High Deposition Efficiency Research Articles

Tantalum Based High-Pressure Cold Spray Coatings on Stainless Steel Substrate

Tantalum as a transition element possesses good corrosion resistant properties, along with ductility and hardness. It is also one of the best heat-resistant material (melting point 2996°C) and is known for its high heat and electrical conductivity. In this research, Tantalum is deposited on stainless steel substrate using high-pressure cold spray (HPCS) method. Cold spray coating technology enables the deposition of powder feedstock without melting. Feedstock particles are propelled through a nozzle at supersonic velocities and they deform plastically on impact, resulting in good bonding strength to the substrate. The low temperature and solid-state deposition associated with cold spray allows refractory materials such as Ta, Mo, and W to be deposited without high temperature requirements. The objective of this work is to achieve a dense and nonporous coating microstructure with a high deposition efficiency. The hardness of as-received tantalum particles is found to be 279 HV0.3and the microstructure is very dense. Tensile testing carried on the sample coated at a stagnation gas pressure of 50 bar and gas inlet temperature of 900°C exhibited an ultimate tensile strength of 442 MPa and adhesion strength of 77 MPa. Further mechanical properties of the coating in terms of hardness is carried out by nanoindentation. These results will be correlated with microstructural imaging and elemental analysis including morphology and composition using scanning electron microscopy and X-ray diffraction techniques.

Effect of laser cladding and laser-induction hybrid cladding coatings on the bending properties and fracture behavior of rails

Laser cladding (LC) and laser-induction hybrid cladding (LIHC) technologies, with low dilution, low deformation and high deposition efficiency, have attracted a lot of notices in repairing and hard-facing the full-scale rail. However, the cladded coatings with different microstructure and properties will also affect the bending stress distributions of rails during service, which may lead to the rails' failure and fracture. In this paper, the bending properties and fracture mechanisms of rails deposited by LC and LIHC were studied systemically by the three-point bending tests coupled with finite element method simulations (FEMS). The results indicate that the ultimate bending strength (UBS), fracture strain (εf) and fracture work (W) of the specimen by LIHC are about 1.35, 4.28 and 7.70 times of that by LC correspondingly. The dramatically difference is mainly caused by the heat affected zones (HAZs) induced by different technologies. Under the bending stress, both the maximum stress and initial damage of the specimen by LC generate in the HAZ, while the cracks extend intergranularly in HAZ and lead to the rapid overall instable fracture. Oppositely, the initial damage of the specimen by LIHC originates from the surface on the tension side where the maximum stress generates, and the HAZ by LIHC is proved to be able to promote both the bending strength and fracture toughness of the rail. On the other hand, the thickness and properties of the cladded coatings are the main factors affect the bending properties of specimens by LIHC. When the parameters are chosen suitably, both the yielding strengths and UBSs of specimens by LIHC are even higher than that of the rail substrate, which means LIHC can adjust the rail's performances reasonably while prevent the rail from bending fracture.

MnO2-decorated hierarchical porous carbon composites for high-performance asymmetric supercapacitors

In this study, the growth of 1-dimensional manganese oxide (δ-MnO2) nanowire on hierarchical ordered mesoporous carbons/graphene composites (C) was synthesized by a relatively low-cost, simple, effective and eco-friendly redox process. It is found in both experimental results and theoretical simulations that the carbon surface, especially the mesoporous channels of ordered mesoporous carbons (amorphous carbons), would be favorable to serve as the nucleated sites for the growth of MnO2 nanowires. Likewise, the strong adsorptive interactions between MnO2 and amorphous carbons result in the high deposition efficiency of MnO2 on C (98%) and the outstanding stability of MnO2-decorated hierarchical porous carbon composites (MnO2@C) together with the relatively low equivalent series resistance. This electrode material exhibits excellent electrochemical behavior with a specific capacitance high up to 756.2 F g−1 in KOH electrolytes. In addition, an asymmetric supercapacitor (ASCs) assembled by using MnO2@C and C as the positive and negative electrodes in 1.0 M Na2SO4 solution achieves a maximum energy density of 34.56 Wh kg−1 at a power density of 450 Wkg-1 and excellent cycling stability. The results demonstrate the MnO2-decorated hierarchical porous carbon composites are promising candidates for the future high-performance supercapacitors.

