RESUMO
SnSe is considered as a promising thermoelectric (TE) material since the discovery of the record figure of merit (ZT) of 2.6 at 926 K in single crystal SnSe. It is, however, difficult to use single crystal SnSe for practical applications due to the poor mechanical properties and the difficulty and cost of fabricating a single crystal. It is highly desirable to improve the properties of polycrystalline SnSe whose TE properties are still not near to that of single crystal SnSe. In this study, in order to control the TE properties of polycrystalline SnSe, polycrystalline SnSe-SnTe solid solutions were fabricated, and the effect of the solid solution on the electrical transport and TE properties was investigated. The SnSe1-xTex samples were fabricated using mechanical alloying and spark plasma sintering. X-ray diffraction (XRD) analyses revealed that the solubility limit of Te in SnSe1-xTex is somewhere between x = 0.3 and 0.5. With increasing Te content, the electrical conductivity was increased due to the increase of carrier concentration, while the lattice thermal conductivity was suppressed by the increased amount of phonon scattering. The change of carrier concentration and electrical conductivity is explained using the measured band gap energy and the calculated band structure. The change of thermal conductivity is explained using the change of lattice thermal conductivity from the increased amount of phonon scattering at the point defect sites. A ZT of ~0.78 was obtained at 823 K from SnSe0.7Te0.3, which is an ~11% improvement compared to that of SnSe.
RESUMO
Heavily doped degenerate semiconductors such as Cu2SnSe3 (CTSe) attracted attention in thermoelectric (TE) and optoelectronic fields, due to their high electrical conductivity and small band gap. The small Seebeck coefficient of undoped CTSe, however, is the major issue in achieving high TE performance (figure of merit, ZT). Here, we report that the Seebeck coefficient of CTSe can be controlled by adding SnS within a CTSe matrix. CTSe-SnS composite has not only high Seebeck coefficient in the range of 300-500 µVolt/K but thermal conductivity which is lower than that of pristine CTSe due to the scattering at the interface between the matrix and the SnS particles. A reasonable ZT of 0.18 is achieved at 570 K by adding a small amount (3 wt.%) of SnS to the CTSe matrix.
RESUMO
BACKGROUND: Raised levels of cholesterol and triglycerides are major risk factors for atherosclerosis, which can lead to coronary heart disease. Both the CRP and Sialic Acid levels are elevated in response to acute as well as chronic inflammatory conditions. This study was conducted to determine the serum lipid profile, CRP and Sialic Acid levels and their relationship with each other in healthy individuals. METHODS: This was a cross-sectional study performed by the Department of Biochemistry, Institute of Basic Medical Sciences (IBMS), Khyber Medical University (KMU) Peshawar. Two hundred healthy subjects in the age group of 18-50 years of either gender was recruited through consecutive sampling. Blood sampling were taken from all the participants and analysed each for serum lipid profile, CRP and Sialic Acid levels through standardized methods. RESULTS: A total of 200 individuals were included, 53.5% being male. Mean age was 33.39±9.76 years. Mean height was 167.86±10.8 cm. Mean weight was 66.87±11.39kg. Mean Hip-Waist ratio was 0.93±0.16 whereas mean BMI was 24.12±3.65. The simultaneous raised levels of serum lipids, CRP and Sialic Acid were observed more commonly in females as compared to males. CRP and Sialic Acid has got statistically significant correlation with HDL. Sialic Acid had statistically significant correlation with triglycerides in the study population with a significant p-value (<0.05), while having a non-significant correlation with total cholesterol and LDL. CRP had got significant correlation with total cholesterol and LDL and non-significant correlation with triglycerides. CONCLUSIONS: The study showed that serum CRP and Sialic Acid had a significant negative correlation with serum HDL. A significant positive correlation was found between serum Sialic Acid and triglycerides. CRP and Sialic Acid though expensive but are useful predictors of atherosclerotic disease.
