Dense Metal Research Articles

Simulation of Porosity Regrowth during Heat Treatment after Hot Isostatic Pressing in Titanium Components

Abstract Additive manufacturing (AM) is driven by design freedom, having fewer process constraints than traditional manufacturing processes. It requires careful process control and qualified parameters to create dense metal parts. However, defects in the form of cavities can be detected in as-built specimens by computed tomography. Post-processing techniques such as hot isostatic pressing (HIP) are applied to eliminate porosity, but regrowth of argon gas pores is observed after additional heat treatment. In this work, a mesoscopic heat treatment simulation of an argon-filled gas pore in titanium components is presented. A combination of HIP and high-temperature heat treatment for β-annealing is simulated. Calculated pore regrowth is qualitatively consistent with experimental observation from the literature. Simulation results support the hypothesis of argon not dissolving in the titanium matrix by assuming a constant amount of argon particles in the pore. Mesoscopic heat treatment simulations may be a part of a simulation-driven optimization of thermal post-processing to improve the quality and performance of AM components.

Enhanced performance of pinned metal foam heat sinks with dielectric coolant – A pore-scale numerical study

Recent advancements in the development of microprocessors have resulted in the design of smaller microchips with improved performance. The new designs require proper cooling systems to prevent performance degradation and permanent damage to the chips. Extended surfaces, including fin, pin, or metal foam, are one of the prominent approaches in cooling systems designs. So far, there has been limited research, especially considering pore-scale analysis on the combination of pin/fin with metal foam, which is expected to offer promising cooling performance. This study aims to evaluate the performance of pinned metal foam heat sinks with dielectric coolant as a potential cooling system for microchips. A three-dimensional pore-scale numerical model is developed to analyze the performance of the proposed heat sinks. The effect of different parameters such as Reynolds number, heat flux, pore density, and different pin shapes are investigated. The results reveal that at a Reynolds number of 100, almost all the metal foam heat sinks enhance the heat transfer performance, which can be as large as 22% in some cases. Furthermore, adding pins increases the heat energy dissipation with a slight penalty of pressure drop depending on its hydrodynamic adaptation. Too dense or loose metal foam either increases the pressure drop or decreases the heat transfer rate, deviating from the optimum range. Lastly, it is revealed that heat flux from the heater does not significantly change the performance of the pinned metal foam heat sinks.

Atomically Dispersed Aluminum Sites in Hexagonal Boron Nitride Nanofibers for Boosting Adsorptive Desulfurization Performance.

The exploitation of highly efficient and cost-effective selective adsorbents for adsorptive desulfurization (ADS) remains a challenge. Fortunately, single-atom adsorbents (SAAs) characterized by maximized atom utilization and atomically dispersed adsorption sites have great potential to solve this problem as an emerging class of adsorption materials. Herein, aiming at improving the efficiency of ADS performance via the economical and feasible strategy, the desirable SAAs have been fabricated by uniformly anchoring aluminum (Al) atoms on hexagonal boron nitride nanofibers (BNNF) via an in situ pyrolysis method. Remarkably, Al-BN-1.0 exhibited a superior adsorption capacity of 46.1 mg S/g adsorbent for dibenzothiophene, with a 45% increase in adsorption capacity compared to the pristine BNNF. Additionally, it demonstrated excellent adsorption of other thiophene sulfides. Moreover, the ADS mechanisms have been investigated through special adsorption experiments combined with density functional theory (DFT) calculations. It was demonstrated that the superior ADS performance and selectivity of Al-BN-1.0 originate from the sulfur-aluminum (S-Al) and π-π interactions cooperating synergistically. This work would cast light on a novel fabrication strategy for the SAAs based on the two-dimensional material with a tunable metal site configurations and densities for varied selective adsorption and separation.

