Dense Metal Research Articles

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.

Hydrogen Permeability of Composite Pd-Au/Pd-Cu Membranes and Methods for Their Preparation.

Thin Pd-40%Cu films were obtained via the classical melting and rolling method, magnetron sputtering, and modified with nanostructured functional coatings to intensify the process of hydrogen transportation. The films were modified by electrodeposition, according to the classical method of obtaining palladium black and "Pd-Au nanoflowers" with spherical and pentagonal particles, respectively. The experiment results demonstrated the highest catalytic activity (89.47 mA cm-2), good resistance to CO poisoning and long-term stability of Pd-40%Cu films with a pentagonal structured coating. The investigation of the developed membranes in the hydrogen transport processes in the temperature range of 25-300 °C also demonstrated high and stable fluxes of up to 475.28 mmol s-1 m-2 (deposited membranes) and 59.41 mmol s-1 m-2 (dense metal membranes), which were up to 1.5 higher, compared with membrane materials with classic niello. For all-metal modified membranes, the increase in flux was up to sevenfold, compared with a smooth membrane made of pure palladium, and for deposited films, this difference was manyfold. The membrane materials' selectivity was also high, up to 4419. The developed strategy for modifying membrane materials with functional coatings of a fundamentally new complex geometry can shed new light on the development and fabrication of durable and highly selective palladium-based membranes for gas steam reformers.

Averaging over atom snapshots in linear-response TDDFT of disordered systems: A case study of warm dense hydrogen.

Linear-response time-dependent density functional theory (LR-TDDFT) simulations of disordered extended systems require averaging over different snapshots of ion configurations to minimize finite size effects due to the snapshot-dependence of the electronic density response function and related properties. We present a consistent scheme for the computation of the macroscopic Kohn-Sham (KS) density response function connecting an average over snapshot values of charge density perturbations to the averaged values of KS potential variations. This allows us to formulate the LR-TDDFT within the adiabatic (static) approximation for the exchange-correlation (XC) kernel for disordered systems, where the static XC kernel is computed using the direct perturbation method [Moldabekov et al., J. Chem. Theory Comput. 19, 1286 (2023)]. The presented approach allows one to compute the macroscopic dynamic density response function as well as the dielectric function with a static XC kernel generated for any available XC functional. The application of the developed workflow is demonstrated for the example of warm dense hydrogen. The presented approach is applicable for various types of extended disordered systems, such as warm dense matter, liquid metals, and dense plasmas.

Research on eddy current and force of non-ferrous metal in eddy current separator

For compensating the gap of present investigations, which did not consider the effect of skin depth before, a novel method is also proposed to obtain the eddy current force. At the beginning, the separating principle of eddy current separator (ECS) is given. Then, based on boundary conditions and the eddy current equations, the internal magnetic flux density, eddy current density and eddy current force density of non-ferrous metal are deduced. By calculating the double integral of eddy current density, the internal eddy current of non-ferrous metal is achieved. The theoretical calculation method (TCM) for solving the eddy current force in the process of non-ferrous metal sorting is proposed. Moreover, to verify the correctness of TCM, taking 24-pole and 30-pole magnetic roller as examples, the finite element models of static and transient magnetic field are established respectively. Additionally, the correctness of TCM is proven by finite element method (FEM) when the x-axis and y-axis component of eddy current force is calculated. At the end, by the theoretical analysis and derivation derived in this paper, based on the relationship between the relative position of N and S poles of the magnetic roller and non-ferrous metal, the internal eddy current force are analyzed by the consistency between the direction of the internal magnetic flux density and the eddy current of non-ferrous metal. The influence of the size relationship between the non-ferrous metal and a single magnetic pole on the separation effect is discussed.

