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Author: Abdeslem Hafidi
Publisher:
ISBN:
Category :
Languages : fr
Pages : 154
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Book Description
Le nitrure d'aluminium suscite à l'heure actuelle un gros intérêt en microélectronique pour ses possibilités d'emploi comme substrat isolant de forte conductivité thermique en remplacement de l'alumine. Dans ce travail, nous avons porte notre effort sur une approche fondamentale visant une meilleure compréhension des phénomènes régissant la conductivité thermique des céramiques a base de nitrure d'aluminium. Il existe une corrélation linéaire négative entre la diffusivité et la teneur en oxygène de la poudre de départ utilisée. La diffusivité thermique est très sensible à la moindre porosité, une décroissance de l'ordre de 30 à 40% étant observée pour une porosité pourtant minime de 0,5%. L'influence de la nature et de la quantité d'ajouts de densification a été mise en évidence. Quel que soit l'ajout, on note une réduction de la diffusivité en présence de faibles teneurs en ajouts par suite de la formation d'aluminates peu conducteurs. En présence de y203 ou de ce02, le comportement est très diffèrent en raison d'un optimum de diffusivité pour une teneur de 7 à 8%. Un tel phénomène s'observant aussi sur des frittes avec Cao obtenus en abaissant la température de frittage pour réduire la fluidité des phases secondaires. On en conclut a l'influence prédominante de la microstructure. C'est ce que confirme l'étude d'analyse d'images que nous avons effectuée sur des microstructures obtenues en microscopie électronique a balayage, la phase secondaire se concentre aux points triples et a des zones particulières de la microstructure pour des teneurs correspondant a un maximum de la diffusivité thermique.
Author: Abdeslem Hafidi
Publisher:
ISBN:
Category :
Languages : fr
Pages : 154
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Book Description
Le nitrure d'aluminium suscite à l'heure actuelle un gros intérêt en microélectronique pour ses possibilités d'emploi comme substrat isolant de forte conductivité thermique en remplacement de l'alumine. Dans ce travail, nous avons porte notre effort sur une approche fondamentale visant une meilleure compréhension des phénomènes régissant la conductivité thermique des céramiques a base de nitrure d'aluminium. Il existe une corrélation linéaire négative entre la diffusivité et la teneur en oxygène de la poudre de départ utilisée. La diffusivité thermique est très sensible à la moindre porosité, une décroissance de l'ordre de 30 à 40% étant observée pour une porosité pourtant minime de 0,5%. L'influence de la nature et de la quantité d'ajouts de densification a été mise en évidence. Quel que soit l'ajout, on note une réduction de la diffusivité en présence de faibles teneurs en ajouts par suite de la formation d'aluminates peu conducteurs. En présence de y203 ou de ce02, le comportement est très diffèrent en raison d'un optimum de diffusivité pour une teneur de 7 à 8%. Un tel phénomène s'observant aussi sur des frittes avec Cao obtenus en abaissant la température de frittage pour réduire la fluidité des phases secondaires. On en conclut a l'influence prédominante de la microstructure. C'est ce que confirme l'étude d'analyse d'images que nous avons effectuée sur des microstructures obtenues en microscopie électronique a balayage, la phase secondaire se concentre aux points triples et a des zones particulières de la microstructure pour des teneurs correspondant a un maximum de la diffusivité thermique.
Author: Gilbert Brandy
Publisher:
ISBN:
Category :
Languages : fr
Pages : 96
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Book Description
Author: Agnes Buka
Publisher: World Scientific
ISBN: 1848167997
Category : Science
Languages : en
Pages : 299
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Book Description
The book intends to give a state-of-the-art overview of flexoelectricity, a linear physical coupling between mechanical (orientational) deformations and electric polarization, which is specific to systems with orientational order, such as liquid crystals. Chapters written by experts in the field shed light on theoretical as well as experimental aspects of research carried out since the discovery of flexoelectricity. Besides a common macroscopic (continuum) description the microscopic theory of flexoelectricity is also addressed. Electro-optic effects due to or modified by flexoelectricity as well as various (direct and indirect) measurement methods are discussed. Special emphasis is given to the role of flexoelectricity in pattern-forming instabilities. While the main focus of the book lies in flexoelectricity in nematic liquid crystals, peculiarities of other mesophases (bent-core systems, cholesterics, and smectics) are also reviewed. Flexoelectricity has relevance to biological (living) systems and can also offer possibilities for technical applications. The basics of these two interdisciplinary fields are also summarized.
Author: International Atomic Energy Agency
Publisher: International Atomic Energy Agency
ISBN: 9789201063205
Category : Technology & Engineering
Languages : en
Pages : 72
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Book Description
This publication results from a technical meeting on phenomenology and technologies relevant to in-vessel melt retention (IVMR) and ex-vessel corium cooling (EVCC). The purpose of the publication is to capture the state of knowledge, at the time of that meeting, related to phenomenology and technologies as well as the challenges and pending issues relevant to IVMR and EVCC for water cooled reactors by summarizing the information provided by the meeting participants in a form useful to practitioners in Member States.
