共查询到20条相似文献,搜索用时 58 毫秒
1.
炭布叠层为预制体,采用等温CVI工艺制备出炭/炭(C/C)复合材料。通过调节丙烯与氢气的比例得到热解炭结构分别为粗糙层(RL),光滑层(SL),各向同性(ISO)的三种C/C复合材料,研究了热解炭组织结构对C/C复合材料热导率的影响,讨论了C/C复合材料的导热机理。结果表明:RL织构C/C复合材料的热导率无论是在平行方向还是在垂直方向上都明显高于SL和ISO织构C/C复合材料,在两个方向上,RL织构C/C复合材料的最大热导率比SL织构C/C复合材料分别大41.0%和31.7%,是ISO织构C/C复合材料的2倍多,且3种C/C复合材料的热导率随温度的升高呈现不同的变化趋势。 相似文献
2.
选择了三种不同基体炭为主体,经成型、炭化与浸渍制备的样品为对象,采用扫描电镜(SEM),XRD和热导率测定等分析手段,分别研究了石墨化前后C/C复合材料的微观结构形态及导热性能变化.结果表明,炭化样品的视密度为1.61g/cm3~1.70g/cm3,石墨化度较低,且热导率较小.以D8μm单束丝经两维编制的样品呈现出整齐排列,热传导各向异性比为4.7倍.采用非编制纤维束黏结压制成型的样品以及石墨粉压制成型的样品,其导热性能在两维方向上表现为各向同性.2 700℃石墨化后样品的视密度在1.61g/cm3~1.69g/cm3,没有显著变化.热导率随石墨化度提高而增大,最大增幅达到石墨化前的15倍.单束丝样品热传导各向异性比从4.7扩大到6.3.非编制纤维束黏结压制成型样品的导热性仍保持各向同性,径向为222.27W/(m.K),轴向为243.40W/(m.K);此外,在室温~300℃范围内,2 700℃石墨化后C/C复合材料的热导率均随温度升高呈现出不同程度的下降趋势. 相似文献
3.
炭/炭复合材料致密化工艺研究现状 总被引:1,自引:1,他引:0
综述了炭/炭复合材料制备过程中所采用致密化工艺的研究现状,详细分析了液相浸渍和化学气相渗积(CVI)的工艺原理。液相浸渍工艺需要进行多次反复浸渍,较为繁杂;等温CVI工艺简单、产品性能稳定,但制备周期长、效率较低。在此基础上发展了强制流动热梯度CVI、感应加热梯度快速致密化技术、等离子体增强CVI、直热式化学气相渗积法(HCVI)等工艺,本文同时对这些工艺的原理及优缺点进行了阐述。 相似文献
4.
5.
李崇俊 《高科技纤维与应用》2015,40(3)
介绍了中间相沥青基碳纤维(MPCF)增强的碳/碳(C/C)复合材料在美国的研制及其在高超音速飞行器上应用概况。MPCF非均衡织物结构可实现2D-C/C复合材料单方向更高的热导率,K321 MPCF增强4∶1结构2D-C/C可达到X向室温368 W/(m˙K)的热导率。P30X MPCF 3∶1非均衡织物、转化法Si C及化学气相沉积Si C和HfC 3层涂层结构C/C复合材料用于X-43A马赫数(Ma)10飞行器C/C鼻锥部件,实现了2 200℃的临近空间环境中高超音速零氧化烧蚀。MER公司研制Ma 10飞行器鼻锥C/C时织物预处理温度是2 500℃,采用沥青碳和酚醛碳混合基体致密,C/C复合材料最终石墨化温度是2 800~3 000℃。 相似文献
6.
以煅烧石油焦为基体原料,配入一定量的陶瓷粉末和粘接剂,经长时间混合球磨,利用热压工艺研制出C/B4C、C/Ti、C/B4C/Ti及C/B4C/Ti/Si四种炭/陶复合材料,并描述了不同的原料配比对材料热导率的影响。 相似文献
7.
8.
9.
C/C多孔体对C/C-SiC复合材料微观结构和弯曲性能的影响 总被引:2,自引:0,他引:2
以4种纤维含量相同(32%,体积分数,下同),用化学气相渗透(chemical vapor infiltration,CVI)法制备了4种密度的碳纤维增强碳(carbon fiber reinforced carbon,C/C)多孔体,基体炭含量约20%~50%.利用液相渗硅法(liquid silicon infiltration,LSI)制备了C/C-SiC复合材料,研究了C/C多孔体对所制备的C/C-SiC复合材料微观结构和弯曲性能的影响.结果表明:不同密度的C/C多孔体反应渗硅后,复合材料的物相组成均为SiC,C及单质Si;随着C/C多孔体中基体炭含量的增加,C/C-SiC复合材料中SiC含量逐渐减少而热解炭含量逐渐增加.C/C-SiC复合材料弯曲强度随着材料中残留热解炭含量增加而逐渐增加,热解炭含量为约42%的C/C多孔体所制备的C/C-SiC复合材料的弯曲强度最大,达到320 MPa. 相似文献
10.
