材料科学与工程杂志

This article provides a summary of the findings from examining a failed industrial bolt used in a vulcaniser for splicing conveyor belt. In summary, the fracture plane is nearly completely catastrophic. There is a small area which does appear to be fatigue failure. The surface is perpendicular to the thread edge and located at the stress concentration at the thread which is typical of fatigue crack initiation. The fatigue failure area is quite small compared to the rest of the failure surface which indicates that the part is susceptible to catastrophic failure after relatively little fatigue which therefore suggests that the inspection for fatigue must be done quite often and in quite a detailed fashion to detect the crack.

Very recently, new exact analytical solutions of the Fourier heat equation have been proposed by Zhukovsky. Since the Zhukovsky solutions are very powerful we applied the Zhukovsky formalism to a specific experimental situation, i.e. to a one dimensional (1D) lattice composed of Au nanoparticles of radius 20 nm in water media, under 20 ns laser pulse irradiation. In addition, we calculated the thermal field in the 2D spatial dimensions case for a single Au nanoparticle in water irradiated under the same conditions but with a different fluence. These results exemplify how the new Zhukovsky formalism contributes to the real physical view of such laser thermalized processes. This new theoretical approach could be easily extended to laser processing in general, and laser additive manufacturing in special.

In recent years Al₂₀₂₄ alloy had increasing applications in all the areas due to its good formability, excellent properties and etc. By using nano size B₄C as size and graphite as reinforcements the fabrication process are done by Powder metallurgy process with overall 12 compositions primary and secondary specimens. Nano B₄C are used as reinforcements from 3-15% with step of 3% as primary specimen and with addition of graphite of 3% in every reinforcements same manufactured. All specimens are manufactured by powder metallurgy technique and had a wide application. Hardness values are taken and each specimen is subjected to aging process. In aging process are subjected to 495°C and soaking for 2 to 10 hours. The cooling process can done by in three medium water. In each case hardness values are taken with micro Vickers tests. All results are taken shows that increase in hardness with aging process. FESEM analysis is conducted to know the microstructure of composites.

Pure and Cu⁺²/Fe⁺³ codoped ZnO nanoparticles were synthesized by polyol method. X-rays diffraction, scanning electron microscopy, dispersion X-rays spectroscopy; UV-Vis spectroscopy and photoluminescence were used for the characterization of the as synthesized nanoparticles. X-ray diffraction study of as synthesized nanoparticles presented the hexagonal wurtzite phase of ZnO structure. Optical studies revealed a blue shift in the absorption spectrum when ZnO was doped with Cu⁺²/Fe⁺³.

The degradation rate of disperse blue dye using ZnO and codoped ZnO nanoparticles were considered under the solar region. ZnO and codoped ZnO degrade dye under consideration however, codoped ZnO nanoparticles proved to be extra efficient catalyst as compared to ZnO nanoparticles. The kinetic study of the dye was also calculated and it was observed that degradation of the respective dye followed pseudo first-order kinetics. The as-synthesized nanoparticles prove to be environment-friendly and active and can be vastly used for the purification of water polluted by different dyes that are carcinogenic in nature.

We present an optical experimental approach and an analytical model to calculate the strain on a brick when an external force-pulse is indirectly applied on its surface. We assumed that the displacement produced on the brick is energy that it transforms to deformation. To measure the displacement, we applied one laser-beam to the brick and took image data of the speckles created by its reflection. The speckles were processed using the digital image correlation technique and allowed us to evaluate the relative displacements caused on the surface of the brick. Then, based on the kinetic energy of forced and damped oscillations, we calculated analytical strain values of the order of ε ≈ 1.52×10^-6.

Electro-anodization of thin Ti film deposited on glass substrate by RF sputtering technique was employed to fabricate TiO₂ Nanotubes (TNTs) annealed from 350°C to 650°C. The morphological analysis were done using Scanning Electron Microscopy (SEM), which showed the change in the surface morphology with increase in annealing temperature. The structural analysis was performed using X-ray Diffraction (XRD) and Raman spectroscopy. XRD revealed the presence of anatase phase TiO₂ with most intense anatase peak found at 550°C, at 2θ of 28, 9° (101). Raman revealed the presence of only anatase phase of TiO₂, and showed well-improved crystallinity of the TNTs upon increasing in annealing temperature.

The new thermal treatment of subcritical annealing and water quenching, applied to boron steels (30MnB5), which we propose in our research, achieve excellent variability in mechanical properties, as a result of obtaining a very versatile dual structure. In addition, there is a significant reduction in energy consumption and process time, which results in the Life Cycle Analysis (LCA) and process costs. The presence of boron favours the success of the thermal treatment. The explanation of the process has been investigated by means of a metallographic study, mechanical characterization and in this work the results obtained by means of the study of the treated and untreated samples by means of X-Ray diffraction are presented. The presence of very small FeB crystals in the structure are the cause of the dual structure and its good characteristics. They have only been detected by X-Ray Diffraction, although we have also tried Transmission Electron Microscopy with unclear results.

In this research paper, the Finite Element Analysis is used for the investigation. The modal of polycarbonate bullet proof glass and the abrasive particle is prepared to study the effect of machining mechanism. Through analysis, it concludes that hard abrasive gives the large stressed zone, which increases the material removal rate. In this experimental study, Boron carbide abrasive gives better material removal rate as compared to Silicon carbide and Alumina Abrasive. It also observed from the analysis, higher material removal rate also encourage the tool wear rate. Boron carbide gives higher tool wear rate as compare to other abrasive. The results are verified with the experimentation, it gives the approximately same results of Finite Element Analysis.

The main goal with the present work has been to study the possibility and thermodynamic stability for a sequential termination with either carboxylic groups (COOH), or amino groups (NH₂), from an initially H-terminated diamond (111) or 100)-2x1 surface. It was shown that it is energetically preferable to terminate both types of surfaces with up to 50% with COOH species. Moreover, it was shown possible to terminate both types of surface with up to 100% coverage with NH₂ species. In order to follow bond energy variations with variations in surface coverage, the averaged adsorption energies were also calculated. As expected, the lowest COOH coverage (of 6.25 %) resulted in the energetically most preferable adsorption energies. The situation with the NH₂ group was identical for the diamond (111) surface, with the lowest surface coverage (of 6.25%) leading to the most preferable adsorption situation. For the situation with diamond (100)-2x1, the preferable adsorption situation was for a surface coverage of 43.75% NH₂ species.

Partial Density of States (pDOS´s) were also calculated with the purpose to analyse the adsorbate-induced surface electronic properties. COOH-terminated diamond (100)-2x1 surface, as well as COOH- and NH₂-terminated diamond (111) surfaces, where shown to display surface conductivities which were not observed for 100% H-terminated surfaces.