IR laser extraction technique applied to oxygen isotope analysis of small biogenic silica samples

An IR-laser fluorination technique is reported here for analyzing the oxygen isotope composition (delta18O) of microscopic biogenic silica grains (phytoliths and diatoms). Performed after a controlled isotopic exchanged (CIE) procedure, the laser fluorination technique that allows one to visually check the success of the fluorination reaction is faster than the conventional fluorination technique and allows analyzing delta18O of small to minute samples (1.6-0.3 mg) as required for high-resolution paleoenvironmental reconstructions. The long-term reproducibility achieved with the IR laser-heating fluorination/O2 delta18O analysis is lower than or equal to +/-0.26 per thousand (1 SD; n = 99) for phytoliths and +/-0.17 per thousand (1 SD; n = 47) for diatoms. When several CIE are taken into account in the SD calculation, the resulting reproducibility is lower than or equal to +/-0.51 per thousand for phytoliths (1 SD; n = 99; CIE > 5) and +/-0.54 per thousand (1 SD; n = 47; CIE = 13) for diatoms. A minimum reproducibility of +/-0.5 per thousand leads to an estimated uncertainty on delta18Osilica close to +/-0.5 per thousand. Resulting uncertainties on reconstructed temperature and delta18Oforming water are, respectively, +/-2 degrees C and +/-0.5 per thousand and fit in the precisions required for intertropical paleoenvironmental reconstructions. Several methodological points such as optimal extraction protocols and the necessity or not of performing two CIE prior to oxygen extraction are assessed.     

On the properties of a radiation-induced defect responsible for the 1.0-eV IR absorption band in gallium arsenide

The IR absorption spectra were measured at 77 K for Te-doped n-GaAs samples irradiated by electrons with an energy of E=3 MeV. It was found that the samples exhibit two absorption bands in the IR range, corresponding to 1.0 and 0.8 eV.     

Effect of colloidal silica on the strength and energy absorption of glass fiber/epoxy interphases

Prior research has demonstrated that fiber-sizings can be designed to yield composite materials that simultaneously possess high energy absorption and structural properties. The improved mechanical properties resulted from control of the fiber surface chemistry and nano-scale topological features within the fiber–matrix interphase. The present study further explains the role of sizing chemistry and surface roughness on composite material performance. Model and commercial glass fiber epoxy specimens were fabricated using these fiber sizing systems resulting in interphase regions with varied surface topology and chemical functionality. Micromechanical measurements were performed using the microdroplet adhesion test method to quantify the fiber–matrix interfacial properties. Improvement in energy absorption and interfacial shear strength due to the presence of the nano-scale silica were quantified. Inspection of the failure modes revealed that the existence of colloidal silica promotes crack propagation along a more tortuous path within the interphase that results in progressive failure and contributes to increased energy dissipation.     

TiO_2-聚乙烯复合膜的制备及红外光谱对其膜层结构的表征

开发了以Ｔｉ４＋为桥联剂制备无机－有机复合膜的新方法以自制的硅藻土多孔陶瓷为基膜（支撑体），使用浸涂法－热致相转化法相结合制备了ＴｉＯ２－聚乙烯复合膜，并用红外光谱表征了复合膜层与层之间的结合方式和强度，支撑体中的ＳｉＯ２通过Ｔｉ４＋与聚乙烯的分子之间形成了新的化合物型膜层     

Influence of Si doping level on the Raman and IR reflectivity spectra and optical absorption spectrum of GaN

The optical absorption (hν) and Raman and Infra Red (IR) spectra of Si doped GaN layers deposited on sapphire through buffer layers have been recorded for electron concentrations from 5×10¹⁷ to 5×10¹⁹ cm⁻³. The (hν) values deduced from photothermal deflection spectroscopy (0.5–3.5 eV) and IR absorption (0.15–0.5 eV) vary between 50 and 10⁴ cm⁻¹ showing doping dependant free electron absorption at low energy, doping independant band gap at high energy, and slowly doping dependant defect absorption in the medium energy range. In our micro Raman geometry, maxima appear or can be deduced near the frequency expected for either the A₁(LO⁻) or the A₁(LO⁺) modes split from the A₁(LO) mode by plasmon phonon interaction. There is a large systematic evolution in the expected way for the IR reflectivity.     

