Material Surface Research Articles

Numerical study of cavitation shock wave emission in the thin liquid layer by power ultrasonic vibratory machining

In the field of power ultrasonic vibration processing, the thin liquid layer nestled between the tool head and the material serves as a hotbed for cavitation shock wave emissions that significantly affect the material's surface. The precise manipulation of these emissions presents a formidable challenge, stemming from a historical deficit in the quantitative analysis of both the ultrasonic enhancement effect and the shock wave intensity within this niche environment. Our study addresses this gap by innovatively modifying the Gilmore-Akulichev equation, laying the groundwork for a sophisticated bubble dynamics model and a pioneering shock wave propagation model tailored to the thin liquid layer domain. Firstly, our study investigated the ultrasound enhancement effect under various parameters of thin liquid layers, revealing an amplification of ultrasound pressure in the thin liquid layer area by up to 7.47 times. The mathematical model was solved using the sixth-order Runge–Kutta method to examine shock wave velocity and pressure under different conditions. our study identified that geometric parameters of the tool head, thin liquid layer thickness, ultrasonic frequency, and initial bubble radius all significantly influenced shock wave emission. At an ultrasonic frequency of 60 kHz, the shock wave pressure at the measurement point exhibited a brief decrease from 182.6 to 179.5 MPa during an increase. Furthermore, rapid attenuation of the shock wave was found within the range of R0-3R0 from the bubble wall. This research model aims to enhance power ultrasonic vibration processing technology, and provide theoretical support for applications in related fields.

Experimental investigation and parametric optimization of rotary ultrasonic machining of different bio-ceramic materials

Rotary ultrasonic machining (RUM) is a highly promising technique for machining bio-ceramic materials due to its ability to achieve high precision and superior surface quality. This research focuses on an experimental investigation and parametric optimization of RUM for different bio-ceramic materials, intending to optimize multiple machining responses simultaneously. The experimental setup involves utilizing a 3-axis CNC ultrasonic machine to machine three different workpieces with slot cutting. Various machining parameters, such as tool feed rate and tool rotating speed, are studied to determine their impacts. An orthogonal array design based on Taguchi optimization is used to execute the experiments effectively. Material removal rate (MRR) and surface roughness (SR) are monitored and statistically analyzed as a consequence of the responses. ANOVA demonstrates that the tool feed rate has a considerable impact on the output reactions, with material type and tool rotational speed also playing a role. For multiple response optimizations, the Taguchi-Grey method is used to achieve the best trade-off between MRR and Sr The results demonstrate that material type has the most substantial impact on surface roughness, followed by feed rate and spindle speed. In contrast, feed rate has the most significant effect on the material removal rate, followed by the material type and spindle speed. The optimal parameter settings for achieving the desired output parameter are determined. The confirmation experiments validate the effectiveness of the optimized parameters. The feed rate of 5 mm min−1, and spindle speed of 2500 rpm were discovered to be the optimal condition for achieving maximum MRR and minimum Ra. The MRR and surface roughness values were measured as 1.7266 mm3 min−1 and 1.5611 microns respectively.

Inverted Optical Functionality of Phase Change Material Surfaces through Mie Resonances of VO₂@Si Core-Shell Structures

Inverted Optical Functionality of Phase Change Material Surfaces through Mie Resonances of VO₂@Si Core-Shell Structures

Harnessing Biomimicry for Controlled Adhesion on Material Surfaces.

Nature serves as an abundant wellspring of inspiration for crafting innovative adhesive materials. Extensive research is conducted on various complex forms of biological attachment, such as geckos, tree frogs, octopuses, and mussels. However, significant obstacles still exist in developing adhesive materials that truly replicate the behaviors and functionalities observed in living organisms. Here, an overview of biological organs, structures, and adhesive secretions endowed with adhesion capabilities, delving into the intricate relationship between their morphology and function, and potential for biomimicry are provided. First, the design principles and mechanisms of adhesion behavior and individual organ morphology in nature are summarized from the perspective of structural and size constraints. Subsequently, the value of engineered and bioinspired adhesive materials through selective application cases in practical fields is emphasized. Then, a forward-looking gaze on the conceivable challenges and associated opportunities in harnessing biomimetic strategies and biological materials for advancing adhesive material innovation is highlighted and cast.

