J Mater Sci(2006)41:7425-7436 7433 100 DIN Particle size (um) 12叮 g1-10 Fig8 Discrete 0001 pole figure (a) and inverse pole figure (b), both measured from electron back-scatter diffraction (EBSD) data 25um sintering shrinkage through original tape thickness in ATZ layer. Figure 1lb-d show a SEM image and EDX omposition maps taken from fine grain ATZ layer The results indicate that the alumina grains are uni- formly distributed among the zirconia matrix in the ATZ For the rBm/TA laminate, the mullite layers were produced by an in situ mullitization reaction. In con trast to the rbaoita and atta laminates the TA layers are now designed in biaxial tension due to the thermal mismatch between adjacent layers, placing 500nm the mullite in residual compression. The expectation as that the mullite layers would be reinforced by the Fig9(a)Particle size distribution for the reaction imposed compressive stresses, while the TA micro- aluminum oxide(RBAO)powder mixture after attrition structure would still promote crack deflection along the (b) The as received Al metal powder,(e)The RBAO mixture after attrition milling basal plane grain boundaries. Figure 12a shows an ptical micrograph of the cross-section of a sintered between zircon and alumina will be difficult to com RBM/TA laminate, in which the thickness ratio of plete, and Fig 12b shows a large unreacted zircon RBM and TA layer is 1: 1(alternating one gel-cast grain in the RBM layer. Phase evolution in RBM green RBM tape and one gel-cast green TA tape). samples with different zircon precursor particle sizes As in the rBAo process, the precursor particle size was therefore studied by X-ray diffraction analysis critical for the successful completion of the rbm The phase contents of both zirconia(M1)and mullite reaction. With a coarse zircon powder, the reaction (M2) were estimated using the following equations 2 Springersintering shrinkage through original tape thickness in ATZ layer. Figure 11b–d show a SEM image and EDX composition maps taken from fine grain ATZ layer. The results indicate that the alumina grains are uni￾formly distributed among the zirconia matrix in the ATZ layer. For the RBM/TA laminate, the mullite layers were produced by an in situ mullitization reaction. In con￾trast to the RBAO/TA and ATZ/TA laminates, the TA layers are now designed in biaxial tension due to the thermal mismatch between adjacent layers, placing the mullite in residual compression. The expectation was that the mullite layers would be reinforced by the imposed compressive stresses, while the TA micro￾structure would still promote crack deflection along the basal plane grain boundaries. Figure 12a shows an optical micrograph of the cross-section of a sintered RBM/TA laminate, in which the thickness ratio of RBM and TA layer is 1:1 (alternating one gel-cast green RBM tape and one gel-cast green TA tape). As in the RBAO process, the precursor particle size is critical for the successful completion of the RBM reaction. With a coarse zircon powder, the reaction between zircon and alumina will be difficult to com￾plete, and Fig. 12b shows a large unreacted zircon grain in the RBM layer. Phase evolution in RBM samples with different zircon precursor particle sizes was therefore studied by X-ray diffraction analysis. The phase contents of both zirconia (M1) and mullite (M2) were estimated using the following equations: 0 2 4 6 8 10 12 0.10 1.00 10.00 Frequency % Particle size (µm) (a) (b) (c) Fig. 9 (a) Particle size distribution for the reaction-bonded aluminum oxide (RBAO) powder mixture after attrition milling; (b) The as received Al metal powder; (c) The RBAO powder mixture after attrition milling Fig. 8 Discrete 0001 pole figure (a) and inverse pole figure (b), both measured from electron back-scatter diffraction (EBSD) data J Mater Sci (2006) 41:7425–7436 7433 123