Role of Colonoscopy in Foreign Body (Needle) Ingestion in Children: A Case Report and Literature Review

Abstract: Foreign body (FB) ingestion is one of the most complex and serious emergency conditions for diagnosis that often occurs in children. Most ingested FBs, intentionally or unintentionally, pass through the gastrointestinal tract without complications, and only a small proportion require surgical intervention inter alia colonoscopy. However, if the patient complains of abdominal pain, complications may occur, especially perforation with peritonitis, and in this case a laparotomy is needed. We reported a case of a 13-year-old girl with the chief complaint of needle ingestion two weeks ago. Patient complained of abdominal pain and was unable to defecate. Plain abdominal radiographs showed needle-shaped metal density in the lower intestinal; therefore, the patient was referred to Prof. Dr. R. D. Kandou Hospital for further treatment. An endoscopy was initially performed but no foreign body was found because they might had been in the intestine. Colonoscopy revealed a foreign body in the proximal ascending colon, transverse position. Extraction of the foreign body, along with pulling the scope and evaluating the transverse, descending, sigmoid and rectum colon which were within normal limits was carried out. Monitoring after removal of the foreign body for two days found no complaints of abdominal pain and bowel movements were normal, therefore, the patient was discharged from the hospital. In conclusion, since a sharp foreign body (a needle) was still in the proximal ascending colon, a colonoscopy was performed with successful removal of the needle. Keywords: foreign body; needle; endoscopy; colonoscopy

The Impact of Fused Filament Fabrication (FFF) Printing Profiles on 17‐4 PH Green and Sintered Parts

AbstractThe aim of this research is to characterize parts from innovative hybrid printing method for obtaining dense metal components using affordable fused filament fabrication (FFF). The introduction of Desktop Metal technology in 2015 really attracts an increase in industrial interest in the FFF printing of highly metal‐filled filament. Even though FFF is a well‐known process, there are not many studies on how to optimize the printing parameters for these feedstocks.The effects of the printing setting on producing high‐quality green parts and enhancing the mechanical properties of the finished 17‐4 PH metallic parts are investigated in this work. The influence of four printing profiles provided by a BASF plugin for Ultimaker Cura slicing software, obtained by combining different printing parameters is investigated.The ASTM E8 tensile test is used to determine the mechanical characteristics of the finished metal components. To identify differences in morphology, optical and scanning electron microscopy (SEM) observations are made on both sections of green and sintered samples. The effect of printing parameters on shrinkage and density are also taken into consideration.The findings demonstrate the importance of optimizing the printing of the green parts in order to produce full metal components that are both strong and dense.

THE MAIN TYPES OF TRAUMATIC INJURIES OF THE CHEST AFTER A EXPLOSIVE INJURY ACCORDING TO X-RAY DATA

Abstract. Introduction. Еxplosive lesions are one of the most severe and specific types of injuries in the structure of military trauma. A special role in the diagnosis of traumatic injuries of the chest belongs to the X-ray method of research, as the most accessible and fastest.
 The purpose of the work is to clarify the types and frequency of traumatic injuries of the chest, received as a result of a mine-explosive injury according to х-ray data.
 Materials and methods. The work presents an analysis of the materials of own observations of radiological methods of examination of 32 victims with explosive injuries of the chest organs who were undergoing inpatient treatment at the SI «Institute of General and Urgent Surgery named after V. T. Zaitsev NAMS of Ukraine» in the period from 23.02.2022 to 17.05.2023. All patients (100 %) underwent a digital polyposition X-ray examination of the chest organs, computer tomography of the chest organs was performed in 18,7 % of patients.
 Research results. It was established that the main types of traumatic injuries of the chest after a explosive injury are rib fractures (93,8 %), hemopneumothorax (93,8 %), the presence of fragments of metal density in soft tissues, in the chest cavity, in the heart (87,5 %) and a wound channel in the lung parenchyma (23,3 %), as well as lung contusion (78,1 %).
 Conclusions. Еxplosive chest trauma in most cases is combined, which significantly aggravates the condition of the victims, therefore, it is necessary to start an X-ray examination of severe patients directly in the operating room or intensive care unit. The main types of traumatic injuries are rib fractures, hemopneumothorax, the presence of fragments of metal density in the chest cavity and a wound channel in the lung parenchyma, as well as lung contusion.

