Hasil untuk "Materials of engineering and construction. Mechanics of materials"

Anisha Joseph, S Deepa, Nivya Mariam Paul et al.

Graphene oxide (GO)–incorporated tin oxide (SnO _2 ) nanocomposites have attracted significant attention due to their tunable structural, optical, and biological properties. In this work, pristine and GO-integrated SnO _2 nanocomposites were synthesized via a co-precipitation method with varying GO concentrations to investigate their physicochemical characteristics and antibacterial performance. X-ray diffraction analysis confirmed the formation of a tetragonal cassiterite SnO _2 structure with an average crystallite size of approximately 26 nm. FESEM and TEM studies revealed well-distributed GO–SnO _2 nanocomposites, while HRTEM analysis confirmed their crystalline nature with d-spacing values consistent with XRD results. Raman spectroscopy identified characteristic vibrational modes (A _1 g, B _2 g, and Eg), indicating structural integrity and defect-related features, whereas FTIR spectra exhibited prominent Sn–O stretching vibrations at 604 and 462 cm ^−1 . TGA/DTA analysis demonstrated good thermal stability with minimal weight loss beyond 400 °C. UV–Visible spectroscopy and Tauc analysis revealed a reduction in band gap upon GO incorporation, attributed to the formation of interstitial energy levels and enhanced electronic interaction. EDS analysis showed increased carbon content and notable variations in the Sn–O ratio with increasing GO concentration, suggesting modified surface reactivity. Antibacterial activity evaluated against Staphylococcus aureus , Escherichia coli , Klebsiella sp., and Pseudomonas sp. showed a significant enhancement for GO-integrated SnO _2 samples, with a maximum increase of approximately 66.7% against Pseudomonas sp and 37.5% against E.coli , calculated from zone of inhibition measurements. This enhancement is attributed to increased reactive oxygen species generation and effective bacterial membrane disruption induced by GO incorporation. The study highlights the potential of GO–SnO _2 nanocomposites as advanced antibacterial materials, contributing to Sustainable Development Goals SDG 3 (Good Health and Well-being) and SDG 9 (Industry, Innovation, and Infrastructure).

Nafel Dogdu

This study examines the dimensional accuracy and thermomechanical behavior of AlSi10Mg cubes (10 × 10 × 10 mm) fabricated using the Laser Powder Bed Fusion (LPBF) method, a widely applied additive manufacturing technique for lightweight alloys. Dimensional accuracy was evaluated experimentally through optical 3D scanning and compared with numerical predictions generated by Simufact Additive, while thermomechanical behavior was analyzed exclusively through simulation. Fabrication was carried out using fixed parameters of 200 W laser power, 0.1 mm spot diameter, and 0.04 mm layer thickness. To investigate process effects, nine volumetric energy density (VED) values ranging from 78.125 to 12.5 J/mm3 were applied by adjusting scanning speed and hatch spacing. Experimental–numerical comparisons showed error rates of 0.19 % along the x–z axis and 0.07 % along the y–z axis, confirming the predictive accuracy of the simulations. Surface deviation analysis indicated maximum and minimum differences of 0.0416 mm and 0.0371 mm. Thermal residual stresses varied between 79 and 300 MPa, with higher VED values causing stress concentrations in the upper layers. The findings demonstrate that VED strongly influences dimensional stability and stress distribution, highlighting Simufact Additive as a reliable and cost-effective tool for pre-production optimization and process control.

Kyriakos Komvopoulos

Yuantiao Xie, Dajian Huang, Wenjie Tang et al.

