Simulation of interphase boundary of Ni_(75)Al_xV_(25-x )alloys using microscopic phase-field method

The evolution of ordered interphase boundary (IPB) of Ni75AlxV25-x alloys was simulated using the microscopic phase-field method. Based on the atomic occupation probability figure on 2D and order parameters, it was found that the IPB formed by different directions ofθ phase has great effect on the precipitation of γ ′ phase. The γ ′ phase precipitated at the IPB that is formed by [1 00]θ direction where the ( 001)θ plane is opposite, and then grows up and the shape is strap at final. The IPB structure between γ ′phase andθ phase is the same. There is no γ ′ phase precipitate at the IPB where the ( 002)θ and ( 001)θ planes are opposite, the ordered IPB is dissolved into disordered area. There is γ ′ phase precipitation at the IPB formed by the [ 001]θ and [1 00]θ directions, and the IPB structure is different between γ ′ phase and the different directions ofθ phase. The IPB where ( 001)γ′ and (1 00)θ plane opposite does not migrate during the γ ′ phase growth, and γ ′ phase grows along [1 00]θdirection.

Quantitative determination of PFC3D microscopic parameters

It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the microscopic parameters of parallel-bonded particle model for three-dimensional discrete element particle flow code(PFC3D).Variation ranges of microscopic of the microscopic parameters are created by analyzing the effects of microscopic parameters on macroscopic parameters(elastic modulus E,Poisson ratio v,uniaxial compressive strengthσc,and ratio of crack initial stress to uniaxial compressive strengthσci/σc)in order to obtain the actual uniform design talbe.The calculation equations of the microscopic and macroscopic parameters of rock materials can be established by the actual uniform design table and the regression analysis and thus the PFC3D microscopic parameters can be quantitatively determined.The PFC3D simulated results of the intact and pre-cracked rock specimens under uniaxial and triaxial compressions(including the macroscopic mechanical parameters,stress−strain curves and failure process)are in good agreement with experimental results,which can prove the validity of the calculation equations of microscopic and macroscopic parameters.

Single-factor analysis and interaction terms on the mechanical and microscopic properties of cemented aeolian sand backfill

The use of aeolian sand(AS)as an aggregate to prepare coal mine cemented filling materials can resolve the problems of gangue shortage and excessive AS deposits.Owing to the lack of research on the mechanism of cemented AS backfill(CASB),the response surface method(RSM)was adopted in this study to analyze the influence of ordinary Portland cement(PO)content(x_(1)),fly ash(FA)-AS(FA-AS)ratio(x_(2)),and concentration(x_(3))on the mechanical and microscopic properties of the CASB.The hydration characteristics and internal pore structure of the backfill were assessed through thermogravimetric/derivative thermogravimetric analysis,mercury intrusion porosimetry,and scanning electron microscopy.The RSM results show that the influence of each factor and interaction term on the response values is extremely significant(except x_(1)x_(3),which had no obvious effect on the 28 d strength).The uniaxial compressive strength(UCS)increased with the PO content,FA-AS ratio,and concentration.The interaction effects of x_(1)x_(2),x_(1)x_(3),and x_(2)x_(3) on the UCS at 3,7,and 28 d were analyzed.In terms of the influence of interaction items,an improvement in one factor promoted the strengthening effect of another factor.The enhancement mechanism of the curing time,PO content,and FA-AS ratio on the backfill was reflected in the increase in hydration products and pore structure optimization.By contrast,the enhancement mechanism of the concentration was mainly the pore structure optimization.The UCS was positively correlated with weight loss and micropore content but negatively correlated with the total porosity.The R^(2) value of the fitting function of the strength and weight loss,micropore content,and total porosity exceeded 0.9,which improved the characterization of the enhancement mechanism of the UCS based on the thermogravimetric analysis and pore structure.This work obtained that the influence rules and mechanisms of the PO,FA-AS,concentration,and interaction terms on the mechanical properties of the CASB provided a certain theoretical and engineering guidance for CASB filling.

