Boehmite Nanoparticle Research Articles

A finite deformation gradient-enhanced damage model for nanoparticle/polymer nanocomposites: An atomistically-informed multiscale approach

To analyze the experimentally observed failure process in nanoparticle/polymer nanocomposites, a variety of factors, including nonlocal characteristics of damage mechanism and nonlinear viscoelasticity, are required to be investigated. This work presents the development and numerical implementation of a finite deformation gradient-enhanced damage model for boehmite nanoparticle (BNP)/epoxy nanocomposites. The parameters identification of the nonlocal constitutive description is realized using a framework based on molecular simulations and experimental tests. In this context, molecular simulations are performed to parameterize the Argon model of viscoelasticity, while damage and nonlocal parameters are determined using experimental data obtained from compact-tension tests. The nonlocal constitutive model integrated into a nonlinear FE analysis is validated by comparing the numerical results of compact-tension tests of BNP/epoxy samples with experimental data. The experimental–numerical validation confirms the predictive capability of the modeling framework. The proposed procedure can be extended to other types of nanoparticle reinforced thermosetting polymers.

In Situ-Grown Cdot-Wrapped Boehmite Nanoparticles for Cr(VI) Sensing in Wastewater and a Theoretical Probe for Chromium-Induced Carcinogen Detection.

In modern society, massive industrialization escalates environmental degradation by liberating various contaminants into the environment. Hexavalent chromium is a heavy metal that is being discharged from tannery and other industries, resulting in various carcinogenic diseases. This study reports a carbon dot (cdot)-based fluorometric probe for detecting hexavalent chromium in water. This is the very first time that cdots are tailored over the boehmite nanoparticle's surface using an in situ approach. Validation of formation of the nanocomposite has been discussed in detail employing the Rietveld refinement-based X-ray crystallography method. Vibrational spectroscopy and electron microscopy of the sample authenticate the nucleation process and the growth mechanism. The Stern-Volmer approach and time-resolved fluorescence measurements justify the sensitivity of the sensor (∼58 nM), and selectivity is analyzed by exposing the material to different ionic environments. Density functional theory (DFT) is applied herein to analyze the origin of fluorescence and the sensing mechanism of the probe, which shows that photoinduced electron transfer is responsible for the turn-off-based sensing of Cr(VI). The molecular docking simulation is carried out to ensure the binding of cdots to the binding pocket of the glutathione enzyme, which is responsible for treating reactive oxygen species-mediated DNA damage due to elements such as hexavalent chromium. Time-dependent density functional calculations show that the fluorometric probe is capable of detecting Cr(VI) in living cells making it an early stage chromium-mediated carcinogen detector.

Ternary ZnO/ZnAl2O4/ Al2O3 composite nanofiber as photocatalyst for conversion of CO2 and CH4

Electrospinning is a flexible synthesis method which not only facilitates the preparation of the nanofibers with dramatically improved surface area, but also takes advantage of the structural defects to form heterojunctions with photocatalytic activities. In this study for the first time, a continuous layer of composite ceramic nanofiber was fabricated by employing two-nozzle electrospinning method to make the nanofiber from a 12: 3: 3: 13: 87 (percent ratio) solution of aluminum acetate: boehmite nanoparticle: zinc acetate: polyacrylonitrile: dimethylformamide respectively. The step by step thermal post-processing was performed on the nanofiber to decompose the polymeric part and achieve a pure ceramic phase. Characterization of the ceramic nanofiber was conducted using Fe-SEM, FTIR, XRD, TGA-DTA, BET and UV–Vis techniques. The SEM and XRD results confirmed that the ceramic nanofiber with average diameter of 160 nm was composed of ZnO, Al2O3 and ZnAl2O4 phases. The resultant nanofiber was used as a photocatalyst for conversion of CO2 in presence of CH4 as the reductant and UV–A irradiation under mild conditions. The maximum conversion percentages of CO2 and CH4 after 240 min were 20% and 11.7% respectively.The present study proposes a method for preparing a ternary nanofiber of Al2O3, ZnO, and ZnAl2O4 with the potential to be used as a photocatalyst for conversion of CO2 in presence of CH4.

