Flexible Low-Melting Point Radiation Shielding Materials: Soft Elastomers with GaInSnPbBi High-Entropy Alloy Inclusions

A polydimethylsiloxane (PDMS) matrix soft elastic composite material with low-melting-point GaInSnPbBi high-entropy alloy (LHEA) inclusions is prepared to evaluate its radiation shielding performance. The LHEA is composed of two different three-component eutectic microstructures, which are grown in a mixed manner to form a complex eutectic structure. The inclusions have excellent mechanical properties that matched the deformation of the PDMS matrix. To evaluate the interaction of the shielding material with photons, the Monte Carlo N-Particle Extended and XCOM codes are used to determine the shielding parameters of the LHEA/PDMS composites, such as mass attenuation coefficient, linear attenuation coefficient, half-value layer, tenth value layer, mean free path, and effective atomic number. The composite with 50-vol% LHEA has the best radiation shielding properties, validated by medical X-ray imaging experiments. The excellent shielding properties of the flexible lightweight composites are attributed to the higher mass attenuation coefficient of the LHEA inclusions than that of lead.     

Relationship between amounts of low-melting-point eutectics and hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification

A systematical study on the relationship between the amounts of different eutectic phases especially the low-melting-point (LMP) eutectics and the hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification was performed. By controlling the concentrations of major alloying elements (Cu, Mg), the amounts of LMP eutectics at the final stages of solidification were varied and the corresponding hot tearing susceptibility (HTS) was determined. The results showed that the Al−4.6Cu−0.4Mg (wt.%) alloy, which contained the smallest fraction of LMP eutectics among the investigated alloys, was observed to be the most susceptible to hot tearing. With the amount of total residual liquid being approximately the same in the alloys, the hot tearing resistance is considered to be closely related to the amounts of LMP eutectics. Specifically, the higher the amount of LMP eutectics was, the lower the HTS of the alloy was. Further, the potential mechanism of low HTS for alloys with high amounts of LMP eutectics among ternary Al−Cu−Mg alloys was discussed in terms of feeding ability and permeability as well as total viscosity evolution during solidification.     

40%唑醚·啶酰菌水分散粒剂配方及工艺研究

通过对润湿剂、分散剂、填料等进行筛选,确定40%唑醚·啶酰菌水分散粒剂配方。分散剂采用Mortwet D425(4%)、AJ-002(2%)、REAX910(2%)与聚羧酸盐分散剂SP-2836(2%)或Geropon T36(2%)复配,以K12为润湿剂,玉米淀粉为填料。所制水分散粒剂有较高的悬浮率,较好的热稳定性。生产中水分散粒剂烘干优选流化床沸腾烘干方式,不同的捏合设备以及捏合时间对产品性能有影响,但粉碎方式对产品影响不大。     

芯片强化散热研究新领域——低熔点液体金属散热技术的提出与发展

近年来,高集成度计算机芯片、光电器件等引发的热障问题,已成为制约其持续发展的技术瓶颈之一。围绕这一紧迫现实需求,提出将室温下呈液体状态的低熔点金属或其合金作为冷却流动工质,以发展先进芯片散热器的技术观念,并在相应的理论分析、试验研究及实际器件的研制等方面取得了进展。随后,国外也启动了类似研究,相应进展立即在产业界及学术界产生重要反响。种种态势表明,液体金属芯片散热技术已成为计算机热管理领域内极具探索价值的新前沿。由于液体金属热导率远高于常规流体,因而在传热效果上可望显著优于传统的液冷方法,该方法的建立为发展高性能芯片冷却技术开辟了一条全新的途径。回顾新方法提出的过程,归纳出其中有待解决的一些重要科学问题,并对其应用前景进行展望。     

聚丙烯酸锂-碱金属盐复合物的离子导电性

以丙烯酸和氢氧化锂为原料用溶液聚合法合成聚丙烯酸锂(PAALi),将其熔于LiClO4/LiNO3/LiOAc低共熔盐中制备了一种新型的聚合物电解质材料,其室温电导率可达6×10-5S·cm-1。用红外光谱(IR)、X射线衍射(XRD)进行了表征。详细讨论了PPALi,低温共熔盐以及冷却处理方式对离子电导率的影响。研究结果表明,PAALi的加入增加了体系的载流子数,提高了Li 的迁移率;低温共熔盐的组成对固体电解质的电导率具有决定性的作用;快速冷却样品是提高聚合物电解质电导率的有效方法。     

低熔点合金/聚合物复合材料的研究进展

低熔点合金/聚合物复合材料是一类新型的功能复合材料.其中的低熔点合金可以在聚合物加工的温度范围内转变为液态,为在加工过程中实现填料的形态转变和导电复合材料中导电通道的设计提供了可能.概述了以低熔点合金为导电填料的导电塑料和导电胶粘荆的研究进展,其中有关低熔点合金在加工过程中的尺寸和形态变化的研究工作值得关注.此外,还概述了低熔点合金/聚合物的流变性质的研究情况.最后指出了研究中存在的问题和有待继续深入研究的方向.     

竹纤维/低熔点涤纶复合毡的性能研究

采用物理方法将竹纤维与双组份低熔点涤纶按一定比例混合,经过开松、梳理、铺网等工序制备出多层纤维网,利用热风烘压方法将多层纤维网制成毡基材料。利用扫描电镜观察并表征了竹纤维和复合毡的形态;测试分析了竹纤维的结晶度、官能团结构、纤维直径及其分布、拉伸断裂强力性能;对双组份低熔点涤纶的长度与熔点进行了表征分析;对竹纤维/双组份低熔点涤纶复合毡的拉伸断裂强力性能、透气性与传热性能进行了分析评价。结果表明,纤维复合毡的性能与竹纤维的含量相关,断裂强力与传热性能及竹纤维含量呈正相关,透气性随着竹纤维含量的增加先变大后变小。     

低温共熔盐LiClO4-LiNO3-LiBr的制备与表征

选取5种常见锂盐LiClO_4、LiBO_2、LiAc、LiNO_3和LiBr,熔融复合后形成共熔盐。通过两次正交实验优化锂盐配比,制备了一种新型低温共熔盐。采用X射线衍射(XRD)和差热分析(DTA)对共熔盐的结构和热性能进行了表征。研究结果表明:当熔盐组成为LiClO_4∶LiNO_3∶LiBr=3∶4∶2(摩尔比)时,其室温电导率最高(3.1110~(-4)S·cm~(-1)),熔点最低(128℃)。熔盐的组成对其电导率和熔点有很大影响。制备低温共熔盐应尽量选择晶格能低、熔点低的锂盐。