Flow-levitation Method Research Articles

Synthesis of Zinc Nanoparticles by the Gas Condensation Method in a Non-Contact Crucible and Their Physical-Chemical Characterization.

This work explored the zinc nanoparticles obtained by the one-stage induction flow levitation method. A 10 kW tube generator with an operating frequency of 440 kHz was used. The process used 8 mm diameter zinc granules (2 g weight) with a purity of 99.9%. Zinc wire was fed to replace the evaporated metal from the granule surface. This method productivity was 30 g/h of nanoparticles. In addition, various methods were used to characterize the resulting nanoparticles: scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray fluorescence analysis (XRF), dynamic light scattering (DLS), porosimetry and inductively coupled plasma atomic emission spectroscopy (ICP-MS). The resulting nanoparticle size, determined by SEM and porosimetry, was 350 nm, while the size of the primary crystallites was 21 nm. The amount of impurities in the resulting nanoparticles did not exceed 1000 ppm.

Preparation of Zinc Nanoparticles by Gas Condensation in a Contactless Crucible

In this work, zinc nanoparticles were obtained. As a production method, a one-stage induction flow levitation method was used. The starting material was spherical granules with a purity of 99.9% and a mass of 2 g; as atoms evaporated from the surface of the molten granule, the drop was fed with a metal wire made of the same material. The productivity of the nanoparticles was 30 g / h. The resulting nanoparticles were characterized by scanning electron microscopy, X-ray phase analysis, porosimetry, and inductively coupled plasma atomic emission spectroscopy.

Albumin Stabilized Fe@C Core-Shell Nanoparticles as Candidates for Magnetic Hyperthermia Therapy.

Carbon-encapsulated iron nanoparticles (Fe@C) with a mean diameter of 15 nm have been synthesized using evaporation–condensation flow–levitation method by the direct iron-carbon gas-phase reaction at high temperatures. Further, Fe@C were stabilized with bovine serum albumin (BSA) coating, and their electromagnetic properties were evaluated to test their performance in magnetic hyperthermia therapy (MHT) through a specific absorption rate (SAR). Heat generation was observed at different Fe@C concentrations (1, 2.5, and 5 mg/mL) when applied 331 kHz and 60 kA/m of an alternating magnetic field, resulting in SAR values of 437.64, 129.36, and 50.4 W/g for each concentration, respectively. Having such high SAR values at low concentrations, obtained material is ideal for use in MHT.

Tomato response to metal nanoparticles introduction into the nutrient medium.

This study is aimed to explore the capacity of metal nanoparticles (NPs) iron, zinc, copper and their combinations introduced in the Murashige-Skoog (MS) nutrient medium (NM) to affect the growth and development of tomato plants (Solanum lycopersicum L.). NPs were prepared by a flow-levitation method. Metal NPs were characterised by transmission and scanning electron microscopy, X-ray phase analysis. Average NPs diameters were: iron - 27.0 nm, zinc - 54.0 nm, copper - 79.0 nm. MS NM was modified by substitution of common metal sulphates by neutral metal NPs instead of salts. Tomato seedlings cultivation on NM MS with NPs instead of salts assures improved seedling parameters (root length and root activity) in comparison with plants grown on standard MS. Venice cultivar tomato seedlings grown on NM with metal NPs demonstrated an increase in: seed germination by 10-180%, root length by 10-20%, and root activity by 10 -125%. After 45 days of cultivation, tomato seedlings were transplanted in a greenhouse and were grown up to the harvest. Effects in seed germination and increase of crop mass depended on metal nature and NPs concentration.

Synthesis of pure titanium carbide and titanium carbide/hydride core-shell nanoparticles via the flow-levitation method, and their characterization

The objective of this work is to synthesize pure stoichiometric titanium carbide and stoichiometric titanium carbide/hydride core-shell nanoparticles using the Guen-Miller Flow-Levitation method. The nanoparticulate are obtained via chemical reaction between nascent titanium nanoparticles and tailored gaseous hydrocarbons. Characterization of the nanoparticles is performed using analytical techniques including transmission electron microscopy, electron and X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis and specific surface area analysis. The results confirm the single-crystal nature and purity of the titanium carbide nanoparticles and demonstrate the coherence of single crystal titanium carbide core and titanium hydride shell in the TiC/TiH2 core-shell nanoparticles.

Synthesis of nanopowders of titanium compounds via Flow-Levitation method and study their properties

Nanopowders of titanium compounds TiH2 and TiC are synthesized via Flow-Levitation method using in situ reaction of nascent titanium nanoparticles with the proper reactants. The influence of manufacturing parameters on the composition and the internal structure of the synthesized nanoparticles is examined. Study of TiH2 nanoparticles using thermal methods revealed hydrogen evolution within the narrow temperature range (390-510°C), while hydrogen evolution temperature of the commercial samples is higher than 500°C.

