Showing papers on "Blisters published in 2019"

Application of scanning Kelvin probe in the study of protective paints.

Abstract: Industrial coatings are composed of layers of different polymers (top coats, primers) containing pigments, corrosion inhibitors, and fillers as well as additives. For corrosion protection, it is vitally important to preserve the strong adhesion and long-term stability of the metal-polymer interface in corrosive environments. In recent decades, the performance of painted materials increased, which requires the application of advanced methods for quick assessing, ranking and predicting corrosion stability. Scanning Kelvin probe (SKP) is a highly sensitive and non-invasive technique to analyze in situ the metal-polymer interface of high-performance industrial coatings. SKP is able to monitor the adhesion and corrosion underneath different kinds of paints without the need for long-term corrosion tests. SKP is a localized electrochemical technique with a spatial resolution in the range of 70-100 µm. Hence, it is possible to obtain information about the intact and corroding portions of the interface at defect sites, corrosion blisters, contaminants and intermetallics, quality of pretreatments, and the development of galvanic couples that lead to corrosion de-adhesion of the polymeric coatings. This article reviews the application of SKP to the determination of the mechanisms of corrosion de-adhesion of model paints, thick marine paints, coatings with zinc rich primers, automotive paints and coil coatings applied on galvanized steel substrates.

On the blistering of thermo-sensitive hydrogel: the volume phase transition and mechanical instability.

Abstract: This paper explores the physical mechanisms responsible for the appearance of small blisters on the surface of temperature sensitive hydrogels as they deswell rapidly during their volume phase transition. For this, we develop a numerical model that couples the processes of hydrogel deswelling and blister growth due to the existence of a thin quasi-impermeable layer on its surface. The model points out that blister inflation originates at defects point under the gel's surface, under the effect of the increasing osmotic pressure in the gel as it undergoes its phase transition. Due to their large deformation, these blisters often experience a mechanical instability that triggers a sudden increase in their growth rate at the expense of their closest neighbors. Using a simple computational model, we then show that blisters are able to communicate via internal pressure and that these interactions are mediated by two characteristic time scales related to solvent transport within and between adjacent blisters. Our study finally indicates that these mechanisms can be controlled by temperature and the gel's cross-link density to achieve diversity of blister patterns on the gel's surface. The proposed analysis provides predictions that agree well with experimental observations of NiPAm gels which deswell in various conditions.

Deuterium and helium ion irradiation of nanograined tungsten and tungsten–titanium alloys

Abstract: Tungsten (W), a primary candidate for the plasma-facing components of nuclear fusion reactors (e.g. the divertor region in ITER) is susceptible to cracks, blisters, bubbles, and other morphological changes when irradiated with energetic particles. This work investigated two new materials, nanograined W and a nanograined W–Ti alloy, for potential use as plasma-facing materials. Their retention properties and morphological changes after exposure to deuterium (D) and helium (He) plasma at 50 eV and surface temperatures of 500 and 1000 K were analyzed. Nanograined W was found to have smaller blisters and be less prone to fuzz formation than commonly-utilized micro-grain polycrystalline W. Additionally, the nanograined W–Ti alloy exhibited a lower concentration of blisters on its surface than pure W, including nanograined W.

Investigation of hydrogen isotope retention mechanisms in beryllium: High resolution TPD measurements

Abstract: The retention of ion-implanted deuterium in beryllium poly- and single crystals at room temperature is studied using high precision temperature programmed desorption spectroscopy (TPD). Slow temperature ramps of 0.01 K/s in combination with well-defined experimental conditions are used to resolve the low temperature desorption regime for the first time revealing three sharp desorption peaks. The comparison to results of a coupled reaction diffusion system (CRDS) model shows, that the corresponding release mechanisms cannot be described by thermally activated rate processes. SEM images of a polycrystalline beryllium sample after implantation of deuterium with 2 keV per D atom show the formation of blisters of roughly 1 µm in diameter. Additionally, cracks on top of the blisters are found as well as spots, on which blisters are peeled off. Both processes are discussed to play a role in the low temperature release regime of the retained deuterium. Investigation of TPD spectra performed on single crystalline beryllium shows a jagged pattern in the low temperature release regime, which can be connected to blisters bursting up, releasing big amounts of deuterium in short time scales.

