A novel technique for making open-cell AI203-ZrO2 ceramic foam with plant seed template

The aim of the present research is to provide a technique for preparing open-cell AI203-ZrO2 ceramic foams with uniform cell size. This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density. Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated. Consolidation was performed at an acceleration of 2,860 g for 60 rain. The effect of the characteristic of plant seeds on the drying behavior of Al2O3- ZrO2 green compact was analyzed. The effects of the solid contents of slurries on segregation phenomena ofAl2O3 and ZrO2 particles and green compact uniformity were investigated. The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed. The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading. The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure. When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm. The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.     

激光功率对超声辅助激光熔覆Al2O3-ZrO2陶瓷力学性能的影响

采用激光熔覆工艺在Ti-6Al-4V合金基体上制备Al₂O₃-ZrO₂陶瓷层,探讨在超声辅助下不同激光功率对熔覆层形貌及性能的影响。通过金相显微镜,X射线衍射,扫描电镜,显微硬度测试仪及摩擦磨损试验机研究了熔覆层的宏观形貌,截面形貌,物相组成,微观结构,显微硬度和磨损行为。结果表明:随着激光功率的增加,熔覆层稀释率先增加后降低,激光功率从1100 W增加到1500 W时,稀释率分别为65.86%、68.55%、76.04%、71.57%和68.23%;熔覆层主要由TiAl、TiO和ZrO₂组成;随着激光功率的增加,熔覆层显微硬度呈现先增加后减小的趋势;与其他3种熔覆层(激光功率为1300、1400和1500 W)相比,激光功率为1200 W的熔覆层平均摩擦因数相对较低,约为0.27,该熔覆层的磨损机理为磨粒磨损,其他3种熔覆层的磨损机理为磨粒磨损和粘着磨损。     

Al2O3-ZrO2-C耐火材料性能的研究

为提高铝锆碳耐火材料的性能。研究了烧成温度对铝锆碳耐火材料气孔率、体积密度、常温耐压强度的影响,得出了适宜的烧成温度范围和最佳的锆莫来石加入量,并对此进行了理论分析。同时,还研究了烧成温度对材料抗氧化性的影响。     

Fe2O3对SiC基泡沫陶瓷过滤器性能的影响

采用有机前驱体浸渍法制备SiC基泡沫陶瓷过滤器,通过对SiC基泡沫陶瓷过滤器热震性、抗压强度的测试以及显微结构的分析,研究了Fe2O3对泡沫陶瓷过滤器强度和烧结等性能的影响.实验表明:随着Fe2O3含量的增加,泡沫陶瓷过滤器的抗压强度随之增加,而抗热震次数显著减少;Fe2O3的加入能够起到助烧作用,但是过量的Fe2O3会导致烧结体产生过量的玻璃相,Fe2O3的含量应控制在1.5wt%以内.     

激光功率对Al2O3-ZrO2共晶陶瓷成形质量的影响

采用激光近净成形系统成形了Al2O3-Zr O2(Y2O3)共晶陶瓷,研究了激光功率对成形形貌以及陶瓷内部裂纹、气孔的影响规律,利用X射线衍射仪和扫描电镜对样件进行相成分分析和微观组织观察。研究表明,相对较高的激光功率可以得到裂纹以及气孔较少的陶瓷样件;陶瓷样件具有紧凑排列的胞状共晶组织,亚微米级t-Zr O2(Y2O3)纤维均匀分布在胞状共晶组织内部。由于激光近净成形加工具有层层堆积的特点,微观组织呈现出垂直于沉积方向的周期性带状组织。     

超声辅助对激光熔覆Al2O3-ZrO2陶瓷涂层力学性能的影响

目的 探究超声辅助对钛合金表面激光熔覆Al2O3-ZrO2陶瓷涂层力学性能的影响。方法 使用COMSOL Multiphysics仿真软件,探究熔覆工件中有无超声作用下流场的变化,并将超声波直接引入熔池微区,研究超声辅助对Al2O3-ZrO2陶瓷涂层截面形貌、微观组织、元素分布、显微硬度和摩擦磨损性能的影响。结果 仿真结果表明,无超声时熔池横截面涡流大小呈对称状,流速较为缓慢,超声辅助下熔池截面的声速大小瞬时变化,熔池内流体的流速提高。实验结果表明,超声辅助下,熔覆层的截面形貌发生了一些变化,但抑制了熔覆层裂纹的产生。熔覆层晶粒尺寸细化,尤其是当激光功率为1700 W时,晶粒尺寸最小且相对更加致密;熔覆层内元素分布更加均匀,且界面效应降低。熔覆层的力学性能提高,激光功率为1700 W时,熔覆层平均显微硬度值为979.4HV0.2,相同激光功率下,超声辅助的熔覆层具有更大的平均显微硬度值。超声辅助下熔覆层的摩擦系数和波动幅值都较小,激光功率为1700 W时的摩擦系数最小(约为0.329)且波动较为平稳。结论 超声波直接引入熔池微区可以有效提高熔池的流动性,同时细化了晶粒,均匀化了元素分布,提高了熔覆层的力学性能。     

