Epitaxial Growth and Thermoelectric Measurement of Bi2Te3/Sb Superlattice Nanowires

Superlattice nanowires are expected to show further enhanced thermoelectric performance compared with conventional nanowires or superlattice thin films. We report the epitaxial growth of high density Bi₂Te₃/Sb superlattice nanowire arrays with a very small bilayer thickness by pulse electrodeposition. Transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy were used to characterize the superlattice nanowires, and Harman technique was employed to measure the figure of merit (ZT) of the superlattice nanowire array in high vacuum condition. The superlattice nanowire arrays exhibit a ZT of 0.15 at 330 K, and a temperature difference of about 6.6 K can be realized across the nanowire arrays.     

Bi2Te3/Sb超晶格纳米线的外延生长和热电测量

通过脉冲电沉积,外延生长出小单元长度的Bi₂Te₃/Sb超晶格纳米线.借助哈曼方法,测量了超晶格纳米线阵列的热电性能,330 K时的ZT值可达0.15.研究了Bi₂Te₃/Sb超晶格纳米线阵列器件的制冷或者加热能力,发现器件的上下表面的最大温差可以达到6.6 K.     

Efficient one-pot synthesis of anti HIV and antitumor compounds: harman and substituted harmans

Anti HIV and antitumor compounds, harman and substituted harmans have been synthesized using electrocyclization reactions as key steps. A one-pot reaction sequence was used to furnish these compounds in good overall yield.     

Thermal Conductivity and Dimensionless Figure of Merit of Thermoelectric Rhodium Oxides Measured by a Modified Harman Method

We have developed a modified Harman method to extract the thermoelectric signal using a squared AC current in the presence of Joule heating, and have measured the thermal conductivity and dimensionless figure of merit of single crystals of the layered rhodium oxide Bi_0.78Sr_0.4RhO_3+d and the pseudo-one-dimensional rhodium oxide Ba_1.2Rh₈O₁₆. We find that these rhodium oxides exhibit a small thermal conductivity of 30 mW/cm K at 200 K and rather large ZT of 0.02 below 200 K. We believe that this method will be a powerful tool for thermal conductivity measurements in sub-millimeter-sized crystals.     

Microstructures and Thermoelectric Properties of an Annealed Ti<Subscript>0.5</Subscript>(Hf<Subscript>0.5</Subscript>Zr<Subscript>0.5</Subscript>)<Subscript>0.5</Subscript>NiSn<Subscript>0.998</Subscript>Sb<Subscript>0.002</Subscript> Ribbon

The thermoelectric half-Heusler compound Ti_0.5(Hf_0.5Zr_0.5)_0.5NiSn_0.998Sb_0.002 was fabricated by spin-casting and subsequent annealing. ZT at room temperature increased with annealing time through an increase in absolute Seebeck coefficients despite a decrease in electrical conductivity. ZT reached 0.10 after annealing at 1050 K for 48 h. In powder x-ray diffraction analysis, each half-Heusler peak was accompanied by a bump at the high-angle side, corresponding to a minor Ti-rich half-Heusler phase. The quantity and Ti composition of the minor phase increased with annealing time, although those of the major half-Heusler phase were almost constant. In transmission electron microscopic analysis, granular domains, several nanometers in size, with atomic ordering or disordering were observed. Thermoelectric properties were␣improved by annealing through the growth of heterogeneous microstructures of the Ti-rich and Ti-poor half-Heusler grains and of the granular domains.     

Efficient one-pot synthesis of anti-HIV and anti-tumour β-carbolines

Thermal electrocyclisation of the azahexatriene system has been used as a key step for the synthesis of anti-HIV and anti-tumour compounds, harman, derivatives of harman and 1-aryl-β-carbolines. A one-pot reaction sequence was used to furnish these compounds in good yield.