11.
Etherification of two alkenes, 2-methyl-1-butene and 2,4,4-trimethyl-1-pentene, was studied with seven different C1- to C4-alcohols. Although etherification was of primary interest, the isomerisation of the alkenes was the main reaction to occur. For the primary alcohols the etherification and isomerisation rates correlated well with the properties of the alcohols. Both rates increased with decreasing polarity and with increasing carbon number, acidity and Mulliken charge of the oxygen atom of the alcohol. It is difficult to distinguish the effect of each property separately, and probably the differences in the reactivities are not due to any one property alone but rather the synergy of the properties affects the reactivities. The secondary alcohols behaved in a different way than the primary ones: the etherification was almost negligible. The effect of alcohol on the isomerisation of alkenes was notable even though alcohol does not directly react in the reaction, which was concluded to be due to the stronger adsorption of the more polar alcohols which hinders the reactions of other components. 相似文献
12.
The effect of addition of tin on the catalytic activity of Ru/C catalysts has been investigated in the liquid phase hydrogenation of -methylstyrene and hydrocinnamaldehyde. On increasing the Sn content, the amount of CO chemisorbed decreases, indicating a decrease in the number of Ru surface atoms. In the hydrogenation of -methylstyrene the specific activity of Ru (calculated per Ru surface atom) remains constant regardless of the Sn/Ru ratio. An increase of specific activity is however observed in the hydrogenation of hydrocinnamaldehyde. It is suggested that tin, present mainly as Sn ions, enhances the reactivity of the C=O group. 相似文献
13.
C. Herranz Agustín J. Costa Lpez F. J. Domingo Campos 《European Journal of Lipid Science and Technology》1984,86(12):478-480
A group of not well known anionic phosphorus-containing surfactants have been obtained. In these surfactants the hydrophobic chain is directly linked to the phosphorus atom through a P-C bond. These products are alkylphosphinates with C10, C12, C14 and C16 alkylic chains. The products have been prepared by direct reaction between sodium hydrophosphite and the corresponding α-olefin, using tert-butyl perbenzoate as reaction initiator. Surfactants properties such as surface tension, foaming power and wetting power of the sodium and ammonium salts of all these alkylphosphinates have been measured. 相似文献
14.
本文介绍了北京首创轮胎公司新建工厂三复合冷喂料挤出生产线的调试情况,对三复合冷喂料挤出机基本结构、工艺特点做了概述,并且通过生产线出型胎面调试过程中遇到的问题,采取相应措施进行解决做了详细说明,通过近两年来的运行情况,总结出本生产线的使用优势。 相似文献
15.
Shraddha SinghV.K. Srivastava 《Ceramics International》2011,37(1):93-98
The electrical properties of carbon/carbon (C/C) and carbon/carbon-silicon carbide (C/C-SiC) ceramic composites were measured. The results show that the capacitance decreases rapidly with an increase in frequency and it becomes constant above a frequency of 500 kHz, whereas the dissipation factor increases with increasing frequency. C/C-SiC composites give higher value than C/C composites due to the presence of microcracks. 相似文献
16.
采用浸渍法制备 Pt/C,Pd/C和 Pd- Bi/C催化剂。将三种催化剂对葡萄糖的脱氢和加氧氧化两种反应的催化效果作对比研究 ,发现三种催化剂对这两个反应有着完全相反的催化顺序 :催化脱氢时 Pt/C效率最高 ,而加氧反应中 Pd- Bi/C却具有绝对优势。为解释此结果 ,结合催化剂的表征 [2 ] ,尝试提出了催化加氧和脱氢的机理 ,并确定了 Pd- Bi/C催化剂中的最佳 Bi/Pd比和两种催化反应的最佳工艺条件。实验结论 :Pt/C用于葡萄糖催化脱氢为可行的工业化途径 ,而 Pd- Bi/C对葡萄糖的催化加氧则具有挑战酶催化过程的能力 ,有一定的市场应用前景 相似文献
17.
18.
Fiber-bundle push-out, single-fiber push-in, and single-fiber push-out tests were conducted in order to examine the applicability of these methods for determining the interfacial shear strength of carbon-carbon composites. The fiber-bundle push-out test resulted mostly in fractures along the fiber/matrix interface but created a small amount of fractures in the matrix. Hence, the evaluated strength was regarded as an approximate value. In order to precisely evaluate the interfacial strength, push-in and push-out tests for a single fiber were performed using a micro-Vickers indentation tester. In these tests, the load has to be placed within a target fiber, and the indentation should not extend to the matrix. This condition restricted the load that could be applied to a carbon fiber. Within this limit, a single carbon fiber could not be pushed-in. For the sake of load reduction, single-fiber push-out tests were conducted using thin specimens. The thickness appropriate for a single-fiber push-out specimen was estimated based on the interfacial shear strength obtained by the bundle push-out tests. Below this thickness, single-fiber push-out tests could be successfully performed. 相似文献
19.