Normal Ambient Air Research Articles

Effects of Sintering Temperature on Phase, Physical Properties and Microstructure of Ca<sub>3</sub>Co<sub>4</sub>O<sub>9</sub> Ceramic

This study investigated the effects of sintering temperature on phase, physical properties and microstructure of calcium cobalt oxide (Ca3Co4O9 or CCO) ceramic. CCO powder was prepared with using the mixed oxide method and calcined at 750°C for 24 h. The ceramics were prepared by sintering the powder at 900, 950, 1000 and 1050°C under a normal air atmosphere for 24 h. A maximum density of 4.02 g/cm3 (~92% relative density) with 12% linear shrinkage was obtained in the sample sintered at 1000°C. XRD patterns of the CCO ceramics indicated pure phase with no detected impurity. SEM images of the ceramics showed plate-like shaped grains. The average grain size value gradually increased as the sintering temperature increased, and reached a maximum value of 8.95 mm at the sintering temperature of 1000°C. The deviation from stoichiometric composition for the samples sintered at low sintering temperatures may be due to the low sample density which in turn affected the EDS analysis results.

New Reference Electrodes for Air and Moisture Stable Ionic Liquids

The use of room temperature ionic liquids (RTILs) for electrochemical applications such as fuel cells, batteries, dye-sensitized solar cells, and supercapacitors, has gained significant interest over the last decade. Despite the increase in attention, a universal reference electrode for use in RTIL electrochemistry has not been adopted. A stable, easy to prepare, and reproducible reference electrode, analogous to Ag/AgCl reference electrodes for aqueous electrochemistry, is crucial for accurately determining redox potentials as well as for comparing these potentials between RTILs and between research labs. Electrochemical work in RTILs often rely on quasi-reference electrodes (QREs),1 such as Ag or Pt wire, which must be calibrated by the addition of a redox couple (e.g. ferrocene/ferrocenium) after each electrochemical measurement. These quasi-reference electrodes are difficult to reproduce, likely due to the quality of the wire used and the presence of surface adsorbates. Furthermore, they have been known to exhibit potential drift during use, with 10s to 100s of mV drift often observed. Ferrocene is added after the experiment, however this one-point calibration of the QRE does not necessarily apply throughout the entire experiment, as the QRE may drift during the measurement.2 We report on reference electrodes designed for use in ionic liquids, which exhibit stable potential over several months of experimental use. One successful example is based on a silver wire coated with silver sulfide.3 The reference electrode potential is determined by the concentrations of Ag+ and S2 −, which are established by the solubility of the Ag2S coating on the Ag wire. Our reference electrode can be prepared and used in a normal air atmosphere, and does not need to be assembled and used in a glovebox, or protected from light. The reference electrode has been characterized by voltammetry measurements of ferrocene and cobaltocenium hexafluorophosphate, and was found to slowly drift to more positive potentials at a rate of <1 mV/day for five RTILs investigated over the course of 2+ months. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM release LLNL-ABS-748348. (1) Electrochemical aspects of ionic liquids, 2nd ed.; Ohno, H., Ed.; John Wiley & Sons Inc., 2011. (2) Torriero, A. A. J.; Sunarso, J.; Howlett, P. C. Electrochim. Acta 2012, 82, 60–68. (3) Horwood, C.; Stadermann, M. Electrochem. Commun. 2018, 88 (December 2017), 105–108.

Effects of preharvest aminoethoxyvinylglycine (AVG) treatment on storage life and quality of ‘Golden Delicious’ apple

