Conventional Deposition Research Articles

Revolutionizing PET fabric performance with advanced metal deposition techniques

This study introduces an innovative approach to enhance both the air stability and conductivity of PET fabric using a novel dual-metal electroless deposition (ELD) technique. The fabric, woven with a combination of open weave (loose) and close weave (compact) designs, underwent coating with the metals nickel (Ni) and copper (Cu). Unlike conventional single-metal deposition methods, which often struggle to achieve optimal stability and conductivity simultaneously, this research pioneers the application of dual deposition to address these challenges effectively. The methodology entailed a series of carefully orchestrated steps including pretreatment, plasma treatment, silanization, polymerization, and ELD. The success of each stage was meticulously validated through water contact angle measurements, ensuring the efficacy of this work. Surface analysis techniques confirmed the uniform deposition of metals, as evidenced by surface morphology and elemental mapping. Additionally, detailed insights into the chemical composition and crystallinity of the coated fabrics were provided through XPS and XRD analyses. The results revealed a significant improvement in air stability and conductivity compared to traditional single-metal deposition methods. While fabrics coated solely with Cu exhibited high initial conductivity, they suffer from poor air stability. Conversely, Ni deposition demonstrated notable enhancements in air stability, with outcomes further influenced by the weave design of the fabric. Notably, in this work, the pioneering dual Ni-Cu deposition strategy not only addresses the air stability concerns associated with copper-coated fabrics but also maintains superior conductivity levels.

Effects of conventional interweaving and secondary deposition on the microstructure and properties of Ti6Al4V/AA2024 alloy component fabricated by laser-directed energy deposition

The connection of dissimilar materials has always been a great challenge, especially titanium alloy and aluminum alloy, which have broad application prospects in the aerospace industry. In this work, the Ti6Al4V/AA2024 alloy component was prepared by laser-directed energy deposition (L-DED) technology based on a conventional interweaving structure, and the microstructure of four typical position interfaces was analyzed. Aiming at the problem of poor forming quality of titanium alloy in the second interweaving layer caused by high laser reflectivity of aluminum alloy, a secondary deposition process was proposed. The microstructure and mechanical properties of Ti6Al4V/AA2024 alloy component fabricated by two different processes were characterized and tested. The problems of discontinuity and penetrating cracks at the Ti6Al4V layer in the second interweaving layer are effectively tackled by secondary deposition. As a result, the mechanical property of the deposited structure can be effectively improved, of which the average compressive shear strength is 8% higher than that of the conventional interweaving Ti6Al4V/AA2024 alloy component. The stress at the Ti6Al4V/AA2024 interface presents a zig-zag distribution because of the interweaving structure, which avoids the generation of continuous stress bands and effectively inhibits the interface crack propagation.

Non-Classical Deactivation Mechanism in a Supported Intermetallic Catalyst for Propane Dehydrogenation.

Platinum-based supported intermetallic alloys (IMAs) demonstrate exceptional performance in catalytic propane dehydrogenation (PDH) primarily because of their remarkable resistance to coke formation. However, these IMAs still encounter a significant hurdle in the form of catalyst deactivation. Understanding the complex deactivation mechanism of supported IMAs, which goes beyond conventional coke deposition, requires meticulous microscopic structural elucidation. In this study, we unravel a nonclassical deactivation mechanism over a PtZn/γ-Al2O3 PDH catalyst, dictated by the PtZn to Pt3Zn nanophase transformation accompanied with dezincification. The physical origin lies in the metal support interaction (MSI) that enables strong chemical bonding between hydroxyl groups on the support and Zn sites on the PtZn phase to selectively remove Zn species followed by the reconstruction towards Pt3Zn phase. Building on these insights, we have devised a solution to circumvent the deactivation by passivating the MSI through surface modification of γ-Al2O3 support. By exchanging protons of hydroxyl groups with potassium ions (K) on the γ-Al2O3 support, such a strategy significantly minimizes the dezincification of PtZn IMA via diminished metal-support bonding, which dramatically reduces the deactivation rate from 0.2044 to 0.0587 h-1. These findings decode the nonclassical PDH deactivation mechanism over supported IMA catalysts and elaborate a new logic for the design of high-performance IMA based PDH catalysts with long-term stability.

