锆英石陶瓷生产工艺对力学性能的影响

对锆英石陶瓷的生产工艺对材料的显微结构、力学性能的影响进行了研究.结果表明:造粒粉颗粒的硬壳与空洞在坯体中形成了颗粒,如果在成型过程中末被完全破坏,遗留在烧结体中而引起材料内部气孔的存在,材料的力学强度和可靠性能明显下降.制定合理的锆英石材料生产工艺、控制气孔的产生,是提高材料强度和可靠性的有效措施.     

烧结合成镁锆熟料的研究

采用轻烧氧化镁和锆英石粉为原料,研究了锆英石配合量、粉料细度及烧成温度对合成料的烧结及显微结构的影响。结果表明：在氧化镁与锆英石反应烧结过程中,锆英石分解后在初始锆英石颗粒内形成的气孔是阻碍合成料烧结致密化的不良因素;粉料细度,特别是锆英石的细度,对合成料的致密化有决定性的影响     

MgO-ZrO2-C材料的性能和显微结构

研究了在MgO-C耐火材料中添加单斜氧化锆或锆英石所形成的MgO-ZrO2-C材料的性能和显微结构.结果表明(1)加入单斜氧化锆和锆英石导致材料的高温抗折强度降低.(2)热震温度低于1000 ℃时,加入不同量的单斜氧化锆或锆英石对材料抗折强度损失率的影响较小;而热震温度为1200 ℃时,不同的添加量有较大的差别,当单斜氧化锆的添加量为5%～7%,锆英石的添加量为1.54%时,MgO-ZrO2-C材料的抗折强度损失率最小.(3)添加的单斜氧化锆在1200 ℃的热震温度下有部分ZrO2固溶到了镁砂颗粒的内部;而添加的锆英石在1200 ℃下变化轻微,但在1400 ℃下,材料中仅存在少量未分解或分解不完全的锆英石,MgO由基质向锆英石颗粒内部扩散,导致分解完全的锆英石颗粒转变为ZrO2、CMS和c- ZrO2小颗粒.     

一种塞棒控流中间包上水口的剖析

对一种塞棒控流中间包上水口的外形尺寸、致密度、化学组成、相组成和显微结构进行了分析。结果表明:该中间包上水口由外套和锆质水口芯两部分组成,其中锆质水口芯由碗口部位的低锆系材料和下段部位的高锆系材料组成。低锆系的水口芯为锆英石-氧化锆质材料,体积密度达到4.30 g·cm-3,w(ZrO2+HfO2)为82%左右,主晶相由锆英石与斜锆石组成,显微结构可观察到相对均匀的、不规则锆英石粒状颗粒,斜锆石细粉,高硅玻璃相以及少量气孔,锆英石颗粒尺寸在100~150μm以及30~50μm,斜锆石粉的粒度为10~15μm。高锆系的水口芯为Mg-PSZ型水口材料,体积密度达到5.08 g·cm-3,w(ZrO2+HfO2)为95%左右,颗粒的尺寸均在40μm以下,由m-ZrO2和c-ZrO2组成,显微结构可观察到相对均匀的、不规则ZrO2颗粒和少量气孔,微量杂质SiO2与MgO反应生成镁橄榄石M2S,在颗粒间起填隙作用。     

锆莫来石材料的反应烧结机制和显微结构特征

研究了用锆英石和工业氧化铝合成锆莫来石材料的反应烧结过程和显微结构。结果表明，添加适量ＭｇＣｌ２·６Ｈ２Ｏ可以促进反应烧结进程。锆英石大颗粒完全分解以后形成ＺｒＯ２聚集体，结构中出现封闭气孔可能与ＺｒＯ２聚集体有密切关系。加入ＭｇＣｌ２·６Ｈ２Ｏ后锆莫来石材料显微结构的主要特征：ＺｒＯ２有聚集体和均匀分布两种赋存形式；封闭气孔一般与ＺｒＯ２聚集体相邻。     

锆英石-莫来石复合材料的热机械行为

锆英石-莫来石复合材料是通过锆荚石粉和莫来石粉反应烧结而制得的。热机械性能（强度和韧性）是通过莫来石和锆英石间的中间相体现出来的。这种复合材料在室温与1000℃之间表现出较好的热震稳定性，在1100℃与1300℃温度区域，将压力由10MPa增加至90MPa来衡量材料的弯曲蠕变。在1000℃与1300℃范围内，当活化能从280kJ·mol^-1增加至900kJ·mol^-1，材料的应力指数在2和3之间变化。从微观结构分析可以看出晶粒间的蠕变机理。莫来石颗粒与锆英石颗粒之间的界面力比锆英石颗粒间的力要重要的多。在锆英石基体中形成莫来石颗粒。可以使材料同时具有莫来石材料的良好的蠕变性能和锆英石材料良好的热震稳定性。     

