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Crystals
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Defects in Crystals
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Defects in Crystals

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Hybrid and Composite Crystalline Materials".

Deadline for manuscript submissions: closed (30 May 2022) | Viewed by 14264

Special Issue Editors

Dr. Alexandre A.S. Goncalves

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Guest Editor
Catalytic and Process Ceramics, Saint-Gobain NorPro, OH, USA
Interests: nanomaterials; sorption; thermal analysis; catalysis; mixed metal oxides; carbons; metal-organic frameworks
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Cristiane Alves Pereira

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Guest Editor
Department of Engineering, Federal University of Lavras, Lavras, Brazil
Interests: nanomaterials; characterization of materials; catalysis; sol-gel method; supported metal oxides; pollutants abatements, biofuels
Dr. Liping Zhang

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Guest Editor
Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, China
Interests: surface chemistry; nanomaterials; semiconductors; adsorption; photocatalysis; micromachines
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Samo Kralj

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Guest Editor
1. Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska 160, 2000 Maribor, Slovenia
2. Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Interests: liquid crystals; nanocomposites; phase transitions; instabilities; wetting; topological defects
Dr. Kele Tatiane Gomes Carvalho

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Guest Editor
Department of Chemical Engineering, Federal University of Sao Carlos, São Carlos, Brazil
Interests: heterogeneous catalysis; photocatalysis; adsorption; nanomaterials; porous materials; material characterization

Special Issue Information

Dear Colleagues,

Defects are an intrinsic feature of materials, meaning that perfect solids or crystals (without defects) do not exist in nature as dictated by thermodynamic constraints of order and disorder in solids. Imperfections in crystalline solids play a critical role in solid-state science since it can determine a variety of properties of materials such as mechanical resistance, spectroscopic behaviour, and mass transport. Thereby, defect-driven phenomena are of great importance in solid-state chemistry, physics, and engineering. The existence of defects occurs from nanomaterials to bulk materials, of single composition or composites, and may affect the material’s performance in several orders of magnitude. For instance, the role of defects in atomic and electronic transport processes intimately reflects the performance of catalysts, photocatalysts, and electrocatalysts, mainly when a defective interface exists between components. Another example is incorporating missing linkers or mismatch of the building block of MOFs (Metal-Organic Frameworks) to create defects to tailor the materials’ adsorption and mass transfer properties. Other fields in which defects play essential roles are, but are not limited to, solid electrolytes and batteries, fuel cells, sensors, photoluminescent and superconducting materials, and sintering of ceramics.

Given the importance of defects in material science as a multidisciplinary topic, we invite researches and scientists to contribute to the Special Issue Defects in Crystals. Our goal is to create a forum that explores two facets of the defect-driven phenomena; the first is to characterize, understand, and foretell the nature and behaviour of defects in solids and solid interfaces. The second facet is to rationally control defects to create functionalized materials with outstanding performance or special features.

Dr. Alexandre A.S. Goncalves
Prof. Dr. Cristiane Alves Pereira
Dr. Liping Zhang
Prof. Dr. Samo Kralj
Dr. Kele Tatiane Gomes Carvalho
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Defect-driven phenomenon
  • Crystal engineering
  • Composite interfaces
  • Metal-organic frameworks
  • Advanced ceramics
  • Catalysts

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Published Papers (5 papers)