Low Temperature NO and CO Conversion with a Mechanistic Approach on Ru-Composed Cerium Oxide.

Catalytic reduction of NO with CO at a lower temperature is an extremely challenging task, thus requiring conceivable surfaces to overcome such issues. Ru-substituted CeO2 catalysts prepared via the solution combustion method were employed in CO oxidation and NO-CO conversion studies. The characterization for material formation and surface structure was carried out through XRD, SEM, TEM, and BET surface area. The catalytic study revealed the promising behavior of 5% Ru in CeO2 for the 100% conversion of NO-CO at 150 °C, proving it to be an excellent exhaust material. These observed results are also supported by temperature-programmed studies, i.e. TPD of NO and CO in addition to NH3-TPD and H2-TPR for their convincible surface interaction that is inclined toward a significant change in the conversion path. Additionally, the proposed mechanism, based on the experimental evidence, sheds light on the NO-CO redox reaction, directing the reaction pathway toward the Langmuir-Hinshelwood and Mars-Van Krevelen-type route. Moreover, the exceptional performance can be attributed to the strategic incorporation of Ru in CeO2, where the strong interaction of Ru-Ce is able to gain a high synergy for NO and CO conversion.

Nonlinear change of ion-induced secondary electron emission in the κ-Al2O3 surface charging from first-principle modelling

Secondary electron emission (SEE) induced by the positive ion is an essential physical process to influence the dynamics of gas discharge which relies on the specific surface material. Surface charging has a significant impact on the material properties, thereby affecting the SEE in the plasma-surface interactions. However, it does not attract enough attention in the previous studies. In this paper, SEE dependent on the charged surface of specific materials is described with the computational method combining a density functional theory (DFT) model from the first-principle theory and the theory of Auger neutralization. The effect of κ-Al2O3 surface charge, as an example, on the ion-induced secondary electron emission coefficient (SEEC) is investigated by analyzing the defect energy level and band structure on the charged surface. Simulation results indicate that, with the surface charge from negative to positive, the SEEC of a part of low ionization energy ions (such as E i = 12.6 eV) increases first and then decreases, exhibiting a nonlinear changing trend. This is quite different from the monotonic decreasing tendency observed in the previous model which simplifies the electronic structure. This irregular increase of the SEEC can be attributed to the lower escaped probability of orbital energy. The results further illustrate that the excessive charge could cause the bottom of the conduction band close to the valence band, thus leading to the decrease of the orbital energy occupied by the excited electrons. The nonlinear change of SEEC demonstrates a more realistic situation of how the electronic structure of material surface influences the SEE process. This work provides an accurate method of calculating SEEC from specific materials, which is urgent in widespread physical scenarios sensitive to surface materials, such as increasingly growing practical applications concerning plasma-surface interactions.

Oil-loaded Mesoporous Silica to Enhance the Lubrication of Polypropylene Resin Composite Materials

Polymer self-lubricating materials have advantages such as low friction coefficient, good wear resistance, and high work efficiency, giving them wide application potential in friction and wear. This work fabricated polymer-based self-lubricating materials by incorporating oil-loaded mesoporous silica nanoparticles (MSNs + YR1800) in the polypropylene resin (PP). The effectsof different content of MSNs + YR1800 on the tribological and mechanicalof the obtained self-lubricating composite materials were studied. The results indicate that the content of MSNs + YR1800 in composite materials significantly impacts their tribological properties.When the content of MSNs + YR1800is 10 wt%, the coefficientof friction reduced to 0.09,which was 84.5% lower than PP and 78.6% lower than composite materials containing 5wt% mesoporous silica nanoparticle (MSNs).Compared with pure PP, the wear rate decreases from 4.93 × 10-11 m3*Nm-1 to 4.43 × 10-13 m3*Nm-1, which can be reduced by two orders of magnitude.The excellent tribological properties of composite materials are attributed to the high specific surface area, large pore volume, strong adsorption capacity, and high oil loading capacity of mesoporous silica nanoparticle as nanofillers. The MSNs + YR1800 release lubricants to form a lubricating oil film during the friction process under load conditions, preventing direct contact between the friction pair and the surface of the composite material. Compared with polymer-silica hybrid oil-loaded microcapsules, MSNs + YR1800 can effectively reduce lubricant leakage, prolong operation life, improve lubrication efficiency, and ensure the continuous and stable existence of lubricating oil films.

