饮料瓶盖无毒PVC泡沫内垫的研制

本文通过研制啤酒等饮料玻璃瓶盖泡沫内垫的过程,将软质PVC塑料捏合工艺、压制烧结工艺,二次热成型工艺等有机地结合起来,形成一种新工艺——软质PVC泡沫塑料烧结发泡工艺。该成型工艺简单、易控制,便于推广应用。     

烧结工艺对Ca3Co4O9基热电氧化物电性能的影响

采用溶胶-凝胶化学法合成了Ca3Co4O9热电氧化物粉末,分别采用陶瓷烧结工艺方法和放电等离子烧结(Spark Plasma Sintering,SPS)的方法制备了Ca3Co4O9热电氧化物块体材料.利用X射线衍射XRD、扫描电子显微镜SEM和电输运参数测试仪分析了所得样品的物相、微观组织结构、晶粒取向度和电输运性能.结果表明,不同制备方法均可得到纯相的Ca3Co4O9热电氧化物块体材料;通过陶瓷烧结工艺方法制备的Ca3Co4O9热电氧化物块体晶粒取向度较低,但随着成型压力的增加而提高;SPS烧结的方法制备的Ca3Co4O9热电氧化物块体晶粒取向度最高;试样电性能随着晶粒取向度的提高逐渐提高,其中SPS烧结方法制备的块体材料电性能最高,在测试温度最高点700℃时功率因子达3.85 μWmK-2,远高于普通烧结试样.     

半导体热电陶瓷ZnO热压成型的研究

研究了半导体热电陶瓷ZnO热压成型技术,采用正交试验研究优化出其热压成型工艺;试验结果表明,所用的热压成型工艺,具有显著的活化烧结功效,可明显地降低压制压力和热压温度并缩短热压时间.试样组织疏松、有较多的孔隙,这有利于降低其热导率提高热电性能.在无粘结剂中、温低压条件下的可制备出具有一定机械强度、热电性能良好的ZnO块体热电陶瓷.     

聚四氟乙烯烧结成型的制备工艺

对聚四氟乙烯（PTFE）进行了压制试验和烧结试验，讨论了成型压力与试件的致密度、压缩强度以及压缩模量之间的关系，且对不同烧结工艺下试件的压缩强度进行了分析，得到较合适的成型压力和烧结工艺。结果表明：咖材料的压缩强度随压制压力的升高而减小，压缩模量随压制压力的升高而增加；闻的成型压力为27．5MPa，烧结温度380℃，保温时间4h。     

制备工艺对La改性的Ca3Co4O9基陶瓷热电性能的影响

利用常压烧结、冷等静压成型后常压烧结及热等静压烧结3种不同制备工艺,合成了(Ca0.9La0.1)3Co4O9热电材料。XRD分析表明：不同工艺制备的样品均为Ca3Co4O9相。样品的SEM照片显示：晶粒为片状结构;热等静压烧结制备的样品,其片状结构不明显,但致密度较之另外两种工艺大幅度提高,其相对密度为95％。制备工艺对(Ca0.9La0.1)3Co4O9热电材料Seebeck系数影响不大,但热压烧结样品能大幅度提高(Ca0.9La0.1)3Co4O9电导率。在一定温度范围内,随温度升高,功率因子大幅度增加,对于热压烧结的样品尤为显著。     

陶瓷制品的试制工艺

生产陶瓷制品包括五道主要工序：粉料制备，坯体压制，坯体加工，烧结和磨削，在必须提高坯体的加工性和改善工艺过程中烧结材料的物理机械悸能的情况下，可增添粉料的液体静压加工工序，坯体和预烧，二次机械加工等，该工艺适用于制作切削工具的工作部件，拉模，制作有色金属合金型材的工具，轴承，铰链，阀门，球阀，水枪喷嘴，压模部件，里衬构件，研磨体等。     

