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1 - Synthesis structural and anti-microbial characterization of nanostructured doped tin oxide
Achyutmohan Chaudhury Utsa Debnath Sujay Munshi Goutam Basak Avigyan Dutta Suvadip Masanta Achintya Singha Aritra Banerjee Debtanu Ghosh Partha Chatterjee Apurba Kanti DebNanocrystalline boron doped tin oxide and boron and silver co-doped SnO2 was successfully prepared by using simple sol-gel method. The structural property of as-prepared nanocrystalline materials was investigated by using X-ray powder diffraction, Raman spectroscopy, Fo أکثرNanocrystalline boron doped tin oxide and boron and silver co-doped SnO2 was successfully prepared by using simple sol-gel method. The structural property of as-prepared nanocrystalline materials was investigated by using X-ray powder diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The infrared spectra of the prepared samples showed an incorporation of B and Ag in the SnO2 nanocrystals. The X-ray powder diffraction pattern of the as prepared sample demonstrated the formation of a rutile structure of SnO2 nanocrystallites with particle size of 35 nm and 98 nm for boron doped and co-doped samples respectively. The two different Sn-O bond distances are found to be varying in a different manner for the doped samples unlike pristine samples. A significant lattice microstrain was observed for co-doped samples indicating local lattice distortion. The prepared samples showed significant anti-microbial activities against some Gram-Positive & Gram-Negative bacteria in both water and DMSO medium. The prepared materials can be effective for water remediation. تفاصيل المقالة -
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2 - Electrodeposition of cobalt oxide thin films for potential applications
Sandra Augustine Azubike Ekpunobi Diemiruaye JerohCobalt oxide thin films at varied molar concentrations were prepared by electrodeposition technique. Ultraviolet-Visible (UV/VIS) analysis conducted on the grown films revealed blue shift in the absorption edge at increased molar concentrations, which is a consequence o أکثرCobalt oxide thin films at varied molar concentrations were prepared by electrodeposition technique. Ultraviolet-Visible (UV/VIS) analysis conducted on the grown films revealed blue shift in the absorption edge at increased molar concentrations, which is a consequence of band gap widening. The band gap values (3.65 eV to 3.85 eV) in this research are greater than the value (2.4 eV) for the bulk phase of cobalt oxide. This increase in band gap can be likened to higher concentration effect and quantum-size phenomenon. Scanning Electron Microscopy (SEM) analysis indicated a porous nature for the material, suggesting its ability in absorbing ultraviolet (UV) radiation, thus confirming its use as an absorber material for solar cells fabrication. Energy Dispersive X-ray (EDX) study confirmed the growth of cobalt oxide. X-ray diffraction (XRD) analysis confirms the crystalline nature of the films with grain sizes within the range of 0.7 nm to 1 nm for varied molar concentrations. Electrical studies reveal a linear relationship of resistivity values with molar concentrations, while the conductivity values reveal inverse relationship with molar concentration. تفاصيل المقالة -
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3 - Electrical conduction in nanoceramic PGT synthesised by high energy ball milling
SKS Parashar Satyendra Narayan Singh Mahmood Ghoranneviss Swarat ChaudhuriAbstractNanocrystalline Pb1–3x/2GdxTiO3 (where x = 0.01) abbreviated as PGT has been synthesised by high energy ball milling at room temperature. X-ray analysis shows that single-phase tetragonal structure of nanocrystalline PGT was formed after 15-h milling. The averag أکثرAbstractNanocrystalline Pb1–3x/2GdxTiO3 (where x = 0.01) abbreviated as PGT has been synthesised by high energy ball milling at room temperature. X-ray analysis shows that single-phase tetragonal structure of nanocrystalline PGT was formed after 15-h milling. The average crystallite size was found to be 17 nm. The frequency-dependent AC conductivity of the PGT ceramic was studied in the range 100°C to 525°C. Complex impedance analysis suggested the dielectric relaxation to be of non-Debye type. The activation energy was found to be 1.04 ev. The mechanism of charge transport in nanocrystalline PGT was successfully explained by correlated hopping model. تفاصيل المقالة -
