Search

In this work, Nb5+ and Cu2+ were selected to partially substitute Zr4+ in Gd2Zr2O7 for studying the phase structure, microscopic morphology and thermal properties. Gd2(Zr1-3x/2NbxCux/2)2O7 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramic materials were synthesized by high-temperature solid-state reaction method. The results show that the Gd2(Zr1-3x/2NbxCux/2)2O7 ceramics present cubic pyrochlore structure with clear grain boundaries and dense cell structure. And the thermal expansion coefficient of Gd2(Zr1-3x/2NbxCux/2)2O7 ceramics gradually decreases because of the incorporation of Nb5+ and Cu2+ into Zr-site in Gd2Zr2O7. Meanwhile, its thermal conductivity decreases firstly and then increases with the doping of Nb5+ and Cu2+, which reaches the lowest value for the composition of Gd2(Zr0.85Nb0.1Cu0.05)2O7.

As a potential material applied for thermal barrier coatings (TBCs), the La2(Ce0.3Zr0.7)2O7-3 wt.%Y2O3 (3Y-LZ7C3) coating was deposited by electron beam physical vapor deposition (EB-PVD). To increase the service life of the coatings, the microstructures of the coatings were optimized by adjusting the deposition parameters. The deposition temperature of 930 °C and the rotation rate of 5, 15 and 25 rpm were selected. Due to the different driving forces, the microstructure of the column tips evolved from ‘roof tips’ to pyramids with increasing the rotation rate. There existed a {001} 〈100〉 sheet texture in the coatings deposited at 5, 15 and 25 rpm. In addition, the {001} 〈100〉 sheet texture in the coatings became weak with increasing rotation rate from 5 to 25 rpm. This indicated that the columnar crystals would be synergistically growing during the deposition process. The growth direction of the columnar crystals tended to be more uniform with reducing rotation rate from 25 to 5 rpm. Cyclic life of the coatings was tested at 1050 °C in a heat circulation furnace. The cyclic life tended to be prolonged by reducing the rotation rate from 25 to 5 rpm and the longest cyclic life was 350 h. This gives an approach to the improvement of the service life of TBCs by optimizing the microstructures.

The La 2 (Ce 0.3 Zr 0.7 ) 2 O 7 -3 wt%Y 2 O 3 coating was deposited by electron beam physical vapor deposition (EB-PVD). In order to reveal the structure evolution of the coating with the deposition parameter, the selected rotation rates of the substrate were 0 rpm, 5, 15 and 25 rpm, while the substrate temperature was fixed at 870 °C based on the structure zone model of 0.3 sub /T mp direction. The tips of the ‘roof top’ or the pyramids were covered by four {111} planes. During rotation deposition, the columnar crystal grew along the direction. If one assumes that the pore fraction has little effect on the thermal conductivity, the ‘C’ shaped Type I pores reduced the thermal conductivity, the straight Type I pores increased the thermal conductivity, the lamellar Type II pores significantly reduced the thermal conductivity. The minimum thermal conductivity was 0.761 W/(m K) at the rotation rate of 15 rpm. This gives an approach to optimize the structure of the La 2 (Ce 0.3 Zr 0.7 ) 2 O 7 -3 wt%Y 2 O 3 coatings.

Pulsed power research for military and civil applications has been conducted at the China Academy of Engineering Physics (CAEP) for more than 50 years. The pulsed power research activities include development of pulsed power components, such as different kinds of high-voltage switches, series of pulsed power sources and pulsed X-ray machines, high-current accelerators for $Z$ -pinch and flash X-ray radiography, as well as medical application and electromagnetic launch. The most recent progress of pulsed power research at CAEP will be presented.

The influences of Er 2 O 3 doping on the structure and thermophysical properties of La 2 Zr 2 O 7 were investigated. The (La 1− x Er x ) 2 Zr 2 O 7 ceramics were synthesized by a solid state reaction method. The XRD results indicate that they all consist of the pure pyrochlore structure. The SEM results show that the microstructure of the sintered ceramics is dense and the grain boundaries are clean. The average thermal expansion coefficients of the (La 1− x Er x ) 2 Zr 2 O 7 ceramics range from 9.57 × 10 −6 K −1 to 9.66 × 10 −6 K −1 . The substitution of Er 3+ for La 3+ effectively reduces the thermal conductivity of La 2 Zr 2 O 7 . With the increasing Er 3+ content, the thermal conductivity significantly decreases at lower temperatures. At higher temperatures, however, the thermal conductivity of the (La 1− x Er x ) 2 Zr 2 O 7 becomes similar, indicating that the thermal conductivity is less sensitive to composition variation. In addition, for the composition with x = 0.10, the thermal conductivity reveals a nearly temperature-independent behavior, which should be ascribed to the strong phonon scattering source (rattlers).

In order to research the uniformity and volatility of thermostatic bath used on electronic thermometer verification, a method based on thermostat technical performance specifications is presented. Including the introduction of calibration device, the choice of standard device and experiment method. In the end the uncertainty analysis on the measurement of thermostatic bath uniformity and volatility is made. Experiment results show that the uniformity and volatility of this thermostatic bath are 0.0091°C and 0.0087°C/10min with the measurement uncertainty of 0.018°C, The results meet the requirements of electronic thermometer verification. It provides guarantee for the next electronic thermometer verification.

