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2 pages, 161 KiB

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Plasmas Processes Applied on Metals and Alloys

by Jian-Zhang Chen and Shih-Hang Chang

Metals 2020, 10(3), 349; https://doi.org/10.3390/met10030349 - 07 Mar 2020

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(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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11 pages, 2632 KiB

Open AccessArticle

A Study on the Effect of Ambient Air Plasma Treatment on the Properties of Methylammonium Lead Halide Perovskite Films

by Masoud Shekargoftar, Jana Jurmanová and Tomáš Homola

Metals 2019, 9(9), 991; https://doi.org/10.3390/met9090991 - 07 Sep 2019

Cited by 12 | Viewed by 3952

Abstract

Organic-inorganic halide perovskite materials are considered excellent active layers in the fabrication of highly efficient and low-cost photovoltaic devices. This contribution demonstrates that rapid and low-temperature air-plasma treatment of mixed organic-inorganic halide perovskite film is a promising technique, controlling its opto-electrical surface properties [...] Read more.

Organic-inorganic halide perovskite materials are considered excellent active layers in the fabrication of highly efficient and low-cost photovoltaic devices. This contribution demonstrates that rapid and low-temperature air-plasma treatment of mixed organic-inorganic halide perovskite film is a promising technique, controlling its opto-electrical surface properties by changing the ratio of organic-to-inorganic components. Plasma treatment of perovskite films was performed with high power-density (25 kW/m² and 100 W/cm³) diffuse coplanar surface barrier discharge (DCSBD) at 70 °C in ambient air. The results show that short plasma treatment time (1 s, 2 s, and 5 s) led to a relatively enlargement of grain size, however, longer plasma treatment time (10 s and 20 s) led to an etching of the surface. The band-gap energy of the perovskite films was related to the duration of plasma treatment; short periods (≤5 s) led to a widening of the band gap from ~1.66 to 1.73 eV, while longer exposure (>5 s) led to a narrowing of the band gap to approx. 1.63 eV and fast degradation of the film due to etching. Surface analysis demonstrated that the film became homogeneous, with highly oriented crystals, after short plasma treatment; however, prolonging the plasma treatment led to morphological disorders and partial etching of the surface. The plasma treatment approach presented herein addresses important challenges in current perovskite solar cells: tuning the optoelectronic properties and manufacturing homogeneous perovskite films. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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13 pages, 3191 KiB

Open AccessArticle

Spatial Distribution of Wettability in Aluminum Surfaces Treated with an Atmospheric-Pressure Remote-Plasma

by José Muñoz, Rocío Rincón and María Dolores Calzada

Metals 2019, 9(9), 937; https://doi.org/10.3390/met9090937 - 27 Aug 2019

Cited by 6 | Viewed by 2358

Abstract

The use of atmospheric-pressure remote plasmas (postdischarge) sustained in argon and argon–nitrogen for the treatment of aluminum surfaces has been studied to better understand the underlying mechanisms responsible for cleaning and activating the surfaces. The effect of the gas composition, treatment distance, and [...] Read more.

The use of atmospheric-pressure remote plasmas (postdischarge) sustained in argon and argon–nitrogen for the treatment of aluminum surfaces has been studied to better understand the underlying mechanisms responsible for cleaning and activating the surfaces. The effect of the gas composition, treatment distance, and speed on the hydrophilicity of commercial aluminum samples has been studied using the sessile drop method to build spatial profiles of the treated zones. In the case of argon–nitrogen postdischarges, neither the distance to the plasma end (2 <

z

< 6 cm) nor the treatment speed (2500 < v < 7500 μm/s) had a significant impact in the spot radius of the treatment, remaining approximately constant around 6–7 mm. This result seems to indicate that the postdischarge experiments a little expansion at the exit of the tube in which the discharge was created but its action can be considered highly-directional. This fact is essential for the possible industrial implementation of the procedure described in this research. These results have been analyzed together with the composition of active species in the postdischarge by using optical emission spectroscopy, revealing that long lived nitrogen species are required to significantly increase the wettability of the aluminum surfaces. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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13 pages, 5040 KiB

