Pre-treatment of karbon fibres for fabrication of metal matrix composites
Rafał Kozera, Jerzy Bieliński, Anna Broda, Alicja Bielińska, Anna Boczkowska5, Krzysztof J. Kurzydłowski
Quarterly No. 1, 2009 pages 78-83
DOI:
keywords: sizing removal, electro-less Ni-P deposition, activation of carbon surface, metallization of carbon fiber
abstract In this work the results of the studies on pre-treatment of carbon fibres (Tenax HTA40) for composites with alumina alloy matrix are presented. The pre-treatment consisted in the replacement of epoxy sizing with Ni-P coating as a barrier to prevent formation of Al4C3. In the first step of the developed process, removal of the epoxy sizing was carried out, to assure adhesion of Ni-P coatings to carbon fibres. Removal of the sizing also decreases the risk of gas formation underneath of metal coatings in contact with liquid metal matrix. Methods of sizing removal included annealing in air (300-600oC), dissolving in solvents (acetone, toluene) and in inorganic solutions (HNO3, H2O2, NaOH), followed by SnCl2/PdCl2 activation. Parameters of annealing in air must be carefully control to avoid surface damages e.g. micro cracks and decrease of fibres tensile strength. It was found that annealing in 400°C in 1 h leeds to micro cracks creating on the surface of annealed fibers also some peaces of the epoxy sizing was observed. Technical data of fibres used at present work indicates that consist of the epoxy sizing is between 1.3-1.5 wt. %. Small amount of the epoxy sizing making almost impossible to use standard methods of test thickness of epoxy coating before and after annealing treatmens. Morphology of carbon fibres surface before and after sizing removal was characterised using SEM technique and in terms of the mass loss. Mass loss of the samples after 24 h treatments in che-mical solutions didn’t exceed 1% what indicates not succesfully sizing removal by chemical methods. Etching 96 h in aceton wasn’t sufficient too. A glycine buffered bath was used for metal coating with a wide range of deposition rates and coating compositions (2-12 wt. % P). Two different pH of metallization bath were chosen (pH = 4.5 and pH = 8.5), time of Ni-P deposition was ranged from 5 to 30 minutes. The obtained results were used for optimization of deposition parameters of Ni-P coatings on carbon fibres and 2D and 3D woven fabrics. Modifies of treatments between following stages of metalization presented in this work allowed to increase time of 2D and 3D woven fabrics deposition to few hours.