生产加工过程对堇青石-莫来石复合材料的影响

本实验主要研究生产加工过程对堇青石-莫来石复合材料的影响。为此,本试验中使用两种不同的加工方法:第1种方法是通过带式浇铸法使堇青石和莫来石层进行原位合成堇青石-莫来石复合材料;第2种方法是通过预制的莫来石粉末以不同的百分含量(0～30%)加入到初始的堇青石粉末中获得所需的复合材料。试验结果表明:通过在堇青石泥浆中加入预先烧制的莫来石粉末所生产的复合材料比通过层压法加工混合所产生复合材料具有更好的致密性和机械强度。     

基于高铝粉煤灰的堇青石-莫来石复合材料制备

为了实现高铝粉煤灰的高值化利用,以高铝粉煤灰为单一铝硅原料,依次对其进行酸、碱预处理,将处理后的高铝粉煤灰与滑石粉混合,通过一步原位烧成制备堇青石-莫来石复合材料,进一步考察原料配比和烧成条件对烧成样品性能的影响规律。结果表明,烧成温度为1 370℃、烧成时间为2 h、堇青石和莫来石理论质量比为50∶50时,可制备出体积密度为1.96 g/cm~3、显气孔率为30.47%、常温抗折强度为66.44 MPa的堇青石-莫来石复合材料,其主要指标均达到YB/T 4549—2016《堇青石-莫来石窑具》的要求,该方法实现了以粉煤灰为主要原料,灵活制备具有不同堇青石和莫来石配比的复合材料,为高铝粉煤灰的高值化利用提供新途径。     

高温气体过滤器支撑体的抗热震性能改进研究

为了改善高温气体过滤器支撑体的强度及抗热震性能,根据复合材料韧化强化原理,本试验采用陶瓷材料复合技术,制备莫来石-刚玉-钛酸铝-堇青石复合陶瓷材料,探索其作为高温过滤器支撑体的可能性.以粒径小于74μm的高铝矾土熟料、钛酸铝、堇青石为原料,以聚乙烯醇的溶液(质量浓度2％)为结合剂,试样成型压力为50MPa,烧结温度为1360℃,保温3小时制备了莫来石-刚玉-钛酸铝-堇青石复合材料.对烧后试样进行体积密度、气孔率、常温抗折强度、抗热震性的测定及XRD、SEM的分析,研究了配料组成对复合材料烧结及抗热震性能的影响.研究结果表明:具有较好烧结性能与抗热震性能的莫来石-刚玉-钛酸铝-堇青石复合材料支撑体的最佳物料配比(％)为:高铝矾土熟料30％、钛酸铝10％、堇青石60％.     

用于热机械设备的传统型堇青石-莫来石陶瓷的成分与性能

评价了用于热机械设备的传统型堇青石-莫来石陶瓷中堇青石合成烧结熟料的适用性。制备了两种堇青石合成烧结熟料和传统的莫来石合成熟料。按照50：50和70：30的比例,将具有中颗粒和／或粗颗粒的堇青石合成烧结熟料与具有中颗粒和,或细颗粒的莫来石进行混合,然后在1350℃进行煅烧来生产传统的堇青石-莫来石料球。评价了与其成分和显微结构相关的物理性能。这些性能包括线性变化、体积密度、显气孔率、荷重软化点以及抗热震性。     

锂电池正极材料LiNixCoyMnzO2承烧用莫来石-堇青石质匣钵的研制

莫来石-堇青石质匣钵对于制备高性能锂电池正极材料尤为重要。本文采用莫来石(1.18～0.6 mm)和堇青石(2～1 mm)为骨料，莫来石(0.074 mm)、煅烧氧化铝(0.044 mm)、佛山黄泥(0.044 mm)和煤矸石(0.044 mm)为基质，在1 380℃下保温3 h烧结制备锂电池正极材料LiNi_xCo_yMn_zO₂(LNCM)承烧用莫来石-堇青石匣钵，并采用埋覆侵蚀法探究了正极材料在烧结过程中对匣钵的侵蚀行为。结果表明：在1 380℃下保温3 h烧结制备的匣钵力学性能和抗热震性均较好，其室温抗折强度为10.02 MPa,经3次热震循环后残余强度保持率在51.52%～53.26%;适当增加粗颗粒(1.18～0.6 mm)莫来石的含量可有效提高莫来石-堇青石匣钵的抗侵蚀性，且经侵蚀25次后匣钵表面的最大反应层厚度为447μm,最小反应层厚度为211μm。     

