Low Oxygen Ratio Research Articles

Quasi-vertical GaN heterojunction diodes with p-NiO anodes deposited by sputtering and post-annealing

Quasi-vertical GaN heterojunction diodes were fabricated with p-NiO anodes deposited by radio frequency magnetron sputtering. The influence of sputtering gas ratio on the quality of the NiO films was investigated and the crystalline quality of the NiO film is better at a lower oxygen ratio. The crystal structure, electrical and optical properties of the NiO thin films after post-deposition annealing (PDA) at various temperatures in oxygen ambient were evaluated. X-ray diffraction and optical results showed that the crystallinity of the NiO films was improved after annealing. With increasing PDA temperature, the carrier concentrations of the NiO films decreased and the bandgap became larger, which is ascribed to the out-diffusion of oxygen interstitial atoms. Moreover, high-performance NiO/GaN heterojunction PN diodes (HJPNDs) were obtained. The ideality factor and reverse voltage characteristics of the HJPNDs were enhanced with increasing PDA temperature. The hard breakdown voltage of the HJPND with PDA at 500 °C was 698 V without optimized termination techniques.

Investigation of rotating detonation fueled by the pre-combustion cracked kerosene

In this study, a method of pre-combustion cracking is adopted in the investigation of the rotating detonation fueled by kerosene. The basic characteristics of the rotating detonation wave (RDW) including the wave speed, pressure, and propagating modes are researched. The wave speed increases when the equivalence ratio is near the stoichiometric ratio, but it is little affected by the flow rates. Different to the wave speed performance, the pressure of the RDW tends to increase when the flow rates rise but show weak relation with the ER. Features and transition of the five rotating detonation modes including the two-co rotating waves, two-counter rotating waves, single-wave, pop-out and failure mode are investigated. The lean fuel boundary of the RDW is broadened with the increase of the flow rates. Also, the effect of the oxygen ratio (50% and 30%) of the oxidizer (oxygen-enriched air) on the characteristics of the RDW is investigated. The rotating detonation using oxidizer with the higher oxygen ratio has a better speed performance than with the lower oxygen ratio.

Mesoporous tubular graphene electrode for high performance supercapacitor

We report the fabrication of mesoporous tubular graphene (MTG) by a chemical vapor deposition method using MgO@ZnO core-shell structure as the template. The unique bi-directional ions transfer in unstack graphene layers and high mesopore ratio of MTGs allows capacitance reach 15μF/cm2 at 0.5A/g, and 11μF/cm2 at 10A/g, which is closer to theoretical value (21μF/cm2) than SWCNTs and DWCNTs at either low or high rate. Meanwhile, MTGs exhibited good structural stability, high surface area (701m2/g), high conductivity (30S/cm) and low oxygen ratio (0.7 atom%), allowing excellent SC performance. The 4V EDLC using MTGs and EMIMBF4 electrolyte exhibited high energy density in wide range of high power density and excellent cycling stability, showing strong potential in EDLC and other electrochemical energy storage systems, in addition, showing significant factor of ion transfer distance for high performance SCs especially operating at high voltage using ionic liquid electrolyte.

Ultra-Low NOx Oxygen-enriched Combustion System using Oscillation Combustion Method

In this study, Periodical combustion method was used to restrain NOx emission at oxygen-enriched combustion. This method periodically changes oxygen concentration in the oxidizer and the oxygen ratio at the same time by controlling the flow rate of air and oxygen periodically to keep same whole oxygen ratio condition of original stationary combustion. In other words, this method switches alternatively two states, state (A) high oxygen ratio with low oxygen concentration, and a state (B) low oxygen ratio with high oxygen concentration alternately. State (A) makes oxidizing atmosphere with relatively low flame temperature, and state (B) high flame temperature with reductive atmosphere.

Heat of explosion and acceleration ability of explosive–inorganic oxidizer mixtures

Experimental results have shown that the use of inorganic oxidizers (ammonium nitrate, ammonium perchlorate, and ammonium dinitramide) as additives does not lead to a considerable increase in the heat of explosion and acceleration ability of HMX. Ammonium perchlorate does not have an effect on the acceleration ability; however, it leads to an increase in the heat of explosion of triaminotrinitrobenzene. Calculations have shown that the acceleration ability of explosives with a low oxygen ratio can be increased through the formation of nanostructured composites with inorganic oxidizers. Calculations suggest that the addition of the studied oxidizers to CL-20 leads to a decrease in the acceleration ability of this promising explosive.

Characterization of Cu2O and Cu2O–Ag2O thin films synthesized by plasma oxidation

Cu2O and Cu2O–Ag2O thin films were synthesized by a plasma oxidation process on uncoated as well as Cu and Cu–Ag(4 at.%) thin-film coated Cu sheets, using an inductively coupled plasma system equipped with four internal antennas. During oxidation, a plasma probe and an optical emission spectrometer were used to characterize the plasma with the variation of O2/(Ar + O2) flow ratios. After oxidation, the structural phases and the growth rate of the oxidized layer were first examined. To compare the photo-electrical properties of Cu2O and Cu2O–Ag2O, the incident-photon-conversion-efficiency of the samples was measured. The results shows that the oxidation rate was increased with the increase of oxygen radicals (O*), which is attributed to the increase of plasma density. Deposited in low oxygen ratio, the oxidized films would have high deposition rate but with more complex structure. The coupling of Ag2O phase into Cu2O can enhance light absorption and create more electron–hole pairs due to the narrower band-gap structure of Ag2O. The effect of Ag2O phase on the enhanced photocurrent is discussed.

S082012 O_2/CO_2吹き2室2段噴流層石炭ガス化炉の数値解析([S082]高効率火力発電およびCCS技術)

A technology of carbon dioxide capture and storage (CCS) is the one of global warming countermeasure. As an oxidizer in advanced integrated coal gasification combined cycle (A-IGCC), the utilization of mixture gas including carbon dioxide (CO_2) and oxygen (O_2) is discussed. In the present study, a coal gasifier with two-stage entrained bed was numerically simulated to investigate the adaption of O_2/CO_2-blown system in gasifier. Thermal loss on the gasifier furnace wall was considered in this simulation. Because the reaction of coal gasification was promoted by CO_2, we can operate the gasifier system for low oxygen ratio compared with the conventional system. By the control of the reactor/total coal ratio, we can easily operate the gasifier system. At the O_2/CO_2-blown system, high level gas heating value was obtained and the operation range with safety combustion became wide. We can expect the enhancement of thermal efficiency of power generation and the reduction of reductor length for the operation of low oxygen ratio.

Shape controlled ZnO nanoparticle prepared by microwave irradiation method

ZnO nanoparticle was successfully prepared by microwave irradiation method in various oxygen/nitrogen ratio atmospheres. In the present method, steel wool was used as a heat generator by microwave irradiation. The highest heating rate of ∼200°C/sec for the reaction was achieved under the highest oxygen concentration, 80%, whereas the lowest hating rate was ∼40°C/sec. The product prepared in a low oxygen ratio atmosphere showed tetra pod shape with high aspect ratio, c/a. On the other hand, the product prepared under high oxygen ratio atmosphere was relatively isotropic. PL spectra of the products with the higher aspect ratios showed higher UV emission intensity than the products with low aspect ratios i.e. isotropic shape.