A convenient solid-state reaction route to nanocrystalline TiB2

Shi, Liang; Gu, Yunle; Chen, Luyang; Yang, Zeheng; Ma, Jing; Qian, Yitai

doi:10.1016/j.inoche.2003.11.005

Cited by 20 publications

(12 citation statements)

References 9 publications

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“…The powder obtained at 700°C (Figure A) consisted of rounded micron‐sized particles highly agglomerated, the nanostructure of a TiB 2 cluster shown in the inset of Figure A has an average crystal size around 20 nm. This powder has a specific surface area of 33 m 2 /g, (Table ) similar to that reported by Shi, 25.93 m 2 /g …”

Section: Resultssupporting

confidence: 79%

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Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride

et al. 2018

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The synthesis of early transition nanocrystals using NaBH 4 and the respective metal oxides at atmospheric pressure was studied at temperatures between 400 and 1000°C. Reaction products were analyzed by x-ray diffraction, the crystallite size was determined after Rietveld refinement of diffraction patterns, while the morphology was analyzed by scanning and transmission electron microscopy. For all the investigated systems the lowest temperature to complete the synthesis was 700°C and the reaction occurred in three subsequent steps: (i) decomposition of NaBH 4 , (ii) formation of crystalline ternary species Na-M-O and Na-B-O, (iii) conversion of intermediary species to MB 2 and NaBO 2 . Syntheses carried out at T > 700°C only caused coarsening of the powders. The synthetized boride powders had the morphology of highly agglomerated nanocrystals.

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Section: Resultssupporting

confidence: 79%

“…The powder obtained at 700°C ( Figure 5A) powder has a specific surface area of 33 m 2 /g, ( Table 1) similar to that reported by Shi, 25.93 m 2 /g. 39…”

Section: Tibmentioning

confidence: 99%

Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride

et al. 2018

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“…Of the various methods to synthesize TiB 2 , carbothermic/borothermic reduction and self‐propagating high‐temperature synthesis (SHS) are the most prevalent. Recent works by others 3–7 have investigated cold milling, rapid carbothermal reduction, and single‐step boronation as low‐energy alternatives. Commercially, carbothermic and borothermic reduction is used to reduce rutile TiO 2 to produce TiB 2 .…”

Section: Introductionmentioning

confidence: 99%

Acid Leaching of SHS Produced Magnesium Oxide/Titanium Diboride

Lok

Logan

Payyapilly

2009

Journal of the American Ceramic Society

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The stoichiometric self-propagating high-temperature synthesis (SHS) thermite reaction involving magnesium (Mg), titanium dioxide (TiO 2 ), and boron oxide (B 2 O 3 ) forms MgO and titanium diboride (TiB 2 ) as final products. Selective acid leaching is used to remove the MgO leaving TiB 2 powder. This study investigates the acid leaching of SHS-produced MgO/TiB 2 powders and a stoichiometric mixture of commercially obtained MgO and TiB 2 powders. Leaching was conducted at pH levels of 4.0, 2.5, and 1.0 by the introduction of concentrated aliquots of HNO 3 . This method maintains a minimum pH target throughout the leaching process, thereby sustaining a dynamic concentration to remove the oxide. The optimal leaching conditions were determined to be at 901C at a minimum pH target of 2.5 for the SHS-produced product. At these conditions, conversion percentages of 83%-84% of MgO were measured with only trace amounts of TiB 2 measured in the solution (o100 lg/L). Conversion percentages for each leaching condition and dissolution mass of solid MgO and TiB 2 at each pH are also reported. Results from powder X-ray diffraction confirm the removal of MgO and minimal dissolution of TiB 2 , and indicate the formation of unidentified compounds. Inductively coupled plasma mass spectrometry (ICP) was used to analyze the ionic composition and extent of leaching. Scanning electron microscopy was used to observe the particle morphology of the leached powders.

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“…To date, only a few nanostructured borides have been reported. This paucity arises mainly because M-B systems are typically synthesized at high temperatures above 1100 8C.[6] Nanoscale materials have been obtained at lower temperatures (25-100 8C), but at the expense of crystallinity and stability, and such approaches yield pyrophoric compounds without applicability.[7] The scarce reported procedures for nanostructured crystalline systems rely on physical [5,8] or chemical methods, [9] and none of them is demonstrated to be generally applicable to the wide and rich family of borides. Moreover, the majority of crystalline metal borides has not yet been approached at the nanoscale, such as hard (HfB 2 ) or ultrahard (MoB 4 ) materials, catalysts, and ferromagnetic compounds (FeB).…”

mentioning

confidence: 99%

A General Solution Route toward Metal Boride Nanocrystals

et al. 2011

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Metal-boron alloys contain a boron covalent framework providing typical high chemical, mechanical, and thermal stability, which allows important applications, for example, for diborides (NbB 2 ) and hexaborides (CaB 6 ) as refractory materials.[1] New properties also arise from alloying; a prime example is the superconductivity of magnesium diboride, which exhibits the highest critical temperature (39 K) among classical superconductors.[2] Hexaborides are also relevant because of their field emission properties [3] and their potential for thermoelectricity (CeB 6 ).[4] Moreover, transition-metal borides are drawing attention as efficient (de)hydrogenation catalysts that can accelerate, for instance, emission of hydrogen from ammonia-borane or borohydrides within energyharnessing devices based on hydrogen technology.[5] Applications in hyperthermia, information storage, thermoelectricity, and catalysis would benefit from scaling down to the nanometer range, which could bring, as for all nanomaterials, modified, enhanced, and even novel properties that arise from the finite particle size. To date, only a few nanostructured borides have been reported. This paucity arises mainly because M-B systems are typically synthesized at high temperatures above 1100 8C.[6] Nanoscale materials have been obtained at lower temperatures (25-100 8C), but at the expense of crystallinity and stability, and such approaches yield pyrophoric compounds without applicability.[7] The scarce reported procedures for nanostructured crystalline systems rely on physical [5,8] or chemical methods, [9] and none of them is demonstrated to be generally applicable to the wide and rich family of borides. Moreover, the majority of crystalline metal borides has not yet been approached at the nanoscale, such as hard (HfB 2 ) or ultrahard (MoB 4 ) materials, catalysts, and ferromagnetic compounds (FeB). The development of a reliable, versatile, and general synthesis procedure towards such systems is therefore still eagerly demanded.One requirement to obtain such nanostructures is the use of relatively mild temperatures, which are still high enough to trigger crystallization but low enough to avoid excessive grain growth, ideally in the range 500-900 8C. Then, development of a solution route instead of standard solid-state reactions may contribute to full kinetic accessibility of the reaction space, which includes control of nanocrystal size and shape. [10] Because of the thermal instability of organic solvents in such conditions, we turned to inorganic molten salts, which are readily available and safe to apply at the targeted temperatures.Herein we present the use of such salt melts for the first general synthesis of metal boride nanocrystals. The method is based on a one-pot ionothermal process which is simple and relies on medium temperature, atmospheric pressure, and environmentally friendly solvents. Applicability to a wide range of compounds, formation of novel nanostructures, and control over the nanocrystal size and the material texture are demons...

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A convenient solid-state reaction route to nanocrystalline TiB2

Cited by 20 publications

References 9 publications

Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride

Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride

Acid Leaching of SHS Produced Magnesium Oxide/Titanium Diboride

A General Solution Route toward Metal Boride Nanocrystals

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