Electrically conductive ceramic composites prepared with printer toner as the conductive phase

Conductive ceramic composite was prepared by sintering the mixture of clay and printer toner at 1050°C and in the N₂ atmosphere. The microstructure and mineral phases of the ceramic composite were characterised by SEM, EDX, TG and XRD, and its electrical conductivity and mechanical properties were also investigated. The results show that, in the sintering process, a series of physical and chemical reactions take place, and mineral phases with excellent electrical conductivity, such as metal iron, carbon and Fe–Al solid solution material, are formed. The electrical conductivity mechanism can be explained by the percolation theory. The threshold value for electrical conductive percolation is between 3.5 and 7.0?wt-%. At the content of printer toner 10?wt-%, the volume electrical resistance of the ceramic composite is as low as 8.5?Ω?cm, and the composite exhibits excellent flexural strength higher than 14?MPa.     

Effects of conductive ceramic on the electrochemical performance of ZnO for Ni/Zn rechargeable battery

A novel ZnO/conductive-ceramic nanocomposite was prepared by a homogeneous precipitation method. The conductive ceramic with the nominal chemical composition of (ZnO)_0.92(Bi₂O₃)_0.054(Co₂O₃)_0.025(Nb₂O₅)_0.00075(Y₂O₃)_0.00025, as the nucleation sites of ZnO, was prepared by ball milling and surface modification process and its effects on electrochemical performance of ZnO were investigated by charge/discharge cycling, slow rate cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared with pure ZnO, the ZnO/conductive-ceramic electrode exhibited improved electrochemical properties, such as superior cycle stability, higher discharge capacity and utilization ratio. When the conductive ceramic content reached 14 wt.%, the discharge capacity of the ZnO/conductive-ceramic nanocomposite hardly declined over 50 cycling test, the average utilization ratio could reach 99.5%, and the electrodes had no obvious weight loss after cycling tests.     

Preparation of conductive Si/C/N/Ni ceramic nanocomposites using phenyl-substituted polysilazane and nickelocene as precursors

In this study, a conductive Si/C/N/Ni nanocomposite was prepared using phenyl-substituted polysilazane and nickelocene (NiCp₂) as precursors. Ni-related nanoparticles were uniformly distributed throughout the Si/C/N/Ni nanocomposite without aggregation because of the large number of nitrogen atoms in the silsesquiazane used as a precursor of the matrix. In addition, the nickel silicide crystalline phase and turbostratic carbon phase grew in the matrix of the Si/C/N/Ni nanocomposite at low temperatures because NiCp₂ acted as a catalyst. Moreover, NiCp₂ contributed to the increase in the turbostratic carbon crystallinity through the dehydrogenation reaction, resulting in an improved electrical conductivity of the Si/C/N/Ni nanocomposite.     

Electrochemical treatment of alizarin red S dye wastewater using an activated carbon fiber as anode material

The simulated dye wastewater containing alizarin red S (ARS) was electrochemically oxidized using an activated carbon fiber (ACF) felt as an anode. The removal efficiency of color and chemical oxygen demand (COD) was evaluated by comparing ACF adsorbents with ACF anodes. The experimental results show that the electrochemical oxidation method using ACF as anode can effectively remove dyestuff pollutant from wastewater. About 98% of the color removal ratio and 76.5% of the maximum COD removal ratio are achieved after 60 min of electrolysis. It is suggested that ARS was adsorbed and concentrated on the ACF anode due to its high surface area; the simultaneously electrochemical oxidation of the ARS may regenerate the ACF anode, which enhance the electrolysis efficiency of the ARS.     

Influence of anode material on electrochemical decomposition of urea

Voltammetric investigations into the process of anodic decomposition of urea using Ti/Pt, Ti/(Pt-Ir)_70:30, Ti/RuO₂, Ti/(RuO₂-TiO₂)_40:60, Ti/(RuO₂-TiO₂-IrO₂)_20:60:20, Ti/(Ta₂O₅-IrO₂)_70:30 electrodes have been carried out. Two anodes namely (Ti/(Pt-Ir)_70:30 and Ti/(Ta₂O₅-IrO₂)_70:30) were found to be stable enough and indicated the required activity to produce non-toxic N₂ and CO₂ in place of nitrites and nitrates, the commonly reported electrochemical urea oxidation products. The kinetics of the process in question using the above two electrodes was further examined in a periodic electrolyzer. The effect of the anodic current density (j = 2-10 A/dm²), initial urea concentration (c_0M = 1-10 g/dm³) and the concentration of sodium chloride (c_NaCl = 1-10 g/dm³) on basic process indices (average rate of urea decomposition, a; current efficiency, W_p, and unit DC power consumption, Z_j) was discussed.     

