Alumina Loading Research Articles

Nanostructured sustainable carbon derived from biomass as catalyst support for alumina in catalytic methanol conversion to DME as hydrogen carrier

A novel series of nanostructured catalysts composed of Al2O3 supported on a phosphorous (P) modified mesoporous carbon (ACP) derived from orange peel residues was formed. The formed, 1−7% (w/w) alumina/ACP, catalysts were investigated for conversion of methanol to dimethyl ether (DME) as a promising hydrogen carrier. The catalysts were characterized with a group of standard characterization techniques. Increasing of alumina loading caused remarkable structural and textural changes. Thus, new bands due to Al–O–P was detected by ATR−FTIR, which was confirmed by XPS as due to surface AlPO4 species. However, no crystalline Al2O3 and/or AlPO4 nanoparticles were detected by XRD or HRTEM. Meanwhile, the mesoporous surface texture was preserved. The loading of alumina led to increasing of Brønsted acidic sites population. The catalyst exhibited high conversion of methanol and complete selectivity for DME at low, DME formation rate of 17.88 and 19.85 mmol g−1 h−1 at 300 and 350 °C, respectively. The catalyst efficiency is among the most efficient traditional and recently reported catalysts. Thus, the work showed successful biomass valorization into efficient, selective, low price catalysts that facilitate hydrogen storage via conversion of methanol to DME. This conversion, which is advantageous in transportation and distribution as H2 carrier, will in fact support and advance the UN's sustainable development goals.

Simulation for performance of storage unit with analyzing water freezing in presence of nanoparticles

The influences of loading alumina with different range of diameter and concentration have been considered in this study. The single phase mixture for predicting the features of nanomaterial was incorporated and equations in unsteady form were presented. For deriving the solution of the model, Galerkin method was used incorporating implicit technique. Validation tests have been provided and reasonable accuracy has been obtained. The geometry has tree shape fins which can help to accelerate the process. Although increasing size of powder can augment the interaction of them, the freezing time increases if the size of particles increases greater than 40 nm. Adding nano-powders can decrease the required time by about 41.26 %. With the changing size of nanoparticles, firstly, freezing time decreases about 20.02 % then it increases about 49.33 %. The minimum required time for freezing is 3991.58 s and this period happens when dp = 40 nm and ϕ = 0.04.

Mechanical and Biological Characterization of PMMA/Al2O3 Composites for Dental Implant Abutments.

The mechanical and biological behaviors of PMMA/Al2O3 composites incorporating 30 wt.%, 40 wt.%, and 50 wt.% of Al2O3 were thoroughly characterized as regards to their possible application in implant-supported prostheses. The Al2O3 particles accounted for an increase in the flexural modulus of PMMA. The highest value was recorded for the composite containing 40 wt.% Al2O3 (4.50 GPa), which was about 18% higher than that of its unfilled counterpart (3.86 GPa). The Al2O3 particles caused a decrease in the flexural strength of the composites, due to the presence of filler aggregates and voids, though it was still satisfactory for the intended application. The roughness (Ra) and water contact angle had the same trend, ranging from 1.94 µm and 77.2° for unfilled PMMA to 2.45 µm and 105.8° for the composite containing the highest alumina loading, respectively, hence influencing both the protein adsorption and cell adhesion. No cytotoxic effects were found, confirming that all the specimens are biocompatible and capable of sustaining cell growth and proliferation, without remarkable differences at 24 and 48 h. Finally, Al2O3 was able to cause strong cell responses (cell orientation), thus guiding the tissue formation in contact with the composite itself and not enhancing its osteoconductive properties, supporting the PMMA composite's usage in the envisaged application.

