Metal Vapor Research Articles

Effect of Copper Vapor on Radiation Properties of C4F7N Gas Mixtures

C4F7N and its mixture with buffer gases are regarded as the most promising SF6-alternative gases in gas circuit breakers. The switching arc can severely ablate the electrodes, producing copper metal vapor that combine with the C4F7N gas mixture to chang radiation characteristics. This paper compares the net emission coefficient of C4F7N mixtures at various mixing ratios and assesses the effect of 20% copper vapor. It is found that adding copper vapor can greatly enhance radiation.

Alkali-modified halloysite for enhanced cadmium/lead vapor capture: Focus on silicic surface via experimental and computational investigations

We attempted to activate the Si surface of Halloysite (Hal) to enhance its adsorption capacity for heavy metal (HM, CdCl2/PbCl2) vapors through thermal-alkali modification. A combination of experimental and simulation methods was used to analyze the stabilization mechanism of CdCl2/PbCl2 comprehensively. FTIR, 1H MAS NMR, and XPS results confirm the generation of Si-OH groups on the alkali-treated Hal (AHal) surface. The adsorption performance of adsorbents was investigated in a two-stage high-temperature adsorption setup, and the results show that a relatively short alkali treatment time (20 min) improved the adsorption capacity of Hal, while a longer treatment time (60 min) led to a negative impact. XPS results revealed that the adsorption of CdCl2/PbCl2 involved both physical and chemical adsorption. Grand Canonical Monte Carlo simulations demonstrated an increased adsorption potential of AHal and enhanced reactivity with the HMs. Density functional theory was employed to investigate the adsorption mechanism of Cd/Pb compounds on the Si surface. Compared to raw Hal, AHal exhibited higher adsorption energy for HMs after introducing Si-OH groups, resulting in a more stable configuration. The stabilization of Cd/Pb monomers on the Si surface primarily relies on promoting the H migration from Si-OH to interlayer O and then forming covalent bonds with the remaining active O atoms, while Si-OH played a role in facilitating the occurrence of De-HCl reaction, thereby transforming the adsorption of metal chlorides into more stable metal monomers adsorption.

Electroplating on Unconventional Ultra-Compliant Substrates for Travelling Wave Tube Amplifiers

We report gold electroplating on ultra-compliant substrates comprising helical slow wave structures (SWSs) for traveling wave tube amplifiers (TWTAs) [1]. The novel ultra-compliant substrates are composed of edge-tethered tri-layer metal ribbons with a helical geometry of microscale diameter. After electroplating with gold, we obtain overall thicknesses of a few um. We discuss different controllable electroplating conditions that influence thickness, uniformity, roughness, and related properties of deposited gold films on helical ribbons. In addition to increasing conductance of the electroplated helical ribbons, electroplating stabilizes the helix at its equilibrium diameter, with the pitch predicted by Prakash et al.[1].Our method of fabrication of ultra-compliant helical ribbons starts with defining strips of width 5 µm to 10 µm by optical lithography, metal evaporation, and lift-off, deposited on Si substrates coated with a sacrificial layer of Ge or GeOx,. We use Cr/Au/Cr tri-layers to create an inherent stress gradient that causes the strip to self-assemble into a helix, after etching with XeF2 for selective removal of a sacrificial layer. Diameter and pitch of the released helices are controlled by varying the thickness, the elastic modulus, the residual stress, and the in-plane geometry of the deposited tri-layer metal strips. The gold electroplating process uses a sulphate-based gold solution in a two-electrode electrochemical setup with the helix as the cathode and a platinized mesh as the anode [2]. We deposit gold to a thickness of a few um, using a pulsed current source with variable parameters. Direct current can also be used with smaller deposition times. Our results demonstrate the application of electroplating to unconventional ultra-compliant helix of nanoscale dimensions. Reference [1] Divya J. Prakash,., Matthew M. Dwyer, Marcos Martinez Argudo, Mengistie L. Debasu, Hassan Dibaji, Max G. Lagally, Daniel W. van der Weide, and Francesca Cavallo. 2020. “Self-Winding Helices as Slow-Wave Structures for Sub-Millimeter Traveling-Wave Tubes.” ACS Nano, 2021, 15, 1229-1239. doi:10.1021/acsnano.0c08296.[2] Max G. Lagally, Anjali Chaudhary, Daniel van der Weide, Divya J. Prakash, and Francesca Cavallo, Improved Self-assembly of Helices via Electrodeposition on Freestanding Nanoribbons for TWT Application, provisional US patent application (P220249US01)Work supported by U.S. AFOSR-Award No FA9550-22-1-0086.

