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Minerals
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Crystallization and Growth of Graphite
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Crystallization and Growth of Graphite

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (19 February 2021) | Viewed by 10895

Special Issue Editors

Prof. Dr. Doru Michael Stefanescu

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Guest Editor
Department of Materials Science and Engineering, The Ohio State University, 2041 College Rd., Columbus, OH 43210, USA
Interests: solidification of metals; process modeling; materials characterization; materials properties; cast iron; aluminum
Prof. Dr. Attila Diószegi

E-Mail Website1 Website2
Guest Editor
Department of Materials and Manufacturing, School of Engineering, Jönköping University, P.O. Box 1026, SE-551 11 Jönköping, Sweden
Interests: molding materials; liquid iron metallurgy; melt treatment and inoculation; mold filling; mold-metal interface interactions; solidification; nucleation and crystal growth; austenite and graphite formation mechanisms; casting defect formation mechanisms; static and dynamic tensile properties; thermophysical properties; volume change related thermal analyses; metallography and stereology; modelling and simulation of casting phenomena
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

While carbon constitutes only about 0.032 mass % of the Earth’s lithosphere (crust and outer mantle), its uses in modern technology span many fields—from graphite-reinforced polymers used in the manufacture of expensive sports cars, competition bicycles and motorbikes, or high-performance sailboats to graphitic cast iron for wind turbine parts, engine blocks, and cooking pans. Graphite is also a natural mineral. Understanding how to produce certain forms of graphite and graphite arrays from nature, such as nanotubes and conical shapes, can have scientific and technological paybacks. In addition, graphene can be obtained from graphite through exfoliation methods, as it is a basic layer of the graphite crystal. It can be used as a nanofiller in polymer composites with enhanced electrical, mechanical, and thermal properties. Hence, whether we consider natural graphite formed from a metamorphic fluid or cast-iron graphite crystallized from an iron–carbon melt, the need to understand its crystallization and growth transcends disciplines in science and technology.

Prof. Dr. Doru Michael Stefanescu
Prof. Dr. Attila Diószegi
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. Minerals 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 2400 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

  • carbon
  • graphite
  • graphene
  • ductile cast iron
  • spheroidal graphite
  • pyrolytic graphite spheres

Published Papers (4 papers)

