Effect of Variation MWCNTs in Synthesis Zirconia Prepared by Uniaxial Pressed Technique

The effect of addition different weight percentage (wt. %) of treated MWCNTs on zirconia matrix as a composite structure using method uniaxial pressed for fabrication and enhancement mechanical, microstructural properties of zirconia have been investigated in the present study. The composite material have prepared by adding yttrium oxide (3% mol. Y2O3) to zirconia for stabilized in the tetragonal phase with homogeneous distribute and reinforcement changed weight percentage of (2%, 5%, 7%, and 10%) wt. of F-MWCNTs to result (3% mol.Y2O3-ZrO2/F-MWCNTs) nanocomposite samples by pressing uniaxiall at pressure of (624) MPs in the metal-die cylinder to results pellets of (10 mm diameter). The resulting pellets were sintered in air at (1550 °C) temperatures for two hours. The samples were characterized by XRD analysis to demonstrate the phase composition of samples, where The retention was observed on the tetragonal phase in zirconia and the microstructure of the materials have been studied using SEM it is observed that F-MWCNTs were homogeneously distributed in the composite powders without the formation of ropes and bundles up to the highest contents of F-MWCNTs, and EDS showed the percentages for presence of carbon in samples, The micro hardness was studied by Vickers indentation method and Brazilian test that shows improved due to a homogeneous distribution of MWCNT in ZrO2 and the densities (Green, Bulk, and theoretical), porosity and liner shrinkage to demonstrate the toughness that reveal many pores and low densification with increasing F-MWCNTs contents, physical and mechanical properties of samples depend on distribution of F-MWCNTs in the matrix.

Mechanical properties of superionic ceramics based on (Cu1–xAgx)7GeSe5I solid solutions

Cu1–xAgx)7GeSe5I-based ceramics were prepared by pressing and sintering from the micro- and nanopowders. The ceramic samples were investigated using microstructural analysis. The microhardness was measured applying the indentation method with use of the Vickers pyramid. It has been shown that the microhardness of (Cu1–xAgx)7GeSe5I-based ceramics decreases with copper content decrease at Cu+→Ag+cationic substitution. The compositional dependences and size effects of microhardness inherent to (Cu1–xAgx)7GeSe5I-based ceramics have been analyzed. The size effects of microindentation have been interpreted within the framework of the gradient theory of plasticity.

Study of the anisotropy of the properties of the ceramic cutting insert obtained by the LCM technology of 3D printing from the composite Al2O3/ZrO2 (ZTA)

The anisotropy of the properties of a ceramic cutting insert (for three faces) obtained by the lithography-based technology from the Al2O3 + ZrO2 composite has been studied. The study was carried out using the indentation method and Mayer’s law. This method, in contrast to the bending test, excludes the sample destruction. All the studies were carried out on three faces of a ceramic cutting insert made of a composite Al2O3 + ZrO2. The behavior of the Mayer index was studied in the range of loads from 2 to 20 kg and from 0.2 to 1 kg. The results of studying the density, phase composition and microstructure of each face of the sample are presented. The study of the adhesion of the printed layers were also carried out using a Knoop indenter. No anisotropy of the hardness was observed in the load range up to 10 kg. It is shown that a layered structure present in the sample, contributes to the hardness anisotropy under the load of 20 kg and more. No anisotropy of the fracture toughness is observed in the load range of 2 – 20 kg. The results of using a Knoop indenter revealed a high adhesion between 3D printed layers. Studies using a Knoop indenter have indicated high adhesion between the layers of 3D printing.

Effects of yttria content and sintering temperature on the microstructure and tendency to brittle fracture of yttria-stabilized zirconia

Purpose: The purpose of this work is to evaluate the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria, based on a study of changes in the microstructure, phase composition, and fracture micromechanisms. Design/methodology/approach: The series of 3YSZ, 4YSZ, and 5YSZ ceramic specimens were sintered in an argon atmosphere. Three sintering temperatures were used for each series: 1450°C, 1500°C, and 1550°C. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The fracture toughness of the material was estimated using both the Vickers indentation method and a single-edge notch beam (SENB) test performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, and mechanical characteristics of YSZ ceramic materials of different chemical and phase compositions sintered in a temperature range of 1450°C to 1550°C are found. Research limitations/implications: To study the actual behaviour of YSZ ceramic materials under operating conditions, it is necessary to evaluate their Young’s moduli, strength, microhardness, and fracture toughness in an operating environment of the corresponding parameters (temperature, pressure, etc.).Practical implications: Based on the developed approach to estimating the propensity to brittle fracture of the formed YSZ ceramic microstructure, it is possible to obtain YSZ ceramic material that will provide the necessary physical and mechanical properties of a wide variety of precision ceramic products. Originality/value: An approach to estimating the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria is proposed based on two methods of evaluating crack growth resistance of materials, namely, the Vickers indentation method and SENB method.