加入Si粉对Al2O3-SiAlON复合材料性能的影响

为了研究加入Si粉对Al2O3-SiAlON复合材料的烧结、高温力学性能、物相组成和显微结构的影响,以电熔白刚玉(3~1 mm、≤1 mm和≤0.043 mm)、矾土基β-SiAlON(≤0.074 mm)和Si粉(d50=19.71μm)为主要原料,配制成Si粉加入量(质量分数)分别为0、2%、5%、8%和11%的5种试样;以纸浆为结合剂,经混练、成型、烘干和1 500℃保温3 h埋炭烧成后,测量试样的质量变化率、线变化率、显气孔率、体积密度、常温耐压强度、常温抗折强度、埋炭条件下的热态(400~1 400℃)抗折强度、应力-应变特性和抗热震性,并进行了XRD、SEM和EDS分析。研究显示:加入Si粉可以降低材料的显气孔率,提高材料常温强度尤其是高温抗折强度,改善材料的抗热震性;加入Si粉的试样在1 500℃埋炭煅烧过程中,单质Si转化为纤维状SiC和颗粒状SiAlON等非氧化物,对试样起到增强、增韧作用,有利于提高材料的高温力学性能和抗热震性。     

SiC/SiAlON对原位SiC结合刚玉材料抗侵蚀性的影响

采用矾土基高铝刚玉为骨料,以电熔刚玉细粉、Si粉、SiC粉或SiAlON粉为基质料,用酚醛树脂为结合剂,试样于1450℃埋炭烧成后,制备了烧结良好的原位SiC结合刚玉复合材料;采用静态坩埚法研究了加入SiC或SiAlON对这种复合材料抗渣性的影响.结果表明:原位SiC结合刚玉材料具有良好的抗侵蚀性能,加入适量SiC或SiAlON后复合材料的抗侵蚀性进一步提高;原位SiC结合刚玉基材料抗侵蚀行为和机理为:熔渣侵蚀材料的过程是SiC和SiAlON等非氧化物先被氧化,然后其氧化产物SiO2和Al2O3与熔渣中的CaO和Al2O3以及材料基质中的Al2O3反应生成钙长石,材料被侵蚀;原位生成的SiC难被熔渣润湿,且填充在气孔中,堵塞了熔渣渗透的主要通道;加入SiC和SiAlON,材料中非氧化物的量明显增多,因此抗侵蚀性明显提高.     

Synthesis of Cerium α-SiAlON with Nuclei Addition

Cerium α-SiAlON ceramics were made from a powder mixture of Si₃N₄-AlN-CeO₂ that contained 1 wt% yttrium α-SiAlON powder. Plasma-activated sintering was used to examine the effect of the cooling rate on the formation of α-SiAlON. The formation of cerium α-SiAlON was suggested to be controlled by the nucleation at the surface of α-SiAlON nuclei, because α-phase formation could not occur without the addition of SiAlON powder. The solubility of cerium in the α-SiAlON was shown to be less than a previously predicted critical value.     

支持向量机算法优化制备赛隆-刚玉浇注料工艺参数

运用可限制过拟合、有较强预报能力的支持向量机算法(SupportVectorMachine,简称SVM)对赛隆-刚玉浇注料的工艺参数进行优化,通过试验数据处理,建立了工艺参数与烧成后常温抗折强度的数学模型。留一法结果表明,用支持向量机算法优化制备赛隆-刚玉浇注料的工艺参数是可行和有效的。     

高铝矾土-硅粉氮化合成SiAlON的过程研究

分别以w(Al2O3)为68.08%和45.56%的两种高铝矾土及硅粉为原料,按合成SiAlON的理论配比配料(Si粉过量5%),成型后在流动N2(流量为0.06~0.1m3.h-1)中进行热重分析,同时测定试样在不同温度(900~1500℃)保温6h后的质量变化,并分析氮化后试样的物相变化,从而探讨该试样的氮化过程及其机理。结果表明,高铝矾土-硅粉试样在流动N2中的氮化反应过程可大致分为3个阶段:1)Si粉氮化阶段(900~1200℃),Si粉氮化生成Si3N4和Si2N2O;2)SiAlON形成阶段(1300~1400℃),生成O’-SiAlON和β-SiAlON;3)β-SiAlON的生长发育阶段(1450~1500℃),部分O’-SiAlON转化为β-SiAlON,Al2O3在β-SiAlON中的固溶度增加。     

