Growth of β-FeSi2 layers deposited from a molten salt

β-FeSi₂ layers have been successfully grown using a molten salt method for the first time. It was found that single phase and homogeneous β-FeSi₂ layers with a columnar domain structure can be grown on FeSi substrates. The layer thickness was demonstrated to be controllable by the growth temperature and time, and was diffusion controlled. It was shown that the layers were void- and crack-free compared to similar layers grown on Fe substrates: this difference is explained in terms of Fe diffusion. This vacuum-free simple growth technique is useful for the fabrication of large area semiconductor devices at low cost.     

Response of inertinites from some Australian coals to non-catalytic hydrogenation in tetralin

Inertinite concentrates from three Australian bituminous coals were hydrogenated at various temperatures ranging from 350 to 475 °C in the presence of tetralin without any added catalyst. Both conversion yields and microscopic observations of the benzene-extracted hydrogenation residues have revealed that the hydrogenation of the inertinite macerals becomes significant only > 400 °C, whereas the dissolution-hydrogenation of the accompanying vitrinite macerals occurs mainly between 350 and 400 °C. The major reaction pathway for the inertinite particles in the hydrogenation process appears to be one of initial mild carbonization followed by hydrogenation. A simplified reaction scheme is proposed which describes the reaction pathway involved in the hydrogenation of inertinite.     

Synthesis of selenium nanoparticles in the presence of silk fibroin

This paper describes a solution-phase approach to the synthesis of selenium nanoparticles by reducing selenious acid solution with ascorbic acid in the presence of silk fibroin. The monodispersed spherical selenium colloid particles obtained were very stable in silk fibroin solution and characterized by Atomic force microscopy and X-ray techniques. The influences of temperature and ultrasonication on the morphology of selenium nanoparticles were also discussed. The experiments showed that the selenium nanoparticles with various morphologies could be obtained under different temperatures and the appropriate ultrasonication time was 60 min. This result indicated that the silk fibroin molecules intimately associated with the surface of the selenium particles and controlled the growth particles.     

Intermediate order in tetrahedrally coordinated silicon: evidence for chainlike objects

In this report, we describe the nature of intermediate order in silicon as determined by recent measurements on thin films using transmission electron microscopy (TEM) and Raman scattering. The TEM images show in addition to the expected continuous random network (CRN), the presence of highly ordered quasi-one-dimensional “chain-like objects” (CLO's) that are 1–2 nm wide and tens of nm long that meander and show some evidence of cross-linking with each other. The presence of these objects correlate to a Raman feature centered at 490 cm⁻¹ whose width is 35–40 cm⁻¹, and is used to quantify the heterogeneity in terms of the CLO and CRN (=475 cm⁻¹ scattering) concentrations. The 490 and 35 cm⁻¹ values are consistent with bond angle deviations approaching 0°, and thus reinforces an association with the CLOs. We find that in reference quality a-Si:H (made using pure SiH₄), the CLO concentration is about 5 vol%, while in state-of-the-art material using high H₂ levels of dilution during processing, it increases to about 15%. Increased stability of such material to light-soaking is thus not mediated by a direct volumetric replacement of poor with high-quality components. Rather, an important characteristic of intermediate order in silicon is the low-dimensional aspect of its order, which allows it to influence more total volume than which it is itself composed. Consistent with these and other recent findings, we propose a tensegrity model of amorphous silicon.     

石蜡微胶囊中脲醛树脂壁材渗透性的研究

利用差示扫描量热法研究了石蜡微胶囊中脲醛树脂壁材对水及甲苯的渗透性 ,结果表明 ,水不能透过脲醛树脂壁材 ,而甲苯则易透过脲醛树脂壁材。因此 ,该石蜡微胶囊不能用于芳香族溶剂存在的场合。     

Modelling and analysis of 3-D arrangements of particles by point processes with examples of application to biological data obtained by confocal scanning light microscopy

Within the concept of point processes, a review is presented of quantities which can be used in studies of three-dimensional (3-D) aggregates of particles. Suitable characteristics and estimators are given for both unmarked and marked point processes. To demonstrate the feasibility of such quantitative approaches, an application in histology, dealing with 3-D arrangements of cell nuclei in rat liver, is described. Using a confocal scanning light microscope, 3-D images are recorded and image analysis used to obtain the coordinates of the centroid, together with the volume and DNA content, of each cell nucleus. Examples of results are given, using both unmarked and marked point processes. In the latter case, cell type, nuclear volume and ploidy group are suitable marks.     

A portable cryo-storage system for low-temperature scanning electron microscopy,suitable for international transport of cryo-specimens

A cryo-specimen storage system for low-temperature scanning electron microscopy (LTSEM) specimens is described, which: liberates multi-specimen experiments from sampling restrictions imposed by the rate at which LTSEM specimens can be examined in the SEM; provides security against experiment loss resulting from breakdown of the SEM or cryo-system; enables collection of specimens in the field or in laboratories remote from the SEM laboratory; and facilitates international air transport of LTSEM specimens. The components of the system, which has a capacity of 98 stub-mounted specimens, are readily made in a laboratory workshop. The details of the design may be altered to suit particular specimen types or experimental approaches.     

Preparation of polyimide-epoxy composites

The formation of a three dimensional network of crosslinked epoxy leads all unmodified epoxies to have inherent brittleness and relatively low degradation temperatures. Polyimides, on the other hand, are widely used for applications that require high degrees of flexibility and thermal resistance. Here, we have focused on the preparation of epoxy systems cured with polyamic acids instead of traditional amino-group-containing hardening agents. The cure behavior and potential reaction mechanisms of EPON 828 resin and polyamic acid mixtures were evaluated by DSC and TGA. Thermal analysis showed a complex reaction sequence taking place in the mixture and also determined the extent of reaction of the polyamic acid with itself and the competitive reaction of the polyamic acid with the epoxy. The compositions of the mixtures were varied to see the dependence of the cure behavior on component concentrations. Solutions of the two components did not phase separate and also phase separation was not apparent either optically or microscopically in the cured samples. This phase behavior was attributed to a unique in situ reaction. A novel solvent system for the polyamic acid precursor was also used.     

On the applied stress dependence of the subgrain size

The present work studies the collection of experimental data from which Raj and Pharr (Mater. Sci. Eng., 81 (1986) 217) deduced a universal empirical dependence of the subgrain size on the applied stress. In accord with their result and some theoretical predictions the normalized subgrain size d_s/b was ssumed to be proportional to G/σ (G is the shear modulus, b the Burgers vector length, σ the applied stress). The evaluated factor of proportionality K₁, having the value within the interval from 0.76 to 180 in the inspected data sets, was discussed from the point of view of various factors which can influence the experimental data.     

球罐活性缺陷的模糊评定方法

根据国内外有关标准和文献,利用模糊数学中的模糊描述和隶属度等概念,首次采用多级模糊综合评定理论,分层次地把活性缺陷的主要监测信息(即声发射源信息)和专家们的经验考虑在内,建立在用球形贮罐声发射源严重度多级模糊综合评定模型和方法,并编制计算机数据分析和处理程序,使评定结果趋于更合理和可靠.并给出在用球形贮罐声发射源严重度多级模糊综合评定算例,结果表明,该评定方法可以达到定量化的程度,与局部无损复验结果有良好的一致性.