Search

Herein, Pebax functionalized h-BNNSs (P-BNNSs) fabricated by a mechanical exfoliation and in-situ modification process are employed to improve the thermal conductivity and antiwear performance of epoxy resin (EP). Pebax can effectively improve the dispersibility of P-BNNSs, achieving hierarchical assembly of P-BNNSs in EP matrix during EP curing process to form a multinetwork structure only at a low P-BNNS filling contents (≤6 wt%). This multinetwork structure can act as excellent heat conductive pathways to realize simultaneously vertical and horizontal heat diffusion, obtaining quasi-isotropical thermal conductive P-BNNS/EP composites. Fascinatingly, a through-plane thermal conductivity of 3.9 W/(m·K) and an in-plane thermal conductivity of 2.9 W/(m·K) are obtained. More importantly, this special structure can simultaneously improve the antiwear, mechanical and electrically insulating performances of pure EP. The friction coefficients and wear rates of P-BNNS/EP composites (P-BNNS contents ≤ 6 wt%) are dramatically decreased to less than 0.2 and 1 × 10-5 mm3/(N·m), comparing with those of pure EP which are over 0.6 and 2 × 10-5 mm3/(N·m), respectively. The enhanced tensile stress of over 110 MPa and electric volume resistivity of over 1.50 × 1013 Ω·cm are also observed for P-BNNS/EP composite films. These improved properties make the P-BNNS/EP composites very promising as packaging or heat dissipation materials in the high density integration systems and high frequency printed circuit boards.

There is an increasing demand for boron nitride nanosheets (BNNSs) for a range of applications such as advanced composite materials, ion/gas selective membranes, and energy storage. These applications require stable, high-concentration BNNS dispersions as a precursor, which is a challenge because BNNSs do not disperse easily. We report a simple, yet efficient, mechanochemical exfoliation technique to prepare functionalized BNNSs with excellent dispersibility in water and organic solvents. The resultant amino-modified BNNSs (BNNS-NH2) are stable in ethanol for 3 months at an unprecedented high concentration of 46 ± 2 mg/mL. We provide insights into the dispersibility mechanism for amino- and hydroxyl-functionalized BNNSs. High-concentration BNNS dispersions enable a facile painting method that can coat a uniform, insulating, and antioxidant BNNS layer on arbitrary surfaces. In addition, different functional groups enhance the selectivity of different ions of the functionalized BNNS membranes for water purification and other ion separation applications. These stable, high-concentration BNNS dispersions make many exciting applications possible.

The rapid development of electronic technology generates a great deal of electromagnetic wave (EMW) that is tremendously hazardous to environment and human health. Correspondingly, the high efficient EMW absorption materials with lightweight, high capacity and broad bandwidth are highly required. Herein, a series of three-dimensional (3D) network-like structure formed by silicon coated carbon nanotubes (NW-CNT@SiO2) are massively prepared through an improved sol–gel process. The as-obtained 3D NW-CNT@SiO2 exhibit low densities of about 1.6 ± 0.2 g/cm3. The formation of this special 3D structure can provide high dielectric loss and good impedance matching for EMW absorption. As expected, a minimum reflection loss (RL) of −54.076 dB is obtained when uses the sample prepared by 0.1 g of CNTs and 0.2 mL of tetraethoxysilane as absorbent with a low loading rate of 10 wt% and thin absorber thickness of 1.08 mm. This specific minimum RL value exceeds many other CNT based EMW absorbers reported in previous literature. These findings featured with a green and scalable preparation process provides a facile strategy to design and fabricate high-performance EMW absorption materials, which can be applied to other materials such as carbon fibers and graphene.

The development of novel structure, fabrication methods, formation mechanisms, and versatile applicability of boron nitride (BN) nanomaterials is still one of the research hotspots. In this report, we developed a novel two dimensional cubic boron nitride nanosheets (2D c-BNNSs) based on the first principles calculations. This structure is converted from hexagonal BN (h-BN) bilayers induced by hydroxyl (OH) radical and fluoride (F) atom codoping. The geometrical, electronic, and optical properties of the novel 2D OH radical and F atom codoped c-BNNSs (OH-F-c-BNNSs) have been systematically investigated. The results reveal that the unpaired electrons appear due to the electronegativity difference between OH radical and F atoms, resulting in the excellent electrical and magnetic properties of OH-F-c-BNNSs. In addition, OH-F-c-BNNSs also exhibit a strong response to the visible light with an absorption range covering the whole visible light region. More importantly, when the doping positions of OH radical and F atom are exchanged (F-OH-c-BNNSs), the F-OH-c-BNNS will have only electrical conductivity, which will make us to regulate the intrinsic properties of c-BNNSs for different applications only by adjusting the element doping positions. This work can provide a theoretical and experimental basis/support for designing and fabricating new types of 2D c-BN nanomaterials for different applications.

