Specific Surface Conductivity Research Articles

Fabrication of single/multi-walled hybrid buckypaper composites and their enhancement of electromagnetic interference shielding performance

Multi-walled carbon nanotubes and single-walled carbon nanotubes show great potential for the application as an electromagnetic interference shielding material. In this paper, the electromagnetic interference shielding the effectiveness of a composite surface coated single/multi-walled carbon nanotube hybrid buckypaper was measured, which showed an average shielding effectiveness of ~55 dB with a buckypaper thickness of 50 µm, and bukypaper density of 0.76 g cm−3, it is much higher than other carbon nanotube/resin materials when sample thickness is on the similar order. The structural, specific surface area and conductivity of the buckypapers were examined by field-emission scanning electron microscopy, specific surface area analyzer and four probes resistance tester, respectively.

Characteristics of carbon aerogel at variation in pyrolysis conditions

Carbon aerogel was obtained by pyrolysis of organic aerogel by ambient pressure drying technique. The effect of pyrolysis conditions on characteristics of carbon aerogel such as density, specific surface area and conductivity was studied. The properties and structure of carbon aerogel samples were investigated by nitrogen adsorption, four-point probe method and XRD diffraction. The results showed that carbon aerogel had structure between amorphous and graphite state. The highest specific surface area was 800 m2/g at pyrolysis temperature of 700oC. The pore-size was distributed in microporous, with the maximum total pore volume of 0.44 cm3/g. The electrical conductivity of carbon aerogel was highest at pyrolysis temperature of 800-900oC with the value in the range of 1.744-1.923 S/cm.

Oxide-Coated Carbon Black for Cathode Catalyst Support

Carbon black is an essential material for PEFC. Due to its specific surface area, conductivity, pore-making structure and stability for acidic environment, carbon black is so far the best choice as the catalyst support for cathode and anode. However, carbon black is being one of the critical elements which limit the lifetime of PEFC. Especially in cathode, oxidative degradation of carbon black support is resulting in the depression of catalyst activity. In order to prevent carbon black support from its oxidative degradation, surface coating with silicon oxide (silica) on acetylene black was tried using sol-gel method. Nanometer-thick amorphous silica layer was formed on almost the whole surface on the acetylene black. Its effect on resistivity against oxidation, Pt supporting function and total behavior of the catalyst is to be discussed.

Electrosurface properties of single-crystalline detonation nanodiamond particles obtained by air annealing of their agglomerates

A complex study of electrosurface properties has been performed for single-crystalline detonation nanodiamond particles with sizes of 4–5 nm obtained by air annealing of their agglomerates. FTIR spectroscopy and X-ray photoelectron spectroscopy data indicate that the investigated properties result from the presence of two types of ionogenic functional groups on the particle surface, i.e., acidic carboxyl and amphoteric hydroxyl groups. Acid-base potentiometric titration, laser Doppler electrophoresis, and conductometry have been employed to measure the Γ H + (pH) and Γ OH - (pH) adsorption isotherms of potential-determining ions, as well as the pH dependences (in a pH range of 3.5–10.5) of the surface charge density, electrophoretic mobility, and specific surface conductivity of detonation nanodiamond particles in aqueous 0.0001–0.01 M KCl solutions.

In-situ controllable growth of α-Ni(OH)2 with different morphologies on reduced graphene oxide sheets and capacitive performance for supercapacitors

The α-Ni(OH)2 nanowires (α-Ni(OH)2 NWs) and nanoparticles (α-Ni(OH)2 NPs) were grown on reduced graphene oxide (RGO) sheets by adjusting the reduction degree of the substrates. The α-Ni(OH)2 NWs/RGO composite was achieved by using graphene oxide (GO) as the substrate. In contrast, the α-Ni(OH)2 NPs/RGO composite was obtained when RGO was applied as the support. The difference in morphology can be attributed to the fact that the hydrophilic function of GO is larger than that of RGO, and sp2 carbon atom concentration in α-Ni(OH)2 NPs/RGO is higher than that in α-Ni(OH)2 NWs/RGO. When α-Ni(OH)2 NWs/RGO and α-Ni(OH)2 NPs/RGO composites were used as electrode materials for supercapacitors, the α-Ni(OH)2 NPs/RGO exhibits superior electrochemical performance than α-Ni(OH)2 NWs/RGO, which is attributed to the fact that the specific surface area, conductivity, and sp2 carbon atom concentration of α-Ni(OH)2 NPs/RGO are larger than those of α-Ni(OH)2 NWs/RGO. The α-Ni(OH)2 NPs/RGO composite is a promising candidate as electrode material for high performance supercapacitor.

