Showing 109 results for Nano
V. Mote, B. Dole,
Volume 12, Issue 1 (3-2015)
Abstract
Mn doped ZnO nanocrystals were prepared by co-precipitation route sintered at 450 °C temperature. XRD
results indicate that the samples having hexagonal (wurtzite) structure. From X-ray data it is found that the lattice
parameters increase with increasing Mn concentration. The X-ray density decreases with increasing Mn concentration
of Zn
1-x
Mnx
O nanocrystals. It indicates that the Mn ions go into the Zn site in the ZnO lattice structure. TEM results
reveal that the pure and Mn substituted ZnO samples are spherical in shape with average particle size about 20-60
nm. The crystalline size and lattice strain were evaluated by Williamson-Hall (W-H) analysis using X-ray peak
broadening
data. All other relevant physical parameters such as strain, stress and energy density were calculated by the different
models Viz, uniform deformation model (UDM), uniform deformation stress model (UDSM) and Uniform deformation
energy density model (UDEDM) considering the Williamson-Hall analysis. These models reveal different strain values
it may be due to the anisotropic nature of the material. It is found that the mean particle size of Zn
1-x
MnxO
nanoparticles was estimated from TEM analysis, Scherrer’s formula & W-H analysis is highly comparable
S. Niksirat, Sh. Raygan, S. Moradi Ghiassabadi,
Volume 12, Issue 2 (6-2015)
Abstract
In this research, two different carbonaceous materials (Graphite:G and Petrocoke:P) were separately
compared in terms of the carbothermic reduction of hematite and anatase in order to synthesize Fe-TiC nanocrystalline composite by mechanically activated sintering method. Powders were activated in a planetary high-energy
ball mill under argon atmosphere for 0, 2, 5, 10,and 20 h. Then, the activated powders were analyzed by XRD and
SEM to investigate phase constituents and microstructure of the mixtures. Results proved that Fe
2
O
3
and TiO
2
were not
reduced by carbonaceous materials even after 20h of milling. SEM investigations showed that G-mixture was more
homogenous than P-mixture after 20h of milling, meaning that graphite-anatase-hematite was mixed satisfactorily.
Thermogravimetry analysis was done on 0 and 20h milled powders. TG and DTG curves showed that mechanical
activation led to almost 300°C decrease in the reduction temperature of hematite and anatase in both mixtures. In the
next step, the powders were sintered in a tube furnace under argon atmosphere. In the G-mixture, anatase was reduced
to titanium carbide at 1100°C but, in the P-mixture, temperature of 1200°C was essential for completely reducing
anatase to titanium carbide.Results of phase identification of the sintered powders showed that anano-crystalline ironbased composite with titanium carbide, as the reinforcement was successfully synthesized after 20 h high-energy
milling of the initial powders and subsequent sintering occurred at 1200˚C for 1h
D. Gharailou, A. Abbasi,
Volume 12, Issue 3 (9-2015)
Abstract
Effect of electro migration on crystal structures of platinum nanowire (Nano bridge) during Nano-gap
formation is investigated by means of Transmission Electron Microscopy (TEM). Selected area diffraction patterns as
well as bright field images are used for this investigation. There were severely recessions in the polycrystalline Nano
bridge and crystal structures around the nanogap changed completely during electro migration. Due to Joule heating,
original small crystal with random orientation disappeared and newly crystals with a preferred orientation grew. They
have [111] orientations (respect to beam direction) with slight misorientations. α and θ was defined to calculate the
misorientation and used to represent Nano-gap formation mechanism. The calculation gives the breaking of Nano
bridge occurred along grain boundaries in most of Nano bridges. The controlling system during eletromigration may
affect on the shapes of tips so that the shape of tips in Nano bridges, in which feedback control is applied, is more
symmetric than others. The effect of temperature on atomic diffusivity might be the reason of the behaviour. {422}
could be a preferred surface plane for mass transport in platinum Nano bridge in which atoms move along it
N. Bahrami Panah, N. Ajami,
Volume 13, Issue 1 (3-2016)
Abstract
The epoxy coatings containing multi-walled carbon nanotube/ poly ortho aminophenol nanocomposite were prepared and used as anticorrosive coatings. The nanocomposites with different contents of carbon nanotube were synthesized in a solution of sodium dodecyl sulfate and ammonium peroxy disulfate as a surfactant and an oxidant, respectively. The morphology and structural properties were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy methods. The mean size of nanocomposite particles was 20-35 nm determined by scanning electron microscopy. The epoxy coatings containing the nanocomposites were applied over mild steel panels and their corrosion performance was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization measurements in a 3.5 % sodium chloride solution. The results showed that epoxy coatings consisting of nanocomposite with 1 wt.% multi-walled carbon nanotube exhibited higher anticorrosive properties than other prepared coatings of different carbon nanotube contents, which could be due to the strong interaction between the mild steel surface and the conjugated nanocomposite.
