Vergleichende Untersuchungen über die Korrosionsbeständigkeit verzinkter und aluminierter Stahlbleche

Untersuchung des Korrosionsverhaltens von spritz- und feuerverzinkten sowie gleichartig aluminierten Stahlblechen im Salzwasser-Sprühversuch, durch Lagerung in Kochsalzlösung und durch Prüfung im Schwitzwasser-Wechselklima ohne und mit Zusatz von Kohlendioxyd und Schwefeldioxyd. Beurteilung der Probenoberflächen; Querschliffuntersuchungen sowie chemische und röntgenographische Untersuchung der Korrosionsprodukte.     

Existence, structure and valence properties of the skutterudites CeyFe4−xCoxSb12

We report on sample preparation, annealing effects, electron microprobe analysis in the series Ce_yFe_4−xCo_xSb₁₂ which shows that a phase separation occurs for substituted samples (0<x<4) annealed at 650 and 550 °C. Single phase samples are obtained for either Ce_yFe₄Sb₁₂ or Ce_yCo₄Sb₁₂ samples annealed at 650 °C and for all compositions when annealed at 700 °C. The valence state of Ce in homogeneous samples has been studied using X-ray absorption spectroscopy (XAS). Ce ions are trivalent throughout the series and the XAS spectra does not show effect of the crystal field on the 5d-final state.     

Mechanism of the Generation of Donor–Acceptor Pairs in Heavily Doped <Emphasis Type="Italic">n</Emphasis>-ZrNiSn with the Ga Acceptor Impurity

The nature of the mechanism of the simultaneous generation of donor–acceptor pairs under heavy doping of n-ZrNiSn intermetallic semiconductor with the Ga acceptor impurity is established. Such spatial arrangement in the crystal lattice of ZrNiSn_1–xGa _x is found when the rate of movement of the Fermi level εF found from calculations of the density distribution of electron states coincides with that experimentally established from dependences lnρ(1/T). It is shown that when the Ga impurity atom (4s²4p¹) occupies the 4b sites of Sn atoms (5s²5p²), structural defects of both acceptor nature and donor nature in the form of vacancies in the 4b site are simultaneously generated. The results are discussed in the scope of the Shklovskii–Efros model of a heavily doped and compensated semiconductor.     

Features of a priori heavy doping of the <Emphasis Type="Italic">n</Emphasis>-TiNiSn intermetallic semiconductor

The crystal structure, the distribution of electron density, and the energy, kinetic, and magnetic properties of the n-TiNiSn intermetallic semiconductor are investigated. It is shown that a priori doping of n-TiNiSn with donors originates from partial, up to 0.5 at %, redistribution of Ti and Ni atoms in crystallographic sites of Ti atoms. The correlation is established between the donor concentration, amplitude of modulation of the continuous energy bands, and degree of filling of low-scale fluctuation potential wells with charge carriers. The results obtained are discussed within the Shklovskii-Efros model of a heavily doped and compensated semiconductor.     

Effect of High-Pressure Torsion on Texture,Microstructure, and Raman Spectroscopy: Case Study of Fe- and Te-Substituted CoSb3

Fe_0.05Co_0.95Sb_2.875Te_0.125, a double-element-substituted skutterudite, was prepared by induction melting, annealing, and hot pressing (HP). The hot-pressed sample was subjected to high-pressure torsion (HPT) with 4 GPa pressure at 673 K. X-ray diffraction was performed before and after HPT processing of the sample; the skutterudite phase was observed as a main phase, but an additional impurity phase (CoSb₂) was observed in the HPT-processed sample. Surface morphology was determined by high-resolution scanning electron microscopy. In the HP sample, coarse grains with sizes in the range of approximately 100 nm to 300 nm were obtained. They changed to fine grains with a reduction in grain size to 75 nm to 125 nm after HPT due to severe plastic deformation. Crystallographic texture, as measured by x-ray diffraction, indicated strengthening of (112), (102) poles and weakening of the (123) pole of the HPT-processed sample. Raman-active vibrational modes showed a peak position shift towards the lower energy side, indicating softening of the modes after HPT. The distortion of the rectangular Sb–Sb rings leads to broadening of Sb–Sb vibrational modes due to local strain fluctuation. In the HPT process, a significant effect on the shorter Sb–Sb bond was observed as compared with the longer Sb–Sb bond.     

三元合金中组元扩散系数的预测模型

提出了预测三元系合金中原子浓度（原子分数,％）低于１０的组元的扩散系数,本征扩散系数的热力学因子的模型：通过此模型预测１４７３Ｋ时,Ｎｉ－Ａｌ－Ｃｒ（富Ｎｉ）三元合金系的扩散系数,并和实验值进行比较,模型预测结果良好。     

Surface Topography and Biocompatibility of cp–Ti Grade2 Fabricated by Laser-Based Powder Bed Fusion: Influence of Printing Orientation and Surface Treatments

The selective laser melting process, commonly known as laser-based powder bed fusion (LB-PBF), enables the production of structures with unprecedented degrees of freedom that represents an excellent condition for development of metallic implants for biomedical applications. Herein, the effects of laser energy density on relative density and microstructure (presence of internal defects) of cp-TiGd2 fabricated by LB-PBF are studied. Additionally, the influence of printing orientation and different surface treatments on surface topography and biocompatibility are investigated. The aim of the research is to develop additive manufacturing process parameters that can achieve full density of cp-TiGd2 with satisfactory biocompatibility, as a low-cost alternative to biomedical materials such as Ti–6Al–4 V and Ti–6Al–7Nb. A wide range variation of process parameters leads to an optimized process with high density up to 99.97 ± 0.008%, improved surface roughness, and noncytotoxicity in horizontal and inclined as-built condition, as well as in Al₂O₃ (blasting angle 0°) condition.