Iranian Journal of Materials Science and Engineering

Effect of Chemical Composition on Microstructure and Hydrophobic Properties of SiO2-TiO2@PDMS Coating

amirreza Sazvar

We report a simple and practical approach for the easy production of superhydrophobic coatings based on TiO₂-SiO₂@PDMS. In this study, we used tetraethylorthosilicate (TEOS) and titanium tetraisopropoxide (TTIP) as a precursor for the sol-gel synthesis of SiO₂ and TiO₂, respectively. Afterward, the surface of nanoparticles was modified by 1,1,1,3,3,3-hexamethyldisilazane (HMDS) before being combined with polydimethylsiloxane (PDMS). The hydrophobic property of coatings was evaluated by static contact angle measurements. The phase composition and structural evolution of the coatings were examined by X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis. It was shown that changing the weight ratio of the solution composition of the coating can affect the hydrophobicity of the surface. The best sample has shown a superhydrophobic property with a 153˚ contact angle which contained (75%TiO₂-25%SiO₂)and PDMS at a weight ratio of 1:1. Moreover, the results showed that the superhydrophobic coating retains its hydrophobic properties up to a temperature of 450 ˚C, and at higher temperatures, it converts to a super hydrophilic with a water contact angle close to 0 ˚. The SiO₂-TiO₂@PDMS coating degrades methylene blue by about 55% and was shown to be capable of photocatalytically decomposing organic pollutants.

Structural and Magnetic Characteristics of Fe72-xCoxCr28 (10
Mohammad loghman Estarki
In the present study, the structural and magnetic characteristics of Fe-Co-Cr system, with 28 at. % of Cr content, during casting, solutioning and thermo-magnetic treatment has been investigated. Based on results, the formation of single α-phase solid solution in the Fe_72-xCo_xCr₂₈ (10The Co content had negligible effects on magnetic characteristics of Fe₆₂Co₁₀Cr₂₈, Fe₆₀Co₁₂Cr₂₈ and Fe₅₈Co₁₄Cr₂₈ alloys. Fe_72-xCo_xCr₂₈(10 with a constant Cr content of about 28 at. %, were outside the miscibility gap in the equilibrium phase diagram, and therefore TMT had no effect on the final magnetic properties.

Tribological Performance of Self-lubricating Cast Al-5Cu-1Mg Nanocomposite Reinforced with Graphene Nano Sheets

Mohammad Alipour

This study was undertaken to investigate the influence of graphene nano sheets on the structural characteristics and dry sliding wear behaviour of Al-5Cu-1Mg aluminium alloy. The optimum amount of GNPs for proper grain refining was selected as 0.5 wt.%. T6 heat treatment was applied for all specimens before wear testing. Significant improvements in wear properties were obtained with the addition of GNPs combined with T6 heat treatment. Dry sliding wear performance of the alloy was examined in normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al-5Cu-1Mg aluminium alloy to the dry sliding wear. The results showed that dry sliding wear performance of without T6 microstructure specimens was a lower value than that of with T6 specimens.

Multicrystalline Silicon Passivation by Hydrogen and Oxygen- Rich Porous Silicon Layer for Photovoltaic Cells Applications

Aqeel Mohammed Hamoudi

In this work, we demonstrate the beneficial effect of introducing a superficial porous silicon layer on the electronic quality of multi-crystalline silicon for photovoltaic cell application. The porous silicon was formed using an acid vapor etching-based method. The porous silicon layer rich in hydrogen and oxygen formed by vapor etching is an excellent passivating agent for the mc-Si surface. Laser beam-induced current (LBIC) analysis of the exponentiation parameter (n) and surface current mapping demonstrates that oxygen and hydrogen-rich porous silicon led to excellent surface passivation with a strong electronic quality improvement of multi-crystalline silicon. It was found that the generated current of treated silicon by acid vapor etching-based method is 20 times greater as compared to the reference substrate, owing to recombination centers passivation of the grains and grain boundaries (GBs); The actual study revealed an apparent decrease in the recombination velocity of the minority carrier as reflected by 25% decrease in the exponentiation parameter (n) of the LBIC versus X-position measurements. These results make achieved porous silicon a good option for advancing efficient photovoltaic cells.