M. R. Khorram, M. R. Shishesaz, Iman Danaee, D. Zaarei,
Volume 13, Issue 1 (3-2016)
Abstract
The micro layers micaceous iron oxide and nano-TiO 2 were incorporated into the epoxy resin by mechanical mixing and sonication process. Optical micrographs showed that the number and diameter size of nanoparticle agglomerates were decreased by sonication. The structure and composition of the nanocomposite was determined using transmission electron microscopy which showed the presence of dispersed nano-TiO 2 in the polymer matrix. The anticorrosive properties of the synthesized nano-composites coating were investigated using salt spray, electrochemical impedance spectroscopy and polarization measurement. The EIS results showed that coating resistance increased by addition of micaceous iron oxide micro layers and nano-TiO 2 particles to the epoxy coatings. It was observed that higher corrosion protection of nanocomposite coatings obtained by the addition of 3 %wt micaceous iron oxide and 4%wt nano-TiO 2 into epoxy resin.
H. R. Sobhani Kavkani, A. Mortezaei, R. Naghizadeh,
Volume 13, Issue 2 (6-2016)
Abstract
Different mineral admixtures of Indian metakaolin, Iranian silica fume and nanosilica were used to produce high performance mortars. Two different sands types with grain size of 0.015-4mm were mixed with type II Portland cement, polycarboxylate superplasticizer,mineral admixture with 650kg/m3 cement content and water/cement ratio of 0.35. Different amount of cement was replaced by metakaolin or silica fume (5-15wt%) or nanosilica (0.8-5wt%). After mixing, moulding and curing, compressive strength, electrical resistivity and abrasion resistance were studied. The maximum compressive strength of 28 days samples were 76MPa, 79MPa and 75MPa for 15wt% substitution of cement with metakaolin, silica fume and 5wt% with nanosilica. The compressive strength of these samples showed 28%, 33% and 26% increment in comparison with reference sample, respectively. X-ray patterns showed that replacing silica fume leads to reduction of Portlandite (Ca(OH)2) phase. This can be attributed to the pozzolanic reaction and formation of new hydrated calcium silicate phase (CSH) that caused improvement of strength of admixtures containing samples. The microstructure of silica fume containing sample also showed better bond between sand and matrix. The electrical resistivity of samples with 15wt% metakaolin or silica fume and 5wt% nanosilica reach to 21kΩ.cm, 15 kΩ.cm and 10kΩ.cm, respectively. These samples showed high durability and corrosion resistance relative to reference samples (3.4 kΩ.cm). The abrasion resistance of different admixtures, specially silica fume containing samples were improved.
H. Adelkhani, Kh. Didehban, R. Dehghan,
Volume 13, Issue 2 (6-2016)
Abstract
In this study, polyaniline-graphene composites with different nano-structures are synthesized and the behaviour of the obtained composites serving as electrode materials in electrochemical capacitors is studied. The morphology, crystal structure, and thermal stability of the composites are examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Thermal gravimetric analysis (TGA). Electrochemical properties are characterized by cyclic voltammetry (CV). According to the results, the obtained composites show different crystal structures and different thermal stabilities, and consequently different electrochemical capacities, when used as electrodes in electrochemical capacitors. A nano-fibre composite is shown to have a good degree of crystallization, 5.17% water content, 637oC degradation onset temperature, and 379 Fg-1 electrochemical capacity.
M. S. Mahmoudi Jozee, S. Sanjabi, O. Mirzaee,
Volume 13, Issue 3 (9-2016)
Abstract
A homogenous TiO2 / multi-walled carbon nanotubes(MWCNTs) composite film were prepared by electrophoretic co-deposition from organic suspension on a stainless steel substrate. In this study, MWCNTs was incorporated to the coating because of their long structure and their capability to be functionalized by different inorganic groups on the surface. FTIR spectroscopy showed the existence of carboxylic groups on the modified carbon nanotubes surface. The effect of applied electrical fields, deposition time and concentration of nanoparticulates on coatings morphology were investigated by scanning electron microscopy. It was found that combination of MWCNTs within TiO2 matrix eliminating micro cracks presented on TiO2 coating. Also, by increasing the deposition voltages, micro cracks were increased. SEM observation of the coatings revealed that TiO2/multi-walled carbon nanotubes coatings produced from optimized electric field was uniform and had good adhesive to the substrate.
