粉末冶金法制备PSZ／Mo复合材料的研究

本文采用粉末冶金法制备了不同成分的PSZ/Mo复合材料。并对其密度、弹性模量和热膨胀系数进行了测量和分析，用XRD进行了物相分析。实验结果表明：纳米氧化锆的烧结性能比金属钼好；弹性模量估算选用简单混合法则进行计算时应进行修正；钼和氧化锆在烧结时不发生化学反应。通过热压PSZ/Mo功能梯度材料的断口扫描分析发现：虽然金属钼和纳米氧化锆具有一定增韧作用，但材料断裂方式仍以脆性断裂为主。     

PSZ/Mo功能梯度材料

利用有限元分析方法,对PSZ/Mo功能梯度材料进行了优化设计,确定了最佳形状因子、层数和每一层的厚度。在此基础上,用热压烧结方法制备了六层结构的PSZ/Mo功能梯度材料。利用自制的FGM热性能测试仪,对制备的试样进行了热震性能实验,通过该实验条件下应力场和温度场的有限元计算,阐述了PSZ/Mo功能梯度材料优良抗热震性的原因。     

纳米氧化锆对氧化镁陶瓷抗热震性的影响

本工作以高纯氧化镁粉、纳米单斜氧化锆粉为原料,通过配料、成型,分别在1 350℃、1 450℃、1 550℃保温2 h后烧结,制备了氧化镁陶瓷试样。研究了单斜氧化锆加入量、烧结温度对氧化镁陶瓷的烧结性能和抗热震性的影响。结果表明:加入纳米单斜氧化锆可以提高氧化镁陶瓷的显微结构均匀性,降低烧结温度和促进试样的致密化;加入纳米单斜氧化锆的试样通过微裂纹增韧、相变增韧以及微裂纹偏转增韧提高氧化镁陶瓷的抗热震性。加入12%(质量分数)的纳米单斜氧化锆的样品在1 450℃烧结而成的试样的抗热震性最优。     

金属Mo对AlN基复相材料性能的影响

以氮化铝、金属Mo 为原料,Y₂O₃为烧结助剂,氮气氛下、1800～1900℃热压烧结制备Mo/AlN 复相材料。利用 XRD、SEM对材料的相组成、显微结构进行表征,四探针法测试复相材料的电阻率,微带线法测试2～20 GHz频率范围内材料的微波衰减特性,探讨了渗流现象与衰减特性之间的内在联系。结果表明;当 Mo 添加量为4. 56 vol %～15. 03 vol %,材料呈现宽频衰减特性,且随着 Mo 含量和烧结温度的增加衰减量增大;当Mo 添加量为16. 18 vol %～24. 88 vol %,材料仅在 6、10、14、18 GHz? 4个频率点出现了明显的谐振峰。根据渗流模型对电阻率数据进行拟合,得到导电相渗流阈值V_c和相应电阻率分别为14. 87 vol %和11. 59 Ω·m。当Mo 体积分数V >V_c时 , 复相材料的衰减特性由宽频向选频转变。      

粉体表面包碳对3Y-TZP陶瓷烧结性能及微观结构的影响

采用对纳米氧化锆陶瓷粉体表面包碳,研究了在不同烧结工艺下,碳含量(0%～7.0%(wt))的变化对纳米氧化锆陶瓷烧结性能及微观结构的影响.分析结果表明:包裹少量碳能明显提高烧结活性,增大烧结坯密度.在本实验条件下,碳含量为1.5wt%的纳米氧化锆陶瓷在1250℃低温氧化气氛中烧结,可得到相对密度约为96%、晶粒尺寸约为85m的陶瓷体,此后随着碳含量的增加,致密度减小;采用真空烧结,由于碳没有被氧化,包裹层的存在阻止了晶界的扩散,延缓了陶瓷体烧结的致密化过程,烧结性能较差;同时碳的加入有效地抑制了晶粒的长大.     

多孔Mo2C/C复合陶瓷材料的制备及吸附性能

以碳化后的松木作为碳模板、金属钼粉作为钼源、硝酸铁作为催化剂制备多孔Mo2 C/C复合陶瓷材料.研究催化剂含量、反应温度和保温时间对多孔Mo2 C/C复合陶瓷材料物相组成和显微结构的影响,并探索了材料对CO2的吸附性能.结果表明:与不加催化剂相比,添加4％(质量分数)的催化剂可促进材料中Mo2 C的生成,其形貌主要为树枝状;而加入过量催化剂会导致生成的Mo2 C晶粒团聚.1150℃的烧成温度及保温4 h的条件有利于材料中Mo2 C的生成,制备的多孔Mo2 C/C复合陶瓷材料具有优异的CO2吸附性能,其吸附量为52 cm3·g-1.     