High drying shrinkage remains a major challenge in alkali-activated materials (AAM). In this study, porous palm fiber (PF) was modified with NaOH solution, saturated with water via vacuum impregnation, and incorporated as an internal curing agent into metakaolin-based AAM. The influence of PF on hydration behavior and microstructure was examined using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Vicat setting tests, and low-field nuclear magnetic resonance (LF NMR). The results showed that PF incorporation promoted the formation of additional hydration products and enhanced microstructural densification. Flexural strength was significantly improved, with the sample containing 1.5 % of 6 mm PF achieving the highest enhancement—an increase of 66.7 % compared with the control. After 28 days, a small amount of PF slightly increased the compressive strength. Vertical mortar expansion tests confirmed that PF effectively reduced drying shrinkage, with the most pronounced reductions observed in mixtures containing 1 % of 3 mm PF and 1.5 % of 6 mm PF, which decreased shrinkage by 42.9 % and 41.1 %, respectively, compared with the MK-AAM control sample (P0, 0 % PF). Overall, PF markedly mitigates drying shrinkage, improves flexural performance, and shows strong potential as a sustainable and environmentally friendly internal curing agent for AAM.

Fenghua Yu, Yongbiao Mu, Meisheng Han et al.

Polymer-based composite solid electrolytes (PCSEs) are increasingly studied in all-solid-state lithium-metal batteries (ASSLMBs) due to the combined advantages of better flexibility of polymer and higher ion conductivity of ceramic electrolytes. However, most reported PCSEs are overly thick, increasing internal resistances. Besides, the poor stability at the Li metal–electrolyte interfaces often leads to severe lithium dendrite formation and reduced cycling stability. Here, we fabricate an ultrathin PCSE with a thickness of 12.4 μ m, incorporating polyacrylonitrile (PAN) nanofibers as the structural matrix, and a filler with polyethylene oxide and Li _6.5 La _3 Zr _1.5 Ta _0.5 O _12 (LLZTO). Due to the formation of the LiCN layer on the surface of the lithium metal and the Li-ion transport pathways induced by the dehydrocyanation reaction at the LLZTO/PAN interfaces, the PCSE exhibits a high critical current density of 1.8 mA cm ^−2 and a low energy barrier of 0.278 eV for Li-ion transfer, accommodating the fast Li-ion migration to avoid Li-dendrite growth. In addition, the stable nitrile groups and the dehydrocyanation reaction ensure the electrochemical stability of the PCSE with a high oxidation voltage of 5.5 V and an exceptional cycling stability (2100 h) in Li||PCSE||Li symmetric cells. Additionally, the Li||PCSE||LiFePO _4 full cells demonstrate a high volumetric energy density of 338.3 Wh L ^−1 at 0.1 C and a robust stability over 100 cycles at 0.5 C. The study offers a new approach for fabricating ultrathin PCSEs and provides insights into the mechanisms of dendrite-free formation, guiding the development of high-performance PCSEs for ASSLMBs.

Lingyan Zhao, Hailong Bai, Xin Gu et al.

Although Sn3.0Ag0.5Cu solder (SAC305) has higher reliability, there are a large number of harmful voids in solder joints. Larger voids can reduce thermal conductivity of solder joints. However, as a microstructure growth inhibitor, the influences of Ag nanoparticles on voids growth are not clear at present. Herein, we prove that Ag nanoparticles can increase SAC305 solderability, but promote voids growth. Ag nanoparticles and SAC305 solder paste were mixed by mechanical stirring for 0.5 h. Next, SAC305- x Ag _P ( x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 wt%) was obtained. The results indicated that solder solderability was improved increasingly with Ag nanoparticles addition. The lower the amount of nanoparticles added, the greater the final loss. After being aged at 100 °C for 150 h, the voids stopped growing. Due to the violent reaction between Ag nanoparticles and flux, the final voids growth rate became faster, and the average voids size changed from 14.34% to 24.91%.

