不同pH条件下再生纤维表面的CPAM/CMC静电逐层自组装

利用静电逐层自组装技术,在再生纤维表面沉积了阳离子聚丙烯酰胺（CPAM）/羧甲基纤维素（CMC）复合膜。研究了不同pH条件下CPAM/CMC在再生纤维表面的静电吸附规律。采用FT-IR、SEM和Zeta电位测试对再生纤维表面的聚电解质多层膜进行表征,而再生纤维力学性能用纸页的裂断长和耐破指数来评价。研究表明,CPAM/...     

层层自组装法制备氧化石墨烯复合单价选择性离子交换膜

将氧化石墨烯(GO)添加到聚丙烯酸(PAA)溶液中,并与聚乙烯亚胺(PEI)在阳离子交换膜表面通过层层自组装(LBL)法制备了单价选择性离子交换膜。结果表明,PEI为表层的复合膜,具有更高的单价离子选择性,随着层层自组装的进行,GO连续地沉积到膜的表面。复合膜的面电阻随组装层数的增加而增大,相比于未添加GO的多层膜,GO的加入有利于膜电阻的降低。同时,随着自组装层数的增加,复合膜的单价离子分离效率提高;GO浓度升高,复合膜的单价离子选择性先升高后降低,当GO浓度升高至0.5 g/L时,复合膜的分离效率最高。     

磷钨铁杂多酸/聚酰胺胺复合膜的制备及电催化性能

通过层层自组装方法在氧化铟锡(ITO)电极上原位制备了Dawson型磷钨铁杂多酸/聚酰胺-胺复合膜。用XPS、UV-Vis、CV、AFM分析表征复合膜的形成过程和电化学性能。结果表明: 杂多酸阴离子和聚酰胺-胺层层自组装形成多层复合膜且增长均匀; 复合膜在酸性溶液中出现了三对氧化还原峰; 用该复合膜修饰的电极稳定性好, 对亚硝酸盐和溴酸盐均具有良好的电催化活性。      

利用可控层层自组装法提高纤维素膜的力学性能EI北大核心CSCD

通过水溶性耦合试剂N-(3-二甲氨基丙基)-N′-乙基碳二亚胺盐酸盐(EDC)/N-羟基琥珀酰亚胺(NHS)将小分子4-羧基苯硼酸(PBA)与壳聚糖以形成酰胺键的方式结合起来,成功制备了苯硼酸官能团接枝的改性壳聚糖,随后将其与聚乙烯醇(PVA)通过pH值可控的层层自组装方法处理再生纤维素膜表面,得到力学强度明显改善的纤维素膜材料。结果表明:在pH为9.5,自组装30层高分子膜时,再生纤维素膜的拉伸强度与伸长率可提高38%和43%。处理后的再生纤维素膜达到了较为理想的力学性能增强效果,本方法对于纤维制品的性能改善有一定的应用价值。     

利用可控层层自组装法提高纤维素膜的力学性能

通过水溶性耦合试剂N-(3-二甲氨基丙基)-N′-乙基碳二亚胺盐酸盐(EDC)/N-羟基琥珀酰亚胺(NHS)将小分子4-羧基苯硼酸(PBA)与壳聚糖以形成酰胺键的方式结合起来,成功制备了苯硼酸官能团接枝的改性壳聚糖,随后将其与聚乙烯醇(PVA)通过pH值可控的层层自组装方法处理再生纤维素膜表面,得到力学强度明显改善的纤维素膜材料。结果表明:在pH为9.5,自组装30层高分子膜时,再生纤维素膜的拉伸强度与伸长率可提高38%和43%。处理后的再生纤维素膜达到了较为理想的力学性能增强效果,本方法对于纤维制品的性能改善有一定的应用价值。     

