Static Air Atmosphere Research Articles

Synthesis and characterization of one-dimensional Co-doped titanate nanostructures prepared in the presence of chitosan

One-dimensional Co-doped titanate nanostructures with modified surface have been synthesized by alkaline hydrothermal method in the presence of bioactive natural polymer–chitosan as the organic reagent. The properties of products as-prepared and annealed under atmospheric air conditions and vacuum were studied by Raman and IR spectroscopy, SEM, HRTEM, XRD, EDX, and magnetic analysis. The results show that numerous Co-containing agglomerates of chitosan derivatives are formed on the surface of one-dimensional nanostructures when chitosan added to the reaction system with CoTiO3 powder. An average cobalt concentration in surface formations is about 6.3wt.% that is noticeably higher than in the body of layered structures. Magnetization measurements show a paramagnetic behavior for as-prepared products. After vacuum treatment at 600°C and higher, the same nanostructures demonstrate the abnormal high ferromagnetic properties. Effect of chitosan as the organic reagent on texture, morphology, phase composition, and surface modification of nanostructured material is discussed.

An Efficient Way To Introduce Hierarchical Structure into Biomass-Based Hydrothermal Carbonaceous Materials

Hydrothermal carbonization of biomass is regarded as the most sustainable technique to fabricate functional carbonaceous materials. The absence of nanoporous structures in the as-obtained materials remains a stumbling block to their wide applications. A hard-templating method and KOH activation are mostly frequently applied to introduce porous structures into HTC materials, but they always suffer from either tedious synthetic processes or massive use of a strong base. Here, the hierarchically porous structure was developed by heat treatment in the static air atmosphere. The textual properties were investigated by TEM and N2 sorption analyses. The structural order and surface chemistry were characterized by XRD, Raman, and XPS. The results show that the activated HTC carbons are rich in micropores and mesopores with high surface areas up to 1704 m2/g. The mesopore volume would reach over 50% of the total pore volume. In addition, these carbons show high performance in CO2 and dye adsorption.

Composite containing nanosized titanium oxide and oxyfluoride and carbon synthesized in plasma of pulse high-voltage discharge

Nanocomposites containing nanocrystalline titanium oxide and oxyfluoride as well as carbon components have been synthesized by a new method employing a combined destruction of titanium electrodes and fluoroplast in the plasma of pulse high-voltage discharge under air atmosphere conditions. Particles sizes from 40nm to 200nm has been obtained. The possibility of application of the obtained composites as anode materials in lithium batteries has been demonstrated.

Dumbbell-shaped polyhedral oligomeric silsesquioxanes/polystyrene nanocomposites: The influence of the bridge rigidity on the resistance to thermal degradation

A comparative study concerning the resistance to the thermal degradation of polystyrene-based nanocomposites loaded with five novel aromatic dumbbell-shaped polyhedral oligomeric silsesquioxanes was carried out in dynamic heating conditions. The fillers were formed by two identical silicon cages R7(SiO1.5)8 (R = isobutyl) linked to several aromatic bridges (Ar, Ar–Ar, Ar–O–Ar, Ar–S–Ar and Ar–SO2–Ar) where Ar = p-C6H4. Nanocomposites were prepared by in situ polymerization of styrene in the presence of 5% of appropriate polyhedral oligomeric silsesquioxanes. The actual filler content in the products obtained, which was checked by 1H NMR spectroscopy, resulted in all cases slightly higher than that in starting mixtures. Glass transition temperature ( Tg) was determined by differential scanning calorimetry. Thermogravimetric (TG) and differential thermogravimetric (DTG) analysis were carried out in both flowing nitrogen and static air atmosphere, and temperatures at 5% mass loss ( T5%) were determined to investigate the resistance to the thermal degradation. The results obtained were compared with each other and discussed. The resistance to the thermal degradation showed modest increments in respect to neat polystyrene, differently from analogous nanocomposites containing as fillers aliphatic bridged polyhedral oligomeric silsesquioxanes, as supported by scanning electron microscopy measurements which evidenced polyhedral oligomeric silsesquioxanes auto-aggregation phenomena. This behaviour was interpreted as due to the rigidity of polyhedral oligomeric silsesquioxane's aromatic bridges, which leads to low miscibility between filler and polymeric matrix.