Synthesis, characterization, and cytotoxicity assay of calcium oxalate dihydrate crystals in various shapes

Various morphologies of calcium oxalate dihydrate (COD) crystals containing cross-shaped, flower-like, thin-bipyramid, thick-bipyramid, and elongated-bipyramid structures, with a size of approximately 5 μm, were prepared by varying the reactant concentration, reaction temperature, stirring speed, and additive. X-ray diffraction (XRD) and infrared spectroscopy (FT-IR) showed that the synthesized crystals were pure-phase COD crystals. The factors affecting the morphology of COD and the mechanism of COD formation were discussed. Physicochemical properties such as specific surface area, pore structure, pore size, zeta potential, and conductivity of the crystals were identified. The cytotoxicity of five different shapes of COD crystals in human kidney proximal tubular epithelial (HK-2) cells was investigated using the Cell Counting Kit-8 (CCK-8) assay and propidium iodide (PI) staining assay. The cytotoxicity was ranked in the following order: COD-elongated-bipyramid > COD-thick-bipyramid ≈ COD-cross-shaped > COD-thin-bipyramid > COD-flower-like. The toxicity of tetragonal bipyramid COD crystals was closely correlated with the area of the Ca2+ ion-rich (100) face; the crystals with large (100) faces showed a higher toxicity to HK-2 cells. The cytotoxicity of cross-shaped COD and flower-like COD was affected by the sharpness of their crystal edges; COD-CS with sharp corners caused more serious injuries to cell membranes. These findings are helpful in understanding the effects of mineralization conditions and additives on crystal morphology as well as to identify the relationship between crystal morphology and cytotoxicity. The results also provide a reference for the injury difference of various shapes of crystals from normal subjects and stone patients to the renal epithelial cells and the formation mechanism of calcium oxalate stones.

In-situ Synthesis and Discharge Performance of Ni-NiCl$lt;inf$gt;2$lt;/inf$gt; Composite as Cathode Materials for Thermal Batteries

As a high potential compound, NiCl2 is an ideal anode material for high powder thermal battery, but its small specific surface area and poor conductivity hinder the application in thermal battery. In present study, The Ni-NiCl2 composite with high specific surface area and conductivity was prepared by sublimation and in-situ synthesis, as cathode materials for thermal batteries. The precursor material NiCl2 center dot 6H(2)O was dried to dehydrate and sublimated at 850 similar to 900 degrees C in Ar atmosphere successively. And then the yellow sublimed powder was reduced at 300 similar to 500 degrees C in Ar + H-2 atmosphere for 1 h. Finally, the Ni and NiCl2 composite powders were formed. Thermoanalysis, crystal structure, in-situ synthesis process and electrochemical performance of the powders were analyzed. The results show that NiCl2 crystal grows along the direction perpendicular to c axis and formed a layered structure of 200-300 mu m in the sublimation process. The resistivity of Ni-NiCl2 composite is reduced with the increase of elemental Ni content. The discharge curve of LiSi vertical bar LiCl-LiBr-LiF vertical bar NiCl2 thermal batteries with Ni-NiCl2 (5wt% elemental Ni) as anode material at 1000 mA/cm(2) is more stable and has a shorter activation time, as compared to the discharge curve with pure NiCl2 as anode material.

Anode modification with peptide nanotubes encapsulating riboflavin enhanced power generation in microbial fuel cells

A novel anode modification method was established based on immobilizing a redox mediator riboflavin (RF) onto carbon cloth using bio-inspired and self-assembled peptide nanotubes (PNTs). The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in Fe(CN)63−/4− solution showed that the RF/PNT electrode demonstrated a higher electrocatalytic activity and faradic charge capacity than the untreated electrode. The chronamperometry analysis showed that RF/PNT electrode in the presence of Shewanella oneidensis MR-1 generated a current density of 28.9 μA cm−2, increased by 263.3% compared to the bare electrode. The MFC operated with the RF/PNT anode generated a maximum power density of 767 mW m−2, which was 2.9 times larger than control. Besides, RF/PNT modification significantly reduced anode total internal resistance of MFCs. The self-organized PNTs could increase specific surface and electrical conductivity of anodes and provide a good carrier for redox mediator immobilization, which may contribute to the improved performance of MFCs.

