Colloids and Surfaces A: Physicochemical and Engineering Aspects (18734359)725
The development of epoxy adhesives with superior adhesion properties has long been a critical requirement in the high-tech applications. In this study, two metal organic frameworks (MOFs), MIL-101(Cr) (MIL, Matérial Institut Lavoisier) and NH2-MIL-101(Cr), were used to enhance the adhesion characteristics. These MOFs, were characterized by different analytical techniques, and subsequently integrated into high-temperature epoxy adhesives to improve their mechanical and thermal properties as well as adhesion strength. Notably, the addition of 0.3 parts per hundred resin (phr) of MIL-101(Cr) to the epoxy matrix resulted in an impressive ∼100 % increase in tensile strength and a remarkable 24 % enhancement in lap shear strength. Furthermore, the incorporation of the amine-functionalized NH2-MIL-101(Cr) into the epoxy matrix led to even more significant improvements in mechanical strength. The addition of just 0.3 phr of NH2-MIL-101(Cr) gave rise in a striking ∼150 % increment in tensile strength compared to the pristine epoxy adhesives, while lap shear strength experienced a substantial 50 % growth. The thermal stability of the epoxy adhesive was notably enhanced in the presence of the MOFs. Differential scanning calorimetry (DSC) analysis indicated an increase in the curing enthalpy upon the incorporation of both MIL-101(Cr) and NH2-MIL-101(Cr) into the epoxy matrices. The use of amine-functionalized MOFs significantly improved the thermal and mechanical properties of the epoxy adhesives, paving the way for the development of innovative epoxy formulations. © 2025
Kadkhodaei, Reihane,
Dini, G.,
Vaezifar, S.,
Mahmoodiyan Najafabadi, Fereshteh,
Ghasemvand F. Polymer Bulletin (01700839)(12)
Controlled drug delivery plays a critical role in modern pharmaceutics, enabling precise and sustained therapeutic effects. This study presents the development of biodegradable composite implants composed of polycaprolactone (PCL), sodium alginate (SA), and chitosan (CS) nanoparticles loaded with doxorubicin (CS-DOX) for long-term, localized cancer therapy. CS-DOX nanoparticles were synthesized via ionic gelation, achieving an encapsulation efficiency of approximately 80%, while 10 µm PCL microparticles were produced using spray drying to form a uniform implant matrix. In this work, tablet implants containing 5, 7, and 10 wt% DOX were fabricated using a 5 mm diameter mold under compression, with an appropriate amount of SA used as a binder. DLS analysis revealed nanoparticle sizes of ~ 110 nm for CS and ~ 135 nm for CS-DOX, with zeta potentials decreasing from + 28 mV (CS) to + 23 mV (CS-DOX), confirming colloidal stability. Drug release studies exhibited a biphasic profile, consisting of an initial burst release followed by sustained release over 15 days. In all fabricated implants containing DOX, the drug release kinetics followed the Korsmeyer–Peppas model. MTT assays on 4T1 breast cancer cells demonstrated an ~ 70% reduction in viability after 72 h for the 10% DOX-loaded implant. These findings highlight the potential of PCL/SA/CS-DOX implants as an effective biodegradable system for localized drug delivery, offering tunable release kinetics and enhanced therapeutic outcomes. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Polymers for Advanced Technologies (10427147)35(1)
In this study, MIL-101 (Cr) and NH2-MIL-101 (Cr) nanoparticles were synthesized by hydrothermal method. Butyl acrylate-styrene copolymer was used along with these nanoparticles to improve the mechanical properties of epoxy adhesive. The results of the Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD) test showed that the synthesis and functionalization of the metal organic framework (MOFs) were successful. The mechanical properties and adhesion features in the lap joint bonding of aluminum foil to the aluminum foil of modified epoxy adhesives were investigated by tensile and lap shear tests. The results of the tensile test showed that by adding 0.3 wt% of NH2-MIL-101 (Cr) and 2.5 wt% of poly(butyl acrylate-block-styrene) to epoxy adhesive, the tensile strength, modulus and toughness of dumbbell samples were increased up to 34.46%, 31.74% and 58.53%, respectively. Furthermore, based on the lap shear test results, by adding 0.3 wt% NH2-MIL-101 (Cr) along with 2.5% poly(butyl acrylate-block-styrene) to the epoxy adhesive, the lap shear strength of samples increased from 1.05 ± 0.08 MPa to 5.25 ± 0.06 MPa compared to the neat epoxy adhesive. According to the TGA test, the highest thermal stability is related to the sample containing 0.3 wt% of NH2-MIL-101 nanoparticles and 2.5 wt% of the copolymer. The image of the fracture surface of the sample containing 0.3 wt%. NH2-MIL-101 (Cr) and 2.5 wt% block copolymer shows that the interface of nanoparticles and the matrix improved due to the chemical reaction of functional groups of nanoparticles and adhesive matrix. © 2023 John Wiley & Sons Ltd.
Microbial Pathogenesis (10961208)196
Today, many infections in plants are related to biofilm-developing bacteria. These infections can result in severe agricultural losses. Thus, this study aims to investigate the synergistic antibiofilm activity of Thymus vulgaris extract on the inherent antibacterial properties of ZnO nanoparticles against Erwinia amylovora and Pseudomonas syringae pv. syringae. Additionally, to gain insight into the molecular mechanisms of phytocompounds’ antibacterial activity, the molecular interactions of T. vulgaris phytochemicals with the TolC protein and TonB-dependent siderophore receptor were investigated through in-silico studies. Green-synthesized ZnO NPs (ZnO@GS) and chemically synthesized ZnO (ZnO@CHS) were evaluated using XRD and SEM techniques, showing a crystalline structure for both powders with average sizes of 50, and 40 nm, respectively. According to FT-IR and EDS spectroscopy, ZnO@GS was covered with thyme extract. Based on the in vitro results, all samples of ZnO NPs exhibited considerable antibacterial activity against both bacteria. At the same time, thyme aqueous extract alone proved considerably less effective at all tested concentrations. Compared to ZnO@CHS and thyme extract, the antibacterial efficacy of ZnO@GS against E. amylovora (MIC = 512 μg/mL) and P. syringae pv. syringae (MIC = 256 μg/mL) was significantly improved upon surface covering with thyme phytocompounds. Moreover, their antibiofilm properties were enhanced by almost 20 % compared to ZnO@CHS. In addition, molecular docking investigations showed that most of the phytocompounds could form stable interactions with the TonB-dependent siderophore receptor (P. syringae) plug domain and the TolC (E. amylovora) external channel. In vitro and in silico studies demonstrate that using the green approach for synthesizing ZnO NPs via thyme extract can notably boost its antibacterial and antibiofilm effects on the tested phytopathogenic bacteria. © 2024 Elsevier Ltd
The Arabian Journal For Science And Engineering (2193567X)(6)
A new protic ionic liquid (IL) was synthesized by the neutralization reaction of 1H-benzotriazole (BTA) and bis(2-ethylhexyl) phosphoric acid (HDEHP) and evaluated as a catalyst in the esterification reaction of oleic acid and polyethylene glycol (PEG) 400, as well as an anti-wear and anti-corrosion additive in the synthesized ester. The response surface methodology (RSM) was used to design the experiments and optimization of the esterification reaction, which at the optimum conditions (1 wt% of IL, at the molar ratio of acid/alcohol of 1.55, the reaction temperature of 200 °C for 24 h) the maximum conversion of esterification was achieved (more than 99%). Unlike most ILs, [BTAH][DEHP] was fully miscible in synthesized ester and did not separate from the esterification process. [BTAH][DEHP] IL significantly reduced corrosion of copper, aluminum, and steel strips. Also, tribological evaluations illustrated that the 1, 2.5, 5, and 7.5 wt% of [BTAH][DEHP] IL in the PEG400 Oleate reduced the coefficient of friction to 30, 42, 46, and 59%, respectively. Using inexpensive raw materials, a simple synthesis procedure, and preparing green lubricant without catalyst separating, as well as suitable anti-corrosion and anti-wear and friction-reducing properties, could be addressed as advantages of the proposed method. © King Fahd University of Petroleum & Minerals 2024.
Saharkhiz S.,
Nasri, N.,
Naderi N.,
Dini, G.,
Ghalehshahi S.S. International Journal of Pharmaceutics: X (25901567)
In this study, we present a targeted and pH-sensitive niosomal (pHSN) formulation, incorporating quantum dot (QD)-labeled Trastuzumab (Trz) molecules for the specific delivery of Palbociclib (Pal) to cells overexpressing human epidermal growth factor receptor 2 (HER2). FTIR analyses confirmed the successful preparation of the pHSNs and their bioconjugation. The labeled Trz-conjugated Pal-pHSNs (Trz-Pal-pHSNs) exhibited a size of approximately 170 nm, displaying a spherical shape with a neutral surface charge of −1.2 mV. Pal encapsulation reached ∼86%, and the release pattern followed a two-phase pH-dependent mechanism. MTT assessments demonstrated enhanced apoptosis induction, particularly in HER2-positive cells, by Trz-Pal-pHSNs. Fluorescence imaging further validated the internalization of particles into cells. In conclusion, Trz-Pal-pHSNs emerge as a promising platform for personalized medicine in the treatment of HER2-positive breast cancer. © 2024 The Authors
Kadi F.,
Dini, G.,
Poursamar, S.A.,
Ejeian, F. Journal of Materials Science: Materials in Medicine (09574530)(1)
In this study, nanocomposite scaffolds of hydroxyapatite (HA)/polycaprolactone (PCL)/gelatin (Gel) with varying amounts of HA (42–52 wt. %), PCL (42–52 wt. %), and Gel (6 wt. %) were 3D printed. Subsequently, a scaffold with optimal mechanical properties was utilized as a carrier for doxorubicin (DOX) in the treatment of bone cancer. For this purpose, HA nanoparticles were first synthesized by the hydrothermal conversion of Acropora coral and characterized by using different techniques. Also, a compression test was performed to investigate the mechanical properties of the fabricated scaffolds. The mineralization of the optimal scaffold was determined by immersing it in simulated body fluid (SBF) solution for 28 days, and the biocompatibility was investigated by seeding MG-63 osteoblast-like cells on it after 1–7 days. The obtained results showed that the average size of the synthesized HA particles was about 80 nm. The compressive modulus and strength of the scaffold with 47 wt. % HA was reported to be 0.29 GPa and 9.9 MPa, respectively, which was in the range of trabecular bones. In addition, the scaffold surface was entirely coated with an apatite layer after 28 days of soaking in SBF. Also, the efficiency and loading percentage of DOX were obtained as 30.8 and 1.6%, respectively. The drug release behavior was stable for 14 days. Cytotoxicity and adhesion evaluations showed that the fabricated scaffold had no negative effects on the viability of MG-63 cells and led to their proliferation during the investigated period. From these results, it can be concluded that the HA/PCL/Gel scaffold prepared in this study, in addition to its drug release capability, has good bioactivity, mechanical properties, and biocompatibility, and can be considered a suitable option for bone tumor treatment. Graphical Abstract: [Figure not available: see fulltext.]. © 2024, The Author(s).
