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Topic Review Peer Reviewed
Conductive Heat Transfer in Thermal Bridges
A thermal bridge is a component of a building that is characterized by a higher thermal loss compared with its surroundings. Their accurate modeling is a key step in energy performance analysis due to the increased awareness of the importance of sustainable design. Thermal modeling in architecture and engineering is often not carried out volumetrically, thereby sacrificing accuracy for complex geometries, whereas numerical textbooks often give the finite element method in much higher generality than required, or only treat the case of uniform materials. Despite thermal modeling traditionally belonging exclusively to the engineer’s toolbox, computational and parametric design can often benefit from understanding the key steps of finite element thermal modeling, in order to inform a real-time design feedback loop. In this entry, these gaps are filled and the reader is introduced to all relevant physical and computational notions and methods necessary to understand and compute the stationary energy dissipation and thermal conductance of thermal bridges composed of materials in complex geometries. The overview is a self-contained and coherent expository, and both physically and mathematically as correct as possible, but intuitive and accessible to all audiences. Details for a typical example of an insulated I-beam thermal bridge are provided.
  • 847
  • 26 May 2022
Topic Review
Corrosion and Scaling in Geothermal Heat Exchangers
Geothermal power is an attractive and environmentally friendly energy source known for its reliability and efficiency. Unlike some renewables like solar and wind, geothermal energy is available consistently, making it valuable for mitigating climate change. Heat exchangers play a crucial role in geothermal power plants, particularly in binary cycle plants, where they represent a significant portion of capital costs. Protecting these components from deterioration is essential for improving plant profitability. Corrosion is a common issue due to direct contact with geothermal fluid, which can lead to heat exchanger failure.
  • 343
  • 31 Oct 2023
Topic Review
Corrosion Mechanisms in Near-Neutral pH Stress Corrosion Cracking
The two major corrosion mechanisms encountered during stress corrosion of carbon steels in a near-neutral pH environment are anodic dissolution and hydrogen embrittlement. Anodic dissolution, also known as metal dissolution, is a process in which the metal is dissolved from the anodic site during corrosion process, and gases are released from the cathodic site and at the metal surface. This in turn reduces the wall strength and may lead to premature pipeline failure. Hydrogen embrittlement can be defined as the reduction of a metal’s tensile strength and ductility due to diffusion of hydrogen atoms into the metal’s crystalline lattices during a corrosion process. It causes premature brittle fracture of normally ductile metals under applied stress usually less than the yield strength of the metal. 
  • 408
  • 06 Sep 2022
Topic Review
Corrosion Monitoring in Atmospheric Conditions
A variety of techniques are available for monitoring metal corrosion in electrolytes. However, only some of them can be applied in the atmosphere, in which case a thin discontinuous electrolyte film forms on a surface. Traditional and state-of-the-art real-time corrosion monitoring techniques include atmospheric corrosion monitor (ACM), electrochemical impedance spectroscopy (EIS), electrochemical noise (EN), electrical resistance (ER) probes, quartz crystal microbalance (QCM), radio-frequency identification sensors (RFID), fibre optic corrosion sensors (FOCS) and respirometry.
  • 530
  • 27 Jan 2022
Topic Review
Crystal Structural Characterization Techniques in Degradation of Perovskite
The general chemical formula of halide perovskite materials is ABX3, where the A site can be occupied by organic cations, such as methyl ammonium (MA), formamidinium (FA), or inorganic cation cesium. The B site can be divalent cations, such as lead(Pb) or tin(Sn), while the X site consists of halide anions, such as chlorine(Cl), bromine(Br) or iodine(I). Due to the great variety of its chemical composition, halide perovskite forms a big material family with tunable optoelectronic properties.
