Article

Plasma Synthesis of Nanoparticles

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Abstract

This paper gives a review on the plasma synthesis of nanoparticulate powders. The concept of plasma synthesis is used quite comprehensively, it covers all processes where charged particles are observed. Therefore, the topic of this paper ranges from high-temperature processes and microwave processes to the laser and flame synthesis of nanopowders. For each of the processes discussed in this paper, the product characteristics are explained. This may be used as guidance for the selection of a process. The presentation of the paper is quite basic; this is to give people working in industry on daily problems a chance to see what is going on in this field. There is a vast amount of literature in the field of plasma synthesis. The literature was therefore selected in a way to demonstrate basic phenomena and not to give a comprehensive review of the literature.

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... A major point, were, the conditions for self-limitating particle growth leading to monosized particles. A recent, more technically oriented review may be found in addition (Vollath 2007). ...
... As all particles carry positive charges, they repel each other. This phenomenon limits particle agglomeration (Vollath and Sickafus 1992a;Vollath andSzabó 2002, 2006). This intermediate case leads to particles carrying both positive and negative charges. ...
... Resonant cavities applying the TE 01 (Vollath and Sickafus 1992a) or a rotating TE 11 (Vollath and Szabó 2002) mode were realized. Experience taught, higher frequencies, leading to smaller plasma zones are of advantage with respect to product quality without loss of output (Vollath andSzabó 2002, 2006). The design, displayed in Fig. 14, is characterized by a reaction tube passing the TE 11 resonant microwave cavity. ...
Article
There is a huge variety of plasma processes for synthesis of nanoparticulate powders. They may be grouped with respect to operating temperature, which is the essential parameter with respect to the properties of the products. In view of industrial production, the highest degree of maturity is found in high temperature processes working under ambient pressure. For products, where well-defined properties are demanded, low temperature microwave plasma processes are best suited. Additionally, these processes allow coating of the produced particles, even with organic phases. Other processes where plasmas are involved, such as laser or flame processes coupled with electric fields have, to some extent, a high potential for development.
... Nanofluids, according to the definition above, have been extensively used in a wide variety of applications. Primarily, this was driven by the potential to develop fluids with significantly increased conductive and convective [59][60][61][62][63][64][65][66][67][68] heat transfer properties. Outside of this work, however, many researchers have been looking for other means of exploiting nanofluids. ...
... emerging synthesis techniques [60][61][62][63][64][65][66][67], mass transport [68][69][70][71][72], boiling phenomena [13], [23], [102][103][104][105][106], absorption and conversion of radiation [80][81][82][83][84][85][86][87][88], optics [88][89][90][91][92][93][94][95][96][97][98][99][100], consumer goods [101], electronics [102][103][104][105][106], and surfaces and catalysts [107][108][109][110][111][112][113][114][115][116][117][118][119]. This wide breadth of recent research has primarily been the due to rapid advances and increasing control in nano-material fabrication techniques [120]. ...
... A number of effective means can be used to evaporate a metal: induction heating, arc plasma, laser ablation, and resistive heating, to name a few. While these processes are applicable to a stationary metal source, plasma torches can be used for the in-flight evaporation of micron-sized (or larger) powders followed by the quenching of the metal vapor to form nanoparticles [60]. Metal nanoparticle formation from an atomic vapor cloud involves numerous steps: 1) Supersaturation of the metal vapor, 2) statistical formation of a nuclei, ...
Article
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Nanofluids-a simple product of the emerging world of nanotechnology-are suspensions of nanoparticles (nominally 1-100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754271]
... A typical gasphase plasma setup using AC or DC is shown in Figure 4. The flow diagram of a production system based on plasma burners is illustrated in Figure 5. 96 Quenching is performed after the synthesis. The plasma process mainly produces large nanoparticles with a broad size distribution. ...
... In some cases, particle clusters are formed. 96 Low-temperature plasmas are always generated at low pressure. Their temperatures are <1000 K. ...
... Particles obtained via the gas-phase, low-discharge plasma treatment have a narrow size distribution. Typical transmission electron microscopy (TEM) images of NPs obtained with RF and microwave sources are shown in Figure 7 99 and Figure 8, 96 respectively. ...
... These building blocks of matter have an electromagnetic potential and at least one remote valence electron (or one added electron). Impurities are removed by liquid-phase and gasphase processes (e.g., CO2, NOx, hydrogen chloride) [187]. Due to the extreme heating and dry environment, plasma synthesis enables the production of nanoparticles with distinct and specific surface textures and shapes that cannot be obtained with conventional methods [188]. ...
Article
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Nanomaterials are materials with one or more nanoscale dimensions (internal or external) (i.e., 1 to 100 nm). The nanomaterial shape, size, porosity, surface chemistry, and composition are controlled at the nanoscale, and this offers interesting properties compared with bulk materials. This review describes how nanomaterials are classified, their fabrication, functionalization techniques , and growth-controlled mechanisms. First, the history of nanomaterials is summarized and then the different classification methods, based on their dimensionality (0-3D), composition (car-bon, inorganic, organic, and hybrids), origin (natural, incidental, engineered, bioinspired), crystal phase (single phase, multiphase), and dispersion state (dispersed or aggregated), are presented. Then, the synthesis methods are discussed and classified in function of the starting material (bot-tom-up and top-down), reaction phase (gas, plasma, liquid, and solid), and nature of the dispersing forces (mechanical, physical, chemical, physicochemical, and biological). Finally, the challenges in synthesizing nanomaterials for research and commercial use are highlighted.
... [43] Through a strict control of precursor residence time and growth quenching, plasma induction allows the single-step production of monodisperse and crystalline NPs at high quantities (up to 30 g/h for 50 kW units) that is easily scalable with higher energy torches and larger reactors. [44] Radio-frequency (RF) plasma induction has already been used for the synthesis of ferric oxide nanoparticles from their corresponding metal nitrate salts, such as ZnFe 2 O 4 [45] and NiFe 2 O 4 . [46] To the best of our knowledge, no mixed ferrite synthesis from a RF plasma reactor has been reported so far. ...
Article
Amine N‐alkylation is a process involved in the production of a wide range of chemicals. Here we describe the synthesis of well‐defined (Ni0.5Cu0.5)Fe2O4 magnetic nanoparticles by plasma induction, and their successful application to amine N‐alkylation using alcohols as coupling agents through a borrowing hydrogen pathway. Plasma induction allows precise morphology and size control over nanoparticle synthesis, while allowing the one‐pot production of decagram quantities of material. Up to date, such nanoparticles have never been applied for organic reactions. By coupling high‐end characterization techniques with catalytic optimization, we showed that small Cu(0) satellite nanoparticles played an essential role in alcohol oxidation, whereas both Ni and Cu were required for the last step of the reaction. Using elemental mapping, we demonstrated that catalyst deactivation occurred through a leaching/re‐deposition mechanism of Cu and Ni. The reactions were conducted under microwave conditions, which exerted a positive effect on catalytic activity. Finally, the catalyst was active at low metal loadings (2 mol%) even on the gram‐scale, and affording unprecedented TON for this reaction catalyzed by Ni/Cu bimetallic systems (19). The three‐body solution. A noble metal‐free, magnetically recyclable (Ni0.5Cu0.5)Fe2O4 catalyst was made under plasma conditions. It catalyzes alcohol amination through a hydrogen borrowing pathway. The role of each metal in the reaction, as well the mechanism for catalytic deactivation was identified, aided by EELS spectroscopy.
... Whereas inorganic matrix nanocomposites use high energetic physical processes as magnetron sputtering, vacuumarc evaporation, laser ablation, flame and plasma nanoparticles synthesis [11,12]. Here, we have to remark that the majority of authors consider that nanoparticles are objects smaller than 100 nm and they can be classified in three main categories: nanoparticles from natural origin (including biological), those already produced in large quantities (well known industrial processes) and those produced by new technologies [13]. ...
Article
Full-text available
The applications of Pulsed Laser Deposition (PLD) for producing nanoparticles, nanostructures and nanocomposites coatings based on recently developed laser ablating techniques and their convergence are being reviewed. The problems of in situ synthesis of hybrid inorganic-organic nanocomposites coatings by these techniques is being discussed. The novel modification of PLD called Pulsed Laser Adaptive Deposition (PLAD) technique is presented. The in situ synthesized inorganic/organic nanocomposites coatings from Magnesium (Mg) alloy/Rhodamine B and Mg alloy/Desoximetasone by PLAD are described. The trends, applications and future development of discussed patented methods based on the laser ablating technologies for producing hybrid nanocomposite coatings have also been discussed in this review.
