排序方式: 共有52条查询结果,搜索用时 15 毫秒
41.
Jinfeng Dong Lei Hu Jue Liu Yukun Liu Yilin Jiang Zhiling Yu Xian Yi Tan Ady Suwardi Qiang Zheng Qian Li Jing-Feng Li Vinayak P. Dravid Qingyu Yan Mercouri G. Kanatzidis 《Advanced functional materials》2024,34(18):2314499
The crystal structure and transport properties of GeBi2Te4 are investigated as a layered compound with potential applications as thermoelectric materials. A disordered arrangement of Ge and Bi atoms in a septuple-layer structure is discovered through synchrotron radiation X-ray diffraction and transmission electron microscopy. Neutron pair distribution function analysis revealed the presence of discordant Ge atoms with an off-centering distance of 0.12 Å at 300 K. The thermal conductivity of GeBi2Te4 is very low due to the strong phonon scattering. This is a result of the three Einstein local oscillators coupled with the disordered arrangement of atoms. This study also explores further the structural characteristics of these materials and their associated phonon scattering processes. The effect of Sb substitution for Ge on the electrical transport properties of the sample is profound, resulting in a change from p-type to n-type conduction. An enhanced thermoelectric figure of merit (ZT) of 0.45 at 523 K in the in-plane direction is obtained. This research provides valuable insights into the crystal structure and transport properties of GeBi2Te4, showcasing its promising role as a thermoelectric material with potential for near-room-temperature applications. 相似文献
42.
Dravid Sampada Viraj Bhosale Shubham Dinkar Datar Suwarna Goyal R. K. 《Journal of Electronic Materials》2020,49(3):1630-1637
Journal of Electronic Materials - In this paper, the electromagnetic interference shielding effectiveness (EMI-SE) of nickel (Ni) nanoparticle-filled high-performance polyetherketone (PEK)... 相似文献
43.
Corrigendum: The Structural Fate of Individual Multicomponent Metal‐Oxide Nanoparticles in Polymer Nanoreactors
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44.
High Thermoelectric Performance in Supersaturated Solid Solutions and Nanostructured n‐Type PbTe–GeTe
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Zhong‐Zhen Luo Xiaomi Zhang Xia Hua Gangjian Tan Trevor P. Bailey Jianwei Xu Ctirad Uher Chris Wolverton Vinayak P. Dravid Qingyu Yan Mercouri G. Kanatzidis 《Advanced functional materials》2018,28(31)
Sb‐doped and GeTe‐alloyed n‐type thermoelectric materials that show an excellent figure of merit ZT in the intermediate temperature range (400–800 K) are reported. The synergistic effect of favorable changes to the band structure resulting in high Seebeck coefficient and enhanced phonon scattering by point defects and nanoscale precipitates resulting in reduction of thermal conductivity are demonstrated. The samples can be tuned as single‐phase solid solution (SS) or two‐phase system with nanoscale precipitates (Nano) based on the annealing processes. The GeTe alloying results in band structure modification by widening the bandgap and increasing the density‐of‐states effective mass of PbTe, resulting in significantly enhanced Seebeck coefficients. The nanoscale precipitates can improve the power factor in the low temperature range and further reduce the lattice thermal conductivity (κlat). Specifically, the Seebeck coefficient of Pb0.988Sb0.012Te–13%GeTe–Nano approaches ?280 µV K?1 at 673 K with a low κlat of 0.56 W m?1 K?1 at 573 K. Consequently, a peak ZT value of 1.38 is achieved at 623 K. Moreover, a high average ZTavg value of ≈1.04 is obtained in the temperature range from 300 to 773 K for n‐type Pb0.988Sb0.012Te–13%GeTe–Nano. 相似文献
45.
Yao Chen Xinming Zhuang Elise A. Goldfine Vinayak P. Dravid Michael J. Bedzyk Wei Huang Antonio Facchetti Tobin J. Marks 《Advanced functional materials》2020,30(40)
Here, a new approach to the layer‐by‐layer solution‐processed fabrication of organic/inorganic hybrid self‐assembled nanodielectrics (SANDs) is reported and it is demonstrated that these ultrathin gate dielectric films can be printed. The organic SAND component, named P‐PAE, consists of polarizable π‐electron phosphonic acid‐based units bound to a polymeric backbone. Thus, the new polymeric SAND (PSAND) can be fabricated either by spin‐coating or blade‐coating in air, by alternating P‐PAE, a capping reagent layer, and an ultrathin ZrOx layer. The new PSANDs thickness vary from 6 to 15 nm depending on the number of organic‐ZrOx bilayers, exhibit tunable film thickness, well‐defined nanostructures, large electrical capacitance (up to 558 nF cm?2), and good insulating properties (leakage current densities as low as 10?6 A cm?2). Organic thin‐film transistors that are fabricated with representative p‐/n‐type organic molecular/polymeric semiconducting materials, function well at low voltages (<3.0 V). Furthermore, flexible TFTs fabricated with PSAND exhibit excellent mechanical flexibility and good stress stability, offering a promising route to low operating voltage flexible electronics. Finally, printable PSANDs are also demonstrated and afford TFTs with electrical properties comparable to those achieved with the spin‐coated PSAND‐based devices. 相似文献
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47.
