PIP工艺制备Cf/SiC-ZrB2陶瓷基复合材料的研究

以聚碳硅烷和硼化锆前驱体为原料,采用前驱体浸渍裂解工艺制备C_f/SiC-ZrB₂复合材料,首先研究了粘度对前驱体溶液浸渍效率和材料致密度的影响,进而研究了浸渍压力等条件对材料性能的影响。结果表明：合理的溶液组分配比关系到混合溶液的粘度,是影响浸渍性能的主要因素;真空加压浸渍的方法可以减少制备周期,快速提高材料致密度,对材料的各方面性能都有明显的改善。     

PIP法制备C/C-SiC复合材料的工艺研究

以聚碳硅烷为原料,利用前驱体浸渍裂解工艺制备了C/C-SiC复合材料。分别研究了以二乙烯基苯和二甲苯为溶剂的聚碳硅烷溶液的粘度值,选择最佳的溶液对复合材料进行浸渍裂解,同时研究了浸渍工艺对复合材料致密度的影响,并对制备的C/C-SiC复合材料进行了微观结构分析。研究表明:以二甲苯为溶剂配制的质量比为0.4的聚碳硅烷溶液在35°C下具有良好的流动性,裂解产率较高;采用超声、真空加压浸渍方式能够有效提高C/C-SiC复合材料的致密度,缩短制备周期。通过9个周期的浸渍裂解,将复合材料的密度快速提升至1.85 g/cm~3,材料的最终开气孔率为12.50%,材料内部结构致密,力学性能优异。     

前驱体浸渍热解法制备C/C-SiC-ZrB_2复合材料及其抗氧化性能研究

以碳化硅前驱体和二硼化锆前驱体的甲苯溶液为浸渍剂,通过对C/C基体进行多次浸渍和热解制备C/C-SiCZr B2复合材料。利用XRD和SEM/EDS对C/C-SiC-Zr B2复合材料的组成和微结构进行了分析和表征,在静态空气气氛中测试了C/C-SiC-Zr B2复合材料的抗氧化性能。研究结果表明,C/C-SiC-Zr B2复合材料在1400℃空气中的抗氧化性能明显优于C/C复合材料,前者氧化1 h后失重率在0.5%左右,3 h后的失重率在9.3%左右,而相同条件下后者的失重率分别为28.5%和77.2%。     

SiC微粉加入对PIP法制备3D-Cf/SiC复合材料的影响

本文采用聚合物先驱体浸渍-裂解法(Precursor infiltration pyrolysis,PIP)制备出三维碳纤维增强SiC基复合材料(3D-C/SiC),研究了不同含量的SiC微粉对其制备周期、材料致密性和材料抗弯强度的影响.实验结果表明,先驱体溶液中加入适量SiC微粉可缩短3D-C/SiC的制备周期.材料致密度与抗弯强度随着先驱体中纳米SiC含量增加而不断增强,当含量达到11.76％时,材料致密度与抗弯强度达到最高,继续增加SiC微粉含量材料致密度与抗弯强度呈下降趋势.     

C/C-ZrB2-ZrC-SiC超高温复相陶瓷基复合材料的性能

以聚合有机锆烷、聚合有机硼氮锆烷与聚碳硅烷组成的共溶前驱体为原料,采用化学气相渗透和聚合物浸渍裂解工艺制备了C/C-ZrB2-ZrC-SiC超高温陶瓷基复合材料,对其物相组成、微观结构、力学性能和抗烧蚀性能进行了研究. 结果表明,所制材料基体由ZrB2和ZrC纳米颗粒均匀弥散分布于连续的SiC相中构成. 随热解炭含量增加,材料的弯曲强度和断裂韧性皆呈先上升再下降的趋势,其含量为22.3%(j)的材料的力学性能最优,弯曲强度和断裂韧性分别为127.9 MPa和6.23 MPa×m1/2,且具有假塑性断裂特性. 材料在1800~2200℃等离子弧中1000 s的线烧蚀率小于1.67 mm/s,质量烧蚀率小于1.66 mg/s.     

