Mg-Gd-Y-Zn合金中长周期堆垛结构形成的原位准动态背散射电子显微研究

本文利用原住准动态背散射电子显微像(BSE)并结合透射电镜观察研究了MgGd1.8 Y0.8Znx(at.%)(x=0.12,0.8,1.3)合金中长周期堆垛结构(LPS)的形成及生长形态.结果表明,当Zn含量较少时(x=0.12),铸态和各种热处理状态的合金中都未形成LPS.而在Zn含量相对较多的铸态合金(x=0.8,1.3)中,发现6层周期LPS的形成,而且Zn含量越多,LPS的体积分数越大.在300℃进行热处理时,LPS可以沿Mg基体{0001}面生长,原位准动态BSE观察可以直接揭示与LPS的生长相关的形貌变化.     

Mg—Gd—Y—Zn合金400℃热处理过程中长周期堆垛结构的形成

利用扫描电镜背散射电子像、透射电镜观察及能谱分析,研究了铸态MgGd1.8Y0.8Zn0.7（at．％）在400℃热处理前后结构的变化。结果发现,400qC热处理可导致铸态合金中初生Mg3Gd型第二相的部分分解及长周期堆垛结构（LPS）的形成。热处理形成的LPS结构为畸变的6H型,多存在于Mg3Cd型相及Mg5RE型相的前沿,并与较密集的堆垛层错（SV）组成一个富Zn元素的混合区——（SF＋LPS）区。Mg5RE型相存在于热处理后的合金中,具有fcc结构,与Mg基体有确定的取向关系,其与（SF＋Lps）区的相界处存在一个宽约10nm的过渡层。     

时效处理快速凝固Mg-5 wt.％Sn合金微观结构的电子显微分析

用显微维氏硬度仪、X射线衍射仪（ XRD）、扫描电子显微镜（ SEM）和透射电子显微镜（ TEM）研究分析了快速凝固Mg?5 wt?％Sn合金条带的时效硬化规律。实验结果表明,快速凝固Mg?5 wt?％Sn合金在593 K温度下时效3 h后达到峰值硬度。时效后峰值硬度下的快速凝固Mg?5 wt?％Sn合金中有β?Mg2 Sn相颗粒析出,大多数的析出相β?Mg2 Sn颗粒分布在晶界,少部分析出相β?Mg2 Sn颗粒分布在晶粒内部。在593 K温度下时效3 h后的合金中观察到析出相β?Mg2Sn 颗粒与基体α?Mg 的一种新取向关系：（202261）β／／（0110）α,（7236）β／／（0001）α,[512]β／／[2110]α。     

热处理条件下变形结构与长周期堆垛结构复合强化镁合金

点冲击变形Mg?Y?Nd?Zn合金中存在高密度孪晶。在400℃热处理过程中,孪晶界附近形成弯折带;孪晶界与弯折带边界向基体发射大量长周期堆垛结构（ LPS）。最终在Mg?Y?Nd?Zn合金中实现高密度孪晶、弯折带和LPS的三重复合强化组态。     

凝固冷却速率影响下Al-Pd-Co复杂合金相的形成及分布特征

复杂合金相具有不同于传统金属的结构特征。为了搞清凝固冷却条件对铸态Al-Pd-Co复杂合金相存在状态的影响,本文应用TEM、SEM、HREM、EDS等多种电子显微学手段,分析了不同凝固冷却速率下Al70Pd10Co20三元合金中复杂合金相形成和分布特征。通过比较不同凝固冷却速率下凝固组织的形貌和成份的变化,推断出Al70Pd10Co20合金凝固过程中,M-Al13Co4和O-Al13Co4型复杂合金相的高温形成具有宽化的成分区间。随着凝固冷却速率的提高可导致另一具有复杂结构的W相的形成并与M-Al13 Co4和O-Al13 Co4型相共生,其结构包含与Al-Pd-Co十面体准晶同类的十面体原子团结构单元。     

铸态Mg96Zn3Y1合金高温热处理显微结构的电子显微研究

本文应用扫描背散射电子(SEM-BSE)像和透射电子显微(TEM)像观察的方法,研究了铸态Mg96Zn3Y1(at.％)合金经过500℃高温热处理后显微组织结构的变化.结果表明铸态Mg96Zn3Y1(at.％)合金中的初生相为网格状形貌,其中多数为面心立方W(Mg3Zn3Y2)相,少数为二十面体准晶Ⅰ(Mg3Zn6Y)...     

Al-Li-Cu-Zr-Ce合金中T1相的TEM观察

Al-Li-Cu-Zr-Ce合金中的T1相是一种层片状析出物,它的形核和长大过程对合金的性能有很大影响.本文用TEM研究了543K时效时T1相的形成过程、形成机理、相结构,并对相变形成的层错调制结构进行了分析.     

