Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl₃ and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m² in a solution containing 1.53 mol/L H₂SO₄ and 0.018 5 mol/L Al₂(SO₄)₃·16H₂O at 20 °C. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.     

RHEOLOGICAL PROPERTIES OF MIXED GELS

The rheological properties of carrageenan/gelatin and agar/gelatin mixed gels were investigated by measuring the rupture properties, the texture parameters and the dynamic viscoelasticities. fie melting point, transparency and syneresis of these gels were measured in order to obtain the relationship with the rheological properties. The physical properties of the two mixed gels were slightly different. The agar/gelatin mixed gels generally showed the hindered effect of gelatin. The brittleness of agar gel disappeared on mixing with gelatin. It then became a flexible, cohesive and transparent gel. Carrageenan/gelatin mixed gels showed a decrease in the values of almost all of the mechanical properties when compared with carrageenan gels. However, the rupture properties of the C0.5 mixed gel were much higher than those of simple carrageenan gels.     

Evaluation of D(d,n)3 He reaction neutron source models for BNCT irradiation system design

A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution were applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code. Three cases of D-D neutron source corresponding to incident deuteron energy of 1000,400 and 150 key were inves- tigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-euergetic and isotropic neutron source model.     

Study on Radial Position of Impurity Ions in Core and Edge Plasma of LHD Using Space-Resolved EUV Spectrometer

Radial profiles of impurity ions of carbon, neon and iron were measured for high-temperature plasmas in large helical device (LHD) using a space-resolved extreme ultraviolet (EUV) spectrometer in the wavelength range of 60 to 400?. The radial positions of the impurity ions obtained are compared with the local ionization energies, Ei of these impurity ions and the electron temperatures TeZ there. The impurity ions with 0.3?Ei?1.0 keV are always located in outer region of plasma, i.e., 0.7?ρ?1.0, and those with Ei?0.3keV are located in the ergodic layer, i.e., 1.0?ρ?1.1, with a sharp peak edge., where ρ is the normalized radial position. It is newly found that TeZ is approximately equal to Ei for the impurity ions with Ei?0.3keV, whereas roughly half the value of Ei for the impurity ions with 0.3?Ei?1.0keV. It is known that TeZ is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at ρ?1.0 and the ergodic layer at ρ?1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D=0.2 and 1.0m2/s, which can be taken as a typical index of the transverse transport.     

湿法化学制备的超薄和极薄二氧化硅/硅膜的光学性能研究

二氧化硅薄膜至今依然属人们广泛研究的材料,这是因为当这种材料制备为高质量的超薄、极薄的氧化物时,可实际应用于不同方面,如超大规模集成电路（VLSI）的栅氧化层以及液晶显示屏（LCD）的生产。本文考察了厚度为3 nm和5 nm的极薄二氧化硅层的结构性质,这些薄层是通过适度掺杂n-型硅（100）晶片而形成。在形成氧化层之前用标准RCA方法清洁,并随后在氮气氛围中退火,部分样品在HCN溶液中钝化。本研究中用傅立叶变换红外光谱（FT-IR）技术获取了复合结构中不同类型的化学键信息。对SiO₂钝化试样和非钝化试样中的Si-O-Si的不对称伸缩振动分别用纵光(LO)和横光(TO)模式进行了鉴别,发现TO模式位置（约1 107 cm^-1）和振幅与试样的厚度无关。另一方面,LO模式的位置从约1 230 cm^-1（厚度约为1.5 nm）改变为1 244 cm^-1 左右（厚度约为4.5 nm）。根据红外光谱峰的偏移,认为超薄和极薄SiO_x复合结构并不均匀。对红外光谱获得的结果进行了反褶积处理并获取相关信息。用次级离子质谱分析法（SIMS,Secondary Ion Mass Spectrometry）考察了试样的原子组成,发现NH键的数量也与技术条件相关。基于记录的试样X-反射率数据的理论处理结果,用原始方法确定了材料的结构性质、层密度、表面粗糙度以及相应界面,并将所得结果与原子力显微镜所获得的结果进行了对比和讨论。借助于深能阶瞬态光谱学中的电荷变形,证实HCN溶液对二氧化硅/硅界面密度的强钝化影响。钝化后,发现新形成的界面深处缺陷阱其密度可以忽略不计,这是因为其形成原因与钝化过程中在界面处引入的NH原子对存在相关。     

高灰熔点煤加压气流床气化特性

在25 kg/h规模的沉降式加压气流床气化实验装置上,研究了高灰熔点煤种在固态排渣温度范围内的气化特性及灰渣熔融特性.结果表明,气化温度、碳转化率均随O/C物质的量比的增加而增加,冷煤气效率则随O/C物质的量比的增加旱现先增大后减小的变换规律;本实验条件下,最佳O/C物质的量比在1.0～1.2之间,此时冷煤气效率达最大值(42%左右),相应碳转化率为90%;对最佳工况下气化炉底部、旋风分离器和布袋除尘器内的灰渣进行SEM分析表明,该工况下气化炉底部、旋风分离器内的灰渣在整体上仍以固态形式存在,只是有部分低熔融成分发生熔融,其熔融部分的粒径在数微米左右,而布袋除尘器内的灰渣没有发生熔融现象.     

Circuit Analysis and Characterization of Contactless Power Transfer System with Variable Impedance

A contactless power transfer system using a repeater coil (repeater Coil topology) has been proposed as a method of suppressing overcurrent without power control during misalignment or no‐load. By installing a repeater coil between the primary and secondary coils, it is possible to increase the input impedance in the case of misalignment of the secondary coil or no‐load condition. In addition, another contactless power transfer system using primary parallel and secondary series resonance capacitors (PS capacitor topology) has been proposed. In the PS capacitor topology, the input impedance can be increased during misalignment of the secondary coil or no‐load condition similar to the repeater coil topology. In this paper, we evaluated the characteristics of both these topologies. First, we conducted a circuit analysis of the repeater coil topology and proposed a design method. In addition, we theoretically clarified the characteristic difference of the two topologies and experimentally evaluated the characteristics.     

Single‐Inductor Dual‐Output DC–DC Converter Design Using RC Ripple Regulator Method

In this paper, we have proposed Single‐Inductor Dual‐Output (SIDO) buck–buck and boost–boost dc–dc converter using improved RC ripple regulator control. The proposed SIDO buck–buck converter has the characteristics of low‐ripple and high control frequency. RC ripple regulator control cannot be applied to SIDO boost–boost converter because RC ripple regulator undergoes self‐excited oscillation and two self‐excited oscillating controllers make the SIDO converter unstable. Thus we proposed the priority circuit for RC ripple regulator control. The proposed control circuit improves response characteristic and simplicity of the control circuit. Simulations are performed to verify the validity of the proposed SIDO converter. Simulation results indicate good performance of the proposed SIDO converter.     

Crack Initiation and Arrest in a SiC Whisker/A12O3 Matrix Composite

The fracture initiation and arrest stress intensity factors were determined for a SiC-whisker-reinforced AI₂O₃ matrix composite. A chevron-notched, three-point-bend specimen was used to genera e the load/displacement curve, which exhibited repeated crack initiation, followed by crack arrest behavior. Corresponding stress intensity factors were determined for both situations using the compliance technique. Calculated crack arrest positions were in agreement with fractographic observations. Both the crack arrest and the crack initiation stress intensity factors exhibited a rising R -curve with increasing crack length, suggesting the presence of wake toughening effects on the crack growth resistance.