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Sökning: WFRF:(Hamawandi Bejan PhD)

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1.
  • Alimohammadi, Vahid, et al. (författare)
  • Hydrophobic Magnetite Nanoparticles for Bioseparation : Green Synthesis, Functionalization, and Characterization
  • 2022
  • Ingår i: MAGNETOCHEMISTRY. - : MDPI AG. - 2312-7481. ; 8:11, s. 143-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, three types of hydrophobized alkyl-modified magnetic nanoparticles (MNPs) comprising direct alkylated-MNPs (A-MNPs), silica-mediated alkyl MNPs (A-SiMNPs), and arginine (Arg)-mediated alkyl MNPs (A-RMNPs) were synthesized successfully. For this purpose, the co-precipitation method was used to synthesize, and octadecyl trimethoxy silane (OTMS) was used as a functionalizing agent. Accordingly, the hydrophobic octadecyl moieties were connected to MNPs. The nanoparticles (NPs) were characterized by XRD, SEM, FTIR, CHN, DLS, and zeta potential analyses. The synthesized coated MNPs represented a decrease in surface charge and magnetization alongside increased surface hydrophobicity and size. It was revealed that the alkylation process was successfully performed to all three MNPs, but A-SiMNPs showed the highest hydrophobicity. Additionally, the novel A-RMNPs, as the most biocompatible type, and A-MNPs showed the highest magnetization among the synthesized MNPs. The results indicate that synthesized NPs can play an important role in bio applications. However, it was revealed that alkyl chains are easily connected to all three MNPs, and that A-MNPs contained the highest alkyl chains and could affect the re-folding and denaturation process of recombinant proteins.
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2.
  • Attyabi, Seyed Nourallah, et al. (författare)
  • Reverse Magnetization Behavior Investigation of Mn-Al-C-(α-Fe) Nanocomposite Alloys with Different α-Fe Content Using First-Order Reversal Curves Analysis
  • 2022
  • Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:19, s. 3303-
  • Tidskriftsartikel (refereegranskat)abstract
    • The reverse magnetization behavior for bulk composite alloys containing Mn-Al-C and α-Fe nanoparticles (NPs) has been investigated by hysteresis loops, recoil, and first-order reversal curves (FORC) analysis. The effect of adding different percentages of α-Fe (5, 10, 15, and 20 wt. %) on the magnetic properties and demagnetization behavior of Mn-Al-C nanostructured bulk magnets was investigated. The fabricated nanocomposites were characterized by XRD and VSM for structural analysis and magnetic behavior investigations, respectively. The demagnetization curve of the sample Mn-Al-C-5wt. % α-Fe showed a single hard magnetic behavior and showed the highest increase in remanence magnetization compared to the sample without α-Fe, and therefore this combination was selected as the optimal composition for FORC analysis. Magnetic properties for Mn-Al-C-5 wt. % α-Fe nanocomposite were obtained as Ms = 75 emu/g, Mr = 46 emu/g, Hc = 3.3 kOe, and (BH)max = 1.6 MGOe, indicating a much higher (BH)max than the sample with no α-Fe. FORC analysis was performed to identify exchange coupling for the Mn-Al-C-0.05α-Fe nanocomposite sample. The results of this analysis showed the presence of two soft and hard ferromagnetic components. Further, it showed that the reverse magnetization process in the composite sample containing 5 wt. % α-Fe is the domain rotation model.
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3.
  • Attyabi, Seyed Nourallah, et al. (författare)
  • Stress-Induced Grain Refinement in Hard Magnetic Mn52Al45.7C2.3 Fabricated Using the Ball-Milling Method
  • 2022
  • Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:22
  • Tidskriftsartikel (refereegranskat)abstract
    • Mn52Al45.7C2.3 flakes with different sizes were prepared with two distinct surfactant-assisted ball-milling methods using cylindrical and barrel containers. Different microstructure and magnetic properties were measured based on the sequence of the container shape and different ball-milling times (2, 5, and 10 h). Morphology investigations showed that for powders milled in a barrel container, the amount of τ-phase was more compared to the samples milled in a cylindrical container. Moreover, in the powders milled with barrel containers, considerably higher magnetic properties were obtained in terms of saturation magnetization (Ms) and remanent magnetization (Mr) compared to those powders milled with cylindrical containers. Magnetic properties were found to be a function of the ball-milling time. High remanent magnetization and saturation magnetization have been found for powders milled in barrel containers, whereas only mediocre remanent magnetization and saturation magnetization have been measured in the case of milling in cylindrical containers. The highest Ms = 52.49 emu g−1 and Mr = 24.10 emu g−1 were obtained for the powders milled in barrel containers for 2 h. The higher magnetic properties taken from the milling in barrel containers is due to the higher shear stress and more uniform strain distribution induced by the barrel configuration, resulting in the stable τ-phase at a reasonably low-strain microstructure.
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4.
  • Azadpour, Behnam, et al. (författare)
  • Covalently-Bonded Coating of L-Arginine Modified Magnetic Nanoparticles with Dextran Using Co-Precipitation Method
  • 2022
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:24
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, L-arginine (Arg) modified magnetite (Fe3O4) nanoparticles (RMNPs) were firstly synthesized through a one-step co-precipitation method, and then these aminated nanoparticles (NPs) were, again, coated by pre-oxidized dextran (Dext), in which aldehyde groups (DextCHO) have been introduced on the polymer chain successfully via a strong chemical linkage. Arg, an amino acid, acts as a mediator to link the Dext to a magnetic core. The as-synthesized Arg-modified and Dext-coated arginine modified Fe3O4 NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Both synthesized samples, XRD pattern and FT-IR spectra proved that the core is magnetite. FT-IR confirmed that the chemical bonds of Arg and Dext both exist in the samples. SEM images showed that the NPs are spherical and have an acceptable distribution size, and the VSM analysis indicated the superparamagnetic behavior of samples. The saturation magnetization was decreased after Dext coating, which confirms successive coating RMNPs with Text. In addition, the TGA analysis demonstrated that the prepared magnetic nanocomposites underwent various weight loss levels, which admitted the modification of magnetic cores with Arg and further coating with Dext.
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5.
  • Batili, Hazal, et al. (författare)
  • A comparative study on the surface chemistry and electronic transport properties of Bi2Te3 synthesized through hydrothermal and thermolysis routes
  • 2024
  • Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 682
  • Tidskriftsartikel (refereegranskat)abstract
    • Bismuth telluride-Bi2Te3 is the most promising material for harvesting thermal energy near room temperature. There are numerous works on Bi2Te3 reporting significantly different transport properties, with no clear connection to the synthetic routes used and the resultant surface chemistry of the synthesized materials. It is of utmost importance to characterize the constituent particles’ surface and interfaces to get a better understanding of their influence on the transport properties, that will significantly improve the material design starting from the synthesis step. Electrophoretic deposition (EPD) is a promising technique, enabling the formation of thick films using colloidally stabilized suspensions of pre-made nanoparticles, which can enable the study of the effect of surface chemistry, in connection to the synthetic route, on the material's transport properties. In order to explore the differences in surface chemistry and the resultant transport properties in relation to the synthetic scheme used, here we report on Bi2Te3 synthesised through two wet-chemical routes in water (Hydro-) and oil (Thermo-) as the solvents. XRD analysis showed a high phase purity of the synthesized materials. SEM analysis revealed hexagonal platelet morphology of the synthesized materials, which were then used to fabricate EPD films. Characterization of the EPD films reveal significant differences between the Hydro- and Thermo-Bi2Te3 samples, leading to about 8 times better electrical conductivity values in the Thermo-Bi2Te3. XPS analysis revealed a higher metal oxides content in the Hydro-Bi2Te3 sample, contributing to the formation of a resistive layer, thus lowering the electrical conductivity. Arrhenius plots of electrical conductivity vs inverse temperature was used for the estimation of the activation energy for conduction, revealing a higher activation energy need for the Hydro-Bi2Te3 film, in agreement with the resistive barrier oxide content. Both the samples exhibited negative Seebeck coefficient (S) in the order of 160–170 mV/K. The small difference in S of Hydro- and Themo-Bi2Te3 films was explained by the effective medium theory, revealing that the magnitude of S is linearly correlated with the surface oxide content. Based on the findings, TE materials synthesized through thermolysis route is recommended for further studies using soft treatment/processing of pre-made TE materials. EPD platform presented here is shown to clearly expose the differences in the electronic transport in connection to nanoparticle surface chemistry, proving a promising methodology for the evaluation of morphology, size and surface chemistry dependence of electronic transport for a wide range of materials.
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6.
