Applied Surface Science Advances最新文献

Incremental sheet forming (ISF) is a controlled and die-less forming process that can produce customized products from the sheets layer by layer using the same setup, i.e., forming tools and machine. This novel and emerging forming technique can potentially be useful as a green aspect of manufacturing by reducing the required power and by saving the resources for producing the components of lightweight materials because material is deformed locally during ISF. The surface quality of the formed parts from sheet material affects the aesthetics aspects, stress concentration, fatigue life and their applicability. This review article aims to provide a state-of-the-art review for various aspects and parameters of ISF process that affect the surface roughness significantly by conducting literature survey quantitatively. Furthermore, the techniques of ISF and roles of various parameters responsible for affecting the surface quality of parts have also been explored for providing the critics for existing literature and setting the further guidelines for the researchers. Various instruments used for measuring the surface roughness of parts formed by ISF has also been discussed. Comparative analysis of exiting literature available in the context of various process parameters, ISF hardware, and surface roughness makes this study comprehensive and exhaustive for the researchers to find the gaps and challenges in this field. The relationship of wall angle with other process parameters can be explored in the future to obtain the desired surface quality of a particular material. Significant parameters responsible for the surface quality have also been discussed critically. Further, the new tool paths can be developed for high surface quality and low forming time. A study on the selection of feed rate for various applications and relation with other parameter is also recommended for the future work. The lubricants with additives can further be tested for high surface quality of ISF. Further, significant study on surface roughness is not conducted on hybrid sheet forming and other advanced variants of ISF (like hot forming, friction stir assisted incremental forming, waterjet forming). It is required to develop the comparisons between the different techniques of ISF. Results also showed that majority of researchers used SPIF technique followed by DSIF and hybrid ISF.

Silicones such Sylgard 184 are widely employed in biological applications due to their versatile properties. However, their inherently adhesive surfaces can restrict their application, especially in direct contact with damaged biological tissues, potentially compromising patient comfort. To enhance the surface properties of Sylgard 184 while maintaining its transparency in the visible spectrum, a novel low-temperature method (70 °C) has been developed. This method involves immersing PDMS in a solution of titanium (IV) ethoxide in THF, thus inducing swelling of the silicone's polymer network, followed by the diffusion and condensation of titanium (IV) ethoxide within the polymer matrix. The resulting hybrid material, incorporating amorphous titanium oxide within the silicone network, exhibits significantly increased surface hardness compared to unmodified Sylgard 184, while retaining transparency and improving biological behaviour. The elaborated method holds promising potential for enhancing the performance of silicone-based materials in diverse biomedical applications.

Flexible piezoelectric nanogenerator (PENG) and triboelectric nanogenerators (TENG) have gained prodigious attention due to the increasing demand of nano and micro energy for driving of miniaturized electronic devices, sensors, and various internet of things. The key challenges that are currently in focus are material selection and simple fabrication techniques for improved electrical performance along with good mechanical properties and flexibility. Herein, a ferroelectric polymer, poly(vinylidenefluoride-co-trifluoroethyne) (PVDF-TrFE), is chosen as a flexible material due to its promising prospect for energy harvesting. To improve the performance, a ceramic material, 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN-PT), with very high piezoelectric properties has been selected as the reinforcement. Further, reduced graphene oxide has been added as a conducting filler to promote charge conduction. A remarkable enhancement in output voltage of nearly 3 fold is achieved in PVDF-TrFE/PMN-PT (PP) polymer composite as compared to the base polymer PVDF-TrFE (P) TENG device. Furthermore, the PVDF-TrFE/rGO/PMN-PT (PPR) as a PENG illustrates a great improvement in output current of the order of 2 as compared to the pristine polymer. The maximum output voltage as shown by the TENG is 200 V and the maximum current that is shown by the PENG is 30 µA. Therefore, the fabricated PMN-PT based PVDF-TrFE nanogenerators have an immense prospect for applications in self-powered systems.

Several anticorrosive treatments have been proposed over time to create protective layers to hinder the corrosion phenomenon. In recent years, organic molecules from plant extracts and expired drugs have been tested due to their potential corrosion inhibition properties. However, direct corrosion inhibition efficiency (IE%) evaluation requires costly reactants and a specific experimental setup. Quantitative-structure activity relationship (QSAR) proposes modeling IE% in terms of variables measured in previous experiments or determined by theoretical approaches. Computed descriptors, such as ionization energy (I), electronic affinity (A), or global hardness, were added to a database of physicochemical properties. This work compares several methodologies to obtain precise yet portable mathematical models for predicting corrosion inhibition efficiency. As an original approach from this research group, nonlinear autoregressive moving average with exogenous inputs (NARMAX), using forward regression with orthogonal least squares (FROLS), models were implemented as a robust method to get nonlinear portable models and to determine the most important variables impacting IE%. Contrastingly, ordinary least squares (OLS) methodology was employed with the novelty of applying power series expansions from the promoted FROLS variables for linear and polynomial regression with only one independent variable, which resulted in clearer graph visualization of trends and the ease of proposing thumb rules based on raw information. Finally, IBM Watson was also compared as a robust yet non-portable and highly parametrized alternative to conventional mathematical approaches, based on extra trees regressor (ETR). The models were compared using mean absolute percentage error (MAPE), mean-squared error (MSE), and root-mean-squared error (RMSE). Overall, models with fewer variables and up to second-order terms show improved performance. The main tendencies of IE%, drawn by inferences for 630 substances by second-order NARX, are analyzed. Also, the determinant role of the highest occupied molecular orbital energy was reported. Experimentalists can take advantage of a “cost-free” general approach that can obtain estimations for IE% values with errors of about 6 %, in particular the second-order NARX model.

