Martin Andritschky | Universidade do Minho (original) (raw)
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Papers by Martin Andritschky
Solution-based metal oxides have been attracting a lot of attention due to the low cost, high thr... more Solution-based metal oxides have been attracting a lot of attention due to the low cost, high throughput a nd simple chemical composition control when compared with vacuum-based systems. These materials have outst anding properties such as high optical transparency, chemical and thermal stability and mechanical toughness. A lso, facile tailoring of solution-based metal oxides leads to multifunctionality allowing their application in different a reas, like sensing, energy and flexible displays. Particularly for large-area electronics the exploration of a crucial co mponent, the thin film transistor (TFT) and their key materials components, the semiconductor, the dielectric, the conductor as well as substrate are demanded. To boost the implementation of TFTs emerging printing techniques and low thermal budget, novel approaches have been and need to be further explored. This paper focuses on rec ent low temperature approaches as combustion synthesis, ultraviolet post annealing treatmen...
Advanced Multilayered and Fibre-Reinforced Composites, 1998
Yttria stabilized zirconia plasma sprayed coatings (PS top coating) were applied to high temperat... more Yttria stabilized zirconia plasma sprayed coatings (PS top coating) were applied to high temperature Ni-based alloys precoated with a thin, dense stabilized zirconia coating produced by Physical Vapour Deposition (PVD bond coating). In this contribution we analyse the residual stress of a multilayered TBC coating system. The coating residual stress was studied experimentally (by X-ray Diffraction and MicroRaman techniques) and numerically in the thermal barrier multilayered coatings (TBC’s) for the as-deposited coatings and after different thermal cycling processes. The temperature gradients within the duplex PVD and Plasma sprayed coatings during thermal cycling were computed using an unsteady heat transfer model. The stress modelling enables us to calculate the transient thermal stresses using an elasto-plastic biaxial stress model which contributes to a better understanding of the failure modes in TBC’s at high temperature. Stress measurements showed that the residual stress in the as-deposited top coating changed from tensile to compressive with increasing substrate temperature. After thermal cycling at high temperature, due to relaxation processes, the coating develops a higher compressive stress on cooling down to room temperature. The residual stress measurements were in good agreement with numerical calculations.
Vacuum, 2008
ESD/EMI shielding coatings based on Cu layers on plastic can be produced very effectively by sput... more ESD/EMI shielding coatings based on Cu layers on plastic can be produced very effectively by sputtering. Certain principles have to be followed to obtain an adequate result in mass production. Coating speed (productivity), outgassing and plastic thickness are factors, which are interrelated. The correlation between these three factors will influence the final product, a metal coating with a defined resistance between two measuring points. Typical values for these factors were sputtering at an Ar partial pressure of 1.1 Â 10 À3 mbar to produce a Cu layer with a specific resistivity of about 1.5 Â 10 À7 Um at a production speed of one plastic part/s. The plastic temperature due to the heating intrinsic to sputter deposition of metals, reached about 84 C at the thinnest areas of the plastic substrate. Coating adhesion does not take part of the correlation of production conditions and achieved coating quality and production speed. Sputter deposition will produce a well adherent Cu coating on almost any clean plastic material.
Applied Surface Science, 1993
TiO2 films have been deposited on glass substrates (75 × 25 mm2) by DC reactive magnetron sputter... more TiO2 films have been deposited on glass substrates (75 × 25 mm2) by DC reactive magnetron sputtering from a pure 99.6% titanium plate of 100 × 100 mm2. During the sputtering process, the oxygen partial and total pressure were 6 × 10-4 and 8 × 10-3 mbar, respectively. The substrate temperature varied from ambient to 500°C. The results of X-ray diffraction show that all films have a anatase crystal structure. The film deposited at ambient has a (101) preferred orientation. With an increase in the substrate temperature, the films tend towards a random orientation. When the substrate temperature is higher than 450°C, the film again has a preferred orientation. However, the preferred orientation is not (101) but (004). As the substrate temperature is varied, the optical properties (refractive index, optical band gap and extinction coefficient) of TiO2 films also change significantly.
It is reported the design, deposition and performance of a multilayer coating for selective absor... more It is reported the design, deposition and performance of a multilayer coating for selective absorption of solar radiation. The optical stacks consist of four layers, a metallic tungsten (W) layer as back reflector, a double AlSiO x :W cermet layers and a AlSiO x layer, as antireflection (AR) layer. The spectral optical constants of a set of the single layers were calculated from the reflectance and transmittance measurements and used to design the optical stack. The coatings were deposited on stainless steel substrates by magnetron sputtering.The X-Ray diffractograms of AlSiO x :W layers show a broad peak around 2θ=40o, which could be assigned to (110) planes of bcc W lattice. The intensity of the broad peak increased with tungsten volume fraction (f), but the FWHM of about 7o, indicates that both, W and AlSiO x , are amorphous. The Chemical analysis was performed using X-ray photoelectron spectroscopy (XPS) and the results show that in the high metal volume fraction AlSiO x :W cerm...
ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high tempera... more ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high temperature Ni-based alloys precoated by Physical Vapor Deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by Atmospheric Plasma Spraying (APS) and Inert gas Plasma Spraying (IPS at 2 bar) for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1,000 C and 1,150 C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables the authors to calculate the transient thermal strains and stresses which contribute to a better understanding of the failure mechanisms of the TBC during thermal cycling. They have also studied experimentally the adherence and failure modes of these coating systems during this hig...
Advanced Multilayered and Fibre-Reinforced Composites, 1998
The present contribution involves numerical modelling of the residual stress distribution within ... more The present contribution involves numerical modelling of the residual stress distribution within a multilayered coating system which consists of a functionally gradient material (FGM). The structure of the graded system is made of a ceramic layer and a metallic layer, where between them there is an interlayer which is a graded composite made of the metal and ceramic. The composition changes gradually from 0% ceramic to 100% ceramic. This graded composite interlayer was modelled as a serie of perfectly bonded finite thin layers, each having slightly different material properties. We analyse the FGM design with respect to thermal stress optimization (e.g. reduction of the interfacial stresses). The case of a bilayer, thick ceramic coating on a metallic substrate and a graded thermal barrier coating (TBC) is considered. The effects on thermal residual stress gradients of the compositional profiles and graded interlayer thickness were studied. This FGM stress model enables us to calculate the thermal strain and stress distributions, which contributes to a better understanding of the failure of a graded coating system and is, therefore, a potential tool for FGM stress optimization to improve the thermo-mechanical stability of multilayer graded structures such as high temperature ceramic coatings for use in thermal barrier applications.
Applied Surface Science, 2015
Coatings with a double absorbing layer based on AlSiN/AlSiON were deposited on stainless steel su... more Coatings with a double absorbing layer based on AlSiN/AlSiON were deposited on stainless steel substrates by magnetron sputtering technique, with different Al:Si ratios. A tungsten layer was used as a back reflector and AlSiO y or SiO x thin films were used as antireflection top layers. Prior the structure design, several single layers were deposited on glass substrates by varying the reactive gases flows, which allowed the stacking of a series of layers with different optical properties. Experimental transmittance and reflectance were modelled for the assessment of the spectral optical constants, which were then used to design a coating stack with optimized solar absorptance and thermal emittance. Optical properties, microstructure, morphology, composition and chemical bonding were investigated by employing optical spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The samples were annealed in air at 400 • C and vacuum at 580 • C with the purpose to evaluate their oxidation resistance and thermal stability, which was subsequently correlated with the Al:Si ratio. Optimum results were achieved for an Al:Si ratio of 2.3:1, whereas for significantly higher Si content resulted in detrimental performance. The solar absorbance and thermal emittance for the optimized multilayer selective coatings is 93-94% and 7-10% (at 400 • C), respectively.
Materials
The present work aims to study the impact of O and N addition on Cr-sputtered coatings on plastic... more The present work aims to study the impact of O and N addition on Cr-sputtered coatings on plastic (polycarbonate, PC) used in automobile parts, as a promisor alternative for auto part metallization, while eliminating the usage of toxic hexavalent chromium. The coatings were deposited using DC magnetron sputtering from a single pure Cr target in a reactive atmosphere (N2 and/or O2). The deposition of the coatings was performed maintaining the total pressure constant and close to 1 Pa by tuning Ar pressure while reactive gases were added. The target current density was kept at JW = 20 mA·cm−2. Structural characterization revealed a mixture of α-Cr, δ-Cr, β-Cr2N, and CrN crystalline structures as well as amorphous oxides. The coating hardness ranged from 9 GPa for the CrON coating to 15 GPa for the CrN coating. All deposited coatings showed a particularly good interface adhesion; adjusting the amount of O and N made it possible to tune the optical properties of the Cr-based coatings as...