Shojaei, F.,
Dini, G.,
Vahabi L.,
Ghasemi P. Journal of Nanoparticle Research (13880764)(11)
In this study, mesoporous silica nanoparticles (MSNs) were synthesized using a microfluidic chip with a continuous flow-focusing platform under different conditions. Subsequently, a product with a higher specific surface area was selected as a carrier for doxorubicin (DOX). Several characterization techniques were employed, along with drug release studies and cell viability assessments, to evaluate the products. The findings indicated that under optimal conditions, MSNs with a spherical morphology and an amorphous structure with an average particle size of about 70 nm and a surface area of ~ 920 m2/g were effectively synthesized. In addition, the cytotoxicity test of bare MSNs on the MCF-7 cell line demonstrated their biocompatibility and low toxicity towards these cells. However, the cytotoxicity test of drug-loaded MSNs, containing approximately 30% DOX, revealed a lethality rate of about 60% after 3 days on the MCF-7 cells. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
Journal of Alloys and Compounds (09258388)984
Herein, as a novel idea, a microwave (MW) post-treatment strategy is proposed to modify the structure and surface characteristics of already prepared activated carbons (ACs) for application in non-aqueous Electric Double-Layer Capacitors. Pistachio nutshell-derived carbon is first KOH-activated and then subjected to MW irradiation for 0, 2, 5, and 10 minutes. X-ray Diffraction and Raman analyses show that MW post-treatment leads to structural modifications, and FTIR and XPS analyses reveal relative elimination of surface functional groups which results in subsequent enhancement in water contact angle and renders more favorable surface wetting of carbon by non-aqueous organic electrolyte. The performance characteristics of symmetrical non-aqueous supercapacitors incorporated with the prepared ACs show a significant positive effect of MW irradiation in such a way that 0 and 10-minute-irradiated ACs demonstrate 152 and 392 F g−1 capacities, respectively, at 1.75 A g−1, with the corresponding specific energies and powers of 340 Wh kg−1 and 11 kW kg−1 for AC-10, respectively. This remarkable enhancement in the electrochemical performance is attributed to the effective role of the MW post-treatment in modifying the AC structure as well as providing AC surfaces that have better wettability with less polar non-aqueous electrolyte. Moreover, this strategy is additionally applicable to make hydrophobic activated carbons for other applications as the absorption of less polar contaminants from liquid or gaseous environments. © 2024 Elsevier B.V.
Arabian Journal Of Chemistry (18785352)17(1)
Bioactive glass is one interesting type of material for bone repair. In this work, a new powder (MBG2) was synthesized by a sol–gel method, in which 5 mol.% Mg and 5 mol.% Zr were incorporated into the structure, to investigate the combined effects of the simultaneous addition of these ions on the biological properties of 45S5 mesoporous bioactive glass. Then, the outcomes of various characterization techniques and in vitro biological analyses performed on this powder were compared with those of pure powder (MBG1). For instance, the XRF investigation proved that Zr and Mg ions were present in powder MBG2′s composition. Additionally, XRD, SEM, and BET tests of the powders MBG1 and MBG2 indicated their amorphous structure and spherical morphology with specific surface areas of 620 and 710 m2/g and average particle sizes of about 30 and 20 nm, respectively. The development of an apatite layer on the surfaces of disc-shaped samples produced from both powders were immersed in phosphate-buffered saline (PBS) and simulated body fluids (SBF), and the behavior of the samples' degradation were observed for 28 days. Furthermore, it was assessed how the Zr and Mg ions in the composition affected the MG-63 cells' survival, growth, and adhesion through in vitro biocompatibility testing. From the obtained results, it can be concluded that 45S5 mesoporous bioactive glass powder with minimal cytotoxicity was entitled to be a safe biomaterial due to the coexistence of 5 mol.% Mg and 5 mol.% Zr in the composition, which successfully enhanced bioactivity, cell proliferation, and biocompatibility. © 2023 The Author(s)
Nasri, N.,
Mansouri-tehrani h.a., H.,
Dini, G.,
Keyhanfar, M. Fish and Shellfish Immunology (10504648)
Copper (Cu) is a crucial element that plays a vital role in facilitating proper biological activities in living organisms. In this study, copper oxide nanoparticles (CuO NPs) were synthesized using a straightforward precipitation chemical method from a copper nitrate precursor at a temperature of 85 °C. Subsequently, these NPs were coated with the aqueous extract of Sargassum angustifolium algae. The size, morphology, and coating of the NPs were analyzed through various methods, revealing dimensions of approximately 50 nm, a multidimensional shaped structure, and successful algae coating. The antibacterial activity of both coated and uncoated CuO NPs against Vibrio harveyi, a significant pathogen in Litopenaeus vannamei, was investigated. Results indicated that the minimum inhibitory concentration (MIC) for uncoated CuO NPs was 1000 μg/mL, whereas for coated CuO NPs, it was 500 μg/mL. Moreover, the antioxidant activity of the synthesized NPs was assessed. Interestingly, uncoated CuO NPs exhibited superior antioxidant activity (IC50 ≥ 16 μg/mL). The study also explored the cytotoxicity of different concentrations (10–100 μg/mL) of both coated and uncoated CuO NPs. Following 48 h of incubation, cell viability assays on shrimp hemocytes and human lymphocytes were conducted. The findings indicated that CuO NPs coated with alga extract at a concentration of 10 μg/mL increased shrimp hemocyte viability. In contrast, uncoated CuO NPs at a concentration of 25 μg/mL and higher, as well as CuO NPs at a concentration of 50 μg/mL and higher, led to a decrease in shrimp hemocyte survival. Notably, this study represents the first quantitative assessment of the toxicity of CuO NPs on shrimp cells, allowing for a comparative analysis with human cells. © 2024 Elsevier Ltd
Metals and Materials International (15989623)29(1)pp. 192-203
In this work, the effect of the accumulative roll bonding (ARB) process on the microstructure, mechanical properties, and corrosion characteristics of AZ31 Mg alloy was investigated. First, the ARB process up to 3 cycles at 350 °C was applied to annealed AZ31 Mg alloy sheets. Then, all samples were characterized via microstructure observations, mechanical investigations, and also, electrochemical analyses, and immersion tests in simulated body fluid (SBF) solution. In addition, the L929 cell line was used to evaluate the cytotoxicity of the samples. The obtained results showed that after the third ARB cycle, the average grain size in the annealed sample decreased from ~ 14 to ~ 3 µm. Some ultra-fine grained (UFG) microstructures that had a grain size of fewer than 1 μm were also observed in the 3-cycle ARB-processed sample. This grain refinement led to an increase in the yield strength and micro-hardness values of the annealed sample from ~ 153 MPa, and ~ 55 Hv to ~ 214 MPa, and ~ 76 Hv. However, the ARB process had an adverse effect on the corrosion characteristics of samples, and the corrosion rate increased after the ARB process. Moreover, the viability of L929 cells in culture media containing extracts obtained from the annealed sample was higher than that for the 3-cycle ARB-processed sample after 3 days of incubation. The influence of microstructural evolution in the ARB-processed AZ31 Mg alloy on the corresponding mechanical properties, corrosion behaviors, and cytotoxicity results was discussed in detail. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.
Esteki, Soheil,
Saeidi, Rasoul,
Dini, G.,
Milani, M. Materials Chemistry and Physics (02540584)
In this work, first, a systematic study has been done to optimize the rheological behavior of silicon carbide (SiC) slurries to produce 20 mm disc-shaped green bodies with the highest relative density by adding sintering aids and changing the most effective parameters of the slip casting process. In the second step, slip-casted SiC green bodies were sintered via spark plasma sintering (SPS) under the same conditions: at a heating rate of 200 °C/min and under a vacuum atmosphere (10−2 Torr), the temperature reached 1900 °C and was maintained for 15 min, then, a pressure of 50 MPa was applied, and sintering was performed for 15 min. Initial powders, as well as green bodies, were well characterized via different methods. Also, the microstructure, physical, and mechanical properties of sintered samples were investigated. Results showed that the optimal concentration of tetramethylammonium hydroxide (TMAH) as a dispersant agent for slurry with 60 wt% of SiC was 2 wt%. In addition, the optimal milling time for slurries containing sintering aids was 24 h. The sintered SiC samples containing a mixture of Al2O3 and Y2O3 powder as a liquid phase sintering aid in a range of 5–10 wt% showed low sinterability and as a result, their microstructures contained pores. In contrast, the use of B4C powder as a solid phase sintering aid in a range of 5–10 wt% resulted in forming of sintered SiC samples with completely uniform and dense structures without visible pores. The optimal percentage of B4C was 7 wt%, and the relative density and the hardness of the corresponding sintered sample were 99.5% and 3300 ± 20 Hv, respectively. © 2023 Elsevier B.V.