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4 - Structural and optical properties of nanocrystalline α-MoO3 thin films prepared at different annealing temperatures
A. Hojabri F. Hajakbari A. Emami MeibodiAbstractNanocrystalline α-MoO3 thin films were prepared successfully by thermal annealing of molybdenum (Mo) thin films deposited on quartz and silicon substrates using DC magnetron sputtering method. The influence of annealing temperatures ranging from 400 to 1,000 °C أکثرAbstractNanocrystalline α-MoO3 thin films were prepared successfully by thermal annealing of molybdenum (Mo) thin films deposited on quartz and silicon substrates using DC magnetron sputtering method. The influence of annealing temperatures ranging from 400 to 1,000 °C on the structural, morphological and optical properties of the prepared films was investigated by X-ray diffraction, Fourier transform infrared spectrophotometer (FTIR) atomic force microscopic and UV–vis spectroscopy, respectively. The results show that the crystallinity and surface morphology of the films are strongly dependent on the annealing temperature. Also, the optimum annealing temperature of Mo films in our experiment was 600 °C and the films formed at this temperature exhibit only the (0k0) reflections and indicated the layered structure of α-MoO3. The FTIR spectra confirm the formation of MoO3. The transmittance of the MoO3 films on quartz substrate was improved with increasing annealing temperature. تفاصيل المقالة -
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5 - Employing constant photocurrent method for the study of defects in silicon thin films
Hitendra K. Malik Sucheta Juneja Sushil KumarAbstractDifferent optical characterization techniques have been performed on a series of microcrystalline silicon thin films deposited using very high-frequency-assisted plasma-enhanced chemical vapor deposition process. The constant photocurrent method has been employe أکثرAbstractDifferent optical characterization techniques have been performed on a series of microcrystalline silicon thin films deposited using very high-frequency-assisted plasma-enhanced chemical vapor deposition process. The constant photocurrent method has been employed to study the defects states in density of states spectra of hydrogenated microcrystalline silicon thin films. The photocurrent measurements demonstrate anisotropy in the optoelectronic properties of the material. We have analyzed the optical absorption coefficient from UV spectroscopy and with the help of constant photocurrent method. The spectra have been analyzed in broad region and are presented for both the cases, i.e., surface and bulk light scatterings. The spectra were interpreted in terms of disorder, resulting defect density, crystalline/amorphous volume fractions and material morphology. The subgap-related parameters such as absorption coefficient, characteristic energy E0 of tail states and density of subgap defect states together with an estimate of the bandgap of silicon films prepared at various crystalline fractions have also been estimated. The density of localized tail states is found to fall exponentially toward the gap with band tail width of about 110 meV. تفاصيل المقالة -
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6 - Microstrain and lattice disorder in nanocrystalline titanium dioxide prepared by chemical route and its relation with phase transformation
Apurba Kanti Deb Partha ChatterjeeAbstractThe microstructure of nanocrystalline titanium dioxide (TiO2), synthesized by chemical route, is studied from X-ray peak profile analysis and transmission electron microscopy. The broadening of the X-ray diffraction peaks indicates the presence of small crystall أکثرAbstractThe microstructure of nanocrystalline titanium dioxide (TiO2), synthesized by chemical route, is studied from X-ray peak profile analysis and transmission electron microscopy. The broadening of the X-ray diffraction peaks indicates the presence of small crystallites with a significant amount of disorder. The progression of broadening at lower annealing temperatures, suggests the decrease in the strain broadening. The nano-TiO2 was found to transform partially to rutile phase from its nanocrystalline anatase phase when annealed at a temperature of 750 °C. No further appreciable change was observed after annealing at higher temperature. The lattice parameters of the anatase phase change non-linearly with temperature. It was found that there is a discontinuous change in the value of crystallite size, microstrain and thermal parameter values accompanying with the phase transformation. The microstrain associated with the nanocrystalline grain is closely associated with thermal disorder and oxygen z-displacement. The value of thermal parameter reveals a significant deviation of the Ti atom from the regular lattice sites. The present study reveals that nanocrystalline anatase TiO2 prepared by chemical route shows significant static disorder, which decreases with the increase in the annealing temperature along with concomitant phase transformation. تفاصيل المقالة -
