高硫煤镜质组热解过程中结构变化及有机硫形态变迁规律研究

用手选富集与离心分离相结合的方法,从两种全硫含量相近的新西兰煤(NXL;St,ad=1.84%)和山西煤(SX;St,ad=1.80%)中分离出高纯度镜质组。在高纯Ar气氛下,分别制备了300、500、700和1 000℃下的镜质组焦。用FT-IR研究了两种镜质组中的脂肪氢、芳香氢随温度的变化,结果表明,SX镜质组中脂肪氢的相对含量较高,在热解过程中活性高于同温度下的NXL镜质组;两种镜质组中的脂肪氢相对含量都随温度升高而降低,温度高于500℃时,SX镜质组中脂肪氢相对含量基本不变,当温度高于700℃时,NXL镜质组中的脂肪氢相对含量基本保持不变;热解过程芳香氢都表现出先增大后减小的趋势。用XPS研究了镜质组中的有机硫含量及形态随温度的变化,结果表明,SX镜质组中易分解的有机硫化物较多,在300℃以下即可分解完全;NXL镜质组中的有机硫化物分解完全在700℃左右,两种镜质组中的噻吩类硫的含量都随热解温度的升高而增加,砜类硫的含量随热解温度的升高而降低。     

红外反射光谱电化学中薄层电解池效应的研究

用双电位阶跃计时电流法,动电位扫描等电化学技术和红外光谱法系统测定了现场红外镜反射式电解池中的薄层厚度,电化学特性和光谱特性。结果表明,红外光谱电化学研究中的电解池存在定量的薄层电解效应。     

高硫煤镜质组热解过程中结构变化及有机硫形态变迁规律研究

用手选富集与离心分离相结合的方法,从两种全硫含量相近的新西兰煤（NXL;S_t,ad=1.84%）和山西煤（SX;S_t,ad=1.80%）中分离出高纯度镜质组。在高纯Ar气氛下,分别制备了300、500、700和1 000 ℃下的镜质组焦。用FT-IR研究了两种镜质组中的脂肪氢、芳香氢随温度的变化,结果表明,SX镜质组中脂肪氢的相对含量较高,在热解过程中活性高于同温度下的NXL镜质组;两种镜质组中的脂肪氢相对含量都随温度升高而降低,温度高于500 ℃时,SX镜质组中脂肪氢相对含量基本不变,当温度高于700 ℃时,NXL镜质组中的脂肪氢相对含量基本保持不变;热解过程芳香氢都表现出先增大后减小的趋势。用XPS研究了镜质组中的有机硫含量及形态随温度的变化,结果表明,SX镜质组中易分解的有机硫化物较多,在300 ℃以下即可分解完全;NXL镜质组中的有机硫化物分解完全在700 ℃左右,两种镜质组中的噻吩类硫的含量都随热解温度的升高而增加,砜类硫的含量随热解温度的升高而降低。     

基于局部口径波前探测的大口径太阳望远镜次镜姿态校正方法

为应对大口径天文望远镜因结构弯沉和形变导致的次镜姿态失调、系统像质退化等问题,本文提出了采用小口径平行光源构造人工星点,配合夏克哈特曼波前传感器,利用局部口径波前探测获得局部波像差信息以计算次镜失调量,并结合精密六足位移平台实现次镜姿态实时校正的方法。本文基于目前正在研制中的1 m口径离轴格里高利太阳望远镜实际参数,采用光学软件模拟和数学仿真方法,分析了局部口径的波前探测可行性。仿真结果表明,当选取局部口径直径为200 mm、波前传感器像点质心偏移探测精度达到0.01μm时,即可有效提取波像差信息,以此计算次镜姿态并加以校正,可满足望远镜光学系统像差要求。     

用扫描电镜测量纳米级标准长度的倾斜误差计算

用扫描电镜测量纳米级长度的时候[1, 2],被测长度的倾斜会导致被测长度产生误差,通常称其为倾斜误差.本文对于倾斜误差进行了实验和分析.给出了倾斜误差与倾斜角度的关系公式和对应数据表,同时提出了减小或消除倾斜误差的方法,为提高测量准确度,建立标准测量方法[3],创造了条件.     

煤岩组分在二硫化碳-N-甲基-2-吡咯烷酮混合溶剂中的可溶性

在常温常压下用二硫化碳Ｎ甲基２吡咯烷酮（ＣＳ２ＮＭＰ）混合溶剂对徐州庞庄煤和淮北童亭煤中的各宏观煤岩组分进行了萃取实验，考察了宏观煤岩组分与其可溶性的关系。结果表明：所研究的两种煤中的各宏观煤岩组分在ＣＳ２ＮＭＰ混合溶剂的可溶性顺序为：镜煤＞亮煤＞暗煤＞丝炭；各宏观煤岩组分的可溶性的差别与其中镜质组成分含量，尤其是无结构镜质体含量密切相关。     

