Thermal expansion is an interesting, ubiquitous and neglected property of materials. Recently, Lenain et al. (1985) and Limaye (1986) have been investigating anisotropy in the low-expansion structures of the sodium zirconium phosphate family. In the hexagonal structure one axis expands while another contracts. In going from the calcium to the strontium analog the anisotropy actually changes sign. A change in anisotropy between CrB2 and TiB2 had been observed by R.V. Sara (1960). The results in Fig. 1 obtained by high temperature x-ray diffraction measurements indicate that for TiB2 the thermal expansion of the c-axis is greater than the expansion of the a-axis, whereas for CrB2 the reverse is true.
The synthesis of N,N′,N″- tris(2-hydroxyethyl)-N,N,N′,N′,N″,N″-hexamethyl-2,2′,2″-nitrilotris( ethylammonium ) trichloride, a potential monomer for the preparation of polyurethane-based ion exchangers, is described and its structure reported based on X-ray diffraction data.
The high-pressure structural chemistry of α-zirconium phosphate, α-Zr(HPO4)2·H2O, was studied usingin-situhigh-pressure diffraction and synchrotron radiation. The layered phosphate was studied under both hydrostatic and non-hydrostatic conditions and Rietveld refinement carried out on the resulting diffraction patterns. It was found that under hydrostatic conditions no uptake of additional water molecules from the pressure-transmitting medium occurred, contrary to what had previously been observed with some zeolite materials and a layered titanium phosphate. Under hydrostatic conditions the sample remained crystalline up to 10 GPa, but under non-hydrostatic conditions the sample amorphized between 7.3 and 9.5 GPa. The calculated bulk modulus,K0= 15.2 GPa, showed the material to be very compressible with the weak linkages in the structure of the type Zr—O—P.
Using potassium carbonate, ammonium phosphate, zirconium dioxide, and cobalt oxide as raw materials, a kind of potassium zirconium phosphate ceramic pigments with bright purple color at high temperature were obtained through a series of optimizing experiments. It’s a novel type of ceramic pigments with chromaticity indexes of L*=55.37, a*=18.52, and b*=-30.56. X-ray diffraction (XRD), TG-DTA and chroma analysis were employed to characterize the pigments. The results reveal that potassium zirconium phosphate type ceramic pigments presenting bright purple color is due to Co2+ partially replace Zr4+ in potassium zirconium phosphate crystal lattice, which leads to the lattice distortion because of the formation of Zr2-xCo2x(PO4)3 phase. Moreover, owing to the limitation of solubility of Co2+ in potassium zirconium phosphate crystal lattice, the contents of cobalt oxide added may not be too much.
Polyamide-6/organointercalated zirconium phosphate nanocomposites (PA-6/ZrPOct) were prepared by melt extrusion. The synthesized lamellar ZrP was expanded with octadecylamine at different amine:phosphate ratio, and its influence was evaluated by tensile test, melt flow rate, water absorption, rheology, scanning electron microscopy, and wide-angle X-ray diffraction. For all nanocomposites, the increase of modulus and decrease of elongation at rupture were observed. The decrease in water uptake was observed as the amine/phosphate increase, indicating that the presence of the amine reduces the hydrophilic nature of PA-6. Rheology revealed by pseudoplasticity indices that the nanofillers dispersion was homogeneous in all nanocomposites. Wide-angle X-ray diffractometry analysis showed that the characteristic basal spacing peak of pristine ZrP was absent for ZrOct 1:1 and 2:1. Also a high decrease in crystallinity was observed for PA-6/ZrOct 2:1 sample, which would be associated to plasticizing effect of octadecylamine avoiding crystallites formation. Evidences showed that structures with different degrees of intercalation and/or exfoliation could have been achieved.
AbstractFor the low-symmetry system of the ion-exchanger zirconium phosphate the influence of irradiation and ion-exchange on the crystal disorder has been investigated by means of photographic x-ray diffraction methods. The weakening and the shifting of Bragg reflections and the broadening of maxima of diffuse scattering allow the estimation of the concentration and the strength of defects induced in this system.
AbstractCrystalline silicotitanate ion exchangers are highly selective for separating Cs from Narich waste streams. However, use of these ion exchangers for removal of Cs from radioactive tank waste will result in large volumes of secondary wastes. Thermal conversion of silicotitanates produces a durable waste form with reduced volumes up to 40%. Leach tests (MCC-l and PCT) have shown that Cs leach rates of IE-91 1-Na (heat treated at 900°C for an hour) are extremely low, ranging from 0.1 to lwt% Cs loss in Cs fraction release, or 10-1 to 10-8g/m2day in normalized Cs mass loss. These are several orders of magnitude lower than that of borosilicate glass. In order to understand the interplay between the structure and high Cs durability, X-ray diffraction, 133Cs NMR, and thermogravimetric analysis have been used to identify phase(s) responsible for trapping Cs in these silicotitanates. Results indicate that Cs is likely to be contained in a crystalline silicate phase.
The α-zirconium phosphate (α-ZrP) and hydrophobically modified α-zirconium phosphate (α-ZrP-I) were prepared. The grafting of octadecyl isocyanate was confirmed by Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The dispersion of α-ZrP-I was studied by environmental scanning electron microscopy (SEM). The wettability of α-ZrP-I was determined by Kruss DSA30. Then, the effects of decompression and augmented injection of α-ZrP-I have been studied. The results of water flooding experiments show that the appropriate concentration of α-ZrP-I has an effect on the decrease of the water injection pressure.
Molecular simulation supported by X-ray diffraction and IR spectroscopy has been used to analyse the structure of α-zirconium phosphate intercalated by ethanol, Zr(HPO4)2.2C2H5OH. Molecular-mechanics simulations using theCrystal Packermodule in theCerius2modelling environment revealed the crystal packing in the interlayer,i.e.the positions of ethanol with respect to the Zr(HPO4)2layers and the layer stacking in the intercalated structure. The average interlayer distanced\,=\,14.03 (13) Å obtained by modelling is in agreement with the experimentaldvalue of 14.05 (4) Å obtained from the X-ray diffraction analysis. The disorder in the Zr(HPO4)2.2C2H5OH structure found by molecular simulation has been confirmed by the character of the X-ray diffraction pattern.
In-situhigh-pressure powder X-ray diffraction study of α-zirconium phosphate
