Enhanced Magnetic Heating for Efficient Oxygen Evolution Reaction by Pinning Effect of Ferromagnetic/Antiferromagnetic Coupling.

The magnetic heating effect under alternating magnetic fields (AMFs) has recently gained attention in catalysis due to its potential to greatly boost catalytic activities by providing localized heating around magnetic nanoparticles. However, nanoparticles still suffer from low magnetic heating efficiency due to their low magnetic anisotropy and thermal fluctuation, which is a key barrier in the wide application of AMF-assisted catalysis. Herein, by introducing the pinning effect of ferromagnetic/antiferromagnetic (FM/AFM) coupling, NiO/NiOOH (AFM/FM) core-shell nanoparticles exhibit significantly enhanced oxygen evolution reaction activity and resistance to thermal fluctuations under AMF, compared to NiOOH nanoparticles. Notably, magnetized NiO/NiOOH nanoparticles provide an overpotential of 186 mV at 10 mA cm-2, outperforming unmagnetized ones (218 mV) under the same conditions, further emphasizing the prominent role of the pinning effect in enhanced magnetic heating efficiency. This work provides valuable inspiration to design advanced magnetic catalysts and meet the challenge of the development of AMF-assisted catalysis.

Stabilized Multi-Electron Reactions in a High-Energy Na4 Mn0.9 CrMg0.1 (PO4 )3 Sodium-Storage Cathode Enabled by the Pinning Effect.

Na superionic conductor (NASICON)-type Na4 MnCr(PO4 )3 has attracted extensive attention among the phosphate sodium-storage cathodes due to its ultra-high energy density originating from three-electron reactions but it suffers from severe structural degradation upon repeated sodiation/desodiation processes. Herein, Mg is used for partial substitution of Mn in Na4 MnCr(PO4 )3 to alleviate Jahn-Teller distortions and to prolong the cathode cycling life by virtue of the pinning effect induced by implanting inert MgO6 octahedra into the NASICON framework. The as-prepared Na4 Mn0.9 CrMg0.1 (PO4 )3 /C cathode delivers high capacity retention of 92.7% after 500 cycles at 5 C and fascinating rate capability of 154.6 and 70.4 mAh g-1 at 0.1 and 15 C, respectively. Meanwhile, it can provide an admirable energy density of ≈558.48 Wh kg-1 based on ≈2.8-electron reactions of Mn2+ /Mn3+ , Mn3+ /Mn4+ , and Cr3+ /Cr4+ redox couples. In situ X-ray diffraction reveals the highly reversible single-phase and bi-phase structural evolution of such cathode materials with a volume change of only 6.3% during the whole electrochemical reaction. The galvanostatic intermittent titration technique and density functional theory computations jointly demonstrate the superior electrode process kinetics and enhanced electronic conductivity after Mg doping. This work offers a new route to improve the cycling stability of the high-energy NASICON-cathodes for sodium-ion batteries.

Viscoelastic Properties of Water-Absorbed Poly(methyl methacrylate) Doped with Lithium Salts with Various Anions.

We investigated the effects of water absorption on the dynamic mechanical properties of poly(methyl methacrylate) doped with various generic lithium salts, such as lithium perchlorate trihydrate (LiClO4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium nonafluorobutanesulfonate (LiC4F9SO3), and lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)). The rates of weight change during water absorption of lithium salt-doped samples were higher in the following order: LiClO4, LiCF3SO3, LiC4F9SO3, and LiN(CF3SO2). Interestingly, the aforementioned order was the same as the order of the terminal relaxation times in the flow region of the viscoelastic measurement in the melting-state. This implies that the water absorption of the salt-doped PMMA occurs due to the factors that affect the pinning of the PMMA molecular chains in the places.

Pinning Effect Enhanced Structural Stability toward a Zero-Strain Layered Cathode for Sodium-Ion Batteries.

