Synthesis Of Nanopowders Research Articles

Molten salt synthesis of TiB2 nanopowder by reduction of TiO2 with MgB2

This research work presents the preparation of TiB2 nanopowders by molten-salt synthesis (MSS) technique from TiO2 and MgB2 as starting active materials and MgCl2 as a molten salt. The pure TiB2 nanopowders were finally prepared using 2M HCl aqueous solution to leach the synthesized samples. The effects of the firing temperature, firing time and reactants to salt ratio on the TiB2 nanopowders formation were examined. The results demonstrated that the TiB2 formation was completed even with reactants to salt mass ratio of 1:2 at 1000 ?C for 4 h. The TiB2 nanopowders synthesized with 1:2, 1:5 and 1:10 reactants to salt mass ratios have different particle sizes. Thus, the average particle sizes estimated from BET surface areas were 59, 55 and 46 nm for the samples synthesized with 1:2, 1:5 and 1:10 reactants to salts mass ratios, respectively. These results illustrated that the high concentration of MgCl2 plays a key role in the particles? size reduction. The above results assured that this research study presents a new low-temperature synthesis route for nano-sized metal diboride powders.

Hydrothermal synthesis of tetragonal barium titanate nanopowders under moderate conditions

Monodispersed tetragonal barium titanate (BaTiO3) nanopowders were synthesized by a convenient hydrothermal route at a low temperature of 200?C in only 24 h. The key point of this method is to promote the generation of ultrafine titanium hydroxide precipitation precursors with the help of absolute ethyl alcohol and ammonia solution during the hydrolysis of Ti(OC4H9)4. The results of X-ray diffraction and Raman spectra show that the as-prepared BaTiO3 nanopowders possess tetragonal-dominant structure. The synthesized tetragonal BaTiO3 nanopowders exhibit relatively uniform size and good dispersity, with the average particle size of 96.1 nm and a tetragonality of 1.0073, which enable broad application prospects in the field of multilayer ceramic capacitors.

Получение нанопорошков тугоплавких оксидов с помощью CO2 и волоконного иттербиевого лазера

The main features of obtaining refractory oxide nanopowders using a repetitively-pulsed CO2-laser (10,6 µm) with an average radiation power of 500 W or a CW ytterbium fiber laser (1,07 µm) with a radiation power of up to 700 W are considered. In particular, the influence of pressure, buffer gas composition and average radiation power on the size of nanoparticles and the productivity of their obtaining were studied. Depending on the thermophysical properties of the material, in atmospheric pressure air the productivity of nanopowder synthesis varies from 15 – 23 g/h (YSZ) to 350 g/h (WO3). The mass yield of nanopowder obtained upon evaporation of one target is usually is 30 wt. % of the weight of the initial target. The obtained nanopowders contain weakly agglomerated nanoparticles of spherical shape. The average size of nanoparticles 11 – 20 nm weakly depends on their material. The most important features of using a CW ytterbium laser to obtain nanopowders of refractory oxides are their high transparency for radiation of 1,07 μm, as well as the spraying of many melt droplets. These features led to a reduction in the productivity of nanopowder production and its mass yield. On the other hand, the scattering of laser radiation in porous of the initial target and its concentration in some regions makes it possible to efficiently evaporate oxide targets from materials with a refractive index of more than 1.7 – 1.75. The transition to a repetitively-pulsed mode of radiation (pulse duration 120 μs, square waveform, and peak power 600 W), an increase in the spot diameter and the speed of beam movement over the target surface made it possible to significantly reduce droplet spattering and increase the yield of Nd: Y2O3 nanopowder from 9,7 to 30 wt.% of the weight of the initial target. However, a twofold decrease in the average radiation power led to the fact that the productivity of obtaining the nanopowder was only 15 g/h. Thus, to obtain nanopowders of refractory oxides, it is desirable to use a quasi-CW fiber ytterbium laser, which is specially designed for operation in a repetitively pulsed mode. The obtained nanopowders YSZ, Nd: Y2O3, Al2O3, etc. are used for the manufacture of ceramic solid electrolytes of the YSZ type and highly transparent laser ceramics.

