. (2015). Edge-hydroxylated boron nitride nanosheets as an effective additive to improve the thermal response of hydrogels. Advanced Materials, 27 (44), 7196-7203.

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Hexagonal boron nitride nanosheets (h-BNNS) have been proposed as an ideal substrate for graphene-based electronic devices, but the synthesis of large and homogeneous h-BNNS is still challenging. In this contribution, we report a facile synthesis of few-layer h-BNNS on melted copper via an atmospheric pressure chemical vapor deposition process. Comparative studies confirm the advantage of using melted copper over solid copper as a catalyst substrate. The former leads to the formation of single crystalline h-BNNS that is several microns in size and mostly in mono- and bi-layer forms, in contrast to the polycrystalline and mixed multiple layers (1–10) yielded by the latter. This difference is likely to be due to the significantly reduced and uniformly distributed nucleation sites on the smooth melted surface, in contrast to the large amounts of unevenly distributed nucleation sites that are associated with grain boundaries and other defects on the solid surface. This synthesis is expected to contribute to the development of large-scale manufacturing of h-BNNS/graphene-based electronics.

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Coatings are routinely applied to protect metallic surfaces, and polymer coatings have been conventionally used where the thickness is not a dramatic issue.[1] For the next generation of nanoelectronics, nanoscale coatings are needed to accommo-date the compact design. 2D materials that can be fabricated into atomically thin film as a coating over the substrate can be a great choice. Graphene has recently been considered for this purpose, since it is robust and flexible, and the hexagonal hon-eycomb structure can effectively block any species, including helium.[2] Mixed results, however, have been reported. [3][4][5][6][7] Good short-term anticorrosion performance was observed, [3][4][5] but over time, accelerated Cu oxidation and corrosion in air were found in the presence of graphene compared to the bare Cu substrate. [8,9] This acceleration is likely due to the high con-ductivity that assists electron transfer in the two-component galvanic cell between Cu and graphene, facilitating oxygen reduction and Cu oxidation around the defects in the long run. Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsKhan, M. Haque., Jamali, S. S., Lyalin, A., Molino, P. J., Jiang, L., Liu, H. Kun., Taketsugu Coatings are routinely applied to protect metallic surfaces, and polymer coatings have been conventionally used where the thickness is not a dramatic issue. [1] For the next generation of nano-electronics, nanoscale coatings are needed to accommodate the compact design. Twodimensional (2D) materials that can be fabricated into atomically thin film as a coating over the substrate can be a great choice. Graphene has recently been considered for this purpose, Submitted to 2 since it is robust and flexible, and the hexagonal honeycomb structure can effectively block any species, including helium. [2] Mixed results, however, have been reported. [3][4][5][6][7] Good shortterm anti-corrosion performance was observed, [3][4][5] but over time, accelerated Cu oxidation and corrosion in air were found in the presence of graphene compared to the bare Cu substrate. [8,9] This acceleration is likely due to the high conductivity that assists electron transfer in the two-component galvanic cell between Cu and graphene, facilitating oxygen reduction and Cu oxidation around the defects in the long run.Hexagonal boron nitride could, therefore, be considered for protection due to its insulating nature, [10][11][12][13] impermeability to small molecules (pore diameter 1.2 Å in the hexagon [14] ), robustness [15] , and transparency. [16] Moreover, it has excellent chemical stability in most aquatic environments. [17,18] Hexagonal boron nitride film (BNNF) (7−8 nm thick, ~20 layers) has been reported to slow down the corrosion of an underlying Cu substrate in a very dilute NaCl solution (0.1 M) for a few minutes. [19] BNNF (5 nm, i.e. ~15 layers, grown on Ni and then transferred to Cu) also improved the oxidation resistance of Cu substrate at 500 °C for 30 minutes. [20] As was learned from the case of graphe...

In this study, hexagonal boron nitride nanosheets (h-BNNS) have been grown on polycrystalline silver substrates via chemical vapor deposition (CVD) using ammonia borane as a precursor. The h-BNNS are of few-atomic-layer thickness and form continuous coverage over the whole Ag substrate. The atomically thin coating poses negligible interference to the reflectivity in the UVvisible range. The nanosheet coating also proves very effective in protecting Ag foil chemically. In contrast to bare Ag foil, the coated one displayed only minor decolorization under high 3 concentration of H2S. The study indicates that h-BNNS can be a promising protective coating for Ag based items such as jewelry or mirrors used in astronomical telescopes.

The quality of hexagonal boron nitride nanosheets (h-BNNS) is often associated with the most visible aspects such as lateral size and thickness. Less obvious factors such as sheet stacking order could also have a dramatic impact on the properties of BNNS and therefore its applications. The stacking order can be affected by contamination, cracks, and growth temperatures. In view of the significance of chemical-vapour-decomposition (CVD) assisted growth of BNNS, this paper reports on strategies to grow carbon- and crack-free BNNS by CVD and describes the stacking order of the resultant BNNS. Pretreatment of the most commonly used precursor, ammonia borane, is necessary to remove carbon contamination caused by residual hydrocarbons. Flattening the Cu and W substrates prior to growth and slow cooling around the Cu melting point effectively facilitate the uniform growth of h-BNNS, as a result of a minimal temperature gradient across the Cu substrate. Confining the growth inside alumina boats effectively minimizes etching of the nanosheet by silica nanoparticles originating from the commonly used quartz reactor tube. h-BNNS grown on solid Cu surfaces using this method adopt AB, ABA, AC', and AC'B stacking orders, which are known to have higher energies than the most stable AA' configuration. These findings identify a pathway for the fabrication of high-quality h-BNNS via CVD and should spur studies on stacking order-dependent properties of h-BNNS.

Effects of rice husk ash and fly ash on properties of red clay collected from Naogaon district of Bangladesh were investigated. Different percentages of rice husk ash (RHA) and fly ash (5%, 10% and 15%) were thoroughly mixed with clay to analyse various physical and chemical properties of clay followed by heat treatment of 800 0 C to 1100 0 C. The samples were tested for compressive strength, linear shrinkage, water absorption, porosity and bulk density. XRD analysis indicates the clay sample was mainly illite type. Water absorption and porosity increased with increasing percentage of ashes. The percentage of water absorption was within 6 to 10% for different mixture which may be suitable for ceramic and tiles purposes. Both fly ash and RHA of 15% could be used to improve some properties of clay. The optimum firing temperature for all the samples was 1050 0 C. XRD pattern of clay with fly ash and rice husk ash heated at 1050 0 C confirms the presence of feldspar and quartz as major phase and hematite (Fe 2 O 3 ) and cristobalite phase as minor phase. This red clay deposits reinforced with different appropriate quantities of rice husk ash and fly ash could be used for various low temperature applications in industry and construction purposes.