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急冷锅炉(TLE)是乙烯热裂解装置的重要设备,在运行中急冷锅炉炉管内壁会有结焦现象,降低急冷锅炉传热系数并增加炉管压力降,严重影响传热效果,需要进行周期性清焦.为了能够有效地抑制结焦,在炉管内壁表面上制备了一层Cr/W/稀土RexOy惰性涂层,借助乙烯裂解结焦模拟装置、金相显微镜、扫描电子显微镜(SEM)和透射电镜(TEM)等设备从试样结焦表面形貌特征和结焦量等方面对所开发的涂层进行了抑焦性能研究.实验结果表明,无涂层试样表面存在催化焦和颗粒状焦,结焦严重;而涂层试样抑焦效果明显,表面不存在催化结焦,且焦层与涂层表面黏附性差结合较弱容易脱落,其结焦抑制率可达79.1%. 相似文献
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采用苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改善BR/乙烯-乙酸乙烯酯共聚物(EVA)/高抗冲聚苯乙烯(HIPS)共混物的界面相容性,通过动态硫化法制备BR/EVA/HIPS TPV,并对其性能进行研究.结果表明:未加入SBS的BR/EVA/HIPS共混物未表现出橡胶类弹性体特征,而加入适量SBS的共混物表现出典型橡胶类弹性体特征;当SBS用量为8~12份时,BR/EVA/HIPS TPV的综合物理性能较好,拉伸断面平滑,界面相容性良好. 相似文献
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采用溶液浸渍及高温煅烧的方法制备了一系列Al/SO42-复合改性CrOx/VOx/SiO2双金属催化剂,并研究了其催化乙烯聚合特性。结果表明:采用较低的m(Al)∶m(S)改性的双金属催化剂活性较未改性催化剂提升20%~40%;改性前后催化剂均表现出稳定的聚合活性,采用改性催化剂制备的聚合物相对分子质量更高,相对分子质量分布更宽;采用改性前后催化剂制备的聚合物相对分子质量分布均呈双峰,采用改性催化剂时其超高相对分子质量部分含量有所增加,而中、高相对分子质量部分含量明显更少。上述结果为单釜高效合成双峰聚乙烯产品及聚合物相对分子质量调控提供了重要手段。 相似文献
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将不同配比的聚丙烯(PP)和乙烯-乙酸乙烯共聚物(EVA)进行共混,测试了共混物的拉伸强度和冲击强度;用差示扫描量热法研究了共混物的结晶性能;用扫描电镜(SEM)二次电子成像系统分析了试样的断口形貌,研究了EVA含量对共混物力学性能的影响。结果表明:EVA的加入提高了EVA/PP共混体系的韧性,同时降低了PP的结晶度。 相似文献
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主要对不同配比的PE、聚乙烯-乙酸乙烯酯(EVA)树脂进行共混改性研究.使用正交实验法设计、运用方差分析法分析,测试了PE/EVA共混物的拉伸强度和屈服强度,使用差示扫描量热法(DSC)研究了PE/EVA的相容性,使用扫描电镜(SEM)二次电子成像分析试样液氮脆断的断口.从而讨论分析EVA在PE/EVA共混物当中的含量、挤出机的螺杆转速以及挤出机出口模的模温对PE/EVA共混物力学性能的影响. 相似文献
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Microcapsules containing phase change materials (microPCMs) can be filled in polymeric matrix forming smart temperature‐controlling composites. The aim of this study was to investigate the relationship between the interface behaviors and the mechanical properties of methanol‐melamine‐formaldehyde shell microPCMs containing paraffin/epoxy matrix composites. The typical microPCMs with core/shell ratio of 2/1 shapely decreased their average diameter from 26.0 ± 1.5 to 13.8 ± 3.4 μm with the increasing of stirring speed from 1,000 to 3,000 r min−1. But, both the thickness and yield point of shells had a little variation. Young's modulus of composites was almost independent on the particle size of microPCMs with lower volume fractions (5%–10%). For composites with higher microPCMs loading (20%–30%), there was a slight decrease in modulus with increasing particle size. The data of tensile strength decreased obviously with the increasing of the average diameter of microcapsules for composite samples with the same particle loading. A repeated heat‐transmission treatment was applied to enhance the interface debonding. The results show that the violent thermal transmission had decreased the mechanical properties of microPCMs/epoxy composites. The scanning electron microscopy morphologies had also proved that these phenomena attributed to the interphase separation and cracks. Moreover, a semiexperiential conclusion is that the increasing of interface area of composites will at the same time give more structure defects leading to poor mechanical properties. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers 相似文献
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Jun‐Feng Su Xin‐Yu Wang Sheng‐Bao Wang Yun‐Hui Zhao Kong‐Ying Zhu Xiao‐Yan Yuan 《Polymer Composites》2011,32(5):810-820
Microcapsules containing phase change materials (microPCMs) have been widely applied in smart temperature‐controlling materials. Interface stability plays a key role in these microPCMs/matrix composites. The aim of this study was to investigate the interface stability behaviors of methanol‐melamine‐formaldehyde (MMF) shell microPCMs containing paraffin/epoxy matrix composites. MMF prepolymer can be applied to fabricated microcapsules with smooth shells. The average diameter of the microPCMs could be controlled in the range of 5–45 μm by stirring speed of 500–6,000 r min−1. From the SEM morphologies of the interphase between the microPCMs and the epoxy‐matrix, it is concluded that the interaction may be enhanced by MMF graft structure due to the increasing of molecular interaction in the interface. During a repeated heat‐transmission process, not only the repeated‐times of thermal absorbing‐releasing process will damage the interface bonding, but also higher thermal conductive speed will make the interface bearing more debonding stress. Large microPCMs in matrix may supply better interface stability. Moreover, the numerical and experimental results are consistent to obtain a clear insight into the rule of interface debonding for microPCMs/matrix composites that the interface perfection can be enhanced by increasing the thickness of interphase. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers 相似文献
