Physical Vapor Deposition Research Articles

Effects of PVD CrAlN/(CrAlB)N/CrAlN Coating on Pin–Disc Friction Properties of Ti2AlNb Alloys Compared to WC/Co Carbide at Evaluated Temperatures

Physical vapor deposition (PVD) coatings could affect the friction performance at the contact interface between Ti2AlNb alloy parts and tool couples. Suitable coating types could improve the friction properties of Ti2AlNb alloy while in contact with WC/Co carbide. In this study, the linear reciprocating pin–disc friction tests between the Ti2AlNb alloy and the WC/Co carbide tool couple, with the sole variation of the PVD CrAlN/(CrAlB)N/CrAlN coating were conducted within the temperature range of 25–600 °C. The antifriction properties of the Ti2AlNb alloy were estimated using the time-varied friction coefficients, the alloy wear rate, worn surface topography, worn surface element, and wear mechanism analysis. The results showed that the PVD CrAlN/(CrAlB)N/CrAlN coating could decrease the average friction coefficient and alloy wear rate compared to the uncoated WC/Co carbide couple. The apparent adhesive wear and abrasive wear of the Ti2AlNb alloy could be improved due to the PVD coating at evaluated temperatures. The PVD CrAlN/(CrAlB)N/CrAlN coating could be utilized to improve the antifriction properties of the Ti2AlNb alloy, which may be deposited on the cutting tool to improve the machining performance of Ti2AlNb alloys in future aerospace machining industry.

Process Development of Aluminum Electroplating from an Ionic Liquid on 150 mm Wafer Level.

This paper focuses on the development of electroplating on 150 mm wafer level for microsystem technology applications from 1-Ethyl-3-methylimidazolium chloride (EMImCl) with Aluminumtrichloride (AlCl3). The deposition was carried out on 150 mm wafers with Au or Al seed layers deposited by physical vapor deposition (PVD). The electrodeposition was carried out using pattern plating. On the Au seed layer, bipolar pulse plating was applied. Compared to the Au seed layer, the electrodeposition on the Al seed layer was favorable, with lower current densities and pulsing frequencies. Utilizing the recurrent galvanic pulses and avoiding ionic liquid convection, inhomogeneities lower than 15% were achieved with a laboratory plating cell. One major aspect of this study was the removal of the native Al oxide prior to deposition. It was investigated on the chip and wafer levels using either current- or potential-controlled removal pulses. This process step was affected by the plasma treatment of the wafer, thus the surface free energy, prior to plating. It turned out that a higher surface free energy hindered proper oxide removal at a potential of 3 V. The theory of oxide breakdown based on electrostriction force via the electrical field was applied to discuss the findings and to derive conclusions for future plating experiments.

Protective layers of zirconium alloys used for claddings to improve the corrosion resistance

Abstract Zirconium alloys are used as a cladding material for fuel elements in nuclear reactors. In the case of severe accident conditions, the possible rapid oxidation of zirconium in steam or/and air may result in intense hydrogen generation and hydrogen–oxide mixture explosion. Advanced technologies for increasing the corrosion resistance of claddings are being investigated in two directions: (a) protective coatings on Zr alloys and (b) the use of new materials for claddings. Coatings with silicon may provide a more protective barrier than the ZrO2 films formed on an alloy cladding during nuclear plant operations. These coatings may also serve as a protective barrier during high-temperature accidents. The current work aimed at developing protective coatings with silicon on zirconium alloys. Multielemental Zr–Si–Cr coatings were formed on Zry-2 alloy using the physical vapor deposition (PVD) method. Long-term oxidation tests were carried out under the following conditions: 360°C/195 bar/63 days/water-simulating PWR water. Obtained results show the protective character of formed layers. The material in the form of silicon carbide grains covered with yttrium–aluminum garnet (SiC + YAG) was prepared using the sol–gel method. The formed powder is the main component for coating formation on Zr–1Nb alloy using the method of suspension plasma spraying (SPS).