Effect of energy parameters on droplet transfer behavior and weld formation in laser-arc hybrid welding with cable-type welding wire

This paper describes the droplet transfer behavior and weld formation of laser-arc hybrid welding with cable-type welding wire (CWW). The droplet transfer behavior was photographed in real time by using a high-speed camera. The effects of energy parameters on arc morphology, droplet transfer behavior and weld formation were studied through experimental and theoretical analyses. The results show that the arc is deflected toward the laser direction, and the deflection degree increases with increasing laser power. The interaction between the laser and arc is enhanced by rotating the arc. The rotating arc enhances the interaction between plasma, the arc is more compressed and the arc volume is smaller as the welding current increases. The droplet transfer frequency increased with increasing laser power and decreased after reaching the critical value. The reaction force of metal vapor and electromagnetic force affect the droplet transfer frequency, and the maximum frequency of droplet transfer is 180.8 Hz under a laser power of 2.5 kW. The rotational force promotes molten droplet transfer and maintains the axial transition, and the welding current has a strong effect on increasing the droplet transfer frequency. The influence of laser power on weld penetration is greater than that of welding current, the weld penetration increases significantly with increasing laser power, and the cross section of the weld seam exhibits laser-arc hybrid welding characteristics.

Coupled Computational Fluid Dynamics-Discrete Element Method Model for Investigation of Powder Effects in Nonconventional Laser Powder Bed Fusion Process.

The present study proposes a comprehensive 3D computational fluid dynamics-discrete element method (CFD-DEM) coupled simulation model to investigate the particle dynamics induced by SS316L metal vapor spouting during single-scan-track laser powder bed fusion (L-PBF) processing. The model provides the ability to examine the effects of nonconventional process variables such as the chamber pressure and gravitational force on the suppression of the spatter and denudation phenomena. The simulation results imply that adjusting the gravitational force provides an effective technique for suppressing both spatter formation and powder bed denudation. In addition, the chamber pressure has only a marginal effect on the denudation phenomenon. In particular, under a higher operating pressure, the metal vapor tends to spout in the upward direction, while under a lower pressure, the spouting is more radially distributed. As a result, the simulation results obtained in this study have suggested that the chamber pressure and gravitational force may both provide feasible approaches for suppressing the spattering and denudation phenomena, particularly in the L-PBF processing of light-weight materials.

Wound Coating Collagen-Based Composites with Ag Nanoparticles: Synthesis, Structure and Biological Activity

The search for materials for a new generation of wound coatings is important due to the increase in antibiotic-resistant microorganisms and the number of patients with untreatable chronic purulent wounds. Metal nanoparticles, specifically silver nanoparticles, have antimicrobial activity and do not induce known bacterial resistance. To obtain new Ag-containing nanocomposites, type I collagen was extracted by an enzyme–acid method from cattle tendons. Silver nanoparticles were obtained by an environmentally safe method, metal-vapor synthesis (MVS), which enables obtaining metal nanoparticles without impurities. For this, metal vapors were cocondensed in a vacuum of 10−2 Pa on the walls of a quartz reactor cooled to 77 K using acetone as an organic dispersion medium. The composition of the collagen surface was determined by XPS using the spectra of C1s, N1s, and O1s. The presence of a peak with a binding energy of approximately 368.57 eV in the Ag 3d5/2 spectrum indicates the state of Ag0 silver atoms in the nanocomposite. SEM images showed that collagen contributes to the effective stabilization of Ag nanoparticles with an average size of 13.0 ± 3.5 nm. It was found that collagen is non-toxic and biocompatible with skin cells and fibroblasts. The collagen–Ag nanoparticle nanocomposites exhibited antimicrobial activity against bacteria Bacillus subtilis, Escherichia coli, and fungi Aspergillus niger.

