Metal Vapor Research Articles

Metal impact and vaporization on the Moon's surface: Nano‐geochemical insights into the source of lunar metals

AbstractMillimeter‐to‐nanometer‐sized iron‐ and nickel‐rich metals are ubiquitous on the lunar surface. The proposed origin of these metals falls into two broad classes which should have distinct geochemical signatures—(1) the reduction of iron‐bearing minerals or (2) the addition of metals from meteoritic sources. The metals measured here from the Apollo 16 regolith possess low Ni (2–6 wt%) and elevated Ge (80–350 ppm) suggesting a meteoritic origin. However, the measured Ni is lower, and the Ge higher than currently known iron meteorites. In comparison to the low Ni iron meteorites, the even lower Ni and higher Ge contents exhibited by these lunar metals are best explained by impact‐driven volatilization and condensation of Ni‐poor meteoritic metal during their impact and addition to the lunar surface. The presence of similar, low Ni‐bearing metals in Apollo return samples from geographically distant sites suggests that this geochemical signature might not be restricted to just the Apollo 16 locality and that volatility‐driven modification of meteoritic metals are a common feature of lunar regolith formation. The possibility of a significant low Ni/high Ge meteoritic component in the lunar regolith, and the observation of chemical fractionation during emplacement, has implications for the interpretation of both lunar remote‐sensing data and bulk geochemical data derived from sample return material. Additionally, our observation of predominantly meteoritic sourced metals has implications for the prevalence of meteoritic addition on airless planetary bodies.

Production of negative ion beams through charge transfer between negative hydrogen ion beams and non-metallic gases

Negative ion beam applications in tandem accelerators are used for nuclear research, environmental studies, materials analysis, medical treatments, and ion implantation in semiconductor devices. Conventional methods for generating negative ions for tandem accelerators rely on metallic vapors (typically alkali) for charge exchange, which pose challenges like contamination, electrical shorting and breakdowns, and maintenance issues. To address these drawbacks, this work explores an alternative approach to produce negative ions using a non-metallic charge exchange process. It involves directing negative hydrogen ions into neutral gases within a specially designed charge exchange cell equipped with an electrostatic accelerator. The method is applied to various gas targets, including He, H2 and O2, to accelerate and measure resulting negative ions. This innovative approach aims to mitigate contamination concerns associated with metallic vapor double-charge exchange methods and explore novel avenues for negative ion production through charge transfer. Any newly formed negative ion beam current conversion ratios from the incident H− beam will be reported as progress in this research.

Influence of argon, helium, and their mixtures on the powder bed fusion of an Al–Cu–Li–Ti alloy using a laser beam: Evaporation, microstructure, and mechanical properties

The role of the inert processing gas during the powder bed fusion of metals using a laser beam (PBF-LB/M) is to prevent oxidation and remove process by-products, such as metal vapor and spatter particles. The present study aims to unveil additional impacts of using argon (Ar), helium (He), and two mixtures thereof as the processing gas on the material properties of a high-strength Al–Cu–Li–Ti alloy fabricated by PBF-LB/M. The part density, microstructure, static tensile properties, and volatile element evaporation were characterized as functions of the processing gas. Decreased porosity levels and increased melt penetration depths were found across a range of processing parameters when increasing the fraction of He in Ar indicating a more stable process and melt pool dynamics. A trend towards increasing yield and ultimate tensile strength was also observed and was attributed to a slightly refined grain size when processing under He-containing gases. The process gas had no significant influence on the evaporation of alloying constituents in the material. Overall, several advantages of using He-containing process gases over pure Ar in PBF-LB/M are demonstrated and discussed.

Mitigation of Gas Porosity in Additive Manufacturing Using Experimental Data Analysis and Mechanistic Modeling.

