Search results for "Micro structure"
showing 5 items of 5 documents
Investigations on The Micro-Structure of Hardened Cement Pastes
1988
Abstract Creep is a mechanical property, that has to be taken into account in the design of concrete constructions. Earlier studies showed that creep of concrete, among other things, depends on the relative humidity of the environment and on the type of cement used. The origin of creep lies in the hydrated cement paste, which is present between the aggregates. This paper, based on a thesis of H.H. Willems (ref. 1) deals with the relation between the creep behaviour and the microstructure of hardened Portland (PC) and Portland-blastfurnace cement (PBC) pastes. At several relative humidities shrinkage and creep experiments have been performed with thin-walled hollow cylindrical specimens. Nex…
Critical currents and micro-structure in YBa2Cu3O7−δ thin films
1996
In an attempt to clarify the origin of the large critical current densitiesJ c observed in Laser Ablated and Sputtered YBa2Cu3O7−δ (YBCO) thin films, we make a systematic study of the low temperatureJ c in samples carefully analysed using STM and AFM.J c (B) is determined from torque-magnetometry performed in ring-patterned thin films. Epitaxial YBCO films nucleate in c-axis oriented single-crystalline islands with sizes ranging between 200 and 700 nm. We show thatJ c can be mainly explained by vortex pinning localised in the island boundaries.
New Developments in Soft Lithography
2003
Abstract The burgeoning area of soft lithography is reviewed with special emphasis on developments within the past three years. Applications in electronics have driven such developments, but more recently, other kinds of device structures and 3D prototyping have also found application, in part, through soft lithography. Microcontact printing (μCP), “lift off” μCP nano transfer printing (nTP), micromolding in capillaries (MIMIC), solvent assisted micromolding (SAMIM), replica molding (REM), and microtransfer molding are the main soft lithography schemes discussed.
Influence of micro-structure in the low temperature critical currents of YBa2Cu3O7?? thin films
1996
Epitaxial YBa2Cu3O7−δ films nucleate in c-axis oriented single-crystalline islands. The surface of the single-crystalline SrTiO3 substrates exhibit steps of one third of the YBa2Cu3O7−δ c-axis. These steps generate a mismatch in the island boundaries between the CuO2 superconducting blocks. We show that these defect regions are strong candidates for being the pinning centers responsible for the large critical currents observed in Laser Ablated and Sputtered thin films.
Relation between microstructure and transport properties of epitaxial YBa2Cu3O7-d thin films.
1997
Abstract In order to understand the origin of the high critical current densities observed in thin superconducting films compared to single crystals we measured in several epitaxial YBa 2 Cu 3 O 7−δ thin films the magnetic field and temperature dependence of the superconducting current density j s and the dynamical relaxation rate Q ≡ d ln j s / d ln( d B/ dt ). For all samples we found that (i) the superconducting current density j s is independent of magnetic field up to a certain field B Φ . The value of this field, which is sample dependent, decreases with increasing temperature; (ii) for fields B>B Φ , the superconducting current density falls off as B −1/2 over several decades; (iii) …