Electrolytic oxidation of trichloroethylene using a ceramic anode

Trichloroethylene (TCE) was transformed to CO₂, CO, Cl^– and ClO₃^– at the anode of a two-chambered electrolytic cell. The working electrode was constructed from Ebonex^®, an electrically conductive ceramic (Ti₄O₇). Under our experimental conditions (anode potential E_a = 2.5 to 4.3 V vs SSCE), the disappearance of TCE was first order in TCE concentration. The transformation rate was independent of pH in the range 1.6 < pH < 11. TCE oxidation occurred only on the anodic surface and was limited by mass transport at high potentials (E_a > 4.0V). The maximum (transport-limited), surface-area-normalized rate constant was about 0.002 43cms^–1. Carbon-containing products included CO₂ primarily with traces of CO. At neutral and alkaline pHs, the only chlorine-containing products were Cl^– and ClO₃^–. Hydroxyl radicals were detected in the anodic compartment using a spin trap (4-POBN). A kinetic model was successfully correlated with experimental results.     

Mixed first and zero order kinetics in the electrooxidation of sulfamethoxazole at a boron-doped diamond (BDD) anode

Pharmaceutical residues in the aquatic environment represent an emerging environmental problem, because many pharmaceuticals are refractory towards conventional waste water treatment. This study focussed on the oxidation of the sulfonamide antibiotic sulfamethoxazole (SMX) at a boron-doped diamond anode, at which reactive hydroxyl radicals are formed. Electrochemical oxidation led to mineralization with high current efficiency, but without the formation of known toxic products of partial oxidation. A “mixed” kinetic order with respect to substrate concentration was observed; the kinetics could be shifted in the direction of either diffusion control (first order in SMX) or current control (zero order in SMX) by adjusting the substrate concentration and current density. Alternatively, the electrooxidation could be described by a model, applicable to a wide range of reaction conditions, in which the kinetic orders with respect to current and initial substrate concentration were approximately 0.4 and 0.5, respectively.     

Electrochemical properties of anatase TiO2 nanotubes as an anode material for lithium-ion batteries

Titanium oxides with a one-dimensional nanostructure are of great significance in electrochemical lithium insertion due to their high specific surface area and pore volume. In this paper, anatase TiO₂ nanotubes with diameters of about 10 nm and lengths of 200–400 nm were synthesized by a hydrothermal process. The phase structure and morphology were analyzed by X-ray diffraction, Raman scattering, and transmission electron microscopy. The electrochemical properties were investigated by constant current discharge–charge and cyclic voltammetry. There is a potential plateau at 1.73 and 1.88 V in the process of Li insertion and extraction, and the initial Li insertion/extraction capacity is 290 and 238 mAh g⁻¹ at 36 mA g⁻¹, respectively. The Li insertion capacity at the potential plateau of 1.73 V in the first cycle is about 150 mAh g⁻¹. In the 20th cycle, the reversible capacity still remains at about 200 mAh g⁻¹, and the coulombic efficiency is approximately 98%, exhibiting excellent cycling stability. The discharging capacity is about 168 mAh g⁻¹ in the 30th cycle at 210 mA g⁻¹, demonstrating a good high-rate performance. Anatase TiO₂ nanotubes might be a promising negative material for lithium-ion batteries.     

Sol-gel derived carbon ceramic electrode for the investigation of the electrochemical behavior and electrocatalytic activity of neodymium hexacyanoferrate

The electrochemical properties of an electroactive rare earth metal hexacyanoferrate, neodymium hexacyanoferrate (NdHCF) were studied by mechanically attaching NdHCF samples to the surface of carbon ceramic electrodes (CCEs) derived from sol-gel technique. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of 0.241 V (versus SCE) at a scan rate of 20 mV s⁻¹ in 0.5 M KCl solution. The voltammetric characteristics of the NdHCF-modified CCEs in the presence of different alkali metal cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) were investigated by voltammetry. The NdHCF-modified CCEs presented a good electrocatalytic activity towards the reduction of hydrogen peroxide (H₂O₂), and was used for amperometric detection of H₂O₂. In addition, the NdHCF-CCEs exhibited a distinct advantage of simple preparation, surface renewal, good stability and reproducibility.     

Progress on the morphological control of conductive network in conductive polymer composites and the use as electroactive multifunctional materials

Since the emergence of large aspect ratio and multifunctional conductive fillers, such as carbon nanotubes, graphene nanoplates, etc., conductive polymer composites (CPCs) have attracted increasing attention. Although the morphological control of conductive networks in CPCs has been extensively investigated as an important issue for the preparation of high performance CPCs, recent extensive progress has not been systematically addressed in any review. It has been observed that the morphological control of conductive networks during the preparation of CPCs has crucial influence on the electrical properties of these composites. Several methods have been shown to be able to control the network structure, and thus, tune the electrical properties of CPCs, including the use of shear, polymer blends, thermal annealing, mixed filler, latex particle etc. Moreover, many novel and exciting applications have been extensively investigated for CPCs, such as stretchable conductor, electroactive sensors, shape memory materials and thermoelectric materials, etc. Therefore, the morphological control of conductive network in CPCs is reviewed here. Issues regarding morphology characterization methods, morphological control methods, resulted network morphology and electrical properties are discussed. Furthermore, the use of CPCs as electroactive multifunctional materials is also reviewed.     