Elasticity of Dense Metal–Organic Framework Compounds

Elasticity of Dense Metal–Organic Framework Compounds

Processing map of the in-situ micro-forging (MF) assisted cold spray for additive manufacturing of fully dense metals without MF particle inclusion

The newly developed in-situ micro-forging assisted cold spraying (MFCS) is an economical and convenient way to deposit dense metals with porosity lower than 0.1%. During this process, forging effect induced by impact of large-size hard micro-forging particles to in-situ densification of the deposited materials. Therefore, a fully dense metallic deposit could be produced at moderate gas temperature and pressure without using expensive helium gas. However, it is found that the porosity is highly dependent on the type of depositing materials, shot-penning particle size, and spraying parameters. Shot-peening particle deposition-induced inclusion is frequently observed for soft depositing materials. This makes the application challenging and a universal processing map is in great demand. In this study, pure Al, pure Ti, pure Ni, 2219 Al, 6061 Al, 7055 Al, and TC4 with different hardness values are used as examples to explore a universal spraying processing map for MFCS. The influence of impact velocity and volume fraction of the shot-peening particle, types of the depositing materials, and spraying parameter on densification and shot-peening particle deposition is investigated. Adding 30vol.% of 410 stainless steel MF particles into the depositing powders decreases the porosity of all deposits and particle deposition-induced inclusion is observed in pure Al, all three Al alloys, and pure Ti deposits. The single particle deposition experiment and the numerical simulation reveal that mechanical interlocking is the prime mechanism for MF particle deposition. A critical embedding MF particle size (dcr,e), above which MF particle inclusion can be avoided, is defined. A new concept of MF intensity (IMF) is proposed to comprehensively consider all main factors influencing the densification of the deposit. Finally, optimized processing maps for depositing fully dense metals without MF particle inclusion are established by plotting the critical embedding velocity and IMF against the hardness of the depositing materials.

The Study of the state of soil cover of the coastal zones of the Caspian Sea, subject to the influence of climatic and anthropogenic factors

This article is dedicated to research of climate impact change and human activity on ecosystems. It is expressed as metals which is called heavy pollution. It covers the coastal territory of northwestern regions of Apsheron. Pollution in the coastal regions of the Caspian Sea with toxic substances, is of great concern, periodic studies of these zones for the presence of heavy metals are necessary. For the first time, a comparative analysis of the content of heavy metals in the territories of the northwestern part of the Absheron was carried out and the hypothetical reasons for their accumulation were presented. The studied soils in the northwestern part of the peninsula were grouped the degree of the density of heavy metals. Zinc (78.62 mg/kg, at a depth of 0–20 sm) copper and cadmium (23.65 mg/kg and 0.92 mg/kg at a depth of 0–20 sm). The concentration of zinc and copper in the northwestern direction of Apsheron by 1.18 and 1.57 times, compared with the allowable norms for clarks. Under the impact of flooding of coastal zones by the waters of the Caspian Sea, the average content of heavy metals, Ni, Cd, Pb in flooded soils at a depth of 0-100 sm increased by 1.7 times.

ELEMENTAL COMPOSITION AND PHYSICOCHEMICAL PROPERTIES OF GEOPHAGIC CLAY (‘EKO’), FROM UBIAJA IN EDO STATE, NIGERIA

In Edo State, Nigeria, geophagia (‘Eko’) is highly prevalent, and men and women, especially pregnant women, are believed to indulge in its consumption as a remedy for vomiting (nausea) and some other related inconveniences in pregnancy. Others are due to a natural craving. These practices are associated with varying health complications; as such, it is pertinent that the physical and chemical composition of the clay be known. In this study, we assessed the levels of heavy metals and trace elements of clinical importance in ‘Eko’, as well as their physical and chemical properties using standard protocols. Tests conducted include: colour, pH, electrical conductivity (EC), cation exchange capacity (CEC), total dissolved solids (TDS), particle density, and concentrations of metals [chloride (Cl), sulphate (S), calcium (Ca), sodium (Na), magnesium (Mg), potassium (K), aluminium (Al), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), chromium (Cr), lead (Pb) and cadmium (Cd)]. The results obtained showed that some of the elements (Cl, Ca, Na and Mg) are present in moderate concentrations (353.33, 182.33, 216, 111.33 mg/kg) respectively. However, concentrations of some of the heavy metals [(Cd, Pb and Cr) (0.30, 0.26, 0.42 mg/kg) respectively], were higher than the permissible limits (65, 35, 25 µg/kg) set by WHO. Though some of the moderately present trace metals may play important biological roles, the high concentrations of some heavy metals could have detrimental health effects. Results from this study suggest that ‘Eko’ can predispose consumers to health hazards. As such, the continuous consumption of “Eko” should be discouraged