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Dileep Singh Jitendra P. Singh Saurin Majumdar David S. Kupperman Eric Cowdin Ramakrishna T. Bhatt 《Journal of the American Ceramic Society》1994,77(10):2561-2568
Fiber/matrix interfacial debonding and frictional sliding stresses were evaluated by single-fiber pushout tests on unidirectional continuous silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. The debonding and maximum pushout loads required to overcome interfacial friction were obtained from load–displacement plots of pushout tests. Interfacial debonding and frictional sliding stresses were evaluated for composites with various fiber contents and fiber surface conditions (coated and uncoated), and after matrix densification by hot isostatic pressing (HIPing). For as-fabricated composites, both debonding and frictional sliding stresses decreased with increasing fiber content. The HIPed composites, however, exhibited higher interfacial debonding and frictional sliding stresses than those of the as-fabricated composites. These results were related to variations in axial and transverse residual stresses on fibers in the composites. A shear-lag model developed for a partially debonded composite, including full residual stress field, was employed to analyze the nonlinear dependence of maximum pushout load on embedded fiber length for as-fabricated and HIPed composites. Interfacial friction coefficients of 0.1–0.16 fitted the experimental data well. The extremely high debonding stress observed in uncoated fibers is believed to be due to strong chemical bonding between fiber and matrix. 相似文献
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本文根据纤维增强复合材料的特性,列出了损伤的主要类型和产生原因;对适用于复合材料制品的无损检测敲击技术进行探讨;对敲击技术的基本原理、方法分类、适用范围进行介绍;对传统敲击法和数字敲击法进行比较;总结敲击法的未来发展状况。 相似文献
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《Journal of the European Ceramic Society》2020,40(3):636-641
Determining the effect of defects in fiber-reinforced materials, such as polymer matrix composites (PMCs), can be studied by creating artificial flaws in these materials, for example by introducing artificial PTFE foil to induce material delaminations. For fiber-reinforced ceramics (CMCs), this approach is more difficult due to the more complicated production routes of CMCs, which involve several processing steps at elevated temperatures. This work deals with the fabrication and introduction of defined defects in carbon fiber reinforced silicon carbide (C/C-SiC) composites in a way, which allows their detection by non-destructive material testing methods during and after each production step of the composite. It was shown that the defects produced using boron nitride (BN) and alumina fiber roving were stable over the entire manufacturing process and could be detected by ultrasound and x-ray tomography techniques. To determine any possible effects, an initial sampling of bending samples with artificial defects was manufactured, tested and compared with defect-free reference materials. These tests showed a lower bending strength and failure strain for the defect samples compared to samples without defects. 相似文献
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Jinyan Liu Li Ren Qiang Wei J.L. Wu Sa Liu Yingjun Wang Guoyuan Li 《Polymer Composites》2012,33(4):501-508