Optical and Gas Sensing Properties of Pr Doped TiO2 Thin Films

Perumal Perumal

In this research, praseodymium (Pr) doped titanium oxide was deposited onto a glass substrate by nebulizer spray pyrolysis technique. The rare earth-doped thin film was subjected to studies on structural, morphological, optical, and gas sensing properties. The structural properties of the deposited thin films exhibit varied texture along with (101) direction. The grain size of the thin film varies with various mole percentages of doped TiO₂ thin films. As various doping concentrations increase, the prepared thin films show different optical properties like band gap, extension coefficient, refractive index, and dielectric constant. Fourier transform infrared (FTIR) results revealed that the reflectance spectra conformed to the existence of functional groups and chemical bonding. Gas sensing studies were carried out for undoped and Pr-doped TiO₂ films. The sensor was exposed to ethanol gas. The response of a TiO₂ thin film at different ethanol concentrations and different operation temperatures was studied. The gas sensitivity of ethanol gas was measured when the fast response of the film with 0.004M Pr-doped TiO₂ thin film showed a response time of 99 s and recovery time of 41 s, as well as the resistance falling to 0.6x10⁶Ω. The sensor operated at maximum effectiveness at an optimum temperature of 200°C.

Influence of Friction Stir Processing Parameters on the Mechanical and Corrosion Properties of Al-Cu-Li Alloy

Vaira Vignesh Ramalingam

Novelty: Most of the open literature research has focused on the microstructural evolution and mechanical properties of AA2050 alloy. Also, a significant study discusses the corrosion behavior of AA2050 alloy based on immersion and electrochemical characteristics. The influence of heat treatment on the microstructure and mechanical properties of friction stir processed AA2050 alloy is scarcely discussed in the open literature. The hot salt corrosion characteristics of friction stir processed AA2050 seldom exists in the available literature. This study concentrates on microhardness, tensile strength, and corrosion properties of friction stir processed AA2050. Also, the work focuses on the influence of artificial aging on the microhardness, and tensile strength of the friction stir processed AA2050.

Magnetic Characteristics of Nanocrystalline Co78Zr17B2Si1W2 Alloy Formed by Melt Spinning and Subsequent Annealing

Majid Tavoosi

Investigation the structural and magnetic properties of nanocrystalline Co₇₈Zr₁₇B₂Si₁W₂ alloy during melt spinning and annealing processes were the main goal of this study. In this regard, samples were prepared using vacuum induction melting, melt spinning and subsequent annealing. The specimens were evaluated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Based on results, nanocrystalline Co₅Zr single phase with hard magnetic properties (Ms=29.5 emu/g and Hc=2.7 kOe) successfully formed during melt spinning process (at wheel speed of 40 m.s^-1). The coercivity value of rapid solidified sample increased to about 3.2 kOe during annealing process up to 400°C. However, more increasing in annealing temperature lead to the transformation of non-equilibrium magnetic Co₅Zr phase to stable Zr₂Co₁₁phase, which has distractive effects on final magnetic properties.

Acceleration of Bone-Implant Graft by Optimizing the Dimention and Crystalline Structure of Titanium, Oxide Nanotubes as the Titanium-Based Implant Coating