Multifunctional Electrolyte Additives for Better Metal Batteries

AbstractThe high energy density of rechargeable metal (Li, Na, and Zn) batteries has garnered a lot of interest. However, the poor cycle stability and low Coulomb efficiency(CE), which are mostly brought on by side reactions and dendrite development on the metal anode, place a cap on commercialization. The rational design of electrolytes via incorporating a small dose of additives is a simple, yet effect strategy to address the above issues. The majority of additives govern uniform metal deposition and significantly improve the cycling performance of metal anodes. However, the battery is a complex system and the electrolyte affects both the anode and cathode. Complex reactions during discharge/charge process put forward higher requirements for the functionality of electrolytes, such as improving the stability of the cathode and flame retardant. Thus, multifunctional additives are necessary and have more advantages in building high‐performance metal batteries. The recent developments in multifunctional additives for stable and dendrite‐free Li/Na/Zn anodes are the major focus of this review. Breakthrough research on multifunctional additives toward the durable cathode and high‐compatible electrolytes is also highlighted. Finally, the critical challenges and new perspectives on the optimization of electrolyte formulation via multifunctional additives are emphasized. This review will provide important insight to develop more effective electrolytes for high‐performance rechargeable metal batteries.

Ultrasound diagnostics in the assessment of traumatic peripheral nerve damage in combat trauma

BACKGROUND: Traumatic peripheral nerve damage is a significant clinical and social problem, which is characterized by a high level of disability in young patients.
 AIM: To assess the diagnostic efficiency of ultrasound in the diagnosis of peripheral nerve damage in combat trauma.
 METHODS: A total of 163 patients (362 peripheral nerves) were examined. The duration of traumatic nerve damage was 2273 days. All patients were men aged 2048 years. Ultrasound was performed with 717 MHz linear transducers on an ACUSSON S2000 device using standard technique in B-mode, in longitudinal and transverse scanning planes, with the use of Doppler techniques. Statistical analysis was conducted to assess diagnostic efficiency. Calculation of operational (sensitivity and specificity) and integral (accuracy) characteristics was performed by the qualitative assessment of the reference method (surgical intervention) and the method under study (ultrasound).
 RESULTS: Peripheral nerve damage resulted from combat trauma. In 120 (73.6%) cases, injuries of the limbs were accompanied by injuries of the osteoarticular apparatus and vessels. A total of 274 (75.7%) nerves had signs of traumatic damage. Multiple nerve injuries were observed in 95 (58.3%) people. Nerves of the upper extremities were damaged more frequently (185 [67.5%]) compared to nerves of the lower extremities (89 [32.5%]). Contusional structural changes were observed in 181 (66%) nerves. Impairment of anatomical integrity was diagnosed in 46 (16.8%) nerves, while complete impairment was found in 29 (10.6%) cases with the presence of diastasis between the nerve ends. Early after injury, a wound canal and hematomas were visualized near the nerve. In 4 cases, a foreign body of metallic density was visualized in the nerve sheath. After 3 weeks from the moment of injury, terminal neuromas were observed. The neuroma sizes for the proximal and distal ends were 0.50.3 to 1.60.6 cm and 0.40.2 to 1.30.6 cm (avascular), respectively. Adjacent sections of the nerve over 35 cm were thickened and characterized by echo structure, however, with thickening of all fasciculi and blood flow observed along the periphery of the nerve. Marginal nerve damage was observed in 17 (6.2%) people. In case of marginal neuroma, a significant nerve thickening of 1.43.2 times over a short distance (from 0.4 cm to 1.5 cm) with loss of bundle differentiation of the part of the nerve, pronounced decrease in echogenicity, and absence of Doppler signal was detected. Nerve compression in 47 cases (17.1%) was accompanied by 1.22.3 times thickening of nerve trunks, indistinct contours, decreased echogenicity, and significant changes in the nerve structure. Compression was due to cicatricial changes, hematomas, foreign bodies, bone fragments, and in 2 cases spokes from external fixation devices. A total of 106 patients underwent surgery.
 CONCLUSIONS: The ultrasound sensitivity and specificity were 96% and 67%, respectively. The peculiarities of the examination included extensive soft tissue defects and external fixation devices, which significantly complicated the examination. The diagnostic accuracy was 91%. A pronounced cicatricial process (70%) was the main cause of false-positive (6.6%) and false-negative (2.8%) results.

