La在Al2O3(sf)/Al-5.0%Cu复合材料界面的分布及界面结构研究

挤压铸造Al2O3（sf）／Al-5．0％Cu复合材料时添加适量稀土La，并研究了界面附近La元素的分布。添加稀土后能明显的改善纤维与基体的润湿性．并促进了界面反应的发生．在纤维与基体合金之间生成致密的厚度约2μm的过渡层．并建立了界面的生成及结构模型。     

稀土La对Al-Si合金复合材料凝固组织与溶质偏析的影响

利用挤压铸造法制备了Al2O3/Al-Si-La复合材料;研究了稀土La对复合材料凝固组织以及基体合金凝固时溶质偏析的影响。结果表明,稀土La可细化基体合金的凝固组织,La富集在界面附近,有利于改善铝合金液对氧化铝短纤维的润湿性,但是未发现任何富稀土相在界面上形成。稀土La对基体合金中镁的偏聚没有明显的影响,镁和稀土La均在界面处富集,且它们的分布位置大致近似。     

添加La2O3对激光烧结(WC-Co)p/Cu金属基复合材料组织和成形性能的影响

研究了稀土氧化物La2O3添加量对激光烧结直接成形(WC-10Co)颗粒增强Cu基复合材料的影响.结果表明,优化La2O3含量(1.0%),可细化激光烧结组织,提高增强颗粒分散均匀性以及颗粒/基体界面结合性能,成形致密度高达理论密度的96.3%,显微硬度HV可达403.1;而过量添加La2O3(≥1.5%),导致激光成形性能降低.讨论了稀土原子对颗粒增强金属基复合材料激光烧结成形的作用机理.     

Fe-23Cr-6Al合金(不含稀土及加La,Ce和Y)高温氧化的扫描电镜研究

本文以扫描电镜(带X射线波长谱仪)为主要工具,对Fe-23Cr-6Al合金(不含稀土及加La,Ce和Y)1300℃高温氧化进行了研究.阐明了不含稀土合金氧化皮粘附性极差的根源,是部分向外扩散的阳离子留在氧化皮/基体界面处的空位聚集成空腔,使氧化皮和基体产生部分脱离的缘故.并认为添加稀土改变氧化皮的生长机制,是稀土改善Fe-Cr-Al合金高温氧化皮粘附性的主要原因.     

La含量对渗铝层/基体界面孔洞生长的影响

采用热浸镀铝的方法在20碳钢上分别制备了不同La含量的热浸镀铝涂层,通过高温氧化试验以及测量孔洞平均直径和形核数量随氧化时间的变化,研究了La含量对渗铝层/基体界面孔洞生长的影响规律.结果表明,渗铝层/基体界面孔洞的生长可划分为快速生长和稳定生长两阶段.在快速生长阶段,当La含量小于0.5wt%时,随La含量的增加,渗铝层/基体界面孔洞的生长速度逐渐减小;当La含量大于0.5wt%时,随La含量的增加,界面孔洞的生长速度逐渐增大.在稳定生长阶段,渗铝层/基体界面孔洞的生长速度随La含量的变化规律与热浸镀铝后合金层厚度随La含量的变化规律相吻合.分析了La含量对渗铝层/基体界面孔洞生长的影响机理.     

稀土对AZ91镁合金干湿交替循环腐蚀行为的影响

镧铈(La,Ce)混合稀土的添加改变了AZ91镁合金微观组织和元素分布。La元素与Ce元素在AZ91镁合金中以不同的形式存在,一部分固溶在镁合金基体中,一部分参与生成了针状的Al4(La,Ce)相和粒状的Al_(10)Ce_2Mn_7相。稀土添加后AZ91镁合金中β相的体积分数有所降低,Al元素分布由晶界向晶内迁移。对不同添加量的稀土镁合金在模拟融雪剂溶液中的干湿交替循环腐蚀行为的研究结果表明,La、Ce混合稀土的添加,可以增加镁合金表面膜的致密度。虽然混合稀土降低了镁合金的自腐蚀电位,但腐蚀电流密度相比较于AZ91明显降低。SECM结果则表明,稀土添加可以减少镁合金表面微区的活性点数量。     

