Transport Properties Of Nanocomposites Research Articles

Enhanced thermoelectric properties through minority carriers blocking in nanocomposites

We use the Boltzmann transport equation under the relaxation time approximation to investigate the effect of minority blocking on the transport properties of nanocomposites (NCs). Taking p-type Bi0.5Sb1.5Te3 NCs as an example, we find that the thermally excited minority carriers can be strongly scattered by engineered interfacial potential barriers. Such scattering phenomena suppress the bipolar effect, which is helpful to enhance the Seebeck coefficient and reduce the electronic thermal conductivity, especially at high temperatures. Further combining with the majority carriers low-energy filtering effect, the power factor and the figure of merit (ZT) can be significantly enhanced over a large temperature range from 300 K to 500 K. Such an improvement of ZT is attributed to the majority carriers low-energy filtering effect at low temperatures and to the minority carriers blocking effect at high temperatures. A principle that is helpful to provide guidance on the thermoelectric device design is identified: (1) blocking the minority carriers as often as possible and (2) filtering the majority carriers whose energy is lower than 2–3kBT near the cold end.

Chlorinated styrene butadiene rubber/ zinc sulfide: novel nanocomposites with unique properties- structural, flame retardant, transport and dielectric properties

Chlorinated styrene butadiene rubber (Cl-SBR)/ zinc sulfide (ZnS) nanocomposites were prepared by a simple two-roll mill mixing technique. The interaction between the ZnS nanoparticles and Cl-SBR was assessed using Fourier transform infrared (FTIR) and UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The dielectric constant, oil resistance, flame retardancy and the transport properties of nanocomposites with aromatic hydrocarbons were also analyzed with special attention to the loading of nanoparticles. The spectroscopic studies revealed the existence of a strong interfacial interaction between rubber chain and ZnS nanoparticles. TEM analysis showed the attachment of ZnS nanoparticles in the chlorinated SBR having nanosize region. SEM and XRD showed the uniform arrangement of nanoparticles in the elastomeric network. The presence of ZnS nanoparticles in the rubber matrix was confirmed through EDX spectroscopy. The thermal stability, flame retardancy and oil resistance properties of the nanocomposites were significantly enhanced by the addition of nanoparticles. Composite with 7 phr loading showed the maximum dielectric constant and beyond this loading, the dielectric property decreased due to the agglomeration of nanoparticles. Transport behavior of nanocomposites in benzene, toluene and xylene were analyzed in the temperature range of 27 to 70 °C. Swelling parameters such as rate constant, sorption, diffusion, and permeation coefficient were estimated. The mechanism of transport of the aromatic solvents in the filled Cl-SBR was found to be following anomalous mode. Temperature dependence of diffusion was used to study the activation parameters of the prepared samples.

Studies on the Mechanical, Electrical Properties and Interaction of Petroleum Fuels with SBR/ Manganous Tungstate Nanocomposites

A novel nanocomposite based on styrene butadiene rubber (SBR) and manganous tungstate (MnWO4) nanoparticles was prepared by a simple and inexpensive open two-roll mixing mill. The interaction of the nanoparticles with SBR matrix was studied by different characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and electrical properties. The effect of loading of MnWO4 nanoparticles on the processing characteristics of mixed rubber compounds, mechanical properties and the transport properties of nanocomposites through petroleum fuels were also analysed. XRD of nanocomposite revealed that the addition of nanoparticles imparts a semi-crystalline or regular arrangement of chains in the composite. SEM analysis showed good dispersion of nanoparticles in the polymer matrix. Also it has been observed that the dispersion of nanoparticles decreases with increase in its loading. TGA analysis indicated better thermal stability of all nanocomposite and thermal stability increases with the loading of the nanoparticles. The AC conductivity and dielectric properties were greatly enhanced in the whole range of frequencies studied. The processing properties of rubber compounds like cure and scorch time decreases with increase in concentration of MnWO4 nanoparticles and the maximum enhancement in torque was observed for 10 phr loading. The tensile strength, modulus, tear resistance, hardness and heat build-up of the composite increased whereas the resilience, compression set and elongation at break decreased with the loading of nanoparticles. Solvent penetration studies of nanocomposites were done in petroleum fuels at different temperatures.The solvent uptake was the minimum for composite with 10 phr of MnWO4 and penetration of solvent increased with further addition of nanoparticles.

Magnetic and electronic transport properties of nanocomposites of superconducting Mo carbides’ nanoparticles embedded in a ferromagnetic carbon matrix

The electronic transport and magnetic properties of nanocomposites, in which nanoparticles of superconducting (SC) molybdenum carbides are embedded in a ferromagnetic (FM) carbon matrix to form a three-dimensional SC-FM network, are studied. The high-resolution transmission electron microscope observation shows that the carbon in the nanocomposites is in both ordered and disordered forms. The magnetic properties of the nanocomposites are ruled by the ferromagnetic carbon matrix. The temperature dependence of electrical resistivity of the nanocomposites is dominated by the carbon matrix, showing the semi-conductivity. The special I-V curves near the zero voltage bias of the nanocomposites are observed at low temperatures, due to the influence of contact barriers between molybdenum carbides and the carbon matrix.