A 4-stage model was proposed based on Raman spectroscopy due to the N2-Ar pressure variations (0.4–10 Pa) during the deposition process of Si-C-N coatings by magnetron sputtering. The stage I (0.4 Pa) was associated to amorphous carbon with high defect density followed by stage II (1 Pa) where the growth of hard nanocrystalline phases took place resulting in increased hardness. The stage III (5 Pa) was linked to increased disorder and finally the growth of the graphitic phase at 10 Pa causing again a decrease in hardness was categorized as stage IV.The model is analogous to the conventional 3-stage Ferrari–Robertson model on the growth features of carbon materials and takes a step further in proposing it for Si-C-N specific to pressure variation and introducing tetrahedral carbon and effects due to nitrogen incorporation The integral intensity of the G (graphitic), disorder (D), tetrahedral (T) and nitrogen (N) peaks namely IG, ID, IT and IN were calculated after the deconvolution of the spectra. The sp 2 domain size and defect parameters were evaluated and correlated with the hardness and different bond formation involving Si, C, and N. Image analysis revealed the atomic migration involved during the growth process leading to crystallization along with the formation of voids and defects. The deposition carried out at 1 Pa yielded the maximum hardness of 22 GPa for a domain size ∼ 25 nm and defect density of 2.25 × 10 11 cm −2 at 500 °C. These optimized Si-C-N hard coatings with previously established fracture toughness, conductivity and thermal stability serves in N/MEMS devices operating in harsh environmental conditions like aerospace. The study provides a structure—property correlation between deposition pressure and mechanical properties of Si-C-N through the 4-stage model based on Raman spectra .
This paper focuses on aluminum alloy and GFRPP composites, investigating the rheological behavior, the optimization of laser surface micro-texturing parameters, and influence of hot-pressing temperature on the interfacial bonding properties. The results showed that GFRPP melt exhibits typical shear-thinning behavior. By optimizing laser parameters (scanning speed of 1000 mm/s, power at 50%, frequency of 35 kHz), a uniform grid microstructure with a depth of approximately 79.42 μm and a width of approximately 40.34 μm was created on the aluminum alloy surface. Hot-pressing temperature significantly affects melt fluidity and the resulting mechanical interlocking effect at the interface. For the PP-GF20% composite, the tensile strength of the joint at 230 °C increased by about 25.55% compared to that at 190 °C.
Corrosion of iron and mild steel in water and in chloride media is a costly problem for industry, and it also raises safety concerns. Organic molecules containing heteroatoms are commonly used to control it. In most of the reported work, though, the electronic structure of the inhibitor molecule and the breakdown of the metal-water interface have been treated as two separate problems. It is therefore still not clear how a simple electronic descriptor is related to the film that actually builds up on a corroding iron surface. Keeping this in view, our study evaluates the iron corrosion inhibition performance of five aromatic compounds, anthracene, anthrone, xanthene, xanthone, and xanthione, using density functional theory (DFT) calculations and reactive molecular dynamics simulations. Simulations revealed the real-time evolution of iron corrosion in aqueous media, showing the formation of iron oxide and hydroxide at the metal surface. Among all inhibitors, xanthione showed the most stable adsorption on the iron surface, driven by van der Waals and electrostatic interactions sustained by electron donation from sulfur and oxygen heteroatoms. This xanthione-surface interaction appears to form a stable interfacial barrier, which should suppress corrosion. Among the five molecules, xanthione has the smallest gap of 3.18 eV between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and it also gives the most compact adsorbed film. Electrochemical tests on mild steel in 3.5 wt% NaCl gave a corrosion current density of 16.4 × 10 −6 A/cm 2 and a corrosion rate of 7.522 mpy, and these values are used here as the reference for the simulated ranking. The comparison made in this work is a qualitative one, since adsorption energies have not been computed and the electrochemical data are for the uninhibited substrate. Even so, the study relates a single electronic descriptor to the packing of the inhibitor film, which can serve as a quick screening route while looking for new inhibitors for iron.
Railway wheel–rail rolling contact inevitably causes wear and rolling contact fatigue (RCF) on the contact surface. This study evaluated the wear and RCF behavior of KS60 rail steel against two wheel materials: legacy rolled steel wheel (RSW) and standard ER8 wheel steel. Although both wheel materials showed similar mechanical properties, including tensile strength and hardness, ER8 exhibited a lower wear rate than RSW. This improvement was attributed to the lamellar pearlite structure of ER8, which enhanced wear resistance through significant work hardening. On the contact surface, ER8 showed considerable plastic deformation and minor pitting due to shallow crack propagation, whereas RSW exhibited severe spalling caused by limited plastic deformation and deeper crack growth.
Porous Ni-Al compounds exhibiting distinct reaction behaviors and pore structure characteristics were fabricated via an instantaneous and synchronous self-exothermic reaction. As the heating rate increased from 2 to 20 °C/min, the porosity decreased significantly from 62.8% to 29.4%. The intensity of the self-exothermic reaction increased with increasing heating rate, and when the heating rate exceeded 5 °C/min, noticeable sample deformation occurred. Cyclic oxidation tests revealed that the oxide layer remained relatively continuous and dense, and adhered well to the product matrix. This layer was identified as an Al2O3, formed because the outward diffusion of Al is kinetically favored over that of Ni, which was strongly influenced by both the diffusion rate and oxidation temperature.