氧化石墨烯/壳聚糖层层自组装复合膜的制备及其在环保领域中的应用

利用层层自组装技术将氧化石墨烯与壳聚糖进行自组装,制备出一种新型的氧化石墨烯/壳聚糖复合膜,并利用原位合成的方法引入纳米银粒子。采用紫外可见光谱(UV-Vis)、红外光谱(FTIR)、X射线衍射(XRD)和原子吸收等分析方法对复合膜的自组装行为和催化性能进行了研究。实验结果表明,氧化石墨烯与壳聚糖可通过层层自组装技术制备出新型复合膜,这种复合膜可包裹纳米银粒子,膜内纳米银粒子对4-硝基苯酚的催化活性较高,并且可实现循环使用。此外,在稳定性实验中,复合膜不会释放纳米银粒子或银离子,避免了给水体带来二次污染。因此,这种材料在水处理等环保领域中可能具有巨大的潜在实用价值。     

基于静电纺-层层组装技术制备[壳聚糖/海藻酸钠]_(c/l)/聚乙烯醇纳米复合膜

静电纺丝技术在近几十年来得到了快速发展,静电纺丝制备的纳米纤维具有比表面积大和孔隙率高的优点,因而广泛应用于海水淡化、电池隔膜和重金属离子吸附等领域。结合层层组装法,以交联的静电纺聚乙烯醇(PVA)为基底,壳聚糖(CTS)和海藻酸钠(SA)为聚电解质,成功制备了复合纳米纤维膜,并对复合膜表面的聚电解质层(PEL)进行了交联,考察复合膜的抗水解性能。结果表明:交联最佳条件为戊二醛/丙酮=2.0%(质量分数)、时间3h、pH=2。     

聚电解质/陶瓷复合膜的制备及超滤性能

采用阳离子聚电解质聚丙烯氯化铵(PAH)、聚乙烯亚胺(PEI),阴离子聚电解质聚苯乙烯磺酸钠(PSS)、聚乙烯磺酸钾(PVS),通过静电自组装技术在多孔陶瓷支撑体上制备了聚电解质分离层,并对不同条件下所制备的复合膜超滤性能进行研究.膜表面的SEM表征显示,自组装过程在支撑体表面及孔道内同时发生,并且随组装层数的增加,聚电解质层在支撑体表面的沉积状态逐渐改善.对复合膜在葡聚糖溶液中的超滤研究表明,随着组装层数,组装时间和电荷密度的增加,膜的截留率随之增加;制膜溶液的pH在两种带相反电荷聚电解质材料电离平衡常数(pKα)之间选择时,膜的截留率有最佳值.     

聚吡咯-二氧化钛自组装复合膜的制备及其光电转换性质

通过原位自组装技术制备了聚吡咯-二氧化钛纳米复合膜,利用紫外-可见光谱、红外光谱、原子力显微镜、电化学循环伏安等方法对所制备的复合膜进行了表征.与利用原位自组装技术制备的聚吡咯膜相比较,由于在复合膜中聚吡咯和TiO2纳米粒子之间的相互作用,复合膜π→π*跃迁吸收峰发生蓝移,氧化还原峰的位置向负电位方向移动.沉积在导电玻璃ITO表面的该纳米复合膜在可见光下表现出一定的光电转换性质.     

改性PAN纳米纤维膜支撑的TFC FO膜制备及其性能

利用层层自组装的方法在聚丙烯腈(PAN)静电纺丝纳米纤维膜(ENMs)表面沉积聚电解质中间层,讨论了中间层的结构变化对于界面聚合制备的聚酰胺(PA)复合膜结构及其性能的影响.结果表明,改性后ENMs的亲水性和机械性能显著提高,而孔径和表面粗糙度减小;在低沉积浓度下,由其制备的复合正渗透(FO)膜的水通量明显增大,且随着聚电解质沉积浓度的增加,复合FO膜对于NaCl截留率从原来的86.30%提升到了95.46%,具有较高的选择性.因此,聚电解质表面沉积是改性ENMs的一种实用而有效的方法,能够显著改善由其制备的薄膜复合(TFC) FO膜性能.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.