Layer Deposition Research Articles

Impact of laser energy density on the structure and properties of laser-deposited Fe‒Ni‒Ti composite coatings

To utilise laser deposition for the preparation of high-strength, wear-resistant components, the service life of components in rail transportation equipment should be improved. Laser deposition technology is used to fabricate Fe‒Ni‒Ti coatings on the surface of AISI 1045 steel substrates. By varying the laser power to adjust the laser energy density, Fe‒Ni‒Ti composite coatings are prepared at various energy densities. The morphology, microstructure, phase composition, tensile strength, microhardness, and friction-wear characteristics of the composite coatings are observed and tested. The influence patterns and mechanisms of laser energy density on the organisational variation and friction-wear performance of composite coatings is investigated. When the laser energy density is 97.2 J/mm2 (1400 W), the residual stresses in the deposition layer are minimised, resulting in fewer cracks and gas pore defects, with a porosity rate reaching its lowest value of 1.2% and a density of 99.1%. With the increase in energy density, both the tensile strength and elongation of the deposited layer exhibited an initial increase followed by a decrease. The hardness and wear resistance of Fe‒Ni‒Ti deposition layers is effectively controlled by regulating the laser energy density.

Cu corrosion in supernatant and sedimentation of bentonite slurry containing chloride

Cu corrosion in aerated NaCl solution containing different bentonite content was investigated using electrochemical impedance spectroscopy and surface analysis techniques. In NaCl solution, Cu corrosion proceeds with CuClads formation and its transformation to Cu2O. The outer deposit layer consists of Cu2O and Cu2(OH)3Cl. The self-catalyzed comproportionation reaction between Cu and CuClx(x−2)− produces CuClx(x−1)−, leading to accelerated Cu corrosion. Bentonite slurry (10–30 wt%) shows supernatant and sedimentation layers. In supernatant layer, Cu corrosion happens with the help of anions dissolved from bentonite minerals. In sedimentation layer, Cu corrosion is hindered due to suppressed cathodic reaction and the self-catalyzed comproportionation reaction.

Interplay of Size and Magnetic Effects in Electrocatalytic Water Oxidation Activity of Sub-10 nm NiOx Supported Porous Hard-Carbons.

This report describes a systematic approach for precise engineering of a catalyst-metal oxide interface through combining complementary approaches of chemical vapor deposition and atomic layer deposition. Specifically, Chemical Vapor Deposition (CVD) fabricated nanostructured hard-carbon framework (NCF) is employed as synergistic support for precise deposition of NiOx particles through Atomic Layer Deposition (ALD). The three variants of NCF-NiOx system (dimensions ranging from 3-12 nm, surface coverage ranging from 0.14 %-2 %) achieved exhibit unique electrocatalytic water oxidation activities, that are further strongly influenced by an external magnetic field (Hext). This confluence of size engineering and associated magnetic field effects interplay to produce the largest lowering in Rct at Hext=200 mT. A comprehensive analysis of electrocatalytic parameters including the Tafel slope and double layer capacitance establishes further insights on co-relation of size effect and magnetic properties to understand the role of nanocarbon supported transition metal oxides in water electrolysis.

Metal‐Organic Chemical Vapor Deposition Grown Low‐Temperature Aluminum Nitride Gate Dielectric for Gallium Nitride on Si High Electron Mobility Transistor

Gate dielectrics for gallium nitride (GaN) high electron mobility transistor (HEMT) technology have always been challenging because of the nonideal semiconductor–dielectric interface, which leads to electronic traps. Plasma‐enhanced chemical vapor deposition and atomic layer deposition are standard techniques, but they require surface treatment and post‐annealing to control these traps. This article explores metal organic chemical vapor deposition‐grown in situ aluminum nitride (AlN) as a gate dielectric. The interface is expected to be pristine as there is no change in the chamber environment. A thin (10 nm) AlN layer is deposited at a low temperature to minimize strain and prevent the formation of an unwanted conductive channel within the device. The electrical and structural properties of this AlN‐capped HEMT are compared to a standard GaN‐capped HEMT, including temperature‐dependent studies. The results show that the AlN‐capped HEMT retains a higher charge in the channel while having an order of magnitude lower gate leakage than the GaN‐capped sample. Furthermore, the AlN‐capped HEMT performs similarly to the GaN‐capped HEMT in terms of temperature‐dependent leakage, dynamic on‐resistance, and temperature coefficient of resistance.

