SiNx钝化膜厚度对pHEMT的性能影响

深入地研究了ＳｉＮｘ钝化膜厚度对ＡｌＧａＡｓ／ＩｎＧａＡｓ／ＧａＡｓ ｐＨＥＭＴ电性能的影响,实验结果表明,ｐＨＥＭＴ器件的截止频率随着氮化硅钝化膜厚度的增加而下降;妆膜厚超过２００ｎｍ时,将影响ｐＨＥＭＴ器件电特性。     

980nm InGaAs／GaAs／AlGaAs应变量子阱激光器

报导了脊形波导ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变量子阱激光器的特性和实验结果，激光器阀值电流最低为９ｍＡ，典型值为１５ｍＡ，线性输出光功率大地１２０ｍＷ，微分量子效率典型值为６０％，５０℃，８０ｍＷ恒定功率条件下老化实验结果表明；该条件下激光器寿命超过１０００小时。     

GaAs Mach－Zehnder型光波导开关／调制器

采用非对称Ｘ结耦合器代替传统的Ｙ分支器，研制了ＧａＡｓＭａｃｈ－Ｚｅｈｎｄｅｒ型２×２光开光，得到了小于－２２．４ｄＢ的串音比和１２Ｖ左右的开关电压，器件的波导传输损耗小于７ｄＢ／ｃｍ。预计该器件可广泛应用于ＧａＡｓ开关列阵及高速光调制等领域。     

1.08μmInAs/GaAs量子点激光器光学特性研究

介绍了ＩｎＡｓ／ＧａＡｓ量子点激光器的材料生长,器件制备及其光学特性的研究。器件为条宽１００μｍ,腔长１６００μｍ未镀膜激器。室温阈值电流密度为２２１Ａ／ｃｍ＾２,激射波长为１．０８μｍ,连续波工作最大光功率输出为２．７４Ｗ（双面）,外微分效率为８８％,经５０℃,１０００ｈ老化,仍有〉１．２Ｗ的光功率输出。     

SI-GaAs晶片的PL mapping表征技术

研究了扫描光致发光光谱（ＰＬｍａｐｐｉｎｇ）在表征半绝缘砷化镓（ＳＩ－ＧａＡｓ）材料中的应用,实验结果表明ＳＩ－ＧａＡｓ晶片的强度及ｍａｐｐｉｎｇ均匀性对器件性能有着十分密切的关系,所以在为制备器件筛选优质的ＳＩ－ＧａＡｓ材料时,除了电阻率、迁移率、位错密度,碳含量,ＥＬ２浓度及其均匀性,晶片表面质量上,ＰＬｍａｐｐｉｎｇ也是表征材料质量的一个重要参数。     

0.1-0.3μmX射线光刻技术在GaAs器件制作中的应用

对同步辐射Ｘ射线光刻及在ＧａＡｓ ＰＨＥＭＴ器件制作中的应用进行了研究,并制作出栅长０．１５μｍ的ＡｌＧａＡｓ／ＩｎＧａＡｓ／ＧａＡｓ ＰＨＥＭＴ晶体管。研究结果表明,Ｘ射线光刻在肃离图形册结构制作工艺中具有极好的光刻图形质量,在混合光刻工艺中,抑止ＧａＡｓ合金点的形成是取得良好的对准标记的关键。     

GaAs的ICP选择刻蚀研究

选择刻蚀在ＧａＡｓ工艺中是非常重要的一步。由于湿法腐蚀存在钻蚀和选择性差,且精度难以控制,因此有必要进行干法刻蚀的研究。虽然采用反应离子刻蚀（ＲＩＥ）、磁增强反应离子刻蚀（ＭＥＲＩＥ）可以进行选择刻蚀,但是这两种方法在挖槽时会对器件造成较大损伤,影响器件性能。感应耦合等离子刻蚀（ＩＣＰ）是一种低损伤、高刻蚀速率高选择比的刻蚀方法,在ＧａＡｓ器件的制造中有突出的优点。本工作进行ＧａＡｓ／ＡｌＧａＡｓ     

