Mechanical and electrical characterisation of anisotropic conductive adhesive particles

This thesis presents research into the mechanical and electrical characterisation of Anisotropic Conductive Adhesive (ACA) particles and their behaviour within typical joints. A new technique has been developed for study of individual ACA particle mechanical and electrical performance when undergoing deformation. A study of the effects of planarity variations on individual electrical joints in real ACA assemblies is presented firstly, followed by the research on the mechanical deformation and electrical tests of individual ACA particles undergoing deformation. In the co-planarity research, experiments introducing deliberate rotation between a chip and substrate were designed and carried out to simulate planarity variations in ACA assemblies. There are two outputs from this part of the research. One is the planarity variation effects on individual electrical joints in ACA assemblies, and the other is the effect of bond thickness on the resistance of a real joint. [Continues.

TLC : une architecture photovoltaïque concentrée (CPV) au potentiel d’efficacité élevé à faible coût

Abstract: Human civilization has grown dependent on ready access to low-cost energy, but the fossil fuels that currently meet the bulk of humanity’s energy needs are causing environmental destruction, including potentially catastrophic global warming. Solar energy has to potential to halt global warming, and, if low enough in cost, to also bring the whole world’s population to a first world living standard. Silicon PV has dramatically reduced costs largely through decreasing the cost and increasing the efficiency of the silicon cells, but silicon is nearing its theoretical efficiency limits, and even if the cells were free, silicon PV would still be too expensive to meet these goals. Tandem CPV cells are roughly twice as efficient as silicon, but previous CPV designs have been unable to compete with silicon on cost in spite of the efficiency advantage. A new CPV architecture, called TLC for its trough, lens and cone concentration stages, proposed using initial concentration by a low-cost trough mirror to shrink the rest of an CPV module by 40X and thus reduce overall module costs. But before this PhD research project, TLC was only a paper study. This PhD research project was started to answer the question of whether TLC could work out as well as it appeared, or whether there were hidden flaws that precluded beating silicon PV on cost, or possibly even precluded TLC from working at all. Thesis chapter 3 details the main optical design aspects, and chapter 4 covers the design of the rest of the TLC module, including leading variations where there is more than one plausible way to achieve low cost and high reliability. The work included building a unified analytical model spreadsheet that linked known aspects of the TLC design together and estimated costs for a given design variation. Thesis chapter 5 covers the economics of the proposed design, with a focus on materials costs since these dominate PV overall costs, and a section on reliability since product lifetime strongly influences life-cycle cost. The work included building 3D-CAD models to refine the TLC design, and then the prototyping of individual parts and processes, and finally building a physical prototype of a TLC mini-module and putting it in sun. This physical confirmation was necessary because even after TLC has been “built” many times, in visualization, on paper, on spreadsheets, and then in COMSOL, until TLC was physically built, hidden flaws could arise at any time. Chapter 6 of this thesis covers the simulation and validation carried out to show that it is plausible that TLC can meet its cost targets. The conclusion of this thesis summarizes the overall project. The project was a success, producing a TLC design with high potential efficiency, very low materials cost, and low estimated process costs, with the potential to beat even the US Department of Energy’s goal for PV pricing in 2030. Ray-tracing a 3D model showed that the design could achieve high concentration with adequate acceptance angles, and tests showed that the prototyping cells were suitable for TLC’s massively parallel microcell-array receiver configuration. The project also successfully tested the proposed manufacturing process for molding semi-dense arrays of tertiary optical elements on the back of a lens tile and assembled a TLC mini module which was tested on sun at the focus of a trough mirror. Four papers have already been published, with a fifth paper accepted, as result of this work.La civilisation humaine est devenue de plus en plus dépendante d'un accès facile à une énergie à faible coût, mais les combustibles fossiles qui répondent actuellement à la majeure partie des besoins énergétiques de l'humanité causent la destruction de l'environnement, y compris un réchauffement climatique potentiellement catastrophique. L'énergie solaire a le potentiel d'arrêter le réchauffement climatique et, si son coût est suffisamment bas, d'amener également la population mondiale entière à un niveau de vie du premier monde. Les coûts de photovoltaïque (PV) à base de silicium ont été considérablement réduits en grande partie en diminuant le prix et en augmentant l'efficacité des cellules en silicium, cependant l’utilisation de silicium a ses limites d'efficacité théoriques, et même si les cellules étaient gratuites, la PV à base de silicium serait encore trop chère pour atteindre ces objectifs. Les cellules de photovoltaïque concentré (CPV) Tandem sont environ deux fois plus efficaces que celles à base de silicium, mais malgré l'avantage de leur efficacité, les architectures des années précédentes de CPV n'ont pas été en mesure de rivaliser avec le silicium en termes de coût. Une nouvelle architecture CPV, appelée TLC (Trough-Lens-Cone) utilise la concentration initiale par un miroir parabolique à faible coût combiné avec un module CPV de 40X et ainsi réduire les coûts globaux du module. Avant ce projet de recherche de doctorat, TLC n'était qu'une étude sur papier. Cette thèse a pour but de répondre à la question de savoir si l’approche TLC pouvait fonctionner aussi bien qu'elle était apparue, ou s'il y avait des défauts cachés qui empêchaient de battre le silicium PV sur le coût, ou pourrait même empêcher la TLC de fonctionner. Ce travail comprenait la construction d'un modèle de tableur unifié qui reliait les aspects connus de la conception TLC et les coûts estimés pour une variation de conception donnée. Nous présentons également la construction de modèles 3D-CAD pour raffiner la conception TLC, puis le prototypage de pièces individuelles et de processus, et enfin la construction d'un prototype physique d'un mini-module TLC qui est mis au soleil. Cette validation physique était nécessaire car même après que TLC ait été théoriquement et numériquement « construit » à plusieurs reprises soit, en visualisation, sur papier, sur des feuilles de calcul, puis dans COMSOL, avant que TLC soit physiquement construit, des défauts cachés pouvaient survenir à tout moment. La mise en œuvre de ce projet a réussi, produisant une conception TLC cohérente qui avait un rendement élevé avec un coût des matériaux très bas et des faibles coûts estimatifs de processus, avec un potentiel de battre même l’objectif du département américain de l'énergie pour la tarification du silicium photovoltaïque en 2030. Le suivi de raies (Ray-tracing) avec un modèle 3D a montré que la conception pouvait atteindre une concentration élevée avec des angles d'acceptation adéquats. Les tests ont également montré que les cellules de prototypage ont été bien adaptées à la nouvelle configuration de TLC de récepteur à matrice de microcellules massivement parallèle. Le projet a également testé avec succès le processus de fabrication proposé pour le moulage de réseaux semi-denses d'éléments optiques tertiaires à l'arrière d'un carreau de lentille. Le projet a également réussi à assembler un mini-module TLC et à tester sous le soleil avec le focus d'un miroir parabolique. Quatre articles ont déjà été publiés, avec un cinquième article accepté, à la suite de ce travail

