褐黄色IaA＋Ib型合成金刚石的光谱测试分析（上）

通过对褐黄色合成金刚石样品进行常规宝石学、红外光谱、紫外一可见光分光光度计,拉曼光谱等测试,结果表明：金刚石结构中的氮作为金刚石中的一种主要杂质,是金刚石呈现颜色的重要原因,并可用能带理论来解释,结构中的氮在金刚石呈色机制研究上有重要的意义。文章重点研究褐黄色合成金刚石的颜色成因,指出金刚石的呈色机制是一个很复杂的问题,它与金刚石中的杂质成分、色心、缺陷均有关系。     

金刚石颜色成因探讨

概述了能带理论，并阐述了关于金刚石致色的能带理论的解释及其致色机理。根据金刚石的色心类型，阐述了其致色的色心理论的解释，列举了氮中心的各个辐射损伤中心的呈色机理。同时，还介绍了金刚石呈色的其它原因。研究认为，金刚石颜色的成因主要由能带理论和色心致色理论来解释，其次，杂质金属离子、氢杂质、包裹体等也可使金刚石致色。     

纳米金刚石传感器在细胞领域中应用

金刚石中的杂质不仅有颜色,而且可以通过杂质使金刚石成为磁场和温度领域的精确传感器。当杂质遇到氮原子时,金刚石晶体结构就会发生改变,一种称为氮-空位中心的就会形成。氮-空位中心里的电子与量子自旋态呈现出了惊人的一致性,而且量子自旋态可以被精确的控制操作。如果纳米金刚石内部电子的连贯性能够维持足够长的时间,这样我们不仅可以实现金刚石成为量子计算机的自旋载体材料之一,而且金刚石也会成为揭示神经细胞秘密信息的完美装置。     

氮与金刚石性能关系综述

氮是金刚石晶体中最最常见的杂质,也是影响金刚石性能的重要因素之一.关于氮对金刚石合成及其性能的影响研究,很多研究者根据各自所得到实验与分析结果做出了许多有价值的描述.文章对其中有一定科学技术意义和对实际有指导作用以及帮助我们了解其最基本性能的内容做一简要综述.     

Ⅱa型工业金刚石的高温高压合成

对Ⅱa型工业金刚石的高温高压合成进行了研究,成功地合成出了优质Ⅱ a型工业金刚石.通过考察有除氮剂、无除氮剂两种体系中合成金刚石的情况,结果发现,合成金刚石的最低压力点及温度并没有发生太大的变化;借助于光学显微镜发现,有除氮剂体系合成出的晶体颜色比原触媒体系合成的晶体要浅,且多为六-八面体;通过IR检测后发现,有除氮剂体系合成金刚石的含氮量明显低于原触媒体系合成金刚石的含氮量;借助扫描电子显微镜(SEM),对两种体系所合成金刚石表面的形貌进行了观察.     

用掺杂N、H化合物的粉末触媒合成金刚石的研究

氮和氢元素是天然及人工合成金刚石中重要的杂质元素，对金刚石的性能有着十分重要的影响。本工作中，先利用有机氮氢化合物三聚氰胺的分解提供氮与氢源，研究了大量的氮和氢在粉末触媒合成金刚石中对金刚石生长的影响。结果表明：大量的氮和氢的存在，将严重抑制金刚石的成核。然而，用含少量的添加剂氮化物MxN的粉末触媒在国产六面顶压机上却能合成出优质金刚石单晶。利用光学显微镜观察，发现所合成的金刚石多为六八面体，晶形完整；在大多数用含添加剂氮化物的触媒合成的金刚石的晶面上有凹线出现。用扫描电镜对凹线的形貌进行了细致的观察。随着铁基粉末触媒中添加剂氮化物含量的增加，合成金刚石的压力和温度条件逐渐增高，金刚石生长的“V形区”上移。     