Galinstan liquid metal as the heat transfer fluid in magnetic refrigeration

Room-temperature magnetic refrigeration is a promising technology in which cooling is achieved by exploiting a special property of some materials, the “magnetocaloric effect” (MCE), i.e., the ability of the material to change its temperature when it undergoes changes in the applied external magnetic field. For magnetic field variations on the order of 1–1.5 T, the MCE results in small adiabatic temperature changes of a few degrees so, in most cases, the designs and prototypes presented by various research groups employ active magnetic regeneration to increase the temperature span required for practical cooling devices. The effectiveness of the regenerator, and thus of the refrigeration device, depends heavily on the properties of the heat transfer fluid, which is usually a water-based mixture. High values of the fluid thermal conductivity greatly affect the heat transfer between the MCE and the fluid allowing faster operation and higher cooling capacity. In this study, the use of a gallium based liquid metal, i.e., Galinstan, is investigated to quantify this improvement. Galinstan was found not to be aggressive to gadolinium at room temperature and it resulted not affected by magnetic induction. The authors report the results of an extensive simulation campaign to characterize the performance of an active magnetic regenerator made of 0.5 mm thick gadolinium sheets using Galinstan as a heat transfer fluid. The results are compared to those of the same device using water; friction is also accounted for since the high density of this liquid metal leads to a high demand for pumping power. On average, a more than tenfold increase in cooling capacity was observed when using Galinstan, but the COP was severely penalized by the higher frictional losses. To avoid this effect, the cycle time and the utilization factor must be adjusted, or the geometry changed by using thicker sheets and ducts for the same Gd weight. In this way a cooling increase of 400% is achieved with the same COP.

Axial Crushing Behaviors of Metal Density Gradient Foam-Filled Square Taper Tubes: Analytical Model and Numerical Calculation

Abstract Metal tube is a traditional energy-absorbing structure, and metal foam is a lightweight material with advantages, i.e., high energy absorption and high specific strength. The foam-filled square tube can improve crashworthiness and has better energy absorption, which is higher than the sum of the energy absorption of the tube and foam. Axial crushing behaviors of metal density gradient foam (DGF) filled square taper tubes are studied analytically and numerically in this paper. An analytical model is presented to study the crushing behavior of DGF-filled square taper metal tube under axial loading, in which the interaction between square taper tube and DGF is considered. The numerical calculation is conducted, and the deformation mode is obtained. The analytical predictions are well consistent with the experimental and numerical results. The influences of taper angle, foam strength, maximum relative density, and minimum relative density of gradient foam on the compressive behavior of metal DGF-filled square taper tubes under axial loading are considered. It is demonstrated that when the taper angle is less than 85 deg, the average crushing force increases as the minimum density of the DGF increases. However, when the taper angle is greater than 85 deg, the average crushing force decreases with the increase of the minimum density of the gradient. This proposed analytical model can effectively predict the axial crushing behaviors of metal DGF-filled square taper tubes.

Anomalous growth of dislocation density in titanium during recovery

It is generally believed that the dislocation density in cold-worked metals decreases during recovery. In this study, we used in-situ synchrotron X-ray diffraction (SXRD) to demonstrate that the dislocation density in α-titanium increases at the initial stages of heating. This phenomenon was clearly reproduced by classical molecular dynamics (MD) simulation. It was concluded, that under conditions of low dislocation mobility, the generation of new dislocations can reduce the overall level of stresses and potential energy during heating of the deformed material. The paper describes the dynamics of dislocations, as well as the dislocation reactions at different stages of heating of a cold-worked titanium sample.

