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10 pages, 3026 KiB

Open AccessArticle

Substrate Impact on MR Characteristics of Carbon Nano Films Explored via AFM and Raman Analysis

by Awais Siddique Saleemi, Muhammad Hafeez, Muhammad Saeed, Ali Abdullah, Muhammad Anis-ur- Rehman and Shern-Long Lee

Materials 2021, 14(13), 3649; https://doi.org/10.3390/ma14133649 - 30 Jun 2021

Cited by 2 | Viewed by 1424

Abstract

Recent advances in the fabrication and classification of amorphous carbon (a-Carbon) thin films play an active part in the field of surface materials science. In this paper, a pulsed laser deposition (PLD) technique through controlling experimental parameters, including deposition time/temperature and laser energy/frequency, [...] Read more.

Recent advances in the fabrication and classification of amorphous carbon (a-Carbon) thin films play an active part in the field of surface materials science. In this paper, a pulsed laser deposition (PLD) technique through controlling experimental parameters, including deposition time/temperature and laser energy/frequency, has been employed to examine the substrate effect of amorphous carbon thin film fabrication over SiO₂ and glass substrates. In this paper, we have examined the structural and magnetoresistance (MR) properties of these thin films. The intensity ratio of the G-band and D-band (I_D/I_G) were 1.1 and 2.4, where the C(sp²) atomic ratio for the thin films samples that were prepared on glass and SiO₂ substrates, were observed as 65% and 85%, respectively. The MR properties were examined under a magnetic field ranging from −9 T to 9 T within a 2-K to 40-K temperature range. A positive MR value of 15% was examined at a low temperature of 2 K for the thin films grown on SiO₂ substrate at a growth temperature of 400 °C using a 300 mJ/pulse laser frequency. The structural changes may tune the magnetoresistance properties of these a-Carbon materials. These results were demonstrated to be highly promising for carbon-based spintronics and magnetic sensors. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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13 pages, 4444 KiB

Open AccessArticle

Evaluation of Anti-Adhesion Characteristics of Diamond-Like Carbon Film by Combining Friction and Wear Test with Step Loading and Weibull Analysis

by Hiroki Mano and Tsuguyori Ohana

Materials 2021, 14(11), 2746; https://doi.org/10.3390/ma14112746 - 22 May 2021

Cited by 1 | Viewed by 1755

Abstract

Anti-adhesion characteristics are important requirements for diamond-like carbon (DLC) films. The failure load corresponding to the anti-adhesion capacity varies greatly on three types of DLC film (hydrogen-free amorphous carbon film (a-C), hydrogenated amorphous carbon film (a-C:H), and tetrahedral hydrogen-free amorphous carbon film (ta-C)) [...] Read more.

Anti-adhesion characteristics are important requirements for diamond-like carbon (DLC) films. The failure load corresponding to the anti-adhesion capacity varies greatly on three types of DLC film (hydrogen-free amorphous carbon film (a-C), hydrogenated amorphous carbon film (a-C:H), and tetrahedral hydrogen-free amorphous carbon film (ta-C)) in the friction and wear test with step loading using a high-frequency, linear-oscillation tribometer. Therefore, a new method that estimates a representative value of the failure load was developed in this study by performing a statistical analysis based on the Weibull distribution based on the assumption that the mechanism of delamination of a DLC film obeys the weakest link model. The failure load at the cumulative failure probabilities of 10% and 50% increased in the order ta-C < a-C:H < a-C and ta-C < a-C < a-C:H, respectively. The variation of the failure load, represented by the Weibull slope, was minimum on ta-C and maximum on a-C:H. The rank of the anti-adhesion capacity of each DLC film with respect to the load obtained by a constant load test agreed with the rank of the failure load on each DLC film at the cumulative failure probability of 10% obtained by Weibull analysis. It was found to be possible to evaluate the anti-adhesion capacity of a DLC film under more practical conditions by combining the step loading test and Weibull analysis. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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11 pages, 3099 KiB

Open AccessArticle

Electrical Conduction Properties of Hydrogenated Amorphous Carbon Films with Different Structures

by Masashi Tomidokoro, Sarayut Tunmee, Ukit Rittihong, Chanan Euaruksakul, Ratchadaporn Supruangnet, Hideki Nakajima, Yuki Hirata, Naoto Ohtake and Hiroki Akasaka

Materials 2021, 14(9), 2355; https://doi.org/10.3390/ma14092355 - 1 May 2021

Cited by 13 | Viewed by 2282

Abstract

Hydrogenated amorphous carbon (a-C:H) films have optical and electrical properties that vary widely depending on deposition conditions; however, the electrical conduction mechanism, which is dependent on the film structure, has not yet been fully revealed. To understand the relationship between the [...] Read more.

