?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F326%2F&rft.title=Deposition+of+Charged+Powder+Particles&rft.creator=Addison%2C+J.&rft.creator=Budd%2C+C.&rft.creator=Forth%2C+S.&rft.creator=Grinfield%2C+M.&rft.creator=Harris%2C+T.&rft.creator=Hogg%2C+A.&rft.creator=Lister%2C+J.&rft.creator=Tabraham%2C+J.&rft.creator=Taylor%2C+J.&rft.creator=Wylie%2C+J.&rft.subject=Materials&rft.description=The+problems+brought+to+the+Study+Group+by+Courtaulds+Coatings+concern+the+electrostatic+deposition+of+powder+paints+onto+an+earthed+metal+workpiece.+The+process+involves+charging+the+paint+particles+as+they+pass+through+a+'gun'%3B+they+then+travel+towards+the+workpiece+under+the+influence+of+aerodynamic+and+electrostatic+forces.+At+present+two+types+of+gun+are+used%2C+these+are%3A%0D%0A-+the+Corona+gun+in+which+particles+are+forced+past+a+high+voltage+electrode+which+ionises+the+surrounding+air+and+hence+particles+are+charged+by+collecting+ions+(Paulthier+Charging).%0D%0A-+the+Tribo+gun+in+which+particles+are+charged+in+an+earthed+gun+directly+by+friction.%0D%0A%0D%0AThe+main+differences+between+these+two+types+of+gun+are%3A%0D%0A-+when+using+a+corona+gun+the+electric+field+is+set+up+not+only+by+the+space-charge+but+also+by+the+applied+potential+difference+between+the+gun+and+workpiece.%0D%0A-+free+ions+constitute+99%25+of+the+charge+in+a+corona+system%2C+whilst+no+free+ions+are+present+when+using+a+tribo+gun.%0D%0A%0D%0AAs+the+corona+gun+involves+many+more+complicated+physical+processes%2C+it+is+the+tribo+gun%2C+with+a+single+species+of+particle%2C+which+is+considered+in+this+report.%0D%0A%0D%0AThe+main+questions+asked+by+Courtaulds+were%0D%0A-+What+factors+affect+deposition+efficiency%3F%0D%0A-+How+is+deposition+efficiency+maximised%3F%0D%0A%0D%0AThis+report+is+organised+into+three+main+sections.%0D%0AFirstly%2C+a+tribo+gun+model+is+presented+and+non-dimensionalised%2C+revealing+that+electrostatic+and+aerodynamic+forces+are+in+balance%2C+whilst+particle+inertia+and+gravity+may+be+neglected+for+the+system+in+question.+%0D%0AThen%2C+a+one-dimensional+model+is+considered+which+gives+vital+information+about+the+orders+of+magnitude+of+relevant+quantities+at+the+workpiece+and+the+effect+of+charge+saturation.%0D%0AFinally%2C+a+model+is+proposed+for+a+narrow+'jet'+of+particles+impinging+on+an+earthed+workpiece+and+it+it+shown+that+geometry+is+by+far+the+most+important+factor+affecting+deposition+efficiency.&rft.date=1996&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F326%2F1%2FDeposition-of-charged-powder-particles.pdf&rft.identifier=++Addison%2C+J.+and+Budd%2C+C.+and+Forth%2C+S.+and+Grinfield%2C+M.+and+Harris%2C+T.+and+Hogg%2C+A.+and+Lister%2C+J.+and+Tabraham%2C+J.+and+Taylor%2C+J.+and+Wylie%2C+J.++(1996)+Deposition+of+Charged+Powder+Particles.++%5BStudy+Group+Report%5D+++++