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

Syntheses and Spectroscopic Properties of Halocadmates(II): Crystal and Molecular Structure of a New Tribromo[N-Benzylpiperazinium]Cadmium(II) Compound

Compounds of formula [CdX4]\ub7(LH2)\ub7(H2O) (LH2 = N-benzylpiperazinium dication X = Cl, Br, I) and one of formula [CdBr3(LH)] (LH = N-benzylpiperazinium monocation) wem prepared and characterized. The crystal structure of the monoprotonated N-benzylpiperazinium tribromocadmate(II) complex was determined by means of X-ray analysis. The [CdBr3\ub7(LH)] salt is triclinic (space group and lattice constants: P1, a = 9.500(3), b = 13.145(7), c = 6.801(1) \uc5, \u3b1 = 103.79(2), \u3b2 = 96.24(2), \u3b3 = 96.17(5)\ub0, Z = 2, R = 0.0392, Rw = 0.0394). Its structure consists of discrete monomeric [CdBr3(LH)] units, in which the coordination polyhedron around the cadmium ion is a distorted tetrahedron. The coordination sphere is comprised of the three anionic bromide ligands and one terminal N atom of the N-benzylpiperazinium monocation. All the compounds were also investigated by means of IR and Raman spectroscopic measurements. The CdBr stretching vibrations of the structurally known [CdBr3\ub7(LH)] salt were unambiguously assigned on the basis of calculations performed on its spectra and by comparison with literature data. The Cd-X stretching vibrations of the [CdX4]\ub7(LH2)\ub7(H2O) compounds, assigned by comparing their spectra with those of the monoprotonated N-benzylpiperazinium tribromocadmate and on the basis of literature data, strongly suggest the presence of discrete [CdX4]2- anions

The structural and spectroscopic properties of 2,4,6-trinitro-diphenylamine and 2,4,6-trinitro-N-methyl-diphenylamine

The structural properties of 2,4,6-trinitro-diphenylamine (I) and 2,4,6-trinitro-N-methyl-diphenylamine (II) are determined by single crystal diffractometry and refined toR factors of 0.0282 for (I) and 0.04213 for (II). (I) crystallizes in the monoclinic space groupP21/n,Z=4, witha=11.436(5),b=7.674(2),c=15.083(4) Å,β=106.47(2)°, and (II) inP21/c,Z=4, witha=12.654(5),b=7.371(1),c=15.083(4) Å,β=101.76(2)°. The amino nitrogens show in both cases bond distances and angles typical of an sp2 character. The presence of the proton on the amino nitrogen constrains ano-nitro group into a more planar geometry than that of the methyl derivative, uv/visible spectral data of both compounds are discussed. The methyl group on the amino nitrogen, of derivative (II) compared with that of (I) produces a relevant red shift which cannot be related to the simple differences in the geometry of the two molecules

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

Monomeric and oligomeric phosphates as deflocculants of concentrated aqueous clay suspensions

The paper discusses on effects of monomeric and oligomeric phosphates as deflocculants of concentrated aqueous clay suspension