Comparative topographic study of surface micro‐relief of primary martensite plates in shape memory alloys with different crystalline structures

The surface micro‐reliefs of primary martensite plates, representative for two shape memory alloys (SMAs) with different crystalline structures were compared from qualitative and quantitative point of view by scanning electron microscopy and atomic force microscopy, respectively. Qualitative evaluations revealed larger widths and heights of the primary plates of ε hexagonal close packed (hcp) martensite, in an Fe‐Mn‐Si‐Cr‐Ni SMA than those of β₂′ orthorhombic (9R) martensite, in a Cu‐Zn‐Al SMA. Quantitative evaluations were based on systematic dimensional measurements of the width and height of primary plate profiles. The measurements were performed on one hundred and twenty five profiles, five on each martensite plate belonging to five typical groups of primary plates, with length above 50 micrometers, of both ε hcp and β₂′ 9R martensites. In order to compare the topographies of the two types of plates a statistical evaluation of the dimensional intervals of width and height of measured plates was performed.     

预应力现浇箱梁施工工艺及质量控制探讨

现浇箱梁有很多优点，但由于预应力现浇箱梁属于超静定结构，造成和简支梁不一样的受力特点，其施工工艺较复杂，技术要求比较高。本文重点对预应力现浇梁施工的工艺和在施工过程中质量控制做进一步的讨论。     

Radiation Treatment of Exhaust Gases, (XIII)

The NH³ consumption by electron beam irradiation has been studied in the moist NO-SO²-O²-N² mixtures containing NH³. The [NH³] decreased linearly with increasing dose at various NH³ initial concentrations. The G(-NH³) increased with NH³ concentration up to about 500 ppm and was held almost constant G(-NH³)=5.8 at 750 ppm NH³) above it. The rate of the NH³ consumption was about 175 ppm/Mrad above 500 ppm NH³ The G(-NH³) increased with H20 and SO² concentrations. On the contrary, the G(-NH³) decreased with increasing NO concentration and was hardly affected by the presence of 3–19.5% O². The G(-NH³) became larger with decreasing temperature in the range of 80–150°C. An apparent activation energy of the NH³ consumption was ?3.82 kcal/mol. The NH³ is mainly consumed by the reactions of NH³ with HNO³ and H²SO⁴, leading to the formations of NH⁴NO³ and (NH⁴)²SO⁴ respectively     

Stress arch bunch and its formation mechanism in blocky stratified rock masses

Stress arch is a common phenomenon occurring in continuous materials and has also been proved to have great influences on the self-stabilization of soils or rock masses after excavation.In this paper,based on UDEC simulation,stress redistribution after excavation is investigated for a kind of special discontinuous material,i.e.blocky stratified rock mass.A layered stress arch system is observed with each stress arch lying over another.This special phenomenon is defined herein as "stress arch bunch".Effects of dip angle of bedding plane,lateral pressure and joint offset on this stress arch bunch are studied.Its formation mechanism is also discussed based on voussoir beam theory.     

Self-equilibrating moments in FRP-reinforced continuous structures

In continuous steel or concrete structures with surface-mounted fibre reinforced polymer (FRP) plates as flexural reinforcement, self-equilibrating moments can influence the loads at first yield and at failure, the latter due to potential buckling of the FRP plate or to end-peel both on account of offsets between points of contraflexure and the nearby FRP curtailments. In this paper, expressions are derived for the total (including self-equilibrating) moments along 2-span continuous structures with differential settlement. The expressions show how moments depend on support-to-member stiffness ratios and on distributions of section stiffness for service and ultimate limit states. Thus, the analysis is generic, applicable to FRP-reinforced steel and concrete structures. This analysis is verified via test data (including observation of end-peel in FRP compression curtailment zones offset from nearby contraflexure) and is used to construct 3D plots that facilitate identification of stiffness ratios which lead to significant self-equilibrating moments and contraflexure offset effects. Use of the plots to assess influences of differential settlement on laboratory test specimens is discussed. The analysis is shown to lead to an unprecedented result, namely that a unique point of load application exists for which changes to the stiffness layout have no impact on the moment distribution.     

Optical scanning system for quality control of GEM-foils

An optical scanning system was commissioned and further developed in the Detector Laboratory of Helsinki Institute of Physics and University of Helsinki. It was designed to automatically scan, perform on-line analysis and to classify the overall quality of GEM-foils especially of the GEM-TPC detectors for Super-FRS at FAIR. The optical scanning system consists of precision positioning table, lighting, optics and operating system with analysis software. It has active scanning area of 95×95 cm² and it can study this area with the minimum resolution of 128 lp/mm. Performance of the system and first results from the GEM-foil uniformity and quality analysis are presented.     