InGaAs/InP中离子注入和新型HPT

ＩｎＧａＡｓ／ＩｎＰ是制作光电器件与微波器件的重要材料。离子注入ＩｎＧａＡｓ／ＩｎＰ做掺杂或制作高阻层是人们十分关注的研究课题。采用Ｆｅ＾＋注入ＩｎＧａＡｓ／ＩｎＰ得到了电阻率升高的好结果。用Ｂｅ＾＋注入制作了新结构ＨＰＴ的基区。研制成功了在１．５５μｍ波长工作的ＩｎＧａＡｓ／ＩｎＰ新结构光电晶体管,在０．３μＷ入射光条件下,光电增益为３５０。     

K波段单片功率放大器

报道了Ｋ波段的ＰＨＥＭＴ ＭＭＩＣ的设计与研制。ＰＨＥＭＴ器件采用０．５μｍ栅长的３ｉｎｃｈ ＧａＡｓ标准工艺制作。三级的ＭＭＩＣ放大器在１８ＧＨｚ处,线性增益１７ｄＢ,输出功率Ｐ－１＝１９ｄＢｍ。Y     

光阴极材料GaAs／AlGaAs的组分分析

为探索砷化我阴极的光电灵敏度的影响因素,利用Ｘ射线光电子能谱、二次离子擀谱和电化学方法测试和分析了国内和国外ＧａＡｓ光阴极材料ＧａＡｓ／ＡｌＧａＡｓ的Ｃ,Ｏ含量的空穴深度分布。实验发现,国内的材料在ＧａＡｓ／ＡｌＧａＡｓ 面及ＡｌＧａＡｓ层的Ｏ含量分别为７．６％和１０．６％,Ｃ深度分别为５．２×１０＾１８ａｔｏｍｓ／ｃｍ＾３和１．０×１０＾１９ａｔｏｍｓ／ｃｍ＾３,而国外的材料的Ｏ含量相应为１．０     

热老化对316LN不锈钢焊缝微观组织和冲击性能的影响

为研究核电站主管道316LN不锈钢焊缝的热老化,开展了316LN不锈钢在400℃下15000h的加速热老化实验。采用TEM和HREM研究热老化后焊缝微观组织演变,利用冲击实验测定不同热老化时间下焊缝夏比冲击性能;以夏比冲击功作为热老化脆化参量,通过拟合法获得了焊缝热老化脆化动力学公式,利用热老化动力学公式预测焊缝在实际运行温度下服役60年内的夏比冲击功变化。结果表明:经1000h热老化后焊缝中的铁素体已经发生了调幅分解,形成了富Fe的α相和富Cr的α′相,同时在铁素体内析出了G相;焊缝中铁素体调幅分解和G相析出导致焊缝冲击功随时间延长而不断下降;夏比冲击功预测结果显示在运行25年内冲击功下降较快,随后的运行过程中下降过程趋缓。     

Precipitation behavior of high-Nb containing modified HR3C heat-resistant steels during isothermal aging

The effect of Cr content on microstructural stability of the modified high-Nb content HR3C austenitic heat-resistant steel has been investigated during thermal aging at 700°C. It was observed that the σ phase precipitated in the 23.5Cr–18Ni–1.7Nb–0.04C–0.1N (wt.%) steel after aging treatment. However, the σ phase was not observed throughout the aging up to 5000?h as the Cr content was reduced from 23.5 to 21.5?wt-%. Experimental results showed that the yield strength of steel with 23.5?wt-% Cr at room temperature increased from 261 to 492?MPa after aging for 5000?h. The strengthening is closely related to the precipitation of σ phase at early stage of aging (500–2000?h). The influence of alloying elements on the formation of σ phase is discussed.     

