Showing papers in "Journal of Non-crystalline Solids in 2018"

Updated definition of glass-ceramics

Abstract: Glass-ceramics are noted for their unusual combination of properties and manifold commercialized products for consumer and specialized markets. Evolution of novel glass and ceramic processing routes, a plethora of new compositions, and unique exotic nano- and microstructures over the past 60 years led us to review the definition of glass-ceramics. Well-established and emerging processing methods, such as co-firing, additive manufacturing, and laser patterning are analyzed concerning the core requirements of processing glass-ceramics and the performance of the final products. In this communication, we propose a revised, updated definition of glass-ceramics, which reads “Glass-ceramics are inorganic, non-metallic materials prepared by controlled crystallization of glasses via different processing methods. They contain at least one type of functional crystalline phase and a residual glass. The volume fraction crystallized may vary from ppm to almost 100%”.

Conductive bio-polymer electrolyte iota-carrageenan with ammonium nitrate for application in electrochemical devices

Abstract: Bio-polymer electrolyte iota-carrageenan (Ι-carrageenan) with ammonium nitrate (NH4NO3) has been prepared by solution-casting technique. The increase in amorphous nature of the bio-polymer electrolyte due to the addition of salt has been confirmed by X-ray diffraction analysis. From the XRD spectra, the average particle size has been calculated using the Debye–Scherrer formula and the value is 0.98 nm. The complex formation between the polymer and the salt has been confirmed by Fourier transform infra-red spectroscopy. The glass transition temperature of the bio-polymer Ι-carrageenan with NH4NO3 electrolytes has been found using differential scanning calorimetric technique. From the AC impedance spectroscopic analysis, the ionic conductivity value has been found to be 1.46 × 10− 3 S/cm at ambient temperature for the composition of 1.0 g Ι-carrageenan: 0.4 wt% NH4NO3. The temperature dependent conductivity of the polymer electrolyte obeys an Arrhenius relationship. The dielectric behavior has been analyzed using dielectric permittivity (e*) and the relaxation frequency (τ) has been calculated from the loss tangent spectra (tan δ). The modulus spectra indicate non-Debye nature of the material. Ionic transference number has been found to be 0.95 for the polymer 1.0 g Ι-carrageenan: 0.4 wt% NH4NO3. The result reveals that the conducting species are predominantly due to ions. Electrochemical stability window of 2.46 V has been measured by using linear sweep voltammetry for the highest ionic conducting membrane. A primary proton battery has been constructed with the highest conductivity sample and open circuit voltage has been found to be 1.04 V. Fuel cell has been constructed with the highest proton conductivity polymer 1.0 g Ι-carrageenan: 0.4 wt% NH4NO3 and the open circuit voltage found to be 442 mV.

Study of short range structure of amorphous Silica from PDF using Ag radiation in laboratory XRD system, RAMAN and NEXAFS

Abstract: At present synchrotron and neutron sources are the preferred choices for the Pair Distribution Function (PDF) analysis, but there is a need to explore PDF in a laboratory XRD system for quick feedback about the short range structure of the amorphous materials. Present work considered both crystalline (quartz) and amorphous silica to study the structural differences in silica by PDF analysis using Ag radiations in laboratory XRD. The structural information about short range ordering of the oxygen (O) atoms around silicon (Si) atoms as obtained by the PDF were compared with the results as obtained by Near Edge X-ray Absorption Fine Structure (NEXAFS) and RAMAN experiments. The PDF studies showed that the amorphous silica possessed short range periodicity within the basic unit of (SiO4)4− tetrahedra with a Si O & O O distance are of about 1.622 A and 2.713 A while the short range as well as long range ordered structure present in quartz with Si O & O O distance are 1.562 A and 2.661 A respectively. Raman spectra showed some asymmetry in amorphous silica which corresponds to the defects present in the lattice and thus forming the n-fold ring structure with Si and O resulting in the wide variation of bridging bond angle Si O Si in amorphous silica. NEXAFS studies revealed the structure of amorphous silica and quartz in the intermediate range (3–5 A) at the Si L and O K edges. The structural information about short range ordering of the O around Si atoms as obtained by these methods were found to be in good match with the results as obtained by PDF, suggesting this technique may be used as a screening tool for routine PDF studies of amorphous materials.