Miad Ali Siddiq

Yttrium zinc oxide (Zn _0.85 Y _0.15 O) nanostructures were stoichiometrically prepared by co-precipitation method. XRD, EDX, XPS, SEM, and TEM spectroscopy were examined to investigate structure, composition, and morphological characteristics. The synthesized nanocomposite exhibited polycrystalline structure with small crystallite size ∼ $27$ nm in which the particles appeared in sheets like shape with high atomic density on surface. The optical parameters including energy gap $({{\rm{E}}}_{{\rm{g}}})$ and refractive index $({\rm{n}})$ were investigated from (T%) and (R%) measurements through wavelength range from 300–900 nm. Al/Y:ZnO/p-Si/Ag Schottky diode was fabricated using thermal evaporating technique and its current–voltage $({\rm{I}}{\rm{\mbox{--}}}{\rm{V}})$ was analyzed using different models. The photodiode showed non-ideal behavior with ideality factor greater than unity and small potential barrier. Under various illuminations, the photodiode has revealed high photosensitivity attributed to trapped charge carriers at the interface. The charge carrier density ${{\rm{N}}}_{{\rm{d}}}$ and built-in voltage ${{\rm{V}}}_{{\rm{bi}}}$ were estimated from Mott Schottky (M–S) function suggesting high Schottky diode efficiency.

S Sudha, A Mary Saral

The goal of this study was to access the green production of zinc oxide nanoparticles (G-ZnO NPs) using aqueous extract of horse gram seeds (Macrotyloma Uniflorum). The precursor to the extract ratio (2.5:1) and pH value (8.5), along with the zinc nitrate concentration (0.5 M), had an impact on the particle size and the green synthesized ZnO nanoparticles. UV Spectroscopy inspection revealed formation of G-ZnO NPs with absorption at 320 nm which is the characteristic absorption of G-ZnO NPs. FTIR, XRD, SEM, EDX and TEM were used to characterize the green synthesized ZnO NPs. The findings demonstrated that the presence of secondary metabolites in the seed extractstabilize and contribute in the production of G-ZnO NPs. A dose-dependent increase in antibacterial activity was seen in evaluation of these NPs against Klebsiella, Staphylococcus aureus , Escherichia coli , Pseudomonas aeruginosa . The antioxidant activity and antidiabetic activity for G-ZnO NPs was also noted to be concentration dependent. The synthesized nanoparticles are found to interact with CT-DNA to produce a hypochromic shift. Further the studies on the G-ZnONPs in MCF-7 cells using the MTT test demonstrated greater cellular inhibition. The results validate that the green synthesized ZnO-NPs from horse gram seed possess good biological activities and can be an excellent biologically derived potential material which could be used in the drug discovery from natural products.

Carmen Alcázar, Rodrigo Moreno

Ceramic foams present special features that do not have the corresponding dense materials and hence they are widely used in a broad variety of applications. Titania has exceptional photoinduced properties with applications in membranes, bioceramics and photocatalysis and photovoltaics. However, in the photoinduced applications, the anatase phase is more active, but the sintering at high temperature leads to the transformation to rutile. The maintenance of anatase would require low sintering temperatures leading to a lack of consistency and very weak struts. To avoid this problem a possible alternative is to produce sintered rutile foams and to coat the strut walls with nanoparticles of anatase. This is a very simple and inexpensive method. In this work rutile foams are obtained by the replica method after a full optimization of the rheological behaviour of titania suspensions that are subsequently infiltrated with a colloidal titania suspension either in vacuum or using microwaves. The infiltrated foam can be sintered at 650 °C while maintaining the anatase phase.

S.D. Capitão, L.G. Picado-Santos, F. Martinho

Yue Kang, Chang Xu, Ling'ao Meng et al.

Exosomes derived from human adipose-derived stem cells (hADSCs-Exos) have shown potential as an effective therapeutic tool for repairing bone defects. Although metal-organic framework (MOF) scaffolds are promising strategies for bone tissue regeneration, their potential use for exosome loading remains unexplored. In this study, motivated by the potential advantages of hADSCs-Exos and Mg-GA MOF, we designed and synthesized an exosome-functionalized cell-free PLGA/Mg-GA MOF (PLGA/Exo-Mg-GA MOF) scaffold, taking using of the benefits of hADSCs-Exos, Mg2+, and gallic acid (GA) to construct unique nanostructural interfaces to enhance osteogenic, angiogenic and anti-inflammatory capabilities simultaneously. Our in vitro work demonstrated the beneficial effects of PLGA/Exo-Mg-GA MOF composite scaffolds on the osteogenic effects in human bone marrow-derived mesenchymal stem cells (hBMSCs) and angiogenic effects in human umbilical endothelial cells (HUVECs). Slowly released hADSCs-Exos from composite scaffolds were phagocytosed by co-cultured cells, stabilized the bone graft environment, ensured blood supply, promoted osteogenic differentiation, and accelerated bone reconstruction. Furthermore, our in vivo experiments with rat calvarial defect model showed that PLGA/Exo-Mg-GA MOF scaffolds promoted new bone formation and satisfactory osseointegration. Overall, we provide valuable new insights for designing exosome-coated nanocomposite scaffolds with enhanced osteogenesis property.