液相等离子喷涂制备纳米ZrO2/Y2O3涂层的研究

传统的喷涂技术制备的ZrO2/Y2O3涂层存在原料需团聚烧结致密,纳米晶粒不定和物理性能不佳等缺点.采用一种新型的液相等离子喷涂法制备了纳米氧化锆热障涂层,初步分析了液相前驱体液滴在等离子焰流中和基体表面的沉积变化过程,研究了雾化液滴尺寸对纳米氧化锆涂层的显微结构,特别是其相结构的影响;同时分析了纳米氧化锆涂层的抗热震循环性能.结果表明,纳米氧化锆涂层可以承受1 000多次的热循环试验,具有优良的抗热震性能.     

纳米碳化钼复合物的制备及其CO加氢反应性能

利用溶胶-凝胶法成功地制备了纳米碳化钼复合物,采用热重、TEM和XRD等对合成的纳米碳化钼复合物的形貌和结构进行了表征,以CO加氢反应为探针对其催化性能进行了评价。结果表明:纳米碳化钼粒度分布均匀,包覆在无定型碳中,随着柠檬酸含量的增加粒径逐渐变小,表面Mo物种越不易被还原。用于CO加氢反应具有较高的活性,主要生成低碳烷烃,当CA/Mo=2.0时具有最高的反应活性。     

氧化锆纳米粉体烧结性能研究

为了研究纳米氧化锆粉体的烧结性能,以4种不同粒度的氧化锆粉体为原料,在热分析仪上测试了室温～1000℃范围内坯体的形变量和热膨胀性能.采用1450℃恒温1～6 h的烧结工艺,制备了氧化锆陶瓷,并进行了性能表征.结果表明:粉料1次粒子粒径越小,其初始烧结温度越低;粉料的团聚粒径越小,分布越窄,坯体的烧结致密化越容易.     

氧化镁掺杂氧化锆/磷酸三钙复合材料的制备及力学性能研究

采用模压和烧结的方法制备了氧化镁掺杂氧化锆/磷酸三钙复合材料。利用电子万能试验机对复合材料的机械性能进行测试,利用热分析仪、热膨胀仪、X射线衍射仪、傅里叶光谱分析、扫描电镜研究复合材的料烧结行为、晶格结构、微观形貌。研究结果表明,随着烧结温度的升高和氧化镁含量的增加,机械性能逐渐增加;1 400℃烧结,10%的氧化镁掺杂量,氧化锆/磷酸三钙复合材料的力学性能最佳,维氏硬度可达到6 350 MPa,断裂强度可达到25 MPa;四方氧化锆相和液相的形成填充了材料内部的孔隙,有效提高了材料的力学性能;氧化镁的存在抑制了氧化锆的逆同素异构转变。     

Fractographic study of the alumina and zirconia particles embedded in mullite prepared by reaction sintering

Four different mullite-alumina-zirconia composites have been prepared by reaction sintering between alumina and zircon powders using magnesia or spinel (MgAl₂O₄) to increase the sintering and reaction rates. The microstructure of these materials can be described as composed of two parts: the first one is the mullite matrix containing various kinds of zirconia and alumina particles, whereas the second part is an amorphous phase in which alumina submatrices, zirconia and spinel particles are embedded. Examination of fracture surfaces allows one to identify the crack paths and shows that the main differences are related to zirconia inclusions. Analysis of mechanical properties and fracture features leads to the conclusion that crack deflection and microcracking are operative toughening mechanisms for the various materials. Moreover, a crack bowing mechanism is proposed to explain the higher modulus of rupture found for the series of materials prepared with magnesia as a reaction sintering aid. On leave from Instituto de Ceramica Y Vidrio, CSIC, Arganda del Rey, Madrid, Spain.     

Alumina-mullite-zirconia composites obtained by reaction sintering: Part I. Microstructure and mechanical behaviour

Zirconia particles can be added to the matrix to overcome the brittleness inherent in ceramic materials, thereby strengthening the material through tetragonal-monoclinic phase transformation of the zirconia. This work focuses on the effect of the percentage of zirconia and mullite in the mechanical and thermomechanical properties of alumina-mullite-zirconia composites that were obtained by reaction sintering of alumina and zircon. Different samples were processed, resulting in composites with an alumina matrix, which was always volumetrically predominant. A percentage of alumina and mullite with maximized mechanical and thermomechanical properties was observed. This maximization is discussed in terms of the microstructure obtained for the composites mentioned above. The toughening mechanisms provided by zirconia and mullite inclusions, based not only on the R-curve behaviour but also on the analysis of the fracture surface, are also discussed in this report. An additional paper will be forthcoming, containing detailed discussions concerning the R-curve behaviour of the same composites.     

MSP试验法评价Mo/PSZ系复合材料的强度特性(Ⅰ)

利用 MSP试验在全组成范围和不同的实验温度下对 Mo/PSZ系两相复合材料进行了高温力学性能的测试,详细讨论了各组成复合材料在不同温度下的破坏模式和强度与温度的依存性.实验结果证明,利用简便的MSP实验法不仅可以精确地表征Mo/PSZ系复合材料的破坏行为,而且MSP强度与抗弯强度有很好的对应关系,利用这种关系可以从测得的MSP强度来预测抗弯强度.     