  • 211
  • 12 Jul 2023
Topic Review
CuCr1Zr Alloy during Direct Heating
Round tensile test specimens of an age-hardened CuCr1Zr alloy were subjected to direct electrical current heating in a Gleeble thermal–mechanical simulator at 800 °C. The mechanical properties were monitored by the Vickers hardness test, and the changes in the grain structure were examined by light metallography. A quantitative analysis of the size and distribution of fine precipitates during annealing was carried out using transmission electron microscopy (TEM). The grain structure showed a gradient corresponding to the gradient of the temperature on the test piece. Annealing for 60 s at 800 °C resulted in a partially (~50%) recrystallized structure with new grains about 45 μm in diameter. In the as-delivered condition, TEM documented tiny (1 to 4 nm) coherent chromium precipitates inducing strain fields in the matrix. During overaging, the particles lost their coherence and gradually coarsened up to a mean diameter of 40 nm after 300 s at 800 °C. The coarsening kinetics obeys Lifshitz, Sloyzov, and Wagner’s theory
  • 388
  • 19 Jul 2021
Topic Review
Defect-Related Etch Pits on Crystals and Their Utilization
Etch pits could form on an exposed surface of a crystal when the crystal is exposed to an etching environment or chemicals. Due to different dissolution rates along various crystalline directions in a crystal, the dissolution process is anisotropic; hence, etch pits usually have a regular shape. The morphology, size, and density of etch pits can be affected by various factors, including the chemical composition of the etchant, etching time, etching temperature, status of the matrix, and so on. Traditionally, etch pits are utilized to evaluate the dislocation density and some defect-related properties. Now, in the modern fabrication industries, the relationship between etch pits and defects has been utilized more skillfully. High-quality crystals can be fabricated by controlling dislocations revealed by etch pits. Meanwhile, with the as-revealed dislocation as the diffusion path of atoms, new crystals will emerge in corresponding etch pits.
  • 739
  • 11 Nov 2022
Topic Review
Design Challenges and Limitations of Injectable Hydrogels
Injectable hydrogels (IHs) are smart biomaterials and are the most widely investigated and versatile technologies, which can be either implanted or inserted into living bodies with minimal invasion. Their unique features, tunable structure and stimuli-responsive biodegradation properties make these IHs promising in many biomedical applications, including tissue engineering, regenerative medicines, implants, drug/protein/gene delivery, cancer treatment, aesthetic corrections and spinal fusions. Regarding their current prospective and ongoing research, hydrogel formulations have some limitations in their applications, clinical practices and sustainability. Many hydrogel systems (natural/synthetic), such as thermosensitive hydrogels, are free-flowing sols at a low temperature, while upon raising to body temperature (physiological temperature), they are converted to a stable visco-elastic gel phase, such as poly (phosphazene), pluronic and poly (N-isopropyl acrylamide). 
  • 2.6K
  • 08 Apr 2022
Topic Review
Development of Fencing Blade Materials
Using two fencing swords manufactured in Europe and China, we investigated the typical materials used for fencing blades and compared the experimental results with the nominal compositions of a variety of steels. By combining the requirements for the safety of athletes, mechanical behaviors of different steels, and production costs for industry, there is possible directions for the heat treatments and processing methods that have the potential to enhance performance and overcome the limitations of previous materials. 
  • 701
  • 17 Feb 2022
Topic Review
Development of Transformation-Induced Plasticity/Twinning-Induced Plasticity Ti Alloys
Metastable β-type Ti alloys that undergo stress-induced martensitic transformation and/or deformation twinning mechanisms have the potential to simultaneously enhance strength and ductility through the transformation-induced plasticity effect (TRIP) and twinning-induced plasticity (TWIP) effect. These TRIP/TWIP Ti alloys represent a new generation of strain hardenable Ti alloys, holding great promise for structural applications. Nonetheless, the relatively low yield strength is the main factor limiting the practical applications of TRIP/TWIP Ti alloys. The intricate interplay among chemical compositions, deformation mechanisms, and mechanical properties in TRIP/TWIP Ti alloys poses a challenge for the development of new TRIP/TWIP Ti alloys. 
  • 48
  • 30 Jan 2024
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