Impact of magnetic field on nanofluid thermophysical treatment within enclosure

Numerical technique for examining the transport of nanofluid within the porous container has been applied. The tank has one curved hot wall which is located in the center of the outer cylinder. The single-phase approach to deriving properties of nanofluid was applied and Darcy law has been implemented to involve the porous term in the equation. The format of the equation has been converted to stream function format to remove the pressure terms and final equations were solved via CVFEM. The written code was verified according to the previous data of the published work. Outputs showed that loading alumina causes Nu to augment by 26.71% when Ha is zero and it can be increased about 41.22% when Ha = 15. Applying a magnetic field can reduce the Nu around 37.93% when [Formula: see text]. With increase of strength of rotating cell with the rise of Ra, Nu increases by about 38.22%. Changing the shape of alumina can increase the Nu by about 11.73% when [Formula: see text] and [Formula: see text].

Synthesis of alumina-carbon framework for efficient sorption of methyl orange from wastewater with factorial design and mechanisms

A series of different activated carbon (AC) based composites were synthesized from municipal agricultural wastes and applied as a support for gamma alumina loading. The adsorptive removal activities on Al2O3 doped ASAC (almond shell activated carbon), PSAC (pea shell AC), and PNSAC (peanut shell AC) adsorbents were evaluated for methyl orange removal from water. The higher breakthrough adsorbent efficacy of the AC-Al2O3 adsorbents is influenced by the H+ ions released from AC and undergoes a chemical ion exchange reaction with the terminal dimethyl nitrogen and produces a positive charge on methylene orange. These materials were characterized using several techniques. Adsorptive activities show that ASAC-Al2O3 achieved an excellent methyl orange removal efficiency of up to 86% responsible for 56.5 mg/g adsorption capacity. In comparison with ASAC-Al2O3, PSAC-Al2O3 and PNSAC-Al2O3 achieved compromising the adsorptive capacity of 77.6% and 60% accountable for the 52 and 45 mg/g adsorption efficiency, respectively. According to the findings, a mechanism for dye adsorption over AC-Al2O3 material was presented. Hence, it can be concluded that the prepared material showed enhanced adsorption efficiency and hence enhance the water quality. Thus, it is recommended to be tested on a larger scale.

Numerical modeling for thermal behavior of nanomaterial laminar flow and convective heat transfer in appearance of magnetic field

The new computational approach has been incorporated for modeling the nanofluid flow through a cavity involving a wavy inner wall which experiences uniform flux. The fluid was created by loading alumina powders with various shapes within the water. The stream function formulation was applied after employing Darcy law and final equations have been generated. The container is under the impact of Lorentz force in addition to buoyancy forces. With loading additives, Nu enhances about 17.07% and 41.57% depending on the amount of Ha. The greater value of Ha makes the effect of adding nanoparticles become more sensible. With increasing the value of shape factor, Nu increases about 11.76%. As Ha grows, the rate of cooling decreases about 41.31%. With augment of Ra, Nu enhances about 50.41% in absence of Ha.

Solidification process and changing the physical behavior of PCM with involve of nanoparticles

To attain a new system with a higher rate of freezing, two approaches were utilized in this paper namely: (1) loading alumina nanoparticles; (2) involving curved walls. The geometry has two cold surfaces and pure PCM is water. The convection role in this mechanism is very low and so the related terms have been neglected in modeling. By adding source term of freezing in energy equations and removing the advection terms, the final form of mathematical model will appear. Finite element method, by involving the implicit technique, has been selected for simulations and to increase the correctness of code, an adaptive grid has been utilized. For better description of efficacy of alumina nanoparticles, influences of size and amount of powders have been examined. As greater sizes are utilized, the period firstly decreases around 19.98% then it augments around 49.13%. Besides, the dispersion of powders results in 70.06% reduction in freezing time.

Improving Thermal Conductivity of Injection Molded Polycarbonate/Boron Nitride Composites by Incorporating Spherical Alumina Particles: The Influence of Alumina Particle Size.