Microstructure and mechanical properties of wire arc additively manufactured AZ80M magnesium alloy

Wire arc additive manufacturing (WAAM) with high deposition efficiencies and material utilization rate was carried out by using AZ80M magnesium alloy in this work. The microstructure and mechanical properties of the WAAM AZ80M were tested and studied. The results showed that the WAAM AZ80M was mainly composed of α-Mg, β-Mg17Al12 and Al2Y phases and had obvious inhomogeneous characteristics along the deposition direction. Because of the microstructure inhomogeneity and micro defects in the interlayer region of the WAAM AZ80M, its average tensile strength at the horizontal and vertical directions was different with the values of 308.7 MPa and 237.3 MPa, respectively.

Cathodic Stripping Voltammetric Study for Determination of Inorganic Arsenic Species in Seaweed Gracilaria fisheri

A simple, rapid, selective and sensitive square wave cathodic stripping voltammetry (SWCSV) at a hanging mercury drop electrode (HMDE) for the determination of As(III), As(V) and inorganic As(total) in seaweed was developed. The method was based on the formation of copper-arsenic intermetallic compound in the presence of HCl onto a HMDE at a constant potential of -0.40 V vs. Ag/AgCl in the deposition step, followed by the reduction of deposited compound to arsine at a potential of -0.78 V in the stripping step. In the system, only As(III) was directly measured, whereas inorganic As(total) was measured by reducing As(V) to As(III) using thiosulfate. In the deposition step, the use of 10 mg L-1 Cu(II) and 1 M HCl was recommended for the determination of 2 µg L-1 As(III) under the optimum instrumental variables obtained at 150 s for deposition time and 2000 rpm for stirring speed with the highest deposition efficiency of 16.15 and 88.49%, respectively. In the determination of As(V), two values of the highest reduction efficiency obtained using concentration of 40 mg L-1 thiosulfate, and reducing time at 300 s were 98.15% and 37.89%, respectively. In the measurement, the quantification limits of As(III) and As(V) were 0.46, and 1.62 µg L-1, respectively. The relative standard deviation (n=10) for 2 ug L-1 As(III) and As(V) were 5.20% and 2.57%, respectively. The proposed method was applied to the determination of inorganic arsenic species in seaweed Gracilaria fisheri.

Size-resolved particle oxidative potential in the office, laboratory, and home: Evidence for the importance of water-soluble transition metals

Particulate matter (PM) oxidative potential (OP) is an emerging health metric, but studies examining the OP of indoor PM are rare. This paper focuses on the relationships between respiratory exposure to OP and PM water-soluble composition in indoor environments. Size-resolved PM samples were collected between November 2015 and June 2016 from an office, home (including bedroom, living room, and storeroom), and laboratory using a MOUDI sampler. Particles from each source were segregated into eleven size bins, and the water-soluble metal content and dithiothreitol (DTT) loss rate were measured in each PM extract. The water-soluble OP (OPws) of indoor PM was highest in the office and lowest in the home, varying by factors of up to 1.2; these variations were attributed to differences in occupation density, occupant activity, and ventilation. In addition, the particulate Cu, Mn, and Fe concentrations were closely correlated with OPws in indoor particles; the transition metals may have acted as catalysts during oxidation processes, inducing ·OH formation through the concomitant consumption of DTT. The OPws particle size distributions featured single modes with peaks between 0.18 and 3.2 μm across all indoor sites, reflecting the dominant contribution of PM3.2 to total PM levels and the enhanced oxidative activity of the PM3.2 compared to PM>3.2. Lung-deposition model calculations indicated that PM3.2 dominated the pulmonary deposition of the OPws (>75%) due to both the high levels of metals content and the high deposition efficiency in the alveolar region. Therefore, because OPws has been directly linked to various health effects, special attention should be given to PM3.2.

