Effect of nitriding atmosphere on the morphology of AlN nanofibers from solution blow spinning

High purity AlN fiber is a promising thermal conductive material. In this work, AlN fibers were prepared using solution blow spinning followed by nitridation under N₂ or NH₃ atmosphere. Soluble polymer, such as polyaluminoxane, and allyl-functional novolac resin were adopted as raw materials to form homogeneous distribution of Al₂O₃ and C nanoparticles within the fibers, which could inhibit the growth of alumina crystal and promote their nitridation process. The effect of nitriding atmosphere on the fiber morphology was investigated. XRD results showed that complete nitridation was achieved at 1300 °C in the NH₃ or at 1500 °C in the N₂ atmosphere. Hollowed fiber structure was observed when fiber was nitrided in N₂ at high temperature, which was caused by gaseous Al gas diffusion, and this phenomenon was eliminated in NH₃ atmosphere. The nitridation mechanisms in different atmosphere were analyzed in detail. It was demonstrated that the nitridation of Al₂O₃ fibers in the NH₃ atmosphere offered the favored AlN morphology and chemical quality. Flexible AlN fiber with O content of 0.7 wt% was achieved after nitriding in NH₃ at 1400 °C. The high quality AlN can be used in thermal conductive composite materials.     

高过滤性能石墨烯复合纳米纤维膜的制备及性能

将石墨烯(GR)纳米颗粒掺杂到聚丙烯腈(PAN)纺丝溶液中,利用静电纺丝技术制备石墨烯/聚丙烯腈(GR/PAN)复合纳米纤维膜。研究PAN质量分数、GR用量、纺丝电压及接收距离对GR/PAN复合纳米纤维膜形貌和过滤性能的影响,发现最优纺丝工艺参数为PAN质量分数14.0%、GR用量1.5%、纺丝电压26 kV、接收距离14 cm、注射速度1 mL/h。此最优纺丝工艺参数制备的GR/PAN复合纳米纤维膜的过滤效率为98.86%,过滤阻力为110.30 Pa。     

Electrochemical hydrogen storage performance of as-cast and as-spun RE-Mg-Ni-Co-Al-based alloys applied to Ni/MH battery

The La-Mg-Ni-Co-Al-based AB₂-type La_0.8–xCe_0.2Y_xMgNi_3.4Co_0.4Al_0.1 (x=0, 0.05, 0.1, 0.15, 0.2) alloys were prepared via melt spinning. The analyses of the X-ray diffraction (XRD) and scanning electron microscopy (SEM) proved that the experimental alloys contain the main phase LaMgNi₄ and the second phase LaNi₅. Increasing Y content and spinning rate lead to grain refinement and obvious change of the phase abundance without changing phase composition. Y substitution for La and melt spinning make the life-span of the alloys improved remarkably, which is attributed to the improvement of anti-oxidation, anti-pulverization and anti-corrosion abilities. In addition, the discharge capacity visibly decreases with increasing the Y content, while it firstly increases and then decreases with increasing spinning rate. The electrochemical kinetics increases to the optimum performance and then reduces with increasing spinning rate. Moreover, all the alloys achieve to the highest discharge capacities just at the initial cycle without activation.     

安泰贝抗菌黏胶大提花面料的开发

安泰贝抗菌黏胶纤维与精细棉混纺,在纺纱过程中需要对安泰贝抗菌黏胶纤维进行预处理,需合理调整流程及工艺参数;对织造过程中整经注意事项、浆料选择及织机参数的设定进行了说明;采用酶退浆后进行烧毛、冷轧堆前处理与染色,工艺参数与染化料用量控制在较低限度内;后整理选用亲水性柔软剂,可以赋予织物持久亲水性。通过工艺调整,成功开发了安泰贝抗菌黏胶大提花面料。     

镍基高温合金锥筒形件拉深旋压成形机理研究

针对镍基高温合金因加工硬化严重成形时极易产生破裂和起皱等典型缺陷的问题,以锥筒形壳体类零件为对象,提出了一种由锥形预制坯经过真空固溶处理后拉深旋压成形锥筒形件的方法,并对其成形机理进行了研究。基于Abaqus/Explicit平台,建立了锥筒形件拉深旋压有限元模型,分析了成形过程中的瞬态等效应力、等效塑性应变、切向应力、壁厚及三向应变分布规律。结果表明:在旋压成形过程中,最大瞬态等效应力位于旋轮接触区及附近区域、最大瞬态等效塑性应变位于坯料口部;瞬态切向压应力最大值位于旋轮接触区,而瞬态切向拉应力最大值位于旋轮接触区附近的两侧区域。筒形段中部壁厚减薄,而坯料口部壁厚增厚。旋压成形试验表明,锥形预制坯经拉深旋压后可获得壁厚均匀的锥筒形件。     

