Helium droplet assisted synthesis of plasmonic Ag@ZnO core@shell nanoparticles

Plasmonic Ag@ZnO core@shell nanoparticles are formed by synthesis inside helium droplets with subsequent deposition and controlled oxidation. The particle size and shape can be controlled from spherical sub-10 nm particles to larger elongated structures. An advantage of the method is the complete absence of solvents, precursors, and other chemical agents. The obtained particle morphology and elemental composition have been analyzed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). The results reveal that the produced particles form a closed and homogeneous ZnO layer around a 2–3 nm Ag core with a uniform thickness of (1.33 ± 0.15) nm and (1.63 ± 0.31) nm for spherical and wire-like particles, respectively. The results are supported by ultraviolet photoelectron spectroscopy (UPS), which indicates a fully oxidized shell layer for the particles studied by STEM. The plasmonic properties of the produced spherical Ag@ZnO core@shell particles are investigated by two-photon photoelectron (2PPE) spectroscopy. Upon excitation of the localized surface plasmon resonance in Ag at around 3 eV, plasmonic enhancement leads to the liberation of electrons with high kinetic energy. This is observed for both Ag and Ag@ZnO particles, showing that even if a Ag cluster is covered by the ZnO layer, a plasmonic enhancement can be observed by photoelectron spectroscopy.

     

Numerical Analysis of the Nb(C,N) Precipitation Kinetics in Microalloyed Steels

Precipitation kinetics of Nb(C,N) in microalloyed steels is crucial for the achievement of favoured steel properties. Therefore, numerous experimental studies have been performed in the past and various theoretical models have been developed to describe Nb(C,N) precipitation. However, the experimental data is sometimes contradictory and even the thermodynamic data for NbC solubility in austenite have a large scatter. In this paper, experimental results on the Nb(C,N) and NbV(C,N) precipitation kinetics in deformed and undeformed austenite are reviewed. Based on these data and with the precipitation kinetics module of the software package MatCalc, computer simulations are performed. The predicted interfacial energy of precipitates is adjusted to match the observed kinetics. A comparison between experimental information and simulation, i.e. time ‐ temperature ‐ precipitation (TTP) diagrams, is drawn and discussed. The results of the computer simulations using modified interfacial energies are in good agreement with the experiments.     

Nanostructured Ca-based sorbents with high CO2 uptake efficiency

Calcium-based carbon dioxide sorbents were made in the gas phase by scalable flame spray pyrolysis (FSP) and compared to the ones made by calcination (CAL) of selected calcium precursors. Such flame-made sorbents consisted of nanostructured CaO and CaCO₃ with twice as much specific surface area (40-60 m²/g) as the CAL-made sorbents. All FSP-made sorbents exhibited faster and higher CO₂ uptake capacity than all CAL-made sorbents at intermediate temperatures. CAL of calcium acetate monohydrate resulted in sorbents with the best CO₂ uptake among all CAL-made ones. At higher temperatures both FSP- and CAL-made sorbents (esp. from CaAc₂·H₂O) exhibited very high initial molar conversions (95%) but sintering contributed to grain growth that reduced the molar conversion down to 50%. In multiple carbonation/decarbonation cycles, the nanostructured FSP-made sorbents demonstrated stable, reversible and high CO₂ uptake capacity sustaining maximum molar conversion at about 50% even after 60 such cycles, indicating high potential for CO₂ uptake. The top performance of flame-made sorbents is best attributed to their nanostructure (30-50 nm grain size) that allows operation in the reaction-controlled carbonation regime rather than in the diffusion-controlled one when sorbents made with larger particles are employed.     

Space Division Multiple Access (SDMA): An Editorial Introduction

Wireless Personal Communications -     

Compatibility Testing of Colored Cosmetics – A New Tool for Objective Testing Near Infrared Remission Spectroscopy (NIR-RS)

The ability to continuously examine the interior hair structure throughout a treatment process is very important in designing effective hair products. Microscopy is commonly used to observe the interior of hair, but this method requires a sliced sample, making continuous observation impossible. Use of X-ray computed tomography (CT) as a non-destructive measurement has been proposed, but this method has a disadvantage in that it is impossible to obtain full-color interior images of the sample. Thus, a non-destructive method for continuous, full-color examination of the interior hair structure has been lacking. In this study a new method is proposed that enables non-destructive and continuous measurement of the interior hair structure with color information. In our method, optical CT is used for reconstruction of the interior hair structure. Our new theories enabled us to solve the crucial problem of the large observational error of traditional optical CT systems caused by internal light scattering and to make its practical application possible. A new optical CT system based on our method was implemented. This system displayed sufficient accuracy when the phantom image was measured, and clear and full-color cross-sectional images were obtained without destruction of the sample when human hair was observed. When the bleaching and dyeing processes were continuously measured, changes in the interior hair with time could be observed. These results clearly indicate that our new method provides a powerful tool for research and product development.     

Microwave assisted HMDSO/oxygen plasma coated polyethylene terephthalate films: Effects of process parameters and uniaxial strain on gas barrier properties,surface morphology,and chemical composition

The coating structure and barrier property relation of coated PET films is of high interest for understanding the difference between predicted and actual barrier performance of coated PET films. In this work the chemical and morphological structure of HMDSO coatings generated with and without oxygen in a microwave plasma has been investigated with XPS and AFM analysis. These results were correlated with oxygen permeation measurements at different strain rates and temperatures. The results show that with a more glass‐like chemical composition the barrier property is improved. The growth of the coatings takes place in a columnar manner and the interfaces between the columns seem to be the low energy passages for the permeation, which cause the difference between predicted and actual barrier performance. When the coatings are strained the barrier fails at a strain higher than 1%. Cracks occur and with higher strain rates the number of cracks increases. Cracking takes place perpendicular to the strain direction and at the interfaces of the columns of the coating. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1485–1495, 2006