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Improved output voltage of 0–3 cementitious piezoelectric composites with basalt fibers
摘要： In this paper, basalt fibers (BF) was employed as high modulus component with good interface bonding with cement matrix to enhance local stress applied on piezoelectric ceramic particles in 0–3 cementitious piezoelectric composites (0–3 CPCs). The effect of content of BF varying from 0.00 vol% to 0.23 vol% on the mechanical, piezoelectric and dielectric properties of 0–3 CPCs and the output voltage of 0–3 CPCs sensor was evaluated. The results showed that amplitude of output voltage of the 0–3 CPCs sensor with 0.12 vol% BF maximized at 4.98 V, which was 60.0% higher than that of the 0–3 CPCs sensor without fibers for the compact structure of the 0–3 CPCs and good interface bonding between BF and cement matrix as a reason of good stress transfer in the composites. While the split tensile strength, piezoelectric voltage constant (g33), piezoelectric strain constant (d33), relative dielectric constant (εr) and dissipation factor (tanδ) was 13.1 MPa, 11.36 × 10?3 V m/N, 43 pC/N, 430.0 and 0.43, respectively. It provided a novel method to improve the mechanical-electrical response of piezoelectric sensor by enhancing local stress applied on piezoelectric ceramic particles in the piezoelectric composites.
关键词： 0–3 cementitious piezoelectric composites,Stress transfer,Basalt fibers,Output voltage
更新于2025-09-23 15:19:57
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Microstructure and mechanical properties of a MoSi2-Mo5Si3 eutectic composite processed by laser surface melting
摘要： Laser surface melting (LSM) of a single-crystal substrate of a MoSi2-Mo5Si3 eutectic composite has been performed to check the feasibility of mechanical property improvement through microstructure re?nement and seeded growth of the eutectic composite on top of the seed composite single crystal by additive manufacturing processes using scanned laser beam. LSM is proved to be capable of obtaining a eutectic composite maintaining the eutectic script-lamellar microstructure as well as crystallographic orientations of the substrate single crystal. The eutectic script-lamellar microstructure is considerably re?ned from several micrometers (the substrate) to several tenths nanometers (43 ± 7 nm) after LSM processing while maintaining the orientation relationship. Due to the microstructure re?nement, the hardness increases by about 38% from 11.60 ± 0.04 GPa (substrate) to 15.96 ± 0.42 GPa (LSMed region) and the fracture toughness increases by about 34% from 3.8 ± 0.3 MPa m1/2 (substrate) to 5.1 ± 1.5 MPa m1/2 (LSMed region).
关键词： Mechanical properties,Microstructure,Molybdenum silicides,Laser processing,Eutectic composites
更新于2025-09-23 15:19:57
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Wear resistance and microstructures of nanocrystals reinforced laser melt deposited composite coating
摘要： The Stellite SF12-TiC-Mo-Sn laser melt deposited (LMD) composite coating was produced on a TA1 titanium alloy. Such composite coating was researched using scanning electron microscope (SEM) and a high-resolution transmission electron microscope (HRTEM). It was con?rmed that Ti3Sn nanocrystals appeared at an intersplat region, which was very compatible to the d-space of the Ti3Sn at an orientation of (101). The Ti3Sn particles were surrounded by the amorphous phases. Under the action of such composite coating, the micro-hardness distribution of the substrate surface is in a range of 1350–1500 HV0.2, and the wear volume loss is 1/13 of a TA1 alloy.
关键词： composites,sliding wear,lasers,titanium
更新于2025-09-19 17:15:36
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[ASME ASME 2018 International Mechanical Engineering Congress and Exposition - Pittsburgh, Pennsylvania, USA (Friday 9 November 2018)] Volume 1: Advances in Aerospace Technology - Lightning Strike Protection and EMI Shielding of Fiber Reinforced Composite Using Gold and Silver Nanofilms
摘要： Carbon fiber reinforced composites are very much imperative to future-generation aircraft structures. However, lightning strike protection (LSP) and electromagnetic interference (EMI) are main concerns. Carbon fibers have very good mechanical properties with the best strength-to-weight ratio, but they are very poor conductors of electricity. These fibers must be reinvented to increase the surface conductance to provide high electrical conductivity to the aircraft structure. The present study deals with preparing composite sandwich structures of carbon fibers used for commercial nacelle applications subject to lightning strike effects with different metallic nanofilm of gold (Au) and silver (Ag) measuring approximately 100 nm. These metallic nanofibers were co-cured on the top layers of composite panels during vacuum curing process. In our laboratory, lightning strike results for a composite sandwich structure using nanofilms were obtained to observe lightning strike damage and structural tolerance necessary tolerance capability. the damage Resistance of composite panels with metallic nanofilm under various strains was studied. It was found that resistance of the metallic nanofilm increased under strain. The voltage was found to be low; hence, an increase in current would help to reduce the damage on composite panels due to lightning strikes, and the same theory would be applicable to EMI. No EMI was absorbed or reflected in the nanofilm using the P-static test. When lightning strikes were applied to composite coupons, the resulting damage from the currents was reduced on those with metallic nanofilms.
