Oscar Jaime Restrepo Baena

Effect of the Fuels Glycine, Urea and Citric Acid on Synthesis of the Ceramic Pigment ZnCr2O4 by Solution Combustion

In this study, ceramic nanopigment ZnCr2O4was prepared by solution combustion using glycine, urea and citric acid as fuels. The objective is to study the influence of fuel on the morphology and the diffuse reflectance spectrum. The nanoparticles were characterized by field emission scanning electron microscopy (FESEM), the phase was investigated by X-ray diffraction (XRD), the thermal behavior was studied by thermogravimetry analysis (TGA) and differential scanning microscopy (DSC), the color was determined by diffuse reflectance spectroscopy and CIE L*a*b* colorimetric analysis. The average crystallite sizes obtained were 18.40 nm, 42.05 nm, and 18.69 nm when are used glycine, urea, and citric acid, respectively. Finally, the effect of fuel in the diffuse reflectance showed that the scattering of the light by the particles depend of the morphology. Also, the nanopigment was obtained by solution combustion at lower temperature than solid state reaction and it could be used in digital decoration.

CoAl2O4 blue nanopigments prepared by liquid-feed flame spray pyrolysis method

CoAl2O4 pigments were synthesized through Liquid-Feed Flame Spray Pyrolysis (LF-FSP) method using metallorganic precursors of cobalt propionate and alumatrane. The precursors were dissolved in ethanol and aerosolized into a methane/oxygen flame where it was combusted to result in nanopowders at a single step. The resulting nanopowders were collected in electrostatic precipitators and analyzed by x-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), colorimetry, Field Emission Scanning Electron Microscopy (FE-SEM) and BET (Brunauer-Emmett-Teller) nitrogen adsorption. Results show formation of single phase blue nanopigments, suggesting that LF-FSP is an excellent method to produce nanoparticles with high quality in a continuous process for new industrial applications. The nanoparticles presented spherical morphology with specific surface area of 50 m2/g, corresponding to average particle size of 27 nm. The pigments were calcined at 500, 600, 800, 1000, 1200 and 1300 °C, aiming to find the color stability whereby the colors were measured using the color space CIE L*a*b* under standardized D65 light. The brightest and bluest was obtained at calcination temperature of 1200°C and its application into a glaze was carried out at 1200 °C to evaluate the color performance and stability after a decoration process. Finally, LF-FSP produced pigments were compared with those produced by solid state reaction. Differences in the color due to the average particle size and process conditions were observed. It is possible to obtain new hues for ceramic applications by LF-FSP method.

Properties of Ceramic Pigment Zn 0.5 Cu 0.5 Cr 2 O 4 Synthesized by Solution Combustion Method

The present study reports the effect of the fuels: glycine, urea, and citric acid on the optical properties of ceramic pigment Zn0.5Cu0.5Cr2O4, synthesized by solution combustion. The powders were characterized by X-ray diffraction, which showed the formation of the expected phases. Scanning electron microscopy (SEM) was also used, and the images showed the formation of agglomerates and porous samples. Finally, VIS-spectroscopy, and CIEL*a*b* color-measurements showed the powders are black. The results demonstrated that the synthesis by the combustion reaction was very fast and safe, and that the heat released in the combustion reaction is a function of fuel, releasing more heat with glycine, and less with citric acid. It was observed that the powder is more black with urea and citric acid that with glycine. The optical properties showed that the powders could be used as ceramic pigments.

Properties of Ceramic Pigment Zn0.5Cu0.5Cr2O4 Synthesized by Solution Combustion Method

The present study reports the effect of the fuels: glycine, urea, and citric acid on the optical properties of ceramic pigment Zn0.5Cu0.5Cr2O4, synthesized by solution combustion. The powders were characterized by X-ray diffraction, which showed the formation of the expected phases. Scanning electron microscopy (SEM) was also used, and the images showed the formation of agglomerates and porous samples. Finally, VIS-spectroscopy, and CIEL*a*b* color-measurements showed the powders are black. The results demonstrated that the synthesis by the combustion reaction was very fast and safe, and that the heat released in the combustion reaction is a function of fuel, releasing more heat with glycine, and less with citric acid. It was observed that the powder is more black with urea and citric acid that with glycine. The optical properties showed that the powders could be used as ceramic pigments.

Portland Cement Clinker Formation: High Temperature Equilibria and Phase Composition Prediction

A computational tool together with a thermodynamic database has been used to study the manufacturing of Portland cement clinker. In this paper is examined the potential of thermodynamic calculation of phase equilibrium to contribute to understanding the cement chemistry. Calculations were performed on a relevant part of the quaternary system CaO-SiO2-Al2O3-Fe2O3 which is the basis of the high temperature chemistry in the rotary kiln. High temperature equilibria calculations were performed in order to study the process taking place in the kiln in a temperature range consistent with the process (700–1600°C). Phases coexisting were determined, their distribution and stability ranges. Phase transformation on cooling was study using a non-equilibrium model to predict the final phase distribution. The results were compared with Bogue calculations. We discuss the scope and limitations of the database and the method used in this research.

Estudio del efecto de la temperatura en el tono de esmaltes pigmentados sobre gres

La industria de decoracion ceramica usa pigmentos ceramicos, mezcla de oxidos, y de esmaltes quienes soportan en matriz vitrea al pigmento para dar la coloracion y constancia tonal que incide en la aceptacion de la pieza ceramica por parte del consumidor. Este trabajo estudia el efecto de la temperatura de coccion de los esmaltes ceramicos sobre el tono de las piezas ceramicas. Se preparo y aplico un esmalte ceramico sobre un soporte de gres por el metodo de serigrafia-pincel a distintas temperaturas. Los resultados determinan la variacion tonal de las muestras, aplicando una tecnica espectrofotocolorimetrica para determinar los parametros CIE L*a*b* y espectros de reflectancia.

Método de evaluación de blancura para el blanqueamiento visual de talcos por adición de pigmento cerámico

El color de las materias primas incide en la aceptacion o rechazo por parte del consumidor. Este trabajo estudia como se modifica la apariencia amarillenta del talco por adicion de pigmentos, brindando una apariencia visual mas blanca. Los resultados presentan un metodo para la evaluacion colorimetrica de agregados en polvo, asi como para determinar la dispersion de la luz incidente como una aplicacion espectrofotometrica en la determinacion de parametros de la medida del color tales como: Las coordenadas colorimetricas CIELAB, ΔE y la blancura, mediante las curvas de reflectancia para el talco con y sin pigmento

Efectos de algunas adiciones minerales colombianas en la fabricación del clínker para cemento pórtland i

En esta investigacion se usaron minerales de origen colombiano tal y como son producidos en sus respectivas minas. Se experimento con la fluorita (Santander), el feldespato (Antioquia) y el manganeso (Antioquia) en cantidades del 0,0%, 0,2%, 0,5%, 1,0%, 1,5% y 2,0%. Se aplicaron varias tecnicas como difraccion de rayos X, fluorescencia de rayos x, microscopia electronica de barrido y microscopia optica para caracterizar los materiales utilizados y analisis termico diferencial para determinar la temperatura de clinkerizacion y se evaluo mineralogicamente el clinker obtenido. Se encontro que el mejor resultado se logro con la adicion de 0,5% de la fluorita al permitir la mayor formacion de alita y la disminucion en el contenido de cal libre. El feldespato y el manganeso (braunita) utilizados no tuvieron un comportamiento apropiado.