添加物对氮化硼材料性能的影响

研究了引入锆英石和氧化铝等添加物的热压氮化硼材料的抗氧化性、热震稳定性及力学性能。结果表明，向氮化硼中引入锆英石和氧化铝后，虽然未能按预期设想生成莫来石，但却对提高氮化硼材料的抗氧化性、热震稳定性及力学性能有利。     

颗粒增强建筑陶瓷板材的研究

采用建筑陶瓷板的制备工艺,将不同粒径的锆英石、刚玉、石英粉体分别加入到陶瓷板材坯料中,研究了粉体种类和粒径对陶瓷板材力学性能的影响。结果表明:在正常配方范围和生产条件下,加入的锆英石、刚玉和石英主要以颗粒的形式弥散分布在基体中,并且都有提高样品抗弯强度的作用。其中,刚玉的增强效果最好。粉体粒度对弥散强化效果也有重要影响。     

锆英石的粒度组成对卫生陶瓷釉乳浊性能的影响

主要研究了不同粒度锆英石的加入量与卫生陶瓷釉乳浊性能之间的关系;分析了不同粒度锆英石的引入对乳浊釉中异相颗粒的大小、形态及分布的影响;得到了生料锆乳浊釉中锆英石引入的合理粒度组成和加入量.     

锆英石质研磨体的研制

本文通过对锆英石原料、成型工艺和烧成工艺的研究，确定了锆英石质研磨体的生产工艺。     

The role of zircon particle size distribution, surface area and contamination on the properties of silica-zircon ceramic materials

Zircon is used as an additive to silica ceramics for use in investment casting to improve their high temperature properties. However, little is known about the mechanisms by which this occurs. To investigate the effect of zircon addition to a silica ceramic a number of silica-zircon formulations were created utilising three different batches of zircon with different particle size distributions (PSDs), surface areas and contaminant inclusions. The contaminant inclusion of the zircon, present in the zircon from the ball-milling stage of manufacture, appeared to have a large effect on the room temperature flexural strength, high temperature flexural strength and high temperature creep properties. It is also suggested that any increase in post-fired cristobalite content and any change to crystal growth morphology was due to the inherent contaminant inclusions and not because of the zircon itself. Hence, use of silica-zircon materials in ceramics for investment casting should account for variation in the contaminant inclusion of the zircon in order to maintain the specific material properties required.     

Dense zircon (ZrSiO4) ceramics by high energy ball milling and spark plasma sintering

The addition of sintering additives has always been detrimental to the mechanical properties of sintered ceramics; therefore, methods to reduce or, as in this case, eliminate sintering additives are usually relevant. In this paper, dense zircon ceramics were obtained starting from mechanically activated powder compacted by spark plasma sintering without employing sintering additives.The high energy ball milling (HEBM) of starting powder was effective to enhance the sintering kinetics. The structural changes of the zircon powder introduced by the HEBM were evaluated. The phase composition and the microstructure of bulk zircon material were analyzed by SEM (EDAX) and XRD. The Vickers hardness and the fracture toughness were evaluated as well.Fully dense materials were obtained at 1400 °C with a heating rate of 100 °C/min, 10 min soaking time and 100 MPa uniaxial pressure. The zircon samples sintered at temperatures above 1400 °C were dissociated in monoclinic zirconia and amorphous silica. The dissociation was detrimental for the mechanical properties. Unlike conventional sintering methods (hot pressing, pressureless sintering) SPS permitted to overcome the dissociation of the zircon material and to obtain additive free, fully dense zircon ceramic with outstanding mechanical properties.     

Preparation of porous spodumene/zircon composite ceramics and its thermal and mechanical properties

Abstract

Porous β-spodumene/zircon (ZrSiO₄) composite ceramics were prepared by addition of zirconia to spodumene mineral using conventional solid reaction methods. The formation of the zircon was investigated by means of the differential scan calorimetry measurements and an X-Ray diffractometer. The microstructure of the composite ceramics was observed through a scanning electron microscope. The results show that the presence of zircon benefited the formation and stability of the porous structure and improved significantly the thermal endurance and mechanical properties of the spodumene matrix. The composites with 10–15% porosity exhibit an excellent thermal shock resistance, a low thermal expansion coefficient of approximately 1·4 × 10^?6 K^?1 in the range of 200–800°C and a high flexural strength about 100 MPa. It is found that the spodumene/zircon composites, widely used as a high temperature structure material, can be synthesised by a cost effective method.     

