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1.
茅东升  郦剑 《材料工程》1997,(8):22-24,37
通过SEM观察和EDXA分析对Al2O3/SiC和SiCw/SiC陶瓷的耐磨粒磨损性进行了比较研究。在低应力下,Al2O3/SiC陶瓷的耐磨性优于SiCw/SiC陶瓷,而在较高应力下则相反。  相似文献   

2.
SiC对MoSi2低温氧化行为的影响   总被引:6,自引:1,他引:5  
利用热重量分析、X射线衍射和扫描电镜观察分析了SiC在MoSi2低温化中的作用。结果表明SiC的加入促进了MoSi2的氧化,但未发现“PEST”现象。  相似文献   

3.
本文对Al2O3基陶瓷复合材料Al2O3-ZrO2-SiCw进行了干摩擦磨损试验,并运用了SEM,TEM和XRD等手段对其显微结构、力学性能及它们与GCr15钢对摩时的摩擦磨损行为进行了系统分析,在此基础上深入探讨了SiC晶须(SiCw)增韧补强作用对复合材料的摩擦磨损性能的影响。  相似文献   

4.
1,3-戊二烯阳离子聚合引发体系(CH3)3SiCl/EtAlCl2的研究   总被引:1,自引:0,他引:1  
研究了阳离子引发体系Me3SiCl(TMSCl)EtAlCL2在正己烷中引发的1,3-戊二烯(PD)聚合反应。研究结果表明,在EtAlCl2引发的PD聚合反应中引入TMSCl后大幅主提高了聚合物产率,同时使聚合反应速率明显提高,在「TMSCl」/「EtAlCl22」=0-1范围内,TMSCl/EtAlCl2体系制备的聚合物分子量高于EtAlCl2引发制备的聚合物,这些结果表明Me3SiCl/EtA  相似文献   

5.
研究了n-β(氨乙基)-γ(氨丙基)三乙氧基硅烷(NH2(CH2)2NH(CH2)3Si(OEt)3)与二甲基二乙氧基硅烷(CH3)2Si(OEt)2)共水解,制备含(CH2)3NH(CH2)2NH2功能基的聚硅氧烷配位体,用IR,^1HNMR和元素分析法对水解产物分析证明,NH2(CH2)2NH(CH2)3Si(OEt)3与(CH3)2Si(OEt)2进行了共水解反应,而且水解程度随NH2(CH  相似文献   

6.
常压MOCVD制备MgO薄膜的研究   总被引:1,自引:0,他引:1  
曾建明  王弘 《功能材料》1996,27(4):342-346
本文首次报道用常压金属有机化学气相沉积(AP-MOCVD)在Si(100),SiO2/Si(100)和Pt/Si(100)衬底上外延高质量的MgO薄膜。研究了衬底温度与薄膜的取向性关系和MgO薄膜的潮解特性。高纯magnesiumacetylacetonate[bis(2,4-pentanetane-diono)magnesium][Mg(CH2COCH2COCH3)2]作为金属有机源,扫描电镜(SEM),透射电镜(TEM)和X-RAY衍射实验显示,在较低的衬底温度(~480℃)下一次淀积成单晶膜。薄膜均匀,致密,结晶性和取向性很好,衬底温度(Ts)在400℃到680℃之间,在Si(100)衬底上生长的MgO薄膜都具有[100]取向,在Si(100)、SiO2/Si(100)和Pt/Si(100)衬底上生长的MgO薄膜也都具有[100]取向。  相似文献   

7.
通过热压烧结技术,SiC、AlN和Y2O3粉末混合体在1920 ̄2050℃、Ar气氛下形成了致密的复相陶瓷。在室温下SiC-AlN-Y2O3复相材料的抗弯强度和断裂韧性分别达到600MPa和7MPa·m^1/2以上。运用XRD、SEM和TEM分析致密样品的断裂裂纹、形貌和组成。SiC-AlN-Y2O3复相陶瓷在1370℃氧化试验30h,其氧化产物为莫来石。  相似文献   

8.
通过热压烧结技术,SiC、AlN和Y2O3粉末混合作在1920~2050℃、Ar气氛下形成了致密的复相陶瓷.在室温下SiC-AlN-Y2O3复相材料的抗弯强度和断裂韧性分别达到600MPa和7MPa·m1/2以上运用XRD、SEM和TEM分析致密样品的断裂裂纹、形貌和组成.SiC-AlN-Y2O3复相陶瓷在1370℃氧化试验30h,其氧化产物为莫来石.  相似文献   