A new transferable interatomic potential for molecular dynamics simulations of borosilicate glasses

Abstract: Borosilicate glasses are traditionally challenging to model using atomic scale simulations due to the composition and thermal history dependence of the coordination state of B atoms. Here, we report a new empirical interatomic potential that shows a good transferability over a wide range of borosilicate glasses—ranging from pure silicate to pure borate end members—while relying on a simple formulation and a constant set of energy parameters. In particular, we show that our new potential accurately predicts the compositional dependence of the average coordination number of boron atoms, glass density, overall short-range and medium-range order structure, and shear viscosity values for several borosilicate glasses and liquids. This suggests that our new potential could be used to gain new insights into the structure of a variety of advanced borosilicate glasses to help elucidate composition-structure-property relationships—including in complex nuclear waste immobilization glasses.

Linear and nonlinear optical properties of gold nanoparticles doped borate glasses

Abstract: Gold nanoparticles (NPs) embedded in sodium antimony borate glass system were fabricated and their optical, physical, structural, ultrafast nonlinear optical properties were studied and analyzed. Metallic gold NPs were synthesized using thermal reducing agent Sb2O3 and demonstrated the reduction mechanism of Au3 +/Au+ → Au0 by using reduction potentials of corresponding redox system. UV–Visible spectroscopy measurements have revealed the characteristic surface plasmon resonance (SPR) of Au NPs at ~ 565 nm, attributed due to interband transition. The micrographs of High-Resolution Transmission Electron Microscopy (HR-TEM) confirmed the existence of uniformly distributed spherical shaped Au NPs with particle sizes in the 8–45 nm range with an average particle size of 25 nm. The ultrafast nonlinear optical properties of gold doped glasses were investigated using the Z-scan technique at a non-resonant wavelength (λ = 800 nm, 80 MHz repetition rate) with femtosecond (fs) Ti:sapphire laser pulses. Z-scan measurements of undoped glass depicted are verse saturable absorption (RSA) type of nonlinearity whereas the gold-doped glass demonstrated saturable absorption (SA) kind of nonlinearity due to intraband (sp → sp) transitions. The Z-scan data demonstrated that the investigated glasses are potential materials for the applications in nonlinear optics devices, particularly in optical switching devices.

Predicting the dissolution kinetics of silicate glasses using machine learning

Abstract: Predicting the dissolution rates of silicate glasses in aqueous conditions is a complex task as the underlying mechanism(s) remain poorly understood and the dissolution kinetics can depend on a large number of intrinsic and extrinsic factors. Here, we assess the potential of data-driven models based on machine learning to predict the dissolution rates of various aluminosilicate glasses exposed to a wide range of solution pH values, from acidic to caustic conditions. Four classes of machine learning methods are investigated, namely, linear regression, support vector machine regression, random forest, and artificial neural network. We observe that, although linear methods all fail to describe the dissolution kinetics, the artificial neural network approach offers excellent predictions, even for untrained data, thanks to its inherent ability to handle non-linear data. We further note that the predictive ability of simpler methods, such as linear regression, could be improved using additional physics-based constraints. Such methods, called as physics-informed machine learning can be used to extrapolate the behavior of untrained compositions as well. Overall, we suggest that a more extensive use of machine learning approaches could significantly accelerate the design of novel glasses with tailored properties.

Effect Bi2O3 on the physical, structural and radiation shielding properties of Er3+ ions doped bismuth sodiumfluoroborate glasses

Abstract: Er3+ ions doped Bismuth sodiumfluoroborate glasses with varying Bi2O3 content (0−50 in wt%) have been prepared following the melt quenching technique. The density, molar volume, FTIR and UV–Visible studies have been used to determine physical and structural properties of the prepared glasses. The FTIR studies explores that, addition of Bi2O3 helps the progressive conversion of [BO4] units into [BO3] units thus lead to the creation of non-bridging oxygens (NBOs). The boron‑boron separation( ), oxygen packing density(OPD), bond density(nb) and calculated Poisson's ratio (μcal) values are found to decrease with the addition of Bi2O3thus reveal the fact that the network connectivity decreases due to the formation of non-bridging oxygen sites and the glass network becomes less tightly packed. Further, ionic nature of the Er3+ − metal ligand bond was identified from the measured optical basicity (Λth), covalent and ionic characteristic factors, and bonding parameter (δ) values.The observed variations in the optical electronegativity, basicity, metallization criterion and optical band gap energy (Eg) values have been discussed in terms of the structural changes that takes place due to the addition of Bi2O3 into the B2O3 network. Additionally, radiation shielding properties of the prepared glasses have been studied in the energy range 0.015–15 MeV. The mass attenuation coefficient has been calculated using MCNP5 code and XCOM software. The MCNP5 results match most of the XCOM data very well. Further, the effective atomic number, mean free path and half value layer (HVL) for the titled glasses were computed. The mass attenuation coefficient and the effective atomic number were found to progressively increase with the increase in the Bi2O3 content. The addition of Bi2O3 led to decrease the half value layer which means that more Bi2O3 content enhances the radiation shielding performance for the prepared glasses.