Investigation of the stress corrosion cracking resistance of SAF2205 and AISI304 weldments for the marine environment application

Stainless steels are used for many industrial applications because of their strength and fabrication characteristics. Stainless steel grades of SAF2205 and AISI304 can readily meet a wide range of design criteria of service life, maintenance, load and corrosion resistance

On-line measurement of partial discharges in high voltage rotating machines.

The on-line condition monitoring of rotating machines is given paramount importance, particularly in Oils and Gas industries where the financial implications of machine shutdown is very high. This project work was directed towards the on-line condition monitoring of high voltage rotating machines by detection of partial discharges (PD) which are indicative of stator insulation degradation. Partial discharge manifests itself in various forms which can be detected using various electrical and non-electrical techniques. The electrical method of detecting small current pulses generated by PD using a Rogowski coil as a sensor has been investigated in this work. Dowding & Mills, who are commercially involved in the condition monitoring of rotating machines, currently use a system called StatorMonotor® for PD detection. The research is intended to develop a new partial discharge detection system that will replace the existing system which is getting obsolete. A three phase partial discharge detection unit was specified, designed and developed that is capable of filtering, amplifying and digitising the discharge signals. The associated data acquisition software was developed using LabVIEW software that was capable of acquiring, displaying and storing the discharge signals. Additional software programs were devised to investigate the removal of external noise. A data compression algorithm was developed to store the discharge data in an efficient manner; also ensuring the backward compatibility to the existing analysis software. Tests were performed in laboratory and on machines on-site and the results are presented. Finally, the data acquisition (DAQ) cards that used the PCMCIA bus was replaced with new USB based DAQ cards with the software modified accordingly. The three phase data acquisition unit developed as a result of this project has produced encouraging results and will be implemented in an industrial environment to evaluate and benchmark its performance with the existing system. Most importantly, a hardware data acquisition platform for the detection of PD pulses has been established within the company which is easily maintainable and expandable to suit any future requirements

Research and Technology 2004

This report selectively summarizes NASA Glenn Research Center's research and technology accomplishments for fiscal year 2004. It comprises 133 short articles submitted by the staff scientists and engineers. The report is organized into three major sections: Programs and Projects, Research and Technology, and Engineering and Technical Services. A table of contents and an author index have been developed to assist readers in finding articles of special interest. This report is not intended to be a comprehensive summary of all the research and technology work done over the past fiscal year. Most of the work is reported in Glenn-published technical reports, journal articles, and presentations prepared by Glenn staff and contractors. In addition, university grants have enabled faculty members and graduate students to engage in sponsored research that is reported at technical meetings or in journal articles. For each article in this report, a Glenn contact person has been identified, and where possible, a reference document is listed so that additional information can be easily obtained. The diversity of topics attests to the breadth of research and technology being pursued and to the skill mix of the staff that makes it possible. For more information, visit Glenn's Web site at http://www.nasa.gov/glenn/. This document is available online (http://www.grc.nasa.gov/WWW/RT/). For publicly available reports, visit the Glenn Technical Report Server (http://gltrs.grc.nasa.gov)

Microstructure and Corrosion Behavior of Advanced Alloys

In many industrial applications, metallic materials are exposed to harsh operating conditions. Due to a combination of chemical and thermal stresses, the constructional and functional materials are degraded, and their utility properties are lost. These undesirable events are of a physicochemical nature and are commonly known as ‘corrosion’. In this Special Issue Book, 3 reviews and 18 original research papers focused on the complex relationships between the microstructure, phase constitution, and corrosion behavior of metallic materials are collected. Both high temperature and low temperature corrosion studies are included as they investigate the physicochemical processes at the material interfaces. Furthermore, possibilities for increasing the corrosion resistance of metallic materials are studied by means of surface modification and application of protective layers. This Special Issue Book, Microstructure and Corrosion Behavior of Advanced Alloys, displays the diversity and complexity of modern corrosion research. It is hoped that it will become a valuable source of reference for corrosion scientists