Open AccessArticle

Comparison of Mechanical and Antibacterial Properties of TiO₂/Ag Ceramics and Ti6Al4V-TiO₂/Ag Composite Materials Using Combined SLM-SPS Techniques

by Ramin Rahmani, Merilin Rosenberg, Angela Ivask and Lauri Kollo

Metals 2019, 9(8), 874; https://doi.org/10.3390/met9080874 - 08 Aug 2019

Cited by 26 | Viewed by 4504

Abstract

In present work, the combination of spark plasma sintering (SPS) and selective laser melting (SLM) techniques was introduced to produce composite materials where silver-doped titania (TiO₂) ceramics were reinforced with ordered lattice structures of titanium alloy Ti6Al4V. The objective was to [...] Read more.

In present work, the combination of spark plasma sintering (SPS) and selective laser melting (SLM) techniques was introduced to produce composite materials where silver-doped titania (TiO₂) ceramics were reinforced with ordered lattice structures of titanium alloy Ti6Al4V. The objective was to create bulk materials with an ordered hierarchical design that were expected to exhibit improved mechanical properties along with an antibacterial effect. The prepared composite materials were evaluated for structural integrity and mechanical properties as well as for antibacterial activity towards Escherichia coli. The developed titanium–silver/titania hybrids showed increased damage tolerance and ultimate strength when compared to ceramics without metal reinforcement. However, compared with titania/silver ceramics alone that exhibited significant antibacterial effect, titanium-reinforced ceramics showed significantly reduced antibacterial effect. Thus, to obtain antibacterial materials with increased strength, the composition of metal should either be modified, or covered with antibacterial ceramics. Our results indicated that the used method is a feasible route for adding ceramic reinforcement to 3D printed metal alloys. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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11 pages, 4546 KiB

Open AccessArticle

Controlling Nitrogen Dose Amount in Atmospheric-Pressure Plasma Jet Nitriding

by Ryuta Ichiki, Masayuki Kono, Yuka Kanbara, Takeru Okada, Tatsuro Onomoto, Kosuke Tachibana, Takashi Furuki and Seiji Kanazawa

Metals 2019, 9(6), 714; https://doi.org/10.3390/met9060714 - 25 Jun 2019

Cited by 9 | Viewed by 4556

Abstract

A unique nitriding technique with the use of an atmospheric-pressure pulsed-arc plasma jet has been developed to offer a non-vacuum, easy-to-operate process of nitrogen doping to metal surfaces. This technique, however, suffered from a problem of excess nitrogen supply due to the high [...] Read more.

A unique nitriding technique with the use of an atmospheric-pressure pulsed-arc plasma jet has been developed to offer a non-vacuum, easy-to-operate process of nitrogen doping to metal surfaces. This technique, however, suffered from a problem of excess nitrogen supply due to the high pressure results in undesirable formation of voids and iron nitrides in the treated metal surface. To overcome this problem, we have first established a method to control the nitrogen dose amount supplied to the steel surface in the relevant nitriding technique. When the hydrogen fraction in the operating gas of nitrogen/hydrogen gas mixture increased from 1% up to 5%, the nitrogen density of the treated steel surface drastically decreased. As a result, the formation of voids were suppressed successfully. The controllability of the nitrogen dose amount is likely attributable to the density of NH radicals existing in the plume of the pulsed-arc plasma jet. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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11 pages, 5069 KiB

Open AccessArticle

Self-Lubricating PEO–PTFE Composite Coating on Titanium

by Limei Ren, Tengchao Wang, Zhaoxiang Chen, Yunyu Li and Lihe Qian

Metals 2019, 9(2), 170; https://doi.org/10.3390/met9020170 - 01 Feb 2019

Cited by 23 | Viewed by 3671

Abstract

A self-lubricating plasma electrolytic oxidation–polytetrafluoroethylene (PEO–PTFE) composite coating was successfully fabricated on the surface of commercially pure titanium by a multiple-step method of plasma electrolytic oxidation, dipping and sintering treatment. The microstructure and tribological properties of the PEO–PTFE composite coating were investigated and [...] Read more.

