Influence of the Al(Co,Ni) layer on the corrosion resistance of a cobalt based alloy (Mar‐M‐509®)

In the present work, the results of studies on the structure and corrosion resistance of Al(Co, Ni) layer are shown. The diffusion Al(Co, Ni) layer was created on the cobalt alloy Mar‐M‐509 substrate by chemical vapor deposition (CVD) method with aluminum trichloride (AlCl₃) under the hydrogen atmosphere. The scanning electron microscope (SEM) observations and microtomography measurements of layers were performed. Also an analysis of the chemical (energy‐dispersive X‐ray spectroscopy (EDS)) and phase (X‐ray diffraction (XRD)) composition was carried out. By the X‐ray diffraction method (sin² φ) also the residual stresses were calculated in the matrix of the material. The corrosion resistance was tested with impedance and potentiodynamic methods in 0.1 M Na₂SO₄, 0.1 M H₂SO₄ solutions and acidulous 0.1 M NaCl solution (pH = 4.2) at room temperature. The results indicate that the analyzed layer with a thickness of about 14 μm have a similar corrosion resistance compared to the base material – Mar‐M‐509^® cobalt alloy. Only in the strongly acidic environments, the corrosion resistance of the layer is remarkably decreased.     

A cell‐based smoothed discrete shear gap method (CS‐FEM‐DSG3) based on the C0‐type higher‐order shear deformation theory for dynamic responses of Mindlin plates on viscoelastic foundations subjected to a moving sprung vehicle

A cell‐based smoothed discrete shear gap method (CS‐FEM‐DSG3) based on the first‐order shear deformation theory (FSDT) was recently proposed for static and dynamic analyses of Mindlin plates. In this paper, the CS‐FEM‐DSG3 is extended to the C⁰‐type higher‐order shear deformation plate theory (C⁰‐HSDT) and is incorporated with damping–spring systems for dynamic responses of Mindlin plates on viscoelastic foundations subjected to a moving sprung vehicle. At each time step of dynamic analysis, one four‐step procedure is performed including the following: (1) transformation of the weight of a four‐wheel vehicle into the sprung masses at wheels; (2) dynamic analysis of the sprung mass of wheels to determine the contact forces; (3) transformation of the contact forces into loads at nodes of plate elements; and (4) dynamic analysis of the plate elements on viscoelastic foundations. The accuracy and reliability of the proposed method are verified by comparing its numerical solutions with those of other available numerical results. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of l‐carnitine supplement on serum inflammatory cytokines,C‐reactive protein,lipoprotein (a), and oxidative stress in hemodialysis patients with Lp (a) hyperlipoproteinemia

Inflammation, oxidative stress, and high concentration of serum lipoprotein (a) [Lp (a)] are common complications in hemodialysis patients. The present study was designed to investigate the effects of l ‐carnitine supplement on serum inflammatory cytokines, C‐reactive protein (CRP), Lp (a), and oxidative stress in hemodialysis patients with Lp (a) hyperlipoproteinemia [hyper Lp (a)]. This was an unblinded, randomized clinical trial. Thirty‐six hyper Lp (a) hemodialysis patients (23 men and 13 women) were randomly assigned to either a carnitine or control group. Patients in the carnitine group received 1000 mg/d oral l ‐carnitine for 12 weeks, whereas patients in the control group did not receive any l ‐carnitine supplement. At baseline and the end of week 12, 5 mL of blood were collected after a 12‐ to 14‐hours fast and serum free carnitine, CRP, interleukin‐1β, interleukin‐6 (IL‐6), tumor necrosis factor‐α, Lp (a), and oxidized low‐density lipoprotein were measured. Serum free carnitine concentration increased significantly by 86% in the carnitine group at the end of week 12 compared with baseline (P<0.001), while serum CRP and IL‐6 showed a significant decrease of 29% (P<0.05) and 61% (P<0.001), respectively. No significant changes were observed in serum free carnitine, CRP, and IL‐6 in the control group. There were no significant differences between the two groups in mean changes of serum interleukin‐1β, tumor necrosis factor‐α, Lp (a), and oxidized low‐density lipoprotein concentrations. l ‐carnitine supplement reduces inflammation in hemodialysis patients, but has no effect on hyper Lp (a) and oxidative stress.     

The effect of ferrite phases on the micromechanical response and crack initiation in the intercritical heat‐affected zone of a welded 9Cr martensitic steel

This paper presents a crystal plasticity model to predict the tensile response and crack initiation in a mixed ferrite‐martensite material with a low volume fraction of pro‐eutectoid ferrite, representative of a welding‐induced intercritical heat‐affected zone. It is shown that small volume fractions of ferrite can have a significant effect on material strength and ductility depending on the ferrite grain orientation. For relatively “soft” ferrite grains, microcracks can grow across interferrite ligaments with damage accumulating in the ferrite, leading to a reduction in strength and strain hardening, but with little influence on ductility; in contrast, relatively “hard” ferrite grains act to accelerate microcrack initiation, leading to reduced ductility, with negligible influence on strain hardening up to the maximum load.     

Inside Front Cover: Self‐Assembly of SiO2 Nanowires and Si Microwires into Hierarchical Heterostructures on a Large Scale (Adv. Mater. 8/2005)

The inside cover shows a scanning electron micrograph of a novel hierarchical heterostructures, as reported by Hu and co‐workers on p. 971. The heterostructures are formed from Si core microwires covered by dense, aligned SiO₂ nanowires, thus forming multiple junctions to the cores. The inset shows a schematic of the Sn‐catalyzed vapor–liquid–solid growth mechanism. These materials are envisaged to become important for optical fibers, low‐dimensional waveguides, scanning near‐field optical microscopes and high‐bandwidth optical signal processing devices.