Synthesis of nanopowders of Fe-C system via Flow-Levitation method and study of their properties

Nanopowders of Fe-C system are synthesized via modified Guen-Miller Flow-Levitation method by in situ reaction of nascent iron nanoparticles with acetylene. Morphology, internal structure, chemical and phase composition are studied by electron microscopy methods, including electron diffraction and element analysis, X-ray phase analysis and CNHS chemical analysis. It is shown that depending on the parameters of the reaction with acetylene (temperature, concentration), particles composition can vary from pure iron with thin carbon coating complex composition consisting predominantly of iron carbide.

Synthesis of TiH2 nanopowder via the Guen-Miller Flow-Levitation method and characterization

Stoichiometric TiH2 nano-crystalline powder with particle mean size of less than 30 nm was synthesized for the first time via the Guen-Miller Flow-Levitation method. Details of the method are explained, and characterization of the synthesized TiH2 nanopowder is performed using high-resolution transmission electron microscopy, electron and X-ray diffraction analyses and X-ray photoelectron spectroscopy. Particle structure analysis confirms the capability and versatility of the Guen-Miller method to synthesize high-grade nano-scaled stoichiometric titanium hydride powder.Hydrogen recovery analyses are conducted and compared to hydrogen recovery from commercial-grade titanium hydride powder. Thermal and mass-spectrometry analyses on the synthesized nanopowder shows that hydrogen recovery starts at 390 °C and peaks at 460 °C, which lowers the energy demand during the process. These temperatures and the energy demand are substantially lower than the required in hydrogen recovery from conventional micro-sized commercial-grade titanium hydride. The results confirm that stoichiometric nano-scaled titanium hydride powder synthesized via the Guen-Miller Flow Levitation method possesses desirable characteristics for hydrogen storage and recovery.

Simulation and Analysis of Three-Dimensional Electromagnetism, Heat Transfer, and Gas Flow for Flow-Levitation System

Magnetic levitation systems are influenced by an intense demand to gain greater feature sizes of metal nanoparticles and to increase the production efficiency for the flow-levitation (FL) method. This paper presents a systematic stability and temperature analysis of the process during the induction heating based on ANSYS. The comprehensive model was a liquid aluminum droplet levitated electromagnetically in an axisymmetric magnetic field induced by different sets of coaxial circular coils. First, we developed an optimized coil with a double helix structure to compare the force applied to the sample, electric field distribution, and temperature distribution in the eddy current field with an initial coil structure. The optimized coil has a more stable and efficient induction heating process for the FL method. We also utilized the optimized coil geometry to predict the maximum parameters of the electromagnetic induction system used to fabricate Al nanoparticles. The results from this approach shows that the turns = 2 + 3, D = 24 mm, I = ∼350 A, d = 1∼2 mm, with an equilibrium coefficient k of 0.30, are the maximum and optimal settings in the frequency of 400 kHz induction heating process.

Electrical resistivity of nanostructured aluminum at low temperature

The nanostructured materials have been revealed to have exclusive physical and chemical properties due to their quantum-size effects, small-size effects and a large fraction of grain boundaries. Especially, the grain boundaries play an important role in the electrical resistivity of nanostructured metal. We use the four-point probe method to measure the values of electrical resistivity () of the nanostructured aluminum samples and the coarse-grained bulk aluminum samples at temperature (T) ranging from 8 K to 300 K to explore the relationship between the electrical resistivity and temperature. The aluminum nanoparticles produced by the flow-levitation method through electromagnetic induction heating are compacted into nanostructured samples in vacuum by the hot pressing and sintering technology. The microstructures of all nanostructured aluminum samples are analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope with the energy-dispersive spectrometer (SEM-EDS). The densities of all nanostructured aluminum samples are measured by using the Archimedes method (the medium is absolute alcohol). The experimental results show that the shape of aluminum nanoparticles is found to keep spherical from the SEM images and the relative density of all nanostructured aluminum samples is about 93% of the coarse-grained bulk aluminum. The XRD spectra state that the face-centered cubic (fcc) phase dominates the samples and no diffraction peak related to impurities appears in the XRD spectrum for each of all nanostructured aluminum samples. Amorphous alumina layers (about 2 nm thick) are found to surround the aluminum nanoparticles and hence connect the grains in the nanostructured aluminum as shown in the high-resolution TEM images. Owing to the scattering of grain boundaries on electrons and the phonon-electron scattering at grain boundaries, the electrical resistivity is far larger in the nanostructured aluminum than in the coarse-grained bulk aluminum and the relationship between the electrical resistivity and temperature for nanostructured aluminum shows a different feature from that for the coarse-grained bulk aluminum. Although the temperature dependent electrical resistivity ((T)) is a function of T4 at low temperatures for the coarse-grained bulk aluminum, it varies with the temperature not only according to the relation T4, but also according to the relation T3 for the nanostructured aluminum. The residual resistivity (0) of the nanostructured aluminum sample is about 5.510-4m, 5-6 orders magnitude larger than that of the coarse-grained bulk aluminum (2.0110-10m) due to the scattering of both the grain boundaries and amorphous alumina on electrons therein.