Determination of gamma-ray shielding properties for silicate glasses containing Bi 2 O 3 , PbO, and BaO

Abstract: The mass attenuation coefficients (μ m ), effective atomic cross section (σ a ), effective atomic number (Z eff ) and effective electron density (N eff ) of silicate glasses containing different concentrations of Bi 2 O 3 , PbO, and BaO (30–70% by weight) were obtained using MCNP-4C code, XCOM and XMuDat programs, in the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Z eff and N eff . The Auto-Z eff software was used to determine the Z eff as well. The MCNP-4C Code, XCOM and XMuDat programs and Auto-Z eff results were in good agreement. It was found that the μ m and σ a values decrease with photon energy. Also the results indicate that σ a and Z eff of glasses improve by increasing their Bi 2 O 3 , PbO and BaO contents, while increasing these contents to the same fraction has no significant effect on μ m in the energy range of 0.3–5 MeV, where the Compton Effect takes over as dominant process and N eff do not follow certain rule. Above 0.1 MeV, lead oxide silicate glass showed the highest values of Z eff and σ a . Wherever possible, the simulated and calculated values were compared with experimental data.

Radiation shielding study of tellurite tungsten glasses with different antimony oxide as transparent shielding materials using MCNPX code

Abstract: The radiation shielding performance of tellurite tungsten glasses with different antimony oxide (Sb2O3) content was studied using Monte Carlo simulation MCNPX and WinXCOM software. The mass attenuation coefficients were computed for photon energies of 0.662, 1.173, 1.274 and 1.332 MeV. Moreover, The transmission factor of the selected glasses was calculated at a different thickness from the incident and transmitted photons. It was found that the transmission factor of the investigated glasses lies within 0.11–0.28 range. Also, it was found that the MCNPX and WinXCOM results were matched with each other. It can also be concluded that the high density TSW5 glass sample has the maximum shielding effect over the other samples because of the high weight fraction of the highest atomic numbers (i.e. W, Z = 74) as well as its high density.

Structural, thermal, optical features and shielding parameters investigations of optical glasses for gamma radiation shielding and defense applications

Abstract: To design new radiation shielding materials instead of conventional materials such as concrete with improved performance in gamma-ray shielding in nuclear reactors, defense applications, and medical sciences, very recently, there exists an increasing interest among researchers. For this purpose, heavy metal oxides based optical glasses attracted much attention, nowadays. In this work, five glass samples with nominal composition of (70-x)B2O3-5SiO2-5TeO2-10ZnO-10Li2O-xBaO (where x = 5, 10, 15, 20, and 25 mol%) were fabricated by melt quenching technique. The structural and thermal studies were carried out using XRD, SEM/EDAX, FTIR, Raman, and TGA/DSC measurements. Different shielding parameters such as mass attenuation coefficients, effective atomic number, mean free path and exposure buildup factor have been calculated in order to investigate the effectiveness of using the prepared glasses as radiation shielding materials. The half-value layer of the prepared glasses has been compared to different types of concretes. The results of shielding properties indicate that addition of BaO significantly enhances shielding capability of the prepared glasses against gamma radiation.

Crystallization, structure and characterization of MgO-Al 2 O 3 -SiO 2 -P 2 O 5 transparent glass-ceramics with high crystallinity

Abstract: Highly crystallinity transparent glass-ceramics based on MgO-Al2O3-SiO2-P2O5 system have been prepared by conventional melt-quenching and “two-step” crystallization method. The crystallization kinetics, phase evolution, structure, physical and light transmittance properties of glass-ceramics were studied. The results reveal that the crystallization mechanism of this glass is believed to be three-dimensional interfacial growth. The predominant crystalline phase is Mg2Al4Si5O18 in these glass-ceramics, and the content of crystalline phase becomes higher with rising of crystallization temperature and time, which the light transmittance of glass-ceramics decreases. It is observed that the main elements are uniformly distributed in glass-ceramics from EDS element distribution maps. All things considered, the optimal heat treatment schedule of parent glass is 840 °C/36 h + 1050 °C/3 h, the prepared glass-ceramics possesses high crystallinity (90.5 vol%), good light transmittance (85%) and excellent mechanical and thermal properties. These findings make this family of transparent glass-ceramics showing potential applications in solid-state optical functional material.

