X.L.Yang1)
,
X.Sun2)
,
C.W. Wang 2)
,
D.Q. Geng2)and C.M. Liu 2) 1)Schoolof Mechanical Engineering and Automation
,
Northeastern University
,
Shenyang 110006
,
China 2)Schoolof Material & Metallurgy
,
Northeastern University
,
Shenyang 110006
,
China
金属学报(英文版)
Thispaperintroducesa valve which useshape memory alloys( SMA) fortemperaturecon trol, which makes useof deformation of SMAcaused by variation oftemperaturetocontrolmechanical parts. Thevalvecan beswitched on or off automatically and hasthe advantages ofsimplestructureand reliable performance.Itcan beusedin adverse workingconditionsor conditions with lower requirementson controlling precision ofthetemperatures. Consequent ly,it hasextensive application prospects.
关键词:
shape memory alloy
,
null
,
null
D.Han
,
S.R.Qiao
,
M.Li
,
J.T.Hou
,
X.J.Wu
金属学报(英文版)
The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.
关键词:
2D-C/SiC
,
null
,
null
邢峰
,
江潮
,
何文望
金属学报
本文研究了Nd_2(Fe_(1-x)M_x)_(14)B的磁性。少量类金属原子C和Si取代部分Fe,能形成四方结构,且具有单轴各向异性。碳取代Fe,使化合物的Curie温度降低,低温下粘结体样品的内禀矫顽力减少;而Si对Fe的取代可使Curie温度升高,并在x=0.15附近达到极大值。含Si样品在0≤x≤0.10范围内,矫顽力显著增加,室温下从x=0的62.7kA/m增加到x=0.06的138.7 kA/m,并且在x=0.06附近,剩磁有一个极值,饱和磁化强度减少不多。
关键词:
Nd-Fe-B合金
,
magnetic properties
,
Curie temperature
吴茜
,
陈永杰
,
曹发斌
,
李郎楷
,
杨英
稀有金属材料与工程
采用高温固相法合成Eu~(2+)激活的碱土金属氯硅酸盐系荧光粉M_7Mg_2(SiO_4)_4C1_2: 0.08Eu~(2+)(M=Ca,Sr,Ba),研究了它们的荧光光谱.结果表明,3种荧光粉均为宽带激发,激发带位置分别在250～500 nm、250～450 nm、250～430 nm.讨论了Eu~(2+)离子的跃迁发射随基质组成的变化规律,随着Ca、Sr、Ba离子半径的依次增大,发射波长逐渐向短波方向移动,分别产生绿(507 nm)、蓝(458、445 nm)不同颜色的发射光.
关键词:
二价铕
,
氯硅酸盐
,
碱土金属
姜奉华
,
徐德龙
硅酸盐通报
doi:10.3969/j.issn.1001-1625.2004.06.006
通过研究Q相与C2S和Q相与C4AF的共存条件,构造Q相-C2S-C4AF水泥系统,对此系统水泥形成条件进行研究.研究表明:Q相与C2S和Q相与C4AF能够共存,可以组成Q相-C2S-C4AF-C12A7水泥系统.在Q相-C2S-C4AF-C12A7水泥系统中,Q相在1270℃开始生成,随着温度的升高,Q相的生成量逐渐增大;采用V2O5对β-C2S具有较好的稳定作用.随着C4AF量的增加,Q相的量也在增加,同时,烧成温度降低.
关键词:
Q相
,
Q相-C2S-C4AF水泥
,
形成条件
,
抗压强度
材料科学技术（英文）
The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr-1Mo stainless steel in 1M H2SO4 solution at a passive potential. The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate:, the characteristics of current response was mainly relative to the process of new surface repassivation. The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate.
关键词:
Hejun Li
材料科学技术（英文）
2D needle-punched fiber felt was infiltrated by a kind of rapid isothermal chemical vapor infiltration technique.
The infiltration process and texture transition of the infiltrated C/C composites were investigated. The porosity
and the variations of the cumulative pore volume were determined by mercury porosimetry. The texture of
matrix carbon was studied under a polarized light microscope. The results show that the relative mass gain
of the sample increases directly as the infiltration time at the initial stage until 20 h, and subsequently the
increasing rate of the relative mass gain decreases gradually with the prolonging of infiltration time. Three layers
of pyrocarbon were formed around fibers. Low-textured pyrocarbon was obtained at the initial stage. With the
densification going on, high-textured pyrocarbon was formed on the surface of low-textured pyrocarbon. Then,
low-textured pyrocarbon was produced again during the final stage of densification. The texture transition is
ascribed to the variation of the ratio of cumulative inner surface area to volume of pores and the gas partial
pressure in pores.
关键词:
C/C composites
,
Isothermal chemical vapor infiltration (ICVI)
,
Pyrocarbon
,
Mercury porosimetry
,
Polarized light microscope
Carbon
In order to improve the mechanical and ablation properties of 2D-carbon/carbon composites, a SiC filler was added to a 2D-preform before isothermal chemical vapor infiltration densification by using a powder infiltration technique. Backscattered electron images showed that the SiC filler was mainly concentrated between the fiber bundles and between the layers. The tensile and flexural strengths of the composites were improved by the addition of the SiC filler because of the increase of interfacial surface areas between the bundles and between the layers, the less residual open porosity, and also the strong bonding between the SiC particles and the pyrocarbon matrix. The composites with filler experienced a 15.2% lower thickness erosion rate and a 51.7% lower mass erosion rate, compared to those C/C without filler. This was attributed to the low oxygen permeability of the SiO2 shielding the exterior inter-bundle pores as well as to a thermal barrier effect. (c) 2006 Elsevier Ltd. All rights reserved.
关键词:
carbon/carbon composites;chemical vapor infiltration;scanning electron;microscopy;mechanical properties;ablation;carbon-carbon composites;thermal-expansion;silicon-carbide;oxidation;behavior
