感应炉用炉衬的性能研究

以试验用石英砂为主要原料,α-Al2O3微粉为烧结剂,硼酸为助烧剂,按5～1mm、1～0mm、<0.088mm的颗粒级配进行配比,干式捣打成形,并在1550℃,烧成4h。通过改变α-Al2O3微粉和硼酸加入量,测试和比较了α-Al2O3微粉和硼酸加入量对试样烧结后性能的影响。实验结果表明:α-Al2O3微粉的适合加入量为3%～4%,硼酸的适合加入量为2%。     

感应炉用炉衬的性能研究

以试验用石英砂为主要原料,α-Al2O3微粉为烧结剂,硼酸为助烧剂,按5～1mm、1～0mm、〈0.088mm的颗粒级配进行配比,干式捣打成形,并在1550℃,烧成4h。通过改变α-Al2O3微粉和硼酸加入量,测试和比较了α-Al2O3微粉和硼酸加入量对试样烧结后性能的影响。实验结果表明：α-Al2O3微粉的适合加入量为3%～4%,硼酸的适合加入量为2%。     

重油直接裂解制乙烯装置用低密度浇注料的研制

采用大颗粒珍珠岩、矾土熟料、漂珠、SiO2超细粉、Al2 O3微粉为主要原料 ,以纯铝酸钙水泥为结合剂 ,研制了用于HCC装置的低密度浇注料。研究了纯铝酸钙水泥、矾土熟料、SiO2 超细粉、Al2 O3微粉的加入量对浇注料的化学组成、体积密度、耐压强度、抗折强度、烧后线变化率及施工性能的影响。结果发现 :结合剂的最佳掺入量是 2 5 % ,超过 2 5 %后 ,提高结合剂用量反而使浇注料的烧后强度下降 ;低温膨胀剂对浇注料的烧后线变化率影响非常明显 ,低温膨胀剂的最佳掺入量是 5 % ;SiO2 -Al2 O3复合微粉对浇注料烧后强度的增强效果非常显著 ,复合微粉的总量为 8% ,m(SiO2 )∶m(Al2 O3)在 1∶4～ 1∶5范围内 ,浇注料的中温强度能大幅度提高。使用证明 ,研制的低密度浇注料是一种较理想的HCC装置用衬里材料。     

不同含铝微粉对原位莫来石结合SiC多孔陶瓷膜支撑体性能的影响

为降低陶瓷膜支撑体的制作成本,以SiC颗粒为骨料,分别以α-Al_2O_3微粉、ρ-Al_2O_3微粉以及Al(OH)3粉作为莫来石相的铝源,利用烧结过程中Si C微粉表面氧化产生的SiO2作为硅源,以木炭粉为造孔剂,碱式碳酸镁作为助烧结剂,于1 350℃保温3 h在空气气氛下无压烧结制备原位莫来石结合SiC多孔陶瓷膜支撑体试样,并研究了三种不同含铝微粉对试样性能的影响。结果表明:经1 350℃烧后,采用活性ρ-Al_2O_3微粉结合的试样抗折强度达到19. 9 MPa,分别高于采用α-Al_2O_3和Al(OH)3结合试样的51. 1%和33. 5%。SEM及XRD分析表明,添加活性ρ-Al_2O_3微粉的试样内部颗粒之间的颈部结合程度最好,原位生成的莫来石相最多。     

ZrO2/Al2O3复相陶瓷的制备及性能研究

本文以工业用ZrO2和α-Al2O3微粉为原料,通过干压成型和常压烧结工艺制备ZrO2/Al2O3复相陶瓷.通过检测复相陶瓷的体积密度、显气孔率、常温抗折强度、烧后线变化率和热震稳定性,研究不同α-Al2O3微粉加入量及添加剂Y2O3对ZrO2/Al2O3复相陶瓷烧结性能、常温强度、热震稳定性及微观结构的影响,并通过SEM方法对烧后试样的微观结构进行表征.结果表明:系统配料中加入Al2O3会降低ZrO2/Al2O3复相陶瓷的致密度,常温强度随着Al2O3加入量增大而呈现先增大后减小趋势,然而热震稳定性有一定程度改善.Y2O3作为一种助烧剂可以促进ZrO2/Al2O3复相陶瓷结构内晶粒长大,加入Y2O3有利于增强复相陶瓷的烧结性.     

