Alumoxane Nanoparticles Research Articles

Synthesis and characterization maleate-alumoxane nanoparticles for removal of reactive yellow 84 dye from aqueous solution

Maleate-alumoxane nanoparticles (Mal-A) were synthesized from boehmite and applied for adsorption of an azo dye (Reactive Yellow 84) from aqueous solution. Its adsorption capacity was compared with three types of carboxylate alumoxane nanoparticles synthesized from boehmite including salicylate alumoxane (Sal-A), para-aminobenzoate alumoxane (Pab-A) and fumarate alumoxane (Fum-A). The characterizations of prepared materials were analyzed using FTIR, SEM, X-ray diffraction and BET measurements. Among utilized alumoxanes at natural pH, the adsorption capacity of Mal-A was 45, 67, 116 and 215% higher than that of Fum-A, Boehmite, Pab-A, Sal-A nanoparticles, respectively. Response surface methodology (RSM) using Box-Behnken design of experiment was employed to investigate the influence of pH, initial concentration of dye and adsorbent dosage on dye removal efficiency of Mal-A. Box-cox transformation was chosen to improve model adequately and a good prediction (R2: 0.998) was achieved. Under optimum condition, i.e., pH: 4.3, dye concentration: 151.5 mg/L and adsorbent dosage: 1.2 g/L, the adsorption capacity and dye removal efficiency were obtained 130.6 mg/g and 99.2%, respectively. The kinetics and equilibrium data were perfectly represented with linear pseudo-second-order and linear Langmuir isotherm models, respectively.

Polycitrate-para-aminobenzoate alumoxane nanoparticles as a novel nanofiller for enhancement performance of electrospun PAN membranes

In the present study, the novel high flux and antifouling polycitrate-para-aminobenzoate alumoxane (PC-PABA) nanoparticles embedded polyacrylonitrile (PAN) microfiltration membranes were prepared by electrospinning method. PC-PABA nanoparticles are modified carboxylate alumoxanes with boehmite core containing extra hydroxyl, carboxylate and citrate alumoxane groups on their surface, which introduced in this study for the first time. The influence of the PC-PABA nanoparticles on morphology and efficiency of the prepared electrospun membranes was studied. The FTIR spectra of the PC-PABA nanoparticles showed that the citrate alumoxane, carboxylate, and hydroxyl groups were successfully formed on the surface of PC-PABA nanoparticles. The morphology studies by field emission scanning electron microscopy (FESEM) revealed that at low concentration of the PC-PABA nanoparticles, the nanofibers at the surface of the membranes was smooth. Nevertheless, at higher PC-PABA nanoparticle concentrations, the nanoparticles were decorated on the nanofibers due to agglomeration of the nanoparticles. The hydrophilicity and permeation flux of the membranes were enhanced by embedding the PC-PABA nanoparticles. The activated sludge filtration results showed that by adding a low amount of PC-PABA nanoparticles, the flux recovery ratio of the membranes was increased. The 3 wt% PC-PABA/PAN membrane, exhibited the highest flux recovery ratio (FRR) of 98.1% and considerable reusability during long-term filtration.

Experimental investigation of carboxylate-alumoxane nanoparticles for the enhanced oil recovery performance

