Magnesium Borate Research Articles

Enhanced Thermal Stability and Flame Retardancy of Poly(Vinyl Chloride) Based Composites by Magnesium Borate Hydrate-Mechanically Activated Lignin

To improve the thermal stability and flame retardancy of poly(vinyl chloride) (PVC) based composites, magnesium borate hydrate-mechanically activated lignin (MBH-MAL) complex was in-situ synthesized by hydrothermal method for using as a novel additive. In addition, MBH-lignin (MBH-L) complex, MAL, MBH, and common mixing of MBH and MAL (MBH+MAL) were also prepared for comparative investigation. MBH-MAL showed synergistic improving effect on PVC as MBH-MAL/PVC composite exhibited excellent thermal stability and flame retardancy. The static thermal stability time was 871 s and limit oxygen index was 32.54%, indicating that MBH-MAL effectively inhibited the generation of HCl from thermal decomposition of PVC and prevented the combustion of PVC based composites in air. MBH-MAL/PVC composite still exhibited outstanding tensile and flexural properties. Moreover, the enhancing mechanism of MBH-MAL on the thermal stability and flame retardancy of PVC based composites was proposed.

Boron Carbide Composites produced by Self-Propagating High-Temperature Synthesis

This work is a study of the conditions for obtaining boron carbide, magnesia, and aluminum oxide composites by self-propagating high temperatures synthesis (SHS). The substances used to synthesize the composites were boron oxide, magnesia, and aluminum oxide. The SHS with the reduction stage was conducted as the following aggregate reaction: 2B2O3+6Mg+xC--->ByCx+6MgO, 2B2O3+4Al+xC=2Al2O3+ByCx. The metallothermic SHS using boron oxide seems
 more attractive than the current carbide production methods characterized by long-time and multistage physico-chemical
 processes requiring increased material, energy, and financial costs. The thermodynamic calculations of the phase composition of the products and the adiabatic combustion temperature for systems B2O3–Mg– C, B2O3–Al–C were made in the FastStage program. The calculations and tests allowed identifying the optimal conditions of SHS. The products of SHS were examined by X-ray phase analysis and the SEM method. The compositions of the B2O3–Mg–C system obtained by SHS were represented mainly by boron carbide, magnesia, magnesium borate, and Mg3B2O6. The products of the B2O3–Al–C system obtained by SHS contained boron carbide, alumina, and aluminum boride.

Performance of two magnesium borate compounds, with thermoluminescent properties, to γ-rays and neutrons

There is a permanent effort to search for natural and artificial materials with thermoluminescent properties useful for radiation dosimetry. In the aim to understand the radiation interactions with these materials, several features are determined. Here, the performance to photons and neutrons of MgB4O7:Dy and Mg2B2O5:Dy,Na were studied. The mass interaction coefficients, the linear attenuation coefficients, the mean free path and the Zeff for photons were calculated. In addition, the absorbed dose response to gamma rays and neutrons were estimated. The linear attenuation coefficients to gamma-rays for MBO:Dy,Na is larger than the coefficients for MBO:Dy due the density and Dy concentration, however the absorbed dose response for both materials are approximately the same due to the Zeff. The absorbed dose response to monoenergetic neutrons and those from isotopic neutron sources, and with Maxwellian distribution has the same trend. This response is larger for 252Cf/D2O; the absorbed dose response to neutrons is larger for MBO:Dy due to the boron concentration.

Enhanced Electrochemical Properties of Lithium‐Rich Cathode Materials by Magnesium Borate Surface Coating

AbstractMagnesium borate oxide (MBO) coated lithium‐rich layered Li1.2Mn0.54Co0.13Ni0.13O2 particles are synthesized via a wet chemical coating method. The X‐ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and X‐ray photoelectron spectrometer results indicate that the cathode particles are uniformly covered with a MBO layer. The results of charge/discharge tests show that the MBO‐coated electrode has enhanced electrochemical properties both in rate capability and cycling stability compared to the bare one. Specifically, 3 wt. % MBO‐coated sample has capacity retention of 98.3 %, much more than the bare one of only 79.2 % after 100 cycles at 1 C. Furthermore, the MBO‐coated electrode retains a superior high‐rate capacity of 90 mAh g−1 at 10 C. The remarkably enhanced rate capability and cycling stability of MBO‐coated electrode is ascribed to the MBO coating layer efficiently isolating the bulk Li1.2Mn0.54Co0.13Ni0.13O2 from direct contact with the electrolyte, and facilitating both charge transfer reaction and the kinetics of lithium ion diffusion through the surface layer.