Polycaprolactone (PCL)/calcium sulfate (CS) particle and whisker composites were prepared by coprecipitation method and studied by evaluating their microstructure, crystallization, and mechanical properties. Results show that both of the CS whisker and particle dispersed in PCL can reduce the spherulite size of PCL and improve the regularity of the spherulite. The nucleation effect of the CS whisker is stronger than that of the CS particle. Mechanical properties of PCL were obviously improved by both of the particle and whisker addition. The flexural modulus and impact strength of the whisker composites are higher than that of the particle composites, which could be explained by the interfacial debonding mechanism. On the basis of the crystallization and mechanical studies, it is found that the size of spherulites and the concentration of CS particles and whiskers have played an important role in the improvement in mechanical properties of the composite. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers 相似文献
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《Ceramics International》2022,48(17):24687-24694
The R-curve behavior and toughening mechanisms of graphene nano-platelets (GNPs) reinforced ceramic composites are investigated. A toughening model is developed with the consideration of interface debonding, crack bridging and pull-out of GNPs, which can be used to quantify the contribution of different mechanisms to the improved toughness of ceramic composites. The theoretical results agree well with the experimental data when GNPs homogeneously dispersed in ceramic matrix. All prepared GNPs/ceramic composites exhibit a raising R-curve behavior owing to the toughening mechanisms induced by GNPs, and the curve becomes steeper with increasing GNPs content, indicating that the fracture resistance and flaw tolerance are improved. The dominant toughening mechanism is GNPs pull-out, which is followed by crack bridging and interface debonding. Furthermore, the analytical model suggests that improving GNPs properties, interfacial sheer strength and reducing GNPs thickness can improve the fracture toughness of ceramic composites. 相似文献
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GF及偶联剂改性PVC/稻壳木塑复合材料 总被引:1,自引:0,他引:1
采用模压成型的方式、通过实验探索玻璃纤维(GF)含量及偶联剂处理对聚氯乙烯(PVC)/稻壳木塑复合材料的力学特性和耐磨性的影响。实验结果表明:PVC/稻壳木塑复合材料的硬度随GF含量增加呈现先减小后增大的趋势。GF含量在15%以下时,随着GF用量的增大,木塑复合材料的拉伸强度与冲击强度总体上随之变大,超过15%则随GF含量增大而减小。而弯曲强度出现先减后增的趋势,弯曲弹性模量则与之相反。木塑复合材料的耐磨损性在GF含量为15%时最佳,摩擦系数在10%时最大。合适的偶联剂处理能增强木塑复合材料的力学性能和耐磨性。其中γ–氨丙基三乙氧基硅烷(KH550)的增强效果比较好,钛酸酯不能提高PVC/稻壳木塑材料的力学性能和耐磨性。 相似文献
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为揭示平纹Cf/SiC复合材料的拉伸损伤演化及失效机理,开展了X射线CT原位拉伸试验,获得材料的三维重构图像,利用深度学习的图像分割方法,准确识别出拉伸裂纹并实现其三维可视化。分析了平纹Cf/SiC复合材料损伤演化与失效机理,基于裂纹的三维可视化结果对材料损伤进行了定量表征。结果表明:平纹Cf/SiC复合材料的拉伸力学行为呈现非线性,拉伸过程中主要出现基体开裂、界面脱黏、纤维断裂及纤维拔出等损伤;初始缺陷易引起材料损伤,孔隙多的部位裂纹数量也多;纤维束外基体裂纹可扩展至纤维束内部,并发生裂纹偏转。基于深度学习的智能图像分割方法为定量评估陶瓷基复合材料损伤演化与失效机理提供了有效分析手段。 相似文献
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Kai Zhang Fangxin Wang Yuezhao Pang Wenyan Liang Zhenqing Wang 《Polymer Engineering and Science》2019,59(9):1818-1829
We successfully added bamboo and glass fibers into bisphenol A‐aniline based benzoxazine (BA‐a) resin by hot‐pressing method. In order to improve the interfacial adhesion between bamboo fibers and the matrix, bamboo fibers were pretreated in 6 wt% NaOH solutions for 12 h. The results showed alkali‐treatment had a positive effect on mechanical properties of the composites at both room and elevated temperatures (60°C, 110°C, 160°C, and 210°C). Due to the incorporation of glass fibers, the bamboo/glass reinforced‐polybenzoxazine hybrid composites exhibited highest strength and modulus among all samples and had high residual mechanical properties at elevated temperatures (residual mechanical properties refers to the ratio of strength and modulus of the composites at elevated temperatures to that measured at room temperature). The fractured surface morphologies of the composites were observed by scanning electron microscope. The results showed with the increase of temperature, the debonding and fiber pull‐out became apparent, and the matrix softening could be clearly observed at 210°C. In addition, thermal and thermomechanical properties of neat benzoxazine and the composites were also investigated through thermogravimetric analysis and dynamic mechanical analyzer, respectively. POLYM. ENG. SCI., 59:1818–1829, 2019. © 2019 Society of Plastics Engineers 相似文献