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7 - Effect of plasma oxidation parameters on physical properties of nanocrystalline nickel oxide thin films grown by two-step method: DC sputtering and plasma oxidation
F. Hajakbari S. Rashvand A. HojabriAbstractNanocrystalline nickel oxide (NiO) thin films were successfully grown on quartz substrates by two-step method. In the first step, nickel films were deposited on quartz substrates by DC magnetron sputtering technique. Then, the plasma oxidation of nickel films wa أکثرAbstractNanocrystalline nickel oxide (NiO) thin films were successfully grown on quartz substrates by two-step method. In the first step, nickel films were deposited on quartz substrates by DC magnetron sputtering technique. Then, the plasma oxidation of nickel films was used for preparation of nickel oxide. The effect of DC plasma power and treatment time on the structural, morphological and optical properties of the NiO films were investigated by different analyses. XRD results indicated that the plasma powers effectively influenced the structure of films, and the best crystallinity was obtained for plasma power of 15 w and treatment time of 20 min. The XPS, RBS and EDS analysis confirmed the presence of Ni and O elements. The FESEM and AFM images showed a granular structure with spherical shapes of grains. The optical band gap of the films synthesized under different plasma oxidation conditions was also discussed. تفاصيل المقالة -
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8 - Spectrophotometric Determination of Hg2+ after Solid Phase Extraction on Microcrystalline Naphthalene
M. Reza Shishehbore Navid Nasirizadeh A. Mohammad AkhoundiMercury is quantitatively retained with 1, 5-diphenylcarbazone (DPC) on microcrystallinenaphthalene in the pH range 6.5-8.5 from a large volume of aqueous solutions of various samples.After filtration, the solid mass consisting of the mercury complex and naphthalene was أکثرMercury is quantitatively retained with 1, 5-diphenylcarbazone (DPC) on microcrystallinenaphthalene in the pH range 6.5-8.5 from a large volume of aqueous solutions of various samples.After filtration, the solid mass consisting of the mercury complex and naphthalene was dissolvedin 5.0 mL of dimethylformamide (DMF) and mercury was determined by spectrophotometricmethod at 542 nm against the reagent blank. The linear calibration range for mercury was 30-18001.tg L-1 in DMF solution with a detection limit of 20 lug L-1. The relative standard deviation foreight replicate measurements of 1.0 [ig of mercury in 5.0 mL of DMF was 2.5%. The effect ofpotential interfering ions was investigated and the proposed method was applied to thedetermination of mercury in water samples. تفاصيل المقالة -
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9 - بررسی جذب CO در نانوساختارهای کبالت با استفاده از تئوری تابعی چگالی (DFT): فازهای کریستالی مکعبی و هگزاگونال
فاطمه دولتی علی نخعی پور وحیدرضا داروگر زهره دولتی وجیهه افخمیدر این مقاله، انرژی جذب و ساختار مونوکسید کربن (CO) در فازهای کریستالی مکعبی(fcc) و هگزاگونال (hcp) در نانو ذرات کبالت با استفاده از محاسبات تابعی چگال (DFT) مورد ارزیابی قرار گرفته است. روند کلی فعالیت سنتز فیشر تروپش (FTS) بر روی کاتالیزورهای کبالت با مقایسه انرژی جذب أکثردر این مقاله، انرژی جذب و ساختار مونوکسید کربن (CO) در فازهای کریستالی مکعبی(fcc) و هگزاگونال (hcp) در نانو ذرات کبالت با استفاده از محاسبات تابعی چگال (DFT) مورد ارزیابی قرار گرفته است. روند کلی فعالیت سنتز فیشر تروپش (FTS) بر روی کاتالیزورهای کبالت با مقایسه انرژی جذب مورد بررسی قرار گرفت. با توجه به محاسبات، کاتالیزورهای کبالت در فازhcp، بازده و کارایی بهتری را نسبت به فاز فلزی fcc نشان می دهد. انرژی جذب CO در سطوح مختلف کبالت و همچنین انرژی فعال سازی جذب CO در تک لایه (1ML) در موقعیت عمودی (top) نسبت به اتم کبالت درفازهای کریستالی مکعبی و شش ضلعی نانوساختارهای کبالت محاسبه شد. نتایج نشان داد که بیشترین مقدار انرژی جذب در فازهای کریستالی fcc نسبت به hcp است. در نتیجه انرژی پایین جذب CO در موقعیت top کبالت در hcp می تواند فعالیت بالاتر این کاتالیست را نسبت به فازهای دیگر آن در واکنش FTS توضیح دهد. تفاصيل المقالة -
