Fonctionnalisation de barrières thermiques aéronautiques YSZ issues de la voie sol-gel : mesure de température et diagnostic de l'endommagement par fluorescence

The aim of this work is to develop and study yttria stabilised zirconia (ZrO2 + 9.8at% Y2O3, YSZ) based thermal barrier coating (TBC) « sensor » systems deposited by a dip coating sol-gel process, and dedicated to temperature measurement and to the monitoring of damaging occuring within the thickness of the coatings, using fluorescence thermometry methods. These methods are based on the monitoring of the fluorescence properties of photoluminescent activators from the trivalent lanthanide ions group (Ln3+), such as samarium Sm3+, europium Eu3+, dysprosium Dy3+, erbium Er3+ and thulium Tm3+. These activators are directly incorporated into the zirconia YSZ host matrix lattice, which is semi-transparent at their emission wavelengths mainly falling in the visible range. An experimental set up was especially developped for the application of these methods. The characterisation of the different YSZ:Ln3+ powders synthesized by a sol-gel process allowed to optimise the compositions, and thus maximize the fluorescence signal intensity while avoidind any alteration of the zirconia crystal structure required from for a TBC material. The sol-gel dip coating process allowed to deposit functionalised multilayer TBC prototypes integrating up to three fluorescent layers with distinct emission wavelengths distributed throughout the thickness. Such coating architectures allow, with the fluorescence thermometry methods identified, to optically probe the coating across the whole thickness for future applications aiming to determine the thermal gradient in TBCs. Functionalised TBCs containing pre-calibrated delamination defects at the metal/ceramic interface were also used to compare the interest of the reflectance enhanced fluorescence method and an IR thermography method for early monitoring of TBC spallation. At last, the potential offered by YSZ:Ln3+ powders as thermal history sensors alternative to temperature sensitive paints was also investigated.L'objectif de la thèse est de développer des systèmes de Barrières Thermiques (BT) « capteurs » base zircone yttriée (ZrO2 + 9.8mol% Y2O3, YSZ) déposés par voie sol-gel selon un procédé de trempage-retrait. Ceux-ci sont dédiés à la mesure de la température par des méthodes de thermométrie par fluorescence et au suivi de l'endommagement dans l'épaisseur des revêtements. Les méthodes proposées sont basées sur le suivi de l'évolution, notamment avec la température, des propriétés de photoluminescence de marqueurs fluorescents lanthanides Ln3+, tels que l'europium Eu3+, le dysprosium Dy3+, l'erbium Er3+, le samarium Sm3+ ou encore le thulium Tm3+. Ceux-ci sont directement incorporés dans la structure de la zircone, semi-transparente dans le domaine d'émission visible de ces marqueurs. Un banc de mesure des propriétés de fluorescence (spectres, intensités et temps de vie) a spécifiquement été développé dans ce but. La caractérisation des différents couples YSZ:Ln3+ sous forme de poudres synthétisées par voie sol-gel a permis d'optimiser les compositions de manière à maximiser l'intensité du signal de fluorescence tout en préservant les propriétés microstructurales requises pour une BT. Les dépôts sol-gel réalisés par trempage-retrait permettent la fabrication de prototypes de BT multicouches fonctionnalisées intégrant jusqu'à trois couches fluorescentes de longueurs d'onde d'émission distinctes. De tels systèmes architecturés permettent de sonder optiquement la totalité de l'épaisseur de zircone déposée pour de futures applications visant à évaluer les gradients thermiques siégeant dans le volume des revêtements. Des BT fonctionnalisées contenant des défauts de délamination pré-calibrés à l'interface métal/céramique ont été également utilisées pour comparer l'intérêt d'une méthode de fluorescence accrue par réflectance et d'une méthode de thermographie infrarouge pour le suivi et l'évaluation des processus d'endommagement précurseurs de l'écaillage. Enfin, le potentiel qu'offrent les poudres de zircone YSZ:Ln3+ dopées en tant que marqueurs fluorescents de l'histoire thermique, alternatifs aux peintures thermiques utilisées industriellement, a aussi été analysé

Feasibility of luminescent multilayer sol-gel thermal barrier coating manufacturing for future applications in through-thickness temperature gradient sensing