Copper deposition-induced efficient signal amplification for ultrasensitive lateral flow immunoassay

This work describes a novel signal amplification strategy via gold nanoparticle (AuNP)–induced copper deposition to develop a highly sensitive and accurate immunochromatographic platform. Copper deposition–assisted signal amplification (CDASA) was first evaluated on commercially HCG test strip. A lower limit of detection (LOD) over the well-known silver enhancement confirms the great potential of this new approach for the visual test strip. Under an optimal condition, an LOD of 1 pg mL−1 and a wide dynamic range from 1 pg mL−1 to 100 ng mL−1 were achieved by the CDASA with rabbit IgG as a model analyte. In terms of LOD, 2–3 orders of magnitude improvement is received by the CDASA as compared with the conventional test strip without any signal amplification. Potential of the proposed strategy for practical application is also validated by detection of Rabbit IgG in human serum, a mimic clinical sample. The CDASA renders much superiority such as a higher deposition efficiency, lower cost, and better reagent stability over the silver enhancement method. The results can be qualitative and quantitative analysis by the naked eyes and the combination of a flatbed scanner and a free imageJ respectively, eliminating any lab equipment.

Reducing arc heat input and obtaining equiaxed grains by hot-wire method during arc additive manufacturing titanium alloy

Arc additive manufacturing technology has high deposition efficiencies and material utilization rates. However, the large heat input and high temperature gradient during arc additive manufacturing process lead to the formation of the coarse columnar grains. Due to the presence of the coarse columnar grains, the mechanical properties of the part have great anisotropy which limits the application of it. In this experiment, a method named hot-wire arc additive manufacturing was adopted to reduce the arc heat input and refine the columnar grains, and four thin-walled samples with the material of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si were manufactured. It is interesting to find that the coarse columnar grains have been greatly refined, and finally a part consisting of equiaxed grains and short columnar grains was obtained. At the same time, the width of the α-lath has also been refined. The mechanical properties are in accordance with the grain changes and the anisotropy almost disappeared. And it seems that a part with comprehensive mechanical properties can be obtained by the hot-wire arc additive manufacturing.

The Effects of Low Frequency on the Microstructure and Mechanical Properties of High-Strength Al-Mg Aluminum Alloys by Wire and Double-Pulsed Arc Additive Manufacturing

An innovative and high deposition efficiency process, the double-pulsed arc additive manufacturing process, is used to produce high-strength Al-Mg wall components. This dissertation investigates the electrical parameter acquisition, bead appearance, porosity morphology, microstructure and mechanical properties of additively manufactured high-strength Al-Mg wall components and how these are affected by the low frequency of the double-pulsed arc additive manufacturing process. Then, using this process at different low frequencies of 0, 1, 3, 5, 7 and 9 Hz, multilayer deposition experiments were performed. It can be observed that the deposit porosity is obviously eliminated compared with cold metal transfer (CMT) process. The bead appearance of the deposited aluminum wall varies clearly with low frequencies, and at a low frequency of 3 Hz, its appearance is the best of all. The optical observation of microstructure proves that the average grain size varies significantly with low frequency, and at a low frequency of 1 Hz, it is the smallest. In addition, the deposited wall showed maximum mean microhardness and maximum ultimate tensile strength at a low frequency of 3 Hz. Considering the deposited porosity and mechanical priorities, double-pulsed arc additive manufacturing with a frequency of 3 Hz is more suitable for making high-strength Al-Mg wall components than at other low frequencies.

