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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.
Amorphous Core Transformers
Published in K.R.M. Nair, Power and Distribution Transformers, 2021
Annealing of the core is done to relieve the quenching stress and also to induce a preferred axis of magnetostriction along the ribbon length. The annealing temperature is such that the glassy nature is preserved and a DC magnetic field of about 2400 A/m is applied to saturate the material at the annealing temperature. Typical annealing temperatures are 310°C–370°C depending on the type of material.
Heat Treatment of Metals
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
Full annealing of steel involves the following steps: Slowly raising the temperature of steel about 30°C above the line A3 (in case of hypo-eutectoid steels) or 30°C above line A1 (in case of hypereutectoid steels) (see Figure 15.2);Holding steel at this temperature for sufficient time to allow complete phase transformation into austenite or austenite-cementite as the case may be;The steel is then slowly cooled at the rate of about 20°C/h in a furnace to about 50°C into the ferrite-cementite range (see Figure 15.3). At this point, it may be cooled in room temperature in air with natural convection.Full annealing of eutectoid steel (Fe-0.77%C alloy) results in coarse pearlite microstructure (see Chapter 7, Figure 7.8). It is evident in Figure 15.2 that full annealing of hypo-eutectoid steel would result in ferrite+pearlite microstructure (see Example 15.2). The purpose of full annealing is to improve machinability and to reduce hardness and brittleness.
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).