A microstructural and kinetic investigation on suppression of grains growth in nanocrystalline copper through silicon carbide nanoparticle dispersion

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Microstructural and kinetic investigation on the suppression of grain growth in nanocrystalline copper by the dispersion of silicon carbide nanoparticles

In this paper, the thermal stability and grain growth kinetics of nanocrystalline Cu, reinforced with SiC nanoparticles and obtained using a mechanical milling process, were investigated during isothermal annealing. The presence of the nanoparticles in the nanocrystalline copper matrix resulted in a significant decrease in grain growth, the formation of partially textured microstructure and twin boundaries at higher temperatures, and an increase in the volume fraction of recrystallized grains, as estimated by grain orientation spread, in comparison to unreinforced Cu during annealing. The lower volume fraction of recrystallized grains at higher temperatures was attributed to dynamic recovery. Normal grain growth was observed in the annealing range of 400-600 degrees C, and significant abnormal grain growth was observed at higher temperatures. An analysis of the grain growth kinetics in the temperature range of 400-600 degrees C revealed a time exponent of n approximate to 3.6 and activation energy of approximate to 34 kJ mol(-1), based on the parabolic equation. The calculated activation energy for grain growth in the SiC dispersion strengthened Cu was found to be less than that of nanocrystalline Cu. The low activation energy and high thermal stability were attributed to high lattice strain and the retarding effect of nanoparticles by the Zener mechanism. (C) 2017 Elsevier Ltd. All rights reserved.116Nsciescopu

Mechanical, tribological and electrical properties of Cu-CNT composites fabricated by flake powder metallurgy method

Cu-CNT composites were fabricated by a flake powder metallurgy method, and their microhardness, electrical conductivity, frictional and wear properties were investigated. Homogenous distribution of CNTs in fine-grained Cu matrix was obtained using this process. Microhardness increased with the addition of CNT vol% up to 8% to the Cu matrix, while the conductivity decreased to 79.2 IACS %. Results showed that CNTs play a major role in improving wear resistance by forming a CNT-rich film that acts as a solid lubricant layer. In the synthesized composites, Cu-4 vol% CNT composite exhibited the best wear and friction properties. The dominant wear mechanisms for the Cu-CNT composites were plastic deformation, abrasion, and flake formation-spalling. Also, a newly modified correlation was proposed for the theoretical calculation of the friction coefficient of Cu-CNT composites consisting agglomerated CNTs. (C) 2019 Politechnika Wroclawska. Published by Elsevier B.V. All rights reserved.11Nsciescopu

Microstructural characterization and enhanced hardness of nanostructured Ni3Ti-NiTi (B2) intermetallic alloy produced by mechanical alloying and fast microwave-assisted sintering process

In this paper, the rapid synthesis of nanostructured NiTi-Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi-B-2 and Ni3Ti, and minor phases of NiTi-B19' and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (similar to 750 H V) were obtained at sintering temperature of 1100 degrees C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni-Ti alloys with improved mechanical properties for biomedical applications.11Nsciescopu

Synergistic Effects of MWCNTs and High-Pressure Torsion-Induced Grain Refinement on Microhardness, Tribological Properties, and Corrosion Behavior of Cu and Cu/MWCNT Nanocomposites

In this study, ultra-fine grained Cu and Cu + carbon nanotube (CNT) nanocomposites were prepared through a processes combining flake powder metallurgy, hot pressing, and high-pressure torsion (HPT). The effects of grain refinement and CNT reinforcement on the microstructure, hardness, wear resistance, and corrosion behavior of the newly developed nanocomposites were investigated. The results indicated that the HPT process decreased the grain size of Cu and Cu + CNT by 67.7% and 68.1%, respectively, and increased their microhardness by 151% and 132%. The addition of CNTs substantially improved the tribological behavior of Cu by generating a mechanically mixed carbon- and oxide-rich layer. Moreover, polarization and electrochemical impedance spectroscopy tests revealed that the CNTs have a negligible adverse effect on the corrosion resistance of the Cu + CNT nanocomposites. The influences of the processing route and CNTs are discussed. Graphic Abstract: [Figure not available: see fulltext.] © 2021, The Korean Institute of Metals and Materials.11Nsciescopuskc

Serum alkaline phosphatase and the risk of coronary heart disease, stroke and all-cause mortality: Tehran Lipid and Glucose Study

