As-received Nanoparticles Research Articles

Controlling the optical properties of nanostructured oxide-based polymer films

A bulk scale process is implemented for the production of nanostructured film composites comprising unary or multi-component metal oxide nanoparticles dispersed in a suitable polymer matrix. The as-received nanoparticles, namely Al_2O_3, SiO_2 and TiO_2 and binary combinations, are treated following specific chemical and mechanical processes in order to be suspended at the optimal size and composition. Subsequently, a polymer extrusion technique is employed for the fabrication of each film, while the molten polymer is mixed with the treated metal oxide nanoparticles. Transmission and reflection measurements are performed in order to map the optical properties of the fabricated, nanostructured films in the UV, VIS and IR. The results substantiate the capability of the overall methodology to regulate the optical properties of the films depending on the type of nanoparticle formation which can be adjusted both in size and composition.

A comparison between hot-rolling process and twin-screw rheo-extrusion process for fabrication of aluminum matrix nanocomposite

Solid-state modification of SiC nanoparticles in a ball-mill is a known method for deagglomeration of as-received nanoparticles in a bed of metallic carriers that will also aid their better injection and releasing into the melt. The melt temperature and condition of the melt is very important for a better interaction of composite powders including ceramic nanoparticles and metallic carrier with the melt. In this study, aluminum A356 matrix nanocomposites were produced by liquid-state stir casting at 715 °C followed by twin-screw rheo-extrusion (TSRE) in the semi-solid state to enhance the produced composite properties. For this purpose, SiC nanocomposite superstructures were prepared using ball-milling of SiC nanopowders with micron-sized titanium and nickel (separately) as carrier agents. Also, hot-rolling (HR) process was applied on liquid-state stir cast nanocomposites to compare the mechanical properties of rolled sheets with TSRE-processed bars. The experimental results indicated that stir-cast samples before TSRE and HR consisted various types of defects with poor dispersion of nanoparticles in some areas. However, more improved dispersions for the nanoparticles were obtained after TSRE and HR and rolled sheets had considerable improved mechanical properties compared with TSRE bars. This latter improvement was determined to be mainly due to extensive fragmentation and dispersion of eutectic silicon, Ti-rich, and Ni-rich intermetallic phases.

Microstructure and morphological study of ball-milled metal matrix nanocomposites

Due to the difficulty of preparation and beneficial properties achievable, copper and iron matrix nanocomposites are materials for which fabrication via the powder metallurgy route is attracting increasing research interest. The presence of ceramic nanoparticles in their matrix can lead to considerable changes in the microstructure and morphology. The effects of the type of metallic matrix and ceramic nanoparticle on the distribution of nano reinforcements and the morphology of ball-milled composite powders were evaluated in this study. For this purpose, 25 wt % of Al2O3 and SiC nanoparticles were separately ball-milled in the presence of iron and copper metals. The SEM, FESEM, and XRD results indicated that as-received nanoparticles, which were agglomerated before milling, were partially separated and embedded in the matrix of both the metals after the initial stages of ball milling, while prolonged milling was not found to further affect the distribution of nanoparticles. It was also observed that the Al2O3 phase was not thermodynamically stable during ball milling with copper powders. Finally, it was found that the presence of nanoparticles considerably reduce the average size of metallic powder particles.

Ferroelectric properties of composites containing BaTiO3 nanoparticles of various sizes

Size effects, including the occurrence of superparaelectric phases associated with small scale, are a significant research topic for ferroelectrics. Relevant phenomena have been explored in detail, e.g. for homogeneous, thin ferroelectric films, but the related effects associated with nanoparticles are usually only inferred from their structural properties. In contrast, this paper describes all the steps and concepts necessary for the direct characterization and quantitative assessment of the ferroelectric properties of as-synthesized and as-received nanoparticles. The method adopted uses electrical polarization measurements on polymer matrix composites containing ferroelectric nanoparticles. It is applied to ten different BaTiO3 particle types covering a size range from 10 nm to 0.8 μm. The influence of variations of particle characteristics such as tetragonality and dielectric constant is considered based on measurements of these properties. For composites containing different particle types a clearly differing polarization behaviour is found. For decreasing particle size, increasing electric field is required to achieve a given level of polarization. The size dependence of a measure related to the coercive field revealed by this work is qualitatively in line with the state of the knowledge for ferroelectrics having small dimensions. For the first time, such results and size effects are described based on data from experiments on collections of actual nanoparticles.

