Understanding the Stability and Recrystallization Behavior of Amorphous Zinc Phosphate

Abstract

Zinc phosphate, an important pigment in phosphate conversion coatings, forms protective films on rubbing surfaces. We have simulated the underlying reactions under shear by ball-milling zinc phosphate and monitored the reaction of hopeite (Zn 3 (PO 4 ) 2 •4H 2 O) and the retarded recrystallization of the amorphous reaction product by powder X-ray diffraction (PXRD) and quantitative infrared (IR) spectroscopy. Abrasion of stainless steel was simulated by addition of pure 57 Fe. The results provide insight into the chemistry of phosphate conversion coatings or during battery cycling of metal phosphates and give theoretical guidance for the preparation of amorphous phosphates. Thermal analysis revealed that the release of structural water is a key step during the reaction of hopeite under shear to ball-milled amorphous zinc phosphate. The back-reaction and associated recrystallization kinetics of amorphous zinc phosphate show a classical Langmuir behavior. Fe impurities inhibit the recrystallization of ball-milled amorphous zinc phosphate strongly. 57 Fe Mossbauer spectroscopy and PXRD revealed that Fe is oxidized to Fe 2+ and Fe 3+ during ball-milling and incorporated locally at the tetrahedral and octahedral sites of the structure. Ball-milled amorphous zinc phosphate is metastable as γ-Zn 3−x Fe x (PO 4 ) 2 . EPR studies showed the incorporation of Fe 3+ to be coupled with the formation of Zn 2+ vacancies. The Fe 3+ defect sites bind water because of their higher Pearson hardness (compared to Fe 2+ and Zn 2+ ), thereby reducing water mobility and inhibiting further reactions like the recrystallization to hopeite. Our findings reveal the amorphization mechanism of Zn 3 (PO 4 ) 2 •4H 2 O in stainless steel ball mills at the atomic scale and highlight how the reactivity of amorphous products is affected by impurities associated with the processing method.

PO43–-Loaded ZIF-8-type Metal–Organic Framework-Decorated Multiwalled Carbon Nanotube Synthesis and Application in Silane Coatings for Achieving a Smart Corrosion Protection Performance

“…Furthermore, the sizes of crystalline MW-OCNT@ZIF-8 and Si­(MW-OCNT@ZIF-8) particles are 24.7 and 26.1 nm, respectively, which are obtained by eq . Finally, regarding the MW-OCNT@ZIF-8-Phosphate nanopowder, there is a broad peak in the range of 25 to 35°, which corresponds to amorphous zinc phosphate, indicating that the phosphate doping has been successfully done on the MW-OCNT@ZIF-8 nanoparticles. , …”

“…Finally, regarding the MW-OCNT@ZIF-8-Phosphate nanopowder, there is a broad peak in the range of 25 to 35°, which corresponds to amorphous zinc phosphate, indicating that the phosphate doping has been successfully done on the MW-OCNT@ZIF-8 nanoparticles. 33,34 3.1.2. FTIR Analysis.…”

Designing Magnesium Phosphate Cement for Stabilization/Solidification of Zn-Rich Electroplating Sludge

“…Broad resonances at 8.5 ppm could be assigned to amorphous Zn phosphate hydrates ( e.g. , Zn 3 (PO 4 ) 2 ·2H 2 O and Zn 3 (PO 4 ) 2 ·4H 2 O), which suggested that the addition of Zn to the MPC system contributed to the formation of low-crystallinity Zn phosphate hydrates in addition to the crystallized Zn phosphate hydrates and MgKPO 4 ·6H 2 O . Small peaks with low density at 5.5 ppm from crystalline MgKPO 4 ·6H 2 O and Zn 3 (PO 4 ) 2 ·4H 2 O were detected in M/P3–2M8Z, M/6–5M5Z, and M/P6–2M8Z samples, indicating a changed orthophosphate environment. , Overall, it could be deduced that incorporating Zn suppressed the formation and crystallization of MgKPO 4 ·6H 2 O in the MPC system, where Zn reacted with phosphate to form crystalline Zn 3 (PO 4 ) 2 ·4H 2 O and a small amount of amorphous Zn phosphate hydrates.…”

“…Isostructural sharp peaks centered at 5.5 ppm in 31 P NMR spectra of M/P3−M, M/P3−5M5Z, and M/P6− M samples corresponded to MgKPO 4 •6H 2 O and Zn 3 (PO 4 ) 2 • 4H 2 O (Figure 2c). 18 Broad resonances at 8.5 ppm could be assigned to amorphous Zn phosphate hydrates (e.g., Zn 3 (PO 4 ) 2 •2H 2 O and Zn 3 (PO 4 ) 2 •4H 2 O), 41 which suggested that the addition of Zn to the MPC system contributed to the formation of low-crystallinity Zn phosphate hydrates in addition to the crystallized Zn phosphate hydrates and MgKPO 4 •6H 2 O. 39 Small peaks with low density at 5.5 ppm from crystalline MgKPO 4 •6H 2 O and Zn 3 (PO 4 ) 2 •4H 2 O were detected in M/P3−2M8Z, M/6−5M5Z, and M/P6−2M8Z samples, indicating a changed orthophosphate environment.…”

Novel optical amorphous phosphate materials with a low melting temperature

“…Soft chemistry methods involving hydrated phosphate synthesis have recently drawn attention in a variety of fields from cement engineering to biomaterial and energy applications. 16–19 Among them, one can mention the chemical reaction via coacervation that has been applied for electrical sealing or biomaterial applications. 20,21 Starting from a Graham salt (Na(PO 3 ) n ) solution, the coacervation process consists of promoting the liquid–liquid phase separation thanks to the presence of long phosphate chains which leads to the formation of a phosphate gel called “coacervate” and a supernatant phase.…”