Surface quality and forming characteristics of thin-wall aluminium alloy parts manufactured by laser assisted MIG arc additive manufacturing

An innovative additive manufacturing (AM) system using low power pulsed laser assisted MIG arc welding (L-M) was proposed to manufacture metal products. With the purpose of revealing how width and height dimension of the manufactured thin-wall component are affected by the laser power, the present study has been carried out. The width decreased with the increasing of the laser power within a certain range of laser power, and the height increased proportionally under the equal deposition rate. The width and height fluctuation reduced while adding the low power laser, both the standard deviation decreased by more than 50％ when the laser power was 400 W. The coefficient of materials utilization was up to 91.12%, and increased by more than 15% while using L-M based AM to fabricate thin-wall parts with a proper laser power. In comparison with the common GMAW-based AM method, the L-M based AM method shows feasibility to manufacture a narrower thin-wall component with better surface quality and higher stability, and also with higher deposition efficiency.

Anisotropic response of cold sprayed copper deposits

Cold spray (CS) is characterized as a solid-state process of high deposition efficiency for metallic coatings as well as additive manufacturing of metals. However, due to high velocity impact and extensive deformation of particles during CS, the as-received coatings or deposits may present anisotropic characteristics which could influence the performance of deposits. Hence this study aims to investigate the anisotropic behaviors of CSed copper deposits in a systematic way. The microstructure and micromechanical properties of the deposits both in the cross-section (v-face) and in the parallel plane to the surface (p-face) were characterized. Tensile tests were performed at various loading angles with respect to the nozzle moving direction in the p-face. It is revealed that there exist strong microstructural and mechanical anisotropies in CSed deposits. Different interparticle interaction results in more severe particle impact deformation in v-face than p-face, with larger elastic modulus and microhardness values. The tensile tests show an unexpected anisotropy in both ultimate tensile strength and elongation, with the highest performance occurring at the angle of 20°. The in-plane tensile anisotropy could be attributed to the parallel multiple passes. Therefore, a novel weave-spraying method was proposed, which can greatly reduce the tensile anisotropy of CSed deposits.

An efficient computational fluid-particle dynamics method to predict deposition in a simplified approximation of the deep lung

High-fidelity simulations of the complete airway tree are still largely beyond current computational capabilities. Towards large-scale simulations of the human lung, the current study introduces a numerical methodology to predict particle deposition in a simplified approximation of the deep lung during a full breathing cycle. The geometrical model employed consists of an idealised bronchial tree that represents generations 10 to 19 of the conducting zone and a heterogeneous acinar model created using a space-filling algorithm. The computational cost of the coupled simulation is reduced by taking advantage of the flow similarity across the central conducting regions in order to decompose the bronchial tree into representative subunits. Topological information is used to account for the correct gravitational force on the particles in the representative bifurcations, emulating their transport characteristics in the actual bronchial tree. Eventually, airflow and particle transport are simulated in a single representative bifurcation and a single acinar model, resulting in great savings in computational cost.An Eulerian-Lagrangian approach has been used for solving the flow and particle equations during sinusoidal breathing in the decomposed domain. The resulting deposition estimates agree rather well with the known deposition trends reported in the literature, while offering additional insights. For 1−5μm particles, deposition during exhalation is comparable to deposition upon inhalation, suggesting the use of breath-hold maneuvers to further increase sedimentation of these particles. Airway orientation relative to gravity was found to have a significant impact on deposition rates, especially for particles above 2μm and to be higher in the more distal generations, due to the wider range of angles relative to the direction of gravity. In the acinus, particles in the 2−5μm range have a quite high average deposition efficiency that reaches approximately 75% and shows considerable variation (12.4%) due to airway orientation. Finally, a simplified semi-analytical approach is introduced that can lead to even further reduction in computational costs, while incurring only a small loss in accuracy.

