Effect of layer thickness on thermal properties of multilayer thin films produced by PVD

Cr/CrN/CrAlN, CrN/CrAlN and Cr/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200 °C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also prepared for comparison purposes. The structural and morphological properties of PVD layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS + WDS microanalyses, stresses were determined by the Newton’s rings methods using the Stoney’s equation and surface hardening and hardness profiles were evaluated by micro hardness measurements. The XRD data and HRTEM showed that both the Cr/CrN, CrN/CrAlN and Cr/CrN/CrAlN multilayer coatings exhibited B1NaCl structure with a prominent reflection along (200) plane, and CrAlN sub-layer microstructures composed of nanocrystallites uniformly embedded in an amorphous matrix. The innovation of this work was to use the thickness of three different coating types to determine the thermal properties. Furthermore, an empirical equation was developed for the thermal properties variations with temperature of AISI4140 steel coated with different multilayer coatings. The thermal conductivity of CrAlN single layered was lower than the multilayer and the bulk material AISI4140. Moreover, the influences of structure and composition of the multilayer coatings on the thermal properties are discussed. The thermal conductivity of nanoscale thin film is remarkably lower than that of bulk materials because of its various size effects.The authors wish to thank the Regional Council of Burgundy and EGIDE for their financial support, and also the technical staff of the Arts et Métiers ParisTech of Cluny: especially Romaric Masset and Pierre-Michel Barbier for the samples preparation

Enhanced light emission from improved homogeneity in biaxially suspended Germanium membranes from curvature optimization

A silicon compatible light source is crucial to develop a fully monolithic silicon photonics platform. Strain engineering in suspended Germanium membranes has offered a potential route for such a light source. However, biaxial structures have suffered from poor optical properties due to unfavorable strain distributions. Using a novel geometric approach and finite element modelling (FEM) structures with improved strain homogeneity were designed and fabricated. Micro-Raman (μ-Raman) spectroscopy was used to determine central strain values. Micro-photoluminescence (μ-PL) was used to study the effects of the strain profiles on light emission; we report a PL enhancement of up to 3x by optimizing curvature at a strain value of 0.5% biaxial strain. This geometric approach offers opportunity for enhancing the light emission in Germanium towards developing a practical on chip light source

ADVANCED FRAUD DETECTION IN CARD-BASED FINANCIAL SYSTEMS USING A BIDIRECTIONAL LSTM-GRU ENSEMBLE MODEL

This article addresses the challenges of fraud in card-based financial systems and proposes effective detection and prevention strategies. By leveraging recent data analytics and real-time monitoring, the study aims to enhance transaction security and integrity. The authors review existing fraud detection methodologies, emerging trends, and the evolving tactics of fraudsters, emphasizing the importance of collaboration among financial institutions, regulatory agencies, and technology providers. Our proposed solution is an ensemble model combining Bidirectional Gated Recurrent Unit (BiGRU) and Bidirectional Long Short-Term Memory (BiLSTM) networks, designed to capture complex transactional patterns more effectively. Comparative analysis of six machine learning classifiers—AdaBoost, Naïve Bayes, Decision Tree, Logistic Regression, Random Forest, and Voting—demonstrates that our BiLSTM-BiGRU ensemble model outperforms traditional methods, achieving a fraud detection performance score of 89.22%. This highlights the advanced deep learning model's superior ability to enhance the robustness and reliability of fraud detection systems

Laser shock a novel way to generate calibrated delamination in composites: concept and first results

Structural Health Monitoring (SHM) has been gaining importance in recent years. SHM aims at providing structures with similar functionality as the biological nervous system and it is organized into four main steps: detection, localization, assessment, and prognosis. This paper considers SHM assessment level and more particularly the estimation of the severity of delamination-type damage in Carbon Fiber Reinforced Polymer (CFRP) laminates. Prior to quantification algorithms implementation, it is critical to properly prepare the supports on which algorithms will be tested. Teflon inserts and conventional drop tower impacts are commonly used techniques in the SHM community to generate or simulate delaminations. However with such techniques it is difficult to generate controlled delaminationtype damage in a realistic manner. Conventional impacts do not necessarily induce uniquely delamination-type damage. Teflon inserts still remain very far from representing a realistic delamination. In the present paper we investigate Laser Shock Wave Technique (LSWT), a new way to generate controlled delaminations in composites. In particular, the symmetrical laser shock approach was applied to CFRP laminates in order to generate delamination-type damage in a calibrated and realistic way. A particular attention was paid to the effect of time delay and laser beams energies on damage position and severity respectively. Post-mortem analyses were performed to characterize the induced damage. Results show a high potential of LSWT for damage calibration in both size and location

Effect of layer thickness on thermal properties of multilayer thin films produced by PVD

Cr/CrN/CrAlN, CrN/CrAlN and Cr/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200 °C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also prepared for comparison purposes. The structural and morphological properties of PVD layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS + WDS microanalyses, stresses were determined by the Newton’s rings methods using the Stoney’s equation and surface hardening and hardness profiles were evaluated by micro hardness measurements. The XRD data and HRTEM showed that both the Cr/CrN, CrN/CrAlN and Cr/CrN/CrAlN multilayer coatings exhibited B1NaCl structure with a prominent reflection along (200) plane, and CrAlN sub-layer microstructures composed of nanocrystallites uniformly embedded in an amorphous matrix. The innovation of this work was to use the thickness of three different coating types to determine the thermal properties. Furthermore, an empirical equation was developed for the thermal properties variations with temperature of AISI4140 steel coated with different multilayer coatings. The thermal conductivity of CrAlN single layered was lower than the multilayer and the bulk material AISI4140. Moreover, the influences of structure and composition of the multilayer coatings on the thermal properties are discussed. The thermal conductivity of nanoscale thin film is remarkably lower than that of bulk materials because of its various size effects.The authors wish to thank the Regional Council of Burgundy and EGIDE for their financial support, and also the technical staff of the Arts et Métiers ParisTech of Cluny: especially Romaric Masset and Pierre-Michel Barbier for the samples preparation

Etude des propriétés microstructurales, mécaniques, thermiques et de la porosité des couches minces de CrAlN déposées par PVD sous différents pourcentages d’aluminium

Several experimental investigations have led to the development of CrAlN (Chrome Aluminum Nitride) hard coatings by varying the aluminum target bias voltage, in preference to the traditional CrN coating. The present work enabled characterisation by physical and mechanical techniques (XRD, AFM, MEB, nano-indentation, Young’s modulus, thermal propriety, Stress, porosity, etc.). Moreover, in order to find improved the adhesion of the different deposition condition of the coatings. The results obtained in this work demonstrate that variation in proportion to aluminum alter the resulting columnar morphology and porosity of the coatings. The thermal properties and the physical property are greatly affected by these morphological alterations. The comparison between the different coating microstructures of CrAlN coatings (columnar and fine-grained) reveals advantages for the fine-grained structure. The results are better wear protection and less profile deviation. Correlation between aluminum proportions in CrAlN coatings and his thermal properties revealed that the conductivity and the diffusivity are influenced primarily by size and shape distribution of the pores and secondarily by decrease of the stitch parameter dimension