聚对苯二甲酰癸二胺(PA10T)的结晶动力学

用差示扫描量热仪详细研究了聚对苯二甲酰癸二胺(PA10T)的等温与非等温结晶动力学。用Avrami方程描述了PA10T等温结晶动力学,发现PA10T在选定的结晶条件下晶体的生长模式是二维生长,成核方式为均相成核,并求出Avrami指数为2,结晶活化能为302.32 kJ/mol;研究PA10T非等温结晶动力学后,发现随着降温速率的增大,结晶峰值温度向低温移动,结晶度和结晶焓增加,结晶速率显著加快。用Mo方程描述了其非等温结晶动力学,F(T)值随着相对结晶度的增加而增加,α值基本保持在1.6,非等温结晶活化能为338.56 kJ/mol。     

分子筛4A填充海藻酸钠的热分解研究

用热重法研究了分子筛4A填充海藻酸钠在空气中的热分解过程,升温速率分别为5,10,15,20和30K/min,从室温升温到1250 K,并利用TGA曲线分析了复合材料的热降解特点。结果表明,热分解反应最剧烈的温度区间介于450～650 K之间;热分解动力学分析表明,该热分解过程为一级反应。通过模型计算确定了热降解反应的动力学参数,以最大失重速率法求得活化能为187.47 kJ/mol,频率因子lnA为38.87 s-1;采用Ozawa等失重法求得活化能为154.50 kJ/mol,频率因子lnA为34.69 s-1。     

甘蔗渣对聚甲基丙烯酸甲酯热降解的影响

目的分析生物质材料对塑料废弃物热降解的影响,以聚甲基丙烯酸甲酯(PMMA)为对象,探讨甘蔗渣对其热分解行为和动力学的作用。方法利用溶液共混法制备PMMA/甘蔗渣混合物,采用热失重法研究其在氮气中的热分解过程,通过最大失重速率法和Ozawa等失重法计算PMMA热分解反应的动力学参数活化能和频率因子。结果甘蔗渣使得PMMA的初期热分解温度明显降低,但是PMMA的热分解活化能和频率因子却都显著增加。最大失重速率法的计算结果表明,PMMA加入甘蔗渣后的热分解活化能增加了26.2 k J/mol,等失重法的结果显示活化能和频率因子分别为168.14 k J/mol和28.41 min-1,比纯PMMA相应地增大了72.6 k J/mol和12.52 min-1。结论甘蔗渣的加入对PMMA的热降解有显著的影响,使其热分解变得困难,因此有必要进一步探讨其他生物质对PMMA热分解的影响。     

尼龙-64的非等温结晶动力学研究

用差示量热扫描热分析仪(DSC)对在超临界CO2下聚合制备的尼龙-64样品进行了非等温结晶研究.用Jeziomy法和莫志深法对Avrami修正的方程进行了非等温结晶动力学处理,计算并得到了相关非等温结晶动力学参数.Jeziomy法处理的结果表明,尼龙-64样品的非等温结晶过程包括2个阶段,在主期结晶阶段,当冷却速率低于10℃/min时,Avrami指教n为3.59～4.12,表明主要是均相成核和晶粒三维增长;当冷却速率高于10℃/min时,晶粒的增长维度受阻;在次期结晶阶段,晶粒主要是一维增长.用莫志深法得到的a值为1.26～1.33,F(T)为6.35～13.02.此外,用Kissinger方法和Takhor方法求得尼龙-64样品的非等温结晶活化能分别为-192.05kJ/mol和-172.61kJ/mol.     

主链含苯基均三嗪联苯型聚芳醚的热稳定性

利用热重分析(TG、DTG)研究了主链含苯基均三嗪联苯型聚芳醚在不同气氛和升温速率时的热降解动力学。比较了升温速率和气体气氛对热降解行为的影响,结果表明,该聚合物具有优异的耐热性和耐热氧化稳定性。用Flynn-Wall-Ozawa,Freeman-carroll等方法进行了动力学处理,计算得热降解反应活化能分别为291.19kJ/mol,286.83kJ/mol,与Kissinger法计算活化能值283.25kJ/mol非常接近。结合Coats-Redfern方法,推测出聚合物在氮气气氛中的热分解机理为F2机理,其机理函数积分式为g(α)=1/(1-α)。     

