铝土矿尾矿多孔陶瓷的制备研究

以铝土矿尾矿为主要原料,分别选用碳粉、石墨粉、碳酸氢钠和淀粉作为造孔剂制备出铝土矿尾矿多孔陶瓷试样,采用抗弯测试、XED、SEM等对其主要力学性能和热物理性能进行测试与表征,结果表明:不同的造孔剂制备的铝土矿尾矿多孔陶瓷试样的抗弯强度、显气孔率、晶相组成和显微组织不同;以碳粉作为造孔剂制备的铝土矿尾矿多孔陶瓷试样的综合性能较好,因此最终选用碳粉作为制备铝土矿尾矿多孔陶瓷试样的造孔剂。     

纤维素基造孔剂对多孔陶瓷微观结构及力学性能的影响

本研究分别以经过3-氨丙基三乙氧基硅烷(APTES)改性的微晶纤维素(MCC)和浆粕纤维作为造孔剂制备高岭土基多孔陶瓷,通过测定孔径分布、显气孔率、断裂挠度和抗弯强度等来探讨两种造孔剂对多孔陶瓷微观结构及力学性能的影响规律。结果表明:(1)以用量10.0wt%以下的改性MCC为造孔剂可以制备出孔径主要分布在0.5~3μm的均匀孔隙结构,而以同样用量的改性浆粕纤维为造孔剂获得的孔隙结构尺寸则为1~8μm;(2)多孔陶瓷的显气孔率会随着改性MCC用量的提高而显著增加,利用20.0wt%的改性MCC可获得54.1%的显气孔比例,而以改性浆粕纤维为造孔剂制备的多孔陶瓷显气孔率提高速率则较慢;(3)以5.0wt%的改性MCC为造孔剂制备所得多孔陶瓷的断裂挠度和三点抗弯强度分别为1.9 mm和21.5 MPa,优于同等条件下以改性浆粕纤维为造孔剂制备的多孔陶瓷。     

以微晶纤维素为造孔剂的多孔陶瓷微观结构和抗弯强度研究

以经过γ-(2,3环氧丙氧)丙基三甲氧基硅烷(GPTMS)改性的微晶纤维素(MCC)为造孔剂、以高岭土为基材制备多孔陶瓷,并研究了该陶瓷样品的微观结构、孔径分布、显气孔率和抗弯强度。研究表明:(1)以经过表面改性的MCC颗粒为造孔剂制备获得的多孔陶瓷材料其孔隙结构受造孔剂用量影响明显;(2)当造孔剂的含量低于10.0 wt%时,多孔陶瓷的孔隙尺寸和显气孔率会随着造孔剂用量的增加而显著增大,但是当造孔剂的用量进一步提高时多孔陶瓷的孔隙结构发展速度开始逐渐下降;(3)多孔陶瓷的抗弯强度主要受其孔隙结构影响,利用5.0 wt%的MCC制备而成的多孔陶瓷材料抗弯强度为21.5 MPa,造孔剂含量提高导致的多孔陶瓷内部孔隙结构比例增大会使多孔陶瓷的抗弯强度出现明显降低。     

造孔剂种类对粉煤灰多孔陶瓷性能的影响研究

以工业废弃物粉煤灰为主要原料,采用添加造孔剂法,分别以淀粉和煤粉为造孔剂,模压成型,在1000℃固相烧结制备粉煤灰多孔陶瓷,用SEM测试分析手段表征不同条件下粉煤灰多孔陶瓷的微观结构变化,研究了造孔剂种类及用量对显气孔率、抗弯强度、吸水率、体积密度、耐酸碱性能的影响.     