Arabian Journal Of Chemistry (18785352)16(6)
The aim of this study was to fabricate and evaluate magnesium-zinc-graphene oxide nanocomposite scaffolds for bone tissue engineering. For this reason, Mg-6Zn, Mg-6Zn-1GO, and Mg-6Zn-2GO scaffolds were fabricated by the powder metallurgy method. The porosity level and also the pore size of the scaffolds were evaluated by SEM which varied from 40 to 46% and 200 to 500 μm, respectively. The chemical composition and microstructure of the scaffolds were characterized by XRD and SEM equipped with EDS; the presence of Mg, Zn, C, and O elements in the structure of the scaffolds was shown. Also, the elemental map confirmed the existence of magnesium, zinc, carbon, and oxygen in the structure of the scaffold. The mechanical properties of the scaffolds were investigated by the compression test; the results showed that by the addition of graphene oxide to the structure, the compressive strength of the samples increased from 5 to 8 MPa. Electrochemical corrosion polarization tests were conducted to evaluate the corrosion resistance of the samples immersed in simulated body fluid (SBF). Furthermore, the biodegradability of the scaffolds was determined by immersion of the samples in phosphate-buffered saline (PBS). The results demonstrated that the polarization resistance value and the corrosion rate for different formulations including Mg-6Zn, Mg-6Zn-1GO, and Mg-6Zn-2GO were 41.58, 35.48, and 55.40 Ω.cm2 followed by 10.60, 14.83, and 9.06 mm.year−1, respectively. Based on the results, the Mg-6Zn-2GO formulation presented the best corrosion resistance among the samples were investigated, which confirmed the results of the immersion test. Moreover, the MTT assay proved that the extract of Mg-6Zn-2GO scaffolds was not cytotoxic in contact with L-929 cells which validated the studied scaffolds for bone tissue applications. © 2023 The Author(s)
Tabeshfar M.,
Dini, G.,
Salehi m., ,
Wiik K. High Temperature Corrosion of Materials (27318400)(1-2)
Oxidation is one of the failure mechanisms of gas turbines under operating temperature. Yttria-stabilized zirconia (YSZ) is well-known ceramic topcoat material of thermal barrier coatings (TBCs), but it has some drawbacks. From this point of view, other new materials such as rare earth zirconate are interesting. In the present research, single-layer Gd2Zr2O7 (GZO), and GZO/YbSZ (Gd2Zr2O7 + 50 wt% YbSZ), and double-layer YSZ + GZO/YbSZ (YSZ/Gd2Zr2O7 + 50 wt% YbSZ) topcoats as TBC were deposited by air plasma spraying. To estimate the phase stability of homogeneous mixtures of GZO (pyrochlore) and YbSZ (tetragonal), heat treatment was conducted at 1400 °C and showed complete conversion to a single-cubic (fluorite) phase after 100 h. The as-sprayed TBCs were subjected to oxidation for different times at 900 °C, and their features were investigated by different analysis techniques (SEM and XRD). The microstructural analysis indicated that the thickness of the thermally grown oxide layer was less for GZO coating due to reduced oxygen diffusion. Conversely, because of the lower fracture toughness and lower thermal expansion of GZO, it had a considerably less lifetime. It was concluded that coatings with the new composition GZO/YbSZ exhibited higher oxidation resistance and longer lifetime than GZO coatings. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Cheraghali, Sedigheh,
Dini, G.,
Caligiuri, Isabella,
Back, Michele,
Rizzolio, Flavio Nanomaterials (20794991)(3)
In this work, MnZn ferrite nanoparticles with hierarchical morphology were synthesized hydrothermally, and their surface characteristics were improved by the PEGylation process. In vitro MRI studies were also conducted to evaluate the ability of the synthesized nanoparticles as a contrast agent. All results were compared with those obtained for MnZn ferrite nanoparticles with normal structure. Microstructural evaluations showed that in ferrite with hierarchical morphology, the spherical particles with an average size of ~20 nm made a distinctive structure consisting of rows of nanoparticles which is a relatively big assembly like a dandelion. The smaller particle size and dandelion-like morphology led to an increase in specific surface area for the hierarchical structure (~69 m2/g) in comparison to the normal one (~30 m2/g) with an average particle size of ~40 nm. In vitro MRI, cytotoxicity and hemocompatibility assays confirmed the PEG-coated MnZn ferrite nanoparticles with hierarchical structure synthesized in the current study can be considered as an MRI contrast agent. © 2023 by the authors.
Nasri, N.,
Saharkhiz S.,
Dini, G.,
Yousefnia S. International Journal of Pharmaceutics (03785173)
In the current study, a new monoclonal antibody conjugated dual stimuli lipid-coated mesoporous silica nanoparticles (L-MSNs) platform was developed and investigated for specific co-delivery of the paclitaxel (PTX) and gemcitabine (Gem) to cancer cells and preventing their side effects during the treatment process. First, MSNs were synthesized and then coated with as-prepared pH-, and thermo-sensitive niosomes to produce L-MSNs. For this aim, Dipalmitoylphosphatidylcholine (DPPC) was used to create thermo-sensitivity, and 1, 2-Distearoyl-sn-glycerol-3-phosphoethanolamine -Citraconic Anhydride-Polyethylene Glycol (DSPE-CA-PEG) polymers were prepared and incorporated to the lipid layer for creation of pH-sensitivity. In the next step, trastuzumab as a monoclonal antibody (mAb) was conjugated to the maleimide groups of the 1, 2-Distearoyl-sn-glycerol-3-phosphoethanolamine DSPE-polyethylene glycol (PEG)-maleimide agents in the lipid bilayer via a disulfide bond. Dynamic light scattering (DLS) and zeta potential measurements, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) analyses were utilized to characterize the synthesized particles before and after surface modification. The encapsulation efficiency (EE%) and loading efficiency (LE%) of the particles were also evaluated. Additionally, the drug release study and MTT assay were done to evaluate the bioactivity potential of the fabricated platforms. The results of DLS and zeta potential measurements revealed an average size of 200 nm and a neutral zeta potential of about −1 mV for mAb-L-MSNs. Also, the FTIR spectra confirmed the formation of mAb-L-MSNs. Moreover, SEM analysis showed spherical-shaped MSNs with amorphous structure confirmed by XRD analysis, and BET test revealed ∼ 820 m2/g specific surface area and pore about 5 nm in size. The values of EE% and LE% of PTX were 90.3 % and 26.7 %, while these values for GEM were 89.5 % and 38.8 % in the co-loaded form, respectively. The thermo-pH-sensitivity examination showed approximately 500 nm of size increase after the change of pH and temperature from 7.4 and 37˚C to 5 and 42˚C. The release profile showed a pH-, and thermo-dependence manner, which led to about 89 % and 95 % of PTX and GEM released from the co-loaded platform at a pH of 5 and 42 °C while these values were 31.1 % and 32.2 % at pH of 7.4 and 37˚C, respectively. MTT assay data presented that when the mAb-L-co-loaded-MSNs platform containing 250 µg/mL drug was used, about 92 % of cells died in human epidermal receptors (HER2)-positive breast cancer cells (SKBR3), while just about 4 % of HER2-negative normal cells were killed. However, the growth inhibition rate of SKBR3 cells was caused by empty-mAb-L-MSNs, pure PTX and GEM combination were 9 % and 87 %, respectively. Moreover, the half inhibitory concentration (IC50) of the pure PTX, pure GEM, and mAb-coloaded-L-MSNs were 33, 17.6, and 6.5 µg/mL. The synergic effect of co-encapsulation of PTX and GEM in addition to trastuzumab conjugated L-MSNs was confirmed by a combinational index (CI) of 0.34. Therefore, this strategy leads to specific targeted drug delivery to cancer cells using a key-lock interaction between the trastuzumab and HER-2 receptors on the cancer cell membrane which stimuli the endocytosis of the particles to the cells followed by the destruction of the lipid layer in the acidic pH and the temperature of the lysosome, leading to enhanced release of PTX and GEM (pH of 5 and 42˚C). So, this platform can be considered a suitable carrier for cancer treatment. © 2023 Elsevier B.V.
Arabian Journal Of Chemistry (18785352)15(11)
Staphylococcus aureus is a common bacterial agent of biofilm formation in medical environments. The formed biofilm of this bacterium in bone tissue is one of the main causes of osteomyelitis, which is a serious health issue. Due to the importance of this infection after traumatic injuries or surgical intervention, it is necessary to develop a system that could release the antibiotics at the site of injury, specifically and gradually. The current study aimed to develop a nanosystem composed of single-stranded G-quadreplex DNA aptamer as the bio-recognition element, mesoporous silica nanoparticles (MSNs) as the carrier for gradual drug release, and Ampicillin as the cargo to be delivered to the site of infection. In silico methods were used to select an optimum binding aptamer against protein A of S. aureus. The binding of aptamer was confirmed via gel retardation assay, DLS, and Zeta potential analyses. The loading of the drug was confirmed by the FTIR method, and the drug release investigation showed almost 30 % of drug release via 48 h dialysis assay. The acquired results from the biofilm suppression assay indicated that this system provides a significant inhibitory effect against the S. aureus biofilm and has a high potential for the desired drug release to prevent the formation of biofilm, and could destroy the biofilm on the mice bone. The results of the MTT assay proved that this system does not pose a significant toxicity thread for MCF-7 cell viability, as a model for eukaryotic cells. In vivo studies are required to further confirm the efficacy of this system against S. aureus biofilm on bone. © 2022 The Authors
Current Drug Delivery (15672018)19(1)pp. 64-73
Aim: In this work, to improve the solubility and bioavailability of the rosuvastatin (RSV) drug, chitosan-coated mesoporous silica nanoparticles (CS-MSNs) as a drug delivery system were fabricated. Methods: To do this, first MSNs with a maximum specific surface area were synthesized from sodium silicate as silica source and different molar ratios of cethyl trimethylammonium bromide (CTAB) and pluronics (P123, PEO20 PPO17 PEO20) as surfactants via the sol-gel process. Then, the synthesized MSNs were coated by CS polymer with the help of (3-glycidoxypropyl)methyldi-ethoxysilane (GPTMS) as a linker between MSNs and CS. Subsequently, the RSV drug was loaded into the synthesized CS-coated MSNs. The products were characterized by different techniques, including X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR). The in vitro drug release profile of the fabricated DDS was evaluated in a typical phosphate-buf-fered saline (PBS) solution at different pH values (i.e., 4, 6, and 7.4) for 48 h. To assess the cyto-toxicity, the viability of the human fibroblast cells exposed to the fabricated DDS was also ex-amined. Results: The results showed that at an optimal molar ratio of P123/CTAB, the amorphous MSNs with a specific surface area of about 1080 m2/g, a pore diameter of 4 nm, a pore volume of 1.1 cm3/g, and an average size of about 30 nm were synthesized. Also, the presence of all the compo-nents, including the CS coating and the RSV drug, was confirmed in the structure of the fabricated DDS by FTIR analysis. Due to the pH-responsive feature of the CS coating, the RSV drug release from the fabricated DDS showed a reasonable environmental response; as the pH value of the PBS solution decreased, the degree of drug release increased. Conclusion: The CS coating enhanced the cytotoxicity of the fabricated DDS and led to sustain-able drug release behavior, which would provide a beneficial approach for drug delivery technolo-gy. © 2022 Bentham Science Publishers.
