TY - JOUR
T1 - Rheological and surface chemical characterization of alkoxysilane treated, fine aluminum powders showing enhanced flowability and fluidization behavior for delivery applications
AU - Ludwig, Bellamarie
AU - Miller, Timothy F.
N1 - Funding Information:
Bellamarie Ludwig received her B.S. in Chemistry and M.S. in Material Science and Engineering from The Pennsylvania State University. She is currently a Ph.D. candidate and an Associate Research and Development Engineer in the Technology, Concepts, and Modeling Department of the Energy Science and Power Systems Division at the Applied Research Laboratory at PSU. She has served as a Principal Investigator for programs funded by the Office of Naval Research (ONR) and as Co-Principal Investigator for two programs funded by the Office of the Secretary of Defense (OSD).
Funding Information:
The material in this article is based upon work supported by the Office of Naval Research under contract no. N00024-12-D-6402, Delivery Order No. 0037. The authors are grateful to Ms. Maria Medeiros for funding this effort and for the acquisition of the powder rheometer. Special thanks to Freeman Technologies and specifically John Yin for his insightful discussions and valuable input on data interpretation.
Publisher Copyright:
© 2015 Elsevier B.V..
PY - 2015/10/1
Y1 - 2015/10/1
N2 - The effect of surface treatment on the properties of fine aluminum powders was investigated using both chemical and rheological characterization techniques. Four different particle size distributions (PSD) were surface treated with methyltriethoxysilane and subsequently evaluated through classic density measurements and by using an FT4 powder rheometer (Freeman Technologies, UK). The chemical surface properties were analyzed using diffuse reflectance infrared spectroscopy (DRIFTs) and X-ray photoelectron spectroscopy (XPS) which confirmed retention of the silane and production of a siloxane-like layer on all PSD samples. The results of the bulk measurements, both direct and empirical, showed enhanced flowability and easier fluidization, indicating reduction of intrinsic cohesion for all samples. Fluidization testing showed decrease in total energy of the uniformly fluidized bed by ~. 80-90% in all cases. Shear stress values as a function of applied normal stress were collected to produce Mohr diagrams which generated extrapolated cohesion and unconfined yield strength values using the Mohr-Coulomb criteria. Cohesion and unconfined yield strength were reduced in all surface treated powders which indicated easier flowability and an increase in the flow function at 6. kPa. The compressibility of the treated powders at 8. kPa was decreased by >. 60% in all cases, indicating significant reduction in entrained air and improvement in packing density. Classical density measurements showed small improvements in the Hausner Ratio and little to no improvement in the Carr index, whereas directly measured properties using powder rheology showed substantial changes in the flow and fluidization properties. Overall, fluidization behavior and flowability properties were enhanced in all PSDs and showed the increased potential for the use of fine aluminum powders after surface treatment in delivery applications.
AB - The effect of surface treatment on the properties of fine aluminum powders was investigated using both chemical and rheological characterization techniques. Four different particle size distributions (PSD) were surface treated with methyltriethoxysilane and subsequently evaluated through classic density measurements and by using an FT4 powder rheometer (Freeman Technologies, UK). The chemical surface properties were analyzed using diffuse reflectance infrared spectroscopy (DRIFTs) and X-ray photoelectron spectroscopy (XPS) which confirmed retention of the silane and production of a siloxane-like layer on all PSD samples. The results of the bulk measurements, both direct and empirical, showed enhanced flowability and easier fluidization, indicating reduction of intrinsic cohesion for all samples. Fluidization testing showed decrease in total energy of the uniformly fluidized bed by ~. 80-90% in all cases. Shear stress values as a function of applied normal stress were collected to produce Mohr diagrams which generated extrapolated cohesion and unconfined yield strength values using the Mohr-Coulomb criteria. Cohesion and unconfined yield strength were reduced in all surface treated powders which indicated easier flowability and an increase in the flow function at 6. kPa. The compressibility of the treated powders at 8. kPa was decreased by >. 60% in all cases, indicating significant reduction in entrained air and improvement in packing density. Classical density measurements showed small improvements in the Hausner Ratio and little to no improvement in the Carr index, whereas directly measured properties using powder rheology showed substantial changes in the flow and fluidization properties. Overall, fluidization behavior and flowability properties were enhanced in all PSDs and showed the increased potential for the use of fine aluminum powders after surface treatment in delivery applications.
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U2 - 10.1016/j.powtec.2015.05.044
DO - 10.1016/j.powtec.2015.05.044
M3 - Article
AN - SCOPUS:84936073770
SN - 0032-5910
VL - 283
SP - 380
EP - 388
JO - Powder Technology
JF - Powder Technology
ER -