极紫外多层膜残余应力初步研究

针对极紫外多层膜在激光等离子体诊断、极紫外光刻等方面的应用,进行了Mo/Si多层膜残余应力的实验研究,讨论了多层膜残余应力的成因。实验结果表明：Mo单层膜表现为张应力, Si单层膜表现为压应力;通过传统方法制备的13.0 nm处高反射率的40对Mo/Si多层膜会产生-500 MPa左右的压应力,其压应力主要是由膜层之间的贯穿扩散引起的;通过改变膜层比率可以在一定程度上补偿因贯穿扩散产生的压应力,但是以牺牲多层膜反射率为代价。     

极紫外多层膜残余应力初步研究

 针对极紫外多层膜在激光等离子体诊断、极紫外光刻等方面的应用,进行了Mo/Si多层膜残余应力的实验研究,讨论了多层膜残余应力的成因。实验结果表明：Mo单层膜表现为张应力, Si单层膜表现为压应力;通过传统方法制备的13.0 nm处高反射率的40对Mo/Si多层膜会产生-500 MPa左右的压应力,其压应力主要是由膜层之间的贯穿扩散引起的;通过改变膜层比率可以在一定程度上补偿因贯穿扩散产生的压应力,但是以牺牲多层膜反射率为代价。     

空间电荷层效应对固体氧化物燃料电池三相界面附近氧空位传输的影响

纳米复合电极是提高中低温固体氧化物燃料电池(solid oxide fuel cell,SOFC)性能的新型前沿技术,其内部三相界面(three phase boundary,TPB)处空间电荷层(space charge layer,SCL)效应凸显,显著影响氧空位传输能力,是其性能优异的重要原因之一.现有研究广泛采...     

金刚石层厚度对复合片(PDC)残余应力的影响

 通过X射线应力测试和有限元分析相结合的方法,研究了金刚石层厚度对聚晶金刚石复合片（PDC）残余应力的影响,并根据实验测试结果推导出了PDC表面中心与边缘的应力随金刚石层厚度变化的关系式。随着金刚石层厚度由0.5 mm增加到2.0 mm,PDC表面中心的压应力从1 800 MPa下降至700 MPa左右,而边缘部分的应力逐渐由压应力转为拉应力。金刚石层加厚虽然对边缘部分的最大拉应力影响不大,但使PDC边缘拉应力区宽度由0.76 mm增加到了2.85 mm。金刚石层厚度的增加还使得PDC边缘界面附近y方向的最大拉应力和位于界面边缘处的最大剪应力显著加大,这是金刚石层较厚的PDC界面容易产生裂纹的主要原因。     

基片曲率法在多孔硅薄膜残余应力检测中的应用

通过基底曲率法设计和制作了一种测量薄膜应力的装置，它具有全场性、非接触性、高分辨率、无破坏、数据获取速度快等特点.使用该装置测量了电化学腐蚀法制作的多孔硅薄膜的残余应力，并研究了孔隙率和基底掺杂浓度对残余应力的影响，结果表明随着孔隙率的增加和硼离子掺杂浓度的提高，多孔硅表面的拉伸应力逐渐加大，由此表明多孔硅薄膜的微观结构与残余应力的大小有着密切的联系. 关键词： 薄膜 残余应力 孔隙率 多孔硅     

AlGaN插入层对6H-SiC上金属有机物气相外延生长的GaN薄膜残余应力及表面形貌的影响

研究了具有不同台阶数目的AlGaN插入层对在6H-SiC衬底上利用金属有机物气相外延（MOVPE）生长的GaN体材料残余应力和表面形貌的影响.高分辨率X射线衍射测试表明样品的c轴晶格常数随台阶数目的增多而增大;低温光荧光谱中GaN发光峰也随着台阶数目增多而发生蓝移,这些变化都反映出GaN中残余张应力的减小.此外,原子力显微镜测试表明样品表面起伏和粗糙度也都随着插入层的引入和台阶数目的增多得到了明显的改善. 关键词： 残余应力 表面形貌 SiC衬底 AlGaN插入层     

