Spherical carbons: Synthesis,characterization and activation processes

Spherical carbons have been prepared through hydrothermal treatment of three carbohydrates (glucose, saccharose and cellulose). Preparation variables such as treatment time, treatment temperature and concentration of carbohydrate have been analyzed to obtain spherical carbons. These spherical carbons can be prepared with particle sizes larger than 10 μm, especially from saccharose, and have subsequently been activated using different activation processes (H₃PO₄, NaOH, KOH or physical activation with CO₂) to develop their textural properties. All these spherical carbons maintained their spherical morphology after the activation process, except when KOH/carbon ratios higher than 4/1 were used, which caused partial destruction of the spheres. The spherical activated carbons develop interesting textural properties with the four activating agents employed, reaching surface areas up to 3100 m²/g. Comparison of spherical activated carbons obtained with the different activating agents, taking into account the yields obtained after the activation process, shows that phosphoric acid activation produces spherical activated carbons with higher developed surface areas. Also, the spherical activated carbons present different oxygen groups’ content depending on the activating agent employed (higher surface oxygen groups content for chemical activation than for physical activation).     

Fouling tendency of ash resulting from burning mixtures of biofuels. Part 1: Deposition rates

Specified mixtures of peat with bark and peat with straw were burned in a lab-scale entrained flow reactor that simulates conditions in the superheater region of a conventional biomass-fired boiler. The deposition rates were recorded on an air-cooled probe that was inserted into the reactor at the outlet. For both mixtures, the deposition behaviour followed a non-linear pattern, which suggests that physico-chemical interaction between the types of ash has taken place. Peat seems to act as a cleansing agent in all mixtures with straw, while it acts as a cleansing agent in mixtures with bark only up to a share of 50 wt% bark. Between 50 and 100 wt% bark, it seems that peat adds to the deposition. The results indicate that it is possible to burn up to 30 wt% bark (renewable biofuel and pulp mill waste) and up to 70 wt% straw (renewable biofuel and agricultural waste) in mixtures with peat (CO₂-neutral fossil fuel) without encountering increased deposition rates.     

Research State of Disposable Non-plastic Straws

The continuous production of disposable plastic straw places a high demand on global petrochemical resources and a significant environmental burden. Biodegradable and eco-friendly straws have therefore been studied and produced worldwide. This article briefly introduces the characteristics of paper straws and polylactic acid (PLA) straws, and focuses on edible straws made using, e.g., hydrophilic colloids, zein, and starch. Raw-material selection, preparation methods, advantages, and defects of straws are summarized, to provide a reference for the development and research of eco-friendly straws.     

颜料涂布纸的涂层结构与性能

介绍了颜料涂布纸涂层的形成过程及其特性,阐述了涂料在原纸上固化时涂料和原纸的相互作用及形成的涂层结构和涂布纸性能之间的关系,并总结了颜料、胶粘剂、涂布方式等对涂层结构及其性能的影响.     

Production strategies of asymmetric BaCe0.65Zr0.20Y0.15O3-δ – Ce0.8Gd0.2O2-δ membrane for hydrogen separation

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 BaCe_0.65Zr_0.20Y_0.15O_3-δ – Ce_0.8Gd_0.2O_2-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.     

滑石颜料高剪切流变性能的研究

使用毛细管高剪切黏度仪研究了滑石颜料分散体系的高剪切黏度性能,以及pH值、固含量、不同分散剂和润湿剂、不同粒径分布对滑石分散体系高剪切黏度的影响。同时还研究了滑石与GCC及高岭土混合浆料的高剪切黏度性能。结果表明,滑石含量越高、粒度越细,其分散浆料的高剪切黏度值越大。同时发现,滑石高剪切黏度受分散剂和润湿剂的影响不大。提高pH值有利于降低滑石分散体系的高剪切黏度。滑石与GCC混合浆料的高剪切黏度随着GCC粒度的变细而降低。当滑石与GCC的体系中加入高岭土后,混合浆料的高剪切黏度大幅增大,且随着GCC粒度的变细而增大。     

Effects of polymer‐grafted natural nanocrystals on the structure and mechanical properties of poly(lactic acid): A case of cellulose whisker‐graft‐polycaprolactone

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     

High-concentration coal–water slurry from Indian coals using newly developed additives

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 (O_OH and O_COOH), ash content and higher O/C ratio of Sirka coal.