Smooth Metal Research Articles

Rapid fabrication of gold microsphere arrays with stable deep-pressing anisotropic conductivity for advanced packaging

Smooth metal microspheres with uniform sizes are ideal for constructing particle-arrayed anisotropic conductive films (ACF), but synthesis is hindered by challenges in controlling anisotropic metal growth. Here, we present a positioned transient-emulsion self-assembly and laser-irradiation strategy to fabricate pure gold microsphere arrays with smooth surfaces and uniform sizes. The fabrication involves assembling gold nanoparticles into uniform colloidosomes within a pre-designed microhole array, followed by rapid transformation into well-defined microspheres through laser heating. The gold nanoparticles melt and merge in a layer-by-layer manner due to the finite skin depth of the laser, leading to a localized photothermal effect. This strategy circumvents anisotropic growth, enables tunable control of microsphere size and positioning, and is compatible with conventional lithography. Importantly, these pure gold microspheres exhibit stable conductivity under deep compression, offering promising applications in soldering micro-sized chips onto integrated circuits.

Tailoring the Electrode-Electrolyte Interface for Reliable Operation of All-Climate 4.8 V Li||NCM811 Batteries.

Combining high-voltage nickel-rich cathodes with lithium metal anodes is among the most promising approaches for achieving high-energy-density lithium batteries. However, most current electrolytes fail to simultaneously satisfy the compatibility requirements for the lithium metal anode and the tolerance for the ultra-high voltage NCM811 cathode. Here, we have designed an ultra-oxidation-resistant electrolyte by meticulously adjusting the composition of fluorinated carbonates. Our study reveals that a solid-electrolyte interphase (SEI) rich in LiF and Li2O is constructed on the lithium anode through the synergistic decomposition of the fluorinated solvents and PF6 - anion, facilitating smooth lithium metal deposition. The superior oxidation resistance of our electrolyte enables the Li||NCM811 cell to deliver a capacity retention of 80 % after 300 cycles at an ultrahigh cut-off voltage of 4.8 V. Additionally, a pioneering 4.8 V-class lithium metal pouch cell with an energy density of 462.2 Wh kg-1 stably cycles for 110 cycles under harsh conditions of high cathode loading (30 mg cm-2), low N/P ratio (1.18), and lean electrolytes (2.3 g Ah-1).

Tailoring the Electrode‐Electrolyte Interface for Reliable Operation of All‐Climate 4.8 V Li||NCM811 Batteries

AbstractCombining high‐voltage nickel‐rich cathodes with lithium metal anodes is among the most promising approaches for achieving high‐energy‐density lithium batteries. However, most current electrolytes fail to simultaneously satisfy the compatibility requirements for the lithium metal anode and the tolerance for the ultra‐high voltage NCM811 cathode. Here, we have designed an ultra‐oxidation‐resistant electrolyte by meticulously adjusting the composition of fluorinated carbonates. Our study reveals that a solid‐electrolyte interphase (SEI) rich in LiF and Li2O is constructed on the lithium anode through the synergistic decomposition of the fluorinated solvents and PF6− anion, facilitating smooth lithium metal deposition. The superior oxidation resistance of our electrolyte enables the Li||NCM811 cell to deliver a capacity retention of 80 % after 300 cycles at an ultrahigh cut–off voltage of 4.8 V. Additionally, a pioneering 4.8 V‐class lithium metal pouch cell with an energy density of 462.2 Wh kg−1 stably cycles for 110 cycles under harsh conditions of high cathode loading (30 mg cm−2), low N/P ratio (1.18), and lean electrolytes (2.3 g Ah−1).

Calcium Doped NASICON Electrolyte with Graphite Coating for Stable All-solid-state Sodium Metal Batteries.

