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Thin films of Pb(Sc 1/2 Ta 1/2 )O 3 (PST) were fabricated using an optimized chemical solution deposition procedure involving the de-hydration of scandium acetate and the addition of up to 30% excess lead in solution. The choice of substrate was found to impact the thermal induced stress in the films as confirmed by wafer bending and in-plane grazing angle x-ray diffraction measurements. The presence of either a compressive or a tensile in-plane stress led to a reduction in the temperature of the dielectric maximum, whereas the value of the dielectric maximum remained relatively unchanged; its value reduced by an order of magnitude compared with ceramic samples. It is concluded that mechanical stress alone is not the sole factor in the reduction of PST thin film permittivity. Microstructural features resulting from processing induced defects or an incomplete transformation to the relaxor state may be responsible for this commonly observed phenomenon.

Stationary gas turbines for power generation are increasingly being equipped with low emission burners. By applying lean premixed combustion techniques for gaseous fuels both NOx and CO emissions can be reduced to extremely low levels (NOx emissions <25vppm, CO emissions <10vppm). Likewise, if analogous premix techniques can be applied to liquid fuels (diesel oil, Oil No.2, etc.) in gas-fired burners, similar low level emissions when burning oils are possible. For gas turbines which operate with liquid fuel or in dual fuel operation, VPL (Vaporised Premixed Lean)-combustion is essential for obtaining minimal NOx-emissions. An option is to vaporise the liquid fuel in a separate fuel vaporiser and subsequently supply the fuel vapour to the natural gas fuel injection system; this has not been investigated for gas turbine combustion in the past. This paper presents experimental results of atmospheric and high-pressure combustion tests using research premix burners running on vaporised liquid fuel. The following processes were investigated: • evaporation and partial decomposition of the liquid fuel (Oil No.2); • utilisation of low pressure exhaust gases to externally heat the high pressure fuel vaporiser; • operation of ABB premix-burners (EV burners) with vaporised Oil No.2; • combustion characteristics at pressures up to 25bar. Atmospheric VPL-combustion tests using Oil No.2 in ABB EV-burners under simulated gas turbine conditions have successfully produced emissions of NOx below 20vppm and of CO below 10vppm (corrected to 15% O2). 5vppm of these NOx values result from fuel bound nitrogen. Little dependence of these emissions on combustion pressure bas been observed. The techniques employed also ensured combustion with a stable non luminous (blue) flame during transition from gaseous to vaporised fuel. Additionally, no soot accumulation was detectable during combustion.

Depth sensing nanoindentation and nanoscratch testing were combined with atomic force microscopy (AFM) and electron microscopy observations to study mechanical properties and fracture behavior of a number of TixAl1-xNyC1-y hard thin films. Various failure modes were activated either by normal loading-unloading or by microscratching of the samples to provide an estimation of the fracture toughness and interfacial fracture energies. By changing chemical composition and deposition conditions various nanostructured thin films including monolitically grown single layer, nanocomposite, and multilayers were coated onto the tungsten carbide-cobalt substrates. All tested films exhibit elevated mechanical properties with high hardness (38 – 45 GPa) and modulus (500 – 570 GPa). Under sufficiently high load indentation the formation of corner Palmqvist type radial cracks were usually observed because of small modulus mismatch between coating and substrate, good adhesion, and in particular high toughness of both substrate and films in spite of great difference in their respective hardness. Various failure modes were activated and the sequences of fracture events were determined using stepwise or continuously increasing load scratch tests. Some other films were found to be more sensitive to tensile stress behind the indenter which generates regularly repeated microcracks on the scratch track. Other films in particular multilayers were appeared more susceptible to compressive stress ahead of the indenter leading to local delamination at the interface between layers and the formation of irregular microcracks under the contact zone.

The effects of hydrostatic pressure and biasing dc electric field on the relaxor dielectric response of samples of Pb[(Mg1∕3Ta2∕3)0.95Zr0.05]O3 with 12%, 15%, and 90% B-site cationic order were investigated. Qualitatively similar decreases in the amplitudes of the real part of the dielectric constant (ε′) at both the peak temperatures (Tm) of the ε′(T,ω) response in the high temperature phase, i.e., above Tm, are observed on increasing the three variables: pressure, biasing field, and B-site order - effects that are interpreted in terms of stiffening of the underlying soft ferroelectric mode of the lattice. Strong deviation of the frequency-independent ε′(T) from the Curie-Weiss law above Tm, attributed to correlations among polar nanodomains, gives way to adherence to this law above the Burns temperature Td. This is the temperature where polar nanodomains first make their presence known. The evolution with decreasing temperature below Td of short-range order in the nanodomains is estimated from the ε′(T) response and shows essentially no dependence on the degree of B-site order. The correlation length for the interaction among the polar nanodomains was also estimated from the dielectric data and found to exhibit strong increase (decrease) with temperature (pressure) as T approaches Tm from above - characteristics of perovskite relaxors. A high temperature dielectric relaxation with an activation energy of 1.27eV is observed for the 90% ordered sample, but not for the 12% and 15% ordered samples. This relaxation is attributed to increased oxygen vacancies in the 90% sample that form during the long (64h) annealing time at 1350°C to achieve this high level of ordering.