Aquaculture (00448486)548
White spot syndrome virus (WSSV) is one of the most threatening viral pathogens of shrimp worldwide. VP28, the major capsid protein of WSSV, is reported to play an essential role in the interaction with the host cells. Usually, the diagnostic test of WSSV is performed by one-step PCR, which is neither field-usable nor rapid enough. Therefore, the development of early diagnostic tests is imperative for the management of disease and to prevent huge economic losses. In this work, a rapid colorimetric aptasensor with high selectivity and sensitivity was introduced. First, a new ssDNA aptamer for the detection of WSSV was designed from a random pool of aptamer sequences based on the docking score and bioconjugate free energy, and then, evaluated experimentally. The designed aptamer was used to prepare an aptasensor conjugate gold nanoparticles (AuNPs) as a recognition element that increased the resistance of AuNPs to salt-induced aggregation. Therefore, the AuNPs with spherical morphology and average particle size of about 20 nm were synthesized for this reason. The results showed that the aptamer didn't attach to the other pathogens (i.e., IHHN and Vibrio harveyi) and healthy shrimp cells, and remained stable. Interestingly, the gray-blue color of aptasensor was seen only by the presence of WSSV, indicating the aptasensor assay showed good specificity to WSSV. The limit of detection (LOD) of the aptasensor was 104 copies of WSSV that could be detected only utilizing naked eyes. It was concluded that the designed aptamer had excellent potential for the detection of WSSV as a rapid visual colorimetric assay in aquaculture shrimp farmers. © 2021 Elsevier B.V.
RSC Advances (20462069)12(38)pp. 24876-24886
Streptococcus mutans is a commensal and opportunistic pathogen that causes several diseases by forming a biofilm in humans and animals in many areas such as nasopharyngeal, cardiac valves, lungs, and oral cavity. Biofilms are very important in prosthetic infections associated with medical implants. The use of nanoparticles is one of the evolving fields in biofilm targeting. Silver nanoparticles can be used for biofilm targeting due to their inherent antimicrobial properties. Hybridization of nanoparticles with small molecules increases their biological properties and makes them multifunctional. The present investigation aimed to design an appropriate silver nanoparticles-aptamer complex that binds to the surface receptors of streptococcal strains. For this reason, silver nanoparticles with particle sizes in a range of 50 to 70 nm were synthesized and connected to a designed aptamer with a streptavidin-biotin linker. Then, the effect of the complex was investigated on the S. mutans biofilm formed on the surface of a medical-grade titanium substrate. The silver nanoparticles-aptamer complex at a concentration of 100 μg mL−1 after 48 h inhibited 43% of the biofilm formation and degraded 63% of the formed biofilm. Also, the cell availability reached 96% and the complex was stable in cell medium culture for 360 min. It was concluded that this complex could be a good candidate for removing the formed biofilms on the surface of titanium implants. © 2022 The Royal Society of Chemistry.
Polymer Bulletin (14362449)79(3)pp. 1627-1645
In this study, for the first time, core/shell nanofibrous mats of polycaprolactone (PCL) and chitosan (CS) as a carrier for the rosuvastatin (RSV) drug were fabricated. To do this, the electrospinning technique using a two-fluid stainless steel coaxial spinneret consisted of two concentrically arranged needles was used. The CS layer as a shell contained 5% (w/w) of the RSV drug. The fabricated nanofibrous mats were characterized by different techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), tensile testing, and hydrophilicity measurements. Then, the fabricated core/shell nanofibrous mats containing the RSV drug as a drug delivery system (DDS) were used to evaluate the in vitro drug release behavior in a typical phosphate-buffered saline (PBS) solution at different pH values (i.e., 4, 6, and 7.4) for 48 h. Moreover, the corresponding drug release mechanism was investigated. To study the cytotoxicity, the viability of the human fibroblast cells exposed to the fabricated DDS was examined. The results showed that under optimum electrospinning conditions, the average diameter of the PCL core was about 120 nm, and the thickness of the CS shell was about 60 nm. Also, the presence of all the components was confirmed in the structure of the fabricated DDS. Moreover, the addition of the RSV drug had no significant effect on the mechanical properties of the PCL/CS core/shell nanofibrous mats. Due to the pH-responsive feature of the CS shell, the RSV drug release from the fabricated DDS showed a reasonable environmental response as the pH value of the PBS solution decreased, the degree of drug release correspondingly increased. It was also found that the prolonged release of the RSV drug from the fabricated DDS followed the Korsmeyer–Peppas kinetic model with the Fickian diffusion mechanism at all the pH conditions. The CS layer enhanced the cytotoxicity and hydrophilicity of the fabricated DDS and led to the controllable drug release behavior, which would provide a beneficial approach for drug delivery technology. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Ahmadi M.,
Dini, G.,
Afshar m., ,
Ahmadpour F. Journal of Materials Research (08842914)(11)
Biphasic calcium phosphate (BCP) bioceramics have shown efficacy for bone repair because of their controllable degradation rate that can be modified by chemical composition and phase ratio. To develop a new BCP ceramic in this work, 5.0 Sr, 0.6 Mg, and 0.2 Si (all in mol%) triple-substituted BCP powder was synthesized and calcined at 550 to 750 °C. The obtained results confirmed the presence of substituted ions in the product and also showed that powder calcined at 650 °C consisted of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) nanoparticles with a weight ratio of ~ 60/40. The apatite layer with a rod-like morphology was formed on the surface of the sample fabricated from this powder after 28 days of soaking in SBF at ~ 37 °C. Also, the substituted ions showed positive effects on viability and the alkaline phosphatase activity of MG63 cells. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive licence to The Materials Research Society.
Journal of Biotechnology (01681656)342pp. 72-78
Today, there is a great interest in using astaxanthin due to its potential health advantages. Application of different types of nanoparticles (NPs) as stress agents to enhance astaxanthin production in Haematococcus pluvialis, a microalgae strain, has been reported in the literature. In this study, the effect of different concentrations of zinc oxide (ZnO) NPs on the enhancement of astaxanthin production in H. pluvialis was investigated. First, ZnO NPs were synthesized from zinc nitrate as the precursor and sodium hydroxide (chemical method), and peel extract of pomegranate (green method) as reducing agents. To study the cell viability and stimulate the astaxanthin production, H. pluvialis cells were exposed to the different concentrations (i.e. 50, 100, 200, and 400 μg.ml−1) of ZnO NPs. The synthesized powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS) methods. The characterization results showed that the pure ZnO NPs were successfully synthesized via both methods with uniform particle size distribution. But, the average particle size of the green synthesized ZnO NPs (about 30 nm) was smaller than that of the chemically synthesized ones (about 80 nm). Maximum astaxanthin production (~ 20 mg.g−1 of dry biomass of H. pluvialis) was achieved at 100 μg.ml−1 of green synthesized ZnO NPs exposure to the H. pluvialis in comparison with the control culture after 15 days. However, ZnO NPs concentration above 200 μg.ml−1 was toxic to the microalgae. From these results, it can be concluded that a specific amount of ZnO NPs could be considered as a worthy candidate for the enhancement of astaxanthin production in H. pluvialis. © 2021 Elsevier B.V.
Tabeshfar M.,
Salehi m., ,
Dini, G.,
Dahl P.I.,
Einarsrud M.-A. Surface and Coatings Technology (02578972)
Gd2Zr2O7 ceramic is considered as a potential candidate for thermal barrier coatings. Here we present hot corrosion behavior of single layer Gd2Zr2O7 (GZO), Gd2Zr2O7 + 50 wt% YbSZ (GZO/YbSZ), YSZ and double-layer YSZ/Gd2Zr2O7 + 50 wt% YbSZ (YSZ + GZO/YbSZ) coatings prepared by air plasma spraying on Inconel 625 substrates. Prior to hot corrosion the fracture toughness of the coatings was assessed by Vickers indentation showing a variation between 0.6 and 2.3 MPa.m1/2 where the GZO/YbSZ coating exhibited the highest fracture toughness. The hot corrosion test was conducted by exposing the coatings to an equimolar mixture of Na2SO4 and V2O5 at 750 °C. After the hot corrosion test, the type of phases, chemical composition, microstructure and crack formation were investigated. Formation of GdVO4 and YVO4 was observed as the corrosion products in the GZO containing coatings and the YSZ coating, respectively. All coatings showed the formation of monoclinic zirconia after the corrosion test. The Gd2Zr2O7 + 50 wt% YbSZ (GZO/YbSZ) coating showed the best hot corrosion resistance due to reduced reactivity and enhanced fracture toughness and represents a new composition with properties promising for TBC applications. © 2020 Elsevier B.V.
Tabeshfar M.,
Salehi m., ,
Dini, G.,
He J.,
Einarsrud M.-A. Journal of Materials Research (08842914)(16)
Abstract: Doped Gd2Zr2O7 materials have interesting properties as thermal barrier coatings (TBC) to replace the YSZ topcoats traditionally used. Here we investigate the thermomechanical properties and phase relations of Gd2Zr2O7 (GZO) alloyed with 5 mol% Yb2O3 stabilized ZrO2 (YbSZ) in the composition range (Gd2Zr2O7)1−x(YbSZ)x, 0 ≤ x ≤ 0.98. With increasing YbSZ content, phase transformations from ordered to disordered pyrochlore to fluorite and tetragonal structures were observed. The thermal expansion coefficient (TEC) and Vickers hardness were correlated showing a maximum hardness (~ 11.5 GPa) and minimum TEC at x = 0.82. At 1000 °C, the TEC for the end members, x = 0 and 0.98, were 11.4 and 11.3 × 10–6 K−1, respectively. The fracture toughness, KIC, showed an average value around 1.5 MPa m0.5 for x ≤ 0.93 and increased significantly at x = 0.98 reaching 5.4 MPa m0.5 due to the presence of a ferroelastic phase. For TBC applications, compounds with x = 0.98 show promise due to high TEC and high KIC. Graphic abstract: Fig. 5a summarize the most important results in the manuscript. Showing a significant increase in fracture toughness for compositions with x=0.98.[Figure not available: see fulltext.] © 2021, The Author(s).
