Role of platinum in the Na2SO4-Induced hot corrosion resistance of aluminum duffusion coatings

Electrochemical corrosion measurements have been carried out with Pt-containing and Pt-free Al-diffusion coatings on IN 738 LC in a 90Na₂SO₄+ 10K₂SO₄ (mol%) melt at 1173 K. Pt improves the resistance to basic fluxing while there are no significant differences between both coating types in their resistance to acidic fluxing. The corrosion resistance of the Pt-containing coating is also higher in the passive potential region where protective scales rich in Al₂O₃ are formed. The reason for the different behavior of both coating types appears to be related to the high corrosion resistance of the Pt-rich surface layer of the coating and an increased Al₂O₃ content in the scale of the Pt-containing type.     

Crystal structure and physical properties of YbCuZnSb2

The crystal structure of YbCuZnSb₂ has been determined for the first time by single-crystal X-ray diffraction analysis. It is shown that YbCuZnSb₂ has a CaAl₂Si₂-type structure, space group is P-3m1, with the following unit cell parameters: a = 4.4394(1) and c = 7.4139(3) Å. Magnetic susceptibility measurements performed in the temperature range from 2 to 300 K show that ytterbium ions are found in a nonmagnetic 4f ¹⁴ ground state (Yb²⁺). YbCuZnSb₂ exhibits p-type conductivity. The temperature dependence of the resistivity has a metallic character. The variations in the Cu/Zn ratio in the synthesized material occur without any disturbance of the structural type. This fact may confirm the existence of a solid solution between the YbZn₂Sb₂ and YbCuZnSb₂ compounds.     

Oxidation und Aufkohlung hochlegierter Werkstoffe für Crackrohre – Teil 2: Das Aufkohlungsverhalten in sauerstoff- und kohlenstoffhaltigen Atmosphären hoher Kohlenstoffaktivität

Oxidation and Carburization of High Alloyed Materials for Cracking Tubes – Part 2: The Carburization Behaviour in Oxygen and Carbon Containing Atmospheres with High Carbon Activity Carburization tests have been carried out with the casting materials (German Designation) Werkstoff-Nr. 1.4848, 1.4857, 2.4813 and an experimental 25/20/5-CrNiSi melt, and with the wrought materials Werkstoff Nr. 1.4301 and 1.4848 in CO-CO₂ mixtures with a_c = 1, and in humid natural gas with a_c > 1 between 1000 and 1200° C. At temperatures below appr. 1050° C oxide layers formed are analogous to those formed in air (substrate/Cr₂O₃/(Mn, Fe)Cr₂O₄) which prevent carburization. Carburization takes place only after the protective oxide layer has been destroyed. In this context several mechanisms of destruction must be considered, i.e. (a) by chemical reaction (transformation of oxide into carbide, reduction of oxide), (b) by mechanical stresses (temperature fluctuation, growth of graphite layers, creep deformation). Reduction processes are encountered with Fe-rich oxide layers only. Scale layers rich in chromium oxide are transformed into carbide above appr. 1050° C in gases with a_c = 1, depending on the CO partial pressure. The rate of this transformation strongly depends on carbon activity in the gas phase. When graphite is deposited on the surface the transformation occurs at a high rate, while it is rather slow even at a_c = 1 when no graphite is deposited. Deposited graphite may have a mechanically destructive effect, too, because it penetrates into cracks and pores in the oxide layer and thus produces spalling of oxide particles. When the surface of the cast material is porous particles of the substrate may become detached, too. This goes to explain the poor behaviour of tubes with as cast surfaces in cracking reactors. The positive effect of silicon is due to the formation of protective silica layers between metal and Cr₂O₃ and metal and external carbide layer respectively. In order to form a continuous silica layer the Si content in the material must not be below a cricital value.     

Verhalten von Gasturbinenschaufelwerkstoffen bei mechanischer Langzeitbeanspruchung unter Heißgaskorrosion. Teil 2: Metallkundliche Nachuntersuchungen

Behaviour of gas turbine blade materials under mechanical long term loading and hot gas corrosion. Part 2: Metallographical and microanalytical investigations Results of metallographical and microanalytical investigations on selected specimens after mechanical long term creep and LCF-loading under hot gas corrosion conditions will be presented. Uncoated and MCrAlY or Al-diffusion coated specimens of the polycristalline materials IN-738 LC and IN-939 and the single crystal alloys M 002 mod., CM-SX-6 and B 1914 were investigated. The corrosion attack increases with increasing impurities of the hot gas. Internal nitridation and sulphidation of base material or coating is observed after deterioration of the protective scales rich in Cr₂O₃ and/or Al₂O₃.     

