金刚石聚晶的抛光方法

 本文介绍一种行之有效、经济的金刚石聚晶（包括复合块）的抛光方法。     

Effect of finishing methods on surface roughness and color stability in all-ceramic systems

The objectives of the study were to evaluate the effect of the finishing methods on the surface roughness, and to investigate changes in CIE L*a*b* color coordinates of all-ceramic systems after different finishing methods and accelerated aging. Sixty specimens were prepared, 20 specimens each for Vitadur-N, IPS Empress II, and Cerec Vita Block Mark II. The surface roughness (Ra) following treatment with the different finishing methods was measured using a profilometer. Surface examinations in all groups were made by using a scanning electronic microscope. CIE L*a*b* values of the specimens were determined. After all specimens were subjected to accelerated aging, color measurements were repeated, and the total color differences (ΔE) were calculated. Data were analyzed statistically. Significant differences in surface roughness among all-ceramics were found (P < 0.05). No significant differences were found between the surface roughness of the glazed and polished all-ceramics (P > 0.05). After accelerated aging, all groups had acceptable color changes (ΔE < 2).     

Quantitative UV-Visible Diffuse Reflectance Spectroscopy of Solid Powders

In spite of difficulties in attaining high resolution, the determination of UV-VIS-NIR spectra via diffuse reflectance spectro-scopic measurements on solid powders; provides several advantages. Compounds which are difficult to obtain as suitable single crystals, or are found to be unstable or insoluble in liquid solution, can only be studied by diffuse reflectance spectroscopy. Also, since no solvents are required, any effects due to solvation are eliminated. However, it is not possible to resolve the observed spectrum into its anisotropic components, as in the case of single crystal spectra.     

Synthesis and characterization of nanometric powders of UO2+x, (Th,U)O2+x and (La,U)O2+x

This paper describes a new way of preparing nanometric powders of uranium oxide, to fit the needs of studies on UO₂ oxidation, through the electrochemical reduction of U(VI) into U(IV). These powders can also be doped with radionuclides if necessary. The precipitation of oxides occurs in reducing and anoxic conditions. This original method makes it possible to synthesize nanometric UO₂ powders with a calibrated size, as well as the Th- and La-doped UO₂ powders with a predefined composition. The powder characterization by the X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron Microscopy shows the formation of spherical crystallites of UO_2+x, (Th,U)O_2+x and (La,U)O_2+x phases. The composition can be defined by the initial Th/(Th+U) and La/(La+U) ratios in solution and the particle size can be controlled by varying the pH.     

α-Al2O3纳米片的自燃烧法控制合成及其抛光性能

以硝酸铝和甘氨酸为原料, 采用自燃烧法, 在不改变制备工艺的前提下, 通过调整原料的配比, 成功实现了α-Al2O3由纳米粒子到纳米片的可控合成, 获得了分散性良好、尺寸均一的α-Al2O3纳米片. 并通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、热重-差示热分析法(TG-DTA)等手段对产物形貌、结构及前驱物的热性质等进行了研究. 系统探讨了α-Al2O3纳米材料不同形貌和尺寸对其抛光性能的影响, 结果表明, 尺寸小且为片状纳米结构的α-Al2O3具有最佳抛光性能. 这些实验结果对于α-Al2O3纳米材料的工业生产及其在抛光领域的实际应用具有借鉴意义.     

A study of energy transfer phenomenon leading to photon up-conversion in Ho3+:Yb3+:CaF2 crystalline powders and its temperature sensing properties

When Ho³⁺:Yb³⁺:CaF₂ crystalline powders prepared by combustion synthesis were exposed to near-infrared (λ ～ 975 nm) radiation, intense photon up-conversion (UC) was observed at the visible with emission bands peaked at ～ 545, ～650 and ～750 nm identified as 4f-4f transitions from higher levels (⁵F₄, ⁵S₂) and ⁵F₅ to lower levels ⁵I₈ and ⁵I₇ of Ho³⁺. The emission bands at the green and red, in particular, have been demonstrated to be useful for temperature sensing based on luminescence intensity ratio technique. However, no model is available in literature to explain the change of the electronic populations of states (⁵F₄, ⁵S₂) and ⁵F₅ with temperature. The UC phenomenon was studied from both theoretical and experimental points of view. A rate equation model with temperature dependent parameters for Ho³⁺ and Yb³⁺ electronic populations considering a high sensitization of Ho³⁺ ions by Yb³⁺ ions was used. High Yb³⁺ → Ho³⁺ energy transfer efficiency was found (～88% at room temperature). The change with temperature predicted by the model for the luminescence intensity ratio of the UC green and red emission lines agrees well with the experimental data.     

Investigation of self-assembled fractal porous-silica over a wide range of length scales using a combined small-angle scattering method

The unique structure of a set of self-assembled porous silica materials was characterized through a combined small-angle scattering (CSAS) method using small- and ultra-small angle neutron scattering as well as small-angle X-ray scattering. The porous silica specimens investigated were prepared by a sol-gel method under the presence of alkylketene dimer (AKD) template particles and through calcination, which leads to the development of porous silica having a mass-fractal structure over length scales from ~ 100 nm to ~ 10 μm. Furthermore, the specimens posses a hierarchical structure, which consist of a fractal porous structure, and also contain primary silica particles less than 10 nm in size, which form a continuous silica matrix. To characterize these complex structures, observation over a broad range of length scales is indispensable. We propose a CSAS technique that serves this purpose well.     

光学元件亚表面缺陷结构的蚀刻消除

 针对强激光光学元件的应用要求,对光学材料在研磨和抛光过程中形成的亚表面缺陷进行了分析,并借鉴小工具数控抛光和Marangoni界面效应,提出采用数控化学刻蚀技术来实现光学表面面形和微结构形貌的高精度加工,对亚表面缺陷具有很好的克服和消除作用。通过实验对亚表面缺陷的分布位置和特性进行了分析,同时实验验证了在静止和移动条件下Marangoni界面效应的存在,对材料的定量去除进行了实验,提出了亚表面缺陷的去除方法。     

电子探针X射线能谱法测定黄金饰品的成色

本文介绍电子探针能谱法测定含金量５０％～９９％黄金饰品的成色，该法无损、快速、准确，对束流稳定性要求不高且操作简便。     

Morphology, internal structure and growth mechanism of electrodeposited Ni and Co powders

In this paper the morphology (SEM analysis), the internal structure (cross-section analysis) and the growth mechanism of Ni and Co powders electrodeposited from ammoniacal electrolyte are investigated. It is shown that morphology and the internal structure of those powders are quite different. For Ni powder, all particles are of the same morphology, cauliflower-like type. In the case of Co powder, generally two types of particles are detected: (1) dendrite particles and (2) different types of agglomerates, compact, spongy-like and ball-like ones. The growth mechanism for all agglomerates is based on the fact that with the time of growth the disperse (dendrite) agglomerate is branching in different directions and at the tip of each branch spherical diffusion takes over the planar one, providing conditions for the growth of compact deposit. After some time, these branches form compact deposit all over the agglomerate surface and the same agglomerate further grows as a compact one, until it falls off from the electrode surface. Characteristic of all agglomerates is the presence of deep cavities on their surface and the fern-like dendrites on the bottom for most of these cavities.