【作者】 于景媛；

【导师】 孙旭东；

【作者基本信息】 东北大学 ， 材料学， 2008， 博士

【摘要】 多孔陶瓷具有密度低、比表面积大、渗透率高、以及耐高温和化学腐蚀的性能,被广泛用作过滤、分离、隔热、吸声、催化剂载体、化学传感器和生物陶瓷等元件材料。如果多孔陶瓷的孔隙呈反蛋白石结构规则排列,将具有许多独特的优越性,如选择性过滤和分离,良好的渗透性能和较高的力学性能。环氧树脂因具有优良的物理和粘结性能、高的电绝缘性能和良好的耐药品性能而引起人们广泛的研究兴趣,它主要用于保护性涂层、涂料、粘结剂、电子封装和浇铸件等。近年来,当在环氧树脂基体中加入适量的填充物可以明显提高其使用性能,使环氧树脂复合材料的研究得到广泛的发展。本文采用一种新颖的方法制备了孔壁致密、孔隙规则排列的Al2O3和Al2O3-ZrO2多孔陶瓷材料。该种方法是将植物种子(小米)或发泡聚苯乙烯(EPS)小球排列成有序的模板,通过离心成型技术在模板间隙内填充陶瓷浆料,生坯经干燥、烧结后得到所需要的多孔复型结构。该种方法可以避免常用的有机海绵在分解过程中形成的孔洞和缺陷,烧结产物具有均匀致密的孔壁组织和良好的力学性能。本文系统地研究了A1203和Al2O3-ZrO2陶瓷浆料的制备过程,分析了单相和复相体系离心成型时的分离行为,探讨了离心成型工艺参数对生坯和烧结产物各种性能的影响,建立了实验参数和Al2O3-ZrO2多孔陶瓷压缩强度的预测模型。本文还以离心成型所制备的孔隙规则排列的A1203多孔陶瓷为骨架,制备了三维连通Al2O3/树脂新型复合材料,并研究了此种复合材料的力学性能、高温尺寸稳定性和耐磨性。在Al2O3多孔陶瓷的制备过程中,通过调整pH值和分散剂的含量可以制备分散性和稳定性良好的高固相含量(50vol%)的A1203浆料。该种浆料在10-180s-1的剪切速度范围内,呈现剪切变稀的特性,其流变模型为：η=3.451+967.9295γ-0.415。50vol%固相含量的Al2O3浆料流动性和稳定性良好,在离心成型过程中无明显颗粒沉降差异导致的质量分离现象。在2860g离心加速度下,离心所得的生坯孔壁均匀,密度较高(63.4%)1500℃烧结2h后,获得孔壁均匀致密(98.9%)、孔隙规则排列、具有反蛋白石结构的A1203多孔陶瓷。SEM观察表明,A1203多孔陶瓷的顶部和底部晶粒尺寸分布均匀。当作用在EPS模板顶部的附加载荷从7.3N增加到19.6N时,A1203多孔陶瓷的孔隙度从71.8%增加到83.2%,压缩强度由3.85MPa降到1.78MPa,可以经受6-8次1100℃—室温的热震。以小米为模板,采用50vol%固相含量的浆料,在2860g加速度下离心所得的Al2O3多孔陶瓷的孔隙度为66.5%,压缩强度为5.06MPa,可以经受5次1100℃—室温的热震。在Al2O3-ZrO2多孔陶瓷的制备过程中,通过改变pH值和分散剂的含量,制备出固相含量为50vol%,分散性和稳定性良好的Al2O3-ZrO2浆料。该浆料在10～180s-1剪切速度范围内,呈现剪切变稀的特性,其流变模型为：η=3.022+1101.4γ-0.4229。采用固相含量为50vol%的Al2O3-ZrO2浆料,离心成型过程中不发生明显的由于Al2O3和ZrO2颗粒尺寸、密度差异所带来的分离的现象。在2860g离心时,离心后样品顶部和底部的孔壁呈现均匀的生坯密度(61.5%)。1550℃烧结2h后,获得孔壁均匀致密(99.1%)、具有反蛋白石结构的Al2O3-ZrO2多孔陶瓷,其顶部和底部孔壁中ZrO2颗粒分布均匀,无明显差异。当EPS模板顶部的附加载荷从7.3N增加到19.6N时,烧结产物的孔隙度从71.5%增加到83%,压缩强度由4.51MPa降到2.07MPa,最高可以经受8-11次1100℃—室温的热震。利用自适应学习速率动量梯度下降反向传播算法建立了预测Al2O3-ZrO2多孔陶瓷压缩强度的BP神经网络模型,该模型能具有较好的学习精度、学习速度,其预测误差在实际应用允许的范围之内。通过神经网络的方法可以减少实验工作量和提高工作效率,在材料性能预测方面具有较大的优越性。采用孔隙规则排列的A1203多孔陶瓷为骨架,制备出三维连通Al2O3/环氧树脂复合材料,与环氧树脂、A1203颗粒／环氧树脂复合材料相比,具有更优越的室温和高温综合力学性能。在室温时,抗弯强度、抗弯模量、抗压强度和抗压模量分别为116MPa、3.6GPa、170MPa、2.4GPa。该种材料具有良好的高温尺寸稳定性,在180℃尚未发现变形。在120℃压缩时,其抗压强度、抗压模量分别为48MPa、0.9GPa。该新型复合材料具有良好的耐磨性,其摩擦系数和磨损量较低。同时摩擦系数稳定性较好,随着载荷、滑行速度和滑行时间的变化不大。更多还原