Design and fabrication of a fast-response and low-energy input micro igniter

In this study, we innovatively combine direct ink writing (DIW) and physical vapor deposition (PVD) to fabricate a novel micro igniter with fast-response and low-energy input characteristics. The igniter comprises a 5×5 mm² metal film bridge with gold contact pads. The metallic resistance is fabricated using a series of photolithography, metal deposition, and lift-off processes. After evaluating titanium and chromium as the resistive filament, titanium was selected due to its superior reactivity when in contact with CuO leading to reduced ignition energy. Onto the resistive titanium layer, either thermite multilayer films and/or energetic inks are deposited to achieve a head-to-head comparison of ignition characteristics. We show that igniters powered by (CuO/Ti)5 bilayers and Al/CuO/PVDF as energetic ink demonstrate the equivalent ignition performance as reactive (CuO/Ti)5 multilayered igniter. The ignition delay and ignition energy are below 1 ms and 2 mJ, respectively, while the flash intensity is approximately one decade higher than what is typically achieved with conventional micro-igniters. Furthermore, its ignition behaviour can be readily adjusted by altering the constituents of the fuel/oxidizer or adjusting the ratio of multilayer/inks, thereby allowing for easy adaptation of the micro-igniter to meet the diverse requirements of various applications.

Electrical properties and field emission characteristics of ITO nanorod thin films synthesized by electron beam physical vapor deposition

Electrical properties and field emission characteristics of ITO nanorod thin films synthesized by electron beam physical vapor deposition

Development of an electrochemical biosensor with TiN nano-electrode arrays for IL-6 detection

In this study, we developed a novel electrochemical biosensor for detecting IL-6 that uses a nano-electrode array (NEA) fabricated via standard CMOS processing. Miniaturizing the electrodes to the nanoscale and arranging them in an array to form an NEA facilitated the creation of a higher electric field magnitude, compared to that available via the use of microelectrodes, that could be used to improve biosensor sensitivity. Additionally, the array configuration of the NEA aided in providing sufficient reaction sites. Each nano-electrode in the NEA was cylindrically shaped, with a radius of 0.1 µm, and a top layer formed by TiN physical vapor deposition. Each NEA biosensor was divided into four independent banks, with each bank including a set of WE, CE and RE. These banks were capable of independently inputting and outputting electrical signals. This design allowed the NEA biosensor to undergo selective modification by CV input. In this study, we discuss and address material and contamination issues associated with CMOS-produced NEAs and their uses as biosensors. To ameliorate these issues, we stored materials and products in a nitrogen-controlled cabinet and conducted pretreatment cleaning on the electrodes. Both steps had a noticeable impact on the cleanliness of the electrode surfaces. These optimized conditions resulted in a remarkable 96.6 % reduction in Rct. The NEA surface was functionalized by electrochemically grafting diazonium salts subsequently immobilized with anti-IL-6 antibodies via EDC/NHS chemistry. The resulting NEA biosensor demonstrated sufficient sensitivity to rapidly distinguish inflammatory conditions and disease severity. This showcases the potential for using NEA devices mass-produced via standard CMOS processing as electrodes for biosensors.

Microstructure evolution of carbon films, grown by physical vapor deposition, when substrate temperature is increased

We study how the increases of substrate temperature influence the structural properties of carbon films deposited by physical vapor deposition (PVD) techniques. We installed and adapted a heating system inside the deposition chamber, which can reach temperatures as high as 700 °C. Here we develop an experimental setup that allows us to obtain large films of the desired material on any substrate, with deposition times of the order of a minute. The characterization is based mainly on the analysis of the Raman spectra, where the evolution of the G and D peaks corresponding to the material in its amorphous phase is observed. With the increase of substrate temperature, the sp2 zones grow. A displacement to the right of the G peak and an increase in the ID/IG ratio is seen. At 700 °C a 2D zone at a frequency greater than 2000 cm−1 appears. Four Lorentzian-shaped bands are necessary to account for the peaks at this zone, whose centers correspond to different combinations of first-order ones. This shows that we are transitioning from an amorphous to a carbon phase with more ordered or graphitic zones and that we are near the crystallization point. This opens the path to produce structures similar to graphene using this method of deposition. The Tauc gap energy ratio decreases as temperature increases indicating that there is a graphitization of the sample. Transmission FTIR study is carried out at some of the intermediate temperatures, determining the type of bond at low frequencies. These bonds are consistent with the ones of the hydrogenated amorphous carbon (a-C:H) structure.

