原位生长莫来石棒晶增强钡长石基复合材料

以煤矸石、碳酸钡和氧化铝为原料,按m(BaO)∶m(Al2O3)∶m(SiO2)=13∶57∶30的配比计算并称量原料,外加3%的白糊精,经球磨、混练、困料后,以10 MPa压力压制成36 mm×20 mm圆柱试样,分别在1500℃3 h、1 550℃3 h、1 550℃6 h、1 550℃9 h和1 600℃3 h条件下进行常压烧结,然后测定烧后试样的体积密度和显气孔率,并进行XRD和SEM分析。结果表明:由BaCO3、α-Al2O3和煤矸石粉料,采用固相反应烧结方法可以制备由单斜钡长石、六方钡长石、莫来石和刚玉4种物相组成的莫来石增强钡长石材料;在本试验条件下,提高煅烧温度和延长保温时间,有利于试样致密化程度的提高,莫来石晶相的发育及其交叉网络结构的形成,以及反应物分布的均匀。     

原位莫来石-堇青石复合物的物理机械性能、耐火性能和显微结构

原位莫来石-堇青石复合物是由高岭石、滑石和氧化铝,在堇青石含量为5%￣35%范围内,于1300℃、1400℃和1500℃烧成并保温3h制成。XRD和SEM结果显示莫来石-堇青石复合物在1400℃完全形成。在1500℃所有堇青石转变为莫来石和玻璃相,导致突然致密,在堇青石为20%时达最佳致密。25%￣35%堇青石试样不能显示良好致密,尽管从堇青石分解中形成了大量熔融物。然而由于莫来石颗粒分布均匀和压实的显微结构,在这些试样中可以获得最高的常温耐压强度。在所有烧成温度下所有试样都显示了抗热震性好,而在1500℃烧成的试样显示由于形成了高耐火莫来石相,故荷重软化温度最高。     

一次低温快烧高强瓷质外墙砖的研制

使用江西的硅灰石、滑石粘土、长石、粘士为原料研制生产一次低温快烧瓷质外墙砖,配方属SiO_(2)－Al_(2)－CaO - MgO四元系统,SiO_(2)/Al_(2)O_(3)=11,其烧成温度仅1120±6℃.研究表明瓷相主要由石英、顽火辉石、钙长石及玻璃相 组成,晶相含量70％－80％。这种组成的配方烧成后不形成莫来石晶相。     

低温常压烧结制备碳化硅-莫来石复相材料

将6H-SiC和α-Al2O3按质量比为7:3混合,添加0～10%的[BaO+TiO2]作为烧结助剂,球磨后的均匀粉体压制成生坯,在1 200℃预氧化1 h后在氢气气氛下常压烧结1h制备SiC-莫来石复相材料。研究了烧成温度和BaO–TiO2含量对该复相材料烧结性能和相组成的影响。结果表明:1500℃下,随着烧结助剂含量的增加,烧结致密性明显提高,当含量(质量分数)达到8%时,获得显气孔率为0.17%的致密复相材料。预氧化时,烧结助剂中的BaO与α-Al2O3及SiC氧化生成的方石英反应,生成钡长石BaAl2Si2O8,烧成过程中,钡长石转化成玻璃相,促进莫来石的生成,同时促进烧结。复相材料主晶相为6H-SiC和莫来石,次相为玻璃相和Al2SiO5。     

晶化时间对BaO-Al2O3-SiO2微晶玻璃相转变和热膨胀系数的影响

用X射线衍射、差示扫描量热法和热膨胀系数测试研究了BaO-Al2O3-SiO2(BAS)系微晶玻璃的不同晶化时间对其相组成和热膨胀系数的影响.结果表明:在850 ℃,BAS玻璃快速晶化析出六方钡长石;随着晶化时间的延长,六方钡长石逐渐向单斜钡长石转变;当晶化时间为24 h时,六方钡长石完全转变为单斜钡长石.微晶玻璃的相组成与热膨胀系数的关系近似满足两相模型,可通过改变晶化时间来控制相组成,方便的获得热膨胀系数在(4～8.75)×10-6/℃范围内可调整的BAS系微晶玻璃.     

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.     

