高温石墨炉用碳素材料的热辐射性能研究

以碳素材料微观结构与表面形貌为基础,研究了不同型号的碳/碳复合材料及石墨材料的光谱发射率。研究表明,石墨微晶结构规整度与表面微观形貌是影响碳素材料光谱发射率差异的因素。为评价碳素热辐射性能、设计高效热场提供理论指导。     

排布特征对碳素纤维红外发射率性能的影响

利用自动分光辐射测量仪系统测试了3种典型碳素纤维预制体样品的法向光谱发射率和法向总发射率,研究了排布特征对碳素纤维红外发射率性能的影响。结果表明,股线型和短切毡型碳素纤维预制体的法向光谱发射率在整个测试波段内均大于编织布状样品,股线型和短切毡型碳素纤维预制体的法向总发射率分别为0.910和0.888,均高于编织布样品。根据SEM微观形貌测试及物体表面的电磁理论分析,松散的纤维排布结构有利于碳素纤维预制体红外发射率的提高。     

3D C/SiC复合材料的热辐射性能

利用稳态量热计法和傅里叶红外光谱仪分别测定了3D C/SiC复合材料在90℃时的半球向总发射率和室温法向光谱反射率,研究了表面形貌、涂层厚度及高温氧化对3D C/SiC热辐射性能的影响。结果表明:3D C/SiC具有优异的热辐射性能,其总发射率可达0.83;随着SiC涂层厚度的增加,3D C/SiC总发射率先降低后上升;高温氧化后,3D C/SiC的热辐射性能有所提高。      

表面除杂处理对碳素纤维毡红外发射率的影响

为优化碳素纤维电热体红外辐射性能,测定了碳素纤维毡表面除杂处理前后的法向光谱发射率和法向总发射率,利用X射线衍射和拉曼光谱进行样品的物相结构分析,研究了表面除杂处理过程物相结构变化与碳素纤维毡法向光谱发射率和总发射率的关系.结果表明：采用硝酸液相除杂和空气瞬时高温2种方式处理时,碳素纤维毡的法向光谱发射率均出现一定的波...     

碳素复合材料热辐射性能的研究进展

介绍了碳素复合材料热辐射性能的重点研究成果,从发射率的测试分析设备及其性能表征、碳素复合材料热辐射性能的相关机理、制备工艺与光谱发射率相关性3个方面的研究工作进行总结,为高温碳素复合热辐射材料的深入研究提供参考.     

石墨化处理对碳素纤维红外发射率的影响

利用自动分光辐射测量仪系统测试了两种碳素纤维在石墨化处理前后的法向光谱发射率和法向总发射率,研究了石墨化处理对碳素纤维红外发射率性能的影响.研究表明：随着石墨化过程中非碳元素的大量脱除和石墨微晶规整程度的提高,T300石墨化碳素纤维和国产石墨碳素纤维毡在2500～5000 nm和5000～6500 nm波段内的光谱发射...     

碳纤维微结构与热辐射性能的相关性研究

利用自动分光辐射测量仪测试了T300和T700两种碳纤维及通电除胶前后T300碳纤维的法向光谱发射率和法向总发射率,研究了碳纤维微结构与热辐射性能的相互关系.结果表明:T700碳纤维和经过表面除胶后的T300碳纤维样品,其法向总发射率有所降低,光谱发射率基本在三个波段范围内变化,这与碳纤维的微结构有关.在2500～5000nm范围内的光谱发射率主要受自由载流子的跃迁机制作用,在5000～6500nm和6500～13000nm波段内的光谱发射率主要与乱层微晶结构中碳网平面内碳碳键的振动以及微结构中无定型碳的物相比例有关.     

自修复微胶囊复合材料的制备及力学性能研究

为了提高树脂基复合材料的使用寿命,以脲醛树脂为壁材,双环戊二烯为囊芯,通过原位聚合法制备了内含修复液的微胶囊,探讨了反应过程中脲醛量比及乳化剂用量等对微胶囊表面形貌和结构的影响.通过优化工艺条件制备出表面致密的微胶囊,并将微胶囊埋植在环氧树脂基体中制备复合材料.采用扫描电镜对胶囊进行形貌表征,运用快速傅里叶变换红外光谱...     

不锈钢表面处理对Cr2O3薄膜太阳能选择吸收性能的影响

采用Sol-gel法以及浸渍提拉法在不锈钢表面制备了Cr2O3选择性吸收薄膜。分别采用喷砂处理和氧化液腐蚀两种方式对不锈钢进行表面处理,考察不同表面处理方式对Cr2O3太阳能选择吸收薄膜性能的影响。用Lambda 750型UV-Vis-NIR分光光度计和Tensor 27型BRUKER红外光谱仪分别测试薄膜在可见-近红外光谱区和红外光谱区的反射光谱。结果表明,氧化液处理的不锈钢基体,其表面所涂覆薄膜的红外发射率明显降低,发射率由喷砂基体的0.465降低到0.186,具有良好的选择吸收性。     

测量光谱发射率的数学模型的建立

作者建立了一套测量300～500 ℃温度区间物体表面法向红外光谱发射率测量装置.在全面了解光电器件、电测设备原理基础上,从发射率定义出发,建立了与装置相对应的测量物体表面光谱发射率的数学(物理)模型,为实验数据的整理和不确定度评估打下了理论基础.     