The effect of erbium oxide in physical and structural properties of zinc tellurite glass system

Abstract: In this research, the melt-quenching method was used to synthesize a series of zinc tellurite glass systems doped with erbium oxide with the chemical composition of [(TeO2)0.7 (ZnO)0.3]1−x (Er2O3)x at different molar fraction, x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05. X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, density, molar volume, elastic and optical measurements were used to characterize the prepared glass samples. At room temperature, the result of the XRD, FTIR, density, elastic and optical properties were all recorded. An amorphous nature of glass samples is proven by the XRD spectra. The analysis of FTIR spectra shows the presence of functional vibration of tellurite network. It is observed that the density of the glass system increase with the molar fraction of Er2O3. The value of molar volume is found to be directly proportional to the density. Thus, the increment in the density value causes the increment of the molar volume due to the increase of erbium concentration. This in turn results in the creation of excess free volume due to the difference of atomic radius between erbium and tellurite. On the other hand, ultrasonic velocity was used to determine the elastic moduli of the glass systems. The elastic moduli such as longitudinal modulus, shear modulus, bulk modulus and Young's modulus give a fluctuating trend against the concentration of Er2O3. The increase of the elastic moduli is due to the mix former effect. In contrast, the decrease of the elastic moduli is due to the breakdown of Er2O3 in the zinc tellurite glass system which weakens the glass structure of the ternary tellurite system. The optical properties of the prepared glasses were determined by UV–vis analysis. The optical absorption was recorded at room temperature in the wavelength ranging from 220 nm to 800 nm. The optical absorption spectra reveal that fundamental absorption edge shifts to higher wavelength as the content of erbium oxide increase. The values of direct and indirect band gap have been calculated and are observed to decrease with the increase content of erbium oxide. However, the Urbach energy, refractive index, molar refraction and electronic polarizability are shown to be increased with an addition content of erbium oxides.

Effect of replacement of Al 2 O 3 by Y 2 O 3 on the structure and properties of alkali-free boro-aluminosilicate glass

Abstract: Alkali-free boro-aluminosilicate glasses were prepared by the melt quenching method. The effect of Al2O3 replaced by different contents of Y2O3 on the structure and various properties of alkali-free boro-aluminosilicate glasses was studied. The changes of glass structure with varying components were investigated by the Fourier transform infrared spectra. Simultaneously, the relationship between the glass structure and the coefficient of thermal expansion, density, vickers hardness, bending strength, glass transmittance and chemical stability was discussed. The results show that the coefficient of thermal expansion and the density of glass increase with the increase of Y2O3 content. While, the chemical stability of the glass is reduced. The vickers hardness and bending strength decrease first and then increase with the Y2O3 content increasing. All the glasses have excellent optical transmittance, reaching more than 85%.

Influence of Ho 3 + ions on structural and optical properties of zinc borotellurite glass system

Abstract: A glass series of Holmium doped Zinc borotellurite glass with chemical formula {((TeO2)0.7 (B2O3)0.3)0.7 (ZnO)0.3}1 − x (Ho2O3)x where x = 0.005, 0.01, 0.02, 0.03 and 0.04 M fraction was prepared by using conventional melt-quenching method. X-ray diffraction analysis (XRD) and Fourier Transform infrared analysis (FTIR) were used to determine the structural properties of the fabricated glass. XRD results confirmed that the prepared glass is amorphous. Density and molar volume of the glass were measured and calculated. The values of the density increase with increase of dopant concentration while molar volume decreases accordingly. Ultraviolet visible spectroscopy analysis (UV–Vis) was used to determine the optical properties of the prepared glass. The refractive index, molar refraction, molar electronic polarizability, metallization criterion, indirect optical energy band gap and Urbach energy were also calculated and analysed. The refractive index was found to increase with increase of holmium ion Ho3 + concentration, optical energy band gap decreases while electronic polarizability increases in conformity with increase of refractive index as the concentration of the dopant increases.