Layered oxides as the cathode materials of sodium-ion batteries are receiving extensive attention due to their high capacity and flexible composition. However, the layered cathode tends to be thermodynamically and electrochemically unstable during (de)sodiation. Herein, we propose the pinning effect and controllable pinning point in sodium storage layered cathodes to enhance the structural stability and achieve optimal electrochemical performance. 0 %, 2.5 % and 7.3 % transition-metal occupancies in Na-site as pinning points are obtained in Na0.67 Mn0.5 Co0.5-x Fex O2 . 2.5 % Na-site pinned by Fe3+ is beneficial to restrain the potential slab sliding and enhance the structural stability, resulting in an ultra-low volume variation of 0.6 % and maintaining the smooth two-dimensional channel for Na-ion transfer. The Na0.67 Mn0.5 Co0.4 Fe0.1 O2 cathode with the optimal Fe3+ pinning delivers outstanding cycle performance of over 1000 cycles and superior rate capability up to 10 C.

SmCo5 with a Reconstructed Oxyhydroxide Surface for Spin-Selective Water Oxidation at Elevated Temperature.

The efficiency of electrolytic hydrogen production is limited by the slow reaction kinetics of oxygen evolution reaction (OER). Surface-reconstructed ferromagnetic (FM) catalysts with a spin-pinning effect at the FM/oxyhydroxide interface could enhance the spin-dependent OER kinetics. However, in real-life applications, electrolyzers are operated at elevated temperature, which may disrupt the spin orientations of FM catalysts and limit their performance. In this study, we prepared surface-reconstructed SmCo5 /CoOx Hy , which possesses polarized spins at the FM/oxyhydroxide interface that lead to excellent OER activity. These interfacial polarized spins could be further aligned through a magnetization process, which further enhanced the OER performance. Moreover, the operation temperature was elevated to mimic the practical operation conditions of water electrolyzers. It was found that the OER activity enhancement of the magnetized SmCo5 /CoOx Hy catalyst could be preserved up to 60 °C.

Two-Dimensional Materials Inserted at the Metal/Semiconductor Interface: Attractive Candidates for Semiconductor Device Contacts.

Metal-semiconductor junctions are indispensable in semiconductor devices, but they have recently become a major limiting factor precluding device performance improvement. Here, we report the modification of a metal/n-type Si Schottky contact barrier by the introduction of two-dimensional (2D) materials of either graphene or hexagonal boron nitride (h-BN) at the interface. We realized the lowest specific contact resistivities (ρc) of 3.30 nΩ cm2 (lightly doped n-type Si, ∼ 1015/cm3) and 1.47 nΩ cm2 (heavily doped n-type Si, ∼ 1021/cm3) via 2D material insertion are approaching the theoretical limit of 1.3 nΩ cm2. We demonstrated the role of the 2D materials at the interface in achieving a low ρc value by the following mechanisms: (a) 2D materials effectively form dipoles at the metal-2D material (M/2D) interface, thereby reducing the metal work function and changing the pinning point, and (b) the fully metalized M/2D system shifts the pinning point toward the Si conduction band, thus decreasing the Schottky barrier. As a result, the fully metalized M/2D system using atomically thin and well-defined 2D materials shows a significantly reduced ρc. The proposed 2D material insertion technique can be used to obtain extremely low contact resistivities in metal/n-type Si systems and will help to achieve major performance improvements in semiconductor technologies.

UV-Resistant and Thermally Stable Superhydrophobic CeO2 Nanotubes with High Water Adhesion.

A novel type of sticky superhydrophobic cerium dioxide (CeO2 ) nanotube material is prepared by hydrothermal treatment without any chemical modification. A water droplet on the material surface shows a static water contact angle of about 157° but the water droplet is pinned on the material surface even when the material surface is turned upside down. Interestingly, the as-prepared CeO2 nanotube material displays durable superhydrophobicity and enhanced adhesion to water under ultraviolet (UV) light irradiation. Importantly, this change in water adhesion can be reversed by heat treatment to restore the original adhesive value of 20 µL. Further, the maximum volume of the water droplet adhered on the material surface of CeO2 nanotubes can be regulated without loss of superhydrophobicity during the heating treatment/UV-irradiation cycling. Meanwhile, the superhydrophobic CeO2 nanotube material shows remarkable thermal stability even at temperatures as high as 450 °C, long-term durability in chemical environment, and air-storage and good resistance to oily contaminant. Finally, the potential application in no-loss water transportation of this sticky superhydrophobic CeO2 material is demonstrated.

