共查询到20条相似文献,搜索用时 875 毫秒
1.
2.
γ射线辐照聚碳硅烷先驱丝协同热交联制备高强度碳化硅纤维 总被引:5,自引:2,他引:3
采用γ射线在空气中辐照聚碳硅烷(polycarbosilane,PCS)先驱丝,将吸收剂量低于凝胶点剂量的PCS先驱丝在选定条件下作特殊的热交联处理,然后在惰性气氛保护下热解转化为SiC陶瓷纤维.通过红外光谱、热重分析、拉伸强度和氧含量测试研究了聚碳硅烷先驱丝的化学结构、热分解特性的变化以及烧成SiC纤维的结构与性能.结果表明:经热处理PCS的先驱丝形成了三维网络不熔不溶结构,其陶瓷产率高于未经热处理的先驱丝的陶瓷产率;经热交联处理的先驱丝所烧成的SiC纤维抗拉强度达2.3 GPa,较未经热交联处理的先驱丝所制得的SiC纤维的拉伸强度大幅提高;辐照协同热交联法制备的SiC纤维的氧含量低于直接辐照不熔化法制备的SiC纤维的氧含量. 相似文献
3.
4.
5.
以三维四向编织方式的碳化硅纤维预制体为增强相,选用聚碳硅烷为先驱体浸渍剂,采用聚合物先驱体浸渍裂解工艺制备了SiC纤维增强SiC陶瓷基(SiC/SiC)复合材料,进而采用自主设计研制的陶瓷基复合材料高温面内剪切测试夹具对SiC/SiC复合材料进行高温面内剪切强度测试,分析研究了试样形状尺寸、加载速率、夹具材料等对SiC/SiC复合材料高温面内剪切强度测试结果的影响,并分析了夹具材料、测试环境等对测试夹具寿命的影响,最终优化确认出一套较优的针对SiC/SiC复合材料的高温面内剪切强度测试方法。 相似文献
6.
7.
8.
9.
10.
《中国陶瓷》2018,(12)
分别以毛竹、竹纤维、脱脂棉为模板,采用聚碳硅烷(PCS)有机溶剂浆料浸渍法,在惰性气氛下低温热解制备了SiC木材陶瓷,分别对烧成产物的微观形貌、线收缩率、体积密度、力学性能和元素组成等特征变化进行了讨论分析。结果表明:以PCS为陶瓷先驱体,选用不同生物模板,在1000℃下可低温烧结制备出SiC木材陶瓷。毛竹模板和竹纤维模板制备得到的木材陶瓷能较好地保留模板材料的原有结构,脱脂棉制模板则形成了不规则的通孔结构。随着PCS含量的增加,三种模板烧成的SiC木材陶瓷的线收缩率均逐渐降低;体积密度逐渐增大;竹纤维和脱脂棉模板制备的SiC木材陶瓷的抗弯强度逐渐增大,毛竹模板制备的SiC木材陶瓷的抗弯强度先上升后下降。相同PCS含量下,毛竹结构SiC木材陶瓷抗弯强度更大。 相似文献
11.
先驱体聚碳硅烷的纺丝工艺是制备高性能连续SiC纤维过程的关键环节,纺丝工艺决定了原丝的性能优劣,而纺丝工艺对聚碳硅烷原丝的损伤程度也将决定最终的SiC纤维性能.为此,利用扫描电子显微镜对整桶纺出原丝的直径、表面和截面缺陷进行了观察,利用统计方法对直径和缺陷的分布进行了分析.研究发现:原丝平均直径从外层到内层大体呈减小的趋势,并且每层数值波动逐渐减小,靠近中间层的原丝直径与整体平均值最为接近.表面划痕由外层到内层划痕逐渐减少.鼓泡在各层之间呈均匀分布.断面气孔主要集中在最外几层原丝中.根据统计结果得到了结构特征分布模型,建立了评价整桶原丝性能优劣的有效方法. 相似文献
12.
Thermostatic pyrolysis process of cured polycarbosilane fiber 总被引:4,自引:0,他引:4
As precursor fiber of advanced SiC fiber, cured polycarbosilane (PCS) fiber is prepared, and thermostatic pyrolysis of this
fiber is studied in detail. Since the weight change is the most important characteristic of the pyrolysis degree of cured
PCS fiber, a precise balance is applied on-line to follow the weight change of the cured PCS fiber, which was carried out
in a standing style furnace. In thermostatic pyrolysis, the degree of pyrolysis, which is characterized by the weight loss
of the fiber, and the properties of the final SiC fibers were found to be strongly dependent on the process conditions such
as N2 flow and the amount of fibers. From much evidence, it is the offgas evacuated in the process that plays an important role
by accelerating pyrolysis and increasing pyrolysis degree. 相似文献
13.