  • Batili, Hazal, et al. (författare)
  • Electrophoretic assembly and electronic transport properties of rapidly synthesized Sb2Te3 nanoparticles
  • 2023
  • Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 637
  • Tidskriftsartikel (refereegranskat)abstract
    • With the recent advances in thermoelectric (TE) technology, there is an increasing demand to develop thick films that would enable large-scale TE devices. Assembly of TE-films from size and morphology-controlled nano particles has been a challenging issue that can be addressed by the use of electrophoretic deposition (EPD) technique. In this work, morphology-controlled Sb2Te3 nanoparticles were synthesized through microwave assisted thermolysis, which were subsequently used for EPD of TE films on specially developed glass substrates. The electronic transport properties were measured in the temp-range of 22-45 degrees C. The as-made EPD films showed a high initial resistance, ascribed to high porosity and the presence of surface oxide/passivating layers. The impact of two types of small organic molecules-as hexanedithiol and dodecanethiol, on the electronic transport was investigated, resulting in a significant improvement in the electrical conductivity of the films. The XPS analysis suggests that the thiols bind to the surface of nanoparticles through formation of sulfides. Seebeck coefficient in the range of + 160 to + 190 & mu;V/K was measured, revealing the p-type transport through the deposited films. Finally, a power factor of about 2.5 & mu;W/K2.m was estimated the first time for p-type EPD films, revealing the potential of the developed nanoparticles and substrate, the small molecule additives and the EPD process presented in this work.
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7.
  • Batili, Hazal, et al. (författare)
  • Electrophoretic Deposition and Characterization of Bi2Te3 Synthesized through Hydrothermal and Thermolysis Routes
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Bismuth telluride-Bi2Te3 is a promising material for harvesting thermal energyfor applications near room temperature, where large-area applications requirenew methods of depositing pre-made particulate materials. Electrophoretic deposition(EPD) technique has the promise of enabling the formation of thickfilms using colloidally stabilized suspensions of pre-made nanoparticles. It isvery important to understand the thermoelectric (TE) materials’ performancein relation to the synthetic process, to enable promising and scalable materialstechnologies. EPD films allow to study the effect of surface chemistry, stronglylinked to the synthetic route, on the material’s physico-chemical and transportproperties. Here we report on the synthesis of Bi2Te3 through wet-chemicalreactions performed in two different media as water (hydrothermal-Hydro) andoil (thermolysis-Thermo). Synthesized materials possess platelet morphology,which were then used to fabricated EPD films on specially developed glass substrates. Characterization of the materials and films reveal significant differencesbetween the surface chemistry of the EPD films of Hydro- and Thermo-Bi2Te3samples, where a higher content of metal oxide phases are observed in the Hydro-Bi2Te3 sample. This has a big impact the electronic transport properties, asrevealed by about nine times higher resistance, confirmed by significantly higheractivation energy, of the Hydro-Bi2Te3 film as compared to the Thermo-Bi2Te3film. Slight difference in the Seebeck coefficient (S) was explained by the effectivemedium theory, revealing that the magnitude of S is linearly correlatedwith the surface oxide content. Based on the findings, TE materials synthesizedthrough thermolysis route is recommended for future studies focusing on EPD of TE materials.
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8.
  • Batili, Hazal, et al. (författare)
  • On the electrophoretic deposition of Bi2Te3 nanoparticles through electrolyte optimization and substrate design
  • 2022
  • Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 649, s. 129537-
  • Tidskriftsartikel (refereegranskat)abstract
    • Assembly of thermoelectric nanostructures with pre-defined morphology and surface chemistry on solid sub-strates has been one of the challenges for in-plane TE devices. Electrophoretic deposition (EPD) has the potential to be used for this purpose, where the use of non-conductive substrates is required to enable a reliable evaluation of the transport property of electrically active films. Bi2Te3 nanoparticles, which were synthesized using microwave-assisted hydrothermal route, were used for the EPD of thermoelectric films on glass substrates. A special substrate was fabricated using maskless photolithography, to evaluate the electronic transport properties of the TE films without the interference of the substrate. Electrolyte composition was optimized for high mobility of the suspended nanoparticles, and Bi2Te3 EPD films were fabricated with a high deposition rate, reaching 10 mu m/min. Initial EPD films showed high resistivity, ascribed to the surface oxide layer and capping ligands. The resistance was significantly reduced by the addition of a dithiol molecular linker, capable of interconnecting the Bi2Te3 nanoparticles through ligand-exchange. Seebeck coefficient in the range-150 to-180 mu V/K was measured, revealing the transport through the deposited films. Finally, a power factor of 169 nW/K-2.m was estimated, revealing the potential for the application of this technology to large area TE films as active coatings using the developed EPD process.
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9.
  • Beigi Kheradmand, Azam, et al. (författare)
  • Effect of Thermomechanical Treatment of Al-Zn-Mg-Cu with Minor Amount of Sc and Zr on the Mechanical Properties
  • 2022
  • Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, the mechanical and microstructural properties of Al-Zn-Mg-Cu-Zr cast alloy with 0.1% Sc under homogeneous, dissolution, and T6 and thermomechanical treatments with the aim of increasing the volume fraction of MgZn2. Al-3(Sc,Zr) reinforcing precipitates were examined by hardness, microscopic examinations, tensile tests and software analysis. The results showed that, firstly, the hardness results are well proportional to the results of the tensile properties of alloys and, secondly, the strength of the alloy with thermomechanical treatments compared to T6 treatments increased from 492 MPa to 620 MPa and the elongation increased from 8% to 17% and was 100% upgraded. Microstructural and fracture cross section investigations showed that Al-3(Sc,Zr) nanosize dispersoids were evenly distributed among MgZn2 dispersoids and the alloy fracture was of semi-ductile type and nanosize dispersoids less than 10 nm were observed at the end of the dimples in the fracture section. The volume fraction of nanosize dispersoids in the whole microstructure of thermomechanical treatment samples was also much higher than that of T6 heat treated samples, so that the percentage of Al-3(Sc,Zr) precipitates arrived from less than 1% in T6 operation to 8.28% in the quench-controlled thermomechanical operation (with 50% deformation). The quality index (QI) in thermomechanical treatment samples is 19% higher than T6 samples, so that this index has increased from 641 in T6 operation to 760 in samples under thermomechanical treatment due to precipitate morphology, volume fraction of precipitates, their uniform distribution in the matrix, and nano sized precipitates in samples under thermomechanical treatment.
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10.
  • Costa, A. L., et al. (författare)
  • Eco design for Ag-based solutions against SARS-CoV-2 and E. coli
  • 2022
  • Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; 9:11, s. 4295-4304
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, we exploited the antiviral and antibacterial properties of Ag NPs stabilised by quaternized hydroxyethyl cellulose (Ag-HEC) against SARS-CoV-2 and Escherichia coli through an eco-friendly process at room temperature in three different environments: 1) water, where Ag was dispersed as a nanosol, 2) textiles, where Ag was applied as a coating, and 3) hydrogel where Ag is embedded. The antiviral performance of Ag-HEC nanosols was quantified through the selectivity index (SI), defined as the ratio between 50% cytotoxic and inhibitory concentration, in order to evaluate the ability to be active in a concentration range below the cytotoxicity value. The collected results pointed out an actual enhanced risk/benefit profile of Ag-HEC NPs with respect to chloroquine, with an SI of 22.2 and 8.4, respectively. Antibacterial and antiviral activities of Ag-HEC NPs immobilized on textiles or mucosa-like hydrogels were also assessed and their efficacy in potential application as protective clothing or nasal molecular masks was verified. This work demonstrated that a modern, safe and sustainable design allows traditional colloidal silver-based technologies to be efficiently exploited for a broad spectrum of antimicrobial solutions against bacterial and viral infections.
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11.
  • Dehghan, Ramin, et al. (författare)
  • Different Stages of Phase Transformation in the Synthesis of Nanocrystalline Sr-Hexaferrite Powder Prepared by a Gaseous Heat Treatment and Re-Calcination Method
  • 2022
  • Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:21
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, the phase transformation in a gaseous heat treatment and re-calcination (GTR) process for preparing nanocrystalline Sr-hexaferrite powder using methane (CH4) was studied. The process included gaseous heat treatment and subsequent re-calcination. Phase composition of the powder and its physical properties were changed significantly owing to formation of different intermediate phases. Sr-hexaferrite powder was prepared by the conventional route as the precursor. The results were represented in a phase transformation map that showed the intermediate phases and clarified the transformation path during the process. As evidenced by the map, the process had four general stages: decomposition of hexaferrite, reduction of iron oxides to pure iron, re-oxidation of iron, and re-formation of hexaferrite with different properties and structure.
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12.
