Morphology, Structural Control, and Magnetic Properties of Carbon-Coated Nanoscaled NiRu Alloys

Abstract

Carbon-coated nanoparticles of NiRu (NiRu@C) have been synthesized by a high-pressure chemical vapor deposition using metallocenes of both metals. Transmission electron microscopy images show an average particle size (core) of 8 ± 3 nm and carbon shell thicknesses between 2 and 3 nm. X-ray diffraction investigation reveals NiRu binary alloys. Analyses of the X-ray diffraction peaks and the magnetization curves approximately confirm the average particle size. The compositions of the nanoalloy cores have been studied by means of energy dispersive X-ray analysis. We find that at constant sublimation temperature (95 °C) a synthesis temperature of 900 °C and a Ni−Ru-metallocene weight ratio of 2:1, an increase of synthesis pressure leads to both a change of the core composition and the thickness of the carbon coatings. The magnetic properties of the coated nanoalloys strongly depend on the synthesis parameters so that, for example, the superparamagnetic blocking temperature and the saturation magnetization can be tailored. Our straightforward of controlled synthesis therefore opens a novel route to complex nanosized functional materials.

The Synthesis of Superparamagnetic Cobalt Nanoparticles Encapsulated in Carbon Through High‐pressure CVD

“…Similar results were already observed in previous in‐house studies, where the synthesis was focused on NiRu@C nanoparticles. The group who carried out this study also mentioned an increase of carbon content with rising pressure, without giving an explanation . It is certain that a higher pressure of argon causes a dilution of precursor in the gas phase simply due to the presence of more argon atoms.…”

Microbial-Physical Synthesis of Fe and Fe3O4 Magnetic Nanoparticles Using Aspergillus niger YESM1 and Supercritical Condition of Ethanol

“…The Fe sample exhibits closed hysteresis loop that reveals superparamagnetic-like behavior with saturation magnetization Ms of 112 emu/g and with small remanence and coercivity. From the initial slope of × curve we can get information regarding the magnetic domain size of the formed particles [15] to be 7 nm for the synthesized Fe nanoparticles (Figure 8 For all the previous investigations, the hysteresis loops were measured at different temperatures in order to determine the blocking temperature which distinguishes between the ferromagnetic and the superparamagnetic behaviors ( Figure 9).…”

Synthesis of Ni–Ru Alloy Nanoparticles and Their High Catalytic Activity in Dehydrogenation of Ammonia Borane

“…Recently, El-Gendy et al successfully synthesized carbon-coated Ni-Ru alloy NPs at 900 8C by high-pressure chemical-vapor deposition by using metallocenes as metal precursors. [34] The impregnation method was also employed to synthesize bimetallic Ni-Ru NPs supported on graphite and SBA-15 silica. [35,36] However, the impregnation method is not conducive for controlling particle size and compositional homogeneity.…”