Poor Wettability Research Articles

Permeable and Durable Liquid-Metal Fiber Mat as Implantable Physiological Electrodes with Long-Term Biocompatibility.

Implantable physiological electrodes provide unprecedented opportunities for real-time and uninterrupted monitoring of biological signals. Most implantable electronics adopt thin-film substrates with low permeability that severely hampers tissue metabolism, impeding their long-term biocompatibility. Recent innovations have seen the advent of permeable electronics through the strategic modification of liquid metals (LMs) onto porous substrates. However, the durability of these electronics is limited by the inherent poor wettability of LMs, particularly within the intricate 3D skeleton of the porous substrate. Herein, the study reports a spatial wettability tuning strategy that solves the wettability issue of LMs within the porous substrates, enabling the LM physiological electrodes with high durability and long-term biocompatibility. The study demonstrates the use of the electrodes as implantable neural interface to realize in vivo acquisition of electrocardiograph and electrocorticogram signals with long-term biocompatibility and high signal-to-noise ratio. This work demonstrates a promising direction for rational design of durable implantable bioelectronics with long-term biocompatibility.

INVITED REVIEW: Recent developments in understanding the rehydration characteristics of high-protein dairy powders.

The use of dairy-based ingredients is increasingly prominent in the food industry due to their functional and nutritional benefits. High-protein powders are highly attractive due to their superior nutritional (e.g., high protein, calcium) and functional benefits (e.g., gelation, emulsification, foaming). Complete rehydration is essential for achieving optimum functionalities. However, poor wettability, slower rehydration, and the presence of insoluble particles are observed in high-protein dairy powders, especially in casein-rich powders, such as milk protein concentrate and micellar casein concentrate. The low solubility of these powders can cause processing difficulties, such as clogged filters and processing lines, leading to a loss of nutritional and functional properties and increased operating costs. Therefore, it is crucial to measure rehydration characteristics before application. Characterizing the different phases of rehydration helps in identifying the rate-limiting stages and strategies to improve them. Various methods for measuring each rehydration stage are discussed in detail in this review. Methods based on changes in conductivity, turbidity, particle size, and rheological properties during powder reconstitution are examined. Various imaging techniques, ultrasound-based methods, and nuclear magnetic resonance techniques that have been used for characterizing rehydration behavior are also elaborated upon here. Apart from these techniques, the methods suitable for in-line application in the industry are also mentioned. In addition to dairy powders, the rehydration of infant formula is discussed. The rehydration of infant formula is important for ease of end-user application and for delivering proper nutritional values. This review discusses common methods such as the insolubility index and wetting time, as well as some newer techniques based on focused beam reflectance measurement, electric resistance tomography, and Lumisizer. Overall, this review elucidates the existing industrial methods and recently developed techniques for characterizing rehydration, their applicability for inline measurement, and their advantages and disadvantages.

Cold-sprayed Cu matrix composite coatings with core-shell structured Co@WC reinforcements on Q235 steel

Tungsten carbide (WC), celebrated for its exceptional strength, hardness, and chemical inertness, serves as an exemplary reinforcement for copper (Cu) matrix composite (CMC) coatings, significantly enhancing their wear and corrosion resistance. However, the inherent poor wettability and interfacial bonding between WC and Cu during the cold spray additive manufacturing process pose challenges to further performance improvement of these coatings. This study investigates cold-sprayed CMC coatings reinforced with WC particles, both with and without an electroless plated cobalt (Co) shell (Co@WC; at 10 wt.% and 20 wt.%), focusing on their microstructure, mechanical properties, tribological behavior, and electrochemical corrosion resistance. The findings indicate a reduction in CMC coatings` porosity and mean free path (MFP) of reinforcement particles with increasing reinforcement content. Despite slight Co shell damage during deposition, ceramic retention is notably enhanced, reaching up to 149.3%. The microhardness and wear resistance of CMC coating are improved with decreased MFP and increased ceramic content. Compared to the Cu coating, the microhardness of CMC coatings escalates by up to 32.9% (151.8HV0.1), and the specific wear rate is dramatically reduced by up to 84.2%. The Co shell effectively prevents the detachment of Co@WC particles, thereby enhancing the bending and wear resistance. Electrochemical corrosion tests, encompassing open circuit potential (EOCP), polarization curve, and electrochemical impedance spectroscopy (EIS), indicate that lower porosity, high ceramic content and the Co shell substantially boost the corrosion resistance of the CMC coating. Specifically, the coating with 20 wt.% Co@WC (Cu20(Co@WC)) demonstrates superior corrosion resistance compared to the Cu coating, hinting at the potential for further enhancement with increased ceramic content.