Ceramic dies selection for electrical resistance sintering of metallic materials

Processing metallic powders by electrical resistance sintering requires the use of insulating ceramics dies. Selecting the appropriate ceramic material according to the electrical, thermal and mechanical properties is a need. Dies produced with several ceramic materials have been tested during the production of cemented carbide in order to check their behaviour in the process and final product properties. Tialite/mullite, zircon/mullite, zirconium phosphate based ceramic, yttria-stabilized zirconia and sialon, in most cases with modified compositions and shaping processes in order to achieve a high density, have been tested. Dry powder processing by cold isostatic pressing and furnace sintering resulted to be the better process for dies production. The effect of die properties on the produced cemented carbide, and the behaviour and life of the die during the production have been analysed. Very smooth die surface increases the number of cycles withstood during metallic parts production, because of lower extraction stresses, as checked for sialon dies. Zirconium phosphate based dies, with low thermal conductivity, show the most densified hard metal parts surface.     

Main characteristics of foams and a study of the production process of zirconia foam ceramics

Conclusions Some combined studies of the syneresis, resistance, and the rheological properties of two-phase foams used to obtain foam ceramics have been carried out. A series of characteristics have been proposed for the evaluation of the properties of the three-phase mineralized foam ceramics. The connection between the technological and rheological properties of mineralized zircon foam and the connection between the properties of the foams and the foam ceramics obtained from them have been shown.A zircon foam ceramic with a total porosity of 78–90% and an ultimate compressive strength of 2–17 MPa has been prepared.It has been shown that it is possible to obtain a no-shrink (on molding) zircon foam ceramic.Translated from Ogneupory, No. 2, pp. 53–57, February, 1980.     

Producing a composite material based on zircon concentrate and nanocrystalline zirconium dioxide

The effects have been examined of adding nanocrystalline zirconium dioxide powder stabilized by yttrium oxide on the production and properties of a composite material based on zircon. It is found that the zirconium dioxide particles at the boundaries of the zircon grains slow the consolidation of the zircon matrix in sintering and zircon grain growth.     

Tailoring of functionally graded zirconia–mullite/alumina ceramics

A new tailored zirconia–mullite/(0–100 vol%) alumina as functionally graded ceramics (FGCs) was designed and synthesized by reaction sintering of zircon and alumina. Zircon and alumina powder mixtures were mixed, stacked, compacted in a cylindrical die and sintered. The sintered samples made of 11 layers and varied gradually in composition by 10 vol% from one layer to the other layer (i.e. from zirconia–mullite layer to alumina layer) resulted in continuous functionally graded ceramics without sharp interfaces. Phase composition and densification behaviors of the samples were investigated. Microstructure, mechanical and thermal properties of FGC and its non-layered composites were studied. Results showed that the tailored FGZM/A gave continuous homogenous structure with highly improved physical, mechanical and thermal properties. The different properties of tailored FGZM/A recorded average values or rather better of its non-layered composites which gave a new way for material design.     

PMZN压电陶瓷的工艺研究

为了优化Pb(Mn1 3Sb2 3) x(Zn1 3Nb2 3) y(Zr ,Ti) zO3系压电陶瓷的介电性能 ,探讨了不同烧结温度及保温时间对材料性能的影响 ,以期获得材料的最佳制备工艺。实验结果表明 ,此四元系材料具有较宽的烧结温度范围 ,随保温时间的延长材料的性能提高 ,最终达到一个饱和值 ;在 12 0 0～ 12 2 0℃烧结工艺条件下 ,材料的机电耦合系数与机械品质因数最大 ,介电损耗最小 ,介电常数适中 ,可望用于高性能超声换能器的研制     

Preparation and corrosion resistance of cordierite–spodumene composite ceramics using zircon as a modifying agent

To prolong the service life of cordierite–spodumene composite ceramics applied to the solar heat transmission pipeline, the zircon modifier was introduced to improve the corrosion resistance of the ceramics. The effects of zircon on the density, bending strength, crystalline phase, microstructure and chemical stability were studied. The results showed that the sintering temperature range of the composite ceramics was broadened to 40–60?°C with the introduction of 5–15?wt% zircon. Moreover, the mechanical strength and corrosion resistance of the ceramic materials were improved with the zircon introduction. In particular, sample C3 containing 15?wt% of zircon and sintered at 1360?°C exhibited the best performance, which had the 0.03% Wa, 0.07% Pa, 2.34?g?cm^?3 Db and 100.17?MPa bending strength. After acid and alkali corrosion, the water absorption was still less than 0.5% and the strength loss rate decreased to less than 5.3%. The XRD and SEM analyses demonstrated that the ZrSiO₄ grains dispersed at the grain boundaries could enhance the mechanical properties. Furthermore, the existence of the Zr⁴⁺ ions not only reduced the cationic solubility of the glassy phases but also led to a reaction with OH^? to form Zr(OH)₄ on the surfaces. This improved the corrosion resistance of the composite ceramics and endowed it with a high residual strength after the acid and alkali corrosion.