共查询到20条相似文献,搜索用时 15 毫秒
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Zhun Liu Seong Chan Kim Jing Wang Weon Gyu Shin Heinz Fissan David Y. H. Pui 《Aerosol science and technology》2013,47(3):333-346
Nanoparticle agglomerates play an essential role in the manufacturing of many nanomaterials and are commonly found in combustion products. Conventional aerosol instruments based on equivalent spheres are not directly applicable to the measurement of nanoparticle agglomerates. The increasing interest in real-time assessment of the structure of engineered nanoparticle agglomerates and the mass concentration of potentially hazardous agglomerates (e.g., diesel soot, welding fume) makes an instrument devoted to online structure and mass measurements for nanoparticle agglomerates highly desirable. A recently developed instrument, universal nanoparticle analyzer (UNPA), utilizes the close relation between agglomerate structure and unipolar charging properties and infers agglomerate structure from measurement of the average charge per agglomerate. It was used in this study to characterize in situ the structure of metal nanoparticle agglomerates generated by spark discharge, to study the effects of sintering on the structure of these agglomerates, and to make real-time assessment of their airborne mass concentration. The primary particles sizes measured by UNPA for the gold (Au), silver (Ag), and nickel (Ni) agglomerates are in reasonable agreement with the TEM (transmission electron microscopy) sizing results, d p = 7.9 ± 1.5, 11.8 ± 3.2, and 6.6 ± 1.0 nm, respectively. In addition, findings from the study of agglomerate structural change during sintering using the UNPA sensitivity coincide with results from TEM and mobility analyses. With regard to the mass concentration of silver agglomerates at room temperature, good agreement was found under our experimental conditions between results given by UNPA, the effective density, and the gravimetric measurement. Copyright 2012 American Association for Aerosol Research 相似文献
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Alberto Clemente Francisco Balas M. Pilar Lobera Silvia Irusta Jesus Santamaria 《Aerosol science and technology》2013,47(8):867-874
A long-lasting generator of continuous silica nanoparticle aerosols based in a fluidized bed of glass beads coated with nanosized silica has been developed. The attrition resulting from the bubbling fluidized bed regime progressively detaches the silica coating from the glass beads, giving rise to a steady production of silica nanosized aerosols with median diameters from 100 to 250 nm depending on the initial size of the coating nanoparticles. Continuous aerosol production could be maintained for more than 12 h, and the nanoparticle concentration can be easily tuned in the range of 2000 to 14,000 #/cm3 by adjusting the fluidization and/or dilution flow rates. Copyright 2013 American Association for Aerosol Research 相似文献
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Sukbyung Chae Dongjoon Lee Min-Cheol Kim Dae Seong Kim 《Aerosol science and technology》2013,47(7):463-471
The electrode configuration in a spark discharge generator plays a critical role in the characteristics of the process. For instance, the rod-to-rod configuration is unable to prevent nanoparticles from agglomerating due to slow local carrier gas velocity. On the other hand, the recently developed pin-to-plate configuration is able to produce unagglomerated nanoparticles; however, the geometric mean diameter and the number concentration of produced nanoparticles change over time as the pin gets eroded. In this work, we present a novel wire-in-hole-type spark discharge generator (WH-SDG) which is able to generate unagglomerated nanoparticles with a constant size distribution over a long time. The WH-SDG, which consists of a metal wire and a grounded plate with a hole in which the metal wire is located in the center, effectively suppressed changes in the electrode morphology and the gap distance, which cause the minimal variation of the spark discharge voltage and frequency in time. Therefore, the WH-SDG was able to maintain a constant size distribution of the generated nanoparticles for 12 h. In addition, it was found that the WH-SDG could control the diameter of nanoparticles by regulating the gas flow rate into generator, and could produce nanoparticles from various metals such as copper and palladium.Copyright 2015 American Association for Aerosol Research 相似文献
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Adelina-Gabriela Niculescu Dan Eduard Mihaiescu Alexandru Mihai Grumezescu 《International journal of molecular sciences》2022,23(15)
Microfluidics is defined as emerging science and technology based on precisely manipulating fluids through miniaturized devices with micro-scale channels and chambers. Such microfluidic systems can be used for numerous applications, including reactions, separations, or detection of various compounds. Therefore, due to their potential as microreactors, a particular research focus was noted in exploring various microchannel configurations for on-chip chemical syntheses of materials with tailored properties. Given the significant number of studies in the field, this paper aims to review the recently developed microfluidic devices based on their geometry particularities, starting from a brief presentation of nanoparticle synthesis and mixing within microchannels, further moving to a more detailed discussion of different chip configurations with potential use in nanomaterial fabrication. 相似文献
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This paper deals with high frequency modeling of silent discharge ozone generators (OGs). The electrical characteristics of two simple silent discharge OGs operated at low and high frequency are analyzed and compared. An equivalent electric model is proposed for the operation of the OG at high frequency. This model can be used to optimize the electronic power converter used to supply silent discharge OGs at high frequency. Experimental results measured in the laboratory for two particular OGs are presented to validate the proposed model. 相似文献
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A. Maisser K. Barmpounis M. B. Attoui G. Biskos A. Schmidt-Ott 《Aerosol science and technology》2013,47(10):886-894
A new method for generating metal clusters in the gas phase is described and characterized in this work. The method is based on material evaporation by spark ablation at atmospheric pressure. The characterization of atomic clusters was done by measuring their electrical mobility. The measured mobilities were compared with values found in literature in order to identify the cluster species. We show that silver clusters consisting from one up to 25 atoms can be produced in helium at atmospheric pressure. In addition, the effect of oxygen concentration on the resulting cluster mobility distribution was investigated. Results show that at higher oxygen level, the mobility distribution is dominated by the abundance of stable clusters (i.e., magic number clusters). This can be attributed to an oxidation etching effect.Copyright 2015 American Association for Aerosol Research 相似文献
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Jae Hong Park Imali A. Mudunkotuwa Jong Sung Kim Aditya Stanam Peter S. Thorne Vicki H. Grassian 《Aerosol science and technology》2014,48(7):768-776
This study introduces a spark discharge system (SDS) as a way to simulate welding fumes. The SDS was developed using welding rods as electrodes with an optional coagulation chamber. The size, morphology, composition, and concentration of the fume produced and the concentration of ozone (O3) and nitrogen oxides (NOX) were characterized. The number median diameter (NMD) and total number concentration (TNC) of fresh fume particles were ranged 10–23 nm and 3.1×107 ? 6×107 particles/cm3, respectively. For fresh fume particles, the total mass concentration (TMC) measured gravimetrically ranged 85–760 μg/m3. The size distribution was stable over a period of 12 h. The NMD and TNC of aged fume particles were ranged 81–154 nm and 1.5×106?2.7×106 particles/cm3, respectively. The composition of the aged fume particles was dominated by Fe and O with an estimated stoichiometry between that of Fe2O3 and Fe3O4. Concentrations of O3 and NOX were ranged 0.07–2.2 ppm and 1–20 ppm, respectively. These results indicate that the SDS is capable of producing stable fumes over a long-period that are similar to actual welding fumes. This system may be useful in toxicological studies and evaluation of instrumentation.