Structural Health Monitoring of Fiber Reinforced Composites Using Integrated a Linear Capacitance Based Sensor.

The demand for fiber-reinforced polymers (FRPs) has significantly increased in various industries due to their attributes, including low weight, high strength, corrosion resistance, and cost-efficiency. Nevertheless, FRPs, such as glass and Kevlar fiber composites, exhibit anisotropic properties and relatively low interlaminar strength, rendering them susceptible to undetected damage. The integration of real-time damage detection processes can effectively mitigate this issue. This paper introduces a novel method for fabricating embedded capacitive sensors within FRPs using a coating technique. The study encompasses two types of fibers, namely glass and Kevlar fiber/epoxy composites. The physical vapor deposition (PVD) technique is employed to coat bundle fibers with conductive material, thus creating embedded electrodes. The results demonstrate the uniform distribution of nanoparticles of gold (Au) along the fibers using PVD, resulting in a favorable resistance of approximately ≈100 Ω. Two sensor configurations are explored: axial and lateral embedding of the coated yarn (electrodes) to investigate the influence of load direction on the coating yarn. Axial-sensor configuration specimens undergo tensile testing, showcasing a linear response to axial loads with average sensitivities of 1 for glass and 1.5 for Kevlar fiber/epoxy composites. Additionally, onset damage is detected in both types of fiber composites, occurring before final fracture, with average stress at the turning point measuring 208 MPa for glass and 144 MPa for Kevlar. The lateral-sensor configuration for glass fiber-reinforced polymer (GFRP) exhibits good linearity towards strain until failure, with average gauge factors of 0.25 and -2.44 in the x and y axes, respectively.

Evolution of 2D MoO3 layer structures on Pd(100): interplay of interfacial interactions and polarity

Abstract We explore the structural evolution of two-dimensional (2D) MoO3 films beyond the monolayer (ML), which have been prepared by physical vapor deposition and post-oxidation onto a Pd(100) surface, and characterized by the tools of surface science and density functional theory (DFT) calculations. According to DFT, the most stable oxide layers are stoichiometric, and derive their energetic stability from the low cost of creating 2D freestanding layers from the orthorhombic bulk phase, good matching to Pd, and the particularly strong adhesion to the substrate. The observed 2D MoO3 layers are distinguished by well-ordered linear defects, such as domain boundaries in the ML, and misfit dislocations in the bilayer (BL). Applying reactive oxidation preparation conditions results in the formation of ordered arrays of nanostructures, nanowires and nanoclusters, in the MoO3 BL. The formation of such linear structures is accounted for in the DFT by models of missing row defects of various orientations and stoichiometries. Their relative stability is rationalized in terms of the number of broken Mo–O bonds, the polar character of the nanostructure edges and the interaction strength with the Pd substrate. Comparison with similar WO3 layers on Pd(100) is provided.