Thermal features and its effect on the properties of AISI 4140 fabricated by conventional and extreme high-speed laser material deposition

The extreme high-speed laser material deposition (EHLA) process has the potential to enable additive manufacturing for mass production by overcoming the limitations of slow scanning speed in conventional laser material deposition (LMD) processes. Thermal features are the key factors to link process and properties. A sound understanding of process-thermal-property relationships is essential for performance control and process optimization of a deposited component. In this study, we studied the thermal characteristics within a single layer and among layers for continuous processing using the numerical method, and reveal the mechanism of microstructure and hardness changes of AISI 4140 material formed by EHLA and LMD processes through the analysis of thermal properties and temperature history results. The grain size and hardness evolution for both processes during single-layer cladding and continuous forming processes were investigated. The results revealed that the grain refinement effect in continuous LMD processing is stronger than that in EHLA process (from 30.0 μm for single layer to 3.2 μm for multi layers vs. from 18.6 μm for single layer to 2.2 μm for multi layers). Similar hardness values were obtained by LMD and EHLA processes, with mean values of 511 HV and 472 HV, respectively. The yield and tensile strengths of EHLA were superior to the conventional cast material, but inferior to those of the conventional material quenched and tempered at lower temperatures. The enhanced tensile results of EHLA process were found similar to those prepared through conventional method with quench and tempering at 600 °C.

Microstructural evolution and interfaces in cold sprayed hybrid aluminum alloy powders of different hardness

The development of thick cold sprayed deposits of hard amorphous/nanocrystalline Aluminum High Entropy Alloys (Al HEA) is limited by their poor plastic deformability. To address this, Al HEA powder (Al90.05Ni4.3Y4.4Co0.9Sc0.35 (at. %)) is blended with soft Al 6061 in a 1:1 wt% ratio and cold sprayed. The microstructure of the composite deposits reveals that while Al HEA splats undergo limited deformation, Al 6061 splats deform extensively. Extreme deformation of Al 6061 captures the hard Al HEA particles, resulting in a composite deposit of 5 mm thickness, compared to 0.2 mm for pure Al HEA. Within the composite, Al HEA particles deform through shear band propagation and viscous flow, whereas Al 6061 splats deform via dislocation slip motion. These deformation mechanisms induce interface nanocrystallization, leading to a 123 % increase in lattice strain, a 67 % reduction in crystallite size, and an 800 % increase in dislocation density compared to the initial feedstock. This microstructural evolution, combined with the presence of hard Al HEA regions, results in a mean hardness of 2.56 GPa and an elastic modulus of 76 GPa. These values represent a 47 % and 6 % improvement over conventional polycrystalline cold-sprayed aluminum deposits. Thus, this study provides insights into the microstructural and interface evolution and its effect on indentation characteristics for making high-strength Al HEA deposits.

Enhancing Stability of n-Type Doped Organic Semiconductors through Low Boiling Point Solvent-Assisted Room Temperature Drying.

The development of n-type organic semiconductors (OSCs) has been lagged behind that of p-type OSCs, mainly due to the limited availability of the electron deficient π-conjugated backbones and facile electron trapping by ambient oxidants. Improving the performance of n-type OSCs through n-doping is essential for realizing p-n junction diodes and complementary circuits. Conventional vacuum deposition doping is costly and time-consuming, while solution doping risks thermal damage through necessary annealing. Therefore, the development of a simpler, more affordable n-doping method is crucial. In this study, we have developed a solution-processed n-doping method using an organic cationic dye in a low boiling point solvent that can be dried at room temperature in 1 h, which eliminates the need for annealing. The effects of different organic cationic dyes and reducing agents on the n-type OSC were evaluated. After n-doping, electron mobility and photoresponsivity in the sample increased by 5.5 and 20 times, respectively, compared to undoped samples. Furthermore, there was no significant degradation in the electron mobility of the n-doped samples under ambient conditions after 15 days. Studying n-doping with various organic cationic dyes in different OSC materials, embracing further research into their applications and mechanisms, would advance the field of organic electronics.

