原位生长莫来石增强钙长石复合材料的制备

采用一步固相烧结法,以高岭土和氢氧化铝原位制备了莫来石晶相增强钙长石复合材料,利用XRD和SEM对材料的显微结构进行了分析.实验结果表明:原位生长莫来石/钙长石的配比组成对材料的显微结构有着极为重要的影响.当钙长石:莫来石=70:30时,该复合材料在1400～1420℃下烧成时,抗折强度高达107 ～ 123.9 MPa.该复合材料比纯的钙长石陶瓷材料的抗折强度提高了1.5 ～2倍.     

凝胶注模法制备多孔莫来石陶瓷的显微结构研究

本文重点研究了凝胶注模法制备多孔莫来石陶瓷的过程中固含量、表面活性剂量、搅拌速度等参数对多孔陶瓷显微结构的影响.结果表明,多孔陶瓷的气孔率、孔径尺寸和连通性可以通过控制制备过程参数来进行调节.当固含量从40wt％增加到70wt％,样品的开孔率和总气孔率分别从88.49％和91.27％降低到76.94％和83.04％,而密度从0.276 g·cm-3增加到0.536 g· cm-3.当表面活性剂浓度由0.25wt％增加到lwt％时,样品开孔率基本保持不变,总气孔率先由84.34％增加到93.26％,再减小到87.63％;密度则由0.413 g·cm-3减小到0.378 g· cm-3,再增加到0.391 g·cm-3.当搅拌速度由1000 r/min增加到1800 r/min时,开孔率由78.12％减小到72.85％,总气孔率则由79.95％先增加至84.18％,再减小到77.09％.     

氟化铝添加量对碳化硅/莫来石复合多孔陶瓷性能的影响

本文以碳化硅(SiC)、气相SiO2、纳米Al2O3和AlF3·H2O为原料,制备出了碳化硅/莫来石复合多孔陶瓷,主要研究了AlFa·H2O添加量、烧结温度对多孔陶瓷抗弯强度、气孔率、孔径分布等性能的影响.用SEM、XRD研究了多孔陶瓷的微观形貌和物相组成.结果表明:AlF3·H2O对莫来石的生成有明显的促进作用,1300℃时,添加AlF3·H2O的样品中检测到莫来石相,多孔陶瓷气孔率随AlF3·H2O加入量增加而升高,而抗弯强度随其增高而先增加后减小,AlF3·H2O添加量为4wt％时,多孔陶瓷气孔率为42.8％,抗弯强度为31.1 MPa.     

刚玉—莫来石质泡沫陶瓷的研制

通过对泡沫陶瓷的研究,制备出了以刚玉－莫来石为主晶相,相对密度为０．３￣１、气孔率为８０％￣９０％的泡沫陶瓷。经过配方及工艺设计,基本掌握了该系材料具有良好的网络结构及强度,证实了添加ＭｇＯ－ＺｒＯ２对该系材料的增强作用。     

莫来石/铝复合摩擦材料

本文研究了莫来石陶瓷细粉与金属铝复合的摩擦材料,实验证明,莫来石粉对金属铝有明显的增强、增加硬度、提高耐磨性等作用,同时添加石墨、磷酸铝等材料,可进一步改善这种复合材料的其它性能.     

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.     

莫来石纳米粉的制备及表征

以正硅酸乙酯和硝酸铝为原料,采用溶胶-凝胶法制备出了超细的纳米莫来石.对于该方法的各种影响因素进行了实验分析,并对制得的样品进行了XRD,TG-DTA,TEM等性能表征.     

低品位煤矸石制备多孔莫来石研究

为了综合利用低品位煤矸石,首先对其原矿进行低温(400℃以下)煅烧和酸洗除杂的预处理,然后以预处理后的煤矸石为主要原料,适量添加氧化铝使n(Al2O3)n(SiO2)=1 1,以平均粒径5.6~6.2μm的交联丙烯酸树脂做造孔剂,PVA溶液为结合剂,经反应烧结制备多孔莫来石,并研究了造孔剂添加量对多孔莫来石显微结构和性能的影响。结果表明:以低品位煤矸石为主要原料,经过低温煅烧和酸处理后,适量添加氧化铝和造孔剂,经1 600℃2 h反应烧结可一步制备出主晶相为莫来石的多孔莫来石;随着造孔剂添加量的增加,多孔莫来石的显气孔率和线收缩率明显增大,体积密度、热导率和耐压强度显著降低,但其质量分数增加到30%后,这些性能的变化趋于平稳。     

