Carbon nanotubes from post-consumer waste plastics: Investigations into catalyst metal and support material characteristics

Carbon nanotubes were produced from post-consumer mixed waste plastics using a pyrolysis-catalysis process. The catalysts used were Ni-Fe bimetals supported over four different porous materials. The Ni-Fe/MCM41 catalyst displayed the highest catalytic activity for the pyrolysis-catalysis of the waste plastics in terms of carbon material yield at 55.60 wt.%. The order of catalytic activity was Ni-Fe/MCM41> Ni-Fe/ZSM5> Ni-Fe/Beta > Ni-Fe/NKF5, which was closely related to their differences in catalyst pore volume and catalyst reducibility. Formation of Ni-Fe alloy with fine particle dispersion over the Ni-Fe/MCM41 catalyst is suggested to be crucial for the promotion of the decomposition of the carbon precursors and subsequent precipitation to form carbon nanotubes. Whereas, the large catalyst particle size for the Ni-Fe/Beta catalyst led to irregular carbon shapes with a simultaneous decrease in purity and graphitization of the nanotubes. By-product production of hydrogen in large quantities (38.10 mmol H2  g−1plastic) could be used as process fuel

Fermi establishes classical novae as a distinct class of gamma-ray sources

A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter from a low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in γ rays and stood in contrast to the first γ-ray-detected nova V407 Cygni 2010, which belongs to a rare class of symbiotic binary systems. Despite likely differences in the compositions and masses of their white dwarf progenitors, the three classical novae are similarly characterized as soft-spectrum transient γ-ray sources detected over 2- to 3-week durations. The γ-ray detections point to unexpected high-energy particle acceleration processes linked to the mass ejection from thermonuclear explosions in an unanticipated class of Galactic γ-ray sources