Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge.Here,a novel Fe-Co/N-doped carbon/reduced graphene oxide(Fe-Co/NC/rGO)composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Cobased metal organic frameworks(Co-MOF)on the sheets of porous cocoon-like rGO followed by calcination.The Fe-Co/NC composites are homogeneously distributed on the sheets of porous rGO.The Fe-Co/NC/rGO composite with multiple components(Fe/Co/NC/rGO)causes magnetic loss,dielectric loss,resistance loss,interfacial polarization,and good impedance matching.The hierarchically porous structure of the Fe-Co/NC/rGO enhances the multiple reflections and scattering of microwaves.Compared with the Co/NC and Fe-Co/NC,the hierarchically porous Fe-Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design.Its minimum reflection loss(RLmin)reaches?43.26 dB at 11.28 GHz with a thickness of 2.5 mm,and the effective absorption frequency(RL≤?10 dB)is up to 9.12 GHz(8.88-18 GHz)with the same thickness of 2.5 mm.Moreover,the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm.This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.

Catalytic performance of hierarchical H-ZSM-5/MCM-41 for methanol dehydration to dimethyl ether

Micro-mesoporous composite molecular sieves H-ZSM-5/MCM-41 were prepared by the hydrothermal technique with alkali-treated H-ZSM-5zeolite as the source and characterized by scanning electron microscopy,transmission electron microscopy,energy dispersive spectroscopy,X-ray diffraction,N2 adsorption-desorption measurement and NH3 temperature-programmed desorption.The catalytic performances for the methanol dehydration to dimethyl ether over H-ZSM-5/MCM-41 were evaluated.Among these catalysts,H-ZSM-5/MCM-41 prepared with NaOH dosage (nNa/nSi) varying from 0.4 to 0.47 presented excellent catalytic activity with more than 80%methanol conversion and 100%dimethyl ether selectivity in a wide temperature range of 170—300℃,and H-ZSM-5/MCM-41 prepared with nNa/nSi=0.47 showed constant methanol conversion of about 88.7%,100% dimethyl ether selectivity and excellent lifetime at 220℃.The excellent catalytic performances were due to the highly active and uniform acidic sites and the hierarchical porosity in the micro-mesoporous composite molecular sieves.The catalytic mechanism of H-ZSM-5/MCM-41 for the methanol dehydration to dimethyl ether process was also discussed.

Catalytic performance of acidic ionic liquid-functionalized silica in biodiesel production

Acidic ionic liquid([BsAIm][OTf]) was immobilized on sulfhydryl-group-modified SiO2(MPS-SiO2) via free radical addition reaction. The[BsAIm][OTf] loading on acidic ionic liquid-functionalized silica([BsAIm][OTf]/SiO2) was controlled through tuning the sulfydryl(SH)content of MPS-SiO2. All the samples were characterized by FT-IR, elemental analysis, N2adsorption-desorption measurements and TGDTA. The catalytic performance of [BsAIm][OTf]/SiO2in the esterification of oleic acid and the transesterification of glycerol trioleate for biodiesel production was investigated. The results showed that with the increase of [BsAIm][OTf] loading on SiO2the specific surface area and pore volume of [BsAIm][OTf]/SiO2decreased, and the pore diameter of [BsAIm][OTf]/SiO2narrowed. In the esterificaiton of oleic acid, the oleic acid conversion increased with the increasing [BsAIm][OTf] loading. In the transesterification of glycerol trioleate, with the increasing[BsAIm][OTf] loading the glycerol trioleate conversion decreased and the selectivities to glycerol monooleate and methyl oleate increased.

高击穿电压聚氨酯漆包线的制备及性能

采用1,1,2,2-四氢全氟-1-癸醇对异佛尔酮二异氰酸酯三聚体的1个异氰酸酯基进行封端,将封端后的三聚体替代部分异佛尔酮二异氰酸酯与全氟聚醚二元醇反应,合成了不同三聚体含量的支链型含氟聚氨酯。然后将支链型含氟聚氨酯配置成漆包线漆,通过高速漆包线机将其制备成漆包线。分别采用红外光谱、热重分析仪、万能试验机和接触角测试仪等对所制备的支链型含氟聚氨酯结构、热稳定性、力学性能以及疏水性进行测试;采用电压试验仪、单向刮漆试验仪、软化击穿试验仪及焊锡试验仪等对漆包线的击穿电压、力学性能、热性能和直焊性进行测试,探究了封端三聚体含量对聚合物结构、性能以及漆包线性能的影响。结果表明,封端三聚体占比30%(摩尔分数)的支链型含氟聚氨酯的拉伸强度可达30.50 MPa、断裂伸长率为952%、初始分解温度提高至216.6℃、接触角增大至96.1°,相较于普通的聚氨酯均有大幅提高;相应漆包线的击穿电压高达7033.8 V,而封端三聚体占比10%的支链型含氟聚氨酯漆包线的击穿电压最高,达到了7513.4 V,是普通聚氨酯漆包线(4719.8 V)的1.6倍。同时,力学性能、热性能和直焊性均满足聚氨酯漆包线的使用要求。

