Materials Letters: X最新文献

Fiber-reinforced polymers are increasingly used in lightweight applications due to their high specific properties. Different polymer materials, and fiber architectures, are commercially available for structural applications. Performing fatigue experiments on all these combinations of fiber–matrix composites up to 10⁹ cycles to mimic their typical lifetime of 15–20 years, at a low testing frequency generally in the range of 5–10 Hz in applications such as the aerospace industry, is expensive and time-consuming. In this study, a test system to investigate the very high cycle fatigue (VHCF) behavior of continuous fiber-reinforced polymers under an axial loading (tension–compression) condition is proposed. To do so, a testing system capable of applying cyclic oscillations at a frequency of 20 kHz and stress ratio, R = -1 was developed. For this investigation, the carbon fiber reinforced in Polyether-ketone-ketone (CF-PEKK) material was chosen. For visualization of the specimen oscillation-mode at 20 kHz, video-imaging using a high-speed camera (HSC) was employed. With the obtained displacement field from the HSC images and with thermography, the desired specimen response due to resonance at 20 kHz is validated.

The work focuses on the potential ability of 1-ethyl-3-methyl imidazolium ethyl sulphate (EMIES) and 1-butyl-3-methyl-imidazolium tetra chloro aluminate (ITCA) ionic liquids (IL) as reducing agents in the synthesis of activated silver colloidal particles without using any external reducing agent. The formation of activated silver colloidal particles from silver nitrate salt is explained based on the characterization results such as EDAX and SEM. The absorbance of the EMIES and ITCA impregnated activated silver particles are analysed by UV spectral study and the presence of functional groups are successfully determined by FT-IR spectrum. In this study, we also investigate antibacterial and antioxidant applications of EMIES, ITCA and impregnated silver colloidal particles. The antibacterial activity investigated by disc diffusion method and antioxidant activity by DPPH method.

A promising arc enhanced glow discharge (AEGD) was developed to enhance hot corrosion resistance of NiCoCrAlY/AlSiY coating. The AlSiY layer exhibited loose texture accompanied by plenty of pores, which triggered the muti-scale diffusion of salt mixture resulting in severe corrosion degradation of coating texture and rapid diffusion of NiCoCrAlY layer. However, the AEGD-assisted AlSiY layer showed dense texture, which effectively prevented the diffusion of salt mixture and suppressed the corrosion reaction as well as the diffusion of NiCoCrAlY layer. The results confirmed that AEGD showed a huge potential to inhibit the corrosion damage and diffusion of thermal protective coatings.

This study focuses on the utilization of mostly available renewable energy resources, such as lignocellulosic biomass, to generate syngas and bioethanol through a hybrid gasification and syngas fermentation process. The lignocellulosic biomass was characterized using TGA, XRD, FESEM with EDX analysis, and gasifying parameters were optimized using Aspen Plus®. In the first stage of this integrated process, hydrogen-containing syngas was generated, and the final product was bioethanol. The forest waste-based syngas produces higher bioethanol than EFB and coconut shell in the presence of biocatalyst. Therefore, bioethanol will be a sustainable biofuel that will satisfy the world's future energy demands.

In the present manuscript visible light induced photo catalytic performance of MWCNTs intercalated CdS nanocomposites has been studied. Methylene blue (MB) organic dye has been used as a probe for determination of catalytic performance. XRD spectra confirms hexagonal structure with average particle size distribution between 10 and 20 nm. SEM images confirm close contact between MWCNTs and CdS with quasi spherical shape. UV–Vis spectra confirms enhanced optical absorption and photocatalytic adsorption. The observed photocatalytic activity was enhanced by 2.6 times attributed the heterojunction between MWCNTs and CdS may lead an enhanced separation efficiency of photo generated e/h pairs.

Direct Laser Interference Patterning (DLIP) is used to generate textured stainless steel surfaces to control the wettability of a liquid nickel-based brazing alloy. The interference of two laser beams leads to periodic line-like structures with a spatial period of 6.0 µm. A maximum structure depth of 2.0 µm is reached by controlling the processing parameters. Moreover, the generation of laser induces periodic surface structures (LIPSS) with a period of ∼ 800 nm is observed on top of the DLIP structures. Depending on the produced texture depth, the contact angle of the molten metal is increased from 13° up to 96°. This allows adjusting the contact angle for various brazing and soldering applications and can also be used as a filler metal stop.

MOFs (Metal-Organic Frameworks) are crystalline porous organic/inorganic hybrid materials with well-defined structures that have proven to possess a great potential in many applications, mostly because during the synthesis of these materials the structure can be controlled to add the desired functionality in either the metal cluster or the linker. Unfortunately, few methods are reported to shape these materials as manipulable and, most importantly, to retain their original properties. Recently, 3D printing of MOF has been proposed and shows promising properties to obtain an object, which can be designed upon request. We propose here to summarize the main development of 3D printing of MOF to determine some prospects and opportunities in this area.

Silver paste is supposed to be a most prospective die-attach material for power electronics. While, the bonding of silver paste with aluminum substrate cannot be easily achieved due to the native oxidation of aluminum. This work provides a direct bonding of aluminum with silver micro flake-based paste under 250℃ with a shear strength of 15 MPa with a propriate surface treatment method of aluminum, and the shear strength even keeps higher than 15 MPa after storing at 250℃for 1000 h. The bonding mechanism was elucidated with high resolution transmission electron microcopy. The results indicate a new route for the wide application of Al based substrate in power electronic with low cost.

This work aims to study the XRD of 5 Boron oxides crystal with different X-ray sources using Quantum Expresso. When XRD was done with angle vs. intensity, a pretty exciting observation was observed: the single high-intensity peak was observed for each source. The high intensity with large Bragg’s angle is observed with Fe-sources among the considered source (Cu, Ag, Mo, and Fe). This shows lower atomic mass sources have higher Bragg’s angle when incidence on a sample of Boron oxides. The high-intensity peak when Fe-sources is used for XRD of B₆O, BO₃, B₂O, B₈O, B₂O₃ was observed at an angle of 44.3, 37.5_, 11, 44.3, 39.8 degrees, respectively.

A new preparation method of hydroxyapatite coating was proposed for the conservation of gypsum crust on historic limestones. by successive introduction of calcium and phosphorus sources into the crust by surface permeation. Due to the formation of hydroxyapatite coating, both surface protection and integral consolidation of the gypsum crust can be accomplished. The performances of the hydroxyapatite coating were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry, water stability, capillary water uptake, color difference and adhesion strength test. The experimental results indicated that the hydroxyapatite coating would be a good solution for the conservation of the gypsified historic limestone surface.