Thermoelectric properties of n-type nanocrystalline bismuth-telluride-based thin films deposited by flash evaporation

The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3 method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 °C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W/m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT=0.7. As compared with a sintered bulk sample with average grain size of 30 µm and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% reduction in the thermal conductivity, but the electrical conductivity also falls 40%. The reduced thermal and electrical conductivities are attributed to increased carrier trapping and scattering in the nanocrystalline film

Effects of a multi-strain probiotic supplement for 12 weeks in circulating endotoxin levels and cardiometabolic profiles of medication naïve T2DM patients: a randomized clinical trial

Background: The present randomized clinical trial characterized the beneficial effects of a multi-strain probiotics supplementation on improving circulating endotoxin levels (primary endpoint) and other cardiometabolic biomarkers (secondary endpoint) in patients with T2DM. Methods: A total of 78 adult Saudi T2DM patients (naïve and without co-morbidities) participated in this clinical trial and were randomized to receive twice daily placebo or probiotics [(2.5 × 109 cfu/g) containing the following bacterial strains: Bifidobacterium bifidum W23, Bifidobacterium lactis W52, Lactobacillus acidophilus W37, Lactobacillus brevis W63, Lactobacillus casei W56, Lactobacillus salivarius W24, Lactococcus lactis W19 and Lactococcus lactis W58 (Ecologic®Barrier)] in a double-blind manner for 12 weeks. Anthropometrics and cardiometabolic profiles were obtained at baseline and after 12/13 weeks of treatment. Results: After 12/13 weeks of intervention and using intention-to-treat analysis, no difference was noted in endotoxin levels between groups [Placebo − 9.5% vs. Probiotics − 52.2%; (CI − 0.05 to 0.36; p = 0.15)]. Compared with the placebo group however, participants in the probiotics groups had a significant but modest improvement in WHR [Placebo 0.0% vs. Probiotics 1.11%; (CI − 0.12 to − 0.01; p = 0.02)] as well as a clinically significant improvement in HOMA-IR [Placebo − 12.2% vs. Probiotics − 60.4%; (CI − 0.34 to − 0.01; p = 0.04)]. Conclusion: Using a multi-strain probiotic supplement daily for 12/13 weeks significantly improved HOMA-IR and modestly reduced abdominal adiposity among medication naïve T2DM patients

Preparation and characterization of Bi0.4Te3.0Sb1.6 nanoparticles and their thin films

In this article, we perform a preliminary study for assembling micro-size thermoelectric devices with low-cost fabrication by a preparation of nanoparticles and their thin films. Bi0.4Te3.0Sb1.6 nanoparticles with an average size of approximately 50 nm are fabricated by a beads-milling method. The nanoparticle solution is prepared by mixing with toluene and a surfactant, and thin films with 1 μm thick are deposited on Al2O3 substrates by a printing method. The thin films are sintered at temperatures ranging from 300 to 500 oC for 60 minutes in hydrogen ambient. We investigate the thin film structures and the thermoelectric properties at room temperature. As the sintering temperature increases, hexagonal-shaped crystals are grown on the film surface while the atomic composition is almost constant throughout all the sintering temperatures. The XRD patterns indicate that all the nanoparticle thin films are found to mostly exhibit the same XRD intensities and have multiple peaks correspond to each other. The in-plane electrical conductivity of the thin films increases but the Seebeck coefficient decreases as the sintering temperature increases. As a result, the best performance of the thermoelectric power factor of 1.3 μW/(cm K2) is achieved at a sintering temperature of 350 oC

Thermoelectric properties of n-type nanocrystalline bismuth-telluride-based thin films deposited by flash evaporation

The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3 method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 °C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W/m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT=0.7. As compared with a sintered bulk sample with average grain size of 30 µm and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% reduction in the thermal conductivity, but the electrical conductivity also falls 40%. The reduced thermal and electrical conductivities are attributed to increased carrier trapping and scattering in the nanocrystalline film