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  • 1.
    Nosko, Oleksii
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Borrajo-Pelaez, Rafael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Porosity and shape of airborne wear microparticles generated by sliding contact between a low-metallic friction material and a cast iron2017In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 113, p. 130-140Article in journal (Refereed)
    Abstract [en]

    The wear of brakes in transport vehicles is one of the main anthropogenic sources of airborne particulate matter in urban environments. The present study deals with the characterisation of airborne wear microparticles from a low-metallic friction material / cast iron pair used in car brakes. Particles were generated by a pin-on-disc machine in a sealed chamber at sliding velocity of 1.3 m/s and contact pressure of 1.5 MPa. They were collected on filters in an electrical low pressure impactor, and an investigation was conducted to quantify their shape and porosity. Scanning electron microscopy revealed that most of the 0.1−0.9 µm particles are flakes and have a breadth-to-length aspect ratio of 0.7 ± 0.2. Particle porosity was determined by milling particles with a focused ion beam and subsequent analysis of the exposed particle cross-sections. Most of the 0.3–6.2 µm particles were revealed to have porosity of 9 ± 6%. Analysis of the relationship between effective particle density, particle material density, dynamic shape factor and porosity showed that the shape factor has a stronger influence on the effective density of airborne wear particles than the porosity factor. The obtained results are useful for accurate prediction of particle behaviour in the atmosphere and in the human respiratory system.

  • 2.
    Nosko, Oleksii
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Effective density of airborne wear particles from car brake materials2017In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 107, p. 94-106Article in journal (Refereed)
    Abstract [en]

    People living in urban environments are subject to high health risks due to various anthropogenicsources of airborne particulate matter, including wear of transport vehicle brakes. Studies ofairborne particles often require an estimate of the effective particle density, a property thatallows correct matching of mass and size characteristics measured by different aerosolinstruments. In this study we investigated the effective density of airborne wear particles emittedfrom car brake materials. The particles were generated by a pin-on-disc machine located in asealed chamber. Two methods were used to determine the effective density. The first method isbased on measurements of PM10 and particle size distribution. The second method involvesmeasurements and subsequent fitting of the mobility size distribution and aerodynamic sizedistribution. Results from the two methods showed good agreement. It was found that theeffective density is 0.75±0.2 g/cm3. The particle emission, size distribution and effectivedensity are sensitive to temperature variations. An intensive emission of ultrafine particles isinitiated at the disc temperature of 185±16 °C. The effective density decreases with thetemperature in the interval 110–360 °C. There is a large difference between the effective densityand the density of the particle material, which suggests that the particles are porous.

  • 3.
    Orrling, Diana
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Fitzgerald, E.
    Department of Chemistry and Biochemistry, University of California.
    Ivanov, A.
    Department of Chemistry and Biochemistry, University of California.
    Molina, M.
    Department of Chemistry and Biochemistry, University of California.
    Enhanced Sulfate Formation on Ozone-Exposed Soot2011In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 42, no 9, p. 615-620Article in journal (Refereed)
    Abstract [en]

    Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on methane soot in the presence of ozone and water vapor. The enhanced formation of sulfate at atmospheric pressure was confirmed by the use of a particle-into-liquid sampler (PILS) coupled with ion chromatography (IC). Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites were observed. The exposure also caused the soot to become hydrophilic, due to the formation of sulfuric acid and also likely the formation of carboxyl groups on the surface. The sulfate yield increased with ozone levels, but no increase was observed at ozone concentrations above 1000 ppm.

  • 4.
    Tornehed, Petter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Modelling lubrication oil particulate emissions from heavy-duty diesel enginesIn: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964Article in journal (Other academic)
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