GO/PI复合纳米纤维的制备及其过滤性能研究

为制备高过滤效率、低过滤阻力的空气过滤材料,将氧化石墨烯纳米颗粒(GO)掺杂到聚酰亚胺(PI)纺丝溶液中,制备氧化石墨烯/聚酰亚胺(GO/PI)复合纳米纤维过滤材料。通过观察其形貌、过滤性能来确定最优纺丝工艺参数。结果表明:当PI质量分数为30%,GO质量分数为1%,纺丝电压为25 kV,接收距离为20 cm时,复合纳米薄膜的纤维形貌较好,过滤性能优良。与PI纯组分纳米纤维过滤材料相比,GO/PI复合纳米纤维过滤材料的过滤性能更好,制得GO/PI复合纳米纤维膜的平均孔径为1.8μm,过滤效率为99.68%,过滤阻力仅为85.35 Pa。     

Solution blow spun titania nanofibers from solutions of high inorganic/organic precursor ratio

In this work titania nanofibers were produced from different precursor solutions by solution blow spinning. Hydrophilic polyvinylpyrrolidone, hydrophobic poly(vinyl acetate) and amorphous and semi-crystalline poly(lactic acid) polymers were used with green-solvents and titanium isopropoxide as the inorganic precursor. Hybrid nanofibers with high inorganic loading content were successfully produced from all precursor solutions. The fibers were calcined at different annealing temperatures for evaluation of phase transitions. The minimum temperature to obtain pure titania fiber was found to be 500 °C, as assessed by thermal characterization. Anatase was the unique polymorph formed at this annealing temperature. This is of paramount importance due to its photocatalytic character. Calcination at high temperatures showed that rutile slightly appeared at 600 °C for the polyvinylpyrrolidone-based system and showed a strong peak at 700 °C for all systems, co-existing with anatase as minor phase. The use of amorphous and semicrystalline poly(lactic acid) polymers did not influence the anatase crystal size and phase conversion. This was found to be dependent on the annealing temperature and medium acidity, as currently found in powder synthesis.     

直纺亮光抗倒伏波浪扁平涤纶FDY的开发

探讨了直纺83 dtex/114 f波浪扁平涤纶全拉伸丝(FDY)的工艺制备过程。试验证明,在熔体输送温度276~282℃,纺丝温度286~290℃,喷丝板规格DIO φ104 mm-114孔、"王"字形,环吹风压10~15 Pa,含油率1.1%~1.2%,卷绕速度3 800~4 200 m/min的工艺参数下纺制83 dtex/114 f波浪扁平涤纶FDY时,生产稳定,满卷率高,外观情况良好,袜带均匀亮丽,可批量生产。此新产品可用于制作高档布艺沙发表层面料,具有抗倒伏、色彩艳丽等功效。     

自旋对角接触球轴承弹流润滑与油膜刚度的影响

根据角接触球轴承自旋运动特征，同时考虑弹流润滑效应，建立角接触球轴承考虑自旋运动的弹流润滑模型；采用多重网格法求解弹性变形，利用有限差分法迭代求解雷诺方程，得到较为精确的数值解；分析不同赫兹接触压力、滚道表面粗糙度下自旋对角接触球轴承弹流润滑和油膜刚度的影响。结果表明：考虑自旋时随着Hertz接触压力、自旋角速度增大，油膜厚度减小，油膜压力增大，油膜承压区域呈细长状，并向接触中心靠近；随着滚道表面粗糙度幅值增大，油膜压力和膜厚均出现了波动，且考虑自旋运动时，轴承油膜厚度明显减小，油膜局部压力峰值更大；随着卷吸速度、润滑油黏度增大，油膜刚度减小，而考虑自旋运动时油膜刚度值更大；随着自旋角速度增大，油膜刚度逐渐增大。