Shielding gas, metal vapors, and gases trapped inside powders during atomization can result in gas porosity, which is known to degrade the fatigue strength and tensile properties of components made by laser powder bed fusion additive manufacturing. Post-processing and trial-and-error adjustment of processing conditions to reduce porosity are time-consuming and expensive. Here, we combined mechanistic modeling and experimental data analysis and proposed an easy-to-use, verifiable, dimensionless gas porosity index to mitigate pore formation. The results from the mechanistic model were rigorously tested against independent experimental data. It was found that the index can accurately predict the occurrence of porosity for commonly used alloys, including stainless steel 316, Ti-6Al-4V, Inconel 718, and AlSi10Mg, with an accuracy of 92%. In addition, experimental data showed that the amount of pores increased at a higher value of the index. Among the four alloys, AlSi10Mg was found to be the most susceptible to gas porosity, for which the value of the gas porosity index can be 5 to 10 times higher than those for the other alloys. Based on the results, a gas porosity map was constructed that can be used in practice for selecting appropriate sets of process variables to mitigate gas porosity without the need for empirical testing.

Fabrication of Metal Contacts on Silicon Nanopillars: The Role of Surface Termination and Defectivity.

The application of nanotechnology in developing novel thermoelectric materials has yielded remarkable advancements in material efficiency. In many instances, dimensional constraints have resulted in a beneficial decoupling of thermal conductivity and power factor, leading to large increases in the achievable thermoelectric figure of merit (ZT). For instance, the ZT of silicon increases by nearly two orders of magnitude when transitioning from bulk single crystals to nanowires. Metal-assisted chemical etching offers a viable, low-cost route for preparing silicon nanopillars for use in thermoelectric devices. The aim of this paper is to review strategies for obtaining high-density forests of Si nanopillars and achieving high-quality contacts on them. We will discuss how electroplating can be used for this aim. As an alternative, nanopillars can be embedded into appropriate electrical and thermal insulators, with contacts made by metal evaporation on uncapped nanopillar tips. In both cases, it will be shown how achieving control over surface termination and defectivity is of paramount importance, demonstrating how a judicious control of defectivity enhances contact quality.

Simulation and experimental study of temperature and mass distributions of indium metal in vacuum evaporation

The temperature field and spatial distribution of metal vapor (i.e., flow field) are critical for the purity and direct yield of metals. However, it is impossible to accurately determine the temperature field and distribution of the metal vapor in a vacuum furnace. This study developed a surface-to-surface thermal radiation and volume of fluid multiphase flow coupling model. The temperature distribution and mass distribution of indium vapor in the vertical vacuum furnace at different temperatures from 1423 to 1573 K under the condition of 1 Pa were obtained. The reliability of the model was verified by experimental data obtained under the same conditions as the simulation. The temperature difference between the inside and outside of the condensing plate was 30–45 K in the temperature interval of 1423–1573 K. The temperature difference between the inside wall and the center of the condensing plate was 10 K. The simulation results of indium vapor mass distribution match with the experimental values; the overall temperature error is 5%, and the volatility error is less than 15%. The model developed in this study can be used to predict the temperature field and metal vapor distribution in a vacuum furnace, which will significantly reduce experimental exploration and accurately guide the production practice of vacuum metallurgy. This will expand the application of vacuum metallurgy technology in metal purification, material preparation, waste recycling, and other industries. This can effectively reduce exploratory experiments in the process of vacuum distillation to prepare high-purity metals, reduce the consumption of resources and energy in the experiment and production process, and achieve clean production.

Effect of Sc on the Wettability of ER5356 Welding Wires and the Porosity of Deposited Metal.

In this study, Al-Mg and Al-Mg-Sc ER5356 welding wires were adopted, and the effects of the Sc element on the wetting behavior of the molten metal and the porosity of the deposited metal were investigated. Al-Mg-Sc and Al-Mg welding wires exhibit wetting angles of 17.2 and 12.4°, respectively, and their porosities of deposited metal were 0.885 and 0.454%, respectively. Adding the Sc element to ER5356 welding wires reduced the surface tension and then increased the pore difference pressure, wettability, and spreadability of the molten pool, which is beneficial for pore overflow. Besides, adding Sc elements could increase the molten droplet size and the metallic vapor recoil for the ER5356 wire and then stabilize droplet transfer.

