酸酶法制备纳米豆渣纤维素

以富含纤维素的豆渣为原料,采用酸预处理粉碎后的豆渣,预处理条件为3 mol/L的HCl,水解温度100℃,水解时间120 min,HCl溶液添加量与原料比值为50∶1(mL∶g)。以酸预处理干燥后得到的样品作为纤维素酶水解的原料,通过单因素和正交实验,获得制备纳米纤维素的最佳酶解条件:酶用量3 000U/g,pH5.0,温度55℃,时间6 h,液料比20 mL/g。通过扫描电镜和透射电镜检测,制备出的纳米豆渣纤维素呈微球状,粒度为15～50nm。     

层状纳米晶Mn_3(PO_4)_2·3H_2O的室温固相合成及表征

以MnSO4.H2O和K2HPO4.3H2O为原料,在表面活性剂聚乙二醇(PEG)-400的存在下,通过室温下研磨反应物进行固相反应,然后在室温下保持混合物5 h,接着用水洗去混合物中的可溶性无机盐并于80℃下干燥,即得层状纳米晶Mn3(PO4)2.3H2O。产品Mn3(PO4)2.3H2O和它的热分解产品用TG/DTA,IR,XRD,SEM,UV-V is和磁化率表征。结果表明,80℃下干燥5 h所得的产品具有高的结晶度[空间群Pmnm(59)],其平均一次粒径为19 nm,平均夹层距离为0.811 2 nm。产品Mn3(PO4)2.3H2O的磁化率分析表明该化合物具有铁磁性质,其铁磁排序温度约为17 K。     

改性非晶和纳米晶FINEMET合金的显微硬度研究

本文研究了用元素W部分替代典型FINEMET合金中Nb和Fe的新型合金Fe73.3Cu1 Nb1 .5W1 .7Si1 3.5B9,在淬火态和不同退火温度及保温时间下 ,结合不同载荷大小和加载时间测试合金带芯部的显微硬度。随着纳米晶化的进行 ,自由体积缺陷含量和纳米晶晶界比例的变化会显著影响Fe73.3Cu1 Nb1 .5W1 .7Si1 3.5B9合金的显微硬度 ;合金在非晶态下有一定的压痕尺寸效应 ,而经过 4 5 0℃和 6 0 0℃退火 1h ,压痕尺寸效应消失 ;在 5 5 0℃退火温度下 ,在 0 .1kgf～ 0 .2kgf之间压痕尺寸效应不明显 ;合金的显微硬度变化趋势不符合超塑性波动公式。     

纳米介孔α- Al2O3制备工艺及性能

以十六烷基三甲基溴化铵(CTAB)为模板剂,以Al(NO3)3和NH3·H2O为原料制备AlOOH勃姆石溶胶,干燥后变成干凝胶,经1 100℃煅烧2 h变成α-Al2O3。通过热分析、X射线衍射(XRD)分析、透射电镜分析(TEM)及N2吸附-脱附等测试对样品进行了表征。结果表明,勃姆石在110 0℃转变成α-Al2O3,随CTAB增多,比表面积和孔体积有最高值,其一次颗粒平均直径约17 nm,气孔孔径约16 nm。     

源于食品加工副产物纳米纤维素晶体的制备及其在食品中的应用

近年来,作为一种环境友好材料——纳米纤维素,其制备及在材料、食品、化工、医药等领域的应用备受人们关注,其中纳米纤维素晶体具有高长径比、高比表面积、高结晶度、高机械强度和良好的热稳定性等优良特性。在介绍纳米纤维素晶体制备方法的基础上,对源于食品加工副产物纳米纤维素晶体的理化特性(形貌、结晶度、稳定性等)及主要应用方面(作为食品包装材料增强剂、Pickering乳液稳定剂、食品配料等)进行了全面综述,并对纳米纤维素晶体研究存在的问题及今后的发展方向进行了展望。     