In this study, two nanoparticle types of functionalized alumina (functionalized boehmite and functionalized pseudo-boehmite which are named B.MA-Alumoxane and S.B.MA-Alumoxane, respectively) were produced by the sol-gel method and were dispersed in deionized water without surfactants. Field emission scanning electron microscopy (FE-SEM) images were taken to observe morphology of the nanoparticles, type of the functional group was characterized by Fourier-transform infrared spectroscopy (FT-IR), zeta potential analysis was conducted for investigating the stability of the nanofluids, the nanoparticles size distribution was measured by dynamic light scattering (DLS), and also Brunauer–Emmett–Teller (BET) analysis was performed to characterize the surface properties of the prepared nanoparticles. For studying the application of these nanofluids in enhanced oil recovery (EOR), nanofluids with different concentrations (200, 300, 400, and 500 ppm) of each nanoparticle were prepared. The interfacial tensions (IFT) of nanofluids with crude oil were measured by pendant drop method and wettability alteration of oil-wet sandstone rock samples was investigated via contact angle measurement method when they were exposed to nanofluids. In order to investigate the adsorption of the nanoparticles on the sandstone rocks, the adsorption tests were performed. In following, micromodel tests were done to observe the effect of nanoparticles in displacing oil from the porous media of the glass micromodel. Coreflood tests were performed in order to observe the application of carboxylate-alumoxane nanofluids in sandstone core plugs. The morphology of S.B.MA-Alumoxane nanoparticle is as agglomerated particles and B.MA-Alumoxane has nanosheet morphology. The size distribution for S.B.MA-Alumoxane and B.MA-Alumoxane is 12 nm to 35 nm and 32 nm to 155 nm, respectively. By increasing the concentration of nanoparticles, IFT value was reduced from 19.34 mN/m for deionized water to 8.52 mN/m for 500 ppm S.B.MA-Alumoxane and to 11.84 mN/m for 500 ppm B.MA-Alumoxane. The rock samples also became more water-wet in higher concentrations of both nanoparticle types. S.B.MA-Alumoxane showed better performance in comparison to B.MA-Alumoxane. The micromodel test showed the maximum increase of 52% in oil recovery for S.B.MA-Alumoxane and 33% for B.MA-Alumoxane with respect to deionized water. Moreover, coreflood test shows that S.B.MA-Alumoxane has better performance in comparison with B.MA-Alumoxane at the concentration of 500 ppm. In this research, for the first time Carboxylate–Alumoxane nanoparticles were used in EOR by two different morphologies and sizes. The smaller size and higher specific surface area of S.B.MA-Alumoxane in comparison with B.MA-Alumoxane provide its better performance in enhanced oil recovery.

Enhancing mechanical properties of epoxy resin using waste lignin and salicylate alumoxane nanoparticles

Extracted lignin from wastewater of Kraft process and lab-made salicylate alumoxane (Sal-A) nanoparticles were used as toughening agents in epoxy matrix. Epoxy/lignin composite, epoxy/Sal-A and epoxy/lignin/Sal-Al nanocomposites with various toughening agent loadings were cured with an aromatic diamine hardener. Lignin as an available cheap material and Sal-A, as multifunctional structures, both containing numerous phenolic hydroxyls on their surfaces, were incorporated into epoxy matrix with the aim of improving thermal and some mechanical properties of the resulting composites. Both particles interacted physically (directly) and chemically (indirectly) with the epoxy chains. Simplex lattice mixture design of experiment was applied for formulation development and optimization. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the extracted lignin, Sal-A nanoparticles and synthesized composites. Differential scanning calorimetry (DSC) was used to interpret thermal curing process. The presence of lignin and Sal-A nanoparticles in the epoxy matrix decreased the exothermic peak temperature and total heat of curing reaction. In the presence of 2.5 wt% lignin and 1.875 wt% Sal-A nanoparticles, tensile strength of epoxy composites was 22.23% and 30.92% higher than that of reference (pure) epoxy resin, respectively. Vickers hardness of epoxy composites in the presence of 2.5 wt% lignin and 2.5 wt% Sal-A nanoparticles was increased by 17.41% and 15.39%, accordingly.

Biofouling alleviation and flux enhancement of electrospun PAN microfiltration membranes by embedding of para‐aminobenzoate alumoxane nanoparticles

ABSTRACTMembrane bioreactor (MBR) as a hybrid technology for wastewater treatment is becoming more popular for wastewater treatment. However, membrane fouling has hindered the widespread application of MBRs. Many efforts have been done for fouling mitigation. In this study, high flux and antifouling microfiltration membranes with unique surface structure, high surface porosity, and permeability were prepared by electrospinning technique. Initially, the optimum thickness of electrospun polyacrylonitrile (PAN) membranes was determined and then, electrospun PAN membrane at optimum thickness were prepared by embedding para‐aminobenzoate alumoxane (PABA) nanoparticles at different concentrations. The effect of PABA nanoparticles on membrane performance was investigated. To investigate the characterization of the prepared membranes Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X‐ray spectroscopy, and water contact angle measurement were employed. The flux recovery ratio results revealed that the antifouling properties of the electrospun PAN membrane were enhanced by modification. The 3 wt % electrospun PABA embedded PAN had the best permeability, hydrophilicity, and antifouling properties among the fabricated membranes and showed remarkable reusability during filtration. The results obtained suggested that the high flux and antifouling electrospun PAN membranes embedded PABA nanoparticles could be used as MBR membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45738.

