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Nanocrystalline Bulk Materials at Multiple Scales

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

Deadline for manuscript submissions: closed (16 December 2022) | Viewed by 11380

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Special Issue Editors

Dr. Wenwu Xu

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Guest Editor

Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
Interests: nanomaterials; nanomechanics; molecular dynamics; density functional theory; electron microscopy

Dr. Fawei Tang

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Guest Editor

Faculty of Materials and Manufacturing, Key Laboratory of Advanced Functional Materials, Ministry of Education of China, Beijing University of Technology, 100124 Beijing, China
Interests: nanomaterials; thermodynamic stability; grain boundary engineering; first-principles calculations; multiscale modeling

Dr. Massoud Malaki

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Guest Editor

Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
Interests: advanced manufacturing; composite materials; ultrasonics; nanomaterials; advanced materials processing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nanocrystalline bulk materials are, by definition, polycrystalline structures with an average grain size below about 100nm. In contrast to microcrystalline counterparts, nanocrystalline materials have a much larger volume fraction of interfaces, including grain boundaries, phase boundaries, and domain interfaces. Owing to their special structures, nanocrystalline materials consisting of either single phase or multiphase exhibit distinctly different physical, chemical, and mechanical properties from those of the microcrystalline materials with the same nominal compositions.

After decades of research development from both academia and industry, it is now a new beginning for the innovative fundamental and applied science of nanocrystalline materials. Many of the challenges of developing nanocrystalline materials are being resolved by using different fabrication and characterization techniques at multiple length scales, from macroscale all the way down to atomistic scale, facilitating real life usages of bulk nanocrystalline materials and parts. Recent advances in experimental and theoretical studies, as well as the integration of experiments and computational materials science about bulk nanocrystalline materials, are expected to lead to the next generation high performance nanocrystalline materials with both structural and functional applications.

This Special Issue discusses the latest research advances of nanocrystalline bulk metals, alloys, and ceramics. Original research papers, state-of-the-art reviews, and short communications are encouraged relevant to the following topics:

Advances in synthesis and fabrication of nanocrystalline bulks (metal, alloys, and ceramics);
Advances in processing development for more stabilized nanograin structures;
Grain boundary engineering for high performance nanocrystalline bulks;
Advances in the characterization techniques of nanocrystalline bulks;
Fundamental (physical, chemical, and mechanical) properties of nanocrystalline bulk materials.

Dr. Wenwu Xu
Dr. Fawei Tang
Dr. Massoud Malaki
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 2600 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

nanocrystalline metals
nanocrystalline alloys
nanocrystalline ceramics
synthesis and processing
characterization
modeling
mechanical properties
deformation nanomechanics
thermal stability
phase stability
nanocomposite
manufacturing

Published Papers (4 papers)

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Research

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21 pages, 7705 KiB

Open AccessArticle

Conversion of Nastrophites to Fibrous Strontium Apatites and Their Crystallographic Characterization

by Akira Furukawa and Yasuhito Tanaka

Crystals 2022, 12(12), 1705; https://doi.org/10.3390/cryst12121705 - 24 Nov 2022

Cited by 1 | Viewed by 1011

Abstract

Strontium apatite has attracted considerable attention from researchers in various disciplines, including the medical field, owing to its excellent biocompatibility and beneficial effects on enhanced bone regeneration. In addition to their chemical characteristics, morphological aspects of apatite crystals are of great importance because they can exert a significant influence on various biological functions. In this study, a versatile method for the synthesis of fibrous strontium apatite is developed for the first time. Highly crystalline strontium apatite nanofibers were prepared by alkaline hydrolysis of strontium hydrogen phosphate (SrHPO₄) at ambient temperature via nastrophite (NaSrPO₄) intermediates. Some strontium ions in the crystal lattice of strontium hydrogen phosphate were substituted with barium (Ba) ions with various molar ratios up to Ba/Sr = 5/5, and their molar ratios were retained in the final products of the substituted fibrous apatites. The products, including hydrogen phosphates, nastrophites, and apatite nanofibers, were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), wavelength dispersive X-ray fluorescence (WDX) analysis, and transmission electron microscopy (TEM) with selected area electron diffraction (SAED). These analyses verified the integrity of the speculated structures of the fibrous apatites. The lattice parameters of apatites and other intermediates were calculated using a newly developed calculation process based on the least-squares method and the results were compared to those of EXPO2014. Full article

(This article belongs to the Special Issue Nanocrystalline Bulk Materials at Multiple Scales)

