Production Of Nanopowders Research Articles

Production of tantalum nanopowders by electric explosion of wire

The possibility of producing metallic tantalum nanopowders using electric explosion of Ta-wire was explored. The regimes of the electric explosion were determined which provided maximum level of energy brought into the wire. The basic properties of the obtained powders were examined using low-temperature nitrogen adsorption, atomic-emission spectrometry, as well as by means of transmission and scanning electron microscopes.

Fugitive emissions from nanopowder manufacturing

In response to health and safety questions and concerns regarding particulate matter emissions from equipment used for synthesizing NiFe and TiO2 nanopowders, a study was undertaken to assess their impact on the air quality inside and outside a laboratory where the manufacturing equipment is operated. Elemental concentrations determined by ion beam analysis (IBA) of air particulate matter (PM) samples collected hourly with a StreakerTM sampler were used to identify possible sources and estimate contributions from nanopowder production and other sources. The fugitive nanopowder emissions were the highest at the indoor sampling location when powders were being manufactured. Average fugitive emissions of 210 ng m−3 (1-h average) (maximum 2163 ng m−3 1-h average) represented 2 % (maximum 20 %) of the average PM collected (9359 ng m−3 1-h average). The measured NiFe alloy or TiO2 PM concentrations were much smaller than the 8-h time-weighted average (TWA) workplace exposure standards (WES) for these materials (≥1,000,000 ng m−3). Most PM was found to be from infiltrated outdoor ambient sources. This suggests that nanopowder production in the laboratory is not likely to have adverse health effects on individuals using the equipment, although further improvements can be made to further limit exposure.

Economical and high throughput synthesis of copper nanopowder using continuous stirred tank and tubular flow reactors

In this work, we present a synthetic protocol for production of sub 10nm copper nanopowder (CuNPs) using continuous stirred tank (CSTR) and tubular flow reactors (PFR). Substantially higher throughputs of CuNPs have been achieved in this new protocol by reducing a copper salt with hydrazine hydrate/sodium borohydride as reducing agent. Copper nanopowder can be prepared from the sol by high speed centrifugation of the colloid. The nanopowder preserves size and shape upon re-dispersion. It has been shown that the contacting patterns do not have significant effect on particle size and shape but the overall yield is heavily dependent on the contacting pattern and reactor design. Scaling has been identified as a key issue in determining the yield.

Production of metallic nanopowders (Mg, Al) by solar carbothermal reduction of their oxides at low pressure

Abstract The carbothermal reduction of MgO and Al 2 O 3 in argon flow at low pressure allows to lower the onset temperature of metal vapor formation. Thermodynamic calculations indicate that metal formation begins at 1400 and 1700 K for a primary vacuum (1000 Pa), respectively, for Mg and Al. In the experimental section, concentrated solar energy was used for the process heating in order to favor energy savings. The products of the reaction between MgO or Al 2 O 3 and 2 varieties of carbon (graphite, carbon black) in flowing argon atmosphere at a total pressure of around 1000 to 1600 Pa were studied using X-ray diffraction, and microstructure observations revealed the formation of metallic nanopowders with some by-products. Metallic conversions close to 45 wt% and 52 wt%, respectively, for Mg and Al, were obtained. The low conversion yield of the carbothermal reduction of MgO can be attributed to a backward reaction reforming MgO powder and to a sintering process between oxide particles at high temperature. Aluminum production challenge is to avoid formation of undesired by-products: Al 2 O, Al 4 C 3 and Al-oxycarbides. Advantages and weaknesses of the used process are described and some improvements are proposed to increase metallic yields.

The development of new metallurgical materials and technologies. Part 2. Powder nanomaterials

Methods of producing nanopowders and consolidated powder nanomaterials are reviewed. Various methods of nanopowder production are analyzed, and the properties of nanopowders are presented. Consolidation of nanopowders by pressing, sintering, and pressure sintering is discussed. The properties of consolidated powder nanomaterials are presented. The prospects for their application as constructional, functional, and high-energy materials are assessed.

