5,498 research outputs found

    Characterization of Synthesized Goethite and Natural Goethite sourced from Itakpe in North Central, Nigeria

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    This study was aimed at characterizing samples of natural and synthetic goethite (α-FeOOH) in order to establish their composition and properties. The natural goethite (NGT) sample was obtained from Itakpe area in North Central, Nigeria while the synthetic goethite (SGT) fine particles were synthesized by the air oxidation method. Techniques employed in the investigation included determination of point of zero charge (pHpzc), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Brauner-Emmet-Teller Isotherm (BET) and particle nano-sizer. Results of the study showed that pHpzc of the NGT and SGT were 7.0 and 8.0 respectively. The main surface functional group from FTIR in both samples was the OH while the XRF studies indicated a high content of iron (66.193 % in NGT and 66.4009% in SGT). The SEM analysis revealed a high porosity being associated with SGT than the natural sample. Furthermore, The surface area of SGT as obtained from BET analysis was 797.662 m2/g while the nano-sizer also revealed a near nano-size for the synthesized goethite with particle size of about 172-173 nm. In view of the results of this study, SGT could relatively be used as a more effective adsorbent. It is also believed that both samples will find applications in lots of other analytical processes.Keywords: Adsorption, BET, Natural goethite, Particle nano-sizer, Synthetic goethit

    Investigations on nano- and submicron-particle generation by spray painting processes

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    [EN] This paper presents experimental and numerical studies to determine the particle size distributions (PSD) and concentrations in paint overspray. Two kinds of paint materials, solvent borne and water borne paints, both with and without manufactured nanomaterials (pigments), and an industrial spray gun were used. Different aerosol measuring techniques, namely the Spraytec Fraunhofer type particle sizer for micro-sized droplets in the spray jet and the Scanning Mobility Particle Sizer (SMPS) for nano particles in paint overspray were applied. It was found, that solvent borne clear coats create significantly higher number concentration of nano-sized droplets than the water borneprimers. Only small differences in PSD between paints with and without manufactured nanomaterials were found. Numerical simulations of droplet trajectories within the spray booth, for both micro and nano sized droplets, were carried out. Based on the experimental and numerical results, a representative particle size distribution (smaller than 1 ÎŒm) for the given spray gun was obtained. Effects of turbulence models on the particle deposition on targets, especially for submicron particles, have been analysed in detailed.The present investigations have been supported by Verkehr, Innovation und Technologie, Austria (BMVIT) and Fraunhofer Society in Germany within a European joint research project NanoGeCo. This support is gratefully acknowledged by the authors.Ye, Q.; Tiedje, O.; Srinivas, SR.; Noest, T.; Uhrner, U. (2017). Investigations on nano- and submicron-particle generation by spray painting processes. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat PolitĂšcnica de ValĂšncia. 122-129. https://doi.org/10.4995/ILASS2017.2017.4666OCS12212

    Aerosol Nucleation and Growth in a Mixture of Sulfuric Acid / Alpha-Pinene Oxidation Products at the CERN CLOUD Chamber

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    The role of α-pinene in aerosol nucleation and growth was investigated using the CERN CLOUD chamber, a nano scanning mobility particle sizer (nanoSMPS) and several condensation particle counters (CPCs) with different diameter cut-offs. Different oxidation conditions for α-pinene - OH⋅ vs. ozone oxidation - were considered to investigate their contributions to particle nucleation and growth. Results from the latest CERN experiment from fall 2012 (CLOUD 7) are presented

    Thermodynamic vs kinetic control of particle assembly and pattern replication

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    This research aims to investigate how particles assemble together through thermodynamic and kinetic control. Particle assembly with thermodynamic control is achieved in part due to electrostatic attraction between particles. Electrostatic attraction between particles can be achieved by functionalizing polystyrene or SiO2 particles with different charges. Particles with different charges will come together in solution slowly and self-assemble to form ordered crystals with different patterns based on size and charge ratios of two oppositely charged particles. Kinetic control of particle assembly is achieved by pattern aided exponential amplification of nanoscale structures. Some of these nanoscale structures are difficult to build with other conventional synthetic methods. On the other hand, as for kinetically controlled particle replication, the patterns can be synthesized by one of two ways i) crystal products which are produced by thermodynamically controlled particle assembly or ii) single particle deposition. Specifically, kinetically controlled particle assembly focuses on constructing SiO2 particles. Exponential replication of SiO2 particles is achieved by growing a bridge layer , between templates of SiO2 particles and next generation SiO2 replicas. By dissolving the bridge layer, two times the amount of the SiO2 particles with the shape of the original templates can be formed. In the next generation, all the particles serve as template particles. Thus, after n cycles of replication, 2n amount of products can be formed. If successful, particle assembly can be thermodynamic controlled and particle exponential replication can be kinetical controlled, which will enable new ways to build particles with well-defined shapes from readily available building blocks

    Measurement of Nanoparticles Release during Drilling of Polymer Nanocomposites

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    Nanomaterials are one of the promising technologies of this century. The Project on Emerging Nanotechnologies [1] reports more than 1600 consumer products based on nanotechnology that are currently on the market and advantages link to the reinforcement of polymeric materials using nano-fillers are not to demonstrate anymore. However, the concerns about safety and its consumer perception can slow down the acceptance of nanocomposites. Indeed, during its life-cycle, a nanotechnology-based product can release nano-sized particles exposing workers, consumers and environment and the risk involved in the use and disposal of such particles is not well known. The current legislation concerning chemicals and environment protection doesn’t explicitly cover nanomaterials and changes undergone by nanoparticles during the products’ life cycle. Also, the possible physio-chemical changes that the nanoparticles may undergo during its life cycle are unknown. Industries need a standard method to evaluate nanoparticles release during products’ life cycle in order to improve the knowledge in nanomaterials risk assessment and the legislation, and to inform customers about the safety of nanomaterials and nanoproducts. This work aims to propose a replicable method in order to assess the release of nanoparticles during the machining of nanocomposites in a controlled environment. For this purpose, a new experimental set-up was implemented and issues observed in previous methods (background noise due to uncontrolled ambient environment and the process itself, unrepeatable machining parameters) were solved. A characterisation and validation of the chamber used is presented in this paper. Also, preliminary testing on drilling of polymer-based nanocomposites (Polyamide-6/Glass Fibre reinforced with nano-SiO2) manufactured by extrusion and injection moulding were achieved

    Ultrafine Aerosol Particle Sizer Based on Piezoresistive Microcantilever Resonators with Integrated Air-Flow Channel

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    To monitor airborne nano-sized particles (NPs), a single-chip differential mobility particle sizer (DMPS) based on resonant micro cantilevers in defined micro-fluidic channels (”FCs) is introduced. A size bin of the positive-charged fraction of particles herein is separated from the air stream by aligning their trajectories onto the cantilever under the action of a perpendicular electrostatic field of variable strength. We use previously described ”FCs and piezoresistive micro cantilevers (PMCs) of 16 ng mass fabricated using micro electro mechanical system (MEMS) technology, which offer a limit of detection of captured particle mass of 0.26 pg and a minimum detectable particulate mass concentration in air of 0.75 ”g/m3. Mobility sizing in 4 bins of a nebulized carbon aerosol NPs is demonstrated based on finite element modelling (FEM) combined with a-priori knowledge of particle charge state. Good agreement of better than 14% of mass concentration is observed in a chamber test for the novel MEMS-DMPS vs. a simultaneously operated standard fast mobility particle sizer (FMPS) as reference instrument. Refreshing of polluted cantilevers is feasible without de-mounting the sensor chip from its package by multiply purging them alternately in acetone steam and clean air
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