B. Yang
,
Y.Q. Wang
,
J. Zhang and B.L. Zhou(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)(Nanchang University
,
Nanchang 330029
,
China)(International Center for Materials Physics
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)
金属学报(英文版)
A novel technique m which TiC particulates are prepared by an in situ reaction in molten aluminum is introduced for producing TiC/Al composite. In order to reveal the characteristic of the technique, the formation mechanism of TiC particulates prepared by this method is studied in this paper. Both theoretical and experimental results have shown that the TiC particulates are formed by a diffusion mechanism when the molar fraction of aluminum in the preforms is higher than 20.02%. On the contrary, the TiC particulates are formed by a solution-precipitation mechanism when the fraction of aluminum in the preforms is lower than 20.02%.
关键词:
in situ reaction
,
null
,
null
B. Yang
,
YQ. Wang
,
J. Zhang and B.L. Zhou (Institute of Metal Research
,
Chinese Academy of Sciellces
,
Shenyang 110015
,
China Nanchang University
,
Nanchang 330029
,
China International Center for Materials Physics
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)
金属学报(英文版)
Some TiAl3 whiskers are found to be produced simultaneously during the formation process of TiB2 Particulates fabricated by in situ reaction in molten aluminum. The thec t of temperature of molten aluminum on the morphologies of the TiAl3 whiskers and the growth mechanism of the whiskers are studied in this paper. The results show that the aspect rutio of the TiAl3 whiskers decreases with the increase of the temperoture. The growth of the whiskers is proved to be controlled by a Vapor-LiquidSoltd (VLS) mechanism. The titanium and aluminum atoms in the catalytic droplet,however, have been coofrmed to react with each othen which is dtherent from other whlskcrs growing by a VLS mcchanism where the compostion in the catalytic droplet is a constant.
关键词:
in situ reaction
,
null
,
null
,
null
B.Q. Jiang
,
L. Gu
,
W.L. Zhang
,
Y.S. Sun and F. Lin Chemical Engineering Department of Nanchang University
,
Nanchang 330029
,
China
金属学报(英文版)
A ceramic tube supported γ alumina silica inorganic composite membrane was made by modifying a ceramic tube supported γ alumina film with a silica sol using sol gel method. The thickness of the silica thin film was 750? and the pore diameter was less than 5?.The prepared silica molecular sieve membrane displayed a high hydrogen permeability and high selectivities of H 2/N 2 and H 2/CO 2 gas mixtures. This composite membrane can be used to separate high purity hydrogen of more than 99 5% from various kinds of industrial waste gas mixtures containing hydrogen.
关键词:
silica
,
null
,
null
,
null
W.L. Zhang
,
B.Q. Jiang
,
Y.S. Sun
,
F. Lin and L. Gu Chemical Engineering Department of Nanchang University
,
Nanchang 330029
,
China
金属学报(英文版)
A stable colloidal boehmite sol was made with the aluminium iso propoxide made in China and used to prepare the supported γ alumina membrane using sol gel method. The γ alumina thin layer was characterized by SEM, N 2 sorption method and permeation measurement. The γ alumina membrane was prepared with uniform surface, thickness of 3 μm and average diameter of about 5 nm. The permeabilities of the single gases of H 2, N 2, Ar and their separation factors were measured. The experimental data explained a behavior of Knudsen diffusion for the gas transport through the thin membrane.
关键词:
boehmite
,
null
,
null
,
null
X.Q. Wei and L. Zhou School of Mechanical Electrical Engineering and School of Chemistry and Materials Science
,
Nanchang University
,
Nanchang 330029
,
China Manuscript received 30 July 1999
金属学报(英文版)
A 3-D cellular automaton model of thermal transfer and solidification has been developed, aiming at a simulational study of the grain structure development in electroslag casting. The program we developed for simulation of the model allows the effects of both metallurgical factors, including solidification point, supercooling required for nucleation and its scattering, and liquid/solid interface energy, and thermophysical factors, including heat conduction coeffcients, heat transfer coefficients and latent heat, to be investigated. The effect of process control can be indirectly inspected with the simulation by varying the melting rate. A box counting algorithm was employed to estimate the local curvature of liquid/solid interface. A series of simulated experiments of electroslag casting processes have been carried out. The simulation started from the beginning of the electroslag casting and proceeds by iteration of certain rules, during which a uniform constant slag temperature and a constant melting rate were assumed. It has been observed that a pool of molten metal forms and deepens gradually under constant melting rate. The deepening of the pool slows down with the simulated electroslag casting process, and the depth and shape of the pool tends to be steady after certain height of cast is formed. A finger-like grain structure with the fingers approximately normal to the bottom of the molten metal pool was generally observed. Higher latent heat was found to enhance dendritic growth. The results agree well with general observation of the grain structures in electroslag castings and demonstrate the applicability of cellular automaton modeling to structural development in casting.
关键词:
electroslay casting
,
null
,
null
B.Q. Jiang
,
W.L. Zhang
,
Y.S. Sun
,
F. Lin and L. Gu Chemical Engineering Dpartment of Nanchang University
,
Nanchang 330029
,
China
金属学报(英文版)
A tubular micro filtration membrane was prepared with α alumina powder and ceramic tube support using dip coating method. The prepared membrane was characterized by SEM, mercury porosimetry and permeability measurement. The effects of the suspension properties and the preparation conditions on the structure and the membrane properties were discussed. The membrane was made with a top layer thickness of 50 μm , an average pore diameter of 0 45 μm , a porosity of 42% and a water flux of 6 5×10 -2 l/(m 2 h Pa). The membrane has a narrow pore distribution and good strength without crack forming, which can be used in industrial micro filtration process.
关键词:
ceramic membrane
,
null
,
null
,
null