Hydrogenated amorphous carbon (a-C:H) films have optical and electrical properties that vary widely depending on deposition conditions; however, the electrical conduction mechanism, which is dependent on the film structure, has not yet been fully revealed. To understand the relationship between the film structure and electrical conduction mechanism, three types of a-C:H films were prepared and their film structures and electrical properties were evaluated. The sp²/(sp² + sp³) ratios were measured by a near-edge X-ray absorption fine structure technique. From the conductivity–temperature relationship, variable-range hopping (VRH) conduction was shown to be the dominant conduction mechanism at low temperatures, and the electrical conduction mechanism changed at a transition temperature from VRH conduction to thermally activated band conduction. On the basis of structural analyses, a model of the microstructure of a-C:H that consists of sp² and sp³-bonded carbon clusters, hydrogen atoms and dangling bonds was built. Furthermore, it is explained how several electrical conduction parameters are affected by the carrier transportation path among the clusters. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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18 pages, 5968 KiB

Open AccessArticle

Synthesis of Multilayered DLC Films with Wear Resistance and Antiseizure Properties

by Yucheng Li, Jun Enomoto, Yuki Hirata, Hiroki Akasaka and Naoto Ohtake

Materials 2021, 14(9), 2300; https://doi.org/10.3390/ma14092300 - 29 Apr 2021

Cited by 1 | Viewed by 1944

Abstract

Diamond-like carbon (DLC) films have attracted considerable interest for application as protective films in diverse industrial parts. This is attributed to their desirable characteristics, such as high hardness, low coefficient of friction, gas-barrier properties, and corrosion resistance. Antiseizure properties, in addition to wear [...] Read more.

Diamond-like carbon (DLC) films have attracted considerable interest for application as protective films in diverse industrial parts. This is attributed to their desirable characteristics, such as high hardness, low coefficient of friction, gas-barrier properties, and corrosion resistance. Antiseizure properties, in addition to wear resistance, are required during the die molding of polymer and polymer-matrix composite parts. Graphite films can be easily peeled because the vertically stacked graphene sheets are bonded via weak van der Waals forces. The present study demonstrates the fabrication of multilayered DLC/Cu films, where the Cu film functions as a catalyst for the formation of a graphite-like layer between the DLC and Cu films. The DLC/Cu film was synthesized on a Si (100) substrate via plasma-enhanced chemical vapor deposition and magnetron sputtering. The peelability, wear resistance, microstructure, texture, and cross-section of the film were experimentally analyzed. The results indicated a variation in the peelability with the deposition conditions of the Cu film that comprised particles with diameters of several nanometers. The DLC film at the interface in contact with the Cu film was transformed into a graphite-like state i.e., graphitized. The surface of the multilayered film exhibited antiseizure properties with the peeling of the upper DLC film. The multilayered film also exhibited wear resistance owing to the repeated appearances of a new DLC film. It is expected that the wear-resistant films with antiseizure properties demonstrated in the present study will be utilized in various industrial sectors. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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13 pages, 3074 KiB

Open AccessArticle

Effect of Energy and Temperature on Tetrahedral Amorphous Carbon Coatings Deposited by Filtered Laser-Arc

by Frank Kaulfuss, Volker Weihnacht, Martin Zawischa, Lars Lorenz, Stefan Makowski, Falko Hofmann and Andreas Leson

Materials 2021, 14(9), 2176; https://doi.org/10.3390/ma14092176 - 23 Apr 2021

Cited by 23 | Viewed by 2093

Abstract

In this study, both the plasma process of filtered laser-arc evaporation and the resulting properties of tetrahedral amorphous carbon coatings are investigated. The energy distribution of the plasma species and the arc spot dynamics during the arc evaporation are described. Different ta-C coatings [...] Read more.

