Characteristics of aqueous silicon nitride whisker suspension and the packing nature of whiskers during consolidation (sedimentation or filtration) were investigated in order to control the microstructure and density of a whisker compact. Silicon nitride whiskers (average size 0.4 μm × 3.7 μm) coated by SiO2 film were well dispersed at pH 10.5 due to the strong repulsion force among negatively charged whiskers. Low viscosity suspension of highly charged whiskers showing Newtonian behavior formed a dense whisker compact with a narrow pore size distribution of small pores. The density increase of green compact was accompanied by the orientation of whiskers where the direction in length of whiskers was perpendicular to the direction of filtration. Application of an external pressure (isostatic pressing) to porous whisker compacts consisting of network structure of randomly packed whiskers or whiskers of low orientation increased the green density.

Low-temperature sintering (under 350°C) of hydroxyapatite was attempted by a hydrothermal hot-pressing technique. The effects of borosilicate glass addition on the characteristics of the solidified body (mechanical strength, microstructure, crystal structure, pore distribution, etc.) and on the densification process during hydrothermal reaction were investigated. The borosilicate glass increased the mechanical strength of the solidified body; compression of 50% content of apatite was 2100 kg/cm2. It is also shown that water acts as a good catalyzer during solidification under hydrothermal conditions, and micropores can increase toughness of the solidified body due to the adsorption of stress. These hydrothermal hot-pressing solidification processes are so similar to sintering with liquid phase under pressure that the initial kinetics was discussed by means of the velocity measurement of shrinkage rate. In addition, these reactions may proceed in water, and are then discussed from the point of view of a heterogeneous reaction between powder and aqueous solution. It was proposed that the solidification process was due to viscous flow with rearrangement of grains in the solidified body, and the rate-determining step followed a core model of extraction from solid to solution.

Transmission electron microscopy observations were conducted on some zwitterionic polymers. Our observations were concentrated on the morphology of the solid state of poly (4-vinyl pyridine-sulfopropyl bctaines), with different degrees of quaternization. Among the morphological features, a microstructure arising from aggregated regions in the range of 50 to 200 Å is observed. Quite striking is the fact that this structure is absent in the micrographs for the base polymer, indicating that the aggregates are due to the interactions of the ion pairs of the polyzwitterions, as in the ionomer case. It is also found that the density of the aggregates increases when we increase the zwitterionic content of the copolymers.

We review our field investigations of construction materials which were initiated after the 1985 Mexico City earthquakes. We report observations on reinforcing steel samples collected in the ruins of collapsed buildings and describe the experiences in the production and testing of HSLA steel reinforcing bars with mechanical and metallurgical properties suitable for earthquake resistant construction. We review some aspects of the cement and concrete industries of Mexico before 1985 and present a description of the properties of polymer modified cements considering the potential not only for construction but for many other applications.