9.
本文对Al2O3基陶瓷复合材料Al2O3-ZrO2-SiCw进行了干摩擦磨损试验,并运用了SEM,TEM和XRD等手段对其显微结构、力学性能及它们与GCr15钢对摩时的摩擦磨损行为进行了系统分析,在此基础上深入探讨了SiC面增韧补强作用对复俣材料的摩擦磨损性能的影响。  相似文献   

10.
碳纤维增强C—SiC梯度基复合材料研究   总被引:3,自引:0,他引:3  
采用CVI工艺均热法共沉积技术制备了碳纤维增强C-SiC梯度基复合材料。C和SiC的原料氛分别是C2H2t CH3SiCl3,Ar和H2分别是载流和稀释气体。基体微观结构的变化通过控制原料气体的成分配比藜得。测试了材料的力学性能、抗氧化性能和摩擦磨损性能。利用金相技术、电子探针成分分析技术、TEM和SEM技术观察和分析了材料的微观结构。试验结果表明,这种材料的组织结构特点是:在微观上是梯度的,即围  相似文献   

11.
A TaC composite with ∼11 wt% in situ TaB2 was fabricated by spark plasma sintering at 1600–1900 °C. The densification process was studied by analysis of the densifying shrinkage of the powder compacts. Three distinct stages for densification were determined. The starting powder mixture of TaC, B4C and Ta completed reaction to form the desired TaC and TaB2 at temperature <1583 °C. At around ∼1750 °C, the TaC/TaB2 material significantly improved relative density to ∼95% with rapid grain growth. The final densification took place very rapidly at 1900 °C by releasing a high pressure vapor.  相似文献   

12.
TaC nanopowders were synthesized by a liquid precursor route. The synthesis procedures include (1) preparation of tantalum ethylate solution by sufficient mixing TaCl5 powders with ethanol, (2) adding activated carbon nanopowders to the solution, (3) dispersing activated carbon nanopowders in the solution evenly to form a liquid precursor by an ultrasonic equipment, (4) brushing the liquid precursor on an alumina crucible and blowing the liquid precursor to dry, (5) heat treatment in a graphitization furnace in a vacuum, and (6) brushing the alumina crucible to obtain products. X-ray diffraction patterns indicated that the products were cubic TaC. The formation temperature (1300 °C) of TaC in this process is lower than that (1700 °C) in the conventional method. The reaction time of forming TaC in this process is half an hour. The observed size of TaC powders by TEM was smaller than 50 nm. The specific surface area of the powders by a surface area analyzer was 28.399 m2/g.  相似文献   

13.
Kim JJ  Shindo D  Murakami Y  Xia W  Chou LJ  Chueh YL 《Nano letters》2007,7(8):2243-2247
The electric potential change in a single TaSi2 nanowire during field emission was visualized by means of electron holography. During the field emission, the interference fringes of the electron hologram were blurred locally between the TaSi2 nanowire and anode. This phenomenon was interpreted as being due to a change in the electric potential of approximately 1 V in the TaSi2 nanowire after each ballistic emission. The experiments on the single TaSi2 nanowire field emission behavior provide the useful information for understanding the field emission in the nano-field-emitting device.  相似文献   

14.
The Si-TaSi2 eutectic in situ composite, which has highly-aligned and uniformly-distributed TaSi2 fibers in the Si matrix, can be obtained when the solidification rate changes from 0.3 to 9.0 mm/min. It is very interesting that one or two TaSi2 fibers are curved when the solidification rate reaches 6.0 mm/min, although it is very brittle in general. The formation mechanism of the curved fiber is discussed and mechanical properties of the TaSi2 fibers are examined by nanoindentation. It is found that the har...  相似文献   

15.
Chueh YL  Ko MT  Chou LJ  Chen LJ  Wu CS  Chen CD 《Nano letters》2006,6(8):1637-1644
TaSi2 nanowires have been synthesized on a Si substrate by annealing NiSi2 films at 950 degrees C in an ambient containing Ta vapor. The nanowires could be grown up to 13 microm in length. Field-emission measurements show that the turn-on field is low at 4-4.5 V/microm and the threshold field is down to 6 V/microm with the field enhancement factor as high as 1800. The metallic TaSi2 nanowires exhibit excellent electrical properties with a remarkable high failure current density of 3 x 10(8) A cm(-2). In addition, effects of annealing temperatures and capability of metal silicide mediation layer on the growth of nanowires are addressed. This simple approach promises future applications in nanoelectronics and nano-optoelectronics.  相似文献   