氮对MPCVD单晶金刚石生长与含量研究进展

微波等离子体化学气相沉积(MPCVD)技术被认为是制备高纯单晶金刚石的首选方法。然而因为氮原子的半径与碳的原子半径相近,容易成为单晶金刚石生长层中的主要杂质,是阻碍MPCVD单晶金刚石推广应用的原因之一。经过国内外研究团队的对氮与MPCVD单晶金刚石的生长与氮杂质含量控制研究取得了一些结果。但是除此之外还需要解决氮掺杂提速与控制单晶金刚石生长层中氮杂质含量的控制统一问题,才能实现MPCVD单晶金刚石的高端领域应用。     

合成含氮金刚石用触媒合金的实验及选择

以实验结果为依据，叙述了含氮合金触媒与合成工艺对金刚石合成过程及其结果所产生的影响；讨论了氮杂质在金刚石晶体中的分布特征及对金刚石晶体性质的影响机理；还简述了合成含氮金刚石与普通金刚石及天然含氮金刚石性质问差异及原因；并指出了提高人造金刚石质量的一些重要途径。     

绿松石呈色机理实验与论证

矿物的成分、结构和键型是复杂的,引起矿物颜色变化的因素也是复杂的,一种矿物的颜色往往是多种呈色机制的总效应.绿松石是一种自色玉石,即它的颜色是由自身的成分和结构决定的.颜色正是决定绿松石经济价值的重要因素,长期以来,对绿松石颜色的研究一直是绿松石宝石学研究的重要内容.绿松石的颜色主要由Cu2 ,Fe3 离子决定,Cu2 离子对绿松石的基色--天蓝色起有益作用,而Fe3 则起相反作用,两者含量多少决定了色调的变化特点.这与用晶体场理论和光谱实验观测解释的呈色机制是一致的.     

可溶性还原红IFBB显色中间产物的分离和鉴别

一、前言可溶性还原红IFBB是一只四硫酸酯型的可溶性还原染料,分子结构为:该染料本身是黄色粉末,溶于水后成为黄色溶液,显色的最终产物呈红色。如果在红IFBB的黄色水溶液中加入少量盐酸和亚硝酸钠,使显色速度较慢,便可以看到溶液颜色的变化是从黄色至蓝光红色,最后至红色。由于物质的颜色和它的结构有关,而蓝光红色不可能是黄色和红色的拼色,因此在红IFBB显色时,有颜色为蓝光红的中间产物。     

HTHP合成钻石在首饰中的鉴别特征（上）

采用宝石显微镜、红外光谱仪、X荧光光谱仪、紫外-可见光分光光谱仪、紫外荧光灯、Diamond View等对HPHT合成钻石做了较详细的测试与分析。结果表明：这些HTHP合成钻石具有较为一致的黄色,放大检查可见合成钻石内部含有大量棒状、柱状、细小微粒状的铁镍合金包裹体,这些合成钻石几乎都有磁性甚至有些磁性较强。HTHP合成钻石的红外反射光谱非常特征均具有明显的1131cm-1的吸收峰,为Ib型钻石（此类钻石在天然钻石中极少见到）。HTHP合成钻石在X荧光光谱仪下有强烈的铁峰和镍峰,并且在短波紫外线下多数具有绿黄色荧光。HTHP合成钻石在Diamond View下具有不同程度的黄绿色荧光,个别具有黑十字现象。     

HTHP合成钻石在首饰中的鉴别特征（下）

采用宝石显微镜、红外光谱仪、X荧光光谱仪、紫外-可见光分光光谱仪、紫外荧光灯、Diamond View等对HPHT合成钻石做了较详细的测试与分析。结果表明：这些HTHP合成钻石具有较为一致的黄色,放大检查可见合成钻石内部含有大量棒状、柱状、细小微粒状的铁镍合金包裹体,这些合成钻石几乎都有磁性甚至有些磁性较强。HTHP合成钻石的红外反射光谱非常特征均具有明显的1131cm^-1的吸收峰,为Ib型钻石（此类钻石在天然钻石中极少见到）。HTHP合成钻石在X荧光光谱仪下有强烈的铁峰和镍峰,并且在短波紫外线下多数具有绿黄色荧光。HTHP合成钻石在Diamond View下具有不同程度的黄绿色荧光,个别具有黑十字现象。     

