Increase In Oxide Concentration Research Articles

Iron dust explosion characteristics with small amount of nano-sized Fe2O3 and Fe3O4 particles

Iron powder, as one of the most abundant metal fuels that can be used as recyclable carriers of clean energy, is a promising alternative to fossil fuels in a future low-carbon economy. It may pose a potential explosion hazard during the process of processing, storage, transport, and reduction/oxidation (redox). The explosion characteristics of iron dust in air were undertaken via a 20 L spherical explosion chamber with an emphasis on minimum explosion concentration (MEC) of iron dust. The alternative method of combustion duration time (tc) was used to determine MEC and compared with the standardized over pressure method. Two kinds of nano-sized iron oxides (Fe2O3 and Fe3O4) were used as inertants to determine the inhibition effect of different oxidation products. The iron dust explosion products with various shapes and sizes were found to be able to grow up 4–6 times of the iron dust for the first time. Adding small amount of Fe2O3 or Fe3O4 could reduce the explosion severity and sensitivity of iron dust. The MEC data determined by both methods were comparable. The addition of 5 % oxide has obvious inhibition effect under 1500 g/m3 concentration. With the increase of oxide concentration to 10 %, the inerting effect increases, and the MEC of iron dust increases more than 3 times. The increase of dust concentration will weaken the inerting effect. When the concentration increases from 500 g/m3 to 3000 g/m3, the weakening effect of 10 % Fe2O3 on the explosion pressure decreases from 38.45 % to 2.24 %, and 10 % Fe3O4 decreases from 46.21 % to 10.63 %. Unlike coal, biomass or aluminum dusts, the iron dust explosion was found to have a unique secondary acceleration of pressure rise rate for the first time. These results provide a fundamental basis to mitigate the iron dust explosion via solid inerting method without adding extra elements.

Study on Oxidant in Chemical Mechanical Polishing of Copper

In this paper, the polishing experiment of copper was carried out. According to the experimental data, when FeCl3 was selected as oxidant, the material removal rate increases gradually with the increase of oxidant concentration. When other conditions remain unchanged, the material removal rate with larger abrasives was higher than that of smaller abrasives, and the material removal rate of pressure 3 psi was higher than that of pressure 2 psi, and the surface roughness became smaller and smaller. When the abrasive size was 1 µm, oxidant concentration was 5 g/L and the pressure was 3 psi, the material removal rate reaches 206.9 nm/min and the surface roughness reached 8 nm. When the type of oxidant was chosen as the variable, the material removal rate of the mixture of FeCl3 and H2O2 was the highest, the maximum removal rate was 105.45 nm/min when the abrasive size was 1 µm and polishing speed was 80 r/min. The surface roughness was the smallest when FeCl3 was used as oxidant and Ra reaches the smallest 5 nm under the conditions of the abrasive size was 1 µm and polishing speed 80 r/min. The results can be used as a reference for further research the ingredients of polishing slurry in the chemical mechanical polishing of copper.

Flavonoid loaded nanoparticles as an effective measure to combat oxidative stress in Ribonuclease A

Flavonoids like quercetin and myricetin serve as naturally occurring antioxidants but their bioactivity is limited due to low aqueous solubility and oxidation under physiological conditions. In this current study, the antioxidant activity of quercetin and myricetin loaded chitosan nanoparticles during the induced oxidation of Ribonuclease A (RNase A) has been compared with the corresponding free flavonoids. Oxidation of RNase A leads to intermolecular dityrosine (DT) bond formation which shows a characteristic fluorescence emission around 405 nm. Although both quercetin and myricetin loaded nanoparticles initially exhibit lower antioxidant property compared to the free flavonoids, however, with increase in oxidant concentration over time the DT fluorescence showed greater increase for free flavonoids in comparison to the nanoparticles. The polyphenol loaded nanoparticles are also found to be effective in preventing bacterial cell damage in oxidizing medium. The slow release of flavonoids from the nanoparticles is responsible for their prolonged antioxidant effect in the oxidizing medium unlike the free flavonoids which are exhausted almost completely in the initial phase.

