ION HEATING PROCESS DURING PLASMA IMMERSION ION IMPLANTATION

1.IntroductionIonbombardmelltusingplasmaimmersionmethodhasprovenaneffectivesurfacemodificationtechnique[2,3].Plasmaimmersionionimplantation(Pill)cansignificantlyimprovethesurfacepropertiesofthecomponents,suchashardness,friction,wear--resistanceandcorrosion--resistanceofthematerials.Meanwhileitsbiggestadvantageistheabilitytotreatirregularlyshapedobjectswithoutthenecessityoftargetmanipulation.Pillprocesscanbeconductedbyeitheratalowtemperature(<100'C)orelevatedtemperatureconditions(usually300'C…     

IN-SITU OBSERVATION OF THERMAL FATIGUE CRACK GROWTH IN STEEL 3Cr2W8V

The growing process of thermal fatigue cracking,in steel 3Cr2WSV was observed under deskSEM fitted with sell-made minisized device for thermal faligue test.Before the growing ofthermal fatigue crack,the main crack tip reveals to blunt firstly,and some holes anduncontinuous microcraeks occur in front of it.The growth is developed by bridging of maincrack together with holes and microcracks.     

钙钛矿型La_(1-x)Sr_xFeO_3和LaNiO_3纳米晶在双功能氧电极上的应用

采用溶胶－凝胶法制备了双功能氧电极催化剂Ｌａ１－ｘ Ｓｒｘ ＦｅＯ３ 和ＬａＮｉＯ３ 纳米晶,用ＸＲＤ、ＴＥＭ 技术对催化剂进行了表征,并采用稳态极化曲线法和循环伏安法考察了不同催化剂对氧电极的催化活性,充放电实验进行了寿命考查。结果表明,纳米级钙钛矿型复合氧化物Ｌａ１－ｘ ＳｒｘＦｅＯ３ 和ＬａＮｉＯ３ 作为催化剂用在双功能氧电极上具有良好的双向催化性能,并且纳米晶Ｌａ１－ｘ Ｓｒｘ ＦｅＯ３ 对氧阴极还原催化性能在ｘ＝ ０．５ 及ｘ＝ ０．２５时最佳,对氧阳极析出催化性能在ｘ＝ ０．７５时最佳。实验结果表明纳米级催化剂催化活性优于传统方法制备的非纳米级催化剂的活性     

MICROSTRUCTURES AND PROPERTIES OF SiC_w/AL COMPOSITES

This paper presents an investigation on the microstructures and properties of the17v.-% SiCw/Al-12Si composites.TEM observations and EDAX analysis revealed that Aldiffuses into the SiC whiskers and that dislocations exist at the whisker/matrix interfaces.Tensile test results showed that the isothermal exposure and thermal cycle at both 573K and733 K caused the UTS reduction of the composites,and the reduction in UTS due to thermalexposure at 733 K was much more significant than that due to thermal cycle at the same tem-perature.The SiC_W/Al-12Si composites were also found to have exellent wear resistance,which does not seem to vary much with the volume content of whiskers in the ronge of 11—17%.     

CRITICAL NOTCH(CRACK)SIZE AS A CHARACTERISTIC PARAMETER EVALUATING CRYOGENIC BRITTLENESS IN LOW CARBON STEEL

The effect of notch depth on the cryogenic fracture behavior has been studied using a low car-bon steel.An analysis was made for the fracture features at T_c~*(cryogenic brittleness-char-acteristic temperature)at which the facture load reaehes a valley value.Furthermore,accord-ing to the experimental results and engineering design practice,a concept of critical notch(crack)'size for cryogenic brittleness,a_c,as well as its limit value a_c~*,was put forward andrecommended to be a basic characteristic parameter for controlling the brittleness.Mathematical derivation was carried out to give the expression of a_c and a_c~*,the reliabilityof which was verified by the modeling tests under both static and cyclic loading conditions.     

SPREADING PHENOMENON OF Al/Cu CONTACTING REACTION BRAZING

The reactive spread behaviour of Cu particles on the surJace of Al has been studied.The roleof oxide film and the .formation mechanism of the joint during Al/Cu contacting reactionbrazing have been discussed.     

FRACTURE BEHAVIOUR OF SiC WHISKER REINFORCED Al COMPOSITES

The dynamic tensile processes of silicon carbide whisker reinforced Al composite(SiC_w/Al)with 22% V_f have been in situ observed with a scanning electron microscope equipped with atensile stand.The results show that a number of microcracks have formed as the tensile stressincreases to 180～190 MPa.Microcracks form in most cases at the whisker ends.The frac-ture behaviour of SiC_w/Al composite observed has been explained theoretically.KEY WORDS composite,fracture,stress distribution,SiC whiskers,aluminum     

施受主杂质La,Mn共掺BaTiO3陶瓷PTC特性的研究

采用溶胶－凝胶法制备施主杂质Ｌａ和受主杂质Ｍｎ均相共掺ＢａＴｉＯ３半导体陶瓷。掺杂过程中以Ｌａ、Ｍｎ的硝酸盐水溶液代替醇盐实现相掺杂,改善组分均匀性。讨论了受主杂质Ｍｎ的浓度与陶瓷ＰＴＣ性能的关系,并结合ＸＰＳ测量结果,对其影响ＰＴＣ效应的生观机制进行探讨。     

Thermal Residual Stresses in SiCw/Al Composite

The SiCw/6061Al composites were fabricated by squeeze casting method. Varia-tions of thermal residual stresses with quenching temperature, cooling manner, aging time and thethermal-cold cycle process in thin specimens,and the distributions of thermal residual stresses alongthe distances from the surface and changes with heating temperatnres in thick specimens were stud-ied by means of X-ray diffraction (XRD). The effects of residual stresses on the mierostructure, di-mensional stability and age-hardening behavior were studied by SEM, TEM observations, and tensiletest. The results showed that there existed macrostress, microstress and thermal mismatch stress inSiCw/Al compo-site,and the presence of microstress and thermal mismatch stress has no influenceon the measurement of macrostress, but the macrostress can affect the measured value of thermalmismatch stress. Thermal res dual stress induced during the composite fabrication process, will be further in-creased when the composite were subjected to the e     

一种离散余弦变换电路的并发故障检测结构…

本文提出了一种离散余弦变换 (DCT)电路的并发故障检测结构。DCT采用 B.G.L ee算法蝶型结构实现 ,检测采用的方法是基于算法的并发故障检测容错方法。与其它并发故障检测容错结构相比 ,本文提出的并发故障检测 DCT结构在硬件及时间冗余度上均优越