Optimizing refuse-derived fuel production from scheduled wastes through Aspen plus simulation

This study aims to improve the quality of fuel with high calorific value namely Sfuel – a commercial high-quality refuse-derived fuel (RDF) from hazardous waste via modifying the process design and operating parameters of thermal conversion process. The study analyses key parameters of RDF quality, such as calorific value and heavy metal content, before and after process modifications based on the combination of experimental and simulation using Aspen Plus. In this study, the temperature and pressure of the simulation system are varied from 100 to 700 °C and from 1 to 5 bar, respectively. Findings indicate that there are a total of eleven heavy metals and 179 volatile compounds in the “Sfuels”. The quality of the targeted product is greatly improved by the metal evaporation at high temperatures and pressures. However, the calorific value of RDF significantly decreases at 700 °C due to a large amount of the carbon content being evaporated. Although the carbon content at high temperatures is significantly lost, the heat from the vapour stream reactor outlet, which is reused to preheat the nitrogen gas stream supplied to the system, reduces energy consumption while improving the thermal conversion efficiency of the system. Besides, low pressure along with high temperature are not the optimal conditions for quality Sfuels improvement by thermal conversion. Results also indicate that electric heating is more economically efficient than natural gas heating.

Influence of reduced pressure on arc and weld pool properties in TIG welding

In this article, transient transport phenomena in the arc and weld pool for different ambient pressures during tungsten inert gas welding were reported. Arc plasma and weld pool behaviour vary with ambient pressure because of changes in arc thermophysical properties. The maximum arc temperature decreases with decreasing ambient pressure because of reduced plasma electrical conductivity. Decreased arc mass density results in a lower maximum weld pool surface temperature and a decrease in maximum metal vapour content as ambient pressure decreases. Arc pressure decreases with decrease in ambient pressure, resulting in shallower penetration. Calculated arc temperature distribution and weld cross-section are compared with experiments to validate the modeling method for simulating heat and mass transfer phenomena in low ambient pressure welding.

Investigating arc and molten metal transport phenomena in gas metal arc welding with Ar–CO2 gas mixtures using a numerical method

This paper presents a numerical investigation of the transient transport phenomena of the arc and molten metal during gas metal arc welding (GMAW) using shielding gas mixtures ranging from 100% Ar + 0% CO2 to 80% Ar + 20% CO2. The thermophysical parameters of the Ar–CO2 mixtures, considering the presence of metal vapor, were calculated as a function for a temperature range of 1000–30 000 K. The influence of metal vapor content and CO2 proportion on the thermophysical properties of the mixed gas was discussed in detail. As the CO2 content increased from 0 to 20%, the shape of the arc changed from a bell to a cone due to the increase in mass density, specific heat, and thermal conductivity. The maximum arc temperature and velocity decreased with increasing CO2 content, resulting in larger droplets and a lower droplet transfer frequency. Although the change in electrical conductivity did not affect the arc shape, it did influence the arc temperature by altering the distribution of current density. Experiments of droplet transfer and arc behavior were carried out, and the results showed that the simulated droplet size, transfer frequency, and arc temperature distribution agreed well with the experimental values. These findings could serve as a theoretical tool for better understanding the underlying physical mechanisms of the GMAW process using different shielding gases, ultimately aiming to achieve high weld quality.

