Particles
Research Activities in Particle TechnologyWell-defined nanoparticle production from the gas phase(Andreas Schmidt-Ott, Jan Marijnissen) New processes are developed for controlled production of nanoparticles. Gas phase processes have the advantage with respect to liquid phase production that they are continuous and clean (free of ligands). They are also clean in an environmental sense, because there is no liquid waste. The particles are mainly crystalline and can be collected as powders or impacted onto surfaces for further processing. The following principles for nanoparticle production are explored:
Electroacoustic spraying (Andreas Schmidt-Ott, Jan Marijnissen) Monodisperse droplets are produced by multinozzle systems, combining electrical and acoustic fields. In particular, electrospray production of droplets or particles is being scaled up to obtain amounts of particles to be used for inhalation purposes or for production of nanoparticulate materials.
Nanomixing(Andreas Schmidt-Ott) By applying the rapid quenching of vapours that occurs in spark ablation, nanoparticles mixed on a scale of nanometers or atomically mixed nanoparticles can be produced. We have shown that materials immiscible on a macroscopic scale can be mixed this way. Applications include catalysts, chemical sensors, hydrogen storage materials and electrodes for batteries or fuel cells.
Hydrogen Storage in Nanoparticles(Andreas Schmidt-Ott) Magnesium stores a high weight percentage of hydrogen, but the kinetics of charging and uncharging is unfavourable for practical use. A probable solution of this problem consists in application of nanoparticles as the storage medium and in the addition of small amounts of material that acts catalytically or prohibits coalescence of nanosized units.
Production of Nanoporous Surfaces by Inertial Impaction of Nanoparticles(Andreas Schmidt-Ott) Well-defined nanoparticles are impacted to a surface, where they form nanoporous networks. Possible applications of such structures are in catalysts, lithium ion batteries, solar cells, chemical sensors and membranes.
Nanoparticle based chemical sensors(Andreas Schmidt-Ott) A confined of beam well defined nanoparticles is directed towards a surface, where a conductive network of nanoparticulate chains is formed. The conductivity of such a network depends on the nature of adsorbed or absorbed molecules. Thus chemical sensors can be produced this way. Such a sensor consisting of Pd particles selectively detects hydrogen in the ppb range.
Production of mesoporous particles by evaporation induced self-assembly on a micron scale (Andreas Schmidt-Ottwith Marc-Olivier Coppens) Micron sized particles that are porous on a micron scale are produced in a continuous process by spraying liquid solutions containing surfactants and a silicon and/or an aluminium source. These droplets are microreactors, in which the desired reaction occurs in seconds, which takes one week in a macroscopic batch. The organic component self-assembles to form a nanostructured template for the silica and/or alumina component.
Production and mobility classification of metal atomic clusters (Andreas Schmidt-Ott) Metal atomic clusters have attracted a lot of attention in recent years, because they mimic elements in the periodic system, forming “superatoms”. In principle, new superatoms with properties not found in the periodic system could be designed and novel materials could be made from these. The new domain of “cluster chemistry” requires a flexible source of producing atomic clusters that are pure with respect to material as well as the number of atoms per cluster. We have built such a source consisting of a glowing wire and a high resolution mobility analyzer. This research should lead to discovery of chemically interesting and stable atomic clusters as building blocks for new materials.
The effect of strong electric fields on catalysis (Andreas Schmidt-Ott) Catalytic nanoparticles in gas suspension have been used to catalyze a model reaction. By varying the charge of the particles, it was demonstrated that strong inhomogeneous electric fields had an influence on the activation energy of this reaction. Possible applications of this effect include better control on catalyst selectivity and “switching” of catalysis in microreactors.
A security feature in documents based on imbedded nanoparticles(Andreas Schmidt-Ott) Nanoparticles are imbedded in documents. Their optical response depends on their material and can further be tuned through particle size. The response can be detected in a very sensitive way.
Photoacoustic spectroscopy on drawings and paintings of old masters (Andreas Schmidt-Ott) Every material has a unique “photoacoustic signature”, which can be used to compare unknown specimens with artwork assigned to specific masters for attribution and authenticity research. In particular, the feature of photoacoustic spectroscopy to “see colours” beneath the surface of paintings will be explored.
Design and development of a nanoparticle sensor to be applied as a safety monitor(Andreas Schmidt-Ott) Solid nanoparticles that are insoluble in water must be considered as potentially toxic, especially in inhalation exposure. A sensor based on charging and electrical detection of nanoparticles is being developed. The sensor should give an alarm when particles below a certain size limit are present in laboratory air.
Identification of superpolluters among passing motor vehicles(Andreas Schmidt-Ott) A small percentage of cars are responsible for a very significant part of urban air pollution. A new particle measurement technique has been applied to prove this statement. It is further being developed to identify vehicles on the roads that emit 100 or 1000 times the particle mass of “clean” vehicles.
More applications of Electrospray orElectro HydroDynamic Atomization (EHDA) to particle production (Jan Marijnissen) Based on a complete fundamental, physical model we have developed mono-sized, nano- and micrometer droplets and particles of various materials are produced. By mixing two oppositely charged sprays, fascinating compounds can be produced. Applications include
Extracting scarce valuable liquids from plants using the EHDA principle (Jan Marijnissen) For example, taxol can be exreacted from yew trees in a repeatable way without harming the plant.
Development of an electrostatic wind energy convertor using EHDA (Jan Marijnissen) Charged water droplets are produced to convert wind energy into electrical energy without moving mechanical parts.
Desalination of sea water using EHDA (Jan Marijnissen) (in co-operation with Wetsus, Leeuwarden, the Netherland)
The design and development of an Aerosol Laser Time of Flight Mass Spectrometer (ALTOFMS)(Jan Marijnissen) The ALTOFMS is an instrument to measure size and complete chemical composition of air-borne particles on-line. The instrument has been expanded by adding a section to apply a matrix coating on the incoming particles (on-line), enabling the instrument to characterize biological particles, s.a. bacteria, on-line.
Construction of a Photon Correlation Spectroscope (PCS)(Jan Marijnissen) This instrument measures in-line the size of nanometer sized particles and has been adapted for the measurement of aerosols. We are developing the instrument such that the measurements go far below the conventional concentration range. Besides the size of the particles the concentration is also determined by this device
Reduction of ambient aerosol concentration(Jan Marijnissen) A method is under development to reduce the ambient particle concentration in both confined and open spaces by the use of electrical precipitation.
Formation of structured and functionalised particles by granulation, coating and grinding (Gabrie Meesters) The objective of the current research is to use and measure the physical properties of coatings and particles and to predict their behaviour. The particles can be coated using polymers or can be immersed into a coating, thus functionalising the polymer. Typical techniques are granulation, fluid bed coating and (nano)-grinding of solids. In the past few years much work has been done on developing tests to assess the strength of particles against attrition, abrasion and crushing. This is a typical problem which accounts for the formation of dust during the use of granulated materials. Currently we are working on determining the physical properties of coatings that influence the attrition, abrasion and crushing resistance.
Nano-grinding of organic materials (Gabrie Meesters) These materials are used to functionalise coatings used in food applications. Here the influence on the distribution, size and morphology of the nano particles in the coating is investigated, as well as the technique of nano-grinding.
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