Effect of Volume Fraction Whiskers on Tensile and Thermal Expansion Properties of Mg2B2O5 Whisker-reinforced Aluminum Composite

This paper prepared magnesium borate whisker reinforced aluminum matrix composites by extrusion casting, and studied the effects of the volume fraction of the reinforced phase on the mechanical properties, thermal expansion properties and microstructure of the composites. The test results show that the reinforced magnesium borate whisker in the composite can be uniformly dispersed in the aluminum matrix to improve the strength. With the increase of the volume fraction, the strength of the composite material increases and the plasticity decreases. When the whisker volume fraction is 30%, the strength of the composite material reaches the maximum, with its tensile strength reaching 244 MPa and elastic modulus 107.6 GPA. When the whisker volume fraction is 20%, the composite has the best plasticity and the fracture elongation is 0.47%. The thermal expansion curve of the composite shows that the increase of whisker volume fraction will reduce the thermal expansion coefficient of the composite.

Study on Mechanical and Thermal Expansion Properties of Oxide Coated Magnesium Borate Whiskers Reinforced Aluminum-based Composite

The surface of magnesium borate whiskers was coated with oxide coatings of different components by chemical precipitation method, and magnesium borate whisker-reinforced aluminum-based composites were prepared by squeeze casting method. The compressive deformation resistance of the prefabricated whisker and the tensile and thermal expansion properties of the composite were tested. The experimental results show that the oxide coating can effectively improve the anti-deformation ability of the whisker preform, and the whisker preform prepared by MgO and Al2O3 coating has better strength, and the compressive strength at room temperature reaches 0.98 MPa and 0.96 MPa. The composite material prepared by Al2O3 coated whiskers has the highest room temperature tensile strength of 263 MPa, and the composite material prepared by ZnO coated whiskers has the lowest room temperature tensile strength of 224 MPa. The thermal expansion curve of the composite material shows that as the temperature increases, the thermal expansion coefficient of the composite material gradually increases, and the thermal expansion coefficient of the composite material decreases slightly after a temperature cycle.

Synthesis and characterization of CuO doped lithium magnesium borate glasses for thermoluminescence dosimetry

In the present study, we have fabricate lithium magnesium borate glasses doped with different Cu2+ contents using the melt quench technique. The fabricated nanocomposites were characterized via FTIR, XRD, Raman and DRS analysis. The XRD pattern of all the nanocomposite definite the amorphous nature and the IR spectra revealed the presence of BO3 and BO4 units in the nanocomposites. The fabricated nanocomposites were used for solid state thermoluminescence dosimetry under the gamma radiation (cobalt, Co-60 source). The optimum annealing temperature was found to be 300 °C within 60 min. The results revealed that an enhancement in the TL intensity with the increment a certain amount of Cu2+ into the Lithium magnesium borate (LMB) samples. The fabricated nanocomposites show excellent TL intensity, reproducibility and a good linearity with linear regression coefficient of 0.9980 and 0.9949 with the dose range of 1–10 Gy and 10–100 Gy, respectively. These attractive outcomes exhibit that our fabricated nanocomposites can be used in personal, environmental and medical radiation therapy applications in future.