Dependence of electron and neutral vapor density distributions on anode mode of high current vacuum arc

The vacuum arc discharge makes transition to a footpoint mode, anode spot type 1 (type 1) mode and anode spot type 2 (type 2) mode under high current conditions. The mode dependence of the electron and metal vapor densities were experimentally quantified using dichroic Shack–Hartmann type laser wavefront sensors. In the type 1 mode, the electron and metal vapor densities were about 2.5 times higher than the footpoint mode. The electron density of the type 2 mode was three times higher than that of the type 1 mode, while significant difference was not found in the metal vapor density. Such higher electron density for the type 2 mode than the type 1 mode was coherent with a previous result obtained by Stark broadening. The present electron and metal vapor density measurement demonstrated that the amount of the electrode erosion was in the following order: footpoint mode < type 1 mode < type 2 mode, which agreed with a previous study.

Composition, Structure and Properties of Antifriction Alloys Based on the Charge Obtained by Electrodispersion of Bronze Waste BrO5C25 in Kerosene

Purpose. Study of the composition, structure and properties of antifriction alloys based on the electroerosion charge of bronze BrO5C25 obtained in a carbon–containing medium lighting kerosene.Methods. Dispersion of the waste of the BrO5S25 alloy was carried out at an installation for electrodispersing electrically conductive materials. The waste of the BrO5C25 alloy was used as metal waste. Lighting kerosene was used as the working fluid.As a result of exposure to short-term electrical discharges between the electrodes and the waste, their destruction occurred with the formation of fine particles. To obtain compacted materials, a Herzog TP 20 manual table press was used. Modern equipment and complementary methods of physical materials science were used to study the composition, structure and properties of the sintered products obtained.Results. Surface analysis showed that the alloys have a fine-grained structure, uniform phase distribution and a small number of pores. The analysis of the elemental composition found that carbon is contained on the surface of the new alloys, and all other elements Sn, Cu and Pb are distributed relatively evenly. The analysis of the studied alloys showed the presence of phases in them: Cu, CuSn, SnO, CuO, PbO, Pb. There are no carbide-forming elements in the alloy. It has been experimentally established that the composition, structure and properties of the charge dispersed by electroerosion of bronze BrO5C25 affect the tribological properties of the alloy blanks. In particular, the presence of free carbon in the alloy from the electroerosion charge obtained in kerosene, which acts as a solid lubricant, leads to a decrease in the coefficient of friction.Conclusion. It is shown that alloys obtained from an electroerosive charge have higher microhardness values in comparison with an alloy obtained from an industrially used charge. A significant increase in the microhardness of alloys is explained by the presence of highly hard particles formed during the quenching of metal vapors in the working fluid during dispersion. The presence of small fractions in electroerosive materials contributes to an increase in the density of compressions and a decrease in the porosity of workpieces.

Zinc Evaporation from Brass Scraps in the Atmosphere of Inert Gas.

A description of the process of metal evaporation from liquid alloys at an atmospheric pressure has a practical value for both the smelting and remelting of their scraps. The quantities of volatile components that are eliminated in these processes depend on many factors of which the type of melting device, the method and conditions of the process performance, the alloy composition and the kind of applied atmosphere are of the greatest importance. In this paper, the results of the research on zinc evaporation from brass scraps containing 10.53 wt% Zn are presented. The experiments were conducted using the thermogravimetric method at 1080 ÷ 1240 °C in a helium atmosphere. In the research, the levels of zinc removal from copper ranged between 82% and 99%. The values of the overall mass transfer coefficient for zinc kZn, determined based on the experimental data, ranged from 4.74 to 8.46 × 10-5 ms-1. The kinetic analysis showed that the rate of the analysed process was determined by mass transfer in the gas phase.