Non-contact ultrasonic vibration-assisted laser metal deposition manufacturing Fe-based powder: Numerical simulation and experimental investigation

Fe-based powder was manufactured on 42CrMoA steel substrate using non-contact ultrasonic vibration-assisted(UVA) laser metal deposition(LMD) process with different exciting distances(d), and the temperature field and stress field distribution, microstructure and mechanical properties of the deposited layers were investigated. The results show that the distribution of temperature field was more uniform, especially at the bottom of the molten pool, and the gradient of temperature field decreased. Compared with the condition without UVA, the residual stress peak value of the tensile stress area decreased significantly after UVA applied. When d=80 mm, the peak tensile stress and compressive stress were 90.5 MPa and 72.6 MPa, respectively, which were reduced by 45.6 % and 25.2 % compared with the condition without UVA. The length of the columnar crystals and the region of the columnar crystals decreased at the interface after UVA applied. The application of UVA can significantly improved the microhardness of deposition layer. With the reduction of the residual stress at the interface and the improvement of uniformity, the tensile properties of the deposit were also significantly improved. The highest tensile strength was 1281.3 MPa when d=80 mm, which was 30.12 % higher than that without UVA.

Multiscale Simulation of Laser-Based Direct Energy Deposition (DED-LB/M) Using Powder Feedstock for Surface Repair of Aluminum Alloy.

Laser-based direct energy deposition (DED-LB/M) has been a promising option for the surface repair of structural aluminum alloys due to the advantages it offers, including a small heat-affected zone, high forming accuracy, and adjustable deposition materials. However, the unequal powder particle size during powder-based DED-LB/M can cause unstable flow and an uneven material flow rate per unit of time, resulting in defects such as pores, uneven deposition layers, and cracks. This paper presents a multiscale, multiphysics numerical model to investigate the underlying mechanism during the powder-based DED-LB/M surface repair process. First, the worn surfaces of aluminum alloy components with different flaw shapes and sizes were characterized and modeled. The fluid flow of the molten pool during material deposition on the worn surfaces was then investigated using a model that coupled the mesoscale discrete element method (DEM) and the finite volume method (FVM). The effect of flaw size and powder supply quantity on the evolution of the molten pool temperature, morphology, and dynamics was evaluated. The rapid heat transfer and variation in thermal stress during the multilayer DED-LB/M process were further illustrated using a macroscale thermomechanical model. The maximum stress was observed and compared with the yield stress of the adopted material, and no relative sliding was observed between deposited layers and substrate components.

Designing a Stable Alloy Interlayer on Li Metal Anodes for Fast Charging of All-Solid-State Li Metal Batteries

The deposition of a thin LixSny alloy layer by plasma vapor deposition (PVD) on the surface of a Li foil is reported. The formation of a Li-rich alloy is confirmed by the volume expansion (up to 380%) of the layer and by the disappearance of metallic Sn peaks in the X-ray diffractogram. The layer has a much higher hardness than bare Li and can withstand aggressive cycling at 1C. Post-mortem scanning electron microscope observations revealed that the alloy layer remains intact even after fast cycling for hundreds of cycles. A concept of double modification by adding a thin ceramic/polymer layer deposited by a doctor blade on top of the LixSny layer was also reported to be efficient to reach long-term stability for 500 cycles at C/3. Finally, a post-treatment after Sn deposition consisting of a plasma cleaning of the LixSny alloy layer led to a strong improvement in the cycling performance at 1C. The surface is smoother and less oxidized after this treatment. The combination of a Li-rich alloy interlayer, the increase in hardness at the electrolyte/Li interface, and the absence of dissolution of the layer during cycling at high C-rates are reasons for such an improvement in electrochemical performance.