(La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics were synthesized using the solid state reaction method and their thermophysical properties were investigated. All (La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics were composed of the pure pyrochlore phase. The average thermal expansion coefficients of the (La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics ranged from 9.54 to 9.78×10 −6 K −1 . The substitution of Yb 3+ and Er 3+ for La 3+ substantially reduced the thermal conductivity of La 2 Zr 2 O 7 . The thermal conductivity decreased from 2.12 W m −1 K −1 for the composition with x =0 to 1.27 W m −1 K −1 for which with x =0.05 at 26 °C. In addition, the thermal conductivity for the composition with x = 0.05 was less sensitive to temperature variation, which ranged from 1.22 to 1.32 W m −1 K −1 in the measuring temperature range. These results suggested promising potential applications of the (La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics for high temperature thermal barrier coatings.

In this paper, single crystal of CuAlNiBe quaternary shape memory alloy was prepared in a high temperature gradient directional solidification furnace with a selective growing crystallizer. And its shape memory performance characters were systematically compared with other series copper base shape memory alloys. The results show that the single crystal of CuAlNiBe quaternary shape memory alloy has better shape memory properties.

With Bridgeman directional solidification method the single crystal alloys of CuAl base shape memory alloy (SMA) with different components were prepared. And their shape memory performance characters were systematically investigated. The results show that the single crystal of CuAlNiBe quaternary shape memory alloy has much better shape memory properties than that of the CuAlBe and CuAlNi ternary alloy. That meant that in the CuAl base SMA alloy the mixed addition of Be and Ni changed the quenching microstructure has a strengthening effect to improve the shape memory performance of the SMA alloy.

Directional solidification continuous casting (DSCC) processing is steady directional growth process of Cu crystal. It was influenced by seven parameters, and very easy to be broken for some disturbance. Therefore, random crystals grew. In this paper, location of liquid-solid interface Z was set as control object. And correction disturbance closed-loop control was set as general control planning in DSCC processing. Then fuzzy control was selected as control mode. And control algorithm was designed. The closed-loop control process in DSCC processing was simulated. The simulation results showed that control object could return to safe rang even existing random disturbance. And the control process had good stability. Designed fuzzy control device could satisfy DSCC process requirement.

In this paper, single crystal of CuAlNiBe shape memory alloy (SMA) was prepared in a high temperature gradient directional solidification furnace with a selective growing crystallizer. And its performance characters were systematically studied. The results show that the mechanical and shape memory properties of the single crystal of CuAlNiBe SMA alloy has much better than that of the polycrystalline material. This may be explained that the stress concentration at grain boundary caused by the difference of bilateral strains is the dominant reason of deterioration of fatigue properties; therefore single crystal alloy possesses the excellent properties duo to its elimination of grain boundary.

An hBN-Y2O3 composite investment moulding material was developed for investment casting Ti-6Al-4V alloy. Hexagonal boron nitride (hBN) powders plus a few Y2O3 powders were used as the investment mould material to prepare the shell mould with colloidal yttria as binder. The results show that the hBN-Y2O3 composite investment mould can be used to cast Ti-6Al-4V alloy, and has lower cost compared with the traditional yttria based investment mould, because of chemically inert of hexagonal boron nitride and its lower density. Moreover the interfacial reaction between the Ti and hBN-Y2O3 composite shell mould was investigated with measurement of microhardness and scanning electron microscopy (SEM) with energy dispersive (EDS).

Two kinds of thick-walled rings, consisted of WCP/Fe-C gradient composites layers containing about 54 and 70 vol.% of WCP and Fe-C alloy core, were cast by centrifugal casting method. The microstructure, mechanical properties and wear resistance of the gradient composites were investigated. Meanwhile the results were compared with those made of the high speed steel. It was found that WCP in the two kind of gradient composites layers were even well distributed, WCP/Fe-C composites layer of 23-28mm was obtained, the transition layer between the composites layer and matrix alloy core was perfect. The tensile strengths of the two gradient composites layers achieved 345MPa, 460MPa and the impact toughness were 4.6J/cm2, 6.2J/cm2 respectively. Moreover the hardness of the composites layers attained HRA81 and HRA 78. The result of the comparison among the gradient composites layers and that made of the high speed steel showed that the wear resistance of the gradient composites layers containing about 50 and 70 vol.% of WCP was more than 20 times higher than that of the high speed steel under loads of 100N and 200N and sliding velocity of 60 m/s. Finally, the wear-mechanism was discussed.

The in situ composite Cu–Cr alloy, a new type of potential electric material that can be used for contact cables, is reported in this paper. The combination property and thermal stability of the in situ composite Cu–Cr alloy were investigated. Experimental results showed that the in situ composite Cu–Cr alloy has not only high room temperature properties, including ultimate tensile strength σb, elongation rate 5, relative conductivity σr, and combination property that is scaled by M index ( σ b 2 κ r ), but also excellent thermal stability of these properties. At room temperature, the combination property of in situ composite Cu–Cr could be up to 18.3 × 106 MPa2%, which is higher than those of commonly used copper contact cables all over the world. After being heated for 3 h at 500 °C, the combination property of the in situ composite Cu–Cr alloy only decreased 3%. In this paper, the relationship between thermal stability and strengthening mechanism of in situ composite alloy was analyzed.

