Chemical Durability, Properties and Structural Approach of the Glass Series xFe2O3-(45-x) PbO-55P2O5 (with 0 ≤ x ≤ 20;mol%)

The synthesis for glasses series xFe2O3-(45-x)PbO-55P2O5, (with 0 ≤ x ≤ 20;mol%) carried out in a temperature (1050 ± 10)°C, leads to obtaining transparent glasses, brown in color and with a non-hygroscopic appearance. The study of glasses dissolution rate, immersed in distilled water at 90°C for 24 days, indicates a considerable chemical durability. The increase in the Fe2O3 content in the vitreous network to the detriment of PbO is a favorable factor for the chemical durability improvement. Different techniques have been used such as X-ray diffraction, infrared spectroscopy, DSC, SEM and density for the study of these glasses. These techniques have led to establish correlations between chemical and structural properties. Thus the results obtained confirmed the creation of P-O-M bonds (M = Pb, Fe) with a strongly covalent nature to the detriment of the hydrated P-O-P bonds and led to the formation, mainly, of pyrophosphate groups. The low melting point of Pb-O makes it possible to play an important role, at the same time, on the viscosity, on the equilibrium between the vitreous bath and the crystallites formed. The dissolution rate obtained is 100 times smaller than that of silicate glasses used as an alternative form for the vitrification of radioactive waste.

Developing Low Temperature Glazes for Omani Clay Artworks: Laboratory Investigation to Reduce Costs by Using Frits

The role of using frits in developing glazes for ceramics has increasingly received attention across a number of industrial ceramics fields in recent years. Over the past decade, the link between using frits for developing ceramics glazes and the reduction of financial costs has been at the center of much attention. Determining the impact of using frits in the local ceramics industry in Oman is important for the future study of this creative field. Using imported ready-made glazes, despite their long commercial success, is associated with a number of problems, including a shortage of suppliers, high costs, and logistical difficulties. Consequently, there is an urgent need to address the importance of developing glazes locally to help establish some workable solutions for the aforementioned problems. To date, no research studies have investigated using local Omani earthenware clays to make glazes by combining them with commercial frits using empirical laboratory methodologies. By developing low temperature chemical glaze recipes, the main aim of this study is to explore the possibilities of using Omani earthenware clays (OECs) and frits to create glazes that are suitable for local Omani ceramic works.

Glass Thickness and Fragmentation Behavior in Stressed Glasses

Breakage patterns, residual stress, and fractured surfaces on tempered glasses are investigated to find the correlation among glass thickness, tempered level, and the number of fragments, particularly when the glass thickness is less than 4 mm. Relatively thin glasses require high compressive stress for producing fragments, and the required compressive stress is increased with decreasing glass thickness (3.2 to 2.1 mm). By analyzing the residual stress of glasses before and after the fragmentation test, we observe that a relatively thin glass spends more stored energy to generate a new fracture surface and stores less energy for the second cracking as compared to thick glasses. Fractography shows that all glasses have a similar characterization on the fractured surface irrespective of glass thickness. However, the only dif- ference is the depth of the compressive layer. By reducing the depth of the compressive layer to less than approx. 20% of the glass thickness, it is observed that the possibility of producing small fragments is dramatically decreased. There- fore, this study confirms that the compressive stress and its depth are essential as key factors contributing to the achievement of a relatively high fragmentation using a thin glass.

Thermal Analysis and Immobilisation of Spent Ion Exchange Resin in Borosilicate Glass

