Papers by Keyword: Conductive Composites

Abstract: Research in improving dielectric materials is rapidly becoming more intense as there are higher demands for novel materials with the ability to store charges. In this work, impedance characterisation and dielectric properties of epoxy composites containing Carbon Black (CB) and a mixture of CB and Carbon Nanotube (CNT), kept at 1:1 wt.% is conducted. For both cases, the total number of fillers are varied from 0.5 wt.% to 6 wt.%. At 20 Hz, the values of dielectric composites, k was recorded to be 2050 for 6 wt.% CB, compared to k = 600, for composites containing dual filler (3 wt.% CB + 3 wt.% CNT). Further analysis revealed that the 6 wt.% sample (CB + CNT) exhibited higher ac conductivity at lower frequency, compared to sample containing only 6 wt.% CB. This could be due to the reason that CNT has more conductivity effects while CB has more storage or capacitive effects. Nyquist plot of impedance for both fillers also revealed the formation of semi-circular shapes for 5 wt.% and 6 wt.%; for both CB and CB + CNT fillers. However, formation of smaller semi-circular shapes is observed for CB + CNT, compared to CB only, indicating formation of conductive network in dual filler composites. This study highlights the potential of CB in enhancing mainly the dielectric properties of epoxy composites.

Abstract: In this research, Silver—nickel alloy nanocomposites has been synthesized by reducing mixture solution of Ni²⁺, Ag⁺ with hydrazine hydrate as reducer and OP-10 as surfactant. Silver—nickel alloy nanocomposites were characterized by FT-IR, XRD, SEM. And the electrochemical properties of the samples were studied by cyclic voltammetry. Ag-Ni/PANI composites were prepared by in-situ synthesis and emulsion polymerization, and the effect of conduction on the conductivity was investigated including content of alloy. The detailed analysis of the synthesis conditions shows that the reduction takes place in alkaline environment and low-temperature is propitious to generate alloy solid-solution grain. Composites prepared by emulsion polymerization in acidic aqueous solutions synthesis of polyaniline shows higher conductivity than pure polymer, due to the strong interaction between alloy particles and doping PANI.

Abstract: Carbon black was activated and then filled into polypropylene to prepare conductive composites, of which the electrical properties, including impedance Z, phase angelθ and dissipation factor tgδ, as a function of frequency and carbon black concentration were investigated using impedance analyzer. The percolation threshold of 5wt% carbon black concentration was obtained. It was found that the variation of AC electrical properties as a function of frequency is dramatic and dependent on the carbon black concentration. It was also found that dependence of the real part and the imaginary part of impedance on frequency decreases with the increased concentration of carbon black, while that of phase angle and dissipation factor increases. Based on the corresponding results, the conductive network model and the corresponding equivalent circuit were constructed.

Abstract: In this paper, Carbon black was activated using titanate-type coupling agent, and then filled into polypropylene to prepare conductive composites, whose alternating current (AC) electrical properties, including impendence Z, phase angel θ, dielectric constantε and dissipation factor tgδ that is a function of frequency and carbon black concentration were investigated by AC impedance spectroscopy. The percolation threshold of 5wt% carbon black concentration was obtained from the experimental result of volume resistivity for the conductive composites. It was found that the variation of AC electrical properties, which is a function of frequency, was dramatic and dependent on the filler concentration. It was also found that dependence of the real and the imaginary parts of impendence on frequency decreased with the increased concentration of carbon black, while the phase angle, dielectric constant and dissipation factor increased. The AC electrical properties were given based on the conductive network model and the corresponding equivalent circuit were concluded

Abstract: The sensing technology based on sensitive conductive composites was used on the reinforced cushion in a coal mine silo foundation. The reinforced belt sensor made from sensitive conductive rubber’s composites was flexible and large deformation. It is the ideal test sensor for the low-modulus and large strain reinforce belt. The results show that the new type of sensor performance is stability and the test is good.

Abstract: A series of carbon nanotube (CNTs) and stainless steel fiber (SSFs) filled nylon 6 (PA6) conductive composites were synthesized for electromagnetic interference (EMI) shielding applications. The materials were prepared by the melt blending method with CNTs weight fraction of 1 and 3 wt% and SSFs of 2, 4, 6, 8, 10, and 12 wt%. The shielding effectiveness, electrical resistance and crystallization behaviors were measured. The results indicate that the shielding effectiveness and electrical properties can be improved by increasing either SSFs or CNTs contents. Higher content of CNTs can bring forward the percolation threshold and enhance the shielding effectiveness to 51.8 dB. Due to the nanoconfinement/multiple nucleation effects, PA6 crystallization behavior is influenced by adding the CNTs and SSFs.

Abstract: With water as solution, ferric chloride (FeCl₃∙6H₂O) as oxidant, sulfuric acid (SA) as dopant, prepared polypyrrole/montmorillonite (PPy/MMT) via chemical oxidation polymerization. We researched the effect that the content of the polypyrrole to the conductivity of composite in the condition of n (Py): n (FeCl₃∙6H₂O): n (SA) =1: 1: 0.5. Using IR, XRD, IR, TEM and SEM modern characterization methods to characterize internal structure of composites, the results show PPy were intercalated into the inner space of MMT. The surfaces of MMT intercalated are coated by conductive polypyrrole particles with equal size and uniform arrangement. MMT dispersed among conductive polypyrrole matrix and overlapped each other, which formed a conductive network. Using percolation theory, we analyzed the conductivity of composites that conform to the classical statistical percolation theory.

Abstract: The conductivity and mechanical properties of carbon black (CB) filled polyethylene (PE) composites depend on the conductive filler, molecular structure of polymer matrix, and the processing methods which are applied. CB filled high density polyethylene without and with glass fibre (GF) composites have been manufactured using single and twin screws extruder. The composite made from the single screw extruder showed a much higher conductivity than that made from twin screws extruder for CB/PE composites with and without glass fibre. The conductive paths are formed at very low CB content (1wt% CB for GF/CB/PE) when using single screw extruder to manufacture. The microstructure of these composites were analysed using SEM.