S. Ghasemi-Kahrizsangi, H. Gheisari-Dehsheikh, M. Boroujerdnia,
Volume 13, Issue 4 (12-2016)
Abstract
In this study the effect of nano meter size ZrO2 particles on the microstructure, densification and hydration resistance of magnesite –dolomite refractories was investigated. 0, 2, 4, 6 and 8 wt. % ZrO2 particles that were added to magnesite –dolomite refractories containing 35 wt. % CaO. The Hydration resistance was measured by change in the weight of specimens after 72 h at 25℃ and 95% relative humidity. The results showed with addition of nano meter size ZrO2 particles, the lattice constant of CaO increased, and the bulk density and hydration resistance of the specimens increased while apparent porosity decreased. With the addition of small amount ZrO2 the formation of CaZrO3 phase facilitated the sintering and the densification process. The mechanism of the nano meter size ZrO2 particles promoting densification and hydration resistance is decreasing the amount of free CaO in the specimens.
F. Sakhaei, E. Salahi, M. Eolya, I. Mobasherpour,
Volume 13, Issue 4 (12-2016)
Abstract
Up to now, lots of materials such as active carbon, iron, manganese, zirconium, and metal oxides have been widely used for removal of dyes from contaminated water. Among these, ferrite nanoparticle is an interesting magnetic material due to its moderate saturation magnetization, excellent chemical stability and mechanical hardness. Graphene, a new class of 2D carbonaceous material with atom thick layer features, has attracted much attention recently due to its high specific surface area. Reduced graphene oxide (rGO) has also been of great interest because of its unique properties, which are similar to those of graphene, such as specific surface area, making it an ideal candidate for dye removal. Thus far, few works have been carried out on the preparation of CoFe2O4-rGO composite and its applications in removal of contaminants from water. In this paper, CoFe2O4 reduced graphene oxide nanocomposite was fabricated using hydrothermal process. During the hydrothermal process, the reduction of graphene oxide and growth of CoFe2O4 simultaneously occurred on the carbon basal planes under the conditions generated in the hydrothermal system. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy contaminant and UV-Vis spectroscopy as the analytical method. The experimental results suggest that this material has great potential for treating Congo red contaminated water.
A. Tadjarodi, M. Imani, A. Iraji Zad,
Volume 14, Issue 3 (9-2017)
Abstract
In this work, we report the synthesis of silver decamolybdate, Ag6Mo10O33, nanostructure by a simple mechanohemical process followed by calcination treatment using acetamide as driving agent. Morphological study by scanning electron microscopy (SEM) images revealed bundles of rods grown closely together with an average diameter of 92 nm for Ag6Mo10O33 sample. Ni-substituted Ag6Mo10O33 compound was prepared via introducing nickel cation to precursor system in mechanical milling step. The particle size decreased to 87 nm by incorporating nickel units in substituted polymolybdate. It was concluded that the suitable selection of reagents can direct solid phase reaction towards producing nanostructured products. This technique is easy and simple for preparation of various mixed metal oxides without using any solvents and or complex procedures. In addition, the photocatalytic activity of the prepared products was studied on the removal of 4-nitro phenol (4-NP) as organic pollutant from water. The obtained results were also discussed in detail.
R. Hasanzadeh, T. Azdast, R. Eungkee Lee, A. Afsari Ghazi,
Volume 14, Issue 3 (9-2017)
Abstract
Material selection is a main purpose in design process and plays an important role in desired performance of the products for diverse engineering applications. In order to solve material selection problem, multi criteria decision making (MCDM) methods can be used as an applicable tool. Bumper beam is one of the most important components of bumper system in absorbing energy. Therefore, selecting the best material that has the highest degree of satisfaction is necessary. In the present study, six polymeric nanocomposite materials were injection molded and considered as material alternatives. Criteria weighting was carried out through analytical hierarchy process (AHP) and Entropy methods. Selecting the most appropriate material was applied using technique for order preference by similarity to ideal solution (TOPSIS) and the multi-objective optimization on the basis of ratio analysis (MOORA) methods respect to the considered criteria. Criteria weighting results illustrated that impact and tensile strengths are the most important criteria using AHP and Entropy methods, respectively. Results of ranking alternatives indicated that polycarbonate containing 0.5 wt% nano Al2O3 is the most appropriate material for automotive bumper beam due to its high impact and tensile strengths in addition to its low cost of raw material. Also, the sensitivity analysis was performed to verify the selection criteria and the results as well.
