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。     

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.     

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     

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     

会议消息

▲三院工艺技术报告会于4月24日至25日在本院召开,到会的院属各单位的工艺师、主管工艺的负责同志和代表共90人,部质量司汪川腾同志出席了会议。王建民副院长在开幕式     

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。     

先进复合材料的发展趋势：第42届国际尖端材料学会年会简介

1概况第42届国际尖端材料学会年会及展览于1997年5月4日至8日在美国加里福尼亚州阿纳汉（Ana－heim，CA）召开，来自世界14个国家和地区，包括：美、中、英、法、德、日伽拿大地利时、澳大利亚。韩、挪威、埃及以及香港和台湾等的代表约150人参加了会议，在会上共宣读了176篇报     

碳纤维/凯夫拉纤维混合复合材料的性能

为了全面研究碳纤维/凯夫拉纤维混合复合材料的性能,日本东丽公司系统地对不同混合配比的复合材料的抗拉强度和模量、抗压强度和模量、抗弯强度和模量以及层间剪切强度进行了测定。碳纤维采用 T300-3000-50A,凯夫拉纤维采用 Kevlar49 T968-14200,采用8H 缎纹编织,经向与纬向每25毫米各有25束,