稀土La及Sn对铸造铝合金组织、力学和阻尼性能的影响

研究了稀土La对含质量分数4%Sn铸造铝合金组织、阻尼和力学性能的影响,从La对Sn的形态和分布、La对Sn和铝合金基体润湿特性的影响等方面探讨了阻尼提高机制。结果表明,La含量为0.2%时,4%Sn的AlMgMnSi合金晶粒尺寸得到细化,β-Sn由大颗粒状变为细小、弥散分布,继续提高La含量至0.83%,晶粒变大,且在晶界处出现块状稀土化合物。La的加入可以有效提高含4%Sn铸造铝合金的阻尼性能,当La添加量为0.2%时,含4%Sn的AlMgMnSi和ZL102合金分别比不添加La的提高了约70%和100%。La改善了β-Sn与铝基体的润湿性,使β-Sn呈弥散、细小分布,从而有利于提高相界面阻尼,是本试样具有较高阻尼性能的主要原因。     

La2O3对钢基陶瓷涂层组织与性能的影响

采用热化学反应法在中碳钢(45钢)基体上,以稀土氧化镧(La2O3)为添加剂,制备A12O3陶瓷涂层,并对其组织和性能进行测试和分析.结果表明:稀土氧化镧(La2O3)可以改善陶瓷涂层的组织及性能,陶瓷涂层的硬度和耐蚀性明显提高;添加了稀土氧化镧(La2O3)的A12O3陶瓷涂层,在900℃固化时有MgFeZr3O4、MgSiO3等新相生成;当陶瓷涂层中稀土添加剂(La2O3)含量约为1.19％时,涂层组织更加致密,涂层与基体的冶金结合更加明显,涂层耐蚀性能更好.     

La对Al2O3f/Al-Mg复合材料凝固溶质偏析的影响

利用挤压铸造法制备了Al2O3／Al-Mg-La复合材料。研究了La在铝合金基体中的分布，并探讨了La对基体凝固时溶质元素偏析的影响。结果表明，La富集在界面附近，有利于改善铝合金液对Al2O3f的润湿性，但是在界面上未发现任何富稀土相的形成。La的加入对基体合金中的Mg的偏聚没有很明显的影响，Mg和La作为表面活性元素都在界面处富集，且它们的分布位置大致一样。     

Al2O3短纤维增强Al-5Cu-0.6La合金的元素分布及其溶质偏析研究

采用挤压铸造法制备了Al2O3r/Al-5Cu-0.6La复合材料,研究了其凝固组织及其溶质在纤维附近的分布.结果表明:Al2O3纤维与基体间润湿良好,生成了致密的界面层;在凝固过程中,α-Al相在短纤维间隙中形核并向纤维表面生长,纤维表面Cu和La元素的浓度增大,纤维间隙中的Cu元素的浓度减小.La的加入改变了凝固过程中的溶质传质参数,根据Clyne-Kurz公式的计算和统计物理的分析,将会生成更多的共晶组织.     

Size-dependent interface energy and related interface stress

General equations for the size-dependence of solid–liquid interface energy, grain boundary energy and the intrinsic interface stress without free parameters are derived. The predicted results correspond to computer simulation results, the first principles calculation, the modified embedded-atom-method potential results and experimental results. In addition, the possible physical background of positive or negative interface stress is analyzed.     

Thermal interface materials

Thermal interface mateials for facilitating heat transfer by conduction across two adjacent surfaces are reviewed. They include thermal fluids and pastes, solders, phase change materials (PCMs), and resilient thermal conductors.     

Surface state density at the semiconductor-glass interface

An investigative technique for the determination of the surface state density (SSD) at the semiconductor-lead-borosilicate-glass interface is proposed. It is shown that this technique involving differentiation of the C-V dependence is a more precise and less labor-consuming method, which shows the uniqueness of the solution.     

