Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields.

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Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications.

Heterocyclic pyrrole molecules are in situ aligned and polymerized in the -absence of an oxidant between layers of the 2D Ti3C2Tx (MXene), resulting in high volumetric and gravimetric capacitances with capacitance retention of 92% after 25,000 cycles at a 100 mV s(-1) scan rate.

Pseudocapacitive Electrodes Produced By Oxidant-Free Polymerization of Pyrrole Between the Layers of 2D Titanium Carbide (MXene)

Graphene-analogous low-dimensional materials

We report on the synthesis of high-quality microporous/mesoporous BN material via a facile two-step approach. An extremely high surface area of 1687?m2?g?1 and a large pore volume of 0.99?cm3?g?1 have been observed in the synthesized BN porous whiskers. The formation of the porous structure was attributed to the group elimination of organic species in a BN precursor, melamine diborate molecular crystal. This elimination method maintained the ordered pore structure and numerous structural defects. The features including high surface area, pore volume and structural defects make the BN whiskers highly suitable for hydrogen storage and wastewater treatment applications. We demonstrate excellent hydrogen uptake capacity of the BN whiskers with high weight adsorption up to 5.6% at room temperature and at the relatively low pressure of 3?MPa. Furthermore, the BN whiskers also exhibit excellent adsorption capacity of methyl orange and copper ions, with the maximum removal capacity of 298.3 and 373?mg?g?1 at 298?K, respectively.

https://iopscience.iop.org/article/10.1088/0957-4484/24/15/155603/pdf

Porous boron nitride with a high surface area: hydrogen storage and water treatment

Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m2/g, a large pore volume of 1.66 cm3/g and a special multimodal microporous/mesoporous structure located at ∼ 1.3, ∼ 2.7, and ∼ 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr3+, Co2+, Ni2+, Ce3+, Pb2+) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation.

/pdf/activated-boron-nitride-as-an-effective-adsorbent-for-metal-3h6csmffb8.pdf

Activated boron nitride as an effective adsorbent for metal ions and organic pollutants

Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m 2 /g, a large pore volume of 1.66 cm 3 /g and a special multimodal microporous/mesoporous structure located at , 1.3, , 2.7, and , 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr 31 ,C o 21 , Ni 21 ,C e 31 ,P b 21 ) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation.

Activated boron nitride as an effective adsorbent for metal ions and organic

We searched for two-dimensional metastable boron sheets by using the particle swarm optimization algorithm combined with first-principles methods. We present several possible boron sheets composed of triangular and hexagonal motifs. The calculated total energy shows that these boron sheets are less stable than α-sheet and two recently predicted 1/8 and 2/15 B-layers. The energy difference between the new proposed struc-1/8 boron sheet and the known α-sheet, 1/8 and 2/15 B-layers, is less than 0.01 eV/atom. The calculated total density states of these boron sheets show that they are metallic. The multicenter chemical bonds of the relatively stable boron sheets are analyzed using the electron localization function. Because two-dimensional sheets are the building blocks of corresponding nanotubes and fullerenes, the proposed metastable boron sheets, not only with the most stable boron sheets, are expected to advance further investigations and understandings on boron nanotubes and fullerenes.

Prediction of Two-Dimensional Boron Sheets by Particle Swarm Optimization Algorithm

Adsorption represents an efficient and economical approach for water purification and substantial research is being performed to develop effective sorbent materials. Porous boron nitride (BN) composed of light elements is considered as a promising candidate for pollution treatment due to its unique polarity of B–N bonds, high specific surface area, numerous structural defects, chemical stability, and oxidation resistance. However, the adsorption performance based on porous BN is hindered by either few activated sites or a low degree of crystallinity. In this work, we have developed a simple chemical method to activate pre-obtained well-crystallized porous BN fibers in acid solution. The successful chemical activation has been identified by FTIR spectra and zeta potential measurements. Benefiting from these advantageous features, the activated BN fibers with high stability exhibited enhanced cationic dye removal performance compared to the un-activated ones. The effects of pH value, contact time, temperature and adsorbent amount on the methylene blue (MB) adsorption properties were analyzed. The adsorption equilibrium data were interpreted in terms of Langmuir and Freundlich models and the results showed that Langmuir isotherms best represent the adsorption system. The maximum adsorbed amount for MB was as high as 392.2 mg g−1 at pH 8.0 and 30 °C. The adsorption rate was sharply enhanced after chemical activation. The excellent reusability of the activated BN was also confirmed. It is shown that chemical activation plays a key role in enhanced dye adsorption performance. Therefore, our developed chemical activation method for porous BN fibers opens the door toward the practical application of activated BN for drinking water purification.

Xuewen Xu

Papers

Porous boron nitride with a high surface area: hydrogen storage and water treatment

Activated boron nitride as an effective adsorbent for metal ions and organic pollutants

Activated boron nitride as an effective adsorbent for metal ions and organic

Prediction of Two-Dimensional Boron Sheets by Particle Swarm Optimization Algorithm

Chemical activation of boron nitride fibers for improved cationic dye removal performance