Journal of Ultrafine Grained and Nanostructured Materials
Volume:57 Issue: 2, Dec 2024

The effects of cross rolling and annealing treatment, as an advanced thermomechanical processing route, on the microstructure and grain refinement of metastable austenitic stainless steels were overviewed. It was summarized that cross rolling promotes the formation of intersecting shear bands and leads to higher dislocation density, which are favorable for the formation of strain-induced α′-martensite. Moreover, contrary to unidirectional rolling, cross rolling retains the equiaxed morphology of grains. It was demonstrated and formulated that cross rolling and reversion/recrystallization annealing treatment leads to more intense grain refinement compared to the unidirectional rolling and annealing route, which is quite important for grain refinement of more stable grades. Future prospects include investigating the effects of special alloying elements, initial grain size, and deformation variables on the cross rolled microstructure, analyzing the kinetics parameters of the deformation-induced martensitic transformation during cross rolling, and characterizing the transformation-induced plasticity (TRIP) effect for the grain refined austenitic stainless steels and high-entropy alloys by cross rolling and annealing treatment.

Banana peel is an organic waste that contains starch and is widely available in the environment. It is biodegradable and potential material for sustainable bioplastic application. Yet the mechanical properties are still limited. Therefore, in this study, we tried to overcome those weaknesses by adding electrochemically exfoliated graphene (ECG) nanoplatelets, enhancing the bioplastic properties. By incorporating 4 wt% graphene into banana peel starch films, we obtained a considerable improvement in mechanical properties, with Young’s modulus and tensile strength increasing to 135.02 MPa (from 23.13 MPa) and 3.74 MPa (from 2.07 MPa), respectively. Furthermore, the modified bioplastic exhibited a good water contact angle from 44.95° to 50.27°. The bioplastics retained their biodegradability, decomposing into small sizes after 6 days in the soil. This study demonstrates the feasibility of enhancing bioplastic mechanical properties and maintaining the biodegradability and eco-friendly bioplastic of banana peel, by using ECG nanoplatelets.

The formation of a tribological layer (i.e., tribolayer) affects friction and wear behavior during sliding. The mechanisms involved can be better understood by the characterization of this layer. The wear corrosion behavior of Ti 6Al 4V was studied using a reciprocating ball-on-flat tribometer at a frequency of 1 Hz and under normal loads of 1 N, 5 N, and 15 N against an alumina ball for 3600 cycles of sliding in a phosphate buffer saline (PBS) solution. Scanning Electron Microscopy (SEM) images, along with EDS analysis showed a greater coverage of a tribolayer under a normal load of 15 N. Transmission electron microscopy (TEM) studies indicated that a tribolayer with thickness up to 1000 nm, consisting of nanograins with diameters of less than 10 nm, formed on the deformed wear surface of Ti 6Al 4V under a normal load of 15 N. This protected tribolayer, under normal loads of 5 N and 15 N, resulted in a decrease of 40% in the coefficient of friction and a 15-20% reduction in the specific tribocorrosion rate compared with that at the lower applied load.

Polyethylene glycol-capped gold nanoparticles (PEG-AuNPs) are highly promising for biological and medical applications due to their biocompatibility, enhanced stability, and low cytotoxicity. The successful synthesis method presented here was a one-step process where both reduction and functionalization took place simultaneously using lower concentrations of gold precursors. Unlike previous methods that used higher concentrations (> 10 mM) and did not explore varying molar ratios, this study investigates the physicochemical properties of PEG-AuNPs synthesized with precursor concentrations ranging from 0.5 mM to 5 mM. Transmission electron microscopy images revealed an increase in the particle sizes of spherical nanoparticles from 14.5nm to 46.7nm as the precursor concentration increased, consistent with dynamic light scattering measurements. UV-Vis spectroscopy confirmed that spherical nanoparticles were formed having surface plasmon resonance peaks ranging from 520-530nm. Fourier transform infrared spectroscopy analyses revealed the interactions between PEG ligands and gold nanoparticles where some specific peaks exist around 1632cm⁻¹ while the O-H stretching peak shifted from approximately 3400 cm⁻¹ to about 3490 cm⁻¹, confirming successful surface modification. Photoluminescence spectroscopy revealed maximum emission particularly observed at the lowest precursor concentration (0.5 mM). Importantly, the synthesized PEG-AuNPs even at the lowest precursor concentration of 0.5mM demonstrated exceptional stability in saline conditions, maintaining dispersion even in the presence of 500 mM NaCl. This one-step synthesis method at reduced precursor concentrations not only enables precise control over the nanoparticles' size and optical properties but also enhances their stability and tunable fluorescence. These findings present a scalable and versatile approach for the tailored synthesis of PEG-AuNPs, making them suitable for advanced biological and medical sensing applications.

