International Journal of Mechanical and Materials Engineering最新文献

Upconversion nanoparticles (UCNPs) have attracted considerable interest for the imaging of solid tumors because of their unique optical features. These applications can be expanded towards anticancer therapeutics by developing UCNP-graphene oxide (GO) composites. This strategy addresses low loading capacity and poor dispersibility of UCNPs in physiological media. These aspects have been covered in this article. We begin by discussing the synthesis methods and challenges associated with UCNPs, along with their surface modification strategies. Next, we describe the approaches of designing UCNP-GO composites and their applications in imaging, biosensing, and different therapeutic platforms.

Graphical Abstract

Surface-activated bonding (SAB) of a 3D-printed Ti-6Al-4V pillar structure (fabricated by selective laser melting) to pure bulk aluminum at room temperature has been investigated. Argon beam irradiation was used to remove surface contaminants and “activate” the surfaces prior to bonding. The surface chemistry of the Ti-6Al-4V surface was analyzed using Electron Spectroscopy for Chemical Analysis (ESCA) to make sure any oxides had been removed by the irradiation procedure. The two materials were successfully bonded via SAB using special bonding apparatus, and scanning transmission electron microscopy (STEM) observation revealed a flat well-bonded interface with no obvious porosity. Furthermore, no thick reaction layer that could compromise the strength of the bond was evident. An oxide layer approximately 2 nm in thickness was observed at the interface by high-resolution TEM, but this is not considered sufficient to have a detrimental effect on bond integrity. The results of the investigation show that 3D-printed materials and structures can be successfully joined to aluminum by SAB techniques.

High-velocity impact response of honeycomb sandwich structures (HSS) with Al/Al₂O₃ and Al/B₄C functionally graded plasma-sprayed (FGPS) faceplates are investigated in present work. FGPS structures improve the specific material properties and make the structure distinct from the substrate material. The metal and ceramic content was varied across the thickness of the FGPS coating in the present work. The HSS having honeycomb core sandwiched between two Al/Al₂O₃ FGPS faceplates were manufactured initially. Further, HSS having honeycomb core sandwiched between two Al/B₄C FGPS faceplates were manufactured. Such HSS are repeatedly impacted with a spherical projectile using a single-stage gas gun at a constant impact energy of 260 J, and the results are quantified and compared. The central deflection and dent diameter of FGPS plates as well as HSS were determined, and they increased with the number of impacts. The HSS’s energy absorption was dissipated by top faceplate indentation and core compression. The incorporation of a core prevented FGPS coating delamination and top faceplate penetration. The Al/Al₂O₃ and Al/B₄C FGPS faceplates had dent diameters that were 14.30% and 18.70% smaller than the non-coated Al 6061-T6 faceplate, respectively, which proves the enhancement of high-velocity impact resistance through FGPS coating. The central deflection and dent diameter of the Al/B₄C FGPS HSS are 6.04% and 3% lesser than the Al/Al₂O₃ FGPS HSS, respectively. The energy absorption of the Al/B₄C FGPS HSS is better than that of the Al/Al₂O₃ FGPS HSS. As a result, the present research enhances the knowledge on the impact energy absorption of two distinct FGPS coated plates and HSS, which is highly useful in aerospace and defence applications.

