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449 results on '"Moldenaers, P."'

157. Percolation-based Nanodielectrics of Conductive and Core-shell Nanoparticles for High-voltage Structural Carbon Fibre Composite Capacitors.

Author

Windey, Ruben, Molina-Lopez, Francisco, Tavernier, Filip, Steyaert, Michiel, Moldenaers, Paula, and Wevers, Martine

Abstract

Electrical storage technologies for high-density energy and power are crucial for the elaboration of electric vehicles with increased driving ranges. Not only improved charging while being connected to the electricity grid is demanded to facilitate a higher driving range, but also technologies for energy harvesting during driving offer great potential. Re-using braking energy during re-acceleration of the vehicle is currently one of these promising harvesting technologies being investigated. Because of the high-power currents generated during a braking event, the recovered energy can only be efficiently stored by a capacitor compared to traditional Li-ion batteries. However, the limited energy density of currently used capacitors prevent them from being a large-scale alternative to electrochemical batteries. This research is addressing this shortcoming and aims to establish fast, light and reliable capacitive energy storage while improving the energy density by boosting the maximal allowable voltage on top of an optimized capacitance. Multifunctional composite materials offer a unique integration method, which allows to embed the functional capacitor materials into structural fibre-reinforced polymers. In this concept, the composite material is not only the structural component, but also the storage capacitor, avoiding adding extra weight. Potential materials to be addressed are carbon fibres as structural electrode material and ceramic nanoparticles embedded in a polymer as solid dielectric in order to create a percolation network. The absence of any electrolyte allows significantly higher voltages to be applied, which can be fully exploited by the current trend in automotive of storing electrical energy at 100s of volts. Structural composite capacitors have been produced by optimized ultrasonication, solution casting and warm pressing of the dielectric polymer/nanoparticles film in between carbon weaves as illustrated in Figure 1a. Next to the commonly used conductive nanoparticles as percolative network, novel core-shell nanoparticles have been manufactured to introduce an insulating shell, as shown by figure 1b. The shell significantly reduces dielectric self-discharge currents while improved dielectric breakdown strength is expected. The electrical performance has been assessed by broadband dielectric spectroscopy at quasi-DC frequencies. As a result of the boost in dielectric constant also the energy density of percolation-based structural composite capacitors was increased significantly. [ABSTRACT FROM AUTHOR]

Published
2022

161. Mixing of immiscible liquids

Author

Janssen, J.M.H., Peters, G.W.M., Meijer, H.E.H., Baaijens, F.P.T., Moldenaers, P., Keunings, R., Processing and Performance, and Soft Tissue Biomech. & Tissue Eng.

Subjects
ComputingMilieux_LEGALASPECTSOFCOMPUTING
Published
1992

164. Viscoelasticity in dispersions of adhesive hard spheres

Author

Woutersen, A.T.J.M., Mellema, J., Blom, C., de Kruif, C.G., Moldenaers, P., Keunings, R., and Physics of Complex Fluids

Subjects
Materials science, Adhesive, Hard spheres, Composite material, Viscoelasticity
Published
1992

176. Origin of nonlinearities in the Bagley plots of thermotropic copolyesters

Author

Moldenaers, P., Vermant, J., Mewis, J., Heynderickx, I.E.J., Moldenaers, P., Vermant, J., Mewis, J., and Heynderickx, I.E.J.

Abstract

The origin of the nonlinearity observed in Bagley plots of thermotropic copolyesters has been investigated experimentally. With the aid of a two-piston slit rheometer the dependence of the viscosity on the hydrostatic pressure has been determined directly. This dependence only accounts for part of the nonlinearity of the Bagley plots. Using slit dies with either a convergent or a divergent entrance, concave as well as convex pressure profiles are obtained. This can only be explained by a change in the molecular orientation induced by the flow in the entrance zone. The presence of wall effects has been evaluated by measuring the pressure profiles in slits of different heights; it does not explain the nonlinearity of the Bagley plots. The origin of the nonlinearity of Bagley plots must be due to both pressure and molecular reorientation effects. The nature and importance of these reorientation effects are shown to depend on the entrance geometry. © 1996 Society of Rheology.

Published
1996

178. Effect of Compression on the Molecular Arrangement of Itraconazole–Soluplus Solid Dispersions: Induction of Liquid Crystals or Exacerbation of Phase Separation?

Author

Singh, Abhishek, Bharati, Avanish, Frederiks, Pauline, Verkinderen, Olivier, Goderis, Bart, Cardinaels, Ruth, Moldenaers, Paula, Van Humbeeck, Jan, and Van den Mooter, Guy

Abstract

Predensification and compression are unit operations imperative to the manufacture of tablets and capsules. Such stress-inducing steps can cause destabilization of solid dispersions which can alter their molecular arrangement and ultimately affect dissolution rate and bioavailability. In this study, itraconazole–Soluplus solid dispersions with 50% (w/w) drug loading prepared by hot-melt extrusion (HME) were investigated. Compression was performed at both pharmaceutically relevant and extreme compression pressures and dwell times. The starting materials, powder, and compressed solid dispersions were analyzed using modulated differential scanning calorimetry (MDSC), X-ray diffraction (XRD), small- and wide-angle X-ray scattering (SWAXS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and broadband dielectric spectroscopy (BDS). MDSC analysis revealed that compression promotes phase separation of solid dispersions as indicated by an increase in glass transition width, occurrence of a peak in the nonreversing heat flow signal, and an increase in the net heat of fusion indicating crystallinity in the systems. SWAXS analysis ruled out the presence of mesophases. BDS measurements elucidated an increase in the Soluplus-rich regions of the solid dispersion upon compression. FTIR indicated changes in the spatiotemporal architecture of the solid dispersions mediated via disruption in hydrogen bonding and ultimately altered dynamics. These changes can have significant consequences on the final stability and performance of the solid dispersions.

Published
2016
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