Evaluation of a dichromate oxidation method for the isolation and quantification of black carbon in ancient geological samples

The dichromate oxidation method is widely used in measurements of black carbon (BC) in geological sediments. The separation of organic carbon (OC) and BC is a critical step in the procedure. A comprehensive evaluation of the dichromate oxidation method was conducted using three types of kerogen with different maturities and two charcoal samples. The residues of each kerogen/BC oxidized under different conditions were quantified to determine the remaining C content. The results showed that the traditional dichromate oxidation method (0.1 M K2Cr2O7/2 M H2SO4) was reliable when the geological sediments contained a Type I kerogen with low maturity (Ro ≤ 0.50%). We compared the dichromate oxidation method under different oxidation times and oxidant concentrations for the separation of OC and BC. The extension of oxidation time improved the removal of all three types of kerogen, but Type I kerogen with high maturity and Types II and III kerogen, still significantly interfered with the isolation of BC in geological sediments. The concentrations of oxidant necessary were tested and indicated that an increase in oxidant concentration significantly improved the separation of BC and OC, and a high concentration of 0.5 M K2Cr2O7/2 M H2SO4 and 300 h oxidation time at 55 °C was effective for the isolation of BC in geological samples. The results of this study also indicated that the stable C isotope values of the remaining C were not affected by the isolation of BC with the dichromate method and that the method can therefore be used for the stable C isotope measurements of BC in geological sediments.

Synergistic degradation of PNP via coupling H2O2 with persulfate catalyzed by nano zero valent iron.

H2O2 and persulfate (PDS) activated by iron are attracting much attention due to their strong oxidation capacity for the effective degradation of organic pollutants. However, they face problems such as requiring an acidic reaction pH and difficulty of Fe2+ regeneration. In this study, the simultaneous activation of H2O2 and persulfate by nanoscaled zero valent iron (nZVI) was investigated for the degradation of p-nitrophenol (PNP). The nZVI/H2O2/PDS oxidation system exhibited significantly higher reactivity toward PNP degradation than the systems with a single oxidant. A synergistic effect was explored between H2O2 and PDS during nZVI-mediated activation, and the molar ratio of H2O2/PDS was a key parameter in optimizing the performance of PNP degradation. The nZVI/H2O2/PDS system could function well in a wide pH range, and even 95% PNP was removed at an initial pH 10, thus markedly alleviating the pH limitations of Fenton-like processes. Both hydroxyl radicals and sulfate radicals could be identified during H2O2/PDS activation, in which H+ produced during PDS decomposition promoted H2O2 activation. The increase of oxidant concentration could significantly enhance the PNP degradation, while the presence of HCO3− and HPO42− exerted great inhibition. Furthermore, five degradation intermediates of PNP were detected and its degradation pathways in the nZVI/H2O2/PDS system were presented. This study reveals that the simultaneous activation of H2O2 and PDS by nZVI is a promising advanced oxidation tool as an alternative to typical Fenton processes for recalcitrant pollutant removal.

Effect of slide to roll ratio on the micropitting behaviour in rolling-sliding contacts lubricated with ZDDP-containing lubricants

Abstract An automated micropitting test rig was applied to study the effect of slide to roll ratio (SRR) on micropitting behaviour in rolling-sliding contacts lubricated with Zinc Dialkyl Dithiophosphate (ZDDP) containing lubricants. The tested specimen surface was examined under an optical microscope and Scanning Electron Microscope(SEM) to study the micropitting behavior of the surface, followed by applying X-ray Photoelectron Spectroscopy(XPS) to study the related tribochemistry behavior. The results show that the increase of SRR can reduce the number of micropits on the worn surface while wear increased and friction did not change much. XPS results indicate that the increase of SRR resulted in the increase of oxide concentration while the decrease of film thickness on the worn surface.