ZrO2/SiO2多层膜中膜厚组合周期数及基底材料对残余应力的影响

ZrO2/SiO2多层膜由相同沉积条件下的电子束蒸发方法制备而成,通过改变多层膜中高(ZrO2)、低(SiO2)折射率材料膜厚组合周期数的方法,研究了沉积在熔石英和BK7玻璃基底上多层膜中残余应力的变化.用ZYGO光学干涉仪测量了基底镀膜前后曲率半径的变化,并确定了薄膜中的残余应力.结果发现,该多层膜中的残余应力为压应力,随着薄膜中膜厚组合周期数的增加,压应力值逐渐减小.而且在相同条件下,石英基底上所沉积多层膜中的压应力值要小于BK7玻璃基底上所沉积多层膜中的压应力值.用x射线衍射技术测量分析了膜厚组合周期数不同的ZrO2/SiO2多层膜微结构,发现随着周期数增加,多层膜的结晶程度增强.同时多层膜的微结构应变表现出了与所测应力不一致的变化趋势,这主要是由多层膜中,膜层界面之间复杂的相互作用引起的.     

中温固体氧化物燃料电池的基本性质测量

介绍了固体氧化物燃料电池的工作原理,测量了中温薄膜固体氧化物燃料电池的开路电压、放电曲线及功率曲线,并分析了电池内阻随电流密度的变化.     

工艺参数对PC光学制品残余应力的影响

先通过光弹实验测量残余应力的分布形态,然后通过应力—光学定律计算出相应的残余应力值,最后把该数值做了数值模拟分析。研究表明:对于同一工艺参数,残余应力的数值从浇口附近至流动末端逐渐减小;对于不同工艺参数,对残余应力的影响程度从大到小的顺序为熔体温度、模具温度、注射压力、冷却时间。     

固体氧化物燃料电池模式阳极内传输与电化学反应耦合机理

模式电极因其结构可控、电化学/化学反应活性位和物质传输路径明确等优势,被广泛应用于固体氧化物燃料电池新型电极研究.现有研究多采用模式电极研究新材料电化学特性、表界面催化反应机理等,尚未涉及几何结构对其内部传输与电化学反应耦合机理的影响,限制了模式电极的应用.本文建立了固体氧化物燃料电池阳极内电荷传输与电化学反应过程的格子玻尔兹曼模拟方法,明确了控制电极过程的关键无量纲参数及其对电极性能的影响规律,研究了模式阳极几何结构的影响机理.根据电极性能对无量纲参数的敏感程度,绘制了指导模式阳极设计与运行的相图,指出相图过渡区(电极性能随操作参数显著变化区域)为进行反应机理研究的最佳操作参数取值范围.同时,研究发现模式阳极电子导体内电子的快速迁移虽不限制阳极性能,其几何结构显著影响过渡区范围;离子导体内离子迁移为影响阳极性能的限速步骤,但其几何结构几乎不影响过渡区范围.本文的数值方法与机理研究结果可为固体氧化物燃料电池模式电极的设计提供重要理论依据.     

Effect of initial stress on Love waves in a piezoelectric structure carrying a functionally graded material layer

The effect of initial stress on the propagation behavior of Love waves in a piezoelectric half-space of polarized ceramics carrying a functionally graded material (FGM) layer is analytically investigated in this paper from the three-dimensional equations of linear piezoelectricity. The analytical solutions are obtained for the dispersion relations of Love wave propagating in this kind of structure with initial stress for both electrical open case and electrical short case, respectively. One numerical example is given to graphically illustrate the effect of initial stress on dispersive curve, phase velocity and electromechanical coupling factor of the Love wave propagation. The results reported here are meaningful for the design of surface acoustic wave (SAW) devices with high performance.     

Oxy-combustion of coal in liquid-antimony-anode solid oxide fuel cell system

A novel system based on the indirect oxy-combustion of coal in a liquid Sb anode solid oxide fuel cell (SOFC) has been used to produce electricity for over 48?h. Pulverized anthracite was fed to the liquid-antimony-anode of the fuel cell, and a peak power density of 47?mW cm^?2 was reached at 1023?K and 35?mW cm^?2 at 973?K. The fuel cell was prepared using a porous stainless-steel tube as a support for an LSM cathode, antimony oxide (Sb₂O₃)/yittria stabilized zirconia (YSZ, Y_0.08Z_0.92O_1.96) composite electrolyte (membrane), while liquid antimony acted as the anode. Liquid antimony/antimony oxide served as the intermediate medium for coal oxidation producing mainly carbon dioxide, which evolved as a separate gas stream. The fuel cell will facilitate carbon capture process, and simultaneously convert the chemical energy of coal directly to electricity. The experiment showed that while the fabricated electrolyte was porous, it became dense during the actual operation, preventing nitrogen leakage into the Sb/C side and producing reasonable open circuit voltage. Analysis of the experimental EIS data illustrates that the Ohmic resistance was the primary loss mechanism in the system. It further suggests approaches to improve the design. Continuous operation of this coal fueled oxy-combustion/fuel cell system achieved an overall efficiency of 28.2% despite of its tiny scale. Simple technologies can be employed to scale up this system at relatively low cost of fabrication and materials.     

