Pure and Gd doped LAMOX powders and thin films obtained by chemical route

Abstract

The present work deals with the preparation of pure and Gd doped LAMOX powders and thin films by a Pechini's based solution method. Gd doping proved to be efficient not only in stabilising the β form at room temperature but also in reducing the particle size and improving the film quality. Best results for both particles and films were achieved using 10 mol.-% dopant, which corresponds to the solubility limit. Concerning substrates, it was verified that they play a key role in film microstructure. Homogeneous and crack free films were obtained on glass, silicon and alumina substrates. Film density is quite dependent on the type of substrate, and glass substrates provided the densest films. The average thickness is ～150 nm for one layer film.     

Integrated Design of an Ionic Polymer–Metal Composite Actuator/Sensor

We are studying the robotic application of ionic polymer–metal composite (IPMC). The characteristics of IPMC greatly depend on the type of counterions, and it is considered that the performance of the actuators can be improved by combining the actuators with several types of counterions and applying an integrated control. IPMC also has a sensor function, as the IPMC film generates an electromotive force when it is deformed. It has the possibility to be integrated into an IPMC actuator with soft actuation. In this paper, we consider an integrated design of an IPMC actuator/sensor, and investigate control of the combined IPMC actuators using H _∞ control and the construction of an IPMC sensor system.     

Water purification using solar energy: effect of sulphur on photocatalytic properties of TiO2

Abstract

The present work considers the effect of sulphur on several properties of titanium dioxide (TiO₂) including electronic structure, defect disorder and photocatalytic properties. While the reports on the mechanism of sulphur incorporation into the TiO₂ lattice are conflicting, there is a consensus that sulphur leads to reduction of band gap and enhanced photocatalytic performance. The latter effect suggests that light absorption, which is determined by an electronic structure, plays the key role in the conversion of the light energy into the chemical energy that is required for photocatalytic decomposition of organic contaminants in water. Analysis of the reported data suggests that different processing procedures result in different doping mechanisms. It is argued that most of the experimental data reported so far are not well defined and, therefore, are not compatible. Consequently, the progress in the science of photocatalysis requires collection of empirical data that are well defined.     

Influence of Mg and Si on the Oxidation of Aluminum

Test materials of pure Al, Al alloyed with 10,50, and 190 ppm Mg, and Al alloyed with 10 ppm Mg + 500ppm Si were oxidized at temperatures ranging from 250 to620°C. The composition and thickness of the oxide film were determined by electronspectroscopy for chemical analysis (ESCA) and Augerspectroscopy. Below the crystallization temperature(400°C) of Al₂O₃,Mg²⁺ is enriched in the interior portion of the oxide. The enrichment of Mg²⁺gives a somewhat thinner oxide compared with the oxideformed on pure Al. Above 400°C, MgO is formed as aseparate phase on the surface of theAl₂O₃. The Si-containing material showed Si⁴⁺ enrichment inthe surface oxide. Mg²⁺ species were notdetectable. Silicon is also strongly enriched in themetal phase just below the metal-oxideinterface.     

Doping effects on robotic systems with ionic polymer–metal composite actuators

Ionic polymer–metal composite (IPMC) materials are one of the most promising electro-active polymer actuators for applications, and have good properties of response and durability. The characteristics of IPMC materials depend on the type of counter-ion. When applied to mechanical systems such as a robot, there exist possibilities to change the properties of the system dynamics by changing the counter-ions and system parameters according to the environment or purpose. We focus on this 'doping effect' property of the system and will verify the effect on robotic applications. In this paper, we consider dynamic walking of a small-sized biped robot and swimming motion of a snake-like robot, and demonstrate the doping effects by numerical simulations and experiments.     

Kinetics and Mechanism of Iodide-Film Growth on Lead-Effect of Short-Circuiting and Lower-Valent Dopant

The influence of Ag as a lower-valent dopant onthe kinetics of lead iodination under normal andshort-circuit conditions in iodine pressures of 0.615 to6.578 kPa in the temperature range of 423 to 523 K was investigated. Like pure Pb, Ag-doped Pbalso follows the parabolic law of film growth. Theisothermal parabolic rate constants are found todecrease in the presence of the dopant. The iodinevapor-pressure dependence of isothermal parabolic rateconstants was observed to be k_P p _I2 ^1/2 . Results for normal iodination areexplained in terms of migration of electron holes underthe influence of Cabrera-Mott's electrical field across the film. Theactivation energy for normal iodination of Ag-doped Pbis estimated to be 84 kJmol^-1 comparedto that of 64 kJmol^-1 for pure lead. Therate of iodide-film growth has been found to decrease further undershort-circuit mode of experiments. Such observationshave been explained with the concept of ion migration asthe ratelimiting step for the film-growth process. The iodine pressure dependence of the rateconstants under short-circuit conditions is observed tobe k_P p _I2 ^1/3 associatedwith an activation energy value of 66kJmol^-1. Unlike pure lead, introduction of additional resistances in series to theshort-circuit Pt path during iodination of Ag-doped Pbcaused an increase in the rates with gradual increasedvalue of resistances. Kinetics results are explained by considering the prevalence ofSchottky-Wagner type of point defects in lead iodide.The driving forces for migration of the defect speciesthrough the growing pure PbI₂ films andAg-doped PbI₂ are confirmed to be Wagner's electrochemical potentialgradient and Cabrera-Mott's electrical field,respectively. The iodide films were characterized bySEM, EDS, EPMA, AES, and XRD analyses to substantiatethe kinetic results.     

Preparation and characterisation of low fusion leucite dental porcelain

Abstract

Low fusion leucite containing dental porcelain was prepared from Egyptian feldspar and talc raw materials by firing for 6 min at 800-950° C. Porcelain frit was first made through fusion of the respective formulations at temperatures between 1100 and 1300° C and then poured into a cold stream of water. The frit was milled to pass a 75 μm sieve. Thermal expansion was followed using a dilatometer. The crystallisation of leucite was regulated by adjusting the rate of heating and by addition of nucleating agents. The main mineral phase developed is the tetragonal leucite form. The amount of crystallised leucite was monitored to control the translucency of the porcelain. Thermal expansion coefficient was in the range 10·0-14·5 × 10^-6 K^-1 (20-500° C). Microstructure was investigated using SEM.     

Structural investigation of nanohydroxyapatite doped with Y3+ and F– ions

Abstract

Pure and 2·5 mol.-%Y³⁺ and F^– doped nanohydroxyapatites were synthesised by a precipitation method and sintered at 900 and 1100°C to investigate their densification and structure. X-ray diffraction and Fourier transform infrared spectroscopy methods were performed to identify the presence of phases and bonds after the sintering respectively. Densification of hydroxyapatite was improved by the addition of these ions. No second phases were observed by X-ray diffraction method. Structure of the materials was hexagonal. Fourier transform infrared spectroscopy investigations showed that the Y³⁺ and F^– doped hydroxyapatites had F^– bonds in addition to OH^– bonds after the sintering.