Synthesis of Novel Niobium Aluminide‐Based Composites

Abstract

A reactive sintering process has been used to produce almost fully dense composites with interpenetrating networks of NbAl 3 and Al 2 O 3 . The process involves the reaction synthesis of niobium aluminides and Al 2 O 3 from compacts of intensively milled aluminum and Nb 2 O 5 powder mixtures. During carefully controlled heating under an inert atmosphere, the oxide reduction by aluminum to form niobium aluminides and Al 2 O 3 proceeds at temperatures below the melting point of aluminum. At temperatures of >1000°C, the reaction-formed niobium aluminides and Al 2 O 3 sinter. The present paper discusses processing parameters, such as attrition milling, the heating cycle, and the metal:ceramic ratio in the starting mixture, that control microstructure development and mechanical properties.

Sliding wear of Cr–Al2O3–ZrO2 and Mo–Al2O3–ZrO2 composites

“…TiO 2 or Fe 2 O 3 , is converted to a composite consisting of aluminides and alumina by a redox reaction between aluminum and the metal oxide. [2][3][4][5][6][7] Because these redox reactions are usually highly exothermic, careful process control is required in order to avoid thermal runaway with possible detrimental effects on the product. In contrast to this, s-MAC precursors consist of Al 2 O 3 , a metal powder such as Cr, Mo, or Fe, and only a small fraction, typically <1 wt.%, of Al.…”

Microstructure of Alumina Composites Containing Niobium and Niobium Aluminides

“…Recently, low-cost processing techniques have been developed to prepare dense alumina-aluminide alloys and alumina-aluminum alloyed metal composites for high-temperature applications. [1][2][3][4][5][6][7] One processing route involves attrition milling of inexpensive raw materials such as alumina, aluminum, and metal oxides, followed by compacting the milled powder mixtures and a heat treatment at moderate temperatures under vacuum or an inert atmosphere. During this process, controlled solid-state exothermic aluminum-based reactions take place which transform the initial materials into an alumina composite containing aluminides and/or elemental metals with high melting temperatures.…”

Reaction-Induced Processing of AI2O3-Based Interpenetrating Phase Composites

“…A controllable balance between heat generation and heat dissipation seems to be the most TRANSACTIONS OF THE INDIAN CERAMIC SOCIETY important criterion for successful 3A processing. 114 The exothermic nature of the reactions involved in the 3A process allows the reaction to be characterized by DTA. 115 Although the reactions occur well below the melting point of AI (660°C}, the high enthalpy of reaction demands careful control of the process between 400° and 700°C.…”