Interfacial Region Research Articles

Molecular Investigation of SNAC as an Oral Peptide Permeation Enhancer in Lipid Membranes via Solid-State NMR.

Oral peptide therapeutics are increasingly favored in the pharmaceutical industry for their ease of use and better patient adherence. However, they face challenges with poor oral bioavailability due to their high molecular weight and surface polarity. Permeation enhancers (PEs) like salcaprozate sodium (SNAC) have shown promise in clinical trials, achieving about 1% bioavailability. One proposed mechanism for enhancing permeation is membrane perturbation or fluidization, though direct experimental proof and quantitative analysis of these effects are still needed. This study employs solid-state NMR (ssNMR) to investigate how SNAC interacts with hydrated DMPC liposomes, measuring enhancements in membrane fluidity across interfacial and transmembrane regions. The methodology involves analyzing phosphate lipid headgroups and acyl chains using static 31P chemical shift anisotropy and 2H quadrupolar coupling measurements alongside 1H and 13C magic angle spinning NMR for motional averaging of 1H-1H and 1H-13C dipolar couplings. Our findings indicate an overall increase in the uniaxial motion of phospholipids with SNAC in a PE concentration-dependent manner. It boosts lipid headgroup dynamics and enhancement plateaus at 25% between 24 and 72 mM concentrations. SNAC effectively enhances the fluidity of the hydrophobic center by 43% at 72 mM PE concentration, more significantly than the interfacial region. It is worth noting that the extent of liposome dissolution and conversion to micelles increases as SNAC concentration rises. Including a model peptide drug, octreotide, introduces a competitive equilibrium in this complex PE-lipid-peptide system, further influencing membrane dynamics for peptide permeation. Interestingly, the membrane enhancement does not show the expected plateau, and a less significant lipid mobility increase is observed in the presence of octreotide, suggesting a less substantial impact compared to peptide-free systems, which is likely due to peptide-PE interactions that consume monomeric SNAC, reducing its interaction with the lipid membrane. This study provides the first quantitative and site-specific ssNMR measurements of membrane mobility influenced by one representative PE as a snapshot of PE lipid interaction in a liposome model, demonstrating how peptide drugs modulate competitive equilibria and PE-induced lipid dynamics.

An Effective Precursor‐Solutioned Strategy for Developing Cu2ZnSn(S, Se)4 Thin Film Toward High Efficiency Solar Cell

AbstractEnhancing the efficiency of Cu2ZnSn (S, Se)4 (CZTSSe) thin‐film solar cells requires the development of well‐crystallized light‐absorbing layers. A deep understanding of the role of precursor solution chemistry in film nucleation and crystal growth processes is essential. Insights into these processes enable the development of innovative strategies to enhance absorber quality, minimize detrimental bulk defects, and ultimately improve device performance. This study elucidates the condensation reactions between thiourea and metal cations, as well as the alcoholysis of 2‐methoxyethanol (MOE), at different concentrations of precursor solutions. The primary focus of this study is implementing a simple and environmentally friendly innovative spin‐coating strategy, aimed at optimizing Cu2ZnSnS4 (CZTS) precursor films and adjusting the Se content within the film bulk to promote grain growth during selenization. This strategy effectively improves absorber morphology while suppressing the formation of deep‐level defects, thereby enhancing carrier transport in both interfacial and bulk regions of the absorber layer. Consequently, CZTSSe absorbers with enhanced crystallinity and reduced defects are synthesized, resulting in a solar cell with an impressive efficiency of 14.10%. These findings underscore the potential for creating highly efficient kesterite CZTSSe solar cells through the manipulation of precursor solution chemistry using environmentally friendly solvents.

Effects of Ca2+ on the Structure and Dynamics of PIP3 in Model Membranes Containing PC and PS.