New approach on the catalytic oxidation of methanol to formaldehyde over MoO3 supported on nano hydroxyapatite catalysts

Molybdenum oxide (20 wt. %) supported on nano hydroxyapatite mixed was prepared by impregnation method and calcinated at 400° 500° 600° and 700°C in static air atmosphere. The catalysts were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and nitrogen sorption measurements. The gas-phase oxidation of methanol to formaldehyde was carried out in a conventional fixed flow bed reactor. The obtained results clearly revealed that the formation of CaMoO4 spinel nano particles was active and selective catalyst towards the formation of formaldehyde. The maximum yield of formaldehyde was 97% on the catalyst calcined at 400 ° C. Moreover, the yield of formaldehyde was found unaffected by increasing the calcination temperature up to 700° C.

Correlation of static aging effects on automotive catalysts

This study identifies and analyzes the effect that aging time and temperature have on the CO light‐off activity of three‐way catalyst samples, aged in a static air (oxidizing) atmosphere. The bench aging time (BAT) equation proposed by the Environmental Protection Agency (EPA), which describes aging as dependent upon time at temperature, was used to calculate a range of oven aging times and temperatures based on a RAT‐A engine bench aging cycle.CO light‐off tests carried out on cores aged between 800 and 900 °C have shown that it is the aging temperature that has the greatest effect on catalyst deterioration for static aging testing, with aging time having little effect. These results were in contradiction to the BAT equation, an industry norm for the aging of catalysts. This demonstrates that static aging, whilst showing how temperature affects aging, gives little or no time effects. The results have shown that static aging is not representative of actual aging on a vehicle.Progressive aging conducted at a temperature of 1000 °C was shown to cause a decrease in catalyst activity as the aging time increased. However, even in these extreme conditions, static aging gave a slower rate of aging with time when compared to engine aging as defined by the BAT equation. Overall, static aging in air has been shown to produce a greater increase in aging due to temperature than predicted by the BAT equation, but less aging due to aging time.

Correlation between structure and thermal properties in 2-hydroxy-benzophenone Co(II) complexes

In this study, simultaneous TG/DTG–DTA technique was used for the simple cobalt(II) complex [Co(dpamH)3]Br2 (1) (dpamH = 2,2′-dipyridylamine) and the novel mixed-ligand complexes [Co(dpamH)2(bpo)]Br (2) and [Co(dpamH)2(opo)]Br (3), (bpo = the anion of 2-hydroxybenzophenone and opo = the anion of 2-hydroxy-4-methoxybenzophenone), in order to determine their thermal degradation in static air and dynamic nitrogen atmospheres. The cationic complexes were characterized by physicochemical methods, spectroscopy (FT-IR, UV–Vis), and single-crystal X-ray analysis, revealing octahedral coordination around cobalt(II) with chromophore CoN4O2, being chelated by one anionic 2-hydroxy-benzophenone ligand and two neutral dpamH molecules. The compounds crystallize as ethanol or ethanol/water solvates, with solvent molecules involved, to a different extent, in hydrogen bonding giving quite different packing modes and thus influencing their stability. The differences in crystal structures are reflected in thermal stabilities of the compounds. Thus, in the crystals of 3 ethanol is more weakly bound than in 2 and anticipate that the former one exhibit lower thermal stability, which is in agreement with the results found by TG–DTA. The thermal decomposition of the title complexes was found to be a multi-step decomposition related to the release of the solvent and ligand molecules, leading at 1,000 °C to pure metallic cobalt in nitrogen atmosphere, while in air atmosphere to the expected cobalt oxides.

The catalytic performance of sulfated zirconia in the dehydration of methanol to dimethyl ether

Sulfated zirconia catalysts were prepared by wetness impregnation of zirconium hydroxide with an aqueous solution of (NH4)2SO4 with SO42− loadings (1–30%, w/w) and calcined at 450°C for 3h in a static air atmosphere. The catalysts were characterized by FT-IR, XRD, TEM and BET measurements. The surface acidity of the catalysts was investigated by the dehydration of isopropanol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The catalysts were tested for dehydration of methanol in a fixed-bed reactor at 230°C using air as a carrier gas. The results revealed that among different catalysts, 10% SO42− supported onto zirconia showed the highest catalytic activity with 83% conversion and 100% selectivity toward dimethyl ether. A good correlation was found between the acidity of the catalysts and their ability to dehydrate methanol.