Structural, optical, and electrical characterization of borate glasses doped with SnO2

Abstract: Synthesis of borate glass matrix of composition 35Li2O–10ZnO–55B2O3 + x SnO2 wt% (x = 0.00, 0.50, 1.00, 1.50, 2.25 and 3.00) has been carried out by solid state reaction method. Nature amorphosity of these glasses was confirmed via X-ray diffraction (XRD) measurements. UV-visible absorption spectra within the 200–1100 nm wavelength range of these samples were performed. The direct/indirect optical energy gap (Egopt), Urbach energy (EU), Fermi energy (EF) were calculated. Both the optical complex dielectric constant (e), and the optical conductivity (σopt) for the prepared glass samples were calculated by using the measured refractive index (n) and extinction coefficient (k). All the optical properties vary depending on the SnO2 content in borate glass samples. Refractive index (n) and the optical conductivity (σopt) increase with increasing SnO2 concentration. Dielectric measurements depict that both the dielectric constant (e′) and dielectric loss (e″) decrease with the increasing of frequency but a constant value was obtained beyond 10 kHz up to 100 kHz. However, ac conductivity (σac) increases with the increasing in frequency.

Preparation and characterization of aerogel/expanded perlite composite as building thermal insulation material

Abstract: Aerogel was a potential substitute for the traditional thermal insulation materials. But aerogel's fragility and high prices have negative effects on the mechanical property and cost of aerogel-based building thermal insulation materials. To solve this problem, a novel thermal insulation composite aerogel/expanded perlite (AEP) was prepared by filling the aerogel into porous structure of expanded perlite (EP). The aerogel in the pores of AEP would be protected by solid skeleton of AEP, and also reduce the thermal conductivity of AEP. The AEP was characterized by X-Ray diffraction, Fourier transformation infrared, digital microscope, scanning electron microscope, N2 adsorption-desorption isotherms and transient hot-wire method. The results reveal that aerogel could be effectively distributed in porous structure of EP and has a positive effect on the pore structure and thermal insulation performance of EP. AEP has typical mesoporous structure and shows chemical stability and hydrophobicity. The mesoporous volumes and BET specific surface areas of AEP were about 100–280 times and 50–150 times as large as those of EP, respectively. And thermal conductivities of AEP were decreased by 14.7–31.8% than EP. All results suggested that AEP can be considered as potential building thermal insulation materials due to good thermal insulation performance and lower cost.

Mixed-modifier effect in alkaline earth metaphosphate glasses

Abstract: Modifier-mixing provides a useful tool for tailoring the structural dynamics of oxide glasses. Its physical basis, however, remains subject to intense discussion. Here, we extend our previous consideration of Ca-Mg mixing in alkaline earth metaphosphate glasses [J. Non-Cryst. Solids 468, 74–81 (2017)] across the broader range of alkaline earth species. We report on the effects of divalent modifier mixing for pairs selected from the group of Mg, Ca, Sr and Ba. For this, short-range structural features as obtained from nuclear magnetic resonance, Raman and far-infrared spectroscopy are related to various physical properties, including ionic mobility. Depending primarily on the difference in ion size and bond localization among the modifier cation species, we find different extents of the mixed-modifier effect. This agrees with the dynamic structure model in which the mismatch of cation sites governs non-linear mixing effects.

Mixed alkali effect and samarium ions effectiveness on the structural, optical and non-linear optical properties of borate glass

Abstract: Borate glasses containing lithium, sodium, and samarium ions were prepared by conventional melt annealing technique. The structural units show the presence of BO3, and BO4 units while samarium ions favored to link with OH group. Density and molar volume show the impact of the replacement sodium ions by lithium. The density values increase with increasing lithium content up to 20 mol% and decrease for free sodium borate glass (30 Li2O or 0 Na2O). Optical and photoluminescence investigations were carried to determine the optical parameters such as optical band gap, refractive index, etc. The optical band gap and refractive index values show the nonlinearity trend due to the change occurred at 10% Li2O content. The non-linear optical parameters were determined and studied in terms of the refractive index and the impact of the mixed alkali effect.

