Showing 111 results for Nano
Mir Habibi A.r., Rabiei M., Agha Baba Zadeh R., Moztar Zadeh F., Hesaraki S.,
Volume 1, Issue 3 (9-2004)
Abstract
ZnS : Cu phosphors were prepared by using laboratory grade chemicals through coprecipitating Cu along with ZnS using H2S and thiourea. Photo- and electroluminescence studies indicate that these phosphors have better emission characteristics compared to the phosphors in which activator is externally added. Phosphors with luminescence at ~530nrn were prepared. The difference between the characteristic properties of the samples seems to be due to formation of nanoparticles during the preparation of the samples by different methods.
Ghobeiti Hasab M., Seyyed Ebrahimi S.a., Badaee A.,
Volume 2, Issue 2 (6-2005)
Abstract
In this research the sol-gel auto-combustion method was used to prepare strontium hexaferrite nanopowder. A solution of distilled water, ferric and strontium nitrates, citric acid, trimethylamine, and n-decyltrimethylammonium bromide cationic surfactant, was heated to form a viscous gel. The gel was heated and then ignited automatically. As-burnt powder was calcined at temperatures from 700 to 900?C in air to obtain SrO.6Fe2O3 phase. The influence of the calcination temperature on the phase composition of the products has been investigated. X-ray diffraction confirmed the formation of single-phase strontium hexaferrite nanopowder at temperature of 800?C.
Baradari H., Amani Hamedani H., Karimi Khoygani S., Rezaei H.r., Javadpour J., Sar Poulaki H.,
Volume 3, Issue 1 (6-2006)
Abstract
Ultrafine hydroxyapatite (HAp) powders with crystallite size in the range of 10-90 nm were synthesized by chemical precipitation process using Ca(OH)2 and H3PO4 solutions as starting materials. Molar ratio of Ca/P=1.68 was kept constant throughout the process and alkaline condition for the reaction was maintained using ammonium hydroxide. The role of raw material concentration on HAp crystallite size and morphology were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The results revealed that variations in crystallite size and morphology of synthesized HAp are strongly affected by the concentration of acid solution. To study the sintering behavior of HAp particles, the powders were pressed at 200 MPa using a uniaxial press. Sintering experiments were carried out at temperatures of 1100, 1250 and 1300°C with various soaking times at maximum temperatures. XRD was also used in determining thephases present after sintering process. The results indicated the decomposition of HAp into a-tricalcium phosphate (TCP) and b-TCP phases at 1300°C. The microstructure of the sintered HAp ceramics was characterized by SEM.
B. Alinejad1,, H. Sarpoolaky1,, A. Beitollahi1, S. Afshar2,
Volume 4, Issue 1 (6-2007)
Abstract
Abstract: Nanocrystalline MgAl2O4 spinel powder was synthesized using metal nitrates and a
polymer matrix-based composed of sucrose and polyvinyl alcohol (PVA). The precursor and the
calcined powders were characterized by simultaneous thermal analysis (STA), X-ray diffraction
(XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy
(SEM). According to XRD results, the inceptive formation temperature of spinel via this technique
was between 600°C and 700°C. The average crystallite size of calcined powder at 800°C for 2h
was in the range of 8-12nm. In addition, SEM micrograph showed that the synthesized powder had
a spherical morphology.
A. Nemati, K. Pourazarang,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: The PZT-based ceramics with a composition of Pb1.1-xLax (Zr0.53Ti0.47)O3, were prepared
by conventional mixed oxide followed by mechanical alloying and sol-gel methods in which x was
chosen in the range of 0.02–0.06. The samples were calcined in the range of 450 °C - 750 °C for
4h. The physical and electrical properties of the samples were determined as a function of the
calcination temperature. The obtained data from two methods were compared with conventional
mixed oxide method. Microstructural and compositional analyses of the samples were carried out
using XRD and SEM. Dielectric properties of the samples were measured with an impedance
analyzer. The ferroelectric properties of the PZT and PLZT samples were measured using the
frequencies applying equipment and d33 tester. The results indicated a complete tetragonal phase
prepared from both methods. It was shown that the addition of La and reduction in calcination
temperature improved both the dielectric and piezoelectric properties. The dielectric constant
tended to increase with doping content, giving the maximum value of about 2000 at 3 mol% La3+.
In addition, the mechanical coupling factor (Qm) of the doped samples showed a significant
decrease. Finally, the value of planar coupling factor (kp) reached the maximum value of 0.47 at 1
mol% La3+.
