Thermo-physical properties of as deposited and aged thermal barrier coatings (TBC) for gas turbines: State-of-the art and advanced TBCs

In the perspective of fuelling the future generations of gas turbines by hydrogen rich syngas, the evaluation of the effect of a higher water vapour content into the flue gases on the TBC used, or potentially usable, is a need. For this purpose YPSZ APS TBC with two different microstructures have been exposed for 500?h at different temperatures in the range 1000?°C–1250?°C either in air and air +20% vol. H₂O. The comparison between the different testing conditions has been performed in terms of sintering kinetics and phase stability, as evaluated by thermal diffusivity measurements and Synchrotron X-Rays diffraction, respectively. Furthermore the characterisation of thermal properties of two innovative TBCs (GZO-YPSZ and YAG) potentially able to withstand the CMAS attack and erosive environments, respectively, has been carried out.No clear evidence of a different behaviour of TBC has been observed, at least in the considered aging time and temperature range.     

Optimal Massing Liquid Volume Determination by Energy Consumption Measurement: Study of the Influence of Some Physical Properties of Solvents and Products Used

This study tried to investigate, by the power comsumption technique, the influence of the powder's and solvent's properties on wet granulation.

It could be shown that the required amount of granulation liquid decreases when the particle size of the powder to be granulated increases. This relationship is however only true when the particle size distribution of the powder to be granulated is rather narrow.

Powders having the same solubility in different solvents require the same optimal liquid quantity for granulation, but the properties of resulting granules depend on surface tension and wetting properties of the solvent.

When the powder to be granulated contains crystallisation water, the temperature rising in the mixer can be sufficient to liberate this water, which must be taken into account in the optimal granulation liquid requirement.

The effect of a macromolecular binder (PVP, HPMC) has also been studied: the optimal liquid quantity required changes with the kind of binder used and the manufacturing process (binder used in solution or added as dry powder).

It was also shown that in the case of lactose, the optimal quantity of PVP or HPMC can be determined from the power consumption records and from the granules friability studies     

Thermal Mechanical Fatigue Behavior of Advanced Overlay Coatings

Environmental protection and cost effectiveness lead to the demand to increase the efficiency of energy conversion. In the past decade gas turbines have become an important factor in efficient power generation. Gas turbine inlet temperatures are being increased continuously to decrease the specific fuel consumption. The development of new base materials and sophisticated processes like single crystal solidification allows higher metal temperatures. This causes higher oxidative stress to the MCrAlY overlay coatings. As shown in an earlier paper (I), an improvement of the high temperature properties is achievable by the addition of Rhenium. In this paper we report on properl ies of MCrAlY coatings containing 8 to 12% Al and 10% Rhenium by weight. The coatings were applied on Inco 738 LC by LPPS (Low Pressure Plasma Spraying). Data for static oxidation and cyclic oxidation data at 950°C, I000°C up to 10,000 hours are presented. However, the main aim of this report is to discuss the thermal-mechanical properties of LPPS-coatings with Re. As known from earlier work, the variation or addition of different elements to overlay coatings lead to a change in the ductile-brittle transition. Ductile-Brittle-Transition-Temperature (DBTT) measurements on 10% Re containing systems under the variation of Co, Cr, Al and Si have been done. In order to get more information about the thermal-mechanical properties of the coating under service like conditions, TCF (Thermal Cycle Fatigue) and TMF (Thermal Mechanical Fatigue) tests were carried out. On discus shaped samples, the TCF behavior of an MCrAlYRe coating in comparison to an MCrAlY coating has been evaluated up to 1,500 cycles. The samples were heated in a radiation oven up to 1000°C and cooled down by compressed air. By this method a differentiation in the thermal fatigue behavior is possible. However, this kind of test does not cover all possible relaxation processes. A more realistic investigation of the thermal mechanical fatigue behavior is given by TMF tests. A service life cycle was taken to study the thermal mechanical behavior. It is shown that Re improves the thermal mechanical properties of MCrAlY coating systems considerably.     

Robust camera model identification using demosaicing residual features

Multimedia Tools and Applications - In this paper, we propose a new framework for performing accurate and robust camera model identification by fully exploiting demosaicing information in a...     