Scale formation on the Ni-base superalloys IN 939 and IN 738 LC

The scales formed on the superalloys IN 939 and IN 738 LC at 700, 900, and 1100°C in air have been investigated by optical, microprobe analysis and x-ray diffraction measurements. Both alloys form very similar scales. The main components are an outer TiO₂ layer, an intermediate Cr₂O₃ layer with dissolved Ti, and an inner layer of (Ti, Nb, Ta)O₂ with rutile structure. Beneath the scale an internal corrosion zone is formed that contained Al₂O₃ directly beneath the external scale and TiN further into the substrate.     

XXIII International Materials Research Congress (IMRC)

The XXIII International Materials Research Congress (IMRC) 2014 was held in August in one of the most pleasant and beautiful places of Mexico, Cancun, situated in the tropical Yucatan Peninsula. It was jointly promoted and organised by the Sociedad Mexicana de Materiales (MRS-Mexico) and the Materials Research Society (MRS-USA), devoted to advancing materials and improving the quality of life. This annual meeting provides a forum to assess advances in the vast field of materials science, technology and engineering. The event has become a tradition for thousands of fundamental and applied researchers and peers from industry as well as graduate and postgraduate students from all over the world.     

Korrosionsschäden am Förderband eines Ofens zur Reinigung von mit organischen Chlorverbindungen kontaminiertem Erdboden

Corrosion damage to the conveyor belt of a furnace for the removal of soil from organic chlorine compounds This paper reports the corrosion behaviour of metallic materials which were used in components of a conveyor belt of a decontamination furnace or of which specimens were attached to the belt for testing purposes. The furnace was used for decontaminating soil containing organic chlorine compounds. A total of 1 ferritic and 8 austenitic steels, 9 nickel base alloys, 2 east steels with 15 % Si and 15 % Si + 5 % Cr respectively, and 3 aluminised steels were tested and afterwards investigated by metallographic and micro-analytical methods. Most of the materials failed due to external and/or internal corrosion, preferentially along grain boundaries. The 2 cast steels revealed fairly good corrosion resistance. The material 2.4061 (LC-Ni 99.6) displayed surprisingly good behaviour, however it remains to be seen whether the inward migration of O and C along grain boundaries causes embrittlement. The materials 2.4610 and 2.4831, containing 14-17 % Mo and 8.5-9,5 % Mo respectively, showed good resistance. The reason for this good corrosion resistance could not be clarified. One reason may be the relatively high Mo content but other materials with a comparable Mo content, like materials 2.4856 and 2.4663, were significantly attacked. It appears necessary to check the long-term behaviour of these two materials.     

Illness intrusiveness and quality of life in end-stage renal disease: Comparison and stability across treatment modalities.

Examined the impact of illness intrusiveness (ILI) on quality of life (QOL) in 99 patients with end-stage renal disease. Ss were interviewed twice, 6 wks apart, to determine differences in perceived ILI across treatment modalities, life domains, and time. Life domains were affected differentially across treatments. Perceived ILI correlated significantly with treatment time requirements, uremic symptoms, intercurrent nonrenal illnesses, fatigue, and difficulties in daily activities. Significant QOL differences emerged across treatment modalities for satisfaction/happiness and pessimism/illness related concerns but not for depression/distress. Perceived ILI correlated significantly with each of these QOL measures. Findings substantiate the construct of ILI as a mediator of the psychosocial impact of chronic, life-threatening illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Artificial Cilia: Generation of Magnetic Actuators in Microfluidic Systems

Magnetic artificial cilia are fabricated from photoreactive copolymer precursors filled with magnetic nanoparticles by a new photolithographic process. Two different crosslinkers and UV‐radiation of two different wavelengths are used to generate arrays of planar magnetically actuatable rubber flaps. The cilia are integrated into a microfluidic channel and operated in water using a rotating permanent magnet.