Synthesis of nanopowders with low agglomeration by elaborating Φ values for producing Gd2O3-MgO nanocomposites with extremely fine grain sizes and high mid-infrared transparency

Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3−6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density.

Facile Synthesis of Single-Phase Alpha-Tungsten Nanopowders from Ammonium Paratungstate by RF Induction Thermal Plasma and Thermochemical Reduction

Facile, economic methods of preparing tungsten (W) nanopowder are critically needed to meet industrial demand. Herein, we report a method of preparing single-phase alpha-W (α-W) nanopowders using ammonium paratungstate (APT) as a starting material and the optimum synthesis conditions. The process involves two stages: i) the radio-frequency (RF) induction thermal plasma treatment of APT, followed by ii) thermochemical reduction at 600-900 <sup>o</sup>C. The crystallographic phase and morphological evolution of all products were systematically investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM), and the effects of the annealing temperature on the phase and particle size of the obtained powders were also evaluated. When the RF induction thermal plasma treatment was conducted with and without H<sub>2</sub>, the XRD and FESEM results showed the formation of mixed-phase α- and beta-W (β-W) nanopowder and WO<sub>3</sub> nanopowder, respectively. Single-phase α-W nanopowder was achieved by annealing the WO<sub>3</sub> nanopowder in an H<sub>2</sub> reductive atmosphere at 700 <sup>o</sup>C for 10 min, resulting in homogenous nanoparticles with a small particle size (d50) of 21.16 nm without any aggregation.

Low-temperature Synthesis of Single Phase Intermetallic NiZn Bulk Nanopowder in Molten LiCl–KCl with CaH<sub>2</sub> Reducing Agent

Low-temperature Synthesis of Single Phase Intermetallic NiZn Bulk Nanopowder in Molten LiCl–KCl with CaH<sub>2</sub> Reducing Agent

Continuous Flow Synthesis of Iron Oxide Nanoparticles Using Water-in-Oil Microemulsion

A continuous laminar flow reactor for the synthesis of nanopowder in microemulsion is described. The reactor is suitable for separated handling with nucleation, growth, and stabilization processes. The synthesis of iron oxide nanoparticles was selected as a model case. A water−sodium dodecyl sulphate−cyclohexene system was used as the microemulsion system for dissolving reactive aqueous solution, precursor, and a particle stabilizer. The product was purified and transferred to the aqueous phase. The result was a colloid solution of iron oxide nanoparticles in water of 50–200 nm in size with a zeta potential ranging from –25 to –57 mV. The product was characterized by UV-VIS spectroscopy, powder XRD, dynamic light scattering, electron microscopy, and electron diffraction. The results showed that water-in-oil microemulsion method is useful for the synthesis of nanopowders to obtain large amounts of stable product.

Preface

The All-Russian Conference on Nanomaterials is regularly held in Russia since 2002 and become one of the biggest scientific forums on its subject. The aim of the All-Russian Conference on Nanomaterials is to provide a platform for the discussion of the problems of research and development of bulk nanomaterials, films and coatings, nanotubes, nanofibers and nanowires, nanoclusters and nanopowders. It provides opportunities for the attendees to exchange new ideas and application experience, to establish scientific relations, and to find partners for mutually beneficial collaborations.The main directions of the conference are: fundamental principles of the synthesis of nanopowders; nanostructured films and coatings in structural and functional materials; bulk nanomaterials; innovative applications of nanotechnology (energy, mechanical engineering, medicine, etc.) and the development of methods for the certification of nanomaterials.List of Organizing Committee, Program committee, Advisory committee and Organizing Institutions are available in this pdf.