Synthesis and spectroscopic characterization of nanoparticles of TiO2 doped with Pt produced via the self-combustion route

Titanium oxide (TiO2) is the most important semiconductor used in photocatalysis. For that reason, most recent scientific studies have focused on improving the absorbance of this material in the visible region. In this paper, we report on the production of nanopowders of TiO2 doped with platinum via the solution combustion synthesis method, using glycine as a fuel at concentrations of 0.3, 0.6, 0.9, and 1.2% w/w of Pt with respect to TiO2 (Pt / TiO2), in order to study the influence of the dopant content on the absorbance spectrum in the visible region. The structure of the samples was characterized using x-ray diffraction and Raman spectroscopy, which confirmed the production of a pure anatase phase. VIS diffuse reflectance spectroscopy confirmed that in the visible region the samples doped with Pt absorb within the range of 400 nm to 800 nm. Field emission scanning electron microscopy and transmission electron microscopy showed the formation of TiO2 nanoparticles with an average size of 13 nm and with spherical morphology. Colorimetry (Commission Internationale de l’Eclairage L*, a*, b*) confirmed photocatalytic activity for the degradation of rhodamine B using visible light. It was concluded that the route of synthesis and the Pt content play important roles in the absorbance spectrum and the activation energy of TiO2.

Influence of technology of nanopowder production on the microstructure of the sintered by spark-plasma material on the example of aluminum oxide

A comparative study of the results of spark-plasma sintering (SPS) of two-types of aluminum oxide nanopowders, obtained by the method of conductor explosion and plasma synthesis. When the parameters of both powders are similar (spherical form of the particles, size, phase composition) as well as SPS modes the properties of the resulting compacts are significantly different both in mechanical properties and microstructure. The reason of differences in the properties of the obtained compacts is in technological impurities in powders, obtained by different methods. Artificial addition of impurities, contained in the nanopowder, obtained by electro explosion of conductor, into the powder, made by synthesis in plasma and not containing these impurities, allowed to reveal their effect on the formation of the microstructure and properties of the sintered by SPS method sample.

Sol–gel technology for innovative fabric finishing—A Review

Sol–gel technology continues to interest researchers from both industries and governmental institutions in many parts of the world decades after its discovery. It offers efficient and high-purity production of nanopowders, fibres, solid structures and thin-film coatings. Possible applications of sol–gel technology can be found in a wide range of sectors, such as pharmacy, medicine, construction, aerospace, transport, food industry, optics, agriculture, semiconductor devices, catalysis and biotechnology. Also in the textile sector, sol–gel technology is expected to lead the production of fabrics with completely novel properties or the combination of various functions in one fabric. The sol–gel reaction is easy to perform and does not require special conditions and high temperatures. The reaction consists of a series of simple hydrolysis and condensation reactions. This paper presents an overview of sol–gel technology and discusses the fabric functions that can be achieved by the technology.

Selective recovery of pure copper nanopowder from indium-tin-oxide etching wastewater by various wet chemical reduction process: Understanding their chemistry and comparisons of sustainable valorization processes

Sustainable valorization processes for selective recovery of pure copper nanopowder from Indium-Tin-Oxide (ITO) etching wastewater by various wet chemical reduction processes, their chemistry has been investigated and compared. After the indium recovery by solvent extraction from ITO etching wastewater, the same is also an environmental challenge, needs to be treated before disposal. After the indium recovery, ITO etching wastewater contains 6.11kg/m3 of copper and 1.35kg/m3 of aluminum, pH of the solution is very low converging to 0 and contain a significant amount of chlorine in the media. In this study, pure copper nanopowder was recovered using various reducing reagents by wet chemical reduction and characterized. Different reducing agents like a metallic, an inorganic acid and an organic acid were used to understand reduction behavior of copper in the presence of aluminum in a strong chloride medium of the ITO etching wastewater. The effect of a polymer surfactant Polyvinylpyrrolidone (PVP), which was included to prevent aggregation, to provide dispersion stability and control the size of copper nanopowder was investigated and compared. The developed copper nanopowder recovery techniques are techno-economical feasible processes for commercial production of copper nanopowder in the range of 100–500nm size from the reported facilities through a one-pot synthesis. By all the process reported pure copper nanopowder can be recovered with>99% efficiency. After the copper recovery, copper concentration in the wastewater reduced to acceptable limit recommended by WHO for wastewater disposal. The process is not only beneficial for recycling of copper, but also helps to address environment challenged posed by ITO etching wastewater. From a complex wastewater, synthesis of pure copper nanopowder using various wet chemical reduction route and their comparison is the novelty of this recovery process.