热处理温度对钛铝酸钙-碳化硅复相材料性能及显微结构的影响

为了钛铁渣的再利用,以钛铝酸钙、碳化硅、α-Al_2O_3微粉、SiO_2微粉和V_2O_5等为原料制备莫来石晶须增强钛铝酸钙-碳化硅复相材料试样,研究热处理温度(1 400、1 450、1 500℃)对试样性能、相组成和显微结构的影响。结果表明:随着烧成温度的增加,体积密度、常温耐压强度增加,显气孔率降低。温度有利于试样的致密化,但是温度越高,试样外部的SiC氧化加重,形成的液相阻碍氧气向试样内部进入,造成较差的颗粒间结合。钛铝酸钙可与SiC氧化产生的SiO_2反应生成钙长石,且V_2O_5的引入促进了莫来石柱状晶的形成与生长。     

以粉煤灰和赤泥为原料烧结陶瓷工艺与性能研究

本文研究了在1050 ℃至1200 ℃之间温度对以粉煤灰赤泥为原料烧结陶瓷的物相和烧结性能的影响.结果表明:实验用粉煤灰原料的主要矿相组成为石英(SiO_2)和莫来石(3Al_2O_3·2SiO_2),赤泥原料的主要矿相组成有钙铝黄长石(Ca_2Al_2SiO_7)、石英(SiO_2)、钙铁榴石(Ca_3Fe_2+3(SiO_4)_3)和钙钛榴石(Ca_3TiFeSi_3O_(12));以粉煤灰赤泥为原料的5组不同配比试样在1200 ℃时试样气孔率相对降低,体积密度和抗压强度相对程度增大;其中5#试样在经1200 ℃烧结后的气孔率为1.67%,体积密度为2.10 g·cm~(-3),抗压强度为123.23 MPa,达到较好的烧结致密状态,试样主要物相是钙钠长石和莫来石.试样内莫来石的形成及玻璃液相的增加促进烧结并在1200 ℃达到致密烧结状态.     

氧化钛对氧化铝瓷的莫来石形成和力学性能的影响

研究了添加氧化钛对标准氧化铝瓷的显微结构和抗折强度的影响。通过挤压原料和TiO2的混合料,制备了含有不同量氧化钛的系列氧化铝瓷,在生产窑内按照工业化制度烧成瓷棒。定量分析了瓷件内的晶化程度和非晶相含量。结果表明,含有TiO2的瓷件内形成了大量莫来石。用场发射扫描电镜分析材料,表明含有TiO2的试样在早期长石颗粒区域出现了密度较高的二次莫来石晶体。测量含TiO2瓷件的力学性能,表明加入少量能提高标准瓷件的抗折强度。     

Al_2O_3多孔陶瓷的制备及性能

以煅烧α-Al_2O_3微粉为原料、粘土为高温烧成粘结剂、羧甲基纤维素为成型粘结剂,采用模压成型法制备了氧化铝多孔陶瓷,运用TG-DSC、SEM、XRD等手段研究了烧成温度、粘土含量对氧化铝多孔陶瓷微观形貌、物相结构、线收缩率、气孔率及力学性能的影响。结果表明:在烧结温度为1400℃时,氧化铝多孔陶瓷出现液相烧结,1500℃时液相烧结随粘土含量的增加更加明显;粘土在高温下促进了氧化铝多孔陶瓷的致密化使得线收缩率增大、气孔率降低、抗折强度提高。烧成氧化铝多孔陶瓷的主晶相为α-Al_2O_3,并有少量的莫来石相,莫来石由粘土在高温下转变得到。1400℃烧成的氧化铝多孔陶瓷综合性能优异,其气孔率介于28.6%~33.7%之间,抗折强度介于37.0~64.0 MPa之间。     

Fracture Behavior of SiC-Whisker-Reinforced Barium Aluminosilicate Glass-Ceramic Matrix Composites

Barium aluminosilicate (BAS) glass-ceramic composites reinforced with various volume percents (0, 10, 20, 30, 40 vol%) of SiC whiskers were fabricated by hot pressing. The microstructure, the whisker/matrix interface structure, the phase constitution, and the mechanical properties of the composites were systematically studied by means of SEM, TEM, and XRD techniques as well as by indentation crack microfracture and single-edge-notched-beam bend testing. It was demonstrated that the incorporation of SiC whiskers could significantly increase the flexural strength and fracture toughness of BAS glass-ceramic matrices. The addition of active Al₂O₃ to the BAS matrix reduced the amount of SiO₂ in the matrix, forming needlelike mullite, which further improved the mechanical properties.     