Novel antifouling nano-enhanced thin-film composite membrane containing cross-linkable acrylate-alumoxane nanoparticles for water softening

A novel thin-film composite (TFC) nanofiltration membrane was prepared using polymerization of pyrrole monomers on the PES ultrafiltration membrane. To improve the characteristics of hydrophobic polypyrrole (PPy) thin-film layer, cross-linkable acrylate-functionalized alumoxane nanoparticles with different concentrations were embedded into the thin-film during polymerization process, and thin-film nanocomposite (TFNC) membranes were prepared. The characteristics and performance of TFC and TFNC membranes were assessed through the morphological analyses (SEM, AFM), measurement of hydrophilicity and solid–liquid interfacial free energy, water permeability and Mg2+ removal tests. Addition of proper amount of nanoparticles into the polymerization mixture led to the preparation of membranes with more hydrophilic, thinner and smoother active layer as well as higher water permeability compared to TFC control membrane. TFNC membrane prepared with 0.025g of nanoparticles was the most efficient membrane since it exhibited the highest rejection of MgCl2 and MgSO4 salts. Antifouling capability of membranes, in terms of flux recovery and fouling parameters, demonstrated the high tolerance of TFNC against fouling.

Carbon and Inorganic Nanostructure Reinforced Polymeric Nanocomposites for Bone Tissue Engineering

Introduction: Poly(propylene fumarate) (PPF) is a biocompatible, biodegradable polymer widely investigated for bone tissue engineering applications. Various nanomaterials such as fullerenes, single- and multi- walled carbon nanotubes (SWCNTs, MWCNTs) and alumoxane nanoparticles have been used as reinforcing agents to improve the mechanical properties of PPF nanocomposites [1, 2, 3]. In this study, we have investigated the mechanical properties of PPF nanocomposites fabricated using various 1D and 2D carbon and inorganic nanomaterials such as single- and multi- walled carbon nanotubes (SWCNT, MWCNT), single- and multi- walled graphene oxide nanoribbons (SWGONR, MWGONR), graphene oxide nanoplatelets (GONP), tungsten di-sulfite nanotubes (WS2) and molybdenum di-sulfite nanoplatelets (MSNP) as reinforcing agents [4]. The objectives of this study were to investigate (1) the effects of nanostructure architecture (1D nanostructure (e.g. nanotube) vs. 2D nanostructure (e.g. graphene)), and (2) effects of chemical composition (inorganic vs. carbon nanoparticles) of reinforcing agents on the mechanical properties of PPF. Materials and Methods: PPF was synthesized using a two-step condensation reaction of diethyl fumarate and propylene glycol as described previously and characterized by H1-NMR (structure) and GPC (molecular weight). Longitudinal unzipping method was used to synthesize SWGONRs and MWGONRs form SWCNTs and MWCNTs, respectively. Modified Hummer’s method was used to synthesize GONPs. Inorganic nanomaterials (WS2 nanotubes and MSNPs) were synthesized using literature methods. Nanomaterials were characterized using Raman spectroscopy, AFM and HRTEM. Specimens were thermally crosslinked (60°C) into sample sizes according to ASTM standards for compression and three-point bend testing. Sol fraction analysis was performed to assess the crosslinking density of PPF nanocomposites after thermal crosslinking. Results and Discussion: PPF nanocomposites with 2D nanostructures showed significant improvements in the mechanical properties compared to positive controls (1D nanostructure reinforced PPF composites) and baseline controls (PPF composites without nanomaterials). For example, 0.2 wt% loading of MSNPs leads to ~ 100% increase in the Young’s modulus compared to PPF composites (baseline control). Additionally, inorganic nanostructures showed better or equivalent mechanical reinforcement compared to carbon nanostructures at all loading concentrations. The results indicate that the extent of mechanical reinforcement is closely dependent on the nanostructure morphology and follows the trend: nanoplatelets > nanoribbons > nanotubes. In general inorganic nanoparticles show equivalent or better mechanical reinforcement compared to carbon nanoparticles. TEM analysis of crosslinked nanocomposites indicates good dispersion of nanomaterials in the polymer matrix. Sol-fraction analysis showed increase in the crosslinking density of PPF nanocomposites at all concentrations of MSNP and WS2, and higher concentrations of GONP and MWGONR (0.1-0.2 wt%). These results suggest that the increase in the mechanical properties of 2D carbon and inorganic nanocomposites is due to increases in the crosslinking density of PPF (maybe due to formation of PPF-nanomaterial crosslinking). Additionally, presence of structural defects and functional groups on the nanostructures can lead to increased polymer-nanomaterial interaction, thereby increasing the mechanical properties. Conclusion: Carbon (SWCNT, MWCNT, MWGONR, SWGONR and GONP) and inorganic- nanoparticles (WS2 nanotubes and MSNPs) as reinforcing agents significantly improve the mechanical properties of PPF. In general, 2D and inorganic nanostructures show equivalent or better mechanical reinforcement than 1D and carbon nanostructures, respectively. Figure Caption: Compressive Modulus of PPF Nanocomposites