稀土氧化物在SiAlON陶瓷材料中的应用研究进展

简要论述了稀土氧化物在SiAlON陶瓷材料中的应用研究概况;介绍了Y_2O_3、Sm_2O-3、Dy_2O_3和Nd_2O_3等单一稀土氧化物以及复合掺杂稀土氧化物在SiAlON陶瓷材料中的应用进展,并比较了它们对SiAlON陶瓷材料性能的影响;最后对稀土氧化物在SiAlON陶瓷材料中的应用前景作了扼要的分析和展望。     

不同气氛下合成的SiAlON结合刚玉或碳化硅材料的研究

以刚玉细粉、碳化硅细粉、氮化硅细粉、α-Al2O3,微粉和金属Al粉为主要原料,聚乙烯醇为结合剂,经球磨、混练、困料和成型后,分别在空气裸烧(氧化气氛)、埋石墨粉(还原气氛)、埋石墨+碳化硅混合粉(还原气氛)3种气氛下进行1 600℃6 h热处理制备了SiAlON结合刚玉或碳化硅复合耐火材料,并研究了刚玉或碳化硅粉加入量(7.5%～90%,质量分数)和烧成气氛对SiAlON相的生成量、晶体形貌以及耐火制品的相组成、显微结构和性能的影响.结果表明:(1)随着刚玉粉含量的增加,3种气氛下烧后的SiAlON结合刚玉材料的致密度均增大,烧结性能增强;但氧化气氛下烧结性能好于还原气氛下的.(2)2种还原气氛下烧成的Si A10N结合刚玉试样的相组成均为刚玉、SiAlON和SiC;而在氧化气氛下烧成的试样出现了分层现象,其非氧化层主要为SiAlON、刚玉和少量的莫来石.(3)不同气氛下烧成的SiAlON结合刚玉材料中均有柱状或纤维状的SiAlON生成,但氧化气氛下的SiAlON柱状物比还原气氛下的要粗壮、完整得多,且成群生长.(4)随着SiC粉含量的增加,SiAlON结合碳化硅材料在2种还原气氛下烧后的致密度降低,烧结性能下降;而在氧化气氛下烧后严重氧化,形成了较厚的釉层.     

SiAlON增强Al_2O_3-SiC-C铁沟料用后分析

对原位SiAlON增强Al2O3-SiC-C铁沟浇注料进行了工业应用试验,并对用后铁沟浇注料残样进行了XRD、SEM和EMPA分析.结果表明:1)SiAlON增强Al2O3-SiC-C铁沟浇注料抗侵蚀性优良,一次性通铁量达到15万t以上;2)用后SiAlON增强Al2O3-SiC-C铁沟浇注料可分为蚀变层、反应层和原质层,各层中均有粒状β-SiAlON分布;3)SiAlON增强Al2O3-SiC-C铁沟浇注料在现场使用环境下比在实验室条件下更容易原位生成β-SiAlON,β-SiAlON的生成是该浇注料具有优良使用性能的根本原因.     

An alternative composite approach to tailor the thermoelectric performance in SiAlON and SiC

The thermoelectric properties of SiAlON and SiC based composites prepared by adding TiCN (5 and 10 vol.%) as a particulate or as a segregated three-dimensional network were investigated. Although the volume fraction of the TiCN phase was the same in both kinds of SiAlON-based composites, the one containing the segregated three-dimensional network exhibited larger power factor and higher figure of merit than the particle-reinforced composite. Such an enhancement was not observed in SiC. This outcome highlights the importance of the microstructure design and indicates that the segregated network approach may be an effective method to tailor the thermoelectric properties of composite systems.     

Reaction of europium-doped α-SiAlON phosphors with sodium borosilicate glass matrices

The quantum efficiency of composites containing Europium(II)-doped Ca-α-SiAlON phosphors and sodium borosilicate glasses has been reported to decrease with an increase in the Na₂O concentration in the glass matrix. To understand the reason for the dependence of this degradation on the glass composition, the reaction between the SiAlON powder and the glass matrix was investigated using a variety of techniques. SEM images of the areas around SiAlON powders showed the formation of a new layer between the SiAlON particles and the glass matrix. EDX images showed that the number of silicon and aluminium atoms decreased while that of boron atoms increased in the new layer. Raman spectra of the composites showed the formation of BN bonds. New layers between the SiAlON phosphor and the glasses were formed owing to exchange between silicon or aluminium and boron; this resulted in the degradation of the composites.