Coagulation is the aggregation of molecules or ions into colloidal particles by physical or chemical methods.
Physical methods include gas condensation method, phase transfer method, atomization method, etc. If the ethanol solution of sulfur is added to water drop by drop, sulfur hydrosol can be obtained, which is prepared by the principle of low solubility of sulfur in water. This method is also called the solvent replacement method; the gas condensation method uses vacuum evaporation. , laser, heating, high-frequency induction and other methods to vaporize the substance or form a plasma, and then quench it to condense it into nanoparticles. Nanoparticles with high purity, good particle dispersion, small particle size and narrow distribution can be prepared by this method.
Chemical methods include chemical vapor deposition, chemical co-precipitation, hydrothermal method, etc. For example, the soluble reactants are chemically reacted to form the desired substance with less solubility, so that it forms a colloid . For example, various metal sols can be prepared by reducing Au 3+ and Ag + plasma to metal by reduction method, sulfur sol can be prepared by oxidizing hydrogen sulfide to sulfur by oxidation method, and metal hydroxide sol can be prepared by hydrolysis method.