On the possible spatial orientation of a radiation-induced defect responsible for the 1.0-eV IR absorption band in gallium arsenide

A possible spatial orientation of a radiation-induced defect responsible for the 1.0-eV IR absorption band in gallium arsenide was determined. The defect has a dipole moment oriented close to the 〈110〉 crystallographic axis and possesses a 〈111〉 atomic symmetry. Taking into account these results and assuming a divacancy character of this defect (suggested by some researchers), the defect is assigned a mixed divacancy structure of the V _Ga+V _As type.     

Development of the surface topography on silica glass due to ion-bombardment

Mechanically polished fused silica surfaces have been bombarded by energetic Ar⁺ ions and the development of surface topography examined by scanning electron microscopy and by transmission electron microscopy of direct carbon replicas in order to study the parameters affecting the surface finish such as charging, angle of ion incidence and rotation of the specimen, A theory based on a simple model of initial surface unevenness on a microscopic scale is proposed to explain the observed surface features due to ion-bombardment.     

原子吸收法测定钠钙玻璃中常量元素的方法改进

传统原子吸收法测定钠钙玻璃中各元素的标准溶液的配制方法既繁琐且不容易消除干扰。通过实验,我们根据标准钠钙玻璃和样品基体元素相近来消除干扰,改进了配制标准溶液的方法,使标准溶液配制简单易行。     

ESCA study on the mechanism of adherence of metal to silica glass

Indium oxide films formed on the surface of silica glass samples by selective oxidation have been shown to greatly improve the adherence of gold-indium alloy to the silica glass. In order to clarify the role that the oxide films play in the reaction, thin indium films have been evaporated onto silica glass and heated at temperatures of between 973 and 1473 K, both in air and in hydrogen gas. Electron spectroscopy for chemical analysis (ESCA) measurements have then been made to investigate the chemical environments around oxygen and indium atoms at the reacting interface between the oxide and glass. Measured 01s and In3d _5/2 spectra reveal the formation of non-bridging oxygen atoms at the interface, in addition to the original bridging oxygen atoms in silica glass. Introduction of the non-bridging oxygen atoms and indium ions into the silica glass is concluded to be an essential factor in promoting good adherence between the gold alloy and silica glass.     

Crushing and energy absorption performance of different geometrical shapes of small-scale glass/polyester composite tubes under quasi-static loading conditions

This paper presents the quasi-static crushing performance of nine different geometrical shapes of small-scale composite tubes. The idea is to understand the effect of geometry, dimension and triggering mechanism on the progressive deformation of small-scale composite tubes. Different geometrical shapes of the composite tubes have been manufactured by hand lay-up technique using uni-directional E-glass fabric (with single and double plies) and polyester resin. Dedicated quasi-static tests (144 tests) have been conducted for all nine geometrical shapes with different t/D (thickness–diameter) ratios and two triggering profiles (45° chamfering and tulip pattern with an included angle of 90°). From this unique study, it was found that the crushing characteristics and the corresponding energy absorption of the special geometrical shapes are better than the standard geometrical shapes such as square and hexagonal cross sections. Furthermore, the tulip triggering attributed to a lower peak crush load followed by a steady mean crush load compared to the 45° chamfering triggering profile which resulted into a higher energy absorption in most of the geometrical shapes of the composite tubes.     

Fatigue in soda-lime silica glass: influence of surface treatment

The influence of surface treatment on fatigue of soda-lime glass has not been previously explained. An explanation based on different distributions of crack tip radii for different treatments is proposed. Fatigue is considered to occur as a result of crack tip sharpening. Freshly abraded glass has crack tips of a minimum radius that cannot sharpen, so such glass has longer fatigue life. Glass aged in water after abrasion has blunter crack tips, and consequently shorter life. Chemical conditions at the crack tip are the same over a wide range of external pH, and also influence the effect of surface treatment on fatigue times.     