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10 - Optimization of Tangential Cutting Force in Turning Operation in Machining of Unidirectional Glass Fiber Reinforced Plastics
Surinder KumarIn this paper, Taguchi method is applied to find optimum process parameters for turning UD-GFRP rods using polycrystalline diamond cutting tool. The process parameters considered include cutting speed, depth of cut, cutting environment (dry and wet) and feed rate. The e أکثرIn this paper, Taguchi method is applied to find optimum process parameters for turning UD-GFRP rods using polycrystalline diamond cutting tool. The process parameters considered include cutting speed, depth of cut, cutting environment (dry and wet) and feed rate. The experiments were conducted by L16 orthogonal array as suggested by Taguchi. Signal to Noise ratio and ANOVA are employed to analyses the effect of turning process parameter on the tangential cutting force. The results from confirmation runs indicated that the determined optimal combination of machining parameters improved the performance of the machining process. The percent contributions of cutting speed (2.46%), depth of cut (73.82%), dry and wet (3.89%) and feed rate (8.02%) in affecting the variation of tangential force are significantly larger (95 % confidence level). It has been found that the wet cutting environment reduces the tangential force. Depth of cut is the factor, which has great influence on tangential force, followed by feed rate. تفاصيل المقالة -
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11 - Mechanical Characteristics and Failure Mechanism of Nano-Single Crystal Aluminum Based on Molecular Dynamics Simulations: Strain Rate and Temperature Effects
R Rezaei H Tavakoli-Anbaran M ShariatiBesides experimental methods, numerical simulations bring benefits and great opportunities to characterize and predict mechanical behaviors of materials especially at nanoscale. In this study, a nano-single crystal aluminum (Al) as a typical face centered cubic (FCC) me أکثرBesides experimental methods, numerical simulations bring benefits and great opportunities to characterize and predict mechanical behaviors of materials especially at nanoscale. In this study, a nano-single crystal aluminum (Al) as a typical face centered cubic (FCC) metal was modeled based on molecular dynamics (MD) method and by applying tensile and compressive strain loadings its mechanical behaviors were investigated. Embedded atom method (EAM) was employed to represent the interatomic potential of the system described by a canonical ensemble. Stress-strain curves and mechanical properties including modulus of elasticity, Poisson’s ratio, and yield strength were determined. Furthermore, the effects of strain rate and system temperature on mechanical behavior were obtained. It was found that the mechanical properties exhibited a considerable dependency to temperature, but they hardly changed with increase of strain rate. Moreover, nucleation and propagation of dislocations along the plane of maximum shearing stress were the mechanisms of the nanocrystalline Al plastic deformation. تفاصيل المقالة -
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12 - An Efficient Green Synthesis of Copper Oxide NanoCrystalline
M. Kargar M. Ghashang M.R. Mohammad ShafieeIn this study, a feasible green method for the synthesis of copper oxide nanocrystalline is described by using sour cherry juice which has a significant effect on crystalline size, and morphology. The benefits of the green method, not only nanometer scale are formed but أکثرIn this study, a feasible green method for the synthesis of copper oxide nanocrystalline is described by using sour cherry juice which has a significant effect on crystalline size, and morphology. The benefits of the green method, not only nanometer scale are formed but also low-cost method are obtained in a normal atmosphere which it has been used (CH3COO)2Cu.H2O individually as Cu sources. All samples have calcination in 600°C. The effect of sour cherry juice concentration to control crystal growth is investigated by changing the amount of it to 20, 40, and 80 mL, respectively. The synthesized particles are characterized by using X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). Powder X-ray Diffraction analysis confirms that pure Copper Oxide nanocrystallines are in a single phase monoclinic structure which the average crystalline size has estimated via Williamson-Hall plot from the highest peak of the XRD was among 15-55 nm for all samples. تفاصيل المقالة -