The Potential of High-Velocity Air-Fuel Spraying (HVAF) to Manufacture Bond Coats for Thermal Barrier Coating Systems

Driven by the search for an optimum combination of particle velocity and process temperature to achieve dense hard metal coatings at high deposition efficiencies and powder feed rates, the high-velocity air-fuel spraying process (HVAF) was developed. In terms of achievable particle velocities and temperatures, this process can be classified between high-velocity oxy-fuel spraying (HVOF) and cold gas spraying (CGS). The particular advantages of HVAF regarding moderate process temperatures, high particle velocities as well as high productivity and efficiency suggest that the application of HVAF should be also investigated for the manufacture of MCrAlY (M = Co and/or Ni) bond coats (BCs) in thermal barrier coating (TBC) systems. In this work, corresponding HVAF spray parameters were developed based on detailed process analyses. Different diagnostics were carried out to characterize the working gas jet and the particles in flight. The coatings were investigated with respect to their microstructure, surface roughness and oxygen content. The spray process was assessed for its effectiveness. Process diagnostics as well as calculations of the gas flow in the jet and the particle acceleration and heating were applied to explain the governing mechanisms on the coating characteristics. The results show that HVAF is a promising alternative manufacturing process.

Dense metal corrosion depth estimation

Introduction: Metal corrosion detection is important for protecting lives and property. X-ray inspection systems are widely used because of their good penetrability and visual presentation capability. They can visually display both external and internal corrosion defects. However, existing X-ray-based defect detection methods cannot present and estimate the dense corrosion depths. To solve this problem, we propose a dense metal corrosion depth estimation method based on image segmentation and inpainting.Methods: The proposed method employs an image segmentation module to segment metal corrosion defects and an image inpainting module to remove these segmented defects. It then calculates the pixel-level dense corrosion depths using the X-ray images before and after inpainting. Moreover, to address the difficulty of acquiring training images with ground-truth dense corrosion depth annotations, we propose a virtual data generation method for creating virtual corroded metal X-ray images and their corresponding ground-truth annotations.Results: Experiments on both virtual and real datasets show that the proposed method successfully achieves accurate dense metal corrosion depth estimation.Discussion: In conclusion, the proposed virtual data generation method can provide effective and sufficient training samples, and the proposed dense metal corrosion depth estimation framework can produce accurate dense corrosion depths.

Bifunctional K3PW12O40/Graphene Oxide-Modified Separator for Inhibiting Polysulfide Diffusion and Stabilizing Lithium Anode.

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation batteries due to their high theoretical energy density. However, the practical application of Li-S batteries is still hindered by several challenges, such as the polysulfide shuttle and the growth of lithium dendrites. Herein, we introduce a bifunctional K3PW12O40/graphene oxide-modified polypropylene separator (KPW/GO/PP) as a highly effective solution for mitigating polysulfide diffusion and protecting the lithium anode in Li-S batteries. By incorporating KPW into a densely stacked nanostructured graphene oxide (GO) barrier membrane, we synergistically capture and rapidly convert lithium polysulfides (LiPSs) electrochemically, thus effectively suppressing the shuttling effect. Moreover, the KPW/GO/PP separator can stabilize the lithium metal anode during cycling, suppress dendrite formation, and ensure a smooth and dense lithium metal surface, owing to regulated Li+ flux and uniform Li nucleation. Consequently, the constructed KPW/GO/PP separator delivered a favorable initial specific capacity (1006 mAh g-1) and remarkable cycling performance at 1.0 C (626 mAh g-1 for up to 500 cycles with a decay rate of 0.075% per cycle).

(Keynote) Parameterize Important Factors for Li Metal Batteries: Cycle Life, Calendar Life and Reactivity

The lithium (Li) metal anode is essential for next-generation high-energy-density lithium metal batteries. The calendar life and reactivity (safety) are equally important to cycle stability for the real application of Li metal anode in different devices. Our recent studies have identified that preventing Li dendrite growth by stacking pressure could improve cycle life by consuming less electrolyte and preventing inactive Li0 accumulation. A similar conclusion is obtained in the study of electrodepositing Li metal anode calendar life and reactivity (safety), in which the porosity of the deposited Li dominates the Li metal corrosion rate and reactivity. The larger the porosity of deposited Li, the faster the corrosion rate/higher reactivity will be. Moreover, all cell components must be considered when it comes to the reactivity (safety) of Li metal batteries because components may react with each other. Our results revealed that dense Li metal anode owns similar reactivity as lithiated graphite/ Li-Si alloy. All results facilitate lithium metal battery design and manufacturing.

