微观结构对膜换湿能力影响研究

对多孔膜换湿过程进行了理论分析,得到了透湿量和湿阻的计算式.同时对三种膜包括PVDF,PES和纤维素膜进行了湿阻的测量实验,通过对实验数据的回归处理,得到了多孔膜的结构参数.结果表明,膜厚、孔径分布、孔隙率及曲折因子对膜的换湿特性都有较大影响,在平均孔径相同的情况下,其它因素仍然导致了不同膜换湿能力的较大差距。在所获得的结构参数基础上,通过数值模拟的方法研究了平均孔径对膜换湿能力的影响。结果表明湿阻随平均孔径的增大而减小,减小趋势逐渐平缓最后趋向一定值。     

用迈克耳孙干涉仪测肥皂膜厚度实验的分析

利用白光干涉原理,借助迈克耳孙干涉仪对肥皂膜的厚度进行了非接触测量.在干涉条纹宽窄相同的条件下,对不同层数的肥皂膜进行对比测量;在干涉条纹宽窄不同的条件下,对相同层数的肥皂膜进行对比测量;通过计算给出了膜的中心厚度和不确定度,对比分析了各种条件下测量时误差产生的原因.结果表明:单层、双层膜适合在宽条纹下测量,四层膜适合在窄条纹下测量.     

用于软X射线激光实验的铝衰减膜的测量

对不同方法制备的不同厚度的铝衰减膜,用微机控制α测厚仪测量了膜的质量厚度以及膜厚均匀性,用Auser电子能谱(AES)对铝膜进行了组分的表面和深度分布分析,根据铝KLL Auger特征谱揭示了氧化膜的化学组分并测量了氧化膜厚度随放置时间的变化,还讨论了膜中其它杂质含量的上限。     

膜厚度测量的椭偏仪法原理分析

薄膜厚度的测量通常有多种方法,但对超薄的膜厚,要达到较高精确度,且测量手段又较为简洁的,则椭偏仪法是理想的选择。本文对这种测量材料膜厚的光学方法从基本原理、仪器特点、测量过程、样品状态等方面,均作了全面的分析。     

弹流油膜彩色光干涉系统的特性研究

彩色光干涉技术是润滑油膜厚度测量的最有效的方法之一,但对其测量光学理论的研究并不十分透彻。以球-盘弹性流体动压润滑油膜测量装置为对象,建立了彩色光干涉的色度学计算模型,对该系统的干涉条纹和色彩进行了数值模拟与分析。分析结果与实验数据的一致性表明了所建立的模型和分析方法的正确。分析表明:铬膜厚度对图像的色彩和对比度有明显的影响,当其厚度为5～10nm时,能够获得对比度和色彩理想的图像;垫层厚度影响各颜色分量强度分布的初相变;LED光源可产生对比度较好的干涉条纹。     

雾化喷射下的波动液膜的电测量

冷却壁面上液膜的特性行为与厚度直接关系到雾化喷射冷却的深入研究。本文报道了在雾化喷射下水平壁面液膜厚度的测量。借助示波器,通过液膜直流信号配以几何尺寸的精确测量,实验研究了给定喷管雾化喷射下液膜波动行为和厚度随压力和喷头高度的变化。结合对流传热系数测量,分析了液膜厚度与雾化喷射冷却条件及效果的关系。     

Al_2O_3微孔膜对60keV O~+离子的“导向”效应

在不同入射角度条件下,研究了60keV的O+离子入射孔径分别为50nm和30nm,厚度为10μmAl2O3微孔膜的角分布.实验结果表明离子透射微孔膜时发生了导向效应,随着入射角度的增大,透射于孔径大的微孔膜离子计数下降比较快,透射于孔径小的微孔膜离子计数下降比较缓慢.建立了一个初步的理论模型,对以上现象给出了较好的解释.     

