Surface Modification Of Alumina Research Articles

Interaction of Surface-Modified Alumina Nanoparticles and Surfactants at an Oil/Water Interface: A Neutron Reflectometry, Scattering, and Enhanced Oil Recovery Study.

The evaluation of the mechanism of nanoparticle (NP)/surfactant complex adsorption at the critical oil/water interface was studied. A sophisticated technique (neutron reflectometry) was used to give a unique insight on NP/oil interactions in oil recovery systems. Herein, the adsorption of two modified alumina NPs with different degrees of hydrophobicity [hydrophilic = 2-[2-(2-methoxyethoxy)ethoxy]acetic acid and hydrophobic = octanoic acid (OCT)] stabilized with two different surfactants were studied at the oil/water interface. A thin layer of deuterated (D) and hydrogenated (H) hexadecane (contrast matching silicon substrate) oil was formed on a silicon block by a spin coating freeze process. The distribution of the NPs across the oil/water interface with the CTAB surfactant is similar between the two systems. NPs coated with CTAB have more affinity toward the oil/water interface, which explains the oil recovery increase by around 5% when flooding the core with the OCT-NP/CTAB system compared to the surfactant flooding alone. These results suggest that the NP/surfactant complexes can have potential usage in EOR recovery applications.

Structurally and Surface-Modified Alumina Particles as a Reinforcement in Polyester-Based Composites with an Improved Toughness

Commercial γ − Al2O3 particles, Al2O3 n, and synthesized Al2O3 doped with iron oxide (Al2O3 Fe) were used as reinforcements to enhance the toughness of an unsaturated polyester resin (UPR). Alumina modification with vinyl, Al2O3 (n, Fe)–VT, and methacryloyl, Al2O3 (n, Fe)–ME functionalities contributed to the increase in the extent of covalent binding at the UPR/filler interface. Tensile tests showed a slight improvement in the toughness of UPR/Al2O3 Fe composite and a significant improvement for the UPR/Al2O3 Fe–VT composite at a 1.0 wt.% particle loading. An enhancement in the micro Vickers hardness for UPR/Al2O3 Fe–VT and improved DMA properties were also evidenced.

Surface modification of alumina with P2O5 and its application in 2-octanol dehydration

Alumina and phosphorus-alumina with different morphologies were synthesized by the sol–gel method. The morphology, structure, size, phase composition, acidic properties, and thermal behavior were examined by FESEM, TEM, XRD, FT-IR, BET, EDS, NH3-TPD, and TGA-DTA, respectively. It can be found that the morphology of alumina can change from worm-like to spherical by using acetonitrile/2-octanol solvent mixture and by modifying the synthesis steps. Also, the semi-crystalline structure of γ-alumina was changed to amorphous with improved surface area (from 150 to 229 m2 g−1). The addition of phosphorus pentoxide to amorphous alumina with the ratios of 1:9, 2:8 and 1:1 reduced the surface area of the catalyst after calcination from 229 to 129, 16 and 39 m2 g−1, respectively. With the increase of phosphorus/aluminum ratio and an increase in calcination temperature, the structure of phosphorus-alumina transformed from amorphous to crystalline. The reactivity and selectivity of 2-octanol over these composites were monitored using GC and GC-mass analyses.

Evaluation of Mechanical Properties and Corrosion Protection Performance of Surface Modified Nano-alumina Encapsulated Epoxy Coated Mild Steel

The incorporation of imidazole-modified nano-alumina on the corrosion protection properties of epoxy coating on mild steel was studied by electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) in 3.5% NaCl solution. The dispersability of the alumina nanoparticles was greatly improved by the surface modification using imidazole in the epoxy matrix. The imidazole-modified nanoparticle was analyzed by Fourier transform infrared spectroscopy. Both EIS and SECM studies confirmed that the corrosion resistance is higher for the alumina–epoxy nanocomposite coated steel than that of the pure epoxy-coated steel. It is evidenced that alumina–epoxy nanocomposite coated mild steel has higher charge transfer resistance values, 156,344 Ω cm2, compared to pure epoxy coated mild steel, 79,546 Ω cm2, at 40 days of immersion. The modified nanoparticles enhanced the adhesive properties of the coatings. Possible chemical interactions between epoxy matrix and surface-modified alumina nanoparticles in nanocomposites cause high protection properties and ionic resistances. FE-SEM/EDX analysis showed the presence of Fe, Al, and O in the corrosion products. Hardness and tensile strength measurements showed that the improved mechanical properties were noticed for alumina–epoxy nanocomposite coated mild steel.

