Aerosol Physics Unit
We have a background in developing various measuring techniques. Currently, our research extends to fields such as aerosol instrumentation, combustion aerosols, atmospheric aerosols, nanoparticle synthesis, and nanostructured coatings. We are organized into two groups described below. We do not take the organization structure too seriously, but nevertheless name some contact persons. Feel free to ask for more information.
Head of the Research Area: Prof. Jorma Keskinen
The Instrumentation, Emissions, and Atmospheric Aerosols Group
The group develops aerosol measurement methods and studies emission and atmospheric aerosols. The measurement methods involve real-time techniques that can be taken to industrial production, but also more fundamental research. Emission aerosol studies have been directed at automotive emissions. The research is focused on particle formation processes and properties that are challenging and potentially have a high impact on health effects. Atmospheric aerosol studies were recently started by applying our own techniques to particles produced by boreal forests. These particles are associated with the biosphere-atmosphere interaction and the climate change.
- Diesel exhaust nanoparticles
- Singly charged particles for calibration
- Atmospheric aerosols
The Aerosol Synthesis Group
Contact person: Prof. Jyrki Mäkelä
The group uses thermal synthesis methods to produce single and multicomponent nanoparticles and to develop nanostructured functional coatings. Their basic tool is the Liquid Flame Spray (LFS) method – a flame synthesis method developed in the Laboratory. The experimental activities are performed mainly in their own flame laboratory, but the applications are tested and scaled up in industrial collaboration, including mass production of optical amplifying fibers and coating of float glass in a real size conveyor belt.
The Instrumentation, Emissions, and Atmospheric Aerosols Group Research
Diesel exhaust nanoparticles
Particle emissions of traffic affect the air quality, especially in urban environments. From the viewpoint of particle exposure the role of traffic is emphasized because the exhaust particles are typically emitted in our immediate environment. To predict and assess the effects of traffic related emissions on human exposure, human health, air quality and atmospheric processes, especially the real-world traffic emissions should be known. The Aerosol Physics Laboratory studies the emissions of engines, vehicles and traffic. Our focus has been on diesel exhaust particles, recently mostly on the emissions and characteristics of diesel exhaust nucleation mode particles. The studies cover experimental measurements in engine and vehicle laboratories and in aerosol laboratory, on-road exhaust measurements of individual vehicles in real-world driving environment, roadside and on-road measurements in urban environment as well as modeling studies.
In general, we think that the scientific understanding of the exhaust particle formation processes and detailed knowledge related to physical and chemical characteristics of exhaust particles are important in order to predict the future trends of traffic emissions, to guide the development of vehicle technologies to the direction which leads to the reduction of overall particle emission and to develop the new and cleaner technologies. The detailed understanding is emphasized in the current continuously developing situation driven by present and future emission limits.
We have a fully equipped mobile aerosol laboratory for ambient aerosol and emission studies.
Single charged particles for calibration
Single Charged Aerosol Reference (SCAR) Single Charged Aerosol Reference is a device, which can produce single charged particles in a wide particle size range (10 nm – 1 µm). Due to the fact that particles have only one elementary charge, the output particle concentration (particles/cubic centimeter) can be measured very accurately by measuring the electrical current carried by the particles. The most important application of the SCAR is to use it as a particle number concentration reference for calibrating other devices.
The operation principle of the SCAR is presented in the adjacent figure. In the device, a small 10 nm particle size distribution is first generated and charged. Due to a very small size of the particles, the charging process produces only neutral and singly charged particles. From the charged particles a narrow size channel is selected with a Differential Mobility Analyzer. These “seed particles” are subsequently growth by condensing a desired amount of vapor on top of the particles and as a result we will have much larger particles with net charge equal to one elementary charge.
We research and develope especially a low pressure impactor(LPI) technology for nanoparticle measurement. LPIs are used in e.g. determining the number size distribution of the aerosol, and the density and physical state of aerosol particles. A single impactor stage classifies particles into two size ranges and the size distribution measurement can be done connecting multiple impactor stages in a series (a cascade impactor). Both experimental and computational research is done in our laboratory. Focus at the theory side is how the collection efficiency changes with the parameters of the LPI. In a cascade impactor teqhniques we are particularly interested in applying advanced inversion methods to electrical low pressure impactor (ELPI) measurement. Also development of cascade impactors with the improved resolution and new innovative applications and properties is in our intentions. One of the latest LPI application we are involved is characterizing the physical state of the nanoparticles by observing the level of the particle bounce in the ELPI measurement.
Atmospheric fine particles affect the Earth’s radiation balance by interacting with solar radiation and by participating in cloud formation. Biogenic volatile organic compounds are key players in new particle formation processes. Hence, terrestrial vegetation has an important role as the newly formed particles cool our climate. The chemical composition of such secondary organic aerosol (SOA) particles formed from volatile compounds emitted by vegetation is very complicated. Thus the scientific community has tried to understand the chemical composition and physical characteristics of SOA particles in order to better understand their climatic implications and also to enable more accurate predictions using global climate models.
In Aerosol Physics Lab we also contribute on the SOA related research by studying the physical properties of SOA particles. We have, for example, developed a method by which the density of 15 nm sized particles can be solved. Recently we have also concentrated on studying the physical phase state of SOA particles. According to our new research published in Nature*, the physical state of SOA particles formed in coniferous forest is solid, most likely glassy soon after their formation. Until now, biogenic SOA particles have been represented as liquid droplets in global climate models.
