Treibacher (Austria)

ABSTRACT The widespread use of pyrethroid and organophosphate pesticides necessitates accurate toxicity predictions for regulatory compliance. In this study QSAR and SSD models for six pyrethroid and four organophosphate compounds using QSAR Toolbox and SSD Toolbox have been developed. The QSAR models, described by the formula 48 h-EC50 or 96 h-LC50 = x + y * log Kow, were validated for predicting 48 h-EC50 values for acute Daphnia toxicity and 96 h-LC50 values for acute fish toxicity, meeting criteria of n ≥10, r 2 ≥0.7, and Q 2 >0.5. Predicted 48 h-EC50 values for pyrethroids ranged from 3.95 × 10−5 mg/L (permethrin) to 8.21 × 10−3 mg/L (fenpropathrin), and 96 h-LC50 values from 3.89 × 10−5 mg/L (permethrin) to 1.68 × 10−2 mg/L (metofluthrin). For organophosphates, 48 h-EC50 values ranged from 2.00 × 10−5 mg/L (carbophenothion) to 3.76 × 10−2 mg/L (crufomate) and 96 h-LC50 values from 3.81 × 10−3 mg/L (carbophenothion) to 12.3 mg/L (crufomate). These values show a good agreement with experimental data, though some, like Carbophenothion, overestimated toxicity. HC05 values, indicating hazardous concentrations for 5% of species, range from 0.029 to 0.061 µg/L for pyrethroids and 0.030 to 0.072 µg/L for organophosphates. These values aid in establishing environmental quality standards (EQS). Compared to existing EQS, HC05 values for pyrethroids were less conservative, while those for organophosphates were comparable.

Abstract Thermal barrier coatings (TBCs) play a vital role in allowing the gas turbine engines to operate at high temperatures. With higher operating temperatures (>1200°C), the standard TBC material, 7-8wt. % Yttria Stabilized Zirconia (YSZ), is susceptible to CMAS (Calcium Magnesium Alumino Silicates) degradation and undesirable phase transformation. New TBC materials such as gadolinium zirconate (GZ) have shown to be capable of overcoming the challenges faced by YSZ. However, GZ has inferior fracture toughness relative to YSZ. In this work, three double layered TBC variations with different GZ and YSZ thickness respectively (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400GZ respectively, where the prefix numbers represent thickness in ìm) were produced by suspension plasma spray (SPS) process. In all the three double layered TBC variations, the overall TBC thickness with GZ as the top layer and YSZ as the base layer was kept the same (500 μm). The objective was to investigate the influence of YSZ thickness on the thermal cyclic fatigue performance of GZ/YSZ double layered TBC. The as sprayed TBCs were characterized by SEM, XRD and porosity measurements and later subjected to thermal cyclic fatigue test at 1100°C. It was observed that the GZ/YSZ double layered TBC with lowest YSZ thickness (400GZ/100YSZ) showed higher thermal cyclic lifetime whereas the TBC with thicker YSZ layer (100GZ/400YSZ) showed lowest thermal cyclic fatigue lifetime. The failure analysis of the thermally cycled TBCs revealed similar failure modes, i.e. spallation of the top coat due to horizontal crack propagation within the thermally grown oxide (TGO). Furthermore, the ceramic top coats in all the three TBC variations after failure showed the widening of column gaps.

Introduction of suspension and solution plasma spraying led to a breakthrough in the deposition of yttria-stabilized zirconia (YSZ) coatings and enabled preparation of new types of layers. However, their deposition with high feed rates needed, for example, for the deposition of thermal barrier coatings (TBCs) on large-scale components, is still challenging. In this study, possibility of high-throughput plasma spraying of YSZ coatings is demonstrated for the latest generation of high-enthalpy hybrid water-stabilized plasma (WSP-H) torch technology. The results show that microstructure of the coatings prepared by WSP-H may be tailored for specific applications by the choice of deposition conditions, in particular formulation of the liquid feedstock. Porous and columnar coatings with low thermal conductivity (0.5-0.6 W/mK) were prepared from commercial ethanol-based suspension. Dense vertically cracked coatings with higher thermal conductivity but also higher internal cohesion were deposited from suspension containing ethanol/water mixture and coarser YSZ particles. Spraying of solution formulated from diluted zirconium acetate and yttrium nitrate hexahydrate led also to the successful deposition of YSZ coating combining regions of porous and denser microstructure and providing both low thermal conductivity and improved cohesion of the coating. Enthalpy content, liquid-plasma interaction and coating buildup mechanisms are also discussed.

Efficiency of a gas turbine can be increased by increasing the operating temperature. Yttria‐stabilized zirconia ( YSZ ) is the standard thermal barrier coating ( TBC ) material used in gas turbine applications. However, above 1200°C, YSZ undergoes significant sintering and CMAS (calcium magnesium alumino silicate) infiltration. New ceramic materials of rare earth zirconate composition such as gadolinium zirconate ( GZ ) are promising candidates for thermal barrier coating applications ( TBC ) above 1200°C. Suspension plasma spray of single‐layer YSZ , double‐layer GZ / YSZ , and a triple‐layer TBC comprising denser GZ on top of GZ / YSZ TBC was attempted. The overall coating thickness in all three TBC s was kept the same. Isothermal oxidation performance of the three TBC s along with bare substrate and bond‐coated substrate was investigated for time intervals of 10 h, 50 h, and 100 h at 1150°C in air environment. Weight gain/loss analysis was carried out by sensitive weighing balance. Microstructural analysis was carried out using scanning electron microscopy ( SEM ). As‐sprayed single‐layer YSZ and double‐layer GZ / YSZ showed columnar microstructure, whereas the denser layer in the triple‐layer TBC was not columnar. Phase analysis of the top surface of as‐sprayed TBC s was carried out using XRD . Porosity measurements were made by water intrusion method. In the weight gain analysis and SEM analysis, multilayered TBC s showed lower weight gain and lower TGO thickness compared to single‐layer YSZ .

Biaxial strength testing of brittle materials using the ball on three balls (B3B) test is a new method for strength testing of disc or plate specimens [1] (see Fig. 1). The analysis of the stress fields and the calculation of the effective volumes and surfaces for several types of specimens and testing geometries has been performed recently. The ball on three balls testing method has several advantages compared to the common three- or four point bending tests: the results are very stable against small geometrical inaccuracies of the specimen or the test assembly, edge defects are not relevant and there exists only a very low influence of friction [2]. This makes this type of experiment ideal for testing very small specimens [3].