In this study, both the plasma process of filtered laser-arc evaporation and the resulting properties of tetrahedral amorphous carbon coatings are investigated. The energy distribution of the plasma species and the arc spot dynamics during the arc evaporation are described. Different ta-C coatings are synthesized by varying the bias pulse time and temperature during deposition. An increase in hardness was observed with the increased overlapping of the bias and arc pulse times. External heating resulted in a significant loss of hardness. A strong discrepancy between the in-plane properties and the properties in the film normal direction was detected specifically for a medium temperature of 120 °C during deposition. Investigations using electron microscopy revealed that this strong anisotropy can be explained by the formation of nanocrystalline graphite areas and their orientation toward the film’s normal direction. This novel coating type differs from standard amorphous a-C and ta-C coatings and offers new possibilities for superior mechanical behavior due to its combination of a high hardness and low in-plane Young’s Modulus. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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17 pages, 2290 KiB

Open AccessArticle

Effect of Soft X-ray Irradiation on Film Properties of a Hydrogenated Si-Containing DLC Film

by Kazuhiro Kanda, Ryo Imai, Shotaro Tanaka, Shuto Suzuki, Masahito Niibe, Takayuki Hasegawa, Tsuneo Suzuki and Hiroki Akasaka

Materials 2021, 14(4), 924; https://doi.org/10.3390/ma14040924 - 15 Feb 2021

Cited by 5 | Viewed by 1923

Abstract

The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas [...] Read more.

The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas there was little change in their elemental composition. The reduction in volume was attributable to photoetching caused by SR, unlike the desorption of hydrogen in the case of exposure of hydrogenated DLC (H-DLC) film to soft X-rays. The ratio of the sp² hybridization carbon and sp³ hybridization carbon in the hydrogenated Si-DLC films, sp²/(sp² + sp³) ratio, increased rapidly from ~0.2 to ~0.5 for SR doses of less than 20 mA·h. SR exposure significantly changed the local structure of carbon atoms near the surface of the hydrogenated Si-DLC film. The rate of volume reduction in the irradiated hydrogenated Si-DLC film was 80 times less than that of the H-DLC film. Doping DLC film with Si thus suppresses the volume reduction caused by exposure to soft X-rays. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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18 pages, 11643 KiB

Open AccessArticle

Structural and Mechanical Properties of a-BCN Films Prepared by an Arc-Sputtering Hybrid Process

by Yuki Hirata, Ryotaro Takeuchi, Hiroyuki Taniguchi, Masao Kawagoe, Yoshinao Iwamoto, Mikito Yoshizato, Hiroki Akasaka and Naoto Ohtake

Materials 2021, 14(4), 719; https://doi.org/10.3390/ma14040719 - 3 Feb 2021

Cited by 7 | Viewed by 2671

Abstract

Amorphous boron carbon nitride (a-BCN) films exhibit excellent properties such as high hardness and high wear resistance. However, the correlation between the film structure and its mechanical properties is not fully understood. In this study, a-BCN films were prepared by an arc-sputtering hybrid [...] Read more.

Amorphous boron carbon nitride (a-BCN) films exhibit excellent properties such as high hardness and high wear resistance. However, the correlation between the film structure and its mechanical properties is not fully understood. In this study, a-BCN films were prepared by an arc-sputtering hybrid process under various coating conditions, and the correlations between the film’s structure and mechanical properties were clarified. Glow discharge optical emission spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy were used to analyze the structural properties and chemical composition. Nanoindentation and ball-on-disc tests were performed to evaluate the hardness and to estimate the friction coefficient and wear volume, respectively. The results indicated that the mechanical properties strongly depend on the carbon content in the film; it decreases significantly when the carbon content is <90%. On the other hand, by controlling the contents of boron and nitrogen to a very small amount (up to 2.5 at.%), it is possible to synthesize a film that has nearly the same hardness and friction coefficient as those of an amorphous carbon (a-C) film and better wear resistance than the a-C film. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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10 pages, 3253 KiB

Open AccessArticle

Surface Reformation of Medical Devices with DLC Coating

by Mao Kaneko, Masanori Hiratsuka, Ali Alanazi, Hideki Nakamori, Kazushige Namiki and Kenji Hirakuri

Materials 2021, 14(2), 376; https://doi.org/10.3390/ma14020376 - 14 Jan 2021

Cited by 14 | Viewed by 2667

Abstract

We evaluated the adhesion, friction characteristics, durability against bodily acids, sterilization, cleaning, and anti-reflection performance of diamond-like carbon (DLC) coatings formed as a surface treatment of intracorporeal medical devices. The major coefficients of friction during intubation in a living body in all environments [...] Read more.

