Electroless Ni-B deposition from an emulsified supercritical carbon dioxide bath

The electroless deposition of boron-containing Ni (EN-B) film from a supercritical carbon dioxide (sc-CO2) bath was introduced. The deposition rate in sc-CO2 bath was one order of magnitude lower than that at ambient pressure without the presence of sc-CO2. A more uniform chemical composition of the EN-B film could be obtained if it was deposited in the sc-CO2 bath. X-ray diffraction analyses revealed that the as-deposited film was amorphous in nature, despite of the deposition condition. Deposition defects such as cracks and voids could be avoided if the deposition was conducted in the sc-CO2 bath. Crystallization and boride precipitation were found after heat treatment at 400 °C for 1 h. The EN-B film deposited from the sc-CO2 bath had a higher hardness as compared with that of the normal EN-B coating. A substantial increase in hardness was obtained due to boride precipitation.