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Thermally insulating lightweight cement-based composites with excellent mechanical properties are urgently needed for the development of sustainably energy-saving buildings. Herewith two types of thermally insulating admixtures, glass bead (GB) and nano-silica aerogel (NSA), were used as the coarse and fine fillers, respectively, to fabricate thermally insulating cement-based composites (GB-NSA). The chemical components, micro-and-pore structures, mechanical and thermal properties of the GB-NSA composites were investigated by various experimental tests comprehensively. The results indicate that NSA can accelerate the hydration of cement and the carbonation of calcium hydroxide due to the loosely compacted matrix microstructure. The GB-NSA composites show complex and multi-scaled material structures due to the distinct characteristic sizes of GB, NSA and cement particles, and their interactions after cement hydration. Increasing the NSA content makes the material matrices more loosely compacted and the fracture surfaces much rougher due to the highly porous structure of the NSA particles and agglomerations, and the local W/C promotion supplied by the adsorbed water in their surfaces and pores. As a result, increasing the NSA content decreases the density and augments the total porosity, specific surface area and pore size distribution of the GB-NSA composites. Due to the fact that NSA weakens the matrices and interactions between the matrices and GB spheres, both the compressive and flexural strengths decay with the NSA percentage, and change linearly against the density and porosity. Also the thermal conductivity varies linearly to the density and porosity, but decays exponentially to the BET specific surface area. A strategy of incorporating NSA and other fillers in cement matrix may be an appropriate and effective way to design new types of thermally insulating cement-based composites for sustainably energy-saving buildings. [ABSTRACT FROM AUTHOR]

Thermoelectric properties of Nd 1− x In x Te 3 ( x = 0, 0.01, 0.03, 0.05) fabricated by high pressure sintering method were investigated in the temperature range of 291 K–673 K. The results indicate that over 623 K–673 K, the thermal conductivity of moderately doped Nd 1− x In x Te 3 ( x = 0.01, 0.03 and 0.05) is 40%–50% lower than that of un-doped NdTe 3 , which can be attributed to alloy scattering. Though the absolute values of the power factor are slightly reduced by the doping, the reduced thermal conductivity results in high values of ZT at 623 K. Specifically, the lightly In-doped compound Nd 0.99 In 0.01 Te 3 exhibits the best thermoelectric performance, with a figure of merit, ZT , of 0.18 at 623 K. This is almost a doubling of that of the un-doped NdTe 3 measured in this study, suggesting that the proper In-doping in NdTe 3 is a promising way to improve its thermoelectric performance. [ABSTRACT FROM AUTHOR]

SnSe has attracted much attention from scientific researchers because of its reported high ZT values. In this study, Sm doped p-type SnSe polycrystal is prepared through melting synthesis and high pressure (6.0 GPa) sintering (HPS) method. The composition and microstructure of the samples was analyzed, and the thermoelectric transport properties were investigated in the temperature range of 303 K to 823 K. The results indicate that the electrical conductivity increases as Sm content increases. The Seebeck coefficient shows a decreasing trend with increasing Sm content. Due to the increase of alloy scattering, the total thermal conductivity decreases with increasing Sm content. The maximum power factor ( PF ) and ZT max value are 214 μW m −1 K −2 and 0.55 for Sn 0.97 Sm 0.03 Se at 823 K, respectively. [ABSTRACT FROM AUTHOR]