Synthesis and mechanical properties of Bi2O3-Al4Bi2O9 nanopowders

As a result of great surface area and a great number of energetic sites, ceramic nanocomposites are being considered as good adsorbents and catalysts. Al2O3 nanoparticles are widely used in high-tech applications owing to their excellent properties. Besides, Bi-based oxides have been the center of attention for applications such as remediation of hazardous wastes and wastewater photochemical degradation of organic contaminants and remediation of hazardous wastes. In this research, the synthesis of Bi2O3-Al4Bi2O9 nanocomposite and its mechanical properties as a novel composition were investigated. The results showed that the prepared Bi2O3-Al4Bi2O9 sample exhibited the Al4Bi2O9 crystalline peaks. Additionally, the prepared nanocomposite showed no impurities. The mechanical properties of the Bi2O3-Al4Bi2O9 sample were improved in comparison with Al2O3, Bi2O3, and Bi2O3- Al2O3, which offer it as a promising alternative to Bi2O3-Al2O3 composite ceramic.

Synthesis of Metal-Organic Framework Structures Based on Copper in a Low-Pressure Arc Discharge Plasma

Plasma-chemical synthesis of nanopowders based on copper oxide and metal-organic framework structures was carried out using low-pressure arc discharge plasma. The study of the obtained material was carried out by several methods (XRD, FTIR, TEM, TGA and EIS). TEM showed that the obtained powder is highly agglomerated particles with an average particle size of 13 nm, and the crystalline ordering of nanoparticles with a large (about 2 nm) lattice parameter is clearly visible. XRD showed the presence of four crystalline phases corresponding to [Cu3 (BTC)2], Cu, Cu2O and CuO. XRD results are in good agreement with FTIR studies. The DTA curve demonstrates a continuous exothermic process associated with a number of features of plasma-chemical synthesis and the morphology of the obtained nanoparticles. The study of the electrochemical properties of the materials obtained by the method of impedance spectroscopy revealed an anomalous accumulation of electrical charges around the electrodes due to electrochemical reactions for [Cu3 (BTC)2], which are associated with various reactions involving copper species in the organic framework.

Synthesis and Characterization of Barium Titanate Nanopowders by Pechini Process

Barium titanate nanoparticles have been synthesized via Pechini method, using barium acetate and an aqueous solution of titanium(IV) triethanolaminato isopropoxide. Structural properties of barium titanate (BaTiO3) are characterized by X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FT-IR). XRD and Rietveld refinement studies revealed that BaTiO3 possesses a cubic structure with a space group of Pm-3m (#221). As estimated by the Scherrer formula, the average crystallite size was accurately determined to be properly 51.9 nm for the calcined temperature at 800ºC.

Synthesis and physical properties of nanopowder and electrical properties of bulk samples of ZnFe2-xNixO4 (x: 0, 0.05, 0.10)

The Ni modified samples ZnFe2-xNixO4 with x = 0, 0.05, and 0.10 were synthesized using the sol-gel combustion method at 60 °C. The phase of obtained samples was determined using X-ray powder diffraction and found that it crystallized into a cubic spinel group. The lattice parameter of samples was decreased with increasing Ni concentration. However, the local symmetry of samples was explored using Raman spectroscopy. The presence of Raman band at 655 cm−1 was assigned to the vibration of Fe-O; found to be shifted towards higher wavenumber reconfirm the incorporation of Ni. The optical bandgap of the samples was determined using the Tauc plot and found to be in the range of 2.50 to 2.95 eV, which reflects the inorganic semiconducting nature of samples. Dielectric properties of samples were studied as a function of frequency and temperature show the presence of interfacial and orientational polarization in the sample. The resistivity of samples has been studied using Arrhenius model, and found three different regions of conduction within investigated temperature range. The first region assigned to the hopping of electron, while the second region to the hopping of polaron via the orientation of dipole (2NiFe'-2h.), or(2NiFe'-Vo..), and the third region assigned to migration of Vo.. or e'/h.. The conductivity of samples found in range of (0.85–8.95) S-cm−1 higher than conventional electrolytes used in IT-SOFCs. Based on these studies, the present materials can be used as a potential candidate for semiconductor devices and electrolytes in IT-SOFCs applications.