Properties of Blisters Formed on Polymer Films and Differentiating them from Nanobubbles/Nanodrops.

Abstract: When studying surface nanobubbles on film-coated substrates, a class of bubble-like domains called blisters are probably forming at the solid–liquid interface together with nanobubbles. This may easily lead to a misunderstanding of the characteristics and applications of surface nanobubbles and thus continue to cause problems within the nanobubble community. Therefore, how to distinguish surface nanobubbles from blisters is a problem. Herein, the morphology and properties of blisters are investigated on both smooth and nanopitted polystyrene (PS) films in degassed water. The morphology and contact angle of blisters are similar to those of surface nanobubbles. However, blisters were observed to be punctured under the tip–blister interaction and be torn broken by an atomic force microscope tip during the process of scanning. At the same time, nanopits on the surface of blisters that formed on a pitted PS film can be seen clearly. These provide direct and visual evidence for distinguishing blisters from surf...

Blistering and hydrogen retention in poly- and single- crystals of aluminum by a joint experimental-modeling approach

Abstract: Aluminum samples have been exposed to a hydrogen plasma generated by a low-pressure – high-density microwave reactor. Aluminum has been chosen as a surrogate for Beryllium. The fluence was kept below 4 × 1024 ions/m2, in order to study the first steps of nucleation and growth of surface and bulk defects, i.e. blisters and bubbles. Experimental analyzes and macroscopic rate equation (MRE) modeling on poly- and single- crystals were made to investigate the role played by grains boundaries in the hydrogen retention. Temperature programmed desorption (TPD) on Al poly-crystals revealed the production of aluminum hydrides (alanes) as majority species in the desorption flux. Comparison of microscopy observations for three different single-crystal orientations (〈100〉, 〈110〉 and 〈111〉) allowed to determine preferential orientations able to attenuate the formation of blisters.

Surface blistering and deuterium retention in tungsten exposed to low-energy deuterium plasma at different temperatures

Abstract: Surface morphology and deuterium retention in tungsten have been examined after exposure to a low-energy deuterium plasma with an ion fluence of 6.0 × 1024 D/m2 at various temperatures. Optical differential interference contrast microscope and scanning electron microscope equipped with focused ion beam were applied for surface observations. D (3He, p) 4He nuclear reaction at 3He energies varying from 0.5 to 4.5 MeV was used to determine the deuterium depth distributions within the depth of 8.0 μm. The thermal desorption spectroscopy was applied for deuterium retention measurement. The observed surface blistering and deuterium retention are found to strongly depend on the exposure temperature. At 230 K, many small blisters are formed on the tungsten surface. As the exposure temperature increases to 370 K, the blisters become sparser and larger. At 520 K no blisters appear. The deuterium retention is 1.4 × 1020 D/m2 at 230 K. Then it increases to 1.1 × 1021 D/m2 as the exposure temperature rises to 370 K, and decreases to 2.3 × 1020 D/m2 at 520 K.

Simple but effective blister-forming trick in suction blister technique

Abstract: Vitiligo is a common skin disorder of our country. Many of the patients are refractory to medical treatment. Dermato-Surgery is very rewarding in these cases. Thus proper selection of technique will play a major role in achieving good therapeutic and end cosmetic results. Suction blister technique is convenient and cost effective, less time consuming, pure epidermal graft, excellent colour match, pigment spread from the graft to surrounding area- upto 46% and maximum pigmentation within 3-4 months happens without any scar. Suction Blister Technique: The in vivo separation of epidermis from rest of the skin by production of a suction blister using 50 ml syringe as a vacuum creating device instead of the expensive and cumbersome vacuum devices as the time taken for the blister formation is the same. The advantage in this method we needn't inject intradermal saline into the blisters as blisters formed are appropriate and chances of improper blisters are very rare.

