Fundamental and technological aspects of glass studied by nuclear techniques

Abstract

Nuclear techniques (Rutherford back-scattering and nuclear reactions) appear very useful in the near surface analysis of glass. These techniques offer a non-destructive method of analysis, with high depth resolution without radiation effects induced by the ion beam.

In this paper we present some experimental results concerning the analysis of glass surfaces obtained by different treatments. Initially the water vapour attack kinetics was investigated with the ²³Na(ρ, α)²⁰Ne nuclear reaction. Measurements were performed on three different flat glasses obtained by different industrial processes.

Another aspect of particular importance from both scientific and applied viewpoints is the kinetics of the surface reaction and diffusion processes occurring in silicate glasses. In particular the Na⁺?K⁺ interdiffusion has been investigated with the RBS technique at different temperatures in aluminosilicate and borosilicate glasses.

Finally, a technological aspect of great interest is connected to the optical properties modification when glasses are covered with different types of coatings. RBS analysis allows helpful information about elemental composition of the coatings and their depth distribution. In many cases it is possible to obtain the stoichiometric composition and the thickness when atomic density is known.     

Electronic properties of SiC surfaces and interfaces: some fundamental and technological aspects

The wide band gap semiconductor silicon carbide (SiC) is the first-choice material for power electronic devices operating at high voltages, high temperatures, and high switching frequencies. Due to their importance for crystal growth, processing, and device fabrication, the electronic properties of SiC surfaces and interfaces to other materials such as metals and dielectrics are of particular interest. Unreconstructed, H-terminated SiC surfaces which are passivated in a chemical as well as an electronic sense are obtained in a thermal hydrogenation process. It is demonstrated that deposition of Al₂O₃ on H-terminated SiC(0001) leads to an interface which is lower in defects than the thermally grown SiO₂/SiC interface. Furthermore, starting from hydrogenated SiC{0001} surfaces it is possible to prepare unreconstructed (1×1) surfaces with one dangling bond per unit cell. These surfaces show indications for strong electron correlation effects. PACS 68.47.Fg; 73.20.At; 79.60.Bm; 68.35.Bs; 68.35.Dv     

新郑西亚斯东周玉器材料属性与加工工艺的科技分析

中国玉文化源远流长,治玉工艺经过各个时代的不断发展和完善,在一定程度上能反映古代社会生产力发展水平及文化、贸易、技术交流等信息。利用能量色散型X射线荧光光谱（EDXRF）、激光拉曼光谱（LRS）、超景深光学显微系统（OM）等分析技术,结合硅胶覆膜微痕复制技术,对河南省新郑西亚斯东周墓地出土的一批玉器进行科技分析。首先利用化学成分和物相结构分析技术确定了玉器材质的矿物属性,其次利用显微分析技术表征了玉器表面及穿孔内部和印模的加工痕迹,特别是阴刻纹饰和穿孔微痕特征,最后探讨了玉器样品的材料属性和加工工艺两者之间的联系。化学成分和物相结构分析结果表明,所分析的西亚斯东周玉器材质丰富,主要矿物组成有滑石、透闪石、水晶、云母等。玉器表面纹饰微痕特征分析表明,所分析玉器阴刻工艺采用了两种加工工具,分别是砣具和手持硬质工具。穿孔微痕分析特征表明,钻孔包括单面钻孔和双面/多面钻孔两种方式,钻孔工艺则有实心钻、管钻等。部分玉器钻孔形状和内部微痕特征表明,尽管均采用了实心钻工艺,但所采用的实心钻头在形状上存在差异,同时,也存在是否配合解玉砂进行钻孔的差异。不同材料属性的玉器采用了不同的加工工艺。滑石质玉器,莫氏硬度1,器型主要为玉片饰,其表面阴刻纹饰主要采用手持硬质工具进行刻画,钻孔主要采用了双面钻孔方式,并使用了实心钻头未添加解玉砂进行加工,钻头形状可能为圆锥状;云母质玉器,莫氏硬度2~3,器型主要为玉玦片饰,纹饰采用了砣具添加解玉砂的加工工艺,钻孔方式为单面钻孔,采用了管钻工艺。透闪石型玉器,莫氏硬度5~6,器型主要为玉片饰,表面纹饰采用砣具配合解玉砂砣刻,以双面钻孔的方式为主,钻孔工艺为实心钻头配合解玉砂工艺,钻头形状与滑石类样品一致,为圆锥状。水晶质玉器,莫氏硬度7,均为珠饰,表面无纹饰,钻孔方式为双面/多面钻孔,钻孔工艺为实心钻配合解玉砂工艺,且钻头可能为圆柱形。研究结果表明,玉器表面纹饰所采用的阴刻工艺和钻孔工艺,与玉器本身的材料属性、器型等存在密切关系。     