Austenite grain growth simulation considering the solute-drag effect and pinning effect.

The pinning effect is useful for restraining austenite grain growth in low alloy steel and improving heat affected zone toughness in welded joints. We propose a new calculation model for predicting austenite grain growth behavior. The model is mainly comprised of two theories: the solute-drag effect and the pinning effect of TiN precipitates. The calculation of the solute-drag effect is based on the hypothesis that the width of each austenite grain boundary is constant and that the element content maintains equilibrium segregation at the austenite grain boundaries. We used Hillert's law under the assumption that the austenite grain boundary phase is a liquid so that we could estimate the equilibrium solute concentration at the austenite grain boundaries. The equilibrium solute concentration was calculated using the Thermo-Calc software. Pinning effect was estimated by Nishizawa's equation. The calculated austenite grain growth at 1473-1673 K showed excellent correspondence with the experimental results.

Improvement of Mechanical and Thermoelectric Properties of AgCuTe by Pinning Effect and Enhanced Liquid-Like Behavior via SiC Alloying.

With the development and application of thermoelectric (TE) devices, it requires not only high-performance of TE materials but also high mechanical properties. Here, we report a medium-temperature liquid material, AgCuTe, with high mechanical properties. The results demonstrate that AgCuTe possesses a multiphase structure characterized by abundant grain boundaries, resulting in reduced lattice thermal conductivity and inherently high mechanical strength. Furthermore, nano-SiC was alloyed into the AgCuTe material to further improve its mechanical and TE properties. Nano-SiC exhibited a button-like distribution within the grain boundaries, introducing a pinning effect that significantly elevated the Vickers hardness of the samples. Additionally, nano-SiC induced strong lattice distortion energy in the vicinity, which promotes Ag/Cu ions to escape from the lattice and enhances the liquid-like behavior of Ag/Cu ions. Finally, these enhancements led to a 21% improvement in the mechanical properties and a 40% improvement in the TE properties for AgCuTe. Notably, AgCuTe achieved its peak TE performance, with a latest peak ZT value of 1.32 at 723 K. This research expands the potential applications of AgCuTe.

Enhanced Thermal Stability of Carbonyl Iron Nanocrystalline Microwave Absorbents by Pinning Grain Boundaries with SiBaFe Alloy Nanoparticles.

Nanocrystalline carbonyl iron (CI) particles are promising microwave absorbents at elevated temperature, whereas their excessive grain boundary energy leads to the growth of nanograins and a deterioration in permeability. In this work, we report a strategy to enhance the thermal stability of the grains and microwave absorption of CI particles by doping a SiBaFe alloy. Grain growth was effectively inhibited by the pinning effect of SiBaFe alloy nanoparticles at the grain boundaries. After heat treatment at 600 °C, the grain size of CI particles increased from ~10 nm to 85.1 nm, while that of CI/SiBaFe particles was only 32.0 nm; with the temperature rising to 700 °C, the grain size of CI particles sharply increased to 158.1 nm, while that of CI/SiBaFe particles was only 40.8 nm. Excellent stability in saturation magnetization and microwave absorption was also achieved in CI/SiBaFe particles. After heat treatment at 600 °C, the flaky CI/SiBaFe particles exhibited reflection loss below -10 dB over 7.01~10.11 GHz and a minimum of -14.92 dB when the thickness of their paraffin-based composite was 1.5 mm. We provided a low-cost and efficient kinetic strategy to stabilize the grain size in nanoscale and microwave absorption for nanocrystalline magnetic absorbents working at elevated temperature.

High-Efficiency Thermal-Shock Resistance Enabled by Radiative Cooling and Latent Heat Storage.