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13 - بررسی برخی خصوصیات ژنی جدایههای بومی باکتری Bacillus thuringiensis از خاکهای مناطق جنگلی استان گلستان
مرضیه شازده احمدی سید افشین سجادی زینالعابدین شهادتی مقدمجدایه های بومی باکتری Bacillus thuringiensis (Bt) از خاک های مناطق جنگلی شهرستان های مختلف استان گلستان جدا سازی و ژن Cry و Vip عامل تولید توکسین و پروتئین مؤثر روی حشرات در آن ها ردیابی شد. از کل 42 نمونه خاک مورد بررسی از طریق بازدارندگی انتخابی استات سدیم، تعداد 160 أکثرجدایه های بومی باکتری Bacillus thuringiensis (Bt) از خاک های مناطق جنگلی شهرستان های مختلف استان گلستان جدا سازی و ژن Cry و Vip عامل تولید توکسین و پروتئین مؤثر روی حشرات در آن ها ردیابی شد. از کل 42 نمونه خاک مورد بررسی از طریق بازدارندگی انتخابی استات سدیم، تعداد 160 جدایه Bt جدا سازی گردید. پس از کشت کلنی ها، رنگ آمیزی اختصاصی و شناسایی میکروسکوپی در 40 درصد از جدایه ها انجام شد، پروتئین کریستالی کشنده برای بسیاری از حشرات مشاهده گردید. بررسی مولکولی جدایه های Bt نشان داد که در 12 جدایه ژن هایCry و Vip وجود داشتند. آزمایشات تعیین ساختار ژنی برای وجود سه ژن Cry 1A (شامل Cry1Aa, Cry1Ab, Cry1Ac) و ژن های Cry1I، Cry1F، Cry2، Cry9 و Vip3Aa با استفاده از 8 جفت آغاز گر اختصاصی انجام شد. ژن های Cry1Ab، Cry2 و Cry1F در همه جدایه ها مشاهده شد، ولی ژن های Cry1Aa، Cry1I و Cry1Ac فراوانی بسیار کم (کم تر از 20 درصد) داشتند و یا در هیچ یک از جدایه ها یافت نشدند. نتایج این تحقیق می تواند برای ردیابی جدایه های بومی باکتری Bt که دارای پروتئین های کریستالی مؤثر روی حشرات هستند، مفید واقع شود. تفاصيل المقالة -
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14 - The effect of saccharin on microstructure and corrosion behavior of nanocrystalline nickel thin films in alkaline solution
Behrooz Shayegh Nima ZaghianIn this study the effect of crystallite size reduction and microstructure on the electrochemical corrosion behavior of nanocrystalline nickel (NC Ni) were investigated using Tafel polarization and electrochemical impedance spectroscopy (EIS) measurements in 10 wt.% NaOH أکثرIn this study the effect of crystallite size reduction and microstructure on the electrochemical corrosion behavior of nanocrystalline nickel (NC Ni) were investigated using Tafel polarization and electrochemical impedance spectroscopy (EIS) measurements in 10 wt.% NaOH. NC Ni coatings were produced by direct current electrodeposition using chloride baths in presence and absence of saccharin as a grain refining agent. The crystallite size of NC surface coatings was calculated and analyzed by X-ray diffractometry (XRD). Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to study coatings microstructure. The chemical composition of NC surfaces was determined using X-ray energy dispersive spectroscopy (EDS). Our results showed Saccharin decreased the crystallite size but increased the grain size. In addition, corrosion resistance of NC Ni in presence of saccharin increased, which is ascribed to the formation of more stable and protective film. The behavior of passive film growth and corrosion were discussed. تفاصيل المقالة -
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15 - Production and Characterization of Nano Crystalline Fe85Si10Ni5 Soft Magnetic Alloys by Mechanical Alloying
Arash Dezhsetan Ali Saidi Reza Ebrahimi-KahrizsangiAbstract There are various methods to produce iron based nano crystalline magnetic alloys. Among these methods, mechanical alloying is one of the most important. In this research, nano crystalline Fe85Si10Ni5 soft magnetic alloy was synthesized by mechanical alloying. أکثرAbstract There are various methods to produce iron based nano crystalline magnetic alloys. Among these methods, mechanical alloying is one of the most important. In this research, nano crystalline Fe85Si10Ni5 soft magnetic alloy was synthesized by mechanical alloying. The effect of alloying time on phase constituents and magnetic properties of the produced powders was investigated, by X-ray diffraction (XRD) and alternating gradient force magnetometer (AGFM). The XRD results showed that alloy formation started after 2 hours of milling. Further milling resulted in the reduction of the grain size and lattice parameter. After 60 hours of milling, the grain size was reduced to 8 nm. AGFM results showed that magnetic saturation and coercivity depends on the alloying time. Increasing the alloying time, causes the