This paper investigates the feasibility of manufacturing sol-gel multilayer thermal barrier coatings (TBC) functionalized with different lanthanide ions Ln3 + having distinct photo-luminescence emission wavelengths (Ln = Sm, Eu, Dy, Er, Tm) for future applications in temperature gradient sensing. Ln3 + doped 9.75 mol% yttria stabilized zirconia (YSZ) powders were produced to study the effect of activator concentration on luminescence intensity and host matrix crystal structure. Self-quenching was found to limit the maximum signal-to-noise ratio achievable with Sm3 +, Dy3 +, Er3 + and Tm3 + activators, which was not the case for Eu3 + in the 1–10 mol% range. The increase in activator was found to affect the crystal structure of YSZ. A solution was proposed that suppressed this effect while significantly increasing the luminescence intensity of all activators. Finally a TBC sensor prototype integrating Eu3 +, Er3 + and Dy3 + doped layers distributed throughout the thickness was successfully deposited by a dip-coating sol-gel process and showed promising through-thickness luminescence sensing capabilities

Apparent Interfacial Toughness of Undoped and Photoluminescent Eu3+-Doped Yttria-Stabilized Zirconia Thermal Barrier Coatings

Most photoluminescence methods for the diagnostic of thermal barrier coatings (TBC) rely on the functionalization of yttria-stabilized zirconia (YSZ) with trivalent lanthanide ions. It consists in determining temperature and detecting preventively damages within the volume of the TBC prior to ceramic topcoat spallation. The latter depends on the interfacial toughness, which is an important factor to address thermal barrier coating’s performance and durability. In this paper, the influence of the addition of rare earth elements (Eu3+) on the interfacial toughness of TBC deposited by atmospheric plasma spray is investigated. Two types of coatings are deposited and investigated: (1) Type I: coating deposited using Eu3+-doped YSZ powder (2 mol.%), (2) Type II: coating deposited using undoped YSZ powder. Both types of coatings are heat-treated at 1100 °C under isothermal conditions using different oxidation exposure times: 100, 300 and 800 h. The morphology of the interface between the topcoat (TBC) and the bond coat is analyzed by scanning electron microscopy. The apparent interfacial toughness is investigated using indentation. It is shown that the interfacial apparent toughness decreases as the oxidation exposure time increases. Concomitantly, the thickness of the thermally grown oxide (TGO) layer between the bond coat and the topcoat increases. Results show as well that the partial substitution of Y3+ ions by a low amount of Eu3+ ions (2 mol.%) does not have influence on the microstructure and the interfacial toughness of the YSZ coatings. In addition, energy dispersive spectrometry reveals that there is no diffusion of Eu3+ into the TGO layer. It is therefore concluded that the use of Eu3+ for damage diagnostic based on photoluminescence methods will not induce any kind of degradation of the properties of TBCs

Epigenetic prediction of response to anti-PD-1 treatment in non-small-cell lung cancer: a multicenter, retrospective analysis

Background: Anti-programmed death-1 (PD-1) treatment for advanced non-small-cell lung cancer (NSCLC) has improved the survival of patients. However, a substantial percentage of patients do not respond to this treatment. We examined the use of DNA methylation profiles to determine the efficacy of anti-PD-1 treatment in patients recruited with current stage IV NSCLC. Methods: In this multicentre study, we recruited adult patients from 15 hospitals in France, Spain, and Italy who had histologically proven stage IV NSCLC and had been exposed to PD-1 blockade during the course of the disease. The study structure comprised a discovery cohort to assess the correlation between epigenetic features and clinical benefit with PD-1 blockade and two validation cohorts to assess the validity of our assumptions. We first established an epigenomic profile based on a microarray DNA methylation signature (EPIMMUNE) in a discovery set of tumour samples from patients treated with nivolumab or pembrolizumab. The EPIMMUNE signature was validated in an independent set of patients. A derived DNA methylation marker was validated by a single-methylation assay in a validation cohort of patients. The main study outcomes were progression-free survival and overall survival. We used the Kaplan-Meier method to estimate progression-free and overall survival, and calculated the differences between the groups with the log-rank test. We constructed a multivariate Cox model to identify the variables independently associated with progression-free and overall survival. Findings: Between June 23, 2014, and May 18, 2017, we obtained samples from 142 patients: 34 in the discovery cohort, 47 in the EPIMMUNE validation cohort, and 61 in the derived methylation marker cohort (the T-cell differentiation factor forkhead box P1 [FOXP1]). The EPIMMUNE signature in patients with stage IV NSCLC treated with anti-PD-1 agents was associated with improved progression-free survival (hazard ratio [HR] 0·010, 95% CI 3·29 × 10 −4–0·0282; p=0·0067) and overall survival (0·080, 0·017–0·373; p=0·0012). The EPIMMUNE-positive signature was not associated with PD-L1 expression, the presence of CD8+ cells, or mutational load. EPIMMUNE-negative tumours were enriched in tumour-associated macrophages and neutrophils, cancer-associated fibroblasts, and senescent endothelial cells. The EPIMMUNE-positive signature was associated with improved progression-free survival in the EPIMMUNE validation cohort (0·330, 0·149–0·727; p=0·0064). The unmethylated status of FOXP1 was associated with improved progression-free survival (0·415, 0·209–0·802; p=0·0063) and overall survival (0·409, 0·220–0·780; p=0·0094) in the FOXP1 validation cohort. The EPIMMUNE signature and unmethylated FOXP1 were not associated with clinical benefit in lung tumours that did not receive immunotherapy. Interpretation: Our study shows that the epigenetic milieu of NSCLC tumours indicates which patients are most likely to benefit from nivolumab or pembrolizumab treatments. The methylation status of FOXP1 could be associated with validated predictive biomarkers such as PD-L1 staining and mutational load to better select patients who will experience clinical benefit with PD-1 blockade, and its predictive value should be evaluated in prospective studies

