聚脲涂层的耐酸、碱、盐腐蚀试验及结果

采用海水浸泡、盐雾试验、硫酸浸泡和氢氧化钠浸泡腐蚀等方法,研究了聚脲涂层的耐腐蚀性能,并采用扫描电镜(SEM)观察了涂层老化后的表面形貌.结果表明,海水浸泡180天后,聚脲涂层的拉伸强度仅下降4%,断裂伸长率增加了1.2%.盐雾试验180天后涂层拉伸强度下降了25.7%,断裂伸长率增加了4.2%,涂层表面局部有孔洞,涂...     

丁腈橡胶混炼胶5870紫外辐照行为研究

将航空用NBR5870丁腈橡胶混炼胶在美国航空材料协会规定的紫外环境下辐照一定时间,测试分析了紫外辐照不同时间的丁腈橡胶的表面形貌,红外光谱,邵氏硬度,拉伸性能。研究结果表明:随着紫外辐照时间的增加,丁腈橡胶的表面出现了固体颗粒状物,分析是原料中的添加剂SiO2析出;傅里叶红外分析显示,双键的峰值减弱,邵氏硬度逐渐增大,而拉伸强度和断裂伸长率持续下降。表明航空丁腈橡胶在紫外辐照环境下辐照63 d后出现了一定程度的老化现象。     

通用不饱和聚酯加速老化失效机理研究

本文研究通用不饱和聚酯树脂人工加速老化失效机理。对通用不饱和聚酯浇注体试样进行了人工加速热氧老化及人工加速氙灯老化试验,用显微镜观察了试样的外观形貌,测试了试样的拉伸强度和弯曲强度,对试样进行了动态力学性能分析（DMA）分析,用FT-IR分析了树脂化学基团的变化。研究表明：不饱和聚酯在老化早期有后固化现象,随着加速老化时间的延长,试样表面出现裂纹并逐渐增加,而拉伸强度,弯曲强度和玻璃化转变温度（Tg）均降低;人工加速氙灯老化所造成的失效比热氧老化要严重得多。分析表明紫外线是造成不饱和聚酯的老化失效的主要影响因子。     

有机玻璃湿热老化行为研究

在3种环境条件下（50℃、85%RH湿热空气,50℃、自来水,50℃、3%NaCl溶液）,对YB-DM-11有机玻璃进行了近60d的加速老化实验,测试了试样的拉伸强度、弯曲强度、黄色指数和吸湿量等性能,得到了这些参量随老化时间的变化规律。同时研究了老化前后YB-DM-11有机玻璃试样的红外吸收光谱特性,探讨了YB-DM-11有机玻璃的老化机理。结果表明：有机玻璃湿热老化以物理变化为主,化学变化非常微弱。湿热老化过程中有机玻璃力学性能的下降,主要归因于水分消弱了高分子链段间的范德华力,同时水分的增塑作用促进了高分子链段的运动。     

核电厂海水蝶阀密封圈失效原因分析

电厂维修人员在日常检修期间发现两台海水蝶阀密封不严，解体后发现其橡胶密封圈存在不同程度的撕裂。通过对失效橡胶密封圈及备件的宏观观察、材质鉴定、硬度测试、拉伸测试和压缩永久变形等分析手段，发现失效密封件为丁腈橡胶，橡胶本体已严重老化，对比新备件，拉伸性能和压缩永久变形各参数已下降，橡胶密封圈在阀门反复开关动作中受到挤压最终导致了开裂。     

典型航空有机玻璃在实验室加速条件下的老化规律

针对典型航空有机玻璃YB-DM-11开展热空气老化、紫外老化、盐雾试验等,通过分析拉伸性能、透光率、抗应力银纹强度等随试验时间的变化,总结典型航空有机玻璃在实验室加速条件下的老化规律。结果表明:YB-DM-11的拉伸强度在95℃热空气老化和紫外老化条件下出现了总体上升趋势,而在盐雾试验条件下出现了下降,影响的拉伸强度加速老化条件的显著性排序为:盐雾试验,紫外老化,95℃热空气老化;YB-DM-11的抗应力银纹强度在95℃热空气老化条件和盐雾试验条件下,其抗应力银纹强度随老化时间呈现出显著上升趋势,而在紫外老化条件下,其抗应力银纹强度随老化时间在总体上升趋势中有一段下降,影响的拉伸强度加速老化条件的显著性排序为:紫外老化,盐雾试验,95℃热空气老化;透光率受实验室加速老化条件影响不大。     

