Search results for "Oct"
showing 10 items of 3052 documents
Surface characterization of functional poly(diacetylene) and poly(butadiene) mono- and multilayers
1982
The surface properties of Langmuir-Blodgett mono- and multilayers of a variety of amphiphilic poly(diacetylene)s and poly(butadiene)s were investigated by contact angle, streaming potentialζ, ellipsometry, and X-ray photoelectron spectroscopic (XPS) measurements. Captive air and octane angles varied between approximately 60° and 105° for hydrophobicx-layers and 31° to 46° for hydrophilic surfaces depending on the particular head group, whereas advancing angles determined via the vertical plate method are considerably higher. Negative streaming potentials were obtained for all surfaces. Positively charged monolayers yielded less negativeζ- potential values (−28 mV) than negatively charged (−…
Aging of Nanosized ZnO Modified Polyoxymethylene Blends with Ethylene–octene Copolymer
2015
The influence of ethylene–octene copolymer and zinc oxide (ZnO) on structure and tensile stress–strain behavior of polyoxymethylene were investigated before and after ultraviolet weathering. Addition of ZnO considerably improved stress–strain characteristics of the ultraviolet-irradiation impaired composites. Crystallinities of ultraviolet-irradiated composites were affected by numerous competitive processes, including suppression of crystallization in the presence of multiple components in the system, nucleation induced by nanofiller, secondary crystallization and amorphization because of the chain scissions of the macromolecules. Addition of ZnO considerably improved stability of the comp…
Online measurement of floc size, viscosity, and consistency of cellulose microfibril suspensions with optical coherence tomography
2021
AbstractIn this study, cellulose microfibril (CMF) suspensions were imaged during pipe flow at consistencies of 0.4%, 1.0%, and 1.6% with optical coherence tomography (OCT) to obtain images of the structure and the local velocity of the suspension. The viscosities obtained by combining pressure loss measurement with the OCT velocity data showed typical shear thinning behavior and were in excellent agreement with viscosities obtained with ultrasound velocity profiling. The structural OCT images were used to calculate the radial and the axial floc sizes of the suspension. A fit of power law to the geometrical floc size–shear stress data gave the same power law index for all consistencies, sug…
Anti-Arrhenian behaviour of conductivity in octanoic acid–bis(2-ethylhexyl)amine systems: a physico-chemical study
2015
Pure surfactant liquids and their binary mixtures, owing to the amphiphilic nature of the molecules involved, can exhibit nano-segregation and peculiar transport properties. The structural and dynamic properties of octanoic acid (OA)–bis(2-ethylhexyl)amine (BEEA) liquid mixtures at various compositions have been studied by Wide Angle X-ray Scattering (WAXS), 1H-NMR and broadband dielectric spectroscopy as a function of temperature. It was found that the self-assembly occurs via proton exchange between the OA COOH group and the BEEA NH one; such self-assembled local structures are affected anisotropically by a temperature increase so that the thermal dilatation is more marked in a direction …
Nano-composite thermochromic thin films and their application in Energy-efficient glazing
2010
A hybrid atmospheric pressure and aerosol-assisted chemical vapour deposition strategy is presented as a facile route for the production of vanadium dioxide nano-composite thin films. The effect of the inclusion of gold nanoparticles and the use of a surfactant molecule, tetraoctylammonium bromide, is discussed. The films were fully characterised using a wide variety of techniques, including scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV/vis/NIR spectroscopy. It is shown that micro-structural changes brought about by careful control of film growth conditions, and/or the use of surfactant, lead to an enhancement of thermochromic properties. Gold nano…
Synthesis and crystal structure of the α polytype of HfNBr
2002
Abstract α-HfNBr has been prepared at 760 °C in a sealed evacuated fused silica tube by reaction between NH4Br and Hf followed by purification through chemical vapour transport under a temperature gradient. The crystal structure of this compound at room temperature has been determined for the first time by Rietveld refinement of X-ray powder diffraction data, electron diffraction and high resolution electron microscopy. It crystallises in the orthorhombic space group Pmmn with the unit cell parameters a=4.1165(2), b=3.5609(2), c=8.6440(3) A. α-HfNBr is isotypic to FeOCl and is built from layers of composition BrHfNNHfBr stacked along c that are separated by a Van der Waals gap. The haf…
Characterization of micro-fibrillated cellulose fiber suspension flow using multi scale velocity profile measurements
2017
Rheological properties and boundary layer flow behavior of Micro Fibrillated Cellulose (MFC) suspended in water was studied using a novel velocity profiling rheometric technique. The method is based on measuring stationary velocity profiles of fluid flow in a straight tube simultaneously by Doppler Optical Coherence Tomography (DOCT) and by Ultrasound Velocity Profiling (UVP). The high resolution DOCT provides velocity profiles near the transparent tube wall, while UVP yields corresponding information in the interior parts of the flow. The data from the two instruments is combined into a comprehensive velocity profile including both the thin boundary layer near the wall and the interior par…
Supercontinuum generation in silicon waveguides based on optical wave-breaking
2014
We theoretically find the third order dispersion that optimizes the spectral broadening induced by optical wave-breaking. It produces supercontinuum spectra spanning beyond 2=3 of an octave in a silicon waveguide pumping at 1550 nm.
Effect of thermal treatment on the structural evolution of 3:2 and 2:1 mullite monophasic gels
2005
Abstract Single phase mullite gels with composition 3Al2O3 · 2SiO2 (3:2) and 2Al2O3 · SiO2 (2:1) were prepared by the semialkoxide method using aluminum nitrate nonahydrate and tetraethylorthosilicate as reagents. The influence of the thermal processing conditions on the reaction sequence was investigated. Both 3:2 and 2:1 mullite gels formed orthorhombic mullite under fast heating (40 °C/min) at 900 °C. Slow heatings delayed the formation of mullite in both gel compositions but no formation of spinel was detected between 1000 °C and 1100 °C. The slow transformation of pentacoordinated aluminum to octahedral and tetrahedral arrangements probably depends on the larger size and extent of the …
Oxygen K-edge x-ray absorption near-edge structure in crystalline and amorphous molybdenum trioxides
2004
X-ray absorption near-edge structure (XANES) signals at the oxygen K edge in polycrystalline α-MoO3 and amorphous a-MoO3 thin film were analysed within the full-multiple-scattering (FMS) formalism. Significantly different XANES signals were found for non-equivalent oxygen atoms in low-symmetry layered-type α-MoO3 structure. The obtained results are in agreement with the experimental data and allow us to interpret all XANES peaks for α-MoO3. Besides, the FMS XANES simulations, performed for several fragments of α-MoO3 structure, allowed us to explain the O K-edge XANES in amorphous a-MoO3 thin film. We found that although the crystallographic structures of α-MoO3 and a-MoO3 are strongly diff…