The structure of phosphate glass evidenced by small angle X-ray scattering

Abstract

Numerous phosphate glass systems with compositions covering the entire glass forming range have been examined by small angle Xray scattering. The experiments were carried out in a widely extended interval of s values between 0.055 and 31 nm À1 . A small angle scattering effect was detected for all samples investigated with the exception of the aluminium metaphosphate glass. The small angle scattering recorded indicates the presence of two differently-sized heterogeneity regions of electron density. The small-scale heterogeneities are present in magnesium and zinc phosphate glasses only. Their size is about 1 nm diameter in the magnesium and about 2 nm in the zinc phosphate glasses. The species do not result from liquid-liquid phase separation. Examinations to extract information on the nature of these heterogeneity regions are described in detail. There is no fundamental knowledge on the large-scale heterogeneities established. The small angle scattering suggests that their occurrence is related to water contamination. Anomalous small angle X-ray scattering experiments of a series of zinc polyphosphate glasses and a strontium metaphosphate glass sample are performed to examine the distribution of the Zn or Sr atoms, respectively.

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

“…Using a simplistic assumption that the tribofilm consists mainly of sulfur (ρ = 2.1 g/cm 3 ) or phosphorous (ρ = 1.8 g/cm 3 ), equation (1) suggests that the average critical glancing angle is less than 0.73 o , as shown in Figure 4, for both P and S at their average k-edge of 2150 eV and 2473 eV, respectively. A more realistic assumption that the ZDDP tribofilm consists mainly of zinc polyphosphate [7] (ρ = 3.3 g/cm 3 [60]) suggests a critical glancing angle of 0.80 o . Another parameter that is as important as the glancing angle is the penetration depth of the incident beam into the probed sample.…”

A review on immobilization of phosphate containing high level nuclear wastes within glass matrix – Present status and future challenges

“…), get depolymerized through conversion of bridging oxygens (P O P) to non-bridging oxygens (P O R) [77]. Thus in case of binary xR 2 O (or R O)-(1 − x)P 2 O 5 glasses (where x is in mole fractions), with increasing molar R 2 O/P 2 O 5 ratios (from 0 to 1 to 2 to finally 3) or [O]/[P] ratios (from 2.5 to 3 to finally >3.5), the structural groups (represented by Q i where 'i' represents the number of bridging oxygens per tetrahedron) passes from cross linked Q 3 (ultraphosphate; O/P = 2.5) to Q 2 (metaphosphate; O/P = 3.0) to Q 1 (pyrophosphate; O/P = 3.5) to Q 0 (orthophosphate; O/P = 4.0), keeping P always in four fold coordination [78,79]. Recently it has been noted that depending on the chemical nature, the cations present within a given phosphate glass can act either as network modifier (e.g.…”

“…On the other hand, radionuclides having high radiotoxicity, geochemical mobility, and long half-lives (e.g. 99 Tc, 129 I, 79 Se, 135 Cs, 239 Pu, 237 Np, 235 U, 36 Cl, and 14 C) are elements of deep concern from environmental pollution point of view [10,11]. Therefore, for protection of biosphere, HLWs need to be 'concentrated and contained'.…”

“…Toward this a number of efforts have been made across the world over the last fifty years, but so far limited progresses have been made to produce such matrices in actual plant scale on regular basis. The probable reason behind this is lack of complete comprehensions of the problem, its 79 Se, 85 Kr, 87 Rb, 89 Sr, 90 Sr, 93 Zr, 95 Zr, 95 Nb 99 Tc, 107 Pd, 115 In, 126 Sn, 129 I, 131 I 135 Cs, 137 Cs, 141 Ce, 142 Ce, 144 Ce, 144 133 Xe, 140 Ba, 134 Te, 93 Mo, 106 Ru, 106 Rh, 107 Pd, 140 La, 154 Eu Activation products 3 H, 10 Be, 14 C, 24 Na, 36 Cl, 39 Ar, 55 Fe, 59 Ni, 60 Co, 63 Ni, 93 Mo, 93m Nb, 94 Nb, 99 Tc, 108m Ag, 113m Cd, 121m Sn, 205 Pb, 210 Po associated difficulties and bottle neck situations. Hence for better understanding of the subject and to take right steps towards feasible solutions it is absolutely necessary to put together the lessons we have learnt from past experiments.…”

SAXS and DSC studies on the structural characteristics of siliconized s-triazine glassy hybrid materials

“…The formations of multi-component organic-inorganic hybrid materials that exhibit a vitreous glassy state have been in the focus of academic and industrial research groups for many years [1][2][3][4][5][6][7][8][9]. The unique ability of these materials to form isotropic and anisotropic matrices at ambient conditions permits their utilization as a dense dispersion medium for doping a broad variety of photo-, electro-, and bio-active substrates for different optoelectronic and biosensor applications [1,2,4].…”