The underground disposal of waste arising from the nuclear industry needs constant evaluation in order to improve upon it through minimizing the volume and cost by reducing the amount of glass used without compromising the safety of any leakage from the radioactive waste form. The immobilization of the spent resin (NRW-40) in borosilicate glass was investigated to meet the acceptance criteria for disposal of nuclear waste. The organic mixed bed resin in granular form was used as a waste target. The analysis of surrogate resin doped with radioactive and non-radioactive cesium (Cs) and cobalt (Co) was carried out to investigate their thermal and chemical properties and their compatibility with an alkaline borosilicate glass. The thermal analysis indicates that the structural damage caused by 1 mSv gamma radiation to the radioactive resin has altered its properties in comparison with the non-radioactive resin, same amount of cesium (8.88 wt%) and cobalt (1.88 wt%) were used in both resins. The immobilization of residue shows that the excess sulfur in the residue caused phase crystallization in the final glass matrix. It was found that the volatilization of Cs-137 and Co-60 from the successful radioactive resin-glass matrix (HG-3-IER-500) were more than that in the non-radioactive resin-glass matrix (HG-3-IEX-500). The study demonstrates comprehensive experimental and analytical works and shows that it is possible to minimise the volume of the waste while keeping the required safety levels, however further research needs to be carried out in this area.

Optical Basicity and Polarizability of Nd³⁺-Doped Bismuth Borate Glasses

This paper reports on different physical and optical properties of Nd3+-doped bismuth borate glasses. The glasses containing Nd3+ in (25 - x)Bi2O3:20Li2O:20ZnO:35B2O3:xNd2O3 (where x = 1, 1.5, 2 mol%) have been prepared by melt-quenching method. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The physical parameters like dielectric constant, refractive index, ionic concentration, oxygen-packing density, inter ionic distance, polaronradius, reflection loss, energy gap, molar refractivity, molar polarizability, electronic polarizability, optical basicity and field strength are computed. On the basis of the measured values of the density and refractive index, the Nd3+ ion concentration in glasses, the polarizability of oxide ions and optical basicity were theoretically determined. The theoretical value of average electronic polarizability and oxide ion polarizability were calculated by using Lorentz-Lorenz formula. Theoretical optical basicity of the glasses is evaluated based on equation proposed by Duffy and Ingram. The metallization criterion has also been calculated on the basis of refractive index and energy gap. The large value of metallization criterion indicates that the glass materials are insulators. The results obtained predict the nature of bonding in the present glasses and provide basis for developing new nonlinear optical material.

Effect of Glass Powder on Concrete Sustainability

As defined by the American Concrete Institute (ACI), alternative supplementary cementitious materials (ASCMs) and local materials are very important in concrete sustainability. As an ASCM, glass powder (GP) shows excellent pozzolanic properties. This paper focuses on characterization and the effect of GP on concrete properties compared to those of Class F fly ash (FFA) and ground granulated blast furnace slag (GGBS). Concrete incorporating 0, 20 and 30% of GP and other concrete mixes containing 30% of FFA or GGBS were cast. The concrete mixes considered in this study have water to binder (w/b) mass ratio ranging from 0.35 to 0.65. The mechanical properties such as compressive strength and durability including chloride ions permeability and chloride ions diffusion are evaluated. The results show that GP develops effects on mechanical properties similar to those of FFA and performs better than GGBS and FFA in terms of permeability reduction. GP reduces dramatically chloride permeability of concrete regardless w/b ratio, favoring an improvement of the concrete durability. Because of the interesting permeability developed by concretes incorporating GP, its use as an ASCM is promising.

Chronology of Bioactive Glass Development and Clinical Applications

The key research and development steps for bioactive glass (45S5 Bioglass) are documented from the date of discovery in 1969 through FDA approvals of the first dental, ENT, maxillo-facial and orthopedic clinical products. Understanding the mechanisms and quantifying the rapid surface reactions to form a bone-bonding hydroxyl-carbonate apatite (HCA) layer on the bioactive glass in contact with living bone was a vital part of the early development of this class of biomaterials. A key later discovery was enhanced osteogenesis and in situ bone regeneration by controlled release of ionic dissolution products from the bioactive glass particulates that leads to up-regulation and activation of seven families of genes, a process called osteostimulation.