Exploration of gamma radiation shielding features for titanate bismuth borotellurite glasses using relevant software program and Monte Carlo simulation code

Abstract: In this work, gamma radiation shielding parameters for six titanate bismuth borotellurite glasses were investigated. The mass attenuation coefficients (μ/ρ) have been calculated using XCOM software and MCNP5 code within the photon energy range 0.015–10 MeV. The (μ/ρ) values were then used to calculate the effective atomic number (Z eff ), electron density (N e ), mean free path (MFP) and half-value layer (HVL) values. By using the Geometric progression (G–P) method, the exposure buildup factor (EBF) values at 0.015 MeV–15 MeV photon energy range, with penetration depths up to 40 mfp at intervals 1, 5, 10, 20, 30, and 40 mfp were evaluated. The 30 TeO 2 –30 B 2 O 3 –30 Bi 2 O 3 –10 TiO 2 (mol %) glass possesses better gamma ray shielding effectiveness due to a higher value of (μ/ρ), Z eff and lower values of HVL and MFP. The studied glasses exhibit excellent gamma ray shielding features compared to different types of concretes.

Effect of CaF2 on viscosity, structure and properties of CaO-Al2O3-MgO-SiO2 slag glass ceramics

Abstract: Bayan Obo tailings (BOTs), fly ash (FAS), and stainless-steel slag (SSS) are industrial wastes that require reasonable, clean, and effective utilization for environment protection. The paper focuses on the structure and properties of glass-ceramics that were prepared by melting BOT, FAS, and SSS raw materials. The effect of CaF2 on the viscosity, structure, and performance of CaO-Al2O3-MgO-SiO2 (CAMS) slag glass-ceramics is determined by viscometer, differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and physicochemical properties measurements. The results show that moderate amounts of CaF2 facilitates depolymerization of the silicate networks, which leads to a decrease in the melting temperature, viscosity and viscous activation energy of glass. However, the content of more than 3% CaF2 results in a dramatic decreases in the chemical stability of the glass-ceramics because of the transformations of the main crystalline phase from diopside to anorthite, which is accompanied by fluorite precipitation.

Marl-based geopolymers incorporated with limestone: A feasibility study

Abstract: The expanding raw materials base is one of the drivers for the further development of inorganic binders, including alkali-activated cements. This research focuses on studying marl with a high calcite/aluminosilicates ratio as a geopolymer precursor, and limestone as a mineral addition to this geopolymer. The calcination of marl at 800 °C resulting in the formation of reactive Si, Al, and Ca due to the dehydroxylation of clay minerals and decarbonation of calcite makes marl suitable for use as a geopolymer precursor. Calcined marl activated with sodium silicate and cured at ambient temperature had a 28-day compressive strength of 34 MPa. When incorporated with 50% limestone, the compressive strength became 39.2 MPa. XRD, TG/DSC, FTIR, optical and SEM have been used to investigate the reaction products, as well as the microstructure of the geopolymer hardened pastes.

Tungsten-based glasses for photochromic, electrochromic, gas sensors, and related applications: A review

Abstract: The present work focuses on reviewing the scientific literature on various types of tungsten-based glasses such as tungsten–phosphate, tungsten–tellurite, tungsten–borate glasses, tungsten–germinate, tungsten–antimonate, and non-traditional tungsten oxide-containing glasses. The glass formation, structure, thermal, some chemical, physical and characterization of materials are discussed. Tungsten-based glasses show a remarkable potential for many photochromic, electrochromic and gas sensing applications.

Dissolution of borate and borosilicate bioactive glasses and the influence of ion (Zn, Cu) doping in different solutions

Abstract: The release of therapeutic ions during dissolution is necessary for the success of bioactive glasses in medical applications. Therefore, different borate and borosilicate glasses undoped and doped with copper or/and zinc based on the 13–93 composition were tested and compared to the well-known 13–93 bioactive glass in several dissolution media. Prior to dissolution studies, all glasses were characterized using SEM-EDX, FTIR, XRD, DTA and hot stage microscopy (HSM). Dissolution studies were carried out using tris(hydroxymethyl)aminomethane (TRIS) buffer and simulated body fluid (SBF) under static conditions. The dissolution rates varied following the trend of borate glasses > borosilicate glasses > silicate glasses. Further, the release of boron from both borate and borosilicate glasses was inhibited in SBF compared to TRIS. The dissolution of the glasses was additionally tested in SBF under dynamic conditions to better mimic the human body environment. Under these conditions, Cu-doped glass released up to 10 mg/L of Cu2+, which is the critical biological level of Cu2+ for the survival of fibroblasts. In order to mimic the conditions that may develop locally during the degradation of a poly(lactic acid) (PLA) composite or during a bacterial infection, dissolution studies were for the first time also carried out using a lactic acid solution at pH = 2. Zinc was only released from the Zn-doped glasses under acidic conditions. Owing to the antibacterial property of Zn2+, these results are especially interesting for the application of the ion-doped glasses in the treatment or prevention of infections.

