جستجوی مقالات مرتبط با کلیدواژه « Electrical conductivity » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Evaluating the characteristics of carbonate reservoirs, given their significant heterogeneity, is always accompanied by challenges and high uncertainties. Water saturation is a crucial parameter in assessing these reservoirs, and the Archie equation is commonly used for water saturation estimation. Moreover, the effect of water saturation on the mechanical behavior of rock is recognized as an important phenomenon in geotechnical engineering. The accuracy of water saturation calculated through the Archie equation depends on the precision of its parameters, including cementation exponent, saturation exponent, and tortuosity exponent. The heterogeneity of carbonate reservoirs significantly affects the Archie equation coefficients and, consequently, water saturation calculations. In this study, various methods, including the electrical efficiency, current zone indicator, and Winland method, were employed to manage reservoir heterogeneity. Subsequently, Archie parameters were calculated for each category, and water saturation was determined and compared with Dean-Stark water saturation. Furthermore, the influential parameters on the accuracy of water saturation were discussed and examined. To achieve the study objectives, 157 Dean-Stark water saturation data, 57 core plug samples for formation resistivity factor (FRF) determination, 20 core plug samples for measuring formation resistivity index (FRI), 1114 porosity and permeability measurements from core plug samples and 1368 thin sections were utilized from an exploration well in the western Gulf of Persian. Our findings highlight the significance of exploring electrical behavior characteristics and pore throat radii as crucial elements influencing the precision of water saturation calculations. As per the results, employing constant Archie parameters leads to an overestimation of water saturation and, consequently, an underestimation of hydrocarbon reserves. Our analysis illustrates that effectively managing reservoir heterogeneity through the electrical efficiency method significantly improves the accuracy of predicted water saturation compared to other approaches. Conversely, the Winland method exhibits the highest uncertainty in predicting water saturation.

By varying the level of graphene's surface oxidation in this paper, the thickness of the interphase region was altered, and its influence on the conductivity was investigated. Due to the similarity of water-based epoxy chemical groups with graphene oxide oxygen groups, the interphase region was reinforced. Infrared spectroscopy and thermal gravimetry were performed to evaluate the graphene oxide synthesis, and Raman spectroscopy was also performed to investigate the structural defects on graphene sheets. At first glance, based on the interphase region theory, it is expected that by increasing the oxidation rate of graphene nanosheets, the electrical conductivity of polymeric coatings will increase, and the percolation threshold will decrease. On the other hand, due to increased oxidation, the structural defect on graphene nanosheets increases, and the conductivity of the coatings is expected to decrease. Due to the opposite effect of the two factors mentioned above, the effectiveness of nanocomposite samples was studied, and the impressment of each factor was investigated in this project.

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Due to the presence of intra- and inter molecular hydrogen bonding in alginate chemical structure, its electrospinning capability is weak. However, this weakness can be improved through substitution of hydroxyl groups by sulfate groups. This article focuses on the role of degree of substitution of sulfate groups on the physicochemical properties of electrospinning solutions, such as viscosity, electrical conductivity and electrospinning conditions.

Sodium sulfated alginate (SSA) was synthesized through the reaction of sodium alginate and chlorosulfonic acid in formamide as the solvent. The amount of chlorosulfonic acid was varied in order to obtain the SSA samples with different degrees of substitution. The chemical structures of neat alginate and SSA were studied by FTIR and 1H NMR spectroscopy. Degree of sulfation of samples was measured using CHNS elemental analysis, and the electrical conductivity and viscosity of SSA solutions were measured. The SSA nanofibers were fabricated using electrospinning and further crosslinked by a solution of calcium chloride to improve its hydrolytic stability. Finally, the fiber diameter and mechanical properties of the nanofibrous mat were studied by SEM and a tensile mechanical machine.

Both FTIR and 1H NMR analyses have confirmed the formation of sulfate groups in SSA structure. Based on elemental analysis, the degree of substitution (DS) of SSA samples has been measured as 0.9 and 0.5 for SSA1 and SSA0.5, respectively. The electrical conductivity and viscosity of the SSA solutions also increased and decreased by increasing DS, respectively.  The SSA1 sample showed better electrospinning capability and higher SSA content in dry electrospun mat compared to those in SSA0.5 sample. Finally, the crosslinked SSA1 mat revealed a lower mechanical strength compared to SSA0.5 mat due to lower crosslink density and higher chain scission of polymeric chains resulted from sulfation reaction.

