S. i et al. / Journal of the European Ceramic Society 25(2005)301-311 ate composite (50%Qtz, 50% CAS) J12-QA N=200 Mean grain size: 45.3 om Grain size J12-QA Mean aspect ratio: 2.0 distribution of quartz in a hot pressed particulate com- posite (J1 onsisting of 50 vol. Qtz and 50 vol %CAS. Measure- ments w aggregates and Qtz-CAs particulate composites, 3-5%in the layered composites and 5-6% in the monolithic Qtz aggregates. From two typical HIPed samples from each category, sev eral polished thin sections were made for characterizing grain size, microstructure and water content of undeformed Fig. 2. Hot isostatical pressed but undeformed Qtz-CAS particulate com materials using optical microscope, SEM, transmission elec posite (a), pure CAS aggregate(b) and pure quartz (Qtz) aggregate(c) tron microscope(TEM), Fourier transform infrared spec- (a and c)Optical micrograph of petrographic thin sections. (b)SEM m trometer(FTIR)and EBSD analyses ograph of a spherulite-free area from a polished and thermally etched (1373K, 30h)sample (1)Grain sizes of Qtz and CAs in the Hiped sample were measured using the linear intercept method24 from petrographic sections and SEM(Zeiss DSM 962, ing pressure of 300 MPa to maximize the densification GFZ-Potsdam, Germany) photographs of polished sec- and to allow the polycrystalline aggregate starting toward tions, respectively. Qtz displays a normal distribution microstructural equilibrium. After samples were retrieved of grain size ranging from 15 to 80 um with a mean from the vessel, the steel jacket was dissolved in a mixture size of 45 um(Fig. 3a). The distribution of Qtz grain of 50/50 vol. HCI/HNO3 acids. Density of each specimen aspect ratios is shown in Fig. 3b, yielding a mean value as determined using Archimedes' method with the accu- of 2.0. The CAS crystals, with a mean aspect ratio of racy of +0.003 g/em. Porosity is <1% in the HIPed CAS 2.2(Fig. 4b), display a log-normal distribution of grainS. Ji et al. / Journal of the European Ceramic Society 25 (2005) 301–311 303 Fig. 2. Hot isostatical pressed but undeformed Qtz–CAS particulate com￾posite (a), pure CAS aggregate (b) and pure quartz (Qtz) aggregate (c). (a and c) Optical micrograph of petrographic thin sections. (b) SEM mi￾crograph of a spherulite-free area from a polished and thermally etched (1373 K, 30 h) sample. ing pressure of 300 MPa to maximize the densification and to allow the polycrystalline aggregate starting toward microstructural equilibrium. After samples were retrieved from the vessel, the steel jacket was dissolved in a mixture of 50/50 vol.% HCl/HNO3 acids. Density of each specimen was determined using Archimedes’ method with the accu￾racy of ±0.003 g/cm3. Porosity is <1% in the HIPed CAS Hot-pressed particulate composite (50% Qtz, 50% CAS) 0 10 20 30 40 50 60 Grain size, m Number of measurements 0 10 20 30 40 50 60 70 80 90 100 N=200 Mean grain size: 45.3 ∝m J12-QA Qtz 0 10 20 30 40 50 Aspect ratio Number of measurements 0 1.0 2.0 3.0 4.0 5.0 6.0 N=200 Mean aspect ratio: 2.0 J12-QA Qtz (a) (b) Fig. 3. Grain size distribution of quartz in a hot pressed particulate com￾posite (J12-QA) consisting of 50 vol.% Qtz and 50 vol.% CAS. Measure￾ments were made from optical photomicrographs. aggregates and Qtz–CAS particulate composites, 3–5% in the layered composites and 5–6% in the monolithic Qtz aggregates. From two typical HIPed samples from each category, sev￾eral polished thin sections were made for characterizing grain size, microstructure and water content of undeformed materials using optical microscope, SEM, transmission elec￾tron microscope (TEM), Fourier transform infrared spec￾trometer (FTIR) and EBSD analyses. (1) Grain sizes of Qtz and CAS in the HIPed samples were measured using the linear intercept method24 from petrographic sections and SEM (Zeiss DSM 962, GFZ-Potsdam, Germany) photographs of polished sec￾tions, respectively. Qtz displays a normal distribution of grain size ranging from 15 to 80
m with a mean size of 45
m (Fig. 3a). The distribution of Qtz grain aspect ratios is shown in Fig. 3b, yielding a mean value of 2.0. The CAS crystals, with a mean aspect ratio of 2.2 (Fig. 4b), display a log-normal distribution of grain