All-solid-state sodium metal batteries face the challenges of low ionic conductivity of solid electrolytes and poor wettability towards metallic Na anode. Herein, Na3Zr2Si2PO12 solid electrolyte is doped with Ca2+, obtaining a high ionic conductivity of 2.09×10-3 S cm-1 with low electronic conductivity of 1.43×10-8 S cm-1 at room temperature, which could accelerate Na+ transportation and suppress sodium dendrite growth. Meanwhile, a graphite-based interface layer is coated on Na3.4Zr1.8Ca0.2Si2PO12 (Na3.4Zr1.8Ca0.2Si2PO12-G) in order to improve the solid-solid contact between solid electrolyte and Na anode, realizing a uniform current distribution and smooth Na metal plating/stripping, and thus achieving a triple higher critical current density of 3.5 mA cm-2 compared with that of Na3.4Zr1.8Ca0.2Si2PO12. In addition, the assembled Na3V2(PO4)3/Na3.4Zr1.8Ca0.2Si2PO12-G/Na all-solid-state battery exhibits excellent electrochemical performances with a reversible capacity of 81.47 mAh g-1 at 1 C and capacity retention of 97.75 % after 500 cycles.

Thermo-mechanical finite element analysis of the solid-state metal deposition via lateral friction surfacing

Lateral friction surfacing (LFS) is a novel variation of the friction surfacing (FS) process for solid-state fabrication of ultra-thin and smooth metal coatings. In the LFS technique, pressing the lateral side of a rotating rod against the substrate's surface generates frictional heat and plastic deformation, leading to the deposition of consumable material from the lateral surface of the rod onto the substrate. This study presents numerical analysis for such a complex coupled thermo-mechanical process to investigate the distribution of various variables such as temperatures, local pressure, stress, and strain throughout the consumable rod and substrate. A finite element model of the process was developed through ABAQUS/Explicit method to investigate the thermo-mechanical response of rod and substrate materials by incorporating various features such as process parameters, mechanical behaviors of materials, temperature-dependent material properties, and failure criteria. The finite element model was validated by conducting experimental analysis using the same materials and values of process parameters. The finite element simulation results were consistent with previous experiments and affirmed that process temperature is lower than in conventional FS and localized in a small area, which can reduce thermal impacts on the consumable rod and substrate materials. Although the majority of the frictional heat was transferred to the Al6061-T6 rod due to its higher thermal conductivity, it was revealed that the maximum process temperature occurred on the mild steel substrate. The results of the study demonstrate that selecting an appropriate dwell-phase duration not only enhances the material's temperature to facilitate improved deposition but also ensures more consistent contact across all points along the rod's side, resulting in a uniform deposition.

Compressible and Elastic Reduced Graphene Oxide Sponge for Stable and Dendrite-Free Lithium Metal Anodes.

Dendritic Li deposition, an unstable solid-electrolyte interphase (SEI), and a nearly infinite relative volume change during cycling are three major obstacles to the practical application of Li metal batteries. Herein, we introduce a compressible and elastic reduced graphene oxide sponge (rGO-S) to simultaneously eliminate Li dendrite growth, stabilize the SEI, and accommodate the volume change. The volume change is contained by compressing and expanding the rGO-S anode, which effectively releases the Li plating-induced stress during cycling. The smooth and dense Li metal is deposited on rGO-S without dendrites, which preserves the SEI, reduces consumption of the electrolyte, and prevents the formation of Li debris. The half-cells employing rGO-S show a steady and high Coulombic efficiency. The Li@rGO-S symmetric cells demonstrate excellent cycling stability over 1200 cycles with a low overpotential. When paired with LiFePO4 (LFP), the Li@rGO-S||LFP full cells exhibit a high specific capacity (150.3 mAh g-1 at 1C), superior rate performance, and good capacity retention.

Accurate Thermal Conductivity Measurements of Porous Thin Films by Time-Domain Thermoreflectance.