Phase equilibria in the ternary systems (MgSO4+MgB4O7+H2O) and (MgSO4+Mg2B6O11+H2O) at 273.15 K and 288.15 K: solubility and polyborate distribution

The solubility isotherms of the two ternary systems (MgSO4 + MgB4O7 + H2O(and (MgSO4+ Mg2B6O11+H2O) were determined using the isothermal dissolution equilibrium method at 273.15 K and 288.15 K. Solubilities and acidities of the liquid phase were determined in detail experimentally. According to the experimental data, the phase diagrams for two ternary systems were given. The results indicate that the two ternary systems are the simple saturated type, and double salt or solid solution are not formed. There are one invariant point corresponding to (epsomite + hungchaoite or inderite), two isothermal dissolution curves, and two crystallization regions in two ternary systems. It was found that the crystallization region areas of magnesium borate were larger than that of epsomite, indicating that the solubility of epsomite was larger in the two systems. The presence of magnesium sulfate can prevent the transformation of hungchaoite into inderite, and magnesium sulfate has a significant solubilizing effect on both magnesium borate at the experimental temperature. The distributions of polyborate species in saturated magnesium borate solution varying with mass fraction of magnesium sulfate were calculated by the Newton iteration method.

Development of Ce3+ and Li+ co-doped magnesium borate glass ceramics for optically stimulated luminescence dosimetry

Magnesium tetraborate, MgB4O7, is an attractive host material for dosimetry due to the two characteristics: its low effective atomic number (Zeff = 8.4) and high neutron capture cross-section of the 10B isotope. Particularly, Ce3+ and Li+ ions co-doped MgB4O7 has shown optically stimulated luminescence (OSL) signal comparable to that of Al2O3:C, which is a well-known OSL dosimetry material. In this work, for further improvement of the dosimetric properties, a new synthesis route for MgB4O7:Ce3+-Li+ is described: glass-ceramic (GC) MgB4O7:Ce3+-Li+ samples were prepared by heat treatment of the magnesium borate glass with the composition, 25MgO–72B2O3–3Li2O-0.3Ce3+. The prepared GC samples show UV-blue radioluminescence assigned to the Ce3+ 5d → 4f transition under X-ray irradiation and two thermoluminescence (TL) glow peaks related to the shallow and deep electron traps. Although fading of the TL and OSL signal was observed due to electron release from the shallow traps, the electrons captured by deep traps were stable at room temperature. Particularly, GC samples annealed at 750 °C and 800 °C, named GC750 and GC800, showed stable OSL up to 10 h following β-ray irradiation, after an initial fading mainly due to the presence of shallow traps in the material. From the viewpoint of this fading ratio, GC750 and GC800 showed potential as a practical OSL dosimeter.

A novel Er3+ ions doped zirconium magnesium borate glass with very high quantum efficiency for green laser and optical amplifier applications

A potential new series of Er3+ ions doped zirconium magnesium borate (ZMB) glasses have been prepared by conventional melt quenching method. Aperiodic nature of the glasses was confirmed by X-ray diffraction analysis. SEM image shows the nonappearance of any defined shape or structure which confirms the amorphous nature. The Refractive index of the glasses increases in the value from 1.611 to 1.671 with increase of Er3+ ion concentration. The optical absorption, excitation and emission spectra of the Er3+ doped glasses were recorded from ultraviolet (UV) to visible (Vis) and near infra-red (NIR) range with different equipment's. The oscillator strength and JO intensity parameter (Ω2, Ω4 and Ω6) were calculated from the absorption spectra. The photoluminescence spectra of the present glasses exhibit two emissions (2H11/2 → 4I15/2 and 4S3/2 → 4I15/2) bands in the visible region by exciting 491 nm and exhibit one emission (4I13/2 → 4I15/2) in the NIR region with the 980 nm as an excitation source. The experimental lifetime (τexp), FWHM, figure of merit (σPE × τexp), gain bandwidth (σPE × Δλeff) and stimulated emission cross-section (σPE) values have been calculated for all the present glasses for visible and NIR emission transition. The decay spectra measured for 4I13/2 → 4I15/2 transition shows single exponentials for all Er3+ ion concentrations of the glasses. CIE 1931 diagram shows the exact emission colour (green) of the prepared glasses. Correlated colour temperature points show along with the block body curve line and can be used for cold lighting purposes. From the all the results, it is observed that, 1ErZMB glass is more potential candidate for green laser, optical amplifier and designing of photonic devices.