R. Ubaid, S. Saroj Kumar, S. Hemalatha,
Volume 15, Issue 3 (9-2018)
Abstract
Drug resistant pathogenic microbes have been causing serious health issues resulting in the substantial increase of death rates and morbidity paving the way for nanoparticles to be utilized as antimicrobial agents. This study was performed to evaluate the effectiveness of CuNPs on the growth of drug resistant clinical isolates of Streptococcus pyogenes, Enterococcus faecium and Enterococcus faecalis. Minimum inhibitory concentration of CuNPs against Streptococcus pyogenes, Enterococcus faecium and Enterococcus faecalis was found to be 1.25. 1.25 and 0.625 mg/ml and minimum bactericidal concentration against the same isolates was found to be 2.5, 2.5 and 5 mg/ml respectively. The ratio of MBC/MIC, referred to as tolerance level, was calculated for all the isolates which signifies the bactericidal or bacteriostatic effect of any antimicrobial agent. For Streptococcus pyogenes and Enterococcus faecium, the tolerance level was 2 while as for Enterococcus faecalis, it was 8. Antibiotic susceptibility results were calculated which showed that the isolates were resistant to Ampicillin (10 µg), Amoxycillin (30 µg) and Aztreonam (30 µg). Susceptibility results were followed by calculating multiple antibiotic resistance indices (MARI). MARI is an important tool which gives an idea about the bacterial resistance in a given population. For all the three isolates, MARI results were equivalent to 1 because of their resistance towards all the three antibiotics used. Antimicrobial activity through well-plate method was carried out and inhibitory effect of CuNPs on biofilm formation was evaluated.
R. Jafari, Sh. Mirdamadi, Sh. Kheirandish, H. Guim,
Volume 15, Issue 3 (9-2018)
Abstract
In this research, the objective was to investigate the stabilized retained austenite in the microstructure resulting from the Q&P heat treatment since the primary goal in Q&P is to create a microstructure consists of stabilized retained austenite and martensite. For this purpose, a low-alloy steel with 0.4wt. % carbon was treated by quench and partitioning (Q&P) process. The Q&P was conducted at different quench temperatures to obtain a considerable amount of retained austenite, while partitioning temperature and time were kept constant. Through analysis of the XRD profiles, volume percent, carbon concentration, and lattice parameters of retained austenite and martensite were calculated. At quench temperature equal to 160°C, 12vol.% austenite was stabilized to the room temperature, which was the highest amount achieved. The microstructural observations carried out on selected samples, revealed that retained austenite has a nanoscale particle size, about 200nm. Distinguishing retained austenite in the SEM micrographs became possible by utilizing SE2 signals via the difference in phases contrast. Two types of morphology, film-like and blocky type, were identified by means of TEM and TKD and a schematic model was proposed in order to explain these morphologies
H. Esfandiar, S. M. Hashemianzadeh, S. Saffary, S. Ketabi,
Volume 15, Issue 3 (9-2018)
Abstract
Gold nanoparticles have become common in many applications of biotechnology due to their specific properties. Shape and size are important attributes which affect their solubility in water. In this study, the outcomes of Monte Carlo Simulation for the solvation of gold nanorods in aqueous solution with the different radii, in terms of solvation free energy, are discussed. Simulation results show a negative solvation free energy for all the samples with radii of 4 to 9Å. The results show that the absolute values of solvation free energy for gold nanorods with smaller radius are larger, which indicate the dependency between the gold nanorods solvation and their radius.
H. Darrudi, M. Adelifard,
Volume 16, Issue 1 (3-2019)
Abstract
In this paper we have investigated the physical properties of reduced graphene oxide (RGO) thin films prepared at various substrate temperatures of 230, 260, 290, 320 and 350 oC using spray pyrolysis technique. We have compared these films from various viewpoints, including structural, morphological, optical, electrical and thermos-electrical properties. XRD analysis showed a phase shift from graphene oxide (GO) to RGO due to elevate the substrate temperature from 200 oC to higher temperatures. FESEM images of RGO thin films reveal that a stacked image of irregular and folding nanosheets, and rod-like features at temperatures below and above 290 oC; respectively. Optical studies showed that the layers have a relatively high absorption coefficient (∼0.8×104 to 1.7×104 cm−1) in the visible range, with an optical band gap of 1.67–1.88 eV. The Hall effect data showed that all samples have a p-type conductivity with a hole concentration of ∼1015 cm−3, and sheet resistance values of about 106 Ω/sq, in agreement with previous reports. The thermoelectric measurements revealed that with increasing applied temperature gradient between the two ends of the samples, the thermoelectric electromotive force (emf) of the prepared RGO thin films increases.
