In situ X-ray analysis under controlled potential conditions: An innovative setup and its application to the investigation of ultrathin films electrodeposited on Ag(1 1 1)

An innovative setup to combine electrochemical and in situ surface X-ray diffraction (SXRD) measurements is described. This electrochemical cell has a different design from the other ones commonly used for X-ray diffraction studies. It allows the sample surface to stay always completely immersed into the solution under controlled potential conditions even during the SXRD measurements. The X-ray beam crosses the liquid (about 1 cm) and the cell walls. Because of the high X-ray energy, the beam attenuation is negligible and by an appropriate positioning of the detector arm slits it is possible to minimize the diffuse scattering induced by the liquid and cell walls in order to still detect the minima of the crystal truncation rods (CTRs). The liquid solution in the cell is managed by a special device, which allows the controlled exchange of the electrolyte solutions necessary in the electrochemical atomic layer epitaxy (ECALE) growth. The whole setup can be remotely controlled from outside the experimental hutch by a dedicated computer. As an example we report measurements on S layers deposited at underpotential on the Ag(1 1 1) surface, and on CdS films of increasing thickness.     

Thermodynamic properties of malonic, succinic, and glutaric acids: evaporation rates and saturation vapor pressures

This work provides thermodynamic data, in particular, liquid-state saturation vapor pressures of three common slightly water soluble secondary organic aerosol components, namely, malonic, succinic, and glutaric acids. A modified tandem differential mobility analyzer system was used to measure evaporation rates of nanometer sized aqueous malonic, succinic, and glutaric acid droplets at relative humidities and temperatures relevant in the lower troposphere. Liquid phase saturation vapor pressures and other thermodynamic properties were derived from the measurements using a binary condensation model. The obtained expressions for liquid phase saturation vapor pressures compare well with extrapolated literature data. The importance of the choice of method for calculating activity coefficients is discussed.     

Application of an equation-oriented framework to formulate and estimate parameters of chemical looping reaction models

Accurate, predictive reaction models are critical for the design and optimization of chemical looping combustion (CLC) reactors. The formulation and estimation of kinetic parameters for these reaction models using a first-principles equation-oriented (EO) approach is particularly beneficial as large amounts of experimental data spanning process-relevant conditions can be used to estimate parameters in a computationally tractable way. This work demonstrates the application of a novel EO framework to develop reduction reaction kinetic models of an iron-based CLC oxygen carrier (OC). An optimization problem is formulated to estimate kinetic parameters that provide the best fit to the experimental data. The model predicts the state of the OC with mean square error values of 2.5%–4.4% across the full range of validation data, including multiple reduction cycles.     

Influence of Various Albumin Concentrations on the Corrosion Resistance of Zr-2.5%Nb Alloy

The Zr-2.5% Nb alloy corrosion resistance in four saline solutions with and without albumin was tested through electrochemical measurements of electrochemical impedance spectroscopy (EIS), linear polarization, and cyclic voltammetry at human body temperature.

The EIS measurements were performed at open circuit potential. The impedance spectra were recorded and the equivalent electric circuits were elaborated. From the linear polarization the Tafel slopes were recorded and the corrosion parameters were calculated. From the potentiodynamic polarization curves, the breakdown potential, the protection potential, and the protection domain were observed.

The amount of ions released from the material was quantified using the ICPMS technique and the results concerning the corrosion resistance were compared with those obtained from linear and cyclic polarization.

Before and after potentiodynamic polarization the topographic measurements were performed; the roughness at the samples surface was observed using AFM. The roughness was co-related to the contact angle measurements.     

Pseudolites/repeaters infrastructure autopositioning approach—mathematics and first simulation-based results

In the various infrastructure-based indoor positioning systems using Global Navigation Satellite System signals, i.e. pseudolites, repeaters, and repealites, there is the need for the terminal to know the positions of the various transmitters. Some techniques have been proposed for high accuracy pseudolite systems, but they require carrier phase measurements and a careful choice of some specific test locations. Other approaches consider that these data are simply available by any means: Of course, this can be achieved through manual distance measurements and the use of maps of the indoor environment. In this paper, we describe a new method that is based on a two-step approach. The first one consists in deploying the system. The second one is the calculation of the position of the transmitters through classic code measurements for a few specific chosen locations. Thus, the system can be deployed without any constraint and the locations of the transmitters calculated through a basic set of elementary measurements. The theoretical method is first described and the resulting accuracy of the position of the transmitters is then evaluated through theoretical calculations. In addition, electromagnetic simulations are carried out in order to estimate the pseudo-range errors of the proposed measurements: The accuracy of the determination of the position of the transmitters is then estimated (note that two receiver tracking loop implementations are considered). Thus, the accuracy of the proposed method is evaluated theoretically and through simulations.     

Optimization of Opto-Electrical and Photocatalytic Properties of SnO<Subscript>2</Subscript> Thin Films Using Zn<Superscript>2+</Superscript> and W<Superscript>6+</Superscript> Dopant Ions

Abstract  

A series of Zn²⁺ and W⁶⁺ doped tin oxide (SnO₂) thin films with various dopant concentrations were prepared by spray pyrolysis deposition, and were characterized by X-ray diffraction, atomic force microscopy, contact angle, absorbance, current density–voltage (J–V) and photocurrent measurements. The results showed that W⁶⁺ doping can prevent the growth of nanosized SnO₂ crystallites. When Zn²⁺ ions were used, the crystallite sizes were proved to be similar with the undoped sample due to the similar ionic radius between Zn²⁺ and Sn⁴⁺. Regardless of the dopant ions’ type or concentration, the surface energy has a predominant dispersive component. By using Zn²⁺ dopant ions it is possible to decrease the band gap value (3.35 eV) and to increase the electrical conductivity. Photocatalytic experiments with methylene blue demonstrated that with zinc doped SnO₂ films photodegradation efficiencies close to 30% can be reached.     

Chemical and sensory changes of different dairy products during storage in packages containing nanocrystallised TiO2

The chemical changes of three types of cheese, yoghurt and kefir were evaluated during storage in packages containing TiO₂ with two different compositions of the mixed anatase–rutile phase. The influence of TiO₂ packaging during storage on titratable acidity and fat content and on the external aspect was investigated. Fourier Transformed Infrared Spectroscopy (FTIR) analyses were performed to establish whether the TiO₂ penetrated the food during storage. The results showed that the TiO₂ nanoparticles deposited on polyethylene surface significantly decreased acidity and fat content of the investigated cheese and yoghurt types. During storage in TiO₂ nanopackages, the change in chemical parameters is accentuated as the content of rutile grows from 2.8% to 6.9%. The sensory evaluation revealed that the dairy products stored for 11 days in TiO₂ nanopackages present similar colour, texture and flavour with that of the references; the samples stored in polyethylene film were found to be unacceptable.