Iranian Journal of Materials Science and Engineering

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The Nano Hydroxyapatite (HAp), HAp/PEG and HAp/PVP powders derived from both Gastropod shell (natural source) and chemical precursor by the precipitation method were characterized through various characterization techniques such as FT-IR, XRD, SEM-EDX, TEM, Antibacterial activity and SBF analysis. Based on the structural, chemical, morphological and biological characteristics, HAp/PVP from natural and chemical precursors have been compared successfully. Calculated structural parameters, crystallinity index, C/P ratio, morphology, antibacterial activity and SBF analysis of the products show that HAp/PVP-S (derived from a natural source) exhibits good mechanical property, rod like morphology, good antibacterial activity and apatite formation ability at 14 days. EDX analysis also shows the presence of carbon and sodium in HAp/PVP-S. Comparative analysis reveals that characteristics of HAp/PVP-S such as high carbonate content, low crystallite size, poor crystalline nature, presence of trace metal, non-stoichiometric elemental composition and rod like crystals which are matched with the characteristics of biological apatite. Thus, the HAp/PVP-S has the ability to form bone apatite.

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In the present study, the early stages of the surface oxidation and fluoridation of liquid AZ91D and AM60B alloys under ultra-high purity (UHP) argon, dry air, and air mixed with two different protective fluorine-bearing gases were studied. The chemical composition, morphology and thickness of the surface films formed inside the trapped bubbles were characterized by SEM and EDS analyses. It is found that the molten AM60B alloy is more sensitive to impurities under UHP argon gas than AZ91D alloy. Under dry air atmosphere, the entire surface of molten AZ91D alloy is covered with an oxide layer and thinner thickness than the surface film formed on AM60B alloy which has a rough surface exhibiting granular growth in later stages of oxidation. The EDS analyses show that film chemistry is mainly composed of Mg, Al, and O elements. Under fluorine-bearing gas/air mixtures with either SF₆ or HFC-R134a at 3.5%vol., a fresh surface film formed with a flat and dense morphology of a uniform thickness composed of mixed Mg, F, Al, and O elements. It is observed that there is a lower O:F intensity ratio in the surface film formed on the molten AZ91D alloy under 1,1,1,2-tetra-fluoroethane (HFC-R134a) mixed with dry air compared to the AM60B alloy under both air/ R134a and air/SF₆ mixtures which shows a higher fluorine concentration in the surface film a leading to a better oxidation resistance .

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The work reported in this paper was focused on the investigation of surface morphological, microstructural, and optical features of polycrystalline BaTiO₃ thin film deposited on p-type Si < 100 > substrate using e-beam PVD (physical vapor deposition) technique. The influence of annealing over the surface morphology of the thin film was analyzed by X-ray diffraction, atomic force microscopy and scanning electron microscopy characterization methods. When the annealing temperature was increased from as-deposited to 800 °C there was a significant growth in the grain size from 28.407 nm to 37.89 nm. This granular growth of BaTiO₃ made the thin film appropriate for nanoelectronic device applications. The roughness of the annealed film got increased from 31.5 nm to 52.8 nm with the annealing temperature. The optical bandgap was computed using Kubelka-Munk (KM) method which got reduced from 3.93 eV to 3.87 eV for the as-deposited to the 800 °C annealed film. The above reported properties made the annealed film suitable for optoelectronic applications. For polycrystalline BaTiO₃ thin film the refractive index varied from 2.2 to 1.98 from 400 to 500 nm and it was 2.05 at 550 nm wavelength. The broad peaks in Raman spectra indicated the polycrystalline nature of the thin film. It had been also observed that with the annealing temperature the intensity of the Raman bands got increased. From these results, it was proved that annealing significantly improved the crystallinity, microstructural, surface morphological and optical features of the barium titanate thin film which made it suitable as sensors in biomedical applications as it is cost-effective, lead-free and environment friendly material.

