Oscar Jaime Restrepo

Sol‐Gel Synthesis NaCrSi2O6 Nanopigments Aided by Statistical Design of Experiments

The synthesis of ceramic nanopigments by non-conventional methods: Sol-Gel technical aided by use of statistical techniques has aroused interest to new colour pigments. In the present work, the mixture experiments was used to evaluate the influence of precursors (sodium silicate, chromium nitrate and colloidal silica) mixture sol-gel process on the main colorimetric properties (evaluated as L*, a*, b* coordinates color); it used to mixture design reticular lattice simplex with replies at centre point to analyst. The powders of NaCrSi206, obtained by sol-gel method and process by one-firing at 850°C; the samples were characterised by X-ray Diffraction (XDR), Scanning Electron Microscopy (SEM), UV-Vis Spectroscopy by diffuse reflectance method and CIE-L*a*b* colour parameters. The colour performance of raw powders obtained by non-conventional methods in glazed stoneware improves that of ceramic samples fired at 1100°C used as reference. Particle size of the nanoparticles obtained by the spinel structures was less 100nm.

RESISTENCIA A LA COMPRESIÓN DE MORTEROS PIGMENTADOS CON AZUL ULTRAMAR

Ultramarine Blue (sodium polisulphurated aluminesilicate, UB) is an inorganic pigment used in different industries (automovilistic, polymers, soap and detergents). Strength in mortars with traditional pigments and with Ultramarine Blue was evaluated in this investigation; we found that UB increase it until 54% to seven days of setting time. However, the mineralogical analysis does not show to UB as a classic pozzolane because the CH drop does not increase the tobermorite quantity, but yes the ettrigite quantity. The ettringite is the responsible of strength increase.

Applications and Opportunities of Nanomaterials in Construction and Infrastructure

New and extraordinary physical-chemical properties of materials at nanoscale open up new applications for the building and infrastructure industry such as structural reinforcements, electronic properties and energy harvesting. Therefore the issues and risks associated with the manufacturing of nanomaterials are now of big concern due to the large volumes and typical processing involved in this industry. This paper presents a discussion and selected applications of nanotechnology in the construction and building materials: from metals and alloys, clay and minerals, ceramics, cement and concrete, asphalt, wood and composites, to finishing systems and some of the most used characterization techniques. Besides the progress in some areas, nanotechnology is just emerging in this field, with many challenges and opportunities, problems unsolved and business opportunities. A discussion regarding the potential health issues and risks of using nanomaterials for workers and the potential environment effects is included as well. New images and diagrams are presented and discussed.

Reduction of CO2 Emissions by Chemical Synthesis Processes in the Cement Industry

Portland cement is obtained by a conventional synthesis process from a mixture of limestone and clay at high temperature (1450°C). This work reports the possibility to obtain cement silicates via alternative methods like Solution Combustion Synthesis (SCS), which optimize both time and temperature, and the consequences to energy efficiency and mitigation of CO2 emissions. The production of one ton of cement emits between 0.62 and 0.97 tons of CO2 into the atmosphere. In this process the CO2 emissions are between 21 and 59%. The combustion methods are chemical redox processes in which, at high temperature, a self-sustaining and fast wave is generated from using chemical precursors and organic fuels.

Optical and Magnetical Properties of FeCr2O4 Nanopigments with Spinel Type Structure

Through solid state reactions at high temperatures, using iron and chromium oxides (Cr2O3 and Fe3O4) in fixed proportions as precursors, was synthesized the nanopigment FeCr2O4 with spinel type structure. For different temperatures synthesis was conducted a characterization of the material obtained through.