溶剂和紫外老化对聚碳酸酯银纹性能及冲击强度的影响

采用应力-溶剂银纹和缺口冲击强度的测试方法,研究了聚碳酸酯(PC)在不同溶剂和紫外老化作用下的银纹性能以及紫外老化和缺口涂覆涂层对聚碳酸酯冲击强度的影响。结果表明:95%乙醇对聚碳酸酯银纹性能影响最小,酯类和二甲苯对其银纹性能影响很大,PC作为结构材料使用的场合,尽量避免使用酯类和二甲苯溶剂;添加紫外吸收剂的PC在经过紫外照射50 h后,其银纹性能略有下降;紫外光老化60 h对PC冲击强度无明显影响,而缺口处涂覆有机硅涂层后其冲击强度显著下降。     

聚碳酸酯的热氧老化特性与断口形貌表征

分别在120、130、140℃温度环境下,对聚碳酸酯进行热氧老化实验。应用电子材料试验机、扫描电子显微镜（SEM）、红外光谱仪（FTIR）等手段,研究了聚碳酸酯热氧老化后的力学性能变化特性和断口形貌。结果表明:聚碳酸酯经120、130、140℃温度热氧老化后,强度和伸长率均随温度的升高而降低;断裂性质也随温度的升高,由塑性断裂转变成了脆性断裂。当聚碳酸酯热氧老化一定程度,断口上会出现孔洞形貌;孔洞是聚碳酸酯发生热氧老化失效的一种断口特征。     

自然老化失效对材料性能的影响：理论预测与试验探究

聚丙烯材料在服役过程中常因受到高温、辐射、臭氧、潮湿、化学介质以及机械应力等因素的影响而发生氧化和分子内部的交联反应,其结构或组分发生破坏,最终影响其使用价值。本文通过分析聚丙烯材料在综合应用场景中的自然老化过程及其对材料力学性能的影响,基于试验分析和理论模型对其老化过程中的力学性能进行预测。结果表明：聚丙烯材料自然老化过程中,1 a时,拉伸强度和断裂伸长率下降速度较快;在1～2 a时,拉伸强度和断裂伸长率基本保持不变;2 a后,其拉伸强度和断裂伸长率则进一步加速下降。自然老化时间对聚丙烯材料的缺口冲击强度的影响不明显,而无缺口冲击强度则在前1 a内下降较快,1 a后无缺口冲击强度趋于稳定。聚丙烯材料在户外暴露的时间越长,其光泽度越低,但前1.5 a内的光泽度变化较大,而后变化逐渐减缓。聚丙烯材料在户外暴露时间越长,其色差越明显,且随着时间的推移,色差变化有逐渐加速的趋势。GM(1,1)模型在聚丙烯材料自然老化失效过程中关于材料性能预测的平均误差约3%,最大误差不超过4%,该模型的预测结果较为可靠。     

双金属氧化物掺杂对CDPF老化性能的影响

本文基于XRD、XPS、H2-TPR等理化特性表征方法与催化剂活性评价方法,研究了掺杂不同双金属氧化物催化型颗粒捕集器（CDPF）样品水热老化状态下的理化特性与催化活性。结果表明：掺杂Ce-Zr双金属氧化物的CDPF样品物相结构和晶胞参数稳定性较好,掺杂Zr-Fe双金属氧化物的CDPF样品能较好地抑制老化后载体表面贵金属分散度的降低程度。掺杂Fe-Ce和Zr-Fe的CDPF样品在高温老化过程中分散的金属氧化物会再次发生固溶而形成较多的固溶体,带来更多氧空位。经历高温水热老化后,CDPF样品的还原峰均不同程度地向高温方向迁移,其中掺杂Fe-Ce的CDPF样品还原峰迁移幅度较低,掺杂Ce-Zr的CDPF样品还原峰向迁移幅度较大。掺杂Fe-Ce和Zr-Fe的CDPF样品老化后对CO的氧化活性较高,劣化程度较小,并且保持较好的NO催化选择性。掺杂Ce-Zr的CDPF样品老化后对C3H8氧化活性略有下降。     

Aging and mechanical properties of NR/BR blends

The mechanical properties and post-thermal aging properties of natural rubber (NR) and polybutadiene rubber (BR) blends at different blending ratios are investigated herein. The experimental results show that both tensile and tear strengths of NR/BR blends increase with increasing NR content. BR has a higher compression stiffness than NR. The deformation of BR is less than that of NR under the same load conditions. With regard to aging properties, both tensile stress and strain of NR/BR blends decrease after prolonged aging. In addition, the stress loss of BR is lower than that of NR, meaning that the aging resistance property of BR is superior to that of NR. Furthermore, accumulated thermal history has shifted the glass transition temperature (T _g) of NR/BR blends toward lower temperatures while the loss tangent (tan δ) value increases with prolonged thermal aging.     

