Al2O3 B2O3 System Research Articles

Rheological behaviour of CaO–MgO–SiO2–Al2O3–B2O3 system with varying B2O3 content up to 30 wt% at basicity of 0.4

A comprehensive theoretical and experimental study describing the effect of B2O3 (0–30 wt%) on softening, liquidus, and crystallization temperatures, flow behaviour, and dynamic viscosity of the glass-based oxide system SiO2(64.64–43.21 wt%)-MgO(10 wt%)-CaO(15.86–7.29 wt%)-Al2O3(9.50 wt%)-B2O3 with a constant basicity of 0.4 was carried out. The experimental data was obtained up to 1550 °C using a high-temperature rheometer and were supported by the study of the internal structure by means of scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray powder diffraction analysis, and Fourier transform infrared spectroscopy. The increasing addition of boron oxide caused a decrease in the start and end softening and liquidus temperatures. At 1550 °C, the systems exhibited Newtonian behaviour, with a dynamic viscosity increasing exponentially with a decreasing temperature and decreasing with increasing B2O3 content. The amorphous character of the samples and the formation of structural units [BO2O−] and [BO3] and [BO4], confirmed by complementary analyses, led to a decrease in the degree of polymerization of the silicate structure. The theoretical insight into the dependence of dynamic viscosity on the temperature and composition was realized based on molecular dynamics. Furthermore, the prediction of viscosity as a function of temperature (1230–1550 °C) and the change in chemical composition (0–30 wt% B2O3) was performed using artificial neural networks.

Effect of Oxides of Various Metals on the Physicochemical Properties of Glass in the PbO–CdO–SiO2–B2O3–Al2O3 System

Effect of Oxides of Various Metals on the Physicochemical Properties of Glass in the PbO–CdO–SiO2–B2O3–Al2O3 System

Effect of Oxides of Various Metals on the Physicochemical Properties of Glass in the PbO–CdO–SiO2–B2O3–Al2O3 System

The physicochemical processes occurring in glasses of the PbO–CdO–SiO2–B2O3–Al2O3 system after high-temperature contact with oxides of various metals—CuO, NiO, Al2O3, TiO2, Nb2O5, and WO3, as well as the electrical resistance of the obtained glasses—are studied by X-ray phase analysis, infrared spectroscopy, and electron paramagnetic resonance. It is established that these properties are determined by the acid-base and redox properties of the oxides and glasses, which directly depend on the content of the O2– ion in each specific composition.

Residual stress versus microstructural effects on the strength and toughness of phase‐separated PbO–B2O3–Al2O3 glasses

AbstractA few authors have reasonably proposed that liquid–liquid phase‐separated (LLPS) glasses could show improved fracture strength, Sf, and toughness, KIc, as the second phase could provide a barrier to crack propagation via deflection, bowing, trapping, or bridging. Due to the associated tensile or compressive residual stresses, the second phase could also act as a toughening or a weakening mechanism. In this work, we investigated five glasses of the PbO–B2O3–Al2O3 system spanning across the miscibility gap: Four of them undergo LLPS—three are binodal (two B2O3‐rich and one PbO‐rich) and one is spinodal—and one does not show LLPS (composition outside the miscibility gap). Their compositions were designed in such a way that the amorphous particles are under compressive residual stresses in some and under tensile residual stresses in others. The following mechanical properties were determined: the Vickers hardness, ball on three balls (B3B) strength, and toughness, KIc‐SEVNB (single‐edge V‐notch beam [SEVNB]). The microstructures and compositions were analyzed using scanning electron microscopy with energy‐dispersive X‐ray spectrometry. The spinodal glass showed, by far, the best mechanical properties. Its KIc‐SEVNB = 1.6 ± 0.1 MPa m1/2, which embodies an increase of almost 50% over the B2O3‐rich binodal composition, and 90% considering the PbO‐rich binodal composition. Moreover, its fracture strength, Sf = 166 ± 7 MPa, is one of the highest ones ever reported for an LLPS glass. Fracture analyses evidenced that the spinodal composition exhibited the lowest net stress at the fracture point. Moreover, calculations indicate that the internal residual stress level is the lowest in the spinodal glass. The overall results indicate that the microstructural effect of the spinodal glass is the most significant factor for its superior mechanical properties. This work corroborates the idea that LLPS provides a feasible and stimulating solution to improve the mechanical properties of glasses.

