Infrared Absorption Due to H2O and D2O in a Fluorozirconate Glass

A comparative study of infrared absorption due to H₂O and D₂O impurities in a fluorozirconate glass (53ZrF₄·20BaF₂·4LaF₃·3AlF₃·20NaF) was carried out. The H₂O and D₂O were introduced into the glass by reaction of the surface at 260°C with H₂O and D₂O vapor entrained in a stream of N₂. Reaction with H₂O produced IR absorption bands at 2.9 μm (O–H stretch) and 6.1 μm (H₂O bend). Reaction with D₂O produced bands at 3.9 μm (O–D stretch) and 8.3 μm (D₂O bend). The ratios of the corresponding D₂O/H₂O peak frequencies are 0.74 for both the stretching and bending vibrations, in good agreement with the value of 0.727 predicted from the difference in the OH and OD reduced masses.     

Effect of Water Content on the Electrical Conductivity of Na2O≅3SiO2 Glass

Na₂O–3SiO₂ glasses with up to ≅12 wt% water were prepared under high-pressure, hydrothermal conditions and their electrical conductivities were measured. The conductivity (σ) was found to depend on H₂O content in a manner similar to the "mixed-alkali" effect. At constant temperature, σ decreased initially with increasing H₂O content to a minimum at 3≅4 wt% H₂O and increased with further increase in water content. Infrared spectroanalysis of these glasses was made to determine the type of water present in the glass and the results were interpreted in the context of the measured activation energy and preexponential factor of dc conductivity. The sodium ion diffusion coefficient for a glass containing 0.76 wt% H₂O was less than that of water-free glass and in agreement with the electrical conductivity results.     

Crystal Chemistry of Hydrous Calcium Silicates: II, Characterization of Interlayer Water

Examination of tobermorite, 4–SCaO.5SiO₂.-5H₂O, and xonotlite, 5CaO.5SiO₂.H₂O, by infrared absorption revealed striking structural similarities and differences in the two phases. In the 8- to 15- μ region, the absorption was the same for both; the differences arose from the manner in which water and hydroxyl ions were bonded. Tobermorite exhibited strong absorption at 6.2 μ , a band which is generally associated with interlayer water, and at 2.9 μ , a band generally attributed to bonded (OH). The mineral xonotlite did not show these two bands but contained the band at 2.75 μ generally associated with free (OH). Synthetic xonotlite prepared at 300°C. was essentially the same as the mineral, but samples prepared at progressively lower temperatures exhibited the 2.9- μ band in increasing intensity. The fibrous form of tobermorite showed a band at 6.5 to 7.0 μ which increased in intensity with increasing amount of CaO in the solid; this band was also found in the 14-a.u. 1.0 CaO: SiO₂ hydrate, but not in xonotlite. The great volume stability of xonotlite during drying and wetting is readily explained on the basis of the present results. Shrinkage of tobermorite during drying at temperatures up to 650°C. may be due to removal of both interlayer water and bonded (OH). The changes in absorption during drying at room temperature were too small, however, to permit drawing any conclusions. Similarities and differences between tobermorite and certain clays are discussed.     

Synthesis of Mesoporous Needle-Shaped Ytterbium Oxide Crystals by Solvothermal Treatment of Ytterbium Chloride

The reaction of rare-earth (RE; Y, Er, and Yb) chloride hydrates in 1,4-butanediol at 300°C for 2 h gave mixtures of RE(OH)₂Cl and RE₂O₃· x H₂O, and the products were composed of irregularly shaped particles. A prolonged reaction (10 h) yielded a mixture of RE(OH)₂Cl and RE₂O₃· x H₂O for Er or Y, but phase-pure RE₂O₃· x H₂O was obtained for Yb. The product for Yb comprised needle-shaped single crystals of Yb₂O₃· x H₂O with a width of 0.2–0.6 μm and a length of 5–15 μm. The Yb₂O₃· x H₂O phase decomposed to Yb₂O₃ at 350°–500°C, preserving the needle-shaped morphology; this was maintained even after calcination at 1100°C. Single crystals of Yb₂O₃ obtained by the calcination of Yb₂O₃· x H₂O at 500°C had very small voids and the voids were enlarged to 35 Å in diameter by calcination at 800°C.     