Two-Parameter Probabilistic Model and Experimental Research on Micron Particle Deposition

The deposition of micron particles in gas pipelines has always been an important problem in ultra-clean ventilation technology in the modern laser fusion, precision electronics, aerospace, and biomedical fields. Combining the mathematical expression of the migration, collision, and deposition of micron particles in a gas pipeline with a simulation of flow fields, a two-parameter particle probability deposition model based on vinl, θcr and collision probability coefficient PP is established, and the distribution law of particle deposition, considering two deposition targets of the pipe wall and deposition layer, is given. Combined with an experiment on particle migration and deposition in a gas pipeline, an interpretation and verification of the particle deposition distribution law are given, and the difference between the model and experiment is discussed through particle deposition efficiency mass distribution. Studies have shown the following: Under the premise of two kinds of deposition targets, different particle sizes in the gas pipeline present different deposition laws; the deposit morphology is a spot deposit of 10 µm particles and a flake deposit of 40 µm particles; the deposit position shows a uniform distribution and a lower wall dominance; and the deposit concentration area of 40 µm shows a more significant distribution. The results are very important for the selection and optimization of gas pipelines for clean spaces.

Customized Photoelectrochemical C-N and C-P Bond Formation Enabled by Tailored Deposition on Photoanodes.

Photoelectrochemistry (PEC) is burgeoning as an innovative solution to organic synthesis. However, the current PEC systems suffer from limited reaction types and unsatisfactory performances. Herein, we employ efficient BiVO4 photoanodes with tailored deposition layers for customizing two PEC approaches toward C-N and C-P bond formation. Our process proceeds under mild reaction conditions, deploying easily available substrates and ultra-low potentials. Beyond photocatalysis and electrocatalysis, customized PEC offers high efficiency, good functional group tolerance, and substantial applicability for decorating drug molecules, highlighting its promising potential to enrich the synthetic toolbox for broader organic chemistry of practical applications.

A study on the effect of mixture constituents on washout resistance, mechanical, and transport properties in the context of underwater 3D concrete printing

Underwater layered concrete depositions, such as those obtained using 3D printing, demonstrate washout resistance, which influences layer stability, transport properties, and inter-layer mechanical strength, thus impacting its final properties. This work first focuses on understanding the compositional effect of 3D printable mortars on their washout resistance. Conventional methods for assessing washout resistance of underwater concrete are ill-suited to 3D printable materials due to different mix designs and material deposition techniques. To address this, a new protocol considering layered deposition during 3D printing was developed to evaluate the washout resistance. Interrogation of the pore structure of the printed specimens (in air and underwater environment) via water absorption and sorptivity test further establishes the influence of washout on water transport properties. The study also investigates the impact of hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA) fiber dosages on mechanical properties, including compressive strength, interlayer split tensile strength, and flexural strength. Results indicate that HPMC addition significantly improves the washout resistance, whereas PVA fibers have detrimental effect. However, optimizing the PVA fiber dosage enhances both mechanical and water transport properties of underwater printed specimen via permeable void and capillary pore structure refinement.

Combined effect of cathodic potential and calcareous deposits on hydrogen evolution and permeation in Q460 steel

Cathodic protection is widely employed to prevent the corrosion of steel in marine environments. However, an inappropriate cathodic potential may lead to the generation of hydrogen and consequently induce cracking. Therefore, this study investigates the relationships between cathodic deposition potential, calcareous deposits, hydrogen evolution, and hydrogen permeation. Combining scanning electron microscopy, Raman spectroscopy, coupled focused ion beam lithography, and energy dispersive X-ray spectroscopy, it is observed that all calcareous deposits formed in artificial seawater at the potential range of −1.0 to −1.3 VSCE have calcium-rich inner and magnesium-rich outer layers, respectively. The thickness and compactness of each layer of the double-layer deposits vary with the cathodic deposition potential. Combining potentiodynamic polarization, hydrogen permeation experiments, and the morphology of calcareous deposits, we can find that the deposits formed at the cathodic deposition potential of −1.1 VSCE exhibit a thin inner layer and a condensed outer layer, which is effective in balancing hydrogen recombination and absorption, thus, inhibiting hydrogen entry. This study provides guidelines for the cathodic protection of steel materials in marine environments.