关键词： Lightning Strike Protection,Electromagnetic Interference,Composites,Metallic Nanofilms
更新于2025-09-19 17:15:36
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Nondestructive imaging of hidden defects in aircraft sandwich composites using terahertz time-domain spectroscopy
摘要： Aircraft sandwich composites are superior to ordinary composites and have been largely used in the manufacture of military aircraft. This study attempts to investigate the efficacy of terahertz (THz) time-domain spectroscopy (TDS) imaging technology in detecting hidden defects in aircraft glass fiber (GF) sandwich composites. The defects of various sizes, such as debonding, delamination, and multi-delamination, at different depths in GF A-sandwich structure composites with foam core, C-sandwich structure composites with honeycomb core, and sheet-to-sheet cementing structure composites were evaluated. The THz frequency-domain amplitude and time-domain amplitude imaging algorithms were used to visualize the defects simulated by ultrathin double-layer Teflon inserts. And the suitable image processing methods which include wavelet-based fusion and multiscale edge representation were employed. With a combination of high-resolution THz C-scan and B-scan imaging, both the horizontal size and location, and the vertical depth and thickness of the defects were obtained in three dimensions. This study experimentally demonstrated that THz imaging technology can clearly detect various hidden defects in aircraft GF sandwich composites through reflection or transmission imaging mode.
关键词： image processing,debonding,multi-delamination,Aircraft sandwich composites,terahertz time-domain spectroscopy,nondestructive testing
更新于2025-09-19 17:15:36
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Robust Polymer Matrix Based on Isobutylene (Co)Polymers for Efficient Encapsulation of Colloidal Semiconductor Nanocrystals
摘要： We introduce new oxygen- and moisture-proof polymer matrices based on polyisobutylene (PIB) and its block copolymer with styrene (poly(styrene-block-isobutylene-block-styrene), PSt-b-PIB-b-PSt) for encapsulation of colloidal semiconductor nanocrystals. In order to prepare transparent and processable composites, we developed a special procedure of the nanocrystal surface engineering including ligand exchange of parental organic ligands to inorganic species followed by attachment of specially designed short-chain PIB functionalized with amino-group (PIB-NH2). The latter provides excellent compatibility of the particles with the polymer matrices. As colloidal nanocrystals, we chose CdSe nanoplatelets (NPLs), since they possess a large surface and thus are very sensitive to the environment, in particular in terms of their limited photostability. The encapsulation strategy is quite general and can be applied to a wide variety of semiconductor nanocrystals, as demonstrated on the example of PbS quantum dots. All obtained composites exhibited excellent photostability being tested in a focus of a powerful white-light source, as well as exceptional chemical stability in a strongly acidic media. We compared these properties of the new composites with those of widely used polyacrylate based materials, demonstrating the superiority of the former. The developed composites are of particular interest for application in optoelectronic devices, such as color-conversion light emitting diodes (LEDs), laser diodes, luminescent solar concentrators, etc.
关键词： photoluminescence,nanocrystals-in-polymer composites,lead sulfide quantum dots,semiconductor nanocrystals,isobutylene (co)polymers,cadmium selenide nanoplatelets,photostability,chemical stability
更新于2025-09-19 17:15:36
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Efficiency Improvement of Cellulose Derivative Nanocomposite Using Titanium Dioxide Nanoparticles
摘要： TiO2 nanoparticles were incorporated into hydroxypropyl methylcellulose (HPMC) nanocomposites films. The nanocomposites were investigated in relation to their structural, mechanical, and surface properties using scanning electron microscopy (SEM). The water solubility of the films showed a small decrease with respect to the nanocomposites films' content of the TiO2 nanoparticles. Incorporation of TiO2 nanoparticles in the films improved their mechanical and barrier properties significantly. SEM images showed that the lower concentration of nanoparticles were better dispersed in the nanocomposite matrix. The disk diffusion studies revealed a great bactericidal effectiveness for nanocomposite films containing smaller concentration of particles. In general, it was observed that the incorporation of the nanoparticles positively affected the structural properties and enhanced the antibacterial applications of the nanocomposites.