Nowadays, energy efficient systems are needed for concentrated juice production. Ohmic heating is one of these systems. In this study, the effect of ohmic heating technique on parameters such as: types of electrode (stainless steel, aluminum and brass), voltage gradient (10, 14, 18 and 22 V/cm), electrical conductivity, heating rate, pH and energy consumption of grape juice samples in the temperature range of 26-90℃ was investigated. The results showed that the effect of voltage gradient was statistically significant on the electrical conductivity, ohmic heating time, heating rate, pH, energy consumption and system performance coefficient (SPC) (p < 0.05). The best efficiency (85.09%) was observed for stainless steel electrodes and 22V/cm voltage gradient. By increasing the voltage gradient in all three electrodes (stainless steel, aluminum and brass), the heating time and energy consumption decreased, but the performance of the system increased. As the voltage gradient increased, time, pH and specific energy consumption decreased. The increase in concentration of grape juice was significantly increased electrical conductivity. The effect of electrodes on the heating rate of grape juice concentrated was not statistically different.

Carbon black is also used in rubber compound in addition to its primary role as reinforcement in the rubber industry to achieve the required electrical or thermal conductivity. In this article, we will discuss different types of carbon black and their differences in conductivity. Also, it will be reviewed how to mix the carbon black with the rubber compound ,effect of the structure and size of the carbon black to create the desired conductivity.

Thermal conductivity of a partially saturated rock sample depends on several parameters such as matrix properties, pore structure, pore filling fluids and their saturations. Indeed, complex pore structure of the rock causes many problems in prediction of its thermal conductivity at different saturation conditions. Numerous investigators presented different correlations and mechanistic predictive models to predict thermal conductivity of porous media. But, most of these models have focused on the prediction of thermal conductivity of single phase saturated porous medium. Analogy between electricity transmission and heat transfer through a rock can be considered as a basis to develop a model for prediction of thermal conductivity. In this paper, thermal conductivity of six carbonate plug samples from one of the Iranian reservoirs has been measured at vacuum condition. Also, for four samples of these six plugs, thermal conductivity has been determined at fully water saturated condition and four different water saturations using divided bar steady-state apparatus; in addition, the second phase has been air. This apparatus has been designed and constructed in Petroleum University of Technology (PUT). Finally, according to the results, it is obvious that rock thermal conductivity at vacuum condition decreases with an increase in porosity. Furthermore, thermal conductivity of partially saturated rock increases with an increase in water saturation. Moreover, a new model for predicting rock thermal conductivity of partially saturated rock has been presented based on the analogy between electricity transmission and heat transfer through the rock. Our experimental results confirmed the suitability of the proposed model.

In this investigation, an ohmic heating system was constructed and was selected for thermal process, three voltage gradient inputs (8.33, 10.83, 13.33 / cm) and three percent weight loss sample (10, 20 and 30%) compared to total weight. During the thermal process, the power consumption, electrical conductivity and coefficient performance system were calculated. All experiments were performed in three replications using factorial experiment and in a completely randomized design. Results were analyzed using SAS software. Statistical analysis results showed that voltage gradient factors and weight loss were significant for electrical conductivity, power consumption, input current, heating process time, and coefficient system efficiency. By increasing the voltage gradient, electrical conductivity, input current and power consumption increased, and the coefficient performance system and heating process time have decreased. The highest electrical conductivity (1.49 S / m) was in the voltage gradient 10.33 and 30% percent weight loss, and for coefficient performance system (0.94) was in the voltage gradient of 8.33 volts and the percent weight loss 10%. Also, the regression equations formed for the coefficient performance system and electrical conductivity were appropriate when the current input data, input voltage gradient and heating process time were used to form these equations. That is, the greater the number of input data variables for the formation of the equation, the accuracy of the equations is also increased.

A review study is presented in relation to polymer/graphene nanocomposites. The research works have shown that the graphene can be considered as the strongest material and the hummer’s method is a suitable method for its production. Functionalization by chemical groups compatible with its matrix can enhance dispersion of the nanoparticles within it. The effect of graphene nanoplatelets on the isothermal and non-isothermal crystallization behavior, nucleation and crystal growth is explained. Several contradicting results including both increase and decrease in crystallinity have been reported. The change of electrical conductivity with the addition of graphene and method of determining percolation threshold are presented. The results showed a significant increase in electrical conductivity by incorporation of graphene nanosheets. The mechanical properties of nanocomposites including elastic modulus, elongation-at-break and tensile strength are reviewed. The reported results revealed that modulus increased due to higher modulus of nanoparticles and there was a contradictory result for tensile strength and elongation-at-break. Functionalization of nanosheets could increase the tensile strength of nanocomposites through stronger adhesion between filler and matrix. The thermal conductivity of these nanocomposites and the desirable method for measurement of thermal conductivity constant are discussed. The results showed that graphene nanoplatelets are less effective in enhancing thermal conductivity in comparison to electrical conductivity. The rheological properties of nanocomposites were affected by addition of nanosheets and the obtained rheological percolation threshold was different from the electrical one. The lower electrical percolation in comparison to rheological one means electrical threshold is obtained from direct contact of nanoparticles.

