Electric Current-Assisted Sintering of 8YSZ: A Comparative Study of Ultrafast High-Temperature Sintering and Flash Sintering

Electric current-assisted sintering (ECAS) is a promising powder consolidation technique that can achieve short-term sintering with high heating rates. Currently, main methods of performing ECAS are indirect heating of the powder compact in a conductive tool or direct heating with current flowing through the powder compact. Various influencing factors have been identified to explain the rapid densification during ECAS, such as ultrahigh heating rates, extra-high temperatures, and electric field. However, the key consolidation-enhancing factor is still under debate. This study aims at understanding the role of heating rate on the enhanced densification during ECAS of 8 mol% Y₂O₃-stabilized ZrO₂ (8YSZ) by experimental and numerical methods. Two different heating modes, ultrafast high-temperature sintering (UHS, indirect heating) and flash sintering (FS, direct heating), are studied. The novel UHS technique is successfully applied to consolidate the 8YSZ samples. Additionally, finite element methods (FEM) combined with a constitutive model is adopted to predict the densification and grain growth. Furthermore, a comparison of UHS and FS is performed to investigate the thermal effect (heating rate) and athermal effect (electric field) individually. The results indicate that the high heating rate is the key factor of the rapid densification during UHS and FS of 8YSZ.     

A Review of Ceramic Sintering and Suggestions on Reducing Sintering Temperatures

Theories and applications associated with sintering of ceramics and reducing of sintering temperature are reviewed. The whole sintering process is divided into three sub-processes as powder preparation, compaction and sintering, and each sub-process is discussed in terms of its possible contribution to the reducing of sintering temperature. New approach for practical optimization of sintering process is investigated. The application of above in the Low Temperature Co-fired Ceramics (LTCC) is discussed. Meanwhile, many successful applications in reducing the sintering temperatures are presented.     

One-Step Synthesis and Sintering of MgB2 by Spark Plasma Sintering

We have studied the one-step procedure for simultaneous synthesis and sintering of SiC-doped MgB₂ by the spark plasma sintering technique. Two types of composition, one in which Mg is strongly deficient, with the atomic ratio $\mathrm{B/Mg} = 3.75$ , and one in which Mg content is slightly higher than the stoichiometric value, specifically $\mathrm{B/Mg} = 1.87$ , were investigated. The amount of SiC was 12 wt.% and 9 wt.%, respectively. For comparison we also studied the way the deficit of Mg can be compensated in a second process of sintering. The sample with Mg deficit shows that SiC is left almost unreacted but the results are spectacular: the highest critical temperature, 36.5 K, the highest upper critical field and the highest self-field critical current density 6.7×10⁵ A/cm² at 10 K. In the sample with overstoichiometric Mg, SiC is decomposed, carbon diffuses within MgB₂ but the critical temperature is only of 35.8 K and the zero-field critical current density is one order of magnitude lower. The compensation of the deficit of Mg in the two-step procedure is not efficient. The critical temperature is even lower, 35.8 K, the upper critical field is also lower despite SiC decomposition and C diffusion within MgB₂ and the critical current density is slightly above 10⁵ A/cm². However, at low temperatures and fields of order 7 T the sample with overstoichiometric Mg and the sample prepared by the two-step procedure have higher critical current density.     

以Al-B4C-C为烧结助剂的SiC陶瓷液相烧结研究

尝试以含Ａｌ、Ｂ、Ｃ的化合物为烧结助剂进行了α－ＳｉＣ粉末的无压烧结,研究了烧结助剂中Ａｌ和Ｂ的配比、烧结温度、保温时间等因素对烧结体密度和力学性能的影响．结果表明,最佳保温时间为１ｈ;当烧结温度为１８５０℃以上时,烧结体的相对密度达到了９０％;当Ａｌ／Ｂ＝３和 ４时,烧结体的性能相对较好．ＸＲＤ显示了Ａｌ_８Ｂ_４Ｃ_７相的存在,表明在烧结过程中反应生成了Ａｌ_８Ｂ_４Ｃ_７,烧结机制是液相烧结．扫描电镜照片显示了断面结构和晶粒形貌．     

含有烧结助剂的复相陶瓷材料烧结过程的元胞自动机模拟

基于晶界能和晶界曲率的晶粒生长驱动力理论,建立了含有烧结助剂的复相陶瓷晶粒生长的元胞自动机模型并进行了模拟。结果表明,烧结助剂对晶界有着强烈的钉扎作用,其晶粒生长指数小于未含烧结助剂时的生长指数。模拟结果与制备的含有烧结助剂的Al2O3／TiN复相陶瓷材料微观形貌组织吻合,表明所建立的模型适用于含有烧结助剂的陶瓷材料烧...     

放电等离子烧结(SPS)技术

放电等离子烧结（SPS）技术是一种新型的材料制备技术。介绍了SPS技术的发展概况、原理、特点及在材料制备领域的应用。最后，对SPS主发展前景进行了展望。     

放电等离子烧结技术

本文介绍了近几年来在日本迅速发展的放电等离子烧结技术,除概要地介绍了这种烧结新技术的原理和特点外,着重介绍了放电等离子烧结技术在制备梯度功能材料和快速烧结细晶粒陶瓷方面的重要应用,其中后者包括了作者最近在日本大阪府立产业技术研究所取得的部分研究结果．     

脉冲电流烧结技术及其在氮化铝透明陶瓷烧结中的应用

脉冲电流烧结(Pulse electric current sintering,PECS)是近十年发展起来的一种特殊的快速烧结技术.介绍了脉冲电流烧结的特征、研究现状及其在氮化铝透明陶瓷烧结中的应用.     