  • Dehghan, Ramin, et al. (författare)
  • Investigation of Microstructure and Magnetic Properties of CH4 Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process
  • 2023
  • Ingår i: MAGNETOCHEMISTRY. - : MDPI AG. - 2312-7481. ; 9:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The microstructure and magnetic properties of methane (CH4) heat-treated Sr-hexaferrite powders during the re-calcination process were investigated and compared with the magnetic properties of conventionally synthesized Sr-hexaferrite powder. Gradual changes in the magnetic behavior of the produced powder in each re-calcination stage were investigated using magnetization curves obtained from the vibration sample magnetometry (VSM) technique. First, the initial Sr-hexaferrite powder was prepared by the conventional route. Then the powder was heat treated in a dynamic CH4 atmosphere in previously optimized conditions (temperature: 950 degrees C, gas flow rate:15 cc min(-1) and time: 30 min), and finally, re-calcined in various temperatures from 200 to 1200 degrees C. By investigating the hysteresis loops, we found the transition temperature of soft to hard magnetic behavior to be 700 degrees C. The maximum ratio M-r/M-s was obtained at temperatures of 800-1100 degrees C. At 1100 degrees C, and despite the Sr-hexaferrite single phase, the magnetic behavior showed a multiphase behavior that was demonstrated by a kink in the hysteresis loop. Uniform magnetic behavior was observed only at 900 degrees C and 1000 degrees C. Although the ratio M-r/M-s was almost the same at these temperatures, the values of M-r and M-s at 1000 degrees C were almost double of 900 degrees C. At 1000 degrees C, the second quadrant of hysteresis curve had the maximum area. Therefore, 1000 degrees C was the optimum temperature for re-calcination after CH4 gas heat treatment in the optimized conditions. Due to the presence of a small amount of hematite soft phase at 1000 degrees C, the most probable reason for the exclusive properties of the optimized product may be the exchange coupling phenomenon between the hard Sr-hexaferrite phase and the impurity of the soft hematite phase.
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13.
  • Demirci, Yunus, et al. (författare)
  • The Effect of Crystal Mismatch on the Thermoelectric Performance Enhancement of Nano Cu2Se
  • 2021
  • Ingår i: FRONTIERS IN MATERIALS. - : Frontiers Media SA. - 2296-8016. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • In the past decades, Cu2-x Se compounds have attracted great attention due to the inclusion of non-toxic and abundant elements, besides having a promising thermoelectric (TE) performance. In this work, we investigated the effect of a crystal mismatch of a nanoinclusion phase on the TE properties of Cu2-x Se. Nano-Cu2Se was synthesized using microwave assisted thermolysis, while the p-type skutterudite, Fe3.25Co0.75Sb12 (FeCoSb), compound was synthesized using a chemical alloying route. Nano-Cu2Se, and (nano-Cu2Se)(1-x )(nano-FeCoSb)( x ) composites, where x = 0.05 and 0.1, were prepared via mechanical alloying followed by Spark Plasma Sintering process. Structural properties were evaluated by PXRD and SEM analysis, while the high temperature transport properties were examined via electrical conductivity, Seebeck coefficient, and thermal conductivity measurements in the temperature range of 300-800 K. Powder X-ray diffraction (PXRD) confirmed a single phase of nano Cu2Se, while the samples with FeCoSb inclusion consist of two phases as Cu2Se and CoSb3. SEM micrographs of all samples show that Cu2Se has randomly oriented grains with different sizes. Cu2Se samples with a FeCoSb inclusion show a rather different structure. In these samples, a rod-shaped FeCoSb phase, with a size varying between 20 and 100 nm, showed an inhomogeneous distribution in the structure and stacked between the Cu2Se layers. Transport data indicate that crystal mismatch between Cu2Se and FeCoSb has a strong effect on the TE transport properties. Electrical conductivity decreases but Seebeck coefficient enhances with nano FeCoSb inclusion. Total thermal conductivity was suppressed by 30% and ZT value enhanced by 15% with 5% nano FeCoSb inclusion at 750 K, likely due to a decrease in the electronic contribution of the thermal conductivity. Structural and transport data show that small amount of nanoinclusion of FeCoSb has a beneficial effect on the TE performance of nano Cu2Se at temperatures below 800 K.
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14.
  • Fang, Y., et al. (författare)
  • The Effects of the Addition of Polyurethane–MgO Nanohybrids on the Mechanical Properties of Ordinary Portland Cement Paste
  • 2022
  • Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:22
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the most important methods of controlling the properties of concrete and cement-based materials is to control the rate and kinetics of cement hydration. In the present study, novel flexible polyurethane-decorated MgO nanohybrids were synthesized using a simple chemical method, added to cement paste in different amounts, and utilized as an effective mechanical performance-enhancing factor for cement paste. It was observed that by adding 3 wt% synthesized PU-MgO nanohybrids to cement paste, its mechanical properties were improved and its compressive strength and flexural strength were increased by up to 13% and 15%, respectively, compared to the plain cement, after 45 days. The effect mechanism of adding PU–MgO nanoparticles on the properties of the cement paste was investigated. The addition of PU–MgO nanohybrids increased the pozzolanic reactions and formed more C-S-H phases. 
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15.
  • Ghanaei, Afshin, et al. (författare)
  • The Effect of Adding V and Nb Microalloy Elements on the Bake Hardening Properties of ULC Steel before and after Annealing
  • 2023
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 16:4, s. 1716-
  • Tidskriftsartikel (refereegranskat)abstract
    • Bake hardening (BH) is a vital part of special steel production. Studies in this field have focused on steels under homogeneous yielding, but until now, none have been conducted on the phenomena that occur for steels under heterogeneous yielding. In the current study, the effect of adding Nb and V alloying elements on the strength of ultra-low carbon (ULC) steel after bake hardening was investigated. The effects of pre-strain, grain size, and recrystallization annealing temperature were analyzed, as well as the effect of Nb and V on the yield stress caused by the bake hardening process. For this purpose, five types of alloys with different V and Nb contents were melted, cast in an induction furnace, and subjected to hot hammering and hot rolling. Then, cold rolling was applied to the samples by similar to 80%. To eliminate the effects of cold working, tensile samples were subjected to recrystallization annealing at 750 and 800 degrees C for 30 min, and the samples were quickly quenched in a mixture of a NaCl solution and ice. The annealed samples were subjected to a pre-tensile strain in the range of 2-12% and then aged in a silicone oil bath at 180 degrees C for 30 min. Then they were subjected to a tensile test. The obtained results showed that with the increase of the pre-strain and the annealing temperature, the values of baking hardness increased. The presence of V in the composition of steel reduced the annealing temperature.
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16.
  • Golbabaei, Mohammad Hossein, et al. (författare)
  • Performance Analysis of Anode-Supported Solid Oxide Fuel Cells : A Machine Learning Approach
  • 2022
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:21
  • Tidskriftsartikel (refereegranskat)abstract
    • Prior to the long-term utilization of solid oxide fuel cell (SOFC), one of the most remarkable electrochemical energy conversion devices, a variety of difficult experimental validation procedures is required, so it would be time-consuming and steep to predict the applicability of these devices in the future. For numerous years, extensive efforts have been made to develop mathematical models to predict the effects of various characteristics of solid oxide fuel cells (SOFCs) components on their performance (e.g., voltage). Taking advantage of the machine learning (ML) method, however, some issues caused by assumptions and calculation costs in mathematical modeling could be alleviated. This paper presents a machine learning approach to predict the anode-supported SOFCs performance as one of the most promising types of SOFCs based on architectural and operational variables. Accordingly, a dataset was collected from a study about the effects of cell parameters on the output voltage of a Ni-YSZ anode-supported cell. Convolutional machine learning models and multilayer perceptron neural networks were implemented to predict the current-voltage dependency. The resulting neural network model could properly predict, with more than 0.998 R-2 score, a mean squared error of 9.6 x 10(-5), and mean absolute error of 6 x 10(-3) (V). Conventional models such as the Gaussian process as one of the most powerful models exhibits a prediction accuracy of 0.996 R-2 score, 10(-4) mean squared, and 6 x 10(-3) (V) absolute error. The results showed that the built neural network could predict the effect of cell parameters on current-voltage dependency more accurately than previous mathematical and artificial neural network models. It is noteworthy that this procedure used in this study is general and can be easily applied to other materials datasets.
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17.
  • Guo, Rui'E, et al. (författare)
  • The Effect of Eco-Friendly Inhibitors on the Corrosion Properties of Concrete Reinforcement in Harsh Environments
  • 2022
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:14
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present research, the synergistic effect of Arabic and guar gum inhibitors on the corrosion efficiency of concrete reinforcement was investigated. Thus, eight types of Arabic and guar gum combinations with 100, 250, 500, 750, and 1000 ppm were added to the steel reinforcement for 1, 7, 28, 48, and 72 days. The corrosion behavior of the samples was investigated by the electrochemical impedance (EIS) test. Water transmissibility, electrical resistivity, and compressive strength of concrete were also studied. The results showed that adding inhibitors generally increased the compressive strength of concrete. It was also found that water transmissibility was reduced by the addition of inhibitors. The electrical resistivity of the samples increased slightly with increasing time up to 72 days. EIS and Tafel results have demonstrated that Arabic and guar gums are effective inhibitors for reinforced concrete structures. Furthermore, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) utilized to analyze the samples indicated that inhibitor grain size was enhanced by enhancing the concentration of the inhibitor combination, showing that the guar and Arabic inhibitor combinations were properly absorbed on the reinforcement surface. Results showed that a sample with 250 ppm Arabic gum and 250 ppm guar gum having a properly distributed inhibitor combination on the reinforcement surface creates a desirable cathode current.