PAA grafting onto new acrylate-alumoxane/PES mixed matrix nano-enhanced membrane: Preparation, characterization and performance in dye removal

Nanoboehmite particles were modified by acrylic acid to produce new alumoxane nanoparticles. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to realize shape, size and functional groups of synthesized acrylate-alumoxane nanoparticles. The analyses declared that spherical acrylate-alumoxane nanoparticles were formed with hydroxyl and acrylate groups on their surface. Boehmite and acrylate-alumoxane were successfully introduced into polyethersulfone (PES) membrane matrix by the phase inversion method. Fabricated membranes were examined for water permeability, dye (acid blue 193) retention capability and fouling resistance against whey proteins. The field emission scanning electron microscopy (FE-SEM) images were used to estimate the changes in skin-layer morphology and bulk porosity of the prepared membranes. As a result, the directly arrayed finger-like macro-voids as well as bulk porosity were gained by adding acrylate-alumoxane nanoparticles compared to pristine PES membrane. However, different quantities of acrylate-alumoxane in the casting solution induced no noticeable alteration in the membranes bulk porosity. The membranes containing 1wt.% of acrylate-alumoxane and 1wt.% of nanoboehmite were selected to be grafted by polyacrylic acid (PAA). Comparison of grafting efficiency for pristine PES membrane and nanofiller blended membranes proved that acrylate-alumoxane offered more effective grafted membrane by providing polymerization initiation sites on mixed matrix membrane surface. In addition to high water permeability (around 19kg/m2hbar), the acrylate-alumoxane mixed/PAA grafted membrane showed superior dye removal and fouling resistance. Atomic force microscopy (AFM) as well as water contact angle test was applied for investigation of membranes surface properties.

Alumoxane/ferroxane nanoparticles for the removal of viral pathogens: the importance of surface functionality to nanoparticle activity

A bi-functional nano-composite coating has been created on a porous Nomex® fabric support as a trap for aspirated virus contaminated water. Nomex® fabric was successively dip-coated in solutions containing cysteic acid functionalized alumina (alumoxane) nanoparticles and cysteic acid functionalized iron oxide (ferroxane) nanoparticles to form a nanoparticle coated Nomex® (NPN) fabric. From SEM and EDX the nanoparticle coating of the Nomex® fibers is uniform, continuous, and conformal. The NPN was used as a filter for aspirated bacteriophage MS2 viruses using end-on filtration. All measurements were repeated to give statistical reliability. The NPN fabrics show a large decrease as compared to Nomex® alone or alumoxane coated Nomex®. An increase in the ferroxane content results in an equivalent increase in virus retention. This suggests that it is the ferroxane that has an active role in deactivating and/or binding the virus. Heating the NPN to 160 °C results in the loss of cysteic acid functional groups (without loss of the iron nanoparticle's core structure) and the resulting fabric behaves similar to that of untreated Nomex®, showing that the surface functionalization of the nanoparticles is vital for the surface collapse of aspirated water droplets and the absorption and immobilization of the MS2 viruses. Thus, for virus immobilization, it is not sufficient to have iron oxide nanoparticles per se, but the surface functionality of a nanoparticle is vitally important in ensuring efficacy.

Wet Catalyst-Support Films for Production of Vertically Aligned Carbon Nanotubes

A procedure for vertically aligned carbon nanotube (VA-CNT) production has been developed through liquid-phase deposition of alumoxanes (aluminum oxide hydroxides, boehmite) as a catalyst support. Through a simple spin-coating of alumoxane nanoparticles, uniform centimer-square thin film surfaces were coated and used as supports for subsequent deposition of metal catalyst. Uniform VA-CNTs are observed to grow from this film following deposition of both conventional evaporated Fe catalyst, as well as premade Fe nanoparticles drop-dried from the liquid phase. The quality and uniformity of the VA-CNTs are comparable to growth from conventional evaporated layers of Al(2)O(3). The combined use of alumoxane and Fe nanoparticles to coat surfaces represents an inexpensive and scalable approach to large-scale VA-CNT production that makes chemical vapor deposition significantly more competitive when compared to other CNT production techniques.

