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Topic Review
Ballast Contamination Mechanisms
Ballasted railway tracks constitute the major transportation grids in many countries across the globe; they convey commuters, as well as freight and bulk cargoes, between cities, mines, farmlands, and ports . The railtrack structure can be categorised into two groups: the substructure and the superstructure. The substructure comprises the subgrade, the sub-ballast, and the ballast, while the superstructure encompasses the sleepers (timber or concrete), the fastening mechanism, and the steel rails.
  • 2.7K
  • 14 Jan 2021
Topic Review
Bamboo Node’s Vascular Bundle
The vascular bundle is an important structural unit that determines the growth and properties of bamboo. A high-resolution X-ray microtomography (μCT) was used to observe and reconstruct a three-dimensional (3D) morphometry model of the vascular bundle of the Qiongzhuea tumidinoda node due to its advantages of quick, nondestructive, and accurate testing of plant internal structure.
  • 2.7K
  • 23 Dec 2021
Topic Review
Band Gap Engineering
Crystalline TiO2 (as rutile, anatase or brookite) can absorb only about 4% of the solar energy due to its large band gap in the range of 3.0–3.2 eV. As a consequence, the true incident photon conversion yield of most sun-light and semiconductor-assisted photoreactions is low. The aim of exploiting visible light can be achieved by applying various techniques such as doping or modification with metals and non-metals, coupling of semiconductors, or dye sensitization. Since only the former technique seems to allow cost-efficient and robust synthesis routes for realistic applications of titania coatings, this chapter will concentrate on metal and non-metal doping.
  • 615
  • 19 Oct 2022
Topic Review
Bark in a Biorefineries Context
Bark-based biorefineries are estimated to become a trending topic in the coming years, particularly with their adsorbent applications and antioxidant production. While the potential benefits of bark-based biorefineries are well-recognized, it is not known how to develop a bark-based biorefinery considering different unit operations and the potential end products.
  • 241
  • 06 Jul 2023
Topic Review
Barrier Layer of Cu Interconnects
The barrier layer in Cu technology is essential to prevent Cu from diffusing into the dielectric layer at high temperatures; therefore, it must have a high stability and good adhesion to both Cu and the dielectric layer. In the past three decades, tantalum/tantalum nitride (Ta/TaN) has been widely used as an inter-layer to separate the dielectric layer and the Cu. However, to fulfill the demand for continuous down-scaling of the Cu technology node, traditional materials and technical processes are being challenged. Direct electrochemical deposition of Cu on top of Ta/TaN is not realistic, due to its high resistivity. Therefore, pre-deposition of a Cu seed layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD) is necessary, but the non-uniformity of the Cu seed layer has a devastating effect on the defect-free fill of modern sub-20 or even sub-10 nm Cu technology nodes. New Cu diffusion barrier materials having ultra-thin size, high resistivity and stability are needed for the successful super-fill of trenches at the nanometer scale. In this review, we briefly summarize recent advances in the development of Cu diffusion-proof materials, including metals, metal alloys, self-assembled molecular layers (SAMs), two-dimensional (2D) materials and high-entropy alloys (HEAs). Also, challenges are highlighted and future research directions are suggested.
  • 3.9K
  • 30 Jul 2021
Topic Review
Barriers to Electric Vehicle Adoption in Thailand
Electric vehicles (EVs) are considered to be a solution for sustainable transportation. EVs can reduce fossil fuel consumption, greenhouse gas emissions, and the negative impacts of climate change and global warming, as well as help improve air quality.
