Sonja V. Smiljanić

The energy efficiency of buildings can be greatly improved by decreasing the energy embodied in installed materials. In this contribution, we investigated the possibility of foaming waste bottle glass in the air atmosphere with the addition of water glass, which would reduce the energy used in the production of foamed glass boards. The results show that with the increased addition of water glass, the crystallinity and the thermal conductivity decrease, however, the remaining crystal content prevents the formation of closed-porous foams. The added water glass only partly protects the carbon from premature oxidation, and the foaming mechanism in the air is different than in the argon atmosphere. The lowest obtained foam density in the air atmosphere is 123 kg m⁻³, while the lowest thermal conductivity is 53 mW m⁻¹ K⁻¹, with an open porosity of 50% for the sample obtained in the air, containing 12 wt% of water glass, 2 wt% of B₂O₃, 2 wt% AlPO₄ and 2 wt% K₃PO₄.

The crystal structure of new lanthanum strontium borate glass-ceramics was refined by the Rietveld method. The results showed that La2SrB10O19 has the monoclinic crystal structure, space group C2 (No. 5) with a = 11.1170(6), b = 6.5667(3), c = 9.2363(3) ?, ? = 91.481?, V = 674.04(7) ?3, two formula units per unit-cell, and density 3.830 g cm?3. The main building units of the crystal structure are BO4 tetrahedra and BO3 triangles. Clusters composed of [B5O12] form an infinite double layer running perpendicular to the c-axis. Lanthanum atoms, situated in [B5O12]n layers, are coordinated with 10 oxygen atom in a form of LaO10 polyhedra, while Sr atoms, located between [B5O12]n layers, are coordinated with 8 oxygen atoms in a form of SrO8 polyhedra. Microstructural measurements contain both crystallite domain sizes and microstrain calculations obtained by the Warren-Averbach and the simplified integral-breadth methods.

Crystallization kinetics of 22.5Li2O?10Al2O3?30GeO2?37.5P2O5 (mol%) glass was studied under non-isothermal condition using the differential thermal analysis (DTA). The study was performed by using the first crystallization peak temperature (Tp1) which belongs to the precipitation of LiGe2(PO4)3 phase in the glass. The activation energy of glass crystallization (Ea) was determined using different isokinetic methods. The dependence of Ea on the degree of glass-crystal transformation (?) was studied using model-free isoconversional linear integral KAS (Kissinger-Akahira-Sunose) and FWO (Flynn-Wall-Ozawa) methods. It was shown that the Ea varies with ? and hence with temperature and consequently the glass/crystal transformation can be described as a complex process involving different mechanisms of nucleation and growth.

In this work, the dissolution behavior of a polyphosphate glass, with the composition 45P2O5?3SiO2?25K2O?15CaO?10MgO?ZnO?MnO (mol %), in simulated body fluid (SBF) at a temperature of 37 ?C for different times was studied. Two powder sizes of the glass (granulation: 0.1?0.3 and 0.3?0.65 mm) and the bulk glass were investigated. The dissolution experiments were conducted under stationary conditions. Changes in the normalized mass release, normalized concentration of ions, pH values, and surface morphology were determined as a function of the dissolution time. The initial rates of glass powder dissolution and leaching of ions, as well as the diffusion coefficient of cations and the releasing rate of ions, during the hydrolysis process of glass were determined. It was shown that the investigated phosphate glass dissolves in SBF incongruently, with neither precipitation nor the formation of newly potentially toxic compounds, in a dissolution period 720 h.

The selected lanthanum-strontium-borate glasses were prepared by a conventional melt-quenching technique. The compositions of the investigated glasses were chosen to be: 5.7, 9.5, 14.3, 19.1 mol % for La2O3, 22.9, 19.1, 14.3, 9.5 for mol % SrO and 71.4 mol % for B2O3. The density, molar volume, oxygen molar volume, oxygen packing density, oxygen/boron ratios and structural transformations in the glass network were investigated according to the substitution of SrO by La2O3. The density and the molar volume increased in parallel with La2O3 content increase. Simultaneously, oxygen molar volume values increased while the oxygen packing density values decreased. A hot stage microscope (HSM) and a differential thermal analysis (DTA) were used to determine the characteristic temperatures. By increasing the content of lanthanum, the glass transition temperatures, changed with the same trend as the molar volume. Glass stability parameters were calculated from the temperatures obtained by DTA and HSM. The HSM results were used to obtain the viscosity curves by applying Vogel-Fulcher-Tamman (VFT) equation.