TY  - JOUR
A1  - McCarthy, Denis N.
A1  - Stoyanov, Hristiyan
A1  - Rychkov, Dmitry
A1  - Ragusch, Huelya
A1  - Melzer, Michael
A1  - Kofod, Guggi
T1  - Increased permittivity nanocomposite dielectrics by controlled interfacial interactions
JF  - Composites science and technology
N2  - The use of nanoparticles in polymer composite dielectrics has promised great improvements, but useful results have been elusive. Here, the importance of the interfacial interactions between the nanoparticles and the polymer matrix are investigated in TiO2 nanocomposites for dielectric materials using surface functionalisation. The interface is observed to dominate the nanocomposite properties and leads to a threefold increase in permittivity at volume fractions as low as 10%. Surface functionalisation of the filler nanoparticles with silanes allows control of this interface, avoiding significant degradation of the other important material properties, particularly electrical breakdown strength, and resulting in a material that is demonstrated successfully as an active material in a dielectric elastomer actuator application with increased work output compared to the pure polymer. Although further permittivity increases are observed when the interface regions have formed a percolation network, the other material properties deteriorate. The observation of percolation behaviour allows the interface thickness to be estimated.
KW  - Ceramics
KW  - Nanocomposites
KW  - Actuator
KW  - Interface
KW  - Electrical properties
Y1  - 2012
U6  - https://doi.org/10.1016/j.compscitech.2012.01.026
SN  - 0266-3538
VL  - 72
IS  - 6
SP  - 731
EP  - 736
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Bruno, Giovanni
A1  - Kachanov, Mark
A1  - Sevostianov, Igor
A1  - Shyam, Amit
T1  - Micromechanical modeling of non-linear stress-strain behavior of polycrystalline microcracked materials under tension
JF  - Acta materialia
N2  - The stress-strain behavior of microcracked polycrystalline materials (such as ceramics or rocks) under conditions of tensile, displacement-controlled, loading is discussed. Micromechanical explanation and modeling of the basic features, such as non-linearity and hysteresis in stress-strain curves, is developed, with stable microcrack propagation and "roughness" of intergranular cracks playing critical roles. Experiments involving complex loading histories were done on large- and medium grain size beta-eucryptite ceramic. The model is shown to reproduce the basic features of the observed stress-strain curves. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
KW  - Nonlinearity
KW  - Stress-strain relations
KW  - Hysteresis
KW  - Tension
KW  - Ceramics
KW  - Rocks
KW  - Polycrystals
Y1  - 2018
U6  - https://doi.org/10.1016/j.actamat.2018.10.024
SN  - 1359-6454
SN  - 1873-2453
VL  - 164
SP  - 50
EP  - 59
PB  - Elsevier
CY  - Oxford
ER  -