Aquaculture (00448486)534
Selenium is one of the essential elements with an important role in improving immune responses. Besides, in humans and animals, the element helps to resist infections. Selenium nanoparticles (Se NPs) have recently been examined for their biological activities. In this study, selenium nanoparticles (Se NPs) were synthesized using the microwave-assisted method under molar ratios of selenious acid to ascorbic acid ranging from 5:1 to 50:1 as starting materials and different irradiation times (5 to 15 min). The results showed that the size and morphology of the synthesized Se NPs were controlled by the selenious acid/ascorbic acid concentration ratio and the microwave irradiation time. The synthesized Se NPs with spherical morphology, small particle size (about 40 nm), and good colloidal stability were selected and coated with aqueous extract of Sargassum angustifolium. The antibacterial activity of the algae-coated and uncoated Se NPs was studied against Vibrio harveyi (a serious pathogen of Penaeus vannamei). In addition, the cytotoxicity of different concentrations (10 to100 μg/mL) of the Se NPs (algae-coated and uncoated) was investigated via the cell viability assay on two cultured cells; shrimp hemocyte and human lymphocyte. The results showed that the antibacterial activity of algae-coated Se NPs against Vibrio harveyi (MIC: 200 μg/mL) was improved compared to uncoated Se NPs (MIC: 400 μg/mL). The cell viability assay revealed that both the algae-coated and uncoated Se NPs showed toxicity effect neither on the human lymphocyte nor on the shrimp hemocyte at 25 μg/mL concentration after 48 h of incubation. Due to the antibacterial effects and no toxicity of the synthesized algae-coated Se NPs on both human and shrimp cells, the current study for the first time reports that the algae coated Se NPs can be considered for further investigation as a potential replacement for antibiotics in controlling Vibrio harveyi infections in Penaeus vannamei farming. © 2020 Elsevier B.V.
Journal of Soil Science and Plant Nutrition (07189508)20(1)pp. 232-243
The present study was done to isolate and characterize two strains of phosphate solubilizing bacteria from rhizospheres of acacia, sugar beet, and wheat, then determine synergic effects of nanosilica and these strains on the vegetative growth of land cress plant. Isolates identification was performed using physiological, morphological, biochemical tests, and 16S ribosomal ribonucleic acid sequencing. Nanosilica was extracted from Equisetum telmateia and characterized via X-ray diffraction, scanning electron microscopy, dynamic light scattering, Brunauer–Emmett–Teller, and X-ray fluorescence techniques. The size and the purity of extracted silica powder were about 30 nm, 97.5 %, respectively. Two strains, namely, Pseudomonas stutzeri and Mesorhizobium sp. were the most efficient strains to grow and solubilize phosphorus in the presence of 860 mM NaCl and various pH conditions. The highest growth of these two strains was observed at 0.05 and 0.07 ppm of nanosilica. The highest amount of dry weight of shoot and root of land cress plant was recorded with the simultaneous application of these strains in combination with nanosilica. The combination of nanosilica and these strains enhanced the soil nitrogen and phosphorus content and the vegetative growth of land cress plant. © 2019, Sociedad Chilena de la Ciencia del Suelo.
Journal of Composite Materials (00219983)(17)
In this study, the rice husk as a source of silica was used to synthesize the Al2O3/SiC composite via the self-propagation high-temperature synthesis (SHS) process. Then, the particle size of the synthesized product was reduced to the nanoscale using a planetary ball mill. Finally, different amounts (5, 10, and 15 wt.%) of Al2O3/SiC nanoparticles were incorporated into an epoxy resin in order to improve the mechanical properties and the dielectric strength of fabricated epoxy-based composites. The results indicated that the Al2O3/SiC composite was successfully synthesized by the SHS process from a mixture of the rice husk ash, Al, and carbon black powders as starting materials. The average size of the synthesized Al2O3/SiC particles decreased to 80 nm after 12-h ball milling. Also, the mechanical properties of the fabricated epoxy-based composite samples were improved with the addition of Al2O3/SiC nanoparticles in the investigated range in comparison with the pure epoxy sample. Additionally, the overall dielectric strength of the fabricated epoxy-based composites containing 5–15 wt.% of Al2O3/SiC nanoparticles was higher than that of the pure epoxy. These results were interpreted in terms of the synthesis mechanism of Al2O3/SiC composite via the SHS process, the rice husk ash structure, the interfacial bonding between the polymer chains and the surface of nanoparticles, and the insulation nature of the synthesized nanoparticles. © The Author(s) 2019.
Journal of Drug Delivery Science and Technology (17732247)56
In this study, an optimal combination of sodium alginate (SA)/polyvinyl alcohol (PVA) hydrogel containing Rosuvastatin-loaded chitosan (CS) nanoparticles was fabricated as the drug delivery system (DDS). First, the drug-loaded nanoparticles were synthesized by the ionic gelation method. Then, several hydrogel films with different ratios of SA:PVA were prepared. Subsequently, different concentrations of drug-loaded CS nanoparticles were added to a hydrogel with an optimal SA:PVA ratio. The results of the tensile test showed that in the SA:PVA ratio of 7:3 and 3 wt % of drug-loaded CS nanoparticles, the hydrogel film was achieved with optimal mechanical properties. The mean size of drug-loaded CS nanoparticles determined by the AFM and DLS methods was in the range of approximately 100–150 nm. The release profile of the Rosuvastatin drug from the fabricated DDS illustrated that all the loaded drug was released within 24 h, and the CS nanoparticles had a significant effect on the release behavior. Also, the cytotoxicity of the fabricated DDS on the human fibroblast cells demonstrated a high cell viability after 72 h of incubation. Therefore, the fabricated SA/PVA hydrogel containing drug-loaded CS nanoparticles depicted a great potential as the delivery system for the controlled release of the Rosuvastatin drug. © 2020 Elsevier B.V.
Ceramics International (02728842)(12)
In this work, the BaAl2O4: Eu2+, Eu2+/L3+ (L= Dy, Er, Sm, Gd, Nd, and Pr) phosphors were synthesized via a facile solid-state reaction method using LiCl as a flux material at 1100 °C. The structural properties, microstructure, adsorption and photoluminescence characteristics of products were evaluated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Uv–vis adsorption and photoluminescence (PL) analyses. The observation of XRD patterns showed that even 10% LiCl is not able to produce any impurity phase in BaAl2O4: Eu2+ crystal structure, although the microstructure morphology is considerably affected. The particle size of BaAl2O4: Eu2+ phosphors was about 220 nm while the use of LiCl flux resulted in a remarkable decrease of this parameter to about 120 nm. Furthermore, the PL patterns disclosed that Eu2+ ions have occupied one type of Ba2+ sites while larger quantities of lanthanides (L3+) occupied the second type of Ba2+ sites. The strongest photoluminescence emission intensity at the wavelength of 495 nm was achieved when 5 wt% LiCl was added to BaAl2O4: Eu2+. Also, the absorption analysis revealed that the addition of flux enriches the adsorption of Congo red (CR) dye on the phosphor powders. The use of 5 wt% flux material led to noticeable improvement of CR adsorption capacity from 38.53 to 48.3 mg g−1. © 2020 Elsevier Ltd and Techna Group S.r.l.
Zamani, Davood,
Azmah Hanim M.A.,
Dini, G.,
Sajuri Z.,
Ismarrubie Z.N. Malaysian Journal of Microscopy (18237010)(2)
The tensile properties and microstructure evolution of Fe–17Mn–2Al–0.6C TWIP steel exposed to 80% cold rolling reduction, and annealed at different temperatures were experimentally investigated in order to promote strength–ductility synergy. For this purpose, uniaxial tensile tests were performed on specimens obtained from 80 % cold-rolled sheets, and subsequent annealed at 550, 575, 610, 650, 750, 850, and 1100 ºC, for 30 min. Then, the resulted microstructures were examined by a scanning electron microscopy and a transmission electron microscopy. The results indicated the yield strength and ultimate tensile strength mainly decreased as annealing temperature increased, while the total elongation greatly increased. The variation in the product of ultimate tensile strength and total elongation against yield strength was linked to the annealing temperature. The most evident change in strength and elongation was located between 575 and 610 °C, due to the fraction of recrystallized areas. The fraction of recrystallized areas and grain size increased with increasing annealing temperature. TWIP steel microstructure designs that rely on annealing treatments in the recovery and also lower limits for the partial recrystallization regions, provide opportunities to develop TWIP steel that offer superior combinations of elevated yield strength (i.e., above 1350 MPa), along with considerable product of ultimate tensile strength and total elongation (i.e., above 25 GPa%). To get maximum value for the product of ultimate tensile strength and total elongation, the grain sizes of 7.4 and 16.8 µm for the TWIP steel were suggested, within which it reached more than 75 GPa%. © Malaysian Journal of Microscopy (2020). All rights reserved.
Materials Science and Engineering: A (09215093)
Accumulative roll bonding (ARB) process at room temperature was used to fabricate a nanostructured twinning-induced plasticity (TWIP) steel. The effect of the number of ARB cycles from 1 to 3 on the microstructure and mechanical properties of Fe-31Mn-3Al-3Si (wt%) TWIP steel was investigated. The results showed that the microstructure of the 1-cycle ARB-processed sample mainly contained the primary and secondary mechanical twins. However, in the microstructure of 2-cycle ARB-processed sample, new configurations of small nanotwins which they are known as the hierarchical nanotwinned (HNT) structures were observed between the secondary mechanical twins. In the microstructure of 3-cycle ARB-processed sample, new subdivided grains with a mean size of about 100 nm were produced. Additionally, the 3-cycle ARB-processed TWIP steel sample exhibited extraordinary strength (about 1.2 GPa) and reasonable ductility (about 15%). The mechanical behavior of ARB-processed TWIP steel was interpreted as the evidence for microstructural features such as the mechanical twins (especially, the HNT structures) and nano/ultrafine grains. © 2018 Elsevier B.V.
