聚硅氧烷先驱体转化制备三维Cf/Si-O-C复合材料的研究

研究了含氢聚硅氧烷(PSO)与二乙烯基苯(DVB)的交联与裂解。结果表明:只有在氯铂酸的催化作用下,PSO与DVB才能完全交联。DVB/PSO质量比对陶瓷产率的影响较大,DVB/PSO＝0.5时陶瓷产率最高,达到76%。裂解产物中Si,C,O的含量分别为38.3wt%,34.3wt%,27.4wt%。以质量比为0.5的DVB/PSO体系为先驱体,采用先驱体转化法制备出三维C_f/Si-O-C复合材料。研究发现:第一次裂解时采用热压辅助可以明显提高材料的力学性能。第一次在1600℃,10MPa的条件下热压裂解5min,后续真空浸渍-常压裂解处理六个周期所制得的材料具有较高的力学性能,其弯曲强度和断裂韧性分别为502MPa,23.7MPa·m 1/2。理想的界面结合状态是其具有高性能的主要原因。     

SiCf/SiC复合材料的制备与力学性能

分别采用先驱体裂解-热压和先驱体浸渍-裂解方法制备出了SiCf/SiC复合材料.重点探讨了不同制备工艺对复合材料纤维/基体间界面和断裂行为的影响.研究表明,采用先驱体裂解-热压工艺制备复合材料时,虽然烧结液相可以促进复合材料的致密化,但其同时导致纤维与基体间的界面结合强以及纤维本身性能的退化,因此复合材料表现为脆性断裂,具有较低的力学性能.而采用先驱体浸渍-裂解法制备复合材料时,由于致密化温度较低,复合材料中纤维与基体的界面结合较弱,而且纤维的性能保留率较高,因此,纤维能够较好地发挥补强增韧作用,复合材料具有较好的力学性能,其抗弯强度和断裂韧性分别为703.6MPa和23.1Pa.m1/2.     

热压辅助先驱体裂解制备三维编织碳纤维增强Si-O-C复合材料的研究

以聚硅氧烷为先驱体 ,采用先驱体转化法制备三维编织 Cf/ Si- O- C复合材料。研究发现 ,第一次裂解时采用热压辅助可以明显提高材料的致密度和力学性能。第一次在 1 6 0 0℃ / 1 0 MPa的条件下热压裂解 5 min,后续真空浸渍 -常压裂解处理六个周期所制得的材料具有较高的力学性能 ,其弯曲强度和断裂韧性分别为 5 0 2 MPa,2 3 .7MPa.m1 /2 。讨论了制备工艺对材料结构和性能的影响 ,理想的界面结构与较高的致密度是其具有高性能的主要原因     

裂解升温速率对聚碳硅烷先驱体转化制备Cf/SiC材料弯曲性能的影响

以聚碳硅烷(PCS)／二乙烯基苯(DVB)为先驱体制备了3D-B Cf／SiC复合材料，研究先驱体转化过程中不同裂解升温速率对材料力学性能的影响。结果表明：随着裂解升温速率的提高，材料致密度增加，界面结合变弱，从而陶瓷基复合材料的力学性能明显提高。以15℃／min裂解升温速率制得的陶瓷基复合材料的室温弯曲强度达到556．7MPa，1300℃真空下测试，材料的弯曲强度达到680．3MPa。     

聚碳硅烷和二乙烯基苯的交联及纳米SiC陶瓷的制备

碳化硅基复合材料是理想的高温结构材料,以聚碳硅烷(PCS)作为碳化硅陶瓷的先驱体,二乙烯基苯(DVB)为交联体,通过改变二者的配比研究了PCS与DVB的交联反应以及PCS/DVB交联体的热裂解过程。通过傅立叶红外光谱详细研究了PCS/DVB配比变化对PCS与DVB的交联反应和交联体微观结构的影响,PCS/DVB配比最终决定碳化硅陶瓷的产率,当PCS/DVB配比为1∶0.5时,经1500℃热裂解后碳化硅陶瓷产率最高,达到63.1%,热裂解产物为纳米碳化硅,粒径为10-40nm。用SEM和XRD研究了不同PCS/DVB配比交联体热裂解产物的微观结构和相组成,通过热重分析研究了PCS/DVB配比为1∶0.5时交联体的热裂解过程,在400-800℃,PCS/DVB交联体失重显著,在800℃热裂解过程基本完成,PCS/DVB配比为1∶0.5时能够制备出纳米碳化硅基复合材料。     