黏土的杂质含量对堇青石-莫来石复合材料相组成及性能的影响

以滑石细粉、高铝矾土细粉和两种不同杂质含量的黏土细粉为原料,经配料、加水混练成型后,分别于1300、1350和1400℃保温3h制备了堇青石-莫来石复合材料的试样,用XRD、SEM等研究了黏土中杂质含量对堇青石-莫来石复合材料相组成及性能的影响。结果表明:1)使用高杂质含量的黏土能有效降低试样的烧结温度,促进堇青石和莫来石晶体的生成发育,提高试样的体积密度与常温抗折强度,但对其抗热震性损害较大。2)使用高杂质含量的黏土时,提高MgO含量虽然可增加堇青石的含量,但玻璃相含量增加且黏度降低,不能有效提高材料的抗热震性;而使用低杂质含量的黏土时,通过控制引入MgO的含量与煅烧温度,可调节试样中晶相的含量与组成,从而可提高材料的抗热震性。     

高强度堇青石-莫来石棚板的研制

以堇青石(1～0.5、0.5～0.2、<0.088 mm)和莫来石熟料(M60,1～0.5 mm)为主要原料,加入25%(w)的由轻烧MgO粉、α-Al2O3微粉及添加剂(紫木节和KOH)组成的混合粉,按堇青石与莫来石的质量比分别为40:35、42.5:32.5和45:30配料、混练、成型后,分别在1 300、1 350和1 400℃均保温3 h条件下烧成,合成出堇青石-莫来石质棚板试样,并检测试样的常温及高温物理性能,同时进行XRD、SEM及EDS分析.结果表明:按m(堇青石):m(莫来石)=45:30配料,在1 350℃ 3 h合成的棚板材料的各项性能指标最好,其主要晶相为堇青石和莫来石,且显微结构均匀,晶间生成大量的原位堇青石和莫来石晶粒,骨料之间的"联接桥"发育良好,材料具有较高的抗折强度.     

堇青石对莫来石-铝矾土浇注料性能的影响

以莫来石、铝矾土为主要原料,铝酸钙水泥为结合系统,分别研究了不同堇青石含量经过不同热处理温度后对莫来石-铝矾土浇注料性能的影响.试样自然干燥24 h脱模后,再经110 ℃烘干24 h,分别于1000 ℃、1300 ℃和1500 ℃热处理3 h.检测各温度热处理后试样的线变化率(P.L.C)、体积密度(B.D)、抗折强度(M.O.R)、耐压强度(C.C.S)以及试样的热膨胀系数和抗热震性能.结果表明,莫来石-铝矾土浇注料的体积密度随着堇青石含量的增加而减小.经过1000 ℃和1300 ℃热处理后,莫来石-铝矾土浇注料的抗折强度随着堇青石含量的增加而下降.莫来石-铝矾土浇注料随着堇青石含量的增加,有助于改善材料的抗热震性,材料的强度保持率逐渐增大,且较低的体积密度有利于材料获得较高的热震后的强度保持率.     

莫来石-磷酸锆复相陶瓷材料性能的研究

本文研究了在莫来石中添加低膨胀第二相磷酸锫的莫来石-磷酸锆复相陶瓷的性能,找到了在保证强度的同时,获得较低热膨胀系数的莫来石-磷酸锆复相陶瓷的制备方法.实验表明：莫来石-磷酸锆复相陶瓷能通过将莫来石粉料与磷酸锆粉料或莫来石粉料与磷酸锆生料粉按不同质量比混合烧结制备;加入1wt％的MgO作为烧结助剂,在1350℃烧成的样品具有最低的热膨胀系数和较小的吸水率.     

