SiO_（2f）/SiO_2复合材料中石英纤维的表面处理

采用两种方法去除石英纤维表面的浸润剂,一种是热处理,另一种是有机溶剂与热处理相结合。比较石英纤维处理前后失重变化,通过SEM、XPS表面形貌和成分变化,得出石英纤维的表面处理,有机溶剂浸泡与高温处理相结合优于单纯的高温处理。采用不同的升温速率对石英纤维进行热处理,结果表明：升温速率越低,石英纤维的机械强度损失越大。     

石英纤维的表面处理工艺对其性能的影响

通过溶剂处理及其与热处理相结合的方法去除石英玻璃纤维表面的浸润剂,对石英纤维表面处理前后的状态变化及其拉伸性能进行了研究,结果表明:单独采用溶剂处理纤维编织体的失重为0.77%,经高温处理后纤维略带黄色,拉伸强度下降明显,逐步趋向变脆并粉化,在复合材料中失去了增强的效果,而采用溶剂+热处理工艺处理后纤维的失重为1.64%,热处理后纤维呈亮白色,不仅可较完全的去除浸润剂,而且还可以使石英纤维本身强度受损较少,可起到增强复合材料的效果。     

针刺石英纤维预制体增强石英陶瓷复合材料的制备研究

以针刺石英纤维预制体、硅溶胶等为原料,采用溶胶-凝胶的方法制备了石英纤维增强石英陶瓷复合材料。研究了热处理温度对纤维形貌和纤维布拉伸性能的影响以及烧结温度对复合材料弯曲强度的影响。结果表明:石英纤维预制体经丙酮浸泡烘干后,经450℃热处理2h,可以完全去除纤维表面的浸润剂;复合材料经450℃烧结2h,材料弯曲强度为78.5MPa,拉伸强度为31.8MPa,抗压强度为88.8MPa,可以达到天线罩材料力学性能的要求。     

磷酸盐基复合材料中石英纤维的表面处理

首先采用三种处理方法除去石英纤维表面的有机层,比较了处理前后石英纤维的失重、拉伸强度和浸润性变化,最终优选出30%硫酸洗涤的方法对石英纤维表面进行处理.然后通过溶胶-凝胶技术制备Al2O2涂层石英纤维,研究Al2O2涂层石英纤维的性能,并考察Al2O2,涂层石英纤维增强的磷酸盐基复合材料的机械性能.实验结果表明,Al2O2涂层提高了石英纤维的强度和热稳定性,其优化涂膜量为4.6%,最佳热处理条件为250℃/10min,Al2O2条层石英纤维增强磷酸盐基复合材料的常温机械性能优良,其高温处理后的机械稳定性优于未涂层纤维增强的复合材料.     

聚倍半硅氧烷树脂／石英纤维复合材料耐高温性能研究。

研究了有机硅树脂/石英纤维复合材料的拉伸性能、耐高温性能和介电性能.研究结果表明,纤维预处理方式对纤维和复合材料力学性能有较大影响.采用甲苯浸泡,继而350℃高温加热400s可在获得较好纤维强度的前提下除去浸润剂.复合材料经热处理后仍能保持很好的力学强度和介电性能,550℃处理后.拉伸强度达到了360MPa以上,介电常数仍在3.30以下,满足导弹天线罩用复合材要求.     

玻纤浸润剂对玻纤增强聚氨酯界面性能影响

选用6种不同牌号的玻璃纤维,通过萃取和热处理分别去除浸润剂中成膜剂与偶联剂,分析二者质量分数,通过测试原玻纤、萃取后玻纤及热处理后玻纤增强聚氨酯的界面剪切强度,以及萃取后玻纤表面的X射线光电子能谱,分析了浸润剂组分和结构对界面力学性能的贡献。结果显示:萃取后,玻纤增强聚氨酯界面剪切强度略有降低,热处理后,界面剪切强度大幅降低,减小50%以上,且萃取后玻纤增强聚氨酯界面剪切强度随玻纤表面N/Si比增大而增大,表明玻璃纤维增强聚氨酯复合材料界面剪切强度主要来自玻璃纤维浸润剂中偶联剂的贡献,且随玻纤表面N元素的增加而增大。     

石英纤维布的界面处理对氰酸酯基胶膜性能的影响

分别采用烧蚀法和KH550/乙醇溶液对石英纤维布表面进行处理,将处理后的石英纤维布与改性氰酸酯树脂复合制备了氰酸酯/石英纤维布载体胶膜。研究结果表明,经过0.5%KH550溶液处理后的石英纤维表面形成一层均一的界面层,与氰酸酯树脂间的界面强度(IFSS)为62.1MPa,相比经过烧蚀法处理纤维的IFSS提高约90%。随着KH550浓度增加,氰酸酯/石英纤维布载体胶膜的剪切强度和石英纤维布界面硅元素的含量均呈现先增高后降低的趋势。采用0.5%KH550溶液对石英纤维布处理后,制备的氰酸酯/石英纤维布载体胶膜的综合性能最佳,400℃剪切强度为6.4MPa,400℃老化1h后强度保持率为90.2%。     