Influence of environmental pressure on the energy coupling and droplet transition behavior in laser welding with filler wire

The influence of environmental pressure on droplet behavior and weld formation in laser welding with filler wire for 304 stainless steel was investigated and the energy coupling behavior was analyzed. As ambient pressure increases from 5 kPa to 700 kPa, the weld depth decreases by 77 %, the variance of the weld width increases approximately 5 times, and the continuity of the weld surface formation deteriorates. During the welding process, a high-speed camera was employed to observe the melt pool, plasma, and melt drop transition behavior. With an increase in the ambient pressure followed by an increase in the metal evaporation temperature, the effects of shielding of the plasma and its internal metal vapor particles on the laser beam lead to a reduction in the depth of the melt. The inverse bremsstrahlung absorption of laser by plasma increased by approximately 36.3 times at 700 kPa compared with that at atmospheric pressure. The number of metal vapor particles at 700 kPa is approximately 3.58 times higher than that at 101 kPa, and the average particle diameter is approximately 0.4 times higher, causing enhanced absorption of laser light by the metal vapor particles. An increase in gas density at elevated ambient pressures resulted in a significant increase in the resistance to droplet descent and decrease in the drive force, leading to an increase in the droplet transition period. This change shifts from a liquid bridge transition to a particle transition, which is the main cause of the deterioration of weld surface formation at high pressures.

Silver-Containing Collagen Scaffold: Synthesis and Structure

A new metal-containing hybrid material is prepared by the modification of a porous collagen sponge with silver nanoparticles obtained by metal vapor synthesis. Isopropanol is used as a dispersion medium for the production of the silver organosol. The composite is characterized by different physicochemical methods.

Multi-Physics Modeling of Melting-Solidification Characteristics in Laser Powder Bed Fusion Process of 316L Stainless Steel.

In the laser powder bed fusion process, the melting-solidification characteristics of 316L stainless steel have a great effect on the workpiece quality. In this paper, a multi-physics model was constructed using the finite volume method (FVM) to simulate the melting-solidification process of a 316L powder bed via laser powder bed fusion. In this physical model, the phase change process, the influence of temperature gradient on surface tension of molten pool, and the influence of recoil pressure caused by the metal vapor on molten pool surface were considered. Using this model, the effects of laser scanning speed, hatch space, and laser power on temperature distribution, keyhole depth, and workpiece quality were studied. This study can be used to guide the optimization of process parameters, which is beneficial to the improvement of workpiece quality.

Metal evaporation dynamics in electron cyclotron resonance ion sources: plasma role in the atom diffusion, ionisation, and transport

We present a numerical study of metals dynamics evaporated through resistively heated ovens in electron cyclotron resonance (ECR) plasma traps, used as metal ion beam injectors for accelerators and multi-disciplinary research in plasma physics. We use complementary numerical methods to perform calculations in the framework of the PANDORA trap. The diffusion and deposition of metal vapours at the plasma chamber’s surface are explored under molecular flow regime, with stationary and time-dependent particle fluid calculations via COMSOL Multiphysics®. The ionisation of vapours is then studied in the strongly energised ECR plasma. We have developed a Monte Carlo (MC) code to simulate the in-plasma metal ions’ dynamics, coupled to particle-in-cell simulations of the plasma physics in the trap. The presence of strongly inhomogeneous plasmas leads to charge-exchange and electron-impact ionisations of metals, in turn affecting the deposition rate/pattern of the metal on the walls of the trap. Results show how vapours dynamics depends both on evaporated metals and the plasma target. The 134Cs, 176Lu, and 48Ca isotopes were investigated, the first two being radioisotopes interesting for the PANDORA project, and the third as one of the most required rare isotope by the nuclear physics community. We present an application of the study: MC computing the γ activity due to the deposited radioactive neutral nuclei during the measurement time, we quantitatively estimated the overall γ-detection system’s efficiency using GEANT4, including the poisoning γ-signal from the walls of the trap, relevant for the γ-tagging of short-lived nuclei’s decay rate in the PANDORA experiment. This work can give valuable support both to the evaporation technique and plasma source optimisation, for improving the metal ion beam production, avoiding huge deposit/waste of metals known to affect the long-term source stability, as well as for radio-safety aspects and reducing material waste in case of rare isotopes.