Preparation of conductive silk fibroin yarns coated with polyaniline using an improved method based on in situ polymerization

In situ polymerization is a prominent current topic in the research of skin-core structure polyaniline (PANI) conductive fibers owing to its advantages such as the convenience of preparation and high conductivity of fiber, but it is difficult to realize the continuous fabrication of conductive fibers using this method. In our previous work, we presented a novel method based on in situ polymerization and achieved the continuous fabrication of conductive yarns. In order to reduce the consumption of raw materials such as aniline, doping acid, and oxidant in the preparation, a further improvement is proposed in this paper. Electrical conductive silk fibroin (SF) yarns covered with PANI were prepared by using an improved method based on in situ polymerization. The results show that the improved method has lower consumption than the previous method, and the reduction of raw materials can reach more than 90% compared to the previous method. The structure and properties of the treated SF yarns were studied in detail. The treated SF yarns characterized using scanning electron microscopy and Fourier transform infrared spectroscopy improved the surface of the SF fibers and the gaps between them were covered by conductive PANI; further, interactions such as van der Waals' force, electrostatic interaction, and hydrogen bonding existed between the SF macromolecules and PANI. Thermogravimetric analysis indicated that the thermal stability of the treated yarns was reduced owing to the existence of PANI. The treated yarns exhibited good conductive properties; with the increase in oxidant concentration, the conductivity of coated yarns increased first and thereafter decreased; the maximum conductivity of coated yarn could reach 60S/m, and the maximum conductivity of PANI was as high as 180S/m. Compared to the SF yarn, the breaking strength, breaking elongation, and initial modulus of coated yarns were reduced and the loss was increased with the increase in oxidant concentration.

The Application of Buckingham π Theorem to Modeling Polypyrrole Synthesis done by Chemical Oxidative Polymerization

Buckingham π theorem was applied to model polypyrrole synthesis done by inverse emulsion polymerization route using Methanesulfonic acid as a dopant and potassium persulfate as an oxidant. A list of independent parameters on which polymerization depends was selected and by means of Buckingham theorem a functional relation between three dimensionless quantities; percent yield, conductivity and temperature was obtained. The actual form of the function was determined on the basis of experimental analysis and linear regression analysis. The accuracy of the proposed application was scrutinized by synthesizing pristine polypyrrole salt by the said polymerization route. It was corroborated from the experiment that the increase in percent yield and conductivity was directly proportional to the increase in oxidant concentration. Conductivity as high as 3.77 S/cm was obtained with a maximum percent yield of 94.54% at a moderate temperature range (293 K-298 K).

Functionalized nanocrystalline cellulose: Smart biosorbent for decontamination of arsenic

This study explored the adsorption capacity of diethylene triamine grafted dialdehyde nanocrystalline cellulose (DETA-g-DA-NCC) for As (III and V) removal from aqueous solution. Nanocrystalline cellulose (NCC) was selectively oxidized using sodium periodate followed by grafting of diethylene triamine (DETA) to obtain their amine derivatives in 80–85% yield. A corresponding increase in carbonyl content of the dialdehyde nanocrystalline cellulose (DA-NCC) with the increase in oxidant concentration was measured by titrimetric analysis and was evidenced by FT-IR spectroscopy. Morphological integrity and crystallinity of the NCC were maintained after the functionalization as studied by AFM, SEM and XRD, respectively. The effect of various operational parameters such as arsenic ion concentration, pH, biosorbent dosage and time was investigated using batch experiments and found that DETA-g-DA-NCC can be used as a cost effective biosorbent for decontamination of arsenic. The experimental data were analyzed by Langmuir, Freundlich, Temkin and Dubinin–Redushkevich (D–R) models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm. The kinetic data were fitted very well in the pseudo-second-order kinetic model and suggested that the chemisorptions were the rate-limiting step. The results indicate that there is significant potential for DETA-g-DA-NCC as a biosorbent for arsenic removal [As(III) 92.84% and As(V) 97.86%] from aqueous solutions.