Composition and Refractory Properties of Mixtures of Moroccan Silica-Alumina Geomaterials and Alumina

Five mixtures (M1 to M5) of silica-alumina geomaterials and two varieties of alumina (AP and AR) were used for the elaboration of mullite refractory materials between 1500℃ and 1600℃. An X-ray diffraction (XRD) analysis showed that the refractory samples are composed of mullite, corundum and silica. The length of the mullite crystals was measured by a method of image analysis of scanning electron microscopy (SEM). Chemical and mechanical properties of these materials were investigated and correlated with their microstructure. Resistance towards Acid Attack test showed that the refractory samples present good resistance, as well as, the alumina powder AR obtained from waste of silica-alumina bricks proves to be efficient for an eventual use.

Effects of SnO₂Addition on the Properties of Alumina-Magnesia Refractory Castables

Alumina-magnesia refractory castables have been widely used in the wall and bottom impact pad of steel ladles. The properties of alumina-magnesia refractory castables with SnO2 additive in 0 - 5 wt% range were investigated. The phase composition, microstructure, physical and mechanical properties of these refractories were studied. The results showed that the addition of SnO2 could have a great influence on the properties of alumina-magnesia refractory castables. The expansion, apparent porosity and strength of refractories with SnO2 were all more prominent than those of reference samples, which were attributed to the formation of CA6 and enhanced bonding. Meanwhile SnO2 could react with spinel and CA6 to form solid solution.

The Characterization and Study of Physical Parameters of Ge Modified Se-Sn-Pb Chalcogenide System

In the present paper, we have studied the effect of Ge addition on the physical properties of Se-Sn-Pb chalcogenide ma- terial. The necessary physical parameters which have important role in determining the structure and strength of the material viz. constraints, coordination number etc. have been calculated. The increasing trend has been found in cohesive energy, heat of atomization and mean bond energy. The glass transition has been studied using the Tichy-Ticha and Lankhorst approaches, which also increases with the increasing Ge contents. The increase in these physical parameters is due to the increasing covalent character in the material.

The Effect of Glass Plate Thickness and Type and Thickness of the Bonding Interlayer on the Mechanical Behavior of Laminated Glass

In this work the effect of the type of the bonding interlayer (polyvinyl butyral (PVB) or Ethyl Vinyl Acetate (EVA)), number of bonding layers, and the position and the thickness of the Glass plates on the maximum load capacity and absorbed energy by laminated glass. Furthermore, this investigation presents a mathematical model that relates the maximum force capacity of the glass laminated structure to the glass plate thickness, type and thickness of the inter-layer regardless the position of the fixed glass plate. Both practical work results and the theoretical model indicate that the maximum load capacity of laminated glass bonded with either PVB or EVA decreases as the interlayer thickness increases. Moreover, the maximum load capacity for the glasses bonded with EVA is greater than those for the PVB bonded ones under the same conditions. On the other hand, it was observed that that laminated glass absorbed energy increases with the increase of the interlayer thickness and the increase of glass plate thickness.

Crystallization Kinematics and Dielectric Behavior of (Ba,Sr)TiO3 Borosilicate Glass Ceramics

Perovskite [(Ba0.6Sr0.4)TiO3]-[2SiO2-B2O3]-[K2O]-La2O3 glass was prepared by conventional melt quench method. The differential thermal analysis (DTA) was performed on glass sample in the temperature range from 100℃ to 1000℃ by different heating rate to study the crystallization kinematics. The kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass samples were subjected to appropriate heat treatment schedules for their suitable crystallization. X-ray diffraction analysis (XRD) of glass and glass ceramic samples were done to check the amorphous state and crystalline nature. XRD of glass ceramic sample shows the major perovskite phase of BaTiO3 (BT) along with the formation of secondary phases Ba2TiSi2O8 (BTS) and Ba2Ti2B2O9 (BTB). Scanning electron microscopy (SEM) is also studied to see the morphology of the grains of major and secondary phase formation in BST glass ceramic samples. La2O3 is played an important role to increase the nucleation of the crystallites in the glassy matrix. The addition of La22O3 results in development of well interconnected crystallites formed as major phase of BST. In this paper, we are reporting the crystallization behavior of BST borosilicate glass system and high temperature dielectric characteristics of their glass ceramics.