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Research

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9 pages, 3371 KiB  
Article
Nodule Count, End of Solidification Cooling Rate, and Shrinkage Porosity Correlations in High Silicon Spheroidal Graphite Iron
by Gorka Alonso, Doru Michael Stefanescu, Beñat Bravo, Gorka Zarrabeitia and Ramon Suarez
Minerals 2021, 11(2), 155; https://doi.org/10.3390/min11020155 - 01 Feb 2021
Cited by 8 | Viewed by 2929
Abstract
High-silicon spheroidal graphite (SG) irons present higher changes of density during the solidification process when compared to normal SG irons. This special behavior is particularly significant in the last stages of solidification, where the graphite expansion may become insufficient to compensate the contraction [...] Read more.
High-silicon spheroidal graphite (SG) irons present higher changes of density during the solidification process when compared to normal SG irons. This special behavior is particularly significant in the last stages of solidification, where the graphite expansion may become insufficient to compensate the contraction of the austenite and the risk of microporosity formation increases. The goal of this laboratory research was to establish correlations between the different levels of nodule count obtained using five commercial inoculants, the cooling rate at the end of solidification, and the shrinkage porosity propensity. The analysis was conducted on thermal analysis cups that were sectioned and evaluated for microstructure by optical metallography and by 2D analysis with the Image J software to quantify the size of the microporosity region. It was found that a higher nodule count, associated with higher cooling rate at the end of solidification, generates lower porosity. SEM analysis was conducted to study the nature of nuclei. Complex (MgSiAl)N nitrides were found as the main nucleation sites for graphite. Full article
(This article belongs to the Special Issue Crystallization and Growth of Graphite)
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17 pages, 6904 KiB  
Article
Graphite Dendrites in Cast Iron and Their Fundamental Role in the Control of Morphology to Obtain Aero-Eutectic Graphite
by Alicia N. Roviglione, Alvaro Y. Tesio, Fernando Fungo and Ricardo W. Gregorutti
Minerals 2021, 11(2), 109; https://doi.org/10.3390/min11020109 - 22 Jan 2021
Cited by 2 | Viewed by 2119
Abstract
This work analyzes the growth of graphite in the eutectic system of gray cast iron, focusing on laminar type A and undercooled type D morphology, and a modified morphology, such as vermicular or compact graphite. The objective of the study is to find [...] Read more.
This work analyzes the growth of graphite in the eutectic system of gray cast iron, focusing on laminar type A and undercooled type D morphology, and a modified morphology, such as vermicular or compact graphite. The objective of the study is to find an optimal graphite structure, from which a new class of lightweight materials results that has been called aero-eutectic graphite (AEG). The method to obtain AEG consists of dissolving the gray iron ferrous matrix by means of a chemical attack. From experiences of unidirectional solidification, it has been found that laminar graphite grows in a non-faceted way, coupled to austenite, while in vermicular the growth is through foliated dendrites. This characteristic allows vermicular graphite to have a higher specific intrinsic surface area. According to the Brunauer-Emmett-Teller (BET) analysis, the surface of the vermicular was 106.27 m2 g−1, while those corresponding to type A and D were 83.390 m2 g−1 and 89.670 m2 g−1, respectively. AEG with graphite type D was used as a cathode in Li-O2 batteries with satisfactory results, reaching more than 70 charge and discharge cycles, and 150 cycles at this time and still cycling, using Ru(bpy)3(ClO4)2 as redox mediator. Full article
(This article belongs to the Special Issue Crystallization and Growth of Graphite)
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15 pages, 10117 KiB  
Article
Lanthanum Role in the Graphite Formation in Gray Cast Irons
by Eduard Stefan, Iulian Riposan, Mihai Chisamera and Stelian Stan
Minerals 2020, 10(12), 1146; https://doi.org/10.3390/min10121146 - 21 Dec 2020
Cited by 3 | Viewed by 2268
Abstract
The present paper reviews original data obtained by the authors from recent separate publications with additional unpublished data, specifically concerning the Lanthanum (La)’s role in the solidification pattern and graphite formation in gray cast irons. Iron melting at 0.018–0.056%S, a 3.7–4.1% carbon equivalent [...] Read more.
The present paper reviews original data obtained by the authors from recent separate publications with additional unpublished data, specifically concerning the Lanthanum (La)’s role in the solidification pattern and graphite formation in gray cast irons. Iron melting at 0.018–0.056%S, a 3.7–4.1% carbon equivalent (CE) and less than 0.005%Alresidual are inoculated with La-bearing FeSi alloys at different associations with other inoculating elements. Complex Al-La small inclusions as possible better nucleation sites for (Mn,X)S compounds and La-Ca presence in the body of these sulfides, which possibly provide better nucleation sites for flake graphite, are identified in 0.026%S cast iron. At a lower sulfur content (0.018%S), La,Ca,Al-FeSi alloy still has a high efficiency, but more complex La-bearing alloys are recommended for a higher dendritic austenite amount (LaBaZrTi–FeSi) or for lower eutectic recalescence (LaBaZr–FeSi). La has limited but specific benefits at 0.05–0.06%S irons, including favorable graphitizing factors (a higher amount of graphite precipitated at the end of solidification), lower eutectic recalescence, and a lower value of the first derivative at the end of solidification. When La,Ca,Ba,Al,Zr,S-FeSi treatment (0.035%S base iron) is used, Scanning Electron Microscopy (SEM) analysis finds that the first formed micro-compound is a complex Al-silicate (Zr,La,Ca,Ba presence), which supports the nucleation of the second compound (Mn,Ca,La)S type. At the sulfide-graphite interface, there is a visible thin (nano size) Al-silicate layer (O-Al-Si-Ca-La system), which is more favorable for graphite nucleation (it has better crystallographic compatibility). La is identified in all three important areas of nucleants (the first is formed oxidic nucleus, the second is nucleated Mn-sulfide and the third is a sulfide-graphite interface), thereby increasing the efficiency of graphite nucleation sites. Full article
(This article belongs to the Special Issue Crystallization and Growth of Graphite)
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Review

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14 pages, 2557 KiB  
Review
Influence of Strain Rate, Temperature and Chemical Composition on High Silicon Ductile Iron
by Henrik Borgström
Minerals 2021, 11(4), 391; https://doi.org/10.3390/min11040391 - 08 Apr 2021
Cited by 3 | Viewed by 2879
Abstract
Today, the use of solution hardened ductile iron is limited by brittleness under certain conditions. If chassis components are subjected to loads having high strain rates exceeding those imposed during tensile testing at sub-zero temperatures, unexpected failure can occur. Therefore, it is the [...] Read more.
Today, the use of solution hardened ductile iron is limited by brittleness under certain conditions. If chassis components are subjected to loads having high strain rates exceeding those imposed during tensile testing at sub-zero temperatures, unexpected failure can occur. Therefore, it is the purpose of this review to discuss three main mechanisms, which have been related to brittle failure in high silicon irons: intercritical embrittlement, the integrity of the ferritic matrix and deformation mechanisms in the graphite. Intercritical embrittlement is mainly attributed to the formation of Mg- and S-rich grain boundary films. The formation of these films is suppressed if the amount of free Mg- and MgS-rich inclusions is limited by avoiding excess Mg and/or by the passivation of free Mg with P. If the grain boundary film is not suppressed, the high silicon iron has very low elongations in the shakeout temperature regime: 300 to 500 °C. The integrity and strength of the ferrite are limited by the reduced ordering of the silicumferrite with increasing silicon content, once the “ordinary” ferrite is saturated at 3% silicon, depending on the cooling conditions. Finally, the graphite damaging mechanisms are what dictate the properties most at low temperatures (sub −20 °C). Full article
(This article belongs to the Special Issue Crystallization and Growth of Graphite)
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