Synergic effect of chelating agent and oxidant on chemical mechanical planarization

Chemically dominant alkaline slurry, which is free of BTA (benzotriazole) and other inhibitors, was investigated. The synergic effect of the chelating agent and oxidant on the chemical mechanical planarization (CMP) was taken into consideration. Copper CMP slurry is mainly composed of an oxidizer, nonionic surfactant, chelating agent and abrasive particles. The effect of different synergic ratios of oxidant with chelating agent on the polishing removal rate, static etch rate and planarization were detected. The planarization results reveal that with the increase of oxidant concentration, the dishing value firstly diminished and then increased again. When the synergic ratios is 3, the dishing increases the least. A theoretical model combined with chemical-mechanical kinetics process was proposed in the investigation, which can explain this phenomenon. Based on the theoretical model, the effect of synergic ratios of oxidant with chelating agent on velocity D-value (convex removal rate minus recessed removal rate) was analyzed. The results illustrate that when the synergic ratio is between 2.5–3.5, the velocity D-value is relatively higher, thereby good planarization can be achieved in this interval. This investigation provides a new guide to analyze and study copper line corrosion in the recessed region during copper clearing polishing.

Surface and interfacial reaction study of InAs(100)-crystalline oxide interface

A crystalline oxide film on InAs(100) is investigated with in situ monochromatic x-ray photoelectron spectroscopy and low energy electron diffraction before and after in situ deposition of Al2O3 by atomic layer deposition (ALD) as well as upon air exposure. The oxidation process leads to arsenic and indium trivalent oxidation state formation. The grown epitaxial oxide-InAs interface is stable upon ALD reactor exposure; however, trimethyl aluminum decreases oxidation states resulting in an unreconstructed surface. An increase in oxide concentration is also observed upon air exposure suggesting the crystalline oxide surface is unstable.

Spray-Pyrolyzed Three-Dimensional CuInS2 Solar Cells on Nanocrystalline-Titania Electrodes with Chemical-Bath-Deposited Inx(OH)ySz Buffer Layers

Three-dimensional (3D) compound solar cells with the structure of <Au/CuInS2/Inx(OH)ySz/porous TiO2/compact TiO2/florin-doped tin-oxide-coated glass plates> have been fabricated by spray pyrolysis deposition of CuInS2 and chemical-bath deposition of Inx(OH)ySz for the light absorber and buffer layer, respectively. The effect of deposition and annealing conditions of Inx(OH)ySz on the photovoltaic properties of 3D CuInS2 solar cells was investigated. Inx(OH)ySz annealed in air ambient showed a better cell performance than those annealed in nitrogen ambient and without annealing. The improvement of the performance of cells with Inx(OH)ySz buffer layers annealed in air ambient is due to the increase in oxide concentration in the buffer layers [confirmed by X-ray photoelectron spectroscopy (XPS) measurement]. Among cells with Inx(OH)ySz buffer layers deposited for 1, 1.5, 1.75, and 2 h, that with Inx(OH)ySz deposited for 1.75 h showed the best cell performance. The best cell performance was observed for Inx(OH)ySz deposited for 1.75 h with annealing at 300 °C for 30 min in air ambient, and cell parameters were 22 mA cm-2 short-circuit photocurrent density, 0.41 V open-circuit voltage, 0.35 fill factor, and 3.2% conversion efficiency.

Aggregation Kinetics of Metal Chalcogenide Nanocrystals: Generation of Transparent CdSe(ZnS) Core(shell) Gels.