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19 pages, 2593 KiB

Open AccessArticle

Frictionless Motion of Diffuse Interfaces by Sharp Phase-Field Modeling

by Michael Fleck, Felix Schleifer and Patrick Zimbrod

Crystals 2022, 12(10), 1496; https://doi.org/10.3390/cryst12101496 - 21 Oct 2022

Cited by 3 | Viewed by 1435

Abstract

Diffuse interface descriptions offer many advantages for the modeling of microstructure evolution. However, the numerical representation of moving diffuse interfaces on discrete numerical grids involves spurious grid friction, which limits the overall performance of the model in many respects. Interestingly, this intricate and detrimental effect can be overcome in finite difference (FD) and fast Fourier transformation (FFT)-based implementations by employing the so-called sharp phase-field method (SPFM). The key idea is to restore the discretization-induced broken translational invariance (TI) in the discrete phase-field equation by using analytic properties of the equilibrium interface profile. We prove that this method can indeed eliminate spurious grid friction in the three-dimensional space. Focusing on homogeneous driving forces, we quantitatively evaluate the impact of spurious grid friction on the overall operational performance of different phase-field models. We show that the SPFM provides superior degrees of interface isotropy with respect to energy and kinetics. The latter property enables the frictionless motion of arbitrarily oriented diffuse interfaces on a fixed 3D grid. Full article

(This article belongs to the Special Issue Nanocrystalline Bulk Materials at Multiple Scales)

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14 pages, 8468 KiB

Open AccessArticle

Laser-Induced Exothermic Bonding of SiCp/Al Composites with Nanostructured Al/Ni Energetic Interlayer

by Guangjie Feng, Bingxu Hu, Xiaojian Liu, Yan Wei, Zhuoran Li, Peng He, Zhiliang Cheng, Yifeng Wang, Dean Deng and Xiuxia Yang

Crystals 2022, 12(7), 938; https://doi.org/10.3390/cryst12070938 - 03 Jul 2022

Cited by 1 | Viewed by 1219

Abstract

In this study, SiCp/Al composites were bonded using the laser-induced exothermic bonding method. The nanostructured Al/Ni energetic materials were prepared by the high-energy ball-milling method and served as the bonding interlayer. The joint microstructure was characterized by SEM, EDS, TEM, and XRD. The effect of Zr content on the joint microstructure and shear strength was investigated. The results indicated that after the ball-milling process the Al and Ni particles underwent strong plastic deformations and were welded to each other, forming the nanostructured Al/Ni energetic materials with a lamellar structure. Compared with the raw powders, the location of the exothermic peak decreased by 42 K, and its exothermic performance was significantly improved. The exothermic reactions that occurred in the Al/Ni interlayer provided the required heat for the bonding process. Near the bonding interface, the interlayer could not react completely due to the cooling effect of the substrates, forming a mixture of residual metal particles and Ni-Al compounds. The addition of Zr content enhanced the interfacial reactions between the bonding interlayer and the SiCp/Al composites. The interlayer products transformed from NiAl to the eutectic organization of NiAl + Ni-Al-Zr, thus decreasing the pores in the joint and improving the bonding quality. With an increase in the Zr content, the joint shear strength first increased and then decreased. When the Zr content was 10 wt.%, the joint shear strength reached a maximum of 22 MPa. Full article

(This article belongs to the Special Issue Nanocrystalline Bulk Materials at Multiple Scales)

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Review

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31 pages, 6703 KiB

Open AccessReview

Nanocrystalline Materials: Synthesis, Characterization, Properties, and Applications

by Amanendra K. Kushwaha, Merbin John, Manoranjan Misra and Pradeep L. Menezes

Crystals 2021, 11(11), 1317; https://doi.org/10.3390/cryst11111317 - 29 Oct 2021

Cited by 31 | Viewed by 6751

Abstract

Nanostructuring is a commonly employed method of obtaining superior mechanical properties in metals and alloys. Compared to conventional polycrystalline counterparts, nanostructuring can provide remarkable improvements in yield strength, toughness, fatigue life, corrosion resistance, and hardness, which is attributed to the nano grain size. In this review paper, the current state-of-the-art of synthesis methods of nanocrystalline (NC) materials such as rapid solidification, chemical precipitation, chemical vapor deposition, and mechanical alloying, including high-energy ball milling (HEBM) and cryomilling was elucidated. More specifically, the effect of various process parameters on mechanical properties and microstructural features were explained for a broad range of engineering materials. This study also explains the mechanism of grain strengthening using the Hall-Petch relation and illustrates the effects of post-processing on the grain size and subsequently their properties. This review also reports the applications, challenges, and future scope for the NC materials. Full article

(This article belongs to the Special Issue Nanocrystalline Bulk Materials at Multiple Scales)

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