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Annealing (metallurgy)

About: Annealing (metallurgy) is a research topic. Over the lifetime, 74877 publications have been published within this topic receiving 1017898 citations.


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TL;DR: In this article, an equiatomic CoCrFeMnNi high-entropy alloy (HEA), produced by arc melting and drop casting, was subjected to severe plastic deformation (SPD) using high pressure torsion.

887 citations

Journal ArticleDOI
TL;DR: A synthetic method using reverse micelles at high pressure and temperature in a bomb that produces Si nanoparticles (n-Si) with various particle sizes without aggregation and thus enables the optimal nanoparticle size for use in anode materials to be chosen is reported.
Abstract: Due to the high theoretical capacity (ca. 4200 mAhg ) of Si when Li4.4Si is formed, it has been extensively investigated for use as a high-capacity anode material that can replace graphite, which is currently used (372 mAhg ). However, Si exhibits significant volume changes (> 360%) during Li alloying and dealloying. These changes cause cracking and crumbling of the electrode material and a consequent loss of electrical contact between individual particles and hence severe capacity drop. However, such mechanical strain induced by volume change can be reduced by employing smaller particles. To this end, synthetic methods such as spark ablation, aerogel techniques, and sputtering have been employed. Formation of crystalline Si nanoparticles requires higher temperatures due to the more covalent nature of these particles compared to Ge particles, and at low temperature amorphous phases become more common. The first commonly recognized successful production of Si nanoclusters was reported byHeath et al. They showed that Si nanocrystals capped with alkyl groups can be produced by reduction of SiCl4 and RSiCl3 (R=H, C8H17) according to the reaction SiCl4+RSiCl3+Na!Si+NaCl. This process was carried out at high temperature (385 8C) and high pressure (>100 atm) in a steel bomb fitted into a heating mantle. A process that utilizes SiCl4 reduction at room temperature under an inert atmosphere was initially reported by Kauzlarich et al. However, the drawback of their method was that the product obtained at room temperature was not fully crystallized and was severely capped with alkyl terminators. Moreover, an annealing process above 900 8C is required to obtain the crystalline phase. Similar solution syntheses have been reported at low or high temperature after reducing Si salts with LiAlH4 [13,14] or alkyl silanes. However, all of these methods produce a broad particle size distribution or involve aggregation of the nanoparticles. Furthermore, they all yield amounts of material too small for use in anode production for lithium secondary batteries. We now report a synthetic method using reverse micelles at high pressure and temperature in a bomb that produces Si nanoparticles (n-Si) with various particle sizes without aggregation and thus enables the optimal nanoparticle size for use in anode materials to be chosen. Figure 1 shows the XRD pattern and TEM images of n-Si prepared with trimethyloctadecylammonium bromide (OTAB) surfactant. The XRD pattern clearly shows forma-

880 citations

Journal ArticleDOI
TL;DR: A systematic study of PMMA decomposition on graphene and of its impact on graphene's intrinsic properties using transmission electron microscopy (TEM) in combination with Raman spectroscopy is reported.
Abstract: Surface contamination by polymer residues has long been a critical problem in probing graphene’s intrinsic properties and in using graphene for unique applications in surface chemistry, biotechnology, and ultrahigh speed electronics. Poly(methyl methacrylate) (PMMA) is a macromolecule commonly used for graphene transfer and device processing, leaving a thin layer of residue to be empirically cleaned by annealing. Here we report on a systematic study of PMMA decomposition on graphene and of its impact on graphene’s intrinsic properties using transmission electron microscopy (TEM) in combination with Raman spectroscopy. TEM images revealed that the physisorbed PMMA proceeds in two steps of weight loss in annealing and cannot be removed entirely at a graphene susceptible temperature before breaking. Raman analysis shows a remarkable blue-shift of the 2D mode after annealing, implying an anneal-induced band structure modulation in graphene with defects. Calculations using density functional theory show that l...

868 citations

Journal ArticleDOI
TL;DR: The role of the temperature used in the annealing process required to convert the as deposited solution into the perovskite material is investigated in this paper, where it is found that the conversion requires sufficiently high temperatures to ensure the vaporization of solvent and the crystallization of the material.
Abstract: Organic-inorganic hybrid perovskites have attracted attention as successful light harvesting materials for mesoscopic solid-state solar cells and led to record breaking efficiencies. The photovoltaic performance of these devices is greatly dependent on the film morphology, which in turn is dependent on the deposition techniques and subsequent treatments employed. In this work the perovskite film is deposited by spin-coating a precursor solution of PbCl2 and CH3NH3I (1 to 3 molar ratio) in dimethylformamide. Here, the role of the temperature used in the annealing process required to convert the as deposited solution into the perovskite material is investigated. It is found that the conversion requires sufficiently high temperatures to ensure the vaporization of solvent and the crystallization of the perovskite material. However, increasing the annealing temperature too high leads to the additional formation of PbI2, which is detrimental to the photovoltaic performance. Furthermore, the effect of the annealing temperature on the film formation, morphology, and composition is examined and correlated with the photovoltaic performance and device working mechanisms.

864 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202294
20211,879
20202,509
20192,722
20182,719
20172,881