低电阻率聚吡咯-碳纤维纸基复合材料的制备

采用浆粕和碳纤维(CF)制备出碳纸前驱体,再把碳纸前驱体浸渍在含有吡咯(PY)和掺杂剂的混合溶液中至饱和后,喷上氧化剂,制备了聚吡咯(PPY)-CF纸基复合材料。探讨了不同的碳纸前驱体、不同种类的氧化剂与掺杂剂和PY浓度对PPY-CF纸基复合材料体积电阻率的影响。结果表明,对比植物浆粕和CF制备的前驱体,选用芳纶浆粕与CF制备的前驱体,在以过硫酸铵(APS)为氧化剂、蒽醌-2-磺酸钠(AQS)为掺杂剂、PY浓度为0.75 mol/L条件下,制备的PPY-CF纸基复合材料体积电阻率最低,为0.152Ω·cm。     

纳米SiO2对先驱体浸渍裂解法制备SiCf/SiC复合材料力学性能的影响

以纳米SiO2为填料,采用先驱体浸渍裂解法制备2.5D-SiCf/SiC（D为维数,SiCf为SiC纤维）复合材料,研究了前驱液中纳米SiO2含量对复合材料力学性能的影响。结果表明,纳米SiO2的添加能有效抑制先驱体裂解过程中的体积收缩,提高致密度,但过量引入易导致浸渍液黏度过高,浸渍效率降低。纳米SiO2含量对材料力学性能有较大影响,添加纳米SiO2后材料的抗弯强度和断裂韧性均高于没有添加的样品,材料抗弯强度随纳米SiO2含量的增加先增大后降低。当浸渍液中纳米SiO2含量为6%时,复合材料具有优异的力学性能,抗弯强度达到211.1MPa。     

ZrC/SiC多组元改性C/C复合材料的微观结构及力学性能研究

以炭毡作为纤维增强体,采用化学气相渗透工艺研制出低密度C/C复合材料,进而以低密度炭/炭复合材料为预制体,采用聚碳硅烷和有机锆前驱体作为复相陶瓷前驱体,采用先驱体浸渍裂解工艺成功制备出ZrC/SiC多组元改性C/C复合材料试样。借助万能电子试验机和扫描电镜进行材料的力学性能和微观结构分析。结果表明:包含ZrC颗粒的SiC相双组元弥散分布在C/C复合材料基体中,且随着前驱体中有机锆含量的增加,力学性能出现先升后降的趋势,当有机锆前驱体质量分数为25%时,改性C/C复合材料弯曲强度和弯曲模量较优,分别为241 MPa和17.25 GPa。。     

C/C–ZrB_2–SiC复合材料的制备及其性能

结合化学气相渗透工艺(chemical vapor infiltration)与前驱体浸渍裂解(precursor infiltration and pyrolysis,PIP)工艺,制备了C/C–Zr B_2–Si C复合材料,并对材料的力学性能和烧蚀性能进行了分析。结果表明:PIP工艺制备的C/C–Zr B_2–Si C复合材料的拉伸、弯曲及剪切强度分别为91.2、214和35.8 MPa,优于通过浆料浸渍工艺制备的复合材料。同时,热流3 200 k W/m~2,时间600 s的氧乙炔火焰试验表明,PIP工艺制备的C/C–Zr B_2–Si C复合材料具有良好的抗氧化烧蚀性能,其线烧蚀率和质量烧蚀率分别为0.002 mm/s和0.7 mg/s。     

SiCf/SiO2复合材料的制备及界面层对其力学性能的影响

以碳化硅(SiC)纤维为增强体,采用真空浸渍法制备了2.5维连续SiC纤维增韧的SiO2基(SiCf/SiO2)复合材料,研究了SiC纤维编织体上不同的界面层对SiCf/SiO2复合材料力学性能的影响.化学气相渗透(CVI)法制备的热解碳(PyC)和PyC/SiC双层界面层分别使材料的抗弯强度由无界面层的52.2 MPa提高至67.4 MPa和180.3 MPa,但均使材料的韧性降低.用扫描电镜观察了材料的断口形貌,结果表明,PyC和PyC/SiC层不仅提高了材料的抗弯强度,而且增加了基体同纤维间的结合力,使基体有效地将载荷传递给纤维.PyC/SiC层能有效地保护SiC纤维,防止烧结过程中释放出的结晶水对纤维的损伤,有助于提高材料的力学性能.     

