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Oxidation kinetics and fringe analysis studies of three "model" carbons, ranging from fullerenic to onion-like nanostructures and a reference diesel soot were performed in a thermogravimetric analyzer. The samples were oxidized isothermally at temperatures ranging from 575 to 775 °C in air. Multiple tests were performed to obtain the most favorable operating conditions to minimize mass-transfer diffusion limitations in the experiments. First-order reaction kinetics and an Arrhenius-type equation were used to extract the rate constants at each temperature. The activation energies for the oxidation of the carbon samples ranges from 124 to 204 kJ/mol, and it was approximately 140 kJ/mol for the reference diesel soot sample. The onion-like structure exhibited a slower kinetic rate compared to the other carbons. Similar kinetic parameters were found for "intermediate structure" model carbon and reference diesel soot. Fringe analysis explained the differences in the kinetic parameters between carbon samples studied. The onion-like carbon "nascent" sample had a broader range of lamellae length with smaller tortuosity distribution, suggesting stacking; the "nascent" fullerenic carbon had much shorter mean lamella length distribution and broader tortuosity, suggesting more curvature. Nanostructure metrics of the reference diesel soot and intermediate model carbon were between the other two carbons. Results confirm a structure-property relationship between oxidative reactivity with carbon nanostructure.

Ultrafine particle (UFP) emissions and particle number size distributions (PNSD) are critical in the evaluation of air pollution impacts; however, data on UFP number emissions from cookstoves, which are a major source of many pollutants, are limited. In this study, 11 fuel-stove combinations covering a variety of fuels and different stoves are investigated for UFP emissions and PNSD. The combustion of LPG and alcohol (∼10 particles per useful energy delivered, particles/MJ), and kerosene (∼10 particles/MJ), produced emissions that were lower by 2-3 orders of magnitude than solid fuels (10-10 particles/MJ). Three different PNSD types-unimodal distributions with peaks ∼30-40 nm, unimodal distributions with peaks <30 nm, and bimodal distributions-were observed as the result of both fuel and stove effects. The fractions of particles smaller than 30 nm (F) varied among the tested systems, ranging from 13% to 88%. The burning of LPG and alcohol had the lowest PM mass emissions, UFP number emissions, and F (13-21% for LPG and 35-41% for alcohol). Emissions of PM and UFP from kerosene were also low compared with solid fuel burning but had a relatively high F value of approximately 73-80%.

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