石墨抗氧化SiC涂层的制备与性能研究

本文以SiC、Si和酚醛树脂为主要原料,通过浸涂和气相渗硅两步法在石墨表面制备了SiC抗氧化涂层。利用XRD、SEM研究了涂层的相组成与形貌。结果表明,气相渗硅后涂层的主相为α-SiC,β-SiC和Si,其中Si是气相渗硅过程中残留的。涂层与基体之间具有过渡结构,致密度良好。抗氧化和抗热震实验表明：由气相渗硅工艺制备的SiC涂层结构致密,具有良好的抗氧化性能,1200℃空气条件下氧化16 h后试样每小时增重量约为2.18 mg/cm₂。涂层具有良好的抗热震性能,经1000 ℃—室温循环热震15次后试样质量变化百分率仅为-0.17%。     

SiC涂层碳纤维增强铝复合丝的机械性能及其界面特性

研究了不同热处理温度对碳化硅涂层碳纤维增强铝复合丝的拉伸强度影响,结果表明:500℃热处理2h及550℃热处理1h后使复合丝的拉伸强度提高,600℃以上的热处理都使复合丝的拉伸强度下降,通过测量从复合丝中分离出来的纤维强度,表明碳化硅涂层对碳纤维具有良好的保护作用,用电子探针及能量损失谱分析了C/Al界面的稳定性。     

反应压力对炭纤维表面SiC涂层制备及组织结构的影响

以硅粉为硅源,采用原位反应法在炭纤维表面制备了SiC涂层,并研究了反应压力对SiC涂层的制备、组织结构及抗氧化性能的影响。结果表明：常压下制备的涂层疏松多孔,表面有较多的SiC纳米线,而负压下制备的涂层致密均匀。静态氧化测试表明：与常压下制备的SiC涂层相比,负压下制备的SiC涂层抗氧化性能更好,主要是由于涂层致密均匀,能够更好地阻隔氧气的扩散。根据实验结果,探讨了反应压力对SiC涂层生长机理的影响。常压下,沉积粒子能量低,难以克服遮蔽效应,因此易形成疏松多孔的涂层;而负压下,沉积粒子能量高,表面扩散率高,易形成致密均匀的涂层。     

原位反应法制备的碳化硅涂层/三维编织碳纤维的氧化性能研究

采用原位反应法在三维编织碳纤维(原纤维)表面制得β-SiC涂层,通过XRD,SEM,等温氧化失重和非等温热重分析等测试手段研究了制备方法对涂层性能的影响.结果表明:利用此法可得到均匀、完整,界面结合良好的涂层,涂层厚度增加,涂层/三维编织碳纤维(复合纤维)抗氧化性能增强.并对复合纤维氧化反应的机理进行了研究.     

SiC对熔铝石墨坩埚抗氧化性能的影响

采用鳞片状石墨、SiC、硅粉和高岭土等主要原料制备含SiC的熔铝石墨坩埚,试样分别在1050、1100、1150和1200℃保温3h烧成,随后将试样分别加热到700、800和900℃保温6h进行氧化试验。研究了SiC的加入量、烧成温度、氧化温度和时间对试样抗氧化性能的影响。结果表明,随着SiC含量的增加,坩埚的抗氧化性能得到明显的改善,这种作用在较高温度下尤为显著;SiC含量较多的试样,失重曲线平缓,失重率较小;试样的最佳烧成温度应控制在1100～1150℃之间;随着氧化温度的升高和氧化时间的延长,试样的失重率增加,尤其是在700～800℃氧化温度下。     

SiC涂层对泡沫炭高温抗氧化性能的影响

采用包埋法在中间相沥青基泡沫炭表面生成了一层致密的高温抗氧化碳化硅涂层,研究了SiC涂层对泡沫炭高温抗氧化性能的影响.通过热重分析仪(TG)对有、无SiC涂层的泡沫炭的抗氧化性能变化进行了分析,采用扫描电子显微镜(SEM)分析了SiC涂层的结构和形貌特征变化,同时在1 200℃空气气氛中对SiC涂层的抗氧化性能进行了测试.结果表明:SiC涂层使泡沫炭的抗氧化性能有了显著的提高,并且随着SiC涂层厚度的增加,泡沫炭的抗氧化性能也随之增强.     

C／C复合材料防氧化涂层SiC／SiC—MoSi2的制备与抗氧化性能

采用包埋法和涂刷法在C/C复合材料表面依次制备了SiC内涂层和SiC-MoSi2外涂层,借助XRD与SEM对涂层的微观结构进行了分析,研究了涂覆后的C/C复合材料在高温静态空气中的防氧化性能.结果表明:SiC/SiC-MoSi2复合涂层有效缓解了MoSi2与C/C热膨胀不匹配问题,涂层无裂纹;复合涂层在900和1500℃静态空气环境下均可对C/C复合材料有效保护100 h以上;涂层的多层、多相结构以及在高温氧化后表面生成的SiO2薄膜是其具有优异防氧化性能的原因.     