The aim of this study was to determine the effects of preharvest aminoethoxyvinylglycine (AVG) treatment on storage life and quality of 'Golden Delicious' apples stored in normal (air) atmosphere (NA) and controlled atmosphere (CA) conditions. For this purpose, ReTain (a commercial product containing 15% (w/w) AVG) was applied to trees of 'Golden Delicious' apple. 125 ppm dose of AVG was sprayed on the apple fruits 7 days before commercial harvest. Harvested fruits were transported to the Postharvest Physiology Laboratory of Horticulture Department immediately. AVG treated and non-treated (control groups) fruits were stored at 0°C and 90±5% relative humidity during 6 months in NA and 10 months in CA conditions (1% O2-3% CO2). The weight loss of fruits was decreased by AVG treatment compared to the control groups in both storage conditions. AVG treatment maintained the flesh firmness of apples during the storage period, especially in CA. AVG also suppressed ethylene production of fruits. Titratable acidity of the treated and non-treated fruits decreased, and soluble solid contents increased during the storage period in NA and CA conditions. According to sensorial evaluation, AVG treated fruits preserved their external appearance and taste for 6 (in NA) and 10 months (in CA). Non-treated fruits lost their marketable quality after 5 (in NA) and 8 (in CA) months of storage. As a result, preharvest AVG application (125 ppm) to 'Golden Delicious' apples 7 days before commercial harvest was effective in delaying softening, ethylene production, respiration rate and weight loss of fruits. These effects were more evident in CA condition compared to NA.

Evaluation of a Ag/Ag2S reference electrode with long-term stability for electrochemistry in ionic liquids

We report on a reference electrode designed for use in ionic liquids, based on a silver wire coated with silver sulfide. The reference electrode potential is determined by the concentrations of Ag+ and S2−, which are established by the solubility of the Ag2S coating on the Ag wire. While potential shifts of >100 mV during an experiment have been reported when using silver or platinum wire quasi-reference electrodes, the reference electrode reported here provides a stable potential over several months of experimental use. Additionally, our reference electrode can be prepared and used in a normal air atmosphere, and does not need to be assembled and used in a glovebox, or protected from light. The reference electrode has been characterized by voltammetry measurements of ferrocene and cobaltocenium hexafluorophosphate, and was found to slowly drift to more positive potentials at a rate of <1 mV/day for five of the six ionic liquids investigated.

One-Step Solution Combustion Synthesis of Cobalt Nanopowder in Air Atmosphere: The Fuel Effect.

In this paper, we report a new modified solution combustion synthesis technique for one-step production of metallic Co nanoparticles. The main unique feature of our approach is the use of microwave-assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine, and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products were investigated. It was shown that the combination of microwave-assisted foam and hexamethylenetetramine as a fuel allows us to produce metallic Co nanoparticles with the broad size distribution (∼5-40 nm), high coercivity (370 Oe), and high value of saturation magnetization (137 emu/g) by the one-step solution combustion synthesis under normal air atmosphere without any post reduction.

Solution Combustion Synthesis of Copper Nanopowders: The Fuel Effect

ABSTRACTPure copper nanoparticles have previously been successfully produced by different combustion methods, but most of them require the use of an inert atmosphere (N2, Ar) during the synthesis process or the usage of addition post reducing of metal oxides. In this article, novel modification of solution combustion synthesis technique for one-step metallic Cu nanoparticles preparation was developed. The main unique feature of our approach is the use of microwave-assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine, and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products was investigated. It was shown that the combination of microwave-assisted foam preparation and use of hexamethylenetetramine as a fuel allows producing pure metallic Cu nanoparticles (~67 nm) by one-step solution combustion synthesis under normal air atmosphere without any post reduction.

One-step solution combustion synthesis of pure Ni nanopowders with enhanced coercivity: The fuel effect

In this paper, we report a new modified one-step combustion synthesis technique for production of Ni metal nanoparticles. The main unique feature of our approach is the use of microwave assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products were investigated. It is observed that the combination of microwave assisted foam preparation and using of hexamethylenetetramine as a fuel allows producing pure ferromagnetic Ni metal nanoparticles with enhanced coercivity (78Oe) and high value of saturation magnetization (52emu/g) by one-step solution combustion synthesis under normal air atmosphere without any post-reduction processing.

Viability of Using Argon Gas in Investment Casting of Pure Aluminium Granules by In-Situ Melting

Oxidation characteristics of pure aluminium granules during in-situ melting were studied. The granules were heated at the temperature of 850 °C, for the duration of 30 min using a high temperature muffle furnace. Experiments were conducted in two different conditions; normal air and argon atmosphere. The flow rate of argon gas was set at 0.5 l/min, 2.5 l/min and 5 l/min. Heated products were visually evaluated for geometrical and physical appearance. The heated products were characterised using field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). Macroscopically, the Al granules failed to melt and unable to replicate the mould due to the oxidation of the granule. The Al granules experienced volumetric shrinkage and the appearance become dusty greyish. The colour of the Al granules heated in normal air and argon atmosphere were corvette blue and silver grey respectively. Argon was found to reduce the oxidation of Al granules during heating. Oxide thickness in normal air was reduced from 8.52 µm to 5.02 µm when the granules were heated in argon atmosphere at the flow rate of 5 l/min. The oxide layer formed on the Al granules surface was mainly Al2O3.

