Changes in Electrical Conductance of Polymer Composites Melts Due to Carbon Nanofiller Particles Migration

Detonation Nanodiamond Soot-A Structurally Tailorable Hybrid Graphite/Nanodiamond Carbon-Based Material

The results of a comprehensive investigation into the structure and properties of nanodiamond soot (NDS), obtained from the detonation of various explosive precursors (trinitrotoluene, a trinitrotoluene/hexogen mixture, and tetryl), are presented. The colloidal behavior of the NDS particles in different liquid media was studied. The results of the scanning electron microscopy, dynamic light scattering, zeta potential measurements, and laser diffraction analysis suggested a similarity in the morphology of the NDS particle aggregates and agglomerates. The phase composition of the NDS nanoparticles was studied using X-ray diffraction, Raman spectroscopy, electron diffraction, transmission electron microscopy, atomic force microscopy, and scanning tunneling microscopy. The NDS particles were found to comprise both diamond and graphite phases. The ratio of diamond to graphite phase content varied depending on the NDS explosive precursor, while the graphite phase content had a significant impact on the electrical conductivity of NDS. The study of the mechanical and tribological characteristics of polymer nanocomposites, modified with the selected NDS particles, indicated that NDS of various types can serve as a viable set of model nanofillers.

Detonation Synthesis Nanodiamond Soot as a Promising Filler for Polymer Composites

In this work, the results of a complex investigation of structure and properties of nanodiamond soot (NDS) of detonation synthesis are presented. Size distribution of NDS particles, dispersed in different liquid media, was investigated using dynamic light scattering and laser diffraction analysis methods. The results of the investigation, as well as the results of zeta-potential measurements, allowed us to characterize the agglomeration process of the NDS particles as independent of the medium, making NDS a good model filler for research of composite-modified nanosized particles. Additional data obtained using scanning electron microscopy, scanning tunneling microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy, demonstrated that in NDS the spherical nanodiamond (ND) particles with diameter ~5 nm are densely packed into strong-coupled aggregates with diameter ~300 nm, surrounded by graphite nanoribbons. X-ray diffraction analysis estimated the volume fraction of NDs in NDS as ~45 vol.%, simultaneously showing that the graphite is not defective, which was confirmed with the electron diffraction method. It was demonstrated that this structure of NDS allows to efficiently use NDS as a filler for polymer composites to increase polymer characteristics such as electrical conductivity or tribological characteristics, similarly to conventionally applied fillers such as carbon black.

Synthesis and microwave absorption studies on 2D graphitic carbon nitride loaded polyaniline/polyvinyl alcohol nanocomposites

A light weight electromagnetic interference (EMI) shielding and microwave absorbing composite films has been developed by loading varying weight content of graphitic carbon nitride (g-C3N4) nanosheets and polyaniline (PANI) into polyvinyl alcohol (PVA) matrix. The prepared PVA/PANI/g-C3N4 (1%, 3%, 5%) composites has been subjected to FTIR, X-Ray powder diffraction, SEM, Thermal studies, Dielectric studies and electromagnetic shielding effectiveness (EMI SE) analysis. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites was discovered to have improved electrical conductivity, dielectric loss, and dielectric constant. It is observed from the SEM images that the sheet layers of g-C3N4 are wrapped by the polymer matrix and the morphology to PVA/PANI composite in the g-C3N4 indicates homogeneous blending of PVA/PANI without any phase separation and has porous in it. The PANI/g-C3N4 fractured surfaces present are smooth but irregular in appearance indicating good compatibility between the PVA and PANI matrices. The dielectric properties was found to increase on increasing the concentration of the g-C3N4 nanofiller and reached a maximum of 9.8 × 106 at 1 MHz for 3% g-C3N4 in PVA/PANI. The incorporation of g-C3N4 into PVA/PANI enhanced the conductivity and the 5% g-C3N4 loaded composite film exhibited a conductivity value of 0.043 S/cm at 1 MHz. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites exhibited potential EMI SE values ranging from 24 to 35 dB at 8.6 GHz and from 42 to 63 dB at 12.4 GHz, for instance the PVA/PANI/g-C3N4 5% composite showed highest value of 63 dB at 12.4 GHz. The PVA/PANI/g-C3N4 5% exhibits the maximum highest reflection loss 8 GHz–12 GHz in which the higher absorption of −36 dB is observed at 10.3 GHz of the X-band region.

Effects of Mechanical Stress on Insulation Structure and Performance of HV Cable

Mechanical stresses generated during manufacturing and laying process of high voltage cables can result in degradation of insulation properties, affecting the stable operation of the transmission system. Traditional test methods for testing the effect of mechanical stress on the insulation properties of polyethylene still have some shortcomings to be explored and it is able to explain the changes of the insulation properties of polyethylene under mechanical stress from a microscopic perspective. In order to further study the effect of stress on the insulation properties of polyethylene, microstructural changes, the breakdown field strength, conductivity and charge distribution of polyethylene at different elongation rates are investigated by a combination of experimental and molecular dynamics simulations. The results show that the increase in stress leads to a decrease in crystallinity and microcrystalline size of the material decrease. The untwisting and orientation of the polyethylene molecular chains during the stretching process can create cavities, resulting in an uneven sample distribution and thickness reduction, leading to a reduction in the breakdown field strength. Meanwhile, some crystal regions are transformed into amorphous regions. The loose amorphous regions facilitate the directional migration of carriers, resulting in the increase of conductivity. When the elongation ratio is smaller, the distance between the molecular chains increases and the trap depth of the specimen becomes shallower. This facilitates the migration of ions and electrons and increases the rate of decay of the surface potential. When the stretch is further increased, new traps are created by broken molecular chains to limit the movement of charges, decreasing the decay rate of the surface potential and reducing the insulation properties of the polyethylene. Meanwhile, the molecular dynamics model of semi-crystalline polyethylene was developed to observe the microstructure and energy changes during the stretching process. The conclusions in terms of tensile tests were verified from a microscopic perspective.