16.
Reaction bonded silicon carbide (RBSiC) ceramics typically contain 10 vol% silicon inherent to the reaction bonding process. However, the relatively low melting point (1410°C) of the silicon phase is a limiting factor in the high temperature use of RBSiC materials. The application temperature can potentially be enhanced by replacing the silicon with more refractory metal disilicide phases. In this paper we report the infiltration of SiC-graphite compacts with alloyed Si-Ta melts in an attempt to precipitate TaSi2 (Tm=2040°C) in place of the residual silicon. High density RBSiC-TaSi2 ceramics with virtually no porosity were readily produced, but subsequent XRD and SEM examination revealed that the silicon phase was not completely removed. In addition, the materials possessed complex, inhomogeneous microstructures and were susceptible to various types of crack formation phenomena.  相似文献   

17.
国内C/C复合材料基体改性研究进展   总被引:2,自引:0,他引:2  
碳/碳(C/C)复合材料在高温含氧气氛下的氧化烧蚀问题严重制约该材料在航空航天领域的推广应用,基体改性技术是提高该材料高温抗氧化抗烧蚀能力的有效手段。介绍了目前发展的化学气相渗透、先驱体转化、反应熔体浸渗、化学气相反应等基体改性技术的主要方法,综述了SiC,ZrC,TaC,HfC,ZrB2,WC,Cu等抗氧化和抗烧蚀组元改性C/C复合材料的研究现状。指出难熔金属碳化物和硼化物,如HfC,ZrC,TaC,HfB2,ZrB2等,具有熔点高、高温性能稳定、抗烧蚀性能优良等特点,是提高C/C复合材料高温抗氧化抗烧蚀的理想基体改性材料,并提出了C/C复合材料基体改性研究中存在的问题和今后潜在的发展方向。  相似文献   

18.
In situ growth of tantalum carbide (TaC) whiskers was synthesized in an α-Al2O3 matrix powder via a carbothermal reduction technique within a temperature range of 1350–1500 °C in an argon atmosphere. The starting materials consisted of Ta2O5, C, Ni and NaCl powders. Different mixing methods and various reaction temperatures were employed. Most of the prepared whiskers were 0.2–0.5 μm in diameter and 5–15 μm in length. The reaction temperature of 1400–1450 °C was suitable for the growth of TaC whiskers and a wet mixing method was beneficial to increase the whisker yield. Some of the whiskers exhibited the needle shape while others exhibited the screw shape. The growth mechanism of the whiskers was a complex mechanism involving a helical screw dislocation mechanism and a vapor–liquid–solid process. No obvious influences of the Al2O3 matrix powder on the growth of TaC whiskers were found and the major impurities in the obtained powder were TaC particles, nickel and unreacted carbon.  相似文献   

19.
采用含1μmTaC微粉4%(体积分数)的料浆向10mm厚的3D碳纤维预制体中引入TaC,得到微粉含量高、中、低的三种预制体, CVI沉积SiC致密化后制得3D C/SiC-TaC多元基复合材料.氧-乙炔烧蚀试验后采用XRD和SEM对烧蚀产物和显微结构进行分析.结果表明:料浆法结合CVI可制备出C/SiC-TaC复合材料,高含量的TaC微粉烧蚀后形成的TaC和Ta2O5的固液混合物,能对烧蚀面进行有效包覆,有助于提高烧蚀性能.  相似文献   

20.
This study describes the microstructure development as dense tantalum carbide (TaC), which is subjected to extreme temperature environments (3,000 °C) in the presence of oxygen. These are conditions that structural materials are expected to experience in hypersonic aero-propulsion applications. The conditions produce molten oxide which may provide a temporary resistance to rapid oxidation and may go some way to repair thermal shock cracks, however, at the same time the liquid is observed to attack the dense ceramic both chemically and mechanically. A reaction mechanism is suggested which involves dissolution of TaC in the oxide melt and a two step oxidation; first the reaction of TaC with oxygen to form Ta(O,C) and TaO x , resulting in dissolved dissociated carbon, followed by the reaction of dissolved carbon with oxygen to produce gas. This microstructural analysis of one of the candidate ultra-high temperature ceramic materials for hypersonic flight provides new insight into the mechanism of TaC oxidation and the role of the liquid oxide layer in acting not only as a protective layer to further oxidation, as is commonly reported, but also as a dynamic component that promotes erosion of the TaC surface and is a source of further oxygenation of the TaC surface. If the formation of the liquid phase can be better controlled and the reaction of the liquid phase with the matrix be slowed and stabilised, then the formation of a liquid phase at the surface of TaC may provide a key to designing materials that can withstand the rigours of hypersonic flight.  相似文献   

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