树皮体加热状态HRTEM变化特征及其热重特性研究

以中国特殊显微组分树皮体作为研究对象,并与镜质体和树皮煤进行比较,通过热重实验分析了树皮体的热行为特性,并运用原位加热透射电镜(HRTEM)研究了树皮体在线受热后其化学结构变化特征,并进一步分析了树皮体热性质特性的原因。研究表明,相比于镜质体和树皮煤,树皮体在受热过程中的失重总量和热解最大速率均高,而三个样品的热解最大速率温度接近。在350℃之后,树皮体和镜质体的化学结构均具有定向性,且随着温度的升高,其定向性越明显。树皮体和镜质体分别在400和450℃时,呈现芳香层片堆积。同一温度条件下比较发现,树皮体和镜质体化学结构中以萘、2×2和3×3条纹为主;其次是4×4和5×5条纹。相比较而言,树皮体的萘含量高于镜质体,而镜质体中的3×3、4×4和5×5条纹的含量高于树皮体。在350-500℃,随着温度的逐渐升高,树皮体和镜质体中的萘含量增加,在450℃时,其萘的含量达到最高。树皮体的热解行为特性与其加热过程中化学结构特征变化有关,尤其是萘的含量变化。     

原位漫反射红外光谱中采用新的实验手段研究煤岩显微组分中的氢键

首次提出采用小瓷片反应器,结合增大载气流量的方法进行产生挥发组分固体的原位漫反射红外光谱实验,研究了两种煤的镜质组和丝质组中的氢键分布及热稳定性.两种显微组分间氢键分布的规律相似;镜质组中SH-N、羧酸二聚体和自缔合羟基等的热稳定性比丝质组中的高.但对OH-N、羟基四聚体和OH-OR₂的热稳定性随煤岩组分的变化无明显规律;随着温度的升高,OH-π含量先升高后降低,于350～380℃达最大值,其中镜质组OH-π的含量增加较快.显微组分中氢键的变化规律反映了其结构上的差异.     

倾斜潮汐分析及海潮负荷效应

本文采用引潮势、太阳热辐射能流和引力潮的非线性效应作为输入函数,同时提出以海潮潮族作为海潮负荷效应的输入函数对一年实测的倾斜潮汐进行总体响应分析,将频率相同的倾斜引力潮、负荷潮、辐射潮和非线性潮分离开。另外还以j,v模型对倾斜潮汐和分离开的各部分倾斜潮进行了调和分析,进而计算其旋转椭圆要素。     

计算海潮产生的地倾斜负荷潮的积分Green函数方法

本文提出的计算地倾斜负荷潮的积分Green函数方法是对目前普遍采用的Farrell方法的改进和发展,是一种新的计算方法。本方法首先求出地倾斜负荷潮Green函数的不定积分,再根据海潮图,通过简单的代数运算即可求出全球海潮分波在地面上任一点产生的地倾斜负荷潮。作为本方法的应用实例,根据Schwiderski海潮图计算了全球海潮M_2分波分别在武昌、泰安、徐州等台站产生的地倾斜负荷潮。     

A new compact interferometer design

The optical layout of a compact interferometer suitable for Fourier transform spectroscopy is presented. The constraints on the practical implementation of this design are discussed. Specifications are given for the collimating optics, the optical finish of the interferometer components, and the allowable mirror tilt.     

Reflective thermal lens detection device

A reflective thermal lens detection device was developed for realizing a portable and sensitive detector for a microsystem. An aluminum mirror was formed on the main plate of a microchip, and a reflected probe beam was detected with a single pick-up unit. The background signal due to light absorption of the aluminum mirror was 60 times reduced when the microchannel and the mirror were separated with an interval of 600 microm. The tilt angle of the microchip significantly affected the precision of the measurement. Then a quadrant photodiode was used to detect the center of gravity of the reflected probe beam to regulate the tilt angle within +/-0.05 degrees , and this value was enough to achieve 1% CV (coefficient of variance) precision in the measurements. The limit of detection (LOD) was 60 nM for xylene cyanol solution, and the absorbance was 9.4 x 10(-6) AU. About 40 times higher sensitivity was obtained in comparison with a spectrophotometer.     

Tilt of atomic force microscope cantilevers: effect on spring constant and adhesion measurements

In atomic force microscopy, the cantilevers are mounted under a certain tilt angle alpha with respect to the sample surface. In this paper, we show that this increases the effective spring constant by typically 10-20%. The effective spring constant of a rectangular cantilever of length L can be obtained by dividing the measured spring constant by cos2 alpha(1 - 2D tan alpha/L). Here, alpha is the tilt angle and D is the size of the tip. In colloidal probe experiments, D has to be replaced by the radius of the attached particle. To determine the effect of tilt experimentally, the adhesion force between spherical borosilicate particles and planar silicon oxide surfaces was measured at tilt angles between 0 degrees and 35 degrees. The experiments revealed a significant decrease of the mean apparent adhesion force with a tilt of typically 20-30% at alpha = 20 degrees. In addition, they demonstrate that the adhesion depends drastically on the precise position of contact on the particle surface.     

Mechanical and charge transport properties of alkanethiol self-assembled monolayers on a au(111) surface: the role of molecular tilt

The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAMs) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant beta = 0.57 +/- 0.03 A-1 was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of approximately 1 A-1 found when the separation is varied by changing the length of the alkanethiol molecules. Calculations indicate that, for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.     

