The effects of water vapour on the hot corrosion of gas turbine blade materials at 700 °C

Future developments in power generation are likely to require gas turbines to operate in novel combustion environments. The level of water vapour in the turbine’s gas stream is one variable that may change as a consequence. This paper explores the effects of water vapour on hot corrosion. The ‘deposit recoat’ technique was used to evaluate the hot corrosion performance of superalloys PWA 1483 and MarM 509 in atmospheres containing between 0 and 20 vol.% water vapour. Exposures were carried out at 700 °C in atmospheres containing 300 ppm SO2 for up to 500 hours. The deposit was an 80% Na2SO4, 20% K2SO4 solution applied with a deposition flux of 1.5 µg/cm2/h. The findings are compared to similar exposures with 3.6 ppm SO2. Increasing levels of water vapour were observed to reduce sound metal loss in atmospheres containing 300 ppm SO2 while increasing sound metal loss in atmospheres containing 3.6 ppm SO2

The role of superalloy precipitates on the early stages of oxidation and type II hot corrosion

To meet materials challenges encountered in gas turbines, superalloys have been developed for high temperature, strength, oxidation and corrosion resistance. One strengthening method is using refractory metal additions to form carbide precipitates. However, such precipitates may be detrimental to the alloy’s environmental resistance. This paper reports how refractory metal carbide precipitates affect the early stages of oxidation and hot corrosion of two alloys: Rene 80 (nickel-based) and MarM 509 (cobalt-based). Samples were exposed at 700 °C in either dry synthetic air or 90 ppm SOx, 10·5% CO2, 8·5% O2, 5% H2O (balance N2) with a 80/20 (Na/K)2SO4 deposit (1·5 μg/cm2/hour flux). The oxidation morphology and corrosion products were investigated by scanning electron microscope and energy dispersive X-ray analysis, to show that refractory metal carbide precipitates close to the metal surfaces disrupt protective oxide scale formation, thus providing inward transport routes for corrosive species

Further investigations into alloy induced acidic fluxing

Gas turbine materials often feature precipitates containing refractory metals to enhance their mechanical strength. This can make them susceptible to alloy-induced acidic fluxing whereby refractory elements increase the acidity of salt deposits. It is not clear to what degree degradation around alloy precipitates is caused by alloy-induced hot corrosion mechanisms, or the inability to develop a protective scale where precipitates are located. The effect of alloy-induced hot corrosion was isolated from the disruption of the protective-scale formation by adding particles of molybdenum to the 80/20 (Na/K)2SO4 deposit for a ‘deposit re-coat’ style hot corrosion test. The resulting morphologies were compared to samples exposed without the addition of molybdenum. Morphology changes were investigated using scanning electron microscopy with energy-dispersive X-ray mapping. Results show a mix of sulphidation and pitting. The effects of molybdenum additions appear more severe for MarM 509 compared to PWA 1483

A combination of amino acids and caffeine enhances sprint running capacity in a hot, hypoxic environment

Heat and hypoxia exacerbate central nervous system (CNS) fatigue. We therefore investigated whether essential amino acid (EAA) and caffeine ingestion attenuates CNS fatigue in a simulated team sport–specific running protocol in a hot, hypoxic environment. Subelite male team sport athletes (n = 8) performed a repeat sprint running protocol on a nonmotorized treadmill in an extreme environment on 4 separate occasions. Participants ingested one of four supplements: a double placebo, 3 mg.kg⁻¹ body mass of caffeine + placebo, 2 × 7 g EAA (Musashi Create)+placebo, or caffeine + EAA before each exercise session using a randomized, double-blind crossover design. Electromyography (EMG) activity and quadriceps evoked responses to magnetic stimulation were assessed from the dominant leg at preexercise, halftime, and postexercise. Central activation ratio (CAR) was used to quantify completeness of quadriceps activation. Oxygenation of the prefrontal cortex was measured via near-infrared spectroscopy. Mean sprint work was higher (M = 174 J, 95% CI [23, 324], p < .05, d = 0.30; effect size, likely beneficial) in the caffeine + EAA condition versus EAAs alone. The decline in EMG activity was less (M = 13%, 95% CI [0, 26]; p < .01, d = 0.58, likely beneficial) in caffeine + EAA versus EAA alone. Similarly, the pre- to postexercise decrement in CAR was significantly less (M = −2.7%, 95% CI [0.4, 5.4]; p < .05, d = 0.50, likely beneficial) when caffeine + EAA were ingested compared with placebo. Cerebral oxygenation was lower (M = −5.6%, 95% CI [1.0, 10.1]; p < .01, d = 0.60, very likely beneficial) in the caffeine + EAA condition compared with LNAA alone. Coingestion of caffeine and EAA appears to maintain muscle activation and central drive, with a small improvement in running performance.13 page(s

