Development and Characterisation of Phenolic Resin Based Liquid Silicon Infiltrated SiC/SiC Composites with SiN_x Fibre Coating

Abstract

SiC/SiC ceramics consist of silicon carbide fibres embedded in a silicon carbide matrix. As an alternative to classic CVI and PIP routes, Liquid Silicon Infiltration (LSI) was chosen as a technique with short process times to obtain composites with low porosity. Silicon carbide composites show good thermal shock resistance, a low coefficient of thermal expansion and excellent physical and chemical stability at elevated temperatures and are therefore regarded as promising candidates for various applications in jet engines and in power engineering. To build up the matrix, different phenolic resin based carbon precursors were infiltrated in fibre preforms and thermally cured, pyrolysed and siliconized. The aim is to obtain a high carbon yield during pyrolysis and to control the pore morphology in a way that the following liquid silicon infiltration leads to a complete reaction of the carbon matrix with silicon to SiC. The siliconization behaviour and conversion into SiC in dependence of pore morphology and chosen precursor is analysed.At the same time a functional fibre coating has to be developed which protects the fibres from liquid silicon and simultaneously provides a weak fibre matrix bonding. A LPCVD-SiNx fibre coating has been chosen and is investigated in fibre composites especially in terms of protection and reactivity in different atmospheres during pyrolysis and siliconization.

Investigation of Different Phenolic Resins and their Behavior during Pyrolysis to Form SiC/C-Composites

“…Continued LSI experiments at the DLR with R2 SiC/C sample show an almost complete conversion of C into SiC matrix. There is nearly no unreacted silicon observed [19]. This proves that silicon can flow in the larger cavities to reach compact carbon areas, where it can be permeate short carbon blocks without "pore-choking".…”

Low‐temperature curable adhesive for joining SiC/SiC components: Their application in wide range of temperatures

“…It is well known that the phenolic resin has been serving as a binder as well as a carbon source for making SiC, C f -SiC, and other ceramic materials on a large scale. [16][17][18] The thermal stability (200-600 • C) and low-temperature bonding strength of phenolic resin are the added advantages for employing it as a binder material. [19][20][21] On the other hand, the inorganic powder materials like B 4 C, SiO 2 , Al 2 O 3 , and Y 2 O 3 are known to form silicates and other glassy oxides under oxidative environments, and these glassy phases have high thermal stability and variable CTE.…”

“…This adhesive is made by combining phenolic resin and ceramic fillers to achieve good binding stability to SiC joints at lower and high‐temperature regions. It is well known that the phenolic resin has been serving as a binder as well as a carbon source for making SiC, C f –SiC, and other ceramic materials on a large scale 16–18 . The thermal stability (200–600°C) and low‐temperature bonding strength of phenolic resin are the added advantages for employing it as a binder material 19–21 .…”

The Matrix Cracking Stress and Residual Thermal Stress of 2D SiC/SiC Composite Fabricated by PIP Process

“…Continue fiber reinforced SiC ceramic matrix composites show a series of advantageous properties including lower density, higher specific strength, higher toughness and better thermal shock resistance than SiC monomer ceramic, in which SiC fiber reinforced SiC ceramic matrix composite was seemed as a most potential material for high temperature structural application [1][2][3][4][5][6]. Precursor impregnated pyrolysis process was one of the most common preparation methods for SiC/SiC composites.…”