Performance and transition mechanism from acidity to basicity of amphoteric oxides (Al2O3 and B2O3) in SiO2–CaO–Al2O3–B2O3 system: A molecular dynamics study

Amphoteric oxides (Al2O3 and B2O3) represent opposite effects on the structure and properties of silicate melts in different conditions, while the understanding about the transition from acidity to basicity is far from complete. Molecular dynamics simulation was adopted in the present study to investigate the performance and acidity-basicity transformation of Al2O3 and B2O3 in the SiO2–CaO–Al2O3–B2O3 system. The results showed that, different from Ca2+ ions, excessive Al3+ or B3+ ions tend to destroy the bridge oxygen structures, showing the function of basic oxide. This is similar to the behavior of Ca2+ ions and other basicity ions. It was found that, on the one hand, B3+ ions tend to form [BO3]3- planar triangular structures with the increase of B3+ ions contents, on the other hand, B3+ ions could reduce the stability of Si–O bonds. Therefore, B3+ ions could make the system structure less stable, which is the reason why the B2O3 is a kind of active agent. In addition, because of the significant differences in lattice energy and atomic structure between Al2O3 and B2O3, the effects of Al2O3 and B2O3 on the thermodynamic properties of silicate melts are quite different.

Thermodynamic Simulation of the Influence of the Temperature and the Basicity of a Boron-Containing Slag on Steel Desulfurization

The results of thermodynamic simulation of the desulfurization of a medium-carbon steel by slags of the CaO–SiO2–MgO–Al2O3–B2O3 system are presented. The HSC Chemistry 6.12 software package is used for the simulation. The thermodynamic simulation is performed for 20 various chemical compositions of slags with various B2O3 contents (1–4%)1 and basicities ((CaO)/(SiO2) = 2–5). The computations are performed using the Equilibrium Compositions module in the temperature range from 1500 to 1700°C with an increment of 50°C at a gas phase pressure of 0.1 MPa. The main results of the calculations are presented as the dependences of the change in the sulfur content in steel [S] on the temperature, the content of B2O3, and the slag basicity. An increase in the temperature of metal desulfurization from 1500 to 1700°C exerts a favorable effect on the sulfur content for the studied range of slag basicities. In particular, the sulfur content in steel decreases from 0.012 to 0.009% when steel is processed with the slag having 3% B2O3 and a basicity (CaO)/(SiO2) = 2. A positive effect of an increase in the slag basicity from 2 to 5 on metal desulfurization is observed: the degree of desulfurization increases from 61.1 to 97.2% at 1600°C and 3% B2O3 content in the slag. As the B2O3 content in a slag increases from 1 to 4%, its refining properties decrease significantly in the range of basicity not higher than 2. In the range of high slag basicities (3–4), the negative effect of acidic oxide B2O3 on the refining properties of the slag decreases, providing low sulfur contents (which do not exceed [S] = 0.003–0.004% at 4% B2O3). At a slag basicity of 5, the sulfur content in steel decreases to 0.001%, all other things being equal. The simulation results can be used for the calculation of steel desulfurization processed by slags containing B2O3.

