Hardness Of Films Research Articles

Radiation hardness evaluation of ε-Ga2O3 thin-film devices under swift heavy ion irradiation

The ultra-wide band gap (∼4.9 eV) and extremely large breakdown field strength (∼8 MV/cm) enable ε-Ga2O3 as an ideal materials candidate for high-performance power devices and solar-blind photodetectors. For the purpose of deep space applications explorations, comprehensive study of the effects of particle irradiation on the lattice stability and electronic properties of ε-Ga2O3 are of pivotal importance. In this work, leveraging a unique Ta radiation source, we interrogate the radiation hardness of ε-Ga2O3 thin films after 1907 MeV Ta swift heavy ion (SHI) irradiation. Detailed characterizations of the structural and optical properties show that the morphology and lattice structure are disrupted, with an increase of the band gap. Additionally, X-ray photoelectron spectroscopy experiments combining density functional theory calculations corroborate extrinsic flux-induced high concentration defects in the film, which lead to truncated photo-response performance of the device. However, even upon irradiation with a fluence of 5 × 1010 cm−2, the overall performance of the device remains robust and substantial. This outstanding radiation hardness of ε-Ga2O3 thin films rationalizes their potential usage for space applications.

Effects of Bias Voltage and Substrate Temperature on the Mechanical Properties and Oxidation Behavior of CrWSiN Films

CrWSiN films were prepared through the co-sputtering technique, and the process variables were substrate bias voltage and temperature. The mechanical properties of hardness and elastic modulus of the CrWSiN films were dominantly affected by their average crystallite size and by substrate bias voltage and temperature. Moreover, the effect of substrate temperature was more evident than that of substrate bias. The highest hardness and elastic modulus of 42.6 and 459 GPa, respectively, were obtained for the Cr20W28Si9N43 film fabricated at a substrate temperature of 400 °C, which exhibits an evident advantage over the 25.0 and 323 GPa values for the Cr21W28Si9N42 film fabricated at room temperature. In contrast, an increase in negative bias voltage to −100 V on the substrate decreased the mechanical properties compared to one prepared using a similar process without applying the negative bias voltage. The oxidation resistance of the Cr-enriched Cr37W4Si10N49 and Cr37W5Si10N48 films was superior to that of the Cr20W28Si9N43 films with near-equal Cr and W contents annealed at 900 °C in air. The formation of a surficial Cr2O3 layer plays a vital role in restricting subsequent oxidation for CrWSiN films.

Growth pattern of soft-spark micro-arc oxide coating on titanium alloy in silicon anion electrolyte

Soft-spark micro-arc oxidation (MAO) is considered a potential solution for eliminating the porosity on the surface coating of titanium alloys during the MAO process. However, the mechanisms behind soft-sparking and the growth of coatings on Ti alloys are not yet fully understood. This study aimed to investigate the growth pattern of soft-spark MAO coating on titanium alloys by using sodium silicate as the electrolyte and manipulating the soft-sparking duration. The research focused on analyzing the positive and negative pulse voltage-time response curves, surface micromorphology, surface composition, cross-sectional structure, phase composition, dynamic potential polarization curve, microhardness, and thickness growth curve during the soft-spark process. The research findings revealed that soft spark discharges occurred in the plasma atmosphere near the surface of the external porous layer. The sparks penetrated the weak points of the amorphous interface layer (existing between the MAO coating and the substrate), forming filamentary discharges within the coating. This phenomenon led to the formation of a significant amount of rutile phases and bubble pores within the soft-spark coating, promoting the expansion of soft-sparks into the coating and facilitating the growth of the soft-spark coating. While the inner hardness of the soft-spark MAO film reached 1146 HV, the plasma atmosphere discharge also led to the formation of numerous filamentary channels and gas pores within the coating. Consequently, the coating's corrosion resistance did not show any improvement.

