纤维增强摩阻材料中树脂含量的确定

选用碳纤维、钢纤维和FB酚醛树脂为主要成分制得纤维增强摩阻材料 ,研究了树脂含量对材料摩阻性能、力学性能的影响 ,确定了摩阻材料的最低树脂含量为 1 6% ,最佳树脂含量为 2 2 %     

玻璃纤维增强硼酸酯改性酚醛树脂复合材料的摩擦学性能研究

将硼酸(BA)和苯基硼酸(PBA)分别引入热塑性酚醛树脂(NR)中合成硼酸酯改性酚醛树脂,并以硼酸酯改性树脂为基体、玻璃纤维为增强体制备复合材料,研究不同硼改性对复合材料摩擦磨损性能的影响.采用DSC、FTIR和TGA分别对其固化反应过程、固化结构及固化树脂热稳定性进行表征,结果表明BA和PBA改性都可以在固化后的体系中引入硼酸酯结构,从而显著提高酚醛树脂(PR)的热稳定性.硼酸酯改性NR可显著改善树脂的摩擦学性能,其中PBA含量为30 phr时复合材料表现出较好的摩擦学性能,摩擦系数降低至0.16.另外,硼酸酯的引入可以提高树脂与纤维的界面粘合性能.     

树脂基纤维增强摩阻材料研究进展

综述了国内外目前树脂基纤维增强摩阻材料的研究进展,主要介绍了树脂基摩阻材料的摩擦学特性及摩擦磨损机理;树脂基体的改性研究成果,归纳了填料种类对摩阻材料摩擦学特性的影响.对常用的增强纤维性能作了对比,尤其是对天然植物剑麻纤维及其增强材料特性作了总结.笔者首次研究了剑麻纤维增强汽车刹车片,认为将剑麻纤维应用于摩阻材料将会是一个新的研究热点.     

碳纤维/芳纶浆粕摩阻复合材料初步研究

以丁睛橡胶改性酚醛树脂为基体,以碳纤维和芳纶浆粕为增强材料,研究了组分含量不同时的摩擦磨损性能。通过试验揭示了组分含量对摩擦磨损性能影响的规律,同时优化了具有良好耐热性、冲击韧性和摩擦性能新型无石棉摩阻复合材料的组分含量。      

SiO_2&Fe改性酚醛树脂的制备及性能研究

采用原位改性技术,将纳米二氧化硅(SiO_2)及其铁(Fe)的复合纳米粒子对酚醛树脂进行了改性处理,通过改变纳米SiO_2和Fe的质量配合比等实验条件制得改性酚醛树脂。对改性酚醛树脂的微观结构进行全面分析,对改性酚醛树脂的游离醛和固含量等性质做了详尽的研究,得到了综合性能最佳的改性酚醛树脂。结果表明,当纳米SiO_2与Fe质量配合比为1∶1.5时,改性树脂的游离醛为7.294%,固含量为74.26%;通过微观结构分析发现,纳米粒子均匀的分散在树脂中,酚醛树脂通过化学键键合在纳米粒子表面,达到了增强复合材料界面键合力的目的。     

基于酚醛三元聚合体系的固化行为及性能EI北大核心

以环氧豆油(ESO)醚化接枝改性酚醛树脂,而后以剩余酚羟基为酚源在树脂结构中引入苯并口恶嗪环,合成了一种具有优异韧性和热稳定性的环氧大豆油、苯并口恶嗪及酚醛三元共聚树脂(ESO-PA-PF)。采用红外光谱(FT-IR)表征了改性树脂的分子结构,以差示扫描量热法(DSC)对改性树脂的固化行为进行了分析,阐述了各组分对树脂固化行为的影响机理。热重分析法(TG)对热稳定性的分析表明,改性树脂的热稳定性较酚醛树脂及环氧豆油改性酚醛树脂有很大程度提高。共聚改性树脂具有较高的冲击韧性及弯曲强度,用扫描电镜(SEM)观察了改性酚醛树脂样品冲击断面的微观形貌,并对树脂的增韧机理进行了探讨。     

基于酚醛三元聚合体系的固化行为及性能

以环氧豆油(ESO)醚化接枝改性酚醛树脂,而后以剩余酚羟基为酚源在树脂结构中引入苯并口恶嗪环,合成了一种具有优异韧性和热稳定性的环氧大豆油、苯并口恶嗪及酚醛三元共聚树脂(ESO-PA-PF)。采用红外光谱(FT-IR)表征了改性树脂的分子结构,以差示扫描量热法(DSC)对改性树脂的固化行为进行了分析,阐述了各组分对树脂固化行为的影响机理。热重分析法(TG)对热稳定性的分析表明,改性树脂的热稳定性较酚醛树脂及环氧豆油改性酚醛树脂有很大程度提高。共聚改性树脂具有较高的冲击韧性及弯曲强度,用扫描电镜(SEM)观察了改性酚醛树脂样品冲击断面的微观形貌,并对树脂的增韧机理进行了探讨。     