Materials Research Express (20531591)6(9)
The medicinal plant of Echinacea purpurea has been used commonly in traditional medicine of Iran for antioxidant and anticancer activity. In this study, ZnO nanoparticles (NPs) were synthesized using Allium jesdianum extract and then the effects of synthetized ZnO NPs on anti-cancer activity and amount of cichoric acid and flavonoid in aerial and root extracts of E. purpurea were investigated. The formation of ZnO NPs was confirmed by UV-visible absorption spectrum, XRD, DLS, FTIR and SEM techniques. The effect of extracts of E. purpurea treated with synthesized ZnO NPs on the MCF-7, MCF-10 and peripheral blood monolayer cells were investigated. The FTIR spectrum confirmed the presence of phytochemicals around the ZnO NPs surface. The effect of synthesized ZnO NPs on anticancer activity of extract of E. purpurea and its biomass was found positive contrary to the untreated and ZnO microparticles (MPs) treated plants. According to HPLC result, the relative retention time for cichoric acid was appeared at 12 min. The plants treated with ZnO NPs produced up to 3.5 times more cichoric acid than the control. To the best of our knowledge, this is the primary study on the synthesis of ZnO NPs by A. jesdianum with to its effects on enhancing anticancer activity, PBMCs proliferation, contents of cichoric acid and flavonoid. © 2019 IOP Publishing Ltd.
Materials Science and Engineering C (09284931)105
In the present study, porous (about 70 vol%) nanocomposite scaffolds made of polycaprolactone (PCL) and different amounts (0 to 15 wt%) of 45S bioactive glass (BG) nanoparticles (with a particle size of about 40 nm) containing 7 wt% strontium (Sr) were fabricated by solvent casting technique for bone tissue engineering. Then, a selected optimum scaffold was coated with a thin layer of chitosan containing 15 wt% Sr-substituted BG nanoparticles. Several techniques such as X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), tensile test, and water contact angle measurement were used to characterize the fabricated samples. In vitro experiments including degradation, bioactivity, and biocompatibility (i.e., cytotoxicity, alkaline phosphate activity, and cell adhesion) tests of the fabricated scaffold were performed. The biomedical behavior of the fabricated PCL-based composite scaffold was interpreted by considering the presence of the porosity, Sr-substituted BG nanoparticles, and the chitosan coating. In conclusion, the fabricated chitosan-coated porous PCL/BG nanocomposite containing 15 wt% BG nanoparticles could be utilized as a good candidate for bone tissue engineering. © 2019 Elsevier B.V.
Vahiddastjerdi H.,
Rezaeian A.,
Toroghinejad M.R.,
Dini, G.,
Ghassemali E. Optics and Laser Technology (00303992)
In the present study, the microstructural and mechanical properties of laser beam-welded thin sheet twinning-induced plasticity (TWIP) steel were investigated. The pulsed neodymium: yttrium-aluminum-garnet (Nd: YAG) laser beam welding process parameters were modeled and optimized based on experimental data and statistical analysis using response surface methodology (RSM) technique. Process parameters range, i.e. the power input (2000–3000 W), welding speed (0.2–1 mm/min), and spot size (0.3–0.7 mm) were selected properly in order to obtain the desired mechanical properties. Main effects of each factor along with interaction effect with other factors were determined quantitatively. The predicted and actual values of the mechanical properties compared using analysis of variance (ANOVA) in order to verify the adequacy of the developed model. Optimal laser beam welding parameters were identified as the power input, welding speed and spot size of 2586 W, 0.53 mm/min, and 0.48 mm, respectively. Using parameters in the optimal conditions, a welding joint with tensile load of 2001 N (% 94 strength of the base metal) was obtained. In addition, the welding zone with an average grain size coarser than the one for the base metal and a random texture was identified. © 2019 Elsevier Ltd
Journal of Magnetism and Magnetic Materials (03048853)
In this work, manganese ferrite (MnFe2O4) nanoparticles (NPs) were successfully synthesized via the hydrothermal method, and the dispersibility and the biocompatibility of the product were improved by the polyethylene glycol (PEG) polymer as a coating onto the surface of the synthesized NPs. The potential of the use of the synthesized PEG-coated NPs as contrast agents in the magnetic resonance imaging (MRI) was also investigated. The XRD results showed that the monophase MnFe2O4 NPs were synthesized at the pH of 11, the temperature of 200 °C for 12 h (optimal conditions) via the hydrothermal method. The FE-SEM and TEM investigations showed that the hydrothermally synthesized NPs had a quite homogeneous size distribution with the average size of about 50 nm. The water-based dispersions of PEG-coated Mn-ferrite NPs showed the higher stability at pH 7 in comparison with the uncoated ones. The PEG-coated Mn-ferrite NPs showed a high saturation magnetization value (60 emu/g). An enhanced MRI contrast effect by the PEG-coated NPs was confirmed via the in vitro MRI study. Moreover, the cytotoxicity activity of the PEG-coated NPs on the HeLa cells demonstrated a high cell viability even at a 0.2 mg/ml of NPs after 48 h of incubation. Also, the in vitro hemocompatibility studies of the synthesized NPs showed that the PEG-coated NPs had no effect on the blood coagulation factors, and the red blood cell (RBC) count measured by complete blood count (CBC) tests in all the investigated concentration range. It can be concluded that, therefore, the hydrothermally synthesized PEG-coated Mn-ferrite NPs in this study can be good candidates as MRI contrast agents. © 2018 Elsevier B.V.
Journal of Superconductivity and Novel Magnetism (15571939)(12)
In this work, a series of silver-substituted cobalt ferrite (AgxCo1-xFe2O4, 0 ≤ x ≤ 0.1) nanoparticles (NPs) were synthesized, and then a sample with monophase structure and optimum magnetic properties was coated with an amorphous silica layer. First, Ag-substituted Co-ferrite NPs were synthesized via a sol-gel auto combustion method from aqueous metal nitrates solutions. Then, all the powders were characterized by several techniques such as X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), and vibrating sample magnetometry (VSM). These results showed that when the Ag content was between 0 and 0.08, the synthesized powders were the cubic spinel structure, having spherical-shaped particles with an average size of about 20–25 nm. Afterward, the silica coating was applied on the surfaces of the selected sample (i.e., Ag0.08Co0.92Fe2O4 NPs with monophase structure and optimum magnetic properties) by a sol-gel approach based on the Stöber process from the tetraethyl orthosilicate (TEOS) as the precursor of silica. Transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and zeta potential investigations were used to study the characteristics of the silica-coated Ag-Co-ferrite NPs. The results of FTIR and TEM analyses confirmed the presence of the silica coating on the surfaces of the Ag-Co-ferrite NPs. Although the silica-coated sample showed the saturation magnetization (MS) value slightly lower than that of the uncoated one, however, its magnetic properties are suitable for use in different biomedical applications. Also, a water-based suspension containing the silica-coated Ag-Co-ferrite NPs showed a more negative zeta potential value at the pH of 7 in comparison with a suspension containing uncoated ones. Therefore, it can be concluded that the synthesized silica-coated Ag0.08Co0.92Fe2O4 NPs in this study could be considered as a good candidate for the preparation of biomedical ferrofluids. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Materials Chemistry and Physics (02540584)223pp. 564-568
In this study, alumina/yttria core/shell nanoparticles with different yttria shell thicknesses were synthesized via a partial wet chemical route. The formation of core/shell nanoparticles was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The yttria shell thickness was determined from the peak broadening and the volume fraction of the coating phase obtained from the XRD pattern via the Rietveld method and compared with the TEM micrograph. The results indicated that the XRD is an effective method for the quantitative analysis of the core/shell nanoparticles structure yielding the shell thickness as a function of the crystallite size within the relatively wide range of shell thickness. © 2018 Elsevier B.V.
In this study, a steel sword belonging to the Safavid dynasty was investigated to identify its chemistry, microstructure, mechanical properties, and processing. To this aim, chemical and phase analyses, optical microscopy investigations and a hardness test were conducted. The results indicated that the sword blade material was plain carbon steel containing 1.42 wt.% C. The microstructure consisted of spheroidal cementite particles in a ferrite matrix, facilitating the formation of a curved sword. It seemed that a combination of heat treatment and metal-forming techniques (thermo-mechanical process) was utilized to obtain this microstructure. © 2017, The Minerals, Metals & Materials Society.
Advances in Natural Sciences: Nanoscience and Nanotechnology (20436262)9(4)
This investigation was done to study the effect of green synthesized ZnO nanoparticles (NPs) on the anticancer activity of callus extracts of Echinacea purpurea in comparison with commercial ZnO microparticles (MPs). Leaf explants of E. purpurea were grown on the Murashinge and Skoog (MS) medium containing different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and naphthalene acetic acid (NAA). Callus induction at optimum concentrations were considered under both light and dark conditions. Among media with diverse concentrations of 2,4-D and NAA, fast-growing friable callus was started within three weeks after culturing on the MS medium containing 2.0 mg . After adding different concentrations of synthesized ZnO NPs and ZnO MPs to the culture medium containing 2 mg , the effect of ZnO NPs on the anticancer activity of plant extracts and callus biomass was found positive contrary to the control and ZnO MPs. However, these extracts did not have any cytotoxic activity on MCF-10 cells and peripheral blood monolayer cells. The frequency and intensity of CD4 expression on peripheral blood monolayer cells was not increased in the presence of all extracts. The highest flavonoid production of the extracts was also achieved in calli treated with different concentration of ZnO NPs. Therefore, it can be concluded that there is a direct relationship between the anticancer activity of E. purpurea and flavonoid contents. © 2018 Vietnam Academy of Science & Technology.
