The fluorinating properties of NF3 and SF6 in heavy-metal fluoride glass processing were investigated between 200 and 1100 °C. Using infrared (IR) absorption spectroscopy the reactions of NF3 with ZrO2 and Al2O3 and the reactions of SF6 with ZrO2, SiO2, and Ni were studied. The reaction of NF3 with zirconia and alumina starts at 300 and 650 °C, respectively (yielding nitrogen oxides, nitrogen oxyfluoride, and presumably the metal fluorides). The reaction of SF6 and zirconia starts at 600 °C, yielding SO2F2. Sulfur hexafluoride and silica yield (above 900 °C) SiF4, SO2F2, and SOF2. Nickel and SF6 react above 700 °C yielding SF4 (and presumably NiF4). The results indicate that both gases are effective in oxide conversion at typical fluoride glass melting temperatures (800–900 °C). In addition NF3 can be used as a low-temperature fluorinating source for both oxide containing fluoride and pure oxide precursors. This offers great advantages over the use of solid NH4HF2, which is typically used and which forms an additional source of contamination.

The structure of shock-loaded polycrystalline titanium diboride was examined with transmission electron microscopy. The shock wave from ballistic impact produces prismatic and basal slip in grains favorably oriented with respect to the shock wave. It can be deduced from annealing experiments with the formation of stacking fault hexagons that there is a high concentration of point defects in deformed regions from the motion of dislocation jogs. Weak-beam microscopy shows that the dislocations in TiB2 are dissociated into partial dislocations. The stacking fault energy measured from a screw dislocation in the basal plane was found to be 120 mJ/m2. Widely dissociated dislocations in the shocked sample suggest that residual stresses are present in some regions.

Analysis of Ti-containing heterogeneities in a hot-pressed Al2O3 has revealed changes in microstructure caused by oxidation that provide some insight regarding the effects of Ti on local grain growth. The most consistent hypothesis is that Ti4+ in solution compensates the Mg2+ ion taken into solution from the MgO additive, probably by forming dipoles, and negates the effect of Mg2+ on grain boundary drag.

Hydration reactions and their rates have been studied qualitatively in CaO-and P2O5-rich compositional regions of the system CaO–SiO2-P2O5-H2O. Using aqueous solutions of Ca (NO3)2–4H2O, Ludox, and H3PO4 as starting materials, amorphous powders made by the sol-gel process were reacted with water. Some “curing” reactions were carried out at several temperatures: room temperature, 90 °C, and under hydrothermal conditions. Some glasses in the phosphate-rich region of the system were also made and hydrated. The hydration products are OH–Ap [OH–Ap = Ca10(PO4)6-(OH)2], Ca(OH)2 [CH = Ca(OH)2],C–S–H crystalline, C–S–P–H (C = CaO,S = SiO2,P = P2O5,H = H2O) crystalline, C–S–H gel, C–S–P–H gel, Ca(H2PO4)2·H2O, and CaHPO4. All phases have been identified and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDAX). The reactivities of the precursor materials and the compositional-structural nature of the hydration products formed are discussed. Some new compositions for “cementlike behavior” have been discovered.

Zirconium tetrafluoride (ZrF4) is the major constituent of many heavy metal fluoride glasses of technological interest. Five samples of commercially available “zirconium fluoride” were analyzed to determine their exact nature. Two samples were found to be anhydrous β-ZrF4, one was found to be α-ZrF4, one was zirconium tetrafluoride monohydrate (ZrF4 · H2O), and the final sample was identified as a hydrated amorphous phase of ZrF4. The behavior of these samples on heating was investigated with particular interest in the removal of water and the loss of fluorine from the hydrated materials. Infrared spectroscopy, x-ray diffractometry, thermogravimetric analysis, and differential scanning calorimetry were used in this investigation.

Precipitated hydrous zirconium oxide can be calcined to produce either a monoclinic or tetragonal product. It has been observed that the time taken to attain the final pH of the solution in contact with the precipitate plays a dominant role in determining the crystal structure of the zirconium oxide after calcination at 500 °C. The dependence of crystal structure on the rate of precipitation is observed only in the pH range 7–11. Rapid precipitation in this pH range yields predominately monoclinic zirconia, whereas slow (8 h) precipitation produces the tetragonal phase. At pH of approximately 13.0, only the tetragonal phase is formed from both slowly and rapidly precipitated hydrous oxide. The present results, together with earlier results, show that both the pH of the supernatant liquid and the time taken to attain this pH play dominant roles in determining the crystal structure of zirconia that is formed after calcination of the hydrous oxide. The factors that determine the crystal phase are therefore imparted in a mechanism of precipitation that depends upon the pH, and it is inferred that it is the hydroxyl concentration that is the dominant factor.