S. Alamolhoda, S. M. Mirkazemi, T. Shahjooyi, N. Benvidi,
Volume 13, Issue 1 (3-2016)
Abstract
Nano-sized NiFe2O4 powders were synthesized by sol–gel auto-combustion method using pH values from 7 to 9 in the sol. The effect of pH variations on complexing behavior of the species in the sol has been explained. Changes in phase constituents, microstructure and magnetic properties by changes in pH values were evaluated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibration sample magnetometer (VSM) techniques. Changes in pH value from 7 to 9 changes the amounts of NiFe2O4, FeNi3 and α-Fe2O3 phases. Calculated mean crystallite sizes are in the range of 44 to 51nm. FESEM micrographs revealed that increasing the pH value to 9 causes formation of coarse particles with higher crystallinity. Saturation magnetization was increased from 36.96emu/g to 39.35emu/g by increasing pH value from 7 to 8 which is the result of increased FeNi3 content. Using higher pH values in the sol reduces the Ms value.
F. Torknik, M. Keyanpour-Rad, A. Maghsoudipour, G. M. Choi,
Volume 13, Issue 1 (3-2016)
Abstract
In order to further enhance the Ni/Ce 0.8Gd0.2O2-δ (Ni/GDC20) cermet anodic performance for low temperature solid oxide fuel cell (LT-SOFC), a study was conducted on the nanostructuring of NiO/GDC composite by only once wet-infiltration of rhodium chloride precursor. By using electrochemical impedance spectroscopy (EIS) analysis, the effect of only one drop of Rh-infiltrating solution on the anodic polarization resistance was examined using symmetric Ni–GDC20|GDC20|Pt electrolyte-supported cell at 400-600 °C. Nanostructural evolution before and after H 2 reduction at 600 °C and also after anodic performance test was investigated by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques in comparison to the anode itself. Despite the fine distribution of Rh-infiltrated nanoparticles having average particle size of 11.7 nm, the results showed ineffectiveness and inability of the Rh nanoparticles to succeed in decreasing of anodic polarization resistance for H 2 oxidation reaction in LT-SOFC.
A. Moosavi, M. A. Bahrevar, A. R. Aghaei,
Volume 13, Issue 1 (3-2016)
Abstract
An actuator is a device that converts input energy into mechanical energy. According to various types of input energy, various actuators have been advanced. Displacement in the electromagnetic, hydraulic and pneumatic actuators achieve by moving a piston via electromagnetic force or pressure, however the piezoelectric actuator (piezoceramic plates) displace directly. Therefore, accuracy and speed in the piezoelectric device are higher than other types of actuators. In the present work, the high-field electromechanical response of high-quality (1−x)(Bi 0.5Na0.5)TiO3–x(Bi0.5K0.5)TiO3 samples abbreviated to BNKTx with x = 0.18, 0.20, 0.22 and 0.24 ceramic materials across its MPB was investigated. The piezoelectrics and actuation characteristics were characterized. Ourresults indicate that x = 0.20, indeed, constitutes the best choice for the MPB composition in the system. Maximum of remanent polarization (37.5 μC cm−2) was obtained for x=0.20. High-field electromechanical responses were also obtained for BNKT0.20 samples. This material exhibited giant field induced strains of 0.13% under 1 kV mm -1 at room temperature.
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.
A. Izadpanahi, S. Baghshahi, A. Shalbaf Zadeh,
Volume 13, Issue 3 (9-2016)
Abstract
In the following research, Lead magnesium niobate relaxor ferroelectric (PMN-PZT) ceramic powders were synthesized using the combustion method grand urea as the fuel for the first time. The starting materials used were lead nitrate, magnesium acetate, niobium oxide, zirconium nitrate, titanium oxide.
The raw materials were first mixed using the general formula of (1-x)Pb(Mg1/3Nb2/3)O3-xPb(Zr0.52Ti0.48)O3, with x=0.3. The synthesized powders were characterized using XRD, SEM and FTIR spectroscopy techniques. The X-ray diffraction patterns revealed that the structure of the prepared samples were tetragonal at 500,600,700 and 800 oC. However, the monoclinic phase was detected in the samples calcined at 800 oC and the amount of pyrocholore phase also drastically decreased at this temperature. The band gap widths of the samples were measured via UV spectroscopy in the wave number range of 400-4000cm-1. The results show that by increasing the calcination temperature, the band gap width of the prepared samples decreases. SEM micrographs verify that by rising the calcination temperature, the structure of the prepared samples becomes more homogenous.
