Interrelationship between atomic species, bias voltage, texture and microstructure of nano-scale multilayers

A matrix of binary and ternary nitrides containing lighter elements (Al, Ti, V and Cr) with atomic mass 89 has been formulated. These have been grown as nano-scale multilayer coatings (bilayer thickness approx. 3.0 nm) on stainless steel substrates using an industrial size multiple-target ABS coater. When lighter elements are incorporated into the multilayer at a lower bias voltage (U-B = -75 V) pronounced {111} or {110}, textures develop which are determined by the dominating species present. A {111} or {110} texture develops when TiAlN or VN and or CrN dominates the matrix, respectively. In contrast when a heavier element is incorporated a {100} texture is observed. Additionally, there is a strong indication that in the case when heavy elements (>89) are involved in the growth process, which evolves by continuous re-nucleation. Conversely, when only light elements (<52) are involved then the coating evolves by competitive growth. This observation is limited only for the lower bias voltage range of U-B -75 to -120 V However, as the bias voltage is increased (up to U-B = -150 V) the texture becomes increasingly sharp and in all cases a {111} texture develops. A lower residual compressive stress (typically -1.8 GPa) is observed when one of the bi-layers is dominated by a heavier element. The stress increases (up to -6.8 GPa) in these coatings when the bias voltage is increased to U-B = -150 V which is always systematically lower than in coatings containing only lighter elements which are typically up to -11.7 GPa at the same bias voltage. In parallel this results in an increase in plastic hardness (80 GPa) and in the sliding wear coefficient by an order of magnitude regardless of the type of lattice growth observed

The effect of (Ti + Al): V ratio on the structure and oxidation behaviour of TiAlN/VN nano-scale multilayer coatings

Nano-scaled multilayered TiAlN/VN coatings have been grown on stainless steel and M2 high speed steel substrates at U-B = - 85 V in an industrial, four target, Hauzer HTC 1000 coater using combined cathodic steered arc etching/unbalanced magnetron sputtering. X-ray diffraction (XRD) has been used to investigate the effects of process parameters (Target Power) on texture evolution (using texture parameter T*), development of residual stress (sin(2) psi method) and nano-scale multilayer period. The composition of the coating was determined using energy dispersive X-ray analysis. The thermal behaviour of the coatings in air was studied using thermo-gravimetric analysis, XRD and scanning electron microscopy. The bi-layer period varied between 2.8 and 3.1 nm and in all cases a {1 1 0} texture developed with a maximum value T* = 4.9. The residual stress varied between -5.2 and -7.4 GPa. The onset of rapid oxidation occurred between 628 and 645 degreesC depending on the (Ti+Al):V ratio. After oxidation in air at 550 degreesC AlVO4, TiO2 and V2O5 Phases were identified by XRD with the AlVO4, TiO2 being the major phases. The formation of AlVO4 appears to disrupt the formation of Al2O3 which imparts oxidation resistance to TiAlN based coatings. Increasing the temperature to 600 and 640 degreesC led to a dramatic increase in the formation of V2O5 which was highly oriented (0 0 1) with a plate-like morphology. At 640 degreesC there was no evidence of the coating on XRD. Increasing the temperature to 670 degreesC led to further formation of AlVO4 and a dramatic reduction in V2O5. (C) 2003 Elsevier B.V. All rights reserved

Seasonal dynamics modifies fat of oxygen, nitrate, and organic micropollutants during bank filtration - temperature-dependent reactive transport modeling of field data

Bank filtration is considered to improve water quality through microbially mediated degradation of pollutants and is suitable for waterworks to increase their production. In particular, aquifer temperatures and oxygen supply have a great impact on many microbial processes. To investigate the temporal and spatial behavior of selected organic micropollutants during bank filtration in dependence of relevant biogeochemical conditions, we have set up a 2D reactive transport model using MODFLOW and PHT3D under the user interface ORTI3D. The considered 160-m-long transect ranges from the surface water to a groundwater extraction well of the adjacent waterworks. For this purpose, water levels, temperatures, and chemical parameters were regularly measured in the surface water and groundwater observation wells over one and a half years. To simulate the effect of seasonal temperature variations on microbial mediated degradation, we applied an empirical temperature factor, which yields a strong reduction of the degradation rate at groundwater temperatures below 11 °C. Except for acesulfame, the considered organic micropollutants are substantially degraded along their subsurface flow paths with maximum degradation rates in the range of 1

Sand box experiments to evaluate the influence of subsurface temperature probe design on temperature based water flux calculation

Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface temperatures. The influence of temperature probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four temperature probe setups were installed into a sand box experiment to measure temporal highly resolved vertical temperature profiles under controlled water fluxes in the range of ±1.3 m d&lt;sup&gt;−1&lt;/sup&gt;. Pass band filtering provided amplitude differences and phase shifts of the diurnal temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to temperature sensor spacing, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of temperature probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small sensor distances of all setups were found to be insensitive to vertical water flux