Copyright 2014 American Association for Aerosol Research 相似文献
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William J. Scharmach Raymond D. Buchner Vasilis Papavassiliou Perry Pacouloute Mark T. Swihart 《Aerosol science and technology》2013,47(12):1083-1088
We present a new flame-based aerosol reactor configuration that combines thermal decomposition and hydrogen reduction to produce metal nanoparticles. This approach uses a fuel-rich hydrogen flame as a source of low-cost energy to initiate particle synthesis, but separates the flame chemistry from the particle formation chemistry. Hot combustion products pass through a nozzle to produce a high-temperature reducing jet. A liquid precursor solution is rapidly atomized, evaporated, and decomposed by the expanding jet, initiating particle formation. In particular, here we have produced carbon-coated copper nanoparticles from an aqueous copper formate precursor solution and characterized them by aerosol mobility distribution measurements, electron microscopy, and x-ray diffraction. Copper serves here as a prototype for non-oxide materials that are generally difficult to produce in flame-based reactors. This work demonstrates that such materials can be produced in substantial quantities with particle diameters below 50 nm in this new process. 相似文献
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Enhanced excipient growth (EEG) is a newly proposed respiratory delivery strategy in which submicrometer or nanometer particles composed of a drug and hygroscopic excipient are delivered to the airways in order to minimize extrathoracic depositional losses and maximize lung retention. The objective of this study was to develop a validated mathematical model of aerosol size increase for hygroscopic excipients and combination excipient–drug particles and to apply this model to characterize growth under typical respiratory conditions. Compared with in vitro experiments, the droplet growth model accurately predicted the size increase of single component and combination drug and excipient particles. For typical respiratory drug delivery conditions, the model showed that the droplet size increase could be effectively correlated with the product of a newly defined hygroscopic parameter and initial volume fractions of the drug and excipient in the particle. A series of growth correlations was then developed that successively included the effects of initial drug and excipient mass loadings, initial aerosol size, and aerosol number concentrations. Considering EEG delivery, large diameter growth ratios (2.1–4.6) were observed for a range of hygroscopic excipients combined with both hygroscopic and nonhygroscopic drugs. These diameter growth ratios were achieved at excipient mass loadings of 50% and below and at realistic aerosol number concentrations. The developed correlations were then used for specifying the appropriate initial mass loadings of engineered insulin nanoparticles in order to achieve a predetermined size increase while maximizing drug payload and minimizing the amount of hygroscopic excipient. 相似文献
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A relatively simple laboratory technique for the simultaneous production of two monodisperse aerosols of different size has been developed and tested. This technique utilizes a standard May spinning-top aerosol generator that has been modified and enclosed under a special dual-cone fractionator. The fractionator efficiently separates the primary and satellite droplets. Illustrative Nacl aerosol generation data, obtained in a series of experiments, show that satellite droplets can provide an important source of the monodisperse aerosol. 相似文献
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In this article, polymer microspheres and silica nanoparticles have been discussed as important filler in polymer composites. Their synthesis methods, properties, and application were particularly stressed. Silica is usually used as nucleating agent, surface enhancement mediator, and as templates and cores. Among polymer/silica composites, various categories including polyaniline, polypyrrole, polystyrene, epoxy, rubber, and acrylate polymer were discussed in detail. It was observed that silica nanoparticles enhanced mechanical strength and overall performance of composites. Furthermore, composites having carbon nanotube along with silica particles possess high electrical and mechanical performance. These composites are important in nanoelectronic devices, nanomedicines, and defense-related applications. 相似文献
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总结了氮肥生产污水处理工程的建设及该工程对造气、脱硫、稀氨水、废油水等工业污水进行综合处理的情况。工程实施后,氮肥生产实现了污水零排放治理目标。 相似文献
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分析了芳烃装置的主要耗能设备加热炉在装置能耗中所处的地位,全面地探讨了芳烃装置加热炉节能减排的8种途径和实施对策,保证芳烃加热炉的高效运行,对芳烃装置的节能减排意义重大。 相似文献