Preparation of Yttria-Stabilized Tetragonal Zirconia Ceramics for Optical Ferrule

Yttria-stabilized zirconia ceramics are considered to be one of the most important ceramic materials for use in structural applications, because of the high strength and toughness of yttria-stabilized tetragonal zirconia polycrystals. In this work, in order to prepare dense and compact yttria-stabilized tetragonal zirconia body after sintering at 1400°C, we used various raw materials with different particle properties, such as crystallinity, particle size distribution, and particle shape. Crystallinity and tetragonal percentage of the sintered samples were analyzed by X-ray diffraction. Microstructure of the sintered samples was evaluated by field emission-scanning electron microscopy.     

Fabrication and microstructure-mechanical property relationships in Ce-TZPs

Ceria-stabilized tetragonal zirconia polycrystals(Ce-TZPs) have been fabricated via conventional sintering of commercially available electrofused and electrorefined CeO₂-doped ZrO₂ powder at 1550°C for various periods from 0.5–30 h. The resultant grain sizes of the sintered materials were in the range 2–15 m. The sintering of such electrorefined powder appears to occur by a liquid state sintering process, evinced in terms of the grain-size dependence on sintering time at 1550°C and by direct TEM observation. The mechanical properties of the sintered materials have been characterized, including single-edge notch bend fracture toughness and three-point bend fracture strength. The grain-size dependence of these properties in the CeO₂-stabilized tetragonal polycrystals is very much different from that in Y₂O₃ stabilized tetragonal zirconia polycrystals (Y-TZPs). The transformation plasticity, which is represented by the yield stress behaviour and the total strain to fracture, plays an important role in the microstructure-property interrelationship in the Ce-TZPs.     

碳包纳米氧化锆粉体的烧结行为与力学性能

采用粉体表面包碳技术和两步烧结方法制备出具有良好力学性能的细晶3Y-TZP材料,研究了在无压烧结和两步烧结条件下,碳含量对碳包3Y-TZP材料烧结行为及力学性能的影响.结果表明:对于包裹少量碳的3Y-TZP,与未包碳的试样相比,采用两步烧结不但能提高材料的密度还能细化晶粒;结构致密和ZrO2相变增韧使材料具有较高的维氏硬度和断裂韧性.在碳含量为1.5%时,3Y-TZP材料的维氏硬度和断裂韧性达最大值,碳含量进一步提高使材料中的气孔和缺陷增多,导致材料的性能下降.     

低温烧结高性能2Y-TZP材料

通过在2Y-TZP中加入一定量的硅酸盐玻璃相添加剂,在较低的烧结温度下,制备出细晶、具有良好综合性能的2Y-TZP材料.研究了添加剂加入后,2Y-TZP材料烧结特性、显微结构及力学性能.发现加入少量的添加剂后,不但可以明显降低材料的烧结温度,而且由于细晶及相变增韧的共同作用,材料仍具有较高的抗折强度和断裂韧性.讨论了稳定剂含量对低温烧结Y-TZP力学性能的影响,发现较低稳定剂含量的2Y-TZP材料,由于临界相变尺寸小,在断裂过程中,有更多的四方相氧化锆转变成单斜相,相变增韧的效果更好,因而具有更高的断裂韧性.     

Sintering of ultra-fine tetragonal yttria-stabilized zirconia ceramics

High-frequency induction heated sintering (HFIHS) is utilized to consolidate ultra-fine grain tetragonal zirconia stabilized with 3 mol%Y₂O₃ (3Y-SZ) ceramics. Densification to near theoretical density in a relatively short time can be accomplished using this method. Samples of 3Y-SZ with a relative density of up to 99.5% and an average grain size of about 170 nm could be obtained by sintering at 950 °C for 5 min under a pressure of 100 MPa pressure. The influence of sintering temperature and mechanical pressure on the final density and grain size of the sintered products was investigated. The sintered materials had fracture toughness and hardness values of 4.4 MPa m^1/2 and 10.7 GPa, respectively.     

可切削的氧化锆陶瓷牙科修复体的制备

通过控制CaO_₂-Al_₂O_₃-SiO_₂硅酸盐玻璃粉体,在1300℃低温下液相烧结获得热膨胀系数在7.19×10 ^-6/℃和8.15×10^-6/℃范围内,与修复体饰瓷相近,其强度在340～360MPa,韧性在2.7～3.5 MPa·m^I/2,可切削性与In-Ceram相当的氧化锆陶瓷牙科修复体.     

Zirconia infiltration toughening of Na-β-alumina

Disc and toroidal shaped samples of composites made from powders of Na--alumina and tin-stabilised tetragonal zirconia by conventional mixing and sintering processes have been used to establish data on the effect of the zirconia on the sintering efficiency, the mechanical strength, hardness and fracture toughness. These data have been compared to the results obtained when the -alumina powder was first pre-sintered and then infiltrated with solutions of zirconium salts or suspensions of the tin-stabilised tetragonal zirconia. The results indicate that significant improvements to the mechanical properties can be made when the zirconia is introduced via an organometallic salt dissolved in an organic solvent. For the conventionally made samples the strength and toughness peak at 15 wt% zirconia addition. Sample densities in excess of 97% are achieved by pressurless sintering at temperatures up to 1600 °C.