超声波预处理对对位芳纶纤维结构的影响

采用粘度法、XRD、光学显微镜及SEM等测试手段对超声波预处理前后对位芳纶纤维的相对分子质量、聚集态结构、形态结构进行研究.探讨超声波功率和处理时间对芳纶纤维结构的影响.结果显示:超声波(600W)处理6rain后,对位芳纶纤维的相对分子质量由2.70万变为2.62万,变化不大;结晶度和晶粒尺寸也变化不大;未处理对位芳纶纤维表面光滑,处理后表面有微细纤维;随着超声波功率增大和预处理时间增加,细纤维化程度提高.     

不同预处理方法对稻草纤维性能的影响

通过物理性超声波和化学性微波酯化相结合的处理方法,对稻草纤维表面进行改性研究,分析了改性后与水的表面接触角、纤维表面形貌变化及化学结构的变化。结果表明各处理改善了秸秆纤维表面的浸润性,增加了纤维的比表面积和反应性能,提高了表面自由基浓度,增强了其在材料领域中的应用。     

超声作用对芳纶纤维表面性质的影响

芳纶纤维表面性质是影响其复合材料界面粘接性能的重要因素。本文作者采用超声技术对芳纶纤维表面进行改性处理,研究了超声作用下,芳纶纤维表面化学组成和表面结构的变化。结果表明:超声处理后,纤维表面极性官能团含量增加,比表面积加大,从而改善了芳纶纤维和环氧树脂之间的浸润性。     

超声蚀刻对PAN纤维组织结构与性能的影响

用傅里叶红外光谱(FTIR)、广角X射线衍射(WAXD)、扫描电镜(SEM)等方法测定并分析超声蚀刻对聚丙烯腈(PAN)纤维的化学结构、结晶、形态结构和机械性能的影响,为利用超声蚀刻方法制备电镜样品、研究PAN纤维结构奠定实验基础。实验结果表明:超声蚀刻处理对PAN纤维化学结构没有影响;溶解的PAN分子量随着超声时间延长而降低,未溶解的PAN分子量基本没有变化;这种处理会使纤维的结晶度和晶粒尺寸均小幅下降;经过超声蚀刻后纤维表面出现大量的原纤结构,能够实现原纤分离;这种处理对纤维的线密度影响不大,而纤维强度、断裂伸长率和初始模量均有所下降。     

不同脱墨方式对纤维形态及超分子结构的影响

对桉木浆进行了碱性脱墨、中性脱墨和酶法脱墨,采用扫描电镜(SEM)、X射线衍射(XRD)及红外光谱(FT-IR)等表征手段研究了不同脱墨方式对纤维形态及超分子结构的作用,并讨论了纤维微观结构的变化与纤维润胀性能的关系。结果表明,脱墨方式对纤维形态及超分子结构都有明显的影响,其中碱性脱墨对纤维形态及超分子结构的作用最为明显,中性脱墨次之,酶法脱墨最小。同时,经脱墨处理后,桉木浆纤维保水值总体呈上升趋势,其中碱性脱墨后保水值增加最大。     

PBO纤维表面超声化学处理工艺及作用机理

研究了多聚磷酸无水乙醇溶液和超声波附加作用处理聚对苯撑苯并双口恶唑(PBO)纤维表面的工艺。利用扫描电镜和纤维电子强力仪等评价了表面处理后PBO纤维的表面形貌、拉伸强度以及与环氧树脂的界面结合性能等,探讨了PBO纤维超声化学表面作用机理。结果表明,当多聚磷酸与无水乙醇体积比为1∶1、超声设备功率54W、反应时间4min时,PBO纤维的表面处理均匀,与原丝相比,单丝拉伸强度只降低了5.7%,而单丝拔出强度则提高了67.2%。超声波的空化作用导致溶液中多聚磷酸分子分散均匀性提高、羟基自由基含量增加,以及纤维表面粗糙度提高,是PBO纤维表面处理质量改善的主要原因。     

