The organic gel-thermal reduction process was used for the preparation of ferromagnetic metal Ni, Co and Fe fine fibers from the raw materials of citric acid, lactic acid and metal salts. The structure, thermal decomp...The organic gel-thermal reduction process was used for the preparation of ferromagnetic metal Ni, Co and Fe fine fibers from the raw materials of citric acid, lactic acid and metal salts. The structure, thermal decomposition process and morphologies of the gel precursors and fibers derived from thermal reduction of these gel precursors were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermo-gravimetric/differential scanning calorimetry and scanning electron microscopy. The results show that spinnability of gel largely depends on molecular structure of metal-carboxylate complex that is a linear-type structure formed in the gel. As a result, the gels exhibit a good spinnability. Metal Ni, Co and Fe fine fibers are featured with diameters of around 1 μm and a high aspect ratio up to 1×106.展开更多
The difference of sintering crunodes of metal powders and fibers is discussed. The mathematical model of the surface diffusion described by the difference in mean curvature is defined as a Hamilton-Jacobi-type equatio...The difference of sintering crunodes of metal powders and fibers is discussed. The mathematical model of the surface diffusion described by the difference in mean curvature is defined as a Hamilton-Jacobi-type equation, and the model is numerically solved by the level set method. The three-dimensional numerical simulations of two metal powders and fibers(the fiber angle is 0° or 90°) are implemented by this mathematical model, respectively. The numerical simulation results accord with the experimental ones. The sintering neck growth trends of metal powders and metal fibers are similar. The sintering neck radius of metal fibers is larger than that of metal powders. The difference of the neck radius is caused by the difference of geometric structure which makes an important influence on the curvature affecting the migration rate of atoms.展开更多
As a key part of the pyrotechnic gas generator,the filter not only removes the particulate matter but also cools the hot gas to a safe level.This paper aims to improve the understanding of the basic heat and flow phen...As a key part of the pyrotechnic gas generator,the filter not only removes the particulate matter but also cools the hot gas to a safe level.This paper aims to improve the understanding of the basic heat and flow phenomenon in the gas generator.The pyrotechnic gas generator is modelling by a simplified filter structure with fiber arrays.A finite-volume model of the heat and fluid flow is proposed to simulate the detailed multi-dimensional flow and energy conversion behaviors.Several verification results are in good agreement with data in different references.Simulation results demonstrate that the filter can not only absorb heat from the gas but also cause the high intensity enhancement of the heat transfer.The performance difference between inline and staggered arrays is also discussed.The findings of the study put a further prediction tool for the understanding and design of the filter system with fibers.展开更多
基金Projects(50474038 50674048) supported by the National Natural Science Foundation of China
文摘The organic gel-thermal reduction process was used for the preparation of ferromagnetic metal Ni, Co and Fe fine fibers from the raw materials of citric acid, lactic acid and metal salts. The structure, thermal decomposition process and morphologies of the gel precursors and fibers derived from thermal reduction of these gel precursors were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermo-gravimetric/differential scanning calorimetry and scanning electron microscopy. The results show that spinnability of gel largely depends on molecular structure of metal-carboxylate complex that is a linear-type structure formed in the gel. As a result, the gels exhibit a good spinnability. Metal Ni, Co and Fe fine fibers are featured with diameters of around 1 μm and a high aspect ratio up to 1×106.
基金Projects(51174236,51134003)supported by the National Natural Science Foundation of ChinaProject(2011CB606306)supported by the National Basic Research Program of ChinaProject(PMM-SKL-4-2012)supported by the Opening Project of State Key Laboratory of Porous Metal Materials(Northwest Institute for Nonferrous Metal Research),China
文摘The difference of sintering crunodes of metal powders and fibers is discussed. The mathematical model of the surface diffusion described by the difference in mean curvature is defined as a Hamilton-Jacobi-type equation, and the model is numerically solved by the level set method. The three-dimensional numerical simulations of two metal powders and fibers(the fiber angle is 0° or 90°) are implemented by this mathematical model, respectively. The numerical simulation results accord with the experimental ones. The sintering neck growth trends of metal powders and metal fibers are similar. The sintering neck radius of metal fibers is larger than that of metal powders. The difference of the neck radius is caused by the difference of geometric structure which makes an important influence on the curvature affecting the migration rate of atoms.
基金This work is supported by the National Natural Science Foundation of China(Grant No.11972194)the Fundamental Research Funds for the Central Universities,No.30918011323China Postdoctoral Science Foundation funded project(Grant No.2015M581797).
文摘As a key part of the pyrotechnic gas generator,the filter not only removes the particulate matter but also cools the hot gas to a safe level.This paper aims to improve the understanding of the basic heat and flow phenomenon in the gas generator.The pyrotechnic gas generator is modelling by a simplified filter structure with fiber arrays.A finite-volume model of the heat and fluid flow is proposed to simulate the detailed multi-dimensional flow and energy conversion behaviors.Several verification results are in good agreement with data in different references.Simulation results demonstrate that the filter can not only absorb heat from the gas but also cause the high intensity enhancement of the heat transfer.The performance difference between inline and staggered arrays is also discussed.The findings of the study put a further prediction tool for the understanding and design of the filter system with fibers.