A self-lubricating plasma electrolytic oxidation–polytetrafluoroethylene (PEO–PTFE) composite coating was successfully fabricated on the surface of commercially pure titanium by a multiple-step method of plasma electrolytic oxidation, dipping and sintering treatment. The microstructure and tribological properties of the PEO–PTFE composite coating were investigated and compared with the PEO TiO₂ coating and the PTFE coating on titanium. Results show that most of the micro-pores of the PEO TiO₂ coating were filled by PTFE and the surface roughness of PEO–PTFE composite coating was lower than that of the PEO TiO₂ coating. Furthermore, the PEO–PTFE composite coating shows excellent tribological properties with low friction coefficient and low wear rate. This study provides an insight for guiding the design of self-lubricating and wear-resistant PEO composite coatings. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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12 pages, 4698 KiB

Open AccessArticle

Time Evolution Characterization of Atmospheric-Pressure Plasma Jet (APPJ)-Synthesized Pt-SnO_x Catalysts

by Chia-Chun Lee, Tzu-Ming Huang, I-Chun Cheng, Cheng-Che Hsu and Jian-Zhang Chen

Metals 2018, 8(9), 690; https://doi.org/10.3390/met8090690 - 01 Sep 2018

Cited by 6 | Viewed by 3546

Abstract

We characterize the time evolution (≤120 s) of atmospheric-pressure plasma jet (APPJ)-synthesized Pt-SnO_x catalysts. A mixture precursor solution consisting of chloroplatinic acid and tin(II) chloride is spin-coated on fluorine-doped tin oxide (FTO) glass substrates, following which APPJ is used for converting the [...] Read more.

We characterize the time evolution (≤120 s) of atmospheric-pressure plasma jet (APPJ)-synthesized Pt-SnO_x catalysts. A mixture precursor solution consisting of chloroplatinic acid and tin(II) chloride is spin-coated on fluorine-doped tin oxide (FTO) glass substrates, following which APPJ is used for converting the spin-coated precursors. X-ray photoelectron spectroscopy (XPS) indicates the conversion of a large portion of metallic Pt and a small portion of metallic Sn (most Sn is in oxidation states) from the precursors with 120 s APPJ processing. The dye-sensitized solar cell (DSSC) efficiency with APPJ-synthesized Pt-SnO_x CEs is improved greatly with only 5 s of APPJ processing. Electrochemical impedance spectroscopy (EIS) and Tafel experiments confirm the catalytic activities of Pt-SnO_x catalysts. The DSSC performance can be improved with a short APPJ processing time, suggesting that a DC-pulse nitrogen APPJ can be an efficient tool for rapidly synthesizing catalytic Pt-SnO_x counter electrodes (CEs) for DSSCs. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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13 pages, 5488 KiB

Open AccessArticle

Mechanical and Microstructural Features of Plasma Cut Edges in a 15 mm Thick S460M Steel Plate

by Javier Aldazabal, Antonio Martín-Meizoso, Andrzej Klimpel, Adam Bannister and Sergio Cicero

Metals 2018, 8(6), 447; https://doi.org/10.3390/met8060447 - 11 Jun 2018

Cited by 8 | Viewed by 3835

Abstract

In general, the thermal cutting processes of steel plates are considered to have an influence on microstructures and residual stress distribution, which determines the mechanical properties and performance of cut edges. They also affect the quality of the surface cut edges, which further [...] Read more.

In general, the thermal cutting processes of steel plates are considered to have an influence on microstructures and residual stress distribution, which determines the mechanical properties and performance of cut edges. They also affect the quality of the surface cut edges, which further complicates the problem, because in most cases the surface is subjected to the largest stresses. This paper studies the influence of plasma cutting processes on the mechanical behavior of the cut edges of steel and presents the characterization results of straight plasma arc cut edges of steel plate grade S460M, 15 mm thick. The cutting conditions used are the standard ones for industrial plasma cutting. The metallography of CHAZ (Cut Heat Affected Zones) and hardness profiles versus distance from plasma cut edge surface are tested; the mechanical behavior of different CHAZ layers under the cut edge surface were obtained by testing of instrumented mini-tensile 300 µm thick specimens. Also, the residual stress distribution in the CHAZ was measured by X-ray diffraction. The results for the mechanical properties, microstructure, hardness, and residual stresses are finally compared and discussed. This work concludes that the CHAZ resulting from the plasma cutting process is narrow (about 700 µm) and homogeneous in plate thickness. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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10 pages, 2805 KiB