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A full factorial design of experiment was applied running 36 experiments to investigate the effects of milling parameters including cutting speed with three levels of 62.83, 94.24 and 125.66 m/min, feed rate with three levels of 0.1, 0.2 and 0.3 mm/tooth, cutting depth with two levels of 0.5 and 1 mm and machining media with two levels, on surface integration properties of magnesium AZ91C alloy such as grain size, secondary phase percent, surface microhardness and surface roughness. In all cases, a fine grained surface with higher secondary phase sediment and microhardness obtained comparing the raw material. According to analysis of variance results, the most effective parameter on grain size, secondary phase percent and microhardness was cutting depth and the most effective parameter on surface roughness was feed rate. although the grain size in all machined samples was smaller than that of the raw material but due to the dual effect of cryogenic conditions, which both cool and lubricate and reduce the temperature and strain rate at the same time, the direct effect of this parameter on grain size was not significant. Also, the all interaction effects of parameters on grain size and microhardness were significant.

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The low velocity impact (LVI) response of pure and glass fiber reinforced polymer composites (GFRP) with 0.1, 0.3 and 0.5 wt% of functionalized single-walled carbon nanotubes (SWCNTs) was experimentally investigated. LS-DYNA simulation was used to model the impact test of pure and incorporated GFRP with 0.3 wt% of SWCNT in order to compare experimental and numerical results of LVI tests. All tests were performed in two different levels of energy. In 30J energy, the specimen containing 0.5 wt% SWCNT was completely destructed. The results showed that the incorporated GFRP with 0.3 wt% SWCNT has the highest energy absorption and the back-face damage area of this sample was smaller than other specimens. TEM images from specimens were also analyzed and showed the incorporation of well-dispersed 0.1 and 0.3 wt% of SWCNT, while in specimens containing 0.5 wt% of CNT, tubes tended to be agglomerated which caused a drop in LVI response of the specimen. The contact time of impactor in numerical and experimental results was approximately equal; however, the maximum contact forces in LS DYNA simulation results were higher than the experimental results which could be due to the fact that in the numerical modeling, properties are considered ideal, unlike in experimental conditions.

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Friction-Stir Processing (FSP) was applied on AA1050 Aluminum Alloy (AA) to find the highest mechanical properties among 28 combinations of the rotational and traverse speed (800-2000 rpm and 50-200 mm.min^-1) and four different tool probe shapes (threaded, columnar, square and triangle). To this aim, the AA standard sheet went through a single pass of FSP. The 1600 rpm and 100 mm.min^-1 with threaded tool probe was chosen as the best combination of rotational and traverse speed. Grain size at the Stirred Zone (SZ) was studied using Optical Microscopy (OM). The results showed that the SZ’s grain size was refined from 30 μm down to about 12 μm due to dynamic recrystallization during FSP. The processed sample exhibited improved hardness, yield stress, ultimate tensile strength, elongation up to 65, 80, 66, and 14%, respectively, compared to the annealed AA sample. Studying fractographic features by OM and field emission scanning electron microscope (FESEM) revealed a dominantly ductile fracture behavior.

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Residual stress measurement is of utmost importance for the safety and reliability of engineering components and has been an active area of scientific research. Relaxation techniques such as hole drilling, slitting and ring core method are widely applied semi destructive techniques for residual stress measurements in polymer composites. This article reviews the recent literature on the measurement of residual stress in polymer composite by employing the above-mentioned relaxation techniques. This article summarizes the categories of residual stresses, causes of formation, techniques of measurements and also briefly outlines the chronological developments of the Hole drilling and slitting method. The article also provides a comparative summary of these relaxation methods.

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Porous nanostructured SnO₂ with a sheet-like morphology was synthesized through a simple green substrate-free gelatin-assisted calcination process using Tin tetracholoride pentahydrate as the SnO₂ precursor and porcine gelatin as the template. Crystalline phase, morphology, microstructure, and optical characteristics of the as-prepared material were also investigated at different calcination temperatures using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-visible absorption, and Photoluminescence spectroscopy (PL), respectively. XRD patterns of all the samples revealed the presence of a tetragonal crystalline structure with no other crystalline phases. Moreover, the synthesized hierarchical sheets assembled with nanoparticles displayed a large surface area and porous nanostructure. The calculated optical band gap energy varied from 2.62 to 2.87 eV depending on the calcination temperature. Finally, photoluminescence spectra indicated that the nanostructured SnO₂ could exhibit an intensive UV-violet luminescence emission at 396 nm, with shoulders at 374, violet emission peaks at 405 and 414 nm, blue-green emission peak at 486 nm, green emission peak at 534 nm and orange emission peak at 628 nm.