Effects of thermal aging on fracture performance of polychloroprene

Measurements of tensile and tearing resistance have been conducted as a function of aging time and aging temperature for a polychloroprene (CR). The steady increase in stiffness indicates that crosslinking is dominant during the aging of CR. In the early stage of aging, tensile strength and tearing energy increase thanks to an optimized balance between the strength enhancement from the crosslink network and the network capability in dissipating energy. Prolonged aging after a characteristic time results in a gradual decrease in strength and tearing energy and this change is more pronounced with higher aging temperatures. The superposition principle between aging time and aging temperature was used to determine the activation energy controlling the change of tearing energy in thermal aging. This value agrees with the activation energy E_a = 91 kJ/mol reported in current literature by monitoring the oxygen consumption rates during the aging of CR, suggesting that the change in tearing energy is controlled by chemical reactions much the same as the change in oxygen consumption dissolved in the material. It was also found that the variation in the strain energy density to break is also controlled by the same activation energy.     

Phase Transformation and Thermal Stability of Aged Ti-Ni-Hf High Temperature Shape Memory Alloys

The use of Ni-rich TiNiHf alloys as high temperature shape memory alloys （SMAs） through aging has been presented. For Ni-rich Ti80-xNixHf20 alloys, their phase transformation temperatures are averagely increased more than 100 K by aging at 823 K for 2 h. Especially for the alloys with Ni-content of 50.4 at. pct and 50.6 at. pct, their martensitic transformation start temperatures （Ms） are more than 473 K after aging. TEM observation confirmed that some fine particles precipitate from the matrix during aging. The aged Ni-rich TiNiHf SMAs show the better thermal stability of phase transformation temperatures than the solutiontreated TiNiHf alloys. The fine particles precipitated during aging should be responsible for the increase of phase transformation temperatures and its high stability.     

高温环境下碳纤维增强树脂复合材料的层间力学性能老化行为与失效预测

为了研究碳纤维增强树脂(CFRP)复合材料层间力学性能在高温环境中的老化失效行为,设计了CFRP复合材料层间拉伸和层间剪切实验,在高温(80℃)环境中进行0(未老化)、 120 h、 240 h、 360 h、 480 h、 600 h和720 h的老化测试,分析CFRP层间失效强度和失效形式随老化时间的变化规律,得到随高温老化的二次应力准则响应面。建立CFRP复合材料层间力学性能预测模型,得到不同老化衰减系数下的退化模型,并通过CFRP复合材料层间仿真模型进行了验证。结果表明:随着高温老化时间的增加,层间拉伸和层间剪切强度总体上都发生了一定程度的退化,层间拉伸时更容易发生碳纤维丝剥离,层间剪切发生局部的树脂剥离,纤维之间的分层更加明显,高温老化使树脂与纤维丝的界面结合力显著下降。通过CFRP复合材料层间力学性能随高温老化的二次应力准则,计算不同老化时间后的内聚力模型参数,预测CFRP复合材料在高温老化条件下的层间强度,发现仿真与实验误差小于10%,说明了CFRP复合材料层间失效预测模型的准确性。     

Microstructural Evolution of P92 Steel During Long-Term Aging

The mechanical properties and microstructure evolution of P92 steel were investigated after aging up to 11,000 h at 923 K. Charpy impact and tensile tests were carried out to study the strength and ductility of aged P92 steel. In addition, microstructure evolution of the samples during long-term aging was investigated with X-ray diffraction, optical microscopy and scanning electron microscope (SEM). Then, statistical quantitative image analysis based on SEM images was used to evaluate the precipitation during long-term aging. The mechanical properties were found to be associated with the evolution of precipitation, especially the coarsening of Laves-phase. Results show that the ductility and strength of P92 steel decrease with the growth of Laves-phase during short-term aging (shorter than 1000 h). However, as the aging time further increasing, the ductility and strength of P92 steel decrease slowly with the coarsening of Laves-phase.     