Optimization of modifier deposition on the alumina surface to enhance mechanical properties and cavitation resistance

Composites based on poly(methyl methacrylate), dimethyl itaconate matrix and alumina particles were prepared. Ferrous oxide-doped alumina particles (Al2O3 Fe) and commercial alumina nanoparticles (Al2O3 n) modified with (3-aminopropyl)trimethoxysilane (AM) and methyl esters of linseed oil fatty acids (biodiesel—BD) were used as reinforcement. The mechanical properties of the prepared composites, containing 1, 3 and 5 wt% of surface-modified alumina particles, are compared to a neat polymer matrix. The particles were characterized by single-beam Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The mechanical properties of the composites were determined by micro-Vickers hardness and impact testing. The morphology of the surface of the composites exposed to cavitation was observed through a field emission scanning electron microscope. AFM analysis was used to compare surface features seen using the SEM and to interpret the surface degradation properties. The hardness, cavitation resistance and high-impact energy resistance of the composites are better in the case of AM surface modification of alumina fillers, but biodiesel modified particles have comparable mechanical properties and a stabilized Al–O–Si bond that could be important when a composite is exposed to humidity or a wet environment.

Thermal Conductivity and Mechanical Properties of Thermoplastic Polyurethane-/Silane-Modified Al2O3 Composite Fabricated via Melt Compounding.

The increase of miniaturization and rise of powerhouses has caused a need for high-performing thermal interface materials (TIMs) that can transfer heat in electronic packaging. In this study, a thermoplastic polyurethane (PU)/alumina composite was produced via twin extrusion and was suggested as a TIM. The surfaces of the alumina particles were modified by γ-aminopropyltriethoxysilane (APTES) and then evaluated using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The field emission scanning electron microscopy (FE-SEM) images revealed that the addition of surface-modified alumina was well adhered in the PU matrix. The tensile strength of the composite remained unchanged, while the Young’s modulus showed improvement as compared to the pure PU. The elongation at the break decreased as the filler loading increased, due to the brittle behavior of the composite. The viscoelastic elastic property analysis results revealed that there was an increase in the storage modulus of the composite and the glass transition temperature curve shifted to the right. The thermal conductivity of the composite showed that there was an 80.6% improvement in thermal conductivity with the incorporation of 40% APTES-treated alumina particles.

Adsorption characteristics of molecular oxytetracycline onto alumina particles: The role of surface modification with an anionic surfactant

The present study investigated the adsorption of molecular oxytetracycline (OTC) from aqueous solution onto surfactant-modified alumina (SMA). An anionic surfactant, sodium dodecyl sulfate (SDS), which was used to modify the alumina surface at high ionic strength induced a significant increase in the removal efficiency of OTC. Some conditions that were effective for the removal of OTC using SMA such as contact time, pH, adsorbent dosage, and ionic strength were systematically studied. The optimum contact time was 180 min, while the pH of the solution, adsorbent dosage and ionic strength were found to be 4, 25 mg/mL and 1 mM NaCl, respectively. The highest removal efficiency for OTC using SMA was >97%. Under the optimal adsorption conditions, OTC removal from an actual water sample collected from shrimp aquaculture achieved a very high removal efficiency of 90%. After the adsorbent was regenerated four times, the removal efficiency of OTC using SMA was still higher than 83%. A two-step adsorption model was successfully applied to fit the experimental results of OTC adsorption isotherms onto SMA at different ionic strengths, while the adsorption kinetics of OTC onto SMA followed a pseudo-second order model. The maximum adsorption capacity of OTC onto SMA was found to be 143 mg/g. The adsorption of OTC onto SMA decreased with the increasing NaCl concentration and pH because the SDS desorption out of the alumina surface was enhanced with an increase in salt concentration and pH. The adsorption mechanisms of OTC onto SMA were discussed in detail based on Fourier transform infrared (FT-IR) spectroscopy, zeta potential measurements, adsorption isotherms of OTC and SDS desorption upon OTC adsorption. Our results demonstrate that the surface modification of alumina with SDS is important to form a novel adsorbent for the removal of tetracycline antibiotics from aqueous solution.

