Stable Surface Research Articles

Concerted Influence of H2O and CO2: Moisture Exposure of Sulfide Solid Electrolyte Li4SnS4.

Although moisture-induced deterioration mechanisms in sulfide solid electrolytes to enhance atmospheric stability have been investigated, the additional impact of CO2 exposure remains unclear. This study investigated the generation of H2S from Li4SnS4 under H2O and CO2 exposure. Li4SnS4 was exposed to Ar gas at a dew point of 0 °C with and without 500 ppm of CO2, and its ion conductive properties were evaluated. Although the lithium-ion conductivity of Li4SnS4 decreased regardless of the presence of CO2, the amount of H2S generated with CO2 was five times higher. To elucidate the underlying mechanism, X-ray diffraction and Raman spectroscopy were used. Without CO2, hydrate Li4SnS4·4H2O formation markedly increased, whereas, with CO2, it increased a little. The difference revealed distinct deterioration mechanisms leading to a decrease in lithium-ion conductivity: without CO2, adsorbed H2O and Li4SnS4·4H2O contributed to the decrease, while with CO2, a weak acid dissociation reaction could reduce the thermodynamic stability of the moisture-exposed Li4SnS4 surface including Li4SnS4·4H2O and adsorbed H2O, promoting H2S release and carbonate formation. This was supported by the recovery of lithium-ion conductivity after vacuum heating. The concerted influence of H2O and CO2 provides valuable insights into the fundamental deterioration mechanisms in sulfide solid electrolytes that could be applied in battery manufacturing processes.

Orthogonal Electrochemical Stability of Bulk and Surface in Lead Halide Perovskite Thin Films and Nanocrystals.

Lead halide perovskites have attracted significant attention for their wide-ranging applications in optoelectronic devices. A ubiquitous element in these applications is that charging of the perovskite is involved, which can trigger electrochemical degradation reactions. Understanding the underlying factors governing these degradation processes is crucial for improving the stability of perovskite-based devices. For bulk semiconductors, the electrochemical decomposition potentials depend on the stabilization of atoms in the lattice-a parameter linked to the material's solubility. For perovskite nanocrystals (NCs), electrochemical surface reactions are strongly influenced by the binding equilibrium of passivating ligands. Here, we report a spectro-electrochemical study on CsPbBr3 NCs and bulk thin films in contact with various electrolytes, aimed at understanding the factors that control cathodic degradation. These measurements reveal that the cathodic decomposition of NCs is primarily determined by the solubility of surface ligands, with diminished cathodic degradation for NCs in high-polarity electrolyte solvents where ligand solubilities are lower. However, the solubility of the surface ligands and bulk lattice of NCs are orthogonal, such that no electrolyte could be identified where both the surface and bulk are stabilized against cathodic decomposition. This poses inherent challenges for electrochemical applications: (i) The electrochemical stability window of CsPbBr3 NCs is constrained by the reduction potential of dissolved Pb2+ complexes, and (ii) cathodic decomposition occurs well before the conduction band can be populated with electrons. Our findings provide insights to enhance the electrochemical stability of perovskite thin films and NCs, emphasizing the importance of a combined selection of surface passivation and electrolyte.

Polarity of homoepitaxial ZnO films grown by Nd:YAG pulsed laser deposition

We investigate the stability of the polar surface of ZnO films grown homoepitaxially on atomically flat ZnO (0001¯) O-face substrates by neodymium yttrium aluminum garnet (Nd:YAG) pulsed laser deposition (PLD). For films grown in the temperature range from 500 to 700 °C, ion scattering spectroscopy showed that the film surface termination was the same as the ZnO substrate. Even for a Mg0.2Zn0.8O/ZnO superlattice, no polarity reversal occurred, indicating that the ZnO (0001¯) O-face is highly stable, despite the film surface sputtering caused by the high kinetic energy of the PLD plume generated by the Nd:YAG laser.

