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in the silicate interlayer, reduction in permeability of volatile decomposition products, and prevention of degradation from occurring
through cross-linking points between polymer chains and the filler
nanoclays. In polyurethane/nanoclay nanocomposites, the degradation temperature was increased throughout the nanocomposite
due to reduced oxygen and volatile product diffusion as a result of
the dispersed layered clays, which are impermeable to the diffusing
species. A similar effect has been seen in polypropylene/nanoclay
nanocomposites, in which the temperature of maximum weight
loss increased significantly due to the thermal robustness of the
clay platelets. Finally, polymer-matrix nanocomposites filled with
layered silicates are also known to improve flammability properties.
The reason for this behavior seems to arise from the formation of
char layers obtained through the collapse of the exfoliated and/or
intercalated structures. It turns out that the layered silicate structure can act as an excellent insulator and mass transport barrier.
For example, a nanoclay/nylon-6 nanocomposite with a small wt%
of filler shows a 60% reduction in peak heat release rate compared
with a pristine polymer.
Let’s now turn the discussion to metal-matrix nanocomposites.
These materials are composed of a metal or alloy matrix that is
ductile and a rigid reinforcement that is typically a ceramic. Therefore, metal-matrix nanocomposites combine the properties associated with metals, such as ductility and toughness, with ceramic
features such as high modulus and strength. In addition, because of
the outstanding properties of nanomaterials, the optical, electrical,
and magnetic properties of metal-matrix nanocomposites can also
be tuned.
Through various processing routes, several nanocomposites have
been produced, namely, aluminum, titanium, copper, and nickel
matrix materials, reinforced with borides, carbides, nitrides, and
oxides. As in the case of polymer-matrix nanocomposites, the
factors that affect their performance are the size of the filler and the
homogeneity of the reinforcement distribution. For example, in situ
fabrication (a process by which the reinforcements are produced by
exothermal reactions between chemical species or between chemical
species and compounds) of Al, Al/Si, and Al/Fe/V/Si metal-matrix
nanocomposites reinforced with nanoparticles of TiC has produced
a uniform dispersion of the reinforcing phase. As a result, these
materials exhibit very good strength within a wide range of temperatures. As expected, the smaller the TiC nanoparticles added and
the larger their volume fraction, the greater the strength achieved in
these nanocomposites.
Special Cases
in the silicate interlayer, reduction in permeability of volatile decomposition products, and prevention of degradation from occurring
through cross-linking points between polymer chains and the filler
nanoclays. In polyurethane/nanoclay nanocomposites, the degradation temperature was increased throughout the nanocomposite
due to reduced oxygen and volatile product diffusion as a result of
the dispersed layered clays, which are impermeable to the diffusing
species. A similar effect has been seen in polypropylene/nanoclay
nanocomposites, in which the temperature of maximum weight
loss increased significantly due to the thermal robustness of the
clay platelets. Finally, polymer-matrix nanocomposites filled with
layered silicates are also known to improve flammability properties.
The reason for this behavior seems to arise from the formation of
char layers obtained through the collapse of the exfoliated and/or
intercalated structures. It turns out that the layered silicate structure can act as an excellent insulator and mass transport barrier.
For example, a nanoclay/nylon-6 nanocomposite with a small wt%
of filler shows a 60% reduction in peak heat release rate compared
with a pristine polymer.
Let’s now turn the discussion to metal-matrix nanocomposites.
These materials are composed of a metal or alloy matrix that is
ductile and a rigid reinforcement that is typically a ceramic. Therefore, metal-matrix nanocomposites combine the properties associated with metals, such as ductility and toughness, with ceramic
features such as high modulus and strength. In addition, because of
the outstanding properties of nanomaterials, the optical, electrical,
and magnetic properties of metal-matrix nanocomposites can also
be tuned.
Through various processing routes, several nanocomposites have
been produced, namely, aluminum, titanium, copper, and nickel
matrix materials, reinforced with borides, carbides, nitrides, and
oxides. As in the case of polymer-matrix nanocomposites, the
factors that affect their performance are the size of the filler and the
homogeneity of the reinforcement distribution. For example, in situ
fabrication (a process by which the reinforcements are produced by
exothermal reactions between chemical species or between chemical
species and compounds) of Al, Al/Si, and Al/Fe/V/Si metal-matrix
nanocomposites reinforced with nanoparticles of TiC has produced
a uniform dispersion of the reinforcing phase. As a result, these
materials exhibit very good strength within a wide range of temperatures. As expected, the smaller the TiC nanoparticles added and
the larger their volume fraction, the greater the strength achieved in
these nanocomposites.
Special Cases