制备工艺对Cf/SiC复合材料力学性能的影响

分别采用先驱体裂解-热压和先驱体浸渍-裂解方法制备出了Cf/SiC复合材料.重点探讨了不同制备工艺对复合材料纤维/基体间界面和力学性能的影响.研究表明,采用先驱体裂解-热压工艺制备复合材料时,由于制备温度较高,复合材料中纤维与基体间的界面结合强,同时纤维本身性能的退化严重,因此复合材料表现为脆性断裂,具有较低的力学性能.而采用先驱体浸渍-裂解法制备复合材料时,由于致密化温度较低,复合材料中纤维与基体的界面结合较弱,而且纤维的性能保留率较高.因此,纤维能够较好地发挥补强增韧作用,复合材料具有较好的力学性能, 其抗弯强度和断裂韧性分别为573.4MPa和17.2 MPa*m1/2.     

不同陶瓷先驱体的裂解过程及粘接性能

研究了三种陶瓷先驱体聚硅氮烷（PSZ）、聚硅氧烷（PSO）、聚碳硅烷（PCS）的裂解过程,并对其裂解产物进行了物相分析,在此基础上分别采用这三种先驱体为粘接剂连接碳化硅陶瓷。结果表明,PSZ、PSO在裂解过程中发生了交联反应,获得了较高的陶瓷产率;PCS交联性能较差,陶瓷产率较低;由XRD分析得出,在1200℃～1400℃温度范围内,随着温度的升高,三种先驱体的裂解产物均发生了由非晶态向晶态的转变。连接实验表明,采用PSZ、PSO为粘接材料均能获得较好的连接效果,连接件剪切强度分别达38．6MPa和33．2MPa,连接层厚度小于5μm,其结构较为均匀致密,与基体间界面接合良好;采用PCS为粘接材料时,不能获得有效的连接强度。     

先驱体陶瓷

综述了用先驱体法制备陶瓷纤维、陶瓷基复合材料等的特点及其研究进展,针对制备陶瓷基复合材料基体的有机聚合物先驱体,提出了先驱体必须满足的理化特性和结构特征,同时还针对先驱体法高气孔率及高收缩率的不足,提出了３个解决办法,并着重讨论了活性填料在先驱体裂解制备陶瓷基复合材料中的特点与应用。     

RTM成型工艺对C_f/SiBCN陶瓷基复合材料性能的影响

采用流变仪研究了聚硼硅氮烷作为RTM树脂的成型工艺性能,进而采用RTM工艺成型出复合材料坯体,再经过重复的浸渍-常压裂解工艺制备了Cf/SiBCN陶瓷基复合材料,详细研究了RTM成型缺陷对复合材料的厚度、密度以及力学性能等方面的影响。结果表明:聚硼硅氮烷完全满足RTM成型工艺对流变性能的要求;RTM成型缺陷会进一步加剧复合材料的膨胀,使复合材料的厚度明显增大;同时会降低浸渍裂解前期复合材料的密度;最终复合材料的抗弯强度和模量均略有降低。     

先驱体转化—热压烧结Cf／SiC复合材料的致密化机理

本文采用先驱体裂解--热压烧结方法制备出了Cf/SiC复合材料，并重点研究了复合材料的致密化过程。结果表明，复合材料主要是通过液相烧结而得到致密化的。由于复合材料中聚碳硅烷（PCS）的裂解不仅有利于烧结液相的形成，而且形成了大量的纳米级SiC颗粒，因此，复合材料能够在较低烧结温度下得到较好的致密化，从而使复合材料具有较好的力学性能。     