常温超声波处理对芳砜纶纤维界面性能的影响

为提高芳砜纶(PSA)纤维表面润湿性和基体界面黏结性能,用超声波在常温下对芳砜纶纤维进行表面改性。研究纤维改性前后润湿性能、界面剪切强度(IFSS)、断裂强度和摩擦性能的变化。用水滴吸收时间和单丝拔抽实验,分析改性前后PSA纤维表面润湿性能和界面剪切强度;并用场发射扫描电子显微镜(FESEM)和X射线光电子能谱仪(XPS)分析纤维表面的形貌和化学元素变化。结果表明,经超声波改性后,PSA纤维的润湿性能大幅提高,水滴吸收时间从大于400s降至13s,且随处理时间增加润湿性能越好;PSA纤维与环氧树脂基体界面黏结性能大幅提高,较未经超声波处理纤维上升44%。同时,经超声波处理后,PSA纤维表面摩擦性能增强;表面氧、氮元素含量分别上升30.2%和18.3%,纤维表面极性基团增加。但是,处理时间过长会使纤维的断裂强度下降幅度加大,综合考虑实验的最佳处理时间为80min。     

超声波在碳纤维水泥基材料制备中的应用研究

为提高碳纤维在水泥基复合材料中的分散性,提出了两种改进的超声波辅助制备工艺——超声波分散纤维和超声波分散纤维加少量硅灰.应用电阻测试法评价了这两种工艺对碳纤维水泥浆的匀化效果,同时研究了超声波处理时间对复合材料匀化效果的影响.研究结果表明:由于超声波空化作用和机械作用可使纤维得到预分散,两种改进的超声波辅助制备工艺都可以提高碳纤维水泥基复合材料的均匀性;而且超声波处理时间越长,匀化效果越好,但达到一定时间后,匀化效果趋于饱和.     

容器壁中超声余振信号的透射衰减特性及其应用

文章对残存于容器壁内的超声波余振信号的衰减特性进行了分析和实验测定，结果表明，由于固液界面中超声波透射性强，所以当容器内部为液态介质时，容器壁中超声余振信号衰减快。而固气界面中超声波的透射性弱，故当容器内部为气态介质时，容器壁中超声余振信号衰减慢。实验表明，两种工况下容器壁中超声余振信号的衰减时间之比可达1：2—1：3。因此，通过检测容器壁中超声余振信号持续时间的大小，即可判定容器内部液位是否达到换能器的安装点。基于这一原理，文章中提出了一种新的超声波非介入式定点液位检测方法及实施方案。     

纤维基纳米结构材料的界面性能

试验研究超声波处理对采用磁控溅射技术在涤纶纺粘非织造材料表面生长Al掺杂ZnO(AZO)纳米结构材料界面性能的影响。结果表明,纤维在温水(45℃~50℃)中经超声波处理30 min后,纤维表面"粗化",表面性能得到了改善,形成了许多极其细微的凹槽,纳米结构薄膜在生长时,犹如在纤维上生了"根",从而提高了纤维与纳米结构薄膜的界面结合牢度。     

半纤维素含量对蔗渣纤维基膜结构和性能的影响

目的 为了更好地了解甘蔗渣半纤维素在加工过程中与原纤化纤维之间的化学反应性,并为甘蔗木聚糖生物聚合物在材料和产品中的应用创造可能性。方法 以甘蔗渣纤维为原料,通过机械法制备原纤化纤维,采用NaOH对纤维素进行处理。通过纳米粒度仪(FLA)、激光粒度仪(LPS)、接触角测试仪(CA)、水蒸气透过率测试仪(WVTR)、扫描电镜(SEM)、X-射线衍射(XRD)等手段对原纤化纤维悬浮液和纤维基薄膜进行表征。研究处理后纤维素悬浮液的组成、粒径与电荷量,以及纤维基薄膜的表观形貌、纤维结构和性能的变化。结果 经质量分数大于10%的NaOH处理后,半纤维质量分数降低约6%,纤维素的结晶区发生变化,纤维悬浮液的稳定性大幅度降低。当半纤维素质量分数大于20%时,原纤化纤维薄膜具有优异的水蒸气阻隔性能及疏水性能,接触角为94°±4°。结论 蔗渣中的半纤维素与原纤化纤维之间的相互作用及半纤维素侧基取代反应对纤维素材料的组成、结构和性能有重要影响。     

