S. Rosiwal - Academia.edu (original) (raw)
Papers by S. Rosiwal
Laser in der Technik / Laser in Engineering, 1992
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Excimer Lasers and Applications III, 1991
ABSTRACT In advanced contact materials one aim in processing is the reduction or even substitutio... more ABSTRACT In advanced contact materials one aim in processing is the reduction or even substitution of precious metals. However, newly developed materials have to exhibit excellent corrosion resistance and good electrical conductivity as well as mechanical stability, especially if abrasive wear loaded contacts are concerned. One strategy is the total substitution of precious metals by non-noble metals such as copper and its conventional alloys. Such materials, however, suffer from their poor mechanical properties. Chromium would be a candidate for an unusual alloying element that may help to overcome these weaknesses, but unfortunately Cr does not mix with Cu by standard metallurgy. For low current contacts a surface layer of a mixed material might be sufficient, and powder metallurgical routes are therefore inefficient and hence inadequate. The excimer laser is an excellent tool to produce the required thin films by surface alloying. This is possible due to its short wavelength and short pulse duration. The present investigations were carried out in order to understand the phenomenon of laser surface alloying using excimer laser irradiation. To achieve technical relevance, the system Cu/Cr was chosen. The irradiations were monitored using difference reflectometry, to check whether alloying occurred at all and to what degree. Structural details of the produced layers were investigated using a diffractometer with glazing incidence. To obtain quantitative information about depth and stoichiometry of the alloyed layer, sputtering AES was applied.
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Laser in der Medizin / Laser in Medicine, 1992
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Laser in der Technik / Laser in Engineering, 1992
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Deutsche Zahnärztliche Zeitschrift
Difference reflectometry is a new method for assessing material surfaces by measuring the relativ... more Difference reflectometry is a new method for assessing material surfaces by measuring the relative amount of light reflected within a range of 300-720 nm. The in vivo and in vitro results of the present study indicate that it is possible to transfer this measuring principle to dental applications. Reflexion measurements allow the detection of hard tooth structures and their pathologic alterations with adequate exactness. With the aid of this method it is possible to differentiate between carious hard tissues and clinically healthy tissues by color and surface structure during excavation. It also allows a reliable demarcation from oral soft tissues. Due to its high measuring frequency it may be used as on-line process control. In contrast to other spectrometric methods it requires a minimum of equipment and is easy to handle.
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The International journal of oral & maxillofacial implants
Diamond layers can be plated with microwave plasma chemical vapor deposition (MWP-CVD) treatment ... more Diamond layers can be plated with microwave plasma chemical vapor deposition (MWP-CVD) treatment on metal bases such as titanium-aluminum-vanadium alloy (Ti-6Al-4V). The bonding strength of the diamond layer to the metal base is very high, so that no fissures and partial loss of coating take place-well known phenomena that may occur with other coatings in tribologic material testing. In an experimental study using 40 New Zealand White rabbits, a new method for coating implant material was tested for stability of the bone-metal interface. The results of histomorphometric and biomechanical evaluation of coated and uncoated probes implanted in the distal femur of 40 rabbits were compared. The animals were divided into 3 groups, with observation times of 42, 84, and 168 days. The bone-implant contact was 5% to 18% less in coated than in uncoated probes. Only the early group, with 42 days healing time showed significant differences. Values for the pull-off force of uncoated material were...
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Surface and Coatings Technology, 2009
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Clinical Oral Implants Research, 2004
The histological differences between the defect and contact areas of the implant surface to bone ... more The histological differences between the defect and contact areas of the implant surface to bone were tested in 35 New Zealand White rabbits in a standardized model. Microwave plasma chemical vapor-coated implant probes were tested in control and uncoated materials. In each femur of 35 rabbits, cylindrical implant rods with a planed side were inserted. Three groups, divided in coated and uncoated material at half, were observed 42, 84 and 168 days. The probes were examined histologically for bone-implant contact in the curved and plane (defect area) sides. Generally the bone-implant contact seems to be nearly constant in time in the curved area of coated and uncoated probes. Here the implant was inserted in the press-fit mode. Diamond-coated probes showed similar bone-implant contact (51.9% (42 days), 62.5% (84 days), 56.1% (168 days)) compared to uncoated material (56.2%, 65.4%, 62.9%). The defect area (plane side) had no bone-implant contact at the time of insertion and showed increasing values on longer observation times with only significant differences in the 42-day group between coated (17.85%, 35.2%, 47.7%) and uncoated materials (35.5%, 40.55%, 51.81%). The evaluation of the curved side of the implant probe showed no great variation of bone-implant contact within the described observation times. This model simulates the usual implant insertion situation. The diamond-coated material becomes osseointegrated at a later time point. The bone-implant contact was only statistically relevant in one group in comparison to uncoated material.