Preparation of Mixed Ionic Electronic Conducting (MIEC) Membrane Supported on Al2O3 Substrate: Effects of Substrate Morphology

Two types of solvents [N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO)] were used in the preparation of alumina (Al2O3) dope suspensions whereby the dope was allowed to experience phase inversion in the coagulation bath. The green body of alumina discs were sintered at 1450°C and the morphologies of prepared alumina-NMP and aluminaDMSO were studied. To improve the catalytic activity of the oxygen transport membrane for oxygen separation purposes, surface modifications of the membranes were carried out using different mixed ionic electronic conducting (MIEC) oxides catalysts (LCF 91 and LSF 55). The oxide powders and viscous sol were synthesised using sol-gel method and calcined at 950°C to form pure perovskite structure of MIEC materials and studied using XRD while the specific surface area of the calcined powder was measured using BET (Brunauer-Emmett-Tellet) technique. The honey-like MIEC sols were used for surface modification and conducted via dip-coating method and the morphology of the surface-modified alumina membranes were analysed using SEM with EDS mapping. From the study, it was found that the amount of MIEC oxide deposited onto alumina-DMSO is higher than alumina-NMP.

CATALYTIC SURFACE MODIFICATION OF ALUMINA MEMBRANE FOR OXYGEN SEPARATION

Two types of alumina ceramic membrane in hollow fibre shape was used in this study. Both alumina hollow fibres (AHF) were sintered at different temperatures; (a) 1350oC and (b) 1450oC. In order to improve the catalytic activity of the alumina membrane for oxygen separation purposes, surface modification of the membranes was carried out using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) perovskite catalyst. LSCF was synthesised using simple Pechini sol-gel method. The evaporation time and temperature of the LSCF-sol were varied to obtain various viscosity of catalytic sol. From XRD analysis, pure LSCF perovskite structure formed at temperature at 850oC. The morphological of unmodified and surface-modified alumina hollow fibre membranes (AHF) were studied using FESEM. The effect of LSCF catalytic sol viscosity was studied and it was found that as the viscosity of the sol increases, the amount of catalyst deposited on the alumina hollow fibre were increased. Besides, the amount of catalyst deposited on 1350 AHF was found to be higher than 1450 AHF. This result is supported by the result of pore distribution data whereby 1350 AHF was observed to be more porous than 1450 AHF, with porosity percentage of 40.38% and 28.80%, respectively. Although higher viscosity of catalytic sol could lead to a high amount of catalyst deposited on the AHF substrate, there is a tendency for micro-cracks to develop. Thus, the viscosity of the catalytic sol is important to control in order to have higher oxygen permeation flux.

Enhanced fouling resistance of surface-modified alumina membranes by controlling humic acid and negatively charged-organosilane concentrations

Enhanced fouling resistance of surface-modified alumina membranes by controlling humic acid and negatively charged-organosilane concentrations

Surface modification of alumina with biosafe molecules: Nanostructure, thermal, and mechanical properties of PVA nanocomposites

ABSTRACTIn this investigation, citric acid (CA) and ascorbic acid (AA) as biocompatible and biodegradable coupling agents were grafted onto surface of Al2O3 nanoparticles (NP)s via ultrasonic process. Then, various percentages of the modified Al2O3 NP were immobilized onto matrix of pristine poly(vinyl alcohol) (PVA) and ameliorated their morphology, mechanical and thermal properties. Transmission electron microscopy photographs were valid criterion for characterizing morphology of Al2O3 with CA and AA. The improvement of the mechanical properties revealed good dispersion of the modified Al2O3 into the matrix of PVA. Finally, thermogravimetric analysis curves displayed an increase in the thermal stability of the nanocomposites upon grafting of the modified Al2O3. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44561.

Implications of handling practices on the ecotoxic profile of alumina nanoparticles towards the bacteria Vibrio fischeri

ABSTRACTThe complex nature and behavior of Engineered Nanomaterials (ENMs) has led to adoption of customized experimental ecotoxicity practices that are prone to possible artefacts in the inherent toxic properties of ENMs. In addition, the lack of standardized handling procedures for the ecotoxicity testing of ENMs prevents the development of experimental protocols for regulatory purposes. In this study, a suite of techniques for dispersion of ENMs was adopted and tested for two types of surface-modified alumina nanoparticles—one hydrophobic and one hydrophilic—towards the bacteria, Vibrio fischeri. The effect of certain handling practices on the observed ecotoxic effects on V. fischeri was examined. The overall goal was to evaluate by what means the handling practices of ENMs may affect the obtained toxicity results. It was realized that the toxicity of the hydrophilic and hydrophobic ENMs was mainly affected by the centrifugation and the salinity of the tested dispersions, respectively. It is more likely that both aluminium and coating substance contributed to the overall toxicity. Toxicity results are discussed with regard to generic physicochemical characteristics of the dispersions.