The System CaO-Al2O3-P2O5-H2O at 200°C

The phase relations were established experimentally for the system CaO-Al₂O₃-P₂O₅-H₂O at 200°C and 1710 kPa. The quaternary compound, crandallite, CaAl₃(PO₄)₂(OH)₅· H₂O, was found to be stable. Compatibility joins in the system were determined. The phase relations are presented on the isothermal-isobaric 90 wt% water plane and by projecting the primary fields of the liquidus surface onto the same plane.     

The System CaO-Al2O3-H2O

Phase equilibria have been determined in the system CaO-Al₂O₃-H₂O in the temperature range 100° to 1000°C. under water pressures of up to 3000 atmospheres. Only three hydrated phases are formed stably in the system: Ca(OH)₂, 3CaO·Al₂O₃·6H₂O, and 4CaO·3Al₂O₃-3H₂O. Pressure-temperature curves delineating the equilibrium decomposition of each of these phases have been determined, and some ther-mochemical data have been deduced therefrom. It has been established that both the compounds CaO·Al₂O₃ and 3CaO·Al₂O₃ have a minimum temperature of stability which is above 1000°C. The relevance of the new data to some aspects of cement chemistry is discussed.     

Dehydration of Hydrous Zirconia with Methanol

The washing of hydrous zirconia with alcohols to reduce the incidence of hard agglomerates on subsequent drying is well known. The results of methanol dehydration of hydrous zirconia (zirconium hydroxide), [Zr₄(μ-OH)₈(OH)₈(H₂O)₈]˙ xH₂O, show that only μ-OH groups are unaffected. This suggests two things: First, the removal of nonbridging hydrooxo groups and water with alcohols such as methanol leads to a reduction/elimination of hard agglomerates. Second, hard agglomerate formation is associated with condensation reactions involving nonbridging hydroxo groups (Zr-OH+HO-Zr→Zr-O-Zr+H₂O).     

Partition of Hydrogen in the Modified Chemical Vapor Deposition Process

In the modified chemical vapor deposition (MCVD) process for making glass fibers, most of the hydrogen coming into the reaction from hydrogen-bearing impurities in the starting materials is not incorporated in the glass. It is instead mostly converted to HCl, which is not absorbed by the newly formed silica particles, and passes out the exhaust stack. The residual partial pressure of H₂O formed in equilibrium with HCl in the presence of O₂ and Cl₂ accounts quantitatively for the OH appearing in the glass when the known solubility of H₂O in silica is considered. The H₂O/HCl equilibrium is quenched at a temperature below that of the reaction zone at a value for which the rate of reaction approximates the transit time across the deposition zone. Quantitative agreement is obtained for published OH concentrations produced by SiHCl₃ doping.     

Reaction Products in the System MgCl2-NaOH-H2O

The precipitation process of solid phases Mg₃(OH)₅CI-4H₂O (phase 5), Mg₂(OH)₃CI-4H₂O (phase 3), and Mg(OH)₂ was followed by the addition of NaOH water solution in MgCl₂ water solutions of different concentrations (0.001 to 4.8 mol dm⁻³) and characterized by chemical, potentiometric, coulometric, and X-ray diffraction analyses. The concentration range in which the precipitation of solid phases occurs was determined. The phase distributions relative to the pH of solution and concentrations of magnesium and chloride were defined by the equilibrium diagram. The approximate solubility products of stable solid phases formed at different ionic strengths and at 293 K were determined.     

