Carbon Nanotubes, Nanocrystal Forms, and Complex Nanoparticle Aggregates in common fuel-gas combustion sources and the ambient air

Abstract

Aggregated multiwall carbon nanotubes (with diameters ranging from 3 to 30 nm) and related carbon nanocrystal forms ranging in size from 0.4 to 2 lm (average diameter) have been collected in the combustion streams for methane/air, natural gas/air, and propane gas/air flames using a thermal precipitator. Individual particle aggregates were collected on carbon/formvar-coated 3 mm nickel grids and examined in a transmission electron microscope, utilizing bright-field imaging, selected-area electron diffraction analysis, and energy-dispersive X-ray spectrometry techniques. The natural gas and propane gas sources were domestic (kitchen) stoves, and similar particle aggregates collected in the outdoor air were correspondingly identified as carbon nanocrystal aggregates and sometimes more complex aggregates of silica nanocrystals intermixed with the carbon nanotubes and other carbon nanocrystals. Finally, and in light of the potential for methane-series gas burning as major sources of carbon nanocrystal aggregates in both the indoor and outdoor air, data for natural gas consumption and corresponding asthma deaths and incidence are examined with a degree of speculation regarding any significance in the correlations.

A Review of Carbon Nanotube Toxicity and Assessment of Potential Occupational and Environmental Health Risks

“…These aggregates were essentially pure carbon or graphene and contained several hundred to several thousand MWCNTs or other related nanocrystal forms with an average diameter of 20 nm. The individual MWCNTs ranged approximately from 3 to 30 nm in diameter (Murr et al, 2004a). These findings indicate that MWCNTs and other carbonaceous nanoparticles are produced also by water heaters, furnaces, and household appliances powered by natural gas.…”

“…The aggregates were similar in structure to those collected indoors except that the outdoor particulate matter also included agglomerates with other common atmospheric mineral nanocrystals, such as silica. According to Murr et al (2004a), about 15% of the El Paso particulate samples were carbonaceous aggregates consisting of MWCNTs and other nanoforms (shells, spheres, and other structures). Diesel-related aggregates accounted for 5% of the sample (Murr et al, 2004a).…”

“…According to Murr et al (2004a), about 15% of the El Paso particulate samples were carbonaceous aggregates consisting of MWCNTs and other nanoforms (shells, spheres, and other structures). Diesel-related aggregates accounted for 5% of the sample (Murr et al, 2004a). Murr's group (Bang et al, 2004) concluded that MWCNTs and carbonaceous nanoparticles are ubiquitous in the environment; they further speculated that MWCNTs are a major component of indoor and outdoor airborne particulate matter.…”

Carbon Nanotube and Fullerene Emissions from Spark-Ignited Engines

“…CNTs have been noted in only a few studies of particles sampled from the ambient air (Murr et al 2004;Murr and Garza 2009). However, after emission, CNTs may combine with larger ambient particles, and thereby escape identification or be misidentified as mineral fibers.…”

“…Emission factors for CNT/FULs from common combustion sources have not been published to our knowledge, though these morphologies have been identified in exhaust from natural gas (NG) stoves (Murr et al 2004) and tentatively from a 157 diesel engine (Evelyn et al 2003) and gasoline engines (Ortner et al 1998). Blom et al (2000) found structures that might have been FULs but were not identified as such by those authors.…”