Phosphatidylinositol phosphates (PIPs) are a family of seven different eukaryotic membrane lipids that have a large role in cell viability, despite their minor concentration in eukaryotic cellular membranes. PIPs tightly regulate cellular processes, such as cellular growth, metabolism, immunity, and development through direct interactions with partner proteins. Understanding the biophysical properties of PIPs in the complex membrane environment is important to understand how PIPs selectively regulate a partner protein. Here, we investigate the structure and dynamics of PIP3 in lipid bilayers that are simplified models of the natural membrane environment. We probe the effects of the anionic lipid phosphatidylserine (PS) and the divalent cation Ca2+ by using full-length lipids in well-formed bilayers. We used solution and solid-state NMR on naturally abundant 1H, 31P, and 13C atoms combined with molecular dynamics (MD) simulations to characterize the structure and dynamics of PIPs. 1H and 31P 1D spectra show good resolution at temperatures above the phase transition with isolated peaks in the headgroup, interfacial, and bilayer regions. Site-specific assignment of the chemical shifts of these reporters enables the measurement of the effects of Ca2+ and PS at the single atom level. In particular, the resolved 31P signals of the PIP3 headgroup allow for extremely well-localized information about PIP3 phosphate dynamics, which the MD simulations can further explain. A quantitative assessment of cross-polarization kinetics provides additional dynamics measurements for the PIP3 headgroups.

Charge characteristics of co-electrospun nanofiber membranes and their application in high-humidity environment

Enhancing the charge density and charge stability is an important approach to improve the filtration performance of electrospun nanofiber air filters. In the present study, the polymers with different electron transport capabilities were co-electrospun in pairs to prepare charge-enhanced nanofiber membranes. The results showed that the average surface potential of the interfacial regions of polyamide 6 (PA6) and polyvinyl chloride (PVC) nanofibers was 165 mV, which was substantially higher than the non-intersection area of nanofibers. The charges induced by the contact-induced electrification between nanofibers accumulated in the intersection area of the hybrid nanofibers, which contributed to the high surface potential of the nanofiber membranes. Moreover, the co-electrospinning of polymers allowed the positively charged PA 6 nanofibers and negatively charged PVC nanofibers to coexist in the nanofiber membranes. Benefiting from these charge characteristics, the co-electrospun PA 6/PVC nanofiber membranes exhibited an average filtration efficiency of 99.73 % for 50–500 nm particles at the face velocity of 5.3 cm/s, and the pressure drop was 130 Pa. A hydrophilic fiber layer was employed to mitigate the influence of humidity on the charge decay and pressure drop growth of thenanofiber membrane. The growth rate of pressure drop of the protected nanofiber membrane was as low as 0.95 Pa/min under the challenge of water droplets. In contrast, the growth rate of pressure drop for common membrane based filters was in the range of 5–120 Pa/min. Additionally, the color of the hydrophilic layer changed corresponding to the water content in the air filters, which could serve as an indicator for the filter service life visible to naked eyes. This study provides a new approach for charging nanofiber membranes and improving their filtration performance stability in practical applications.

Tailoring the interfacial properties of glass fiber-epoxy microcomposites through the development of a self-healing poly(ϵ-caprolactone) coating

The aim of this study was the development and characterization of a continuous poly(ε-caprolactone) (PCL) coating, which was applied on glass fibers by a fluid coating method, in order to tailor the interfacial properties in glass fiber-epoxy microcomposites. Scanning electron microscopy revealed that a uniform coating was formed without noticeable discontinuities or irregularities, and its thickness increased with the deposition speed. To achieve consistent results with this approach, it is essential to consider the homogeneity of the coating thickness, which is influenced by the viscosity of the solution. The PCL-coated fibers were used for the preparation of microcomposites combined with epoxy resin (EP). The samples were tested in the microdebonding configuration to determine the interfacial shear strength (IFSS) and to assess their interfacial self-healing capability. For all deposition speeds, no significant degradation of interfacial adhesion was observed indicating the applicability of PCL coating on glass fibers. However, a decrease in self-healing efficiency was observed after multiple self-healing stages. The possible cause was identified in the progressive alteration of the EP droplet's shape after repeated microdebonding tests. This phenomenon altered the stress distribution along the fiber-matrix contact area and, therefore, underestimated the values of interfacial adhesion and self-healing efficiency. Hence, the experimental results from microdebonding tests were presented along with a finite element analysis of the interfacial region, in order to provide a comprehensive understanding of the debonding and self-healing mechanisms after multiple repairing steps.