The Spatiotemporal Surface Velocity Variations and Analysis of the Amery Ice Shelf from 2000 to 2022, East Antarctica

The surface velocity of the Amery Ice Shelf (AIS) is vital to assessing its stability and mass balance. Previous studies have shown that the AIS basin has a stable multi-year average surface velocity. However, spatiotemporal variations in the surface velocity of the AIS and the underlying physical mechanism remain poorly understood. This study combined offset tracking and DInSAR methods to extract the monthly surface velocity of the AIS and obtained the inter-annual surface velocity from the ITS_LIVE product. An uneven spatial distribution in inter-annual variation in the surface velocity was observed between 2000 and 2022, although the magnitude of variation was small at less than 20.5 m/yr. The increase and decrease in surface velocity on the eastern and western-central sides of the AIS, respectively, could be attributed to the change in the thickness of the AIS. There was clear seasonal variation in monthly average surface velocity at the eastern side of the AIS between 2017 and 2021, which could be attributed to variations in the area and thickness of fast-ice and also to variations in ocean temperature. This study suggested that changes in fast-ice and ocean temperature are the main factors driving spatiotemporal variation in the surface velocity of the AIS.

Oxygen-close-packed (310)-plane substrates of β-Ga2O3 grown by the casting method

The highly anisotropic crystal structure of β-Ga2O3 gives rise to a variety of crystal planes, among which the (310) plane is a potentially stable close-packed plane for the O sublattice. In this paper, we report the β-Ga2O3 single crystal and substrates with a (310) major plane grown by the spontaneous nucleation technique in the casting method. High-quality crystal growth and substrate processing were confirmed by the 25.67 arc sec full width at half maximum and the 0.25 nm surface roughness. The nanoindentation experiments revealed the (310) substrate's better elastic recovery than that of (100) substrate. The Young's modulus and hardness of (310) substrates were 200 and 7.6 GPa, respectively. The surface barrier height and the Schottky barrier height were 1.25 and 0.92 eV, respectively. First principles calculations identified the (310)-Ga-I plane as the most stable surface configuration of the (310) plane under oxygen-poor condition, with a surface energy density of 1.48 J/m2. The (310) twin boundary formation around the O sublattice has a high energy density of 0.55 J/m2, suggesting its unlikelihood of spontaneous formation. These properties of (310) plane facilitate a high-quality crystal processing and epitaxial growth, thus endowing potential applications in high-quality power devices. Furthermore, the growth and fabrication of the (310) plane provide a route toward understanding the properties of β-Ga2O3 and advancing the growth techniques of oxide crystals.

Oscillation mechanism and predictive model of explosion load for natural gas in confined tube

Gas explosion in confined space often leads to significant pressure oscillation. It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibration frequency of the structure. To reveal the oscillation mechanism of gas explosion load, the experiment of gas explosion was conducted in a large-scale confined tube with the length of 30 m, and the explosion process was numerically analyzed using FLACS. The results show that the essential cause of oscillation effect is the reflection of the pressure wave. In addition, due to the difference in the propagation path of the pressure wave, the load oscillation frequency at the middle position of the tunnel is twice that at the end position. The average sound velocity can be used to calculate the oscillation frequency of overpressure accurately, and the error is less than 15%. The instability of the flame surface and the increase of flame turbulence caused by the interaction between the pressure wave and the flame surface are the main contributors to the increase in overpressure and amplitude. The overpressure peaks calculated by the existing flame instability model and turbulence disturbance model are 31.7% and 34.7% lower than the numerical results, respectively. The turbulence factor model established in this work can describe the turbulence enhancement effect caused by flame instability and oscillatory load, and the difference between the theoretical and numerical results is only 4.6%. In the theoretical derivation of the overpressure model, an improved model of dynamic turbulence factor is established, which can describe the enhancement effect of turbulence factor caused by flame instability and self-turbulence. Based on the one-dimensional propagation theory of pressure wave, the oscillatory effect of the load is derived to calculate the frequency and amplitude of pressure oscillation. The average error of amplitude and frequency is less than 20%.

