Influence Of Glass Composition Research Articles

Influence of glass composition on the network structure and mineralization of europium containing mesoporous bioactive glass nanoparticles

A mesoporous bioactive glass nanoparticle (MBN) containing functional elements effectively enhances its healing effect in medical applications. The MBN mainly comprises SiO2 structure and controls the composition by incorporating functional ions into the glass network, which affects the network structure and bioactivity. Europium has already been identified to have luminescence properties for drug delivery systems and positively affects osteogenic properties. Therefore, in this study, we recognize the changes in the glass network according to different compositions with the same amount of europium oxide (10 mol%).The MBN compositions with SiO2–CaO–P2O5–Eu2O3 were synthesized by sol-gel method, and we control the contents of SiO2 and CaO, respectively. The obtained Eu-containing MBNs had spherical morphology with mesoporous structure. Changes in bioactivity and mineralization properties would be investigated to apply the dental products. After soaking in simulated body fluid (SBF), Eu-containing MBNs with substituted SiO2 form an amorphous calcium phosphate phase on their surface. The results indicate that incorporating Eu in the bioactive glass network is an effective strategy for mineralization and developing novel multifunctional MBNs for bone tissue and drug delivery carriers.

Composition dependence visible fluorescence from praseodymium ions doped Al2O3–CaO-M(M=B2O3, GeO2, Ga2O3) glasses

Pr3+ doped Al2O3–CaO based glasses were excellent candidate optical gain mediums for visible solid-state lasers due to its wide transmittance region and excellent mechanical properties. However, poor glass-forming ability limited its further application in visible fiber laser. In this work, B2O3, GeO2, Ga2O3 were employed for modifying the glass-forming ability and lowing the melting temperature of the Al2O3–CaO based glasses. By introducing 15 mol% GeO2 and Ga2O3, the thermal stability ΔT were enlarged to be 199 and 264 °C, respectively. The influence of glass composition on the fluorescence characteristic of Pr3+ were systematically investigated. For lower doping concentration, different multiphonon relaxation rare of 3P0 and 1D2 energy levels accounting for the different fluorescence spectra of Pr3+ doped Al–Ga, Al–Ge and Al–B glasses, while for the higher doping concentration, cross relaxation processes lead to the fluorescence was gradually dominated by the transition of 3P0 with increasing Pr3+ concentration.

Network Structure and Properties of Lithium Aluminosilicate Glass.

Based on lithium aluminosilicate glass, the composition of glass was optimized by replacing SiO2 with B2O3, and the influence of glass composition on structure and performance was studied. With the increase in B2O3 concentrations from 0 to 6.5 mol%, Al2O3 always existed in the form of four-coordinated [AlO4] in the network structure, and B2O3 mainly entered the network in the form of four-coordinated [BO4]. The content of Si-O-Si linkages (Q4(0Al)) was always dominant. The incorporation of boron oxide improved the overall degree of polymerization and connectivity of the lithium aluminosilicate glass network structure. An increase in the degree of network polymerization led to a decrease in the thermal expansion coefficient of the glass and an increase in Vickers hardness and density. The durability of the glass in hydrofluoric acid and NaOH and KOH solutions was enhanced overall.

Gamma irradiation-induced defects in borosilicate glasses for high-level radioactive waste immobilisation

Gamma irradiation-induced defects at doses of 0.5 and 5 MGy were studied in lithium sodium-borosilicate (LiNaBSi) and sodium barium-borosilicate (NaBaBSi) glasses, used for high-level radioactive waste immobilisation in the UK and India, respectively. X-band electron paramagnetic resonance (EPR), Raman and UV-Vis-nIR spectroscopies were used to characterise the glasses before and after irradiation. EPR and UV-Vis-nIR absorption spectroscopies revealed the formation of boron-oxygen hole centres (BOHC), electrons trapped at alkali cations or ET centres and peroxy-radicals (PORs) as defects common to both glasses. In addition, E− or polaron centres were observed in NaBaBSi glasses, possibly related to formation of elemental sodium colloids. Time-dependent thermal annealing at a range of temperatures, including those relevant to canister centreline cooling (CCC), which may be of relevance to geological disposal in future technical assessments, was carried out to study thermal stability of these radiation-induced defects. It was observed that PORs are the most thermally-stable defects in both glasses. The influence of glass composition on the segregation of sodium and the possible formation of metal colloids upon irradiation have been discussed.