低密度碳纤维复合材料耐高温抗氧化技术研究

低密度碳纤维复合材料具有轻量化、耐高温、低热导等优异特性,在航空航天热防护领域有较大的应用潜力。为了提高低密度碳纤维复合材料高温抗氧化性能,本文设计并研制了耐高温低密度抗氧化碳纤维复合材料。首先,采用气相沉积工艺对传统低密度碳纤维复合材料进行了强韧化处理,沉积210h时后材料拉伸强度和压缩强度分别提高275%和341%。其次,采用刷涂浸渍和高温原位烧结方法设计并制备了双层超高温抗氧化涂层,采用高温马弗炉对材料在空气环境、不同温度下的高温抗氧化性能进行了测试。结果表明,在1700~1750℃考核条件下材料表现出优异的抗氧化性能,质量增重率为1.1~1.5×10_-5 g/cm₂?s,表面形成的致密氧化硅氧化膜和氧化铪镶嵌氧化硅氧化膜为材料提供了优异的抗氧化性能。     

SiC涂层工艺对三维碳纤维编织物抗氧化性的影响

采用先驱体浸渍裂解(PIP)法在碳纤维表面制备SiC涂层.研究了涂层制备工艺对编织体抗氧化性能的影响.结果表明,经质量分数为10%的聚碳硅烷(PCS)溶液循环浸渍裂解所得样品的抗氧化性能最佳.对SiC/碳纤维非等温条件下氧化反应的动力学研究结果表明,SiC涂层/碳纤维的非等温氧化过程呈现自催化特征.氧化机理为随机成核,动力学参数为1g A=15.223 min-1,E=157.15 kJ·mol-1.     

扫描间距对激光制备纳米SiC抗氧化涂层的影响

目的 研究激光的扫描间距对纳米SiC涂层形貌、生长机理和抗氧化涂层的影响。方法 以不同扫描间距的激光辐照制备SiC纳米涂层。分别利用体视显微镜、扫描电镜(SEM)和激光共聚焦显微镜分析涂层表面、截面的三维形貌,研究扫描间距对涂层形貌的影响,探究微米SiC颗粒转变为纳米SiC颗粒的演变及生长机理。用热失重法(TGA)研究试样高温抗氧化性能,包括试样的氧化失重率随温度变化和650、800℃两种温度下的恒温抗氧化性能对比分析,并用阿伦尼乌斯线性拟合进行了验证。结果 激光能够促使预置于石墨基体上的微米SiC颗粒在Ar保护下的密闭反应室中转变为纳米SiC颗粒,且涂层主要由结晶度良好的α–SiC、β–SiC纳米晶颗粒组成。当扫描间距为0.08 mm时,形成的涂层表面较为平滑均匀,粗糙度较小,最高处与最低处的高度差仅为135.829μm,且此间距下,试验活化能值Ea=11.014×10⁴ J/mol最大,抗氧化性能最好。其次试样在600～850℃范围内,试样氧化失重率较低,小于8%,其氧化失重率与氧化时间呈现出较好的一次线性的拟合度。结论 激光辐照制备的SiC纳米涂层的形貌、生...     

ZrB2-MoSi2/SiC涂层C/C复合材料的制备及氧化性能（英文）

为了提高C/C复合材料的抗氧化性,在C/C复合材料基体上制备了ZrB2-MoSi2/SiC涂层。采用包埋法制备SiC中间层,采用喷涂法制备ZrB2-MoSi2外涂层。用XRD和SEM分别分析、测试所制备涂层的物相组成和显微结构,研究涂层复合材料的高温抗氧化性能。结果表明:C/C复合材料的外涂层由ZrB2、MoSi2和SiC三相组成;在1273K和1773K下分别氧化30h和10h后ZrB2-MoSi2/SiC涂层试样的质量损失分别为5.3%和3.0%,涂层表面长有纳米SiC晶须。C/C复合材料ZrB2-MoSi2/SiC涂层具有自愈合特性和良好的高温抗氧化性能。     

Double SiC coating on carbon/carbon composites against oxidation by a two-step method

To improve the oxidation resistance of C/C composites, a double SiC protective coating was prepared by a two-step technique. Firstly, the inner SiC layer was prepared by a pack cementation technique, and then an outer uniform and compact SiC coating was obtained by low pressure chemical vapor deposition. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD analyses. Oxidation behaviour of the SiC coated C/C composites was also investigated. It was found that the double SiC coating could protect C/C composites against oxidation at 1773 K in air for 178 h with a mass loss of 1.25%. The coated samples also underwent thermal shocks between 1773 K and room temperature 16 times. The mass loss of the coated C/C composites was only 2.74%. Double SiC layer structures were uniform and dense, and can suppress the generation of thermal stresses, facilitating an excellent anti-oxidation coating.     