Electrochemical performance of polycrystalline CuO nanowires as anode material for Li ion batteries

CuO nanowires were prepared by wet-chemical method through the reaction of CuSO₄, KOH and ammonia in aqueous solution and subsequent aging process. The XRD, SEM, TEM, HRTEM, CV and galvanostatic method are used to characterize the structure, morphology and electrochemical performance of the as-prepared CuO nanowires. The CuO nanowires are polycrystalline microstructure, which facilitates the electrochemical storing Li. Therefore, the polycrystalline CuO nanowires exhibit a good electrochemical performance as Li ion batteries anode. The CuO nanowires showed a high reversible capacity of 720 mAh/g. The capacity keeps up 650 mAh/g over 100 cycles.     

Electrochemical performance and morphology evolution of nanosized ZnO as anode material of Ni-Zn batteries

Nanosized ZnO with prismatic form was prepared using homogeneous precipitation process and its electrochemical performance was investigated by the measurements of electrochemical cycle behaviors and passivation polarization curves. The discharge capacity delivered by nanosized ZnO still achieved about 600 mAh/g until the 250th cycle. Nanosized ZnO exhibited higher midpoint discharge voltage, better cycle stability and passivation toleration than commercial ZnO. Furthermore, nanosized ZnO showed the morphology evolution process differed slightly from that of the commercial ZnO, including morphology maintenance, orientation growth and the formation of Zn dendrites. The epitaxial growth, texture growth and crystal growth habit were put forward to illuminate the morphology evolution process.     

Effectiveness of a conductive cementitious mortar anode for cathodic protection of steel in concrete

The paper reports a study on the behaviour of a cementitious conductive overlay anode used for cathodic protection (CP) of steel in concrete. The anode is made of nickel-coated carbon fibres in a cementitious mortar. Tests were carried out on concrete specimens with two layers of rebars that simulated reinforced concrete slabs. Anodic current densities in the range 10-100 mA/m² with respect to the anode surface were imposed. Steel and anode potentials, as well as feeding voltage, were monitored. Four-hour decay and the distribution of current and potential were regularly measured. Galvanostatic polarisation tests were also carried out on the anode material immersed in saturated calcium hydroxide solutions. The maximum anode current output was evaluated. The effectiveness of patch repair of the anode, on areas damaged by excessive current output, is also discussed.     

Fabrication of CuFe2O4@g-C3N4@GNPs nanocomposites as anode material for supercapacitor applications

The aim of this study was to synthesize CuFe₂O₄ together with g-C₃N₄ and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe₂O₄ was successfully synthesized together with g-C₃N₄ and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm² at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm² and 300 mW/cm², respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications.     

Phase composition,microstructure, and properties of ceramic tile prepared using ceramic polishing waste as raw material

Polished ceramic products are currently the most popular in architectural decoration, but a significant amount of ceramic polishing waste (CPW) is produced during the preparation process. Determining how to handle the CPW is a pressing task for enterprises. This work investigated the feasibility of recycling CPW in porcelain tile, and its influence on the phase composition, microstructure, and properties of the ceramic body. The CPW was found to have a similar composition to the traditional ceramics and worked as a flux. The SiC within CPW began to decompose into SiO₂ with CO₂ generation at about 1100°C, resulting in a porous structure. Microstructure observation indicated that a high CPW sample produced sufficient liquid phase when fired at temperatures ≤1100°C, which was not only beneficial for mullite growth but also for matrix densification by the viscous flow mechanism. But a high-content CPW caused the body to foam or even expand at temperatures >1100°C, thus significantly reducing mechanical properties. Finally, a series of porcelain tiles were successfully prepared with a CPW content of ≤30 wt% at a firing temperature of 1125-1200°C. The results of this study are considered to be valuable for the utilization of CPW.     