Mechanical properties of synthetic type IIa diamond crystal

The mechanical behavior of synthetic type IIa diamond has been investigated by the Knoop hardness measurement and observation of the cleavage surfaces. It was clarified that the Knoop hardness in (100)100 of synthetic diamonds increases with decreasing of the nitrogen impurities concentration, and that the synthetic type IIa diamond, having few nitrogen impurities, has the highest hardness of synthetic diamonds. In addition, it was found that the Knoop hardness in (100)110 of synthetic type IIa diamond is extremely high, and the anisotropy in the hardness of the diamond is different from those of natural diamond and synthetic type Ib diamond. The cleavage surfaces of the synthetic type IIa diamonds were very smooth and showed remarkably regular cleavage patterns. These results indicate that there are very few impurities and crystal defects in the synthetic type IIa diamond, and also suggest that the diamond has high resistance to plastic flow.     

Spectroscopic and microscopic characterizations of color lamellae in natural pink diamonds

Nineteen natural, untreated, type IaAB pink diamonds from various localities were studied. They display microscopic (～ 1 μm thick) pink lamellae along {111} in an otherwise colorless diamond. This coloration concentrated in lamellae is commonly referred to as “graining”. The diamonds were examined using high spatial resolution spectroscopic methods and transmission electron microscopy. TEM revealed that a pink lamella consists of a cluster of paired microtwins created under stress by plastic deformation. Raman line shift and broadening associated with the twinned pink lamellae indicate the presence of residual stress. Ultraviolet–visible absorption spectra from each of the samples showed a broad absorption band centered at ～ 550 nm, the source of the pink color. Cathodoluminescence spectra of the pink lamellae are different from those of the bulk, colorless diamond matrix. Within the lamellae only, the H3 center is observed along with a less intense N3 center. In some samples, instead of the N3 center a new center with a zero phonon line at 405.5 nm is observed. This previously unreported 405.5 nm center has phonon sidebands qualitatively identical to the N3 center, and may be an N3 center modified by a specific environment. These results suggest that lattice vacancies were created during twinning resulting from plastic deformation, and that impurity centers (such as those containing nitrogen) trap some of the diffusing vacancies. Since the pink lamellae are still under residual stress, new or modified defect centers are created, e.g. H3 and N3. The color center(s) responsible for the pink color (550 nm absorption) was not identified, but likely is only present in diamonds that experienced plastic deformation. Reported annealing of plastically deformed brown diamonds, which results in a residual pink color, suggests that the pink color is stable under these high pressure, high temperature conditions. The reported observations that annealing plastically deformed brown diamonds results in a residual pink color and that the pink color does not anneal out under similar high pressure, high temperature conditions, suggests that the deformation inducing pink color occurs inside the Earth's mantle, whereas brown coloration might be induced during a more recent event such as the ascent of the diamond to the surface in a kimberlitic/lamproitic eruption.     