Synthesis of zinc ultrafine powders via the Guen–Miller flow-levitation method

Zinc ultrafine powders (UFPs) with the average particle size of 0.175 to 1.24 μm are synthesized via the flow-levitation method. The peculiarities of the formation of zinc UFPs are considered with respect to the carrier gas properties (heat capacity, thermal conductivity, and diffusion coefficient), as well as the gas flow parameters (pressure and flow rate). The obtained zinc particles are studied via scanning electron microscopy and X-ray diffraction. The factors determining the crystal structure of zinc particles and their size distribution are discussed as well. The data on oxidation of zinc stored in unsealed containers under normal conditions are also presented.

Bulk Synthesis of Fe3Al Intermetallic Compound Nanoparticles by Flow-Levitation Method

Metallic nanopowders have an increasing application in magnetic materials, catalysts and chemical and metallic industries. In this research, a novel bulk synthesis method for preparing high pure intermetallic Fe 3 Al nanoparticles was developed by flow-levitation (FL) method. The Fe and Al vapors ascending from the high-temperature levitated droplet were condensed by cryogenic argon gas under atmospheric pressure. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) were used to identify and characterize the prepared nanopowders exhibiting a Fe 3 Al phase. Measurement of transmission electron microscopy (TEM) indicated that the Fe 3 Al particles are nearly spherical, and the particle size of the compound ranges from 10 nm to 200 nm in diameter. The chemical composition of the nanoparticles were determined with energy dispersive spectrometer. The magnetic properties of the nanopowder indicate that Fe 3 Al intermetallic compound is a soft magnet at room temperature, with coercivity of 24.2 Oe and saturation magnetization of 173.2 emu/g. The production rate of Fe 3 Al nanoparticles was estimated to be about 4 g/h in a continuous manner, by using the FL method. This method has great potential in mass production of Fe 3 Al nanoparticles.

Aluminum/HMX nanocomposites: Synthesis, microstructure, and combustion

Aluminum particles with a diameter of ≈50 nm were synthesized by means of the Gen-Miller flow-levitation method with alumina or trimethylsiloxane coatings formed on the surface of these particles. Aluminum/HMX nanocomposites manufactured by suspension atomization drying or dry mechanical mixing were investigated by x-ray diffraction analysis, scanning electron microscopy, and local x-ray analysis. The combustion of these mixtures with changing particle size of the components and composition of the coating on the metal particles was studied. It was found that, when the composites produced by atomization drying were stored as loose powder, HMX crystals grew, which increased the burning rate of compressed samples from 19 to 55 mm/s in the pressure range 3–10 MPa, and the pressure exponent varied from 0.34 to 0.84, depending on how the burning rate correlates with the pressure.

Phase evolution and alloying mechanism of titanium aluminide nanoparticles

The evolution of phase composition of titanium aluminide nanoparticles synthesized by the flow-levitation method was systematically investigated by adjustment of the evaporating temperature of the mixed metallic droplet and the X-ray diffraction spectrum. Their alloying mechanism was analyzed according to the variation of phase composition. ε(h, l)-TiAl3, γ-TiAl and α2-Ti3Al phases are gradually formed in TiAl alloy nanoparticles with the increasing of evaporating temperature of the mixed droplet. The alloying reaction is possible to perform between the small clusters of Ti and Al during the cooling process with high cooling rate. And the alloying mechanism can be explained based on the Gibbs free energy of alloying reaction of Ti and Al small clusters.

Preparation and characterization of copper-nickel bulk nanocrystals

Copper-nickel nanoparticle was directly prepared by flow-levitation method (FL) and sintered by vacuum sintering of powder (VSP) method. Several characterizations, such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential thermal analysis (DTA), and energy-dispersive X-ray spectroscopy (EDX) were used to investigate the prepared nanostructures. The results of the study show that flmethod could prepare high purity Cu-Ni nanocrystals of uniform spheres with size distribution between 20 and 90 nm. After sintering the bulk nanocrystalline copper-nickel has obvious thermal stability and the surface Webster hardness increases with the rising sintering temperature. At the temperature of 900 °C, the specimen shows higher surface Webster hardness, which is about two times of traditional materials. When the sintering temperature arrives at 1 000 °C the relative density of bulk nanocrystals can reach 97.86 percent. In this paper, the variation tendency of porosity, phase and particles size of bulk along with the changing of sintering temperature have been studied.