堇青石-莫来石材料的研究进展及应用前景

根据近年来堇青石-莫来石材料的研究成果,从高温固相法、湿化学法等制备工艺角度综述了堇青石-莫来石材料的研究进展,并介绍了堇青石-莫来石材料的应用前景。     

Hot corrosion of cordierite/mullite composites by Na-salts

Cordierite/mullite (C/M) ceramic composites were corroded by NaCl and Na₂SO₄ at 1000 °C for 24 h. The predominant corrosion products in attack by the Na-salts were found to be nepheline and carnegieite for the cordierite and mullite component, respectively. NaCl attacked both components with different corrosion rates, producing corrosion layers consisting of two distinct regions where both cordierite and mullite were chemically attacked near the surface region and only the cordierite phase was damaged in the succeeding inner part. In the hot corrosion by Na₂SO₄, on the other hand, only the cordierite component was severely attacked in the composites, resulting in occurrence of selective corrosion. Thus, the corrosion of the C/M composites by the Na-salts proceeded through the path of the less resistive cordierite component at 1000 °C in air.     

Preparation of Mullite Cordierite Composite Powders by the Sol-Gel Method: Its Characteristics and Sintering

Mullite/cordierite composite powders containing different proportions of cordierite were prepared by the sol-gel method using boehmite, colloidal silica, and Mg(NO₃)₂·6H₂O. Mullite and cordierite sols were prepared separately and mixed to form the composite sol. Mullitization temperature depends on the cordierite content in the composite. Also, α-cordierite crystallizes at a lower temperature in a mullite-rich (MC20) composite. The XRD patterns of the powders calcined at 1450°C for 12 h showed that mullite and cordierite exist as two different phases, and no additional phases were observed. The IR absorbance spectra of composites showed characteristic peak corresponding to both mullite and cordierite. The sintered density of the powders increases with temperature up to 1450°C and decreases beyound the melting point of cordierite (1455°C). The microstructure of MC30 sintered at 1440°C for 3 h consisted of acicular grains, whereas in MC40 and MC50 equiaxed grain morphology was observed under similar sintering conditions. The flexural strength and Vickers hardness decreases with the increase of cordierite content in the composite. Dielectric constant and thermal expansion showed a similar behavior.     

Effect of the processing on the production of cordierite–mullite composite

In this study, effect of process on the production of cordierite–mullite composite was studied. For this reason two different processing methods were used in the production of cordierite–mullite composites. In first process, in situ cordierite–mullite composites were produced from cordierite and mullite layers which were formed by using aqueous tape casting method. In second one, composite was produced by addition of pre-produced mullite powders (in different weight percents, 0–30) into cordierite starting powders. The results show that the addition of pre-sintered mullite powders to the cordierite slip has more effect on densification behavior and mechanical properties of composites than layered production method.     

Electrical properties and thermal expansion of cordierite and cordierite-mullite materials

Commercially available cordierite and mullite powders were used to obtain cordierite and composite materials with mullite content up to 65 wt.% by attrition milling, uniaxial pressing and sintering. The employed cordierite powders were the coarse, medium and fine single granulometric fractions and the binary mixtures of them with 30, 50 and 70 wt.% of the smaller size component. Mullite powder employed in composites was a 7 h-attrition milled one. The dielectric constant (), dielectric loss tangent (tan δ), resistivity (ρ) and thermal expansion coefficient () were measured. The influence of the porosity, mullite and glassy phase contents and grain size in the electrical parameters was analyzed. The thermal expansion coefficient as a function of the composition was studied.     

莫来石-堇青石复合材料的制备与性能研究

由热压和液相烧结方法制得了具有各种莫来石含量和显微结构的莫来石-堇青石复合体.研究了各种烧结温度、时间、气氛条件下复合体的致密度和显微结构的改善.还研究了复合体弹性模量、断裂韧性、热膨胀系数与组成之间的关系.研究结果表明,复合体的断裂韧性随莫来石含量和杨氏模量线性增加,粗的针状莫来石由于其穿晶断裂模式而有较高的断裂韧性.     