Gd(III)-Doped Boehmite Nanoparticle: An Emergent Material for the Fluorescent Sensing of Cr(VI) in Wastewater and Live Cells.

This article reports the effect of Gd(III) doping on the structure, microstructure, and optical properties of boehmite nanoparticles. The bright-blue fluorescence along with a long lifetime makes our material an efficient candidate for optical applications. Our material particularly targets and eliminates hexavalent chromium ions (Cr(VI)) from aqueous media, which turns it into a multifunctional fluorescent nanosensor (MFNS). The development of an efficient hexavalent chromium ion (Cr(VI)) sensor to detect and quantify Cr(VI) ions is still a serious issue worldwide. Thus, this work will be very beneficial for various environmental applications. No such work has been reported so far which includes cost-effective and biocompatible boehmite nanoparticles in this field. Detailed synthesis and characterization procedures for the MFNS have been incorporated here. The biocompatibility of the MFNS has also been studied rigorously by performing cell survivability assay (MTT) and cellular morphology assessments. Our extensive research confirmed that the "turn-off" sensing mechanism of this sensor material is based on a collisional quenching model which initiates the photoinduced electron transfer (PET) process. High selectivity and sensitivity (∼1.05 × 10-5 M) of the MFNS toward hexavalent chromium ions even in real life wastewater samples have been confirmed, which makes this fluorescent probe a potential candidate for new age imaging and sensing technologies.

A viscoelastic damage model for nanoparticle/epoxy nanocomposites at finite strain: A multiscale approach

Experimental tests show that nonlinear viscoelasticity characterizes the mechanical behavior of boehmite nanoparticle (BNP)/epoxy nanocomposites. This paper presents the development and numerical implementation of a physically based constitutive model for BNP/epoxy nanocomposites undergoing finite strain. The proposed constitutive model allows capturing the main features of the stress-strain relationship of BNP/epoxy nanocomposites, including the nonlinear hyperelastic, time-dependent and softening behavior. The characterizing feature of this study is to propose a methodological framework based on molecular dynamics simulations and experimental tests to identify the material parameters for the model. Molecular simulations in conjunction with the Eyring viscosity theory are used to characterize the viscoelastic deformation of epoxy resins under loading. The concept of strain amplification is also adopted to account for the effect of nanoparticles on the stress–strain response of the nanocomposites. The stress softening behavior is captured by a monotonically increasing function of deformation, so-called damage variable. The results show that the model predictions of stress-strain relationships are in good agreement with experimental data at different BNP weight fractions. Finally, the constitutive model is implemented in the finite element analysis and examined by means of a benchmark example. Experimental–numerical validation confirms the predictive capability of the present modeling framework, which provides a suitable tool for analyzing BNP/epoxy nanocomposites.

Cure kinetics and rheology modelling of boehmite (AlOOH) nanoparticle modified epoxy resin systems

Nanoparticles can effectively increase the resin matrix properties, which is especially attractive for fabrication of high-performance fiber composites by liquid composite molding (LCM) processes. However, the cure kinetics and rheological behavior of the matrix, which are the most critical aspects in LCM processes, could be affected by the introduction of nanoparticles, depending on the surface functionalization and concentration. In this paper, the cure kinetics and rheology of a boehmite nanoparticle modified epoxy matrix is characterized and modelled. The influence of boehmite nanoparticles on cure and rheological behaviors is analyzed. By optimization of the regression method combined with model parameter analysis, a good correlation between the model parameters and nanoparticle concentration is determined. Finally, a generalized model is put forward to describe and predict the cure kinetics and rheology depending on time, temperature, and concentration of nanoparticles.

