Flow properties of fine powders in powder coating

Three types of nanoparticles and their combinations were blended into a fine powder,which has been used in the powder coating industry.To study their effects on flow properties,the modified powder samples were characterized using a variety of techniques that tested the powder under different powder states ranging from dynamic to static.It was found that all three nanoparticles improved the flow properties of the powder to some degree,though the amounts of the nanoparticles needed were different depending on...     

等离子体技术几个方面的研究进展

等离子体技术是近20年间发展起来的。它可以在很大的温度和压力范围内为不同的用途提供纯净热源气体或高温、低温反应工质,因而从一开始就引起科学家和工程师们对它的关心和兴趣。对它的研究进展很迅速,仅从1985年7月在荷兰召开的第7届国际等离子体化学会议(ISPC-7)来看,到会科学家587人,提出论文263篇,内容极其广泛,显示     

Biotransformation,multifunctional recycling mechanism of nanostructures,and evaluation of the safety of nanoscale materials

Current evidence of concept analyses recommending nanotechnology for biomedical uses abounds in recent research. The area of biotechnology interfaces with nanostructures, reconfigures their composition, and alters their characteristics; which influences the dispersion of the particles, the biotransformation they cause, and their potential toxic effect. It is vital to link the idea of the lifecycle of nanostructures to the biological impacts and use methodologies to identify, estimate, and track the gradual bioprocessing of nanostructures in vivo, from a body-wide level to a nanoscopic size. This is necessary because understanding how nanostructures processing, degradation, persistence, and recycling predict potential exposure risks. The safe implementation of nanotechnology-based products in biomedical applications necessitates an extensive understanding of the recycling and transformations of nanomaterials in a living organism. Long-term fate in the body is crucial, as it governs potential environmental risks to human health. Strategies may be used to manage the long-term outcome of nanostructures in an organism since, in addition to composition, their design also affects how long they last and how easily they degrade. The lifespan of nanoparticles, a flexible and biocompatible category of nanostructures that have made it into clinical trials, is the subject of this article. Strategies may be used to manage the long-term outcome of nanoparticles in an organism since, in addition to composition, their design also affects how long they last and how easily they degrade. This review explained the safety of nanoscale materials, biotransformation, and the multifunctional recycling mechanism of nanostructures.     

NANOPARTICLE AEROSOL SCIENCE AND TECHNOLOGY： AN OVERVIEW

As a new scientific discipline, nanoparticle aerosol science and technology （NAST） deals with the formation, properties and behavior of nanoparticles in gases. Driven by its practical applications in many different fields, NAST has been undergoing rapid development. A conceptual framework of the discipline, with its own basic principles, experimental methods and computational techniques, is now taking shape. This paper presents an overview of the current status and research needs of the new discipline. The presentation begins with a discourse on the relationship among various particle systems, which occur frequently in nature and industry. The properties and behavior of nanoparticle aerosols are then discussed, with emphasis on the key roles played by particle size and morphology. Similar to fluid dynamics, NAST is an enabling discipline in the sense that it has provided the concepts and methodology needed for the development of many other fields. Applications of nanoparticle aerosol science and technology are highlighted in three important areas： （1） aerosol processes for synthesis of nanoparticles, （2） atmospheric nanoparticles and global climate, and （3） dosimetry of inhaled nanoparticles. These fields have features in common insofar as nanoparticie aerosols follow the same basic laws of physics and chemistry.     

Characterization of gold]PMMA hybrid nanomaterials synthesized by hard X-ray synchrotron radiation

In this study, new types of hybrid gold poly（methyl methacrylate） （PMMA） nanomaterials are synthesized. Both PMMA spheres coated with gold nanoparticles and gold nanoparticles coated with PMMA can be synthesized using different ratios of HAuCl4 and MMA precursors, by exposing the mixtures to hard X-ray synchrotron radiation without the use of a reducing agent. According to the photochemical mechanism, gold nanoparticles will precipitate from a solution of HAuCl4 on exposure to synchrotron radiation, followed by the synthesis of PMMA by the polymerization of MMA monomers. These reactions can result in the formation of two different types of new hybrid nanomaterials. When a 1：1 volume ratio of HAuCI4 to MMA is used, we obtain PMMA spheres coated with gold nanoparticles. When a 10：1 ratio of HAuCl4 and MMA is used, we obtain gold nanoparticles coated with PMMA. The hybrid gold/PMMA nanostructures are characterized by transmission electron microscopy, elemental analysis, dynamic-light scattering analysis, gel permeation chromatography and Raman spectroscopy. The hybrid nanomaterials have potential application in the fields of biosensors and drug delivery.     