Open AccessArticle

Crystal Structures of GaN Nanodots by Nitrogen Plasma Treatment on Ga Metal Droplets

by Yang-Zhe Su and Ing-Song Yu

Metals 2018, 8(6), 419; https://doi.org/10.3390/met8060419 - 04 Jun 2018

Cited by 7 | Viewed by 3493

Abstract

Gallium nitride (GaN) is one of important functional materials for optoelectronics and electronics. GaN exists both in equilibrium wurtzite and metastable zinc-blende structural phases. The zinc-blende GaN has superior electronic and optical properties over wurtzite one. In this report, GaN nanodots can be [...] Read more.

Gallium nitride (GaN) is one of important functional materials for optoelectronics and electronics. GaN exists both in equilibrium wurtzite and metastable zinc-blende structural phases. The zinc-blende GaN has superior electronic and optical properties over wurtzite one. In this report, GaN nanodots can be fabricated by Ga metal droplets in ultra-high vacuum and then nitridation by nitrogen plasma. The size, shape, density, and crystal structure of GaN nanodots can be characterized by transmission electron microscopy. The growth parameters, such as pre-nitridation treatment on Si surface, substrate temperature, and plasma nitridation time, affect the crystal structure of GaN nanodots. Higher thermal energy could provide the driving force for the phase transformation of GaN nanodots from zinc-blende to wurtzite structures. Metastable zinc-blende GaN nanodots can be synthesized by the surface modification of Si (111) by nitrogen plasma, i.e., the pre-nitridation treatment is done at a lower growth temperature. This is because the pre-nitridation process can provide a nitrogen-terminal surface for the following Ga droplet formation and a nitrogen-rich condition for the formation of GaN nanodots during droplet epitaxy. The pre-nitridation of Si substrates, the formation of a thin SiN_x layer, could inhibit the phase transformation of GaN nanodots from zinc-blende to wurtzite phases. The pre-nitridation treatment also affects the dot size, density, and surface roughness of samples. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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14 pages, 4808 KiB

Open AccessArticle

Influence of Solvent and Electrical Voltage on Cathode Plasma Electrolytic Deposition of Al₂O₃ Antioxidation Coatings on Ti-45Al-8.5Nb Alloys

by Xu Yang, Zhipeng Jiang, Xianfei Ding, Guojian Hao, Yongfeng Liang and Junpin Lin

Metals 2018, 8(5), 308; https://doi.org/10.3390/met8050308 - 01 May 2018

Cited by 7 | Viewed by 3882

Abstract

Al₂O₃ coatings were prepared on Ti-45Al-8.5Nb alloys via cathodic plasma electrolysis deposition (CPED) in both 1.2 M Al(NO₃)₃ aqueous and ethanolic solutions. Different voltages were also applied during the deposition process to optimize coating properties. Coatings deposited [...] Read more.

Al₂O₃ coatings were prepared on Ti-45Al-8.5Nb alloys via cathodic plasma electrolysis deposition (CPED) in both 1.2 M Al(NO₃)₃ aqueous and ethanolic solutions. Different voltages were also applied during the deposition process to optimize coating properties. Coatings deposited in both solutions mainly consisted of γ-Al₂O₃, with some Al(OH)₃ found in coatings prepared in aqueous solution. Coatings prepared in ethanol solution exhibited better oxidation resistance at 900 °C as well as better substrate adhesion, which was mainly due to smaller crater sizes on coating surfaces. The deposition process was discussed in detail and the reason for the smaller craters examined. The results suggested that solution surface tension mainly influenced the average diameter of hydrogen bubbles that formed on cathode surfaces during the process. Smaller bubbles lead to both lower current densities on cathodes and smaller crater sizes on coatings. Full article

(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)

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