造孔剂种类及含量对高孔隙率多孔陶瓷性能的影响

本文以碳粉和淀粉为造孔剂制备高孔隙率多孔陶瓷,研究了造孔剂的种类和含量对多孔陶瓷气孔率、体积密度和力学性能的影响。结果表明:碳粉和淀粉造孔剂含量分别小于37.5%和25%时,多孔陶瓷形态结构完整,无破损。随着两种造孔剂含量增加,多孔陶瓷气孔率均呈增长趋势,体积密度和抗弯强度相应降低。当造孔剂的含量相同时,该体系中淀粉造孔剂的造孔效果优于碳粉造孔剂,其多孔陶瓷孔隙率最高可达33%、体积密度为1.7 g/cm3。但研究发现,碳粉造孔剂制备的多孔陶瓷强度高于淀粉造孔剂多孔陶瓷。     

铝粉造孔制备多孔氧化铝陶瓷的研究

研究了成型压力与铝粉引入量对多孔氧化铝陶瓷气孔状态、烧成收缩率、抗弯强度的影响,通过SEM观察了多孔氧化铝陶瓷材料的微观结构。研究发现,铝粉的加入可有效制备多孔结构高铝陶瓷,并降低了高铝陶瓷材料的烧成收缩率。且随着成型压力增大,达到同一显气孔率所需的铝粉加入量会减少。结合样品的断面形貌分析认为:铝粉在陶瓷基体中造孔机理是铝粉爆炸造孔和氧化膨胀造孔这两种机制共同作用的结果。     

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.     

造孔剂和增强剂对工业固废基多孔陶瓷性能的影响

以镁渣,粉煤灰为原料,添加造孔剂(电石渣、碳粉)和增强剂(高岭土、膨润土)制备多孔陶瓷,并研究造孔剂和增强剂种类和含量对多孔陶瓷性能的影响.结果表明,添加造孔剂后,多孔陶瓷的烧失率、吸水率和气孔率升高,体积密度和强度降低.同等含量时,碳粉具有较好的造孔效果;多孔陶瓷的烧失率、吸水率和气孔率最高可分别达到30％,38％和53％,体积密度最小达到1.4 g/cm3;添加增强剂后,多孔陶瓷的强度大为提高,但其吸水率、气孔率降低,体积密度增加.高岭土的含量不大于10％时,其粘结增强效果明显优于同等含量膨润土的;多孔陶瓷的压缩强度可至28 MPa.     

造孔剂对粉煤灰-城市污泥多孔陶瓷性能的影响

以粉煤灰和城市污泥为主要原料,使用淀粉和稻壳为造孔剂,再辅以膨润土、无水硅酸钠为添加剂制备多孔陶瓷。对多孔陶瓷的性能进行了研究,采用XRD、SEM表征多孔陶瓷的微观结构。结果表明,使用稻壳和淀粉作造孔剂都能制备出具有一定的强度和显气孔率的多孔陶瓷,使用稻壳作造孔剂时性能略优于淀粉。当使用40%量稻壳作造孔剂时,可制备出的显气孔率为52.81%,抗折强度9.12 MPa,气孔呈三维连通的优质多孔陶瓷。     

制备工艺对Al2O3多孔陶瓷性能的影响

研究了Ａｌ２Ｏ３粉料粒径、烧成温度及有机造孔剂对Ａｌ２Ｏ３多孔陶瓷的气孔率、孔径大小及分布的影响，结果表明，随造孔剂加入量的增加，气孔率呈线性增大，加入造孔剂后，平均气孔孔径变大，孔径分布范围变宽。     

Ultra-low cost porous mullite ceramics with excellent dielectric properties and low thermal conductivity fabricated from kaolin for radome applications

Near-net-shape mullite ceramics with high porosity were prepared from ultra-low cost natural aluminosilicate mineral kaolin as raw material and polystyrene micro-sphere (PS) as pore-forming agent. Microstructure, flexural strength, thermal conductivity and dielectric properties of the ceramics were systematically researched. Results show that the porous mullite ceramics possess fibrous skeleton structure formed by a large quantity of interlocked mullite whiskers, which results in good mechanical properties and low-to-zero sintering shrinkage. Flexural strength of the porous mullite ceramics can be up to 41.01 ± 1.12 MPa, even if the porosity is as high as 62.44%. The dielectric constant and loss tangent of the porous mullite ceramics at room temperature are lower than 2.61 and 5.9 × 10⁻³, respectively. Besides, dielectric constant is very stable with the rising of temperature, and the dielectric loss can be consistently lower than 10⁻² when the temperature is not higher than 800 °C. In addition, thermal conductivity at room temperature is as low as 0.163 W/m/K when the porosity of mullite ceramics is 80.05%. The infiltration of SiO₂ aerogels (SiO₂ AGs) can further decrease the thermal conductivity to 0.075 W/m/K, while has just little effects on the dielectric properties. Excellent mechanical, thermal and dielectric properties show that the porous mullite ceramics have potential applications in radome fields. The porous mullite ceramics prepared from kaolin not only have low cost, but also can achieve near-net-shape.     

