Papers by Keyword: Phase Formation

Abstract: Hydrotalcite are anionic clay material presenting LDH arrangement and high porosity and specific areas, which make it a good adsorbent for pollutant species in water. Besides that, that material type can be used as catalyst or catalyst support in several industrial processes. The most common compositions is based on metallic mix hydroxide with high content of magnesium, but their adsorptive properties arise from aluminum replacement in layer structure. The present work presents the synthesis of carbonated magnesium-aluminum hydrotalcite through the precipitation method in order to investigate the co-insertion of iron (III) in aluminum site. It was found the iron (III) co-inserted samples obtained at 100 and 200 oC for 4 hours present no substantial harming in relation to the common magnesium-aluminum composition. All of the samples presented high porosity and specific area, becoming an alternative anionic adsorptive.

Abstract: The study of diffusion processes in the aluminum - copper system was carried out at the temperature 350 and 520 °C. Special attention was paid on the chemical composition of the system near Al/Cu interface. It was determined that the intermediate phases in the system, corresponding to the equilibrium phase diagram, were not formed at low temperature. At high temperature the intermediate phases forms starting with Cu - rich phases. In both cases supersaturated solid solution of copper in aluminum could be observed near the interface.

Abstract: CaCu₃Ti₄O₁₂ (CCTO) is an electroceramic material with complex cubic perovskite-like oxide. It possessed a giant dielectric constant of about 10⁵ over a wide temperature range (100-600 K). In this work, CCTO was synthesized through solid state method. The effect of different heating rate during sintering process was studied. The raw materials - CaCO₃, CuO and TiO₂ were wet ball milled for 24 hours and calcined at 900 °C for 10 hours. Then the calcined powder was pressed into pellet shape at 300 MPa. Sintering was done at 1040 °C for 12 hours with different heating rates: 3, 5 and 10 °C/min. The phase formation and surface morphology was investigated by X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM), respectively. The density was measured by Archimedes Principle. XRD pattern proves the CCTO single phase formation for the calcined powder and sintered pellet. The SEM images show the different grain size for different heating rate. The density of the pellet was found to be reduced when faster sintering heating rate was used.

Abstract: This research concentrates to the effect of changing sand proportion on the physical, mechanical and thermal properties of building wall materials (Cellular lightweight concrete). The density, water absorption and compressive strength of the 7.0 cm x 7.0 cm x 7.0 cm concrete sample were studied. It was found that there are an increase of density and a reduction of water absorption with an increase of sand content. The higher compressive strength can be confirmed by higher density and lower water absorption. The physical and mechanical properties of lightweight concrete conditions conformed to the Thai Industrial Standard 2601-2013. The phases of CaCO₃ and calcium silicate hydrate (C-S-H) in the material indicate an important factor in thermal insulating performance.

Abstract: This research studied the effect of the different preparation technique on phase transition and electrical properties of Ba_0.8Sr_0.2TiO₃. The samples compared 3 preparation technique, there are conventional mix-oxide, molten-salt and seed-induced method. The samples prepared by molten-salt calcined at 800 °C, the samples prepared by conventional mix-oxide and seed-induced method was calcined at 1200 °C for 3 h. All of samples sintered at 1400 °C for 3 h. The phase formation and morphology of samples were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The dielectric properties of the samples were measurement by LCR-meter.

Abstract: In this work the peculiarities of phase formation of the cement stone at presence of nanostructured modifier of the silica composition were identified using the method of x-ray diffraction and raster electronic microscopy. Also the character of influence of modifier on the structure formation of the cement stone was defined. Polydisperse modifier with the presence of a highly active colloidal component, on the one hand, acts as a pozzolanic component, and on the other hand – as a submicron filler.

Abstract: Iron contamination from scrapped materials is always a problem in producing high quality secondary aluminium alloys. Consequently, the iron removal during recycling of aluminium alloys is essential and important in industrial practice. This work aims to study the effect of extra Mn addition on the effectiveness and efficiency of iron removal during recycling. The thermodynamics assessment was carried out for Al-Si-Cu alloys to find out the variation of balanced iron and manganese in the liquid melt and in the sediment solid Fe-rich intermetallics with different levels of extra Mn addition. The effect of alloy composition and processing temperatures was investigated. The findings help to understand the capability and fundamentals of iron removal in aluminium alloys.

Abstract: The results of the studies of phase formation and the structural state of diffusional zinc coatings formed in zinc powder with nanocrystallized surface of the particles are presented. The sequence of iron-zinc phases formation during the process has been established, which is the reciprocal of those obtained during the annealing of "hot dip" coatings. The microstructure of δ-phase in the coating, a change in its texture and structural parameters through the thickness of the coating have been studied.

Abstract: Effect of Ca doped by rare-earth elements, Nd and Er (x=0.10) on the structural and transport properties of low density Bi_1.6Pb_0.4Sr₂Ca_1,9RE_0.1Cu₃O_δ (RE=Nd,Er) samples have been investigated. The samples have been prepared via co-precipitation (COP) method from precipitate of saturated solutions of metal acetates, iso-propanol solution and oxalic acid. The metal oxalates powder was subjected to thermal treatment of 24 hours calcination at 845oC and mixed with 0.10 g sucrose C₁₂H₂₂O₁₁ which is used as supplementary filler. The pelletized powder was heated for 2 hours at 400 oC and sintered for at 850oC for 48 hours. All samples show a single step transition in the R-T curves. The critical current density (J_c) and transition temperature (T_{c zero}) for both Nd and Er doped with x = 0.10 were found to be lower than standard samples. T_{c zero} obtained varies between 98 K and 66 K. XRD data showed the decrease of volume fraction for the Bi-2223 phase and increase of the volume fraction Bi-2212 phase with the doping of Nd and Er.

Abstract: This paper presents the results of the numerical study of the coating composition evolution deposited on a cylindrical specimen from plasma containing aluminum and nitrogen. Calculations were based on a coupling model, which accounted for various transfer mechanisms and staged chemical reactions in the coating and in the transient zone. The evolution of the coating composition is connected with transfer processes, chemical reactions, and with the change of effective properties.