Author Affiliations
Abstract
1 Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering, Xi’an, P. R. China
2 State Key Laboratory for Mechanical Manufacturing System, Xi’an Jiaotong University, Xi’an 710049, P. R. China
Lead-free piezoelectric sodium bismuth titanate (()TiO3, BNT) thin films were epitaxially grown onto (001)-, (110)-, and (111)-oriented Nb:SrTiO3 (STO) single crystal substrates prepared by sol–gel processing. Highly oriented growth in (001), (110), and (111) BNT thin films was obtained in this work benefiting from the lattice match between the BNT film and the STO substrate. The different growth models in thin films with various orientations result in various surface morphologies dependent on the film orientation. The piezoresponse of the BNT thin films was represented exhibiting a strong orientation dependence that (110)>(001)>(111). This is contributed by the various domain switching contribution related to the crystal symmetry and polarization distribution in the three oriented thin films.
Sodium bismuth titanate lead-free orientation dependence thin films piezoelectric properties Journal of Advanced Dielectrics
2023, 13(4): 2341003
1 北京城市学院，北京3D打印研究院，北京 100083
2 北京恒创增材制造技术研究院有限公司，北京 100083
采用激光选区熔化成形技术制备Ti6Al4V合金试件，通过光学显微镜、扫描电镜和断口形貌分析，系统研究了成形态试样显微组织对力学性能的影响。对比不同打印参数下的微观组织特征，显示沿沉积方向形成β柱状晶，晶内主要分布着针状马氏体α′相，α′相含量越高塑性越差，控制工艺参数可以使针状马氏体α′相原位分解形成α+β相，有利于提高塑性。通过调节激光功率和扫描速度，制备了综合力学性能优异的试件，其抗拉强度达到1 301 MPa，屈服强度达到1 102 MPa，延伸率为7.94%。选区激光熔化成形钛合金经组织调控发生原位分解后，拉伸性能得到提高。
激光选区熔化成形 Ti6Al4合金 工艺参数 显微组织 力学性能 原位分解 selective laser melting Ti6Al4V alloy process parameter microstructure mechanical property in situ decomposition
利用自主开发的选区激光熔化设备以钴铬合金为成型材料，在进行了系统的工艺优化研究的基础上，对选区激光熔化(SLM)制件成型过程中表面粗糙度演化、微观形貌、致密度以及硬度之间的内在联系进行了研究。研究发现：成型过程中粉层的熔化收缩以及厚度的累积是造成成型质量变差的重要原因；较小的表面粗糙度累积效应，可大大减少成型件内部的孔隙数量从而提高致密度，粉层厚度的降低是减小表面粗糙度累积效应和提高致密度的关键；制件的宏观硬度比显微硬度对制件致密度存在更显著的依赖关系：致密度越大，宏观硬度越大。通过优化工艺制得的工件致密度达到98.04%，宏观硬度为40HRC，符合美国材料实验协会(ASTM)标准。
光学制造 选区激光熔化 表面粗糙度 致密度 硬度 中国激光
2015, 42(11): 1103006
采用选区激光熔化进行钴铬合金成型,是当今牙齿种植体制造的新方法,然而SLM成型试样表面粗糙度的累积效应对于制件的性能具有重要影响。实验首先获得了适于多道成型的单熔道以及相应的工艺参数,在此基础上进行正交实验,研究激光线能量密度(E)、粉末粒度、粉层厚度以及层间扫描策略对于多层成型制件表面粗糙度及致密度的影响规律并进行原因分析。实验结果表明P/V＞1.6时,多层成型试样的成形质量明显改善;粉末层厚是影响多层制件成型质量的最主要因素,在一定范围内线能量密度越大、小颗粒粉末比重越大、粉层厚度越小可以有效降低表面粗糙度和提高致密度;采用层错正交叠加的策略有助于熔池的浸润和铺展从而降低表面粗糙度。
表面粗糙度 线能量密度 粉末层厚 SLM SLM surface roughness linear energy density powder layer thickness
Author Affiliations
Abstract
Key Laboratory for Physical Electronics and Devices, Ministry of Education, Shanxi Key Laboratory of Information Photonic Technique, Xi'an Jiaotong University, Xi'an 710049, China
Polarization dependence of the enhancement and suppression of four-wave mixing (FWM) in a multi-Zeeman level atomic system is investigated both theoretically and experimentally. A dressing field applied to the adjacent transition can cause energy level splitting. Therefore, it can control the enhancement and suppression of the FWM processes in the system due to the effect of electromagnetically induced transparency. The results show that the pumping beams with different polarizations select the transitions between different Zeeman levels that, in turn, affect the enhancement and suppression efficiencies of FWM.
四波混频 抑制增强 偏振 塞曼能级 270.1670 Coherent optical effects 190.4180 Multiphoton processes 190.4223 Nonlinear wave mixing Chinese Optics Letters
2011, 9(7): 072701