Development of fine solid-crystal suspension with enhanced solubility, stability, and aerosolization performance for dry powder inhalation

Dry powder for inhalation (DPI) is an attractive approach for the treatment of local lung diseases. However, the application of drugs with poor water solubility is often limited due to the dissolution obstacles in the fluid layer of the lung lining. In this study, fine solid-crystal suspension (FSCS) was proposed as a solvent-free method to improve the solubility of a drug with poor solubility (itraconazole) and achieve high deposition efficiency simultaneously. The FSCS, in which the crystalline drug particle was highly dispersed in the crystalline excipient, was initially prepared as drug-excipient extrudate by hot melt extrusion, followed by jet milling into fine particles. Unlike the amorphous solid dispersion in the high-energy state, which is liable to recrystallize and aggregate, the FSCS was expected not only to improve the solubility of itraconazole, but also to maintain excellent physical stability. As evidenced in the solubility and stability studies, the solubility of itraconazole in the FSCS was approximately 145-fold greater than that of the raw material, and the crystalline form of itraconazole in the FSCS was also unchanged after storage in the accelerated condition for 6 months (40°C and 75% relative humidity [RH]). The improved solubility might be ascribed to the reduced crystal size and increased wettability, as confirmed by the particle size and contact angle test. The FSCS also showed an encouragingly high fine-particle fraction of 50.59±0.67%, which might have benefited from the appropriate particle size. Therefore, the FSCS was suggested as a promising DPI for delivery of drugs with poor water solubility.

Dependency of deposition behavior, microstructure and properties of cold sprayed Cu on morphology and porosity of the powder

Effect of the Cu feedstock morphology and microstructure on cold spray deposition behavior and coating microstructure was investigated in this study. Deposition efficiency, coating porosity, electrical conductivity and corrosion behavior of coatings sprayed with conventional gas atomized Cu (GA Cu) powder and electrolytic porous and dendritic Cu (E Cu) powder sprayed coating were comparatively studied. Correlation of the detailed pore structure with electrical conductivity and corrosion resistance were examined. It is found that, under the same conditions, E Cu powder shows a high deposition efficiency (DE) of 70.5% while GA Cu powder yields a low DE of only 34.4%. Although both the coatings have relatively low porosity of ~0.5%, GA Cu coating presents a much higher in-plane electrical conductivity of 73% of IACS, but a poorer corrosion resistance than E Cu coating. Detailed pore structrue examination indicates that the numerous intra-splat interfaces arising from the inter-branch gaps in E Cu powder introduce extra contact electrical resistance to the E Cu coating and thus lead to low electrical conductivity. In the GA coating, the inter-particle pores connected by poorly bonded inter-particle boundaries provide fast pathway for corrosive medium and consequently result in a poor corrossion resistance.

Production of Babbitt Coatings by High Velocity Oxygen Fuel (HVOF) Spraying

This work presents HVOF as an alternative means to produce dense Babbitt coatings by thermal spray. A radial injection setup and low fuel flow rates were used to minimize heat transfer to the low melting point alloy. In-flight particle diagnostic systems were used to correlate spray parameters with the changes in particle velocity and thermal radiation intensity. The use of particles with larger diameters resulted in higher deposition efficiencies. It was shown that HVOF Babbitt coatings combine a dense structure and a fine distribution of intermetallic phases when compared to more traditional babbitting techniques.

Electrospray as a Sample Preparation Tool for Electron Microscopic Investigations: Toward Quantitative Evaluation of Nanoparticles

The potential of electrospray deposition, for the controlled preparation of particles for imaging in electron microscopes, is evaluated on various materials: from mono-modal suspensions of spherical particles to multimodal suspensions and to real-world industrial materials. It is shown that agglomeration is reduced substantially on the sample carrier, compared with conventional sample preparation techniques. For the first time, it is possible to assess the number concentration of a tri-modal polystyrene suspension by electron microscopy, due to the high deposition efficiency of the electrospray. We discovered that some suspension stabilizing surfactants form artifact particles during electrospraying. These can be avoided by optimizing the sprayed suspension.