M. Pirhadi Tavandashti, M. Zandrahimi, B. Akbari,
Volume 6, Issue 1 (3-2009)
Abstract
Abstract: Nanoparticles exhibit a high reactivity and strong tendency towards agglomeration. In this study, aluminum
oxide (alumina) nanoparticles were characterized by gas adsorption (BET), transmition electron microscopy (TEM)
and photon correlation spectroscopy (PCS) techniques to assess the agglomeration of the particles. There is a good
correlation between the BET and TEM measurements but PCS was larger in the mean and median size and with a
degree of agglomerates being detected. Some agglomeration was evident, but most of the particles existed as discrete
objects as observed in the (HR) TEM images which were in good agreement with the agglomeration factor.
M. Ebrahimi-Basabi,, J. Javadpour,, H. Rezaie, M. Goodarzi,
Volume 6, Issue 1 (3-2009)
Abstract
Abstract: Nano- size alumina particles have been synthesized by mechanical activation of a dry powder mixture of
AlCl3 and CaO. Mechanical milling of the above raw materials with the conditions adopted in this study resulted in
the formation of a mixture consisting of crystalline CaO and amorphous aluminum chlorides phases. There was no
sign of chemical reaction occurring during milling stage as evidenced by x-ray diffraction studies. Subsequent heat
treatment of the milled powder at 350ºC resulted in the occurrence of displacement reaction and the formation of
Al2O3 particles within a water soluble CaCl2 matrix. The effect of higher temperature calcinations on the phase
development in this powder mixture was followed by X-ray diffraction (XRD) analysis and scanning electron
microscope ( SEM). Differential thermal analysis (DTA) was used to compare the thermal behavior between the
milled and unmilled powders. Perhaps the most important result in this study was the observation of á-Al2O3 phase
at a very low temperature of 500ºC.
Ali. A. Hosseini,, F. Ghaharpour, H. Rajaei ,
Volume 6, Issue 3 (9-2009)
Abstract
Abstract: In this paper‚ the physical and mechanical properties of Al nanocomposite reinforced with CNTs wereinvestigated. High purity Al powder and Carbon Nanotubes (CNTs) with different percentage were mixed by ballmilling method and the composite was fabricated by cold pressing followed by sintering technique. The variation ofdensity and hardness of composite with CNTcontent was investigated. The microstructure of composite was evaluatedby SEM (Scanning Electron Microscope) and XRD (X -Ray Diffraction). The results show that the density and hardnessincrease with CNTpercentage.
S. Zavareh, F. Majedi,, M. Sh. Sharif, F. Golestanifard,
Volume 6, Issue 3 (9-2009)
Abstract
Abstract: Multiwalled carbon nanotubes (MWCNTs) were coated with MgO nano particles using simple precipitationmethod. The growth of Mg(OH)2particles was controlled by adjusting the alkaline concentration, salt concentrationand feed rate in simple precipitation method. The nanometer-sized Mg(OH)2particles were precipitated on the surfaceof functionalized MWCNTs by reaction between MgSO4 solution and NH4OH. The samples have been characterizedby scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction and thermal gravimetricanalysis. The results showed a nominally complete MgO coating over the entire outer surface of MWCNTs resulting inimprovement of their oxidation durability.
M. Banoee,z. Ehsanfar, N. Mokhtari,m. R. Khoshayand, A. Akhavan Sepahi, P. Jafari Fesharaki,h. R. Monsef-Esfahani,, A. R. Shahverdi,
Volume 7, Issue 1 (3-2010)
Abstract
Abstracts:
nanoparticles. All the extracts were used separately for the synthesis of gold nanoparticles through the reduction of
aqueous AuCl
gold ions to gold nanoparticles. The ethanol extract of black tea and its tannin free ethanol extract produced gold
nanoparticles in the size ranges of 2.5-27.5 nm and 1.25-17.5 nm with an average size of 10 nm and 3 nm, respectively.
The prepared colloid gold nanoparticles, using the ethanol extract of black tea, did not show the appropriate stability
during storage time (24 hours) at 4
showed no particle aggregation during short and long storage times at the same conditions. To the best of our
knowledge, this is the first report on the rapid synthesis of gold nanoparticles using ethanol extract of black tea and
its tannin free fraction.
In this research the ethanol extract of black tea and its tannin free fraction used for green synthesis of gold4¯. Transmission electron microscopy and visible absorption spectroscopy confirmed the reduction ofoC. In contrast, gold colloids, which were synthesized by a tannin free fraction
A.m. Rashidi, A. Amadeh,
Volume 7, Issue 2 (6-2010)
Abstract
Abstract:
nanocrystalline nickel samples with the grain size of ~25 nm were prepared via direct current electrodeposition and
aluminized for different durations by pack cementation method at 500
means of SEM, EDS and XRD techniques. According to results, short time aluminizing resulted in the formation of a
single aluminide layer whereas at long duration two distinct aluminide layers were formed. The growth kinetics of the
coating was non-parabolic at short times while it obeyed the parabolic law at long duration. The parabolic growth
rate constant of single phase coating formed on electrodeposited samples was about 30 ìm / h1/2 approximately 3 times
greater than the data reported for coarse grained nickel (8.4 ìm / h1/2). Meanwhile, the overall growth rate constant
was decreased to 11.7 ìm / h1/2, when double aluminide layers formed on nanocrystalline nickel.
