Yazar "Shahed, Chowdhury Ahmed" seçeneğine göre listele

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    Antibacterial mechanism with consequent cytotoxicity of different reinforcements in biodegradable magnesium and zinc alloys: A review
    (KeAi Communications Co., 2023) Shahed, Chowdhury Ahmed; Ahmad, Faiz; Günister, Ebru; Foudzi, Farhana Mohd; Ali, Saad; Malik, Khurshid; Harun, Wan Sharuzi Wan
    Benefits achieved by the biodegradable magnesium (Mg) and zinc (Zn) implants could be suppressed due to the invasion of infectious microbial, common bacteria, and fungi. Postoperative medications and the antibacterial properties of pure Mg and Zn are insufficient against biofilm and antibiotic-resistant bacteria, bringing osteomyelitis, necrosis, and even death. This study evaluates the antibacterial performance of biodegradable Mg and Zn alloys of different reinforcements, including silver (Ag), copper (Cu), lithium (Li), and gallium (Ga). Copper ions (Cu2+) can eradicate biofilms and antibiotic-resistant bacteria by extracting electrons from the cellular structure. Silver ion (Ag+) kills bacteria by creating bonds with the thiol group. Gallium ion (Ga3+) inhibits ferric ion (Fe3+) absorption, leading to nutrient deficiency and bacterial death. Nanoparticles and reactive oxygen species (ROS) can penetrate bacteria cell walls directly, develop bonds with receptors, and damage nucleotides. Antibacterial action depends on the alkali nature of metal ions and their degradation rate, which often causes cytotoxicity in living cells. Therefore, this review emphasizes the insight into degradation rate, antibacterial mechanism, and their consequent cytotoxicity and observes the correlation between antibacterial performance and oxidation number of metal ions.
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    Influence of drilling parameters on the delamination and surface roughness of insulative-coated glass/carbonhybrid composite
    (Hindawi, 2023) Kabir, Sarower; Ahmad, Faiz; Shahed, Chowdhury Ahmed; Günister, Ebru
    Drilling in synthetic fiber-reinforced polymer composites is facing challenges due to their anisotropic, inhomogeneity, and abrasive machining behavior. The joining of composite parts using fasteners is commonly done by the drilling, and the generated heat is one of the main causes to damage the drilled hole in the composite. Moreover, the quality of drilled hole is crucial for joining parts effectively. The paper presents the design, fabrication, and drilling of a hybrid fiber-reinforced polymer (HFRP) based on insulative coating. These composites were fabricated using vacuum infusion molding (VIM) and coated with different thicknesses to investigate the influence of drilling parameters and associated damages. Cutting speed, feed rate, and coating thicknesses were varied, and a full factorial design of the experiment was formulated. High-speed steel (HSS) twist drill bit was used to drill the coated composite and test samples, and delamination factor and surface roughness were measured. ANOVA and full factorial response optimizer were used to evaluate the influence and optimum drilling parameters. The delamination factor (DF) at the entry and surface roughness were found to decrease with the increasing cutting speed. However, the DF at the exit showed the opposite. Coating thickness influenced the delamination at the entry whereas delamination at the exit has been found insignificant. For drilling HFRP composite with 1 mm coating thickness, 3000 RPM spindle speed and 0.08 mm/rev feed rate were found optimum parameters in minimizing surface roughness and delamination damage. However, 6000 RPM and 0.02 mm/rev were found optimum parameters for drilling HFRP composite with 1.5 mm coating thickness.
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    Mechanical investigation of kenaf/carbon hybrid composites for building and construction applications
    (American Society of Civil Engineers, 2024) Malik, Khurshid; Ahmad, Faiz; Yunus, Nurul Azhani; Günister, Ebru; Shahed, Chowdhury Ahmed
    Single-kenaf fiber-reinforced polymer composites are typically characterized by relatively low strength and stiffness properties that make them unsuitable for structural applications. However, they are lightweight, economical, and ecofriendly. This paper presents a study on the manufacturing and mechanical characterization of bidirectional kenaf (K) fiber-reinforced epoxy composites hybridized with carbon (C) fibers in various stacking sequences and the effects of hybridization on salient physical and mechanical properties. Single and hybrid fiber composites were fabricated utilizing the vacuum infusion molding technique. The density, tensile, flexural, and interlaminar shear properties in hybrid composites increased significantly when carbon fiber volume increased from 9% to 16%. Stacking sequences in a hybrid affected the mechanical properties of the composites. The highest tensile strength and modulus were shown by the seven-layer hybrid composite with an alternate K/C stacking sequence and C layers as skin layers, i.e., C/K/C/K/C/K/C, among all tested hybrid composites. Sandwich design in the hybrid (C2/K3/C2) had higher flexural strength (+300%), flexural modulus (+414%), interlaminar shear strength (+278%), lower water absorption (−46%), and thickness swelling (−30%) compared to single-fiber kenaf/epoxy composites. Density increased by 5% in hybrid composites. The highest fracture toughness (+134%) was achieved using the dual sandwich design structure hybrid (C/K2/C2/K2/C). The developed composite has applications in stairways, walkways, and bridges.
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    Microstructure and mechanical performance of low-cost biomedical-grade titanium-316L alloy
    (Elsevier, 2023) Shahed, Chowdhury Ahmed; Ahmad, Faiz; Günister, Ebru; Altaf, Khurram; Ali, Saad; Raza, Abbas; Malik, Khurshid; Haider, Waseem
    A 316L stainless steel (SS) alloy was developed with 1, 3, and 5 vol% titanium (Ti) reinforcement using the powder injection molding route, representing a low-cost option for biomedical implants. The investigation encompassed 1300 °C, 1350 °C, and 1380 °C sintering temperatures to ascertain the optimal physical and mechanical properties. Both sintering temperature and Ti influenced sintered density, and Ti mitigated the deleterious effects of residual carbon. At higher sintering temperatures, carbon and silicon tended to migrate and accumulate at the brink of Ti, leading to the formation of intermetallic compounds and increased brittleness. Dispersed Ti particles within the 316L matrix acted as nucleation sites and enhanced solid solubility with improved density. An astounding 96.11 % sintered density was achieved at 3 vol% Ti sample sintered at 1380 °C. During the tensile test, 5 vol% Ti at 1380 °C exhibited a low modulus of 58.9 GPa, which is highly desirable for orthopedic implant application. The XRD, SEM, tensile test, and nano-indentation results collectively provide evidence of beta-titanium formation during the sintering process. Conversely, the sample incorporating 3 vol% titanium, sintered at 1380 °C, demonstrated a balanced performance, showcasing 432.94 ± 12.8 MPa ultimate tensile strength, 3.06 ± 0.17 % elongation, 74.2 GPa modulus, and 322 MPa and 423 MPa 0.2 % offset flexural and compressive yield strengths, respectively. Notably, an improvised wear resistance test underscored its aptitude for sliding wear resistance, solidifying its potential as a promising candidate for biomedical implants.