Bulk Synthesis of Monodisperse Magnetic FeNi<SUB>3</SUB> Nanopowders by Flow Levitation Method

In this work, a novel bulk synthesis method for monodisperse FeNi3 nanoparticles was developed by flow levitation method (FL). The Fe and Ni vapours ascending from the high temperature levitated droplet was condensed by cryogenic Ar gas under atmospheric pressure. X-ray diffraction was used to identify and characterize the crystal phase of prepared powders exhibiting a FeNi3 phase. The morphology and size of nanopowders were observed by transmission electron microscopy (TEM). The chemical composition of the nanoparticles was determined with energy dispersive spectrometer (EDS). The results indicated that the FeNi3 permalloy powders are nearly spherical-shaped with diameter about 50-200 nm. Measurement of the magnetic property of nanopowders by a superconducting quantum interference device (SQUID, Quantum Design MPMS-7) showed a symmetric hysteresis loop of ferromagnetic behavior with coercivity of 220 Oe and saturation magnetization of 107.17 emu/g, at 293 K. At 5 K, the obtained saturation magnetization of the sample was 102.16 emu/g. The production rate of FeNi3 nanoparticles was estimated to be about 6 g/h. This method has great potential in mass production of FeNi3 nannoparticles.

Synthesis and characterization of FeAl nanoparticles by flow-levitation method

The synthesis of high purity intermetallic FeAl nanoparticles using the flow-levitation (FL) method was reported. Iron and aluminium droplets were levitated stably at about 2 230 °C. The morphology, crystal structure and chemical composition of FeAl nanoparticles were investigated by transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction and energy dispersive spectrometry. The results show that the average particle size of these nanoparticles is about 34.5 nm. Measurements of the d-spacing from X-ray diffraction and electron diffraction studies confirm that the intermetallic nanoparticles have the same crystal structure (B2) as the bulk FeAl. A thin oxidation coating is formed around the particles when being exposed to air. Based on the XPS measurements, the surface coating of the FeAl nanoparticles is composed of Fe2O3 and FeAl2O4. Besides, hysteresis curve reveals that saturation magnetization (M s) of FeAl is 1.66 A/m2, and the coercivity is about 1.214×103 A/m.

Synthesis and characterization of single-phase nanocrystalline Ag2Al particles

Single-phase Ag2Al intermetallic nanoparticles, and Ag and Al metallic nanoparticles were synthesized by the flow-levitation (FL) method. Measurements of d-spacings from X-ray diffraction and electron diffraction confirmed that the intermetallic nanoparticles had the hexagonal Ag2Al structure. The morphology, crystal structure and chemical composition of Ag2Al nanoparticles were investigated by transmission electron microscopy, X-ray diffraction and induction-coupled plasma spectroscopy. A thin amorphous coating was formed around the particles when exposed to air. Based on the XPS measurements, the surface coating of the Ag2Al nanoparticles could most likely be aluminum oxide or silver aluminum oxide. Therefore, the single-phase nanocrystalline Ag2Al intermetallic compound particles can be produced by adjusting some experimental parameters in FL method.

复合纳米金属间化合物Ag2Al的制备及其结构表征

Ag2Al intermetallic compound nanoparticles were synthesized by the flow-levitation method. The morphologies, granularity and phase structure were investigated by transmission electron microscope, X-ray diffractometer, and energy dispersive spectrometer. The results indicate that the prepared nanoparticles are regular spheres, with the grain size ranging from 20 to 110 nm. The nanoparticles are mainly composed of Ag2Al, including a little Al. The data of chemistry elementary analysis indicate that the atomic ratio of Ag to Al in the nanoparticles is about 66.5∶33.5. The grain size of Ag2Al in the prepared nanoparticles is about 33 nm, and that of Al is about 21 nm.

Synthesis and Characterization of Ultrafine Nanocrystalline Ti-Al Nanoparticles

Ti-Al nanoparticles and have been synthesized by the flow-levitation (FL) method. The morphology, crystal structure and chemical composition of Ti-Al nanoparticles obtained were investigated by transmission electron microscopy, X-ray diffraction and induction-coupled plasma spectroscopy. Results showed that the average grain size of these nanoparticles is about 30 nm, and it can be controlled availably by altering procedure parameters. The structure of powder is mainly double phase Ti-Al particulate composite. In addition, there are certain corresponding relation between the compositions of evaporate source master material and phase composition of alloy compound nanoparticle. The expected nanoparticle, which is mainly composition of nanocrystalline intermetallic compound, can be obtained through changing the compositions of evaporating source mastermaterial.