Electronic Immunoassay Using Enzymatic Metallization on Microparticles.

We present here an inexpensive method for generating a sensitive direct electronic readout in bead-based immunoassays without the use of any intermediate optical instrumentation (e.g., lasers, photomultipliers, etc.). Analyte binding to capture antigen-coated beads or microparticles is converted to probe-directed enzymatically amplified silver metallization on microparticle surfaces. Individual microparticles are then rapidly characterized in a high-throughput manner via single-bead multifrequency electrical impedance spectra captured using a simple and inexpensive microfluidic impedance spectrometry system we develop here, where they flow through a three-dimensional (3D)-printed plastic microaperture sandwiched between plated through-hole electrodes on a printed circuit board. Metallized microparticles are found to have unique impedance signatures distinguishing them from unmetallized ones. Coupled with a machine learning algorithm, this enables a simple electronic readout of the silver metallization density on microparticle surfaces and hence the underlying analyte binding. Here, we also demonstrate the use of this scheme to measure the antibody response to the viral nucleocapsid protein in convalescent COVID-19 patient serum.

Synthesis and characterisation of graphene-reinforced AA 2014 MMC using squeeze casting method for lightweight aerospace structural applications

The need for lightweight materials towards aerospace has increased prominently. This paper focuses on introducing a novel reinforcement mixture of graphene with Al 2014 powder synthesised through ball milling technique. The synthesized powder was utilized as a reinforcement to fabricate Al 2014 based MMCs through squeeze casting technique. The results exhibited that Al 2014 mixture with embedded and interlocked 2D-Grnp (2.517 g/cm3) matched the density of the matrix metal (2.771 g/cm3) that facilitated homogeneous dispersion of 2D-Grnp and solved the dispersion problems during stir casting. As a result, AA 2014 embedded with 2D-Grnp acted as a carrier to homogeneously disperse combined with the squeeze casting process leading to the production of homogeneously reinforced MMC. This can be considered as a potential fabrication route for the launch vehicle super lightweight fuel tank (SLWT) structural application. The final casted plate after T6 heat treatment with 0.5 wt% 2D-Grnp exhibited an improved tensile strength of 361 MPa (52% higher than the monolithic 2014 aluminium alloy) with total elongation of 21% and improved hardness of 119 HRB (45.5 % increase). Furthermore, SEM and TEM results exhibited that squeeze casting led to enhanced interfacial bonding between the 2D-Grnp and Al 2014.

The effect of size, orientation and temperature on the deformation of microcast silver crystals

Monocrystalline microwires of silver are produced by means of a novel casting process that combines precise mold production by silicon microfabrication with molten metal pressure infiltration. The wires have a shape amenable to tensile testing and a diameter from a few to several tens of micrometer. Displacement-controlled in-situ tensile tests are conducted at room-temperature, 200 °C and 400 °C. Data are compared with bulk counterparts of the same silver cast to have a diameter near 1 mm. Results show clear evidence of small-scale plasticity. The influence of size, crystal orientation, and temperature on the deformation, yield, strain burst statistics and strain hardening of these micrometric dense metal samples is analyzed. Yield stress values agree with the single arm source model provided that the density of forest dislocations comprises a scale-dependent component likely resulting from thermal mismatch stresses. Statistics of strain burst amplitudes agree with an exponentially truncated power-law complementary cumulative distribution. The power-law exponent agrees with predictions of mean-field theory, while the cutoff intensity exhibits no visible dependence on sample diameter or test temperature and agrees with predictions of current theory.