Influence of a cyclic butylene terephthalate oligomer on the processability and thermoelectric properties of polycarbonate/MWCNT nanocomposites

The thermoelectric properties of melt-processed nanocomposites consisting of a polycarbonate (PC) thermoplastic matrix filled with commercially available carboxyl (–COOH) functionalized multi-walled carbon nanotubes (MWCNTs) were evaluated. MWCNTs carrying carboxylic acid moieties (MWCNT-COOH) were used due the p-doping that the carboxyl groups facilitate, via electron withdrawing from the electron-rich π-conjugated system. Preliminary thermogravimetric analysis (TGA) of MWCNT-COOH revealed that the melt-mixing was limited at low temperatures due to thermal decomposition of the MWCNT functional groups. Therefore, PC was mixed with 2.5 wt% MWCNT-COOH (PC/MWCNT-COOH) at 240 °C and 270 °C. In order to reduce the polymer melt viscosity, a cyclic butylene terephthalate (CBT) oligomer was utilized as an additive, improving additionally the electrical conductivity of the nanocomposites. The melt rheological characterization of neat PC and PC/CBT blends demonstrated a significant decrease of the complex viscosity by the addition of CBT (10 wt%). Optical and transmission electron microscopy (OM, TEM) depicted an improved MWCNT dispersion in the PC/CBT polymer blend. The electrical conductivity was remarkably higher for the PC/MWCNT-COOH/CBT composites compared to the PC/MWCNT-COOH ones. Namely, the PC/MWCNT-COOH/CBT processed at 270 °C exhibited the best values with electrical conductivity; σ = 0.05 S/m, Seebeck coefficient; S = 13.55 μV/K, power factor; PF = 7.60 × 10⁻⁶μW/m K⁻², and thermoelectric figure of merit; ZT = 7.94 × 10⁻⁹. The PC/MWCNT-COOH/CBT nanocomposites could be ideal candidates for large-scale thermal energy harvesting, even though the presently obtained ZT values are still too low for commercial applications.     

Intercellular signaling in Stigmatella aurantiaca: purification and characterization of stigmolone, a myxobacterial pheromone

The myxobacterium Stigmatella aurantiaca passes through a life cycle that involves formation of a multicellular fruiting body as the most complex stage. An early step in this differentiation process depends on a signal factor secreted by the cells when nutrients become limited. The formation of a fruiting body from a small cell population can be accelerated by addition of this secreted material. The bioactive compound was found to be steam volatile. It was purified to homogeneity by steam distillation followed by reversed-phase and normal-phase HPLC. The pheromone was named stigmolone, in accordance with the structure 2,5, 8-trimethyl-8-hydroxy-nonan-4-one, as determined by NMR and mass spectrometry. Stigmolone represents a structurally unique and highly bioactive prokaryotic pheromone that is effective in the bioassay at 1 nM concentration.     

A rural perspective on health care for the whole person.

The authors summarize the health care problems facing rural and frontier America by addressing five key issues within the framework of health care for the whole person: how to (a) provide health care access, (b) ensure health care quality, (c) provide a range of health care or meet the scope of practice demands, (d) address regional, rural-specific characteristics that may exist, and (e) address health professionals' quality of life. When working in rural and frontier areas it is crucial for providers to collaborate across all types of health care to provide better care and better utilize a region's tautly stretched resources. Rural health care resources are provided. The authors attempt to demonstrate characteristics of rural culture and rural and frontier populations' health care disparities, highlighting the need for collaborative care. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metallic nickel nanorod arrays embedded into ordered block copolymer templates

We report on metallic Nickel nanorods prepared by utilizing a mask of ordered nanostructured hollow channels in a block copolymer matrix. These polymeric templates were formed by a self organized process in block copolymer supramolecular assemblies. Nickel was filled into with two different techniques, electrodeposition and washing in. We monitor the formation process of these nanorods by means of atomic force microscopy and synchrotron radiation soft X-ray based photoelectron emission microscopy. The oxidation state of the nickelrods is evaluated with X-ray absorption spectroscopy and X-ray photoelectron spectroscopy at the Ni L edges and lateral distributions of the Ni nanorods were detected with micrometer resolved X-ray absorption spectroscopy. The finding is that the Ni rods were metallic despite their preparation under ambient conditions, inside the particles no hints for NiO complexes were found. This indicates that the polymer protects Ni nanoparticles against oxidation.