In this work, the influences of alumina (Al2O3) particle size and loading concentration on the properties of injection molded polycarbonate (PC)/boron nitride (BN)/Al2O3 composites were systematically studied. Results indicated that both in-plane and through-plane thermal conductivity of the ternary composites were significantly improved with the addition of spherical Al2O3 particles. In addition, the thermal conductivity of polymer composites increased significantly with increasing Al2O3 concentration and particle size, which were related to the following factors: (1) the presence of spherical Al2O3 particles altered the orientation state of flaky BN fillers that were in close proximity to Al2O3 particles (as confirmed by SEM observations and XRD analysis), which was believed crucial to improving the through-plane thermal conductivity of injection molded samples; (2) the presence of Al2O3 particles increased the filler packing density by bridging the uniformly distributed BN fillers within PC substrate, thereby leading to a significant enhancement of thermal conductivity. The in-plane and through-plane thermal conductivity of PC/50 μm-Al2O3 40 wt%/BN 20 wt% composites reached as high as 2.95 and 1.78 W/mK, which were 1183% and 710% higher than those of pure PC, respectively. The prepared polymer composites exhibited reasonable mechanical performance, and excellent electrical insulation properties and processability, which showed potential applications in advanced engineering fields that require both thermal conduction and electrical insulation properties.

A PMMA bone cement with improved antibacterial function and flexural strength

A novel non-leaching antibacterial bone cement has been developed and evaluated. An antibacterial furanone derivative was synthesized and covalently coated onto the surface of alumina filler particles, followed by mixing into a conventional poly(methyl methacrylate) bone cement. Flexural strength and bacterial viability were used to evaluate the modified cements. Effects of coated antibacterial moiety content, coated alumina filler particle size and loading were investigated. Results showed that almost all the modified cements showed higher flexural strength (up to 10%), flexural modulus (up to 18%), and antibacterial activity (up to 67% to S. aureus and up to 84% to E. coli), as compared to original poly(methyl methacrylate) cement. Increasing antibacterial moiety and filler loading significantly enhanced antibacterial activity. On the other hand, increasing coated filler particle size decreased antibacterial activity. Increasing antibacterial moiety content and particle size did not significantly affect flexural strength and modulus. Increasing filler loading did not significantly affect flexural modulus but reduced flexural strength. Antibacterial agent leaching tests showed that it seems no leachable antibacterial component from the modified experimental cement to the surrounding environment. Within the limitations of this study, the modified poly(methyl methacrylate) bone cement may potentially be developed into a clinically useful bone cement for reducing in-surgical and post-surgical infection.

Platinum-alumina modified SO42−-ZrO2/Al2O3 based bifunctional catalyst for significantly improved n-butane isomerization performance

In this study, sulfated zirconia with loading of platinum (Pt) and platinum alumina (PA-Al2O3) promoted sulfated zirconia (SZ) catalysts were synthesized by hydro-thermal route. The samples were characterized by XRD, BET, FT-IR, NH3-TPD, and TGA. The catalytic efficiency of all the synthesized catalysts was tested on the isomerization of n-butane. The results indicated that the conversion of n-butane (71.04%), selectivity to i-butane (98.96%), and yield of i-butane (70.30%) is significantly high for PA/SZ sample than that of Pt modified SZ and bare SZ. The results of this study suggest that the SZ modified by Pt/Al2O3 (PA) provided better catalytic performance and higher stability (within 25 h of TOS), when compared with SZ, and Pt-modified SZ.

Defluorination by ion exchange of SO42− on alumina surface: Adsorption mechanism and kinetics

Electrostatic and complexation effects have been considered as the primary adsorption mechanisms for defluorination using aluminum based materials, while the effect of ion exchange between anions and fluorine ion has been mostly ignored, although synthesized alumina materials usually contain a large amount of anions, such as SO42−, NO3−, and Cl−. In this study, the effect of anions exchanges and its key role on defluorination were systematically investigated for adsorption by aluminas loaded with various typical anions (SO42−, NO3− and Cl−). Experimental results showed that SO42-- loading alumina had the best defluorination performance (94.5 mg/g), much higher than NO3− (45.0 mg/g) and Cl− (19.1 mg/g). The contribution ratio of ion exchange between SO42− and F− was as high as 20–60% in all potential defluorination mechanisms. By using Density Functional Theory calculation, the detailed mechanism revealed that the ion exchange process was mainly driven by the tridentate chelation of SO42− which reduced the exchange energy (ΔF−−SO42− 4.8 eV). Our study clearly demonstrated that ion exchange between SO42− and F− is a critical mechanism in defluorination using aluminum-based materials and provides a potential alternative method to enhance the adsorption performance of modified alumina.

