Surface Roughness Research Articles

Waterborne superhydrophobic bio-epoxy coating on Al alloy for corrosion-resistant and self-cleaning applications

Aluminum (Al) and its alloys are important engineering materials in modern industry due to their numerous advantages and have been widely used in various fields, including aerospace, marine, civilian industries and so on. However, they are prone to corrosion and contamination under harsh environmental conditions, particularly in marine environment when exposed to salty water or moisture for a long time, which can adversely affect their aesthetic appearance and desired functionalities or even cause economic losses and serious accidents. To prevent or delay the corrosion, the hydrophilic nature of Al and its alloy surfaces can be transformed to be hydrophobic or superhydrophobic. In this study, we reported an environment-friendly waterborne superhydrophobic bio-epoxy coating (WSBC) without using volatile solvents. The coating is composed of bio-epoxy resin, nano silica, silane coupling agent as well as hydrophobic curing agent, and applied by spin method on Al alloy substrates. The surface morphology and roughness were characterized by a field emission scanning electron microscope (FESEM) and an atomic force microscope (AFM). The WSBC with 22.2 wt% nano silica loading without considering the solvent of DI water displays a water contact angle (CA) as high as 165.8 ± 3.3° and a sliding angle (SA) as low as 5.3 ± 2.5°. Electrochemical measurement results showed that the as-prepared WSBC has a significant shift from −1.160 V to −0.708 V in the corrosion potential (Ecorr) and 3 orders of magnitude decrease in the corrosion current density (Jcorr), indicating excellent corrosion resistance. The WSBC was further proven to function well after immersion in deionized (DI) water and common organic solvents including ethanol and acetone for 48 h, and weathering resistance test. In addition, the as-prepared WSBC also showed good self-cleaning performance. The developed coating is green and no harm to human health and environment. The facile and eco-friendly process is of great importance for many industrial applications which can provide an attractive way towards anti-wetting surfaces for corrosion protection and self-cleaning effect on a variety of engineering substrates.

Synthesis of silver-decorated titanium dioxide nanostructured films for enhanced visible light photocatalysis

Titanium dioxide (TiO2) has been extensively investigated for applications in photocatalysis due to its stability, nontoxicity, and robust photocatalytic properties. Although thin films of TiO2 are effective in wastewater treatment, their dense structure limits surface accessibility. The oblique angle deposition (OAD) technique can be used to create high surface area nanostructured thin films essential for photocatalytic applications. In this study, OAD was used to grow TiO2 thin films. To extend the activity to the visible light region, plasma-reduced silver (Ag) particles were coupled to the TiO2 surface. The Ag-decorated TiO2 (Ag-TiO2) nanostructured films were fabricated using a custom-built magnetron sputter deposition system with OAD technique capability. Different substrate angles of 0°, 35°, and 70° with respect to the target normal were used. The films were characterized for their structural, compositional, and optical properties. The photodegradation performance was evaluated using methylene blue (MB) as the test analyte under visible light irradiation. The results showed a significant improvement in degradation efficiency using plasma-reduced Ag-TiO2. Substrates tilted at 70° achieved the highest MB degradation efficiency of 89.84% after 5 h exposure. This tilt angle also revealed high surface roughness and high surface area. By tilting the substrate with respect to the target, high surface area thin films can be fabricated. This technique is ideal for applications that depend on the area of contact, such as photocatalysis.

Phase-Controlled Construction of Copper-Leaf-like 2D NiS for Enhanced Supercapacitor Performance: A Supercritical Fluid Process

This study investigates a rapid and straightforward approach for constructing phase-controlled two-dimensional NiS nanosheets using the supercritical fluid (SCF) method. Through structural and morphological analyses, it is observed that the single-phase NiS nanosheets exhibit a rough and hierarchical surface, potentially offering a versatile electroactive area for energy storage. The electrochemical performance of fabricated single-phase NiS-based supercapacitors are measured in both three-electrode and two-electrode systems. In asymmetric supercapacitor (ASC) configuration with H2SO4 electrolyte, α-NiS demonstrated a remarkably high specific areal capacitance of 1664.61 mF.cm-2 at a current density of 1mA.cm-2. In asymmetric supercapacitor mode, NiS nanostructures achieved an exceptionally high volumetric energy density of 1953.61 mWh.cm-3 at a highest power density of 45.5W.cm-3. Furthermore, it showed an outstanding cycling performance of 95.77% retention after 5000 cycles at a high current density of 10mA.cm-2.