Reactions and Equi ibria in Magnesium Oxych oride Cements

Phase equi ibria in the system MgO-MgC ₂-H₂O at 2°±3°C were determined and the reactions by which the equi ibrium phases, 5Mg(OH)₂ MgC ₂ 8H₂O and 3Mg(OH)₂ MgC ₂8H₂O, deve op were studied by X-ray diffractometry. As reactive MgO is disso ved by magnesium ch oride so utions, a thixotropic suspension is converted to a ge, which then crysta izes to form the ternary oxych oride phases. Insufficient y active MgO disso ves more s ow y so that, in an open system, bu k composition can shift by evaporation of water, resu ting in crysta ization of a nonequi ibrium phase assemb age, with residua magnesium ch oride so ution and unreacted MgO. Imp ications of these nonequi ibrium reactions for the performance of magnesium oxych oride cements are discussed.     

Low-Temperature Formation of Aluminum Orthophosphate

Factors influencing the low-temperature formation of AIPO₄ and its precursor phases, AIPO₄· x H₂O (1 x 2), were investigated. AIPO₄ formed by reaction between 33.3 wt% H₃PO₄ solution and alumina. Five aluminas (three anhydrous and two hydrated) were utilized. Each differed in particle size, surface area, and crystallinity. The reaction temperatures investigated were 113°, 123°, and 133°C. The high-surface-area aluminas were sufficiently reactive in the phosphoric acid solution at these temperatures to produce crystalline reaction products. However, only hydrated forms of AIPO₄, AIPO₄· x H₂O (1 x 2), crystallized directly out of solution. x generally decreased as the curing temperature was increased. Upon dehydration of these hydrated reaction products, anhydrous AIPO₄ was formed, primarily in the berlinite and/or cristobalite modifications. Both the temperature of reaction and the alumina used influence the hydrates that form. In turn, the hydrates which form, the macroscopic assemblages into which they may crystallize, and the morphologies of the crystallites all affect the polymorphic form and the crystallinity of the anhydrous AIPO₄ phase ultimately produced on dehydration. Phase-pure and highly crystalline AIPO₄-cristobalite (the high-temperature modification) was formed by the dehydration of AIPO₄·H₂O at a temperature as low as 113°C.     

Effects of Melt Chemistry on the Spectral Absorption Coefficient of Molten Aluminum Oxide

Values of the spectral absorption coefficient (α) of liquid aluminum oxide were determined by transmission of a pulsed dye laser beam incident on continuous-wave (CW) CO₂-laser-melted pendant drops attached to sapphire filaments. Measurements were made on molten drops of Verneuil sapphire at wavelengths of 0.450 and 0.633 μm, at ambient oxygen partial pressures from 10^-10 to 1 bar in eight pure gases (Ar, CO, CO₂, H₂, H₂O, HCI, N₂ and O₂), in CO/CO₂ mixtures, and in H₂/H₂O mixtures, and at a temperature of ca. 2400 K. Specimens contaminated with iron, magnesium, silicon, and tungsten were also investigated in an oxygen atmosphere. At a wavelength of 0.633 μm, the value of α was greater than 50 cm^-1 under reducing or inert gas conditions. It decreased to a minimum at intermediate oxygen partial pressures of 5 × 10^-5 bar in CO/CO₂ mixtures and 5 × 10^-3 bar in H₂/H₂O mixtures, and increased at larger oxygen partial pressures. The specimens were opaque (α > 55 cm^-1) in hydrogen, in HCI at pressures above 0.04 bar. Specimens contaminated with 5000-10000 ppm of Fe, Mg, Si, or W were also opaque. At a wavelength of 0.45 μm the liquid aluminum oxide specimens were opaque in Ar and oxygen, and gave α= 46 cm^-1 in CO₂. The dynamic response when the ambient gas was changed from CO₂ to argon showed that the transmission maximum for = 0.45 μm was at p (O₂) < 0.1 bar.     