微粉对矾土基超低水泥浇注料性能的影响

以高铝矾土熟料为主原料 ,加入 2 %的铝酸钙水泥及总量为 6 %的Al2 O3 微粉和SiO2 微粉 ,配制了矾土基超低水泥浇注料 ,研究了微粉对浇注料的烧结性能、力学性能及热震稳定性的影响。结果表明 :(1 )SiO2 微粉对浇注料的促烧结作用优于Al2 O3 微粉。这是因为与Al2 O3 微粉相比 ,由气相沉积生成的SiO2微粉的粒度小 ,比表面积大 ,活性较高。 (2 )随着SiO2微粉加入量的增加 ,在 1 1 0 0℃和 1 4 0 0℃处理后的常温强度以及在 1 30 0℃和 1 4 0 0℃下的高温抗折强度和抗热震性明显提高。这是由于引入的SiO2 微粉在高温下与Al2 O3 反应生成的针状莫来石穿插进入刚玉骨架 ,起着明显的强化和韧化作用     

助烧剂和造孔剂对真空烧结SiC多孔陶瓷性能的影响

以粒度≤0.063mm的SiC为主要原料,分别加入30%(质量分数)的Al2O3-Y2O3与10%的Al2O3-高岭土复合助烧剂,并外加不同量(分别为12.8%、26.3%、30.0%和36.4%)的造孔剂羧甲基纤维素钠(CMC),制样后首先在空气炉中经过300℃2h或1100℃4h的预烧,然后在真空炉中于1550℃4h真空烧结而制备成SiC多孔陶瓷,并研究了助烧剂种类以及造孔剂CMC外加量对SiC多孔陶瓷显微组织、显气孔率及抗折强度的影响。结果显示:采用Al2O3-Y2O3作为助烧剂的SiC多孔陶瓷比Al2O3-高岭土作助烧剂的具有较高的抗折强度,显气孔率稍有减小;随着羧甲基纤维素钠量的增加,加入两种助烧剂的SiC多孔陶瓷均表现为显气孔率增加,抗折强度降低。     

SiO2微粉加入量对Al2O3-SiC-Al耐火材料性能的影响

以电熔白刚玉、SiC粉、α-Al2O3微粉、Al粉和SiO2微粉为主要原料,以有机硅树脂作结合剂,制备了Al2O3-SiC-Al复合材料。借助差热分析、XRD、SEM等方法研究了SiO2微粉加入量(分别为0、2%、4%、6%)对分别于300℃、500℃、800℃、1100℃、1300℃和1600℃保温3h处理后试样的烧结性能、物相组成和显微结构等的影响。结果表明:随着SiO2微粉加入量的增加,试样的强度逐渐升高,体积密度增大,显气孔率降低,并在SiO2加入量为4%时试样的物理性能达到最好;加入的SiO2微粉不仅能降低Al与周围空气中氧的反应,且与Al反应生成的Si能改善Al与SiC的润湿性,提高材料的结合能力。     

添加剂对超硬材料陶瓷结合剂性能的影响

以金属Al粉与α-Al2O3微粉作为陶瓷结合剂的添加剂,研究其对陶瓷结合剂抗弯强度、矿物组成及气孔分布等性能的影响.结果表明:金属Al粉添加量为4wt％,在620℃下烧结时,试样抗折强度最高为29.97 MPa,较基础陶瓷结合剂试样提高了10.3％;单独添加α-Al2O3微粉能够提高结合剂的黏度,防止试样在烧成过程中产生不均匀变形,提高陶瓷结合剂的网络致密度;在680℃下烧结,试样抗折强度大幅提高,最高强度为65.46 MPa,较基础陶瓷结合剂提高了140％,并且与陶瓷结合剂发生反应生成霞石(NaAlSiO4),霞石的生成有拓宽烧结范围,抑制裂纹延伸的作用;金属Al粉与α-Al2O3微粉共同加入对陶瓷结合剂抗折强度的提高有更好的效果,在680℃下烧结,当金属Al粉添加量为2wt％,α-Al2O3微粉添加量为30wt％时,试样抗折强度最高为80.33 MPa,较基础陶瓷结合剂试样提高了195.5％;金属Al粉的加入不会影响陶瓷结合剂气孔的形成,气孔分布均匀且较多,具备容纳磨屑与携带冷却液的性能.     

Al2O3微粉和SiO2微粉对刚玉-莫来石材料性能的影响

在板状刚玉细粉中添加粘土或Al2O3微粉和不同种类的SiO2微粉制成刚玉-莫来石试样,分别于1200℃、1400℃和1600℃保温5 h烧成后,测定试样的体积密度、显气孔率和烧后线收缩率,利用XRD分析了试样在不同温度段的莫来石生成量,研究了添加Al2O3微粉和不同种类的SiO2微粉对材料的烧结性能和莫来石化的影响,并利用SEM观察了试样的显微结构.结果表明(1)加入Al2O3微粉和SiO2微粉均有利于材料的烧结;加入SiO2微粉的纯度和晶形不同,对试样莫来石化的影响也不同,无定形态SiO2微粉(即硅灰)的纯度越高,试样的莫来石生成量也越高.(2)加粘土的试样,其显微结构中柱状莫来石的晶体特征比较明显;而加入SiO2微粉的试样,其莫来石晶体和刚玉晶体相互交错,晶粒较小.     