Rotating-Magnetic-Field-Assisted Electrodeposition of Copper for Ambulance Medical Equipment

This study examines the influence of the application of a rotating magnetic field in the electrodeposition of copper (Cu). During the electrodeposition, five constant magnets were rotated (500 and 800 rpm) towards the bottom of the sample. To investigate deposition rate, surface morphology, phase, structure, corrosion resistance, and hardness in deposited Cu using a weighing scale, a scanning electron microscope equipped with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), potentiodynamic polarization, and hardness tester respectively. Bacterial activity was also evaluated through this research. Morphological surface observations showed that the increase in the rotational speed of the magnets during the electrodeposition process led to a smooth surface. A perfect Cu phase covers Al alloy with no oxide. The potentiodynamic polarization demonstrated by the increase in the rotating led to a shift to the more positive value of the corrosion potential. Moreover, the corrosion current also decreases with the increase in the rotating speed of the magnets. Less crystallite size promoted forming a higher hardness and inhibition zone of the Cu films.

Film Hardness Evaluation in Hard Film/Substrate Composites by Conical Indentation

Film Hardness Evaluation in Hard Film/Substrate Composites by Conical Indentation

A smart electroplating approach to fabricate mechanically robust and fluorine-free Ni-W alloys based superhydrophobic coating on Al alloy

In this study, a novel and smart electroplating method was presented to fabricate a mechanically robust superhydrophobic coating on Al alloys. The superhydrophobic coating was composed of Ni-W alloy film with high hardness and stearic acid (STA) with low surface energy, providing excellent abrasive resistance, anti-corrosion properties, and self-cleaning ability. Specifically, a thin transition layer of Al-Ni-W was pre-electroplated on the Al alloy substrate by utilizing Al as anode and Al alloys as cathode in Ni-W ions aqueous solution, which overcome the difficulty of directly electroplating alloys coating on the Al alloys surface. Finally, a robust composite superhydrophobic film was achieved after coating STA layer on Al alloy/Al-Ni-W/Ni-W substrate. As anticipated, the as-prepared Al alloys demonstrates excellent mechanical durability and chemical stability, including wear resistance, hardness, corrosion resistance and self-cleaning with a champion water contact angle of 163° and corrosion protection efficiency of 99.4%. The Leeb hardness of superhydrophobic film coated Al alloys was enhanced by 87.1% compared to the pristine Al alloys, increasing from 325 ± 3 to 608 ± 4. This method provides a universal pathway for fabricating robust superhydrophobic film on the active metallic substrates.

Synthesis and comprehensive synchrotron-based structural analysis of Si-doped nanodiamond composite films deposited on cemented carbide

Si-doped nanodiamond composite (NDC) films were deposited on unheated WC − Co substrates by coaxial arc plasma deposition for advanced cutting tools applications. The nanoindentation test revealed changes in films hardness and Young's modulus attributed to various Si doping concentrations (0, 1, 5, and 20 at.%) and the catalytic effects of Co diffused from the substrate surface into the films. To reveal the physical origin behind these changes, the films' structure was examined by synchrotron-based Auger electron spectroscopy (AES), soft X-ray photoemission spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The AES and XPS analysis showed a consistent correlation between nanoindentation measurements and the estimated C sp3 fraction in the films. The NEXAFS spectra revealed intense C − C σ* resonance, consistent with the measured film hardness. The 1 at.% Si-doped film, deposited with an undoped NDC buffer layer to mitigate the Co catalytic effects, exhibited the highest hardness of 60 GPa, the largest C sp3 fraction, and the most intense CC σ* peak. Si doping resulted in the formation of C − Si sp3 bonds at the expense of C sp2 bonds, increasing the fraction of C sp3 bonds and enhancing film hardness. The synchrotron-based analysis effectively revealed the electronic states of NDC hard coatings, particularly after the removal of surface contaminants through mechanical polishing.

