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Chemical Sciences and Applications
An International Journal
               
 
 
 
 
 
 
 
 
 
 

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Microwave-assisted synthesis of nanocrystalline LaCoO3 perovskite: Phase formation, characterization and catalytic activity studies

Rabei M.Gabr, Maher M. Girgis, Ahmed M.El-Awad, Rasha M.K.Mohamed,
Abstract :
Abstract:Combustion synthesis method was applied for LaCoO3 production, with a view to boosting its activity towards the dehydrogenation and/or dehydration reaction pathways of 2-propanol. With a highly exothermic and self-sustaining reaction, this perovskite was quickly prepared via sol-gel auto-combustion method using citric acid as a combustion complexing agent. Calcination was adopted in the temperature range 400- 800C in a dynamic air atmosphere. XRD analysis showed the formation of the nanostructure rhombohedral phase. The particle size and pore structure were determined from the XRD data and analysis of the adsorption isotherms of N2 at 77K. The results were supported by SEM and TEM examinations. TGA and DTA analysis revealed a sharp exothermic peak around 358C and a gradual weight loss up to ~ 600C. Dehydrogenation/ dehydration pathways of 2-propanol processed via the redox couple in the perovskite. The dehydrogenation was the predominant pathway forming acetone. A good correlation between the dehydrogenation selectivity and the evaluated redox couple species were established. A possible reaction mechanism consistent with the data obtained was proposed.

 

Investigation on Wear Properties of AZ31 Magnesium Based Hybrid Nanocomposites through MWCNT Addition Processed by Hot Compaction Technique

Nariman E. Elbaly, Ayman Elsayed, Hoda Abdel-kader, Simo-Pekka Hannula,
Abstract :
Alloy AZ31 is a magnesium alloy used for structural and transport applications. It contains aluminium and zinc as main alloying elements. Wear behavior of particle reinforced magnesium matrix composites plays critical role for potential application in industries such as automotive and aerospace. In order to improve the wear behavior of AZ31 magnesium alloy under dry sliding conditions 5.6 wt.% Ti and carbon nanotubes (CNTs) reinforcements were added to the alloy. The nanocomposites of AZ31magnesium alloy (Mg-3wt.% Al-1wt.% Zn) and AZ31-5.6wt.% Ti reinforced with multi-wall carbon nanotubes (MWCNTs) were fabricated by hot compaction technique. Friction coefficient and wear loss under dry conditions were evaluated for the different compacts using ball-on-disc wear test apparatus at applied loads of 1N and 5N. The surface topography and volume loss were recorded for all samples. The effect of MWCNT addition on the wear properties of AZ31and AZ31-5.6 wt.% Ti nanocomposites was studied. Coefficient of friction was found to be lower at the higher applied load. The maximum decrease in wear volume loss, for both nanocomposites, occurred at 0.25 wt.% CNT addition. Microstructural investigations on the worn surfaces were undertaken using a scanning electron microscope (SEM) for pointing out the wear mechanism.

 

Dry Sliding Wear of AZ31 and AZ31-5.6 wt.% Ti Based Nanocomposites Reinforced with Nano-sized Alumina Particulates

Nariman E. Elbaly, Ayman Elsayed, Simo-Pekka Hannula,
Abstract :
Abstract: In this study, 5.6 wt.% Ti and nano-alumina (n-Al2O3) particles reinforcement were added to AZ31 magnesium alloy to improve the wear behavior under dry sliding conditions. The composites contain reinforcement of 5.6 wt.% Ti and (0.5, 1 and 2 wt.%) of n-Al2O3,respectively. Compacts of the composites were fabricated by hot compaction technique at 475C. The dry sliding wear tests of the base material and nanocomposites were carried out at room temperature using the standard ball-on-disc equipment and applying loads of 1N and 5N. The wear mechanisms were studied detecting the wear tracks by scanning electron microscopy (SEM). The influence of test parameters on volume loss of the discs is reported. Results show that the coefficient of friction decreases as the load applied increases. The wear volume loss depends on the addition of n-Al2O3. The minimum wear volume loss for both nanocomposites occurs at the addition of 1wt.% n-Al2O3.

