TEM studies of carbon nanofibres formed on Ni catalyst by polyethylene pyrolysis

Abstract

Carbon nanofibres (CNF) have been formed by polyethylene pyrolysis, using a Ni catalyst and a hydrogen–argon gaseous mixture. The temperature interval of 500–700 °C was chosen, because small sized Ni catalyst particles are formed in this case. TEM and high resolution TEM studies revealed catalyst particles of spherical, oval, conical and faceted shapes, some of which have been twinned. The variety of shapes and sizes can be explained by the different values of the surface tension forces in the catalyst and in graphite in the various cases. Unusual ‘burst’ CNFs, distinguished by the alternation of dense and sparse regions, have been found in the deposit. A model of a periodic process, based on the decay of Ni carbide, is assumed for the explanation of the ‘burst’ CNF formation.

Structural Peculiarities of FCC and BCC Catalyst Particles and Fillings Inside Carbon Nanotubes (Nanofibers) Studied by Means of Electron Microscopy

“…Faceted shape of the catalyst indicates that diffusion of carbon atoms (bulk and surface) takes place, because otherwise catalyst particles of spherical shape are usually supposed. Authors of [1,2] found other orientations ofNi particles inside carbon nanofibers in addition to the above mentioned: We have found also fcc-Fe particles inside carbon nanotubes. The existence of these particles which are not stable under normal conditions can be explained by the effect of hard graphite shell, covering these particles.…”

Characterization of CVD TiN coating at different deposition temperatures and its application in hydrocarbon pyrolysis

“…7(a), a lot of interwoven filamentous coke covers the cracks and gaps completely on the surface of 310S substrate, and the bright points are found at the filaments tips or in the filaments. According to the viewpoints of Kulnitskiy et al [34] and Xu et al [35], these bright points on the filamentous tips are most likely the metallic atoms extracted from the metal substrate which catalyze filamentous coke growth. To obtain more information on the coking mechanism, the coked 310S substrate after burning at 700°C and the cross section of the coked 310S substrate were characterized by SEM and EDX line scan, as shown in Fig.…”

Fabrication of Tunable Submicro‐ or Nano‐Structured Polyethylene Materials from Immiscible Blends with Cellulose Acetate Butyrate

“…For example, PE microspheres have been employed as core materials for fabricating hollow alumina microspheres and non‐porous silica ultramicrospheres for HPLC column packing 1, 2. PE fibers can serve as filtration materials, absorber materials of heavy particle irradiation for space exploration or precursors of carbon fibers in the presence of a catalyst 3–7. Moreover, PE film materials, surface‐modified via plasma irradiation, have found wide applications as support materials for immobilizing DNA, proteins and cells, and as anticoagulants in the development of DNA‐chips, biosensors and extracellular matrix for tissue engineering and vessels.…”