română GEORGETA VELCIU, FLORENTINA GRIGORE, CRISTIAN ŞEITAN, VIRGIL MARINESCU
Abstract
The aim of the experimental work was to obtain the hollow microspheres alumina, used as fillers in the preparation of insulating coating materials.
As a method of preparation was approached sol-gel technique combined with ion extraction method by emulsified sols. Synthesized gels were calcined at different temperatures and were characterized in order to determine the structure and morphology of oxide microspheres obtained.
The conditions for formation of hollow microspheres and was followed to establish the influence of organic components on the morphology of Al2O3 microspheres, and the influence of technological parameters (speed of soils mixing, drying and sintering temperature) on the formation of hollow alumina microspheres were examined.
The gel microspheres and hollow microspheres were characterized by using thermogravimetriy analysis, differential thermal analysis, X-ray diffraction, microstructural analysis. XRD results indicated the formation of αAl2O3 at 12000C, and optical and scanning electronic microscopy confirmed the cavitary morphology of the gel calcined.
Keywords
sol-gel, emulsified soil, microstructure, microspheres, hollow, αAl2O3
ALINA DUMITRU, GEORGETA VELCIU, VIRGIL MARINESCU, GABRIELA SBARCEA
Abstract
The elaboration of bulk (1-x)Pb(Mg1/3Nb2/3)-xPbTiO3 by using the columbite method is presented. The main aim of the processing was to avoid the formation of an unwanted pyrochlore phase. Optimized sintering temperatures have been chosen in correlation with the densification evolution. Samples with the PMN/PT ratio of 1.0/0.0, 0.9/0.1 and 0.65/0.35 have been processed; X-Ray diffraction and scanning electronic microscopy investigation are presented. The results showing the formation of pyrochlore-free structure in all the investigated samples at sintering temperatures around 1,100 0C.
Keywords
ceramics, PMN-PT, sintering, relaxors, X-ray methods
LU SHUANG, WANG ZHENG
Abstract
On-site corrosion sensor was developed to monitor the adverse effects in the chloride – contaminated concrete structures. Galvano-static Pulse Technique(GPT) was applied to measure the polarization resistance of the anodes and the electrical resistance of the surrounded concrete using the sensor. This paper presents the analysis of GPT measurements performed in the chloride-contaminated concrete for the laboratory tests. The relationship between the corrosion rate of steel electrodes and surrounded concrete resistance measured by corrosion sensor confirms the reliability of developed corrosion sensor. The results further show that the concrete resistance is also an indicative parameter which is related to the corrosion state of concrete structures.
Keywords
corrosion monitoring, concrete structures, GPT, polarization resistance