Thermal and mechanical properties enhancements obtained by reinforcing a bisphenol-a based phthalonitrile resin with silane surface-modified alumina nanoparticles

A new type of nanocomposites based on a high performance bisphenol-A phthalonitrile resin and surface-modified alumina nanoparticles was prepared by a hot compression molding technique. The effect of adding different amounts of the reinforcing phase on the thermal and mechanical properties of the resulting nanocomposites was investigated. Thermogravimetric analysis showed that the starting decomposition temperatures and the residual weight at 800°C were highly improved upon adding the nanofillers. At 15 wt% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced, reaching 346°C and 3.4 GPa, respectively. The tensile strength and modulus as well as the microhardness values increased with the increasing amount of the nanoparticles. The tensile modulus calculations were investigated using Series, Halpin-Tsai, and Kerner models. Haplin-Tsai model was found to reproduce the experimental data with the best accuracy. Estimation of the nanofillers shape factors for both Haplin-Tsai and Kerner models significantly improved the precision of the cited predictive models. The fractured surface of the nanocomposites analyzed by SEM exhibited homogeneous and rougher surfaces compared to that of the pristine resin. Finally, this new kind of nanocomposites is a highly attractive candidate for use in advanced technological applications such as the aerospace and military fields.POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Support interaction of Ni nanocluster based catalysts applied in CO2 reforming

Surface-tuned mesoporous alumina has been prepared using a template-assisted solvo thermal method, and Ni nanoclusters (4–5nm) have been synthesized on this support using a very facile organic matrix decomposition approach to dry reforming of methane. The catalyst system demonstrates very good catalytic activity toward CH4 and CO2 conversion (>90%), with a H2/CO ratio in syngas of almost unity, remarkable stability for more than 100h, and is proven to be a very interesting catalyst system in dry reforming with methane. Both fresh and spent catalyst have been thoroughly characterized using different techniques such as N2 physisorption studies, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, temperature-programmed reduction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis to determine the structure–activity relationship. Characterization results show that Ni nanoclusters are highly dispersed on the surface of modified alumina. In addition, an excellent metal-support interaction evolves that clearly enhances the stability of the Ni clusters, providing better resistivity toward sintering. The presence of balanced acidic and basic sites in the surface-modified alumina drastically lowers coke formation and enhances the catalyst lifetime. The structures of adsorbed methane and carbon dioxide on the catalyst surface and the corresponding energy of adsorption have been computed using density functional theory calculations. It has been found that CO2 is adsorbed and dissociated into CO and O, while methane is adsorbed as CH3∗ and H∗ on the catalyst system.

Preparation and frictional investigation of the two-components silanes deposited on alumina surface

Abstract Functionalization and pattering technique that permits two-component pattern-specific modification of alumina surface with silanes molecules are reported. The method relies on a two-component molecular system that simultaneously decreases coefficient of friction of the alumina surface and provides uniform chemical functionality suitable for further elaboration. Pattern/two-component modification is achieved via gas-phase deposition of the silanes using polydimethylsiloxane stamp. The frictional behaviors of the two-component films of the silane molecules with different chain length covalently absorbed on alumina surfaces, were characterized by the ball-disk (microtribometer) tester. The surfaces of the substrate modified by two-component molecular films were examined by atomic force microscopy (AFM). The measured tribological results showed that the mixing of the fluoroalkylsilane and alkylsilane enhance the lubrication and decrease the friction compared to the one-component thin films.

Mechanical Properties and the Microstructure of Al2O3/Al/Al2O3 Joints with the Surface Modification of Alumina by a Thin Layer of Ti + Nb

Al2O3/Al/Al2O3 joints were formed by liquid-state bonding of alumina substrates covered with a thin Ti + Nb coating of 900 nm thickness with the use of an Al interlayer of 30 μm at 973 K under a vacuum of 0.2 mPa for 5 min. The bond strength of the joints was examined by a four-point bending test at 295, 373, and 473 K. Optical, scanning, and transmission electron microscopies were applied for detailed characterization of the interface structure and failure characteristics of fractured joint surfaces. The analysis of the results has shown that (i) bonding occurred due to the formation of a reactive interface on the metal side of the joint in the presence of Al3Nb(Ti) precipitates and (ii) modification of Al2O3 by a thin layer of Ti + Nb increases the hardness at the interface and makes it possible to achieve reliable joints working at elevated temperatures.

