Hafnium carbide (HfC) coatings were deposited on carbon/carbon (C/C) composites by low pressure chemical vapor deposition (LPCVD) using HfCl4–CH4–H2–Ar system. The effect of the ratio of CH4 to HfCl4 (input C/Hf ratio) on the deposition of HfC coatings was investigated. It was found that the input C/Hf ratio in the feed gas mixture is a crucial factor in determining the deposition rate, microstructure and growth behavior of HfC coatings. The increased input C/Hf ratio is effective in increasing the linear deposition rate of HfC coating. When deposited with 1:1 input C/Hf ratio, the coating growth is dominated by the crystal growth, the deposited coating exhibits a column-arranged structure. While deposited with 2:1 and 3:1 input C/Hf ratios, the formation of coating is dominated by the nucleation of HfC, the rapid nucleation results in the particle-stacked structure of the deposited HfC coating.

Radioisotope Thermoelectric Generator(RTG) is the perfect power source used in the lunar and the deep space exploration,which it has no effect by the sun's rays and the other severe environments,and can supply simultaneously power and heat for space probes.The paper reviews international application history of RTG and its state of RD.For the moment,the RTG's study focuses on high efficiency and high specific power to meet with the future of deep space explorations.And the paper recommends something about the RTG's application in deep space exploration.In the end,the paper discusses on the key technologies,including the technology of the RTG's designs,thermoelectric converter technology,isotope heat sources management and nuclear safety,thermal management and power sources management.

Radioisotope Thermoelectric Generator (RTG) is an ideal device for power and heat supply for lunar and deep space exploration because it is no influence by sunlight and environment. The paper introduces the principle, reviews the space application history and the R D tendency of RTG. Then, the paper discusses some consideration for optimization of disposition and the key technologies of RTG for lunar and deep space explorations including RTG design, thermoelectric converter, radioisotope heat sources and nuclear safety, the interfaces of RTG with electric power supply and thermal control subsystems, and so on. Finally, the paper put forward a proposal of R D strategy of RTG in China.

The conversion efficiency of heat to electricity is the basic parameter of thermoelectric element, thermoelectric unicouple and thermoelectric devices. In principle, the heat to electricity conversion efficiency of thermoelectric element has been defined as the electrical output power of the element divided by its thermal input power. Due to the heat loss by convection and radiation heat transfer the test result of the heat to electricity conversion efficiency has a large errors. The authors present a test method for heat to electricity conversion efficiency of thermoelectric unicouple. The thermal input power of thermoelectric unicouple has been divided into the electrical output power plus thermal output power out of the cold end of the unicouple. The later has been determined by a thermoelectric thermal power meter. The method avoids the difficulties to measure the input thermal power into the hot side of the unicouple, so that the convection and radiation heat lose out of the unicouple side can be ignored. Owing to Seebeck Coefficient of the thermoelectric semiconductor materials could be many times of the metals, the thermoelectric thermal power meter has high sensitivity, so that high test precision could be gained in test for conversion efficiency of thermoelectric unicouple. The paper presents some test results for heat to electricity conversion efficiency of thermoelectric unicouple, and discusses about the factors which affect the test results.

放射性同位素温差发电器(Radioisotope Thermoelectric Generator,RTG),也称放射性同位素温差电池,是利用塞贝克效应将放射性同位素的衰变热直接转换成电能的发电器件.尽管RTG效率低、成本高,但结构紧凑、可靠性高、生存力强,与迄今已知的其它化学和物理电源相比,它的质量比能量高、寿命长,且无需维护,也不受环境影响.因此,在军用侦察卫星、通信卫星中得到了成功应用,在星际探测任务中(如月球表面和深太空),它仍是目前的首选核电源.

The heat to electricity conversion efficiency is the basic parameter of thermoelectric element, thermoelectric unicouple and thermoelectric devices. The authors present a new test method for heat to electricity conversion efficiency of thermoelectric unicouple. The input heat of thermoelectric unicouple has been divided into two parts including the output electric power and output heat out of the unicouple cold side. The later has been determined by a thermoelectric heat meter. The thermoelectric heat meter has a high sensitivity, so that high test accuracy could be gained on the determination of heat out of the unicouple cold side. The paper presents test results for heat to electricity conversion efficiency of some thermoelectric unicouple, and discusses about the factors which affect the test results, especially about the calibration of the heat meter

The paper reports a new technology for integration of PbTe elements. In traditional procedure, the first step is to prepare PbTe materials, then to bond them together with electrodes. We press the PbTe powder together with the powder of electrode and buffer materials by powder metallurgy after PbTe alloy was prepared, and obtain the elements directly. The paper described the technical process in detail. The authors prepared some samples of N-type PbTe elements using the technology. The electrode, buffer, PbTe material and their interfaces of the prepared samples are characterized by SEM and ED. The contact resistances have been measured and compared with the sample prepared by traditional technology. The results indicate that the proposed technology is easy, economic and feasible. It may simplify preparation process of PbTe elements, reduce the times PbTe materials suffered at high temperature and decrease the contact resistance

Lead telluride is traditional thermoelectric material at middle temperature and widely applied for electricity generation. They have been attracting many scientists to research on. The paper reports an N-type PbTe materials with high thermoelectric performances based on the traditional halogen-doping mechanism with additional indium.The PbTe based materials doped indium and PbI2 are prepared by powder metallurgy technology. We use an intermediate frequency induced furnace for primary alloy preparation. The alloy shows very homogeneous with the desired composition. Then, the comminuted powder particles are hot pressed under certain temperature, pressure and so on. The prepared samples have been examined by FETEM and their thermoelectric properties have been measured. The results indicate that doping with the appropriate PbI2 and indium leads to remarkable improvement of the thermoelectric properties, and we gained high figure of merit over a wide temperature range.

