The influence of substituting strontium for calcium in the following glass series 49.46 SiO 2 –1.07 P 2 O 5 –(23.08-X) CaO–X SrO–26.38 Na 2 O was studied on the physical properties. Solid state nuclear magnetic resonance and vibrational spectroscopy showed that the glasses were predominantly composed of Q 2 silicate chains. Addition of strontium did not result in any structural alteration of the glass network due to the similar role of SrO compared with that of CaO. The density increased with strontium content whilst the oxygen density decreased indicating a more expanded glass network. The glass transition temperature reduced with strontium substitution in a linear fashion and there was no evidence of a mixed alkaline earth effect with a lower than expected glass transition temperature. Dilatometric softening points also reduced with increasing strontium content, whilst the thermal expansion coefficients increased. The results are consistent with a weaker network as a result of the lower charge to size ratio of Sr 2+ compared to Ca 2+ .

Strontium containing bioactive glasses: Glass structure and physical properties

Rare earth (RE) doped oxyfluoride glass ceramics possess interesting optical properties with applications in telecommunications and optoelectronics, such as solid state lasers, optical amplifiers, etc. These materials combine the transparency and mechanical and chemical resistance of aluminosilicate glasses with the low phonon energy and facile incorporation of RE ions in the fluoride crystals. The incorporation of RE ions in the crystalline phases enhances the laser emission intensity, a major property of these materials. Transparency is achieved when crystal size is in the nanometric scale, usually below 40 nm, which avoids light scattering. A strict control of the nucleation and crystal growth processes is therefore necessary which requires a deep knowledge of the crystallisation mechanisms. The great activity and publications in this field in the last decades merit a review providing a comparative study of the different nanoglass ceramic systems, their structural and optical characterisation and their main properties and applications. This is the objective of this review paper which includes 227 references. A general discussion on glass nucleation and crystallisation theories and more relevant crystallisation parameters and characterisation techniques are put forward in the first section of the review, focused on nanocrystallisation processes in oxyfluoride systems. In the second section, the principal RE doped glass ceramics are presented. After a general introduction about the luminescence processes, including up- and down-conversion, the behaviour of RE elements in glasses and crystals are discussed. Glass ceramic compositions have been divided as follows: glass ceramics with a glass composition following Wang and Ohwaki’s oxyfluoride glass ceramic, and glass ceramics with different matrix compositions, arranged by crystalline phases. Relevant properties, mainly optical and laser, are described in each system along with the most relevant applications of these materials.

/pdf/nanocrystallisation-in-oxyfluoride-systems-mechanisms-of-3vsuzuu2ij.pdf

Nanocrystallisation in oxyfluoride systems: mechanisms of crystallisation and photonic properties

A novel generation of flexible opto-electronic smart applications is now emerging, incorporating photovoltaic and sensing devices driven by the desire to extend and integrate such technologies into a broad range of low cost and disposable consumer products of our everyday life and as a tool to bring together the digital and physical worlds. Several flexible polymeric materials are now under investigation to be used as mechanical supports for such applications. Among them, cellulose, the most abundant organic polymer on the Earth, commonly used in the form of paper, has attracted much research interest due to the advantages of being recyclable, flexible, lightweight, biocompatible and extremely low-cost, when compared to other materials. Cellulose substrates can be found in many forms, from the traditional micro-cellulose paper used for writing, printing and food/beverage packaging (e.g. liquid packaging cardboard), to the nano-cellulose paper which has distinct structural, optical, thermal and mechanical properties that can be tailored to its end use. The present article reviews the state-of-the-art related to the integration and optimization of photonic structures and light harvesting technologies on paper-based platforms, for applications such as Surface Enhanced Raman Scattering (SERS), supporting remarkable 107 signal enhancement, and photovoltaic solar cells reaching ∼5% efficiency, for power supply in standalone applications. Such paper-supported technologies are now possible due to innovative coatings that functionalize the paper surfaces, together with advanced light management solutions (e.g. wave-optical light trapping structures and NIR-to-visible up-converters). These breakthroughs open the way for an innovative class of disposable opto-electronic products that can find widespread use and bring important added value to existing commercial products. By making these devices ubiquitous, flexible and conformable to any object or surface, will also allow them to become part of the core of the Internet of Things (IoT) revolution, which demands systems’ mobility and self-powering functionalities to satisfy the requirements of comfort and healthcare of the users.

Multifunctional cellulose-paper for light harvesting and smart sensing applications

A fining agent for reducing the concentration of seeds or bubbles in a silicate glass. The fining agent includes at least one inorganic compound, such as a hydrate or a hydroxide that acts as a source of water. In one embodiment, the fining agent further includes at least one multivalent metal oxide and, optionally, an oxidizer. A fusion formable and ion exchangeable silicate glass having a seed concentration of less than about 1 seed/cm 3 is also provided. Methods of reducing the seed concentration of a silicate glass, and a method of making a silicate glass having a seed concentration of less than about 1 seed/cm 3 are also described.