Physical and technological aspects of ultrasonic imaging of brain structures through thick skull bones: 1. Theoretical and model studies

The basic effects that restrict the potentialities of the ultrasonic imaging of brain structures by echo sounding through thick skull bones are considered. It is demonstrated that the main interfering factors are the echo signals from multiple reflections in the bone, its unknown inhomogeneity in depth, and the strong attenuation. To eliminate these effects, the use of a matched spatial processing and complex wideband signals with their subsequent correlation compression is proposed. A simulation of the proposed signal processing techniques confirmed the possibility of brain structure imaging with a spatial resolution of about 1 mm by ultrasonic echo sounding with acceptable intensities through bones up to 20 mm thick at frequencies of 1–2 MHz.     

Behaviour of E. coli 0157:H7 strains in model system and in raw meat by hpp: Microbial and technological aspects

Abstract

Verotoxigenic Escherichia coli (VTEC) is an important pathogen which can cause serious illnesses in humans. It is of particular importance to the meat industry to be able to completely destroy E. coli. A technique used to destroy E. coli could be the high pressure process. For this reason a mixture of 8 strains of E. coli 0157:H7 was inoculated in raw minced meat and in broth. These samples were treated at pressures up to 700 MPa at WC, causing up to 5 decimal reductions. HP treatment is also effective in decreasing microbial contamination and increasing the shelf-life of raw minced meat under refrigerated conditions. The texture of raw minced meat improved with HP level, while the colour was less characteristic in HP-treated samples; a combined HP-treatment caused less colour change than an individual HP-treatment. No difference in colour of cooked minced meat was observed in untreated and HP-treated samples. The texture of cooked minced meat improved in HP-treated samples.     

Physicochemical and technological peculiarities of multicomponent oxide crystal growth from melt by modified Stepanov technique

The peculiarities of the modified Stepanov technique are considered. The advantages of the method for growth of oxide crystals from melts of complex compositions are shown. Crystallization conditions are given to obtain optically homogeneous Sr _x Ba_{1 − x} Nb₂O₆, BaWO₄, SrMoO₄, LiNbO₃, and Ca₃(Nb, Ga)₂Ga₃O₁₂ single crystals using dies of capillary type.     

Experimental aspects of angle-resolved photoemission from clean and adsorbate-covered metal surfaces

Instrumental techniques for the observation of angle-resolved photoelectron spectra from surfaces are reviewed. Results from the work of various groups on clean metals, particularly tungsten, copper, nickel and palladium, are described. Spectra induced by adsorption of hydrogen, oxygen, carbon monoxide and benzene on some of these metals are discussed.     

Structural and physical aspects of the formation of salt crystals from solutions

The peculiarities of the crystallization of about 100 solutions of different salts have been experimentally studied. A correlation is established between the maximum attainable supercooling temperature of the solution and the structure of the crystals formed. It is found that the highest supercoolings are characteristic of solutions of acentric crystals.     

Thermoluminescence and dosimetric aspects of topaz from Yono Shigar mine in Pakistan

Topaz shows thermoluminescence (TL) on heating after exposure to ionising radiation. A study was carried out to explore the possibility to design and develop a TLD (thermoluminescence dosimeter) from locally occurring topaz. Topaz was collected from a mine in Yono Shigar valley in northern Pakistan. The samples were identified as topaz by neutron irradiation, X-ray diffraction and X-ray fluorescence. The crystals of topaz were cut into chips of dimensions compatible to the commercial TLD readers. The chips were exposed to ⁶⁰Co and/or ¹³⁷Cs gamma irradiators. The investigation features included glow curve, dose and energy responses, sensitivity, fading, reproducibility and mechanical stability. The TL glow curves revealed a stable peak at about 250 °C, whose height rose linearly with increase of irradiation dose. The TL response versus dose (calibration curve) showed the linear behaviour between 10^?2 and 10² Gy. The dose response was independent of gamma energies of ⁶⁰Co and ¹³⁷Cs. The response of topaz chips remained constant within 10% deviation from the initial value after 30 cycles of reuse. The rate of fading of topaz was very fast just after irradiation and slowed after a few days. Mechanical stability of the chips remained constant during handling in all investigation experiments. The topaz from Yono Shigar mine may be recommended as a TLD for gamma dose within 10^?2–10² Gy.     