Room temperature deposited highly conductive HfNx films for high-performance HfN/Si junction diodes

Transition metal nitrides are valuable materials for many technological applications due to their favorable physical characteristics, including conductivity, high temperature stability, and hardness. Among them, hafnium nitride (HfN) thin films of high attributes are crucial for semiconductor applications. However, achieving performance efficiency of HfN films with desired electrical performance via conventional deposition methods is a challenging task. Herein, we have achieved room temperature growth of highly oriented cubic HfN thin film grown on Si substrate by process optimization of radio frequency (RF) magnetron sputtering. HfN thin films were structurally, morphologically, and electrically characterized. The metallic behavior of HfN films was confirmed through current-voltage measurements; it showcased excellent electrical conductivity, signifying low resistivity (≈ 0.55 kΩ sq-1), revealing promising evidence for its potential practical application. Moreover, the first-principles calculations were also conducted to gain further insights into the electrical performance of the HfN films. These findings lay a solid foundation for further exploration and development of HfN-based junction diodes, as the observed characteristics offer significant potential for enhancing device performance in various electronic domains.

Investigation of the cooling hole blockage induced by different thermal spray TBC deposition processes

High-temperature turbine airfoils and combustion chamber walls in jet engines require sufficient cooling via cooling holes and thermal barrier coating systems (TBCs) to protect them from hot combustion gases. As the demand for greater efficiency and higher firing temperatures in jet engines increases, there is a corresponding need for more advanced film cooling methods, such as the use of more complex hole geometries. The use of Additive Layer Manufacturing (ALM) techniques allows the production of such intricate cooling holes, enhancing the flow of cooling air onto component surfaces. Conventional TBC deposition techniques, for example Atmospheric Plasma Spraying (APS) or Electron Beam Physical Vapor Deposition (EB-PVD), often lead to partial or complete blockage of cooling holes. This study compares the blockage of TBCs deposited on conventionally-sheet alloys with standard cooling holes and ALM alloys with more complex cooling holes using APS as a baseline process. Additionally, alternative plasma spray deposition technologies such as Suspension Plasma Spraying (SPS) and Plasma Spray-Physical Vapor Deposition (PS-PVD) were explored. The aim was to determine the effectiveness of these processes in preventing blockage compared to the traditional APS process. The experimental results showed that the formation of the coating, whether originating from splats or from the vapor phase, the feedstock particle size, and the cooling hole geometry can all affect the blockage. It was demonstrated that PS-PVD, with its vapor-induced deposition, is highly effective in minimizing blockage, regardless of the cooling hole geometry.

Ultrathin Ge-YF3 antireflective coating with 0.5 % reflectivity on high-index substrate for long-wavelength infrared cameras

Abstract Achieving long-wavelength infrared (LWIR) cameras with high sensitivity and shorter exposure times faces challenges due to series reflections from high-refractive index lenses within compact optical systems. However, designing effective antireflective coatings to maximize light throughput in these systems is complicated by the limited range of transparent materials available for the LWIR. This scarcity narrows the degrees of freedom in design, complicating the optimization process for a system that aims to minimize the number of physical layers and address the inherent large refractive mismatch from high-index lenses. In this study, we use discrete-to-continuous optimization to design a subwavelength-thick antireflective multilayer coating on high-refractive index Si substrate for LWIR cameras, where the coating consists of few (e.g., five) alternating stacks of high- and low-refractive-index thin films (e.g., Ge-YF3, Ge-ZnS, or ZnS-YF3). Discrete optimization efficiently reveals the configuration of physical layers through binary optimization supported by a machine learning model. Continuous optimization identifies the optimal thickness of each coating layer using the conventional gradient method. As a result, considering the responsivity of a LWIR camera, the discrete-to-continuous strategy finds the optimal design of a 2.3-μm-thick antireflective coating on Si substrate consisting of five physical layers based on the Ge-YF3 high-low index pair, showing an average reflectance of 0.54 % within the wavelength range of 8–13 μm. Moreover, conventional thin-film deposition (e.g., electron-beam evaporator) techniques successfully realize the designed structure, and Fourier-transform infrared spectroscopy (FTIR) and thermography confirm the high performance of the antireflective function.

