The Experts below are selected from a list of 65718 Experts worldwide ranked by ideXlab platform
Yiqi Yang - One of the best experts on this subject based on the ideXlab platform.
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preparation of lightweight polypropylene composites reinforced by cotton stalk fibers from combined steam flash explosion and Alkaline Treatment
Journal of Cleaner Production, 2014Co-Authors: Xiuliang Hou, Fangfang Sun, Dandan Yan, Zhen Dong, Yiqi YangAbstract:Abstract A new method of combined steam flash-explosion and Alkaline Treatment (SFE-AT) was developed to extract cellulose fibers from bark of cotton stalks, and lightweight composites with favorable properties were made from the obtained fibers and polypropylene (PP). It was reported that the cellulose fibers from bark of cotton stalks had higher mechanical properties than those from most lignocellulosic byproducts. However, conventional method of using strong Alkaline condition (30–100 g/L NaOH) for extraction of cellulose fibers from lignocellulosic byproducts led to environmental pollution and high cost. In this study, bark of cotton stalks were treated using three methods, including Alkaline Treatment (AT), steam flash-explosion (SFE) and SFE-AT. The different cotton stalk fibers were blended with PP fibers and compression-molded into composites under optimized conditions (temperature of 170 °C, pressure of 3 MPa, 4 min). The results showed that PP composites reinforced by cotton stalk fibers from SFE-AT had the best mechanical properties and stability to water, attributing to the largest surface area and highest cellulose content of cotton stalk fibers by SFE-AT. SFE could separate bark of cotton stalks with high efficiency and subsequent mild AT could sufficiently remove the non-cellulose impurities by using NaOH solution with concentration as low as 5 g/L. Ultra-lightweight PP composites with the bulk density of 0.27 g/cm3 could be prepared with cotton stalk fibers by SFE-AT. Overall, the method of SFE-AT with high efficiency and low cost could be very useful in exploring industrial applications of bark of cotton stalks and other lignocellulosic byproducts.
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chemical free extraction of cotton stalk bark fibers by steam flash explosion
Bioresources, 2014Co-Authors: Xiuliang Hou, Fangfang Sun, Li Zhang, Jun Luo, Yiqi YangAbstract:Cotton stalk bark fibers (CSBF) were extracted by steam flash explosion, completed within 0.09 s, and the extracted fibers were compared with those obtained by conventional Alkaline Treatment. Results indicate that the optimum steam pressure was 2.5 MPa when steaming time was set to 2 min for extracting CSBF. Under the optimized conditions, the obtained CSBF had a cellulose content of 72%, length of 48 mm, fineness of 45 dtex, crystallinity index of 68, moisture regain of 8%, water retention of 98%, and tensile strength of 2.4 cN/dtex, which were similar to results obtained by conventional Alkaline Treatment. Compared with bark of cotton stalks, CSBF had lower moisture regain and water retention, and higher onset decomposition temperature. The results show that moderate steam flash explosion is a chemical-free, quick, and effective method for exploring the industrial applications of bark of cotton stalks as natural cellulose fibers.
Julien Bras - One of the best experts on this subject based on the ideXlab platform.
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Alkaline Treatment combined with enzymatic hydrolysis for efficient cellulose nanofibrils production
Carbohydrate Polymers, 2020Co-Authors: Gabriel Banvillet, Gael Depres, Naceur Belgacem, Julien BrasAbstract:Abstract Cellulose nanofibrils were efficiently produced from eucalyptus fibers using a combined NaOH and enzymatic Treatment followed by a pilot scale grinding process. The structural changes of fibers were assessed after NaOH Treatments at 5, 10 and 15 wt% concentrations. A progressive shift from a cellulose I to a cellulose II crystalline structure was observed with X-ray diffraction (XRD) and nuclear magnetic resonance (NMR). The further enzymatic hydrolysis was improved for the NaOH treated samples. The increase of crystallinity indices due to enzymatic hydrolysis was of + 4.7 %, + 3.5 %, and +10.3 % for samples treated with NaOH 5, 10 and 15 wt% respectively, and DP values were drastically reduced to 340, 190 and 166 respectively. A morphological analysis underlined an optimum with the combination of NaOH 10 wt% and enzymatic hydrolysis. This Treatment followed by the grinding process resulted in CNF with a rigid structure, with diameters ranging from 10 to 20 nm and lengths between 150 and 350 nm. A multi-scale analysis enabled to study the impact of this combined Treatment on CNF properties and energy consumption. A decrease in mechanical properties of nanopapers was observed for the combined Treatment and NaOH Treatment alone compared to enzymatic hydrolysis alone, with Young’s modulus of 8.94, 4.84 and 11.21 GPa respectively. However, optical properties were improved, with transmittance values of 42.2, 15.4 and 7.1 % respectively. This new preTreatment can therefore lead to CNF with tunable properties depending on the application, with possible industrialization thanks to the reduction of energy needs.