Effect of SiC whiskers on the oxidation protective properties of SiC coatings for carbon/carbon composites

In order to effectively employ the unique high temperature mechanical properties of carbon/carbon composite substrates, SiC coatings reinforced by SiC whiskers were prepared by pack cementation method. The effect of SiC whiskers on the oxidation resistance properties of the single-layer coating and double-layer coating was investigated. SiC whiskers in the single-layer SiC coating have little effect on the anti-oxidation property but obviously improve the thermal shock property. The double-layer coating with inner-layer reinforced coating exhibits more perfect anti-oxidation ability than the double-layer coating with SiC inner-layer coating.     

Effect of oxygen content on tensile strength of polymer-derived SiC fibers

Air-curng is usually applied to the polymer-derived SiC fibers and,as a result,oxygen is embedded to the material.An effective relationship between oxygen content of the SiC fibers and mass gain of their precursor fibers was established.Results also showed that oxygen content has a great influence on the mechanical properties and excellent tensile strength is usually obtained at the oxygen content of 12%-13%,similar to the density of SiC fibers.Oxygen content has a positive effect on the ceramic yield,and thus,is good to the density and tensile strength;while,oxygen content is also negative to volume content of SiC phase and crystallization of the SiC fibers,and thus,detrimental to the density and tensile strength.Both of the two effects result in the peak behavior of the tensile strength of SiC fibers.     

Anti-oxidation behavior of chemical vapor reaction SiC coatings on different carbon materials at high temperatures

To protect carbon materials from oxidation, SiC coatings were prepared on carbon/carbon(C/C) composites and graphite by chemical vapor reaction. SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated, and then their oxidation mechanisms were studied. Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures (1 623 K and 1 823 K). In the oxidation process, the oxidation curves of SiC coated C/C composites are linear, while those of SiC coated graphite follow a quasi-parabolic manner. The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results. The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.     

Catalytic graphitization of polyacrylonitrile (PAN)-based carbon fibers with Fe-Cr2O3 composite coating

The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile(PAN)-based carbon fibers and its catalytic graphitization were studied.Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD,Raman spectroscopy and SEM.The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures.When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300°C,the interlayer spacing(d002) and ratio of relative peak area(AD/AG) reach 3.364-and 0.34,respectively.Whereas,the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800°C and the values of d002 and AD/AG are 3.414  and 0.68,respectively.The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating.The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution  precipitation mechanism.     

CVD法SiC纤维的涂层研究

纤维表面涂层法是解决CVD SiC纤维增强复合材料界面问题的有效途径。从涂层选取原则、涂层分类和制备方法三方面对该技术进行了介绍,并对几种典型涂层进行了重点评述。最后,指出了目前该领域研究所存在的一些问题,也对今后的发展趋势进行了展望。     

石墨靶电流对类石墨镀层摩擦性能的影响

用非平衡磁控溅射离子镀技术制备含铬类石墨镀层,研究了石墨靶电流对磁控溅射法制备类石墨镀层摩擦性能的影响.通过扫描电镜、原子力显微镜、透射电镜等分析了镀层的表面形貌与组织.结果表明:所制备镀层的硬度随着石墨靶电流的升高而增加;镀层的摩擦系数和比磨损率随靶电流的增大呈现先降后升的趋势;扫描电镜和原子力显微镜图片分析表明镀层表面呈典型的岛团状聚集态,且随着石墨靶电流增大,镀层表面岛团状尺寸变大、镀层表面粗糙度随之增大.用高分辨透射电镜分析显示:靶电流较小时碳层中出现Cr元素富集区,随着石墨靶电流的增大,表面层中的Cr弥散分布.     

真空退火处理对掺Cr类石墨碳膜力学和摩擦学性能的影响

采用闭合场非平衡磁控溅射离子镀技术制备了掺Cr类石墨镀层,研究了真空退火温度对镀层的硬度、结合强度、摩擦系数和比磨损率的影响规律,通过X射线衍射(XRD)分析了镀层结构随退火温度的变化.结果表明:随退火温度的升高,镀层有新相生成,镀层的膜基结合强度降低,镀层硬度随温度的升高先增加后降低,退火温度为500℃时,镀层显微硬度最大;随退火温度的升高镀层摩擦系数呈现出先降低后升高的变化趋势,比磨损率逐渐增大.     

原位生成SiC／TiSi2纳米复合材料的显微结构

采用Ｓｉ和ＴｉＣ为原料,通过反应热压可制得纳米ＳｉＣ粒子复合的ＴｉＳｉ２材料,生成的纳米ＳｉＣ粒子聚集分布在ＴｉＳｉ２基体中,ＳｉＣ粒子与ＴｉＳｉ２的同没有晶界相存在,但由于残余应力的作用,ＴｉＳｉ２晶格发生扭曲并有位错出现。