C/C复合材料抗氧化耐高温SiC陶瓷涂层的研究

采用高温反应法和PVD法在SiC工业合成炉内制备了C/C复合材料耐高温抗氧化SiC陶瓷涂层.用XRD、SEM对其物相组成和显微结构进行了表征与分析,讨论了涂层的形成机理,并研究了其高温氧化性能.研究结果表明,所制备的陶瓷涂层主要由α-SiCβ-SiC组成,晶粒发育完整,涂层表面致密、无裂纹,且与碳基体结合紧密,涂层厚度约600μm,涂层抗氧化性良好,在1500℃空气中氧化10h失重约为0.3%.     

C/C预制体孔隙率与气相硅浸渗制备C/SiC复合材料性能关系的模型研究

建立了C/C预制体孔隙率与C/SiC复合材料组成的关系模型,并通过表征不同孔隙率的C/C预制体气相硅浸渗制备的C/SiC复合材料的组成和力学性能对模型进行了验证。研究发现,实验结果与模型预测结果基本一致。随着C/C预制体孔隙率的增大,C/SiC复合材料的密度出现先上升后下降的规律,力学性能也遵从同样的规律。XRD分析和相含量测试结果均表明复合材料的相含量与模型预测结果基本一致。实验结果与模型预测结果产生偏差的主要原因是裂解碳反应不完全。     

单向复合材料C/SiC平面磨削力实验研究

纤维增韧陶瓷基复合材料由于优越的力学性能被广泛应用于航空航天等重大国防领域.为探究复合材料平面磨削的磨削力影响因素,设计制备了一种单向C/SiC复合材料,采用平面磨床对其典型方向进行磨削,结合磨削力物理模型对磨削力影响因素进行分析.此外,分析了材料的表面形貌和磨削机理.结果表明:磨削力与进给速度和磨削深度成正比,与砂轮转速成反比;磨削力遵循规律:法向>纵向>横向.纤维的各向异性是是造成磨削力各向差异的主要原因,此外加工过程中材料破坏以脆性断裂为主.研究结果可为提高复合材料磨削效率提供理论基础,同时可为多相复合材料研究提供一定借鉴作用.     

纤维类型对C/SiC复合材料性能的影响

利用化学气相浸渗法制备了Cf-C/SiC复合材料,借助SEM、TEM等研究了纤维类型对Cf-C/SiC复合材料力学性能的影响.实验证明T300碳纤维增韧补强效果优于M40碳纤维,利用T300碳纤维制备出弯曲强度为459M,断裂韧性为20.0MPa*m1/2,断裂功为25170J/m2的Cf-C/SiC复合材料.2种碳纤维增韧效果的差异是由纤维的原始强度、热膨胀系数和弹性常数的不同决定的.     

SiC/SiC复合材料及其应用

日本开发的Nicalon和Tyranno两种品牌的SiC纤维占有世界上绝对性的市场份额。SiC/SiC复合材料典型的界面层是500 nm厚的单层热解碳(PyC)涂层或多层(PyC-SiC)n涂层,在湿度燃烧环境及中高温条件下界面层的稳定性是应用研究的重点。SiC/SiC复合材料,包括CVI-SiC基体和日本开发的Tyranno hex和NITE-SiC基体等,具有耐高温、耐氧化性和耐辐射性的特点,在航空涡轮发动机部件、航天热结构部件及核聚变反应堆炉第一壁材料等方面正开展工程研制应用。     

电泳沉积-烧结两步法制备C/SiC复合材料

采用电泳沉积法在石墨基体上制备厚度可控的Si涂层,考察了电泳沉积参数(电压、沉积时间、固含量及添加剂量)对涂层沉积量的影响。所制备的Si涂层通过烧结与石墨基体发生在位反应形成SiC涂层。涂层成分的XRD分析表明烧结后生成β-SiC。用SEM观察涂层烧结前后的形貌,烧结后Si渗入基体内部。孔径分布数据表明所形成的SiC涂层导致石墨孔径变小。1200℃的抗氧化实验表明涂层起到了良好的防护作用。实验提供了一种制备C/SiC复合材料的新方法。     

SiC反射镜镜坯制备工艺的综述与探讨

本文从SiC和C／SiC复合材料的制备工艺出发,综述了各种制备SiC及C／SiC复合材料反射镜镜坯工艺的机理、优缺点和国内外研究现状。并对SiC及C,SiC复合材料用作反射镜镜坯提出了一些建议。     

反应浸渗法制备SiC/FeSix复合材料

研究了在SiC+C坯体中加入Fe粉,用熔融Si进行反应浸渗,以制备不合游离Si的SiC/FeSix复合材料.结果表明:用本实验方法通过调整坯体中Fe含量可以制得不合游离Si的SiC/FeSix复合材料,该材料在室温下的抗弯强度为(220±10)MPa.文中推导了Fe含量与第2相组成的理论模型,同时讨论了热处理工艺对烧结的影响.     