Friction Reduction through Ultrasonic Vibration Part 2: Experimental Evaluation of Intermittent Contact and Squeeze Film Levitation.

In part 1 of the current study of haptic displays, a finite element (FE) model of a finger exploring a plate vibrating out-of-plane at ultrasonic frequencies was developed as well as a spring-frictional slider model. It was concluded that the reduction in friction induced by the vibrations could be ascribed to ratchet mechanism as a result of intermittent contact. The relative reduction in friction calculated using the FE model could be superimposed onto an exponential function of a dimensionless group defined from relevant parameters. The current paper presents measurements of the reduction in friction, involving real and artificial fingertips, as a function of the vibrational amplitude and frequency, the applied normal force and the exploration velocity. The results are reasonably similar to the calculated FE values and also could be superimposed using the exponential function provided that the intermittent contact was sufficiently well developed, which for the frequencies examined correspond to a minimum vibrational amplitude of ∼1 µm P-P. It was observed that the reduction in friction depends on the exploration velocity and is independent of the applied normal force and ambient air pressure, which is not consistent with the squeeze film mechanism. However, the modelling did not incorporate the influence of air and the effect of ambient pressure was measured under a limited range of conditions, Thus squeeze film levitation may be synergistic with the mechanical interaction.

Luminescence and energy transfer properties of single-component Mg0.5Ti2(PO4)3:Dy3+, Eu3+ for warm white UV LEDs

Mg0.5Ti2(PO4)3:Dy3+/Eu3+ phosphors were prepared via solid-state reaction method under normal ambient air. The phosphors were characterized by X-ray, photoluminescence excitation and emission spectra. The XRD patterns showed that Dy3+ and Eu3+ could be effectively doped into the Mg0.5Ti2(PO4)3 host. The concentration quenching mechanism of Dy3+ in the Mg0.5Ti2(PO4)3 host was proven to be dipole-dipole interaction. The emission intensity and the decay lifetime of Dy3+ decreased with the increase of Eu3+ concentration, which proved the existence of the energy transfer from Dy3+ to Eu3+ in the Mg0.5Ti2(PO4)3 host. It was found that the energy was transferred from 4F9/2 level of Dy3+ to the 5D0 level of Eu3+ by dipole-dipole interaction. Besides, the correlated color temperature is improved with the introduction of Eu3+ ions. The experiment presents that Mg0.5−x−yTi2(PO4)3:xDy3+, yEu3+ phosphors are promising materials for warm white UV LEDs.

Effects of dust particles on body weight and some haematological parameters in rats in Maiduguri metropolis, Nigeria

Maiduguri metropolis in Northern Nigeria is a typical Sahel region characterized by dry hot climate for a greater part of the year during which dust pollution is a major concern with regard to human and animal health. In order to understand some effects of prolonged dust exposure, this study investigated the effects of dust exposure on body weight and some haematological parameters of rats in Maiduguri metropolis. Sixty (60) rats of both sexes were used for the study. The rats were randomly divided into two groups of 30 rats each and designated groups I and II, being the experimental and control groups respectively. Rats in group I were exposed to dust concentration of 477 mg/m3 for 3 h per day for 10 weeks consecutively, while those in group II were confined to normal ambient air, dust concentration of 243 mg/m3 for the same period of time. The result of the investigation showed a significant (p 0.05) variations in lymphocyte counts. This study has shown that prolonged exposure of mammals (using rats as a model) to dust particles has adverse haematological consequences such as anemia and hypoxia, which predispose the animal to serious health challenges and even death.