Nuclear magnetic resonance(NMR) microscopic simulation based on random-walk: Theory and parameters analysis

The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was employed as an alternative approach to verify some theoretical aspects of NMR responses. Firstly, the basic principles of pore-scale NMR simulation based on random-walk method(RWM) were introduced. The RWM-simulated results were benchmarked with the analytical results for an ideal spherical pore model. Then, the effects of two numerical parameters, namely diffusion radius and walk numbers, were studied on the simulation accuracy. The simulation method is then applied to various pore models with different pore sizes and pore shapes filled with different fluids to study the microscopic NMR response characteristics. The numerical experiments are useful for understanding and interpreting NMR measurements and the simulation code provides a numerical tool to perform pixel-based digital rock analysis.

Monte Carlo method in optical atomic force microscopy

Scanning probe microscopy(SPM)is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen.Atomic force microscopy is one of the SPM family which is considered as a very versatile tool for surface imaging and measurements.A wide range of various samples can be measured regardless of being conductive,no-conductive,in vacuum,in air or in a fluid as a unique feature.One of the most challenges in atomic force microscopes(AFMs)is to evaluate the associated uncertainty during the surface measurements by AFMs.Here,an optical AFM is calibrated through the calibration of XYZ stage.The approach is to overcome difficulties experienced when trying to evaluate some uncertainty components which cannot be experimentally determined i.e.tip surface interaction forces and tip geometry.The Monte Carlo method is then used to determine the associated uncertainties due to such factors by randomly drawing the parameters according to their associated tolerances and their probability density functions(PDFs).The whole process follows supplement 2 to“the guide to the expression of the uncertainty in measurement”(GUM).The approach validated in the paper shows that the evaluated uncertainty in AFM is about 10 nm.

Quantitative XRD Analysis of Cement Clinker by the Multiphase Rietveld Method

Quantitative phase analysis of Portland cement clinker samples was performed using an adaptation of the Rietveld method.The Rietveld quantitative analysis program,originally in Fortran 77 code,was significantly modified in visual basic code with windows 9X graph user interface,which is free from the constraint of direct utilizable memory 640 k,and can be conveniently operated under the windows environment.The Rietveld quantitative method provides numerous advantages over conventional XRD quantitative method,especially in the intensity anomalies and superposition problems.Examples of its use are given with the results from other methods.It is concluded that,at present,the Rietveld method is the most suitable one for quantitative phase analysis of Portland cement clinker.

Preparation of YAG:Ce^(3+) phosphor by sol-gel low temperature combustion method and its luminescent properties

YAG:Ce3+ phosphor was prepared by sol-gel low-temperature combustion method. The effects of the precursor properties and calcining temperature on the crystallization process, microscopic morphology and luminescent properties of phosphor were studied. The results indicate that the pure phase of YAG can be obtained at 800 ℃ by sol-gel low temperature combustion method, using citric acid as complexing agent. When the molar ratio of metal ion to citric acid is 2.0 and pH value is 2, the crystallinity increases and the phosphor particle size grows up gradually with the increase of the calcining temperature. The powders were characterized through thermal analysis, X-ray diffraction analysis and scanning electron microscope analysis. The excitation spectra of YAG:Ce3+ phosphor take on a double peak structure, and the peak value of the main excitation spectra occurs at 460 nm and that of the emission spectra is near 530 nm. With the gradual increase of the calcining temperature, the peak position of excitation and emission spectra remains basically unchanged, but its relative intensity increases gradually.

The Preparation of Nano Silver by Chemical Reduction Method

A silver nanostructures prepared by using chemical reduction method. The silver nanoparticles were prepared with diameters of about (20 nm). Numerous techniques had been used to study the optical, structural like the UV-Vis absorption spectrometer, Ttransmission Electron Microscopy (TEM), Field-Emission Scanning Electron microscope (FESEM), and X-ray diffraction (XRD). The practical results exhibited the absorption spectrum of the prepared nanoparticles at (357 nm), it was found that there is a relationship between the positions of the optical absorption peak and the size of the silver nanoparticles. The analysis of TEM results showed the presence of nanoparticles in the range (20 nm). The analyzing of XRD results explained the crystal structure for silver nanoparticles. It is found a cubic unit cell have a lattice constants (a = 4.0855 Å), with the Miller indices were (111), (002), (002), and (113).