Efficient Degradation of Methylene Blue by the Nano TiO2-functionalized Graphene Oxide Nanocomposite Photocatalyst for Wastewater Treatment

Herein, an efficient nano TiO2-functionalized graphene oxide nanocomposite photocatalyst was readily prepared, using an ordinary solvothermal technique. It was noted that the as-prepared nanocomposite yielded a quadruple degradation capacity of the previously reported P25-graphene composite photocatalyst towards methylene blue (MB). To elucidate this, the Brunauer–Emmett–Teller (BET)-specific surface area, conductivity, and water contact angle measurements were all carried out. It was found out that graphene oxide was endowed with nontrivial photocatalytic activity by increasing its content in the nanocomposite (from 1/100 to 1/9, with respect to the dosage of nano TiO2). Overall, the nano TiO2-functionalized graphene oxide nanocomposite is a promising candidate in applications of environment remediation.

Fabrication of poly(p-styrenesulfonate) grafted reduced graphene oxide/polyaniline/MnO2 hybrids with high capacitance performance

Reduced graphene oxide grafted with poly(p-styrenesulfonate) (rGO-g-PSS) was synthesized by in-situ free radical polymerization. The rGO-g-PSS was used to induce formation of polyaniline (PANI) nanorod array and then assembled with MnO2 to form rGO-g-PSS@PANI-MnO2 hybrids. The rGO-g-PSS@PANI-MnO2 hybrids were applied to modify electrodes and the specific capacitance (SC) of the rGO-g-PSS@PANI-MnO2 hybrid reached 425 F/g at the scan rate of 20 mV/s, which was much higher than those of rGO-g-PSS (190 F/g), MnO2 (203 F/g), rGO-g-PSS@PANI (305 F/g) and rGO-MnO2 (295 F/g). In addition, the rGO-g-PSS@PANI-MnO2 hybrid also showed good stability. These good electrochemical performances are due to that rGO-g-PSS@PANI-MnO2 hybrid could make full use of the high SC of PANI and MnO2, high specific surface area and conductivity of rGO, and good interfacial properties of PSS linker.

Colloido-chemical characteristics of nanoporous glasses with different compositions in solutions of simple and organic electrolytes. 1. Structural and transport characteristics of membranes

The regularities of variations in the structural (bulk porosity, structural resistance coefficient, and average pore radius) and transport (specific electrical conductivity and ion transport numbers) characteristics of nanoporous glass membranes with different compositions have been studied as depending on their preparation conditions and the type of electrolyte (sodium, potassium, ammonium, tetramethylammonium, and tetraethylammonium chlorides). An additional alkaline treatment of the porous glasses, which increases the average pore radius and modifies the morphology of pore channels, leads to variations in the electrotransport characteristics of the glasses. In solutions containing inorganic counterions, the dependences of the transport characteristics of the porous glasses on the solution concentration and pore size have a classic character. The high specificity of tetraalkylammonium ions in relation to the surface gives rise to a region of negative values of the specific surface conductivity and complex dependences of efficiency coefficients and transport numbers on electrolyte concentration and pore channel size. The duration of the thermal treatment of initial sodium-borosilicate glass containing small amounts of phosphorus oxide and fluoride ions, as well as the conditions of its leaching, has almost no effect on the properties of the membranes in tetraethylammonium chloride solutions.

Sulfonated Reduced Graphene Oxide: A High Performance Anode Material for Lithium Ion Battery

In this work, the sulfonated reduced graphene oxide (SRGO) was synthesized and proposed as an enhanced anode material for lithium ion battery (LIB). The result shows that the SRGO has an improved battery performance (i.e., ∼341.7 mAh/g and ∼190.6 mAh/g corresponds to SRGO and RGO at the 100th cycle with a current density of 200 mA/g) and superior cycling stability compared with pristine reduced graphene oxide (RGO). These are attributed to the improved specific surface area (448.35 m2/g) and conductivity (2.5 × 10-4 S/m). Further, the SRGO exhibits good rate capability and excellent energy density at various current densities ranging from 50 mAh/g to 2000 mAh/g, suggesting that SRGO could be a promising anode material for high capacity LIB.