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Indium tin oxide (ITO) nanoparticles were synthesized by green combustion method using indium (In) and tin (Sn) as precursors, and Carica papaya seed extract as novel fuel. This paper highlights effect of tin concentration (5%, 10% and 50%) on microstructural, optical and electrical properties of ITO nanoparticles (NPs). The indium nitrate and tin nitrate solution along with the fuel were heated at 600 °C for 1 h in muffle furnace and obtained powder was calcinated at 650 °C for 3 h to produce ITO NPs. The above properties were investigated using XRD, FTIR, UV-Vis spectroscopy, SEM, TEM and computer controlled impedance analyser. The XRD, SEM and TEM investigations reveals the synthesized NPs were spherical in shape with an increase in average grain size (17.66 to 35 nm) as Sn concentration increases. FTIR investigations confirms the In-O bonding. The optical properties results revealed that the ITO NPs band gap decreased from 3.21 to 2.98 eV with increase in Sn concentration. The ac conductivity of ITO NPs was found to increase with increase in Sn concentration. These synthesised ITO NPs showed the excellent properties for emerging sensor and optical device application.

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The energy release rate for delamination in a laminated composite is supposed to be the material property being considered as independent of non-material property variables. However, Mode I fracture toughness(G_I) is found to vary with lamina arrangement, geometrical dimensions, and process-induced stresses.  In this investigation, the influence of lamina stacking arrangement on process-induced stresses and their effects on G_I of laminated composites are studied. Unidirectional (UD) ([0]₁₆) and cross-ply ([90₂/0₆]s, [90₄/0₄]s and [90₆/0₂]s) Glass/ epoxy (GE) composites with the delamination plane at 0◦//0◦ were prepared by manual layup method and post-cured at 120 °C for 4 hours. G_I of composite laminates were experimentally determined using a double cantilever beam(DCB) specimen as per ASTM D 5528. The slitting method was applied to determine the Process-induced stresses in GE laminates. The stacking sequence of laminas was found to have a noticeable effect on the state of residual stresses and G_I of GE laminates. Residual stresses do not have much influence on the G_I for delamination initiation, whereas G_I  for the crack propagation was found to increase with a gradual increase in compressive residual stresses in GE laminates.

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In the present study, the effects of boron on the structural and magnetic properties of AlCrFeNiMnSiB_x high entropy alloys (HEAs) were investigated. In this regards, different percentages of boron element were added to the based composition and the samples were identified using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Based on results, the tendency of Si element to formation of silicide phases prevents from the stabilization of single FCC and BCC solid solution phases in AlCrFeNiMnSi alloy. The boron element has significant effects on destabilization of silicide phases and by increasing in the percentage of this element, the simple BCC solid solution phase has been dominate phase. Of course, boron has distractive effects on magnetic properties of prepared alloys and the saturation of magnetization of AlCrFeNiMnSiB_x HEAs decrease from 29.8 emu/g to about 6 emu/g by increasing the boron content.  

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Recently, using calcium phosphates and at the top of them, hydroxyapatite (HA) has been considered in medical and dental applications as an artificial biomaterial due to their chemical and structural similarity to the bodychr('39')s skeletal tissues such as bone and tooth. Because of reinforcement of hydroxyapatitechr('39')s mechanical and biological properties by substitution of OH- groups by F- ions to produce fluorapaptite (FA) has been proven, in this article synthesis methods, properties and medical applications of fluorapatite and its pros and cons in comparison with hydroxyapatite have been reviewed.