Specificity and affinity of phenosafranine protein adduct: Insights from biophysical aspects

Phenosafranine is a toxic and recalcitrant compound, whose capacity to intercalate with double stranded DNA has been shown. In this contribution, a biophysical discuss on the conjugation of phenosafranine with two model proteins human serum albumin (HSA) and lysozyme (Lys) has been identified utilizing a combination of molecular modeling, steady state and time-resolved fluorescence and circular dichroism (CD) approaches. The accurate binding domain of phenosafranine in protein has been characterized from molecular modeling, subdomain IIIA of HSA and Trp-62, Trp-63 and Trp-108 residues of Lys was designated to possess high-affinity for this compound, the dominant forces in the protein–phenosafranine adduct are hydrogen bonds and π–π interactions, but hydrophobic interactions between dye and Lys are also not exclude. The data of fluorescence displayed that the complex of phenosafranine with protein produces quenching through static property, this corroborates the time-resolved fluorescence results that the ground state complex formation with a moderate affinity of 10⁴ M^?1. Moreover, via synchronous fluorescence, CD and three-dimensional fluorescence we indicated some extent of polypeptide chain of protein partially unfolding upon conjugation with phenosafranine. Through this work, we anticipate it can supply salient clues on the toxicological action of phenosafranine and other azines, which have analogous configuration with phenosafranine.     

New aspects of energy transfer from an alternating magnetic field to a pendulum with ferromagnetic suspension

New data are presented about energy transfer from an alternating magnetic field to a pendulum with ferromagnetic suspension. For each frequency of the alternating magnetic field there is a certain field intensity for which energy transfer is maximum.     

Medieval glass from the Cathedral in Paderborn: a comparative study using X-ray absorption spectroscopy, X-ray fluorescence, and inductively coupled laser ablation mass spectrometry

We have investigated four stained glass samples recovered from an archaeological excavation at the Cathedral in Paderborn (Germany) between 1978 and 1980. On two of the samples there are parts of paintings. Concentrations of major elements were determined using two independent techniques: LA–ICP–MS (a UV laser ablation microsampler combined with an inductively coupled plasma mass spectrometer) and synchrotron radiation X-ray excited X-ray fluorescence (SR-XRF). The SR-XRF data were quantified by using the program package PyMCA developed by the software group of the ESRF in Grenoble. Significant differences were found between the concentrations determined by the two techniques that can be explained by concentration gradients near the surface of the glasses caused, for example, by corrosion/leaching processes and the different surface sensitivities of the applied techniques. For several of the elements that were detected in the glass and in the colour pigments used for the paintings X-ray absorption near edge structure (XANES) spectra were recorded in order to determine the chemical speciation of the elements of interest. As was expected, most elements in the glass were found as oxides in their most stable form. Two notable exceptions were observed: titanium was not found as rutile—the most stable form of TiO₂—but in the form of anatase, and lead was not found in one defined chemical state but as a complex mixture of oxide, sulphate, and other compounds.     

稀土硅钨杂多配合物与半菁复合材料的合成及光学性质

通过Keggin结构稀土硅钨杂多配合物K₁₃[Ln(SiW₁₁O₃₉)₂] (其中Ln=La,Ce,Pr,Nd,Sm,简写为Ln(SiW₁₁)₂)与碘化(E)-N-甲基-4-(2-(4-二甲氨基苯基)乙烯基)吡啶(C₁₆H₁₉N₂I,AI)反应,制备了一系列含轻稀土元素的硅钨杂多配合物与半菁衍生物的复合材料。应用元素分析和TG-DTA确定配合物的组成为(C₁₆H₁₉N₂)₁₀K₃[Ln(SiW₁₁O₃₉)₂]。利用红外光谱、紫外-可见光谱和荧光光谱研究了上述复合材料的光学性质及复合材料中无机组分与有机组分间的相互作用。     

