高转变温度聚合物PTC材料的研究

研究了以尼龙12（PA12）为基体树脂，炭黑（CB）为导电填料的高转变温度聚合物正温度系数（P11C）材料。采用熔融共混方法制备了PA12/CB聚合物PTC复合材料，研究了炭黑种类、炭黑含量、炭黑表面改性等因素对PA12/CB复合材料PTC性能的影响。结果表明：Vxc305炭黑填充的PA12复合材料，当炭黑含量为30％时，PTC强度可达到105；炭黑表面改性能够抑制材料的NrC效应。     

摩擦学机敏材料中的相变控制润滑剂

探讨了摩擦学机敏材料的核心部件聚乙烯基复合导电自润滑材料的制备工艺与电性能，不同方法制得的复合材料的电阻率与导电组分炭黑含量的关系亦表现出很大的差别，与干法相比，湿法电阻率较低，过滤区组分范围更宽。据此，确定出用作复合导电自润滑材料的炭黑含量宜大于３５％。但经实验得出可以自加热发生熔融相变的合适的炭黑含量为４０％，加入润滑剂后的成复合导电自润滑材料。     

摩擦学机敏材料中的相变控制润滑剂

探讨了摩擦学机敏材料的核心部件聚乙烯基复合导电自润滑材料的制备工艺与电性能，不同方法制得的复合材料的电阻率与导电组分炭黑含量的关系亦表现出很大的差别。与干法相比，湿法电阻率较低，而过渡区组分范围更宽。据此，确定出用作复合导电润滑材料的炭黑含量宜大于３５％（质量，不同），但经实验得出可以自加热发生熔融相变的合适的炭黑含 量为４０％，加入润滑剂后构成复合导电自润滑材料，通电加热，显示出快速、易控、热性     

聚乙烯/石墨复合材料PTC效应的研究

以聚乙烯为基体材料,用石墨代替炭黑作为填充材料制作了具有明显PTC效应的有机复合导电材料,并系统研究了材料配比、加工工艺对材料PTC强度、电阻转变温度及转变规律;实验结果证明,石墨/聚乙烯体系具有明显的PTC效应和良好的综合性能。     

体积膨胀的稀释作用对聚合物基导电复合材料PTC效应的影响

聚合物基PTC复合材料中,导电填料的体积分数是一个绝缘体-导体的转换开关。理论分析表明,PTC转变区的电阻率突变与渗流曲线在临界体积分数附近的电阻率突变在导电机制上是同一的,聚合物基体体积膨胀的稀释作用对PTC效应有重要影响,在一定的温度范围内(小于PTC/NTC的转变温度),存在着定量的炭黑浓度稀释。      

导电聚苯胺纳米纤维对聚乙烯/炭黑复合体系电阻行为的影响

采用水溶液氧化聚合和热掺杂相结合的技术制备十二烷基苯磺酸掺杂的聚苯胺(PANI-DBSA)纳米纤维,并将PANI-DBSA纳米纤维与低密度聚乙烯(LDPE)和炭黑(CB)进行熔融共混制得PANI-DBSA/LDPE/CB导电复合材料,研究了PANI-DBSA纤维的引入对导电复合材料电阻行为的影响。结果表明,添加PANI-DBSA纳米纤维,复合材料的逾渗阀值移向较低炭黑含量,复合材料的PTC强度得到一定程度的提高,复合材料的电阻率-温度曲线的热循环稳定性得以改善。     

一种有机结晶物对丁腈橡胶/炭黑复合材料电性能的影响

将一种低分子量有机结晶物加入到丁腈橡胶/炭黑复合体系中制备导电复合材料。实验得出, 其电阻率随温度的变化呈不同强度的正温度系数(PTC) 效应。讨论了低分子量有机结晶物对复合材料室温电阻率及PTC 效应的影响。      

电流冲击和接枝对CB/HDPE PTC材料导电稳定性的影响

尝试了利用电流冲击和化学接枝两种方法来改善炭黑填充高密度聚乙烯 (CB HDPE)PTC材料的导电稳定性。发现对化学接枝后的PTC材料再进行电流冲击 ,能大幅度改善其导电稳定性 ,试样经多次热循环后 ,PTC曲线位移非常小     

碳系分散体填充聚合物基PTC复合材料的研究进展

总结了碳系分散体(包括碳黑、石墨、碳纤维)作为导电填料填充聚合物形成聚合物基PTC复合材料的研究进展。对聚合物基体及碳系导电填料进行共混或接枝改性是当前主要的研究方向。认为在碳系／聚合物体系中加入合适的金属系导电填料可能会更有利于提高复合材料的PTC强度和稳定性。     

导电炭黑填充PP-EAA 复合材料的形态及电性能

以聚丙烯(PP) 和乙烯-丙烯酸共聚物( EAA) 的共混物为基体材料, 以导电炭黑为填料, 通过熔融共混的方法制备了导电复合材料。探讨了导电炭黑在两相基体中的分散情况以及聚丙烯结晶度对复合体系导电性能的影响。扫描电镜测试结果表明, 在共混物中炭黑粒子选择性分散在极性EAA 树脂中, 同时EAA 树脂在聚丙烯基体中形成连续网络结构, 从而显著降低了复合体系的渗滤阈值。电性能测试结果表明, 材料在相同导电炭黑含量下的体积电阻率相对于单基体体系有7～8 个数量级的降低, 并且结晶度较高的PP 更有利于降低复合体系的体积电阻率。此外, 炭黑/ PP-EAA 复合材料的拉伸强度相对于炭黑/ PP 体系有所下降, 而断裂伸长率有所提高。      

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.     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

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.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.