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International Journal of Biological Macromolecules (01418130) 254
Cellulose/poly (glycerol citrate) reinforced with thiol-rich polyhedral oligomeric silsesquioxane and apple peel (POSS-SH@CAG-CEL/AP) was synthesized using gelation method in the presence of glutaraldehyde as a crosslinker agent and used as an efficient composite hydrogel for elimination of Tl(Ι) from aqueous solutions. This composite hydrogel and synthesized thiol-rich polyhedral oligomeric silsesquioxane were characterized by elemental analysis, FT-IR, NMR, TGA, and FE-SEM techniques. The effects of synthetic and environmental parameters on the adsorption capacity of the composite hydrogel were investigated and it was found that thiol-rich polyhedral oligomeric silsesquioxane has improved the hydrogel properties including the Tl(Ι) uptake and the thermal stability. The maximum adsorption capacity of 352.3 mg g−1 was obtained within 30 min under optimum reaction conditions. A typical Langmuir adsorption isotherm with was observed for adsorption of Tl(I) onto POSS-SH@CAG-CEL/AP and pseudo-second-order kinetic model provided the best correlation between experimental data. Thermodynamic studies showed that the Tl(I) adsorption was spontaneous process and exothermic. Also, the reusability tests confirmed that the POSS-SH@CAG-CEL/AP can be reused for four times without any remarkable change in its adsorption capacity. Thus, this reusable biobased composite hydrogel can be an ideal candidate for elimination of Tl(I) from aqueous solutions. © 2023
Chemosphere (00456535) 349
The eco-friendly polymeric nanocomposite hydrogels were prepared by incorporating dendritic fibrous nanosilica (DFNS) and apple peel (AP) as reinforcements into the crosslinked polymer produced by cellulose (CL) and poly (glycerol tartrate) (TAGL) via gelation method and used for efficient adsorption of Pb2+, Co2+, Ni2+, and Cu2+ metal ions. DFNS and DFNS/TAGL-CL/AP samples were characterized by FESEM, FTIR, TEM, TGA, and nitrogen adsorption/desorption methods. The results of TGA analysis showed that the thermal stability of the prepared hydrogels improved significantly in the presence of DFNS. Both synthetic and environmental parameters were investigated and the adsorption capacity reached 560.2 (pH = 4) and 473.12 (pH = 5) mg/g for Pb2+ and Cu2+ respectively, using initial ion concentration of 200 mg/L. Also, the maximum adsorption capacity was 340.9, and 350.3 mg/g for Co2+ and Ni2+, respectively under optimum conditions (pH = 6, initial ion concentration of 100 mg/L). These experiments indicated that the DFNS/TAGL-CL/AP nanocomposite hydrogel has an excellent performance in removal of Pb2+ and can adsorb this toxic metal in only 30 min while the optimum contact time for other metals was 60 min. Pseudo-second-order and Langmuir models were used to define the kinetic and adsorption isotherms, respectively and thermodynamic studies demonstrated that the adsorption was endothermic for Co2+, Ni2+ and Cu2+, exothermic for Pb2+, and spontaneous in nature for all metal ions. Furthermore, the reusability tests indicated that the hydrogels could maintain up to 93% of their initial adsorption capacity for all metal ions after four cycles. Therefore, the prepared nanocomposite hydrogels can be suggested as efficient adsorbents to remove the toxic metals from wastewater. © 2023
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.
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.
Materials Chemistry and Physics (02540584) 258
This study aimed to obtain high-density green pieces from α-alumina/amorphous alumina core-shell nanocomposite powder. This nanocomposite was initially obtained in the form of a pellet with high-green density using the slip-casting process. Then, it was sintered by a pressureless sintering method under vacuum conditions. The effects of slurry parameters, such as dispersant content, solid loading, and agglomeration for viscosity and green density, are investigated for optimizing the slip-casting conditions. The green sample with a density of 63% was obtained by using α-alumina/amorphous alumina core-shell nanocomposite powder after 13 h of wet milling and casting at 70% solid loading, 5 wt% Dolapix, and pH = 10.5. The sintered sample showed a relative density of 99.5% and a transmission of 72% in the IR region at 1300 °C under a vacuum condition. The application of the amorphous phase in the initial powder, as a shell, led to the sintering-aid of this phase and decreased sintering temperature. The slip-casting method also resulted in high-green density and consequently high-final density using pressureless sintering. © 2020 Elsevier B.V.
