This comprehensive study delves into the intricate process of exfoliating and functionalizing boron nitride nanosheets (BNNSs) extracted from hexagonal boron nitride (h-BN), and meticulously explores their potential application within epoxy composites. The extensive research methodology encompasses a sequence of treatments involving hydrothermal and sonication processes aimed at augmenting the dispersion of BNNSs in solvents. Leveraging advanced analytical techniques such as Raman spectroscopy, X-ray diffraction, and FTIR spectroscopy, the study rigorously analyzes a spectrum of changes in the BNNS’s properties, including layer count variations, interlayer interactions, crystal structure modifications, and the introduction of functional groups. The research also rigorously evaluates the impact of integrating BNNSs, specifically glycidyl methacrylate (GMA)-functionalized BNNSs, on the thermal conductivity of epoxy composites. The conclusive findings exhibit notable enhancements in thermal properties, predominantly attributed to the enhanced dispersion of fillers and enhanced interactions within the epoxy matrix. This pioneering work illuminates the wide potential of functionalized BNNSs for significantly enhancing the thermal conductivity of epoxy composites, paving the way for advanced materials engineering and practical applications.

Water electrolysis is a representative technology for tritium enrichment in water. Proton exchange membrane (PEM) water electrolysis has received great attention to replace traditional alkaline water electrolysis which generates concentrated tritiated water containing a large amount of salts. Nafion has been widely used as a polymeric electrolyte for the PEM electrolyzer. However, its low gas barrier property causes explosion, corrosion or degradation of electrolyzer. Furthermore, the traditional polymeric electrolytes have negligible differences in conductivity between hydrogen isotopes. To enhance the tritium separation by water electrolysis, we designed a composite membrane (Nafion/ hexagonal boron nitride (hBN)). The monolayer hBN has a high proton conductivity and gas barrier property, and the hBN can enhance conductivity differences between hydrogen isotopes. We prepared Nafion/hBN composite membranes, and water electrolysis performances and proton/deuterium separation behaviors were investigated.

The mechanical properties and microstructures of hexagonal boron nitride (h-BN)-reinforced cement composites are experimentally studied for three and seven curing days. Various sizes (5, 10, and 18 μm) and concentrations (0.1%, 0.25%, 0.5%, and 1.0%) of h-BN are dispersed by the tip ultrasonication method in water and incorporated into the cement composite. The compressive strength of the h-BN reinforced cements increases by 40.9%, when 0.5 wt% of 18 μm-sized h-BN is added. However, the compressive strength decreases when the 1.0 wt% cement composite is added, owing to the aggregation of the h-BNs in the cement composite. The microstructural characterization of the h-BN-reinforced cement composite indicates that the h-BNs act as bridges connecting the cracks, resulting in improved mechanical properties for the reinforced cement composite.

Hybrid graphene/h-BN model is studied via molecular dynamics simulation to observe the evolution of graphene layer upon heating. Model containing 20,064 atoms is heated up from 50 to 8000 K via Tersoff and Lennard–Jones potentials. Various thermodynamic quantities, structural characteristics, and the occurrence of liquid-like atoms are studied. The Lindemann criterion for 2D case is calculated and used to observe the appearance of liquid-like atoms. The atomic mechanism of structural evolution upon heating is analyzed on the basis of the occurrence/growth of liquid-like atoms, the formation of clusters, the coordination number, and the ring statistics. The liquid-like atoms tend to form clusters and the largest cluster increases slightly in order to form a single largest cluster of liquid-like atoms. The other models such as free-standing graphene, zigzag GNR, and armchair GNR are also presented to have an entire picture about the evolution of graphene upon heating in different models. Note that the largest clusters of free-standing graphene as well as zigzag GNR, and armchair GNR tend to decrease to form a ring-like 2D liquid carbon.

