热致相分离法高性能聚偏氟乙烯中空纤维膜先进制备技术及应用

膜分离技术已经成为国际上市政污水和工业废水处理的核心技术。十年来清华大学化学工程系在先进膜材料制备及应用技术研究上开展了大量工作,以膜材料配方设计、膜材料先进制造、膜组件设计与应用为主线,突破多个技术难题和瓶颈,实现了热致相分离（TIPS）法高性能聚偏氟乙烯（PVDF）中空纤维膜的工业化。首先,基于对TIPS法成膜过程的热力学及动力学研究,制备出具有大通量、高强度、亲水性好的PVDF微孔膜;接着,有机结合材料加工和单元操作,形成PVDF中空纤维膜先进制造技术;最后针对不同的工业环境和市政要求,开发出不同规格的高性能膜组件。研究成果表明TIPS法突破了传统非溶剂致相转化法的限制,可以作为市政污水和工业废水处理的首选膜材料制备技术。     

耐温超滤膜在焦化废水处理中的应用研究

采用耐温型环氧树脂,结合高性能热致相分离(TIPS)法聚偏氟乙烯(PVDF)超滤膜丝制备出可耐温的TIPS法PVDF超滤膜组件,将其应用在焦化废水深度处理回用项目中.结果表明,耐温TIPS法PVDF超滤膜运行稳定,高温清洗(50℃)的效果明显优于常规清洗(30～35℃)的效果,并且大幅改善了振动膜的进水水质从而延长了振动膜的清洗周期,为难处理的焦化废水深度处理回用提供了一种新的思路.     

二元稀释剂对热致相分离法制备PVDF微孔膜的结构影响

采用热致相分离法(TIPS)制备PVDF平板和中空纤维微孔膜,研究了二元稀释剂对PVDF微孔膜的结构的影响。当二元稀释剂由邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二丁酯(DBP)、三乙酸甘油酯(GTA)中的一种,与邻苯二甲酸二辛酯(DOP)、癸二酸二丁酯(DBS)、苯甲酸苄酯(BB)中的一种混合而成时,TIPS法制备的PVDF膜的断面均具有双连续结构;当二元稀释剂由二苯甲酮(DPK),与DOP、DBS、BB中的一种混合而成时,TIPS法制备的PVDF膜的断面为胞腔结构,断面孔的孔径按如下顺序依次增大:BB、DOP、DBS。GTA/DBS为二元稀释剂,采用TIPS法制备PVDF中空纤维微孔膜,随着二元稀释剂中GTA的质量分数由30%增加至50%,膜的断面由双连续结构变为球晶结构。     

超滤/微滤膜的结构控制与性能

膜材料是膜技术的核心,膜材料制备过程中的结构控制对膜性能起着决定性的作用.首先简要介绍了近年来国内外UF/MF膜技术与产业的现状,在此基础上综述了研究组近年来在TIPS法制备聚乙烯(PE)中空纤维微孔膜、双向拉伸法制备聚四氟乙烯(PTFE)微孔膜、熔融-纺丝法制备聚偏氟乙烯(PVDF)微孔膜、溶液相转化法制备PVDF超滤膜的膜结构控制和表面改性方面取得的研究进展.     

热致相分离法制备聚偏氟乙烯微孔膜的结构及性能研究

以聚偏氟乙烯(PVDF)和邻苯二甲酸二丁酯(DBP)作为膜材料和稀释剂,采用热致相分离法(TIPS法)制备了聚偏氟乙烯(PVDF)微孔膜.通过差示扫描量热仪(DSC)测试了不同混合体系的固-液相分离温度,利用扫描电镜(SEM)观察和研究了稀释剂、冷却条件、聚合物浓度对膜断面微观结构的影响.     

