Influence Of Al2O3 Nanoparticles Research Articles

Comparative assessment of Al2O3-modified biomasses from agricultural residues for nickel and cadmium removal

The biodiversity of aqueous environments has been affected due to the disposal of wastewater highly contaminated with heavy metal ions, causing much damage to ecosystems. These pollutants are very toxic and bioaccumulate in living organisms. This work attempts to evaluate the adsorption of nickel ad cadmium ions using three biomasses from agricultur-al residues (corn cob – CC, orange peel – OP, and oil palm bagasse – PB) modified with alumina nanoparticles. The bio-masses were characterized via compositional analysis and a point of zero charges to quantify the presence of lignin, cellu-lose, hemicellulose, and the feasible pH, taking advantage of the biomass charge. After modification with Al2O3 nanoparti-cles. The resulting adsorbents were characterized via FT-IR analysis to identify the functional groups that most contributed to the adsorption performance. Furthermore, the influence of Al2O3 nanoparticles was analysed on the adsorption capacities of the evaluated biomasses using batch systems at a temperature of 25°C and pH 6. All biomasses displayed a high content of cellulose, estimating a weight percentage of about 19.9%, 14.3%, and 13.1% for PB, OP, and CC samples, respectively. The FT-IR spectrum confirmed hydroxyl and carboxyl functional groups, which contribute to enhancing the adsorption capacities of the modified biomasses. Functional adsorption capacity was observed for all biomasses after modification with Al2O3 nanoparticles, achieving at pH 6.0 a cadmium removal from 92% (CC-Al2O3 and PB-Al2O3) up to 95.8±0.3% (OP-Al2O3). In nickel ions, it was estimated a broader adsorption capacity at pH 6.0 of about 86±0.4% after using the CC-Al2O3 sample, 88±0.1% for the PB-Al2O3 adsorbent, and 98±0.2% for the OP-Al2O3 sample, confirming the suitability of these Al2O3-modified biomasses for the removal of heavy metal ions.

Retraction Notice to: The influence of Al2O3 nanoparticles on the properties of traditional concrete with ground granulated blastfurnace slag as binder

By the decision of the Editor-in-Chief, article (1) has been withdrawn from Issue 6 Volume 16 (2011) of the Cement Wapno Beton journal. The withdrawn article contains content borrowed without citation, e.g. from Jo et al. (2). The presented cement composition is iden-tical to the cement composition presented in the work of Givi et al. (3). Also, some images were reused, from other paper submitted at a similar time (4) claiming, that they present different material.We would like to apologize to the Readers of Cement Wapno Beton for this situation. We assure You that the Editorial Board makes every effort to avoid such situations. The authors did not respond to messages regarding the withdrawal of the article sent to them by the Editorial Of ce.

Retraction Notice to: The influence of Al2O3 nanoparticles on the properties of traditional concrete with ground granulated blastfurnace slag as binder

By the decision of the Editor-in-Chief, article (1) has been withdrawn from Issue 5 Volume 17 (2012) of the Cement Wapno Beton journal. The withdrawn article contains content borrowed without citation, e.g. from Jo et al. (2). The presented cement composition is identical to the cement composition presented in the work of Givi et al. (3). Also, some images taken from (2) were reused in other paper submitted at a similar time (4, 5) claiming, that they present different materials.We would like to apologize to the Readers of Cement Wapno Beton for this situation. We assure You that the Editorial Board makes every effort to avoid such situations. The authors did not respond to messages regarding the withdrawal of the article sent to them by the Editorial Office.

Influence of radiative heat transfer on the thermal characteristics of nanofluid flow over an inclined step in the presence of an axial magnetic field

This research analyzes the influences of radiation heat transfer and Brownian movement on the thermal characteristics of nanofluid flow over an inclined step in the presence of an axial magnetic field. The Rosseland approximation is applied to simulate the divergence of radiative heat flux in the energy equation. The Al2O3–H2O and CuO–H2O nanofluids are considered as the working fluid. The $${\text{KKL}}$$ correlation is used for modeling the Brownian movement influence on the effective viscosity and thermal conductivity. The impacts of radiation parameter $$\left( {0 \le Rd \le 1} \right)$$, nanoparticles concentration $$\left( {0 \le \phi \le 0.04} \right)$$ and Lorentz force $$\left( {0 \le Ha \le 60} \right)$$ on temperature fields, mean bulk temperature and convective, radiative and total Nusselt numbers are examined with full details. The results show that the impact of CuO nanoparticles on the average of total heat transfer rates is greater that the influence of Al2O3 nanoparticles on them. Besides, the highest values of total heat transfer rates occur in the absence of magnetic field and for the highest values of $$Rd$$ and $$\phi$$ parameters.