... Many inorganic nanoparticles, including oxides, nitrides, and carbides are produced as powders by combustion [1], sol-gel [2], laser ablation [3] and other [4][5][6] methods. Their utilization is almost always in dispersion or suspension form. ...
Article
Many inorganic nanoparticles are produced as powders, but their utilizationis almost always in dispersion or suspension form. We present a novel nanolatex that is very effective at producing the first reported stable waterborne dispersions of nanoparticulate WC, starting with highly aggregated WC nanopowder. Transmission electron micrographs show that the nanopowder is highly dispersed in/on the hydrogel nanolatex particles. Thermal diffusivity, dielectric loss, optical, and mechanical properties of thin films derived from waterborne dispersions are presented. Such waterborne dispersions and nanocomposite films represent new materials for photothermal, hardening, abrasive/polishing and catalysis applications.
... This area was also selected to obtain diffraction patterns shown in Fig. 6.8(b). The stress required for a dislocation to cross a particle is expressed using Orowan stress equation [154]. ...
Article
Sn–Ag–Cu (SAC) alloys are regarded as the most promising alternative for traditional Pb-Sn solders used in electronic packaging applications. However, the higher reflow temperature requirement, possible intermetallic formation, and reliability issues of SAC alloys generate several key challenges for successful adoption of Pb-free solder for next generation electronic packaging needs. Localized heating in interconnects can alleviate thermal stresses by preventing subjection of entire package to the higher reflow temperatures associated with the SAC solders. It had been demonstrated that SAC solder-FeCo magnetic nanoparticles (MNP) composite paste can be reflowed locally with AC magnetic fields, enabling interconnect formation in area array packages while minimizing eddy current heating in the printed circuit board. Solder/magnetic nanocomposite pastes with varying MNP concentration were reflowed using AC magnetic fields. Differential scanning calorimetry results show a reduced undercooling of the composite pastes with the addition of MNPs. TEM results show that the FeCo MNPs are distributed in Sn matrix of the reflowed solder composites. Optical and SEM micrographs show a decrease in Sn dendrite regions as well as smaller and more homogeneous dispersed Ag3Sn with the addition of MNPs. The MNPs promote Sn solidification by providing more heterogeneous nucleation sites at relatively low undercoolings. The mechanical properties were measured by nanoindentation. The modulus, hardness, and creep resistance, increase with the MNP concentration. The enhanced mechanical properties are attributed to grain boundary and dispersion strengthening. The reflow of solder composites have been modeled based on eddy current power loss in the substrate and magnetic power losses in the solder bumps. Induction reflow of pure solder bumps (< 300 μm) in an area array package using 500 Oe magnetic field at 300 kHz requires excessive eddy current power loss in the substrate, resulting in extreme temperatures that lead to blistering and delamination of the substrate. Solder-MNP composites with modest MNP loading showed temperature increases sufficient to achieve solder reflow when subjected to the same AC magnetic fields. Thermomechanical behavior of a solder joint was also modeled under cyclic temperature variations. The stress and strain are highly localized at the interface between solder and substrate. Plastic work accumulated per cycle can be used for lifetime prediction. In this article we review lead-containing and lead-free solder systems, and the electronic packaging technologies pertinent to soldering process. Recent research on the effects of MNPs on localized heating, microstructure evolution, mechanical properties, and thermomechanical reliability are summarized.
... There is a wide variety of gas-phase techniques to synthesize nanoparticles, e.g. flame synthesis (Wegner and Pratsinis, 2000), thermal evaporation (Granqvist and Buhrman, 1976), and plasma synthesis (Vollath, 2007;Binns, 2001). The technique presented in this article is a plasma-based technique based on high-power pulses similar to what is used in the HiPIMS disclmge. ...
Article
Full-text available
Pulsed plasma processes open up the possibility of using very high plasma densities and modulated deposition in the synthesis of thin films and nanoparticles. The high plasma densities lead to a high degree of ionization of the source material, which creates new possibilities for surface engineering. Ions can, in contrast to atoms, be easily controlled with regard to their energy and direction, which is beneficial for thin film growth. Furthermore, ions can also increase the trapping probability of material on nanoparticles growing in the gas phase. The pulsed sputter ejection of source material also has other consequences: the material in the plasma and the material arrival on the growth surface will fluctuate strongly resulting in high level of supersaturation during pulse-on time. In this paper, an overview of the generation and properties of highly ionized pulsed plasmas is given. In addition, the use and importance of these types of discharges in the fields of thin-film and nanoparticle growth are also summarized.
... The aim of the present work is to explore the impurity chemistry and surface passivation of the Cu nanopowders as a function of the operating conditions in a DC thermal plasma synthesis. Among other gas-phase processes for the fabrication of nanopowders, the thermal plasma synthesis [15,16] delivers greater flexibility in creating chemically diverse working environments by appropriate choice of the plasma-forming gas and the feedstock. However, these processing capabilities remain largely untapped as an effective means of taking control over the product purity and passivation. ...
Article
A range of copper nanopowders (BET particle size 20–70 nm) has been prepared through a DC thermal plasma synthesis under varying operating conditions. A thermal evolution analysis was performed on these materials to quantify the nonmetallic impurities (O, C, N, H) which originated from the working and ambient environments. A temperature-programmed oxidation-infrared detection (TPO) was used for carbon and hydrogen determinations, an inert gas fusion-infrared/conductometric detection (GFA) for oxygen and nitrogen determinations. The TPO and GFA evolution patterns provided an insight into impurity speciation in terms of the free and chemically bound carbon, oxidic and adsorbed oxygen, as well as the possible types of organic functionalities. The impurity uptake and speciation were found to be a strong function of the operating conditions, including the choice of the plasma gas and the Cu feedstock. The operating conditions were identified under which the oxidation of the product nanopowder was minimized upon exposure to ambient laboratory environment. The product passivation during the synthesis was attributed to the presence in the working environment of the gaseous species (CO, CN), which are capable of strong chemisorption on the freshly prepared copper surface.
... It is known that the agglomeration can be influenced by charges on the particle surface utilizing Coulomb interaction. If the particles attain a unipolar charge, they are less likely to collide and agglomerate [35][36][37][38][39] . ...
Article
Full-text available
Inline particle coating after the particle formation process to preserve its specific properties is hardly investigated scientifically. Tackling that issue, we have studied the use of three different vaporized organo-siloxanes (tetraethyl orthosilicate TEOS, hexamethyldisiloxane HMDSO, and octamethylcyclotetrasiloxane OMCTS) as precursors for direct inline coating of pristine titanium dioxide (TiO2) nanoparticles made via spray-flame synthesis. The inline silica (SiO2) coating of the formed titanium dioxide nanoparticles is achieved by vaporizing and sending the chosen organo-siloxane precursors into a cylindrical coating nozzle downstream the particle formation zone of the spray-flame. To further explore the effects on morphology and the quality of the resultant TiO2|SiO2 core-shell nanoparticles, a plasma discharge – i.e., dielectric barrier discharge source – is applied after the coating step. The TiO2|SiO2 core-shell nanoparticles are characterized using Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM), X-Ray Diffraction (XRD), Fourier-Transform InfraRed spectroscopy (FTIR), Brunauer-Emmett-Teller surface area analysis (BET), elemental analysis, and dynamic light scattering (DLS). Results showed distinct core-shell nanoparticles with shell thicknesses of around 1.5 nm alongside the formation of unattached SiO2 nanoparticles due to homogenous nucleation of SiO2. As the precursor silicon content increased (TEOS < HMDSO < OMCTS), the homogenous nucleation rose to generate materials with high BET surface areas. When employing OMCTS, the high homogeneous nucleation rate led to SiO2 agglomeration, which resulted in large TiO2|SiO2 agglomerates. Morphologically, the phase composition of anatase/rutile of the produced coated nanoparticles did not vary significantly when compared with the reference uncoated TiO2 nanoparticles, indicating that the SiO2 coating is purely a surface phenomenon. Plasma discharge was shown to reduce coated particle agglomeration up to certain extend. Based on these findings, we conclude that the best studied parameters to benefit the synthesis of homogeneously coated TiO2|SiO2 nanoparticles are (i) using TEOS as a coating precursor to minimize SiO2 homogeneous nucleation and (ii) applying a plasma discharge to slightly reduce coated particle agglomeration.
