Effect of amine and thiol addition on the surface chemistry and agglomeration of fine Cu powders

The effect of propylamine, sec-butylamine, and benzenethiol addition on the surface chemistry, apparent particle size and agglomeration of fine copper powders (<2 μm mean dia.) prepared by aqueous-phase precipitation was investigated using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), diffuse reflectance infrared spectroscopy (DRIFTS) and scanning electron microscopy (SEM). XPS analysis of the raw, agglomerated copper powders suggests a particle morphology consisting of a metallic core surrounded by a thin oxide shell. Atomic force microscopy (AFM) force measurements on model systems suggest that amines may be effective in preventing agglomeration, whereas the addition of benzenethiol may promote particle aggregation. DRIFTS results indicate that the propylamine, sec-butylamine, and benzenethiol are chemically bound to the copper particle surface in all cases. TGA analysis indicates that at elevated temperatures propylamine is easily removed, whereas butylamine decomposes on the surface leaving a surface hydrocarbon residue. Benzenethiol is removed above 300 °C, however, some atomic sulfur remains on the particle surface which is subsequently removed above 400 °C.