碳化硅/堇青石复相多孔陶瓷的制备及性能研究

采用碳化硅、烧高岭土、氢氧化铝、滑石为主要原料,石墨为造孔剂制备了碳化硅/堇青石复相多孔陶瓷.研究了烧结温度和烧结助剂二氧化铈对碳化硅/堇青石复相多孔陶瓷气孔率和强度的影响,并分别用XRD和SEM分析晶相组成和断面显微结构表明:制备出的SiC多孔陶瓷的主相是SiC,结合相是堇青石与方石英,多孔陶瓷具有相互连通的开孔结构;在1350℃烧结,并保温3h,当造孔剂含量为15％时,碳化硅/堇青石复合多孔陶瓷性能最佳,其气孔率31.80％,相应的弯曲强度为63.74 MPa.在1200℃下,添加不同含量的CeO2,对烧结样品的相组成有影响,能够降低生成堇青石的温度,在CeO2含量为3％的样品中,堇青石的峰最明显,但是过量的氧化铈会抑制了堇青石的生成;随着CeO2加入量的增加,其气孔率和弯曲强度也会随之变化,1200℃下,在CeO2加入量为4％时其弯曲强度最优.但随着CeO2的含量的增加,其气孔率逐渐下降.     

SiC/莫来石复相多孔陶瓷气孔率和强度的影响因素

以煅烧高岭土、Al(OH)3粉末、SiC粉末为主要原料,以石墨为造孔剂制备了SiC/莫来石复相多孔陶瓷,研究了造孔剂含量、碳化硅颗粒粒径以及烧结温度对SiC/莫来石复相多孔陶瓷抗弯强度和气孔率的影响,并分别用XRD和SEM分析晶相组成和断面显微结构.结果表明:当SiC粒径为60 μm,造孔剂含量为15％时,在1400℃下保温3h制备的样品综合性能最佳,其孔隙率为30.3％,抗折强度达到58.0 MPa.     

煤矸石中杂质含量对堇青石多孔陶瓷烧结与性能的影响

通过不同酸浸处理时间控制煤矸石原料中的杂质含量,研究煤矸石原料中杂质含量对有机海绵浸渍法制备的多孔堇青石陶瓷烧结过程和性能的影响.通过X射线衍射分析和扫描电镜研究了烧结过程中的物相结构的演变及微观结构变化等特性.并考察了酸浸处理时间和烧结温度对多孔陶瓷样品的显气孔率和抗压强度影响.结果表明,使用酸浸处理后的煤矸石为原料制备的多孔堇青石陶瓷气孔率和抗压强度均显著增加,1200℃下,使用未经酸浸的煤矸石制备的多孔堇青石陶瓷,气孔率为73.69％,抗压强度为2.23 MPa;而酸浸处理8h后,陶瓷样品的气孔率保持在78.78％,抗压强度提高至3.33 MPa.讨论了酸浸处理对煤矸石原料中起烧结助剂作用的杂质含量的调控以及杂质含量对物相形成和陶瓷性能的影响规律.煤矸石原料中这些杂质的存在也降低了堇青石陶瓷的烧结温度.     

水基冷冻干燥工艺制备莫来石结合多孔SiC陶瓷

以微米级SiC和纳米级α-Al2O3为原料,经水基冷冻干燥及原位反应烧结工艺制备莫来石结合多孔SiC陶瓷.XRD分析表明多孔陶瓷主相是α-SiC,结合相是莫来石.多孔陶瓷的孔径分布呈现双峰分布特点,大孔孔径峰值介于3 ～20 μm,小孔孔径峰值为0.5 ～1 μm.体系中SiC固相含量及烧结温度对多孔陶瓷显微结构及性能有显著影响.当SiC固相含量由20vol％增至30vol％时,多孔陶瓷的孔结构由间距为20～ 30 μm、且定向排列的层状结构演变为孔径约为4μm的定向通孔结构.当烧结温度由1200℃升至1500℃时,多孔SiC陶瓷开气孔率由66％下降至64％,抗压缩强度由4.5 MPa升至16 MPa.     