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18.
  • Gupta, Govind, et al. (författare)
  • Silver nanoparticles with excellent biocompatibility block pseudotyped SARS-CoV-2 in the presence of lung surfactant
  • 2022
  • Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Silver (Ag) is known to possess antimicrobial properties which is commonly attributed to soluble Ag ions. Here, we showed that Ag nanoparticles (NPs) potently inhibited SARS-CoV-2 infection using two different pseudovirus neutralization assays. We also evaluated a set of Ag nanoparticles of different sizes with varying surface properties, including polyvinylpyrrolidone (PVP)-coated and poly (ethylene glycol) (PEG)-modified Ag nanoparticles, and found that only the bare (unmodified) nanoparticles were able to prevent virus infection. For comparison, TiO2 nanoparticles failed to intercept the virus. Proteins and lipids may adsorb to nanoparticles forming a so-called bio-corona; however, Ag nanoparticles pre-incubated with pulmonary surfactant retained their ability to block virus infection in the present model. Furthermore, the secondary structure of the spike protein of SARS-CoV-2 was perturbed by the Ag nanoparticles, but not by the ionic control (AgNO3) nor by the TiO2 nanoparticles. Finally, Ag nanoparticles were shown to be non-cytotoxic towards the human lung epithelial cell line BEAS-2B and this was confirmed by using primary human nasal epithelial cells. These results further support that Ag nanoparticles may find use as anti-viral agents.
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19.
  • Hamawandi, Bejan, PhD, et al. (författare)
  • A Comparative Study on the Thermoelectric Properties of Bismuth Chalcogenide Alloys Synthesized through Mechanochemical Alloying and Microwave-Assisted Solution Synthesis Routes
  • 2020
  • Ingår i: Frontiers in Materials. - : Frontiers Media S.A.. - 2296-8016. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • The way a material is synthesized and processed has an immense effect on its microstructure, which in turn has a big impact on its transport properties. Here, we compare the thermoelectric (TE) properties of n- and p-type Bi2−xSbxTe3 (x: 0 and 1.5) materials synthesized through two different routes, specifically mechanochemical alloying (MA)—as a solid-state synthesis route—and microwave(MW)-assisted polyol synthesis—as a solution synthesis route. Reaction time is significantly reduced in the MW synthesis, leading to significantly lower energy consumption (i.e., higher energy efficiency) per batch than using the MA route. The resultant materials are compared for their crystallinity, phase purity, morphology, and microstructure. Spark plasma sintering was used to prepare pellets, and the resultant consolidates were evaluated for their transport properties. TE properties and microstructure of the specimens were investigated in relation to processing conditions and composition. MA samples formed fused structures (from 200 nm to several micrometers in size) composed of smaller particles. MW-synthesized materials exhibited hexagonal platelet morphology, high crystallinity, and phase purity. They also showed lower thermal conductivity, leading to a higher resultant TE figure-of-merit ZT. TE properties of Bi2−xSbxTe3 samples were studied on sintered cylindrical pellet samples, where the highest ZT values achieved were 1.04 (at 440 K) for MW-Bi2Te3 and 0.76 (at 523 K) for MW-Bi0.5Sb1.5Te3 samples, while MA-Bi2Te3 and MA-Bi0.5Sb1.5Te3 samples showed maximum ZT values of 0.74 (at 460 K) and 0.27 (at 300 K), respectively, as n- and p-type TE materials. The observed trend is much higher ZT values for MW samples, ascribed to their higher degree of texturing and nanostructured grains reducing the thermal conductivity, thus achieving a better overall performance, verifying the prospect to enhance ZT using MW-assisted solution synthesis approach.
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20.
  • Hamawandi, Bejan, PhD, et al. (författare)
  • Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and their Thermoelectric Property Evaluation
  • 2020
  • Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 10:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Reduced energy consumption and environmentally friendly, abundant constituents are gaining more attention for the synthesis of energy materials. A rapid, highly scalable, and process-temperature-sensitive solution synthesis route is demonstrated for the fabrication of thermoelectric Cu2−xSe. The process relies on readily available precursors and microwave-assisted thermolysis, which is sensitive to reaction conditions; yielding Cu1.8Se at 200 °C and Cu2Se at 250 °C within 6–8 min reaction time. Transmission electron microscopy (TEM) revealed crystalline nature of as-made particles with irregular truncated morphology, which exhibit a high phase purity as identified by X-ray powder diffraction (XRPD) analysis. Temperature-dependent transport properties were characterized via electrical conductivity, Seebeck coefficient, and thermal diffusivity measurements. Subsequent to spark plasma sintering, pure Cu1.8Se exhibited highly compacted and oriented grains that were similar in size in comparison to Cu2Se, which led to its high electrical and low thermal conductivity, reaching a very high power-factor (24 µW/K−2cm−1). Density-of-states (DOS) calculations confirm the observed trends in electronic properties of the material, where Cu-deficient phase exhibits metallic character. The TE figure of merit (ZT) was estimated for the materials, demonstrating an unprecedentedly high ZT at 875 K of 2.1 for Cu1.8Se sample, followed by 1.9 for Cu2Se. Synthetic and processing methods presented in this work enable large-scale production of TE materials and components for niche applications.
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21.
  • Hamawandi, Bejan, PhD (författare)
  • Design, Synthesis and Characterization of Nanostructured Thermoelectric Materials
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The demand for energy is rapidly increasing, triggering more carbon emission and global warming. Alternative green energy sources are essential to secure the future generation from the effect of pollution and global warming. During the last few decades, thermoelectric (TE) materials gained interest, due to their capability of directly interconverting between heat and power, which can be used to convert waste heat to electricity.  One of the strategic TE adaptation approaches is to develop high efficiency TE materials from earth-abundant and non-toxic components. Not only the TE materials’ composition, but also the synthesis method, has to be environment friendly in order to create a green transition, with minimum adverse environmental impacts. Bottom-up microwave (MW) assisted synthesis routes, using water and polyalcohol as green solvents were demonstrated feasible to generate binary and ternary compositions of Bi2-xSbxTe3, which were effective in room temperature. A more earth abundant and environment friendly material composition, copper selenide (Cu2-XSe), effective at intermediate temperature regime (200-600 °C), was synthesized by MW-assisted thermolysis. The synthesized materials were characterized in terms of structure, microstructure, surface chemistry and TE transport properties, and showed significant improvement of TE performance compared to materials synthesized using conventional methods - mainly attributed to the preservation of nanostructure. Significant results have been achieved with improved material characteristics, while the time and the energy investment were substantially reduced. The developed processes with reduced time and carbon footprint offer excellent sustainable synthesis routes for large-scale synthesis of high-performance nanostructured TE materials as strategic energy materials. 
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22.
  • Hamawandi, Bejan, PhD, et al. (författare)
  • Facile Solution Synthesis, Processing and Characterization of n- and p-Type Binary and Ternary Bi-Sb Tellurides
  • 2020
  • Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 10:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The solution synthesis route as a scalable bottom-up synthetic method possesses significant advantages for synthesizing nanostructured bulk thermoelectric (TE) materials with improved performance. Tuning the composition of the materials directly in the solution, without needing any further processing, is important for adjusting the dominant carrier type. Here, we report a very rapid (2 min) and high yield (>8 g/batch) synthetic method using microwave-assisted heating, for the controlled growth of Bi2-xSbxTe3 (x: 0-2) nanoplatelets. Resultant materials exhibit a high crystallinity and phase purity, as characterized by XRD, and platelet morphology, as revealed by SEM. Surface chemistry of as-made materials showed a mixture of metallic and oxide phases, as evidenced by XPS. Zeta-potential analysis exhibited a systematic change of isoelectric point as a function of the material composition. As-made materials were directly sintered into pellets by using spark plasma sintering process. TE performance of Bi2-xSbxTe3 pellets were studied, where the highest ZT values of 1.04 (at 440 K) for Bi2Te3 and 1.37 (at 523 K) for Sb2Te3 were obtained, as n- and p-type TE materials. The presented microwave-assisted synthesis method is energy effective, a truly scalable and reproducible method, paving the way for large scale production and implementation of towards large-area TE applications.
  •  
23.
  • Hamawandi, Bejan, PhD, et al. (författare)
  • Minute-Made, High-Efficiency Nanostructured Bi2Te3 via High-Throughput Green Solution Chemical Synthesis
  • 2021
  • Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Scalable synthetic strategies for high-quality and reproducible thermoelectric (TE) materials is an essential step for advancing the TE technology. We present here very rapid and effective methods for the synthesis of nanostructured bismuth telluride materials with promising TE performance. The methodology is based on an effective volume heating using microwaves, leading to highly crystalline nanostructured powders, in a reaction duration of two minutes. As the solvents, we demonstrate that water with a high dielectric constant is as good a solvent as ethylene glycol (EG) for the synthetic process, providing a greener reaction media. Crystal structure, crystallinity, morphology, microstructure and surface chemistry of these materials were evaluated using XRD, SEM/TEM, XPS and zeta potential characterization techniques. Nanostructured particles with hexagonal platelet morphology were observed in both systems. Surfaces show various degrees of oxidation, and signatures of the precursors used. Thermoelectric transport properties were evaluated using electrical conductivity, Seebeck coefficient and thermal conductivity measurements to estimate the TE figure-of-merit, ZT. Low thermal conductivity values were obtained, mainly due to the increased density of boundaries via materials nanostructuring. The estimated ZT values of 0.8-0.9 was reached in the 300-375 K temperature range for the hydrothermally synthesized sample, while 0.9-1 was reached in the 425-525 K temperature range for the polyol (EG) sample. Considering the energy and time efficiency of the synthetic processes developed in this work, these are rather promising ZT values paving the way for a wider impact of these strategic materials with a minimum environmental impact.
