Influence of cerium ions on the anatase-rutile phase transition of TiO_2 prepared by sol-gel auto-igniting synthesis

The anatase-rutile phase transformation of TiO_2 doped cerium up to 5 molpercent was studied by X-ray diffraction and X-ray photoelectron spectroscopy. The samples wereprepared by sol-gel auto-igniting synthesis process from a TiO(NO_3)_2-Ce(NO_3)_2-NH_4NO_3-citricacid complex compound system. The combusted amorphous powders were calcined at differenttemperatures. Significant structural changes were observed during the various stages of the phasetransformation. It was concluded that at low dopant contents, cerium ions were incorporated into theTiO_2 structure, and the anatase phase was stabilized; but at larger amounts, part of the dopantwas segregated on the surface of TiO_2 and the rutile formation was accelerated at elevatedcalcination temperature.

Oxide and Sulfide Dispersive Precipitation and Effects on Microstructure and Properties of Low Carbon Steels

Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strips. Dimension of them is about 10~20 nm. Electron diffraction study showed that the structure of these precipitates consists with cubic system spinel structure. Their lattice parameter is about 0.83 nm. The results implied that they should be complex oxides of Fe, Al et al. Small sulfide particles with 100-300 nm in size have also been observed. Remarkable strengthening and grain refinement effects can be obtained by the precipitations. The oxygen and sulfur in steels could play beneficial role under certain conditions.

PHASE TRANSFORMATION AND CHARACTERISTICS IN FRECKLE AREAS FOR INCONEL 625 SUPERALLOY

The freckle formation and their phase characterizatics in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in an Inconel 625 allay. These results show that in freckle areas a large number of M6C, MC, Laves and δ phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and Nb during solidification, which results in almost of these freckle areas covered by these complex precipitated phases and induces small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give a reasonable interpretation of the freckle feature for this alloy.

Platinum-polyaniline-modified carbon fiber electrode for the electrooxidation of methanol

Platinum was electrodeposited onto a polyaniline-modified carbon fiberelectrode by the cyclic voltammetric method in sulfuric acid, which may enable an increase in thelevel of platinum utilization currently achieved in electrocatalytic systems. This electrodepreparation consists of a two-step procedure: first electropolymerization of aniline onto carbonfiber and then electrodeposition of platinum. The catalytic activity of theplatinum-polyanihne-modified carbon fiber electrode (Pt/PAni/C) was compared with that of a barecarbon fiber electrode (Pt/C) by the oxidation of methanol. The maximum oxidation current ofmethanol on Pt/PAni/C is 50.7 mA centre dot cm^(-2), which is 6.7 times higher than 7.6 mA centredot cm^(-2) on the Pt/C. Scanning electron microscopy was used to investigate the dispersion of theplatinum particles of about 0.4 um.

Fundamental of Inclusion Removal from Molten Steel by Rising Bubble

The corundum plates with a groove were used to freeze molten flux into solid slice to simulate the flux film formed in continuous casting mold, and thereby to study the formation mechanism of flux film with different surface roughness. The effect of some factors on the surface roughness of flux film, such as reheating rate, cooling rate, flux film thickness and crystallization ratio, was discussed.

Synthesis and Deposition of TiC-Fe Coatings by Oxygen-acetylene Flame Spraying

A simpler and more convenient method for producing wear-resistant, TiC-reinforced coatings were investigated in this study. It consists of the simultaneous synthesis and deposition of TiC-Fe materials by oxyacetylene flame spraying. Solid reagents bound together to form a single particle are injected into the flame stream where an in-situ reaction occurs. The reaction products are propelled onto a substrate to form a coating. Microstructural analyses reveal that TiC and Fe are the dominant phases in the coatings. The reaction between Ti and C happens step by step along with the reactive spray powder flight, and TiC-Fe materials were mainly synthesized where the spray distance is 125-170 mm. The TiC-Fe coatings are composed of alternate TiC-rich and TiC-poor lamellae with different microhardness of 11.9-13.7 and 3.0-6.0 GPa, respectively. Submicron and round TiC particles are dispersed within a ductile metal matrix. The peculiar microstructure is thought to be responsible for its good wear resistance, which is better nearly five times than WC-reinforced cermet coatings obtained by traditional oxyacetylene flame spray.