Low defect density in MoS2 monolayers grown on Au(111) by metal-organic chemical vapor deposition

Monolayers of transition metal dichalcogenides (TMDs) possess high potential for applications in novel electronic and optoelectronic devices and therefore the development of methods for their scalable growth is of high importance. Among different suggested approaches, metal-organic chemical vapor deposition (MOCVD) is the most promising one for technological applications because of its lower growth temperature compared to the most other methods, e.g., conventional chemical vapor or atomic layer deposition (CVD, ALD). Here we demonstrate for the first time the epitaxial growth of MoS2 monolayers on Au(111) by MOCVD at 450 °C. We confirm the high quality of the grown TMD monolayers down to the atomic scale using several complementary methods. These include Raman spectroscopy, non-contact atomic force microscopy (nc-AFM), X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). The topographic corrugation of the MoS2 monolayer on Au(111), revealed in a moiré structure, was measured as ≈20 pm by nc-AFM. The estimated defect density calculated from STM images of the as-grown MoS2 monolayers is in the order of 1012 vacancies/cm2. The defects are mainly caused by single sulfur vacancies. Our approach is a step forward towards the technologically relevant growth of high-quality, large-area TMD monolayers.

Treelike PS-PVD coating: Hierarchical branching by shading and sintering

A structure zone model (SZM) with columnar structures for conventional physical vapor deposition (PVD) has been assigned to plasma spray-physical vapor deposition (PS-PVD) coatings. However, many different comprehensive properties between PS-PVD and conventional PVD coatings reveal the essential different microstructures. In this work, an impact-diffusion model was established based on the impact and diffusion behavior of depositing units. The microstructure formation of PS-PVD coatings was simulated. Results clearly display that the PS-PVD coating shows a novel treelike structure with hierarchical branches rather than a well-known columnar structure. The hierarchical branching is determined by the shadowing effect. Besides, temperature-promoting diffusion of vapor units can generate the in-situ sintering of the coatings. In-situ sintering happens during the deposition process and can govern the branching behavior. A novel treelike SZM is established as an enlargement of the conventional one, marked by successive transformations in branching and densifying. The treelike SZM is experimentally proved by the electron microscopy images and mechanical properties of typical PS-PVD YSZ coatings.

A back-to-back diode model applied to van der Waals Schottky diodes

The use of metal and semimetal van der Waals contacts for 2D semiconducting devices has led to remarkable device optimizations. In comparison with conventional thin-film metal deposition, a reduction in Fermi level pinning at the contact interface for van der Waals contacts results in, generally, lower contact resistances and higher mobilities. Van der Waals contacts also lead to Schottky barriers that follow the Schottky-Mott rule, allowing barrier estimates on material properties alone. In this study, we present a double Schottky barrier model and apply it to a barrier tunable all van der Waals transistor. In a molybdenum disulfide (MoS2) transistor with graphene and few-layer graphene contacts, we find that the model can be applied to extract Schottky barrier heights that agree with the Schottky-Mott rule from simple two-terminal current-voltage measurements at room temperature. Furthermore, we show tunability of the Schottky barrierin-situusing a regional contact gate. Our results highlight the utility of a basic back-to-back diode model in extracting device characteristics in all van der Waals transistors.

Polymer assisted deposition of YIG thin films with thickness control for spintronics applications

The use of magnetic garnets in new technologies such as spintronic devices requires fine-structured thin films. Classical fabrication techniques for these materials, typically physical vapor deposition methods, lead to excellent magnetic behavior. However, availability and scalability for potential applications are well restricted. In this study, we propose an innovative approach to fabricating Yttrium Iron Garnet thin films with precise thickness control achieved through iterative layer deposition via a chemical synthesis route. Remarkably, the iterative deposition process results in films exhibiting exceptional crystallinity. Magnetic characterization provides saturation magnetization and coercivity values on par with those reported in literature, summed to narrow ferromagnetic resonance lines. Therefore, in this work we demonstrate the viability of polymer assisted deposition as a promising alternative thinking about scalability to conventional deposition techniques for this material. Notably, our findings reveal energy conversion efficiencies comparable to those achieved with materials synthesized via physical vapor deposition methods.