Target detection of defence technologies is being rapidly upgraded with modern surveillance technologies. The latest techniques of surveillance are already being implemented for defence applications. Self-protection and hiding from opposing forces are the key principles for the protection of special team in defence. Camouflage textiles aim to create confusing objects for target detection of military personnel. These textiles are applied for military protection such as clothing, weapons, vehicles and location hiding nets/tents. The urgent need for camouflage textiles has been formulated with a technical solution and implementation of the right camouflage materials for concealment of defence target signature against dry leaves, green leaves and tree bark-woodland combat background; water-marine combat background; sand-desertland combat background; stone-stoneland combat background; snow-snowland combat background; sky combat background; ice-iceland combat background; and concrete-concreteland combat background (DGTWSICB) in ultraviolet–visible-infrared (UV–Vis-IR) spectrums. This hypothesis of optical and surveillance engineering, digital imaging and hyperspectral imaging has been coalesced for the advancement of UV–Vis-IR-DGTWSICB camouflage textile technology. The principle of camouflage engineering has been approached by broader spectrum probes in UV–Vis-IR rather than Vis ranges only. Furthermore, camouflage materials, camouflage weapon designs, and formulations of camouflage textiles have been proposed for multidimensional CBs-DGTWSICB. The electromagnetic spectrum, reflection, electron energy, photonic signal and imaging mechanism in UV–Vis-IR have been presented for optical engineering of concealment, detection, recognition and identification of target signature against DGTWSICB. The spectrum relationship of camouflage materials and DGTWSICB materials has been illustrated and compared in UV–Vis-IR spectrums. Camouflage material design, method design and spectral design; textile colorants and technologies; adaptive camouflage; techniques for camouflage textile assessment for digital camera and hyperspectral camera imaging; image processing techniques; and a hierarchical model have been demonstrated for augmentation of camouflage textiles in UV–Vis-IR illumination. Therefore, the anticipated design of camouflage textiles may enhance high-performance innovation for modern surveillance of military protection related to digital camera, hyperspectral camera and radar. This hypothesis includes advanced guidelines for the advanced design of camouflage textiles for multidimensional CBs-DGTWSICB. The challenges, limitations, innovation and defence applications of camouflage engineering for multidimensional combat backgrounds have been coalesced for concealment, detection, recognition and identification of defence target signature.

Plasmonic metal nanostructure prepared by photolithography technology can be used as a uniform and stable substrate with high SERS activity. However, there is only limited research on the precisely regulated metal nanostructures and the systematic studies on the relation between the structure and SERS response. Herein, different gold nanostructure arrays (including circles, equilateral triangles, squares, regular pentagons, regular hexagons, pentagrams, and hexagram) have been prepared using electron beam lithography (EBL). Rhodamine B were employed as the probe molecule. The effect of the shapes, sizes (s), spacing (d), and rotation angle (α) of different shapes gold on SERS activities were systematically investigated under the excitation of 532 nm laser. Further finite element method based electromagnetic field simulations unveiled the correlation between the local electromagnetic field strengths and the SERS activities, which also verified the proportional relation between the fourth power of the electromagnetic field intensity (L_E) and enhancement factor (EF).

In dental implants, zirconia is well-known as a crown material due to its excellent acid and base resistances and appearance close to natural teeth. In addition, its extraordinary mechanical properties render zirconia to be a potential candidate as an implant component of a whole implanted tooth, if its biocompatibility can be improved to promote adhesion to natural hard tissues. This study aims to enhance the bioactivity of zirconia with the aim of improving its integration with gum bone. Hydroxyapatite is the major component of natural bone and is thus selected as the modifier to improve the bioactivity of zirconia. A series of zirconia/hydroxyapatite composites with varied compositions were prepared under different conditions in order to find the optimal composites for the target application. Various analytical technologies and mechanical tests are employed to characterise the structure and properties of resultant composites. Results show that the component ratio and sintering temperature have a significant influence on the composite properties. An increase in hydroxyapatite component tends to enhance bioactivity but decline mechanical strength. Composites containing 10 wt% of hydroxyapatite maintain sufficient mechanical strength under the optimal sintering conditions whilst possessing excellent bioactivity, demonstrating that hydroxyapatite-modified zirconia has the potential as dental implant materials. Sintering results suggest that mechanical strength is obtained at 1400 °C for 2 h for the composite containing 10 wt% of hydroxyapatite.