Investigation of CMAS corrosion resistance for gradient Y2O3 stabilized ZrO2

The threat of calcium‑magnesium-alumina-silicate (CMAS) melt corrosion in thermal barrier coatings (TBCs) is significant at elevated working temperatures. In this study, a gradient Y2O3 stabilized ZrO2 coating (gradient YSZ coating) was designed and prepared by electron beam physical vapor deposition (EB-PVD) and its CMAS corrosion resistance was examined. The CMAS corrosion resistance test on the YSZ pellets highlighted the significance of dissolved Y2O3 and identified the critical Y2O3 content. Compared with the classical 8 wt% Y2O3 stabilized ZrO2 (8YSZ) coating, new crystal phases generated in the gradient YSZ coatings effectively blocked the CMAS melt infiltration for a short time; further, even after a long time, the CMAS melt was primarily distributed in the upper part of the gradient YSZ coating. In addition, the impact of coating microstructure on the CMAS resistance was investigated. The results showed the dense-gradient YSZ coating outperformed the 8YSZ coating on the resistance to CMAS infiltration. Finally, it is demonstrated that the gradient YSZ coating has potential applications against CMAS attacks, providing valuable design guidelines for TBCs with balanced corrosion resistance and promising mechanical properties.

Oxidative corrosion resistance of a CrxFeyNi1-x-y composition spread alloy film (CSAF) in dry air

Composition Spread Alloy Films (CSAFs) were used to study the resistance to oxidative corrosion of CrxFeyNi1-x-y alloys in dry air and determine the critical Cr composition, xCr∗, necessary to prevent bulk oxidation. CrxFeyNi1-x-y CSAFs were made using physical vapor deposition (PVD) and then oxidized in dry air between 100 – 500 °C for periods of 1 h. A sharp passivation boundary was observed at 300 °C separating alloys showing evidence of heavy oxidation from Cr-rich alloys that were passivated. X-ray photoelectron spectroscopy (XPS) depth profiling was used to measure the extent of oxidation and penetration depth of the oxide layer on either side of the passivation boundary. XPS measurements confirmed the presence of a critical Cr composition, xCr∗, ranging from 18 to 26 at.%. For alloys with xCr≥xCr∗, a sufficiently thick passivating layer of oxidized Cr, Cr(ox), had formed on the top surface preventing the oxidative corrosion of either Fe or Ni. On the other hand, when xCr<xCr∗, bulk oxidation was observed, with appreciable Fe(ox) and/or Ni(ox) measured on the surface and often penetrating through the entire alloy film thickness. The trajectory of xCr∗ plotted within CrxFeyNi1-x-y composition space supports the trend towards using higher Cr-content stainless steel grades in harsh oxidative environments.

Dielectric Study of n-Propanol during Physical Vapor Deposition: NoSurface Mobility and No Kinetic Stability.

Dielectric relaxation experiments have been performed on n-propanol (NPOH) films during physical vapor deposition at temperatures above and below its glass transition, Tg = 97 K. The results for NPOH are compared with those of analogous experiments on methyl-m-toluate (MMT) and 2-methyltetrahydrofuran (MTHF), with all three deposited at the same reduced temperature, 0.82Tg. While MMT and MTHF display clear signs of a highly mobile surface layer, no such feature is observed for NPOH. The existence of this in situ observed mobile surface layer correlates perfectly with the material's ability to form kinetically stable glasses, as NPOH differs from MMT and MTHF by not displaying kinetic stability.

Nanotransfer Printing for Synthesis of Vertically Aligned Carbon Nanotubes with Enhanced Atomic Penetration

AbstractVertically aligned carbon nanotubes (VACNTs) exhibit outstanding mechanical strength, chemical stability, and electrical characteristics; however, their constrained mechanical elasticity and chemical responsiveness spurred research on atomic decoration techniques for enhancing their mechanochemical attributes. Nevertheless, achieving uniform atomic decoration on the VACNT surface is difficult because of the high density and large aspect ratio of VACNT. Herein, a strategy to design and apply nanopatterned VACNTs (nVACNTs) based on a nanotransfer printing process is proposed to improve atomic penetrability. Nanopatterns inherent to nVACNTs facilitate atomic penetration, allowing for the more consistent and higher quality deposition of functional materials such as zinc oxide and alumina by atomic layer deposition. Furthermore, physical vapor deposition provides an improved coating of metal catalysts such as gold. The uniform deposition of ceramic layers on the entire surface of nVACNTs strengthens its mechanical resilience, owing to the diminished van der Waals forces of CNTs. Surface‐decorated nVACNTs display an increased sensitivity to NO2 gas, which is attributed to the enhanced quality of the reactive catalyst deposition and augmented permeability. This strategy achieves a larger decorated area while increasing a catalytically active reaction area. The obtained results promise that the enhanced nVACNTs will expand the industrial applications of carbon nanotubes.