Mechanical performance of coal ash based interlocking bricks wall panel: A sustainable and viable solution

The use of interlocking brick incorporating waste coal ash (CA) in masonry construction is an innovative, sustainable and viable solution to address the consequences associated with burnt clay bricks. In this research, the main focus was to study the double interlocking brick incorporating CA for its potential use in masonry construction. The studied dosages of CA were 30 %, 35 %, 40 %, 45 %, 50 % and 55 %. Cement was varied between 5 % and 30 % in order to make the total binder (cement and CA) contents equal to 60 %. Moreover, wall panels using developed interlocking bricks were casted and tested for out-of-plane loading. It was observed that the incorporation of higher dosage of CA decreased the compressive strength owing to porous nature of used CA. However, interlocking bricks having 30 % of CA exhibited compressive strength higher than 8 MPa, satisfying the local building code requirement. Higher water absorption was observed for interlocking bricks having higher dosage of CA compared to identical bricks with lower CA. Interlocking bricks exhibited higher shear strength due to mechanical anchorage provided by the keys and notches in comparison with the conventional bricks. Maximum double key shear strength of 2.34 MPa was observed for developed interlock bricks incorporating 30 % of CA. Interlocking brick wall panel exhibited flexural strength of 1.05 MPa compared to 0.81 MPa for wall panel constructed using conventional burnt clay brick. Higher flexural strength of interlock CA based brick wall panel was due to the higher mechanical anchorage provided by the projected keys and grooves in between various courses of the wall panel. The cracking patterns of interlocking brick wall panel exhibited diagonal failure rather than the horizontal slide shear failure observed for conventional burnt clay brick wall panel. The experimental cracking load values were comparable with the theoretically predicted cracking loads for the tested wall panels. This study highlights the use of water cured interlocking brick incorporating waste CA for eco-friendly and economical construction leading to avoid the devasting effects of manufacturing process of conventional burnt clay bricks and deposition issues of CA. Moreover, this study motivates the construction stakeholders to employ double interlocking bricks of similar conventional size bricks to be used in a similar manner for masonry construction.

Preparation of Highly Efficient and Stable All-Inorganic CsPbBr3 Perovskite Solar Cells Using Pre-Crystallization Multi-Step Spin-Coating Method

All-inorganic CsPbBr3 perovskite solar cells have garnered extensive attention in the photovoltaic domain due to their remarkable environmental stability. Nevertheless, CsPbBr3 prepared using the conventional sequential deposition method suffers from issues such as inferior crystallinity, low phase purity, and poor film morphology. Herein, we propose a pre-crystallization methodology by introducing a minute quantity of CsBr into the PbBr2 precursor solution to generate a small amount of CsPb2Br5 crystals within the PbBr2 film, leading to a porous PbBr2 film with enhanced crystallinity. Under the influence of more pores and CsPb2Br5 crystals as nucleation sites for inducing growth, a CsPbBr3 film with a larger crystal size, lower grain boundary density, stronger crystallinity, and higher phase purity is formed. Compared with untreated devices, photovoltaic devices prepared using the pre-crystallization method achieved a champion photovoltaic conversion efficiency (PCE) of 8.62%. Furthermore, pre-crystallized devices demonstrate higher stability than untreated ones and can still retain 94% of the original PCE after being exposed to air for 1000 h without encapsulating.

New method for high-efficiency keyhole-based wire direct energy deposition: Process innovation and characterization

Wire laser direct energy deposition enables the mass production of large-scale industrial components and parts. However, energy utilization efficiency is limited in conventional wire laser material deposition to avoid keyhole defects, resulting in a low deposition efficiency. This work presents a high-efficiency wire laser material deposition process that increases energy utilization by generating a keyhole in the filler wire, which can also avoid the keyhole defects in the deposited sample. The influence of process parameters on deposition quality and efficiency was thoroughly examined to determine the process window. A high deposition efficiency of 0.87 kg/(h kW) for 316L stainless steel was achieved with a laser power of 3 kW, approximately three times that of the conventional wire laser material deposition process. The defect-free multitrack and multilayer deposition demonstrated the feasibility of our proposed high-efficiency process.