四方相氧化锆分步加压辅助闪烧烧结制备及性能

开发了一种四方相氧化锆陶瓷材料的二次分步加压辅助闪烧烧结工艺,该工艺对加压辅助闪烧工艺进行了优化,消除了临界闪烧温度下高功率闪烧导致的微观组织结构劣化现象。结果表明:多次分步加压辅助闪烧工艺保留了闪烧方法低温、瞬时烧结的优点,规避了复杂生坯压制工序和贵金属电极高昂成本,钇稳氧化锆可通过多次闪烧获得致密化,该工艺烧结温度低于1 050℃,烧结时间小于200 s,制备的四方氧化锆陶瓷材料的密度达到90%以上。     

四方相氧化锆分步加压辅助闪烧烧结制备及性能EI北大核心CSCD

开发了一种四方相氧化锆陶瓷材料的二次分步加压辅助闪烧烧结工艺,该工艺对加压辅助闪烧工艺进行了优化,消除了临界闪烧温度下高功率闪烧导致的微观组织结构劣化现象.结果表明:多次分步加压辅助闪烧工艺保留了闪烧方法低温、瞬时烧结的优点,规避了复杂生坯压制工序和贵金属电极高昂成本,钇稳氧化锆可通过多次闪烧获得致密化,该工艺烧结温度低于1050℃,烧结时间小于200 s,制备的四方氧化锆陶瓷材料的密度达到90%以上.     

热电材料的研究进展

本文简要介绍了热电效应的应用状况和热电材料的基本特性,重点评述了热电烧结材料、高ＺＴ值热电材料以及具有梯度热电材料的研究进展。     

CNTs-Al-Zn复合材料的制备与性能

采用球磨机械混粉的方法制备了锌基复合粉末,并通过真空烧结的方法制备了CNTs-Al-Zn复合材料,重点研究了球磨转速、压制压力、烧结温度等因素对复合材料的影响,进而获得最佳工艺。结果表明,最佳工艺条件为:球磨转速400 r/min,压制压力300 MPa,烧结温度480℃,在此工艺下制备的CNTs-Al-Zn复合材料的屈服强度、拉伸强度、拉伸率、烧结密度及显微硬度等性能都得到显著提高,且材料内部组织均匀致密,无明显孔隙现象。     

Reaction Sintering of Polycarbosilane-Impregnated Compact of Silicon Carbide Hollow Particles and the Resultant Thermoelectric Properties

Porous SiC ceramics fabricated from hollow particles and polycarbosilane (PSC) are promising materials for high-temperature thermoelectric energy conversion. Reaction sintering of PCS-impregnated compacts of SiC hollow particles gave rise to porous microstructures with the hollow shape remaining. The repetition of the PCS-impregnation and sintering process resulted in only a slight increase in density but in a great improvement in thermoelectric properties.     

Cold sintering and co‐firing of a multilayer device with thermoelectric materials

Cold‐sintered ZnO and Ca₃Co₄O₉ polycrystalline materials were shown to have thermoelectric properties comparable to those of conventionally sintered ceramics. Extending these processing conditions into a cold sintering co‐fired ceramic (CSCC) technology, we integrated n‐type and p‐type thermoelectric oxides and a separating insulating layer to demonstrate functional multilayer thermoelectric generator devices. A co‐fired structure with an insulating 8 mol% yttria‐stabilized zirconia (8YSZ) layer enabled multilayer thermoelectric generators (TEG) to be fabricated with a 5 n‐p junction device (20 layers). A transmission electron microscopy analysis of the interfaces between the various materials under the co‐firing cold sintering showed some interdiffusion of chemical constitutes in a 2.0 μm interface region between the respective ceramic phases. The co‐firing of multilayer ceramic and polymer structures were also shown to be possible using insulation layers of polytetrafluoroethylene (PTFE) thermoplastic layers. This demonstrated the feasibility of a single‐step process for new structures with both ceramics and polymers, opening up new directions for many new device designs.     