玻璃纤维表面处理用热源初探

玻璃纤维表面处理加热设备按其用途可以分为两类:一是热处理(即热清洗)炉,主要用来去除纺织型浸润剂,二是化学处理炉,主要用来被覆各种特定的处理液,使被处理的玻纤织物或纱线具有理想的性能。     

PBO纤维表面改性与热处理研究

运用扫描电镜对自制的聚对苯撑苯并二噁唑(PBO)纤维表面进行观察,发现未经烘干的PBO纤维表面有许多的裂纹和沟槽,而烘干的纤维表面则较光滑。通过单丝拔出实验研究了偶联剂对不同表面形态纤维的表面处理情况,结果表明:用偶联剂表面处理后,纤维与树脂间的界面剪切强度得到提高,偶联剂对未经烘干纤维表面处理比对烘干纤维处理的效果要好,与原丝相比,提高率可达69.4%。对自制的PBO纤维进行了热处理,发现未烘干的PBO纤维比经烘干而干燥致密化的纤维的热处理效果要好,模量有很大提高,强度也有一定的增加。     

玄武岩纤维浸润剂研究综述

玄武岩纤维浸润剂可有效提高玄武岩纤维的黏结强度、拉伸强度等性能,在玄武岩纤维成型及纤维复合材料生产过程中均具有重要作用。介绍了增强型浸润剂、纺织型浸润剂和增强纺织型浸润剂的材料性能、化学组成及应用效果,分析了各种浸润剂的优缺点,总结了浸润剂应用现状,展望了玄武岩纤维浸润剂的发展方向。     

Poly(vinylidene fluoride)/silica nanocomposite membranes by electrospinning

Poly(vinylidene fluoride) (PVDF)/silica nanocomposite membranes containing up to 30% silica were prepared by electrospinning using colloidal silica as the source of silica and dimethyl formamide as the solvent. The fiber morphology was observed by field emission scanning electron microscopy. The average fiber diameter is about 0.3 μm for PVDF/silica composite fibers having 10–30% silica. Silica nanoparticles were observed on all fiber surfaces with fairly good dispersion and distribution. Fourier transform infrared spectroscopy and differential scanning calorimeter were used to investigate the crystallization behavior of PVDF and showed that a mixture of α‐, β‐, and γ‐phase crystals was obtained with little content of α phase and all the PVDF/silica composite membranes have similar degree of crystallinity. Static water contact angle measurements were performed to investigate the surface wettability of the membranes. The mechanical properties were evaluated by tensile tests, showing strong reinforcement effect. The tensile modulus and tensile strength increase significantly when silica is present. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hybridized reinforcement of natural rubber with silane‐modified short cellulose fibers and silica

Natural‐rubber‐based hybrid composites were prepared by the mixture of short cellulose fibers and silica of different relative contents with a 20‐phr filler loading with a laboratory two‐roll mill. The processability and tensile properties of the hybrid composites were analyzed. The tensile modulus improved, but the tensile strength and elongation at break decreased with increasing cellulose fiber content. The scorch safety improved with the addition of 5‐phr cellulose fiber in the composites. The Mooney viscosity significantly decreased with increasing cellulose fiber content. To modify the surface properties of the cellulose fiber and silica fillers, a silane coupling agent [bis(triethoxysilylpropyl)tetrasulfide, or Si69] was used. The effects of Si69 treatment on the processing and tensile properties of the hybrid composites were assessed. We found that the silane treatment of both fillers had significant benefits on the processability but little benefit on the rubber reinforcement. The strength of the treated hybrid composite was comparable to that of silica‐reinforced natural rubber. Furthermore, to investigate the filler surface modification and to determine the mixing effects, infrared spectroscopic and various microscopic techniques, respectively, were used. From these results, we concluded that the fillers were better dispersed in the composites, and the compatibility of the fillers and natural rubber increased with silane treatment. In conclusion, the hybridized use of short cellulose fibers from a renewable resource and silica with Si69 presented in this article offers practical benefits for the production of rubber‐based composites having greater processability and more environmental compatibility than conventional silica‐filler‐reinforced rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of Processing Parameters on the Strength of Fluoride Glass Fibers

The different factors affecting the tensile strength of heavy-metal fluoride glasses are presented. Surface crystals were found to be responsible for the lower fiber strength. The tensile strength of fluoride glass fibers can be increased by controlling the preform surface and drawing in a dry atmosphere. Using lower draw temperature and dual polymeric coatings increases the strength. Finally, phosphate glass overclad on fluoride glass fiber can be used to prevent surface hydrolysis during the drawing process and increases the tensile strength of fibers due to formation of compressive stress on the outside of the glass fiber.     

Effect of Moist Ammonia on the Strength of Polymer-Coated Optical Fibers

The tensile strength of polymer-coated fused silica optical fibers aged in a moist ammonia environment at 23°C was drastically reduced compared to that of fibers aged under ammonia-free high-humidity conditions. However, most of the strength lost on aging in ammonia was recoverable by ambient desorption of the ammonia, in analogy to the strength recovery which occurs when fibers aged in water are dried.     