High acidity notably influences acid mine drainage treatment performance in constructed wetlands packed with composite organic substrates by affecting both abiotic and biotic routes

The impact of influent pH value (2.0–5.0) on remediation performance of constructed wetlands (CWs) packed with composite organic solids consisting of walnut shells, biochar and plastic filters for acid mine drainage (AMD) was evaluated in this study. Reed straw broth was supplemented to drive the microbial remediation process. Influent pH had a notable impact on both abiotic and biotic remediation performance, with very low efficacy at pH 2.0 and the best performance achieved at pH 5.0. The adsorption capacity of CW substrates for heavy metals and the growth of functional microbes for AMD treatment were restrained at high acidity. Moreover, the removal of conventional pollutants, plant growth and metal deposition in the CWs were negatively impacted by the dosing of AMD with low pH. A low pH of 2.0 resulted in a distinctive microbial community in the CWs with almost no sulfate-reducing bacteria (SRB). In other CW systems, SRB (Desulfosporosinus and Desulfobulbus) and organic degrading bacteria (Cellulomonas and Geobacter) were identified as keystone taxa to carry out AMD bioremediation synergistically in phase Ⅱ. CWs filled with composite organic substrates are promising systems for AMD treatment, but the pH of AMD should be preneutralized to ≥ 3.

Grain engineering of solution-processed Sb2S3 thin film by tuning precursor fabrication environments

Antimony sulfide (Sb2S3) has garnered significant attention recently due to its remarkable photovoltaic properties and low toxicity. However, the conventional physical vapor deposition approach faces challenges in achieving high-quality films due to Sb2S3 having a quasi-one-dimensional nanoribbon structure. In contrast, solution-processed Sb2S3 thin films have shown improved photovoltaic behavior, offering a low-cost and scalable fabrication method. Nonetheless, the sensitivity of the solution process to the chemical composition of the precursor poses a challenge, often requiring noble gas protection to prevent exposure to toxic solvents or moisture-sensitive chemicals. Despite this, the impact of precursor fabrication conditions on film growth behavior remains unexplored. In our study, we investigate how different processing atmospheres of precursors, namely nitrogen (N2) and air, affect grain growth and the associated optical and electronic performance of Sb2S3 thin films. Our findings reveal that the presence of oxygen in the precursor can hinder grain growth by obstructing surface integration sites, resulting in undesired (hk0) orientation and even the formation of Sb2O3 on the surface of the Sb2S3 films, despite identical post-deposition conditions. This research sheds light on how the ambient conditions during precursor preparation can influence grain engineering, thereby providing valuable insights for controlling the grain size and producing high-quality Sb2S3 absorber films.

Solar Cell Enhancement from Supercritical CO2 Dye Surface Modification of Mesoporous TiO2 Photoanodes.

In recent years, in an effort to reach Net Zero Emissions, there has been growing interest by various academic and industry communities to develop chemicals and industrial processes that are circular, sustainable and green. We report the rapid, simple and effective surface modification of a porous metal oxide with organic dyes using supercritical carbon dioxide (scCO2). Titanium dioxide (TiO2) photoanodes were coated in very short times, under mild conditions and the excess dye recovered afterwards for reuse. The process obviates the need for conventional toxic solvents, the generation of unwanted waste streams, and more importantly, we see an unexpected device performance enhancement of 212 and 163 % for TerCOOTMS, 2 a and TerCN/COOTBDMS, 4 dyes, respectively, when compared to the conventional solvent deposition method.

Shaping sub-10 nm metallic nanogaps by laser shock-induced extreme plasticity

The nanoscale metallic gaps generate the unique local electromagnetic field enhancement effect due to the strong electromagnetic coupling between closely spaced nanostructures. Besides the conventional material deposition or removal strategy, laser shock reshaping (LSR), based on the ultrahigh-strain-rate deformation of the nanometals, provides a viable process for ultrafine-gap fabrication. However, the extreme deformation behavior of nanometals during the high-speed forming process, which significantly determines the forming precision and quality, is largely unexplored. In this study, the scalable fabrication of the nanogaps was achieved using the LSR process; the extreme deformation behaviors of the nanometals were comprehensively investigated. The results indicated that the geometry of the primary structure and the LSR process will signally affect the microstructure evolution and deformation behavior of the sidewall during the LSR reshaping processes, and further affect the final geometrical morphology and optical properties of the generated nanogaps. The discovery of geometry-dependent deformation behaviors of the metallic structures is of great significance to the understanding of the mechanical deformation based nano-manufacturing processes.