Can pulsed laser treatment reduce microbial adhesion on the surface of resin denture base materials?

Abstract Objectives: The present work investigates the influence of pulsed nanosecond laser patterning of two commercial heat cure poly (methyl methacrylate) denture base materials, Trevalon and DPI heat cure, on their surface characteristics such as roughness, hydrophobicity, and microbial adhesion. 
Methods: A Q-switched Nd-YAG solid state nanosecond pulsed laser at a wavelength of 532 nm with a fluence of 2.55x1010 W/cm2 having a pulse frequency of 10 Hz was used at varying translation stage speed and vertical spacing for the surface patterning of denture base materials. The surface properties of control and patterned materials were characterized by measuring the compositional changes, wettability, and roughness. Microbial adhesion was assessed by incubating the specimens in Candida albicans suspension at 37°C for 2 hours followed by estimating the number of adherent Candida cells. 
Results: The micro-Raman spectroscopic studies indicated no chemical changes in the materials due to laser patterning. However, laser patterning increased the average surface roughness from 0.02 ± 0.005 and 0.04 ± 0.003 µm to 3.85 ± 0.20 µm and 3.70 ± 0.12 µm respectively for Trevalon and DPI heat cure materials. In addition, a reduction in the surface wettability was evident as manifested by an increase in water contact angle from 76 ± 2° to 105 ± 1° for Trevalon and from 72 ± 1° to 97 ± 1° for DPI heat cure. Finally, the microbial adhesion studies clearly indicated that the surfaces with higher hydrophobicity and roughness following laser patterning exhibited reduced microbial adhesion. 
Significance: Laser patterning can be utilized to tune the surface features of denture base materials and thus offer a promising method to create microbial adhesion resistant surfaces. Clinically, such surfaces help in reducing the incidence of denture stomatitis, especially in immunocompromised patients, without altering the composition and bulk properties of denture base materials.

Laser-induced breakdown spectroscopy as a method for millimeter-scale inspection of surface flatness

A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy (LIBS) is investigated experimentally. The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness, ranging from 0 to 4.4 mm, by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm. It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases, implying that the method investigated here is feasible. It is also found that, for achieving the inspection of surface flatness within such a wide range, when univariate analysis is applied, a piecewise calibration model must be constructed. This is due to the complex dependence of plasma formation conditions on the surface flatness, which inevitably complicates the inspection procedure. To solve the problem, a multivariate analysis with the help of Back-Propagation Neural Network (BPNN) algorithms is applied to further construct the calibration model. By detailed analysis of the model performance, we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm.

An energy concisions analytical modelling approach with experimental verification for cutting performance assessment in EDM of Ti-based superalloy

Abstract Electric discharge machining (EDM) is a stochastic process which is commonly engaged for cutting of Ti-based difficult-to-cut alloys. Experimental investigation in EDM is costly and requires significant amount of time due to the complex nature of the process. Moreover, the energy intensive nature is another criticism associated to this technique. Therefore, this research is focused on developing an energy conscious mathematical model of the process while considering the categorical parameters like type of dielectric, electrode and nano-powder along with pulse time ratio. Taguchi design of experiment (DOE) has been executed for the experimentation. The comprehensive analysis of the findings depicts transformer oil (TO) delivers a remarkable improvement in MRR and SEC in comparison to other dielectric choices. Furthermore, brass electrode stands out for achieving the best surface finish. When it comes to micro-additives, SiC exhibits substantial potential in increasing MRR, and graphite gives a better surface finish. The process has also been effectively modeled which helps to predict material removal rate (MRR), surface roughness (SR) and specific energy consumption with decent precision which is the key contribution of this study. 3D simulation for EDM illustrates that the features of the crater are defined by the liquefied region, whilst the dynamics of the mushy zone play a crucial role in controlling and characterizing the microstructure size progression. The confirmatory experimental results revealed that the use of optimized parametric combinations demonstrate 90.87% improvement in MRR, 52.07% reduction in SR and 96.19% decrease in SEC in contest to the responses’ values obtained at non-optimal settings.