Radiative cooling technology is well known for its subambient temperature cooling performance under sunlight radiation. However, the intrinsic maximum cooling power of radiative cooling limits the performance when the objects meet the thermal shock. Here, a dual-function strategy composed of radiative cooling and latent heat storage simultaneously enabling the efficient subambient cooling and high-efficiency thermal-shock resistance performance is proposed. The electrospinning and absorption-pressing methods are used to assemble the dual-function cooler. The high sunlight reflectivity and high mid-infrared emissivity of radiative film allow excellent subambient temperature of 5.1 °C. When subjected the thermal shock, the dual-function cooler demonstrates a pinning effect of huge temperature drop of 39 °C and stable low-temperature level by isothermal heat absorption compared with the traditional radiative cooler. The molten phase change materials provide the heat-time transfer effect by converting thermal-shock heat to the delayed preservation. This strategy paves a powerful way to protect the objects from thermal accumulation and high-temperature damage, expanding the applications of radiative cooling and latent heat storage technologies.

Enhancing Ablation Resistance of TaB2-Based Ultra-High Temperature Ceramics by Mixing Fine TaC Particles and Dispersed Multi-Walled Carbon Nanotubes.

Ultra-high temperature ceramics (UHTCs) have been widely applied in many fields. In order to enhance the comprehensive properties of TaB2-based UHTCs, the first collaborative use of fine TaC particles and dispersed multi-walled carbon nanotubes (MWCNTs) was employed via spark plasma sintering (SPS) at 1700 °C. The derived UHTCs exhibited an average grain size of 1.3 µm, a relative density of 98.6%, an elastic modulus of 386.3 GPa, and a nano hardness of 21.7 GPa, leading to a greatly improved oxidation resistance with a lower linear ablation rate at -3.3 × 10-2 µm/s, and a markedly reinforced ablation resistance with mass ablation rate of -1.3 × 10-3 mg/(s·cm2). The enhanced ablation resistance was attributable to the physical pinning effect, sealing effect and self-healing effect. Thus, this study provides a potential strategy for preparation of UHTCs with bettered ablation resistance and physical properties.

Precursor-film-driven ultra-early depinning of the three-phase contact line.

HYPOTHESIS: Despite its importance in colloid and interface science, contact line pinning remains poorly understood, especially in the presence of a precursor film. We hypothesized that this is due to a lack of an experimental method capable of directly observing their physics at the nanoscale. METHODS: Using coherence scanning interferometry, we visualized the three-dimensional behavior of contact lines with a precursor film near a nanogroove structure composed of flat terrace surfaces and steps with an inclination angle of 30° while achieving nanoscale vertical resolution. FINDINGS: We found that even when the contact line is pinned at the edge of the step, the precursor film is not and advances beyond the edge. Furthermore, we discovered that the precursor film has two distinct effects on contact line motion. Specifically, the precursor film facilitates depinning when the contact line descends the step - a contact angle change was 0.9°, only 3.0% of the value predicted by a classical theory of contact angle at a solid edge. This ultra-early depinning is attributed to the formation of a new liquid film past the edge, driven by the progression of the precursor film that overcomes the pinning effect. In contrast, when the contact line ascends the step, the precursor film acts as a resistance to movement due to steric interaction.

Dramatically Enhanced Mechanical Properties of Nano-TiN-Dispersed n-Type Bismuth Telluride by Multi-Effect Modulation.