Integration Plasma Strategy Controlled Interfacial Chemistry Regulation Enabling Planar Lithium Growth in Solid‐State Lithium Metal Batteries

AbstractSolid‐state lithium metal batteries (SSLMBs) are identified as a highly promising candidate for next‐generation energy storage devices, yet they still face uncontrollable dendritic lithium (Li) growth originating from interfacial incompatibility. To address this issue, an “integration plasma (IP)” strategy for interlayer construction is proposed that integrates metal reduction and vapor deposition functions, featuring the ability to give a manipulable and quantifiable chemical regulation for controlling the surface concentration (Csurface) and the atomic ratio of the introduced metal element and electronegative element (ARE/M) on solid‐state electrolyte (SSE). This IP‐formed interlayer can in situ react with Li anode to synchronously produce metal‐Li alloy, Li salt and amorphous carbon, thus offering an “integrated function” to promote a spherical and hexagonal Li growth, preventing the dendrite propagation from SSE. When Csurface of metal elements and corresponding ARE/M is regulated as ≈1.13 nmol cm‐2 and ≈2.6, the IP‐modified SSE prolongs the lifespan of SSLMBs with LiNi0.8Co0.1Mn0.1O2 cathode to over 1000 cycles with a low‐capacity attenuation of 0.03% per cycle, highlighting the multiply functions of IP to accelerate the practical application of SSLMBs.

Plasma-activated silicon–glass high-strength multistep bonding for low-temperature vacuum packaging

Si-glass bonding is one of the most crucial vacuum packaging methods in semiconductor devices; however, high temperatures (>300 °C) are required to achieve a high bonding strength, which limits its applications. Current low-temperature Si-glass bonding requires a humid environment and is not compatible with vacuum environments. In this study, a low-temperature vacuum multistep bonding method based on plasma activation was proposed. Traditional plasma-activated low-temperature bonding relies on water-molecule bridging in the atmosphere to lower the bonding temperature. In contrast, the proposed multistep bonding process uses plasma-activated vacuum anodic bonding for initial bonding, and then utilizes direct bonding to balance the bonding surface energy and sufficiently eliminate the bonding surface micro gap, thus achieving a high bonding strength of 18 MPa at 150 °C under vacuum. The effects of plasma activation on the hydrophilicity, surface morphology, and chemical conditions of the wafer surfaces were investigated. The morphologies of the bonding interfaces under different bonding conditions were characterized, and cross-sectional elemental scanning was used to analyze the microscopic factors. Based on the aforementioned investigations and the gap closure theory, the mechanism of multistep bonding was analyzed. Finally, the proposed bonding method was validated by fabricating micro alkali metal vapor cells. The results demonstrate that the proposed method meets the requirements for vacuum device packing at low temperatures.

Silver Vapor Supersonic Jets: Expansion Dynamics, Cluster Formation, and Film Deposition.

Supersonic jets of metal vapors with carrier gas are promising for producing nanostructured metal films at relatively low source temperatures and high deposition rates. However, the effects of the carrier gas on the jet composition and expansion dynamics, as well as on film properties, remain virtually unexplored. In this work, the free-jet expansion of a mixture of silver vapor with helium in a rarefied regime at an initial temperature of 1373 K is investigated through mass spectrometry and direct-simulation Monte Carlo methods. Introducing the carrier gas into the source is found to result in a transition from a collisionless to a collision-dominated expansion regime and dramatic changes in the Ag jet, which becomes denser, faster, and more forward-directed. The changes are shown to be favorable for the formation of small Ag clusters and film deposition. At a fairly high helium flow, silver Ag2 dimers are observed in the jet, both in the experiment and the simulations, with a mole fraction reaching 0.1%. The terminal velocities of silver atoms and dimers are nearly identical, indicating that the clusters are likely formed due to the condensation of silver vapor in the expanding jet. A high potential of supersonic Ag-He jets for the deposition of nanostructured silver films is demonstrated. The deposited jet Ag2 dimers appear to serve as nucleation centers and, thus, allow for controlling the size of the produced surface nanostructures.

