Zhong Chen

Bio: Zhong Chen is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Chemistry & Catalysis. The author has an hindex of 80, co-authored 1000 publications receiving 28171 citations. Previous affiliations of Zhong Chen include Institute of High Performance Computing Singapore & National Institute of Education.

Influence of Phosphorus Content on the Interfacial Microstructure Between Sn–3.5Ag Solder and Electroless Ni–P Metallization on Cu Substrate

Abstract: Under bump metallization (UBM), which usually consists of a few thin metallic layers, provides good solderable surface while protecting the underlying metallization from reacting with solder. Electroless nickel (Ni-P) with a thin layer of immersion gold has been considered as one of the promising candidates for under bump and substrate metallizations. However, the presence of P in electroless Ni-P causes more complicated interfacial reactions with solder than pure Ni. The amount of P in the Ni-P layer affects the soldering reaction in terms of microstructure and reaction kinetics. In this paper, influence of P content on the interfacial microstructure between Sn-3.5Ag solder and electroless Ni-P metallization on Cu substrate has been investigated. Electroless Ni-P layers of three different P contents (6.1, 8.8, and 12.3 wt.%) with the same thickness were plated on Cu substrate. Multilayered samples with Sn-3.5Ag/Ni-P/Cu stack were then prepared and subjected to multiple reflows. Various types of interfacial compounds (IFCs) such as Ni3Sn4, Ni3P, Ni-Sn-P, Cu-Sn, and Ni-Cu-Sn formed depending upon the number of reflows. Ni3Sn4 intermetallic compound that formed in the low P sample was found to be more stable, whereas, Ni3Sn4 that formed in the medium and high P samples mostly spalled off into the molten solder during reflow. The Ni 3Sn4 spallation was found responsible for thicker Cu-Sn and Ni-Cu-Sn intermetallics in the medium and high P samples as compared to that of low P sample. Explanation for the observed interfacial microstructure is proposed in the paper in detail

Modification of graphene aerogel with titania nanotubes for efficient methylene blue adsorption kinetics

Abstract: Titania nanotubes (TNTs) with high length–diameter ratio are incorporated into reduced graphene oxide (rGO) aerogel to modify the porous structure of the obtained rGO/TNTs aerogel for efficient methylene blue (MB) adsorption. A hydrothermal method along with freeze drying is applied for the preparation of the rGO/TNTs composite aerogel. The uniformly dispersed TNTs in rGO matrix can effectively support the network structure and hinder the π–π bonding interaction between graphene sheets, thus resulting in a three-dimensional mesoporous network with high specific surface area. The rGO/TNTs aerogel shows favorable adsorption property toward MB and the maximum adsorption capacity can be 380.7 mg g−1 with the adsorption efficiency of 92.2%. Besides, the adsorption kinetic analysis reveals that a dispersion process is found to be the rate-limiting step when the adsorbent dosage is low. With the increase of adsorbent content, chemical sorption such as the π–π interaction or the reaction of the polar functional groups between MB and rGO–TNTs-C aerogel becomes the rate-limiting step.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...