Fabrication of stable slippery lubricant-infused porous surface on polymethyl methacrylate/thermoplastic polyurethane by supercritical CO2 foaming

The development of sustainable and efficient methods to prepare slippery lubricant-infused porous surface (SLIPS) is a profound work. In this study, using bilayer polymers restricting foaming mutually, bimodal cells were prepared through bilayer poly(methyl methacrylate) (PMMA). At the same time, uniform cells were prepared by bilayer PMMA /thermoplastic polyurethane (TPU). The prepared porous surfaces exhibited a high porosity (57% or more). TPU as dispersed phase increased the cell density of the PMMA/TPU surface with a maximum cell density of 5.5 × 107 cells/cm2 and an average cell size of 1.0 μm. SLIPS prepared on PMMA/TPU surface with high porosity and uniform microcellular had better stability, and the sliding angle (SA) remained less than 10° after centrifugal rotation at 8000r/min. Therefore, this work provides an approach to improve the surface cell density and produce SLIPS sustainably and efficiently.

Creasing instability of polydomain nematic elastomers in compression

Polydomain liquid crystalline (nematic) elastomers exhibit unique mechanical properties such as soft elasticity, where the material largely deforms at nearly constant stress, due to microstructural evolution. In this paper, we numerically study the effect of such remarkable soft behavior on the surface instability of a half-space polydomain nematic elastomer, which is uniformly compressed parallel to the interface under a plane-strain condition. We compare the creasing instability of nematic elastomers with that of neo-Hookean elastomers by presenting bifurcation diagrams, stress and strain development in the elastomers, energy relaxation, and surface morphology at the creased state. Our results reveal that soft elasticity stabilizes nematic elastomers in plane-strain compression. Remarkably, the critical strain and stress at which the crease nucleates depend nonlinearly on the degree of anisotropy in nematic elastomers. Moreover, we find that the morphology of the creased surface in nematic elastomers exhibits the universal cusp shape previously observed in neo-Hookean elastomers.

In-situ formed stable Pt nanoclusters on ceria-zirconia solid solutions induced by hydrothermal aging for efficient low-temperature CO oxidation

Pt nanoclusters (PtC) on the surface of ceria-zirconia solid solutions exhibit superior low-temperature CO oxidation activity compared to Pt single atoms (Pt1). However, the redispersion behavior of the PtC to Pt1 lowers the efficiency of CO Oxidation. In this work, the stable surface hydroxyl groups were constructed by high-temperature hydrothermal aging treatment. Specifically, the Pt1 catalyst (Pt/CZOe-SA) prepared by atom trapping was subjected to high-temperature hydrothermal treatment to obtain the stable PtC catalyst (Pt/CZOe-HT) with in-situ formed PtC. The experimental results showed that PtC with 2–3 nm size could achieve excellent low-temperature activity and thermal stability. In addition, the ab initio molecular dynamics and density functional theory calculations revealed the specific evolution process of dynamic dispersion for PtC with or without hydroxyl groups from the femtosecond scale, suggesting that the hydroxyl groups limited the dispersion of PtC in the form of “energy fence”. The hydrothermal treatment not only introduced high-temperature stable hydroxyl groups to improve the stability of the in-situ formed PtC, but also optimized the ratio of Pt1 and PtC, and then enhanced the low-temperature activity by the synergistic effect between Pt1 and PtC. The present work can provide theoretical guidance for developing high-performance and high-stability Pt-based catalysts.

The effects of metal oxides doping on the surface stability of In2O3 for CO2 hydrogenation

The effects of metal oxides doping on the surface stability of In2O3 for CO2 hydrogenation

Enhancing osseointegration and angiogenesis of Titanium implants through KMnO4-Modified Montmorillonite nano-clay coating

