Papers by Keyword: Ni Nanoparticles

Abstract: A well-dispersed Ni nanoparticles on multi-walled carbon nanotubes (Ni@MWCNTs) was prepared by chemical vapor deposition (CVD) method using a vacuum quartz tube furnace at the temperature of 600°C. The scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to characterize the synthesized catalyst. It shows an unfirom dispersion of Ni nanoparticles on MWCNTs with the average particle size of 8.6 nm. The as synthesized catalyst was applied in a redox reaction of 4-nitrophenol, which showed very high catalytic activity, stability and well conversion. The catalyst can be easily separated due to the magnetical performance

Abstract: SiAlON Was Mixed with Ni Nanoparticle Precipitated cBN (SiAlON-cBN/Ni) and Sintered by Spark Plasma Sintering at 1923 K for a Holding Time (t_H) of 0 to 1.8 Ks. the Effect of Ni Nanoparticle and Holding Time on the Phase Transformation of cBN to Hexagonal (hBN), Densification, Microstructure and Hardness of the SiAlON-cBN Composites Was Studied. At t_H =1.8 Ks , the Relative Density of the SiAlON-20 Vol% cBN/Ni Was 99%, 7% Higher than that of SiAlON-20 Vol% cBN, Indicating that Ni Nanoparticle on cBN Promoted the Densification of SiAlON-cBN Composites. The BN Grains in SiAlON-20 Vol% cNB Showed a Round Morphology, whereas the BN Grains in SiAlON-20 Vol% cBN/Ni Composite Showed a Flake Morphology Characteristic of hBN. The Phase Transformation of cBN Was Accelerated by Ni. the Maximum Hardness of SiAlON-20 Vol% cBN/Ni Was 16.3 GPa Obtained at t_H = 0 Ks.

Abstract: The chitosan derivatives(S-CTS and RS-CTS) were prepared and the application of the derivatives in surface activation process for Ni electroless plating was exploited. S-CTS was prepared by shiff-base reaction of CTS with salicylic aldehyde and RS-CTS was prepared by reduction reaction of S-CTS with KBH4. The results of FT-IR spectroscopic characterization showing the formation of C＝N in S-CTS and C－N in RS-CTS indicated that the above reactions occurred in the supposed route. The thermal properties of the derivatives were studied by Thermogravimetry-Differential thermal analysis (TG-DTA) methods. It is suggested that the thermal stabilities of CTS derivatives were better than that of CTS. Furthermore, RS-CTS is capable of forming even films on ABS surface and adsorbing adequate Ni nano-catalysts for follow-up electroless plating. Optic tight and dense plating layers were finally obtained. It is showed that RS-CTS could be applied as a biopolymer film in activation process for electroless plating.

Abstract: CNTs were decorated with Ni nanoparticles to decrease floatation of CNTs and improve the wettability between CNT and Al melt by electroless plating method. The as-received size of multi-wall CNTs with 99.5% purity was 10~20nm in diameter and 20um in length. Before Ni deposition, the wet ball milling was tried to improve the dispersion of CNTs in the Ni sulfate solution for several hours. After wet ball milling, the Ni electroless platings have been performed for 1hours at electroless deposition temperature. The Ni deposited CNTs have been characterized in respect of dispersion and size changes of CNTs and Ni particles with field emission scanning electron microscopy(FESEM). The deposited Ni nanoparticles onto the CNTs were 50nm in diameter without ball milling, but they increased in size with increasing milling times up to 120nm. Also, the milled CNTs were damaged and changed from its original morphology due to the high ball milling energy. The addition of surfactant improved the distribution and spheroidization of precipitated Ni nanoparticles. From this study, the multi-wall CNTs have been deposited and decorated with spherical Ni nanoparticles by electroless deposition at a proper milling time and surfactant addition.

Abstract: Colloid stability of the suspensions of Ni nanoparticles has been investigated with adding polymeric dispersant in various organic media. We characterized the dispersion stability of Ni nanoparticles by means of visual inspection, transmission profiles measured by Turbiscan, the particle size distribution, and the zeta potential. 0.01 wt% of Ni nanoparticles were found to be optimally dispersed in ethanol among various organic media employed in this study with adding the dispersant (0.6 wt%-2 wt%). As the concentration of the dispersant increased, the particle size decreased in size from 300 nm to 200 nm due to less coalescence. The zeta potential values of the Ni nanoparticles in suspensions with the dispersant were greater than -40mV. Such stable Ni nanoparticle suspensions are attributed to the electrosteric effect of the polymeric dispersant.

Abstract: The stability of nanosized Ni dispersions with varying concentrations of poly (1-vinyl-2- pyrrolidone) (PVP) was investigated by means of a visual inspection, transmission profile measured by Turbiscan, zeta potential, and transmission electron microscopy. For dispersions with PVP, the ζ potential values varied from positive charge to negative charge. For dispersion with a 0.04 weight percentage of PVP, the ζ potential value showed 31.71 mV, which was the highest value, and the flocculation of Ni nanoparticles was not observed. Stable dispersions of Ni nanoparticles were produced by electrostatic, steric interactions, and the formation of bridging aggregation.