Structural and Piezoelectric Properties of Sr_(0.6)Ba_(0.4)Nb_2O_6 Micro-rods Synthesized by Molten-Salt Method

Sr0.6 Ba0.4 Nb2 O6 micro-rods are prepared by the molten-salt method with K2 SO4,KCl-K2 SO4,and KCl as fluxes.It reveals that the Sr0.6 Ba0.4 Nb2 O6 synthesized with KCl as a flux exhibits a single phase with tetragonal tungsten bronze structure.The measurement of X-ray diffraction indicates that the Sr0.6 Ba0.4 Nb2 O6 micro-rods synthesized at 1 300℃are anisotropic.The morphology of the powers is examined by transmission electron microscope.It reveals that the length-diameter ratio of Sr0.6 Ba0.4 Nb2 O6 micro-rods increases with increasing annealing temperature from 900℃to 1 300℃.At 1 300℃,the rod possesses a large length-diameter ratio of 8∶1.Moreover,the analysis of the piezoelectric properties of single micro-rods using apiezo-response force microscope indicates that the domains of the material are arranged along its radial direction.

Fabrication and Characterization of Au Nanoparticle-aggregated Nanowires by Using Nanomeniscus-induced Colloidal Stacking Method

We fabricate and characterize Au nanoparticle-aggregated nanowires by using the nano meniscus-induced colloidal stacking method. The Au nanoparticle solution ejects with guidance of nanopipette/quartz tuning fork-based atomic force microscope in ambient conditions, and the stacking particles form Au nanoparticle-aggregated nanowire while the nozzle retracts from the surface. Their mechanical properties with relatively low elastic modulus are in situ investigated by using the same apparatus.

Film-Forming Properties of Fullerene Derivatives in Electrospray Deposition Method

Thin films of three types of fullerene derivatives were prepared through the electrospray deposition (ESD) method. The optimized conditions for the fabrication of the thin films were investigated for different types of fullerene derivatives: [6,6]-phenyl-C61-butyric acid methyl ester, [6,6]-phenyl-C71-butyric acid methyl ester, and indene-C60-monoadduct. The spray diameter during the ESD process was observed as a function of the supply rate achieved by changing the applied voltage. In all cases, the spray diameter increased with increasing applied voltage, reaching the maximum diameter (Dmax) in the voltage range 4 to 6 kV. It was clear that Dmax was influenced by the dipole moments of the fullerene derivatives (as calculated by density functional theory methods). Scanning electron microscopy observation of the?fabricated thin films showed that imbricated structures were formed through the stacking of the fullerene-derivative sheets. Atomic force microscopy images revealed that the density of the imbricated structure was dependent on the spray diameter during the ESD process, and the root-mean-square roughness of the film surface decreased with increasing applied voltage. These findings suggest that the ESD method will be effective for the preparation of fullerene-derivative thin films for the production of organic devices.

银耳多糖对麦醇溶蛋白纳米体系的影响及复合物的特性研究

该研究是以提高麦醇溶蛋白(gliadin,Gli)纳米颗粒(gliadin nanoparticles,GNPs)稳定性为目标,利用银耳多糖(Tremella fuciformis polysaccharides,TFPs)的乳化性能,探究TFPs添加量对GNPs稳定性的影响。采用反溶剂法制备银耳多糖和麦醇溶蛋白复合载体颗粒(gliadin-Tremella fuciformis polysaccharides composite nanoparticles,G/T NPs),并利用纳米粒度仪、傅里叶变换红外光谱仪、热场发射扫描电镜对G/T NPs的粒径和电位、相互作用、微观结构进行分析。结果表明,TFPs和Gli之间通过静电作用力和氢键作用力相结合,形成GNPs在内、TFPs外层附着的复合颗粒;TFPs的添加能够有效提高GNPs体系的稳定性,减少颗粒之间的聚集,制得的G/T_(4∶1)NPs的平均粒径、多分散指数(polydispersion index,PDI)、ζ-电位分别为(198.5±2.6)nm、0.269±0.005、(36.7±0.6)mV,且具有pH响应性。该研究为后续构建疏水营养成分的包埋和运载体系奠定了基础。

