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颗粒增强复相陶瓷残余应力和增韧机制分析 总被引:7,自引:1,他引:7
对颗粒增强复相陶瓷在增强颗粒密排分布条件下材料内残余应力的大小和分布进行了理论分析,探讨了αp〉αm和αp〈αm情况下的强化增韧机制以及在这两种情况下所存在的增韧机制的差别。研究结果表明,残余应力不仅与基体和颗粒的物理参量有关,而且还与所在点位置和增强颗粒体积含量有关。颗粒增强复相陶瓷在αp〉αm和αp〈αm情况下,都可能达到强化增韧的效果。在αp〈αm情况下,主要增韧机制是裂纹偏转和残余应力场强 相似文献
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在TiB2/SiCw基体中加入适量的SiCw可以明显地提高其断裂韧 性KIC,其它机械性能也有不同程度的改善。SEM、TEM微观分析表明:在具有较高KIC值的TiB2/BiCw陶瓷复合材料中,SiCw与TiB2晶粒之间有较适宜的界面结合,两相之间未发现有明显的界面化学反应用,当该复合材料发生断裂时,其内部出现晶须拔出,裂纹桥连,裂纹偏转三种增韧机制。 相似文献
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SiC基层状复合材料界面层的选择 总被引:5,自引:1,他引:4
利用凝胶注模成型SiC基体层 ,以喷涂法、流延法、金属箔法、浸涂法分别加涂W ,W -2 % (质量分数 ,下同 )Co ,Ta,BN界面层 ,通过热压烧结制备了SiC/W ,SiC/W -2 %Co ,SiC/Ta ,SiC/BN层状复合材料 .在复合材料高温制备过程中 ,金属W ,W -2 %Co ,Ta与SiC反应生成了碳化物和硅化物 ,失去了金属塑性 ,未能实现裂纹尾流区桥接、残余应力增韧等金属界面层层状复合材料赖以大幅度提高其强韧性的增韧机制 ,其增韧效果仅与BN陶瓷界面层的增韧效果相当 .此外 ,研究表明 ,提高基体层力学性能可以显著提高层状复合材料的强韧性 .制备的SiC/BN层状复合材料的室温三点弯曲强度为 72 9.86± 114 .0 2MPa、室温断裂韧性为 2 0 .5 8± 2 .77MPa·m1 /2 ,其主要增韧机制包括裂纹分叉钝化、裂纹偏转、裂纹并行扩展以及裂纹尾流区片层拔出等 相似文献
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以碳化硼(B4C)、二硼化钛(TiB2)、碳化钛(TiC)为原料,采用无压烧结法在2 130℃制备了含20%(质量分数)和30%TiB2的B4C基复相陶瓷,分析所制样品的密度、硬度、弯曲强度和断裂韧性。结果表明:在2 130℃,直接加入30%的TiB2亚微米颗粒,复相陶瓷的抗弯强度和断裂韧性分别达到277.6 MPa和5.38 MPa·m1/2。陶瓷中颗粒拔出和裂纹微桥接对复相陶瓷增韧作用显著。B4C–TiB2复相陶瓷的增韧机理主要是由于TiB2与B4C热膨胀系数不匹配产生的残余应力导致的微裂纹增韧和裂纹偏转增韧。 相似文献
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本文对非晶态SiBON纳米粉末热压烧结研究,发现SiBON材料在1400℃时开始致密化同时开始析晶,析出晶体为h—BN,其余成分以非晶态存在。h—BN析出量随着烧结温度的升高而增多。在1400℃、1600℃和1700℃时,材料中BN形态分别为近等轴颗粒、大片晶和小片晶。这种从玻璃基体中析出的BN比通常所见的BN粉末有更完整的层片状晶体结构。这种原位析出片晶韧化相的SiBON玻璃陶瓷具有很高的力学性能。分析认为较高的强度主要归因于BN析出相对玻璃基体产生的压应力,而较高的断裂韧性来自于BN晶片所产生的裂纹偏转、桥接和晶片拔出增韧机制。 相似文献
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CePO4/Ce-ZrO2可加工陶瓷加工机理的研究 总被引:10,自引:2,他引:10
以CePO4/Ce-ZrO2为基体,通过复合不同加入量的第二相CePO4颗粒,并借助扫描电子显微镜对材料压痕、磨削及切削表面进行分析,研究了CePO4/Ce-ZrO2陶瓷材料的可加工机理。单相CePO4材料的弯曲断口显示出层片状断裂机制;而复相CePO4/Ce-ZrO2陶瓷由于两相之间弱结合界面的存在,压痕裂纹扩展形式发生明显变化,由连续扩展机制过渡为不连续扩展。基于上述两种重要机制形成的大量微裂纹是赋予材料可加工性的主要原因,材料加工去除是以微裂纹的连接来实现的。同时,大量微裂纹起到耗散主裂纹扩展能量的作用,有效阻止了较大裂纹的形成,使材料加工损伤大大降低。最后,给出了CePO4/Ce-ZrO2陶瓷加工机理的简单模型。 相似文献
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马满珍 《玻璃钢/复合材料》1986,(1)
本文介绍了由无规羧基丁腈橡胶、双酚A、韧性稀释剂Zh-122增韧的环氧E-51体系,不仅提高了树脂基体的韧性和某些力学性能,而且明显改善了工艺性,适合复合材料干、湿法多种成型工艺。断口电镜观察表明,新树脂体系是两相体系,两相界面结合力强,橡胶颗粒分布宽,从而消耗导致裂纹扩展的能量,提高了材料的韧性。本文还考察了新树脂基体的韧性对单向玻璃纤维复合材料性能的影响。 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively.
There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized.
High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without
the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of
fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to
achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic
SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve
F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender
particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing,
and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing
or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually
preserves suspension stability during freezing.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago,
IL. Tied for first place in The John A. Gordon Best Paper Competition. 相似文献
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Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US
In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae
and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted
in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures
(release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species
(Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species
to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were
exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of
separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles
from the southeastern region of the US. 相似文献
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Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed. 相似文献
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中蓝晨光化工研究院有限公司《塑料工业》编辑部 《塑料工业》2009,37(3)
收集了2007年7月~2008年6月世界塑料工业的相关资料,介绍了2007~2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍. 相似文献
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中蓝晨光化工研究院《塑料工业》编辑部 《塑料工业》2007,35(3):1-25,67
收集了2005年7月~2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、通用热固性树脂(酚醛、聚氨酯、不饱和树脂、环氧树脂)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。 相似文献