A highly branched glucomannan from the fruiting body of Schizophyllum commune: Structural characteristics and antitumor properties analysis

In this study, a highly branched glucomannan (SCP-1) from Schizophyllum commune fruiting body with good solubility was isolated, and its structural characteristics and antitumor properties were analyzed. The monosaccharides of SCP-1 were fucose, glucosamine hydrochloride, galactose, glucose and mannose with a relative molar ratio of 14:6:210:593:177, and the molecular weight (Mw) of SCP-1 was 15.1 kDa. SCP-1 showed a rough and dense surface, and it was aggregated to particles in distilled water, though it might have triple-helix conformation. The main backbone chain of SCP-1 was →[3)-β-D-Glcp-(1]3→3)-β-D-Glcp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Glcp-(1→ and three sides chains including α-D-Glcp-(1→[6)-β-D-Glcp-(1]2→, α-D-Glcp-(1→3)-α-D-Manp-(1→ and α-D-Glcp-(1→[6)-α-D-Galp-(1]3→ were linked with 1,6-glycosidic bond, which was significantly different with the schizophyllan isolated from the mycelia of S. commune. SCP-1 could significantly inhibit the growth of A549 cells, the inhibition rate reached 41.62 % and the percentage of cells in S phase increased from 27.17 % to 56.40 % (400 μg/mL, 48 h). Moreover, SCP-1 could induce cell apoptosis and the total apoptosis rate reached 28.13 %. SCP-1 exerted apoptosis inducing effect probably by reducing the expression ratio of Bcl-2/Bax and the p-PI3K, p-Akt and p-mTOR expression level. The results showed that SCP-1 might have the potential to act as an antitumor agent for lung cancer therapy.

Commercial organomineral fertilizer produced through granulation of a blend of monoammonium phosphate and pulp and paper industry waste post-composting

This study investigates a commercial granular organomineral fertilizer (GOF) produced by physically mixing landfill paper and cellulose industry waste composted over a long period with monoammonium phosphate (MAP), focusing on its morphological properties, and phosphate release into the water. The organic base used in the GOF composition is rich in humic and fulvic acids due to its long-term composting, rebalances the soil's organic matter, and eliminates a critical environmental liability. No studies have involved long-term lignocellulosic waste composting as the organic base of organomineral fertilizers. Most GOF and MAP granules range from 2 to 4 mm in size, with rough and macroporous surfaces observed through scanning electron microscopy. The specific surface area values of fertilizers are low compared to other fertilizers with different organic matrices. However, 2–4 mm granules exhibit similar values, indicating uniformity of granules. Infrared spectroscopy reveals bands from mineral and organic bases, with possible clay additives confirmed by the silicon detected in Energy Dispersive Spectroscopy analysis. Thermogravimetric curves exhibit improved thermal stability for GOF over the composted organic base, with a 31 °C increase in the second decomposition stage and delayed completion of the subsequent stages. However, this did not significantly alter the Tonset of the ammonium phosphate decomposition, as GOF presented a similar thermal behavior to MAP. GOF and MAP exhibit similar kinetic profiles, with rapid phosphorus release in the first 4 hours, reaching about 77 % of the available phosphorus. GOF shows an increase in specific surface area 29 times after 240 hours of contact with water, facilitating phosphorus release from the commercial mixture. MAP and GOF exhibit a release rate exceeding 84 %, indicating rapid phosphate availability. These values are comparable to those of other organomineral fertilizers. The results demonstrate that the GOF performs similarly to MAP, with lower phosphorus dosages, rebalance of soil organic matter, and increased nutrient application efficiency.

