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Structure and mechanical properties of ceramic mat
« on: December 22nd, 2020, 9:55am »
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Structure and mechanical properties of ceramic materials based on alumina and zirconia with strontium hexaaluminate additives
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In this study, the effect of a small amount of strontium hexaaluminate (3 wt %) additives on the properties of alumina- and zirconia-based ceramics is discussed. α-Al2O3, 3Y-ZrO2 and SrO submicron powders are used as the starting materials. Specimens are prepared by water suspension dispersion in a bead mill, spray drying granulation, isostatic pressing and pressureless sintering. Structural studies are conducted using a scanning electron microscope. The Archimedes approach is employed to determine the density and porosity of the specimens. Microhardness, flexural strength at three-point bending and fracture toughness are determined by the single-edge V-notch beam (SEVNB) method and indentation. A material containing 50-wt. % Al2O3 and 50-wt. % ZrO2 exhibited the most rational combination of characteristics such as strength (950 ± 50 MPa), microhardness (1800 HV) and fracture toughness (6.5 MPa m1/2). The SEVNB fracture toughness tests showed that the highest recorded value of a critical stress intensity factor was 9 MPa m1/2 for specimens containing 47-wt. % Al2O3, 3-wt. % SrAl12O19 and 50-wt. % ZrO2. The length of strontium hexaaluminate platelets decreased with an increase in the zirconia content in the materials and reached 0.8–2.6 μm. A pronounced fragmentary structure is characteristic of the strontium hexaaluminate platelets. The platelets under study comprised one or two boundary-separated blocks with a thickness of ~150–200 nm. Each block is divided into smaller fragments. The structure of strontium hexaaluminate platelets affects the crack propagation trajectory. The identified mechanisms of crack propagation are as follows: transcrystalline and intercrystalline fractures of alumina grains, crack deflection from the propagation trajectory, crack branching and failure of SrAl12O19 platelets.fused alumina wholesale distributors
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