Nanocomposites obtained using high pressure zone infiltration method
Anna Świderska-Środa, Stanisław Gierlotka, Ewa Grzanka, Grzegorz Kalisz, Svetlana Stelmakh, Bogdan F. Pałosz Instytut Wysokich Ciśnień PAN, ul. Sokołowska 29/37, 01-142 Warszawa
Quarterly No. 3, 2005 pages 16-20
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abstract The high-pressure zone infiltration of the nanocrystaline powders of SiC and diamond was used to obtain two-phase nanocomposites. The processes were carried out in toroidal cell (Fig. 1) under pressure up to 8 GPa at temperature up to 2000oC. We used different type of powders; with crystalite size 5÷60 nm and particle size from single to hundreds of nanometers (Fig. 2, Tab. 1). The experiments indicated that the powder morphology was the dominant factor for efficiency of the infiltration process. The porosity studies of the green bodies prepared (2 and 8 GPa, room temperature) from the investigated powders showed that: (i) in all samples open porosity was maintained, (ii) in the powder with fine particle size (in the range of several nanometers) fractal structure promoted infiltration (Tab. 1). We tested the infiltration method to obtain nanocomposites with metals, semiconductors, ionic glasses, and polymers. In the successful experiments we obtained the composites with a homogenous, two nano-phase microstructure (Fig. 3). The volume fraction, crystal size of the second phase and mechanical properties of the composites were dependent on the process conditions and powder granularity (Tab. 2, 3). The volume fraction of different second phases varied from 20÷45% for the particular matrix. However, the volume fraction of the given second phase was constant for given matrix phase, independently of powder morphology and p-T conditions (Tab. 2). The crystal size of the second phase was smaller in the composites with finer matrix, obtained under higher pressure at lower temperature (Tab. 3). The same factors caused increase of the nanocomposites microhardness HV02 (Tab. 3). Key words: nanocomposites, infiltration, high pressure