Improvement in mechanical and thermal properties of unsaturated polyester- based hybrid composites

Polymer matrix composites are used in automobile, structure and aerospace industries due to their light weight and high strength. The present research has an aim to reinforce locally developed silica nanoparticles and glass fibers in unsaturated polyester to produce polymer-based hybrid composites. Composites were synthesized by hand lay-up method with 1, 2, 3 and 4 wt% of silica sand nanoparticles and glass fiber. Mechanical tests like tensile, impact and micro-hardness were performed on the obtained polymer hybrid composites. The results of mechanical properties of the hybrid polymer matrix composites revealed an increasing trend. The SEM analysis was performed on the developed and fractured tensile testing samples. The SEM analysis showed the presence of silica nanoparticles in the samples and pulling action of fibers were seen under fractured tensile tests. The pulling actions of fibers from polymer matrix delayed the fractured mechanism and enhanced the mechanical properties. Silica nanoparticles filled the cavities generated during tensile test and extensive enhancement was revealed in tensile as well as impact energy. Toughness of the hybrid composite was also enhanced as a result. The thermal properties of the hybrid polymer composites were analyzed using thermogravimetric analysis. Thermal stability of the composite has been marginally increased with increasing wt% of reinforcement.     

Effects of corrosion in liquid fluoride salt on the tensile strength of domestic SiC fibers

The relationship between the tensile strength of corroded domestic second-generation (2ed-gen) SiC fibers at various temperatures for 500 h in 46.5LiF-11.5NaF-42.0KF (mol. %) eutectic salt and the typical microstructure was studied. Weibull theory was used to analyze the critical defects that caused the tensile fracture, and the microstructure of fibers before and after corrosion was characterized. It is concluded that the decrease of tensile strength after corrosion at 800 °C is caused by the surface injury of fibers, which led to the shift of critical defects from the internal defects of virgin fibers to surface defects. Moreover, corrosion at higher temperature accelerates the corrosion process and dissolve the surface O-contained layer thoroughly. This shifts the critical defects back to the internal defects and will be helpful for the recovery of tensile strength of corroded fibers at the higher temperature.     

Modeling birefringence in SiO2 glass fiber using surface stress relaxation

The retardance of silica glass fibers was evaluated using photoelastic techniques. Here, surface birefringence in glass fibers is shown to be a consequence of surface stress relaxation for as-received fibers drawn from Suprasil II. The surface features of the birefringent fibers were compared to a model of the residual axial stress profile resulting from a diffusion-controlled surface stress relaxation. Additionally, a uniform birefringence in the fiber equivalent to a constant tensile stress was recognized and attributed to structural anisotropy produced during fiber drawing. The contribution of structural anisotropy to the observed birefringence remained constant as the surface features were successively etched away. Surface compressive stress generation was also observed, as retardance corresponding to a surface compressive stress was found to increase with applied tensile stress during short heat treatments. Significant features of the retardance profile in as-received silica glass fibers, with a thin surface compressive stress layer and compensating interior tensile stress, agreed with the residual stress profiles predicted by the surface stress relaxation model after correcting for this observed structural anisotropy.     

甩丝法制备多晶氧化铝纤维

使用溶胶-凝胶法制备氧化铝质量分数为80%的多晶氧化铝纤维。以结晶氯化铝、铝粉和硅溶胶为主要原料制备出不同粘度的胶体,采用甩丝法制备纤维。研究了胶体粘度、甩丝盘转速对纤维直径和拉伸强度影响。并对热处理过程中升温制度对纤维拉伸强度的影响进行了研究。结果表明：当胶体粘度为20,Pa·s、甩丝盘转速为6,000,r/min、升温速度为240,℃/h时得到的纤维拉伸强度较高,该纤维经1,200,℃烧成后,平均单丝拉伸强度超过1,100,MPa,是一种性能较优异的氧化铝纤维。     

Improvement of silicon carbide fibers mechanical properties by Cl2 etching

Silicon carbide fibers combine structural and refractory properties making them good candidates for ceramic matrix composite reinforcement, driving their ultimate failure. The fractographic observation after tensile tests of various silicon carbide fibers, belonging to first, second or third generations, reveals the critical flaw location i.e. internal or surface. An etching treatment under pure chlorine at 500–850?°C can be used to transform the fibers surface on hundreds of nanometers and alter the surface-located flaw population. This way, first-generation SiC-based fibers successfully show an asymptotic improvement of tensile strength (up to 60%) and Weibull modulus (up to twice), when etched on 0.3–1?μm depth range. The lifetime of bundles, under static fatigue conditions at intermediate temperature, is consequently multiplied by a factor ranging from 10 to 40 with a narrower dispersion. Nevertheless, the tensile strength could neither be increased on second-generation Hi-Nicalon nor dramatically dropped on third-generation Hi-Nicalon-S fiber.