Ceramics International (02728842) 47(15)pp. 21285-21292
In this study, magnesium fluoride (MgF2) nanoparticles were synthesized through the fluoridation method, by dissolving magnesium chloride and hydrofluoric acid (HF) in deionized water. The influences of some parameters, including pH, concentration ratio of reactants, F:Mg mole ratio, washing method and calcination temperature were investigated on the particle size, morphology, chemical purity and phase purity of MgF2 nanoparticles. In order to study the impact of pH on the properties of MgF2 nanoparticles, different samples at pH values of 1, 5 and 9 were synthesized. The obtained results revealed that as pH value increased from 1 to 9, the morphology of MgF2 nanoparticles changed from rod to spherical shape. The effect of mole ratio of fluorine ions to magnesium ions on the MgF2 nanoparticles at three ratios of 2, 6 and 12 also demonstrated that by increment of F:Mg mole ratio, the particle size was decreased from 150 nm to 30 nm. In addition, it was figured out that by the increment of F:Mg mole ratio, the MgO phase was eliminated. Afterwards, by decreasing the HF:MgCl2 molar ratios from 0.1 to 0.03 the particle size reduced from 300 nm to 30 nm. After determining the optimal synthesis conditions, magnesium fluoride nanoparticles were calcined at 470, 530 and 600 °C. Regarding the results, the powder that was calcined at 600 °C with a particle size of about 30–40 nm was selected as the optimal sample. Ultimately, the resulting powder was sintered using hot-press (HP) at a temperature of 700 °C for 45min in the vacuum pressure of 10−3 bar. After polishing the sintered piece, its inferred (IR) transparency was over 90% in the wavelength ranges of 3–5 μm. © 2021 Elsevier Ltd and Techna Group S.r.l.
Iranian Journal of Science and Technology - Transactions of Mechanical Engineering (22286187) 44(4)pp. 1091-1102
In this paper, the relationship between the cutting conditions and the wear mechanisms in turning Inconel718 from both modeling and experiment points of view has been studied. The tool chosen consists of a hard fine-grained WC with 6% Co with TiAlN layer. As a result, the recommended machining conditions with minimal wear would be the selection of a tool with a radius of 1.6 mm and the cutting velocity in the range of 45 to 55 m/min. The optimal variables obtained from artificial neural networks and genetic algorithm are found to be in good agreement with the results of laboratory findings on the wear mechanism map. Also, the results showed that at lower cutting velocities and feed rates, the TiAlN layer acts to prevent the transfer of elements between the tool and workpiece (mild and transient wear zones), causing the turning forces to stabilize over time. However, with an increase in the cutting velocity and feed rate (severe zone), the TiAlN layer breaks off the tool surface resulting in a considerable increase in the friction coefficient, cutting forces, and the adhesive wear. The main reason for this phenomenon is the transfer of elements such as nickel, chrome, and iron to the flank face. © 2019, Shiraz University.
Materials Research Express (20531591) 7(11)
The aim of this study was to fabricate a YAG/Al2O3 ceramic composite with different alumina nanoparticles using slip casting and the atmospheric sintering process. In addition, some mechanical properties such as hardness and elastic modules of this ceramic were evaluated using the nanoindention technique. The results showed that the rheological behavior of the slurry was optimized to the solid loading of 55 wt%; also, the relative density of the green body was enhanced up to 65%. Relative density was increased to 99.5% after sintering at 1700 °C for 12 h; further, the pore size (150 nm) was reduced to half of that of powder particles. It should be, however, noted that the optimum amount of alumina nanoparticles as a reinforcing agent in the matrix was less than 5%wt and the composite hardness was increased to 7.3%, as compared to the pure YAG ceramic. © 2020 The Author(s). Published by IOP Publishing Ltd.