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.
N. Maskani, R. Naghizadeh, A. Mirhabibi, H. Rezaie,
Volume 14, Issue 1 (3-2017)
Abstract
The synthesis of micro-sized, uniformly distributed Al2O3-15Vol% Ni powders were studied through three step co-precipitation of hydroxides mixtures from proper solution, calcination at air atmosphere and final step of calcined powders in a carbon bed. Al and Ni hydroxide and amorphous phase were first obtained from their salt’s solutions through chemical co-precipitation method by adjusting pH. The precipitated powders were then calcined to obtain a mixture of their oxides as NiO and NiAl2O4 which were reduced in a carbon bed at various temperatures up to 1300. Proper temperature for calcination in air was determined through TG analysis; 900. SEM observation of powders after reduction, revealed micro-sized Ni particles, along with fin distribution of Ni and Al2O3 elements. XRD analysis of the calcined sample showed the presence of NiAl2O4 and NiO and the same analysis for the reduced sample confirmed the formation of Al2O3 and Ni.
M. Nouri, P. Alizadeh, M. Tavoosi,
Volume 14, Issue 3 (9-2017)
Abstract
In this study, the crystallization behavior of a 65GeO2-15PbO-10MgF2-10MgO glass (prepared by the conventional melt quenching technique) has been investigated. The microstructure and crystallization behaviors of this glass were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), non-isothermal differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that a fully glassy phase can successfully be prepared by the conventional melt quenching technique exhibiting one-stage crystallization on heating, i.e., the glassy phase transforms into crystalline MgGeO3 and Pb5GeO7 phases. The activation energy for the crystallization, evaluated from the Kissinger equation, was approximately 202±5 kJ/mole using the peak temperature of the exothermic reaction. The Avrami exponent or reaction order, n, indicates the nucleation rate in this glass to increase with time and the crystallization to be governed by a three-dimensional interface-controlled growth.
G. Maghouli, B. Eftekhari Yekta,
Volume 15, Issue 1 (3-2018)
Abstract
Commercial dental lithium disilicate based glass-ceramics containing various amounts of P2O5 were synthesized. Regarding the crystallization behavior and physico-chemical properties of the glasses, the optimum percent of P2O5 was determined.as 8 %wt.
Crystallization behavior of the glasses was investigated by X-ray diffraction (XRD) and differential thermal analysis (DTA). The micro-hardness and chemical resistance of both glass and glass-ceramic searies were also determined.
According to our results, lithium phosphate was precipitated prior to crystallization of the main phases, i.e lithium meta silicate and lithium disilicate. This early precipitation led to evacuation of residual glass phase from lithium ions, which caused increasing the viscosity of glass and so shifting of crystallization to higher temperatures.
In addition, increasing in P2O5 amounts and consequently increasing in Li3PO4, led to significant decrease in the crystallite size and aspect ratio of crystals.
Furthermore, while the chemical resistance of the glasses was decreased with P2O5, it was increased with P2O5 after heat treatment process.
The chemical solubility of these three glass-ceramics was between 2080~1188 μg/cm2.
M. Krishna, R. Nandini, A.v. Suresh, K. Narasimha Rao ,
Volume 15, Issue 2 (6-2018)
Abstract
An efficient solid-state approach was established to synthesize (K0.5Na0.5) NbO3 ceramics using calcination kinetics and microwave assisted sintering. Milling of carbonate and oxide raw materials were carried out for 15h to obtain homogeneous nano particles. The crystallite size of 5.30 nm was obtained for the KNN system after calcination through optimized parameters and observed to be stoichiometric in nature. The obtained nano particles showed phase transition from orthorhombic to tetragonal crystal structure without any secondary phases. The high relative density and tetragonality ratio of KNN ceramics obtained through optimized sintering parameters yielded with significant piezoelectric and ferroelectric properties.