Effects of the mold rotating speeds on the gradient microstructure and properties of heavy cross-sectional WCP/Fe-C composites made in a self-made centrifugal machine have been investigated with SEM, EDS etc. The results show the ring sample of WCP/Fe-C composites made in a centrifugal machine was free of any defects. And the transition layer between the working layer of WCP/Fe-C composites and matrix Fe-C alloy core was also perfect. The experimental results also show that the WCP-radius-directional distribution in the composites was a continuous component gradient one, which was changed with the various mold rotating speeds. At 1000 rpm the volume fractions of the WC particle from outer layer to inner layer were about 70 vol% to 50 vol% and, at 1400 rpm the volume fractions were about 80 vol% to 65 vol% respectively. The hardness and impact toughness of the working layer of WCP/Fe-C composites were changed with increasing of the mold rotating speeds respectively. Finally, the mechanism of the effects of the mold rotating speeds was discussed in the paper.

In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel casting. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magnetic particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Based on the analysis, a new casting technology of the chain wheel was designed and used m the casting production successfully.

By SIMPLE method and Van-Leer scheme, a program on numerical simulation for 3D mold filling has been developed. The fluid flow field of gas and liquid is calculated in couples by a single phase N-S equation using SIMPLE method, and free surface control equation is handled by Van-Leer scheme. Then it is verified by an anti-gravity mold filling of thin wall plate. In order to demonstrate its ability to simulate 3D casting, an anti-gravity mould filling of a cube is computed by the program.

Spatial resolution of Distributed optical fiber temperature sensor (DTS) system has a great effect on the applications. The principle of spatial resolution is briefly introduced in this paper. An experiment system is presented to test the value of spatial resolution. A method to compensate the spatial resolution while the value has not meet the requirement is proposed and been proved effective to improve the spatial resolution.

This theory is in order to apply the remote calibration technology to industrial resistance thermometer calibration activities. It sets forth the difference between the traditional calibration process and the remote calibration process. A remote calibration system design plan was presented. With the system hardware was given, the data sources and characteristics of industrial resistance thermometer in the remote calibration process was analyzed. On this basis, the system software and database were designed in the platform of VC 6.0 and SQL Server2008. Meanwhile, the good results were achieved in practical applications.

This paper summarizes the design scheme and testing results in the development of a Ka-band transmitter for the future deep space communication systems applications in China. The integrated component of all-digital baseband data coding and modulation of the Ka band downlink transmitter for deep space communications is achieved on the Xilinx FPGA circuit. The modulation schemes of PCM / BPSK / PM, NRZ/BPSK and SRRC-QPSK are separately chosen corresponding to the code rate ranges of 16bps∼20kbps, 20kbps ∼200kbps and 200kbps∼2Mbps by the external control commands in the circuits. 2W output power of the transmitter at 31.84GHz center frequency is obtained by a Ka band solid state power amplifier (KaSSPA).

With the organic combination of melt supercooling and directional solidification techniques, a new concept of rapid directional solidification excited from supercoded melt has been advanced. In this paper, the experimental method of this new technique is reviewed. The difference between the new and the conventional directional solidification processing is illustrated diagramatically. The latest experimental results are given for Cu Ni alloy, which indicate the attractive prospects of the new technique.

This paper presents a model for generator maintenance scheduling in the generation expansion planning of large-scale interconnected power system. The reliability requirements of all the systems including the whole interconnected system and its subsystems, and the influence of the power transferred in the interconnected lines are all taken into account by the model. Meanwhile, the traditional algorithms can also be applied to this model. So the model presented by this paper is of great practicability.

This paper focuses on the relationships between complex problems, sense-making, and exploration. We argue that we increasingly face complex problems for which we do not yet have effective coping methods. We further argue that, given the nature of these problems, it is useful to explore the role of play and games as effective coping methods. Through play we can make sense of complex phenomena and explore features thereof. Games, and in particular online games, seem to provide interesting features for capturing and dealing with complex problems. However, we argue that the games are not yet matured enough to fit the requirements for coping with specific professional settings. This leads us to propose a framework that includes games as one of four mechanisms. The framework is tested in a professional case. ©2009 IEEE. This paper focuses on the relationships between complex problems, sense-making, and exploration. We argue that we increasingly face complex problems for which we do not yet have effective coping methods. We further argue that, given the nature of these problems, it is useful to explore the role of play and games as effective coping methods. Through play we can make sense of complex phenomena and explore features thereof. Games, and in particular online games, seem to provide interesting features for capturing and dealing with complex problems. However, we argue that the games are not yet matured enough to fit the requirements for coping with specific professional settings. This leads us to propose a framework that includes games as one of four mechanisms. The framework is tested in a professional case