高能激光光束质量β因子测量方法

高能激光光束质量β因子测量装置主要用于强激光系统状态调试和综合性能参数诊断,用于评价激光系统出光性能以及远场光斑可聚焦的能力。针对接近衍射极限光束质量β因子测量过程中被测光斑在面阵相机上所占的像素点太少等缺陷,研究了采用聚焦显微放大与高精度扫描狭缝相结合的光束质量β因子测量方法,并对相关方案进行了分析计算。此外还设计了采用固定像差元件及平行光管光源组合的激光光束质量β因子测量结果验证方案,对研制的高能激光光束质量β因子测量装置进行了不确定度分析,测量不确定度优于10%。

一种高密度织物的织物密度测试方法研究

对织物密度的定义和测试方法进行了简要阐述。针对高密度织物的织物密度,采用现有标准检测方法分辨困难而导致的检测难度较大的问题,提出一种全新的检测方法——显微镜法。该方法可以降低检测的错误率,提高检测效率,并且可以利用现有实验室设备完成检测,无需增加额外的仪器成本。

颗粒离散元岩石模型的宏细观抗拉强度关联

颗粒离散元数值模型由于具有反映材料宏细观力学特征的天然优势,而被大量学者采用开展岩石力学课题相关研究,但DEM数值模型涉及的跨尺度关联和参数标定问题给研究者带了挑战,且尚未形成获得统一认可的定量分析方法.基于规则排列的圆形颗粒DEM岩石试件拉伸模型,开展细观接触破裂模式与宏观拉伸破坏强度相关性的力学分析,指出岩石试样宏观抗拉强度取决于内部细观接触破裂模式,而细观破裂模式则受到接触抗拉强度、接触抗剪强度、接触法向刚度、接触切向刚度,甚至颗粒大小及排列方式的共同影响.根据理论分析及数值模拟结果提出了4种细观破裂模式及相应宏观抗拉强度理论计算公式,并将公式修正应用于随机颗粒排列的类岩石材料DEM模型,从细观角度揭示了宏观DEM岩石材料拉伸破坏机理,构建了宏细观抗拉强度参数关联.所建立关联公式的合理性得到了大量随机数值模拟结果的有效验证,可为研究者利用颗粒DEM数值模型进行岩石和混凝土等类脆性材料模拟的参数选取及标定工作提供重要的参考依据.

显微仪器产品美度指标构建及评价方法研究

显微仪器外观美感能体现其产品的高端品质,同时提升操作者使用体验的愉悦性。建立显微仪器产品美度指标及评价方法能够量化显微仪器的外观美感,便于客观的形式美与人主观的感受美达成一致,从而有效指导显微仪器产品的美学设计。首先针对显微仪器产品的特点,基于形式美法则,依据Ngo和Birkhoff美度计算模型构建了显微仪器产品美度评价的7个量化指标,即平衡度、对称度、比例度、节奏度、整体度、秩序度、色彩美度;然后分析了7个美度指标间的相关性,建立了计算产品美度模糊评价矩阵R;最后以四款激光扫描共聚焦生物显微镜为样本,采用美度评价指标与模糊综合评价方法对其外观美感进行了主客观综合评价,结果显示哈工大设计的样本4的模糊综合评价向量B 4=[0,0.3534,1.0425,0.8883,1.2562],表明其美度等级较高,具有更好的整体感与秩序性。

JH油田含蜡原油析蜡温度测试与分析

采用显微镜观察法、黏温曲线法、DSC法分别测试了JH油田六个不同区块的原油析蜡温度。在DSC法中,测定了降温速率5、10℃/min下的析蜡点。在黏温曲线法中,测定了剪切速率10、20、50、100 s^(-1)下的析蜡点。在显微镜观察法中,测定了降温速率0.5、5℃/min下的析蜡点。实验结果表明,不同方法测量的析蜡点有所差异,一方面与不同测试方法的原理有关,另一方面与仪器的分辨率、操作者的经验有关。若原油中的活性物质和大分子不溶物影响较大时,也会表现不同。