Encapsulation of Sn(II) and Sn(IV) Chlorides in Composite Cements

The hydration of two high replacement composite cements (3:1 blast furnace slag:ordinary Portland cement (BFS:OPC), and 3:1 pulverized fuel ash:OPC (PFA:OPC)) with the addition of both SnCl₂ and SnCl₄ has been investigated and the results from X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) are presented. Adding 5% or 1% SnCl₂·2H₂O or SnCl₄·5H₂O to the mix water resulted in the formation of Friedel's salt, Ca₃Al₂O₆.CaCl₂·10H₂O, and calcium hydroxo-stannate CaSn(OH)₆, which also involved the consumption of calcium hydroxide. After 90 days hydration at lower levels of addition (i.e., 1%) there was no longer evidence for CaSn(OH)₆, indicating that it too had been consumed in the pozzolanic reaction due to the lack of calcium hydroxide present. Results from SEM and EDS showed that bright regions between the BFS or PFA grains were tin containing and they were incorporated into the hydrated cement matrix. The tin was, therefore, localized rather than spread throughout and intimately incorporated into the microstructure.     

Attenuated Toatal Reflectance Fourier-Transform Infrared Spectra of a Hydrated Sodium Soilicate Glass

Attenuated total reflectance Fouriertransform infrared (ATR-FTIR) spectra were measured in the region from 4300 to 400 cm⁻¹ for a hydrated Na₂O–SiO₂ glass containing 35 wt% water. The Si–OH bending vibration mode was observed. It was found that the incorporated water, molecular water as well as hydroxyls, affected the Si–O vibrations. The effect of incorporated water upon the glass structure is discussed.     

Aqueous Solubility Diagrams for Cementitious Waste Stabilization Systems: II, End-Member Stoichiometries of Ideal Calcium Silicate Hydrate Solid Solutions

Solubility in the fully hydrated CaO–SiO₂–H₂O system can be best described using two ideal C-S-H-(I) and C-S-H-(II) binary solid solution phases. The most recent structural ideas about the C-S-H gel permit one to write stoichiometries of polymerized C-S-H-(II) end-members as hydrated precursors of the stable tobermorite and jennite minerals in the form of 5Ca(OH)₂·6SiO₂·5H₂O and 10Ca(OH)₂·6SiO₂·6H₂O, respectively. For thermodynamic modeling purposes, it is more convenient to express the number of basic silica and portlandite units in these stoichiometries using the coefficients n _Si and n _Ca. Thermodynamic solid-solution aqueous-solution equilibrium modeling by applying the Gibbs energy minimization (GEM) approach shows the best generic fits to the available experimental solubility data at solid 0.8 < Ca/Si < 2.0 if both stoichiometry and thermodynamic constants of the end-members are normalized to n _Si= 1.0 ± 0.3. Recommended stoichiometries and thermodynamic data for the C-S-H end-members provide a reliable basis for the subsequent multicomponent extension of the ideal C-S-H solid solution model by incorporation of end-members for the (radio)toxic elements or trace metals.     

Internal Friction of Glasses with Low Water Contents

Internal friction was measured for NaPO₃ glasses containing from 0.0004 to 0.146 wt% H₂O. In glasses containing ≤ 0.001 wt% H₂O, the only internal friction peak observed was that resulting from the Na⁺ ions, i.e. the alkali peak; it was ∼ 30% larger than in as-melted glasses. The second peak normally observed in as-melted NaPO₃ glass was completely absent when the water content was < 0.001 wt%, consistent with the interpretation that it is caused by a reorientation of proton-Na⁺ elastic dipoles. The concept that the second peak in as-melted alkali phosphate and silicate glasses results from nonbridging oxygen ions is not substantiated by these studies of NaPO₃ glasses, which contain a high percentage of these ions but do not exhibit this peak when the proton concentration is sufficiently low.     

