Enhanced thermoelectric transport properties of La0.98Sr0.02CoO3-BiCuSeO composite

We report a facile method to enhance the thermoelectric efficiency of La0.98Sr0.02CoO3 by introducing BiCuSeO as a secondary phase with ultra-low thermal conductivity. Inclusion of secondary phase results in reducing the total thermal conductivity by suppressing the lattice and electronic thermal conductivities and also contributes to enhancement in the Seebeck coefficient. The wide grain size distribution of La0.98Sr0.02CoO3-BiCuSeO composite facilitates in breaking the interlinked transport properties through increased scattering of different wavelength phonons. The combined effect of enhanced Seebeck coefficient and ultra-low thermal conductivity, results in an improved ZT value of 0.07 at 923 K. The proposed strategy can be opted for improvement in the thermoelectric efficiency of other thermoelectric materials as well

Classical risk factors of cardiovascular disease among Chinese male steel workers: a prospective cohort study for 20 years

<p>Abstract</p> <p>Background</p> <p>Cardiovascular disease (CVD) constitutes a major public health problem in China and worldwide. We aimed to examine classical risk factors and their magnitudes for CVD in a Chinese cohort with over 20 years follow-up.</p> <p>Methods</p> <p>A cohort of 5092 male steelworkers recruited from 1974 to 1980 in Beijing of China was followed up for an average of 20.84 years. Cox proportional-hazards regression model were used to evaluate the risk of developing a first CVD event in the study participants who were free of CVD at the baseline.</p> <p>Results</p> <p>The multivariable-adjusted hazard ratio (HR) associated with every 20 mmHg rise in systolic blood pressure (SBP) was 1.63 in this Chinese male population, which was higher than in Caucasians. Compared to non-smokers, men who smoked not less than one-pack-a-day had a HR of 2.43 (95% confidence interval [CI], 1.75-3.38). The HR (95% CI) for every 20 mg/dl increase in total serum cholesterol (TC) and for every point rise in body mass index (BMI) was 1.13 (1.04-1.23) and 1.06 (1.02-1.09), respectively.</p> <p>Conclusions</p> <p>Our study documents that hypertension, smoking, overweight and hypercholesterolemia are major conventional risk factors of CVD in Chinese male adults. Continued strengthening programs for prevention and intervention on these risk factors are needed to reduce the incidence of CVD in China.</p

Self-Assembled Nanocomposites and Nanostructures for Environmental and Energy Applications

Self-assembled nanocomposites are attracting considerable attention owing to their controllable architectures and self-assembly processes, as well as the increase in worldwide environmental effects and energy needs. Further understanding of the self-assembly procedure for improving environmental and energy applications would advance the design and manufacture of nanomaterials for various applications. These materials can be grouped into major categories for various application fields, including powder photocatalysts, membrane photocatalysts, and thin-film thermoelectric nanomaterials. These self-assembled nanomaterials can be used for environmental and energy applications, such as wastewater purification, hydrogen production by water splitting, energy storage, and energy harvesting. In this review, a brief introduction to the definitions and classifications of self-assembled nanocomposites is provided. We aim to provide a summary of the recent research related to self-assembled nanocomposites and nanostructures used for environmental and energy applications. Moreover, typical examples and discussions are aimed at demonstrating the advantages of self-assembled nanostructures. At the end of each section, the structural properties and the application of the nanocomposite or nanostructure are summarized. Finally, we provide perspectives for future research on the design and fabrication of self-assembled nanocomposites and nanostructures

Improved thermoelectric performance of BiCuSeO by Ag substitution at Cu site

BiCuSeO oxyselenide-based thermoelectric materials are attracting much attention due to their ultra-low intrinsic thermal conductivity (ĸ) and moderate Seebeck coefficient (S). However, the low conversion efficiency limits their application in energy conversion systems. This paper investigated the effect of monovalent Ag-doping in BiCuSeO at Cu site in the presence of polyvinyl alcohol (PVA). The results show that Ag is effectively doped at Cu site. The heavy atom substitution in BiCu1−xAgxSeO at Cu site can enhance S and reduce its total thermal conductivity (k) by phonon scattering. Further, the incorporation of heavy atom (Ag) with different ionic radii results in the improved ZT of 0.64 for BiCu1−xAgxSeO, which is 16% more than that for pure BiCuSeO (ZT = 0.55) at 923 K. It is believed that the Cu site should be an efficient dopant site to improve the efficiency of oxyselenide-based thermoelectric materials

Enhanced thermoelectric efficiency of Cu2-xSe-Cu2S composite by incorporating Cu2S nanoparticles

