Damage Effect of Space Proton Irradiation with the Low Energy of 50-200 keV on Methyl Silicone Rubber

The damage effects and mechanisms of proton irradiation with 50-200 keV energy to space-grade methyl silicone rubber was performed using a ground-based simulator for space irradiation environment. The changes in surface morphology, mechanicai properties, cross-linking density, glass temperature, infrared attenuated total reflection spectrum, mass spectrum and pyrolysis gas chromatography-mass spectrum indicated that, under lower energy, the proton irradiation would induce cross-linking effect, resulting in an increase in tensile strengths and hardness of the methyl silicon rubber. However, after the irradiation of protons for more than 150 keV, the irradiation induced degradation, which decreased the tensile strengths and hardness, became a dominant effect. A macromolecular network destruction modei for the silicone rubber radiated vvith the protons was proposed.     

真空蒸镀聚乙烯醇薄膜

采用真空蒸发沉积(蒸镀)聚乙烯醇薄膜,通过SEM和光学显微镜观察聚乙烯醇薄膜呈现典型的岛状形式并均匀分布于衬底表面,且以梯田状台阶式长大.衬底温度是影响PVA薄膜沉积速度的主要因素.红外光谱分析表明其蒸镀薄膜的主要化学结构特点是羰基代替了部分羟基.     

Reflection and Absorption Techniques for Optical Characterization of Chemically Assembled Nanomaterials

This review discusses recent developments in the areas of fabrication, certain types of optical characterization, and applications of a selected class of chemically assembled nanomaterials, namely i) gold and silver nanoparticles deposited onto optically transparent glass substrates; ii) thiol‐functionalized self‐assembled monolayers (SAMs); iii) chemically stabilized gold and silver nanoparticles (monolayer protected clusters, MPCs); and iv) MPCs linked to metallic substrates and adsorbates. Six linear optical techniques for the characterization of these materials are discussed: transmission localized surface plasmon resonance spectroscopy, T‐LSPR; propagating surface plasmon resonance spectroscopy, P‐SPR; polarization‐selective Fourier transform infrared reflection absorption spectroscopy, PS‐FTIRRAS; polarization‐modulation Fourier transform infrared reflection absorption spectroscopy, PM‐FTIRRAS; surface‐enhanced infrared reflection absorption spectroscopy, SEIRRAS; and infrared ellipsometry. The review focuses particularly on providing a unified treatment of these six optical techniques by using a relatively simple stratified multilayer model.     

Growth and optical properties of Er,Yb:YAl3(BO3)4 crystal

Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl₃(BO₃)₄(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl₃(BO₃)₄ crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl₃(BO₃)₄ crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g °C.     

Synthesis and characterization of thorium phosphate phases by spray pyrolysis: chemistry of thorium phosphates

This paper describes the synthesis of some thorium phosphate compounds with different Th/P ratio (1/2, 2/3 and 3/4) by a spray pyrolysis technique. The so-prepared rough compounds were annealed at different temperatures for 2 h and then analyzed by mainly X-ray diffraction on powder and infrared spectroscopy. Every rough compound is composed by very badly crystallized ThO₂ phase polluted by carbon residue. An annealing treatment at 800 °C leads to the thorium diphosphate phase, α-ThP₂O₇ in every case. At 900 °C, such a phase is decomposed into a thorium phosphate diphosphate phase (Th₄(PO₄)₄P₂O₇, called TPD). However, a thorium excess in the initial mixture (Th/P = 3/4) leads also to observe the ThO₂ phase. The TPD phase is stable up to 1200 °C and does not react with the ThO₂ compound. Beyond 1200 °C, the TPD phase is slowly decomposed into a thorium phosphate compound which should be a thorium oxide phosphate; this compound does not contain any diphosphate species.     

SiO2/Si(100) interface characterization using infrared spectroscopy: estimation of substoichiometry and strain

The transverse optical (TO) and longitudinal optical (LO) phonons of the asymmetric stretch of the O in SiOSi bridging bond in thermal SiO₂ show red shift with decreasing oxide thickness. These shifts are primarily due to interface effects like strain and substoichiometric silicon oxides (suboxides). A method to isolate the contributions of strain and suboxide concentration towards the observed shifts is proposed. The procedure, which utilizes simple optical model and effective medium approximation, allows estimation of the average strain and suboxide concentration in films of different thickness. Analysis of infrared spectra shows that suboxide-rich layers in low temperature dry and wet oxides are confined to a distance of ∼1.5 nm from the interface; wet oxidation may generate lower stress near the interface.     

Plasma copolymer membranes of acrylic acid and the adsorption of lysozyme on the surface

Plasma copolymerization was carried out from the monomer mixtures of acrylic acid with hexamethylxdisilozane and hexametydisillazane, and the membranes composed of the Si-C and/or Si-O networks sustaining carboxylic acid group were fabricated. The carboxylic acid contents were dependent on the discharge power conditions as well as the monomer ratio, and carboxylic acid was introduced at the more density in the polymerization by plasmas under the moderate power conditions. The plasma polymer coatings were effective for the adsorption of lysozyme especially on the plasma copolymer films of acrylic acid.     

An information-theoretic methodology for the resolution of pure component spectra without prior information using spectroscopic measurements

The resolution of pure component spectra based on spectroscopic measurements from a reaction system is a challenging task for chemometric systems in the absence of a priori knowledge about the reaction components involved. A popular approach in the literature is based on constrained entropy minimization of the second-order derivative of the resolved pure component spectra. Using an analytical information theoretic framework, it can however be shown that minimization of this cost function is not sufficient to completely separate the underlying components from a set of mixture spectra. Instead, an augmented objective function derived from this analysis is proposed for complete minimization of the mutual information between separated components. The final optimization approach is further shown to be analog to independent component analysis (ICA), a signal processing technique successfully applied to biomedical and speech data to separate linear source mixtures in the absence of a priori information. The developed theoretical insights and proposed methodologies in this paper are illustrated in a simulation study on the separation of three component spectra based on absorbance data acquired from a first-order kinetic reaction system.     

Influence of the common varistor dopants (CoO, Cr2O3 and Nb2O5) on the structural properties of SnO2 ceramics

The influence of dopants commonly used in SnO₂ varistor ceramics, such as CoO, Cr₂O₃ or Nb₂O₅, on the structural properties of SnO₂ was investigated. Several SnO₂-based ceramics containing only one of the dopants were prepared and characterized. Spectroscopic investigations [visible, near infrared (IR) and IR region] were performed to obtain information about dopants valence states inside the ceramics, as well as about their influence on electronic structure of the material. Structural properties were investigated by X-ray diffraction analysis and mechanisms of dopant incorporation were proposed. Obtained results were confirmed with results of the electrical measurements. Microstructural changes in doped ceramics were investigated by scanning electron microscopy (SEM) analysis that showed great differences in densities, grain size, and morphology of the SnO₂ ceramics depending on type of dopants and their distribution.     

Thermal and Spectroscopic Analyses of Caustic Side Solvent Extraction Solvent Contacted with 16 Molar and 8 Molar Nitric Acid

Abstract

Thermal and spectroscopic analyses were performed on multiple layers formed when Caustic Side Solvent Extraction (CSSX) solvent was contacted with 16 M or 8 M nitric acid. A rapid (i.e., minutes to hours) chemical reaction occurs between the solvent and 16 M or 8 M nitric acid as evidenced by color changes and the detection of nitro groups in the infrared spectrum of the aged samples. Thermal analysis revealed that decomposition of the resulting mixture does not meet the definition of explosive or deflagrating material.