فصلنامه سرامیک ایران
سال هجدهم شماره 2 (پیاپی 70، تابستان 1401)

Treatment and repair of bone defects, has been a major challenge for bone regeneration activists for a long time. In treating bone defects, using a proper bone graft is essential. Among various kinds of bone grafts, bio ceramics alloplastic grafts are considered, owing to their excellent non-toxicity, non- allergenicity, anti-inflammatory, biocompatibility and bio-functionality. The bio-ceramics like Whitlockite (WH: Ca18Mg2(HPO4)2(PO4)12) possess same chemical, structural and biological properties with human bones, have been widely used as bone substitutes. It is the second most abundant mineral in living bone, which can contain 26-58 wt% of bone tissues. In this study, we investigated the biocompatibility, bioactivity and biodegradability of Whitlockite nano powders, by immersing samples in Simulated Body Fluid (SBF) for 3,7,14 and 21 days. The obtained samples were characterized using X-ray Diffraction (XRD), Fourier transform infared spectroscopy (FT-IR) and inductively coupled plasma -optical emission spectrometry (ICP-OES).  Results indicated that, WH nano powders had significantly biocompatibility and biodegradability due to formation of Ca3(PO4)2 , (Ca, Mg)3(PO4)2 and Whitlockite on surface of WH samples. Additionally, the WH nano powders exhibited excellent mineralization ability in vitro with continuously released Ca2+, Mg2+ and HPO42- when immersed in (SBF). Furthermore, the pH changes of both samples were in the range of natural biological pH of the human body, which indicates the appropriate biocompatibility of the samples. However, the stability of whitlockite in SBF is at the highest level in 4<ph<5.< span=""> The results of the ICP analysis of the raw Whitlockite sample showed that about 150 ppm of magnesium ions are released from Whitlockite inside the Simulated Body Fluid during 21 days of immersion, which can provide a part of the body's daily magnesium needs. Also, by examining the weight changes of the samples within the SBF, it will be seen that the weight loss rate of the raw whitlockite sample is concerning 32.11% quite the heat treated whitlockite sample, which indicates the upper biodegradability.</ph<5.<>

Portland cement is known as the third most important material in the construction industry. In this research, the effect of borax on the properties of Portland cement including setting time, hydration percentage and compressive strength has been investigated. For this purpose, borax was used in amounts of 0.2, 0.4, 0.6 and 1 wt%. The obtained results showed that the setting time of Portland cement increases with increasing the amount of borax. The addition of 0.6 wt% of borax increased the setting time of Portland cement by about 50%, and the initial setting increased from 120 minutes to 170 minutes. The presence of borax in amounts less than 0.6 wt% led to an increase in the percentage of hydration and compressive strength of cement. The highest values of degree of hydration and compressive strength were obtained for the sample containing 0.6 wt% of borax. The 28-day compressive strength was 57 MPa for this sample, which was 42 MPa for the pure Portland cement sample. The increase in strength is attributed to the higher degree of hydration and lower porosity. By increasing the amount of borax to 1 wt%, there was a significant drop in the compressive strength of cement, which is related to the lower degree of hydration and a higher percentage of porosity.

Transparent conductive oxides have recently been used in solar cells. Hence, transparent conductive oxide, especially SnO2:F (FTO) is considered promising by researchers for solar cell applications due to its inexpensive and efficiency. In the current research, a sol-gel combustion technique was used to prepare fluorine-doped tin dioxide (FTO) powder. Stannous chloride pentahydrate, ammonium fluoride, and citric acid as fuel were used with various ratios of fuel to salt and different pH values. The structure, morphology, and composition of the synthesized powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The results revealed that the average particle size increased from 125 nm to 300 nm with morphological transformation as the pH value increased from 1 to 6, respectively and the average particle size decreased from 125 nm to 50 nm with round morphology as the fuel to salt ratio decreased from 2 to 1. The presence of fluorine additive in the optimal sample with 50 nm particle size was determined by XPS and it can be a suitable candidate for use in solar cells.

In this research, the process of growth and the optimum length of ZnO nanorods has been studied as a subject of semiconductors, that are used in the photoelectrochemical solar cell made by Sol-Gel and Hydrothermal method.These Nano structures, having suitable gap, cause the decomposition of water into its constructing elements, hydrogen and oxygen.The most length of nanorods achieved by the FTO sublayer and deionized water solvent, at 95°C growth temperature, while 3 hours growing time, and on these conditions caused the length of nanorods to be 1500 nanometers, with the biggest length to width ratio 15.Also, at the final stage, photoelectrochemical experiments and the effects of nanorods length to the decompositionof water was studied. The results of photoelectrochemical experiments showed the optimum quantity for nanorods.The best result of photoelectrochemical has been reached to the maximum ratio of length to width 10, and the maximum length of nanorods 1000 nanometers that has been grown at the temperature of 95°C and during 2 hours.

The main focus of this review article is related to non-destructive testing methods used to evaluate thermal spray nanocoatings. These techniques include eddy currents, infrared imaging, phase thermal emission spectroscopy, acoustic, photoacoustic, mid-infrared reflection, electrochemical impedance spectroscopy, photoluminescence piezospectroscopy, and interferometry techniques. These techniques have been used to identify surface defects and interface between ceramic layers and metal interface, its shape, size and location and to measure porosity and thickness.

In this research, metakaolin-based geopolymers reinforced with aluminosilicate fibers were investigated at room temperature and after exposure to 700 oC. Geopolymers were synthesized from metakaolin, micro silica and potassium hydroxide. The different molar ratios of silica to alumina and water content were studied. 1, 3, 5 and 7 weight percent of aluminosilicate fibers were added to the geopolymer composition. The mechanical strength and microstructure of the samples were studied. The results showed that the flexural and compressive strength values of the optimal sample at ambient temperature are equal to 5.87 and 19.05 MPa, respectively. By adding 5 wt% aluminosilicate fibers, the maximum of flexural and compressive strength values were obtained. However, by heating the composite samples at 700 oC, flexural and compressive strength values were 10.34 and 17.86 Mpa, respectively. Decrease in the mechanical strength at 700 oC is due to the strong chemical connection between aluminosilicate fibers and geopolymer binder during the heat treatment.