Characterisation of rare earth minerals with field emission scanning electron microscopy

Abstract

Rare earth elements are becoming increasingly in demand, due to their prevalence in both renewable energy devices and high end electronics. The characterisation of the composition and morphology of the various phases that have valuable rare earth elements in the ores are needed in conjunction with the study of their physicochemical properties to optimise industrial process to extract the minerals containing the rare earth elements. Rare earth bearing minerals contain many elements with overlapping X-ray peaks (L- and M-lines) with an energy dispersive spectrometry detector, requiring a high degree of X-ray energy resolution. A program was developed to obtain the intensity of each peak by deconvolution of the X-ray spectrum. Low accelerating voltage of less than 5 kV and small beam diameter of less than 10 nm of a cold field emission scanning electron microscope allow x-ray microanalysis on the nanometre scale. A 100 nm wide phase was observed at 4 kV on a backscattered electron micrograph. Furthermore, a small beam diameter of less than 10 nm was used for identification of small phases of a few micrometres.

Les éléments de terre rare sont de plus en plus en demande, grâce à leur prévalence tant dans les dispositifs d’énergie renouvelable que dans l’électronique de haute gamme. On a besoin de caractériser la composition et la morphologie des différentes phases qui contiennent des terres rares de valeur dans les minerais, en combinaison avec l’étude de leurs propriétés physico-chimiques, afin d’optimiser le procédé industriel d’extraction des minéraux contenant les terres rares. Les minéraux porteurs de terre rare contiennent plusieurs éléments ayant des pics de rayons x qui se chevauchent (lignes L et M) avec un détecteur de spectroscopie à dispersion d’énergie, nécessitant une haute résolution énergétique. On a développé un programme visant à obtenir l’intensité de chaque pic par déconvolution du spectre de rayons x. Un faible voltage d’accélération de moins que 5 kV et un faisceau à faible diamètre de moins que 10 nm d’un microscope électronique à balayage par cathode froide permettent la microanalyse des rayons x à l’échelle du nanomètre. On a observé une phase de 100 nm de largeur à 4 kV sur une micrographe d’électrons rétrodiffusés. De plus, on a utilisé un faisceau de faible diamètre de moins que 10 nm pour l’identification de petites phases de quelques μm.     

热轧加热炉内步进梁及立柱耐火材料粘渣原因分析

分析了热轧加热炉内步进梁与立柱粘渣的原因,认为所用耐火材料荷重软化温度低、变形大是主要原因之一。从侵蚀结构分析看,氧化铝溶解进入炉衬的粘接渣相中,增加了渣的黏度,可能导致炉衬的严重挂渣,不利于生产的正常顺行。常规的加热炉耐火材料控制标准没有荷重软化温度等指标,不利于控制炉衬实物质量。     

Reactivity and deuterium retention properties of titanium-beryllium intermetallic compounds

Beryllium intermetallic compounds (beryllides), such as Be₁₂Ti and Be₁₂V, are the most promising advanced neutron multipliers in demonstration (DEMO) fusion power reactors because of higher stability, lower retention, and swelling. The advanced neutron multipliers are being developed by Japan and the EU as a framework of Broader Approach (BA) activities, targeted at broadening the research fields to not only establish fabrication methods but also for their characterization. Our group has proposed a plasma sintering method for the synthesis of beryllides. When the mixed powder was plasma-sintered at the beginning of the experiment, consolidation of the target composition was so insufficient that single-phase beryllides could not be synthesized. In order to obtain single-phase beryllides, an additional homogenization treatment of the sintered beryllides at 1473 K was necessary, resulting in increased porosity. Using the homogenized powder as the starting material, single-phase Be₁₂Ti and Be₁₇Ti₂ intermetallic compounds were successfully synthesized. As experimental results, the hardness of the compounds was relatively low owing to low sintering density. In addition, the oxidation behavior of the beryllides, when exposed to 15% H₂O/Ar at high temperatures, were investigated and the results indicate the presence, gray colored Be oxide formed on the surface in Be₁₂Ti tested at above 1073 K and Be oxide with a small fraction of white colored Ti oxide even tested at 873 K in Be₁₇Ti₂ phase resulting in the bigger increase of the weight gain than Be₁₂Ti. In addition, this oxidation occurring at lower temperature can be reasoned by the assumption that the existence of BeO (=oxygen content) in Be₁₂Ti (1.95%) and Be₁₇Ti₂ (2.95%) may facilitate increased reactivity. Furthermore, thermal expansion of Be₁₇Ti₂ was found out to be bigger than that of Be₁₂Ti because Be₁₇Ti₂ has more complex crystal structure and higher melting temperature. In terms of deuterium desorption and retention properties, the maximum peaks are detected around 600 K in beryllides, while those in beryllium occur at 800 and 980 K. From the comparison of deuterium retention, it was obvious that Be₁₇Ti₂ has a lower retention than Be₁₂Ti, while Be has the highest value.