Remarkable reinforcement of natural rubber by deformation-induced crystallization in the presence of organophilic montmorillonite

A remarkable reinforcement of natural rubber (NR) was achieved by adding a low content of organically modified montmorillonite (OMMT). Mechanical tests demonstrated that the most noticeable enhancement in the tensile strength of NR was at a OMMT content of 5 wt.%. In order to gain further insight into the mechanism of reinforcement by OMMT, the deformation-induced crystallization behavior and morphology of NR/OMMT nanocomposites with different OMMT contents were investigated by synchrotron wide angle X-ray diffraction and transmission electron microscopy. The results show that the variation in the degree of strain-induced crystallization is consistent with that of tensile strength. The peak in tensile strength at 5 wt.% OMMT content can be ascribed to the fact that strain-induced crystallization is the essential factor in reinforcement of NR. Further, the nanomorphology of OMMT dispersed in a NR matrix plays a decisive role in the crystallization behavior of NR during deformation. An increase in the exfoliation of OMMT leads to an increase in the promotion of deformation-induced crystallization of NR.     

2050铝锂合金薄板拉伸性能及晶间腐蚀与时效的相关性

采用拉伸性能测试、浸泡腐蚀及透射电镜(TEM)观察,研究了2050铝锂合金薄板T6及T8态时效时后的拉伸性能、晶间腐蚀(IGC)及微观组织。结果表明,T8态时效2050铝锂合金强度及伸长率均明显高于T6态时效。T6及T8态时效时,合金IGC敏感性随时效延长至峰时效阶段而逐渐降低;进一步延长至过时效阶段,IGC敏感性有所增加。另外,T8态时效时IGC敏感性明显低于T6态时效。基于提高强度、伸长率及降低IGC敏感性的综合考虑,2050铝锂合金薄板适宜的时效制度为T8态峰值时效,相应合金具有最高的强度(抗拉强度529 MPa)、良好的伸长率(10%)及最低的IGC敏感性。     

航天器用GD414硅橡胶材料的湿热老化试验与贮存寿命预测

采用加速老化的试验方法对航天器用GD414硅橡胶材料的湿热老化性能进行研究，建立航天器用GD414硅橡胶材料贮存寿命的湿热老化模型，并利用该模型对GD414硅橡胶的贮存寿命进行预测。结果表明:温湿度对GD414硅橡胶材料的力学性能和电气性能影响较大，随着老化时间的延长，拉伸强度和击穿电压总体呈下降趋势；拉伸试样表面颜色逐渐加深，断口形貌没有发生明显的改变；红外光谱测试结果显示，GD414硅橡胶在湿热老化试验过程中没有产生新的官能团；在20 ℃、相对湿度为60%的条件下，GD414硅橡胶材料的贮存寿命为17.1 a。     

自然时效对A7N01铝合金光纤激光-变极性TIG复合焊接头组织和性能的影响

对4 mm厚的A7N01铝合金光纤激光-变极性TIG复合焊接头进行自然时效，通过金相显微试验、力学性能测试、差热分析、透射电镜分析等方法研究了自然时效对复合焊接头显微组织、力学性能的影响规律. 结果表明，自然时效30天后，焊接接头力学性能明显提高并达到稳定，接头抗拉强度较焊态时提高了约15%，均值达到369 MPa，为母材的83%，其断后伸长率从焊态3.1%提高到4.4%. 去除余高后，抗拉强度进一步提高到394 MPa，达到母材94%断后伸长率提高到7.6%. 断裂位置均在焊缝处，断口为韧窝状，为典型的韧性断裂. 自然时效后，焊缝显微组织没有发生明显改变，但焊缝中的析出相数量和尺寸比焊态时增多，焊缝中主要析出相主要为GP区及部分亚稳态η′相和η稳定相. 这些析出相能够钉扎位错，提高焊接接头强度.     

