Zhifeng Ren

Bio: Zhifeng Ren is an academic researcher from Texas Center for Superconductivity. The author has contributed to research in topics: Thermoelectric effect & Thermoelectric materials. The author has an hindex of 122, co-authored 695 publications receiving 71212 citations. Previous affiliations of Zhifeng Ren include Massachusetts Institute of Technology & University of Cincinnati.

Realizing High Energy Conversion Efficiency in a Novel Segmented‐Mg3(Sb, Bi)2/Cubic‐GeTe Thermoelectric Module for Power Generation

Abstract: The performance of thermoelectric materials has been improved considerably in recent decades, making the concept of generating energy from waste heat via solid‐state thermoelectric devices more realistic. The construction of multi‐stage modular structures based on complex parameter optimization to maximize the efficiency of each material over its optimal operating temperature range has become an effective strategy for improving device performance. Here, multi‐segmented n‐type Mg3(Sb, Bi)2 with low‐contact‐resistance buffer layers is first fabricated, and phase‐transition‐suppressed cubic p‐type GeTe with enhanced thermoelectric performance is subsequently designed to match the segmented n‐type legs. A 3D finite‐element analysis model is then used to optimize the module size, providing higher energy conversion efficiency with an optimal average figure of merit over the entire operating temperature range. As a result, the prepared segmented‐Mg3(Sb, Bi)2/cubic‐GeTe module exhibits a high conversion efficiency of (12.8 ± 0.8)% at a hot‐side temperature of 773 K with a temperature difference of ≈480 K, which is also comparable to that of previously reported thermoelectric modules. This study increases the number of matching combinations among n‐/p‐type thermoelectric materials and further broadens the potential candidate material library for segmented thermoelectric devices.

Thermoelectric skutterudite compositions and methods for producing the same

Abstract: Compositions related to skutterudite-based thermoelectric materials are disclosed. Such compositions can result in materials that have enhanced ZT values relative to one or more bulk materials from which the compositions are derived. Thermoelectric materials such as n-type and p-type skutterudites with high thermoelectric figures-of-merit can include materials with filler atoms and/or materials formed by compacting particles (e.g., nanoparticles) into a material with a plurality of grains each having a portion having a skutterudite-based structure. Methods of forming thermoelectric skutterudites, which can include the use of hot press processes to consolidate particles, are also disclosed. The particles to be consolidated can be derived from (e.g., grinded from), skutterudite-based bulk materials, elemental materials, other non-Skutterudite-based materials, or combinations of such materials.

Methods of synthesizing thermoelectric materials

Abstract: Methods for synthesis of thermoelectric materials are disclosed. In some embodiments, a method of fabricating a thermoelectric material includes generating a plurality of nanoparticles from a starting material comprising one or more chalcogens and one or more transition metals; and consolidating the nanoparticles under elevated pressure and temperature, wherein the nanoparticles are heated and cooled at a controlled rate.

Magnetic resonance of Cu and of Gd in insulating GdSr2Cu2NbO8 and in superconducting GdSr2Cu2RuO8

Abstract: Weak-ferromagnetic (or antiferromagnetic) resonance of Cu and electron spin resonance (ESR) of Gd are observed both in insulating GdSr2Cu2NbO8 and in superconducting GdSr2Cu2RuO8. The Cu resonance implies that the CuO2 planes are magnetic and indicates that the superconducting layer of GdSr2Cu2RuO8 is SrO (not CuO2), as in its related superconducting compound without cuprate planes, doped Sr2YRuO6.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Carbon Nanotubes--the Route Toward Applications

Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.