Reversal μCP using hard stamps

In this work, we present a new method of Micro-Contact Printing (μCP) which we call reversal μCP using hard stamps which can be used for the fabrication of different structures like negative index materials, e.g., split ring resonators (SRRs), dots and squares made of gold. Typically soft stamps made of PDMS (polydimethylsiloxane) inked with thiols are used for μCP. The softness of the stamp material entails a lot of problems like deformation of the structures, sagging and pairing of the protruding features and reliability of the process. We use hard stamps which are spin coated with a thiol solution so that the thioles stay in the recessed areas of the stamp. In the following μCP process an EVG^®620 is used to bring the stamp and substrate into contact so that the thiols on the stamp diffuse and bind to the gold surface and serve as an etch mask for succeeding wet chemical etching. Using this method overcomes the disadvantage of a soft stamp material. Smallest feature sizes down to 100 nm are shown.     

Chemical sensing materials based on electrically‐conductive immiscible polymer blends

Two families of electrically‐conductive immiscible polymer blends were studied as liquid sensing materials for an homologous series of alcohols. The systems studied include: multiphase matrices [containing carbon black (CB)] consisting of either polypropylene or high‐impact polystyrene as the major phase and thermoplastic polyurethane as the minor dispersed phase; and polyaniline (PANI) dispersed within a polystyrene matrix. Extruded filaments, produced by a capillary rheometer at various shear‐rate levels were used in the sensing experiments. The electrical resistance of these filaments was selectively sensitive to the various alcohols. Moreover, the responses displayed by these filaments are reproducible and reversible. The sensing behaviour of these blends is determined by the nature of the blend components, the blend composition and the processing conditions. An attempt is made to identify the dominant mechanisms controlling the sensing process in CB‐containing immiscible polymer blends and PANI‐containing blends. In addition, the sensing performances of these blends are compared in the light of their sensing mechanisms. Copyright © 2005 Society of Chemical Industry     

Progress of the NbAl3 Combustion Synthesis Reaction

Parallelopipedal (60 × 10 × 10-mm) bars obtained by uniaxial compaction of Nb-Al powder mixtures with a stoichiometric NbAl₃ composition (75 a/o Al) were submitted to reaction synthesis using the SHS mode (self-propagating high-temperature synthesis). The experimental procedures used were such as to allow for the reaction ignition, propagation, and extinction at a certain plane along the bar length. The microstructure of the reacted bars was characterized by optical microscopy, scanning electron microscopy, and EDS. The various phases present along the bar length evidenced that the local composition was changed due to the presence of a molten aluminum flux during the reaction. All the observed phases are predicted by the Nb-Al equilibrium phase diagram. A possible explanation for the reaction sequence is advanced based on the experimental observations.     

Influence of aqueous medium on mechanical properties of conventional and new environmentally friendly regenerated cellulose fibers

Comparative investigations between the new lyocell fibers and the regular viscose and modal types were made in order to explain the reasons for the differences in the mechanical properties of the fibers. The purpose was a systematic analysis of structure characteristics and of influence of aqueous medium on the mechanical properties. The properties determined in the wet state reflect the effect of the aqueous medium on the changes in the supermolecular structure during wet treatments [1, 2]. The new lyocell fibers consist of longer molecules and have a higher degree of crystallinity. Smaller but longer crystallites are oriented in the fiber axis direction and the voids structure is similar to that of viscose fibers [3]. Good mechanical properties are conditioned by the structure of the lyocell fibers, above all by high values of the orientation factor and crystallinity index. Sorption properties place lyocell fibers between the viscose and modal fibers. The water influence on the mechanical properties of lyocell fibers is considerably smaller compared to the viscose and modal fibers. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

“Lean” Comparison Using Process Charts of Complex Seismic Retrofit Projects

This paper compares the delivery of two retrofit projects where seismic isolation bearings were installed. The comparison is retrospective. The design teams on these projects did not implement “lean” thinking to develop their approach, nevertheless, observed process differences are characterized using a “lean” process evaluation and optimization tool, and then gauged and rationalized from that perspective. Cross-functional process charts identify functional parties with interrelated material or information handoffs. They help to identify (un)necessary steps or complexity as measured by number of handoffs and interacting parties. Analysis of these charts shows that project value may stem from the owner integrating design development with product procurement and construction method selection. On one project, integration was made possible by structural engineers evaluating the impacts of product procurement on overall project performance, expert consultants providing construction process reviews, and experienced contractors participating in installation sequence development. This paper illustrates the value of developing a symbiotic relationship between designers and suppliers in a niche market. It stresses the need for work structuring early on in the delivery process, integrating process with product development, to improve project delivery.     

The economical and environmental performance of miscanthus and switchgrass production and supply chains in a European setting

The purpose of this study is to analyse the economical and environmental performance of switchgrass and miscanthus production and supply chains in the European Union (EU25), for the years 2004 and 2030. The environmental performance refers to the greenhouse gas (GHG) emissions, the primary fossil energy use and to the impact on fresh water reserves, soil erosion and biodiversity. Analyses are carried out for regions in five countries. The lowest costs of producing (including storing and transporting across 100 km) in the year 2004 are calculated for Poland, Hungary and Lithuania at 43–64 € per oven dry tonne (odt) or 2.4–3.6 € GJ^?1 higher heating value. This cost level is roughly equivalent to the price of natural gas (3.1 € GJ^?1) and lower than the price of crude oil (4.6 € GJ^?1) in 2004, but higher than the price of coal (1.7 € GJ^?1) in 2004. The costs of biomass in Italy and the United Kingdom are somewhat higher (65–105 € odt^?1 or 3.6–5.8 € GJ^?1). The doubling of the price of crude oil and natural gas that is projected for the period 2004–2030, combined with nearly stable biomass production costs, makes the production of perennial grasses competitive with natural gas and fossil oil. The results also show that the substitution of fossil fuels by biomass from perennial grasses is a robust strategy to reduce fossil energy use and curb GHG emissions, provided that perennial grasses are grown on agricultural land (cropland or pastures). However, in such case deep percolation and runoff of water are reduced, which can lead to overexploitation of fresh water reservoirs. This can be avoided by selecting suitable locations (away from direct accessible fresh water reservoirs) and by limiting the size of the plantations. The impacts on biodiversity are generally favourable compared to conventional crops, but the location of the plantation compared to other vegetation types and the size and harvesting regime of the plantation are important variables.     

Determination of the accuracy of phase analysis measurements on spherical surfaces through X-ray diffraction

This research analyzes the effect on measurement accuracy when taking X-ray diffraction (XRD) measurements on spherical rather than flat surfaces in the assessment of the proportion of retained austenite and martensite phases. By calculating the difference in X-ray absorption paths between a flat surface and spherical surface, this study demonstrates that only in spherical surfaces of small diameter (0.381 cm) will the difference in X-ray absorption path affect the accuracy of measurements derived from XRD. To improve the accuracy of such measurements, the research presents a model for quantifying the absorption path that X-rays follow when measuring spherical surfaces.