Impact of route of particle engineering on dissolution performance of posaconazole

Even when they have similar particle size, micron sized drug crystals prepared via different process routes may still exhibit considerable variability in pharmaceutical properties, due to the anisotropy of molecular crystals. This study aims to evaluate the dissolution performance of micronized posaconazole obtained through both milling and precipitation, with and without polymer coating. To overcome the problem of pressure-induced amorphization of posaconazole, powder dissolution was performed instead of intrinsic dissolution, which requires compressing powder into pellets. However, direct powder dissolution was challenged by the poor dispersibility of micronized posaconazole powders because of their extremely poor wettability. To solve this problem, we pretreated powders by dispersing them in an aqueous solution with a surfactant. Despite posaconazole forming a hydrate after pretreatment, differences in measured powder dissolution rates are meaningful in predicting impact of routes of API engineering on biopharmaceutical performance since hydration of posaconazole also occurs in vivo. This case study presents a systematic approach in addressing challenges when characterizing dissolution performance of drug powders.

Enhancing Quasi-Solid-State Lithium-Metal Battery Performance: Multi-Interlayer, Melt-Infused Lithium and Lithiophilic Coating Strategies for Interfacial Stability in Li||VS2-DSGNS-LATP|PEO-PVDF||NMC622-Al2O3 Systems.

The development of quasi-solid-state lithium metal batteries (QSSLMBs) is hindered by inadequate interfacial contact, poor wettability between electrodes and quasi-solid-state electrolytes, and significant volume changes during long-term cycling, leading to safety risks and cataclysmic failures. Here, we report an innovative approach to enhance interfacial properties through the in situ construction of QSSLMBs. A multilayer design integrates a microwave-synthesized Li1.3Al0.3Ti1.7(PO4)3 (LATP) ceramic electrolyte, which is surface-coated with a lithiophilic conductive ink comprising VS2 and disulfonated functionalized graphene nanosheets (VS2-DSGNS) using a low-cost nail-polish binder. Subsequently, a few drops of LiPF6 in EC/DMC liquid electrolyte (LE) are impregnated into the uncoated side of the LATP surface. The quasi-solid-state electrolyte pellet of LATP-VS2-DSGNS surface was allowed to be in contact with the molten Li and held until Li flowed into the LATP-VS2-DSGNS surface completely via a "melt-infusion strategy" as an anode side. Additionally, a heterogeneous polymer matrix consisting of poly(ethylene oxide) (PEO) and poly(vinylidene difluoride) (PVDF) as a polymer interlayer is fabricated using a solution casting technique for improving the wettability between the LE impregnated side of LATP and cathode, to enhance overall charge transfer kinetics. The assembled symmetric cells, Li||LATP-VS2-DSGNS||Li and Li||PEO-PVDF/LE-LATP||Li, demonstrate high lithium-ion conductivities of 3.69 × 10-4 and 1.02 × 10-3 S cm-1, respectively, with impressive lithium-ion transfer numbers of 0.84 and 0.93 at 25 °C. Both cells exhibit a highly reversible lithium stripping/plating cycling process for over 600 h, with minimal voltage polarization of 10 and 31.6 mV, across a broad redox window (-1 to 6 V), effectively inhibiting lithium dendrite formation. Furthermore, the combination of a surface-modified Al2O3 dry-coated, high-nickel NMC622 cathode with the PEO-PVDF|LATP-VS2-DSGNS||Molten-Li architecture in a CR2032 coin-type full-cell delivers a galvanostatic discharge capacity of 130.6 mAh g-1 at a 1C rate after 200 cycles, achieving 84.3% capacity retention, thereby demonstrating substantial reduction in interfacial resistance and enhanced stable battery performance of QSSLMBs.

