K Nubian et al. / Journal of the European Ceramic Society 20(2000)537-544 ÷150m composition 85wt% filament density 3. 4 g/cm3 number of filaments / bundle 400 of a bundl 0,57 specific surface of bundle 9,8·10cm2g substrate siz 50 mm x 50 mm Fig 1. Schematic view of the Nextel 720 fiber fabri which was introduced into the system above about 400C 3. Results and discussion [Fig. 4(a)and (b)]. For both cases, the pressure was applied at about 1100 C, as soon as the first shrinkage 3. 1. Deposition of zro2 occurs. Hot-pressing was carried out mould-free between Sic-punches in order to achieve a homogeneous tem- Fig. 5 shows the measured deposition rate on the perature distribution on the sample plate fabric and on the Al2O3 wafer vs the reciprocal absolute temperature. The temperature dependence of the 2.4. Characterization of composites deposition rate can be described by an Arrhenius plot Phase analysis of the matrix and the coating were im exp( T<370°C carried out by X-ray powder diffraction at room tem- perature(SIEMENS, D5000, Germany) using Ni-fil tered CuKg radiation. Difiraction patterns were Thus, the activation energy E= 24+-3 kJ/mol of recorded in step scan mode(3s/0.05, 20)in the 10-800 20 ZrO2 deposition on the fabric was calculated. The cal range. Microstructural investigations were carried out culated activation energy E for the fiber fabric is much with optical and electron microscopy studies were done smaller than the values given in literature for ZrO2- with LEO field emission scanning electron microscopy deposition on flat substrates(E=80+-7 kJ/mol).4A and with PHILLIPS EM 430 transmission electron plane Al2O3-wafer was coated as a reference under the microscopy (TEM), 300 kV accelerating voltage. Sam- same conditions. The activation energy was E=66+-5 ple preparation performed by dimple grinding and kJ/mol which is in good accordance with literature.4 sequent ion beam milling. Samples were coated with The deposition rate related to the fiber surface on the carbon to avoid charging effect fabric is much lower than on the AlO3-wafer. This iswhich was introduced into the system above about 400C [Fig. 4(a) and (b)]. For both cases, the pressure was applied at about 1100C, as soon as the ®rst shrinkage occurs. Hot-pressing was carried out mould-free between SiC-punches in order to achieve a homogeneous tem￾perature distribution on the sample plate. 2.4. Characterization of composites Phase analysis of the matrix and the coating were carried out by X-ray powder di€raction at room tem￾perature (SIEMENS, D5000, Germany) using Ni-®l￾tered CuKa radiation. Di€raction patterns were recorded in step scan mode (3s/0.05, 2) in the 10±80 2 range. Microstructural investigations were carried out with optical and electron microscopy studies were done with LEO ®eld emission scanning electron microscopy and with PHILLIPS EM 430 transmission electron microscopy (TEM), 300 kV accelerating voltage. Sam￾ple preparation performed by dimple grinding and sub￾sequent ion beam milling. Samples were coated with carbon to avoid charging e€ect. 3. Results and discussion 3.1. Deposition of ZrO2 Fig. 5 shows the measured deposition rate on the fabric and on the Al2O3 wafer vs the reciprocal absolute temperature. The temperature dependence of the deposition rate can be described by an Arrhenius plot n : m  exp…ÿ E RT†T < 370 C …2† Thus, the activation energy E ˆ 24 ‡ ÿ3 kJ/mol of ZrO2 deposition on the fabric was calculated. The cal￾culated activation energy E for the ®ber fabric is much smaller than the values given in literature for ZrO2- deposition on ¯at substrates (E ˆ 80 ‡ ÿ7 kJ/mol). 4 A plane Al2O3-wafer was coated as a reference under the same conditions. The activation energy was E=66+ÿ5 kJ/mol which is in good accordance with literature.4 The deposition rate related to the ®ber surface on the fabric is much lower than on the Al2O3-wafer. This is Fig. 1. Schematic view of the Nextel 720 ®ber fabric. K. Nubian et al. / Journal of the European Ceramic Society 20 (2000) 537±544 539