Nowadays, the use of scaffolds in tissue engineering to repair and regenerate human lesions, including nervous injuries has been widely considered. Also, nanofibrous scaffolds due to their structural similarity with the extracellular matrix (ECM) in the body are found to be suitable substrates for cell growth. Therefore, the main focus of the present work is on the production of conductive nanofibrous scaffolds for neural cell culture and their electrical stimulation performance. Two biocompatible polymers including polycaprolactone (PCL) and poly(lactic-co-glycolicacid) (PLGA) were used as main materials, and polyaniline (PANI) was applied as a conductive polymer to create conductivity in the substrates. After determination and optimization of the electrospinning process factors, 4 types of nanofibrous scaffolds with 4 levels of conductive polymer (0%, 1%, 10% and 18%) were prepared. To investigate the effect of scaffolds' conductivity and electrical stimulation on the nerve cells behavior, a plate with steel electrodes was designed to apply electrical field to the scaffolds during cell culture experiments. SEM, Dino-Lite digital microscopy, Potentiostat-Galvanostat and 3-(4,5-dimethylthiazed-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were used to study the properties of scaffolds including hydrophilicity, conductivity, fiber diameter and the results of cell culture. By investigation of the physical properties of the scaffolds it was shown that increasing the amount of PANI in scaffolds causes significant drop in the fiber diameter and hydrophilicity. In cell culture experiment, shape and proliferation of nerve cells were studied. MTT assay and SEM images showed that electrical stimulation, proportional to the amount of polyaniline, enhanced neurite outgrowth compared to the scaffolds that were not subjected to electrical stimulation. Furthermore, proliferation of cells on conductive scaffolds (by 10% v/w of PANI) increased and subsequently the cell proliferation decreased with increasing conductive polymer content due to its toxicity.

Hypothesis: We investigated the effect of thermally-reduced graphene (TRG) nanosheets on electrical conductivity, dielectric constant, electromagnetic interference shielding performance, rheological behavior and thermal stability of polypropylene/polyethylene terephthalate (PP/PET) blend. For this purpose, 50/50 PP/PET blends were prepared through melt compounding in presence of different volume fractions of TRG. The direct current (DC) conductivity, the AC electrical conductivity and EMI shielding effectiveness of composites were measured. The morphology of blends was examined by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Findings: The morphology of the samples was co-continuous, and preferential localization of the nanoparticles led to a double percolated structure. This structure enhanced electrical conductivity of the samples considerably. The rheological analysis indicated that a percolated network was formed at low volume fractions of TRG. At 0.1 vol% loading, the conductivity of the composites satisfies the antistatic criterion (10−6 S/m) for thin films. At 2 vol% of graphene, a high electrical conductivity of0.16 S/m was achieved which was considered sufficient for electronic device applications. The dielectric constant and the electromagnetic interference shielding efficiency (EMI SE) of the blends significantly increased with TRG addition. By incorporating 2 vol% of TRG, the dielectric constant increased from 4 (for neat sample) to 9×107 at 10 Hz and the EMI SE increased from 1 dB (for neat sample) to 42 dB at 10 GHz, satisfying the target value for commercial applications. Thermogravimetric analysis (TGA) indicated that addition of TRG effectively enhanced the thermal stability of the samples. Incorporation of TRG not only increased the initial decomposition temperatures but also decreased the rate of decomposition. The enhanced thermal stability of the composites was attributed to the high aspect ratio of TRGs, which served as a barrier and prevented the emission of gaseous molecules during thermal degradation.