Characterization of gold/PMMA hybrid nanomaterials synthesized by hard X-ray synchrotron radiation

In this study,new types of hybrid gold poly(methyl methacrylate) (PMMA) nanomaterials are synthesized.Both PMMA spheres coated with gold nanoparticles and gold nanoparticles coated with PMMA can be synthesized using different ratios of HAuCl4 and MMA precursors,by exposing the mixtures to hard X-ray synchrotron radiation without the use of a reducing agent.According to the photochemical mechanism,gold nanoparticles will precipitate from a solution of HAuCl4 on exposure to synchrotron radiation,followed by the synthesis of PMMA by the polymerization of MMA monomers.These reactions can result in the formation of two different types of new hybrid nanomaterials.When a 1:1 volume ratio of HAuCl4 to MMA is used,we obtain PMMA spheres coated with gold nanoparticles.When a 10:1 ratio of HAuCl4 and MMA is used,we obtain gold nanoparticles coated with PMMA.The hybrid gold/PMMA nanostructures are characterized by transmission electron microscopy,elemental analysis,dynamic-light scattering analysis,gel permeation chromatography and Raman spectroscopy.The hybrid nanomateriais have potential application in the fields of biosensors and drug delivery.     

High-throughput synthesis of size-controlled Pt-based catalysts

Pt catalysts are commonly used for chemical reaction processes due to its high catalytic activity and selectivity. Notably, the size of metal particles often has a significant impact on the performance of the metal-loaded catalysts. Therefore, developing highly efficiently synthesis method for the size control of Pt catalysts has great development prospects and research value. In this study, high-throughput size tuning of Pt-based catalysts was achieved by carbonizing the carriers. The experimental and characterization results showed that the size of the loaded Pt nanoparticles varied with different concentrations of glucose solution during carriers carbonization process. The reduction of 4-nitrophenol as a template reaction indicated that the reaction rate constant of the catalyst is approximately linear with the size of Pt particles. Importantly, a laboratory-built high-throughput synthesis system was applied for the catalyst synthesis, which enhances the automation of the laboratory exploratory experiments and makes it possible to synthesize catalysts with controllable size in batches.     

A collaboration into research on nanoparticles (ACORN)

This paper describes the operation and outcome of one of the United Kingdom's largest multi-partner research activities in nanoparticles.The research covers the discovery and development of organic and inorganic crystals/nanoparticles,nanoparticle properties towards specific product applications,The research also encompassed bespoke measurement technology for nanoparticles and structure interactions.Significant research outcomes are summarised.The paper illustrates the advantages from industrially motivated research and value of collective action between a broad group of researchers in a nation.     

Influence of nanoparticle surface coating on pool boiling

The purpose of this work is to study the effects of nanostructured surface coatings on boiling heat transfer and CHF. Boiling experiments are performed on a 100 μm diameter platinum wire immersed in saturated water or pentane at 1 bar. Nanostructured surface coating is obtained by deposition of charged γ-Fe₂O₃ nanoparticles (average diameter of 10 nm) on the platinum wire. Two different processes are compared: vigorous boiling and electrophoresis.The deposition of nanoparticles onto the heated surface induces a significant increase of the boiling critical heat flux (CHF) related to the increase of wettability. It also induces a decrease of the heat transfer coefficient when the wire is entirely covered with nanoparticles. The critical heat flux enhancement depends on the wettability of the fluid compared with the bare heater. Different physical mechanisms are also studied to explain the evolution of the characteristic parameters of the boiling on nanostructured surfaces.     

Influence of intrinsic parameters on the particle size of magnetic spinel nanoparticles synthesized by wet chemical methods

The synthesis of magnetic spinel ferrites at the nanoscale is a field of intense study, because the mesoscopic properties enable their novel applications. Spinel nanoparticles have a promising role because of their extraordinary properties compared with those of micro and macro scale particles. Several colloidal chemical synthetic procedures have been developed to produce monodisperse nanoparticles of spinel ferrites and other materials using sol–gel, co-precipitation, hydrothermal, and microemulsion techniques. To improve the synthesis method and conditions, quality and productivity of these nanoparticles, understanding the effect of extrinsic (pH, temperature, and molecular concentration) and intrinsic parameters (site preferences, latent heat, lattice parameters, electronic configuration, and bonding energy) on the particle size during synthesis is crucial. In this review, we discuss the effect of the intrinsic parameters on particle size of spinel ferrites to provide an insight to control their particle size more precisely.     

