Huarui Xu

Biomorphic Synthesis of Mesoporous Co3O4 Microtubules and Their Pseudocapacitive Performance

A novel meosoporous tubular Co3O4 has been fabricated by a simple and cost-effective biomorphic synthesis route, which consists of infiltration of cotton fiber with cobalt nitrate solution and postcalcination at 673 K for 1 h. Its electrochemical performance as a supercapacitor electrode material is investigated by means of cyclic voltammetry and chronopotentiometry tests. Compared with bulk Co3O4 prepared without using cotton template, biomorphic Co3O4 displays 2.8 fold enhancement of pseudocapacitive performance because of the unique tubular morphology, relative high specific surface area (3 and 0.8 m(2)/g for biomorphic Co3O4 and bulk Co3O4, respectively), and mesoporous nature.

Elucidation of carrier injection and recombination characteristics with impedance and capacitance in organic light-emitting diodes and the frequency effects

Impedance (Z), phase (φ) and capacitance (C) versus bias voltage (V) characteristics are studied to clarify carrier injection and recombination characteristics in organic light-emitting diodes (OLEDs). The Z–V transition starts at a characteristic voltage (Vc), which is strongly frequency dependent, i.e. Vc shifts to a high voltage with increasing measuring frequency. The electron–hole recombination starts at a voltage above Vc revealed by the φ–V and C–V transitions, which correspond to a phase approaching 0, a sharp rise in current density and a decrease in capacitance. Hole injection starts at a low Vc and corresponds to charge carrier accumulation and a slight rise in capacitance. Cole–Cole impedance plots illustrate that the interfacial resistance corresponds to the impedance at ultrahigh frequencies and shows bias independence, while the impedance at low frequencies represents the sum of interfacial resistance and organic stacks, and exhibits considerable bias dependence.

Supercapacitive properties of Mn3O4 nanoparticles bio-synthesized from banana peel extract

A green approach to the synthesis of Mn3O4 nanoparticles using banana peel extract as both reducing and capping agent has been described. The as-obtained Mn3O4 electrode exhibits acceptable electrochemical performance (216 F g−1 at 0.3 A g−1, 93% capacity retention after 2000 cycles).

Sintering behavior and refining grains of high density tin doped indium oxide targets with low tin oxide content

High density indium tin oxide (ITO) ceramic targets with low SnO2 content were prepared successfully by sintering co-precipitationally synthesized powders. The sintering behavior, properties and refining grains of the ITO targets were studied in normal pressure oxygen ambience. Higher sintering temperature promoted sintering densification, resulted in abnormal grain growth and decreased bending strength. By a two-step sintering method, the uniform and fine-grained microstructures were obtained. The sintered density of the ITO targets was further improved. Furthermore, the grain size was reduced, and the bending strength was also enhanced.

Effect of Target Density on Microstructural, Electrical,and Optical Properties of Indium Tin Oxide Thin Films

In this paper, indium tin oxide (ITO) targets with different densities were used to deposit ITO thin films. The thin films were deposited from these targets at room temperature and annealed at 750°C. Microstructural, electrical, and optical properties of the as-prepared films were studied. It was found that the target density had no effect on the properties or deposition rate of radiofrequency (RF)-sputtered ITO thin films, different from the findings for direct current (DC)-sputtered films. Therefore, when using RF sputtering, the target does not require a high density and may be reused.

Mesoporous ZnMn2O4 Microtubules Derived from a Biomorphic Strategy for High-Performance Lithium/Sodium Ion Batteries

ZnMn2O4 microtubules (ZMO-MTs) with a mesoporous structure are fabricated by a novel yet effective biomorphic approach employing cotton fiber as a biotemplate. The fabricated ZMO-MT has approximately an inner diameter of 8.5 μm and wall thickness of 1.5 μm. Further, the sample of ZMO-MT displays a large specific surface area of 48.5 m2 g-1. When evaluated as a negative material for Li-ion batteries, ZMO-MT demonstrates an improved cyclic performance with discharge capacities of 750.4 and 535.2 mA h g-1 after 300 cycles, under current densities of 200 and 500 mA g-1, respectively. Meanwhile, ZMO-MT exhibits superior rate performances with high reversible discharge capacities of 614.7 and 465.2 mA h g-1 under high rates of 1000 and 2000 mA g-1, respectively. In sodium ion batteries applications, ZMO-MT delivers excellent high discharge capacities of 102 and 71.4 mA h g-1 after 300 cycles under 100 and 200 mA g-1, respectively. An excellent rate capability of 58.2 mA h g-1 under the current density of 2000 mA g-1 can also be achieved. The promising cycling performance and rate capability could be benefited from the unique one-dimensional mesoporous microtubular architecture of ZMO-MT, which offers a large electrolyte/electrode accessible contact area and short diffusion distance for both of ions and electrons, buffering the volume variation originated from the repeated ion intercalation/deintercalation processes.