An experimental investigation and modelling of the thermal and caloric properties of nanofluids isopropyl alcohol - Al2O3 nanoparticles

An influence of Al2O3 nanoparticles on the thermodynamic properties of isopropyl alcohol in the liquid phase has been studied. Experimental measurements of the two-phase specific heat capacity have been performed in the temperature range from 184 to 340 K for samples with the mass fractions of the nanoparticles 0.0201, 0.0511 and 0.0996 kg·kg-1. The method of monotonic heating in an adiabatic calorimeter of variable temperature has been applied. The saturated vapor pressure of the nanofluids has been measured at the temperatures from 297 to 352 K and concentrations of the nanoparticles in isopropyl alcohol 0.0253, 0.0444, 0.0687, 0.0955 kg·kg-1. The results obtained have shown that the specific isobaric heat capacity of the nanofluids decreases up to 8.6% at 0.0996 kg·kg-1 of Al2O3 nanoparticles in comparison with pure isopropyl alcohol. In addition, the influence of Al2O3 nanoparticles on the specific enthalpy and specific entropy of isopropyl alcohol in the liquid phase has been examined. It is established that both the specific heat capacity of the material of the nanoparticles and structural changes of the base fluid around the nanoparticles are main factors that determine a decrease of the specific isobaric heat capacity of isopropyl alcohol. It was shown that the excess molar volume and excess molar isobaric heat capacity are determined by properties of the interfacial phase of structurally oriented isopropyl alcohol molecules on the surface of nanoparticles. A new three-phase model for prediction the molar isobaric heat capacity of nanofluids is proposed. To predict caloric properties of nanofluids the proposed model requires only data for the molar volume of the investigated samples.

Influence of Al2O3 nanoparticles on the stability and viscosity of nanofluids

Improving the performance of heat transfer fluids is becoming significantly important. One of the most effective methods for increasing thermal conductivity is the addition of solid nanoparticles to fluids. The molecular dynamics simulation method has the proper ability to diagnose the stability of fluids. This method can be used with a view to the low cost and high repeatability as a suitable method for studying different materials. In this study, the stability and viscosity of the nanofluid at different percentages of base fluid [water–ethylene glycol (EG)] in contact with Al2O3 nanoparticles, was investigated by molecular dynamics simulation with using some analyzes such as total energy, kinetic energy, radial distribution function diagrams and dispersion diagrams. The results show that, the stability of Al2O3 is better where the percentage of water in the base fluid is higher. The molecular dynamics simulation properly predicts the nanofluid viscosities in all concentrations, temperatures and for each base fluid. The maximum discrepancy between experimental and simulation results is 15.1% at 40 °C for 0.5% Al2O3 nanoparticles in the water–EG (60:40) mixture. The obtained results can provide useful understanding of the structural and transport properties of nanofluids, not only in the EG–water nanofluids, but also in other types of nanofluids.

Influence of Al₂O₃ Nanoparticles on Corrosion Inhibition Performance of Benzotriazole to Brass.

The influence of Al2O3 nanoparticles on corrosion inhibition of benzotriazole (BTA) in brass/ simulated water system was studied by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The results show that BTA has good corrosion inhibition effect on brass. Al2O3 nanoparticles could reduce the corrosion inhibition performance of BTA. The higher the concentration of Al2O3 nanoparticles in simulated water, the lower corrosion inhibition performance of BTA. The isothermal adsorption of BTA on brass surface in simulated water and Al2O3 nanofluids was analyzed. The results indicated that the adsorption of BTA on brass surface followed the Langmuirs' adsorption isotherm, the adsorption Gibbs free energy ΔG was less than -40 kJ/mol, corresponding to chemical adsorption, in both simulated water and Al2O3 nanofluids. The -ΔG value of BTA on brass surface decreased in Al2O3 nanofluids, indicating the weakening of the BTA adsorption on the brass surface. Surface analysis of brass samples by optical microscope and X-ray diffraction confirmed the above results.

