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。     

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/℃。     

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/℃。     

利用煤矸石制备堇青石多孔陶瓷

为了综合利用煤矸石,以煤矸石、滑石等为原料,按堇青石的理论组成配料,分别外加质量分数为0、5%、10%、15%、20%的活性炭粉为造孔剂,在1 400℃下分别保温3和6 h烧结后制备了堇青石多孔陶瓷,通过检测显气孔率和常温抗折强度及其显微结构分析探讨了其合成工艺制度。结果表明:利用煤矸石为主原料,外加5%(w)的活性炭为造孔剂,在1 400℃下保温6 h可以合成性能优良的堇青石多孔陶瓷。所合成的堇青石多孔陶瓷的抗折强度为29.1 MPa,显气孔率为39.8%;显微结构分析显示,该多孔陶瓷中以堇青石相为骨架,内部形成了贯通气孔的多孔结构。     

以稻壳为硅源和碳源制备多孔堇青石陶瓷的研究

稻壳是以C、O、H和Si为主要元素组成的一种农业废弃物。本文以稻壳为硅源和碳源合成了多孔堇青石陶瓷载体,讨论了多孔堇青石的最佳烧成温度、碳质组分含量对堇青石微观结构和性能的影响。实验结果表明:以稻壳中碳质成份为造孔剂,当其添加量为堇青石原料总量的8 wt%、烧成温度为1300℃时,可获得性能较好的多孔堇青石陶瓷。经测试,此样品的显气孔率为37.18%、抗折强度为19.48 MPa、热膨胀系数为3.1×10-6℃-1,可满足工业载体的要求。     

酸处理对堇青石质蜂窝陶瓷性能的影响

用硝酸溶液对堇青石质蜂窝陶瓷样品进行处理。测定了酸处理时间不同的样品的热膨胀系数、气孔率和吸水率及抗压强度，研究了酸处理对堇青石质蜂窝陶瓷性能的影响规律，通过SEM分析了酸处理前后样品的断面形貌．并用ICP测定了酸处理液中的各种离子浓度，探讨了酸处理影响性能的机理。试验结果表明：酸处理能显著降低堇青石质蜂窝陶瓷的热膨胀系数，增加显气孔率和吸水率，但削弱了材料的机械强度。     

不同铝源对SiC/堇青石复相多孔陶瓷的制备及性能影响

以碳化硅、氮化铝、层析氧化铝、氢氧化铝、氟化铝、滑石为主要原料,石墨为造孔剂通过原位反应烧结技术制备碳化硅/堇青石复相多孔陶瓷.研究了含铝化合物种类、烧结温度、石墨含量对SiC/堇青石复相多孔陶瓷相组成、微观结构、气孔率和抗折强度的影响,同时对S0组在1200℃烧结温度下制得的SiC/堇青石复合多孔陶瓷的孔径分布进行了测试分析.结果表明:以AlN为铝源在1200℃下烧结,石墨含量在15％时,堇青石结合SiC多孔陶瓷的抗弯强度和气孔率两项综合性能达到最优,气孔率为31.99％,相应的弯曲强度86.20 MPa.S0组的平均孔径大小在3.0191 μm.     

脱硝催化剂用堇青石多孔陶瓷的制备与性能研究

以偏高岭土、氧化铝和滑石为原料,利用压制成型制备出堇青石多孔陶瓷并采用浸渍涂覆法制备锰基低温脱硝催化剂.通过气孔率、抗折强度、热膨胀系数、SEM、BET等测试探究了碳粉和淀粉两种造孔剂及添加量、不同酸处理时间等因素对堇青石性能的影响并考察了不同浸渍次数的催化剂在80~200 ℃间的脱硝性能.结果表明:造孔剂为碳粉且添加量为4%时,得到的堇青石具有良好的性能,此时气孔率达31.12%,热膨胀系数为3.10×10-6/K,抗折强度为21.41 MPa;适当的酸处理有助于堇青石表面孔结构的丰富且能大幅提升其比表面积,最佳处理时间为2 h;当浸渍次数为4次时,整体式催化剂的性能最佳,牢固度可达90.18%,140 ℃时的脱硝率可达74.5%以上.     

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.     

堇青石加入方式对堇青石-莫来石窑具材料性能的影响

为满足锂离子电池正极材料烧成的需要,以堇青石、莫来石、高岭土和氧化铝为原料制备堇青石-莫来石窑具材料,研究了堇青石颗粒和细粉加入量对堇青石-莫来石窑具材料的常温性能、高温抗折强度和抗热震性的影响.并用XRD和SEM分析了试样烧后的物相变化与显微结构.结果表明:随着堇青石颗粒或细粉加入量从0到30％(质量分数),试样的线变化率、显气孔率、高温抗折强度增大,体积密度下降;而对常温抗折强度的影响不大,试样的耐压强度分别呈现下降或提高的趋势,试样的抗热震性先增加后降低,当堇青石颗粒含量为20％,细粉含量为20％时,试样的抗热震性最好.     