【Abstract】 Ceramic foams have been widely used in catalyst carriers, hot gas collectors, molten metal filters, thermal insulators, bio-ceramics, chemical sensors and separation membranes because they have unique three-dimensional skeleton structure, high porosity, low density, high thermal stability and resistance to chemical attack. If the pores can be orderly arrayed with reverse opal structure, porous ceramic will have a lot of unique advantages such as selective filtration and separation, good permeability and high mechanical properties. The increasing interest in epoxy resin has been associated mainly with their specific properties, such as excellent mechanical and adhesive properties, high electronic insulation and good chemical resistance. These characteristics make epoxy resin useful in an array of applications including protective coatings, paints, adhesives, electronics encapsulation and various cast products. Recently, with the expected improvement in properties from the incorporation of fillers into epoxy resin, research into epoxy composites has become a fast expanding field.Porous Al2O3 and Al2O3-ZrO2 ceramics with dense cell struts and ordered pore structure were fabricated by a novel process which can be described as forming a close-packed template with plant seeds (millet) or epispastic polystyrene spheres, filling the interstitial spaces with ceramic slurries by centrifugal slip casting, and removing the template to obtain a porous inverse replica. This novel process has the particular advantage that defects (holes and cracks) that often exist in the cell struts for the commonly used organic sponge pyrolysis method can be avoided, inducing homogenous and dense cell struts and good mechanical properties of sintered products. In this paper, preparation process of Al2O3 and Al2O3-ZrO2 slurries, segregation phenomenon in mono-phase and multi-phase systems during centrifugal slip casting and effect of centrifugal experimental parameters on properties of green compacts and sintered products were studied. A BP neural network model for predicting compressive strength of porous Al2O3-ZrO2 ceramics was built. 3D interpenetrated Al2O3/epoxy composites were fabricated using the ordered porous Al2O3 ceramics as the frame. Mechanical properties, high temperature dimension stability and friction characteristics of the composites were investigated.In the process of fabricating porous Al2O3 ceramic, highly dispersed and stable Al2O3 suspensions with 50vol% solid content were prepared by adjusting pH values and the amount of the dispersant. In the shear rate range of 10～180 s-1, the slurry has shear thinning characteristic, with a rheological model expressed asη= 3.451+967.9295γ-0.415. No obvious mass segregation due to sedimentation difference of the initial Al2O3 particles was observed in the slurry with 50 vol% solid loading because of its good fluidity and stability The cell wall of green compacts centrifuged at acceleration of 2860 g has high and uniform density of 63.4 %. After sintering at 1500℃, a reverse opal structured Al2O3 porous ceramic with uniform and high wall density (98.9 %TD) and ordered pore array was produced. SEM observation showed that the Al2O3 grains distribute homogeneously in both the top and the bottom of the sintered products. When changing the load applied on the EPS templates from 7.3 N to 19.6 N, porosity of the porous Al2O3 ceramics increased from 71.8% to 83.2% and the compressive strength decreased from 3.85 MPa to 1.78 MPa. The porous alumina ceramics can resist 6-8 times repeated thermal shock from 1100℃to room temperature. Choosing millet as the templates, the porosity and compressive strength of the porous Al2O3 ceramics are 66.5% and 5.06 MPa, respectively, and the porous ceramics can resist 5 repeated thermal shock from 1100℃to room temperature.In the process of fabricating porous Al2O3-ZrO2 ceramic, highly dispersed and stable Al2O3-ZrO2 slurries with 50vol% solid content were prepared by adjusting pH values and the amount of the dispersant. In the shear rate range of 10～180 s-1, the slurry of Al2O3-ZrO2 has a shear thinning characteristic and its rheological model can be expressed asη= 3.451+967.9295γ-0.415. Mass and phase segregation due to the sedimentation difference of Al2O3 and ZrO2 particles was hindered in the slurries with 50 vol% solid loading. The cell wall of green compacts centrifuged at acceleration of 2860 g had high and uniform density of 61.5%. After sintering at 1550℃, a reverse opal structured Al2O3-ZrO2 porous ceramic with high and uniform wall density (99.1 %TD) and homogenous ZrO2 particle distribution at both the top and the bottom was produced. When changing the load applied on the EPS spheres from 7.3 N to 19.6 N during packing, the porosity of the porous Al2O3-ZrO2 ceramics increased from 71.5% to 83% and the compressive strength decreased from 4.51 MPa to 2.07 MPa. The Al2O3-ZrO2 porous ceramic can resist 8-11 times repeated thermal shock from 1100℃to room temperature.A BP neural network model for predicting the compressive strength of porous Al2O3-ZrO2 ceramic was built by the gradient descent arithmetic with momentum and adaptive learning rate. The model is high in learning rate and accuracy and the predicted results agree with the actual data within reasonable experimental error. The BP neural network method is superiors in predicting materials properties with less experimental data and high efficiency and preciseness. 3D interpenetrated Al2O3/epoxy composites were fabricated using the ordered Al2O3 porous ceramic as the frame. Compared with epoxy resin and Al2O3-particle/epoxy composites, the 3D interpenetrated Al2O3/epoxy composites have better room temperature and high temperature mechanical properties. At room temperature, flexural strength, flexural modulus, compressive strength and compressive modulus of the composite are 116 MPa,3.6 GPa,170 MPa and 2.4 GPa, respectively. The composites have good dimensional stability at high temperature and no deformation can be observed at 180℃. Its compressive strength and modulus are 48 MPa and 0.9 GPa, respectively at 120℃. The new composites have good wear resistance, low friction coefficient and wear mass loss. The composites have stable friction coefficient with the change of load, sliding velocity and sliding time.更多还原