Ag/Fe/Ag 纳米颗粒膜磁特性和微结构

"利用对靶磁控溅射法制备了一系列Ag/Fe/Ag纳米薄膜,沉积态样品Fe层厚度固定为35 nm,Ag层厚度为1、2、3、4、5 nm．随后对沉积态样品进行了退火处理,退火温度分别为200、300、400、500、600 ℃ , 退火30 min． 利用VSM测量了样品的磁特性, 利用SPM观察样品表面形貌和磁畴结构,并且利用XRD分析了样品的晶体结构．研究结果表明,沉积态样品随Ag层厚度的变化,垂直和平行膜面矫顽力均先增加后减小．当Ag层厚度为3 nm时,垂直膜面矫顽力最大约为260 Oe,样品颗粒分布均     

多孔氧化铝薄膜的制备和光学特性研究

采用阳极氧化法制备了二维有序纳米孔氧化铝膜.研究了工艺参数对多孔薄膜有序性、孔径、膜厚度等的影响，测量了多孔氧化铝有序膜的光透过、光吸收和光发射等光学特性.结果表明，在波长360 nm附近多孔氧化铝有序膜的光透过谱线和光吸收谱线发生突变，波长大于360 nm时，光透过增强；波长小于360 nm时，光吸收增强.多孔氧化铝有序膜的光致发光强度和峰位与激发光波长有关，光致发光谱范围在340~600 nm.     

8.0 nm反射式偏振膜的设计和制备

讨论了软X射线反射式偏振膜的设计原理和方法,利用设计软件模拟设计了8.0 nm处的Mo/B4C偏振膜.对影响多层膜性能的参量进行了详细的误差分析.利用磁控溅射镀膜机进行了偏振膜的制备研究,X射线小角衍射测量了多层膜的周期厚度,测量数据的拟合结果与设计值吻合很好.     

Ni-GDC microtubular cermets

Ni-GDC cermet tubes (~ 3 mm inside diameter, 0.3–0.4 mm wall thickness and ～ 100 mm in length) with different amounts of porosity have been prepared by sintering of NiO-Ce_0.9Gd_0.1O_1.95 (NiO-GDC) nanopowders and further reduction. The NiO-GDC nanopowders were synthesized by chemical route and the different pore density was obtained by modifying the processing conditions (calcining and adjustment of carbonous remains).Ni-GDC cermets were obtained from the sintered NiO-GDC composites using reduction treatment at 700 °C for 3 h in reducing atmosphere (5 vol.% H₂–95 vol.% Ar). After the reduction process, tubes with 25–32% porosity were obtained. Gas permeability and Hg porosimetry studies were used to evaluate permeability, pore distribution and pore density. Electrical conductivity studies of the cermets were also performed.     

氢化多孔石墨烯反渗透特性及机理分析

单层石墨烯凭借超薄的厚度和优异的力学化学防污性能,成为新一代纳滤膜材料的最佳选择之一.本文采用经典分子动力学方法,研究了氢化多孔石墨烯反渗透膜对盐水的反渗透特性.结果表明,水渗透量会随着驱动力、孔径和温度的增加而增加;而孔径大于水合半径的条件下,盐离子截留率会随驱动力和温度的增加而降低.当反渗透膜和盐水存在切向运动时,随着切向速度的增加可以有效提高盐离子截留率和减弱浓差极化现象,但也在一定程度上牺牲了水通量.通过分析水流沿渗透方向的能障分布、水分子的氢键分布和离子水合状态,解释了各参数变化对盐水在氢化多孔石墨烯中反渗透特性的影响机理.研究结果将提供基于单层多孔石墨烯反渗透特性的理论认识,并将为纳米级反渗透膜的设计提供帮助.     

基于低场核磁共振的抚顺油页岩孔隙连通性演化研究

油页岩原位注热开采过程中，储层内部孔隙结构的连通性直接影响载热介质的流动行为和传热效率，同时对油气产物的扩散和流动行为起控制作用.本文利用低场核磁共振（LF NMR）技术，考察了不同热解终温（23~650℃）处理时，饱和水及束缚水状态下抚顺油页岩的T₂谱，分析了可动流体T₂截止值、束缚流体孔隙度、饱和流体孔隙度、渗透率等NMR孔隙参数，定量研究了随热解终温升高，抚顺油页岩孔隙结构的连通性演化规律.研究结果表明热解终温对抚顺油页岩孔隙连通性及渗透率的变化起控制作用，且可动流体孔隙度对总孔隙度的增加起主要促进作用，这说明热解终温升高加大了渗透率及油气产物的输运能力.本文为深入认识油页岩原位热解过程中孔隙结构的演化提供了依据.     