Environmental Earth Sciences (18666299) 79(13)
In the present study, an experimental investigation was conducted to examine the effect of the size of additives on the improvement of collapsible soils. For this purpose, three collapsible soils with severe collapse potential were selected from Varamin Plain, Iran. The selected soils were then treated in the laboratory by the addition of alumina materials in two sizes of 70 nm (nano-alumina) and 685 nm (micro-alumina) and in different contents to improve their mechanical properties. Soil properties including collapse potential, uniaxial compressive strength, compressive modulus of elasticity, direct tensile strength, and tensile modulus of elasticity were selected as the target parameters for the improvement. These parameters were measured and determined before and after the treatment and the behaviors of treated soils were studied in both compression and tension states. The obtained results indicated that the nanometric and micrometric additives have diverse effects on the performance of the treated soil under compression and tension conditions. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Yazdani, I. ,
Naeimi, M. ,
Sattary, M. ,
Rafienia m., M. ,
Movahedi, B. Bioinspired, Biomimetic and Nanobiomaterials (20459858) 9(3)pp. 175-183
In the present study, polyurethane (PU) nanocomposite scaffolds containing bioactive glass nanoparticles (BG-NPs) were successfully fabricated through the electrospinning process. The BG-NPs were synthesized through the sol-gel method. PU solutions (10%w/v) containing different weight percentages of the BG-NPs (5, 10 and 15wt.%) in dimethylformamide/tetrahydrofuran were prepared. To determine both the size of BG-NPs and the diameter of the nanofibers, transmission electron microscopy and scanning electron microscopy were carried out. The surface morphology, mechanical properties, bioactivity and degradation rate of the scaffolds were studied. Fourier transform infrared spectroscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy confirmed the presence of BG within the scaffolds. The tensile strength of nanocomposite scaffolds was in the range 5-8MPa, which is in good agreement with the tensile strength of cancellous bone tissue. MG63 cells attached to and proliferated well within the scaffolds; therefore, cellular growth was also improved in the nanocomposite scaffolds. Based on the results, the novel PU/BG-NP (10wt.%) nanocomposite scaffold has a great potential to be applied in cancellous bone tissue engineering. © 2020 ICE Publishing: All rights reserved.
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.
Journal Of Ultrafine Grained And Nanostructured Materials (24236845) 52(2)pp. 154-163
In this study, the effect of slip casting parameters on the ultrafine microstructure and the density of pore-free YAG ceramic was evaluated. A stable, high concentrated aqueous YAG slurry using Dolapix-CE64 as a dispersant was prepared and the effect of dispersant concentration as well as the solid load on the stability and rheological behavior of the slurry was also studied. The optimum dispersant content for the suspension was 1.5 wt% which led to the slurry with minimum viscosity and near-Newtonian behavior. The results showed that increasing the solid load of the YAG slurry causes higher viscosity and alters the rheological behavior of the slurry to a slight shear thinning. By increasing the solid load of the slurry up to a specific amount of 75 wt%, relative green density of the slip cast sample was increased to about 65%, but further increase reduced the green density. The microstructure and the density of the sintered body in the air and vacuum atmospheres comprise a direct relationship to the green density of the slip cast body. © (2019), (University of Tehran). All rights reserved.
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.
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 Molecular Liquids (18733166) 265pp. 243-250
HIV-1 P24 protein-derived peptides-loaded chitosan nanoparticles (CS-NPs) were synthesized, based on the ionic gelation method and development of electrostatic interactions between CS-NPs and negatively charged of HIV-1 P24 protein-derived peptides. Dynamic light scattering analysis (DLS) revealed that CS-NPs had a mean diameter of 22 nm. The prepared peptides loaded CS-NPs showed that peptide loading via incubation method led to an increase in the particle size to 70 nm, in comparison to CS-NPs. The results obtained by Zetasizer revealed that the surface charge of CS-NPs is positive due to the presence of amine groups on its surface. Peptide adsorption on the nanoparticles would have decreased the positive surface charge of the cationic chitosan molecule and led to the decline in the values of zeta-potential in CS-NPs from+30.3 to+23.2 mV. The rate of loading efficiency became 96%, the peptide was very quickly released in the first 24 h, and after that the releasing rate was decreased. After 216 h, >70% of the drug was released. Since the use of peptides in high concentrations is not economically feasible, this paper attempts to use the nano-carrier to overcome this limitation. The novelty of this work is to use of chitosan nanoparticles to increasing the effectiveness of peptides at low concentrations. © 2018 Elsevier B.V.
