Copper chrome black (Copper Chrome Black) is a novel spinel-type pigment synthesized from copper oxide and chromium oxide at high temperature. As a representative metal oxide pigment, it is the most widely used black pigment among inorganic pigments. Because copper and chromium are combined in the spinel lattice, they offer excellent stability, are environmentally friendly, and are non-toxic, making them widely used in high-temperature resistant coatings, engineering plastics, and art pigments.
This study utilized both solid-phase and liquid-phase methods to prepare Copper Chrome Black. In the solid-phase preparation of Copper Chrome Black, spinel-type Copper Chrome Black pigment was prepared using Cr2O3 and CuO as raw materials via high-energy ball milling and high-temperature solid-phase method. The structure, morphology, and particle size of the prepared pigment were characterized using XRD, SEM, and laser particle size analysis. The effects of precursor mixing method, ball milling time, calcination temperature, and calcination time on the crystal form and particle size of Copper Chrome Black pigment were systematically investigated. The effect of doping on the tinting strength of Copper Chrome Black pigment was also explored.
The study demonstrated that high-energy ball milling can effectively control particle size and uniformity, and that the incorporation of NiO and CoO significantly improves its tinting strength. Copper chrome black pigment with uniform particle size distribution and excellent tinting strength was prepared by high-energy ball milling for 10 minutes, calcination at 900°C, and holding time for 3 hours.
In the liquid-phase preparation of copper chrome black, ultrafine spinel copper chrome black pigment was synthesized by urea co-precipitation using chromium and copper nitrate as raw materials and sodium dodecylbenzenesulfonate as a surfactant. The effects of precipitant, calcination temperature, and surfactant on the crystal form, morphology, and particle size of copper chrome black pigment were systematically investigated. The influence of synthesis conditions on the tinting strength of copper chrome black pigment was also explored. The results showed that urea and sodium dodecylbenzenesulfonate effectively controlled the morphology, particle size, and uniformity. With a urea dosage of 4 times the theoretical amount, a surfactant addition of 5%, and a calcination temperature of 800°C, an ultrafine copper chrome black pigment with a hexahedral morphology, an average particle size of 300 nm, and a uniform particle size distribution was prepared.
Based on research on liquid-phase nitric acid systems, and based on the principle that chromium forms complex ions with sulfate during the chemical preparation of chromium compounds, and that sulfate has a counterion effect, copper chrome black was prepared by replacing copper nitrate with copper sulfate. The effects of chromium ion concentration, surfactant addition, and its dosage on the particle size and tinting strength of copper chrome black were investigated. The results showed that the introduction of sulfate significantly alleviated the agglomeration problem of the precursor, facilitated the production of a loose precursor powder, and produced a copper chrome black pigment with uniform particle size and excellent tinting strength.
Based on these experiments, a scaled-up pilot study was conducted using copper sulfate and chromium nitrate as raw materials using a chemical coprecipitation method. The results demonstrated that the resulting copper chrome black pigment exhibited excellent performance.