烧结助剂含量对多孔Si3N4/BN复合陶瓷力学性能和介电性能的影响

以Si3N4和BN为原料,叔丁醇为溶剂,SiO2、Y2O3和Al2O3为烧结助剂,采用凝胶注模成型工艺制备具有高强度、低介电常数多孔Si3N4/BN复合陶瓷。研究了Y2O3和Al2O3含量对多孔陶瓷气孔率、孔径分布、物相组成、显微结构、抗弯强度和介电常数的影响。结果表明:通过调节Y2O3和Al2O3含量,多孔Si3N4/BN复合陶瓷的气孔率由55%增加到68%,气孔尺寸呈单峰分布,平均孔径为0.89～1.02μm;抗弯强度和相对介电常数随Y2O3和Al2O3含量的增加而单调增大,抗弯强度和相对介电常数的变化范围分别为29.9～60.9 MPa和2.30～2.85;通过调节Y2O3和Al2O3含量调控气孔率,能够获得介电性能和力学性能可调的高性能透波材料。     

孔隙率和孔径对反应烧结多孔氮化硅陶瓷介电性能的影响

研究添加成孔剂法制备的有球形宏观孔的多孔氮化硅陶瓷在不同孔隙率和孔径下的介电性能.通过控制成孔剂苯甲酸的加入量和调节成孔剂的粒径可达到烧结体的气孔率和孔径可控的目的.结果表明:随着成孔剂量的增加,样品气孔率变大,反应烧结后烧结体中的α-Si3N4相增多,样品的介电常数ε'和介电损耗tanδ降低.在成孔剂加入的质量分数为30%时,随着成孔剂的粒径变大,反应烧结后烧结体中气孔的直径变大而气孔率不变,样品的ε'和tan δ也相应降低.得到的样品中最低的ε'值为2.4297.     

High performance porous Si3N4 ceramics prepared by coated pore-forming agent method

Coated pore-forming agent method (CPFAM) was introduced to improve the pore-forming agent method (PFAM) for the preparation of porous silicon nitride ceramics. Using SEM in combination with measurements of porosity and flexural strength, it has been found that the flexural strength of the porous silicon nitride ceramics produced with the CPFAM method is significantly higher than those without the coating process: a 100% increase in flexural strength for samples with a porosity of 50%. The porous silicon nitride ceramics also have a very low dielectric constant, which is ideal for applications in wave-transmitting systems. The enhanced mechanical strength of the silicon nitride made by the CPFAM method is a result of a more uniform distribution of the spherical pores and the formation of a dense layer of rod-like microstructures near the surface of the pores.     

Preparation of calcium hexaluminate porous ceramics by gel-casting method with polymethyl methacrylate as pore-forming agent

Calcium hexaluminate (CA₆) porous ceramics were prepared by gel-casting method, with α-Al₂O₃ and CaCO₃ as raw materials and polymethyl methacrylate (PMMA) microspheres as pore-forming agent. The effects of the amount of pore-forming agent PMMA microspheres on the phase composition, bulk density, apparent porosity, flexural strength, microstructure, thermal shock stability and thermal conductivity of CA₆ porous ceramics were systematically studied. The pores of CA₆ porous ceramics are mainly formed by the burning loss of PMMA microspheres and the decomposition of organic matter. Adding an appropriate amount of PMMA microspheres as pore-forming agent has a positive effect on the thermal shock stability of CA₆ porous ceramics. When the amount of pore-forming agent is 15 wt%, the volume density of CA₆ porous ceramics is 1.33 g/cm³, the porosity is 63%, the flexural strength is 13.9 MPa, the thermal shock times can reach 9 times, and the thermal conductivity is 0.293 W/(m·K), which can meet the application in refractory, ceramics or high temperature cement industries.     