Fabrication of high-purity silica glass through the WSPA-sol-gel process

High-purity and large-size silica glass was prepared by a wet process silica and pH adjustment (WSPA)-sol-gel process which involved the following steps: (1) colloidal silica synthesis through the hydrolysis reaction of TEOS catalysed by ammonia solution; (2) sol preparation through the hydrolysis reaction of TEOS by hydrochloric acid; (3) mixing the colloidal silica and sol solution; (4) adjusting the pH values of the mixed solution to 4–6; (5) gelling; (6) drying to a dry gel; (7) heat treatment of the gel to collapse the pores, finally to become a silica glass. The purity of the derived silica glass was examined in relation to the metallic impurities and -OH impurities. The relation between ultraviolet absorption of silica glass and metallic impurities was investigated. Ti addition to the silica glass gave a strong absorption at 200 m, for which the ultraviolet absorption coefficient, , was found to be 1.57×10⁴ l mol^–1 cm^–1. The effects of the properties of colloidal silica on the -OH concentration and also the relations between the sintering conditions and residual -OH concentration in silica glass were examined. Using colloidal silica with a large particle size and heat treatment in vacuum resulted in a silica glass with a low concentration of residual -OH.     

Intercalation of IR absorber into layered double hydroxides: Preparation,thermal stability and selective IR absorption

N-phosphonomethyl aminodiacetic acid (PMIDA) was intercalated into the interlayer spacing of layered double hydroxides (LDH) by an anion-exchange method. The intercalated LDHs were characterized by various techniques such as powder X-ray diffraction (XRD), FT-IR spectroscopy, elemental analysis and simultaneous thermogravimetric and mass spectrometry (TG-MS) in details. The results show the formation of Mg₂Al-PMIDA LDH based on the expansion of d-spacing from 0.89 nm to 1.22 nm and the disappearance of the characteristic IR absorption band at 1384 cm^?1 for NO₃^? anions. The incorporation of Mg₂Al-PMIDA LDH into the low density polyethylene (LDPE) as an additive enhances the selectivity of IR absorption in the main wavelength region 9–11 μm for radiant heat loss at night. Mg₂Al-PMIDA LDH as a heat-retaining additive has practical application in agricultural plastic films.     

Low temperature synthesis of a monolithic silica glass by the pyrolysis of a silica gel

The reaction process in the pyrolysis of silica gel has been investigated as the basic study on the low temperature synthesis of monolithic glass from a metal alkoxide. A large volume change which may cause stress-induced fracture of a gel occurred in the following process stages: (a) the decompostion of residual organic compounds into carbon dioxide (300 to 500° C); (b) small pore collapse (400 to 500° C); (c) larger pore collapse (700 to 900° C). A fracture-free monolithic silica glass was successfully prepared from a dry silica gel formed by the hydrolysis of silicon methoxide by careful heat-treatment. The properties of the synthetic silica glass were similar to those of commercial vitreous silica.     

Examination of the optical inhomogeneity of materials in the IR spectrum range

Measurement Techniques -     

Absorption band saturation in the near-IR spectrum of molybdenum blue

Nonlinear absorption of a picosecond laser pulse in an aqueous solution of a partly reduced heptamolybdate and citric acid was studied. We report on the first observations of the absorption band saturation in the near-IR spectrum of molybdenum blue and its relaxation on a picosecond time scale. A stepwise character of the intensity dependence of the absorption band saturation is demonstrated. Qualitative interpretation of the experimental results is based on the concept of self-defocusing in a three-level system that exhibits two-photon transitions via an intermediate level upon high-power excitation.     

Application of ion implantation and backscattering techniques to the analysis of nuclear waste glass corrosion

Ion implantation and Rutherford backscattering depth profile analysis have been used to study changes in the near-surface composition of nuclear waste glasses that were corroded in aqueous media. The dissolution rate of the glass network during early stages of corrosion and effects of solution chemistry on the glass surface-layer composition were investigated. Properties of the altered layer were found to vary significantly as a function of the pH of the corroding solution.     

Dispersion relation of surface plasmons near photonic band gaps: Influence of the interaction with light

Abstract

We present an experimental and theoretical study of the photonic band gap in the propagation of surface plasmons (SPs) on periodically corrugated surfaces. Our main purpose is to investigate the case where the band gap width is larger than the energy distance between the SP dispersion curve for a flat surface and the light line. We introduce a physical model of the interaction of light waves with SPs and derive an analytical expression for the SP wave vector near band gaps based on the coupled-mode approach involving three interacting modes (two of them are SP modes and one is a light mode). By using the interferometric measurement we have studied, for the first time, the SP propagation parameters in the vicinity of the photonic band gap (10 μm wavelength region). The predictions of our theory are in good agreement with the experimental data.