自动铺放成型热塑性复合材料的非等温结晶动力学研究

利用差示扫描量热仪结合Avrami方程研究玻璃纤维增强聚丙烯复合材料自动铺放成型过程非等温结晶动力学,推导非等温结晶动力学模型,并通过构建冷压辊下方铺层的冷却模型,将结晶动力学模型和传热模型相结合,设定自动铺放成型过程中的冷却条件,探讨冷却速率及冷却时间对基体材料结晶行为的影响,求解出不同冷却速率下的最大铺放速率。研究结果表明:铺层树脂基体的结晶度随冷却速率的增大而依次减小;随着冷却速率的提高,树脂结晶起始温度和结晶完成温度均向低温方向移动,且树脂相对结晶度随温度变化规律接近反S形曲线;自动铺放成型实验件的压缩强度及层间剪切强度随着铺层结晶度的增大基本呈增大趋势,而冲击强度与铺层结晶度的变化趋势完全相反,随着结晶度的增大,材料韧性越差。     

不同质量PET切片的非等温结晶动力学

用DSC方法研究了三种不同质量聚对苯二甲酸乙二醇酯(PET)切片非等温结晶动力学。结果表明，PET切片都很好遵循Avrami方程和Ziabicki方法描述冷却速率对聚合物结晶形态的影响。PET切片中增加二甘醇(DEG)含量，可降低切片结晶速率，使熔融结晶温度向低温方向移动。结晶速率小，结晶温度低的切片，不一定结晶能力小。     

SiO2对聚氨酯杂化膜微孔结构及性能的影响

用热致相分离法制备了PU/SiO2杂化膜,研究了不同SiO2及其用量对PU/SiO2/溶剂体系微孔膜微孔结构的影响,并测试了膜的水通量.结果表明:具有不同结构的SiO2能够提高溶剂二氧六环的结晶温度,即冷却速率加快,使微孔膜的微孔尺寸细化,同时使微量水的结晶温度也有所不同,水的冻结温度与孔尺寸的大小直接相关.在冷却速率较快的体系中,形成的微孔尺寸较小,因此其水的冻结温度较低;而冷却速率较慢,形成的微孔尺寸较大,因此其水的冻结温度较高.SiO2的结构将影响与PU之间界面成孔的形态不同,SiO2的粒径越小,其与PU膜接触面积加大,增加了膜孔的连通性,使PU膜的水通量增大.     

界面应力对HDPE/CaCO3增韧体系基体结晶动力学影响的研究

采用了一种可表征体系冷却收缩应力对聚合物结晶影响的动力学方法,研究了不同冷却速率条件下HDPE/CaCO3增韧体系的基体结晶动力学行为及其与材料界面相粘结性及CaCO3含量之间的关系.结果表明,在材料缺口冲击强度较高的界面相粘结及组成条件下,体系熔体冷却收缩过程中所引起的界面应力的应变诱导结晶作用引起了基体晶体生长指数n1、生长速率常数k1及其k1随冷却速率a的变化率△k,/△a的显著增大;材料基体结晶动力学参数的影响因素及其变化规律与其材料缺口冲击强度的影响因素及其变化规律之间存在着良好的一致性.     

聚乙烯醇/纳米氧化锌复合材料的非等温结晶动力学

为了研究聚乙烯醇/纳米氧化锌复合材料的结晶性能,通过熔融共混挤出的方法制备了复合材料,并在差示扫描量热分析(DSC)的基础上通过Jeziomy法和Liu法研究了聚乙烯醇薄膜和聚乙烯醇/纳米氧化锌复合材料的非等温结晶动力学行为.结果表明,聚乙烯醇薄膜和聚乙烯醇/纳米氧化锌复合材料的非等温结晶行为强烈地依赖于冷却速率,随着冷却速率的提高,结晶速率常数增大,结晶的不完善程度也增大.在相同的冷却速率下,复合体系的Avrami指数n值和结晶速率常数Z。较大,晶体的完善程度较高.要达到相同的结晶度,复合材料所需的冷却速率要小于聚乙烯醇薄膜,即纳米氧化锌的加入使材料中聚乙烯醇的结晶速率增加,对聚乙烯醇具有异相成核作用.     

