Investigation of the shape transferability of nanoscale multi-tip diamond tools in the diamond turning of nanostructures

In this article, the shape transferability of using nanoscale multi-tip diamond tools in the diamond turning for scale-up manufacturing of nanostructures has been demonstrated. Atomistic multi-tip diamond tool models were built with different tool geometries in terms of the difference in the tip cross-sectional shape, tip angle, and the feature of tool tip configuration, to determine their effect on the applied forces and the machined nano-groove geometries. The quality of machined nanostructures was characterized by the thickness of the deformed layers and the dimensional accuracy achieved. Simulation results show that diamond turning using nanoscale multi-tip tools offers tremendous shape transferability in machining nanostructures. Both periodic and non-periodic nano-grooves with different cross-sectional shapes can be successfully fabricated using the multi-tip tools. A hypothesis of minimum designed ratio of tool tip distance to tip base width (L/Wf) of the nanoscale multi-tip diamond tool for the high precision machining of nanostructures was proposed based on the analytical study of the quality of the nanostructures fabricated using different types of the multi-tip tools. Nanometric cutting trials using nanoscale multi-tip diamond tools (different in L/Wf) fabricated by focused ion beam (FIB) were then conducted to verify the hypothesis. The investigations done in this work imply the potential of using the nanoscale multi-tip diamond tool for the deterministic fabrication of period and non-periodic nanostructures, which opens up the feasibility of using the process as a versatile manufacturing technique in nanotechnology

Investigation on interaction reaction mechanism between metallic interconnect and electrodes in solid oxide fuel cell

Solid oxide fuel cell (SOFC) is probably the most efficient energy conversion device with very low greenhouse gas emission. Recently significant progress has been achieved to lower the operating temperature of SOFC from traditional 1000oC to intermediate temperatures of 600-800oC. The low SOFC operating temperature enables the use of cheap chromia-forming alloys as interconnect materials for SOFC. This study aims to understand the interaction reactions between the metallic interconnect and the cathodes under the SOFC operating conditions.DOCTOR OF PHILOSOPHY (MAE

Three dimensionals α-Fe2O3/polypyrrole (Ppy) nanoarray as anode for micro lithium ion batteries

Three dimensional, self-supported α-Fe2O3/Ppy composite electrode with enhanced specific areal capacity and rate performance was successfully fabricated by a simple, low-cost, two-steps process consisting of direct heating of iron foil in air and subsequent coating of conducting polymer Ppy on the α-Fe2O3 nanoflakes. By using α-Fe2O3/Ppy as the anode materials with iron foil as the current collector, the unique structure affords a highly conductive pathway for electron, a short diffusion length for ions, a fast mass transport channel for electrolyte, and sufficient void space for accommodating large volume variations during Li intercalation/diintercalation for Li-ion battery. A relatively high specific capacity of 0.42 mA h/cm2 can be achieved at 0.1 mA/cm2 even after 100 charge/discharge cycles, with a plateau potential of 1 V and nearly 100% Coulombic efficiency, suggesting the feasibility to use this unique 3D nanostructured hybrid composite for microbattery in both small and large scale applications

In Situ Activation of Nitrogen-Doped Graphene Anchored on Graphite Foam for a High-Capacity Anode

We report the fabrication of a three-dimensional free-standing nitrogen-doped porous graphene/graphite foam by in situ activation of nitrogen-doped graphene on highly conductive graphite foam (GF). After in situ activation, intimate sheet contact was observed between the graphene sheets and the GF. The sheet contact produced by in situ activation is found to be superior to the point contact obtained by the traditional drop-casting method and facilitates electron transfer. Due to the intimate contact as well as the use of an ultralight GF current collector, the composite electrode delivers a gravimetric capacity of 642 mAh g-1 and a volumetric capacity of 602 mAh cm-3 with respect to the whole electrode mass and volume (including the active materials and the GF current collector). When normalized based on the mass of the active material, the composite electrode delivers a high specific capacity of up to 1687 mAh g-1, which is superior to that of most graphene-based electrodes. Also, after ∼90 s charging, the anode delivers a capacity of about 100 mAh g-1 (with respect to the total mass of the electrode), indicating its potential use in high-rate lithium-ion batteries. (Graph Presented). © 2015 American Chemical Society161611sciescopu

In Situ Activation of Nitrogen-Doped Graphene Anchored on Graphite Foam for a High-Capacity Anode

We report the fabrication of a three-dimensional free-standing nitrogen-doped porous graphene/graphite foam by in situ activation of nitrogen-doped graphene on highly conductive graphite foam (GF). After in situ activation, intimate "sheet contact" was observed between the graphene sheets and the GF. The sheet contact produced by in situ activation is found to be superior to the "point contact" obtained by the traditional drop-casting method and facilitates electron transfer. Due to the intimate contact as well as the use of an ultralight GF current collector, the composite electrode delivers a gravimetric capacity of 642 mAh g(-1) and a volumetric capacity of 602 mAh cm(-3) with respect to the whole electrode mass and volume (including the active materials and the GF current collector). When normalized based on the mass of the active material, the composite electrode delivers a high specific capacity of up to 1687 mAh g(-1), which is superior to that of most graphene-based electrodes. Also, after similar to 90 s charging, the anode delivers a capacity of about 100 mAh g(-1) (with respect to the total mass of the electrode), indicating its potential use in high-rate lithium-ion batteries