Iranian Journal of Materials Science and Engineering

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The control of silicone rubber’s viscoelastic properties namely loss factor, storage and loss moduli during crosslinking are crucial as its malleable behaviour changes differently under different conditions and affecting the final product. Hence, it becomes the objective of this study to investigate the rheological behaviour of silicone rubber cured under different formulation ratios with platinum catalysts and triethylamine, methanol & ethanolamine solvent. Measurement was conducted for the silicone rubber to crosslinker ratios of 2.5:7.5, 5:5, 7.5:2.5 and 10:1 at different elevated temperatures, and for the silicone rubber with triethylamine, methanol and ethanolamine at different angular frequencies. While the crossover of storage and modulus curve which signifies a gel point was not observed at higher ratios of platinum used across the temperature range of 25 – 100°C, it was found at 89°C and 95°C with the formulation ratios of 10:1 and 7.5:2.5, respectively. On the other hand, the crossover point was observed for silicone rubber at 100 s^-1 for triethylamine, 3 s^-1 and 100 s^-1 for methanol, and 70 s^-1 alongside 290 s^-1 for ethanolamine. The presence of gel point indicates that crosslinking of silicone rubber successfully took place and this study proves that controlling the crosslinking behaviour was possible.

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Biocompatible ceramics, commonly known as “bioceramics”, are an extremely versatile class of materials with a wide range of applications in modern medicine. Given the inorganic nature and physico-mechanical properties of most bioceramics, which are relatively close to the mineral phase of bone, orthopedics and dentistry are the preferred areas of usage for such biomaterials. Another clinical field where bioceramics play an important role is oculo-orbital surgery, a highly cross- and interdisciplinary medical specialty addressing to the management of injured eye orbit, with particular focus on the repair of orbital bone fractures and/or the placement of orbital implants following removal of a diseased eye. In the latter case, orbital implants are not intended for bone repair but, being placed inside the ocular cavity, have to be biointegrated in soft ocular tissues. This article reviews the state of the art of currently-used bioceramics in orbital surgery, highlighting the current limitations and the promises for the future in this field.

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The optimization of biomaterials biodegradation rate similar to tissue regeneration, is one of the main
goals in the field of tissue engineering. However, the necessity to assess their possible toxicity is always considered.
The aim of this study was cytotoxicity and genotoxicity evaluation of fluorapatite/bioactive glass (FA/BG)
nanocomposite foams with two various weight ratios to determine the optimal composition. Nanocomposite foams
were made by gel-casting method with FA and BG as precursors in two weight ratios (A and B). Nanocomposite
foam extracts (CFEX) were prepared by shaking 100 mg/mL of each foam in a complete culture medium for 72 h in
a shaker incubator at 120 rpm/37ºC. Saos-II cells were exposed to different concentrations of CFEXs for 24 and
48 h and then cytotoxicity and genotoxicity were evaluated by MTT and comet assay, respectively. Based on the MTT
assay results after 24 h exposure, CFEX A at concentrations ≥75% and CFEX B at concentrations ≥50% had a
cytotoxic effect, while after 48 h, both CFEXs showed similar cytotoxicity at concentrations ≥25%. According to the
result of the comet assay, DNA damage increased with the increase of CFEXs concentration and exposure time.
Both CFEXs showed significantly higher comet tails elongation scores at concentrations ≥50% and ≥25% after 24
and 48 h exposure, respectively. Both composite foams could be considered as a non-toxic candidate for tissue
engineering at concentrations <25% which was less than FA50%/BG50% composite. Therefore, the composite with
equal FA/BG proportion has priority if similar results are obtained in in vivo complementary experiments.

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Temperature is one of the key factor that affecting the electrical, physical, structural, and morphological properties as well as the crystallinity of the nanomaterials. The current study investigates the effect of annealing temperature on the structural and electrical properties of lanthanum oxide (La2O3) thick films. La2O3 thick films were prepared on a glass substrate using a conventional screen printing technique. In this work, T1 is an unannealed prepared film, whereas T2 and T3 are annealed in a muffle furnace for 3 hours at 350°C and 450°C, respectively. XRD technique was exploited to investigate the crystallization behavior of the films. It was found that the crystal structure of La2O3 thick films are pure hexagonal phase. The annealing temperatures were revealed to have influence on the crystallite sizes of the films. SEM and EDS was used to study the morphology and elemental analysis of the films respectively. The electrical properties of the films were explored by measuring resistivity, temperature coefficient of resistivity (TCR), and activation energy at lower and higher temperatures regions. The film annealed at 450°C has high resistivity, a high TCR, and small crystallite size. The thickness of the La2O3 thick films was also found to decrease as the annealing temperature increased.

