Characteristics of Magnetic Mesoparticles Fabricated by Electroless Nickel Deposition

Abstract

A low-cost wet chemical process, viz., the electroless nickel deposition, was successfully developed to produce magnetic nickel−tungsten−phosphorus (NiWP) mesoparticles with diameters ranging from 100 to 500 nm on silica templates of ca. 102 nm and gold templates of ca. 3 nm. An X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDX), a superconducting quantum interference device (SQUID), and a vibrating sample magnetometer (VSM) were employed to characterize these particles. The averaged sizes of the NiWP particles could be conveniently regulated with the duration of the electroless plating process, in which exponential growth kinetics of the NiWP particles was observed. Both XRD and electrodiffraction (ED) patterns of these NiWP alloys indicate existence of diffraction peaks close to the (111), (200), (220), and (311) reflections of bulk face-centered cubic (fcc) Ni. The zero-field-cooled (ZFC) and field-cooled (FC) measurements also indicate the irreversibility temperatures of magnetization of these particles are in between 300 and 380 K. Dependent on the plating baths, the Curie temperatures of the resulting NiWP particles are around 330 K and higher than 380 K. Hence, weak ferromagnetic behaviors were evidently observed on all of these NiWP particles. Their saturation magnetization and coercivity were found in the range from 6 to 28 emu/g of sample and from 26 to 50 Oe, respectively.

Electroless Ni–P Deposition on AZ91 D Magnesium Alloy Prepared by Molybdate Chemical Conversion Coatings

“…The deposited Ni-P alloy also acts as a catalyst, and thus, the deposition process continues at a certain rate limited by the pH decrease and depletion of ions in the bath. [15][16][17] To investigate the onset of Ni-P deposition, SEM images were taken for PMoAEN, PEN, and PAEN samples at the early stage of the plating process. Figure 5 shows PMoAEN samples plated for 20 and 60 s. Although Ni deposition is hardly seen at 20 s in Fig.…”