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排序方式: 共有137条查询结果,搜索用时 31 毫秒
21.
《International Journal of Hydrogen Energy》2020,45(12):7468-7478
Mixed proton and electron conductor ceramic composites are among the most promising materials for hydrogen separation membrane technology especially if designed in an asymmetrical configuration (thin membrane supported onto a thicker porous substrate). However a precise processing optimization is needed to effectively obtain planar and crack free asymmetrical membranes with suitable microstructure and composition without affecting their hydrogen separation efficiency. This work highlights for the first time the most critical issues linked to the tape casting process used to obtain BaCe0.65Zr0.20Y0.15O3-δ – Ce0.8Gd0.2O2-δ (BCZY-GDC) asymmetrical membranes for H2 separation. The critical role of the co-firing process, sintering aid and atmosphere was critically investigated. The optimization of the production strategy allowed to obtain asymmetric membranes constituted by a dense 20 μm-thick ceramic-ceramic composite layer supported by a porous (36%) 750 μm-thick BCZY-GDC substrate. The asymmetric membranes here reported showed H2 fluxes (0.47 mL min−1 cm−2 at 750 °C) among the highest obtained for an all-ceramic membrane. 相似文献
22.
In this work, polysaccharide nanocrystals—rodlike cellulose whiskers (CWs)—were surface‐grafted with polycaprolactone (PCL) via microwave‐assisted ring‐opening polymerization, and filaceous cellulose whisker‐graft‐polycaprolactone (CW‐g‐PCL) nanoparticles were produced. Moreover, the resultant nanoparticles were incorporated into poly(lactic acid) (PLA) as a matrix, and they showed superior function for enhancing the mechanical performance of PLA‐based materials in comparison with platelet‐like nanoparticles of starch nanocrystal‐graft‐PCL. The optimal loading level of CW‐g‐PCL was 8 wt %, and this resulted in simultaneous enhancements of the strength and elongation of approximately 1.9‐ and 10.7‐fold, respectively, over those of the neat PLA material. In this case, the rigid CW nanoparticles contributed to the endurance of higher stress, whereas the grafted PCL chains improved the association between the PLA matrix and the CW‐g‐PCL filler and hence facilitated the transfer of stress to the rigid CW nanoparticles. Furthermore, such a fully biodegradable PLA‐based nanocomposite shows great potential for environmentally friendly materials because of its high mechanical performance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
23.
《Fuel Processing Technology》2004,85(1):31-42
Coal–water slurry (CWS) holds promise to offer a long-term alternative to fuel oil, and also it is being conceived as an attractive fuel for power generation industry in India. The essential requirements of the CWS technology, viz., the additive package, concentration of additives, particle size distribution (PSD) of coal, solids loading, methodology for CWS formulation and its rheological properties, have been discussed and reported here. The effect of the two newly developed anionic additives in the formulation of CWS has been studied. The basic parameters were established taking beneficiated Ledo coal samples with 9.7% ash content. Ball milling of the coal samples in a wet grinding process could produce particle size distributions most suited for highly loaded CWS. Coal loadings to the extent of 70% in the CWS have been achieved using a concentration of 0.8 wt.% (on coal charge) of the naphthalene-based additive referred to as ‘P’. Using 0.9 wt.% of the naphthalene-toluene-based additive denoted as ‘R’, a coal loading of 69% has been achieved. The viscosities of the slurries were found to be below 1000 mPa s. The shelf lives of slurries were found to be 22 and 20 days with the use of additives P and R, respectively, in the CWS formulation. The two additives functioned well in CWS formulation with Sirka coal having relatively higher ash content (14.4%). Using the specified concentration of the additives P and R, the solid loadings of 67% and 65%, respectively, could be obtained under the established parameters. The lower values of solids loading from Sirka coal than that from Ledo coal in CWS formulation may be attributed to the higher percentages of oxygen-containing functional groups (OOH and OCOOH), ash content and higher O/C ratio of Sirka coal. 相似文献
24.
25.