Advanced Powder Technology (09218831) 28(2)pp. 340-345
In this paper the formation as well as the stability of Nb3Al intermetallic compounds from pure Nb and Al metallic powders through mechanical alloying (MA) and subsequent annealing were studied. According to this method, the mixture of powders with the proportion of Nb-25 at% Al were milled under an argon gas atmosphere in a high-energy planetary ball mill, at 7, 14, 27 and 41 h, to fabricate disordered nanocrystalline Nb3Al. The solid solution phase transitions of MA powders before and after annealing were characterized using X-ray diffractometry (XRD). The microstructural analysis was performed using scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). The results show that in the early stages of milling, Nb(Al) solid solution was formed with a nanocrystalline structure that is transformed into the amorphous structure by further milling times. Amorphization would appear if the milling time was as long as 27 h. Partially ordered Nb3Al intermetallic could be synthesized by annealing treatment at 850 °C for 7 h at lower milling times. The size of the crystallites after subsequent annealing was kept around 45 nm. © 2016 The Society of Powder Technology Japan
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science (10735623) 48(3)pp. 1474-1483
In this study, Fe-based metallic glass was served as the matrix in which various ratios of hard B4C nanoparticles as reinforcing agents were prepared using a high-energy mechanical milling. The feedstock nanocomposite powders were transferred to the coatings using a high-velocity oxygen fuel process. The results showed that the microstructure of the nanocomposite coating was divided into two regions, namely a full amorphous phase region and homogeneous dispersion of B4C nanoparticles with a scale of 10 to 50 nm in a residual amorphous matrix. As the B4C content is increased, the hardness of the composite coatings is increased too, but the fracture toughness begins to be decreased at the B4C content higher than 20 vol pct. The optimal mechanical properties are obtained with 15 vol pct B4C due to the suitable content and uniform distribution of nanoparticles. The addition of 15 vol pct B4C to the Fe-based metallic glass matrix reduced the friction coefficient from 0.49 to 0.28. The average specific wear rate of the nanocomposite coating (0.48 × 10−5 mm3 Nm−1) was much less than that for the single-phase amorphous coating (1.23 × 10−5 mm3Nm−1). Consequently, the changes in wear resistance between both coatings were attributed to the changes in the brittle to ductile transition by adding B4C reinforcing nanoparticles. © 2016, 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.
Kafili g., G. ,
Loghman-estarki, M.R. ,
Milani, M. ,
Movahedi, B. Journal of the American Ceramic Society (00027820) 100(9)pp. 4305-4316
In this work, pure yttrium aluminum garnet was obtained by the partial chemical method at the low temperature. In this approach, alpha-alumina nanoparticle, yttrium nitrate, urea, and tetraethyl orthosilicate (TEOS) were used as Al3+, Y3+, precipitation agent, and both dispersant and phase formation assistant agents, respectively. The results showed that TEOS molecules as a dispersant agent caused the less agglomeration of the alumina-yttria core-shell structure with a diameter of 200-300 nm, as compared to particles obtained without using TEOS molecules. Furthermore, by using 0.5 and 1 wt% of TEOS, the YAG formation temperature was decreased from 1400°C to 1200°C through the liquid-phase diffusion mechanism. Thus, in this case, the TEOS molecules acted as phase formation assistant agent for the constitution of YAG phases. © 2017 The American Ceramic Society
Materials Chemistry and Physics (02540584) 183pp. 136-144
Alumina/yttria nanocomposite powder as an yttrium aluminum garnet (YAG) precursor was synthesized via partial wet route using urea and ammonium hydrogen carbonate (AHC) as precipitants, respectively. The products were characterized using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. The use of urea produced very tiny spherical Y-compounds with chemical composition of Y2(CO3)3·nH2O, which were attracted to the surface of alumina nanoparticles and consequently, a core-shell structure was obtained. The use of ammonium hydrogen carbonate produced sheets of Y-compounds with chemical composition of Y(OH)CO3 covering the alumina nanoparticles. A fine-grained YAG ceramic (about 500 nm), presenting a non-negligible transparency (45% RIT at IR range) was obtained by the spark plasma sintering (SPS) of alumina-yttria nanocomposite synthesized in the urea system. This amount of transmission was obtained by only the sintering of the powder specimen without any colloidal forming process before sintering or adding any sintering aids or dopant elements. However, by spark plasma sintering of alumina-yttria nanocomposite powder synthesized in AHC system, an opaque YAG ceramic with an average grain size of 1.2 μm was obtained. © 2016 Elsevier B.V.