碳化硅-堇青石多孔陶瓷的制备及其性能

以碳化硅粉末、高岭土和滑石等为原料,按堇青石的化学计量比设计原料配比,制备了堇青石理论生成量分别为0、10%、15%、20%、100%的碳化硅-堇青石多孔陶瓷,测定了试样的抗折强度、显气孔率和热膨胀系数,并分别用XRD和SEM分析了试样的晶相组成和断面形貌。结果表明:与碳化硅多孔陶瓷相比,碳化硅-堇青石多孔陶瓷的抗折强度显著提高,热膨胀系数明显降低,但显气孔率有所降低。SEM分析结果表明:碳化硅-堇青石多孔陶瓷中碳化硅颗粒排列较紧密,断面呈“网格状”结构;而在多孔碳化硅陶瓷中,晶粒形貌清晰且排列较疏松,气孔平均孔径较大。     

碳化硅-堇青石复相陶瓷窑具材料的制备及表征

本文对碳化硅、堇青石的优点整合制备碳化硅/堇青石复相陶瓷窑具,并从力学性能方面研究了碳化硅及堇青石的含量对复相窑具性能的影响,确定碳化硅含量在75%,堇青石含量在8%~10%得到性能优异的复相陶瓷窑具,同时对烧成温度进行了研究,发现在1 390℃下保温3小时有利于产品的完全烧结。通过X-射线衍射(XRD)分析,复相陶瓷窑具中并未有杂质相出现。     

多孔碳化硅复合陶瓷的制备与性能研究

以SiC粉和铝矾土为原料,石墨为造孔剂,通过干压成型,在空气气氛中烧结,制备了莫来石结合碳化硅多孔陶瓷。研究了其物相组成、微观结构、孔径分布、显气孔率和抗弯强度。结果表明:气孔主要来自于SiC颗粒的堆积间隙以及石墨的燃烧分解。在高温下,铝矾土与SiC氧化生成的SiO2原位反应,生成莫来石。石墨含量对多孔陶瓷的气孔率、抗弯强度以及孔径分布都有重要影响。石墨含量10 wt%,1400℃下烧结,保温3 h,制备的SiC多孔陶瓷的显气孔率为44.9%,抗弯强度高达41.0 MPa。     

镍渣制备多孔堇青石陶瓷的研究

以镍渣、Al_2O_3和SiO_2为原料,按偏镁铝方案确定堇青石的组成,无需添加额外的烧结助剂和造孔剂,成功制备出多孔堇青石陶瓷。测定了试样的显气孔率、抗弯强度和热膨胀系数,用XRD分析了试样在烧结过程中的物相变化,并用SEM观察其断面的显微结构。结果表明:在1200~1380℃保温4 h,制备的多孔陶瓷的显气孔率为38.13~31.39%,抗弯强度为25.53~32.54 MPa,热膨胀系数为3.17×10~(-6)~1.43×10~(-6)/℃,且其主晶相为堇青石。SEM图谱显示多孔堇青石陶瓷中堇青石晶体呈六方棱柱状,还存在大量孔洞。     

以MAS为添加剂的碳化硅复合多孔材料的制备

在碳化硅(SiC)中加入MAS(镁铝硅)玻璃相,经过750℃×2h/1200℃×2h的热处理,制得了高强度的α-堇青石微晶玻璃结合碳化硅复合多孔材料。利用热膨胀仪测得了添加剂微晶玻璃的热膨胀系数,通过DTA研究了微晶玻璃的核化温度和晶化温度;分别利用XRD和SEM分析了材料的物相和显微结构;利用多功能试验机,对材料的强度进行了测试。通过建立的模型,近似计算了基体碳化硅和结合相的残余应力值。经研究制得了热膨胀系数为4.04×10-6/K的与基体碳化硅相匹配的结合相堇青石微晶玻璃、抗折强度为131Mpa复合多孔材料。     

锂辉石对堇青石多孔陶瓷性能的影响

通过堇青石颗粒料制得的堇青石多孔陶瓷,与加入一定比例锂辉石制得的堇青石多孔陶瓷,在不同的温度下烧成,对气孔率、抗折强度、热膨胀系数等性能进行测试对比研究,对比实验数据表明加入锂辉石对堇青石多孔陶瓷的性能起到了优化作用。结果表明加入5%锂辉石烧成温度1280℃制得堇青石多孔陶瓷气孔率45.83%、抗折强度22.64MPa、热膨胀系数1.73×10-6/℃。     

Electrical,thermal, and mechanical properties of porous silicon carbide ceramics with a boron carbide additive

The effects of the boron carbide (B₄C) content and sintering atmosphere on the electrical, thermal, and mechanical properties of porous silicon carbide (SiC) ceramics were investigated in the porosity range of 58.3%–70.3%. The electrical resistivities of the nitrogen-sintered porous SiC ceramics (∼10^–1 Ω·cm) were two orders of magnitude lower than those of argon-sintered porous SiC ceramics (∼10¹ Ω·cm). Both the thermal conductivities (3.3–19.8 W·m^–1·K^–1) and flexural strengths (8.1–32.9 MPa) of the argon- and nitrogen-sintered porous SiC ceramics increased as the B₄C content increased, owing to the decreased porosity and increased necking area between SiC grains. The electrical resistivity of the porous SiC ceramics was primarily controlled by the sintering atmosphere owing to the N-doping from the nitrogen atmosphere, and secondarily by the B₄C content, owing to the B-doping from the B₄C. In contrast, the thermal conductivity and flexural strength were dependent on both the porosity and necking area, as influenced by both the sintering atmosphere and B₄C content. These results suggest that it is possible to decouple the electrical resistivity from the thermal conductivity by judicious selection of the B₄C content and sintering atmosphere.     