Evolution of Material Properties and Residual Stress with Increasing Number of Passes in Aluminium Structure Printed via Additive Friction Stir Deposition.

Additive friction stir deposition (AFSD) is an emerging solid-state additive manufacturing process with a high deposition rate. Being a non-fusion additive manufacturing (AM) process, it significantly eliminates problems related to melting such as cracking or high residual stresses. Therefore, it is possible to process reactive materials or high-strength alloys with high susceptibility to cracking. Although the residual stresses are lower in this process than with the other AM processes, depending on the deposition path, geometry, and boundary conditions, residual stresses may lead to undesired deformations and deteriorate the dimensional accuracy. Thermal cycling during layer deposition, which also depends on the geometry of the manufactured component, is expected to affect mechanical properties. To this day, the influence of the deposit geometry on the residual stresses and mechanical properties is not well understood, which presents a barrier for industry uptake of this process for large-scale part manufacturing. In this study, a stepped structure with 4, 7, and 10 passes manufactured via AFSD is used to investigate changes in microstructure, residual stress, and mechanical property as a function of the number of passes. The microstructure and defects are assessed using scanning electron microscopy and electron backscatter diffraction. Hardness maps for each step are created. The residual stress distributions at the centreline of each step are acquired via non-destructive neutron diffraction. The valuable insights presented here are essential for the successful utilisation of AFSD in industrial applications.

Numerical and experimental study of attenuation inspection during FDM with ultrasonic leaky waveguide

ABSTRACT This work proposes an ultrasonic leaky waveguide (ULWG) for in-situ structural integrity inspection during fused deposition modeling (FDM). Since the ultrasonic wave propagation speed (m·s−1) is much higher than the deposition speed (mm·s−1), a quasi-static finite element model is first established to simulate the wave propagation during this dynamic process. The amplitude and energy attenuation coefficients (α and ζ) are chosen as the inspection features. Processing parameters including deposition layer thickness and number, inspection frequency, plate thickness and interface impedance are explored. For the first layer printing, a thinner thickness, higher frequency and proper interface impedance will enable a better inspection with high sensitivity. For multilayer printing, the multimodal dispersion curves change continuously and α oscillation is observed due to waveform aliasing that ζ is more reliable. Printing failures such as detachment can be predicted as well from the model established. The ULWG is then integrated into a commercial FDM machine to capture the attenuation coefficients of an “S” shape sample. The poor adhesion, local and global detachments, path planning impact can all be revealed by ζ experimentally. Moreover, being consistent to the simulation, the fluctuation of α in multilayer printing increases, which prevents a further printing evaluation.

A Study of the EH36 Surface Sediment Layer under Joint Protection from Seawater Electrolysis Antifouling and Impressed Current Cathode Protection (ICCP) in a Marine Environment

A joint protection device for seawater electrolysis antifouling and ICCP was constructed, and comparative experiments were conducted to study the composition of the EH36 surface deposition layer under joint protection in a marine environment. Surface morphology analysis, energy-dispersive spectroscopy (EDS) imaging analysis, and X-ray diffraction (XRD) composition analysis were performed on the surface deposition layers of the experimental samples. The experimental results showed that under joint protection, a sedimentary layer was rapidly formed on the surface of EH36 to isolate the seawater medium, and this layer was mainly composed of Mg(OH)2 and a small amount of CaCO3. There was no corrosion on the surface of the EH36 substrate. When only ICCP was used, a relatively thin layer of calcium magnesium was deposited on the surface of EH36. Marine fouling organisms adhere to the surface of calcium and magnesium sedimentary layers and the EH36 substrate, and their attachment affects the formation of calcium and magnesium sedimentary layers. Moreover, marine fouling organisms cause corrosion on the surface of the EH36 substrate. The joint protection of seawater electrolysis antifouling and ICCP can simultaneously prevent electrochemical corrosion and marine biological fouling corrosion on the surface of EH36.

