Iranian Journal of Materials Science and Engineering

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Ultraviolet–Visible (UV–Vis) spectroscopy was used, in the current investigation, to explore the dispersion and stability of titania nanoparticles in an aqueous media with different types of dispersants. Hydrochloric and nitric acids as well as ammonia were used to determine the stability of the suspension in the acidic region (pH=2.5) and basic area (pH=9.5), respectively. In addition, for measuring sustainability of suspension and creating steric, and electrosteric repulsive forces, ethylene glycol and ethylene glycol plus ammonia were employed, respectively. UV–V is
spectrometry was applied to realize the effect of nano titania concentrations and different types of dispersants of samples containing different amounts of nano titania and different types of dispersants on stability of TiO2-containing suspensions. In addition, the stability of dispersion could be evaluated in colloidal mixtures containing ethylene glycol plus ammonia. It was demonstrated that the mixtures containing ethylene glycol plus ammonia were stable over a period of 4 days. To support the UV–Vis results, other techniques such as atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to study the degree of agglomeration of titania nanoparticles in terms ofmorphology and size.

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Abstract: Nickel was electrodeposited onto copper substrates with high {111} and {400} peak intensities. The grain size of coatings deposited onto the copper substrate with a higher {111} peak intensity was finer. Spheroidized pyramid morphology was obtained at low current densities on both copper substrates. By increasing the deposition current density, grain size of the coating was increased for both substrates and eventually a mixed morphology of pyramids and blocks was appeared without further increase in grain size. This decreased the anodic exchange current density probably due to the decrease of surface roughness and led to a lower corrosion rate.

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C-SiC composites with carbon-based mesocarbon microbeads (MCMB) preforms are new type of highpreformance and high-temperature structural materials for aerospace applications. In this study MCMB-SiC composites with high density (2.41 g.cm-3) and high bending strength (210 MPa,) was prepared by cold isostatic press of mixed mesophase carbon powder derived from mesophase pitch with different amount (0, 2.5, 5%) nano SiC particles. All samples were carbonized under graphite bed until 1000 °C and finally liquid silicon infiltration (LSI). Microstructure observations resultant samples were performed by scanning electron microscopy and transition electron microscopy (SEM & TEM). Density, porosity and bending strength of final samples were also measured and calculated. Results indicates that the density of samples with nano additive increased significantly in compare to the free nano additives samples.

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Yellow-colored nitrogen doped TiO2 photocatalyst and a pure TiO2 powder were synthesized via sol-gel method using TiCl4 and urea as raw materials. However, the synthesis procedure for nitrogen doped TiO2 was catalyzed by acid that dialed with controlled precipitation and slow nucleation. According to XRD analysis, the nitrogen doped TiO2 consisted of anatase phase of titania which was a significant achievement regarding its possible photocatalytic applications. The band gaps of nitrogen doped TiO2 and pure TiO2 were estimated from UV-Vis spectroscopy data to be 2.8 and 3.3 ev, respectively. Photocatalytic properties of the nitrogen doped TiO2 nanocatalyst and pure TiO2 were compared for degradation of crystal violet dye in visible light irradiation. In comparison to pure TiO2, nitrogen doped TiO2 showed superior photocatalytic efficiency towards the dye.

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Abstract:Nanostructured titania was synthesized by colloidal and polymeric sol-gel routes. Stable colloidal and polymeric titania sols were prepared by adjusting the proper values of the acid/alkoxide and the water/alkoxide molar ratios. The properties of sols were determined by dynamic light scattering technique and synthesized titania was characterized by thermogravimetry and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, optical microscopy and field emission scanning electron microscopy. The results showed particle size distribution of colloidal sol 10-50 nm compared to polymeric one which was 0.5-2 nm. Phase analysis of the colloidal sample revealed anatase as the major phase up to 550 °C, while the polymeric route resulted only anatase phase up to 750 °C. On the basis of results, titania prepared by the polymeric route showed better thermal stability against phase transformation than the sample prepared by the colloidal route. Also, microstructural studies showed that titania nanopowder can be produced by both sol-gel routes

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In the present study, bioceramic composites based hydroxyapatite (HAp) reinforced with carbon nanotubes (CNTs) was synthesized via sol-gel technique. The dried gels were individually heated at a rate of 5°C/min up to 600°C for 2 h in a muffle furnace in order to obtain HAp-MWCNTs mixed powder. Composites were characterized by XRD, FT-IR, SEM, TEM/SAED/EDX and Raman spectroscopy techniques. Results showed the synthesis of HAp particles in the MWCNTs sol which was prepared in advance, leads to an excellent dispersion of MWCNTs in HAp matrix. Apparent average size of crystallites increased by increasing the percentage of MWCNTs. The average crystallite size of samples (at 600°C), estimated by Scherrer’s equation was found to be ~50-60 nm and was confirmed by TEM. MWCNTs kept their cylindrical graphitic structure in composites and pinned and fastened HAp by the formation of hooks and bridges.