Radiation Measurements (13504487) 89pp. 14-22
In this study, lithium-tetraborate (LTB) was synthesized by three methods of high-temperature solid state, wet and combustion reactions. Copper was added to pure LTB by solution assisted method, to improve the thermoluminescence (TL) properties. The pellets of LTB were produced using pressing and sintering operations at 850 °C. The synthesized LTB pellets, exposed to the gamma radiation of 60Co source in the dose range of 5-20Gy and glow curves as well as dose-response diagrams were obtained. Ultimately, the effects of different factors on TL behaviors like dopant, crystallite size and particle morphologies were studied. The results show that between pure samples, LTB which synthesized by combustion method has higher TL sensitivity than those of other methods. However, it was seen a weak glow peak for 5Gy, due to the nanocrystalline structure of LTB. This property led to decrease TL intensity at low-doses and postponed saturation at high-doses. Fading of this sample was also less than others and has relatively better reproducibility. Among LTB:Cu pellets which synthesized by the wet reaction showed the higher TL response than others due to the creation of more traps and luminescence centers and had promising properties in the case of dose response linearity and fading. © 2016 Elsevier Ltd. All rights reserved.
RSC Advances (20462069) 5(94)pp. 77255-77263
Nowadays, iron oxide nanoparticles are among the most interesting carriers in simultaneous drug delivery and magnetic resonance imaging applications (theranostics). In this study, Fe3O4 magnetic nanoparticles were synthesized by a co-precipitation method followed by coating with an active-bioglass layer. This nanostructure is functionalized with hyperbranched polyglycerol through ring-opening polymerization of glycidol. The carrier was characterized using TEM, FT-IR, XRD, TGA, and elemental analysis. The results showed that the diameter of the carrier was between 20-30 nm. The cytotoxicity and cellular uptake results indicated that this nanostructure did not induce any cytotoxicity while expressing good potential as a contrast agent for magnetic resonance imaging. Moreover, curcumin was loaded on the carrier as a hydrophobic sample drug. The results showed a significant increase in curcumin solubility, which revealed the potential of this nanostructure in simultaneous cancer diagnosis and therapy. © 2015 The Royal Society of Chemistry.
Applied Surface Science (01694332) 357pp. 1758-1764
In the present study, bioactive glass (BG), carbon nanotube (CNT), and chitosan (Cs) were used with different ratios for the fabrication of nanocomposite scaffold for bone tissue engineering. BG was synthesized by sol-gel process and CNT was functionalized by immersing in sulfuric acid as well as nitric acid. Nanocomposite scaffold was produced using a novel technique, hot press, and salt leaching process and cross-linked by Hexamethylene diisocyanate (HDI). The optimum porosity of the scaffold with respect to the ratio of salt and precursor was kept around 70%. Mechanical properties of the scaffolds were increased by the addition of CNT and hence, the compressive strength of them with 4 wt% CNT was increased up to 5.95 ± 0.5 MPa. The nanocomposite scaffolds were characterized by FT-IR, SEM, XRD, and electrochemical analysis. Furthermore, scaffolds were immersed in PBS for evaluating the biodegradability, water absorption, and CNT release. The results indicated that water absorption of the scaffolds was increased by adding CNT to the scaffold. The amount of released CNT after 30 days was measured within 6 × 10 -4 and 1 × 10 -3 mg/ml. Attachment and proliferation of MG63 osteoblast cell line on Cs/BG/CNT scaffolds were investigated by MTT assay indicating no toxicity for this nanocomposite scaffolds. According to the results of the experiments, the nanocomposite scaffold with modified composition (Cs/BG/CNT, 80:20:2 wt%) was the best one in matters of mechanical, chemical, and cellular properties and also the most appropriate for trabecular bone tissue. © 2015 Elsevier B.V. All rights reserved.
