More on Characterization Qualitative size distribution dynamics Particle chemistry Particle chemical characterization

Size distributions may change over time Starter size distribution:

Processes in which volume is conserved Coagulation, communition or breakup, restructuring

Processes in which volume not conserved Condensation, evaporation, nucleation, sedimentation,

In class project – changing shapes of distributions

Chemical composition not always same Varying degrees of chemical homogenaity in particle mixtures Particles all of one chemical species (ie salt granules) – chemically homogeneous Particles are all of one chemical species, but the particles are mixed – externally mixed Particles are of two or more chemical components, but composition of each particle is same – internally mixed Individual particles have different compositions

Chemical composition may vary with size Pharmaceutical powders for inhalation - want small drug particles mixed with and loosely bound to larger inert particles Emissions from incinerators – some high volatility compounds evaporate in high temperature zone and nucleate downstream forming ultrafine high surface area particles More examples

How to measure chemical composition? Many techniques – survey of analytical chemistry Some need large sample of material, so need to take average over whole size distribution, and/or time Some need extremely small amounts of material so representative sampling is crucial Some can tell you composition on-line or nearly on-line Some require off-line analysis

SADK – secret acronym decoder kit a.Atomic absorption spectroscopy (AAS) b.Inductively coupled plasma- atomic emission spectroscopy (ICP-AES) c.Laser induced breakdown spectrometry (LIBS) d.Time of Flight Mass spectrometry of aerosols (TOF-MS) e.X-ray Fluorescence (XRF) f. Proton Induced X-Ray Emission (PIXE) g.Neutron activation analysis (NAA) h.X-ray photoelectron spectroscopy (XPS) i.Auger spectroscopy j.X-ray diffraction (XRD) k.Energy dispersive X-ray spectroscopy (EDX or EDS) l.Electron energy loss spectrometry (EELS)

Analytical situations: in class problem