In situ X-ray diffraction investigation of porous silicon strains induced by the freezing of a confined organic fluid

High resolution X-ray diffraction is used to perform an in situ measurement of the variations of the lattice parameter of the nanometer size crystallites of porous silicon, induced by the freezing of a confined organic fluid, dodecane. Two p⁺ type PS layers of 60 and 70% porosity are investigated, and the variations of their lattice parameter with the temperature (in the range 150–300 K) are measured. The experimental curves are discussed in relation with the results of a previous calorimetric study of the freezing of confined dodecane. We explain the observed strains by the presence of capillary stresses, that appear in the layer due to the formation of internal liquid-vapour meniscus during the freezing process of the confined fluid. Received 22 October 1999 and Received in final form 25 March 2000     

Ultrasonic role to activate persulfate/chlorite with foamed zero-valent-iron: Sonochemical applications and induced mechanisms

The novel system, consisting of composite oxidants (persulfate/chlorite, S₂O₈²⁻/ClO₂⁻) and stationary phase activator (zero-valent-iron foam, Fe⁰_f) driven by ultrasonic (US) field, was applied to treat the triphenylmethane derivative effectively even at low temperature (≈ 289 K). By comparisons of sub-systems, the US roles to S₂O₈²⁻, ClO₂⁻, and Fe⁰_f were seriatim analyzed. US made the reaction order of multi-component system tend to within 1 (leading to de-order reaction), and widened pH activating range of the Fe⁰_f by sonicate-polishing during the process of ClO₂⁻ co-activating S₂O₈²⁻. US and Fe⁰_f were affected by fluid eddy on activating S₂O₈²⁻/ClO₂⁻. The Fe⁰_f had slight effect on the temperature of US bubble-water interface but the addition of ClO₂⁻ lowered it. The partitioning capacity of the above US reactive zone increased during the reaction. US and ClO₂⁻ could enrich the kinds of degradation intermediates. The contributions of free radicals (ClO_x-based radicals, sulfate radicals (SO₄⁻), and hydroxyl radicals (OH)) and non-free radicals (ClO₂, and O = Fe^IV/V from ionic Fe under “-O-O-” of S₂O₈²⁻ and cyclic adjustment reaction of ClO₂⁻) processes by sonochemical induction were equally important by corresponding detection means. Especially, real-time and online high-resolution mass spectrum by self-developing further confirmed the chain transfers of different free radicals due to US role. The findings expanded the application of sono-persulfate-based systems and improved understanding on activation mechanism.     

紫外可见分光光度法测定铜及铜合金抛光液中的硝酸根

研究了紫外可见分光光度计在301.7 nm处测定铜及铜合金抛光液中硝酸根的浓度.方法的线性范围为0.9662-9.6621 g/L,适合于该类型抛光液中硝酸根的检测.该方法快速简便、准确度高、精密度好.     

K9基片的亚表面损伤探测及化学腐蚀处理技术研究

 研究了几种类型的腐蚀液对K9基片化学腐蚀的影响。通过腐蚀液对基片纵向腐蚀速度的变化初步判断了K9基片重沉积层的深度。考察了腐蚀前后基片表面参数的变化以及腐蚀对激光损伤阈值的影响。研究表明,特定的腐蚀液能够对K9基片进行平稳可控的腐蚀,并且腐蚀能提高其激光损伤阈值,其主要原因是去除了重沉积层及表面、亚表面缺陷中的污染物,但过多的腐蚀会暴露本来为重沉积层所掩盖的划痕等亚表面缺陷,所以腐蚀并非越深越好。同时,表面各种杂质与缺陷的去除能够提高材料的机械强度,从而也有利于提高材料的激光损伤阈值。     

Microwave heating in high pressure reaction vessels

Abstract

We report the use of microwave -hydrothermal processing to synthesize various ceramic powders. Microwave-hydrothermal processing is compared with conventional hydrothermal processing in the crystallisation of MoO₂. The presence of microwave field leads to accelerated kinetics of crystallization of the finely divided molybdenum dioxide particles. Existing microwave heated pressure vessels for chemical synthesis cannot be used above 250 MPa and 270°C because they contain parts made of polymeric materials. The objective of this work is to associate a microwave source to a high pressure vessel in a way such that it might be used to carry out reactions in aqueous media at pressures around 100 MPa and temperatures above the critical point of water.     

胶束增敏分光光度法测定高纯石英粉中微量铝

选择阳离子表面活性剂氯化十六烷基吡啶(CPC)作为铝与铬天青S(CAS)显色体系的增敏剂,利用胶束增敏分光光度法测定高纯石英粉中微量铝,方法回收率为98%-104%,相对标准偏差低于2.7%(n=6).     

Influence of the polymer architecture on the high temperature behavior of SiCO glasses: A comparison between linear- and cyclic-derived precursors

Two series of cross-linked polysiloxanes, precursors for silicon oxycarbide glasses, have been synthesized from a linear and a cyclic Si-H-containing siloxane having the same chemical formula (SiCOH₄). The crosslinking has been achieved by hydrosilylation reaction with various amounts of divinylbenzene (DVB). A detailed structural characterization has been performed by ²⁹Si and ¹³C MAS NMR, FT-IR and chemical analysis. As a result, two different structural models have been proposed for the two series of resins. The two resins have been pyrolyzed at 1400 °C and the resulting SiCO ceramics characterized by X-ray diffraction. It has been shown that the stability of the amorphous silica phase present in the SiCO ceramics is strongly influenced by the molecular organization of the starting precursors. The presence of siloxane rings in the cyclic-derived polysiloxane decreases the stability of the amorphous SiO₂ and promotes the crystallization of cristobalite.     

Application of mixed mode resins for the purification of antibodies

The downstream processing of monoclonal antibodies from cell culture supernatant is usually done by a number of chromatographic and non-chromatographic steps. Efforts are taken to reduce the costs associated to those steps, while maintaining a high product purity. A possibility to reach this goal is the reduction of the number of chromatographic steps using mixed mode resins that offer more than one functionality in one chromatographic step. In this work, a commercially available mixed mode resin was evaluated systematically with respect to the adsorption of proteins. The Henry coefficient, which quantifies the adsorption strength, was measured for the full working range of the stationary phase as a function of the salt concentration and the pH. The results were compared to a conventional anion exchange and a hydrophobic interaction resin. Furthermore, the resin was applied for the polishing step of an antibody from an industrial clarified cell culture supernatant.     

纳米级均分散氧化钇粉末的制备

运用素分解法及“交替淬冷－快热”技术，成功地制备了经钇的纳米级均分散胶体粒，运用ＴＥＭ对产物分析后发现颗粒分散性好，分布窄，呈规则球形。最小粒径为６５ｎｍ。并对产物进行纯度分析，确定了杂质元素及含量。详细讨论了“交替淬冷－快热”技术运用于配方的基本原理。     

Characterization of chemosynthetic Al2O3-2SiO2 geopolymers

Pure chemosynthetic Al₂O₃-2SiO₂ geoploymers displaying positive alkali-activated polymerization properties and high compressive strength at room temperature were effectively fabricated utilizing a sol-gel method. The molecular structure of the precursor powder and resulting geopolymers were investigated by X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) analysis. In addition, the mechanical and alkali-activated polymerization properties of these materials were also studied. NMR data revealed that the chemosynthetic powders began to contain 5-coordinated Al atoms when the calcination temperatures exceeded 200 °C. These calcined powders were capable of reacting with sodium silicate solutions at calcination temperatures exceeding 300 °C, which is, however, much lower than the temperature required to convert kaolin to Metakaolin.