轻质高强钇硅氧多孔陶瓷的可控制备、微观结构和性能

发布时间：2018-06-26 18:29

本文选题：γ-Y_2Si_2O_7多孔陶瓷 + Y_2SiO_5多孔陶瓷　；参考：《中国科学技术大学》2015年博士论文

【摘要】：多孔陶瓷具有孔隙率高、比强度高、密度低和热导率低的优点,其重要应用之一是作为高温绝热材料。但是,目前常见的多孔陶瓷绝热材料(SiO2、Al2O3、YSZ和莫来石多孔陶瓷等)存在一些不足之处,比如：Si02多孔陶瓷的强度较低而且工作极限温度低、A1203多孔陶瓷的热导率较高、YSZ多孔陶瓷的烧结收缩率很大而且密度较高,以及莫来石多孔陶瓷强度较低等。所以,研发综合性能更加优良的新型多孔陶瓷是未来的趋势。本工作选取熔点高、热导率极低且高温热学和化学稳定性好的γ-Y2Si207和X2-Y2Si05作为新型多孔陶瓷的基体材料,通过有机泡沫浸渍法和原位反应发泡-注凝法制各样品并详细表征其微观结构,深入研究所制各样品的微观结构与性能(压缩强度和热导率)间的关系及其高温性能。首次制备出γ-Y2Si2O7多孔陶瓷。以Y2SiO5粉末和硅溶胶为原料,采用有机泡沫浸渍法结合反应烧结过程成功制备了高孔隙率和纯相的γ-Y2Si207多孔陶瓷。制备的材料是白色开孔的网眼状多孔陶瓷,孔尺寸分布为200～700μm,孔道相互连通且孔筋分布均匀。增加涂覆浆料次数可显著提高样品的性能。另外,由PEI预处理海绵模板得到样品的性能最佳,如高孔隙率(84.5%)、相对较高的压缩强度(1.28MPa)和低密度(0.62g/cm3)。以Y203和Si02粉末为原料,N-羟甲基丙烯酰胺为单体,通过原位反应发泡-注凝法制备出具有独特多级孔结构的γ-Y2Si207多孔陶瓷,包括70～250gm的球形大孔和骨架上0.1～1.5μm的小孔。多级孔结构中小孔的形成机制主要来自于原位反应烧结过程,而且该结构的热稳定性极佳,可维持到1700℃。此外,改进制备工艺—使用无毒环保的明胶作为凝胶剂,通过原位反应发泡-注凝法合成出高性能的γ-Y2Si207多孔陶瓷。样品具有优异的力学和热学性能,当孔隙率为64.3～89.3%时,样品的压缩强度可达46.5～3.4MPa；对于孔隙率为57.2～90.0%的样品,室温热导率为0.918～0.147W/(m·K). γ-Y2Si207多孔陶瓷还具有优良的高温性能,包括良好的高温强度和较低的热循环烧结收缩率。所制备的γ-Y2Si207多孔陶瓷具有轻质、高孔隙率、高强度、低热导率和热稳定性高的优点。采用发泡-注凝工艺,通过研究制备途径(原位反应烧结和直接烧结法)和烧结温度对样品结构与性能的影响,发现了目前Y2Si05多孔陶瓷相关研究工作中存在较大烧结收缩率的原因：所使用的原料为精细的Y2Si05粉末,其烧结活性较高；另外浆料的固含量较低。随后提出了解决办法：以Y203和Si02粉末为原料,使用高固含量的浆料并通过原位反应发泡-注凝法来制备Y2Si05多孔陶瓷。获得的Y2Si05多孔陶瓷拥有优良的综合性能,如1.0～4.7%的低收缩率、0.79～0.88g/cm3的低密度、82.1-80.1%的高孔隙率和3.54～6.90MPa的高强度(烧结温度1350～1550℃。另外,样品还具有较低的热导率、优异的高温相稳定性和较高的热稳定性。采用无毒的明胶为凝胶剂,经原位反应发泡-注凝法制备出高性能的Y2SiO5多孔陶瓷,并研究了材料的结构与强度和热导率之间的关系以及其高温性能。样品具有独特的多级孔结构和相互连通的三维网络结构。Y2SiO5多孔陶瓷具有优异综合性能,如高孔隙率(60.2-87.1%)、线收缩率小(6.3～4.5%)、体密度低(1.74～0.52g/cm3)和压缩强度高(38.2～0.90MPa)。样品还有极低的热导率,室温下的热导率仅有0.513～0.119W/(m.K)(孔隙率：60.2～87.1%)。Y2SiO5多孔陶瓷还具有优异的高温热稳定性和高温力学性能。本论文发展出两类钇硅氧多孔材料的可控制备方法,通过调节工艺参数能够控制样品的孔径尺寸或者孔隙率(结构),从而获得不同性能的样品。制备的钇硅氧多孔陶瓷具有轻质、低热导率、高孔隙率、高强度、优良的热稳定性,以及优异的高温力学性能的优点,可成为应用前景广阔的高温绝热材料。
[Abstract]:Porous ceramics have the advantages of high porosity, high specific strength, low density and low thermal conductivity. One of the important applications of porous ceramics is to be a high-temperature thermal insulation material. However, there are some shortcomings in the common porous ceramic insulation materials (SiO2, Al2O3, YSZ and mullite porous ceramics), for example, the low strength and working limit of Si02 porous ceramics. Low temperature, high thermal conductivity of A1203 porous ceramics, high sintering shrinkage of YSZ porous ceramics and high density of porous ceramics, and low strength of mullite porous ceramics. Therefore, it is the future trend to develop a new porous ceramic with better comprehensive properties. This work selects high melting point, very low thermal conductivity, high temperature thermal and chemical stability. Good gamma -Y2Si207 and X2-Y2Si05 are used as matrix materials of new porous ceramics. The microstructure of each sample is characterized by organic foam impregnation and in situ reaction foaming and coagulation method. The relationship between microstructure and properties (compressive strength and thermal conductivity) of the samples and its high temperature properties are investigated.
Gamma -Y2Si2O7 porous ceramics were prepared for the first time. With Y2SiO5 powder and silica sol as raw materials, high porosity and pure phase of gamma -Y2Si207 porous ceramics were prepared by organic foam impregnation and reaction sintering process. The preparation materials were white open hole mesh porous ceramics with Kong Chi inch distribution of 200~700 mu m, interconnected channels and holes. The distribution of the reinforcement is uniform. Increasing the number of coating sizes can significantly improve the performance of the sample. In addition, the PEI pretreatment of the sponge template has the best performance, such as high porosity (84.5%), relatively high compression strength (1.28MPa) and low density (0.62g/cm3).