A CuZr-based bulk metallic glass composite with excellent mechanical properties by optimizing microstructure

Abstract: The dependence of microstructure and mechanical properties on alloy composition of a series of Cu48Zr48−xAl4Nbx (x = 0, 0.3, 0.8, 1.2, 1.5, 2.0 at.%) bulk metallic glass composites (BMGCs) was studied in detail. It was found that the doping element Nb exerts a crucial role on the mechanical properties of the studied BMGCs. By adjusting Nb content, a BMGC possessing an excellent combination of high strength (~1.3 GPa) and significant tensile plasticity (~8%) was obtained. Such superior mechanical performance can be attributed to the formation of multiple shear bands and the deformation-induced martensitic transformation from a cubic primitive B2 phase to a monoclinic B19′ phase.

Influence of thermal and compositional variations on conduction mechanisms and localized state density of amorphous Cd 50 S 50-x Se x thin films

Abstract: This work reports the study of dc-electrical conductivity of the amorphous chalcogenide Cd50S50−xSex (30 ≤ × ≤ 50 at.%) thin films and its dependent upon the temperature and composition. Thin films were prepared by the thermal evaporation process onto normal glass substrates in a vacuum about 8.2 × 10−4 Pa. The deposition rate and the film thickness were maintained constant at about 8 nm/s and 200 nm, respectively. X-ray diffraction was used to check the amorphous nature of thin-film samples. The resistance of the film samples has been measured in the temperature range 293 K to 473 K by using the two-point probe technique. DC-electrical conductivity was determined from the resistance measurements. The sheet resistance, the conduction mechanisms, activation energies, Mott parameters, barrier potential energy, trapping state energy and the density of localized states near the Fermi level, were investigated and studied. Obtained electrical data of the ternary Cd-S-Se thin films were investigated and studied in terms of Mott's variable range hopping model. All studied electrical parameters were found to be strongly dependent on the Se-content.

Vibrational, thermal features, and photon attenuation coefficients evaluation for TeO2-B2O3-BaO-ZnO-Na2O-Er2O3-Pr6O11 glasses as gamma-rays shielding materials

Abstract: Sodium zinc barium borotellurite glass systems doped with singly Er, Pr, and Er/Pr-codoped ions were fabricated via melt quenching method to study their structural, thermal, and gamma radiation shielding features. Both FTIR and Raman spectroscopic results revealed that the glass network matrix is prevailingly formed by TeO4, TeO3 + 1, TeO3, BO3 and BO4 structural clusters. The characteristic temperatures (glass transition (Tg), onset crystallization (Tx), peak crystallization (Tc), and melting (Tm)) and thermal stabilities (ΔT) were determined by differential scanning calorimetry (DSC). An increase in ‘Tg’ and (ΔT) variation within the temperature range 123–164 °C with an addition of Er2O3, Pr6O11, and Er2O3/Pr6O11 oxides indicates that synthesized glasses possess good thermal stability. For selected glasses, mass attenuation coefficient (μ/ρ) values calculated using both XCOM software and MCNP5 simulation code in the 0.015–15 MeV photon energy range were matched well. Moreover, based on the (μ/ρ) values, various shielding parameters like effective atomic number (Zeff), electron density (Ne), mean free path (MFP) and half-value layer (HVL) are evaluated. Additionally, exposure buildup factor (EBF) values have been determined using Geometric Progression (G–P) fitting method in the energy range 0.015–15 MeV and up to a penetration depth of 40 mfp, and variation of all the shielding parameters is discussed for the effect of singly Er, Pr and doubly Er/Pr ions inclusion into the host glass. As an example, the prepared rare-earth (RE)-doped glasses show lower HVL values compared to 80TeO2-20MgO and 80TeO2-20MoO3 (mol %) glasses suggesting their potentiality as good gamma radiation shielding materials.

