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1.
Cellulose microfibrils were isolated from the skin of Opuntia ficus indica (prickly pear fruits). Defatted skin powder was processed through consecutive extraction steps in order to remove mucilage, pectin and hemicelluloses. The cellulosic residue was made up of disencrusted cell-ghosts, having ovoid or elongated shapes, as revealed by optical microscopy. Transmission electron microscopy showed that, at the ultrastructural level, the cell walls of these cell-ghosts consisted of a loose network of cellulose microfibrils. This residue was subjected to mechanical homogenisation, leading to a stable and non-flocculating suspension by cellulose microfibril individualisation. This cellulosic material was characterised in terms of chemical composition, morphology and crystallinity, using sugar analyses, transmission electron microscopy and X-ray diffraction, as well as solid state NMR 13C spectroscopy.  相似文献
2.
以漂白阔叶木浆为原料,通过控制浓度0.1%左右硫酸溶液(以下简称超低酸)水解温度和水解时间以及后续机械球磨时间制备不同特性的纤维素纳米纤丝(CNF),考察了不同过程参数对CNF得率的影响,并使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、热重分析仪(TGA)和纳米粒度仪分析了CNF的表面形貌、结晶度、热稳定性及粒度均一性变化。结果表明,水解温度由100℃增加到140℃,CNF得率降低了37.6个百分点,CNF的聚合物分散性指数(PDI)数值逐渐减小,CNF中长纤维和块状纤维逐渐减少,当水解温度达到140℃时,CNF长度约100 nm,分布均匀;而CNF的结晶度随水解温度的增加呈先升高后略微降低的趋势;水解时间由1 h增加到3 h,CNF得率从62.8 %下降到49.8 %,CNF的PDI数值和结晶度值均呈现先上升后下降规律,当水解时间达到3 h时才能获得直径约100 nm左右的CNF;球磨时间由8 h增加到24 h,CNF的直径均已达到100 nm,CNF马尔文粒度的PDI数值不断上升,CNF颗粒均一性下降。球磨16 h制备的CNF热稳定性提高。  相似文献
3.
利用阳离子纳米纤维素与瓜尔胶组成双元体系,研究其对烟草浆料的滤水留着性能。结果表明,在单元体系中,单独添加0.18%阳离子纳米纤维素时较好,浆料的滤水时间为23.8 s,填料留着率为19.3%,滤液阳离子需求量82.2μmol/L;单独添加0.1%瓜尔胶时较好,浆料的滤水时间为19.3 s,填料留着率为31.7%,滤液阳离子需求量84.8μmol/L。在用量为0.18%的阳离子纳米纤维素与用量0.1%的瓜尔胶组成的双元体系下,浆料滤水时间为18.6 s,填料的留着率为40.1%,滤液的阳离子需求量为73.8μmol/L。另外,在造纸法烟草薄片的实验中,阳离子纳米纤维素与瓜尔胶组成的双元体系较单独使用瓜尔胶或阳离子纳米纤维素可明显改善烟草浆料的滤水留着性能,有效降低滤液对阳离子的需求量。  相似文献
4.
In this study, the characteristics of nanocellulose extracted from bleached softwood and hardwood pulps by formic acid hydrolysis followed by TEMPO-mediated oxidation were compared using transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared analysis (FT-IR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The experimental results showed that the nanocellulose products derived from spruce pulp exhibited a relatively larger particle size, higher crystallinity, and higher thermal stability, compared with the corresponding products obtained from aspen pulp under the same conditions. Furthermore, the study helped establish that the properties of the nanocellulose products were highly dependent on the nature of the starting materials under identical processing conditions.  相似文献
5.
In this study, cellulose nanocrystals (CNC) with surface carboxylic groups were prepared from bleached softwood pulp by hydrolysis with concentrated citric acid at concentrations of 60 wt%~80 wt%. The solid residues from acid hydrolysis were collected for producing cellulose nanofibrils (CNF) via post high-pressure homogenization. Citric acid could be easily recovered after hydrolysis reactions through crystallization due to its low water solubility or through precipitation as a calcium salt followed by acidification. Several important properties of CNC and CNF, such as dimension, crystallinity, surface chemistry, thermal stability, were evaluated. Results showed that the obtained CNC and CNF surfaces contained carboxylic acid groups that facilitated functionalization and dispersion in aqueous processing. The recyclability of citric acid and the carboxylated CNC/CNF give the renewable cellulose nanomaterial huge potential for a wide range of industrial applications. Furthermore, the resultant CNC and CNF were used as reinforcing agents to make sodium carboxymethyl cellulose (CMC) films. Both CNC and CNF showed reinforcing effects in CMC composite films. The tensile strength of CMC films increased by 54.3% and 85.7% with 10 wt% inclusion of CNC and CNF, respectively. This study provides detailed information on carboxylated nanocellulose prepared by critic acid hydrolysis; a sustainable approach for the preparation of CNC/CNF is of significant importance for their various uses.  相似文献
6.