Transparent CdSe(ZnS) sol-gel materials have potential uses in optoelectronic applications such as light emitting diodes (LEDs) due to their strong luminescence properties and the potential for charge transport through the prewired nanocrystal (NC) network of the gel. However, typical syntheses of metal chalcogenide gels yield materials with poor transparency. In this work, the mechanism and kinetics of aggregation of two sizes of CdSe(ZnS) core(shell) NCs, initiated by removal of surface thiolate ligands using tetranitromethane (TNM) as an oxidant, were studied by means of time-resolved dynamic light scattering (TRDLS); the characteristics of the resultant gels were probed by optical absorption, transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). At low concentrations of NCs (ca. 4 × 10(-7) M), the smaller, green-emitting NCs aggregate faster than the larger, orange-emitting NCs, for a specific oxidant concentration. The kinetics of aggregation have a significant impact on the macroscopic properties (i.e. transparency) of the resultant gels, with the transparency of the gels decreasing with the increase of oxidant concentration due the formation of larger clusters at the gel point and a shift away from a reaction limited cluster aggregation (RLCA) mechanism. This is further confirmed by the analyses of the gel structures by SAXS and TEM. Likewise, the larger orange-emitting particles also produce larger aggregates at the gel point, leading to lower transparency. The ability to control the transparency of chalcogenide gels will enable their properties to be tuned in order to address application-specific needs in optoelectronics.

Room temperature synthesis and characterization of polythiophene thin films by chemical bath deposition (CBD) method

Polythiophene thin films were deposited successfully on glass substrate by chemical bath deposition method using FeCl 3 as an oxidant and chloroform as solvent. The effect of oxidant concentration on the properties of polythiophene thin films was studied. The surface morphology was influenced by oxidant concentration and deposition time. The oxidation concentration also strongly affects the optical properties of the polythiophene thin films. The transmittance decreases while the absorption, band gap and refractive index increases due to increase in oxidant concentration.

Characterization of poly (3-methyl thiophene) thin films prepared by modified chemical bath deposition

Poly (3-methyl thiophene) thin films were prepared by chemical bath deposition technique on glass substrate; the prepared thin films were characterized for structural, morphological and optical properties. The variation in the oxidant concentration has an influence on the properties of the P3MeT thin films. The increase in the oxidant concentration leads to increase in the thickness of the film. The binding energy increases due to increase in oxidation concentration. The P3MeT thin films show smooth surface morphology with increase in oxidant concentration whereas the contact angle of the thin film decreases with increase in oxidant concentration. The optical absorbance of these thin films was found to increase with decrease in the optical band gap due to increase in oxidant concentration.

Enhanced oxidative desulfurization of model fuels using a film-shear reactor

A film-shear reactor was used to enhance the oxidative desulfurization of thiophenes in fuels. With selected conditions, one pass of a model fuel through the film-shear reactor provided up to 55% removal of benzothiophene in only seconds at temperatures as low as 10 °C. Recirculation experiments showed that, if the flow rate and all other experimental parameters were held constant, the extent of thiophene removal increased as the residence time increased. Experiments using various concentrations of hydrogen peroxide and different fuel:oxidant ratios showed that, above a minimum amount, an increase in oxidant concentration did not lead to increased thiophene removal.

Iridium(III) catalyzed oxidation of toluene and ethyl benzene by cerium(IV) in aqueous acidic medium

Iridium(III) chloride catalyzed oxidation of toluene and ethyl benzene by cerium(IV) sulphate in aqueous sulphuric acid medium was studied. Change in the concentration of oxidant shows a specific effect that the rate increases in the beginning at low concentrations, it reaches to a maximum and further increase in oxidant concentration decreases the rate. Oxidation was highly selective as it oxidizes toluene to benzaldehyde and ethyl benzene acetophenone. It is proposed that the complex formed between cerium(IV) and the organic substrate in first equilibrium step gives another complex in the presence of iridium(III) which ultimately gives rise to products of oxidation. Order of the reaction follows first order kinetics at low concentrations tending to become zero order at higher concentrations of organic substrate in both the cases. Rate of the reaction follows direct proportionality with respect to catalyst concentrations, while the rate decreases sharply with increasing hydrogen ion and cerium(III) concentrations. Change in ionic strength of the medium and the effects of changing concentrations of acetic acid, Cl − ions, and HSO 4 − ions on the rate were studied. Energy of activation, free energy of activation and entropy parameters were also calculated.