Influence of composition of nuclear waste glasses on vapor phase hydration

For the first time, the influence of glass composition on the vapor hydration kinetics of the French AVM nuclear waste glass simulants was investigated. Three complex borosilicate glasses (>20 oxides) along with three simplified Na/(Ca, Na)/(Mg, Na)-alumino-borosilicate glasses with four or five oxides were altered at 50 °C in water vapor (95% RH) for up to 557 days. The solid characterization of the altered samples (by SEM, TEM, XRD, ToF-SIMS, SAXS) revealed that the rate-controlling vapor hydration mechanism is composition dependent. The vapor hydration rate of the more durable glasses, whose molar ratio of Al2O3/(CaO or MgO) is ≥ 1, seems to be limited by network-hydrolysis, whereas the overall glass alteration rate of the less durable glasses, whose Al2O3/MgO ratio is < 1, seems to be driven by the precipitation of Mg-rich secondary phases. All the vapor hydrated glasses show the presence of a homogeneous gel layer of a few tens of nm thickness. The more durable glasses have a smaller quantity of secondary phases precipitated on their surface. The less durable glasses have a relatively significant quantity of secondary phases precipitated above the gel layer and irregularly shaped, scattered and highly porous altered zones formed beneath the gel layer. The overall alteration rate of the less durable glasses was 10–20 times faster than the more durable glasses. For all glasses, FTIR spectroscopy indicated an inflexion in the vapor hydration rate after 120–200 days of alteration, likely due to a passivating effect of the altered layer formed under unsaturated conditions. The average pore size of the altered layer in certain vapor hydrated glasses measured by SAXS is similar to the pore sizes of the gel layer formed in aqueous medium and varies very slightly with glass composition.

Influence of glass composition on photoluminescence from Ge2+ or Ag nano‐cluster in germanate glasses for white light‐emitting diodes

AbstractGermanium glass has attracted much interest because of its potential application as the optical waveguides and communication devices. In this work, germanium glass was prepared, exhibiting the blue luminescence at the 410 nm from the Ge2+. The influence of SiO2 addition in the germanate glass on the 410 nm luminescence of the Ge2+ was observed. The SiO2 addition promoted the formation of Ge2+, which is because the Si4+ ions can deprive the O2− ions from the Ge4+ ion caused by the lower optical basicity of Si4+ ions than Ge4+ ion. The germanium glasses containing the Ag nano‐clusters were prepared using ion‐exchange method. The influence of SiO2 concentration on the size of Ag nano‐clusters was observed, which stabilize the size distribution and lead to the miniaturization of Ag nano‐clusters. The Ag nano‐clusters size dependence of their photoluminescence was observed in germanate glasses, and the tunable photoluminescence of Ag nano‐clusters was obtained by controlling the size of Ag nano‐clusters. It is noticed that the Ag nano‐clusters formed in the germanate glass showed the white light emission characteristic excited at the blue chip, exhibiting the practical application as the blue converted white light‐emitting diodes.

Influence of glass composition on the kinetics of glass etching and frosting in concentrated HF solutions

During etching of a multicomponent glass in concentrated hydrofluoric acid (HF) solutions, a crust can gradually appear on the glass surface, depending on the chemical etching parameters. This crust deposition is the result of the precipitation of hexafluorosilicate anions released by the glass dissolution reaction, with cations coming either from the etching solution or from the glass (like Na+, K+ or Ca2+). To understand the impact of this crust on the overall kinetics of both the etching and frosting process, we have studied the dissolution of four types of commercial glass substrates in etching solutions containing various concentrations of HF. The kinetics of the frosting process was investigated by two independent methods: on the one hand the chemical analysis by ICP-OES of the amount of Si dissolved from the glass as a function of time, and on the other hand the measurement of the glass weight loss with time. These two methods showed that the glass etching rate decreases with time as a result of crust formation which gradually becomes more protective. Both methods also indicated that increasing the amount of HF in the etching solution increases the etching rate in a non-linear way, and that the etching rate increases with the alumina content of the glass. A separate chemical analysis of the amount of Si present in the crust also revealed that the amount of HF in the etching solution has an impact on the amount of crust deposited on the glass surface. Finally, we have been able to rationalize all these kinetic data based on a semi-empirical quantitative etching and frosting model, allowing to extract a characteristic dissolution and precipitation constant (Kdiss and Kdep), respectively.