界面应力对HDPE/CaCO3增韧体系基体结晶动力学影响的研究

采用了一种可表征体系冷却收缩应力对聚合物结晶影响的动力学,方法研究了不同冷却速率条件下HDPE／CaCO2增韧体系的基体结晶动力学行为及其与材料界面相粘结性及CaCO3含量之间的关系。结果表明,在材料缺口冲击强度较高的界面相粘结及组成条件下,体系熔体冷却收缩过程中所引起的界面应力的应变诱导结晶作用引起了基体晶体生长指数n1、生长速率常数k1及其k1随冷却速率a的变化率Δk1Δa的显著增大;材料基体结晶动力学参数的影响因素及其变化规律与其材料缺口冲击强度的影响因素及其变化规律之间存在着良好的一致性。     

母料中弹性体不同配比对HDPE/E-TMB共混物热性能及结晶形态的影响

用自制增韧母料(E-TM B)与HDPE热机械共混制得HDPE/E-TM B共混物。通过DSC分析仪和偏光显微镜研究了共混物的熔融、结晶行为和结晶形态,并将其结晶形态与简单共混对照样加以对比研究。结果表明,和纯HDPE相比,共混物的熔点降低、结晶温度升高,成核速率和结晶速率增大;随母料中乙丙弹性体含量的增加,共混物的熔点逐渐降低、结晶温度逐渐升高,结晶细化程度增大、数目增多;共混物的结晶比原料HDPE及简单共混对照样都显著细化。     

聚（1，3-己二酸丙二醇酯）功能化羟基多壁碳纳米管的非等温结晶

以羟基多壁碳纳米管、1,3-丙二醇、己二酸为原料,采用原位聚合法合成聚（1,3-己二酸丙二醇酯）功能化羟基多壁碳纳米管。采用差热扫描量热法测定产物的结晶和熔融行为。羟基多壁碳纳米管的添加量和冷却速率对聚（1,3-己二酸丙二醇酯）功能化羟基多壁碳纳米管的非等温结晶行为有一定的影响。在一定范围内,随着羟基多壁碳纳米管含量的增加,产物结晶温度增加。冷却速率增加,产物的结晶温度降低。羟基多壁碳纳米管起到异相成核的作用并促进结晶生长。少量羟基多壁碳纳米管对促进聚合产物结晶更加有效。Jeziorny方法描述聚合产物的非等温结晶行为出现偏离,Avrami-Ozawa方法可以更有效地描述其非等温结晶行为。     

聚己内酯/纳米Si3N4复合材料的非等温结晶研究

采用溶液成膜法制备纳米Si3N4/聚己内酯(PCL)复合材料,并通过DSC、偏光显微镜及透射电镜等研究手段分析了纳米Si3N4颗粒对PCL的非等温结晶行为和微观形态的影响。结果表明:改性后的纳米Si3N4粒子在PCL基质中的分散性好于未改性纳米Si3N4;纳米Si3N4具有明显的成核效应,加快了PCL的前期结晶速率,对由成核控制的聚合物结晶前期阶段具有积极作用,而对晶体的生长则具有限制作用,导致聚合物结晶后期速率缓慢,晶体尺寸变小,结晶度下降;当纳米Si3N4的含量为5%时,聚合物结晶温度出现最大值;加快降温速率与添加纳米粒子对聚合物结晶行为的影响具有相似的效果。     

成核PP注塑样品的非等温结晶行为与熔融特性

用DSC研究了两种成核剂成核PP的非等温结晶行为与熔融特性,致命伤中成核剂均使PP的降温结构温度提高,结晶峰半高宽变窄,结晶度与熔点略有提高,但结晶峰对称性变差,熔融峰半高宽加大,成核样品的结晶温度对冷却速率的依赖性较纯PP的小,根据过冷度和成核PP与纯PP的结晶温度之差,成核剂成核作用大小顺序为：A＞D。     

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.     

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.     

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.……     

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.