Thermal and Structural Characterization of Transparent Rare-Earth Doped Lead Fluoride Glass-Ceramics

The devitrification of glasses with composition 50GeO2-40PbO-10PbF2-xREF3, RE = Gd, Eu, 0 3+: β-PbF2 nanocrystals embedded in a glassy oxide matrix. This transformation is investigated using thermal analysis, X-ray diffraction and electron microscopy. A comparison with RE3+: β-PbF2 ceramics prepared by standard ceramic techniques is performed. The Rare Earth cations show a strong nucleating effect for the precipitation of the RE3++: β-PbF2 nanocrystals. The evolution of the unit cell parameters of the REF3: β-PbF2 solid solution results from a combined effect of Pb2+-RE3+ substitution and interstitial F– introduction. In the glass ceramics, RE3+: β-PbF2 nanocrystals are constrained by the glassy matrix when they form with a pressure equivalent to 1.6 GPa. The constrained nanocrystals can return to a relaxed state by chemical dissolution of the embedding glassy matrix, followed by thermal treatments.

Electrical and Spectroscopic Studies of the CdO Substituted Lead Vanadate Glass System vs Crystalline Form

Results of the direct current (DC) Electrical Conductivity, thermoelectric power and Electron Spin Resonance (ESR) of CdO substituted PbO-V2O5 glass system are reported. Conduction in these glasses is found to be electronic and the hoping of polaron seems to be the dominant process in the transport mechanism. There is a remarkable decrease in the activation energy for conduction in the annealed and devitrified samples when compared to their amorphous counter parts. It is observed that there is remarkable improvement in the conductivity of the crystalline samples when compared to their amorphous counter parts. The thermoelectric power measurements indicates that the amorphous samples are n-type at room temperature where as the crystalline samples are p-type at room temperature. In crystalline samples the hyperfine structure is nearly smeared out and a relatively broad line with an isotropic g value characterizes the spectra.

Advantage of NMR and FTIR Spectroscopy to Determine Structure Role of CeO₂in Complicated Borosilicate Glasses: New Approach

Microstructure of complicated glasses in the system 30Na2O-2Al2O3-25 SiO2-xCeO2 (43-x) B2O3, x changes from 0.5 to 20 mol% have been extensively studied. Structural determination of glasses containing high cerium oxide content (≥8 mol% CeO2) was carried out by 11B NMR and FTIR spectroscopy. On the other hand, 29Si MAS NMR experiment is hardly to be applied to glasses of CeO2 > 8 mol%. This is due to the paramagnetic action which is raised by cerium cations causing dilution or delaying in the resonance phenomenon. It is evidenced from NMR data that sodium oxide is high enough to modify the glass forming units which constitute the skeleton of the glass. Ceria is as well as silica and B2O3 all are acting as glass forming species. Decreasing of both fraction of boron tetrahedral units (N4) and chemical shift of silicon nuclei (δ) confirm the role of CeO2 as a glass former. On the other hand, fast decrease in N4 and chemical shift of Si nuclei with further increasing CeO2 contents (≥8 mol%) gives a clear evidence that the ability of cerium oxide to participate as a network former increases with increasing its content. New approach is applied to determine the fraction of CeO4 as a glass forming units. In this approach, we use the common advantage of 11B NMR and FTIR spectroscopy to obtain Ce4 fraction. The latter species cannot be determined from NMR spectroscopy, since very high relaxation time and magnetization of ceria cause intensive spectral broadening which prevent resonance spectra to be appeared.