F. Salehtash, H. Banna Motejadded Emrooz, M. Jalaly,
Volume 15, Issue 2 (6-2018)
Abstract
Mesoporous SiO2 nanopowder was synthesized under an acidic condition by a sol-gel method using various amounts of cetyltrimethyl ammonium bromide (CTAB) as structure directing agent. The samples were investigated with XRD, SEM, FTIR, TEM and N2 absorption-desorption analysis. Also, the incremental effect of surfactant were examined. The results obtained from the analysis suggested that an increase in the amount of surfactant resulted in increasing specific surface area, pore size and pore volume, of the synthesized particles up to 549 m2.g-1, 17.3 nm, and 2 cm3.g-1, respectively. Absorption behavior of the mesoporous silica was investigated for degradation of methylene blue pigments (MB) in aqueous solutions. The samples SC0, SC0.5 and SC1 showed the maximum absorption capacities of 333, 454 and 526 mg/g, respectively
M. R. Ghaani, P. Marashi,
Volume 15, Issue 3 (9-2018)
Abstract
Na super ionic conductive (NASICON) materials are ceramics with three-dimensional scaffolds. In this study, Li1.4Al0.4Ti1.6(PO4)3 with NASICON structure was synthesized by Pechini method. As a result, a sample having a total conduction of 1.18×10-3 S cm-1 was attained. In addition, various parameters were studied to obtain high value of conductivity, by optimizing the process. The optimization was made using L16 Taguchi based orthogonal array, followed by ANOM, ANOVA and stepwise regression. As a result, the optimum synthesis parameters can be obtained, while pH of the solution was adjusted to 7. The ratio between the concentration of citric acid to metal ions and ethylene glycol concentration stuck to 1 and 2.5, respectively. The best heat treatment can be carried out with a combination of pyrolysis at 600 ºC and sintering at 1000 ºC.
N. Maragani, K. Vijaya Kumar,
Volume 15, Issue 4 (12-2018)
Abstract
An attempt has been focused to develop a new aluminum ion conducting non aqueous polymer electrolyte for high power rechargeable batteries having applications in rapidly growing markets, such as laptops, handy tele communication equipments, electric vehicles, camcorders, etc. These features have given a thrust to develop a suitable Nano composite GPE based on PAN as polymer host and Sodium fluoride (NaF) as dopant salt and Al2O3 as nano filler in the form of thin films through solution casting technique consuming N,N-dimethyl formamide (DMF) as a common solvent. NCGPE films have been prepared by solution casting technique. The XRD pattern of 70PAN-30NaF with addition of wt% Al2O3 ceramic filler indicates reducing degree of crystallinity. Using IR studies revealed that the complexation of the polymer poly (acrylonitrle) with NaF. The conductivity of the GPEs was studied with enhancement of nano fillers. The sample containing 3% of Al2O3 exhibits the highest conductivity of 4.82x10-3S cm-1 at room temperature (303K) and 5.96x10-3S cm-1 at 378K. With the help of Wagner’s polarization technique electronic (te) and ionic (ti) values can be determined.To determine profiles of discharge characteristics (70PAN-30NaF-3wt% Al2O3) NCGPE solid-state electrochemical cell was fabricated and various cell profiles were evaluated
N. Yazdani, J. Javadpour, B. Eftekhari Yekta, M. Hamrang,
Volume 16, Issue 1 (3-2019)
Abstract
This study focuses on the physical, magnetic, biological and antibacterial behaviour of cobalt-doped HAp powder samples. Pure and Cobalt- doped HAp nanoparticles were synthesized by hydrothermal method. Calcium nitrate, di- ammonium hydrogen phosphate and cobalt nitrate were used as precursor materials. The synthesized powders were characterized using x-ray diffraction pattern (XRD), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), Raman spectroscopy as well as MTT assay and cell adhesion test. Disc diffusion method was used to investigate antibacterial activity of the samples. The results confirmed the substitution of Ca by Co ions in the HAp lattice. In addition, this substitution induced size reduction and morphology change in HAp particles. All cobalt substituted HAp powder samples displayed paramagnetic properties, as opposed to the diamagnetic behaviour observed in the pure HAp samples. In addition, these nanoparticles exhibited cell adhesion, biocompatibility and antibacterial activity against S.aureus bacteria.