Collaboration in the Semantic Grid: a Basis for e-Learning

The CoAKTinG project aims to advance the state of the art in collaborative mediated spaces for the Semantic Grid. This paper presents an overview of the hypertext and knowledge based tools which have been deployed to augment existing collaborative environments, and the ontology which is used to exchange structure, promote enhanced process tracking, and aid navigation of resources before, after, and while a collaboration occurs. While the primary focus of the project has been supporting e-Science, this paper also explores the similarities and application of CoAKTinG technologies as part of a human-centred design approach to e-Learning

Treatment of white coat HYpertension in the Very Elderly Trial (HYVET 2) - feasibility of a randomized controlled trial (study protocol)

The results of HYpertension in the Very Elderly Trial (HYVET) were crucial in providing evidence of benefit of the treatment of hypertension in those 80 years or older. Following a subsequent sub study analysis of the HYVET data there is a suggestion that 50% of patients in the main study had White Coat Hypertension (WCH), defined as clinic BP readings >140/90 mmHg and ambulatory BP readings <135/85 mmHg. Currently, definitive evidence in support of treatment for such individuals is not available. HYVET 2 has been designed in order to assess the feasibility of conducting a randomized controlled trial which might determine whether the treatment of WCH in the very elderly is clinically beneficial. One hundred participants aged ≥75 years diagnosed with WCH will be recruited from General Practices (GPs) in UK. Randomization will be 1:1 to a treatment arm (indapamide and perindopril) and control arm (no treatment) and follow up will be for 52 weeks. HYVET 2 will report on feasibility outcomes including participant recruitment, adherence and withdrawal rates, willingness of GPs to recruit and randomize patients and the frequency of a composite of cardiovascular events. Simple descriptive statistics will be presented

Unravelling social constructionism

Social constructionist research is an area of rapidly expanding influence that has brought together theorists from a range of different disciplines. At the same time, however, it has fuelled the development of a new set of divisions. There would appear to be an increasing uneasiness about the implications of a thoroughgoing constructionism, with some regarding it as both theoretically parasitic and politically paralysing. In this paper I review these debates and clarify some of the issues involved. My main argument is that social constructionism is not best understood as a unitary paradigm and that one very important difference is between what Edwards (1997) calls its ontological and epistemic forms. I argue that an appreciation of this distinction not only exhausts many of the disputes that currently divide the constructionist community, but also takes away from the apparent radicalism of much of this work

Discovery of novel inhibitors of human 11β-hydroxysteroid dehydrogenase type 1

International audienc

Representing environmental harm and resistance on Twitter: The case of the TAP pipeline

This research explores a new methodological path for doing green cultural criminological research via social media. It provides original case-study data and aims to stimulate further empirical and theoretical debate. In particular, the study explores how Twitter users have represented the harms related to an ongoing pipeline project in Italy (referred to as TAP), and the resistance to those harms. To these ends, it offers a virtual and visual ethnography of Twitter posts and posted images

Corrosion of potential first stage blade materials in simulated supercritical CO2

Global power consumption is predicted to double by 2050, notably driven by the transportation and energy sectors necessitating limitations of emissions. Due to its compact turbomachinery, better thermal efficiency, and simpler layout, supercritical-CO2 cycles have received attention, with numerous variations proposed (either indirect-fired/closed cycles or direct-fired-open cycles). One technical challenge is degradation pathway quantification of turbine materials in sCO2 as selection is crucial to successfully and economically operate new plants. This requires degradation assessment in representative environments simulating the Allam cycle. Laboratory tests were conducted on a first stage turbine blade alloy, CM247, with either an environmentally resistant coating or bond coat/thermal barrier coat at one atmosphere and 800°C, with potential exposure including (O2, H2O, N2, SO2) for up to 1000 h. Weight change and metallographic measurements tracked scale development. Scanning electron microscopy/energy dispersive X-ray spectroscopy studied scales and internal precipitates. Locations of contaminant element in the CO2-rich environment were investigated