Comparative analysis of micro patterned PDMS-based piezoresistive pressure sensors with multifunctional strain and health monitoring applications

Flexible strain and pressure sensors are widely utilized for healthcare and wearable applications. But the majority of the sensors include sophisticated fabrication methodology, are less adaptable, expensive, and need to provide higher sensitivity. In this work, addressing these issues, we have investigated four different micropatterned Poly Dimethyl Siloxane (PDMS)-based device configurations to develop a cost-effective, high performance physical sensing form for both pressure and strain sensing. PDMS is poured into four different micropatterned molds, and the patterned surface of the PDMS is rendered conductive by the thermal evaporation of copper metal. Given the ease of fabrication and clean room-free approach, the optimized pressure sensor yields a sensitivity of 1.77 kPa−1 over the dynamic range of 100 N – 600 N and a response time of 0.31 s. Further, the PDMS-based pressure sensor is used for an ultrasensitive carotid arterial pulse and speech detection to demonstrate its real-time applications. When utilized as a strain sensor, the fabricated device exhibits a (GF) Gauge Factor of 22 and 0.2 s response time and could detect compressive and tensile strains ranging from 9.2–61.6 %. To illustrate its practicality, the PDMS-based strain sensor is also used for gesture detection. This excellent response of the fabricated sensor can be attributed to a piezoresistive working mechanism. The concept presented here paves the way for developing adaptive, low-cost, clean-room-free, simpler multipurpose sensors for medical applications and wearable consumer electronics by exploring different types of novel architectures with optimal performance.

Influencing mechanisms of melt behavior on metal vapor characteristic and columnar grain formation in wire-arc directed energy deposition of titanium alloy

The metal vapor characteristic and columnar grain formation, influenced by the melt behavior in wire-arc directed energy deposition (WA-DED) of titanium alloy, have great effects on the tungsten electrode contamination and component performance. In this study, a spectroscopic system was adopted to measure the arc temperature and metal vapor distributions, and a multi-physical wire-melt pool model was developed to investigate the wire metal transfer and melt pool convection in WA-DED of titanium alloy. The microstructures of the fabricated components were studied. The influencing mechanisms of melt behavior on the metal vapor characteristic and columnar grain formation, and the tungsten electrode contamination mechanism were revealed. The experimental and numerical results showed that a stable liquid bridge transfer mode was achieved during the WA-DED process. Compared with the one-layer case, the molten metal flow patterns in the multi-layer case were unchanged, but the higher melt temperature caused stronger Ti evaporation; then more Ti vapor entered the arc plasma and absorbed its energy, causing a higher concentration of Ti+ ion in the whole arc region, and thus the arc temperature was decreased. The Ti+ ion can be transported to the negative electrode surface by the cataphoresis, dominating the electrode contamination. Low heat input and high arc force were beneficial to the columnar to equiaxed grain transition.

3D Carbon-Based Conductive Network Printed for Glucose Sensors on Curved and Flexible Substrates.

The rising prevalence of diabetes has led to an increased focus on real-time glucose monitoring. Wearable glucose sensor patches allow noninvasive, real-time monitoring, reducing patient discomfort compared to invasive sensors. However, most existing glucose sensor patches rely on complex and contaminating metal vapor deposition technologies, which pose limitations in practical production. In this study, we propose a novel approach for preparing graphite/multiwall carbon nanotubes (MWCNT)/reduced graphene oxide (rGO) using a high-viscosity ink, which can be easily obtained through simple mechanical stirring. To create intricate patterns and enable printing on curved substrates, we employed a 3D printer equipped with an infrared laser ranging system. The ink served as a working electrode, and we developed a three-electrode system patch with a concentric circle structure. Subsequently, the working electrode underwent enzymatic modification with glucose dehydrogenase with flavin adenine dinucleotide (GDH-FAD) using a polymer embedding method. The resulting wearable glucose sensor exhibited a sensitivity of 2.42 μA mM-1 and a linear detection range of 1-12 mM. In addition, the glucose sensor has excellent anti-interference capability and demonstrates good repeatability in simulated real human wear scenarios, which meets the requirements for accurate human detection. These findings provide valuable insights into the development of human health monitoring technologies.

