EFFECTS OF RARE EARTH ELEMENTS ON THE CHARACTERISTICS OF AUTO-TEMPERING AND DECOMPOSITION OF MARTENSITE FOR A LOW CARBON Si-Mn-V STEELS

The effect of rare earth metals(REM)on the characteristics of auto-tempering and decomposition of martensite for low-carbon and low-alloy steels(20SiMn2V and 20SiMn2VRE)was investigated using TEM,dilatometer and microhardness test.Results show that both ε.and θ carbides,during auto-tempering, may precipitate from the low-carbon martensite matrix at the same time in the 20SiMn2V steel,however,the precipitation of the ε-carbides can be inhibited by the REM contained in the 20SiMn2 VRE steel,resulting in change of the type of precipitated carbides and decrease of the extent of auto-tempering.The“in-situ”ob- servations show that the decomposition of martensite is also inhibited by the REM contained in the 20SiMn2 VRE steel during low temperature tempering.

Effect of Facet Displacement on Radiation Field and Its Application for Panel Adjustment of Large Reflector Antenna

Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low effi- ciency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is pre- sented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics （PO）, the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition （SVD）, the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, thediscussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.

Effect of Nb on Austenite Formation and Decomposition in an X80 Linepipe Steel

Advanced high strength steels for pipeline applications,e.g.X80 grades,have complex microstructures and are frequently microalloyed with Nb.In the hot rolled product it is sought to have Nb precipitated as Nb(CN).However,when processing these steels Nb may be in solution and critically affects the microstructure evolution,e.g.austenite decomposition on the run-out table of a hot mill.Further,microstructure changes in the heat affected zone (HAZ) during girth welding of these linepipe steels may occur with Nb precipitated or in solution.In the HAZ,depending on welding procedures,the material undergoes a number of austenite formation and decomposition cycles and the amount of Nb in solution varies along these stages.In selected positions of the HAZ,thermal cycles peak at the intercritical region and the partial formation of austenite and subsequent decomposition constitutes additional complexity.Developing reliable process models for run-out table cooling and the HAZ hinges on an accurate tracking of microstructure evolution,which is strongly influenced by the amount of Nb in solution.The present study provides more insight into the effect of Nb on austenite formation and decomposition.Firstly,a novel experimental methodology is presented to measure quantitatively the effect of Nb on transformation temperatures pertinent to austenite decomposition,notably ferrite.A model for ferrite formation that accounts for solute drag of Nb is proposed to describe the experimental observations.Secondly,an experimental study will be presented to quantify the effect of Nb in and out of solution on austenite formation in the intercritical region.It is found that the morphology of intercritical austenite,as well as the kinetics of its formation is strongly affected by the starting microstructure and the state of Nb.

Studies on the solid state reactions of coordination conpounds——XLⅤⅢ.The effect of KSCN on the thermal decomposition of cobalt(Ⅲ)-ammine complexes

The evolved gaseous analysis (EGA),infrared spectra,and XRD have been applied to the study of solid state reactions of KSCN with five cobalt(Ⅲ)-ammine complexes:[Co- (NH_3)_5N_3]Cl_2,[Co(NH_3)_5(NO_2)]Cl_2,[Co(NH_3)_5(H_2O)]Cl_3,[Co(NH_3)_5Cl]Cl_2,and [Co(NH_3)_6]Cl_3 in a hydrogen atmosphere.It is found that the existence of KSCN shifts the thermal decom- position of these complexes to a lower temperature.The corresponding peak temperatures are near 140℃.The effect of KSCN is discussed and kinetic parameters of deammine reactions are calculated.

Zn-Co bimetallic supported ZSM-5 catalyst for phosgene-free synthesis of hexamethylene–1,6–diisocyanate by thermal decomposition of hexamethylene–1,6–dicarbamate

A set of mono-and bimetallic（Zn-Co） supported ZSM-5 catalysts was first prepared by PEG-additive method. The physicochemical properties of the catalysts were investigated by FTIR, XPS, XRD, N2adsorption-desorption measurements, SEM, EDS and NH3-TPD techniques. The physicochemical properties showed that the Zn Co2O4 spinel oxide was formed on the ZSM-5 support and provided effectual synergetic effect between Zn and Co species for the bimetallic catalyst. Furthermore, bimetallic supported ZSM-5 catalyst exhibited weak, moderate and strong acidic sites, while the monometallic supported ZSM-5 catalyst showed only weak and moderate or strong acidic sites. Their catalytic performances for thermal decomposition of hexamethylene–1,6–dicarbamate（HDC） to hexamethylene–1,6–diisocyanate（HDI） were then studied. It was found that the bimetallic supported ZSM-5 catalysts,especially Zn-2Co/ZSM-5 catalyst showed excellent catalytic performance due to the good synergetic effect between Co and Zn species, which provided a suitable contribution of acidic sites. HDC conversion of 100% with HDI selectivity of 91.2% and by-products selectivity of 1.3% could be achieved within short reaction time of 2.5 h over Zn-2Co/ZSM-5 catalyst.