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The main characteristics of amorphous alloys
Published in A. M. Glezer, A. I. Potekaev, A. O. Cheretaeva, Thermal and Time Stability of Amorphous Alloys, 2017
A. M. Glezer, A. I. Potekaev, A. O. Cheretaeva
The atomic structure of the amorphous alloys can be determined by experiments using diffraction investigation methods. The scattering of the X-rays, neutrons and electrons on the amorphous substance makes it possible to determine the general structural factor of the multi-component system I(k) (Fig. 1.1), which corresponds to the sum of the partial structural factors Iij(k) [4]: Ik=∑i∑jWijkIijk, $$ I\left( k \right) = \sum\limits_{i} {\sum\limits_{j} {W_{{ij}} \left( k \right)I_{{ij}} } \left( k \right)} , $$
Photovoltaic (PV) power technology
Published in John Twidell, Renewable Energy Resources, 2021
Amorphous. Amorphous materials are solids with short-range order of only a relatively few atoms and therefore are not crystalline (e.g. solid glass). Amorphous silicon (α-Si) can be produced by thin film deposition with Si vapor deposition techniques. It retains basic tetrahedral semiconductor properties; in particular n- and p-type dopants allow photovoltaic junctions to be formed as in crystalline material. However, the amorphous structure produces a very large proportion of unattached ‘dangling’ chemical bonds that trap electron and hole current carriers, thereby drastically reducing photovoltaic efficiency. To counteract this, the amorphous material is initially formed in an atmosphere of silane (SiH4) so that hydrogen atoms bond chemically at the previously unattached sites, thus greatly reducing the number of electron-hole traps. Amorphous Si may be used in thin film solar cells with semiconductor thickness about 1 μm (i.e. ∼1/100 of the thickness of a conventional single-crystal cell). The band gap of α-Si is 1.7 eV, as compared with crystalline Si of 1.1 eV, which is a better fit to the solar spectrum (see Fig. R4.12). Development with multiple junctions within that 1 μm increased efficiency to about 10%. A practical difficulty may be reduced efficiency with age, especially in the first few years of operation. An advantage is that the output of α-Si cells does not change significantly with an increase of temperature. However, by about 2012, despite many improvements, α-Si modules were out-competed by the lower price of mass-produced crystalline Si modules.
In situ TEM microscopy of α–Ge films in laser annealing conditions
Published in A G Cullis, S M Davidson, G R Booker, Microscopy of Semiconducting Materials, 1983, 2020
J Marfaing, P Pierrard, W Marine, B Mutaftschiev, F Salvan
Under various experimental conditions, crystallization of amorphous materials can be described through different processes. One of them is the explosive crystallization which occurs by a rapid propagation of an exothermic crystallization wave through the amorphous material initiated by a localized energy impulse. Another process includes the possibility that melting occurs before crystallization and a liquid zone is then induced between the crystalline and the amorphous regions. But both experimental results (such as reflectivity, transmissivity, Raman scattering measurements…) and advanced theories have not yet concluded in a decisive way whether or not a thin supercooled liquid layer is always present during the crystallization process.
Strain energy evolution analysis of elastic-plastic deformation on polycarbonate by infrared radiation characteristics
Published in Nondestructive Testing and Evaluation, 2023
Lu Chen, Dejian Li, Mingyuan Zhang, Muao Shen, Junhao Huo, Yingjun Li
Amorphous polymers have been extensively used in engineering due to their excellent mechanical property and lower cost of production. Polycarbonate is a thermoplastic polymer, which can supply the obvious plastic flow characteristics and good toughness when it subjected to a load [1]. It has a variety of engineering applications such as transportation, aerospace and construction safety [2–4]. As a response to the increasing demands in the engineering applications, the physical and mechanical properties of polycarbonate under quasi-static loading have been investigated universally [5]. While a huge volume of the literature exists on mechanical behaviour of polycarbonate at different strain rates and temperature [6–10], numerous studies have focused on the tension and compression behavior of polycarbonate. However, the focus on strain energy of polycarbonate at high loading rates has been rarely explored. The deformation and fracture on polycarbonate are caused by the slippage, reconstruction and destruction of its internal molecular chain fibre network [11]. And it is accompanied by the energy conversion of different forms within polycarbonate and energy exchange with the surroundings. Consequently, an accurate understanding and analysing the principle of energy conversion and dissipation are of great significance for investigating the deformation and failure mechanism of polycarbonate.
Impact properties of thermoplastic composites
Published in Textile Progress, 2018
Ganesh Jogur, Ashraf Nawaz Khan, Apurba Das, Puneet Mahajan, R. Alagirusamy
Amorphous thermoplastic polymers find their applications in medicine, communications, transportation, chemical processing, electronics and aerospace either in unfilled or in short-fibre reinforced composite form. Whereas the unfilled polymers are used in aircraft canopies, cookware, power tools, corrosion resistance piping, business machines, and medical instruments, the short-fibre reinforced forms find applications in printed circuit boards, electrical connections, jet-engine components, transmission parts, and under-the-hood automotive applications. Continuous fibre-reinforced amorphous thermoplastic composites are also used in more-demanding applications such as in the fabrication of aircraft interior components, floorings, wing skins, and fuselage sections.
Computational approach to increasing the packing fraction of amorphous powders
Published in Powder Metallurgy, 2021
Jungjoon Kim, Junhyub Jeon, Yeonjoo Lee, Seok-Jae Lee, Youngkyun Kim, Hwi-Jun Kim, Youngjin Kim, Hyunjoo Choi
Figure 2(e) shows XRD patterns of the powders with different sizes. Regardless of the size, all the powders exhibited the broad halo patterns generally observed in amorphous structures. Amorphous powders are usually manufactured using a liquid master alloy in powder form followed by crystallisation through rapid cooling using water or gas. As the powder size increases, the time for the powder to cool increases, which may lead to crystallisation in the powder. The powders used in this study were amorphous. The metalloid elements (i.e. B and C) used in the alloy system also exhibited a relatively small atomic radius, possibly because they were located between large atoms in the Fe-based alloy, thereby preventing the formation of a crystal structure [32–34].