Abstract
A dynamic model based on mass balance of fine aerosol particles was developed in order to tackle the problem of accurate quantification of mechanically stimulated particle emission (MSPE) from nanofunctionalized and solid lubricating materials. In contrast to the conventional approach, the model accounts for the effect of air turbulization caused by moving parts of the experimental tribological setup on the enhancement of particle deposition velocity. The increase of the velocity of the moving parts results in an increase of the deposition velocity that leads to a significant underestimation of experimentally measured particle emission rates. The developed model was experimentally verified using natural and artificial nanoparticle aerosols. Finally, the new methodology of particle emission rate quantification was employed for the analysis of fine particle emission produced when the solid lubricating materials were tested against a sliding steel surface. The developed method paves the way for defining a standard method of experimental assessment of nanoparticle triboemission enabling the experimental results obtained in various laboratories to be compared. It also bridges the gap between the phenomenological models and experimental measurements.
Highlights
Since the beginning of the broad introduction of engineered nanomaterials (ENMs) in various applications and consumer products, there has been a concern over the potential risks of release of these materials into the environment [1,2,3]
Our experiments demonstrated that air turbulization by moving parts of the experimental setup can significantly affect the measured nanoparticle emission rate resulting in underestimated results
It was found that the dynamics of aerosol particle concentration obeys first order exponential approach with two time constants corresponding to the setup at a standstill and the setup in motion, respectively
Summary
Since the beginning of the broad introduction of engineered nanomaterials (ENMs) in various applications and consumer products, there has been a concern over the potential risks of release of these materials into the environment [1,2,3]. For quite a long time, mechanical solicitations such as machining [4], erosion, abrasion, sanding, rubbing (including brake, road and tyre wear) and weathering have been considered the most typical liberation processes responsible for non-exhaust particle emission [5,6,7], the reported experimental results are surrounded by controversy [8,9]. The early studies employed the experimental setups being a simple combination of the aerosol generator and an aerosol measurement system. The aerosol generators were a standard Taber abrader or a sander, whereas the aerosol measurement system normally consisted of a simple non-airtight hood surrounding the mechanically affected zone [8,10,13,14] and a standard aerosol measurement
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