Theoretical and computational aspects of scattering from periodic surfaces: one-dimensional transmission interface

Abstract

We consider the scattering from and transmission through a one-dimensional periodic surface. For this problem, the electromagnetic cases of TE and TM polarization reduce to the scalar acoustic examples. Three different theoretical and computational methods are described, all involving the solution of integral equations and their resulting discrete matrix system of equations for the boundary unknowns. They are characterized by two sample spaces for their discrete solution, coordinate space and spectral space, and labelled by the sampling of the rows and columns of the discretized matrices. They are coordinate-coordinate (CC), the usual coordinate-space method, spectral-coordinate (SC) where the matrix rows are discretized or sampled in spectral space and spectral-spectral (SS) where both rows and columns are sampled in spectral space. The SS method uses a new topological basis expansion for the boundary unknowns.

Equations are derived for infinite surfaces, then specialized and solved for periodic surfaces. Computational results are presented for the transmission problem as a function of roughness, near-grazing incidence as well as many other angles, density and wavenumber ratios. Matrix condition numbers and different sampling methods are considered. An error criterion is used to gauge the validity of the results.

The computational results indicated that the SC method was by far the fastest (by several orders of magnitude), but that it became ill-conditioned for very rough surfaces. The CC method was most reliable, but often required very large matrices and was consequently extremely slow. It is shown that the SS method is computationally efficient and accurate at near-grazing incidence and can be used to fill a gap in the literature. Extensive computational results indicate that both SC and SS are highly robust computational methods. Spectral-based methods thus provide viable computational schemes to study periodic surface scattering.     

Theoretical and computational aspects of scattering from periodic surfaces: one-dimensional transmission interface

We consider the scattering from and transmission through a one-dimensional periodic surface. For this problem, the electromagnetic cases of TE and TM polarization reduce to the scalar acoustic examples. Three different theoretical and computational methods are described, all involving the solution of integral equations and their resulting discrete matrix system of equations for the boundary unknowns. They are characterized by two sample spaces for their discrete solution, coordinate space and spectral space, and labelled by the sampling of the rows and columns of the discretized matrices. They are coordinate-coordinate (CC), the usual coordinate-space method, spectral-coordinate (SC) where the matrix rows are discretized or sampled in spectral space and spectral-spectral (SS) where both rows and columns are sampled in spectral space. The SS method uses a new topological basis expansion for the boundary unknowns.

Equations are derived for infinite surfaces, then specialized and solved for periodic surfaces. Computational results are presented for the transmission problem as a function of roughness, near-grazing incidence as well as many other angles, density and wavenumber ratios. Matrix condition numbers and different sampling methods are considered. An error criterion is used to gauge the validity of the results.

The computational results indicated that the SC method was by far the fastest (by several orders of magnitude), but that it became ill-conditioned for very rough surfaces. The CC method was most reliable, but often required very large matrices and was consequently extremely slow. It is shown that the SS method is computationally efficient and accurate at near-grazing incidence and can be used to fill a gap in the literature. Extensive computational results indicate that both SC and SS are highly robust computational methods. Spectral-based methods thus provide viable computational schemes to study periodic surface scattering.     

Sputtering—a review of some recent experimental and theoretical aspects

After a brief outline of the present sputtering theory for a random solid, recent results of the sputtering yieldS for polycrystalline targets are discussed, in particular in view of the influence of the projectile mass and the bombarding angle. The angle dependence ofS at low bombarding energies, and results on the angular distribution of sputtered particles for oblique ion incidence point out necessary modifications of present sputtering theories with respect to the anisotropy of the collision cascades in the solid and the influence of the target surface. The energy distribution of the neutral particles ejected along the target normals is related to the theoretically predictedE ^?2-distribution of low energy recoils in the Recent mass spectrometric studies of postionized sputtered neutrals are discussed in view of the formation of sputtered molecules and the application of sputtered neutral mass spectroscopy for surface analysis. Finally, the paper deals with ion-induced surface effects on non-elementary sputtering targets, and the protracted removal of foreign atoms from a matrix.