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24.
  • Kheradmand, Azam Beigi, et al. (författare)
  • Tribological Characterization of Reinforced Fe Matrix Composites with Hybrid Reinforcement of C, Cu, and SiC Particulates
  • 2022
  • Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 12:5, s. 598-
  • Tidskriftsartikel (refereegranskat)abstract
    • This study sought to design and characterize the Fe, SiC, Cu, and C metal matrix composite (MMC) with optimum SiC content to obtain sufficiently good wear resistance performance. For this purpose, Fe, Cu, graphite, and BaSO4 (Fe-11Cu-6.5G-6BaSO(4)) with 2, 4, 6, 8, and 10 wt.% SiC powders (in the range of 45-150 um) were milled for the fabrication of the composite. Then, sintering was performed by hot press at 1000 degrees C under 400 MPa in a controlled atmosphere furnace. Wear, and coefficient of friction (COF) were then carried out on the samples under 20 N and 700 rpm for 1000 m. SEM micrographs and EDS analysis were also utilized for the wear mechanism. According to the studies of worn surfaces, it was found that at the beginning of the sliding distance, the abrasion mechanism was predominant, and by increasing the sliding distance of plastic deformation, adhesive wear and oxidation were activated. It was concluded that the weight loss decreases less and has a constant and more appropriate COF due to an increase in SiC to an optimal value, i.e., 10%. In addition, wear resistance and hardness increase due to increased SiC. Therefore, due to the low wear rate and suitable coefficient of friction, composite Fe-11Cu-10SiC-6.5G-6BaSO(4) can be introduced as brake pad applications.
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25.
  • Khosravi, Payam, et al. (författare)
  • Anisotropic Magnetoresistance Evaluation of Electrodeposited Ni80Fe20 Thin Film on Silicon
  • 2022
  • Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 13:11, s. 1804-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, a simple growth of permalloy NiFe (Py) thin films on a semiconductive Si substrate using the electrochemical deposition method is presented. The electrodeposition was performed by applying a direct current of 2 mA/cm(2) during different times of 120 and 150 s and thin films with different thicknesses of 56 and 70 nm were obtained, respectively. The effect of Py thickness on the magnetic properties of thin films was investigated. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), ferromagnetic resonance (FMR), anisotropic magnetoresistance (AMR), and magneto-optic Kerr effect (MOKE) analyses were performed to characterize the Py thin films. It was observed that the coercivity of the Py thin film increases by increasing the thickness of the layer. Microscopic images of the layers indicated granular growth of the Py thin films with different roughness values leading to different magnetic properties. The magnetic resonance of the Py thin films was measured to fully describe the magnetic properties of the layers. The magnetoresistance ratios of deposited Py thin films at times of 120 and 150 s were obtained as 0.226% and 0.235%, respectively. Additionally, the damping constant for the deposited sample for 120 s was estimated as 1.36 x 10(-2), which is comparable to expensive sputtered layers' characteristics.
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26.
  • Kördel, Mikael, et al. (författare)
  • Quantitative conversion of biomass in giant DNA virus infection
  • 2021
  • Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Bioconversion of organic materials is the foundation of many applications in chemical engineering, microbiology and biochemistry. Herein, we introduce a new methodology to quantitatively determine conversion of biomass in viral infections while simultaneously imaging morphological changes of the host cell. As proof of concept, the viral replication of an unidentified giant DNA virus and the cellular response of an amoebal host are studied using soft X-ray microscopy, titration dilution measurements and thermal gravimetric analysis. We find that virions produced inside the cell are visible from 18 h post infection and their numbers increase gradually to a burst size of 280-660 virions. Due to the large size of the virion and its strong X-ray absorption contrast, we estimate that the burst size corresponds to a conversion of 6-12% of carbonaceous biomass from amoebal host to virus. The occurrence of virion production correlates with the appearance of a possible viral factory and morphological changes in the phagosomes and contractile vacuole complex of the amoeba, whereas the nucleus and nucleolus appear unaffected throughout most of the replication cycle.
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27.
  • Lajmorak, Asma, et al. (författare)
  • The Effect of Trehalose Coating for Magnetite Nanoparticles on Stability of Egg White Lysozyme
  • 2022
  • Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 23:17
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, the protein stability of hen egg-white lysozymes (HEWL) by Fe3O4 and Fe3O4-coated trehalose (Fe3O4@Tre) magnetic nanoparticles (NPs) is investigated. For this purpose, the co-precipitation method was used to synthesize magnetic NPs. The synthesized NPs were characterized by XRD, FT-IR spectroscopy, FE-SEM, and VSM analysis. In addition, the stability of HEWLs exposed to different NP concentrations in the range of 0.001-0.1 mg mL(-1) was investigated by circular dichroism (CD) spectroscopy, fluorescence, and UV-Vis analysis. Based on the results, in the NP concentration range of 0.001-0.04 mg mL(-1) the protein structure is more stable, and this range was identified as the range of kosmotropic concentration. The helicity was measured at two concentration points of 0.02 and 0.1 mg mL(-1). According to the results, the alpha-helix at 0.02 mg mL(-1) of Fe3O4 and Fe3O4@Tre was increased from 35.5% for native protein to 37.7% and 38.7%, respectively. The helicity decreased to 36.1% and 37.4%, respectively, with increasing the concentration of Fe3O4 and Fe3O4@Tre to 0.1 mg mL(-1). The formation of hydrated water shells around protein molecules occurred by using Fe3O4@Tre NPs. Hence, it can be concluded that the trehalose as a functional group along with magnetic NPs can improve the stability of proteins in biological environments.
  •  
28.
  • Lalegani, Z., et al. (författare)
  • Modeling, design, and synthesis of gram-scale monodispersed silver nanoparticles using microwave-assisted polyol process for metamaterial applications
  • 2020
  • Ingår i: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 108
  • Tidskriftsartikel (refereegranskat)abstract
    • High-yield monodispersed silver (Ag) nanospheres were modeled, designed, and synthesized by microwaveassisted (MW-assisted) polyol method from AgNO3, polyvinyl pyrrolidone (PVP), and ethylene glycol (EG), as precursors, at 145 degrees C within a short reaction time of 2 min, and the results were compared to those of conventional polyol method. Maintaining the PVP:AgNO3 molar ratio, the effect of increasing the amounts of AgNO3 and PVP at a constant amount of EG (40 mL) on the final product was evaluated. The synthesized nanoparticles (NPs) were characterized by SEM, UV-Vis spectroscopy, FTIR and DLS analysis. The results showed that with increasing the amount of AgNO3 to 0.5 and 1 g, monodispersed Ag nanoparticles (Ag NPs) with particle sizes of 54 and 61 nm were formed, as per the plasmon absorption peaks at 436 and 442 nm, respectively. Moreover, using 40 mL of the EG solution, we could obtain a high yield of the NPs (similar to 90%). The sub-gram yield was excellently high, offering great opportunities for commercializing the procedure. Also, the proposed study paves a new way for Ag NPs realization for different practical applications ranging from MW to optics.
  •  
29.
  • Lalegani, Z., et al. (författare)
  • Targeted dielectric coating of silver nanoparticles with silica to manipulate optical properties for metasurface applications
  • 2022
  • Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 287, s. 126250-
  • Tidskriftsartikel (refereegranskat)abstract
    • An epsilon-negative metamaterial (ENM) containing core@shell nanoparticles (NPs) was designed, where silver (Ag) NPs served as core and silica (SiO2) was used as spacer shell. AgNPs were synthesized in large scale, using microwave-assisted polyol method, in three average particle sizes, as 30, 54, and 61 nm, with a narrow particle size distribution. Optical absorption of Ag NPs was investigated using UV-Vis spectroscopy. Their optical behavior was also theoretically predicted for different thicknesses of the SiO2 shell immersed in media of different refractive indices using the Clausius Mossotti equation. Based on the results, optimal outputs were obtained with a SiO2 shell of 10 nm in thickness encompassing 54 nm Ag NPs based on the analytical model and numerical simulations here developed for core-shell structures. Then 10 nm SiO2 shell was grown on 54 nm Ag NPs by sol-gel synthesis. The NPs were then characterized by UV-Vis, TEM, SEM, EDX, DLS, and zeta potential analyses. The synthesized core-shell NPs can be used to establish epsilon-negative properties in polymer layers within visible range of wavelengths.
