Over the past few decades, two-dimensional (2D) and layered materials have emerged as new fields. Due to the zero-band-gap nature of graphene and the low photocatalytic performance of MoS2, more ...advanced semiconducting 2D materials have been prompted. As a result, semiconductor black phosphorus (BP) is a derived cutting-edge post-graphene contender for nanoelectrical application, because of its direct-band-gap nature. For the first time, we report on robust BP@TiO2 hybrid photocatalysts offering enhanced photocatalytic performance under light irradiation in environmental and biomedical fields, with negligible affected on temperature and pH conditions, as compared with MoS2@TiO2 prepared by the identical synthesis method. Remarkably, in contrast to pure few layered BP, which, due to its intrinsic sensitivity to oxygen and humidity was readily dissolved after just several uses, the BP@TiO2 hybrid photocatalysts showed a ~92% photocatalytic activity after 15 runs. Thus, metal-oxide-stabilized BP photocatalysts can be practically applied as a promising alternative to graphene and MoS2.
Flash sintering of strontium titanate (SrTiO3) is studied at different applied fields to understand its effect on density and grain growth. In particular, the defect structure is investigated by ...optical and structural analysis. SrTiO3 exhibited a trend in densification opposite that of ionically or electronically conductive ceramics: as the applied voltage decreased, the density increased. Abnormal grain growth in conventionally sintered SrTiO3 is arrested by flash sintering. Interestingly, undoped SrTiO3 behaved differently than undoped Al2O3, which did not exhibit any signs of flash sintering. Previous attempts at flash sintering could only be achieved in MgO‐doped Al2O3. We believe that non‐stoichiometric Ruddlesden‐Popper phases in SrTiO3, as indicated by ultrafast optical spectroscopy, X‐ray diffraction, conductivity measurements, and transmission electron microscopy, assist flash sintering by increasing local conductivity through enhanced defect content.
Non-toxic hypergolic propellants have considerably generated recent research interest in the field of green propulsion technology because they can replace highly toxic hypergolic combinations ...currently used. In this experimental research, sodium borohydride-based non-toxic hypergolic fuel was prepared by blending sodium borohydride in the mixture of energetic hydrocarbon solvents. In a drop test, sodium borohydride as an ignition source enabled the hydrocarbon mixture to initiate hypergolic interactions with H2O2 oxidizer. Two different heating methods were utilized to analyze the characteristics of autoignition and combustion of the hypergolic fuel. As a reference fuel, a non-hypergolic fuel which has the identical chemical compositions to the hypergolic fuel except for sodium borohydride was tested and compared. As a one of the heating methods, thermogravimetric analysis was not suitable for evaluating the inherent thermophysical properties of the hypergolic fuel. In a droplet combustion chamber test, the autoignition and combustion of the hypergolic fuel droplets occurred exposed to elevated temperatures (in a range of 400–800°C) at atmospheric pressure (1bar), whereas the non-hypergolic fuel droplet was automatically ignited only at 800°C. The ignition delay and total combustion time of the hypergolic fuel droplet were lower than those of the non-hypergolic fuel droplet. According to the temporal histories of the droplet size, sodium borohydride-based hypergolic fuel droplets did not obey the d2-law of diffusion-controlled combustion, which indicates the droplet evaporation rate was not a controlling factor in the combustion process. Consequently, the addition of sodium borohydride into the hydrocarbon mixture expedited the autoignition and combustion process of the fuel at elevated temperatures.
Diesel fuel exhibits excellent combustion characteristics and stability. However, diesel use is becoming restricted because of its associated environmental problems. Fuel emulsification, which ...increases efficiency and reduces pollution, became the solution of environmental problem. In this study, five water:diesel emulsions with mass ratios (0.3, 0.6, 1.0, 1.2, and 1.5) via ultrasonication were synthesized with and without surfactant. The optimal water:diesel ratio (=1:1) of an emulsion containing the surfactant was found by analyzing fuel concentration, mixing time, and viscosity. The combustion characteristics of single-droplet optimal emulsions were studied through ignition delay, burning rate, and total droplet lifetime at high temperature (400–700 °C) and pressure (1–15 bar), and micro-explosion phenomenon was observed. Although the ignition delay of emulsion increased, the total lifetime of the emulsion droplet was lower than that of diesel under 5 bar, 600 °C condition.
We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were ...prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) - approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) - resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications.
Autoignition of an ethanol-based gel droplet was experimentally investigated by adding 10 wt % of methylcellulose as gellant to liquid ethanol. Experimental studies of the ignition behavior of the ...gel droplet were found to be quite rare. The initial droplet diameter was 1.17 ± 0.23 mm. The gel droplet was suspended on a K-type thermocouple and its evaporation, ignition and combustion characteristics were evaluated and compared with pure ethanol at an ambient temperature of 600, 700, and 800 °C under atmospheric pressure conditions. The gel droplet exhibited swelling and vapor jetting phenomena. Before ignition, a linear decrease in droplet diameter followed by a sudden increase was repeatedly observed, which was caused by evaporation and swelling processes, respectively. Major droplet swelling was detected just before the onset of ignition at all temperatures. But no further swelling was detected after ignition. For the gel droplet, the ignition delay accounted for 93% of the droplet lifetime at 600 °C, and 88% at 700 °C, but only 31% at 800 °C. Its average burning rate was also evaluated for all temperatures. At 800 °C, the gellant layer no longer exerts any influence on the combustion of the gel droplet.
