Presence Of Air Atmosphere Research Articles

Environmental stability and ageing of ScN thin films from XPS Ar+ depth profiling

A basic knowledge on chemical stability and reactivity of a wide band gap ScN semiconductor in the presence of air atmosphere, where O2 and H2O represent the main degradation or corrosive agents, is of vital importance for a long-term performance of ScN-based devices for thermoelectric applications. Here, we present a systematic XPS Ar+ depth profiling analysis and optical and TEM characterizations of naturally room temperature air-aged thin ScN films prepared by a high-temperature DC sputtering on MgO(001) and SiO2 substrates. We find that superior crystalline quality ScN/MgO films degrade weakly after their quick initial surface oxidation and/or hydrolysis. Their oxidation is rather local and associated with the film-penetrating void-like interfaces. Significant initial surface oxidation and subsequent bulk oxidation after ageing is, however, observed for polycrystalline ScN/SiO2 films. Ab initio calculations of pure ScN and ScN with diluted nitrogen vacancies and/or substitutional oxygen impurities, which assist our experimental research, reveal pronounced impact of these defects on the ScN electronic structure. The modeled compositions reflect homogeneously and weakly oxidized films, while the real films correspond to relatively pure ScN crystallites with interfaces rich in oxygen.

In-situ photochemical synthesis and dielectric properties of nanocomposite thin films containing Au, Ag and MnO nanoparticles

Thioxanthone-Anthracene (TX-A) was used as a one-component Type II photoinitiator for the photopolymerization of PEGMEA/PEGDA monomer mixture consisting of AgNO3, HAuCI4 and MnCI2 metallic salts. In this study, we have seen that nanoparticles (NPs) are distributed differently in solution and in polymer matrices and that the particle size also changes. The size of the AuNPs (8–16 nm) synthesized in the solution in the presence of air atmosphere is smaller than the AuNPs (18–25 nm) synthesized in the polymer matrix. It is also important to state the effect of the atmosphere on the shape and size of the NPs. Thanks to the endoperoxide formation in air atmosphere, the formation of AgNPs in the range of 45–53 nm is possible in solution, while the size of AgNPs increased up to 1900 nm in nitrogen atmosphere. Additionally, radical spin densities were calculated with Density Functional Theory to understand which radical is mainly responsible for the reduction of metal ions to form metal and metal oxide nanoparticles. Peroxy radicals were found to be mainly responsible due to their much higher electron spin density compared to the other radicals. Moreover, the dielectric properties of in-situ formed AuNPs, AgNPs and MnONPs in the nanocomposite films were investigated at room temperature. For all nanocomposite films containing metal NPs, the frequency dependent dielectric constant and dielectric loss are higher than the polymeric films up to about 50 times.

Exploring the effect of Co concentration on magnetic hyperthermia properties of CoxFe3−xO4 nanoparticles

Although enhanced ferrite nanoparticles (NPs) have been envisioned for use in future biomedical applications, less attempt has been made to tailoring and optimizing their detailed magnetic properties and specific loss power (SLP) values. Herein, CoxFe3−xO4 (0 ≤ × ≤ 1) NPs are synthesized using a co-precipitation method at 80 °C in the presence of air atmosphere. The effect of varying Co concentration on crystalline, morphological, magnetic and hyperthermia properties is also investigated in detail. Hysteresis loop measurements showed an increase in coercivity (Hc) from 7.75 to 340.50 Oe, and a decrease in saturation magnetization (Ms) from 59.10 to 32.70 emu g−1 with increasing x = 0 (pure magnetite) to x = 1 (pure Co ferrite), respectively. In addition to confirming the hysteresis loop results, first-order reversal curve (FORC) analysis estimated a 52% decrease in superparamagnetic (SP) fraction. Hyperthermia measurements carried out under an alternating magnetic field with intensity of 400 Oe and a frequency of 400 kHz showed an increase in SLP from x = 0 to x = 0.4, and a decrease in SLP for 0.4 < × ≤ 1. SLP was maximized at 395 W g−1 for the intermediate concentration of x = 0.4. The optimized heat generation of Co0.4Fe2.6O4 NPs comprising approximately 50%–50% SP–ferromagnetic fractions may result from the simultaneous contribution of the three following mechanisms: hysteresis loop loss, Brownian and Neel relaxation together with relatively high Hc and moderate Ms.