OPTIMIZING THE WELDING OF PLASTICS WITH THE USE OF DIFFERENTIAL SCANNING CALORIMETRY AND THERMOGRAVIMETRIC ANALYSIS

Plastics have different thermal stability, depending on the structure of the polymer chains. It is therefore very important to know their thermal properties, which influence the temperature regime of processing equipment. This paper presents examples of differential scanning analysis (DSC) and thermogravimetry analysis (TG) of selected plastics in an Ar protective atmosphere and also in an oxidative atmosphere of static air. These analyses can be used for proposing a welding temperature regime.

Magnetic M–H loops family characteristics in the microstructure evolution of BaFe12O19

A polycrystalline magnetic materials series produced from the same batch of high-reactivity powder by multi-sample sintering in a range of increasing temperatures can supposedly reveal its property and microstructural evolution through magnetic property measurement and clear morphological changes. Hence, in our work, we attempt to find out the variation of magnetic properties of BaFe12O19 against its evolving microstructure. Hexagonal BaFe12O19 nanometer-sized powder with the M-type structure was synthesized by the mechanical alloying method. The crystal structure, grain size and magnetic properties were studied by means of XRD, field emission scanning electron microscopy and a vibrating sample magnetometer. The ferrite materials were obtained from a mixture of barium carbonate and iron oxide by mixing them using conventional ball milling (12 h) and then assisted by high energy ball milling for 6 h. The comminuted powder was divided into several batches, moulded in pellet shape and sintered at different temperatures ranging from 400 to 1400 °C for a constant sintering time of 10 h in a static air atmosphere. Effects of sintering temperature on the formation, crystallite size, morphology and magnetic properties were systematically studied. In the sintering temperature range from 800 to 1200 °C, the coercivity (Hc) gradually increased due to the effect of rapid grain growth. This is because the fine starting powder was so reactive that rapid grain growth easily occurred. In the grains, strong interaction of magnetic moments within domains due to exchange forces led to strong anisotropy. It was also observed that three M–H-loop groups each belonging to a particular range of grain sizes exhibited different strengths of magnetism. It is believe of similar results have never been reported before and should be useful to the permanent-magnet industry.

Survival of Listeria monocytogenes on Fresh Blueberries (Vaccinium corymbosum) Stored under Controlled Atmosphere and Ozone

Listeria monocytogenes is a foodborne pathogen that represents a high risk for consumers because it can grow under refrigeration conditions and can also develop acid tolerance. Fresh blueberries are hand-picked, packed, and transported under refrigeration without receiving a microbial inactivation treatment. The aim of this work was to study the survival of L. monocytogenes in fresh highbush blueberries stored at 4 or 12°C under different controlled atmosphere conditions, including air (control); 5% O2, 15% CO2, 80% N2 (controlled atmosphere storage [CAS]); or ozone gas (O3), 4 ppm at 4°C or 2.5 ppm at 12°C, at high relative humidity (90 to 95%) for a total of 10 days. Fresh blueberries inside a plastic clamshell were spot inoculated with the bacteria and were stored at 4 or 12°C in isolated cabinets under air, CAS, and O3 atmospheric conditions. Samples were evaluated on days 0, 1, 4, 7, and 10 for microbial growth using modified Oxford agar. CAS did not delay or inhibit L. monocytogenes growth in fresh blueberries after 10 days. O3 achieved 3- and 2-log reductions when compared with air treatment at 4 and 12°C, respectively. Low concentrations of O3 together with proper refrigeration temperature can ensure product safety throughout transportation. O3 is a strong antimicrobial that safely decomposes to oxygen and water without leaving residues and can be used as an alternative method to prevent bacterial growth during a long transport period.