Thermoelectric Materials: A New Rapid Synthesis Process for Nontoxic and High‐Performance Tetrahedrite Compounds

The feasibility to synthesize, in large quantity, pure, and nontoxic tetrahedrite compounds using high‐energy mechanical‐alloying from only elemental precursors is reported in this study for the first time. Our processing technique allows a better control of the final product composition and leads to high thermoelectric performances (ZT of 0.75 at 700 K), comparable to that reported on sealed tube synthesis samples. Combined with spark plasma sintering, the production of highly pure and dense samples is achieved in a very short time, at least 8 times shorter than in conventional liquid–solid–vapor synthesis process. The process described in this study is a promising way to produce high‐performance tetrahedrite materials for cost‐effective and large‐scale thermoelectric applications.     

Thermoelectric Ca0.9Yb0.1MnO3−δ grain growth controlled by spark plasma sintering

n-Type Ca_0.9Yb_0.1MnO_3?δ thermoelectric (TE) powders were prepared by solid state synthesis (SSS) and co-precipitation method (Cop). The bulk TE materials were consolidated using conventional sintering (CS) and spark plasma sintering (SPS) respectively. The shrinkage behavior, as well as the sample densification strongly depends on the starting particle size. Consequently, the bulk samples from normal powder (SSS) and nano-powder (Cop) were prepared with similar density by using different sintering temperatures, of 1400 °C and 1200 °C, then 1200 and 950 °C for CS and SPS respectively. Such a decrease (up to 200 °C) of the sintering temperature is a consequent progress in terms of engineering for applications. Another advantage of the co-precipitation process compared to the conventional solid state synthesis is that, due to the small particle sizes and the decreased sintering temperature, grain growth was limited and TE properties were enhanced. The interest of the SPS process was also evidenced and we are presenting here the structural and microstructural investigations. In addition, the thermoelectric properties of samples prepared with two different processes were studied with the figure of merit of 0.18 at 750 °C.     

Combined hot extrusion and spark plasma sintering method for producing highly textured thermoelectric Bi2Te3 alloys

Hot extrusion is a promising method for producing high-performance thermoelectric bismuth telluride alloys because of its ability to create textured microstructures. However, hot extrusion is less favourable for scaling-up because of temperature and strain gradients along the radial direction, and only <110> -textured thermoelectric legs can be obtained because of the fibre-like texture. We suggest a way to overcome these disadvantages by implementing an additional spark plasma sintering process on a stack of extrudates. Using this combined process, we demonstrate the fabrication of 12 × 15 × 13 mm³ p-type (Bi_0.2Sb_0.8)₂Te₃ samples from extrudates that had originally been 3 mm in diameter. The evolution of sheet-like texture revealed by SEM, XRD, and EBSD allows us to obtain both <110> - and <001> -textured thermoelectric legs from a single specimen that are desirable for low- and high-temperature applications, respectively. Our results demonstrate the combined method as an industry-friendly process for fabricating high-performance thermoelectric materials.     

Simulation of thermoelectric materials efficiency: The case study of Sr1−xYxTiO3 thermoelectric ceramic

Nowadays, production of thermoelectric ceramics with high efficiency (high figure-of-merit or ZT) is one of the main concerns for the researchers. However, many challenges have arisen due to inadequate knowledge about the influence of each process parameter on ZT. In the present research, we attempted for the first time to scrutinize the way each parameter influences the efficiency of thermoelectric ceramics. We also tried to estimate the percentage of the dependency of efficiency on these parameters. For this purpose, a case study has been done on the Sr_1−xY_xTiO₃ thermoelectric ceramic. Different methods of synthesis as well as all the parameters affecting the efficiency were simulated. The simulation was carried out by gene expression programming (GEP). Accordingly, 10 different models were suggested and their adequacy for measuring the ZT value of Sr_1−xY_xTiO₃ thermoelectric ceramic was examined. The eighth GEP model was eventually selected as the most appropriate model. On the basis of GEP, 3D, data, and frequency simulations were carried out and the obtained results were compared. The results of data simulation indicated that ZT has minimum dependency on compact pressure and the sintering temperature and that it has maximum dependency on the process temperature and the additive content. In comparison, as a consequence of frequency simulation, it was revealed that ZT has minimum dependency on the sintering temperature and maximum dependency on the sintering time and the additive content. Also, the 3D analyses demonstrated a better performance by combustion synthesis in comparison with other synthesis routes.     