多孔碳化硅陶瓷的原位氧化反应制备及其性能

以SiC为陶瓷骨料,Al2O3作为添加剂,通过原位氧化反应制备了Sic多孔陶瓷,并对其氧化反应特性及性能进行了研究.结果表明:在1 300～1 500℃,随烧结温度的升高,SiC的氧化程度增加,SiC多孔陶瓷的强度逐渐增加,但开口孔隙率有所降低.莫来石相在1 500℃开始生成·当烧结温度升高到1 550℃时,莫来石大量生成,得到了孔结构相互贯通且颈部发育良好的莫来石结合SiC多孔陶瓷;由于在SiC颗粒表面上覆盖了致密的莫来石层,SiC的氧化受到抑制,开口孔隙率因而升高,SiC多孔陶瓷的强度因莫来石的大量生成而增加.由平均粒径为5.0um的SiC,并添加20%(质量分数)Al2O3,经1 550℃烧结2h制备的SiC多孔陶瓷具有良好的性能,其抗弯强度为158.7MPa、开口孔隙率为27.7%.     

聚碳硅烷粘结法低温制备碳化硅多孔陶瓷

分别以平均粒径为10μm和20μm的两种规格碳化硅(SiC)粉末为原料、聚碳硅烷(PCS)为粘结剂,通过包混、过筛、模压成型、1000℃热解等工序制备了SiC多孔陶瓷,研究了PCS含量对SiC多孔陶瓷微观形貌、线收缩率、孔隙率与抗弯强度的影响,并对两种规格粉末制备的SiC多孔陶瓷性能进行了对比。结果表明:随着PCS含量的增加,两种规格粉末制备的SiC多孔陶瓷微观形貌都逐渐变得致密,当PCS含量为13%时,两种规格粉末制备的多孔陶瓷都出现了微观裂纹。随着PCS含量的增加,两种规格粉末制备的SiC多孔陶瓷孔隙率都逐渐降低,线收缩率都逐渐增大,抗弯强度先增大后降低,在PCS含量为10%时,平均粒径为10μm与20μm的SiC粉末制备的多孔陶瓷抗弯强度取得最大值,分别为31.6MPa与29.0MPa。     

Recycling of waste red mud for fabrication of SiC/mullite composite porous ceramics

SiC/mullite composite porous ceramics were fabricated from recycled solid red mud (RM) waste. The porous ceramics were formed using a graphite pore forming agent, RM, Al(OH)₃ and SiC in the presence of catalysts. The influence of firing temperature and the pore-forming agent content on the mechanical performance, porosity and the microstructure of the porous SiC ceramics were investigated. Optimal preparation condition were determined by some testing. The results indicated that the flexural strength of specimens increased as a function of firing temperature and a reduction in graphite content, which concomitantly decreased porosity. The ceramic prepared under optimal conditions having 15?wt% graphite and sintered at 1350?°C, demonstrated excellent performance. Under optimal preparation conditions the flexural strength and porosity of the ceramic were 49.4?MPa and 31.4%, respectively. Scanning electron microscopy observation result showed that rod-shape mullite grains endowed the samples with high flexural strength and porosity. X-ray diffraction analysis indicated that the main crystallization phases of the porous ceramics were 6H-SiC, mullite, cristobalite and alumina. This work demonstrates that RM can be sucessfully reused as a new raw material for SiC/mullite composite porous ceramics.     

Processing and properties of cordierite-silica bonded porous SiC ceramics

Cordierite-silica bonded porous SiC ceramics were fabricated by infiltrating a porous powder compact of SiC with cordierite sol followed by sintering at 1300–1400 °C in air. The porosity, average pore diameter and flexural strength of the ceramics varied 30–36 vol%, ~ 4–22 µm and ~ 13–38 MPa respectively with variation of sintering temperature and SiC particle sizes. In the final ceramics SiC particles were bonded by the oxidation-derived SiO₂ and sol-gel derived cordierite. The corrosion behaviour of sintered SiC ceramics was studied in acidic and alkaline medium. The porous SiC ceramics were observed to exhibit better corrosion resistance in acid solution.     