Fining agents for silicate glasses

Fluoride glass-ceramics doped with lanthanide ions are very promising materials for optical devices. In this study, transparent fluoride glass-ceramics have been obtained from oxy-fluoride glasses in the Na2O–Al2O3–SiO2–LaF3 system by heat treatment slightly above Tg, upon which NaLaF4 nano-crystals with a size of up to 20 nm precipitate. The crystallisation mechanism is suggested to involve the formation of a SiO2-enriched shell around the nano-crystals which hampers their further growth, limits Ostwald ripening, and promotes uniformity in size. This desired enrichment of lanthanide ions inside nano-crystals with an adjustable and uniform size distribution is essential for future photonic applications. To validate the crystallisation mechanism of this glass system, the structure and composition of the crystalline phase, glass matrix and the developing interface have been studied by viscosity, dilatometry, X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques.

Design of oxy-fluoride glass-ceramics containing NaLaF4 nano-crystals

The aim of the study was an analysis of two groups of glasses from the SiO2–P2O5–K2O–CaO–MgO system with various content of network formers in the form of P2O5 and SiO2, modified by the addition of ZnO. Their effect on glass-forming ability, glass transition effect, crystallization process and the kind of crystallizing phases was examined using DSC and XRD methods. It was observed that in both matrixes, the addition of ZnO decreases the glass transition temperature (T
 g). The lower T
 g values observed in the phosphate matrix glasses and the accompanying higher values of the changes in molar heat capacity (Δc
 p) in contrast to the silicate matrix glasses may be considered an indicator of the degree of the reconstruction of their amorphous structure, which facilitates the process of their crystallization. It was found that the crystallizing products of the silicate matrix glasses were silicates and phosphates whose structure contained zinc. In the phosphate matrix glasses, it was observed that zinc inhibited the crystallization of silicate phases.

/pdf/comparative-study-of-zinc-addition-effect-on-thermal-2yqqiday8j.pdf

Comparative study of zinc addition effect on thermal properties of silicate and phosphate glasses

The influence of fluorine content on the structure and crystallization of oxyfluoride glasses from the Na2O–Al2O3–SiO2–LaF3 system was studied by DTA/DSC, XRD, FTIR and SEM methods. It has been found that the increase in the fluorine content in the structure of oxyfluoride glasses causes the increase of the flexibility of their structure, which inhibits the process of crystallization of the silicate- aluminium matrix. Simultaneously the ability of the glass for LaF3 crystallization, which shows a multistage character, is increasing. Analysis of the local atomic interactions in the structure of glasses has been used to explain the course of the crystallization.

Thermal and structural studies of nanocrystallization of oxyfluoride glasses

The relation between change of the specific heat (ΔC p) accompanying the glass transformation and the chemical composition of glasses (Na2O, CaO, MgO)-Al2O3-SiO2 system has been studied. The exchange of modifiers in the glass structure causes the ΔC p increase in the sequence Na>Ca>Mg. Change the glass network composition by introducing Al into it makes smaller increase of the ΔC p values. It has been shown that degree of ΔC p value changes is dependent on the iconicity/covalence of chemical bonds of cations with oxygen of glass structure network.

Thermal study of the influence of chemical bond ionicity on the glass transformation in (Na2O, CaO, MgO)-Al2O3-SiO2 glasses

Thermal behaviour and biochemical activity of potassium-silicate-phosphate glasses modified by addition of Ca, Mg, acting as ecological fertilisers of controlled release rate of the nutrients for plants were studied. It has been found that the biochemical activity of silicate-phosphate glasses depends on the nature and the number of components forming the glassy framework and is related to the thermal stability of glass demonstrated by the formation of new compounds during the process of crystallisation. It is proved that these seemingly different properties are determined by the same parameters which are the strengths bonds of glass network-formers and modifiers as well as their chemical affinity.

Thermal analysis of glasses for proecological applications

The thermal decomposition of vesuvianite was studied by means of thermal, FTIR and X-ray methods. It was found that two structural forms of vesuvianite, a high-temperature (disordered) and a low-temperature (ordered) one, differ distinctly in the mechanism of their decomposition (dehydroxylation). Dehydroxylation of low vesuvianites begins at lower temperatures (ca. 900°C), and the strong endothermic peak with maximum at ca. 1020°C is usually followed by an exothermic peak. Dehydroxylation of high vesuvianites begins at ca. 1000°C, and the OTA curve usually displays two endothermic peaks not followed by an exothermic effect. The crystallization products of vesuvianite are grossular, gehlenite and anorthite. Vesuvianite melts in the temperature range 1100–1200°C.

Thermal decomposition of vesuvianite

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