[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

Microcones arrays of cobalt were prepared by electrodeposition with special crystallization conditioning agent. The influence of electrodepositing conditions and form factor effect on the morphology of microcones array is reported. X-ray diffraction result indicated that the Co arrays growing with (110) preferred orientation. The Co array had an obvious magnetic anisotropy. The coercive and saturation field perpendicular and parallel to the surface of Co were FE-SEM, XRD and VSM, respectively.

Preparation of Microcones Array Material for Microelectronic Package

Copper nanowire is a promising material in the electronic packaging industry. However, at present, most of the preparation methods of Cu nanowires growing on substrates are highly dependent on templates or need relatively high temperature. In this study, Cu nanowires growing on substrates are synthesized by both pulse current electrodeposition and electroless plating, which is both template-free and conducted under mild conditions. The final morphology and structure of the products have been studied by X-ray diffraction method, scanning electron microscope and transmission electron microscope respectively. The Cu nanowires have smooth surfaces, with length between 10-30μm and diameter between 60-70nm. Moreover, the Cu nanowires have single-crystal structure of face-centered-cubic copper growing along the [100] direction.

Synthesis of copper nanowires on the substrates in aqueous solution

Stacked bonding has become one of the key technologies of 3D IC This paper reports a low-temperature solid state bonding method based on metallic microcone array for potential use in 3D integration applications Sn-30Ag-05Cu solder balls with 760 µm diameter were used for the low-temperature BGA bonding Ni micro cone layer was prepared by electro deposition and Cu micro cone layer was deposited by electroless plating, respectively Bonding joints were shear tested to evaluate the joint strength of samples bonded at each pressure and temperature Microscopic observation showed sufficient insertion between Sn and cone-structured Ni or Cu Results showed that bonding strength was superior with proper bonding conditions

Low-temperature bonding method based on metallic microcone array for interconnection application

Copper metallization on LCP was carried out by means of electroless plating followed by electroplating and the effect of pretreatment on the adhesive strength of the Cu-plated LCP was investigated in detail. Compared with the other etching agents used here, potassium permanganate was found to be the most effective and the optimum etching time is 20min. With potassium permanganate as the etching agent, the adhesion strength could reach 12.08MPa, which is much higher than the reported maximum adhesion strength of 8.0MPa. Furthermore, it is more environment-friendly to use potassium permanganate as an etching agent compared with the other common chromium-containing chemicals like Chromic Acid. ATR FT-IR spectra of LCP film indicated that hydrophilic groups were introduced into the LCP surface by etching, creating a nanometer-scale surface roughness and improving the wettability between copper and LCP. SEM and AFM observations revealed that the distinctly increased adhesion strength could be attributed to the improved wetting and the mechanical interlocking effect. The failure mode of Cu-plated LCP film was found to be dependent on the etching time and it was adhesive failure for the short etching time and cohesive failure for the long etching time.

Electroless and eletroplating copper on liquid crystal polymer (LCP) for high frequency applications

Nano-coned array of Cu were prepared by electroless plating with special crystallization conditioning agent. The morphologies of nano-coned array were observed by FE-SEM. The influences of active time in PdCl 2 , concentration of NiSO 4 ·6H 2 O, crystallization conditioning agent, pH and temperature of plating solution were discussed. Then, the possible reasons of the influence on the growth of nano-coned array were investigated. NiSO 4 ·6H 2 O was proved as catalytic active agent. The optimum preparation conditions were fixed. The crystal crystallographic orientation and elements of the nano-coned array were measured using TEM and EDX. The nano-cones consist of 95.57% copper and 4.43% nickel. The crystal crystallographic orientation of them is typical copper FCC single crystal.

Ming Li

Papers

Preparation of Microcones Array Material for Microelectronic Package

Synthesis of copper nanowires on the substrates in aqueous solution

Low-temperature bonding method based on metallic microcone array for interconnection application

Electroless and eletroplating copper on liquid crystal polymer (LCP) for high frequency applications

Electroless plating of copper nano-coned array for high reliability packaging