Substrate-Modification Method for Enhancing Performance of a Direct Electron Transfer-Type Biocathode and a Biofuel Cell

Introduction Biofuel cells, which are electric generators that utilize redox enzymes as catalysts, are very secure devices due to the enzyme reactions that can operate under mild conditions (room temperature, atmospheric pressure and neutral pH). Generally, enzymes in the biofuel cells oxidize several biologically related reductants such as alcohols, sugar, amines, organic acids, or hydrogen at the anode and reduce dioxygen (O2) at the cathode. There are two types of electric connection between enzymes and electrodes to realize bioelectrocatalysis. One is mediated electron transfer (MET)-type, in which the mediator shuttle the electron between the enzyme and the electrode. The other is direct electron transfer (DET)-type, in which the enzyme can directly transfer the electron to the electrode. Although the number of redox enzymes capable of direct communication with electrodes is limited, DET-type biofuel cell has several advantages over the MET-type one. Mediator-less configuration does not require any separator, which leads to simplifications, and DET-type cell can also reduce the possible health hazard problems due to artificial mediators and thermodynamic losses arising from the difference in the redox potentials between the active site. For enhancing the performance of DET-type biofuel cells, controlling the enzyme orientation on the electrode surface is one of the major concerns, since the electron transfer rate constant decreases exponentially with an increase of the distance between redox sites and electrode. In this study, we focus on bilirubin oxidase (BOD), the promising DET-type enzyme for O2 reduction at a biocathode. Biologically, BOD oxidizes bilirubin at T1 copper site and reduces O2 at T2-3 coppers site. We have a hypothesis that when the electrode is modified with the substrate of BOD, BOD will attractively interact with the modified compound in such an orientation that the electron-accepting T1 site faces the electrode surfaces. The orientation seems to be convenient in the DET-type bioelectrocatalysis.Experimental Ketjien Black (KB) powder, one of the carbon materials, was mixed with PTFE and homogenized. The KB slurry was applied to glassy carbon electrode (GCE). Subsequently, bilirubin solution was applied on the KB-modified GCE (KB-GCE) and dried. BOD solution was then applied to the electrode. Rotating disk voltammograms were recorded in an O2-saturated phosphate buffer (pH 7) at room temperature. Air-breathing gas-diffusion-type electrode was prepared by applying KB slurry to the carbon paper electrode (CPE). Similar modification with bilirubin was carried out on KB-modified CPE (KB-CPE). Cyclic voltammograms were recorded and one compartment fructose/O2 biofuel cell was constructed by combining with a bioanode, which fructose dehydrogenase was adsorbed on the mesoporous carbon electrode.Results and Discussions The effect of the bilirubin-modification on the catalytic reduction of O2 was examined using BOD-adsorbed bilirubin-KB-GCE and BOD-adsorbed KB-GCE. Under O2-saturated conditions, the cathodic waves are observed with both BOD-adsorbed electrodes. The catalytic wave at the BOD-adsorbed bilirubin-KB-GCE is much larger than that at the BOD-adsorbed KB-GCE and shows sigmoidal characteristics, while the BOD-adsorbed KB-GCE shows rather straight characteristics in the voltammograms. The sigmoidal and straight characteristics of the catalytic waves can be ascribed to the controlled and random orientation of the adsorbed enzyme, respectively. Therefore, we may assume that bilirubin adsorbed on the electrode can assist BOD to face the electrode surface in an orientation convenient for the DET catalysis. In the case of air-breathing gas-diffusion-type electrode, the cathodic wave of BOD-adsorbed bilirubin-KB-CPE also shows sigmoidal characteristics, therefore we succeeded in applying bilirubin-modification method to the practical electrode for biofuel cells. Finally, we constructed a DET-type fructose/O2 biofuel cell, and the maximum power density was 2.6 mW cm-2 under quiescent and air atmospheric conditions at room temperature.