Javier Bilbao - One of the best experts on this subject based on the ideXlab platform.
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Improving the DME steam reforming catalyst by Alkaline Treatment of the HZSM-5 zeolite
Applied Catalysis B-environmental, 2012Co-Authors: Jorge Vicente, Ana G. Gayubo, Javier Ereña, Andrés T. Aguayo, Martin Olazar, Javier BilbaoAbstract:Abstract Dimethyl ether (DME) steam reforming for hydrogen production has been studied on a bifunctional catalyst prepared by the (wet) physical mixing (at 50 wt%) of a metallic function of CuO–ZnO–Al2O3 (Cu/Zn/Al atomic ratio = 4.5:4.5:1.0, prepared by co-precipitation) and an acidic function of HZSM-5 zeolite modified by Alkaline Treatments of different severity. The runs have been carried out in a fluidized bed reactor. The results obtained by using treated HZSM-5 zeolites and γ-Al2O3 as acid functions have been compared. The Alkaline Treatment affects both the acid properties of the zeolite (attenuating total acidity and acid strength) and its porous structure (increasing the mesoporous surface and decreasing the microporous volume and BET surface area). The attenuation in acidity hinders the formation of undesired hydrocarbons from oxygenates (methanol + DME). Consequently, Alkaline Treatment (with 0.2–0.4 M NaOH solutions for 300 min) is suitable for improving the kinetic performance of the bifunctional catalyst, as it provides high selectivity and a high yield of H2 at 300 °C without hydrocarbon formation, as well as minimizing CO formation and avoiding deactivation by Cu sintering. The catalyst is stable, and its kinetic performance remains constant throughout long runs.
Kewei Xu - One of the best experts on this subject based on the ideXlab platform.
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characterization and stability of hydroxyapatite coatings prepared by an electrodeposition and Alkaline Treatment process
Journal of Biomedical Materials Research, 2001Co-Authors: Tao Fu, Jian Lu, Kewei XuAbstract:Hydroxyapatite (HA) coatings on titanium alloy substrates were prepared by an Alkaline Treatment of electrodeposited precursors. The structure, residual stress, and bond strength of the coatings were investigated. Test results showed that the coatings processed in this study exhibited fairly low tensile residual stress, high crystallinity, and were free of an amorphous phase. The bond strength of the coatings increased with the decrease of current density in the range of 0.2–15 mA/cm2, and reached 14 MPa at 0.2 mA/cm2. Evaluation of the coatings was performed together with the evaluation of the plasma-sprayed HA coatings immersed in distilled water. It was revealed that the dissolution and bond strength degradation of the coatings were much lower than those of the plasma-sprayed HA coatings. © 2000 John Wiley & Sons, Inc.
Yong Han - One of the best experts on this subject based on the ideXlab platform.
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characterization and stability of hydroxyapatite coatings prepared by an electrodeposition and Alkaline Treatment process
Journal of Biomedical Materials Research, 2001Co-Authors: Yong HanAbstract:Hydroxyapatite (HA) coatings on titanium alloy substrates were prepared by an Alkaline Treatment of electrodeposited precursors. The structure, residual stress, and bond strength of the coatings were investigated. Test results showed that the coatings processed in this study exhibited fairly low tensile residual stress, high crystallinity, and were free of an amorphous phase. The bond strength of the coatings increased with the decrease of current density in the range of 0.2-15 mA/cm(2), and reached 14 MPa at 0.2 mA/cm(2). Evaluation of the coatings was performed together with the evaluation of the plasma-sprayed HA coatings immersed in distilled water. It was revealed that the dissolution and bond strength degradation of the coatings were much lower than those of the plasma-sprayed HA coatings.