碳／碳复合材料的研究与发展

本文简述碳／碳复合研究与发展的概况，包括洲际导弹端头材料、抗氧化热结构材料、飞机刹车材料、先进碳／碳和抗氧化涂层。指出了进一步研究发展的方向。     

氧化对碳-碳复合材料杨氏模量、抗弯强度、断裂韧性和断裂功的影响

碳-碳复合材料是一种高级宇航材料,由于它具有卓越的烧蚀性能、力学性能和耐磨性能,而且重量轻、比重较小、热物理性能也较好,因此已经广泛地被用作战略核武器的再入防热材料,特别是州际导弹的鼻锥材料、火箭发动机的喷管喉衬材料,以及飞机的刹车片材     

碳布叠层碳-碳复合材料刹车片的微观结构和断裂破坏

本文用扫描电子显微镜对碳-碳复合材料刹车片的微观结构和断裂破坏进行了比较系统的研究。研究表明,碳布叠层碳-碳复合材料的薄弱环节在叠层问。“球团状沉积碳”的出现与断裂破坏有密切关系。兰州炭素厂研制的碳布叠层碳-碳复合材料刹车片的微观结构形态与美国本狄克斯公司半乱短纤维模压碳-碳复合材料刹车片有很大差别。     

AG-80环氧树脂固化的DSC热分析

本文用差动扫描量热计研究了四官能环氧树脂AG-80与三氟化硼单乙胺构成的固化体系。使用不同固化剂用量、不同升温速度、不同气氛以及不同型号的固化剂对AG-80/BF_3·MEA体系的固化的DSC热分析作了大量试验研究。试验结果表明,使用DSC方法可以对环氧树脂的固化进行监控,可以对AG-80/BF_3·MEA体系的固化工艺进行指导。其数据和结论对该体系的研究有普遍意义。     

新型高性能蜂窝芯KOREX

ＫＯＲＥＸ是最近由杜邦公司研制出的蜂窝芯材，在强度、模量、耐温性能、湿热性能、抗疲劳、吸湿性、热膨胀和介电性能等方面全面优于ＮＯＭＥＸ芯材。     

选用灌封材料的热机械准则

灌封材料通常指的是浇注在电子元器件周围的塑性材料,用来防护电子元器件,在搬运或振动时作为支撑,有时要具有导热、介电等其它作用。由于灌封材料与电子元器件材料在热膨胀系数间的差别,可能在灌封材料中造成     

Spherule beds 3.47-3.24 billion years old in the Barberton Greenstone Belt,South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution

Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approximately 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record.     

复合材料研制发展的新动向

增强合作,联合投资开发是目前世界各国复合材料研制发展的新动向。Hercules公司和Aerospatiale公司正合作致力于高温复合材料的研究与开发,两家公司希望进一步改进复合材料技术,以满足下一世纪对高温飞行器构架和发动机的要求。Hercules公司是美国的最大的复合材料供应者之一,下属Hercules Aerospace公司则是世界上复合材料最大用户之一。早在1984年Hercules公司就选用Aerospatiale公司的自动三向编织技术用于碳纤维     

碳-碳材料微观结构和断裂破坏的分析

前言碳—碳复合材料是一种新型材料,已经逐步应用于再入飞行器鼻锥、火箭发动机喉衬以及飞机的刹车片等,取得了很好的效果。为了进一步提高其性能,以满足更高级产品的要求,也为了保证其应用的可靠性,急需对它的断裂破坏机理和烧蚀机理等进行进一步的研究。近年来国内外很多研