In this research, aluminizing behavior of ultra fine-grained nickel was investigated. For this purpose,oC. The aluminide layers were examined by
Mr Mohammadtaher Safarzadeh, Mr Seyed Mohammad Ali Boutorabi, Mr Asghar Arab,
Volume 7, Issue 3 (8-2010)
Abstract
The effects of anodizing condition and post treatment on the growth of nickel nanowires, were investigated. A two-step anodizing process was applied in phosphoric and oxalic acid solution. Nickel electrochemical plating was applied to fill Anodic Aluminum Oxide (AAO) pores. For pore filling enhancement, AAO surfaces were treated by silver predeposition. After electroplating, aluminum and oxide layer of some specimens were removed. The results showed that silver preplating increases the pore filling and as the applied voltage becomes higher, the pores diameter decreases.
Mrs Somaye Alamolhoda, Dr Saeed Heshmati-Manesh, Dr Abolghasem Ataie,
Volume 7, Issue 3 (8-2010)
Abstract
In this research an ultra-fine grained composite structure consisting of an intermetallic matrix together with dispersed nano-sized Al2O3 obtained via mechanical activation of TiO2 and Al in a high energy ball mill and sintering of consolidated samples. Phase composition and morphology of the milled and sintered samples were evaluated by XRD and SEM techniques Thermal behavior of the powder sample milled for 8 hours was evaluated by DTA technique. DTA results showed that, the reaction happens in two steps. The first step is the aluminothermic reduction of TiO2 with Al. XRD observations reveals that minor amount of Ti3Al phase formed during reduction reaction together with TiAl and Al2O3 major phases. This intermetallic phase disappeared when sintering temperature was increased to 850 ºC. The second step in DTA is related to a reaction between residual Al in the system (partly dissolved in TiAl lattice) and the Ti3Al phase produced earlier at lower temperatures. SEM micrographs reveal that by completion of the reduction reaction more homogeneous and finer microstructure is observable in sintered samples.
Z. Ghaferi, K. Raeissi, M. A. Golozar,, A. Saatchi, S. Kabi,
Volume 7, Issue 4 (10-2010)
Abstract
Abstract:
current densities. Electrochemical impedance spectroscopy (EIS) results showed that the codeposition mechanism of
tungsten in Ni-W deposition is the reduction of tungsten oxide which changed to the reduction of tungsten-containing
ion complexes at higher current densities. In Co-W electrodeposition, the tungsten codeposition takes place via
reduction of tungsten oxide, although, the role of tungsten-containing complexes at higher current densities cannot be
ruled out. The surface morphology of Ni-W coatings was crack-free and was strongly dependent on deposition current
density. In addition, higher grain size and lower tungsten content were obtained by increasing the current density. In
Co-W coatings, no obvious variation in surface morphology was observed except for the fine cracks appeared at
higher current densities. In this system the grain size remained almost constant with increasing current density. The
microhardness values of Ni-W and Co-W coatings decreased due to the increase in the grain size and/or decrease in
tungsten content.
Ni-W and Co-W alloy nanocrystalline coatings were electrodeposited on copper substrate at different
M. Kazemimoghadam, and T. Mohammad,
Volume 8, Issue 1 (3-2011)
Abstract
Abstract: Nano pore Mordenite membranes were prepared on the outer surface of ceramic tubular tubes via hydrothermal synthesis and evaluated for dehydration pervaporation of water unsymmetrical dimethylhydrazine UDMH mixtures. Highly water-selective mordenite membranes were prepared and the optimum reaction condition was found to be 24 h crystallization time and 170 °C crystallization temperature. Effect of gel composition on separation factor and water flux of the water-UDMH mixtures was investigated. X-ray diffraction (XRD) patterns showed that mordenite is the only zeolite material which presents in the membrane. Morphology of the supports subjected to crystallization was characterized by Scanning electron microscopy (SEM). In PV of the water-UDMH mixtures, the membrane exhibits a hydrophilic behavior, with a high selectivity towards water and a good flux. The best membranes had a water flux of 2.67 kg/m2.h at 27 °C. The best PV selectivity was obtained to be 264.