Coating-assisted picosecond laser ablation for microstructure fabrication of SiC ceramics

Silicon carbide (SiC) ceramics have emerged as critical materials in the production of high-precision components. Ultrafast laser processing is deemed the optimal technique for micro-nano manufacturing of SiC. However, the permanent deposition layer induced by laser ablation can critically impact the precision of the component. In this work, a coating-assisted picosecond laser ablation (CAPLA) method was proposed, in which sacrificial photoresist coating was utilized to improve surface quality without efficiency loss. The coating serves to prevent the uncooled plasma from contacting with the substrate, thereby preventing the formation of a permanent deposition layer. By comparing the CAPLA method with laser direct ablation, the influence of laser parameters and photoresist coating characteristics on the deposition layer was investigated systematically. A processed surface devoid of deposition layers can be achieved by CAPLA with low pulse energy and a high number of scans. The uniformity is critical to ensure the transmission of the laser beam, and a larger thickness can improve the processing efficiency by increasing the limit of pulse energy capacity. Pin arrays and vacuum grooves for SiC ceramic vacuum chucks were fabricated to demonstrate the superiority of the CAPLA method. These results suggest that this method can be a novel and promising approach for high-precision component manufacturing.

Generation of nano-to-microplastics from polypropylene surfaces via femtosecond laser ablation in liquids with different viscosities

Preparation of polypropylene (PP) nano and microparticles, crucial for investigating the effects of plastics on both human health and the environment, presents a significant and immediate challenge. Utilizing an fs laser system in different liquid mediums such as water, dodecane, and hexadecane, we have successfully generated PP particles with sizes ranging from 1.8 to 4911 nm. This outcome is partly attributed to the constraint on plasma expansion caused by the viscosity of the liquid media. We investigated the areas of material removal and observed a transition from ordered to disordered removal patterns during this process. The formation of filaments and pillars within the material removal cavity, along with the deposition layer at the cavity edge, primarily occurred due to insufficient plasma formation at low laser energy levels. Furthermore, we observed neck-shaped filaments and nano cracks on the deposition surface, which were attributed to the heat effect during laser interaction with the PP substrate. Moreover, we collected distinct nano-Fourier transform infrared spectroscopy (FTIR) signals from both the nanoparticle area and the deposition layer, revealing a 2 cm−1 wavenumber difference between the two regions. This discrepancy proved to be a valuable method for distinguishing between the nanoparticle area and the deposition layer.

Targeting Manganese Amidinate and ß-Ketoiminate Complexes as Precursors for Mn-Based Thin Film Deposition.

With a focus on Mn based organometallic compounds with suitable physico-chemical properties to serve as precursors for chemical vapor deposition (CVD) and atomic layer deposition (ALD) of Mn-containing materials, systematic synthetic approaches with ligand variation, detailed characterization, and theoretical input from density functional theory (DFT) studies are presented. A series of new homoleptic all-nitrogen and mixed oxygen/nitrogen-coordinated Mn(II) complexes bearing the acetamidinate, formamidinate, guanidinate and ß-ketoiminate ligands have been successfully synthesized for the first time. The specific choice of these ligand classes with changes in structure and coordination sphere and side chain variations result in significant structural differences whereby mononuclear and dinuclear complexes are formed. This was supported by density functional theory (DFT) studies. The compounds were thoroughly characterized by single crystal X-ray diffraction, magnetic measurements, mass spectrometry and elemental analysis. To evaluate their suitability as precursors for deposition of Mn-based materials, the thermal properties were investigated in detail. Mn(II) complexes possessing the most promising thermal properties, namely Bis(N,N'-ditertbutylformamidinato)manganese(II) (IV) and Bis(4-(isopropylamino)pent-3-en-2-onato)manganese(II) (ßIII) were used in reactivity studies with DFT to explore their interaction with oxidizing co-reactants such as oxygen and water which will guide future CVD and ALD process development.

