Mark Ⅲ型碳化硅纤维的研制

碳化硅(SiC)纤维是具有比强度高、比模最高、耐高温、抗氧化的新型增强材料。本文对 Mark Ⅲ型 SiC 纤维制备过程中聚二甲基硅烷、派松、聚碳硅烷的合成,聚碳硅烷纺丝、予氧化、高温烧成等工艺的原理、工艺参数和产物结构分析进行了讨论。     

由PDMS与PVC共热解聚碳硅烷制备SiC-C纤维

以聚二甲基硅烷(PDMS)与聚氯乙烯(PVC)为原料,经过共热解聚合反应合成了聚碳硅烷(PCS P),并制备出SiC C纤维.利用IR、XRD、XPS等分析方法对先驱体PCS P与SiC C纤维的组成、结构与性能进行了研究.结果表明,在PVC的引入量适当的条件下,通过共热聚将少量的短碳链引入到聚碳硅烷结构中,使SiC-C纤维的电阻率显著降低到10-1～101Ω·cm,并保持了良好的结晶性和耐氧化性.     

Cf/SiC制备过程中纤维热应力损伤研究

采用束丝碳纤维和聚碳硅烷先驱体浸渍裂解工艺制成C_f/SiC丝束,并进行了分析表征,研究了其中的纤维受损情况。实验结果表明,由于先驱体聚碳硅烷在浸渍裂解时倾向于以纤维为依托进行热解,并且其中较多量的氧及杂质的存在将对纤维造成损伤,因而会形成较强的纤维基体界面;纤维基体热膨胀系数失配等因素造成的热应力将使纤维进一步受损。      

SiC－C纤维有机先驱体流变可纺性研究

用SiC纤维的先驱体聚碳硅烷与碳纤维先驱体沥青共混得到叮制备SiC-C纤维的先驱体PC-P共混物。它的流变纺丝性与组份聚碳硅烷和沥青的性质相关,只有两组份的可纺丝温度区间叠合,才可以得到可纺性好的PC-P共混先驱体。此研究结果对SiC-C纤维选择聚碳硅烷和沥青组份及共混工艺有指导意义。     

SiC－C纤维有机先驱体流变可纺性研究

用SiC纤维的先驱体聚碳硅烷与碳纤维先驱体沥青共混得到叮制备SiC-C纤维的先驱体PC-P共混物。它的流变纺丝性与组份聚碳硅烷和沥青的性质相关,只有两组份的可纺丝温度区间叠合,才可以得到可纺性好的PC-P共混先驱体。此研究结果对SiC-C纤维选择聚碳硅烷和沥青组份及共混工艺有指导意义。      

用聚碳硅烷与其它聚合物的共混物制造SiC纤维

碳化硅(SiC)纤维具有高强度、高模量、低密度、极好的耐高温氧化性、耐化学腐蚀性、耐热冲击性以及与金属、树脂、陶瓷良好的复合相容性等杰出的性能,因此在原子能工业、火箭、高温工程等尖端技术领域有广泛的应用前景。本文对用聚碳硅烷与其它聚合物的共混物制造碳化硅纤维及其性能进行了研究。     

含前驱体SiC粉体低压成型低温烧结SiC多孔陶瓷

采用聚碳硅烷和SiC粉体为原料低压成型低温烧结制备SiC多孔陶瓷,研究了聚碳硅烷含量对SiC多孔陶瓷性能的影响。SEM分析表明,聚碳硅烷裂解产物将SiC颗粒粘结起来,多孔陶瓷具有相互连通的开孔结构。烧成SiC多孔陶瓷的孔隙孔径为单峰分布、分布窄,室温至800℃之间多孔陶瓷的平均热膨胀系数为4.2×10-6 K-1。随着聚碳硅烷含量的增大,SiC多孔陶瓷的孔隙率降低、三点弯折强度增大,当聚碳硅烷质量分数为10%时分别为44.3%和31.7MPa。     

聚碳硅烷SiC纤维的高温氧化行为研究进展

概述了聚碳硅烷前驱体制备的SiC纤维高温氧化研究进展,讨论了SiC纤维的三类氧化类型,总结了近几年来国外对SiC纤维高温氧化机理研究进展,分别讨论了不同氧分压、不同CO2分压、水蒸气、盐份等不同气氛下对SiC纤维高温氧化行为的影响.     

聚碳硅烷制备连续SiC纤维的不熔化处理工艺研究进展

综述了先驱体转化法制备SiC纤维过程中聚碳硅烷(PCS)的各种不熔化处理方式及其发展状况.通过不熔化方式对终烧产物SiC纤维性能的比较,讨论了各种不熔化方式的优缺点及其对SiC纤维中氧含量的影响,并指出了制备高性能SiC纤维不熔化技术研究的国内外差距及发展趋势.     

先驱体转化法制备低电阻率Si-O-C纤维

通过采用将聚二甲基硅烷（PDMS）与聚氯乙烯（PVC）共裂解合成碳化硅－炭纤维先驱体,并经熔融纺丝及不熔化处理,最后经过烧成制得Si-C-O陶瓷纤维。讨论了影响合成产物的因素。研究表明纤维的强度随纤维中碳含量增加而下降。纤维的电阻率比单纯通过聚碳硅烷纤维得到SiC纤维大大降低。     

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 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.     

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.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.