Facile synthesis and electrochemical performances of hollow graphene spheres as anode material for lithium-ion batteries

The hollow graphene oxide spheres have been successfully fabricated from graphene oxide nanosheets utilizing a water-in-oil emulsion technique, which were prepared from natural flake graphite by oxidation and ultrasonic treatment. The hollow graphene oxide spheres were reduced to hollow graphene spheres at 500°C for 3 h under an atmosphere of Ar(95%)/H₂(5%). The first reversible specific capacity of the hollow graphene spheres was as high as 903 mAh g^-1 at a current density of 50 mAh g^-1. Even at a high current density of 500 mAh g^-1, the reversible specific capacity remained at 502 mAh g^-1. After 60 cycles, the reversible capacity was still kept at 652 mAh g^-1 at the current density of 50 mAh g^-1. These results indicate that the prepared hollow graphene spheres possess excellent electrochemical performances for lithium storage. The high rate performance of hollow graphene spheres thanks to the hollow structure, thin and porous shells consisting of graphene sheets.

PACS

81.05.ue; 61.48.Gh; 72.80.Vp     

二硫化钼复合导电碳作为高性能钠离子电池负极材料的研究

通过水热法制备出导电碳负载的二硫化钼纳米片（MoS2@C），显著改善了二硫化钼循环稳定性和倍率性能：在0.1 A/g电流密度下，循环100次后，可逆比容量依然高达466.3 mA·h/g，容量保持率达90.6%；在10 A/g的电流密度下，可逆比容量高达321.5 mA·h/g；在1A/g电流密度下长循环500次后，可逆比容量为313 mA·h/g，未发生衰减。这是因为二硫化钼以导电碳作为基底后，既可以提高电子和钠离子在复合材料中的扩散效率，又可以抑制二硫化钼的团聚，另外，小尺寸的二硫化钼可以缩短钠离子的传递路径，之间的空隙为二硫化钼体积的膨胀提供了空间。通过对两个电极的动力学分析，发现钠离子在MoS2@C内部具有更高的扩散效率，赝电容控制行为是MoS2@C电极具有优异倍率性能的主要原因。     

Effect of melting and crystallization on the conductive network in conductive polymer composites

Investigation on the effect of melting and crystallization of polypropylene (PP) on the conductive network of multi-wall carbon nanotubes (MWNTs) and carbon black (CB) in MWNT/PP and CB/PP composites is performed. The conductive networks formed by fillers with different aspect ratios (MWNTs and CB) are compared during melting and cooling experiments. The network is found to be deformed during melting and re-constructed again due to the re-agglomeration of fillers during isothermal annealing of the melt. Both deformation and re-construction of the network result in a substantial increase/decrease of the thermal resistivity of MWNT/PP and CB/PP composites. For the modelling of the dynamic network reformation three different approaches are tested: classic percolation theory, general effective medium theory (GEM) and Fournier equation.     

Electrochemical performance of Li4Ti5O12 anode material synthesised using polyethylene glycol as a template agent

Low capacity and rate performance are important factors restricting the development of Li₄Ti₅O₁₂ (LTO). The addition of an appropriate amount of polyethylene glycol (PEG) is an effective method to increase the capacity and rate performance of LTO anode material. In this study, LTO anode material was synthesised by the sol–gel method using PEG as a template agent. X-ray diffraction (XRD) results show that the addition of PEG can improve the crystallinity of the material and retain the spinel lattice type of LTO. Scanning electron microscopy (SEM) results show that the addition of an appropriate amount of PEG can promote the formation of a more uniform and much finer morphology. The results of high-resolution transmission electron microscopy (HRTEM) show that the material with PEG had good crystallinity. The charge and discharge data verify that the electrochemical performance of the material could be improved by adding PEG. P2-LTO exhibits a smaller particle size, largest capacity, best cycling performance and best rate performance. The capacity of P2-LTO at 0.2C can reach 224.3 mAgh^?1, which is much higher than the theoretical specific capacity of LTO (175 mAgh^?1). The discharge capacity of P2-LTO in the first cycle at 10C is 178.9 mAgh^?1. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) show that the electrode polarisation and electrochemical impedance of P2-LTO were lower than that of pure LTO. Better capacity and rate performance can be obtained by adding PEG as a template agent to a LTO system. It is a simple and effective method to produce high-performance LTO anode materials.     

Effect of synthesis temperature on the phase structure,morphology and electrochemical performance of Ti3C2 as an anode material for Li-ion batteries

Ti₃C₂, the most widely studied MXene, was successfully synthesised by etching Al layers from Ti₃AlC₂ in HF solution. Given its distinct 2D layered structure, Ti₃C₂ is a promising anode material in Li-ion batteries because of its efficient ion transport, available large surface areas for improved ion adsorption and fast surface redox reactions. Herein, the effects of synthesis temperature on the phase structure, morphology and electrochemical performance were investigated. The materials synthesised at different temperatures were characterised by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Optimal etching occurred at 100?°C, and the synthesised Ti₃C₂ exhibited smooth surface and large layer space. The synthesised Ti₃C₂, as anode material for Li-ion batteries, can accommodate more Li⁺ than those of others, and it exhibits the most ideal electrochemical performance.