Accurate measurements of the thermal conductivity (κ) of porous thin films are still limited due to challenges to deposit flat and continuous metal transducers on porous samples, a necessity for many thermal measurement techniques for nanostructures. In this paper, we introduce an approach based on time-domain thermoreflectance (TDTR) to accurately and conveniently measure κ of porous thin films by transferring a flat and smooth metal film unto porous samples as the transducer for TDTR measurements. We demonstrate our approach by measuring κ of a series of microscale holey SiO2 films with diameters of 1-3.5 μm and porosity of 13-50%. To achieve a measurement uncertainty of <12%, we ensure that the metal transducer films are sufficiently stiff and establish good thermal contact with the holey SiO2 samples. Our κ measurements agree well with calculations of κ from effective medium theory. Our approach could provide a convenient way to further investigate the thermal transport properties of porous films.

A flexible transparent graphene/metal–organic framework complex hybrid chemical sensor for highly sensitive ethanol detection

AbstractHigh‐performance flexible and transparent chemical sensors are key to achieving wearable electronics. Graphene with high transmittance and electrical properties is a suitable material for flexible and transparent chemical sensors. However, graphene has low detectivity to chemical substances. Here, we report hybrid chemical sensors fabricated by introducing a highly flat and smooth metal–organic framework (MOF) on graphene. The graphene chemical sensors functionalized with MOF on SiO2/Si wafer exhibit 22 times higher sensitivity of 6.07 μA ppm−1 in detecting ethanol than that of pristine graphene transistors of 0.28 μA ppm−1 and a low detection limit of 1 ppm. Furthermore, a flexible transparent 7 × 7 chemical sensor array exhibits great driving stability after the bending cycles of 105 at a bending radius of 1.0 mm and shows sensitivity of 0.11 μA ppm−1. Our findings demonstrate an efficient way to improve the chemical sensing ability of graphene for application in wearable chemical sensors.image

Quantum structure of the surface layer of metals

In this paper, we propose a model for determining the thickness of the surface layer of metals and the quantum structure of this layer. An atomically smooth metal is represented as a diagram: nanolayer → mesolayer → bulk phase, which differ from each other in the nature of size effects. There is no size effect in the bulk phase. The thickness of the surface layer of metals R(I) has a size from 1 nm to 10 nm, except for cesium, i.e. they represent a nanostructure. It is shown that the energy levels En of the nanolayer are determined by one fundamental parameter - the lattice constant of the metal à. As soon as the parameter à stops changing, the spectrum of quantum states passes into a continuous spectrum. The nanolayer R(I) is a step function in En, which can be easily reduced to the Lebesgue integral, which plays an important role in quantum theory. Quantum threads (quantum planes) in the nanolayer R(I) can be interpreted as solitons, crowdions, discrete breathers turning into nanocracks. Quantum threads in the R(I) nanolayer and the nanolayer itself can be represented as a nanoparticle with a diameter of R(I) and pre-melting occurs in it in a stepwise manner. It is finally shown that all metal monolayers differ significantly from each other.

SURFACE QUALITY AND CORROSION RESISTANCE OF 316L STAINLESS STEEL ELECTROPOLISHED USING PHOSPHORIC – SULFURIC ACIDS

Electropolishing is an electrochemical surface finishing technique. It is commonly applied to equipment that requires a gleaming finish. This surface property is frequently required in 316L stainless steel (SS) medical implants. Electropolishing removes a thin layer from the metal's surface through electrochemical processes. This results in a very clean, smooth, and bright metal surface. The process parameters, such as electrolyte solution, electrical current, and electropolishing time, influence surface roughness and glossiness. The dissolution of metallic ions during the process may also affect the corrosion resistance of the treated material in addition to producing a shiny surface. This study investigated the surface glossiness, surface roughness, and corrosion of electropolished 316L SS. Electropolishing experiments on 316 SS were carried out using various H3PO4 (50%) and H2SO4 (32%) electrolyte solution compositions. The influences of electrolyte solution composition, electric current, and electropolishing time were studied. The results showed that increasing the H2SO4 content of the mixture and electropolishing the 316L SS for a longer period of time improved the surface roughness and glossiness. Under 10 Amp electric currents, the best surface glossiness was discovered. A corrosion test revealed that the electropolishing produced a Cr and Ni-rich layer that improved the corrosion resistance of the samples.

