Effects of Ca and Zr substitution upon structure and properties of Ba5LaTi3Ta7O30 low-loss dielectric ceramics

Effects of Ca and Zr substitution upon the dielectric properties of Ba₅LaTi₃Ta₇O₃₀ ceramics were investigated together with the structural characterization. All the samples of Ba₅La(Zr_xTi_1−x)₃Ta₇O₃₀ formed a filled tungsten-bronze structures, whereas the solid solution limit was determined as x=0.25 in (Ca_xBa_1−x)₅LaTi₃Ta₇O₃₀. Beyond this limit secondary phase of CaTa₂O₆ was detected and it would become the major phase for the Ca-rich compositions. The temperature coefficient of dielectric constant was improved with increasing Zr content while the dielectric constant decreased and the low dielectric loss varied little (in the order of 10⁻⁴). In the case of (Ca_xBa_1−x)₅LaTi₃Ta₇O₃₀, small temperature coefficient of dielectric constant could be obtained with increasing Ca content while the dielectric constant decreased significantly, and a small amount substitution of Ca for Ba induced decrease in dielectric loss.     

Effect of hot pressing on processing and properties of BBN ceramics

BBN (BaBi₂Nb₂O₉) is very interesting and promising lead free material with relaxor properties in capacitors, sensors and actuators.     

Development of a Ceramic Micro Heat Exchanger – Design,Construction, and Testing

This article presents the development of a ceramic micro heat exchanger. Starting from its geometrical design, results obtained from a simplified simulation of the heat exchanger efficiency will be given. The alumina microcomponents were manufactured by a rapid prototyping process chain. Here, stereolithography was combined with a low‐pressure injection molding process for the rapid and precise manufacturing of ceramic components down to the micrometer range. A micro heat exchanger, joined from sintered components using a glass solder, was applied as a prototype and checked for its performance at a system pressure of 8 bar.     

Red clays from Central and Eastern Crete: geochemical and mineralogical properties in view of provenance studies on ancient ceramics

The existing geochemical diversity of clay deposits consists the underlying assumption for the determination of provenance of archaeological ceramics on the basis of their chemical composition. This assumption was tested on Quarternary red clayey alluviums from Central and Eastern Crete (Greece), an area rich in archaeological pottery and very popular for ceramics provenance studies. This type of clay has been used for pottery production on the island since the antiquity and it is still in use by traditional workshops. Altogether, 17 samples of clayey raw materials were collected from 7 different locations in Central and Eastern Crete, and characterised by chemistry, mineralogy and petrography. The study was focussed on the internal variability within deposits and the diversity among different deposits.It was possible to distinguish all seven deposits from each other on the basis of their chemical composition, taking into account the available mineralogical and petrographical information, although some deposits presented compositional relations. Compared to Neogene clay deposits in the same area, the variability among the examined red clayey deposits was clearly higher and exceeded by far the intra-deposit variability.     

A novel in situ synthesis of dicalcium phosphate dehydrate nanocrystals in biodegradable polymer matrix

In the paper, we found a novel method to synthesize dicalcium phosphate dehydrate (DCPD) nanocrystals by in situ reaction in biodegradable PDLLA matrix. Calcium hydrid was selected as calcium source of DCPD, which is different from general methods. The method is not only simple and effective to synthesize Ca–P particles, but also can avoid the aggregation of inorganic nanoparticles in the course of their being dispersed into polymer matrix.     

氧化锆增韧陶瓷的相变及相变增韧

本文阐述了氧化锆增韧陶瓷（ＺＴＣ）的相变增韧机理，并探讨了热处理工艺对ＺＴＣ的相变及显微组织的影响规律。     

High Temperature Solid Oxide Fuel Cells(SOFC)

The history and the state of the art of solid oxide fuel cells(SOFC)is reviewed in this paper.Itdescribes mainly on the material selection,structure design and technological economics of SOFC.The appli-cation of great amount of rare earth materials in SOFC may well extend the market potential of rare earthmaterials in the world.A research project to be carried out as early as possible in China on the SOFC tech-nology will be far-reaching.     

ZrO2—SiO2—Al2O3系复相陶瓷制备及其耐磨性试验研究

利用等离子分解锆英石（PDZ）和锆英粉与Al2O3反应烧结制备了ZiO2-SiO2-Al2O3系复相陶瓷。利用XRD、SEM、反光显微镜、显微硬度计等测试手段，对烧成试样的物相组成、显微结构、显微硬度、气孔状况及耐磨性进行了测试分析与讨论。研究结果表明：含镁助剂的加入促进了反应烧结；由PDZ制备的试样的性能优于锆英粉原料的试样：较佳的原料配比为No.4即Al2O3:PDZ=3:1，其耐磨性优于氧化铝质研磨体，适宜的烧成温度范围是1580℃－1600℃。