Toward Novel Porous Boronized Ti6Al4V/FHA Composite Implants by Combined Microwave Sintering and Temporary Space Alloying

Titanium alloys are unsuitable implants for patients with low bone quality due to their high moduli and bioinertness. In this study, porous boronized Ti6Al4V/fluorohydroxyapatite (FHA) composites are synthesized via microwave sintering of mixed Ti6Al4V, FHA and TiB2 powders at 1050 °C for 30 min, with 0–10 wt% urea as a space holder material. It is shown that increasing urea addition leads to higher porosity, promoting microwave penetration and microwave “lens effect”, which improves boronization and restrains degradation of mechanical properties of the composites caused by the increased porosity. With the urea addition of 0–3 wt%, the compressive strength and modulus decrease from 380.3 MPa and 14.5 GPa to 134.4 MPa and 3.26 GPa, respectively, while the Vickers microhardness declines from 360.3 to 300.0 HV. The increased exposure of FHA improves chemical and biological properties of the composite, with water contact angle decreased by nearly half and osteogenesis increased by sixfold. By adding more urea, the microhardness decreases evidently, with poorer wettability and biocompatibility due to looser structure and FHA decomposition. By adding 3 wt% urea, the composite achieves an optimal balance between ultralow modulus and enhanced bioactivity, making it ideal for rapid osseointegration in patients with poor bone conditions.

Organic Solvent-Based PEDOT:PSS Solution for Air-Processed Organic Photovoltaics.

PSS is one of the best hole transport materials in organic photovoltaics (OPV). However, due to poor wettability, the aqueous PEDOT:PSS (a-PEDOT) is not applicable for inverted structured OPV as a hole transport layer (HTL) on top of the active layer. In this work, organic solvent-based PEDOT:PSS (o-PEDOT) with improved wettability was prepared by the solvent-replacement method through centrifugal ultrafiltration, dialysis membrane, and thermal evaporation. Adopting o-PEDOT as the HTL on the top surface of the active layer, the inverted OPVs were successfully prepared through a solution process. Importantly, due to good conductivity and suitable work function, the o-PEDOT can also act as the interconnection layer (ICL) in air-processed tandem OPV devices. The tandem device achieved a champion PCE of 15%, among the best reports of solution-processed homotandem OPV under open-air conditions. The flexible tandem OPV using o-PEDOT as an ICL was also demonstrated, with an efficiency of over 14%.

Reinforced Li/Garnet Interface by Ceramic Metallization‐Assisted Room‐Temperature Ultrasound Welding

ABSTRACTSolid‐state lithium metal batteries (SSLMBs), heralded as a promising next‐generation energy storage technology, have garnered considerable attention owing to inherent high safety and potential for achieving high energy density. However, their practical deployment is hindered by the formidable interfacial challenges, primarily stemming from the poor wettability, (electro) chemical instability, and discontinuous charge/mass transport between solid‐state electrolytes and Li metal. To overcome these obstacles, taking garnet‐based electrolyte (Li6.5La3Zr1.5Ta0.5O12, LLZTO) as a pathfinder, the ceramic metallization‐assisted room‐temperature ultrasound werlding (UW) has been developed to reinforce the Li/LLZTO interface. This ultrasound welding approach constructs a compact interface that facilitates rapid Li+/e− transport, while the formation of Li−M (M = Au, Ag, and Sn) alloy homogenizes the distribution of Li+/e− at the interface. By optimization, the atomic‐level contact achieved by ultrasound welding, coupled with a nanosized Au modification layer, significantly reduces the Li/LLZTO interfacial resistance to 5.4 Ω cm2, a marked decrease compared to the resistance achieved by static pressing methods (1727 Ω cm2). The symmetric cell exhibits a high critical current density of 1 mA cm−2 and sustains long‐term stability for over 1600 h at 0.3 mA cm−2, with a Li plating/stripping overpotential of < 45 mV. By incorporating a robust anode‐side interface into solid‐state lithium metal batteries, the LiFePO4‐based full battery contributes 118.4 mAh g⁻1 after 600 cycles at 1 C (capacity: ∼100%). This study offers a facile and effective approach to bolster the interfacial stability between Li and solid‐state electrolytes, paving the way for the development of high‐performance solid‐state lithium metal batteries.