CeO2 和MgO助烧剂对矾土基莫来石合成料烧结的影响

以高铝矾土碎矿(w(Al2O3)为75%~84%)和煤矸石(w(Al2O3)约45%)为原料,按矾土基莫来石合成料的设计成分要求(w(Al2O3)为68%~72%)进行配比,于1500~1700℃分别保温3h煅烧合成了矾土基莫来石,并分别研究了助烧剂CeO2和MgO单独加入,CeO2 MgO复合加入,复合加入时CeO2与MgO的比例以及复合加入量对矾土基莫来石合成料烧结性能的影响。结果表明:加入CeO2 MgO复合助烧剂比单独加入CeO2或MgO的促烧结效果要好,当CeO2 MgO外加量为0.75%,CeO2与MgO质量比为1/1时,可使试样的烧结温度降至1600℃(不加助烧剂的为1700℃),得到显气孔率0.9%,体积密度为2.84g·cm-3,荷重软化开始温度为1570℃的合成莫来石;显微结构分析表明,此合成料荷重软化温度较高的原因是发育良好的柱状莫来石构成了交错连锁的网络结构,同时TiO2大部分固溶在莫来石晶体中。     

Flash microwave sintering of zirconia by multiple susceptors cascade strategy

In the field of flash sintering, microwave energy represents an interesting way to densify ceramics complex shapes, thanks to a contactless volumetric heating. Attaining a fast and homogeneous heating is a critical parameter and hybrid heating, using silicon carbide susceptors, is generally used. In this study, an original multiple susceptors cascade strategy is developed, using both SiC and 3D-printed ZrO₂ susceptors. This novel configuration follows perfectly the flash heating scheme, even for high heating rates up to 1000 K.min^-1 and leads to a high stability of the “flash” hybrid heating. Flash microwave sintering produced dense (97 % relative density) microstructures within 45 s. Based on comprehensive multiphysics simulations of the overall process, in-situ dilatometry measurements, kinetics method analysis and microstructural characterizations, this work highlights the sintering behavior of zirconia and the temperature distribution during flash microwave sintering.     

An interface nucleation rate limited sintering kinetic model applied to in situ sintering Al2O3-SmAlO3 composites

A nucleation rate limited sintering model was recently developed based on observations of bicrystal sintering. This work validates the applicability of this model for sintering of polycrystalline clusters of Al₂O₃-SmAlO₃ at high temperature in the range of 1130–1610 ℃. The model fits the data well and agrees with trends observed during bicrystal sintering. A temperature dependence to the dominant sintering strain deformation modes is observed from in situ heating experiments performed in a transmission electron microscope (TEM). The observations provide insights into how temperature influences the early stages of sintering by affecting the pore size distribution through local de-sintering. This provides insights into the role heating rate and sintering schedule play in microstructural evolution that influences the grain size versus density trajectory.     

热压烧结金刚石工具用石墨模具抗氧化研究

采用氧化失重实验,对热压烧结金刚石工具用石墨模具的氧化腐蚀性能进行了研究。着重讨论了抗氧化剂组分、总磷酸盐浓度和抗氧化浸渍工艺等因素对石墨模具抗氧化性能的影响。结果表明:以复合磷酸盐为主体,添加金属氟化物和氮化物制备出的抗氧化剂,对石墨模具的抗氧化性和抗压强度有明显提高。当抗氧化剂总磷酸盐浓度大于25%,采用真空加压抗氧化浸渍工艺,对石墨模具的抗氧化效果最好。     

添加物对LaCrO3材料烧结的影响

以钙质铬酸镧微粉为主原料,研究了分别添加ZrO2、CaO、MgO、SiO2或Al2O3五种微粉对铬酸镧材料烧结的影响。通过测定试样的体积密度、显气孔率,并借助电镜观察分析,对铬酸镧材料的烧结性进行了探讨。结果表明:在铬酸镧材料中分别添加ZrO2、CaO、MgO、SiO2或Al2O3,均能促进材料的烧结,使材料达到致密,并能使烧结温度降到1650℃。从显微结构看,添加ZrO2、MgO或CaO的铬酸镧烧结体,晶粒以固-固结合为主,而添加SiO2或Al2O3的铬酸镧烧结体晶粒间则以液相结合为主,且结构中有较多的封闭气孔。当温度再升高时,由于铬离子的挥发以及具有较低体积密度的相的生成,反而会使铬酸镧材料的密度下降。     

