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High frequency magnetics and nanopor...

Zhou, Yang.

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High frequency magnetics and nanoporous silver for energy applications.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	High frequency magnetics and nanoporous silver for energy applications./
作者:	Zhou, Yang.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2015,
面頁冊數:	163 p.
附註:	Source: Dissertation Abstracts International, Volume: 77-03(E), Section: B.
Contained By:	Dissertation Abstracts International77-03B(E).
標題:	Physical chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3730222
ISBN:	9781339163925

High frequency magnetics and nanoporous silver for energy applications.
Zhou, Yang.

High frequency magnetics and nanoporous silver for energy applications. - Ann Arbor : ProQuest Dissertations & Theses, 2015 - 163 p.

Source: Dissertation Abstracts International, Volume: 77-03(E), Section: B.

Thesis (Ph.D.)--University of Delaware, 2015.

In this study, soft magnetic materials/composites and nanoporous silver materials are developed for improving efficiency in energy conversion processes, namely direct-current-to-direct-current (DC-DC) voltage converters and alkaline fuel cells.

ISBN: 9781339163925Subjects--Topical Terms:

1981412
Physical chemistry.

High frequency magnetics and nanoporous silver for energy applications.
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245 1 0 $a High frequency magnetics and nanoporous silver for energy applications.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2015
300 $a 163 p.
500 $a Source: Dissertation Abstracts International, Volume: 77-03(E), Section: B.
500 $a Adviser: John Q. Xiao.
502 $a Thesis (Ph.D.)--University of Delaware, 2015.
520 $a In this study, soft magnetic materials/composites and nanoporous silver materials are developed for improving efficiency in energy conversion processes, namely direct-current-to-direct-current (DC-DC) voltage converters and alkaline fuel cells.
520 $a Switch-mode power electronics operating above 1 megahertz (MHz) have drawn a lot of attention due to the increasing demand for miniaturization and faster transient response. Soft magnetic materials are often employed as core materials for inductors in these electronic devices. During the operation, magnetizations of the core materials are rapidly switched and/or rotated. The magnetization switching process is irreversible, costing energy dissipation (core loss). To achieve efficient operation in these devices, soft magnetic materials with low core loss, large permeability and high saturation magnetization are in high demand. In this study, we propose to develop two dimensional (2D) magnetic materials/composites for the above demands. First, polymer composite materials consisting of aligned metallic iron-nickel (FeNi or permalloy) flakes have been developed to take advantage of their magnetic softness, limited eddy current losses, high saturation magnetization, and low cost fabrication methods. The high energy ball milling method is used to deform permalloy powders into flakes. A sol-gel method is adopted to coat the surface of each individual flake with silica to ensure the insulation between flakes. A technique combining of tape casting and hot press is developed to fabricate the flake/polymer composite. Second, weakly crystallized iron-hafnium-boron (FeHfB) ribbons are synthesized by melt-spinning technique. Heat treatments in controlled oxygen atmosphere are carried out to fabricate the iron-hafnium-boron-oxide (FeHfBO) materials. At 5 MHz and a peak magnetic induction of 20 mT, the core losses of the flake/polymer composite and FeHfBO material developed in this study show comparable values to those of commercial low temperature co-fired ceramic (LTCC) ferrite materials. However, higher saturation magnetizations and larger permeability are achieved in the current study.
520 $a Electrochemical reduction of oxygen in alkaline environment is of tremendous importance for many electrochemical devices that are directly related to efficient energy conversion and storage applications. Among those applications, alkaline fuel cells (AFC) are promising future power sources due to the recent progress on hydrogen oxidation reaction (HOR) catalysts and hydroxide exchange membranes; lithium (Li)-air and zinc (Zn)-air secondary batteries are advanced energy storage devices for future electric vehicles and electrical grids of solar and wind power plants providing much higher capacity than current state-of-the-art lithium ion batteries. However, the successful large-scale implementation of these technologies relies on the development of active and stable oxygen reduction reaction (ORR) catalysts. In this work, nanoporous silver (np-Ag) material is fabricated through a two-step chemical de-alloying method. The porous structure is proposed to improve the interactions between oxygen molecules and the catalyst surface, promoting the reaction rate at low overpotentials. The np-Ag catalyst exhibits higher ORR activity in the low overpotential regime and shows better stability in the alkaline electrolyte than the state-of-the-art Pt/C catalysts.
590 $a School code: 0060.
650 4 $a Physical chemistry. $3 1981412
650 4 $a Materials science. $3 543314
690 $a 0494
690 $a 0794
710 2 $a University of Delaware. $b Department of Physics and Astronomy. $3 1033911
773 0 $t Dissertation Abstracts International $g 77-03B(E).
790 $a 0060
791 $a Ph.D.
792 $a 2015
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3730222