In the present study, influence of Scandium (Sc) content (0.025 and 0.25 wt%) on microstructure, texture and mechanical properties of a thermo-mechanically processed AA2195 alloy has been ...investigated. Addition of Sc to AA2195 alloy results in grain refinement and enhanced precipitation kinetics. TEM analysis revealed the presence of Al3(Sc,Zr) dispersoids in the Sc containing AA2195 alloys. Solution treatment and peak aging of the Sc containing alloys revealed partially recrystallized microstructure. Texture of Sc containing alloys displayed weaker Brass component compared to the Sc free material. A clear improvement in hardness and strength was observed which could be attributed to grain refinement as well as the presence of fine Al3(Sc,Zr) dispersoids. Ductility decreased slightly on Sc addition and there was an associated change in fracture mode as a result of Sc addition.
•Addition of Sc to AA2195 alloy leads to the formation of Al3(Sc,Zr).•Sc addition leads to grain refinement and retards recrystallization.•Sc addition weakens Brass component of texture, hence reducing anisotropy.•Strengthening occurs due to grain refinement and due to fine Al3(Sc,Zr).•On Sc addition, ductility decreases and there is a change in fracture mode.
Adsorption by activated alumina is considered to be one of the most practiced methods for defluoridation of freshwater. This study was conducted, therefore, to investigate the effect of natural ...organic matters (NOMs) on the removal of fluoride by activated alumina using response surface methodology. To the authors’ knowledge, this has not been previously investigated. Physico-chemical characterization of the alumina was determined by scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray diffractometer (XRD). Response surface methodology (RSM) was applied to evaluate the effect of single and combined parameters on the independent variables such as the initial concentration of fluoride, NOMs, and pH on the process. The results revealed that while presence of NOM and increase of pH enhance fluoride adsorption on the activated alumina, initial concentration of fluoride has an adverse effect on the efficiency. The experimental data were analyzed and found to be accurately and reliably fitted to a second-order polynomial model. Under optimum removal condition (fluoride concentration 20 mg/L, NOM concentration 20 mg/L, and pH 7) with a desirability value of 0.93 and fluoride removal efficiency of 80.6 %, no significant difference was noticed with the previously reported sequence of the co-exiting ion affinity to activated alumina for fluoride removal. Moreover, aluminum residual was found to be below the recommended value by the guideline for drinking water. Also, the increase of fluoride adsorption on the activated alumina, as NOM concentrations increase, could be due to the complexation between fluoride and adsorbed NOM.
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•RM, as a novel low-cost photocatalysts, has been firstly applied for degradation of TC.•RM-350 showed the best photocatalytic activity for TC degradation under visible ...light.•Modified-RM has better photoelectron transfer efficiency.
Antibiotics wastewater poses a major threat to the global environment and human health. In this work, red mud (RM) and modified RM (after calcination treatment), as industrial solid wastes discharged from the aluminum industry, were used as effective photocatalysts for removal of tetracycline (TC) from water under visible light irradiation. The results showed that the photocatalytic degradation activity of modified RM on TC was obviously better than that of original RM (RM-raw). Furthermore, RM-350 (calcination temperature is 350 °C) exhibits the best photocatalytic performance (100 mL, 10 mg/L; 88.4% degradation of TC within 80 min) under visible light as well as outstanding stability after three reaction cycles. The improvement in photocatalytic performance by modified RM is mainly due to an increase in specific surface area and crystallinity, which is benefit for promoting adsorption of organic pollutants and accelerating photo-induced charges. The effects of catalyst dosage and initial concentration on the catalytic degradation of TC were studied. Our work has proved that RM is a novel low-cost photocatalyst, which not only provides a useful solution for the reuse of RM, but also plays an important role in environmental protection.
It has long been known that the stoichiometry of C–S–H varies with the calcium hydroxide concentration in solution. However, this issue is still far from understood. We revisit it in both ...experimental and modelling aspects. A careful analysis of the solubility confirms the existence of three different C–S–H phases, defined as Ca4H4Si5O16, Ca2H2Si2O7 and Ca6(HSi2O7)2(OH)2, respectively. The variation of the Ca/Si ratio of the three phases has been described by surface reactions: the increase of the Si content is accounted for by silicate bridging, the increase of calcium content and the surface charge are accounted for by reactions involving silanol groups via deprotonation and complexation with calcium. In the presence of Al in solution, the uptake of Al by C–S–H is experimentally observed. The Al content increases with Al concentration. C–A–S–H formation is modelled by the competition between silicate and aluminate tetrahedra for the bridging of the dimeric silicates in C–S–H.
