Jian Chun Cao

Solubility Product of MoC with NaCl Type Cubic Crystal Structure in Iron

In this paper, firstly, the equilibrium solubility product formula of MoC with NaCl type cubic crystal structure in ferrite has been deduced by thermodynamic method, according to the free energy change of molybdenum and carbon dissolved in ferrite and the formation energy of MoC. On the basis of deducing activity coefficients of Mo in iron, the solubility product formula of MoC in austenite has been obtained according to the relationship of solubility product of MoC in austenite and ferrite. Finally, the solubility products for MoC and NbC in iron are compared. The solubility product formulae of MoC deduced would play an important role in related theoretical research and practical production.

On Effect of Microstructure about Bi for AgSnO2 Compositions by Reaction Synthesis

This paper adopted XRD, SEM and DTA/TGA methods to discuss the microstructure of sinter AgSnO2 compositions with bismuth and without bismuth. The results showed that microstructures AgSnO2 compositions are different whether or not include bismuth. The introduction of Bi does not produce the expected SnO2 and Bi2O3 phase, but generated SnO2 and Sn2Bi2O7 phase. The reason with different microstructure has relation with early melting of Bi-rich alloys having low melting point and silver oxide decomposition rate and sinter temperature. Therefore, bring third element should be cautious for preparation composite metal oxide increase silver matrix electrical contact materials.

Effects of Different Microalloying and Controlled Cooling Technology on Microstructure and Properties of 500MPa High-Strength Rebars

The mechanical properties and microstructures of three different VN, Nb, V-Nb microalloyed rebars were investigated by using tensile testing machine, impact machine, metallographic microscopy, scaning electron microcopy, transmission electron microscopy and X-ray diffraction apparatus. The results showed that the microstructure of V-Nb microalloyed specimen is consisted of ferrite, pearlite and a small amount of fine bainite (6.7wt%), and obvious effect of grain refinement was obtained with more than 10 size grade of ferrite grain, showing optimal comprehensive properties. SEM micrograph of tensile fracture surface for V-Nb microalloyed 500MPa high-strength rebar is dimple and ductile, ductile-brittle transformation temperature is lower than-30°C, which has good plasticity-toughness and impact toughness at low temperature. The results of precipitates have shown that a large number of small and dispersive V(CN) and Nb (CN) precipitates with size of 5~30nm are formed, good effect of precipitation strengthening was achieved in 500MPa high-strength rebars produced by different microalloying and controlled cooling technology.

Solid-State Reaction and Gas Sensor Properties of Porous SnO2-In2O3 Composites

Mixtures of ITO and SnO2 powders were prepared by a solid-state reaction method in order to produce porous composite materials. X-ray diffraction, scanning electron microscope and gas sensing testing system have been used to analyze the microstructure and properties of it .It has been concluded that when the sintering temperature is 1573K,it has better gas-sensing properties. The pore structure and CO gas sensing property of porous SnO2-In2O3 composite materials can be improved with the increase of SnO2 contents.

First Principles Study on Rutile SnO2 Improving Gas Sensor Properties of Porous SnO2-In2O3 Composites

we built the rutile SnO2 to study SnO2 improving gas sensor properties for rutile structure of SnO2 existing in the SnO2-In2O3 composite materials by X-ray analysis. The surface (110) of SnO2 is a stable structure by analysis of surface energy. Compared with oxidized surface (110), reduced surface (110) has better conductivity and stability. As a result, the CO adsorption changes the electric conductivity of the whole reductive (110) surface, and leads to the deviation of Fermi energy. Therefore, it is an important reason affecting gas sensor properties of the SnO2-In2O3 composite materials. By calculating and simulating the density functional first-principal, the research of the adsorption of rutile SnO2 towards CO provides a theoretical foundation for the argument of the gas sensitivity of porous SnO2-In2O3 composite materials towards CO with the increasing of SnO2 contents.