Functionalisation of thermal barrier coatings synthesized by a sol-gel route : temperature measurement and damage monitoring by fluorescence methods

L'objectif de la thèse est de développer des systèmes de Barrières Thermiques (BT) « capteurs » base zircone yttriée (ZrO2 + 9.8mol% Y2O3, YSZ) déposés par voie sol-gel selon un procédé de trempage-retrait. Ceux-ci sont dédiés à la mesure de la température par des méthodes de thermométrie par fluorescence et au suivi de l'endommagement dans l'épaisseur des revêtements. Les méthodes proposées sont basées sur le suivi de l'évolution, notamment avec la température, des propriétés de photoluminescence de marqueurs fluorescents lanthanides Ln3+, tels que l'europium Eu3+, le dysprosium Dy3+, l'erbium Er3+, le samarium Sm3+ ou encore le thulium Tm3+. Ceux-ci sont directement incorporés dans la structure de la zircone, semi-transparente dans le domaine d'émission visible de ces marqueurs. Un banc de mesure des propriétés de fluorescence (spectres, intensités et temps de vie) a spécifiquement été développé dans ce but. La caractérisation des différents couples YSZ:Ln3+ sous forme de poudres synthétisées par voie sol-gel a permis d'optimiser les compositions de manière à maximiser l'intensité du signal de fluorescence tout en préservant les propriétés microstructurales requises pour une BT. Les dépôts sol-gel réalisés par trempage-retrait permettent la fabrication de prototypes de BT multicouches fonctionnalisées intégrant jusqu'à trois couches fluorescentes de longueurs d'onde d'émission distinctes. De tels systèmes architecturés permettent de sonder optiquement la totalité de l'épaisseur de zircone déposée pour de futures applications visant à évaluer les gradients thermiques siégeant dans le volume des revêtements. Des BT fonctionnalisées contenant des défauts de délamination pré-calibrés à l'interface métal/céramique ont été également utilisées pour comparer l'intérêt d'une méthode de fluorescence accrue par réflectance et d'une méthode de thermographie infrarouge pour le suivi et l'évaluation des processus d'endommagement précurseurs de l'écaillage. Enfin, le potentiel qu'offrent les poudres de zircone YSZ:Ln3+ dopées en tant que marqueurs fluorescents de l'histoire thermique, alternatifs aux peintures thermiques utilisées industriellement, a aussi été analysé.The aim of this work is to develop and study yttria stabilised zirconia (ZrO2 + 9.8at% Y2O3, YSZ) based thermal barrier coating (TBC) « sensor » systems deposited by a dip coating sol-gel process, and dedicated to temperature measurement and to the monitoring of damaging occuring within the thickness of the coatings, using fluorescence thermometry methods. These methods are based on the monitoring of the fluorescence properties of photoluminescent activators from the trivalent lanthanide ions group (Ln3+), such as samarium Sm3+, europium Eu3+, dysprosium Dy3+, erbium Er3+ and thulium Tm3+. These activators are directly incorporated into the zirconia YSZ host matrix lattice, which is semi-transparent at their emission wavelengths mainly falling in the visible range. An experimental set up was especially developped for the application of these methods. The characterisation of the different YSZ:Ln3+ powders synthesized by a sol-gel process allowed to optimise the compositions, and thus maximize the fluorescence signal intensity while avoidind any alteration of the zirconia crystal structure required from for a TBC material. The sol-gel dip coating process allowed to deposit functionalised multilayer TBC prototypes integrating up to three fluorescent layers with distinct emission wavelengths distributed throughout the thickness. Such coating architectures allow, with the fluorescence thermometry methods identified, to optically probe the coating across the whole thickness for future applications aiming to determine the thermal gradient in TBCs. Functionalised TBCs containing pre-calibrated delamination defects at the metal/ceramic interface were also used to compare the interest of the reflectance enhanced fluorescence method and an IR thermography method for early monitoring of TBC spallation. At last, the potential offered by YSZ:Ln3+ powders as thermal history sensors alternative to temperature sensitive paints was also investigated