Synthesis of Bi2S3-sensitized TiO2 photoanodes for enhanced photovoltaic performance in solar cell application

The synthesis of Bi2S3 nanoparticles for sensitizing TiO2 photoanodes were synthesized through a cost-effective and straightforward approach using modified chemical bath deposition (M-CBD) or successive ionic atomic layer adsorption reactions (SILAR) at room temperature. Initially, a TiO2 seed layer was synthesized at room temperature via the chemical bath deposition method, followed by deposition of a mesoporous TiO2 layer using the doctor blade method. This study investigated the influence of the number of SILAR cycles and the choice of counter electrodes on the performance of Bi2S3/TiO2-based photoelectrodes. Characterization of the prepared Bi2S3/TiO2 photoanode involved various techniques, including X-ray diffraction, UV–Vis spectroscopy, scanning electron microscopy, and Raman spectroscopy, enabling the analysis of its structural, optical, and morphological properties. The Bi2S3/TiO2-based cell exhibits a maximum conversion efficiency of 0.8%, demonstrating the potential of this combination for photovoltaic applications. This study contributes to the field of solar cell technology by presenting a novel approach for sensitizing TiO2 photoanodes with Bi2S3 nanoparticles, offering insights into the optimization of fabrication parameters and performance enhancement strategies for future device design and development.

Mechanical and hydraulic properties of unsaturated layered pyroclastic ashes in landslide-prone areas of Campania (Italy)

Air-fall pyroclastic soil deposits usually display a loose fabric composed of alternating layers of ashes and pumices. Such deposits, when lying on steep slopes, represent a major geohazard due to the occurrence of landslides. This is the case of the carbonate massifs in Campania (southern Italy), a wide landslide-prone area of approximately 400 km2 covered with pyroclastic soils. In such cohesionless deposits, the additional shear strength provided by soil suction in unsaturated conditions is important for ensuring slope stability and can be jeopardized by soil wetting during rainwater infiltration. This paper provides a comprehensive view of the hydraulic and shear strength characteristics of different layers of pyroclastic deposits at different sites in Campania, revealing a broad view of their similarities and differences. To that end, some datasets from previous studies and novel data are gathered, linking the index properties, the hydraulic behavior of the soils and the contribution of suction to the shear strength of the studied materials. Two types of ashes at different positions within the stratigraphic sequence are identified: ashes interbedded between pumice layers, where landslide failure surfaces usually occur, and altered ashes in contact with the bedrock, which affects water leakage from the overlying soil profile. The former show quite uniform characteristics, and this allowed testing some predictive models for the assessment of the unsaturated shear strength of pyroclastic ashes in the absence of direct measurements. In contrast, the latter may exhibit significantly different behaviors, with great variability in hydraulic and mechanical properties.

Identification of Technosols formed from industrial dust in the area of Yazd city (Central Iran) by ground-based radiometry

Intensive industrial development in the form of metallurgical plants and quarries for mining of mineral resources in the vicinity of the city of Yazd resulted in significant dustiness of the ground layer of atmosphere and accumulation of industrial dust on the soil surface. At the locations of alloy steel production facilities, dust composition was dominated by particulate matter less than 1 μm (PM1), while near sand quarries, dust particles less than 10 μm (PM10) were predominant. The dust from these sources also differs in chemical composition (iron/silicon content ratio, pH). Registration with a pyranometer with a dark green filter with transmittance at a wavelength of 550 nanometers with a time interval of 20 seconds at a speed of 30 km/h during the movement along the specified routes allowed authors to identify zones with a stable increased content of particles of different sizes in the near-surface atmosphere. Sampling soil pits in these zones confirmed the presence on their surface of layers of dust deposits with a thickness of more than 5 cm, which allows them to be attributed to Technosols in accordance with the WRB soil classification. The soil map of the research area was compiled at a scale of 1 : 25 000 with the reflection of Technosols participation in the soil patterns. According to the map, more than three quarters of the study area are soil complexes including Technosols. Arid climatic conditions of the region lead to the accumulation of dust on the soil surface, which are practically not transformed and not removed from the soil, which results in their degradation and deterioration of the environmental conditions. Dust accumulation on the soil surface affects the state of vegetation cover of the region, which serves as a basis for indirect satellite indication of dusting zones. The method of revealing the dust layer on the soil surface based on the assessment of dustiness of the near-surface atmosphere using pyranometer can serve as a good complement to remote sensing methods.