Low‐Temperature Synthesis of Hafnium Diboride Powder Via Magnesiothermic Reduction in Molten Salt

Bao, Ke; Massey, J.; Huang, Juntong; Zhang, Shaowei

doi:10.1002/9781119474746.ch12

Cited by 2 publications

(7 citation statements)

References 36 publications

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“…At the test temperatures, the NaCl (melting point~714 • C) melted, forming a homogeneous molten salt medium in which the Al (melting point 660.3 • C) melted, forming corresponding droplets. Although the exact solubility data of the Al, Mo and B in the NaCl molten salt are not available, based on the previous studies on the molten salt synthesis of Mo 2 C [17], borides [18][19][20] and TiB 2 -Al 2 O 3 [21], it can be considered that the solubility values should be in the following order: Mo> Al> B. At a relatively low firing temperature (850 • C), Mo was partially dissolved in the liquid salt, diffused quickly through it onto the Al droplets (or met with dissolved Al) and B particles and then reacted to form intermediate phases Al 8…”

Section: Discussionmentioning

confidence: 99%

Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

et al. 2020

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MoAlB fine powders were prepared in molten NaCl from Al, B and Mo powders. The effects of key parameters affecting the synthesis process and phase morphology were examined and the underpinning mechanisms proposed. MoAlB product particles exhibited different shapes/sizes, as follows: spherical grains (1~3 µm), plate-like particles (<5 µm in diameter) and columnar crystals with lengths up to 20 µm and diameters up to 5 µm, resultant from different reaction processes. Phase pure MoAlB was synthesised under the following optimal conditions: use of 140% excess Al and 6 h of firing at 1000 • C. This temperature was at least 100 • C lower than required by other methods/techniques previously reported. At the synthesis condition, Mo first reacted with Al and B, forming Al 8 Mo 3 and MoB, respectively, which further reacted with excess Al to form Al-rich Al-Mo phases and MoAlB. The Al-rich Al-Mo phases further reacted with the residual B, forming additional MoAlB. The molten NaCl played an important role in accelerating the overall synthesis process.

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Section: Discussionmentioning

confidence: 99%

Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

et al. 2020

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“…As well documented in the literature [47][48][49][50][51][52][53][54][55][56][57][58][59] depending on solubility values of the two reactants in molten salt under synthesis conditions, MSS could be dominated by different mechanisms. A 'template-growth' mechanism is dominant when one of the reactants has a much higher solubility than the other, whereas a 'dissolution and precipitation' mechanism is dominant when both reactants have relatively high solubility.…”

Section: Mechanismsmentioning

confidence: 99%

“…Such a technique is commonly used to synthesise a variety of oxides and non-oxides (borides, carbides, nitrides, alloys, etc.). [47][48][49][50][51][52][53][54][55][56][57][58][59] Figure 3 illustrates schematically the main steps involved in a typical MSS process, 51 including, combining raw materials and salt(s) in appropriate ratios, firing the powder mix in a reaction vessel (e.g. a crucible) to a target temperature above the melting/eutectic point of the salt(s) and holding at the temperature for a requisite time period, water-leaching repeatedly any residual salt(s) in the reacted mass after cooling to room temperature, and collecting and drying the final product.…”

Section: Principle and Advantagesmentioning

confidence: 99%

“…Benefiting from all of these, the overall production process is more economical than a conventional synthesis one. [47][48][49][50][51][52][53][54][55][56][57][58][59]…”

Section: Principle and Advantagesmentioning

confidence: 99%

“…MgO) may react with some of the unreacted B 2 O 3 , forming intermediate phases (e.g. magnesium borates), and the metal oxide precursor also may be partially reduced to some oxygen-deficient oxides, for example, Ti 2 O 3 and VO 2 in the cases of using TiO 2 and V 2 O 5 , respectively, [54][55][56][57][58]124,125 which, if remained, would be difficult to remove via water and acid leaching, affecting the final product purity. Fortunately, this could be avoided by optimising processing parameters/conditions, for example by using extra Mg, to reduce them further to elemental B and metal, and to make the reaction complete.…”

Section: Conventional and Molten Salt Mediated Metallothermic Reducti...mentioning

confidence: 99%

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Low temperature controllable synthesis of transition metal and rare earth borides mediated by molten salt

Liu,

Jia,

Zhang

et al. 2024

International Materials Reviews

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Transition meal and rare earth borides have been subjected to extensive investigations because of their unique structures, superior properties and diverse applications. Conventional methods for their syntheses suffer from various drawbacks. So several alternative approaches have been explored. Among them, the so-called ‘molten salt synthesis (MSS)’ technique has proved promising. Over the past 10–15 years, it has been used to prepare a range of transition metal and rare earth borides. In this paper, the main results from these studies are reviewed. Initially, the relevant background on metal borides and their conventional synthesis methods are introduced, followed by the main principles/mechanisms of MSS. The following three sections provide an overview of the main work on MSS of binary and ternary borides, boride solid solutions, and boride-based composite powders. Then, two newly modified MSS approaches are presented. Finally, the main issues covered in this paper are summarised, and future prospects considered.

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Low‐Temperature Synthesis of Hafnium Diboride Powder Via Magnesiothermic Reduction in Molten Salt

Cited by 2 publications

References 36 publications

Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

Low temperature controllable synthesis of transition metal and rare earth borides mediated by molten salt

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