فهرست مطالب
Advanced Ceramics Progress
Volume:10 Issue: 2, Spring 2024
- تاریخ انتشار: 1403/11/07
- تعداد عناوین: 6
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Pages 1-8Addition of MoSi2 to Si3N4 matrix leads to an improvement in the mechanical properties and oxidation resistance as well as an increase in the electrical conductivity of the produced composite, thus allowing for machining via Electrical Discharge Machining (EDM) or its potential applications as pieces of tinder (igniter) in diesel engines or aerospace devises. In this study, Si3N4 powder was mixed with MoSi2 (synthesized in the previous work through SHS) and additives such as MgO, CeO2, and Y2O3 in varying percentages. Some of the mixed powders were milled using a SPEX 8000. All material powders were then formed into pellets using a uniaxial press. The pellets were then sintered in an atmosphere-controlled tube furnace in argon at a maximum temperature of 1500 °C with a soaking time of 2 or 3 hours through Pressureless Sintering (PLS) process. The sintered samples were analyzed at different stages: density measurements, phase and microstructure studies using XRD and SEM, and HV microhardness measurements. The results demonstrated that Si3N4-MoSi2 structural porous composites were successfully prepared and optimized by controlled parameters such as pressing pressure, milling process, type and percentage of additives, and soaking times.Keywords: Porous Composite, Si3n4, Mosi2, Additive, Paritially Sintered
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Pages 9-16In this study, Ni-Co-La₂O₃-CeO₂ composite coatings were deposited on an AISI 430 steel substrate using the electroless method. The microstructure and corrosion behavior of coatings obtained at different bath pHs (8, 8.5, 9, 9.5, and 10) were investigated. Coating characterization was performed using a scanning electron microscope (SEM). To assess corrosion resistance, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were conducted in a 3.5% NaCl aqueous solution. Microstructural examination showed that the coating formed at pH 9 has greater uniformity than the other coatings. Additionally, under this condition, the highest weight percentage of reactive elements (La and Ce) was present in the coating. The Tafel polarization test results demonstrated that applying the composite coating significantly reduces the corrosion current density of the uncoated sample. The positive effect of the coating on increasing the corrosion resistance of the steel is particularly significant for the coating formed at pH 9. In this case, the corrosion current density was reduced by more than 20 times (from 17.35 µA·cm⁻² to 0.8 µA·cm⁻²) compared to the uncoated sample. The results obtained from electrochemical impedance spectroscopy (EIS) further support these findings. According to the EIS data, the charge transfer resistance for the uncoated sample was 4089 Ω·cm², while applying coatings at pH levels of 8, 8.5, 9, 9.5, and 10 increased the charge transfer resistance to 13,214, 19,840, 28,318, 17,060, and 9446 Ω·cm², respectively.Keywords: Corrosion Resistance, Composite Coating, Potentiodynamic Polarization, Electrochemical Impedance Spectroscopy
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Pages 17-22
Microwave sintering has emerged as a promising technique for the fabrication of Ti-based alloys, offering unique advantages over conventional sintering methods. The selective and volumetric heating capabilities of microwaves can result in rapid densification, microstructural refinement, and enhanced properties in Ti-Cu alloy systems. Therefore, this study aimed to synthesize an intermetallic alloy of Ti-50 at. % Cu through high-energy mechanical milling and a microwave-assisted sintering method. The objective was to expedite the sintering process of the Ti-Cu alloy using microwave assistance and analyze how this method influences the phases formed and the properties of the alloy. A Ti-50 at. % Cu powder mixture was milled for 30 hours under an argon atmosphere, then uniaxially compacted to form green samples, which were subsequently sintered by microwave heating. This method allowed for rapid consolidation without significant grain growth within a short sintering period. The effects of the sintering method and temperature on microstructure and mechanical properties were studied. The density of the sintered samples increased with rising temperatures, with the highest density of 6.54 g/cm³ obtained at 900°C. Microstructural examination revealed that the Ti3Cu4 and TiCu phases primarily formed, with an average grain size of approximately 28 nm. A high micro-hardness of ~880 HV was achieved for the dense alloy prepared using this method.