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Research

15 pages, 959 KiB  
Article
Ab-Initio Study of Calcium Fluoride Doped with Heavy Isotopes
by Martin Pimon, Andreas Grüneis, Peter Mohn and Thorsten Schumm
Crystals 2022, 12(8), 1128; https://doi.org/10.3390/cryst12081128 - 11 Aug 2022
Cited by 1 | Viewed by 2281
Abstract
Precision laser spectroscopy of the 229-thorium nuclear isomer transition in a solid-state environment would represent a significant milestone in the field of metrology, opening the door to the realization of a nuclear clock. Working toward this goal, experimental methods require knowledge of various [...] Read more.
Precision laser spectroscopy of the 229-thorium nuclear isomer transition in a solid-state environment would represent a significant milestone in the field of metrology, opening the door to the realization of a nuclear clock. Working toward this goal, experimental methods require knowledge of various properties of a large band-gap material, such as calcium fluoride doped with specific isotopes of the heavy elements thorium, actinium, cerium, neptunium, and uranium. By accurately determining the atomic structure of potential charge compensation schemes by using a generalized gradient approximation within the ab-initio framework of density functional theory, calculations of electric field gradients on the dopants become accessible, which cause a quadrupole splitting of the nuclear-level structure that can be probed experimentally. Band gaps and absorption coefficients in the range of the 229-thorium nuclear transition are estimated by using the G0W0 method and by solving the Bethe–Salpeter equation. Full article
(This article belongs to the Special Issue Defects in Crystals)
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17 pages, 19836 KiB  
Article
Effect of Prior Surface Textures on the Resulting Roughness and Residual Stress during Bead-Blasting of Electron Beam Melted Ti-6Al-4V
by Mustafa Rifat, Saurabh Basu, Edward C. De Meter and Guha Manogharan
Crystals 2022, 12(3), 374; https://doi.org/10.3390/cryst12030374 - 10 Mar 2022
Cited by 6 | Viewed by 3146
Abstract
The finishing of additive manufactured (AM) components is crucial for endowing them with fatigue resistance. Unfortunately, current AM processes naturally promote anisotropic surface characteristics that make it challenging to optimize finishing processes. In this study, bead-blasting is explored as a process for finishing [...] Read more.
The finishing of additive manufactured (AM) components is crucial for endowing them with fatigue resistance. Unfortunately, current AM processes naturally promote anisotropic surface characteristics that make it challenging to optimize finishing processes. In this study, bead-blasting is explored as a process for finishing Electron Beam Melted (EBM) Ti-6Al-4V. The effects of anisotropic roughness characteristics on the mechanics of bead-blasting are delineated using surface texture measurements via optical profilometry and residual stress measurements via X-ray diffraction. As-received surfaces resulting from AM, as well as those that have been Electrical Discharge Machined (EDM), are studied. It is seen that pre-processed roughness textures heavily influence the final textures and residual stresses. These linkages are quantified using a plasticity index as the governing metric—a rougher surface features a larger plastic index, which results in comparatively greater evolution of its texture characteristics than a smoother surface after equivalent bead-blasting treatments. The mechanics of this evolution are delineated using energy-controlled indentation as a model representing a single impact in bead-blasting. It is seen that rougher surfaces featuring complex textures in as-received states also produce complex stress states featuring a greater level of locally tensile stresses during indentation compared with smoother surfaces. Approaches to address these complications are proposed that can potentially transform a printed, non-functional surface into one that is optimized for fatigue resistance. Full article
(This article belongs to the Special Issue Defects in Crystals)
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10 pages, 1883 KiB  
Article
Cyclic Tension Induced Pattern Formation on [001] Single-Crystal Aluminum Foil
by Kuznetsov Pavel and Khon Yury
Crystals 2022, 12(1), 28; https://doi.org/10.3390/cryst12010028 - 24 Dec 2021
Viewed by 1969
Abstract
Cyclic tension of (100)[001]-oriented single-crystal aluminum foils with the frequency 5 Hz forms a tweed pattern. Its period is several microns and increases by a factor of 1.5 in the temperature range 233–363 K. A model is proposed for structural relaxation of the [...] Read more.
Cyclic tension of (100)[001]-oriented single-crystal aluminum foils with the frequency 5 Hz forms a tweed pattern. Its period is several microns and increases by a factor of 1.5 in the temperature range 233–363 K. A model is proposed for structural relaxation of the medium on spatial and time meso- and macroscales under cyclic loading. Conditions under which a steady pattern forms are found based on the analysis of kinetic equations. The number of bands in the steady pattern is found to be related to the strain rate. The process activation energy is determined. Full article
(This article belongs to the Special Issue Defects in Crystals)
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13 pages, 6957 KiB  
Article
In Situ Evolution of Pores in Lithium Hydride at Elevated Temperatures Characterized by X-ray Computed Tomography
by Yifan Shi, Lei Peng, Wangzi Zhang, Qiang Li, Qishou Li and Linsen Ye
Crystals 2021, 11(9), 1093; https://doi.org/10.3390/cryst11091093 - 8 Sep 2021
Cited by 3 | Viewed by 1946
Abstract
The evolution of defects such as pores at elevated temperatures is crucial for revealing the thermal stability of lithium hydride ceramic. The in situ evolution of pores in sintered lithium hydride ceramic from 25 °C to 500 °C, such as the statistics of [...] Read more.
The evolution of defects such as pores at elevated temperatures is crucial for revealing the thermal stability of lithium hydride ceramic. The in situ evolution of pores in sintered lithium hydride ceramic from 25 °C to 500 °C, such as the statistics of pores and the 3D structure of pores, was investigated by X-ray computed tomography. Based on the statistics of pores, the porosity significantly increased from 25 °C to 200 °C and decreased after 200 °C, due to the significant change in the number and total volume of the round-shaped pores and the branched crack-like pores with an increasing temperature. According to the 3D structure of pores, the positions of pores did not change, and the sizes of pores went up in the range of 25–200 °C and went down after 200 °C. Some small round-shaped pores with an Equivalent Diameter of less than 9 μm appeared at 200 °C and disappeared at elevated temperatures. Some adjacent pores of all types connected at 200 °C, and some branched crack-like pores gradually disconnected with an increasing temperature. The expansion of pores at 200 °C caused by the release of residual hydrogen and the contraction of pores after 200 °C because of the migration and diffusion of some hydrogen in pores might be the reason for the evolution of pores with an increasing temperature. Full article
(This article belongs to the Special Issue Defects in Crystals)
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16 pages, 3678 KiB  
Article
Curvature Potential Unveiled Topological Defect Attractors
by Luka Mesarec, Aleš Iglič, Veronika Kralj-Iglič, Wojciech Góźdź, Epifanio G. Virga and Samo Kralj
Crystals 2021, 11(5), 539; https://doi.org/10.3390/cryst11050539 - 12 May 2021
Cited by 8 | Viewed by 2603
Abstract
We consider the theoretical and positional assembling of topological defects (TDs) in effectively two-dimensional nematic liquid crystal films. We use a phenomenological Helfrich–Landau–de Gennes-type mesoscopic model in which geometric shapes and nematic orientational order are expressed in terms of a curvature tensor field [...] Read more.
We consider the theoretical and positional assembling of topological defects (TDs) in effectively two-dimensional nematic liquid crystal films. We use a phenomenological Helfrich–Landau–de Gennes-type mesoscopic model in which geometric shapes and nematic orientational order are expressed in terms of a curvature tensor field and a nematic tensor order parameter field. Extrinsic, intrinsic, and total curvature potentials are introduced using the parallel transport concept. These potentials reveal curvature seeded TD attractors. To test ground configurations, we used axially symmetric nematic films exhibiting spherical topology. Full article
(This article belongs to the Special Issue Defects in Crystals)
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