Fabrication of Ag/PP terahertz hollow waveguide by vacuum evaporation method and transmission performance investigations

This work proposed a vacuum evaporation method in preparing an Ag/polypropylene (PP) terahertz (THz) hollow waveguide (HWG). Rray model and COMSOL were used to optimize the geometric structure parameters of the HWG. Accordingly, a 5 mm bore PP tube with a wall thickness of 360 μm was selected as the structural and dielectric tube, and a silver reflective layer was deposited onto the outer surface of the PP tube using vacuum evaporation process. The as-deposited Ag layer consists of small Ag particles (about 100 nm) which contribut to form a more uniform and smoother metal reflective layer than that could be prepared via the wet chemical method. Terahertz time-domain spectroscopy (THz-TDS) analysis confirms that the Ag/PP THz HWG exhibits a low-loss window centered at the frequency of 0.1 or 0.3 THz. The HWG sample shows low transmission losses of 2.26 dB/m at 0.1 THz and 1.23 dB/m at 0.3 THz, respectively. The THz waves could be stably transmitted through the as-fabricated Ag/PP waveguide at low (−78.5 °C) and high (65 °C) temperatures. This research opens a simple and environmentally friendly avenue for the fabrication of low-loss metal/dielectric THz HWG. It is helpful for promoting the applications of THz HWG in future THz imaging, sensing and 6G communication.

Stable Inner 2H Tautomer of N-Confused-like Porphyrin Embedded with a Carbazole Subunit: Synthesis, Metal Coordination, and Magnetic and Anion Sensing Studies.

A new class of N-confused porphyrin 1 embedded with a carbazole subunit was prepared via [3 + 1] acid-catalyzed condensation of appropriate precursors. 1 underwent smooth metal complexation with Pd(II) and Cu(II) salts to provide the corresponding diamagnetic 1-Pd and paramagnetic 1-Cu, respectively. The single-crystal X-ray structure of 1-Pd is evident with a square-planar Pd-center through C-H activation of inverted pyrrole. Superconducting quantum interference device analysis combined with electron paramagnetic resonance (EPR) results provided insights into the paramagnetic nature of 1-Cu. Further, a ratiometric enhancement of near-IR fluorescence at 746 nm was found to be reversible upon adding CN- and F- ions. The solid-state structure of 1-Pd confirms that the anionic species is due to NH deprotonation.

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).

Current density profiles at thin layer electrochemical cells under laminar and turbulent regimes

The transition of laminar to turbulent regimes on smooth electrocatalysts in thin-film electrochemical cells is a subject of study with the aim of predicting current density profiles. Analytical solutions are obtained for velocity profiles under steady state conditions for both hydrodynamic conditions applying a proper velocity contour condition on the catalyst surface. This state is necessary to describe electrochemical cell performances since in these cases, electrode reactions occur at the surface and not in the bulk of the electrolyte. The obtained equations for linear momentum under asymptotic conditions reduce to the solutions obtained by classical Power Series methods years ago. Concentration and current density profiles are also solved accordingly and compared with experimental data of fast redox and dissolved gas reactions on smooth noble metal electrocatalysts.

Practical level of low-N/P ratio sodium metal batteries: On the basis of deposition/dissolution efficiency in the aspects of electrolytes and temperature