Investigating physiological responses and fine particulate matter retention of urban trees in Budapest

The urban environment is posing substantial challenges to both human well-being and the growth of plantations. Deploying advanced urban trees that effectively interact with atmospheric pollution will be a crucial step in urban planning. However, there is a paucity of knowledge in Hungary regarding these aspects. We studied the photosynthesis activities of three commonly planted trees (Acer platanoides, Fraxinus excelsior, and Tilia tomentosa) from two locations in Budapest, as well as their potential of capturing fine particulate matter on leaf surfaces. Our results reveal that T. tomentosa has developed a denser canopy and better photosynthetic activities, hence enhancing its adaptation to the urban environment in Budapest. F. excelsior showed a higher amount of fine PM wash-off, as it has a smoother leaf surface and was subjected to influences from wind speed and precipitation, making the captured particles more easily dislodged. Whereas fine PM concentration of A. platanoides and T. tomentosa were influenced by ambient PM10 and PM2.5, which might retain on their rough and hairy leaf surfaces. Approximately 38.17 tons of fine PM could be retained on urban greenery of Budapest at any given moment, highlighting the significant ecological and economic benefits of urban greenery. However, more accurate and long-term modeling is needed to develop a sustainable strategy for maximizing these benefits.

The Effect of Differences in Fiber Sizes on the Cutting Force During the Drilling Process of Natural Fiber-Reinforced Polymer Composites

This experiment aimed to analyze the impact of different fiber sizes on cutting forces during the drilling of Natural Fiber-Reinforced Polymer Composites (NFRPC) while also evaluating surface quality attributes, including delamination, fiber pullout, and overhanging fibers, influenced by variations in coconut fiber dimensions within the NFRPC material. The manufacturing process for composite panels utilized various methods, including hand layup for 200 mm long coconut fibers and composite casting for shorter fibers (2, 4, and 6 mm) mixed with polymer-epoxy. The results indicate that panels made from NFRPC with continuous fiber lengths of 200 mm exhibit higher cutting force values (253,650 N) compared to epoxy panels without fibers (235,288 N), suggesting that a significant force is required to sever the continuous fibers within the NFRPC. Conversely, the incorporation of short coconut fibers measuring 2, 4, and 6 mm reduces the cutting forces on the composite panels. However, excessive surface roughness in the final hole quality can be detrimental, primarily due to issues of delamination and fiber pull-out.

A novel green CeO2 polishing slurry and its chemical mechanical action mechanism for achieving atomic-level smoothing of fused silica glass surfaces

Pitch-based tools are integral to computer-controlled optical surfacing (CCOS) for polishing fused silica but face limitations such as low material removal rates (MRR) and challenges in achieving atomic-level smoothing while ensuring environmental sustainability. While chemical mechanical polishing (CMP) excels in processing planar surfaces, it struggles with complex freeform geometries. CCOS addresses this gap with specialized tool head designs that enable precise machining of intricate surfaces. This study introduces an eco-friendly CeO2-based polishing slurry suited for CCOS with pitch tools. By incorporating green reagents, such as polyethylene glycol (PEG) and ethylene glycol (EG), and minimizing harmful chemical usage, the slurry achieves significant breakthroughs in performance. Experimental results reveal a surface roughness (Sa) of 0.075nm, meeting atomic-level smoothing standards, alongside an MRR of 40.5 μm /h, marking substantial improvements over traditional methods. Physicochemical analyses of the CeO2 abrasives, including particle size, morphology, and Ce element content, revealed that abrasives with sharp edges and high Ce content are key factors for obtaining high surface quality and MRR. Molecular dynamics (MD) simulations highlight the synergistic effects of the components, optimizing chemical-mechanical interactions to enhance surface quality. These findings demonstrate the potential of green polishing technologies in advancing the precision machining of fused silica, particularly for complex geometries. The study provides a sustainable and high-performance solution for achieving atomic-level smoothing, paving the way for broader applications in precision optics.