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Acta Materialia, 2011
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FISCHER:FRICTION, WEAR O-BK, 2011
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Surface and Coatings Technology, 1999
Polycrystalline diamond layers were deposited onto the titanium alloy Ti–6Al–4V via microwave pla... more Polycrystalline diamond layers were deposited onto the titanium alloy Ti–6Al–4V via microwave plasma chemical vapor deposition (CVD). It is shown that the diamond film reduces wear and friction immensely compared with uncoated titanium/titanium tribo systems. An additional polishing process of the CVD-diamond layer improves the wear behavior even further. An influence of air humidity is found.In addition, different ceramic materials (Al2O3, SiC, Si3N4, ZrO2) were tested against as-deposited and polished CVD-diamond layers. Al2O3 and Si3N4 exhibit very good wear behavior accompanied by very low friction against as-deposited CVD-diamond. SiC and ZrO2, however, show somewhat inferior wear and friction behavior. Suggestions are made to explain the different performance. Again, a wear increase is found with increasing humidity. Polishing of CVD-diamond layers improves the tribological performance further.
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Surface and Coatings Technology, 1999
ABSTRACT The solid-particle erosion resistance of Ti–6Al–4V can be improved significantly by appl... more ABSTRACT The solid-particle erosion resistance of Ti–6Al–4V can be improved significantly by applying a chemical-vapor-deposited diamond coating under conditions where physical-vapor-deposited coated substrates fail. In particular, diamond coatings grown with relatively high methane concentrations (4–10%) in the process gas atmosphere exhibit superior performance. The reason for this behavior is a higher in-plane strength of these coatings due to growth defects like twin formation and secondary nucleation.
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Journal of Superhard Materials, 2007
ABSTRACT We designed a new hot-filament plant which features some new operating states for chemic... more ABSTRACT We designed a new hot-filament plant which features some new operating states for chemical vapor infiltration with diamond. Complete infiltration of porous substrates with diamond by using standard hot filament plants is not possible. Chemical vapor infiltration with diamond is limited by the overgrowing diamond layer at the surface primarily caused by high recombination rates of atomic hydrogen on surfaces. As a consequence, the pore mouth is closed before the pore is completely infiltrated (“bottleneck” effect). Porous substrates were infiltrated by using a forced flow through the substrate. In order to achieve good infiltration results, it was necessary to use very low methane concentrations.
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14. Symposium Verbundwerkstoffe und Werkstoffverbunde, 2006
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... l, D-91058 Erlangen, GermanyAbstractIn contrast to their excellent mechanical properties, tit... more ... l, D-91058 Erlangen, GermanyAbstractIn contrast to their excellent mechanical properties, titaniumalloys possess poor ... The mechanical properties of the titanium are strongly influenced by the processing ... As a result of the hydrogen adsorption, grain coarsening and formation of ...
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International Journal of Modern Physics B, 2002
ABSTRACT Diamond materials have become progressively significant in the fabrication of heat sinks... more ABSTRACT Diamond materials have become progressively significant in the fabrication of heat sinks for power devices and lasers. To investigate the influence of polishing on CVD-Diamond, the surfaces of <100> and <110> coatings were analyzed, after a first abrasive treatment on a 30μm diamond grit by scanning thermal microscopy based on a resistive platinum-probe. This technique describes in first order approximation the heat transfer of a metal-diamond interface. Through this method it was possible to diagnose a relevant reduction in thermal conductivity by a harsh sample preparation depending on the crystal orientation. The thermal conductivity of as deposited <100> diamond was measured at 1290 W/mK and was reduced to 250 W/mK. The thermal conductivity of as deposited <110> diamond was determined at 1780 W/mK whereas the same diamond surface, but abraded, shows a thermal conductivity of just 460 W/mK. Additionally the received images which represents the thermal conductivity qualitatively bring forward micro structures like e.g. grain boundaries.