Density Functional Theory Study of Synergistic Gas Sensing Using an Electrically Conductive Mixed Ligand Two-Dimensional Metal-Organic Framework.

Two-dimensional conductive metal-organic frameworks (2D-cMOFs) have been adopted in electrochemical sensing applications owing to their superior electrical conductivity and large surface area. Here, we performed a density functional theory (DFT) analysis to study the synergistic impact of introducing a secondary organic ligand to the 2D-cMOF system. In this study, cobalt-hexaiminobenzene (Co-HIB) and cobalt-2,3,6,7,10,11-hexaiminotriphenylene (Co-HITP) were combined to form a mixed ligand MOF named, Co-HIB-HITP. A DFT-level comparative study was designed to access stability, synergistic gas adsorption capability, and gas adsorption mechanism, important factors in sensing material development. A potential energy surface calculation predicted the structural stability of Co-HIB-HITP at larger interlayer displacements around 3.6-4.2 Å regions along the ab-plane than its unmixed states, Co-HIB and Co-HITP, indicating the tunability of the stacking mode using the mixed ligand system. Furthermore, the adsorption capabilities toward toxic gases, NH3, H2S, NO, and NO2, were investigated, and Co-HIB-HITP revealed superiority over unmixed 2D-cMOFs in H2S and NH3 gas adsorption energies by showing 158 and 170% improvement, respectively. Finally, an electron charge density analysis revealed Co-HIB-HITP's unique stacking mode and Co-metal density as contributing factors to its gas-selective synergy effect. The AB stacked layers and an intermediate metal density (5.25%) significantly improved the electrostatic interactions with H2S and NH3 by inducing a change in the chemical environment of the gas binding sites. This work proposes the dual-ligand 2D-cMOF as the promising design strategy for the next-generation sensing material.

Numerical Simulations of Metallic Ion Density Perturbations in Sporadic E Layers Caused by Gravity Waves

AbstractTidal signatures in sporadic E (Es) layer have been confirmed by observations and simulations. However, the effect of gravity waves (GWs) on the Es layer formation process has not yet been fully understood. In this paper, the modulation of Es layers by GWs is examined through numerical simulations, in which a physics‐based model of Es layer is forced by neutral winds from the High Altitude Mechanistic General Circulation Model that can resolve GWs with horizontal wavelengths longer than 156 km (λh > 156 km). Comparison of the simulation results with and without the GWs (1,350 km > λh > 156 km) forcing reveals that the inclusion of GWs leads to short‐period (1.2–3 hr) density perturbations in Es layers, which are also seen in ground‐based ionosonde observations. At a given time, the metallic ion density at altitudes between 120 and 150 km can either increase (by up to ∼+600%) or reduce (by up to −90%) in response to GW forcing. The relative density perturbations are smaller (by up to 60%) between 90 and 120 km altitude. It is also found that the GW effect on the metallic ion density relates to the longitude, which is mostly explained by the geographical distribution of GWs activity in the mesosphere and lower thermosphere region. The longitudinal variation of the background geomagnetic field plays only a secondary role.

Adopting a Standard Track Routing Architecture for Next-Generation Hybrid AC/DC-Biased Logic Circuits

The adiabatic quantum-flux-parametron (AQFP) and rapid single flux quantum (RSFQ) logic families both provide distinct advantages for data processing using superconductor electronics. The development of next-generation AQFP-RSFQ hybrid logic circuits provides the opportunity to combine the benefits of both of these logic families. Adopting a standard track routing architecture for both AQFP and RSFQ layouts provides a unified framework for physical layout synthesis. We demonstrate a standard track routing architecture developed under the ColdFlux project and its implementation within AQFP. An additional advantage of the standard track routing architecture is that it provides a systematic way to overcome metal density requirements for modern-day fabrication processes. It also provides a methodical approach towards strategic moat placement for protection against unwanted flux trapping. Implementations of passive transmission line (PTL) connections and their physical placement for hybrid AQFP-RSFQ circuits are discussed. Several AQFP layouts for the ColdFlux project are redesigned to adopt the standard track routing architecture. Experimental simulation of moat performance is also presented.