Effect of MgO/Al2O3 ratio on the structure and properties of blast furnace slags: a molecular dynamics simulation

Abstract: SiO2-Al2O3-CaO-MgO is the most significant slag system in the blast furnace ironmaking process and it is very important to investigate the microstructure and viscosity of the system. In this paper, molecular dynamics simulations were carried out to explore the effects of MgO/Al2O3 ratio on structure and properties of the system. Based on the self-diffusion coefficients, the viscosities were calculated by Einstein-Stokes equation and compared with the experimental value and the Factsage value. The results showed that with the increase of MgO/Al2O3 ratio, the stability of [SiO4]4− and [AlO4]5− tetrahedron became weaken and the relative proportions of bridge and non-bridge oxygen showed a decrease. And due to the increase of MgO, more Mg2+ ions are used as network modifiers to reduce the degree of polymerization of the system, resulting in a decrease in the viscosity, which is consistent with experimental results. Finally, based on the present study, in the case of increasing Al2O3 content of blast furnace slag, the fluidity of slag could be adjusted by controlling MgO/Al2O3 ratio, thereby providing a basis for stable operation of blast furnace ironmaking.

Effect of PbO on the shielding behavior of ZnO-P2O5 glass system using Monte Carlo simulation

Abstract: In this work, MCNP5 as a Monte Carlo code is used to calculate gamma ray attenuation coefficient of x PbO-(50 − x) ZnO- 50 P2O5 glasses where x = 10, 20, 30, 40 and 50 mol% at 0.122, 0.356, 0.511, 0.662, 0.84, 1.17, 1.275 and 1.33 MeV photon energies. The simulated results of mass attenuation coefficients were compared with the output of XCOM program. Good agreement was observed between simulated and XCOM results. The obtained mass attenuation coefficients were further used to calculate the effective atomic number, electron density, half value layer and mean free path. The maximum values of mass attenuation coefficients and effective atomic number were found for PZPb50 glass sample. The results from this study indicate that the MCNP5 code used in this work may be utilized as a better alternative to experimental work to make supplementary calculations on the photon attenuation characteristics of other materials and glass systems. The lower values of the mean free path of the selected samples as compared to the standard shielding concretes; establishes them as suitable gamma shields. PZPB50 is the best among the selected shielding glasses.

Role of Mo addition on structure and magnetic properties of the Fe 85 Si 2 B 8 P 4 Cu 1 nanocrystalline alloy

Abstract: The amorphous-forming ability (AFA), crystallization structure and magnetic properties of the melt-spun Fe85 − xSi2B8P4Cu1Mox (x = 0–2) alloys were investigated. The addition of 1–2 at% Mo in the Fe85Si2B8P4Cu1 alloy enhances the AFA with increasing the critical thickness for amorphous formation from ~ 14 to ~ 20 μm. The Mo alloying refines the microstructure and reduces the coercivity of the annealed alloys, and weakens the dependence of the coercivity on the heating rate, although it decreases the saturation magnetic flux density. After annealing under a low heating rate of 50 K/min, the average α-Fe grain size and coercivity of the Fe84Si2B8P4Cu1Mo1 alloy are ~ 25 nm and 23.9 A/m, respectively, which are lower than those of ~ 32 nm and 40.5 A/m for the base alloy. In addition, the mechanism related to the effects of Mo on the structure and magnetic properties was discussed in term of the crystallization activation energy.

Different property studies with network improvement of CdO doped alkali borate glass

Abstract: Quaternary alkali borate glass matrix doped with CdO (0, 2, 4, 6, 8, 10 mol%) have been prepared by using conventional melting and quenching technique. For these glass systems structural properties were investigated by using X-ray diffraction, FE-SEM, EDS, FTIR and Raman spectroscopy characterization techniques. X-ray diffraction pattern and FE-SEM studies confirms the amorphous nature of prepared oxide glass. The optical absorption studies were done by using UV–Vis spectroscopy technique at room temperature. The physical parameters of all the glass samples were evaluated with respect to the composition, such as bulk density (ρ), average molar mass (M), molar volume (Vm), ionic concentration (N), interionic distance (ri). They exhibit the non-linearity supporting evidence for the borate glass network modification. Investigations of FTIR and Raman spectroscopy of prepared glass samples have been employed to confirm the role of oxides in the formation of glass network. These glasses are made up from converting [BO3] to [BO4] units without increasing the concentration of non-bridging oxygen. Experimental fraction of 4-coordinated boron atoms expressed by the parameter N4 was calculated and represented with the addition of concentration of CdO (mol%). The optical absorption studies revealed that the average refractive index (nav), optical band gap energy (Eg) nonlinearly increases. The electronic polarizability and optical basicity of the oxide ion (αO2−), as function of refractive index and optical band gap energy were also examined.