Curing and pyrolysis of polysiloxane/divinylbenzene and its derived carbon fiber reinforced Si—O—C composites

The curing and pyrolysis of hydrogen-containing polysiloxane (PSO) and divinylbenzene (DVB) were investigated in this paper. It was found that H₂PtCl₆ was an effective catalyst for the curing of DVB/PSO. The mass ratio of DVB/PSO had great effect on ceramic yield. The cured DVB/PSO with a mass ratio of 0.5:1 had the highest ceramic yield (76%) at temperature up to 1000°C, and its pyrolysates consisted of 38.3 wt% silicon, 27.4 wt% oxygen, and 34.3 wt% carbon of which 26.3 wt% was free carbon. The composition and structure of pyrolysates of DVB/PSO were changed with increasing pyrolysis temperature. The pyrolysis behavior of DVB/PSO was characterized by thermal analysis. DVB/PSO-derived Si–O–C composites reinforced with carbon fiber cloth (C_f/Si–O–C) were fabricated. The results showed that the flexural strength of C_f/Si–O–C composites could be increased from 118.00 ± 5.00 MPa to 139.78 ± 7.68 MPa if the pyrolysis temperature was elevated from 1000 to 1400°C, which was ascribed to the weakened interfacial bonding.     

聚硅氧烷先驱体转化制备低成本Si-O-C陶瓷基复合材料

研究了廉价聚硅氧烷的交联与裂解情况 ,并以其为先驱体制备出Si O C陶瓷基复合材料。结果表明 ,在氯铂酸的催化下 ,聚硅氧烷与二乙烯基苯可以交联固化。当聚硅氧烷 二乙烯基苯摩尔比为 1∶0 5时 ,陶瓷产率达 6 0 5 2 %。经 6次浸渍 交联 裂解过程制备出碳纤维三维编织物增强陶瓷基复合材料 ,其密度达到1 5 9g cm3 ,弯曲强度达到 32 1MPa ,断裂韧性达到 9 38MPa·m1 2 。     

裂解工艺对先驱体转化制备Cf/SiC材料结构与性能的影响

以聚碳硅烷(PCS)/二乙烯基苯(DVB)为先驱体,经8个周期的反复真空浸渍-交联-裂解处理制备出三维编织碳纤维增强碳化硅(3D-B C_f/SiC)复合材料,考察了裂解工艺对材料结构与性能的影响。结果表明:提高裂解升温速率可以提高材料密度,形成较理想的界面结合,从而提高材料的力学性能。裂解温度对材料性能也有较大的影响,C_f/SiC复合材料在第6个周期采用1600℃ 裂解可以弱化纤维与基体之间的界面,提高材料致密度,材料的力学性能也得到较大改善。裂解升温速率为15℃/min,第6个周期采用1600℃裂解制备的C_f/SiC材料性能较好,弯曲强度达到556.7 MPa。      

聚碳硅烷／二乙烯基苯的高温裂解

研究了聚碳硅烷／二乙烯基苯的裂解过程，并对裂解产物的结构进行了表征，分析了造成其裂解产物的结构与形貌不同的原因。     

A simple way to prepare precursors for zirconium carbide

A precursor for zirconium carbide was obtained by just blending zirconium butoxide Zr(OC₄H₉)₄ (ZTB) and divinylbenzene (DVB). This precursor satisfied the requirements for use in ceramic matrix composites fabrication via precursor infiltration and pyrolysis (PIP) process, that is, it was a solution, cross-linked at 150 °C for 2 h, and transformed to ZrC matrix upon heat treatment at 1,600 °C with a ceramic yield around 40%. The cross-linking behavior, pyrolysis process, and optimal molar ratio (ZTB and DVB) of the precursor were investigated by IR, DSC–TGA, and XRD analysis. ZTB and DVB decomposed into ZrO₂ and carbon, respectively, at 400–500 °C, and ZrO₂ and carbon reacted with each other via carbo-thermal reaction at higher temperature to form ZrC.     