Effect of Zn Substitution on the Magnetic and Magnetocapacitance Properties of Nanosized Multiferroic GaFeO₃Ceramics

This article aims to investigate the possibility to turn the multiferroic orders and magnetocapacitance effect close to/above room temperature in nanosized GaFeO3 ceramics by a sol-gel preparation method and substitution with non-magnetic Zn atoms. Therefore, in this work, we have synthesized a series of nanocrystalline Ga1-xZnxFeO3(GZFO, x = 0, 0.01, 0.05 and 0.1) ceramic samples and study the effect of Zn substitution on their structural, magnetic, and electric properties. All the GZFO samples have an orthorhombic structure with Pc21n space group and the value of lattice parameters increase systematically with increasing Zn concentration. Interestingly, it shows that magnetic and electric properties are strongly dependent on the Zn substitution concentration. Based on the results of temperature-dependent magnetizations, M(T), it is observed that with increasing Zn-content up to 0.10, the ferrimagnetic transition temperature (TC) increases from 306 to 320 K. It is also found that the nanocrystalline Zn-doped GaFeO3 (GFO) samples exhibit the characteristics of ferroelectricity at room temperature. Furthermore, the?magnetization, ferroelectric polarization and magnetocapacitance of Zn-doped GFO nanosized ceramics are enhanced compared to those of the pristine sample of GFO ferrite. These results open wide perspectives for the applications of room temperature multiferroic devices.

High-Density Ceramics of Al_2-xMe_x(WO₄)₃, (Me = Sc or In) Solid Solutions

Al2-xMex(WO4)3, (Me is Sc or In;x varies from 0 to 2) ceramics are sintered by two methods: 1) cold pressing with subsequent sintering at different temperatures and durations and 2) hot pressure sintering. The row materials are nanoparticles with average particle size of 20, 90 and 200 nm obtained by co-precipitation method. Density, particle size and anisometricity of the obtained ceramics are tested. The results show that optimal initial nanosized dimensions and optimal pressing conditions are needed to obtain compact ceramics. The hot pressure method provides possibilities for obtaining ceramics with a density of about 99.8%. These ceramics possess some level of transparency.

More Insight on Structure of New Binary Cerium Borate Glasses

The structure of glasses in the system of xCeO2(100?-?x)B2O3, x = 30, 40, 50 mol% CeO2 has been explored for the first time by correlation between data obtained from XRD, FTIR and 11B NMR analyses. NMR spectroscopy andFTIR spectroscopy have confirmed that transformation rate of BO3 to BO4 groups is reduced by CeO2 addition.The concentration of Ce4-O-Ce4 is increased at the expense of both B4-O-Ce4 and B3-O-B4 linkages. Boron atoms are mainly coordinated with Ce4 sites as second neighbors due to increasing CeO4 species with further increase of CeO2 concentration. Increasing B4 fraction is considered due to forming of CeO4 with rate higher than that of BO4 units. The change of chemical shift of 11B nuclei upon exchanging B2O3 with CeO2 confirms that the central boron atoms would be coordinated with tetrahedral cerium atoms as second neighbors. The X-ray diffraction of cerium rich glass is clearly indicated that the formation of crystalline phases refers to CeO4, CeBO3and Ce(BO2)3 species.

Self-Cleaning Properties of Vanadium Doped TiO₂Sol-Gel Derived Thin Films

In this study, vanadium doped TiO2 thin films were deposited on glass substrates using a sol-gel dip-coating process. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer were used to characterize the structural, chemical and the optical properties of the thin films. The photo-catalytic activities of films were investigated by methylene blue degradation. Water contact angle on the film surfaces was measured by a water contact angle analyzer. The results indicated that vanadium doping had a significant effect on the self-cleaning properties of TiO2 thin films.

Sol-Gel Processed Indium-Doped Zinc Oxide Thin Films and Their Electrical and Optical Properties

Transparent conducting films of zinc oxide and indium-doped zinc oxide have been prepared by a simple and economical sol-gel technique. This process is feasible for the fabrication of high quality TCO thin films when the processing parameters are optimized. It was found that the out-diffusion of oxygen during the vacuum annealing step was a crucial factor to prepare thin layer with superior properties. Annealing lowers the resistivity down to 4.7 10-3?Ω&#183cm for the 1 at.% doped films due to the liberation of high-valency In-dopants and the enhanced film density. At high indium concentrations, the free electron density stabilizes because an increasing number of dopant atoms form some kinds of neutral defects. The neutralized indium atoms do not contribute free electrons. The feasibility to deposit highly transparent ZnO thin films has been demonstrated.