We evaluated the adhesion, friction characteristics, durability against bodily acids, sterilization, cleaning, and anti-reflection performance of diamond-like carbon (DLC) coatings formed as a surface treatment of intracorporeal medical devices. The major coefficients of friction during intubation in a living body in all environments were lower with DLC coatings than with black chrome plating. DLC demonstrated an adhesion of approximately 24 N, which is eight times stronger than that of black chrome plating. DLC-coated samples also showed significant stability without being damaged during acid immersion and high-pressure steam sterilization, as suggested by the results of durability tests. In addition, the coatings remained unpeeled in a usage environment, and there was no change in the anti-reflection performance of the DLC coatings. In summary, DLC coatings are useful for improving intracorporeal device surfaces and extending the lives of medical devices. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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15 pages, 8999 KiB

Open AccessFeature PaperArticle

A Comprehensive Study about the Role of Crosslink Density on the Tribological Behavior of DLC Coated Rubber

by Suleyman Bayrak, Dominik Paulkowski, Klaus Werner Stöckelhuber, Benjamin Staar and Bernd Mayer

Materials 2020, 13(23), 5460; https://doi.org/10.3390/ma13235460 - 30 Nov 2020

Cited by 7 | Viewed by 2347

Abstract

The friction and wear behavior of coated rubber components is strongly dependent on the substrate properties. This work deals with the impact of the crosslink density, i.e., the hardness of the rubber substrate on the tribological performance of uncoated and coated rubber. The [...] Read more.

The friction and wear behavior of coated rubber components is strongly dependent on the substrate properties. This work deals with the impact of the crosslink density, i.e., the hardness of the rubber substrate on the tribological performance of uncoated and coated rubber. The hardness of nitrile butadiene rubber (NBR) is varied altering the sulfur content. Both the uncoated and coated rubber samples are characterized in terms of surface and mechanical properties. Tribological tests comprise the examination of the macroscopic contact area and the temperature in the contact zone. It was found that the functional layer enhances the wear resistance significantly. Apparently, the wear and friction behavior of the coated rubber correlates with the hardness and the bulk properties of the substrate material. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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26 pages, 4585 KiB

Open AccessEditor’s ChoiceReview

Properties and Classification of Diamond-Like Carbon Films

by Naoto Ohtake, Masanori Hiratsuka, Kazuhiro Kanda, Hiroki Akasaka, Masanori Tsujioka, Kenji Hirakuri, Atsushi Hirata, Tsuguyori Ohana, Hiroshi Inaba, Makoto Kano and Hidetoshi Saitoh

Materials 2021, 14(2), 315; https://doi.org/10.3390/ma14020315 - 9 Jan 2021

Cited by 90 | Viewed by 8539

Abstract

Diamond-like carbon (DLC) films have been extensively applied in industries owing to their excellent characteristics such as high hardness. In particular, there is a growing demand for their use as protective films for mechanical parts owing to their excellent wear resistance and low [...] Read more.

Diamond-like carbon (DLC) films have been extensively applied in industries owing to their excellent characteristics such as high hardness. In particular, there is a growing demand for their use as protective films for mechanical parts owing to their excellent wear resistance and low friction coefficient. DLC films have been deposited by various methods and many deviate from the DLC regions present in the ternary diagrams proposed for sp³ covalent carbon, sp² covalent carbon, and hydrogen. Consequently, redefining the DLC region on ternary diagrams using DLC coatings for mechanical and electrical components is urgently required. Therefore, we investigate the sp³ ratio, hydrogen content, and other properties of 74 types of amorphous carbon films and present the classification of amorphous carbon films, including DLC. We measured the sp³ ratios and hydrogen content using near-edge X-ray absorption fine structure and Rutherford backscattering-elastic recoil detection analysis under unified conditions. Amorphous carbon films were widely found with nonuniform distribution. The number of carbon atoms in the sp³ covalent carbon without bonding with hydrogen and the logarithm of the hydrogen content were inversely proportional. Further, we elucidated the DLC regions on the ternary diagram, classified the amorphous carbon films, and summarized the characteristics and applications of each type of DLC. Full article

(This article belongs to the Special Issue DLC (Diamond-Like Carbon) Film Formation and Application)

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