Spray drying formation of metal oxide (TiO2 or SnO2) nanoparticle coated boron particles in the form of microspheres and their physicochemical properties

In the present study, metal oxide (TiO2 or SnO2) nanoparticles were coated on boron particles using a facile spray drying technique. The coating of metal oxide nanoparticles on the boron surface was varied by changing the weight ratio of metal oxide nanoparticles to boron particles. The crystalline structure of the metal oxide nanoparticles was mainly retained without any additional phase formation on the metal oxide coated boron particles, as identified by XRD. FIB-SEM images showed that the TiO2 or SnO2 coated boron particles formed microspheres with diameters between 5 and 10 μm. FIB-cross sectional images indicated the microspheres had a porous structure, and every individual boron particle was coated by metal oxide nanoparticles. The line scanning profile, elemental mapping and corresponding EDAX spectra results indicated the boron particles were well coated with metal oxide nanoparticles, and confirmed the presence of respective elements in the samples, respectively. TEM study showed the fine coating of metal oxide nanoparticles on the surface of the boron particles. The surface elemental composition was identified with XPS, and revealed the strong interaction between the metal oxide and boron particles. The thermal behavior of the boron, metal oxide and metal oxide nanoparticle coated boron particles was studied in the presence of nitrogen and air atmosphere using thermogravimetric analysis. The TGA of the metal oxide nanoparticle coated boron particles showed enhanced oxidation-resistance performance in the presence of air atmosphere.

Gamma rays irradiation effects in thin film polyethylene terephthalate polymer

The effect of gamma rays irradiation on structural properties of polyethylene terephthalate (PET) has been studied using Fourier Transform Infrared Spectroscopy (FTIR), X-rays diffraction (XRD) and UV–Visible spectrophotometry techniques. The gamma rays irradiations were performed, using 60Co source with mean energy of 1.25 MeV, at Nuclear Research Centre of Algiers, Algeria. The gamma absorbed dose rate was about 1.3 kGy/h as measured using the Frick dosimeter. Several PET samples with a thickness of 6 μm were irradiated at room temperature with the presence of air atmosphere at different doses (0.05–5 MGy). The FTIR analysis reveals that the intensities of the different absorption bands decrease with increasing gamma rays dose. This is attributed to the chain scission induced by gamma rays irradiation. It is found from XRD analysis that the crystallinity is reduced after irradiation. The variation in crystallite size is also observed. The UV–vis spectra show a large absorption band extended from 310 to 355 nm assigned to the formation of extended systems of conjugate bonds with the creation of carbon clusters. The optical absorbance in this range increases linearly with the gamma rays dose. An empirical relation is established to estimate gamma dose from this correlation. Both direct and indirect energy gaps are found to decrease with increasing gamma rays dose indicating the appearance of new electronic transitions. Moreover, it is also observed that the Urbach energy increases with the gamma rays dose. This indicates the disorganization of the PET structure after irradiation.