C/SiC复合材料轻型反射镜光学改性涂层技术研究进展

轻型反射镜在空间光学系统中发挥着非常关键的作用,现在已发展到第四代C/SiC复合材料.C/SiC反射镜通常采用坯体+涂层的结构形式来满足轻量化和高分辨率的双重要求.因此,在反射镜制备过程中,涂层制备技术已成为制备反射镜材料的关键技术之一.目前涂层制备技术主要有CVD-SiC涂层技术、浆料预涂层Si/SiC涂层技术等.文章介绍了第四代C/SiC反射镜光学改性涂层的设计、制备,并介绍了近些年国内外的研究进展.     

SiC纤维及其增强SiCf/SiC复合材料的研究进展

SiC_f/SiC复合材料的低密度、耐高温、抗环境腐蚀及抗氧化等突出性能,使其在航天及空天飞行器的热端部件、热防护结构、发动机热端部件及核工业等领域取得了重大应用,是新一代最佳的高温结构材料。SiC纤维作为增强相,自身抗拉强度高、抗蠕变性能好、兼具耐高温、抗氧化等优点,且与陶瓷基体有着优异的相容性,可使陶瓷复合材料克服脆性,具有韧性,极大地推动了陶瓷复合材料的应用。文章以碳化硅纤维研发技术的三个重要发展阶段为例,详细阐述了碳化硅纤维的制备方法及性能特点,同时对碳化硅纤维增强陶瓷基复合材料的不同制备工艺进行了介绍,并分析了该复合材料当前国内外的应用现状,文章简述了SiC_f/SiC复合材料的发展及推广前景。     

SiC基反射镜制备工艺研究进展

空间系统用的高性能轻质反射镜的研究和应用正逐年稳定发展,本文从几种卫星反射镜材料的性能和特性出发,得出SiC及其复合材料作为反射镜材料性能最佳的结论;通过比较各种工艺制备SiC基反射镜性能,结果显示:只有CVD SiC能够作为反射镜反射光学表面.本文重点详细介绍了SiC及其复合材料反射镜制备工艺及方法特点,并对其工艺发展前景进行了展望.     

先驱体转化法制备C/C-SiC复合材料研究

以多孔C/C复合材料为预制型,聚碳硅烷(PCS)为先驱体,制备了C/C-SiC复合材料。研究了浸渍液浓度和不同C/C复合材料预制体密度等级对C/C-SiC复合材料的密度和力学性能的影响。结果表明:当浸渍液浓度为50%时,复合材料的密度均达到最佳值;不同的预制体密度对制得的复合材料性能有很大的影响,其中初始密度为1.2g/cm3试样制得的复合材料性能达到最优,其密度达到1.786g/cm3,弯曲强度达204.1MPa,剪切强度为16.1MPa,断裂韧性为6.83MPa·m1/2。     

Reactive alloy melt infiltration for SiC composite matrices: Mechanistic insights

A comparative study of reactive melt infiltration using Si and Si‐Y alloys is presented to provide insight into the governing processes that control the effectiveness of the melt interaction with a carbonaceous preform and the temperature capability of the SiC matrix for ceramic matrix composites. Through experiments on two substantially different scales of capillaries in porous graphite tubes using Si and Si‐Y alloys, the current study has characterized the phenomena that play a role in the infiltration of the melt and its reaction with the preform. It is shown that (i) the interface reaction controls wetting in both large and small capillaries and the climb rate is enhanced by the presence of Y; (ii) reaction choking occurs at critical throats within the pore network, usually behind the infiltration front; and (iii) different residual silicides can form during reaction and upon cooling. A potential mechanism for SiC growth is described, and the implications for the interplay between SiC growth and infiltration are discussed.     