Design and synthesis of metal oxide hollow nanopowders for lithium-ion batteries by combining nanoscale Kirkendall diffusion and flame spray pyrolysis

This study introduces an efficient process that combines a gas phase reaction method and nanoscale Kirkendall diffusion for the large-scale production of metal-oxide hollow nanopowders. Core-shell-structured NiO@SiO2 nanopowders prepared by flame spray pyrolysis are transformed into hollow NiO@SiO2 nanopowders via a nanoscale Kirkendall diffusion process. The SiO2 coating layer plays a key role in preventing the sintering and growth of the Ni or NiO nanopowders during the preparation process. The mean size of hollow core and shell thickness of the hollow NiO nanopowders are 11 and 7nm, respectively. At a current density of 0.5Ag−1, the NiO@SiO2 nanopowders with hollow and filled structures exhibit 100th cycle discharge capacities of 885 and 338mAhg−1, respectively. In addition, the hollow NiO@SiO2 nanopowders, which exhibit low charge transfer resistances and fast Li-ion diffusion rates, also show better cycling and rate performance than the nanopowders with filled structures.

Bench- and pilot-scale continuous-flow hydrothermal production of barium strontium titanate nanopowders

Barium strontium titanate (Ba(1−x)SrxTiO3) nanopowders have been prepared at both bench- and pilot-scales using a fully hydrothermal continuous-flow system. A mixed solution of barium nitrate (and/or strontium nitrate) with titanium bis (ammonium lactato) dihydroxide was mixed in-flow with a sodium hydroxide stream before meeting a pre-heated flow of supercritical water at a counter-current mixing point which resulted in the crystallisation of Ba(1−x)SrxTiO3. The obtained nanopowders were characterised by ICP-MS, powder X-ray diffraction, transmission electron microscopy and Raman spectroscopy. All products were found to be sub-stoichiometric with the total M2+:Ti ratio varying between 0.8:1 and 0.96:1, attributed to the formation of divalent metal carbonates preventing full incorporation of the M2+ ions into the perovskite structure in the extremely short reaction times employed. The obtained products were found to adopt the expected perovskite structure, while increasing strontium content led to a decrease in both particle size and lattice parameter. Products with target compositions of Ba(1−x)SrxTiO3 (0⩽x⩽1) were produced for the first time by a fully hydrothermal route at both the bench-scale of ∼5gh−1 and pilot-scale at ∼80gh−1.

Development of cryogenic technology for the production of nano-powders from topinambour using liquid and gaseous nitrogen

Запропоновано та розроблено кріогенну технологію отримання нанопорошків із топінамбуру, яка відрізняється від традиційних застосуванням кріогенного «шокового» заморожування,низькотемпературного дрібнодисперсного подрібнення та сублімаційного сушіння. Нова технологія дозволяє більш повно вилучити біологічно активні речовини із зв’язаного з біополімерами наноасоціатів у вільний стан та зруйнувати полісахарид інулін на 45-55 % до окремих його мономерів – фруктози.

Engineering Perspective and Economic Evalution of The Synthesis Zinc Oxide Nanopowder by Co-Precipitation Method

The purpose of this study is to evaluate the engineering and economic evaluation of the manufacture of zinc oxide (ZnO) Â nanopowder by coprecipitation method. Economic evaluation is carried out with several parameters such as: GPM (Gross Profit Margin), PBP (Payback Period), and CNPV (Cumulative net present value) based on simple mathematical calculations using the Microsoft Excel Application. From the project feasibility test it was found that the project suffer a financial loss if the tax paid was 100% and the selling price was less than 90%. The project can produce as many as 1,1017 tons/year of ZnO nanopowder. ZnO nanopowder production can provide benefits up to 76%. Economic evaluations show positive results because the payback period (PBP) occurs around the 4th year, and profits will continue to increase until the 20th year. Thus, the production of ZnO nanopowder can be considered a lucrative project.

Plasma column and nano-powder generation from solid titanium by localized microwaves in air

This paper studies the effect of a plasma column ejected from solid titanium by localized microwaves in an ambient air atmosphere. Nanoparticles of titanium dioxide (titania) are found to be directly synthesized in this plasma column maintained by the microwave energy in the cavity. The process is initiated by a hotspot induced by localized microwaves, which melts the titanium substrate locally. The molten hotspot emits ionized titanium vapors continuously into the stable plasma column, which may last for more than a minute duration. The characterization of the dusty plasma obtained is performed in-situ by small-angle X-ray scattering (SAXS), optical spectroscopy, and microwave reflection analyses. The deposited titania nanoparticles are structurally and morphologically analyzed by ex-situ optical and scanning-electron microscope observations, and also by X-ray diffraction. Using the Boltzmann plot method combined with the SAXS results, the electron temperature and density in the dusty plasma are estimated as ∼0.4 eV and ∼1019 m−3, respectively. The analysis of the plasma product reveals nanoparticles of titania in crystalline phases of anatase, brookite, and rutile. These are spatially arranged in various spherical, cubic, lamellar, and network forms. Several applications are considered for this process of titania nano-powder production.

