复杂氮陶瓷的相平衡及组份设计

氮陶瓷尤其是以氮化硅为基的陶瓷,是一个重要的材料系统。和一类硅酸盐材料以［ＳｉＯ４］四面体为基本结构单元相似,以Ｓｉ３Ｎ４为基础的氮陶瓷是以［（Ｓｉ,Ａｌ）（Ｏ,Ｎ）４］四面体为基本结构单元的一大家族材料。氮化硅基陶瓷具有耐高温、高强度、高硬度和耐磨损等优异性能,可用作密封磨环、陶瓷车刀和陶瓷发动机部件等。氮化硅陶瓷的优异性能大多应归因于Ｓｉ－Ｎ键的高共价性。但是,高的共价键导致扩散系数低,若没有适当的添加剂,材料无法烧结到致密。因此,寻找有效的添加剂,主要是金属氧化物,已成为发展氨化硅基陶瓷的…     

Dissecting the contributions of organic nitrogen aerosols to global atmospheric nitrogen deposition and implications for ecosystems

Atmospheric deposition of particulate organic nitrogen(ON_p) is a significant process in the global nitrogen cycle and may be pivotally important for N-limited ecosystems.However,past models largely overlo oked the spatial and chemical inhomogeneity of atmospheric ON_p and were thus deficient in assessing global ON_p impacts.We constructed a comprehensive global model of atmospheric gaseous and particulate organic nitrogen(ON),including the latest knowledge on emiss...     

A filtration error in nitrogen determinations

Filtration through standard filter papers may introduce a serious error in total and non-protein nitrogen determinations particularly when the procedure involves repeated filtration prior to analysis. Evidence is presented which indicates that some, if not all, of the soluble nitrogen in filter paper is present as ammonia or ammonium salts. This error can be completely eliminated by the use of small sintered glass filters.