Synthesis,structural characterization,and hydrolysis of Ammonia Borane (NH3BH3) as a hydrogen storage carrier

In the present study, synthesis, structural characterization, and hydrolysis of the promising hydrogen storage carrier ammonia borane (NH₃BH₃), were investigated. NH₃BH₃ was prepared by one-pot chemical reaction between sodium borohydride (NaBH₄) and different ammonia salts [NH₄X, X: SO₄, CO₃, Cl] in the presence of solvent, tetrahydrofurane (THF). Synthesizes with different temperatures (20–40 °C), reaction times (30–130 min), amount of added THF volume (50–200 ml) and NaBH₄/(NH₄)₂SO₄ input molar ratios (0.47–0.75) were performed in order to find the optimum reaction conditions for obtaining maximum product yield. The characterization of NH₃BH₃ products was carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), elemental analysis (C, H, N, O) and NMR spectroscopy. Characterization results indicated that NH₃BH₃ as a crystalline powder at 98% purity was achieved with 92.18% production yield. Additionally, hydrolysis of product NH₃BH₃ in the presence of amorphous Co–B catalyst at 22–80 °C under magnetic stirring (700 rpm) was performed. The maximum hydrogen generation rate was 5447.80 ml min⁻¹ g cat⁻¹ and the hydrolysis reaction kinetics were clarified based on zero-order, first-order and Langmuir–Hinshelwood kinetic models.     

Recent progress in food processing applications of air impingement technology: A review

Air impingement method has been widely used in a variety of industrial applications, such as textile and paper drying, turbine cooling, and glass quenching, because it is an efficient technology with high heat and mass transfer rates. This technology has received increasing interest in the field of food processing over the last two decades, such as drying, baking, blanching, freezing, and thawing. In a food processing equipment using air impingement, jets of high-velocity air (with speeds of 10–50 m/s) are directed at a food product. The performance of the system is influenced by several critical elements, including jet velocity, nozzle array diameter and layout, jet distance, and boundary layer characteristics. The use of computational fluid dynamics, an emerging tool, has been shown to be valuable in the analysis of fluid flow and heat and mass transfer in jet impingement systems. The physical properties of impinging jets, such as turbulent mixing in the free jet zone, stagnation, boundary layer formation, recirculation, and their interactions with food products in terms of heat and mass transfer, have been discussed in this article. The benefits and disadvantages of air jet impingement technology in different food processing applications together with potential trends for improving impingement technology performance were identified and discussed. This review not only contributes to a better understanding of the research status of impingement technology on food processing but also triggers new research opportunities in this field in order to provide more healthy and nutritious food in a more sustainable way to the world's growing population.     

Closing the hydrogen cycle with the couple sodium borohydride-methanol,via the formation of sodium tetramethoxyborate and sodium metaborate

Methanolysis of sodium borohydride (NaBH₄) is one of the methods efficient enough to release, on demand, the hydrogen stored in the hydride as well as in 4 equiv of methanol (CH₃OH). It is generally reported that, in methanolysis, sodium tetramethoxyborate (NaB(OCH₃)₄) forms as single component of the spent fuel. It is, however, necessary to clearly investigate some critical aspects related to it. We first focused on the methanolysis reaction where NaBH₄ was reacted with 2, 4, 8, 16, or 32 equiv of CH₃OH. With 2 equiv of CH₃OH, the conversion of NaBH₄ is not complete. With 4 to 32 equiv of CH₃OH, NaBH₄ is totally methanolized (conversion of 100%). The best conditions are those involving 4 equiv of CH₃OH as they offer the highest effective gravimetric hydrogen storage capacity with 4.8 wt%, an attractive H₂ generation rate with 331 mL(H₂) min⁻¹—a performance achieved without any catalyst—and the formation of NaB(OCH₃)₄ as single product as identified by X-ray diffraction, Fourier transform infrared spectroscopy, and nuclear magnetic resonance. We then focused on the transformation of this product NaB(OCH₃)₄ into sodium metaborate (NaBO₂), via the formation of sodium tetrahydroxyborate (NaB(OH)₄). NaB(OCH₃)₄ is easily transformed in water, by hydrolysis, at 80°C and for 90 minutes, into NaB(OH)₄ and 4 equiv of CH₃OH. In doing so, the cycle with CH₃OH is closed. Subsequently, NaB(OH)₄ is recovered and converted into NaBO₂ under heating at 500°C. This reaction liberates 4 equiv of H₂O, which allows to close the cycle with water. Based on these achievements, we have finally proposed a triangular recycling scheme aiming at closing the cycle with the protic reactants of the aforementioned reactions. This scheme may be used as base for implementing a closed cycle with the couple NaBH₄-CH₃OH.     