Understanding Fatigue Crack Growth Behavior at Low Frequencies for a Mn–Ni–Cr Steel in 3.5 % NaCl Solution Under Controlled Cathodic Potential

Abstract Fatigue crack growth behavior at low loading frequencies for a Mn–Ni–Cr steel immersed in 3.5 % NaCl solution, with and without cathodic polarization, is investigated and presented in this paper. Frequency shedding method is used to estimate fatigue crack growth rate over a range of frequencies between 0.01 and 5 Hz at a constant stress intensity factor range of 15 MPa √m. The effectiveness of cathodic potential of −900 mV SCE in containing corrosion contribution to crack growth is estimated by comparing with published data on fatigue crack growth rate in lab air and 3.5 % NaCl solution without cathodic polarization. It is noted that there are three regions of crack growth rate as a function of applied frequencies when the data is plotted in log–log scale: linear crack growth rate, plateau crack growth rate, and high crack growth rate. The crack growth rate of steel in 3.5 % NaCl solution at 15 MPa √m is scanned for different cathodic potentials between −760 mV SCE and 1150 mV SCE at 0.01 and 0.1 Hz. The potentials at which the crack growth rates are the maximum and the minimum are found to be −760 and −950 mV, respectively. The optimum cathodic protection potential for the minimum corrosion fatigue crack growth rate ranges between −900 and −950 mV. This optimum potential for the minimum corrosion crack growth rate is more negative than the cathodic potential required for restraining the corrosion effects on fatigue strength of steel to normal ambient air behavior.

Deteriorating effect on bone metabolism and microstructure by passive cigarette smoking through dual actions on osteoblast and osteoclast.

There is no clear evidence to show the direct causal relationship between passive cigarette smoking and osteoporosis. Furthermore, the underlying mechanism is unknown. The objective of this study is to demonstrate the effects of long-term passive cigarette smoking on bone metabolism and microstructure by a mouse model and cell culture systems. BALB/c mice were exposed to 2 or 4 % cigarette smoke for 14 weeks. The bone turnover biochemical markers in urine and serum and also the bone micro-architecture by micro-CT were compared with the control group exposed to normal ambient air. In the cell culture experiments, mouse MC3T3-E1 and RAW264.7 cell lines to be employed as osteoblast and osteoclast, respectively, were treated with the sera obtained from 4 % smoking or control mice. Their actions on cell viability, differentiation, and function on these bone cells were assessed. The urinary mineral and deoxypyridinoline (DPD) levels, and also the serum alkaline phosphatase activity, were significantly higher in the 4 % smoking group when compared with the control group, indicating an elevated bone metabolism after cigarette smoking. In addition, femoral osteopenic condition was observed in the 4 % smoking group, as shown by the decrease of relative bone volume and trabecular thickness. In isolated cell studies, osteoblast differentiation and bone formation were inhibited while osteoclast differentiation was increased. The current mouse smoking model and the isolated cell studies demonstrate that passive cigarette smoke could induce osteopenia by exerting a direct detrimental effect on bone cells differentiation and further on bone remodeling process.

Effect of a Modified Atmosphere on Drying and Quality Characteristics of Carrots

Many quality degradation problems are related to the high O2 content of normal air atmosphere during drying. To reduce O2 content in drying atmosphere and obtain food products with high quality, modified atmosphere drying was conducted. In this study, carrots were used as experimental materials to investigate the effects of drying parameters on the drying characteristics and product quality. Results showed that the increase in drying temperature and the decrease in O2 content positively influenced drying rate and effective moisture diffusivity. High carotenoid content, ascorbic acid retention ratio, and rehydration ratio were produced with low drying temperature and O2 content. The color parameters of products were highly correlated with carotenoid content, and low color difference could be achieved as drying temperature and O2 content decreased. Drying temperature and O2 significantly influenced carotenoid content, ascorbic acid content, rehydration, and color difference of dried products. Good quality parameters were obtained only at low drying temperature under the drying condition of normal atmosphere and could be achieved at drying temperatures of 40 to 70 °C when O2 content is 5 %. Therefore, the modified atmosphere drying is a promising method to protect the quality of dried products.

Increase in thermo-oxidation stability of conjugated polymers at high temperatures

The effect of PCBM on the thermal stability of three conjugated polymers widely used in organic electronic applications, namely P3HT, MDMO-PPV and PFO, was studied under induced thermal stress (thermolysis and thermo-oxidation) using both dynamic and isothermal thermogravimetric analysis. The aim of this study was to test the potential anti-oxidant effect of PCBM on conjugated polymer:PCBM blends at high temperatures relevant to polymer melt techniques, and to evaluate the corresponding time and temperature windows of processability. Under thermolysis conditions (N2 atmosphere), most of the blends are less stable than the pure compounds. However, all the blends considered showed increased thermo-oxidation stability (air atmosphere) in comparison to the pure conjugated polymers. These results show that PCBM can be used as an efficient anti-oxidant to increase the time and temperature windows of processability of conjugated polymers at high temperatures under a normal air atmosphere.