Reaction forming of silicon carbide ceramic using phenolic resin derived porous carbon preform

SiC ceramics were prepared with porous carbon preforms derived from phenolic resin by a reaction-forming method. The effects of the structure of the preform pores and the infiltration process on the properties of SiC ceramics were investigated, and components with complex shapes were fabricated by combining this process with stereolithography (SLA). Dense SiC ceramics were obtained from carbon preforms with high apparent porosities, but SiC ceramics with many macrodefects resulted from a carbon preform with an apparent porosity of 39%. The infiltration of molten silicon into the preform pore channel was accelerated under vacuum pressure, resulting in an increase in the depth of the Si infiltration. The growth of SiC was predominantly controlled by carbon diffusion at the last stage of the reaction. The extended grain growth caused the SiC grains to coalesce and some free Si was enveloped in the SiC grains. SiC components with complex geometries were fabricated by combining reaction forming with SLA. The geometry was controlled by SLA.     

Fabrication and characterization of cordierite-bonded porous SiC ceramics

A reaction bonding technique was used for the preparation of cordierite-bonded porous SiC ceramics in air from α-SiC, α-Al₂O₃ and MgO, using graphite as the pore-forming agent. Graphite was burned out to produce pores and the surface of SiC was oxidized to SiO₂ at high temperature. With further increasing the temperature, SiO₂ reacted with α-Al₂O₃ and MgO to form cordierite. SiC particles were bonded by the cordierite and oxidation-derived SiO₂. The reaction bonding characteristics, phase composition, open porosity, pore size distribution and mechanical strength as well as microstructure of porous SiC ceramics were investigated. The pore size and porosity were strongly dependent, respectively, on graphite particle size and volume fraction. The porous SiC ceramics sintered at 1350 °C for 2 h exhibited excellent combination properties, the flexural strength of 26.0 MPa was achieved at an open porosity of 44.51%.     

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.     

Microstructure and properties of porous SiC ceramics by LPCVI technique regulation

A new gradient pore structure in porous SiC ceramics was fabricated by low pressure chemical vapor infiltration (LPCVI). Effects of deposition duration on the mechanical properties and permeability of porous SiC ceramics were investigated. Results demonstrated that pore diameter and shapes decreased from the surface to the interior along with LPCVI duration. Porous SiC ceramics with deposition duration of 160 h exhibited flexural strength of 48.05 MPa and fracture toughness of 1.30 MPa m^1/2, where 221% and 189% improvements were obtained compared to porous SiC ceramics without LPCVI, due to CVI-SiC layer strengthening effect. Additionally, at the same gas velocity, pressure drop increase rate was faster due to apparent porosity and pore size change.     

堇青石质多孔陶瓷的制备及性能研究

采用氧化铝、烧高岭、烧滑石为原料,可溶于水的有机物质尿素作为造孔剂,TiO2为添加剂,于6MPa压力下干压成形,1350℃下保温60min进行烧成,制备出以堇青石为主晶相的多孔陶瓷体。通过XRD分析手段对不同温度合成堇青石主晶相进行了分析,并用SEM观察了烧结后多孔陶瓷的微观结构。探讨了可溶性造孔剂用量、TiO2添加量、烧成制度等因素对堇青石质多孔陶瓷性能的影响。制备的多孔陶瓷体气孔率接近于70%,抗压强度达到3.310MPa。     

烧成温度对多孔SiC陶瓷管性能的影响

以SiC为骨料,添加低共熔混合物烧结促进剂,煤粉作为造孔剂,在不同的温度下烧成制备多孔陶瓷管.考察了烧成温度对多孔SiC陶瓷管的孔隙率、气体渗透通量、孔径分布以及抗弯强度等性能的影响,并通过SEM对其结构形貌进行了表征.结果表明:随着烧成温度的提高,孔隙率、气体通量及抗弯强度下降,孔径分布变宽.     

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.     

蜂窝陶瓷蓄热材料的研究现状

蜂窝陶瓷蓄热材料应该具有热膨胀系数低、比热容大、比表面积大、导热性能好、抗热震性好等特性。本文详细介绍了几种多孔陶瓷材料的优缺点,指出堇青石质复相材料是目前研究最广泛的蜂窝陶瓷材料。堇青石与多种催化剂匹配性好,比表面积大、热膨胀系数小,但耐热性稍差,于是通过添加一些添加剂来提高堇青石作为蜂窝陶瓷蓄热体的性能。这些添加剂与堇青石结合形成复相材料,可以降低热膨胀系数、提高抗热震性等。     

A new approach for the net-shape fabrication of porous Si3N4 bonded SiC ceramics with high strength

In this study, Si₃N₄ bonded porous SiC ceramics with high strength had been net-shapely fabricated by a new approach. In this approach, we proposed a two-step processing route composed of freeze casting and carbothermal reduction reactions in which carbon aerogels, derived from sol infiltration and pyrolysis, involved. The phase components, microstructures and properties of the prepared ceramics were investigated. The results showed that carbon aerogels with high apparent surface area had been completely reacted and new SiC and Si₃N₄ grains had been produced. The porous ceramics with flexural strength of 164.3 MPa at 33% porosity and 80.5 MPa at 46% porosity were obtained, whose linear shrinkages were only 1.06% and 1.94% during the whole processing respectively.