The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Recent advances in friction-stir welding : Process, weldment structure and properties

Plasticity in small-sized metallic systems: Intrinsic versus extrinsic size effect

Shear-banding is a ubiquitous plastic-deformation mode in materials. In metallic glasses, shear bands are particularly important as they play the decisive role in controlling plasticity and failure at room temperature. While there have been several reviews on the general mechanical properties of metallic glasses, a pressing need remains for an overview focused exclusively on shear bands, which have received tremendous attention in the past several years. This article attempts to provide a comprehensive and up-to-date review on the rapid progress achieved very recently on this subject. We describe the shear bands from the inside out, and treat key materials-science issues of general interest, including the initiation of shear localization starting from shear transformations, the temperature and velocity reached in the propagating or sliding band, the structural evolution inside the shear-band material, and the parameters that strongly influence shear-banding. Several new discoveries and concepts, such as stick-slip cold shear-banding and strength/plasticity enhancement at sub-micrometer sample sizes, will also be highlighted. The understanding built-up from these accounts will be used to explain the successful control of shear bands achieved so far in the laboratory. The review also identifies a number of key remaining questions to be answered, and presents an outlook for the field.

Shear bands in metallic glasses

Friction stir processing (FSP), developed based on the basic principles of friction stir welding (FSW), a solid-state joining process originally developed for aluminum alloys, is an emerging metalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed.

Friction stir processing technology: A review

http://www.nano.nsysu.edu.tw/nano/V2007/Papers/317_Relationship%20between%20Grain%20Size%20and%20Working%20Strain%20Rate%20and%20Temperature%20during%20Friction%20Stir%20Processing%20in%20AZ31%20Mg%20Alloy.pdf

Relationship between grain size and Zener¿Holloman parameter during friction stir processing in AZ31 Mg alloys

http://www.nano.nsysu.edu.tw/nano/V2007/Papers/590_Achieving%20ultrafine%20grain%20size%20in%20Mg-Al-Zn%20alloy%20by%20friction%20stir%20processing.pdf

Achieving ultrafine grain size in Mg–Al–Zn alloy by friction stir processing

http://www.nano.nsysu.edu.tw/nano/V2007/Papers/491_Texture%20and%20weak%20Grain%20Size%20Dependence%20of%20Yield%20Stress%20in%20Friction%20Stir%20Processed%20Mg-Al-Zn%20Alloy.pdf

Texture and weak grain size dependence in friction stir processed Mg–Al–Zn alloy

https://www2.nsysu.edu.tw/MSE/papers/Paper%20in%20PDF/164%20Zr%20Pillar%20Scripta.pdf

Bulk and microscale compressive behavior of a Zr-based metallic glass

https://www2.nsysu.edu.tw/MSE/papers/Paper%20in%20PDF/165%20Scripta%20FSP%20two-step.pdf

C.I. Chang

Papers

Relationship between grain size and Zener¿Holloman parameter during friction stir processing in AZ31 Mg alloys

Achieving ultrafine grain size in Mg–Al–Zn alloy by friction stir processing

Texture and weak grain size dependence in friction stir processed Mg–Al–Zn alloy

Bulk and microscale compressive behavior of a Zr-based metallic glass

Producing nanograined microstructure in Mg–Al–Zn alloy by two-step friction stir processing