Consolidation of unidirectional CF/PEEK composites from commingled yarn prepreg

Relationships between impregnation mechanisms, consolidation quality and resulting mechanical properties of CF/PEEK thermoplastic composites manufactured from a commingled yarn system have been investigated. A small compression mould was used to apply the different processing conditions (i.e. pressure, holding time and processing temperature). The consolidation quality of finished samples was characterized mainly through microscopic studies of the microstructure of the material associated with density measurements and evaluations of mechanical properties using a small transverse flexure testing facility. A model for qualitatively describing the impregnation and consolidation processes in commingled-yarn-based thermoplastic composites was developed, which predicts variations of void content during consolidation as well as the time, temperature and pressure required to reach full consolidation. Good correlations between predictions and the experimental data indicate the success of the approach. For a desired, minimum level of void content (X_v = 0.5%), optimum processing windows for manufacturing of CF/PEEK composite parts from the commingled yarn preform are suggested.     

TEM Investigations of Fine Niobium Precipitates in HSLA Steel

Commercially produced 0.03 % C, 0.08 % Nb, 0.01 % Ti high strength low alloyed (HSLA) steel in the form of 20 mm thick plates was investigated. The steel was thermomechanically processed and the mechanical properties of the steel were evaluated by tensile testing. Using analytical and high resolution transmission electron microscopy the distribution, morphology, composition, crystal structure and particle size of niobium and titanium carbonitrides were observed and identified in these steels. The distribution of the precipitates was found to be nearly random, with occasional occurrence of precipitation free zones. Complex agglomerates with a cubic TiN seed crystal overgrown by a cubic NbC particle were the most commonly observed precipitates. Further TEM analysis in the accelerated cooled and tempered specimens in 1/4 plate thickness did not reveal any evidence that additional precipitation in the ferrite occurred. Precipitation in ferrite was only detected after subsequent cold deformation and tempering of the same samples. By a combination of EFTEM, STEM, HRTEM in addition to EDX spectroscopy, a large population of strain induced NbC precipitates with fcc crystal structure ranging in size down to 2 nm were identified in the ferrite matrix.     

Review of ECSC research work in ironmaking

The Treaty of the European Coal and Steel Community (ECSC), which expired in 2002, states in its Article 55 to promote technical and economic research with respect to the production and growing application of coal and steel. The results of funded research projects shall be made available to all representatives and partners concerned. For the European steel industry Article 55 was the basis for building up a steel research programme covering topics from raw materials to steel application and instigated a European network of researchers from the steel industry, research institutes and universities. On the basis of these research and development activities carried out by the ECSC steel research, the iron and steel industry has shown important advances in technology and environmental compatibility. Furthermore, the ECSC steel research has contributed to nearly all important technological developments. The main objective of the ECSC steel Research and Technology Development (RTD) programme was to sustain and develop the Community steel industry's competitiveness. The following report describes fundamental developments and activities within the framework of ECSC research with particular respect to hot metal production in the last 15 years.     

Relative quantification of proteins in human cerebrospinal fluids by MS/MS using 6-plex isobaric tags

A new 6-plex isobaric mass tagging technology is presented, and proof of principle studies are carried out using standard protein mixtures and human cerebrospinal fluid (CSF) samples. The Tandem Mass Tags (TMT) comprise a set of structurally identical tags which label peptides on free amino-terminus and epsilon-amino functions of lysine residues. During MS/MS fragmentation, quantification information is obtained through the losses of the reporter ions. After evaluation of the relative quantification with the 6-plex version of the TMT on a model protein mixture at various concentrations, the quantification of proteins in CSF samples was performed using shotgun methods. Human postmortem (PM) CSF was taken as a model of massive brain injury and comparison was carried out with antemortem (AM) CSF. After immunoaffinity depletion, triplicates of AM and PM CSF pooled samples were reduced, alkylated, digested by trypsin, and labeled, respectively, with the six isobaric variants of the TMT (with reporter ions from m/z = 126.1 to 131.1 Th). The samples were pooled and fractionated by SCX chromatography. After RP-LC separation, peptides were identified and quantified by MS/MS analysis with MALDI TOF/TOF and ESI-Q-TOF. The concentration of 78 identified proteins was shown to be clearly increased in PM CSF samples compared to AM. Some of these proteins, like GFAP, protein S100B, and PARK7, have been previously described as brain damage biomarkers, supporting the PM CSF as a valid model of brain insult. ELISA for these proteins confirmed their elevated concentration in PM CSF. This work demonstrates the validity and robustness of the tandem mass tag (TMT) approach for quantitative MS-based proteomics.     

Reaktives Magnetronsputtern von Dünnschichtsolarzellen

Reactive Magnetron Sputtering of Thin Film Solar Cells We show that reactive magnetron sputtering is well suited to deposit CuInS₂‐thin film absorber layers of high electronic quality. Using metallic targets and substrate temperatures below 500 °C, compact films with grain sizes in the micrometer range can be obtained. The structural and electronic properties of these layers are comparable to CuInS₂ thin films prepared by a 2‐step sulfurization process, which is being commercialized at present. In particular, the reactively sputtered films show minority carrier diffusion lengths larger than the layer thickness (≈ 2μm). This results in solar cells with conversion efficiences larger than 10 %, comparable to the best conversion efficiencies for CuInS₂‐solar cells obtained from other deposition processes. These results are promising for the potential application of magnetron sputtering as a large area deposition process for absorber layers in thin film solar cells.     

Encapsulation of bacteria and viruses in electrospun nanofibres

Bacteria and viruses were encapsulated in electrospun polymer nanofibres. The bacteria and viruses were suspended in a solution of poly(vinyl alcohol) (PVA) in water and subjected to an electrostatic field of the order of 1?kV?cm(-1). Encapsulated bacteria in this work, (Escherichia coli, Staphylococcus albus) and bacterial viruses (T7, T4, λ) managed to survive the electrospinning process while maintaining their viability at fairly high levels. Subsequently the bacteria and viruses remain viable during three months at -20 and -55?°C without a further decrease in number. The present results demonstrate the potential of the electrospinning process for the encapsulation and immobilization of living biological material.     

Interferometric null test of a deep parabolic reflector generating a Hertzian dipole field

We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided by means of ray tracing simulations. It turns out that the usual misalignment approximations fail under these extreme conditions.     

Contact and edge effects in graphene devices

Electrical transport studies on graphene have been focused mainly on the linear dispersion region around the Fermi level and, in particular, on the effects associated with the quasiparticles in graphene behaving as relativistic particles known as Dirac fermions. However, some theoretical work has suggested that several features of electron transport in graphene are better described by conventional semiconductor physics. Here we use scanning photocurrent microscopy to explore the impact of electrical contacts and sheet edges on charge transport through graphene devices. The photocurrent distribution reveals the presence of potential steps that act as transport barriers at the metal contacts. Modulations in the electrical potential within the graphene sheets are also observed. Moreover, we find that the transition from the p- to n-type regime induced by electrostatic gating does not occur homogeneously within the sheets. Instead, at low carrier densities we observe the formation of p-type conducting edges surrounding a central n-type channel.     

Fabrication of an array of single-electron transistors for a scanning probe microscope sensor

A technique for the fabrication of single-electron transistors (SETs) on tips for use in scanning probe microscopy is presented. The tips are micromachined out of an MBE-grown AlGaAs-GaAs heterostructure with a trench within each tip. The SETs are produced by aluminum evaporation and oxidation, and natural shadowing by the trench is used to separate the source and drain electrodes. By separating adjacent tips also by trenches, the concept allows the fabrication of tip arrays for parallel probing.