  • 1.3K
  • 09 Dec 2021
Topic Review
Basalt Fiber-reinforced Polymer Properties
Reducing the fingerprint of infrastructure has become and is likely to continue to be at the forefront of stakeholders’ interests, including engineers and researchers. It necessary that future buildings produce minimal environmental impact during construction and remain durable for as long as practicably possible
  • 2.4K
  • 08 May 2021
Topic Review
Base
In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances which react with acids as originally proposed by G.-F. Rouelle in the mid-18th century. In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form Hydroxide ions OH−. These ions can react with hydrogen ions (H+ according to Arrhenius) from the dissociation of acids to form water in an acid–base reaction. A base was therefore a metal hydroxide such as NaOH or Ca(OH)2. Such aqueous hydroxide solutions were also described by certain characteristic properties. They are slippery to the touch, can taste bitter and change the color of pH indicators (e.g., turn red litmus paper blue). In water, by altering the autoionization equilibrium, bases yield solutions in which the hydrogen ion activity is lower than it is in pure water, i.e., the water has a pH higher than 7.0 at standard conditions. A soluble base is called an alkali if it contains and releases OH− ions quantitatively. Metal oxides, hydroxides, and especially alkoxides are basic, and conjugate bases of weak acids are weak bases. Bases and acids are seen as chemical opposites because the effect of an acid is to increase the hydronium (H3O+) concentration in water, whereas bases reduce this concentration. A reaction between aqueous solutions of an acid and a base is called neutralization, producing a solution of water and a salt in which the salt separates into its component ions. If the aqueous solution is saturated with a given salt solute, any additional such salt precipitates out of the solution. In the more general Brønsted–Lowry acid–base theory (1923), a base is a substance that can accept hydrogen cations (H+)—otherwise known as protons. This does include aqueous hydroxides since OH− does react with H+ to form water, so that Arrhenius bases are a subset of Brønsted bases. However, there are also other Brønsted bases which accept protons, such as aqueous solutions of ammonia (NH3) or its organic derivatives (amines). These bases do not contain a hydroxide ion but nevertheless react with water, resulting in an increase in the concentration of hydroxide ion. Also, some non-aqueous solvents contain Brønsted bases which react with solvated protons. For example in liquid ammonia, NH2− is the basic ion species which accepts protons from NH4+, the acidic species in this solvent. G. N. Lewis realized that water, ammonia, and other bases can form a bond with a proton due to the unshared pair of electrons that the bases possess. In the Lewis theory, a base is an electron pair donor which can share a pair of electrons with an electron acceptor which is described as a Lewis acid. The Lewis theory is more general than the Brønsted model because the Lewis acid is not necessarily a proton, but can be another molecule (or ion) with a vacant low-lying orbital which can accept a pair of electrons. One notable example is boron trifluoride (BF3). Some other definitions of both bases and acids have been proposed in the past, but are not commonly used today.
  • 1.5K
  • 29 Sep 2022
Topic Review
Basic Nanoarchitectonics
Although various synthetic methodologies including organic synthesis, polymer chemistry, and materials science are the main contributors to the production of functional materials, the importance of regulation of nanoscale structures for better performance has become clear with recent science and technology developments. Therefore, a new research paradigm to produce functional material systems from nanoscale units has to be created as an advancement of nanoscale science. This task is assigned to an emerging concept, nanoarchitectonics, which aims to produce functional materials and functional structures from nanoscale unit components. This can be done through combining nanotechnology with the other research fields such as organic chemistry, supramolecular chemistry, materials science, and bio-related science. In this review article, the basic-level of nanoarchitectonics is first presented with atom/molecular-level structure formations and conversions from molecular units to functional materials. Then, two typical application-oriented nanoarchitectonics efforts in energy-oriented applications and bio-related applications are discussed. Finally, future directions of the molecular and materials nanoarchitectonics concepts for advancement of functional nanomaterials are briefly discussed.
  • 719
  • 27 May 2021
Topic Review
Basic Principles of COF-Based Sensing
Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with polygonal porosity and highly ordered structures. The most prominent feature of the COFs is their excellent crystallinity and highly ordered modifiable one-dimensional pores. Since the first report of them in 2005, COFs with various structures were successfully synthesized and their applications in a wide range of fields including gas storage, pollution removal, catalysis, and optoelectronics explored. In the meantime, COFs also exhibited good performance in chemical and biological sensing, because their highly ordered modifiable pores allowed the selective adsorption of the analytes, and the interaction between the analytes and the COFs’ skeletons may lead to a detectable change in the optical or electrical properties of the COFs.
  • 547
  • 17 May 2022
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