Hildewintera-colademononis-like hexagonal boron nitride carbon nanotubes (BN@CNT) composites can be fabricated via two steps: a composite structure predesign in a solvent and a subsequent thermal treatment process at high temperature. The as-obtained hildewintera-colademononis-like BN@CNT composites contain porous h-BN microrods as stems and CNTs as spines. The densities and specific surface area of these BN@CNT composites can be tuned by adjusting the relative amounts of CNTs in the composites, which can reach 0.072 ± 0.0046 g/cm3 and 583.63 m2/g, respectively. These BN@CNT composites based absorbers show excellent microwave absorption (MA) properties which have effective frequency absorption width (≤-10 dB) from 2.8 to 18 GHz when the absorber thicknesses are in the range of 1.0–6.0 mm, and the minimum RL values can reach up to −48.45 dB for BN@CNTs-3 based absorber with an absorber thickness only of 1.4 mm. Moreover, the widest absorption bandwidth of 4.24 GHz (12.96–17.20 GHz) can be obtained for BN@CNTs-2 based absorber when the absorber thickness is 1.6 mm. Therefore, these hildewintera-colademononis-like BN@CNT composites are expected to be used as microwave absorption materials as they are lightweight and have broad absorption bands and strong absorption with thin thickness. This facile and controllable fabrication process offers a new strategy for designing and fabricating diverse h-BN/carbon based composites for different applications.

The superhydrophobicity of polyvinylidene fluoride (PVDF) membranes can be achieved by adding a small amount of hexagonal boron nitride nanosheets ( h-BNNSs) during the preparation process. The h-BNNSs can be fabricated by two steps of facile ultrasonication of commercial h-BN powders in water and subsequent centrifugation process. The introduction of a small amount of h-BNNSs into PVDF will result in structure and morphology changes of final PVDF membranes. The changes of the structure and morphology can significantly reduce the surface wettability of PVDF membranes, even generating superhydrophobicity. However, the superoleophilicity of PVDF membranes is well kept, which is not influenced by the introduction of h-BNNSs. The excellent superhydrophobicity and superoleophilicity make these porous h-BNNS/PVDF composites to be promising candidates for separating oil and water as membranes in practical oil-polluted waste water treatment.

The effect of specific cathode surface area (SCSA; 2, 4 and 8 m2/m3) on biogas production and biofouling control was investigated in anaerobic electrochemical membrane bioreactors (AnEMBRs). Nickel-based hollow fibers were used as both a cathode for hydrogen evolution and a membrane for the filtration of treated water. Varying the SCSA was found to influence the current density, biogas quantity and composition, and trans-membrane pressure (TMP). In situ gas generation was monitored using a high-speed camera; where the 8 m2/m3 AnEMBRs were found to mainly evolve smaller sized bubbles (45–114 µm) compared to the 2 and 4 m2/m3 AnEMBRs. This correlated with the lowest TMP (0.37 bars) compared to the other reactors (4 m2/m3, 0.76 bars; 2 m2/m3, 1.18 bars). The cathodic microbial community varied with SCSA, with Acetobacterium dominating at a relative abundance that reached 62% (4 m2/m3), while hydrogenotrophic methanogens (represented by Methanocorpusculum) comprised up to 2.5% of the total community. This community variability apparently influenced both the hydrogen (QH2) and methane (QCH4) production rates, reaching a maximum QH2 of 0.416 m3/m3/day (SCSA 8 m2/m3). Overall, this study discloses the cumulative effect of QH2, QCH4, bubble distribution and frequency on biofouling with SCSA variation in AnEMBRs, demonstrating that with higher SCSA the in situ gas scouring effect is more pronounced leading to a lower fouling propensity.

Herein, we demonstrate that hexagonal boron nitride nanosheets (h-BNNSs) can be used as water dispersible lubricant additive through simple fluoride modification. The fluorination of h-BNNSs (F-BNN...

Herein, large scale fabrication of porous boron nitride (BN) microrods has been achieved via a facile process, which involves the synthesis of melamine diborate precursors and subsequent thermal treatment process. The fabrication can be scaled up to ultra-large scale which is limited by the furnace. The characterization results show that the as-obtained products are porous BN microrods with diameters in the range of ten to tens of micrometers and length of a few millimeters, respectively. The specific surface area and porosity of these porous BN microrods are tunable by adjusting the synthesis processes of precursors. A highest specific surface area of 653.66 m2/g is obtained for the sample of BN-4, corresponding to the differential pore volume of 0.289 cm3/(g nm) and pore size of about 1.928 nm. Further measurement shows that the as-obtained porous BN microrods possess excellent copper ion adsorption property with a highest adsorption capacity of 365.4 mg/g. This adsorption capacity is superior to those of most copper ion adsorbents reported in recent literature. The high copper ion adsorption capacity combining with the unique properties of hexagonal BN makes them promising candidates for copper ions adsorption in practical wastewater treatment.

Herein, a scalable and controllable approach is proposed to exfoliate high quality hexagonal boron nitride nanosheets (h-BNNSs) from h-BN flakes, which relies on the efficient reduction of h-BNNS interlayer interaction by rapid volume expansion of water in icing. Water can enter into the h-BNNS interlayer through the “entry” caused by the hydroxyl induced local structure distortion as demonstrated by molecular dynamics simulations. The entered water could form fairly compact initial nuclei, and then ice and rapidly expand as temperature drops sharply, resulting in the interlayer space increase and interlayer force reduction between h-BNNSs and thus achieving efficient exfoliation of h-BNNSs in subsequent ultrasonication. The thicknesses of h-BNNSs are dominated by freezing and exfoliation cycles, and monolayer h-BNNSs can be obtained after five cycles of freezing and exfoliation currently. The as-obtained h-BNNSs have excellent dispersibility in water enabling their versatile applications as polymer additives, thermal conductive fillers, and flame-retardants, etc.