Understanding the fast formation mechanism of hard nanoporous alumina films on aluminum in acidic solutions containing nitric acid

Nanoporous alumina films formed on aluminum via anodization are widely used for scientific and technical purposes owing to their various advantageous properties, including excellent corrosion and wear resistance, good thermal and electrical insulation, and facile producibility at low cost. Herein, we report a novel approach to fabricate hard porous anodic alumina (PAA) films by adding an appropriate amount of nitric acid to sulfuric-, oxalic-, and phosphoric-acid solutions at critical high current densities. The effects of the nitric additives on the anodizing behavior, film growth mechanism, microstructure, chemical composition, film thickness, microhardness, and appearance of the PAA films formed from various solutions were systematically investigated. The addition of nitric acid enhanced the formation of alumina and resulted in fast growth rates of 196 μm/h and 166 μm/h for sulfuric- and oxalic-based solutions, respectively, while maintaining high hardness of approximately 380 and 430 HV0.1, respectively. The surface hardness of the films decreased to some extent with the increase in nitric acid concentration and/or film thickness owing to the strong corrosive nature of nitric acid during prolonged anodization, although nitrogen inclusion in anodic alumina films was not detected through X-ray photo-electron spectroscopy, which differs from the other acidic anions. In particular, the barrier layer thickness and pore intervals of PAA films increased with the nitric concentration in the aforementioned solutions, leading to a fast growth rate and high hardness inside the films.

Study on the tribological properties and corrosion resistance of the in-situ grown Zn–Al-LDHs film on anodic aluminum surface

In this study, the LDHs film was successfully prepared in-situ on the surface of AAO substrate. By using SEM, EDS, XRD, Vickers microhardness tester, pull-off tester, electrochemical workstation and tribometer, the morphology, composition, crystal structure, hardness, binding force, corrosion resistance and tribological performance of the LDHs film produced within a range of pH values (6.5/7.5/8.5/9.5) were researched. The results revealed that the pH of solution is important in the formation of Zn-Al-LDHs film and their characteristics: when the pH of 8.5, the LDHs film surface is the most smooth and flat, the crystal structure of LDHs nanosheets is the most complete and grows perpendicular to the substrate surface, the thickness of the film reaches to about 96.77 μm, and the interfacial bonding force achieves to about 8.50 MPa. The LDHs film could effectively enhance the corrosion resistance by sealed the anodic aluminum oxide film, and the dry friction coefficient of alumina substrate decreases to about 0.2 for 3600 s, which exhibits excellent tribological properties.

Piezoelectric and nanomechanical properties of lead-free K0.1Na0.9Nb0.97Sb0.03O3 (KNNS) thin films grown by radio frequency sputtering

Ferroelectric (piezoelectric) lead-free K0.1Na0.9Nb0.97Sb0.03O3 (KNNS) thin films were grown on (111) Pt/Ti/SiO2/Si substrates, using radio frequency sputtering. The aim of this work is to determine both the ferroelastic and piezoelectric behaviors associated with the redirection of domains in the lead-free piezoelectric KNNS material. The d33 piezoelectric coefficient was measured using Piezoresponse Force Microscopy (PFM). The value of the piezoelectric parameter (d33 = 73 pm/V) observed for KNNS films is more than 25% higher than d33 values for other lead-free piezoelectric materials reported in the literature. The value of the yield point for the tetragonal KNNS films is Y= 3,83 ± 0.5 GPa. The Elastic modulus is Ef = 122 GPa, and the hardness is Hf= 8.95 GPa. The scratch hardness of the KNNS thin films is Hscr = 5.45 ± 0.2 GPa. Resistance to abrasion is less affected by surface morphological changes than by the indentation measurements.