Materials Science in Semiconductor Processing (13698001) 29pp. 337-344
The piezoelectric nanocrystalline ceramics of (Bi0.5Na0.5) TiO3, 0.94(Bi0.5Na0.5) TiO3-0.06BaTiO3, 0.82(Bi0.5Na0.5) TiO3-0.18(Bi0.5K0.5) TiO3 and 0.85(Bi0.5Na0.5) TiO3-0.144 (Bi0.5K0.5)TiO3-0.006BaTiO3 (abbreviated as BNT, BNBT6, BNKT18 and BNT-BT-BKT, respectively) have been synthesized by a modified solid state approach using high-energy planetary ball-milling. The crystal structures of ceramics were determined using X-ray diffraction (XRD) method and that the microstructures as well as the morphology of the sintered ceramic specimens were observed using scanning-electron microscopy (SEM). The dielectric coefficient was also calculated based on its relation with a constant capacitance measured by an electrical circuit on the basis of the Wetston-Bridge and the piezoelectric coefficient (d33) measured with a d33-meter. On the calcination of powders the XRD results showed that the perovskite phase was formed perfectly and the crystallite sizes of BNT, BNBT6, BNKT18 and BNT-BT-BKT were estimated at about > 100, 55, 36 and 63 nm, respectively. Also, the crystallite sizes of the calcinated BNT powders over the course of 5, 10, 20, 30 and 40 h of ball-milling were estimated at about 86, 82, 72, 53, 81 nm, respectively. Moreover, the results of XRD and SEM analysis of the sintered powders at 750-1150°C confirmed the positive effect of nanocrystalline formation during ball-milling in decreasing the sintering temperature and increasing the density of the sintered samples. Furthermore, electrical calculations such as dielectric and piezoelectric coefficients showed that the modified BNKT18 nanocrystalline ceramic sintered at 1150°C was to have the best values of dielectric (εr=792 at 1 kHz) and piezoelectric coefficients (d33=85.9 pC/N) in comparison with the other synthesized piezoelectric ceramics. © 2014 Elsevier Ltd. All rights reserved.
Journal of Thermal Spray Technology (10599630) 23(3)pp. 477-485
The mechanical and tribological behavior and microstructural evolutions of the Ni(Al)-reinforced nanocomposite plasma spray coatings were studied. At first, the feedstock Ni(Al)-15 wt.% (Al2O3-13% TiO 2) nanocomposite powders were prepared using low-energy mechanical milling of the pure Ni and Al powders as well as Al2O3-13% TiO2 nanoparticle mixtures. The characteristics of the powder particles and the prepared coatings depending on their microstructures were examined in detail. The results showed that the feedstock powders after milling contained only α-Ni solid solution with no trace of the intermetallic phase. However, under the air plasma spraying conditions, the NiAl intermetallic phase in the α-Ni solid solution matrix appeared. The lack of nickel aluminide formation during low-energy ball milling is beneficial hence, the exothermic reaction can occur between Ni and Al during plasma spraying, improving the adhesive strength of the nanocomposite coatings. The results also indicated that the microhardness of the α-Ni phase was 3.91 ± 0.23 GPa and the NiAl intermetallic phase had a mean microhardness of 5.69 ± 0.12 GPa. The high microhardness of the nanocomposite coatings must be due to the presence of the reinforcing nanoparticles. Due to the improvement in mechanical properties, the Ni(Al) nanocomposite coatings showed significant modifications in wear resistance with low frictional coefficient. © 2013 ASM International.