Titanium (Ti) is a widely used and favored material for dental implants, with research efforts focusing on enhancing its osseointegration capabilities. Montmorillonite (MMT), a nano-clay, has shown significant potential in drug delivery, wound healing, and other biomedical applications. Implant coatings based on MMT have demonstrated promising results; however, challenges remain in terms of surface bond strength, stability, and uniformity. Studies have indicated that manganese (Mn) can enhance cell viability, proliferation, and adhesion by activating integrin receptors. Here, a KMnO4-modified MMT (MAO-MMT-Mn) coating was developed on Ti through the micro-arc oxidation (MAO) technique. The MAO-MMT-Mn coating significantly strengthens its bond, enabling it to withstand greater loads. The incorporation of Mn, silicon (Si) and phosphorus (P) resulted in the formation of uniformly distributed lamellar MMT, facilitating the sustained release of these elements. In vitro experiments demonstrated that the MAO-MMT-Mn coating promoted osteoblast adhesion and endothelial cell migration, and led to a significant increase in the expression of osteogenic and angiogenic genes compared to uncoated Ti. Moreover, in vivo assessments using micro-CT scans and histological staining revealed improved local osseointegration and angiogenesis after 4 weeks of implantation. In conclusion, the MAO-MMT-Mn coating offers a safe, simple, and cost-effective method to enhance the surfaces of Ti implants, thereby potentially enhancing the clinical outcomes of dental implant procedures.

Diffusion behavior assessment of underwater active venting for combustible gases: An experimental study with helium instead of hydrogen

In the active venting process of the burn pond, the hydrogen diffusion behavior underwater directly affects their uniformity on the water surface and the stability of the safety burning. A series of visualization experiments are conducted to assess the influence of disposal structure, flow rate, and water seal depth on the diffusion area and fountain height for rising plume formation. Helium is used as a substitute for hydrogen in the experiments. The study demonstrates that the plume structure is notably smaller in bubble cap mode compared to the nozzle mode, regardless of the conditions. This mode minimizes water surface fluctuation efficiently, making it ideal for constructing a disposal-array burn pond with multiple bubble cap units. Additionally, through dimensionless analysis, the study quantifies the parameters related to water surface stability with various venting conditions, thus establishing a foundation for the underwater active venting of hydrogen and other combustible gases.

Numerical simulations of wedge-induced oblique detonation waves in ammonia/hydrogen/air mixtures

In this study, two-dimensional numerical simulations of oblique detonation waves (ODWs) under a flight altitude of 10 km were performed. Because of their high importance in a zero-carbon economy, ammonia and hydrogen are considered as the fuel for aircrafts. Six cases with various hydrogen addition ratios in the fuel mixture were considered to explore the effects of hydrogen addition on the ignition structure, surface instability and NO emission of ODWs. It was found that as the hydrogen addition ratio decreases, the ODWs become more difficult to initiate with increased ignition length, and more complicated multi-wave system emerges with a second oblique detonation wave (SODW). The oblique wave angle is rarely influenced by hydrogen addition ratio. Two types of reaction surfaces, i.e. “saw-tooth” and “key-stone”, along with a series of transverse waves and vortices can be observed for the case with a hydrogen addition ratio of 20% by volume in the fuel mixture. The oscillation amplitude of the reaction zone length, which quantifies the surface instability, increases with decreasing hydrogen addition ratios. The mass fraction of NO is the highest in the case with a hydrogen addition ratio of 40%. NO concentration is higher in detonation compared to that in deflagration in all cases. The pathway analysis of NO indicates that the thermal NO is the primary contributor to NO production in the cases with high hydrogen addition ratios, while the HNO pathway becomes more significant in the cases with low hydrogen addition ratios.

Investigating the microscopic enhancement mechanisms of adsorption-based CO2 capture with Cu-loaded γ−Al2O3 using density functional theory