AZ61＋xCe（x=0～1.5）合金的微观组织研究

研究了不同铈含量对AZ61镁合金铸态及热处理态显微组织的影响。结果表明：与AZ61合金铸态组织相比,加入铈后,合金中的β相数量减少,形态变细,铸态晶粒得以细化;含铈合金中大部分铈与铝结合生成高熔点、高热稳定性的Al3Ce稀土相;在固溶处理中,β相完全溶解而Al3Ce相仍以针状或棒状存在于晶界附近,起到了阻碍晶粒长大的作用。基于XRD、SEM、EDS测试结果,并应用Miedema混合焓模型对稀土相的形成进行了分析,由于Ce与Al的亲和力远大于Ce与Mg的亲和力,合金中Ce与Al结合形成Al3Ce稀土相。     

Ti-6Al-4Cr（Mo）合金热处理显微组织的研究

本文采用扫描电镜与透射电镜分析研究了Ti-6Al-4Cr和Ti-6Al-4Mo合金固溶和时效过程中显微组织的变化。结果表明：Ti-6Al-4Cr和Ti-6Al-4Mo合金经过相似的两相区固溶处理后,组织差别较大;两种合金经过β相区固溶后再时效,形成典型的魏氏组织,且硬度值较两相区处理的样品有很大提高;两种合金在相同热处理制度下,硬度值变化趋势相似,但前者的硬度值明显大于后者;Ti-6Al-4Cr合金在各种热处理条件下都有富Cr的固溶体区产生,经过1000℃/45min/空冷＋600℃/2h/空冷处理后,有Laves相和界面相析出。     

低温注入硅片中的锗在快速热处理后的再分布

大剂量(4×1016cm-2)的Ge离子在77K低温下被注入于(100)硅片中,并结合随后的1080℃快速热处理(RTP)以形成Si/SiGe异质结构.用卢瑟福背散射技术和二次离子质谱技术研究注锗硅片退火前后Ge的分布.结果表明,快速热处理退火不仅能使注锗硅片发生固相外延生长,表层形成合金层,而且导致Ge向表面的质量运输.最终出现平台式的Ge分布形态.快速热处理后Ge这种再分布被认为有利于提高HBT的增益和获得表面应变沟道.     

On the periodic coupling of propagating structures

An analysis of two propagating structures periodically coupled together, based on a method developed by J. R. Pierce, is presented. A periodic structure that supports a backward wave may be coupled to a structure that supports a forward wave by coupling to alternate cells of the former. The coupling is completely analogous to the case of continuously coupled waves; i.e., energy is transferred back and forth between the two guides periodically and the period of the transfer is inversely proportional to the strength of the coupling. The period of the transfer is also a function of the number of couplers per unit length. A method of measuring the coupling coefficient is presented and application to a coupled-structure attenuator is discussed.     

Investigation of the generation characteristics of metal-insulator-semiconductor structures

A method for determining the surface and volume generation-recombination parameters of MIS structures based on nonequilibrium C(V) and dC/dV(V) measurements using the linear voltage sweep technique is proposed. A theory is developed enabling simple treatment of experimental data and taking into account the dependence of the surface generation velocity, S_g, on the minority carrier concentration p_s. It is shown that the linearity of Zerbst plots can be obtained by using the trustworthy S_R(p_s) relation. Some experimental data concerning the generation properties of the Si---SiO₂ interface are presented. In particular, the experimental S_R(p_s) curves are shown to be in qualitative agreement with the theoretical predictions.     

几种新结构的室外光缆

文章首先综述了几种新结构的室外光缆，其次推测出室外光缆结构的变化趋势．     

新型多层波导全息存储结构的设计

提出了一种新型多层波导全息存储结构，该结构由波导输出光栅和体全息层为单元构成，其光的衍射效率得到很大的改善，读出光的耦合效率理论上可达到50%。同时，该结构不同单元记录层的信号读出时串扰很小。有望在全息光存储、三维立体彩色显示等方面得到应用。     

Analysis of microstrip antenna structures using the `add-on'technique

Microstrip antennas and antenna arrays are analyzed using the add-on technique. The goal of this work is to provide a way of handling more than 1000 unknowns while maintaining agreement with the moment method. The problem of a 1008-unknown finite array, with 11 elements and connecting and feeding lines, is an example of the capability of the method. In a CPU time of 1.5 h for each frequency point, accurate impedance results are obtained from the resultant standing-wave pattern along the feeding microstripline. The accuracy of the method is established by comparison with published results when possible, and by the computation of the root mean square (RMS) error in the boundary condition on the conductor     

Simulation of Finline structures using the tlm method

A new model of absorbing boundary for the TLM Method, based on absorvence condition on the node, is presented. Numerical and experimental results are presented; and the convergence aspect is discussed.     

Properties of MNOS structures

The properties of thin oxide MNOS structures are studied. An analytical theory for the switching time constant is derived and curves of the switching time constant versus the nitride field are computed. These curves are useful in the design of MNOS-memory transistors. The theory is compared with experiments. The normal current in the thin oxide MNOS structures is assumed to be a modified Fowler-Nordheim current. At small oxide thicknesses and low nitride field, an additional current is shown to exist that is attributed to direct tunneling into traps in the nitride. The discharge of MNOS structures is briefly discussed and is shown to be due to a direct tunneling of charge carriers from traps in the nitride into the semiconductor.     

Moulding of arrowhead structures

Micron-sized dot-like arrowhead structures were replicated by moulding with an elastomer. In order to address the impact of prepolymer viscosity on stamp filling of the structures and the impact of elasticity on stamp separation of these structures three different PDMS materials were investigated. The moulding results obtained for different geometries of the arrowhead structures were evaluated with respect to typical defects. The results could be well understood in view of the material properties derived from simple characterisation measurements. Sylgard 184 provided the best replication results.     

Eigenmodes of multiwaveguide structures

Finite periodic structures for multichannel waveguiding are analyzed by self-consistent field matching at the interfaces and matrix formalism for lateral propagation. The characteristic eigenvalue equation for a symmetric system with N coupled slab waveguides is shown to be of the same functional form as that of a single-slab waveguide. The eigenmodes of the system are exactly calculated and compared to the approximate results of coupled mode theory. Basic features of multiwaveguide structures not derivable from the coupled-mode theory (CMT) are uncovered by rigorous formulation and solutions. More complicated structures are solved, and ways of mode shaping and mode filtering are suggested