Femtosecond-Laser-Induced Blister Formation on Polymer Thin Films

Abstract: We present the formation of protruding ‘blister’ microstructures in polyimide and PMMA thin films using tightly-focused femtosecond pulses. We also show that implanting a reflective metal layer in the polymer film lowers the required pulse energies for forming blisters and prevents film rupture.

Dry powder inhaler with blister bursting device

Abstract: A multi-dose dry powder inhaler with a blister folding device is provided. The inhaler comprises a housing containing a blister strip, and a blister opening device. The blister strip comprises a plurality of individual blisters, each blister containing a dose of medicament for inhalation by a user. The blister opening device comprising a blister support element for supporting one of said blisters, and a blister folding element co-operable with the blister support element, the blister folding element and the blister support element being movable relative to each other between a first position, permitting movement of said blister into or onto the blister support element, and a second, burst, position in which the blister folding element has co-operated with the blister support element. Movement from the first position to the second position causes two spaced apart portions of said blister to each fold relative to the remainder of the blister to produce two spaced apart openings, each opening extending along the circumference of the blister bowl, beginning and terminating at points located on the fold line No piercing of the blister at any stage is required.

Determination of residual stress and interface adhesion toughness of thin films by blisters

Abstract: Circular blisters and telephone cord blisters (TCBs) can spontaneously occur in thin films under constant bi-axial compressive residual stress. In this work, new mechanical models are used in conjunction with measurements of blister morphology parameters to determine the residual stress in films and the adhesion toughness at interfaces. These new models are based on the hypothesis that pockets of energy concentration (PECs) drive the nucleation and growth of blisters instead of buckling, as in the conventional models, since the thin films are under constant compressive residual stress. Predictions from the models are in excellent agreement with independent experimental data.

Effects of He+ and H+ Co-Implantation with High Energy on Blisters and Craters of Si and SiO2-On-Si Wafers

Abstract: In this paper, effects of He+ and H+ co-implantation with high implantation energy on surface blisters and craters at different annealing conditions are systematically investigated. Surface morphology as well as defect microstructure are observed and analyzed by various approaches, such as scanning electron microscopy (SEM), optical microscopy (OM), atomic force microscopy (AFM), and Raman spectroscopy. It is found that after 500 °C annealing and above for 1 h, surface blisters and exfoliation are observed for Si and SiO2-on-Si wafers except for the samples implanted with only He+ ions. AFM images reveal that the heights of blisters in Si and SiO2-on-Si wafers are 432 nm and 397 nm respectively and the thickness of transfer layer is at the depth of about 1.4 μm, which is consistent with the projected range of He+ and H+ ions. Raman spectroscopy demonstrates that higher annealing temperature can lead to a stronger intensity of the VH2 peak. Under the same implantation parameters, surface morphology of Si and SiO2-on-Si wafers is different after annealing process. This phenomenon is discussed in detail.

Femtosecond-Laser-Induced Blisters in Polymer Thin Films and Application as Microlenses

Abstract: We present the phenomenology of blister formation by nonlinear absorption of femtosecond pulses in polyimide films, characterized by atomic force microscopy. We demonstrate a novel implementation of blisters as microlenses. © 2019 The Author(s)

Method for evaluating cleanliness of steel materials

Abstract: A method for evaluating the cleanliness of steel materials, according to an embodiment of the present invention, comprises the steps of: providing a steel specimen; allowing hydrogen to penetrate the specimen by means of an electrochemical method; quantifying blisters by counting the number of the blisters generated on the surface of the specimen by the hydrogen having penetrated therein; and comparing the quantified number of the blisters with the reference number of blisters so as to evaluate whether the steel material is suitable for shipment. Compared to a conventional evaluation method, a method for evaluating the cleanliness of steel materials, according to an embodiment of the present invention, clearly shows blisters on the surface of a specimen. Therefore, reliability for the evaluation of the cleanliness of steel materials is improved over that of a conventional method.