Investigation the influences of B2O3and R2O on the structure and crystallization behaviors of CaO–Al2O3based F-free mold flux

The influences of B2O3and R2O on the structure and crystallization of CaO–Al2O3based F-free mold flux were investigated by Raman Spectroscopy and Differential Scanning Calorimetry Technique, respectively, for developing a new type of F-free mold flux. The results of structural investigations showed that B3+is mainly in the form of [BO3]. And [BO3] appears to form BIII–O–Al linkage which will produce a positive effect on forming [AlO4] network. The number of bridging oxygen and the degree of polymerization of [AlO4] network structure for CaO–Al2O3system were also increased with the increasing of B2O3. On the contrary, with the addition of R2O into CaO–Al2O3–B2O3system, the number of bridging oxygen and the degree of polymerization of [AlO4] network were decreased. DSC results showed that the crystallization process became more sluggish with the increase of B2O3, which indicated that the crystallization ability was weakened. While the quenched mold fluxes crystallized more rapidly when introducing R2O. In other word, the crystallization rates of CaO–Al2O3based slags were accelerated by the introduction of R2O. The liquidus temperature and crystallization temperature were decreased with the increasing amount of B2O3or by addition of R2O into CaO–Al2O3system. Only one kind of crystal was precipitated in 8% B2O3and %R2O-containing samples, which was CaAl2O4identified by SEM-EDS. When the content of B2O3increased from 8% to 16%, Ca3B2O6is clearly observed, demonstrating that the crystallization ability of Ca3B2O6is enhanced by the increasing concentration of B2O3in mold flux. The Ca/Al ratio of the generated calcium aluminate has been altered from 1:2 to 1:4 with the increasing of B2O3. The size of CaAl2O4crystal is gradually increased with the addition of R2O. The crystallization ability of CaAl2O4is promoted by R2O.

Thermodynamic Modeling of Metal Desulfurization with Boron-Containing Slags of the CaO–SiO2–MgO–Al2O3–B2O3 System

In thermodynamic modeling of the desulfurization of steel by CaO–SiO2–MgO–Al2O3–B2O3 slag on the basis of HSC 6.12 Chemistry software (Outokumpu), the influence of the temperature (1500–1700°C), the slag basicity (2–5), and the B2O3 content (1–4%)1 on the desulfurization is analyzed. It is found that the sulfur content is reduced with increase in the temperature from 1500 to 1700°C, within the given range of slag basicity. At 1600°C, the sulfur content in the metal is 0.0052% for slag of basicity 2; at 1650°C, by contrast, its content is 0.0048%. Increase in slag basicity from 2 to 5 improves the desulfurization, which increases from 80.7 to 98.7% at 1600°C. If the B2O3 content in the slag rises, desulfurization is impaired. At 1600°C, the sulfur content in the metal may be reduced to 0.0052 and 0.0098% when using slag of basicity 2 with 1 and 4% B2O3, respectively; in the same conditions but with slag of basicity 5, the corresponding values are 0.00036 and 0.00088%, respectively. Note that desulfurization is better for slag without B2O3. According to thermodynamic modeling, metal with 0.0039 and 0.00019% S is obtained at 1600°C when using slag of basicity 2 and 5, respectively, that contains no B2O3. The results obtained by thermodynamic modeling for the desulfurization of metal by CaO–SiO2–MgO–Al2O3–B2O3 slag of basicity 2–5 in the range 1500–1700°C are consistent with experimental data and may be used in improving the desulfurization of steel by slag that contains boron.

The effect of glass composition and structure on photochromic properties of LiF–Al2O3–B2O3 glassy materials

The glass-forming region of the LiF–Al2O3–B2O3 system and the phase diagram of this region have been studied. Properties of glasses and devitrified glasses, as well as the crystallization products, are investigated. The effect of metastable liquation and the free volume on photochromic properties of glasses and glass–crystalline materials activated with AgCl and Cu2O has been revealed. Photosensitive glass ceramics characterized by the linear thermal expansion coefficient (30–45) × 10–7 K–1 and high transparency in the visible spectral region have been synthesized.

