渗钛Si3N4/Q235钎焊界面反应对接头强度的影响

说明了渗钛Ｓｉ３Ｎ４／Ｑ２３５钎焊界面反应与微观结构对接头强度的关系，并对各主要工艺因素对砂强度的影响规律进行了探讨，为渗钛陶瓷／金属钎焊规范的优化选择提供了试验及理论依据。     

Joining alumina to inconel 600 and UMCo-50 superalloys using an Sn10Ag4Ti active filler metal

Alumina ceramics were brazed to Inconel 600 and UMCo-50 superalloys at 900 °C for 10 min using an Sn10Ag4Ti active filler metal. The brazing filler showed good wettability on alumina and superalloys. The flexural strengths were 69 and 57 MPa for alumina/Inconel 600 and alumina/UMCo-50 joints, respectively. In both cases, the brazed specimens fractured along the Sn10Ag4Ti/superalloy interfaces after four-point bending tests. Electron probe microanalysis (EPMA) elemental mapping revealed that the Ni of Inconel 600 and the Co of UMCo-50 dissolved into Sn10Ag4Ti filler metal, which serves to reinforce the weak Sn10Ag4Ti matrix.     

压电陶瓷换能器收发系统幅频特性建模与分析验证

压电陶瓷超声波系统是实现物体探测的重要方法。本文基于压电陶瓷换能器收发系统的等效电路模型,通过引入声波衰减系数建立了发射换能器激励电压与接收换能器输出电压间的关系,并求解出了该等效电路模型的传递函数。实测数据与传递函数仿真数据对比表明,收发系统幅频特性的仿真曲线与实测曲线基本一致,验证了所给等效电路模型与传递函数的正确性。     

LVQ神经网络在磁瓦表面缺陷分类中的运用

在基于磁瓦表面缺陷图像直方图、纹理、投影和形状的特征提取的基础上,提出了一种用LVQ神经网络进行缺陷分类的方法,对现场采集到的6种主要缺陷类型进行了试验。试验结果表明,基于LVQ神经网络的分类器训练与分类的时间短,多缺陷种类分类时准确率高。     

Investigation of machining characteristics in rotary ultrasonic machining of alumina ceramic

Alumina ceramic is well documented as a much-demanded advanced ceramic in the present competitive structure of manufacturing and industrial applications owing to its excellent and superior properties. The current article aimed to experimentally investigate the influence of several process variables, namely: spindle speed, feed rate, coolant pressure, and ultrasonic power, on considered machining characteristics of interest, i.e., chipping size and material removal rate in the rotary ultrasonic machining of alumina ceramic. Response surface methodology has been employed in the form of a central composite rotatable design to design the experiments. Variance analysis testing has also been performed with a view to observing the consequence of the considered parameters. The microstructure of machined rod samples was evaluated and analyzed using a scanning electron microscope. This analysis has revealed and confirmed the presence of plastic deformation that caused removal of material along with brittle fractures in rotary ultrasonic machining of alumina ceramic. The validity and competence of the developed mathematical model have been verified with test results. The multi-response optimization of machining responses (material removal rate and chipping size) has also been attempted by employing a desirability approach, and at an optimized parametric setting the obtained experimental values for material removal rate and chipping size were 0.4166?mm³/s and 0.5134?mm, respectively, with a combined desirability index value of 0.849.     

SiC_p/A356复合材料微弧氧化陶瓷膜的生长规律与性能EI北大核心CSCD

采用微弧氧化法在SiC_p/A356复合材料表面沉积获得连续致密的陶瓷膜,测定了陶瓷膜的生长曲线和显微硬度,利用SEM与XRD分析了陶瓷膜的组织形貌和相组成,考察了金属基复合材料微弧氧化膜的耐磨和防腐性能。结果表明:SiC增强体阻碍了微弧氧化膜的生长,但它并未破坏其完整性;微弧氧化处理初始阶段,陶瓷膜生长方式以向外生长为主,陶瓷膜主要由γ-Al_2O_3相组成;30min后,向外生长逐渐变慢,向内生长开始增强;处理20min之后,陶瓷膜主要由γ-Al_2O_3,α-Al_2O_3相和莫来石相构成;膜层耐磨性良好,耐腐蚀性能得到明显改善。     