Gd3+/Sm3+energy transfer behavior and spectroscopic study of lithium gadolinium magnesium borate for solid state lighting material

We report the luminescence and energy transfer features in (B2O3)0.55-x(Li2O)0.30 (MgO)0.10(Gd2O3)0.05 (Sm2O3)x glasses, prepared via melt-quenching rout. By employing the Judd–Ofelt (JO) theory, the spectral parameters such as oscillator strengths, stimulated emission cross-sections, radiative transition probability and branching ratios are evaluated from the absorption and emission spectra. The dipole-dipole interaction as a dominant interaction mechanism is confirmed from Inokuti–Hirayama (IH) model. The luminescent color falls in the orange part of commission International de I'Eclaiage (CIE). The ultra-violet (UV) sensitization of visible emission of Sm3+ is analyzed by the photoluminescence (PL) emission spectra and the lifetime measurement. The Gd: 6P7/2–8S7/2 emission in UV range and the Sm3+:4G5/2 –6HJ luminescence at 598 nm were observed upon the excitation of Gd:4f level by λexc = 275 nm. Moreover, the impact of energy transfer on the donor-acceptor luminescence, quantum efficiency, and donor luminescence decay kinetics are investigated. It is found that efficient orange luminescence originates from Sm3+ emitting centers. These findings show that these as-prepared luminescent glasses are promising in orange LEDs and laser applications.

Direct preparation of magnesium borate (Mg2B2O5) ceramic from boron-bearing slag: Super-gravity separation and microwave dielectric properties

In this study, a novel method was developed for direct preparation of magnesium borate (Mg2B2O5) ceramic from boron-bearing slag. The amorphous boron was efficiently enriched into Mg2B2O5 via crystalline phase transformation in the condition of B/S (B2O3/SiO2) = 1.20 and wt.% (MgO) = 36.00. High-purity Mg2B2O5 crystals were fully recovered from molten slag by super-gravity separation at G ≥ 500 and t ≥ 240 s. The Mg2B2O5 ceramic was directly prepared at various temperature by using the recovered Mg2B2O5, and the Mg2B2O5 ceramic displayed a favourable microwave dielectric properties including the dielectric constant (εr) of 6.05, the quality factor (Q × f) of 38,147 GHz and the temperature coefficient of resonant frequency (TCF) of -20.98 ppm/K. Compared with synthetic methods that use high-purity oxides, this study provides a green and economical method for direct utilisation of industrial slag to prepare microwave dielectric materials.

Effect of sintering temperature on sensitivity of MgB4O7:Tm,Ag obtained by the solution combustion method

Borates are appropriate TL materials for radiation dosimetry, because of their equivalence with tissue. Magnesium borate is a tissue equivalent material and its most important advantage over lithium borate, is that this material is insoluble in water. In this work the effect of sintering temperature on the sensitivity of magnesium borate obtained by the solution combustion technique is presented. The results showed that the material doped with Tm and Ag, subjected to 1223 K, for 3 h, had a sensitivity between two and four times higher than that of the commercial dosimeter TLD-100 making it highly appropriate for applications in clinical dosimetry.

Spectroscopic behaviour of Dy3+ and Sm3+ impurity-doped strontium magnesium borate glasses: A comparative evaluation

Two new series of strontium magnesium borate glasses with Dy3+ and Sm3+ activation (both in the concentration range of 0.1–1.0 mol%) were prepared using the standard melt-quenching and characterized. The optical and physical properties of these singly impurity-doped glass series were compared. The optical and physical properties of these glasses were determined in terms of the density, molar volume, optical band gap, absorption and emission intensities, oscillator strength, refractive index and molar polarizability. The XRD analyses confirmed the amorphous nature of the as-quenched samples. The EDX spectra revealed the actual elemental compositions and FESEM images showed the samples homogeneity without cracks. The UV–vis-NIR absorption spectra of the Dy3+- and Sm3+-doped glasses showed nine and ten characteristics bands respectively. The PL spectra of the Dy3+- and Sm3+-doped glasses displayed three ((at 481 nm, blue; 570 nm, yellow; and 661 nm, red) four (559, 596, 643 and 709 nm) significant peaks, respectively. The lasing potentials of the Dy3+- and Sm3+-doped glasses were compared via Judd-Ofelt evaluation. The values of branching ratio and stimulated emission cross-section for the 4F9/2 → 6H13/2 transition in Dy3+ and 4G5/2 → 6H7/2 transitions in Sm3+ was maximum, indicating their effectiveness towards photonic devices assembly. The studied glasses have demonstrated high viability for the cutting-edge innovations in the solid―state lighting and high gain optical fibre construction.