... Whereas inorganic matrix nanocomposites use high energetic physical processes as magnetron sputtering, vacuumarc evaporation, laser ablation, flame and plasma nanoparticles synthesis [11,12]. Here, we have to remark that the majority of authors consider that nanoparticles are objects smaller than 100 nm and they can be classified in three main categories: nanoparticles from natural origin (including biological), those already produced in large quantities (well known industrial processes) and those produced by new technologies [13]. ...
Article
Full-text available
Abstract: The applications of Pulsed Laser Deposition (PLD) for producing nanoparticles, nanostructures and nanocomposites coatings based on recently developed laser ablating techniques and their convergence are being reviewed. The problems of in situ synthesis of hybrid inorganic-organic nanocomposites coatings by these techniques are being discussed. The novel modification of PLD called Pulsed Laser Adaptive Deposition (PLAD) technique is presented. The in situ synthesized inorganic/organic nanocomposites coatings from Magnesium (Mg) alloy/Rhodamine B and Mg alloy/ Desoximetasone by PLAD are described. The trends, applications and future development of discussed patented methods based on the laser ablating technologies for producing hybrid nanocomposite coatings have also been discussed in this review.
... Metal nanoparticles can be synthetized by physical methods that involve the evaporation of the bulk metal precursor followed by its condensation. Chemical synthesis approaches include plasma synthesis of metal oxide, nitride, and carbide nanoparticles [33], chemical precipitation and chemical vapor deposition [34] . The morphology and structure of nanoparticles are often evaluated by characterization methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), or X-ray powder diffraction (XRD). ...
Article
As an abundant, cheap and pollution-free renewable energy resource, solar energy offers a great alternative to conventional fossil resources and is expected to play an increasingly significant role in our global energy future. Solar thermal collectors are conventional devices for capturing solar radiation. Direct absorption solar collector (DASC) is a new generation of solar thermal collectors in which the transport medium is directly exposed to the incident solar radiation. To improve direct absorption collectors absorption and heat transfer capabilities, molecular-level additives are added to their working fluids. As a production of the emerging world of nanotechnology, nanofluids – which are engineered suspensions of nanoscale materials in host fluids – have shown remarkable improvement in thermo-physical and optical properties of conventional heat transfer fluids. This review presents a comprehensive survey of the recent studies on optical characterization, relevant equations and theoretical modeling approaches, and application of nanofluids in direct absorption solar collectors. Possible issues and challenges encountered in potential exploitation of nanofluids in DASCs are addressed as well.
... Additionally, the product must be separated and purified of by-products. This leads to an increase in processing times and costs [13]. ...
Article
Synthesis of cobalt boride nanoparticles and h-BN nanocage encapsulation were conducted using a triple direct current (DC) thermal plasma jet system. Mixed cobalt and boron powder were used as the starting material. The thermal plasma jet was generated using mixed Ar–N2 and Ar–H2 gases. The nanostructure of the synthesized nanoparticles varied according to the gas composition. In the Ar–N2 plasma, the dissociated nitrogen anticipated a chemical reaction with the boron precursor and synthesized h-BN nanocages that encapsulated cobalt boride nanoparticles, additionally, c-BN nanoparticles were synthesized. In the Ar–H2 plasma, only <20 nm spherical cobalt boride nanoparticles were synthesized and their size distribution was controlled by the growth time or quenching rate, which was controlled by changing the flow rate of plasma forming gasses. These synthetic processes were comparatively investigated thermodynamically.
... The plasma processing method is frequently used in CVD area [329][330][331][332]. A detailed report on plasma types, synthesis, and processing regarding nanocomposites have been widely reported [333][334][335][336][337][338][339][340][341][342][343][344]. Plasma processing is applicable for a variety of metals and provides better accuracy, high efficiency, and high productivity. ...
Chapter
The efforts of the scientific community to mimic nature in terms of living styles related to creatures accept their actions as a function of ecological conditions to advance the standard of survival style. In this logic, smart polymers propose materials that react to many stimuli such as pH, temperature, light, magnetic and electric fields, light intensity, biological molecules, etc. Smart polymers have gained an enormous amount of attention in this new era due to their countless applications in zones including biosensors, switchable wettability, actuators, and several therapeutic and environmental-based applications. Several rigorous researches have been carried out to improve smart polymers using different stimuli-responsive polymeric moieties. This chapter summarizes the basic introduction/classification of smart polymers and their importance at a nanocomposite level. Some introduction related to the most familiar applications of smart polymer nanocomposite materials are also summarized in this chapter.
... The intense laser beam evaporates the target explosively, and many atoms and molecules are ejected from the target [1]. There are many methods for NP synthesis, which are usually based on sol-gel colloidal chemistry [2], plasma precursor decomposition [3], electrochemical etching [4], etc. Among these is the synthesis of NPs by laser ablation [5], Nanoparticles (NPs), i.e., particles with dimensions in the nanometer range, are important nanomaterials useful in a number of applications in physics [6], chemistry [7], engineering [8], and biology [9]. ...
Research Proposal
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Zinc, nickel and silver oxide were prepared by the method of pulsed ablation laser in liquid, with different preparation conditions, where the number of pulses was changed (25, 50 and 75) and the frequency was 1 Hz and the energy was 600 mJ and at room temperature. We have used UV-visible spectroscopy, field emission scanning electron microscopy (FSEM), the EDX system, then these materials were added to the local dye and the photo-catalytic activity was applied to them using a UV-500 lamp for different periods of time (0, 30, 60 and 120 mint) and they acted as photo�cataly
... The intense laser beam evaporates the target explosively, and many atoms and molecules are ejected from the target [1]. There are many methods for NP synthesis, which are usually based on sol-gel colloidal chemistry [2], plasma precursor decomposition [3], electrochemical etching [4], etc. Among these is the synthesis of NPs by laser ablation [5], Nanoparticles (NPs), i.e., particles with dimensions in the nanometer range, are important nanomaterials useful in a number of applications in physics [6], chemistry [7], engineering [8], and biology [9]. ...
Article
Full-text available
Zinc, nickel and silver oxide were prepared by the method of pulsed ablation laser in liquid, with different preparation conditions, where the number of pulses was changed (25, 50 and 75) and the frequency was 1 Hz and the energy was 600 mJ and at room temperature. We have used UV-visible spectroscopy, field emission scanning electron microscopy (FSEM), the EDX system, then these materials were added to the local dye and the photo-catalytic activity was applied to them using a UV-500 lamp for different periods of time (0, 30, 60 and 120 mint) and they acted as photo-catalysts.
... Thus, fundamental theory of plasmas and particle production processes in plasmas is not repeated here. The microwave plasma system chosen for the TRAPS apparatus is a low pressure system with a resonant microwave cavity [Vollath, 2007;Vollath, 2008]. These systems are simple in design and universal in application. ...
Article
Die Bedeutung von Nanopartikeln für Prozesse in der Atmosphäre rückt zunehmend in das Interesse von Forschern. In vielen natürlichen Kondensationsprozessen sind die Kondensationskeime kleiner als 10 nm im Durchmesser. Die ist genau der Übergangsbereich vom Cluster zum Festkörper, in dem physikalische und chemische Eigenschaften größenabhängig sind und stark von Obenflächenkontaminationen und Kontakt zu anderen Oberflächen abhängen. Bisher gab es keine Möglichkeit die fundamentalen Eigenschaften von freien, massenselektierten Nanopartikeln mit definiertem Ladungszustand und Durchmessern von 3 bis 30 nm in Laborexperimenten zu untersuchen. Diese Arbeit zeigt die Notwendigkeit auf Laborexperimente zu entwickeln, die freie Nanopartikeln ohne vorherige Abscheidung auf Substraten oder Filtern zu untersuchen. Als Anwendungsbeispiel in der Atmosphärenforschung werden Eiswolken diskutiert, die sich an Nanopartikeln meteorischen Ursprunges in der Mesosphäre bilden. Mit der TRAPS Apparatur ist es nun möglich verschiedene spektroskopische Methoden an freien Nanopartikelstrahlen oder gefangenen Nanopartikelwolken anzuwenden. Massenspekrometrie, optische Extinktionsspektroskopie und Innerschalen-Photoionisationsspektroskopie werden als Anwendungsbeispiele gezeigt. Als wissenschaftliches Novum werden Experimente zur Untersuchung von Eisnukleation an Nanopartikeln und die Bestimmung von Eiswachstumsgeschwindigkeiten unter mesosphärischen Bedingungen sowie XPS Messungen an sub-10 nm SiO2 Partikeln gezeigt.
