The entropy per nucleon (ital S/ital A) has been extracted for the Au (150--800)ital A MeV + Au reaction by using the phase I setup of the 4pi facility at GSI, Darmstadt. The entropy has been ...obtained from the comparison of various observables characterizing the ital dM/ital dZ fragment multiplicity distributions, extending up to ital Zsimilar to15, with those calculated with the quantum statistical model. It is the first time that ital S/ital A values are determined by considering the full ensemble of charged products detected in the reaction. Consistent values of ital S/ital A are found from different methods. These entropy values are shown to be fairly independent of the volume of the participant'' region considered. They are somewhat lower than those extracted in earlier works but are in good agreement with hydrodynamic calculations and suggest a low viscosity for the hot and dense nuclear matter.
Mixed lithium–zinc borophosphate glasses were prepared and studied in three compositional series xLi2O–(50−x)ZnO–50P2O5, xLi2O–(50−x)ZnO–10B2O3–40P2O5 and xLi2O–(50−x)ZnO–20B2O3–30P2O5 with x = 0, ...10, 20, 30, 40 and 50 mol% Li2O. The obtained glasses were characterized by the measurements of the density (ρ), molar volume (VM), glass transition temperature (Tg) and thermal expansion coefficient (α). For the investigation of structural changes 11B and 31P MAS NMR and Raman spectroscopy were applied. The replacement of zinc by lithium in borophosphate glasses slightly decreases VM and Tg, while α increases. In Li–Zn metaphosphate glasses the compositional dependence of Tg reveals a minimum, while at the borophosphate series Tg decreases monotonously with increasing Li2O content. Chemical stability of Li–Zn borophosphate glasses is very good for glasses with x = 0–30 mol% Li2O. Spectral studies showed in the glass series with 10 mol% B2O3 only the presence of BO4 sites. In the glasses with 20 mol% B2O3 the presence of BO3 and two BO4 sites was revealed in ZnO-rich glasses and only one BO4 site in Li2O-rich glasses; the number of BO3 groups decreases with increasing Li2O content which is ascribed to the formation of P–O–Zn covalent bonds in ZnO-rich glasses.
A review on the investigation of the structure and properties of zinc and lead borophosphate glasses is given. Structural studies with the application of Raman and infrared spectroscopy and 31P and ...11B MAS NMR spectroscopy are manifested on several borophosphate glasses. Structural studies were realized in several compositional series and thus compositional dependencies and the evolution of basic structural units in the glasses was established. The modification of phosphate and borophosphate glasses with other oxides e.g. Sb2O3 and transition metal oxides like TiO2 and Nb2O5 is presented.
Thermal behaviour of the glass series (100-
x
)50ZnO-10B
2
O
3
-40P
2
O
5
·
x
Sb
2
O
3
(
x
=0-42 mol%) and (100-
y
)60ZnO-10B
2
O
3
-30P
2
O
5
·
y
Sb
2
O
3
(
y
=0-28 mol%) was investigated by DSC and ...TMA. The addition of Sb
2
O
3
results in a decrease of the glass transition temperature and crystallization temperature in both compositional series. All glasses crystallize on heating in the temperature range of 522–632°C. Thermal expansion coefficient of the glasses monotonously increases with increasing Sb
2
O
3
content in both series and varies within the range of 6.6–11.7 ppm °C
−1
. From changes of thermal capacity within the glass transition region it was concluded that with increasing Sb
2
O
3
content the ‘fragility’ of the studied glasses increases.
The structure of 50ZnO–10B
2O
3–40P
2O
5+
xTiO
2 glasses prepared by slow cooling (for
x=0–24
mol% TiO
2) or by quenching (for
x=28–64
mol% TiO
2) was studied by Raman,
31P and
11B MAS NMR ...spectroscopy. TiO
2 incorporates into the glass structure, which results in a decrease in the molar volume and an increase in the glass transition temperature. According to Raman spectra Ti atoms form distorted TiO
6 octahedra and their incorporation into the structural network results in the depolymerization of phosphate chains.
11B NMR spectra of the glasses with increasing TiO
2 content show gradual changes from one symmetrical signal of B(OP)
4 units to a broad complex signal which was separated into five signals ascribed to four different types of BO
4 units and one BO
3 unit. With increasing TiO
2 content a part of boron atoms changes from tetrahedral BO
4 to trigonal BO
3 units, which is ascribed to the formation of TiO
6 units in the glass structure.
The compositional dependence of the amount of basic structural borate units in 50ZnO–10B
2O
3–40P
2O
5+
xTiO
2 glasses.
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