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30.
  • Luo, Jie, et al. (författare)
  • Microstructure, Mechanical and Thermal Properties of Al/Cu/SiC Laminated Composites, Fabricated by the ARB and CARB Processes
  • 2023
  • Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 13:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the current work is to investigate the effect of SiC particle weight percent and rolling passes on Al/Cu/SiC laminated composites, fabricated by accumulative roll-bonding (ARB) and cross-accumulative roll-bonding (CARB) processes. The optical microscopy (OM) images of composites revealed that despite the good bonding of the layers, they underwent plastic instabilities as a consequence of strain hardening of the layers. However, these instabilities occurred more in ARBed composites than in composites fabricated by the CARB process. This is because in the latter process, the composites are rolled in two directions, which leads to better strain distribution. Furthermore, with an increase in passes, SiC particles were well distributed in the matrix and interfaces. The mechanical findings showed that, by increasing passes, there was a growth in the values of strengths and elongation. This behavior is believed to be related to increased work-hardening of layers, better distribution of reinforcing particles, and an enhanced bonding of interfaces at higher rolling passes. In addition, the results of thermal conductivities showed a downward trend with an increase in passes; in fact, the increased number of Al/Cu interfaces declined the heat conduction of composites.
  •  
31.
  • Moharramzadeh, Fereshteh, et al. (författare)
  • Synthesis and Characterization of Hydrogel Droplets Containing Magnetic Nano Particles, in a Microfluidic Flow-Focusing Chip
  • 2023
  • Ingår i: Gels. - : MDPI AG. - 2310-2861. ; 9:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic hybrid hydrogels have exhibited remarkable efficacy in various areas, particularly in the biomedical sciences, where these inventive substances exhibit intriguing prospects for controlled drug delivery, tissue engineering, magnetic separation, MRI contrast agents, hyperthermia, and thermal ablation. Additionally, droplet-based microfluidic technology enables the fabrication of microgels possessing monodisperse characteristics and controlled morphological shapes. Here, alginate microgels containing citrated magnetic nanoparticles (MNPs) were produced by a microfluidic flow-focusing system. Superparamagnetic magnetite nanoparticles with an average size of 29.1 & PLUSMN; 2.5 nm and saturation magnetization of 66.92 emu/g were synthesized via the co-precipitation method. The hydrodynamic size of MNPs was changed from 142 nm to 826.7 nm after the citrate group's attachment led to an increase in dispersion and the stability of the aqueous phase. A microfluidic flow-focusing chip was designed, and the mold was 3D printed by stereo lithographic technology. Depending on inlet fluid rates, monodisperse and polydisperse microgels in the range of 20-120 & mu;m were produced. Different conditions of droplet generation in the microfluidic device (break-up) were discussed considering the model of rate-of-flow-controlled-breakup (squeezing). Practically, this study indicates guidelines for generating droplets with a predetermined size and polydispersity from liquids with well-defined macroscopic properties, utilizing a microfluidic flow-focusing device (MFFD). Fourier transform infrared spectrometer (FT-IR) results indicated a chemical attachment of citrate groups on MNPs and the existence of MNPs in the hydrogels. Magnetic hydrogel proliferation assay after 72 h showed a better rate of cell growth in comparison to the control group (p = 0.042).
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32.
  • Mousavi, Seyed Fereidon, et al. (författare)
  • Thermal cycles behavior and microstructure of AZ31/SiC composite prepared by stir casting
  • 2022
  • Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, the effect of thermal cycles on the physical and thermal properties of AZ31 alloy and AZ31/5wt%SiC and AZ31/10wt%SiC composites was investigated. Samples were prepared using the stir casting method and then subjected to precipitation hardening. Thermal cycles were done for as-cast and aged samples with V-shaped notch under 300, 600, and 900 heating and cooling cycles at 150 and 350 degrees C. The crack length (CL) was evaluated using optical microscope (OM), scanning electron microscope (SEM), and energy-dispersive scanning electron (EDS) analysis. Also, density, porosity, thermal expansion coefficient of the samples were evaluated. X-ray diffraction (XRD) analysis was employed to assess the phases present in the material. The results demonstrated that by increasing the number of thermal cycles up to 600 at 150 degrees C and 350 degrees C, the porosity and density of the as-cast and aged AZ31 alloy decreased and increased, respectively; however, the density and open porosity were remained constant for the composite samples. The crack's length enlarged with increasing the thermal cycles from 300 to 600 mu m at 150 degrees C and 300 to 900 mu m at 350 degrees C. It was found that the reinforcement and precipitates prevented the rapid growth of the crack in the magnesium matrix. All in All, composite and the aged samples demonstrated better thermal fatigue resistance compared with that of the unreinforced alloy and as-cast samples, respectively.
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33.
  • Ning, Weiqing, et al. (författare)
  • Characterization and photocatalytic activity of CoCr2O4/g-C3N4 nanocomposite for water treatment
  • 2023
  • Ingår i: Environmental Science and Pollution Research. - : Springer Nature. - 0944-1344 .- 1614-7499. ; 30:31, s. 76515-76527
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the materials that has recently been used to remove environmental pollution from industrial effluents with photocatalytic technology is cobalt chromate (CoCr2O4) nanoparticles. An effective way to improve the photocatalytic properties of materials is to composite them with other photocatalysts to prevent recombination of electron-holes and accelerate the transfer of oxidation/reduction agents. Graphitic carbon nitride (g-C3N4) is an excellent choice due to its unique properties. In this research, CoCr2O4 and its composite with g-C3N4 (5, 10, and 15%) were synthesized by polyacrylamide gel method and characterized by X-ray diffraction, scanning electron microscopy, FTIR, UV–Vis spectroscopy techniques. The photocatalytic behavior of synthesized nanoparticles was investigated in the degradation process of methylene blue dye. The results showed that the composite samples have higher efficiency in photocatalytic activity than the pure CoCr2O4 sample. Using CoCr2O4-15 wt%g-C3N4 nanocomposite, after 80 min, methylene blue was completely degraded. The mechanism of degradation by CoCr2O4-g-C3N4 nanocomposite was the superoxide radical produced by the reaction of electrons with oxygen absorbed on the catalyst surface, as well as optically produced holes directly.
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34.
  • Nojehdehi, Ali Maleki, et al. (författare)
  • Evaluation of Mechanical Properties of Glass Ionomer Cements Reinforced with Synthesized Diopside Produced via Sol-Gel Method
  • 2023
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 16:5
  • Tidskriftsartikel (refereegranskat)abstract
    • This study aimed to fabricate a glass ionomer cement/diopside (GIC/DIO) nanocomposite to improve its mechanical properties for biomaterials applications. For this purpose, diopside was synthesized using a sol-gel method. Then, for preparing the nanocomposite, 2, 4, and 6 wt% diopside were added to a glass ionomer cement (GIC). Subsequently, X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), and Fourier transform infrared spectrophotometry (FTIR) analyses were used to characterize the synthesized diopside. Furthermore, the compressive strength, microhardness, and fracture toughness of the fabricated nanocomposite were evaluated, and a fluoride-releasing test in artificial saliva was also applied. The highest concurrent enhancements of compressive strength (1155.7 MPa), microhardness (148 HV), and fracture toughness (5.189 MPa center dot m(1/2)) were observed for the glass ionomer cement (GIC) with 4 wt% diopside nanocomposite. In addition, the results of the fluoride-releasing test showed that the amount of released fluoride from the prepared nanocomposite was slightly lower than the glass ionomer cement (GIC). Overall, the improvement in mechanical properties and optimal fluoride release of prepared nanocomposites can introduce suitable options for dental restorations under load and orthopedic implants.
  •  
35.
  • Oztan, Cagri Y., et al. (författare)
  • Thermoelectric performance of Cu2Se doped with rapidly synthesized gel-like carbon dots
  • 2021
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 864
  • Tidskriftsartikel (refereegranskat)abstract
    • As an earth-abundant, inexpensive and non-toxic compound, Copper Selenide (Cu2Se) is a frequently investigated material for thermoelectric (TE) conversion applications. In this research, stoichiometric Cu2Se compounds were systematically doped with gel-like Carbon Dots (CDs), that were fabricated using a rapid and straightforward solvothermal method, at weight ratios of 2, 5 and 10%. The resultant ingots were spark plasma sintered and their TE performance was characterized. Scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDX) and powder X-ray diffraction (PXRD) were used to correlate the microstructure to the TE properties. Based on these measurements, CD doping strategy on Cu2Se yielded highly compacted, single phase grains with minimal oxidation. Characterization demonstrated a continuous enhancement of TE figure of merit (ZT) to a maximum of 2.1 at the optimum dopant ratio of 2 wt %. This enhancement was mainly due to the energy filtering effect of CD interfaces along the grain boundaries, and phonon scattering which increased the Seebeck coefficient and reduce the thermal conductivity. Doping beyond 2 wt% was recorded to inhibit this improvement. This research paved the path towards broader utilization of rapidly fabricated CDs to enhance TE conversion performance.