Xiali Zhen Xueliang Pei Yanfei Wang Xiqiang Zhong Liu He Zhifang Chai Zhengren Huang Qing Huang 《Journal of the European Ceramic Society》2019,39(6):2028-2035
Crosslinking is favorable for increasing the ceramic yield of polycarbosilane precursor (PCS), so PCS fiber with crosslinked skin-uncrosslinked core structure may contribute to formation of hollow SiC fiber. In this study, diffusion-controlled ozone oxidation crosslinking method was adopted. EDS verified the oxygen element contributing to crosslinking mainly distributed in the outer layer of ozone-crosslinked PCS fiber (O ? PCSf). After pyrolysis, SEM confirmed the formation of continuous hollow fiber and XRD indicated the presence of β-SiC structure. N2 adsorption-desorption measurement demonstrated that a lot of micropores and mesopores, which were the main escape paths for degradation product of uncrosslinked core part of O ? PCSf and contributed to the formation of continuous hollow SiC fiber, formed along fiber during pyrolysis and disappeared after the pyrolysis temperature was increased. In addition, by adjusting ozone oxidation time and applying vacuum pyrolysis method, the morphology of resulting hollow SiC fiber could be further modified. 相似文献
14.
《Journal of the European Ceramic Society》2023,43(4):1385-1396
The polymer-derived ceramics (PDCs) technique enables relatively low-temperature fabrication of Si-based ceramics, with silicon carbide fiber as a representative product. Polycarbosilane (PCS) has Si-C backbone structures and can be converted to silicon carbide. In the PDCs method, residual or excess carbon is generated from the precursor (C/Si ratio = 2 for polycarbosilane). Because of the non-stoichiometry of SiC, the physicochemical properties of polymer-derived SiC are inferior to those of conventional monolithic SiC. Herein, a silicon carbide-hafnium carbide nanocomposite fiber was optimized by crosslinking oxygen into the PCS fiber by regulating the oxidation curing time. During pyrolysis, carbothermal reduction, and sintering, carbon was removed by reaction with hydrogen and cross-linked oxygen. Non-destructive techniques (X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and high-temperature thermomechanical analysis) were used to investigate the effects of excess carbon. The microstructure of the near-stoichiometric SiC-HfC nanocomposite fiber was more densified, with superior high-temperature properties. 相似文献
15.
《Ceramics International》2019,45(13):16008-16014
The polycarbosilane (PCS) as a ceramic precursor is mainly synthesized using an autoclave and is modified via the reflux method to add organometallic compounds. However, in this study, a zirconium source was added to PCS in order to improve the heat resistance of the polymer-derived SiC fibers using an easy and simple blending method. The zirconium-added PCS solution was spun via electrospinning and converted to Si–Zr–C–O fiber felts at 1300 °C through the processes of curing and pyrolysis. In order to investigate their thermal-degradation behavior, the zirconium added SiC fiber felts were heat-treated at 1500 °C or 1600 °C for 1 h in an Ar atmosphere. The results indicated that the aforementioned felts retained blackness and flexibility, whereas SiC fiber felts deteriorated and were discolored to gray. Moreover, the results confirmed that the growth of crystalline size (approximately calculated via XRD analysis) was significantly inhibited by the presence of zirconium. Therefore, zirconium acetylacetonate as a zirconium source was cross-linked with the PCS structure via the blending method and its role for heat resistance was exhibited at high temperature. 相似文献
16.
Rapid Preparation of SiC Fibers Using a Curing Route of Electron Irradiation in a Low Oxygen Concentration Atmosphere 下载免费PDF全文
Zhiming Su Litong Zhang Yongcai Li Siwei Li Lifu Chen 《Journal of the American Ceramic Society》2015,98(7):2014-2017
Polycarbosilane (PCS) fiber was irradiated by electron beam at low dose in a flowing N2/O2 mixture with O2 concentration of 1%. After the pyrolysis of the irradiated precursor fibers, SiC fibers with high strength of 2.4 GPa were obtained. Microstructural evolutions of the resultant fibers were explored. It was found that during the irradiation, free radicals were formed in the PCS and were oxidized by oxygen as Si–OH groups. The Si–OH groups then transformed into Si–O–Si linkage and resulted in further cross‐linking of the PCS during pyrolysis. A remarkable structure gradient along the fiber diameter was formed under the coupled effects of irradiation and oxidation. The content of oxygen decreased from the fiber surface to the core, whereas the crystallinity of β‐SiC increased in the same direction. The electrical resistivity of the as‐prepared ceramic fiber was 80.7 Ω cm, showing good potential for being as electromagnetic wave absorber. 相似文献
17.