Cf/SiC复合材料的原料高效改性及其3D打印制备研究进展

选用3D打印制备的碳纤维增强碳化硅陶瓷基（Cf/SiC）复合材料被广泛应用在航空航天、国防军事等重大领域。碳纤维（Cf）作为陶瓷基复合材料的主要候选增强体之一,由于表面惰性的存在,为了提高其与碳化硅（SiC）陶瓷基体的粘附性,对原料Cf的表面改性工作是十分必要的。粉末原料的高效改性制备是3D打印成型陶瓷的重要途径。本文综述了近年来国内外针对Cf改性的各种方法及特点,对Cf/SiC复合材料的3D打印成型及其高效制备方法进行归纳总结。     

Joining of Cf-SiC composites and ZrB2-SiC based composites for ultra high temperature applications

Gas tungsten arc welding (GTAW) of Cf–SiC composites to themselves and to ZrB₂-SiC based composites have been carried out with a filler material of (ZrB₂-SiC-B₄C-Y₂O₃-Al₂O₃) composite. The weld interfaces of joints of composites were clean and free from porosity and cracks. Penetration of filler material into voids and pores existing in the Cf-SiC composites was observed. An average shear strength of 25.7?MPa was achieved. The ZrB₂-SiC based composite joined to Cf-SiC (CVD) composite was exposed for 300?s to the oxy-propane flame at 2300?°C. The joint and interfaces between the filler material and parent composites were found to be unaffected by thermal cycling and oxidation during the exposure to the oxy-propane flame.     

Al2O3–SiC composites prepared by infiltration of pre-sintered alumina with a poly(allyl)carbosilane

The Al₂O₃/SiC nanocomposites containing 3–8 vol.% SiC were prepared through infiltration and in situ thermal decomposition of a preceramic polymer SiC precursor (poly(allyl)carbosilane) in pre-sintered alumina matrix. The volume fraction of SiC, and the microstructure of composites were adjusted by concentration of the polymer solution, and by the conditions of pyrolysis and sintering. The specimens were densified by pressureless sintering at temperatures between 1550 and 1850 °C in flowing argon. The use of powder bed producing SiO, CO and other volatile species suppressed decomposition reactions in the composites and was vital for their successful densification. The experimental results are discussed against thermodynamic analysis of the system Al₂O₃/SiC/SiO₂ in an inert Ar atmosphere.     

Mechanical behaviour and microstructure of Cf/ZrC,Cf/SiC and Cf/ZrC – SiC composites

Cf/ZrC, Cf/SiC and Cf/ZrC–SiC composites were successfully prepared by polymer infiltration and pyrolysis (PIP) using polycarbosilane and a liquid ZrC precursor. The densification process, mechanical properties and microstructures were studied in a view of comparison. After the same total 20 PIP cycles, the Cf/ZrC, Cf/SiC and Cf/ZrC–SiC composites had flexural strengths of 50.1±5.3, 285.7±22.6, 141.5±13.1?MPa respectively; elastic moduli of 7.8±0.9, 57.1±3.2 and 45.1±2.6?GPa respectively; and fracture toughness of 2.5±0.2, 10.4±0.9 and 10.9±1.1?MPa m^1/2 respectively. With the introduction of high modulus SiC phase into the ZrC matrix, the densification and modulus of the matrix were improved; as a result, the Cf/ZrC–SiC composite showed higher mechanical properties compared to Cf/ZrC.     

Carbon nanotube reinforced pyrocarbon matrix composites with high coefficient of thermal expansion for self-adapting ultra-high-temperature ceramic coatings

The mismatch in the coefficients of thermal expansion (CTE) of the carbon fiber reinforced pyrocarbon (Cf/C) composites and their thermal barrier coatings (TBCs) has significantly restricted the service life of Cf/C composites in high-temperature environments. Owing to the high CTE of TBCs, it is vital to find a material with similar mechanical properties and higher CTE than Cf/C composites. In this work, carbon nanotube reinforced pyrocarbon (Ct/C) nanocomposites with high CTEs were prepared to self-adapt to the TBCs. Different CTEs (～4.0–6.5 × 10^?6/°C) were obtained by varying the carbon nanotube (CNT) content of the Ct/C composites. Owing to the decreased mismatch in the CTEs, no cracks were formed in the TBCs (SiC and HfB₂-SiC-HfC coatings) deposited on the Ct/C composites. After heat treatment at 2100 °C, several wide cracks were found in the TBCs on the Cf/C composite, whereas the TBCs on the Ct/C composites were intact without cracks. We found that the CTE-tunable Ct/C composites can self-adapt to different TBCs, protecting the composites from oxidation at high temperatures.     