Homogeneous electron liquid in arbitrary dimensions beyond the random phase approximation

Abstract The homogeneous electron liquid is a cornerstone in quantum physics and chemistry. It is an archetypal system in the regime of slowly varying densities in which the exchange-correlation energy can be estimated with many methods. For high densities, the behavior of the ground-state energy is well-known for 1, 2, and 3 dimensions. Here, we extend this model to arbitrary integer dimensions and compute its correlation energy beyond the random phase approximation (RPA). We employ the approach developed by Singwi, Tosi, Land, and Sjölander (STLS), whose description of the electronic density response for 2D and 3D for metallic densities is known to be comparable to Quantum Monte-Carlo. For higher dimensions, we compare the results obtained for the correlation energy with the values previously obtained using RPA. We find that in agreement with what is known for 2 and 3 dimensions, the RPA tends to over-correlate the liquid also at higher dimensions. We furthermore provide new analytical formulae for the unconventional-dimensional case both for the real and imaginary parts of the Lindhard polarizability and for the local field correction of the STLS theory, and illustrate the importance of the plasmon contribution at those high dimensions.

Casting process design of high pressure and heat resistant steam chamber casting

This paper is about the casting process of high pressure and heat resistant steam chamber casting. The castings are made of ZG15Cr2Mo1. The internal and external quality requirements of the casting are demanding. There are many grade 0 and grade 1 defect areas in castings, which requires that these positions should not have shrinkage cavity and porosity and other defects.This casting scheme includes the design scheme of modeling, modeling material selection, coating selection, parting surface and casting system establishment, process parameters establishment, sand core design, casting riser design, cold iron design and so on. By using AnyCasting and MAGMA to simulate and predict the feasibility of the casting process scheme, a more appropriate casting process design scheme was finally determined to ensure the density of the casting metal at the flaw detection site, and eliminate the defects of shrinkage porosity and porosity of the casting, so as to ensure the requirements of leakage of the casting in practice, and make the casting meet the defect rating. At the same time, the production rate of the scheme is relatively high, which can reduce the production cost.

Tungsten separation behavior on preparation of high-purity cerium by combined vacuum gravity sedimentation–directional solidification

In light of the difficult removal of harmful impurity tungsten (W) in Ce metal, in this paper a combined vacuum gravity sedimentation‒directional solidification method was innovatively designed and the W separation behavior was investigated. By reducing the electron beam power instantly and gradually at reduction rates of 1, 3 and 5 kW/min, it is found that W is enriched at the bottom of ingots as the melt solidifies. The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases, attributed to the k0(W) ＞ 1 and ρ(W) ＞ ρ(Ce). Overall, the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot, and the purity of Ce increases from 99.932 wt% to 99.995 wt% by this combined method. Additionally, this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.

Thermal instability-induced formation of hierarchically structured porous GaN/nitrogen-doped carbon with high performance for supercapacitor