An experimental investigation of process parameters on material removal and surface roughness improvement in abrasive flow machining

Abstract Today, there is huge demand for mechanical components with long life cycles, and superior surface finishes as a result of the industrial revolution. New methods for nano-finishing complex structures, including abrasive flow machining (AFM), have been developed in response to the need for superior surface finish. This is a relatively new technique in non-conventional machining techniques. Because abrasion only happens in locations where flow is restricted, this approach is utilized to polish metallic parts as well as interior, inaccessible cavities, and recesses using a semi-liquid paste. It has evolved to flow of abrasives with a viscoelastic polymer (referred to as abrasive media) over complex geometries, and edges to deburr, and radius those surfaces. This paper focuses on investigating the impact of process parameters on material removal, and percentage improvement in surface roughness on cylindrical brass workpieces using Taguchi L9 orthogonal array, the number of cycles, extrusion pressure, and grit size of abrasives have been selected. The abrasive medium employed in this investigation is composed of a blend of polymer, hydrocarbon gel, and aluminium oxide abrasive particles with varying grit sizes. The outcome shows which process parameters to optimize for material removal, and improvement in percentage improvement in surface roughness. The number of cycles that have the largest percentage contribution to material removal was 83.74%. For the response material removal, the percentage contributions of the abrasive particle grit size, and extrusion pressure are 2.03%, and 14.16%, respectively. N2P2G3 has the optimal level used for material removal. The largest percentage contribution to improvement in surface roughness, or 83.48%, was the result of the number of cycles. Extrusion pressure, and abrasive particle grit size account for 7.38%, and 8.88% of the total percentage contribution, respectively. N3P2G3 has the optimal level obtained for percentage improvement in surface roughness improvement.

Understanding the carbendazim adsorption from water using biochar derived from apple pomace and industrial wastewater sludge: experimental and DFT approaches.

Biochars derived from apple pomace (AP-BC) and industrial wastewater sludge (IS-BC) were used to investigate adsorption performance and mechanism for removing carbendazim from water and compare its performance with commercial biochar (commercial BC). The results showed that the adsorption capacity of AP-BC and IS-BC were 76 mg g-1 and 82 mg g-1 respectively that was comparable with the commercial BC (80 mg g-1). The adsorption kinetics and isotherms were best described by the Pseudo-second-order and Langmuir models. Thermodynamic analysis suggested thathigher temperatures can enhance the mobility of molecules, increased mobility facilitates more frequent and stronger interactions between the adsorbate molecules and the surface of the adsorbent material, leading to greater adsorption capacity. Density functional theory (DFT) calculations confirmed carbendazim's weak electrophilic nature, supporting the primary physisorption mechanism. Even after five cycles of recycling, both biochars maintained a consistent carbendazim removal efficiency of around 82%, highlighting their high reusability. In this study, the examination of waste-derived biochar's economic feasibility revealed that using biochars derived from waste biomass for large-scale wastewater treatment applications is an economically viable choice.

Reversible Laser Imprinting of Phase Change Photonic Structures in Integrated Waveguides.

Formation of laser-induced periodic surface structures (LIPSS) is known as a fast and robust method of functionalization of material surfaces. Of particular interest are LIPSS that manifest as periodic modulation of phase state of the material, as it implies reversibility of phase modification that constitute rewritable LIPSS, and recently was demonstrated for chalcogenide phase change materials (PCMs). Due to remarkable properties of chalcogenide PCMs─nonvolatality, prominent optical contrast and ns switching speed─such novel phase change LIPSS hold potential for exciting applications in all-optical tunable photonics. In this work we explore phase change LIPSS formation in thin films of Ge2Sb2Te5 (GST) integrated with planar and rib waveguides. We demonstrate that by fine-tuning laser radiation, the morphology of phase change LIPSS can be controlled, including their period and fill factor, and investigate the limitations of multicycle rewriting of the structures. We also demonstrate the formation of phase change LIPSS on a 1D waveguide, which has potential for use as tunable Bragg filters or structures for on-demand light decoupling into the far-field. The presented concept of applying phase change LIPSS offers a promising approach to enable fast and simple tuning in integrated photonic devices.

