Gemological Characteristic Difference between Colorless CVD Synthetic Diamonds and Natural Diamonds

CVD synthetic diamond plays an important role in the jewelry market due to its excellent performance and low cost. In this paper, colorless CVD synthetic diamonds produced by a Chinese company were investigated in detail with their gemological, spectroscopic, and luminescent properties compared with natural colorless diamonds. Compared with natural diamonds, CVD synthetic diamonds have high-order interference color and more apparent abnormal birefringence. The results of infrared spectra indicate that all the CVD samples are classified as type IIa, while the natural samples belong to type Ia. The CVD samples show lamellar growth and mottled luminescence pattern and have blue, orange red, purple red, and blue fluorescence, respectively, while most of the natural samples show blue fluorescence. CVD diamonds show lamellar growth structure, and natural diamonds show irregular ring-like growth structure. Thus, multiple methods combined with analysis are required to distinguish synthetic diamonds from natural diamonds. This work provides an experimental basis for the identification of CVD synthetic diamonds.

Phase Field Study of Microstructure Evolution in Eutectoid Phase Transformation – I Nucleation

Eutectoid growth, as the important reaction mechanism of the carbon steel heat treatment, is the basis to control the microstructure and performance. At present, most studies have focused on lamellar growth, and did not consider the nucleation process. Mainly due to the nucleation theory is inconclusive, a lot of research can support their own theory in a certain range. Based on the existing nucleation theory, this paper proposes a cooperative nucleation model to simulate the nucleation process of eutectoid growth. In order to ensure that the nucleation process is more suitable to the theoretical results, different correction methods were used to amend the model respectively. The results of numerical simulation show that when the model is unmodified, the lateral growth of single phase is faster than that of longitudinal growth, so the morphology is oval. Then, the effects of diffusion correction, mobility correction and ledges nucleation mechanism correction on the morphology of nucleation and the nucleation rate were studied respectively. It was found that the introduction of boundary diffusion and the nucleation mechanism of the ledges could lead to a more realistic pearlite.

Theory of X-ray reflection broadening for textures with double-axis averaging: from semicrystalline polymers exhibiting twisted lamellar growth to discotic liquid crystals

It is shown that textures with double-axis averaging similar to thea-texture, or Keller–Machin Type I texture, are not specific to semicrystalline polymers exhibiting twisted lamellar growth. In this work, such texture is observed in extruded fibers of a typical discotic molecule,trans-diC60-Zn porphyrin. Experimentally, these textures can be detected from the characteristic `comma'-like azimuthal profiles of the non-equatorial diffraction peaks in two-dimensional X-ray patterns. Analytical expressions for the azimuthal intensity distribution are developed, which are in good agreement with the experiment. In the proposed generalized coordinates, the diffraction peak shape becomes universal. This provides a simple means of checking the closeness of the sample morphology to thea-texture from just one two-dimensional pattern, without constructing the whole X-ray pole figure.

Electrochemical Synthesis of Lamellar Structured Inorganic Films Using Interfacial Surfactant Templating

Zinc oxide and cobalt hydroxide films with ordered lamellar structures were electrochemically produced via interfacial surfactant templating. This method utilizes interfacial amphiphile assemblies on a working electrode as a template to electrodeposit inorganic nanostructures. Surfactants with anionic head groups (e.g. sodium dodecyl sulfate, 1-hexadecanesulfonate sodium salt, dodecylbenzenesulfonate sodium salt, and dioctyl sulfosuccinate sodium salt) formed bilayer assemblies with Zn2+ and Co2+ ions on the working electrode and guided the lamellar growth of ZnO and Co(OH)2 films. In order to gain the ability to precisely tailor inorganic lamellar structures, the effect of co-solvent and type of working electrode on the repeat distances, homogeneity and orientation of the interfacial amphiphilic bilayers were investigated. The results described here will provide a useful foundation to design and optimize synthetic conditions for electrochemical construction of inorganic lamellar structures.