Strengthening Mechanisms and Microstructure of Vanadium and Nitrogen Microalloyed High Strength Seismic Rebar

Using metallographic test, physicochemical phase analysis, X-ray diffraction and transmission electron microscope, the microstructure of seismic rebars with yield strength of 500MPa, which were fabricated by vanadium and nitrogen microalloying and controlled rolling and controlled cooling, were investigated. The results of metallographic test show that the microstructure in centre and interlayer of tested rebar samples are made up of ferrite, pearlite and a small amount of bainite, but tempered sorbite with thickness of 0.9mm on the edge of the rebars. Physicochemical phase analysis indicates that vanadium in the rebars had precipitated by VN mainly, and the precipitation rates of V and N are 60% and 70%, respectively. The result of strengthening mechanisms analysis shows that fine grain strengthening and transformation strengthening are the dominated contributions to strength and strengthening increments of them are 184.4 MPa and 111.6 MPa, respectively.

Effective Means of Microstructure Homogenization for AgMeO: Cumulative Extrusion Severe Plastic Deformation

This paper mainly aimed at uniform microstructure generally of particulate reinforced metal matrix composites and put forward the method, which was severe plastic deformation, for microstructure homogenization of particulate reinforced metal matrix composites. Basis on introducing origin of severe plastic deformation and the theory of cumulative extrusion severe plastic deformation, the paper researched the microstructure homogenization of silver metal oxide by cumulative extrusion severe plastic deformation. The result showed that microstructure homogenization of silver metal oxide could be uniformed by cumulative extrusion severe plastic deformation. The results also showed that condition of microstructure homogenization was obtained fine or nanometer second phase particles in fabrication and selected intensity of severe plastic deformation according to system and character of particulate reinforced metal matrix composites.

Effect of Cooling Rate after Deformation on Microstructure of V-N Microalloying High Strength Aseismic Rebar

Thermo-simulated test was conducted to study the effect of cooling rate from 1 °C/s to 15 °C/s on microstructure of V-N microalloying high strength aseismic rebar. Microstructure investigation was done using both optical and scanning electron microscopes. Microstructures in center of the rebar mainly consist of ferrite, pearlite, and bainite. The percentage of bainite increases below 5 °C/s cooling rate and decreases between 5 °C/s and 15 °C/s with the increase in cooling rate. At the cooling rate of 15 °C/s the fraction of bainite is about 7.7%, and the finest ferrite with 5.3 μm was obtained. Higher strength value obtained at the cooling rate 8~10 °C/s is due to the combination of smaller ferrite and about 10 % bainite.

First-Principles Calculation of Carbides in Niobium Microalloyed Medium and High Carbon Steels

The binding energies, formation energies and DOS (density of state) of several carbides(Fe3C, Fe2C, Fe5C2, NbC) in Nb micro-alloyed steels are investigated using the first-principle pseudo potential plane-wave method. The results show that the structure type with the strongest alloying ability and the highest structure stability is NbC with fcc structure. After compared the DOS of these different structure types, the results show that the discrepancy in structural stability of carbides can be attributed to the difference in the bonding electron numbers at Feimi level. The less the valence electrons at Feimi level are, the better the structural stability of carbides. Therefore, the theory predicts that the existence form of Nb in medium and high carbon steels are the same as low carbon steels. Nb is still the effective alloying element in medium and high carbon steels.

ME Molecular Dynamics Simulation of the Sintering Process of the Porous ITO Material

Simulated the sintering process of the porous ITO gas-sensitive material with Materials Explorer 5.0. Observed the the process of neck formation and growth, grain growth and pore shrunk. Than, compared the result with experimentation. We found that the simulation results were similar to the microstructure photos. At the same time, we could observe the migration process of atoms in simulation results which we cannot observe in actual experiment. It proves that we get the theory basis of the experiment result estimate and proved the guiding effect of molecular dynamics simulation to the actual experiment.