Oxidation and diffusion study on AlCrVN hard coatings using oxygen isotopes O and O

The present work aims to investigate the oxidation behaviour of AlCrVN hard coatings of equal composition but of different crystal structure. In order to gain more information about the mechanisms that are active during oxidation, a two-stage oxidation procedure has been applied where different isotopes, ¹⁶O and ¹⁸O, were introduced in each step. The analysis by means of secondary ion mass spectrometry depth profiling with its inherent isotope selectivity provided information on the general oxidation behaviour as well as the oxygen diffusion during the oxidation process. The single-phase coating with its face-centred cubic (fcc) structure presents a higher oxidation resistance as compared to the dual-phase coating containing a wurtzite and an fcc phase. After the annealing treatment the surface of the latter is entirely covered by VO₂ and V₂O₅ as evidenced by Raman spectroscopy. The single-phase coating, on the other hand, reveals unoxidised coating material and AlVO₄ crystals. However, even though exhibiting a significantly different oxidation resistance, the oxygen diffusion is similar. In both cases the peak values of ¹⁸O, which was introduced in the second stage, were found near the oxide-nitride interface indicating that O atoms diffused through the already formed oxides. Additional experiments using a gas mixture comprising natural water vapour H₂¹⁶O and ¹⁸O₂ revealed that mainly the presence of molecular oxygen causes oxidation as with increasing water vapour partial pressure the oxide layer thickness was significantly reduced.     

X-ray photoelectron spectroscopy and thermal desorption spectroscopy comparative studies of L-CVD SnO2 ultra thin films

In this paper we present the results of comparative studies of the chemical stability of L-CVD SnO₂ ultra thin films (20 nm) deposited on the atomically clean Si(100) substrate after their subsequent in situ hydrogenation and oxidation, and then after air exposure. For the control of surface chemistry of these films we used in a comparative way the X-ray Photoemission Spectroscopy (XPS) combined with ion depth profiling (DP XPS) and Thermal Desorption Spectroscopy (TDS). Our XPS experiments showed that the L-CVD SnO₂ ultrathin films after subsequent in situ hydrogenation and oxidation consist of strongly nonstoichiometric layer at the top of Si dioxide substrate. After subsequent air exposure they were covered with undesired 3 monolayers of C contamination and various forms of oxygen. During the TDS procedure a two-step desorption of molecular hydrogen (H₂), water vapor (H₂O), carbon dioxide (CO₂) and atomic oxygen (O) at the temperatures of ~ 530 K and 600 K was observed, respectively. The TDS results were in a good correlation with evident decreasing of the relative concentration of C contaminations, as well as variation of nonstoichiometry of the L-CVD SnO₂ ultra thin films as determined by XPS combined with ion depth profiling.     

The development of a time of flight spectrometer for LARN

An elastic recoil detection time of flight system to depth profile light elements has been developed on ALTAÏS, the new Tandetron accelerator at LARN. The detector mounted at 45° from the beam axis consists of two isochronous electron detectors for the timing signal (START and STOP) and a 450 mm² heavy ion PIPS detector that detects the energy of the recoil atoms. The 2MV Tandem accelerator provides heavy ion beams with a maximum energy of 16 MeV depending on the charge transfer efficiency of the gas exchange canal located in the middle of the machine. A large variety of primary ion beams like ²⁸Si, ³⁵Cl, ⁶³Cu, ¹²⁷I or ¹⁹⁷Au can be produced with the SINIX heavy ion source and accelerated on the target. Typical current around 1 nA can be obtained. The energy transfer to the recoil atoms is typically in the MeV range and depends on the mass and the energy of the projectile. Some secondary effects like the energy loss in the carbon foils of the timing detector but also in the entrance window of the energy detector should not be neglected if we try to depth profile light elements with this technique. Time resolution of about 1 ns for the electrons detectors is suitable to obtain 1 amu mass resolution. Some examples of applications will be developed in this paper.     

Detection system for depth profiling of radiotracers

A reliable and efficient detection system essentially needed in the depth profiling of radiotracers consisting of two large PIN-diode arrays has been constructed. The requirements put forward to the detector system and the ability of the PIN-diode array to meet these demands are discussed. A comparison to a conventionally used liquid scintillation detector is presented by measuring an as-implanted ³¹Si profile in amorphous T21 ceramic by both apparatuses.     

垂直地震剖面的KIRCHHOFF积分偏移

把垂直地震剖面(VSP)资料转换到偏移距—深度域,可以通过 VSP CDP叠加来实现,也可用偏移技术来达到。但是,由于 VSP 为共炮点道集,所含数据量较少,所以用常规偏移方法很难获得良好的偏移效果。本文把传统的 Kirchhoff 积分算法推广到变速的叠前 VSP 资料偏移。要把Kirchhoff 积分算法用于 VSP 资料,其关键在于确定 Kirchhoff 轨迹,这相当于确定以源点和接收点为焦点的一等时轨迹。此轨迹与常规地面地震资料所用的常速 Kirchhoff 积分偏移形成的椭圆轨迹不同。本文采用射线方程来确定这种变速 Kirchhoff 轨迹。这种偏移方法的具体实现步骤和一般叠前偏移方法是一样的,主要包括成像时间的确定、近似的 Kirchhoff 积分记录波场外推和求和成像处理等内容。     

About the role of boundary conditions on compositional imaging with a scanning electron microscope

We consider the effects of different boundaries on the visibility of a specimen detail providing a compositional contrast in scanning electron microscopy, operating with backscattered electrons or secondary electrons. An object characterized by a gradual variation in composition, an As-doped region in Si, is investigated. The different boundaries in the cross-sectioned specimen correspond to the absence or presence of a poly-Si layer on top of the implanted region, deposited after the annealing treatment. It is shown that the interpretation model used for image formation is of paramount relevance for understanding the experimental results, indicating that the boundaries of the doped region are important in hindering or enhancing its visibility. The relevance of experimental parameters such as electron energy and probe dimension is also reported.     

水平井调堵技术最新进展

水平井在开采过程中更容易出现过多产水产气现象，需要采用适当的调堵技术。本文归纳了复杂结构井调堵中应遵循的基本原则，比较详细地介绍了调堵剂置入方式不同的三大类调堵技术：①分隔注入技术，如使用预置式工作筒；②定位注入技术，在割缝套管水平井中使用环空化学封隔层，在连续套管水平井中使用二元注入法；③笼统注入技术。通过对众多现场试验的分析，讨论了高产气、高含水的原因，调堵措施，施工工艺，调堵结果及成功与失败的经验。图2参17。     

Cyclical changes in volatile acidic metabolites of human vaginal secretions and their relation to ovulation

The major volatile constituents in human vaginal secretions were identified. Data collected during the course of 29 cycles from 9 subjects showed that the nature and abundance of the vaginal organic constituents differed with respect to subject. Only 3 of 9 subjects investigated consistently had C₃-C₅ aliphatic acids; acetic acid was present in all subjects. Lactic acid was the major acidic compound consistently found in the vaginal secretion of all subjects near the time of ovulation. Cyclical changes in the acidic constituents were demonstrated.