Effects of densification atmosphere on optical properties of ionic copper-activated sol–gel silica glass: towards an efficient radiation dosimeter

Ionic copper-doped pure silica glass, with high photoluminescence (PL) quantum yield (QY), has been prepared using the sol–gel technique and densification of the porous xerogel under inert atmosphere. The optical properties of the obtained glass, and especially the green light emission due to Cu+ ions under UV excitation, have been studied and compared to those of the glass produced in air atmosphere conditions. We have shown that the sintering process under helium increases the quantum efficiency of this emission by a factor 40. Moreover, the resulting copper-doped silica rod has been used in the fabrication of a high numerical aperture microstructured optical fiber, which shows similar luminescent properties to the sol–gel preform. The obtained fiber exhibits promising characteristics to be employed in an all-fibred UV sensor. In particular, the high emission efficiency and the specific air-clad geometry of the fiber made it possible to perform measurements without removing the polymer coating.

Increased biomass production and glycogen accumulation in apcE gene deleted Synechocystis sp. PCC 6803.

The effect of phycobilisome antenna-truncation in the cyanobacterium Synechocystis sp. PCC 6803 on biomass production and glycogen accumulation have not yet been fully clarified. To investigate these effects here, the apcE gene, which encodes the anchor protein linking the phycobilisome to the thylakoid membrane, was deleted in a glucose tolerant strain of Synechocystis sp. PCC 6803. Biomass production of the apcE-deleted strain under photoautotrophic and atmospheric air conditions was 1.6 times higher than that of strain PCC 6803 (1.32 ± 0.01 versus 0.84 ± 0.07 g cell-dry weight L−1, respectively) after 15 days of cultivation. In addition, the glycogen content of the apcE-deleted strain (24.2 ± 0.7%) was also higher than that of strain PCC 6803 (11.1 ± 0.3%). Together, these results demonstrate that antenna truncation by deleting the apcE gene was effective for increasing biomass production and glycogen accumulation under photoautotrophic and atmospheric air conditions in Synechocystis sp. PCC 6803.

Effect of multiple vacuum packs on colour development and stability in beef steaks

Avilés, C., Juárez, M., Larsen, I. L., Rodas-González, A. and Aalhus, J. L. 2014. Effect of multiple vacuum packs on colour development and stability in beef steaks. Can. J. Anim. Sci. 94: 63–69. The aim of this study was to compare the colour stability of steaks from longissimus dorsi muscle previously submitted to four treatments of vacuum packaging and aged for 15 d. Muscle portions were either vacuum packed and aged for 15 d (NRP), or repacked after 2 h (RP2h), 8 d (RP8d) and after 2 h and 8 d (RP2h+8d). Purge loss values from RP8d and RP2h+8d treatments were higher (P=0.019) than those from NRP and drip loss was higher (P=0.001) for RP2h and RP8d. Colour changes during a 30-min period of exposure to atmospheric oxygen immediately after opening the packages were similar for repackaged-aged steaks and NRP steaks (P>0.05). Nevertheless, colour stability during subsequent retail display under atmospheric air conditions was affected by the packaging treatment. The decrease in chroma values (P=0.043) and the increase in hue (P=0.011) between day 3 and day 6 was minimum for RP2h+8d, compared with NRP, RP2h and RP8d. Also, the proportion of pigment in the myoglobin form in these three treatments dramatically increased from day 3 to day 6, while no effect was observed for RP2h+8d (P=0.005). Similarly, the decrease over time in the proportion of pigment in the oxymyoglobin form in meat from the RP2h+8d treatment was much lower (P=0.002) than for the other three packaging treatments. Changes in colour stability associated with multiple vacuum packagings may confound results in experimental designs. Thus, if beef colour is to be evaluated, repeated vacuum packaging should be limited.

Palladium supported on zinc oxide nanoparticles: Synthesis, characterization, and application as heterogeneous catalyst for Mizoroki–Heck and Sonogashira reactions under ligand-free and air atmosphere conditions

In this paper, a novel Palladium (Pd) supported on ZnO nanoparticles was readily synthesized and characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and BET specific surface area measurement. The total amount of palladium particles on ZnO was determined by induced coupled plasma (ICP) analysis and atomic absorption spectroscopy (AAS) which is 9.8 wt%. Percentage of accessible Pd as active catalyst is also estimated to 2.72% based on the thermogravimetric (TG) analysis. Nano Pd/ZnO was found as a new, novel, and excellent heterogeneous catalyst for ligand-free C–C bond formation through the Mizoroki–Heck and Sonogashira reactions under air atmosphere without the use of any Ar or N2 flow. The catalyst can be recovered and recycled several times without marked loss of activity.