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36.
  • Rastan, Hamidreza, et al. (författare)
  • Heat transfer study of enhanced additively manufactured minichannel heat exchangers
  • 2020
  • Ingår i: International Journal of Heat and Mass Transfer. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0017-9310 .- 1879-2189. ; 161
  • Tidskriftsartikel (refereegranskat)abstract
    • Three-dimensional (3D) printing, known as additive manufacturing, provides new opportunities for the design and fabrication of highly efficient industrial components. Given the widespread use of this technique by industries, 3D printing is no longer limited to building prototypes. Instead, small-to-medium scale production units focus on reducing the cost associated with each part. Among the various industrial components that can be developed with this manufacturing technology are heat transfer components such as heat exchangers. To this end, this study investigated the heat transfer characteristics of minichannel-based heat exchangers embedded with longitudinal vortex generators, both experimentally and numerically. Three enhanced prototypes with different vortex generator design parameters and a smooth channel as a reference case were printed with an aluminum alloy (AlSi10Mg) using direct metal laser sintering (DMLS). The rectangular minichannel had a hydraulic diameter of 2.86 mm. Distilled water was used as the test fluid, and the Reynolds number varied from 170 to 1380 (i.e., laminar flow). Prototypes were tested under two different constant heat fluxes of 15 kW m(-2) and 30 k m(-2). The experimental results were verified with a commercial simulation tool, Comsol Multiphysics (R), using the 3D conjugate heat transfer model. In the case of the smooth channel, the experimental results were also compared with well-known correlations in the field. The results showed that 95% and 79% of the experimental data were within 10% of the numerical simulation results and the values from the existing correlations, respectively. For the channel enhanced with the vortex generators, the numerical predictions agreed well with the experimental results. It was determined that the vortex generators can enhance the convective heat transfer up to three times with the designed parameter. The findings from this research underline the potential of additive manufacturing in the development of more sophisticated minichannel heat exchangers.
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37.
  • Saladino, Giovanni, et al. (författare)
  • Carbon Quantum Dots Conjugated Rhodium Nanoparticles as Hybrid Multimodal Contrast Agents
  • 2021
  • Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 11:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanoparticle (NP)-based contrast agents enabling different imaging modalities are sought for non-invasive bio-diagnostics. A hybrid material, combining optical and X-ray fluorescence is presented as a bioimaging contrast agent. Core NPs based on metallic rhodium (Rh) have been demonstrated to be potential X-ray Fluorescence Computed Tomography (XFCT) contrast agents. Microwave-assisted hydrothermal method is used for NP synthesis, yielding large-scale NPs within a significantly short reaction time. Rh NP synthesis is performed by using a custom designed sugar ligand (LODAN), constituting a strong reducing agent in aqueous solution, which yields NPs with primary amines as surface functional groups. The amino groups on Rh NPs are used to directly conjugate excitation-independent nitrogen-doped carbon quantum dots (CQDs), which are synthesized through citrate pyrolysis in ammonia solution. CQDs provided the Rh NPs with optical fluorescence properties and improved their biocompatibility, as demonstrated in vitro by Real-Time Cell Analysis (RTCA) on a macrophage cell line (RAW 264.7). The multimodal characteristics of the hybrid NPs are confirmed with confocal microscopy, and X-ray Fluorescence (XRF) phantom experiments.
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38.
  • Saladino, Giovanni, et al. (författare)
  • Click chemical assembly and validation of bio-functionalized superparamagnetic hybrid microspheres
  • 2020
  • Ingår i: Applied Nanoscience. - : Springer Nature. - 2190-5509 .- 2190-5517.
  • Tidskriftsartikel (refereegranskat)abstract
    • Surface derivatized magnetic nanoparticles have been commonly used for magnetic separation. Facile mechanisms are needed to be developed for the design of bio-functionalized magnetic hybrid materials, where the surfaces can be re-generated for the re-use of the developed platforms. Superparamagnetic iron oxide nanoparticles with a diameter below 10 nm were synthesized via a novel microwave-assisted hydrothermal method in the presence of citrate ions, which allowed to obtain uniform and negatively charged nanoparticles. These were then coupled with Poly-l-lysine (PLL), forming micrometer-sized self-assembled spherical entities. Cross-linking the PLL within these microspheres with glutaraldehyde stabilized them chemically and mechanically. The active bio-functionality was introduced by a protein grafting methodology, using m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester (SMBS). The Moringa oleifera Coagulant Protein (MOCP) from a seed extract was employed for its characteristic coagulation activity. The performance of the MOCP functionalized microspheres was evaluated as a function of turbidity removal of problematic colloidal clay from water via magnetic separation, resulting in over 80% of activity within 15 min. Surface of these hybrid materials can be re-generated by treatment with alcohol, allowing their easy magnetic separation and re-use. The rapid and strong response with tunable magnetic property makes these hybrid microspheres a powerful tool for many potential applications, due to the general applicability of the developed methodology.
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39.
  • Saladino, Giovanni Marco, et al. (författare)
  • A versatile strategy to synthesize sugar ligand coated superparamagnetic iron oxide nanoparticles and investigation of their antibacterial activity
  • 2021
  • Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 613
  • Tidskriftsartikel (refereegranskat)abstract
    • For the time being, a great attention has been given to the search of green and reusable materials with antibacterial properties. The present research focused on the design and synthesis of hybrid structures constituting superparamagnetic iron oxide nanoparticles (SPIONs) coated with sugar ligands (SL), synthesized using a green and efficient microwave (MW)-assisted hydrothermal synthesis. The sugar ligands were selectively engineered to obtain antibacterial characteristics towards multi-drug resistant bacterial strains, which are among the most problematic bacterial species in antibiotic development efforts. The superparamagnetic behavior was obtained by synthesizing core iron oxide nanoparticles with a diameter below twenty nm. The MW-assisted hydrothermal method yielded a uniform coating of SPIONs with several sugar ligands, granting strongly negative-charged surfaces, which have eventually contributed to their bactericidal activity. The research work allowed to get insights into the magnetic properties of the sugar ligand coated SPIONs, as well as on morphological and functional characteristics of the hybrid nanoparticles, by employing both spectroscopy and imaging techniques, such as FT-IR, Scanning/Transmission Electron Microscopy (S/TEM). Detailed characterizations of the nanoparticles' charge, using zeta potential analysis helped to identify the highly charged hybrids for antibacterial applications. Furthermore, studies on the bactericidal properties of selected SL-SPION hybrids highlighted a high selectivity towards both gram-negative and gram-positive bacteria along with improving bactericidal activity of streptomycin/penicillin mixture. Detailed studies done on Pseudomonas aeruginosa revealed that the SPIONs selectively downregulated the virulence factor pyoverdine and altered bacterial morphology depending on the SL chemistry. The synthesized materials with antibacterial activity pave the way for an effective path towards the design and development of nanostructures and coatings against antibiotic-resistant bacterial species.
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40.
  • Saladino, Giovanni Marco, et al. (författare)
  • Functional Coatings for X-ray Fluorescent Nanoparticles
  • 2022
  • Ingår i: Proceedings of the 6th International Conference on Theoretical and Applied Nanoscience and Nanotechnology, TANN 2022. - : Avestia Publishing.
  • Konferensbidrag (refereegranskat)abstract
    • In recent years, the design and synthesis of bio-compatible coatings leading to hybrid nanoparticles (NPs) as the contrast agents have gained substantial relevance. Furthermore, the addition of several functionalities for bio-imaging applications represents a key step for non-invasive bio-diagnostics. In this context, we design and utilize hybrid nanostructures for X-ray fluorescence computed tomography (XFCT). The combination of a ceramic or metallic core–based on MoO2, Rh or Ru–with a protective shell allows the generation of bio-compatible nanohybrids for dual mode bio-imaging, where the core NPs constitute the X-ray fluorescence (XRF) contrast agents [1]–[3]. Core NPs are synthesized via polyol, hydrothermal or microwave-assisted hydrothermal methods, yielding uniform shape and high dispersibility in aqueous media. Different approaches have been pursued for the fabrication of a bio-compatible shell coating. A modified sol-gel based silica coating process, doped with a commercial fluorophore (Cy5.5), was developed and shown to be applicable to both ceramic and metallic NPs [4], forming core-shell NPs with both optical and X-ray fluorescence properties. Alternatively, carbon quantum dots (CQDs) were synthesized via citrate pyrolysis using microwave-assisted hydrothermal method, exhibiting uniform size distribution (1.6±0.4 nm) and excitation-independent emission (440 nm). Conjugation of these CQDs, via cross-linking, with Rh NPs led to excitation-independent hybrid NPs, with a red-shifted emission wavelength (520 nm), attributed to the reduction of pyrrolic nitrogen on CQDs [5]. These hybrid NPs exhibit improved in vitro biocompatibility in comparison with bare XRF contrast agents. Furthermore, the optical fluorescence–provided by Cy5.5 or CQDs–allows the localization of the NPs in the intracellular environment while the XRF signal from the core NPs is utilized for XFCT, in small animals, leading to both a microscopic and macroscopic bio-imaging contrast agent.
