Journal of Ultrafine Grained and Nanostructured Materials
Volume:56 Issue: 1, Jun 2023

The increasing industries and population growth, make various new needs for water. So, scientists and researchers try to invent new methods for processing and synthesizing new materials to recycle used water sources. In this research, Zn (NO3)2.6H2O (zinc nitrate) and C2H5NO2 (glycine) were used as raw materials in Solution Combustion Synthesis technique (SCS) to synthesize ZnO nanoparticles. Also, the bentonite is added to the reaction container during the synthesis to act as substrate for nanoparticles to produce Bentonite-ZnO nanocomposite in-situ in less than 10 min at the air atmosphere. The successful synthesis was confirmed by X-ray diffraction analysis and the reason of that was explained by DSC-TGA of raw materials. It proved the same thermal behaviors of zinc nitrate as oxidizer and glycine as fuel could carry out the reaction. The SEM and TEM images demonstrated the decoration of ZnO on bentonite. Finally, the photodegradtaion of an antibiotic (ciprofloxacin) in presence of synthesized nanocomposite was examined under direct sunlight. The results showed about 97% degradation efficiency and 81% for total organic carbon removal after 3h reaction at the rate constants of 1.04 h-1. The blank test from just bentonite shows less than 10% degradation efficiency that proves the presence of ZnO increases this value more than 87%.

In this research, the influence of friction stir processing (FSP), on structural and mechanical properties of Al6061-T6 was investigated. Friction stir processing with tool rotational rate (ω) of 630, 800 and 1000rpm and traveling speed (v) of 50,100,160 and 200mm/min was employed on 13mm thick Al6061-T6. Results indicated that FSP decreases grain size from 78µm to 6µm because of the dynamic recrystallization. The finest grain size was obtained at the rotational rate of 630 rpm and traveling speed of 100 mm/min. Results have recommended that when the ratio of ω/v was less than 5(rpm/mm.min-1), due to inadequate heat input, microscopic voids were produced in nugget zone (NZ). Microhardness and tensile strength in the stir zone decreased, but elongation raised compared to those for the base metal. This is due to the loss of hardening precipitates during FSP.With increasing the tool travelling speed, grain size in nugget NZ and mechanical properties were improved. The best mechanical properties at NZ have been obtained at ω=630 rpm and v=100 mm/min due to the finest grain size.

In the current research the role of silica nanoparticles on the viscoelastic behavior of polyethylene (PE) has been investigated. To do so PE reinforced with different content of silica nanoparticles (i.e. 0, 1, 3 ,5 and 10 Wt%) have been produced using extrusion and injection molding methods. In order to investigate the viscoelastic properties, Dynamic mechanical thermal analysis (DMTA) has been performed. The results showed that at constant frequency (1 HZ) the storage modulus of all materials including PE and its nanocomposites decreased as temperature increased from -150 up to 120 oC. For example the storage modulus of neat PE and PE reinforced with 5Wt% SiO2 decreased from 2900 and 3400 MPa to 80 and 250 MPa respectively. Also the value of loss modulus increased as the polyethylene and it nanocomposites approached from low temperatures to the glass transition temperature. The loss modulus of PE and its nanocomposite has not any significant difference at low frequency. But this difference becomes more as frequency increases gradually. For example the difference between loss modulus of pure PE and PE/1Wt% SiO2 at 50 HZ and 250 HZ are about 8 and 15 MPa respectively. The highest amount of tanδ is for the pure polyethylene sample, and with the addition of SiO2 nanoparticles, the decreasing trend of tanδ observed. The lower values of tanδ indicating a reduction in the damping effect in composite samples compared to pure polyethylene.

An appropriate fraction of a second phase for controlling the dynamic grain growth of the fine-grained microstructure during hot deformation can be easily achieved for the high and ultrahigh carbon steels as well as the duplex stainless steels (dual-phase ferritic-austenitic steels), which leads to good superplastic forming behaviors. However, the austenitic stainless steels are typically single-phase alloys at elevated temperatures, which might limit their tensile ductility, and hence, inducing superplastic ductility in these ferrous alloys needs special considerations. In the present review article, firstly, the methods for the grain refinement of austenitic stainless steels are summarized, which includes the formation of deformation-induced martensite during cold deformation and its reversion to austenite at elevated temperatures, severe plastic deformation (SPD) techniques, and thermomechanical processing routes that utilize the dynamic recrystallization (DRX). These methods are used to process fine-grained microstructures that are suitable for activating the grain boundary sliding (GBS) with strain rate sensitivity index (m) of ~0.5 at elevated temperatures. Afterward, the reported works on the superplasticity of austenitic stainless steels are critically discussed. It is revealed that the methods such as nitrogen addition, incorporating the carbonitride forming elements such as vanadium, increasing the carbon content of the material for the formation of carbides, and the incomplete reversion treatment for the retention of a small volume fraction of martensite can be used to increase the thermal stability of the ultrafine grained (UFG) microstructure against grain coarsening during superplastic deformation. Finally, some distinct suggestions for future works are introduced.