MAIN CHARACTERISTICS OF SYNTHESIZING PROCESSES OF MAGNETITE AND IRON NANOPOWDERS BY HYDROGEN REDUCTION FROM HYDROXIDE COMPOUND

Purpose. Study of the main characteristics of synthesizing processes of magnetite and iron nanopowders by hydrogen reduction from hydroxide compound (α-FeOOH). Materials and methods. α-FeOOH hydroxide nanopowder was obtained by chemical precipitation from aqueous solutions of iron (III) nitrate Fe(NO3)3 (10 wt. %) and alkali NaOH (10 wt. %) at room temperature, pH = 11, under the condition of continuous stirring. Synthesizing processes of Fe3O4 and Fe nanopowders by hydrogen reduction of hydroxide α-FeOOH were carried out in a tubular furnace SNOL 0.2/1250. The study of the crystal structure as well as the composition of the powder samples was performed by X-ray phase analysis. The size and morphology of nanopowder particles were investigated by scanning and transmission electron microscopes. The specific surface area of the powders was measured by using BET method by low-temperature nitrogen adsorption. The average size of the powders articles was determined via the measured value of specific surface area. Results. It has been established that the optimal temperatures corresponding to the values of the maximum specific rate for carrying out the synthesizing processes of Fe3O4 and Fe nanopowders by hydrogen reduction are 340 and 500 °C, respectively. The resulting products are nanopowders of pure Fe3O4 and Fe after being through hydrogen reduction process for 2 hours. It was shown that Fe3O4 nanoparticles consist of particles with indefinite shape, which are prone to the formation of flakes. They have a nanometer size (about tens of nm) and are in a sintered state with connections to several neighboring particles by isthmuses. Fe nanoparticles are mainly rounded and spherical, up to one hundred nm in size and distributed separately. Originality. For the first time, the optimal temperatures have been established for synthesizing processes of Fe3O4 and Fe nanopowders by hydrogen reduction from hydroxide compound. Practical value. The research results will serve as a basis for the synthesis of nanopowders based on Fe3O4 and Fe, guarantee the acceleration of processes, ensure the necessary properties of nanopowders and can be used for various fields of science, technology, ecology and oth.

Rapid Synthesis of Aluminum Nitride Nanopowders from Gaseous Aluminum Chloride

The synthesis of aluminum nitride (AlN) powders is traditionally completed through a thermal nitridation process, in which the reacting aluminum powders are combined with nitrogen at high temperatures with a long reaction time (usually several hours). Moreover, the occurrence of agglomeration within the melting Al particles results in a poor dispersibility of AlN powders, with a low efficiency of nitridation. In this study, an atmosphere-pressure microwave plasma preceded the rapid gas-gas synthesis process. In the reactor, the gaseous aluminum chloride (AlCl3) reactant was fed at different positions (R1, R2, R3) to react with nitrogen at various reaction temperatures (690~1150°C) to rapidly produce AlN nano powders (in several seconds). The process was operated at a total flow rate of 13 slm with NH3 gas content of 0 or 0.77% and an applied power of 1200/1400 W. Results showed that the high purity and dispersibility of AlN powders were found at a AlCl3 feeding position closer to the resonant cavity of the reactor (R3, 1150°C). The AlN particle size was in the range of 25-50 nm. The experiments indicated that the gas-gas reaction for rapidly synthesizing AlN nanopowders can be successfully carried out via an AlCl3-N2 plasma-chemical approach.

