硝酸イオンを含む非懸濁めっき浴からのNi-Al（OH）₃複合薄膜の電析

抄録

This study investigated electrodeposition of Ni-Al（OH）₃ composite films from a Watts type bath containing Al³⁺ and NO₃⁻. Because of NO₃⁻ reduction during nickel electrodeposition, the solution pH near the cathode increases. Then hydrolysis of Al³⁺ proceeds. Scanning electron microscopy（SEM）was used to characterize the composite surface. The aluminum hydroxide produced by the hydrolysis of Al³⁺ was estimated using energy dispersive X-ray spectrometry（EDX）. Surface roughness of the deposits was measured using a three-dimensional surface profiler. Also, results obtained using X-ray diffractometry（XRD）and electron backscatter diffractometry（EBSD）revealed that the preferred crystallographic orientation of nickel changed from the ［100］ direction to ［110］ because of the aluminum hydroxide particles. By increasing the Al³⁺ concentration to 5.0×10³ mol dm³, the deposit surface became smooth and the crystal size was found to decrease. Moreover the Vickers hardness increased in comparison to that obtained from an Al³⁺ free bath. These phenomena are regarded as strengthening effects related to grain size reduction.