ChemInform Abstract: Copper‐Catalyzed Synthesis of Nitriles by Aerobic Oxidative Reaction of Alcohols and Ammonium Formate.

An efficient methodology has been developed for the synthesis of nitriles through an aerobic oxidative reaction of alcohols and ammonium formate with copper as a homogeneous catalyst under a normal air atmosphere and solvent-free conditions. This protocol uses the air as a green oxidant and ammonium formate as the nitrogen source. A wide range of substrates were well tolerated in the reaction that gave water as a byproduct.

Numerical simulation on combustion processes of a diesel engine under O2/CO2 atmosphere

A new diesel engine combustion model where the fuel is sprayed into the combustion chamber and burnt under O2/CO2 atmosphere is presented. The new combustion model can break through the bondage of the compromise NO x –soot emission curve which can make the engine meet the more stringent emission regulations. The numerical simulation model for diesel engine combustion analysis is built by AVL-FIRE software. The pressure, temperature and emissions field distribution in cylinder are calculated under O2/CO2 atmosphere and under normal air atmosphere, respectively, by maintaining the engine basic parameters unchanged. Simulation results show that when the O2 ratio is under 50%, fuel cannot be ignited and the temperature variation in the cylinder is small. The content of 65% O2 and 35% CO2 is the optimal ratio under O2/CO2 atmosphere. Soot emission under O2/CO2 atmosphere is ultra-low, while CO emission is comparable to that under the normal air atmosphere.

Thermal stability of P3HT and P3HT:PCBM blends in the molten state

The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investigated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including thermogravimetric analysis (TGA), rotational rheometry, infrared spectroscopy (FTIR-ATR), proton nuclear magnetic resonance spectroscopy (1H-NMR), gel permeation chromatography (GPC), UV-Vis and fluorescence spectroscopy. The results obtained strongly suggest that the processing of P3HT in its molten state is possible, without noticeable degradation, if carried out under nitrogen atmosphere and if the processing (residence) times are relatively short. Conversely, as expected, in a normal air atmosphere P3HT degrades rapidly at temperatures above its melting point. The effect of PCBM on the thermal stability of P3HT:PCBM blends in the molten state was also studied using TGA, and in air atmosphere PCBM is shown to delay oxidation.

Fabrication and properties of YBa2Cu3O7−x ceramics at different sintering temperatures

The influence of sintering temperatures on the fabrication of YBCO ceramics under normal air atmosphere was investigated in this study. YBCO ceramics were prepared by mixing starting compounds of Y2O3, BaCO3 and CuO powders, which were calcined at 850°C for 12 h. The powder was pelletized and sintered at different temperatures, from 930°C–1050°C, for 12 h. Phase identification was carried out by x-ray diffraction (XRD) technique. Scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study microstructure and chemical composition. In addition, density, Vickers hardness properties, the change of resistance and dielectric properties with temperature above Tc were investigated. It was found that, at 950°C–1000°C, high-purity YBCO ceramic could be obtained. Outside this temperature range, either impurity phases were present or melting occurred. SEM images showed that grain size, which ranged from 1.5–2.5 µm, and hardness were related to density and liquid phase present in the sample. Furthermore, the sintering temperature affected oxygen content which, in turn, determined the conductive or semi-conductive behavior observed by electrical property measurement.

Copper‐Catalyzed Synthesis of Nitriles by Aerobic Oxidative Reaction of Alcohols and Ammonium Formate

AbstractAn efficient methodology has been developed for the synthesis of nitriles through an aerobic oxidative reaction of alcohols and ammonium formate with copper as a homogeneous catalyst under a normal air atmosphere and solvent‐free conditions. This protocol uses the air as a green oxidant and ammonium formate as the nitrogen source. A wide range of substrates were well tolerated in the reaction that gave water as a byproduct.