Small-angle X-ray scattering in type Ia diamonds

The results of a small-angle X-ray scattering (SAXS) investigation of natural and synthetic diamonds, with different types of nitrogen-related defects, are presented. They reveal a presence of impurity-rich spherical clusters with a diameter of approximately 90 Å in an IaB diamond. SAXS scattering in an IaA diamond has a much lower intensity, and originates from larger clusters with a considerable variation in size. It is likely that the dominant impurity in these clusters is nitrogen. Present data suggest the possibility that some of the nitrogen-related point defects (A- and B-centers) are not randomly distributed in the diamond lattice, but instead are concentrated in clusters. It is suggested that, although optical manifestations of the A-nitrogen are similar in different diamonds, IaA diamonds can be divided into two sub-groups. The IaA₁ group includes annealed, synthetic, and some natural diamonds. They contain randomly distributed nitrogen pairs, which do not influence mechanical properties and do not produce X-ray scattering. In the IaA₂ group, the diamond aggregation process went further and the formation of nitrogen-containing clusters began. The process of nitrogen aggregation is described in terms of the decay of a supersaturated solid solution of nitrogen in diamond. The driving force for the creation of impurity clusters is the lowering of the free energy of nitrogen dissolution in the diamond lattice, and the decrease of strain.     

Characterization of pink diamonds of different origin: Natural (Argyle,non-Argyle), irradiated and annealed,treated with multi-process,coated and synthetic

One of the commercial challenges today in the gem industry is to quickly identify the origin of color in pink diamonds — natural, treated and synthetic by use of standard and advanced gemological instruments.An analytical technique that is used by many gem labs involves UV fluorescence. The principle factors in the technique are the excitation wavelengths and the emission spectra. No systematic study of fluorescence of pink natural diamonds, pink treated and pink synthetic diamonds has been undertaken. This study is mainly focused on using fluorescence techniques to characterize pink diamonds and to compile a reference library of emission spectra. Longwave (LW) and shortwave (SW) fluorescence of 365, 254 and 220 nm illumination were used in a custom built microscope with a fluorescence camera to record images and a spectrometer to record spectral data with which to establish a correlation with the cause of color.Other advanced instruments (CL imaging, UV–VIS–NIR, FTIR, PL spectroscopy and electrical conductance) were used to establish additional criteria for distinguishing natural, treated and synthetic pink diamonds and to find a correlation with the “EGL USA CIS (Cross-reference Identification System) fluorescence method”.     

Characterization of top-quality type IIa synthetic diamonds for new X-ray optics

We have performed a complex analysis of top-quality synthetic diamond HPHT type IIa single crystals in view of their potential application as X-ray optics elements, namely as free electron laser mirrors. We have employed X-ray topography and high-resolution diffractometry along with optical spectroscopy techniques for characterization of our synthetic diamonds.     

Formation mechanism of synthetic carbonado type polycrystalline diamond

Carbonados are naturally occurring polycrystalline diamonds in which grain boundary contamination impairs the transparency and renders a dark color to the gemstone. A similar material known as type carbonado synthetic polycrystalline diamond, CSPD, can be synthesized by volume transformation in bulk graphite. In this work the mechanism associated with the formation of CSPD in the reaction chamber of an anvil with concavity high pressure device was studied. This study was based on computational simulation of the field of temperatures developed inside the reaction chamber at the moment of the graphite to diamond transformation. It was found that during the CSPD synthesis, nonsteady conditions of temperature take place resulting in changes in the thermodynamic equilibrium parameters. Experimental results on the microhardness profile of the CSPD were compared with the simulated field of temperature, disclosing a direct relationship. The study has also shown that this microhardness/temperature relationship indicates competing mechanisms occurring during the CSPD synthesis.     

Defects in coloured natural diamonds

Characterization of different types of gem-quality diamonds with UV-VIS-NIR, FTIR and EDXRF spectroscopy reveals a number of optical centers. The colour of the diamonds is clearly caused by a combination of some or all of these centers. Other optically inactive defects can have an effect on the colour of a diamond by influencing the Fermi-level: the relative concentrations of different charged states of a defect in diamond is determined by the Fermi-level. A topographic short-wave UV (225 nm) fluorescence study of growth sector-dependent inclusion of defects in natural diamonds with different colours is also presented. These measurements show that fluorescencent defect centers decorate defect structures connected to growth history of the diamond. On the basis of these characterisation techniques, some interrelationships between different coloured diamonds are highlighted.