低温制冷机冷头焊接工艺研究

冷头是低温制冷机的关键零部件,是制冷机的重要结构件,同时也是制冷机与热载荷的接口部位。文中对冷头的焊接工艺进行研究,提出一种爆炸焊复合材料与激光焊结合的冷头焊接工艺。     

Protective sol-gel coating on silicate phosphor used in light emitting diodes

In this study, an orange-red silicate phosphor that is used in light emitting diodes (LEDs) was coated with a SiO₂ blocking layer via a sol-gel reaction of tetra-ethyl ortho-silicate (TEOS) to investigate its reliability as an encapsulant. A sol-gel coating protects the phosphor surface from moisture and reactive materials and improves the reliability of the phosphor. The efficacy of the phosphor coating following an 85 °C and 85 relative humidity (Rh)% test decreased by 7%, whereas an uncoated phosphor coating decreased by 35%. A SiO₂ sol-gel coating decreases the luminous efficiency by a small amount with each coating.     

Improvement of water and oil repellency on wood substrates by using fluorinated silica nanocoating

We have investigated a one-step fabrication of fluoro-containing silica coating on wooden substrates, showing multi-functions including super repellency toward water and sunflower oil, low sliding angles, good durability, and low adsorption capacity of moisture. The repellent slurry, consisting of well-mixing silica nanospheres and perfluoroalkyl methacrylic copolymer, is simply prepared and subsequently sprayed over wooden substrates with good adhesion. It has shown that the decoration of silica nanospheres on microscaled wooden texture acts as a crucial role in improving the repellency toward water and sunflower oil droplets. The maximal contact angles can reach as high as 168.3° and 153.6° for water and sunflower oil drops, respectively. These analyses of wetted fraction and work of adhesion also demonstrate the improved repellency due to the addition of silica. This improvement of the repellencies is ascribed to the fact that the drops partially sit on F-coated silica spheres, leaving a layer of air underneath the droplet (i.e., Cassie state). On the basis of the results, the multi-functional coating on wooden substrates delivers a promising commercial feasibility on a variety of woodworks.     

Trace elements in bovine muscle: an ongoing project for a new certified reference material

In the framework of the activities of the Community Reference Laboratory (CRL) for residues at the Istituto Superiore di Sanità (ISS) of Rome, a number of proficiency tests were performed in order to assess and improve, wherever necessary, the quality of regulatory residue analysis within the EU. In this context, a pilot study was undertaken with the purpose of ascertaining the feasibility of a project for the certification of a new reference material for trace elements in bovine muscle. On behalf of the ISS, approximately 70 kg of bovine muscle, collected at a slaughterhouse in Geel (Belgium), were freeze-dried, homogenized, stabilized and bottled under argon atmosphere by the Institute for Reference Materials and Measurements, Joint Research Centre, European Commission (IRMM-JRC-EC). Preliminary analyses were carried out with Quadrupole (Q) and High Resolution (HR) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to evaluate the content of As, Cd, Cu and Pb, whereas the Flow Injection Mercury System (FIMS) was used to quantify Hg. Digestion of the matrix was achieved by acid-assisted microwave irradiation. The mean values of experimentally obtained data were the following (in nanograms per gram): As, 24.2±1.2; Cd, 5.48±0.29; Cu, 4765±95; Hg, 3.37±0.73; and Pb, 184±7. Subsequently, 16 National Reference Laboratories (NRLs) for residues in the Member States plus the Norwegian one and eight Italian public laboratories were accepted to participate in the project and received one bottle of the freeze-dried bovine muscle. The laboratories were requested to perform three different analytical runs (in three different days), each consisting of three individual measurements. Preliminary results showed good agreement and fair evidence for homogeneity of the entire mass, thus setting the stage for the future certification of this candidate CRM.     