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Abstract:In recent years, there have been many attempts to improve the properties of dental amalgam. The aim of the present investigation was fabrication and characterization of dental amalgams containing TiO2 nanoparticles and evaluation of their compressive strength, antibacterial and corrosion behavior. In this experimental research, TiO2 nanoparticles (TiO2 NPs) were added to reference amalgam alloy powder and then, dental amalgam was prepared. In order to investigate the effect of TiO2 NPs on properties of dental amalgam, 0, 0.5, 1, 2 and 3 wt. % of TiO2 NPs were added to amalgam alloy powder and the prepared composite powder was triturated by a given percent of mercury. Xray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) techniques were used to characterize the prepared specimens. Potentiodynamic polarization corrosion tests were performed in the Normal Saline (0.9 wt. % NaCl) Solutions as electrolytes at 37°C. The results showed that the corrosion behavior of the dental amalgam with 0.5 or 1 wt. % TiO2 NPs is similar to the corrosion behavior of the reference amalgam, while with increasing the weight percent of TiO2 NPs, the corrosion rate increases. Also, the results of this investigation indicated that adding TiO2 NPs in amounts of up to 1 wt. % to amalgam alloy powder improve compressive strength of dental amalgam and has no destructive influence on its corrosion behavior. As well as, according to antibacterial results, TiO2 NPs can increase the biocompatibility and antibacterial activity of dental amalgam. The results of present study suggest that amalgam/ TiO2 NPs nanocomposite with 1% of TiO2 NPs could be regarded as a biocompatible and bioactive dental material that provide better characters for dental applications.

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Ni and Cu elemental powder mixtures containing 25, 50, and 75% at Cu were subjected to mechanical alloying in a planetary ball mill under various milling times. Structural evolution was analyzed by means of X-ray diffraction and scanning electron microscopy. Experimental results indicated that nanostructured solid solution alloy powders having homogeneous distribution of Ni and Cu were formed by milling-induced interdiffusion of the elements. Average crystallite size of the as-milled powders was decreased with increasing Ni content and milling duration, and found to be in the order of 15-40 nm after 30 h of milling for all powder compositions. Moreover, lattice parameter and lattice strain of solid solutions were increased with the time of MA, which was more intense for nickel-rich alloys

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Mono dispersed nano SiC particles with spherical morphology were synthesized in this project by hydrolysis and condensation mechanism during sol gel processing. pH, temperature and precursor’s ratio considered as the main parameters which could influence particles size. According to DLS test results, the smallest size of particles in the sol (<5nm) was obtained at pH<4. It can be observed from rheology test results optimum temperature for achieving nanometeric gel is about 60 ˚C. The optimum pH values for sol stabilization was (2-5) determined by zeta potentiometery. Si 29NMR analysis was used in order to get more details on final structure of gel powders resulted from initial sol. X-ray diffraction studies showed sythesized powder consists of β-SiC phase. Scanning electron microscopy indicated agglomerates size in β-SiC synthesis is less than 100 nm. Finally, TEM studies revealed morphology of β-SiC particles treated in 1500˚C and after 1hr aging is spherical with (20-30) nm size

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Accumulative roll-bonding process (ARB) is an important severe plastic deformation technique for production of the ultrafine grained, nanostructured and nanocomposite materials in the form of plates and sheets. In the present work, this process used for manufacturing Al/SiO 2 nanocomposites by using Aluminum 1050 alloy sheets and nano sized SiO 2 particles, at ambient temperature. After 8 cycles of ARB process, the tribological properties and wear resistance of produced nanocomposites were investigated. The wear tests by abrasion were performed in a pinon-disc tribometer. Results show that by increasing ARB cycles and the amount of nano powders, the friction coefficient of produced nanocomposites decreases.

