S. Swaroop

Bio: S. Swaroop is an academic researcher from Bharat Heavy Electricals. The author has contributed to research in topics: Cubic zirconia & Creep. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

Role of small amount of MgO and ZrO2 on creep behaviour of high purity Al2O3

Abstract: Small levels of various dopants have a significant effect on creep in polycrystalline alumina. While most previous studies have examined the effect of ionic size, the influence of valency of dopants on creep has not yet been completely characterized. The present detailed experimental study, utilizing magnesia and zirconia with a similar ionic size, demonstrates that the ionic valency of dopants also plays a crucial role in creep since magnesia does not significantly alter creep whereas zirconia retards creep substantially. Magnesia doped alumina deforms by Coble diffusion creep whereas zirconia doped alumina deforms by an interface controlled diffusion creep process.

Microstructure and mechanical properties of carbon fibre-reinforced alumina composites fabricated from sol

Abstract: Alumina matrix composites reinforced with the laminated and stitched carbon fibre cloth preform were fabricated through the infiltration–drying–heating route using the $$\hbox {Al}_{2}\hbox {O}_{3}$$ sol with a high solid content as raw materials. The investigation was focussed on the characteristics of sol and the mechanical properties and high-temperature resistance of $$\hbox {C}/\hbox {Al}_{2}\hbox {O}_{3}$$ composites. $${\upalpha }\hbox {-Al}_{2}\hbox {O}_{3}$$ with favourable sintering activity can be obtained after heat treatment of sol at $$1200{^{\circ }}\hbox {C}$$ . The as-received $$\hbox {C}/\hbox {Al}_{2}\hbox {O}_{3}$$ composites with a total porosity of 16.8% exhibit a flexural strength of 271.3 MPa and a notch toughness of 13.0 MPa $$\hbox {m}^{1/2}$$ , respectively. As a result of the evolution of interface and matrix, the flexural strength of $$\hbox {C}/\hbox {Al}_{2}\hbox {O}_{3}$$ composites is decreased by 28.5% after heat treatment at $$1600{^{\circ }}\hbox {C}$$ for 1 h under inert atmosphere. At the same time, fracture mode of composites is transformed from tough to brittle behaviour.

High Temperature Deformation Behaviour of a High Purity AI2O3 Reinforced with Isolated Second Phases of Spinel (MgAI2O4), YAG (Y3AI5O12) and Zirconia (t-ZrO2)

Abstract: High temperature compression experiments were carried out on high purity alumina based composites containing second phases of spinel (MgAI2O4), YAG (yttrium aluminium garnet, Y3AI5O12) and zirconia (t-ZrO2) at a temperature range of 1623-1723 K, stress range of 10-200 MPa and a grain size range of ∼1-10 μm. It was observed that 5 vol% of these second phases had no significant influence on the creep rate of alumina. The stress exponent of ∼1.0 and the inverse grain size exponent of ∼3.0 suggested no change in the creep mechanism of pure alumina with 5% second phase addition. Deformation enhanced grain growth, which was prominent in pure alumina, was not observed in the composites. The creep behaviour of the composites was discussed based on ionic radii and ionic charge, room temperature mechanical properties and grain size of individual phases. A new model was developed which took into account the creep rate of the second phase while calculating the creep rate of the composite.