Fabrication of LTCC Micro-fluidic Devices Using Sacrificial Carbon Layers

Ease of fabrication and design flexibility are two attractive features of low temperature co-fired ceramics (LTCC) technology for fabrication of complex micro-fluidic devices. Such structures are designed and processed using different shaping methods, the extent and complexity of which depends on the final device specifications (dimensions, mechanical and functional properties). In this work, we propose a sacrificial layer method based on carbon-black paste, which burns out during the LTCC firing stage. The paper will summarize the preparation of the paste, influence of processing conditions on the final dimensions, and demonstrate the mechanically integrated structures obtained using this technique. Some of those are membranes of various diameters (7-12mm) with a thickness of 40µm and a variety of internal spacing (15-60µm), free-hanging thick-film resistors (TFR) bridges on LTCC for heating micro-volumes. The main methods of the study will be thermo gravimetric analysis (TGA), scanning electron microscopy (SEM) and dilatometry in addition to electronic instruments for device characterization

Formation, caractérisation et propriétés mécaniques sous contrainte uniaxiale du Bi,Pb(2223) dans les rubans à gaine d'argent

Divers rubans supraconducteurs à base de Bi,Pb(2223) ont été fabriqués, leurs traitements thermo-mécaniques ont été optimisés afin d'améliorer leurs propriétés de transport. Dans un second temps, nous nous sommes concentrés sur l'étude de ces propriétés sous contrainte mécanique. Un modèle théorique destiné à prévoir le comportement du courant critique sous élongation uniaxiale a ainsi été développé, les paramètres à introduire dans le modèle (module de Young et contrainte de rupture des filaments polycristallins de Bi,Pb(2223)) ont été déterminés expérimentalement. Le modèle a ensuite été testé et validé en comparant les prédictions théoriques avec les valeurs mesurées. La dernière partie du travail est consacrée aux excroissances: défauts de texture du Bi,Pb(2223) où certains grains sortent des filaments et pénètrent dans la matrice d'argent. Nous avons discuté et testé différents mécanismes pour décrire leur formation

Development of Bi(2223) Multifilamentary Tapes with Low ac Losses

A significant reduction of ac losses in twisted Bi(2223) multifilamentary tapes with Ag sheaths has been achieved by using oxide (BaZrO₃ and SrZrO₃) barriers between filaments. These barriers have two important effects: they increase the transverse resistivity, which suppresses induced coupling currents, and they reduce filament bridging, which in pure Ag sheath tapes largely cancels the beneficial effect of filament twisting. The decoupling can be gauged by the frequency at which loss shows a maximum in a low-amplitude ac field applied perpendicular to the tape. So far, the frequency of the loss maximum, fm, in Ag-sheathed tapes has been enhanced from 5 Hz (untwisted) to 82 Hz (11 mm in twist pitch length). Different ways to introduce oxide barriers in tapes with 19–95 filaments are presented. The critical current density in the filaments varied between 10,000 and 20,000 A/cm². Ac loss measurements as well as the electrical and mechanical characterization are discussed in detail. The variation of the critical current density with bending strain is shown to be similar to that of tapes without barriers