Synthesis and Electronic Structure of Bimetallic AuFe Nanocomposites

Au, Fe, and AuFe nanoparticles were obtained by metal vapor synthesis using acetone as the dispersion medium. The composition and electronic structure of the particles were studied by TEM, SEM, XPS, XANES, and EXAFS. The Au and Fe particles with average diameters of 5.3 and 1.8 nm, respectively, were obtained. According to X-ray diagnostic methods, gold was in the main Au0 state, and the Au+ and Au3+ states are present in small amounts while iron existed as mixture of non-stoichiometric oxides with states close to Fe2+ and Fe3+. Bimetallic nanoparticles were solid solutions with a disordered structure and Au–Fe–O and Au–O–Fe bonds. A carbon-containing shell was detected for all types of metal particles. The obtained materials may be promising for the development of improved antimicrobial agents and new methods for treating cancer diseases.

Review of Visual Measurement Methods for Metal Vaporization Processes in Laser Powder Bed Fusion.

Laser powder bed fusion (LPBF) is of great importance for the visual measurement and analysis of the metallization process, which is the process of solid, liquid, and gas phase transformations of metal powders under high-energy laser irradiation due to the low boiling point/high saturated vapor pressure. Since the evaporation of metals involves the interaction of driving forces such as vapor back pressure, surface tension, and gravity, the movement of the melt pool is not stable. At the same time, it also produces vaporization products such as vapor plumes and sprays, which cause defects such as bubbles, porosity, lack of fusion, inclusions, etc., during the manufacturing process of the parts, affecting the performance and manufacturing quality of the parts. More and more researchers are using imaging technologies, such as high-speed X-ray, high-speed visible light cameras, and high-speed schlieren imaging, to perform noncontact visual measurements and analyses of the melt pool, vapor plume, and spatter during the metal evaporation process, and the results show that the metal evaporation process can be suppressed by optimizing the process parameters and changing the processing atmosphere, thereby reducing part defects and improving part performance and built part quality. This paper reviews the research on metal evaporation mechanisms and visual measurement methods of metal evaporation, then discusses the measures of metal evaporation, and finally summarizes and prospects the future research hotspots of LPBF technology, according to the existing scholars' research on numerical simulation analysis and visual measurement methods of the metal evaporation process.

Experimental study on the formation characteristics of PM0.4 from preheating combustion of sewage sludge

Municipal sewage sludge (SS) is gaining increasing attention as a carbon–neutral fuel. Preheating combustion has been applied in coal combustion to reduce both PM0.4 and NOx. It is a promising technology for SS disposal while PM formation from preheating combustion of SS is still unknown. This study investigated the formation characteristics of PM0.4 from preheating combustion of SS. The effects of preheating temperature (Tp) and combustion temperature (Tc) on PM0.4 were analyzed. The experimental results showed that simultaneous reduction of PM0.4 and NOx from preheating combustion of SS can be achieved with Tp ≤ 1300 °C and Tc ≤ 1200 °C. The reduction of PM0.4 in preheating combustion compared to conventional combustion is mainly attributed to reduction in vaporization of Ca. Tc has more significant effect on PM0.4 while Tp can affect NOx more effectively. Because SS has a low content of fixed carbon, vaporization of refractory elements (Ca, Mg, Fe, Si and Al) through reduction reaction of refractory oxides mainly occurs under reductive atmosphere in preheating furnace. Increasing Tc will significantly increase vaporization of alkali metals (Na and K), S and Cl, while has no significant effect on vaporization of refractory elements. These are different with the results from high-alkali coal in our previous research (Reference [28]). Fe-precipitation agent used in waste water treatment results in uniform distribution of Fe in SS particles, which enhanced interaction between Fe and Si-Al containing minerals. This decreases reaction between Si-Al containing minerals and Na containing compounds. Therefore, even SS contains less Na and more Si-Al than high alkali coal, Na is easier to transfer to PM0.4 in preheating combustion of SS than high alkali coal.