Evolution of residual stress of SiCf/Ti17 composites at high temperature evaluated by micro-Raman spectroscopy

SiCf/Ti17 composites are considered promising lightweight high-temperature structural materials for the aerospace field due to their excellent mechanical properties. However, during the manufacturing process, differences in the coefficients of thermal expansion between various material components inevitably generate thermal residual stresses at the interfaces. These thermal residual stresses can lead to stress concentration and other failure modes, thereby affecting the mechanical properties of SiCf/Ti17 composites. Therefore, it is crucial to systematically study the residual stresses in the interfacial C coating and the W/SiC interfacial regions, as well as the evolution of these stresses at high temperatures. In this study, samples were first subjected to vacuum heat treatment, followed by systematic micro-Raman experiments conducted radially on the fibers. Subsequently, the Raman spectra were subjected to peak deconvolution to obtain precise target peaks. By combining Raman peak shifts with Hooke's law, the evolution of high temperature residual stresses in the C coating and W/SiC interfacial regions were determined. Additionally, changes in the Raman spectral data at different temperatures were analyzed to investigate the variations in the micro-composition of different regions. The results showed that at 850°C, both the C coating and the W/SiC interfacial region exhibited good mechanical properties and strength retention. However, at 1050°C, the mechanical properties of both regions gradually deteriorated, with the W/SiC interfacial region showing a sharp increase in compressive stress. At this point, the SiCf/Ti17 composite material may face a risk of failure.

Influence of the warped scale on the internal oxidation of hot-rolled Si-Mn high-strength steels

As a lightweight material with excellent performance, high-strength steel is of great importance in achieving lightweight, safety, and energy efficiency in automobile body construction. However, the occurrence of internal oxidation following hot-rolled coils can adversely affect the surface quality of the product. In this investigation, our focus centered on exploring the influence of warped scale on internal oxidation in hot-rolled coils (IOHC). The findings suggest that the decomposition of the warped scale seriously affects the IOHC behavior. Pure Fe particles appear preferentially at the location of the warped scale front, and the depth of internal oxidation is much greater than that at the location of the normal oxide scale. In addition, it is found that IOHC is controlled by the ambient oxygen partial pressure, and the rate of the phase transition of the oxide scale increased dramatically as the ambient oxygen partial pressure decreased. Additionally, the interface region between the warped scale and the substrate is meticulously characterized through the utilization of FIB/TEM techniques, enabling a comprehensive understanding of the structure and composition of the oxide at the interface.

Effect of post-weld heat treatment on microstructure and mechanical properties of induction roll welded joint for A283GRC steel and 5052 aluminum alloy

Steel-aluminum transition joints are commonly produced through explosive welding and friction welding techniques, serving to link aluminum pressure vessels with steel pipes within cold boxes in air separation unit. This study investigates the impact of PWHT on the microstructure and mechanical properties of steel-aluminum transition joints created via IRW, utilizing A283GRC steel and 5052 aluminum alloy as substrates. The findings suggest that the types of intermetallic compounds (IMCs) in IRW joints remain unchanged before and after heat treatment. The thickness of interfacial IMCs increases with higher annealing temperature and longer annealing time, with a faster growth rate at higher annealing temperatures. After PWHT, the grain size near the interface of the joint on the steel side decreased, with the most significant decrease observed when annealed at 300 °C for 2 hours. While cracks in the interface zone gradually diminish or disappear with PWHT, excessive heat treatment temperature or duration may result in new transverse cracks. At an annealing temperature of 200 °C, there is limited growth range for IMCs and noticeable repair effect on cracks within the interface region. When annealed at 300 °C and 400 °C, there is a decrease in joint hardness compared to before heat treatment levels, and this decreasing rate accelerates with higher annealing temperature and longer duration. Following annealing at 300 °C for 2 hours, the shear strength of the sample reached 70.52 MPa, which is 32% higher than that before heat treatment. Overall findings suggest that the annealing temperature exerts a more pronounced impact on the mechanical properties of joints in comparison to the annealing duration across the investigated time and temperature ranges. The fracture mode exhibited by the samples before and after heat treatment in IRW is characterized by a mixed fracture mode. However, the predominant fracture mode observed without heat treatment is brittle fracture, whereas after heat treatment, ductile fracture becomes the primary mode of fracture.