... Similarly, I do not address nanoparticle synthesis in plasma and laser reactors, including laser ablation, because of their limited contribution to large-scale manufacture materials until recently. Nevertheless, several excellent studies have been published on the topic: Vollath (2007) has reviewed plasma synthesis of materials, focusing on microwave plasmas that allow even organic coatings on nanoparticles; Semaltianos (2010) has examined nanoparticle synthesis by laser ablation; and Van Erven and colleagues (2009) have focused on the scale-up of laser reactors. ...
Chapter
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Aerosol Science and Technology: History and Reviews captures an exciting slice of history in the evolution of aerosol science. It presents in-depth biographies of four leading international aerosol researchers and highlights pivotal research institutions in New York, Minnesota, and Austria. One collection of chapters reflects on the legacy of the Pasadena smog experiment, while another presents a fascinating overview of military applications and nuclear aerosols. Finally, prominent researchers offer detailed reviews of aerosol measurement, processes, experiments, and technology that changed the face of aerosol science. This volume is the third in a series and is supported by the American Association for Aerosol Research (AAAR) History Working Group, whose goal is to produce archival books from its symposiums on the history of aerosol science to ensure a lasting record. It is based on papers presented at the Third Aerosol History Symposium on September 8 and 9, 2006, in St. Paul, Minnesota, USA.
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Nanofluids -one simple product of the emerging world nanotechnology -where nanoparticles (nominally 1-100 nm in size) are mixed with conventional base fluids (water, oils, glycols, etc.). Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995 [1]. In the year 2010 alone there were nearly 500 research articles where the term nanofluid was used in the title, showing rapid growth from 2000 (12) and 2005 (78). Much of the first decade of nanofluid research was focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, convection coefficients). Recent research, however, has started to highlight how nanofluids might perform in a wide variety of other applications. These applications range from their use in nanomedicine [2] to their use as solar energy harvesting media [3]. By analyzing the available body of research to date, this article presents trends of where nanofluid research is headed and suggests which applications may benefit the most from employing nanofluids. Overall, this review summarizes the novel applications and uses of nanofluids while setting the stage for future nanofluid use in industry.
Article
Since the inception of matrix assisted pulsed laser evaporation (MAPLE), a large body of research has focused on the structure and property preservation of soft materials. Departing from this precedent, a variation of MAPLE to grow complex inorganic nanoparticles and nanoporous thin films from acetate precursors is presented. While some aspects of MAPLE are retained, a weakly absorbing matrix solvent is used to promote absorption by the precursors, leading to photothermal decomposition. The diffusion of ions within the laser interaction volume results in the formation of nanoparticles, which are then ejected by subsequent pulses. The acetate precursors were processed into colloidal suspensions in deionized water and frozen to form solid targets, followed by irradiation with a pulsed excimer laser at fluences ranging from 0.25 to 0.75J/cm2. Nanoparticles and nanoporous films of unary, binary, and ternary metallic and oxide systems were deposited at room temperature onto substrates of Si and electron-transparent grids. Size distributions varied between different material systems with negligible pressure and energy effects, with distribution extrema ranging from 2 to 100 nm in diameter. Characterization of the nanoparticles was performed by high resolution scanning and transmission electron microscopy, and energy dispersive x-ray spectroscopy.
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The demand of nanoparticles has been increasing tremendously. However, the traditional methods of synthesis are mostly based on wet-chemical synthesis, that generally need chemical precursors that may not be environment friendly. Due to this, new greener techniques need to be designed and tested. PLAL technique has been demonstrated as a promising method that can be used to synthesize nanoparticles from almost the entire periodic table and requires much cheaper precursors than chemical synthesis techniques. The nanoparticles produced can have clean ligand-free surfaces, due to which they are ready for functionalization and act as better catalysts. In this work, a single step method, PLA in H2O and supercritical CO2, was used to produce TiO2 nanoparticles and TiO2-carbon core-shell nanoparticles, by utilizing CO2 in the process. Pressurized CO2, in the form of gaseous, liquid, and supercritical CO2 was demonstrated as a promising solvent for producing well-dispersed agglomerate free nanoparticles and core-shell nanoparticles using PLA technique. With the proposed techniques, it is possible to produce stable rutile-TiO2 as nanoparticle suspension by PLA in H2O, while PLA in scCO2 can be used to produce well dispersed non-agglomerate anatase-TiO2 nanoparticles directly as a dry nanoparticle powder. Further, core-shell nanoparticles of anatase-TiO2 as core and carbon as shell can be prepared by PLA in pressurized CO2 and their size can be controlled by simply controlling the CO2 pressure and temperature
Chapter
Nowadays, thermal plasma is one of the upcoming technologies used for the synthesis of magnetic nanoparticles. Plasma is a fourth state of matter alongside solid, liquid, and gases. Quasi-neutral gas of charged particles (electrons and ions) and neutrals particles (atoms or molecules) characterized by their collective behavior is known as plasma. Thermal plasma technology is widely used for technology-oriented materials processing applications such as plasma cutting, spraying, sintering, melting, welding, waste management, ore segregation, alloy formation, etc. Tremendous thermal flux associated with the plasma plume enhances its applicability manifold. It is possible to achieve the temperatures of the order of 5 × 10³ K to well above 10 × 10³ K with a well-stabilized arc. In comparison, the conventional heat sources can attain temperature only up to 3000K. This facilitates high-temperature chemical reactions and extractive metallurgy (e.g., formation of oxides of ceramic materials). Here emphasis is given on the various features of thermal plasma processing technology and the way in which these plasmas can contribute to the advancement of the frontiers of materials-development capabilities. As an example of magnetic materials thermal plasma processing of few selected systems viz. CoFe2O4, (Ni-Co)Fe2O4 are discussed in detail whereas processing of other magnetic system is mentioned in the present chapter.
Chapter
The present chapter explores how the distinctive characteristics of magnetic nanoparticles (MNPs), particularly when at different interfaces, account for many novel potential applications in the oil industry. According to the chosen synthesis method, MNPs may be engineered in a particular manner and therefore give rise to skills such as selective adsorption, long distance transport, localized heat, intelligent tracking, and recovery. Thus, the magnetic materials may achieve properties suitable for several developments in petroleum production. This chapter reviews progress in the application of magnetic materials in the oil industry, such as enhanced oil recovery, heavy oil recovery, reservoir monitoring, drilling, well completion, and flow assurance and conformance control.
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Magnetic nanoparticles (MNPs) are widely used for myriad in vivo and in vitro biomedical applications via targeted drug delivery in cancer therapy, hyperthermia, photocatalysis, contrast enhancement magnetic resonance, antibacterial activity, etc. These applications are owing to their large surface area to the volume ratio. MNPs have become indispensable for in vivo therapeutic purposes, due to their easy binding with biomolecules such as proteins, enzymes, antibodies or nucleotides. All the in vivo biomedical applications require that the MNPs exhibit good saturation magnetization, particle size, morphology, and surface functionalization that is biocompatible and biodegradable. The various sizes of MNPs can be control through the synthesis procedures and the materials used for the surface functionalization which enables their comparison to biological organisms from cells, genes, proteins, and virus. In conclusion, the recent advances and future functionalization perspective in the development of MNPs for different biomedical applications will be summarized in this chapter.
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The present study addresses the feasibility to synthesize aluminium nanoparticles (NPs) from micron-sized aluminium powder with the use of a customized atmospheric plasma spraying (APS) technique. Using APS, nanoparticle synthesis can be achieved via rapid melting and vaporization of the initial micrometric particles and their subsequent re-nucleation. A custom mantle system was designed and developed with the aid of relevant simplified CFD simulations. The mantle provided the necessary inert environment (argon), at ambient pressure, in order to avoid any oxidation of the metal during plasma spraying while promoted rapid quenching of the gasified metal. The particles formed were collected with the aid of a quartz filter downstream of the plasma flame and the production rate achieved was 2 g min−1. Ex situ post-characterization of the particles via X-ray diffraction, specific surface area measurement (BET), transmission electron microscopy (TEM) coupled with energy dispersive spectrometry (EDS) and thermogravimetric analysis (TGA) under air revealed that the powders obtained primarily comprised of monocrystalline metallic aluminium nanoparticles of almost spherical shape. The NPs possessed a 2–5 nm oxide coating layer. By regulating the conditions inside the mantle, a variety of different size distributions were obtained.