Effect of nanoclusters formed by metal impurity on magnesium vapor condensation in silicothermic process: a molecular dynamics study

In the silicothermic process, some metal oxide impurities that coexist with dolomite are inevitably reduced to metal vapors, which condense to metal impurities in the magnesium crystallizer. In this paper, the molecular dynamics simulation method was adopted to investigate the effect of impurity clusters on the crystallization transition of undercooled magnesium vapor. The results showed that saturated vapor atoms tend to nucleate on the pre-existing impurity cluster, promoting the crystallization rate of magnesium vapor. The promoting effects of impurity clusters on the crystallization of magnesium vapor depend on their sizes and species. The cluster with a larger size demonstrated a more substantial promoting impact. Moreover, in the three impurities studied in this paper, magnesium vapor condenses on the Fe cluster at the fastest rate due to the bcc structure of the Fe cluster and the strong interaction between Fe and Mg atoms. For Ni and Cu clusters with the same fcc structure, the promoting effect of the Ni cluster on the crystallization of Mg vapor is more evident because the interaction between Ni-Mg atoms is stronger than between Cu-Mg atoms.

Investigation of the dielectric recovery process of vacuum arc in double breaks by planar laser-induced fluorescence

The multibreak vacuum circuit breaker uses multiple short gaps to interrupt the fault current, greatly improving the dielectric strength, and is a viable method to realize high-voltage interruption. The metal vapor distribution near the current zero is crucial for the dielectric recovery process in the multibreak vacuum circuit breaker. Due to the complicated dielectric construction and the interaction between the breakers, the vacuum arc inevitably deviates from the axisymmetric distribution during the interruption process. The traditional diagnosis method limited to 0D or 1D is not sufficient to study the real distribution of metal vapor near the current zero. To address these issues, we developed a planar laser-induced fluorescence method to measure the 2D distribution of copper vapor near the current zero by detecting 510.6 nm fluorescence intensity. The results indicate that for the butt contacts, the copper vapor is diffused in the gap of the high-voltage break and aggregated on the cathode surface of the low-voltage break. The axial magnetic field and transverse magnetic field affect the 2D copper vapor distribution and eliminate the inconsistency, which is achieved by affecting the motion of charged particles and the ionization-recombination process. Furthermore, the copper vapor density exhibits a positive dependence on the arc current, and the magnetic field impacts the density increase rate and distribution mode.

Understanding the bonding mechanism in short-time resistance projection welding: a comprehensive analysis

Capacitor discharge welding (CDW) is characterized by a pulsed electrical current profile. It is primarily utilized for resistance projection welding tasks, offering high power densities and short welding times. According to the latest findings, the welding process can be divided into different phases: contacting, activating, material connection, and holding pressure. During the activation phase, high-speed video-imaging reveals the generation of metal vapor which effectively eliminates impurities and oxide layers from the contact zone. The result of this is an activated surface. The purpose of this paper is to describe the physical effects of the bonding mechanism during short-time resistance welding. The Chair of Joining Technology and Assembly at the Technische Universität Dresden has a laboratory facility that can interrupt the welding current at any desired time during capacitor discharge welding. This allows different welding current profiles with always the same current rise time to be scientifically investigated. The experimental findings were supplemented with simulative analyses to clarify the bonding mechanism in resistance projection welding. Three different surface conditions are considered to generalize the findings on the bonding mechanism. Temperature and current density distributions were assessed to provide a physical description of the activation phase. The power density in the joining zone at different interruption times is determined, which gives an indication of activation by metal vaporization. The material connection is determined experimentally for the same interruption times. The numerical simulation model can be used to describe the bonding mechanism in short-time resistance welding. In resistance welding, the bond is formed due to the molten phase (solidification structure). In short-time resistance welding, the bond is formed due to surface activation by metal vaporization.