Permeability of cellulose acetate membranes to selected solutes

The permeability of cellulose 2.5-acetate films to several electrolytes and nonelectrolytes was measured. Permeabilities were determined by a desorption-rate method in which diffusion and distribution coefficients were measured. The rejection of the same solutes by modified cellulose acetate membranes in reverse osmosis experiments was also measured. A comparison was made between intrinsic water and solute permeabilities and the reverse osmosis semipermeability data using a noncoupled flow model of solute and water transport. The results were in reasonable agreement, indicating that flow coupling is not generally important in these films. Some of the factors, such as thermal history and casting environment, affecting the transport properties of acetone-cast cellulose acetate films were examined.     

Diffusion Limitations and Translocation Barriers in Atomically Thin Biomimetic Pores

Ionic transport in nano- to sub-nano-scale pores is highly dependent on translocation barriers and potential wells. These features in the free-energy landscape are primarily the result of ion dehydration and electrostatic interactions. For pores in atomically thin membranes, such as graphene, other factors come into play. Ion dynamics both inside and outside the geometric volume of the pore can be critical in determining the transport properties of the channel due to several commensurate length scales, such as the effective membrane thickness, radii of the first and the second hydration layers, pore radius, and Debye length. In particular, for biomimetic pores, such as the graphene crown ether we examine here, there are regimes where transport is highly sensitive to the pore size due to the interplay of dehydration and interaction with pore charge. Picometer changes in the size, e.g., due to a minute strain, can lead to a large change in conductance. Outside of these regimes, the small pore size itself gives a large resistance, even when electrostatic factors and dehydration compensate each other to give a relatively flat—e.g., near barrierless—free energy landscape. The permeability, though, can still be large and ions will translocate rapidly after they arrive within the capture radius of the pore. This, in turn, leads to diffusion and drift effects dominating the conductance. The current thus plateaus and becomes effectively independent of pore-free energy characteristics. Measurement of this effect will give an estimate of the magnitude of kinetically limiting features, and experimentally constrain the local electromechanical conditions.     

Synthesis and characterization of polyester bionanocomposite membrane with ultrasonic irradiation process for gas permeation and antibacterial activity

Optically active bionanocomposite membranes composed of polyester (PE) and cellulose/silica bionanocomposite (BNCs) prepared with simple, green and inexpensive ultrasonic irradiation process. It is a novel method to enhance the gas separation performance. The novel optically active diol containing functional trifluoromethyl groups was prepared in four steps reaction and it was fully characterized by different techniques. Commercially available silica nanoparticles were modified with biodegradable nanocellulose through ultrasonic irradiation technique. Transmission electron microscopy (TEM) analyses showed that the cellulose/silica composites were well dispersed in the polymer matrix on a nanometer scale. The mechanical properties nanocomposite films were improved by the addition of cellulose/silica. Thermo gravimetric analysis (TGA) data indicated an increase thermal stability of the PE/BNCs in compared to the pure polymer. The results obtained from gas permeation experiments showed that adding cellulose/silica to the PE membrane structure increased the permeability of the membranes. The increase in the permeability of the gases was as follows: P_CH4 (38%) <P_N2 (58%) <P_CO2 (88%) <P_O2 (98%) Adding silica nanoparticles into the PE matrix, improved the separation performance of carbon dioxide/methane and carbon dioxide/nitrogen gases. Increasing the cellulose/silica mass fraction in the membrane increased the diffusion coefficients of gases considered in the current study. Further, antimicrobial test against pathogenic bacteria was carried out.     