In this paper, the impact of the number of passes of equal channel angular pressing (ECAP) on mechanical properties and corrosion behavior of Al5085 alloys in an HNO3 solution is investigated. After a single pass of ECAP, the ultimate tensile strength (UTS) was increased noticeably from 275 MPa to 342 MPa. Also, the yield strength (YS) and microhardness were improved from ~82 MPa to ~118.5 MPa and 94 HV to 136 HV, respectively. After the second pass all UTS, YS, and microhardness increased by ~13.5%, ~17.8%, and ~11.7% compared to the first pass. Meanwhile, the elongation to failure was reduced by ~15% and ~7.5% after one and two passes of the ECAP, respectively. According to scanning electron microscope (SEM) micrographs, unlike the unprocessed sample in which there is no evidence of pitting corrosion occurrence, after one pass ECAP, the pitting corrosion occurred through all the surfaces of the sample. Also, there is no evidence of pitting corrosion after two passes of ECAP.

Friction stir processing (FSP) and friction stir welding (FSW) methods are two types of severe plastic deformation (SPD) processes. SPD methods are useful in producing nanoparticle or ultrafine-grained materials (UFG) microstructure. In FSP and FSW, a rotating cylinder tool (pin), which could take the form of various geometries, pierces into the workpiece with a particular angle and depth. Furthermore, it refines grains by moving in the direction of interest along with the tool's movements. The uniform distribution of nanoparticles in the stir zone is one of the main challenges of using nanoparticles. Controlling variables such as tool rotational speed, tool travel speed, number of passes, etc., the distribution of nanoparticles and the grain size can be changed in the stir zone. Microstructure, texture, and grain size directly affect the hardness of the stir zone. Recent studies have shown that using nanoparticles enhances the mechanical properties of the stir zone. The main aim of this review article is to collect the results of previous articles focused on analyzing the operation of FSW and FSP, the microstructure of the stir zone in FSW and FSP, the impact of effective parameters on the microstructure after adding nanoparticles to the stir zone, and the applications of FSW and FSP in various industries. Moreover, the fundamental mechanisms of grain refinement throughout FSW and FSP, including morphology and grain boundaries forming, were discussed.

Surface Mechanical Attrition Treatment (SMAT) is recognized as an effective technology for enhancing hardness and surface abrasion resistance. This study examined the influence of SMAT on the microstructure, surface roughness, hardness, and wear behavior of the AZ31 magnesium alloy. For the experiments, steel balls of different diameters – 3.2mm, 4mm, and 5.6mm – were used to perform the SMAT process, which was consistently timed at 8.5 minutes. Detailed analyses of the resultant microstructures were then conducted using tools such as a scanning electron microscope and X-ray diffraction. The hardness and wear were measured using the Vickers and the disk pin methods, respectively. It was observed that the SMAT process significantly reduced the grain size on the sample surfaces. For example, when a steel ball with a diameter of 5.6mm was utilized, the grain size was reduced from 225nm to just 96nm. The process also led to a substantial increase in hardness, with measurements rising from 65 HV to 190 HV, once again when a steel ball of 5.6mm diameter was utilized. Furthermore, the SMAT process, when executed with a tool diameter of 5.6mm, eliminated weight loss in the wear test, which had been previously recorded at 0.26mg, indicating an increase in surface abrasion resistance. An observed correlation suggested that as the tool diameters increased, the abrasion resistance of the surface improved. Abrasion was adhesive on untreated samples; on treated samples, it was ridged and scratched. However, as the tool diameter—and consequently, the surface hardness—increased, the scratches were seen to reduce gradually.

