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  • 1.  environmental: particle size distributions for post-spray material, dust

    Posted 11-24-2021 15:19
    I just got a question from the company we work with to help with our environmental reporting. It's a bit outside of my normal scope: 
    "What is the particle size distribution of the overspray that enters our dust collectors?" 
    For flame especially. 

    I was thinking that before I collected samples to do this that I'd pose it out there to you all. 

    I was thinking, since this is a very fine particle, in general, that I would get backscattered electron images, probably as binary as I can make them, and do image analysis on those images to measure sizes. 

    Ideas? Input? Derisive laughter?

    Joe Zanter
    R&D Engineer
    Thermal Spray Technologies
    Sun Prairie WI
    (608) 318-5077
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  • 2.  RE: environmental: particle size distributions for post-spray material, dust

    Posted 11-25-2021 00:43

    HI Joe,


    Thanks for highlighting what is, and will increasingly be, an important issue for the industry.


    Your idea of BSE images of the powder will work but is perhaps not the best route to getting a representative and quantitative size analysis.  Preparing a representative sample for quantitative size analysis by SEM is challenging.....as it is difficult to ensure that you have a representative sample from the bulk powder, that the big particles don't fall off, that the fine particles are not shadowed by larger particles, that you do not have agglomerated cakes of finer particles, it is hard to image nanosized particles etc etc....you get the idea.


    As an alternative, I would suggest using a laser based particle size analyser.  With our system in the lab we have had our best success with the "wet" analysis, which analyses the powder in a water carrier through the system.  This will immediately give you the statistics of your size distribution for a large number of particles, and can measure from 10s of nanometers up to 1-2mm.  This system has its limitations as well....the biggest challenge I have found is that the amount of material analysed is very small and so it is important to ensure that you have a representative sample.  Also, important to make sure that your sample does not dissolve or react with water! You could get an XRD analysis done to confirm the average composition of the powder, which the environmental report would also appreciate knowing.


    Hope this helps and best of luck.


    Best regards

    Steve Matthews


    Steven Matthews, PhD


    Department of Chemical and Materials Engineering

    The University of Auckland, Auckland, New Zealand

    Email: s.matthews@auckland.ac.nz

    Phone: +64 9 9236373 or +64 9 3737599 ext 86373


    University Profile Page: University Profile/Research Summary Link

    Associate InvestigatorThe MacDiarmid Institute for Advanced Materials and Nanotechnology  www.macdiarmid.ac.nz

    Associate Investigator"Surface Engineering for Advanced Materials" www.arcseam.com.au


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  • 3.  RE: environmental: particle size distributions for post-spray material, dust

    Posted 11-25-2021 10:03
    Thanks Steve. Just what I was hoping for!

    jzanter (at) gmail (dot) com
    The task of the modern educator is not to cut down jungles but to irrigate deserts.  C.S.Lewis

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