近年来,纤维素纳米纤丝(CNF)因其独特的物理化学性能受到了广泛关注。当前,CNF主要采用化学或酶处理等方法对纤维进行预处理,再通过机械法对预处理后的纤维进行机械处理而得到。随着人们环保意识的日渐增强,可回收的有机酸水解法,低共熔溶剂预处理结合机械法制备CNF等已成为CNF制备领域的研究热点。本文综述了CNF的制备和改性研究进展,总结了CNF在制备和改性过程中存在的问题。此外,讨论了不同制备方法的优缺点,并介绍了环保、高效的CNF制备方法及其最新的应用领域。  相似文献
7.
董凤霞  戴磊 《中国造纸》2020,39(5):63-69
纤维素纳米纤丝(CNF)作为一种来源丰富的可再生纳米材料,具有优异的机械性能、高比表面积及化学可修饰性等优点,采用物理或化学交联所制备的CNF基水凝胶具有较好的机械性能和溶胀率等,在工业废水处理领域具有良好的应用前景。本文主要介绍了纯CNF水凝胶和CNF纳米复合水凝胶的相应制备方法及性能,同时也介绍了其在工业废水中对染料或重金属离子吸附方面的应用进展,最后指出了CNF基水凝胶在废水处理应用中存在的问题及未来主要研究方向。  相似文献
8.
为改善羧甲基纤维素钠(sodium carboxymethyl cellulose,CMC)薄膜的机械性能,利用2,2,6,6-四甲基哌啶氮氧化物氧化法制备的纳米纤维素纤丝(2,2,6,6-tetramethyl-1-piperidinyloxy-oxidized cellulose nanofibrils,TOCNs)增强CMC膜的拉伸强度,利用阳离子聚丙烯酰胺(cationic polyacrylamide,CPAM)在水溶液中电解形成的阳离子与其他两者在水中形成的COO-之间的静电作用及化学反应增强其断裂伸长率,从而制备强度及韧性两者兼优的生物可降解薄膜。研究发现,按照m(CMC)∶m(TOCNs)∶m(CPAM)为50∶10∶1配比制备的复合膜较纯CMC膜拉伸强度增加约177%,断裂伸长率增加约36%,透光率、热稳定性均有提高,但阻氧性略有下降,结果表明,TOCNs的添加能明显提高CMC膜的拉伸强度、热稳定性,CPAM的加入能提高CMC膜的断裂伸长率和透光性,三者之间存在着相互作用和良好的相容性,三者共混能明显改善CMC膜的性能。  相似文献
9.
太阳能光热转化材料在海水淡化应用方面具有巨大的潜力和广阔的前景,因此开发水蒸发效率高、成本低、可生物降解的光热转化材料对海水淡化技术的发展有着重要的意义。本研究采用纤维素纳米纤丝(CNF)为原料,辅以炭黑、胶黏剂等,制备出炭黑/CNF复合光热转化材料,并对其光吸收性能、海水平均蒸发效率、隔热性能进行了研究。结果表明,该材料具有良好的光吸收性能、海水平均蒸发效率和隔热性能。最佳炭黑用量为1.0%,此时其太阳能总吸收率为92.05%,海水平均蒸发速率可达到1.17 kg/(m2•h),导热系数为0.05 W/(m•K)。  相似文献
10.
Recently, cellulose nanofibril (CNF) has emerged as a promising, sustainable reinforcement with outstanding potential in material science. Owing to the properties of CNF, it has been explored in food, cosmetic, and pharmaceutical applications, as well as in industrial applications such as paints, drill muds, packaging, and papermaking. The application of CNF in papermaking is expected to be implemented in the near future to broaden the commercial market of cellulose. Numerous studies and patents have reported on the manufacturing, properties, and applications of nanocellulose. This present paper focuses on the recent progresses in the application of CNF as a wet-end additive in papermaking.  相似文献
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