Study on hydrothermal migration and interface cracking mechanisms of supporting reinforcing bodies in the root erosion zones of rammed earth sites in arid regions

The characteristics of hydrothermal migration and strain variations manifest differently in soils with contrasting properties. The primary objective of this study is to investigate the patterns of hydrothermal transfer and strain changes between the root erosion zone of rammed earth sites and the supporting reinforcing body during the process of desiccation, which leads to the differentiation and cracking of the interface between the reinforcing body and the site itself. This paper presents experimental monitoring conducted on-site regarding temperature, moisture content, strain, and the development of interface cracks in the supporting reinforcing body (including rammed earth repair body, cushion layers, and the site itself) during the drying process. The results indicate that the variations in temperature field, moisture field, and shrinkage strain field during the desiccation of the reinforcing body are distinct, with changes in moisture content predominantly influencing the shrinkage strain of the reinforced soil. Notably, the shrinkage of the reinforcing soil exhibits significant location and directional variability. The suction pressure of the site is a critical factor that leads to the rapid loss of moisture at the interface, as well as changes in the moisture distribution of the reinforcing body; the differential shrinkage between the site material and the reinforcing soil in the interface region is the fundamental reason for the development and propagation of interface cracks.

A New TiO2‐Based Cathode Material with Interface‐Dominated Storage Mechanism for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc‐ion batteries (AZIBs) are highly desirable for large‐scale energy storage applications, yet the lack of suitable cathode materials hinders their deployment. Here, for the first time, a new and promising TiO2‐based cathode material (TOC‐AI) is reported for AZIBs and unveil a novel energy storage mechanism that enables Zn2+ storage predominantly originating from the interface. The TOC‐AI composed of ultrafine TiO2 nanocrystals embedded within an amorphous carbon matrix, featuring abundant atomic interfaces and strong interactions, triggers a decoupled and rapid transport of Zn2+ ions and electrons in the interfacial space charge region, similar to an electrostatic capacitor. Moreover, the presence of titanium vacancies facilitates Zn2+ intercalation into the TiO2 bulks, contributing extra capacity to the composite. Finally, a high capacity of 111 mAh g−1 and excellent cycling performance with 77% capacity retention after 17 000 cycles are achieved. Such interface‐dominated storage mechanism has also been successfully extended to other composite systems, broadening the scope of potential applications for materials traditionally deemed inactive for Zn2+ storage.

Ruthenium Nanoparticles Supported on Bentonite: Enhanced Crystallinity, Conductivity, and Dielectric Performance for Advanced Applications

We used the wet impregnation method to synthesize Ru nanoparticles supported on bentonite (Ru/Bento). The X-ray diffraction and Energy-Dispersive (EDX) Spectrometer characterisations of the synthesized structures revealed that the montmorillonite is the predominant phase. The reduced crystallite size and lower diffraction peak intensities for Ru/Bento indicate improvement in crystallinity. EDX confirmed the successful incorporation of Ru, suggesting fewer reactive hydroxyl groups on the bentonite surface. Dielectric studies show a decrease in permittivity with increasing frequency, consistent with the Maxwell-Wagner polarization mechanism. Ru/Bento exhibits higher permittivity at elevated temperatures due to enhanced interfacial polarization, and higher low-frequency dielectric loss attributed to resistive interfacial regions. Electric modulus analysis indicates significant relaxation processes in Ru/Bento at higher temperatures. Conductivity studies demonstrate increased charge carrier mobility with frequency and temperature, following a correlated barrier hopping mechanism, with Ru nanoparticles enhancing conductivity by reducing barrier height. HOMO and LUMO analysis suggest improved conductivity and reactivity for Ru/Bento due to lower energy gaps and chemical hardness. Molecular dynamics calculations confirm the geometric stability of Ru nanoparticles on bentonite, making Ru/Bento bentonite a promising material for high conductivity applications.