原位生成堇青石结合红柱石太阳能热发电储热陶瓷的抗热震性能

为提高储热陶瓷材料的抗热震性能,采用原位生成堇青石增强技术,以红柱石为主要原料,通过半干压成型,无压烧结研制了用于太阳能高温热发电红柱石储热陶瓷材料样品。研究了配方组成、烧成温度、相组成、微观结构对样品抗热震性能的影响。结果表明：红柱石添加量为 70%,经1 400 ℃烧成的样品抗热震性能最佳：30 次热震实验（热震条件：1 100 ℃～室温,风冷）的强度不仅没有损失,反而增加了 26.20%。相组成和微观结构分析表明样品的晶相为堇青石、莫来石、硅线石、α-方石英、α-石英等,原位生成的堇青石晶体均匀分布在由红柱石转化的莫来石晶体之间,赋予样品较好的抗热震性能     

Novel Low-Temperature Processing Route of Dense Mullite Ceramics by Reaction Sintering of Amorphous SiO2-Coated γ-Al2O3 Particle Nanocomposites

Dense mullite ceramics were successfully produced at temperatures below 1300°C from amorphous SiO₂-coated gamma-Al₂O₃ particle nanocomposites (AS-gammaA). This method reduces processing temperatures by similar/congruent300°C or more with respect to amorphous SiO₂-coated alpha-Al₂O₃ particle microcomposites (AS-alphaA) and to other Al₂O₃-SiO₂ reaction couples. The good densification behavior and the relatively low mullite formation temperature make AS-gammaA nanocomposites an excellent matrix raw material for polycrystalline aluminosilicate fiber-reinforced mullite composites.     

High-toughness mullite ceramics fabricated by hot-press sintering of pyrophyllite and AlOOH at low temperatures

High-toughness mullite ceramics were fabricated through hot-press sintering (HPS) of pyrophyllite and AlOOH, which were wet-milled and well mixed using a planetary ball mill. The impacts of sintering temperatures and contents of AlOOH on mullite phase formation, densification, microstructure and mechanical properties in ceramic materials were investigated through XRD, SEM and mechanical properties determination. The results indicated that high-toughness mullite ceramics could be successfully prepared by HPS at temperatures higher than 1200°C for 120 min. Increasing the sintering temperature from 1000 to 1300°C significantly enhanced the flexural strength and fracture toughness of samples. The highest flexural strength of 297.97±25.32 MPa and fracture toughness of 4.64±0.11 MPa⋅m^1/2 were obtained for samples sintered at 1300°C. Further increase of temperature to 1400°C resulted in slight decrease of flexural strength and fracture toughness. Compared with the mullite ceramics prepared only using pyrophyllite as raw material, incorporation of AlOOH into raw material significantly increased the mechanical properties of final mullite ceramics. And stoichiometric AlOOH and pyrophyllite as starting material gave the best performance in fracture toughness. The high-toughness of mullite ceramics were ascribed to the high mullite phase content, fine mullite whiskers and in situ formed, intertwined three-dimensional network structure obtained through HPS at a low temperature of 1300°C.     

针刺碳纤维增强莫来石基复合材料的制备及性能

采用溶胶-凝胶法制备了针刺碳纤维增强莫来石基复合材料。借助于TG-DTA和XRD对合成凝胶的莫来石化过程进行研究,结果表明,在热处理过程中,凝胶在920°C左右形成铝硅尖晶石,1198°C左右形成莫来石。研究了烧结温度对复合材料性能的影响,结果表明,烧结温度为1500°C制备的复合材料弯曲强度最高,达到142.2 MPa,断裂韧性为8.77 MPa·m~(1/2)。借助于对复合材料微观结构的观察对复合材料力学性能的变化进行了解释。     

热压烧结细晶粒氧化铝陶瓷(英文)

以沉淀法制各的商业α-Al2O3粉体为原料,自制镁铝硅玻璃为烧结助剂,采用热压烧结工艺低温制备高性能氧化铝陶瓷.用Archimedes法、电子探针和三点弯曲法研究了氧化铝陶瓷的致密化行为、显微结构和力学性能.结果表明:在1400℃烧结的氧化铝陶瓷的相对密度高达98.9%,晶粒细小,平均晶粒尺寸约为0.6μm,晶界上有莫来石相析出,样品的抗弯强度和断裂韧性分别达442MPa和4.7MPa·m1/2.     

