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．     

放电等离子烧结(SPS)技术与新材料研究

放电等离子烧结(SPS)作为一种材料的绿色制备新技术,正成为国内外材料领域的研究热点.介绍了SPS的工艺特点和装置、国内外发展状况以及特殊的烧结机理;阐述了SPS在功能梯度材料、生物材料、超细或纳米晶WC-Co硬质材料、镁合金等新材料制备方面的应用及优势.最后分析了SPS技术亟待解决的问题和今后的发展趋势.     

放电等离子烧结技术的应用

本文主要介绍了一种粉末烧结技术——放电等离子烧结。首先从结构设计上进行了介绍,放电等离子烧结的主要原理是在粉末进行压力烧结的同时施加电流,最终实现材料的致密化。放电等离子烧结的主要优点是烧结温度低、时间短、升温快、材料致密等。最后列举了放电等离子烧结技术在热电材料、硬质材料、功能梯度材料等的应用实例,论述表明放电等离子烧结技术是一种可以制备高性能材料的烧结技术。     

Nb-Si超高温材料的放电等离子烧结(SPS)工艺研究EI北大核心CSCD

以Nb,Si粉末为原料,采用放电等离子烧结(SPS)技术制备了二元Nb-Si超高温材料,研究了烧结温度、保温时间、加热速率和冷却速率等工艺参数对材料物相组成、微观组织和室温力学性能的影响。结果表明:烧结温度在1300℃以上时,材料主要由Nbss(铌基固溶体)和α-Nb5Si3两相组成,材料的致密度和室温力学性能随着烧结温度的升高而不断提高,在1600℃制备的材料力学性能最好;在1600℃时,随着保温时间的延长,材料的物相组成和微观组织基本没有变化,而其力学性能有小幅度提高;较慢的加热速率和烧结完成后较快的冷却速率均有利于提高材料的室温力学性能。应用优化后的SPS工艺,制备出了室温综合力学性能优异的Nb-Si超高温材料。     

Spark Plasma Sintering as a Useful Technique to the Nanostructuration of Piezo‐Ferroelectric Materials

This review gathers detail on the processing of piezo‐ferroelectric ceramic materials by spark plasma sintering for the first time. The results reported here clearly indicate that it is a powerful technique and opens the possibility of processing ceramics with controlled sub‐micron or even nanoscale grain sizes.     

放电等离子烧结(SPS)制备金属材料研究进展

综述了放电等离子烧结(SPS)技术在制备纳米/超细晶、大块非晶、准晶、金属间化合物、功能梯度材料、多孔材料、硬质合金等多种金属材料中的应用情况.重点阐述烧结过程中的致密化机理,焦耳热生成机制,关于等离子活化效应的争议,电流、温度、位移量和应力分布的不均匀性及其影响,粉末的预处理工艺及其对性能的影响.并总结了SPS技术现存问题及发展趋势.     

放电等离子烧结技术及其在陶瓷制备中的应用

综述了放电等离子烧结(SPS)技术在国内外的发展概况,简单介绍了SPS系统的基本配置,深入探讨了SPS的烧结机理及其技术特点,着重介绍了SPS技术在制备高致密度、细晶粒陶瓷等方面的应用,并对燃烧合成氮化硅粉体进行了放电等离子烧结的试验研究,得到了机械性能优于热压烧结的氮化硅陶瓷.结果证明放电等离子烧结在陶瓷的快速致密化中显示出了极大的优势,是一项有重要使用价值和广泛前景的新技术.     

Transparent Alumina/Ceria Nanocomposites By Spark Plasma Sintering

The influence of oxides (such as MgO, TiO₂, CaO, etc.) on the transparency of polycrystalline alumina compacts are widely studied in the literature. In this work, a completely different approach is developed, consisting of precipitating 0.5 wt.‐% CeO₂ nanoparticles (< 5 nm) on the surface of the starting alumina nanopowder (d₅₀ approximately 170 nm) using cerium(III) acetate as precursor. It is shown that the ceria nanoparticles strongly enhance the transparency of the spark plasma sintered compacts due to: i) the ceria nanoparticles acting as powder lubricant, increasing by around 15% the initial density of the powder in the SPS die, and, ii) the CeO₂ nanoparticles, having a very low solid solubility in the alumina grains, locating at grain boundaries, hindering alumina grain growth by pinning during SPS sintering at 1 430 °C, 80 MPa for 2 min. This effect is found to be effective only under SPS vacuum conditions. In order to explain the light scattering behavior in the near‐infrared and visible range, a light scattering model under the Rayleigh‐Gans‐Debye approximation for polycrystalline alumina is used. This model offers an additional and simple tool for a completed bulk evaluation of the SPS compacts microstructure.     