Polyaniline Stabilized Magnetite Nanoparticle Reinforced Epoxy Nanocomposites

Magnetic epoxy polymer nanocomposites (PNCs) reinforced with magnetite (Fe(3)O(4)) nanoparticles (NPs) have been prepared at different particle loading levels. The particle surface functionality tuned by conductive polyaniline (PANI) is achieved via a surface initiated polymerization (SIP) approach. The effects of nanoparticle loading, surface functionality, and temperature on both the viscosity and storage/loss modulus of liquid epoxy resin suspensions and the physicochemical properties of the cured solid PNCs are systematically investigated. The glass transition temperature (T(g)) of the cured epoxy filled with the functionalized NPs has shifted to the higher temperature in the dynamic mechanical analysis (DMA) compared with that of the cured pure epoxy. Enhanced mechanical properties of the cured epoxy PNCs filled with the functionalized NPs are observed in the tensile test compared with that of the cured pure epoxy and cured epoxy PNCs filled with as-received NPs. The uniform NP distribution in the cured epoxy PNCs filled with functionalized NPs is observed by scanning electron microscope (SEM). These magnetic epoxy PNCs show the good magnetic properties and can be attached by a permanent magnet. Enhanced interfacial interaction between NPs and epoxy is revealed in the fracture surface analysis. The PNCs formation mechanism is also interpreted from the comprehensive analysis based on the TGA, DSC, and FTIR in this work.

Ranking of As-Received Micro/Nanoparticles by their Surface Energy Values at Ambient Conditions

Nanoparticles have been widely applied in many applications due to their specific physical or chemical properties that differ from the bulk counterparts. Because nanoparticles vary significantly in composition and geometry, the comparison of their interaction with another matter is difficult, although in many cases, to characterize and assort nanoparticles in a quantified way is highly desired. Among the many properties of nanoparticles, the surface energy is especially important in evaluating their potential affinity to the environment. Pretty elegant techniques have been developed to evaluate the surface energy of pure metal oxides. However, heating or acid treatment would destroy the real surface conditions, for example, organic coatings outside of the particles. An effective method has to be developed to determine the surface energy of the as-received natural particles, whether they are pure, contaminated, or prehydrated. We designed a technique to quantitatively evaluate the surface energy of the as-received nanoparticles. The surface energies of a series of as-received nanoparticles can be evaluated and ranked at ambient conditions without heating or acid/base treatment. The values obtained for TiO2 solid and for 0.1 μm aluminum particles match those records in the literature well. The result out of this research also enables the comparison between solid particles on different size levels, for example, from millimeter to the nanoscale. The surface energy of nanoparticles is closely related to their wettability performance. Therefore, the ranking of solids on a various size scales according to the surface energy would enable the quantitative study of their interactions with their environmental neighbors, for example, proteins and cells.

Electrospun Polyimide Nanocomposite Fibers Reinforced with Core−Shell Fe-FeO Nanoparticles

Both pure polyimide (PI) and Fe-FeO nanoparticles reinforced PI nanocomposite fibers with a particle loading of 5, 10, 20, and 30 wt % are produced by electrospinning with optimized operational parameters such as polymer concentration, applied electrical voltage, and tip-to-collector distance. The morphology of the resulting products is correlated to the corresponding rheological behaviors of the pure PI and Fe-FeO/PI nanocomposite solutions. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) reveal an enhanced thermal stability of the nanocomposite fibers after introducing the Fe-FeO nanoparticles. The glass transition temperature (Tg) and melting temperature (Tm) of the nanocomposite fibers increase by 10−12 and 15−17 °C, respectively, as compared to those of the pure PI fibers. The magnetic properties of the Fe-FeO nanoparticles in the polymer nanocomposite fibers are different from those of the as-received nanoparticles. An increased shell thickness by 7.4% is deduced after the nanoparticles experiencing the high-voltage electrospinning.

