Thermally Highly Stable Amorphous Zinc Phosphate Intermediates during the Formation of Zinc Phosphate Hydrate

Abstract

The mechanisms by which amorphous intermediates transform into crystalline materials are still poorly understood. Here we attempt to illuminate the formation of an amorphous precursor by investigating the crystallization process of zinc phosphate hydrate. This work shows that amorphous zinc phosphate (AZP) nanoparticles precipitate from aqueous solutions prior to the crystalline hopeite phase at low concentrations and in the absence of additives at room temperature. AZP nanoparticles are thermally stable against crystallization even at 400 °C (resulting in a high temperature AZP), but they crystallize rapidly in the presence of water if the reaction is not interrupted. X-ray powder diffraction with high-energy synchrotron radiation, scanning and transmission electron microscopy, selected area electron diffraction, and small-angle X-ray scattering showed the particle size (≈20 nm) and confirmed the noncrystallinity of the nanoparticle intermediates. Energy dispersive X-ray, infrared, and Raman spectroscopy, inductively coupled plasma mass spectrometry, and optical emission spectrometry as well as thermal analysis were used for further compositional characterization of the as synthesized nanomaterial. (1)H solid-state NMR allowed the quantification of the hydrogen content, while an analysis of (31)P{(1)H} C rotational echo double resonance spectra permitted a dynamic and structural analysis of the crystallization pathway to hopeite.

Zinc Phosphate Nanoparticles Produced in Saliva

“…However, the presence of a low‐molecular organic compound (diethylene glycol) in the structure are thought to be responsible for the observed delay in crystallization. Similarly, in an elaborate study by Bach et al, the presence of non‐crystalline zinc phosphate nanoparticles as intermediate species, during the formation of crystalline zinc phosphate hydrates, was confirmed . This is consistent with the observed delay, of more than 24 hours, for the appearance of Bragg reflections in a BSA‐templated synthesis of zinc phosphate nanocomposites, as reported by Song et al Therefore, we speculate that the particles observed in sample C initially consist of a non‐crystalline zinc phosphate and, similar to that reported by Roming et al, exhibit a significant delay in crystallization due to organic components of the artificial saliva.…”

Drastic Change in Zinc Speciation during Anaerobic Digestion and Composting: Instability of Nanosized Zinc Sulfide

“…The X-ray diffraction (Figure S5) pattern is in accordance with the result obtained by Bach et al (2015). 32 Reference compounds were diluted in polyvinylpyrrolidone powder, ground and pressed into pellets for EXAFS analysis.…”

Role of Water During Crystallization of Amorphous Cobalt Phosphate Nanoparticles

“…Solid-state NMR revealed water to occur as a molecular entity with little evidence for proton exchange, but with a reorientation on a time scale of milliseconds. 26 (ii) Configuration: The formation and configuration of the amorphous phase are difficult to unravel. An appealing formation model of a hydrated amorphous phase is the agglomeration of small cluster nuclei with solvation water molecules trapped by hydrogen bonding in between.…”