Rechargeable sodium metal batteries have drawn immense interest as next-generation batteries, owing to their high theoretical energy density and the natural abundance of Na resources. However, Na metal batteries with excess amounts of Na metal which typically employ traditional organic electrolytes, are plagued by a myriad of electrochemical deficiencies that cause low Coulombic efficiencies, severe dendrite formation, thermal runaways, and fire hazards during operations. To establish a pathway for high energy density Na metal batteries, this work focuses on the practicability of the Na lean-metal battery and presents an in-depth perspective into the electrochemical mechanisms of utilizing a bis(fluorosulfonyl)amide ionic liquid electrolyte at both room- and intermediate temperatures. Here, the ionic liquid electrolyte is confirmed to yield a higher Na metal deposition/dissolution efficiency than common organic electrolytes. Electrochemical and computational investigations entailing the ionic liquid performance reveal that elevating the operating temperature to 90 °C increases the number of anions coordinated with Na+ and leads to the formation of a robust anion-based interfacial layer that facilitates effective and smooth Na metal deposition/dissolution. Furthermore, full cells comprising a Na metal negative with restricted loading mass and a Na3V2(PO4)3 positive electrode (low negative/positive electrode capacity ratio of 1.97, weight ratio of 0.19) demonstrates outstanding cycleability with high Coulombic efficiency (∼100%) and practical energy density (280 Wh kg–1).

Proliferating particle surface area via microbial decay has profound consequences for remineralisation rate: a new approach to modelling the degradation of sinking detritus in the ocean

Sinking detritus particles in the ocean help to regulate global climate by transporting organic carbon into deep waters where it is sequestered from the atmosphere. The rate at which bacteria remineralise detritus influences how deep particles sink and the length-scale of carbon sequestration. Conventional marine biogeochemical models typically represent particles as smooth spheres where remineralisation causes surface area (SA) to progressively shrink over time. In contrast, we propose that particle SA increases during degradation as microbial ectoenzymes cause a roughening of surfaces in a process similar to acid etching on previously smooth glass or metal surfaces. This concept is investigated using a novel model, SAMURAI (Surface Area Modelling Using Rubik As Inspiration), in which the biomass of individual particles is represented as a 3D matrix of cubical sub-units that degrades by progressive removal of sub-units that have faces in contact with the external environment. The model rapidly generates microscale rugosity (roughness) that profoundly increases total SA, giving rise to biomass-specific remineralisation rates that are approximately double those of conventional models. Faster remineralisation means less carbon penetrates the ocean’s interior, diminishing carbon sequestration in deep waters. Results indicate that both SA and microbial remineralisation are highly dynamic, as well as exhibiting large variability associated with particles of different porosities. Our work highlights the need for further studies, both observational and modelling, to investigate particle SA and related microbial dynamics in order to reliably represent the role of ocean biology in global biogeochemical models.

Calculating the Surface Layer Thickness and Surface Energy of Aircraft Materials

The surface layer determines the physical properties of aviation materials and, based on these properties, the calculation of surface energy anisotropy can be implemented. Moreover, the value of the surface energy determines the service time and the destruction of aircraft structures surface layer, while the surface layer thickness determines the distance at which this process usually takes place. In this work, a new atomically smooth crystal empirical model is built without considering the surface roughness. This model can be used to theoretically predict the surface energy anisotropy and surface layer thickness of metals and other compounds, in particular the aviation materials. The work shows that the surface layer of an atomically smooth metal, like other compounds, consists of two nanostructured layers: d(I) and d(II). Having sufficient accuracy, the proposed model would allow the prediction of aviation materials performance properties without the need for ultrahigh vacuum or other complicated theoretical methods to analyze the surfaces of nanosystem atomic structures.

A point cloud preprocessing method for complicated thin-walled ring parts with irregular section

Metallic W-ring is a typically complicated thin-walled ring part with irregular section (CTWRPIC). However, there is a lack of effective measurement methods to inspect its geometric quality in the forming process, which leads to the failure of finding the forming defects in time. Due to the smooth metal surface, complex section shape, small section size and annular closed overall structure, point cloud of the section profile obtained by the line laser scanners has serious noise, outliers and missing. To this problem, this article proposes a point cloud preprocessing method for CTWRPIC. In this method, historical measurement data based outliers statistics, initial-fine rigid registration and non-rigid registration of CAD model are introduced. Firstly, the optimal alignment of point cloud from the CAD model and measurement point cloud is realized by initial-fine rigid registration. Secondly, the point cloud of CAD model is transformed by non-rigid registration to approximate the measurement profile points, the transformed point cloud of CAD model is considered as the real profile. Thirdly, based on the transformed point cloud of CAD model and distance threshold, the adaptive removal of outliers and repair of missing are realized. Finally, the correction of profile point cloud noise is completed by combining the Alpha Shapes algorithm and the proposed repair method. Based on the proposed preprocessing method and a measurement platform equipped with line laser scanners, an on-machine measurement method for metallic W-ring is proposed, and experimental results demonstrate the advantage of the proposed method. Compared with the destructive inspection method, the mean value, standard deviation and root mean square of the distance deviation of the preprocessed point cloud are all within 11 μm.

