http://www.mdpi.com/journal/materials/special_issues/amorphous-alloys/ Dear Colleagues, Amorphous alloys are metastable materials that lack the long range order of conventional crystalline metals. They are often produced by casting and rapid quenching techniques, when nucleation and growth of crystalline phases are suppressed during cooling of liquid alloys. In addition, amorphous alloys can be obtained by several other methods such as electro-deposition, physical and chemical vapor deposition, spray deposition, solid state reactions and mechanical milling. In spite of their non-crystalline structure, the attractive interactions and the size differences between atomic species constituting an amorphous alloy, lead to a short and medium-range order characterized by clusters of atoms which connect to fill the space nearly as densely as their crystalline counterparts. The amorphous structure leads to a combination of exceptional mechanical, electrochemical, tribological and magnetic properties which are often superior to those of their crystalline counterparts and therefore attractive for “high-end” applications. Thus, amorphous alloys have emerged with the progress in Materials Science as an important new category of materials with unique properties, unusual structures and high potential for cutting edge applications in various industrial sectors. Alain. R. Yavari, Ph.D. Konstantinos Georgarakis, Ph.D. Guest Editors Related Special Issue Amorphous Alloys in International Journal of Molecular Sciences {snippet name="submission_info"} http://www.mdpi.com/1996-1944/4/9/1564/ Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy) materials: (i) metallic; (ii) thin films; (iii) organic and inorganic thermoplastics; and (iv) amorphous permanent networks. Some fundamental questions about the atomic arrangements remain unresolved. This paper focuses on the models of atomic arrangements in amorphous materials. The earliest ideas of Bernal on the structure of liquids were followed by experiments and computer models for the packing of spheres. Modern approach is to carry out computer simulations with prediction that can be tested by experiments. A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphous solids. http://www.mdpi.com/1996-1944/4/9/1564/ Thu, 15 Sep 2011 00:00:00 CEST Materials 2011-09-15 4 9 Review 1564 1598 1996-1944 On Structure and Properties of Amorphous Materials 2011-09-15 doi: 10.3390/ma4091564 Zbigniew H. Stachurski http://www.mdpi.com/1996-1944/4/4/716/ In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties. http://www.mdpi.com/1996-1944/4/4/716/ Wed, 13 Apr 2011 00:00:00 CEST Materials 2011-04-13 4 4 Review 716 781 1996-1944 New Approaches to the Computer Simulation of Amorphous Alloys: A Review 2011-04-13 doi: 10.3390/ma4040716 Ariel A. Valladares Juan A. Díaz-Celaya Jonathan Galván-Colín Luis M. Mejía-Mendoza José A. Reyes-Retana Renela M. Valladares Alexander Valladares Fernando Alvarez-Ramirez Dongdong Qu Jun Shen http://www.mdpi.com/1996-1944/4/1/37/ Inductance spectroscopy is a particular formulation variant of the well known complex impedance formalism typically used for the electric characterization of dielectric, ferroelectric, and piezoelectric materials. It has been successfully exploited as a versatile tool for characterization of the magnetization dynamics in amorphous ribbons and wires by means of simple experiments involving coils for sample holding and impedance analyzer equipment. This technique affords the resolution of the magnetization processes in soft magnetic materials, in terms of reversible deformation of pinned domain walls, domain wall displacements and spin rotation, for which characteristic parameters such as the alloy initial permeability and the relaxation frequencies, indicating the dispersion of each process, can be defined. Additionally, these parameters can be correlated with chemical composition variation, size effects and induced anisotropies, leading to a more physical insight for the understanding of the frequency dependent magnetic response of amorphous alloys, which is of prime interest for the development of novel applications in the field of telecommunication and sensing technologies. In this work, a brief overview, together with recent progress on the magnetization dynamics of amorphous ribbons, wires, microwires and biphase wires, is presented and discussed for the intermediate frequency interval between 10 Hz and 13 MHz. http://www.mdpi.com/1996-1944/4/1/37/ Thu, 23 Dec 2010 00:00:00 CET Materials 2010-12-23 4 1 Article 37 54 1996-1944 Magnetization Dynamics of Amorphous Ribbons and Wires Studied by Inductance Spectroscopy 2010-12-23 doi: 10.3390/ma4010037 Israel Betancourt http://www.mdpi.com/1996-1944/3/12/5320/ Alloying addition, as a means of improving mechanical properties and saving on costs of materials, has been applied to a broad range of uses and products in the metallurgical fields. In the field of bulk metallic glasses (BMGs), alloying additions have also proven to play effective and important roles in promoting glass formation, enhancing thermal stability and improving plasticity of the materials. Here, we review the work on the role of alloying additions in glass formation and performance improvement of BMGs, with focus on our recent results of alloying additions in Pd-based BMGs. http://www.mdpi.com/1996-1944/3/12/5320/ Tue, 21 Dec 2010 00:00:00 CET Materials 2010-12-21 3 12 Review 5320 5339 1996-1944 Role of Alloying Additions in Glass Formation and Properties of Bulk Metallic Glasses 2010-12-21 doi: 10.3390/ma3125320 Na Chen Laura Martin Dmitri V. Luzguine-Luzgin Akihisa Inoue http://www.mdpi.com/1996-1944/3/12/5263/ Nanoscale structural information of amorphous structures has become obtainable by using nanobeam electron diffraction in combination with high resolution imaging. In addition, accurate radial distribution function analysis using energy filter has also become available to know averaged amorphous structures. In this paper, we introduce some applications of these techniques, especially to several Fe-based metallic glasses. On the basis of these results, we discuss a relationship between the glass structure and the glass stability in Fe-based metallic glasses http://www.mdpi.com/1996-1944/3/12/5263/ Mon, 13 Dec 2010 00:00:00 CET Materials 2010-12-13 3 12 Article 5263 5273 1996-1944 Structure Analyses of Fe-based Metallic Glasses by Electron Diffraction 2010-12-13 doi: 10.3390/ma3125263 Akihiko Hirata Yoshihiko Hirotsu http://www.mdpi.com/1996-1944/3/12/5212/ Ni0.25Fe0.75Zr3 metallic glassy ribbons were annealed in evacuated quartz ampoules beyond the crystallization temperatures (Tx ~655 K) over the range 773 to 1,173 K for varying periods of time. The resistivity of samples annealed over the temperature range 923 to 1,073 K for periods less than four hours increased as a function of decreasing temperature, while it decreased for samples annealed for more than four hours or at temperatures below 923 K or above 1,073 K for any period of time. All the annealed samples were found to contain only Ni, Fe and Zr from energy dispersive X-ray (EDX) analyses. http://www.mdpi.com/1996-1944/3/12/5212/ Tue, 07 Dec 2010 00:00:00 CET Materials 2010-12-07 3 12 Article 5212 5219 1996-1944 Positive and Negative Temperature Dependence in the Resistivity of Crystallized Zr-Fe-Ni Metallic Glasses 2010-12-07 doi: 10.3390/ma3125212 Fathalla Hamed