Electrochemical sensor based on multi-walled carbon nanotubes–boehmite nanoparticle composite modified electrode

A sensitive electrochemical sensor was developed for the analysis of dobutamine (Dob) using a glassy carbon electrode modified with multi-walled carbon nanotubes–boehmite nanoparticle composite (BNP–MWNTs/GCE). Scanning electron microscopy was used for the characterization of synthesized BNPs and the morphology of BNP–MWNTs on the surface of GCE. Under the optimized experimental conditions, the BNP–MWNTs/GCE exhibited higher peak current than bare GCE due to synergetic effect of BNPs and MWCNTs on the electrochemical oxidation of Dob. The effect of various experimental parameters such as pH, scan rate, accumulation time on the voltammetric response of Dob was studied and optimized. A wide linear range from 0.005 to 1.0 µM with a low detection limit of 8.9 nM was found for voltammetric quantification of Dob. The prepared sensor exhibited the acceptable repeatability, high reproducibility along with good stability which makes it appropriate candidate for determination Dob in pharmaceutical preparations.

Synthesis of core–shell AlOOH hollow nanospheres by reacting Al nanoparticles with water

A novel route for the synthesis of boehmite nanospheres with a hollow core and the shell composed of highly crumpled AlOOH nanosheets by oxidizing Al nanopowder in pure water under mild processing conditions is described. The stepwise events of Al transformation into boehmite are followed by monitoring the pH in the reaction medium. A mechanism of formation of hollow AlOOH nanospheres with a well-defined shape and crystallinity is proposed which includes the hydration of the Al oxide passivation layer, local corrosion of metallic Al accompanied by hydrogen evolution, the rupture of the protective layer, the dissolution of Al from the particle interior and the deposition of AlOOH nanosheets on the outer surface. In contrast to previously reported methods of boehmite nanoparticle synthesis, the proposed method is simple, and environmentally friendly and allows the generation of hydrogen gas as a by-product. Due to their high surface area and high, slit-shaped nanoporosity, the synthesized AlOOH nanostructures hold promise for the development of more effective catalysts, adsorbents, vaccines and drug carriers.

Disulfonated copolyimide-boehmite nanocomposite fuel cell membranes with improved chemical resistance

Here we present a fundamental investigation of a conceptual strategy for simultaneously strengthening the tolerance to radical degradation, and improving the proton conduction capability, of polymer electrolyte membranes (PEMs) for fuel cells. A random disulfonated polyimide (SPI) containing 1 wt% of hydrophilic silica nanoparticles is used as a polymer matrix model, for dispersing boehmite nanoparticles, with the help of a non-ionic surfactant, L92. The mixture of boehmite and L92 in the micelle form results in enhanced boehmite distribution to a certain content. Boehmite nanoparticle acts as an inorganic scavenger to decompose hydrogen peroxide, known as a radical presursor, and as an inorganic conductor to transport protons owing to their acidity in PEMs. When proton conductivity and electrochemical single cell performance are considered, the optimal boehmite content chosen in this study is 2 wt% in the SPI matrix. This study provides valuable information on the rational design of chemically durable and proton-conductive fuel cell membrane materials. Open image in new window

Influence of Boehmite Nanoparticle Loading on the Mechanical, Thermal, and Rheological Properties of Biodegradable Polylactide/Poly(ϵ‐caprolactone) Blends

AbstractBlends of polylactide (PLA) and poly(ϵ‐caprolactone) (PCL) were melt‐processed with boehmite (BAI) nanoparticles to produce ternary biocomposites with the intent of broadening the potential applications of PLA. The mechanical properties of the prepared composites exhibited remarkable improvement in the elongation‐at‐break of between 60 and 430% for increasing loadings of PCL and BAI in the blends. Furthermore, the melting temperatures of PLA and PCL were observed to shift approximately 2 °C toward each other in the composites, an indication of improved compatibility. This partial compatibility was also observed from the electron microscopy images, which also revealed a good dispersion of PCL in the PLA. The composite with balanced properties was found to be consisting of 70 wt% PLA, 30 wt% PCL, and 4 wt% BAI.

Boehmite nanoparticle catalyst for the one-pot multicomponent synthesis of 3,4-dihydropyrimidin-2-(1H)-ones and thiones under solvent-free conditions

A simple, green, and efficient synthesis protocol for the synthesis of 3,4-dihydropyrimidin-2-(1 H )-ones using boehmite nanoparticles as catalyst was developed. It did not use any toxic metal catalysts or corrosive acidic reagents. The method gave good to excellent yields and has short reaction time, operational simplicity, and a recyclable catalyst. Boehmite nanoparticles are a highly active and green catalyst for the synthesis of highly substituted 3,4-dihydropyrimidin-2-(1 H )-ones and thiones under solvent-free conditions.