Thermal behaviour of a series of novel aliphatic bridged polyhedral oligomeric silsesquioxanes (POSSs)/polystyrene (PS) nanocomposites: The influence of the bridge length on the resistance to thermal degradation

Abstract The thermal degradation of Polystyrene based nanocomposites, containing as fillers novel dumbbell-shaped bridged POSSs in which two identical silicon cages R 7 (SiO 1.5 ) 8 (R = isobutyl), are linked to aliphatic bridges (CH 2 ) n of different lengths ( n = 2, 4, 6, 8 and 10), was studied. Various nanocomposites were prepared by in situ polymerization of styrene in the presence of 5% of appropriate POSS. The obtained compounds were characterized by 1 H NMR spectroscopy, to verify their actual filler content, which was slightly higher than that in starting mixtures, and by Differential Scanning Calorimetry (DSC) to determine glass transition temperature ( T g ). Thermogravimetric (TG) and Differential Thermogravimetric (DTG) analysis, in both flowing nitrogen and static air atmosphere, were carried out and temperatures at 5% mass loss ( T 5% ) were determined to investigate the resistance to the thermal degradation. The results obtained for various samples were compared with each other and with those of virgin Polystyrene, and were interpreted and discussed.

Synthesis, characterization and thermal stability of new dumbbell-shaped isobutyl-substituted POSSs linked by aromatic bridges

Five new dumbbell-shaped polyhedral oligomeric silsesquioxanes (POSSs), in which two identical silicon cages R7(SiO1.5)8 (with R = isobutyl), linked to various aromatic bridges (Ar, Ar–Ar, Ar–O–Ar, Ar–S–Ar and Ar–SO2–Ar, where Ar = p-C6H4) were prepared through a literature method opportunely modified by us to make easier preparation and increase yield, which was higher than 70 % in all cases. The obtained products were the expected ones, as supported by the results of elemental analysis and 1H NMR spectra. Their resistance to the thermal degradation in both flowing nitrogen and static air atmosphere was checked by degrading samples at 10 °C min−1 and determining temperatures at 5 % mass loss (T5%) and residues at 700 °C. The T5% values in air were lower than the corresponding ones in nitrogen, but the trend among the various POSSs investigated was the same in both used atmospheres, with the most high value for the compound having the Ar–O–Ar aromatic bridge. The residues at 700 °C in air of the compounds having not hetero-atoms (O or S) in the aromatic bridge were higher than those in nitrogen, whilst no substantial difference was observed for the other ones.

Оценка воздействия автотранспорта на состояние атмосферного воздуха и почвенного покрова на территории города Энгельса (Саратовская область)

Оценка воздействия автотранспорта на состояние атмосферного воздуха и почвенного покрова на территории города Энгельса (Саратовская область)

Synthesis, spectral characterization, thermal and biological studies of lanthanide(III) complexes of oxyphenbutazone

Lanthanide(III) complexes of 4-butyl-1-(4-hydroxyphenyl)-2-phenyl-3,5-pyrazolidinedione (OPB) were prepared by homogeneous precipitation. The solid complexes were characterized by elemental analysis, magnetic susceptibility data, molar conductivity measurements and IR, UV-Vis, mass, 1H NMR and 13C NMR spectral methods. The thermal decomposition of the complexes under static air atmosphere was investigated by simultaneous TG/DTG at a heating rate of 10 °C/min. The final decomposition products were found to be metal oxides. The spectroscopic data suggested that OPB acted as a bidentate, mono-ionic ligand coordinating through two carbonyl oxygens of the pyrazolidinedione ring. The kinetic and thermodynamic parameters such as activation energy, pre-exponential factor and entropy of activation for each step of the decomposition reactions were evaluated using Coats-Redfern and MacCallum-Tanner equations. The negative entropy values of the complexes indicated that the activated complexes had a more ordered structure than the reactant and that the reactions were slower than normal. Investigations of antimicrobial activity of the compounds were carried out by the disk diffusion technique.