A device for dynamic testing of the refractory ceramic resistance to biomass ash

The corrosive effects of biomass ash on refractory materials in combustion chambers pose challenges. Development of new castable refractory materials which are more resistant to corrosion requires tests that accurately reflect the conditions occurring in real devices. This article describes the Computational Fluid Dynamics (CFD) design and construction of a device for evaluating the corrosion of refractory materials in dynamic regime. The device allows to simulate combustion chamber conditions accurately, to regulate an injection of corrosive medium on the tested material surface under the specified conditions (temperature, time, and flow). In the present investigation the conventional refractory material was exposed to attack of biomass ash at the temperature of 1300 °C for 3 h to test the functionality of the device. A burner with technology oxygen–enriched combustion was used to heat the device. The corrosion tests were conducted in accordance with the standard P CEN/TS 15,418 and the standard STN EN ISO 21404. The operational state required for corrosion tests at 1300 °C was achieved within 1.12 h. The extent of refractory material degradation in the dynamic corrosion regime was evaluated using electron microscopy-energy dispersive spectroscopy (EM-EDS) and compared with the results of a static crucible test (3 h at 1300 °C). The dynamic test provided sufficient information on the interactions of corrosion medium with the refractories. Its main advantages are the maintenance of non-equilibrium conditions by controlled deposition of the corrosion medium in quantity from 1 to −100 g/h, fast heating rate to operating temperature (20 °C/min), and the possibility of conditions variability during tests (temperature, ox-red. atmosphere, fuel gas flow etc.).

Synergistic Effect of Microconvex Texture and Particle Medium on the Tribological Property of the Rubber Sliding Interface.

In this study, we examined how surface topography and particle medium interact to affect the tribological performance of rubber sliding interfaces, uncovering the mechanisms of particle lubrication under various conditions. We found that microtextured surfaces, created using a mold transfer method, modestly reduced the friction coefficient of rubber under both dry and lubricated states, primarily by altering the real contact area. Additionally, the presence of different microconvex textures on the surface topography significantly influenced rubber's tribological properties. Our three-dimensional morphological analysis revealed that microtextured rubber surfaces with higher Sa, Sku, and Sal and lower Str values consistently showed lower friction coefficients during sliding. The friction mechanism was attributed to the combined effects of the material properties, surface topography, and contact area. With the addition of a particle medium, the dry friction coefficient of the rubber interface decreased but exhibited an initial increase, followed by a decrease with increasing particle diameter. When particles were mixed with a water-based cutting fluid, the concentration, diameter, and wettability of the particles significantly impacted the tribological properties due to the synergistic effects of surface topography and particle lubrication. This work enhances our understanding of tribological control for viscoelastic materials through surface design, providing a theoretical basis for the tribological optimization of rubber surfaces.

In vitro antifungal and physicochemical properties of polymerized acrylic resin containing strontium-modified phosphate-based glass

Acrylic resins are widely used as the main components in removable orthodontic appliances. However, poor oral hygiene and maintenance of orthodontic appliances provide a suitable environment for the growth of pathogenic microorganisms. In this study, strontium-modified phosphate-based glass (Sr-PBG) was added to orthodontic acrylic resin at 0% (control), 3.75%, 7.5%, and 15% by weight to evaluate the surface and physicochemical properties of the novel material and its in vitro antifungal effect against Candida albicans (C. albicans). Surface microhardness and contact angle did not vary between the control and 3.75% Sr-PBG groups (p > 0.05), and the flexural strength was lower in the experimental groups than in the control group (p < 0.05), but no difference was found with Sr-PBG content (p > 0.05). All experimental groups showed an antifungal effect at 24 and 48 h compared to that in the control group (p < 0.05). This study demonstrated that 3.75% Sr-PBG exhibits antifungal effects against C. albicans along with suitable physicochemical properties, which may help to minimize the risk of adverse effects associated with harmful microbial living on removable orthodontic appliances and promote the use of various materials.