Journal of Biomedical Materials Research - Part A (15493296)(8)
In this study, biodegradable nanocomposites consisting of poly (glycerol sebacate) (PGS) elastomeric matrix and the reinforcing phase of calcium titanate (CaTiO3) nanoparticles were fabricated as a nerve guidance conduit (NGC) for peripheral nerve regeneration. CaTiO3 nanoparticles were synthesized via the sol-gel method and calcined at 800°C for 60 min. PGS elastomer was synthesized via the polycondensation reaction of glycerol and sebacate (1:1) and 2.5 and 5 wt. percentages of the synthesized CaTiO3 nanoparticles were added to the PGS prepolymer solution. The composites obtained were heated in order to make crosslinks in the pre-polymer. CaTiO3 nanoparticles, PGS elastomer, and the composites fabricated were characterized in terms of their structural, chemical, physical, mechanical, and cell response properties to evaluate the feasibility of using the nanocomposite for NGC applications. The results indicated that CaTiO3 nanoparticles were 50 nm in size. When the nanoparticles were added to the PGS, the elastic modulus and tensile strength of the nanocomposite reached values of about 1 and 0.5 MPa, respectively that are near those of natural nerves. The degradation behavior and swelling of the nanocomposites, as compared with those of the PGS elastomer, were controlled by introducing CaTiO3 into the PGS, which swelling limitation could prevent nerve compression. It was observed that Ca2+ ions established chemical bonds with PGS, which led to high crosslink densities that, in turn, contribute to improved mechanical properties of the composite. The Ca2+ ions released from the nanocomposite samples were in the nontoxic range. The PC12 cell line on the surface of the nanocomposite specimens showed good cell adhesion and proliferation with improved axon outgrowth and extension. Based on the results obtained the fabricated PGS/CaTiO3 nanocomposite may be recommended as a suitable NGC with desirable effects on peripheral nerve regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2181-2189, 2018. © 2018 Wiley Periodicals, Inc.
Journal of the European Ceramic Society (09552219)38(9)pp. 3297-3304
In this study, α-Al2O3@amorphous alumina nanocomposite core-shell structure was synthesized from AlCl3 and the commercial α-Al2O3 nanoparticles as the starting materials via a wet chemical route. The results indicated that the shell material mainly comprised of ammonium chloride and boehmite phases. Boehmite was transformed to the amorphous and γ-Al2O3 phases after the calcination process and the shell material was completely converted to γ-Al2O3 at 1000 °C. However, for the α-Al2O3@amorphous alumina core-shell nanoparticles were completely converted to α-Al2O3 at 1000 °C. It can be concluded that α-Al2O3 core particles, as the seed crystalline, help to transforming of γ-Al2O3 phase as the shell material directly without forming transitional phases to α-Al2O3. The optical polycrystalline alumina was fabricated using spark plasma sintering of α-Al2O3@amorphous alumina core-shell nanocomposite. The body sintered has a final density of ∼99.8% and the in-line transmittance value is ∼80% within the IR range. © 2018 Elsevier Ltd
Journal of Materials Engineering and Performance (10599495)(12)
In the paper, structural parameters and mechanical properties of Al5083 alloy sheet during equal channel angular rolling (ECAR) process and their relationship are studied. In order to evaluate the effect of ECAR process, Al5083 strips were subjected to the ECAR process for 1, 2, and 3 passes through the die channel angles 110°, 120°, and 130° at two routes. The effect of the process on the microstructural evolution of samples was investigated by means of x-ray diffraction and EBSD techniques. X-ray pattern has been analyzed using Rietveld method to compute structural parameters, including microstrain, average crystallite size, and dislocation density. The results showed that the dislocation density and microstrain were increased, and crystallite size was decreased during ECAR process. It was found that the behavior of variations in mechanical properties was in accordance with the dislocation density changes. This paper revealed that the increase in the strength of ECARed samples could be attributed to reduction in high-angle grain boundaries and the increase in dislocation density. Moreover, the yield strength estimated from Taylor equation was found in accordance very well with the experimentally measured yield strength of the samples. © 2017, ASM International.
Zamani, Davood,
Golshan A.,
Dini, G.,
Ismarrubie Z.N.,
Azmah Hanim M.A. Journal of Materials Engineering and Performance (10599495)(8)
This research work studied the effect of cold rolling reduction and subsequent annealing temperature on the microstructural evolution and the mechanical properties of Fe-32Mn-4Si-2Al twinning-induced plasticity steel plates. For this, uniaxial tensile tests were carried out for three cold rolling reductions (50, 65 and 80%) and subsequent annealing treatment at 550-750 °C for 1.8 ks. The results were discussed in terms of the yield strength, ultimate tensile strength and total elongation and its dependence on the introduced microstructure. Regression analysis was used to develop the mathematical models of the mechanical properties. Moreover, analysis of variance was employed to verify the precision of the mathematical models. Finally, desirability function was used as an effective optimization approach for multi-objective optimization of the cold rolling reduction and annealing temperature. It is considerable that there is no research attempting to find optimum mechanical properties of the steels using this approach. The results indicated that applying large cold rolling reduction (upper than 75%) and subsequent annealing treatment in the recovery region and also the application of large cold rolling reduction and the subsequent annealing treatment in the lower limit of partial recrystallization region were effective methods to obtain an excellent combination of mechanical properties. © 2017, ASM International.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science (10735623)(7)
For the first time, martensite treatment was used to fabricate an ultrafine-grained (UFG) twinning-induced plasticity (TWIP) steel. The effects of cold rolling with 70 pct reduction at the liquid nitrogen temperature and subsequently annealing at 973 K (700 °C) for 5 to 20 minutes on the microstructure and mechanical properties of Fe-22Mn-0.4C-1.5Al-1Si TWIP steel were investigated. The results showed that a fully recrystallized UFG TWIP steel with a mean grain size of about 400 to 600 nm can be produced by the designed martensite treatment. The UFG TWIP steel exhibited high yield and tensile strengths and relatively high ductility. © 2017, The Minerals, Metals & Materials Society and ASM International.
Materials Science Forum (02555476)904pp. 107-111
In this study, α-Al2O3-CeO2 core-shell nanoparticles were synthesized from the cerium acetate and the commercial α-Al2O3 nanoparticles as the starting materials via a wet chemical method. Poly (acrylic acid) (PAA) as an additive compound was used for the surface modification of alumina nanoparticles. Also, the effects of PAA content, pH value and calcination temperature on the synthesis behavior of α-Al2O3-CeO2 nanoparticles were investigated. The formation of core-shell structure was investigated using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The results indicated that at the PAA=1.5 wt. %, pH=6 and calcination temperature=1150oC (as optimal conditions), the core-shell nanoparticles with alumina core and ceria shell and homogeneous size distribution were synthesized successfully. © 2017 Trans Tech Publications, Switzerland.
Torabian n., ,
Ziaei-rad s., ,
Jafari M.,
Dini, G. Metallography, Microstructure, and Analysis (21929262)(2)
In this paper, a dislocation density-based finite element model is developed to study the behavior of twinning-induced plasticity (TWIP) steels in which mechanical twinning plays a significant role in the plastic deformation process. The model is calibrated for Fe-31Mn-3Al-3Si TWIP steel using experimental data. Comparison of the computational results with experimental observations suggests that the numerical model acceptably predicts the macroscopic behavior and the twinning content of the material. Next, the developed numerical model is employed to investigate some microstructural characteristics of the material. The effect of grain size on twinning is also studied. In addition, different loading conditions on a representative volume element are considered to reveal the existence of any relationship between twinning and triaxiality. © 2016, Springer Science+Business Media New York and ASM International.
Menati, S.,
Amiri rudbari, H.,
Askari, B.,
Farsani, M.R.,
Jalilian, F.,
Dini, G. Comptes Rendus Chimie (18781543)19(3)pp. 347-356
The condensation reaction of 1,2-bis(2'-aminophenoxy)benzene with 2-pyridinecarbaldehyde in a mole ratio of 1:2 gives a new Schiff base ligand (L). Four Schiff base complexes, CoL(NO3)2 (1), NiLCl2 (2), ZnL(NO3)2 (3) and Pd2LCl4 (4) have been prepared by direct reaction of the ligand (L) and appropriate metal salts. The Schiff base ligand (L) has been characterized by IR, 1H NMR and 13C NMR spectroscopy and elemental analysis. Also, all complexes have been characterized by IR and XRD spectroscopy techniques and elemental analysis. The synthesized complexes have very poor solubility in all polar and non-polar solvents such as: H2O, MeOH, EtOH, CH3CN, DMSO, DMF, CHCl3, CH2Cl2, THF, etc; therefore, they have been used as heterogeneous catalysts. Catalytic performance of the complexes was studied in oxidation of thioanisole using hydrogen peroxide (H2O2) as the oxidant. Various factors including the reaction temperature, amount of oxidant and catalyst amount were optimized. The palladium Schiff base complex, Pd2LCl4 (4), shows better catalytic activity than other complexes. Therefore, the Pd(II) Schiff base complex has been used as a catalyst for oxidation of different sulfides to their corresponding sulfones in acetonitrile with hydrogen peroxide as the oxidant. The palladium Schiff base complex, Pd2LCl4 (4), has shown a very good recyclability, up to five times, without any appreciable decreases in catalytic activity and selectivity. © 2015 Académie des sciences.
Popkiadeh M.S.,
Rezaeian A.,
Dini, G.,
Toroghinejad M.R. ISIJ International (09151559)(3)
Hot deformation behavior of 30Mn-0.5C-3.7Al-4Si TWIP steel was investigated in this study. Cylindrical specimens were used for hot compression tests at temperatures ranging from 750 to 1 000°C and the strain rate range of 0.001-0.5 s-1. The effect of temperature and strain rate on the flow curves was addressed. Then, processing maps of hot deformation of the steel at the selected strains of 0.5 and 0.6 were developed. In addition, standard metallography procedures were conducted on the specimens after the hot compression tests. The generated processing maps indicated that there were only one unstable region and two stable regions in which dynamic recrystallization occurred. In addition, power dissipation was generally decreased with increasing the strain, while stability flow zone was gradually expanded. In the stable region, the dynamic recrystallization zone with a maximum efficiency 0.35 at a temperature of about 1 000°C and the strain rate 0.1 s-1 was enlarged with increasing the strain up to 0.6. Finally, an optimum hot working condition for the TWIP steel was predicted from the processing maps. © 2015 ISIJ.
Behjati P.,
Dini, G.,
Dastjerdi H.V.,
Mahdavi R. Materials Science and Technology (17432847)(4)
In the present work, the ultrasonic velocity measurement was used as a non-destructive technique for flow stress determination of a twinning induced plasticity steel. For this purpose, first, a relationship between mechanical twinning and ultrasonic velocity was found out and then, it was used in the flow stress model previously suggested by the authors. Comparison of the obtained results with the experimental values revealed a good agreement. © 2012 Institute of Materials, Minerals and Mining.