The study of thermoelectric transport properties in Cu2-x Se and Cu2S has gained an importance in the thermoelectric research during last few years due to their superionic behavior and low cost. Here, we reported a facile method to enhance the thermoelectric efficiency of Cu2-x Se by introducing Cu2S nanoparticles (NPs) in the matrix of Cu2-x Se. The observed efficiency is a direct result of simultaneous improvement of Seebeck coefficient (S) because of the external strain induced by Cu2S nanoinclusions in Cu2-x Se and decline in the total thermal conductivity by suppressing both electronic and lattice thermal contributions. Such higher S and lower thermal conductivity is realized for a composite structure with 10wt% nanoinclusions of Cu2S which effectively contributed to higher ZT value of 0.90 at moderate temperature of 773K. Thus, it is believed that the proposed hybrid structure is a promising p-type thermoelectric material for mid-temperature range energy harvesting applications

Surface reinforcements of TA15 titanium alloy with laser induced Co base multiphase composites

© 2020 Elsevier Ltd Ultrafine particles (UPs)/amorphous phases (APs) reinforced composites was deposited on the TA15 titanium alloy via a laser cladding (LC) of the Co-Al-B4C-CeO2 mixed powders; a LC technique (the laser power 900 W, the scanning speed 2.5 mm/s) favored APs/UPs to be produced owing to the transient existence of the laser molten pool (laser pool), its COF was in a range of 0.390–0.425. Then, the monolayer graphene oxide sheets (MGOSs)/carbon nanotubes (CNTs) reinforced composites were formed on this LC fabricated coating by a mean of LC of Co-Al-B4C-CeO2-(MGOSs/CNTs). Noting that a laser beam irradiated on MGOSs/CNTs also the pre-melted powders, huge amounts of MGOSs/CNTs were melted but kept partial MGOSs/CNTs in the solid states; also lots of UPs were produced in the atomic arrangements of APs/MGOSs, considering that partial UPs could obtain large quantity of the energy from a laser beam, forming lattice distortions. Identification of the synthetic UPs and MGOSs/CNTs in such LC composites, more importantly an UPs’ effect, contributes the theoretical/experimental basis to improve quality of the laser 3D print fabricated composites

Cd-doping a facile approach for better thermoelectric transport properties of BiCuSeO oxyselenides

BiCuSeO-based thermoelectric materials have spurred tremendous interest among the thermoelectric community due to their ultra-low thermal conductivity and relatively large Seebeck coefficient (S). In this work, we have reported the effect of Cd-doping at the Bi site, instead of the previously studied Cu site, on the thermoelectric performance of BiCuSeO by modifying the insulating layer. While maintaining good phase purity, Cd was successfully doped at the Bi site as confirmed by X-ray absorption fine structure spectroscopy. The Cd-doping substantially improves the electrical conductivity by a factor of 20 through bond anharmonicity at room temperature while increasing the Cd concentration over 5%. Further, the incorporation of the lighter atom at the Bi site creates phonon scattering centers and results in weak bonding between the layers, resulting in a remarkable perturbation of the local geometric and electronic structure. BiCuSeO with 5% Cd-doping maintains a large S and a high electrical conductivity up to 923 K and exhibits the highest power factor values (600 μW m-1 K-2 at 323 K and 447 μW m-1 K-2 at 923 K) and the largest ZT (0.98 at 923 K). Cd-doping at the Bi site in p-type thermoelectric BiCuSeO was shown to be a very good technique for improving the thermoelectric performance and could be extended to other thermoelectric materials to enhance the efficiency of thermoelectric devices for energy-harvesting

Combined effects of smoking and systolic blood pressure on risk of coronary heart disease: a cohort study in Chinese women

Objectives: To quantify the combined effects of systolic blood pressure (SBP) and cigarette smoking on incident coronary heart disease (CHD) in women.Methods: Overall, 86,338 women aged ≥40 years were enrolled in 1991. The follow-up evaluation was conducted in 1999–2000, with a response rate of 92.9%.Results: A total of 829 CHD events (fatal and nonfatal) were observed among the participants who were free of cardiovascular diseases (CVD) at baseline. Higher SBP was significantly associated with more risk of CHD in both nonsmokers and current smokers (all p < 0.0001 for linear trends). Comparing with never smoking, both low and high levels of cigarettes smoked per day (1–7, and ≥8 cigarettes per day) and pack-years (<10, and ≥10 pack-years) were associated with increased risk of CHD in those with normal and high SBP. The multivariate adjusted relative risks (RRs) of CHD were 2.54 (95% confidence interval [CI] 2.00-3.23), 1.28 (1.01-1.63), and 1.57 (1.33-1.86) for current smokers with high SBP, current smokers with normal SBP, and nonsmokers with high SBP, respectively, compared with nonsmokers with normal SBP. The present study identified a statistically significant additive interaction between these two factors on CHD.Conclusions: Our study indicated that the combined effects of cigarette smoking and high SBP could be expected to have extra adverse effects on CHD in women, which highlights the importance of multifactorial interventions to decrease the risk of CHD, for example, quitting smoking and treatment of high blood pressure in Chinese women