Transition-metal-loaded γ−alumina (Al2O3) is considered to be an effective adsorbent for CO2 capture, but its microscopic process and mechanisms of CO2 adsorption are not fully understood. To investigate the microscopic enhancement role of Cu atoms in CO2 adsorption, this work compares various adsorption configurations and parameters of CO2 on γ−Al2O3 (110) facets with or without Cu atoms and small Cu cluster loading (Cun (n=1,2,3)/γ−Al2O3) using the first-principles approach. According to the adsorption energy, charge transfer, difference charge density, and other parameters of different configurations, the γ−Al2O3 (110) slab loaded with the Cu atom is found to exhibit enhanced adsorption of CO2 molecules compared to that without Cu loading. Moreover, the surface stability increases with the number of loaded Cu atoms. However, the hydroxyl groups in the active sites partially undermine the adsorption effect during the CO2 adsorption process. The density of states indicates that the doping of Cu atoms in the system creates an orbital peak closer to the Fermi energy level. This facilitates the transfer of charge within the slab, making the activation of CO2 easier and promoting stable adsorption. Finally, the amount of crystal orbital overlap population and crystal orbital Hamilton population shows that the stability of adsorption is due to the formation of C-Cu and C-Al bonds. It is demonstrated that the Cun-loaded γ−Al2O3 (110) slab improves the adsorption performance and contributes to a better understanding of the effect of transition-state metal loaded γ−Al2O3 on CO2 adsorption.

Interfacial stability and electronic properties of YBCO/ABO3 heterostructures: A comparative DFT study

In this study, we utilized density functional theory (DFT) to analyze the interfacial properties of YBa2Cu3O7 (YBCO) with perovskite metal oxides LaAlO3 (LAO), KTaO3 (KTO), and SrTiO3 (STO). We focused on surface energies, lattice mismatches, strain energies, and adhesion energies to gauge the stability and compatibility of these interfaces. Our findings indicate that KTO exhibits the highest surface preference due to its lowest surface energy (0.054 eV/Å 2), suggesting superior surface stability. Moreover, LAO and STO show minor lattice mismatches with YBCO, implying effective interface integration, while YBCO/KTO interfaces experience significant strain due to extensive lattice mismatches. STO is distinguished by the lowest strain energy (0.07 eV), indicating minimal energy requirement for lattice mismatch accommodation, unlike KTO, which demonstrates high strain energy (0.42 eV) and potential structural distortions. The strongest interfacial bond, as indicated by an adhesion energy of −2.16 eV, was observed at YBCO/LAO, while the weakest was found at the YBCO/KTO interface, with an adhesion energy of −0.56 eV. Additionally, charge density difference (CDD) analysis highlighted electron density redistribution at the interfaces, predominantly around interfacial oxygen atoms, indicating a mix of ionic and covalent bonding. This study provides comparative insights into the interfacial characteristics of YBCO/ABO3 heterostructures, suggesting pathways for optimizing their design and performance.

Seed-Assisted Reversible Dissolution/Deposition of MnO2 for Long-Cyclic and Green Aqueous Zinc-Ion Batteries.

Manganese oxide (MnO2) based aqueous zinc-ion batteries (AZIBs) are considered to be a promising battery for grid-scale energy storage. However, they usually suffer from the great challenge of capacity attenuation due to Mn dissolution and irreversible structural transformation. Herein, full use of the shortcomings is made to design high-performance cathode-free AZIBs. Manganese-based Prussian blue analog (Mn-PBA) is selected as a seed layer to provide a stable MnO2 electrodeposition surface. Thanks to the large specific surface area and manganophilic nature of Mn-PBA, the deposition/dissolution kinetics between Mn2+ and MnO2 are significantly enhanced. Systematic studies revealed the mechanism of MnO2 deposition-dissolution related to the reversible transformation of manganese oxide hydroxide and zinc hydroxide sulfate hydrate. Based on this, the developed cathode-free AZIBs exhibit outstanding rate performance (with a specific capacity of 273.7 mAh g-1 at 1 A g-1) and extraordinary cycle stability (maintaining a specific capacity of 52.3 mAh g-1 after 50000 cycles at 20 A g-1). Furthermore, the AZIBs with non-toxic, biocompatible materials can be directly discarded after use, without causing pollution to the environment, which is expected to help achieve the sustainable development goals.