测量不确定度及其在化学计量中的应用实例

介绍了测量不确定度的评定方法及其在基准试剂纯度、干涉滤光片波长标准物质、锌合金成分标准物质中的应用实例。     

热冲击下分区均质材料耦合热弹性问题的变分原理

针对分区均质材料，考虑了热冲击产生的惯性效果和较大的应变速率对温度场的影响，建立了描述热冲击问题的理论模型，证明了热冲击下分区均质材料耦合热弹性问题的变分原理．为热冲击下分区均质材料耦合热弹性问题的定量求解，提供了理论基础．     

Novel Protonic Conductive Silicates Produced by the Sol-Gel Method

ABSTRACT

Materials which display ionic conductivity were produced by the sol-gel and microemulsion-gel methods. The charging and discharging characteristics were investigated and it was found that a single ionic species was responsible for the conduction, the ionic species being residual protons from the initial component mixture. The complex impedence of various samples was measured and the ionic conductivities ranged in value from 9 × 10^?8 to 1 × 10^?5 ohm^?1 cm^?1. An Arrhemius plot for a microemulsion-gel revealed that the energy of activation was 0.15 eV.     

Structure and dynamics of polymeric materials in nano-scale

The nano-palpation technique,i.e.,nanometer-scale elastic and viscoelastic measurements based on atomic force microscope,is introduced.It is demonstrated to be very useful in analyzing nanometer-scale materials properties for the surfaces and interfaces of various types of soft materials.It enables us to obtain not only structural information but also mechanical information about a material at the same place and at the same time.     

Synthesis and properties of phenothiazylene vinylene‐based polymers: New organic semiconductors for field‐effect transistors and solar cells

A series of new phenothiazylene vinylene‐based semiconducting polymers, poly[3,7‐(4′‐dodecyloxyphenyl)phenothiazylene vinylene] ( P1 ), poly[3,7‐(4′‐dodecyloxyphenyl)phenothiazylene vinylene‐alt‐1,4‐phenylene vinylene] ( P2 ), and poly[3,7‐(4′‐dodecyloxyphenyl)phenothiazylene vinylene‐alt‐2,5‐thienylene vinylene] ( P3 ), have been synthesized via a Horner‐Emmons reaction. FTIR and ¹H NMR spectroscopies confirmed that the configurations of the vinylene groups in the polymers were all‐trans (E). The weight‐averaged molecular weights (M_w) of P1 , P2 , and P3 were found to be 27,000, 22,000, and 29,000, with polydispersity indices of 1.91, 2.05, and 2.25, respectively. The thermograms for P1 , P2 , and P3 each contained only a broad glass transition, at 129, 167, and 155 °C, respectively, without the observation of melting features. UV–visible absorption spectra of the polymers showed two strong absorption bands in the ranges 315–370 nm and 450–500 nm, which arose from absorptions of the phenothiazine segments and the conjugated main chains. Solution‐processed field‐effect transistors fabricated from these polymers showed p‐type organic thin‐film transistor characteristics. The field‐effect mobilities of P1 , P2 , and P3 were measured to be 1.0 × 10^?4, 3.6 × 10^?5, and 1.0 × 10^?3 cm² V^?1 s^?1, respectively, and the on/off ratios were in the order of 10² for P1 and P2 , and 10³ for P3 . Atomic force microscopy and X‐ray diffraction analysis of thin films of the polymers show that they have amorphous structures. A photovoltaic device in which a P3 /PC₇₁BM (1/5) blend film was used as the active layer exhibited an open‐circuit voltage (V_OC) of 0.42 V, a short circuit current (J_SC) of 5.17 mA cm^?2, a fill factor of 0.35, and a power conversion efficiency of 0.76% under AM 1.5 G (100 mW cm^?2) illumination. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 635–646, 2010     

Novel luminescent Ir(III) dyes for developing highly sensitive oxygen sensing films

New sensing films have been developed for the detection of molecular oxygen. These films are based on luminescent Ir(III) dyes incorporated either into polystyrene (with and without plasticizer) or metal oxide, nanostructured material. The preparation and characterization of each film have been investigated in detail. Due to their high sensitivity for low oxygen concentration, the parameters pO₂(S=1/2) and ΔI_1% have been also evaluated in order to establish the most sensitive membrane for controlling concentrations between 0 and 10% and low oxygen concentrations (lower than 1%), respectively. The results show that the use of nanostructured material increased the sensitivity of the film; the most sensitive membrane for controlling O₂ between 0 and 10% is based on N1001 immobilized in AP200/19 (k_sv = 2848 ± 101 bar⁻¹ and pO₂(S=1/2)=0.0006), and the complex N969 incorporated into AP200/19 seems to be the most suitable for applications in oxygen trace sensing (ΔI_1% = 93.13 ± 0.13%).