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Surface and Coatings Technology, 2007
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Surface & Coatings Technology, 2006
Adherent and homogeneous diamond films were deposited on 41Cr4 steel substrates employing chemica... more Adherent and homogeneous diamond films were deposited on 41Cr4 steel substrates employing chemical vapor deposited (CVD) TiBN interlayers. The suitability of CVD-TiBN interlayers for diamond deposition was investigated. The CVD intermediate layers showed excellent barrier properties against the diffusion of iron from the bulk substrate to the surface and against diffusion of carbon from gas phase during diamond deposition. Various
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CVD diamond coatings on Ti-6Al-4V substrates were found to be highly effective in reducing fretti... more CVD diamond coatings on Ti-6Al-4V substrates were found to be highly effective in reducing fretting fatigue which, for example, can occur in the root section of aerospace compressor blades. Optimization of a mechanical polishing process leads to significant improvements in the tribological properties of these diamond coatings. This is shown by extremely low wear rates and low coefficients of friction against bearing steel, alumina and diamond. The wear and friction behavior was investigated in a ball-on-disk tribometer and characterized by profilometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman spectroscopy.
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Biomedizinische Technik. Biomedical engineering, 1998
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Laser in der Technik / Laser in Engineering, 1992
Bookmarks Related papers MentionsView impact
Excimer Lasers and Applications III, 1991
ABSTRACT In advanced contact materials one aim in processing is the reduction or even substitutio... more ABSTRACT In advanced contact materials one aim in processing is the reduction or even substitution of precious metals. However, newly developed materials have to exhibit excellent corrosion resistance and good electrical conductivity as well as mechanical stability, especially if abrasive wear loaded contacts are concerned. One strategy is the total substitution of precious metals by non-noble metals such as copper and its conventional alloys. Such materials, however, suffer from their poor mechanical properties. Chromium would be a candidate for an unusual alloying element that may help to overcome these weaknesses, but unfortunately Cr does not mix with Cu by standard metallurgy. For low current contacts a surface layer of a mixed material might be sufficient, and powder metallurgical routes are therefore inefficient and hence inadequate. The excimer laser is an excellent tool to produce the required thin films by surface alloying. This is possible due to its short wavelength and short pulse duration. The present investigations were carried out in order to understand the phenomenon of laser surface alloying using excimer laser irradiation. To achieve technical relevance, the system Cu/Cr was chosen. The irradiations were monitored using difference reflectometry, to check whether alloying occurred at all and to what degree. Structural details of the produced layers were investigated using a diffractometer with glazing incidence. To obtain quantitative information about depth and stoichiometry of the alloyed layer, sputtering AES was applied.
Bookmarks Related papers MentionsView impact
Laser in der Medizin / Laser in Medicine, 1992
Bookmarks Related papers MentionsView impact
Laser in der Technik / Laser in Engineering, 1992
Bookmarks Related papers MentionsView impact
Deutsche Zahnärztliche Zeitschrift
Difference reflectometry is a new method for assessing material surfaces by measuring the relativ... more Difference reflectometry is a new method for assessing material surfaces by measuring the relative amount of light reflected within a range of 300-720 nm. The in vivo and in vitro results of the present study indicate that it is possible to transfer this measuring principle to dental applications. Reflexion measurements allow the detection of hard tooth structures and their pathologic alterations with adequate exactness. With the aid of this method it is possible to differentiate between carious hard tissues and clinically healthy tissues by color and surface structure during excavation. It also allows a reliable demarcation from oral soft tissues. Due to its high measuring frequency it may be used as on-line process control. In contrast to other spectrometric methods it requires a minimum of equipment and is easy to handle.