Alumina/tungsten nanocomposites obtained by Spark Plasma Sintering

In the present work, the parameters controlling the alumina/W nanopowders Spark Plasma Sintering (SPS) process are studied. The important and crucial role of C diffusion from the SPS die in the microstructure, fraction of porosity and new phases formation (W₂C) is discussed. It is also pointed out the importance of the processing parameters of the starting powder on the density and mechanical properties of the final compacts. In this regard, dense alumina/nW compacts containing 4 vol.% W with a hardness value as high as 24.6 ± 0.9 GPa were obtained.     

Functionally Graded Dual-nanoparticulate-reinforced Aluminium Matrix Bulk Materials Fabricated by Spark Plasma Sintering

Functionally graded（FG） carbon nanotubes（CNT） and nano-silicon carbide（nSiC） reinforced aluminium（Al）matrix composites have been successfully fabricated using high-energy ball milling followed by solid-state spark plasma sintering processes.The CNTs were well-dispersed in the Al particles using the nSiC as a solid mixing agent.Two different types of multi-walled CNTs were used to add different amounts of CNTs in the same volume.The ball milled Al—CNT—nSiC and Al—CNT powder mixtures were fully densified and demonstrated good adhesion with no serious microcracks and pores within an FG multilayer composite.Each layer contained different amounts of the CNTs,and the nSiC additions showed different microstructures and hardness.It is possible to control the characteristics of the FG multilayer composite through the efficient design of an Al—CNT—nSiC gradient layer.This concept offers a feasible approach for fabricating the dualnanoparticulate-reinforced Al matrix nanocomposites and can be applied to other scenarios such as polymer and ceramic systems.     

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.     

放电等离子烧结制备Ti3SiC2材料的研究

本文报道分别以Ti/Si/C,Ti/SiC/C为原料,采用放电等离子烧结工艺制备Ti3SiC2材料的研究结果.以元素单质粉为原料,掺加适量Al作助剂能加速Ti3SiC2的反应合成并提高材料的纯度,在1200～1250℃的温度下能制备出经XRD、SME和EDS表征不含TiC和SiC等杂质相的纯净TiSiC2材料.而以Ti/SiC/C为原料时,有无Al作助剂都难以制备出纯净的Ti3SiC2,其反应合成温度明显高于以元素单质粉为原料的.     

Bioinspired Nacre‐Like Ceramic with Nickel Inclusions Fabricated by Electroless Plating and Spark Plasma Sintering

Hybrid composites of layered brittle‐ductile constituents assembled in a brick‐and‐mortar architecture are promising for applications requiring high strength and toughness. Mostly, polymer mortars have been considered as the ductile layer in brick‐and‐mortar composites. However, low stiffness of polymers does not efficiently transfer the shear between hard ceramic bricks. Theoretical models point to metals as a more efficient mortar layer. However, infiltration of metals into ceramic scaffold is non‐trivial, given the low wetting between metals and ceramics. The authors report on an alternative approach to fabricate brick‐and‐mortar ceramic‐metal composites by using electroless plating of nickel (Ni) on alumina micro‐platelets, in which Ni‐coated micro‐platelets are subsequently aligned by a magnetic field, taking advantage of ferromagnetic properties of Ni. The assembled Ni‐coated ceramic scaffold is then sintered using spark plasma sintering (SPS) to locally create Ni mortar layers between ceramic platelets, as well as to sinter the ceramic micro‐platelets. The authors report on materials and mechanical properties of the fabricated composite. The results show that this approach is promising toward development of bioinspired ceramic‐metal composites.