Effect of Ultrasonic Treatment on the Magnetization Enhancement of Fe3O4 Nanocrystallines

The effect of ultrasonic treatment on the morphology changes and magnetization enhancement of Fe₃O₄ nanocrystallines (NCs) is reported. The samples were characterized by various techniques such as X-ray diffraction, scanning transmission electron microscopy, etc. The crystallinity and the morphology of Fe₃O₄ NCs are obviously changed when the as-grown Fe₃O₄ NCs are irradiated by ultrasonic for 30 min. The magnetization of these Fe₃O₄ NCs after ultrasonic radiation is found to be 20 % enhanced compared to the sample without this treatment. A well dispersive magnetic fluid with the chemisorbed –OH as the surfactant is composed after ultrasonic irradiation. The mechanism of the morphology changes, magnetization enhancement and dispersibility of Fe₃O₄ NCs are also discussed in detail.     

Biomimetic synthesis of hierarchical crystalline hydroxyapatite fibers in large-scale

Crystalline hierarchical hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂, HAp)] fibers were successfully synthesized via a biomimetic route by using cotton cloth as a natural bio-template. The effects of pH value, aging time, ultrasonic cleaning time, and calcination temperature on the purity and morphology of the resulting hydroxyapatite (HAp) were monitored by scanning election microscope (SEM), X-ray diffraction (XRD), and infrared spectrophotometer (IR) to obtain an optimized reaction condition, namely, pH 9, ultrasonic cleaning for 1 min, aging for 24 h, and calcination at 600 °C for 4 h. We found that the natural cellulose could not only control the morphology of HAp but also lower its phase transformation temperature. The impact of this method lies in its low cost and successful production of large-scale patterning of three-dimensional hierarchical HAp fibers.     

Low density polyethylene composites containing cellulose pulp fibers

Unbleached and bleached Kraft cellulose pulp fibers modified with a long chain carboxylic acid, i.e. oleic acid in cold plasma conditions have been used as reinforcements in low density polyethylene (LDPE). The purpose of the modification is to enhance the interfacial adhesion between cellulose and matrix and to increase the dispersability. Composites containing up to 10 wt.% of untreated and modified cellulose pulp fibers with LDPE were prepared by melt mixing. The samples were characterized by processing behavior, mechanical and rheological properties, SEM, contact angle measurements, TGA and DSC. It was found that when the modified pulp fibers were incorporated into composites matrix, most of the properties have been improved.     

超声波作用下对位芳纶纤维的超微结构

用X射线衍射和扫描电子显微镜（SEM）对超声波处理的对位芳纶纤维的结晶结构和形态结构进行研究,以揭示对位芳纶纤维的超微结构特点。研究表明,对位芳纶纤维具有皮芯层结构和多重原纤结构特征,纤维表层大量原纤沿纤维轴向高度取向,直径约600 nm;纤维内部圆柱状的微原纤平行于纤维轴,直径为30 nm,且微原纤间存在缝隙和孔洞;...     

Fabrication of advanced “green” composites using potassium hydroxide (KOH) treated liquid crystalline (LC) cellulose fibers

Advanced green composites having excellent strength and stiffness were fabricated using liquid crystalline (LC) cellulose fibers and soy protein isolate (SPI) resin. Further, LC cellulose fibers were treated with potassium hydroxide (KOH) to improve their tensile strength and Young’s modulus by increase the crystallinity of cellulose. The improvements were significant when the treatment was carried out while keeping the fibers under tension. The Young’s modulus (stiffness) of the LC cellulose fibers increased by about 33 % from 47.8 to 63.7 GPa and the strength increased by about 18 % from 1483 MPa to 1749 MPa. X-ray diffraction (XRD) study of the LC cellulose fibers showed over 50 % increase in crystallinity after the KOH treatment. The mechanical properties of the LC cellulose fiber-reinforced composites were also high and improved further when the KOH treated fibers were used. With 65 % fiber volume it should be possible to obtain composites with strength above 1020 MPa and modulus of over 37 GPa, making them truly advanced green composites that could be used for structural applications.     

