CERAMIC SCIENCE & ENGINEERING
Year:2019 | Volume:8 | Issue:3 |Papers Count:7

Recently, a series of three-component compounds with the combination of Mn+1AXn known as Max phases have been considered as a new material. One of the most important features of Max phases, is the self-healing property of them. The main reason for considering Max Phases is a unique collection of unusual properties including their metallic, ceramic, physical, and mechanical properties. One of these Max Phases is Ti3SiC2 triple composition. The mechanical properties of this type of max phase can be improved by using various reinforcements such as carbides (like silicon carbide). High hardness, high melting temperature, high mechanical strength and high elasticity modulus are the hallmark properties of silicon carbide. The oxidation resistance of silicon carbide is also high due to the formation of the silica layer. Ti3SiC2-SiC composite can be synthesized in a mixture of Si and TiC with a suitable stoichiometric ratio by hot pressing method. In this research, the main objective of the study is to investigate the mechanical properties of in-situ fabricated Ti3SiC2-SiC composite compare it with ex-situ composite. Therefore, Ti3SiC2-SiC composites were prepared via in-situ and ex-situ routs by hot pressing at a temperature range of 1400-1600 ° C under pressure of 30-40 MPa for 30-60 min, and its physical and mechanical properties included density, hardness, flexural strength and fracture toughness were evaluated and compared. X-ray diffraction patterns (XRD) and scanning electron microscopy (SEM) were used for phase and microstructural analysis, respectively.

Citrate was used as chelating or morphology regulating agent in this study. In the presence of regulating agent a two-dimensional monetite phase evolved into three-dimentional hydroxyapatite microspheres with an average diameter of 4 µ m. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed the importance of Ca/citrate ratio in regulating the particle morphology. The results indicate that the surface morphology of microspheres can be engineered from nanosheets to nanorods by regulating agent’ s concentration. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed crystallinity and purity in the synthesized powders. Brunauer-Emmett-Teller (BET) revealed an increase in the specific surface area with adding citrate. Possible mechanisms are proposed to account for the formation of different morphologies based upon thermodynamic theories.

In the present study, the effect of Iron Nitrate as catalytic precursor to in situ formation of nano-Fe particles in phenolic resin and microstructural evolution of MgO-C refractories has been investigated. Therefore, various samples according to matrix section formulation of low carbon MgO-C refractories (LCMCR’ s) with 0 and 6 wt% (Fe/Phenolic resin) were prepared and phase and microstructure changes after coking at temperatures 800-1400º C studied by XRD and FESEM analyses. Based on attained results, iron nitrate transfer to Fe nano particles with 60-80 nm in diameter during firing in reduced atmosphere. In situ formed Fe nano-particles as catalytic agent promotes graphitization behavior of phenolic resins. Increasing temperature led to a more effective graphitization level. In addition, the different nano crystalline carbon shapes such as onion and bamboo like and carbon nanotubes (CNTs) were in situ formed. Phase and microstructure analysis of LCMCR’ s samples reveal that different ceramic whiskers such as MgO, MgAl2O4 spinel, Al4C3 and AlN formed after coking at 1000 º C and the amount of whiskers phases significantly increased at higher coking temperatures. It was also clarified the presence of Fe nano-particles have effective influence on the formation of gases components and promote ceramic phases formation. Microstructural observation showed the graphitic carbons like carbon nano-tubes (CNTs) and ceramic whiskers mainly formed in the bonding phase between the aggregates according to the V-L-S and V-S growth mechanism.

Yttrium Aluminum Garnet (Y3Al5O12) is a transparent ceramic with a wide range of applications such as high mechanical strength windows, high power laser sources and radiation detectors. The most important challenge in making these ceramics is the problem of low light transmittance, especially in the visible area in the range of 400 to 700 nm, which is greatly affected and reduced by various factors. So far, many efforts have been made to reduce the structural and microstructural defects of components made using this material to bring the optical properties of the material closer to theoretical values. In the present study, YAG transparent ceramics with high optical properties were fabricated by solid state synthesis method using Y2O3 and Al2O3 nanopowders and then Sintered under vacuum furnace at 1730° C during 12 hours And the combination of TEOS (tetraethyl orthosilicate) was used as sintering aid. Then bodies were annealed in two steps at 1200° C for 4 hours and about 1300° C for 5 hours. SEM, PL, EDX, UV-Vis characterization tests were used for microstructural and optical examination of ceramic bodies. The results showed that the structural and atomic defects as well as the presence of some impurities such as Ce+3 caused the absorption and reduction of light transmittance in the visible wavelength ranges. Studies have shown that the most important factor in reducing optical properties is the defects in structure that cause light scattering.

Translucent tiles are among the tiles that have recently been featured. Passing part of the light is an important feature of these tiles. The passage of light from within, create a beautiful effect. In particular, it can be combined with LED, in which its beauty will be multiplied. In this research, the effect of using transparent frit and feldspar on porcelain tile composition was studied to obtain semi-transparent properties. Compositions of 10-%50 frits and feldspars were prepared by powder pressing and fired in a rapid roller furnace at 1150 ℃ and 70 minutes. The phase composition and microstructure were investigated by X-ray diffraction (XRD) and electron microscopy (SEM). A light spectrometric test was used to examine the light transmission and the white index of the samples was determined using a spectrophotometer. The flexural strength, density, and water absorption were also measured. The results showed that 50% frit, along with 20% feldspar, have a semi-transparent property and a better white index than other samples.

In this study, the photocatalytic and bleaching properties of pure and doped titanium dioxide nanoparticles with 1%, 3%, 5% and 10% Ce dopant were studied using Ce(NO3)3 precursor. The results showed that the highest methylene blue degradation of the sample with 5% cerium impurity was 97% in neutral medium (pH=7) after 75 minutes. The bleaching response to wastewater treatment with 5% cerium impurity was 80% at wavelength of 490 nm.

Nickel field composite coatings have a high ability to improve surface properties, such as increased corrosion resistance and abrasion resistance. In this study, Ni-P-TiO2-ZrO2 composite coating on AISI 316L steel substrate was deposited by direct current flow method and the effects of different pH 3, 3. 5, 4 and 4. 5 on coating morphology and corrosion resistance were investigated. Scanning electron microscopy (SEM) was used to investigate the microstructure. In order to investigate the corrosion behavior of the coatings, a potentiodynamic polarization test was used in 3. 5% NaCl solution. The results of SEM and EDX analysis showed that the coating produced at pH = 4 had the highest uniformity and the highest amount of titanium oxide and zirconium oxide particles was related to this pH. Also, the polarization results showed that the highest corrosion resistance is related to the precipitation produced in pH = 4. At low pH and more than pH=4, the coating was not continuous and in some parts of the coating crack and pit were observed.