Among the various available nanoparticles ‘inorganic nanoparticles’ are more promising due to their wide range of application. MgO Nanoparticles (MgO NPs) is a very important inorganic metal oxide nanoparticle due to their diverse field of applications. There are so many physical and chemical methods are available to fabricate potentially useful MgO NPs. The proposed research work highlighted a novel green synthesis method for the fabrication of MgO NPs by using waste material peanut shell as a precursor. The green synthesized MgO NPs are characterize by the techniques like XRD, SEM, FTIR, UV-Vis Spectroscopy. The green synthesized MgO NPs are crystalline in nature & the tetragonal structure of MgO NPs was determined by XRD, various functional groups present on the surface of the synthesized nanoparticles was determined by FTIR and average particle size of green synthesized MgO NPs is 25-30 nm, found as result by SEM and XRD analysis. Two important applications photocatalytic activity and antibacterial activity of the synthesized nanoparticles was investigated in the proposed research work. The green synthesized MgO NPs show remarkable photo catalytic activity against the Indigo Ceramine and Rhodamine dyes and approximately after 60 min the photocatalyst completely remove the dyes from the solution. The Green synthesized MgO NPs show highest antibacterial activity against the pseudomonas aeruginosa (19 mm) bacteria.

Over the last 20-30 years, severe plastic deformation (SPD) technologies have caused a significant resonance in the production of ultrafine grained and nanostructured materials. However, the growth of demand for such technologies is largely limited by the high cost of making products from such materials due to the high energy and labour intensity of their production. Therefore, this article analyzes modern technologies for the production of ultra-fine grained metals and alloys with high strength and ductility, using relatively simple and inexpensive equipment and with minimal time required for their production. The development and proliferation of continuous casting machines in the second half of the 20th century led to the development of many continuous press methods used for deformation of long billets, among which Conform, Extrolling, Linex and combined rolling-press technologies stand out. Therefore, in the present article all combined and continuous processes currently available for the production of long products with ultrafine grains and nanostructures will be considered. Such structures are fundamentally different from conventional materials, because they combine high strength properties with high ductility. This is relevant for applications where weight, size or special performance characteristics of the parts are important.

In the present study, the TiO2 nanotubes were coated on the surface of porous Ti foam by the anodization method. The surface of Ti foam before and after coating of TiO2 nanotubes was structurally and morphologically characterized by X-ray diffraction (XRD), field emission electron microscope (FESEM) equipped with energy-dispersive X-ray (EDX). Additionally, the cytocompatibility of TiO2-coated porous Ti foam was evaluated by methyl thiazol tetrazolium (MTT) assay. The results have shown that the anatase crystalline phase was formed on the surface with a uniform thickness of 2.5 µm. Finally, TiO2-coated porous Ti foam was biocompatible and significantly enhanced the proliferation and attachment of MG-63 osteoblast cells compared to the uncoated substrate. All the results postulated that the coating of Ti substrate with TiO2 nanotube shows an excellent promise for dental implant application.

Li-doped ZnO thin films prepared by sol-gel spin coating method, have been studied in this research to increase the p-type ZnO layers conductivity. For this purpose, the lithium dopant concentration was changed and structural, electrical, and opti-cal properties of the layers were investigated. For structural analysis, XRD and FESEM were used. Besides, thin films electri-cal properties including resistivity and majority carriers’ type were determined. Eventually, optical properties were studied by UV-Visible and PL spectroscopy. Structural investigations showed that the single phase layers with wurtzite hexagonal structure and 40-50 nm average grain size were formed. For obtaining p-type layers and enhancing their electrical conductiv-ity, there was an optimum in moderate Li concentrations. Furthermore, regarding the optical properties, it was concluded that the band gap energy is sensitive to Li concentration and the refractive index of ZnO layer decreased with Li doping. Fi-nally, the effect of Li doping was further studied by DFT calculation. These calculations propose activation of a self-compensation mechanism by Li doping which can be responsible for decrease of the conductivity at high Li concentra-tions. In the proposed mechanism, Zni donor defect sites, accompanying LiZn sites, cause self-compensation.

Graphene quantum dots (GQDs) are one of the most uprising nanomaterials that have been used in biomedical applications because of their interesting luminescent properties. This work presents a facile way to attach the LCysteine onto the surface of GQDs, which enhances the applicability of the final molecules in biomedical applications. Furthermore, the luminescent properties of synthesized GQDs and LCysteine-GQDs with different methods of prevalent spectroscopy. The obtained GQDs- LCysteine show a red shift in PL results with an increase in wt.% LCysteine compared to GQDs. According to the results, this platform has the potential to be used in many biological applications, such as bio-imaging and bio-labeling.