Effect of Steam-Assisted Hybrid Cooking on Textural Quality Characteristics,Cooking Loss,and Free Moisture Content of Beef

Semitendinosus muscles were cooked in a steam-assisted hybrid oven and also convection ovens at three different oven temperatures (180, 210, and 240°C) until three different end point temperatures [65°C (medium-rare), 72°C (medium), 80°C (medium-well)] were reached. Textural properties of cooked beef were investigated by the Warner Bratzler shear test and texture profile analysis. Cooking loss and free moisture content of muscle tissue was determined for each cooking condition. In addition, sensory analysis was carried out in order to compare with the instrumental results and correlations between instrumental texture parameters and sensory results. Steam-assisted hybrid oven cooking of beef resulted in a tougher texture, higher cooking loss, and lower free moisture content than convection cooking. High correlation coefficients (r² > 0.70) were observed between instrumental texture measurements and sensory results for all ovens, especially in terms of tenderness. The free moisture content and adhesiveness values were also correlated well with juiciness (r² > 0.70) for all oven types.     

Magnetic Characterizations of Cobalt Oxide Nanoparticles

Cobalt oxide (Co₃O₄) nanoparticles were synthesized by a novel microwave-assisted decomposition reaction of the cobalt nitrate hexahydrate, Co(NO₃)₂?6H₂O. While most of the traditional methods for the preparation of Co₃O₄ are at relatively high temperature, microwave-assisted decomposition was adapted to have better control in the production of Co₃O₄ nanoparticles. The temperature dependence of the magnetic properties for the Co₃O₄ was investigated by vibrating sample magnetometer (VSM) and electron spin resonance (ESR) techniques. VSM and ESR measurements have shown a phase transition occurring at around 31?K, as the antiferromagnetic transition temperature for the bulk Co₃O₄ crystal exhibits almost the same value. The average particle size of the sample at around the transition temperature is estimated as 2.015?nm. The title compound was characterized and identified by an x-ray powder diffraction (XRD).     

Caffeic Acid Detection Using an Inhibition-Based Lipoxygenase Sensor

An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) inhibitor. LOX was immobilized in carbon paste electrode and the amperometric detection of hydroperoxy linoleic acid due to the enzymatic reaction using linoleic acid as a substrate was monitored at +0.9 V versus Ag/AgCl. The decrease in biosensor response in the presence of caffeic acid was found to be correlated with the inhibitor concentration. Diode array detector and LOX biosensor was used as an electrochemical detector for the analysis of this compound. All data were given as a comparison of two systems.     

The Hypercube Separation algorithm: A fast and efficient algorithm for on-line handwritten character recognition

This paper introduces a new neural network training algorithm, Hypercube Separation (HCS) algorithm which is very fast and guaranteed to learn. HCS is a simple algorithm suitable for hardware implementation which classifies different input patterns presented to it through the formation of multiple hyperplanes. The performance of the HCS algorithm is compared to that of the Binary Synaptic Weights (BSW) algorithm and to the Backpropagation (BP) algorithm in solving the two spiral problem, which is an almost pathological problem for pattern separation. The HCS algorithm was able to successfully separate the input patterns, requiring three orders of magnitude less training time than the BP algorithm and one order of magnitude less hidden layer nodes than the BSW algorithm. We also present the application of HCS to on-line handwritten character recognition with good results, especially when the simple nature of the algorithm is taken into consideration.     

Suction Removal of Sediment from between Armor Blocks. II: Waves

When a stone/armor layer on a sand bed is exposed to flow, the sand underneath will be agitated by the flow turbulence. When the flow velocity reaches a critical value, the sand will be sucked (winnowed out) from between the armor blocks. In a previous investigation, we studied suction removal of sediment in steady currents. The present study is an extension of our previous investigation to waves. The critical condition for the onset of suction is determined. It is found that the onset of suction is governed by three parameters: (1) the sediment mobility number (based on the sediment size); (2) the ratio of sediment size to stone size, d/D; and (3) the Keulegan-Carpenter (KC) number, based on the armor block/stone size. The variation of the critical mobility number for suction as a function of d/D and KC is determined for the ranges of the parameters 0.001相似文献   

Hydrolysis characteristics of calcium hydride (CaH2) powder in the presence of ethylene glycol,methanol, and ethanol for controllable hydrogen production

Calcium hydride (CaH₂) reacts vigorously with water, liberating hydrogen gas. For the development of an effective hydrogen storage system, it is an absolute necessity to control the rate of hydrogen production. In the present study, the effects of different solvent, ethylene glycol, methanol, and ethanol, on the hydrolysis of CaH₂ for controllable hydrogen production were investigated. Reactions were performed at different temperatures (20, 40, and 60°C) in order to calculate the kinetic parameters. The Arrhenius equation was used to calculate the activation energies. The activation of energy of the hydrolysis reaction of CaH₂ in an ethanol solution (E_a = 20.03 kJ/mol) was found to be less than the other reactions.