A series of Ce-incorporated SBA-15 mesoporous materials were synthesized through direct hydrothermal synthesis method and further impregnated with 12 wt.% Ni. The samples were characterized by ...ICP-AES, XRD, N
2 physisorption, XPS, TPR, H
2 chemisorption, TGA, temperature-programmed hydrogenation (TPH) and TEM measurements. The low-angle XRD and N
2 physisorption results showed the Ce successfully incorporated into the framework of SBA-15. The catalytic properties of these catalysts were investigated in methane reforming with CO
2. The Ce/Si molar ratio had a significant influence on the catalytic performance. The highest catalytic activity and long-term stability were obtained over the Ni/Ce-SBA-15 (Ce/Si = 0.04) sample. The improved catalytic behavior could be attributed to the cerium impact in the framework of SBA-15, where cerium promoted the dispersion of nano-sized Ni species and inhibited the carbon formation. In comparison with the effect of CeO
2 crystallites in SBA-15, cerium in the framework of SBA-15 promoted the formation of the nickel metallic particles with smaller size. The XRD and TGA results exhibited that carbon deposition was responsible for activity loss of Ni/SBA-15 and Ni/Ce-SBA-15 (Ce/Si = 0.06) catalysts. TEM results showed that the hexagonal mesopores of SBA-15 were still kept intact after reaction and the pore walls of SBA-15 prevented the aggregation of nickel.
Graphene oxide (GO) and reduced graphene oxide (RGO) platelets were pillared with carbon nanotubes (CNTs) by using the chemical vapor deposition (CVD) method with acetonitrile as the carbon source ...and nickel nanoparticles as the catalyst, aimed to prepare graphene-based materials with a high surface area and a good electrical conductivity. Characterization data showed that the composite materials with RGO layers pillared by CNTs formed a robust three-dimensional (3D) porous structure of specific surfaces as high as 352 m2/g. The amount and length of the CNT pillars connecting the RGO layers were controlled by changing the amount of the nickel metal catalyst and the time of CVD. The CNT-pillared RGO composite materials exhibited an excellent visible light photocatalytic performance in degrading dye Rhodamine B because of the unique porous structure and the exceptional electron transfer property of graphene. Such CNT−RGO composites represent a new family of innovative carbon materials for visible-light-activated photocatalysis.
This review provides a summary of recent research progress towards biomass-derived carbon electrode materials, including specific cellulose-, lignin- and hemicellulose-derived carbon electrode ...materials, for supercapacitors. Various lab-scale methods for preparing biomass-derived carbons, including carbonisation and/or activation conditions are discussed. Control over the pore structure, electrical conductivity, and surface functional groups of biomass-derived carbons for enhancing electrocapacitive performance is analysed. Emphasis is made on discussing cellulose-, lignin- and hemicellulose-derived carbon electrode materials for supercapacitor applications. Future research trends in this field are projected.
In order to study the temporal and spatial variations of PM2.5 and its chemical compositions in the region of Beijing, Tianjin, and Hebei (BTH), PM2.5 samples were collected at four urban sites in ...Beijing (BJ), Tianjin (TJ), Shijiazhuang (SJZ), and Chengde (CD), and also one site at Shangdianzi (SDZ) regional background station over four seasons from 2009 to 2010. The samples were weighted for mass concentrations and analyzed in the laboratory for chemical profiles of 19 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, Sr, Ti, V, and Zn), eight water-soluble inorganic ions (Na+ , NH4+ , K+ , Mg2+ , Ca2+ , Cl- , NO3- , and SO42- , and carbon fractions (OC and EC). The concentrations of PM2.5 and its major chemical species were season dependent and showed spatially similar characteristics in the plain area of BTH. The average annual concentrations of PM2.5 were 71.8-191.2 μg m-3 at the five sites, with more than 90% of sampling days exceeding 50 μg m-3 at BJ, TJ, and SJZ. PM2.5 pollution was most serious at SJZ, and the annual concentrations of PM2.5 , secondary inorganic ions, OC, EC, and most crustal elements were all highest. Due to stronger photochemical oxidation, the sum of concentrations of secondary inorganic ions (NH4+ , NO3- , and SO42- was highest in the summer at SDZ, BJ, TJ, and CD. Analysis of electric charges of water-soluble inorganic ions indicated the existence of nitric acid or hydrochloric acid in PM2.5 . For all five sites, the concentrations of OC, EC and also secondary organic carbon (SOC) in the spring and summer were lower than those in the autumn and winter. SOC had more percentages of increase than primary organic carbon (POC) during the winter. The sums of crustal elements (Al, Ca, Fe, Mg, Ti, Ba, and Sr) were higher in the spring and autumn owing to more days with blowing or floating dust. The concentrations of heavy metals were at higher levels in the BTH area by comparison with other studies. In Shijiazhuang and Chengde, the PM2.5 pollution was dominated by coal combustion. Motor vehicle exhausts and coal combustion emissions both played important roles in Tianjin PM2.5 pollution. However, motor vehicle exhausts had played a more important role in Beijing owing to the reduction of coal consumption and sharp increase of cars in recent years. At SDZ, regional transportation of air pollutants from southern urban areas was significant.
