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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.

In this study, the synthesis of uncontaminated, dispersible, single-crystal, stoichiometric iron carbide (Fe 3 C) nanoparticulate is pioneered successfully by using the flow-levitation (FL) method. The technique facilitates conditions for clean and direct iron-carbon gas-phase reaction at high temperature, and for the purpose of this work, production regimes and parameters were selected and customized in order to manufacture Fe 3 C nanoparticles (NPs) of mean size 20 nm for subsequent characterization and evaluation. Characterization is performed using analytical techniques that include transmission electron microscopy (TEM/HRTEM/STEM), electron and X-ray diffraction, X-ray photoelectron spectroscopy, elemental CHNS analysis, specific surface area analysis and vibrating sample magnetometry analysis. The results confirm the uncontaminated and stoichiometric character of the iron carbide NPs and demonstrate their single-crystal nature. The synthesized product exhibits chemical inertness and excellent stability at room temperature over extended periods of time. A detailed analysis of magnetic properties of the nanoparticulate was also performed. The saturation magnetization ( M s ) of the product was experimentally determined to be 124 A m 2 kg –1 , which is highly comparable to that of bulk iron carbide. The successful results merit to further investigate the clear advantages of the FL method to manufacture stoichiometric iron carbide nanoparticulate. The technique favours a significant level of parameter controllability during synthesis, which allows repeatability, and effective customization of size and magnetic properties of the resulting nanoproduct. Graphic abstract

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.

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 (Ms) of FeAl is 1.66 A/m2, and the coercivity is about 1.214×103 A/m.

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.

Silver nano-particles with average diameter of about 60 nm were compacted in a high-strength mold under different pressures at 523 K to produce nano-structured Ag solid materials. The structure and characteristic of the nano-structured Ag solid materials (NSS-Ag) were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectrometer. The NSS-Ag could be used as highly efficient surface-enhanced Raman scattering (SERS) active substrates. The common probe molecules Rhodamine 6G (R6G, 1×10−10 mol/L) were used to test the SERS activity on these substrates at very low concentrations. It is found that the SERS enhancement ability is dependent on the density of NSS-Ag. When the relative density of NSS-Ag is 83.87%, the materials reveal great SERS signal.

Nano-Cu powders were prepared by flow levitation method. The morphologies, granularities, structure and properties of nano-Cu particles were systematically investigated by transmission electron microscopy, X-ray diffraction analysis, UV visible absorption spectroscopy and X-ray photoelectron spectroscopy. The results show that the mean granularity of the almost spheric nano-Cu particles prepared in Ar is 50 nm. The maximum specific absorption appears at the wavelength of 590 nm. On the surface of the nano-Cu particles, the number of Cu atoms versus O atoms is about 94·88 : 5·12 resulting from XPS spectra.

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.