Bismuth telluride (Bi2Te3)-based alloys have been extensively employed in energy harvesting and refrigeration applications for decades. However, commercially produced Bi2Te3-based alloys using the zone-melting (ZM) technique often encounter challenges such as insufficient mechanical properties and susceptibility to cracking, particularly in n-type Bi2Te3-based alloys, which severely limit the application scenarios for bismuth telluride devices. In this work, we seek to enhance the mechanical properties of n-type Bi2Te2.7Se0.3 alloys while preserving their thermoelectrical performance by a mixed mechanism of grain refinement and the TiN composite phase-introduced pinning effect. These nanoscale processes, coupled with the addition of TiN, result in a reduction in grain size. The pinning effects of nano-TiN contribute to increased resistance to crack propagation. Finally, the TiN-dispersed Bi2Te2.7Se0.3 samples demonstrate increased hardness, bending strength and compressive strength, reaching 0.98 GPa, 36.3 MPa and 74 MPa. When compared to the ZM ingots, those represent increments of 181%, 60% and 67%, respectively. Moreover, the thermoelectric performance of the TiN-dispersed Bi2Te2.7Se0.3 samples is identical to the ZM ingots. The samples exhibit a peak dimensionless figure of merit (ZT) value of 0.957 at 375 K, with an average ZT value of 0.89 within the 325-450 K temperature range. This work has significantly enhanced mechanical properties, increasing the adaptability and reliability of bismuth telluride devices for various applications, and the multi-effect modulation of mechanical properties demonstrated in this study can be applied to other thermoelectric material systems.

Electronic States Tailoring and Pinning Effect Boost High-Power Sodium-Ion Storage of Oriented Hollow P2-Type Cathode Materials.

Fierce phase transformation and limited sodium ion diffusion dynamics are critical obstacles that hinder the practical energy storage applications of P2-type layered sodium transition metal oxides (NaxTMO2). Herein, a synergistic strategy of electronic state tailoring and pillar effect was carefully implemented by substituting divalent Mg2+ into Na0.67Ni0.33Mn0.67O2 material with unique oriented hollow rodlike structures. Mg2+substitution can not only facilitate the anionic oxygen redox reactions and electronic conductivity through increasing the electronic states at Femi energy but also act as pillars within TMO2 layers to alleviate the severe phase transformation to improve structure stability. Moreover, the oriented hollow structure incorporating sufficient buffer spaces and rationally exposed electrochemically active facets effectively alleviates the stresses induced by low volume changes of 8% and provides more open channels for Na+ ion diffusion without crossing multiple grain boundaries. Hence, the Na0.67Mg0.08Ni0.25Mn0.67O2 cathode showed a superior rate capability with high energy density and cycling stability for sodium-ion storage. The underlying mechanisms of these achievements were deciphered through diversified dynamic analysis and the first principle calculations, providing new insights into P2-type NaxTMO2 cathodes for the infinite prospect as an alternative to lithium-ion batteries.

A Bionic Interface to Suppress the Coffee-Ring Effect for Reliable and Flexible Perovskite Modules with a Near-90% Yield Rate.

The inhomogeneity, poor interfacial contact, and pinholes caused by the coffee-ring effect severely affect the printing reliability of flexible perovskite solar cells (PSCs). Herein, inspired by the bio-glue of barnacles, a bionic interface layer (Bio-IL) of NiOx /levodopa is introduced to suppress the coffee-ring effect during printing perovskite modules. The coordination effect of the sticky functional groups in Bio-IL can pin the three-phase contact line and restrain the transport of perovskite colloidal particles during the printing and evaporation process. Moreover, the sedimentation rate of perovskite precursor is accelerated due to the electrostatic attraction and rapid volatilization from an extraordinary wettability. The superhydrophilic Bio-IL affords an even spread over a large-area substrate, which boosts a complete and uniform liquid film for heterogeneous nucleation as well as crystallization. Perovskite films on different large-area substrates with negligible coffee-ring effect are printed. Consequently, inverted flexible PSCs and perovskite solar modules achieve a high efficiency of 21.08% and 16.87%, respectively. This strategy ensures a highly reliable reproducibility of printing PSCs with a near 90% yield rate.

A Novel Way to Fill Green Gap of GaN-Based LEDs by Pinning Defects in Nanorod Array.

Nanorod array and planar green-emission InGaN/GaN multi-quantum well (MQW) LEDs were fabricated by lithography, nano-imprinting, and top-down etching technology. The defect-pinning effect of the nanostructure was found for the first time. The ratio of the bright regions to the global area in the panchromatic CL images of green MQW samples increased from 30% to about 90% after nano-fabrication. The overall luminous performance significantly improved. Throughout temperature-dependent photoluminescence (TDPL) and time-resolved PL (TRPL) measurements, the migration and recombination of carriers in the MQWs of green LEDs were analyzed. It was proved that nanostructures can effectively prevent carriers from being captured by surrounding nonradiative recombination centers. The overall PL integral intensity can be enhanced to above 18 times. A much lower carrier lifetime (decreasing from 91.4 to 40.2 ns) and a higher internal quantum efficiency (IQE) (increasing from 16.9% to 40.7%) were achieved. Some disputes on the defect influence were also discussed and clarified.