Extraction, characterization, and neuroprotective effects of polysaccharides the stems of Panax ginseng C. A. Meyer by three different solvents (water, acid, alkali)

The purpose of this study was to optimize the extraction process of polysaccharides from the stems of Panax ginseng C. A. Meyer using different solvents (water, acid and alkali), and investigate their protective effects on PC12 cells against Amyloid-β1–42 (Aβ1–42)-induced cell apoptosis. Three polysaccharides (W-GSP, Ac-GSP and Al-GSP) were prepared and optimized: liquid to material ratio 27:1 mL/g, extraction temperature 89°C, extraction time 2.9 h and 0.3 mol/L HCl/NaOH. The results of characterization indicated that the monosaccharides of W-GSP (703.80 kDa), Ac-GSP (641.38 kDa) and Al-GSP (457.04 kDa) all composed mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose and arabinose with different molar ratios. Interestingly, W-GSP possessed a lower uronic acid, higher molecular weight, rougher surface and poorer thermal stability, whereby W-GSP exhibited a protective effect against Aβ1–42-induced apoptosis in PC12 cells by mediating the JNK signaling pathway, restoring the mitochondrial membrane potential and reducing intracellular ROS levels. This study should be provided the theoretical basis for the study and exploitation of polysaccharides from the stems of Panax ginseng C. A. Meyer.

Self-draining microchannel surface structure for droplet condensation with controlled droplet radius distribution

Surface dewetting is technically important in industrial applications, particularly where phase change processes are involved. We present an intrinsically driven water-permeable microchannel surface system. It has two important advantages: its self-draining capability to remove surface droplets and its ability to limit both the maximum size of droplets condensing on the surface and the thickness of the water film in the microchannel system. This results in a reduction in the overall thermal resistance of the condensate on the cooled surface. We have successfully applied this surface drainage concept to water condensation. An improved condensation efficiency of 5%–9% has been achieved operating the device in an environmental chamber (60% relative humidity, 30 °C chamber temperature, 6 °C cooling temperature) without any optimization of the stable surface structure involved.

Mitigating degradation and modulating electronic structure via an epitaxial perovskite protection for Li-rich layered oxides

Li-rich layered oxides are highly promising cathode materials for the next-generation lithium-ion batteries due to their extraordinary specific capacity and hence high energy density. However, their practical application is hindered by the structural and surface instabilities as well as sluggish reaction kinetics. Herein, a low-crystallinity perovskite oxide (NdTiO3) is developed to epitaxially conform the surface of a typical Li-rich layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 to overcome these drawbacks. Experimental and computational results confirm that this surface phase not only mitigates structural deformation and interfacial side reactions, but also can modulate the electronic structure of Li2MnO3 for the higher electron conductivity. As a result, the epitaxially-protected cathode material displays much better cycle stability (222.02 mA h g−1 after 200 cycles at 1C compared to 185.06 mA h g−1 for the uncoated one) and excellent rate capability (155.71 mA h g−1 at 5C). A pouch-type full cell using commercial graphite anode demonstrates an energy density (381.38 Wh kg−1 based on the cathode and anode) and a capacity retention of 91.1% after 100 cycles.

Co-deposition of tannic acid and bottle-brush polymer to construct stable antifouling surface via hydrogen-bonding

The convenient preparation and excellent stability are two specific demands for antifouling surfaces. We designed a hydrogen-bonded network composed of tannic acid (TA) and bottle-brush polymer (BBP) to form an antifouling coating on diverse substrates. The BBP contained polyurethane backbone and polyethylene glycol (PEG) side chains which provided abundant hydrogen bond acceptors. Molecular dynamics (MD) simulation, 2D-IR and 1H NMR spectra confirmed that TA could interact with both the backbone and side chains of BBP. Owing to the strong affinity of TA to substrates and the hierarchical structure of bottle-brush polymer, TA/BBP coating possessed more intricate non-covalent network than TA/linear polymer coating and was more stable at physiologic pH. The excellent antifouling properties against serum albumin, red blood cells, fibroblasts and bacteria were demonstrated using different techniques. This work provided a strategy to prepare a stable antifouling coating relying solely on the hydrogen-bonded network of TA and BBP. Additionally, TA/BBP coating could be completely detached by strongly basic solution due to the dissociation of TA, which provided a possibility of cleaning and recycling substrates if necessary.