The Experts below are selected from a list of 3624 Experts worldwide ranked by ideXlab platform
Esko I Kauppinen - One of the best experts on this subject based on the ideXlab platform.
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Direct Synthesis of high-quality single-walled carbon nanotubes by the physical nucleation of iron nanoparticles in an atmospheric pressure carbon monoxide flow
Carbon, 2012Co-Authors: Kimmo Mustonen, Albert G. Nasibulin, Toma Susi, Hua Jiang, Esko I KauppinenAbstract:Abstract We demonstrate a direct and stable Aerosol Synthesis of single-walled carbon nanotubes (SWCNTs) using a hot wire generator (HWG) method, with iron physically evaporated in a carbon monoxide (CO) atmosphere as the catalyst source. A small amount of added carbon dioxide increased the lifetime of the Fe wire in reacting CO up to several weeks. This approach allowed us to significantly increase the yield of SWCNTs as compared to the previously employed inert hydrogen-containing flow through the wire. High quality and purity SWCNTs were produced, as demonstrated by high-resolution transmission electron microscopy and Raman and optical absorption spectroscopy.
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Aerosol Synthesis and applications of single-walled carbon nanotubes
Russian Chemical Reviews, 2011Co-Authors: Albert G. Nasibulin, Sergey D. Shandakov, M Yu Timmermans, Esko I KauppinenAbstract:Aerosol methods for the chemical Synthesis of Aerosol methods for the chemical Synthesis of single-walled carbon nanotubes are considered. Character- single-walled carbon nanotubes are considered. Character- istic features and advantages of these methods are indicated. istic features and advantages of these methods are indicated. The possibility of controlling the growth and vapour depo- The possibility of controlling the growth and vapour depo- sition processes of single-walled nanotubes are discussed. It sition processes of single-walled nanotubes are discussed. It is shown that nanotubes prepared by Aerosol Synthesis can is shown that nanotubes prepared by Aerosol Synthesis can be directly used in various fields of technology. The bib- be directly used in various fields of technology. The bib- liography includes 171 references liography includes 171 references..
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Preparation of solid DNA nanoparticles for use in gene therapy
Drug Discovery Today, 2010Co-Authors: Martina Hanzlíková, Janne Raula, Esko I Kauppinen, Juho Hautala, Arto Urtti, Marjo YliperttulaAbstract:: Non-viral gene therapy, basedon nanosized particles, is a potential thera-peutic option in various diseases. The successis mainly dependent on an efficient genedelivery vector. Aerosol Synthesis can providepure solid DNA particles with substantial highdose of DNA per particle and thereby increasethe amount of DNA delivered into cells ascompared to commonly used DNA polymercomplexes. The purpose of this study was totest the suitability of plasmid DNA alone or incomplex with cationic polymers for the prepa-ration of solid DNA nanoparticles by an Aerosolflow reactor method.
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Aerosol Synthesis of Inhalation Particles via a Droplet-to-Particle Method
Particulate Science and Technology, 2006Co-Authors: Anna Lähde, Janne Raula, Esko I Kauppinen, Wiwik Watanabe, Petri Ahonen, David P. BrownAbstract:ABSTRACT Inhalation powders with consistent particle properties, including particle size, size distribution, and shape were produced with an Aerosol Synthesis method. Compared to conventional spray drying, the Aerosol method provides better control of the thermal history and residence time of each droplet and product particle due to the laminar flow in the heated zone of the reactor where the droplet drying and particle formation take place. A corticosteroid, beclomethasone dipropionate, generally used for asthma treatment was chosen as a representative material to demonstrate the process. Spherical particles were produced with a droplet-to-particle method from an ethanolic precursor solution. The droplets produced with an ultrasonic nebulizer were carried to a heated zone of the reactor at 50–150°C where the solvent was evaporated and dry particles formed. The mass mean diameter of the particles were well within the respirable size range (approximately 2 μm). The geometric standard deviation (GSD) of pro...