Crystallization features and physico-chemical properties of alkali and alkaline aluminoborate glass–ceramics

Preparation and characterization of glass–ceramics based on CaO–Al2O3–B2O3 system, modified by replacing CaO by different alkali and alkaline earth oxides, and In2O3/Al2O3 substitustion were implemented. Different crystalline phases, including β-CaAl2B2O7, Na2Al2B2O7, LiAl5O8, Li4Al4B6O17, Li2AlBO4, SrAl2B2O7, BaAl2B2O7, α-(Ca1-x,Inx)Al2B2O7, and InBO3, were developed from the heat-treated glasses. The incorporation of In3+ in the position of Ca2+ in β-CaAl2B2O7 crystal lattice was responsible for phase transition of β-CaAl2B2O7 to α-CaAl2B2O7 phase. The coefficient of thermal expansion CTE of prepared glass–ceramics was between −65 × 10−7 and 72 × 10−7 K−1 in the temperature range from 25 to 600 °C. The glass–ceramic specimens containing XAl2B2O7 as the principal crystalline phase were characterized by negative CTE values. In contrast, the replacement of CaO in the base glass by alkali oxides like Na2O and Li2O led to a dramatic transformation of the negative CTE to postive values. The complete replacement of calcium oxide in the base glass by various alkali and alkaline earth oxides markedly decreased the chemical durability of the investigated glass–ceramic specimens, while substitution of Al2O3 by In2O3 resulted in improving the chemical stability of the crystalline samples. The density of the glass specimens were found to be within the range 2.35–3.38 g/cm3, while the density of the glass–ceramic samples was in the range of 2.37–3.13 g/cm3.

Formation, microstructure and properties of aluminum borate ceramics obtained from alumina and boric acid

The formation of aluminum borates (Al18B4O33 and Al4B2O9) from alumina and boron oxide occurs between 600 and 800°C. These materials have refractory properties and corrosion resistance. The objective of this work is to develop materials from the Al2O3-B2O3 system, employing alumina and boric acid as starting powders, to study the critical processing variables and describe the developed microstructure and properties.Three formulations (13, 19.5 and 26wt% B2O3) were studied. In order to confirm the formation of borates, the differential thermal analysis and thermogravimetric analysis were carried out. Afterwards, uniaxially pressed disc-shaped specimens were fired at four temperatures above the formation temperature. The textural properties of the ceramics were evaluated by the immersion method, this permit to evaluate the sintering processes. Then the degree of borate formation was confirmed by X-ray diffraction.Finally, the developed microstructures were characterized by scanning electron microscopy, and the diametral compression behavior was evaluated.A series of porous (≈50%) refractory materials from the Al2O3-B2O3 system were developed. The processing strategy resulted in materials with Al18B4O33 as the main crystalline phase. Needle grains with diameters between 0.2 and 1µm and an aspect ratio over 20:1 were obtained. Thus, based on the information gathered from our research, aluminum borate ceramic materials can be designed for structural, insulating or filtering applications employing only alumina and boric acid as boron oxide source.

Glass structure and NIR emission of Er3+ at 1.5 μm in oxyfluoride BaF2–Al2O3–B2O3 glasses

The glass structure, photoluminescence properties of Eu3+, Judd–Ofelt analysis, and near infrared emissions of Er3+ at 1.5μm in the oxyfluoride glasses and glass–ceramics of 1Eu2O3- or 1Er2O3-doped 50BaF2–xAl2O3–(50−x)B2O3 (x=0–25mol%) were investigated. It was clarified on the ground of Raman scattering spectroscopy and F1s and O1s XPS measurements that the glass with no Al2O3 (1Er2O3–50BaF2–50B2O3) is composed of BO3, BO2F and BO3F units with F–Ba bonds. The glasses with 25Al2O3 (1Er2O3–50BaF2–25Al2O3–25B2O3) is mainly composed of BO3− and Al(O,F)x units. Existence of non-bridging oxygen was not detected by O1s-XPS spectra. It was proposed that these structures are largely affected on crystallization behavior, e.g., the glass with no Al2O3 forms BaF2 and β-BaB2O4 due to Ba–F bonds and the glass with 25Al2O3 forms BaAlBO3F2 because the glass structure composed of BO3 and Al(O,F) units is similar to the BaAlBO3F2 crystal structure. Judd–Ofelt parameters of Er3+ and Eu3+ in the glasses showed almost the same values in Ω4 and Ω6 for each glass, on the other hand Ω2 decreased with addition of Al2O3. The emission spectra of Er3+ at 1.5μm in the glasses and glass–ceramics with BaAlBO3F2 crystals showed broad peaks. It is proposed that oxyfluoride glasses and glass–ceramics based on the BaF2–Al2O3–B2O3 system have a high potential for optical device applications such as broadband optical amplifiers.