FEA Assisted Optimization of Bump Shear Test Method for Assessment of Back-End-of-Line Mechanical Integrity

An enhanced Cu pillar bump shear test (BST) method has been developed to quantify wafer level back-end-of-line (BEOL) mechanical integrity and assess the risk of white bump failure. First, three different types of failure mode in the BST and the one that corresponds to the white bump failure in which delamination occurs at an ultra-low-k (ULK) dielectric layer, were identified by studying the load-displacement data together with focused ion beam (FIB) and scanning electron microscopy (SEM) analysis. To find the reason for different failure modes in BST and the effects of BST conditions, first, the difference in the stress modes between the bump shear test and the assembly solder reflow process was compared using finite element analysis (FEA) stress simulations. Then, parametric studies on the bump shear angle and the bump shear height were performed to find the optimal conditions at which the BST stress modes best mimic those of the solder reflow. Based on these studies, special high Cu pillar bump test samples were built in order to apply the optimal shear height and angle condition. The new optimal BST method has shown to significantly increase the probability of ULK delamination failure mode and was shown to be in good agreement with reflow hammer test results. Also, the method was used to verify the effect of metal density as well as process and design changes. Finally, a machine learning based correlation for quantifying the pure BEOL integrity regardless of the bump and far-BEOL dimensions was developed for application of the method to various products.

Facile Synthesis of Metallosalphen-Based 2D Conductive Metal-Organic Frameworks for NO2 Sensing: Metal Coordination Induced Planarization.

As an emerging class of promising porous materials, the development of two-dimensional conductive metal organic frameworks (2D c-MOFs) is hampered by the few categories and tedious synthesis of the specific ligands. Herein, we developed a nonplanar hexahydroxyl-functionalized Salphen ligand (6OH-Salphen) through a facile two-step synthesis, which was further applied to construct layered 2D c-MOFs through in situ one pot synthesis based on the synergistic metal binding effect of the N2 O2 pocket of Salphen. Interestingly, the C2v -symmetry of ligand endows Cu-Salphen-MOF with periodically heterogeneous pore structures. Benefitting from the higher metal density and shorter in-plane metal-metal distance, Cu-Salphen-MOF showcased excellent NO2 sensing performance with good sensitivity, selectivity and reversibility. The current work opens up a new avenue to construct 2D c-MOF directly from nonplanar ligands, which greatly simplifies the synthesis and provides new possibilities for preparing different topological 2D c-MOF based functional materials.

Facile Synthesis of Metallosalphen‐Based 2D Conductive Metal‐Organic Frameworks for NO2 Sensing: Metal Coordination Induced Planarization

AbstractAs an emerging class of promising porous materials, the development of two‐dimensional conductive metal organic frameworks (2D c‐MOFs) is hampered by the few categories and tedious synthesis of the specific ligands. Herein, we developed a nonplanar hexahydroxyl‐functionalized Salphen ligand (6OH‐Salphen) through a facile two‐step synthesis, which was further applied to construct layered 2D c‐MOFs through in situ one pot synthesis based on the synergistic metal binding effect of the N2O2 pocket of Salphen. Interestingly, the C2v‐symmetry of ligand endows Cu‐Salphen‐MOF with periodically heterogeneous pore structures. Benefitting from the higher metal density and shorter in‐plane metal‐metal distance, Cu‐Salphen‐MOF showcased excellent NO2 sensing performance with good sensitivity, selectivity and reversibility. The current work opens up a new avenue to construct 2D c‐MOF directly from nonplanar ligands, which greatly simplifies the synthesis and provides new possibilities for preparing different topological 2D c‐MOF based functional materials.

Neutron tomography of sealed copper alloy animal coffins from ancient Egypt

Animal mummification was commonplace in ancient Egypt, with the remains of many animals placed inside statues or votive boxes with representations of animals or hybrid human–animal creatures. Votive boxes were made from a variety of materials and often sealed; some boxes are still preserved in this state in museum collections. A prior study of sealed copper alloy votive boxes from the collection of the British Museum used X-ray computed tomography to search for animal remains, where poor image quality resulted due to attenuation from the boxes and apparent dense metals inside. In this study, neutron tomography was applied to six of the votive boxes previously examined. Animal remains, likely from lizards, and fragments of textile wrappings were discovered inside three of the boxes. Evidence of the manufacturing process and subsequent repairs of the boxes were uncovered by neutrons. Significant quantities of lead were also identified in three boxes. The findings demonstrate the effectiveness of neutron tomography for the study of mummified remains inside sealed metal containers, and give evidence linking the animal figures represented on top of votive boxes to the concealed remains.