Effect of Shot Peening on Surface Characteristics and Fatigue Properties of T5-treated ZK60 Alloy
(2009)
In view of the complexity of thin-film solar cells, which are comprised of a multitude of layers, interfaces, surfaces, elements, impurities, etc., it is crucial to characterize and understand the
chemical and electronic structure of these components. Because of the high complexity of the Cu2ZnSn(S,Se)4 compound semiconductor absorber material alone, this is particularly true for kesterite-based devices. Hence, this paper reviews our recent progress in the characterization of Cu2ZnSnS4 (CZTS) thin films. It is demonstrated that a combination of different soft x-ray spectroscopies is an extraordinarily powerful method for illuminating the chemical and electronic material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of these properties. The focus of the article will be on secondary impurity phases, electronic structure, native oxidation, and the CZTS surface composition.
Resonant inelastic soft X-ray scattering (RIXS) has been used to study the
electronic structure of glycine and lysine in aqueous solution. Upon variation of the pH
value of the solution from acidic to basic, major changes of the nitrogen K edge RIXS data
are observed for both amino acids, which are associated with the protonation and
deprotonation of the amino groups. The experimental results are compared with
simulations based on density functional theory, yielding a detailed understanding of the
spectral changes, as well as insights into the ultrafast proton dynamics in the intermediate
core-excited/ionized state of the RIXS process.
Ti-90Al (in at.%) coatings were deposited on Ti-45Al-8Nb alloy at two different temperatures, 300 and 540 °C. The coatingsputtered at 300 °C consisted of Al and TiAl3 with columnar grain structure. The morphology, chemical composition and microstructureof the coating sputtered at540 °Cwere strongly dependent on the substrate microstructure. The two coating variantsformed oxidation-resistant Al2O3 scales during oxidation. The special morphological features of the coatings make them interestingfor geometrically structuring the surfaces to provoke the lotus effect.
Tensile and high cycle fatigue (HCF) properties of the hot-rolled Mg-12Gd-3Y (wt.%) magnesium alloyhave been investigated. The magnesium alloy exhibits a fatigue strength of about 150 MPa, which ismuch higher than that of the commercial Mg-8Al-Zn alloy AZ80. Aging heat-treatment (T5) improvedthe fatigue life of the Mg-12Gd-3Y alloy. Fatigue cracks nucleated at the intense slip bands in theas-rolled alloy. After T5 treatment, however, the fatigue crack nucleation site shifted to the phase boundariesbetween MgGdY particles and Mg matrix. T5 heat-treatment retarded the crack initiation and thusimproved the fatigue life of the Mg-12Gd-3Y alloy.
Motivated by promising results from experiments on the noise reduction performance of finite wall-mounted airfoils with a porous tip in an aeroacoustic wind tunnel, corresponding measurements were performed in a dedicated rotor test rig. This rig features a 3 kW direct-drive electric motor with three rotor blades of 1.1 m diameter. In the experiments, a variety of different tip modifications was tested regarding their noise reducing performance, including different porous materials that were manufactured using rapid prototyping. Acoustic measurements were performed at different rotationals speeds and blade angles using a ring-shaped microphone array consisting of 60 evenly spaced microphones. The rotational speed was measured using a laser sensor. Different beamforming algorithms were used in post-processing to help analyzing the data. The results show that porous tips can lead to a notable noise reduction at low frequencies, but a small penalty at medium and high frequencies which may be due to the surface roughness of the porous tips. This trend seems more severe for lower blade angles than for higher ones. These findings agree well with those obtained from the previous wind tunnel measurements.