Microstructure and Fracture Toughness of Yttria-Daped Tetragonal Zirconia Polycrystal/Mullite Composites Prepared by an in Situ Method

Yttria-daped tetragonal zirconia polycrystal (Y-TZP)/ mullite composites were prepared by three methods: in situ whisker growth (IS), physical mixing (PM) of zirconia powder and mullite whiskers, and reaction sintering (RS). Microstructures and fracture toughness values were compared. All the composites with 15 vol% of mullite could be densified to more than 95% relative density by firing at 1500° to 1500°C for 10 h. The fracture toughness of the composites as measured by the indentation method showed a clear enhancement compared with that of pure Y-TZP; the ranking was Y-TZP ≦ RS composite < PM composite < IS composite. Enhancement of the fracture toughness in composites was found to relte strongly to the aspect ratio of mullite particles.     

Firing properties and corrosion resistance of mullite-Al2TiO5 saggar materials

Conventional refractory materials used for calcining ternary lithium-ion battery cathode materials, such as mullite, cordierite, and magnesia-alumina spinel, are vulnerable to attack by Li(Ni_xCo_yMn_1−x−y)O₂ (LNCM) materials and therefore have a short service life. In order to improve the corrosion resistance of refractory materials to LNCM materials, mullite-Al₂TiO₅ materials with different contents were synthesized in this paper by using calcined mullite powder, TiO₂ powder, and La₂O₃ powder as raw materials, which were calcined at 1500–1600°C temperature, respectively. In this study, the potential of the materials for the preparation of LNCM materials was investigated in terms of its physical properties, resistance to the corrosion of LNCM materials, and resistance to thermal shock. The results showed that mullite-Al₂TiO₅ composites can be successfully synthesized at 1500–1600°C, and the physical properties of the materials met the production requirements. The prepared mullite-Al₂TiO₅ composites also exhibited better physical properties, good corrosion resistance, and proper thermal shock resistance compared with mullite refractories.     

注凝成型制备莫来石–钛酸铝复相陶瓷(英文)

引入10%(摩尔分数,相对于A12O3,下同)MgO和15%SiO2双组分添加剂合成了钛酸铝粉体.采用不同质量比的钛酸铝粉体和工业莫来石,用干压和注凝成型工艺制备了莫来石-钛酸铝(mullite-aluminium titanate,MAT)复相陶瓷.用X射线衍射分析了双组分添加剂对钛酸铝相组成和热稳定性的影响.通过扫描电镜表征了MAT复相陶瓷的微结构.研究了钛酸铝含量对采用于压、注凝2种成型工艺制备的MAT复相陶瓷的弯曲强度和平均热膨胀系数(室温～1 000℃)的影响.结果表明:MgO和SiO2双组分添加剂促进了钛酸铝的形成,增强了钛酸铝的热稳定性.通过注凝成型制备的MAT复相陶瓷比于压成型制备的MAT复相陶瓷具有史均匀的结构和更高的机械性能.当铸酸铝含量为lO%(质量分数,下同),运用注凝成型工艺 制备的MAT复相陶瓷的弯曲强度最大,达110.05 Mpa.     

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.     

Properties of multiple oxide-bonded porous SiC ceramics prepared by an infiltration technique

Multiple oxide-bonded porous SiC ceramics were fabricated by infiltrating a porous powder compact of SiC and alumina with cordierite sol followed by sintering at 1300-1400°C in air for 3 hours. The microstructures, phase components, mechanical properties, and air permeation behavior of the developed porous ceramics were examined and compared with materials obtained by the traditional powder processing route. The porosity, average pore diameter, and flexural strength of the ceramics varied from 33 to 37 vol%, ~12-14 μm and ~23-39.6 MPa, respectively, with variation in sintering temperature. The X-ray diffraction results reveal that both the amount of cordierite and mullite as the binder increased with increase in sintering temperature. In addition, it was found that the addition of alumina in powder form effectively enhanced the strength due to formation of mullite in the bond phase in contrast to the samples prepared without alumina additive. To determine the suitability of the material in particulate filtration application, particle collection efficiency of the filter material was evaluated theoretically using single collector efficiency model.