This paper describes the syntheses and electrochemical properties of a new niobate compound, aluminum niobate (AlNb11O29), for Li+ storage. AlNb11O29-microsized particles and nanowires were ...synthesized based on the solid-state reaction and solvothermal methods, respectively. In situ X-ray diffraction results confirmed the intercalating mechanism of Li+ in AlNb11O29 and revealed its high structural stability against cycling. The AlNb11O29 nanowires with a novel bamboo-like morphology afforded a large interfacial area and short charge transport pathways, thus leading to the observed excellent electrochemical properties, including high reversible Li+-storage capacity (266 mA h g–1), safe operating potential (around 1.68 V), and high initial Coulombic efficiency (93.3%) at 0.1 C. At a very high rate (10 C), the AlNb11O29 nanowires still exhibited a capacity as high as 192 mA h g–1, indicating their good rate capability. In addition, at 10 C, 96.3% capacity was retained over 500 cycles, indicating superior cycling stability. A full cell fabricated with AlNb11O29 nanowires as the anode and LiNi0.5Mn1.5O4 microparticles as the cathode delivered a high energy density of 390 W h kg–1 at 0.1 C. This work suggests that the AlNb11O29 nanowires hold a great promise for the development of high-performance lithium-ion batteries for large-scale energy-storage applications.
A mobilized dilation angle model for rocks Zhao, X.G.; Cai, M.
International journal of rock mechanics and mining sciences (Oxford, England : 1997),
04/2010, Letnik:
47, Številka:
3
Journal Article
Recenzirano
Experimental and field observations of rock failure show that the failure process is closely associated with rock dilation, an indicator of volumetric increase during rock deformation. The most ...common concept used to describe dilation is the dilation angle. The conventional Mohr–Coulomb model considering strain-softening often makes an assumption of constant dilation, but it is observed that the approach is not successful in characterizing the nonlinear deformation behavior of rocks. In the present study, based on published data acquired from modified triaxial compression tests with volumetric strain measurement, a mobilized dilation angle model considering the influence of both confining stress and plastic shear strain is established. Based on the model response and in combination with the grain size description and the uniaxial compressive strength, the model parameters for four rock types (coarse-grained hard rock, medium-grained hard rock, fine-medium-grained soft rock, and fine-grained soft rock) are suggested. For coal and quartzite representing fine-grained soft rock, and coarse-grained hard rock, respectively, the dilation angle model is used to predict the volumetric-axial strain relationships, and the predictions are found to be in good agreement with experimental results.
Chemically modified graphene and polyaniline (PANI) nanofiber composites were prepared by in situ polymerization of aniline monomer in the presence of graphene oxide under acid conditions. The ...obtained graphene oxide/PANI composites with different mass ratios were reduced to graphene using hydrazine followed by reoxidation and reprotonation of the reduced PANI to give the graphene/PANI nanocomposites. The morphology, composition, and electronic structure of the composites together with pure polyaniline fibers (PANI-F), graphene oxide (GO), and graphene (GR) were characterized using X-ray diffraction (XRD), solid-state 13C NMR, FT-IR, scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). It was found that the chemically modified graphene and the PANI nanofibers formed a uniform nanocomposite with the PANI fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge−discharge process when used as supercapacitor electrodes. A specific capacitance of as high as 480 F/g at a current density of 0.1 A/g was achieved over a PANI-doped graphene composite. The research data revealed that high specific capacitance and good cycling stability can be achieved either by doping chemically modified graphenes with PANI or by doping the bulky PANIs with graphene/graphene oxide.
Pancreatic cancer (PC) is one of the most lethal cancers known worldwide, and its prognosis is poor in most patients. Exosomes are nanosized extracellular vesicles, which are released from various ...cell types. They are involved in cellular communication. The diagnosis and treatment of PC were improved substantially with exosomes. In this study, we isolated PC‐derived exosomes and investigated their proteomic profile. Then, we conducted bioinformatic analysis on proteomic data. Differential ultracentrifugation was performed to isolate exosomes from human serum samples and four PC cell lines. Transmission electron microscopy and Western blot analysis were used to characterize the isolated exosomes. Liquid chromatography coupled with tandem mass spectrometry was conducted to identify the proteome of serum exosomes. Proteomic analysis demonstrated that all the serum exosomes were derived from three cohorts of human subjects; these serum exosomes contained a total of 655 proteins, out of which 315 proteins overlapped with ExoCarta database. Gene oncology and kyoto encyclopedia of genes and genomes analyses provided the functional annotation of the proteome. Interestingly, 18 or 14 proteins were upregulated and 11 or 14 proteins were downregulated in serum exosomes derived from patients with PC as compared with in serum exosomes derived from healthy volunteers or from pancreatitis patients respectively. Annexin A11, a calcium‐dependent phospholipid‐binding protein, was expressed in a PC cell line (CFPAC‐1)‐derived exosomes and in tumor tissues of patients with PC, respectively. Our data provided a basic foundation for further studies on the protein composition of PC‐derived exosomes and its involvement in PC biology.
Functionalized graphene was prepared by reducing functionalized graphene oxide with poly(diallyldimethylammonium chloride) (PDDA), transferring the surface charge of reduced graphene oxide (RGO) from ...negative to positive. A composite material of functionalized RGO with manganese dioxide (MnO2) nanosheets can be obtained by dispersing negatively charged MnO2 nanosheets on the functionalized RGO sheets via an electrostatic coprecipitation method. The structures of composites were investigated by high-resolution transmission electron microscopy (HRTEM), which indicated that the MnO2 nanosheets dispersed on functionalized RGO sheets, exhibiting a layered structure. The composite material exhibited enhanced capacitive performances than those of pure functionalized RGO and Na-typed birnessite (Na/MnO2) sheets, attributing to the synergic effect of both components. Additionally, over 89% of original capacitance was retained after 1000 cycles, indicating a good cycle stability of the composite materials.
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