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41.
  • Serrano-Claumarchirant, José F., et al. (författare)
  • Thermoelectric Inks and Power Factor Tunability in Hybrid Films through All Solution Process
  • 2022
  • Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:17, s. 19295-19303
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermoelectric (TE) materials can have a strong benefit to harvest thermal energy if they can be applied to large areas without losing their performance over time. One way of achieving large-area films is through hybrid materials, where a blend of TE materials with polymers can be applied as coating. Here, we present the development of all solution-processed TE ink and hybrid films with varying contents of TE Sb2Te3 and Bi2Te3 nanomaterials, along with their characterization. Using (1-methoxy-2-propyl) acetate (MPA) as the solvent and poly (methyl methacrylate) as the durable polymer, large-area homogeneous hybrid TE films have been fabricated. The conductivity and TE power factor improve with nanoparticle volume fraction, peaking around 60-70% solid material fill factor. For larger fill factors, the conductivity drops, possibly because of an increase in the interface resistance through interface defects and reduced connectivity between the platelets in the medium. The use of dodecanethiol (DDT) as an additive in the ink formulation enabled an improvement in the electrical conductivity through modification of interfaces and the compactness of the resultant films, leading to a 4-5 times increase in the power factor for both p- and n-type hybrid TE films, respectively. The observed trends were captured by combining percolation theory with analytical resistive theory, with the above assumption of increasing interface resistance and connectivity with polymer volume reduction. The results obtained on these hybrid films open a new low-cost route to produce and implement TE coatings on a large scale, which can be ideal for driving flexible, large-area energy scavenging technologies such as personal medical devices and the IoT. 
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42.
  • Talaeizadeh, Mohammad, et al. (författare)
  • Characterization of the Nano-Rod Arrays of Pyrite Thin Films Prepared by Aqueous Chemical Growth and a Subsequent Sulfurization
  • 2022
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:19
  • Tidskriftsartikel (refereegranskat)abstract
    • Pyrite is an earth-abundant and low-cost material with a specific collection of properties including a low band gap and high absorption coefficient of solar light. These properties make pyrite a good choice in a wide variety of applications such as catalysts, batteries, and photovoltaic devices. A thin film composed of vertically aligned pyrite nano-rods was processed via a hydration-condensation method followed by subsequent aging and sulfurization. In this process, no ionic salt was used which resulted in a lower cost process with a lower level of impurities. Field emission scanning electron microscopy, X-ray diffraction, and Raman spectroscopy analyses were used to characterize the thin films in different steps of the process. The major impurity of the final thin films was the marcasite phase according to the Raman analysis which could be minimized by lowering sulfurizing time to about 60 min. In addition, after structural, electrical, and optical characterization of thin films, these layers' performances in a photovoltaic device were also examined. After deposition of a thin aluminum layer, Schottky-type solar cells of pyrite formed which were then illuminated to measure their current-voltage characteristics. The results show that a combination of low-cost materials and a low-cost preparation method is applicable for building future solar cells.
  •  
43.
  • Wang, Yang-Yang, et al. (författare)
  • Microstructural Evolution during Accelerated Tensile Creep Test of ZK60/SiCp Composite after KoBo Extrusion
  • 2022
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:18
  • Tidskriftsartikel (refereegranskat)abstract
    • In the current study, the creep properties of magnesium alloy reinforced with SiC particles were investigated. For this purpose, ZK60/SiCp composite was produced by the stir casting method following the KoBo extrusion and precipitation hardening processes. The creep tests were performed at 150 degrees C under 10-110 MPa. The results showed that the stress exponent (n) and the average true activation energy (Q) was changed at high stresses, was found with increasing stress, the creep mechanism changing from grain boundary sliding to dislocation climb. The results of microstructure characterization after the creep test showed that at low stresses, the dynamic recrystallization resulting from twinning induced the GBS mechanism. However, at high stresses, with increasing diffusion rates, conditions are provided for dynamic precipitation and the dislocation climb of the dominant creep mechanism. Examination of the fracture surfaces and the surrounding areas showed that the cavity nucleation in the ternary boundary and surrounding precipitation was the main cause of damage. The evaluation of the samples texture after creep showed that the unreinforced alloy showed a moderately strong fiber texture along the angle of phi(1) = 0-90 degrees, which was tilted about phi = 10 degrees. A new strong texture component was observed at (90 degrees, 5 degrees, 0 degrees) for the composite sample, which crept due to minor splitting of the basal pole by similar to 5 degrees toward RD.
  •  
44.
  • Yusuf, Aminu, et al. (författare)
  • Multi-objective optimization of concentrated Photovoltaic-Thermoelectric hybrid system via non-dominated sorting genetic algorithm (NSGA II)
  • 2021
  • Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 236
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermoelectric generators harvest additional electrical power when used in combination with concentrated photovoltaic cells given rise to a hybrid system. Overall cost of the system is high; therefore, the parameters of the system need to be optimized to obtain high output performance. This study determines the output performances of four sets of equations (models) used in the hybrid system, using the performance of recently developed nanostructured thermoelectric materials. Seven parameters of the system were optimized through these models using non-dominated genetic algorithm. Models 1 and 2 have the highest performance chosen by TOPSIS decision-making method. The power output and conversion efficiencies of the hybrid system in models 1 and 2 are 426.5 W, 11.45% and 461.12 W, 10.77%, respectively. Likewise, the highest TOPSIS solution for power output of one TEG module operating in the hybrid system and its corresponding efficiency is obtained in model 4 and are 1.97 W and 0.078%, respectively. This validates the fact that TEG operating in a hybrid system has optimum performance at a point when the load resistance is less than its internal resistance.
  •  
45.
  • Zali, Amir, et al. (författare)
  • Fabrication of TiFe-Based Electrodes Using High-Energy Ball Mill with Mn Additive for NiMH Batteries
  • 2022
  • Ingår i: BATTERIES-BASEL. - : MDPI AG. - 2313-0105. ; 8:10, s. 182-
  • Tidskriftsartikel (refereegranskat)abstract
    • Binary and ternary (with the addition of Mn) TiFe-based intermetallic compound powders were fabricated by high energy ball milling, and their electrochemical behavior as negative electrodes was investigated in 6M-KOH. X-ray diffraction exhibited the single phase of nanostructured binary and ternary TiFe-based crystallites after 20 h of milling followed the amorphous phase formation. Addition of Mn increased peak broadening and in turn decreased the nanocrystallite size of TiFe. Electrode properties of 20, 40, 60, and 70 h binary milled products showed that the discharge capacity of the 60 h one offered a maximum discharge capacity of similar to 169 mAhg(-1). Although substitution of Mn for Ti (TixFeMnx,( )x = 0.1, 0.2) caused a decrease in initial discharge capacity, the periodic stability increased compared to the binary TiFe and ternary TiFe1-xMnx (x = 0.1, 0.2). The ternary Ti0.9FeMn0.1 electrode maintained similar to 53% of its initial discharge capacity after five cycles of charge-discharge; this was just 28% in the case of binary TiFe electrode.
  •  
46.
  • Zuo, Zhaoyang, et al. (författare)
  • Microstructure, Fractography, and Mechanical Properties of Hardox 500 Steel TIG-Welded Joints by Using Different Filler Weld Wires
  • 2022
  • Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:22
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper deals with the effects of three low-carbon steel filler metals consisting of ferritic and austenitic phases on the weld joints of the tungsten inert gas (TIG) welding of Hardox 500 steel. The correlation between the microstructure and mechanical properties of the weld joints was investigated. For this purpose, macro and microstructure were examined, and then microhardness, tensile, impact, and fracture toughness tests were carried out to analyze the mechanical properties of joints. The results of optical microscopy (OM) images showed that the weld zones (WZ) of all three welds were composed of different ferritic morphologies, including allotriomorphic ferrite, Widmanstätten ferrite, and acicular ferrite, whereas the morphology of the heat-affected zone (HAZ) showed the various microstructures containing mostly ferrite and pearlite phases. Further, based on mechanical tests, the second filler with ferritic microstructure represented better elongation, yield strength, ultimate tensile strength, impact toughness, and fracture toughness due to having a higher amount of acicular ferrite phase compared to the weld joints concerning the other fillers consisting of austenitic and ferritic-austenitic. However, scanning electron microscopy (SEM) images on the fracture surfaces of the tensile test showed a ductile-type fracture with a large number of deep and shallow voids while on the fracture surfaces resulting from the Charpy impact tests and both ductile and cleavage modes of fracture took place, indicating the initiation and propagation of cracks, respectively. The presence of acicular ferrite as a soft phase that impedes the dislocation pile-up brings about the ductile mode of fracture while inclusions may cause stress concentration, thus producing cleavage surfaces.
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