Advanced Powder Technology (09218831) 25(3)pp. 871-878
The synthesis and microstructural evolutions of the NiAl-15 wt% (Al 2O3-13% TiO2) nanocomposite powders were studied. These nanocomposite powders are used as feedstock materials for thermal spray applications. These powders were prepared using high and low-energy mechanical milling of the Ni, Al powders and Al2O3-13% TiO2 nanoparticle mixtures. High and low-energy ball-milled nanocomposite powders were also sprayed by means of high-velocity oxy fuel (HVOF) and air plasma spraying (APS) techniques respectively. The results showed that the formation of the NiAl intermetallic phase was noticed after 8 h of high-energy ball milling with nanometric grain sizes but in a low-energy ball mill, the powder particles contained only α-Ni solid solution with no trace of the intermetallic phase after 25 h of milling. The crystallite sizes in HVOF coating were in the nanometric range and the coating and feedstock powders showed the same phases. However, under the APS conditions, the coating was composed of the NiAl intermetallic phase in the α-Ni solid solution matrix. In both of the nanocomposite coatings, reinforcing nanoparticles (Al2O3-13% TiO2) were located at the grain boundaries of the coatings and pinned the boundaries, therefore, the grain growth was prohibited during the thermal spraying processes. © 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder.
Mokhtari homami r., R. ,
Fadaei tehrani, A. ,
Mirzadeh, H. ,
Movahedi, B. ,
Azimifar, F. International Journal of Advanced Manufacturing Technology (14333015) 70(5-8)pp. 1205-1217
In the current work, some experiments were performed based on a design of experiment (DOE) technique called full factorial design. The experimental results are discussed in statistical analysis, and the system was modeled using the artificial neural network (ANN) and subsequently optimized by a genetic algorithm (GA). The statistical analysis shows that the main effects and some 2-interaction effects affect the surface roughness and flank wear. The results show that the feed rate, nose radius, and approach angle have a significant effect on the flank wear and the surface roughness, but the cutting velocity has a significant effect on the flank wear alone. The optimum values of cutting parameters were identified and the resultant optimum values of flank wear and surface roughness were found to be in good agreement with the results of a validation experiment under a similar condition. The optimized values showed a significant reduction in roughness and flank wear. © 2013 Springer-Verlag London.
Surface and Coatings Technology (02578972) 235pp. 212-219
The fracture toughness and wear behavior as well as the microstructural evolutions of the NiAl intermetallic and NiAl-15wt% (Al2O3-13% TiO2) reinforced nanocomposite HVOF coatings were studied. Depending on their microstructures, the characteristics of the coatings were examined in detail by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. The results indicated that the microhardness increased by adding Al2O3-13% TiO2 nanoparticles serving as reinforcing materials, which must be due to the interaction of nanoparticles with mobile dislocations during plastic deformation. It should be that the NiAl-15wt% (Al2O3-13% TiO2) nanocomposite coating was tougher (7.12MPam1/2) than the pure NiAl intermetallic coating (4.28MPam1/2). It seems to be a consequence of grain boundary and nanoparticles pinning mechanism to limit the initial crack propagation over the course of indention test. The wear test studies also showed improved wear resistance of the nanocomposite coating compared with the NiAl intermetallic coating. On the other hand, the average specific wear rate for NiAl-15wt% (Al2O3-13% TiO2) nanocomposite coating (0.78±0.33×10-15m3/N{dot operator}m) is much less than that for NiAl intermetallic coating (4.11±1.98×10-15m3/N{dot operator}m). Consequently, the changes in wear resistance between both coatings were attributed to the changes in the susceptibility to crack propagation by adding Al2O3-13% TiO2 reinforcing nanoparticles. © 2013 Elsevier B.V.
In this work, a new composition of Fe-15Cr-4Mo-5P-4B-1C-1Si (wt.%) amorphous powder was produced by mechanical alloying of elemental powder mixture. Thermal spraying of amorphous powder was done by high velocity oxy fuel spraying technique at various spraying conditions to obtain the desirable amorphous and nanocrystalline coatings. It was found that α-Fe based supersaturated solid solution is first formed during mechanical alloying which transforms to amorphous structure at longer milling times. The crystallization kinetic parameters suggest that the crystallization mechanism is dominantly governed by a three-dimensional diffusion-controlled growth. The crystallization of amorphous structure occurs in one single stage. By carefully controlling the spraying parameters and proper selection of powder composition, the desired microstructure with different fraction of amorphous and nanocrystalline phases and therefore with different properties could be obtained.