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In this study, iron oxide nanoparticles were synthesized using FeCl 3 (0.1 M and 0.3 M) with myrtle leaf extract for of methylene blue dye (MBD) degradation under visible light irradiation (100-watt halogen lamp) as environmental application. X-ray diffraction analysis showed the polycrystalline structure of Fe 2 O 3 material with miller indices confirmed the presence of iron oxide with average crystalline sizes (15.59-16.8 nm) synthesized by (0.1M - 0.3mM) concentrations of FeCl 3 . Field emission-scanning electron microscopy revealed rods-like and spherical shapes of Fe 2 O 3 nanoparticles, with an average particle size of 25 to 67 nm, covered the whole top surface of structure. Moreover, the change of the color of the iron oxide NPs from brown to dark brown enhances the transformation of the properties of the material obtained by adding the biomass which gives the absorbance peaks around 265-350 nm and energy band gaps (3 and 3.7 eV) using UV/VIS spectrometer. The methylene blue degradation efficiencies of Fe 2 O 3 NPs prepared by plant extract and FeCl 3 with concentrations (0.1 M and 0.3 mM) were 86.3% after 150 min and 90% after 120 min respectively.
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In this work, the authors propose a method to obtain micro- and nano-structures on the stainless steel mesh (SSM), whichshowed the potential application for the treatment of water pollution based on its hydrophobicity and oleophilicity. The tex-tured surfaces with the micrometer scale pore array patterns on the SSM are formed by three-beam laser interference lithog-raphy. And the nanostructures, such as nanorods, nanowires, and nanoflakes, are obtained on the surfaces of the SSMs afterlaser irradiation by heating for 70 min at approximately 600 °C under ambient conditions. The results showed that the nano-structures can be easier to grow on the rough surface than the smooth ones. In addition, these nanostructures are also grownon the surfaces of the laser irradiated SSM with the candle soot (LISSM@C). Raman spectrum proves that the nanostructuresareα-Fe2O3andα-Fe2O3/reduced graphene oxide (rGO). The measurement of the contact angle indicates that the oil-waterseparation can be realized on the LISSM@C after the thermal treatment.
Chapter
This contribution describes different designs for the synthesis of nano-sized particles, using microwave plasma technologies. These technologies for synthesis may be classified according to different aspects: The plasma can be generated at low or higher gas pressure. As a consequence, the temperature of the plasma is high at higher gas pressure or low at lower gas pressure. A further criterion to distinguish plasma processes is the electrical charge of the particles. There are three possibilities: the particles carry either positive or negative charges or there is no preferred sign of the electrical charges. As a consequence, the product shows a narrow particle size distribution in the case of unipolar charged particles or a broad size distribution in the case that within the plasma particles carrying electrical charges with both signs are possible. A further consequence of the gas pressure of the plasma is the production quantity: In case of higher gas pressure, the production quantities are larger as compared to systems working under reduced pressure. The contribution describes the design for both types of systems for synthesis and shows examples of the products. Synthesis of the most advanced products, particles coated with a ceramic or a polymer layer, is described, too.
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Copper nanoparticles have been prepared by pulsed wire discharge (PWD) using copper wire in deionized water at various relative energy (K) from 0.8 to 5.5, which is ratio of the charged energy of capacitor in the electrical circuit to the vaporization energy of the wire. From the X-ray diffraction analysis of the prepared nanoparticles in deionized water at various K, the nanoparticles prepared at all conditions were identified as Cu and Cu2O. The Cu content in prepared nanoparticles was increased with the decrease in K, and changed from 77 to 95 [%]. Additionally, the deposited energy in the arc discharge after the wire heating was decreased with decreasing K. From these results, we considered that the Cu content was increased with decreasing the deposited energy in the arc discharge during particle formation.
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High-purity aluminum nitride nanopowder was synthesized using the RF induction thermal plasma technique. The nitrogen gas flow rate, plasma power and reactor pressure were controlled to increase the conversion rate of Al powder to AlN nanoparticles. The compositions of the obtained powders were investigated through XRD and EDS analysis. The synthesized aluminum nitride nanoparticles included polygonal and rod-shaped nanoparticles and ultra-fine particles below 10 nm. The particle sizes generally ranged from 20-60 nm in TEM analysis. The specific surface area, band structure and impurities of aluminum nitride nanoparticles were also evaluated by BET, FTIR and ICP-OES analysis.
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Nanosize cobalt boride particles were synthesized from the vapor phase using a 30 kW-4 MHz radio frequency (RF) thermal plasma. Cobalt and boron powder mixtures used as precursors in different composition and feed rate were evaporated immediately in the high temperature plasma and cobalt boride nanoparticles were produced through the quenching process. The X-ray diffractornetry (XRD) patterns of cobalt boride nanoparticles prepared from the feed powder ratio of 1:2 and 1:3 for Co:B showed peaks that are associated with the Co2B and COB crystal phases of cobalt boride. The XRD analysis revealed that increasing the powder feed rate results in a higher mass fraction and a larger crystalline diameter of cobalt boride nanoparticles. The images obtained by field emission scanning electron microscopy (FESEM) revealed that cobalt boride nanoparticles have a spherical morphology. The crystallite size of the particles estimated with XRD was found to be 18-22 nm.
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Atmospheric pressure plasmas (APPs) have achieved great scientific and technological advances for a wide range of applications. The synthesis and treatment of materials by APPs have always attracted great attention due to potential economic benefits if compared to low-pressure plasma processes. Nonetheless, APPs present very distinctive features that suggest atmospheric pressure operation could bring other benefits for emerging new technologies. In particular,materials synthesized by APPs which are suitable candidates for third generation photovoltaics are reviewed here.
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This paper presents a comparison of two very different options for removal of undesirable microorganisms and airborne pollutants from the indoor environment of hospitals, schools, homes and other enclosed spaces using air purifiers and photocatalytic coatings based on nano titanium dioxide (TiO2 ). Both products were assessed by Life Cycle Assessment (LCA) methodology from cradle to grave. The assessment also includes comparison of two different nano TiO2 production technologies, one by continuous hydrothermal synthesis and the other by a sulfate process. Results of the study showed a relatively large contribution of photocatalytic coatings to reducing the effects of selected indices in comparison with an air purifier regardless of which nano TiO2 production method is utilized. Although the impacts of the sulfate process are significantly lower compared to those of hydrothermal synthesis when viewed in terms of production alone, taken in the context of the entire product life cycle, the net difference becomes less significant. The study has been elaborated within the Sustainable Hydrothermal Manufacturing of Nanomaterials (SHYMAN) project, which aims to develop competitive and sustainable continuous nanoparticle (NP) production technology based on supercritical hydrothermal synthesis. This article is protected by copyright. All rights reserved.
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Aerosol Science and Technology: History and Reviews captures an exciting slice of history in the evolution of aerosol science. It presents in-depth biographies of four leading international aerosol researchers and highlights pivotal research institutions in New York, Minnesota, and Austria. One collection of chapters reflects on the legacy of the Pasadena smog experiment, while another presents a fascinating overview of military applications and nuclear aerosols. Finally, prominent researchers offer detailed reviews of aerosol measurement, processes, experiments, and technology that changed the face of aerosol science. This volume is the third in a series and is supported by the American Association for Aerosol Research (AAAR) History Working Group, whose goal is to produce archival books from its symposiums on the history of aerosol science to ensure a lasting record. It is based on papers presented at the Third Aerosol History Symposium on September 8 and 9, 2006, in St. Paul, Minnesota, USA.
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Nonmonotonous variation of the optical properties of iron nanoparticles with a temperature increase during heating behind reflected shock waves is discovered. Iron nanoparticles, within 12 nm in size, were formed at 0.5–1% Fe(CO)5 pyrolysis in argon behind the incident shock waves. Using a laser extinction method, a variation of the volume fraction of the condensed phase was registered at the main wavelength of 633 nm and, in several experiments, at the additional wavelengths of 405, 520, and 850 nm. At the second heating of the produced nanoparticles behind the reflected shock waves within the temperature range 800–1500 K, the function of the complex refractive index, E(m), decreased at all the wavelengths. Within the temperature range of 1500–2250 K, it increased with the temperature increase behind the reflected shock wave almost up to the values that we observed behind the incident shock wave. At the temperatures above 2250 K, due to the essential evaporation of the iron nanoparticle material, the optical properties were not measured. The iron nanoparticle E(m) variations within the temperature range 800–2250 K are possibly related to their structure variations.
Chapter
Smart polymers (SP) have been extensively developed for inventive and valuable resolutions in diverse applications such as in the electrical and biomedical fields. Numerous synthetic techniques that have been introduced to form unique smart polymers with desired properties (e.g., size, shape, and geometry) are discussed. Specific design of SP is a prerequisite for specific applications, which is a fundamental and significant factor to acquire structures with desired properties. In this chapter, a comprehensive review of the basic manufacturing and designing of smart polymers is discussed to provide elementary information about physical, chemical, and biological modes along with physiochemical processing for designing SP. This chapter also describes the advancement in technology for the synthesis of smart polymers in a systematic and efficient methodology to benefit mankind.