Thermosensitive coating dedicated to smart TPS for very high temperature - 850 °C to 1650°C

International audienceThis paper presents the recent development of a new thermosensitive coating and its associated reading device, which allows to determine thermal history in the 850°C- 1650°C temperature range, providing access to a new easy way to detect hot spot on smart Thermal Protection System with a much better thermal resolution than commercially available thermochromic paints. This technology is suitable to be rapidly integrated on re-usable launcher or vehicle parts as a paint on the thermostructural surfaces or inside small machined cavities. A new device dedicated to detection of overheated zones in the overall range of temperatures achieved in the whole Thermal Protection System (from CMCs to Metallics) is presented, thus promising a considerable reduction in the effort required for post-flight inspection

Fonctionnalisation de barrières thermiques sol-gel YSZ pour la mesure de température et le CND par fluorescence

International audienc

Fonctionnalisation de barrières thermiques sol-gel YSZ pour la mesure de température et le CND par fluorescence

International audienc

Correlation between microstructure heterogeneity and multi-scale mechanical behavior of hybrid LPBF-DED Inconel 625

International audienceThe two additive manufacturing processes Powder Bed Fusion (LPBF) and Directed Energy Deposition (DED) have different geometrical resolutions and production flexibilities, making their hybridization attractive. LPBF microstructure displays fine grains, with weak preferential crystal orientation. DED generates a highly textured and inhomogeneous microstructure with equivalent grains diameters ranging from a few micrometers to over a millimeter. The microstructure of the hybrid LPBF-DED sample is the addition of these two microstructures with an interface free from cracks or particular pores. The effect of this strong heterogeneity of the hybrid microstructure on mechanical behavior is analyzed by tensile tests instrumented with local strain gauges, others using digital image correlation method and finally on samples tested inside a scanning electron microscope. This multi-scale characterization showed that the difference in the elastic properties causes the localization of the strain field and generates a plastic incompatibility at the interface. An optimized heat treatment leads to isotropic and homogeneous hybrid microstructure, with a larger DED grain size. It leads to identical plasticity mechanisms during tensile tests and lowers the strain gradient around the interface

Modelling and characterization of novel honeycomb structures with mass gradient produced by additive manufacturing

International audienceThe dissemination of additive manufacturing methods has facilitated the design and production of complex structures which have a high strength-to-weight ratio. Cellular materials such as honeycombs have low-weight and high capacity to absorb energy which makes them desirable for the aerospace and automotive industries. The present work covers the study and comparison of metal-based regular honeycombs and functionally graded honeycombs. The latter encompass radial and linear/longitudinal gradients. Three repeating unit cells were studied: regular hexagons, Plateau and lotus. The structures were produced in aluminium using the laser powder bed fusion technique. Selected samples were submitted to a stress-relieving heat treatment. Numerical and experimental methods were used to assess the in-plane compressive properties. Finite element analysis was used to obtain the simulated force–displacement curves of each structure, allowing for the calculation of specific stiffness, absorbed energy and yield strength. The experimental method consisted of the compression of three specimens of three types of regular structures with and without stress-relieving heat treatment. The heat treatment reduced the yield strength and stiffness whilst increasing the ductility of the samples. The mechanical behaviour of the structures was found to depend upon a combined effect of the type of gradient, relative density, and unit cell structure. The results showed that an increase in the relative density would enhance the specific mechanical properties. The lotus configuration displayed the highest specific mechanical properties, as its geometry reduces the stress concentrations. The numerical results showed a reasonable match with the experimental results