PEO/LiClO4复合体系中PEO的等温结晶动力学研究

用差示扫描量热法研究了聚氧化乙烯(PEO)和PEO/LiClO4复合体系中PEO的等温结晶过程.用Avrami方程分析了PEO和复合体系中PEO的等温结晶动力学,得到PEO在不同体系中等温结晶时的动力学参数.PEO的Avrami指数n都趋近2.5,说明PEO晶体以三维方式依热成核生长.动力学参数表明,复合体系中的PEO以异相成核为主.LiClO4对PEO等温结晶过程的影响为:作为PEO结晶的成核剂而加快其结晶过程;增加了复合体系的粘度,缩短了PEO的半结晶时间,使其结晶总速率增大;降低了复合体系中PEO的绝对结晶度.PEO和复合体系中的PEO等温结晶时成核和生长活化能△E分别为59.28kJ/mol、70.85kJ/mol.     

乳化炸药中硝酸铵-亚硝酸钠的发泡动力学研究

为了了解和控制乳化炸药中硝酸铵-亚硝酸钠反应的发泡速率,采用减重法和量气法研究了该反应过程的反应机理和反应动力学。结果表明,酸可作为催化剂,对整个反应过程起促进作用;其次,在酸作为催化剂条件下,反应速率随着实验温度的增加而增加,且反应符合Arrhenius模型。其中,反应活化能为57.87 kJ/mol,指前因子为1.48×10~6 mol/L·s。对比实验值和计算值可知,反应动力学方程合理。为实际生产中化学敏化反应速率的控制提供了理论依据。     

双粒度分布碳酸钙对聚丙烯/碳酸钙非等温结晶动力学的影响

将纳米/微米CaCO3按照不同比例混合,并以10%(质量分数)的填充量与聚丙烯(PP)熔融共混制备了CaCO3/PP复合材料。采用广角X射线衍射仪和差示扫描量热分析研究了各样品的PP结晶形态及非等温结晶动力学。结果表明,CaCO3粒子能够诱导β晶产生,且NCP2(纳米/微米CaCO3的质量比为1∶4)中β晶的含量达到最高值1.21%;NCP2的非等温结晶动力学参数和半结晶时间在冷却速率Ф<15℃/min时相比单粒度分布CaCO3填充改性PP分别升高和降低;同一组份样品,随着结晶度增加,F(T)增加;相同结晶度下,NCP2的F(T)值最小;Kissinger法计算出PP及NCP2的结晶活化能分别为205.81 kJ/mol,201.01 kJ/mol。     

熔融聚合耐高温聚酰胺的非等温结晶动力学研究

通过差示扫描量热仪(DSC)研究了熔融聚合耐高温聚酰胺10T以及10T/11树脂在不同降温速率下的非等温结晶行为。通过Jeziorny法、Ozawa法以及Mo法分析了PA10T和PA10T/11的非等温结晶动力学,并采用Kissinger法、Takhor法以及Vyazovkin法计算了体系的结晶活化能。结果表明,在初期结晶阶段,PA10T和PA10T/11晶体的生长方式是一维针状生长和二维片状生长并存,同时存在异相成核现象;Jeziorny法、Mo法适合研究PA10T和PA10T/11树脂的非等温结晶过程,而Ozawa法不适合研究其非等温结晶过程;随着11-氨基十一酸含量增加,非等温结晶活化能的绝对值呈现先减小后增大再减小的变化趋势,说明结晶速率呈现先增加后减少再增加的变化趋势。     

Ge-Sb-Te-O相变薄膜的结晶动力学研究

用磁控溅射法制备了Ge-Sb-Te和Ge-Sb-Te-O相变材料薄膜,由热处理前后薄膜的X射线衍射(XRD)发现,热处理使薄膜发生了从非晶态到晶态的相变.通过非晶态薄膜粉末的示差扫描量热(DSC)实验测出不同加热速率条件下的结晶峰温度,并计算了材料的摩尔结晶活化能、原子激活能和频率因子.根据结晶动力学结晶活化能E判据得出结论为:与Ge-Sb-Te相比,掺杂氧后的Ge-Sb-Te更容易析晶,具有更快的结晶速率.     

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...     

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.     

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.     

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.……     

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.     

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.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.