Cu对Fe-NiAlMn合金析出强化过程的影响EI北大核心CSCD

将Fe-NiAlMn和Fe-CuNiAlMn合金在900℃固溶2 h后水淬,并在500℃时效不同时间。利用显微硬度测试和原子探针层析技术(APT)研究Cu的添加对Fe-NiAlMn合金析出强化过程的影响。结果表明:Cu的添加增强了时效初期的析出强化效果,加快了整个析出强化进程。时效过程中,Cu元素首先偏聚形核成为富Cu相,并促使Ni,Al,Mn元素在富Cu相与基体界面处偏聚形核形成Ni(Al,Mn)相,两相为核壳结构。随着时效时间的延长,富Cu相由BCC结构转变为FCC结构,与Ni(Al,Mn)相逐渐分离。     

Influence of post-weld heat treatments on microstructure and mechanical properties of gas tungsten arc maraging steel weldments

Abstract

The response to post-weld heat treatment of an 18%Ni (250 grade) gas tungsten arc weld metal has been investigated. The post-weld heat treatments are (a) direct aging at 480°C/3 h/air cooling, (b) solutionising at 815°C/1 h/air cooling+aging at 480°C/3 h/air cooling and (c) homogenisation at 1150°C/1 h/air cooling+solutionising at 815°C/1 h/air cooling+aging at 480°C/3 h/air cooling. Metallographic characterisation of fusion zone revealed pronounced segregation of titanium and molybdenum along the interdendritic and intercellular boundaries. This led, during subsequent aging, to austenite reversion at temperatures much lower than in wrought (unwelded) material. Solutionised treatment at 815°C does not remove the segregation. Homogenisation treatment (1150°C/1 h/air cooling) succeeded in making the composition become homogenised. Mechanical properties including tensile, hardness and impact toughness were evaluated. Tensile test results showed that directly aged weldments exhibited lower strength but higher ductility than the other cases; this was attributed to the presence of reverted austenite. Homogenisation at 1150°C/1 h/air cooling+solutionising at 815°C/1 h/air cooling+aging at 480°C/3 h/air cooling resulted in optimum tensile properties. A substantial increase in fusion zone toughness was observed after homogenisation+solutionising+aged condition due to a decrease in the content of austenite content compared to the directly aged condition. The reduction in microsegregation by diffusion of alloying elements from cell boundaries to the cell during homogenisation treatment is responsible for the decrease in austenite content.     

Effects of rapid heating on aging characteristics of T6 tempered Al–Si–Mg alloys using a fluidized bed

Effects of rapid heat transfer using a fluidized bed on the heat-treating response of Al–Si–Mg alloys (both unmodified and Sr modified) were investigated. Heating rate in fluidized bed (FB) is an order of magnitude greater than in conventional air convective furnaces (CF). On aging using FB, it was observed that the nucleation rate of Mg₂Si particles was greater than in CF. Thermal analyses show an endothermic reaction during aging in CF. No such transformation was observed during aging in FB. The endothermic transformation could be due to the dissolution of GP zones or metastable phase(s). The total heat treatment time for T6 temper was reduced to less than 2 h using FB.     

Wetting Behavior and Interfacial Reactions in (Sn-9Zn)-2Cu/Ni Joints during Soldering and Isothermal Aging

The wetting property of (Sn-9Zn)-2Cu (wt pct) on Ni substrate and the evolution of interfacial microstructure in (Sn-9Zn)-2Cu/Ni joints during soldering as well as isothermal aging were studied.The wetting ability of eutectic Sn-9Zn solder on Ni substrate was markedly improved by adding 2 wt pct Cu into this solder alloy.Plate-like Cu5Zn8 intermetallic compounds (IMCs) were detected in (Sn-9Zn)-2Cu solder matrix.A continuous Ni5Zn21 IMC layer was formed at (Sn-9Zn)-2Cu/Ni interface after soldering.This IMC layer kept its type and integrality even after aging at 170℃ for up to 1000 h.At the early aging stage (before 500 h), the IMC layer grew fast and its thickness followed a linear relationship with the square root of aging time.Thereafter,however, the thickness increased very slowly with longer aging time.When the joints were aged for 1000 h,a new IMC phase, (Cu,Ni)5Zn8, was found in the matrix near the interface.The formation of (Cu,Ni)5Zn8phase can be attributed to the diffusion of Ni atoms into the solder matrix from the substrate.