Multi-scale characterization of lightweight aggregate and superabsorbent polymers influence on autogenous shrinkage and microstructure of ultra-high performance concrete

This study investigates the effects of internal curing agents on the autogenous shrinkage, hydration, and microstructure of ultra-high-performance concrete (UHPC). Lightweight aggregate (LWA) and superabsorbent polymers (SAP) were examined across various dosages as representative internal curing agents. Measurements were taken for the mechanical properties, autogenous shrinkage, and internal relative humidity of the UHPC. The mechanisms of internal curing were analyzed using thermogravimetry, pore structure, and microstructural evaluations. Additionally, porosity and microhardness in the matrix around the fibers and internal curing agents were tested to quantitatively assess their impact on the properties of the UHPC matrix. Results indicate that high dosages of LWA or SAP negatively affect the compressive strength of UHPC. A dosage of 15 % LWA increased flexural strength by 11 %, whereas SAP showed no significant improvement in flexural strength. LWA effectively reduced autogenous shrinkage by 49.4 %-88.8 %, while a SAP dosage of 0.3 % reduced autogenous shrinkage by 82 %. Both LWA and SAP increased porosity by 33.9 %-55.9 %. SAP released water within the matrix, forming voids filled with calcium hydroxide. The interface between LWA and the matrix was dense, with porosity near the LWA and SAP interfaces being 23.5 %-53.9 % and 26.0 %-38.2 % lower, respectively, compared to other areas. The microhardness in the LWA and SAP interface regions was 20 % and 16.2 % higher than in different places. The LWA pre-saturated method can effectively reduce autogenous shrinkage, and 15 % LWA has no adverse effect on mechanical strength.

Effect of heat treatment on the microstructure of additive manufactured Ni-based hardfacing alloy deposits on stainless steel

Ni based (NiCrFeSiBC) hardfacing alloy was deposited on 304 L SS build plate by laser rapid manufacturing (LRM) process. As-deposited specimen showed nearly a precipitate free zone at the interface, grain boundary (GB) precipitation in stainless steel up to 10 µm, thin dilution layer (∼60 µm) followed by formation of zones with distinct microstructure, microhardness and microchemistry in the deposit. To investigate the effect of thermal exposure on the interface microstructure, deposits were heat treated in the temperature range of 823-1123 K for 5-100 h. Up to 923 K, structure of the LRM deposits resembled that of as-deposited specimen. A planar interface region devoid of precipitates was present even after thermal exposure up to 923 K. With further increase in the temperature, formation of CrB precipitates with globular morphology was observed along the deposit/build plate interface with simultaneous increase in hardness. Thermal exposures beyond 923 K promoted coarsening of M7C3 and Cr2B precipitates. Diffusion of carbon and boron from the deposit to the build plate promoted the grain boundary precipitation of chromium carbides up to a maximum distance of ∼1000 µm for the highest temperature of 1123 K.

Radiomics based on brain-to-tumor interface enables prediction of metastatic tumor type of brain metastasis: a proof-of-concept study.

