“…For instance, the calculated resistance at the interface between octane and single-layer graphene sheets (GS, which shows extremely high values of thermal conductivity, i.e., 3000–5000 Wm −1 k −1 [ 63 ]), has been reported to be 10 times smaller when the alkane chains are covalently bonded at the edges of these GSs [ 64 ]. Pal and Puri found higher rectification using a single-wall carbon nanotube (SWCNT) covalently bonded near one end to polyacetylene (PA) chains [ 65 ]. This composite structure shows rectification up to 204%, which is higher than the values reported for single wall carbon nanotubes (SWCNTs).…”
Section: Effect Of Thermal Properties Of Polymer Composites On Crystallization and Meltingmentioning
confidence: 99%
“…Indeed, a way to originate a material potentially owning rectification properties consists in the use of two or more homogeneous substances whose thermal conductivities show different temperature dependency. As a matter of fact, the opposite temperature dependence of thermal conductivity for polydimethylsiloxane (PDMS) and graphite powder has been considered to be responsible for thermal rectification of their composites [ 65 ].…”
Section: Effect Of Thermal Properties Of Polymer Composites On Crystallization and Meltingmentioning
confidence: 99%
“… a [ 1 , 45 , 46 , 47 , 48 , 49 , 50 , 57 ], b [ 67 , 71 ], c [ 81 , 83 , 92 ], d [ 93 ], e [ 66 , 93 , 94 ], f [ 60 , 61 , 62 , 63 , 64 , 65 ]. …”
Morphological analysis at different levels is fundamental to understand properties of materials, as these latter are dictated not only by the chemical composition but also by the shape. Solid structures arise from a balance between thermodynamic and kinetic factors, which, especially for polymer composites, depend also on interactions amongst components. In particular, morphology is strongly affected by the heat transfer pattern during crystallization and by the difference in thermal behavior between polymer matrix and filler. Polymers show a spherulitic structure, arising from the start of crystallization in several points of the liquid phase. Within a general rounded shape, spherulites show variability in growth patterns, morphology, and geometry of boundaries. The appearance and the number of spherulites, as well as their growth mechanism, may vary not only in dependence of the chemical composition and the crystalline structures but also, for a same polymer, in consequence of experimental conditions and incorporation of fillers. This article reviews the crystallization process of polymer matrices in the framework of crystal growth and heat transport theories, and explains microstructural differences between composites and neat matrices on the basis of the differences in thermal capacity and conductivity between polymers and additives.
“…For instance, the calculated resistance at the interface between octane and single-layer graphene sheets (GS, which shows extremely high values of thermal conductivity, i.e., 3000–5000 Wm −1 k −1 [ 63 ]), has been reported to be 10 times smaller when the alkane chains are covalently bonded at the edges of these GSs [ 64 ]. Pal and Puri found higher rectification using a single-wall carbon nanotube (SWCNT) covalently bonded near one end to polyacetylene (PA) chains [ 65 ]. This composite structure shows rectification up to 204%, which is higher than the values reported for single wall carbon nanotubes (SWCNTs).…”
Section: Effect Of Thermal Properties Of Polymer Composites On Crystallization and Meltingmentioning
confidence: 99%
“…Indeed, a way to originate a material potentially owning rectification properties consists in the use of two or more homogeneous substances whose thermal conductivities show different temperature dependency. As a matter of fact, the opposite temperature dependence of thermal conductivity for polydimethylsiloxane (PDMS) and graphite powder has been considered to be responsible for thermal rectification of their composites [ 65 ].…”
Section: Effect Of Thermal Properties Of Polymer Composites On Crystallization and Meltingmentioning
confidence: 99%
“… a [ 1 , 45 , 46 , 47 , 48 , 49 , 50 , 57 ], b [ 67 , 71 ], c [ 81 , 83 , 92 ], d [ 93 ], e [ 66 , 93 , 94 ], f [ 60 , 61 , 62 , 63 , 64 , 65 ]. …”
Morphological analysis at different levels is fundamental to understand properties of materials, as these latter are dictated not only by the chemical composition but also by the shape. Solid structures arise from a balance between thermodynamic and kinetic factors, which, especially for polymer composites, depend also on interactions amongst components. In particular, morphology is strongly affected by the heat transfer pattern during crystallization and by the difference in thermal behavior between polymer matrix and filler. Polymers show a spherulitic structure, arising from the start of crystallization in several points of the liquid phase. Within a general rounded shape, spherulites show variability in growth patterns, morphology, and geometry of boundaries. The appearance and the number of spherulites, as well as their growth mechanism, may vary not only in dependence of the chemical composition and the crystalline structures but also, for a same polymer, in consequence of experimental conditions and incorporation of fillers. This article reviews the crystallization process of polymer matrices in the framework of crystal growth and heat transport theories, and explains microstructural differences between composites and neat matrices on the basis of the differences in thermal capacity and conductivity between polymers and additives.
“…Moreover, graphene possesses outstanding mechanical performance, as the reported data of modulus and strength were 1 TPa and 130 GPa, respectively [10]. Thus, GNPs are an excellent choice for performance improvement and multi functionalities achievement of polymers in practical applications [11][12][13]. Usually, the thickness of GNPs ranges from several to dozens of nanometres with the lateral dimension at the micron scale, leading to a high specific surface area (theoretical value is 2630-2965 m 2 /g) and aspect ratio [14].…”
Graphite nanoparticles (GNPs) were introduced into poly(p-phenylene benzobisoxazole) (PBO) matrix to produce composites via in situ polymerisation. Films of various composites were fabricated through the solution casting method in methanesulfonic acid (MSA) with the help of two sand core plates. The interlayer spacing of GNPs increased slightly confirmed by XRD as a result of an expanding effect caused by continuously formed PBO chains between the graphene nanosheets of GNPs during polymerisation. Also, due to the uniform dispersion of GNPs into PBO matrix, composite films exhibited an improved tensile strength (258 MPa, 72% higher than that of pure PBO) with 5 wt% loading of GNPs fillers. The initial decomposition temperature of the composite is ∼630°C. Besides, benefitting from the interfacial polarisation in this conductive filler/polymer system, the dielectric constant of the composites with 10 wt% loading of GNPs reached 6.96, which were over two times higher than that of pristine PBO polymer (2.91).
Carbon nanomaterials have extraordinary thermal properties, such as high conductivity and stability. Nanocarbon combined with phase change materials (PCMs) can yield exceptionally high thermal effusivity composites optimal for thermal energy harvesting. The progress in synthesis and processing of high effusivity materials, and their application in resonant energy harvesting from temperature variations is reviewed.
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