Currently, the application of polyimide (PI) based materials often demands mutual additional properties, such as high thermal conductivity, good flexibility, high thermal stability and low dielectric constant and loss, etc.. Herein, a well-aligned hierarchical “brick and plank” architecture by rational assembly of dopamine modified hexagonal boron nitride flakes and nanoparticles (PDA-BNF@BNNPs) which can effectively improve the thermal conductivity, thermal stability, electrical conductivity, dielectric properties and shape memory performance of pure PI. The alternating stacking of vertically arranged h-BNNPs and horizontally laid h-BNFs yield a quasi-isotropic thermal conductivity of PI films with a high through-plane thermal conductivity of 6.43 W/(mK) and an in-plane thermal conductivity of 11.85 W/(mK) because of the simultaneously vertical and horizontal phonon scattering enabled by the vertically arranged h-BNNPs and horizontally laid h-BNFs. Besides, this special structure also endues PI films high thermal stability of over 560 oC, prominent electrical resistance of over 1.40 × 10-13 Ω•cm, and low dielectric loss of less than 0.02 in the high frequency. Moreover, the PDA-BNF@BNNP/PI films exhibit excellent flexibility and shape memory performance with faster recovery response time reduced over 50 % comparing with that of pure PI film. These outstanding properties combining with the facile and scalable fabrication process make PDA-BNF@BNNP/PI films are very promising in diverse electronic device applications, especially in flexible electronic devices or circuits requiring additionally high thermal conductivity and low dielectric loss.

Three dimensional hexagonal boron nitride nanosheet decorated carbon nanotube composites (3D h-BNNS/CNTs) have been fabricated through a facile thermal treatment process. h-BNNSs randomly distribute among CNTs to form 3D network structure. The microwave absorption properties of these 3D h-BNNS/CNTs are obviously improved comparing with those of CNTs. And the minimum reflection loss (RL) can reach up to −36.5 dB when the absorber thickness is 2.5 mm for 3D h-BNNS/CNTs1 derived from the precursor with boric acid, urea and CNTs molar ratio of 2:4:1. Besides, the maximum absorption bandwidth (RL ≤ −10 dB) is as large as 4.0 GHz when the absorber thickness drops to 2.0 mm. More important, h-BNNS/CNTs1 has a low density of 112.6 ± 3.6 mg/cm3, which is beneficial for practical applications. The significant enhancement in MA performance of h-BNNS/CNTs is mainly attributed to the improvement of impedance matching, interfacial polarization and multiple scattering after introduction of h-BNNSs.

Novel SiC/SiO2 bead-string like core-shell nanochains have been fabricated via a thermal chemical vapor deposition process without using any catalysts and templates. These SiC/SiO2 bead-string like core-shell nanochains are made up of SiO2 spheres as beads and SiC/SiO2 core-shell nanowires as strings, respectively. A Vapor–Solid growth mechanism is proposed to explain the formation of these SiC/SiO2 hetero-nanostructures in the absence of catalysts on the basis of the characterization results, the possible reactions among the solid phases, intermediate gas phases and surface energy minimization. Moreover, these SiO2-SiC bead-string like nanochains exhibit good hydrophobicity with a water contact angle over 140°, which is caused by the special surface composition. This hydrophobicity makes these SiO2-SiC bead-string like nanochains promising candidates as surface protective or self-cleaning materials in harsh environments.

Herein, we report a facile process to massively synthesize three-dimensional (3D) boron and nitrogen co-doped carbon@Fe 2 O 3 /Fe 3 C/Fe nanoparticle decorated carbon nanotubes (B/N co-doped C@Fe 2 O 3 /Fe 3 C/Fe-CNTs). The fabrication involved a simple one-step chemical vapor deposition process. These as-synthesized 3D B/N co-doped C@Fe 2 O 3 /Fe 3 C/Fe-CNTs based absorbers exhibited excellent microwave absorption properties with tunable strong absorption wavebands in the frequency range of 2–18 GHz. A minimum reflection loss (RL) value of −42.6 dB was observed at 6.88 GHz with absorber thickness of 3.5 mm. Moreover, the absorption bandwidth for RL less than −10 dB was as large as 4.14 GHz when the absorber thickness dropped to 2.0 mm. A possible absorption mechanism was proposed in detail, which can be attributed to the synergy of the impedance matching and enhancement of multiple reflection among 3D B/N co-doped C@Fe 2 O 3 /Fe 3 C/Fe nanoparticles.

