• M EL HADRI

      Articles written in Bulletin of Materials Science

    • Effect of sol–gel method on colour properties of the classical cobalt olivine (Co$_2$SiO$_4$) ceramic pigment

      M EL HADRI H AHAMDANE M A EL IDRISSI RAGHNI

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      A sol–gel method based on (H$_2$S$_2$O$_5$)$_{aq}$ as silicon precursor in the presence of NaCl and KCl mineralizers was used for the synthesis of the classical cobalt olivine (Co2SiO4) ceramic pigment. The effect of this synthesisroute on the colour properties was studied. Highly pure olivine phase was obtained after firing at 1200$^{\circ}$C for 3 h. The resulting powders exhibited very intense violet colour, while their addition at only 1 wt% to an industrial transparent glaze was enough to produce a very intense blue–violet colouration. Based on the aspect of glazed ceramics, addition of pigments even at 0.5 wt% to the glaze resulted in a very interesting colour and opacity. By this appropriateminimization of the used pigment amount without compromising the colouring properties required during application, the obtained Co olivine could be more efficient, less toxic and less expensive.

    • Cu- and Mn-doped forsterite: sol–gel synthesis, and optical and colorimetric investigation

      N SIRAGI M EL HADRI H AHAMDANE M A EL IDRISSI RAGHNI

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      Cu-doped forsterite Mg$_{2-x}$Cu$_x$SiO$_4$ ($0.1 \leq x \leq 0.6$) and Mn-doped forsterite Mg$_{2-x}$Mn$_x$SiO$_4$ ($0.2 \leq x \leq 1$) powders have been prepared by sol–gel method and characterized by XRD, SEM–EDS mapping, UV–Vis–NIR spectroscopyand CIE $L^*a^*b^*$ colour measurements to be explored as powdered ceramic pigments. The use of a sol–gel method based on silicic acid (H$_2$Si$_2$O$_5$)$_{\rm aq}$ and mineralizers (KCl and NaCl) along with a thermal treatment at 1200$^{\circ}$C for 3 h, led to the formation of highly pure materials. The presence of Cu and Mn ions in the M1 and M2 sites was the main origin of the pigments colour. The latter was mostly affected by the chromophore’s valence state and concentration, andsome formed minor phases. Besides that, the pigments with low doping levels showed very nice and attractive blue (Cu) and purple (Mn), making them interesting less toxic and less expensive ceramic pigment candidates.

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      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
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      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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      Posted on July 25, 2019

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