Production technology for low-carbon, low-sulfur boron steel

A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite.

Design, selection and characterization of novel glasses and glass-ceramics for use in prosthetic applications

The objective of this work is to design and characterize crystallizable silicate and borosilicate compositions for use in the production of smart, unconventional coatings on bioceramic implants. The concept behind this research is the development of a three-layer implantable system (joint prosthesis) comprising a ceramic substrate, a glass-derived trabecular coating and a glass-ceramic interlayer that joins the other two elements together. The outer porous coating should exhibit bone-like architecture, high mechanical strength and good bioactivity to bond to bone, whereas the interlayer should be chemically stable in biological fluids to avoid detachment between the joined parts. Glasses in the SiO2–Na2O–K2O–CaO–P2O5–B2O3–Al2O3 system have been synthesized by a melting route and thermally treated to obtain glass-ceramic products. A selection of potentially suitable materials for the trabecular coating and interlayer was carried out on the basis of thermal properties and tendency to dissolve in simulated body fluids (SBF) so that the integrity of the final device might be maintained upon implantation. The glass selected for the trabecular coating was processed by sponge replica method to produce glass-ceramic scaffolds, in order to evaluate the material properties and performance in an embodiment plausibly close to the final application. The mechanical properties of the porous glass-ceramic, which mimicked the 3-D pore architecture of cancellous bone, were adequate for load-bearing applications such as joint prostheses. Formation of a surface apatite layer on scaffold struts upon soaking in SBF confirmed the excellent bioactivity of the material, which is a key precondition for in vivo osteointegration.

Effect of X-ray radiation on a potassium aluminaborate glass system

Glass of the K2O–Al2O3–B2O3 system containing Ag, Sb, Ce, KCl, and KBr has been studied. It is shown that an intense additional absorption is induced in this glass by the action of X-ray radiation in the region of 300–400 nm, which is caused by the creation of hole centers. The assumption is expressed that ions of oxygen, chlorine, and bromine included in the environment of the aluninum tetrahedric complex are the donors of electrons generated under the action of X-ray radiation. The hypothesis is proposed about the inclusion of halides in the tetrahedric environment of aluminum (halide effect). It is shown that a red shift of the maximum in the induced absorption spectrum is observed in succession: oxygen, chlorine, and bromine. Ions and nanoparticles of silver, ions of Sb+5, and defects of matrix glass are the acceptors of the induced electrons. The acceptor properties in this succession are increased, which leads to an increase in the induced absorption intensity.

Synthesis, characterisation and kinetic study of a glassy material in the BaO–TiO2–Ta2O5–B2O3–Al2O3 system obtained by a traditional glass fusion–casting method

Through several different compositions based on the system BaO–TiO2–Ta2O5–B2O3–Al2O3 it was possible to obtain a glassy material that is stable to spontaneous crystallisation with a relatively low melting temperature (1450°C). This glass was obtained by the traditional method (fusion–casting), which increased the possibility of forming a solid piece of glass free of imperfections, such as pores and microcracks. Through X-ray diffraction analysis, the characteristic amorphous phase of the glassy state was determined. The glass transition temperature, 620°C, was determined using differential thermal analysis. Additionally, two exothermic crystallisation peaks were observed, one at 715°C and the other at 760°C. The Al2O3 content (18mol%) determined the stability (resistance to thermal shock) of the glass sample, and increasing the content of B2O3 resulted in the formation and stabilisation of the glassy phase. The methodology and parameters for casting and annealing were influential obtaining the stable glass. A study of the crystallisation kinetics was performed, and the activation energy (Ea), frequency (v) and Avrami's number (n) were determined to be Ea=50.5kJ/mol, v=7.4×1033min−1 and n=1.5, respectively. The obtained glassy materials are promising for developing crystalline dielectric phases.