基于高岭土制备轻量微孔莫来石骨料结构与性能研究

以高岭土细粉和α-Al2O3微粉为主要原料,采用原位分解法制备轻量微孔莫来石骨料,研究了铝硅摩尔比及热处理温度对轻量微孔莫来石骨料结构与性能的影响.结果表明:经过1400～1600℃热处理后,富铝莫来石试样中除主要物相莫来石相外,还残余一定量刚玉相,接近理论莫来石组成试样及富硅试样均仅检测到莫来石相;所制备的轻量骨料孔径分布主要集中于0.1 ～4 μm范围,均具有微孔结构;随着热处理温度的升高,骨料的体积密度上升,显气孔率下降,耐压强度上升;经1500℃热处理后,富铝试样体积密度为2.49 g/cm3、显气孔率为25.6％、耐压强度为146 MPa;接近理论莫来石组成试样及富硅试样体积密度均小于1.95 g/cm3、显气孔率大于38.0％,1000℃时导热系数均小于0.77 W/(m·K).     

Study on preparation of thermal storage ceramic by using clay shale

Shale was used as main raw material for developing thermal storage ceramics. The samples were fabricated via semi-dry pressing followed by pressureless sintering. The result showed that the sample (75% shale, 10% kaolin, 10% potash feldspar and 5% soda feldspar) fired at 1080 °C exhibited the best comprehensive performance. Ocular examination reveals that no cracks were observed after 30 cycle times thermal shock tests (wind cooling from 600 °C to room temperature). The results presented that the high bending strength remained after 20 cycle times thermal shock tests but plummeted at the thirtieth time. Other properties were given as follows: bulk density: 2.60 g/cm³; thermal conductivity: 2.33 W/(m °C); and heat storage density: 578.50 mJ/m³. XRD analysis indicated that the quartz and hematite were the main solid phases in the sample. Some isolated pores, quartz crystals, granular hematite crystals and needle-like mullite crystals were observed in the matrix according to the SEM (Scanning Electron Microscope) analysis. More pores were found with temperature rizing according to SEM analysis. The relatively high content of Fe₂O₃ contributed to the formation of the vitreous phase and favored the densification. Overall, the introduction of shale effectively reduced the firing temperature and performed the better thermal storage properties.     

Effects of sintering temperature on mechanical properties of 3D mullite fiber (ALF FB3) reinforced mullite composites

A new method to weaken the interfacial bonding and increase the strength of 3D mullite fiber reinforced mullite matrix (Mu_f/Mu) composites is proposed and tested in this paper. Firstly, Mu_f/Mu composites were fabricated through sol–gel process with varied sintering temperature. Then, the effects of sintering temperature on mechanical properties of the composites were tested. As sintering temperature was raised from 1000 °C to 1300 °C, the three-point flexural strength of the composites firstly decreased from 66.17 MPa to 41.83 MPa, and then increased to 63.17 MPa. In order to explain the relationship between composite strength and sintering temperature, morphology and structure of the mullite fibers and mullite matrix after the same heat-treatment as in the fabrication conditions of the composites were also investigated. Finally, it is concluded that this strength variation results from the combined effects of matrix densification, interfacial bonding and fiber degradation under different sintering temperatures.     

Barium Aluminosilicate Reinforced In Situ with Silicon Nitride

Advanced ceramic composite materials that exhibit high strength and toughness with good thermal shock resistance are needed for emerging high-temperature engineering applications. A recently developed in situ reinforced barium aluminosilicate glass-ceramic shows promise of meeting many of the requirements for these types of applications with the added benefit of low-cost fabrication through densification by pressureless sintering. The material is toughened through in situ growth of rodlike β-Si₃N₄ grains resulting from the α–β silicon nitride phase transformation. Microstructural development and material properties for temperatures up to 1400°C are discussed. When compared to monolithic barium aluminosilicate, barium aluminosilicate reinforced with 70% by volume of Si₃N₄ shows a significant increase in flexural strength (from 80 to 565 MPa) and fracture toughness (from 1.8 to 5.74 MPa·m^1/2) with a high resistance to thermal shock.