Papers by Keyword: High Temperature Materials

Abstract: High temperature squeeze casting enables the fabrication of composite structures for alloys with high melting points, suitable for structural and tribological applications at high temperatures. Nickel-chromium alloys with chromium contents of about 20 wt% are extremely resistant to corrosion and exhibit operation temperatures up to 1000 °C due to the high solubility of chromium in nickel and its high melting point. The creep and wear resistance of the metal matrix composite material (MMC) is achieved by a stable ceramic backbone of Alumina with a bimodal pore structure. The fabrication of interpenetrating nickel-chromium/alumina MMCs, namely NiCr8020/Al₂O_3/50_pp, at temperatures above 1550 °C is shown. A special infiltration tool geometry has been used to withstand thermal and mechanical strain, necessary for the infiltration of preforms with 40 mm in height. The infiltration was performed in a unique high temperature squeeze casting device with tool temperatures of about 700 °C. Infiltration duration (pore filling) was as long as about 12 s. For this, the thermal management of the tool is the demanding part. Whereas the inner cavity has to be as hot as possible to enable infiltration and to prevent premature solidification. In contrast the outer side of the infiltration tool has to be as cold as possible to withstand the infiltration pressure applied directly to the squeeze casting tool.

Abstract: Reusable spacecraft/supersonic aircraft is research and development towards the realization of a new aerospace transportation system.Because these transport aircraft is to flight at a speed of more than Mach 5,are considering the use of scramjet engine.Because this engine uses air as an oxidant and liquid hydrogen as a fuel,the combustion gas temperature is more than 2500°C.So the combustor is required lightweight material and super-heat-resistant material.In the field of aerospace,SiC-based ceramics that is heat-resistant materials are well known as to maintain the mechanical properties at high temperatures and have a high oxidation resistance.However, this material limit as heat-resistant material is about 1600 °C .Therefore, it can not be used in an environment of scramjet engine combustor.There are the measures by metal structure to be force-cooled by refrigerant fuel,but apply is difficult because the system is complexity and very heavy. In this study use the hafnium-based super heat-resistant ceramics that is having a melting point more than 2000°C. Purpose is to develop a new technique for forming the ceramics mainly composed from Hafnium Carbide (Melting point:3950°C) that is very high melting point and have oxidation resistance by melt impregnation to inside C/C composite.In addition, implement the evaluation of changes in the organization after each process by the cross-sectional observation and strength assessment by three-point bending test.

Abstract: In the framework of the European Fusion Research Program, a great effort has been made to develop an innovative carbon-based ceramic material to meet all of all operational requirements. After a decade of research and development, It is succeeded to develop an advanced material: namely, a 3D CFC, contains about 8-10 at% of Silicon with porosity is about 3-5% . This advanced ceramic material possess very high thermal conductivity, dimensional stability under the neutron irradiation, lower chemical erosion (longer life time), lower tritium retention and lower reactivity with water and oxygen (safety concern) . This innovative ceramic materials seems very promising for application in the high temperature, neutron and hydrogen environment. A detailed discussion on development , properties and application of material is presented.