Fabrication of finegrained Al2O3 ceramic at low sintering temperature

A research on fabrication of finegrained Al2O3 ceramic at lower sintering temperature was carried out.Al2O3 powder with 50 nm in diameter is compounded with 11.24%Al and 4.75% Fe(mass fraction) by high-energy ball-milling. AI is got from Al powder which is a component of the materials being milled and Fe from steel milling balls and milling jar during the milling. In this way, nearly no impurity is brought into the composite powder during milling. With hot pressing of the composite powder and pure Al2O3 powder, it is proved that Al2O3 powder can be densified at lower sintering temperature when the powder is compounded in this way. Al2OC and AlFe form during sintering process of the composite powder. With the reactive sintering and multiphase sintering mechanisms, finegrained Al2O3 ceramic is fabricated at low sintering temperature.     

Al2O3-CeO2-ZrO2-Ni复合球磨粉末的热稳定性研究

采用高能球磨法制备Al2O3-CeO2-ZrO2-Ni复合粉末,并模拟催化剂的工作环境对球磨粉末进行焙烧。运用XRD研究了球磨粉体的组织结构,测定其耐热性能。结果表明,经30h球磨的复合粉体中Al2O3,CeO2和ZrO2均明显细化,而Ni较难磨细。该球磨粉体在600℃低温下的热稳定性良好。若温度不超过1000℃短时焙烧,粉末基本保持活性相,但温度一旦高达1100℃,则完全变成无活性相。     

Optimization of steel casting feeding system based on BP neural network and genetic algorithm

The trial-and-error method is widely used for the current optimization of the steel casting feeding system, which is highly random, subjective and thus ineff icient. In the present work, both the theoretical and the experimental research on the modeling and optimization methods of the process are studied. An approximate alternative model is established based on the Back Propagation(BP) neural network and experimental design. The process parameters of the feeding system are taken as the input, the volumes of shrinkage cavities and porosities calculated by simulation are simultaneously taken as the output. Thus, a mathematical model is established by the BP neural network to combine the input variables with the output response. Then, this model is optimized by the nonlinear optimization function of the genetic algorithm. Finally, a feeding system optimization of a steel traveling wheel is conducted. No shrinkage cavities and porosities are induced through the optimization. Compared to the initial design scheme, the process yield is increased by 4.1% and the volume of the riser is decreased by 5.48×10~6 mm3.     

Al2O3纤维对Al2O3基陶瓷型芯材料性能的影响

采用常压烧结制备Al2O3基陶瓷型芯材料，通过XRD，SEM分析表征了材料的成分和内部结构。测量了Al2O3基陶瓷型芯气孔率、抗蠕变性能、80℃饱和NaOH溶液中侵蚀性能，并讨论了材料性能随Al2O3纤维含量变化的原因。     

铝的润湿行为以及Al2O3和SiC陶瓷过滤器的过滤行为

检测了工业用Al2O3过滤器和SiC过滤器与液态铝的润湿性并在工厂使用以上2种陶瓷过滤器过滤铝液。实验结果表明：Si C过滤器比Al2O3过滤器更易于润湿液态铝。提高液态铝与过滤器的润湿性有助于铝液透过过滤器,提高夹杂物的去除率,同时,易于去除与铝不浸润的杂质。     

Bonding of Al2O3 ceramic and Nb using transient liquid phase brazing

The brazing of Al2O3 to Nb was achieved by the method of transient liquid phase (TLP) bonding. Ti foil and Ni-5V alloy foil were used as interlayers for the bonding. The base materials were brazed at 1423-1573 K for 1-120 min. The results show that the shear strength of the joint first increases and then decreases with increasing holding time and brazing temperature. The joint interface microstructure and elements distribution were investigated. It can be concluded that a composite structure, in which the base metals are solid solution Nb(V) and Nb(Ti) reinforced by Ni3Ti, is formed when the brazing temperature is 1473 K and holding time 15 min, and a satisfactory joint strength can be achieved. The interaction of Ti foil and Ni-5V foil leads to the formation of liquid eutectic phase with low melting point, at the same time the combination of Ti come from the interlayer with O atoms from Al2O3 results in the bonding of Al2O3 and Nb.     