腰果壳油改性酚醛树脂的合成及复合材料的性能

采用正交实验研究了腰果壳油用量、摩尔配比、催化剂用量和反应时间等4个因素对改性酚醛树脂性能的影响,以腰果壳油改性酚醛树脂为基体制备了复合材料并对其性能进行了测试。正交实验结果表明,催化剂用量是聚速、水分、树脂游离酚和苯酚反应率的主要影响因素,而腰果壳油用量是黏度、软化点和废水游离酚的主要影响因素。制备复合材料用的腰果壳油改性酚醛树脂的优选实验方案为:腰果壳油用量为20%,摩尔配比为0.89,催化剂用量为0.6%,反应时间为3 h。采用腰果壳油改性酚醛树脂制备的复合材料具有更好的韧性。     

摩阻材料用亚麻油改性酚醛树脂的研究

合成了亚麻油改性酚醛树脂(PF),FT-IR谱图说明亚麻油成为PF分子结构的一部分。综合热分析表明改性PF在320℃~600℃间失重53.11%,普通PF失重73.51%;普通PF热分解峰为400℃~425℃和540℃~600℃,而亚麻油改性PF热分解峰在440℃~470℃和600℃~660℃。亚麻油改性PF作基体的摩阻材料的摩擦磨损性能和力学性能测试表明,改性PF的粘接性和韧性均得到提高,摩阻材料摩擦系数大,摩擦性能稳定,磨损率低,冲击强度大,硬度适中,改性PF可作为高性能摩阻材料基体。     

BMI改性剂──烯丙基系列化合物

文中介绍了几类双马来酰亚胺树脂改性剂烯丙基化合物──二烯丙基双酚Ａ、烯丙基甲酚、烯丙基酚环氧树脂、烯丙基酚醛树脂和Ｎ－烯丙基芳胺。报导了用它们改性的双马来酰亚胺树脂及其复合材料的性能。     

Fabrication of magnetic nanodot arrays for patterned magnetic recording media

Fabrication processes of arrayed magnetic nanodots for the use of patterned magnetic recording media were reviewed. One candidate for the patterned media is ordered assemble of magnetic nanoparticles, and the other is patterned magnetic thin films fabricated using various micro/nano scale machining processes. For the formation of patterned masks and molds, lithography processes as well as self-organized pattern formation are utilized. For the deposition processes of magnetic dots, electrochemical deposition processes were widely used. These fabrication processes are reviewed mainly from recent reports. The recording systems for the patterned media including probe-type-recording are also overviewed.     

A Monte Carlo simulation model for stationary non-Gaussian processes

A class of stationary non-Gaussian processes, referred to as the class of mixtures of translation processes, is defined by their finite dimensional distributions consisting of mixtures of finite dimensional distributions of translation processes. The class of mixtures of translation processes includes translation processes and is useful for both Monte Carlo simulation and analytical studies. As for translation processes, the mixture of translation processes can have a wide range of marginal distributions and correlation functions. Moreover, these processes can match a broader range of second order correlation functions than translation processes. The paper also develops an algorithm for generating samples of any non-Gaussian process in the class of mixtures of translation processes. The algorithm is based on the sampling representation theorem for stochastic processes and properties of the conditional distributions. Examples are presented to illustrate the proposed Monte Carlo algorithm and compare features of translation processes and mixture of translation processes.     

A phenomenological theory of damaging and Adaption Processes of Solids

In the present paper the attempt is made to develop a phenomenological concept based on the assumption that the mechanical resistance of the material decreases as result of the structural and geometrical changes which take place in the solids during loading. This model is described in terms of damaging and adaptation parameters. The growth of structural and geometrical imperfections, as well as other softening processes leading to the loss of the mechanical strength of the solid regarded here as damaging processes. These damaging processes can occur simultaneously with the processes of material resistance (for example, strain-hardening) to the aggressive action of the external load. Development of the damaging and adaptation processes is described by properly kinetic equations. Several simple typical examples are discussed.     