Boron nitride nanotubes (BNNTs) are receiving great attention because of their unusual material properties, such as high thermal conductivity, mechanical strength, and electrical resistance. However, high-throughput and highefficiency synthesis of BNNTs has been hindered due to the high boiling point of boron (~ 4000℃) and weak interaction between boron and nitrogen. Although, hydrogen-catalyzed plasma synthesis has shown potential for scalable synthesis of BNNTs, the direct use of H2 gas as a precursor material is not strongly recommended, as it is extremely flammable. In the present study, BNNTs have been synthesized using radio-frequency inductively coupled thermal plasma (RF-ITP) catalyzed by solid-state ammonium chloride (NH4Cl), a safe catalyst materials for BNNT synthesis. Similar to BNNTs synthesized from h-BN (hexagonal boron nitride) + H2, successful fabrication of BNNTs synthesized from h-BN+NH4Cl is confirmed by their sheet-like properties, FE-SEM images, and XRD analysis. In addition, improved dispersion properties in aqueous solution are found in BNNTs synthesized from h-BN +NH4Cl.

Much attention has been paid to thermally conductive materials for efficient heat dissipation of electronic devices to maintain their functionality and to support lifetime span. Hexagonal boron nitride (h-BN), which has a high thermal conductivity, is one of the most suitable materials for thermally conductive composites. In this study, we synthesize h-BN nanocrystals by pyrolysis of cost-effective precursors, boric acid, and melamine. Through pyrolysis at 900oC and subsequent annealing at 1500oC, h-BN nanoparticles with diameters of ~80 nm are synthesized. We demonstrate that the addition of small amounts of Eu-containing salts during the preparation of melamine borate precursors significantly enhanced the crystallinity of h-BN. In particular, addition of Eu assists the growth of h-BN nanoplatelets with diameters up to ~200 nm. Polymer composites containing both spherical Al2O3 (70 vol%) and Eu-doped h-BN nanoparticles (4 vol%) show an enhanced thermal conductivity (λ ~ 1.72W/mK), which is larger than the thermal conductivity of polymer composites containing spherical Al2O3 (70 vol%) as the sole fillers (λ ~ 1.48W/mK).

The development of machining technology has coincided with the recent development of a diverse amount of materials and tools. The developed materials largely consist of hardened steel for vehicle and the mechanical industry. The machining of the hardened steel is performed in a lathe and many kind of machining centers, but it is difficult to machine because its hardness is the most difficult-to-cut materials. Hard-turning is a kind of machining process which omits the final grinding process and replaces it with a single accurate cutting process. In this paper, the turning of SKD 11(HRC 58) was performed using the CBN tool in order to recognize the optimum process conditions. The cutting force, tool life and wear, surface roughness were measured. Examining the machining characteristics when cutting of high hardened steel, low cutting speed and high conveying speed were identified to be effective in cutting conditions of SKD 11. Tool life was most effective in the conditions with 65m/min of cutting speed and 0.193mm/rev of feedrate and approximately 0.5um of very good surface profile was acquired at 0.079mm/rev of feedrate. Therefore, when cutting with Low CBN tool, it could be considered to be sufficient in reducing the steps of precision machining or replacing the polishing

C/SiC composites were prepared by boron nitride (BN)-assisted liquid silicon infiltration (LSI), and their anti-oxidation and mechanical properties were investigated. The microstructures, bulk densities, and porosities of the C/SiC composites demonstrated that the infiltration of liquid silicon into the composites improved them, because the layered-structure BN worked as a lubricant. Increasing the amount of BN improved the anti-oxidation of the prepared C/SiC composites. This synergistic effect was induced by the assistance of BN in the LSI. More thermally stable SiC was formed in the composite, and fewer pores were formed in the composite, which reduced inward oxygen diffusion. The mechanical strength of the composite increased up to the addition of 3% BN and decreased thereafter due to increased brittleness from the presence of more SiC in the composite. Based on the anti-oxidation and mechanical properties of the prepared composites, we concluded that improved anti-oxidation of C/SiC composites can be achieved through BN-assisted LSI, although there may be some degradation of the mechanical properties. The desired anti-oxidation and mechanical properties of the composite can be achieved by optimizing the BN-assisted LSI conditions.

The microstructure and mechanical properties of nanocomposites synthesized by chemical processing were investigated. The nanocomposites containing 15 vol% hexagonal BN (h-BN) were fabricated by hot-pressing powders covered with turbostratic BN (t-BN). The t-BN coating on particles was prepared by heating particles covered with a mixture of boric acid and urea in hydrogen gas. TEM observations of this nanocomposite revealed that nano-sized h-BN particles were homogeneously dispersed within grains as well as at grain boundaries. The strength and thermal shock resistance were significantly improved in comparison with the microcomposites.