Enhanced strength and ductility of boron nitride nanosheet reinforced cu composites through constructing an interfacial three-dimensional structure

To address the poor wettability and weak interface bonding between boron nitride nanosheet (BNNS) and Cu, BNNS/CuTi composites were prepared through matrix microalloying by adding 1 wt% Ti. Solid-state interfacial reactions resulted in the formation of TiN transition layers and TiB whiskers (TiBw), collectively constructed a BNNS-(TiN&TiB)-Cu interfacial three-dimensional structure (I-3DS). The coherent I-3DS significantly reduced the interfacial energy, improved the interfacial stability, and achieved a favorable combination of strength and ductility in BNNS/CuTi composites. The 0.1 wt% BNNS/CuTi composite achieved an ultimate tensile strength (UTS) of 485 MPa, representing increases of 114 % and 62 % over pure Cu and 0.1 wt% BNNS/Cu composite, respectively. The interlocking structure formed by I-3DS and Cu doubled the theoretical interface shear strength limit and improved load transfer efficiency. This study offered new insights into the innovative design of high-performance Cu matrix composites (CMCs) by constructing I-3DS.

Effectiveness of amine plasma-functionalized 3D PLGA scaffolds immobilized with Fibroblast Growth Factor in periodontal tissue regeneration

Polylactic-co-glycolic acid (PLGA) has widely been used as a biodegradable material for three-dimensional (3D) printed scaffolds. However, the lack of surface chemicals and poor wettability limit the application of the polymer. Therefore, we modified the 3D scaffold surface using plasma surface modifications and evaluated its biocompatibility. To introduce amine functional groups on the 3D PLGA scaffold surface, amine plasma-polymerization was performed using 1, 2-diaminocyclohexane (DACH) monomers. Then, Fibroblast Growth Factor (FGF) was immobilized on the amine-functionalized 3D PLGA scaffold surface using a 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. Human Gingival Fibroblast (HGF-1) cell behaviors were evaluated through cell adhesion, migration, proliferation, and western blot. The results showed that DACH plasma-polymerization provided the amine-functionalized surface which is capable of immobilizing FGF bioactive molecules on the 3D PLGA scaffold. Cell adhesion, proliferation, and migration on plasma surface-modified scaffolds have greatly improved compared to pristine 3D PLGA scaffolds. Notably, FGF-immobilized groups demonstrated the highest proliferation. These results suggest that the FGF-immobilized scaffold surface had a significant effect on accelerating oral gingival cell proliferation. In the future, 3D PLGA scaffolds with surface functionalized by plasma-polymerization and biomolecule immobilization can be used as a good alternative to autogenous soft tissue grafts for damaged soft tissue restoration.

Diagnosis for wetting condition of silicon/graphite (Si/Gr) anode in lithium ion batteries

The need for the longer mileage of electric vehicles has pushed the energy density of lithium ion batteries (LIBs) to their limits. However, enhancing the energy density of LIBs usually causes poor wetting of an anode electrode and its higher ionic resistance (Rion), resulting in lithium (Li) plating. Therefore, it is highly crucial to monitor the anode Rion influenced by wetting condition of the anode during formation process. Here, we introduce the electrochemical indicator to estimate the Rion of the silicon (Si)/graphite (Gr) blended anode in 21700 cylindrical cells depending on its wetting condition, which can be utilized as a screening tool for manufactured cells. It is attributed to the better rate capability of Si compared to Gr in the blended electrode, and their overpotential difference enables the appearance of the diagnostic signal on differential voltage profiles. In practice, we confirm that the proposed indicator has a strong correlation with the overpotential of the Si/Gr anode, and further is related to the cycle performance and whether Li plating occurs or not. Therefore, the indicator can be utilized as a diagnostic tool for inspecting wetting condition of manufactured cells, which can ensure the safety of LIBs.