CeO2对Al2O3基陶瓷涂层耐蚀性的影响

通过优化Al2O3基陶瓷涂层配方和工艺,并加入适量的稀土氧化物CeO2,对陶瓷涂层的界面形貌、组织结构、结合力和耐蚀性进行了研究。结果表明,添加适量的稀土氧化物CeO2,使Al2O3基陶瓷涂层致密性、结合力和耐蚀性得到提高。     

激光熔覆纳米Al2O3等离子喷涂陶瓷涂层

采用X射线衍射仪、扫描电镜和显微硬度计研究了45#钢表面激光熔覆纳米Al2O3改性Al2O3 13%TiO2(质量分数)陶瓷涂层的相组成、微观结构和显微硬度,同时对涂层的磨损特性进行了考察.结果表明,激光重熔区亚稳相γ-Al2O3转变成稳定相α-Al2O3,熔覆层由粗颗粒α-Al2O3和TiO2以及纳米α-Al2O颗粒组成,在激光的作用下,等离子喷涂层的片层状结构得以消除; 纳米Al2O3颗粒仍然保持在纳米尺度,填充在涂层的大颗粒之间,使涂层致密化程度得以提高,因此纳米Al2O3改性涂层的显微硬度较高,且其耐磨性能明显优于等离子喷涂层.     

等离子喷涂制备镍基Al2O3-TiB2金属陶瓷涂层

利用X射线衍射仪和扫描电镜分析了机械合金化对Ni、Al、TiO₂、B₂O₃混合粉末组织的影响。采用等离子喷涂在铝合金基体表面制备了Al₂O₃-TiB₂金属陶瓷涂层,并对涂层进行了显微硬度的测试。结果表明,30%Ni-(Al-TiO₂-B₂O₃)粉末球磨20 h后作为喷涂原料效果最好;在铝合金基体表面成功制备了Al₂O₃-TiB₂金属陶瓷涂层,涂层显微硬度高于铝合金,达到了1400 HV0.1。     

Selective laser sintering of polymer-coated Al2O3／ZrO2／TiC ceramic powder

A type of polymer-coated Al2O3/ZrO2/TiC ceramic powder was prepared. The laser sintering mechanism of polymer-coated Al2 O3/ZrO2/TiC powder was investigated by studying the dynamic laser sintering process.It is found that the mechanism is viscous flow when the sintering temperature is between 80 ℃ and 120 ℃, and it is melting/solidification when the temperature is above 120 ℃. The process parameters of selective laser sintering were optimized by using ortho-design method. The results show that the optimal parameters include laser power of 14 W,scanning velocity of 1 400 mm/s, preheating temperature of 50 ℃ and powder depth of 0.15 mm. A two-step posttreatment process is adopted to improve the mechanical properties of laser sintered part, which includes polymer debinding and high temperature sintering. After vacuum sintering for 2 h at 1 650 ℃, the bending strength and fracture toughness of Al2O3/ZrO2/TiC ceramic part reach 358 Mpa and 6.9 Mpa · m1/2 , respectively.     

模板浸渍法制备Al_2O_3-ZrO_2-Y_2O_3复合陶瓷纤维及其烧结工艺

以蚕丝为模板,Al、Zr、Y的硝酸盐乙醇溶液为浸渍液,采用模板浸渍法制备了Al2O3-ZrO2-Y2O3,复合陶瓷纤维.采用FE-SEM,XRD,TG-DTG和DTA对复合陶瓷纤维的制备及烧结工艺进行了分析研究,实验结果表明所得陶瓷纤维保留了原蚕丝模板纤维的形貌,随着烧结温度的提高,蚕丝基体逐渐热解,纤维直径逐渐变小,在1200℃烧结后的主要相组成为:-Al2O3、θ-Al2O3、Y2O3稳定t-ZrO2和m-ZrO2.     

火焰喷涂工艺对Al2O3陶瓷涂层的影响

采用火焰喷涂技术对基体金属表面喷涂Al2O3陶瓷。通常该陶瓷涂层易出现“剥落”、“龟裂”、孔隙率偏高等缺陷，这些缺陷的产生严重影响涂层的性能。本文通过制定和改善其喷涂工艺。有效地解决了其产生上述缺陷的问题。     

Al2O3对电沉积Ni-Co／AlO3复合镀层性能的影响

应用直流复合电沉积技术制备Ni—Co／Al2O3复合镀层，并研究了Al2O3对电沉积Ni—Co／Al2O3复合镀层性能的影响。结果表明：在本试验范围内，镀层的硬度和耐磨性随着Al2O3含量的增加而提高。