Early and accurate identification of the metastatic tumor types of brain metastasis (BM) is essential for appropriate treatment and management. A total of 450 patients were enrolled from two centers as a primary cohort who carry 764 BMs originated from non-small cell lung cancer (NSCLC, patient = 173, lesion = 187), small cell lung cancer (SCLC, patient = 84, lesion = 196), breast cancer (BC, patient = 119, lesion = 200), and gastrointestinal cancer (GIC, patient = 74, lesion = 181). A third center enrolled 28 patients who carry 67 BMs (NSCLC = 24, SCLC = 22, BC = 10, and GIC = 11) to form an external test cohort. All patients received contrast-enhanced T1-weighted (T1CE) and T2-weighted (T2W) MRI scans at 3.0T before treatment. Radiomics features were calculated from BM and brain-to-tumor interface (BTI) region in the MRI image and screened using least absolute shrinkage and selection operator (LASSO) to construct the radiomics signature (RS). Volume of peritumor edema (VPE) was calculated and combined with RS to create a joint model. Performance of the models was assessed by receiver operating characteristic (ROC). The BTI-based RS showed better performance compared to BM-based RS. The combined models integrating BTI features and VPE can improve identification performance in AUCs in the training (LC/NLC vs. SCLC/NSCLC vs. BC/GIC, 0.803 vs. 0.949 vs. 0.918), internal validation (LC/NLC vs. SCLC/NSCLC vs. BC/GIC, 0.717 vs. 0.854 vs. 0.840), and external test (LC/NLC vs. SCLC/NSCLC vs. BC/GIC, 0.744 vs. 0.839 vs. 0.800) cohorts. This study indicated that BTI-based radiomics features and VPE are associated with the metastatic tumor types of BM.

An In-depth Analysis of Quiet-Sun IRIS Brightenings

Small-scale brightenings are ubiquitous, dynamic, and energetic phenomena found in the chromosphere. An advanced filter-detection algorithm applied to high-resolution observations from the Interface Region Imaging Spectrograph enables the detection of these brightenings close to the noise level. This algorithm also tracks the movement of these brightenings and extracts their characteristics. This work outlines the results of an in-depth analysis of a quiet-Sun data set including a comparison of a brighter domain—associated with a supergranular boundary—to the quiescent internetwork domains. Several characteristics of brightenings from both domains are extracted and analysed, providing a range of sizes, durations, brightness values, travel distances, and speeds. The “active” quiet-Sun events tend to travel shorter distances and at slower speeds across the plane of the sky than their “true” quiet-Sun counterparts. These results are consistent with the magnetic field model of supergranular photospheric structures and the magnetic canopy model of the chromosphere above. Spectroscopic analyses reveal that bright points demonstrate blueshift (as well as some bidirectionality) and that they may rise from the chromosphere into the transition region. We believe that these bright points are magnetic in nature, are likely the result of magnetic reconnection, and follow current sheets between magnetic field gradients, rather than travel along magnetic field lines themselves.

Variation in the intensity ratio at each wavelength point of the Si IV 1394/1403 A lines. Spectral diagnostics of a bifurcated eruption

This study aims to investigate the deviation of the intensity ratio of the Si IV and 1403 emission lines from the expected value of 2 in the optically thin regime, as has been observed in many recent studies. We analyzed the integrated intensity ratio ($R$) and the wavelength-dependent ratio ($r( in a small bifurcated eruption event observed by the Interface Region Imaging Spectrograph (IRIS). Despite the relatively complex line profiles the intensity ratio, $R$, of Si IV lines mostly remains greater than 2 in the loops. The ratio $r( varies in the line core and wings, changing distinctly from 2.0 to 3.3 along the wavelength. At certain positions, the Si IV and 1403 lines exhibit different Doppler velocities. When diagnosing the spectra of small active region events, not only the impact of opacity but also the influence of resonance scattering should be considered. We propose that the ratio $r( can serve as an indicator of the resonance scattering and opacity effect of the Si IV line.

Influence of cooling rate on microstructure, dislocation density, and associated hardness of laser direct energy deposited Inconel 718

This work deals with the effect of cooling rate on microstructure, dislocation density, and microhardness of laser direct energy deposited Inconel 718. Thermocycles were captured during direct energy deposition process using an infrared pyrometer. Cooling rate was estimated from the thermocycles at various laser powers and scanning speeds. In addition, a numerical model was developed to calculate cooling rate at different laser process parameters, and the same was verified with the experimental results. Microstructure and phases of the direct energy deposited Inconel 718 were observed using a scanning electron microscope and X-ray diffractometer, respectively. Top layer of the cladding was found to consist of fine equiaxed grains, whereas columnar dendrites were observed at the interface region of cladding layer and substrate. This is attributed to the variation in cooling rates between the top layer of the cladding and the interface region. γ, γ′, γ″ and Laves phases were identified to be the primary phases in the cladding layer. Moreover, niobium content was found to be high and varying with the cooling rate in the direct energy deposited Inconel 718. Dislocation density at varying scanning speed, i.e., cooling rate was estimated using the Williamson-Hall method. An increase in the dislocation density and concomitant improvement in the hardness was found with an increase in the cooling rate.