Porous granular ceramic adsorbents containing dispersed aluminum and iron oxides were synthesized by impregnating with salt solutions followed by precipitation at 600°C. In the present work detailed ...studies were carried out to investigate the effect of contact time, adsorbent dose, initial solution pH and co-existing anions. Characterization studies on the adsorbent by SEM, XRD, EDS, and BET analysis were carried out to clarify the adsorption mechanism. The adsorbents were sphere in shape, 2–3mm in particle size, highly porous and showed specific surface area of 50.69sqm/g. The fluoride adsorption capacity of prepared adsorbent was 1.79mg/g, and the maximum fluoride removal was obtained at pH 6. Both the Langmuir and Freundlich isotherm models were found to represent the measured adsorption data well. The experimental data were well explained with pseudo-second-order kinetic model. Results from this study demonstrated potential utility of Al/Fe dispersed in porous granular ceramics that could be developed into a viable technology for fluoride removal from aqueous solution.
•The distribution of Al3+ and hydroxyl polymeric aluminum ions was investigated.•The best pH value was about 3.0 at initial aluminum concentration 0.15mol/L.•It was easier to remove aluminum from ...solutions with low aluminum concentration.•Another operating approach is suggested.
The present research investigates the effect of aluminum ions distribution on the removal of aluminum from rare earth solutions using saponified naphthenic acid. The effect of extraction type on the extraction rate of aluminum and rare earth was studied and the results indicated that aluminum influences the purity of rare earth seriously. For the removal of aluminum, the distribution fractions of aluminum ions and hydroxyl polymeric aluminum ions at different pH value at 0.15mol/L initial aluminum concentration were calculated by MATLAB software. The plot of distribution fraction of aluminum ions and hydroxyl polymeric aluminum ions with pH value are obtained. Based on these, the effect of pH value and saponification value on the extraction of aluminum and rare earth were studied. The results show that the extraction rate of aluminum was highest at pH value 3.0 at initial aluminum concentration 0.15mol/L in the absence of emulsification. This is consistent with the distribution of aluminum ions and hydroxyl polymeric aluminum ions. For the solutions containing low aluminum concentration, it is easy to separate aluminum from rare earth at 0.3–0.5 saponification value at pH value 3.
Honeycomb sandwich structures are increasingly used in the automotive, aerospace and shipbuilding industries where fuel savings, increase in load carrying capacity, vehicle safety and decrease in gas ...emissions are very important aspects. The aim of this study was to develop the theoretical methods, initially proposed by the authors and by other researchers for the prediction of low-velocity impact responses of sandwich structures. The developed methods were applied to sandwich structures with aluminium honeycomb cores and glass-epoxy facings for the assessment of impact parameters and for the prediction of limit loads. The values of model parameters were compared with data reported in literature and the predictions of the limit loads were validated by means of the experimental data. Good achievement was obtained between the results of the theoretical models and the experimental data. The failure mode and the internal damage of the sandwich panels have been investigated using 3D computed tomography, which allowed the evaluation of parameters of energy balance model, and infrared thermography, which allowed the detection of the temperature evolution of the specimens during the tests. The experimental and theoretical results demonstrated that the use of glass-epoxy reinforcement on aluminium honeycomb sandwiches enhances the energy absorption and load carrying capacities.
Involvement of abscisic acid (ABA) was studied for aluminium (Al) sensitivity through functioning of sub1A quantitative trait loci in rice cultivars. sub1A quantitative trait loci bearing cv. Swarna ...Sub1 was found almost compatible with non sub1A quantitative trait loci bearing cv. Swarna for abscisic acid accumulation all through the aluminium concentrations. However, abscisic acid was self inductive by over expression of its biosynthetic gene in nine-cis-epoxycarotenoid dioxygenase 3 (NCED3) more in cv. Swarna than other. The effect of abscisic acid pretreatment was variable for specific leaf weight, leaf mass ratio and others for the cultivars. Bio-accumulation of aluminium had revealed the sensitivity of toxicity more in cv. Swarna than other. In connection to oxidative stress generation of reactive oxygen species was detected by both histochemical and in vitro assays through hematoxylin, Evans blue and schiff's reactions. Abscisic acid pretreatment had significantly reversed the effects of aluminium toxicity for reactive oxygen species generation. Regardless of varieties sensitivity of aluminium was more prone in shoot than root as detected by nitro blue tetrazolium and 3,3′-diaminobenzidine mediated signalling. Activity in metal chelation in extra cellular spaces monitored through esterase activity and that also established independence of abscisic acid pretreatment for cv. Swarna Sub1. The specific polymorphism of esterase at protein level strengthened the bio-monitoring of aluminium through the rice varieties as well its modulation with abscisic acid. Abscisic acid has been discussed an important effectors to modulate the tolerance pathway of rice cultivars through intrusion of sub1A quantitative trait loci.
•ABA may be differentially expressed in rice cultivars for Al sensitivity.•NCED3 gene is more expressed in sensitive cultivar than tolerant one.•cv. Swarna Sub1 through Al toxicity is independent to ABA metabolism.•sub1A QTL bearing cultivar is more tolerant to Al toxicity than the other one.
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