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On-line detection of single-walled carbon nanotube formation during Aerosol Synthesis methods
Carbon, 2005Co-Authors: Anna Moisala, Sergey D. Shandakov, Albert G. Nasibulin, Hua Jiang, Esko I KauppinenAbstract:Differential electrical mobility (DMA) method for the on-line detection of single-walled carbon nanotubes (SWCNTs) formation was used for the first time. Three different gas-phase Synthesis processes were used to produce SWCNTs via CO disproportionation in the presence of catalyst nanoparticles formed either by a hot wire generator method or via thermal decomposition of ferrocene or iron pentacarbonyl. The typical product measured with the DMA method was bundles of SWCNTs, which further agglomerated prior to the measurement. Despite the different product morphology and concentration, the on-line measurement was able to distinguish SWCNT formation in each experimental set-up as an increase in the geometric mean particle diameter and as a decrease in the total particle number concentration. Furthermore, information regarding the relative SWCNT concentration can also be obtained from the DMA measurement. A theoretical approach to the mobility of nonspherical particles in the electric field was successfully developed in order to convert the electrical mobility size of the high aspect ratio SWCNTs measured with DMA to the physical size of the product. Size-selected SWCNTs were studied with transmission electron microscopy in order to find the correlation between the on-line DMA measurement data and the SWCNT morphology.
Sotiris E Pratsinis - One of the best experts on this subject based on the ideXlab platform.
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air entrainment during flame Aerosol Synthesis of nanoparticles
Aerosol Science and Technology, 2014Co-Authors: Oliver Waser, Maximilian L Eggersdorfer, Arto J. Groehn, Sotiris E PratsinisAbstract:Enclosed flames typically produce substantially larger particles than open flames under identical reactant flows and composition. The enclosure hinders air entrainment to the flame and reduces heat losses by radiation and convection, facilitating particle coagulation and coalescence. Here the effect of natural air entrainment on flame Aerosol Synthesis is investigated by lifting off the enclosing tube from the burner surface and utilizing tracer gas (Ne) analysis after calibration with forced air entrainment. That way the effect of air entrainment on product primary particle diameter and mobility size distribution dynamics is investigated by microscopy, scanning mobility particle sizing, and N2 adsorption, while temperature is measured by Fourier-transform infrared spectroscopy. So air entrainment during flame spray pyrolysis is examined here for its versatility in scalable manufacture of an array of material compositions, while copper oxide (CuO) is used for its electro-chemical applications (e.g., batte...
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fluid particle dynamics during combustion spray Aerosol Synthesis of zro2
Chemical Engineering Journal, 2012Co-Authors: Arto Juhani Grohn, Sotiris E Pratsinis, Karsten WegnerAbstract:Abstract Owing to its versatility and low cost, flame spray pyrolysis (FSP) is becoming an increasingly promising method for industrial production of a broad spectrum of nanoparticles. To assist understanding and scale-up of the current laboratory process, a computational model has been constructed for the example of zirconia nanoparticle Synthesis. Therefore, a computational fluid dynamics (CFD) description of the spray flame originating from a twin-fluid atomizer and coaxial diffusion burner was combined with droplet and nanoparticle dynamics. The model predicted well average primary ZrO 2 particle diameters even though global chemical reactions, immediate nanoparticle formation upon precursor oxidation and monodisperse particle dynamics were employed. This model is self-containing and does not rely on experimental input data such as temperature or velocity fields. The model was validated at different process conditions with phase-Doppler anemometry (PDA) for spray characteristics, Fourier-transform infrared spectroscopy (FTIR) flame temperature measurements as well as nanoparticle sampling in and above the flame.
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continuous flame Aerosol Synthesis of carbon coated nano lifepo4 for li ion batteries
Journal of Aerosol Science, 2011Co-Authors: Oliver Waser, Robert Buchel, Andreas Hintennach, Petr Novak, Sotiris E PratsinisAbstract:Core-shell, nanosized LiFePO4-carbon particles were made in one step by scalable flame Aerosol technology at 7 g/h. Core LiFePO4 particles were made in an enclosed flame spray pyrolysis (FSP) unit and were coated in-situ downstream by auto thermal carbonization (pyrolysis) of swirl-fed C2H2 in an O2-controlled atmosphere. The formation of acetylene carbon black (ACB) shell was investigated as a function of the process fuel-oxidant equivalence ratio (EQR). The core-shell morphology was obtained at slightly fuel-rich conditions (1.0 < EQR < 1.07) whereas segregated ACB and LiFePO4 particles were formed at fuel-lean conditions (0.8 < EQR < 1). Post-annealing of core-shell particles in reducing environment (5 vol% H2 in argon) at 700 °C for up to 4 hours established phase pure, monocrystalline LiFePO4 with a crystal size of 65 nm and 30 wt% ACB content. Uncoated LiFePO4 or segregated LiFePO4-ACB grew to 250 nm at these conditions. Annealing at 800 °C induced carbothermal reduction of LiFePO4 to Fe2P by ACB shell consumption that resulted in cavities between carbon shell and core LiFePO4 and even slight LiFePO4 crystal growth but better electrochemical performance. The present carbon-coated LiFePO4 showed superior cycle stability and higher rate capability than the benchmark, commercially available LiFePO4.
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Flame Aerosol Synthesis of Metal Oxide Catalysts with Unprecedented Structural and Catalytic Properties
ChemCatChem, 2011Co-Authors: Bjoern Schimmoeller, Sotiris E Pratsinis, Alfons BaikerAbstract:In the past two decades flame Aerosol Synthesis of novel materials has experienced significant growth in both industry and academia. Recent research is focused on the development of new materials in the nanosized range to be used in various applications, such as catalysts, gas sensors, pigments, and batteries. Several studies indicate that this scalable Synthesis method can result in novel and metastable phases of mixed metal oxides of high purity, which may not be easy accessible by conventional wet- or solid-state processes. Especially for catalytic applications this Synthesis method is emerging as an attractive fast and single-step production route for high surface area materials, often with unprecedented structural and catalytic properties. The large variety of possible organometallic precursors especially for the liquid-fed Aerosol flame Synthesis makes this technique very versatile for catalyst Synthesis. Using the example of the widely used vanadia-based mixed oxide catalysts, we analyze the structural and catalytic properties of flame-derived catalysts and compare them to corresponding catalysts prepared by classical wet-chemistry methods. The often unique structural properties along with their control at proper Synthesis conditions and their influence on catalyst performance in selected reactions are discussed. Subsequently, we give an overview of other recent flame-made mixed metal oxide based catalysts and make an attempt to assess the potential and limitations of flame Synthesis for the preparation of catalytic mixed metal oxide materials, and finally we identify future challenges in research.
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Aerosol Synthesis of chemoresistive gas sensors: Materials, structures and performances
2010 IEEE Sensors, 2010Co-Authors: Antonio Tricoli, Marco Righettoni, Sotiris E PratsinisAbstract:The sensing performance of nanoparticle films obtained by Aerosol Synthesis is investigated as a function of material composition (e.g. SnO 2 , TiO 2 , WO 3 ), film morphology and layout. It is shown that highly porous (98%) films are obtained by direct deposition from the gas phase. Utilization of a flame spray pyrolysis (FSP) reactor as particle source was found to be a flexible alternative for the Synthesis of single and multi oxides at high production rates. More in detail, low content Si-doping of SnO 2 or WO 3 FSP-made nanoparticles drastically increased their response to ethanol and acetone, respectively. This was attributed to the high thermal stability of these nanocomposites at the elevated operation temperatures of metal oxide gas sensors. However, mechanical stabilization of these films was required to avoid their disintegration. Sufficient mechanical stabilization was obtained by rapid in-situ annealing with an impinging particle free flame leading to highly sensitive metal oxide-based gas sensors. In conclusion, Aerosol Synthesis of chemoresistive gas sensors is critically reviewed focusing on the opportunities offered by novel flame methods, such as FSP, while assessing some of its current limitations.
Albert G. Nasibulin - One of the best experts on this subject based on the ideXlab platform.
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Aerosol synthesized carbon nanotube films for stretchable electronic applications
2015 IEEE 15th International Conference on Nanotechnology (IEEE-NANO), 2015Co-Authors: Evgenia Gilshteyn, Albert G. NasibulinAbstract:Electronics based on nanomaterials (e.g. nanoparticles, nanotubes, nanowires, thin films) have been attracting interest recently due to their strain sensing characteristics. Strain sensors comprised of carbon nanotubes (CNTs) and silver nanowires, or graphene serve as good alternatives for developing new sensors because of their outstanding properties. Here, we report about thin films of single-walled carbon nanotubes (SWCNTs) which can be used as a key component of different electronic devices. The electrical properties of these devices can exhibit excellent characteristics compared to the traditional sensors due to a combination of high elastic moduli and outstanding electrical properties. The SWCNT films used in this study were obtained by Aerosol Synthesis and characterized by high structural quality.
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Aerosol Synthesis of Single-Walled Carbon Nanotubes for Electronic Applications
2013Co-Authors: Albert G. NasibulinAbstract:Synthesis methods of carbon nanotubes are considered. The possibility of separationof individual singlewalled nanotubes from the bundle in the gas phase and control of their parameters withthe help of etching agents is shown. The advantage of the Aerosol Synthesis methods of nanotubes both forvariation of parameters of carbon nanotubes (diameter and morphology) and for their subsequent use in hightech areas (electronics, optics, electrochemistry) is discussed.
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Direct Synthesis of high-quality single-walled carbon nanotubes by the physical nucleation of iron nanoparticles in an atmospheric pressure carbon monoxide flow
Carbon, 2012Co-Authors: Kimmo Mustonen, Albert G. Nasibulin, Toma Susi, Hua Jiang, Esko I KauppinenAbstract:Abstract We demonstrate a direct and stable Aerosol Synthesis of single-walled carbon nanotubes (SWCNTs) using a hot wire generator (HWG) method, with iron physically evaporated in a carbon monoxide (CO) atmosphere as the catalyst source. A small amount of added carbon dioxide increased the lifetime of the Fe wire in reacting CO up to several weeks. This approach allowed us to significantly increase the yield of SWCNTs as compared to the previously employed inert hydrogen-containing flow through the wire. High quality and purity SWCNTs were produced, as demonstrated by high-resolution transmission electron microscopy and Raman and optical absorption spectroscopy.
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Synthesis of single-walled carbon nanotubes by Aerosol method
Inorganic Materials: Applied Research, 2011Co-Authors: Albert G. Nasibulin, Sergey D. Shandakov, M Yu Timmermans, O. V. Tolochko, E. I. KauppinenAbstract:Two Aerosol Synthesis methods of carbon nanotubes are considered. The possibility of separation of individual single-walled nanotubes from the bundle in the gas phase and control of their parameters with the help of etching agents is shown. The advantage of the Aerosol Synthesis methods of nanotubes both for variation of parameters of carbon nanotubes (diameter and morphology) and for their subsequent use in hightech areas (electronics, optics, electrochemistry) is discussed.
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Aerosol Synthesis and applications of single-walled carbon nanotubes
Russian Chemical Reviews, 2011Co-Authors: Albert G. Nasibulin, Sergey D. Shandakov, M Yu Timmermans, Esko I KauppinenAbstract:Aerosol methods for the chemical Synthesis of Aerosol methods for the chemical Synthesis of single-walled carbon nanotubes are considered. Character- single-walled carbon nanotubes are considered. Character- istic features and advantages of these methods are indicated. istic features and advantages of these methods are indicated. The possibility of controlling the growth and vapour depo- The possibility of controlling the growth and vapour depo- sition processes of single-walled nanotubes are discussed. It sition processes of single-walled nanotubes are discussed. It is shown that nanotubes prepared by Aerosol Synthesis can is shown that nanotubes prepared by Aerosol Synthesis can be directly used in various fields of technology. The bib- be directly used in various fields of technology. The bib- liography includes 171 references liography includes 171 references..
Wolfgang Peukert - One of the best experts on this subject based on the ideXlab platform.
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Single-step Aerosol Synthesis of oxygen-deficient blue titania
Chemical Engineering Science, 2019Co-Authors: Maximilian Domaschke, Lea Strunz, Wolfgang PeukertAbstract:Abstract We present a novel approach for the single-step, continuous Aerosol Synthesis of blue, oxygen-deficient titania in a hot-wall reactor operated under reducing conditions by adding hydrogen. The precursor titanium(IV) tetraisopropoxide is evaporated in a bubbler and consecutively carried into the reactor by a nitrogen stream where it undergoes thermal decomposition. According to X-ray diffraction analysis, several reduced titania states, among them the Magneli phases Ti4O7 and Ti5O9, are formed via the intermediates anatase and rutile. By slight modifications in the reactor setup both nanoparticles in the size range from 20 to 50 nm with high surface area and well-defined spherical submicron particles of 100 to 160 nm diameter can be produced. In particular, crystallographically phase-pure Ti4O7 is formed at high reactor temperatures. The presented Synthesis process is scalable and poses an attractive alternative for the multi-step Synthesis of oxygen deficient titania nanoparticles that is currently done via batch-wise annealing. Such nanoparticles are attractive material in the field of photocatalysis. They can be used for both water splitting to produce hydrogen and the decomposition of organic pollutants.
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Aerosol Synthesis of germanium nanoparticles supported by external seeding: Theoretical and experimental analysis
Journal of Aerosol Science, 2019Co-Authors: Lukas Wergen, Maximilian Domaschke, Patrick Herre, Erdmann Spiecker, Wolfgang PeukertAbstract:Abstract In this work we present a detailed study of the effect of heterogeneous nucleation on the formation of germanium nanoparticles (Ge NPs) produced from monogermane (GeH4) in a hot wall reactor gas phase Synthesis. As external seeding unit we use a hot wire generator (HWG) which produces a stable concentration of Aerosol particles. The particle concentration and size of the seeds is easily controllable via the applied voltage and used metal. We demonstrate the importance of seed particles for the production of narrowly distributed Ge NPs with geometrical standard deviations (GSD)
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Aerosol Synthesis of silicon nanoparticles with narrow size distribution part 1 experimental investigations
Journal of Aerosol Science, 2010Co-Authors: Richard Kormer, Michael P M Jank, H Ryssel, Hansjoachim Schmid, Wolfgang PeukertAbstract:Abstract A study on the feasibility of Aerosol processing of nearly monodisperse silicon nanoparticles via pyrolysis of monosilane in a hot wall reactor is presented. For optimal conditions silicon nanoparticles with a geometric standard deviation of 1.06 were synthesized at a production rate of 0.7 g/h. The size of the particles could be precisely controlled in the range of 20–40 nm, whilst maintaining a geometric standard deviation in the range of 1.06–1.08, by proper choice of the governing parameters temperature, residence time and precursor concentration. The results show that narrow particle size distributions can only be obtained in the temperature range between 900 and 1100 °C, as long as both the initial silane concentration (1 mbar silane partial pressure) and the reactor total pressure are low (25 mbar). This regime for the production of narrow particle size distributions has not been identified in prior work on the thermal decomposition of silane. Narrowly distributed particles can be obtained under conditions where nucleation and particle growth are separated and the agglomeration rates are negligible.
Alfons Baiker - One of the best experts on this subject based on the ideXlab platform.
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Flame Aerosol Synthesis of Metal Oxide Catalysts with Unprecedented Structural and Catalytic Properties
ChemCatChem, 2011Co-Authors: Bjoern Schimmoeller, Sotiris E Pratsinis, Alfons BaikerAbstract:In the past two decades flame Aerosol Synthesis of novel materials has experienced significant growth in both industry and academia. Recent research is focused on the development of new materials in the nanosized range to be used in various applications, such as catalysts, gas sensors, pigments, and batteries. Several studies indicate that this scalable Synthesis method can result in novel and metastable phases of mixed metal oxides of high purity, which may not be easy accessible by conventional wet- or solid-state processes. Especially for catalytic applications this Synthesis method is emerging as an attractive fast and single-step production route for high surface area materials, often with unprecedented structural and catalytic properties. The large variety of possible organometallic precursors especially for the liquid-fed Aerosol flame Synthesis makes this technique very versatile for catalyst Synthesis. Using the example of the widely used vanadia-based mixed oxide catalysts, we analyze the structural and catalytic properties of flame-derived catalysts and compare them to corresponding catalysts prepared by classical wet-chemistry methods. The often unique structural properties along with their control at proper Synthesis conditions and their influence on catalyst performance in selected reactions are discussed. Subsequently, we give an overview of other recent flame-made mixed metal oxide based catalysts and make an attempt to assess the potential and limitations of flame Synthesis for the preparation of catalytic mixed metal oxide materials, and finally we identify future challenges in research.
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flame Aerosol Synthesis of vanadia titania nanoparticles structural and catalytic properties in the selective catalytic reduction of no by nh3
Journal of Catalysis, 2001Co-Authors: Wendelin J Stark, Sotiris E Pratsinis, Karsten Wegner, Alfons BaikerAbstract:Abstract Flame Aerosol Synthesis has been used to prepare vanadia–titania nanoparticles with high activity for the selective catalytic reduction of NO by NH3. The mixed oxides were prepared from vanadium and titanium alkoxides which were evaporated into an argon stream and burned in a methane oxygen diffusion flame. Silica-containing samples were produced in a similar way by mixing hexamethyldisiloxane vapor into the precursor stream. Different flame structures were investigated for the effect of temperature and residence time on particle morphology, vanadia surface species, and overall catalytic activity. By changing the oxygen flow rate into the flame, particles with specific surface areas between 23 and 120 m2/g could be produced. High-resolution transmission electron microscopy (HRTEM) revealed that nanoparticles were spherical with diameters of 10 to 50 nm. X-ray photoelectron spectroscopy analysis indicated that vanadia was dispersed on the surface of the titania spheres. No indication for the presence of crystalline V2O5 could be found by X-ray diffraction or HRTEM. Catalysts with a vanadia surface loading of 10 μmol/m2 showed high activity with less than 1% N2O formation up to 350°C. Catalytic activity strongly depended on the vanadia loading; an increase from 2.5 to 7 μmol/m2 resulted in a 30 times higher activity per vanadium. Addition of silica lowered the overall activity but did not change the activation energy. Raman spectroscopy indicated the presence of vanadate clusters. Temperature-programmed reduction corroborated that no significant amount of vanadia entered the titania lattice to form an interstitial solution. The selective catalytic reduction activity of as-prepared vanadia–titania is comparable to the best catalysts obtained by wet chemical methods.
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Flame Aerosol Synthesis of Vanadia–Titania Nanoparticles: Structural and Catalytic Properties in the Selective Catalytic Reduction of NO by NH3
Journal of Catalysis, 2001Co-Authors: Wendelin J Stark, Sotiris E Pratsinis, Karsten Wegner, Alfons BaikerAbstract:Abstract Flame Aerosol Synthesis has been used to prepare vanadia–titania nanoparticles with high activity for the selective catalytic reduction of NO by NH 3 . The mixed oxides were prepared from vanadium and titanium alkoxides which were evaporated into an argon stream and burned in a methane oxygen diffusion flame. Silica-containing samples were produced in a similar way by mixing hexamethyldisiloxane vapor into the precursor stream. Different flame structures were investigated for the effect of temperature and residence time on particle morphology, vanadia surface species, and overall catalytic activity. By changing the oxygen flow rate into the flame, particles with specific surface areas between 23 and 120 m 2 /g could be produced. High-resolution transmission electron microscopy (HRTEM) revealed that nanoparticles were spherical with diameters of 10 to 50 nm. X-ray photoelectron spectroscopy analysis indicated that vanadia was dispersed on the surface of the titania spheres. No indication for the presence of crystalline V 2 O 5 could be found by X-ray diffraction or HRTEM. Catalysts with a vanadia surface loading of 10 μmol/m 2 showed high activity with less than 1% N 2 O formation up to 350°C. Catalytic activity strongly depended on the vanadia loading; an increase from 2.5 to 7 μmol/m 2 resulted in a 30 times higher activity per vanadium. Addition of silica lowered the overall activity but did not change the activation energy. Raman spectroscopy indicated the presence of vanadate clusters. Temperature-programmed reduction corroborated that no significant amount of vanadia entered the titania lattice to form an interstitial solution. The selective catalytic reduction activity of as-prepared vanadia–titania is comparable to the best catalysts obtained by wet chemical methods.