Synthesis and characterization of core–shell SiO2@(Er3+,Yb3+):Lu2O3

We synthesized crystalline Erbium Er³⁺ and Ytterbium Yb³⁺ codoped -Lu₂O₃ nanolayers on SiO₂ microspheres using the modified Pechini method. Two different kinds of precursors, nitrates and chlorides, have been used leading to a layer-to-layer morphology and necklaces structures, respectively. In both cases, the size of nanocrystallites constituting the optical active layer is around 5 nm. We performed X-ray powder diffraction to confirm the cubic crystalline structure of the sesquioxides layer. High resolution transmission electron microscopy analyses corroborate the crystalline nature of the layer. The optical emission of Er³⁺ in the visible range has been recorded.     

Synthesis of SiC nanorods from bleached wood pulp

Unbleached and bleached soft wood pulps have been used as templates and carbon precursors to produce SiC nanorods. Hydrolyzed tetraethylorthosilicate (TEOS), silicic acid was infiltrated into the pulps followed by a carbothermal reduction to form SiC nanorods at 1400 °C in Ar. Residual carbon formed along with SiC was removed by gasification at 700 °C in air. The SiC materials prepared from unbleached pulp were non-uniform SiC with a thick SiO₂ coating, while the SiC nanorods prepared from the bleached pulp were uniform and straight with dimensions of 250 nm in diameter and 5.0 mm long. The formation of uniform camelback structure of SiC in the reaction between silica and bleached pulp is attributed to more silica deposited in the amorphous region of cellulose.     

Physicochemical characterization of pulp and nanofibers from kenaf stem

The aim of this study was to isolate cellulose nanofibers from kenaf (Hibiscus cannabinus) stem using chemo-mechanical treatments. The fiber purification method included pulping and bleaching processes whereas the mechanical treatments employed to isolate kenaf nanofibers were grinding and high pressure homogenizing. Kenaf nanofibers were found to have diameters in the range of 15-80 nm while most nanofibers have diameters within the range 15-25 nm. Fourier transform infrared spectroscopy (FTIR) showed that the chemical treatments removed lignin and most of the hemicelluloses from the fibers. The thermal characteristics of the fibers were analyzed using the technique of thermogravimetric analysis (TGA) which demonstrated that these characteristics were enhanced noticeably both for the bleached pulp and nanofibers. On the other hand, the X-ray analysis indicated that both chemical and mechanical treatments can improve the crystallinity of fibers.     

Potential of all‐cellulose composites in corrugated board applications: Comparison of chemical pulp raw materials

All‐cellulose composites (ACCs) were produced using various commercially available chemical pulps by partial dissolution method using an aqueous zinc chloride (ZnCl₂) solvent. Characterization methods used for defining material performance, keeping especially corrugated board products in mind, were as follows: scanning electron microscopy, tensile strength, 2‐point bending stiffness, concora medium test, and short‐span crush test. Hardwood (bleached eucalyptus), softwood (bleached spruce, bleached and unbleached pine), speciality softwood pulps (sulphite dissolving with 530 and 398 mL/g intrinsic viscosities), and annual plant pulp (bleached abaca) were investigated to give a broad overview of the potential for making ACCs. Softwood pulps, especially bleached, showed highest increase in mechanical properties across the board. Hardwood pulp showed relatively good results, and the selected annual plant pulp (abaca) responded partially negatively to treatment. Comparing unbleached and bleached softwood ACCs, it seems that bleaching is beneficial for tensile properties. However, when material comes under compressive or bending loads, unbleached pulp performs very well. Comparing sulphite dissolved pulps, it could be proven that pulps with higher intrinsic viscosities, thus higher polymerization grade, respond better to partial dissolution. It was proven that a wide set of pulps, also of lesser cellulose purity, used in the paper industry are viable for ACC production. Furthermore, results from short‐span crush test and concora medium tests show high potential of ACCs for corrugated board applications.