Using Y203 and Si02 powders as raw materials and N- hydroxymethyl acrylamide as a monomer, the porous structure of gamma -Y2Si207 porous ceramics with unique multilevel pore structure was prepared by in situ reaction foaming and coagulation method, including 70 to 250gm spherical pores and 0.1 to 1.5 micron pores on the skeleton. The formation mechanism of the small pores in the multistage pore structure mainly comes from the in-situ reaction sintering. The thermal stability of the structure is excellent and can be maintained at 1700 degrees C. In addition, the preparation process is improved - using non-toxic environmental gelatin as a gel, the high performance gamma -Y2Si207 porous ceramics are synthesized by in situ reaction foaming coagulation method. The sample has excellent mechanical and thermal properties. When the porosity is 64.3 to 89.3%, the sample is compressed. The strength can reach 46.5 to 3.4MPa; for the samples with porosity of 57.2 to 90%, the thermal conductivity of the chamber is 0.918 ~ 0.147W/ (M. K). The porous ceramics of gamma -Y2Si207 also has excellent high temperature properties, including good high temperature strength and low thermal cycle sintering shrinkage. The prepared gamma -Y2Si207 porous ceramics are light, high porosity, high strength and low. The advantages of high thermal conductivity and high thermal stability.
By studying the effect of the preparation methods (in situ reaction sintering and direct sintering) and the sintering temperature on the structure and properties of the samples, the reasons for the larger sintering shrinkage of Y2Si05 porous ceramics are found: the raw materials used are fine Y2Si05 powder, and their sintering activity is higher. In addition, the solid content of the slurry is low. Then the solution is put forward: using Y203 and Si02 powder as the raw material, using the slurry with high solid content and using in situ reaction foaming and coagulation to prepare the Y2Si05 porous ceramics. The obtained Y2Si05 porous ceramics have excellent comprehensive properties, such as 1 to 4.7% low shrinkage, 0.79 to 0.88g/cm3 low density, 82. The high porosity of 1-80.1% and the high strength of 3.54 ~ 6.90MPa (sintering temperature 1350~1550 C). In addition, the sample also has low thermal conductivity, excellent high-temperature phase stability and high thermal stability.
High performance Y2SiO5 porous ceramics were prepared by in situ reaction foaming and coagulating method with non-toxic gelatin. The relationship between the structure and the strength and thermal conductivity of the materials and its high temperature properties were studied. The samples have unique multi-stage structure and interconnected three-dimensional network structure of.Y2SiO5 porous ceramics with excellent synthesis. Properties, such as high porosity (60.2-87.1%), low linear shrinkage (6.3 ~ 4.5%), low bulk density (1.74 ~ 0.52g/cm3) and high compressive strength (38.2 ~ 0.90MPa). Samples have very low thermal conductivity. The thermal conductivity at room temperature is only 0.513 to 0.119W/ (m.K) (porosity: 60.2 to 87.1%).Y2SiO5 porous ceramics with excellent thermal stability and high temperature force. Learning performance.
In this paper, two types of yttrium silicon oxygen porous materials have been developed to control the sample size or porosity (structure) by adjusting the parameters of the process. The prepared yttrium silicon oxygen porous ceramics have light, low thermal conductivity, high porosity, high strength, excellent thermal stability and excellent thermal stability. The advantages of high temperature mechanical properties can be applied to high temperature insulation materials.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.1

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