فصلنامه سرامیک ایران
سال هجدهم شماره 3 (پیاپی 71، پاییز 1401)

In recent years, piezoelectric materials have received great attention due to their wide applications in transducers, actuators, and sensors. In the meantime, lead-based piezoelectric materials have become the most successful piezoelectric materials in practical applications due to their excellent electrical properties, but due to the toxicity of lead and its harms to human health and the environment, their use has been limited. Among lead-free piezoelectric compounds, potassium-sodium niobate compound (KNN) has shown promising dielectric, ferroelectric and piezoelectric properties. KNN-ZnO ceramic compound with high density (ρth=95%), favorable microstructure, suitable dielectric and piezoelectric properties (K=875.12, d33=125pC/N, D=0.01) was chosen as the ceramic phase for composite fabrication. On the other hand, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) polymer with favorable piezoelectric and mechanical properties was selected as the polymer phase. To achieve special properties of the composition, ceramic-polymer composites were made, and the electrical behavior of these composites was evaluated. In this research, the cold sintering process was used to make KNN-ZnO/PVDF-HFP composites and the effect of adding different amounts of nano SnO2 on the final properties of the composites was investigated. According to the results, adding small amounts of SnO2 to the composite containing 80% by weight of KNN-ZnO increased the density and dielectric constant of the composite, but there were no specific changes in the piezoelectric properties of the composite. Among the composite samples, the sample with 1wt% of nano tin oxide had the highest values ​​of voltage coefficient and figure of merit

In the last two decades, many scientific researches in the field of refractories technology have focused on increasing the use of monolithic refractories. Many countries have focused more than half of their production on amorphous refractories, which is due to the advantages of these refractories, such as no need for forming and baking processes during manufacturing, and similar properties to shaped refractories. The advantages of monolithic refractories are the main driving force for increasing researchers in this area which have shown great progress. From other hand the application of nano materials in refractories researchers have recently started which might end in unexpected results. After clay purification by mechanical methods and obtaining layer nano-silicate, the characterizations were conducted by using XRD (X-ray Diffraction), SEM (Scanning Electron Microscope) and LPSA (Laser Particle Size Analyzer). Then, the produced nano-silicate particle was added to the ultra-low cement Alumina castable and rheological and mechanical properties of castable were studied before and after firing in 1000°C, 1250°C and 1500°C. Also for phase investigation XRD was used.
The results showed that d-spacing between nano-silicate layers was about 1.2 nm. Flow ability of the castable showed an increase of 5%. Which meant that filler materials such as micro silica and reactive Alumina where decreased. Finally XRD results of fired samples indicated that existence of mullite as a desired phase in the system.

In this research, zirconium carbide nanoparticles were synthesized by sol-gel method using pH and temperature parameters and controlling it during the process. Zirconium propoxide and phenolic resin were used as Zr and carbon raw materials, respectively. The effect of pH and temperature parameters in the synthesis process of these nano powders was investigated. The results in the case of tuberculosis showed that by controlling the pH in the range of 5, Zr-containing precursor particles can be synthesized in sizes below 10 nm. In FTIR data, Zr-O and Zr-C bonds were detected in the range of 560 and 1505 cm-1, respectively. The XRD results showed that no zirconium carbide particles were formed at the temperature of 700ºC and the initial compounds containing carbon and zirconia did not perform any chemical reaction yet. At the temperature of 1320 ºC, the initial buds of zirconium carbide have started to form. By increasing the temperature up to 1420 ºC, through carbothermal reactions, raw materials are converted into zirconium carbide. At a temperature of 1420 ºC, the size of the resulting crystallites is about 5 nm. In the characterization of the Raman spectrum, two relatively strong bands are seen in the ranges of 600 and 530 cm-1, which are related to the Zr-C bands of ZrC particles. During the hydrolysis of zirconium alkoxide in the presence of carbon phase and condensation at 60 ºC, a gel with Zr-O-C bonds was formed. These conditions made it possible to obtain the ZrC product at low temperatures, which was confirmed by DTA analysis. DTA/TG analysis showed that the initial buds of ZrC particles were formed in the temperature range of 1320 ºC, which is confirmed by the X-ray diffraction pattern. SEM microstructure images showed that zirconium carbide particles were formed in the range of dimensions below 100 nm and the particle size distribution was in a narrow and uniform range.

Among the carbon materials, graphene oxide and graphene quantum dots have attracted many researchers’ attention due to their luminescent properties. Graphene quantum dots are graphene sheets smaller than 100 nm that exhibit unique optical and electronic properties due to quantum confinement and edge effects. Carbonization of carbon materials is one of the methods of preparing quantum dots, which leads to the control of particle size. In this research, graphene quantum dots were prepared by the citric acid carbonization method, and pH’s effect on photoluminescence and particle size was investigated. Examining the properties of the synthesized samples showed that when the pH changes, the size of the graphene quantum dots increases with the introduction of OH groups, and the surface chemistry changes a little compared to pH 8, and at pH 10 and 12, the radiation wavelength and, accordingly, the particle size increase.

Lanthanum strontium manganese oxide (LSMO) nanoparticles, which have shown favorable magnetic properties, have recently been introduced as a new class of magnetic nanoparticles in the hyperthermia application. The purpose of this study is to look into the behavior of nanocrystalline La0.7Sr0.3MnO3 (LSMO) synthesized by the combustion solution method at various temperatures. Glycine, which acts as a fuel and complexing agent, has been used in this synthesis. LSMO nanocrystals were calcined at different temperatures of 600-1000 °C. The produced LSMO nanocrystals were examined in terms of structural and magnetic characteristics. Based on X-ray diffraction (XRD) study, the crystallite size of LSMO nanocrystals at temperatures of 600, 700, 800, 900, and 1000 degrees Celsius will be 16.6, 9.2, 18.4, 13.8, and 33.2, respectively. The (M-H) curve investigated the magnetic characteristics of LSMO nanocrystals at various temperatures, revealing that the saturation magnetization value at 700 and 900°C temperatures is lower than at 600 and 800°C temperatures, possibly explaining the reduction in nanocrystal size. The effective bonding of LSMO nanocrystals were examined using Fourier transform infrared spectroscopy (FTIR). A field emission electron microscope (FESEM) was used to examine the shape and size distribution of nanocrystals. The micrographs suggested that the particle size range was 20-60 nm.

Among various forms of mesoporous silica materials, mesoporous coatings are one of the most favorable in various applications such as optics, electronics, different types of sensors, corrosion protection coatings, etc. To investigate the fabrication of process and its effect on coating properties, in this study, single-layer mesoporous silica coating fabricated by Evaporation Induced Self-Assembly method and Cetrimonium bromide was used as the structure-directing agent. After preparing the stable solution and aging it for 7 days, the deposition was performed by the spin coating method and in order to remove the template, the sample was calcined for 4 hours at 450 ° C. To evaluate the fabrication conditions, the stability of the sol and surfactant removal process were studied. The sample was exhaustively characterized by low-angle X-ray diffraction and electron microscopy. The results of the tests showed a continuous and very smooth coating with a thickness of 500 nm and had an ordered structure with a pore size of 3 nm.