Extrinsic and intrinsic mode of hydrogen occurrence in natural olivines: FTIR and TEM investigation     

N. R. Khisina  R. Wirth  M. Andrut  A. V. Ukhanov 《Physics and Chemistry of Minerals》2001,28(5):291-301

Olivine crystals from two mantle nodules in kimberlites (pipe Udachnaya and pipe Obnazennaya, Yakutiya, Siberia) were investigated using EMP, TEM, AEM and FTIR techniques to determine the mode of hydrogen occurrence in olivine. Olivine contains three types of nanometer-sized inclusions: “large” inclusions of hexagonal-like shape up to several hundred nm in size (1), lamellar defects (2) and small inclusions of hexagon-like shape up to several 10?nm in size (3). Lamellar defects and small inclusions are considered to be a “hydrous” olivine. All three types of inclusions contain OH^? or water, but they are different with respect to their phase composition. In “large” inclusions (1) hydrous magnesium silicates, such as serpentine?+?talc (“kerolite”?) and 10-Å phase?+?talc were identified. Lamellar defects (2) and small inclusions (3) are depleted in Mg and Fe compared to the olivine matrix, while the silica content is the same as that of olivine. Modulations in the periodicity of the olivine structure are observed in SAED patterns and HREM images of (2) and (3). The superperiodicity can be referred to OH^?-bearing point defect ordering in the olivine structure. If this is the case, the material of both lamellar defects and small inclusions can be assumed to be a “hydrous olivine” Mg_{2– x} v _x SiO₄H_{2 x} with a cation-deficient olivine crystal structure. Thus, both an extrinsic mode of hydrogen occurrence in olivine, such as nanometer-sized inclusions of OH^?-bearing magnesium silicates, and an intrinsic mode of hydrogen incorporation into the olivine structure, such as “hydrous olivine” in itself, were found. The data obtained here show that the OH absorption bands observed in olivine spectra at 3704(3717) and 3683(3688) cm^?1 can be unambiguously identified with serpentine; the band at 3677(3676) cm^?1 can be associated with talc. The absorption bands observed at 3591 and 3660?cm^?1 in olivine match those of the 10-Å phase at 3594, 3662 and 3666?cm^?1.  相似文献   

Ionizing radiation-induced defects in smectite clays     

D. Gournis  A. E. Mantaka-Marketou  M. A. Karakassides  D. Petridis 《Physics and Chemistry of Minerals》2001,28(4):285-290

 The interaction of γ-rays with smectites induces paramagnetic defects in the structure of these clay minerals. The EPR spectra of three different smectites detect the creation of structural defects and trapping of organic free radicals in the clay structure upon irradiation. The defects are assigned to positive holes or trapped electrons stabilised by existing local charge imbalances in the mineral lattice. The organic radicals are derived from organic compounds present as impurities in the crystal lattice of the clay minerals. In addition, γ-rays cause migration of small interlayer cations (such as Li⁺) into the layers, as clearly evidenced by EPR and FT-IR reflectance spectroscopies. Received: 20 April 2000 / Accepted: 2 December 2000  相似文献   

Point defects in crystalline zircon (zirconium silicate), ZrSiO<Subscript>4</Subscript>: electron paramagnetic resonance studies     

W. C.?TennantEmail author  R. F. C.?Claridge  C. J.?Walsby  N. S.?Lees 《Physics and Chemistry of Minerals》2004,31(4):203-223

This article outlines the present state of knowledge of paramagnetic defects in crystalline zircon as obtained mainly, but not exclusively, from electron paramagnetic resonance (EPR) studies in crystalline zircon (zirconium silicate, ZrSiO₄). The emphasis is on single-crystal studies where, in principle, unambiguous analysis is possible. Firstly, the crystallography of zircon is presented. Secondly, the relationships between available crystal-site symmetries and the symmetries of observed paramagnetic species in zircon, and how these observations lead to unambiguous assignments of point-group symmetries for particular paramagnetic species are detailed. Next, spin-Hamiltonian (SH) analysis is discussed with emphasis on the symmetry relationships that necessarily exist amongst the Laue classes of the crystal sites in zircon, the paramagnetic species occupying those sites and the SH itself. The final sections of the article then survey the results of EPR studies on zircon over the period 1960–2002.  相似文献   

Features of coated diamonds from the Snap Lake/King Lake kimberlite dyke, Slave craton, Canada, as revealed by optical topography     

A.P Yelisseyev  N.P. Pokhilenko  J.W. Steeds  D.A. Zedgenizov  V.P. Afanasiev 《Lithos》2004,77(1-4):83-97

Confocal photoluminescence (PL) and local absorption spectroscopy were used to study the types and spatial distribution of point defects in coated diamonds, the input of which is about 30% in the Snap Lake deposit, Canada. Nitrogen concentration is on the level of several hundreds of ppm in the core, with a nitrogen-poor layer in its outer part, whereas in the coat it is usually several times higher as a result of fast growth. Nitrogen defects in the core are strongly aggregated with N3, B and B′-forms dominating, whereas A-defects are typical of the coat. The rounded shape of the coated diamonds is a result of the combined effect of partial dissolution of the octahedral core and the “abnormal” growth of the coat, which produces a fibrous structure. Analysis of PL and PL excitation spectra showed that structureless yellow-green PL of the coat is likely to be due to nickel-nitrogen complexes with their fine structure broadened in the strain fields. The presence of irradiation/annealing products such as vacancies V⁰ and nitrogen-vacancy complexes NV⁻, N₂V₂ shows that the diamonds studied have undergone post-growth ionizing irradiation with further low-temperature annealing in natural conditions.  相似文献   