Milad Hooshyar

Titanium implants are one of the most durable and conventional orthopedic and dental implants. The goal of this research is to improve the bio-compatibility of these implants by implementing nano coating of titanium oxide nanotubes (TNT) to enhance bone graft on the implant surface, and reduction of wound healing duration and risk of implant surgery at the same time. For this purpose, the effects of dimension and atomic structure of titanium oxide nanotubes are examined on the surface properties and biological performance and tried to introduce an optimum status of this nano-tubular structure. TNTs were synthesized by anodizing method on the surface of titanium sheets. Dimensions of TNT can be controlled by anodizing process parameters. Heat treatment affects the atomic structure of TNTs. Contact angle measurement as one of the important surface properties was investigated on different dimensions and structures of TNTs, to study human blood's physical interaction with the implant surface. In addition, the quality and quantity of bone material sediment on the surface were examined by SBF test and SEM analysis. Finally, cell culture provided informative data on bone cells' response to these nanotubular coatings by analyzing MTT results and SEM photography of cells. As a result, the optimum dimension and atomic structure of TNTs were defined and the required process parameters were introduced to obtain this state. This setup can be used as an optimum state of TNT as a nano coating on titanium implant with orthopedic functions to enhance the cell adhesion and acquire the highest proliferation rate which means faster bone graft and shorter convalescence.

Effect of Poly(3-Hexylthiophene):Mixed Fullerene Indene-C60 Multi-Adducts Ratios on the Performance of Organic Solar Cells

Furqan Almyahi

In this study, poly(3-hexylthiophene) (P3HT) and fullerene Indene-C₆₀ multi-adducts (ICxA) were blended to create a formulation as a solution and thin films, which were prepared under ambient conditions. The optical properties of various compositional ratios were studied using UV-Visible absorbance and photoluminescence (Pl) measurements. The energy gaps of the prepared thin films and solutions were determined, and their values increased with increasing fullerene ratio because of the isolation of P3HT chains from their neighbors. Intensity ratio (I_C=C/I_C-C) with a small value in addition to a low value of full width at high maximum (FWHM) of Raman spectra are associated with increased conformation and high aggregation of composition. Furthermore, according to X-ray diffraction (XRD) results the 1:0.8 and 1:0.6 ratios have the largest crystallite sizes in comparison to the other ratios. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels for blends by electrochemical measurements were determined, which are sandwiched between those of the pure materials. In ambient conditions, binary organic photovoltaic cells (OPVs) at different ratios of the photoactive layer were evaluated. The device with a ratio of 1:0.6 had the best performance, with power conversion efficiency (PCE) of 1.21 %, open circuit voltage (V_OC) of 0.53 V, short circuit current density (J_SC) of 5.71 mA.cm^-2, and fill factor (FF) of 39.5 % at a small V_loss of 1.39 V.

The Effects of Rapid Solidification on the Microstructure and Mechanical Properties of Al5083

Maryam Salehi

In the present study, bulk refined-structured Al 5083 alloy with high mechanical properties was successfully fabricated by hot consolidation process of nanostructured melt- spun flakes. The influence of cooling rate and pressing conditions on the microstructure and mechanical properties of the alloy were investigated using X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), microhardness, and compression tests. Rapid solidification combined with the hot consolidation at T=753 K (480 °C) and P= 800 MPa for 20 min produced a bulk sample with the desirable bonding, good microhardness (184.2±12.4 HV), and high strength (273±8 MPa) combined with 7 pct. fracture strain. These amounts are 78.6±5.1 HV, 148 ±9 MPa and about 5 pct. for the as-cast sample. Microstructural refinement during the controlled consolidation of nanostructure rapidly- solidified flakes contributes to such high mechanical properties of the bulk sample.

Light-Emitting Diodes Based on Van Der Waals Heterostructures: a Review

Mohammad Jafar Molaei

The introduction of the 2D materials in recent years has resulted in an emerging type of the constructed structures called van der Waals heterostructures (vdWHs) that take advantage of the 2D materials in forming atomically thin components and devices. The vdWHs are constructed by the stacking of 2D materials by van der Waals interactions or edge covalent boning. The electron orbitals of the 2D layers in vdWHs extend to each other and influence the electronic band structures of the constituent layers. The tunable optical response over a wide range of the wavelengths (NIR to visible) can be obtained by assembling vdWHs through combining of the monolayers. By application of 2D layers in vdWHs, p-n heterojunctions without lattice mismatch can be formed. The photodiodes based on the van der Waals interactions could be considered as promising candidates for future optoelectronic devices. Furthermore, on-chip quantum optoelectronics can move to the next generation by using 2D materials in vdWHs. In this review, the vdWHs are introduced and their properties and applications in light-emitting diodes (LEDs) have been discussed. The vdWHs allow bandgap engineering, and hence, LEDs working in a range of the wavelengths can be realized. The applications of vdWHs in forming atomically thin components in optoelectronic devices and LEDs have been addressed.