Enhancement of Flow Boiling Heat Transfer Characteristics on Diamond/Cu Heterogeneous Surface

Surface treatment is an effective method of enhancing the heat transfer performance of flow boiling. Diamond/Cu, as a particle‐reinforced composite, exhibits heterogeneous surface properties and surface microstructures that play distinct roles in heat transfer. To elucidate the synergistic effect of heterogeneous material surfaces and microstructures, pure copper surface (PC), untreated diamond/Cu surface (DC), and surface‐treated diamond/Cu surface (SDC) are prepared for this experiment. These surfaces demonstrate various combinations of diamond, copper, and their corresponding surface microstructures. DC, characterized by heterogeneous wetting properties, demonstrates a heat transfer coefficient (HTC) that is 9%–24% higher than that of PC. The surface treatment of SDC results in the formation of a superhydrophilic CuO nanosheet structure, significantly enhancing both surface roughness and energy. SDC develops microcracks on the surface of diamond. The increased roughness provides numerous nucleation areas for the hydrophobic diamond, enhancing the overall wettability of the surface when combined with the superhydrophilic CuO region. SDC demonstrates the advantage of enhanced flow boiling on the surface of heterogeneous materials. At the identical heat flux, SDC exhibits a reduction of 5–10 °C in wall superheat and an increase of 38%–47% in HTC.

Preparation of 3D printed silicon nitride bioceramics by microwave sintering

Silicon nitride (Si3N4) is a bioceramic material with potential applications. Customization and high reliability are the foundation for the widespread application of Si3N4 bioceramics. This study constructed a new microwave heating structure and successfully prepared 3D printed dense Si3N4 materials, overcoming the adverse effects of a large amount of 3D printed organic forming agents on degreasing and sintering processes, further improving the comprehensive performance of Si3N4 materials. Compared with control materials, the 3D printed Si3N4 materials by microwave sintering have the best mechanical performance: bending strength is 928 MPa, fracture toughness is 9.61 MPa·m1/2. Meanwhile, it has the best biocompatibility and antibacterial properties, and cells exhibit the best activity on the material surface. Research has shown that the excellent mechanical performance and biological activity of materials are mainly related to the high-quality degreasing, high cleanliness sintering environment, and high-quality liquid-phase sintering of materials in microwave environments.

Casimir Effect in MEMS: Materials, Geometries, and Metrologies—A Review

Casimir force densities, i.e., force per area, become very large if two solid material surfaces come closer together to each other than 10 nm. In most cases, the forces are attractive. In some cases, they can be repulsive depending on the solid materials and the fluid medium in between. This review provides an overview of experimental and theoretical studies that have been performed and focuses on four main aspects: (i) the combinations of different materials, (ii) the considered geometries, (iii) the applied experimental measurement methodologies and (iv) a novel self-assembly methodology based on Casimir forces. Briefly reviewed is also the influence of additional parameters such as temperature, conductivity, and surface roughness. The Casimir effect opens many application possibilities in microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS), where an overview is also provided. The knowledge generation in this fascinating field requires interdisciplinary approaches to generate synergetic effects between technological fabrication metrology, theoretical simulations, the establishment of adequate models, artificial intelligence, and machine learning. Finally, multiple applications are addressed as a research roadmap.

Casimir Effect in MEMS: Materials, Geometries, and Metrologies—A Review

Casimir force densities, i.e., force per area, become very large if two solid material surfaces come closer together to each other than 10 nm. In most cases, the forces are attractive. In some cases, they can be repulsive depending on the solid materials and the fluid medium in between. This review provides an overview of experimental and theoretical studies that have been performed and focuses on four main aspects: (i) the combinations of different materials, (ii) the considered geometries, (iii) the applied experimental measurement methodologies and (iv) a novel self-assembly methodology based on Casimir forces. Briefly reviewed is also the influence of additional parameters such as temperature, conductivity, and surface roughness. The Casimir effect opens many application possibilities in microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS), where an overview is also provided. The knowledge generation in this fascinating field requires interdisciplinary approaches to generate synergetic effects between technological fabrication metrology, theoretical simulations, the establishment of adequate models, artificial intelligence, and machine learning. Finally, multiple applications are addressed as a research roadmap.