Da Gong, Zhenghang Li, Yuyan Song et al.

Industrial design (ID) refers to industrial product design based on engineering, aesthetics, and economy. Traditional industrial design refers to the creative activities of designing and designing products produced by industrial means to make the best match with the environment and the people who use them. This paper aims to study how to analyze and study the application of aesthetic art, that is, the concept of industrial design, based on functional nanomaterials, and this paper describes the electrospinning technology. This paper puts forward the problem of the industrial design concept, which is based on design aesthetics. Therefore, this paper focuses on the development of industrial design and related elements. The application of functional nanomaterials in industrial design is designed and analyzed. The experimental results show that when the acid soaking time is 4∼12 days, the mechanical strength of the nanofiber membrane is 7∼9 MPa. Compared with the untreated nanofiber membrane, it increased by 25.4%∼48.8%, and the ductility decreased from 81.5% to 44.1%.

Yaping Wang, Xinguang Xu, Xian Zhao et al.

Abstract Electrically controlled half-metallicity in antiferromagnets is of great significance for both fundamental research and practical application. Here, by constructing van der Waals heterostructures composed of two-dimensional (2D) A-type antiferromagnetic NiI2 bilayer (bi-NiI2) and ferroelectric In2Se3 with different thickness, we propose that the half-metallicity is realizable and switchable in the bi-NiI2 proximate to In2Se3 bilayer (bi-In2Se3). The polarization flipping of the bi-In2Se3 successfully drives transition between half-metal and semiconductor for the bi-NiI2. This intriguing phenomenon is attributed to the joint effect of polarization field-induced energy band shift and interfacial charge transfer. Besides, the easy magnetization axis of the bi-NiI2 is also dependent on the polarization direction of the bi-In2Se3. The half-metallicity and magnetic anisotropy energy of the bi-NiI2 in heterostructure can be effectively manipulated by strain. These findings provide not only a feasible strategy to achieve and control half-metallicity in 2D antiferromagnets, but also a promising candidate to design advanced nanodevices.

Jongmin Byun, Young-In Lee, Sung-Tag Oh

An optimum route to fabricate the Ni-based superalloy with homogeneous dispersion of Y2O3 particles is investigated. Ni-based ODS powder was prepared by high-energy ball milling of gas-atomized alloy powders and Y2O3 particles treated with a high-pressure homogenizer. Decrease in particle size and improvement of dispersion stability were observed by high-pressure homogenization of as-received Y2O3 particles, presumably by the powerful cavitation forces and by collisions of the particles. Microstructural analysis for the ball-milled powder mixtures reveal that Ni-based ODS powders prepared from high-pressure homogenization of Y2O3 particles exhibited more fine and uniform distribution of Ni and Y elements compared to the as-received powder. These results suggested that high-pressure homogenization process is useful for producing Ni-based superalloy with homogeneously dispersed oxide particles.

D. Gonzalez-Ortiz, C. Salameh, M. Bechelany et al.

Nanocomposite materials are widely studied because of their unique design opportunities and properties. They can be classified into three main groups in function of the matrix used: polymer-based, ceramic-based, and metal-based nanocomposites. The nanofiller choice is one of the most important steps because it will improve the nanocomposite properties. This review focuses on boron nitride as nanofiller because of its extraordinary properties: high thermal and chemical stability, good mechanical strength, superior resistance to oxidation, good thermal conductivity, and electrical insulation. The goal of this review is to provide an overview on the synthesis methods to produce boron nitride–based nanocomposites, particularly polymer- and ceramic-based nanocomposites, and on their potential applications in promising fields, such as energy, environment, and health.