非饱和黄土侧限压缩和湿陷试验的宏微观离散元特性分析

为了深入探讨非饱和黄土在侧限压缩和快速增湿作用下的宏微观特性,本文采用颗粒流方法对黄土的力学特性开展了3维离散元仿真模拟分析。采用软胶结模型模拟了颗粒间的化学胶结作用,并考虑了颗粒间的范德华力和毛细力作用,着重分析了微观参数的变化规律。结果表明:软胶结接触模型能够准确地复现非饱和黄土侧限压缩和快速增湿试验中的力学响应行为。微观力学配位数随着竖向压力的增加而不断加速增长,同时颗粒间接触力与接触力矩均随含水率的增加呈现逐渐减小的趋势,而对于饱和试样则出现增长的情况。颗粒间的剪切破坏和拉破坏随着竖向压力的增加而逐渐增加,在大约100kPa达到最大值。随着含水率的增加,剪切破坏逐渐占据主导;此外,随着竖向压力的逐渐增加,应变能、滑动耗能与阻尼耗能逐渐增加,应变能数值远大于滑动耗能与阻尼耗能;应变能的增速随着竖向压力的增加逐渐加快,直至200kPa附近达到最大,含水率越大应变能终值越低;滑动耗能与阻尼耗能的终值均在小范围内波动。

咸水层CO_(2)残余埋存机理的微观数值模拟研究

基于矿场岩心铸体电镜扫描图生成的二值化图片建立二维气液两相渗流模型,利用相场法研究微观条件下CO_(2)的赋存状态与埋存机理,并分析了储层润湿性、气液两相界面张力及地层水回流速度等因素对CO_(2)残余埋存效果的影响。结果表明:当地层水回流后,CO_(2)被大量封存下来,此时CO_(2)赋存状态主要以柱状、孤滴状和盲端状为主;地层水回流时的速度对于残余气饱和度影响较大,而储层润湿性与气液两相界面张力对于残余气饱和度影响较小。此研究对于从微观角度认识CO_(2)残余埋存机理具有指导意义。

致密砂岩气藏注CO_(2)提高天然气采收率微观机理

中国致密砂岩气藏资源储量丰富,复杂的气水渗流关系和气水同产特征制约了单井产能的发挥和天然气采收率提高,注CO_(2)是提高气藏采收率(EGR)和实现碳埋存的双赢途径。为明确致密砂岩气藏CO_(2)驱替微观渗流和提高天然气采收率机理,指导致密砂岩气藏CO_(2)-EGR方案设计,基于格子玻尔兹曼方法(LBM)建立了孔隙尺度多相多组分流动模型,揭示了致密砂岩气藏储层微观气水分布特征和CO_(2)-EGR的微观渗流机理,并明确了CO_(2)-EGR的主控因素。研究结果表明:①驱动压差显著影响了致密砂岩气藏的气水微观分布和水锁程度,使得气水流动能力和气水相对渗透率特征不同;②CO_(2)-EGR微观渗流过程包括气水两相的非混相驱替和CO_(2)-CH_(4)的混相驱替,对应EGR机理为分别受生产压差和地层压力控制的黏性驱替和混相扩散;③注入的CO_(2)可有效缓解水锁现象和贾敏效应,与CH_(4)良好的混相能力能促进沟通分散气泡,微观驱气效率可达42%~94%;④含水饱和度、孔隙结构和驱动压差显著影响微观驱气的作用机制和驱气效率的改善幅度。结论认为,在进行致密砂岩气CO_(2)-EGR的方案设计时,可优先考虑中—低含水饱和度的区块作为试验靶区,并根据靶区储层孔隙结构特征,优化不同注气阶段的注采参数,可充分发挥CO_(2)对CH_(4)的黏性驱替和混相扩散作用。