Tailoring asymmetric Al2O3 membranes by combining tape casting and phase inversion

This study aimed to combine the techniques of tape casting and phase inversion to produce highly permeable ceramic membranes suitable for microfiltration in a single sintering step. The morphological, mechanical and textural characterization was performed using SEM, flexural strength measurement, mercury porosimetry and X-ray micro-computed tomography. Alumina membranes were produced using different slurry formulations and solidified via phase inversion, followed by sintering at 1400 or 1500 °C. Additionally, a co-casting strategy was successfully used for some membranes aiming to reduce the flux resistance caused by the dense layer usually formed at the bottom of ceramic membranes produced by phase inversion while the thin skin layer is preserved. Ceramic membranes with large pore sizes of the skin layer (0.30–0.42 μm) and high total porosity (46–75%) were obtained, and a clear increase of the mechanical resistance is observed when increasing alumina loading. Pure water flux of 52.4 and 26.60 m3 m-2 h-1 at 1 bar, and 27.60 and 41.11 MPa maximum flexural strength were achieved for membranes produced from slurries containing 45 and 50 wt% alumina, respectively. Simulations of permeability carried out from X-ray micro-computed tomography images in three axes proved a preferential fluid flow in the z-axis (from top to bottom) for different membrane regions and demonstrated that permeability is mainly influenced by the top skin and bottom layer morphology, which is in agreement with the experimental results.

Study on surface alkalinity of alumina and molybdenum metal loading

Study on surface alkalinity of alumina and molybdenum metal loading

An antibacterial dental light-cured glass-ionomer cement with improved hardness

An antibacterial dental light-cured glass-ionomer cement has been developed and evaluated. An antibacterial furanone derivative was synthesized and covalently attached onto the surface of alumina filler particles. The formed antibacterial fillers were then mixed into a light-curable glass-ionomer cement formulation. Surface hardness and bacterial viability were used to evaluate the modified cements. Effects of coated furanone moiety content on the modified fillers, modified alumina filler particle size and loading, and total glass filler content were investigated. Results showed that increasing antibacterial furanone content, modified particle size and loading, and total glass filler content generally increased surface hardness. Increasing furanone moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size decreased antibacterial activity. The leaching tests indicate that the modified experimental cement showed no leachable antibacterial component to bacteria and cells

A self-cured glass-ionomer cement with improved antibacterial function and hardness.

A novel antimicrobial dental self-cured glass-ionomer cement has been developed and evaluated. Alumina filler particles were covalently coated with an antibacterial polymer and blended into a self-cured glass-ionomer cement formulation. Surface hardness and bacterial viability were used to evaluate the modified cements. Results showed that the modified cements exhibited a significantly enhanced antibacterial activity along with improved surface hardness. Effects of antibacterial moiety content, alumina particle size and loading, and total filler content were investigated. It was found that increasing antibacterial moiety content, particle size and loading, and total filler content generally increased surface hardness. Increasing antibacterial moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size showed a negative impact on antibacterial activity. The leaching tests indicate no cytotoxicity produced from the modified cements to both bacteria and 3T3 mouse fibroblast cells.

A dental filling composite resin restorative with improved antibacterial function and hardness

A novel antimicrobial dental composite resin has been developed and evaluated. Alumina filler particles were covalently coated with an antibacterial resin and blended into a composite resin formulation. Surface hardness and bacterial viability were used to evaluate the modified composite resin. Results showed that almost all the modified composite resins exhibited higher antibacterial activity along with improved surface hardness, as compared to unmodified one. Effects of antibacterial moiety content on the modified fillers, modified alumina particle size and loading, and total filler content were investigated. It was found that increasing antibacterial moiety content, particle size and loading of the modified filler, and total filler content generally increased surface hardness. Increasing antibacterial moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size showed a negative impact on antibacterial activity. The leaching tests indicate that the modified experimental composite resin showed no leachable antibacterial component to bacteria and 3T3 mouse fibroblasts.

