Evaluation of alumina reinforced oil fly ash composites prepared by spark plasma sintering

The thermomechanical behavior of micro/nano-alumina (Al₂O₃) ceramics reinforced with 1-5 wt.% of acid-treated oil fly ash (OFA) was investigated. Composites were sintered using spark plasma sintering (SPS) technique at a temperature of 1400°C by applying a constant uniaxial pressure of 50 MPa. It was evaluated that the fracture toughness of micro- and nanosized composites improved in contrast with the monolithic alumina. Highest fracture toughness value of 4.85 MPam^1/2 was measured for the nanosized composite reinforced with 5 wt.% OFA. The thermal conductivity of the composites (nano-/microsized) decreased with the increase in temperature. However, the addition of OFA (1-5 wt.%) in nanosized alumina enhanced the thermal conductivity at an evaluated temperature. Furthermore, a minimum thermal expansion value of 6.17 ppm*K⁻¹ was measured for nanosized Al₂O₃/5 wt.% OFA composite. Microstructural characterization of Al₂O₃-OFA composites was done by x-ray diffraction and Raman spectroscopy. Oil fly ash particles were seen to be well dispersed within the alumina matrix. Moreover, the comparative analysis of the nano-/microsized Al₂O₃/OFA composites shows that the mechanical and thermal properties were improved in nanosized alumina composites.     

Taguchi Optimization of Solvent-Antisolvent Crystallization to Prepare Ammonium Perchlorate Particles

The sphericity and size of ammonium perchlorate (AP) particles significantly influence the properties of composite propellants. As the AP particles become more spherical, the accumulation coefficient increases, the viscosity during casting decreases, and the particle loading and burning rate increase. Hence, the production of micronized AP particles with an average size between 1 and 20 μm is important to increase the loading percentage of AP in the composite propellant. Here, the Taguchi experimental design was used to optimize the solvent-antisolvent crystallization (SAC) process for the preparation of micronized AP particles with higher sphericity. SAC parameters such as the type of antisolvent, the solvent-to-antisolvent ratio, the antisolvent temperature, the stirring speed, and the retention time were investigated at four levels. The type of antisolvent and the solvent-to-antisolvent ratio were found to mainly contribute to improving the sphericity and size of the AP particles, respectively.     

Numerical modelling of rotating packed beds used for CO2 capture processes: A review

Over the last decades, renewable and clean energy sources are being rigorously adopted along with carbon capture technologies to tackle the increasing carbon dioxide (CO₂) concentration level in the environment. CO₂ capture is a quintessential option for tackling global warming issues. In this context, the present paper has reviewed the process intensification equipment called a rotating packed bed (RPB), which is highly industry applicable due to high gravity (HiGee) force. This facilitates strong mass transfer characteristics, a compact design, and low energy consumption. In this review, the current research scenario of RPBs using numerical, computational fluid dynamics (CFD), and mathematical modelling, along with different machine learning approaches in the CO₂ capture process, has been reviewed. The different geometry designs, hydrodynamic characteristics, performance parameters, research methods, and their effects on CO₂ removal efficiency have been discussed. Furthermore, the latest experimental studies are also summarized, especially in the absorption and adsorption domain. Finally, recommendations have been given to support the RPBs in different industrial and commercial applications of CO₂ removal.     

Computational analysis of citric acid pertraction in emulsion liquid membranes

Citric acid is one of the most widely used acids in industry, and its recovery from waste streams is critical. Emulsion liquid membrane (ELM) is one of the most effective recovery methods that has been investigated in recent years. Numerous transport phenomena parameters affect the efficiency of this process. From the process equipment design point of view, optimization based on overall cost is of great importance, and important equipment sizing decisions/constraints must be considered. A physics-based model for a full-scale simulation of ELM systems is very useful. This work is focused on developing and verifying such a model. A coupled particle/mixture simulation was carried out in this work, and the modelling results were fitted on the experimental data. The novelty of this modelling work is physics-based results based on the system's geometry and its effects on the mass transfer resistances. Since the model is physics-based, the model is capable of simulating similar systems with any geometry or experimental conditions.     

Development of the Acidity of Zirconia-Supported Niobia Catalysts

A series of NbO _x /ZrO₂ catalysts containing up to 2.67wt Nb (ca. 80 nominal surface coverage) was prepared by incipient wetness impregnation from niobium oxalate and oxalic acid solution. The structure of the catalysts was monitored by X-ray diffraction and Raman spectroscopy. The results indicated the presence of a surface Nb phase. No evidence for the formation of crystalline Nb₂O₅ species was found. The development of the acidity as a function of Nb loading was monitored by adsorption of a basic probe molecule followed by infrared spectroscopy. The results indicated the appearance of Brnsted acid sites for a threshold of Nb loading. The abundance of Brnsted acid sites correlated well with the isopropanol dehydration activity. The overall behavior was very similar to that reported earlier for the WO _x /ZrO₂ system.     