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Neoplastic cells have co-opted inflammatory receptors and signaling molecules that potentiate inflammation. Activated inflammatory pathways lead to neo-angiogenesis, lymph-angiogenesis, immunosuppression, tumor growth, proliferation and metastasis. This cancer-sustaining inflammation is a critical target to arrest cancer growth. Multiple drug resistance, high cost, low oral bioavailability and serious side effects have rendered conventional cytotoxic chemotherapeutics less impressive. The aim of this research was to achieve cancer debulking and proliferation prevention by limiting ‘cancer-sustaining’ tumor niche inflammation through non-conventional oral approach employing anti-inflammatory agents and avoiding conventional cytotoxic agents. Synergistic anti-inflammatory agents, i.e. celecoxib as selective COX-2 inhibitor and montelukast as cysteinyl leukotriene receptor antagonist, were selected. Silver nanoparticles (AgNPs) were used as nanocarriers because of their efficient synergistic anti-neoplastic effects and excellent oral drug delivery potential. Specifically, selected drugs were co-conjugated onto AgNPs. Synthesized nanoparticles were then surface-modified with poly(vinyl alcohol) to control particle size, avoid opsonization/preferred cellular uptake and improve dispersion. Surface plasmon resonance analysis, particle size analysis, DSC, TGA, XRD, FTIR and LIBS analysis confirmed the successful conjugation of drugs and efficient polymer coating with high loading efficiency. In-vitro, the nanoparticles manifested best and sustained release in moderately acidic (pH 4.5) milieu enabling passive tumor targeting potential. In-vivo, synthesized nanoparticles exhibited efficient dose-dependent anti-inflammatory activity reducing the dose up to 25-fold. The formulation also manifested hemo-compatibility, potent anti-denaturation activity and dose-dependent in-vitro and in-vivo anti-cancer potential against MCF-7 breast cancer and Hep-G2 liver cancer cell lines in both orthotopic and subcutaneous xenograft cancer models. The anti-inflammatory nanoparticles manifested tumor specific release potential exhibiting selective cytotoxicity at cancerous milieu with slightly acidic environment and activated inflammatory pathways. The formulation displayed impressive oral bioavailability, sustained release, negligible cytotoxicity against THLE-2 normal human hepatocytes, low toxicity (high LD₅₀) and wide therapeutic window. Results suggest promise of developed nanomaterials as hemo-compatible, potent, cheaper, less-toxic oral anti-inflammatory and non-conventional anti-cancer agents.

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The present study aimed to assess the effect of replacing copper as a multi-functional ingredient in the brake pad material with potassium titanate platelet (PTP) and a particular type of ceramic fiber (CF) copper-free composite. Chase dynamometer tests were conducted to compare a brake padchr('39')s tribological behavior when PTP and CF are added to the composition with that of the copper-bearing pad. The results concluded that PTP and CF demonstrated promising outcomes such as a stable coefficient of friction (COF), lower wear rate, and better heat resistance in copper-free friction composite. Scanning electron microscope (SEM/EDS) analysis was conducted to investigate the role of main elements such as Ti, Fe, K, O, and C on the formation of contact plateaus (CPs) upon the worn surface of friction composites. PTP maintained both continuous contact and smooth friction braking application of a brake pad. The uniform distribution of Ti on the wear track on the disc worn surface depicts the role of PTPs on stabilizing the friction film formation and eventually on the stability of COF.

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The goal of the present study is to prepare a room temperature cured hydrophobic and self-cleaning nano-coating for power line insulators. As a result, the installed insulators operating in power lines can be coated without being removed from the circuit and without the need to cut off power. For this purpose, hydrophobic silica nanoparticles were synthesized by sol-gel method using TEOS and HMDS. The synthesized hydrophobic silica nanoparticles were characterized by XRD, FTIR, SEM, and TEM analyses to investigate phase formation, particle size, and morphology. Then the surface of the insulator was cleaned and sprayed by Ultimeg binder solution, an air-dried insulating coating, as the base coating. Then the hydrophobic nano-silica powder was sprayed on the binder coated surface and left to be air-cured at room temperature. After drying the coating, the contact angle was measured to be 149^o. Pull-off test was used to check the adhesion strength of the hydrophobic coating to the base insulator. To evaluate the effect of environmental factors, UV resistance and fog-salt corrosion tests were conducted. The results showed that 150 hours of UV radiation, equivalent to 9 months of placing the samples in normal conditions, did not have any significant effect on reducing the hydrophobicity of the applied coatings.