关键词： Biomaterial,Nano-Structures,Polymer-Matrix Composites,Mechanical Properties
更新于2025-09-19 17:15:36
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Surface grafting of fluorescent polymers on halloysite nanotubes through metal-free light-induced controlled polymerization: Preparation, characterization and biological imaging
摘要： Halloysite nanotubes (HNTs) are a kind of aluminosilicate clay with a unique hollow tubular structure that has been intensively explored for various applications especially in biomedical fields owing to their excellent biocompatibility, biodegrading potential and low cost. Surface modification of HNTs with functional polymers will greatly improve their properties and endow new functions for biomedical applications. In this work, a light-induced reversible addition-fragmentation chain transfer (RAFT) polymerization was introduced to successfully prepare HNTs based fluorescent HNTs/poly(PEGMA-Fl) composites in the presence of oxygen using diacrylate-fluorescein and poly (ethylene glycol) methyl ether methacrylate (PEGMA) as the monomers. Without other catalysts, heating, and deoxygenation procedure, the polymerization process can take place under mild conditions. Besides, owing to the introduction of fluorescein and PEGMA on the surface of HNTs, the resultant HNTs/poly(PEGMA-Fl) composites display high water dispersibility and stable fluorescence. The results from cell viability examination and confocal laser scanning microscopy also demonstrated that HNTs/poly(PEGMA-Fl) composites could be internalized by L929 cells with bright fluorescence and low cytotoxicity. Taken together, we developed a novel photo-initiated RAFT polymerization method for the fabrication of HNTs based fluorescent polymeric composites with great potential for biomedical applications. More importantly, many other multifunctional HNTs based polymer composites could also be fabricated through a similar strategy owing to good designability of RAFT polymerization.
关键词： fluorescent composites,biomedical applications,Halloysite nanotubes,light-induced polymerization,surface-initiated RAFT polymerization
更新于2025-09-19 17:13:59
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Selective synthesis of Bi2S3/BiOCl composites as electrode for high performance photodetector
摘要： Bi2S3/BiOCl composites were synthesized through a facile polyol refluxing process. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectrometer (UV-vis DRS). Herein, a junction was constructed by simply depositing a new Bi2S3/BiOCl nanocomposite film on FTO (Fluorine Doped Tin Oxide) substrate. The new Bi2S3/BiOCl-based photodetector exhibit high sensitivity, high on/off ratio of 330 times, fast rise time of 0.07 s and decay time of 0.07 s, which is the first report among all reported Bi2S3/BiOCl composites-based optoelectronic devices. Our results imply that the new type of photodetector based on Bi2S3/BiOCl composites has great potential in next generation high-performance optoelectronic devices. According to the sensing mechanism discussed, the good optoelectronic performance may be attributed to the Bi2S3/BiOCl composites as well as the schottky junction between FTO electrodes and Bi2S3/BiOCl products.
关键词： photodetector,polyol refluxing process,optoelectronic devices,Bi2S3/BiOCl composites
更新于2025-09-19 17:13:59
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Graphenea??based polymer composites with ultraa??high ina??plane thermal conductivity: A comparison study between optothermal Raman spectroscopy and laser flash method
摘要： We developed a simple solution mixing and molding process for the incorporation of graphene nano-flakes (GNFs) in polymer films. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(ethylene-co-methacrylic acid) (PEMAA) were used for preparation of the samples. The orientation and stacking of GNFs were confirmed using a scanning electron microscope. The thermal conductivity values for these composites were obtained using (1) laser flash method (commercially available) and (2) an optothermal Raman (OTR) technique (homemade device). The former measures the thermal diffusivity (α) and one needs to measure the density (ρ) and the heat capacity (Cp) of the composites in order to measure the in-plane thermal conductivity (κ = α.ρ.Cp), while the latter measures the in-plane thermal conductivity directly from the relation between the excitation power and the position of the Raman resonance. The data obtained from Raman spectroscopy were analyzed, assuming heat propagation in three and two dimensions. The Raman results obtained based on the two-dimensional model were very close to the results obtained using the laser flash method with less than 10% difference. The OTR spectroscopy was found to be a promising technique for measuring the in-plane thermal conductivity of carbon-based polymer composites. PVDF-HFP and PEMAA composite films with very high in-plane thermal conductivity (25 W m?1 K?1) were obtained through the incorporation of GNFs (20 wt % concentration). Considering a very low thermal conductivity of these polymers (<0.2 W m?1 K?1), this corresponds to a large enhancement of roughly 12 400%. ? 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48927.
关键词： nanotubes,conducting polymers,fullerenes,graphene,thermal properties,composites
更新于2025-09-19 17:13:59