Lipid-conjugated siRNA hitchhikes endogenous albumin for tumor immunotherapy

With the development of a small interfering RNA(siRNA)delivery strategy,increasing siRNA therapeutics for tumor treatment appeared in clinical trials and pre-clinical development.However,the test results of such therapeutics unveiled that efficient siRNA delivery to tumor tissues is still challenging.Albumin is considered an ideal carrier for delivering hydrophobic agents into tumor tissue because it is highly concentrated and long-circulating in blood and has propensity of tumor enrichment.Herein,we synthesized lipid conjugated siRNAs(LsiRNAs),which showed high affinity to albumin.Mechanistically,LsiRNAs non-covalently bind to the hydrophobic core of albumin through its octadecyl tails.The small size of albumin/LsiRNAs allows the complex to penetrate tumor tissue efficiently.Biodistribution test proved that albumin extremely prolonged circulation time and increased tumor retention of associated LsiRNAs.Notably,LsiRNA against programmed death ligand-1(Pdl1)efficiently suppressed tumor growth as well as prolonged survival time of tumor bearing mice by increasing infiltration of CD8^(+)T cells as well as promoted the maturation of dendritic cells both in tumor and lymph.Together,LsiRNAs provide a simple but effective way for siRNA tumor delivery that“hitchhikes”on albumin.

Visualizing grain boundaries in monolayer MoSe2 using mild H2O vapor etching

Beyond graphene, two-dimensional （2D） transition metal dichalcogenides （TMDs） have attracted significant attention owing to their potential in next-generation nanoelectronics and optoelectronics. Nevertheless, grain boundaries are ubiquitous in large-area as-grown TMD materials and would significantly affect their band structure, electrical transport, and optical properties. Therefore, the characterization of grain boundaries is essential for engineering the properties and optimizing the growth in TMD materials. Although the existence of boundaries can be measured using scanning tunneling microscopy, transmission electron microscopy, or nonlinear optical microscop~ a universal, convenient, and accurate method to detect boundaries with a twist angle over a large scale is still lacking. Herein, we report a high-throughput method using mild hot H20 etching to visualize grain boundaries of TMDs under an optical microscope, while ensuring that the method is nearly noninvasive to grain domains. This technique utilizes the reactivity difference between stable grain domains and defective grain boundaries and the mild etching capacity of hot water vapor. As grain boundaries of two domains with twist angles have defective lines, this method enables to visualize all types of grain boundaries unambiguously. Moreover, the characterization is based on an optical microscope and therefore naturally of a large scale. We further demonstrate the successful application of this method to other TMD materials such as MoS2 and WSe2. Our technique facilitates the large-area characterization of grain boundaries and will accelerate the controllable growth of large single-crystal TMDs.

Cu/Co/Cr Nanocomposites Obtained from Hydrotalcite Precursors as Catalysts for Thermal Decomposition of Ammonium Perchlorate

A series of Cu/Co/Cr nanocomposites with different Cu/Co/Cr molar ratios were obtained by calcination of Cu/ Co/Cr hydrotalcites precursors, which were prepared by a co-precipitation reaction. X-ray diffraction, inductively coupled plasma analysis, and transmission electron microscopy were used to characterize the structure, composition, and mor- phology of Cu/Co/Cr nanocomposites. The results show that Cu/Co/Cr nanocomposites have both CuCr204 and CoCr204 spinel phase. The particle size of Cu/Co/Cr nanocomposites is 15-20 nm and the specific surface area is 95-115 m2/g. Cu/ Co/Cr nanocomposites were used as new catalysts for improving thermal decomposition of ammonium perchlorate （AP）. Their catalytic activities were investigated using differential thermal analysis and thermal gravimetric analyzer coupled with an online mass spectrometer. The results show that the decomposition temperature of AP lowered 132-146℃ by adding 4 wt% Cu/Co/Cr nanocomposites. Catalytic activities of the prepared nanocomposites depend on the calcinations temperature and addition amount of corresponding nanocomposites. The possible catalytic mechanism of Cu/Co/Cr nanocomposites was also studied and discussed.

Preparation of Ferrioxalate Submicrorods/Graphene Composites and Their Photocatalytic Properties

Ferrioxalate submicrorods/graphene composites were synthesized through a simple solvothermal process in a mixture of ethylene glycol and water. The in situ growth of ferrioxalate submicrorods and the reduction of graphene oxide （GO） were completed in a one-step reaction. Fourier transform infrared and Raman spectroscopy confirmed the reduction of GO. Uniform rod-like ferrioxalates with diameter of about 600 nm and length of several micrometers were well distributed on the graphene sheets. As-obtained composites exhibited better photocatalytic properties than pure ferrioxalate submicrorods. The influence of different contents of GO on photocatalytic performance was also investigated. A possible photocatalytic mechanism of ferrioxalate submicrorods/graphene composites was proposed.