莫来石晶须原位增强堇青石-莫来石多孔陶瓷制备

为实现煤矸石资源化利用,以高岭土粉、煤矸石粉、滑石粉、氢氧化铝粉为主要原料,制备了莫来石晶须原位增强堇青石-莫来石多孔陶瓷。研究了煤矸石掺量(质量分数分别为0、9%、17%、26%、33%)和AlF₃添加量(质量分数分别为0、1.5%、2.0%、2.5%、3.0%)对多孔陶瓷物相组成、显微结构和性能的影响。结果表明：1)当煤矸石掺量(w)≤17%、AlF₃添加量(w)≤2.5%时,试样主要矿物组成为堇青石和莫来石。2)增加煤矸石掺量可明显提高试样的体积密度和耐压强度,但对保持显气孔率不利;增加AlF₃添加量导致试样体积密度和耐压强度减小,但可提高显气孔率。3)随着煤矸石掺量和AlF₃添加量的增加,莫来石晶须直径增加,长径比增加,呈四方柱状或针状。4)当煤矸石掺量(w)为17%,AlF₃添加量(w)为2.5%时,经1 350℃保温2 h,可获得体积密度1.86 g·cm^-3,显气孔率31.0%,耐压强度27.8 MPa的多孔陶瓷;其针状莫来石晶须形成互锁结构...     

莫来石复合纳米晶制备机理探讨

煅烧处理过的高岭土经水热反应后得到纳米级莫来石复合晶体,TEM观测到其晶粒发育良好。XRD分析主晶相为莫来石。TG—DTA测试结果表明：复合纳米品的热稳定性好。实验中还探讨了水热条件下晶粒的形成机理。     

Mechanical Properties of Mullite

The mechanical properties of alkoxy-derived, high-purity, translucent, theoretically dense mullite (3AI₂O₃.2SiO₂) were investigated over the temperature range room temperature to 1500°C. Large agglomerates were found to contribute to the formation of porosity nests which act as strength-controlling flaws at room temperature as well as at high temperatures. Despite the slow crack growth above 1300°C, a slight increase in fracture stress and a large increase in K_Ic were observed up to 1500°C. These increases are explained by the dominance of energy dissipation through plastic relaxation in the plastic zone over grain-boundary sliding due to the presence of the glassy phase.     

凝胶注模莫来石/碳化硅复合陶瓷的显微结构与力学性能

以SiC粉和莫来石粉为原料,采用凝胶注模成型工艺制备莫来石/碳化硅复合陶瓷,研究了莫来石含量对复合陶瓷显微结构和力学性能的影响,结果表明:随莫来石含量增加,复合陶瓷气孔率先降低后升高,而力学性能呈相反变化趋势。当莫来石含量为20%(体积分数)时,材料气孔率达到最小值9.4%,线收缩率以及弹性模量达到最大值26.5%和148.6 GPa;在莫来石含量为30%时抗弯强度和断裂韧性达到最大值397.7 MPa和4.17MPa.m1/2。适量莫来石的加入明显改善了材料的力学性能,过多则由于莫来石挥发而在材料中产生缺陷,材料性能下降。     

Sintering and Mechanical Properties of Stoichiometric Mullite

Stoichiometric mullite powder (3Al₂O₃·2SiO₂) prepared by spray pyrolysis and sintered at 1650°C attained 95% of theoretical density. The flexural strength was 360 MPa at room temperature and decreased slightly at 1400°C. A fairly high K_Ic value (2.8 MN/m^3/2) was obtained. These mechanical properties can be attributed to the highly homogeneous stoichiometric composition of the raw powder.     

工艺制备对钙长石/莫来石复合材料力学性能的影响

利用钙长石和自制莫来石晶须为主要原料,通过固相法制备莫来石/钙长石复合材料。研究了工艺制备方法对钙长石/莫来石复合材料性能的影响。实验结果表明:合适的保温点(1000℃,保温1h)在1400℃烧结对复合材料的力学性能有至关重要的影响,二次重烧结法比一次烧成所制备的复合材料力学性能有所提高。XRD和SEM分析表明:由于钙长石相和莫来石相通过玻璃相紧密结合,提高了材料的力学性能。     

莫来石／聚丙烯复合材料的制备与性能研究

采用熔融共混工艺制备了莫来石/聚丙烯复合材料,考察了莫来石用量对材料力学性能、结晶性能及热稳定性的影响,并用扫描电镜(SEM)观察了复合材料中莫来石在基体聚丙烯中的分散形貌.结果表明,莫来石粉体在PP基体中能均匀分散,但团聚现象严重;随莫来石用昔的增加,复合材料的杨氏模量、拉伸强度增大,而断裂伸长率和冲击强度下降;莫来石对聚丙烯有成核作用,能诱导β晶生成,但对熔点影响不大;加入莫来石后聚丙烯的热分解温度升高,耐热性提高.     