《Biomass & bioenergy》2002,22(4):295-304
We studied the production of furfural by acid hydrolysis of olive stones, which in Spain are an abundant lignocellulosic residue derived from the production of olive oil. We focused on the hydrolysis in dilute sulfuric acid (0.05 to ), at high temperature (220–240°C), and short reaction times, of a few minutes at the most. The experimental study was performed in a tubing-bomb reactor system that approximately reproduces the temperature profiles obtained in a continuous tubular reactor. We obtained maximum furfural yields ranging from 50% to 65% of the potential depending on acid concentration and temperature. 相似文献
26.
27.
《Ceramics International》2019,45(8):9799-9806
(Nb1-xTax)4AlC3 (x = 0–0.5) ceramics were prepared by the hot press sintering method. The XRD results show that the second phase (Nb1-xTax)C is formed when the Ta content increases to 25 mol%. The SEM micrographs show that (Nb1-xTax)C has a core/rim structure, whose formation mechanism was also investigated. Substituting some Ta for Nb can significantly improve the mechanical properties of Nb4AlC3. (Nb0.75Ta0.25)4AlC3 exhibits an excellent fracture toughness of 8.3 ± 0.3 MPa m1/2 at room temperature (RT). The highest Young's modulus (349 ± 16 GPa) and Vickers hardness (4.5 ± 0.3 GPa) at RT are exhibited by the (Nb0.5Ta0.5)4AlC3 sample, which correlate to increases of 18% and 80%, respectively, compared with those of Nb4AlC3. The flexural strengths of (Nb0.5Ta0.5)4AlC3 are 439 ± 18 MPa at RT and 344 ± 22 MPa at 1100 °C, which correlate to increases of 27% and 45%, respectively, compared with those of Nb4AlC3. The solid solution of Ta and the formation of (Nb1-xTax)C are beneficial to the strengthening of Nb4AlC3. The coefficient of thermal expansion (CTE) increases slightly from 7.08 × 10−6 K−1 for Nb4AlC3 to 7.24 × 10−6 K−1 for (Nb0.75Ta0.25)4AlC3 at 25–1400 °C. The thermal conductivity of (Nb0.75Ta0.25)4AlC3 (28.4–29.8 W/m·K) is higher than that of Nb4AlC3 (18.1–21.2 W/m·K) over the whole test range (25–1000 °C). Owing to their excellent mechanical and thermal properties, Ta-doped Nb4AlC3 ceramics have good potential as structural materials. 相似文献
28.
《Water science and technology》1998,37(4-5):353-357
The relationships between the structure of minimally perturbed activated sludge flocs and the sorption of organic contaminants were studied. Sorption, settling velocity, size distributions, floc structure and EPS composition were all examined. The results show significant removal of selected halogenated hydrocarbons and polycyclic aromatic hydrocarbons by biosorption to activated sludge flocs. However, statistically significant effects on the settling or size of the flocs caused by this sorption were not observed. The addition of chromium (Cr(III)) metal ions to the biomass caused observable changes in the floc structure and decreased ruthenium red binding to the acidic polysaccharides of the floc matrix. At low concentrations (0.6 mg/1), chromium caused an increase in the sorption of organic compounds to flocs, suggesting that changes in the floc structure can be induced, which can have an impact on the sorption of pollutants to the flocs. 相似文献
29.
《International Journal of Hydrogen Energy》2020,45(19):11062-11076
Cyclohexanone is largely generated in the direct or indirect conversion of lignin-derived bio-oils. Hence, the upgrading of cyclohexanone, i.e. deoxygenation in the presence of hydrogen is of great interest. In this regard, two nickel-molybdenum catalysts on alumina support were investigated in the temperatures up to 400 °C and pressures up to 15 bar. High activity, selectivity, and yield were achieved by utilizing these catalysts at the studied condition. The main products of the upgrading of cyclohexanone were C6, C7, and C12 cyclic, aromatic, and bicyclic including cyclohexane, cyclohexene, benzene, and cyclohexylbenzene. The results of the present study imply that these catalysts are beneficial in producing hydrocarbon-rich products from cyclohexanone and lignin-derived bio-oils. Based on the achievements of the present study, the nickel-molybdenum catalyst composed of 1.14 wt% nickel and 14.27 wt% molybdenum showed about 87%, 100%, and 116% conversion of cyclohexanone, total hydrocarbon selectivity, and total hydrocarbon yield, respectively. The optimum condition for obtaining such results was at 400 °C and 8 bar. 相似文献
30.