PVDF热致相分离法成膜体系铸膜液流变性能研究

利用流变仪对聚偏氟乙烯(PVDF)/己内酰胺(CPL)热致相分离法(TIPS)成膜体系铸膜液的流变性能进行研究.考察了剪切频率、温度、PVDF质量分数对PVDF/CPL铸膜液体系的黏度、非牛顿性指数、黏流活化能、溶液黏弹性的影响,利用TIPS法制备PVDF膜,进一步探讨了铸膜液体系的流变性能对刮膜速率、制膜温度等成膜条件的指导作用.实验结果表明:PVDF/CPL铸膜液体系为非牛顿性流体,随着PVDF质量分数的升高,PVDF/CPL铸膜液体系的黏度增加,非牛顿性指数增加,黏流活化能升高,对应膜的结构越致密,水通量降低,截留率升高,膜的拉伸强度增强.PVDF质量分数低的铸膜液体系,制膜时对温度的灵敏度低,刮膜速率对膜的制备影响大,制膜过程需要对刮膜速率精确地控制;PVDF质量分数高的铸膜液体系,对温度的灵敏度高,可以在较宽的刮膜速度范围下制膜.     

热致相分离法制备聚偏氟乙烯微孔膜的微观结构研究

以邻苯二甲酸二丁酯(DBP)和十二醇组成的混合溶剂为稀释剂,采用热致相分离法(TIPS法)制备了聚偏氟乙烯(PVDF)微孔膜.测试了不同体系的固-液相分离温度,研究了稀释剂、冷却条件、聚合物浓度对膜断面微观结构的影响.     

碳酸钙对热致相分离制备聚偏氟乙烯多孔膜结构的影响

通过熔融共混聚偏氟乙烯(PVDF)/CaCO3/复合稀释剂拟三元体系,采用热致相分离法(TIPS)制备了PVDF多孔膜。研究了复合稀释剂含量、CaCO3含量、粒径以及后期酸处理对膜结构的影响。结果表明:CaCO3含量和粒径对膜结构有明显的影响。在采用复合稀释剂的基础上,通过控制CaCO3粒子添加量,改变粒径,可以实现对膜结构的优化,并且经酸处理提高了PVDF膜孔隙率。     

热致相分离法制备聚偏氟乙烯微孔膜

对聚偏氟乙烯(PVDF)/碳酸二苯酯(DPC)体系,采用热致相分离(TIPS)法制备了PVDF微孔膜.通过稀释剂的溶度参数对体系的相容性进行分析,热力学相图和不同PVDF质量浓度下制备的微孔膜断面照片均证明该体系具有较宽的液-液相分离区.PVDF/DPC体系偏晶点对应的PVDF浓度约为质量分数56%,低于此浓度体系降温后先发生液-液相分离,随着PVDF浓度的增大,微孔膜断面结构由双连续结构转变为蜂窝状结构,且膜孔孔径减小,高于此浓度体系降温后只发生固-液相分离,微孔膜断面呈块状紧密堆积结构.较快的冷却速率有利于低PVDF浓度时较小孔径膜和高PVDF浓度时较小球粒尺寸膜的生成.     

热致相分离法聚偏氟乙烯多孔膜制备及微结构调控

以邻苯二甲酸二辛酯(DBP)和己二酸二辛酯(DOA)组成混合稀释剂,采用热致相分离法(TIPS)制备了聚偏氟乙烯(PVDF)平板膜。通过冷场发射扫描电子显微镜观察所得膜形貌,采用差示扫描量热仪测试膜热力学性能,并对其渗透性能及力学性能进行测试表征。研究了稀释剂配比与聚合物浓度对PVDF平板膜结构和性能的影响。结果表明,PVDF/DBP/DOA体系成膜过程以S-L分相为主,呈典型的球晶结构。随PVDF浓度和混合稀释剂中DOA比例增加,膜横截面球晶结构尺寸及球晶结构晶粒间空隙均变小,同时膜表面孔隙率减小,致密度增加。此外,混合稀释剂中DOA比例增加,能够改善膜的力学性能,但会减小膜的纯水通量。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.