Cathodic arc deposition of nanocrystalline titanium nitride thin film on fluorine doped tin oxide coated glass substrate: Crystal structural, microstructural, mechanical, optical and electrical properties

The nanocrystalline titanium nitride (TiN) films were deposited on fluorine doped tin oxide (FTO) coated glass substrates for the first time by cathodic arc deposition. The crystalline phase and orientation, growth morphology, surface roughness, hardness, scratch adhesion, electrical resistivity, optical absorption and bandgap of the TiN films were investigated. The GI-XRD confirmed the formation of cubic TiN and crystallographic orientation growth. The 2150 nm thick TiN film showed (111) orientation due to columnar growth patterns, while the 650 nm TiN film formed with the (200) orientation. The grain size of TiN films was 50–200 nm by FESEM and AFM analyses, and it was formed as elongated nanocrystals of 65–125 nm width and 120–250 nm lengths. The microhardness of the 650, 1000 and 2150 nm TiN thin films was measured to be 836, 943 and 1281 HV0.05 respectively. The scratch adhesion test demonstrated a good adhesive strength up to a critical load of 10 N and beyond the delamination occurred. The electrical resistivity of TiN film found to vary with thickness, the 650 nm TiN film showed a low resistivity of 16 × 10-6 Ω cm, which is comparable with the electrical resistivity of platinum and magnetron sputtered TiN film. The UV-Vis-NIR diffused reflectance spectroscopic studies of the TiN thin film showed a sharp absorption at 448 nm due to plasmon absorption and Tauc plot showed direct band gap of 2.1 eV. The results demonstrated that cathodic arc deposited nanocrystalline TiN thin film deposited on FTO glass substrate can be used as counter electrode for dye sensitized solar cell (DSSC) applications.

Influence of Surface Roughness on Nanocrystalline Diamond Films Deposited by Distributed Antenna Array Microwave System on TA6V Substrates

In this study, the characteristics of nanocrystalline diamond films synthesized at low surface temperature on Ti-6Al-4V (TA6V) substrates using a distributed antenna array microwave reactor aiming at biomedical applications were investigated. The surface roughness of the TA6V substrates is varied by scratching with emery paper of 1200, 2400, 4000 polishing grit. Nanocrystalline diamond (NCD) coatings with morphology, purity, and microstructure comparable to those obtained on silicon substrates usually employed in the same reactor and growth conditions are successfully achieved whatever the polishing protocol. However, the latter has a significant effect on the roughness parameters and hardness of the NCD films. The use of the finest polishing grit thus permits us to enhance the hardness value, which can be related to the work-hardening phenomenon arising from the polishing process.

Sustainable Flame Retardant Coatings Derived from Chinese Lacquer Blend with Synergistic Flame Retardant Silicon-Modified Ammonium Polyphosphate

The intumescent flame retardant has a high efficiency of carbonization, oxygen barrier, and thermal interruption effect, which is considered to be a promising green and environmentally friendly flame retardant. Herein, we demonstrated a new approach to improve the flame retardant performance of Chinese lacquer films by adding silicon modified ammonium polyphosphate (SAPP), leading to superior flame retardant. SAPP drastically raised the limiting oxygen index (LOI) from 20.1% to 30.6%, and at the same time, the impact resistance was increased from 7 cm to 20 cm without changing the hardness of the lacquer films. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy were used to investigate the chemical components and morphology of the residual char of Chinese lacquer and SAPP composite films. The thermal degradation process of films was detected and analyzed by thermogravimetry and microcalorimetry, and the possible flame retardant mechanism was discussed. This simple approach opens up a new way to design for improved flame retardancy of organic film polymers.

Enhanced wear resistance and surface properties of oxide film coating on biocompatible Ti45Nb alloy by anodization method