During recent years, graphene as a solid lubrication material have been thoroughly studied under nano or micro scales, but rarely reported at industrial conditions. In present work, graphene films as solid lubricant were prepared on the surface of 201 stainless steel substrates by pencil sketch. And then the friction tests from 5 to 65 N were carried out via a homemade tribo-tester and used GCr15 balls (o = 5 mm) as friction pairs. Not surprisingly, graphene films cannot bear the loads beyond 5 N, but interestingly, via gradually increasing the loads, graphene films show prominent load performance and steady state of friction coefficients at about 0.12 while the loads varied from 5 to 65 N. Compared with bare steel, the coefficient of graphene films reduced by about 80%, and the wear volume reduced to 1/28 when variable load (from 5 N to 30 N) were applied. Raman spectra shown that the structure of graphene had been changing into diamond-like carbon films with graphene distributed inside, which was confirmed by HRTEM that graphenes were coming with amorphous carbon. Considering the roughness of steel wafers (170 nm), one can speculate that, with graphene films' protection, the steel has no abrasion but plastic deformation instead. It is concluded that the shearing force induced the film densification via sp2 to sp3 changing that enforced cross-linking. This cross-linking carbon matrix was responsible for high load bearing and the graphene exfoliated into graphene under shearing force contribute to low steady-state friction. Benefiting from sketch, one can get a lubrication film on any substrates with complex topography, our results shed light on the growth of graphene films for industrial use.

Polymer-based thermal management materials (TIMs) show great potentials as TIMs due to their excellent properties, such as high insulation, easy processing, and good flexibility. However, the limited thermal conductivity seriously hinders their practical applications in high heat generation devices. Herein, highly transparent, insulating, and super-flexible cellulose reinforced polyvinyl alcohol/nylon12 modified hexagonal boron nitride nanosheet (PVA/(CNC/PA-BNNS)) films with quasi-isotropic thermal conductivity are successfully fabricated through a vacuum filtration and subsequent self-assembly process. A special structure composed of horizontal stacked hexagonal boron nitride nanosheets (h-BNNSs) connected by their warping edges in longitudinal direction, which is strengthened by cellulose nanocrystals, is formed in PVA matrix during self-assembly process. This special structure makes the PVA/(CNC/PA-BNNS) films show excellent thermal conductivity with an in-plane thermal conductivity of 14.21 W m-1 K-1 and a through-plane thermal conductivity of 7.29 W m-1 K-1 . Additionally, the thermal conductive anisotropic constants of the as-obtained PVA/(CNC/PA-BNNS) films are in the range of 1 to 4 when the h-BNNS contents change from 0 to 60 wt%, exhibiting quasi-isotropic thermal conductivity. More importantly, the PVA/(CNC/PA-BNNS) films exhibit excellent transparency, super flexibility, outstanding mechanical strength, and electric insulation, making them very promising as TIMs for highly efficient heat dissipation of diverse electronic devices.

As a new type of quantum dots (QDs), hexagonal boron nitride quantum dots (BNQDs) exhibit promising potential in the applications of disease diagnosis, fluorescence imaging, biosensing, metal ion detection, and so on, because of their remarkable chemical stability, excellent biocompatibility, low cytotoxicity, and outstanding photoluminescence properties. However, the large-scale fabrication of homogeneous BNQDs still remains challenging. In this article, the properties and common fabrication methods of BNQDs are summarized based on the recent research progress. Then, the corresponding yields, morphologies, and fabrication mechanisms of these as-obtained BNQDs are discussed in detail. Moreover, the applications of these as-obtained BNQDs in different fields are also discussed. This article is expected to inspire new methods and improvements to achieve large-scale fabrication of homogeneous BNQDs, which will enable their practical applications in future.

We demonstrate that novel three-dimensional (3D) B(OH)3 and α-Fe2O3 nanoparticles decorated carbon microspheres (B(OH)3/α-Fe2O3-CMSs) can be fabricated via a facile thermal treatment process. The carbon microspheres with diameter of 1-3μm and decorated B(OH)3 and α-Fe2O3 nanoparticles with diameters of several to tens of nanometers are successfully fabricated. These novel 3D B(OH)3/α-Fe2O3-CMS composites exhibit enhanced microwave absorption with tunable strong absorption wavebands in the frequency range of 2-18GHz. They have a minimum reflection loss (RL) value of -52.69dB at a thickness of 3.0mm, and the effective absorption bandwidth for RL less than -10dB is as large as 5.64GHz. The enhanced microwave absorption performance arises from the synergy of the impedance matching caused by the B(OH)3 nanoparticles, dielectric loss as well as the enhancement of multiple reflection among 3D α-Fe2O3 nanocrystals. These results provide a new strategy to tune electromagnetic properties and enhance the capacity of high-efficient microwave absorbers.

We report herein the synthesis of a novel hexagonal boron nitride nanocrystal/graphite nanoflake (h-BNNC/GNF) composite through a wet-chemistry coating of graphite nanoflakes and subsequent in-situ thermal treatment process. The characterization results of X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy demonstrate that h-BNNCs with diameter of tens of nanometers are highly crystallized and anchored on the surfaces of graphite nanoflakes without obvious aggregation. The minimum reflection loss (RL) value of the h-BNNC/GNF based absorbers could reach −32.38 dB (>99.99% attenuation) with the absorber thickness of 2.0 mm. This result is superior to the other graphite based and some dielectric loss microwave absorption materials recently reported. Moreover, the frequency range where the RL is less than −10 dB is 3.49–17.28 GHz with the corresponding thickness of 5.0–1.5 mm. This reveals a better electromagnetic microwave absorption performance of h-BNNC/GNFs from the X-band to the Ku-band. The remarkable enhancement of the electromagnetic microwave absorption properties of h-BNNC/GNFs can be assigned to the increase of multiple scattering, interface polarization as well as the improvement of the electromagnetic impedance matching of graphite nanoflakes after being coated with h-BNNCs.