CNTs-Al_2O_3多孔陶瓷复合材料的制备与性能

利用冰模板法制备一种具有高孔隙率的碳纳米管强化氧化铝(CNTs-Al_2O_3)多孔陶瓷复合材料。采用SEM,XRD及Raman对样品进行表征,研究碳纳米管(CNTs)含量对复合材料微观形貌、性能的影响。结果表明:随着CNTs含量的增大,复合材料的体积密度、孔隙率和抗压强度均发生改变;添加适量的CNTs能促进陶瓷孔壁烧结致密度,提高材料的抗压强度;但加入过量CNTs会导致CNTs团聚,嵌于陶瓷内壁形成微孔,反而降低了材料致密度与抗压强度;当CNTs含量达2.0%(质量分数)时,多孔陶瓷的抗压强度达到最大值4.52MPa,相对纯Al_2O_3多孔陶瓷提高了66%。     

生物质基SiC陶瓷制备的研究进展

传统工艺制备的碳化硅(SiC)陶瓷性能优异,应用前景广阔,但高温制备造成的成本增加限制了其进一步发展。相比之下,生物质因其自身丰富的孔隙结构成为低温制备SiC陶瓷的理想替代品。本文综述了生物质基SiC陶瓷的结构特性、制备方法、热解机理和影响因素,并探讨碳源和硅源预处理、热解工艺以及应用研究等在制备生物质基SiC陶瓷中存在的问题和发展趋势。     

CeO2掺杂制备Ba0.9Ca0.1Ti1-xSnxO3压电陶瓷的结构及电性能

采用传统的陶瓷烧结技术,通过添加0.15%(摩尔分数)CeO2,在1120℃烧结2h,成功制备了新型无铅压电陶瓷Ba0.9 Ca0.1 Ti1-x Snx O3,并且检测了陶瓷样品的微结构和电性能.XRD显示所有陶瓷样品均具有纯的钙钛矿结构,在室温下为典型的四方相,SEM显示适量添加锡离子可以提高陶瓷致密性.在室温下,锡离子改性的BaTiO3基压电陶瓷在x=0.02处显示了优异的压电、介电和铁电性能(d33=276 pC/N,kp=46%,εr=3678,tanδ=2.4%,Pr=18.2μC/cm2,EC=1.12 kV/mm).这些优异的检测结果证实适当添加锡离子能改善BaT iO3基压电陶瓷的电性能.     

Effect of Powder Processing and Sintering Conditions on the Microstructural,Thermal, and Mechanical Properties of Reticulated Zinc Oxide Ceramic Foams

Ceramic foams are made of zinc oxide using different amounts of Sb₂O₃ and Bi₂O₃ as sintering aids. The effect of a ball milling processing of the starting powders and the sintering temperature on the microstructure and the properties of the ZnO foams is investigated. The focus is set on the evolution of the secondary phases formed within the microstructure of ZnO. A determining effect is identified in the amount of an Al₂O₃ impurity which is introduced by abrasion of the milling vessels during ball milling. Alumina is partially dissolved in a spinel α–Zn₇Sb₂O₁₂ secondary phase which is stabilized by a reduction of the unit cell volume. Remaining Al₂O₃ is incorporated into zinc oxide under formation of a defect wurtzite phase. The phase evolution is a complex function of the content of sintering aids, the Al₂O₃ impurity level and the sintering temperature. The shrinkage during sintering and the porosity evolution are correlated to the phase composition within the ZnO material. The thermal conductivity and the compressive strength of the foams are determined, normalized with respect to their porosity, and correlated to the microstructure and phase composition of the ZnO strut material.