Influence of Surface Modification of Alumina on Improvement of Wetability in Aluminium Matrix Composite

In this research, aluminium powder (50 wt%) and alumina (50 wt%) were first milled at a specific ball-to-powder ratio in a high-energy planetary mill at different times to manufacture Al-Al2O3composite. Then, the capsules of powdery composites (Al-Al2O3)CPproduced at the milling stage were added to aluminium melt and cast through ex situ. Scanning electron microscope SEM was used to study the morphology of the capsules and the microstructure of the produced composite. The percentage of powdery composite capsules and reinforcing particles present in the microstructure of Al-Al2O3composite was measured by Image Tool software. The results of the tests showed that, by optimizing the milling time to 5 hours, the alumina particles are sufficiently placed in the matrix of the capsules; on the other hand, alumina particles are also properly coated with aluminium powder. When these capsules are added to aluminium melt, the rate of the wetting of alumina particles greatly increases and accordingly the percentage of the reinforcing particles in the cast composite matrix increases dramatically. By surface modification and accordingly increasing percentage of Al2O3, the tensile strength increases and the tensile strength of the composites is higher than that of the matrix alloy.

Surface Modification of Alumina/ Zirconia Ceramics Upon Different Fluoride‐Based Treatments

The aim of this study was to prepare and to characterize the structure of Al2O3–3YSZ composites with 5% TiO2 addition as well as the surface modification upon treatments with SnF2 and NaBF4, respectively. SEM micrographs showed the controlled densification of the composites as an effect of 3YSZ and TiO2 addition to alumina matrix. By FTIR and XRD, the characteristics of Al‐O and Zr‐O vibrations, respectively, the diffractions lines related to α‐corundum and zirconia in tetragonal phase were discussed. Qualitative and quantitative results obtained by XPS and ATR FTIR demonstrated that the proposed materials are more sensitive to SnF2 than to NaBF4 treatment.

Chemical modification of alumina surface by immobilization of 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide for extractive concentration of silver ions

A column, solid phase extraction (SPE), preconcentration method was developed for determination of silver by using alumina coated with 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide and determination by flame atomic absorption spectrometry. The separation/preconcentration conditions for the quantitative recovery were investigated. At pH 2, the maximum sorption capacity of Ag+ was 7.5 mg g−1. The linearity was maintained in the concentration range of 0.02–11.0 µg mL−1 in the final solution or 0.14–1.10 × 104 ng mL−1 in the original solution for silver. The preconcentration factor of 140 and relative standard deviation of ±1.4% was obtained, under optimum conditions. The limit of detection (LOD) was calculated as 0.112 ng mL−1, based on 3σbl/m (n = 8) in the original solutions. The proposed method was successfully applied to the determination trace amounts of silver in the environmental samples such as tea, rice and wheat flour, mint, and real water samples.

Investigation of the structure of fluoroalkylsilanes deposited on alumina surface

This paper presents investigation of the structure of fluoroalkylsilanes on alumina surface by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), Fourier transform infrared (FT-IR) spectroscopy and atomic force microscopy (AFM).The fluoroalkylsilanes were prepared on alumina surface using the vapor phase deposition (VPD) method. XPS and ToF-SIMS measurements confirm the presence of fluoroalkylsilanes on the alumina surface. AFM was used to compare the frictional behavior of samples after modifying the alumina surface by fluoroalkylsilanes. Nanotribological studies of fluoroalkylsilanes films with different head groups on the alumina surface include, besides frictional studies, also adhesive forces investigations.It is shown that surface modification of alumina by fluoroalkylsilanes decreases coefficient of friction and adhesive forces values by more than 50% compared to unmodified alumina. In comparison to a non-modified alumina surface all tested silanes, particularly compounds with three reactive atoms in the head group, cause a decrease in the friction coefficients in nanofriction tests. The same effect was also observed for adhesion measurements. It was found that the alumina modified by trifunctional fluoroalkylsilanes have a higher degree of hydrophobicity, lower adhesion, and lower coefficient of friction than the monofunctional fluoroalkylsilanes covered alumina surface.