Energy transfer in microwave assisted Combustion Synthesis of inorganic compounds

In this work microwaves (MWs) were used to ignite and sustain, the Combustion Synthesis (CS) of micrometric metallic powders in order to obtain thick intermetallic coatings as well as joining between advanced materials. MW heating possess the peculiarity to transfer energy, and not heat directly, to the reactive powders, thus it becomes possible to continue to provide energy to the reactive specimen during and after the CS, thus controlling the heating and the cooling behaviour at the reaction front. Investigations concerning the separate effect of positioning the sample in predominant electric field or magnetic field will be presented as well

Role of praseodymium on zirconia phases stabilization

The system zirconia-praseodymia (Pr content 0-15 mol %) has been investigated to evaluate the praseodymium solubility and its role in the zirconia phase stability. The powders have been synthesized by coprecipitation and subsequent calcination at different temperatures (400-1000 degreesC) for 2 h. The crystal structure of the obtained nanocrystalline (Zr, Pr)-O-2 powders has been studied by X-ray diffraction. By applying the Rietveld method, the dopant effect on the zirconia phase stability was found and discrimination between the different zirconia polymorphs was possible

Synthesis of zirconia nanoparticles in a continuous-flow microwave reactor

Monodispersed zirconia colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of Tetra-n-propylzirconate (TPZ) by using a continuous microwave synthesis process. The flow rate was varied from 50 to 100 ml/min in order to establish the optimum conditions required to obtain unagglomerated zirconia nanopowders. The results were compared with those obtained in batch systems. In particular as the flow rate is decreased from 100 to 50 ml/min the particle became spherical with a mean particle size of about 100 nm

Synthesis of a novel Yellow Tb-doped ZrSiO4 Pigment by Suspension Spray Drying

The colloidal processing route has several advantages over other processing methods for obtaining dense and homogeneous microstructures. The aim of the present work is to obtain a yellow pigment based on the substitutional doping of Tb4O7 into the ZrSiO4 structure using a colloidal route and to investigate its feasibility as a coloring agent for fast double firing tiles

Synthesis and characterization of nanosized ceria powders by microwave-hydrothermal method

Nanocrystalline ceria powders (CeO2) have been prepared by adding NaOH to a cerium ammonium nitrate aqueous solution under microwave-hydrothermal conditions. In particular the effect of the synthesis conditions (time, pressure and concentration of both the precursor and the precipitant agent solutions) on the physical properties of the crystals have been evaluated. Microwave-hydrothermal treatment of 5 min at 13.4 atm allows to obtain almost crystallized powders (amorphous phase 4%) as underlined by Rietveld-reference intensity ratio (RIR) results

Rietveld structure refinement of Pr doped zirconia

This work deals with the synthesis and Rietveld structure refinement of a zirconium-praseodymium yellow pigment prepared either by a traditional ceramic process route and by an unconventional synthesis method based on SHS (Self-Propagating High-Temperature Synthesis). in order to confirm the effective formation of the solid solutions, SEM imaging and EDS analysis, and leaching tests have also been performed. The results proved the applicability of the unconventional processing route for obtaining yellow solid solutions

Synthesis, infrared, and X-ray study of di-µ-thiocyanato-1χN,S′:2χN′,S-bis-[bis(2,2′-bipyridine)di-isothiocyanatobismuth(III)]: a case of eight-co-ordinated bismuth

The synthesis, i.r., and X-ray structural characterization of the complex [Bi(CNS)3(bipy)2]2(bipy = 2,2′-bipyridine) are described. Crystals are triclinic, space group P[1 with combining macron], Z= 2, a= 9.935(1), b= 14.487(4), c= 9.916(2)Å, α= 92.29(2), β= 119.81 (1), γ= 99.71 (1)°R= 0.0315. The complex molecules consist of dimeric units in which bismuth is eight-co-ordinated by seven nitrogens belonging to two bipyridyl molecules and to three thiocyanate groups, the last co-ordination site being provided by a sulphur atom of an adjacent molecule which acts as a bridge connecting two polyhedra forming centrosymmetric dimers. The i.r. ν(CN) frequencies are consistent with µ-N,S and terminally N-bonded thiocyanate groups