Rolls are the most critical yet vulnerable parts of cold rolling mills. It is crucial for them to withstand long rolling campaigns without losing surface roughness or incurring damage. Newly developed rolls are made from tool-grade steel with high roughness, lower wear, and high damage resistance. One of the most important advantages is the elimination of the need for chrome plating, which is currently widely used on standard steel rolls but is ecologically harmful. We investigated a type of steel with 8% chromium for use in cold rolling using light optical microscopy (LOM), X-ray crystallography (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), hardness measurements, and tribological tests. In this study, a roll with a diameter of 325 mm was electro-slag remelted and forged, machined to a diameter of 305 mm, and quenched and tempered to simulate industrial roll production. A forged roll was induction heated and hardened at four different feed rates (i.e., 24 mm/min, 30 mm/min, 36 mm/min, and 42 mm/min), tempered at 515℃ for 24h and again at 480℃ for 24h, and dissected for in-depth analysis. We identified a clear relationship between the feed rate of the roll during induction hardening and the depth of hardness, the sizes of carbides, and the wear properties of the roll. By reducing the feed rate of the roll through the inductor, we increased the depth of the hardened layer from 16 mm (at a feed rate of 36 mm/min) to 25 mm (at a feed rate of 24 mm/min), which is a 56.25% increase. Such an increase is expected to extend the lifespan of the working roll without having negative effects on the wear resistance and other important parameters. XRD analysis showed that the sample had a 0.4% residual austenite, which means it had a significantly lower risk of roll damage during operation than standard steel grades

In this study, the possible influences of thermal modification of wood on the quality of laser texturing of beech veneers are investigated by comparing native and thermally modified samples. By varying the process parameters of a CO₂ laser, the surfaces of both types of veneer were textured and the resulting surface roughness and aspect ratios were analyzed in order to evaluate the efficiency of the laser texturing and the quality of the textures produced. The main results show that the thermal modification of the wood influences the cutting widths, the removal depths, and the surface roughness, with thermally modified veneers generally having larger cutting widths and different removal depths compared to native veneers, indicating the influence of the wood modifications on the material physical and chemical properties and their interaction with the laser processing. Furthermore, the study shows how the laser processing parameters—feed rate and laser power—influence the surface quality and structural dimensions of the engraved lines, and establishes that the moisture content of the wood has a significant influence on its thermal conductivity and thus on the laser cutting process. The research work highlights the complexity of laser texturing of wood and emphasizes the need to take into account the change in the intrinsic properties of the material as a result of thermal modification.

A titanium oxynitride catalyst for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells was synthesized through the direct ammonia nitridation of titanium complexes. Titanium polyacrylate was employed as the catalyst precursor, and the effect of the calcination temperature between 600 and 1000 °C on the catalyst structure was studied. The catalysts were characterized via X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, cyclic voltammetry, and powder electrical resistivity measurements. The formation of titanium oxynitride particles and deposited carbon was observed for all the samples; however, significant variations in the catalyst structure and catalytic activity were also observed. With an increase in the calcination temperature, nitridation of titanium oxynitride progressed, and the conductivity of the catalyst powder increased. The highest rest potential and ORR current density were achieved with calcination at 800 °C. Importantly, the results suggest that maintaining an optimal nitrogen doping level within the catalyst particles, along with ensuring the formation of electroconductive deposited carbon, is essential for achieving a high ORR current. This work introduces the direct ammonia nitridation of metal complexes as a promising process for designing metal oxynitride catalysts.

Okra fiber is the bast fiber, extracted from the stem of the Abelmoschus esculentus plant which belongs to the Malvaceae family. In the whole world, India is the largest producer of okra for the cultivation of “okra fruit”, which is one of the main vegetables in the Indian Diet. After collecting vegetables, a huge amount of okra plant stem is discarded on the field annually as agricultural waste. Okra stem is an abundant source of okra fiber which can be used for various textile applications. This study aims understand the basic morphological, thermal and structural characteristics of okra fibre and compare it with other bast fibres generally used for textile application to prove the suitability of okra fibre for textile application.