Growth rates of different polymorphs from interspherulitic boundary profiles

Quantitative data on the crystallization kinetics of polymorphic polymers can be derived from the investigation of gross spherulitic morphology formed in isothermal conditions. Depending on distance between centers, and the time lag between their formation and relative growth rates, various types of boundary lines can be generated by the impinging of two spherical bodies whose radii increase linearly with time, In polymorphic polymers, different types of spherulites often develop simultaneously at different rates from sporadic or predetermined nuclei. In same cases, the so-called growth transformation, in which a nucleus of the fast growing specie is formed at the tip of an advancing lamella of the slower crystal form, provides an alternative mode of nucleation, It is shown that if only one event of growth transformation takes place at the front of a slow growing body, the fast growing spherulite swallows the parent one and the resultant shape of interspherulitic boundary is described by two symmetrical logarithmic spirals whose parameters can be extracted from micrographs taken at the end of crystallization. These concepts are applied to determine the radial growth rate of gamma form spherulites of polypivalolactone in a wide range of temperatures through analysis of the alpha/gamma interspherulitic profiles formed in isothermal conditions and direct measurement of the growth rate of the alpha counterparts at the same temperature.

Phase transformation in the surface region of zirconia detected by UV Raman spectroscopy

The phase transformation of zirconia from tetragonal to monoclinic is characterized by UV Raman spectroscopy, visible Raman spectroscopy, and XRD. Electronic absorption Of ZrO2 in the UV region makes UV Raman spectroscopy more sensitive at the surface region than XRD or visible Raman spectroscopy. Zirconia changes from the tetragonal phase to the monoclinic phase with calcination temperatures elevated and monoclinic phase is always detected first by UV Raman spectroscopy for the samples calcined at lower temperatures than that by XRD and visible Raman spectroscopy. When the phase of zirconia changes from tetragonal to monoclinic, the slight changes of the phase at very beginning can be detected by UV Raman spectroscopy. UV Raman spectra clearly indicate that the phase transition takes place initially at the surface regions. It is found that the phase change from tetragonal to monoclinic is significantly retarded when amorphous Zr(OH)(4) was agglomerated to bigger particles and the particle agglomeration of amorphous zirconium hydroxide is beneficial to the stabilization of t-ZrO2 phase.

The surface sites of sulfated zirconia studied in situ by laser-induced fluorescence spectroscopy

The surface sites of sulfated zirconia were investigated in situ by laser-induced fluorescence spectroscopy using aniline as the probe molecule. Different from the cases for many other oxides, the aniline adsorbed on the unique active sites of sulfated zirconia at r.t. is changed into another species, which emits a characteristic fluorescence band at 422 nm. The results illustrate that the sulfate groups in sulfated zirconia are favorable for the generation of these unique active sites, which also rarely exist on pure zirconia composed of tetragonal and monoclinic phases but do not exist on pure zirconia composed of monoclinic phase. (C) 2004 Elsevier B.V. All rights reserved.

Asymptotic analysis of plane-strain mode I steady-state crack growth in transformation toughening ceramics (II)

Based on a constitutive law which includes the shear components of transformation plasticity, the asymptotic solutions to near-tip fields of plane-strain mode I steadity propagating cracks in transformed ceramics are obtained for the case of linear isotropic hardening. The stress singularity, the distributions of stresses and velocities at the crack tip are determined for various material parameters. The factors influencing the near-tip fields are discussed in detail.

Influence of LiB3O5 structure on microstructure and optical properties of ZrO2, thin films prepared by electron beam evaporation

ZrO2 thin films were deposited bill using an electron beam evaporation technique on three kinds of lithium triborate (LiB3O5 or LBO) substrates with the surfaces at specified crystalline orientations. The influences of the LBO structure on the structural and optical properties of ZrO2 thin films are studied by spectrophotometer and x-ray diffraction. The results indicate that the substrate structure has obvious effects on the structural end optical properties of the film: namely. the ZrO2 thin film deposited on the X-LBO, Y-LBO and Z-LBO orients to m(-212), m(021) and o(130) directions. It is also found that the ZrO2 thin film with m(021) has the highest refractive index and the least lattice misfit.