Sintering of titanium metal

Stoichiometric TiH₂ powder, which is stable in air, was used as a starting material in the sintering of titanium metal. Powder compacts of stoichiometric TiH₂ , finely ground in air, were fired in vacuum to remove the hydrogen, and then sintered. Using this method the Ti particles did not experience surface oxidation, which would otherwise usually occur, and the powder showed good sinterability, giving a sintered density above 98% of theoretical at the relatively low temperature of 1000°C     

微波烧结CuTi-金刚石复合体

采用微波烧结方法制备出CuTi-金刚石复合体,并对复合体的工艺、组织和结构进行了研究．结果表明,金刚石颗粒在烧结过程中没有发生石墨化转变,CuTi-金刚石复合体中金刚石颗粒与CuTi基体间能形成良好的结合．CuTi-金刚石复合体的致密度随金刚石含量的增加出现先增加后降低的变化趋势,当金刚石含量为18.75～25vol％时达到最大值．     

纳米氧化钛陶瓷的烧结

将醇盐水解制备的纳米氧化钛粉体（～13nm）在500～800℃下煅烧,用XRD研究氧化钛相变过程中粉体的热稳定性,发现在加入0．4wt％的金红石相作为晶种后;晶粒生长受到较好的控制,同时分别在30、57和200MPa下对纳米氧化钛样品进行热压烧结,用密度仪、压汞仪和SEM对烧结前后的样品进行表征后表明,700℃的热压烧结样品已开始致密化,200MPa、800℃热压烧结样品的相对密度为97．2％,此时3～15nm的小气孔仍难以消除,这些小气孔的存在是纳米氧化钛陶瓷在较高的压力下难以完全致密的主要原因．     

陶瓷材料微波烧结研究

陶瓷微波烧结技术是一门具有实用价值和应用前景的新颖烧结技术。它与常规烧结法相比具有：（１）改进材料的显微结构和宏观性能；（２）省时节能；（３）极高的升温速率等优点。本文对微波烧结的优点、机理、设备、工艺及发展和展望进行了分析和讨论。     

以Al-B4C-C为烧结助剂的SiC陶瓷液相烧结研究

尝试以含Al,B,C的化合物烧结助剂进行α－SiC粉末的无压烧结，研究了烧结助剂中Al和B的配比，烧结温度，保温时间等因素对烧结体密度和力学性能的影响。结果表明，最佳保温时间为1h；当烧结温度为1850℃以上时，烧结体的相对密度达到了90％；当Al/B=3和4时，烧结体的性能相对较好，XRD显示了Al8B4C7相的存在，表明在烧结过程中反应生成了Al8B4C7，烧结机制是液相烧结。扫描电镜照片显示了断面结构和晶粒形貌。     

Sintering of biphasic calcium phosphates

Biphasic calcium phosphate (BCP) discs were fabricated and then sintered using two different sintering programs to establish whether the phases present could be controlled at low and high sintering temperatures. X-ray diffraction (XRD) was used to establish the phases present after sintering and scanning electron microscopy (SEM) determined the microstructure. Sintering program 1 involved a simple heating and cooling schedule and temperatures of 1100, 1250, 1275 and 1300°C. It produced samples containing an additional alpha-tricalcium phosphate (α-TCP) phase at temperatures above 1100°C. The original ratio of hydroxyapatite/beta-tricalcium phosphate (HA/β-TCP) could not be maintained above this temperature. Sintering program 2 combined the heating and cooling schedules of the first program with a 900°C hold stage to allow α-TCP to β-TCP conversion to take place. At temperatures of 1250 and 1275°C, this program was successful in completely removing the α-TCP phase and preserving the HA:β-TCP ratio. The SEM results show that the surface morphology of the discs was not greatly affected by choice of sintering program.     

Sintering behaviour of spinel-alumina composites

Study of alumina-magnesia binary phase diagram reveals that around 40–50 wt% alumina dissolves in spinel (MgAl₂O₄) at 1600°C. Solid solubility of alumina in spinel decreases rapidly with decreasing temperature, which causes exsolution of alumina from spinel phase. Previous work of one of the authors revealed that the exsolution of alumina makes some interlocking structures in between alumina and spinel phases. In the present investigation, refractory grade calcined alumina and spinel powder were used to make different batch compositions. Green pellets, formed at a pressure of 1550 kg cm⁻² were fired at different temperatures of 1500°, 1550° and 1600°C for 2 h soaking time. Bulk density, percent apparent porosity, firing shrinkage etc were measured at each temperature. Sintering results were analysed to understand the mechanism of spinel-alumina interactions. SEM study of present samples does not reveal the distinct precipitation of needle shaped α-alumina from spinel, but has some effect on densification process of spinel-alumina composites. Microstructural differences between present and previous work suggest an ample scope of further work in spinel-alumina composites.     

Sintering of diamond with cobalt

Diamond powder was sintered by aid of a cobalt at 1600–1800°C and 80–100 kbar. The microstructural observation of the resultant compacts showed that the masses were held together by diamond-to-diamond bonding. The compacts had Knoop microhardness of 5000–8000 kg/mm². The sintering process of the specimen is described.     

低纯度 β-Si3N4粉末的无压烧结及其性能

为了降低氮化硅材料的成本，运用便宜的低纯度β-Si