Enayati m.h., ,
Karimzadeh f., ,
Tavoosi m., ,
Movahedi, B. ,
Tahvilian a., Journal of Thermal Spray Technology (10599630) 20(3)pp. 440-446
Nanocrystalline NiAl intermetallic powder was prepared by mechanical alloying (MA) of Ni 50Al 50 powder mixture and then deposited on low carbon steel substrates by high velocity oxy fuel (HVOF) thermal spray technique using two sets of spraying parameters. X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), differential scanning calorimetry (DSC), and hardness test were used to characterize the prepared powders and coatings. The MA of Ni 50Al 50 powder mixture led to the formation of NiAl intermetallic compound. The resulting powder particles were three dimensional in nature with irregular morphology and a crystallite size of ~10 nm. This powder was thermally sprayed by HVOF technique to produce coating. The deposited coating had a nanocrystalline structure with low oxide and porosity contents. The hardness of coatings was in the range of 5.40-6.08 GPa, which is higher than that obtained for NiAl coating deposited using conventional powders. © 2010 ASM International.
Materials Letters (0167577X) 64(9)pp. 1055-1058
The crystallization behavior and thermal stability of Fe-Cr-Mo-B-P-Si-C amorphous alloy, prepared by mechanical alloying (MA), were investigated by using differential scanning calorimetry (DSC). One exothermic peak was observed on DSC traces, implying that the crystallization process undergoes only one stage. The crystallization kinetic parameters, including activation energy (Ea), Avrami exponent (n) were determined with non-isothermal analysis method based on the DSC data. The results suggest that the crystallization mechanism is governed dominantly by a three-dimensional diffusion-controlled growth. In addition a relatively high value of activation energy of crystallization (386.04 ± 10 kJ/mol) was found, indicating that this amorphous alloy has high thermal stability. © 2010 Elsevier B.V. All rights reserved.
Journal of Thermal Spray Technology (10599630) 19(5)pp. 1093-1099
The microstructure, thermal behavior, and mechanical properties of amorphous/nanocrystalline 70Fe-15Cr-4Mo-5P-4B-1C-1Si (wt.%) coatings produced by high velocity oxy fuel (HVOF) spraying of mechanically alloyed powders were investigated by x-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Thermal stability of samples was investigated using differential scanning calorimetry (DSC). The results show that by adjusting the HVOF parameters especially fuel/oxygen ratio and proper selection of powder composition, the desired microstructure with different amount of amorphous and nanocrystalline phases and therefore with different mechanical properties could be obtained. © 2010 ASM International.
Materials Science and Engineering: B (09215107) 172(1)pp. 50-54
A new composition of Fe-Cr-Mo-B-P-Si-C amorphous powder was produced by mechanical alloying (MA) of elemental powder mixtures. The structure of powder particles was studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Continued milling of Fe-Cr-Mo-B-P-Si-C powder mixture first led to the formation of a Fe-base solution which transformed to the amorphous structure on further milling. It was found that the amorphization starts at the edge of particles and progresses into the internal regions as MA proceeds. Increasing milling time to 80 h yielded a fully amorphous structure. Thermal stability and crystallization characteristics of amorphous alloy were determined by means of differential scanning calorimetry (DSC), XRD and HRTEM and discussed next. © 2010 Elsevier B.V. All rights reserved.
Surface Engineering (02670844) 25(4)pp. 276-283
Ni-10 wt-%Al composite powders, as a self-bonding spray material, were prepared by low energy mechanical milling process and then sprayed by plasma and flame spray techniques. The phase identification, microstructure, hardness and adhesion strength of the coatings were investigated by X-ray diffraction, SEM, ASTM E384-99 and ASTM C633-01 respectively. The size and microstructure of powder particles are two important parameters for thermal spraying. Morphological and microstructural investigation of the Ni-10 wt-%Al powders showed that the powder particles after 23 h of milling time had the optimum properties with respect to their size and microstructure. X-ray diffraction patterns of powder particles included only the elemental Ni and Al peaks without any traces of oxides or intermetallics phases. Powder particles produced by mechanical milling had a fine lamellar structure consisting of pure Al and Ni layers. This structure encourages the Ni/Al exothermic reaction during flight in plasma spraying. The adhesive tests also showed that the plasma and flame failure were cohesive, that is, within the coating itself, because adhesive on steel in both coatings is much higher than cohesive. © 2009 Institute of Materials.
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