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191.
Youren Xu Avigdor Zangvil Martine Landon François Thevenot 《Journal of the American Ceramic Society》1992,75(2):325-333
A flexural strength of up to 1 GPa was achieved in SiC-AIN materials and is attributed to a dense, equiaxial grain structure of the 2H(δ) SiC-AIN solid solution, with a relatively uniform grain size of ∼ 1 μm. The strength was found to decrease with increasing grain size. While the β→α phase transformation and the formation of various metastable polytypes make microstructural control difficult in SiC materials, excellent control is facilitated in SiC-AIN materials as a result of the stable 2H solid solution. Several mechanisms of grain refinement during the β→ 2H transition were observed, most notably the direct formation of several 2H grains from a single β grain. In addition, grain growth is limited by the diffusion-controlled nature of the transition. These mechanisms could be utilized to achieve even higher strength values, with potentially higher reliability of the materials in structural applications. 相似文献
192.
Tilahun Geleto D. G. Tanner Tekalign Mamo Getinet Gebeyehu 《Nutrient Cycling in Agroecosystems》1995,44(3):195-204
In trials conducted at 2 highland Vertisol sites in Ethiopia in 1990 and 1991, 2 locally popular wheat cultivars, 1 spring bread wheat (Triticum aestivum L.) and 1 durum wheat (T. durum Desf.), were supplied with nitrogen (N) fertilizer at 0, 60 and 120 kg N ha–1 in the form of large granular urea (LGU), standard urea prills or ammonium sulfate. N was applied all at sowing, all at mid-tillering or split-applied between these two stages (1/3:2/3). While durum wheat exhibited the highest N concentration in grain and straw, bread wheat, because of its higher productivity, resulted in a greater grain and total N uptake. In general, split application of N and use of LGU as N source enhanced grain and total N uptake, apparent N recovery and agronomic efficiency of N, particularly under severe water-logging stress. Where significant, the interactions among the experimental factors substantiated the superior responsiveness of the bread wheat cultivar to fertilizer N, and the beneficial effects of split N application and LGU as an N source. Split application of N tended to nullify the positive effects of LGU, presumably by approximating the delayed release of N achieved with LGU. Considering the potential benefits to Ethiopian peasant farmers and consumers, split application of N should be advocated, particularly on water-logged Vertisols; LGU could be an advantageous N source assuming a cost comparable to the conventional N source urea. 相似文献
193.
194.
通过应用含碳氨水集成分离技术改造氨回收装置,提高了分离效率及处理通量,经济与环保效益显著,氨回收率达99%,处理量提高60%,塔阻力下降80%,蒸汽耗量下降42%,装置出口废液含氨量达国家一级排放标准。 相似文献
195.
196.
197.
Xiaohong Wang Guanzhong Lu Yun Guo Yuye Xue Liangzhu Jiang Yanglong Guo Zhigang Zhang 《Catalysis Today》2007,126(3-4):412-419
The Si-doped Ce–Zr–O solid solutions have been prepared by the reverse microemulsion method. The effects of Si and its content on the structure characters, thermal-stability and reducibility of the Ce–Zr–O solid solution have been studied by N2 adsorption, XRD, laser Raman (LR), TPR, FT-IR, NMR and XPS methods. The results indicate that, there are the bonds of Si–O–M (Ce or Zr) in the Ce–Zr–Si–O solid solutions, and the presence of Si can increase obviously the surface area, thermal-stability, crystal lattice distortion rate, and reducibility of the solid solution. The surface area of the sample with 20 wt.% Si reaches 153 m2 g−1 after being calcined at 900 °C for 6 h. The Ce–Zr–O solid solution with 5.2–10 wt.% Si shows excellent thermal-stability and reducibility. 相似文献
198.
吸附型固载二氧化氯释放特性的测定与应用研究 总被引:2,自引:1,他引:2
通过实验研究 ,定义并测定了吸附型固载二氧化氯的释放特性参数 ,并以临界释放速率UC =0 .0 0 5μg/(h·cm3)作为释放终点 ,将其分为长效、快速和中速释放 3种类型。长效型释放速率峰值Umax <2 0 μg/(h·cm3) ,峰值时间τmax >360h ,有效释放时间τcs >60d ;快速释放型Umax >60 μg/(h·cm3) ,τmax <1 2h ,τcs <7d ;中速释放型则处于两者之间。讨论了固载二氧化氯释放特性的控制方法和不同类型产品的适用范围 ,为产品释放特性的定量研究和应用开发提供了依据。 相似文献
199.
200.
On the Predominant Electron-Donicity of Polar Solid Surfaces 总被引:2,自引:0,他引:2
The reasons for the predominant electron-donicity of almost all solid polar surfaces and its implications are discussed in this paper. By contact angle or interfacial tension measurements, the electron-accepting as well as the electron-donating properties of polar liquids can be ascertained, through the interplay between their energies of adhesion and cohesion. For the solid-liquid interface, direct interfacial tension measurements are not possible, but indirectly, solid/liquid interfacial tensions of polar systems can be obtained by contact angle measurement. However, as the energy of cohesion of a solid does not influence the contact angle formed by a liquid drop placed upon its surface, one can only measure the solid surface'ks residual polar property, manifested by the energy of adhesion between solid and liquid. This residual polar property is of necessity the dominant component; in most cases this turns out to be its electron donicity. When, by means of contact angle measurements with polar liquids, both electron-accepting and electron-donating potentials are found on a polar solid, it is most likely still partly covered with a polar liquid: usually water. The amount of residual water of hydration of a polar solid follows from its polar (Lewis acid-base) surface tension component (γAB). The degree of orientation of the residual water of hydration on a polar solid can be expressed by the ratio of the electron-donating to electron-accepting potentials (γ⊖/γ⊕), measured on the hydrated surface. 相似文献