Synthesis and magnetic properties of PrFeO3 nanopowders by the co-precipitation method using ethanol

Synthesis and magnetic properties of PrFeO3 nanopowders by the co-precipitation method using ethanol

Synthesis and characterization of zinc oxide nanopowder

Several batches of zinc oxide (ZnO) nanopowders were obtained using the electrospark method. The samples differed in starting reagents. The electrospark method for producing ZnO nanoparticles is based on using the energy of an electric spark discharge generated between the electrode and the target. The morphology and phase composition of the synthesized samples were studied. The average particle size ranged from 10 to 25 nm. Particle morphology was diverse and represented mainly by flake nanoparticles. We recorded peaks characteristic of zinc and intensive peaks characteristic of ZnO on the X-ray pattern. The calculated sizes corresponded to coherent scattering for the crystalline phases of ZnO. The band gap was calculated for the synthesis of ZnO nanopowders. A slight narrowing of the band gap indicated the predominant crystalline phase in ZnO nanoparticles and an insignificant effect of the surface states of growth defects.

Effect of sintering aids on sintering kinetic behavior of praseodymium doped ceria based electrolyte material for solid oxide cells

The present study investigates the effect of sintering additives (Li, Co, Fe, and Mg) on the sintering kinetic behavior of the praseodymium-doped-ceria (PDC) electrolyte of solid oxide electrolyzer cell. 3Li-PDC, 3Co-PDC, 3Fe-PDC, and 3 Mg-PDC pellets were obtained from the synthesis of PDC nano-powder by microwave-assisted co-precipitation method using isopropyl alcohol as a solvent and followed by sintering additive wetness impregnation method. Linear shrinkage and shrinkage rate data suggest a positive sintering effect for 3Li-PDC and 3Co-PDC pellets and a negative sintering effect for 3 Mg-PDC and 3Fe-PDC pellets than compared to PDC pellets alone. The addition of lithium as a sintering additive (3Li-PDC) had reduced the sintering temperature of PDC from 1100 °C to 850 °C. For PDC, 3Li-PDC, 3Co-PDC, 3Fe-PDC and 3 Mg-PDC pellets sintered at 1100 °C, 850 °C, 1000 °C, 1200 °C, 1100 °C for 2 h resulted in a relative density of 93.6 ± 0.25, 95.8 ± 0.45, 95.0 ± 0.20, 92.7 ± 0.10, and 94.5 ± 0.10%, respectively. The XRD patterns of the sintered PDC pellets suggested a secondary phase formation (PrO2) in 3Co-PDC, 3Fe-PDC, and 3 Mg-PDC pellets indicating that the addition of these sintering aids results in poor solubility limit of Pr in CeO2. On the other hand, XRD patterns of PDC and Li-PDC sintered pellets displayed no secondary peak indicating good solid-solution formation. The activation energy of the 3Li-PDC pellet is obtained from CHR and Dorn methods and was found to be 182 kJ/mol and 196 kJ/mol. From the CHR method, for the 3Li-PDC pellet, the initial sintering behavior is by the grain boundary diffusion mechanism (m = ~2).

Preparation and Optical Absorption Properties of Ternary Rare Earth Boride LaxPr1-xB6 Submicron Powders.