Effects of the thickness of copper phthalocyanine (CuPc) film (2, 5, 10, 15, 20, 30 and 40 nm) on the surface morphology, optical and electrical properties of Au/CuPc/n-Si heterojunction have been ...investigated. The optical band gap of CuPc film was increased with increase in the thickness of the CuPc film. The electrical properties of the Au/n-Si Schottky junction and Au/CuPc/n-Si heterojunctions were characterized by current–voltage (
I–V
) and capacitance–voltage (
C–V
) measurements. The barrier height, ideality factor and series resistance were estimated based on the
I–V
, Cheung’s and Norde’s methods. The barrier heights increased with increasing CuPc interlayer thickness up to 15 nm and remained constant for thickness above 20 nm, associated with the incapability of the generated carriers to reach the interface. The discrepancy in the barrier heights obtained from
I–V
and
C–V
measurements indicates the presence of barrier inhomogeneity at the interface as evidenced by higher ideality factor values. It can be concluded that the electrical properties of Au/n-Si Schottky junction can be significantly altered with the variation of CuPc thickness as interlayer.
The effect of swift heavy ions (SHI) on magnetic ordering in ZnS thin films with Co ions substituted on Zn sites is investigated. The materials have been synthesized by pulsed laser deposition on ...substrates held at 600°C for obtaining films with wurtzite crystal structure and it showed ferromagnetic ordering up to room temperature with a paramagnetic component. 120MeV Ag ions have been used at different fluences of 1×1011ions/cm2 and 1×1012ions/cm2 for SHI induced modifications. The long range correlation between paramagnetic spins on Co ions was destroyed by irradiation and the material became purely paramagnetic. The effect is ascribed to the formation of cylindrical ion tracks due to the thermal spikes resulting from electron–phonon coupling.
► Effect of swift heavy ions on magnetic ordering in Co doped ZnS thin films are presented. ► Magnetization in the pristine films is composed of ferromagnetic and paramagnetic components. ► The films become purely paramagnetic after swift heavy ions irradiation. ► The magnetic transition is ascribed to the formation of ion track (or cylindrical defects) due to the thermal spikes.
In this study, experiments were conducted to investigate the combustion characteristics of an water-in-oil W/O emulsion droplet under elevated temperature and pressure conditions. The base fuel used ...was n-decane, and total volume ratios of 10, 20, and 30% of distilled water were mixed for producing the emulsion fuel. Span 80 with a volume ratio of 2% was added as a surfactant, and the emulsion fuel was homogeneously mixed via ultrasonication. The combustion process of an emulsion droplet was divided into five stages: droplet heating, classical combustion, puffing, secondary classical combustion, and surfactant combustion. The ignition delay decreased with elevated ambient temperatures, whereas an increase in the ambient pressure and water volume ratio resulted in longer ignition delays. The droplets did not ignite in 500 °C or 600 °C conditions at 1 bar because of the significant Stefan flow of fuel vapor. After droplet ignition, the droplet combustion process, including classical combustion, puffing, and surfactant combustion, followed. The average burning rate increased with ambient pressure, but it was insensitive to ambient temperatures and water volume ratios. After flame extinction, a secondary flame reappeared because of the combustion of surfactant and residues.
•Combustion of a water/n-decane fuel emulsion droplet at high pressure and temperature condition was studied.•Changes of ignition delay and combustion stage of emulsion fuel droplet were observed.•The changes of average burning rate in experimental conditions were discussed.
•Evaporation of a water/n-decane fuel emulsion droplet in various temperature and pressure conditions was studied.•Changes of evaporation characteristics including droplet inflation and ...micro-explosion were observed.•Occurrence of droplet inflation and micro-explosion in various temperature and pressure conditions were discussed.
The evaporation characteristics of water/n-decane emulsion droplet at various temperatures and pressures were experimentally observed. Emulsion fuel was made by adding pure water to the base n-decane fuel with a volume ratio of 0.2. Span 80 was used as a surfactant, and ultrasonification was conducted for the mixing process. The temporal variation of the droplet diameter was optically observed by using a high-speed camera, and the changes in droplet temperature were also measured. The evaporation process of emulsion droplets was divided into three stages, namely, droplet heating, inflation/puffing, and pure evaporation. As the ambient temperature increased, the behavior of droplet inflation shifted to puffing during the inflation/puffing stage. A decline in the inflation/puffing incidence rate was noted at high-pressure conditions. The evaporation rate during the pure evaporation stage and the overall droplet lifetime were affected by the ambient temperature but not by the ambient pressure. The inflation of the droplet mostly occurred at relatively lower temperature and pressure conditions; it changed to puffing, however, at higher temperature and pressure conditions.
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