Bookmarks Related papers MentionsView impact
The International journal of oral & maxillofacial implants
Diamond layers can be plated with microwave plasma chemical vapor deposition (MWP-CVD) treatment ... more Diamond layers can be plated with microwave plasma chemical vapor deposition (MWP-CVD) treatment on metal bases such as titanium-aluminum-vanadium alloy (Ti-6Al-4V). The bonding strength of the diamond layer to the metal base is very high, so that no fissures and partial loss of coating take place-well known phenomena that may occur with other coatings in tribologic material testing. In an experimental study using 40 New Zealand White rabbits, a new method for coating implant material was tested for stability of the bone-metal interface. The results of histomorphometric and biomechanical evaluation of coated and uncoated probes implanted in the distal femur of 40 rabbits were compared. The animals were divided into 3 groups, with observation times of 42, 84, and 168 days. The bone-implant contact was 5% to 18% less in coated than in uncoated probes. Only the early group, with 42 days healing time showed significant differences. Values for the pull-off force of uncoated material were...
Bookmarks Related papers MentionsView impact
Surface and Coatings Technology, 2009
Bookmarks Related papers MentionsView impact
Clinical Oral Implants Research, 2004
The histological differences between the defect and contact areas of the implant surface to bone ... more The histological differences between the defect and contact areas of the implant surface to bone were tested in 35 New Zealand White rabbits in a standardized model. Microwave plasma chemical vapor-coated implant probes were tested in control and uncoated materials. In each femur of 35 rabbits, cylindrical implant rods with a planed side were inserted. Three groups, divided in coated and uncoated material at half, were observed 42, 84 and 168 days. The probes were examined histologically for bone-implant contact in the curved and plane (defect area) sides. Generally the bone-implant contact seems to be nearly constant in time in the curved area of coated and uncoated probes. Here the implant was inserted in the press-fit mode. Diamond-coated probes showed similar bone-implant contact (51.9% (42 days), 62.5% (84 days), 56.1% (168 days)) compared to uncoated material (56.2%, 65.4%, 62.9%). The defect area (plane side) had no bone-implant contact at the time of insertion and showed increasing values on longer observation times with only significant differences in the 42-day group between coated (17.85%, 35.2%, 47.7%) and uncoated materials (35.5%, 40.55%, 51.81%). The evaluation of the curved side of the implant probe showed no great variation of bone-implant contact within the described observation times. This model simulates the usual implant insertion situation. The diamond-coated material becomes osseointegrated at a later time point. The bone-implant contact was only statistically relevant in one group in comparison to uncoated material.
Bookmarks Related papers MentionsView impact
Acta Materialia, 2011
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FISCHER:FRICTION, WEAR O-BK, 2011
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Surface and Coatings Technology, 1999
Polycrystalline diamond layers were deposited onto the titanium alloy Ti–6Al–4V via microwave pla... more Polycrystalline diamond layers were deposited onto the titanium alloy Ti–6Al–4V via microwave plasma chemical vapor deposition (CVD). It is shown that the diamond film reduces wear and friction immensely compared with uncoated titanium/titanium tribo systems. An additional polishing process of the CVD-diamond layer improves the wear behavior even further. An influence of air humidity is found.In addition, different ceramic materials (Al2O3, SiC, Si3N4, ZrO2) were tested against as-deposited and polished CVD-diamond layers. Al2O3 and Si3N4 exhibit very good wear behavior accompanied by very low friction against as-deposited CVD-diamond. SiC and ZrO2, however, show somewhat inferior wear and friction behavior. Suggestions are made to explain the different performance. Again, a wear increase is found with increasing humidity. Polishing of CVD-diamond layers improves the tribological performance further.
