Neoker is a Spin-Off company that is currently producing c-axis single crystal alpha-alumina fibers via Vapor-Liquid-Solid mechanism, a procedure developed at the Institute of Ceramic Materials of Galicia.
During the growth process, sapphire fibers produced via VLS mechanism are affected by the deposition of surface impurities. The composition of such impurities are mainly Fe, Si and Ni, and they are self-deposited as a consequence of several chemical reactions, having their origin in the raw materials used for fiber growth, at 1500ºC in an inert atmosphere furnace.
Such impurities are considered to originate undesired surface chemical reactions and they also likely affect wettability of fibers, and therefore the mechanical performance of composites. As a consequence, a process to clean the surface of the fibers was needed, in order to control the properties of the metal matrix composites based on our VLS alumina fibers.
Neoker has been able to develop a new process to treat the surface ot it's NKR fibers (single crystal c-axis grown sapphire fibers). This method involves the use of vacuum atmospheres at high temperatures.
In this work we present this cleaning treatment, and the properties of a 2024 Al matrix composite material, in which a 20% of treated NKR fibers have been included. The composite has been produced at the IUMA, using pressure casting, and a subsequent mechanical characterization has been performed at UPM, Madrid.
As a summary, it has been demonstrated that the mechanical strength of the composite material is much higher compared to bulk 2024 Al, and that the incorporation of treated NKR fibers allows increasing the maximum useful temperature of this Al in about 100ºC, a result that opens a strong potential for their use in high added value applications.