P-type ZnO:N thin films deposited at room temperature on different substrates for p-channel Thin Film Transistor fabrication

A series of ZnO:N thin films were deposited by means of reactive pulsed laser deposition at room temperature on SiO2 glass slides, quartz, Al2O3, polyimide, silicon, and thermally oxidized SiO2. The p-type conductivity was confirmed by Hall effect-Van der Pauw measurements, with electrical parameters varying depending on the substrate deposition as follow: hole concentration between 2.4×1018 - 3.8×1017 cm-3, resistivity between 0.5 - 4 Ωcm, and mobility between 2 - 8 cm2V-1s-1. In situ X-ray photoelectron spectroscopy revealed identical binding energy values of the ZnO:N thin films across all substrates; the relative atomic concentrations varied between 49-53.8 at.%, 44-49 at.% and 2-2.4 at.% for zinc, oxygen and nitrogen respectively, due to over-quantification related to zinc particle splashing. Scanning electron microscopy confirmed a surface roughness of the films below 2 nm. Several wide and defect-related emissions were found by Cathodoluminescence; but the film deposited on quartz exhibited a unique, intense, and narrow blue band, the deconvolution of which revealed peaks at wavelengths of 430 nm and 461 nm. A growth rate of 14 nm/hour, and an etching rate of 2 nm/sec were found; these parameters were confirmed with the fabrication of smooth-walled ZnO:N thin films microstructures using photolithography. Finally, Thin Film Transistors (TFT) were fabricated. The devices exhibited low, but clear field effect current amplification, with a Ion/Ioff = 10. The feasibility of using room-temperature deposited p-type ZnO:N thin films for p-channel TFT fabrication was demonstrated.

Effects of Beads and Shot Peening Intensity on the Surface Integrity and Fatigue Performance of a Stainless Gear Steel

Shot peening was performed on stainless gear steel using multiple kinds of beads at multiple intensities. The effects of shot peening on surface integrity and the rotational bending fatigue performance were tested with the crack origin location observed. The results showed that the average surface roughness increases from Sa0.408 μm to Sa1.165 μm as the shot peening intensity increases, which does not necessarily lead to an increase in surface stress concentration coefficient. The compressive residual stress profile and the depth of the hardened layer increase with the increase of shot peening intensity. During ceramic bead peening, the fatigue improvement, with a maximum of 25 times, increases with the raise of intensity (0.06–0.20 mmA), while the fatigue improvement decreases when intensity (0.2–0.30 mmA) increases using cast steel shot. Based on ceramic shot peening, a method was proposed to predict the origin location of rotational bending fatigue cracks of gear stainless steel, in which the effects of surface stress concentration, compressive residual stress, and external load introduced were all considered. By using the superposition method of external load and residual stress, the maximum actual stress corresponding depth is obtained, which is the origin position of the rotational bending fatigue crack.

Effect of isomeric polysaccharides on heteroaggregation of nanoplastics in high ionic strength conditions: Synergies of morphology and molecular conformation

Polysaccharides with various molecular structures and morphology may influence the aggregation kinetics of nanoplastics. This study used various characterization methods to elucidate the heteroaggregation mechanism of polystyrene nanoplastics (PSNPs) in the presence of polysaccharides (ionic strength (IS) 1-800mM NaCl and 0.01-60mM CaCl2). The results showed that under high IS, cellulose (CL) accelerated the heteroaggregation of PSNPs, and the aggregation rate of PSNPs increased by approximately 62.05%, while amylose (AM) had little effect (10.38%). Compared with AM (43.2nm), the morphology of the CL (78.4nm) gully had improved surface roughness, leading to its decisive role in the heteroaggregation of PSNPs. Quantum chemistry calculations indicated that van der Waals forces of PSNPs-CL systems (-217.28kJmol-1) were stronger than those of PSNPs-AM systems (-184.62kJmol-1) based on the subtle molecular conformation differences between CL and AM (opposite and same sides of OH groups in CL and AM, respectively). The morphology and molecular conformation of polysaccharides collaboratively controlled the heteroaggregation of PSNPs. Because the morphology of polysaccharides was based on their molecular conformation, the latter is the most critical factor. These findings provide new insights into the effects of PSNPs stability in the environment.

