Colored cement bricks such as ceramic glazed tiles are widely used as raw materials of iron oxide red. Therefore, the amount of iron oxide red pigment in ceramic pigments is relatively large, which is estimated to be above 1 10,000 tons per year. At present, the production methods of iron oxide red pigment for ceramic pigments are mainly divided into sulfuric acid method and mixed acid method (nitric acid method). Iron oxide red pigment with bright red appearance was obtained from thin iron plate.
1. Application of Iron Oxide Red in Brown Series
Among the pigments of ceramic glaze, brown series pigments occupy a large market. Especially in the production of ceramic tiles and retro bricks, two series of gold and reddish brown are widely used.
Brown series is mainly Fe-Cr-Zn-Al and Fe-Cr-Zn crystal structure, and iron oxide red pigment is mainly added in the form of colorant. Trivalent iron ions remain red, and through the composite coloring with chrome green, the earth tones from gold to black are produced. In this study, the following experiments were done: using a frit with chemical composition and adding 3% pigment to the frit, with the increase of iron oxide red pigment in the formula, the redness and yellowness values decreased accordingly, the color of the pigment changed from golden yellow to reddish brown, and the lightness value of the pigment also decreased accordingly; At the same time, it is found that the pinhole of glaze increases accordingly.
This is because with the increase of iron oxide red pigment in the formula, the unsaturated iron ions in the pigment increase, which are easy to precipitate from the high temperature liquid phase of frit glaze, and the pinholes increase, while the color saturation decreases accordingly. From the appearance of the pigment, with the increase of iron red pigment content, the sintering degree of the pigment increases, which shows that iron red pigment can reduce the sintering temperature in brown series products.
Second, the application of iron oxide red in blank black materials
In the production of ceramic wall and floor tiles, three medium tones of black, yellow and coffee are mainly used, in which the ceramic body black material accounts for more than 35% of the body color, and the manufacturers consume more than 60,000 tons of body black material every year. Iron oxide red pigment is the main raw material of green-black material formula, and its content can usually reach 50%~80%. The hue of iron oxide red products produced by different manufacturers is quite different.
Third, the application of iron oxide red in glaze black material
The cost of black pigment for glaze is higher than that of other pigments for glaze, and the pure blue tone of cobalt black pigment is the best. Bright black pigment does not contain cobalt oxide, and its cost is slightly lower than that of cobalt black. However, there are also some bright black products on the market, whose pure black tone can rival cobalt black.
Iron oxide red pigment mainly plays an auxiliary role in glaze black material. It is generally believed that NiO-Cr2O3 formed in the oxidation atmosphere of 1000℃ has a blue-green tone, NiO-Fe2O3 has a black band with a red tone, and Co-Fe2O3 has a blue-black tone, and it appears pure black through composite coloring. At the same time, CuO-Fe2O3 can also present a blue-black tone in the glaze.
Because iron red has a great influence on the firing temperature and color tone, iron red should be selected according to the design requirements for the production of black materials for ceramic glaze, and whether it meets the requirements can be tested by calcining the production formula.