increase of magnetic saturation and decrease of coercivity. Abstract There are various methods to produce iron based nano crystalline magnetic alloys. Among these methods, mechanical alloying is one of the most important. In this research, nano crystalline Fe85Si10Ni5 soft magnetic alloy was synthesized by mechanical alloying. The effect of alloying time on phase constituents and magnetic properties of the produced powders was investigated, by X-ray diffraction (XRD) and alternating gradient force magnetometer (AGFM). The XRD results showed that alloy formation started after 2 hours of milling. Further milling resulted in the reduction of the grain size and lattice parameter. After 60 hours of milling, the grain size was reduced to 8 nm. AGFM results showed that magnetic saturation and coercivity depends on the alloying time. تفاصيل المقالة -
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16 - Effect of Heat Treatment on Structural and Magnetic Properties of Nanocrystalline SrFe12O19 Hexaferrite synthesized by Co-Precipitation Method
Mansoureh Ganjali Monireh Ganjali Arvin Eskandari Masoud AminzareNanocrystalline strontium hexaferrite (SrFe12O19) powders have been successfully synthesized using the facile Co-precipitation method. The ferrite precursors were achieved from mixtures of strontium and ferric chloride in an aqueous medium without any surfactant and sof أکثرNanocrystalline strontium hexaferrite (SrFe12O19) powders have been successfully synthesized using the facile Co-precipitation method. The ferrite precursors were achieved from mixtures of strontium and ferric chloride in an aqueous medium without any surfactant and soft template. The as-received powders were calcined at 800 and 1000 ˚C for 2 hours in air. The final powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area analysis and Vibrating Sample Magnetometer (VSM). The effects of the calcination temperature on the phase composition, particle size and shape as well as the magnetic properties of the products have been investigated. The results indicated that the higher calcination temperature (1000 oC) resulted in higher particle sizes (98.1 nm), maximum saturation magnetization (60.53 emu/g), remanence value (36.23 emu/g) and less surface area (12 m2g-1). The magnetocrystalline anisotropy constant, K, calculated from the Stoner–Wohlfarth theory are increased by increasing temperature up to 15.1 (HA2/kg). تفاصيل المقالة -
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17 - Effect of Heat Treatment Time on the Characteristics of Coating Formed on Nanocrystalline Finemet Foils
Sima Mirzaei Ali Jazayeri GharehbaghIn the present research, amorphous Fe73.5Si13.5B9Nb3Cu1 Finemet foils, 21-26µm in thickness and 5mm in width, were prepared by Planar Flow Casting (PFC) process. Wound cores of amorphous Finemet foils were simultaneously annealed and heat treated at 540°C for أکثرIn the present research, amorphous Fe73.5Si13.5B9Nb3Cu1 Finemet foils, 21-26µm in thickness and 5mm in width, were prepared by Planar Flow Casting (PFC) process. Wound cores of amorphous Finemet foils were simultaneously annealed and heat treated at 540°C for 60, 120 and 240 minutes in steam and air flow to form oxide insulating coating layer on both surfaces of the foils. The structure of nanocrystalline foils was examined by X-ray diffractometry (XRD). The thickness and chemical composition of the insulating coating layer were studied by Field Emission Scanning Electron Microscopy (FE-SEM), Grazing Incidence XRD (GI-XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The results show that the coating thickness formed on air and wheel surfaces of the foil was in the range of 65-310 nm and these thin coating layers contain a mixture of iron, silicon, boron and niobium oxides. The study of magnetic properties in amorphous and nanocrystalline states revealed that nanocrystalline cores have superior soft magnetic properties compared with the amorphous ones. In other words, the heat treatment gives rise to a decrease in hysteresis loss and a significant increase in saturation induction and magnetic permeabilities. تفاصيل المقالة -
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18 - Finite Element Modeling of Strain Rate and Grain Size Dependency in Nanocrystalline Materials