In vivo bone biocompatibility and degradation of porous fumarate‐based polymer/alumoxane nanocomposites for bone tissue engineering

The objective of this study was to determine how the incorporation of surface-modified alumoxane nanoparticles into a biodegradable fumarate-based polymer affects in vivo bone biocompatibility (characterized by direct bone contact and bone ingrowth) and in vivo degradability. Porous scaffolds were fabricated from four materials: poly(propylene fumarate)/propylene fumarate-diacrylate (PPF/PF-DA) polymer alone; a macrocomposite consisting of PPF/PF-DA polymer with boehmite microparticles; a nanocomposite composed of PPF/PF-DA polymer and mechanically reinforcing surface-modified alumoxane nanoparticles; and a low-molecular weight PPF polymer alone (tested as a degradation control). Scaffolds were implanted in the lateral femoral condyle of adult goats for 12 weeks and evaluated by micro-computed tomography and histological analysis. For all material groups, small amounts of bone, some soft tissue, and a few inflammatory elements were observed within the pores of scaffolds, though many pores remained empty or filled with fluid only. Direct contact between scaffolds and surrounding bone tissue was also observed in all scaffold types, though less commonly. Minimal in vivo degradation occurred during the 12 weeks of implantation in all materials except the degradation control. These results demonstrate that the incorporation of alumoxane nanoparticles into porous PPF/PF-DA scaffolds does not significantly alter in vivo bone biocompatibility or degradation.

Fabrication and in vitro degradation of porous fumarate‐based polymer/alumoxane nanocomposite scaffolds for bone tissue engineering

In this work, the fabrication and in vitro degradation of porous fumarate-based/alumoxane nanocomposites were evaluated for their potential as bone tissue engineering scaffolds. The biodegradable polymer poly (propylene fumarate)/propylene fumarate-diacrylate (PPF/PF-DA), a macrocomposite composed of PPF/PF-DA and boehmite microparticles, and a nanocomposite composed of PPF/PF-DA and surface-modified alumoxane nanoparticles were used to fabricate porous scaffolds by photo-crosslinking and salt-leaching. Scaffolds then underwent 12 weeks of in vitro degradation in phosphate buffered saline at 37 degrees C. The presence of boehmite microparticles and alumoxane nanoparticles in the polymer inhibited scaffold shrinkage during crosslinking. Furthermore, the incorporation of alumoxane nanoparticles into the polymer limited salt-leaching, perhaps due to tighter crosslinking within the nanocomposite. Analysis of crosslinking revealed that the acrylate and overall double bond conversions in the nanocomposite were higher than in the PPF/PF-DA polymer alone, though these differences were not significant. During 12 weeks of in vitro degradation, the nanocomposite lost 5.3% +/- 2.4% of its mass but maintained its compressive mechanical properties and porous architecture. The addition of alumoxane nanoparticles into the fumarate-based polymer did not significantly affect the degradation of the nanocomposite compared with the other materials in terms of mass loss, compressive properties, and porous structure. These results demonstrate the feasibility of fabricating degradable nanocomposite scaffolds for bone tissue engineering by photo-crosslinking and salt-leaching mixtures of fumarate-based polymers, alumoxane nanoparticles, and salt microparticles.

Degradation and biocompatibility of a poly(propylene fumarate)‐based/alumoxane nanocomposite for bone tissue engineering

In this work, we evaluated the in vitro cytotoxicity and in vivo biocompatibility of a novel poly(propylene fumarate) (PPF)-based/alumoxane nanocomposite for bone tissue engineering applications. The incorporation of functionalized alumoxane nanoparticles into the PPF-based polymer was previously shown to significantly increase the material's flexural mechanical properties. In the current study, samples underwent accelerated in vitro degradation to allow the study of biological responses to these materials over the course of their degradation on a shortened timescale. The polymer, a macrocomposite composed of the polymer and micron-sized particles, and the nanocomposite were evaluated at three stages of degradation for in vitro cytotoxicity with a fibroblast cell line and in vivo soft-tissue response after 3 and 12 weeks of implantation in adult goats. All three material groups experienced mass loss during degradation, but the nanocomposite group eroded significantly faster than the other groups. Nondegraded materials demonstrated minimal cytotoxicity and a minor inflammatory response in soft tissue. On the contrary, predegraded samples elicited more pronounced responses, though these were due to the increase in surface area, surface roughness, and fragmentation associated with the degradation process. The presence of alumoxane nanoparticles in the PPF-based nanocomposite did not significantly affect its cytotoxicity or biocompatibility.