Effect of burnishing strategies on surface integrity, microstructure and corrosion performance of wire arc additively manufactured AZ31 Mg alloy

AZ31 Mg alloy is an emerging material that has received considerable attention in aerospace, automotive, and temporary biodegradable implant applications owing to its attractive properties, such as low density, high specific strength, and biodegradability. Nevertheless, some shortcomings in Mg alloys are their low ductility, which is associated with challenging its manufacturing, and poor corrosion resistance associated with unreliable components. Therefore, a cold metal transfer wire arc additive manufacturing (CMT-WAAM) process is used to manufacture AZ31 Mg alloy and achieved 29.4 % ductility by controlling the gas porosity, keyhole porosity, and internal cracks. Further, severe plastic deformation is induced on the surface of deposited parts by low plasticity burnishing (LPB) with parallel and cross-pattern burnishing to modulate their surface to slow down the kinetics of the corrosion damage. The average surface roughness (Sa) of the cross-burnishing pattern is 0.235 μm, which is 123.6 % lower than the parallel burnished and 261.7 % lower than the milled specimens. The residual stress (RS) of WAAM is 40 MPa with a tensile nature; however, it is drastically reduced and develops compressive RS of 45 MPa under a parallel burnishing pattern and 62 MPa under a cross-burnishing pattern. Moreover, LPB with cross pattern deformed ∼395 μm depth of WAAMed AZ31 workpiece, which is ∼ 45 % higher than deformed depth (∼272 μm) by parallel pattern burnishing. The electrochemical corrosion rate of the WAAM specimen is 9.71 mm/year, and it is reduced to 1.82 mm/year under LPB caused by compressive residual stress and grain refinement.

Synthesis and characterization of new quaternized galactomannan derivatives with antibacterial activity.

The continuous increase in bacterial resistance requires the study and development of new biocompatible antibacterial materials. Galactomannan gum was extracted from endosperms of Dimorphandra gardneriana seeds, modified through quaternization reactions (with NaOH/CHPTAC), and evaluated for antimicrobial activity. Four quaternized derivatives were obtained (QG1-QG4). The derivatives were characterized by FTIR, NMR, and rheology, which confirmed the cationization. The galactomannan structure was theoretically studied, and Zeta potential exhibited positive increase in the charge of quaternized derivatives, changing from -3.2mV (unmodified galactomannan) to +59.35mV (QG4). Elemental analysis revealed an increase in degree of substitution (DS) between the derivatives, of which QG4 exhibited the highest DS (0.51). QG4 exhibited a bactericidal effect in the antimicrobial test for determination of minimal inhibitory and bactericidal concentrations, against Gram-positive bacteria. Atomic force microscopy showed an increase in bacterial cell surface roughness and decrease in cell height after treatment with QG4. QG3 and QG4 demonstrated antibiofilm potential, showing 50% and 40% of inhibition, respectively. After MTT assay, cell viability was maintained approximately 100% for all derivatives at concentrations of 20mg/mL on RAW 264.7 macrophages and 86% with 250μg/mL on L929 cells. Galactomannan was successfully modified, demonstrating strong antibacterial activity, concomitant to the increase in DS, Zeta potential and reduction of molar mass, with good biocompatibility. Therefore, this study presents a new material with potential for development of formulations for biomedical applications, from industrial waste, strengthening of the D. gardneriana production chain.

