Fracture and adhesion of coatings for use in steam environments

Abstract

The fracture and adhesion properties of five different commercial high velocity oxygen fuel (HVOF) coatings have been evaluated as a function of temperature. Tests were carried out on coatings in the as-received, aged and densified conditions. Under all conditions the adhesion of the coatings was excellent. The strain to cracking was generally low for coatings in the ‘as-coated’ condition, however this was improved by densification or thermal ageing. It was observed that in some cases the crack path changed with treatment.     

Initiated chemical vapor deposition of poly(2-hydroxyethyl methacrylate) hydrogels

Initiated chemical vapor deposition (iCVD), a low temperature variant of hot-wire chemical vapor deposition (HWCVD) is a solvent-free polymerization technique. It was used to synthesize thick, free-standing films of the hydrogel poly(2-hydroxyethyl methacrylate) (PHEMA). In this work, we show that the iCVD technique can yield PHEMA which is free from residual entrained monomer, has low non-specific protein adsorption and is capable of supporting good cell adhesion and proliferation.     

Adhesion-dependent rupturing of Saccharomyces cerevisiae on biological antimicrobial nanostructured surfaces

Recent studies have shown that some nanostructured surfaces (NSS), many of which are derived from surfaces found on insect cuticles, rupture and kill adhered prokaryotic microbes. Most important, the nanoscale topography is directly responsible for this effect. Although parameters such as cell adhesion and cell wall rigidity have been suggested to play significant roles in this process, there is little experimental evidence regarding the underlying mechanisms involving NSS-induced microbial rupture. In this work, we report the NSS-induced rupturing of a eukaryotic microorganism, Saccharomyces cerevisiae. We show that the amount of NSS-induced rupture of S. cerevisiae is dependent on both the adhesive qualities of the yeast cell and the nanostructure geometry of the NSS. Thus, we are providing the first empirical evidence that these parameters play a direct role in the rupturing of microbes on NSS. Our observations of this phenomenon with S. cerevisiae, particularly the morphological changes, are strikingly similar to that reported for bacteria despite the differences in the yeast cell wall structure. Consequently, NSS provide a novel approach for the control of microbial growth and development of broad-spectrum microbicidal surfaces.     

Characterization and development of an active scintillating target for nuclear reaction studies on actinides

This article presents the development of a new kind of active actinide target, based on organic liquid scintillators containing the dissolved isotope. Amongst many advantages one can mention the very high detection efficiency, the Pulse Shape Discrimination capability, the fast response allowing high count rates and good time resolution and the ease of fabrication. The response of this target to fission fragments has been studied. The discrimination of alpha, fission and proton recoil events is demonstrated. The alpha decay and fission detection efficiencies are simulated and compared to measurements. Finally the use of such a target in the context of fast neutron induced reactions is discussed.     

Explanation for the appearance of alumina nanoparticles in a cold wall Atomic Layer Deposition system and their characterization

An explanation for the possible mechanism of formation of alumina nanoparticles in Atomic Layer Deposition process of Alumina using Trimethyl aluminum (TMA) and water in a cold wall ALD chamber is given based on the physisorption of TMA and surface energy of alumina thin films. The sorption mechanism proposed is physisorption at the cold walls rather than the conventional chemisorption at the hot substrates as in the case of typical ALD. It is argued that when the surface energy of alumina is larger than the physorption energy, the newly forming film will try to reduce the surface area and assume spherical shape forming nano particles. Synthesized particles were characterized using XRD, SEM, HRTEM, SAED, FTIR and EDS. It was found that the particle size varied from ∼20 nm to 45 nm. The samples were identified as slightly aluminum rich alumina. The as prepared samples were amorphous whereas annealing at 1200 deg C made them crystalline. Dielectric studies of pelletized samples yielded a dielectric constant of 9.08 which agreed well with reported values.     

亚微米i线投影曝光机曝光能量积分和快门控制系统

主要介绍了亚微米ｉ线投影曝光机上使用的曝光能量积分快门控制系统。论述了新的设计方法和工作原理,在曝光期间挡光快门旋转３６０°是本系统的一个重要特点。该系统获得了小于０．５％的控制精度。     

Ellipsometer measurements using focused and masked beams

While optical spectroscopic measurements using ellipsometry may be made in air and are non-destructive, the relatively large (> 2 mm) spot size has limited their use to surface regions greater than 2 mm in lateral extent. Recent developments in focusing instruments have made spot sizes on the order of 20 to 25 μm possible. The work to be presented explores the use of the 25 μm spot size to probe non-uniform nanostructured thin films. Measurements were performed on a highly non-uniform film (0 to 2 μm in thickness across 4 mm in lateral dimension) using such a 25 μm spot. Further reduction of the spot size is possible using mechanical masking with a slit. Measurements have been made to the range of a few microns in width. The practical resolution limits of beam masking may be decreased by increasing incident light intensity, improving slit alignment, and improving detection methods.     

Synthesis and characterization of large area well-aligned carbon nanotubes by ECR-CVD without substrate bias

Large area, well-aligned carbon nanotubes (CNTs) were synthesized on porous silicon by electron cyclotron resonance chemical vapor deposition (ECR-CVD). No bias was applied on the substrate in this experiment. CH₄ and H₂ were used as source gases and Fe₃O₄ nanoparticles as the catalyst. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), and Raman spectrum were used to evaluate the structure and composition. The results show that these CNTs have varying outer diameters from 10 to 90 nm and uniform length over 10 μm. They display hollow tubular and chain structures. The possible formation mechanism of aligned CNTs is discussed.     

Real-time radiography at the NECTAR facility

A feasibility study has shown that real-time radiography using fission neutrons is possible at the NECTAR facility, when using an improved detection system for fast variations (Bücherl et al., 2009 [1]).Continuing this study, real-time measurements of slowly varying processes like the water uptake in medium sized trunks (diameter about 12 cm) and of slow periodic processes (e.g. a slowly rotating iron disk) are investigated successfully using the existing detection system.     

Discrimination of pile up in a fission fragment detection experiment

In this work the problem introduced in a fission experiment by the pile-up due to a strong -background has been addressed. A novel scheme has been developed, able to reject more than 90% of pile-up affected pulses in a plutonium sample with an activity of 1 MBq. This procedure is necessary in order to improve the resolution to an acceptable level. With a proper calibration, however, the global mean energy and mass of the fragments are correctly reproduced both with and without pile-up rejection.     

Increase in the fluorescence intensity of ZnO nanoparticle by laser irradiation

We increased fluorescence intensity of ZnO nanoparticles by irradiation of laser to nanoparticles in solvent. The intensity of laser-irradiated nanoparticles became 1.4 times larger than that of non-irradiated one. The ZnO nanoparticles were synthesized by precipitation method. The laser for irradiation to ZnO nanoparticles was He-Cd cw laser. It was found that the average particle size was slightly increased during laser irradiation by red-shifted absorbance onset. These highly-fluorescent nanoparticles in solvent are useful for biomedical field such as biological imaging.     

Oxide glass used as inorganic template for fluorescent fluoride nanoparticles synthesis

We report an original way to synthesise single-crystal PbF₂ nanoparticles by selective chemical attack of a bulk nanocomposite oxyfluoride glass–ceramic. Free of impurities and homogeneously doped with Er³⁺ ions, the particles are of narrow size dispersion around 15 nm and weakly aggregated. The nanocrystallites emit a very intense green and blue up conversion fluorescence after infrared excitation. The doping level and the size of the particles is finely driven through the precursor glass–ceramic synthesis and composition.