In situ growth magnesium borate whiskers and synthesis of porous ceramics for sound-absorbing

A new idea to improve the performance of porous sound absorbing ceramics is introduced in this study. By in-situ growth of magnesium borate whiskers in the prepared porous sound-absorbing ceramic matrix, the sound absorption coefficient of middle and low frequency is increased by 28.9% and the compressive strength is increased by 5 times. Because the ceramic system has high thermal stability and good chemical stability, this method provides a new possibility for the wide application of porous sound absorbing ceramics in sound absorbing field.

Judd−Ofelt calculations for spectroscopic characteristics of Dy3+-activated strontium magnesium borate glass

Some new type of strontium magnesium borate glass system doped with Dy3+ (various contents 0.1, 0.3, 0.5, 0.7 and 1.0 mol%) were produced using the conventional melt-quenching. Obtained glasses were thermally stable, highly transparent, and moisture resistant. As-prepared samples were characterized to determine their spectroscopic traits. The Judd-Ofelt (J-O) intensity Ωλ (λ = 2, 4, 6) and radiative parameters were calculated to validate the experimental results on the optical characteristics. The XRD pattern of the as-quenched samples verified their glassy nature, FESEM images showed uniform textures and EDX analyses detected the presence of appropriate constituents in the host matrix. Glass containing 0.7 mol% of Dy3+ revealed the optimum optical traits where the luminescence emission intensity was attenuated beyond this content. The optical gain for two intense emission transitions (4F9/2→6H15/2 and 4F9/2→6H13/2) was evaluated. The values of Ωλ (λ = 2, 4, 6) determined the ionic nature of the bonding and symmetry environment of the Dy―ligand matrix based on the viscosity and rigidity of the host glass. The 6H15/2→6F11/2 transition was hypersensitive. The ratio of the yellow to blue (Y/B) emission intensity less than unity indicated the lower degree of covalence between Dy3+ and O2− ions thereby makes these glasses effective for the near UV―LEDs. The higher values of the branching ratio (≥ 50 %) and stimulated emission cross-section enabled the proposed glass composition potential for the optical amplifiers and fibres fabrication. The resonant energy transfer and cross-relaxation processes in the Dy3+ were attributed to be responsible for the improved optical features.

Unique optical traits of Sm3+ -doped magnesium borate glass

A series of Sm3+-doped magnesium borate glasses were prepared using the melt quenching and characterized to determine the effects of various Sm3+ contents on their optical traits. The absorption and luminescence spectra of the glasses revealed ten and four significant peaks, respectively. In addition, the experimental results on the optical properties were validated using the Judd-Ofelt (J−O) analyses. The obtained J−O intensity parameters (Ωλ with λ = 2, 4, 6) confirmed the structural changes in the host network due to the Sm3+ doping. The value of Ω2 for the studied glasses indicated the covalent and asymmetric nature of the Sm3+− O2 linkages. The achieved J−O radiative parameters (quality factor, branching ratio and stimulated emission cross-section) were highest for the glass made with 0.5 mol% of Sm3+, demonstrating its lasing potency. The proposed glass compositions may be beneficial for the photonic devices.

