Synthesis of magnesium borate nanorods

doi:10.1016/j.matlet.2007.02.002

Materials Letters

Volume 61, Issue 22, September 2007, Pages 4358-4361

https://doi.org/10.1016/j.matlet.2007.02.002 Get rights and content

Abstract

Single-crystalline magnesium borate Mg₂B₂O₅ nanorods have been synthesized via a simple route based on the calcinations of mixed powders containing Mg(OH)₂ and H₃BO₃. The nanorods have the typical diameters in the range of 70–120 nm and the lengths up to a few micrometers. An optimal synthesis temperature for Mg₂B₂O₅ nanorods was obtained, and the possible growth mechanism was also presented.

Introduction

Nanoscale materials have stimulated great interest due to their importance in basic scientific research and potential technological applications, which exhibit unique chemical and physical properties, differing substantially from the bulk counterpart. The synthesis of one-dimensional (1D) nanostructures such as nanotubes, nanowires and nanorods, are critical and important work directed towards understanding the fundamental properties of small structures, creating new functional materials, and developing nanotechnologies [1], [2], [3].

As is well known, metal borates are the most important technical ceramics owing to their interesting properties, such as high heat-resisting, corrosion-resisting, supermechanical strength, superinsulation, light weight, high strength, high coefficient of elasticity etc. Therefore, the synthesis of such metal borates in nanowires/nanorods form is in favor of understanding the growth mechanism of one-dimensional nanomaterials and exploring the possible application compared to bulk materials. Recently, single crystalline nanostructures of metal borates compounds such as aluminum borates (Al₁₈B₄O₃₃ and Al₄B₂O₉) nanowires or nanotubes [4], [5], [6], [7], [8], [9], [10] and magnesium borates made of MgB₄O₆, Mg₂B₂O₅ and Mg₃B₂O₆ nanowires/nanotubes [4], [11], [12] have been synthesized successfully.

Magnesium borates have many potential applications such as the catalysts useful for the conversion of hydrocarbons [13], the thermo-luminescence phosphor [14], and as fused cast refractory that possesses corrosion–erosion resistance in basic oxygen steel making environments and high degree of thermal shock resistance [15]. We also believe that when reducing the bulk size of magnesium borates into one-dimensional nanostructures may offer outstanding features for developing and improving the aforementioned potential applications. In this paper, we report an alternative fabrication and characterization of one-dimensional single crystalline magnesium borate composed of Mg₂B₂O₅ nanorods. The developed route in this study may be useful to explore the possibilities of commercial application of the single-phase magnesium borate nanostructures.

Section snippets

Experimental

The starting materials of Mg(OH)₂ and H₃BO₃ were commercial grades and used without further purification. The preparation of Mg₂B₂O₅ precursor powder followed a simple route. 233.36 mg of Mg(OH)₂ and 370.89 mg of H₃BO₃ were mixed together and homogenized in an agate pestle and mortar. The mixture was placed in an alumina crucible and used as initial reaction constituent. The alumina crucible was situated into alumina tube and fired at 900 °C for 3 h in air conditions using a traditional

Results and discussion

Fig. 1 shows the X-ray diffraction (XRD) pattern of as-prepared Mg₂B₂O₅ nanorods. All diffraction peaks could be indexed as a monoclinic Mg₂B₂O₅ with lattice parameters of a = 1.233, b = 0.3132 and c = 0.9170 nm. These results are in good accordance with those reported in (JCPDS Card no: 16-0168) of bulk crystal. The shape diffraction peaks suggest that the samples should be well crystallized. No XRD peaks arising from impurities could be detected, indicating that only elemental Mg₂B₂O₅ rods with

Conclusion

In summary, single-crystalline nanorods were successfully synthesized by directly calcining Mg(OH)₂ and H₃BO₃ powders in air without catalysts. The characterization of the nanostructure through TEM and SEM shows that the straight nanorods possess a diameter of 70–120 nm and almost are free of contamination. The nanorods' growth is attributed to solid–liquid–solid (SLS) mechanism. This simple and low-cost method may account for commercial production in order to find applications such as

Acknowledgements

This work was supported by the Fok Fing Tong Education Foundation (Grant No. 91050), the National Natural Science Foundation of China (Grant No. 50202007).

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Magnesium borates (MB) nanorods are widely used as reinforcing materials due to high mechanical strength and resilience to heat and corrosion. However, difficulties in synthesis of single-phase MB continue to reduce the mechanical properties of composites. Herein, a single-phase Magnesium borate (Mg₂B₂O₅) in the form of nanorod has been synthesized using an optimized molar ratio of magnesia (MgO) and boric acid (H₃BO₃) by combining solution reaction and sintering process. Phase and microstructural changes of as synthesized magnesium borate (MB) crystals during the reaction sintering process in between 700 °C and 1200 °C has been closely examined with the help of various characterization techniques. Phases of magnesium borate starts appearing on thermal treatment above 700 °C. Phase transformation of magnesium borate from monoclinic to orthorhombic followed by triclinic was also observed during the thermal treatment. The optimum temperature to obtain pure triclinic Mg₂B₂O₅ phase was found to be in between 1100°C and 1200 °C.
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Surface coating is an effective strategy to suppress side reactions at the electrode/electrolyte interface and improve cycling stability of the Ni-rich LiNi_xCo_yMn_1-_x_-_yO₂ electrodes. It is difficult to prepare a complete coating layer on the secondary particles by traditional methods, due to the alkaline substances and oxidative property on surface. In this work, a coating process of Mg₃B₂O₆ running counter to traditional routes was designed to modify LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode material. In a weak polar ethanol medium, BH₄^- ions are uniformly lain on particle surface by the interaction between its electronegativity and oxidizing surface, which also change the charge state into negative atmosphere around the NCM811 surface. Then Mg²⁺ ions are also completely dispersed by the mutual attraction between metal cations and the hydrolyzed BO₃^-. Then a full surface coverage of Mg₃B₂O₆ was prepared in situ on the NCM811 secondary particles. The complete coating layer protects the surface crystal structure of the NCM811 and limits the irreversible phase transition. The optimized composite with a suitable coverage of 1 % Mg₃B₂O₆ exhibits enhanced rate capability and excellent cycling performance. At a high current density of 10C, it delivers a specific capacity of 162.7 mAh g⁻¹. Especially, it maintains 160.6 mAh g⁻¹ after 400 cycles at a high cut-off voltage of 4.5 V at 1C with a retention of 80.3 %. In addition, Mg₃B₂O₆ is a non-toxic and non-polluting material. The simple coating process with low-cost raw materials as well as mild operating conditions endow this technology with potential practical application value.
Activated treatment of magnesite for preparing size-controlled Mg<inf>2</inf>B<inf>2</inf>O<inf>5</inf> whiskers and their microwave dielectric properties
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Synthesis of magnesium borate nanorods

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusion

Acknowledgements

J. Chem. Phys. Lett.

J. Cryst. Growth

Chem. Phys. Lett.

Mater. Lett.

Nucl. Instrum. Methods Phys. Res., Sect. A, Accel. Spectrom. Detect. Assoc. Equip.

Appl. Phys. Lett.

Nature

Science