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1.
莫来石基陶瓷复合材料的力学性能   总被引:7,自引:4,他引:7  
采用热压工艺制得致密的莫来石陶瓷和莫来石基陶瓷复合材料(ZTM、SiC晶须-莫来石、SiC晶须-ZTM)。通过引入SiC晶须或ZrO_2,使莫来石基陶瓷的力学性能有明显改善,SiC晶须和ZrO_2复合强韧则效果更为显著。组成为20vol.%SiC晶须-15vol.%ZrO_2-莫来石陶瓷材料,其室温及800℃的抗弯强度和断裂韧性分别为559MPa及425MPa,7.5MPa·m~(1/2)及7.4MPa·m~(1/2)。实验结果表明,莫来石基复合材料的相变增韧与晶须增韧机制的作用对韧性的贡献有良好的加和性。  相似文献   

2.
顾培芷  肖义新 《硅酸盐学报》1991,19(4):381-384,311
制备了含10vol%,20vol%及30vol%SiC晶须的Si_3N_4基复合材料,对其室温及高温机械强度的测试研究表明,SiC晶须对基体的高温机械性能有明显的增强作用。含20vol%SiC晶须的复合材料1200℃下强度达780MPa,比基体材料提高50%。通过SEM和TEM研究,讨论了SiC晶须增强的原因。  相似文献   

3.
肖汉宁  黄启忠 《中国陶瓷》1993,(2):13-14,23
研究了SiC/B复合超细粉末在1800~2000℃下的热压烧结特性及显微结构。在1900℃下热压,获得了相对密度为98.8%,室温弯曲强度和断裂韧性分别为590Mpa和5.8MPa·m~(1/2)的致密烧结材料,其显微构造是由短径约0.2μm、长径0.5~1.0μm的针晶相互交织而成的超晶须补强结构。  相似文献   

4.
以ZrB_2为基体材料,分别采用添加SiC颗粒(SiC_p)、SiC晶须(SiC_w)和SiC晶片(SiC_(pl))作为增韧相,采用热压烧结技术制备了SiC/ZrB_2陶瓷基复合材料,分析了不同增韧相的种类和添加量对ZrB_2陶瓷强韧化效果的影响,并通过层状结构设计,采用放电等离子体烧结工艺制备出ZrB_2基层状复合陶瓷材料,研究了层状结构对ZrB_2陶瓷强韧化效果的影响。结果表明:添加SiC颗粒、晶须或晶片,采用热压烧结可以制备出接近完全致密的SiC/ZrB_2陶瓷基复合材料;与单独添加SiC颗粒或晶须相比,同时添加SiC颗粒和晶须的增韧效果更加明显,而SiC晶片也可以起到较好的强韧化效果;通过层状结构设计,能够较大幅度地提高ZrB_2陶瓷的断裂韧性,显示了很好的增韧效果。  相似文献   

5.
热压烧结工艺制备Si/SiC陶瓷的研究   总被引:2,自引:0,他引:2  
α—SiC粉末为原料,Si为助烧剂,采用适当的热压烧结工艺,在1800℃,25MPa条件下获得了致密的SiC块体陶瓷,其抗弯强度为253MPa。  相似文献   

6.
柱状自生长莫来石的制备及显微结构   总被引:13,自引:2,他引:11  
通过对莫来石材料的分析,设计了在莫来石先质中添加AlF3进行密封条件下热处理,生成莫来石晶须晶种,并以其作为生长点,在以后的烧结过程中发育成为柱状颗粒,获得类昌须复合材料的显微结构的实验线路,含AlF3莫来石先质试样密闭处理的温度条件是1150℃,大于这个温度处理的试样无法获得致密烧结。莫来石柱状生长条件是富铝莫来石晶粒的存在和液相的产生。本工作中经1150℃处理后的试样获得良好的烧结密度,材料的  相似文献   

7.
研究了烧结温度达到1550℃时原位形成莫来石-锆英石-碳化硅复合物的成分,在SiC微粉存在情况下,锆刚玉会按化学计量反应完全生成莫来石产物。在中性气氛下烧结,复合物会依SiC含量而表现出良好的致密性。但是,在1550℃时,SiC对物相形成的影响不可忽略,我们用两种氧化方式来评价该烧结体.分别为被动表面氧化和主动内部氧化。SEM分析表明:烧结致密化在微观结构上有非常大的差别,ZrO2和莫来石颗粒会析出,以小颗粒包裹在SiC大颗粒的外面,建议在以后的研究中采用热压法和等静压法。  相似文献   

8.
由氨基乙酸/硝酸盐闷烧方法制备了含8%Y2O3的纳米晶钇稳定氧化锆粉末,用火花等离子体烧结(SPS)、热压(HP)和传统烧结法(CS)研究了其致密性。SPS技术比其余烧结方法优异,能在较低温度和较短烧结时间获取具有均匀形态的致密化材料(≥96%)。经SiX5、热压和传统烧结方法制备的材料,其晶粒尺寸分别是0.21、0.37和12μm。材料的总电导率与晶粒尺寸并无明确关系,但SPS烧结材料的活化能比其余两种致密化方法的稍高。由Vickers压痕法测得的硬度与晶粒尺寸无关,而断裂韧性(由压痕法测得)随晶粒尺寸增大而轻微下降。  相似文献   

9.
以SiC晶须作为增强体,通过酚醛树脂高温碳化裂解获得碳包覆的SiC晶须,与纳米碳化硅粉体、炭黑混合均匀形成复合陶瓷乙醇浆料.经过干燥、造粒、成型和排胶后获得SiCw-C-SiC素坯,利用反应熔渗法制备高体积分数的SiC晶须增强SiC陶瓷基复合材料.研究了碳黑含量对复合材料力学性能与显微结构的影响.通过扫描电镜照片显示,碳包覆的SiC晶须经高温反应熔渗后仍保持表面的竹节状形貌,且晶须与碳化硅基体间形成适中的界面结合强度,材料断口处有明显的晶须拔出;当炭黑含量为15wt%时,抗弯强度和断裂韧性达到最高值分别为315 MPa和4.85 MPa·m1/2,比未加晶须的SiC陶瓷抗弯强度提高了25%,断裂韧性提高了15%;当炭黑含量为20wt%时,复合材料中残留部分未反应的炭黑,制约其力学性能的提高.  相似文献   

10.
以Cu包裹SiC颗粒为增强体,分别采用真空热压烧结和常压氩气气氛保护烧结方式制备含5%(体积分数)SiC颗粒的SiC/Cu–Al复合材料。研究了不同烧结温度对样品密度、Vickers硬度和弯曲强度的影响。采用X射线衍射、扫描电镜对样品的晶相组成和结构进行了测定。结果表明热压制品相对常压烧结制品的晶相组织均匀,晶粒细小。热压烧结可以大大提高SiC/Cu–Al复合材料的致密度,最高达到理论密度的99.9%。热压烧结的制品的硬度得到提高,550℃热压烧结的制品硬度最高可达到65MPa,575℃烧结时,其最大抗弯强度为190MPa,断裂机制主要是增强的颗粒断裂和基体撕裂。  相似文献   

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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   

13.
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   

14.
Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.  相似文献   

15.
A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by 1H MAS NMR. For direct comparison purposes, an SiO2 coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N2 absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.  相似文献   

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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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