电沉积超细晶与纳米晶镍镀层的摩擦学行为比较

采用无/有柔性摩擦辅助电沉积技术在不含添加剂的Watts镀液中制备了超细晶和纳米晶镍镀层。对比研究了两种镍镀层的显微结构、纳米压痕力学性能以及干摩擦磨损行为。研究结果表明,纳米晶镍具有比超细晶镍更加细小均匀的晶粒尺寸、更大的纳米压痕硬度、弹性模量以及硬模比。2种镀层的主要磨损机制均为粘着磨损,但因载荷不同而表现出不同的摩擦学行为。在低载荷(1~3 N)下,纳米晶镍的表面粗糙度低,磨损表面相对平整致密,因而摩擦系数相对较低;在高载荷(5 N)下,纳米晶镍的氧化磨屑疏松,磨损表面较为粗糙,因而摩擦系数相对较高;在测试载荷条件下,纳米晶镍的磨痕深度和磨损体积更小,其耐磨性更优。     

Grain growth and thermal stability of nanocrystalline Ni–TiO2 composites

The grain growth and thermal stability of nanocrystalline Ni–TiO₂ composites were systematically investigated. The nanocrystalline Ni–TiO₂ composites with different contents of TiO₂ were prepared via electroplating method with the variation of TiO₂ nano-particles concentration. The effect of TiO₂ content on the grain size, phase structure and microhardness was investigated in detail. The corresponding grain growth and diffusion mechanisms during the heating process were also discussed. The optimal microhardness of HV₅₀ 270 was achieved for the composite with addition of 20 g/L TiO₂ nano-particles after annealing at 400 °C for 90 min. The calculation of the activation energy indicated that lattice diffusion dominated at high temperatures for the nanocrystalline Ni–TiO₂ composites. It was indicated that the increase of TiO₂ nano-particles content took effect on restricting the grain growth at high temperatures by increasing the grain growth activation energy.     

纳米晶纤维素悬浮液流变性能的研究

采用TAARES/RFS型高级旋转流变仪系统研究了纳米晶纤维素悬浮液的稳态、动态流变性能。稳态流变性能研究表明,在低浓度时(0.5%),纳米晶纤维素悬浮液的粘度随剪切速率的增大而降低,达到一定值后即趋于稳定,而在较高浓度时,纳米晶纤维素悬浮液的粘度则一直随剪切速率的增大而不断降低;动态流变性能研究表明,在较高浓度时(1.5%),纳米晶纤维素悬浮液的粘度随频率的增大有规律地下降;动态时间扫描结果表明,当浓度较高时(1.5%),纳米晶纤维素悬浮液的粘度随时间的增加而增大。     

On the Development and Applications of Cellulosic Nanofibrillar and Nanocrystalline Materials

Nanoscience, where physics, chemistry, biology and materials science converge, deals with the manipulation and characterization of matter at molecular to micron scale. Nanotechnology is the emerging engineering discipline that applies nanoscience to create products. Because of their size, nanomaterials have the ability to impart novel and/or significantly improved physical (strength, stiffness, abrasion, thermal), chemical (catalytic, ion‐exchange, membranes), biological (anti‐microbial, compatibility) and electronic (optical, electrical, magnetic) properties. While chemistry and physics of simple atoms and molecules are fairly well understood, predictable and no longer considered overly complex, serious attempts to bridge across the length scales from nano to macro remain a major challenge, and will occupy researchers and scientists for years ahead. This review paper highlights the potential significant benefits emanating from fibre engineering and selective design of lignocellulosics using evolutionary developmental processes with the objective of producing high value‐added products of superior end‐use performance for existing and new markets. The development and application of nanotechnologies to increase the potential utilization of renewable biomaterials so as to reduce supply chain costs (better with less material) and add functionality will improve the competitiveness of forestry materials and consolidate their utilization in "smart" packaging, E‐paper, advanced engineering and structural composite materials, and cosmetics.