Papers by Keyword: Conductivity

Abstract: In this paper, we developed a three-dimensional percolation model to investigate the effects of the concentration and morphology of CNTs (carbon nanotubes) on the electrical conductivity of the nanocomposites. In the model, we judged the connections between CNTs by range search algorithm based on KD-Tree structure. At the same time, DIJKSTRA-Melissa algorithm was applied to efficiently find all the conductive paths instead of finding conductive network in traditional methods. From the simulation results, CNTs with higher aspect ratio were easier to form the conductive network. In a certain range of CNT’s concentration, the relationship between the conductivity of the conductive network and the carbon nanotubes was basically consistent with the classical percolation theory. To verify our simulation model, the morphological, electrical properties of Carbon nanotubes (CNTs)/poly(dimethyl siloxane) (PDMS) nanocomposites with different aspect ratio (AR) of MWNTs were systematically studied. In conclusion, these unique advantageous properties could be exploited to suggest potential applications of artificial electronic skin.

Abstract: In this work, the film contained a mixture of PMMA, salt, and plasticizers are studied. PMMA as a host polymer, ammonium trifluoromethane sulphonate or ammonium triflate (NH₄CF₃SO₃) as a doping salt and ethylene carbonate (EC) as a plasticizer is used in this present study. PMMA salt complexes system and plasticized PMMA salt complexes system are prepared by solution cast technique at room temperature. FTIR is used to study the interaction between polymer and salt, and between polymer–salt and plasticizer. The carbonyl group C=O asymmetric stretching mode observed at 1721 cm^-1 is broadened and shifted to lower wavenumber when ammonium triflate was added into PMMA. The broadening, shifting and reduction in wavenumbers of FTIR spectra show that the complexation has occurred between the polymer and salt. EIS is performed to measure the electrical conductivity of the polymer–salt system prepared at ambient temperature. The electrical conductivity of film containing 1.0 g of PMMA–35 wt% NH₄CF₃SO₃–16 wt% EC exhibit the highest electrical conductivity with the value of 2.461 x 10^-4 S/cm². XRD is carried out to study the pattern of pure PMMA, PMMA–NH₄CF₃SO₃ and PMMA–NH₄CF₃SO₃–EC. The XRD analysis shows the addition of plasticizer to the polymer–salt system increase the amorphousness of the polymer electrolytes hence increases in conductivity.

Abstract: Composite La_0.88Bi_0.12Mn₀.₈₀Ni_0.20O₃ was synthesized using the conventional solid-state reaction method with sintering temperature of 1200 °C for 12 hours and the dielectric properties investigated. The X-ray diffraction result shows that the composite has a rhombohedral structure with lattice parameter of a = b = c = 5.5136 Ǻ. Scanning electron microscope shows grains with approximately from 0.8 to 5.4 μm in size with presence of voids. The dielectric permittivity, εʹ and dielectric loss, εʺ were measured in the range of 298 K to 473 K where both are temperature and frequency dependent. At 1 kHz to 100 kHz, the εʹ is around 10000 and the dielectric loss tangent, tan δ is below 1.5. The electric behavior of this composite is best represented by Quasi-dc model which consists of two universal capacitors in parallel. Parameters value from the fitting indicated that high correlations of electrons between inter and intra-clusters. The activation energy, E_a calculated from the conductivity of the sample gives a value of 0.116 eV. Vibrating sample magnetometer shows that the La_0.88Bi_0.12Mn₀.₈₀Ni_0.20O₃ has a magnetic coercivity, H_c of 36.109 G and retentivity, B_r, valued 2.7504 x 10^-3 emu/g.

Abstract: Candlenut Shells is one of the many commodities growing in Indonesia and experiencing rapid progress production development. The shell of candlenut has good characteristic that allow it to be used as carbon. activated carbon is one of material that can be applied for various application. In this paper, we reported the synthesis of activated carbon from candlenut shell in order to get high quality of carbon by controlling the heating temperature in synthesis. Variation of heating temperature in to produce carbon were 300, 400, 500, 600 and 700 °C . FTIR Spectroscopy was carried out to determine the functional groups on the carbon from candlenut shells. FTIR analysis during the carbonization process was indicated the change in functional group of chemical structure from the candlenut shell, which is shown by decreasing the absorption spectrum of some functional groups of the candlenut shell after the carbonization process. The carbonization process has formed aromatic C = C and reduction functional group OH (aromatic compounds), C-H (aromatic ring), C-O (vibration ether structure) dan C=O (Ester compounds). And results of carbonization of candlenut shells at various temperatures have an electrical conductivity value that increases with increasing carbonization temperature. The carbonization temperature that is raised to 700 °C causes carbon to be more conductive with an increased electrical conductivity value. XRF characterization results also showed that in addition to carbon elements in the cundlenut shells, other elements were also found such as calcium, magnesium, aluminum, potassium, strontium, manganese, iron and zinc. Ca and Mg are the largest content besides carbon.