一种新型纳米纸质文物、档案保护技术的应用研究

目的提高纸质文物、档案的防水、防酸、抗老化等性能。方法把样品放入JRP镀膜设备中,控制真空、温度、电场、磁场等条件对化学原料进行真空聚合,在样品表面形成纳米级保护膜。通过老化前后色度值、水接触角、耐折度、拉伸强度和海水浸泡等测试,来分别评价样品的防水、防酸、抗老化、抗撕裂等性能,并通过扫描电镜对制备的纳米级厚度的聚合物保护膜进行了检测和分析。结果镀膜纸在湿热老化前后、紫外和酸雨老化前后的色差均较小。JRP镀膜后的宣纸样品正反面接触角平均值均大于90°,而未镀膜的宣纸的接触角为0°,是处于完全润湿状态。SEM照片显示镀膜后纸张纤维宏观尺寸没有变化,纤维之间的孔洞也未见堵塞。耐折度测试结果表明,镀膜处理后可略微提高纸张的纵向耐折度。纸张拉伸强度测试表明,镀膜纸张的横向拉伸强度明显高于原纸张。酸蚀实验和海水浸泡实验表明,镀膜后的纸张样品抗酸和海水腐蚀性能优于未镀膜纸张。结论镀膜对纸张的颜色没有影响,保持了其原貌,同时能一定程度地减小湿热老化和紫外老化对纸张颜色的影响。镀膜使纸张具有良好的疏水防水功能,耐折度和拉伸强度有一定的提高,具有防酸蚀和海水腐蚀的膜层保护了基材。     

Ti2ZrNbV高熵合金的相稳定性和时效强化

采用真空电弧熔炼法制备了具有体心立方结构的Ti₂ZrNbV(at%)高熵合金。研究了固溶体相的稳定性,以及金属间化合物V₂Zr析出对拉伸性能的改善。结果表明：合金在900℃以上是稳定单一均质固溶体相,低于此温度时,Laves相V₂Zr容易在基体中析出。单一固溶相的不稳定性可用于强化Ti₂ZrNbV高熵合金。经过固溶和时效处理后,合金的拉伸屈服强度可达1145 MPa,塑性伸长率为8.3%。     

Development of 70/30 Poly-L-DL-Lactic Acid Filaments for 3D Printers (Part 2): Mechanical and Surface Properties of Bioabsorbable Printed Plates for Biomedical Applications

The mechanical, chemical, roughness and wettability properties of 70/30 poly (L,DL-lactide acid) three-dimensional (3D)-printed surgical plates made with extruded polymer filaments developed in the first part of this work were investigated. The plates were printed with horizontal (HRZ) and vertical (VRT) running layer orientations and evaluated by tensile, Fourier transform infrared (FTIR), optical perfilometry and wettability tests before and after degradation in simulated body fluid (SBF) for 21 days. The results show that the ultimate tensile strength (UTS) of HRZ plates before immersion in SBF was higher (34.1 MPa) than that of VRT plates (31.8 MPa). The Young’s modulus (E) of HRZ plates and VRT plates are similar (4 GPa). After immersion in SBF, the UTS of HRZ plates dropped to 20.5 MPa and E decreased to 3.3 GPa. VRT were not tested after SBF immersion due to the large degradation. FTIR analysis showed no evidence of chemical change in the plates after immersion in SBF. The roughness parameter R3z of VRT surfaces (19.54 µm) was higher than that of the HRZ surfaces (12.80 µm). The roughness parameters increased after degradation in SBF (p = 0.7048). The contact angles of HRZ surfaces before immersion in SBF (66.28°) were higher than after immersion in SBF (18.12°); the same behavior was also observed in VRT plates.     

Aging strengthening of 8 mol% yttria-fully-stabilized zirconia

To examine the changes in the fracture strength and isothermal Young’s modulus of 8 mol% yttria-fully-stabilized zirconia (8YSZ) with aging, the tensile test was performed using an 8YSZ polycrystal before and after aging. All the stress–strain relationships before and after aging indicated a linear relationship till fracture, and Young’s modulus did not change with aging. The tensile strength of the aged specimen was about 35% higher that that of the unaged. The increase in the tensile strength with aging was attributed to the microstructural changes observed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM), which were the grain refinement and the phase transformation to the tetragonal phase only at the surface.     

Development of a Cast Al-Mg2Si-Si In Situ Composite: Microstructure, Heat Treatment, and Mechanical Properties

An Al-11Mg₂Si-Si in situ composite was prepared by a modified investment casting technique that employs sub-pressure for castability improvement and immersion of ceramic shell molds in fluidized beds of silica sand and iron particles for heat extraction improvement. The microstructure of the as-cast composite is explained according to the pseudoeutectic Al-Mg₂Si phase diagram. The positive effect of a decreased number of mold investment layers and cooling assisted by immersion of the mold in a metallic bed on the tensile strength and hardness of the heat treated composite is noted. A minor presence of Fe in the master alloys constitutes an essential factor for the brittleness of the composite. Solution treatment notably improves the tensile strength of the composite; however, prolonged treatment deteriorates its ductility. The effect of time and temperature of the aging treatment on the hardness of the composite is investigated. The positive influence of cooling assisted by a metallic fluidized bed on the effectiveness of the aging treatment is noticed.