Preparation and characterization of Ni(OH) 2 nanoparticles coated with dialkyldithiophosphate
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Preparation and characterization of Ni(OH)2 nanoparticles coated with dialkyldithiophosphate Junyan Zhang, Shengrong Yang, and Qunji Xue Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Science, Lanzhou 730000, People’s Republic of China (Received 10 February 1999; accepted 10 November 1999)
Ni(OH)2 nanoparticles modified with di-n-hexadecyldithiophosphate (DDP) were prepared by a chemical surface modification method. The structure of the nanocluster was investigated using infrared spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and 31P nuclear magnetic resonance spectroscopy. The thermal stability of DDP coating on the Ni(OH)2 nanoparticles was compared to that of pyridinium di-n-hexadecyldithiophosphate (PyDDP) using thermogravimetric analysis. It was found that coated Ni(OH)2 nanoparticles had an average diameter of about 5 nm. Surface modification with DDP prevented water adsorption and effectively improved the dispersive capacity and antioxidative stability of Ni(OH)2 nanoparticles. The thermal stability of DDP coatings on the surface of nano-Ni(OH)2 particles was higher than that of PyDDP coatings because of the chemical interaction between PyDDP and Ni(OH)2 during the coating process.
I. INTRODUCTION
Nano-sized particles have received considerable attention in recent years because of their special physical and chemical properties. A variety of methods for preparing nanoparticles and evaluating their properties have been developed recently.1–5 In the past few years, preparation of nanoparticles using surface modification has been studied extensively.6–9 By coating the surface with highmolecular-weight hydrocarbons, the nanoparticles have good dispersive capacity in organic solvents and in lubricating oil. It is well known that Ni films, Ni/Mo, and Ni/Cu multilayer films deposited on metal surfaces have good anticorrosion and antifriction properties.10,11 However, no work has been done to investigate the friction and wear behavior of Ni organic salts as additives in lubricants. It is of great interest to note that similar copper-containing deposits were detected on the frictional mating surfaces when different copper-containing compounds were incorporated in base oils.12 In our previous work, it was also found that during the rubbing process Cu(II) ions were reduced to Cu(0) deposited on metal surface to form a Cu ultrathin film which had anticorrosion, antiwear, and antifriction properties.13 We think it is worthwhile to prepare nanoclusters containing Ni(OH)2 which can be dispersed in oil as an additive, and, during rubbing, Ni(II) ions also may be reduced to Ni(0) and form a ultrathin film. Nanoparticles of di-n-hexadecyldithiophosphate (DDP)-coated MoS2 and organic-acid-coated TiO2 were J. Mater. Res., Vol. 15, No. 2, Feb 2000
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successfully synthesized in our laboratory and the antiwear ability of the modified
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