Effect of Heat-Treatment on the Constitution and Mechanical Properties of Some Hydrated Aluminous Cements

The compound compositions of four aluminous cements were determined on anhydrous as well as hydrated specimens which had been heat-treated at temperatures between room temperature and 1400° C. Phases were identified by X-ray diffraction and differential thermal analysis. Specimens were also tested for transverse strength, dynamic modulus of elasticity, and thermal length change. A study of the dehydration characteristics of CaO - Al₂O₈ - 10H₂O₃ 3CaO.Al₂O₃. 6H₂O, and Al₂O₃. 3H₂O was included. The data indicated that CaO. Al₂O₃ 10H₂O was the primary crystalline hydrate formed in the cements at room temperature. At 50° C., 3 CaO Al₂O₃-6H₂O and Al₂O₃. 3H₂O were formed as by-products of the dehydration of CaO.Al₂O₃.10H₂O. When heated alone in an open system, CaO.Al₂O₃.10H₂O did not convert to 3CaO. Al₂O₃. 6H₂O and A1₂O₃. 3H₂O. A correlation between the mechanical properties and compound compositions was noted.     

Electroceramics from Source Materials via Molecular Intermediates: BaTiO3 from TiO2 via (Ti(catecholate)3)2-

Rutile or anatase may be depolymerized and complexed by sequential treatment with (i) H₂SO₄/(NH₄)₂SO₄, (ii) H₂O, and (iii) catechol/NH₄OH to produce the intermediate (NH₄)₂(Ti(catecholate)₃) · 2H₂O. Treatment with Ba(OH)₂· 8H₂O leads to an acid-base reaction generating Ba(Ti(catecholate)₃) · 3H₂O, in which the Ba:Ti ratio is held at 1:1 at the molecular level. Calcination produces BaTiO₃ powder.     

Studies in the System CaO-Al2O3-SiO2H2O: III, New Data on the Polymorphism of Ca2SiO2 and Its Stability in the System CaO-SiO2- H2O

The nature of the low-temperature inversions γ-α' and α'-β was investigated by various techniques: hydrothermal and "dry" quenching runs, differential thermal analysis at atmospheric and elevated nitrogen pressures, X-ray diffractometer patterns obtained at elevated temperatures, "static" pressure techniques, and infrared absorption spectrometry. A revised energy-temperature diagram is presented for Ca₂SiO₄, with the transition γ' to α' taking place at about 725°C. and the α'-β transition, although not reversible at an exact temperature, taking place at about 670° C. At low water pressures (2000 lb. per sq. in.) the inversion γ-α' was placed at 675°C. Attempts to extrapolate the value obtained at 2000 lb. per sq. in. to obtain a more accurate reversible inversion temperature at atmospheric pressure, although limited in accuracy by the reliability of heat-of-transition data, would indicate a temperature of about 725° C. at atmospheric pressure. Three new compounds, 8CaO.3SiO₂ -3H₂O (X), 6CaO 3SiO₂.H₂O (Y), and 9CaO-6SiO₂ H₂O (Z), were found to be stable above 700°C. at H₂O pressures greater than 7500 lb. per sq. in.     

Studies on 4CaOAl2.O3.13H2O and the Related Natural Mineral Hydrocalumite

Single-crystal X-ray and electron-diffraction studies show the existence in one polymorph of 4CaO.Al₂O₃. 13H₂O of a hexagonal structural element with α= 5.74 a.u., c = 7.92 a. u. and atomic contents Ca₂(OH)₇- 3H₂O. These structural elements are stacked in a complex way and there are probably two or more poly-types as in SiC or ZnS. Hydrocalumite is closely related to 4CaO.A1₂O₃.13H₂O, from which it is derived by substitution of CO₃^2-for 20H^-+ 3H₂O once in every eight structural elements; similar substitutions explain the existence of compounds of the types 3CaO Al₂O₃.Ca Y ₂- xH₂O and 3CaO Al₂O₃ Ca Y xH₂O. On dehydration, 4CaO.Al₂O₃.13H₂O first loses molecular water and undergoes stacking changes and shrinkage along c. At 150° to 250°C., Ca(OH)₂ and 4CaO.3Al₂O₃.3H₂O are formed and, by 1000°C., CaO and 12CaO.7Al₂O₈. The dehydration of hydrocalumite follows a similar course, but no 4CaO.3Al₂O₃.3H₂O is formed.