Topic Review
Hydraulic Actuators
Hydraulic actuators are elements converting the energy of the working fluid into mechanical energy related to the reciprocating motion. The most frequently applied materials used in power hydraulics are described, and various surface modifications of the discussed elements, which are aimed at improving the operating parameters of actuators, are presented. The most frequently used materials for actuators elements are iron alloys. However, due to rising ecological requirements, there is a tendency to looking for modern replacements to obtain the same or even better mechanical or tribological parameters. Sealing systems are manufactured mainly from thermoplastic or elastomeric polymers, which are characterized by low friction and ensure the best possible interaction of seals with the cooperating element. In the field of surface modification, among others, the issue of chromium plating of piston rods has been discussed, which, due, to the toxicity of hexavalent chromium, should be replaced by other methods of improving surface properties.
  • 1891
  • 23 Mar 2021
Topic Review
Carbon fiber-reinforced Thermoplastic polymers
Carbon fiber-reinforced thermoplastic polymers are considered a promising composite for many industrial applications including in the automation, renewable energy, and aerospace industries. They exhibit exceptional properties such as a high strength-to-weight ratio and high wear resistance and stiffness, which give them an advantage over other conventional materials such as metals.
  • 567
  • 17 Aug 2021
Topic Review
Graphene, Graphene-Derivatives and Composites
Graphene has accomplished huge notoriety and interest from the universe of science considering its exceptional mechanical, physical and thermal properties. Graphene is an allotrope of carbon having one atom thick size and planar sheets thickly stuffed in a lattice structure resembling a honeycomb structure. Numerous methods to prepare graphene have been created throughout a limited span of time. Due to its fascinating properties, it has found some extensive applications to a wide variety of fields. So, we believe there is a necessity to produce a document of the outstanding methods and some of the novel applications of graphene. 
  • 359
  • 09 Oct 2021
Topic Review
Solvent-Free Synthesis of Zeolites
The traditional hydrothermal method to prepare zeolite will inevitably use a large amount of water as a solvent, which will lead to higher autogenous pressure, low efficiency, and wastewater pollution. The solvent-free method can be used to synthesize various types of zeolites by mechanical mixing, grinding, and heating of solid raw materials, which exhibits the apparent advantages of high yield, low pollution, and high efficiency. This review mainly introduces the development process of solvent-free synthesis, preparation of hierarchical zeolite, morphology control, synthesis mechanism and applications of solvent-free methods. It can be believed that solvent-free methods will become a research focus and have enormous industrial application potential.
  • 310
  • 25 Mar 2021
Topic Review
Bifacial Photovoltaics
In 2016 the first >2 MWp fixed tilt bifacial PV system (“La Hormiga”) was built by MegaCell in San Felipe, located in the region of Valparaiso in Chile, using nPERT BiSoN modules. The innovations in this system were the adapted mounting structures (which were not covering the rear side of the modules), as well as the enhancement of albedo using white quartz stones below them. The bifacial gain was about 15% with the natural albedo of ca. 28%, whereas the albedo enhancement to 75% provided by the white stones led to a bifacial gain of about 25%. After that, Sunpreme installed their SHJ (Silicon HeteroJunction) modules in a 10 MWp bifacial system on a US industrial rooftop, and large bifacial systems were installed in China in the TopRunner program, where the Chinese Government was supporting innovations to be introduced into the market. Yingli installed a fixed tilt 50 MWp system with bifacial nPERT Panda modules, followed by a 100 MWp “Panda PV system” in 2018. Since then large bifacial PV systems are entering the PV market. In 2021 bifacial PV became bankable and will become main-stream in the coming 5 years.
  • 304
  • 08 May 2021
Topic Review
Thermosets with Flame Retardants
Epoxy and unsaturated polyester resins are the most used thermosetting polymers.They are commonly used in electronics, construction, marine, automotive and aircraft industries.Moreover, reinforcing both epoxy and unsaturated polyester resins with carbon or glass fibre in a fabric form has enabled them to be used in high-performance applications. However, their organic nature as any other polymeric materials made them highly lammable materials. Enhancing the flame retardancy performance of thermosetting polymers and their composites can be improved by the addition of flame-retardant materials, but this comes at the expense of their mechanical properties. In this regard, a comprehensive review on the recent research articles that studied the flame retardancy of epoxy resin, unsaturated polyester resin and their composites were covered. Flame retardancy performance of different flame retardant/polymer systems was evaluated in terms of Flame Retardancy index (FRI) that was calculated based on the data extracted from the cone calorimeter test. Furthermore, lame retardant selection charts that relate between the flame retardancy level with mechanical properties in the aspects of tensile and lexural strength were presented. This review paper is also dedicated to providing the reader with a brief overview on the combustion mechanism of polymeric materials, their flammability behaviour and the commonly used flammability testing techniques and the mechanism of action of flame retardants.
  • 297
  • 29 Mar 2021
Topic Review
MOFs for Mercury Detection
The advantages of metal organic frameworks (MOFs) are: existence of porosity to adsorb specific analyte, improved aqueous solubility, exceptional photophysical and chemical properties. MOFs are noted as exceptional candidates towards the detection and removal of specific analytes, particular for the detection/removal of environmental contaminants, such as heavy metal ions, toxic anions, hazardous gases, explosives, etc. Among heavy metal ions, mercury has been noted as a global hazard because of its high toxicity in the elemental (Hg0), divalent cationic (Hg2+), and methyl mercury (CH3Hg+) forms. To secure the environment and living organisms, many countries have imposed stringent regulations to monitor mercury at all costs. Regarding the detection/removal requirements of mercury, researchers have proposed and reported all kinds of MOFs-based luminescent/non-luminescent probes towards mercury.This review provides valuable information about the MOFs which have been engaged in detection and removal of elemental mercury and Hg2+ ions. Moreover, the involved mechanisms or adsorption isotherms related to sensors or removal studies are clarified for the readers. Finally, advantages and limitations of MOFs in mercury detection/removal are described together with future scopes.
  • 256
  • 01 Jul 2021
Topic Review
CeO2-based transition metal catalysts
The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions, opening up new horizons for the development of highly active and robust materials. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, polyhedra) in catalysis are revealed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metal-ceria interactions, providing the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.
  • 222
  • 22 Apr 2021
Topic Review
Acoustic Metamaterials in Aeronautics
Metamaterials, man-made composites that are scaled smaller than the wavelength, have demonstrated a huge potential for application in acoustics, allowing the production of sub-wavelength acoustic absorbers, acoustic invisibility, perfect acoustic mirrors and acoustic lenses for hyper focusing, and acoustic illusions and enabling new degrees of freedom in the control of the acoustic field. The zero, or even negative, refractive sound index of metamaterials offers possibilities for the control of acoustic patterns and sound at sub-wavelength scales. The potential of metamaterial-based technologies has recently caught the interest of the aeronautics community. Their effect in the presence of realistic flows in the surrounding domains, with boundary layer, turbulence, is currently a hot research topic. The interaction with flow requires a careful design of the metamaterial to avoid detrimental effects and enabling the device maximum capabilities in aeronautics.
  • 218
  • 25 Jun 2021
Topic Review
Environmental Stability of Perovskite
This entry introduces the environmental stability of MAPbI3 perovskite thin film and MAPbBr3 perovskite single crystal.
  • 183
  • 04 May 2021
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