共查询到20条相似文献,搜索用时 78 毫秒
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以丁烷加空气为流态化渗碳气源,系统试验研究了充态化渗碳温度气氛碳势、刚玉粒径及表面流态化速度等对碳传递系数的影响。利用单纯形方法回归建立了不同条件下流态化渗碳碳传递系数数学模型和综合影响因素数学模型,试验验证表明,该数学模型具有较高的拟合精度。 相似文献
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本工作采用气相氢渗透技术,测定了220—420℃温度范围内,Fe-Ni-Co基超合金Incoloy 903的氢渗透率和扩散系数,讨论了该合金时效处理后强化相γ′对氢渗透和扩散特性的影响。结果表明:该合金的氢透率和扩散系数几乎与热处理状态无关,不受时效析出的γ′沉淀相的影响。氢渗透率和扩散系数与温度的关系可分别表示为φ=9.36×10~(-5)exp[-54.20(kJ/mol)/RT]mol/m·s·MPa~(1/2), D=4.24×10~(-7)exp[-49.07(kJ/mol)/RT]m~2/s。 相似文献
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20Cr钢铸铁浴渗碳碳的激活能的测定 总被引:1,自引:1,他引:0
本文将20Cr钢试样在铸铁浴中进行不同温度和时间的渗碳。用金相法测定层深,根据公式:ρ~2=K_0τ·e~(-Q/RT)对碳的激治能(Q)进行了计算,实验结果表明,与气体渗碳法相比激活能下降了50%。 相似文献
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利用气体渗碳物质传递数学模型来仿真计算碳浓度分布。并根据计算结果在计算机上拟合出碳浓度与时间、温度、气氛碳势之间的关系式.此关系式对气体渗碳的动态控制有指导意义. 相似文献
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碳/碳复合材料既有良好的生物相容性,又有良好的力学性能,是一种极具潜力的新型生物材料。为提高其硬度、耐磨性,降低摩擦系数,需对其表面进行处理。本研究先利用包埋法在其表面制备SiC涂层,后利用非平衡磁控溅射技术在SiC涂层表面制备了掺铬碳膜。通过XRD,Raman,SEM,EDAX和XPS对其结构和形貌进行了表征,用MM-200型环块磨损试验机对膜的摩擦学性能进行了测定。研究结果表明:掺铬碳膜在XRD及拉曼光谱上都没有明显的峰,为非晶态结构。碳原子主要为类石墨碳。非晶态掺铬碳膜的摩擦系数约为0.100,比碳/碳复合材料低;磨损率为0.45×10-6mm3·(Nm)-1,也比碳/碳复合材料低。 相似文献
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Microstructure of carbon fiber preform and distribution of pyrolytic carbon by chemical vapor infiltration 总被引:3,自引:0,他引:3
The carbon/carbon composites were made by chemical vapor infiltration(CVI) with needled felt preform. The distribution of the pyrolytic carbon in the carbon fiber preform was studied by polarized light microscope (PLM) and scanning electronic microscope(SEM). The experimental results indicate that the amount of pyrolytic carbon deposited on the surface of chopped carbon fiber is more than that on the surface of long carbon fiber. The reason is the different porosity between the layer of chopped carbon fiber and long carbon fiber. The carbon precursor gas which passes through the part of chopped carbon fibers decomposes and deposits on the surface of chopped carbon fiber. The pyrolytic carbon on the surface of long carbon fibers is produced by the carbon precursor gas diffusing from the chopped fiber and the Z-d fiber. Uniform pore distribution and porosity in preform are necessary for producing C/C composites with high properties. 相似文献
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Hyun -Seung Jung Seung Yong Lee Jae -Pyoung Ahn Jong-Ku Park 《Metals and Materials International》2006,12(5):417-423
Carbon nanofibers (CNFs) are synthesized by the dissociation of ethylene gas in the presence of Ni−Cu alloy catalysts; helical
CNFs are favored by Ni−Cu alloy catalysts. The role of alloy compositions and reaction time in the morphology of CNFs were
determined by varying both the Cu content in the alloy catalyst and the holding time at a particular synthesis temperature.
The chemical composition, the size, and the shape of the catalyst particles were shown to affect the morphology of CNFs. Two
kinds of growth mechanism are suggested to explain the growth of helical and straight CNFs. 相似文献
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采用剥层分析和模拟试验研究了渗碳过程中的升温、排气、强渗、扩散和降温各阶段的碳势变化对工件渗层最终碳浓度梯度的影响,结果表明,升温、排气和强渗阶段的碳势波动对工件最终表面碳浓度梯度的影响较小,而扩散阶段碳势波动的影响则较大,特别是降温阶段,碳势波动0.1%就会导致自表面至100μm处的渗层中碳浓度变化超过0.05%。 相似文献
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新型SiC-MoSi2/Al-O-Ti炭/炭抗氧化复合涂层的制备及其性能研究 总被引:1,自引:1,他引:0
采用包埋和涂刷法制备出一种新型的炭/炭复合材料抗氧化涂层,它由自愈合内涂层、热膨胀系数匹配过渡层、氧阻挡层三层复合而成.用SEM,XRD对它的组分和形貌进行了表征,同时测试了涂层在1 000,1 300和1 400℃下的抗氧化性能和抗热震性能.实验结果表明:该涂层能在1 400℃下有效保护炭/炭材料达50 h以上,经过... 相似文献
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Oxidation protective Si-Mo coatings were prepared by pack cementation on the surface of C/SiC coated carbon/carbon composites. The influences of Mo/Si mass ratio in the pack powders on the microstructure and oxidation resistance of the coating were investigated. It showed that with the Mo/Si ratio increasing from 0.1 to 0.4, the MoSi2 proportion and the dimension of cracks in the coating increased, and the oxidation protective ability of the coated specimens firstly increased and then decreased. The coating... 相似文献