Tuning molecular orientation with STM at the solid/liquid interface

Triptycene molecular orientation has been tuned with a STM tip at a Cu(111) surface in solution from flat, to tilt, to vertical. The tuning is completely bias dependent and reversible. The study is important in the fields of nanoscience and technology.     

Glass fracture surfaces seen with an atomic force microscope

Fracture surfaces of Suprasil 2, Herasil 2, AR glass and Duran glass rods have been studied by an atomic force microscope (AFM) in the contact mode. They could be characterized in the fracture mirror, the mist and the hackle zones. The RMS (root mean square) roughness in the fracture mirror of all glasses investigated increased with growing distance from the origin of the fracture. On several fracture surfaces of different glasses steps have been observed, due to fracture in shear mode. Furthermore changes in the fracture surfaces during scanning have also been observed. They are thought to stem from reactions of the freshly broken glass surface with the surrounding atmosphere and forces between the scanning tip and the soft surface.     

Interaction of scanning probes with semiconductor nanocrystals; physical mechanism and basis for near-field optical imaging

We investigate the modification of photoluminescence (PL) from single semiconductor nanocrystal quantum dots (NCs) in the proximity of metal and semiconducting atomic force microscope (AFM) tips. The presence of the tip alters the radiative decay rate of an emitter via interference and opens efficient nonradiative decay channels via energy transfer to the tip material. These effects cause quenching (or enhancement) of the emitter's PL intensity as a function of its distance from the interacting tip. We take advantage of this highly distance-dependent effect to realize a contrast mechanism for high-resolution optical imaging. AFM tips are optimized as energy acceptors by chemical functionalization with InAs NCs to achieve optical resolution down to 30 nm. The presented experimental scheme offers high-resolution optical information while maintaining the benefits of traditional AFM imaging. We directly measure the PL intensity of single NCs as a function of the tip distance. Our results are in good agreement with calculations made by a classical theoretical model describing an oscillating dipole interacting with a planar mirror.     

Large-scale molecular dynamics simulations of alkanethiol self-assembled monolayers

Large-scale molecular dynamics simulations of self-assembled alkanethiol monolayer systems have been carried out using an all-atom model involving a million atoms to investigate their structural properties as a function of temperature, lattice spacing, and molecular chain length. Our simulations show that the alkanethiol chains of 13-carbons tilt from the surface normal by a collective angle of 25 degrees along next-nearest-neighbor direction at 300 K. The tilt structure of 13-carbon alkanethiol system is found to depend strongly on temperature and exhibits hysteresis. At 350 K the 13-carbon alkanethiol system transforms to a disordered phase characterized by small collective tilt angle, flexible tilt direction, and random distribution of backbone planes. The tilt structure also depends on lattice spacing: With increasing lattice spacing a the tilt angle increases rapidly from a nearly zero value at a=4.7 A to as high as 34 degrees at a=5.3 A at 300 K for 13-carbon alkanethiol system. Finally, the effects of the molecular chain length on the tilt structure are significant at high temperatures.     

AES depth profiling with a tilted sample in front of a cylindrical mirror analyzer: quantification and profile shape changes according to an extension of the conventional MRI model

The influence of the tilt angle of a sample in front of a cylindrical mirror analyzer (CMA) on AES depth profiles is calculated with the conventional mixing‐roughness‐information (MRI) depth model and an extended MRI model. While the conventional model works with an average electron escape depth value, the extended model takes into account the intensity from different segments along the azimuth angle corresponding to different escape depth values before summing up for the total, measured intensity. The deviation between both approaches is generally less than 4%, even for the worst case at 47.7° tilt angle. The shape of the profile is slightly different for both approaches. Because, for a CMA with coaxial gun, the sample tilt angle varies as the electron beam incidence angle, the influence of the latter has to be additionally taken into account for quantification of AES. In reasonable agreement with experimental results it is shown that above 45° the Auger peak intensity of Cu (914 eV) increases up to about a factor of two for an incidence angle of 85°. Copyright © 2006 John Wiley & Sons, Ltd.     

Imaging Nanometre‐Sized Hot Spots on Smooth Au Films with High‐Resolution Tip‐Enhanced Luminescence and Raman Near‐Field Optical Microscopy

A novel near‐field optical microscope based on a parabolic mirror is used for recording high‐resolution tip‐enhanced photoluminescence (PL) and Raman images with unprecedented sensitivity and contrast. The measurements reveal small islands on the Au surface with dimensions of only a few nanometres with locally enhanced Au PL. These islands appear as nanometre‐sized hot spots in tip‐enhanced Raman microscopy when benzotriazole molecules adsorbed on the Au surface serve as local sensors for the optical field. The spectra show that localized plasmons are the cause of both the locally enhanced Au PL and enhanced Raman scattering. This finding suggests that the dispersive background in the surface‐enhanced Raman spectra can be explained simply by the enhanced Au PL in the gap. Furthermore, our results show that the surface flatness must be better than 1 nm, to provide an optically homogeneous substrate for near‐field enhanced PL and Raman spectroscopy.