掺杂对CuAlO_2晶体结构影响研究

采用溶胶-凝胶法制备CuAlO2热电材料,研究其合成的烧结温度,并研究了用Sr2+、Ba2+离子掺杂对其结构的影响。研究发现:制备CuAlO2的烧结温度为1000℃,在CuAlO2中分别掺杂Ba2+、Sr2+,分别在1000℃和1200℃煅烧2h,均没有得到单相的CuAlO2。     

Reactive sintering process and thermoelectric properties of boron rich boron carbides

Dense boron rich boron carbides were reactive sintered by hot pressing at 2050 °C using elementary boroncarbon compositions with carbon contents of 9.1, 11.1, 13.3 and 18.8 at.%. The following material characteristics are presented: relative density, SEM images, EDX, X-ray diffraction and corresponding lattice parameters, Seebeck coefficient, electrical conductivity and thermoelectric power factor. Significant grain growth has been obtained with increasing boron content. A deeper understanding of the boron and carbon reaction and the overall sintering process is gained by thermal and chemical analysis in combination with X-ray diffraction. Additionally a thermal experiment with boron and carbon layers illustrates the solid state diffusion behaviour. The found results of boron carbide properties of this paper correspond with results by other authors. The aim is to correlate technological aspects of sintering procedure with material properties. This should help to improve the thermoelectric efficiency of boron carbide based materials.     

Thermoelectric properties and thermal stability of metal-doped cuprous sulfide thermoelectrics

Mn doping and S-evaporation are strategies used to improve the thermoelectric properties and thermal stability of cuprous sulfide thermoelectric materials. Cu_1.8S and Mn-alloyed Cu_1.8S powders were prepared via ball milling, and different samples were obtained via current-assisted sintering at different times. It was found that Mn and S-evaporation optimized the carrier concentration and thus improved the figure of merit (ZT) of the samples. The introduction of pore defects induced by S-evaporation also improved the ZT. The maximum ZT of the optimized sample reached 0.89 at 500 °C. Mn in the samples reacted with oxygen to form an oxide film on the surface of the block, which inhibited the kinetic process of Cu_1.8S decomposition and improved the thermal stability of the samples. However, the reaction between Mn and oxygen led to a continuous loss of metal cations in the material, resulting in changes in the thermoelectric properties.     

Effect of excess Ge and Te on thermoelectric performance of GeTe

GeTe is a medium-temperature thermoelectric material with excellent performance. The thermoelectric performance of GeTe is affected by the carrier concentration generated by Ge vacancy. Therefore, it is of important to study the effect of excess Ge or Te on the thermoelectric performance of GeTe. In this paper, Ge_xTe_y materials (x:y = 1:1.08, 1:1.06, 1:1.04, 1:1, 1.05:1, 1.075:1, and 1.1:1) were fabricated by high-pressure sintering (HPS) and spark plasma sintering (SPS), respectively, to study the effects of different Ge/Te atomic ratios and preparation process on the thermoelectric properties of polycrystalline GeTe. The composition and microstructure were investigated by an X-ray diffraction method (XRD) and field-emission scanning electron microscope (FESEM). The thermoelectric performance was tested from 303 to 703 K. The measurement results show that the Seebeck coefficient of Ge_xTe_y increases and the conductivity decreases with the decreasing in Te content or the increasing in Ge content. Ge₁Te₁ exhibits the highest power factor because its Seebeck coefficient and conductivity are at an average level. Owing to the presence of pure Ge and the decrease of Ge vacancy, the lattice thermal conductivities of samples with excess Ge are higher than that of Ge₁Te₁. Ge₁Te₁ sintered by HPS has the highest ZT_max value, reaching 1.37 at 723 K.