Application of alumoxane nanoparticles as precursors for 3D alumina features

Acetate- and methoxy(ethoxyethoxy)acetate-functionalized alumina nanoparticles (A-alumoxane and MEEA-alumoxane, respectively) have been investigated as processable, water soluble precursors to 3-dimensional (3D) ceramic features. The ceramic features were formed by slip-casting aqueous solutions of the alumoxanes into polydimethylsiloxane molds, into which negative images of the desired features were molded. The features ranged from 50 to 450 μm in width and approximately 70 μm in depth. Drying the aqueous solution, and removal from the molds revealed free-standing thin film ‘green bodies’ on which are the positive images of the features, which upon firing (1200°C) resulted in their conversion to α-alumina. The formation of the ‘green body’ upon drying of the alumoxane solution and its sintering to ceramic was studied with regard to shrinkage and cracking. Ceramic 3D features formed from A-alumoxane faithfully reproduced the dimensions of the green body. However, shrinkage and cracking during the drying phase was observed. In contrast, MEEA-alumoxane was found to remain ‘plastic’ in its green body state, allowing for the retention of large features, but the shrinkage upon sintering (due to MEEA-alumoxane’s lower ceramic yield) was often accompanied by cracking of features. Physical mixtures of the two alumoxanes were investigated to determine optimum conditions for the controlled fabrication of ceramic features. The best combination of properties was obtained for a 2:1 mixture of A-alumoxane and MEEA-alumoxane. If metal-doped MEEA-alumoxane was employed, the appropriate aluminate ceramic was formed. Green body and ceramic samples were characterized by SEM, XRD, BET, and Vickers hardness measurements.

Relative Risk Analysis of Several Manufactured Nanomaterials: An Insurance Industry Context

A relative risk assessment is presented for the industrial fabrication of several nanomaterials. The production processes for five nanomaterials were selected for this analysis, based on their current or near-term potential for large-scale production and commercialization: single-walled carbon nanotubes, bucky balls (C60), one variety of quantum dots, alumoxane nanoparticles, and nano-titanium dioxide. The assessment focused on the activities surrounding the fabrication of nanomaterials, exclusive of any impacts or risks with the nanomaterials themselves. A representative synthesis method was selected for each nanomaterial based on its potential for scaleup. A list of input materials, output materials, and waste streams for each step of fabrication was developed and entered into a database that included key process characteristics such as temperature and pressure. The physical-chemical properties and quantities of the inventoried materials were used to assess relative risk based on factors such as volatility, carcinogenicity, flammability, toxicity, and persistence. These factors were first used to qualitatively rank risk, then combined using an actuarial protocol developed by the insurance industry for the purpose of calculating insurance premiums for chemical manufacturers. This protocol ranks three categories of risk relative to a 100 point scale (where 100 represents maximum risk): incident risk, normal operations risk, and latent contamination risk. Results from this analysis determined that relative environmental risk from manufacturing each of these five materials was comparatively low in relation to other common industrial manufacturing processes.

Nanoreinforcement of poly(propylene fumarate)-based networks with surface modified alumoxane nanoparticles for bone tissue engineering.

A novel composite material has been fabricated for bone tissue engineering scaffolds utilizing the biodegradable polymer poly(propylene fumarate)/poly(propylene fumarate)-diacrylate (PPF/PPF-DA) and surface-modified carboxylate alumoxane nanoparticles. Various surface-modified nanoparticles were added to the polymer including a surfactant alumoxane, an activated alumoxane, a mixed alumoxane containing both activated and surfactant groups, and a hybrid alumoxane containing both groups within the same substituent. These nanocomposites, as well as polymer resin and unmodified boehmite composites, underwent flexural and compressive mechanical testing and were examined using electron microscopy. Hybrid alumoxane nanoparticles dispersed in PPF/PPF-DA exhibited over a 3-fold increase in flexural modulus at 1 wt % loading compared to polymer resin alone. No significant loss of flexural or compressive strength was observed with increased loading of hybrid alumoxane nanoparticles. These dramatic improvements in flexural properties may be attributed to the fine dispersion of nanoparticles into the polymer and increased covalent interaction between polymer chains and surface modifications of nanoparticles.