In the current report, we have demonstrated that the high-efficient production of SiC/SiO2 core-shell nanowires can be achieved through the introduction of trace of water vapor during the chemical vapor deposition process. The yield of the SiC/SiO2 core-shell nanowires is dramatically improved due to the introduction of water vapor. The SiC/SiO2 core-shell nanowires exhibit an excellent microwave absorption property in the frequency range of 2.0–18.0 GHz with a very low weight percentage of 0.50 wt.% in the absorbers. A minimum reflection loss value of −32.72 dB (>99.99% attenuation) at 13.84 GHz has been observed with the absorber thickness of 3.0 mm. Moreover, the SiC/SiO2 core-shell nanowires based absorber can reach an effective absorption bandwidth (

In this report, we have developed a scalable approach to massive synthesis of hexagonal/turbostratic composite boron nitride nanosheets (h/t-BNNSs). The strikingly effective, reliable, and high-throughput (grams) synthesis is performed via a facile chemical foaming process at 1400 °C utilizing ammonia borane (AB) as precursor. The characterization results demonstrate that high quality of h/t-BNNSs with lateral size of tens of micrometers and thickness of tens of nanometers are obtained. The growth mechanism of h/t-BNNSs is also discussed based on the thermogravimetric analysis of AB which clearly shows two step weight loss. The h/t-BNNSs are further used for making thermoconductive h/t-BNNSs/epoxy resin composites. The thermal conductivity of the composites is obviously improved due to the introduction of h/t-BNNSs. Consideration of the unique properties of boron nitride, these novel h/t-BNNSs are envisaged to be very valuable for future high performance polymer based material fabrication. Keywords: Turbostratic, Boron nitride nanosheets, Large scale fabrication, Growth mechanism, Thermal conductivity

Due to the different interfacial effects of oil and water, utilizing the special wettability of solid surfaces to design an oil and water separation process has been demonstrated to be an effective approach for oil/water separation. In this report, a simple process has been developed to fabricate special surface wettability mesh membranes. The carbon nanoparticles with diameters of 10 nm were first coated onto the surface of steel wires based on a candle soot coating process. These templates of carbon nanoparticles were then coated with a more stable layer of silica (SiO2) particles via a facile chemical vapor deposition route. After being modified by two separate methods, a superhydrophobic/superoleophilic membrane was obtained by the use of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) and a oleophobic/superhydrophilic membrane was obtained by using poly(diallyldimethylammonium-perfluorooctanoate) (PDDA–PFO). Separation experiments show that these superhydrophobic/superoleophilic or oleophobic/superhydrophilic mesh membranes can be used to selectively separate oil/water with a high flux of more than 930 L m−2 h−1 and a collecting efficiency of over 97%. Furthermore, the repetitions of the separation experiments demonstrate that these superhydrophobic/superoleophilic or oleophobic/superhydrophilic mesh membranes are durable, stable and reusable, making them encouraging candidates for practical oil-polluted water treatment.

Graphene has been regarded as a promising candidate in microwave absorption field but still faces some major challenges, including the limitation of mass production and poor impedance matching. Here, we demonstrate a simple approach to fabricate multilayer graphene in a kilo-mass/hour (≥2.5 kg/h) scale through an oxidation-thermal expansion-air convection shearing process. The subsequent incorporation of hexagonal boron nitride nanoparticles (h-BNNPs) can effectively tailor the dielectric and magnetic properties of the as-obtained multilayer graphene, which can significantly boost its microwave absorption performance. The as-obtained multilayer graphene/h-BNNP hybrid with 40 wt.% of h-BNNPs, exhibits extremely low reflection loss value of −67.35 dB at 8.04 GHz when the absorber thickness is 3.29 mm, ranking it as one of the most attractive absorbers reported to date. Moreover, the multilayer graphene/h-BNNP hybrids possess low densities less than 0.45 g/cm3, making them very attractive for practical microwave absorption application.

Hexagonal boron nitride nanosheets (h-BNNSs), with a crystal lattice structure similar to graphene by over 98%, exhibit good lubrication properties as lubricant additives. However, the poor dispersibility in solvents has limited their wide practical applications as lubricant additives. In the present report, water dispersible Pebax functionalized h-BNNSs (Pebax-BNNSs) have been prepared through a one-step solvent-free mechanical exfoliation process which relies on a simple exfoliation of h-BN layers by shearing force in molten Pebax at 200 °C. In this process, Pebax molecules can synchronously react with the dangling bonds formed during the exfoliation process to achieve in situ functionalization of h-BNNSs. The reciprocating friction tests demonstrate that the as-obtained Pebax-BNNSs possess excellent antifriction and antiwear performance as water-based lubricant additive with a low concentration of 0.3 mg/mL under atmospheric condition. The friction coefficients can be h-BNNSs can achieve superlubrication as water-based lubricant additives via facile surface modification, making them very promising candidates as lubricant additives in practical applications.