Surface Wetting Properties of Lithium Anode Characterized Using Laser Scanning Confocal Microscopy

Surface wettability between the lithium metal anode and liquid electrolyte is a critical performance characteristic. Poor wettability can result in nonuniform stripping and deposition of lithium metal, nonuniform SEI formation, formation of dead lithium and; thus, shorter cycle life. Imaging techniques such as laser-induced fluorescence imaging using laser scanning confocal microscopy (LSCM), have become a valuable tool for investigating the surface properties of lithium metal anodes.1 Laser scanning confocal microscopy is an advanced microscopy technique that allows improved depth resolution relative to traditional optical microscopy.Arcadium Lithium Corporation has developed LIOVIX®printable lithium technology, a formulation that can be printed, at industrial speed, on most common substrates, such as Cu foil to produce thin lithium metal foil with thickness in the range of 5 µm to 50 µm with no limitation in width.2 LIOVIX®-based lithium film has a different microstructure when compared to a commercial foil (Figures 1a and 1b). LIOVIX-based thin foil retains rheology modifiers used in the formulation that serve as a 3D skeleton. This unique structure can change lithium metal surface plating behavior. Therefore, the 3D structure might mitigate the growth of dendritic lithium, reduce mechanical degradation, and improve safety and cycle life of the battery.LSCM was used for in-situ, in operando observations of the difference in surface properties and wettability properties of commercial lithium foil and LIOVIX-based lithium foil (Figures 1c and 1d). Lithium metal surface is dynamic and prone to forming various structures and compounds, depending on the conditions it is exposed to. The results showed that LIOVIX-based foil lithium activity is more homogenous and had a shallower interaction when compared to the commercial lithium foil. This potentially signifies more uniformity to the lithium activity in LIOVIX-based foil vs. commercial lithium foil; thus, more uniform surface activity within a battery system.Reference Nishikawa et al., 2010 J. Electrochem. Soc. 157 A1212Yakovleva et al., Battery utilizing printable lithium, U.S. Patent 11, 824, 182, B2, Nov. 21, 2023 Figure 1. Microscope image of A) LIOVIX® -based lithium foil (20um), B) commercial lithium foil (20um); and 3D Confocal microscope images of C) LIOVIX®-based lithium foil (20um) and D) commercial lithium foil (20um). Figure 1

Effects of Metal Interlayers between Li7La3Zr2O12 Solid Electrolyte and Li Anode on Li Dissolution/Deposition Cycles

Garnet-type oxide solid electrolyte, Li7La3Zr2O12 (LLZ), has relatively high ionic conductivity and high reduction stability for metallic Li. It is considered as a promising candidate for use in all-solid-state batteries. However, practical applications of LLZ are currently hindered by large interfacial resistances at LLZ electrolyte/Li electrode interfaces. One of the reasons for this issue is believed to be the poor wettability of metallic Li on the LLZ surface, resulting in a poor contact interface. To reduce the interfacial resistance, intermediate layers have been introduced.[1-3] In this study, we investigated the effects of intermediate layers such as Sn, In, Bi, etc., which alloy with Li, at the LLZ/Li interface on Li dissolution/deposition reactions.Li6.7La3Zr1.7Ta0.3O12 (LLZ, φ10 mm, 1 mmt) pellets, produced by TOSHIMA Manufacturing Co., Ltd., were used as solid electrolytes. The LLZ surfaces were polished with sandpaper in an Ar-filled glovebox. Bi interlayers were deposited on both sides of the LLZ pellets by thermal evaporation with varying thickness. Subsequently, Li electrodes (10 μmt) were deposited to obtain Li symmetric cells (Li|LLZ|Li). Electrochemical impedance measurements and Li dissolution/deposition tests of the Li|LLZ|Li cells were performed at the temperature of 60°C. In the dissolution/deposition test, the current density was set to 0.2 and 0.5 mA/cm2, and the direction of current flow was switched every 0.5 hours. After the Li dissolution/deposition test, cross-sections of the LLZ pellet were observed by scanning electron microscope (SEM) and analyzed by energy dispersive X-ray spectroscopy (EDX).Figure 1 shows Li dissolution/deposition cycle performance in Li|LLZ|Li cells both with and without a Bi interlayer. The Li|LLZ|Li cell without the interlayer exhibited stable cycle operation for 50 cycles at a current density of 0.2 mA/cm². However, when the current density was increased to 0.5 mA/cm², the overvoltage increased rapidly due to the formation of voids, which decreased the contact area at the LLZ/Li interface. On the other hand, when an 80 nm Bi interlayer was introduced, stable cycling was observed even at a current density of 0.5 mA/cm² with no increase in overvoltage during cycling. EDX analysis of the LLZ/Li interface after the dissolution/deposition tests revealed the presence of the Bi layer at the interface, as shown in Fig. 2, which remained even after repeated dissolution/deposition cycles. It is believed that the Bi layer remains at the LLZ/Li interface after dissolution/deposition cycles, thereby maintaining a good contact interface between LLZ and Li, and improving cycle life. Acknowledgments This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number 22H01967.