Basic Study on the Influence of Glass Composition and Aluminum Content on the Ag/Al Paste Contact Formation to Boron Emitters

Abstract In this study, the contact formation of aluminum containing silver metallization pastes for boron emitters was investigated. Model pastes with varied glass composition (PbO-containing and PbO-free) and Al content were prepared. It was found, that glass viscosity as well as Al content have a strong influence on densification behavior of the pastes. The most significant effect of the aluminum addition is the change of the thermodynamic conditions in the system silver-glass-silicon. For investigations of the contact formation an in-situ-contact resistance measurement was performed. The interface morphology of the pastes in dependence on the firing temperature was investigated by means of cross section samples in SEM and EDX. Finally, n-type Si solar cells were electrically characterized and the IV-data were correlated to the interface morphology.

The influence of glass composition on crystalline phase stability in glass-ceramic wasteforms

Zirconolite glass-ceramic wasteforms were prepared using a suite of Na2O–Al2O3–B2O3–SiO2 glass matrices with variable Al:B ratios. Zirconolite was the dominant crystalline phase only for the most alumina rich glass compositions. As the Al:B ratio decreased zirconolite was replaced by sphene, zircon and rutile. Thermodynamic data were used to calculate a silica activity in the glass melt below which zirconolite is the favoured crystalline phase. The concept of the crystalline reference state of glass melts is then utilised to provide a physical basis for why silica activity varies with the Al:B ratio.

Stability of Protective Oxide Layer Against Corrosion: Solubility Measurements of Chromium in Soda Lime Silicate Melts

The solubility of chromium oxide (Cr2O3) in soda lime silicate glasses was studied as a function of temperature (1,200 °C ≤ T ≤ 1,350 °C), oxygen fugacity (−12 ≤ log fO2 ≤ −0.6) and glass composition (Na2O–CaO–xSiO2; x = 3, 4, 5 and 6). The fO2 was proved to induce several oxidation states of Cr for a given glass composition at a fixed temperature. The influence of glass composition on the Cr solubility was interpreted in terms of the optical basicity Λ concept. An increase in the melt basicity led to an increase in the Cr solubility for the experiments conducted under oxidizing conditions. The total dissolved Cr also showed a significant increase with increasing temperature for a given fO2 and glass composition. The results proved that the stability of Cr2O3 scale against corrosion was profoundly influenced by fO2, T and melt basicity.

Characterization of mechanical properties of BaTiO3 ceramic with different types of sintering aid by nanoindentation

The influence of glass composition on mechanical property of BaTiO3 ceramics was investigated with nanoindentation technique and also its effect on densification and dielectric property was analyzed. Two different glasses of BaO-CaO-SiO2 and BaO-ZrO2-SiO2 system were used as the sintering aid of BaTiO3 powder. It was found that the addition of BaO-ZrO2-SiO2 glass to BaTiO3 was beneficial for the densification compared to that of BaO-CaO-SiO2 glass, resulting in high dielectric constant over 2500, the hardness vale of 13.6 GPa and the elastic modulus of 167.9 GPa after sintering at 1240°C.

Factors Affecting &lt;i&gt;In Vitro &lt;/i&gt;Bioactivity of Glasses

In this work we summarize the most important findings of the influence of glass composition, sample shape and fluid circulation on in vitro behavior of bioactive glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2. The sample shapes included plates, particulates, powdered glasses, glass fibers and sintered cones with interconnected porosity. The in vitro bioactivity was measured as the changes observed in the immersion solution, SBF, and the formation of reaction layers on the samples at 4 to 168 h immersion. A lower surface area to volume ratio gave smaller changes on the ion concentrations and pH of the immersion solution but thicker reaction layers on the glass surfaces. In particulate systems with circulating fluid the pH gradients in SBF were lower but surface layers more even than in static systems. The influence of glass composition on reaction layer formation as suggested by glass plates correlated with the in vitro behavior of glass particulates larger than 250 µm, porous cones and fibers when using similar SA/V ratio.