Nowadays, conductive nanocomposites are widely utilized in many applications of electronic equipment, telecommunications, the internet of things (IOT), and biosensors. Enhancing electrical properties, transparency, mechanical strength, or surface adhesion in materials for printed circuits can drive advancements in related industries. To improve the conductivity, it’s significant to pay more attention to the types of electrical resistance (ER) in nanostructures such as tunneling resistance, contact resistance, and their mechanisms. Several review papers examine the synthesis processes of nanowires and how their diameter affects conductivity. Others concentrate on the mechanical properties and stability of reinforcement particles, along with efforts to synthesize rGOs and analyze their mechanical and electrical properties. However, none of these studies specifically address how morphology and synthesis impact conductivity in optoelectronic materials. This paper reviewed the various data obtained about the conductivity of single and multiple silver micro-flake, nanowires, nanoparticles, and rGO systems as 2D, 1D, and 0D nanostructures. To obtain the best conductivity by statistical methods, tried to find a mathematical relation between ER and structural parameters. Proportions of 20 wt.% for silver Micro-flakes, 20 wt.% for silver nanowires, and 5 wt.% for silver nanoparticles, respectively, may be suitable. Further, the most efficient result was obtained at the lowest aspect ratio for Ag-NWs. In general, it can be concluded that the higher the aspect ratio consequent the lower the ER. Also, probably, rGO especially without metal heteroatom can be a proper substitute for Ag micro-flakes.

Water pollution poses a significant global challenge, with toxic and carcinogenic dyes in wastewater threatening human health. Developing efficient and reusable photocatalysts is essential for advanced and sustainable water treatment solutions. In this project, Magnetic Cu0.5Zn0.5FeAlO4 nanoparticles were prepared through an eco-friendly method utilizing tragacanth gel as a stabilizing agent. The resulting nanoparticles were characterized using XRD, BET, FESEM, UV–Vis-DRS, TEM, EDX, Mapping and VSM techniques. The XRD pattern confirms the presence of the cubic spinel crystal structure in the Cu0.5Zn0.5FeAlO4 MNPs, with an average crystallite size of 12 nm. The TEM image showed an average particle size of 25–30 nm. The EDX and mapping analysis reveal all elemental compositions in Cu0.5Zn0.5FeAlO4 MNPs, indicating a pure phase. The band gap was determined from UV–vis DRS spectra by using the tauc equation and it was found to be of about 1.95 ev. The VSM analysis demonstrated superparamagnetic properties with a saturation magnetization value of approximately 3.74 emu/g. The Cu0.5Zn0.5FeAlO4 MNPs exhibited efficient photodegradation of reactive blue 222 dye when under visible light. The sample was easily recovered and reused due to the magnetic properties of the nanoparticles. This showed excellent catalytic efficiency, maintaining strong performance for up to four cycles with very little loss in activity.