Solvent free synthesis of carboxylate–alumoxane nanoparticles using mechanical shear

Carboxylate-substituted alumina nanoparticles are produced solvent free using a Rheomixer. The general nature of this method has been demonstrated for L-lysine-, stearate-, and p-hydroxybenzoate-derived materials. The reaction rate and particle size are controlled by a combination of temperature and shear rate. The nanoparticles are spectroscopically equivalent to those reported from aqueous syntheses, however, the average particle size can be decreased and the particle size distribution narrowed depending on the reaction conditions.

A simple approach to hierarchical ceramic ultrafiltration membranes

Asymmetric alumina ultrafiltration membranes with a hierarchical structure have been fabricated using carboxylic acid surface stabilized alumina nanoparticles (alumoxanes). Pre-formed hollow α-alumina spheres (3 μm nominal diameter) were prepared, using 2, 5, or 8 wt.% alumoxane solutions, and suspended in an aqueous solution of acetic-alumoxane (A-alumoxane) nanoparticles. This suspension was contacted with an α-alumina support. Firing to 600 °C gave a defect-free alumina hierarchical membrane with a total thickness of ca. 2 μm. The flux and permeability for the membrane containing alumina spheres derived from 2 wt.% solution of A-alumoxane is comparable to the porous support, while those derived from 5 and 8 wt.% solution of alumoxane are similar to a “flat” alumoxane-derived membrane. An alternative route to increasing the flux and permeability of the asymmetric membranes was developed whereby colloidal polystyrene beads of either 0.75, 3, or 15 μm diameter, were suspended in an aqueous solution of either A-alumoxane (1 wt.%) or methoxy(ethoxyethoxy)acetic acid alumoxane (MEEA-alumoxane, 10 wt.%). The surface of an α-alumina support was dip coated in the polystyrene/alumoxane colloidal solution, dried then fired to 600 °C, resulting in an asymmetric alumina membrane with a hierarchical tertiary structure. As the polystyrene out-gasses during pyrolysis the top of the coated spheres burst, resulting in a macroporous membrane in which the ceramic walls have a pore size and hence MWCO defined by the alumina formed from the alumoxane nanoparticles (A-alumoxane versus MEEA-alumoxane) rather than the macroporous structure of the membrane itself. The permeabilities of these membranes are equivalent or better than the support.

Characteristics of ultrafiltration ceramic membranes derived from alumoxane nanoparticles

Alumoxanes nanoparticles were cast onto α-alumina supports by slip-coating to develop asymmetric ultrafiltration ceramic membranes. Membrane layers as thin as 1 or 2 μm were achieved. The effect of sintering conditions was investigated. Membrane surface morphology was imaged by SEM and AFM. The molecular weight cut off was evaluated for these membranes and compared to pore size data obtained by nitrogen adsorption in an effort to correlate pore size and actual performance of the membrane. Membranes were sintered at temperatures between 600 and 1100 °C. The pore sizes increased with higher sintering temperature, from 7 nm at 600 °C to 10 nm at 1000 °C, followed by a sharp increase due to the transformation to α-alumina at higher firing temperatures. The molecular weight cut off showed no considerable variation up to 1000 °C. These results are in good agreement with equations reported by several authors that correlate molecular weight with size.

Particle size control and dependence on solution pH of carboxylate–alumoxane nanoparticles

A series of water dispersible carboxylate–alumoxane nanoparticles were prepared by the reaction of various carboxylic acids with the mineral boehmite. The acids used were: acetic (A–H), methoxyacetic (MA–H), methoxyethoxyacetic (MEA–H), methoxyethoxyethoxyacetic (MEEA–H), and lysine (L–H). For each of the derived carboxylate–alumoxanes, particle size measurements were obtained by means of photon correlation spectroscopy (PCS) as a function of solution pH. In all cases, at higher pHs, slight increases in solution basicity corresponded to large increases in particle size. At lower pHs, however, changes in solution basicity yielded only slight to moderate increases in particle size. It was also found during these investigations that methoxyacetic–alumoxane (MA–A) had a large buffering capacity, and that this effect could be explained by correlation with the aluminum:carboxylate group ratio for the various carboxylate–alumoxanes.