Low-temperature fabrication and characterization of porous SiC ceramics using silicone resin as binder

Commercially available silicone resin and silicon carbide (SiC) powders were adopted as the starting materials for the fabrication of porous SiC ceramics. During the heat treatment process, silicone resin experienced an organic–inorganic transformation and acted as the bonding material between SiC particles at a low temperature of 1000 °C. The mean particle size of starting SiC powders and silicone resin content can control the pore size, open porosity and fracture strength. The flexural strength of porous SiC ceramics increases with increasing silicone resin content and decreasing mean particle size of SiC powders. Larger pores can be obtained with coarser starting SiC powders and higher silicone resin content. The fracture surface of porous SiC ceramics was observed.     

Porosity control of porous silicon carbide ceramics

Porous SiC ceramics were fabricated by the carbothermal reduction of polysiloxane-derived SiOC containing polymer microbeads followed by sintering. The effect of the SiC powder:polysiloxane-derived SiC (SiC:PDSiC) ratio on the porosity and flexural strength of the porous SiC ceramics were investigated. The porosity generally increased with decreasing SiC:PDSiC ratio when sintered at the same temperature. It was possible to control the porosity of porous SiC ceramics within a range of 32–64% by adjusting the sintering temperature and SiC:PDSiC ratio while keeping the sacrificial template content to 50 vol%.The flexural strengths generally decreased with increasing porosity at the same SiC:PDSiC ratio. However, a SiC:PDSiC ratio of 9:1 and a sintering temperature of 1750 °C resulted in excellent strength of 57 MPa at 50% porosity. Judicious selection of the sintering temperature and SiC:PDSiC ratio is an efficient way of controlling the porosity and strength of porous SiC ceramics.     

Processing and properties of porous SiC ceramics prepared by yttrium aluminum garnet infiltration

Oxide bonded porous SiC ceramics were synthesized by infiltrating a liquid precursor of yttrium aluminum garnet into porous powder compact of SiC followed by sintering at 1300‐1500°C in air. Infiltration rate was estimated using weight gain by the liquid precursor sol into porous SiC powder compact as a function of time and was explained by Darcy's and Ficks's laws. The effects of SiC particle sizes and sintering temperatures on the formation of bonding phases, microstructure, SiC oxidation degree, flexural strength, porosity, and pore size distribution of porous SiC ceramics were studied. Various crystalline oxide phases were detected by XRD analysis. Depending on the starting SiC powder sizes and sintering temperatures, the porosity of the final ceramics varied nearly in the range of ~29‐41 vol. % with the variation of average pore diameter between ~5 and 30 μm. Flexural strength varied from 41 to 8 MPa depending on porosity. The effect of corrosion on oxide bond phases was investigated in strong acidic and basic medium at 90°C. The ceramics showed better corrosion resistance in acidic medium compared to basic medium. In basic medium, significant reduction in flexural strength (~42%) was arisen.     

SiC纳米线增强反应烧结碳化硅陶瓷的性能研究

以单晶SiC纳米线作为增强体,碳化硅-碳为陶瓷基体,在1550℃下,采用反应烧结制备碳化硅基陶瓷复合材料(SiCnf/SiC).结合X射线衍射、万能试验机和扫描电镜等检测和分析,研究SiC纳米线对复合材料的微结构和力学性能的影响.研究表明:与未加入SiC纳米线的反应烧结碳化硅陶瓷相比,添加SiC纳米线的复合陶瓷的抗弯强度和断裂韧性都得到显著的提高,抗弯强度提高了52％,达到320 MPa(SiC纳米线含量为12wt％),断裂韧性提高了40.6％,达到4.5 MPa· m1/2(SiC纳米线含量为15wt％);反应后的SiC纳米线仍然可以保持原有的竹节状结构,且随着SiC纳米线的加入,复合陶瓷的断口可以观察到SiC纳米线拔出现象.但由于SiC纳米线“架桥”的现象,添加过量的纳米线会降低复合陶瓷的密度和限制复合陶瓷力学性能的提高.同时还讨论了SiCnf/SiC的增强机理.     

Fabrication of mullite-bonded porous silicon carbide ceramics by in situ reaction bonding

An in situ reaction bonding technique was developed to fabricate mullite-bonded porous silicon carbide (SiC) ceramics in air from SiC and α-Al₂O₃, using graphite as the pore-former. Graphite is burned out to produce pores and the surface of SiC is oxidized to SiO₂ at high temperature. With further increasing the temperature, the amorphous SiO₂ converts into cristobalite and reacts with α-Al₂O₃ to form mullite (3Al₂O₃·2SiO₂). SiC particles are bonded by the mullite and oxidation-derived SiO₂ to obtain porous SiC ceramics. The reaction bonding behavior, open porosity, pore size distribution and mechanical strength of porous SiC ceramics were investigated as a function of the sintering temperature, forming pressure and graphite content. In addition, the phase composition and microstructure were also studied.