β-Titanium alloys have become increasingly popular as biomaterials because of their low modulus of elasticity and superior corrosion properties in recent years. β-titanium alloy containing niobium is also a biocompatible and non-toxic material. Among β-Ti alloys, Ti45Nb is one of the most remarkable alloys for its superior properties as a biomaterial. This alloy has superior properties due to low elasticity modulus and non-toxic elements, but its surface properties are inadequate for biomaterial applications. Therefore, various surface treatments are applied to improve the surface properties of these alloys. In this study, an oxide film layer was formed on the Ti45Nb surface under different potential conditions by the anodizing method. The effects of these factors on friction, wear, and contact angle measurements were investigated. The structural properties of the oxide film coated samples were analyzed with XRD and their surfaces and cross-sectional images were observed by SEM. Also, the surface roughness and nanoindentation tests were performed. In this regard, it was determined that oxide film thickness, surface roughness and hardness increased with the increase of anodization potential. The contact angle of the samples decreased with the increase in the anodization potential and the surface tension of the materials increased. The highest nanohardness of about 4.19 GPa was obtained from 150 TA samples. The elasticity modulus of the untreated sample was about 63 GPa, while the anodized samples ranged from an average of 31 to 83 GPa. The wear results revealed that the anodization process improved the wear resistance of the Ti45Nb alloy. As a result, the sample anodized at 200 V for 30 min exhibited optimum surface roughness, morphology and high wear resistance.

Wear Mechanism of TC4 Titanium Alloy with TiN Coating against Self-Lubricating Fabric

Vapor deposition technology can improve the surface wear resistance of titanium alloys, and prepare lightweight and corrosion-resistant self-lubricating spherical plain bearings made of titanium alloys. However, titanium alloys with hard films can be worn by soft self-lubricating fabrics. This paper focuses on the wear problem of TiN coating on the surfaces of self-lubricating spherical plain bearings based on titanium alloys. Ring-to-plate wear tests were carried out to study the tribological properties of TiN coating on TC4 titanium alloy against self-lubricating fabric under different working conditions (load: 500–2000 N and speed: 100–500 r/min), along with the investigation of the wear mechanism of TiN coating, and the evaluation of applicable working conditions of GE15 type self-lubricating spherical plain bearings through swing tests. The results have revealed that TiN coatings can maintain a certain friction distance without wear. Increasing friction speed and load can make TiN coatings more prone to wear. A thick transfer film can protect the TiN coating from wear. The main wear mechanism is attributed to fatigue wear induced by the repeated formation and peeling of transfer films. The GE15 bearing has achieved a self-lubricating fabric wear of approximately 0.04 mm when the swinging for 500 m (25,000 times) is under a specific condition of 27 kN and 0.2 Hz without damaging the inner ring of the bearing. The bearing is suitable for swing conditions with applied loads below 27 kN. This study provides a fundamental understanding of designing self-lubricating spherical plain bearings made of titanium alloys.

Preparation of Nanocellulose from Coffee Pulp and Its Potential as a Polymer Reinforcement.

Coffee is one of the most valued agricultural products regarding its high commercialization rate. During the production of coffee beans, coffee pulp is obtained as one of the main byproducts with a cellulose content of more than 30% of dry weight. This research focused on the value-added potential of coffee pulp fiber as the reinforcement in composite materials. The nanocellulose coffee pulp (NCP) from the coffee pulp (CP) was prepared and subsequently used as a filler to reinforce the polyvinyl alcohol (PVA) matrix for the improvement of PVA composite properties. The CP was treated via alkali and bleaching treatment before the production of NCP using the acid hydrolysis treatment. The TEM result of NCP showed the successful preparation of NCP with an average diameter of 16.03 ± 4.70 nm with increasing crystallinity size and crystallinity index. The effect of glycerol (G) in the PVA matrix was observed. The result showed that glycerol had a play-role as a plasticizer for increased flexibility and decreased hardness and brittleness of PVA nanocomposite film. The nanocomposite film of PVA/G/NCP was fabricated with various ratios of NCP through the casting method. It was shown that the physical properties were improved with the presence of NCP in the PVA matrix compared to the neat PVA film.