Effect of low nanosized alumina loading fraction on the physicomechanical and tribological behavior of epoxy

The primary objective of the present study is to investigate how alumina nanoparticles with a low loading fraction by weight affect the physicomechanical and tribological characteristics of epoxy nanocomposites. Alumina nanoparticles with loading fractions of zero, 0.1, 0.2, 0.3, and 0.4 wt% are homogeneously dispersed in the epoxy matrix. Density, hardness, Young's modulus, compressive yield strength, toughness, elasticity, friction coefficient, and specific wear rate of the epoxy composites were estimated experimentally. A finite element model for the friction process is constructed to study the contact stress distribution during composite samples sliding. Results indicate an enhancement in the mechanical and tribological properties of the epoxy nanocomposite. Finally, scanning electron microscopy is used to inspect the worn surfaces of samples to elucidate the wear mechanism.

Near‐net shape manufacture of macroporous nanosized alumina monolith by aqueous gel casting method

AbstractA potentially near‐net‐shape manufacturing procedure for macroporous alumina monoliths with 20%‐75% porosity was presented by gel casting of nano γ‐Al2O3. Although monolith obtained by nano alumina had a high surface area and low sintering temperature, an optimum fraction of micron alumina needed to be added to achieve the proper rheological and mechanical properties of slurries. The preparation parameters including alumina loading, sintering temperature, monomer concentration, and the fraction of nano alumina were investigated. The green densities ranging from 0.66 to 0.86 g cm−3 were obtained by raising alumina loading from 10 to 20 vol%. Depending on the monomer concentration and sintering temperature, the mean pore size ranging from 45 to 412 nm, total porosity (20%–75%), and open porosity varying from 12% to 89% were obtained. The sintered density (from 0.95 to 3.15 g cm−3) and compressive strength (CS) (from 4.2 to 31.46 MPa) were suitable for use in different fields.

The influence of alumina particle size on the properties and performance of alumina hollow fiber as support membrane for protein separation

The advantages offered by ceramic membranes compared to the polymeric membrane have attracted more interest, especially in fluid separation application owing to its ability to withstand harsh operating conditions. In this study, five alumina hollow fiber membranes were prepared from different loading ratios of alumina particle sizes which are 1 µm, 0.5 µm, and 0.01 µm. The membranes were prepared via phase-inversion technique using water as an external and internal coagulant and sintered at 1400 °C. The effect of the alumina powder particle sizes on membrane morphology, pore size distribution, mechanical strength, surface roughness, pure water flux, and Bovine Serum Albumin (BSA) rejection was investigated in this study. By varying the overall loading and particle size of alumina, different morphologies of membranes were obtained. Higher loading of coarse particles produced more porous and low mechanical strength membranes, whereas reducing the amount of coarse particles produced a more compact membrane with the highest mechanical strength of 27 MPa. Meanwhile, BSA rejection is declining when more coarse particles were used to fabricate the membrane. Among all the membranes, the 5:3:2 ratio able to reject up to 66% of protein (BSA) with the flux of 138.7 L m−1 h−1.

Enhanced thermal conductivity of alumina and carbon fibre filled composites by 3-D printing

In this work, we report a fabrication of oriented carbon fibres/alumina/silicon rubber composites by 3-D printing. The 3-D printed composites possess higher thermal conductivity up to 7.36 W/m K at 12 vol% CFs and 30 vol% alumina loading than that of cast composites (4.22 W/m K) at the same components. The orientation caused by 3-D printing produces a synergism of the thermal conductivity enhancement for CFs and alumina hybrid filled composites. We attribute the synergism to the decrease of thermal interface resistance, while the reduction of thermal interface resistance has a bigger effect on thermal conductivity of CASR composites. This study provides a novel way to obtain thermal conductive composites with orientation, which has a great significance for the development of high-performance thermal conductive products.