Leaching of zinc sulfide concentrate from the ganesh-himal deposit of nepal

The leaching of zinc concentrate obtained from the zinc ore located in the Ganesh-Himal region of Nepal has been carried out in the presence of ammonium persulfate (APS) as an oxidant. Leaching variables such as time, temperature, acid, and oxidant concentration, E h , and particle size of sphalerite concentrate were studied to optimize the condition and to understand the mechanism of the reaction. The zinc extraction increased up to a temperature of 333 K and a further rise in the temperature to 343 K resulted in lowering of metal extraction. A decrease in particle size and increase in oxidant concentration enhanced the dissolution rate of zinc. The leaching data best fitted to the mixed controlled kinetic model. An activation energy of 43 kJ/mol was obtained for the dissolution of zinc in the temperature range 303 to 333 K with APS. The leaching mechanism was further established by characterizing the original concentrate and the leach residue by X-ray diffraction (XRD) phase identification and scanning electron microscopy (SEM) studies.

Change Of Photochemical OxidantConcentration By Increase Of VOCs EmissionFrom Vegetations Due To Global Warming

VOCs emission experiments were conducted in a growth chamber in which temperature and luminous intensity can be controlled. Temperature was set at the typical summer temperature in Osaka and luminous intensity was set at 1000(μmol/m/s) during daytime. The standard VOCs emissions from four representative Japanese plant species (Cryptomeria japonica, Chamaecyparis obtuse, Pinus densiflora and Quercus serrata) and rice plants were measured. The species distributions and their leaf biomass densities in the Kinki district were determined by the forest database and the use of a geophysical information system. Consequently, the detail emission distributions of isoprene and monoterpenes were estimated. Photochemical oxidant concentration was simulated by considering VOCs emissions from forests and paddy fields that changed with temperature and luminous intensity. The simulated results of NO, NO2 and O3 reasonably agreed with the observed data at 12 monitoring locations. The numerical experiment of temperature increment by 1C that causes both the increment of VOCs and the promotion of photochemical reaction, could represent the recent increase of oxidant concentration by global warming.

Annual and seasonal variations in oxidant concentration in Matsue, Japan

Abstract Annual and seasonal trends in surface oxidant concentrations were investigated between January 1989 and December 1997 at Matsue in the Japan Sea coastal margin where the westerly winds predominate. The mean value of oxidant concentration was 39.1 ppb during this period. The monthly oxidant concentrations in spring were at their annual maximum values, while those recorded in summer and autumn showed their lowest levels for the year as a whole. These seasonal variations were observed throughout the period. Oxidant concentrations above 80 ppb were observed between February and October, especially in April and May. Trajectory analysis indicated that when photochemical oxidant levels in excess of 80 ppb were observed in Matsue, the region was affected by a greater number of air masses flowing in from Korea and China than from other directions. The yearly mean oxidant concentration showed a steady annual increase at a rate of 0.89±0.21 ppb (or 2.0%: R =0.87) a year on average during this period. The rate of annual increase in oxidant concentration for the westerly wind (with Korea and China to the windward) was greater in comparison to SE-SW winds (with Japan to the windward). The deposition flux of nitric ion also showed an annual increase at a rate of 2.39±0.37 meq m −2 (or 5.9%: R =0.92) a year on average from 1989 to 1997. The NO x emissions have been rapidly increasing in the windward region. It can therefore be concluded that the elevated oxidant concentration in Matsue is due to an increase in the amount of NO x emissions in East Asia, especially in Korea and China to the west of Matsue.