正交设计优化粉煤灰-煤矸石质多孔陶粒的制备过程

以粉煤灰为主要原料,采用添加造孔剂法制备出了多孔陶粒。为了优化工艺参数,得到性能较好的粉煤灰多孔陶粒,通过正交试验设计,系统地研究了煤矸石的掺量、成孔剂、烧结温度对多孔陶粒的物理化学性能的影响,如气孔率、吸水率、抗压碎强度、物相组成和显微形貌等。研究结果表明,成孔剂是影响多孔陶粒性能的最主要因素。当煤矸石掺量20%、成孔剂15%,经1160℃烧成的多孔陶粒样品有着较大的抗压碎强度,显气孔率也达到58.22%。样品的晶相组成为钙长石,及少量的方石英和赤铁矿。其内部孔隙丰富,大孔与小孔交错分布,是一种兼具较高气孔率和较强力学强度的优质多孔陶瓷。     

钛酸铝多孔陶瓷的研制

本文探讨了成孔剂和烧结温度对钛酸铝多孔陶瓷性能的影响，研究表明，不同成孔剂对显气孔率的影响不同，成孔剂含量提高，显气孔率增加。但不宜过量，烧结温度上升，强度和化学稳定性提高，显气孔率和热膨胀系数下降。     

Preparation and properties of a low-cost porous ceramic support from low-grade palygorskite clay and silicon-carbide with vanadium pentoxide additives

A low-cost porous ceramic support was prepared from low-grade palygorskite clay (LPGS) and silicon carbide (SiC) with vanadium pentoxide (V₂O₅) additives by a dry-press forming method and sintering. The effects of SiC-LPGS ratio, pressing pressure, carbon powder pore-forming agent and V₂O₅ sintering additives on the microstructure and performance of the supports were investigated. The addition of an appropriate amount of SiC to the LPGS can prevent excessive shrinkage of the support during sintering, and increase the mechanical strength and open porosity of the supports. The presence of SiC (34.4%) led to increases in the open porosity and mechanical strength of 40.43% ± 0.21% and (17.76 ± 0.51) MPa, respectively, after sintering at 700 ℃ for 3 h. Because of its low melting point, V₂O₅ can melt to liquid during sintering, which increases the mechanical strength of the supports and retains the porosity. Certainly, this can also encourage efficient use of the LPGS and avoid wasting resources.     

高温烟气过滤用多孔陶瓷材料的研制

以氧化铝纤维和玻璃粉为主体材料,活性炭粉为造孔剂,通过半干压成型工艺制备了高温烟气过滤陶瓷.详细研究了玻璃粉含量、造孔剂含量以及烧成温度对材料过滤阻力、抗折强度、显气孔率等性能的影响,并对原料配方和烧成制度进行了优化,最优配方为:氧化铝70wt%、玻璃粉30wt%、外加造孔剂25wt%、羧甲基纤维素钠8wt%,最佳的烧成温度为1100 ℃,制得的高温烟气过滤陶瓷抗折强度8.9 MPa,过滤阻力95 Pa,显气孔率达59%.     

Dielectric and mechanical properties of porous Si3N4 ceramics prepared via low temperature sintering

Borophosphosilicate bonded porous silicon nitride (Si₃N₄) ceramics were fabricated in air using a conventional ceramic process. The porous Si₃N₄ ceramics sintered at 1000–1200 °C shows a relatively high flexural strength and good dielectric properties. The influence of the sintering temperature and contents of additives on the flexural strength and dielectric properties of porous Si₃N₄ ceramics were investigated. Porous Si₃N₄ ceramics with a porosity of 30–55%, flexural strength of 40–130 MPa, as well as low dielectric constant of 3.5–4.6 were obtained.