Epoxy, one of the most important thermosetting polymers, is used in a wide range of applications as adhesives, coatings, and materials for composite structures due to its outstanding performance, low processing capacity and low cost. Due to the superior properties of carbon nanomaterials in thermal conductivity, flame retardation, mechanical stability, electrical conductivity and environmental compatibility, these nanomaterials have attracted global attention. In the present article, a review of past literature on improving the performance of epoxy resin by adding carbon nanomaterials is presented. The correlation of structural performance for epoxy modified with various carbon nanomaterials has been closely analyzed. Improvement of mechanical, electrical, thermal conductivity and flame deterioration for epoxy resin has been investigated. Challenges and opportunities in the composite of functionalized nano-materials epoxy are also discussed. The purpose of this research is to provide a comprehensive understanding of the multi-purpose epoxy resins including carbon nanomaterials to date and assess its future prospects. Also, the relationship and comparison of the structure and performance of various carbon nanomaterials has been evaluated. The improvement of mechanical, electrical, thermal conductivity and carbon dioxide epoxy flame retardant properties has been thoroughly investigated. Finally, the conclusions and prospects for the future and the hope of facilitating progress are presented at the end of the paper.

Hypothesis: Electrospinning of nanoparticles/polymer solutions offers the potential to achieve novel composite nanofibers in a variety of high performance applications. In this respect, the aspect ratio and purity of multi-walled carbon nanotubes (MWCNTs) were examined to study the morphological and electrical properties of the electrospun composite nanofibers. In the first step, MWCNTs samples were characterized using scanning electron microscopy (SEM) and Raman spectroscopy. Next, nanocomposite solutions containing MWCNTs were prepared by physical dispersion method in presence of a non-ionic surfactant. Finally, the prepared composite solutions were loaded to a glass syringe and connected to a DC power supply device. The electrospinning was performed by applying a high voltage of 15kV between the needle and the rotating collector. Findings: It is generally accepted that a combination of G-band intensity and G/D ratio is useful to evaluate the purity and crystallinity of MWCNTs. The morphological properties of the electrospun composite nanofibers showed their high dependency on carbon nanotubes dimensions, so that at higher aspect ratios the morphological properties generally improved. The morphological analysis of the composite nanofibers revealed that the deformation of the nanofibers increased with increasing MWCNTs diameter. Very smooth surfaces of the composite electrospun nanofibers even with 1 wt% MWCNT concentration were successfully achieved because of the high stability of MWCNT dispersions. The composite nanofibers with higher purity and aspect ratio presented better electrical conductivity. The electrical conductivity of electrospun composite nanofibers could be adjusted from ~10–8 S/cm (insulator) to ~10–3 S/cm (conductor) by different aspect ratios and purities of MWCNTs. MWCNTs with high aspect ratio and high purity offer a promising way to develop electrospun composite nanofibers with improved morphological and electrical properties.

Polymer solar cells (PSCs) as one of the new types of solar cells have attracted a lot of attention due to their some advantages such as flexibility, light weight, low-cost large-scale manufacturing and solution processability. This category of PSCs is composed of three main layers including anode, active layer and cathode. The layers entitled "hole transporting layer" (HTL) and "electron transporting layer" (ETL) are generally designed in the main structure of a PSC. These layers improve the solar cell performance in conversion of solar energy to electricity. HTL as a layer can block electron movement to anode and only allows holes to move. Various compounds are introduced as "hole transporting" materials. Today, the most successful candidate material as "hole transporting" material for polymer solar cells is poly(3,4-ethylene dioxythiophene) polystyrene sulfonate or PEDOT:PSS which is composed of conductive PEDOT and PSS insulator. In this paper, the synthesis methods of PEDOT:PSS and its properties and components are introduced and its electrical property is optimized in order to enhance the performance of PSC, while the "hole transportation mechanism" has been considered in the polymer solar cell structure.

Graphene is a monolayer two-dimensional material in which the carbon atoms form a honeycomb lattice. The outstanding electrical, thermal, optical and mechanical properties of graphene due to its electronic structure have made graphene a promising nanostructure for vast range of applications. In this zero-gap semiconductor material, electron/ hole carriers concentration is around 〖10〗^13 cm^(-2) and it possesses high electron mobility (500000 s^(-1) V^(-1) cm^2) at room temperature. Adding graphene to a polymeric matrix enhances the polymer properties noticeably, various researches have been devoted to studying the fabrication methods of polymer/graphene coatings and achieving the optimum properties in them. In this paper, the general structure, properties and various procedures of graphene production are briefly investigated. Then the fabrication methods of polymer/graphene coatings are studied. The main part of this paper has focused on electrical conductivity of various coatings based on epoxy, polyurethane, polypropylene, polystyrene, polyester and etc. In which achieving the lowest possible electrical percolation threshold (minimum amount of graphene required to convert an insulator coating to a conductor), finding and controlling the factors that affect the percolation threshold are discussed.