This study focuses on the physical, magnetic, biological and antibacterial behaviour of cobalt-doped HAp powder samples. Pure and Cobalt- doped HAp nanoparticles were synthesized by hydrothermal method. Calcium nitrate, di- ammonium hydrogen phosphate and cobalt nitrate were used as precursor materials. The synthesized powders were characterized using x-ray diffraction pattern (XRD), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), Raman spectroscopy as well as MTT assay and cell adhesion test. Disc diffusion method was used to investigate antibacterial activity of the samples. The results confirmed the substitution of Ca by Co ions in the HAp lattice. In addition, this substitution induced size reduction and morphology change in HAp particles. All cobalt substituted HAp powder samples displayed paramagnetic properties, as opposed to the diamagnetic behaviour observed in the pure HAp samples. In addition, these nanoparticles exhibited cell adhesion, biocompatibility and antibacterial activity against S.aureus bacteria.
T. Ebadzadeh, S. Ghaffari, M. Alizadeh, K. Asadian, Y. Ganjkhanlou,
Volume 16, Issue 1 (3-2019)
Abstract
The densification behavior, structural and microstructural evolution and microwave dielectric properties of Li2TiO3 + xZnO (x = 0, 0.5, 1, 1.5, 2, 3, and 5 mol%) ceramics have been investigated using X-ray diffraction, Field Emission Scanning Electron Microscopy, Raman spectroscopy and microwave resonant measurement. The Maximum density of 3.33 g/cm3 was obtained in Li2TiO3 + 2ZnO ceramic at low sintering temperature of 1100˚C. SEM investigations revealed good close packing of grains when x = 2 and preferential grain growth when x ≥ 3. The maximum values of Q × f = 31800 GHz and εr = 22.5 were obtained in Li2TiO3 + 3ZnO and Li2TiO3 + 2ZnO compositions, respectively. The observed properties are attributed to the microstructural evolution and grain growth (first case) or high density of the obtained ceramic (second case).
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. Tavakoli Harandi, M. Askari-Paykani, H. Shahverdi, M. Nili Ahmadabadi,
Volume 16, Issue 1 (3-2019)
Abstract
One-step and two-step annealing techniques were used to examine the relationship between microstructure and mechanical properties during compression tests in iron-based ribbons and nanostructured 1- and 2.5mm cylindrical rods. The X-ray diffraction, microstructural, and mechanical results showed that substituting Nb for Fe had a minor effect on glass-forming ability but increased the formability index. The novel two-step annealing process resulted in a remarkable formability index of 16.62 GPa, yield stress of 2830 MPa, ultimate strength of 3866 MPa, and 4.3% plastic strain. A ductile nanosized α-Fe framework and boron-containing nano precipitations, which caused Zener pinning effect, were responsible for these novel mechanical properties.
J. Ngoret, V. Kommula,
Volume 16, Issue 1 (3-2019)
Abstract
This paper investigates premature failure of High Pressure (HP) PT6A-114A Compressor Turbine (CT) blades used for short-haul aircraft fleet at 6378 hours, contrary to 10000 hours pre-set by the manufacturer. The CT blades were sectioned both transversely and longitudinally and subjected to several microstructural examinations; X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Energy Dispersive Spectroscopy-Scanning Electron Microscopy (EDS-SEM) of the tips, airfoils, as well as the bases. It was observed that from repeated elevated heating, incomplete solutioning and recrystallization of the substrate material, brittle carbides were initiated and developed. The tips were more affected, followed by the airfoils and least at the bases. Impingement of heat from the combustors on the CT blades led to rapid graining and rafting with eventual cracking upon cooling. The results further suggested that pores which are typically manufacturing defects were pronounced at the bases than either at the airfoils and the tips. However, contrary to the expectation that the bases would degrade more and rapider, a more near uniform distribution of the cuboidal phase was evident relative to the tips and airfoils, confirming that degradation of the CT blades originated from creep and fatigue.
A. Bahrami, M. R. Hosseini, F. Kazemi, S. Kheiri, M. Bakhshi, M. H. Rahimi,
Volume 16, Issue 1 (3-2019)
Abstract
Petroleum coke contains high amounts of carbon and is used in the manufacturing of anode electrodes for the aluminum extraction. In the process of aluminum production, some particles separate from anodes as waste which contain petroleum coke. Therefore, recycling and processing of these petroleum coke particles is the subject of this study. The ash content reduced to 31% and 13% in the jig and shaking table concentrate, respectively. These two steps were considered as the pre-processing methods and heavy media separation was used to decrease the ash content much more. Finally, flotation was performed in order to purify the particles with the size of less than one millimeter.
