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- Chalangar, Ebrahim, PhD student, 1984-
(författare)
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Graphene-based nanocomposites for electronics and photocatalysis
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of future electronics depends on the availability of suitable functional materials. Printed electronics, for example, relies on access to highly conductive, inexpensive and printable materials, while strong light absorption and low carrier recombination rates are demanded in photocatalysis industry. Despite all efforts to develop new materials, it still remains a challenge to have all the desirable aspects in a single material. One possible route towards novel functional materials, with improved and unprecedented physical properties, is to form composites of different selected materials.In this work, we report on hydrothermal growth and characterization of graphene/zinc oxide (GR/ZnO) nanocomposites, suited for electronics and photocatalysis application. For conductive purposes, highly Al-doped ZnO nanorods grown on graphene nanoplates (GNPs) prevent the GNPs from agglomerating and promote conductive paths between the GNPs. The effect of the ZnO nanorod morphology and GR dispersity on the nanocomposite conductivity and GR/ZnO nanorod bonding strength were investigated by conductivity measurements and optical spectroscopy. The inspected samples show that growth in high pH solutions promotes a better graphene dispersity, higher doping and enhanced bonding between the GNPs and the ZnO nanorods. Growth in low pH solutions yield samples characterized by a higher conductivity and a reduced number of surface defects.In addition, different GR/ZnO nanocomposites, decorated with plasmonic silver iodide (AgI) nanoparticles, were synthesized and analyzed for solar-driven photocatalysis. The addition of Ag/AgI generates a strong surface plasmon resonance effect involving metallic Ag0, which redshifts the optical absorption maximum into the visible light region enhancing the photocatalytic performance under solar irradiation. A wide range of characterization techniques including, electron microscopy, photoelectron spectroscopy and x-ray diffraction confirm a successful formation of photocatalysts.Our findings show that the novel proposed GR-based nanocomposites can lead to further development of efficient photocatalyst materials with applications in removal of organic pollutants, or for fabrication of large volumes of inexpensive porous conjugated GR-semiconductor composites.
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- Messing, Ingmar, et al.
(författare)
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Soil particle size distribution – comparison between laser diffraction, integral suspension pressure and sedimentation (pipette) methods
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- <p>The sedimentation (pipette) (SP) method has been in use for a long time as a solid reference method to estimate particle size distribution (PSD) in soil. The procedure is demanding, not the least concerning the manual extraction of soil fractions at given depth and time intervals during the sedimentation process and their subsequent drying and weighing. The more recent laser diffraction (LD) and integral suspension pressure (ISP) methods are promising alternatives. They have the advantage that the extraction-drying-weighing procedure for the finer soil fractions (clay and silt) is replaced by automatic registration of particle volumes (for LD) and pressures at given depth during the sedimentation process (for ISP). Due to these differences in measurement technics, PSD:s determined with LD and ISP methods often deviate more or less from PSD:s by SP method, which have implications for the matching with historical SP soil databases. We present some draft results of studies comparing the three methods on samples from agricultural soils in Sweden. The results show that there is still a need for further fine-tuning in the methodologies to align PSD composition from one method to the other.</p>
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- Messing, Maria, et al.
(författare)
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Characterization of Nanoparticles from Spark Ablation
- 2019. - 1st edition
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Ingår i: Spark Ablation : Building Blocks for Nanotechnology - Building Blocks for Nanotechnology. - 9789814800822 - 9780367817091 ; , s. 191-221
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Messing, Maria
(författare)
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Engineered Nanoparticles Generation, Characterization and Applications
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is predicted that novel nanometer-sized structures incorporating nanoparticles will have a considerable impact on our lives during the coming decades. Engineered nanoparticles are already found in a number of commercially available products. However, many applications of these nanoparticles have only reached the stage of promising ideas or research demonstrations. The number of nanoparticle-based products on the market is therefore expected to increase considerably during the coming decades. For engineered nanoparticles to be useful in different commercial applications, it is important that their generation can be controlled. This means a stable generation process resulting in reproducible, high-quality nanoparticles with properties tailored for specific applications. In order to develop such production methods, thorough characterization of the particles generated is essential. In addition, since the impact of nanoparticles on human health and the environment has not been fully explored, the entire lifecycle of engineered nanoparticles must be thoroughly investigated. Engineered nanoparticles should not cause any harm to human health or the environment, during manufacturing or use of the product, or during disposal of the product after use. This thesis describes the manufacture of engineered nanoparticles, mainly by inert gas evaporation using a spark discharge generator and an evaporation/condensation furnace. Considerable effort has been put into investigating how different generation parameters affect particle production, so that the particle properties can be controlled and tailored to meet specific applications. To achieve this, the as-generated nanoparticles have been systematically characterized by various methods; transmission electron microscopy being the key characterization tool. The nanoparticles generated were then used in three different areas of application: as seed particles for so-called nanowires which may be useful in future devices, as model catalyst systems to provide deeper knowledge about the atomic-scale mechanisms involved in catalysis, and finally for research in the area of nano safety to learn how nanoparticles should be handled in a safe and sustainable manner.
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- Novakovic, Maja, et al.
(författare)
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Analysis of Exhaust PM Composition Emitted from Non-Sooting Volatile Alcohols
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The combustion engine, a well-known source of aerosols, has seen remarkable improvements regarding efficiency and emissions. A drawback of the conventional compression ignition (CI) engine is its requirement for a high cetane number fuel, i.e. diesel which contains long carbon chains forming particulate matter (PM) when combusted in the conventional diesel combustion (CDC) process. A previous study of PM from partially premixed combustion (PPC) and CDC utilizing ethanol and methanol in a Scania D13 engine without emission after treatment systems (EATS) showed that the particle sizes from the alcohol combustion never exceeded 30 nm in diameter. Until now, the characteristics (origin, formation and constituents) of these nano-sized particles formed in the PPC and CDC process were unknown. It has been hypothesized that they originate from lubrication oil and engine wear.
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