由炭布制备C／C复合材料工艺及性能的研究

为通过快速增密和低设备成本降低C／C复合材料的成本,采用中压浸渍、炭化多次循环的工艺制备了快速增密的C／C复合材料。该工艺以Z向增强的层叠炭布为增强体,不同软化点的中间相沥青和改性沥青为浸渍剂。考察了浸渍工艺,并研究了所得C／C复合材料的力学性能和断裂形貌。结果表明,中间相沥青及改性沥青等高残炭收率沥青是C／C复合材料极佳的浸渍剂,有利于快速增密。8次循环后（约2周时间）,复合材料的密度从0.84g/cm^3增至1.76g/cm^3。炭布层叠Z向增强的C／C复合材料有良好的力学性能,而且其性能随着密度的增加而提高。所得复合材料的密度达到1.76g/cm^3时,拉伸强度为87.03MPa,弯强为113.56MPa,压缩强度为199.49MPa。     

沥青基炭纤维γ-射线改性对炭/ 炭复合材料力学性能的影响

为了提高沥青基炭纤维表面活性, 采用γ-射线辐照对沥青基炭纤维表面改性。用AFM、XPS 研究了γ-射线辐照改性后沥青基炭纤维表面结构的变化, 用浸润仪测定了改性前后沥青基炭纤维表面能的变化。研究了γ-射线辐照沥青基炭纤维对炭/ 炭复合材料力学性能的影响, 并用SEM 分析了炭/ 炭复合材料断口形貌。结果表明,γ-射线辐照使炭纤维表面含氧官能团和表面粗糙度增加, 提高了沥青基炭纤维的表面能; 降低了炭/ 炭复合材料孔隙率, 提高了炭/ 炭复合材料力学性能。     

Effects of processing methods and parameters on the mechanical properties and microstructure of carbon/carbon composites

The influence of the fabrication parameters during carbonization and densification processes on the mechanical properties and the microstructure of carbon/carbon (C/C) composites were investigated. The C/C composites were made by using phenolic resin as precursor and two-dimensional carbon fabrics as reinforcements for the first carbonization. The effects of heating rate and heat-treatment temperature during the initial carbonization process on the properties of C/C composites are presented. Further densification treatment was completed by chemical vapour infiltration (CVI) and a liquid-resin impregnation process. The CVI route was found to be more efficient than the resin-impregnation process. The interlayer spacing of C/C composites did not change after resin re-impregnation for several times. However, the interlayer spacing of the C/C composites was reduced when the processing temperature in the CVI process was increased. Higher flexural strength and flexural modulus were obtained because the densities of the composites were enhanced either by the chemical vapour infiltration process or by the resin-impregnation route. The variation in thickness of the CVI deposited carbon within the preformed composite was studied and the morphology of the fracture surface of the C/C composites was also examined.     

Mechanical and tribological properties of 2-D carbon/carbon composites densified through pulse chemical vapor infiltration

This paper presents the mechanical and tribological properties of 2-D carbon/carbon composites (C/C) fabricated by the Pulse Chemical Vapor Infiltration (PCVI) process. In the PCVI process, various fabrication temperatures and different reactant pressures were adopted to investigate the influence of processing condition on physical properties, microstructure and mechanical properties. In the densification process by PCVI, holding time and pulse number are two parameters which significantly affect physical properties (such as density, porosity, and weight gain) and mechanical properties (such as interlaminar strength and wear properties). It is found that the wear properties of carbon/carbon composites can be improved obviously after the densification by 1000 pulses. Effects of initial open porosity on density of the fabricated composites are also studied. In this work, tribological performance of the specimens fabricated through the Isothermal Chemical Vapor Infiltration (ICVI) process and the PCVI process under different pulse cycles are compared. Scanning Electronic Microscopy (SEM) was used to examine the morphology of worn surface. The relationship between the tribological performance and surface morphology was studied.     

Effects of pressure on the pore formation of carbon/carbon composites during carbonization

In this study, porosity and graphitizability of coal tar pitch with the treatment pressure were investigated. 4-directional carbon/carbon composites (4D C/C) were made from the matrix precursor of coal tar pitch through the process of impregnation and carbonization. Then the effects of applied pressure during the densification on the composites were observed. The matrix pitch which had 600 bar applied during the carbonization process had one and a half times less pore area ratio than that treated at 1 bar. When the pitch was heat treated up to 2300°C after the high pressure carbonization, the degree of graphitization was improved on a small scale and the crystal size tended to reduce. As the applied pressures to 4D C/C composites increased from 1 to 600 bar, the densification ratio was greatly improved. In the pore size distribution of the 4D C/C composites, the macropore portion was decreased while the mesopore portion increased, when high pressures were applied.