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Mechanical Properties
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2022
The densification of superconductors is a crucial property for efficient grain connectivity, the prerequisition for a good current percolation. The density of materials, ρ = mV−1 (mass per volume) depends on the preparation and processing technique which can be a melt process, a sinter process or a chemical reaction as in bulk with inter diffusion of different materials or crystal growth from vapour, solution or melt. Important aspects are phase purity and the presence of open or closed pores. Especially for superconductors processed via the powder route, such as BSCCO wires and tapes and MgB2, the nonperfect density in the sense of densification has direct consequences for the reaction process, the grain growth and grain connections with the correlated transport current percolation and finally also the mechanical stability of the material.
Rock Forming Minerals
Published in Aurèle Parriaux, Geology, 2018
Crystal growth also depends on external factors such as pressure and temperature conditions as well as the nature of the fluid phase. In rocks, the form and also the perfection of a crystal depend on the degrees of freedom it has for its development (Fig. 5.11). Automorphic crystals (mineral with a perfect crystal shape) are formed in a very deformable environment: magma in a magma chamber, gas, water in geodes or open fissures. They have well-developed, regular faces, often of large size. But most of the time, crystallization takes place in an already solid environment. The mineral grows in a space limited by neighboring minerals. This creates xenomorphic crystals whose faces are hardly visible. This difference is shown by quartz: its crystals are magnificent in geodes, but altogether ordinary in granite where they are the last minerals to form (Fig. 6.13).
Rock Forming Minerals
Published in Aurèle Parriaux, Geology, 2018
Crystal growth also depends on external factors such as pressure and temperature conditions as well as the nature of the fluid phase. In rocks, the form and also the perfection of a crystal depend on the degrees of freedom it has for its development (Fig. 5.11). Automorphic crystals (mineral with a perfect crystal shape) are formed in a very deformable environment: magma in a magma chamber, gas, water in geodes or open fissures. They have well-developed, regular faces, often of large size. But most of the time, crystallization takes place in an already solid environment. The mineral grows in a space limited by neighboring minerals. This creates xenomorphic crystals whose faces are hardly visible. This difference is shown by quartz: its crystals are magnificent in geodes, but altogether ordinary in granite where they are the last minerals to form (Fig. 6.13).
Machine learning of fake micrographs for automated analysis of crystal growth process
Published in Science and Technology of Advanced Materials: Methods, 2022
Takamitsu Ishiyama, Toshifumi Imajo, Takashi Suemasu, Kaoru Toko
Crystal growth is a fundamental technology for various electronics with semiconductor thin films. To address the question of how to grow high-quality thin films, numerical research has been conducted to understand and control various crystal growth techniques. With the development of the information society in recent years, to add electronic functions to various items, there is a strong need for technology to synthesize semiconductor thin films on the applied insulators. Solid-phase crystallization (SPC) is the oldest and most representative synthesis method in which crystallization is induced by annealing an amorphous thin films [1–4]. Recently, SPC has been in the spotlight because it provides an extremely high carrier mobility of Ge-based materials [5–8], which are leading candidates for replacing Si. To understand and discuss the SPC of a system, it is important to observe the phase transition from amorphous to crystalline, determine the lateral growth velocity and nucleation frequency of the crystalline domains, and determine the activation energies and frequency factors [1–4]. These physical properties have been obtained by repeating the annealing of the samples and conducting ex-situ observations and manual analyses (i.e. a calculation of the crystal domain size d and nuclei density ρ) (Figure 1) [8–10]. However, this process is time-consuming, labor-intensive, and is inevitably subject to systematic errors among the measurers.
Band-gap-tailoring in Liquid Crystals: Organizing Metal Atoms and Nanoclusters in LC Media
Published in Liquid Crystals, 2022
Archana Kumari Singh, Satya Pal Singh
In the nucleation process, an atom may act as a seed, also referred to as nuclei, which results in crystal growth [25–28]. This process is of two types, namely the homogeneous nucleation and the heterogeneous nucleation. The homogeneous type nucleation is one in which the growth process uniformly takes over the nuclei. The heterogeneous nuclei are formed by structural inhomogeneities like impurities, grain boundaries, dislocations, container surfaces, etc. There are different theories for the nucleation and growth of nanoparticles from seed atoms, molecules or particles as LaMer Mechanism, Ostwald Ripening and Digestive Ripening, Finke-Watzky Two Step Mechanism, Coalescence and Orientated Attachment and Interaparticle Growth [25]. In the LaMer mechanism, first, the concentration of monomers in the solution increases rapidly. Then it undergoes nucleation burst, and as a result of that, the concentration of free monomers decreases in the solution following which, further nucleation is seized. Ostwald Ripening growth mechanism occurs by the change in the solubility of nanoparticles depending on their sizes. Smaller particles have a higher solubility and have large surface energy within the solution. So, these particles redissolve and allow larger particles to grow more. In digestive ripening, smaller particles grow expansively at the cost of the larger ones. It is just the inverse of the Ostwald ripening. In this process, larger particles redissolve and allow the smaller particles to grow more. In the Finke-Watzky two-step mechanism, two steps occur simultaneously, as shown below
Nanowire Transistors: A Next Step for the Low-Power Digital Technology
Published in IETE Journal of Research, 2021
D. Ajitha, K. N. V. S. Vijaya Lakshmi, K. Bhagya Lakshmi
In particular, bottom-up synthetic approaches, involving both gas-phase and solution-phase chemistry methods have enabled the creation of many novel composite materials and morphologies with better crystallographic and chemical properties. The gas-phase synthesis uses VLS or the VSS growth mode. The most widely used crystal growth method is Vapour Liquid Solid (VLS) one to build semiconductor NW because of its excellent flexibility [21,22]. The semiconductor Nanowire with improved control is developed by using the Vapour Solid method (VSS), which creates a new feature of Nanowire growth. The Nanowire growth using VLS methods includes three important levels: nucleation, growth and alloying. These three stages are called kinetics. In the conventional growth conditions, these are very fast. The detection of the events at different stages of the VLSI growth method is very difficult. Lieber and co-workers reported an iterative development approach to the growth in the rational-wise, composed of measurement lengthwise of straight divisions and the positions of the joints of the two-dimensional zigzag semiconductor Nanowire, shown in Figure 1(a – e) [20,21]. It is noticed that growth time determines the segment length of silicon nanowires.