M. Karimi Sahnesarayi, H. Sarpoolaky, S. Rastegari,
Volume 16, Issue 2 (6-2019)
Abstract
In this study nanosized TiO2coatings on the 316L stainless steel substrate were prepared by means of dip-coating technique in which thickness of the coating layer increased byrepeating the coating cycles in two different routes: (I) dipping and drying,respectively, were repeated one, three and five times and finally the dried coated sample was heat treated (single); (II) multiple heat treatment performed after each dipping and drying cycle, respectively.The structural, morphological and optical characterizations of coatings as well as thickness of coatings were systematically studied.The photocatalytic activity of the various TiO2 coatings was investigated based on the degradation of an aqueous solution of Methyl orange.Moreover, thecorrosion protective properties of coatings were evaluated in both dark and UV illumination conditions based on the obtained polarization curves. The results indicated 1.75 times improvement in photocatalytic reaction rate constant, a two orders of magnitude decrease in corrosion current density in dark condition and about 140 mV electrode potential reduction under UV illumination with optimum coating preparation procedure, repeating the cycle from dipping to heat treatment three times, than the sample prepared with one time coating and heat treatment since this procedure provided not only high thickness and defect-free coating but also transparent one.
A. Ostovari Moghaddam, A. Shokuhfar, A. Cabot,
Volume 16, Issue 4 (12-2019)
Abstract
Metal sulfides containing non-toxic and earth abundant elements have emerged as new environmentally friendly thermoelectric materials. In the present work, a new, fast and large scale route to synthesise bulk nanostructured Co1-xCuxSbS paracostibite is presented. Stoichiometric compositions of Co1-xCuxSbS nanoparticles with 0 ≤ x ≤ 0.08 were first processed by high energy ball milling for 3 h, and then annealed at different temperatures between 400 ºC to 650 ºC for 1 h. The phase transitions and diffusion process during annealing were thoroughly studied by x-ray diffraction (XRD) and scanning electron microscopy (SEM). Agglomerated nanoparticles with sizes in the range from 40 nm to 80 nm were obtained after 3 h of ball milling, and remained below 100 nm after annealing and hot pressing. The thermoelectric properties of hot pressed samples, including the Seebeck coefficient (S), electrical conductivity (σ) and thermal conductivity (k), were measured from room temperature up to 723 K. All the samples exhibited a p-type semiconductor character at room temperature and underwent a transition from p-type to n-type conduction above 473 K. a maximum ZT value of 0.12 was obtained for Co0.06Cu0.04SbS4 at 723 K.
A. R. Abbasian, M. R. Rahimipour, Z. Hamnabard,
Volume 16, Issue 4 (12-2019)
Abstract
In this work, lithium meta titanate (Li2TiO3) nanocrystallites were synthesized by hydrothermal method and subsequent heat treatment. The shrinkage of the powder compact was measured under constant heating rate in order to study the sintering behavior of the synthesized powders. Densification curves of the synthesized powders were also constructed via the dilatometry analysis and evaluated at several heating rates. Two separate methods of analytical procedure and master curve sintering were employed to determine the activation energy of the initial sintering stage. The activation energy values were estimated based on these two distinct methods as 229±14 and 230 kJ/mol respectively, consistenting with each other. Moreover, surface diffusion was determined as the dominant mechanism of densification on initial sintering of Li2TiO3 nanocrystallites.
V. Tajer Kajinebaf, M. Zarrin Khame-Forosh, H. Sarpoolaky,
Volume 17, Issue 1 (3-2020)
Abstract
In this research, the nanostructured titania-coated silica microsphere (NTCSM) membrane consisting of titania-silica core-shell particles on α–alumina substrate was prepared by dip-coating method. The silica microspheres were synthesized by the Stöber method, and the nanostructured titania shell was obtained from a polymeric sol. Then, the prepared core-shell particles were deposited on alumina substrates. The samples were characterized by DLS, TG-DTA, XRD, FTIR and SEM. The photo-catalytic activity of the NTCSM membranes was evaluated using photo-degradation of methyl orange solution by UV–visible spectrophotometer. Also, physical separation capability was investigated by filtration experiment based on methyl orange removal from aqueous solution using a membrane setup. The mean particle size distribution of silica microspheres was determined to be about 650 nm that by deposition of titania nano-particles increased up to about 800 nm. After 60 min UV-irradiation, the dye removal efficiency was determined to be 80% by the membrane. By coupling separation process with photo-catalytic technique, the removal efficiency was improved up to 97%. Thus, the NTCSM membranes showed simultaneous photo-degradation and separation capabilities for dye removal from water.