Core-shell nanoparticles have emerged as an important class of functional nanostructures with potential applications in many diverse fields, especially in health sciences. We have used a modified aqueous sol-gel route for the synthesis of size-selective FePt@SiO2 core-shell nanoparticles. In this approach, oleic acid and olyel amine stabilized FePt nanoparticles are first encapsulated through an aminopropoxysilane (APS) monolayer and then subsequent condensation of triethoxysilane (TEOS) on FePt particle surface. These well-defined FePt@SiO2 core-shell nanoparticles with narrow size distribution become colloidal in aqueous media, and can thus be used as carrier fluid for biomolecular complexes. In comparison, the scarce hydrophilic nature of oleic acid monolayers on FePt particle surface yields an edgy partial coating of silica when only TEOS is applied for the surface modification. The synthesized core-shell nanoparticles were characterized by direct techniques of high resolution transmission electron microscopy (HRTEM), EDS and indirectly via UV-vis absorption and FTIR studies. The FePt@SiO2 nanoparticles exhibit essential characteristics of superparamagnetic behavior, as investigated by SQUID magnetometry. The blocking temperatures (T(B)) of FePt and FePt@SiO2 (135 and 80 K) were studied using zero field cooled (ZFC)/field cooled (FC) curves. 相似文献
48.
Miniaturized chemical multiplexed sensor array 总被引:4,自引:0,他引:4
Miniaturized tin oxide semiconductor sensors are fabricated directly by site-specific dip-pen nanopatterning using precursor inks derived from the sol-gel method. The good flow characteristics and strong affinity of the sols to measurement electrodes enable intimate contact. The measurable, reproducible, and proportionate changes in the resistance of the sensors when exposed to trace quantities of oxidative and reducing gases constitute the basis for such sensors. These sensors show rapid response and ultrafast recovery for the detection of nitrogen dioxide and acetic acid. Furthermore, an array of eight miniaturized sensors is created by doping the pristine tin-based sol ink with different metal ions; the different responses of each sensor to certain gases constitute a reference response spectrum that can be used to recognize the gas. Such recognition ability, instant response and rapid recovery, compact size, and integration with the current microelectronics platform make the miniaturized sensor array a significant development for the on-site and real-time detection of life-threatening gases. 相似文献
49.
Steam etched porous graphene oxide network for chemical sensing 总被引:1,自引:0,他引:1
Han TH Huang YK Tan AT Dravid VP Huang J 《Journal of the American Chemical Society》2011,133(39):15264-15267
Oxidative etching of graphene flakes was observed to initiate from edges and the occasional defect sites in the basal plane, leading to reduced lateral size and a small number of etch pits. In contrast, etching of highly defective graphene oxide and its reduced form resulted in rapid homogeneous fracturing of the sheets into smaller pieces. On the basis of these observations, a slow and more controllable etching route was designed to produce nanoporous reduced graphene oxide sheets by hydrothermal steaming at 200 °C. The degree of etching and the concomitant porosity can be conveniently tuned by etching time. In contrast to nonporous reduced graphene oxide annealed at the same temperature, the steamed nanoporous graphene oxide exhibited nearly 2 orders of magnitude increase in the sensitivity and improved recovery time when used as chemiresistor sensor platform for NO(2) detection. The results underscore the efficacy of the highly distributed nanoporous network in the low temperature steam etched GO. 相似文献
50.
Thermoelectrics with earth abundant elements: high performance p-type PbS nanostructured with SrS and CaS 总被引:1,自引:0,他引:1
Zhao LD He J Wu CI Hogan TP Zhou X Uher C Dravid VP Kanatzidis MG 《Journal of the American Chemical Society》2012,134(18):7902-7912
We report high thermoelectric performance in nanostructured p-type PbS, a material consisting of highly earth abundant and inexpensive elements. The high level of Na doping switched intrinsic n-type PbS to p-type and substantially raised the power factor maximum for pure PbS to ~9.0 μW cm(-1) K(-2) at >723 K using 2.5 at. % Na as the hole dopant. Contrary to that of PbTe, no enhancement in the Hall coefficient occurs at high temperature for heavily doped p-type PbS, indicating a single band model and no heavy hole band. We also report that the lattice thermal conductivity of PbS can be greatly reduced by adding SrS or CaS, which form a combination of a nanostructured/solid solution material as determined by transmission electron microscopy. We find that both nanoscale precipitates and point defects play an important role in reducing the lattice thermal conductivity, but the contribution from nanoscale precipitates of SrS is greater than that of CaS, whereas the contribution from point defects in the case of CaS is greater than that of SrS. Theoretical calculations of the lattice thermal conductivity based on the modified Callaway model reveal that both nanostructures and point defects (solid solution) effectively scatter phonons in this system. The lattice thermal conductivity at 723 K can be reduced by ~50% by introducing up to 4.0 at. % of either SrS or CaS. As a consequence, ZT values as high as 1.22 and 1.12 at 923 K can be achieved for nominal Pb(0.975)Na(0.025)S with 3.0 at. % SrS and CaS, respectively. No deterioration was observed after a 15 d annealing treatment of the samples, indicating the excellent thermal stability for these high performance thermoelectrics. The promising thermoelectric properties of nanostructured PbS point to a robust low cost alternative to other high performance thermoelectric materials. 相似文献