Exploring role of microbatteries in enhancing sustainability and functionality of implantable biosensors and bioelectronics

Microbatteries are emerging as a sustainable, miniaturized power source, crucial for implantable biomedical devices. Their significance lies in offering high energy density, longevity, and rechargeability, facilitating uninterrupted health monitoring and treatment within the body. The review delves into the development of microbatteries, emphasizing their miniaturization and biocompatibility, crucial for long-term, safe in-vivo use. It examines cutting-edge manufacturing techniques like physical and chemical vapor deposition, and atomic layer deposition, essential for the precision manufacture of the microbatteries. The paper contrasts primary and secondary batteries, highlighting the advantages of zinc-ion and magnesium-ion batteries for enhanced stability and reduced reactivity. It also explores biodegradable batteries, potentially obviating the need for surgical extraction post-use. The integration of microbatteries into diagnostic and therapeutic devices is also discussed, illustrating how they enhance the efficacy and sustainability of implantable biosensors and bioelectronics.

Implementation of Numerical Model for Prediction of Temperature Distribution for Metallic-Coated Firefighter Protective Clothing

The aim of this study is to predict the distribution of temperature at various positions on silver-coated firefighter protective clothing when subjected to external radiant heat flux. This will be helpful in the determination of thermal protective performance. Firefighter clothing consists of three layers, i.e., the outer shell, moisture barrier and thermal liner. The outer shell is the exposed surface, which was coated with silver particles through a physical vapor deposition process called magnetron sputtering. Afterwards, these uncoated and silver-coated samples were exposed to radiant heat transmission equipment at 10 kW/m2 as per the ISO 6942 standard. Silver-coated samples displayed better thermal protective performance as the rate of temperature rise in silver-coated samples slowed. Later, a numerical approach was employed, contemplating the impact of metallic coating on the exterior shell. The finite difference method was utilized for solving partial differential equations and the implicit method was employed to discretize the partial differential equations. The numerical model displayed a good prediction of the distribution of temperature at different nodes with respect to time. The comparison of time vs. temperature graphs at different nodes for uncoated and silver-coated samples acquired from numerical solutions showed similar patterns, as witnessed in the experimental results.

Investigation of Cu-doped amorphous carbon film in improving corrosion resistance and interfacial conductivity of proton exchange membrane fuel cell

This study investigated Cu-doped a-C films prepared under a substrate bias gradually reducing from 120 to 60 V and different Cu target currents of 0, 0.15, 0.2, 0.3, 0.5 A, respectively, using closed field unbalanced magnetron sputtering physical vapour deposition technique. While the Cu-doped a-C film at the lowest Cu target current of 0.15 A (A0.15) remained an amorphous microstructure, Cu nanoprecipitates occurred at Cu target currents of 0.2–0.5 A. All the Cu-doped a-C films prepared exhibited good combination of corrosion resistance to a corrosive chemical mixture of 0.5 M H2SO4 + 5 ppm HF (as suggested by the corrosion current densities) and interfacial electric conductivity (as demonstrated by the interfacial contact resistance, ICR). Among all coatings, A0.15 showed the best corrosion resistance and interfacial electric conductivity, which is attributable to the precipitate-free Cu-doped amorphous microstructure. The measured current density of A0.15 was 1.95 × 10−7 A/cm2 at 0.6 V (vs. SCE) during potentiodynamic polarization, which was lower than that of the Cu-free a-C film at 7.34 × 10−7 A/cm2. The ICR value of A0.15 was 4.40 mΩcm2 at an assembly pressure of 1.4 MPa, which is about one third of the Cu-free a-C film. This study demonstrates a new deposition strategy combining Cu-doping and the control of substrate bias to improve the corrosion resistance and interfacial electric conductivity of a-C films for PEMFC.

