The capability of Transmission Kikuchi Diffraction technique for characterizing nano-grained oxide scales formed on a FeCrAl stainless steel

This letter focuses on the capability of Transmission Kikuchi Diffraction (TKD) in Scanning Electron Microscope (SEM) for obtaining microstructural and micro-textural information from nano-grained oxide scales formed on a FeCrAl alloy. Orientation maps, with an indexing rate of 85%, showed the formation of grains in the range 20-300 nm. TKD revealed the existence of an orientation relationship at the alloy/oxide interface as well as the presence of a single grain (40 nm) with spinel structure in the alumina scale. A pre-tilted sample holder was designed for 110 investigations at short working distances with minimized mechanical drift of the thin foils. (C) 2015 The Authors. Published by Elsevier B.V

High-temperature oxidation behaviour of AlxFeCrCoNi and AlTiVCr compositionally complex alloys

Compositionally complex alloys (CCAs), also termed as high entropy alloys (HEAs) or multi-principal element alloys (MPEAs), are being considered as a potential solution for many energy-related applications comprising extreme environments and temperatures. Herein, a review of the pertinent literature is performed in conjunction with original works characterising the oxidation behaviour of two diverse Al-containing alloys; namely a lightweight (5.06 g/cm(3)) single-phase AlTiVCr CCA and a multiple-phase Al0.9FeCrCoNi CCA (6.9 g/cm(3)). The thermogravimetric results obtained during oxidation of the alloys at 700 and 900 degrees C revealed that both alloys tended to obey the desired parabolic rate law. Post-exposure analysis by means of electron microscopy indicated that while the oxide scale formed on the AlTiVCr is adherent to the substrate, the scale developed on the Al0.9FeCrCoNi displays a notable spalling propensity. This study highlights the need for tailoring the protective properties of the oxide scale formed on the surface of the CCAs

On the capability of in-situ exposure in an environmental scanning electron microscope for investigating the atmospheric corrosion of magnesium

The feasibility of environmental scanning electron microscope (BEM) in studying the atmospheric corrosion behavior of 99.97% Mg was investigated. For reference, ex-situ exposure was performed. A model system was designed by spraying few salt particles on the metal surface and further promoting the corrosion process using platinum (Pt) deposition in the form of 1 x 1 x 1 pm(3) dots around the salt particles to create strong artificial cathodic sites. The results showed that the electron beam play a significant role in the corrosion process of scanned regions. This was attributed to the irradiation damage occurring on the metal surface during the BEM in-situ experiment. After achieving to a reliable process route, in a successful attempt, the morphology and composition of the corrosion products formed in-situ in the ESEM were in agreement with those of the sample exposed ex-situ

On the early stages of localised atmospheric corrosion of magnesium–aluminium alloys

The surface film on pure magnesium and two aluminium-containing magnesium alloys was characterised after 96\ua0h at 95% RH and 22\ua0\ub0C. The concentration of CO2 was carefully controlled to be either 0 or 400\ua0ppm. The exposed samples were investigated using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electron microscopy. The results showed that when the alloys were exposed to the CO2-containing environment, aluminium cations (Al3+) was incorporated into a layered surface film comprising a partially “hydrated” MgO layer followed by Mg(OH)2, and magnesium hydroxy carbonates. The results indicated that aluminium-containing magnesium alloys exhibited considerably less localised corrosion in humid air than pure magnesium. Localised corrosion in the materials under investigation was attributed to film thinning by a dissolution/precipitation mechanism

A new semi-solid casting technique for fabricating SiC-reinforced Mg alloys matrix composites

The capability of the newly developed rheocasting (RC) technique in combination with the RheoMetal process for producing SiC particulate-reinforced AM50 and AZ91D matrix composites (Mg-based MMCs) was investigated. The quality of the MMCs was studied by analyzing the fraction of casting pores, number density of SiC clusters and the uniformity of SiC particles. Solid fraction, particle size and oxidation of SiC particles had strong impacts on the overall quality of the MMCs. The MMCs produced by 40% solid fraction and oxidized micron-sized SiC particles exhibited an excellent casting quality. A low-quality MMC was obtained when non-oxidized sub-micron sized SiC particles were employed. The results showed the formation of various types intermetallic particles and carbides such as MgO, Mg2Si, Al2MgC2, Mg2C3, Al4C3 as the interfacial reaction products of SiC/Mg alloy's melts. Mg hydride (alpha-MgH2) was also identified in inter-dendritic regions of the MMCs for the first time

