Download or read book Corrosion des verres de phosphates d condens s du syst me no 2o p 2o 5 zno en milieux non agit s written by Rodolphe Delaval and published by . This book was released on 1996 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ce travail a concerne la corrosion des verres de phosphates décondensés et mixtes du système (na#2o.p#2o#5)#1#-#x.zno#x. L'étude initiale de la formulation des verres montre que la longueur moyenne des phosphates diminue régulièrement selon l'addition de l'oxyde de zinc. La dépolymérisation du réseau conduit à un mélange d'entités de taille variable, notamment d'espèces courtes. Les ions Zn#2#+ occupent des positions terminales au niveau de ces différents enchainements phosphates, qu'ils réticulent très faiblement. Ils se trouvent principalement en sites octaédriques, et l'oxyde de zinc participe partiellement à l'ossature du réseau vitreux, qui est dit mixte. L'évolution de la vitesse de corrosion des verres en fonction de leur proportion d'oxyde de zinc se présente sous la forme d'une courbe non-linéaire qui définit trois zones. Leur existence correspond aux phénomènes antagonistes de la décondensation et de la réticulation du réseau phosphate par l'oxyde de zinc. Dans les mécanismes de corrosion qui ont été étudiés sur plusieurs formulations, l'étape limitative correspond toujours au délitement des enchainements phosphates, dont hydratation est facilitée par leur décondensation. Le verre de pyrophosphate double à un comportement spécifique, car cette formulation ne contient plus assez d'entités phosphatées suffisamment complexant es. Leur absence implique alors un mode de dissolution non-congruent. Elle permet des phénomènes d'adsorption ionique, ce qui conduit à une résistance à la corrosion particulièrement bonne.

Download or read book Flexoelectricity in Liquid Crystals written by Agnes Buka and published by World Scientific. This book was released on 2013 with total page 299 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Nonlinear Optical Materials written by Jerome V. Moloney and published by Springer Science & Business Media. This book was released on 1998-08-13 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.