Influence of oxalic additive on etidronic acid anodizing of aluminum alloy

The anodizing in etidronic acid (HEDP) and oxalic acid (H2C2O4) mixed electrolytes was conducted. The anodizing parameters were optimized based on the evaluation of energy consumption, growth efficiency, and hardness of PAA film. The results indicate that continuous and uniform PAA films can be fabricated in HEDP/H2C2O4 solutions in any proportion, and both the anodizing voltages and roughnesses of PAA films decreased with the H2C2O4 content. The moderate amount of H2C2O4 could lead to an increase in the formation efficiency of PAA films. The hardness of the PAA film prepared in HEDP/H2C2O4 electrolyte could reach up to ∼660 HV. Moreover, a surface resembling lotus leaves could be formed due to the corrosion of PAA films with sub-micron interpore distance by H2C2O4 during anodizing, and a superhydrophobic surface with a contact angle of ∼153° could be obtained after it was modified via stearic acid.

Structure and mechanical properties of diamond‐like carbon films prepared by pulsed laser‐induced cathodic vacuum arc technique

Diamond‐like carbon (DLC) films are prepared by pulsed laser‐induced cathodic vacuum arc technique with various arc voltages. The purpose of the research is to investigate the influence of the arc voltage on the structure, mechanical, and tribological properties of DLC films. The results from Raman spectra and XPS show that with increasing arc voltage from 180 to 280 V, the sp3 content in the DLC film increases from 43.2 to 56.9 at%, then follows by a significant decrease with further increasing arc voltage to 330 V. The trend in the mechanical properties of DLC films correlates well with the sp3 content in the films. The maximum hardness, modulus, and adhesion critical load (Lc) of the DLC film is obtained in the film deposited at 280 V; the values of that are 46.4 GPa, 380.6 GPa, and 620 mN, respectively. The friction coefficient of the films is between 0.1 and 0.2, and the film deposited at 280 V has the minimum wear rate with a value of 3.2 × 10−17 m3/m.N. It is concluded that the DLC films with high sp3 content (ta‐C, tetrahedral amorphous carbon) not only have good mechanical properties but also have excellent tribological properties, which provides a promising application for wear resistance parts.

Low-Regioregularity Polythiophene for a Highly Sensitive and Stretchable Gas Sensor

In this study, we examined how the regioregularity of poly(3-hexylthiophene) (P3HT) affects molecular packing, free volume, charge transport, and gas sensing properties. Our results showed that the presence of regular alkyl side chains on the polymer backbone promoted a high degree of structural order in regioregular P3HT molecules, leading to a compact packing density and reduced free volume. Consequently, it was more challenging for NO2 molecules to interact with the hole charge carriers in the conductive channel. On the other hand, the regiorandom P3HT films displayed a larger free volume, attributed to the irregular side chains, which facilitated the gas-analyte interaction while impeding efficient charge transport. Thus, these films exhibited greater sensitivity to analyte gas molecules. The molecular order, packing density, and hardness of P3HT films were confirmed through the use of multiple techniques, including UV-vis spectroscopy, atomic force microscopy, and grazing-incidence X-ray diffraction. Additionally, the regiorandom P3HT films showed enhanced mechanical flexibility compared to the regioregular films. In conclusion, our findings emphasize that the regularity of polymer molecules plays a significant role in determining the charge carrier transport and gas adsorption characteristics.

Characteristics and corrosion resistance of hard-anodised 6061-T6 aluminium alloy

ABSTRACT Hard anodic coatings were formed on 6061-T6 aluminium alloy samples using direct current. Surface morphology and cross-section of coatings, as well as their hardness and corrosion behaviour, were studied. It was found that decreasing the applied current density from 55 to 35 mA cm−2 resulted in more uniform coatings with fewer surface defects, lower porosity, and higher hardness values. The optimum electrolyte concentration and hard-anodising time, where less defective coatings were achieved, were found to be 180 g L−1 and 50 min, respectively. The hardness of the optimum film was around 500 HV, and its corrosion current density was 3.2 × 10−9A cm−2. All other samples that were produced at different current densities (30-55 mA cm−2), times (40-100 min), and electrolyte concentrations (25-220 g L−1) had lower hardness and corrosion resistance than the optimum coating. The polarisation resistance of the optimum coating was about 1100 times higher than the bare substrate.