Al-Al3Ni composites due to their high strength, creep resistance, fatigue resistance, good ductility, adequate toughness, high corrosion resistance and hardness have gained considerable attention in recent years. In the present investigation, powder metallurgy (PM) method was used to in-situ produce Al-Al3Ni composites. Commercially pure aluminum powders (63-125 μm) and the same sized pure nickel powders used as starting materials. The Al/Ni powder mixtures with different Ni contents subjected to cold pressing and then sintering at different temperatures for various times. Samples of Al powders without Ni addition were also prepared using identical procedures as for Al/Ni composites to serve as the reference samples. In order to increase effectiveness of interaction between Al and Ni during sintering, Ni powders subjected to high-energy ball milling. The increased milling time of Ni particles from 1.5h to 6h resulted in progressive reaction between Ni flakes and spherical Al particles presented in Al-20wt.% Ni samples which was sintered at 655˚C for 15min. This was accompanied by the increased content of hard Al3Ni phase and thereby continuous increased hardness of composites. The XRD results confirmed that sintering at 655˚C of the Al/Ni powder compact containing 15wt.% of ball-milled Ni resulted in complete reaction and Al-Al3Ni eutectic formed without any unreacted Ni. The porosity level of the samples increased with increasing percentage of Al3Ni phase in the matrix. Brinell hardness values of all the composite samples were higher than that of their reference counterpart. The Al-20wt.% Ni sample prepared by milled Ni exhibited the maximum hardness value being almost three times of that of the reference sample. However, the increased content of milled Ni to 25wt.% resulted in some unreacted Ni particles in the matrix as was confirmed by XRD studies.

Long-term indwelling urinary catheters are associated with complications like infection and encrustation, which have brought patients burdens of health problems. Considering the damages caused by urinary tract infections, development of antibiofilm catheter coatings is a practical way to address this issue. Herein, we developed a PHEMA (poly(2- hydroxyethyl methacrylate))-PANI (polyaniline) based coating for stabilizing silver nanoparticles resulting in a high-performance antibiofilm catheter. For this purpose, silicone catheters were functionalized with OH groups and then 2- hydroxyethyl methacrylate (HEMA) was polymerized on the catheter by atom transfer radical polymerization (ATRP). The OH groups of PHEMA were converted into amine groups by reaction with para-anthranilic acid, and in the next step, PANI was produced by oxidation-reduction polymerization. In order to investigate the synergistic effects of silver nanoparticles on the antibacterial property of polyaniline, Ag nanoparticles were coated on polyaniline. Coated catheters were evaluated at each step using attenuated total reflection-fourier transform infrared (ATR-FTIR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), and atomic force microscopy (AFM). The water contact angle and consequently the hydrophilicity of the coated catheter have increased from 121˚ for the uncoated catheter to 101˚ for catheter-PHEMA-PANI and 73˚ for the catheter-PHEMA-PANI-Ag. Therefore, a hydrophilic PHEMA-PANI-Ag-coated catheter was developed with excellent thermal stability, antibacterial and antibiofilm properties against Escherichia coli and Pseudomonas aeruginosa during 24 and 48 hours and also improved biocompatibility on L929 fibroblast cells. It is concluded that the PHEMA-PANI-Ag-coated catheter with significant activity against antibiofilm formation is a potential candidate for indwelling urinary catheters and supports further clinical investigations.

To preserve environmental and human health, remediation of the produced wastewater from various industries such as textile and metalworking is of prime significance. The present investigation strives to draw a meaningful comparison between the metalworking fluid (MWF) wastewater chemical oxygen demand (COD) removal ability of three different methods, including coagulation-flocculation, Fenton oxidation, and heterogeneous nano-zeolite catalyzing Fenton-like oxidation processes. The results illustrated that the highest COD removal efficiency achieves through the application of a heterogeneous Fenton-like oxidation process. Also, the influence of nanocatalyst dosage and solution pH on COD removal efficiency of the heterogeneous Fenton-like process is addressed. The concentration of the used catalyst in this method plays a crucial role in its removal ability, wherein COD removal efficiency increases with an increase in the catalyst amount. Besides, the COD removal efficiency of this process is not affected by the pH value of the treated solution. Moreover, the sludge production rate as well as affecting parameters of each method is evaluated. The heterogeneous Fenton-like process provides the lowest sludge production rate, while the maximum sludge production rate is encountered with the coagulation-flocculation route. Therefore, the heterogeneous Fenton-like process overcomes the common challenges facing the successful industrial use of the conventional Fenton process.

