, whereas for tension and bending samples no significant effect was visible. Up to a temperature of approx. 125 °C discolouration is prevented by drying samples in nitrogen atmosphere.     

Evolution of diffraction and self-diffraction phenomena in thin films of Gelite Bloom/Hibiscus Sabdariffa

In this work, we present a study of non-linear optical response in thin films elaborated with Gelite Bloom and extract of Hibiscus Sabdariffa. Non-linear refraction and absorption effects were studied experimentally (Z-scan technique) and numerically, by considering the transmittance as non-linear absorption and refraction contribution. We observe large phase shifts to far field, and diffraction due to self-phase modulation of the sample. Diffraction and self-diffraction effects were observed as time function. The aim of studying non-linear optical properties in thin films is to eliminate thermal vortex effects that occur in liquids. This is desirable in applications such as non-linear phase contrast, optical limiting, optics switches, etc. Finally, we find good agreement between experimental and theoretical results.     

Automated three-dimensional X-ray analysis using a dual-beam FIB

We present a fully automated method for three-dimensional (3D) elemental analysis demonstrated using a ceramic sample of chemistry (Ca)MgTiO(x). The specimen is serially sectioned by a focused ion beam (FIB) microscope, and energy-dispersive X-ray spectrometry (EDXS) is used for elemental analysis of each cross-section created. A 3D elemental model is reconstructed from the stack of two-dimensional (2D) data. This work concentrates on issues arising from process automation, the large sample volume of approximately 17 x 17 x 10 microm(3), and the insulating nature of the specimen. A new routine for post-acquisition data correction of different drift effects is demonstrated. Furthermore, it is shown that EDXS data may be erroneous for specimens containing voids, and that back-scattered electron images have to be used to correct for these errors.     

In situ polymerized polyaniline films: The top and the bottom

Polyaniline (PANI) films of submicrometer thickness were deposited in situ during the polymerization of aniline on polystyrene support. Aqueous poly(N-vinylpyrrolidone) solution was subsequently evaporated on the top of PANI films. During peeling off, the PANI film was transferred to a poly(N-vinylpyrrolidone) film. Both sides of the PANI film, the top surface of the film deposited on polystyrene, and the bottom surface originally in contact with a polystyrene dish, became subsequently available for the analysis by Raman and X-ray photoelectron spectroscopies. The molecular structures of both surfaces in protonated state were different, the top side corresponded to protonated emeraldine, while the bottom side to partly deprotonated cross-linked structure containing phenazine-like constitutional units. This result supports the concept of hydrophobic phenazine-like oligomers that are adsorbed at immersed surfaces during the oxidation of aniline, and PANI chains that grow from them, thus creating a brush-like PANI morphology.     

The reduction of silver nitrate to metallic silver inside polyaniline nanotubes and on oligoaniline microspheres

Polyaniline (PANI) reduces silver nitrate to metallic silver. Composites based on conducting polymer and silver have been prepared with equimolar proportions of reactants. Polyaniline bases having different morphologies – granular or nanotubular – and oligoaniline microspheres have been left to react with silver nitrate in acidic, neutral, and alkaline media. The content of silver, typically 20–30 wt.%, was determined by thermogravimetric analysis. Clusters of 40–80 nm silver particles are produced in the granular form of PANI. The formation of silver inside PANI nanotubes has been observed. With oligoaniline microspheres, silver was produced on their surface, and on PANI agglomerates accompanying them. The highest conductivity, 943 S cm^?1, was found with silver reduced by nanotubular PANI base in 0.1 M nitric acid at 17.3 wt.% silver content. The standard granular PANI, used as a reference material, yielded a composite having a much lower conductivity of 8.3 × 10^?5 S cm^?1 at 24.3 wt.% Ag. There is no simple correlation between the conductivity and silver content. Infrared and Raman spectroscopies have been used to study the changes in the molecular structure of the PANI bases of various morphologies before and after reaction with silver nitrate.     

The polymerization of aniline in polystyrene latex particles

Polystyrene latex particles were swollen with aniline and subsequently exposed to ammonium peroxydisulfate solution. The polyaniline membrane was produced at the particle interface and separated both reactants. The electrons from aniline monomer are transferred to oxidant molecules through conducting polyaniline membrane. The aniline and peroxydisulfate thus react without the need to physically meet. Polyaniline gradually penetrated inside latex particle, in contrast to core–shell morphology obtained in classical coating of latex particles with polyaniline.