 

The Effect of the Activation Conditions of the Activated Carbons Made from Peanut Shells on the Adsorption Capacity of Phenol from Aqueous Solution

Maher M. Girgis, Bahaa M. Abu-Zied, Fatma. S. Durrat,
Abstract :
Activated carbons made from peanut shells were used for removal of phenol from aqueous solution. Ten samples variable in their activation method were selected. Three samples (PS55, PS56 and PS76) were prepared by one-step activation with H3PO4 in steam / nitrogen atmosphere. The P56 and CK samples were prepared using H3PO4 and KOH, respectively. The S800 and S900 samples were prepared by one-step steam/nitrogen activation at 800 and 900oC, whereas the last three samples (C15, C27 and C33) were prepared by two-step CO2 activation (15, 27 and 33% burn off at 700oC). Characterization of the products was performed using physicochemical techniques. Porosity characteristics were evaluated by analysis of the respective N2/77 K adsorption-desorption isotherms. The phenol number (Xm (mg/g)) and carbon surface area occupied by phenol (Sph (m2/g)) were calculated using the Langmuir and Freundlich adsorption isotherm equations. The Langmuir adsorption isotherm model gives better fit as compared to Freundlich model. Ratios of surface areas occupied by phenol to nitrogen surface area were evaluated and discussed. Removal of phenol from aqueous solution is governed by the chemical nature of the carbon surface as well as the diffusion through the intricate internal porosity. The capacity of these carbons for adsorption of phenol is reduced considerably by surface acidic groups and is promoted on basic ones. Higher pH values (pH > 10) were found to increase sharply the capacity for phenol adsorption on CO2-activated carbons.

 

Electrochemical Reduction and Electrode kinetics of Selenite Ions from Tartaric Acid Solution

Majidzade V.A., Guliyev P.H., Aliyev A.Sh., Mahmoud Elrouby,
Abstract :
The kinetics and mechanism of the electrochemical reduction of selenite ions on the cathode has been studied in the electrolyte containing selenite and tartaric acids. The influence of different factors on the cathodic reduction of selenite ions has been studied. The effective activation energy of the reduction process is also calculated based on cyclic polarization curves. From the deduced mechanism of reaction, it is established that the studied electroreduction process depends mainly on concentration and chemical polarization.

 

Extraction of Amino Acids From Beet Juice Using Ion Exchange Bed Chromatography

Emad Mohamed Ebrahem Bayuome,
Abstract :
The amino acids in beet juice are scarcely studied and there are few contradictory reports dealing with the number and concentration of the amino acids therein. Amino acids are added to ration to increase the nutritional value. It is thought that amino acids can be separated from beet juice using chromatographic techniques. To separate the amino acids from inorganic salts and other organic substances (viz, sugars and colloidal matter) in the samples, a small bed (15 cm high 0.3 cm dia) of Amberjet-1200 cation exchange resin (630μm) is used and the elution mechanism of amino acids with ammonia solution was investigated in operating conditions: 40C, pH ≤ 2, and 90 min operation time (1.1 ml/min). In these conditions, the overall recovery yields of 20 amino acids extracted from beet juice were 5.13% dry matter (%w/w) with the elimination percent of 94.3%.

 

Synthesis, Antimicrobial Evaluation and Docking Study of Novel Heterocyclic Compounds Containing a Biologically Active Sulfadiazine Moiety (part 2)

Hend M. El Sehrawi,
Abstract :
Development of new antimicrobial agents is our target to overcome drug resistance problems. In the present work, new chromenopyridone III- V, thiazole VI, hydrazone VIIa-e, isoxazole IX, pyrazole X, pyrazolopyrimidine XI and pyridazine XII derivatives bearing sulfadiazine moiety were synthesized and evaluated for both their in vitro antibacterial and antifungal activities. Among the synthesized compounds, the hydrazones VIIa, VIIc and pyrazole X displayed significant antibacterial and antifungal activity . Generally, most of the newly synthesized compounds exhibited better antimicrobial activities than sulfadiazine. Docking study indicated that the newly synthesized compounds could occupy both p-aminobenzoic acid (PABA) and pterin binding pockets of the dihydropteroate synthase (DHPS), suggesting that the target compounds could act by the inhibition of microbial DHPS enzyme. The results provide important information for the future design of more potent antimicrobial agents.

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