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The conical nanostructure improves the applications of alumina membranes and provides three dimensional nanometer scale systems to study the chemical and physical properties. In this study, the nano cone structure is produced in porous anodic alumina (PAA) by two-step anodizing. This conical nanostructure will improve the application of PAA membranes. This approach is novel generation of the so-called "gradually decreased voltage" technique, in which the voltage- time curve is divided into three stages and the effect of each step is investigated for different electrolytes. The effect of the decreasing voltage is examined in two types of electrolytes oxalic and phosphoric acid with a constant decrease in voltage rate. The results of SEM, FE-SEM images show the slope of the inner cone layer in the oxalic acid to be considerably larger compared with phosphoric acid.

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The synthesis of mesoporous CuFe2O4 spinel by several nanocasting strategies (i.e., multi-step nanocasting, one step nanocasting, modified solid-liquid), in which copper and iron nitrates are used as precursors and Pluronic P123 as surfactant, is explored. We have also checked the effect of pH, citric acid and sodium citrate in multi-step nanocasting method. The modified solid-liquid method which contains impregnating mesoporous silica by molten state salts in a non-ionic solvent seems to be the best choice to obtain single phase ordered mesoporous copper ferrite. Other methods suffer from the presence of copper oxide or hematite as impurities or lack of integrity in the mesoporous structure. Increasing pH up to 9.5 does not enhance the phase formation inside the pores of the silica matrix. The citric acid yields a fine structure but does not facilitate the phase formation. Adding sodium citrate neither heals the phase formation nor the structure of the final product. Moreover, vinyl- functionalized mesoporous silica exploited in this study as a hard template entraps both metal nitrates in the pores, assisting impregnation procedure

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Ni-P Electroless coatings provide appropriate resistance to wear and corrosion. Co-deposition of particles between layers can improve their properties, especially general corrosion and erosion-corrosion behavior by means of nano diamond as reinforcing particles. In this study Ni-P/nano diamond composite deposition were deposited on steel substrate. Structure of the coatings and corrosion resistance of theme were investigated by scanning electron microscopy and corrosion tests in salty media. The composite structure of the deposit was evaluated as nano size without using any surfactants. Also results for the composite coating show better corrosion protection and higher hardness comparing with as -deposited Ni-P. The optimum concentration of diamond nanometer particles were found by evaluation of scanning electron microscopy pictures, hardness measurement, linear polarization and electrochemical impedance spectroscopy results

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Well crystallized pure calcium zirconate (CaZrO3 ) nanopowder was successfully synthesized using the molten-salt method. CaCl2 , Na 2CO3, micro-ZrO 2and nano-ZrO 2 were used as starting materials. On heating, Na2CO3 reacted with CaCl 2to form NaCl and CaCO 3. Nano CaZrO 3 was formed by reacting equimolar amounts of in situformed CaCO 3 (or CaO) and ZrO 2 in molten Na 2CO3-NaCl eutectic mixture. CaZrO 3 particle size and synthesis temparture was tailored as a function of ZrO 2particle size. Due to the usage of nano-ZrO 2 , the molten salt synthesis (MSS) temperature was decreased and possible impurity phases in the final product were suppressed. The synthesis temperature was lowered to 800°C and soaking time of the optimal synthesis condition was reduced to 3h. After washing with hot-distilled water, the n-ZrO2sample heated at 800°C for 3h, was single phase CaZrO 3with 70-90 nm in particle size, while the m-ZrO 2sample heated at 1000°C for 3h, was single phase CaZrO 3 with 250-400 nm in particle size. Based on the TEM observation and thermodynamic analysis, the synthesized CaZrO 3 grains retained the morphology of the ZrO2 nanopowders, which indicated that a template formation mechanism play a dominant role in synthesis process

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Silver nanoparticles are being given considerable attention because of their interesting properties and potential applications. One such exploitable use is as the major constituent of conductive inks and pastes used for printing various electronic components. This paper presents a novel direct-writing process for fabrication of the first deposited silver nanoparticles (AgNPs) (50-200nm) electrode via a thermal inkjet printer. In this method, AgNPs were chemically deposited by ejection of ascorbic acid and silver nitrate solutions onto different substrates such as paper and textile fabrics. Silver deposited patterns were used as electrodes in different electrochemical experiments and their morphology was also investigated in SEM observations. The highest conductivity of deposited electrodes obtained on paper as the substrate was found to be around 5.54x105 S/m. Inkjet fabricated electrodes exhibited acceptable electrochemical behavior in experiments designed for measuring the concentration of hydrogen peroxide as a fundamental procedure for early determination of glucose. This novel inkjet silver deposition technique is introduced to be considered as a promising method for ultimate single step fabrication of different electrochemical bio-sensors.