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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.
 

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Glasses in the B₂O₃-Li₂ (O, Cl₂, I₂) system were prepared through the conventional melt-quenching method. Then, the conductivity of the molten and glassy states of these compositions was evaluated. Furthermore, the thermal and crystallization behavior of the glasses was determined using simultaneous thermal analysis (STA) and X-ray diffractometry (XRD). The electrical conductivity of the melts was measured at temperatures ranging from 863 to 973 K, and the activation energy of the samples was calculated using the data obtained from ion conduction in the molten state and found to be in the vicinity of 32 kcal/mol. In glassy states, electrical conductivity was also measured. To determine this property, the electrochemical impedance spectroscopy method (EIS) was used. In the molten state, temperature played an important role in the ion conductivity; however, at lower temperatures, other factors became important. Based on the results, the addition of LiI and LiCl to the B₂O₃-Li₂O base glass system (75 B₂O₃, 10 Li₂O, 7.5 LiI, 7.5 LiCl) (mol%) increases the ionic conductivity of the glass from 3.2 10^-8 S.cm^-1 to 1.4 10^-7 S.cm^-1 at 300 K.
 

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ZrO₂ is commonly incorporated into ceramic glass substrates to enhance radiopacity, mechanical strength, and chemical durability. Experience has shown that the crystallization of tetragonal zirconia in glass will have a greater effect on the mechanical properties of ceramic glass. To achieve optimal properties in zirconia, stabilizing oxides are often added to enhance its structural and mechanical qualities. In this research, in order to stabilize the tetragonal phase of zirconia, MgO and CeO₂ were added to the glass ceramic composition of the Li₂O-SiO₂-ZrO₂ system and the desired dental substrate was synthesized through the sinter process. The behavior of sintering and crystallization of basic and optimized glass was investigated using HSM and DTA thermal analysis, respectively. The results showed that the optimal sinter temperature, heat press and heat treatment are equal to 730°C, 900°C and 825°C, respectively. Then, in order to determine the crystallization behavior of the prepared samples, X-ray diffraction and microstructure images were used. The results also showed that the presence of the main Li₂ZrSi₆O₁₅ phase crystallizes at a temperature of 825°C in the base sample and the sample containing ceria. Also, due to early formation of MgSiO₃ crystals, magnesia prevents sintering and formation of Li₂ZrSi₆O₁₅ phase and stability of tetragonal zirconia phase. In the sample containing ceria, during crystallization, ZrO₂ entered its crystal structure and led to the stability of the tetragonal zirconia phase at room temperature.

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This study explores the fabrication, structural analysis, and cytocompatibility of cobalt-doped bioactive glass scaffolds for potential applications in bone tissue engineering. A specific glass composition modified from Hench's original formulation was melted, quenched, and ground to an average particle size of 10 μm. The resulting amorphous powder underwent controlled sintering to form green bodies and was extensively characterized using simultaneous differential thermal analysis (DTA), Raman spectroscopy, and Fourier Transform Infrared analysis (FTIR). After mixing with a resin and a dispersant, the composite was used in digital light processing (DLP) 3D printing to construct scaffolds with interconnected macropores. Thermal post-treatment of 3D printed scaffolds, including debinding (Removing the binder that used for shaping) and sintering, was optimized based on thermogravimetric analysis (TG) and the microstructure was examined using FE-SEM and XRD. In vitro bioactivity was assessed by immersion in simulated body fluid (SBF), while cytocompatibility with MC3T3 cells was evaluated through SEM following a series of ethanol dehydrations. The study validates the fabrication of bioactive glass scaffolds with recognized structural and morphological properties, establishing the effects of cobalt doping on glass behavior and its implications for tissue engineering scaffolds. Results show, Low cobalt levels modify the glass network and reduce its Tg to 529 ^oC, while higher concentrations enhance the structure in point of its connectivity. XRD results shows all prepared glasses are amorphous nature, and DTA suggests a concentration-dependent Tg relationship. Spectroscopy indicates potential Si-O-Co bonding and effects on SiO2 polymerization. Cobalt's nucleating role promotes crystalline phases, enhancing bioactivity seen in rapid CHA layer formation in SBF, advancing the prospects for bone tissue engineering materials.