Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles
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University of Cincinnati / OhioLINK
2018
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523629055773887 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-ucin15236290557738872021-08-03T07:06:04Z Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles Mulderig, Andrew J. Materials Science Fractal Emergence Aggregate Screening Scattering Nanoparticle Many commercially and industrially important materials aggregate to form nanoscale mass-fractal structures. Ultra-small angle X-ray scattering is coupled to a hierarchical scattering model, the Unified scattering function, to obtain topological parameters, binary interaction strength and the thermodynamics of nanoparticle aggregation. The mass-fractal structures of fumed silica aggregates were determined using literature methods and the ramified structures are then compared with simple visualizations of fractal aggregates. Surprisingly, a single parameter, the sticking probability, can empirically account for complex topological differences in the materials studied. Samples of higher specific surface area display higher branch fraction and hyper-branched structures are observed for samples of highest specific surface area. Unlike hard aggregates such as fumed silica, pigment-based inks consist of weakly bound nanoparticles stabilized by a surfactant. Bound by relatively weak van der Waals forces, these soft aggregates can easily break apart and re-form. The emergence of structure under semi-dilute conditions is related to the structure of the dilute particles, the particle spacing (mesh size), processing history, and the interaction potential. The final properties of a pigment emerge from a complex interplay between nanoparticle aggregation and dispersion of aggregates as a function of concentration. Emergent properties may enable prediction of properties such as brilliance and opacity. Samples of pigment yellow 14 were milled to four primary particle sizes to study the effect of particle size on emergence. The interactions between surfactant-stabilized PY14 aggregates in an aqueous media were quantified by the second virial coefficient, A2, in the expansion of osmotic pressure. In such systems, A2 describes long-range binary interactions. A2 was then translated into a repulsive interaction potential for use in dissipative particle dynamics simulations to enable predictive modeling. Further experiments on non-milled samples of pigment yellow 14 and pigment blue 15:3 were employed to explore the thermodynamics of nanoparticle aggregation in these pigment-based inks across a range of temperatures. It was determined that nanoparticle aggregation can be described solely by the change in free energy of dissociation and the change in free energy of mixing in the context of a subunit being removed from a cluster. Change in free energy, change in enthalpy and change in entropy were compared for each temperature measurement and were found to be in good agreement. Therefore, a single set of small-angle scattering measurements may be used to determine the structure of hierarchical nano-fractal aggregates, the binary interactions of dispersed aggregates and the thermodynamics of nanoparticle aggregation in a wide variety of nano-fractal materials. 2018-06-07 English text University of Cincinnati / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523629055773887 http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523629055773887 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Materials Science Fractal Emergence Aggregate Screening Scattering Nanoparticle |
| spellingShingle |
Materials Science Fractal Emergence Aggregate Screening Scattering Nanoparticle Mulderig, Andrew J. Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles |
| author |
Mulderig, Andrew J. |
| author_facet |
Mulderig, Andrew J. |
| author_sort |
Mulderig, Andrew J. |
| title |
Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles |
| title_short |
Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles |
| title_full |
Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles |
| title_fullStr |
Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles |
| title_full_unstemmed |
Structure, Interactions and Aggregation Thermodynamics of Dispersed Mass-Fractal Nanoparticles |
| title_sort |
structure, interactions and aggregation thermodynamics of dispersed mass-fractal nanoparticles |
| publisher |
University of Cincinnati / OhioLINK |
| publishDate |
2018 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523629055773887 |
| work_keys_str_mv |
AT mulderigandrewj structureinteractionsandaggregationthermodynamicsofdispersedmassfractalnanoparticles |
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1719453798605258752 |