Chemical Mapping and Electrochemical Performance of Manganese Dioxide/Activated Carbon Based Composite Electrode for Asymmetric Electrochemical Capacitor

A MnO2@BP nanocomposite was synthesized by simultaneously reduction of KMnO4 with Mn(CH3COO)2.4H2O and highly porous Black Pearls 2000 at room temperature. The specific surface area, porosity, crystalline form and conductivity of MnO2@BP nanocomposite were characterized by nitrogen gas adsorption measurements, scanning electron microscopy, X-ray diffraction and 4-point probe measurements, respectively. The content of MnO2 and BP in the composite was determined by thermogravimetric analysis. Chemical mapping using Raman spectroscopy was performed to investigate the distribution of MnO2 and BP in a composite electrode film prepared with polytetrafluoroethylene (PTFE) as binder. This composite electrode exhibits more homogeneously distributed MnO2 particles when compared to an electrode made by physical mixing of MnO2, BP and PTFE (MnO2/BP-PTFE). Also, Raman spectroscopy data of both composite electrodes indicates a loss of electrical conductivity of BP in the case of MnO2@BP-PTFE. The electrochemical properties were characterized by cyclic voltammetry in aqueous 0.65 M K2SO4. The specific capacitance of MnO2@BP-PTFE composite electrode was 122 ± 5 F/g, which is statistically equivalent to the capacitance of MnO2/BP-PTFE composite electrode (129 ± 6 F/g).

Optimization of Fabrication Parameters to Enhance the Performance of Activated Carbon Air-Cathode

The aim of this work was to investigate the effect of three key fabrication factors (i.e. pressure, AC/PTFE mass ratio, and AC load) on the performance of activated carbon air-cathode (ACAC). The design of experiment work was performed with the response surface methodology (RSM) using the central composite design. 20 combinations of the three variables were optimized based on the responses evaluated by linear sweep voltammetry (LSV). The results showed that the proposed mathematical model in the RSM could be used adequately for prediction and optimization within the factor levels investigated. The combined optimum fabrication parameters that gave the highest performance of ACAC were pressure 10 MPa, AC/PTFE mass ratio 6 and AC load 0.3 g. The fabricated ACACs were characterized by Electrochemical Impedance Spectroscopy (EIS), Brunauer-Emmett-Teller (BET) test and fuel cell test. The characterization results demonstrated that the improved performance of ACAC owed to the increase of both specific surface area and conductivity, and the controlled surface hydrophilicity/hydrophobicity.

Examining the Electrodeposition Mechanism of Manganese Dioxide Using In-Situ Small Angle X-ray Scattering

Manganese dioxide thin films, produced by anodic electrodeposition, have been found to exhibit extremely high specific capacitance. However, their capacitive performance decreases markedly as the film thickness increases, so despite exhibiting specific capacitance values of up to 2000 F/g (for extremely thin films), their applications are limited due to their low volumetric capacitance.The enhanced performance of thin films is largely due to their high specific surface area and conductivity, both of which decrease as the film thickness increases. Improving the performance of thicker films requires synthesis methods in which the morphology of the films can be tailored to optimise surface area and conductivity. To achieve this, the mechanism by which manganese dioxide is electrodeposited must be fully understood.In this work, manganese dioxide was deposited onto a platinum electrode from a solution of MnSO4 in H2SO4. The deposition process was examined in-situ using small angle x-ray scattering (SAXS) using a synchrotron x-ray beam.SAXS analysis was used characterise the material at different stages throughout the deposition. Features such as the pore size and particle size and shape were obtained from the data, showing how the morphology of the film changes as deposition is occurring. The deposition solution and deposition potential were varied in order to find the optimum deposition conditions required to create high performance thin film capacitors.The performance of the thin films was analysed using standard electrochemical techniques including cyclic voltammetry and constant current charge discharge.

Improving the electrochemical properties of nanosized LiFePO4-based electrode by boron doping

Electrode materials with homogeneous distribution of boron were obtained by heating mixtures of nanosized carbon-coated lithium iron phosphate and BPO4 in 3-9% weight at 700°C. The materials can be described as nanocomposites containing i) LiFePO4, possibly doped with a low amount of boron, ii) FePO4 and iii) an amorphous layer based on Li4P2O7-derived material that surrounds the phosphate particles. The thermal treatment with BPO4 also triggered changes in the carbon coating graphitic order. Galvanostatic and voltammetric studies in lithium half-cells showed smaller polarisation, higher capacity and better cycle life for the boron-doped composites. For instance, one of the solids, called B6-LiFePO4, provided close to 150 and 140 mAhg-1 (87% and 81% of theoretical capacity, respectively) under C/2.5 and C regimes after several cycles. Improved specific surface area, carbon graphitization, conductivity and lithium ion diffusivity in the boron-doped phospholivine network account for this excellent rate performance. The properties of an amorphous layer surrounding the phosphate particles also account for such higher performance.