Regulating the Solvation Shell Structure of Lithium Ions for Smooth Li Metal Deposition in Quasi-Solid-State Batteries.

Gel polymer electrolytes (GPE) are promising next-generation electrolytes for high-energy batteries, combining the multiple advantages of liquid and all-solid-state electrolytes. Herein, we a synthesized GPE using poly(ethylene glycol)acrylate (PEGDA) in order to understand how the GPE efficiently inhibits lithium dendrite formation and growth. The effects of PEGDA on the solvation shell structure of the lithium ion are investigated using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, which are also supported by Raman spectroscopy. The GPE electrolytes with optimal PEGDA concentration exhibit high transference numbers (t =0.72) and ionic conductivity (σ=3.24 mS cm-1 ). A symmetric lithium ion battery using GPE can be stably cycled for 1200 h in comparison to 320 h in a liquid electrolyte (LE), possibly owing to the high content of LiF (17.9 %) in the solid-electrolyte interphase film of the GPE cell. The observed concentration/electric field gradient observed through the finite element method also accounts for the good cycling performance. In addition, a LiCoO2 |GPE|Li cell demonstrates excellent capacity retention of 87.09 % for 200 cycles; this approach could present promising guidelines for the design of high-energy lithium batteries.

Evaluating shielding gas-filler wire interaction in bi-metallic wire arc additive manufacturing (WAAM) of creep resistant steel-stainless steel for improved process stability and build quality

This study investigates the effect of shielding gases (namely, 98%Ar-2%CO2 and 96%Ar-3%CO2–1%O2) on the bi-metallic wire arc additive manufacturing (WAAM) of creep resistant steel (CRS) and stainless steel (SS). Contrary to the conventional practice of using material-specific gas, i.e., two gases for bi-metallic deposition, the aim here is to find a common shielding gas that creates a favorable mix with alloying elements of each filler wire to facilitate smooth arcing and metal transfer. The appropriateness of the shielding gas is broadly evaluated in terms of two criteria, viz. (a) arc stability and (b) bead uniformity and the penetration pattern. The stability of the arc (in terms of cyclograms, probability density distribution, voltage signal analysis), the accuracy of the bead (visual inspection, X-ray radiography, geometric deviation), and the quality of the deposit (penetration pattern) are first evaluated for single bead-on-plate deposits for the two candidate material and shielding gas pairs. The result of the analysis suggests the appropriate gas, which is then validated by depositing and investigating actual bi-metallic walls of CRS and SS. The change of the gas without alteration of other parameters significantly affects the bead shape, metal-transfer pattern, chemical composition of the welding arc, and bead penetration, all of which contribute to the ability of materials to fuse without any defects at the bi-metallic interface. Higher CO2 and O2 contents in the shielding gas stabilize the welding arc by increasing the metal vapor (i.e., more ionized particles) because of exothermic reaction and reduced surface tension, respectively. The stability leads to bead uniformity and an increase in the weld penetration at the edges and weld dilution, which negates the lack of fusion when two materials are deposited side-by-side to create a bi-metallic wall. The presence of O2 in the gas increases molten metal fluidity, which minimizes the flatness variation on both sides of the bi-metallic wall. The reported results are fundamental and have high significance, serving as guidelines for a wide array of multi-material service components fabricated using WAAM.