岩石颗粒边界缺陷分布的概率模型   总被引：1，自引：0，他引：1  

王庚荪  袁建新 《岩土力学》1995,16(1):26-34

本文应用概率理论，研究了颗粒结构材料初始边界缺陷的分布问题，提出了一个概率模型，认为材料中的初始边界缺陷不会全部都是孤立地分布，总会有二个、三个或更多个基本边界缺陷相连在一起组成缺陷族的情况，缺陷簇的个数的数学期望值相对于其尺度符合指数衰减强度，衰减指数与缺陷发生的概率及边界网络的相似维数有关。推导得出了颗粒结构材料的拉伸强度与试样尺度、颗粒尺度及缺陷发生概率之间的关系，从理论上论证了材料强度的尺  相似文献   

基桩桩身完整性检测中的影响因素浅析          下载免费PDF全文

薛桂霞  王鹏 《地球物理学进展》2008,23(5):1646-1650

近年来,桩基础的广泛应用带动了检测技术的进一步发展,基桩检测技术也越来越受到人们的重视.本文从反射波理论出发介绍了反射波法的基本原理,指出了桩身完整性的判定标准,并系统的分析了基桩检测中的多种影响因素.本文通过分析和总结,指出了反射法测桩存在的不足,并提出了相应的注意事项及解决办法.  相似文献   

基于贝叶斯理论的灌注桩多个缺陷统计特性分析   总被引：1，自引：0，他引：1  

李典庆  吴帅兵  周创兵 《岩土力学》2008,29(9):2492-2497

由于施工技术水平、岩土工程条件等不确定性因素的影响,基桩中经常出现各种缺陷。为此,提出了基于贝叶斯理论的灌注桩多个缺陷统计特性的分析方法。在考虑钻芯法检测不确定性的基础上,采用泊松分布模型模拟基桩中多个缺陷的出现概率,推导了缺陷平均出现率后验分布的计算公式。提出了估计缺陷尺寸修正的贝叶斯抽样方法,给出了评价钻芯法检测概率的方法。算例分析表明,钻芯法的检测概率对准确地估计缺陷平均出现率有明显的影响,如果不考虑检测不确定性因素的影响,缺陷平均出现率将被低估。随着检测到缺陷数目的增加,更新的缺陷平均出现率的均值逐渐增加,更新的变异系数逐渐减小。此外,先验的信息能够有效地减小缺陷平均出现率和缺陷尺寸估计的不确定性。  相似文献   

均匀黏弹性地基中现浇X形桩低应变动测响应数值模拟          下载免费PDF全文

范玉明  丁选明  朱振生  付强 《地震工程学报》2015,37(2):612-618

建立现浇X形桩(XCC桩)桩-土体系三维有限元模型,对XCC桩低应变检测动力响应进行数值模拟,得到完整桩和缺陷桩的桩顶速度响应结果,并分析完整桩及缺陷XCC桩桩顶速度响应特性及规律。计算结果表明:XCC桩低应变瞬态动测时桩顶速度响应存在明显的三维效应,桩心(激振点)附近点的入射波峰值较大,且到达时间较早;距离桩心越远点的入射波峰到达时间越滞后,入射波峰值从桩心到尖角边界先减小后增大。桩顶距桩心距离相同的环向上各点的入射波和反射波区别不大,而各点所受的高频干扰情况并不相同。变模量桩的入射波和完整桩相同,反射波峰值较完整桩小,反射波峰对应时间较完整桩滞后。局部缺陷桩桩顶距桩心距离相同环向各点的第一个缺陷反射波有微小差别,而第二个缺陷反射波有较大差别。  相似文献   

钢箱梁典型病害分析及其检测与维护技术研究   总被引：3，自引：0，他引：3  

姜竹生  瞿涛  吕磊  吉伯海 《地震学刊》2011,(5):572-577

基于对我国钢箱梁桥的钢箱梁病害调查,总结出我国钢箱梁典型病害的类型,分析各种钢箱梁典型病害产生的机理及导致其破坏的原因,提出了钢箱梁病害的日常检测与维护技术。针对钢箱梁的涂装劣化、钢材腐蚀、结构性损伤等病害,给出了日常检测与维护的主要项目,介绍了人工目视检测、超声波检测、磁粉检测及涡流检测等主要的检测方法的工作原理、优缺点和适用范围。  相似文献   

山西省原平市神经管畸形时空分析     

陈会宴  廖一兰  张宁旭  徐冰 《地球信息科学学报》2017,19(4):502-510

神经管畸形是发生于中枢神经系统的一种先天性异常,在所有的新生儿出生缺陷中所占比例较高。在我国,作为矿业大省的山西,神经管畸形最为严重,原平市又是山西省出生缺陷的高发市之一。本文利用山西省原平市2007-2012年的神经管畸形病例资料,基于贝叶斯理论的时空建模方法,综合考虑时间组分和时空交互组分,对神经管畸形的时空规律进行研究。研究识别了研究区内疾病发生的热点区域、冷点区域、温点区域,并对这些区域随时间的变化趋势进行了分析。研究发现,原平市18个乡镇中有1个热点区域、17个温点区域,整体发病率较高;原平市神经管畸形整体上随时间变化呈缓慢下降趋势,但该趋势并不明显;1个热点区域疾病风险下降趋势慢于整体趋势,4个温点区域疾病风险下降趋势快于整体趋势,13个温点区域疾病风险时间变化趋势与整体趋势趋同。本文识别了山西省原平市神经管畸形发病的时间趋势和空间趋势,可以揭示神经管畸形潜在的风险因子或控制措施供进一步流行病学研究,也可以为公共卫生部门制定及时有效的防治控制措施提供一定的科学参考。  相似文献