Influence of thickness and permeability of endothelial surface layer on transmission of shear stress in capillaries

The molecular coating on the surface of microvascular endothelium has been identified as a barrier to transvascular exchange of solutes. With a thickness of hundreds of nanometers, this endothelial surface layer(ESL) has been treated as a porous domain within which fluid shear stresses are dissipated and transmitted to the solid matrix to initiate mechanotransduction events. The present study aims to examine the effects of the ESL thickness and permeability on the transmission of shear stress throughout the ESL. Our results indicate that fluid shear stresses rapidly decrease to insignificant levels within a thin transition layer near the outer boundary of the ESL with a thickness on the order of ten nanometers. The thickness of the transition zone between free fluid and the porous layer was found to be proportional to the square root of the Darcy permeability. As the permeability is reduced ten-fold, the interfacial fluid and solid matrix shear stress gradients increase exponentially two-fold. While the interfacial fluid shear stress is positively related to the ESL thickness, the transmitted matrix stress is reduced by about 50% as the ESL thickness is decreased from 500 to 100 nm, which may occur under pathological conditions. Thus, thickness and permeability of the ESL are two main factors that determine flow features and the apportionment of shear stresses between the fluid and solid phases of the ESL. These results may shed light on the mechanisms of force transmission through the ESL and the pathological events caused by alterations in thickness and permeability of the ESL.     

Analysis of multiscale scattering and poroelastic attenuation in a real sedimentary rock sequence

Compressional waves in heterogeneous permeable media experience attenuation from both scattering and induced pore scale flow of the viscous saturating fluid. For a real, finely sampled sedimentary sequence consisting of 255 layers and covering 30 meters of depth, elastic and poroelastic computer models are applied to investigate the relative importance of scattering and fluid-flow attenuation. The computer models incorporate the known porosity, permeability, and elastic properties of the sand/shale sequence in a binary medium, plane layered structure. The modeled elastic scattering attenuation is well described by stochastic medium theory if two-length scale statistics are applied to reflect the relative thickness of the shale layers when compared to the sand layers. Under the poroelastic Biot/squirt flow model, fluid-flow attenuation from the moderate permeability (10(-14) m2) sands may be separated in the frequency domain from the attenuation due to the low permeability (5 x 10(-17) m2) shale layers. Based on these models, the overall attenuation is well approximated by the sum of the scattering attenuation from stochastic medium theory and the volume weighted average of the attenuations of the sequence member rocks. These results suggest that a high permeability network of sediments or fractures in a lower permeability host rock may have a distinct separable attenuation signature, even if the overall volume of high permeability material is low. Depending on the viscosity of the saturating fluid, the magnitude of the flow-based attenuation can dominate or be dominated by the scattering attenuation at typical sonic logging frequencies (approximately 10 kHz).     

气孔分布特性对含水多孔介质气体扩散的影响

本文基于多孔介质的气孔分布特性,计算了多孔介质在含水状态下的扩散性能,并且比较了采用两种方式计算相对渗透率时的相对扩散性能。其结果表明,基于气孔分布的计算结果低于与气孔分布无关的计算结果。另外,疏水性含水多孔介质的扩散性能低于亲水性含水多孔介质的扩散性能,基于气孔分布计算含水多孔介质的气体扩散性能时,Wyllie公式并不适用。     

Dissolution and Regeneration in Films of Natural Luffa in 1-butyl-3-methylimidazolium Chloride

Regenerated cellulose film was successfully prepared from natural luffa, a new cellulose raw material. A pretreatment of natural luffa was carried out by an alkali and hydrogen peroxide mixed solution. The dissolution process of the pretreated luffa in 1-butyl-3-methylimidazolium chloride ([BMIM]C1) was observed by polarized optical microscope. The structures and properties of the luffa films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TGA), and porosity measurements. The results showed that the luffa fibers were transformed to fibrils after the pretreatment. [BMIM]Cl was a good non-derivatizing solvent for the luffa cellulose. The solution conditions were 80°C and 10 h for a 15% solution. After being regenerated, as films, from the luffa/[BMIM]Cl solution, the crystalline structure of the luffa film was transformed completely from cellulose I to cellulose II. The film showed the strong characteristic functional groups of cellulose in FTIR results. The surface of the film was smooth with a compact structure. The porosity of the film was 66.2% and the average pore size was 17.8 nm. It was thermally stabile up to 280°C.