Spectral analysis of Eu 3+:B 2O 3–Al 2O 3– MF 2 ( M = Zn, Ca, Pb) glasses

The influence of glass composition on the optical properties of Eu 3+-doped borate glasses modified with Zn 2+, Ca 2+ and Pb 2+ cations has been investigated. These glasses have been prepared by melt quenching technique and characterized through optical absorption, photoluminescence and decay times. An intense red luminescence is observed from the 5D 0 emitting level of Eu 3+ ions in these glasses. The relative luminescence intensity ratio of 5D 0 → 7F 2 to 5D 0 → 7F 1 transitions has been evaluated to estimate the local site symmetry around the Eu 3+ ions. Judd–Ofelt parameters have been evaluated from the absorption spectra. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak stimulated emission cross-sections for the 5D 0 → 7F J ( J = 0, 1, 2, 3 and 4) transitions. Decay curves of the 5D 0 level of Eu 3+ ions in these three glass systems have been measured by monitoring the 5D 0 → 7F 2 transition at room temperature.

The Development of Thermally Stable Sealing Glass in the BaO–B2O3–SiO2 System for Planar SOFC Applications

The purpose of the present paper is to study the influence of glass composition on the thermal stability in the SiO2–B2O3–BaO system, and three glasses were consequently investigated. Although Glass A has a coefficient of thermal expansion (CTE) that shows the best match with those of anode and electrolyte materials of solid oxide fuel cells (SOFCs), the thermal stability of Glass A is quite poor, where after being heat treated at 800°C for only 8h, the CTE of the glass increased more than 24%. The change of the CTE value was mainly attributed to the fast crystallization that formed high CTE value phases such as BaB2O4 and Ba2Si3O8. In order to improve the thermal stability, BaO in Glass A was replaced by B2O3 (Glass B) and SiO2 (Glass C). It was found that the decrease in the BaO content improved the thermal stability of the resultant glasses. Glass B showed less than 8% change of the CTE during annealing time at 800°C, while Glass C exhibited superior long-term thermal stability, where the change of the CTE was within the equipment detection limit after being heat treated for 300h at 800°C. The good thermal stability of Glass C was believed to be due to the formation of a more compact glass network after the substitution as compared with that of Glass A. The good thermal stability makes Glass C attractive to be used as the sealing material for SOFC applications.

Influence of glass composition and alteration solution on leached silicate glass structure: A solid-state NMR investigation

A multinuclear solid-state NMR investigation of the structure of the amorphous alteration products (so called gels) that form during the aqueous alteration of silicate glasses is reported. The studied glass compositions are of increasing complexity, with addition of aluminum, calcium, and zirconium to a sodium borosilicate glass. Two series of gels were obtained, in acidic and in basic solutions, and were analyzed using 1H, 29Si, and 27Al MAS NMR spectroscopy. Advanced NMR techniques have been employed such as 1H– 29Si and 1H– 27Al cross-polarization (CP) MAS NMR, 1H double quantum (DQ) MAS NMR and 27Al multiple quantum (MQ) MAS NMR. Under acidic conditions, 29Si CP MAS NMR data show that the repolymerized silicate networks have similar configuration. Zirconium as a second nearest neighbor increases the 29Si isotropic chemical shift. The gel porosity is influenced by the pristine glass composition, modifying the silicon–proton interactions. From 1H DQ and 1H– 29Si CP MAS NMR experiments, it was possible to discriminate between silanol groups (isolated or not) and physisorbed molecular water near Si (Q 2), Si (Q 3), and Si (Q 4) sites, as well as to gain insight into the hydrogen-bonding interaction and the mobility of the proton species. These experiments were also carried out on heated samples (180 °C) to evidence hydrogen bonds between hydroxyl groups on molecular water. Alteration in basic media resulted in a gel structure that is more dependent on the initial glass composition. 27Al MQMAS NMR data revealed an exchange of charge compensating cations of the [AlO 4] − groups during glass alteration. 1H– 27Al CP MAS NMR data provide information about the proximities of these two nuclei and two aluminum environments have been distinguished. The availability of these new structural data should provide a better understanding of the impact of glass composition on the gel structure depending on the nature of the alteration solution.