测量薄膜微粗糙度的总积分散射仪

介绍了一种检测光学薄膜表面总积分散射（TIS）分布的总积分散射仪。对仪器的基本结构、理论基础、测量原理以及系统性能等进行了阐述，提出了抑制系统噪音和提高测量精度的有效措施。利用该仪器对K9基底上的银（Ag）膜和氧化锆（ZrO2）薄膜进行了测量，并根据标量散射理论得到了表面均方根（RMS）粗糙度。利用光学轮廓仪和原子力显微镜（AFM）分别测量了上述Ag膜和ZrO2薄膜的表面均方根粗糙度，并与总积分散射仪所得的粗糙度进行了比较。结果表明，根据测量的薄膜表面总积分散射计算得到的表面均方根粗糙度与光学轮廓仪及原子

Layer uniformity of glancing angle deposition

Some results of an investigation on the layer thickness uniformity of glancing angle deposition are presented. A zirconia monolayer has been deposited by glancing angle deposition to analyze the layer thickness uniformity. The experimental results indicate that the thickness variation over the substrate is less than 0. 1%, which is considered as good uniformity. It is found that the non-uniformity of experimental results is larger than that of the theoretical results. (c) 2005 Elsevier Ltd. All rights reserved.

Influence of oxygen plasma treatment on properties of ZrO2 films prepared by e-beam evaporation techniques

Zirconia films were prepared by e-beam evaporation, and oxygen plasma treatment was used to modify film properties. Spectrophotometry, x-ray diffractometry (XRD), and atomic force microscopy were used to characterize refractive index, extinction coefficient, rnicrostructure, and surface roughness, respectively. The experimental results indicate that both refractive index and extinction coefficient of the films were reduced slightly after oxygen plasma treatment, with the decrease of intrinsic stress and surface roughness. From XRD spectra, the intensity decrease of the T(110) diffraction peak was clearly observed after the treatment, which was caused by the restructuring of the film atoms. (C) 2008 Elsevier Ltd. All rights reserved.

Influence of ytterbia content on residual stress and microstructure of Y2O3-ZrO2 thin films prepared by EB-PVD

Y2O3 stabilized ZrO2 (YSZ) thin films with different Y2O3 molar contents (0, 3, 7, and 12 mol%) are deposited on BK7 substrates by electron-beam evaporation technique. The effects of different Y2O3 contents on residual stresses and structures of YSZ thin films are studied. Residual stresses are investigated by means of two different techniques: the curvature measurement and x- ray diffraction method. It is found that the evolution of residual stresses of YSZ thin films by the two different methods is consistent. Residual stresses of films transform from compressive stress into tensile stress and the tensile stress increases monotonically with the increase of Y2O3 content. At the same time, the structures of these films change from the mixture of amorphous and monoclinic phases into high temperature cubic phase. The variations of residual stress correspond to the evolution of structures induced by adding of Y2O3 content.

沉积温度对氧化钇稳定氧化锆薄膜残余应力的影响

采用自制掺摩尔分数12%的Y2O3的ZrO2混合颗粒料为原料,在不同的沉积温度下用电子束蒸发方法沉积氧化钇稳定氧化锆(YSZ)薄膜样品。利用ZYGOMarkⅢ-GPI数字波面干涉仪对氧化钇稳定氧化锆薄膜的残余应力进行了研究,讨论了沉积温度对残余应力的影响。实验结果表明:随沉积温度升高,氧化钇稳定氧化锆薄膜中残余应力状态由张应力变为压应力,且压应力值随着沉积温度升高而增大;用X射线衍射仪表征了不同沉积温度下氧化钇稳定氧化锆薄膜的微观结构,探讨了薄膜微观结构与其应力的对应关系,并对比了纯ZrO2薄膜表现出的应力状态。

Influence of ZrO2 in HfO2 on reflectance of HfO2/SiO2 multilayer at 248 nm prepared by electron-beam evaporation

Influence of ZrO2 in HfO2 on the reflectance of HfO2/SiO2 multilayer at 248 nm was investigated. Two kinds of HfO2 with different ZrO2 content were chosen as high refractive index material and the same kind of SiO2 as low refractive index material to prepare the mirrors by electron-beam evaporation. The impurities in two kinds of HfO2 starting coating materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum (GDMS) technology and secondary ion mass spectrometry (SIMS) equipment, respectively. It showed that between the two kinds of HfO2, either the bulk materials or their corresponding films, the difference of ZrO2 was much larger than that of the other impurities such as Ti and Fe. It is the Zr element that affects the property of thin films. Both in theoretical and in experimental, the mirror prepared with the HfO2 starting material containing more Zr content has a lower reflectance. Because the extinction coefficient of zirconia is relatively high in UV region, it can be treated as one kind of absorbing defects to influence the optical property of the mirrors. (C) 2008 Elsevier B.V. All rights reserved.