Understanding the dielectric properties and electromagnetic shielding efficiency of zirconia filled epoxy-MWCNT composites

In the present study, hybrid composites are prepared by reinforcing various concentrations of high permittivity zirconia nanofiller into epoxy/CNT compositions to test their usability in EMI shielding applications in the X and Ku bands. ZrO2 nanofiller is added in different proportions to improve absorbance shielding while maintaining the composite conductivity uniform by adding constant CNT concentration to restrict the reflectance shielding. The microscopic studies have revealed an efficient dispersion of ZrO2 nanoparticles in the CNT networks and provided a smoother surface. The presence of zirconia nanofillers increased the dielectric properties, viz. the dielectric constant (194 at 0.1 Hz) and loss tangent (1.57 at 0.1 Hz), respectively, whereas the conductivity was found to be invariantly constant. The increased permittivity of composites enhanced the shielding by absorption, while the shielding by reflection is least influenced by the addition of zirconia nanofiller. The addition of zirconia nanofillers increased the permittivity and tan delta, allowing charges to accumulate at the interfacial areas for incoming EM radiations, resulting in increased absorbance shielding. Limiting the CNT concentration in all composites to the same level resulted in the formation of conductive networks, thus resulting in uniform reflectance shielding for all the hybrid composites in the present study. The dynamic mechanical analysis showed the improvement in the storage modulus and activation energy due to the enhanced interfacial adhesion and cross-linked polymer density.

Half and full cell researches of ternary MoS2/graphene/CNT aerogel compostie for enhanced lithium storage performances

Without using any templates, a ternary MoS2/graphene/carbon nanotubes (MoS2/GN/CNT) aerogel compostie is prepared by convenient hydrothermal synthesis method. The free-standing MoS2/GN/CNT aerogel can be cut directly as binder free electrodes in lithium-ion batteries. The MoS2/GN/CNT electrodes can hold as high as 695 and 579 mAh g−1 discharge capacities after 200 cycles at 200 mA g−1 in MoS2/GN/CNT//Li half cells and MoS2/GN/CNT//LiCoO2 full-cells, respectively. The strengthened electrochemical properities are owed by the thin GN/CNT layers and their jagged and wrinkled surfaces, which can enhance the composite conductivity and shorten the Li+ diffusion distance, as well as buffer the volume change of electrodes druing the charge-discharge cycles.

Synthesize and characterization of conductive nano silver/graphene oxide composites

To meet the high-precision needs of conductive ink in the field of microelectronic circuit printing, nano silver-coated graphene oxide (GO) composites were prepared as the conductive functional unit of the composites. The results show that compatibility of the GO grafted with ethylene glycol diglycidyl ether is better in the organic matrix than in the inorganic solvents. The nano silver particles attached to the surface of the grafted GO are evenly distributed and uniform in size. Moreover, the conductivity of grafted GO coated with silver particle composites is effectively improved. The composite conductivity is higher than 108 S/m, which is close to the electrical conductivity of silver.

Effects of poly(ethylene glycol)-grafted graphene on the electrical properties of poly(lactic acid) nanocomposites

PEG-grafted GN has been synthesized and the effects of modification on the PLA composite conductivity, mechanical properties are investigated.

Optimization of thermal conductivity in composites loaded with the solid-solid phase-change materials

This work focuses on identifying the thermal conductivity of composites loaded with phase-change materials (PCMs). Three configurations are studied: (1) the PCMs are divided into identical spherical inclusions arranged in one plane, (2) the PCMs are inserted into the matrix as a plate on the level of the same plane of arrangement, and (3) the PCMs are divided into identical spherical inclusions arranged periodically in the whole matrix. The percentage PCM/matrix is fixed for all cases. A comparison among the various situations is made for the first time, thus providing a new idea on how to insert PCMs into composite matrices. The results show that the composite conductivity is the most important consideration in the first case, precisely when the arrangement plane is parallel with the flux and diagonal to the entry face. In the present work, we are interested in exploring the solid-solid PCMs. The PCM polyurethane and a wood matrix are particularly studied.

Acid Fracture Conductivity Behavior of Tahe Carbonate: High Closure Stress, Long-Term Conductivity, and Composite Conductivity

Acid fracture conductivity is a key parameter in acid fracturing designs and production performance prediction. It depends on the fracture surface etching pattern, rock mechanical properties, and closure stress. The fracture surfaces undergo creep deformation under closure stress during production. Preservation of fracture conductivity becomes a challenge at elevated closure stress. In this paper, we investigated acid fracture conductivity behavior of Tahe deep carbonate reservoir with high closure stress and high temperature. A series of acid fracture conductivity experiment was conducted in a laboratory facility designed to perform acid fracture conductivity. Gelled acid and cross linked acid with different acid-rock contact times were tested for analyzing the effect of acid type and acid-rock contact time on the resulting conductivity. Closure stress up to 100MPa was tested to verify the feasibility of acid fracturing for elevated closure stress. Long-term conductivity up to 7-day was tested to determine the capability of conductivity retaining after creep deformation. Composite conductivity of acid fracture with prop pant was also carried out. The study shows that the fracture retained enough conductivity even under effective closure stress of 70MPa. The gelled acid has a much higher conductivity than the cross linked acid for the same contact time. For the gelled acid, contact time above 60-minute does not lead to conductivity increase. Acid fracture with prop pant has a lower conductivity at low closure stress and a higher conductivity at high closure stress than the acid fracture, which shows composite conductivity is a feasible way to raise conductivity at high closure stress. The long-term conductivity tests show that the acid fracture conductivity decreases fast within the first 48-hour and then levels off. The conductivity keeps stable after 120-hour. An acid fracture conductivity correlation was also developed for this reservoir.

Electrical Conductivity of Nanodimensional Polyaniline Particles in Nanoporous Dielectric Matrix of MIL-101

We investigated an electrical conductivity of aniline polymerized inside nanopores of chromium terephthalate dielectric matrix MIL-101. We found that temperature dependences of conductivity (T) are described by the fluctuation-induced tunneling model, which means that the main contribution to a net conductivity is caused by contacts between particles of the polyaniline. We also found that the nanoporous matrix affects the composite conductivity via the size reduction of the conducting polyaniline phase encapsulated in the pores. Dependence of conductivity from a current was thoroughly investigated. This dependence is resulted from a reduction of energy gap for current carriers which is, in turn, induced by an increasing electric field applied.