Effect of Heat-Treatment Temperatures on Magnetite Oxidation in 20SiO2.50FeO.30CaO Glass Ceramic Prepared by the Sol-Gel Method

mohammad rezvani

Abstract
The effect of different heat-treatment temperatures on the magnetic, crystallization, and structural properties of 20SiO2.50FeO.30CaO (mol%) glass ceramics was studied. The initial glass was synthesized by the sol-gel method at 25℃ with a precursors to solvent ratio of 1/5. After aging the resulted gel for 24 h at room temperature, it was dried in an electric dryer at 110 ℃ . By heat treatment at different temperatures, different phases such as magnetite, maghemite, and hematite were crystallized in the glass. The maximum stability temperature of magnetite and maghemite were 360℃ and 440℃ respectively. By increasing the heat treatment temperature to higher than 440℃ , the oxidation of maghemite to hematite was occureds. The highest magnetization amount (1.9 emu/g) belonged to sample heat treated at 680℃ . By increasing the heat treatment temperature to 840℃ , the magnetization decreased to 0.8 emu/g, due to the oxidation of maghemite. By increasing the heat treatment temperature from 440℃ to 680℃ , crystalline size of maghemite was increased from 40 to 200 nm. By forther increment of temperature to 840℃ , the size of maghemite crystals decreased to 17nm, due to the oxidation of maghemite to hematite.
Abstract
The effect of different heat-treatment temperatures on the magnetic, crystallization, and structural properties of 20SiO2.50FeO.30CaO (mol%) glass ceramics was studied. The initial glass was synthesized by the sol-gel method at 25℃ with a precursors to solvent ratio of 1/5. After aging the resulted gel for 24 h at room temperature, it was dried in an electric dryer at 110 ℃ . By heat treatment at different temperatures, different phases such as magnetite, maghemite, and hematite were crystallized in the glass. The maximum stability temperature of magnetite and maghemite were 360℃ and 440℃ respectively. By increasing the heat treatment temperature to higher than 440℃ , the oxidation of maghemite to hematite was occureds. The highest magnetization amount (1.9 emu/g) belonged to sample heat treated at 680℃ . By increasing the heat treatment temperature to 840℃ , the magnetization decreased to 0.8 emu/g, due to the oxidation of maghemite. By increasing the heat treatment temperature from 440℃ to 680℃ , crystalline size of maghemite was increased from 40 to 200 nm. By forther increment of temperature to 840℃ , the size of maghemite crystals decreased to 17nm, due to the oxidation of maghemite to hematite.

Preparation and Characterization of P2O5 Containing Canasite Glass-Ceramics as Potential Materials for Dental Restorations

Sara Banijamali

Various analysis techniques were used to investigate the effects of P₂O₅ on the crystallization, mechanical features, and chemical resistance of canasite-based glass-ceramics. The results showed that canasite-type crystals were the primary crystalline phase in the examined glass-ceramics subjected to the two-step heat treatment, while fluorapatite was the secondary crystalline phase in some specimens. The microstructural observations by field emission electron microscope indicated that the randomly oriented interlocked blade-like canasite crystals decreased with an increase in the P₂O₅ content of the parent glasses. Among the examined glass-ceramics, the Base-P2 composition (containing 2 weight ratios of P₂O₅ in the glass) showed the most promising mechanical features (flexural strength of 176 MPa and fracture toughness of 2.9 MPa.m^1/2) and chemical resistance (solubility of 2568 µg/cm²). This glass-ceramic could be further considered as a core material for dental restorations.