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The present study reveals the synthesis of metallic particles at atmospheric pressure using a radiofrequency low-temperature argon plasma jet. Copper bulk material of the powered electrode acted as solid precursor in the process and the metallic particles were obtained directly in gaseous environment. The particles were collected onto Si (100)-oriented substrates downstream of the atmospheric plasma jet and were ex situ characterized via optical microscopy, scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. We obtained copper particles, reddish brown in color, either of nano- or micro-metric sizes. Additionally, the plasma species and gas temperature were determined by OES. In conclusion, it was demonstrated that conversion of bulk metals into particles is possible at atmospheric pressure using a radiofrequency plasma jet and the development of several applications is recommended.
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Gallium nitride (GaN) based light-emitting nanoparticles were synthesized by microwave plasma chemical vapor synthesis under slightly reduced pressure condition. A novel 2.45 GHz microwave resonant cavity was developed that facilitated the ignition and stable operation. The cavity was designed with the aid of electromagnetic field simulations to match the microwaves in the transverse magnetic (TM) 010-like mode before plasma ignition and in a transverse electromagnetic (TEM)-like mode after plasma ignition. The produced nanoparticles were amorphous and emitted light at the same wavelength as bulk gallium nitride.
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Plasma synthesis has previously been shown to be a viable route to producing nanocrystalline magnetite and Ni ferrite nanoparticles. In this work nanocrystalline powders of Mn and Mn–Zn ferrites have been synthesized using a 50 kW–3 MHz rf (radio frequency) induction plasma torch. We investigate these materials for soft magnetic applications. High-energy ball milled Mn + Fe powders and (Mn+Zn) +Fe powders (<10 μm) in the stoichiometric ratio of 1:2 were used as precursors for the ferrite synthesis. Compressed air was used in the oxygen source for oxidation of metal species in the plasma. X-ray diffraction patterns for the plasma-torched Mn ferrite and MnZn ferrite powders were indexed to the spinel ferrite crystal structure. An average grain size of ∼20 nm was determined from Scherrer analysis confirmed by transmission electron microscopy studies. The particles also exhibited faceted polygonal growth forms with the associated truncated cuboctahedral shapes. Room-temperature vibrating sample magnetometer measurements of the hysteretic response revealed saturation magnetization Ms and coercivity Hc of Mn ferrite are 23.65 emu/g and 20 Oe, respectively. The Néel temperatures of Mn ferrite powders before and after annealing (500 °C, 30 min) were determined to be 200 and 360 °C, respectively. Inductively coupled plasma chemical analysis and energy dispersive x-ray analysis data on the plasma-torched powders indicated deviations in the Mn or Zn contents than the ideal stoichiometry. MnZn ferrite was observed to have a Néel temperature increased by almost 400 °C as compared with as-synthesized Mn ferrite but with a larger coercivity of ∼35 Oe. © 2003 American Institute of Physics.
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A combined hot filament/direct current (dc) plasma approach to chemical vapor deposition of carbon nanofibers (CNFs) using an acetylene/ammonia feedstock has been explored. As a part of the study, the impact of filament usage and substrate holder design has been examined by scanning electron microscopy imaging of deposition products and monitoring of downstream products by residual gas analysis (RGA). It is demonstrated that the filament wire is important primarily in the pretreatment of the substrate, improving CNF growth quality. However, the filament has a more minor impact when combined with the dc plasma, increasing growth rate but reducing growth quality. The substrate holder is modified by introducing a graphite spacer into the electrode. By varying the size of the spacer, the effective surface area of the cathode is modified, allowing control over the power input to the reactor while holding the voltage constant. This allows for some independent control of physicochemical processes that are typically inseparable in plasma processing, including gas phase chemistry, substrate heating and etching by ion bombardment, and growth alignment effects due to the electric field. This work demonstrates how separating these processes allows for better control over the desired growth product. © 2003 American Institute of Physics.
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Ceramic particles with sizes below 10 nm consisting of two different oxides in the core and the coating have been prepared by using a two-step microwave plasma process. Precursors for the synthesis are the chlorides. The structures occurring in such particles are demonstrated in the system alumina (Al2O3)-zirconia (ZrO2). When the alumina kernels covered with zirconia are small, or alternatively when the alumina coating on the zirconia kernels are thin, no special structural features are observed. In this case, the alumina is glassy and the zirconia is crystallized. In contrast, particles consisting of a crystallized zirconia core and a crystallized γ-alumina coating exhibit structural defects similar to dislocations that adjust to the different structures. These could be sessile dislocations in the {211} plane of the γ-alumina. Additionally, maghemite (γ-Fe2O3) particles coated with cubic zirconia were studied. The coating of this material is free of dislocations.
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The microwave plasma process inherently produces nanoparticulate powders with very narrow particle size distribution. During synthesis, the particles carry electric charges of equal sign. Therefore, by electrostatic repulsion, particle growth is reduced and agglomeration thwarted. This is shown by gas kinetic considerations and experimental results. Furthermore, this process allows coating of the particles with organic or inorganic phases, reducing interaction of different particles. This makes it possible to technically exploit properties, characteristic for isolated particles. Additionally, the coating process allows the combination of different properties such as superparamagnetism and luminescence, as it is demonstrated in different examples.
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Microwave plasma decomposition of metal carbonyls has been used to synthesize a series of carbon-supported monometallic (Fe, Co) and bimetallic (Co-Mo) materials. The average metal particle diameters in all cases were less than 10 nm. By using 10% H2/Ar instead of pure Ar as a carrier gas, the mean particle diameters could be decreased to less than 2 nm. Although the distribution of particles is slightly broader than those generated by other nanoparticle synthesis methods, the mean diameter of the particles generated using 10% H2/Ar is as small as any previously reported for Fe-, Co-, Ni-, or Mo-containing compounds. The ultrafine metal particles were dispersed on moderate surface area amorphous carbon support matrixes derived from the concomitant microwave decomposition of the toluene solvent.
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Increasing research efforts are being made towards studying reactions in the gas phase for synthesizing carbide and nitride-base sinter powders. With the aid of these processes it is possible to directly produce optimum powders of high purity in the submicron range. Plasma reactors are used for these purposes because such reactions require high temperatures. Plasma properties, plasma installations and the properties of the sinter powder thus produced compared with powders synthesized by other processes are dealt with in this paper.
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The use of nonconventional powder preparation techniques such as vapor-phase routes are receiving increased research attention as a result of the potential technical benefits associated with these processing routes. Current research at the UNM/NSF Center for Micro-Engineered Ceramics is concentrating on ceramic particle generation in glow discharges and by aerosol decomposition. These processes together allow generation of multicomponent oxide and non-oxide ceramics with a variety of chemical compositions and morphologies. A brief description of these processes is presented. Examples of ceramic powder synthesis, advantages and disadvantages for powder generation, and future research opportunities for these processes are discussed.
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Ultrafine ZnO nanopowders were successfully synthesized by the dc thermal plasma process with a high production rate of 1.2 kg/h. The combination of plasma was found to affect the nanoparticles morphology. Both X-ray diffraction and Raman spectrum analysis confirmed a high quality wurtzite structure of the ZnO nanopowders. Photoluminescence study exhibited strong ultraviolet emission corresponding to the near band edge emission in the ZnO nanopowders. Random laser action observed in the ZnO nanostructures by optical pumping demonstrated high optical and crystal quality of the ZnO nanopowders fabricated by the dc thermal plasma synthesis.
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Nanosized zinc ferrite spinel powders of various compositions were produced in a radiofrequency (RF) thermal plasma from oxide mixtures and from co-precipitated hydroxides. Bulk and surface chemical compositions of the products were measured by ICP-AES and XPS. Phase conditions were determined by XRD. Morphology was investigated by SEM and TEM. In spite of the short residence time of reagents in the plasma reactor, a high degree of spinel formation was achieved. The Zn enrichment on the surface determined by quantitative XPS is attributed to a thin ZnO layer on the surface of the zinc ferrite particles. In zinc ferrous ferrites, an inhomogeneous distribution of Zn inside the grains may also exist.