Fluorescence Behavior of Cyanine Fluorophore Cy3 Confined in Anodic Porous Alumina: Advanced Surface Analysis

In this study, an advanced analysis of the three-dimensional (3-D) surface microtexture of anodic porous alumina (APA) arrays was conducted to investigate their efficacy in confining cyanine fluorophore Cy3. The microstructural characterization of APA plays a pivotal role in enhancing the understanding of the material's surface properties, especially when applied to biological arrays and fluorescent dye confinement. To achieve this, Atomic Force Microscopy (AFM) was employed to obtain precise 3-D surface microtexture data. These measurements were complemented by stereometric analyses, adhering to ISO 25178-2: 2012 standards, ensuring a robust quantitative and qualitative evaluation of the surface micromorphology. The analysis revealed a clear correlation between surface roughness parameters and micromorphological changes as a function of varied processing conditions. Notably, the increase in certain fabrication parameters led to significant alterations in the superficial texture, with observable changes in the fractal dimension of the surface structure. The APA arrays, fabricated using a specialized anodization technique followed by a tailored annealing procedure, exhibited extraordinarily large pore sizes, ranging from 1 to 2 μm, which are well-suited for accommodating the Cy3 dye molecules. These pore dimensions offer an enhanced capacity for dye confinement, providing a stable environment for the cyanine fluorophore while promoting optimal fluorescence behavior.

Effect of film thickness on phase structure of epitaxial non-doped hafnium oxide films

HfO2 has been widely used in the electronics industry as a dielectric material with excellent properties. It has attracted much attention since HfO2 was first reported to be ferroelectric in 2011. With the continuous advancement of research, various methods such as oxygen vacancy control and interface control have been proven to be able to stabilize the metastable polar o-phase structure in doped hafnium oxide thin films. However, there are still some shortcomings in the relevant issues concerning non-doped hafnium oxide thin film materials. Here, polycrystalline non-doped HfO2 thin films were grown on SrTiO3 substrates by pulsed laser deposition (PLD). Atomic force microscopy investigation suggests that the surface roughness of HfO2 thin films increases as the film thickness increases. X-ray photoelectron spectroscopy analyses indicate that the HfO2 thin film has a high purity and contain only Hf4+ ions. The band gap of HfO2 was measured by valence EELS and UV–visible spectra. Atomic structures of the HfO2/SrTiO3 heterointerface have been studied by the aberration-corrected transmission electron microscopy and energy-dispersive X-ray spectroscopy. The HfO2/SrTiO3 heterointerface is atomically abrupt and incoherent. Our findings suggest that non-doped HfO2 films with o-phase structure through PLD technology.

Molecular dynamics mechanism of incorporating ZnO with varying particle sizes into ECTFE coatings and its impact on corrosion resistance

A composite coating of zinc oxide/chlorotrifluoroethylene copolymer (ZnO/ECTFE) was prepared on the surface of carbon steel via electrostatic spraying and heat treatment at 260 ℃. The influence of ZnO particle size variations on the anticorrosive properties of ECTFE coating was investigated by characterizing the microstructure, adhesion, hydrophilic/hydrophobic properties, electrochemical corrosion performance, as well as the dynamics simulation analysis on water molecule and chloride ions diffusion in the coating. The results show that the ECTFE coating incorporated with 100nm ZnO has the highest surface roughness (Roughness coefficient Ra = 30.6nm), the most robust adhesion (Bonding pull-out strength = 5.22MPa), and the lowest corrosion current density after a 90-day immersion (Icorr,90d = 4.05 × 10⁻⁸ A∙cm⁻²). These improvements represent an increase of 81.67% and 59.9% compared to the pure copolymer coating (Icorr,90d = 2.21 × 10⁻⁷ A∙cm⁻²) and the coating incorporated with 200nm ZnO (Icorr,90d = 1.01 × 10⁻⁷ A∙cm⁻²), respectively. This phenomenon can be attributed to the addition of small-sized ZnO, which enhances the density of the coating, induces a hydrophobic transition on its surface, strengthens the double electric layer effect, thereby improving its resistance against water molecule and chloride ions diffusion and ultimately enhances the corrosion resistance.