Modulating Co-catalyst/Facet Junction for Enhanced Photoelectrochemical Water Splitting.

Rational construction of electric field via assembling appropriate co-catalysts on anisotropic facets is of great significance for improving the photogenerated charge separation efficiency. However, this strategy usually gives rise to Fermi-level pinning which is not contributive to the charge separation but deleterious to the photoelectrochemical performance through consuming the measurable photovoltage. Herein, we demonstrate that manganese dioxide electrodeposited on the (111) facet of titanium dioxide nanorods could tremendously boost the catalytic activity of pristine photoanode via a stronger interface electric field and less photovoltage decay compared with the counterpart grown on the (110) facet. A photocurrent density of 1.65 mA·cm-2 at 1.23 V (vs reversible hydrogen electrode), nearly the theoretical maximum of titanium dioxide, is achieved by the optimum photoanode with an extremely high separation efficiency of 95.15%. This study offers more in-depth insights into the design of carrier separation strategy through loading co-catalysts on different substrate surfaces for more efficient solar energy conversion.

A P3-Type K1/2Mn5/6Mg1/12Ni1/12O2 Cathode Material for Potassium-Ion Batteries with High Structural Reversibility Secured by the Mg-Ni Pinning Effect.

Mn-based layered oxides are very attractive as cathodes for potassium-ion batteries (PIBs) due to their low-cost and environmentally friendly precursors. Their transfer to practical application, however, is inhibited by some issues including consecutive phase transitions, sluggish K+ deintercalation/intercalation, and serious capacity loss. Herein, Mg-Ni co-substituted K1/2Mn5/6Mg1/12Ni1/12O2 is designed as a promising cathode material for PIBs, with suppressed phase transitions that occurred in K1/2MnO2 and improved K+ storage performance. Part of Mg2+ and Ni2+ occupies the K+ layer, playing the role of a "nailed pillar", which restrains metal oxide layer gliding during the K+ (de)intercalation. The "Mg-Ni pinning effect" not only suppresses the phase transitions but also reduces the cell volume variation, leading to the improved cycle performance. Moreover, K1/2Mn5/6Mg1/12Ni1/12O2 has low activation barrier energy for K+ diffusion and high electron conductivity as demonstrated by first-principles calculations, resulting in better rate capability. In addition, K1/2Mn5/6Mg1/12Ni1/12O2 also delivers a higher reversible capacity owing to the participation of the Ni element in electrochemical reactions and the pseudocapacitive contribution. This study provides a basic understanding of structural evolution in layered Mn-based oxides and broadens the strategic design of cathode materials for PIBs.

Microstructural Evolution of Cold-Rolled AA7075 Sheet during Solution Treatment.

The influence of heating rate on the microstructural evolution of a cold-rolled AA7075 alloy sheet during solution heat treatment was examined using electrical conductivity, scanning electron microscopy, X-ray diffraction, transmission electron microscopy and electron backscatter diffraction. The results indicate that the dissolution of soluble phases takes place during the heating process. The heating rates affect the dissolution process of soluble phases, and these phases completely dissolve into matrix after solution treatment. Recrystallized and elongated grains are produced after solution treatment by both fast and slow heating rates, while the grains of the rapidly heated sample are much finer. The elongated grains are attributed to the difference in the pinning pressure of boundary migration between the rolling and normal directions. The {111}<110> texture, as well as typical recrystallization textures, were found in both fast and slowly heated samples after solution treatment, but the textures, especially the {111}<110> component in the slow-heated sample, are much stronger, leading to an anisotropy in the tensile properties after artificial aging.