Multi-Component Evaporation and Uneven Aluminum Distribution during High-Power Vacuum Laser Welding of Ti-6Al-4V Titanium Alloy

Titanium alloy is an important material for the manufacture of key components of deep-sea submersibles. High-power vacuum laser welding is an important method for welding TC4 thick plate (40–120 mm) structures. However, due to the low melting point of aluminum, its uneven distribution in the weld caused by evaporation during welding affects the quality of joints. This paper conducted experimental and simulation studies to investigate the effect of process parameters on multi-component evaporation and uneven aluminum distribution. Based on a three-dimensional model of vacuum laser welding, the mechanism of the uneven distribution of aluminum in the weld is explained. The results show that the uneven distribution of aluminum in the weld is mainly related to the metal vapor behavior and keyhole morphology. As the welding speed rises from 1 m/min to 3 m/min, the proportion of aluminum in the metal vapor and the degree of compositional unevenness increase. When the laser power increases from 6 kW to 18 kW, the proportion of aluminum in the metal vapor and degree of unevenness increase, peak at 12 kW, and then decrease. This work facilitates the selection of suitable process parameters to reduce aluminum evaporation during the high-power vacuum welding of Ti-6Al-4V alloys. Joints with a more stable performance can be obtained by avoiding the uneven distribution of aluminum.

The mechanism study of TIG-MIG hybrid welding process based on simulation

Tungsten inert gas-metal inert gas (TIG-MIG) hybrid welding combines the advantages of tungsten inert gas (TIG) welding and metal inert gas (MIG) welding. Due to the benefits of the two welding techniques, it is an effective strategy to enhance welding quality and productivity. To investigate the mechanism of arcs interaction in TIG-MIG hybrid welding, a three-dimensional transient model for arc-droplet-weld pool behavior was established. The temperature field, metal vapor content, flow fluid, current density and electromagnetic force in the arc space and weld pool were simulated and analyzed. The calculation results showed that the introduction of the TIG arc decreased the content of metal vapor and increased the arc temperature. Compared with single MIG welding, the amplitudes of maximum arc temperature and plasma velocity in TIG-MIG hybrid welding were lower. Experimental results demonstrated that the droplet deflection angle, droplet transfer frequency, weld bead cross-section, and arc temperature distribution all agreed well with calculated values.

Molecular dynamics simulation of cathode crater formation in the cathode spot of vacuum arcs

A three-dimensional model based on molecular dynamics has been developed to describe the formation of a single cathode spot in vacuum arcs. The formation of the cathode spot is assumed to be controlled by the plasma ions, the effect of which is simulated in LAMMPS through the process of ion bombardment. The cathode is represented by structured copper atoms, while the ions are continuously injected into the domain with a certain velocity towards the cathode surface. Ion bombardment leads to the appearance of a crater, which is caused by the accumulation of pressure effect against the relaxation of substrate temperature. The size of the crater is found to be determined by the spatial distribution of the injected ions. The formation of the cathode spot is also scrutinised by electron emission from the cathode surface with variable surface temperature during the cathode spot development process. In addition, the evaporated atoms forming the metal vapour are observed. This study provides a description of the formation of the cathode spot at microscale, which shall be helpful to further studies of the arc rooting and arc contact (electrode) erosion in vacuum environment.

Application of coating based on 5 nm octadecylamine-functionalized gold-nanoparticles for protecting the spin-polarization of atoms confined in a vacuum cell

We report on the expressed atomic spin-polarization protection properties of thin layers of Octadecylamine capped gold-nanoparticles applied to the inner surface of an alkali metal vapor cell. The work aims to reveal the potential of using appropriately functionalized gold nanoparticles as a novel approach to forming efficient coatings on the inner surface of vacuum cells for atomic spectroscopy. The performed layer characterization uses parameters of electromagnetically induced transparency/absorption resonances observed in the Hanle configuration. We show at the Rb D2 absorption line that cells with such a coating provide conditions for achieving high-contrast and narrow, bright, and dark resonances, comparable to those reported by others for Octadecyltrichlorosilane coatings. Using visualization software for structural analysis, we represent the possible interaction scenarios between the alkali atoms and the surface building blocks. We demonstrate and discuss the main structural and functional differences introduced by covering the cell surface with passivated nanoparticles instead of directly using molecules to form monolayers. Having gold-nanoparticles in the coating allows preserving at the same time the earlier discovered advantage for high-speed control over the Rb vapor density by light-induced desorption of atoms. That enables significant problem-solving in atomic clocks and magnetometers and eases their considerable miniaturization.

Effect of electrode locations on the matching of the pumping generator with the load in metal vapor laser

Effect of electrode locations on the matching of the pumping generator with the load in metal vapor laser