Minoo TabanfardNanocrystalline materials show a higher strain-rate sensitivity in contrast to the conventional coarse-grained materials and a different grain size dependency. To explain these phenomenon, a finite element model is constructed that considers both grain interior and grai أکثرNanocrystalline materials show a higher strain-rate sensitivity in contrast to the conventional coarse-grained materials and a different grain size dependency. To explain these phenomenon, a finite element model is constructed that considers both grain interior and grain boundary deformation of nanocrystalline materials. The model consist of several crystalline cores with different orientations and grain boundary phase. The nonlinear behavior of the nanocrystalline core is implemented by a grain size dependent crystal plasticity. The boundary phase is assumed to have the mechanical properties of quasi-amorphous material. The constitutive equations for both grains interior and boundary phase are implemented into the finite-element software Abaqus. A calibration procedure was used to tune some parameters of the model with the previously published experimental data on the nanocrystalline copper. Then the model is used to predict the material behavior in various strain rates and grain sizes. The stresses obtained from these simulations match well with the experimental data for nanocrystalline copper at different strains and strain rates. Deviation from the Hall-Petch law and inverse Hall-Petch effect are also well illustrated by the model. تفاصيل المقالة -
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19 - مدلسازی ترانسفورمرهای پالسی با هستههای نانو بلوری
امیر بکتاش ابوالفضل واحدیامروزه هستههای نواری مدور نانو بلوری بهواسطه ویژگیهای مغناطیسی مطلوبی که دارند به طور گستردهای در ترانسفورمرهای پالسی و فرکانس بالا مورد استفاده قرار میگیرند. ساختار حلزونی این هستهها بر روی نحوه توزیع شار درون آن تأثیر گذاشته و باعث پیچیدگی زیاد تحلیل مغناطیسی ا أکثرامروزه هستههای نواری مدور نانو بلوری بهواسطه ویژگیهای مغناطیسی مطلوبی که دارند به طور گستردهای در ترانسفورمرهای پالسی و فرکانس بالا مورد استفاده قرار میگیرند. ساختار حلزونی این هستهها بر روی نحوه توزیع شار درون آن تأثیر گذاشته و باعث پیچیدگی زیاد تحلیل مغناطیسی این هستهها شده است. در این مقاله با استفاده از روش شبکههای رلوکتانسی یک مدل برای این هستهها ارائه شده است. این مدل قادر به تعیین شار در نقاط مختلف هسته میباشد. ویژگی غیرخطی مغناطیسی هسته نیز با استفاده از یک مدل پسماند در مدل هسته گنجانده شده که با استفاده از آن به آسانی میتوان تلفات مغناطیسی هسته را معلوم نمود. سادگی پیادهسازی مدل از ویژگیهای مثبت آن میباشد. نتایج شبیهسازی مدل با استفاده از نرمافزار اجزاء محدود و همچنین تستهای عملی بررسی شدهاند. مقایسه نتایج نشان میدهند که روش ارائه شده علاوه بر سادگی دارای دقت مطلوب بوده و سرعت همگرایی آن در شبیهسازی نیز بالا است. تفاصيل المقالة -
حرية الوصول المقاله
20 - Improving methodology for the preparation of highly substituted imidazoles using nano-MgAl2O4 as catalyst under microwave irradiation
Javad Safari Soheila Gandomi-Ravandi Zahra AkbariAn efficient synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by one-step condensation of an aldehyde, benzil, ammonium acetate and primary amine in the presence of nanocrystalline magnesium aluminate under microwave irradiation is described. Th أکثرAn efficient synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by one-step condensation of an aldehyde, benzil, ammonium acetate and primary amine in the presence of nanocrystalline magnesium aluminate under microwave irradiation is described. The advantages of this catalyst are including simple work-up, low cost and reusability. Compared with conventional methods, the main advantages of the present procedure are its being a green method, its milder conditions, necessary shorter reaction time, and its higher yields and its selectivity. The structures of products were characterized by 1H NMR, 13C NMR, IR, elemental analyses, MS and UV spectral data. Their melting points were compared with literature report. تفاصيل المقالة -
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21 - Nanocrystalline TiO2 as an efficient and reusable catalyst for the one-pot synthesis of polyhydroquinolien derivatives via Hantzsch reaction
Farhad Shirini Seyyed Vahid Atghia Meysam Alipour KhoshdelAn efficient synthesis of polyhydroquinoline derivatives was reported via four-component coupling reactions of aldehydes, 1,3-dicarbonyl ketones (dimedone or 1,3-cyclohexanedione), ethyl acetoacetate or methyl acetoacetate and ammonium acetate in the presence of a catal أکثرAn efficient synthesis of polyhydroquinoline derivatives was reported via four-component coupling reactions of aldehydes, 1,3-dicarbonyl ketones (dimedone or 1,3-cyclohexanedione), ethyl acetoacetate or methyl acetoacetate and ammonium acetate in the presence of a catalytic amount of nanocrystalline TiO2 under solvent free conditions. The reported method is mild, rapid and has the advantages such as heterogeneous catalysis, simple work-up procedure, recyclability of the catalyst and purification of products without chromatographic methods. تفاصيل المقالة -