Electrode materials with high specific surface area (SBET) and high stacking density face a dilemma, making it difficult for supercapacitor electrodes to simultaneously exhibit high areal discharge specific capacitance (Ca,dis) and high volumetric discharge specific capacitance (Cv,dis). By exploiting the high stacking density and thermal instability of metal (after group VIB) nitrides, an electrode material of GaN honeycombs/nitrogen-doped carbon is achieved that simultaneously exhibits high Ca,dis (730 mF cm−2) and Cv,dis (251 F cm−3) at 200 mF cm−2 and manifests a linear relationship between Ca,dis and electrode loading ranging from 3.4 to 7.6 mg cm−2. The GaN honeycomb-based symmetric supercapacitors can deliver high areal/volumetric specific energy of 21.8 μW h cm−2/3.12 mW h cm−3 at 5 mW cm−2/714.3 mW cm−3 after 20,500 cycles at varied current densities from 10 to 50 and then to 10 mA cm−2. The high performance of the GaN honeycomb-based electrodes is attributed to the synergistic effect of high SBET (378.3 m2 g−1), suitable pore sizes (concentrated at 1.4 nm), surface capacitive effect, and promoted kinetics of the faradaic reaction, due to the hierarchical structure combining the high SBET and fast kinetics of nanomaterials with the high stacking density of micron materials.

A Lean‐Zinc and Zincophilic Anode for Highly Reversible Zinc Metal Batteries

AbstractLean‐zinc anode is a promising configuration that can eliminate the trade‐off of energy density and cycle lifetime of zinc metal (Zn0) batteries. However, there are rare investigations of lean‐Zn anode designs and it remains a grand change to sustain high zinc reversibility under lean zinc conditions. Herein, a lean‐Zn anode design based on a hierarchical and zincophilic cobalt metal (Co0) nanowire‐decorated carbon host, which is derived from a ZnCo bimetallic organic framework, is reported. Within the lean‐Zn anode, the trace amount of Zn0 acts as a zinc reservoir to make up for any irreversible loss of zinc source upon cycling, while the zincophilic Co0 nanowires can guide uniform zinc nucleation and growth through a lattice matching mechanism. Consequently, high Zn0 reversibility (average Coulomb efficiency of 99.6% for 4250 cycles), low nucleation overpotential (50.8 mV at 1 mA cm−2), and uniform and compact zinc electrodeposition are realized. When coupling the lean‐Zn anode with a Zn‐containing cathode, the full cell delivers high Coulomb efficiency (99.6% for 4250 cycles on average) and a long lifetime of more than 5000 cycles.

Numerical study on the ductility improvement mechanism of dilute Mg-Ca alloys

In recent years, magnesium (Mg) alloys have attracted extensive attention because of their potential use as alternatives to dense metals and Al alloys. Therefore, the low ductility of Mg alloys should be improved. Previous studies indicated that the addition of low concentrations of Ca improves the ductility of Mg alloys; however, the associated mechanisms are not well understood. The present numerical study demonstrates that the ratio of the critical resolved shear stresses associated with prismatic and basal < a > slip systems is significantly reduced (to a value of approximately 1) in a Mg-0.1 at.% Ca alloy. The incorporation of Ca was also found to harden the basal slip system while softening the prismatic slip system. The addition of Ca to Mg evidently provides a thermal-like effect that promotes the nucleation of kinks and enhances the dislocation motion. This effect is significantly more pronounced in the case of a prismatic slip system. The difference in importance of the thermal effect between the basal and prismatic slip systems and the Ca-promoted nucleation of kinks are the two main factors responsible for softening the prismatic slip system and improving the ductility of dilute Mg-Ca alloys.

T-Square Dependence of the Electronic Thermal Resistivity of Metallic Strontium Titanate.

The temperature dependence of the phase space for electron-electron (e-e) collisions leads to a T-square contribution to electrical resistivity of metals. Umklapp scattering is identified as the origin of momentum loss due to e-e scattering in dense metals. However, in dilute metals like lightly doped strontium titanate, the origin of T-square electrical resistivity in the absence of umklapp events is yet to be pinned down. Here, by separating electron and phonon contributions to heat transport, we extract the electronic thermal resistivity in niobium-doped strontium titanate and show that it also displays a T-square temperature dependence. Its amplitude correlates with the T-square electrical resistivity. The Wiedemann-Franz law strictly holds in the zero-temperature limit, but not at finite temperature, because the two T-square prefactors are different by a factor of ≈3, like in other Fermi liquids. Recalling the case of ^{3}He, we argue that T-square thermal resistivity does not require umklapp events. The approximate recovery of the Wiedemann-Franz law in the presence of disorder would account for a T-square electrical resistivity without umklapp.