Improved Three-Dimensional Reconstructions in Electron Ptychography through Defocus Series Measurements.

A detailed analysis of ptychography for three-dimensional (3D) phase reconstructions of thick specimens is performed. We introduce multi-focus ptychography, which incorporates a 4D-STEM defocus series to enhance the quality of 3D reconstructions along the beam direction through a higher overdetermination ratio. This method is compared with established multi-slice ptychography techniques, such as conventional ptychography, regularized ptychography, and multi-mode ptychography. Additionally, we contrast multi-focus ptychography with an alternative method that uses virtual optical sectioning through a reconstructed scattering matrix (S-matrix), which offers more precise 3D structure information compared to conventional ptychography. Our findings from multiple 3D reconstructions based on simulated and experimental data demonstrate that multi-focus ptychography surpasses other techniques, particularly in accurately reconstructing the surfaces and interface regions of thick specimens.

Tailoring nanotwinned Cu interlayers for localizing anisotropic plastic deformation during low energy input ultrasonic welding of robust Cu-Cu joints

Ultrasonic welding, known for its severe plastic deformation, faces the challenge of balancing sufficient deformation at the welding interface with minimizing damage to the substrate. This study utilizes the anisotropic deformation mechanisms and mechanical properties of nanotwinned Cu (nt-Cu). Specifically, Cu coatings featuring nanotwin layers aligned parallel to the ultrasonic vibration direction were employed as interlayers in ultrasonic welding of Cu-Cu joints. The effects of the nt-Cu interlayer on the welding quality and the deformation mechanisms under the various welding pressures are investigated. Experimental and molecular dynamics simulations demonstrate that at low welding pressures, the nt-Cu interlayer undergoes deformation and detwinning primarily through twin boundary migration. This mechanism effectively mitigates work hardening during the welding process, localizes deformation at the welding interface, and significantly enhances the strengths of the Cu-Cu joints. The maximum enhancement proportion occurs at a welding pressure of 8 psi, up to 26.75% compared to conventional coarse-grained copper. As the welding pressure increases, the strengthening effect gradually weakens. The deformation mechanism of nt-Cu transitions to dislocation transverse and threading. The interaction between dislocations and twin boundaries forms incoherent twin boundaries and 9R phases, resulting in work hardening of the interfacial regions and reduction of the strengthening effect.

PHYSICAL-MECHANICAL PROPERTIES OF DYNAMICALLY VULCANIZED BASALT CONTAINING PLASTICS BASED ON COMPATIBILIZED POLYPROPYLENE

The influence of the content of basalt and Exxelor PО1020 compatibilizer on the main physical-mechanical and thermophysical characteristics of composites based on polypropylene is considered. It has been established that the use of a compatibilizer in an amount of 1.0–3.0 wt. % can significantly improve such properties of basalt plastics as tensile strength, yield strength, elongation at break, flexural strength, Vicat softening temperature, and melt flow rate. The possibility of cross-linking basalt plastics with sulfur and dicumyl peroxide is considered, and their role in changing their basic physical-mechanical parameters is determined. A theoretical analysis is given of the formation of an interfacial region with the participation of a compatibilizer and basalt. A micrograph showing the redistribution of basalt in the composition of compatibilized polypropylene is given by electron microscopy. The optimal concentrations of vulcanizing agents are determined, at which the highest strength properties are achieved, provided that elongation at break and the melt flow rate are maintained at a satisfactory level. It has been established that the optimal content of dicumyl peroxide is 0.25–0.5% wt