Effective factors on synthesis of the hematite–silica red inclusion pigment

Nano encapsulation of hematite into silica matrix as a red inclusion ceramic pigment

“…4. TEM micrographs of NaF fluxed powders fired at 900 • C/3 h. (Table 1), it seems that the poor red shade of these powders is due to this nanometric size of hematite crystals [10][11][12].…”

Nanocomposite Fe2O3–SiO2 inclusion pigments from post-functionalized mesoporous silicas

“…22 The effect of surface area of silica precursor has been also analyzed. 14,15,19 In this respect, Bondioli et al found that the red shade of the pigment obtained by the ceramic method can be slightly improved by using fine-sized colloidal (fumed) silica with higher surface area (up to 400 m 2 /g). 14 Hosseini-Zori et al 15 also reported a slight increase of the red color with increasing surface area of fumed silica.…”

“…At around 1000 • C or even higher temperatures, amorphous silica crystallizes into metastable cristobalite (or also trydimite), and the resulting red shades are normally poorer. In a more recent study, however, both the thermostability and reddish color improved after cristobalite crystallization at a temperature range of 1100-1200 • C. 15 Anyway, the use of hematite-silica ceramic pigment is normally limited to low temperature ceramic glazes. In glazes with high firing temperatures (above 1000-1050 • C) the color usually becomes darker (dark brown or even grey) due to the dissolution of non-protected hematite into the glassy phase, 12,15,16 and also as a result of the partial reduction of hematite to give magnetite (Fe 3 O 4 ).…”

Substitution of a fraction of zircon by cristobalite in nano hematite encapsulated pigment and examination of glaze application

“…Of course, the host lattice must have adequate thermal stability and remain insoluble to withstand the aggressive action of the glazes (ceramic frits and/or sintering additives) in which they are formulated. Based on the glaze formulation, some pigments will be useful to apply [4,5].…”

“…In particular, in order to achieve high efficiency of chromophore agent encapsulation, the matrix sintering and/or crystallization must be synchronized with the nucleation and growth of the occluded chromophore agent. Crystallization, sintering and inclusion process are thus considered to take place simultaneously, and consequently, the control of particle size of the raw powders is one of the main steps [5][6][7][8][9][12][13][14][15][16].…”