A Novel Approach to Fabricate Fe-based Thin Film Metallic Glass With Commercial Boron Carbide and AISI M42 Tool Steel

In this study, we report a Fe-based thin film metallic glass (Fe-Cr-Mo-C-B-X TFMG) fabricated by magnetron sputtering with commercial boron carbide (B4C) target and AISI M42 tool steel pellets. Varied number of M42 pellets were co-sputtered with B4C target, resulting in Fe content ranged from 48.1 at% to 62.8 at%. X-ray diffraction and transmission electron microscopy confirmed that all sample films were amorphous. All samples showed glass transition and crystallization in differential scanning calorimetry (DSC), similar to typical metallic glasses. However, glass transition was barely observable in B4m owing to its high oxygen content. The sample films also had extremely low surface roughness of 0.14 – 0.26 nm. The sample films also showed tribological properties comparable to conventionally deposited TFMG, where the highest hardness and reduced modulus obtained was 9.0 GPa and 150.8 GPa respectively. The sample films also demonstrated specific wear rate K0 as low as 1.6 × 10-5 mm3Nm-1. Our work demonstrates a more cost-effective and sustainable way of fabricating Fe-based TFMG, in which both AISI M42 are readily available and can be easily recycled after use.

A machine learning-based method for predicting the shear behaviors of rock joints

In this study, machine learning prediction models (MLPMs), including artificial neural network (ANN), support vector regression (SVR), K-nearest neighbors (KNN), and random forest (RF) algorithms, were developed to predict the peak shear stress values and shear stress-displacement curves of rock joints. The database used contained 693 records of peak shear stress and 162 original shear stress-displacement curves derived from direct shear tests. The results demonstrated that the MLPMs provided reliable predictions for shear stress, with the mean squared errors (MSEs) between their predicted and measured shear stress varying from 0.003 to 0.069 and the coefficients of determination (R2 values) varying from 0.964 to 0.998. The feature importance values indicate that the joint surface roughness coefficient (JRC) is the most important influential factor in determining the peak shear stress, followed by the joint wall compressive strength (JCS), basic friction angle (φb), and shear surface area (As). Similarly, for the shear stress-displacement curve, the JRC is the dominant factor, followed by As, φb, and JCS. Additional direct shear tests were conducted for model validation. The validation shows that the MLPM predictions demonstrate improved consistency with the experimental results in relation to both the peak shear stress and peak shear displacement.

Suppression of melt flow instabilities by amplifying high-frequency melt waves in laser fusion cutting

High-frequency resonant melt waves locally increase the stability of melt flow and enhance cut flank quality. To amplify these waves along the melt flow, an acoustically tuned cutting nozzle, termed the cutting whistle, generates gas flow oscillations based on a resonant cavity. The nozzle cavity is designed for 6 mm thick sheets, causing the gas flow to oscillate at 15 kHz within the kerf, creating a uniform melt flow with synchronized oscillating melt waves. Performance evaluations on stainless steel sheets show that, compared to a standard conical nozzle, the cutting whistle reduces surface roughness across the entire cutting depth and prevents coarse structures near the upper sheet surface and at the bottom in burr-free cuts.

Effect of non-static pre-oxidation treatment on the cyclic ablation behavior of SiC-ZrC/SiC multilayer coated graphite

SiC-ZrC based ceramics have caught much attention as coatings for graphite materials. However, the coefficient of thermal expansion (CTE) mismatch between coatings and matrix severely limits their application in harsh environments. Herein, we proposed a non-static pre-oxidation treatment under an air pressure of 0.05 MPa to increase the surface roughness of graphite matrix to 18.054 μm and then prepared the SiC-ZrC/SiC multilayer coating on the pre-oxidized graphite. The results demonstrate that a firm interlocking structure was formed between SiC-ZrC/SiC multilayer coating and graphite matrix, which effectively improved the bonding strength and enhanced the cyclic ablation resistance of coatings. The bonding strength of SiC-ZrC/SiC multilayer coated on graphite pre-oxidized under negative pressure was 5.70±0.42 MPa, which was 54.89% higher than that on graphite pre-oxidized under atmospheric pressure (3.68±0.08 MPa). After the plasma ablation for 360 s (60 s × 6), the linear and mass ablation rates of SiC-ZrC/SiC multilayer coated graphite which was pre-oxidized under negative pressure were -0.083 μm/s and 0.101 mg/s, respectively.