Exploring failure modes of alumina scales on FeCrAl and FeNiCrAl alloys in a nitriding environment

Two high-temperature FeCrAl and FeNiCrAl alloys were exposed in a strongly nitriding environment at 900 \ub0C and the morphology of nitridation was studied. Quasi-in-situ experiments revealed that nitridation started at specific surface sites directly related to the alloy microstructure where the alumina scale was permeable to nitrogen. FeCrAl alloy grains with (112) orientation formed outward-growing alumina scales and were susceptible to nitridation. Outward-growing scales and substrate nitridation was also observed at chromium carbide precipitates in the FeNiCrAl alloy. Both alloys suffered nitridation at reactive element-rich (Y and Zr) inclusions larger than a certain critical size. The latter type of attack is caused by cracks and pores in the scale. The findings open new avenues of research for developing the next generation of high temperature alloys with superior properties

Association of heat shock protein70-2 (HSP70-2) gene polymorphism with obesity

Peer reviewedPublisher PD

Association between the rs2241883 polymorphism of the fatty acid-binding protein-1 (FABP1) gene and obesity in a population of MASHAD study cohort

Funding Information: We would like to thank Mashhad University of Medical Sciences Research Council for their financial supports.Peer reviewedPublisher PD

Association between obesity categories with cardiovascular disease and its related risk factors in the MASHAD cohort study population

Background Cardiovascular disease (CVD) is a significant cause of morbidity and mortality globally. Obesity is an important CVD risk factor and is increasing in prevalence. Methods In this study, 3829 men and 5720 women (35‐65 years) were enrolled as part of the MASHAD cohort study. Four categories were identified according to body mass index and waist circumference that was defined by the World Health Organization. Logistic regression analysis was used to determine the adjusted odds ratio (OR) for the occurrence of CVD, and Cox regression model was used to evaluate the association of obesity with CVD incidence. Results We found that the higher risk groups defined by categories of adiposity were significantly related to a higher prevalence of a high serum total cholesterol (TC), and triglycerides (TG), and lower high‐density lipoprotein cholesterol (HDL), and higher fasting blood glucose (FBG) in both genders and a higher low‐density lipoprotein cholesterol (LDL) in women (P < .001). Additionally, a high percentage of participants with dyslipidemia, high LDL, high TC, and low HDL and a high percentage of participants with metabolic syndrome, diabetes, hypertension, and a high serum TG were observed across obesity categories (P < .001). Moreover, women with the very high degrees of obesity had a greater risk of CVD (HR: 1.91, 95% CI: 1.06‐3.43, P = .03). Conclusion Obesity strongly predicts several CVD risk factors. Following 6 years of follow‐up, in individuals within increasing degrees of obesity, there was a corresponding significant increase in CVD events, rising to approximately a twofold higher risk of cardiovascular events in women compared with men

Overweight and obesity are potential risk factors for disrupted nocturnal sleep in Iranian adults: a cross-sectional study

Objectives: Obesity is a risk factor for several chronic conditions, including sleep disorders. We aimed to analyze the relationship between BMI, body fat percentage (FAT%), hip and waist circumference, and weight on the duration of nocturnal sleep. Methods: This study was part of the MASHAD cohort study. In all participants BMI and FAT% were measured. BMI was used to categorize individuals as obese, overweight, and normal subjects. FAT% was used to categorize individuals into tertile: tertile 1 (low) 41. The level of nightly sleep duration was categorized into three groups: 8 h. Results: There was a significant inverse association between body weight and duration of sleep (p < 0.05). Obese and overweight participants had 1.152 OR (CI:1.083–1.225) and 1.126 OR (CI:1.063–1.194) for a short duration of nocturnal sleep, respectively, relative to those with a normal BMI. Conclusion: BMI was an independent determinant of nocturnal sleep duration; obesity and overweight may have negative consequences on sleep duration. Weight control should be considered as a factor in adjusting sleep quality