Bookmarks Related papers MentionsView impact
Surface and Coatings Technology, 1999
ABSTRACT The solid-particle erosion resistance of Ti–6Al–4V can be improved significantly by appl... more ABSTRACT The solid-particle erosion resistance of Ti–6Al–4V can be improved significantly by applying a chemical-vapor-deposited diamond coating under conditions where physical-vapor-deposited coated substrates fail. In particular, diamond coatings grown with relatively high methane concentrations (4–10%) in the process gas atmosphere exhibit superior performance. The reason for this behavior is a higher in-plane strength of these coatings due to growth defects like twin formation and secondary nucleation.
Bookmarks Related papers MentionsView impact
Journal of Superhard Materials, 2007
ABSTRACT We designed a new hot-filament plant which features some new operating states for chemic... more ABSTRACT We designed a new hot-filament plant which features some new operating states for chemical vapor infiltration with diamond. Complete infiltration of porous substrates with diamond by using standard hot filament plants is not possible. Chemical vapor infiltration with diamond is limited by the overgrowing diamond layer at the surface primarily caused by high recombination rates of atomic hydrogen on surfaces. As a consequence, the pore mouth is closed before the pore is completely infiltrated (“bottleneck” effect). Porous substrates were infiltrated by using a forced flow through the substrate. In order to achieve good infiltration results, it was necessary to use very low methane concentrations.
Bookmarks Related papers MentionsView impact
14. Symposium Verbundwerkstoffe und Werkstoffverbunde, 2006
Bookmarks Related papers MentionsView impact
... l, D-91058 Erlangen, GermanyAbstractIn contrast to their excellent mechanical properties, tit... more ... l, D-91058 Erlangen, GermanyAbstractIn contrast to their excellent mechanical properties, titaniumalloys possess poor ... The mechanical properties of the titanium are strongly influenced by the processing ... As a result of the hydrogen adsorption, grain coarsening and formation of ...
Bookmarks Related papers MentionsView impact
International Journal of Modern Physics B, 2002
ABSTRACT Diamond materials have become progressively significant in the fabrication of heat sinks... more ABSTRACT Diamond materials have become progressively significant in the fabrication of heat sinks for power devices and lasers. To investigate the influence of polishing on CVD-Diamond, the surfaces of <100> and <110> coatings were analyzed, after a first abrasive treatment on a 30μm diamond grit by scanning thermal microscopy based on a resistive platinum-probe. This technique describes in first order approximation the heat transfer of a metal-diamond interface. Through this method it was possible to diagnose a relevant reduction in thermal conductivity by a harsh sample preparation depending on the crystal orientation. The thermal conductivity of as deposited <100> diamond was measured at 1290 W/mK and was reduced to 250 W/mK. The thermal conductivity of as deposited <110> diamond was determined at 1780 W/mK whereas the same diamond surface, but abraded, shows a thermal conductivity of just 460 W/mK. Additionally the received images which represents the thermal conductivity qualitatively bring forward micro structures like e.g. grain boundaries.
Bookmarks Related papers MentionsView impact
Surface and Coatings Technology, 2007
Bookmarks Related papers MentionsView impact
Surface & Coatings Technology, 2006
Adherent and homogeneous diamond films were deposited on 41Cr4 steel substrates employing chemica... more Adherent and homogeneous diamond films were deposited on 41Cr4 steel substrates employing chemical vapor deposited (CVD) TiBN interlayers. The suitability of CVD-TiBN interlayers for diamond deposition was investigated. The CVD intermediate layers showed excellent barrier properties against the diffusion of iron from the bulk substrate to the surface and against diffusion of carbon from gas phase during diamond deposition. Various
Bookmarks Related papers MentionsView impact
CVD diamond coatings on Ti-6Al-4V substrates were found to be highly effective in reducing fretti... more CVD diamond coatings on Ti-6Al-4V substrates were found to be highly effective in reducing fretting fatigue which, for example, can occur in the root section of aerospace compressor blades. Optimization of a mechanical polishing process leads to significant improvements in the tribological properties of these diamond coatings. This is shown by extremely low wear rates and low coefficients of friction against bearing steel, alumina and diamond. The wear and friction behavior was investigated in a ball-on-disk tribometer and characterized by profilometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman spectroscopy.
Bookmarks Related papers MentionsView impact
Biomedizinische Technik. Biomedical engineering, 1998
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