As multifunctional materials, rare-earth hexaborides (RB6) display many interesting physical properties such as optical absorption, magnetic and thermionic emission. With the wide application of rare earth hexaboride and the continuous extension of its research fields, researchers have studied the synthesis of multi-rare earth hexaboride nano-powders and their thermal emission and light absorption properties. In the present work, ternary Single-phase LaxPr1-xB6 submicron powders are successfully synthesized using a solid-state reaction, in which lanthanum chloride (LaCl₃) and praseodymium chloride (PrCl₃) are used as rare-earth source and NaBH₄ as the boron source under continuous vacuum conditions. The reaction temperature is 1150 °C and the holding time is 2 h. The Pr doping effects on crystal structure, grain morphology, and optical absorption properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and ultraviolet-vis absorption measurements. The XRD patterns show that the diffraction peaks are sharp and well-defined, and no other extra impurity peaks were detected, indicating the characteristics of well-crystallized materials. It is found that all the LaxPr1-xB6 solid powders are of single phase. The SEM results demonstrate that the cubicshaped ternary LaxPr1-xB6 submicron crystals with a size of 50~200 nm are obtained. The TEM images reveal the cubic single-crystalline nature, and the FFT patterns implies the lattice fringe d = 0.416 nm which agrees well with the (100) crystal plane. The elements mapping results indicates that the Pr atoms occupied the lattice sites of LaB6. The optical absorption results show that the absorption valley of LaB6 are located at 591 nm. With the increase of Pr doping contents from 0.2 to 0.8, the absorption valley moves from 596.3 nm to 612.9 nm, indicating the characteristics of visible light high transparency. The first-principle calculation results manifest that the move of the absorption valley of LaB6 in the visible region after doping Pr is related to the decrease of kinetic energy of electrons near the Fermi plane. X-ray photoelectron spectroscopy (XPS) analysis shows that the La and Pr exist in the type of La3+ and Pr3+ in LaxPr1-xB6. Therefore, it exists as an efficient optical absorption material. The LaxPr1-xB6 should open up a new route to extend the optical applications of rare-earth hexaborides.

One-step synthesis of diopside (CaMgSi2O6) ceramic powder by solution combustion method

We report the synthesis of diopside (CaMgSi2O6) ceramic powder, a multifunctional material, through an energy efficient, quick and one-step solution combustion (SC) method. Synthesis of diopside by SC method requires oxidizers, especially metal-nitrates, and a suitable fuel. However, unavailability of the silicon-nitrate makes the process of diopside formation by SC method challenging, which forces researchers to synthesize diopside by alternate high temperature solid state reaction route. Here, we demonstrate a simple way to overcome this difficulty by using an extra amount of ammonium nitrate (AN, as the suitable oxidizer), but still using the fumed-silica (an economical ceramic powder) and the solution of Ca-nitrate, Mg-nitrate and the fuel. A systematic investigation was carried out using different extra amounts (0, 5 or 10 mol) of AN, in combination with stoichiometric amounts of one of the three chosen fuels, viz., urea, glycine and alanine. For a specific combination of the fuel and extra oxidizer, namely ‘alanine and 10 mol of AN’, we observed the formation of nano-crystalline diopside phase, which generates enough heat for the incorporation of Si atoms from the SiO2 precursor into diopside phase directly during the combustion process in one-step. This one-step process does not require any extra high temperature calcination step, thereby saving time, cost and complex equipments, whereas all other powders synthesized using other fuels require an extra calcination step, although the calcination temperature is low (≤ 900 °C), for crystalline diopside phase formation. Hence, our work demonstrates the one-step synthesis of diopside nanopowders by SC method through the direct use of the earth abundant SiO2 ceramics.

Synthesis and spectroscopic investigations of calcium cadmium phosphate hydrate nanopowders via doping divalent (Mn2+) and trivalent (Fe3+) cations

Calcium Cadmium Phosphate Hydrate (CaCdPH) powders with transition metal ions (Mn2+ & Fe3+) as dopants are synthesized via solid state route. The prepared nanopowders phase was confirmed by using XRD analysis. The surface morphology was analyzed by recording their SEM images. The quantitative chemical analysis of CaCdPH: Mn2+ and CaCdPH: Fe3+ was confirmed from energy dispersive spectroscopy (EDS). From the optical and Electron paramagnetic resonance (EPR) spectra, the site symmetries of CaCdPH: Mn2+ and CaCdPH: Fe3+ are ascribed as distorted octahedral. Various EPR parameters such as spin Hamiltonian parameters (g-value), hyperfine (HF) parameter A, number of spins (N) and paramagnetic susceptibility (χ) are evaluated.