Keywords: Mechanical Alloying, Sintering, Densification, Ti-Cu Alloy -
Pages 23-31Stainless steel 316L (SS316L) is a good candidate for metal implants due to its excellent tensile strength and high corrosion resistance. However, its surface needs to be improved to enhance biocompatibility, bioactivity, and antimicrobial functions. Among bioceramics, hydroxyapatite (Ca10(PO4)6(OH)2) is widely used in medical applications due to its mineral composition, which is similar to the natural hard tissues of the body, and its biomimetic morphology. Chitosan possesses attractive biological properties such as good biodegradability, non-toxicity, biocompatibility, and cellular bioavailability. Graphene oxide demonstrates antibacterial activity against bacteria, fungi, and viruses, which can help limit cancer-causing infections in surgeries. Accordingly, an HA-based nanocomposite (HA-CS-GO) was deposited on SS316L sheets by electrophoretic deposition. Nanoparticle HA was synthesized via the sol-gel method. The coating was applied at 80V for 1 minute. To study the products and coating, various analyses were employed, including XRD, SEM, FTIR, electrochemical impedance spectroscopy (EIS), and polarization analysis. The results confirmed the successful synthesis of HA. The nanocomposite coating (thickness ~12.7 µm) was properly deposited on SS316L. The corrosion resistance improved with the coating; the current density decreased from 7.6 to 1.4 µA·cm⁻². The mechanism of corrosion was evaluated by EIS data. The corresponding equivalent circuit was proposed, and the dielectric capacitor and resistance values were estimated.Keywords: Nanocomposite, Coating, Single-Layer Graphene Oxide, Hydroxyapatite, Chitosan, Corrosion
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Pages 32-39This study systematically examined the incorporation of graphene oxide (GO) and silver nanoparticles (Ag NPs) into chitosan (CS) films (CS-GO/Ag) to understand their impact on structural, mechanical, and electrical properties. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed the successful integration of GO and Ag NPs into the chitosan matrix. The XRD patterns revealed the presence of GO and silver nanoparticles, with peaks indicating the face-centered cubic structure of silver and partial oxidation. FTIR spectra showed strong interactions between chitosan's amino and hydroxyl groups and the GO and Ag NPs. Field Emission Scanning Electron Microscopy (FESEM) revealed that pure chitosan films had a smooth, uniform surface, whereas the addition of GO introduced surface roughness due to GO sheet agglomeration. The CS-GO/Ag films displayed further roughness, with spherical and cubic Ag NPs enhancing surface texture and potentially improving mechanical and electrical properties. Mechanical testing showed that CS-GO/Ag films had superior performance, exhibiting increased Young's modulus and tensile strength, suggesting that GO and Ag NPs significantly enhanced the film’s stiffness and flexibility. Electrical conductivity measurements indicated that, while pure chitosan films were insulating, the addition of GO improved conductivity. CS-GO/Ag films demonstrated the highest electrical conductivity due to the excellent conductive properties of Ag NPs, which facilitated charge transfer. These findings suggest that CS-GO/Ag composite films hold promise for applications requiring enhanced mechanical and conductive properties.Keywords: Chitosan, Ag Nanoparticles, Mechanical Properties, Graphene Oxide, Composite
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Pages 40-46Due to the wide range of applications of strontium ferrite in various industries and the increasing demand for lightweight devices with enhanced magnetic properties, this study aims to fabricate and optimize the magnetic performance of strontium ferrite nanofibers using the electrospinning method. The purpose of this research is to investigate the effects of different polyvinylpyrrolidone (PVP) concentrations and electrospinning parameters—such as applied voltage, feed rate, and the distance between the collector and nozzle—on the microstructure and magnetic properties of the nanofibers. The results of energy-dispersive spectroscopy (EDS) confirmed the presence of Fe, O, and Sr elements, while X-ray diffraction (XRD) analysis indicated the successful synthesis of single-phase strontium ferrite. Field-emission scanning electron microscopy (FE-SEM) images showed that optimizing the electrospinning parameters resulted in nanofibers with diameters of less than 100 nm and considerable lengths. Vibrating sample magnetometry (VSM) analysis of the optimized sample yielded a saturation magnetization of 60 A·m²/kg, residual magnetization of 23 A·m²/kg, and a coercivity of 4.29×10⁵ A/m. The high coercivity is attributed to shape anisotropy in the nanofibers. These results demonstrate that, by carefully adjusting electrospinning parameters, strontium ferrite nanofibers with desirable magnetic properties can be successfully fabricatedKeywords: Ceramic Nanofibers, Srfe12o19, Electrospinning, Magnetic Ceramics, Nanomaterials