Effect of deposition efficiency on microstructure and property of 316L stainless steel fabricated by laser engineered net shaping

Laser engineered net shaping is a promising technique to fabricate high-performance components with complex geometry rapidly. Excellent properties of fabricated specimen and high deposition efficiency are both important for this additive manufacturing method, but few researches have been done on the relationship between them. In this paper, single-bead multilayer structures of 316L stainless steel are fabricated by laser engineered net shaping (LENS). Using the same laser power and scanning speed, different deposition efficiencies are achieved by adjusting powder flow rate and layer increment. Microstructures and mechanical properties of the deposited structures under different deposition efficiencies are discussed. The results show that, for certain laser power and scanning speed, the deposition efficiency increases from 12.41 mm3/s to 22.62 mm3/s with the increase of the powder flow rate and layer increment , which increases by 86.3% compared with the initial process. Laser energy consumed by depositing unit effective volume reduces from initial 98.84 J/mm3 to 53.06 J/mm3 and the energy efficiency increases by 46.32%. Microstructures of the specimen consist of columnar dendrite and the dendrite length increases obviously with the deposition efficiency. Property test shows that properties of the specimen under different deposition efficiencies are consistent and do not decrease with the deposition efficiency. Tensile strength and yield strength are stable in 510 MPa and 290 MPa, respectively. The elongation rate is around 40% while the micro-hardness is about 180 HV, all of which have reached the same level of forging. The results illustrate that the deposition efficiency and mechanical property can be optimized, which achieves fabrication of high performance parts with low energy consumption and high efficiency.

Design and optimization of rectangular cold spray nozzle: Radial injection angle, expansion ratio and traverse speed

A cold spray nozzle with radially injected powder was numerically modeled and experimentally validated. The gas flow field and particle trajectories were simulated for various injection angles and expansion ratios. Injection angle was seen to affect particle distribution and injection pressures. The effect of expansion ratio was numerically studied and experimentally verified with stainless steel powders. For this material system, highest deposition efficiency was observed at an overexpanded flow regime. High deposition rate was accompanied by strain rate induced phase change. In addition, the effect of traverse speed (between 1 and 6mm/s) was assessed experimentally. While the speed did not affect bond strength and coating hardness, an optimum speed was found where there was a substantial increase in deposition rate.

Morphologies, microstructures, and mechanical properties of samples produced using laser metal deposition with 316 L stainless steel wire

Laser metal deposition (LMD) with a filler has been demonstrated to be an effective method for additive manufacturing because of its high material deposition efficiency, improved surface quality, reduced material wastage, and cleaner process environment without metal dust pollution. In this study, single beads and samples with ten layers were successfully deposited on a 316L stainless steel surface under optimized conditions using a 4000W continuous wave fibre laser and an arc welding machine. The results showed that satisfactory layered samples with a large deposition height and smooth side surface could be achieved under appropriate parameters. The uniform structures had fine cellular and network austenite grains with good metallurgical bonding between layers, showing an austenite solidification mode. Precipitated ferrite at the grain boundaries showed a subgrain structure with fine uniform grain size. A higher microhardness (205–226 HV) was detected in the middle of the deposition area, while the tensile strength of the 50 layer sample reached 669MPa. In addition, ductile fracturing was proven by the emergence of obvious dimples at the fracture surface.

Electrochemical CO2 Reduction to Fuels Using Pt/CNT Catalysts Synthesized in Supercritical Medium

The electrochemical reduction of CO2 in the gas phase has been carried out in a solid polymer electrolyte type cell (25 cm2 geometric area) in continuous operation mode using carbon nanotube-supported platinum catalysts (Pt/CNT). The main novelty of this work relies on the use of supercritical media (supercritical CO2) for Pt deposition on CNT. Supercritical synthesis has allowed obtaining small Pt nanoparticles divided into two modal distributions (for 3–4 nm and 8–9 nm, respectively) with a high deposition efficiency (about 80%). The main reaction products of the electrocatalytic conversion of CO2 have been formic acid (59–89%), methane (2–33%), CO (3–11%), methanol (0–1.9%), and small amounts of acetone, isopropanol, and methyl acetate. The CO2 conversion rate multiplies almost by four when increasing current density, although selectivity barely changes. Lower temperature promotes further reduction of CO2 to methane (33% of selectivity) to the detriment of formic acid and CO. However, increases of temp...