حرية الوصول المقاله
22 - Green Synthesis of Silver Nanoparticles Using Pimpinella anisum L. Seed Aqueous Extract and Its Antioxidant Activity
Hashem Akhlaghi Sedighe sadat AkhlaghiAn aqueous extract of Pimpinella anisum was used for green synthesis of silver nanoparticles by bio reduction of an aqueous solution of silver nitrate. Silver nanoparticles were characterized by UV–Vis spectrometry, Fourier transform infrared spectroscopy (FTIR), X-ra أکثرAn aqueous extract of Pimpinella anisum was used for green synthesis of silver nanoparticles by bio reduction of an aqueous solution of silver nitrate. Silver nanoparticles were characterized by UV–Vis spectrometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX). The increase in absorption at 420 nm was used for recording the formation of a colloidal suspension of silver nanoparticles. The binding properties of the capped Ag nanoparticles synthesized from aqueous extract of P. anisum were analyzed by FTIR. XRD studies revealed that most of the nanoparticles were cubic and face centered cubic in shape. SEM analysis showed the size and shape of silver nanoparticles and EDAX confirmed the presence of silver. The synthesized silver nanoparticles showed DPPH free radical scavenging activity. تفاصيل المقالة -
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23 - بررسی تاثیر متغیرهای تولید بر رسانایی الکتریکی و ریزسختی آلیاژ نانوکریستالی Cu-5 at. %Ta
روح اله رحمانی فرد محسن اسدی اسد آباد سید میثم جاویداندر پژوهش حاضر از روش آلیاژسازی مکانیکی برای تولید آلیاژهای نانوکریستالی Cu-5 at. % Ta استفاده شد. به منظور دستیابی به نمونه های با خواص مطلوب اثر تغییر اندازه گلوله های آسیا، اتمسفر و دمای تف جوشی بر ریزساختار، رسانایی الکتریکی و ریزسختی نمونه فوق مورد بررسی قرار گرفتند أکثردر پژوهش حاضر از روش آلیاژسازی مکانیکی برای تولید آلیاژهای نانوکریستالی Cu-5 at. % Ta استفاده شد. به منظور دستیابی به نمونه های با خواص مطلوب اثر تغییر اندازه گلوله های آسیا، اتمسفر و دمای تف جوشی بر ریزساختار، رسانایی الکتریکی و ریزسختی نمونه فوق مورد بررسی قرار گرفتند. بررسی های ریزساختاری از دو شرایط گلوله های به قطر 10 میلی متر و مخلوطی از گلوله های 10 و 5 میلیمتری نشان داد که نمونه ی آسیاشده با استفاده از گلوله های مخلوط، متوسط اندازه کریستالیت ریزتری دارد. پس از آسیاکاری، روش پرس سرد و تف جوشی در کوره در اتمسفرهای نیتروژن، آرگون و خلأ در دمای ℃550 انجام شد، نمونه های تف جوشی شده در شرایط خلأ مجموعه خواص بهتری را از خود نشان دادند. به منظور بررسی اثر دمای تف جوشی بر خواص محصول دماهای 700 و ℃850 نیز در شرایط خلأ مورد بررسی قرار گرفتند، نتایج نشان دادکه نمونه ی تف جوشی شده در دمای ℃850 بیشترین میزان رسانایی الکتریکی و ریزسختی را دارد. درمجموع نمونه ی آسیاشده با گلوله های مخلوط و تف جوشی شده در دمای ℃850 در شرایط خلأ میزان رسانایی الکتریکی برابر IACS %7/15 و ریزسختی HV 2/196 را نشان داد که بیشترین میزان رسانایی الکتریکی و ریزسختی در بین نمونه های مس- تانتالم تولیدشده در این پژوهش بود. تفاصيل المقالة -
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24 - Evaluation of Tool Performance With Nanocrystalline Multilayer Coatings on the Machinability of Superalloy Inconel 718
رسول مختاری همامی بهروز موحدی ایرج لیرابی مهدی بازرگان حقیقیIn this paper, the performance of the cutting tool with nanocrystalline multilayer coatings (TiN+TiAlN) for machining of superalloy Inconel 718 in the dry and wet conditions was studied. The multi layer TiN and TiAlN with nanocrystalline structure was applied by physica أکثرIn this paper, the performance of the cutting tool with nanocrystalline multilayer coatings (TiN+TiAlN) for machining of superalloy Inconel 718 in the dry and wet conditions was studied. The multi layer TiN and TiAlN with nanocrystalline structure was applied by physical vapor deposition technique (arc evaporation) on the WC-Co inserts. The results of the ball on disc wear test and the machining of superalloy Inconel 718 in wet and dry conditions indicated that the nanocrystalline coatings could produce better performance of tools in turning. Abrasion and adhesive wear resistance improved by nanocrystalline and modified Aluminum composition in TiAlN coating as well as toughness and thermal stability. تفاصيل المقالة
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