Absorption and luminescence spectral analysis of Dy3+-doped magnesium borate glass

This paper reports the luminescence potential of the dysprosium ion (Dy3+)-doped (varying contents from 0.1 to 1.0 mol%) magnesium borate glasses prepared by the melt-quenching method. As-quenched samples were characterized systematically to determine the effects of various Dy3+ contents on their structure, physical and optical traits. The Judd−Ofelt (J−O) intensity parameters (Ω2, Ω4, Ω6) and radiative properties of the best sample (with 0.7 mol% of Dy3+ doping) was evaluated to complement the experimental optical data. The studied glasses revealed three luminescence emission peaks at 382 nm (4F9/2→6H15/2, intense Blue), 572 nm (4F9/2→6H15/2, intense Yellow) and 661 nm (4F9/2→6H11/2, weak Red) under the excitation wavelength of 347 nm. The emission intensity was first increased up to the Dy3+ content of 0.7 mol% and then quenched. The observed luminescence intensity quenching was due to the resonant energy transfer from the excited state to the neighbouring ground state of Dy3+. The obtained high value of Ω2 signified the strong degree of covalency between the Dy3+ and ligand environment. The optimum glass sample (with 0.7 mol% of Dy3+) showed higher values of the branching ratio and stimulated emission cross-cross section for the 4F9/2→6H15/2 (yellow) emission transition, indicating its potential as bright yellow luminescent material and high gain visible laser applications.

Improved Non-Grignard Electrolyte Based on Magnesium Borate Trichloride for Rechargeable Magnesium Batteries

The high anodic stability of electrolytes for rechargeable magnesium batteries enables the use of new positive electrodes, which can contribute to an increase in energy density. In this study, novel Ph3COMgCl-, Ph3SiOMgCl-, and B(OMgCl)3-based electrolytes were prepared with AlCl3 in triglyme. The Ph3COMgCl-based electrolyte showed anodic stability over 3.0 V vs. Mg but was chemically unstable, whereas the Ph3SiOMgCl-based electrolyte was chemically stable but featured lower anodic stability than the Ph3COMgCl-based electrolyte. Advantageously, the B(OMgCl)3-based electrolyte showed both anodic stability over 3.0 V vs. Mg (possibly due to the Lewis acidic nature of B in B(OMgCl)3) and chemical stability (possibly due to the hard acid character of B(OMgCl)3). B(OMgCl)3, which was prepared by reacting boric acid with a Grignard reagent, was characterized by nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray absorption spectroscopy (XAS). The above analyses showed that B(OMgCl)3 has a complex structure featuring coordinated tetrahydrofuran molecules. 27Al NMR spectroscopy and Al K-edge XAS showed that when B(OMgCl)3 was present in the electrolyte, AlCl3 and AlCl2+ species were converted to AlCl4−. Mg K-edge XAS showed that the Mg species in B(OMgCl)3-based electrolytes are electrochemically positive. As a rechargeable magnesium battery, the full cell using the B(OMgCl)3-based electrolyte and a Mo6S8 Chevrel phase cathode showed stable charge-discharge cycles. Thus, B(OMgCl)3-based electrolytes, the anodic stability of which can be increased to ~3 V by the use of appropriate battery materials, are well suited for the development of practical Mg battery cathodes.

Effects of Boric Acid Ester Modified Magnesium Borate Whisker on the Mechanical Properties and Crystallization Kinetics of Polypropylene Composites.

Polypropylene (PP) is notch sensitive and brittle under severe conditions of deformation, limiting wider range of its usage as a structural load-bearing polymer. Hence, in this work the magnesium borate whisker (MBw), with similar mechanical properties to carbon fiber but much less expensive than polycrystalline silicon carbide, was modified by boric acid ester (BAE) and then used to fabricate PP composites. The mechanical properties, morphology, and non-isothermal crystallization property of virgin PP, PP/MBw, and PP/BAE-MBw composites were studied through mechanical testing, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), respectively. The non-isothermal crystallization data was analyzed via Mo, Kissinger, and Dobreva methods. The results reveal that the incorporation of BAE-MBw into PP matrix results in higher tensile strength and impact strength than those of virgin PP and PP/MBw composite. The activation energies based on Kissinger were 190.20 kJ/mol for virgin PP, 206.59 kJ/mol for PP/MBw, and 218.98 kJ/mol for PP/BAE-MBw. The nucleation activities of whiskers determined by the Dobreva model were 0.86 for PP/MBw and 0.75 for PP/BAE-MBw. As a result, the whiskers, especially the modified whiskers, act as active substrates to facilitate heterogeneous nucleation, which leads to an increase in crystallization rate.