电子陶瓷和器件的低温共烧技术

较系统地介绍了电子器件用低温共烧陶瓷(low temperature cofired ceramics,LTCCs)材料,探讨了其工艺中的若干问题。电子器件用低温共烧陶瓷材料包括:玻璃/陶瓷复合材料、结晶化玻璃、晶化玻璃/陶瓷复合材料以及液相烧结陶瓷,其中典型的和最为常用的LTCCs为玻璃/陶瓷(特别是氧化铝)复合材料。正在研究的一些陶瓷介质材料中,Bi基介质材料引起了人们的关注。玻璃/陶瓷复合材料的制备工艺中,应当着重关注和加深了解玻璃的流动性和结晶性、玻璃的起泡、玻璃和陶瓷颗粒间的反应、共烧材料的匹配等问题,从优选材料配方和优化工艺着手,从而获得优质可靠的材质和器件。     

纳米稀土复合固体超强酸催化合成乙酸苄酯

采用共沉淀法制备了纳米稀土复合固体超强酸SO4^2-／ZrO2-2％Nd2O3催化剂，电镜分析表明，催化剂颗粒直径在25nm左右，比表面积测定：71．03m^2／g。酸强度-12．70〈Ho〈-11．99。并对合成乙酸苄酯的最佳反应条件进行了研究。研究表明：当苯甲醇与乙酸的物质的量比为1：2，反应时间为5h，反应温度为120℃，催化剂用量为6％苯甲醇的质量时，酯化率可达92．04％。研究发现，该催化剂可重复使用并可活化再生。     

Research on the friction and wear mechanism of Poly(vinyl alcohol)/hydroxylapatite composite hydrogel

Poly(vinyl alcohol)/Hydroxylapatite (PVA/HA) composite hydrogel was prepared with poly(vinyl alcohol) and hydroxylapatite as raw materials, using the method of repeated freezing and thawing. The morphologies of PVA/HA composite hydrogel were observed by means of high-accuracy 3D profiler and scanning electron microscope (SEM). The compressive elastic modulus and the stress relaxation characteristics of PVA/HA composite hydrogel were measured using the flat-head cylinder indenter. The friction and wear tests between PVA/HA composite hydrogel and bovine knee articular cartilage were performed on the micro-tribometer. The worn morphologies of PVA/HA composite hydrogel were observed with environmental scanning electron microscope (ESEM). The results showed that PVA/HA composite hydrogel has the cross-link network microstructure which is similar to that of the natural bovine knee articular cartilages. With the increase of freezing-thawing cycles and the HA content, the degree of cross-link and the crystallization of PVA/HA composite hydrogel both increase, the elastic modulus increases evidently, the rate of stress relaxation is improved and the value of balance stress decreases. The friction coefficient decreases with the increase of the freezing-thawing cycles and the HA content. The more the freezing-thawing cycles are, the earlier the friction coefficient reaches the stable balance value. The friction deformation depth between PVA/HA composite hydrogel and bovine knee articular cartilage is inversely proportional to freezing-thawing cycles and the HA content. The main wear mechanisms of PVA/HA composite hydrogel are plastic flowing and adhesive flaking. The wear severity degree decreases with the increase of freezing-thawing cycles and the HA content. Supported by Key Program of the National Natural Science Foundation of China (Grant No. 50535050), Program for New Century Excellent Talents in University (Grant No. NCET-06-0479) and Natural Science Foundation of Jiangsu Province (Grant No. BK2005403)     

聚丙烯/弹性体复合材料的性能研究

通过共混改性的方法制备了PP/EPDM复合材料。然后对复合材料的性能进行分析,研究了EPDM的含量对复合材料的拉伸强度、冲击强度、维卡软化温度以及流动性等方面的影响规律,并对此影响规律进行合理的解释。     

Milled fibre reinforced epoxy resin — an engineering polymer composite

A milled fibre reinforced epoxy resin composite (MFRE) has been developed for low temperature use. It is resistant to fracture at temperatures down to at least 77 K in direct contact with liquefied gases. It can be used as an adhesive, a gap-filling mastic or a moulding compound for difficult cryogenic applications. The characteristics of the material and some applications are described.     

Probabilistic and interval reliability design of the composite pressure vessel

Considering the randomness or interval character of physical parameters and applied loads of composite pressure vessels (COPV), the COPV reliability-analyzing model is built. And then the computational expressions for the mean value, standard deviation and deviation of fiber stress are deduced by the random factor method. The probabilistic and interval reliability designs on COPV are implemented by utilizing the probabilistic method and interval method combined with the improved particle swarm optimization (PSO) algorithm, respectively. The influence of fluctuation of structure uncertain parameters on COPV design thickness is inspected. Finally, examples are given to demonstrate that both probabilistic and interval reliability methods can satisfy the safety requirement and both are of higher rationality than the traditional safety factor method. And probabilistic method has a lower relative error but a higher computational complexity contrasted with the interval method.     

Dynamic buffering performance of the honeycomb paperboard filled with polyurethane

A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material＇s dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffeting area of the composite material.     

我国宏观经济与证券市场关系的实证分析--基于名义 GDP 和上证指数发展速度的视角

宏观经济和证券市场的关系一直受到人们的关注,由于数据的选取和研究方法上的不同,导致宏观经济与证券市场的关系存在不同的结论或解释。从名义 GDP 和上证指数发展速度的视角,运用 HP 滤波以及 SVAR 等方法实证研究了宏观经济和证券市场的关系。研究发现：宏观经济和证券市场存在显著的因果关系;短期证券市场的波动是经济偶然性波动的预期,两者之间的滞后期效应与当期效应相互影响;方差分解表明宏观经济对于证券市场的长期贡献度很大。     

Oxidation Performance of Fe-Al/WC Composite Coatings Produced by High Velocity Arc Sprayed at 650 ℃

Fe-Al intermetallics with remarkable high-temperatureintensity and excellent erosion,high-temperatureoxidation and sulfuration resistance are potential lowcost high-temperature structural material.ProducingFe-Al/WC composite coating by high velocity arcspraying(HVAS)on structural materials would notonly obviate the problems faced in fabrication of thesealloys into useful shapes,but also allow the effectiveuse of their outstanding high-temperature performance,which might thus promisingly mak…     

纳米金刚石的应用

纳米金刚石不仅具有金刚石所固有优异特性，而且还具有纳米材料所拥有的奇异性能。正是这些综合技术特性，使得它在传统的和新的技术领域中得到应用，并初见成效，本文从超精抛光、润滑、复合镀、磁性录音系统和医疗等方面的应用做了扼要的叙述，指出，纳米金刚石颗粒具有球形和准球形的特点，使得摩擦表面形成滚珠轴承效应，而表现出良好的润滑性，从而避免于摩现象的发生，而对一些主要因接触疲劳或高温磨损而失效的工件，纳米金刚石金属的复合涂层，则具有明显的优越性。