Optics & Laser Technology
AIP Conference Proceedings, 1990
ABSTRACT
AIP Conference Proceedings, 1988
Materials Science Forum, 1999
ABSTRACT
The International Journal of Applied Radiation and Isotopes, 1985
ABSTRACT
Proceedings of the 1989 IEEE Particle Accelerator Conference, . 'Accelerator Science and Technology, 1989
Solution-based metal oxides have been attracting a lot of attention due to the low cost, high thr... more Solution-based metal oxides have been attracting a lot of attention due to the low cost, high throughput a nd simple chemical composition control when compared with vacuum-based systems. These materials have outst anding properties such as high optical transparency, chemical and thermal stability and mechanical toughness. A lso, facile tailoring of solution-based metal oxides leads to multifunctionality allowing their application in different a reas, like sensing, energy and flexible displays. Particularly for large-area electronics the exploration of a crucial co mponent, the thin film transistor (TFT) and their key materials components, the semiconductor, the dielectric, the conductor as well as substrate are demanded. To boost the implementation of TFTs emerging printing techniques and low thermal budget, novel approaches have been and need to be further explored. This paper focuses on rec ent low temperature approaches as combustion synthesis, ultraviolet post annealing treatmen...
Advanced Multilayered and Fibre-Reinforced Composites, 1998
Yttria stabilized zirconia plasma sprayed coatings (PS top coating) were applied to high temperat... more Yttria stabilized zirconia plasma sprayed coatings (PS top coating) were applied to high temperature Ni-based alloys precoated with a thin, dense stabilized zirconia coating produced by Physical Vapour Deposition (PVD bond coating). In this contribution we analyse the residual stress of a multilayered TBC coating system. The coating residual stress was studied experimentally (by X-ray Diffraction and MicroRaman techniques) and numerically in the thermal barrier multilayered coatings (TBC’s) for the as-deposited coatings and after different thermal cycling processes. The temperature gradients within the duplex PVD and Plasma sprayed coatings during thermal cycling were computed using an unsteady heat transfer model. The stress modelling enables us to calculate the transient thermal stresses using an elasto-plastic biaxial stress model which contributes to a better understanding of the failure modes in TBC’s at high temperature. Stress measurements showed that the residual stress in the as-deposited top coating changed from tensile to compressive with increasing substrate temperature. After thermal cycling at high temperature, due to relaxation processes, the coating develops a higher compressive stress on cooling down to room temperature. The residual stress measurements were in good agreement with numerical calculations.
Vacuum, 2008
ESD/EMI shielding coatings based on Cu layers on plastic can be produced very effectively by sput... more ESD/EMI shielding coatings based on Cu layers on plastic can be produced very effectively by sputtering. Certain principles have to be followed to obtain an adequate result in mass production. Coating speed (productivity), outgassing and plastic thickness are factors, which are interrelated. The correlation between these three factors will influence the final product, a metal coating with a defined resistance between two measuring points. Typical values for these factors were sputtering at an Ar partial pressure of 1.1 Â 10 À3 mbar to produce a Cu layer with a specific resistivity of about 1.5 Â 10 À7 Um at a production speed of one plastic part/s. The plastic temperature due to the heating intrinsic to sputter deposition of metals, reached about 84 C at the thinnest areas of the plastic substrate. Coating adhesion does not take part of the correlation of production conditions and achieved coating quality and production speed. Sputter deposition will produce a well adherent Cu coating on almost any clean plastic material.
Applied Surface Science, 1993
TiO2 films have been deposited on glass substrates (75 × 25 mm2) by DC reactive magnetron sputter... more TiO2 films have been deposited on glass substrates (75 × 25 mm2) by DC reactive magnetron sputtering from a pure 99.6% titanium plate of 100 × 100 mm2. During the sputtering process, the oxygen partial and total pressure were 6 × 10-4 and 8 × 10-3 mbar, respectively. The substrate temperature varied from ambient to 500°C. The results of X-ray diffraction show that all films have a anatase crystal structure. The film deposited at ambient has a (101) preferred orientation. With an increase in the substrate temperature, the films tend towards a random orientation. When the substrate temperature is higher than 450°C, the film again has a preferred orientation. However, the preferred orientation is not (101) but (004). As the substrate temperature is varied, the optical properties (refractive index, optical band gap and extinction coefficient) of TiO2 films also change significantly.
It is reported the design, deposition and performance of a multilayer coating for selective absor... more It is reported the design, deposition and performance of a multilayer coating for selective absorption of solar radiation. The optical stacks consist of four layers, a metallic tungsten (W) layer as back reflector, a double AlSiO x :W cermet layers and a AlSiO x layer, as antireflection (AR) layer. The spectral optical constants of a set of the single layers were calculated from the reflectance and transmittance measurements and used to design the optical stack. The coatings were deposited on stainless steel substrates by magnetron sputtering.The X-Ray diffractograms of AlSiO x :W layers show a broad peak around 2θ=40o, which could be assigned to (110) planes of bcc W lattice. The intensity of the broad peak increased with tungsten volume fraction (f), but the FWHM of about 7o, indicates that both, W and AlSiO x , are amorphous. The Chemical analysis was performed using X-ray photoelectron spectroscopy (XPS) and the results show that in the high metal volume fraction AlSiO x :W cerm...
ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high tempera... more ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high temperature Ni-based alloys precoated by Physical Vapor Deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by Atmospheric Plasma Spraying (APS) and Inert gas Plasma Spraying (IPS at 2 bar) for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1,000 C and 1,150 C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables the authors to calculate the transient thermal strains and stresses which contribute to a better understanding of the failure mechanisms of the TBC during thermal cycling. They have also studied experimentally the adherence and failure modes of these coating systems during this hig...
Advanced Multilayered and Fibre-Reinforced Composites, 1998
The present contribution involves numerical modelling of the residual stress distribution within ... more The present contribution involves numerical modelling of the residual stress distribution within a multilayered coating system which consists of a functionally gradient material (FGM). The structure of the graded system is made of a ceramic layer and a metallic layer, where between them there is an interlayer which is a graded composite made of the metal and ceramic. The composition changes gradually from 0% ceramic to 100% ceramic. This graded composite interlayer was modelled as a serie of perfectly bonded finite thin layers, each having slightly different material properties. We analyse the FGM design with respect to thermal stress optimization (e.g. reduction of the interfacial stresses). The case of a bilayer, thick ceramic coating on a metallic substrate and a graded thermal barrier coating (TBC) is considered. The effects on thermal residual stress gradients of the compositional profiles and graded interlayer thickness were studied. This FGM stress model enables us to calculate the thermal strain and stress distributions, which contributes to a better understanding of the failure of a graded coating system and is, therefore, a potential tool for FGM stress optimization to improve the thermo-mechanical stability of multilayer graded structures such as high temperature ceramic coatings for use in thermal barrier applications.
Applied Surface Science, 2015
Coatings with a double absorbing layer based on AlSiN/AlSiON were deposited on stainless steel su... more Coatings with a double absorbing layer based on AlSiN/AlSiON were deposited on stainless steel substrates by magnetron sputtering technique, with different Al:Si ratios. A tungsten layer was used as a back reflector and AlSiO y or SiO x thin films were used as antireflection top layers. Prior the structure design, several single layers were deposited on glass substrates by varying the reactive gases flows, which allowed the stacking of a series of layers with different optical properties. Experimental transmittance and reflectance were modelled for the assessment of the spectral optical constants, which were then used to design a coating stack with optimized solar absorptance and thermal emittance. Optical properties, microstructure, morphology, composition and chemical bonding were investigated by employing optical spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The samples were annealed in air at 400 • C and vacuum at 580 • C with the purpose to evaluate their oxidation resistance and thermal stability, which was subsequently correlated with the Al:Si ratio. Optimum results were achieved for an Al:Si ratio of 2.3:1, whereas for significantly higher Si content resulted in detrimental performance. The solar absorbance and thermal emittance for the optimized multilayer selective coatings is 93-94% and 7-10% (at 400 • C), respectively.
Materials
The present work aims to study the impact of O and N addition on Cr-sputtered coatings on plastic... more The present work aims to study the impact of O and N addition on Cr-sputtered coatings on plastic (polycarbonate, PC) used in automobile parts, as a promisor alternative for auto part metallization, while eliminating the usage of toxic hexavalent chromium. The coatings were deposited using DC magnetron sputtering from a single pure Cr target in a reactive atmosphere (N2 and/or O2). The deposition of the coatings was performed maintaining the total pressure constant and close to 1 Pa by tuning Ar pressure while reactive gases were added. The target current density was kept at JW = 20 mA·cm−2. Structural characterization revealed a mixture of α-Cr, δ-Cr, β-Cr2N, and CrN crystalline structures as well as amorphous oxides. The coating hardness ranged from 9 GPa for the CrON coating to 15 GPa for the CrN coating. All deposited coatings showed a particularly good interface adhesion; adjusting the amount of O and N made it possible to tune the optical properties of the Cr-based coatings as...
Optics & Laser Technology
AIP Conference Proceedings, 1990
ABSTRACT
AIP Conference Proceedings, 1988
Materials Science Forum, 1999
ABSTRACT
The International Journal of Applied Radiation and Isotopes, 1985
ABSTRACT
Proceedings of the 1989 IEEE Particle Accelerator Conference, . 'Accelerator Science and Technology, 1989