Zuo Tieyong

Fracture toughness of sintered Mo–La2O3 alloy and the toughening mechanism

Abstract The K IC of sintered Mo–La 2 O 3 alloy and pure molybdenum was tested and the micro-structure was investigated by SEM, TEM and AES. The results show that the K IC of Mo–La 2 O 3 alloy reaches 24.76 MPa m 1/2 , which is 2.5 times as much as that of pure Mo. The sintered Mo–La 2 O 3 alloy and pure molybdenum have similar equiaxed grain structure. The AES analysis revealed that the same content of interstitial impurities exist on grain boundaries of Mo–La 2 O 3 alloy and pure molybdenum. A toughening mechanism was proposed to be that large number of dislocations were pinned around La 2 O 3 particles, shortening the efficient slip length and decreasing the dislocation pile-up on grain boundaries of Mo. The improvement of toughness of Mo–La 2 O 3 alloy was attributed to the relief of stress concentration at the grain boundaries of Mo–La 2 O 3 alloy and the weaker tendency to intergranular fracture on grain boundaries.

A study of diffusion behavior of elements lanthanum and oxygen in Mo–La2O3 cathode

Abstract The diffusion behavior of elements lanthanum and oxygen in Mo–La2O3 cathode has been carried out by using Auger Electron Spectroscopy. Lanthanum and oxygen ions (La3+ and O2+) diffuse from the grain boundaries to the surface. The experimental results were analyzed by kinetics of grain boundary diffusion. In the temperature range 1123 K–1423 K, the diffusion coefficients of La3+ and O2+ ions were found to fit with the following expression: D La =3.6703×10 −16 exp (−1.01639×10 5 / RT ) m 2 s −1 D O =1.5122×10 −16 exp (−8.13066×10 4 / RT ) m 2 s −1

A study of chemical behavior of lanthanum in La2O3–Mo thermionic cathode materials

The chemical reaction of La2O3 and Mo2C in La2O3–Mo cathode materials has been studied by thermal analysis, X-ray diffraction, scanning electron microscopy and in-situ X-ray photoelectron spectroscopy (XPS). The thermal analysis and X-ray diffraction results show that molybdenum is one of the reaction products of lanthanum oxide and molybdenum carbide. In-situ XPS results show that chemical state of lanthanum changes during heating. We proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of cathode material at high temperature.

A study of the effect of chemical state of lanthanum on the emission properties of La2O3–Mo filament

Abstract The ion implanting method has been used for implanting metallic lanthanum into the surface of molybdenum wires to study the effect of chemical state of lanthanum on the emission properties of the filaments. The chemical reaction of La 2 O 3 and Mo 2 C can take place during the operating of the La 2 O 3 –Mo filament, and the metallic lanthanum layer improves emission capabilities of the La 2 O 3 –Mo filament. During filament carbonizing and operating, to control the evaporation rate of lanthanum from the filament surface is very important. On the basis of experimental results, the optimum carbonizing and operating temperatures have been presented. On application of the new technique, the life of this filament has exceeded the minimum life for practical uses.

Material life cycle assessment in china

From the very beginning, the research of Material Life Cycle Assessment (MLCA) has been an important part of the ecomaterials research in China, and large numbers of researchers have been focusing their efforts on it. From 1998, and supported by the National High-tech Program-863 Projects, the study of some typical materials has been put into practice. Thus far, the first phase of the project has been finished smoothly. The practical MLCA methods have been developed, and the manufacturing technologies and processes of the steel and iron, aluminum, cement, ceramic, polymer and construction coatings have been assessed. The relevant assessment software has been developed. Reference systems are being set up for evaluation by studying typical materials. In this paper, the main achievements are reviewed. Some other developments of MLCA in China are also introduced.

A study on carburized La-Mo cathode material

Abstract The effect of carburization on the thermionic electron-emission properties of the La 2 O 3 -doped molybdenum (La–Mo) cathode has been systematically studied, and the optimal carburizing technology has been obtained. The optimal carburizing technology is that the La–Mo cathode is exposed to benzene vapour for 8 min at about 1500°C, and the pressure of benzene vapour is about 8.5–9.5 Pa. The thermionic electron-emission capacity of the La–Mo cathode has reached the level of the traditional thoriated tungsten (Th–W) cathode, and the service lifetime of the 6T51-type electron tube equipped with the La–Mo cathode has been about 1657 h under on–off working conditions. So it is possible that the La–Mo cathode will replace the Th–W cathode with the problems of radioactive pollution and drastic brittleness as cathode material of some powerful electron tubes, and this is also the purpose of the study.

High magnetic performance NdFe10.5Mo1.5Nx prepared by mechanical alloying

Spherical or nearly regular hexagonal Nd powders with the size of 20–150 nm, Fe powders with the size of 20–150 nm and Mo powders with the size of 80–100 nm were prepared by Argon and Hydrogen arc plasma. The nanostructural NdFe10.5Mo1.5 compound with ThMn12-type structure have been formed after having been mechanically alloyed for 6–12 hours and crystallized at 700–850 °C under high purified Argon atmosphere. After having been nitrided at 400–500 °C for 2 hours, NdFe10.5Mo1.5Nx nanopowders with ThMn12-type structure can be obtained, which have excellent permanent magnetic properties such as iHc within range of 360.4–716.2 kA/m (4528–8997 Oe), Br within range of 0.6363–0.9831 T (6363–9831 Gs), (BH)max within range of 42.87–166.2 kJ/m3 (5.386–20.88 MGOe).