As a new type of quantum dots (QDs), boron nitride QDs (BNQDs), show promising potentials in disease diagnosis, fluorescence imaging and bio-sensing due to its good biocompatibility, low cytotoxicity and excellent photoluminescence performance. However, there are still challenges in preparing BNQDs with uniform and small size. In this paper, the BNQDs with uniform and small size have been prepared through a hydrothermal process with the exfoliated hexagonal boron nitride nanosheets (h-BNNSs) as precursor. The as-prepared BNQDs were characterized by transmission electron microscope (TEM), high-resolution TEM, fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis and photoluminescence spectra (PL) for morphology, surface functional groups, element composition and optical properties. The as-prepared BNQDs have uniform particle size distribution with an average lateral size of 1.65 nm, and a PL quantum yield of 2.49 %. In addition, the as-prepared BNQDs exhibit strong blue fluorescence under UV-vis (365 nm) irradiation and nanosecond luminescent decay. Furthermore, the effect of preparation parameters on the fluorescence performance of BNQDs was investigated which provides an optimal condition for the preparation of BNQDs with excellent fluorescence performance. Together with other advantages, such as excellent physical/chemical properties, good biocompatibility and low cytotoxicity, the as-prepared BNQDs have great potentials in medical diagnosis, biosensing, photoelectric devices and other fields in the future.

In the past decades, great progress in electromagnetic microwave absorption (MA) materials in both civil and military fields have been made due to the high demand for the elimination of electromagnetic interference. Recently, hexagonal boron nitride (h-BN) based materials have been regarded as one of the promising MA composite materials because of their remarkable dielectric property, excellent thermal conductivity, low density, and outstanding chemical stability. Developing efficient h-BN–based MA materials has aroused wide interest, aiming to achieve ideal MA materials with thin thickness, low density, high thermal stability, strong absorption capacity, wide absorption bandwidth, and low filling rate. This review presents an overview of the progresses in h-BN based MA materials. It starts with a brief introduction of the MA mechanism, followed by reviewing the fabrication and potential application of different h-BN–based MA materials. Finally, the research perspectives on the h-BN based MA materials are proposed. It is expected that the research interest in h-BN based MA materials from the basic fabrication to engineering application will be instigated in future.

Herein, lightweight amorphous carbon blocks with hierarchically hollow structure are fabricated through a facile thermal treatment of furfuryl alcohol with silica nano/microparticles as template. The walls formed the spherical voids are also porous structure, which generates a heterogeneously porous structure. This unique structure can effectively reduce the densities of the carbon blocks (≤87 ± 2.1 mg/cm3). The thermal treatment temperature has a great effect on the porosity and graphitization of the final samples, and a lowest density of 59 ± 1.4 mg/cm3 is obtained from the sample prepared under the carbonization temperature of 950 °C. More importantly, the as-obtained lightweight amorphous carbon shows excellent microwave absorption (MA) properties, and a minimum reflection loss value of −57.2 dB and absorption bandwidth of 4.4 GHz are gained for the absorber with a thin thickness of 1.7 mm possessing the lowest density with a low filling rate of 7.5 wt%. The excellent MA properties combining with the lightweight density and low loading rate make the heterogeneously porous carbon materials be promising candidates for practical application in MA absorption field.

Wastewater treatment and separation technologies are critical to meet global challenges of insufficient water supply and inadequate resources. However, simple adsorption can no longer satisfy these demands, and thus more and more water recovery technologies have attracted attention. Here, we report a novel kind of porous BN nano/microrods with excellent features including high surface area of 1109.11 m²/g, large pore volume of 0.454 cm³/g and small pore size of 2.60 nm. These unique properties make the as-obtained porous BN nano/microrods show an ultrafast adsorption rate for the cationic dye methylene blue (MB+), and they can also be able to selectively adsorb cationic dyes from the mixtures of anionic and cationic dyes. The corresponding selective adsorption mechanism is also proposed based on the microstructure and surface property of the as-obtained porous BN nano/microrods. Furthermore, the cytotoxicity test was performed and the results show that the as-obtained porous BN nano/microrods have good biocompatibility with the cell survival rate of 80 % after a test period of 5 days, and this result is much higher than that of commercial BN. This finding provides a new application field for BN nanomaterials to selectively adsorb/separate anionic and cationic dyes in organic dye-containing wastewater treatment.

The friction and wear of amorphous diamond-like carbon (DLC) films will dramatically increase with the increment of ambient humidity. This drawback can lead to lubrication failure, which greatly impedes the practical applications of DLC films in humid environment. Herein, a simple method is proposed to improve the tribological performance of DLC films in humid environment by adding hexagonal boron nitride nanosheet wrapped carbon nanoparticles (CNP@h-BNNSs) as lubricants. The reciprocating friction tests demonstrate that DLC films with CNP@h-BNNSs as lubricants possess excellent antifriction and antiwear performance at the relative humidity (RH) of 7.5–55%. Especially, it can achieve a superlow friction and wear at the RH of 45–55% which decrease by respectively 13 and 25 times as compared to those obtained from DLC films without lubricants. The investigation on the steel ball surface after friction test shows that a protective tribo-layer containing carbon, boron and nitrogen elements is formed. The existence of this tribo-layer can effectively reduce the friction and protect the steel ball surface from excessive wear. Noteworthy, the h-BNNSs are exposed at the friction interface acting as lubricating layer while the carbon nanoparticles are adsorbed on steel ball surface playing as binding binder. Furthermore, the ball movement mode of CNP@h-BNNSs and the interaction between water molecules and CNP@h-BNNSs are also considered as key factors to reduce friction. All these results indicate that CNP@h-BNNSs which can be massively produced have the potential to reduce the friction and wear of DLC films in humid environment.