Our research is more and more concentrated in studying the generality of the observation of amorphous solid SOA and also on understanding the atmospheric implications of the finding. The research is done in close co-operation with several national and international partners (the most important ones are listed below).
More information: Miikka Dal Maso
Nanoparticle Synthesis Group research
Liquid Flame Spray Synthesis
Flame aerosol synthesis methods are widely used both in industry and research. The advantage of flame methods is high production rate of materials, even up to kg/h. This is difficult to achieve by other nanoparticle synthesis methods. Liquid Flame Spray was invented at TUT. It is a versatile and environmental friendly way of synthesizing nanoparticles. Many different precursor materials can by sprayed and evaporated in the clean, high temperature hydrogen-oxygen flame, eventually leading to pure nanoparticle products. Multicomponent and composite particles are also achievable with the method. The morphology and particle size can be determined by choosing optimal precursor chemistry. Recently, the research of the group has been focused on ceramic and metal materials and combinations of them, e.g. TiO2, SiO2, ZrO2, Al2O3, Fe2O3 and Fe3O4 together with Pt, Pd, Ag and so on. Practically, all metal salts and metal organic materials dissolved in water or organic solvents can be used as precursors.
LFS can be utilized in deposition of nanoparticle into thin nanostructured coatings. A wide selection of substrate materials can be coated, including soft easily flammable materials, if only the coating speed is remains enough. We have an ongoing research in various fields. Self cleaning and antimicrobial coatings can be created from TiO2-Ag nanocomposites. Palladium particles have been synthesised for fuel cell catalysts. SiO2 particles are used as etching masks in patterning of medical instruments. And reversible switching between hydrophilic and hydrophobic state of packaging materials can be also manufactured with LFS deposited nanoparticles.
LFS is a sophisticated method of synthesising variety of nanoparticles. One application of nanoparticles is in a non-scientific field of glass colouring. LFS method is unique in giving a thin hue of colour for design glass objects. No other glass colouring method is able to produce such a thin and translucent layer of colour in the object. The intensity of the colour is easily tuned and selection of colours gives the glass artist various different opportunities in design. However, pure scientific research is also carried out in order to develop the colour effects and much effort is put into finding out the physical mechanisms of the origin of the colorant materials.
When generating aerosol nanoparticles with a tube furnace, a small ceramic crucible containing the desired particle material is placed in the center of a high-temperature furnace. If the temperature of the furnace is sufficiently high, for metals usually around 1000 ℃, the material starts to evaporate. An inert gas stream, for example nitrogen, carries the vaporized material to the colder parts of the flow system where it starts to condensate to become aerosol particles. Tube furnaces can be used to generate nanoparticles from different materials, both elemental and compounds. In addition, multiple subsequent furnaces in the same flow line give the opportunity to generate core-shell particles. The diameter of the generated particles usually varies between 2 and 300 nanometers depending mainly on the material of the particles. Different working parameters, for example, the temperature of the furnace and the flow rate of the carrier gas also influence the size distribution of the nanoparticles.
Collaborators of Instrumentation, Emissions and Atmospheric Aerosols group:
Univ. Eastern Finland (Dos. Jorma Joutsensaari), Finnish Meteorological Inst. (Prof. Ari Laaksonen), University of Helsinki (Prof. Markku Kulmala), Aerodyne Research Inc. (Prof. Douglas Worsnop), Harvard Univ. (Prof. Scot Martin), Bielefeld Univ. (Prof. Thomas Koop), Max Planck Institute for Chemistry (Dos. Ulrich Pöschl), Aristotle University of Thessaloniki(Prof. Zissis Samaras, Prof. Leonidas Ntziachristos, Max Planck Institute(Prof. Frank Arnold), German aerospace center ( Prof. Hans Schlager), Helsinki Metropolia University of Applied Sciences(Dr. Liisa Pirjola), Finnish Meteorological Insititute (Prof. Risto Hillamo), Helsinki Region Environmental Services Authority (Dr. Jarkko Niemi), VTT Technical Research Centre of Finland (Dr Matti Kytö), Aalto Univ. (Prof. Martti Larmi), Univ. Lund (Prof. Reine Wallenberg), Queensland Univ. Tech. (Prof. Zoran Ristovski)
MAN (Dr. Dieter Rothe), BOSMAL, Ford(Dr. Matti Maricq), Ecocat, Neste Oil, Kemira, Proventia Group, Wärtsilä, Dekati, Pegasor, Environics
Collaborators of Aerosol Synthesis Group:
ETH Zurich (Prof Sotiris Pratsinis), Lund University (Prof Knut Deppert),Czech Academy of Sciences (Prof Jiri Smolik),Tampere University of Technology(Dept Materials Sci, Lab of Paper Converting), Aalto University School of Art and Design, Åbo Akademi, Aalto University School of Science and Technology(Micronova)
Beneq Oy, nLight Ltd, IDO Bathroom Ltd, Stora Enso Oyj, UPM Oyj, Kemira Oyj, Iittala-Group Oyj
We organized the Aerosol Technology 2015 conference at Tampere: