By thermoplastic ceramic injection moulding (CIM) ceramic components of high complexity can be pr... more By thermoplastic ceramic injection moulding (CIM) ceramic components of high complexity can be produced in a large number of items at low dimensional tolerances. The cost advantage by the high degree of automation leads to an economical mass-production. The structure of injection-moulded components is determined by the form filling behaviour and viscosity of the feedstock, the machine parameters, the design
ABSTRACT The innovative High-Velocity Suspension Flame Spraying (HVSFS) process, whereby a conven... more ABSTRACT The innovative High-Velocity Suspension Flame Spraying (HVSFS) process, whereby a conventional gas-fuelled HVOF torch is modified in order to allow the processing of liquid feedstock, was employed in order to spray a TiO2 nanopowder suspension. Three different sets of parameters were employed. The structure, microstructure, nanohardness, tribological properties and photocatalytic activity of the resulting coatings were studied and compared to conventional atmospheric plasma sprayed (APS) and HVOF-sprayed TiO2 coatings, manufactured using commercially available feedstock. Compared to the APS and HVOF techniques, HVSFS enabled the deposition of thinner (20 μm – 60 μm thick), yet high-quality layers. Moreover, it was found that the HVSFS process leaves a fairly large freedom to adjust coating properties (thickness, porosity, anatase content, hardness, etc…) according to the desired objective. Layers with higher anatase content and higher porosity can be produced, in order to achieve higher photocatalytic efficiency than conventional APS and HVOF TiO2. Alternatively, it is possible to deposit dense layers, with lower porosity and pore interconnectivity and better hardness and wear resistance than as-deposited APS and HVOF coatings.
The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Sprayi... more The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Spraying (HVSFS) from a suspension of titania nanoparticles, were investigated by Focused Ion Beam (FIB)+Scanning Electron Microscopy (SEM) techniques, by Transmission Electron Microscopy (TEM) and by micro-Raman spectroscopy, and were compared to those of conventional HVOF-sprayed TiO2. Proper selection of the HVSFS deposition parameters results in coatings consisting
High Velocity Suspension Flame Spraying (HVSFS) is a new approach for spraying micron, submicron ... more High Velocity Suspension Flame Spraying (HVSFS) is a new approach for spraying micron, submicron and nanoparticles with hypersonic speed by feeding a suspension directly into the combustion chamber of a HVOF torch. The aim in mind is to achieve dense coatings with an improved microstructure — probably reaching the nanoscale, from which superior physical properties are expected. Compared to the
Al2O3 coatings were manufactured by the high-velocity suspension flame spraying (HVSFS) technique... more Al2O3 coatings were manufactured by the high-velocity suspension flame spraying (HVSFS) technique using a nanopowder suspension. Their structural and microstructural characteristics, micromechanical behavior, and tribological properties were studied and compared to conventional atmospheric plasma sprayed and high-velocity oxygen-fuel-sprayed Al2O3 coatings manufactured using commercially available feedstock. The HVSFS process enables near full melting of the nanopowder particles, resulting in very small
High-velocity suspension flame spraying (HVSFS) has been developed to thermally spray suspensions... more High-velocity suspension flame spraying (HVSFS) has been developed to thermally spray suspensions containing micron, submicron, and nanoparticles with hypersonic speed. For this purpose, the suspension is introduced directly into the combustion chamber of a modified HVOF torch. The aim in mind is to achieve dense coatings with a refined microstructure. Especially from nanostructured coatings superior physical properties are expected for
The paper reports the first attempt at employing the innovative high-velocity suspension flame sp... more The paper reports the first attempt at employing the innovative high-velocity suspension flame spraying (HVSFS) technique in order to deposit bioactive glass coatings. Fine (micrometric) glass particles having a composition similar to that of the A–W (apatite–wollastonite) bioactive glass–ceramic as proposed by Kokubo were dispersed into a 50% water+50% isopropanol solvent mixture and the resulting suspension (containing 20wt.% glass powder)
By thermoplastic ceramic injection moulding (CIM) ceramic components of high complexity can be pr... more By thermoplastic ceramic injection moulding (CIM) ceramic components of high complexity can be produced in a large number of items at low dimensional tolerances. The cost advantage by the high degree of automation leads to an economical mass-production. The structure of injection-moulded components is determined by the form filling behaviour and viscosity of the feedstock, the machine parameters, the design
ABSTRACT The innovative High-Velocity Suspension Flame Spraying (HVSFS) process, whereby a conven... more ABSTRACT The innovative High-Velocity Suspension Flame Spraying (HVSFS) process, whereby a conventional gas-fuelled HVOF torch is modified in order to allow the processing of liquid feedstock, was employed in order to spray a TiO2 nanopowder suspension. Three different sets of parameters were employed. The structure, microstructure, nanohardness, tribological properties and photocatalytic activity of the resulting coatings were studied and compared to conventional atmospheric plasma sprayed (APS) and HVOF-sprayed TiO2 coatings, manufactured using commercially available feedstock. Compared to the APS and HVOF techniques, HVSFS enabled the deposition of thinner (20 μm – 60 μm thick), yet high-quality layers. Moreover, it was found that the HVSFS process leaves a fairly large freedom to adjust coating properties (thickness, porosity, anatase content, hardness, etc…) according to the desired objective. Layers with higher anatase content and higher porosity can be produced, in order to achieve higher photocatalytic efficiency than conventional APS and HVOF TiO2. Alternatively, it is possible to deposit dense layers, with lower porosity and pore interconnectivity and better hardness and wear resistance than as-deposited APS and HVOF coatings.
The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Sprayi... more The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Spraying (HVSFS) from a suspension of titania nanoparticles, were investigated by Focused Ion Beam (FIB)+Scanning Electron Microscopy (SEM) techniques, by Transmission Electron Microscopy (TEM) and by micro-Raman spectroscopy, and were compared to those of conventional HVOF-sprayed TiO2. Proper selection of the HVSFS deposition parameters results in coatings consisting
High Velocity Suspension Flame Spraying (HVSFS) is a new approach for spraying micron, submicron ... more High Velocity Suspension Flame Spraying (HVSFS) is a new approach for spraying micron, submicron and nanoparticles with hypersonic speed by feeding a suspension directly into the combustion chamber of a HVOF torch. The aim in mind is to achieve dense coatings with an improved microstructure — probably reaching the nanoscale, from which superior physical properties are expected. Compared to the
Al2O3 coatings were manufactured by the high-velocity suspension flame spraying (HVSFS) technique... more Al2O3 coatings were manufactured by the high-velocity suspension flame spraying (HVSFS) technique using a nanopowder suspension. Their structural and microstructural characteristics, micromechanical behavior, and tribological properties were studied and compared to conventional atmospheric plasma sprayed and high-velocity oxygen-fuel-sprayed Al2O3 coatings manufactured using commercially available feedstock. The HVSFS process enables near full melting of the nanopowder particles, resulting in very small
High-velocity suspension flame spraying (HVSFS) has been developed to thermally spray suspensions... more High-velocity suspension flame spraying (HVSFS) has been developed to thermally spray suspensions containing micron, submicron, and nanoparticles with hypersonic speed. For this purpose, the suspension is introduced directly into the combustion chamber of a modified HVOF torch. The aim in mind is to achieve dense coatings with a refined microstructure. Especially from nanostructured coatings superior physical properties are expected for
The paper reports the first attempt at employing the innovative high-velocity suspension flame sp... more The paper reports the first attempt at employing the innovative high-velocity suspension flame spraying (HVSFS) technique in order to deposit bioactive glass coatings. Fine (micrometric) glass particles having a composition similar to that of the A–W (apatite–wollastonite) bioactive glass–ceramic as proposed by Kokubo were dispersed into a 50% water+50% isopropanol solvent mixture and the resulting suspension (containing 20wt.% glass powder)
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Papers by Johannes Rauch