This work was supported by the National Natural Science Foundation of China(51102060, 51172050, 51302049, and 51372052), the Postdoctoral Science Foundation of China (2013M531036), and Shangdong Province Young and Middle-Aged Scientists Research Awards Fund(BS2013L003).

Excellent and robust hydrophobic materials generally benefit from specifically exposed surfaces i.e. always the low-energy surfaces, and well-defined micro/nano-structures that are achieved through advanced facilities and complicated process with a high cost. We hereof demonstrate that the superhydrophobicity and further self-cleaning properties are also attainable based on high-energy crystalline facets by an appropriate chemical modification. Specifically, anatase TiO 2 microspheres were large-scale synthesized to exhibit isotropically exposed high-energy {0 0 1} facets through optimizing the HF/H 2 O 2 /H 2 O ratio during hydrothermal processes. The formation of the microspheres was uncovered to be an in-situ “growth-cum-assembly” grown mechanism. Such high-energy {0 0 1} facets facilitate the strong coupling between the resultant TiO 2 microspheres and the modifier (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) because the {0 0 1} facets offer abundant active sites for chemical bonding, showing great merits for superhydrophobicity (with water contact angle of 154 ± 2°, 6 μl droplets), and further stably surface self-cleaning i.e. easily removing surface contamination (e.g. Al 2 O 3 powders). This integrated strategy represents a milestone in design and fabrication of delicate composites with high-energy surfaces for specific functions and properties.

The outstanding electrical insulativity greatly restricts the applications of hexagonal boron nitride nanosheets (h-BNNSs) in semiconductive or conductive micro and nano electromechanical systems (M/NEMSs). Therefore, regulating the electrical conductivity of h-BNNSs becomes critical for their applications in semiconductive or conductive M/NEMSs. In this report, a facile and effective method via introduction of F and H atoms to regulate the electrical conductivity of h-BNNS bilayers is proposed based on first-principle calculations within the framework of density functional theory. The geometry and electronic density of states of F and H codoped h-BNNS bilayers are systematically investigated. The results demonstrate that F and H atoms can strongly bind to h-BNNSs realizing the conversion of h-BNNSs from insulator to semiconductor or conductor. More importantly, due to the electron redistribution induced by the introduction of F and H atoms, the doped h-BNNS bilayers exhibit very low interlayer friction under a certain compressive interlayer spacing. These F and H codoped h-BNNS bilayers with improved electrical conductivity, high structural stability, lower interlayer friction and higher load-bearing capacity will bring prosperous applications of h-BNNSs in semiconductive or conductive M/NEMSs.

The application of hexagonal boron nitride nanosheets (h -BNNSs) in electronical and optical fields is limited due to their wide band gap. In this letter, we report a first-principles study on the electronic and optic properties of phosphorus (P) functionalized h -BNNSs. The results show that the introduction of P atoms leads to a valid modification of h -BNNS band structure which can reduce the width of band gap from 4.643 eV to 0.824 eV. The transformation from insulator to semiconductor of h-BNNSs is achieved through this band width regulation, and all P-doped h -BNNSs exhibit an active response to the visible light. In particular, with the increase in the number of doped P atoms, the absorption wavelength range can cover the whole visible region. In terms of the analysis of electronic structures and absorption spectra of the P-doped h -BNNSs, an enhancement mechanism of the visible-light response for the effect of the introduction of P atoms is proposed. It is expected that P-doped h -BNNSs could be used as potential metal-free efficient visible-light–driven photocatalysts.

Hexagonal boron nitride nanoflakes (h-BNNFs) are usually selected as fillers to improve the thermal conductivity of polymer materials. However, previous research mainly focused on the influence of h-BNNF content and orientation. In this report, the effects of the content, geometry, thickness, modification and orientation of h-BNNFs on the thermal conductivity of h-BNNF/polymer composites were systematically investigated based on the h-BNNF/silicone rubber (h-BNNF/SR) composites. The thermal conductivity of h-BNNF/SR composites increased tremendously with the increase of h-BNNF content. Meanwhile, the h-BNNF contents also show great effects on the viscosity, hardness and thermal stability of the composites, and the h-BNNF content of 20% is more advantageous for processing and application of the composites. Besides, modified, flake-like and thinner h-BNNFs can result in better reinforcement in thermal conductivity than unmodified, agglomerated and thicker ones. h-BNNF/SR composites with shear force induced oriented h-BNNFs showed further enhanced thermal conductivity, and the composite with 40 wt% oriented h-BNNFs exhibits the best thermal conductivity of 0.901 W/(m K).

A novel boron nitride nanosheets (BNNSs)–amorphous carbon (a-C) hybrid film has been deposited successfully on silicon substrates by simultaneous electrochemical deposition, and showed a good integrity of this B–C–N composite film by the interfacial bonding. This synthesis can potentially provide the facile control of the B–C–N composite film for the potential optoelectronic devices.

