Search

The large-scale synthesis and the stabilization of noble metal nanocatalysts with ultrasmall sizes are crucial to their practical application. Herein, Pd, Au, and Pt nanoparticles (NPs) are in situ embedded on boron nitride nanosheets (BNNSs) via the reduction of precursor salts induced by 60Co γ-irradiation, which is a mature technique widely used in industry. The reduction mechanism was elucidated by pulse radiolysis experiments. In comparison with other BN substrates like hexagonal BN (h -BN), BNNSs had not only large surface area of 263 m2 g−1, but also abundant hydroxyl groups produced during the sonicated exfoliation, resulting in ultrasmall sizes, large loading amounts, and uniform distribution of the anchored NPs. The particle sizes of the loaded Pd, Au, and Pt NPs were measured to be 2.9, 3.1, and 3.0 nm, respectively. As a consequence, in the model reaction of 2-nitroaniline reduction, the Pd-, Au- and Pt-BNNSs composite nanocatalysts showed much higher catalytic activities than those composites loading the corresponding NPs on other BN substrates. Particularly, most of the 2-nitroaniline could be reduced within merely 40 s when using Pd-BNNSs as catalysts, performing a rate constant of 1.1 × 10−1 s−1. The number of hydroxyl groups on BNNSs support as well as the catalytic performance of the corresponding NPs-loaded BNNSs composites could be improved by extending the sonicated exfoliation time, because more NPs were loaded and the hydroxyl groups were also proved to play an important role in enhancing the catalytic activity. Moreover, Pd-BNNSs catalysts still displayed prominent activity even after five cycles owing to the high stability of BNNSs and their strong affinity for PdNPs. This work not only demonstrates BNNSs as ideal supports to load noble metal NPs for catalysis, but also reveals the feasibility to synthesize and in situ embed ultrasmall noble metal NPs on BNNSs via γ-irradiation. γ-Radiation-induced reduction achieved facile loading of noble-metal nanoparticles on BNNSs as ideal supports for extraordinary catalytic activity and excellent reusability. [Display omitted] • BNNSs with hydroxyl groups, prepared from sonicated exfoliation, were suitable to load noble metal nanoparticles (NPs). • Noble metal NPs of Pd (Au or Pt) were in situ embedded on BNNSs by facile γ-radiation-induced reduction. • The reduction mechanism was elucidated by pulse radiolysis experiments. • NPs loaded on BNNSs possessed the smaller sizes and higher loading amounts, compared with those on other BN substrates. • NPs-loaded BNNSs showed excellent catalytic activity and reusability for 2-nitroaniline reduction. [ABSTRACT FROM AUTHOR]

• BCN was successfully modified by silane coupling agent. • The mechanical properties of SR were enhanced by BCN after irradiation. • BCN decreased the radiation crosslinking of SR. • BCN lessened the gas generated by SR side chain after irradiation. • The mechanism of BCN to improve the radiation resistance of SR was explained. The developing nuclear technology has increased the need for radiation-resistant and shielding materials. It is crucial to study the radiation resistance of polymers in order to prevent safety incidents brought on by the degradation of polymer performance in a nuclear environment. In this work, γ-aminopropyltriethoxy silane (KH550) was successfully grafted onto carbon-doped boron (BCN) to obtain modified BCN (BCN-KH550), then BCN-KH550 was added in silicone rubber and refined and vulcanized. The elongation at break of silicone rubber composite doped with 0.3 phr BCN-KH550 can retain (54 ± 2)% of the initial value. The addition of BCN and BCN-KH550 both increases the initial decomposition temperature of the irradiated SR. The radiation caused changes in crystallinity and glass transition temperature (T g) were measured using differential scanning calorimetry. The difference T g of BCN-KH550/SR0.3 before and after irradiation is 0.9 °C higher than that of SR. It is supposed that BCN protects the side group of SR during irradiation through differential thermogravimetric analysis curve and gas phase infrared spectra of the irradiation-induced gas products. BCN and BCN-KH550 can lower the hydrocarbon, CO 2 and CO production by side chain breakdown in both air and nitrogen atmospheres. The presence of BCN and BCN-KH550 decrease the radiation crosslinking of SR. The outcomes demonstrate that BCN-KH550 can reduce the effects of γ-radiation crosslinking on SR by declining side chain decomposition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchically porous boron nitride (HPBN) was modified with diamide pyridine (DAPy). • Assistance of radiation-induced hydroxylation was essential to modify inert HPBN. • Hierarchically porous structure endowed HPBN-DAPy ultrafast adsorption kinetics. • HPBN-DAPy selectively adsorbed U due to the strong affinity between uranyl and DAPy. • HPBN-DAPy retained 86% of the original adsorption amount after 5 cycles. Uranium (U) released by nuclear accident raises concerns about human health owing to its long half-life and toxicity. Diamide-pyridine-modified hierarchically porous boron nitride (HPBN-DAPy) was prepared for efficient removal of U. HPBN, which could hardly adsorb U, gained the ability to uptake U only after functionalization with diamide pyridine (DAPy) groups. The hierarchically mesoporous structure with bimodal mesopores around 20 and 3 nm endowed HPBN-DAPy with unique adsorption kinetic. Uranyl ions (UO 2 2+) easily approached the adsorption sites in those large mesopores and thus the adsorption rapidly reached temporary equilibrium within 0.5 min with a relatively high adsorption of amounts (q e) of 87.5 mg g−1 (adsorbent dosage = 0.4 g L−1, [U] 0 = 100 mg L−1, pH = 4.0 ± 0.1, T = 298 ± 1 K), which was beneficial for rapid decontamination. Small mesopores and the inner large mesopores, which were connected through small mesopores, provided extra adsorption sites, leading to a further increased q e of 115.7 mg g−1 after achieving final equilibrium. Investigation of adsorption mechanism showed that UO 2 2+ were chemically adsorbed in monolayer at a low initial concentration while they were physically adsorbed in the form of polynuclear complexes at a high initial concentration. Benefited from the strong affinity between UO 2 2+ and DAPy, HPBN-DAPy performed excellent selectivity for UO 2 2+ toward other most concerned radionuclide ions. Furthermore, HPBN-DAPy also exhibited adequate salt tolerance and outstanding reusability, which should be promising in removal of U from contaminated water. [ABSTRACT FROM AUTHOR]