Characterizing the interface of nickel-zincate-aluminum thin films

The manufacture of plated computer memory disks requires a complex sequence of processing steps. One of the most important factors affecting disk surface topography and adhesion between nickel and aluminum was found to be the formation and diffusion of a zincate thin film at the nickel-aluminum interface. To improve the adhesion, the strength of the weak link (the zinc layer) must be increased. This can be accomplished by alloying the zinc layer with the aluminum and nickel layers by co-diffusion, which is accelerated at high temperatures, or by keeping the zinc layer very thin. Surface topography can be modified by changing the metallurgical properties of the substrate, promoting the diffusion of elements between layers at elevated temperatures, or adjusting the zincating bath parameters.

     

Properties and determination of the interface stiffness

The chemical potential of a curved interface contains a term that is proportional to the product of the interface curvature and the interface stiffness. In crystalline materials, the interface stiffness is a tensor. This paper examines several basic issues related to the properties of the interface stiffness, especially the determination of the interface stiffness in particular directions (i.e. the commonly used scalar form of the interface stiffness). Of the five parameters that describe an arbitrary grain boundary, only those describing the inclination are crucial for the scalar stiffness. We also examine the influence of crystal symmetry on the stiffness tensor for both free surfaces and grain boundaries. This results in substantial simplifications for cases in which interfaces possess mirror or rotational symmetries. An efficient method for determining the interface stiffness tensor using atomistic simulations is proposed.     

Roughness effect on the measurement of interface stress

Stimulated by a recent paper by Spaepen (Acta mater. 48 (2000) 31) we concentrate on the effect of roughness parameters on stress measurements in thin films for self-affine and mound rough interfaces. A self-affine interface is characterized by a lateral correlation length ξ, an rms roughness amplitude σ, and a roughness exponent H (0<H<1). With increasing long wavelength roughness ratio σ/ξ, the ratio between the measured and the actual interface stress decreases. It decreases with a decreasing roughness exponent H that leads to rougher interfaces at short roughness wavelengths (<ξ). For mound roughness which is characterised besides σ by an average mound separation λ and a system correlation length ζ, the force ratio decays in an oscillatory manner as a function of σ/λ as long as λ<ζ. It is concluded that for both cases a more precise knowledge of roughness morphology is required in order to address the influence of interface roughness on the interface stress in thin films.     

Charge transfer at the antiscale composite layer-electrolyte interface

Properties of composite coatings based on oxide layers formed on a titanium surface using the plasmic electrolytic oxidation method and processed using Forum? superdispersed polytetrafluorinethylene were investigated. A combination of electrochemical impedance spectroscopy, differential thermal analysis, and thermal gravimetry methods allowed one to establish the change of the surface state as a result of heating that determines the charge transfer mechanism at the heterostructure-electrolyte phase interface and the difference in the thermodynamic stability of the temperature fractions of the employed polymer. Original Russian Text ? S.V. Gnedenkov, S.L. Sinebryukhov, D.V. Mashtalyar, V.S. Egorkin, A.K. Tsvetnikov, A.N. Minaev, 2007, published in Korroziya: Materialy, Zashchita, 2006, No. 5, pp. 27–33.     

Parabolic vs linear interface shift on the nanoscale

It was shown very recently that diffusion nonlinearity, caused by the strong composition dependence of diffusion coefficients, can lead to surprising effects on the nanoscale: a nonparabolic shift of interfaces (both in ideal and phase separating systems) and sharpening of an initially diffuse interface in ideal systems. Some of these can not be interpreted even qualitatively from Fick’s classic equations. For instance, the nonparabolic shift of an interface at the very beginning is a consequence of the violation of Fick’s first equation on the nanoscale, and the transition from this to the classic parabolic behavior depends on the strength of the nonlinearity and the value of the solid solution parameter V (proportional to the heat of mixing). Experimental and theoretical efforts to explore the above phenomena are summarized in this paper.