SiO2气凝胶纤维隔热复合材料的常压制备及性能表征

SiO₂气凝胶的力学性能较差,隔热性能较强,为了使其成为良好的隔热材料,本文提出一种SiO₂气凝胶纤维隔热复合材料的制备方法。以正硅酸乙酯(TEOS)为前驱体,玻璃纤维和陶瓷纤维为增强体,硅烷偶联剂KH550和KH570为纤维处理剂,在常压条件下制备SiO₂气凝胶纤维隔热复合材料,并对材料性能进行表征。结果表明:前驱体中十六烷基三甲基溴化铵(CTAB)含量越高,复合材料中SiO₂气凝胶导热系数越低,低至0.028 W/(m·K);使用硅烷偶联剂KH550时,基体和纤维之间结合的紧密程度更高;纤维的加入使SiO₂气凝胶的力学性能达到很高水平;当前驱体中TEOS与CTAB摩尔比为1∶0.022时,经KH550处理的玻璃纤维/SiO₂气凝胶复合材料导热系数为0.054 W/(m·K),力学性能良好,隔热性能最优。     

PANI/TIO复合材料的制备及其在聚氨酯涂料中的应用

采用原位聚合的方法在锑掺杂氧化锡/氧化钛复合材料（TIO）上包覆一层完整的聚苯胺（PANI）膜,成功制备了PANI/TIO复合材料,将其作为水性聚氨酯涂料的填料,制备了水性聚氨酯导电涂料。利用X射线粉末衍射、透射电镜、红外光谱等分析方法对复合材料进行表征,利用涂层机械性能测试对导电涂料进行了测试。同时得到了制备PANI/TIO三元复合材料的最佳工艺条件：苯胺（An）包覆量为15%、m(An)/m[磺基水杨酸（SSA）]=0.4、m(An)/m[过硫酸铵（APS）]=3。在最佳工艺条件下,得到的PANI/TIO复合材料体积电阻率为15.3Ω·cm。实验结果表明：当填料比为15%时涂层机械性能最佳,硬度为2B、耐冲击力为50 cm、附着力为1级、涂层表面电阻为3.56×105Ω/m2,该导电涂料有较好的应用前景。     

Manufacturing of ceramic matrix composite using a hybrid process combining TiSi2 active filler infiltration and preceramic impregnation and pyrolysis

The manufacturing of silicon carbide reinforced ceramic matrix composites by a hybrid process is explored. Fibre preforms are infiltrated with TiSi₂ powders using the slurry method. Using TiSi₂ active filler leads to reduce the porosity by the subsequent formation of nitride phases after treatment under N₂ atmosphere at low temperatures (≤1100 °C). Taking into account the influence of the specific surface area of the powder on the nitridation rate, it is shown that it is possible to produce nitrides TiN and Si₃N₄ at 1100 °C with an interesting volume expansion inside the composite. To complete the densification of the composite, a polymer impregnation and pyrolysis (PIP) process are performed with a liquid polymeric precursor. Characterizations of the composites show that mechanical properties are improved with the presence of the TiN and Si₃N₄ phases, and the number of PIP cycles.     

Preparation of alumina supported molybdena catalysts by new slurry impregnation method: MoO3/Al2O3 sulfide hydrodesulfurization catalyst

A new slurry impregnation method (SIM) of the preparation of a catalyst or catalyst precursor MoO₃/Al₂O₃ is described. Aqueous slurry of powdered MoO₃ is mixed with alumina extradátes and the mixture is refluxed. A low solubility of MoO₃ is sufficient for transport of MoO₃ from powder form via solution to the surface of the support. The catalysts were tested by hydrodesulfurization of thiophene at 1.6 MPa and 280–400°C. Their activity was similar to the activity of industrial and laboratory MoO₃/Al₂O₃ samples prepared by conventional impregnation with solution of ammonium heptamolybdate. The advantage of the SIM method is that calcination, producing nitrogeneous waste gases, is not required and that all deposited molybdenum species are adsorbed and not precipitated.