NMR relaxation study of hardening acid-base dental cements

2001

Synthesis and characterization of α-hopeite, Zn3(PO4)2·4H2O

1999

Orthorhombic α-Zn3(PO4)2·4H2O, α-hopeite, was synthesized from an aqueous solution of zinc acetate and orthophosphoric acid. The synthesis from these starting materials yielded best results with respect to purity and crystallinity. Structural characteristics of the compound were investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). Supplemental data came from surface area, particle size distribution, and density measurements. The obtained compound proved to be highly crystalline and stoichiometric. Dehydration of α-hopeite is accompanied by at least two endothermic effect…

Vibrational analysis of iron and zinc phosphate conversion coating constituents

2001

Abstract The FT-MIR/FT-FIR and NIR-FT-Raman spectra of orthorhombic α -Zn 3 (PO 4 ) 2 ·4H 2 O (α-hopeite) and monoclinic Zn 2 Fe(PO 4 ) 2 ·4H 2 O (phosphophyllite), including deuterated samples, have been measured in the polycrystalline state at room temperature and below. The distribution of vibrational levels was related to the results of complete unit-cell group analyses. The number of uncoupled OD stretching modes of α-hopeite (isotopically dilute samples) strongly exceeds that expected from the number of hydrogen positions of the structure reported. In contrast, unequivocal assignment of the four hydrogen bonds of phosphophyllite has been performed. The distortion of the phosphate tetr…

Applications of conduction calorimetry to the setting reaction of zinc phosphate dental cement

1999

The kinetics of the exothermic setting reaction of zinc phosphate dental cement can be successfully investigated by conduction calorimetry. The primary objective of this study is to examine the effects arising from the addition of various additives to the liquid and calcination of cement powder. The rate of heat evolution versus time shows the occurrence of merely one maximum. In the case of unmodified orthophosphoric acid a sharp peak occurs early after onset of mixing due to the formation of crystalline α-hopeite. Commercial cement liquids contain aluminum and zinc. From the calorimetric curves it has been found that these cations act as a setting retarders, and ensure sufficient working …