采用热模压辅助聚合物先驱体浸渍裂解工艺制备了国产近化学计量比SiC纤维增强SiC陶瓷基复合材料,通过阿基米德排水法和SEM技术对SiC/SiC复合材料致密化过程进行表征,采用弯曲强度、拉伸强度和断裂韧性对SiC/SiC复合材料力学性能和力学行为进行评价。研究表明,热模压压力是影响材料结构和性能的重要因素,热模压在提升材料致密度的同时,亦造成纤维的损伤。随着热模压压力的增加,SiC/SiC复合材料力学性能先增加后降低。热模压压力适中时,致密度增加因素占优,材料力学性能较为优异;热模压压力较大时候,热模压操作对纤维性能的损伤因素逐渐凸显,基体致密化和纤维损伤两种作用机制相当。 相似文献
18.
《Journal of the European Ceramic Society》2020,40(2):290-297
Continuous carbon fiber (Cf) reinforced silicon carbide (SiC) matrix composite (Cf/SiC) was processed through hot pressing (HP) using polycarbosilane (PCS) in matrix and polysilazane in interphase regions as polymer binders. HP experiments were conducted at 4 MPa, 1200 °C and 1 h; followed by PCS polymer impregnation and pyrolysis (PIP) at 1200 °C under vacuum. The BN/SiC-Si3N4 interphase formed on the Cf cloth during BN dispersed polysilazane polymer coating and pyrolysis. The influence of PCS quantity during HP experiments on Cf/SiC composites was studied. Results suggest that sintering of SiC matrix in Cf/SiC composite improves by increasing PCS content during HP; however, high PCS content increases the liquidity of SiC-PCS mixture to flow out of the composite structure. The Cf/SiC composites with relative density ranging from 79 to 83% and flexural strength from 67 to 138 MPa was achieved. 相似文献
19.
Mingwei Chen Haipeng Qiu Qiyue Zhang Xin Ma Bingyu Zhang 《International Journal of Applied Ceramic Technology》2022,19(6):3238-3246
The SiC/SiC composites were manufactured by polymer precursor impregnation pyrolysis process with near stoichiometric SiC fiber 2D preform as the reinforcing phase, the mixed solution of polycarbosilane (PCS), and xylene as impregnant. The effects of PCS concentration on the densification process, microstructure, and mechanical behavior of SiC/SiC composites were investigated using mechanical property testing, scanning electron microscopy, and other characterization techniques. Results showed the porosity and flexural strength of SiC/SiC composites increased first and then decreased with the increase of PCS concentration. When the concentration of PCS was 55% and 60%, the flexural strength of SiC/SiC composites reached 565.77 and 573.02 MPa, respectively. The mechanical behavior of SiC/SiC composites presented typical pseudoplastic characteristics such as fiber pulling-out, fiber bridging, and interface layer peeling, which would meet the dual requirements of optimizing the matrix and interface structure. 相似文献
20.
《Ceramics International》2020,46(5):5602-5609
SiC fibers can be obtained by the spinning, curing, and heat treatment of polycarbosilane (PCS); however, the properties of the PCS precursor must be considered to set the correct spinning conditions. Although many studies have focused on the synthesis conditions, the characterization (in particular, the structural characteristics) of PCS fibers, and the polymer itself has limitations. In this study, PCS was prepared in two steps, and the growth of the polymer with respect to the reaction conditions was analyzed. We found that PCS is formed and grown by the rearrangement and subsequent condensation reactions of polydimethylsilane (PDMS). Further, fiber formation was affected by the reaction temperature, time, and pressure. Three types of PCS were obtained under different synthetic conditions, and they were all characterized. Regardless of the structural similarity of the PCS fibers (based on the spectroscopic analysis), the polymers showed different thermal and rheological properties. Our findings will be important in improving the production of PCS fibers (and subsequent SiC fibers) with finely controlled properties. 相似文献