Synthesis of highly porous alumina-based materials

γ-Alumina-based materials with high porous volume, tunable pore size, were synthesized by the addition of both PEO/PPO/PEO triblock copolymers (Pluronics® F127 and P123) and metal nitrates (Al3+, Mn2+, Cu2+) in a boehmite (AlOOH) nanoparticle hydrosol. During the subsequent thermal treatment, the surfactant was removed leaving a highly porous framework.The pore size distribution was strongly dependent on the metal nitrate added and its concentration. By this simple process it was possible to modify the porous volume in the range 0.3–2.6cm3g−1 and the median pore diameter in the range 5–40nm. All these materials presented high surface areas in the range 300–500m2g−1.During the drying AlOOH particles aggregate to form linear objects (flat rods, laths) in order to minimize electrostatic repulsion. We think that the improvement of the textural characteristics of γ-alumina could be explained by the adsorption of copolymer onto these fiber-like objects, preventing the compact rearrangement of the boehmite nanoparticles in a compact “card-pack” microstructure during the drying.The addition of electrolytes induces a reduction of electrostatic repulsions, leading to the formation of both fiber-like objects at lower AlOOH concentration, and a 3D network by bridging these 1D objects. This bridging is reversible since the gel returns to a sol state under shearing, but polymer adsorption can prevent the full collapsing of this network during the drying step and a huge porosity can be maintained after calcination.

Electrospun Fe2O3–Al2O3 nanocomposite fibers as efficient adsorbent for removal of heavy metal ions from aqueous solution

In this study, Iron oxide–alumina mixed nanocomposite fiber was prepared by electrospinning method and its performance was evaluated as a heavy metal ion adsorbent. Here boehmite nanoparticle was synthesized by sol–gel method and was impregnated in PVP-iron acetylacetonate solution in a ratio of 1:1:2. These boehmite impregnated polymer solution was electrospun to form nanocomposite polymer fiber. The electrospun nanofiber was sintered at 1000°C for converting it to pure oxide form for further application as adsorbent. Iron oxide–alumina mixed nanocomposite fiber was characterized by UV–vis-DRS, IR, SEM–EDX, TEM, BET and TGA–DTA analytical techniques. Batch adsorption experiments were carried out to study the sorption behavior of Cu2+, Pb2+, Ni2+ and Hg2+ ions as a function of initial concentration, contact time and pH. The removal percentage was in the order of Cu2+<Pb2+<Ni2+<Hg2+. The maximum sorption capacities by applying the Langmuir equation were found to be 4.98mg/g for Cu2+, 32.36mg/g for Ni2+, 23.75mg/g for Pb2+ and 63.69mg/g for Hg2+ ions. The regeneration studies of mixed nanocomposite adsorbents were also reported here.

Rheological and Kinetic Characterization of UV Photopolymerizable Formulations as a Function of the Boehmite Nanoparticle Content

Several innovative photopolymerizable siloxane-modified acrylic formulations were characterized, both in presence or absence of organically Boehmite (OMB) nanoparticles, in order to assess their rheological and kinetic behavior. The experimental formulations were mainly intended for the surface protection of porous stones or wood elements. The importance of the experimental investigation lies in the specific requirements necessary for the proposed applications, i.e. the innovative UV coatings developed should possess adequate viscosity, photopolymerization reaction rate and time. The kinetics of the radical photopolymerization mechanism, induced by UV radiations, was studied by calorimetric analysis and FTIR spectroscopy as function of the mixtures composition and test conditions (air or nitrogen atmosphere). The addition of a silane coupling agent or a high molecular weight polysiloxane monomer to the acrylic resin was found to reduce the heat of reaction. On the other hand, the presence of Boehmite nanoparticles in the UV photopolymerizable formulations does not seem to modify the reactivity of the siloxane-modified acrylic formulations. The effect of the presence of oxygen on the kinetic reaction was also investigated and correlated to the composition of the systems. Finally, the viscosity of the formulations was studied at ambient temperature with a parallel plates rheomether as a function of composition and shear rate. The viscosity curves were also fitted according to theoretical models as function of shear rate and composition, obtaining a good agreement between experimental data and model predictions.