Fluorescence properties of Eu 3+ ions doped borate and fluoroborate glasses containing lithium, zinc and lead

The influence of glass composition on the fluorescence properties of Eu 3+ ions doped borate and fluoroborate glasses modified with Li +, Zn 2+ and Pb 2+ cations have been investigated. The magnitude of splittings of 7F 1 levels are analyzed using crystal-field (CF) analysis. The relative intensities of 5D 0 → 7F 2 to 5D 0 → 7F 1 transitions, crystal-field strength parameters and decay times of the 5D 0 level have been determined and are found to be lower for Pb based glasses than those of Zn/Li based glasses. The lifetimes of 5D 0 level are found to increase when borate glasses are modified with pure fluorides than with oxides and oxyfluorides. The fluorescence decay of 5D 0 level fits perfect single exponential in the Eu 3+:glass systems studied which indicates the absence of energy transfer between Eu 3+ ions in these glasses.

Glasses for High-Resistivity Thick-Film Resistors

Knowledge about the role of the glass matrix in thick-film resistors is necessary for improvement of their electrical properties for use in high-performance components. The influence of glass composition on the microstructure of ruthenate conductor and resistor parameters has been studied. Additions of TiO 2 , GeO 2 , and TeO 2 , which in dilute concentrations markedly increase the resistivity, improve the temperature coefficient of the resistance and the voltage stability. The oxide enrichment of the glass film between the conducting particles reduces the ruthenium-ion solubility and decreases the tunneling conductivity between the conductor grains.

Influence of glass composition on the properties of glass polyalkenoate cements. Part IV: influence of fluorine content

The influence of fluorine content of the glass in a series of glasses based on: 4.5SiO 2–3.0Al 2O 3–1.5P 2O 5–(5.0- X)CaO– XCaF 2 was investigated on their cement formation with poly(acrylic acid). Increasing the fluorine content of the glass was found to reduce the glass transition temperature, as a result of fluorine replacing bridging oxygens by non-bridging fluorines. Working and setting times of the cement pastes reduced with increasing fluorine content of the glass. Compressive strength and Young's moduli increased with fluorine content initially and then remained approximately constant. Fracture toughness, toughness and un-notched fracture strength were not significantly influenced by fluorine content. The results are consistent with fluorine simultaneously disrupting the glass network and reducing the basicity of the glass.

Influence of glass composition on the properties of glass polyalkenoate cements. Part III: influence of fluorite content

The influence of fluorite content of the glass on the formation and properties of glass polyalkenoate cements was investigated. A series of glass powders based on 1.5SiO 2·0.5P 2O 5·Al 2O 3·CaO· XCaF 2 were synthesised. The glass transition temperature of the glass fell with increasing fluorite content. Setting and working times of the cement pastes decreased with increasing fluorite content of the glass. Compressive strength and un-notched fracture strength increased with increasing fluorite content of the glass. Fracture toughness and toughness of the cements were relatively insensitive to fluorite content.

Influence of glass composition on the properties of glass polyalkenoate cements. Part II: influence of phosphate content

The influence of phosphate content of the glass on the formation of glass polyalkenoate cements was investigated. Glasses were synthesised based on (4.5−2 X)SiO 2–3.0 Al 2O 3–(3.0− X)CaO–(1.5+ X)P 2O 5–2.0 CaF 2 and X was varied from −1.5 to 0.8. The setting and working time of the cement pastes increased with the phosphate content of the glass ( X). Increasing the phosphate content resulted in an initial increase in compressive strength followed by a sharp reduction in strength. Young's modulus and un-notched fracture strength exhibited a maximum at intermediate phosphate contents. Fracture toughness reduced at high phosphate contents, whilst toughness increased. Phosphate in the glass is thought to aid glass degradation by providing additional phosphorus–oxygen bonds for hydrolysis, but may also reduce the amount of aluminium released by reducing the susceptibility of aluminium–oxygen–silicon bonds to acid hydrolysis. The released phosphate may also compete with the carboxylate groups in the polysalt matrix cement for cations inhibiting the crosslinking reaction.