Steel Research International (16113683)(4)
The effects of grain size and grain orientation on substructure in Fe-31Mn-3Al-3Si TWIP steel at a true strain of 0.06 were investigated. The results of the TEM observations indicated that where the grain size was 18.4 μm, the dislocations structure showed orientation dependence so that the mixture of both planar and tangled dislocations structure can be found in the deformed structure before the mechanical twinning initiation. Regardless of the grain orientation, however, the dislocation entanglements were mainly observed in the case of 2.1 μm grain size. Additionally, the reason for the suppression of the mechanical twinning as a result of the grain refinement at higher strains was described by the change of dislocations structure during initial stages of deformation. During past decade, the mechanical properties and microstructural evolutions of twinning induced plasticity (TWIP) steels have been investigated in detail. However, there are some unclear concepts or unanswered questions on the work hardening behavior of TWIP steel, especially at the initial stages of deformation. So, in this study, transmission electron microscopy (TEM) has been utilized to answer to some of these questions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Dini, G.,
Ueji R.,
Najafizadeh A.,
Vaghefi, S. Materials Science and Engineering: A (09215093)(10-11)
In this study, the rate of dislocation accumulation in the tensile strained twinning induced plasticity (TWIP) steel was calculated via the X-ray diffraction (XRD) measurements and compared with other fcc metals and alloys. The results indicated that the XRD technique is an alternative method to estimate the dislocation density. Moreover, flow stress analysis of Fe-31Mn-3Al-3Si TWIP steel with the grain size of about 18 μm indicated that, beside a direct effect of the dislocation interactions on the flow stress, another strengthening mechanism is also required to describe the flow behavior. For this reason, the strengthening contribution due to the formation of mechanical twins was considered as a reduction of dislocation mean free path. Interestingly, the estimated flow stress equation consisting of the strengthening effects of both dislocation interactions and dynamic microstructure refinement due to mechanical twinning (i.e., the dynamic Hall-Petch effect) are in good agreement with the experimental data and equation proposed by Ludwigson for low SFE materials. © 2010 Elsevier B.V. All rights reserved.
Materials Science Forum (02555476)
The effect of grain size on the flow stress in TWinning Induced Plasticity (TWIP) steel was investigated via the X-ray diffraction (XRD) measurements of dislocation density. The results indicated that the hardening behavior of fine grained samples (mean grain sizes in the range of 2.1-3.8μm) can be described as typical dislocation interactions. However in coarse grained samples (mean grain sizes in the range of 4.7-38.5μm) where extensive mechanical twinning occurs, another strengthening mechanism is required. Consequently, the effect of grain size on the flow stress parameters of the proposed equation was considered and it was found that in the fine grained samples, the Holloman analysis can describe the hardening behavior. However, in coarse grained samples, a second hardening term due to the strengthening effect of mechanical twin boundaries needs to be added to the Holloman equation. © (2010) Trans Tech Publications.
Dini, G.,
Najafizadeh A.,
Vaghefi, S.,
Ueji R. Journal of Materials Science and Technology (10050302)(2)
The aim of the present work was to study the effect of austenite grain size (AGS) on the martensite formation in a high-manganese twinning-induced plasticity (TWIP) steel. The results of a quantitative microstructural characterization of the steel by the whole X-ray pattern fitting Rietveld software, materials analysis using diffraction (MAUD), indicated that the volume fraction of αbcc-martensite increases with increasing AGS. However, the value of the stacking fault probability (Psf) does not show a large variation for samples with different values of AGS under water-quenching conditions. ©2010 by The Editorial Board of Journal of Materials Science Technology.
Dini, G.,
Najafizadeh A.,
Ueji R.,
Vaghefi, S. Materials Letters (0167577X)(1)
The effects of cold rolling reduction and annealing temperature on the mechanical properties of twinning induced plasticity (TWIP) steel have been investigated. The results indicated that the strengthening effect of unrecrystallized areas with a high density of nano-scale mechanical twins increased with increasing cold rolling reduction. In addition, the ductility also increased with increasing annealing temperature. Therefore, utilization of large cold rolling reduction and subsequently annealing treatment in the partial recrystallization region was suggested as an effective method to obtain submicron grained TWIP steel with an excellent combination of strength and ductility. © 2009 Elsevier B.V. All rights reserved.
Dini, G.,
Najafizadeh A.,
Ueji R.,
Vaghefi, S. Materials and Design (02641275)(7)
The tensile deformation behavior and microstructural evolutions of twinning induced plasticity (TWIP) steel with the chemical composition of Fe-31Mn-3Al-3Si and average grain sizes in the range of 2.1-72.6μm have been analyzed. For each grain size, the Hollomon analysis and also the Crussard-Jaoul (C-J) analysis as an alternative method to describe the work hardening behavior were investigated. The results indicated that the optimum mechanical properties as a function of work hardening capacity can be obtained by changing the grain size. The microstructural observations showed that the pile-ups of planar dislocations are necessary for triggering the mechanical twinning and grain refinement suppresses the mechanical twinning in TWIP steel. Furthermore, the mechanical twinning increases with increasing applied strain. As a result, a high instantaneous work hardening due to the mechanical twin boundaries enhances the uniform elongation. The contribution from the strain of twinning and hardening due to an increase in the hardness of the twinned regions (i.e., the Basinski mechanism) may be also useful in achieving the high strength-ductility in TWIP steels. © 2010 Elsevier Ltd.
Bina, Mohammad Hosein,
Dini, G.,
Vaghefi, S.,
Saatchi, Ahmad,
Raeissi, K. Engineering Failure Analysis (13506307)(5)
In this work, several cycles of homogenization heat treatments were employed to improve continuous-annealing furnace roller fractures at Mobarakeh Steel Company. Previous studies revealed that roller fractures were caused by sigma phase embrittlement and an increase of precipitations in the microstructure. Therefore, impact samples were prepared from failed rollers and homogenization treatments were carried out at temperatures ranging from 950 to 1100 °C in increments of 50 °C for 2 h. After cooling the samples in different mediums (furnace, air, oil and water), the impact energy was experimentally determined. In order to investigate the microstructures, the sigma phase and precipitation contents, and fractured surfaces, optical microscopy metallography, X-ray and SEM examinations were performed respectively on fractured samples. The results of these investigations indicate that homogenization treatment at 1100 °C for 2 h, followed by cooling in air, resulted in a significant increase in impact energy, a decrease in sigma phase and other precipitation contents, and produced a ductile fracture surface. © 2009 Elsevier Ltd. All rights reserved.
Dini, G.,
Najafizadeh A.,
Vaghefi, S.,
Ebnonnasir A. Computational Materials Science (09270256)(4)
In this work, an artificial neural network (ANN) model was established in order to predict the mechanical properties of transformation induced plasticity/twinning induced plasticity (TRIP/TWIP) steels. The model developed in this study was consider the contents of Mn (15-30 wt%), Si (2-4 wt%) and Al (2-4 wt%) as inputs, while, the total elongation, yield strength and tensile strength are presented as outputs. The optimal ANN architecture and training algorithm were determined. Comparing the predicted values by ANN with the experimental data indicates that trained neural network model provides accurate results. © 2009 Elsevier B.V. All rights reserved.
Dini, G.,
Vaghefi, S.,
Lotfiani, Mostafa,
Jafari, Majid,
Safaei-Rad, Mohammad Engineering Failure Analysis (13506307)(5)
Radiant tubes of a continuous-annealing furnace at Mobarakeh Steel Company failed after a fraction of their rated service life. The tubes were manufactured from INCONEL alloy 601 superalloy. In this study, a failure analysis of the radiant tubes was performed by careful visual inspection of the failed tubes, scanning electron microscopy observation of crack region samples, energy-dispersive X-ray spectroscopy and X-ray diffractometer analysis of the tube metals and oxide scales. The temperature distribution for steady-state heat transfer and the structural stresses induced by the weight of the tube material were also studied in this paper. The finite element method (FEM) was employed to compute the effect of increasing temperature on tube service life and to define the critical regions. The experimental results showed that the mode of tube failure was a combination of creep damage and high-temperature oxidation attack which led to cracking. Significant growth of carbide precipitates was also observed in the failed zones; these precipitates result in both the drastic reduction of material ductility and the propagation of creep cracking. The simulation results showed that the damaged region in radiant tubes is susceptible to high-temperature creep. Tube failure occurred as a result of bending in the tube length, which may be responsible for subsequent hot-spot formations and high-temperature oxidation. Furthermore, the tube failure verified experimental results. Moreover, a simulation indicated that modification in radian tube installation is necessary because utilization of supports in specific locations can extend creep life. © 2007 Elsevier Ltd. All rights reserved.
Dini, G.,
Bina, Mohammad Hosein,
Vaghefi, S.,
Raeissi, K.,
Safaei-Rad, Mohammad Engineering Failure Analysis (13506307)(7)
In this study, a failure analysis of an austenitic G-40CrNiSi25-12 steel furnace roller was performed by using chemical analysis, metallographic examination, Vickers micro-hardness measurements, X-ray diffractometer analysis and investigation of the crack propagation path in failed samples of the roller metal. The examination results revealed that roller fracture was caused by precipitation of the sigma phase during prolonged heating at temperatures exceeding 650 °C, resulting in a detrimental decrease in steel toughness at lower temperatures occurring during shut-down, straightening or heating-up periods. © 2007 Elsevier Ltd. All rights reserved.
ISIJ International (09151559)(1)
Wiht the aim of replacing quenched and tempered forging parts and reducing by this way costly and time consuming operations; an industrial forging procedure was developed to evaluate the influence of thermo-mechanical processing parameters on the microstructure and mechanical properties of vanadium microalloyed steel. In order to study the influence of reheating temperature, after determining the dissolving temperature of vanadium carbonitrides precipitates, samples were heating in temperature rang 1 000 to 1 200°C. After austenitization at 1 100°C, the microalloyed steel billets were forged in a hydraulic press and then cooled with different cooling rates. The metallography and mechanical testing results indicated that by increasing the reheating temperature, the strength and toughness of V-microalloyed steel have not change significantly and so the temperature of 1 200°C was selected for forging. By increasing cooling rate, both strength and toughness improve. © 2006 ISIJ.