Extreme value distributions for nonlinear transformations of vector Gaussian processes

Approximations are developed for the marginal and joint probability distributions for the extreme values, associated with a vector of non-Gaussian random processes. The component non-Gaussian processes are obtained as nonlinear transformations of a vector of stationary, mutually correlated, Gaussian random processes and are thus, mutually dependent. The multivariate counting process, associated with the number of level crossings by the component non-Gaussian processes, is modelled as a multivariate Poisson point process. An analytical formulation is developed for determining the parameters of the multivariate Poisson process. This, in turn, leads to the joint probability distribution of the extreme values of the non-Gaussian processes, over a given time duration. For problems not amenable for analytical solutions, an algorithm is developed to determine these parameters numerically. The proposed extreme value distributions have applications in time-variant reliability analysis of randomly vibrating structural systems. The method is illustrated through three numerical examples and their accuracy is examined with respect to estimates from full scale Monte Carlo simulations of vector non-Gaussian processes.     

Mechanics of damage processes in series and in parallel: a conceptual framework

A conceptual framework for damage processes in materials is presented. In this framework, the mechanics of damage processes in materials is investigated. These processes are categorized into either damage processes described in terms of stiffness degradation or damage processes described in terms of cross-sectional area reduction. Furthermore, the damage processes are visualized to occur as sequences either in series or in parallel. Schematic diagrams are used to illustrate these processes in a similar way to what is done with elastic springs and electric circuits. Different kinds of combinations and interactions of the damage processes are illustrated with various examples. The generalization to three-dimensional states of deformation and damage is also presented. This work is currently limited to linear elastic materials. The concepts presented in this work could be linked to homogenization methods. It is hoped that this work will lay the groundwork to open new areas of research in damage mechanics.     

Selective membranes in water and wastewater treatment: Role of advanced materials

Membrane separation has enjoyed tremendous advances in relevant material and engineering sciences, making it the fastest growing technology in water treatment. Although membranes as a broad-spectrum physical barrier have great advantages over conventional treatment processes in a myriad of applications, the need for higher selectivity and specificity in membrane separation is rising as we move to target contaminants at trace concentrations and to recover valuable chemicals from wastewater with low energy consumption. In this review, we discuss the drivers, fundamental science, and potential enabling materials for high selectivity membranes, as well as their applications in different water treatment processes. Membrane materials and processes that show promise to achieve high selectivity for water, ions, and small molecules—as well as the mechanisms involved—are highlighted. We further identify practical needs, knowledge gaps, and technological barriers in both material development and process design for high selectivity membrane processes. Finally, we discuss research priorities in the context of existing and future water supply paradigms.     

作业成本分析法在BPR中的应用研究

本方法是应用作业成本分析法(ABC法)解决目前企业在业务流程中存在的问题,但又不是严格遵循ABC法的计算方法,而是从产品是否增值的角度来分析业务流程中的作业及其动因类型,及应用ABC法进行业务流程重构(BPR)的方法。结合具体企业案例,运用ABC法对该企业的采购、销售及库存等物流业务流程进行了重构。结果表明,ABC法具有简化业务流程、提高业务流程运作效率和降低成本的作用。案例分析可为实施BPR的企业提供参考。     

A survey of the application of gamma processes in maintenance

This article surveys the application of gamma processes in maintenance. Since the introduction of the gamma process in the area of reliability in 1975, it has been increasingly used to model stochastic deterioration for optimising maintenance. Because gamma processes are well suited for modelling the temporal variability of deterioration, they have proven to be useful in determining optimal inspection and maintenance decisions. An overview is given of the rich theoretical aspects as well as the successful maintenance applications of gamma processes. The statistical properties of the gamma process as a probabilistic stress-strength model are given and put in a historic perspective. Furthermore, methods for estimation, approximation, and simulation of gamma processes are reviewed. Finally, an extensive catalogue of inspection and maintenance models under gamma-process deterioration is presented with the emphasis on engineering applications.     

空分流程中几个基本热力过程的分析

简介了的概念及计算方法 ,对空分流程中几个基本热力过程进行了分析 ,从更深层次揭示了这些基本热力过程的实质 ,从而为优化这些热力过程、进一步降低不可逆损失指明方向。把这些基本的分析方法用于整体空分流程 ,将会对流程的改进和优化有较好的指导作用。     

Special Considerations when Planning Experiments in a Continuous Process

Discontinuous processes dominate experimental applications in practice as well as in literature. Continuous processes constitute a significant part of goods production, and the need to gain knowledge using experiments are as relevant in such environments as in, for example, parts production. We argue that the characteristics of continuous processes affect the prerequisites for experimental efforts to such an extent that they need special attention. To describe considerations when planning experiments in a continuous process, experiments performed in a blast furnace process are studied. We propose a tentative list of special considerations, which are discussed and summarized in a thirteen-step check list.