Surface Enhancement of Titanium-Based Coatings on Commercial Hard Steel Cutting Tools

This study investigates the mechanical properties, surface integrity, and chemical configuration of PVD-coated high-speed steel (HSS) cutting tools, with a particular focus on titanium nitride (TiN) and titanium aluminium nitride (TiAlN) coatings. A range of characterisation methodologies were employed to examine the impact of pre-coating surface conditions on the resulting coatings. This impact includes the effects of gas bubble production and unequal distribution of elements, which are two unwanted occurrences. Notwithstanding these difficulties, coatings applied on surfaces that were highly polished exhibited more consistency in their mechanical and elemental characteristics, with a thickness ranging from 2 to 4 µm. The study of mechanical characteristics confirms a significant increase in hardness, from an initial value of roughly 1000 HV0.5 for untreated tools to 1300 HV0.5 for tools with physical vapour deposition (PVD) coatings. Although PVD coatings produced on an industrial scale might not exceed the quality of coatings manufactured in a laboratory, they do offer substantial enhancements in terms of hardness. This study highlights the significant importance of thorough surface preparation in achieving enhanced coating performance, hence contributing to the efforts to prolong the lifespan of tools and enhance their performance even under demanding operational circumstances.

Tool life experiment of coated cermet during nodular cast iron turning

AbstractIn this study, the application of physical vapor deposition (PVD) coatings on various cermet substrates for the machining of nodular cast iron was investigated, given that cermet materials are traditionally not the primary choice for such applications. Through the evaluation of key parameters including wear on the flank face and surface roughness, and with vibration analysis serving as a supplementary measurement, it was discovered that machining stability is compromised by the inherent brittleness of cermet and the adhesion of material on the rake face. While the application of coatings was found to extend tool life, the cermet-coating combinations did not surpass the performance of other materials such as cemented carbide with multi-layer coatings. Notably, the stability of surface roughness across various stages of tool wear was observed.

Wear performance of Ti-based alloy coatings on 316L SS fabricated with the sputtering method: Relevance to biomedical implants.

This investigation was conducted to encapsulate 316L SS with a Ti-based alloy coating. The aim was to fabricate a coating using TiN, TiO2, and TiCoCr powders on 316L SS through the physical vapor deposition (PVD) sputtering process. The powders were consecutively coated on 316L SS through the PVD sputtering process with coating durations of 30, 60, and 90 min. Further microhardness, surface roughness, microabrasion, and adhesion strength tests were also carried out. A 60% improvement in abrasion resistance was observed in TiCoCr-coated samples compared to the uncoated substrate. The X-ray diffraction results confirmed the optimal formation of Ti alloy coatings with corresponding orientation over the SS substrates. Moreover, TiCoCr with a 90 min coating duration had much better surface characteristics than TiO2 and TiN. The 90 min coating duration should be optimal for coating in steel for bio-implants.

Comprehensive study on the nonlinear optical properties of Ag/MoSe2 composite films

MoSe2 thin films and Ag/MoSe2 composite thin films were prepared by physical vapour deposition (PVD). The morphology and structure of the composite film were characterized by scanning electron microscopy and absorption spectroscopy. The UV–visible absorption spectrum characterizes the linear absorptivity of the composite films. Due to the plasma effect of Ag nanofilms, the Ag/MoSe2 composite films showed a significant increase in the absorption intensity of the films compared to the MoSe2 films. The nonlinear absorption properties of MoSe2 thin films were investigated using the open-aperture Z-scan technique. The calculated nonlinear absorption coefficient (β) showed that the nonlinear absorption coefficient of the Ag/MoSe2 composite film is an order of magnitude higher than that of the MoSe2 film, indicating that the Ag nanofilm can better improve the nonlinear absorption properties of the MoSe2 film.