Marine macrofouling: a review of control technology in the context of an on-line experiment in the turbine condenser water box of Al-Jubail Phase-1 power/MSF plants

The problem of macrofouling has serious implications in the performance of desalination and power plants. Intake structures, screens, seawater piping systems and heat-exchanger tubes are the sites worst affected in the plants, causing an overall decline in plant efficiency at great economic cost. The last half century has witnessed significant advancements in the development ofmacrofouling control technologies. Materials of inherent antifouling properties are widely used in the construction sector. Control technologies available include antifouling paints and coatings, injection of biocides, marine bio-active compounds, materials of inherent antifouling properties, heat treatment, pulse-power devices, UV and nuclear radiation, scrubbing devices, biological control, etc. A literature search carried out during the last few years has yielded about 450 references. This paper presents, in a very concise manner, state-of-the- art macrofouling control technologies pertinent to desalination and power plants in the Kingdom. The paper also discusses the issues of biofouling control in the Al-Jubail plants based on the results of an on-line macrofouling experiment conducted in one of the turbine condensers of Al-Jubail phase-I MSF/power plants.     

Electrochemical Synthesis of Cu (II) Coordination Polymer Coatings Based on 2,2′-Thiodiacetic Acid and 1,2,4,5-Benzenetetracarboxylate

Electrochemical synthesis of coordination polymers of Cu(II), [Cu(TDA)]_n and [Cu₂(BTC)(H₂O)₆?6H₂O]_n in which H₂TDA is 2,2′-thiodiacetic acid and BTC stands for 1,2,4,5-benzenetetracarboxylate was carried out by the electrochemical oxidation of Cu anode in the presence of H₂TDA (a flexible ligand), and 1,2,4,5-benzentetracarboxylic acid (H₄BTC) (a rigid ligand) in aqueous solutions. The structure of coordination polymers were characterized by scanning electron microscopy, X-ray powder diffraction, elemental analysis, thermal gravimetric and differential thermal analyses. The crystal structure of the compounds consists of one-dimensional cubical crystal polymeric units of [Cu(TDA)]_n and [Cu₂(BTC)(H₂O)₆?6H₂O]_n. Furthermore, the coordination number of Cu (II) ions in synthesized coordination polymers to be found five. The main advantages of electrosynthesis are the minor synthesis time, the milder conditions and the facile synthesis of coordination polymer coatings.     

Degradation of drag reducing polymers in aqueous solutions

The performance of drag reducing polymers in turbulent flow is restricted by their mechanical degradation. This study examines how the working fluid can affect the degradation behavior of diluted drag reducing polymeric solutions. Solutions having different proportions of tap water and de-ionized water served as the working fluids. Three commercially available water soluble polymeric agents, namely, an anionic copolymer of polyacrylamide, xanthan gum, and polyethylene oxide, were then added to these solutions. All experiments had identical flow rates corresponding to turbulent conditions in a laboratory scale pipe line. Variation of pressure drop in the pipe line was then measured for 2 hours. It was found that polymer degradation is accelerated in tap water solutions compared to that in de-ionized water solutions. However, this is dependent on the specification of the polymer used, namely, the molecular weight of the polymer and the rigidity of its molecular backbone. Furthermore, a new mathematical relation has been developed to investigate degradation of the polymers over time.     

Effect of various efficient vulcanization cure systems on the compression set of a nitrile rubber filled with different fillers

Effect of various efficient vulcanization (EV) sulfur cure systems on the compression set of a nitrile rubber filled with carbon black and silica/silane fillers was examined. The cure systems had different amounts of thiuram and sulfenamide accelerators and elemental sulfur, whilst the loading of zinc oxide and stearic acid activators was kept constant. The fillers had surface areas from 35 to 175 m²/g. In this study, the lowest compression set was measured for the rubber filled with carbon black with 78 m²/g surface area, which was cured with an EV cure system made of a small amount of elemental sulfur and large amounts of the two accelerators. Interestingly, a small change in the amount of elemental sulfur had a bigger effect on the compression set than did large changes in the loading of the accelerators in the cure system. Among the fillers, carbon black caused less compression set of the rubber vulcanizate than the silica/silane system did. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41512.