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Nanocrystalline aluminum nitride powders were synthesized by introducing high velocity and high temperature aluminum plasma vapor discharge into the nitrogen and ammonia gas mixture. By employing high-current pulse power, aluminum electrodes were explosively vaporized and ionized in a capillary plasma device to generate the metal plasma vapor. The effect of ammonia addition on the AlN content and average particle size in reacting gas has been studied by various techniques of material characterization such as XRD, XPS, and TEM. At the nitrogen/ammonia volume ratio of 50:50, synthesized nanopowders was found to be free of aluminum metal and the content is pure AlN nanopowders in the form of hexagonal phase. The smallest average particle size of 8nm and highest content of AlN was achieved at 100% ammonia composition.
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The electron impact charging properties of submicron (∼ 0.04–0.25 μm diameter) particles of inorganic salts, and metal and semiconductor oxides were investigated using a particle beam apparatus. The results indicate that the particle saturation charge is approximately a linear function of diameter, and is relatively insensitive to particle shape and chemical composition. A linear least-squares fit to all our data on inorganic and organic particles (14 different compounds) provides a simple equation that can be used to calculate saturation charge to within ∼ 15% for these broad classes of materials. This result is important for the application of a new particle beam mass spectrometric technique we have developed for sizing submicron particles sampled from low-pressure environments. The saturation charging curves can be explained by using the results of a series of measurements on KCl particles to extend a charging model developed earlier for organic particles.
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This paper describes a novel process using a microwave plasma as a source of energy to synthesize ceramic oxide powders with mean particle size in the range of 5 to 30 nm. The process works without solvents by evaporation of chlorides of the elements used in ceramics. The process was demonstrated by the synthesis of alumina-, titania- and zirconia-based ceramic powders. Air or one of the noble gases mixed with any amount of oxygen and water was used as process gas. Electron microscopy revealed that through proper selection of synthesis conditions, it is possible to obtain nanocrystalline powders. Due to the extreme conditions during synthesis it is possible to prepare non-equilibrium phases or solid solutions in systems exhibiting no equilibrium solubility.
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This work describes the use of microwave plasma synthesis technique to prepare cobalt nanopowders. The effects of flow rate of plasma gas and carrier gas to the average particle size were studied. Modification of the microwave plasma unit can be used to produce Co nanopowders with SiC coating. The Co and SiC-coated Co nanopowders were characterized by means of transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and X-ray diffraction (XRD).
Article
Silver nanopowder was synthesized by the microwave plasma synthesis method. The effect of feeding rate of precursor raw material to the average particle size and crystallinity were studied. The microwave plasma unit can be modified to prepare silver nanopowder with polymeric coating. The silver nanopowder was characterized by means of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDAX) and X-ray diffraction (XRD).
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Gas phase plasma synthesis methods have been used to prepare nano-scale particles of C doped boron powder that are well suited for powder-in-tube (PIT) fabrication of superconducting wire. Mixtures of H2, BCl3, and CH4 gas are injected into an induction plasma where doped boron powder is formed and collected on a stainless steel screen. The particles typically are ∼20nm in size and collect into lacy agglomerates in the 1–50μm size range. Pressed pellets of these powders heated in a Mg atmosphere are transformed to the MgB2 phase at temperatures ranging from 600°C to 1200°C. Critical current densities, Jc, at 5K run from about 106A/cm2 at self-field to 4×104A/cm2 at 7T. At 20K, Jc ranges from 5×105A/cm2 at self-field to about 104A/cm2 at 3T. Samples of pure B powder and B with 7.4%C powder were prepared as PIT wires having a combination Fe inner jacket and a cupro-nickel outer jacket. These PIT Jc values are lower than, but comparable to the pressed pellet values. The PIT samples can be reacted in times on the order of 10min and still exhibit greater than 105A/cm2 at 5K and 2T.
Article
A Nd:YAG pulsed laser was used to ablate a 0.5-mm-diameter iron wire in a sealed chamber in a mixed gas flux of N2 and O2 to generate pure γ-Fe2O3 nanoparticles at atmospheric pressure. Structural characteristics and sizes of the prepared nanoparticles were determined by X-ray diffraction and TEM. The effects of laser power density, total mixed gas pressure and the oxygen ratio on the mean particle size were investigated, respectively. The results showed that the mean particle size decreased with the increase of the laser power density, total gas pressure and the oxygen ratio, respectively. Besides, the nanoparticle formation mechanism by laser ablation of iron wires was also discussed.
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Doped cerium oxide (CeO2) based electrolytes are attractive alternative materials to replace the existing yttria-stabilized zirconia (YSZ) used as electrolyte for SOFC (solid oxide fuel cells). Cerium oxide electrolytes offer a similar performance to YSZ electrolytes at a lower cell operating temperature (~600--800 °C), therefore reducing thermal stresses and solid state reactions among the cell components.Doped Ce1-xMexO2-x/2(Me = Gd, Sm or Y) fine \hbox{powders} were synthesized from nitrate salts dissolved in water using a radio frequency inductively coupled plasma reactor. It was demonstrated that the relative concentrations of Ce and dopants fed in the solutions were retained in the synthesized powders. The products were all nano-crystalline with the basic crystal structure of CeO2 and the crystal size of the products was essentially independent of the dopant used. The particle size distributions obtained were multimodal and in most cases trimodal. The results obtained differ from a previously reported mechanism of particle synthesis from liquid precursors.
Article
Nanoparticles of nickel have been prepared by laser-driven decomposition of nickel carbonyl. In this method, an infrared laser rapidly heats a dilute mixture of nickel carbonyl and a photosensitizer in a carrier gas to decompose the precursor and initiate particle nucleation. To produce nickel nanoparticles, nickel carbonyl was generated in situ from activated nickel powder and CO at room temperature, so that we never maintained any inventory of this highly toxic compound. During the synthesis process, laser heating allows for rapid cooling of the freshly nucleated particles by mixing with unheated gas. By varying the precursor flow rate, laser energy, and unheated gas flow rate to change the residence time, precursor concentration, and reaction temperature, the average particle size can be controlled over a range of primary particle diameters from 5 to 50 nm. The particle size and crystalline structure have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen physisorption surface area measurement (the BET method), and X-ray photoelectron spectroscopy (XPS). Results of magnetization measurements for small superparamagnetic nickel nanoparticles (about 8-nm diameter) are also presented.
Article
A plasma synthesis method has been devised to produce nanosize YSZ powders with various yttria contents. The powders are synthesized by introducing a mixture of coarse-grained zirconia and yttria into an r.f. inductively coupled plasma flame. The average particle size of the as-prepared powders is in the range 20–40 nm and the specific surface area is 18–50 m2g–1. The phase and granulometric composition of the produced powders depend on the degree of evaporation of raw powders, reagent concentration in the gas flow and quenching rate, and on the content of Y2O3. Up to 5.5 mol% yttria, the major phase of nanosize powders is tetragonal ZrO2, mostly as the non-transformable (t) form. For yttria contents higher than 6 mol%, the major phase is cubic ZrO2.
Article
The single phase powders of NbN, NbN1-yCy, Nb1-xTixN1-yCy with a mean particle size of 10–70nm were prepared in the nitrogen plasma flow of a microwave discharge at a hydrogen reduction of NbF5 only, or in a mixture with C5H12, or with the addition of TiCl4. It was established that the critical magnetic field of ultra-fine niobium–titanium carbonitride powders is about three times higher as compared with bulk samples of the same composition. The critical magnetic field ran up to 55T for ultra-fine powders with the optimal composition Nb0.8Ti0.2N0.8C0.2. This material may be interesting for the technical superconductivity in the helium temperature range.
Article
The effect of ambient Ar pressure on the mean diameters and aggregate state of cobalt (II,III) oxide nanoparticles prepared by pulsed-laser ablation is investigated. TEM images show that the mean diameters of the primary nanoparticles are in the range 1.2–3.2nm when the ambient pressure is varied from 13.3Pa to 13.3kPa. With the increase of Ar pressure, the mean diameters of the primary nanoparticles increase and show a maximum at a pressure of 100Pa. A further increase of ambient pressure results in a decrease in mean diameter of the primary nanoparticles. In the pressure range from 267Pa to 2.67kPa, the mean diameters of the prepared nanoparticles are almost constant, and aggregated nanoparticles are observed. Above 2.67kPa, aggregated Co3O4 particles dominate the ablated product and the mean diameter of the primary nanoparticles decreases with increasing ambient pressure. A dynamic process is suggested to explain the experimental results.
