Kaunas University of Technology Department of Mechanical Engineering and Design T450M105 HIGH TEMPERATURE MATERIALS INTERMETALLICS Professor Submitted by Kandrotaitė-Janutienė Rasa JAGANNATHAN GURUNATHAN

INTRODUCTION Oxide Ceramics – Aluminum Oxide (Al 2 O 3 )(Alumina)  Oxide ceramics are inorganic compounds of metallic (e.g., Al, Zr, Ti, Mg) or metalloid (Si) elements with oxygen.  Oxides can be combined with nitrogen or carbon to form more complex oxy-nitride or oxy-carbide ceramics.  Oxide ceramics have high melting points, low wear resistance, and a wide range of electrical properties. TECHNICAL CERAMICS  This class of ceramics combine common crystalline ceramics properties with one or more a-typical properties like superconductivity, high transparency or low brittleness.  These properties are either a result of the materials composition or chemical or heat treatment, which stabilizes the materials structure (partially).

Physical and Mechanical Properties of alumina /aluminum oxide  Very good electrical insulation (1x1014 to 1x1015 Ωcm)  Moderate to extremely high mechanical strength (300 to 630 MPa)  Very high compressive strength (2,000 to 4,000 MPa)  High hardness (15 to 19 GPa)  Moderate thermal conductivity (20 to 30 W/mK)  High corrosion and wear resistance  Low density (3.75 to 3.95 g/cm3)  Operating temperature without mechanical load 1,000 to 1,500°C.  Bioinert

GRAPHS AND CHART DIFFERENTIATING - Alumina

Process of alumina ceramics Alumina ceramics obtained by chemical synthesis using conventional and microwave sintering. Preparation of alumina powders by chemical synthesis  Aluminum nitrate salt was used for the chemical synthesis of the alumina powders.  The salt was dissolved in an aqueous solution of citric acid in the proportion of 3:1, under constant agitation and heating.  Ethylene glycol was then added in a 40:60 (citric acid: ethylene glycol) ratio. Ceramics processing and characterization  The samples were uniaxially pressed under 40 MPa into cylindrical compacts.  After which they were cold pressed under 150 MPa.

CONVENTIONAL SINTERING  The samples obtained by the conventional sintering process, cS ceramics, were sintered in an electrical furnace at 1650 ºC for 5, 30, 60 min, at 5 ºC/min. MICROWAVE SINTERING  The µS ceramics were sintered at 1650 ºC at 400 ºC/min for different times.  The microwave furnace used in this work was modified from a domestic model, with a nominal power of 1450 W and 2.45 GHz operating frequency.

DEFINING THE MICROSTRUCTURE OF THE CERAMIC MATERIAL Abnormal grain growth Improved porosity CONVENTIONAL SINTERING MICROWAVE SINTERING

APPLICATION OF ALUMINIUM CERAMICS  Chemically inert and white, aluminium oxide is a favored filler for plastics- Aluminium oxide is a common ingredient in sunscreen and is sometimes present in cosmetics such as blush, lipstick, and nail polish.  Alumina is used to manufacture tiles which are attached inside pulverized fuel lines and flue gas ducting on coal fired power stations to protect high wear areas.

 Aluminum Nitride (AlN), a Covalently-bonded ceramic, is synthesized from the abundant elements aluminum and nitrogen.  It does not occur naturally.  AlN is stable in inert atmospheres at temperatures over 2000°C.  It exhibits high thermal conductivity but is, uniquely, a strong dielectric.  This unusual combination of properties makes AlN a critical advanced material for many future applications in optics, lighting, electronics and renewable energy Aluminum Nitride (AlN) CERAMICS OTHER ALUMINIUM CERAMICS

Aluminum Titanate (Al 2 TiO 5 )  The special feature of aluminum titanate (Al 2 TiO 5 ) is its excellent thermal shock resistance.  Components made of this material can withstand even the most abrupt temperature changes of several hundred degrees without damage, although they have low strength. Advanced Ceramic Tubes