High temperature oxidation behavior of interconnect coated with LSCF and LSM for solid oxide fuel cell by screen printing

The current study examined the effect of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) and La_0.7Sr_0.3MnO₃ (LSM) coatings on the electrical properties and oxidation resistance of Crofer22 APU at 800 °C hot air. LSCF and LSM were coated on Crofer22 APU by screen printing and sintered over temperatures ranging from 1000 to 1100 °C in N₂. The coated alloy was first checked for compositions, morphology and interface conditions and then treated in a simulated oxidizing environment at 800 °C for 200 h. After measuring the long-term electrical resistance, the area specific resistance (ASR) at 800 °C for the alloy coated with LSCF was less than its counterpart coated with LSM. This work used LSCF coating as a metallic interconnect to reduce working temperature for the solid oxide fuel cell.     

Electrochemical performance of mixed ionic–electronic conducting oxides as anodes for solid oxide fuel cell

Mixed ionic–electronic conducting (MIEC) oxides, SrFeCo_0.5O_x, SrCo_0.8Fe_0.2O_3−δ and La_0.6Sr_0.4Fe_0.8Co_0.2O_3−δ have been synthesized and prepared on yttria-stabilized zirconia as anodes for solid oxide fuel cells. Power output measurements show that the anodes composed of such kinds of oxides exhibit modest electrochemical activities to both H₂ and CH₄ fuels, giving maximum power densities of around 0.1 W/cm² at 950°C. Polarization and AC impedance measurements found that large activation overpotentials and ohmic resistance drops were the main causes for the relative inferior performance to the Ni-YSZ anode. While interlayered with an Ni-YSZ anode, a significant improvement in the electrochemical performance was observed. In particular, for the SrFeCo_0.5O_x oxide interlayered Ni-YSZ anode, the maximum power output reaches 0.25 W/cm² on CH₄, exceeding those of both SrFeCo_0.5O_x and the Ni-YSZ, as anodes alone. A synergetic effect of SrFeCo_0.5O_x and the Ni-YSZ has been observed. Future work is needed to examine the long-term stability of MIEC oxide electrodes under a very reducing environment.     

Catalytic activity of carbon-supported iridium oxide for oxygen reduction reaction as a Pt-free catalyst in polymer electrolyte fuel cell

Iridium oxide supported on Vulcan XC-72 carbon black (IrO₂/C) as a cathode catalyst for polymer electrolyte fuel cell (PEFC) has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurement. The IrO₂ particles were 8-160 nm in diameter. The oxygen electroreduction activity was studied by cyclic voltammetry (CV). It was found that IrO₂/C had high oxygen reduction reaction (ORR) activity. The performance of the membrane electrode assemble (MEA) was also tested in a single PEFC and showed that IrO₂/C catalyst would be potential candidates for use as cathode catalyst in PEFC.     

Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3-20 μm by the Ni 70 Mn 25 Co 5 alloy infiltration technique at high temperature and high pressure (HPHT).The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD).Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa,which increase with th...     

Fabrication of solid oxide fuel cell based on doped ceria electrolyte by one-step sintering at 800 °C

Ce_0.8Gd_0.05Y_0.15O_1.9 (GYDC) electrolyte was prepared by a carbonate co-precipitation method. Lithium nitrate at 1, 1.5, 2 and 3 mol% was added to GYDC as sintering additive. 96% relative density was achieved for GYDC at sintering temperature of 800 °C with addition of 1.5 mol% LiNO₃. The conductivities of GYDC with sintering aids LiNO₃ were measured by a.c. impedance spectroscopy and showed comparable values to that of pure GYDC sample sintered at 1400 °C. A single cell with 1.5 mol% LiNO₃ infiltrated GYDC electrolyte was fabricated by sintering at 800 °C for only 2 h. Lithiated NiO was synthesized by the glycine-nitrate combustion method and employed as cathode material. The cell was tested at temperatures from 500 to 575 °C and a maximum power density of 73 mW cm^− 2 was obtained at 575 °C. These preliminary results indicate that LiNO₃ is a very effective sintering additive for intermediate temperature solid oxide fuel cell fabrication.