Showing 30 results for Glass
Rahida Wati Sharudin, Nik Salwani Md Azmi, Muhammad Shafiq Mat Shayuti, Masahiro Ohshima,
Volume 18, Issue 2 (6-2021)
Abstract
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.
Sara Ahmadi, Bijan Eftekhari Yekta, Hossein Sarpoolaky, Alireza Aghaei,
Volume 18, Issue 4 (12-2021)
Abstract
In the present work, monolithic gels were prepared through different drying procedures including
super critical, infrared wavelengths and traditional drying methods. Dense and transparent glasses
were obtained after controlled heat treatment of the dried porous xerogels in air atmosphere.
The chemical bonding as well as different properties of the prepared gels and the relevant glasses
were examined by means of Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmitt-
Teller (BET) and UV-Vis spectrometer. Based on the obtained results, different drying conditions
affect the average pore size and the total pore volume of the studied gels. The mean pore size was
found to be 8.7 nm, 2.4 nm and 3.2 nm for super critical, IR radiation and slow drying in air
atmosphere, respectively. The glass network structure was significantly changed by heat treatment temperature so that the B-O-Si bonds were formed only after 450 °C. It was found that the gel dried under super critical condition was unable to reach to its full density all over the selected sintering temperature interval.
Nihel Hsouna, Mohsen Mhadhbi, Chaker Bouzidi,
Volume 19, Issue 1 (3-2022)
Abstract
Phosphate glass with different Al2O3 and Na2CO3 compositions [80NaH2PO4-(20-x) Na2CO3-xAl2O3 with a step from 0 to 4] were prepared through melt quenching technique furnace at 900 °C. In order to determine the structure and microstructure modification of the samples after heat treatment the IR and Raman spectroscopy were performed. The X-ray diffraction (XRD) result shows an amorphous character of the prepared glass. The result obtained by differential scanning calorimetry (DSC) reveals a good thermal stability in the temperature range of 25 to 400 °C. The impedance Nyquist diagrams were investigated and modeled by resistors and constant phase elements (CPE) equivalent circuits. These measurements show a non-Debye type dielectric relaxation. Both AC and DC conductivity, dielectric constant, and loss factors were determined. Thermal activation energies were also calculated. A changes in the electrical conductivity and activation energy depend upon the chemical composition were observed. Also, a transition in the conduction mechanism from ionic to mixed ionic polaronic was noted. In the same line, electrical modulus and dielectric loss parameters are also deduced. Their frequency and temperature dependency exhibited relaxation behavior. Likewise, activation energies value obtained from the analysis of M’’ and those obtained from the conductivity are closes, which proves the optimal character of the preparation conditions.
Silvana Artioli Schellini, Lucieni Cristina Barbarini Ferraz, Abbas Rahdar, Francesco Baino,
Volume 19, Issue 2 (6-2022)
Abstract
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.
Ebrahim Zabihi, Roghayeh Pourbagher, Seyedali Seyedmajidi,
Volume 19, Issue 4 (12-2022)
Abstract
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.
Sonali Wagh, Umesh Tupe, Anil Patil, Arun Patil,
Volume 19, Issue 4 (12-2022)
Abstract
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.
Parisa Rastgoo Oskoui, Mohammad Rezvani, Abbas Kianvash,
Volume 20, Issue 2 (6-2023)
Abstract
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.
Zahra Shamohammadi Ghahsareh, Sara Banijamali, Alireza Aghaei,
Volume 20, Issue 2 (6-2023)
Abstract
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.m1/2) and chemical resistance (solubility of 2568 µg/cm2). This glass-ceramic could be further considered as a core material for dental restorations.
Bijan Eftekhari Yekta, Omid Banapour Ghafari,
Volume 20, Issue 4 (12-2023)
Abstract
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.
Ahad Saeidi, Sara Banijamali, Mojgan Heydari,
Volume 21, Issue 2 (6-2024)
Abstract
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.