• BCN was surface modified with two silane coupling agents. • Composites exhibited excellent properties before and after gamma irradiation. • The performance of composites can be improved by improving the interfacial compatibility. • Modified BCN could weaken oxidative degradation of EP under γ irradiation. Polymer matrix composites reinforced with boron nitride (BN) have attracted much attention in the nuclear industry due to their attractive properties. Nevertheless, the performance of such composites largely depends on matrix–filler interactions. Herein, carbon-doped boron nitride (BCN), modified by two silane coupling agents, was used to fabricate epoxy composites, and the effect of gamma irradiation on the properties of epoxy resin composites was investigated. The research showed that the modified BCN/epoxy composites prepared herein exhibited excellent mechanical and thermal properties before and after gamma irradiation. The tensile strength of the composites increased up to 63.1 MPa at 0.5 wt % loadings compared to neat epoxy (54.7 MPa). After irradiation at 900 kGy, the tensile strength of the composites was 32.5% higher than that of neat EP. This improvement was ascribed to the excellent compatibility of the modified BCN and epoxy. Moreover, the char yield and the glass transition temperature significantly increased with incorporation of modified BCN before and after irradiation. The mechanism for the enhanced performance was that the barrier consisting of BN protected the matrix from further oxidative degradation. This study suggested that functionalized BN more effectively enhanced epoxy properties before and after irradiation. [ABSTRACT FROM AUTHOR]

