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|Title: ||Synthesis and applications of porous silicon-based functional materials|
|Other Titles: ||Ji yu duo kong xi de gong neng cai liao de he cheng yu ying yong yan jiu|
|Authors: ||Cheng, Hua ( 程化)|
|Department: ||Department of Physics and Materials Science|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2011|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Porous silicon.|
|Notes: ||CityU Call Number: TK7871.15.S55 C45 2011|
xv, 109 leaves : ill. (some col.) 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2011.
Includes bibliographical references.
|Abstract: ||Porous silicon (P-Si) is a material with sponge-like structure formed by
electrochemically etching the crystalline silicon wafer in hydrofluoric acid solutions. Due
to its porous structure, high surface area, controllable porosity and optical response, it has
been extensively applied in the field of photonics, micro-system engineering, solid state
electronics, biomedical devices, etc. In this dissertation, we study P-Si and P-Si-based
nanocomposites and apply them for sensors, photonics, and anodes materials for
rechargeable lithium-ion batteries (LIBs).
The first chapter gives a briefly review of P-Si with an emphasis on its fabrication,
functionalization and applications.
The second chapter demonstrates a simple and effective method to fabricate P-Si
photonic crystal-based hybrid particles by soft lithographic and microfluidic techniques.
The fabricated hybrid particles are composed of pristine P-Si structures strengthened by a
polymer infused nanocomposite framework. The pristine P-Si moiety serves as a sensor
because of its environmentally sensitive optical features, while the polymer-infused
moiety provides a mechanically resilient scaffold and its invariant optical features can be
used as both an optical barcode and a built-in self-reference for optical sensing.
The third chapter explores the fabrication method of metal-based porous photonic
films using P-Si as the sacrificial template. Metals, such as Ni, Co, Co-Ni, Ag, and Sn,
have been successfully deposited into the pores of the P-Si template. The Ni-based films
thus obtained feature nanoporous structures and distinct optical responses in the visible spectra. Moreover, their optical responses can be conveniently controlled by adjusting the
nanostructure of the P-Si template (e.g., its periodcity). The application of the fabricated
porous Ni photonic films as optical sensors has been demonstrated.
The fourth chapter investigates the application of both pristine P-Si and P-Si-based
nanocomposites as the anode materials for LIBs. First, the electrochemical performance
of free-standing P-Si films as anode materials for LIBs has been studied: the P-Si
electrodes display superior electrochemical properties with a high reversible specific
capacity of > 2500 mAh/g and capacity retention of > 83 % after 60 cycles. For further
improvement, we have fabricated functionalized freestanding P-Si films via carbonization
of the P-Si/polymer composites in an Ar/H2 atmosphere and studied their electrochemical
performance as the anode material for LIB. The carbonization treatment coats the walls of
the porous structure of P-Si with highly conductive carbon, and considerably increases
the electrical conductivity of P-Si. The functionalized P-Si anode materials show
significantly enhanced electrochemical performance. Moreover, we have attempted to
apply metal (e.g., Ag and Sn) deposited P-Si films as the LIB anode materials. To
effectively fabricate Ag deposited P-Si, Ag-mirror reaction was tested but did not generate
satisfactory results. However, this failure inspired a related project and the Ag-mirror
approach proves to be a facile method to decorate other nanomateirals (e.g., Co3O4 nanowires) with Ag nanoparticles and improve its capability as LIB electrodes, which
will be presented in Chapter 5.
The fifth Chapter demonstrates that the Ag-mirror method is an effective approach to
decorate nanomateirals (e.g., Co3O4 nanowires) with Ag nanoparticles and improve its
capability as LIB electrode materials. Highly electrically conductive silver nanoparticles facilitate electron transportation between the current collectors and the active materials.
High capacity as well as remarkable rate capability has been achieved through this simple
The sixth chapter summarizes the work of the dissertation and suggests the future
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b4086242|
|Appears in Collections:||AP - Doctor of Philosophy |
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