[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Damascene copper electroplating for on-chip interconnections, a process that we conceived and developed in the early 1990s, makes it possible to fill submicron trenches and vias with copper without creating a void or a seam and has thus proven superior to other technologies of copper deposition. We discuss here the relationship of additives in the plating bath to superfilling, the phenomenon that results in superconformal coverage, and we present a numerical model which accounts for the experimentally observed profile evolution of the plated metal.

Damascene copper electroplating for chip interconnections

Hydrogen evolution reaction (HER) in alkaline medium is currently a point of focus for sustainable development of hydrogen as an alternative clean fuel for various energy systems, but suffers from sluggish reaction kinetics due to additional water dissociation step. So, the state-of-the-art catalysts performing well in acidic media lose considerable catalytic performance in alkaline media. This review summarizes the recent developments to overcome the kinetics issues of alkaline HER, synthesis of materials with modified morphologies, and electronic structures to tune the active sites and their applications as efficient catalysts for HER. It first explains the fundamentals and electrochemistry of HER and then outlines the requirements for an efficient and stable catalyst in alkaline medium. The challenges with alkaline HER and limitation with the electrocatalysts along with prospective solutions are then highlighted. It further describes the synthesis methods of advanced nanostructures based on carbon, noble, and inexpensive metals and their heterogeneous structures. These heterogeneous structures provide some ideal systems for analyzing the role of structure and synergy on alkaline HER catalysis. At the end, it provides the concluding remarks and future perspectives that can be helpful for tuning the catalysts active-sites with improved electrochemical efficiencies in future.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201700464

Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

Hybrid supercapacitors with their improved performance in energy density without altering their power density have been in trend since recent years. The hybrid supercapacitor delivers higher specific capacitance in comparison to the existing electric double layer capacitor (EDLC) and pseudocapacitors. Generally, the asymmetric behavior of hybrid supercapacitors which is the combination of EDLC and pseudocapacitor acts as an enhancer in its respective capacitance values. This asymmetric approach marks a new beginning towards the much-needed pollution free, long lasting and proficient energy-storing performance. Corresponding to their utilization in hybrid electric vehicles and similar sort of power necessity based devices; the research in developing new advanced storage devices finds an enormous and vast future ahead. The most significant factor for the energy efficient applications demands a considerably higher ratio of surface to the volume by incorporation of new materials. This review article gives an overview of recent advances in the development of hybrid supercapacitors, storage mechanism, criteria of formation, components, different electrode and electrolyte materials, electrochemical profile assessment, design fabrication and their applications.

A review on recent advances in hybrid supercapacitors: Design, fabrication and applications

Low-Temperature Solid State Bonding of Sn and Nickel Micro Cones for Micro Interconnection

Hydrothermal synthesis of porous copper microspheres towards efficient 4-nitrophenol reduction

Since Au is used as the end finish on Pd preplated leadframes (Pd PPFs), the weak adhesion between the surface noble metal Au and the epoxy molding compound (EMC) often causes delamination and reduces the reliability of integrated circuit (IC) packages, which greatly limits the application of Pd PPFs. This paper reports on a novel application of arrays of nanocones prepared by a special electrodeposition method to improve the adhesion between the leadframe and EMC. Nanocone-arrayed structures greatly increase the area of the interface between the Pd PPF and the EMC. Shearing strength tests indicate that the adhesion between the EMC and nanocone-arrayed PPF is three to four times higher than that of the conventional PPF. Apart from increased interfacial area, the effect of a physical inlay may also increase the adhesion strength.

Study on the Adhesion Between Epoxy Molding Compound and Nanocone-Arrayed Pd Preplated Leadframes

A facile hydrothermal method has been presented to prepare free-standing nanoporous Cu foils (NPCFs) having a thickness of ~1.4 μm and an area of up to ~10 cm2, which were grown on the inwall of a Teflon-lined autoclave by assembling and reducing CuxO nanoparticle intermediates and then peeling themselves off in the cooling period of the reaction. The pore sizes of NPCFs can be adjusted by varying the reaction time. It is observed that the NPCFs with water absorbed inside their nanopores show excellent flexibility while dried ones exhibit a highly hydrophobic nature. Compared with commercially available Cu foils, the as-synthesized NPCFs show enhanced ability to absorb light over a wide range of wavelengths from 200 to 1000 nm because of their nanoporosity. The highest absorbance and the biggest enhancement can reach 86% at 300 nm and 43% at 575 nm, respectively. The smooth side of NPCFs with a hemisphere-like surface demonstrates outstanding surface-enhanced Raman scattering performance by employing Rhodamine 6G as the probe molecule, which agrees well with the results of finite-difference time-domain simulation.

Ming Li

Papers

Low-Temperature Solid State Bonding of Sn and Nickel Micro Cones for Micro Interconnection

Hydrothermal synthesis of porous copper microspheres towards efficient 4-nitrophenol reduction

Study on the Adhesion Between Epoxy Molding Compound and Nanocone-Arrayed Pd Preplated Leadframes

One-pot preparation of thin nanoporous copper foils with enhanced light absorption and SERS properties

Effect of Sn surface diffusion on growth behaviors of intermetallic compounds in cu/Ni/SnAg microbumps