ZnO and CuO crystal precipitation in sintering Cu-doped Ni-Zn ferrites. II. Influence of sintering temperature and sintering time

This paper presents a study of the precipitation of ZnO and CuO crystals during the sintering of Cu-doped Ni-Zn ferrites. The nature of the resulting crystal precipitates were analysed using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), confirming the findings of a previous paper (Part I). This study examines the influence of sintering temperature and sintering time of the thermal cycle on their formation, and on their microstructure and electromagnetic properties. The same two consecutive chemical reactions proposed in Part I can be used to explain the bulk precipitation and subsequent re-dissolution of the zinc and copper oxides observed during sintering. The effect of these crystal precipitates on the final properties of this type of soft ferrite was also analysed, revealing a deterioration in its electromagnetic performance.     

Vapor-phase assisted sintering of lutetium oxide

Conventional methods of green-body formation of powder compacts, along with temperature/pressure processing methods, were optimized to sinter and post-HIP Lu₂O₃ compacts to optical transparency (99.1 % of theoretical transparency at 1100 nm). Fissures between remnants of spray-dried granules, yielding opaque spheroids around them, were eliminated by lower temperature heat treatment schedules which minimized fissure coarsening via preferential intragranular densification. A key development was the use of LiF vapor produced adjacent to the compact in the furnace environment, which physisorbed onto particle surfaces of the pre-sintered compact. This acted as a grain growth inhibitor and hence sintering aid.     

Effective diffusion distance for isothermal sintering of hydroxyapatite

Abstract

The microstructural evolution of hydroxyapatite (HAp) was quantified for isothermal sintering at 1100°C. The aggregated state of the powder particles is thought to be responsible for the relatively high value of the average pore separation throughout isothermal sintering. The measured grain size exponent of 6·7 is not compatible with the values expected for volume diffusion or grain boundary diffusion under the assumptions of the Combined Stage Sintering Model and hence the Master Sintering Curve. The measured exponent for a previously defined flux weighted effective diffusion distance gave a more reasonable value of 3·4. The theoretical exponent in the Combined Stage Sintering Model was then corrected to accommodate a non-linear relationship between the effective diffusion length and pore size. The results demonstrate how the effective lengthscale in the Combined Stage Sintering Model can be corrected to accommodate aggregation in the microstructure.     

复合烧结剂对高铝质干式料烧结性能的影响

以粒度3～5mm,1～3mm,≤1mm,≤0.088mm的高铝矾土为主要原料,以粒度≤0.1mm的硼酸(H3BO3>99.6%)、粒度≤0.05mm的粘土、粒度≤0.1mm的钾长石和粒度≤0.1μm的硅灰(SiO2>90%)为复合烧结剂,按m(骨料)∶m(细粉)=65∶35的配比配料。将混合料在陶瓷模具中手工捣打成型,将成型好的试样分别在600℃、700℃、800℃、900℃和1000℃下均保温2h后脱模。测量热处理后各试样的耐压强度和显气孔率;采用XRD分析了试样的物相组成。结果表明:复合烧结剂中钾长石和硼酸在中温、低温下具有良好的烧结作用,在700～800℃热处理后,试样耐压强度和显气孔率明显增加。硼酸含量为2%的试样,在800～1000℃热处理后,显气孔率增幅较大。添加硅灰可以降低钾长石烧结温度;而复合烧结剂中的粘土在中温、低温下不利于干式料的烧结,低于800℃热处理后的试样,耐压强度和显气孔率没有随粘土含量增加而变化;900～1000℃热处理后的试样,耐压强度随粘土含量的增加而降低,显气孔率增加不大。     

Flash sintering of ceramics

Flash sintering is a novel densification technology for ceramics, which allows a dramatic reduction of processing time and temperature. It represents a promising sintering route to reduce economic, energetic and environmental costs associated to firing. Moreover, it allows to develop peculiar and out-of-equilibrium microstructures.The flash process is complex and unusual, including different simultaneous physical and chemical phenomena and their understanding, explanation and implementation require an interdisciplinary approach from physics, to chemistry and engineering. In spite of the intensive work of several researchers, there is still a wide debate as for the predominant mechanisms responsible for flash sintering process.In the present review, the most significant and appealing mechanisms proposed for explaining the “flash” event are analyzed and discussed, with the aim to point out the level of knowledge reached so far and identify, at least, possible shared theories useful to propose future scientific activities and potential technological implementations.