Additive manufacturing (AM) has emerged as a transformative technology that produces complex, high-performance components, enabling unprecedented design flexibility and material efficiency. This paper explores the potential of additive manufacturing processes to produce ultrafine/nano-grained microstructures, which are characterized by superior mechanical properties, enhanced corrosion resistance, and improved thermal stability. The study delves into various AM techniques based on the physical phenomenon incorporated to additively bond the material portions. Accordingly, the reported results in the literature were reviewed by categorizing the methods into melting-based and deformation-based approaches and examining the conditions and parameters critical to achieving ultrafine/nano-grained microstructures. Key factors, including the optimization of process parameters as well as the specification of initial feedstock material, are discussed. This comprehensive review shows that in melting-based methods, lower power and higher scan speed result in reduced heat input, leading to smaller melt pools and faster solidification rates, which in turn produce finer grains. On the other hand, in deformation-based methods, smaller initial particle sizes and higher particle velocities generate greater impact energy, which can lead to grain size reduction. This review article also highlights the current potential and achievements in the field of additive manufacturing for producing ultrafine/nano-grained materials, which may contribute to the development of high-performance materials and components for the next generation.

In the present study, the Al/Al2O3/Graphene hybrid metal matrix composite was processed by accumulative roll bonding (ARB). A mixture of Al2O3 and Graphene (0.5 Wt% for each powder) was poured between two Al layers. The process continued up to five cycles, revealing particle-free zones and clusters in the composite's microstructure. Increasing the ARB cycles improved the distribution of reinforcing particles in the aluminum matrix. Irregular porosities appeared in the early cycles and elongated in the middle ones. SEM investigation showed that better interface bonding in the last cycles increases internal stresses, promoting aluminum matrix flow and reducing porosities, crack sizes, and debonding. Mechanical tests such as tensile tests in RD directions, microhardness, fractography, and potentiodynamic corrosion tests in 3.5 wt-% NaCl solution have been performed to characterize the produced composites for the first time. Results showed that the tensile strength of the produced composites increases by increasing the ARB cycles and reaches the maximum value in the fifth cycle. Microhardness measurement indicated that the hardness of individual layers increases continuously by increasing the ARB cycles. The tensile fracture mode is a mixed fracture mode consisting of the cleavage and dimple rupture fracture in all cycles. The corrosion rate decreased from the first to the third ARB cycle relative to pure Aluminium alloy, arising from the presence of the inert particle and good bonding. However, it increased abruptly in the fifth cycle.

Three commercial stents (Palmaz-Schatz, NIR, and BioMatrix) with either an open-cell (20% open-cell) or a closed-cell (80% closed-cell) design, and one new hybrid stent design were numerically modeled using the ABAQUS/Explicit finite element software (Dassault Systèmes, France) to compare their behaviors during deployment in a stenotic artery. The ABAQUS/Explicit dynamic explicit solver was utilized to efficiently capture the complex interactions between the balloon, stent, artery, and plaque during the stent expansion process. The effect of changing the material from stainless steel (SS 316L) to cobalt-chromium (CoCr) and platinum-chromium (PtCr), as well as the reduced thickness of struts from 0.1 mm to 0.08 mm, were investigated. The new hybrid stent design featured reduced axial strut spacing (from 1.2 mm to 0.8 mm), larger corner radii (from 0.2 mm to 0.3 mm), and smaller amplitudes in the ring (from 1.0 mm to 0.8 mm). For the simulations, a balloon-stent-artery model with plaque and average blood pressure of 80 mmHg was used. The results showed that the new hybrid stent did not perform worse in any of the studied biomechanical parameters compared to the commercial open-cell (20% expansion) and closed-cell (15% expansion) stents, and exhibited better performance in maximum expansion (22%) and recoil responses (5% recoil). Changing the material in the new hybrid stent from SS 316L to CoCr or PtCr improved the biomechanical behavior, such as expansion (25%), recoil (3%), and dogboning (0.9), but increased the maximum von Mises stress on the artery-plaque system by 18%. Reducing the strut thickness from 0.1 mm to 0.08 mm decreased the maximum stress on the artery-plaque system by 12%, but undesirably increased dogboning (1.1) and recoil (7%).