Preparation of a hyperbranched polycarbosilane precursor to SiC ceramics following an efficient room-temperature cross-linking process

Room-temperature cross-linking of a hyperbranched polycarbosilane (HBPCS) with divinylbenzene (DVB) in the presence of the cyclohexanone peroxide–cobaltous naphthenate (CHP–CN) initiator system was studied. According to the Fourier transform infrared spectroscopy (FT-IR) and ¹H nuclear magnetic resonance (¹H NMR) results, the cross-linking reaction occurred via the vinyl polymerization. The GPC analysis confirmed the molecular weight of the cross-linked HBPCS significantly increased. Thermal behaviors of cross-linked HBPCS and original HBPCS were investigated by thermal gravimetric analysis-differential thermal analysis (TGA–DTA). The TGA results indicated that the ceramic yield of HBPCS remarkably increased by the cross-linking treatment. For the HBPCS/10 wt% DVB system, the maximum of reaction degree of HBPCS was obtained, which might be responsible for the highest ceramic yield of 70.1 wt% at 1000 °C. However, the ceramic yield of the non-crosslinked HBPCS was only 45 wt% at 1000 °C. The evolution of crystal structure of SiC as a function of pyrolysis temperature was traced by means of X-ray diffraction (XRD) and FT-IR. With the pyrolysis temperature increasing, the β-SiC peaks became sharper and the grain size also grew larger. As the DVB content increased, the intensity of β-SiC peaks significantly reduced, indicating smaller β-SiC grain size.     

三维整体编织物增强陶瓷基复合材料的制备工艺及性能表征

本文研究了以连续碳纤维(C_f)三维整体编织物(3D-B)为增强体,以聚碳硅烷(PCS)裂解转化成碳化硅(SiC)为基体的陶瓷基复合材料(CMC)的制备工艺,探讨了不同工艺方法对复合材料微观和宏观性能的影响,并提出进一步改善制各工艺,提高复合材料性能的途径。研究结果表明,采用聚碳硅烷/二乙烯基苯(PCS/DVB)体系浸渍经交联固化后可以大大缩短裂解时间,致密化效率较聚碳硅烷/二甲苯溶液(PCS/Xylene)体系有着显著提高。对于3D-B C_f/SiC CMC用PCS/DVB体系浸渍经7个浸渍裂解周期后试样密度为1.65g/cm3,弯曲强度达326MPa,断裂韧性K_IC为13.72MPa·m1/2;用PCS/Xylene体系浸渍的试样密度为1.54g/cm3,弯曲强度为243MPa,断裂韧性K_IC为8.19MPa·m1/2。研究中利用扫描电镜观察了弯曲试样的断口以分析材料破坏时纤维的断裂、拨出形貌。     

Synthesis of nickel ferrite-dispersed carbon composites by pressure pyrolysis of organometallic polymer

Nickel ferrite-dispersed carbon could be synthesized by pressure pyrolysis of divinylbenzene (DVB)-vinylferrocene (VF)-nickelocene (Cp₂Ni) polymer in the presence of water under 125 MPa and at temperatures below 700°C. By heat treatment at 550°C with water, nickel ferrite particles could be dispersed finely in the carbon matrix, although a small amount of nickel-iron carbide also began to form above 600°C. The morphologies of the carbon particles formed were observed to be polyhedral, coalescing spherulitic and spherulitic. When 30 wt% H₂O, spherulitic carbons a few micrometres in diameter were prepared, in which nickel ferrite particles from 10–30 nm were dispersed in the carbon matrix. The saturation magnetization of carbon composites formed from DVB-3.0 mol% Cp₂Ni-6.0 mol% VF and 20 wt% H₂O at 550°C was about 30 e.m.u.g^–1 and increased with pyrolysis temperature. The coercive force of the carbon composite was 120 Oe and was affected by the amount of added water using pressure pyrolysis. Thermomagnetic measurement shows that the Curie temperature of nickel ferrite-dispersed carbon was about 580 °C.