Author: Jerome V. Moloney
Publisher: Springer Science & Business Media
ISBN: 9780387985817
Category : Business & Economics
Languages : en
Pages : 270
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Book Description
Mathematical methods play a significant role in the rapidly growing field of nonlinear optical materials. This volume discusses a number of successful or promising contributions. The overall theme of this volume is twofold: (1) the challenges faced in computing and optimizing nonlinear optical material properties; and (2) the exploitation of these properties in important areas of application. These include the design of optical amplifiers and lasers, as well as novel optical switches. Research topics in this volume include how to exploit the magnetooptic effect, how to work with the nonlinear optical response of materials, how to predict laser-induced breakdown in efficient optical devices, and how to handle electron cloud distortion in femtosecond processes.
Author: David Adler
Publisher: Springer Science & Business Media
ISBN: 1489922601
Category : Science
Languages : en
Pages : 448
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Book Description
The Institute for Amorphous Studies was founded in 1982 as the international center for the investigation of amorphous mate rials. It has since played an important role in promoting the und er standing of disordered matter in general. An Institute lecture series on "Fundamentals of Amorphous Materials and Devices" was held during 1982-83 with distinguished speakers from universities and industry. These events were free and open to the public ,and were attended by many representatives of the scientific community. The lectures themselves were highly successful inasmuch as they provided not only formal instruction but also an opportunity for vigorous and stimulating debate. That last element could not be captured within the pages of a book I but the lectures concentrated on the latest advances in the field I which is why their essential contents are he re reproduced in collective form. Together they constitute an interdisciplinary status report of the field. The speakers brought many different viewpoints and a variety of back ground experiences io bear on the problems involved I but though language and conventions vary I the essential unity of the concerns is very clear I as indeed are the ultimate benefits of the many-sided approach.
Author: Claude Bathias
Publisher: John Wiley & Sons
ISBN: 1118623371
Category : Technology & Engineering
Languages : en
Pages : 415
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Book Description
The design of mechanical structures with improved and predictable durability cannot be achieved without a thorough understanding of the mechanisms of fatigue damage and more specifically the relationships between the microstructure of materials and their fatigue properties. Written by leading experts in the field, this book (which is complementary to Fatigue of Materials and Structures: Application to Damage and Design, also edited by Claude Bathias and André Pineau), provides an authoritative, comprehensive and unified treatment of the mechanics and micromechanisms of fatigue in metals, polymers and composites. Each chapter is devoted to one of the major classes of materials or to different types of fatigue damage, thereby providing overall coverage of the field. The book deals with crack initiation, crack growth, low-cycle fatigue, gigacycle fatigue, shorts cracks, fatigue micromechanisms and the local approach to fatigue damage, corrosion fatigue, environmental effects and variable amplitude loadings, and will be an important and much used reference for students, practicing engineers and researchers studying fracture and fatigue in numerous areas of mechanical, structural, civil, design, nuclear, and aerospace engineering as well as materials science.
Author: Georges Cailletaud
Publisher: John Wiley & Sons
ISBN: 1848215800
Category : Technology & Engineering
Languages : en
Pages : 293
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Book Description
This book focuses on a particular class of models (namely Multi-Mechanism models) and their applications to extensive experimental data base related to different kind of materials. These models (i) are able to describe the main mechanical effects in plasticity, creep, creep/plasticity interaction, ratcheting extra-hardening under non-proportional loading (ii) provide local information (such us local stress/strain fields, damage, ….). A particular attention is paid to the identification process of material parameters. Moreover, finite element implementation of the Multi-Mechanism models is detailed.
Author: Jacques Besson
Publisher: Springer Science & Business Media
ISBN: 9048133564
Category : Science
Languages : en
Pages : 433
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Book Description
In mechanical engineering and structural analysis there is a significant gap between the material models currently used by engineers for industry applications and those already available in research laboratories. This is especially apparent with the huge progress of computational possibilities and the corresponding dissemination of numerical tools in engineering practice, which essentially deliver linear solutions. Future improvements of design and life assessment methods necessarily involve non-linear solutions for inelastic responses, in plasticity or viscoplasticity, as well as damage and fracture analyses. The dissemination of knowledge can be improved by software developments, data base completion and generalization, but also by information and training. With such a perspective Non-Linear Mechanics of Materials proposes a knowledge actualization, in order to better understand and use recent material constitutive and damage modeling methods in the context of structural analysis or multiscale material microstructure computations.
Author: L. Remy
Publisher: Elsevier
ISBN: 0080542328
Category : Technology & Engineering
Languages : en
Pages : 397
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Book Description
This volume contains a selection of peer-reviewed papers presented at the International Conference on Temperature-Fatigue Interaction, held in Paris, May 29-31, 2001, organised by the Fatigue Committee of the Societé Française de Métallurgie et de Matériaux (SF2M), under the auspices of the European Structural Integrity Society. The conference disseminated recent research results and promoting the interaction and collaboration amongst materials scientists, mechanical engineers and design engineers. Many engineering components and structures used in the automotive, aerospace, power generation and many other industries experience cyclic mechanical loads at high temperature or temperature transients causing thermally induced stresses. The increase of operating temperature and thermal mechanical loading trigger the interaction with time-dependent phenomena such as creep and environmental effects (oxidation, corrosion). A large number of metallic materials were investigated including aluminium alloys for the automotive industry, steels and cast iron for the automotive industry and materials forming, stainless steels for power plants, titanium, composites, intermetallic alloys and nickel base superalloys for aircraft industry, polymers. Important progress was observed in testing practice for high temperature behaviour, including environment and thermo-mechanical loading as well as in observation techniques. A large problem which was emphasized is to know precisely service loading cycles under non-isothermal conditions. This was considered critical for numerous thermal fatigue problems discussed in this conference.