T. Rostamzadeh, H. R. Shahverd,
Volume 8, Issue 1 (3-2011)
Abstract
Abstract: In this study Al-5 (Vol) % SiCp nanocomposite powder has been successfully synthesized by high-energy planetary milling of Al and SiC powders for a period of 25 h at a ball-to-powder ratio of 15:1. The changes of the lattice strain, the crystallite size of the matrix phase, and the nanocomposite powder microstructure with time have been investigated by X-ray diffraction (XRD), X-ray mapping, and scanning electron microscopy (SEM) analyses. The morphologies of the nanocomposite powders obtained after 25 h of milling have also been studied by transmission electron microscopy (TEM). The results showed that nanocomposite powders were composed of near-spherical particles and, moreover, the SiC particles were uniformly distributed in the aluminum matrix.
A. Najafi, F. Golestani-Fard, H. R. Rezaie, N. Ehsani,
Volume 8, Issue 2 (6-2011)
Abstract
Abstract: SiC nano particles with mono dispersed distribution were synthesized by using of silicon alkoxides and phenolic resin as starting materials. After synthesis of sample, characterizations of the obtained powder were investigated via Fourier Transform Infrared Spectroscopy (FTIR) with 400-4000 cm-1, X-ray Diffractometry (XRD), Laser Particle Size Analyzing (LPSA), Si29 NMR analysis, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). FTIR and Si29 NMR results of the gel powder indicated that Si-O-C bonds were formed due to hydrolysis and condensation reactions . FTIR results showed a very strong peak for heat treated powder at 1500°C after carbon removal which is corresponded to Si-C bond. Obtained pattern from X-ray diffractometry showed that the final products contain -SiC phase with poly crystalline planes and little amounts of residual carbon. PSA results showed that the average particles size were 50.6 nm with monosized distribution. Also microstructural studies showed that the SiC nano powders have semi spherical morphology with mean particles size of 30-50 nm and also there are some agglomerates with irregular shape.
B. Akbari, M. Pirhadi Tavandashti, M. Zandrahimi,
Volume 8, Issue 2 (6-2011)
Abstract
Abstract: Most properties of nanoparticles are size-dependent. In fact, the novel properties of nanoaprticles do not prevail until the size has been reduced to the nanometer scale. The particle size and size distribution of alumina nanoparticle, as a critical properties, have been determined by transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), surface area analysis (BET) and x-ray diffraction peak broadening analysis. The particle size was found to be in the range of 5-95nm. Cumulative percentage frequency plot of the data extracted form TEM images indicates that particle size distribution obeys the log-normal function. The TEM images also reveal that particles are spherical in shape and loosely agglomerated. Comparing of the XRD and TEM results shows that the particles are single-crystal. The HRTEM images also verify that the particles have a single-crystal nature. In comparison, there is a good correlation between the BET, XRD and TEM measurements other than PCS that is sensitive to the presence of the agglomerates.
Y. Safaei-Naeini, F. Golestani-Fard, F. Khorasanizadeh, M. Aminzare, S. Zhang,
Volume 8, Issue 3 (9-2011)
Abstract
Abstract:
composition of MgO and nano boehmite. The reactant and potassium chloride, as the reaction media, were fired at
800-1000 °C at different dwell times (0.5-5 h) in the ambient atmosphere. After washing and filtration, the spinel nano
powder was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Brunauer-Emmett-
Teller (BET) techniques. It was demonstrated that the formation temperature decreased to 850
particles revealed an average size of 30 nm with a narrow size distribution. The mechanism of MgAl
was found to be a template type where the morphology and size of product were similar to those of alumina formed
from boehmite decomposition. Prolonging the reaction time from 0.5 to 3 h, the reaction was further completed and
crystallinity was improved. However, the increase of temperature was more effective in this regard.
MgAl2O4 (MA) nano powder was synthesized via molten salt technique, by heating stochiometric°C. The nano spinel2O4 formation
A. A. Hosseini, A. Sadigzadeh, S. Mohammadi,
Volume 8, Issue 3 (9-2011)
Abstract
Abstract: In this study, carbon nanotubes (CNTs) were grown directly in the pores of micro porous pyrex membranes
and consequently ceramic membranes with very fine pores and high porosity were achieved. Our experiment was done
in two stages. Initially cobalt powder with different percent was homogeneously mixed with pyrex powder. In order to
produce row membranes, each of these mixtures were compacted in the form of tablet by use of a uniaxial cold press
and in a stainless steel mould, and then the tablets were sintered at different temperature in an electric furnace. In
second stage chemical vapor deposition (CVD) method was used to grow CNTs within the pores of the membranes.
Argon and ammonia were used as carrier and reactive gas respectively and acetylene was used as the carbon
feedstock. Morphology of the membranes before and after CVD process was studied by scanning electron microscopy
(SEM). After CVD process CNTs were grown in the pores of membranes and the pores size was decreased but total
porosity of the membrane was not changed considerably. In this way membranes with high porosity and fine pores were
fabricated.