NEW TETRA (1,4-DITHIN)PORPHYRAZINES AND THEIR APPLICATION AS PHOTOCATALYSTS FOR PURIFYING ENVIRONMENTAL WATERS: AN APPROACH TO GREEN CHEMISTRY

2,3-Dichloro-5,6-dimethylbenzoquinone reacted with di(sodiothio)maleonitrileto produce heterocyclic thianone, 6,7-dimethyl-5,8-dioxo-5,8-dihydro-1,4-benzodithin-2,3-dicarbonitrile which was cyclo-tetramerizedin the presence of lithium/pentanol and acetic acid producing tetra 6,7-dimethyl-5,8-dioxo-5,8-dihydro-1,4benzodithin-porphyrazine (2H-Pz). Likewise, the dicarbonitrile compound was cyclo-tetramerized in the presence of metal salt and quinoline affording tetra 6,7-dimethyl-5,8-dioxo-5,8-dihydro-1,4-benzodithinporphyrazinato-metal II (M-Pz), M is Co, Ni or Zn. Photoactivity of the synthesized porphyrazines was reached out to the visible light range. The prepared porphyrazines showed efficient sensitized catalysts by using of solar energy for the completely photocatalytic oxidation of thiophenol and benzyl thiol to their disulfides (with an average yield of 93% and 90%, respectively) in the presence of air atmosphere within 20 minutes.

Catalytic Enantioselective Aza-Reformatsky Reaction with Cyclic Imines.

A catalytic highly enantioselective aza-Reformatsky reaction with cyclic aldimines and ketimines for the synthesis of chiral β-amino esters with good yields and excellent enantioselectivities is reported. A readily available diaryl prolinol is used as a chiral ligand, ZnMe2 as a zinc source and ethyl iodoacetate as reagent in the presence of air atmosphere. The reaction with cyclic ketimines generates a quaternary stereocenter with excellent levels of enantioselectivity. Furthermore, five-membered N-sulfonyl ketimines were used as electrophiles with good enantiomeric excesses, under the optimized reaction conditions. Moreover, several chemical transformations were performed with the chiral β-amino esters.

Statistical optimization of microencapsulation process for coating of magnesium particles with Viton polymer

The surface of magnesium particles was modified by coating with Viton as an energetic polymer using solvent/non-solvent technique. Taguchi robust method was utilized as a statistical experiment design to evaluate the role of coating process parameters. The coated magnesium particles were characterized by various techniques, i.e., Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and thermogravimetry (TG), and differential scanning calorimetry (DSC). The results showed that the coating of magnesium powder with the Viton leads to a higher resistance of metal against oxidation in the presence of air atmosphere. Meanwhile, tuning of the coating process parameters (i.e., percent of Viton, flow rate of non-solvent addition, and type of solvent) influences on the resistance of the metal particles against thermal oxidation. Coating of magnesium particles yields Viton coated particles with higher thermal stability (632°C); in comparison with the pure magnesium powder, which commences oxidation in the presence of air atmosphere at a lower temperature of 260°C.

Synthesis, characterization and spectroscopic investigation of pyrazinoporphyrazine network polymer-supported metal (II)-based catalysts

Chloranil through condensation reaction with vicinal diamine such as diaminomaleonitrile produced heterocyclic monomer, p-benzoquinonebis[2,3-b; 2′,3′-b′]pyrazine-5,6-dinitrile. The tetranitrile monomer was cyclo-tetramerised using lithium/pentanol and acetic acid affording the corresponding tetra p-benzoquinone bis[2,3-b; 2′,3′-b′]pyrazinoporphyrazine)]-based network polymer (2H-Pz). The tetranitril monomer was cyclo-tetramerised using metal salt and quinoline affording the corresponding porphyrazinato-metal II-based network polymers (M-Pz), M = Co, Ni or Cu. Elemental analytical results, IR and NMR spectral data of the prepared molecules are consistent with their assigned formulations. Molecular masses and metal contents of the synthesized polymers proved to be of high molecular masses which confirm the efficiency of tetramerization polymerization and complexation reactions. The prepared pyrazinoporphyrazines were used as efficient catalysts for the oxidation of thiophenol and benzylthiol to their disulfides in the presence of air atmosphere. The results of oxidation of thiophenol and benzylthiol show that after 15 min the maximum yield of the corresponding disulfides reached 95%, 91%, respectively.

