Low Cost Fabrication of 2G Wires for AC Applications

Ink-jet printing has been demonstrated as an adaptable technology for printing YBCO filaments using a Metal Organic (MO) YBCO precursor. The technology was demonstrated using AMSC's proprietary metal organic TFA-based YBCO precursor and a commercial piezoelectric print-head on RABiTS templates. Filaments with a width of 100 um and spacing of 200 um were successfully printed, decomposed and processed to YBCO. Critical currents of {approx} 200 A/cm-w were achieved in a series of filaments with a 2 mm width. The single nozzle laboratory printer used in the Phase 1 program is capable of printing {approx} 100 um wide single filaments at a rate of 8-10 cm/sec. The electrical stabilization of filaments with a Ag ink was also evaluated using ink-jet printing. The overall objective of the Phase 1 Project was the evaluation and demonstration of inkjet-printing for depositing YBCO filaments on textured templates (RABiTS, IBAD, ISD, etc. substrates) with properties appropriate for low loss ac conductors. Goals of the Phase 1 program included development of an appropriate precursor ink, demonstration of the printing process, processing and characterization of printed YBCO filaments and evaluation of the process for further development

Low cost, single crystal-like substrates for practical, high efficiency solar cells

It is well established that high efficiency (20%) solar cells can be routinely fabricated using single crystal photovoltaic (PV) materials with low defect densities. Polycrystalline materials with small grain sizes and no crystallographic texture typically result in reduced efficiences. This has been ascribed primarily to the presence of grain boundaries and their effect on recombination processes. Furthermore, lack of crystallographic texture can result in a large variation in dopant concentrations which critically control the electronic properties of the material. Hence in order to reproducibly fabricate high efficiency solar cells a method which results in near single crystal material is desirable. Bulk single crystal growth of PV materials is cumbersome, expensive and difficult to scale up. We present here a possible route to achieve this if epitaxial growth of photovoltaic materials on rolling-assisted-biaxially textured-substrates (RABiTS) can be achieved. The RABiTS process uses well-established, industrially scaleable, thermomechanical processing to produce a biaxially textured or single-crystal-like metal substrate with large grains (50-100 {mu}m). This is followed by epitaxial growth of suitable buffer layers to yield chemically and structurally compatible surfaces for epitaxial growth of device materials. Using the RABiTS process it should be possible to economically fabricate single-crystal-like substrates of desired sizes. Epitaxial growth of photovoltaic devices on such substrates presents a possible route to obtaining low-cost, high performance solar cells

Schools out : Adam Smith and pre-disciplinary international political economy

In this article, I argue that invocations of Adam Smith in international political economy (IPE) often reveal the influence therein of a disciplinary ontological disaggregation of economic and non-economic rationality, which I claim is obscured by the tendency to map its complex intellectual contours in terms of competing schools. I trace the origins of the disciplinary characterisation of Smith as the founder of IPE's liberal tradition to invocations of his thought by centrally important figures in the perceived Austrian, Chicago and German historical schools of economics, and reflect upon the significance to IPE of the reiteration of this portrayal by apparent members of its so-called American and British schools. I additionally contrast these interpretations to those put forward by scholars who seek to interpret IPE and Smith's contribution to it in pre-disciplinary terms, which I claim reflects a distinct ontology to that attributed to the British school of IPE with which their work is often associated. I therefore contend that reflection upon invocations of Smith's thought in IPE problematises the longstanding tendency to map its intellectual terrain in terms of competing schools, reveals that the disciplinary ontological consensus that informs this tendency impacts upon articulations of its core concerns and suggests that a pre-disciplinary approach offers an alternative lens through which such concerns might be more effectively framed

Irradiation performance of rare earth and nanoparticle enhanced high temperature superconducting films based on YBCO

The new series of commercially produced high temperature superconducting (HTS) tapes based on the YBa2Cu3O7 (YBCO) structure have attracted renewed attention for their performance under applied magnetic fields without significant loss in supercurrent compared to the earlier generation of conductors. This adaptability is achieved through rare earth substitution and dopants resulting in the formation of nanoparticles and extended defects within the superconducting film matrix. The electrical performance of Zr-(Gdx,Y1−x)Ba2Cu3O7 and (Y1−x,Dyx)Ba2Cu3O7 coated conductor tapes were tested prior to and after neutron exposures between 6.54×1017 and 7.00×1018 n/cm2 (E > 0.1MeV). Results showed a decrease in superconducting current with neutron irradiation for the range of fluences tested, with losses in the Zr-(Gdx,Y1−x)Ba2Cu3O7 conductor being more rapid. Post-irradiation testing was limited to evaluation at 77K and applied fields of up to 0.5Tesla, and therefore testing at lower temperatures and higher applied fields may result in improved superconducting properties as shown in previous ion irradiation work. Under the conditions tested, the doped conductors showed a loss in critical current at fluences lower than that of undoped YBa2Cu3O7 tapes reported on in literature