Article
FePt nanoparticle is expected as a candidate for the magnetic material of the high density recording media. We attempted to synthesize FePt alloy nanoparticles using 13.56MHz glow discharge plasma with the pulse operation of a square-wave on/off cycle of plasma discharge to control the size of nanoparticles. Vapors of metal organics, Biscyclopentadienyl iron (ferrocene) for Fe and (Methylcyclopentadienyl) trimethyl platinum for Pt, were introduced into the capacitively coupled flow-through plasma chamber, which consisted of shower head RF electrode and grounded mesh electrode. Synthesis experiments were conducted at room temperature under the conditions of pressure 0.27Pa, source gas concentration 0.005Pa, gas residence time 0.5s and plasma powers 60watts. Pulse width for plasma duration was chosen from 0.5 to 30s and plasma off period was 4s to each pulse operation. Visual observations during the particle growth showed plasma emission in the bulk region was increased with the particle growth. These were theoretically explained by using the model for both transient particle charging in the plasma and single particle behavior in the stationary plasma as well as assuming the similarity between the negative charged particle and negative gas containing plasma. Synthesized nanoparticles were directly collected onto TEM grid, which was placed just below the grounded mesh electrode in the plasma reactor downstream. TEM pictures showed two kinds of particles in size, one of which was nanometer size and isolated with crystal structures and the other appeared agglomerate of nanometer size particles. The size of agglomerated particle was controlled in the 10–120nm range by varying the plasma-on time from 0.5 to 30s, although the nanometer size particles did not change. The composition of FePt alloy particles could be altered by adjusting the source gas feed ratio. Also magnetization of FePt nanoparticles was measured by use of SQUID (superconducting quantum interference device) magnetometry measurements. As-synthesized FePt nanoparticles did not exhibit loop-shape characteristic, which indicated superpamagnetic property. Annealed nanoparticles with the composition of Fe58Pt42 at 650°C in atmospheric hydrogen showed clear hysterisis loop with the coercivity as large as 10KOe.
Article
The existence of fullerenes (as allotropes of carbon) was established in the mid-1980s and during the last 15–18 years, systematic efforts have been devoted to improve the methods of their synthesis, including plasma-based system methods. The work presented here is focused on the investigation of fullerenes synthesis, using a radio frequency plasma reactor. The main objectives were to explore the use of induction plasma technology for the synthesis in-continuo of carbon fullerenes and to predict their formation conditions through conduct of theoretical studies. Thus, a thermodynamic study was carried out to predict the equilibrium composition of fullerenes produced at several combinations of operating conditions. Additionally, a statistical factorial design experiment, employing four factors at two levels, was also developed, in order to study the influence of the system’s operating parameters on the eventual C60 fullerene yield. The results obtained showed that the reactor pressure, the electrical power and the raw material feed rates all have an important effect on the synthesis of fullerenes. The highest C60 concentration in the products was found to be about 7.7 wt.%. Various other carbon nanostructures, such as nanotubes and nano-onions, were also successfully produced.
Article
Different iron oxide-based nanosized powders were obtained by the IR laser synthesis from gas phase reactants by using iron pentacarbonyl vapor as iron donor. In the flowing gas mixture, oxidizers (like nitrous oxide and air) and sensitizers (like sulfur hexafluoride and ethylene) have been used. A major amount of γ-Fe2O3 was obtained after a series of experiments in which α-Fe2O3 and iron fluorides were the dominant phases. The mean size of the obtained γ-iron oxide particles was in the range 3–7 nm. The structural characterization of the new elaborated materials points out to the crucial influence that the experimental parameters (particularly the combined choice of the oxidizer/sensitizer agents) have on the specific oxide phase formation as well as on its purity.
Article
A microwave plasma processing technique was used to synthesize iron nanopowders. The average particle size of these powders was ~10 nm and the surface area was measured to be 42m2/g. Powder production rates as high as 50 gm/hour were achieved. Magnetic property measurements on iron nanopowders yielded coercivities as high as 60 kA/m at 4 K, which decreased to ~0 A/m (a superparamagnetic transition) at room temperature. In this paper, the microwave plasma processing technique has been compared with other nanopowder synthesis techniques. Since the successful application of nanomaterials depends highly on the processing technology, results from consolidation studies on iron nanopowders are also presented. Iron nanopowders were consolidated to study performance parameters such as density, grain growth and other morphological changes. The nanopowder was consolidated using Plasma Pressure Consolidation (P2C) technique to 95% density, at a temperature and pressure of 850 °C and 63 MPa respectively. Microwave plasma synthesis is capable of producing metallic and ceramic nanopowders, which will sustain interest in research areas including magnetic storage, nano-fabrication of electronic materials and nanoglass, besides the field of catalysis.
Article
Spherical titanium suboxide nanoparticles (Ti5O9, Ti9O17, TiO) are synthesized by arc plasma. A mixture of Ar, H2 and H2O at 10 mbar pressure is used as the working gas. The variations of the proportion of H2O in the mixture gas during the synthesis induce a clear change in the size, color, composition, and optical properties of these nanoparticles. A reduction of H2O partial pressure reduces the grain size of the product. The titanium suboxide nanoparticles (Ti5O9, Ti9O17) show a blue luster. The UV–Vis–NIR absorption spectra present a substantial absorption in the range 400–800 nm. In particular, there is a uniform and stable absorption from 800 to 3000 nm. FT-IR spectra reveal the H2O partial pressure significantly affects the –OH groups content on the surface or in the bulk of the nanoparticles.
Article
The paper presents a magnetic and morphological characterization of iron- and iron-carbide-based nanopowder obtained by the laser synthesis from a sensitized gas phase mixture containing acetylene and iron pentacarbonyl vapor. The analysis was performed on the as-prepared material and the annealed material. We report here the results of TEM, XRD, Mossbauer and magnetic measurements. Phase transformations taking place during annealing when core-shell-like nanostructures appear are discussed. (C) 2004 Published by Elsevier B.V.
Article
A laboratory unit based on an inductively coupled plasma has been developed for the synthesis of ceramic powders. The design of the torch, the reaction chamber and the powder separation system will be described. The operational parameters of the unit and the characteristics of silicon nitride powders prepared from silane and ammonia will be discussed.
Article
Conventional plasma spraying was used to process atomized liquid droplets of precursor solutions to produce alumina, zirconia and yttria stabilized zirconia nanoparticles and deposits. An electrostatic precipitator collected the plasma synthesized ceramic particles at a rate of ~0.2 mg s−1, with ~5–20% collection efficiency. Spray processing produced 1–50 nm size ceramic particles. The size, shape and phase composition of the nanomaterials depend on the spray feedstock. Organo-metallic precursors gave rise to a narrow range of fine-grained material, while aqueous solutions produced wider distributions of larger size grains. Spray processing of liquid feedstock produced nanodeposits with a powdery morphology. Plasma spraying of liquid precursors is a viable technique to produce nanoparticles and deposits.
Article
Flame aerosol technology is used for large-scale manufacture of ceramic commodities such as pigmentary titania, fumed silica and alumina. In addition, the introduction of this technology to the manufacture of optical fibers and its potential for cheap synthesis of ultrafine particles (e.g. nanoparticles) has renewed the research interest for better understanding of flame aerosol reactors. Here, after an overview of the history of this technology, the current state of knowledge on the role of flame process variables (additives, mixing etc.) on the characteristics of product powders is summarized in a tutorial fashion. The fundamentals of particle formation and growth are highlighted by summarizing the dynamics of spherical particles that are reasonably well understood. The latest advances on the theory of aggregate particle dynamics that are typically encountered in flame synthesis of powders are presented. Specific applications in the manufacture of fumed silica, pigmentary titania, alumina, and other oxide and non-oxide ceramic powders are reviewed. Finally, research needs are highlighted by pointing out the most promising areas for advancing the field with emphasis on instrumentation and need for detailed simulators of the process accounting for the concurrent chemistry, transport and aggregate particle dynamics. With major recent advances in diagnostics and understanding in both combustion and aerosol science and engineering, this field is ready for a new leap forward.
Article
The paper presents a thermodynamic analysis for predicting the conditions for the plasma synthesis of TiC powders. The paper also investigates the effects of feeding rate and molar ratio. The experimental results show that TiC powders are synthesized by thermal plasma and the average size of the TiC powders is less than 100 nm.
Article
Breakdown electric field strengths have been measured in four S-band cavities filled with high purity SF6 at room temperature in the approximate pressure range from 0.01 to 200 Torr. Measurements were made for submicrosecond effective pulse widths under essentially `single pulse' conditions, and also under conditions equivalent to continuous wave breakdown. The results are used to calculate an average elastic collision frequency of vc = 1.0 × 1010p sec-1.
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