X-ray-absorption spectroscopic studies of sodium polyphosphate glasses

Yin, Zhanfeng; Kasrai, M.; Bancroft, G.M.; Tan, K. H.; Feng, Xiaoping

doi:10.1103/physrevb.51.742

Cited by 107 publications

(85 citation statements)

References 52 publications

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“…30 The absorption at the edge is attributed to the transition of a 1s core electron to the 3p lowest unoccupied antibonding molecular orbital. 12, 13,31,32 For all samples, the energy position of the white line peak (A) ranges from 2152-2153 eV. In addition, solid K-PO 4 samples display a visible shoulder (B) at ∼4-5 eV above the edge with energy KH 2 PO 4 > K 2 HPO 4 ≈ K 3 PO 4 .…”

Section: Resultsmentioning

confidence: 99%

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

et al. 2009

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Phosphorus K-edge X-ray absorption fine structure (XAFS) was explored as a means to distinguish between aqueous and solid phosphates and to detect changes in phosphate protonation state. Data were collected for H 3 PO 4 , KH 2 PO 4 , K 2 HPO 4 and K 3 PO 4 solids and solutions and for the more complex phosphates, hydroxylapatite (HAP) and struvite (MAP). The X-ray absorption near-edge structure (XANES) spectra for solid samples are distinguishable from those of solutions by a shoulder at ∼4.5 eV above the edge, caused by scattering from cation sites. For phosphate species, the intensity of the white line peak increased for solid and decreased for aqueous samples, respectively, with phosphate deprotonation. This was assigned to increasing charge delocalization in solid samples, and the effect of solvating water molecules on charge for aqueous samples. In the extended X-ray absorption fine structure (EXAFS), backscattering from first-shell O atoms dominated the (k) spectra. Multiple scattering (MS) via a four-legged P-O 1 -P-O 1 -P collinear path was localized in the lower k region at ∼3.5 Å -1 and contributed significantly to the beat pattern of the first oscillation. For EXAFS analysis, increasing Debye-Waller factors suggest more disorder in the P-O shell with addition of protons to the crystal structure due to the lengthening effects of P-OH bonds. This disorder produces splitting in the hybridized P 3p-O 2p band in the density of states. For aqueous samples, however, increased protonation reduced the structural disorder within this shell. This was linked to a change from kosmotropic to chaotropic behavior of the phosphate species, with reduced effects of H bonding on structural distortion. The intensity of MS is correlated to the degree of disorder in the P-O shell, with more ordered structures exhibiting enhanced MS. The observed trends in the XAFS data can be used to distinguish between phosphate species in both solid and aqueous samples. This is applicable to many chemical, geochemical and biological systems, and may be an important tool for determining the behavior of phosphate during the hydrothermal gasification of biomass.

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Section: Resultsmentioning

confidence: 99%

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

et al. 2009

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“…Spectrum [A] is a spectrum of an antiwear film produced on the A1 alloy (A-390) surface at 60~ and 30 N. Spectrum [B] was produced by digitally removing the ZDDP signal from spectrum [A]. The resulting spectrum [B] reveals that the intensity of peaks a I and b are greater than those in spectrum [C], which is from a steel (A2) coupon worn at 60~ 220 N. Yin et al [17] found that the polyphosphate chain length increased with the intensity polyphosphate. A shoulder at position 2, and the broad peak a ~ reveal that there is ZDDP present as well.…”

Section: Methodsmentioning

confidence: 99%

X-ray absorption spectroscopy of antiwear films on aluminum alloys generated from zinc dialkyldithiophosphate

et al. 1995

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The boundary lubrication of A1 alloys 6061 (AI-6% Si) and A-390 (Al-18 wt% Si), by a sec-ZDDP (zinc dialkyldithiophosphate) oil blend was examined at 60 andl00~ The wear performance in the ZDDP blend was an improvement on base stock. At 100~ the ZDDP prevented scuffing, though no antiwear films could be detected due to the severe wear. At 60~ all samples showed initial scuffing followed by a more controlled wear given by an embedded antiwear film. P L-edge X-ray near-edge structure (XANES) spectroscopy using synchroton radiation was used to characterize the antiwear and thermally generated deposition films on the A1 alloys. P L-edge XANES results of the antiwear films at 100~ showed the absence of a polyphosphate film. A well-developed polyphosphate film was indicated at 60~ very similar to that formed on steel at 100~ P L-edge XANES results of the thermal deposition films showed the presence of only unchanged sec-ZDDP at 125~ with no polyphosphate present. A polyphosphate film was present at 200~ similar to the antiwear film for A1 alloy at 60~ and steel at 100~

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“…They showed peaks at 136.7, 137.7 and 139 eV as well as a wider peak at 146.8 eV, similarly to the measured reference polyphosphate compound ( Figure 3). These XANES spectra could be assigned to polyphosphates based on existing libraries of P-containing compounds [40][41][42]. When transferred to MS-2 medium, both strains lost their polyphosphate granules, and produced Ca-carbonates only ( STEM-EDXS microanalyses showed that polyphosphate granules generally contained about 53%-63% of phosphorus (atomic proportion of P over P + Ca + K + Mg), ~13% to ~29% of calcium, ~2% to ~18% of magnesium and ~7% to ~15% of potassium (Figures 1d and 2d, Tables A1 and A3).…”

Section: Chemical Composition Of Carbonate and Polyphosphate Inclusiomentioning

confidence: 99%

Biomineralization Patterns of Intracellular Carbonatogenesis in Cyanobacteria: Molecular Hypotheses

Margaret-Oliver

Cam

et al. 2016

Minerals

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Abstract:The recent discovery of intracellular carbonatogenesis in several cyanobacteria species has challenged the traditional view that this process was extracellular and not controlled. However, a detailed analysis of the size distribution, chemical composition and 3-D-arrangement of carbonates in these cyanobacteria is lacking. Here, we characterized these features in Candidatus Gloeomargarita lithophora C7 and Candidatus Synechococcus calcipolaris G9 by conventional transmission electron microscopy, tomography, ultramicrotomy, and scanning transmission X-ray microscopy (STXM). Both Ca. G. lithophora C7 and Ca. S. calcipolaris G9 formed numerous polyphosphate granules adjacent or engulfing Ca-carbonate inclusions when grown in phosphate-rich solutions. Ca-carbonates were scattered within Ca. G. lithophora C7 cells under these conditions, but sometimes arranged in one or several chains. In contrast, Ca-carbonates formed at cell septa in Ca. S. calcipolaris G9 and were segregated equally between daughter cells after cell division, arranging as distorted disks at cell poles. The size distribution of carbonates evolved from a positively to a negatively skewed distribution as particles grew. Conventional ultramicrotomy did not preserve Ca-carbonates explaining partly why intracellular calcification has been overlooked in the past. All these new observations allow discussing with unprecedented insight some nucleation and growth processes occurring in intracellularly calcifying cyanobacteria with a particular emphasis on the possible involvement of intracellular compartments and cytoskeleton.

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X-ray-absorption spectroscopic studies of sodium polyphosphate glasses

Cited by 107 publications

References 52 publications

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

X-ray absorption spectroscopy of antiwear films on aluminum alloys generated from zinc dialkyldithiophosphate

Biomineralization Patterns of Intracellular Carbonatogenesis in Cyanobacteria: Molecular Hypotheses

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