Growth process of Cu2Al6B4O17 whiskers

The reactions occurred and growth process in the preparation of copper aluminum borate (Cu2Al6B4O17) whiskers based on flux method (Al2(SO4)3/CuSO4/H3BO3 as raw materials, K2SO4 as flux) were investigated. The thermogravimetric and differential scanning calorimetry analysis (TG-DSC), inductively coupled plasma atomic emission spectrum analysis (ICP-AES) and X-ray diffraction analysis (XRD) results of reactants mixture quenched at various temperatures and phase diagrams of K2SO4–Al2(SO4)3 system and B2O3–Al2O3 system showed that the reaction process proceeds through three steps: the formation and decomposition of two different kinds of potassium aluminum sulfate (K3Al(SO4)3 and KAl(SO4)2); the formation of aluminum borate (Al4B2O9) and decomposition of copper sulfate (CuSO4) and boric acid (H3BO3); growth and formation of copper aluminum borate (Cu2Al6B4O17) whiskers. The scanning electron microscopy (SEM) analysis results indicated that morphology in growth of Cu2Al6B4O17 whiskers develops through three stages: nanoparticles, fan-shaped whiskers and agminate-needlelike whiskers.

Thermal, structural and crystallization kinetics of SiO2–BaO–ZnO–B2O3–Al2O3 glass samples as a sealant for SOFC

The present work describes the development of a glass-ceramic in SiO2–BaO–ZnO–B2O3–Al2O3 system. The prepared glass samples were found to have good compatibility to act as a sealant in planar solid oxide fuel cell (SOFC) in terms of coefficient of thermal expansion (TEC) and glass transition temperature (Tg). The crystallization kinetics of present glass samples were investigated by various characterization techniques such as differential thermal analyzer (DTA), Dilatometery, X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization behavior of the chosen glass samples was influenced by replacing B2O3 with Al2O3. With the addition of Al2O3 there is increase in glass transition temperature (Tg) and glass crystallization temperature (Tc). Also with the addition of Al2O3 crystallization phenomenon is hindered. XRD and SEM study was done at various temperatures for different time durations. The detail of the above discussed study is done in the present paper.

Fabrication of Eu:SrAl2O4-based glass ceramics using Frozen sorbet method

The Frozen sorbet (FS) method is applied to the SrO–Al2O3–B2O3 system in order to fabricate glass ceramics consisting of Eu2+,Dy3+-doped SrAl2O4 phosphors, and their luminescent properties are examined. Through the quenching of melts (e.g., 55SrO–27Al2O3–18B2O3 with Eu2O3 and Dy2O3), composites (glass ceramics) consisting of the glass phase and SrAl2O4 crystals with a diameter of ∼40 µm are fabricated. It is found that SrAl2O4 crystals in the glass ceramics show excellent long persistent phosphorescent properties and improved excitation efficiency at ∼460 nm in the PL excitation spectra compared with SrAl2O4 phosphors prepared using a conventional solid state reaction. It is suggested that the Al3+-sites in SrAl2O4 crystals are partially substituted by B3+-ions. The present study proposes that the Frozen sorbet method can be a useful technique for the design of new SrAl2O4-based phosphor composites which can be used under white light emitting diode (LED) excitation (∼460 nm).

Kinetic study of the crystallization processes of some decorative ceramic glazes

A kinetic study of the crystallization processes was performed for some decorative ceramic glazes in the PbO-SiO2-Na2O-K2O-CaO(BaO)-Al2O3-B2O3 system with addition of 10% TiO2 and ZnO. The crystallization kinetics has been studied in non-isothermal conditions using DTA technique. The apparent activation energies of the crystallization processes were calculated using the Kissinger method. The main crystalline phase, which provides the decorative effect, is rutile. This has been identified by X-ray diffraction and it is clearly visible in the optical microscopy images taken in transmitted light, as needle-like or even prismatic crystals arranged in radial-fibrous aggregates.