Cell membrane-encapsulated nanoparticles for vaccines and immunotherapy

Functionalized nanoparticles are widely used in drug targeted delivery and immune microenvironment regulation. As a new type of biomaterial, cell-derived carriers are receiving considerable attention in clinical translation owing to their desirable biocompatibility and lower toxicity. Importantly, cell membrane-encapsulated nanoparticles can achieve specific biological effects from the benefit of their parent cell characteristics. In this review, we introduce the cell membrane coating technologies that are under extensive investigation, we also summarize various applications that have been developed for immunotherapy, and discuss the prospects in this field. With further understanding and integration with advanced biotechnology methods, it is believed that the continuing development of cell membrane-encapsulated nanoparticles will achieve promotion in clinical application.     

Scalable gas-phase processes to create nanostructured particles

The properties of nanoparticles are often different from those of larger grains of the same solid material because of their very large specific surface area. This enables many novel applications, but properties such as agglomeration can also hinder their potential use. By creating nanostructured particles one can take optimum benefit from the desired properties while minimizing the adverse effects. We aim at developing high-precision routes for scalable production of nanostructured particles. Two gas-phase synthesis routes are explored. The first one - covering nanoparticles with a continuous layer - is carried out using atomic layer deposition in a fluidized bed. Through fluidization, the full surface area of the nanoparticles becomes available. With this process, particles can be coated with an ultra-thin film of constant and well-tunable thickness. For the second route - attaching nanoparticles to larger particles - a novel approach using electrostatic forces is demonstrated. The micron-sized particles are charged with one polarity using tribocharging. Using electrospraying, a spray of charged nanoparticles with opposite polarity is generated. Their charge prevents agglomeration, while it enhances efficient deposition at the surface of the host particle. While the proposed processes offer good potential for scale-up, further work is needed to realize large-scale processes.     

Nanoparticles assembly-induced special wettability for bio-inspired materials

Through billions of years of evolution, nature has optimized the programmed assembly of the nano- and micro-scale structures of biological materials. Nanoparticle assembly provides an avenue for mimicking these multiscale functional structures. Bio-inspired surfaces with special wettability have attracted much attention for both fundamental research and practical applications. In this review, we focus on recent progress in nanoparticle assembly-induced special wettability, including superhydrophilic surfaces, superhydrophobic surfaces, superamphiphobic surfaces, stimuli-responsive surfaces, and self-healing surfaces. A brief summary and an outlook of the future of this research field are also provided.     

An acetic acid refluxing-electrochemistry combined strategy to activate supported-platinum electrocatalysts

Surfactant removal from the surface of platinum-based nanoparticles prepared using solution-based methods is a prerequisite to realize their high catalytic performance for electrochemical reactions. Herein, we report an effective approach combining acetic acid refluxing with an electrochemical process for the removal of amine- or thiol-based capping agents from the surface of supported-platinum nanoparticles. This strategy involves surfactant protonation by refluxing the supported-platinum particles in acetic acid followed by surfactant removal by subsequent electrochemical treatment at high potential. We demonstrate that this combined activation process is essential to enhance platinum particle performance in catalyzing direct methanol fuel cell reactions, including methanol oxidation and oxygen reduction reactions. The studies in this work show promise in electrocatalysis applications of solution-based materials synthesis.     

Conductive hydrogels incorporating carbon nanoparticles: A review of synthesis,performance and applications

As one of the most rapidly expanding materials, hydrogels have gained increasing attention in a variety of fields due to their biocompatibility, degradability and hydrophilic properties, as well as their remarkable adhesion and stretchability to adapt to different surfaces. Hydrogels combined with carbon-based materials possess enhanced properties and new functionalities, in particular, conductive hydrogels have become a new area of research in the field of materials science. This review aims to provide a comprehensive overview and up-to-date examination of recent developments in the synthesis, properties and applications of conductive hydrogels incorporating several typical carbon nanoparticles such as carbon nanotubes, graphene, carbon dots and carbon nanofibers. We summarize key techniques and mechanisms for synthesizing various composite hydrogels with exceptional properties, and represented applications such as wearable sensors, temperature sensors, supercapacitors and human-computer interaction reported recently. The mechanical, electrical and sensing properties of carbon nanoparticles conductive hydrogels are thoroughly analyzed to disclose the role of carbon nanoparticles in these hydrogels and key factors in the microstructure. Finally, future development of conductive hydrogels based on carbon nanoparticles is discussed including the challenges and possible solutions in terms of microstructure optimization, mechanical and other properties, and promising applications in wearable electronics and multifunctional materials.     