We demonstrate that novel three-dimensional (3D) B(OH)

Porous carbon nanotube/polyvinylidene fluoride (CNT/PVDF) composite material can be fabricated via formation and freeze-drying of a gel. The field emission scanning electron microscopy, nitrogen adsorption–desorption and pore size distribution analysis reveal that the introduction of a small amount of carbon nanotubes (CNTs) can effectively increase the surface roughness and porosity of polyvinylidene fluoride (PVDF). Contact angle measurements of water and oil indicate that the as-obtained composite material is superhydrophobic and superoleophilic. Further experiments demonstrate that these composite material can be efficiently used to separate/absorb the insoluble oil from oil polluted water as membrane/absorbent. Most importantly, the electrical conductivity of such porous CNT/PVDF composite material can be tuned by adjusting the mass ratio of CNT to PVDF without obviously changing the superhydrophobicity or superoleophilicity. The unique properties of the porous CNT/PVDF composite material make it a promising candidate for oil-polluted water treatment as well as water-repellent catalyst-supporting electrode material.

Herein, we demonstrate that amorphous carbon can be converted to lightweight superior MA materials only via a facile inside three dimensional ordered hollow (3DOH) architecture fabrication. The as-fabricated 3DOH carbon (3DOHC) blocks consist of ordered spherical voids formed by connected thin porous amorphous carbon walls. The diameter of the voids has a great influence on the MA performance, and a minimum reflection loss (RL) value of −66.24 dB is observed at 15.68 GHz for the 3DOHC blocks with inside void diameter of 500 nm (3DOHC-500) at a low filling rate of 5.0 wt% and absorber thickness of 1.6 mm. Moreover, the widest absorption bandwidth for RL values below −10 dB is 4.78 GHz when the absorber thickness is 1.7 mm while still keeping a low RL value of −45.85 dB. The enhancement of the MA performance of 3DOHC-500 based absorber can be attributed to the synergic effect of dielectric loss and impedance matching. The excellent MA performance combining with the low filling rates (2.5–5.0 wt%), thin thickness and lightweight (≤100 mg/cm−3) makes these 3DOHC-500 very promising candidate for practical MA applications.

The reduction of interfacial friction among hexagonal boron nitride nanosheets (h-BNNSs) is important for their application in nanoelectromechanical systems. In this work, a novel method via adjusting the electron redistribution to reduce the interlayer friction of the h-BNNS bilayers is proposed based on the theoretical calculation of the relationship between electron distribution state and corresponding friction performance. The theoretical calculation is performed based on density functional theory with a fluoride h-BNNS bilayer as a model. Calculations suggested that fluorine atoms can strongly bond to the h-BNNS and promote electron redistribution, inducing interesting surface behaviors of the h-BNNS bilayer. Fluorine doping can reduce the interlayer friction and even make the upper layer bend when the fluorine doping ratios increase further. This bending can promote the upper layer slide relative to the lower one, achieving superlubricity. The reduction is related to the electron transfer between layers and within layers, which is caused by the change in electrostatics and van der Waals interaction between the layers that resulted from the electron redistribution. This work opens up a new strategy to control the frictional properties of two-dimensional nanomaterials and provides a favorable proof for experimental analysis.

In this communication, the humidity sensing properties of single boron nitride nanotubes (BNNTs) with and without Au decoration have been investigated. The current–voltage measurement shows that the decoration of Au nanoparticles on the surface of BNNTs effectively improves the conductance. The resistance of single BNNT and Au-BNNT decreases slowly at the low relative humidity (RH) from 20% to 50%; but decreases fastly at the high RH from 50% to 90%. Moreover, the adsorption and desorption tests indicate that the Au-decorated boron nitride nanotube (Au-BNNT) has a fast and sensitive response and recovery to RH at room temperature. The good humidity-sensing properties of the Au-BNNT combined with its excellent chemical stability, make it a promising candidate for the fast detection of humidity in various wild environments. Keywords: Boron nitride nanotubes, Au decoration, Humidity sensing property

The separation of oil and water from wastewater generated in the oil-production industries, as well as in frequent oil spillage events, is important in mitigating severe environmental and ecological damage. Additionally, a wide arrange of industrial processes require oils or fats to be removed from aqueous systems. The immiscibility of oil and water allows for the wettability of solid surfaces to be engineered to achieve the separation of oil and water through capillarity. Mesh membranes with extreme, selective wettability can efficiently remove oil or water from oil/water mixtures through a simple filtration process using gravity. A wide range of different types of mesh membranes have been successfully rendered with extreme wettability and applied to oil/water separation in the laboratory. These mesh materials have typically shown good durability, stability as well as reusability, which makes them promising candidates for an ever widening range of practical applications.

A facile approach for large-scale fabrication of boron nitride nanocups (BNNCs) via a ball milling, annealing and subsequent mechanical treatment process was developed. The resultant BNNCs have a uniform size distribution with a diameter of 50–200 nm and a length of 100–200 nm, which can be attributed to the intrinsic structure characteristic of the as-synthesized bamboo-like boron nitride nanotubes (BNNTs). The gold nanoparticles filling experiments demonstrate that the BNNCs can be used as nanoscale containers, which provide a significant potential application to integrate this new structure of boron nitride nanomaterials for use in nanodevices of energy storage and biomedicine science.