Preparation of C/C‐SiC Composites from All‐Cellulose Precursors

All‐cellulose composites (ACCs) are manufactured from high‐performance cellulose fibers and a cellulose‐containing ionic liquid (IL) as matrix‐forming dope via wet‐winding processes, using different concentrations of cellulose in the IL. ACCs are carbonized at 1650 °C and then infiltrated with liquid silicon. Application of a carbonization aid (ammonium dihydrogenphosphate, ADHP) substantially improves the carbon yield after carbonization but also results in the depletion of the mechanical properties of the final carbon/carbon silicon carbide (C/C‐SiC) material. The microstructure of the porous carbon/carbon preforms strongly depends on both the concentration of cellulose in the IL and the concentration of ADHP. A C/C‐SiC composite manufactured from 6 wt% cellulose in the matrix‐forming dope, in the absence of ADHP, has a maximum flexural strength of 60 MPa. New C/C‐SiC composites with different shapes including Z‐profiles and tubes are successfully manufactured from pre‐shaped ACC precursors. These composites keep their shape during carbonization and the final siliconization process step.     

Pressure‐less joining of C/SiC and SiC/SiC by a MoSi2/Si composite

A MoSi₂/Si composite obtained in situ by reaction of silicon and molybdenum at 1450°C in Ar flow is proposed as pressure‐less joining material for C/SiC and SiC/SiC composites. A new “Mo‐wrap” technique was developed to form the joining material and to control silicon infiltration in porous composites. MoSi₂/Si composite joining material infiltration inside coated and uncoated C/SiC and SiC/SiC composites, as well as its microstructure and interfacial reactions were studied. Preliminary mechanical strength of joints was tested at room temperature and after aging at service temperatures, resulting in interlaminar failure of the composites in most cases.     

Effect of the incorporation of SiC nanowire with double protective layers on SiC coating for C/C composites

To maintain the thermal stability of SiC nanowires during SiC coating fabrication process, carbon and SiC double protective layers were covered on the surface of nanowires. And SiC nanowires with double protective layers toughened SiC coating were prepared by pack cementation. The results showed that after introducing the SiC nanowires with double protective layers, the fracture toughness of the SiC coating was increased by 88.4 %. The coating protected C/C for 175 h with a mass loss of 3.67 %, and after 51 thermal shock cycles, the mass losses of the oxidized coating were 3.96 %. The double protective layers are beneficial to improve the thermal stability of nanowires, leading to good fracture toughness and thermal shock resistance of SiC coating. SiC nanowires consume the energy of crack propagation by fracture, pullout and bridging, leading to an increase in fracture toughness.     

Fabrication of C/C-SiC composites using high-char-yield resin

Carbon fiber reinforced ceramic matrix composites (C/C-SiC composites) were fabricated using a type of high-char-yield phenolic resin with the char yield of 81.17 wt.%. Firstly, the fabric prepreg was prepared by spreading the phenolic resin solution onto the two dimensional carbon fiber plain weave fabric and dried consequently. Afterward, the resin was cured and then the carbon fiber reinforced polymer (CFRP) was pyrolyzed to get amorphous carbon. Finally, C/C-SiC composites were obtained through liquid silicon infiltration (LSI) process. SEM micrographs showed that the Si/SiC area was homogeneously dispersed in the matrix, and during the siliconization process, a layer of SiC was formed along the surface of carbon fibers or carbon matrix. The fiber volume of CFRP was about 40 vol.%, which was much lower than other studies. XRD result indicated that only β-SiC type was formed. The result of X-ray computed tomography clearly showed the structure changes before and after the melt infiltration process. Mechanical property test showed that the composites had fracture strength of 186 ± 23 MPa, and a flexural modulus of 106 ± 8 GPa.     

Formation of Ti3SiC2 interphase coating on SiCf/SiC composite by electrophoretic deposition

To improve the oxidation resistance of SiC composites at high temperature, the feasibility of using Ti₃SiC₂ coated via electrophoretic deposition (EPD) as a SiC fiber reinforced SiC composite interphase material was studied. Through fiber pullout, Ti₃SiC₂, due to its lamellar structure, has the possibility of improving the fracture toughness of SiC_f/SiC composites. In this study, Ti₃SiC₂ coating was produced by EPD on SiC fiber; using Ti₃SiC₂‐coated SiC fabric, SiC_f/SiC composite was fabricated by hot pressing. Platelet Ti₃SiC₂ powder pulverized into nanoparticles through high‐energy wet ball milling was uniformly coated on the SiC fiber in a direction in which the basal plane of the particles was parallel to the fiber. In a 3‐point bending test of the SiC_f/SiC composite using Ti₃SiC₂‐coated SiC fabric, the SiC_f/SiC composite exhibited brittle fracture behavior, but an abrupt slope change in the strength‐displacement curve was observed during loading due to the Ti₃SiC₂ interphase. On the fracture surface, delamination between each layer of SiC fabric was observed.