Application of annexation principle to the study of thermodynamic properties of ternary molten salts CaCl_2-MgC_2-NaCl

Based on the practical basis of measured activities and phase diagrams aswell as in the light of the mass action law. the model of inseparable cations and anions of moltensalts and mattes, and the annexation principle of two kinds of solutions in binary melts, thecalculating model of mass action concentrations of molten salts CaCl_2-MgCl_2-NaCl was formulated.The results of calculation not only agree with experimental values, but also obey the mass actionlaw, testifying that the model formulated can embody the structural characteristics of these ternarysalts, and that the model of inseparable cations and anions as well as the annexation principle oftwo kinds of solutions in binary melts are also applicable to these ternary salts.

Spark plasma sintering on mechanically activated W-Cu powders

Mechanically activated W-Cu powders were sintered by a spark plasma sinteringsystem (SPS) in order to develop a new process and improve the properties of the alloy. Propertiessuch as density and hardness were measured. The microstructures of the sintered W-Cu alloy sampleswere observed by SEM (scanning electron microscope). The results show that spark plasma sinteringcan obviously lower the sintering temperature and increase the density of the alloy. This processcan also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders withhigh density and superior physical properties.

Carbon Diffusion in Hot Strips of Low Carbon Steel Produced by CSP Line under Different Thermal Histories

Two experiments were carried out on the same compact strip production (CSP) line, which differs in that one of them experienced γ→α→γ thermal history. The differences in microstructure, precipitation, misorientation etc between two experiments were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back-scattered diffraction (EBSD) and positron annihilation technique (PAT). The carbon concentration in matrix is more inhomogeneous in the experiment than that with γ→α→γ7 thermal history. The specific precipitation characteristic in the experiment without γ→α→γ thermal history is discussed on the basis of different carbon diffusion behavior and interaction between dislocation and excess carbon.

Experiment research on grain drying process in the heat pump assisted fluidized beds

A heat pump assisted fluidized bed grain drying experimental system wasdeveloped. Based on this system, a serial of experiments was performed under four kinds of air cycleconditions. According to the experimental analysis, an appropriate drying medium-air cycle for theheat pump assisted fluidized bed drying equipment was decided, which is different from the commonlyused heat pump assisted drying system. The experimental results concerning the drying operationperformance of the new system show that the averaged coefficient of performance (COP) can reach morethan 2.5. The economical evaluation was performed and the power consumption for removing a kilogramwater from grains was about 0.485 kW-h/kg (H_2O), which shows its reasonable commercial efficiencyand great application potentiality in future market.

Optimization of RPC technique for refining the intermediate transformation microstructure

The influence of processing parameters ofrelaxation-precipitation-controlling phase transformation (RPC) technique, finish rollingtemperature, reduction ratio and relaxing time on the microstructure was studied bythermo-simulation for a low carbon Nb and Ti containing micro-alloyed steel. The microstructure wasinvestigated by optical microscope, transmission electron microscope and electron back scatterdiffraction (EBSD). The statistical results of the packet size were calculated. It shows that, afterRPC process, the steel is a composite microstructure of bainite and matensite. The bestthermo-simulation process for refinement in this experiment is deformation for 30 percent at 850 degC, and then relaxing at this temperature for 60 s to 200 s. Increasing the reduction ratio from 30percent to 60 or decreasing the deformation temperature to 800 deg C would cause the best relaxationtime to become shorter, increasing the deformation temperature to 900 deg C would cause therefinement effect to be weak.

Quantitative analysis on strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP technique

Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.

Synthesis of β-Sialon from Coal Gangue

It is worth to study the synthesis of β-Sialon from coal gangue, because coal gangue is a waste of coal production andis a high quality kaolin contained carbon which is a perfect raw material of contained reducer itself for synthesis of β-Sialon. The study showed that a high conversion rate of 95% from coal gangue to β-Sialon could be obtained by usingprocess of carbothermal reduction nitridation when strictly controlled the thermodynamic conditions of synthesis. Forcontrolling the synthesis conditions easy, the details of the effects of pco, po2 and T on the conversion rate of β-Sialon were discussed detailedly and the phase diagrams of oxygen pressure vs composition for Si3N4-AlN-Al2O3-SiO2system at 1350, 1500, and 1600℃ were constructed in the paper.

Precipitation and growth of titanium nitride during solidification of clean steel

With the help of solidification kinetics, precipitation and growth of TiNhave been studied theoretically and the effect of cooling rate on the growth of TiN has beendiscussed. Through induction electric furnace experiment and electroslag remelting experiment withdifferent cooling rates, the distribution and particle size of TiN were investigated. It is provedthat the higher cooling rate is, the smaller the final size of TiN is and the more TiN particles canbe found in the steel. That TiN can restrain the growth of columnar crystal and enhance theproportion of equiaxed crystals to refine solidification structure as the heterogeneous nucleationsites of δ-ferrite is confirmed preliminarily. A new method to reduce macrosegregation incontinuous cast steel is provided.