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Achieving extreme hardness in the newly synthetic steel formed by converting from initial amorphous state to subse-quent crystalline structure –named as devitrification process- was studied in this research work. Results of TEM observa-tions and XRD tests showed that crystallized microstructure were made up four different nano-scale phases i.e., α-Fe, Fe 36 Cr12 Mo10 , Fe 3 C and Fe3 B. More, Vickers hardness testing revealed a maximum hardness of 18.6 GPa which is signifi-cantly harder than existing hardmetals. Detailed kinetic and structural studies have been proof that two key factors were contributed to achieve this extreme hardness supersaturation of transition metal alloying elements (especially Nb) and also reduction in the structure to the nano-size crystals.

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B4C and its composites with TiB2 as second phase continues to be extensively used as the preferred ceramic material in military applications as armor systems for absorbing and dissipating kinetic energy from high velocity projectiles. It also exhibits a high melting point (2427 °C), and high neutron absorption cross section. Pressureless sintering of the B 4C-nanoTiB2 nanocomposite using small amount of Fe and Ni (≤3 Wt%) as sintering aids was investigated in order to clarify the role of Fe and Ni additions on the mechanical and microstructural properties of B4C-nanoTiB2 nanocomposites. Different amount of Fe and Ni, mainly 1 to 3 Wt% were added to the base material. Pressureless sintering was conducted at 2175, 2225 and 2300 °C. It was found that Addition of 3 Wt% Fe and 3 wt% Ni and sintering at 2300 °C resulted in improving the density of the samples to about 99% of theoretical density. The nanocomposite samples exhibited high density, hardness, and microstructural uniformity.

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Coating of a surface by droplet spreading plays an important role in many novas industrial processes, such as plasma spray coating, ink jet printing, nano safeguard coatings and nano self-assembling. Data analysis of nano and micro droplet spreading can be widely used to predict and optimize coating processes. In this article, we want to select the most appropriate statistical distribution for spread data of aluminum oxide splats reinforced with carbon nanotubes. For this purpose a large class of probability models including generalized exponential (GE), Burr X (BX), Weibull (W), Burr III (BIII) distributions are fitted to data. The performance of the distributions are estimated using several statistical criteria, namely , Akaike Information Criterion (AIC), Baysian Information Criterion (BIC), LogLikelihood (LL) and Kolmogorove-Smirnove distance. Also, the fitted plots of probability distribution function and quantile-quantile (q-q) plots are used to verify the results of different criteria. An important implication of the present study is that the GE distribution function, in contrast to other distributions, may describe more appropriately in these datasets.

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High energetic aluminum nanoparticles are mainly used as additive in solid rocket propellants. However, fabrication of these aluminized energetic materials is associated with decreasing the burning rate of propellants due to problems such as oxidation and agglomeration of nanoparticles. In this study, to improve combustion performance of aluminum nanoparticles, coating by metallic Ni shell was studied. Nickel coating of aluminum nanoparticles was performed through electroless deposition (ED) subsequently, morphology and chemical composition of Ni-coated nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). These studies show that a uniform Ni layer with a thickness of 10nm is coated on the surface of Al nanoparticles. Thermal analysis of uncoated and Ni-coated aluminum nanoparticles was done using differential thermal analysis (DTA) and thermo gravimetric analysis (TGA). The results of thermal analysis indicate that, coating the aluminum particles by Ni, leads to improvement in combustion performance of aluminum nanoparticles through decreasing critical ignition temperature, ignition delay time of the nanoparticles and promoting the ignition by exothermic chemical reactions between Al and Ni

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A method for producing high surface area nano-sized mesoporous alumina from inexpensive Iranian kaolin as raw material is proposed. In this method, first, kaolin was purified for purifying Kaolin, High Grade Magnetic Separation and leaching with HCl and chemical bleaching treatment by using sodium dithionite (Na 2 S 2O4 ) as reducing agent in acidic media (H 2SO 4 ) were used. Purified kaolin was calcined. After that, Al (hydr) oxide from acid -leachates of calcined kaolin was precipitated with ammonia, in presence of polyethylene glycol. Finally, a white powder of nano-sized alumina particles was obtained after calcination. BET surface area, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize the sample. The resulting alumina with relatively high surface area (201.53 m 2 g -1 ) and narrow mean pore diameter (6.91 nm), consists of a particle size distribution ranging from 22 to 36 nm.