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61.
The nature and growth of the interaction layers between solid Nb and liquid Al has been studied by carrying out the tests on Nb(s)-Al(l)and Nb(s)-Al(l)-Ni(s) reaction couples isothermally reacted between 700℃and 900℃for different time intervals.It has been found that the interaction layer between Nb and Al contains two parts:a thin continuous layer of NbAl3 adjacent to the Nb surface and a two-phase zone constituted of NbAl3 particles dispersed in an Al matrix.Although the nature and growth of interaction layers follows the sour-stage mechanism,a typical cruciform pattern does not occur in Nb(s)-Al(l) reaction couples.However,a cruciform pattern was observed in Nb(s)-Al(l)-Ni(s)reaction couples.The movement of NbAl3 particles is important to the production of cruciform pattern in the reaction couples. 相似文献
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40000m~3/h空分设备主换热器的设计及制造 总被引:1,自引:0,他引:1
通过对进口 4 0 0 0 0m3 /h空分设备主换热器进行结构分析及对比模拟计算 ,用国产传热翅片进行设计、采用真空钎焊工艺制造的主换热器 ,经并网运行 ,设计指标优于原空分设备 ,为今后成套大型空分设备板翅式换热器国产化设计、制造创造了条件。 相似文献
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Electrospinning of hydroxyapatite fibrous mats 总被引:1,自引:0,他引:1
Xiaoshu Dai 《Materials Letters》2007,61(13):2735-2738
Polyvinyl alcohol (PVA) with an average molecular weight between 40,500 and 155,000 g/mol was electrospun with a calcium phosphate based sol. The sol was prepared by reacting triethyl phosphite and calcium nitrate and was directly added to an aqueous solution of PVA. This mixture was electrospun at a voltage of 20 kV. The results indicate that the sol was distributed uniformly in the PVA fibers, whose diameter was on the order of 2 μm. This electrospun structure was calcined at 600 °C for 6 h to obtain a residual inorganic, fibrous network, with fiber diameters between 200 and 800 nm. The fibrous structure consists predominantly of hydroxyapatite with an average crystal size of almost 10 to 30 nm. A variety of structures including non-woven mats of solid or micro-porous hydroxyapatite fibers and highly porous scaffolds could be obtained by varying the polymer molecular weight and the sol volume fraction. These structures can have many potential uses in the repair and treatment of bone defects, drug delivery and tissue engineering. 相似文献
66.
Electrostatic fields of macromolecules (e.g., protein molecules) in solvents are often described by the Poisson-Boltzmann equation. This paper introduces two substantial amendments to the electrostatic model: first, the effective dielectric permittivity of the aqueous solvent layer on the molecular surface is drastically different from its bulk value of ~80 and, second, the recently developed flexible local approximation methods produce different schemes with much higher accuracy than the classical ones 相似文献
67.
In China,RFID technology has been applied to some extents,and also has a huge market and development margin. During this progress,the government will help to build up the basic information construction,then to make the basic informa- tion resource open,at the same time to avoid the policy management over-commercialized,and push RFID technology applica- tion forward and speed up its development. 相似文献
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