Production of WO3 tungsten oxide nanopowders by evaporation-condensation process using focused 24-GHz microwave radiation

Fabrication of WO3 tungsten oxide nanoparticles by evaporation of the initial oxide material with a focused beam of 24-GHz electromagnetic radiation generated in a 5-kW gyrotron complex at a design microwave power density of 10 kW/cm2 has been experimentally studied. Tungsten oxide powders consisting of particles, which sizes are in range of 20 nm up to 1 μm, have been obtained. The particles have different shapes, close to spherical or octahedral, suggesting their formation via both the “vapor-liquid-crystal” and the “vapor-crystal” mechanism. The maximal evaporation rate was 100 g/h. The feasibility of powder dispersity controlling by varying the flow rate of cooling air has been revealed.

Nanocrystal production in the presence of microwave radiation fields

A technology of production of nonmetal nanopowders and nanocrystals with characteristic dimensions of about 10 nm in the presence of microwave radiation fields is developed. Specially designed in the National Research Nuclear University (NRNU) MEPhI experimental microwave setup with a power of 5 kW and an operating frequency of 2450 MHz was used as a radiation source. Hydroxides/oxyhydroxides Zr — Y, Dy — Zr, and Dy — Hf placed in a special crucible located in a resonator chamber were used as parent materials.

Production of Iron Nanopowders by the Electric Explosion of Wire

The work presents the study of the properties of nanopowders produced bythe electric explosion of wire (EEW) in the atmosphere of Ar, CO, CO2, N2. It was established that with the increase of theelectric strength of a gas the wire acquires more energy, enabling the reduction of a particle average size. The EEW in gaseous media that have high dissociation energy (N2 and CO) produces metal powders that consist of crystalline α-Fe и γ-Fe. EEW products obtained in СО2 consist of α-Fe and bivalent iron oxide.

Application of the nanopowder production of azide SHS technology for the reinforcement and modification of aluminum alloys

The survey for types and fabrication methods of aluminum matrix composite materials discretely reinforced with ceramic particles and nanoparticles of refractory compounds is given. It is shown that the azide technology of self-propagating high-temperature synthesis (SHS-Az), which uses sodium azide NaN3 as a solid nitriding agent, makes it possible to fabricate numerous comparatively inexpensive micropowders and nanopowders of nitrides, carbonitrides, carbides, and their compositions, which are of interest for the reinforcement and modification of aluminum alloy. Along with the mentioned target ceramic particles, the SHS-Az product contains side haloid salts (sodium and potassium chlorides and fluorides), which can play the role of fluxes with the addition of ceramic particles into the aluminum melt. The results of experiments on the introduction of the nanopowder composition into the melt of AK6M2 alloy, %, β-SiC 48.6, α-Si3N4 27.0, β-Si3N4 5.8, and Na3AlF6 18.6 in the composition of the compacted pseudo-master alloy with the copper powder, which evidence the modifying effect, are presented.

Influence of the type of electric discharge on the properties of the produced aluminium nanoparticles

The effect of the method of aluminum nanopowder production on the aluminum products with water reaction is described. It has been established that the interaction of aluminum nanopowder prepared by the electric wire explosion, the phase composition of the reaction products mainly consists of boehmite (AlOOH) and has a fibrous structure. Therefore, that boehmite (AlOOH) can be used for modification of polymer membranes. The modified membranes can be used as water treatment from the impurity of formed true solutions according to adsorptive mechanism, and from colloidal nanometer and micron particles according to the mechanism of mechanical separation of particles depending on sizes.

Metal Oxide Nanopowder Production by Evaporation–Condensation Using a Focused Microwave Radiation at a Frequency of 24 GHz

The new method for metal oxide nanopowder production is proposed. It is the evaporation–condensation using a focused microwave radiation. The source of microwaves is technological gyrotron with frequency of 24 GHz and power up to 7 kW with the energy density flux of 13 kW/cm2. Radiation was focused on the layer of powder of the treated material to ensure its evaporation, subsequent condensation of vapor in the gas stream, and deposition of particles on the water-cooled surface. Deposited powders consist of particles whose sizes are in the range of 20 nm to 1 μm. The powder consists of particles having different shapes—close to spherical shape as well as octahedral, which indicates that the mechanism of particles formation is “vapor–liquid–crystal” as well as “vapor–crystal.” The maximum evaporation rate was 100 g/hr. The proposed approach is original and extends the possible methods of producing nanoparticles.