Three-Layer Electrorefining of Molten Zinc Held on Porous Carbon or Silica Sheets in Molten LiCl–KCl–ZnCl2

A three-layer electrolysis process utilizing porous holding materials with the impermeability to liquid metals due to the poor wettability but permeability to molten salt electrolytes was investigated, which enables to establish a three-layer configuration of metal(l)/electrolyte(l)/metal(l) by holding metals above the electrolyte regardless of their densities. Porous carbon or silica sheets were selected as the holding materials of liquid Zn, and upper electrode to hold liquid Zn was prepared. Electrorefining experiments was carried out in molten LiCl–KCl–ZnCl2 at 723 K. Three types of experiments were carried out focusing on anodic polarization, electrorefining with cathodic carbon, and three-layer electrolysis using liquid Zn as cathode.Anodic polarization experiments clarified that evolution of a large amount of Cl2 gas was observed from the graphite components of the upper electrode when a more positive potential than the Cl2/Cl− was applied. The use of insulating silica fiber sheets and holding material allowed for dissolution of Zn at higher current density without gas evolution. In the electrorefining experiments, synthesized crude zinc and ISP crude zinc were electrolyzed to obtain purified Zn at the cathode. The concentration of impurity elements in the cathode Zn was reduced by a factor of 8 to 200 compared to the value in the crude zinc, highlighting the purification effectiveness of the method. In the Zn(l)/electrolyte(l)/Zn(l) three-layer electrolysis, it was verified that the upper electrode was applicable as either an anode or cathode. Current efficiencies were close to 100% in all electrorefining and three-layer electrolysis experiments. From the results obtained, challenges associated with the three-layer electrolysis process were identified, and countermeasures to solve them were proposed.Acknowledgement: This work is conducted as a collaboration research of Laboratory of Design of Sustainable Materials and Processing, and Laboratory of Non-ferrous Extractive Metallurgy, Department of Materials Science and Engineering, Graduate School of Engineering, Kyoto University. Laboratory of Non-ferrous Extractive Metallurgy is an endowed chair by Mitsubishi Material Corp. We would like to acknowledge Prof. Hisaaki Fukushima at Kyushu University, Prof. Takashi Nakamura at Tohoku University, and Dr. Akihiro Kishimoto at Kyoto University for their valuable discussion. We also acknowledge Mitsui Mining & Smelting Co., Ltd., for supplying the prime western grade metal zinc (ISP crude zinc).

Highly Reversible Lithium Deposition and Stripping Under Practical Conditions through Improved Wettability of Polyolefin Separator to Highly Concentrated Electrolytes

Lithium metal is regarded as a promising negative electrode material for rechargeable batteries, but several challenges such as the dendritic growth of lithium metal and side reactions between lithium metal and electrolyte hinder the practical application of lithium metal batteries (LMBs). In recent years, several research groups reported that highly concentrated electrolytes (HCEs) are effective in suppressing side reactions and improving the electrode reversibility of lithium metal.[1] However, the poor wettability of conventional polyolefin separators toward HCEs remains a critical issue to be addressed. Although porous glass fiber filters are often used as separators for HCEs, lithium dendrites easily penetrate the separator during repeated lithium deposition/stripping at areal capacities over 1 mA h cm−2, leading to an internal short circuit. Here, we present the effective strategies to solve the electrolyte wettability issue and to achieve stable cycling of LMBs under practical conditions. The use of a functional polyolefin separator coated on both sides with an aramid layer improves the electrolyte wettability because polar functional groups provide a better affinity between the polyolefin separator and HCE.[2] The combined use of HCE (5 mol dm-3 LiN(SO2F)2 in 1,2-dimethoxyetahne) and aramid-coated polyolefin separator increases the reversible lithium deposition capacity up to >10 mA h cm−2 and results in stable lithium deposition/stripping cycling with high Coulombic efficiency of ~99% at practical areal capacity of 4 mA h cm−2. From these results, the possibility of developing practical high-energy LMBs with HCEs will be discussed.