The impact of humidity on the efficiency of gas sensors has become highlighted in the realm of gas detection. Due to the complex relationship between humidity and gas sensor performance, the development of gas sensors has recently focused on minimizing humidity-related interference. This research aims to address humidity-related challenges in zinc oxide (ZnO) gas sensors designed to detect triethylamine. The ZnO nanostructures (NSs) were synthesized using thermal decomposition methods at varying temperatures (380 °C, 480 °C, and 580 °C) and annealing times (3 h, 7 h, 12 h, and 21 h). X-ray diffraction (XRD) confirmed the formation of a wurtzite hexagonal close-packed structure in ZnO NSs. Scanning electron microscopy (SEM) images provided insights into the morphologies of ZnO NSs at different annealing temperatures, while energy dispersive spectroscopy (EDS) demonstrated the elemental distribution. Subsequently, gold (Au) nanoparticles were uniformly sputtered onto ZnO sensors with thickness variations (0.1 nm, 0.6 nm, 1 nm, 5 nm, and 10 nm). XPS was employed to analyse the elemental composition and oxygen vacancies of the synthesized sensing materials. The effectiveness of 0.6 nm-thick Au nanoparticles in mitigating humidity effects was observed in ZnO sensors synthesized at 380 °C. The results indicated that ZnO sensors coated with 0.6 nm-thick Au nanoparticles exhibited highly stable responses to ethanol and triethylamine at different humidity levels from 50 % to 90 %. Notably, these sensors demonstrated promising selectivity towards triethylamine (with a response of 17.57) compared to various gas targets at room temperature. The sensor exhibited rapid response and recovery times of 9.8 s and 4.4 s, respectively, toward triethylamine with excellent stability in variable humid environments. The sensor maintained a consistent response over 24 days, demonstrating good stability at high humidity.

This study delves into the corrosion resistance enhancement of stainless steel through laser processing, focusing on the interplay between surface chemistry, morphology, and electrochemical properties. Two sets of 3 × 3 full factorial design of experiment (DoE) designs were employed to explore the influence of laser process parameters, including power, scan speed, frequency, and hatching distance. The findings underscore the superiority of reduced areal energy in producing optimal corrosion resistance 10 times better then unprocessed stainless steel, demonstrating the best results under optimized conditions of a 15 µm hatching distance, 250 mm/s scan speed, 100 kHz frequency, and 80 % power. X-ray Photoelectron Spectroscopy (XPS) analysis reveals the predominant surface composition of iron and chromium oxides, with variations in the oxide combinations correlating closely with areal energy. Depth profiling revealed the transformation of oxide layers and highlights the importance of chromium-to-iron ratio in surface corrosion behaviour. Cyclic polarisation results demonstrate the formation of passive, transpassive, and pitting domains, with metastable pitting observed in some samples. The direct positive correlation recorded between corrosion current and Cr/Fe ratio underscores the significance of oxide composition in corrosion resistance. Electrochemical impedance spectroscopy (EIS) further confirmed the superior corrosion resistance of laser-processed samples to non-laser processed samples, with lower areal energy exhibiting higher resistance compared to higher areal energy. SEM morphology analysis revealed the removal of surface defects and the formation of a protective oxide layer in laser-processed samples, with lower areal energy samples exhibiting the lowest level of surface defects. The 3D optical profilometer measurements of corrosion pits corroborate these findings, with lower areal energy samples demonstrating the lowest pit depth and area, indicating superior corrosion resistance. Overall, this study provides comprehensive insights into optimizing laser processing parameters to enhance the corrosion resistance of stainless steel, offering valuable understanding and strategy for improving the metal surface corrosion resistance.