Couple analyzing the acoustic emission characters from hard composite rock fracture

Rock mass is fractured media. Its fracture is a nonlinear process. Theaccumulation of acoustic emission (AF) is closely related to the degree of damage. The dynamicsproblem is simply described based on the non-equilibrium statistical theory of crack evolvement,trying to use the hybrid analysis of the statistical theory and scan electron microscopy (SEM), thecharacters of AE signals from rock damage in a mined-out area is synthetically analyzed andevaluated. These provide an evidence to reverse deduce and accurately infer the position of rockfracture for dynamical hazard control.

Effects of rare earth elements on the microstructure and properties of magnesium alloy AZ91D

The effects of rare earth elements on the microstructure andproperties of magnesium alloy AZ91D alloy were studied. The differentproportion of rare earth elements was added to the AZ91D and thetensile tests were carried out at different temperatures. Theexperimental results show that at room temperature or at 120 deg. Cthe AZ91D's strength decrease with the increasing amount of the rareearth elements. However, the ductility is improved. The influence of0.14/100Sb(mass fraction)on the AZ91D's strength is like that of rareearth elements(0.2/100-0.4/100)(mass fraction). Microstructure graphsdemonstrate that appropriate amount of rare earth elements(0.1/100-0.2/100)can fine AZ91D's grain and improve its ductility.

High Temperature Properties of Refractory Oxide—Nonoxide Composites

High temperature properties(strength,thermal shock resistance,oxidation resistance,etc.) have been studied for oxide-nonoxide composites(e.g ZCM-SiC,ZCM-BN,O’－Sialon-ZrO2,β-Sialon-Al2O3,etc.), The results indicate that:(1) The oxide-nonoxide composites investigated posess much superior hot strength over carbon bonded materials.(2) Addition of nonoxide to oxide matrix leads to noticeable increase in thermal shock resistance.(3)Addition of oxide to nonoxide matrix leads to marked improvement of oxidation resistance.

Analysis of the thermal profile of work rolls in the hot strip rolling process

A 2-dimension axisymmetric model was developed by the finite-differencemethod, which can be used to predict the transient temperature field and thermal profile of workrolls in the hot strip rolling process. To demonstrate the accuracy and reliability of the solutiondeveloped, the calculation results were compared with the production data of a 1700 mm hot striprolling mill and good agreement was found between them. The effect of strip width and roll shiftingon the thermal expansion of the work rolls was studied. It is found that the strip width has markedeffect on the efficient thermal crown. Initially, when the rolling strip changes from narrow towide, a bigger efficient thermal crown can be quickly achieved; afterwards, when the rolling stripchanges from wide to narrow, not only the influence of uneven wear can be reduced but also theexcessive efficient thermal crown can be avoided. It is also found that the work roll shifting has adeterminate but not obvious effect on the reduction of the efficient thermal crown, and will makethe strip shape unstable without being used properly.

Approach to Generalized Synchronization with Application to Chaos-Based Secure Communication

A constructive theorem is established for generalized synchronization (GS) related to C1 diffeomorphic transformations of unidirectionally coupled dynamical arrays. The theorem provides some interpretations about the underlying mechanism of various GS phenomena in nature. As a direct application of the theorem, a chaos-based secure Internet communication scheme is proposed. Moreover, a cellular neural network (CNN) of Chen's chaotic circuits with GS property is designed and studied. Numerical simulation shows that this Chen's CNN has high security and is fast and reliable for secure Internet communications.

Optimum design and layout of the cooling apparatus for long compaignship blast furnace

Generally, the cooler life can determine the blast furnace life. Theslag-metal skull frozen on the cooler can separate the cooler from the hot gas flow in blastfurnace. The key problem is how to freeze liquid slag-metal on the cooler, and the main measure isto decrease the hot surface temperature of the cooler. The computational technology of heat transferwas practically used for long campaign blast furnace design. The optimum design of the cast ironstave, copper stave, plate-stave combined system and flange stave was given by the computingresults. According to the results, the optimum arrangement of different coolers (cast iron or copperstave, flange stave and plate-stave combined system) on different height of blast furnace wall canbe found through all these temperature fields.