Sustainable Semi-Continuous Rare Earth Alloy Production in Chloride Based Molten Salts

Rare earth elements have numerous uses ranging from green energy to defense applications. Nd metal production uses a neodymium/lithium fluoride molten salt with a consumable carbon anode where dissolved neodymium oxide and carbon are converted to neodymium metal and CO2. In addition to producing CO2, the process releases PFCs, making it environmentally unsustainable. We have shown that neodymium chloride can be electrolyzed to produce Nd metal at the cathode and chlorine gas at the anode. The chlorine can be recycled in the conversion of the neodymium oxide (from ore) to neodymium chloride. In our process, the anode is non-consumable which allows for continuous processing without producing deleterious greenhouse gases. Chloride rare earth electrowinning historically suffered from low Coulombic efficiency obtained in lab-scale efforts (10-50%). The electrolytic reduction of neodymium chloride is a two-step reaction where a stable intermediate (Nd2+) is formed,1-2 The intermediate species can diffuse away from the cathode resulting in efficiency losses. Further, anodic overpotentials for the chlorine evolution reaction are significant due to the somewhat sluggish kinetics and poor wetting characteristics of the salt on traditional graphite anodes. Solid metal electrowinning in molten salts tends to produce rough deposits which trap significant salt impurities necessitating downstream purification. However, producing liquid metal allows for easy density separation from the salt, leading to a purer as-deposited product as well as faster metal deposition kinetics (i0 ~ 1 A/cm2) which reduces the effects of Nd2+ out diffusion, and chlorine evolution kinetics (i0 ~ 0.2 A/cm2) because of the higher temperature. In this talk, we report our work on improvements to Coulombic efficiency (~85%), and a stable anode that catalyzes chlorine evolution. The combination of improved Coulombic efficiency and reduced anode overpotentials results in low specific energy consumption (~3 kWh/kg) and thus lower operating costs. We will also report on efforts to produce liquid metal in the form of an NdFe alloy at ~800 °C which can be collected semi-continuously at rates of >1 A/cm2. References : R. Akolkar, J. Electrochem. Soc., 169, 043501 (2022). D. Shen and R. Akolkar, J. Electrochem. Soc., 164, H5292–H5298 (2017). Holcombe et al., ACS Sustainable Chem. Eng. 2024, 12, 10, 4186–4193, (2024). Holcombe et al., Holcombe et al 2024 Electrochem. Soc. Interface 33 49, (2024). Rohan Akolkar. System and Process for Sustainable Electrowinning of Metals. US Patent 20230279572. Sept. 2023 Portions of this work were performed by LLNL under Contract DE-AC52-07NA27344.

Electrospun nanofiber surface-modified polyethylene separator for enhanced cycling stability and low-temperature performance of sodium-ion batteries

Sodium-ion batteries (SIBs) are emerging as promising low-cost and long-cycle energy storage systems. However, the poor wettability of the conventional polyolefin separators with polar electrolytes leads to low ionic conductivity and high battery resistance, causing rapid capacity decay. Herein, we propose using a polyethylene (PE) separator coated with a nanofiber composited of poly(vinylidene fluoride) (PVDF) and Al2O3 filler via electrospinning. Compared to the standard PE separators, this composite separator offers much improved electrolyte wettability, mechanical strength, and electrochemical stability. Electrochemical tests demonstrate that the Na[Ni1/3Fe1/3Mn1/3]O2||hard carbon pouch cells based on the PVDF-Al2O3/PE composite separator exhibit a capacity retention of 95.1% after 800 cycles at 1C. Additionally, the separator significantly enhances low-temperature discharge performance and cycling stability. Characterizations based on Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction confirm the successful integration of Al2O3 nanoparticles into the PVDF matrix, resulting in a homogeneously dispersed and well-connected structure, which improves ion transport efficiency and stability, thereby effectively boosting battery performance. This research highlights the potential of PVDF-Al2O3 nanofiber composite separators for advanced SIBs with high reversibility, a wide operating temperature range, and long cycling life.