Synthesis of powdered silver nanoparticles using hydrogen in aqueous medium

Environmentally benign one-pot protocol is used in the synthesis of silver nanoparticles (AgNPs) in powder form, involving the reduction of silver nitrate in the presence of fully hydrolyzed polyvinyl alcohol (PVA) as stabilizer by hydrogen (H₂) as reducing agent in aqueous medium. Fully hydrolyzed biodegradable PVA has extremely low cytotoxicity, making it a favorable stabilizer from green perspective. In the present methodology, essentially naked silver nanoparticles are obtained in good yield. The prepared silver nanoparticles were characterized by TEM, XRD, EDAX, UV–Vis spectroscopy and DLS histogram, and studied for its activity as a recyclable catalyst for synthesis of different enaminones.     

等离子体加工过程中尘埃微粒行为的研究

在等离子体加工过程中产生的尘埃微粒是影响半导体集成电路生产质量的关键问题,近年来吸引了不少科学家的注意力．尘埃等离子体已成为等离子体物理中一个重要的前沿分支．本文综述低气压等离子体加工过程中关于尘埃微粒的形成及生长过程、带电机制、作用力、输运特性及尘埃等离子体的强耦合性质等方面的研究进展,并介绍其主要测量手段,观测结果及理论模型      

Experimental investigation of heat conduction in polyester-Al2O3 and polyester-CuO nanocomposites

This paper presents an experimental analysis of the thermal conductivity of nanocomposite systems composed of unsaturated polyester resin (UPR) as matrices and two different metal-oxides nanoparticles as fillers: alumina (aluminum oxide) and tenorite (copper oxide). The nanoparticles used were alpha-Al₂O₃ (30-40 nm) and CuO (30-50 nm). Samples were fabricated using simple molding and homogenization using magnetic stirring. Thermal conductivities were measured using a device that complies with ASTM norms C518-04 and E1530-06. Measurements were taken at three different temperatures (0 °C, 25 °C and 50 °C), for different sets of samples, varying the nanoparticle fraction used in composite systems. Finally, the experimental data are compared with traditional models for predicting the thermal conductivity of composite materials, showing that the traditional models underestimate the measured values.     

Convection in rotating porous media: The planetary geostrophic equations,used in geophysical fluid dynamics,revisited

In this paper, we give some mathematical results for a system of partial differential equations arising for instance in oceanography and meteorology. This model is called the planetary geostrophic equations or thermohaline equations. Different systems exist depending on the different viscous operators used to parameterize the small-scale processes. These choices made by physicists are empirical and are subject to numerous numerical studies. These parametrizations sometimes provide some models like Bénard convection in a rotating thin porous medium. Unfortunately this observation seems to be unknown to people working on geophysical fluid dynamics. Thus, in a first section, we discuss models which are sometimes known by several names. We compare the results obtained by people working on porous media and by people working on geophysical fluid dynamics. The last section is devoted to mathematical results. More precisely, we prove that it is possible in particular domains to extend some recent mathematical results by the use of some simple relations between the vertical velocity and the temperature. Many applications exist with such domains in meteorology. This system is also used in the food processing industry or in centrifugal filtration processes. In the last part, we indicate how to extend the results to a domain with a vanishing depth on the shore in the case of the hyperviscous parametrization. This has some applications in oceanography for instance. Received March 21, 2002 / Accepted 21 November 2002 // Published online May 9, 2003 / Brian Straughan, Durham RID="a" ID="a" e-mail: didier.bresch@math.univ-bpclermont.f RID="b" ID="b" e-mail: mamadou@math.univ-bpclermont.fr     

Effect of correcting near-wall forces on nanoparticle transport in a microchannel

This paper studies the importance of corrections that account for the presence of walls on the forces act- ing on nanoparticles during their transport in microchannels.Theoretical and experimental investigations have reported anisotropic and hindered motion of nanoparticles near a microchannel wall. To investigate the influence of the near-wall effects, various conditions were examined. In particular, computer simu- lations were performed with and without the near-wall correction of forces. The corresponding capture efficiency and the average penetration of the captured nanoparticles were compared, and the importance of the near-wall corrections was assessed. Effects were evaluated for the nanoparticle diameter, the chan- nel width, the channel length, and the pressure gradient. The results indicate that the inclusion of wall effects is crucial for the analysis of nanoparticle transport in microchannels.