4,340 research outputs found
Fabrication and electromagnetic characteristics of microwave absorbers containing carbon nanofibers and NiFe particles
No full textThe objective of this study is to develop microwave absorbers by using both dielectric and magnetic lossy materials. Carbon nanofibers (CNFs) were used as dielectric lossy materials and NiFe particles were used as magnetic lossy materials. Twelve kinds of composite specimens were fabricated and classified into dielectric, magnetic, and mixed types. Their complex permittivities and permeabilities in the range of 2-18 GHz were measured. Parametric studies to aid in the design of single-layered radar absorbing materials (RAMs) were performed. The mixed RAMs generally showed improved absorbing characteristics with thinner matching thicknesses. The present mixed RAM showed the 10 dB absorbing bandwidth of 4.0 GHz in the X-band (2.00 mm thickness) and 6.0 GHz in the Ku-band (1.49 mm thickness). The measured absorbing properties of selected specimens were in very good agreements with simulations. (c) 2009 Elsevier Ltd. All rights reserved.KIMS, MOCI
Dilute Sb Doping Yields Softer p‐Type Bi2Te3 Thermoelectrics
No full textAbstract In this study, the Sb content within p‐type Bi2Te3 by employing phase diagram engineering is strategically tuned. This method retains the advantages of Sb doping but mitigated the brittleness typically seen in high‐Sb Bi0.5Sb1.5Te3 (BST). The as‐constructed phase diagram demonstrates the asymmetrical homogeneity of (Bi, Sb)2Te3, guiding focus toward developing an optimized p‐type (Bi2Te3)0.96(Sb2Te)0.04 with reduced Sb content. The resulting crystal of (Bi2Te3)0.96(Sb2Te)0.04 exhibit an exceptional peak zT of 1.3 at 303 K, surpassing the mechanical robustness of standard high‐Sb BST. Additionally, it matches the energy conversion efficiency of traditional BST, achieving 2.3% at a temperature difference ΔT of 150 K. This significant advance makes (Bi2Te3)0.96(Sb2Te)0.04 a potential competitor to the well‐established BST, thanks to its enhanced thermoelectric performance owing to the elevated carrier concentration and a less brittle nature due to the diluted Sb dopant
Selective-Area MOCVD Growth and Carrier-Transport-Type Control of InAs(Sb)/GaSb Core-Shell Nanowires
No full textWe
report the first selective-area growth of high quality InAs(Sb)/GaSb
core–shell nanowires on Si substrates using metal–organic
chemical vapor deposition (MOCVD) without foreign catalysts. Transmission
electron microscopy (TEM) analysis reveals that the overgrowth of
the GaSb shell is highly uniform and coherent with the InAs(Sb) core
without any misfit dislocations. To control the structural properties
and reduce the planar defect density in the self-catalyzed InAs core
nanowires, a trace amount of Sb was introduced during their growth.
As the Sb content increases from 0 to 9.4%, the crystal structure
of the nanowires changes from a mixed wurtzite (WZ)/zinc-blende (ZB)
structure to a perfect ZB phase. Electrical measurements reveal that
both the n-type InAsSb core and p-type GaSb shell can work as active
carrier transport channels, and the transport type of core–shell
nanowires can be tuned by the GaSb shell thickness and back-gate voltage.
This study furthers our understanding of the Sb-induced crystal-phase
control of nanowires. Furthermore, the high quality InAs(Sb)/GaSb
core–shell nanowire arrays obtained here pave the foundation
for the fabrication of the vertical nanowire-based devices on a large
scale and for the study of fundamental quantum physics
Origin of the low thermal conductivity of the thermoelectric material beta-Zn(4)Sb(3): An ab initio theoretical study
No full textBy modeling beta-Zn(4)Sb(3) material as a Zn(36)Sb(30) crystal with defects, the crystal structure and thermal properties of beta-Zn(4)Sb(3) are studied by ab initio method to explain its extremely low thermal conductivity at moderate temperature. The formation and migration energies of defects are calculated and used to explain the partial occupation of Zn at the lattice sites, the disordered local structures and the origin of the low thermal conductivity of beta-Zn(4)Sb(3). Our study also unravels the puzzling dependence of thermal conductivity on doping in beta-Zn(4)Sb(3). A doping strategy is proposed to improve the thermoelectric performance of beta-Zn(4)Sb(3). (C) 2011 American Institute of Physics. [doi:10.1063/1.3599483
Stability of Sb-Te layered structures: First-principles study
Full text linkUsing an effective one-dimensional cluster expansion in combination with first-principles electronic structure calculations we have studied the energetics and electronic properties of Sb-Te layered systems. For a Te concentration between 0 and 60 at. % an almost continuous series of metastable structures is obtained consisting of consecutive Sb bilayers next to consecutive Sb2Te3 units, with the general formula (Sb2)n(Sb2Te3)m (n,m=1,2,...). Between 60 and 100 at. % no stable structures are found. We account explicitly for the weak van der Waals bonding between Sb bilayers and Sb2Te3 units by using a recently developed functional, which strongly improves the interlayer bonding distances. At T=0 K, no evidence is found for the existence of two separate single-phase regions ? and ? and a two-phase region ?+?. Metastable compounds with a Te concentration between 0 and 40 at. % are semimetallic, whereas compounds with a Te concentration between 50 and 60 at. % are semiconducting. Compounds with an odd number of Sb layers are metallic and have a much higher formation energy than those with an even number of consecutive Sb layers, thereby favoring the formation of Sb bilayers.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin
Legal and Financial Problems of International Joint Custody of Children
Full text linkThe aim of this article is to analyze very interesting and currently up-to-date area of children living in international joint custody from the legal and financial point of view. This covers the situation when custody of a child is awarded to both parents living in different states of the European Union (or also other states). The number of marriages contracted between Czech nationals and foreign nationals and also between nationals from two different states (not necessarily inside European Union) increases every year while free movement of people is a real practice today. Because these international marriages are becoming more common they bring new problems that must be solved by contemporary law. This regulation needs to result from the knowledge of the children psychology that is affecting family law the most but also has its practical aspects in the area of taxation and payment issues that will be analyzed deeply as well.juridical problems, financial problems, international joint custody, family.
Raw data for 'Effects of Bi and Sb ion incorporation on the optoelectronic properties of mixed lead-tin perovskites'
No full textRaw data for 'Effects of Bi and Sb ion incorporation on the optoelectronic properties of mixed lead-tin perovskites'. Authors: F. M. Rombach, L. Gregori, A. Sidler, J. Whitworth, S. Zeiske, H. Jin, E. Hung, S. Motti, P. Caprioglio, A. Ardalan, M. Lenz, D. Meggiolaro, F. De Angelis, H. J. Snait
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