LIU Xiao-hui, WANG Shuai-xing, DU Nan et al.

Micro-arc oxidation (MAO) ceramic coatings were prepared on Ti₂AlNb alloy in silicate/phosphate electrolytes with different concentrations of Na₂WO₄. The influence of Na₂WO₄ on the coating growth process, coating structure and composition was analyzed by SEM, XRD and XPS. The tribological behavior of MAO coatings was evaluated by the ball-disc wear test. The results show that the growth rate of MAO coating in electrolyte without Na₂WO₄ is only 0.08<i>μ</i>m/min, meanwhile, the coating is loose and rough, and "networks" connecting with big pores exist on the coating surface.The main phase compositions of this coating are rutile TiO₂, anatase TiO₂, Al₂O₃, and Nb₂O₅. The addition of Na₂WO₄ in the electrolyte shortens the time before sparking of Ti₂AlNb alloy, increases the growth rate of the coating, improves the uniformity of coating and meanwhile, a small amount of WO₃ is introduced in the coating. Besides, MAO coatings formed in the participation of Na₂WO₄ have better wear resistance. Severe abrasive wear occurs when the test is made on Ti₂AlNb alloy with Si₃N₄, the friction coefficient reaches 0.5-0.7. Both the friction coefficient and wear rate decrease obviously when Ti₂AlNb is treated by MAO. The friction coefficient and wear rate of MAO coating prepared in the electrolyte with 4g/L Na₂WO₄ are 0.24 and 6.2&#215;10^-4mm³/(N&#183;m), respectively. Only "fish scales" caused by fatigue wear appears on the coating surface.

Vilor L. Zakovorotny, Valery E. Gvindzhiliya

Introduction. Any metal-cutting machine has errors of the executive elements movement depending on its geometric accuracy and state. These errors change the forming motions indirectly, through their transformation by the dynamic cutting system with account for the elastic deformations of the tool and the workpiece. Materials and Methods. Laws of the relation between the executive elements and forming paths for the longitudinal cutting case are considered. All deformation displacements are counted off from the independent coordinate system anchored to the carrier system of the machine which is considered to be absolutely rigid and non-deforming. Research Results. A mathematical transformation model consisting of two elastic-deformation subsystems on the part of the tool and workpiece that interact through the dynamic link generated by the cutting process is proposed. This model allows for the errors of the executive elements movement. They are specified by the kinematic disturbances and spindle wavering, and a workpiece in the space. Discussion and Conclusions. Therefore, as opposed to the known studies, it is shown how the mathematical formulation and parameters of the dynamic link generated under the cutting process are changed depending on the kinematic and other types of disturbances. Two types of disturbances are fully considered: those inducing speed variations of the tool motion relative to the workpiece in the direction to the caliper mobility, and disturbances in the form of oscillating displacements in the orthogonal direction to the feed velocity attitude. These disturbances are generated as radial and axial spindle wavering, and as speed variations of the longitudinal feed and variations of the caliper position relative to the ideal rotation axis of the part. It is shown, that the law of the disturbance transformation into the forming movements trajectories depends on the frequency content of the disturbances. The examples are provided, and the conclusions about the transformation properties are made. In particular, it is shown that the speed variations in the direction to the longitudinal feed with the frequency equal to or multiple of the spindle rotation frequency in no way image into the forming movement trajectories.

Michael V. Swain, N. Dorin-Ruse, S.N. Aqida

T. Raghavendra, B.C. Udayashankar

Miriam Ledererova

Nanotechnology is an interdisciplinary, cross-cutting technology and incorporates a number of other areas. There are several definitions for it. Nanomaterials are now used for many purposes and in almost all industries, healthcare, engineering, construction, chemical industry, automobile industry to the aerospace industry. Construction is one of the industrial sectors that among the first identified nanotechnology as a promising technology. Nanotechnology, Department of the 21st century, has already become almost a normal part of construction.