Properties of Boehmite AlO(OH) Nanoparticles as the Coatings and Fillers

Boehmite nanoparticles with different shapes and lengths were used in the preparation of the boehmite films and coatings, and as the fillers for an organic polymer. Then, it was investigated how the shapes and lengths of the particles reflected the characteristics of the films, coatings and fillers. The films were prepared by casting an aqueous sol of the nanoparticles on a Teflon-lined plate, drying and peeling. The coatings were fabricated on porous alumina tubes or graphite sheets by dipping the substrates into a sol of the nanoparticles. The boehmite-polyvinyl alcohol (PVA) composite films, in which the nanoparticles are fillers, were prepared by casting a mixture of a boehmite nanoparticle sol and PVA. The films, coatings and composites were characterized by TEM, TG-DTA, gas permeability, pore size distribution and thermal expansion measurements. In the films, fibrous particles with aspect ratios over 50 aggregated in parallel to each other to form slit-like micropores, on the other hand, plate- and rod-like particles with aspect ratios below 10 randomly aggregated to form meso pores. Corresponding to this, for the coatings on porous alumina tubes and graphite sheets, the fibrous particles gave much low gas permeability and high thermostability, respectively, compared with the plate-like and rod-like particles. For the boehmite-PVA composite films, the fibrous particles gave lower thermal expansion than the plate-like and rod-like particles.

In Situ High‐Energy Synchrotron Radiation Study of Boehmite Formation, Growth, and Phase Transformation to Alumina in Sub‐ and Supercritical Water

Boehmite (AlOOH) nanoparticles have been synthesized in subcritical (300 bar, 350 degrees C) and supercritical (300 bar, 400 degrees C) water. The formation and growth of AlOOH nanoparticles were studied in situ by small- and wide-angle X-ray scattering (SAXS and WAXS) using 80 keV synchrotron radiation. The SAXS/WAXS data were measured simultaneously with a time resolution greater than 10 s and revealed the initial nucleation of amorphous particles takes place within 10 s with subsequent crystallization after 30 s. No diffraction signals were observed from Al(OH)(3) within the time resolution of the experiment, which shows that the dehydration step of the reaction is fast and the hydrolysis step rate-determining. The sizes of the crystalline particles were determined as a function of time. The overall size evolution patterns are similar in sub- and supercritical water, but the growth is faster and the final particle size larger under supercritical conditions. After approximately 5 min, the rate of particle growth decreases in both sub- and supercritical water. Heating of the boehmite nanoparticle suspension allowed an in situ X-ray investigation of the phase transformation of boehmite to aluminium oxide. Under the wet conditions used in this work, the transition starts at 530 degrees C and gives a two-phase product of hydrated and non-hydrated aluminium oxide.

Fabrication and characterization of a boehmite nanoparticle impregnated electrospun fiber membrane for removal of metal ions

The fabrication of a composite electrospun fiber membrane with sorptive characteristics intended for removal of heavy metals was investigated. The electrospun fiber membrane was impregnated with nano-boehmite particles. The latter had been selected to increase surface area of the active component. Cd (II) was chosen as the challenge bivalent cation. The sorption capacity of the nano-boehmite was studied as a function of pH and time. Electrospinning was used to prepare the composite submicron fiber membrane impregnated with boehmite nanoparticles. The later was blended with the polymer to produce a homogenous mixture before electrospinning. Two polymers, the hydrophobic/PCL/and hydrophilic/Nylon-6/, were chosen to serve as the support for the boehmite. The nanoparticles and resulting composite membranes were characterized using SEM, TEM, and XRD techniques. XRD data confirmed the presence of nano-boehmite particles in the nanofibers membrane. The membranes so prepared were challenged with aqueous solutions of Cd in batch isotherm tests. Atomic absorption spectroscopy results show sorption of Cd (II) by boehmite impregnated electospun membrane was possible and a capacity of 0.20 mg/g was achieved.