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18 pages, 10461 KiB

Open AccessArticle

Nonuniform Distribution of Crystalline Phases and Grain Sizes in the Surface Layers of WC Ceramics Produced by Spark Plasma Sintering

by Ksenia E. Smetanina, Pavel V. Andreev, Evgeny A. Lantsev, Aleksey V. Nokhrin, Artem A. Murashov, Natalia V. Isaeva, Yury V. Blagoveshchensky, Maksim S. Boldin and Vladimir N. Chuvil’deev

Coatings 2023, 13(6), 1051; https://doi.org/10.3390/coatings13061051 - 6 Jun 2023

Cited by 1 | Viewed by 1876

Abstract

The research results conducted on binderless tungsten carbide (WC) ceramics obtained by spark plasma sintering (SPS) of WC powders with different average particle sizes (95, 800, 3000 nm) are presented. Nonuniform distribution of crystalline phases and microstructure of the WC ceramics was studied using layer-by-layer X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Surface layers of the WC-based ceramics are characterized by nonuniform distribution of W₂C crystalline phase and grain sizes, including the appearance of abnormally large grains. Thickness of the nonuniform layer was at least 50 μm. The effect under study is associated with an intense carbon diffusion from graphite foil. On the one hand, this contributed to a decrease in the intensity of W₂C phase particle formation, which is transformed into α-WC phase due to the carbon. On the other hand, it caused abnormal grain growth in the layer where the carbon diffused. The obtained value of the carbon diffusion depth (50 μm) exceeds the values known from the literature (up to 1 μm in the case of volume diffusion even at temperature of 2370 °C and exposure time of ~60 h). The use of boron nitride (BN) as a protective coating on graphite mold parts did not prevent the formation of nonuniform layer on the ceramic surface. Full article

(This article belongs to the Special Issue Trends in Spark Plasma Sintering of Advanced Materials)

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12 pages, 6109 KiB

Open AccessArticle

Development of Ti PVD Films to Limit the Carburization of Metal Powders during SPS Process

by Maria-Rosa Ardigo-Besnard, Aurélien Besnard, Mathias Moser and Florian Bussière

Solids 2021, 2(4), 395-406; https://doi.org/10.3390/solids2040025 - 3 Dec 2021

Cited by 4 | Viewed by 3613

Abstract

Spark plasma sintering technique is used for the fabrication of dense materials with a fine-grained microstructure. In this process, a powder is placed into a graphite mold and a uniaxial pressure is applied by two graphite punches. A graphite foil is inserted between the punches and the powder and between the mold and the powder to ensure good electrical, physical and thermal contact. One of the major drawbacks during sintering of metal powders is the carburization of the powder in contact with the graphite foils. In this study, a PVD coating of titanium was applied on the graphite foils in contact with the metal powder (pure iron). The results are promising, as the investigations show that the application of a Ti PVD film of 1.5 and 1.1 µm thickness is effective to completely avoid the carburization of iron powder. Carbon diffuses inside the PVD film during sintering. In parallel, iron diffusion was revealed inside the Ti coating of 1.5 µm thickness. On the other hand, a Ti PVD film of 0.5 µm thickness provides a protection against carbon diffusion just on the sides in contact with the mold, proving that the coating thickness represents an important parameter to consider. Full article

(This article belongs to the Special Issue Solids in Europe)

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8 pages, 2209 KiB

Open AccessArticle

Mechanism of Carbon Contamination in Transparent MgAl₂O₄ and Y₃Al₅O₁₂ Ceramics Sintered by Spark Plasma Sintering

by Hussein Hammoud, Vincent Garnier, Gilbert Fantozzi, Etienne Lachaud and Solène Tadier

Ceramics 2019, 2(4), 612-619; https://doi.org/10.3390/ceramics2040048 - 13 Dec 2019

Cited by 17 | Viewed by 4297

Abstract

An investigation of MgAl₂O₄ spinel and Y₃Al₂O₅ (YAG) materials sintered by spark plasma sintering (SPS) was performed. The optical properties of the materials are modified depending on the powder source and the SPS sintering conditions. Spectrophotometer and Raman analysis are presented in this work, along with optical and scanning electron microscope (SEM) observations and cathodoluminescence analysis. The results show a correlation between carbon contamination and the optical properties of the materials. Herein, the source of the contamination is explained, along with its genesis and diffusion. The carbon contamination originates from the powder itself (carbonates), as well as the SPS environment (papiex^® graphite foil, graphite die, graphite felt) to form carbon clusters. During the high-temperature SPS process, carbon from those carbon clusters diffuses, resulting in an increase in the contamination volume, thereby increasing the light absorption. Full article

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7 pages, 1994 KiB

Open AccessCommunication

Three-Dimensional Copper Foil-Powder Sintering Current Collector for a Silicon-Based Anode Lithium-Ion Battery

by Jin Long, Huilong Liu, Yingxi Xie, Weijin Tang, Ting Fu, Yong Tang, Longsheng Lu, Xinrui Ding and Xingxian Tang

Materials 2018, 11(8), 1338; https://doi.org/10.3390/ma11081338 - 2 Aug 2018

Cited by 10 | Viewed by 4816

Abstract

In this work, we propose a facile method for manufacturing a three-dimensional copper foil-powder sintering current collector (CFSCC) for a silicon-based anode lithium-ion battery. We found that the CFSCC is suitable as a silicon-based paste electrode, and the paste-like electrodes are commonly used in industrial production. Compared with flat current collectors, the CFSCC better constrained the silicon volume change during the charging-discharging process. The capacitance of electrodes with CFSCC remained as high as 92.2% of its second cycle after 40 cycles, whereas that of electrodes with a flat current collector only remained at 50%. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 6614 KiB

Open AccessArticle

The Flexural Strength and Fracture Toughness of TC4-Based Laminated Composites Reinforced with Ti Aluminide and Carbide

by Yanhan Fei, Taotao Ai, Qunfei Niu, Wenhu Li, Xinqiang Yuan, Ran Jing and Hongfeng Dong

Materials 2017, 10(10), 1175; https://doi.org/10.3390/ma10101175 - 13 Oct 2017

Cited by 9 | Viewed by 4006

Abstract

TiC–Ti–Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti₃Al, Ti₂AlC, and Ti₃AlC₂ phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti₂AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m^1/2, respectively. Full article

(This article belongs to the Section Advanced Composites)

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