Microtensile testing of submicrometer thick functional polymer samples

Organic electronic devices are currently being introduced in commercial applications such as flexible displays. Due to the mechanical loading of these devices during bending, it is important to know the mechanical properties in order to assess reliability. It is therefore essential to develop experimental setups for the mechanical characterization of submicrometer thick functional polymer layers. In this paper a new microtensile approach is presented along with first results for Young's modulus of polyimide (PI) and the conductive polymer PEDOT:PSS obtained using this method. The microtensile specimen are made of a bilayer consisting of PI as the substrate layer and of a submicron layer of PEDOT:PSS deposited on top of it. The mechanical properties are derived from comparison of measurements performed on samples with and without the functional layer and by varying this layer's thickness. A thorough error analysis is also presented to provide an overview of the precision inherent in this approach. The experiments yield Young's moduli of 3.28 ± 0.34 GPa for PI and of 4.51 ± 0.34 GPa for PEDOT:PSS.     

On the use of peak-force tapping atomic force microscopy for quantification of the local elastic modulus in hardened cement paste

A surface of epoxy-impregnated hardened cement paste was investigated using a novel atomic force microscopy (AFM) imaging mode that allows for the quantitative mapping of the local elastic modulus. The analyzed surface was previously prepared using focussed ion beam milling. The same surface was also characterized by electron microscopy and energy-dispersive X-ray spectroscopy.We demonstrate the capability of this quantitative nanomechanical mapping to provide information on the local distribution of the elastic modulus (from about 1 to about 100 GPa) with a spatial resolution in the range of decananometers, that corresponds to that of low-keV back-scattered electron imaging. Despite some surface roughness which affects the measured nanomechanical properties it is shown that topography, adhesion and Young's modulus can be clearly distinguished.The quantitative mapping of the local elastic modulus is able to discriminate between phases in the cement paste microstructure that cannot be distinguished from the corresponding back-scattered electron images.     

Simulation of Fluid Flow and Oscillation of the Argon Oxygen Decarburization (AOD) Process

The oscillation of argon oxygen decarburization (AOD) converters is flow related and depends on the process parameters (e.g., vessel geometry, melt fill height, process gas type and blowing rate, vessel tilting angle, as well as geometry, number, and arrangement of the side-wall nozzles). For a 120-ton AOD converter with seven submerged side-wall nozzles, plant tests, physical simulations on a 1:4 scale water model, and computational fluid dynamics simulations have been done. The investigations show that the penetration depth of an inert gas jet into the melt does not exceed approximately 0.4 m. The plumes are located close to the nozzle-side converter wall and induce a large-scale primary vortex as well as intensive surface movements; both are responsible for the oscillation. Several process mechanisms were investigated. The oscillation is highest in the last stage of the dynamic blow and is still high during the reduction stage. As the amount of inert gas increases, the vibration level also increases. Inert gas has a greater influence on the oscillation than oxygen. Tilting the converter around 8 deg clearly leads to more intensive oscillations. Increasing the blowing rate increases the forces and torques acting on the vessel, whereas the oscillation frequency remains nearly constant. A varying fill level does not influence the vibration level the same way as the blowing rate. The operational test shows, for example, that the maximum torque does not depend on the heat size when the latter varies between –8 pct and +21 pct of the nominal heat size. The water model test shows decreasing forces and torques with a rising fill level.     

Complexities of operating in foreign property markets

The world is on the brink of an unprecedented growth-related ecological crisis that could well undermine prospects for global civilization. Nevertheless, the global community seems ‘in flight from thinking’ about the implications of the threat and unwilling to contemplate the policy remedies necessary to change the course of history. Biological and cultural factors combine to inhibit clear understanding and effective corrective action. Mainstream ‘solutions’ – hybrid cars, green buildings, smart growth, the new urbanism – are thus rooted in denial and delusional. These approaches do not address the fundamental problem of ‘overshoot’, but rather attempt to maintain the growth-bound status quo through efficiency gains and related technological ‘fixes’. This might actually worsen the situation. Achieving sustainability requires that such marginal reform give way to a complete rethink of society's relationship with nature. Developed societies need a new, more adaptive cultural mythology. The building sector arguably has greater material leverage in reducing the human ecological footprint than any other major industrial sector. Acceptance of the guidelines developed in this paper would revolutionize the industry and reorient it geographically. The question is: does the industry have the intellectual courage and practical momentum to assume a lead role in the sustainability campaign?

Le monde est au bord d'une crise écologique sans précédent, liée à la croissance, qui pourrait bien saper les perspectives d'avenir de la civilisation mondiale. Néanmoins, la communauté mondiale semble se refuser à penser aux implications de cette menace et ne pas se résoudre à envisager les remèdes politiques nécessaires pour modifier le cours de l'histoire. Les facteurs biologiques et culturels se conjuguent pour entraver une compréhension claire et la prise de mesures correctives efficaces. C'est la dénégation et l'illusion qui se trouvent ainsi être à l'origine des « solutions » dominantes – voitures hybrides, bâtiments verts, croissance intelligente, le nouvel urbanisme. Ces approches ne traitent pas du problème fondamental du « dépassement écologique » [des capacités productives de la Terre], mais tentent de maintenir le statu quo lié à la croissance grâce à des gains de rendement et aux « palliatifs » technologiques qui leur sont liés. Cela pourrait en fait aggraver la situation. Parvenir à un environnement durable nécessite qu'une réforme aussi minime cède le pas à une relation de la société à la nature totalement repensée. Les sociétés développées ont besoin d'une nouvelle mythologie culturelle, dotée d'une plus grande capacité d'adaptation. L'on peut soutenir que, s'agissant de réduire l'empreinte écologique de l'humanité, le secteur du bâtiment a une influence matérielle plus grande qu'aucun autre secteur industriel important. L'acceptation des directives développées dans cet article révolutionnerait l'industrie et la réorienterait géographiquement. La question est: l'industrie a-t-elle le courage intellectuel et le dynamisme pratique pour assumer un rôle leader dans la campagne en faveur d'un environnement durable?

Mots clés: comportement, cadre bâti, changement climatique, comportement cognitif, narrations culturelles, dépassement écologique, développement durable     

Quenched phosphorescence detection in cyclodextrin-based electrokinetic chromatography

Quenched phosphorescence detection is a sensitive detection method recently introduced in capillary zone electrophoresis. It is based on the dynamic quenching interaction of the analytes (quenchers) with a phosphorophore, 1-bromo-4-naphthalenesulfonate (BrNS), present in the separation buffer. In this study, it is shown that this detection method can also be used in cyclodextrin-based electrokinetic chromatography (CD-EKC) despite the presence in the buffer solution of cyclodextrins, which are known to reduce the luminescence quenching rate constants. Experiments indicate that BrNS mainly resides in the aqueous phase, while the analytes are distributed between both phases. In principle, the observed quenching might arise from the interaction of BrNS with uncomplexed as well as complexed analytes. However, from the dependence of the fractional quenching on the capacity factor (the normalized fractional quenching was found to be equal to the fraction of analyte in the aqueous phase), it was concluded that only aqueous-phase quenching contributes significantly to the observed quenching. Nevertheless, separation and detection can be regarded as fully compatible, because the capacity factors encountered in CD-EKC are generally low (in this study they ranged from about 0.1 to 2.5). Indeed, with nitroaromatic compounds as the target analytes, limits of detection in the 10(-8) M range were achieved.