The authors prepared N-type PbTe samples by super high pressing. The performance of the samples has been reported and discussed in the paper. The authors measured the density and bending strength of the samples prepared with different super high pressing technological parameters in order to judge their mechanical properties, made SEM analysis in order to observe their microscopic structure, tested electrical conductivity, Seebeck coefficient and calculated the power factor in order to estimate their thermoelectric performance. Comparing data of samples prepared by super high pressing with those of samples prepared by cold press, it is evident that the performances of the samples by super high pressing under suitable technological conditions are better than those of the samples by cold press.

A basic model of semiconductor thermoelectric generator was constituted. Based on the model, the expression of thermoelectric generators thermal conductivity was derived, which is closely associated with the thermal conductivity of N type semiconductor, P type semiconductor and ceramic plate. Experimental research on the relationship between temperature and thermal conductivity was preceded, and curves about the relationship were plotted. Result indicates that theoretical value is approximate with experimental data.

利用固相反应和SPS(放电等离子体烧结)技术烧结了CoSb3+BN块体材料.X射线衍射(XRD)测试表明,两者没有发生固溶或者化学反应,成功制备了CoSb3/BN复合材料.扫描电子显微镜(SEM)表征发现BN(氮化硼)均匀地分散在CoSb3基体中.测试了复合材料的电导率和热导率随温度的变化.在室温时BN的引入同时降低了电导率和热导率,而在高温时,对电导率的影响减弱,但仍然有效地降低晶格热导率.

A practical technique has been developed to measure the thermal conductance and cooling power of TE modules. The principle of this technique and the measuring equipment has been given. Good agreement between this technique and a Z-meter or Harman Technique has been obtained. Experimental errors of the entire system at about room temperature do not exceed 2%

Many solutions for line generalizations have already been proposed. Most of them, however, are geometric solutions, not cartographic ones. The position we take in this paper is to observe school-case solutions available in standard cartographic books and try to replicate those automatically. A central criterion guiding the process of cartographic generalization is line structure, which itself can be decomposed into a series of line bends. Hence our solution is to preserve the overall structure with line bends which are mathematically defined according to size, shape, and context. Rules are subsequently applied using operators such as elimination, combination, and exaggeration. The algorithms that were used are both procedural and knowledge based. Various experiments were conducted on physical and political geographic lines, and we show the graphical results so that readers may visually assess them. Further research to improve the present solutions is discussed, particularly options for avoiding conflicts in large-scale reductions.

Cartography has had a long tradition of symbolisation, but until Bertin introduced systematic guidelines for symbolisation in the 1960s, the rules followed by cartographers were largely based on convention and experience. In recent years, as computerised mapping systems have become widely available and easily accessed by a large community of users who are cartographically untrained, poorly designed maps have been noticed everywhere, in magazines, in newspapers, even in scientific literature. This is because the current software opens all the possibilities for symbol selection to the user. In order to diminish the potential for misuse, expert systems should be developed, systems that encapsulate the expertise which provides guidance and control during symbol design and so ensure a good product.

A combination of procedural algorithms and predicate logic formalisms is proposed to generalize complex coastlines. The advantage of this combined strategy is to cover both the geometric and conceptual aspects of the generalization process. The geometric part is dedicated to simplification and displacement operations for graphical presentation. The conceptual part handles the problem of river selection based on geometrical and semantic criteria. The derivation of a hierarchical model reflecting the hierarchical structure of the bay/river network of the coastline is a requirement for river selection. A case study was carried out, and results show an improvement over more conventional procedural approaches. The idea of building a hierarchical model to prepare the ground for feature selection can be applied to other hierarchically structured objects such as road networks or nested buildings in urban areas.

A solution to the automated generalisation of one particular class of geographical objects is proposed. Those objects are area patches distributed over a two-dimensional space. They are assumed to be semantically identical; hence the competition for space occurs on the basis of geometric considerations only. The solution proposed is algorithmic, stepwise and works for vector data only. The steps include data preprocessing, area expansion and contraction, elimination, reselection, aggregation, displacement, integrity check, smoothing and reduction. Among the generalisation rules which were applied are: (1) emphasis on larger patches at the expense of smaller ones, (2) preservation of the overall figure/group relationship, (3) Partial topological integrity, and (4) differential displacement according to patch area. Results are discussed within the wider framework of topographic map generalisation where diversified objects must be simultaneously generalised.