Ceramic Pigments and the European REACH Legislation: Black Fe2O3-Cr2O3, a Case Study

Abstract

A Rietveld study for three ceramic pigments is presented. Two commercial black ceramic pigments, belonging to the (Cr x Fe 1Àx ) 2 O 3 family, are shown to be single crystalline phase with a negligible amorphous phase content. This conclusion is drawn from the existence of a unique crystalline phase and from the analysis of the values of the unit cell parameters. Furthermore, a much complex laboratory-prepared brown ceramic pigment has also been studied. This sample was synthesized by adding Al 2 O 3 and MgO dopants in small quantities, below 3 wt%, to the previous system. The Rietveld analysis has shown the stabilization of two corundum structures with a compositions close to Cr 0.50 Fe 1.50 O 3 and Al 0.30 Cr 1.70 O 3 , plus a spinel structure with composition close to MgCr 2 O 4 . An aluminum-rich amorphous oxide phase in low percentage is needed to balance the chemical analysis derived from the Rietveld study and that from XRF. Full mineralogical phase analyses of commercial pigments, plus the required solubility tests, may allow narrowing down of the number of toxicity tests required by REACH Int.

Highly Solar Radiation Reflective Cr2O3–3TiO2 Orange Nanopigment Prepared by a Polymer-Pyrolysis Method

“…However, cool colored materials are often preferred for the cases where the use of light colors creates glare problems or when the aesthetics of darker colors is preferred. ,, Complex inorganic color pigments, which reflect near-infrared (NIR) radiation irrespective of the selective visible light reflection/adsorption and thus may be in any color, have well-known applications in masking products, interior car paint, materials for spectator areas of stadiums, and parking areas to fire-resistant paints, ,, and moreover, they are also used specifically in cool materials for exterior surface of buildings. Chromium oxide (Cr 2 O 3 ), green pigment with a medium high NIR reflectance in the range of 50–57%, is a good candidate to make nonwhite cool materials. , On the basis of Cr 2 O 3 , different complex color pigment systems with excellent reflectance have been developed, such as green, gray, and black. − However, very few studies report orange pigments based on Cr 2 O 3 .…”