Preparation and Mechanical Properties of SiC Whisker and Nanosized Mullite Particulate Reinforced TZP Composites

The influence of the addition of nanometer mullite particulates and SiC whiskers coated with alumina on the mechanical properties of tetragonal zirconia polycrystals (TZP) was studied. With increasing mullite( p ) content the high-temperature flexural strength increased, and a maximum value of 360 MPa at 1000°C was reached at 15 vol% mullite( p . Furthermore, 10 vol% SiC( w ) reinforced 15 vol% mullite/TZP composites improved the high-temperature strength up to 490 MPa at 1000°C, 2.7 times that of pure TZP matrix. This high-temperature strengthening is attributed to load transfer from TZP matrix to SiC( w ) and mullite particulates. Significant whisker pull-out and interface debonding were also observed on the fractured surfaces when SiC( w ) was coated with Al₂O₃ film.     

Preparation and Properties of Zirconia-Toughened Mullite Ceramics

Compacts formed from high-purity fused submicrometer mullite powders, both pure and with the additions of 5 to 25 vol% ZrO₂ of particle size 1, 2, or 4 μm (average), were sintered in air at 1610°C for 6 h to form dense ceramic bodies. Mechanical properties (flexural strength, K _ic, and Young's modulus) were measured both before and after thermal shock. The strength after thermal shock increased considerably in systems containing additions of 10 to 20 vol% ZrO₂; K _ic also increased, but not so markedly. The low fraction of tetragonal ZrO₂ (0.1 to 0.2) in the as-fired samples and the increase in Young's modulus after thermal shock for some strengthened samples supported the view that the interaction of residual internal stresses induced by quenching and the accompanying martensitic transformation of ZrO₂ result in potential nucleation sites for microcracking. Thus, microcracking may be the predominant energy-absorbing mechanism responsible for strengthening and toughening the quenched ceramic bodies.     

High-Temperature Mechanical Properties of Mullite Under Compression

The high strength potential of single-phase mullite was investigated under compressive stress-strain and creep testing conditions at 1400° and 1500°C. In single-crystal experiments, no plastic deformation and, hence, no dislocation glide was observed. Polycrystalline mullite was deformed via the Nabarro-Herring mechanism accompanied by grain-boundary sliding and some cavitation. In stress-strain tests, deformation was enhanced by intergranular separation.     

Mullite: Crystal Structure and Related Properties

Mullite is certainly one of the most important oxide materials for both conventional and advanced ceramics. Mullite belongs to the compositional series of orthorhombic aluminosilicates with the general composition Al₂(Al_2+2xSi_2‐2x)O_10‐x. Main members are sillimanite (x = 0), stoichiometric 3/2‐mullite (x = 0.25), 2/1‐mullite (x = 0.40), and the SiO₂‐free phase ι‐alumina (x = 1, crystal structure not known). This study gives an overview on the present state of research regarding single crystal mullite. Following a short introduction, the second part of the review focuses on the crystal structure of mullite. In particular, the characteristic mullite‐type structural backbone of parallel chains consisting of edge‐sharing MO₆ octahedra and their specific cross‐linkage by TO₄ tetrahedra is explained in detail, the role of cation disorder and structural oxygen vacancies is addressed, and the possibility of cation substitution on different sites is discussed. The third part of the study deals with physical properties being relevant for technical applications of mullite and includes mechanical properties (e.g., elasticity, compressibility, strength, toughness, creep), thermal properties (e.g., thermal expansion, heat capacity, atomic diffusion, thermal conductivity), electrical conductivity, and optical properties. Special emphasis is put on structure–property relationships which allow for interpretation of corresponding experimental data and offer in turn the possibility to tailor new mullite materials with improved properties. Finally, the reported anomalies and discontinuities in the evolution of certain physical properties with temperature are summarized and critically discussed.     

莫来石/SiC复相多孔陶瓷的制备及性能研究

用高岭土、Al2O3粉和SiC粉末为原料,活性碳为造孔剂制备莫来石/SiC多孔陶瓷.测定了试样的显气孔率、气孔孔径分布和抗弯强度,并分别用XRD和SEM分析晶相组成和断面显微结构.结果表明:莫来石的理论设计质量的分数小于10%时,莫来石/SiC多孔陶瓷的显气孔率随其设计量的增多而急剧降低;莫来石理论设计量继续增加时,试样显气孔率缓慢降低并趋于稳定.气孔孔径随莫来石设计量的增加而急剧减小.抗弯强度随莫来石设计量的增加而先增大,在莫来石理论设计量为20%时达到最大值,此后逐渐降低.SEM分析结果表明:与其他试样相比,莫来石设计量为40%的试样中存在较多的多孔"微区".