Influence of Al2O3 nanoparticles on the corrosion behavior of brass in simulated cooling water

The influence of Al2O3 nanoparticles on the corrosion behavior of brass in simulated cooling water (SCW) with or without sodium dodecyl benzene sulfonate (SDBS) was investigated by means of electrochemical impedance spectroscopy, polarization curves, scanning electron microscope, energy spectrum analysis, X-ray diffraction and Fourier transform infrared spectroscopy. Results indicate that the brass suffered severe corrosion in SCW and the SCW-Al2O3 nanofluid. The main corrosion product was Zn5(OH)6(CO3)2. Al2O3 nanoparticles promoted both anodic and cathodic processes in the brass electrode, and dezincification was most serious in the SCW-Al2O3 nanofluid. The adsorption of SDBS on the brass surface was enhanced, and a more compact protective film was formed on the brass surface in the SCW-Al2O3-SDBS nanofluid. As a result, the corrosion resistance of brass was increased in this medium.

Physicomechanical Properties of Composite Electrochemical Coatings and Foils Based on Nickel and Reinforced with Al2O3

We describe an electrochemical method for the formation of composite electrochemical coatings and foils based on nickel and reinforced with nanosized aluminum oxide from a sulfamate electrolyte. We propose a mechanism of formation of composites and a mathematical model that reflects the relationship between the content of the hardening phase in composite electrochemical coatings and the concentration of Al2O3 hydrosol in the electrolyte. The influence of Al2O3 nanoparticles on the morphology and grain sizes of the composites is established by the methods of SEM and X-ray microanalysis. We determine the topography of composite electrochemical coatings and foils by the method of atomic force microscopy and establish the formation of a uniformly globular structure after the addition of Al2O3. The incorporation of nanosized particles of Al2O3 into the matrix of the base metal promotes a decrease in the grain size and the improvement of the mechanical properties of the composites: the microhardness and ultimate strength of the composites become 1.5–2 times higher and a substantial increase in the yield strength (as compared with nickel coating) is observed. The corrosion resistance of the composite electrochemical coatings increases as a result of the incorporation of aluminum oxide particles and, according to the depth index of corrosion k h = 10- 3 mm/yr we can attribute Ni–Al2O3 to the group of corrosion-resistant materials.

Nucleate pool boiling heat transfer of binary nano mixtures under atmospheric pressure around a smooth horizontal cylinder

Influence of Al2O3 nanoparticles on nucleate pool boiling heat transfer of diluted binary water-glycerol mixtures has been experimentally measured up to heat flux 91 kW/m2 at diluted volume fractions of 1% to 5% of glycerol into pure water at volumetric concentrations 0.5%, 1% and 1.5% of Al2O3 nanoparticles. Obtained results indicate that presence of nanoparticles into the mixtures result in increasing the pool boiling heat transfer coefficient values and also result in decreasing the wall superheat temperature of surface. Increased values of heat transfer are increased with increasing the volume fractions of Al2O3 too. Generally, it is concurred that Al2O3 nanoparticles typically enhance the pool boiling heat transfer coefficient of binary water-glycerol mixture in comparison with absence of nanoparticles circumstances, up to 25% at 1.5% Al2O3. Additionally, new simple semi - mathematical model has been proposed for a rough estimating of enhanced values with uncertainty about 8%.

Influence of Al2O3 nanoparticles on the isothermal cure of an epoxy resin

The influence of Al2O3 nanoparticles on the curing of an epoxy thermoset based on diglycidyl ether of bisphenol Awas investigated using temperature-modulated differential scanning calorimetry (TMDSC)and rheology. Diethylene triamine was used as a hardener. TMDSC not only allows for asystematic study of the kinetics of cure but simultaneously gives access to the evolution ofthe specific heat capacities of the thermosets. The technique thus provides insight into theglass transition behaviour of the nanocomposites and hence makes it possible to shed somelight on the interaction between the nanoparticles and the polymer matrix. TheAl2O3 fillers are shown to accelerate the growth of macromolecules upon isothermal curing.Several mechanisms which possibly could be responsible for the acceleration are described.As a result of the faster network growth chemical vitrification occurs at earlier timesin the filled thermosets and the specific reaction heat decreases with increasingnanoparticle concentration. Rheologic measurements of the zero-shear viscosity confirmthe faster growth of the macromolecules in the presence of the nanoparticles.

The influence of nano-Al2O3 additive on the adhesion between enamel and steel substrate

The influence of Al2O3 nanoparticles on the adhesion between SbMo, NiO enamels, and steel substrate has been investigated. The results of press test indicated that the adhesion strength was greatly improved by addition of Al2O3 nanoparticles into enamel frit. Scanning electronic microscope (SEM) revealed that the amount of dendrite increases in the interface and meanwhile its average size decreases. The energy dispersive X-ray (EDS) analysis identified the existence of Al in the dendrite, which confirmed that the nano-Al2O3 additives were closely related to the change of interface morphology and the improvement of adhesion strength. The reason for adhesion improvement was discussed as well.