Synthesis And Characterization Of Red, Green And Blue Pigments For Temperature Resistance

Pigments are very important materials for many industries.Owing to organic pigments have strong limitations such as a very costs（up to ten times the inorganic compound prices） and thermal and UV instability, so,many inorganic pigments have been widely used in various industries, such as paints,plastics and ceramics.Unfortunately,many inorganic pigments are cadmium sulfoselenide, lead molybdate and iron（Ⅲ） oxide,which is dangerous for public health and the enviroment.They are increasingly regulated,even banned by legislation in many countries.The impact of legislation on limiting the use of some pigments has given an impetus to the search for new inorganic,non-toxic pigment.In this thesis,red,green and blue pigments with advantages of non-toxic and temperature resistance were synthesized and their reflection properties were investigated.1.The effect of boric acid on the synthesis of red pigmentγ- Ce₂S₃γ-Ce₂S₃ red pigment were obtained by using high temperature solid state reaction,anhydrous cerium sulfate as the main raw material,boric acid and sodium carbonate as additives,calcinated in the CS₂/N₂ atmosphere at 800-1000℃for 3 h.Pureγ-Ce₂S₃ phase was obtained when the mass percentage of boric acid to the anhydrous cerium sulfate is 1.5～4.5 wt.%;while the mass percentage of boric acid adding to the anhydrous cerium sulfate is 7.5～9.0 wt.%,and a new phase CeBO₃ which is a white substance was formed,its reflectivity was increased for the color purity;when the mass content percentage of boric acid is 9.0 wt.%,the reflectivity and color purity of the pigment decreased due to the existence of a new phase B₂S₃. All pigments are thermal stability at 600℃in air.2.The effect of Na⁺,Ca²⁺ on the property of red pigmentγ-Ce₂S₃The effects of alkali metals and alkaline-earth metals on the property of red pigmentγ-Ce₂S₃ were studied.The experiment indicated that some CaCO₃ added into initial material can increase the L^*a^*b^* value and the reflectivity of 700 nm. The result is best when Na⁺ and Ca²⁺ are co-dopedγ-Ce_2.67V_0.33S₄ in half of total vacancy and the mole ratio of Na⁺ to Ca²⁺ ranged from 2:1 to 1:2. When the mole ratio of Na⁺ to Ca²⁺ was 1:5,orange would appear. Compared to the product of France company Rhone-Poulenc,the best of sample we synthesized successfully made the lightness of the pigment from 47 to 52,reflectivity to 86.6%at 700 nm in the same case of a^*b^* value.3.Synthesis and Characterization of Cobalt blue pigmentA series of cobalt blue pigments were synthesized by combustion method.Reflection spectra indicated that the color purity is the best when the molar rate of Co/Al is equal to 1:3.When the rate is 1:6,the pigment has very low cobalt content,but it is not good enough for color purity or reflectivity in the red zone.Doping a small amount of Mg²⁺, the reflectivity decreases at 600 nm and the color purity increased.The optimal sample with Mg/Co equal to 0.15 is more economical and environmentally friendly because of its lower cobalt content although it was some poorer in color purity than the former. 4.Synthesis and characterization of cobalt green pigmentCobalt green pigment were prepared by co-precipitated method. oxalic acid used as the precipitate agent and the mole ratio of Co/Zn is equal to 0.02,the sample which has the best L^*a^*b^* value and color purity could be obtained.In additional,the average diameter of particle size distribution is about 20μm.