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A facile hydrolysis-precipitation was used to elaborate antimony oxide Sb2O3(valentinite) and to study its semiconducting and photo-electrochemical properties. The X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis diffuse reflectance, Raman and FTIR spectroscopies were used to characterize the oxide. The XRD analysis indicates an orthorhombic phase (SG: Pccn) with a crystallite size of 102 nm. The optical measurements gave a direct gap of 3.32 eV due to a charge transfer O2−: 2p–Sb3+: 6swhile the capacity-potential (C−2–E) plot provides a flat band potential of − 0.46 VAg/AgCl. The valence and the conduction bands are located at (− 7.29 eV/2.56 V) and (− 3.97 eV/− 0.76 V), and the energy band diagram of the junction Sb2O3/KOH shows the efficacy of Sb2O3as photocatalyst. As application, 81% of Rhodamine B (Rh B), a recalcitrant dye with an initial concentration of 5 mg L−1, were mineralized after 7 h under UV light by Sb2O3. According to the inhibitors study, the ·OH radical is the first active specie in the Rh B photo-oxidation, followed by O2·−. The photodegradation follows a zero order kinetic with a photocatalytic half time of 3.8 h, smaller than the photolysis (10.5 h) under UV light (254 nm).

The use of gypsum plaster for interior covering of walls and ceilings in the Portuguese architecture was particularly expressive in the period between the XVIII and the XX century. However, information about this important heritage is almost inexistent, which is leading to a fast loss of important patrimony. In this paper, the results of the characterization of gypsum plaster samples belonging to two buildings from the same historical period (end of the XIX century and beginning of the XX), situated in distant geographical regions of Portugal are presented and discussed. XRD, TGA-DTA, optical microscopy and SEM-EDS observations were used for the chemical and microstructural characterization. Some physical and mechanical properties, such as capillary absorption, dynamic elasticity modulus and compressive strength were also determined and a relationship between the characteristics observed in the samples and the technology associated to their use and application on site, as well as the possible existence of regional influences on all these aspects, are discussed.

The pulseecho method used for the measurement of distances is based on the determination of the flytime, employed by the wave a pulse or a short train to travel from the sensor to the object and back. It is easy to measure with accuracy the precise moment of the emission, but determining the precise moment of the arrival of the echo is somewhat more complex.

This paper presents some aspects of the research activities on sensors for robots, developed in the Instituto de Automatica Industrial IAI during the last years. The demand for greater precision in the measurement of distances using US techniques, makes it necessary to compensate for alterations in the soundspeed in the interposed medium due to temperature. In this paper we will describe a method for calculating this correction in order that no other external sensor be necessary. The method is based on the resonancefrequency variation of the piezoelectric elements with temperature. The accuracy reached with this correction is higher than normally would be needed in robotics applications.