Application of PACz-Based Self-Assembled Monolayer Materials in Efficient Perovskite Solar Cells.

Due to the advantages of low interface resistance, high work function, and high stability, PACz family materials have developed rapidly in p-i-n structure perovskite solar cells (PSCs) in recent years. Numerous studies have shown that PSCs prepared on the basis of PACz family materials or their derivatives as hole transport layers (HTLs) generally exhibit superior performance compared to PSCs prepared on the basis of organic HTL PTAA and inorganic HTL NiOx, especially in terms of stability, demonstrating unparalleled charm. Since the application of PACz-like molecule V1036 as a HTL in PSCs in 2018, research reports on high-performance PSCs based on the PACz family HTL have been widely disseminated. Currently, PSCs based on the PACz HTL exhibit a world record value of 26.7% power conversion efficiency (PCE), breaking the long-standing world record held by n-i-p-structured PSCs, indicating its great potential for application in PSCs. The main problem with using PACz as a HTL is that it exhibits poor wettability toward perovskite precursor solutions, is sensitive to the thickness of the HTL and the roughness of the substrate, has poor thermal stability, and lacks preparation methods, making it difficult to achieve large-area device fabrication. This review summarizes the outstanding achievements of PACz to date, describes the mechanism and unique properties of PACz in PSCs, and looks forward to the future development prospects of PACz.

Effects of Carbon Type and Composition on the Properties of Carbon-Copper Composite as Pantograph Slide in Railway Application

Carbon-copper composites have wide application prospects as high-speed railway pantograph slides due to the self-lubricating ability of carbon and good conductivity of copper. However, carbon-copper composites produced through powder metallurgy may still encounter challenges, such as poor wettability and lower conductivity. The experimental approach in this work involved the fabrication of carbon-copper composites using the warm compaction method, with different types and proportions of carbon materials, namely local carbon from palm kernel shells (PKS) and graphite. Characterisation and testing of hardness, density, resistivity, transverse rupture strength (TRS), and microstructure of the composites have been conducted. An increase in graphite content was found to improve the electrical conductivity of the carbon-copper composite, while the addition of local carbon has enhanced its hardness. Furthermore, the addition of graphene oxide (GO) as filler has significantly improved the mechanical strength of this composite by up to 61.34%. This research has highlighted the potential of locally sourced carbon for developing advanced pantograph slide materials for railway applications. The findings provided valuable insights into the optimisation of composite compositions to achieve the desired balancebetween electrical conductivity and mechanical performance. These carboncopper composites hold the promise of more efficient and durable pantograph slides, which can contribute to the overall reliability and sustainability of railway systems.

Fluid dynamics of gas–liquid slug flow under the expansion effect in a microchannel

The expansion of bubbles in viscous fluids in microchannels is normally overlooked. The bubble dynamics in liquids with varying viscosities (1.15 ∼ 101.47 mPa·s) and contact angles (29.3 ∼ 137.6°) in a microchannel were investigated under various inlet pressure drops (8 ∼ 202 kPa). The findings indicate that bubble formation occurs within a squeezing-shearing regime over a wide Capillary number range of 0.0023–0.43. Interestingly, the wettability affects the bubble length rather than the bubble shape, and the poor wettability can hinders the decrease of length in higher viscosity fluids. Bubble expansion causes decreasing curvature radii of bubble caps, and non-linear rapid increases in its length and velocity along the microchannel. The bubble’s pressure–volume relation at the inlet and outlet confirms the validation of Boyle’s law in slug flow. A linear decline in pressure along the microchannel was deduced from this law. Further analysis suggests that besides the friction of the liquid slug, the pressure drop is influenced by the interface effect, film flow, and liquid circulation. Finally, a model for total pressure drop was developed, which effectively predicted the length and velocity of bubbles in the expansion process. This study offers valuable insights for a deeper understanding of bubble expansion behaviors in microchannels.