Many organic inhibitors have been proposed for corrosion protection of 304 stainless steel (SS), but its effectiveness in acidic and high temperature environment is challenged. We utilized Tithonia diversifolia (Hemsl) A. grey leaf extract (TDLE) as an eco-friendly organic inhibitor to protect 304 stainless steel (SS) in acidic environment (1 M HCl) at high temperature (65 °C). The performance of TDLE was studied electrochemically using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The surface of the metal was characterized using scanning electron microscopy (SEM). The theoretical calculation was also studied to understand the inhibition process. The corrosion inhibition efficiency increases reaching 98.48 % at 65 °C in the presence of 3.5 g/L TDLE. The inhibition of TDLE on 304 SS surface was adsorption spontaneously based in Langmuir's adsorption isotherm. The SEM images show significant improvement of the 304 SS surface with TDLE. A theoretical study indicates that methyl 3.5-dicaffeoyl quinate is the most active inhibitor in TDLE. The study revealed that TDLE had good performance for inhibiting in acidic and high temperature environment.

Nowadays, titanium-based implants are widely used to replace damaged or missing body organs. Poor chemical bonding with the bone and infection caused by formation of biofilm on the implant surface are the most common problems with them. So, antibacterial properties and osteoblast adhesion improvement have been intended to address these issues. The aim of this research is cell adhesion improvement and prevention of bacterial infection using surface roughness and in-situ antibiotic drug release. Here, micromachining (nanoseconds) laser with a groove distance of 10, 30, and 50 µm, was used to surface modification. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), hardness, roughness, and wettability tests were used for physical and metallurgical characterization of surface-modified samples to find the optimum laser processing conditions. Roughness has increased as a result of laser surface modification and surface characteristics of alloy exhibit sensitivity to the groove distance. The lower groove distance indicated the higher roughness and wettability. Martensite phase, α phase, and, Ti₃Al were observed in the fusion zone. Also, the dissolution of the beta phase has occurred in the fusion and the heat-affected zones. No oxidation was observed. All these occurred without any change in bulk. Then optimized sample surfaces were coated by the vancomycin-loaded polyvinyl alcohol solution using electrospinning process, and toxicity, cell adhesion, and drug release rate were evaluated. The results showed laser surface modification and coating did not hurt cell viability. Modified samples demonstrated high cell adhesion and improvement in drug release compared to the unmodified samples. The drug release rate was extended from 4 h to 25 h for modified samples. So, the modified implants could indicate a sustained release of antibiotics as well.

Nanoconstructs of gold nanoparticles (AuNPs) conjugated with SARS-CoV-2 specific antisense oligonucleotides (ASO) have been utilized to develop sensitive electrochemical nucleic acid biosensor for the detection of SARS-CoV-2 RNA. AuNPs were prepared through a one-pot synthesis method by utilizing Poly-L-Lysine (PLL) biopolymer and as synthesised AuNP were characterized by various analytical techniques such as UV–Vis spectroscopy, X-ray Diffraction (XRD) analysis, Fourier Transform Infra-Red spectroscopy (FT-IR), zeta potential, and Transmission Electron Microscopy (TEM). Poly-L-Lysine functionalized AuNPs (PLL-AuNPs) nanoconstructs platform was employed for immobilization of SARS-CoV-2 specific antisense oligonucleotides (ASO-conjugated PLL-AuNPs) via electrostatic interactions. The PLL-AuNPs were drop casted on glassy carbon electrode (GCE) following immobilization of ASO for fabrication of electrochemical biosensor. The ASO-conjugated PLL-AuNPs nanoconstructs were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The responsiveness of ASO-conjugated PLL-AuNPs nanoconstructs in presence SARS-CoV-2 RNA was monitored using the DPV, SWV and EIS technique, where methylene blue was employed as an electrochemical indicator for DNA-RNA hybridization detection. The biosensor exhibits a detection range for SARS-CoV-2 RNA infection ranging from 0 to 100 nM, with a limit of detection at 30.2 nM. The electrode, modified with ASO-conjugated PLL-AuNPs, was employed for the detection of SARS-CoV-2 RNA from clinical samples collected from COVID-19-positive individuals.

This paper investigates the impact of duplex plasma nitriding and diamond-like carbon (DLC) coatings on the pure fatigue and fretting fatigue properties of 16MnCr5 steel extracted from industrial piston pins used in combustion engines. Two different nitriding and DLC coating processes were performed: "DLC-A" and "DLC-B". The Raman spectrometry and microhardness tests were utilized to evaluate the formation of DLC coating on the sample. Subsequently, the pure and fretting fatigue tests (at 350 MPa and under 100 Hz of the frequency) were performed on as-cast and DLC-coated specimens to obtain the effect of coatings on the fatigue behaviors of the 16MnCr5 steel. Finally, the formation of the DLC layer and the fracture mechanisms were also briefly investigated using field-emission scanning electron microscopy. Then, the obtained results demonstrated that DLC coating ("DLC-B") increased the fatigue lifetime of 16MnCr5 steel by 47.7 % and 85.3 % in pure and fretting fatigue conditions, respectively. This layer can improve the surface properties of engineering materials and components, which can enhance the fatigue lifetime by increasing microhardness and compressive residual stress, reducing wear and friction, and improving adhesion between the substrate and coating. However, due to the white layer, the “DLC-A” improperly enhanced the material performance.