Electrospun polyacrylonitrile nanocomposite fibers reinforced with Fe3O4 nanoparticles: Fabrication and property analysis

The manufacturing of pure polyacrylonitrile (PAN) fibers and magnetic PAN/Fe3O4 nanocomposite fibers is explored by an electrospinning process. A uniform, bead-free fiber production process is developed by optimizing electrospinning conditions: polymer concentration, applied electric voltage, feedrate, and distance between needle tip to collector. The experiments demonstrate that slight changes in operating parameters may result in significant variations in the fiber morphology. The fiber formation mechanism for both pure PAN and the Fe3O4 nanoparticles suspended in PAN solutions is explained from the rheologial behavior of the solution. The nanocomposite fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectrophotometer, and X-ray diffraction (XRD). FT-IR and XRD results indicate that the introduction of Fe3O4 nanoparticles into the polymer matrix has a significant effect on the crystallinity of PAN and a strong interaction between PAN and Fe3O4 nanoparticles. The magnetic properties of the nanoparticles in the polymer nanocomposite fibers are different from those of the dried asreceived nanoparticles.

Electrospun Polyacrylonitrile Nanocomposite Fibers Reinforced with Magnetic Nanoparticles

AbstractThe manufacturing of magnetic PAN/Fe3O4 nanocomposite fibers is explored by an electrospinning process. The nanocomposite fibers were characterized by scanning electron microscopy (SEM). The magnetic properties of the nanoparticles in the polymer nanocomposite fibers are different from those of the dried as-received nanoparticles.

Silica Coating of Nanoparticles by the Sonogel Process

A modified aqueous sol-gel route was developed using ultrasonic power for the silica coating of indium tin oxide (ITO) nanoparticles. In this approach, organosilane with an amino functional group was first used to cover the surface of as-received nanoparticles. Subsequent silica coating was initiated and sustained under power ultrasound irradiation in an aqueous mixture of surface-treated particles and epoxy silane. This process resulted in a thin but homogeneous coverage of silica on the particle surface. Particles coated with a layer of silica show better dispersability in aqueous and organic media compared with the untreated powder. Samples were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and the zeta potential.

Fabrication and characterization of iron oxide nanoparticles reinforced vinyl-ester resin nanocomposites

Robust magnetic vinyl ester resin nanocomposites reinforced with iron oxide (Fe 2O 3) nanoparticles were fabricated. The particle functionalization with a bi-functional coupling agent methacryloxypropyl-trimethoxysilane (MPS) was observed to have a significant effect on the curing process and subsequent physical properties of the nanocomposites. Particle functionalization favors the composite fabrication with a lower curing temperature as compared to the as-received nanoparticles filled vinyl ester resin nanocomposites. Thermo-gravimetric analysis showed an increased thermo-stability in the functionalized nanoparticles filled vinyl ester resin nanocomposites as compared to the unmodified nanoparticle filled counterparts. The more uniform particle dispersion and the chemical bonding between nanoparticle and vinyl ester resin matrix were found to contribute to the increased thermal stability and enhanced tensile strength. The nanoparticles become magnetically harder after incorporation into the vinyl ester resin matrix.

Multifunctional Nano-Architecture for Biomedical Applications

A multifunctional architecture for biomedical applications has been developed by deliberately combining the useful functions of superparamagnetism, luminescence, and surface functionality into one material. Good control of the core−shell architecture has been achieved by employing a sol−gel synthesis. Superparamagnetic iron oxide nanoparticles are first coated with silica to isolate the magnetic core from the surrounding. Subsequently, the dye molecules are doped inside a second silica shell to improve photostability and allow for versatile surface functionalities. The architecture has been characterized by transmission electron microscopy, UV−vis absorption and emission spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and magnetometry. The hybrid nanoparticles exhibit improved superparamagnetic behavior over the as-received nanoparticles with a significant decrease in the blocking temperature. The architecture shows emission properties similar to those of the free dye molecules, sug...

Synthesis and characterization of Fe–Ti nanoparticles by nitrogen plasma metal reaction

The plasma state and nanoparticle formation of Ti–Fe alloys were studied by nitrogen plasma metal reaction. The nitrogen plasma state is dependent on the nitrogen partial pressure and the master alloy composition. Synthesis of Ti–Fe nanoparticles can be carried out only when the nitrogen partial pressure is smaller than 10% or the Ti composition is larger than 50 at.%. The as-received nanoparticles are composed of TiN and Fe phases with the mean particle diameters ranging from 25 to 40 nm; the TiN and Fe nanoparticles have quadrangular and spherical appearance, respectively. The nitrogen plasma promotes Fe evaporation more strongly than Ti, and as a result the as-received nanoparticles are Fe-rich. Compared with the hydrogen plasma, the nitrogen plasma has a smaller effect on evaporation enhancement, but stronger reactivity.