The influence of mechanical activation on sintering process of BaCO3-SrCO3-TiO2 system

In this article the influence of mechanical activation on sintering process of bariumstrontium-titanate ceramics has been investigated. Both non-activated and mixtures treated in a planetary ball mill for 5, 10, 20, 40, 80 and 120 minutes were sintered at 1100-1400?C for 2 hours in presence of air atmosphere. The influence of mechanical activation on phase composition and crystal structure has been analyzed by XRD, while the effect of activation and sintering process on microstructure was investigated by scanning electron microscopy. It has been established that temperature of 1100?C was too low to induce final sintering stage for this system. Electrical measurements have been conducted for the densest ceramics sintered at 1400?C for 2 hours.

Porous Morphology and Selective Metal-Adsorption of Burned Human Hairs

were between 20 ~ 30 years old. The hairs were burned in a furnace at 300 o C for 1 h in the presence of air atmosphere. BHH was immersed in water, and the solution was analyzed for metals content. The mixture was stirred for 1 h at room temperature. Then, the solution was filtered off, and the solution was analyzed for metal concentrations and the amount of metal adsorbed was estimated. BHH was characterized by EDX, IR, TGA, and SEM. BHH is a brittle stable solid under air and moisture. SEM images show that BHH has a main channel with diameters in the range of 20 ~ 40 µm and satellite channels with diameters in the range of 1 ~ 2 µm as shown in Figure 1 and Supporting Information. The formation of channels indicates that the surface of hairs is different from the bulk of hairs in chemical properties. The human hairs take a weight-loss of 23% at 300 o C, and then a weight-loss of 76% at 600 o C (Figure S2). According to EDX results (Supporting Information), BHH [C (66%), O (30%), S (4%)] shows increase in oxygen, and decrease in sulfur, relative to non-burned human hairs [C (64%), O (21%), S (15%)]. Such a porous morphology has wide surface area, and thus may be a driving force for metal-adsorption. Of course, the formation and preservation of porous morphology may be indebted to the part burning rather than the complete burning of the human hairs.

Ultrasonic Decomposition of Ammonia-Nitrogen and Organic Compounds in Coke Plant Wastewater

The investigations of the ultrasonic decomposition of NH3-N and organic compounds (i.e., CODCr) in coke plant wastewater are presented in this work. The process parameters were controlled with respect to the presence (or absence) of air atmosphere, initial pH value, initial concentration, and ultrasonic power density in the process of ultrasonic decomposition. It is noted that the ultrasonic removal efficiencies for both the NH3-N and the CODCr were increased in the presence of the air atmosphere and significantly affected by the initial pH value. The removal efficiencies increased with increasing the ultrasonic power density while they decreased with increasing the initial concentration. The effects of n-butyl alcohol as an effective OH radical scavenger on the removal efficiencies indicates that the ultrasonic decomposition of the NH3-N was carried out mainly via the mechanism of thermal decomposition in cavitation bubbles or in the interfacial region, whereas the ultrasonic decomposition of the CODCr mainly resulted from the reactions with OH radicals in the bulk solution. The GC/MS analysis indicates that most of the organic compounds in the wastewater were effectively destroyed by ultrasound.

클로로프렌 고무의 난연성 및 내방사선 특성 향상

This study has investigated radiation degradation of chloroprene rubber in the presence of some fire retardant. Ammonium polyphosphate, aluminium trihydroxide, magnesium hydroxide, calcium carbonate and antimony trioxide were selected as flame retardant. Samples were irradiated using a Co<TEX>$^{60}$</TEX> <TEX>${\gamma}$</TEX> -ray and ray up to 2000 kGy at a dose rate of 5 kGy/hr in the presence of air atmosphere at room temperature. After irradiation, samples were assessed fire retardancy with electrical properties and mechanical properties. Some considerations concerning the effects of the fire retardants added to chloroprene rubber on the radiation and thermal stability of chloroprene rubber are presented. From fire retardancy with electrical and mechanical property measurements, it was found that addition of magnesium hydroxide resulted in maximum fire retardant effect.