Simple, Low-Cost Synthesis of an Iron Oxide and Carbon Foam Composite for Supercapacitor Electrodes

Iron oxide-carbon foam (IOCF) materials with a high specific surface area and conductivity have been synthesized via a facile, cost-effective, and one-step template-free method. The structure and morphology of the IOCF composite have been investigated by electron microscopy, cyclic voltammetry, and Raman spectroscopy. The as-prepared IOCF was coated on a nickel metal foam electrode as an active material for constructing supercapacitor electrodes. The electrochemical performance of IOCF composite electrodes was tested by cyclic voltammetry and galvanostatic charge/discharge in a Na2SO4 electrolyte. The as-assembled symmetric supercapacitor with optimal mass ratio can be operated reversibly over a wide voltage range of 0 to -1.0 V, and presents a high capacitance of 170 F g-1 in Na2SO4 aqueous electrolyte. Moreover, the supercapacitor exhibits excellent rate capability and retains a high capacity with extended cycling. These attractive results make this material promising as a component of an aqueous electrolyte-based supercapacitor having high energy and power densities.

Inorganic/Organic Doped Carbon Aerogels As Biosensing Materials for the Detection of Hydrogen Peroxide

In this article, three different inorganic/organic doped carbon aerogel (CA) materials (Ni-CA, Pd-CA, and Ppy-CA) were, respectively, mixed with ionic liquid (IL) to form three stable composite films, which were used as enhanced elements for an integrated sensing platform to increase the surface area and to improve the electronic transmission rate. Subsequently, the effect of the materials performances such as adsorption, specific surface area and conductivity on electrochemistry for myoglobin (Mb) was discussed using N2 adsorption-desorption isotherm measurements, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Moreover, they could act as sensors toward the detection of hydrogen peroxide (H2O2) with lower detection limits (1.68 μM, 1.02 μM, and 0.85 μM, for Ni-CA/IL/Mb-CPE, Pd-CA/IL/Mb-CPE, and Ppy-CA/IL/Mb-CPE, respectively) and smaller apparent Michaelis-Menten constants KM. The results indicated that the electroconductibility of the doped CA materials would become dominant, thus playing an important role in facilitating the electron transfer. Meanwhile, the synergetic effect with [BMIm]BF4 IL improved the capability of the composite inorganic/organic doped CA/IL matrix for protein immobilization. This work demonstrates the feasibility and the potential of a series of CA-based hybrid materials as biosensors, and further research and development are required to prepare other functional CAs and make them valuable for more extensive application in biosensing.

Amperometric determination of hydroquinone and catechol on gold electrode modified by direct electrodeposition of poly(3,4-ethylenedioxythiophene)

Poly(3,4-ethylenedioxythiophene) (PEDOT) was directly deposited onto a gold electrode through potentiostatic technology, and the PEDOT modified electrode was developed for the amperometric determination of hydroquinone and catechol in 0.1M phosphate buffer solution (pH 7.0). Compared with the bare electrode, both hydroquinone and catechol exhibited well-defined redox peaks and much larger peak currents at PEDOT modified gold electrode, which suggested the higher specific surface area and conductivity of the PEDOT film. Under the optimized condition, the amperometric current response on PEDOT modified electrode were linear over ranges from 1.0×10−7M to 4.9×10−5M for hydroquinone, and from 9.1×10−8M to 9.8×10−4M for catechol, with the detection limits of 1.2×10−8M and 0.9×10−8M, respectively. The proposed method was applied on the determination of the mixture of hydroquinone and catechol with satisfactory results.

Conductance of island and granular metal films

Results of measurements of the specific surface conductance of island metal films at different temperatures are presented. The study of conduction allowed us to establish processes, which determine the transfer of charge carriers in granular and island metal structures. These processes determine the excess charge carriers concentration in film and, on the other hand, characterize the transfer speed of excess charge carriers from one island to another (i.e. mobility). Moreover, these processes occur independently from each other.