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Sputter Deposited Nanostructured Coatings as Solar Selective Absorbers
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Functional Thin Films Technology, 2021
The general requirements for the high-temperature absorber coatings is the high thermal stability. The structure and phase do not change in the high-temperature working environment. Most of the SSCs are made of metal and dielectric material. Some metals, such as W or Mo, with extreme high melting points are suitable for the high-temperature SSC. Some oxides, such as Cr2O3, Al2O3, and SiO2 already possess great thermal performance. Generally speaking, a qualified high-temperature SSC fits the requirements of high absorptance (𝛼 > 90%), low emittance (𝜀 < 10%), and low thermal degradation (PC < 5%). In the early days, the thermal test was carried out in a vacuum chamber. Recently, some researches test the thermal stability with lower level of vacuum, or even in air. The annealing time also extends from a couple hours to a couple weeks.
Mechanical Behavior of Materials
Published in Snehanshu Pal, Bankim Chandra Ray, Molecular Dynamics Simulation of Nanostructured Materials, 2020
Snehanshu Pal, Bankim Chandra Ray
Annealing is performed to increase the ductility of a material by diminishing the hardness property to make machining process easier. Annealing is performed by heating the material above the recrystallization temperature, where it is held at a certain temperature for some amount of time and then cooled again slowly. During annealing, the grain size refinement of the material takes place, as atoms migrate in crystal lattice and the dislocation number in the crystal is reduced, which in turn leads to the variation in ductility and hardness. Based on the annealing temperature, the processes involved are recovery (generally takes place at low temperatures) and recrystallization (occurs at high temperatures), and owing to these processes, the materials have a tendency to have a microstructural transformation (i.e., from microstructurally metastable state to stable state, which means low-energy state); furthermore, annealing material leads to grain growth. Increase in point defect and dislocation densities strengthen the material in cold work process, but in the annealing process, the material has a tendency to drop the stored strain energy. This makes the material ductile. Cold work material and stages of annealing are shown in Figure 2.32 [18].
Materials for Tissue Engineering
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Annealing is a heat treatment in which a material is exposed to an elevated temperature for an extended time period and then slowly cooled. This is used to increase softness, ductility, and toughness, as well as to produce a specific microstructure. A variety of annealing heat treatments are possible. They are characterized by the changes that are induced. These changes are usually microstructural and are responsible for the alteration of the mechanical properties. Any annealing process consists of three stages. First, the material is heated to the desired temperature, then it is held or “soaked” at that temperature. Finally, it is cooled, usually to room temperature. Process annealing is a heat treatment that is used to negate the effects of cold work. It softens and increases the ductility of a previously strain-hardened metal. It is used during fabrication procedures that require extensive plastic deformation. This allows a continuation of deformation without fracture. Ordinarily a fine-grained microstructure is desired, and therefore the heat treatment is terminated before appreciable grain growth has occurred.
Improved Hybrid Method for the Generation of Ground Motions Compatible with the Multi-Damping Design Spectra
Published in Journal of Earthquake Engineering, 2023
Jianbo Li, Feng Cheng, Gao Lin, Chenglin Wu
SAA, derived from the principle of solid annealing, is a method of approximate optimal solution based on the Monte Carlo iterative concept. The term annealing refers to heating a material and then cooling it at a specific rate to modify its properties. Thus, different from metallurgy, the term temperature in SAA is not the actual temperature, but just a parameter used in stop criterion. Metropolis (1953) first proposed this concept, and subsequently, Kirkpatrick (1983) utilized the concept of annealing in combinatorial optimization. The SAA introduces random factors in the search process, i.e. it accepts a slightly worse solution with a certain probability and finally escapes the local solution. The simulated annealing method is a probabilistic technique for approximating the global optimization in a large search space for an optimization problem (Ingber 1993; Lin et al. 2008; Junior et al. 2012).
Post-processing treatments to enhance additively manufactured polymeric parts: a review
Published in Virtual and Physical Prototyping, 2021
F. Tamburrino, S. Barone, A. Paoli, A. V. Razionale
Annealing is the process of heating a part to a specific temperature, holding the temperature constant for a certain amount of time, and then slowly cooling the part to room temperature. This treatment is used to enhance the mechanical and thermal conductivity properties of 3D printed parts because temperatures above the glass transition allow the material to reflow, thus filling porosities and interlayer gaps to a significant extent (Hart et al. 2018; Prajapati et al. 2019; Singh et al. 2019). In (Hart et al. 2018), an improvement of around 2700% in fracture toughness was reported on ABS-FDM samples because of thermal annealing at 135 °C for 168 h. In (Prajapati et al. 2019), a similar post-process carried out at the same temperature for 96 h produced a 150% increase in thermal conductivity, thus restoring the part's thermal conductivity to nearly that of the underlying material.
A comprehensive study on variability of relative density in selective laser melting of Ti-6Al-4V
Published in Virtual and Physical Prototyping, 2019
Amir Mahyar Khorasani, Ian Gibson, AmirHossein Ghasemi, Alireza Ghaderi
During SLM, large thermal gradients, associated with cooling and heating processes, lead to the accumulation of residual stress and generation of martensitic and the results are lower ductility and higher tensile strength. To enhance mechanical properties and machinability, annealing is recommended (Yasa et al. 2010; Khorasani et al. 2016; Khorasani, Gibson, Goldberg, Littlefair 2017). Table 2 shows the heat treatment conditions that were used in this experiment. The heating and resident time were each fixed at two hours, with the heating gradient gradually increasing from ambient to the set temperature at 4.8–8.6°C/min. To remove the cooling effect, the cooling rate was kept fixed at 5°C/min across all samples (Welsch, Boyer, and Collings 1993).