OBJECTIVES: To investigate the association of alkaline phosphatase (ALP) levels with the risk of the composite end point of cardiovascular disease (CVD), and all-cause mortality as well as each of them separately. DESIGN: Prospective cohort study. SETTING: Within the framework of the Tehran Lipid and Glucose Study (TLGS) cohort, participants were followed from baseline examination (1999-2001) until March 2014. PARTICIPANTS: A total of 2578 participants, aged ≥30 years free of prevalent CVD at baseline examination. PRIMARY OUTCOME: The main outcome measures were composite end point of coronary heart disease (CHD), stroke, all-cause mortality and each per se. RESULTS: During a median follow-up of 11.3 years, 369, 68, 420, 170 and 495 participants experienced CHD, stroke, CVD, all-cause mortality and the composite outcome, respectively. In the multivariable Cox regression models, the adjusted HRs (95 CI) for mentioned events per one SD increase in ALP level after full adjustment were 1.11 (1.01 to 1.22), 1.20 (0.97 to 1.49, p=0.058), 1.10 (1.01 to 1.21), 1.16 (1.01 to 1.33) and 1.11 (1.02 to 1.21), respectively. Furthermore, participants with ALP levels in the highest tertile had significant adjusted HRs (95 CI) for stroke (1.88 (1.00 to 3.61)), CVD (1.30 (1.01 to 1.68)) and composite outcome (1.27 (1.00 to 1.61)). The cut-off value of ALP ≥199 IU/L for predicting composite outcome was derived using Youden's index, based on which this cut-off point was associated with significant risk of 80, 26, 43 and 26 for incident stroke, CVD, all-cause mortality and composite outcome. Additionally, no improvement was seen in the predictive ability of traditional risk factors models after adding ALP values, considering the levels of Akaike information criterion, C-index and Net Reclassification Index. CONCLUSION: Independent associations between ALP levels and the risks of CVD and mortality events were shown, despite the fact that adding the data of ALP to known risk factors did not improve the prediction of these events. © Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ

Serum interleukin-18 and its relationship with subclinical atherosclerosis in systemic lupus erythematosus

BACKGROUND: Interleukin-18 (IL-18) is a pro-inflammatory and pro-atherogenic factor, and its blood level has shown a direct correlation with atherosclerosis. We aimed to evaluate the serum IL-18 level in patients with systemic lupus erythematosus (SLE) and its relationship with the intima-media thickness (IMT) of the carotid artery in these patients, as an indicator of atherosclerosis. METHODS: In this cross-sectional study, 60 patients as the patient group and 30 healthy volunteers as the control group matched sex, age, and body mass index (BMI) were selected, and their disease status and general data were gathered using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) form. A blood sample was also obtained from all participants to determine the serum level of IL-18 and other metrics, including high-sensitivity C-reactive protein (hs-CRP), cholesterol, triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), anti-double stranded deoxyribonucleic acid (anti-dsDNA), complement 3 (C3), and C4. The IMT of the carotid artery was calculated in both groups. We also evaluated the clinical cardiovascular manifestations. RESULTS: The serum IL-18 levels in patients were significantly higher than in the control group (P � 0.005). It had no significant correlation with disease activity (P = 0.10). The patients with SLE with high IL-18 serum levels (> 280 pg/ml) had higher SLEDAI-2K (P = 0.02) than the patients with a low level (< 280), where 280 was the median of the IL-18 levels. The serum IL18 level had no significant correlation with the carotid artery IMT. CONCLUSION: A high level of IL-18 reflects the disease activity, but it was not significantly correlated with subclinical atherosclerosis, denoted by the carotid artery IMT. © 2022, Isfahan University of Medical Sciences(IUMS). All rights reserved

Immunity to Hepatitis-A virus: A nationwide population-based seroprevalence study from Iran

Background: The mortality rate of acute Hepatitis A increases from 0.1 in the children to 1.2, in the adults. Hepatitis A is efficiently prevented by HAV-vaccine, but the strategy for distributing this vaccine among countries is dependent on their level of immunity to HAV. This study aimed to detect the level of immunity to HAV in Iran. Methods: In this population-based seroprevalence study, 5419 participants from 12 of provinces of Iran, including 57 urban and 120 rural areas were chosen through a multi-stage cluster random sampling. Participants were interviewed by filling checklists and 3 cc of blood sample was obtained from each of them. IBM SPSS statistics V.21 software was used for univariable and multivariable analysis of data. Results: Mean of age of Interviewees was 26.4 ± 16 years, ranging from 1 to 94 years with a male to female ratio 1.02. Overall, 3603 (66.5) of subjects were seropositive for HAV-IgG. Among the age groups, 41.1 of children by the age 15 years and 82.6 of adults around 30 years old were immune to HAV. The Mid-point age of population immunity was 21 years. Residents of the borders of the country, people who had less access to the safe water or sanitary toilet, individuals with low socioeconomic status and persons who were a member of dense families had the most probability of seropositivity. Conclusions: This study showed that Iran is among HAV low endemic countries and vaccination against HAV is recommended only in the high-risk population, including patients with chronic liver diseases, patients with coagulopathy, travelers to the high endemic areas, and homosexuals. Establishment of national HAV surveillance system, concerning of health system about the occurrence of the HAV outbreaks, implementation of harm reduction strategies, improving economic indices and sanitation and access to the safe water in the deprived regions is recommended. © 2020 Elsevier Lt