Synthesis of Novel Nanostructures by Metal−Polytetrafluoroethene Thermolysis

Abstract

Novel ceramic and carbon nanostructures have been created by thermolysis of mixtures containing polytetrafluoroethene (PTFE) and a pure metal or metal alloy in a calorimetric bomb. The influence of the stoichiometry was studied for Si-containing reactants for which the yield of the nanofibers was the highest. The process was monitored by measuring the heat of reaction and by differential thermal analysis/ thermogravimetric techniques. The reaction temperatures were measured, and the heating rates of the reactants during thermal wave propagation were estimated. Elemental analysis, X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray spectrometry were employed to characterize the chemical composition and structural features of the products. Well-crystallized elongated single-crystal Si nanofibers, coated with a thin SiO 2 amorphous layer, and crystallized carbon nanoparticles containing metals (e.g., Fe) and Si dominate. The highest yields of nanofibers and carbon particles were obtained from PTFE and Si-containing precursors, due to the volatility of SiF 4 .

Synthesis of Multiwalled Carbon Nanotubes by Catalytic Combustion of Polypropylene

“…Syntheses of CNTs or other nanostructured materials in situ through thermal decomposition of polymer/catalyst or polymer/metal mixtures from polyethylene, poly(vinyl alcohol), and polytetrafluoroethene under inert atmosphere have also been reported. [26][27][28][29] Herein, we demonstrate a novel catalytic combustion method of synthesizing multiwalled carbon nanotubes (MWNTs) in situ in high yield from polypropylene (PP) as the carbon source in the presence of an organic-modified clay (OMC) and a supported nickel catalyst (Ni-cat; see Experimental Section). Maleated polypropylene (PP-MA) was used as a compatibilizer to improve the dispersion of OMC and Nicat in the PP matrix.…”

Studies on spontaneous formation of 1D nanocrystals of silicon carbide

“…The selected products containing different components were chemically purified by controlled oxidation in air at 700 o C (free C removal), Si leaching (KOH solution) and CaF 2 dissolution (HCl acid treatment). Thus, comparing to bulk product [9] almost pure SiC could be obtained as confirmed by XRD analysis.…”

“…Following the results of preliminary tests [9] Si-containing reactants were selected for further studies. Not only PTFE, but also other halogenohydrocarbons were used as oxidizing agents.…”

“…Thermolysis was carried out under an Ar or air (0.5 MPa) atmosphere in a calorimetric bomb [9]. The starting two-component mixtures were prepared in the form of a 2 cm dia pellet (5 g) made from fine powders (particle size below 100 µm) compressed at 10 MPa, i.e.…”

“…Thermolysis is a quick and energy-efficient way to prepare valuable materials. During the course of reaction, rapid solidification generates structures that would be unstable under normal conditions [8]. This capability makes it possible to create materials that are otherwise difficult to make, such as elongated 1D nanostructures.…”