Abstract: The synthesis of LiFeSi_0.03P_0.97O₄/C (LFSP/C) composites have been done by solid state method. This study investigates the effects of carbon coating on the structure, microstructure and electrical conductivity of LFSP/C cathode materials. The carbon coating on Lithium Ferro Phosphate (LFP) plays a crucial role in determining its electrical conductivity. The variation of carbon content is 0wt.%; 6wt.%; 7wt.%; 8wt.% (LFP-0%, LFP-6%, LFP-7% and LFP-8%). The characterization was performed using X-Ray Diffraction (XRD), Scanning Electron Microscopy - Energy Dispersive X-ray (SEM-EDX), HighResolution-Transmission Electron Microscopy (HR-TEM) and LCR Meter tests. The XRD result have shown single-phase olivine (LiFePO₄) in all samples. The analysis microstructure using SEM have shown increasing carbon content can reduce agglomeration. The particles size of LFSP is 845.570 nm, and after coating carbon the particles size decreased up to 457.191 nm. The EDX results showed that the amount of atomic percentage for carbon tends to increase as the amount of carbon content increased. HR-TEM images indicates that the formation of carbon layer have formed, but not perfectly coat the LFP particle. The average carbon layer size is 78,31 nm with the size of LFSP particle is 352.82 nm. The LCR Meter result showed that LFP-7% had the largest electronic conductivity (2,275x10^-7 S/cm). The carbon coating led to significant enhancement in electronic conductivity from ~10^-9-10^-10 S/cm to ~10^-7 S/cm.

Abstract: The performance of adding 0–3 wt% B₂O₃-CuO as a sintering aid to lower the sintering temperature of La_0.5Sr_0.5Co_0.96Ni_0.04O_3-δ (LSCN) was investigated through solid-state reaction method. Results of linear shrinkage curve, bulk density, and microstructure indicated that BCu addition could promote the sintering process and enhance the densification of LSCN ceramics. With the increase of BCu content, low absolute value of TCR could be achieved, while the conductivity was deteriorated obviously. For LSCN ceramics sintered at 950 °C, the bulk density, conductivity, and TCR were worse than those sintered at higher temperatures. Consequently, the BCu-doped LSCN ceramics might not suitable for the application in the field of LTCC.

Abstract: The effect of different additives Ni, Fe, Cu on the structure and properties of electrolyte system 78% Na₃AlF₆- -9.5%AlF₃-5.0%CaF₂-7.5%Al₂O₃ at 1200K and 1.01Mpa was studied by molecular dynamics method. The radial distribution function, coordination number, diffusion coefficient, conductivity, and viscosity of the system were discussed in detail. The results demonstrated that the order of the self-diffusion coefficient of ions in the electrolyte system is: Na⁺ > F^- > O^2- > Ca²⁺ >Al³⁺. The addition of Ni and Fe connected the free aluminum composite ion groups in the system through fluorine bridges, which enhanced the interaction between Al³⁺ and Al³⁺. The addition of Cu weakened the interaction between Al^{3 +} and Al³⁺ and the F^-. The interaction between Al³⁺ and Na⁺, [AlF₇]^4- ionic groups might appeared in the melt system. After adding NiO, Fe₂O₃, and Cu, the electrical conductivity of the system increased, and the viscosity decreased. The research work revealed the influence of Ni, Fe, Cu on the ion existence form, mobility, inter-ion interaction and diffusion mechanism of cryolite molten salt system, which has important guiding significance for aluminum electrolysis production.

Abstract: Ionic devices consisted of ion-conductive ceramics such as solid oxide fuel cells (SOFC) and oxygen separation membranes have been developed in the last decades. La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF), which is a mixed ionic-electronic conductive ceramics, is especially expected to play an important role in those ionic devices and so its electrochemical properties have been intensively studied.

Abstract: Copper Ferro Alloys (CFAs) have an excellent shielding effect in the electromagnetic field, as well as the similar good conductivity and ductility with copper, and strong magnetism and toughness as analogous to iron. Consequently, it is considered to be novel structural and functional materials with huge development potential and wide application foreground. The influence of the content, size and distribution of Fe phase in the Cu matrix on the electromagnetic shielding property of CFAs is crucial. In the present study, CFAs with various Fe content were fabricated via powder metallurgy (P/M) combining with deformation processing. The microstructure, electrical conductivity, magnetic and mechanical properties of CFAs were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), and tensile test. The results indicated that P/M CFAs with the homogenous and fine in-situ Fe particles showed better comprehensive performance compared to those prepared by conventional casting. Based on the microstructure observation, mechanical properties were discussed.

Abstract: β-AgI thin films with thicknesses of 0.09–8.9 µm were prepared on polyethylene terephthalate (PET) substrate. Dependence of ionic conductivity on the thickness of the β-AgI thin film was measured via impedance spectroscopy in the temperature range of 300–330 K. It has been confirmed that the ionic conductivity of the b-AgI thin film is several hundred times higher than the b-AgI bulk. The enhancement of ionic conductivity is considered to be due to the formation of a high ion-conducting region near the hetero-interface region of b-AgI and PET. Furthermore, it has been suggested that the activation energy and carrier density may change depending on the distance from the interface, and the thickness dependence of enhancement in ionic conductivity may be related to the film thickness dependence of crystal orientation and structural disorder of β-AgI thin films.