[Display omitted] • BCN was functionalized by Phenanthroline diamide with high density. • Functionalized BCN exhibited ultrahigh adsorption capacity for U(VI). • Functionalized BCN showed excellent selectivity for U(VI) from lanthanides. • Adsorption mechanism was explored by combining two-site model and DFT calculations. Separating and recovering uranium (U(VI)) efficiently from lanthanides is crucial for mitigating the radioactive hazard generated by hydrometallurgical residual solutions of lanthanide minerals and ensuring the long-term sustainability of uranium resources. The present work exploited phenanthroline diamide functionalized porous carbon doped boron nitride (BCN-DAPhen) as an adsorbent, which displayed outstanding adsorption performance for the separation of U(VI) from lanthanides. The results of batch adsorption tests indicated that BCN-DAPhen exhibited rapid adsorption kinetics and the adsorption process achieved equilibrium within 10 min. BCN-DAPhen also performed ultra-high maximum adsorption capacity that was calculated to be 2050.8 mg g−1 by fitting with the two-site Langmuir model. Theoretical calculation and experimental results of adsorption were combined to illustrate the adsorption mechanism as well, the results showed that two structures of DAPhen groups on BCN performed discrepant adsorption properties for U(VI). BCN-DAPhen retained excellent adsorption ability owing to the strong affinity of DAPhen groups with U(VI) even in the solution with high concentration of salt and acid. The selectivity coefficients of U(VI) toward various lanthanides were beyond 192.5 at a high nitric acid concentration of 5 mol L−1. This study suggested a general technique for the functionalization of porous BCN, which is expected to be useful in the treatment of residual solution in lanthanides hydrometallurgy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cationic-surfactant-assisted solvothermal exfoliation method was developed to prepare monolayer BNNSs. • Over 60% of the exfoliated BNNSs were monolayer with the assistance of CTAB. • DAPhen funtionalized BNNSs (BNNSs-DAPhen) achieved high adsorption amounts and ultrafast adsorption rate of U(VI). • BNNSs-DAPhen maintained good adsorption performance under high concentrations of acid and salts. • BNNSs-DAPhen performed excellent selectivity for U(VI) over lanthanides in strongly acidic conditions. The efficient separation and recovery of uranium(VI) (U(VI)) from lanthanides is pivotal to reduce the radioactive threat of hydrometallurgical residue solution of lanthanide minerals and benefits the sustainability of U resources. Here, we develop a cationic-surfactant-assisted solvothermal exfoliation method to prepare monolayer boron nitride nanosheets (BNNSs) for the ultrafast and selective separation of U(VI) from lanthanides. With the assistance of the strong "cation–π" interaction between cationic surfactants and BN, the monolayer BNNSs were prepared. Functionalization with diamide phenanthroline (DAPhen) groups endows the pristine BNNSs, which can hardly adsorb U(VI), with outstanding U(VI) adsorption performance. Batch adsorption experiments demonstrate that the obtained DAPhen modified BNNSs (BNNSs-DAPhen) exhibited high maximum adsorption capacity and ultrafast adsorption kinetics. The adsorption process reached equilibrium less than 1 min and the maximum adsorption capacity was estimated to be 313 mg g−1 by fitting with Langmuir model. Even under high concentrations of salts and acids, BNNSs-DAPhen still maintained excellent adsorption performance owing to the strong complexing ability of DAPhen groups with U(VI). The selectivity coefficients of U(VI) toward various lanthanides including lanthanum(III), cerium(III), europium(III), gadolinium(III), ytterbium(III), and lutetium(III) were beyond 120 at a high nitric acid concentration of 5 mol L−1. This work proposed a universal strategy for the production of monolayer BNNSs and the subsequent functionalization, which might be promising in the treatment of residual solution for lanthanides hydrometallurgy and decontamination of U(VI). [ABSTRACT FROM AUTHOR]

• The mechanical property and T g of the EP were improved by introducing h -BN. • The low contents of h -BN were favorable to enhance the radiation resistance of EP. • h -BN could weaken oxidative degradation of EP under γ irradiation. • h -BN endowed the EP with excellent neutron shielding by absorbing neutrons. Improving the radiation resistance of epoxy resin (EP) is pivotal for the reliability of equipment and the safety of facilities in the nuclear industry. Hexagonal boron nitride (h -BN) is attractive in the preparation of radiation-resistant materials due to its good radiation stability and neutron shielding capability. In this work, h -BN/EP composites with enhanced radiation resistance were fabricated by solution blending. The tensile strength and thermal properties of the composites after γ-ray and neutron irradiation were investigated. The results showed that the addition of h -BN improved the mechanical property and the glassy transition temperature of the resin. The presence of low-level h -BN was favorable to enhance the radiation resistance of EP. As for composites with the 0.05% mass percentage of h -BN, the absorbed dose required to decrease relative tensile strength by 50% was about 300 kGy, which was higher than that of neat EP. The intrinsic mechanism of radiation resistance was attributed to the oxygen barrier effect as investigated by XPS and EPR. Then, benefiting from the absorbing neutrons capability of boron atoms, an addition of 0.55% h -BN to the EP resin could reduce the neutron transmittance of the resin by 5.6%. This study demonstrates that the blending with h -BN can increase the radiation-resistant property of EP resin, meanwhile augmenting the neutron shielding ability. [Display omitted] [ABSTRACT FROM AUTHOR]

• Carbon-doped BN (BCN) nanosheets were prepared by a facile pyrolysis method. • The band structure and pore texture were tuned subtly by controlling carbon level. • BCN showed high activity and stability in vis-induced photocatalytic UO 2 2+ reduction. • U(VI) can be reduced to U(IV) by photoinduced electrons and formed ketyl radicals. Effectively separating uranium from aqueous solution is pivotal in the sustainable development of the nuclear industry and environmental protection. In this work, non-metal photocatalysts, carbon-doped BN (BCN) nanosheets were used to extract uranium by the photocatalytic reduction technique, and the doping in the form of carbon rings can regulate the bandgap and electronic structure by manipulating carbon amount. Benefiting from the porous structure and strong visible-light absorption, the U(VI) separation ratio of 97.4% could be achieved after 1.5-hour visible irradiation with an apparent rate value of 2.97 h−1 over BCN-80. Additionally, BCN-80 displayed good reusability and stability with the U(VI) separation ratio > 90% even after five cycles, and the enhanced U(VI) photoreduction was attributed to the synergistic effect of photoinduced electrons and formed ketyl radicals. This work demonstrates the great potential of BCN materials in U(VI) enrichment and will lay the foundation for further developing novel semiconductor photocatalysts. [ABSTRACT FROM AUTHOR]